Nuclear Repressors in Genomic Control of Healthful Obesity

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 DESCRIPTION (provided by applicant): It has long been recognized that central (visceral) obesity is associated with adverse metabolic health including insulin resistance, yet peripheral (subcutaneous) body fat is healthful or benign, a distinction believed to underlie the sexually dimorphic risk of cardiometabolic disease with obesity. However, the molecular determinants that control the origins and physiology of these functionally distinct depots are poorly defined. Using conditional genetic engineering, we have identified a surprising role for the B cell lymphoma 6 (BCL6) transcriptional repressor in depot-specific adipose tissue programming. We find that BCL6 co-localizes with key adipocytic transcriptional regulators PPARγ, C/EBP, and EBF1 to control a metabolic gene regulatory network through cis-regulatory sites in differentiated adipocytes. Consequently, adipocyte-specific loss of BCL6 in utero results in spontaneous and selective expansion of subcutaneous, but not visceral, adipose tissue, identifying BCL6 as a new key regulator of sexually dimorphic obesity and distribution. Herein, we propose to dissect the genomic integration of BCL6 with nuclear receptor and hormonal signaling pathways to determine its role as a key regulator of adipose tissue distribution and function, using comprehensive cell and molecular, genomic, and physiologic approaches with endpoints of insulin sensitivity by euglycemic-hyperinsulinemic clamp, adipokine production, and lipid metabolism. Given that distinct adipose tissue depots exert differential risk of insulin resistance and cardiometabolic disease, our studies of BCL6 will reveal new therapeutic pathways to reduce the morbidity of obesity including type 2 diabetes mellitus (DM2).