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

Abstract

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.

A study of autologous free fat transplantation for augmentation of contour deformities of face: a study of 10 cases with review of literature

“…Resorption rates between 30% and 60% have been reported in the literature. 15,26 In our study, we observed that 90% of our patients have 40-50% of fat resorption, which is consistent with the above studies. Some authors have reported success rate with needle transplantation of fat from 0% to 100%.…”

Interactions of insulin and dexamethasone in the control of pyruvate kinase activity and glucose metabolism in sheep adipose tissue

“…Thus, when maintained in culture in the absence of exogenous hormones, pyruvate kinase activity declines in rat hepatocytes (Miyanaga et at., 1982(Miyanaga et at., , 1983Evans et al, 1984;Fleig et al, 1984), whereas it increases in adipose tissue from man (Smith et al, 1976) and cattle (Vernon et al, 1985). In addition, although glucocorticoids act in concert with insulin to maintain pyruvate kinase in rat hepatocytes maintained in culture (Feliu et al, 1982;Miyanaga et al, 1982Miyanaga et al, , 1983Evans et al, 1984;Fleig et al, 1984), we now show that they antagonize the effects of insulin on the enzyme activity in sheep adipose tissue.…”

“…When adipose tissue from sheep was maintained in tissue culture for 24 h, the rate of glucose utilization increased; this was accompanied by an increase in pyruvate kinase activity, whereas the activity of a number of other enzymes, including hexokinase and phosphofructokinase, did not change (Robertson et al, 1982). A selective increase in pyruvate kinase activity has also been observed when human adipose tissue is maintained in tissue culture (Smith et al, 1976). In contrast with its lack of effects during short-term incubations, insulin stimulated glucose uptake and also increased pyruvate kinase activity of bovine adipose tissue during incubations for 24 h or longer (Vernon et al, 1985).…”

Cytokine release from adipose tissue of nonobese individuals

“…The biopsies were cleaned of blood and tissue debris, dissected into 10-20 mg biopsies and incubated in medium 199 containing 4% human albumin, 25 mM HEPES, and 5.6 mM glucose according to previously reported procedures. 11,12 The biopsy procedure was approved by the Ethical Committee of Göteborg University. Biopsies were cultured with or without 20 ng/ml TNFa for 24 h.…”