Lipolysis induced by alloxan in rat adipocytes is not inhibited by insulin.

Isolated rat adipocytes were incubated with adrenaline, adrenaline plus insulin, alloxan or alloxan plus insulin. Glycerol release was taken as a measure of lipolysis. It was observed that alloxan in the concentration of 3, 10 and 20 mmol/l intensifies lipolysis in adipocytes in the absence of adrenaline. Insulin (10(-6) mol/l) treatment of cells did not inhibit lipolysis caused by this compound, but significantly restricted lipolysis induced by adrenaline (10(-6) mol/l). It was also shown that alloxan in the concentration of 3 and 10 mmol/l intensified lipolysis stimulated by adrenaline (10(-6) mol/l). Addition of 20 mmol/l of alloxan strongly inhibited glycerol release in the presence of adrenaline. The results presented here clearly indicate that the action of alloxan concerns cells of the white adipose tissue.

Effect of some phytoestrogens on metabolism of rat adipocytes.

The aim of this experiment was to evaluate the direct effect of genistein, daidzein and zearalenone on basal and hormone-induced lipogenesis and lipolysis in isolated rat adipocytes. In lipogenesis, daidzein and zearalenone were used at concentrations of 0.01, 0.1 and 1 mmol x L(-1) and genistein at concentrations of 0.01, 0.3, 0.6 and 1 mmol x L(-1). In lipolysis, concentrations of tested compounds were 0.01, 0.1 and 1 mmol x L(-1). All tested compounds clearly inhibited basal and insulin (1 nmol x L(-1)) stimulated lipogenesis. Basal lipolysis was particularly enhanced by genistein and daidzein at its higher concentrations. The ability of zearalenone to potentiate of basal lipolysis was less marked. Epinephrine (1 micromol x L(-1))-stimulated lipolysis was inhibited by genistein at 1 mmol x L(-1). At a concentration of 0.1 mmol x L(-1) daidzein also augmented epinephrine-stimulated lipolysis and at its highest concentration exhibited an inhibitory effect, similar to genistein. Zearalenone reduced stimulated lipolysis, particularly at the highest concentration.

The effect of myo-inositol on ethanol-induced metabolic changes and insulin concentration in the rat.

Myo-inositol was found to possess several beneficial effects on the organism. The effect of myo-inositol on ethanol-induced metabolic changes and insulin concentration was investigated in growing rats. The increase in liver triglycerides induced by ethanol drinking (10% ethanol solution as the only drinking fluid for 10 days) was completely abolished by simultaneous treatment with myo-inositol (0. 1 g/100 g b.w., every day given intragastrically). The ethanol-evoked decrease in blood insulin and the increase in liver glycogen were also partially prevented by myo-inositol. Myo-inositol did not cause any undesirable metabolic changes in the rats. The results indicate that myo-inositol may be useful in the treatment of some metabolic consequences of alcohol drinking.

Alloxan in vivo does not only exert deleterious effects on pancreatic B cells.

The aim of the experiment was to investigate the mechanism of harmful alloxan action in vivo. 75 mg/kg b.w. of this diabetogenic agent were administered to fasting rats. Two minutes later the animals were decapitated. It was observed that alloxan caused a distinct rise in blood insulin and glucose levels with a concomitant drop of free fatty acids. The amount of sulfhydryl groups in the liver of alloxan-treated rats was decreased and glutathione peroxidase activity was substantially higher. These results indicate that some changes observed in alloxan-induced diabetes can not only be the consequence of B cells damage by alloxan but may also be the result of its direct influence on other tissues. It was also observed that glucose given 20 min before alloxan injection only partially protected against the deleterious effects of alloxan.

Genistein-induced changes in lipid metabolism of ovariectomized rats.

The effect of the isoflavone, genistein, on the lipid metabolism of ovariectomized rats was studied. Three types of experiments were performed. In the first one, the rats were fed diets supplemented with 0.01 or 0.1% of genistein for 14 days. In the second and third experiments, the direct effect of genistein on the liver and fat tissue were measured respectively by means of liver perfusion or incubation of isolated adipocytes with the isoflavone. Genistein in food significantly decreased blood serum and muscle triglyceride concentrations and increased the level of free fatty acids in serum. Serum free cholesterol was diminished and liver cholesterol was enhanced after genistein ingestion. When genistein acted directly on the liver during perfusion, a smaller incorporation of 14C-glucose into lipids was observed, and in parallel a greater output of free fatty acids into the medium was noticed. These changes were accompanied by diminution of the liver triglyceride contents. Genistein, acting on the adipocytes strongly depressed both basal and insulin-induced lipid synthesis, when glucose was used as a substrate. The effect of the isoflavone alone on the lipolysis in the adipocytes was negligible. However, it intensified lipolysis induced by epinephrine. The results obtained let us conclude that genistein in food can reduce the fattening processes in ovariectomized rats. This effect of genistein may be attributed, at least in part, to its direct influence on lipid metabolism in the liver and adipose tissue.