Carbohydrate (CHO) oxidation in patients with type B insulin resistance

Total body carbohydrate (CHO) and fat oxidation rates, plasma glucose, free fatty acid, and insulin concentrations were determined in two patients with the type B syndrome of severe insulin resistance and in normal controls in response to insulin infusions (1-100 mU/kg/min) and to a test meal. In addition, insulin was infused at higher rates (10-1000 mU/kg/min) in one of the two patients while plasma glucose concentrations were clamped first at 195 and later at 244 mg/dl. During the postabsorptive state, resting metabolic rates (RMR) were 914 and 979 cal/min/1.73 m2 in the two patients (controls: 1018 +/- 85 cal/min/1.73 m2). Patients met 85% and 83% of their caloric requirements by oxidizing fat (controls: 63 +/- 7%). Protein oxidation accounted for 15% and 13% (controls: 14 +/- 3%) of energy requirements and CHO oxidation for 0% and 0%, respectively, in both patients (controls: 23 +/- 5%). Infusion of insulin at a rate of 10 mU/kg/min raised plasma insulin concentrations from 1400 and 440 microU/ml to 6000 and 2500 microU/ml, respectively, in patients 1 and 2 (controls: from 4 +/- 0.3 to 1288 +/- 50 microU/ml), but had no effects on rates of CHO, fat, or protein oxidation in either patient. By comparison, the rate of CHO oxidation in controls rose about sixfold from 40 +/- 8 to 234 +/- 12 mg/min/1.73 m2. Infusion of 1000 mU/kg/min in combination with an increase in plasma glucose from 195 +/- 1.1 to 244 +/- 1.9 mg/dl in patient 1, however, raised CHO oxidation from 0 to 36 mg/min/1.73 m2 and lowered fat oxidation from 105 to 69 mg/min/1.73 m2.(ABSTRACT TRUNCATED AT 250 WORDS)