Epigenetics of Obesity and Insulin Resistance

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DESCRIPTION (provided by applicant): The goals of this proposal are two-fold: (i) to investigate epigenetic regulation of transcription in insulin target tissues in obesity and (ii) to generate a platform for future R01 funding. The PI is an NIH-trained pediatric endocrinologist skilled in basic science research, currently on faculty at UCSD. Obesity and insulin resistance are major risk factors to the development of type 2 diabetes, cardiovascular disease, and stroke. These metabolic diseases are associated with profound alterations in gene expression caused by both genetic and environmental factors. Epigenetics provides a mechanism by which environmental factors modify gene expression and the predisposition to disease at all ages. Epigenetic mechanisms of gene regulation include DNA methylation and histone modifications. Highly inbred rodent strains such as C57BL/6 mice are nearly genetically identical. Yet these strains show substantial variation in longevity, adiposity, and insulin resistance. Epigenetic variation is a likely factor to account for this high phenotypic variability. In this proposal, we exploit the wide metabolic variation in high- fat diet (HFD)-fed C57BL/6 male mice as a means to investigate how epigenetic modifications regulate transcriptional control in obesity and insulin resistance. In order to achieve this goal, we will apply high throughput techniques (ChIP-Seq and RNA-Seq) to survey global epigenetic histone modification and transcriptome profiles in adipose and liver tissue of C57BL/6 mice. We hypothesize that i) HFD alters histone modification patterns in liver and adipose tissues (Aim 1), and ii) that epigenetic differences account for the wide variation in insulin resistance following HFD (Aim 2). In Aim 1, we will compare tissues collected from age-matched mice fed either HFD or standard chow. In Aim 2, we will surgically remove and bank tissues from young mice, place all mice on HFD, and perform metabolic testing to define 2 distinct subgroups of mice with either severe or mild insulin resistance. We will then analyze tissues collected at study initiation, comparing differences between both phenotypic groups. In both aims, tissues will be subjected to ChIP-Seq analysis to determine histone methylation patterns that mark active promoter and repressor elements (namely H3K4me3 and H3K27me3). These data will be integrated with gene expression profiles obtained by RNA-Seq. This work will be conducted in collaboration with Dr. Bing Ren at UCSD, a well-recognized expert in high throughput techniques and computational analysis. Dr. Ren's lab will perform all sequencing and assist with bioinformatics analysis. The in vivo experiments will be conducted in the lab of my K08 mentor, Dr. Jerrold Olefsky. This approach is designed to draw on my strengths as a bench scientist and pediatric endocrinologist, providing an independent focus of research and platform for future R01 funding.