Objective: To study the effect of weight loss in response to a lifestyle modification program on the circulating levels of adipose tissue derived cytokines (adipokines) in obese individuals with insulin resistance.
Research Methods and Procedures: Twenty-four insulin-resistant obese subjects with varying degrees of glucose tolerance completed a 6-month program consisting of combined hypocaloric diet and moderate physical activity. Adipokines [leptin, adiponectin, resistin, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6)] and highly sensitive C-reactive protein were measured before and after the intervention. Insulin sensitivity index was evaluated by the frequently sampled intravenous glucose tolerance test.
Results: Participants had a 6.9 ± 0.1 kg average weight loss, with a significant improvement in sensitivity index and reduction in plasma leptin (27.8 ± 3 vs. 23.6 ± 3 ng/mL, p = 0.01) and IL-6 (2.75 ± 1.51 vs. 2.3 ± 0.91 pg/mL, p = 0.012). TNF-α levels tended to decrease (2.3 ± 0.2 vs. 1.9 ± 0.1 pg/mL, p = 0.059). Adiponectin increased significantly only among diabetic subjects. The reductions in leptin were correlated with the decreases in BMI (r = 0.464, p < 0.05) and with changes in highly sensitive C-reactive protein (r = 0.466, p < 0.05).
Discussion: Weight reduction in obese individuals with insulin resistance was associated with a significant decrease in leptin and IL-6 and a tendency toward a decrease in circulating TNF-α, whereas adiponectin was increased only in diabetic subjects. Further studies are needed to elucidate the relationship between changes of adipokines and the health benefits of weight loss.