Abstract
The influence of isoflavone - genistein on some hormones and metabolic parameters in sexually immature, female rats was studied. Rats (34 days old) were divided into three groups: control (receiving no genistein), receiving 1 or 5 mg of genistein/kg body weight (BW). The tested compound was administered intragastrically, i.e. by using a cannula inserted via oesophagus into the stomach once a day for seven days. In genistein-treated rats body weight gains were unchanged in comparison to control animals. Genistein at a higher dose caused a significant (P≤0.01) decrease in blood insulin concentrations. Simultaneously, in animals treated with this phytoestrogen (5 mg/kg BW) blood leptin was significantly reduced (P≤0.01). This latter effect was probably due to the direct inhibitory influence of genistein on leptin secretion from adipocytes. Thyrotropin, total and free triiodothyronine and thyroxine were not changed by the tested phytoestrogen. Several metabolic parameters determined in blood (glucose, triglycerides, free fatty acids, cholesterol), liver (glycogen, triglycerides and cholesterol) and muscle (glycogen and cholesterol) were also unaltered in rats receiving genistein. However, genistein administered at a higher dose evoked a significant reduction (P≤0.01) of muscle triglyceride stores. Results obtained in the experiment indicate that genistein may affect insulin and leptin - hormones responsible for metabolism, energy expenditure and food intake in young, sexually immature female rats. The muscle triglicerydes are the only metabolic parameter affected by the compound in these rats.
Highlights
Genistein is a plant-derived, isoflavone compound which belongs to the group called phytoestrogens
In the performed experiment it was demonstrated that genistein at the dose 5 mg/kg body weight administered for seven days significantly decreased blood insulin concentration in the immature female rats
These results imply that the influence of genistein on insulin concentration is sexindependent and may occur in both very young and older rats
Summary
Genistein is a plant-derived, isoflavone compound which belongs to the group called phytoestrogens. It is present predominantly in leguminous plants, and in other vegetables, fruits and whole grains consumed by animals and humans. Genistein may exist in plants as a bioactive aglycone - genistein or - more frequently - as an inactive glycoside - genistin (Price and Fenwick, 1985). After absorption in the small intestine genistein is conjugated with glucuronic acid and sulphate by hepatic phase II enzymes. These conjugates are excreted by urine and bile, undergo enterohepatic circulation and can be deconjugated once again by gut bacteria and reabsorbed (Xu et al, 1995)
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