To estimate the relative contributions of gluconeogenesis and glycogenolysis to the increase in hepatic glucose output (HGO) during glucose counterregulation under conditions simulating clinical insulin hypoglycemia, we induced moderate hypoglycemia (approximately 55 mg/dl) with a continuous infusion of insulin that resulted in physiological hyperinsulinemia (approximately 20 microU/ml) in eight normal volunteers and estimated gluconeogenesis by two methods: an isotopic approach in which appearance of plasma glucose derived from lactate was determined and another approach in which we infused alcohol along with insulin to block gluconeogenesis and used the exogenous glucose required to prevent greater hypoglycemia as an index of gluconeogenesis. Both methods gave similar results. Initially glycogenolysis accounted for approximately 85% of HGO; however, once hypoglycemia became established, the contribution of gluconeogenesis increased progressively to 77 +/- 10 (isotopic method) and 94 +/- 10% (alcohol method) of overall HGO. We conclude that in normal humans during moderate protracted hypoglycemia induced by physiological hyperinsulinemia, gluconeogenesis is the predominant factor responsible for the counterregulatory increase in HGO and that increased gluconeogenesis rather than increased glycogenolysis is the primary mechanism preventing development of greater hypoglycemia.

The influence of serum calcium concentration on total circulating parathyroid hormone (PTH) and on the relative amount of intact PTH-(1-84) and large carboxyterminal fragments was studied in the canine and bovine species and in man. Serum calcium was modified through infusions of CaCl2 or EDTA and samples obtained in time for the measurement of serum calcium and PTH concentrations. Pools of serum, corresponding to specific serum calcium concentrations, were analyzed by gel chromatography in all species. PTH was measured with a carboxyterminal radioimmunoassay. In basal conditions, total serum PTH was composed mostly of large carboxyterminal fragments, intact PTH-(1-84) representing less than 25% of the hormone in any species. With hypercalcemia, (greater than or equal to 2.0 mg/dl), total serum PTH decreased only to 40% of the original value measured in all species, despite serum calcium concentrations of over 13 mg/dl. The relative amount of intact PTH-(1-84) remained unchanged in the bovine and canine species and slightly decreased in man. Hypocalcemia (less than or equal to 2.0 mg/dl) induced a 300-450% increase in the basal PTH value measured. The relative amount of intact PTH-(1-84) became as or more important than carboxyterminal fragments in the canine species and in man, respectively, and remained slightly less in the bovine species. Despite small quantitative variations between species, these results indicate that changes in serum calcium concentration induced acute modification in PTH secretion or PTH peripheral metabolism, altering the ratio of intact hormone to carboxyterminal fragments in circulation.

No abstract

The present study was designed to compare continuous subcutaneous insulin infusion (CSII) using the Mill-Hill Infuser (Muirhead Medical Products Ltd., London, England) with multiple injections (MI) using the Medi-Jector (Derata Corporation, Minneapolis, Minnesota) in the treatment of insulin-dependent diabetes mellitus (IDDM), and to assess the effect of glucose control on diabetes complications. Twelve diabetic subjects were treated 3 mo with CSII and 3 mo with MI (bedtime ultralente and premeal boluses of regular insulin) in a randomized fashion. Prestudy preprandial/postprandial glucose levels were 147-215 mg/dl and improved to 108-138 mg/dl during CSII, and to 115-139 mg/dl during MI with glycosylated hemoglobin of 12.9%, 9.1%, and 8.7%, respectively. This improved glucose control with either CSII or MI was associated with an increase in sural nerve conductivity from 42.9 to 45 m/s and a decrease in proteinuria from 1.9 to 0.5 g/24 h. The 24-h insulin dose consisted of 45 U before the study, 44 U during CSII, and 56 U during MI. After the study, seven patients opted to continue with the Mill-Hill Infuser, and five with the Medi-Jector. We conclude the following: (1) treatment with both the Mill-Hill Infuser and the Medi-Jector was well accepted by the patients and resulted in similar improvement in measured blood glucose and glycosylated hemoglobin; (2) this improved metabolic control was associated with an increased nerve conductivity and a decreased protein excretion; and (3) MI required 20% more insulin than CSII to achieve similar glycemic control.

No abstract