Lessons From the First Decade of the Native American Summer Research Internship at the University of Utah.

PROBLEM: American Indian/Alaska Native (AI/AN) populations are facing multiple health crises, including limited access to care, high rates of chronic disease, and early mortality that is far worse than other underrepresented minorities in the United States. According to the Association of American Indian Physicians, AI/AN people represent 2.0% of the U.S. population but only 0.2% of medical students and 0.1% of full-time faculty at MD-granting institutions. Increasing the number of AI/AN clinicians and scientists is one strategy to improve health outcomes in the AI/AN population and address these crises. APPROACH: In 2010, the University of Utah partnered with research, cultural, and professional mentors to create a 10-week summer Native American Research Internship (NARI) program for AI/AN college students across the United States who are interested in pursuing biomedical careers. NARI attracts and supports AI/AN students by offering mentored summer research internships in an innovative, culturally aware framework that adapts to observed challenges to optimize educational experiences and support biomedical career aspirations. OUTCOMES: During the first decade of the NARI program, 128 students from 22 U.S. states, representing 46 tribal nations and 57 colleges and universities, participated. Of those 128 students, 113 (88%) have completed a bachelor's degree and the remaining 15 (12%) are currently working toward a bachelor's degree. No NARI student has dropped out of college. Twenty-six (20%) NARI alumni have matriculated to medical school and 30 (23%) to graduate school. Eight (6%) participants have completed medical school, and 3 (2%) are pursuing a PhD in science. An additional 36 (28%) have gained employment in biomedical research fields. NEXT STEPS: The NARI program has increased the participation of AI/AN students in medicine and the biomedical sciences. The innovative, culturally aware, and adaptive framework is a model for other programs for AI/AN students and students in other underrepresented communities.

Targeted deletion of Tcf7l2 in adipocytes promotes adipocyte hypertrophy and impaired glucose metabolism.

OBJECTIVE: Activation of the Wnt-signaling pathway is known to inhibit differentiation in adipocytes. However, there is a gap in our understanding of the transcriptional network regulated by components of the Wnt-signaling pathway during adipogenesis and in adipocytes during postnatal life. The key intracellular effectors of the Wnt-signaling pathway occur through TCF transcription factors such as TCF7L2 (transcription factor-7-like 2). Several genetic variants in proximity to TCF7L2 have been linked to type 2 diabetes through genome-wide association studies in various human populations. Our work aims to functionally characterize the adipocyte specific gene program regulated by TCF7L2 and understand how this program regulates metabolism. METHODS: We generated Tcf7l2F/F mice and assessed TCF7L2 function in isolated adipocytes and adipose specific knockout mice. ChIP-sequencing and RNA-sequencing was performed on the isolated adipocytes with control and TCF7L2 knockout cells. Adipose specific TCF7L2 knockout mice were challenged with high fat diet and assessed for body weight, glucose tolerance, and lipolysis. RESULTS: Here we report that TCF7L2 regulates adipocyte size, endocrine function, and glucose metabolism. Tcf7l2 is highly expressed in white adipose tissue, and its expression is suppressed in genetic and diet-induced models of obesity. Genome-wide distribution of TCF7L2 binding and gene expression analysis in adipocytes suggests that TCF7L2 directly regulates genes implicated in cellular metabolism and cell cycle control. When challenged with a high-fat diet, conditional deletion of TCF7L2 in adipocytes led to impaired glucose tolerance, impaired insulin sensitivity, promoted weight gain, and increased adipose tissue mass. This was accompanied by reduced expression of triglyceride hydrolase, reduced fasting-induced free fatty acid release, and adipocyte hypertrophy in subcutaneous adipose tissue. CONCLUSIONS: Together our studies support that TCF7L2 is a central transcriptional regulator of the adipocyte metabolic program by directly regulating the expression of genes involved in lipid and glucose metabolism.

Dietary iron controls circadian hepatic glucose metabolism through heme synthesis.

The circadian rhythm of the liver maintains glucose homeostasis, and disruption of this rhythm is associated with type 2 diabetes. Feeding is one factor that sets the circadian clock in peripheral tissues, but relatively little is known about the role of specific dietary components in that regard. We assessed the effects of dietary iron on circadian gluconeogenesis. Dietary iron affects circadian glucose metabolism through heme-mediated regulation of the interaction of nuclear receptor subfamily 1 group d member 1 (Rev-Erbα) with its cosuppressor nuclear receptor corepressor 1 (NCOR). Loss of regulated heme synthesis was achieved by aminolevulinic acid (ALA) treatment of mice or cultured cells to bypass the rate-limiting enzyme in hepatic heme synthesis, ALA synthase 1 (ALAS1). ALA treatment abolishes differences in hepatic glucose production and in the expression of gluconeogenic enzymes seen with variation of dietary iron. The differences among diets are also lost with inhibition of heme synthesis with isonicotinylhydrazine. Dietary iron modulates levels of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a transcriptional activator of ALAS1, to affect hepatic heme. Treatment of mice with the antioxidant N-acetylcysteine diminishes PGC-1α variation observed among the iron diets, suggesting that iron is acting through reactive oxygen species signaling.