Lack of effect of nicardipine and diltiazem on glucose- and arginine-induced insulin release in obese subjects.

The metabolic effects of calcium channels blockers have already been studied both in normal and diabetic humans and results were quite controversial, depending on the drug used, the dose administered, and the type of patient. Little information exists on the use of Ca2+ antagonists in obese people, even if these persons are a population risk group for developing diseases in which these drugs may be requested for treatment. Thus, we evaluated, in obese humans, the metabolic effects of two Ca2+ antagonist drugs recently made commercially available to treat diseases such as hypertension and ischemic heart disease: nicardipine and diltiazem. Sixteen obese subjects were submitted to an intravenous glucose tolerance test (0.33 g/kg) (IVGTT) and an arginine test tolerance (30 g in 30 minutes) (ATT) before and after a week of oral treatment with nicardipine (60 mg/day) or diltiazem (360 mg/day). Plasma values of glucose, insulin, and C-peptide during IVGTT, and of glucose, insulin and glucagon during ATT did not show any modification during treatment with either drug. Thus the Ca2+ antagonists, nicardipine and diltiazem, at therapeutic doses in obese subjects do not significantly affect glucose tolerance or insulin and glucagon release.

Perioperative management of diabetic subjects. Subcutaneous versus intravenous insulin administration during glucose-potassium infusion.

The purpose of this study was to validate methods for the perioperative management of diabetic patients that meet the prerequisites of simplicity, applicability in the absence of a diabetologist, and flexibility, to rapidly meet changing metabolic requirements. The patients were divided into two groups that were comparable for age, sex distribution, type of diabetes, and type of surgical procedures. The results show that intravenous insulin administration achieved better glycemic control during the intraoperative period, whereas it did not offer advantages over the subcutaneous route during the pre- and postoperative periods. The satisfactory degree of steady glycemic control achieved and the absence of hypoglycemic episodes indicate that the separate administration of insulin and glucose plus electrolytes is an effective and safe management modality for diabetic patients undergoing major surgery.

Effect of domperidone on the release of insulin after intravenous glucose load in man.

To determine whether the blockade of the dopaminergic system is capable of modifying glucose-induced insulin release in man, the responses of insulin to an iv glucose load were measured at various domperidone infusion rates. The infusion of 5 micrograms/kg/min of domperidone increased significantly plasma insulin levels during the acute phase of glucose-induced insulin release and lowered plasma glucose values at 50 and 60 min; the k of glucose disappearance improved significantly. At lower domperidone infusion rates the acute increment of insulin after glucose load was indistinguishable from the response observed at 5 micrograms/kg/min until 0.5 microgram/kg/min, while similar responses in control and experimental tests were observed at 0.25 microgram/kg/min. A group of subjects was submitted to an arginine load in order to establish whether the effect observed with domperidone was specific for the glucose-induced insulin release; but, this time, we did not observe any significant effect during the domperidone-induced dopaminergic blockade. Furthermore, we also measured the plasma prolactin levels, to see whether the specific and well known effect of domperidone on prolactin release matches with the effect on beta-cell function. As far as prolactin is concerned, we observed a dose response effect of domperidone infusion, with a detectable elevation of prolactin at infusion rate of 0.25 microgram/kg/min. Since domperidone is a specific antagonist of dopamine D2-receptors, we propose that dopamine might exert a specific inhibiting effect on glucose-induced insulin release through this class of dopamine receptors.