- Diabetes and Metabolism
Vice Chair for Academic Affairs, Department of Medicine, Stanford (2004 - Present)
Board Certification: Endocrinology, Diabetes and Metabolism, American Board of Internal Medicine (1981)
Internship:Massachusetts General Hosp Harvard Med School (1977) MA
Fellowship:Massachusetts General Hospital (1982) MA
Fellowship:National Institutes of Health (1980) MD
Residency:Massachusetts General Hospital (1978) MA
Board Certification: Internal Medicine, American Board of Internal Medicine (1979)
Medical Education:Stanford University School of Medicine (1976) CA
BA, University of Michigan, History (1971)
MD, Stanford, Medicine (1976)
Current Research and Scholarly Interests
The laboratory is interested in examining the role of insulin-like growth factors (IGF) in normal physiology and in oncogenesis. We are studying the molecular biology of IGF with an emphasis on long range chromatin interactions.
Effects of Growth Hormone on Cognition and Cerebral Metabolism in Adults
Patients with Growth hormone (GH) deficiency often report impaired quality of life and difficulty with mental functioning. It has been suggested that GH replacement in such patients leads to improvement in cognitive function. The aim of this study is to elucidate the effects of GH replacement in patients with GH deficiency on cognitive function using structural and functional neuroimaging and cognitive testing.
- Hormones in a Performance-Enhanced Society
MED 71N (Win)
Independent Studies (8)
- Directed Reading in Cancer Biology
CBIO 299 (Aut, Win, Spr, Sum)
- Directed Reading in Medicine
MED 299 (Aut, Win, Spr, Sum)
- Early Clinical Experience in Medicine
MED 280 (Aut, Win, Spr, Sum)
- Graduate Research
CBIO 399 (Aut, Win, Spr, Sum)
- Graduate Research
MED 399 (Aut, Win, Spr, Sum)
- Medical Scholars Research
MED 370 (Aut, Win, Spr, Sum)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Sum)
- Undergraduate Research
MED 199 (Aut, Win, Spr, Sum)
- Directed Reading in Cancer Biology
- Prior Year Courses
Graduate and Fellowship Programs
Long noncoding RNA-mediated intrachromosomal interactions promote imprinting at the Kcnq1 locus
JOURNAL OF CELL BIOLOGY
2014; 204 (1): 61-75
Kcnq1ot1 is a long noncoding ribonucleic acid (RNA; lncRNA) that participates in the regulation of genes within the Kcnq1 imprinting domain. Using a novel RNA-guided chromatin conformation capture method, we demonstrate that the 5' region of Kcnq1ot1 RNA orchestrates a long-range intrachromosomal loop between KvDMR1 and the Kcnq1 promoter that is required for maintenance of imprinting. PRC2 (polycomb repressive complex 2), which participates in the allelic repression of Kcnq1, is also recruited by Kcnq1ot1 RNA via EZH2. Targeted suppression of Kcnq1ot1 lncRNA prevents the creation of this long-range intrachromosomal loop and causes loss of Kcnq1 imprinting. These observations delineate a novel mechanism by which an lncRNA directly builds an intrachromosomal interaction complex to establish allele-specific transcriptional gene silencing over a large chromosomal domain.
View details for DOI 10.1083/jcb.201304152
View details for Web of Science ID 000329347100007
View details for PubMedID 24395636
Implications of COMT long-range interactions on the phenotypic variability of 22q11.2 deletion syndrome
2013; 4 (6): 487-493
22q11.2 deletion syndrome (22q11DS) results from a hemizygous microdeletion on chromosome 22 and is characterized by extensive phenotypic variability. Penetrance of signs, including congenital heart, craniofacial, and neurobehavioral abnormalities, varies widely and is not well correlated with genotype. The three-dimensional structure of the genome may help explain some of this variability. The physical interaction profile of a given gene locus with other genetic elements, such as enhancers and co-regulated genes, contributes to its regulation. Thus, it is possible that regulatory interactions with elements outside the deletion region are disrupted in the disease state and modulate the resulting spectrum of symptoms. COMT, a gene within the commonly deleted ~3 Mb region has been implicated as a contributor to the neurological features frequently found in 22q11DS patients. We used this locus as bait in a 4C-seq experiment to investigate genome-wide interaction profiles in B lymphocyte and fibroblast cell lines derived from both 22q11DS and unaffected individuals. All normal B lymphocyte lines displayed local, conserved chromatin looping interactions with regions that are lost in atypical and distal deletions, which may mediate similarities between typical, atypical, and distal 22q11 deletion phenotypes. There are also distinct clusterings of cis interactions based on disease state. We identified regions of differential trans interactions present in normal, and lost in deletion-carrying, B lymphocyte cell lines. This data suggests that hemizygous chromosomal deletions such as 22q11DS can have widespread effects on chromatin organization, and may contribute to the inherent phenotypic variability.
View details for DOI 10.4161/nucl.27364
View details for Web of Science ID 000330387500013
View details for PubMedID 24448439
Genomic Interaction Profiles in Breast Cancer Reveal Altered Chromatin Architecture
2013; 8 (9)
Gene transcription can be regulated by remote enhancer regions through chromosome looping either in cis or in trans. Cancer cells are characterized by wholesale changes in long-range gene interactions, but the role that these long-range interactions play in cancer progression and metastasis is not well understood. In this study, we used IGFBP3, a gene involved in breast cancer pathogenesis, as bait in a 4C-seq experiment comparing normal breast cells (HMEC) with two breast cancer cell lines (MCF7, an ER positive cell line, and MDA-MB-231, a triple negative cell line). The IGFBP3 long-range interaction profile was substantially altered in breast cancer. Many interactions seen in normal breast cells are lost and novel interactions appear in cancer lines. We found that in HMEC, the breast carcinoma amplified sequence gene family (BCAS) 1-4 were among the top 10 most significantly enriched regions of interaction with IGFBP3. 3D-FISH analysis indicated that the translocation-prone BCAS genes, which are located on chromosomes 1, 17, and 20, are in close physical proximity with IGFBP3 and each other in normal breast cells. We also found that epidermal growth factor receptor (EGFR), a gene implicated in tumorigenesis, interacts significantly with IGFBP3 and that this interaction may play a role in their regulation. Breakpoint analysis suggests that when an IGFBP3 interacting region undergoes a translocation an additional interaction detectable by 4C is gained. Overall, our data from multiple lines of evidence suggest an important role for long-range chromosomal interactions in the pathogenesis of cancer.
View details for DOI 10.1371/journal.pone.0073974
View details for Web of Science ID 000324338200085
View details for PubMedID 24019942
Intrachromosomal Looping Is Required for Activation of Endogenous Pluripotency Genes during Reprogramming
CELL STEM CELL
2013; 13 (1): 30-35
Generation of induced pluripotent stem cells (iPSCs) by defined factors is an extremely inefficient process, because there is a strong epigenetic block preventing cells from achieving pluripotency. Here we report that virally expressed factors bound to the promoters of their target genes to the same extent in both iPSCs and unreprogrammed cells (URCs). However, expression of endogenous pluripotentcy genes was observed only in iPSCs. Comparison of local chromatin structure of the OCT4 locus revealed that there was a cohesin-complex-mediated intrachromosomal loop that juxtaposes a downstream enhancer to the gene's promoter, enabling activation of endogenous stemness genes. None of these long-range interactions were observed in URCs. Knockdown of the cohesin-complex gene SMC1 by RNAi abolished the intrachromosomal interaction and affected pluripotency. These findings highlight the importance of the SMC1-orchestrated intrachromosomal loop as a critical epigenetic barrier to the induction of pluripotency.
View details for DOI 10.1016/j.stem.2013.05.012
View details for Web of Science ID 000329570100010
View details for PubMedID 23747202
Interruption of intrachromosomal looping by CCCTC binding factor decoy proteins abrogates genomic imprinting of human insulin-like growth factor II
JOURNAL OF CELL BIOLOGY
2011; 193 (3): 475-487
Monoallelic expression of IGF2 is regulated by CCCTC binding factor (CTCF) binding to the imprinting control region (ICR) on the maternal allele, with subsequent formation of an intrachromosomal loop to the promoter region. The N-terminal domain of CTCF interacts with SUZ12, part of the polycomb repressive complex-2 (PRC2), to silence the maternal allele. We synthesized decoy CTCF proteins, fusing the CTCF deoxyribonucleic acid-binding zinc finger domain to CpG methyltransferase Sss1 or to enhanced green fluorescent protein. In normal human fibroblasts and breast cancer MCF7 cell lines, the CTCF decoy proteins bound to the unmethylated ICR and to the IGF2 promoter region but did not interact with SUZ12. EZH2, another part of PRC2, was unable to methylate histone H3-K27 in the IGF2 promoter region, resulting in reactivation of the imprinted allele. The intrachromosomal loop between the maternal ICR and the IGF2 promoters was not observed when IGF2 imprinting was lost. CTCF epigenetically governs allelic gene expression of IGF2 by orchestrating chromatin loop structures involving PRC2.
View details for DOI 10.1083/jcb.201101021
View details for Web of Science ID 000290676400008
View details for PubMedID 21536749
Systematic review: The safety and efficacy of growth hormone in the healthy elderly
ANNALS OF INTERNAL MEDICINE
2007; 146 (2): 104-115
Human growth hormone (GH) is widely used as an antiaging therapy, although its use for this purpose has not been approved by the U.S. Food and Drug Administration and its distribution as an antiaging agent is illegal in the United States.To evaluate the safety and efficacy of GH therapy in the healthy elderly.The authors searched MEDLINE and EMBASE databases for English-language studies published through 21 November 2005 by using such terms as growth hormone and aging.The authors included randomized, controlled trials that compared GH therapy with no GH therapy or GH and lifestyle interventions (exercise with or without diet) with lifestyle interventions alone. Included trials provided GH for 2 weeks or more to community-dwelling participants with a mean age of 50 years or more and a body mass index of 35 kg/m2 or less. The authors excluded studies that evaluated GH as treatment for a specific illness.Two authors independently reviewed articles and abstracted data.31 articles describing 18 unique study populations met the inclusion criteria. A total of 220 participants who received GH (107 person-years) completed their respective studies. Study participants were elderly (mean age, 69 years [SD, 6]) and overweight (mean body mass index, 28 kg/m2 [SD, 2]). Initial daily GH dose (mean, 14 microg per kg of body weight [SD, 7]) and treatment duration (mean, 27 weeks [SD, 16]) varied. In participants treated with GH compared with those not treated with GH, overall fat mass decreased (change in fat mass, -2.1 kg [95% CI, -2.8 to -1.35] and overall lean body mass increased (change in lean body mass, 2.1 kg [CI, 1.3 to 2.9]) (P < 0.001), and their weight did not change significantly (change in weight, 0.1 kg [CI, -0.7 to 0.8]; P = 0.87). Total cholesterol levels decreased (change in cholesterol, -0.29 mmol/L [-11.21 mg/dL]; P = 0.006), although not significantly after adjustment for body composition changes. Other outcomes, including bone density and other serum lipid levels, did not change. Persons treated with GH were significantly more likely to experience soft tissue edema, arthralgias, carpal tunnel syndrome, and gynecomastia and were somewhat more likely to experience the onset of diabetes mellitus and impaired fasting glucose.Some important outcomes were infrequently or heterogeneously measured and could not be synthesized. Most included studies had small sample sizes.The literature published on randomized, controlled trials evaluating GH therapy in the healthy elderly is limited but suggests that it is associated with small changes in body composition and increased rates of adverse events. On the basis of this evidence, GH cannot be recommended as an antiaging therapy.
View details for Web of Science ID 000243901000004
View details for PubMedID 17227934
CTCF mediates interchromosomal colocalization between Igf2/H19 and Wsb1/Nf1
2006; 312 (5771): 269-272
Gene transcription may be regulated by remote enhancer or insulator regions through chromosome looping. Using a modification of chromosome conformation capture (3C) and fluorescence in situ hybridization, we found that one allele of the insulin-like growth factor 2 (Igf2)/H19 imprinting control region (ICR) on chromosome 7 colocalized with one allele of Wsb1/Nf1 on chromosome 11. Omission of CCCTC-binding factor (CTCF) or deletion of the maternal ICR abrogated this association and altered Wsb1/Nf1 gene expression. These findings demonstrate that CTCF mediates an interchromosomal association, perhaps by directing distant DNA segments to a common transcription factory, and the data provide a model for long-range allele-specific associations between gene regions on different chromosomes that suggest a framework for DNA recombination and RNA trans-splicing.
View details for DOI 10.1126/science.1123191
View details for Web of Science ID 000236765300050
View details for PubMedID 16614224
A methylated oligonucleotide inhibits IGF2 expression and enhances survival in a model of hepatocellular carcinoma
JOURNAL OF CLINICAL INVESTIGATION
2003; 111 (2): 265-273
IGF-II is a mitogenic peptide that has been implicated in hepatocellular oncogenesis. Since the silencing of gene expression is frequently associated with cytosine methylation at cytosine-guanine (CpG) dinucleotides, we designed a methylated oligonucleotide (MON1) complementary to a region encompassing IGF2 promoter P4 in an attempt to induce DNA methylation at that locus and diminish IGF2 mRNA levels. MON1 specifically inhibited IGF2 mRNA accumulation in vitro, whereas an oligonucleotide (ON1) with the same sequence but with nonmethylated cytosines had no effect on IGF2 mRNA abundance. MON1 treatment led to the specific induction of de novo DNA methylation in the region of IGF2 promoter hP4. Cells from a human hepatocellular carcinoma (HCC) cell line, Hep 3B, were implanted into the livers of nude mice, resulting in the growth of large tumors. Animals treated with MON1 had markedly prolonged survival as compared with those animals treated with saline or a truncated methylated oligonucleotide that did not alter IGF2 mRNA levels in vitro. This study demonstrates that a methylated sense oligonucleotide can be used to induce epigenetic changes in the IGF2 gene and that inhibition of IGF2 mRNA accumulation may lead to enhanced survival in a model of HCC.
View details for DOI 10.1172/JCI200315109
View details for Web of Science ID 000180672900018
View details for PubMedID 12531883
- Imprinting of the Angelman syndrome gene, UBE3A, is restricted to brain NATURE GENETICS 1997; 17 (1): 12-13
PROMOTER-SPECIFIC IMPRINTING OF THE HUMAN INSULIN-LIKE GROWTH FACTOR-II GENE
1994; 371 (6499): 714-717
Genomic imprinting is a mechanism whereby only one of the two parental alleles is expressed. Loss or relaxation of genomic imprinting has been proposed as an epigenetic mechanism for oncogenesis in a variety of human tumours. Although the mechanism of imprinting is unknown, differential CpG methylation of the parental alleles has been implicated. The human insulin-like growth factor-II (IGF2) gene, which is transcribed from four promoters, P1-P4 (ref. 13), is imprinted in fetal liver but biallelic expression occurs in adult liver. Like most tissues, fetal liver uses primarily promoters P3 and P4 (ref. 17). Adult liver, however, transcribes IGF2 from promoter P1, and it has been suggested that the recruitment of P1 may be responsible for the absence of imprinting in human liver, and in choroid plexus and leptomeninges. We report here that in liver and chondrocytes, IGF2 transcripts from promoter P1 are always derived from both parental alleles, whereas transcripts from promoters P2, P3 and P4 are always from one parental allele. These findings demonstrate that imprinting and a lack of imprinting can both occur within a single gene in a single tissue, suggesting that regional imprinting factors may be important.
View details for Web of Science ID A1994PM77300060
View details for PubMedID 7935819
A novel antisense long noncoding RNA within the IGF1R gene locus is imprinted in hematopoietic malignancies.
Nucleic acids research
2014; 42 (15): 9588-9601
Dysregulation of the insulin-like growth factor type I receptor (IGF1R) has been implicated in the progression and therapeutic resistance of malignancies. In acute myeloid leukemia (AML) cells, IGF1R is one of the most abundantly phosphorylated receptor tyrosine kinases, promoting cell growth through the PI3K/Akt signaling pathway. However, little is known regarding the molecular mechanisms underlying IGF1R gene dysregulation in cancer. We discovered a novel intragenic long noncoding RNA (lncRNA) within the IGF1R locus, named IRAIN, which is transcribed in an antisense direction from an intronic promoter. The IRAIN lncRNA was expressed exclusively from the paternal allele, with the maternal counterpart being silenced. Using both reverse transcription-associated trap and chromatin conformation capture assays, we demonstrate that this lncRNA interacts with chromatin DNA and is involved in the formation of an intrachromosomal enhancer/promoter loop. Knockdown of IRAIN lncRNA with shRNA abolishes this intrachromosomal interaction. In addition, IRAIN was downregulated both in leukemia cell lines and in blood obtained from high-risk AML patients. These data identify IRAIN as a new imprinted lncRNA that is involved in long-range DNA interactions.
View details for DOI 10.1093/nar/gku549
View details for PubMedID 25092925
- ASSOCIATION BETWEEN THYROID FUNCTION AND OBJECTIVE AND SUBJECTIVE SLEEP QUALITY IN OLDER MEN: THE OSTEOPOROTIC FRACTURES IN MEN (MROS) STUDY ENDOCRINE PRACTICE 2014; 20 (6): 576-586
Association Between Thyroid Function and Objective and Subjective Sleep Quality in Older Men: The Osteoporotic Fractures in Men (MrOS) Study.
2014; 20 (6): 576-586
Objective: To determine the association between thyroid hormone levels and sleep quality in community-dwelling men.Methods: Among 5,994 men aged ≥65 years in the Osteoporotic Fractures in Men (MrOS) study, 682 had baseline thyroid function data, normal free thyroxine (FT4) (0.70 ≤ FT4 ≤ 1.85 ng/dL), actigraphy measurements, and were not using thyroid-related medications. Three categories of thyroid function were defined: subclinical hyperthyroid (thyroid-stimulating hormone [TSH] <0.55 mIU/L), euthyroid (TSH, 0.55 to 4.78 mIU/L), and subclinical hypothyroid (TSH >4.78 mIU/L). Objective (total hours of nighttime sleep [TST], sleep efficiency [SE], wake after sleep onset [WASO], sleep latency [SL], number of long wake episodes [LWEP]) and subjective (TST, Pittsburgh Sleep Quality Index score, Epworth Sleepiness Scale score) sleep quality parameters were measured. The association between TSH and sleep quality was examined using linear regression (continuous sleep outcomes) and log-binomial regression (categorical sleep outcomes).Results: Among the 682 men examined, 15 had subclinical hyperthyroidism and 38 had subclinical hypothyroidism. There was no difference in sleep quality between subclinical hypothyroid and euthyroid men. Compared to euthyroid men, subclinical hyperthyroid men had lower mean actigraphy TST (adjusted mean difference [95% confidence interval (CI)], -27.4 [-63.7 to 8.9] minutes), lower mean SE (-4.5% [-10.3% to 1.3%]), and higher mean WASO (13.5 [-8.0 to 35.0] minutes]), whereas 41% had increased risk of actigraphy-measured TST <6 hours (relative risk [RR], 1.41; 95% CI, 0.83 to 2.39), and 83% had increased risk of SL ≥60 minutes (RR, 1.83; 95% CI, 0.65 to 5.14) (all P>.05).Conclusion: Neither subclinical hypothyroidism nor hyperthyroidism is significantly associated with decreased sleep quality.
View details for DOI 10.4158/EP13282.OR
View details for PubMedID 24449663
- Rapid and Efficient Conversion of Integration-Free Human Induced Pluripotent Stem Cells to GMP-Grade Culture Conditions PLOS ONE 2014; 9 (4)
Epigenetic reprogramming reverses the malignant epigenotype of the MMP/TIMP axis genes in tumor cells
INTERNATIONAL JOURNAL OF CANCER
2014; 134 (7): 1583-1594
Cancer progression is characterized by extensive tumor invasion into the surrounding extracellular matrix (ECM) and migration to metastatic sites. The increased proteolytic degradation of the ECM during tumor invasion is directly dependent on the activity of matrix metalloproteinases (MMPs), counter-balanced by tissue inhibitors of matrix metalloproteinases (TIMPs). In this study, we found that unbalanced expression of MMP/TIMP axis genes in tumors was correlated with aberrant epigenotypes in the various gene promoters. The malignant epigenotypes could be therapeutically corrected by a simple defined factor-mediated reprogramming approach. Correction of the abnormal epigenotypes by nuclear remodeling leads to a rebalance in the gene expression profile, an alteration in tumor cell morphology, attenuation of tumor cell migration and invasion in vitro, and reduced tumorigenicity in nude mice. We further identified the downregulation of the MKK-p38 MAPK signal pathway as an important underlying mechanism for reduced tumorigenicity in this epigenetic reprogramming model. These data demonstrate that the malignant phenotypes seen in cancer can be corrected by a nuclear remodeling mechanism, thus highlighting a novel non-chemotherapeutic, non-radiotherapeutic approach for the treatment of cancer.
View details for DOI 10.1002/ijc.28487
View details for Web of Science ID 000329579500007
View details for PubMedID 24105737
Rapid and efficient conversion of integration-free human induced pluripotent stem cells to GMP-grade culture conditions.
2014; 9 (4)
Data suggest that clinical applications of human induced pluripotent stem cells (hiPSCs) will be realized. Nonetheless, clinical applications will require hiPSCs that are free of exogenous DNA and that can be manufactured through Good Manufacturing Practice (GMP). Optimally, derivation of hiPSCs should be rapid and efficient in order to minimize manipulations, reduce potential for accumulation of mutations and minimize financial costs. Previous studies reported the use of modified synthetic mRNAs to reprogram fibroblasts to a pluripotent state. Here, we provide an optimized, fully chemically defined and feeder-free protocol for the derivation of hiPSCs using synthetic mRNAs. The protocol results in derivation of fully reprogrammed hiPSC lines from adult dermal fibroblasts in less than two weeks. The hiPSC lines were successfully tested for their identity, purity, stability and safety at a GMP facility and cryopreserved. To our knowledge, as a proof of principle, these are the first integration-free iPSCs lines that were reproducibly generated through synthetic mRNA reprogramming that could be putatively used for clinical purposes.
View details for DOI 10.1371/journal.pone.0094231
View details for PubMedID 24718618
Promoter histone H3K27 methylation in the control of IGF2 imprinting in human tumor cell lines
HUMAN MOLECULAR GENETICS
2014; 23 (1): 117-128
Aberrant imprinting of the insulin-like growth factor II (IGF2) gene is a molecular hallmark of many tumors. Reactivation of the normally suppressed maternal allele leads to upregulation of the growth factor that promotes tumor growth. However, the mechanisms underlying the loss of imprinting (LOI) remain poorly defined. We examined the epigenotypes at the gene promoters that control IGF2 allelic expression. Using chromatin immunoprecipitation, we found that in cells characterized by maintenance of IGF2 imprinting, three IGF2 promoters were differentially modified, with the suppressed allele heavily methylated at histone H3K27 while the active allele was unmethylated. In the LOI tumors, however, both alleles were unmethylated, and correspondingly there was no binding of SUZ12, the docking factor of the polycomb repressive complex 2 (PRC2), and of the zinc finger-containing transcription factor (CTCF) that recruits the PRC2. Using chromatin conformation capture, we found that the CTCF-orchestrated intrachromosomal loop between the IGF2 promoters and the imprinting control region was abrogated in cells with LOI. SUZ12, which docks the PRC2 to IGF2 promoters for H3K27 methylation, was downregulated in LOI cells. These data reveal a new epigenetic control pathway related to the loss of IGF2 imprinting in tumors.
View details for DOI 10.1093/hmg/ddt405
View details for Web of Science ID 000328482300010
View details for PubMedID 23962719
- Chromatin looping is needed for iPSC induction. Cell cycle 2014; 13 (1): 1-2
Targeted gene suppression by inducing de novo DNA methylation in the gene promoter.
Epigenetics & chromatin
2014; 7: 20-?
Targeted gene silencing is an important approach in both drug development and basic research. However, the selection of a potent suppressor has become a significant hurdle to implementing maximal gene inhibition for this approach. We attempted to construct a 'super suppressor' by combining the activities of two suppressors that function through distinct epigenetic mechanisms.Gene targeting vectors were constructed by fusing a GAL4 DNA-binding domain with a epigenetic suppressor, including CpG DNA methylase Sss1, histone H3 lysine 27 methylase vSET domain, and Kruppel-associated suppression box (KRAB). We found that both Sss1 and KRAB suppressors significantly inhibited the expression of luciferase and copGFP reporter genes. However, the histone H3 lysine 27 methylase vSET did not show significant suppression in this system. Constructs containing both Sss1 and KRAB showed better inhibition than either one alone. In addition, we show that KRAB suppressed gene expression by altering the histone code, but not DNA methylation in the gene promoter. Sss1, on the other hand, not only induced de novo DNA methylation and recruited Heterochromatin Protein 1 (HP1a), but also increased H3K27 and H3K9 methylation in the promoter.Epigenetic studies can provide useful data for the selection of suppressors in constructing therapeutic vectors for targeted gene silencing.
View details for DOI 10.1186/1756-8935-7-20
View details for PubMedID 25184003
Abdominal Myosteatosis Is Independently Associated with Hyperinsulinemia and Insulin Resistance Among Older Men Without Diabetes
2013; 21 (10): 2118-2125
OBJECTIVE: Skeletal muscle adipose tissue (AT) infiltration (myosteatosis) increases with aging and may contribute to the development of Type 2 diabetes mellitus (T2DM). It remains unclear if myosteatosis is associated to glucose and insulin homeostasis independent of total and central adiposity. DESIGN AND METHODS: The association between intermuscular AT (IMAT) in the abdominal skeletal muscles (total, paraspinal, and psoas) and fasting serum glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) in 393 nondiabetic Caucasian men aged 65+ was evaluated. Abdominal IMAT, visceral AT (VAT), and subcutaneous AT (SAT) (cm(3) ) were measured by quantitative computed tomography at the L4-L5 intervertebral space. RESULTS: In age, study site, height, and muscle volume adjusted regression analyses, total abdominal and psoas (but not paraspinal) IMAT were positively associated with glucose, insulin, and HOMA-IR (all P < 0.003). The associations between total abdominal and psoas IMAT and insulin and HOMA-IR remained significant after further adjusting for lifestyle factors, as well as duel-energy x-ray absorptiometry (DXA) measured total body fat, VAT, or SAT in separate models (all P < 0.009). CONCLUSIONS: A previously unreported, independent association between abdominal myosteatosis and hyperinsulinemia and insulin resistance among older Caucasian men was indicated. These associations may be specific for particular abdominal muscle depots, illustrating the potential importance of separately studying specific muscle groups.
View details for DOI 10.1002/oby.20346
View details for Web of Science ID 000325427300021
Cyclic Hypobaric Hypoxia Improves Markers of Glucose Metabolism in Middle-Aged Men
HIGH ALTITUDE MEDICINE & BIOLOGY
2013; 14 (3): 263-272
Chronic hypoxia increases dependence on glucose in men and increases insulin sensitivity in men and women. Cyclic Variations in Altitude Conditioning (CVAC) is a novel technology that provides exposure to rapidly fluctuating cyclic hypobaric hypoxia (CHH).To test the hypothesis that markers of glucose metabolism would change with CVAC CHH, two groups of middle-aged men were exposed to 10 weeks (40 min/day, 3 day/week) of either CHH or sham (SH) sessions.CHH subjects (age: 48 ± 6, weight: 86 ± 12 kg, BMI: 27.1 ± 3, n=11) experienced cyclic pressures simulating altitudes ranging from sea level to 3048 m (week 1) and progressing to 6096 m (by week 5 through week 10). SH subjects (age: 50 ± 4, weight: 89 ± 15 kg, BMI: 27.5 ± 3, n=10) were exposed to slowly-fluctuating pressures up to 607 m (all subjects blinded to elevation). Physical function and blood markers of glucose metabolism were measured at baseline, 3, 6, and 10 weeks.Two CHH subjects were dropped from analysis for failure to progress past 3048 m (CHH: n=9). Weight and physical activity remained stable for both groups. There was a group-by-time interaction in fasting glucose (CHH: 96 ± 9 to 91 ± 7 mg/dL, SH: 94 ± 7 to 97 ± 9 mg/dL, p<0.05). Reduction in plasma glucose response to oral glucose tolerance test [area under the curve] was greater in CHH compared to SH after 10 weeks of exposure (p<0.03). Neither group experienced changes in fasting insulin, insulin response during the OGTT, or changes in a timed walk test.Ten weeks of CVAC CHH exposure improves markers of glucose metabolism in middle-aged men at risk for metabolic syndrome.
View details for DOI 10.1089/ham.2012.1057
View details for Web of Science ID 000324834700019
View details for PubMedID 24028640
Gene therapy for colorectal cancer by an oncolytic adenovirus that targets loss of the insulin-like growth factor 2 imprinting system
Colorectal cancer is one of the most common malignant tumors worldwide. Loss of imprinting (LOI) of the insulin-like growth factor 2 (IGF2) gene is an epigenetic abnormality observed in human colorectal neoplasms. Our aim was to investigate the feasibility of using the IGF2 imprinting system for targeted gene therapy of colorectal cancer.We constructed a novel oncolytic adenovirus, Ad315-E1A, and a replication-deficient recombinant adenovirus, Ad315-EGFP, driven by the IGF2 imprinting system by inserting the H19 promoter, CCCTC binding factor, enhancer, human adenovirus early region 1A (E1A) and enhanced green fluorescent protein (EGFP) reporter gene into a pDC-315 shuttle plasmid. Cell lines with IGF2 LOI (HCT-8 and HT-29), which were infected with Ad315-EGFP, produced EGFP. However, no EGFP was produced in cell lines with maintenance of imprinting (HCT116 and GES-1). We found that Ad315-E1A significantly decreased cell viability and induced apoptosis only in LOI cell lines in vitro. In addition, mice bearing HCT-8-xenografted tumors, which received intratumoral administration of the oncolytic adenovirus, showed significantly reduced tumor growth and enhanced survival.Our recombinant oncolytic virus targeting the IGF2 LOI system inhibits LOI cell growth in vitro and in vivo, and provides a novel approach for targeted gene therapy.
View details for DOI 10.1186/1476-4598-11-86
View details for Web of Science ID 000314051700001
View details for PubMedID 23171475
The Association of Concurrent Vitamin D and Sex Hormone Deficiency With Bone Loss and Fracture Risk in Older Men: The Osteoporotic Fractures in Men (MrOS) Study
JOURNAL OF BONE AND MINERAL RESEARCH
2012; 27 (11): 2306-2313
Low 25-hydroxyvitamin D (VitD), low sex hormones (SH), and high sex hormone binding globulin (SHBG) levels are common in older men. We tested the hypothesis that combinations of low VitD, low SH, and high SHBG would have a synergistic effect on bone mineral density (BMD), bone loss, and fracture risk in older men. Participants were a random subsample of 1468 men (mean age 74 years) from the Osteoporotic Fractures in Men Study (MrOS) plus 278 MrOS men with incident nonspine fractures studied in a case-cohort design. "Abnormal" was defined as lowest quartile for VitD (<20 ng/mL), bioavailable testosterone (BioT, <163 ng/dL), and bioavailable estradiol (BioE, <11 pg/mL); and highest quartile for SHBG (>59 nM). Overall, 10% had isolated VitD deficiency; 40% had only low SH or high SHBG; 15% had both SH/SHBG and VitD abnormality; and 35% had no abnormality. Compared to men with all normal levels, those with both SH/SHBG and VitD abnormality tended to be older, more obese, and to report less physical activity. Isolated VitD deficiency, and low BioT with or without low VitD, was not significantly related to skeletal measures. The combination of VitD deficiency with low BioE and/or high SHBG was associated with significantly lower baseline BMD and higher annualized rates of hip bone loss than SH abnormalities alone or no abnormality. Compared to men with all normal levels, the multivariate-adjusted hazard ratio (95% confidence interval [CI]) for incident nonspine fracture during 4.6-year median follow-up was 1.2 (0.8-1.8) for low VitD alone; 1.3 (0.9-1.9) for low BioE and/or high SHBG alone; and 1.6 (1.1-2.5) for low BioE/high SHBG plus low VitD. In summary, adverse skeletal effects of low sex steroid levels were more pronounced in older men with low VitD levels. The presence of low VitD in the presence of low BioE/high SHBG may contribute substantially to poor skeletal health.
View details for DOI 10.1002/jbmr.1697
View details for Web of Science ID 000313729500011
View details for PubMedID 22777902
Successful long-term treatment of Cushing disease with mifepristone (RU486).
2012; 18 (5): e114-20
We describe a girl with Cushing disease for whom surgery and radiation treatments failed and the subsequent clinical course with mifepristone therapy.We present the patient's clinical, biochemical, and imaging findings.A 16-year-old girl presented with classic Cushing disease. After transsphenoidal surgery, Cyberknife radiosurgery, ketoconazole, and metyrapone did not control her disease, and she was prescribed mifepristone, which was titrated to a maximal dosage of 1200 mg daily with subsequent symptom improvement. Mifepristone (RU486) is a high-affinity, nonselective antagonist of the glucocorticoid receptor. There is limited literature on its use as an off-label medication to treat refractory Cushing disease. Over her 8-year treatment with mifepristone, her therapy was complicated by hypertension and hypokalemia requiring spironolactone and potassium chloride. She received a 2-month drug holiday every 4 to 6 months to allow for withdrawal menstrual bleeding with medroxyprogesterone acetate. Urinary cortisol, serum cortisol, and corticotropin levels remained elevated during mifepristone drug holidays. While on mifepristone, her signs and symptoms of Cushing disease resolved. Repeated magnetic resonance imaging demonstrated stable appearance of the residual pituitary mass. Bilateral adrenalectomy was performed, and mifepristone was discontinued after 95 months of medical therapy.We describe the longest duration of mifepristone therapy thus reported for the treatment of refractory Cushing disease. Mifepristone effectively controlled all signs and symptoms of hypercortisolism. Menstruating women who take the drug on a long-term basis should receive periodic drug holidays to allow for menses. The lack of reliable serum biomarkers to monitor the success of mifepristone therapy requires careful clinical judgment and may make its use difficult in Cushing disease.
View details for DOI 10.4158/EP11391.CR
View details for PubMedID 22441000
Promotion of the induction of cell pluripotency through metabolic remodeling by thyroid hormone triiodothyronine-activated PI3K/AKT signal pathway
2012; 33 (22): 5514-5523
Generation of induced pluripotent stem cells (iPSCs) from somatic cells by defined factors is a mechanism-unknown, yet extremely time-consuming process. Inefficient reprogramming leads to prolonged periods of in vitro iPSC selection, resulting in subtle genetic and epigenetic abnormalities. To facilitate pluripotent reprogramming, we have identified the thyroid hormone triiodothyronine (T3) as an endogenous factor that can enhance reprogramming of human dermal fibroblasts (HDF) and umbilical cord mesenchymal stem cells (UCMSC). This potentiation of iPSC induction is associated with metabolic remodeling activity, including upregulation of key glycolytic genes, an increase in cell proliferation, and the induction of mesenchymal-epithelial transition (MET). We further identify the activation of the PI3K/AKT signal pathway by T3 as an underlying mechanism for the enhanced conversion to cell pluripotency in this model. These studies demonstrate that T3 enhances metabolic remodeling of donor cells in potentiating cell reprogramming.
View details for DOI 10.1016/j.biomaterials.2012.04.001
View details for Web of Science ID 000305366500003
View details for PubMedID 22575839
Validation of FRC, a Fracture Risk Assessment Tool, in a Cohort of Older Men: The Osteoporotic Fractures in Men (MrOS) Study
JOURNAL OF CLINICAL DENSITOMETRY
2012; 15 (3): 334-342
We evaluated the performance of the Fracture Risk Calculator (FRC) in 5893 men who participated in the baseline visit (March 2000-April 2002) of the Osteoporotic Fractures in Men Study. FRC estimates for 10-yr hip and major osteoporotic (hip, clinical spine, forearm, and shoulder) fractures were calculated and compared with observed 10-yr fracture probabilities. Possible enhancement of the tool's performance when bone mineral density (BMD) was included was evaluated by comparing areas under receiver operating characteristic curves and by Net Reclassification Improvement (NRI). A total of 5893 men were followed-up for an average of 8.4 yr. For most quintiles of predicted fracture risk, the ratios of observed to predicted probabilities were close to unity. Area under the curves improved when BMD was included (p<0.001; 0.79 vs 0.71 for hip fracture and 0.70 vs 0.66 for major osteoporotic fracture, respectively). Using National Osteoporosis Foundation clinical treatment thresholds, BMD inclusion increased NRI significantly, 8.5% (p<0.01) for hip and 4.0% (p=0.01) for major osteoporotic fracture. We conclude that the FRC calibrates well with hip and major osteoporotic fractures observed among older men. Further, addition of BMD to the fracture risk calculation improves the tool's performance.
View details for DOI 10.1016/j.jocd.2012.01.011
View details for Web of Science ID 000307262000013
View details for PubMedID 22445858
Thyroid Function and Mortality in Older Men: A Prospective Study
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
2012; 97 (3): 862-870
Mild abnormalities of thyroid function have been associated with both beneficial and detrimental effects on mortality.Our objective was to determine the association between continuous TSH as well as categories of thyroid function with total and cause-specific mortality in a cohort of older men.Data were analyzed from the Osteoporotic Fractures in Men (MrOS) study, a cohort of community-dwelling U.S. men aged 65 yr and older. A total of 1587 participants randomly selected for thyroid function testing were included in this analysis. TSH and free T4 were measured at baseline, and four categories of thyroid function were defined. (subclinical hyperthyroid; euthyroid; subclinical hypothyroid TSH<10 mIU/liter; and subclinical hypothyroid, TSH?10 mIU/liter.)Total mortality, cardiovascular (CV) and cancer deaths were confirmed by review of death certificates.There were 432 deaths over a mean follow-up of 8.3 yr. In fully adjusted models, there was no association between baseline TSH and any death [relative hazard (RH)=1.01 per mIU/liter, 95% confidence interval (CI)=0.95-1.06], CV death (RH=1.05 per mIU/liter, 95% CI 0.96-1.15), or cancer death (RH=0.96 per mIU/liter, 95% CI=0.85-1.07). There was also no statistically significant association between thyroid function category and total or cause-specific mortality, but few men (n=8) had subclinical hypothyroidism with TSH levels of 10 mIU/liter or higher.A single measurement of thyroid function did not predict total or cause-specific mortality in this cohort. These data support neither a beneficial nor a detrimental effect of subclinical thyroid dysfunction in older men.Subclinical thyroid dysfunction is not associated with an increased risk of all-cause or CV mortality in older men.
View details for DOI 10.1210/jc.2011-2684
View details for Web of Science ID 000301229600051
View details for PubMedID 22238396
- Long-Term Surveillance of Growth Hormone Therapy JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM 2012; 97 (1): 68-72
Higher Testosterone Levels Are Associated with Less Loss of Lean Body Mass in Older Men
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
2011; 96 (12): 3855-3863
Little information exists about longitudinal changes in body composition and physical function in relation to sex hormone levels in older men.The aim of the study was to determine associations of testosterone, estradiol, and SHBG with changes in body composition and physical function.We conducted a prospective cohort study within the Osteoporotic Fractures in Men (MrOS) study at six U.S. clinical centers.A total of 5994 ambulatory men aged 65 yr or older enrolled in the MrOS. We examined 1183 men with complete measures of sex steroid hormones, body composition, and some measure of physical function. Intervention: There were no interventions.Sex steroids were measured by mass spectrometry in serum collected at baseline. Measurements of body composition using dual-energy x-ray absorptiometry and physical performance (grip strength, leg power, timed chair stands, narrow walk, and 6-m walk) were performed at baseline and repeated 4.5 yr later.Overall, men lost 1.3 kg (±4.4 sd) weight between study visits. Lean mass, especially appendicular, declined less at higher baseline testosterone levels (P < 0.05). These associations were most evident in the 40% of men who lost more than 2.0 kg during follow-up. In weight losers, higher testosterone was associated with less decline in timed chair stands. Estradiol was not related to body composition or physical function changes. Higher SHBG was associated with less loss of appendicular lean mass and grip strength.Higher endogenous testosterone is associated with reduced loss of lean mass and lower extremity function in older men losing weight. Endogenous testosterone may contribute to healthy aging.
View details for DOI 10.1210/jc.2011-0312
View details for Web of Science ID 000298295200061
View details for PubMedID 21976718
IGFBP-2 Enhances VEGF Gene Promoter Activity and Consequent Promotion of Angiogenesis by Neuroblastoma Cells
2011; 152 (9): 3332-3342
IGF binding protein (IGFBP)-2 is one of the most significant genes in the signature of major aggressive cancers. Previously, we have shown that IGFBP-2 enhances proliferation and invasion of neuroblastoma cells, suggesting that IGFBP-2 activates a protumorigenic gene expression program in these cells. Gene expression profiling in human neuroblastoma SK-N-SHEP (SHEP)-BP-2 cells indicated that IGFBP-2 overexpression activated a gene expression program consistent with enhancement of tumorigenesis. Regulation was significant for genes involved in proliferation/survival, migration/adhesion, and angiogenesis, including the up-regulation of vascular endothelial growth factor (VEGF) mRNA (>2-fold). Specific transcriptional activation of the VEGF gene by IGFBP-2 overexpression was demonstrated via cotransfection of a VEGF promoter Luciferase construct in SHEP-BP-2. Cotransfection of VEGF promoter Luciferase construct with IGFBP-2 protein in wild-type SHEP cells indicated that transactivation of VEGF promoter only occurs in the presence of intracellular IGFBP-2. Cell fractionation and immunofluorescence in SHEP-BP-2 cells demonstrated nuclear localization of IGFBP-2. These findings suggest that transcriptional activation of VEGF promoter is likely to be mediated by nuclear IGFBP-2. The levels of secreted VEGF (up to 400 pg/10(6) cells) suggested that VEGF might elicit angiogenic activity. Hence, SHEP-BP-2 cells and control clones cultured in collagen sponge were xenografted onto chick embryo chorioallantoic membrane. Neomicrovascularization was observed by 72 h, solely in the SHEP-BP-2 cell xenografts. In conclusion, our data indicate that IGFBP-2 is an activator of aggressive behavior in cancer cells, involving nuclear entry and activation of a protumorigenic gene expression program, including transcriptional regulation of the VEGF gene and consequent proangiogenic activity of NB cell xenografts in vivo.
View details for DOI 10.1210/en.2011-1121
View details for Web of Science ID 000294161000006
View details for PubMedID 21750048
Optimized clinical performance of growth hormone with an expanded genetic code
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2011; 108 (22): 9060-9065
The ribosomal incorporation of nonnative amino acids into polypeptides in living cells provides the opportunity to endow therapeutic proteins with unique pharmacological properties. We report here the first clinical study of a biosynthetic protein produced using an expanded genetic code. Incorporation of p-acetylphenylalanine (pAcF) at distinct locations in human growth hormone (hGH) allowed site-specific conjugation with polyethylene glycol (PEG) to produce homogeneous hGH variants. A mono-PEGylated mutant hGH modified at residue 35 demonstrated favorable pharmacodynamic properties in GH-deficient rats. Clinical studies in GH-deficient adults demonstrated efficacy and safety comparable to native human growth hormone therapy but with increased potency and reduced injection frequency. This example illustrates the utility of nonnative amino acids to optimize protein therapeutics in an analogous fashion to the use of medicinal chemistry to optimize conventional natural products, low molecular weight drugs, and peptides.
View details for DOI 10.1073/pnas.1100387108
View details for Web of Science ID 000291106200035
View details for PubMedID 21576502
Mortality Risk in Older Men Associated with Changes in Weight, Lean Mass, and Fat Mass
JOURNAL OF THE AMERICAN GERIATRICS SOCIETY
2011; 59 (2): 233-240
To evaluate risk of all-cause mortality associated with changes in body weight, total lean mass, and total fat mass in older men.Longitudinal cohort study.Six U.S. clinical centers.Four thousand three hundred thirty-one ambulatory men aged 65 to 93 at baseline.Repeated measurements of body weight and total lean and fat mass were taken using dual-energy X-ray absorptiometry 4.6 ± 0.4 years apart. Percentage changes in these measures were categorized as gain (+5%), loss (-5%), or stable (-5% to +5%). Deaths were verified centrally according to death certificate reviews, and proportional hazard models were used to estimate the risk of mortality.After accounting for baseline lifestyle factors and medical conditions, a higher risk of mortality was found for men with weight loss (hazard rat (HR)=1.84, 95% confidence interval (CI)=1.50-2.26), total lean mass loss (HR=1.78, 95% CI=1.45-2.19), and total fat mass loss (HR=1.72, 95% CI=1.34-2.20) than for men who were stable for each body composition measure. Men with total fat mass gain had a slightly greater mortality risk (HR=1.29, 95% CI=0.99-1.67) than those who remained stable. These associations did not differ according to baseline age, obesity, or self-reported health status (P for interactions >.10), although self-reported weight loss intent altered mortality risks with total fat mass (P for interaction=.04) and total lean mass (P for interaction=.09) change.Older men who lost weight, total lean mass, or total fat mass had a higher risk of mortality than men who remained stable.
View details for DOI 10.1111/j.1532-5415.2010.03245.x
View details for Web of Science ID 000287240700006
View details for PubMedID 21288234
Putative Tumor Suppressor miR-145 Inhibits Colon Cancer Cell Growth by Targeting Oncogene Friend Leukemia Virus Integration 1 Gene
2011; 117 (1): 86-95
Tumor suppressor microRNA miR-145 is commonly down-regulated in colon carcinoma tissues, but its specific role in tumors remains unknown.In this study, the authors identified the Friend leukemia virus integration 1 gene (FLI1) as a novel target of miR-145. FLI1 is involved in t(11;22)(q24:q12) reciprocal chromosomal translocation in Ewing sarcoma, and its expression appears to be associated with biologically more aggressive tumors.The authors demonstrated that miR-145 targets a putative microRNA regulatory element in the 3'-untranslated region (UTR) of FLI1, and its abundance is reversely associated with FLI1 expression in colon cancer tissues and cell lines. By using a luciferase/FLI1 3'-UTR reporter system, they found that miR-145 down-regulated the reporter activity, and this down-regulation was reversed by anti-miR-145. Mutation of the miR-145 microRNA regulatory element sequence in the FLI1 3'-UTR abolished the activity of miR-145. miR-145 decreased FLI1 protein but not FLI1 mRNA, suggesting a mechanism of translational regulation. Furthermore, the authors demonstrated that miR-145 inhibited cell proliferation and sensitized LS174T cells to 5-fluorouracil-induced apoptosis.Taken together, these results suggest that miR-145 functions as a tumor suppressor by down-regulating oncogenic FLI1 in colon cancer.
View details for DOI 10.1002/cncr.25522
View details for Web of Science ID 000285368300013
View details for PubMedID 20737575
Targeted tumor gene therapy based on loss of IGF2 imprinting
CANCER BIOLOGY & THERAPY
2010; 10 (3)
Loss of imprinting (LOI) of the insulin-like growth factor 2 gene (IGF2) is one of the most common epigenetic abnormalities seen in human neoplasms. LOI may be associated with the lack of Zinc-finger DNA binding protein CTCF-mediated enhancer insulation, presumably due to the gain of methylation on the maternal allele of the differentially methylated domain (DMD) of the imprinting control region. This results in an interaction between the IGF2 promoters and enhancers; and IGF2 is produced from both alleles. In this study we investigated the feasibility of a novel anti-cancer adenovirus (AdDC312-DT-A) driven by H19 enhancer DMD-H19 promoter complex. Cell lines with IGF2 LOI (HCT-8, HT-29 and H-522) that were infected with AdDC312-EGFP produced the EGFP protein. However, in cells in which imprinting was maintained (MOI) (MCF-7 and GES-1), no EGFP protein was produced. The AdDC312-DT-A significantly decreased cell viability and induced apoptosis only in LOI cells in vitro, and suppressed tumour development in HCT-8 xenografts in nude mice. In conclusion, the toxin gene therapy proves effective in inhibiting LOI cell growth in vitro and in vivo and provides a novel option for targeted gene therapy based on loss of IGF2 imprinting.
View details for Web of Science ID 000281005600012
View details for PubMedID 20592487
Serum 25-OH vitamin D levels and risk of developing prostate cancer in older men
CANCER CAUSES & CONTROL
2010; 21 (8): 1297-1303
Multiple studies have shown clear evidence of vitamin D's anti-tumor effects on prostate cancer cells in laboratory experiments, but the evidence has not been consistent in humans. We sought to examine the association between vitamin D and prostate cancer risk in a cohort of older men.We conducted a prospective case-cohort study nested within the multicenter Osteoporotic Fractures in Men (MrOS) study. Baseline serum 25-OH vitamin D was measured in a randomly selected sub-cohort of 1,433 men > or = 65 years old without a history of prostate cancer and from all participants with an incident diagnosis of prostate cancer (n = 297). Cox proportional hazards models were used to evaluate the associations between quartiles of total 25-OH vitamin D and incident prostate cancer, as well as Gleason score.In comparison with the lowest quartile of 25-OH vitamin D, the hazard ratio for the highest quartile of 25-OH vitamin D was 1.22 (CI 0.50-1.72, p = 0.25), no trend across quartiles (p = 0.94) or association with Gleason score was observed. Adjustment for covariates did not alter the results.In this prospective cohort of older men, we found no association between serum 25-OH vitamin D levels and subsequent risk of prostate cancer.
View details for DOI 10.1007/s10552-010-9557-y
View details for Web of Science ID 000280065400015
View details for PubMedID 20383574
Targeted knockdown of Bcl2 in tumor cells using a synthetic TRAIL 3 '-UTR microRNA
INTERNATIONAL JOURNAL OF CANCER
2010; 126 (9): 2229-2239
Targeting tumor-related overexpression of anti-apoptotic Bcl2 protein by RNAi has been suggested as a potential treatment for cancer. However, the stability of RNAi and its delivery are still major obstacles to the clinical testing of Bcl2 RNAi. Here, we explore a novel strategy of expressing a synthetic Bcl2 microRNA (smRNA) in the 3' untranslated region (UTR) of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), an apoptosis-inducing protein without apparent toxic effects in normal cells. TRAIL was specifically expressed from the human telomerase reverse transcriptase promoter (pTRT) that is active in many human tumors. Using this approach, we demonstrated that pTRT drove the tumor-specific expression of Bcl2 smRNA, which was processed by the host RNAi machinery and silenced endogenous Bcl2 expression in tumor cells. Bcl2 smRNA induced tumor cell apoptosis by activating caspase-3 and led to significant sensitization of tumor cells to TRAIL-induced apoptosis, while normal cells were spared. We also showed that the combined therapy of TRAIL-induced apoptosis and Bcl2 downregulation was superior to the mono-therapy of TRAIL or Bcl2 smRNA alone. This study proves a general paradigm for cancer therapy by using 3' UTR microRNA technology.
View details for DOI 10.1002/ijc.24821
View details for Web of Science ID 000276173700022
View details for PubMedID 19676053
Transient in vitro epigenetic reprogramming of skin fibroblasts into multipotent cells
2010; 31 (10): 2779-2787
Multipotent stem cells have the potential to establish a new field of promising regenerative medicine to treat tissue damage, genetic disorders, and degenerative diseases. However, limited resource of stem cells has turned to be an evitable obstacle in clinical applications. We utilized a simple in vitro epigenetic reprogramming approach to convert skin fibroblasts into multipotent cells. After transient reprogramming, stem cell markers, including Oct4 and Nanog, became activated in the treated cells. The reprogrammed cells were multipotent as demonstrated by their ability to differentiate into a variety of cells and to form teratomas. Genomic imprinting of insulin-like growth factor II (Igf2) and H19 was not affected by this short period of cell reprogramming. This study may provide an alternative strategy to efficiently generate patient-specific stem cells for basic and clinical research, solving major hurdles of virally-induced pluripotent stem (iPS) cells that entail the potential risks of mutation, gene instability, and malignancy.
View details for DOI 10.1016/j.biomaterials.2009.12.027
View details for Web of Science ID 000275777800009
View details for PubMedID 20044135
Loss of IGF2 imprinting is associated with abrogation of long-range intrachromosomal interactions in human cancer cells
HUMAN MOLECULAR GENETICS
2010; 19 (5): 901-919
Nuclear architecture and chromatin geography are important factors in the regulation of gene expression, as these components may play a vital epigenetic role both in normal physiology as well as in the initiation and progression of malignancies. Using a modification of the chromosome conformation capture (3C) technique, we examined long-range chromatin interactions of the imprinted human IGF2 gene. We demonstrate that numerous intrachromosomal interactions occur along both parental alleles in normal tissues, where the IGF2 is paternally expressed, as well as in normal liver where gene expression is biallelic. Long-range and allele-specific interactions occur between the IGF2/H19 imprinting control region-1 (ICR1) and ICR2, a region which regulates an imprinted gene cluster nearly a megabase distant from IGF2. Loss of genomic imprinting is a common epigenetic event in cancer, and long-range interactions have not been examined in malignant cells. In cancer cell lines in which IGF2 imprinting is maintained (MOI), essentially all of the 3C interactions seen in normal cells were preserved. However, in cells in which IGF2 imprinting was lost (LOI), nearly all of the long-range chromatin interactions involving IGF2 were abrogated. A three-dimensional computer model depicts the physical interactions between the IGF2 promoter and ICR1 in MOI cells, while the model of LOI lung cancer cells is flattened with few long-range interactions. This dramatic change in the three-dimension configuration of the chromatin at the IGF2 locus in LOI cancer cells suggests that the loss of imprinting may lead to a variety of changes in gene expression in addition to changes in IGF2 transcription.
View details for DOI 10.1093/hmg/ddp558
View details for Web of Science ID 000274341400014
View details for PubMedID 20015958
Serum 25-Hydroxyvitamin D and the Risk of Hip and Nonspine Fractures in Older Men
JOURNAL OF BONE AND MINERAL RESEARCH
2010; 25 (3): 545-553
The association between vitamin D levels and incident fractures in older men is uncertain. To test the hypothesis that low serum 25-hydroxyvitamin D [(25(OH)D] levels are associated with an increased risk of fracture, we performed a case-cohort study of 436 men with incident nonspine fractures, including 81 hip fractures, and a random subcohort of 1608 men; average follow-up time 5.3 years. Serum vitamin D(2) and vitamin D(3) were measured on baseline sera using mass spectrometry and summed for total vitamin D. Modified Cox proportional hazards models were used to estimate the hazard ratio (HR) of fracture with 95% confidence intervals (CIs). Multivariable models included age, clinic, season, race, height, weight, and physical activity. The mean (SD) total 25(OH)D was 24.6 (7.8) ng/mL in nonspine fracture subjects, 21.5 (7.9) ng/mL in hip fracture subjects, and 25.2 (7.8) ng/mL in controls (nonspine fracture subjects versus nonpatients, p = .14; hip fracture subjects versus controls, p < .0001). 25(OH)D levels were unrelated to nonspine fractures. One SD decrease in total 25(OH)D was associated with an increased risk of hip fracture (multivariate HR = 1.60; 95% CI 1.18-2.17). Compared with men in the top quartile of total 25(OH)D (> or =28), the HR of hip fracture was 2.36 (95% CI 1.08-5.15) for men in the lowest quartile (<20) (p = .009 for trend). Adjusting for hip bone mineral density attenuated the association by more than 50% (p = .065 for trend). Low serum 25(OH)D concentrations are associated with a higher risk of hip fracture in older men. Measurement of 25(OH)D may be useful in identifying men at high risk of hip fracture.
View details for DOI 10.1359/jbmr.090826
View details for Web of Science ID 000276767700016
View details for PubMedID 19775201
Bone Mass and Strength in Older Men With Type 2 Diabetes: The Osteoporotic Fractures in Men Study
JOURNAL OF BONE AND MINERAL RESEARCH
2010; 25 (2): 285-291
The effects of type 2 diabetes mellitus (T2DM) on bone volumetric density, bone geometry, and estimates of bone strength are not well established. We used peripheral quantitative computed tomography (pQCT) to compare tibial and radial bone volumetric density (vBMD, mg/cm(3)), total (ToA, mm(2)) and cortical (CoA, mm(2)) bone area and estimates of bone compressive and bending strength in a subset (n = 1171) of men (> or =65 years of age) who participated in the multisite Osteoporotic Fractures in Men (MrOS) study. Analysis of covariance-adjusted bone data for clinic site, age, and limb length (model 1) and further adjusted for body weight (model 2) were used to compare data between participants with (n = 190) and without (n = 981) T2DM. At both the distal tibia and radius, patients with T2DM had greater bone vBMD (+2% to +4%, model 1, p < .05) and a smaller bone area (ToA -1% to -4%, model 2, p < .05). The higher vBMD compensated for lower bone area, resulting in no differences in estimated compressive bone strength at the distal trabecular bone regions. At the mostly cortical bone midshaft sites of the radius and tibia, men with T2DM had lower ToA (-1% to -3%, p < .05), resulting in lower bone bending strength at both sites after adjusting for body weight (-2% to -5%, p < .05) despite the lack of difference in cortical vBMD at these sites. These data demonstrate that older men with T2DM have bone strength that is low relative to body weight at the cortical-rich midshaft of the radius despite no difference in cortical vBMD.
View details for DOI 10.1359/jbmr.090725
View details for Web of Science ID 000275215500011
View details for PubMedID 19594301
Nocturnal Arrhythmias Across a Spectrum of Obstructive and Central Sleep-Disordered Breathing in Older Men Outcomes of Sleep Disorders in Older Men (MrOS Sleep) Study
ARCHIVES OF INTERNAL MEDICINE
2009; 169 (12): 1147-1155
Rates of cardiac arrhythmias increase with age and may be associated with clinically significant morbidity. We studied the association between sleep-disordered breathing (SDB) with nocturnal atrial fibrillation or flutter (AF) and complex ventricular ectopy (CVE) in older men.A total of 2911 participants in the Outcomes of Sleep Disorders in Older Men Study underwent unattended polysomnography. Nocturnal AF and CVE were ascertained by electrocardiogram-specific analysis of the polysomnographic data. Exposures were (1) SDB defined by respiratory disturbance index (RDI) quartile (a major index including all apneas and hypopneas), and ancillary definitions incorporating (2) obstructive events, obstructive sleep apnea (OSA; Obstructive Apnea Hypopnea Index quartile), or (3) central events, central sleep apnea (CSA; Central Apnea Index category), and (4) hypoxia (percentage of sleep time with <90% arterial oxygen percent saturation). Multivariable logistic regression analyses were performed.An increasing RDI quartile was associated with increased odds of AF and CVE (P values for trend, .01 and <.001, respectively). The highest RDI quartile was associated with increased odds of AF (odds ratio [OR], 2.15; 95% confidence interval [CI], 1.19-3.89) and CVE (OR, 1.43; 95% CI, 1.12-1.82) compared with the lowest quartile. An increasing OSA quartile was significantly associated with increasing CVE (P value for trend, .01) but not AF. Central sleep apnea was more strongly associated with AF (OR, 2.69; 95% CI, 1.61-4.47) than CVE (OR, 1.27; 95% CI, 0.97-1.66). Hypoxia level was associated with CVE (P value for trend, <.001); those in the highest hypoxia category had an increased odds of CVE (OR, 1.62; 95% CI, 1.23-2.14) compared with the lowest quartile.In this large cohort of older men, increasing severity of SDB was associated with a progressive increase in odds of AF and CVE. When SDB was characterized according to central or obstructive subtypes, CVE was associated most strongly with OSA and hypoxia, whereas AF was most strongly associated with CSA, suggesting that different sleep-related stresses may contribute to atrial and ventricular arrhythmogenesis in older men.
View details for Web of Science ID 000267239300010
View details for PubMedID 19546416
Vitamin D Deficiency in Older Men
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
2009; 94 (4): 1214-1222
Vitamin D deficiency is not adequately evaluated in older men.The aim of the study was to determine the prevalence of vitamin D deficiency and identify risk factors for its occurrence.We conducted a cross-sectional evaluation of 1606 older men in the general community who were enrolled in the Osteoporotic Fractures in Men Study.A randomly selected subcohort of a large population of men from six U.S. communities participated in the study.Serum concentrations of 25-hydroxyvitamin D(2) [25(OH)D(2)] and 25(OH)D(3) were measured using mass spectrometry.Deficiency [25(OH)D <20 ng/ml] was present in 26%, and insufficiency (<30 ng/ml) was present in 72%. Deficiency was particularly common among men during the winter and spring (especially in the northern communities) and in the oldest and more obese men. For instance, in Caucasian men in winter or spring who were >80 yr old, did not engage in lawn/garden work, and had a body mass index greater than 25 kg/m(2) and vitamin D intake below 400 IU/d, the prevalence of vitamin D deficiency was 86%. 25(OH)D(2) levels were present in a small fraction of men and accounted for a low proportion of total 25(OH)D levels. The use of vitamin D supplements was reported by 58% of men, but supplement use had a small effect on total 25(OH)D levels and, despite supplement use, low levels remained frequent.Vitamin D deficiency is common in older men and is especially prevalent in obese, sedentary men living at higher latitudes. Use of vitamin D supplements at levels reported here did not result in adequate vitamin D nutrition.
View details for DOI 10.1210/jc.2008-1784
View details for Web of Science ID 000265145100027
View details for PubMedID 19174492
CTCF regulates allelic expression of Igf2 by orchestrating a promoter-polycomb repressive complex 2 intrachromosomal loop
MOLECULAR AND CELLULAR BIOLOGY
2008; 28 (20): 6473-6482
CTCF is a zinc finger DNA-binding protein that regulates the epigenetic states of numerous target genes. Using allelic regulation of mouse insulin-like growth factor II (Igf2) as a model, we demonstrate that CTCF binds to the unmethylated maternal allele of the imprinting control region (ICR) in the Igf2/H19 imprinting domain and forms a long-range intrachromosomal loop to interact with the three clustered Igf2 promoters. Polycomb repressive complex 2 is recruited through the interaction of CTCF with Suz12, leading to allele-specific methylation at lysine 27 of histone H3 (H3-K27) and to suppression of the maternal Igf2 promoters. Targeted mutation or deletion of the maternal ICR abolishes this chromatin loop, decreases allelic H3-K27 methylation, and causes loss of Igf2 imprinting. RNA interference knockdown of Suz12 also leads to reactivation of the maternal Igf2 allele and biallelic Igf2 expression. CTCF and Suz12 are coprecipitated from nuclear extracts with antibodies specific for either protein, and they interact with each other in a two-hybrid system. These findings offer insight into general epigenetic mechanisms by which CTCF governs gene expression by orchestrating chromatin loop structures and by serving as a DNA-binding protein scaffold to recruit and bind polycomb repressive complexes.
View details for DOI 10.1128/MCB.00204-08
View details for Web of Science ID 000259634800026
View details for PubMedID 18662993
A complex deoxyribonucleic acid looping configuration associated with the silencing of the maternal Igf2 allele
2008; 22 (6): 1476-1488
Alternate interactions between the H19 imprinting control region (ICR) and one of the two Igf2 differentially methylated regions has been proposed as a model regulating the reciprocal imprinting of Igf2 and H19. To study the conformation of this imprint switch, we performed a systematic structural analysis across the 140 kb of the mouse Igf2-H19 region, which includes enhancers located both between the two genes as well as downstream of H19, by using a scanning chromosome conformation capture (3C) technique. Our results suggest that on the active paternal Igf2 allele, the various enhancers have direct access to the Igf2 promoters, whereas the imprinted silent maternal Igf2 allele assumes a complex three-dimensional knotted loop that keeps the enhancers away from the Igf2 promoters and allows them to interact with the H19 promoter. This complex DNA looping of the maternal allele is formed by interactions involving differentially methylated region 1, the ICR, and enhancers. Binding of CTC-binding factor to the maternal, unmethylated ICR in conjunction with the presence of multicomplex components including interchromosomal interactions, create a barrier blocking the access of all enhancers to Igf2, thereby silencing the maternal Igf2. This silencing configuration exists in newborn liver, mouse embryonic fibroblast, and embryonic stem cells and persists during mitosis, conferring a mechanism for epigenetic memory.
View details for DOI 10.1210/me.2007-0474
View details for Web of Science ID 000256307800017
View details for PubMedID 18356289
Systematic review: The effects of growth hormone on athletic performance
ANNALS OF INTERNAL MEDICINE
2008; 148 (10): 747-U59
Human growth hormone is reportedly used to enhance athletic performance, although its safety and efficacy for this purpose are poorly understood.To evaluate evidence about the effects of growth hormone on athletic performance in physically fit, young individuals.MEDLINE, EMBASE, SPORTDiscus, and Cochrane Collaboration databases were searched for English-language studies published between January 1966 and October 2007.Randomized, controlled trials that compared growth hormone treatment with no growth hormone treatment in community-dwelling healthy participants between 13 and 45 years of age.2 authors independently reviewed articles and abstracted data.44 articles describing 27 study samples met inclusion criteria; 303 participants received growth hormone, representing 13.3 person-years of treatment. Participants were young (mean age, 27 years [SD, 3]), lean (mean body mass index, 24 kg/m2 [SD, 2]), and physically fit (mean maximum oxygen uptake, 51 mL/kg of body weight per minute [SD, 8]). Growth hormone dosage (mean, 36 microg/kg per day [SD, 21]) and treatment duration (mean, 20 days [SD, 18] for studies giving growth hormone for >1 day) varied. Lean body mass increased in growth hormone recipients compared with participants who did not receive growth hormone (increase, 2.1 kg [95% CI, 1.3 to 2.9 kg]), but strength and exercise capacity did not seem to improve. Lactate levels during exercise were statistically significantly higher in 2 of 3 studies that evaluated this outcome. Growth hormone-treated participants more frequently experienced soft tissue edema and fatigue than did those not treated with growth hormone.Few studies evaluated athletic performance. Growth hormone protocols in the studies may not reflect real-world doses and regimens.Claims that growth hormone enhances physical performance are not supported by the scientific literature. Although the limited available evidence suggests that growth hormone increases lean body mass, it may not improve strength; in addition, it may worsen exercise capacity and increase adverse events. More research is needed to conclusively determine the effects of growth hormone on athletic performance.
View details for Web of Science ID 000256372200004
View details for PubMedID 18347346
Effects of growth hormone and pioglitazone in viscerally obese adults with impaired glucose tolerance: A factorial clinical trial
PLOS CLINICAL TRIALS
2007; 2 (5)
Recombinant human growth hormone (GH) and pioglitazone (PIO) in abdominally obese adults with impaired glucose tolerance were evaluated under the hypothesis that the combination attenuates GH-induced increases in glucose concentrations, reduces visceral adipose tissue (VAT), and improves insulin sensitivity over time.Randomized, double-blind, placebo-controlled, 2 x 2 factorial design.Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States.62 abdominally obese adults aged 40-75 with impaired glucose tolerance.GH (8 microg/kg/d, or placebo) and pioglitazone (30 mg/d, or placebo) for 40 wk.Baseline and after 40 wk of treatment, VAT content was quantified by CT scan, glucose tolerance was assessed using a 75-g oral glucose tolerance test, and insulin sensitivity was measured using steady-state plasma glucose levels obtained during insulin suppression test.BASELINE: body mass index (BMI), plasma glucose, and visceral fat content were similar. 40 wk: visceral fat area declined 23.9 +/- 7.4 cm(2) in GH group, mean difference from placebo: -28.1 cm(2) (95% CI -49.9 to -6.3 cm(2); p = 0.02). Insulin resistance declined 52 +/- 11.8 mg/dl with PIO, mean difference from placebo of -58.8 mg/dl (95% CI -99.7 to -18.0 mg/dl; p = 0.01). VAT and SSPG declined with GH and PIO combined, mean differences from placebo of -31.4 cm(2) (95% CI -56.5 cm(2) to -6.3 cm(2); p = 0.02) and -55.3 mg/dl (95% CI -103.9 to -6.7 mg/dl; p = 0.02), respectively. Fasting plasma glucose increased transiently in GH group. No significant changes in BMI were observed.Addition of PIO to GH attenuated the short-term diabetogenic effect of GH; the drug combination reduced VAT and insulin resistance over time. GH plus PIO may have added benefit on body composition and insulin sensitivity in the metabolic syndrome.
View details for DOI 10.1371/journal.pctr.0020021
View details for Web of Science ID 000246737100002
View details for PubMedID 17479164
Correction of aberrant imprinting of IGF2 in human tumors by nuclear transfer-induced epigenetic reprogramming
2006; 25 (22): 5329-5338
Loss of genomic imprinting of insulin-like growth factor II (IGF2) is a hallmark of many human neoplasms. We attempted to correct this aberrant epigenotype by transferring nuclei from human tumor cells that showed loss of IGF2 imprinting into enucleated mouse and human fibroblasts that had maintained normal IGF2 imprinting. After nuclear transfer, the abnormal biallelic expression of IGF2 in tumor nuclei transiently converted to normal monoallelic imprinted expression in the reconstructed diploid cells. In tetraploid hybrid cells, however, normal IGF2 imprinting was permanently restored in the tumor genome. Inhibition of the synthesis of putative trans imprinting factors with cycloheximide led to loss of IGF2 imprinting in normal cultured fibroblasts, suggesting that normal cells produce proteins that act in trans to induce or maintain genomic imprinting. These data demonstrate that an abnormal tumor epigenotype can be corrected by in vitro reprogramming, and suggest that loss of imprinting is associated with the loss of activity of non-CTCF trans imprinting factor(s) that are either inactivated or mutated in tumors.
View details for DOI 10.1038/sj.emboj.7601399
View details for Web of Science ID 000242215000009
View details for PubMedID 17082775
Endocrine responses to acute and chronic high-altitude exposure (4,300 meters): modulating effects of caloric restriction
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
2006; 290 (6): E1078-E1088
High-altitude anorexia leads to a hormonal response pattern modulated by both hypoxia and caloric restriction (CR). The purpose of this study was to compare altitude-induced neuroendocrine changes with or without energy imbalance and to explore how energy sufficiency alters the endocrine acclimatization process. Twenty-six normal-weight, young men were studied for 3 wk. One group [hypocaloric group (HYPO), n = 9] stayed at sea level and consumed 40% fewer calories than required to maintain body weight. Two other groups were deployed to 4,300 meters (Pikes Peak, CO), where one group (ADQ, n = 7) was adequately fed to maintain body weight and the other [deficient group (DEF), n = 10] had calories restricted as above. HYPO experienced a typical CR-induced reduction in many hormones such as insulin, testosterone, and leptin. At altitude, fasting glucose, insulin, and epinephrine exhibited a muted rise in DEF compared with ADQ. Free thyroxine, thyroid-stimulating hormone, and norepinephrine showed similar patterns between the two altitude groups. Morning cortisol initially rose higher in DEF than ADQ at 4,300 meters, but the difference disappeared by day 5. Testosterone increased in both altitude groups acutely but declined over time in DEF only. Adiponectin and leptin did not change significantly from sea level baseline values in either altitude group regardless of energy intake. These data suggest that hypoxia tends to increase blood hormone concentrations, but anorexia suppresses elements of the endocrine response. Such suppression results in the preservation of energy stores but may sacrifice the facilitation of oxygen delivery and the use of oxygen-efficient fuels.
View details for DOI 10.1152/ajpendo.00449.2005
View details for Web of Science ID 000237803300003
View details for PubMedID 16380390
Efficacy of a long-acting growth hormone (GH) preparation in patients with adult GH deficiency
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
2005; 90 (12): 6431-6440
Treatment of adult GH deficiency (AGHD) with daily injections of GH results in decreased adipose mass, increased lean body mass (LBM), increased bone mineral density, and improved quality of life.This study seeks to determine whether a depot preparation of GH given every 14 d would lead to comparable decreases in trunk adipose tissue as daily GH.This open-label, randomized study compares subjects receiving depot GH, daily GH, or no therapy.The study was performed at 23 university or local referral endocrine centers.One hundred thirty-five adults with AGHD syndrome participated in the study.Subjects were randomized to receive depot GH (n = 51), daily GH (n = 53), or no treatment (n = 31) for 32 wk. The dose of GH was titrated so that IGF-I was less than or equal to +2 SD of the age-adjusted normal range.Trunk adipose tissue was the main outcome measure as measured by dual energy x-ray absorptiometry.The percentage of the trunk region that is fat increased by 0.4 in the no treatment group, but decreased by 3.2 (P = 0.001 vs. untreated) in the GH depot group and by 2.5 (P < 0.004 vs. untreated) in the daily GH group. Visceral adipose tissue area decreased by 9.1% in the GH depot group and by 6.8% in the daily GH group. LBM and high-density lipoprotein increased in both treatment groups. Side effect profiles were similar. Three subjects receiving GH experienced serious episodes of adrenal insufficiency.GH diminishes trunk and visceral adipose tissue and increases LBM in AGHD. A depot form of GH that is administered every 14 d is as safe and effective as daily GH injections.
View details for DOI 10.1210/jc.2005-0928
View details for Web of Science ID 000233754000015
View details for PubMedID 16159930
Promoter-restricted histone code, not the differentially methylated DNA regions or antisense transcripts, marks the imprinting status of IGF2R in human and mouse
HUMAN MOLECULAR GENETICS
2004; 13 (19): 2233-2245
Imprinting of the mouse Igf2r depends upon an intronic differentially methylated DNA region (DMR) and the presence of the Air antisense transcript. However, biallelic expression of mouse Igf2r in brain occurs despite the presence of Air, and biallelic expression of human IGF2R in peripheral tissues occurs despite the presence of an intronic DMR. We examined histone modifications throughout the mouse and human Igf2r/IGF2R using chromatin immuno-precipitation (ChIP) assays in combination with quantitative real time PCR. Methylation of Lys4 and Lys9 of histone H3 in the promoter regions marks the active and silenced alleles, respectively. We measured di- and tri-methyl Lys4 and Lys9 across the Igf2r and Air promoters. While both di- and tri-methyl Lys4 marked the active Igf2r and the active Air allele, tri-methyl Lys9, but not di-methyl Lys9, marked the suppressed Air allele. We show here that enrichment of parental allele-specific histone modifications in the promoter region, rather than the presence of DNA methylation or antisense transcription, correctly identifies the tissue- and species- specific imprinting status of Igf2r/IGF2R. We discuss these findings in light of recent progress in identifying specific components of the epigenetic marks in imprinted genes.
View details for DOI 10.1093/hmg/ddh244
View details for Web of Science ID 000223941500007
View details for PubMedID 15294879
Activating and silencing histone modifications form independent allelic switch regions in the imprinted Gnas gene
HUMAN MOLECULAR GENETICS
2004; 13 (7): 741-750
Activation and suppression of gene transcription is tightly controlled by epigenetic modifications. The imprinted Gnas1 gene region contains closely juxtaposed maternally expressed (Nesp) and paternally expressed (Nespas, Gnasxl, Exon 1A) transcripts, providing a unique opportunity to study how epigenetic modifications change in nucleosomes from active to silenced promoters. Using 30 polymorphic sites across the Gnas1 gene region in (C57BL/6JxMus spretus) F(1) mice and chromatin immunoprecipitation (ChIP) assays we identified two allelic switch regions (ASRs) that mark boundaries of epigenetic information. We show that activating signals (histone acetylation and methylation of H3 Lys4) and silencing signals (histone methylation of H3 Lys9 and DNA methylation) segregate independently across the ASRs and suggest that these ASRs allow the transcriptional elongation to proceed through the silenced domain of nearby imprinted promoters. We discuss these findings in light of recent progress in the conceptualization of nucleosome remodeling during transcriptional elongation and in the development of histone code.
View details for DOI 10.1093/hmg/ddh081
View details for Web of Science ID 000220179900007
View details for PubMedID 14962976
An imprinted PEG1/MEST antisense expressed predominantly in human testis and in mature spermatozoa
JOURNAL OF BIOLOGICAL CHEMISTRY
2002; 277 (16): 13518-13527
PEG1 (or MEST) is an imprinted gene located on human chromosome 7q32 that is expressed predominantly from the paternal allele. In the mouse, Peg1/Mest is associated with embryonic growth and maternal behavior. Human PEG1 is transcribed from two promoters; the transcript from promoter P1 is derived from both parental alleles, and the transcript from P2 is exclusively from the paternal allele. We characterized the P1 and P2 transcripts in various normal and neoplastic tissues. In the normal tissues, PEG1 was transcribed from both promoters P1 and P2, whereas in six of eight neoplastic tissues, PEG1 was transcribed exclusively from promoter P1. Bisulfite sequencing demonstrated high levels of CpG methylation in the P2 region of DNA from a lung tumor. In the region between P1 and P2, we identified a novel transcript, PEG1-AS, in an antisense orientation to PEG1. PEG1-AS is a spliced transcript and was detected as a strong 2.4-kilobase band on a Northern blot. PEG1-AS and PEG1 P2-sense transcript were expressed exclusively from the paternal allele. Fragments of DNA from within the 1.5-kilobase region between PEG1-AS and the P2 exon were ligated to a pGL3 luciferase reporter vector and transfected into NCI H23 cells. This DNA exhibited strong promoter activity in both the sense and antisense directions, indicating that PEG1-AS and P2 exon share a common promoter region. Treatment of the transfected DNA fragments with CpG methylase abolished the promoter activity. Of interest, PEG1-AS was expressed predominantly in testis and in mature motile spermatozoa, indicating a possible role for this transcript in human sperm physiology and fertilization.
View details for DOI 10.1074/jbc.M200458200
View details for Web of Science ID 000175096000025
View details for PubMedID 11821432
One year of insulin-like growth factor I treatment does not affect bone density, body composition, or psychological measures in postmenopausal women
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
2001; 86 (4): 1496-1503
The activity of the hypothalamic-GH-insulin-like growth factor I (hypothalamic-GH-IGF-I) axis declines with age, and some of the catabolic changes of aging have been attributed to the somatopause. The purpose of this investigation was to determine the impact of 1 yr of IGF-I hormone replacement therapy on body composition, bone density, and psychological parameters in healthy, nonobese, postmenopausal women over 60 yr of age. Subjects (n = 16, 70.6 +/- 2.0 yr, 71.8 +/- 2.8 kg) were randomly assigned to either the self-injection IGF-I (15 microg/kg twice daily) or placebo group and were studied at baseline, at 6 months, and at 1 yr of treatment. There were no significant differences between the IGF-I and placebo groups in any of the measured variables at baseline. Fasting blood IGF-I levels were significantly elevated above baseline values (65.6 +/- 11.9 ng/mL) at 6 months (330.0 +/- 52.8) and 12 months (297.7 +/- 40.8) in the IGF-I treated group but did not change in the placebo subjects. Circulating levels of IGF-binding protein-1 and -3 were unaffected by the IGF-I treatment. Bone mineral density of the forearm, lumbar spine, hip, and whole body [as measured by dual-energy x-ray absorptiometry (DXA)] did not change in either group. Similarly, there was no difference in DXA-measured lean mass, fat mass, or percent body fat throughout the treatment intervention. Muscle strength values (grip, bench press, leg press), blood lipid parameters (cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides), and measures of postmeal glucose disposal were not altered by IGF-I treatment, although postmeal insulin levels were lower in the IGF-I subjects at 12 months. IGF-I did not affect bone turnover markers (osteocalcin and type I collagen N-teleopeptide), but subjects who were taking estrogen had significantly lower turnover markers than subjects who were not on estrogen at baseline, 6 months, and 12 months. Finally, the psychological measures of mood and memory were also not altered by the intervention. Despite the initial intent to recruit additional subjects, the study was discontinued after 16 subjects completed the protocol, because the preliminary analyses above indicated that no changes were occurring in any outcome variables, regardless of treatment regimen. Therefore, we conclude that 1 yr of IGF-I treatment, at a dose sufficient to elevate circulating IGF-I to young normal values, is not an effective means to alter body composition or blood parameters nor improve bone density, strength, mood, or memory in older women.
View details for Web of Science ID 000168243000010
View details for PubMedID 11297574
- DELAYED INCREASE OF ADRENAL TH AND PNMT ACTIVITIES FOLLOWING COLD STRESS IN MOUSE LIFE SCIENCES 1975; 17 (4): 557-562