Objective To investigate the association between C-reactive protein (CRP) and insulin resistance.
Materials and Methods This study included 1,624 Japanese participants (652 men and 972 women) aged 40 to 69 years who were non-diabetics or did not have medication for hypertension or dyslipidemia, a history of cardiovascular disease or CRP levels >10 mg/l. Serum CRP level, fasting glucose level, and fasting insulin level were measured, and the degree of insulin resistance was assessed using the homeostasis model assessment of insulin resistance (HOMA-IR). Categories of CRP were defined by the following tertiles: <0.25 mg/l, 0.25-0.59 mg/l, and ≥0.60 mg/l.
Results Elevated CRP levels were associated with increased fasting insulin levels, fasting glucose levels, and HOMA-IR in both men and women. Although the adjustment for body mass index in addition to age, cigarette smoking, and alcohol consumption attenuated the associations between CRP and fasting insulin, fasting glucose, and HOMA-IR, elevated CRP levels were associated with increased insulin levels and HOMA-IR in both sexes. Stratified analyses by CRP level and obesity showed that obesity status was associated with increased fasting insulin levels, fasting glucose levels, and HOMA-IR in both sexes and that fasting insulin levels, fasting glucose levels, and HOMA-IR were higher among obese individuals than among non-obese individuals at the same level of CRP.
Conclusion These results suggest a possible role of subclinical inflammation in insulin resistance and glucose intolerance in Japanese, but it only partly explains the link between obesity and impaired glucose homeostasis.