[Proinsulin and insulin secretion in obese females before and after administration of metformin].

In 49 normal and overweighty women the basal and reactive proinsulin and insulin level as well as serum cholesterol and triglycerides were determined before and after the application of N,N-dimethylbiguanide-hydrochloride (metformin, Glucophage retard-R). The proinsulin fraction of the basal total insulin is 70 percent in normal women. With increasing overweight the percentage of proinsulin decreases in favor of insulin. Stimulation with 100 g oral glucose, in analogy to the total insulin, significantly increased proinsulin levels, remaining, however, below the insulin levels. Accordingly the increased secretion of total insulin in overweighty persons consists mostly of insulin and to a lesser degree of proinsulin. Additionally there exists a significant correlation between the triglycerides and the degree of overweight. After 4 weeks application of 1.7 g metformin daily the weight reduction reached on an average 1.4 kg, after 16 weeks 5.2 kg. In relation to the weight reduction lower proinsulin and insulin levels were noticed before and after stimulation with glucose. Even those test persons who did not lose weight under metformin showed lower proinsulin and insulin levels. It might be that metformin leads to a slow-down in glucose absorption and as a consequence to a decrease of insulin secretion. Lower triglyceride values after treatment with metformin not only were a sign of weight reduction: biguanides also influence the fat metabolism independently of the carbohydrate metabolism. Additional to the reduction diet the treatment with metformin seems to be very appropriate for overweighty patients with hyperinsulinism and hypertriglyceridemia.