The present study was designed to evaluate the effects of
tyrosol, a phenolic compound, on the activities of key
enzymes of carbohydrate metabolism in the control and
streptozotocin-induced diabetic rats.
Diabetes mellitus was induced in rats by a single
intraperitoneal injection of
streptozotocin (40 mg/kg
body weight). Experimental rats were administered
tyrosol 1 ml intra gastrically at the doses of 5, 10 and 20mg/kg
body weight and
glibenclamide 1 ml at a dose of 600 μg/kg
body weight once a day for 45 days. At the end of the experimental period, diabetic control rats exhibited significant (p<0.05) increase in plasma
glucose,
glycosylated hemoglobin with significant (p<0.05) decrease in plasma
insulin, total
hemoglobin and
body weight. The activities of key
enzymes of carbohydrate metabolism such as
phosphoenolpyruvate carboxykinase,
fructose-1,6-bisphosphatase and
glucose-6-phosphatase were significantly (p<0.05) increased and the activities of
hexokinase and
glucose-6-phosphate dehydrogenase were significantly (p<0.05) decreased in the liver and kidney of diabetic control rats. Further,
antioxidants were lowered in diabetic control rats. A significant (p<0.05) decline in
glycogen level in the liver and muscle and
glycogen synthase activity in the liver and a significant (p<0.05) increase in the activity of
liver glycogen phosphorylase were observed in diabetic control rats compared to normal control rats.
Oral administration of
tyrosol to diabetic rats reversed all the above mentioned biochemical parameters to near normal in a dose dependent manner.
Tyrosol at a dose of 20mg/kg
body weight showed the highest significant effect than the other two doses. Immunohistochemical staining of pancreas revealed that
tyrosol treated diabetic rats showed increased
insulin immunoreactive β-cells, which confirmed the biochemical findings. The observed results were compared with
glibenclamide, a standard oral
hypoglycemic drug. The results of the present study suggest that
tyrosol decreases
hyperglycemia, by its
antioxidant effect.