Elevated levels of interleukin 6 are reduced in serum and subcutaneous adipose tissue of obese women after weight loss

The aim of this study was to investigate the potential role of adipose cyto kines in the obesity-associated insulin resistance. To that end, we compare d: 1) serum concentrations of interleukin 6 (IL-6), tumor necrosis factor a lpha(TNF alpha), and leptin in eight healthy lean control females and in an droid obese female without (n = 14) and with (n = 7) type 2 diabetes; and 2 ) the levels of these cytokines both in serum and in sc adipose tissue in t he 14 obese nondiabetic women before and after 3 weeks of avery low-calorie diet (VLCD). As compared with lean controls, obese nondiabetic and diabeti c patients were more insulin resistant and presented increased values for l eptin, IL-6, TNF alpha, and C-reactive protein. In the whole group, IL-6 va lues were more closely related to the parameters evaluating insulin resista nce than leptin or TNF alpha values. VLCD resulted in weight loss and decre ased body fat mass (similar to 3 kg). Insulin sensitivity was improved with no significant change in bath serum and adipose tissue TNF alpha levels. I n contrast, VLCD induced significant decreases in IL-6 and leptin levels in both adipose tissue and serum. These results suggest that, as for leptin, circulating IL-6 concentrations reflect, at least in part, adipose tissue p roduction. The reduced production and serum concentrations after weight los s could play a role in the improved sensitivity to insulin observed in thes e patients.