Modulation of PPAR-gamma phosphorylation at S273 regulates insulin sensitivity

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DESCRIPTION (provided by applicant): PPAR-gamma is the target of highly effective but controversial diabetes medications, the thiazolidinediones. We recently demonstrated that these drugs reverse insulin resistance through a previously unappreciated mechanism-reversing an inhibitory PPAR-gamma-phosphorylation event. Phosphorylation of PPAR-gamma at serine 273 occurs shortly after the onset of high fat diet feeding and increases with progressive obesity. This phosphorylation correlates with dysregulation of PPAR-gamma target genes, such as adiponectin. Treatment of patients or mice with thiazolidinediones reverses phosphorylation as it improves insulin sensitivity. Utilizing a new mouse model we will investigate whether preventing this obesity-mediated PPAR-gamma S273 phosphorylation will alter adipose tissue morphology, gene expression and systemic insulin-sensitivity in vivo. To do this, we have generated mice with an adipose-specific knock-out of the relevant PPAR-gamma kinase, Cdk5. We predict that these mice will be a model of healthy obesity due to insulin-sensitive adipose tissue. Following the induction of diet-induced obesity in these mice, we will examine body composition, glucose homeostasis and PPAR-gamma target gene expression in adipose tissue from obese mice. We will compare the metabolic and transcriptional consequences of treating wild type Cdk5 KO mice treated with full agonists such as rosiglitazone against non-agonists such as SR1664. Furthermore, we will examine whether a diabetes susceptibility gene, Cdkal1, regulates PPAR-gamma S273 phosphorylation and adipocyte gene expression in mouse and human cells. This proposal defines a new mechanism whereby selectively targeting PPAR-gamma S273 phosphorylation may allow for specifically promoting the beneficial effects of PPAR-gamma activation without the adverse effects. The candidate, Dr. Alexander Banks, has a strong track record of innovative research with a focus on generating and characterizing genetically modified mouse models of human metabolic disease. He has performed postdoctoral training at Columbia and Harvard Universities and has experience in the study of mammalian physiologic response to aging, obesity, and diabetes. The candidate's career goal is to become an independent academic investigator and faculty mentor with a research laboratory contributing towards understanding and reversing metabolic diseases. This research will be conducted in the laboratory of Bruce Spiegelman, PhD at Harvard Medical School, who is a leader in field of molecular diabetes research. Co-mentorship will be contributed by David Altshuler, MD, PhD also of Harvard Medical School. Career development activities to augment the training experience include instruction using cutting-edge methods, attending scientific meetings, and the support of a scientific advisory committee with broad expertise in relevant subjects.