In vivo insulin clearance in 10 subjects with non-insulin-dependent diabetes mellitus (NIDDM) has been compared with clearance in eight equally obese nondiabetic control subjects by two different methods. The first approach consisted of determining the metabolic clearance rates of exogenously infused insulin (MCRI) during hyperinsulinemic (100 mU/m2/min) glucose clamp studies. The results indicated that mean (+/- SEM) MCRI was 1.4-fold greater in the diabetic subjects (436 +/- 22 ml/m2/min) than in the controls (325 +/- 24 ml/m2/min, P less than 0.005), resulting in a lower steady-state plasma insulin concentration in the diabetic (255 +/- 8 microU/ml) compared with the nondiabetic subjects (329 +/- 29 microU/ml, P less than 0.001). The impact of NIDDM on insulin removal rates was also estimated by a second method in which extraction of endogenously secreted insulin (EXTI) in response to an oral glucose load was calculated from the integrated area above basal of plasma insulin (IRI) and of plasma C-peptide (CPR), an estimate of beta-cell secretion. The results demonstrated that fractional extraction of endogenously secreted insulin (EXTI = 100 [(CPR - IRI)/CPR]) was also 1.2-fold greater for diabetic subjects (88.9 +/- 2.5%) than for nondiabetic controls (72.0 +/- 2.8%, P less than 0.001). Finally, these two independent measurements of in vivo insulin removal rates (MCRI and EXTI) were significantly correlated with each other (r = 0.71, P less than 0.002). These observations are consistent with the view that elevated insulin clearance may contribute to the postchallenge hypoinsulinemia of NIDDM in Pima Indians.

Sixteen newly diagnosed non insulin dependent diabetic patients were treated for 3 months with an individual energy restricted diet. The effect on weight, hyperglycaemia and insulin response to oral glucose was measured in all subjects, and in 7, peripheral insulin resistance was estimated using a hyperinsulinaemic glucose clamp at two insulin infusion rates (40 and 400 mU m-2 X min-1). After diet, fasting plasma glucose fell from 12.0 +/- 0.7 mmol/l (mean +/- SEM) to 7.4 +/- 0.5 mmol/l (P less than 0.001) and weight fell from 92.9 +/- 4.2 kg to 85.0 +/- 3.1 kg (P less than 0.001). The plasma insulin response to oral glucose was unchanged after diet therapy. Insulin induced glucose disposal (M) was also unaffected by diet at insulin infusion rates of 40 mU m-2 X min-1 (12.5 +/- 1.5 mumol X kg-1 X min-1 vs 15.7 +/- 1.6 mumol X kg-1 X min-1) and 400 mU m-2 X min-1 (49.5 +/- 2.7 mumol X kg-1 X min-1 vs 55.1 +/- 2.5 mumol X kg-1 X min-1). These results show that 3 months reduction of energy consumption with weight loss in newly diagnosed non insulin dependent diabetics improves B-cell responsiveness to glucose but has no effect on liver glucose output or on peripheral insulin action.

SUMMARYAn increased serum level of the MB isoenzyme of creatine kinase (CK‐MB) is a useful marker for acute myocardial infarction. Although described extensively in clinical chemistry literature, there is little information in standard medical references about false positives for this test. We report two cases where high levels of measured CK‐MB activity were in fact due to another form of CK, associated with internal malignancy.