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620 : 2002 Vol 43(12) Singapore Med J

normal and experimental rats is summarised in Table II and III respectively. A marked increase in the frequency of cholesterol, free fatty acids,

triglycerides and phospholipids were observed in diabetic control rats. Treatment with CFEt significantly reduced the lipid levels.

Hepatic hexokinase and glucose-6-phosphatase The activities of carbohydrate enzymes are represented in Table IV. Activity of hexokinase in liver decreased markedly while the glucose-6-phosphatase activity increased significantly in diabetic control rats. Treatment with CFEt in diabetic rats increased the hexokinase activity and decreased the glucose- 6-phosphatase activity.

DISCUSSION Streptozotocin is well known for its selective pancreatic islet -cell cytotoxicity and has been extensively used to induce diabetes mellitus in animals. It interferes with cellular metabolic oxidative mechanisms(23). Intraperitoneal administration of streptozotocin (45 mg/kg) effectively induced diabetes in normal rats as reflected by glycosuria, hyperglycaemia, polyphagia, polydipsia and body

weight loss when compared with normal rats(24)

. In

our present study we have observed that an aqueous extract of Cassia auriculata flower can reverse these effects. The possible mechanism by which CFEt brings about its antihyperglycemic action may be by potentiation of pancreatic secretion of insulin from -cell of islets or due to enhanced transport of blood glucose to peripheral tissue. This was clearly evidenced by the increased level of insulin in diabetic rats treated with CFEt. In this context a number of other plants have also been reported to have antihyperglycemic and insulin-release stimulatory effect(25,26).

We have observed a decrease in total haemoglobin during diabetes and this may be due to the formation of glycosylated haemoglobin. Increase in the level of haemoglobin in animals given CFEt may be due to decreased level of blood glucose and glycosylated haemoglobin.

CFEt administration to streptozotocin dosed animals reversed the weight loss. The ability of CFEt to recover body weight loss seems to be due to its antihyperglycemic effect.

Excess of fatty acids in serum produced by the streptozotocin-induced diabetes promotes conversion of excess fatty acids into phospholipids and cholesterol in liver. These two substances along with excess triglycerides formed at the same time in liver may be discharged into blood in the form of

lipoproteins(27). The abnormal high concentration of serum lipids in the diabetic subject is due, mainly to increase in the mobilisation of free fatty acids from the peripheral fat depots, since insulin inhibits

the hormone sensitive lipase. Hypercholesterolemia and hypertriglyceridemia have been reported to occur in streptozotocin diabetic rats(28,29) and significant increase observed in our experiment was in accordance to these studies. The marked hyperlipidaemia that characterise the diabetic state may therefore, be regarded as a consequence of the uninhibited actions of lipolytic hormones on the fat depots(30).

The antihyperlipidaemic effect of CFEt may be due to the down regulation of NADPH and NADH, a cofactor in the fat metabolism. Higher activity of glucose-6-phosphatase provides H+ which binds with NADP+ in the form of NADPH and is helpful in the synthesis of fats from carbohydrates. When glycolysis slows down because of cellular activity, the pentose phosphate pathway still remain active in liver to breakdown glucose that continuously provides NADPH which converts acetyl radicals into long fatty acid chains. CFEt may be capable of oxidising NADPH. Enhanced hexokinase activity in CFEt treated rats suggests greater uptake of glucose from blood by the liver cells.

Activities of enzymes suggest that enhanced lipid metabolism during diabetes is shifted towards carbohydrate metabolism and it enhances the utilisation of glucose at the peripheral sites. One of the possible actions of CFEt may be due to its inhibition of endogenous synthesis of lipids.

Metabolic aberration in streptozotocin diabetic rats suggest a high turnover of triglycerides and phospholipids. CFEt may antagonise the metabolic aberration and thereby restore the normal metabolism by tilting the balance from high lipids to high carbohydrate turnover. Alteration of fatty acid composition by increased lipid levels contribute to lowering the resistance of tissues and higher rate of oxidative stress. Decreased activity of glucose- 6-phosphatase through pentose phosphate shunt results in high reduced glutathione to oxidised glutathione ratio (GSH/GSSG)(27), which is coupled

with conversion of NADPH to NADP. CFEt may produce high NADP+ which results in down regulation of lipogenesis and lower risk of the tissues for oxidative stress and high resistance for diabetes.

It can be concluded from the data that CFEt significantly reduces the levels of serum and tissue lipids, which are actively raised in streptozotocin diabetes rats. CFEt has beneficial effect on plasma insulin and hexokinase activity. Moreover

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