Effects of hyperglycemia on memory and hormone levels in dementia of the Alzheimer type: a longitudinal study.

The effect of hyperglycemia on hormone levels, metabolite levels, and memory performance was examined in 22 subjects with very mild and mild probable dementia of the Alzheimer type (DAT) and in 12 normal elderly adults. Subjects were tested in 3 plasma glucose conditions (fasting baseline, 175 mg/dl, and 225 mg/dl) at initial and 18-month follow-up sessions. Initially, adults with very mild DAT showed memory facilitation and elevations in plasma insulin in the 225-mg/dl glucose condition relative to baseline. At follow-up, very mild DAT patients whose dementia had progressed showed significant decreases in insulin and hyperglycemic memory facilitation. Changes in basal insulin and cortisol levels over time were correlated with memory changes for DAT subjects. These results suggest that glucoregulatory abnormalities may contribute to the pathophysiology of DAT.

Glycemic actions of alanine and terbutaline in IDDM.

OBJECTIVE: To test the hypothesis that the amino acid Ala and the beta 2-adrenergic agonist terbutaline raise plasma glucose concentrations substantially, and do so through different mechanisms, in IDDM patients. RESEARCH DESIGN AND METHODS: We administered these (Ala: 20 and 40 g, orally; terbutaline: 2.5 and 5.0 mg orally and 0.25 mg subcutaneously) and placebos in random sequence to 6 nondiabetic subjects and 6 insulin-infused, initially euglycemic IDDM patients, each studied on six different occasions. Inhaled terbutaline, 0.4 mg, was also tested on a seventh occasion in IDDM patients. RESULTS: Ala administration raised plasma glucagon (P = 0.0219), C-peptide (P = 0.0014), and insulin (P = 0.0094), with no significant change in plasma glucose, in nondiabetic subjects. In patients with IDDM it raised glucagon (P = 0.0001), but not C-peptide or insulin, and plasma glucose rose to 8.3 +/- 0.3 (Ala 20 g, P = 0.0006) and 10.0 +/- 1.0 mM (Ala 40 g, P = 0.0094). Catecholamine levels were unchanged. Terbutaline ingestion raised plasma glucose minimally (e.g., to 6.3 +/- 0.3 mM, P = 0.0133) in nondiabetic subjects but substantially, to 10.2 +/- 1.0 (terbutaline 2.5 mg, P = 0.0078) and 14.0 +/- 0.6 mM (terbutaline 5.0 mg, P = 0.0001), in IDDM patients; subcutaneous terbutaline raised plasma glucose (to a peak of 10.3 +/- 0.7 mM, P = 0.0017) with an initial effect within 10 min, but inhaled terbutaline did so more slowly. In addition to its direct glycemic actions, terbutaline stimulated sympathetic neural norepinephrine release (P = 0.0151) and increased nonesterified fatty acid levels (P = 0.0104), potential indirect glycemic actions. Glucagon levels were unchanged; insulin levels increased in the nondiabetic subjects. CONCLUSIONS: These data demonstrate substantial glycemic responses to Ala and terbutaline, through different mechanisms, in IDDM patients. Thus, Ala and terbutaline represent potential new approaches to the treatment, and perhaps the prevention, of iatrogenic hypoglycemia in IDDM.

Alanine and terbutaline in treatment of hypoglycemia in IDDM.

OBJECTIVE: To test the hypothesis that, in contrast to administration of glucose or glucagon, administration of the amino acid Ala or of the beta 2-adrenergic agonist terbutaline produces sustained glucose recovery from hypoglycemia. RESEARCH DESIGN AND METHODS: We developed a model of clinical hypoglycemia using subcutaneous injection of insulin (0.15 U/kg) in patients with IDDM. In comparison with nondiabetic subjects, patients with IDDM exhibited reduced glucagon (P = 0.0001), epinephrine (P = 0.0060), and pancreatic polypeptide (P = 0.0001) responses to hypoglycemia. In addition to placebos, the following were administered during hypoglycemia (2 h after insulin injection) in IDDM patients: oral glucose, 10 and 20 g; subcutaneous glucagon, 1.0 mg; oral Ala, 40 g; oral terbutaline, 5.0 mg; and subcutaneous terbutaline, 0.25 mg. RESULTS: Glucose (10 and 20 g) and glucagon raised plasma glucose (P = 0.0163, 0.0060, and 0.0001, respectively) from 3.0-3.3 mM to peaks of 5.4 +/- 0.4, 6.8 +/- 0.7, and 11.8 +/- 0.8 mM within 30, 45, and 60 min, respectively, but the responses were transient. Oral Ala raised glucose levels (P = 0.0401) to 4.0 +/- 0.4 mM within 30 min; glucose levels then rose gradually to a 6-h value of only 7.1 +/- 0.9 mM. Oral terbutaline raised glucose levels (P = 0.0294) to 4.3 +/- 0.3 mM within 30 min; glucose levels then rose substantially. In contrast, subcutaneous terbutaline raised glucose levels (P = 0.0249) to 3.7 +/- 0.1 mM within 15 min; the levels plateaued at 5.0 mM from approximately 60-150 min and then paralleled the placebo curve. CONCLUSIONS: Ala and terbutaline produce sustained glucose recovery from hypoglycemia in IDDM and are therefore potentially useful agents for the treatment of mild or moderate iatrogenic hypoglycemia, or the prevention of iatrogenic hypoglycemia, when food intake is not anticipated over the following several hours.

Eccentric exercise induces transient insulin resistance in healthy individuals.

Euglycemic-hyperinsulinemic clamps were performed on six healthy untrained individuals to determine whether exercise that induces muscle damage also results in insulin resistance. Clamps were performed 48 h after bouts of predominantly 1) eccentric exercise [30 min, downhill running, -17% grade, 60 +/- 2% maximal O2 consumption (VO2max)], 2) concentric exercise (30 min, cycle ergometry, 60 +/- 2% VO2max), or 3) without prior exercise. During the clamps, euglycemia was maintained at 90 mg/dl while insulin was infused at 30 mU.m-2.min-1 for 120 min. Hepatic glucose output (HGO) was determined using [6,6-2H]glucose. Eccentric exercise caused marked muscle soreness and significantly elevated creatine kinase levels (273 +/- 73, 92 +/- 27, 87 +/- 25 IU/l for the eccentric, concentric, and control conditions, respectively) 48 h after exercise. Insulin-mediated glucose disposal rate was significantly impaired (P less than 0.05) during the clamp performed after eccentric exercise (3.47 +/- 0.51 mg.kg-1.min-1) compared with the clamps performed after concentric exercise (5.55 +/- 0.94 mg.kg-1.min-1) or control conditions (5.48 +/- 1.0 mg.kg-1.min-1). HGO was not significantly different among conditions (0.77 +/- 0.26, 0.65 +/- 0.27, and 0.66 +/- 0.64 mg.kg-1.min-1 for the eccentric, concentric, and control clamps, respectively). The insulin resistance observed after eccentric exercise could not be attributed to altered plasma cortisol, glucagon, or catecholamine concentrations. Likewise, no differences were observed in serum free fatty acids, glycerol, lactate, beta-hydroxybutyrate, or alanine. These results show that exercise that results in muscle damage, as reflected in muscle soreness and enzyme leakage, is followed by a period of insulin resistance.