Glucose Tolerance Response Research Articles

Biochemical investigations of CAPD: Plasma levels of trace elements and amino acids and impaired glucose tolerance during the course of treatment

Investigations have been initiated into the effect of CAPD on the plasma concentrations of trace elements and amino acids, and in particular the response of patients to an oral glucose tolerance test (OGTT) during the course of treatment. Six months CAPD had no effect on the plasma concentrations of aluminium, fluoride, zinc and copper. Levels of aluminium and fluoride were above the normal range. Loss of amino acids in the dialysate correlated with their plasma concentrations. No changes were observed in the E/NE, Val/Gly or Tyr/Phe ratios during nine months treatment. Five CAPD patients demonstrated an impaired glucose tolerance in response to an OGTT after one month of treatment and a further deterioration occurred in the glucose tolerance of three patients after another six months CAPD. In a preliminary investigation with fructose substituted for glucose in the dialysate of one patient, an improvement in the OGTT and rate of insulin secretion was observed after 3 days dialysis against fructose.

Role of Liver in Glucose Homeostasis

The liver has a unique role in regulation of blood glucose in the postabsorptive state, after ingestion of glucose-containing meals, and in circumstances of glucopenia. It is soley responsible for the delivery of glucose to the bloodstream in the fasted state, thereby maintaining blood glucose concentration for the ongoing needs of body tissues, particularly the brain. An equally important role is played by the liver in the maintenance of normal glucose tolerance in response to carbohydrate ingestion. The liver is the principal site of glucose deposition after glucose feeding, while muscle and adipose tissue represent relatively minor sites of disposal of ingested glucose. In addition, the rise in glucose and insulin caused by glucose ingestion inhibits endogenous hepatic glucose production, which serves to minimize postprandial elevations in blood glucose. When blood glucose is reduced by small increments in circulating insulin, a rebound increase in glucose output from the liver is the initial or principal mechanism counteracting the fall in blood glucose concentration. Studies in juvenile-onset diabetes indicate that the liver is capable of altering its release of glucose in response to changes in blood glucose concentration when small, physiologic doses of insulin are infused. These findings may provide an explanation for the efficacy of preprogrammed insulin delivery systems in the treatment of diabetes.

Effects of Hypocalcemia and Theophylline on Glucose Tolerance and Insulin Release in Human Beings

A study was carried out to investigate the role of serum calcium in the regulation of insulin secretion and glucose tolerance in response to an oral glucose load on human subjects in hypocalcemie and normocalcemic states. The subjects for this study comprised three groups. Group 1 consisted of 15 patients with hypoparathy-roidism. They were subjected to an oral glucose load, and blood samples were taken at 0, 30, 60, 90, 120, 150, and 180 minutes to determine the blood glucose and serum insulin levels. These patients were treated with vitamin D2; after normocalcemic states were achieved the same study was repeated. This group of patients showed an abnormal glucose tolerance test and a markedly reduced insulin release during their hypocalcemie state; these abnormalities returned to normal after treatment. Group 2 consisted of six patients with hypoparathyroidism and one patient with vitamin-D-resistant rickets. These patients were subjected to an oral glucose load and a theophylline infusion (1 gm. in three hours) when they were hypocalcemie. The theophylline infusion increased the insulin release to the level of control subjects' in spite of hypocalcemia. Ten healthy volunteers served as a control group (group 3). Our results indicate that serum calcium has an important role in glucose utilization by insulin release. This is the first experiment to be performed on human beings and shows that theophylline has a stimulatory effect on insulin secretion in the presence of hypocalcemia.