Association Between Insulin Resistance and the Inflammatory Marker C-reactive Protein in a Representative Healthy Adult Canadian Population: Results From the Canadian Health Measures Survey

Objectives: 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.

Methods: 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.

Results: 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.

Conclusions: 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.