Hyperinsulinemia in Individuals with obesity: Role of Insulin Clearance

OBJECTIVE: Several studies have shown decreased insulin clearance rate (ICR) in individuals with obesity, but it remains unclear whether this is predominately due to obesity-associated insulin resistance (IR) or obesity itself. We aimed to clarify the complex interrelationship that exists between obesity, IR and ICR. METHODS: Healthy volunteers (n = 277) had measurement of IR and ICR using the insulin suppression test (IST). IR was quantified by determining the steady-state plasma glucose (SSPG) during the IST. ICR was estimated by dividing the insulin infusion rate by the steady-state plasma insulin concentration. We performed our analysis by stratifying the experimental population into 4 dichotomous categories, varying in obesity and IR. Obesity was defined as a body mass index (BMI) ≥ 30 kg/m(2), and IR was defined as SSPG ≥ 150 mg/dl. RESULTS: Individuals with obesity had higher fasting insulin compared with individuals without obesity, regardless of IR. ICR was similar between individuals with and without obesity but was higher in IR individuals compared with insulin sensitive individuals. In multivariate analysis, both fasting insulin and SSPG were significantly associated with ICR. No significant relationships were observed between BMI and ICR. CONCLUSIONS: Reduced ICR in obesity is secondary to IR, not excess adiposity.