C-reactive protein and the insulin-like growth factor (IGF)-system in relation to risk of cardiovascular disease in different ethnic groups

Inflammatory processes, marked in part by the acute phase reactant C-reactive protein (CRP) and insulin resistance are implicated in atherogenesis. Low insulin-like growth factor-I (IGF-I) and IGF binding protein-1 (IGFBP-1) concentrations are closely associated with insulin resistance. We examined CRP in ethnic groups with differing risk for cardiovascular disease and type 2 diabetes and its relationship with insulin sensitivity (Homeostasis model assessment (HOMA)-S) and the IGF system. European (n=155), Pakistani (n=108) and African-Caribbean (African Caribbean) (n=177) origin participants were randomly sampled from population registers. All underwent basic anthropometry, glucose tolerance testing and measurement of insulin sensitivity, CRP and other metabolic variables. CRP was significantly lower in African Caribbean men and women than in other ethnic groups. Across all groups CRP correlated negatively with (HOMA-S) (rho=-0.29, P<0.001). Regression analysis which included ethnicity and body mass index (BMI) showed that low HOMA-S (beta=-0.17, P<0.001) and low IGFBP-1 (beta=-0.14, P<0.001) were independently and inversely associated with CRP, but the effect was modified by obesity. In obese subjects insulin sensitivity was not associated with CRP. However, for the whole population, a 2.7 mg/l increase in CRP was associated with a 50% (95% confidence interval (CI) 10-210%) greater risk of WHO defined metabolic syndrome, independent of IGF-I (odds ratio (OR) 0.46 (95% CI 0.22-0.96)), IGFBP-1 (OR 0.58 (0.44-0.76)), female sex (OR 0.43 (0.22-0.84)), NEFA (OR 1.06 (1.03-1.09)) and Pakistani ethnicity. High CRP (as a measure of chronic subclinical inflammation), low IGF-I and low IGFBP-1 are independently associated with the presence of the metabolic syndrome and with insulin resistance. In obese subjects insulin sensitivity is not associated with changes in CRP whilst in non-obese subjects CRP independently contributes to variation in HOMA-S.