Diverse Effect of Inflammatory Markers on Insulin Resistance and Insulin‐Resistance Syndrome in the Elderly

Abstract

Objectives: To evaluate the potential association between different inflammatory markers and insulin resistance (IR), as well as insulin‐resistance syndrome (IRS) in a large, population‐based study of older, nondiabetic persons. Design: Cross‐sectional study. Setting: Outpatient clinic in Greve in Chianti and Bagno a Ripoli (Italy). Participants: One thousand one hundred forty‐six nondiabetic subjects ranging in age from 22 to 104. Measurements: Anthropometric measurements; plasma fasting levels of glucose, insulin, and cholesterol (total, high‐density lipoprotein, low‐density lipoprotein); homeostasis model assessment to estimate degree of insulin resistance; tumor necrosis factor α (TNF‐α), interleukin 6 (IL‐6), soluble IL‐6 receptor (sIL‐6R), interleukin receptor antagonist (IL‐1ra), and C‐reactive protein (CRP) plasma concentrations; diastolic, systolic, and mean arterial blood pressure; and echo‐color‐Doppler duplex scanning examination of carotid arteries. Results: Insulin resistance correlated with age (r=0.102; P<.001) and plasma levels of TNF‐α (r=0.082; P=.007), IL‐1ra (r=0.147; P<.001), IL‐6 (r=0.133; P<.001), sIL‐6R (r=−0.156; P<.001), and CRP (r=0.83; P<.001). Subjects in the upper tertile of IR degree were older and had higher serum levels of TNF‐α, IL‐1ra, and IL‐6 and lower levels of sIL‐6R than subjects in the lowest tertile. Independent of age, sex, body mass index, waist‐to‐hip ratio, triglycerides, drug intake, diastolic blood pressure, smoking habit, and carotid atherosclerotic plaques, higher IL‐6 (t=2.987; P=.003) serum concentrations were associated with higher IR, whereas sIL‐6R levels (t=−5.651; P<.001) were associated with lower IR. Furthermore, IL‐1ra concentrations (t=2.448; P=.015) were associated with IRS, and higher sIL‐6R plasma levels continued to correlate negatively with IRS. Conclusion: Different inflammatory markers are associated with a diverse effect on IR and IRS in elderly nondiabetic subjects.