Role of pectin from cucumber (Cucumis sativus) in modulation of protein kinase C activity and regulation of glycogen metabolism in rats.

The regulatory role of protein kinase C (PKC) in glycogen metabolism in pectin fed rats was investigated. Administration of pectin (5 g/kg body wt/day) from cucumber (Cucumis sativius L.) led to inhibitory effects on PKC activity in the liver of rats. In the brain and pancreas, PKC activity was significantly higher in pectin-treated rats as compared to the control group. Level of blood glucose was significantly lowered and the level of glycogen in the liver was significantly increased in pectin-administered rats. Glycogen synthase activity was enhanced, while glycogen phosphorylase enzyme showed inhibition in pectin-treated rats. Results indicated that pectin administration might have caused an increase in the secretion of the insulin, which, in turn, had a stimulatory effect on the PKC activity in the pancreas. The decreased PKC activity in the liver and increased PKC activity in the brain and pancreas on pectin administration indicated enhanced glycogenesis and reduced glycogenolysis.

Alterations in lipids & lipid peroxidation in rats fed with flavonoid rich fraction of banana (Musa paradisiaca) from high background radiation area.

BACKGROUND & OBJECTIVE: A group of villages in Kollam district of Kerala, southern part of India are exposed to a higher dose of natural radiation than global average. Yet no adverse health effects have been found in humans, animals and plants in these areas. The present study was carried out to understand whether radiation affects the quantity and quality of flavonoids in plants grown in this area of high radiation, and to assess the effect of feeding flavonoid rich fraction (FRF) of the two varieties of banana to rats on their biochemical parameters like lipids, lipid peroxides and antioxidant enzyme levels. METHODS: A total of 42 albino rats were equally divided into 7 groups. Rats fed laboratory diet alone were grouped under group I (normal control). Groups II and V received flavonoid rich fraction (FRF) from the fruits of two varieties of Musa paradisiaca, Palayamkodan and Rasakadali respectively from normal background radiation area (Veli) and treated as controls. Rats of groups III and IV received FRF of Palayamkodan from high background radiation areas (HBRAs) - Neendakara and Karunagappally respectively while groups VI and VII received FRF of Rasakadali from HBRAs. At the end of the experimental period of 45 days, lipids, lipid peroxides and antioxidant enzymes from liver, heart and kidney were analyzed. RESULTS: FRF of Palayamkodan and Rasakadali varieties showed significant hypolipidaemic and antioxidant activities. But these activities were found to be lowered in plants grown in HBRAs, particularly in Karunagappally area. Of the two, Palayamkodan variety was more effective in reducing lipids and lipid peroxides. MDA and hydroperoxides were significantly diminished in rats given FRF of banana from Veli (control area) only. FRF from plants grown in HBRAs exerted inhibition in the activities of antioxidant enzymes in the liver of rats and this inhibitory effect was maximum in rats fed FRF from Karunagappally. INTERPRETATION & CONCLUSION: Banana grown in HBRAs is of lower quality with less efficient antioxidant system. Palayamkodan was superior with its effect on hypolipidaemic and antioxidant activities. High background radiation seems to have no enhancing effect on the radioprotective action of flavonoids of banana and thereby to those consuming these fruits.

Effect of catechin on intestinal lipid metabolism.

On analysing the effect of catechin on intestinal lipid metabolism, an increase in the concentration of cholesterol in the duodenum and jejunum was observed along with an increase in the HMGCoA reductase activity. In the in vitro experiments also it was found that cholesterol and free fatty acid (FFA) levels were increased in these two regions. Binding of catechin with cholesterol in the lumen, reduces the availability of cholesterol for absorption which may in turn stimulate cholesterol biosynthesis and a rise in the HMGCoA reductase activity. These alterations produced by catechin may also be related to the degradation of cholesterol to bile acids, as endogenous cholesterol is the preferred substrate for bile acid synthesis.

Effect of catechin on carbohydrate metabolism.

Effect of varying concentrations of catechin on blood glucose levels was examined in male rats. Catechin exerted maximum hypoglycemic action at a dose of 10 mg/kg BW/day. Above this dose, the activity decreased gradually and blood sugar returned to almost normal levels at a concentration of 100 mg/kg BW/day. At optimum dose of catechin there was increase in the hepatic glycogen levels. Incorporation of [14C] glucose into glycogen in vitro was also increased. Glycogen synthase activity was found increased significantly whereas glycogen phosphorylase showed a decrease showing that hypoglycemic effect of catechin is due to increased glycogenesis and decreased glycogenolysis.