NO DIFFERENTIAL-EFFECTS OF PORCINE AND HUMAN INSULIN ON MUSCLE SYMPATHETIC-NERVE ACTIVITY DURING EUGLYCEMIA OR HYPOGLYCEMIA

On the basis of some clinical studies in diabetic patients, and experi mental studies in normal humans, it has been suggested that hypoglycae mic autonomic responses are augmented with porcine (PI) compared to hu man insulin (HI). A difference in sensory processing has been reported following insulin-induced hypoglycaemia with PI compared to HI, and h as been interpreted as different insulin effects on the central nervou s system. In a double blind crossover comparison of HI and PI in nine healthy subjects, microneurographic recordings of muscle sympathetic n erve activity (MSNA) were performed, as well as measurements of cardio vascular and hormonal responses during a low dose hyperinsulinaemic eu glycaemic glucose clamp (plasma insulin 60.1 +/- 1.9 mU ml(-1) (mean /- SEM)), followed by a period of insulin-induced hypoglycaemia Plasma insulin and glucose were identical in the two sessions. Plasma glucos e nadir during hypoglycaemia was 2.4 +/- 0.2 mmol l(-1) for HI and 2.5 +/- 0.1 mmol l(-1) for PI. During euglycaemia, MSNA increased from 24 +/- 2 to 34 +/- 3 and 23 +/- 2 to 30 +/- 2 burst/min (P:NS) for HI an d PI, respectively, and during hypoglycaemia to 49 +/- 4 and 45 +/- 2 bursts min(-1) (P:NS), respectively. The maximal hypoglycaemic increme nts of MSNA were not different (HI 15 +/- 4; PI 15 +/- 2 bursts min(-1 ) (P:NS)) Responses of plasma noradrenaline and haemodynamic parameter s did not differ either. This study does not indicate differing sympat hetic responses to PI and HI in healthy humans. Evidence for a modulat ing effect of insulin on central sympathetic outflow was not found.