A simplified method using somatostatin to assess in vivo insulin resistance over a range of obesity

Twenty-one nondiabetic subjects, their weights ranging from 56 to 165 kg, received an infusion of glucose (420 mg/min), insulin (0.77 mU/kg/min), and somatostatin (500 μg/h) for 150 min. A steady state level of plasma insulin and glucose was attained after 90 min. Endogenous insulin secretion, determined by C-peptide measurement, and glucagon secretion remained suppressed throughout the period. With similar steady state levels of plasma insulin (SSPI) maintained in all subjects, the height of the steady state plasma glucose concentration (SSPG) was considered an index of total body sensitivity to insulin-mediated glucose uptake. A positive correlation between SSPG and the degree of obesity, as determined by the body mass index (BMI), was demonstrated (r=0.70, P<0.001). No correlation was found between SSPI and BMI. The fasting plasma insulin concentration correlated with BMI (r=0.82, P<0.0001) and SSPG (r=0.80, P<0.0001). This method provides a simple safe measure of total body insulin resistance over a wide range of obesity and is independent of endogenous insulin secretion.