LEPTIN SECRETION FROM SUBCUTANEOUS AND VISCERAL ADIPOSE-TISSUE IN WOMEN

Upper body obesity is a risk factor for type 2 diabetes. Little is kno wn about the regulation of body fat distribution, but leptin may be in volved. This study examined the secretion of leptin in subcutaneous an d omental fat tissue in 15 obese and 8 nonobese women. Leptin secretio n rates were two to three times higher in subcutaneous than in omental fat tissue in both obese and nonobese women (P < 0.0001 and P < 0.001 , respectively). There was a positive correlation between BMI and lept in secretion rates in both subcutaneous (r = 0.87, P < 0.0001) and ome ntal (r = 0.74, P < 0.0001) fat tissue, Furthermore, leptin secretion rates in subcutaneous and omental fat tissue correlated well with seru m leptin levels (r = 0.84, P < 0.0001 and r = 0.73, P = 0.001, respect ively), although in multivariate analysis, the subcutaneous leptin sec retion rate was the major regressor for serum leptin (F = 42). Subcuta neous fat cells were similar to 50% larger than omental fat cells, and there was a positive correlation between fat cell size and leptin sec retion rate in both fat depots (r = 0.8, P < 0.01), Leptin (but not ga mma-actin) mRNA levels were twofold higher in subcutaneous than in ome ntal fat tissue (P < 0.05). Thus the subcutaneous fat depot is the maj or source of leptin in women owing to the combination of a mass effect (subcutaneous fat being the major depot) and a higher secretion rate in the subcutaneous than in the visceral region, which in turn could b e due to increased cell size and leptin gene expression.