Mark E. Pepin, MD, MS, PhD

All Publications

• The Role of Endothelial Cells in Atherosclerosis Insights from Genetic Association Studies AMERICAN JOURNAL OF PATHOLOGY Pepin, M. E., Gupta, R. M. 2024; 194 (4): 499-509

  Abstract

  Endothelial cells (ECs) mediate several biological functions that are relevant to atherosclerosis and coronary artery disease (CAD), regulating an array of vital processes including vascular tone, wound healing, reactive oxygen species, shear stress response, and inflammation. Although which of these functions is linked causally with CAD development and/or progression is not yet known, genome-wide association studies have implicated more than 400 loci associated with CAD risk, among which several have shown EC-relevant functions. Given the arduous process of mechanistically interrogating single loci to CAD, high-throughput variant characterization methods, including pooled Clustered Regularly Interspaced Short Palindromic Repeats screens, offer exciting potential to rapidly accelerate the discovery of bona fide EC-relevant genetic loci. These discoveries in turn will broaden the therapeutic avenues for CAD beyond lipid lowering and behavioral risk modification to include EC-centric modalities of risk prevention and treatment.

  View details for DOI 10.1016/j.ajpath.2023.09.012

  View details for Web of Science ID 001224049400001

  View details for PubMedID 37827214

  View details for PubMedCentralID PMC10988759

• Deep phenotyping of two pre-clinical mouse models and a cohort of RBM20 mutation carriers reveals no sex-dependent disease severity in RBM20 cardiomyopathy. American journal of physiology. Heart and circulatory physiology Lennermann, D. C., Pepin, M. E., Grosch, M., Konrad, L., Kemmling, E., Hartmann, J., Nolte, J. L., Clauder-Munster, S., Kayvanpour, E., Sedaghat-Hamedani, F., Haas, J., Meder, B., van den Boogaard, M., Amin, A. S., Dewenter, M., Kruger, M., Steinmetz, L. M., Backs, J., van den Hoogenhof, M. M. 2022

  Abstract

  Aims RBM20 cardiomyopathy is an arrhythmogenic form of dilated cardiomyopathy caused by mutations in the splicing factor RBM20. A recent study found a more severe phenotype in male RBM20 cardiomyopathy patients than in female patients. Here, we aim to determine sex differences in an animal model of RBM20 cardiomyopathy, and investigate potential underlying mechanisms. Additionally, we aim to determine sex and gender differences in clinical parameters in a novel RBM20 cardiomyopathy patient cohort. Methods and Results We characterized a Rbm20 knockout (KO) mouse model, and show that splicing of key RBM20 targets, cardiac function, and arrhythmia susceptibility do not differ between sexes. Next, we performed deep phenotyping of these mice, and show that male and female Rbm20-KO mice possess transcriptomic and phosphoproteomic differences. Hypothesizing that these differences may influence the heart's ability to compensate for stress, we exposed Rbm20-KO mice to acute catecholaminergic stimulation, and again found no functional differences. We also replicate the lack of functional differences in a mouse model with the Rbm20-R636Q mutation. Lastly, we present a patient cohort of 33 RBM20 cardiomyopathy patients, and show that these patients do not possess sex and gender differences in disease severity. Conclusions Current mouse models of RBM20 cardiomyopathy show more pronounced changes in gene expression and phosphorylation of cardiac proteins in male mice, but no sex differences in cardiac morphology and function. Moreover, other than reported before, male RBM20 cardiomyopathy patients do not present with worse cardiac function in a patient cohort from Germany and the Netherlands.

  View details for DOI 10.1152/ajpheart.00328.2022

  View details for PubMedID 36367695

• Fostering a diverse regional community of physician-scientist trainees JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION Pepin, M. E., Souder, P., Weaver, A. N., Lorenz, R. G., Yacoubian, T., Seay, R. L. 2022; 114 (3): 251-257

  Abstract

  Among the many academic challenges faced by dual-degree MD-PhD students is access to professional support networks designed to overcome the unique academic and personal barriers to physician-scientist training. In the current study, we hypothesized that regional access to a student MD-PhD conference, termed the Southeastern Medical Scientist Symposium (SEMSS), would enhance medical and/or graduate training by fostering such relationships between physician-scientist trainees, doing so by discussing both the challenges of physician-scientist training and effective strategies to overcome them. In the current study, we used a mixed-methods approach to evaluate the overall usefulness of SEMSS over a ten-year period (2010-2020) to identify key areas of particular benefit to trainees. The authors used conference registration data to compile self-reported demographic and regional attendance, followed by a post-conference survey to gauge attendee satisfaction. Over the reporting period, SEMSS was attended by equivalent proportions of MD-PhD and undergraduate students, among which were a high-percentage of students from underrepresented minority (URM) groups relative to the national MD-PhD applicant pool; nearly one-third of URM students attendees later matriculated into MD-PhD programs, far exceeding the national MD-PhD matriculation rate. Among the benefits reported by students were "opportunities to network with peers" and opportunities to learn about the physician-scientist career track. Therefore, we therefore propose regional MD-PhD conferences as an effective model to promote diversity within the physician-scientist training pipeline.

  View details for DOI 10.1016/j.jnma.2022.01.010

  View details for Web of Science ID 000812717600003

  View details for PubMedID 35232610

  View details for PubMedCentralID PMC9189008

• A novel curricular framework to develop grant writing skills among MD-PhD students JOURNAL OF CLINICAL AND TRANSLATIONAL SCIENCE Souder, J. P., Pepin, M. E., Seay, R. L., Lorenz, R. G., Geisler, W. M., Yacoubian, T. 2022; 6 (1): e54

  Abstract

  Physician-scientists have long been in high demand owing to their role as key drivers of biomedical innovation, but their dwindling prevalence in research and medical communities threatens ongoing progress. As the principal avenue for physician-scientist development, combined MD-PhD training programs and NIH-funded Medical Scientist Training Programs (MSTPs) must address all aspects of career development, including grant writing skills.The NIH F-series grants - the F30 grant in particular - model the NIH format of federal funding, and are thus ideal opportunities to acquire biomedical research grant preparation experience. Therefore, in this report, we describe a curricular model through which predoctoral MSTP students obtain exposure to - and training for - F-series grant conceptualization, writing, and evaluation.Since the development of these longitudinal courses, we observed trending improvements in student funding success rates, particularly among original submissions, and perceived benefits among participating students.

  View details for DOI 10.1017/cts.2022.384

  View details for Web of Science ID 000795982100001

  View details for PubMedID 35656336

  View details for PubMedCentralID PMC9120620

• A case of "smoldering" immune-mediated thrombotic thrombocytopenic purpura manifesting as recurrent cardioembolic stroke CLINICAL CASE REPORTS Pepin, M. E., Saca, E., Kwon, S. Y., May, J. 2021; 9 (10): e04850

  Abstract

  Prompt recognition and treatment for thrombotic thrombocytopenic purpura (TTP) are critical to prevent the irreversible manifestations of this rare and quickly fatal hematologic disorder. Untreated TTP is typically a rapid-onset disease with mortality exceeding 90% within days in the absence of appropriate treatment. In the current report, we describe a case of immune-mediated TTP (iTTP) in a 62-year-old man manifesting as longstanding thrombocytopenia, recurrent cardioembolic strokes, and valvular thrombogenesis over a period of 3 years. We provide correlative evidence to support the potential contribution of adalimumab, a TNFα inhibitor, to the development of iTTP. We offer several educational insights regarding the identification of atypical presentations of iTTP owing to the longstanding disease course and numerous clinical comorbidities seen in this patient.

  View details for DOI 10.1002/ccr3.4850

  View details for Web of Science ID 000724731500100

  View details for PubMedID 34667601

  View details for PubMedCentralID PMC8507438

• Racial and socioeconomic disparity associates with differences in cardiac DNA methylation among men with end-stage heart failure AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY Pepin, M. E., Ha, C., Potter, L. A., Bakshi, S., Barchue, J. P., Asaad, A., Pogwizd, S. M., Pamboukian, S., Hidalgo, B. A., Vickers, S. M., Wende, A. R. 2021; 320 (5): H2066-H2079

  Abstract

  Heart failure (HF) is a multifactorial syndrome that remains a leading cause of worldwide morbidity. Despite its high prevalence, only half of patients with HF respond to guideline-directed medical management, prompting therapeutic efforts to confront the molecular underpinnings of its heterogeneity. In the current study, we examined epigenetics as a yet unexplored source of heterogeneity among patients with end-stage HF. Specifically, a multicohort-based study was designed to quantify cardiac genome-wide cytosine-p-guanine (CpG) methylation of cardiac biopsies from male patients undergoing left ventricular assist device (LVAD) implantation. In both pilot (n = 11) and testing (n = 31) cohorts, unsupervised multidimensional scaling of genome-wide myocardial DNA methylation exhibited a bimodal distribution of CpG methylation found largely to occur in the promoter regions of metabolic genes. Among the available patient attributes, only categorical self-identified patient race could delineate this methylation signature, with African American (AA) and Caucasian American (CA) samples clustering separately. Because race is a social construct, and thus a poor proxy of human physiology, extensive review of medical records was conducted, but ultimately failed to identify covariates of race at the time of LVAD surgery. By contrast, retrospective analysis exposed a higher all-cause mortality among AA (56.3%) relative to CA (16.7%) patients at 2 yr following LVAD placement (P = 0.03). Geocoding-based approximation of patient demographics uncovered disparities in income levels among AA relative to CA patients. Although additional studies are needed, the current analysis implicates cardiac DNA methylation as a previously unrecognized indicator of socioeconomic disparity in human heart failure outcomes.NEW & NOTEWORTHY A bimodal signature of cardiac DNA methylation in heart failure corresponds with racial differences in all-cause mortality following mechanical circulatory support. Racial differences in promoter methylation disproportionately affect metabolic signaling pathways. Socioeconomic factors are associated with racial differences in the cardiac methylome among men with end-stage heart failure.

  View details for DOI 10.1152/ajpheart.00036.2021

  View details for Web of Science ID 000661571000013

  View details for PubMedID 33769919

  View details for PubMedCentralID PMC8163657

• The human aortic endothelium undergoes dose-dependent DNA methylation in response to transient hyperglycemia EXPERIMENTAL CELL RESEARCH Pepin, M. E., Schiano, C., Miceli, M., Benincasa, G., Mansueto, G., Grimaldi, V., Soricelli, A., Wende, A. R., Napoli, C. 2021; 400 (2): 112485

  Abstract

  Glycemic control is a strong predictor of long-term cardiovascular risk in patients with diabetes mellitus, and poor glycemic control influences long-term risk of cardiovascular disease even decades after optimal medical management. This phenomenon, termed glycemic memory, has been proposed to occur due to stable programs of cardiac and endothelial cell gene expression. This transcriptional remodeling has been shown to occur in the vascular endothelium through a yet undefined mechanism of cellular reprogramming.In the current study, we quantified genome-wide DNA methylation of cultured human endothelial aortic cells (HAECs) via reduced-representation bisulfite sequencing (RRBS) following exposure to diabetic (250 mg/dL), pre-diabetic (125 mg/dL), or euglycemic (100 mg/dL) glucose concentrations for 72 h (n = 2).We discovered glucose-dependent methylation of genomic regions (DMRs) encompassing 2199 genes, with a disproportionate number found among genes associated with angiogenesis and nitric oxide (NO) signaling-related pathways. Multi-omics analysis revealed differential methylation and gene expression of VEGF (↑5.6% DMR, ↑3.6-fold expression), and NOS3 (↓20.3% DMR, ↓1.6-fold expression), nodal regulators of angiogenesis and NO signaling, respectively.In the current exploratory study, we examine glucose-dependent and dose-responsive alterations in endothelial DNA methylation to examine a putative epigenetic mechanism underlying diabetic vasculopathy. Specifically, we uncover the disproportionate glucose-dependent methylation and gene expression of VEGF and NO signaling cascades, a physiologic imbalance known to cause endothelial dysfunction in diabetes. We therefore hypothesize that epigenetic mechanisms encode a glycemic memory within endothelial cells.

  View details for DOI 10.1016/j.yexcr.2021.112485

  View details for Web of Science ID 000634823700004

  View details for PubMedID 33515594

  View details for PubMedCentralID PMC8038422

• Increased Glucose Availability Attenuates Myocardial Ketone Body Utilization JOURNAL OF THE AMERICAN HEART ASSOCIATION Brahma, M. K., Ha, C., Pepin, M. E., Mia, S., Sun, Z., Chatham, J. C., Habegger, K. M., Abel, E., Paterson, A. J., Young, M. E., Wende, A. R. 2020; 9 (15): e013039

  Abstract

  Background Perturbations in myocardial substrate utilization have been proposed to contribute to the pathogenesis of cardiac dysfunction in diabetic subjects. The failing heart in nondiabetics tends to decrease reliance on fatty acid and glucose oxidation, and increases reliance on ketone body oxidation. In contrast, little is known regarding the mechanisms mediating this shift among all 3 substrates in diabetes mellitus. Therefore, we tested the hypothesis that changes in myocardial glucose utilization directly influence ketone body catabolism. Methods and Results We examined ventricular-cardiac tissue from the following murine models: (1) streptozotocin-induced type 1 diabetes mellitus; (2) high-fat-diet-induced glucose intolerance; and transgenic inducible cardiac-restricted expression of (3) glucose transporter 4 (transgenic inducible cardiac restricted expression of glucose transporter 4); or (4) dominant negative O-GlcNAcase. Elevated blood glucose (type 1 diabetes mellitus and high-fat diet mice) was associated with reduced cardiac expression of β-hydroxybutyrate-dehydrogenase and succinyl-CoA:3-oxoacid CoA transferase. Increased myocardial β-hydroxybutyrate levels were also observed in type 1 diabetes mellitus mice, suggesting a mismatch between ketone body availability and utilization. Increased cellular glucose delivery in transgenic inducible cardiac restricted expression of glucose transporter 4 mice attenuated cardiac expression of both Bdh1 and Oxct1 and reduced rates of myocardial BDH1 activity and β-hydroxybutyrate oxidation. Moreover, elevated cardiac protein O-GlcNAcylation (a glucose-derived posttranslational modification) by dominant negative O-GlcNAcase suppressed β-hydroxybutyrate dehydrogenase expression. Consistent with the mouse models, transcriptomic analysis confirmed suppression of BDH1 and OXCT1 in patients with type 2 diabetes mellitus and heart failure compared with nondiabetic patients. Conclusions Our results provide evidence that increased glucose leads to suppression of cardiac ketolytic capacity through multiple mechanisms and identifies a potential crosstalk between glucose and ketone body metabolism in the diabetic myocardium.

  View details for DOI 10.1161/JAHA.119.013039

  View details for Web of Science ID 000574867600029

  View details for PubMedID 32750298

  View details for PubMedCentralID PMC7792234

• Differential DNA Methylation Encodes Proliferation and Senescence Programs in Human Adipose-Derived Mesenchymal Stem Cells FRONTIERS IN GENETICS Pepin, M. E., Infante, T., Benincasa, G., Schiano, C., Miceli, M., Ceccarelli, S., Megiorni, F., Anastasiadou, E., Della Valle, G., Fatone, G., Faenza, M., Docimo, L., Nicoletti, G. F., Marchese, C., Wende, A. R., Napoli, C. 2020; 11: 346

  Abstract

  Adult adipose tissue-derived mesenchymal stem cells (ASCs) constitute a vital population of multipotent cells capable of differentiating into numerous end-organ phenotypes. However, scientific and translational endeavors to harness the regenerative potential of ASCs are currently limited by an incomplete understanding of the mechanisms that determine cell-lineage commitment and stemness. In the current study, we used reduced representation bisulfite sequencing (RRBS) analysis to identify epigenetic gene targets and cellular processes that are responsive to 5'-azacitidine (5'-AZA). We describe specific changes to DNA methylation of ASCs, uncovering pathways likely associated with the enhancement of their proliferative capacity. We identified 4,797 differentially methylated regions (FDR < 0.05) associated with 3,625 genes, of which 1,584 DMRs annotated to the promoter region. Gene set enrichment of differentially methylated promoters identified "phagocytosis," "type 2 diabetes," and "metabolic pathways" as disproportionately hypomethylated, whereas "adipocyte differentiation" was the most-enriched pathway among hyper-methylated gene promoters. Weighted coexpression network analysis of DMRs identified clusters associated with cellular proliferation and other developmental programs. Furthermore, the ELK4 binding site was disproportionately hyper-methylated within the promoters of genes associated with AKT signaling. Overall, this study offers numerous preliminary insights into the epigenetic landscape that influences the regenerative capacity of human ASCs.

  View details for DOI 10.3389/fgene.2020.00346

  View details for Web of Science ID 000530464400001

  View details for PubMedID 32351540

  View details for PubMedCentralID PMC7174643

• The SETD6 Methyltransferase Plays an Essential Role in Hippocampus-Dependent Memory Formation BIOLOGICAL PSYCHIATRY Webb, W. M., Irwin, A. B., Pepin, M. E., Henderson, B. W., Huang, V., Butler, A. A., Herskowitz, J. H., Wende, A. R., Cash, A. E., Lubin, F. D. 2020; 87 (6): 577-587

  Abstract

  Epigenetic mechanisms are critical for hippocampus-dependent memory formation. Building on previous studies that implicate the N-lysine methyltransferase SETD6 in the activation of nuclear factor-κB RELA (also known as transcription factor p65) as an epigenetic recruiter, we hypothesized that SETD6 is a key player in the epigenetic control of long-term memory.Using a series of molecular, biochemical, imaging, electrophysiological, and behavioral experiments, we interrogated the effects of short interfering RNA-mediated knockdown of Setd6 in the rat dorsal hippocampus during memory consolidation.Our findings demonstrate that SETD6 is necessary for memory-related nuclear factor-κB RELA methylation at lysine 310 and associated increases in H3K9me2 (histone H3 lysine 9 dimethylation) in the dorsal hippocampus and that SETD6 knockdown interferes with memory consolidation, alters gene expression patterns, and disrupts spine morphology.Together, these findings suggest that SETD6 plays a critical role in memory formation and may act as an upstream initiator of H3K9me2 changes in the hippocampus during memory consolidation.

  View details for DOI 10.1016/j.biopsych.2019.05.022

  View details for Web of Science ID 000514816800014

  View details for PubMedID 31378303

  View details for PubMedCentralID PMC6906268

• Dysregulation of the Mitochondrial Proteome Occurs in Mice Lacking Adiponectin Receptor 1 FRONTIERS IN ENDOCRINOLOGY Pepin, M. E., Koentges, C., Pfeil, K., Gollmer, J., Kersting, S., Wiese, S., Hoffmann, M. M., Odening, K. E., von zur Muehlen, C., Diehl, P., Stachon, P., Wolt, D., Wende, A. R., Bode, C., Zirlik, A., Bugger, H. 2019; 10: 872

  Abstract

  Decreased serum adiponectin levels in type 2 diabetes has been linked to the onset of mitochondrial dysfunction in diabetic complications by impairing AMPK-SIRT1-PGC-1α signaling via impaired adiponectin receptor 1 (AdipoR1) signaling. Here, we aimed to characterize the previously undefined role of disrupted AdipoR1 signaling on the mitochondrial protein composition of cardiac, renal, and hepatic tissues as three organs principally associated with diabetic complications. Comparative proteomics were performed in mitochondria isolated from the heart, kidneys and liver of Adipor1 -/- mice. A total of 790, 1,573, and 1,833 proteins were identified in cardiac, renal and hepatic mitochondria, respectively. While 121, 98, and 78 proteins were differentially regulated in cardiac, renal, and hepatic tissue of Adipor1-/- mice, respectively; only 15 proteins were regulated in the same direction across all investigated tissues. Enrichment analysis of differentially expressed proteins revealed disproportionate representation of proteins involved in oxidative phosphorylation conserved across tissue types. Curated pathway analysis identified HNF4, NRF1, LONP, RICTOR, SURF1, insulin receptor, and PGC-1α as candidate upstream regulators. In high fat-fed non-transgenic mice with obesity and insulin resistance, AdipoR1 gene expression was markedly reduced in heart (-70%), kidney (-80%), and liver (-90%) (all P < 0.05) as compared to low fat-fed mice. NRF1 was the only upstream regulator downregulated both in Adipor1-/- mice and in high fat-fed mice, suggesting common mechanisms of regulation. Thus, AdipoR1 signaling regulates mitochondrial protein composition across all investigated tissues in a functionally conserved, yet molecularly distinct, manner. The biological significance and potential implications of impaired AdipoR1 signaling are discussed.

  View details for DOI 10.3389/fendo.2019.00872

  View details for Web of Science ID 000504729000001

  View details for PubMedID 31920982

  View details for PubMedCentralID PMC6923683

• DNA methylation reprograms cardiac metabolic gene expression in end-stage human heart failure AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY Pepin, M. E., Drakos, S., Ha, C., Tristani-Firouzi, M., Selzman, C. H., Fang, J. C., Wende, A. R., Wever-Pinzon, O. 2019; 317 (4): H674-H684

  Abstract

  Heart failure (HF) is a leading cause of morbidity and mortality in the United States and worldwide. As a multifactorial syndrome with unpredictable clinical outcomes, identifying the common molecular underpinnings that drive HF pathogenesis remains a major focus of investigation. Disruption of cardiac gene expression has been shown to mediate a common final cascade of pathological hallmarks wherein the heart reactivates numerous developmental pathways. Although the central regulatory mechanisms that drive this cardiac transcriptional reprogramming remain unknown, epigenetic contributions are likely. In the current study, we examined whether the epigenome, specifically DNA methylation, is reprogrammed in HF to potentiate a pathological shift in cardiac gene expression. To accomplish this, we used paired-end whole genome bisulfite sequencing and next-generation RNA sequencing of left ventricle tissue obtained from seven patients with end-stage HF and three nonfailing donor hearts. We found that differential methylation was localized to promoter-associated cytosine-phosphate-guanine islands, which are established regulatory regions of downstream genes. Hypermethylated promoters were associated with genes involved in oxidative metabolism, whereas promoter hypomethylation enriched glycolytic pathways. Overexpression of plasmid-derived DNA methyltransferase 3A in vitro was sufficient to lower the expression of numerous oxidative metabolic genes in H9c2 rat cardiomyoblasts, further supporting the importance of epigenetic factors in the regulation of cardiac metabolism. Last, we identified binding-site competition via hypermethylation of the nuclear respiratory factor 1 (NRF1) motif, an established upstream regulator of mitochondrial biogenesis. These preliminary observations are the first to uncover an etiology-independent shift in cardiac DNA methylation that corresponds with altered metabolic gene expression in HF.NEW & NOTEWORTHY The failing heart undergoes profound metabolic changes because of alterations in cardiac gene expression, reactivating glycolytic genes and suppressing oxidative metabolic genes. In the current study, we discover that alterations to cardiac DNA methylation encode this fetal-like metabolic gene reprogramming. We also identify novel epigenetic interference of nuclear respiratory factor 1 via hypermethylation of its downstream promoter targets, further supporting a novel contribution of DNA methylation in the metabolic remodeling of heart failure.

  View details for DOI 10.1152/ajpheart.00016.2019

  View details for Web of Science ID 000487239300002

  View details for PubMedID 31298559

  View details for PubMedCentralID PMC6843013

• Gamification: an Innovative Approach to Reinforce Clinical Knowledge for MD-PhD Students During Their PhD Research Years MEDICAL SCIENCE EDUCATOR Pepin, M. E., Webb, W. M., Boppana, S., Weaver, A. N., Seay, R. L., Dempsey, D. M., Willig, J. H., Geisler, W. M., Lorenz, R. G. 2019; 29 (3): 739-747

  Abstract

  A longstanding challenge facing MD-PhD students and other dual-degree medical trainees is the loss of clinical knowledge that occurs during the non medical phases of training. Academic medical institutions nationwide have developed continued clinical training and exposure to maintain clinical competence; however, quantitative assessment of their usefulness remains largely unexplored. The current study therefore sought to both implement and optimize an online game platform to support MD-PhD students throughout their research training. Sixty three current MD-PhD students completing the PhD research phase of training were enrolled in an institutionally-developed online game platform for 2 preliminary and 4 competition rounds of 3-4 weeks each. During preliminary game rounds, we found that participation, though initially high, declined precipitously throughout the duration of each round, with 37 students participating to some extent. Daily reminders were implemented in subsequent rounds, which markedly improved player participation. Average participation in competition rounds exceeded 35% (23/63) active participants each round, with trending improvement in scores throughout the duration of PhD training. Both player participation and progress through the research phase of the MD-PhD program correlated positively with game performance and therefore knowledge retention and/or acquisition. Coupled with positive survey-based feedback from participants, our data therefore suggest that gamification is an effective tool for MD-PhD programs to combat loss of clinical knowledge during research training.

  View details for DOI 10.1007/s40670-019-00725-1

  View details for Web of Science ID 000624414300018

  View details for PubMedID 32071793

  View details for PubMedCentralID PMC7028303

• Prolactin Receptor Signaling Regulates a Pregnancy-Specific Transcriptional Program in Mouse Islets ENDOCRINOLOGY Pepin, M. E., Bickerton, H. H., Bethea, M., Hunter, C. S., Wende, A. R., Banerjee, R. R. 2019; 160 (5): 1150-1163

  Abstract

  Pancreatic β-cells undergo profound hyperplasia during pregnancy to maintain maternal euglycemia. Failure to reprogram β-cells into a more replicative state has been found to underlie susceptibility to gestational diabetes mellitus (GDM). We recently identified a requirement for prolactin receptor (PRLR) signaling in the metabolic adaptations to pregnancy, where β-cell-specific PRLR knockout (βPRLRKO) mice exhibit a metabolic phenotype consistent with GDM. However, the underlying transcriptional program that is responsible for the PRLR-dependent metabolic adaptations during gestation remains incompletely understood. To identify PRLR signaling gene regulatory networks and target genes within β-cells during pregnancy, we performed a transcriptomic analysis of pancreatic islets isolated from either βPRLRKO mice or littermate controls in late gestation. Gene set enrichment analysis identified forkhead box protein M1 and polycomb repressor complex 2 subunits, Suz12 and enhancer of zeste homolog 2 (Ezh2), as novel candidate regulators of PRLR-dependent β-cell adaptation. Gene ontology term pathway enrichment revealed both established and novel PRLR signaling target genes that together promote a state of increased cellular metabolism and/or proliferation. In contrast to the requirement for β-cell PRLR signaling in maintaining euglycemia during pregnancy, PRLR target genes were not induced following high-fat diet feeding. Collectively, the current study expands our understanding of which transcriptional regulators and networks mediate gene expression required for islet adaptation during pregnancy. The current work also supports the presence of pregnancy-specific adaptive mechanisms distinct from those activated by nutritional stress.

  View details for DOI 10.1210/en.2018-00991

  View details for Web of Science ID 000469515200018

  View details for PubMedID 31004482

  View details for PubMedCentralID PMC6475113

• Epigenetics in the development of diabetic cardiomyopathy EPIGENOMICS Pepin, M. E., Wende, A. R. 2019; 11 (5): 469-472

  View details for DOI 10.2217/epi-2019-0027

  View details for Web of Science ID 000477702100001

  View details for PubMedID 30895816

• Genome-wide DNA methylation encodes cardiac transcriptional reprogramming in human ischemic heart failure LABORATORY INVESTIGATION Pepin, M. E., Ha, C., Crossman, D. K., Litovsky, S. H., Varambally, S., Barchue, J. P., Pamboukian, S. V., Diakos, N. A., Drakos, S. G., Pogwizd, S. M., Wende, A. R. 2019; 99 (3): 371-386

  Abstract

  Ischemic cardiomyopathy (ICM) is the clinical endpoint of coronary heart disease and a leading cause of heart failure. Despite growing demands to develop personalized approaches to treat ICM, progress is limited by inadequate knowledge of its pathogenesis. Since epigenetics has been implicated in the development of other chronic diseases, the current study was designed to determine whether transcriptional and/or epigenetic changes are sufficient to distinguish ICM from other etiologies of heart failure. Specifically, we hypothesize that genome-wide DNA methylation encodes transcriptional reprogramming in ICM. RNA-sequencing analysis was performed on human ischemic left ventricular tissue obtained from patients with end-stage heart failure, which enriched known targets of the polycomb methyltransferase EZH2 compared to non-ischemic hearts. Combined RNA sequencing and genome-wide DNA methylation analysis revealed a robust gene expression pattern consistent with suppression of oxidative metabolism, induced anaerobic glycolysis, and altered cellular remodeling. Lastly, KLF15 was identified as a putative upstream regulator of metabolic gene expression that was itself regulated by EZH2 in a SET domain-dependent manner. Our observations therefore define a novel role of DNA methylation in the metabolic reprogramming of ICM. Furthermore, we identify EZH2 as an epigenetic regulator of KLF15 along with DNA hypermethylation, and we propose a novel mechanism through which coronary heart disease reprograms the expression of both intermediate enzymes and upstream regulators of cardiac metabolism such as KLF15.

  View details for DOI 10.1038/s41374-018-0104-x

  View details for Web of Science ID 000459687600008

  View details for PubMedID 30089854

  View details for PubMedCentralID PMC6515060

• Resident macrophages reprogram toward a developmental state after acute kidney injury JCI INSIGHT Lever, J. M., Hull, T. D., Boddu, R., Pepin, M. E., Black, L. M., Adedoyin, O. O., Yang, Z., Traylor, A. M., Jiang, Y., Li, Z., Peabody, J. E., Eckenrode, H. E., Crossman, D. K., Crowley, M. R., Bolisetty, S., Zimmerman, K. A., Wende, A. R., Mrug, M., Yoder, B. K., Agarwal, A., George, J. F. 2019; 4 (2)

  Abstract

  Acute kidney injury (AKI) is a devastating clinical condition affecting at least two-thirds of critically ill patients, and, among these patients, it is associated with a greater than 60% risk of mortality. Kidney mononuclear phagocytes (MPs) are implicated in pathogenesis and healing in mouse models of AKI and, thus, have been the subject of investigation as potential targets for clinical intervention. We have determined that, after injury, F4/80hi-expressing kidney-resident macrophages (KRMs) are a distinct cellular subpopulation that does not differentiate from nonresident infiltrating MPs. However, if KRMs are depleted using polyinosinic/polycytidylic acid (poly I:C), they can be reconstituted from bone marrow-derived precursors. Further, KRMs lack major histocompatibility complex class II (MHCII) expression before P7 but upregulate it over the next 14 days. This MHCII- KRM phenotype reappears after injury. RNA sequencing shows that injury causes transcriptional reprogramming of KRMs such that they more closely resemble that found at P7. KRMs after injury are also enriched in Wingless-type MMTV integration site family (Wnt) signaling, indicating that a pathway vital for mouse and human kidney development is active. These data indicate that mechanisms involved in kidney development may be functioning after injury in KRMs.

  View details for DOI 10.1172/jci.insight.125503

  View details for Web of Science ID 000456684900017

  View details for PubMedID 30674729

  View details for PubMedCentralID PMC6413788

• Glucagon Receptor Signaling Regulates Energy Metabolism via Hepatic Farnesoid X Receptor and Fibroblast Growth Factor 21 DIABETES Kim, T., Nason, S., Holleman, C., Pepin, M., Wilson, L., Berryhill, T. F., Wende, A. R., Steele, C., Young, M. E., Barnes, S., Drucker, D. J., Finan, B., DiMarchi, R., Perez-Tilve, D., Tschoep, M., Habegger, K. M. 2018; 67 (9): 1773-1782

  Abstract

  Glucagon, an essential regulator of glucose and lipid metabolism, also promotes weight loss, in part through potentiation of fibroblast growth factor 21 (FGF21) secretion. However, FGF21 is only a partial mediator of metabolic actions ensuing from glucagon receptor (GCGR) activation, prompting us to search for additional pathways. Intriguingly, chronic GCGR agonism increases plasma bile acid levels. We hypothesized that GCGR agonism regulates energy metabolism, at least in part, through farnesoid X receptor (FXR). To test this hypothesis, we studied whole-body and liver-specific FXR-knockout (Fxr∆liver) mice. Chronic GCGR agonist (IUB288) administration in diet-induced obese (DIO) Gcgr, Fgf21, and Fxr whole-body or liver-specific knockout (∆liver) mice failed to reduce body weight when compared with wild-type (WT) mice. IUB288 increased energy expenditure and respiration in DIO WT mice, but not Fxr∆liver mice. GCGR agonism increased [14C]palmitate oxidation in hepatocytes isolated from WT mice in a dose-dependent manner, an effect blunted in hepatocytes from Fxr∆liver mice. Our data clearly demonstrate that control of whole-body energy expenditure by GCGR agonism requires intact FXR signaling in the liver. This heretofore-unappreciated aspect of glucagon biology has implications for the use of GCGR agonism in the therapy of metabolic disorders.

  View details for DOI 10.2337/db17-1502

  View details for Web of Science ID 000442337900009

  View details for PubMedID 29925501

  View details for PubMedCentralID PMC6110317

• Glucagon-Receptor Signaling Regulates Mitochondrial Bioenergetics via Hepatic Farnesol X Receptor Kim, T., Nason, S., Antipenko, J. P., Vestri, C. S., Smith-Johnston, K., Pepin, M. E., Wende, A. R., Finan, B., Dimarchi, R., Perez-Tilve, D., Moellering, D. R., Habegger, K. M. AMER DIABETES ASSOC. 2018

  View details for DOI 10.2337/db18-1978-P

  View details for Web of Science ID 000462825104225

• Antiretroviral therapy potentiates high-fat diet induced obesity and glucose intolerance MOLECULAR METABOLISM Pepin, M. E., Padgett, L. E., McDowell, R. E., Burg, A. R., Brahma, M. K., Holleman, C., Kim, T., Crossman, D., Kutsch, O., Tse, H. M., Wende, A. R., Habegger, K. M. 2018; 12: 48-61

  Abstract

  Breakthroughs in HIV treatment, especially combination antiretroviral therapy (ART), have massively reduced AIDS-associated mortality. However, ART administration amplifies the risk of non-AIDS defining illnesses including obesity, diabetes, and cardiovascular disease, collectively known as metabolic syndrome. Initial reports suggest that ART-associated risk of metabolic syndrome correlates with socioeconomic status, a multifaceted finding that encompasses income, race, education, and diet. Therefore, determination of causal relationships is extremely challenging due to the complex interplay between viral infection, ART, and the many environmental factors.In the current study, we employed a mouse model to specifically examine interactions between ART and diet that impacts energy balance and glucose metabolism. Previous studies have shown that high-fat feeding induces persistent low-grade systemic and adipose tissue inflammation contributing to insulin resistance and metabolic dysregulation via adipose-infiltrating macrophages. Studies herein test the hypothesis that ART potentiates the inflammatory effects of a high-fat diet (HFD). C57Bl/6J mice on a HFD or standard chow containing ART or vehicle, were subjected to functional metabolic testing, RNA-sequencing of epididymal white adipose tissue (eWAT), and array-based kinomic analysis of eWAT-infiltrating macrophages.ART-treated mice on a HFD displayed increased fat mass accumulation, impaired glucose tolerance, and potentiated insulin resistance. Gene set enrichment and kinomic array analyses revealed a pro-inflammatory transcriptional signature depicting granulocyte migration and activation.The current study reveals a HFD-ART interaction that increases inflammatory transcriptional pathways and impairs glucose metabolism, energy balance, and metabolic dysfunction.

  View details for DOI 10.1016/j.molmet.2018.04.006

  View details for Web of Science ID 000439549400005

  View details for PubMedID 29731256

  View details for PubMedCentralID PMC6001921

• Class-Wide Access to a Commercial Step 1 Question Bank During Preclinical Organ-Based Modules: A Pilot Project ACADEMIC MEDICINE Banos, J. H., Pepin, M. E., Van Wagoner, N. 2018; 93 (3): 486-490

  Abstract

  The authors examined the usefulness of a commercially available Step 1 question bank as a formative academic support tool throughout organ-based modules in an integrated preclinical medical curriculum. The authors also determined the extent to which correlation between question bank utilization and academic metrics varied with Medical College Admission Test (MCAT) scores.In 2015, a cohort of 185 first-year medical students at University of Alabama School of Medicine were provided with 18-month full access to a commercially available Step 1 question bank of over 2,100 items throughout organ-based modules, although there were no requirements for use. Data on student use of the question bank were collected via an online administrative portal. Relationships between question bank utilization and academic outcomes including exams, module grades, and United States Medical Licensing Examination (USMLE) Step 1 were determined using multiple linear regression.MCAT scores and number of items attempted in the question bank significantly predicted all academic measures, with question bank utilization as the stronger predictor. The association between question bank utilization and academic outcome was stronger for individuals with lower MCAT scores.The findings elucidate a novel academic support mechanism that, for some programs, may help bridge the gap between holistic and mission-based admissions practices and a residency match process that places a premium on USMLE exam scores. Distributed formative use of USMLE Step 1 practice questions may be of value as an academic support tool that benefits all students, but particularly those entering with lower MCAT scores.

  View details for DOI 10.1097/ACM.0000000000001861

  View details for Web of Science ID 000426274700040

  View details for PubMedID 28817433

  View details for PubMedCentralID PMC6706270

• Gene expression analysis to identify mechanisms underlying heart failure susceptibility in mice and humans BASIC RESEARCH IN CARDIOLOGY Koentges, C., Pepin, M. E., Muesse, C., Pfeil, K., Alvarez, S., Hoppe, N., Hoffmann, M. M., Odening, K. E., Sossalla, S., Zirlik, A., Hein, L., Bode, C., Wende, A. R., Bugger, H. 2018; 113 (1): 8

  Abstract

  Genetic factors are known to modulate cardiac susceptibility to ventricular hypertrophy and failure. To determine how strain influences the transcriptional response to pressure overload-induced heart failure (HF) and which of these changes accurately reflect the human disease, we analyzed the myocardial transcriptional profile of mouse strains with high (C57BL/6J) and low (129S1/SvImJ) susceptibility for HF development, which we compared to that of human failing hearts. Following transverse aortic constriction (TAC), C57BL/6J mice developed overt HF while 129S1/SvImJ did not. Despite a milder aortic constriction, impairment of ejection fraction and ventricular remodeling (dilation, fibrosis) was more pronounced in C57BL/6J mice. Similarly, changes in myocardial gene expression were more robust in C57BL/6J (461 genes) compared to 129S1/SvImJ mice (71 genes). When comparing these patterns to human dilated cardiomyopathy (1344 genes), C57BL/6J mice tightly grouped to human hearts. Overlay and bioinformatic analysis of the transcriptional profiles of C57BL/6J mice and human failing hearts identified six co-regulated genes (POSTN, CTGF, FN1, LOX, NOX4, TGFB2) with established link to HF development. Pathway enrichment analysis identified angiotensin and IGF-1 signaling as most enriched putative upstream regulator and pathway, respectively, shared between TAC-induced HF in C57BL/6J mice and in human failing hearts. TAC-induced heart failure in C57BL/6J mice more closely reflects the gene expression pattern of human dilated cardiomyopathy compared to 129S1/SvImJ mice. Unbiased as well as targeted gene expression and pathway analyses identified periostin, angiotensin signaling, and IGF-1 signaling as potential causes of increased HF susceptibility in C57BL/6J mice and as potentially useful drug targets for HF treatment.

  View details for DOI 10.1007/s00395-017-0666-6

  View details for Web of Science ID 000419063900001

  View details for PubMedID 29288409

  View details for PubMedCentralID PMC5764079

• Glucose transporter 4-deficient hearts develop maladaptive hypertrophy in response to physiological or pathological stresses AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY Wende, A. R., Kim, J., Holland, W. L., Wayment, B. E., O'Neill, B. T., Tuinei, J., Brahma, M. K., Pepin, M. E., McCrory, M. A., Luptak, I., Halade, G. V., Litwin, S. E., Abel, E. 2017; 313 (6): H1098-H1108

  Abstract

  Pathological cardiac hypertrophy may be associated with reduced expression of glucose transporter 4 (GLUT4) in contrast to exercise-induced cardiac hypertrophy, where GLUT4 levels are increased. However, mice with cardiac-specific deletion of GLUT4 (G4H-/-) have normal cardiac function in the unstressed state. This study tested the hypothesis that cardiac GLUT4 is required for myocardial adaptations to hemodynamic demands. G4H-/- and control littermates were subjected to either a pathological model of left ventricular pressure overload [transverse aortic constriction (TAC)] or a physiological model of endurance exercise (swim training). As predicted after TAC, G4H-/- mice developed significantly greater hypertrophy and more severe contractile dysfunction. Somewhat surprisingly, after exercise training, G4H-/- mice developed increased fibrosis and apoptosis that was associated with dephosphorylation of the prosurvival kinase Akt in concert with an increase in protein levels of the upstream phosphatase protein phosphatase 2A (PP2A). Exercise has been shown to decrease levels of ceramide; G4H-/- hearts failed to decrease myocardial ceramide in response to exercise. Furthermore, G4H-/- hearts have reduced levels of the transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator-1, lower carnitine palmitoyl-transferase activity, and reduced hydroxyacyl-CoA dehydrogenase activity. These basal changes may also contribute to the impaired ability of G4H-/- hearts to adapt to hemodynamic stresses. In conclusion, GLUT4 is required for the maintenance of cardiac structure and function in response to physiological or pathological processes that increase energy demands, in part through secondary changes in mitochondrial metabolism and cellular stress survival pathways such as Akt.NEW & NOTEWORTHY Glucose transporter 4 (GLUT4) is required for myocardial adaptations to exercise, and its absence accelerates heart dysfunction after pressure overload. The requirement for GLUT4 may extend beyond glucose uptake to include defects in mitochondrial metabolism and survival signaling pathways that develop in its absence. Therefore, GLUT4 is critical for responses to hemodynamic stresses.

  View details for DOI 10.1152/ajpheart.00101.2017

  View details for Web of Science ID 000417328400003

  View details for PubMedID 28822962

  View details for PubMedCentralID PMC5814656

• My Sweetheart Is Broken: Role of Glucose in Diabetic Cardiomyopathy DIABETES & METABOLISM JOURNAL Brahma, M. K., Pepin, M. E., Wende, A. R. 2017; 41 (1): 1-9

  Abstract

  Despite overall reductions in heart disease prevalence, the risk of developing heart failure has remained 2-fold greater among people with diabetes. Growing evidence has supported that fluctuations in glucose level and uptake contribute to cardiovascular disease (CVD) by modifying proteins, DNA, and gene expression. In the case of glucose, clinical studies have shown that increased dietary sugars for healthy individuals or poor glycemic control in diabetic patients further increased CVD risk. Furthermore, even after decades of maintaining tight glycemic control, susceptibility to disease progression can persist following a period of poor glycemic control through a process termed "glycemic memory." In response to chronically elevated glucose levels, a number of studies have identified molecular targets of the glucose-mediated protein posttranslational modification by the addition of an O-linked N-acetylglucosamine to impair contractility, calcium sensitivity, and mitochondrial protein function. Additionally, elevated glucose contributes to dysfunction in coupling glycolysis to glucose oxidation, pentose phosphate pathway, and polyol pathway. Therefore, in the "sweetened" environment associated with hyperglycemia, there are a number of pathways contributing to increased susceptibly to "breaking" the heart of diabetics. In this review we will discuss the unique contribution of glucose to heart disease and recent advances in defining mechanisms of action.

  View details for DOI 10.4093/dmj.2017.41.1.1

  View details for Web of Science ID 000397400800001

  View details for PubMedID 28236380

  View details for PubMedCentralID PMC5328690

• Diabetes and Glucose Alone Regulate Cardiac ABAT Levels Pepin, M. E., Wende, A. R. FEDERATION AMER SOC EXP BIOL. 2016

  View details for Web of Science ID 000406444707600

• Regulation of Myocardial Ketone Oxidative Proteins by Increased <i>O</i>-GlcNAcylation Brahma, M. K., McCrory, M. A., Paterson, A. J., Pepin, M. E., Young, M. E., Wende, A. R. FEDERATION AMER SOC EXP BIOL. 2016

  View details for Web of Science ID 000406444707595

• Inhibition of Myostatin Signaling through Notch Activation following Acute Resistance Exercise PLOS ONE MacKenzie, M. G., Hamilton, D., Pepin, M., Patton, A., Baar, K. 2013; 8 (7): e68743

  Abstract

  Myostatin is a TGFβ family member and negative regulator of muscle size. Due to the complexity of the molecular pathway between myostatin mRNA/protein and changes in transcription, it has been difficult to understand whether myostatin plays a role in resistance exercise-induced skeletal muscle hypertrophy. To circumvent this problem, we determined the expression of a unique myostatin target gene, Mighty, following resistance exercise. Mighty mRNA increased by 6 h (82.9 ± 24.21%) and remained high out to 48 h (56.5 ± 19.67%) after resistance exercise. Further examination of the soleus, plantaris and tibialis anterior muscles showed that the change in Mighty mRNA at 6 h correlated with the increase in muscle size associated with this protocol (R(2) = 0.9996). The increase in Mighty mRNA occurred both independent of Smad2 phosphorylation and in spite of an increase in myostatin mRNA (341.8 ± 147.14% at 3 h). The myostatin inhibitor SKI remained unchanged. However, activated Notch, another potential inhibitor of TGFβ signaling, increased immediately following resistance exercise (83 ± 11.2%) and stayed elevated out to 6 h (78 ± 16.6%). Electroportion of the Notch intracellular domain into the tibialis anterior resulted in an increase in Mighty mRNA (63 ± 13.4%) that was equivalent to the canonical Notch target HES-1 (94.4 ± 7.32%). These data suggest that acute resistance exercise decreases myostatin signaling through the activation of the TGFβ inhibitor Notch resulting in a decrease in myostatin transcriptional activity that correlates well with muscle hypertrophy.

  View details for DOI 10.1371/journal.pone.0068743

  View details for Web of Science ID 000321341000179

  View details for PubMedID 23844238

  View details for PubMedCentralID PMC3699505

• Reversible control of electrochemical properties using thermally-responsive polymer electrolytes Kelly, J. C., Pepin, M., Huber, D. L., Bunker, B. C., Roberts, M. E. AMER CHEMICAL SOC. 2012

  View details for Web of Science ID 000324621808176

• Reversible Control of Electrochemical Properties Using Thermally-Responsive Polymer Electrolytes ADVANCED MATERIALS Kelly, J. C., Pepin, M., Huber, D. L., Bunker, B. C., Roberts, M. E. 2012; 24 (7): 886-+

  Abstract

  A thermally responsive copolymer is designed to modulate the properties of an electrolyte solution. The copolymer is prepared using pNIPAM, which governs the thermal properties, and acrylic acid, which provides the electrolyte ions. As the polymer undergoes a thermally activated phase transition, the local environment around the acid groups is reversibly switched, decreasing ion concentration and conductivity. The responsive electrolyte is used to control the activity of redox electrodes with temperature.

  View details for DOI 10.1002/adma.201103340

  View details for Web of Science ID 000299944200003

  View details for PubMedID 22253076