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Biomedical subjects

U Adamson

Publications and source records attributed to U Adamson.

98 records · Page 6Linked to original sources
PubMedDate not supplied

Pyridine nucleotides in glucose metabolism and diabetes: a review.

Nicotinamide adenine dinucleotide (NAD) and its derivatives NADH, NADP and NADPH have regulatory functions in the generation of triose phosphates and pyruvate from glucose. In many studies of the influence of the diabetic state on relationships between pyridine nucleotide and glucose metabolism, the focus has been on the sorbitol pathway. Less attention has been paid to other aspects of the role of pyridine nucleotides in pyruvate formation from glucose, in particular the effects of the NAD precursors nicotinamide and nicotinic acid on glucose metabolism. This paper reviews current knowledge of the involvement of pyridine nucleotides and their precursors in glucose catabolism in the normal and diabetic state. Reference is also made to the following three current hypotheses for mechanisms underlying diabetic microangiopathy: 1. Chronic glucose overutilization, caused by hyperglycemia, in tissues which lack insulin receptors and therefore are freely permeable to glucose. 2. Enhancement of sorbitol pathway activity with an ensuing decrease in the ratio of NAD/NADH. 3. Enhanced utilization of both glucose and pyridine nucleotides in formation of triose phosphates and pyruvate. Therapy with NAD precursors like nicotinamide might have corrective effects on these proposed biochemical aberrations, thereby retarding progression of microangiopathy.

Animals↗
PubMedDate not supplied

Previous exposure to glucose enhances insulin and suppresses glucagon responses to arginine in man.

UNLABELLED: The effects of previous exposure to glucose on the insulin, glucagon, growth hormone and blood glucose responses to subsequent stimulation with L-arginine were investigated in normal man. During control conditions (i.e., after 120 min of saline infusion), the i.v. administration of arginine enhanced the release of all three hormones and caused a small and transient rise in blood glucose. When arginine was preceded by i.v. glucose during 0-60 min, followed by a 'rest period' of 60-120 min, the insulin release induced by the amino acid was further enhanced, glucagon and GH release were unaffected and blood glucose depressed below control levels. When arginine was preceded by a small oral glucose load (0.5 g/kg) the initial insulin response to arginine was augmented, the initial glucagon response was slightly but significantly depressed and blood glucose lowered while the growth hormone response was unaffected. CONCLUSIONS: (1) a near-physiological intake of glucose increases insulin and depresses glucagon secretion evoked by amino acids resulting in increased glucose disposal; (2) the modifications of the insulin and glucagon responses constitute separate components in the feed-back regulation of glucose homeostasis.

Adult↗
PubMedDate not supplied

Patients with type 1 diabetes lack vasoconstrictor response in skin microcirculation during insulin-induced hypoglycemia.

Disturbed hemodynamic reactions to insulin-induced hypoglycemia have been documented in diabetic patients and considered related to hyperinsulinemia and impairment of autonomic nervous functions. In the present study we investigated the effect on skin microcirculation of insulin-induced hypoglycemia obtained during moderate hyperinsulinemia, in 7 men with type 1 diabetes and in 8 healthy age- and sex-matched controls. The patients had all normal cardiovascular reflexes as assessed by respiratory sinus arrhythmia and Valsalva ratio. The skin microcirculation of the left fourth finger nailfold was investigated by laser Doppler fluxmetry, and the skin temperature within the same area was measured by a thermistor. Hypoglycemia was induced by a constant insulin infusion of Actrapid Human, 0.034 U kg-1 h-1 during 120 min. Plasma adrenaline, noradrenaline and pancreatic polypeptide increased significantly in both groups during hypoglycemia and the insulin levels never exceeded 50 mUl-1. A close to identical arterial hypoglycemia was obtained in the two groups 60 min after onset of insulin infusion. During hypoglycemia the control subjects revealed a significant decrease in laser Doppler flux (p < 0.025), while it was unchanged in the diabetic patients. Simultaneously, the skin temperature decreased (p < 0.05) in the controls, but was unchanged in the diabetic patients. The present study indicates that type 1 diabetic patients with normal cardiovascular reflexes have an abolished vasoconstrictor response in skin microcirculation of fingers during insulin-induced hypoglycemia, despite the fact that neurogenic and neuroglucopenic symptoms developed in these patients during hypoglycemia.

Adult↗
PubMedDate not supplied

Variation of insulin absorption during subcutaneous and peritoneal infusion in insulin-dependent diabetic patients with unsatisfactory long-term glycaemic response to continuous subcutaneous insulin infusion.

The aim of present study was to analyse the reproducibility of plasma-free insulin profiles of subcutaneously (CSII) and intraperitoneally (CIPII) administered insulin in 6 C-peptide-negative, type 1, diabetic patients. The patients were selected for CIPII because of unsatisfactory, long-term, metabolic response to CSII. Plasma-free insulin was measured repeatedly, twice during subcutaneous infusion and twice during intraperitoneal infusion, for 4 hours, following a standard breakfast. In the CSII experiment, insulin was given as a meal-dose of 0.1 U per kg body weight, and in the CIPII experiment the meal-dose was 0.05 U per kg body weight. The dose-induced peak occurred earlier after the CIPII than with the CSII (60.0 +/- 8.0 vs 133.6 +/- 16.3 min). In conclusion, the intra-patient coefficient of variation (C.V.) of plasma-free-insulin profiles at 0-60 min and 0.240 min, as well as the peak time, were markedly lower for CIPII insulin than for CSII, indicating a more reproducible way of insulin administration with CIPII in this selected group of patients.

Absorption↗
PubMedDate not supplied

Mental alertness in response to hypoglycaemia in normal man: the effect of 12 hours and 72 hours of fasting.

To study the influence of hypoglycaemia and starvation on mental functions eight healthy male students age 25-34 years with an ideal body mass of 99.9% +/- 2.5% (mean +/- SEM) were recruited. Hypoglycaemia was induced in random order by an insulin-glucose clamp technique (insulin: 2.4 mU/kg/min + glucose at variable rate) keeping the venous blood glucose at 2.2 mmol/l both after an overnight fast and after 72 h fasting. Mental alertness was assessed by measuring the recognition time, moving time and total reaction time to a visual signal and by a verbal mental clearness test and a synonym learning test during normo- as well as hypoglycaemia. Hypoglycaemia prolonged the total reaction time (p less than 0.05) and the time required for the mental clearness test (p less than 0.05). Compared with a control study performed at normoglycaemia the learning effect of the synonym test was reduced by hypoglycaemia. Fasting, which resulted in a body weight reduction of 2.6 +/- 0.3 kg and ketonuria prolonged the total reaction time (p less than 0.005) by increasing the moving time but did not affect the mental clearness test. When hypoglycaemia was preceded by 72 h fasting it did not increase the total reaction time, nor did it modify the mental clearness test. Moreover, the learning effect of the synonym test was less impaired. In conclusion, mental alertness was reduced by moderate hypoglycaemia after an overnight fast while similar hypoglycaemia did not reduce mental alertness after prolonged fasting. This may illustrate a decrease of the glucose dependency of the central nervous system during prolonged fasting.

Adult↗