Association Between Insulin Resistance and the Inflammatory Marker C-reactive Protein in a Representative Healthy...

Insulin resistance (IR) leads to type 2 diabetes mellitus. Multiple IR causes have been identified, including inflammation. This study determines the association between IR and the inflammatory marker C-reactive protein (CRP) in a healthy Canadian population and examines potential differences by sex and age.

Participants were adults with no self-reported history of diabetes, a glycated hemoglobin (A1C) of <6.5%, and a fasting blood glucose of <7 mmol/L, and who had participated in the Canadian Health Measures Survey, cycles 1 to 4 (2007-2015). IR was calculated using the Homeostasis Model of Insulin Resistance (HOMA-IR) assessment. The crude geometric mean HOMA-IR was calculated using a one-way analysis of variance. The association between CRP levels and HOMA-IR was examined using multivariate linear regression.

A total of 4,024 eligible nondiabetic adults (1,994 [49.5%] men and 2,030 [50.4%] women) were identified. Eighty percent of the subjects were Caucasian. Among all subjects, 36% had a CRP of ≥2 mg/L. The crude geometric mean HOMA-IR was 1.33 in men and 1.24 in women. Participants with a CRP of <0.7 mg/L had a crude geometric mean HOMA-IR of 1.15 (1.13 to 1.16), compared with 1.41 (1.39 to 1.43) for those with a CRP of ≥2 mg/L. After adjusting for sex, age, race, high-density lipoprotein cholesterol, triglycerides, body mass index, smoking, and diastolic blood pressure, the HOMA-IR-CRP association remained significant. A positive trend for CRP values in men with increasing values of HOMA-IR was observed. However, this trend was not consistent with the increase in women's CRP levels.

Elevated CPR levels are independently associated with IR in men. Prospective cohort studies can confirm the causal relationship between high CRP levels and IR and identify the underlying mechanisms.