Differentiation between obesity and insulin resistance in the association with C-reactive protein

Background - Plasma C-reactive protein (CRP) concentrations are increased in obese and/or hyperinsulinemic individuals. The goal of this study was to determine if the relation between insulin resistance and CRP was independent of obesity. Methods and Results - Plasma CRP concentrations were measured before and after 3 months of calorie restriction in 38 healthy, obese women. Steady-state plasma glucose (SSPG) concentration during a 180-minute infusion of octreotide, glucose, and insulin was used to stratify participants into insulin-resistant (IR, n=20) or insulin-sensitive (n=18) groups, similar in terms of mean age (46±2 versus 44±2 years), body mass index (32.0±0.4 versus 31.4±0.3 kg/m²), and waist circumference (96±2 versus 95±2 cm). Mean CRP (0.39±0.08 versus 0.12±0.03 mg/dL, P=0.003) concentrations were higher in the IR group, as were day-long plasma glucose and insulin responses (P<0.001). There was a significant correlation at baseline between CRP and day-long plasma integrated insulin response (r=0.47, P=0.001) but not between CRP and body mass index (r=0.14) or waist circumference (r=0.10). Weight loss was similar in the two groups (8.7±0.9 versus 8.4±0.8 kg) but was associated with significant (P<0.001) decreases in SSPG and CRP concentrations in the IR group only. Regression analysis showed that SSPG and day-long plasma insulin response were the only significant predictors of CRP concentration. Conclusions - CRP concentrations are elevated predominantly in obese individuals who are also insulin resistant and fall in parallel with weight loss-associated improvements in insulin resistance. The relation between CRP concentrations and insulin resistance is independent of obesity.