The Effect of Starvation and Diabetes on Glycolytic Enzymes in Human Adipose Tissue

Galton, D. J.; Wilson, J. P. D.

doi:10.1042/cs0410545

Cited by 22 publications

(14 citation statements)

References 11 publications

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“…The present data are thus in harmony with previous work on human adipose tissue where only small changes in enzyme activities were noted in response to starvation-refeeding experiments [33], a glucose load [31] or to a variation in the feeding pattern [34]. These findings are in sharp contrast to the results with rat adipose tissue, where adaptation of key enzymes may easily be shown [35, 361 . With the exception of PK the enzyme activities were similar in freshly excised specimens and in the explants cultured for one week in vitro.…”

Section: Discussionsupporting

confidence: 91%

“…The fact that the increased cellular rate of metabolism is maintained when the short-term incubations are performed in the same glucose concentration suggests an adaptation of the cellular metabolism either due to an enzyme induction or to a change in the membrane permeability. Although the presence of insulin was found to increase the activity of G6PDH, PK and LDH the activity of HK and PFK, which presumably are the rate-limiting enzymes for the glycolysis [31], was not increased. The evidence presently at hand thus suggests that the stimulating long-term effect of insulin on glucose metabolism is mainly due to an effect on the translocation of the hexose across the membrane.…”

Section: Discussionmentioning

confidence: 81%

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Human adipose tissue in culture V. Studies on the metabolic effects of insulin

1976

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Summary.Specimens of human adipose tissue were cultured for one week with or without the addition of insulin. The basal as well as the noradrenaline-stimulated lipolysis were enhanced in the explants cultured with insulin, showing that the long-term effect of the hormone is lipolytic. However, an acute antilipolytic effect of insulin could be demonstrated in these explants in the subsequent short-term incubations. The basal rate of glucose incorporation into the lipids was enhanced in the explants cultured with insulin. When insulin was added in the short-term incubations these explants did not further respond to the hormone while this was the case with the explants cultured without insulin. Thus, it seems that prolonged exposure to insulin leads to a diminished acute effect of the hormone on glucose metabolism. However, the same explants responded to the antilipolytic effect showing that insulin was able to bind itself to the membrane. The activities of hexokinase (HK), glucose-6-phosphate dehydrogenase (G6PDH), pyruvate kinase (PK) and lactate dehydrogenase (LDH) were increased in large fat cells both in freshly excised tissue and in the cultured explants. However, the activity of phosphofructokinase (PFK) did not correlate with the cell size. The presence of insulin during the culture period enhanced the activities of G6PDH, PK, and LDH, while this was not found for HK or PFK. The data thus suggest that the metabolic capacity of human fat cells is enhanced by long-term exposure to insulin. Although enzyme induction could be shown for G6PDH, PK and LDH it seems unlikely that this is of importance for the increased rates of glucose metabolism in these explants since the rate-limiting enzymes, HK and PFK, were not increased. Most probably, *Part of these data were presented at the First International Congress on Obesity in London, England on 9-11 October, 1974. then, this stimulating effect of insulin is exerted on the membrane and the rate of glucose transport.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 81%

Human adipose tissue in culture V. Studies on the metabolic effects of insulin

1976

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“…In rodents it seems quite clear that insulin as well as an increase in the glucose concentration may enhance the cellular activity and de novo synthesis of several enzymes in adipocytes as well as other cells (36,37). In man, however, no clear evidence has yet been obtained for induced enzyme activities in fat cells in starvation-refeeding experiments (38), in response to a glucose load (39) or by a variation in the feeding pattern (40). However, further investigations are required to settle this problem in man and the presently employed tissue culture technique seems well suited for such studies.…”

Section: Discussionmentioning

confidence: 97%

Studies of Human Adipose Tissue in Culture III INFLUENCE OF INSULIN AND MEDIUM GLUCOSE CONCENTRATION ON CELLULAR METABOLISM

Smith¹

1974

J. Clin. Invest.

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A B S T R A C T Explants of human adipose tissue were maintained in culture for 1 wk in different glucose concentrations with or without the addition of insulin. After this period of time the explants were carefully washed and then subjected to short-term incubations in the same glucose concentration and in the absence of insulin. With this experimental design the influence of long-term exposure to insulin and different glucose concentrations on adipose tissue metabolism could be studied.The results of these studies show that an increase in the glucose concentration of the culture medium enhanced the basal as well as the catecholamine-stimulated lipolysis in the short-term incubations. The presence of insulin in the culture medium enhanced the lipolytic process as well. Analogous results were obtained with the cellular rate of glucose conversion to triglycerides in the short-term incubations. The stimulating effects of insulin and glucose were most pronounced in the larger adipose cells possibly due to their enlarged surface areas.The data suggest that the metabolism of adipose tissue as revealed by short-term studies may be profoundly influenced by the antecedent biochemical environment.

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“…Administration of subcutaneous insulin restored enzyme activities in this group of diabetics indicating that the adipose organ was unresponsive, or resistant to the action of prevailing levels of plasma insulin, but this could be overcome by additional insulin therapy [4].…”

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confidence: 99%

Insulin-independent diabetes: A defect in the activity of lipoprotein lipase in adipose tissue

1979

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Summary. The activity of lipoprotein lipase (E.C.3.1.1.3.) has been measured in adipose tissue from insulin-independent diabetics with hypertriglyceridaemia, non-diabetics with hypertriglyceridaemia and control patients, all of whom were obese.Although all groups showed an increase of plasma insulin after oral glucose, both the diabetic and nondiabetic hypertriglyceridaemics had impaired activities of lipoprotein lipase in adipose tissue compared to the obese normals (p<0.02, p<0.03, respectively). A course of insulin therapy (20 u.o.d.) for one week increased the activity of lipoprotein lipase extracted from adipose tissue, lowered plasma triglycerides and improved triglyceride clearance from plasma in a group of diabetics with hypertriglyceridaemia (mean plasma triglyceride 8.7 mmol/1). Our results suggest that a feature in the development of insulin resistance in adult diabetics may be a failure of maintenance of key intracellular enzyme activities involved in lipid metabolism.

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The Effect of Starvation and Diabetes on Glycolytic Enzymes in Human Adipose Tissue

Cited by 22 publications

References 11 publications

Human adipose tissue in culture V. Studies on the metabolic effects of insulin

Human adipose tissue in culture V. Studies on the metabolic effects of insulin

Studies of Human Adipose Tissue in Culture III INFLUENCE OF INSULIN AND MEDIUM GLUCOSE CONCENTRATION ON CELLULAR METABOLISM

Insulin-independent diabetes: A defect in the activity of lipoprotein lipase in adipose tissue

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