Adipokine expression is associated with adipocyte volume in baboons

Baboons show significant variation in body weight and composition, coupled with insulin resistance and phenotypes associated with the metabolic syndrome. An omental adipose tissue biopsy and a fasting blood sample were collected from 40 unrelated adult baboons from the colony at Southwest Foundation for Biomedical Research in San Antonio, TX. Serum was separated for analyses of circulating levels of glucose, insulin, adiponectin, resistin, interleukin 6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1or CCL-2). Adipose tissue biopsies were analyzed for cell volume and number. Total RNA was isolated from adipose tissue and adiponectin, resistin, δ-resistin, MCP-1 and IL-6 mRNA abundance were measured using real time, quantitative RT-PCR. Partial correlation coefficients were calculated among adipokine expression, fat tissue cell volume, and circulating levels of proteins. Cell volume was significantly correlated with expression of MCP-1 (r = 0.44, p < 0.05) and IL-6 mRNA (r = 0.47, p < 0.01). A step wise regression analysis was conducted with adipose tissue cell volume as dependent variable. The model identified IL-6 mRNA levels in adipose tissue as the only predictor. These observations support the role of IL-6 as a possible paracrine regulator in adipose tissue.