To evaluate the roles of counterregulatory hormones and insulin antibodies in the impairment of plasma glucose recovery from hypoglycemia in diabetes mellitus, and to assess the relationship between the glucagon response and duration of the disease, 21 insulin-dependent diabetic patients and 10 nondiabetic subjects were studied. The diabetics consisted of 5 patients with recent onset of diabetes (less than 1 mo); 11 with 2.6 +/- 0.3 (mean +/- SEM) yr duration of diabetes, 5 of whom had insulin antibodies; and 5 patients with long-term diabetes (21 +/- 3 yr), insulin antibodies, and autonomic neuropathy. During insulin-induced hypoglycemia (28 mU/m2 X min for 60 min) in patients with recent-onset diabetes, plasma free insulin, glucose, and counterregulatory hormone concentrations did not differ from those of nondiabetic subjects. In patients with insulin antibodies, the disappearance of insulin after insulin infusion was delayed, and both restitution of normoglycemia and plasma glucagon response were blunted compared with patients without antibodies. When glucagon was infused (80-130 ng/m2 X min) during hypoglycemia in diabetics with impaired glucagon responses in order to simulate normal glucagon responses, plasma glucose recovery was normalized in patients without antibodies but not in those with antibodies. In patients with long-standing diabetes, restitution of normoglycemia was further impaired and this was associated with an absent plasma glucagon response and a diminished plasma epinephrine response. Plasma glucagon responses to hypoglycemia were inversely correlated to the duration of diabetes (r = -0.943; P less than 0.0005). It is concluded that impaired A-cell secretion is the predominant mechanism for the delayed glucose recovery after hypoglycemia in diabetic patients without insulin antibodies and normal epinephrine responses. Slowed disappearance of insulin due to the presence of insulin antibodies further delays the restoration of normoglycemia. Patients with long-standing diabetes and autonomic neuropathy exhibit decreased epinephrine secretion, which leads to an additional retardation of glucose recovery. Since plasma glucagon and epinephrine responses to hypoglycemia were normal at the onset of diabetes but diminished in long-term diabetes, it appears that the impaired glucagon and epinephrine responses to hypoglycemia are acquired defects that develop subsequent to B-cell failure.

The Biostator GCIIS was used to clamp circulating glucose at hypoglycemic (42 +/- 1 mg/dl), euglycemic (86 +/- 2 mg/dl), and hyperglycemic (142 +/- 1 mg/dl) levels in normal subjects during a concomitant infusion of insulin (0.1 U/kg/h). Because of limitations in maximal glucose infusion (1 g/min) from the Biostator, a supplementary infusion of glucose was required to accomplish euglycemic and hyperglycemic clamps. The coefficients of variation of blood glucose were 7.06 +/- 1.3%, 5.9 +/- 0.5%, and 6.1 +/- 0.9 for 120 minutes of hypoglycemic, euglycemic, and hyperglycemic clamps, respectively. Despite the occasional interruption of blood flow in the double-lumen catheter and the occasional poor correlation between Biostator and reference glucose method, satisfactory glucose clamps could be maintained for 2 hours.

Fasting hypoglycemia, which persisted for 3 days after insulin treatment was stopped, occurred in a patient with non-insulin-dependent diabetes mellitus who had inappropriate plasma free-insulin levels (18-25 microU/ml) and extremely high antibody-bound insulin (greater than 20,000 microU/ml) but normal counter-regulatory hormone secretion and plasma C-peptide levels. The amount of antibody-bound insulin decreased in a biphasic pattern over 13 mo of observation with an initial half-life of 35 days and a more gradual decrease with a half-life of 160 days. The number of high-affinity antibody binding sites was virtually identical to the amount of antibody-bound insulin in the patient's plasma. We conclude that the patient's fasting hyperinsulinemia and hypoglycemia were due to release of antibody-bound insulin.

The dose-response relationship between glucose and insulin concentration and utilization in skeletal muscle was examined in hindlimbs of overnight fasted normal male rats. The perfusion was by flow-through technique utilizing an artificial perfusate containing beef erythrocytes. Glucose disappearance correlated significantly with insulin concentration. Insulin effect was detected within 5 minutes. When arterial glucose was 10 mM, glucose disappearance during maximal insulin stimulation was fivefold greater than glucose disappearance in the absence of insulin. A half-maximal effect occurred at an insulin concentration of 411 U per ml. Arteriovenous difference of immunoreactive insulin during a single passage thorugh the hindlimb averaged 16.7% over the range of 50 to 10,000 U per ml. In the presence or absence of insulin, glucose disappearance was positively correlated with glucose concentration up to a glucose concentration range of 30 to 45 mM. In this range and above glucose uptake averaged twelvefold above that observed for 5 mM glucose. When insulin (500 muU/ml) was added at any glucose concentration, glucose disappearance was augmented. The data thus indicate that rat skeletal muscle is a major site of insulin metabolism. In addition to the effect of insulin on glucose uptake by the muscle cell, glucose mass action appears to be quantitatively equipotent.