Effect of insulin on serum amino-terminal propeptide of type III procollagen in non-insulin-dependent diabetes mellitus.

The effect of insulin on the serum levels of the amino-terminal propeptide of type III procollagen (PIIINP) was investigated in patients with non-insulin-dependent diabetes mellitus, whose disease was unsatisfactorily controlled by oral drugs. Before insulin therapy the PIIINP values of the patients (3.2 +/- 1.3 micrograms/l, n = 38) varied within the range of healthy subjects (3.1 +/- 0.6 micrograms/l, n = 50, NS). Insulin therapy (6-20 IU at bedtime plus the oral drugs) improved the glycemic control and increased the serum PIIINP during a 4 week (3.1 +/- 0.9 to 3.8 +/- 1.1 micrograms/l, P less than 0.01, n = 8) and an 8 week period (3.2 +/- 1.3 to 3.8 +/- 1.6 micrograms/l, P less than 0.001, n = 22). The values were still elevated after 6 months on insulin (3.5 +/- 1.5 to 4.0 +/- 1.7 micrograms/l, P less than 0.01, n = 12). Placebo-insulin did not alter the concentration of PIIINP (3.1 +/- 0.6 to 2.8 +/- 0.6 micrograms/l, NS, n = 8) whereas the glycemic control improved and body weight decreased. The PIIINP values correlated with fasting insulin before (r = 0.403, P less than 0.05, n = 30) and after the therapy (r = 0.452, P less than 0.001, n = 60). Insulin therapy, while correcting the hormone deficiency and restoring glucose and protein metabolism, seems to activate the synthesis of type III procollagen in patients with NIDDM. This may promote the atherosclerotic process.

Effects of enzyme induction therapy on glucose and drug metabolism in obese mice model of non-insulin dependent diabetes mellitus.

We evaluated the effects of phenobarbital, an inducer, on plasma glucose and serum immunoreactive insulin levels and on hepatic glucose and drug metabolism using an animal model of non-insulin dependent diabetes mellitus. Genetically obese (ob/ob) mice, characterized by hyperglycaemia, hyperinsulinaemia, fatty liver and obesity were selected. The impairment of diabetic state with age was associated with increased activities of NADPH producing enzymes, whereas mixed function oxidase system remained unaltered. Phenobarbital reduced serum immunoreactive insulin and plasma glucose levels and decreased gluconeogenesis. Hepatic glucose phosphorylating enzyme activity increased and glucose releasing enzyme activity decreased. The demand for NADPH in drug oxidation reactions, caused by the induction phenomenon, was reflected in the elevated activities of the NADPH producing enzymes in pentose phosphate pathway and in the activities of isocitrate dehydrogenase and malic enzyme from mitochondrial oxidation reactions. Glucose metabolism of lean littermates indicated that phenobarbital induction normalizes impaired intracellular glucose handling but leaves normal glucose metabolism unaltered. Hepatic glucose production rate was related to plasma glucose, NADPH producing enzyme activities and cytochrome P450 content in the obese and lean mice.