Showing papers by "K. G. M. M. Alberti published in 1988"

Blood Glucose, Lactate, Pyruvate, Glycerol, 3-Hydroxybutyrate and Acetoacetate Measurements in Man Using a Centrifugal Analyser with a Fluorimetric Attachment

Abstract: Summary: Methods are described for the analysis of glucose, lactate, pyruvate, alanine, glycerol, 3-hydroxybutyrate and acetoacetate in perchloric acid extracts of human blood, using the Cobas Bio centrifugal analyser fitted with a fluorimetric attachment. Intra-assay and inter-assay coefficients of variation ranged from 1.9 to 7.9% and from 1.0 to 7.2% respectively. Correlation coefficients ranged from 0.96 to 0.99 against established continuous-flow and manual spectrophotometric methods. All seven metabolites can be measured using a single perchloric acid extract of 20 μΐ of blood. The versatility of the assays is such that as little as 100 pmol pyruvate, 3-hydroxybutyrate or as much as 15 nmol glucose can be measured in the same 20 μΐ extract. In relation to budgetary control the centrifugal analyser methods are quicker, less labour intensive, and more economical with both small and large numbers of samples.

Glucagon responses to intravenous arginine and oral glucose in insulin-dependent diabetic patients during six months conventional or continuous subcutaneous insulin infusion

Abstract: To elucidate the impact of subcutaneous insulin infusion (CSII) treatment on the glucagon response to intravenous (IV) arginine and to oral glucose a 6-month prospective randomized study in insulin-dependent diabetics was carried out. The effects were investigated of CSII (7 patients) and conventional insulin treatment (UCT) (9 patients) on the changes in glucagon, growth hormone, glucose, lactate, glycerol, 3-hydroxybutyrate, and alanine to IV arginine and to oral glucose in insulin-dependent diabetics who were made euglycemic and isoinsulinemic using the artifical pancreas (Biostator, Miles, Elkhart, IN). HbA 1c was significantly lower in the group treated by CSII. Despite the improved glycemic control no significant change in the responses of A-cell secretion to arginine or glucose challenges was found. In addition, there were no significant differences in hormone or metabolite values between the two groups at entry to the study or after 6 months of either therapy. Thus, normalization of the A-cell sensitivity to glucose in insulin-dependent diabetic subjects requires further amelioration of the intermediary metabolism than can be achieved with insulin pump treatment.

Decreased insulin sensitivity and muscle enzyme activity in elderly subjects.

Abstract: Skeletal muscle glycogen deposition, and the activation of muscle glycogen synthase and pyruvate dehydrogenase during a hyerinsulinaemic euglycaemic clamp have been measured in six young and six elderly males matched for body mass index, physical activity and diet. Clamp glucose requirement (insulin, 0·1 U kg-1 h-1) was significantly lower in the older subjects (8·0 ± 0·4 mg kg-1 min-1) than in younger subjects (10·5 ± 0·6 mg kg-1 min-1, P < 0·02). Although the older subjects had a 6·5% decrease in lean body mass, clamp glucose requirement expressed per unit of lean body mass was also significantly decreased in the older subjects (10·2 ± 0·5 vs. 12·4 ± 0·6 mg kg-1 min-1, P < 0·05). The increase in muscle glycogen with the clamp was decreased by 33% in the older subjects (elderly: 13·1 ± 1·3 mg g-1 protein, young: 19·6 ± 2·2 mg g-1 protein; P < 0·05), and was strongly correlated with clamp glucose requirement (r= 0·72, P < 0·01). Glucose-6-phosphate independent glycogen synthase activity increased significantly between fasting and the end of the clamps in both groups (P < 0·001), but was lower at the end of the clamp in the older subjects (P < 0·05). Glycogen synthase activity at the end of the clamp correlated with both clamp glucose requirement (r= 0·83, P < 0·01) and muscle glycogen deposition (r= 0·73, P < 0·01). Skeletal muscle pyruvate dehydrogenase activity increased significantly between fasting and end of clamp in the young subjects (P < 0·05) but not in the elderly males. Pyruvate dehydrogenase activity at the end of the clamp, however, did not differ between the two groups and was not related to clamp glucose requirement. Thus the impaired glucose handling of the elderly may be related to decreased insulin action on muscle and muscle enzymes.

The effect of high glucose and high insulin concentrations on pentose phosphate shunt enzymes and malic enzyme in cultured human endothelial cells.

Abstract: The influence of glucose and insulin on pentose phosphate shunt enzymes and malic enzyme activity in cultured human endothelial cells has been investigated. Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and malic enzyme were present in endothelial cells. Enzyme activities were not altered either by 20 mM glucose or 10(-8) M insulin after 3, 6 and 12 hour incubations respectively. Neither increased glucose nor increased insulin alter the activity of the pentose phosphate shunt. As a consequence fatty acid and cholesterol synthesis in the endothelial cell is unlikely to be altered in the presence of increased glucose or increased insulin.