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 DESIGN AND METHODS: 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.