Cellular Dynamics of Subcutaneous Fat Distribution in Obese Women

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DESCRIPTION (provided by applicant): Adipose tissue expandability and the distribution of stored fat in the body are stronger predictors of health risk. A better understanding of the factors that determine regional fat mass growth may lead to developing new strategies for prevention or treatment of metabolic complications of obesity. The objective of this proposal is to study the responsiveness of lower- body fat mass, the inflammatory state of upper-body fat, ectopic fat, and insulin resistance to adipogenic stimulation in upper-body obese (UBO) women waist-to hip ratio (WHR) >0.85 and lower-body obese (LBO) women with WHR <0.75. Adipogenesis will be stimulated using pioglitazone (Pio). The hypothesis is that in UBO; adipogenesis in femoral fat is impaired, which leads to ectopic fat deposition, promoting insulin resistance. On the other hand, the ScA depot in UBO undergoes hypertrophy, leading to a chronic inflammatory state of the adipose tissue and consequential insulin resistance. Our specific aims are to test that: Aim 1. Impaired adipogenesis in the Sc fat of UBO women contributes to impaired adipogenesis in UBO women and to a) Limited leg fat expandability, which promotes insulin resistance via ectopic fat deposition; and b) The inflammatory response of upper-body fat which contributes to insulin resistance via inflammatory adipokines.; Aim 2. Cellular senescence contributes to impaired adipogenesis in UBO women and to identify candidate intrinsic or environmental factors that cause the depot-specific adipogenic regulation. UBO and LBO women (30 each) will be treated with Pio or placebo for 16 weeks. The adipocyte progenitor number, adipogenesis, the morphology and inflammatory response of adipose tissue, and systemic glycemic control will be determined before, during, and after the intervention. Distribution of fat in fat depots and ectopic sites will be measured. Stromal vascular cultures will be employed to assess preadipocyte kinetics in ScA and Sc femoral (ScF) fat depots and the mechanisms of their regulation. We will also assess in vivo Sc regional adipogenesis by measuring incorporation of deuterium (D) from D2O drinking water into the DNA of plastic adherent stroma-vascular (SV) cells by determining their fractional replacement (fSV cells).