Reciprocal association of plasma IGF-1 and interleukin-6 levels with cardiometabolic risk factors in nondiabetic subjects

OBJECTIVE— To examine the relationship between plasma IGF-1 and interleukin-6 (IL-6) levels in Caucasian nondiabetic subjects and evaluate the association of IGF-1 and IL-6 with the cardiometabolic risk factors characterizing metabolic syndrome (MetS). RESEARCH DESIGNANDMETHODS— The study group consisted of 186 Caucasian nondiabetic subjects who underwent an oral glucose tolerance test and an euglycemic hyperinsulinemic clamp. A logistic regression analysis, adjusted for age and sex, was used to determine the association between tertiles of IGF-1 and IL-6 and the MetS and its components. RESULTS— After adjusting for age and sex, both IGF-1 and IL-6 were correlated with insulin resistance and individual components of MetS, but in opposite directions. In the logistic regression model adjusted for age and sex, higher IL-6 and lower IGF-1 levels confer increased risk of having MetS and its two underlying pathophysiological abnormalities, i.e., visceral obesity and insulin resistance. CONCLUSIONS— The present results raise the possibility that lowered protection against inflammation, i.e., lower IGF-1 levels, may have a role in the development of MetS and its features, resulting in an imbalance between proinflammatory and anti-inflammatory proteins.