Differences in adiponectin content and secretion as a function of adipose tissue depots (subcutaneous vs. intra-abdominal or visceral) or diabetic status or in response to treatment with pioglitazone were examined in a sample of 50 obese subjects (26 of them with diabetes). Over the first two days of culture, no depot or diabetes-related differences were observed in the rate of adiponectin secretion by adipose tissue. In the subcutaneous adipose depot of nondiabetic subjects, the secretion fell after 2-4 days but was sustained at greater levels compared to the subcutaneous adipose depot of diabetic subjects. Adiponectin secretion was low in the intra-abdominal depot of both diabetic and nondiabetic individuals, similar to that of the subcutaneous depot of diabetic subjects. However, and in contrast to decreases in adiponectin secretion during the culture period, adiponectin content increased in cultured adipose tissue from nondiabetic subjects, regardless of depot. Adiponectin content remained unchanged in the adipose tissue of diabetic subjects over the culture period. Pioglitazone increased adiponectin secretion and content in the subcutaneous adipose tissue depot. Pioglitazone failed to increase adiponectin secretion of the intra-abdominal adipose tissue depot but increased cellular content of adiponectin in intra-abdominal adipose tissue of nondiabetic subjects. Taken together, these results suggest that subcutaneous but not intra-abdominal fat appears to be a major contributor to increased circulating adiponectin concentrations following pioglitazone treatment. This notion is consistent with the greater recognized role of the subcutaneous adipose tissue depot acting as a “metabolic sink” and having beneficial effects on insulin sensitivity.
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