The Effect of Glucose Loading on Adiponectin Levels in Diabetes Mellitus Type 2: Implications for Endothelial Dysfunction

Aim: Adiponectin levels are decreased in patients with type II Diabetes Mellitus (DM) but it is unclear whether Impaired Glucose Tolerance (IGT) affects adiponectin's release, or whether glucose intake modifies its release from adipocytes. We examined the effect of glucose loading on serum adiponectin and endothelial function in patients with newly diagnosed DM, IGT subjects and healthy individuals. Methods: Seventy nine patients with newly diagnosed DM, eighteen with IGT, and sixteen healthy individuals were recruited. All participants received 75g oral glucose. Endothelium-Dependent Dilation (EDD) was evaluated by gaugestrain plethysmography before glucose loading (baseline) and every 1h until 3h post-loading. Blood samples were obtained at baseline and at 3 hours postloading and serum adiponectin and insulin levels were measured. Results: Glucose loading significantly increased adiponectin levels in healthy and IGT but not in diabetic individuals. Although insulin was correlated with adiponectin both at baseline (r=-0.375, p=0.0001) and at 3h (r=-0.286, p=0.006), insulin variations did not follow the same pattern in our three groups. There was no association between the changes of insulin and those of adiponectin (p=NS). EDD was similarly decreased in healthy, in IGT and DM patients after glucose loading (p=NS for all). Conclusion: Glucose intake increases adiponectin levels in healthy individuals and subjects with IGT, but not in those with DM. This effect is independent of insulin variations. On the contrary, endothelial function was similarly impaired after glucose intake in all study groups, suggesting that deregulation of adiponectin's expression after glucose loading precedes the development of endothelial dysfunction in diabetes mellitus type II.