The effect of glucose ingestion on inflammation and oxidative stress in obese individuals

Ingestion of 75 g glucose during an oral glucose tolerance test (OGTT) increases systemic inflammation and oxidative stress in healthy subjects and patients with type 2 diabetes mellitus, but the effect in overweight/obese nondiabetic individuals is uncertain. The aim of the present study was to determine the effect of an OGTT on plasma concentrations of inflammatory cytokines and peroxides in 33 subjects with body mass index >27 kg/m2. After an overnight fast, blood samples were taken from participants immediately before and at 30, 60, 90, and 120 minutes after ingestion of 75 g glucose. Plasma glucose, insulin, free fatty acid, interleukin (IL)-6, tumor necrosis factor α, and peroxides were measured during the tests. Plasma IL-6 concentrations decreased (13%) significantly (P < .001) at 30 and 60 minutes, whereas plasma peroxide concentrations decreased slightly (3%, P = .003) at 30 minutes during the tests. The 30-minute decrease in plasma IL-6 was correlated significantly and inversely with the concomitant increase in plasma insulin (r = −0.410, P = .02) and with the ratio of insulin to glucose at 30 minutes during the OGTT (r = −0.366, P = .04). These data suggest that plasma concentrations of IL-6 are acutely decreased possibly because of the predominance of the anti-inflammatory effect of hyperinsulinemia over the proinflammatory effect of hyperglycemia after ingestion of a large quantity of glucose in obese individuals.