Potential Interactions between Cinnamon and Metformin Treatment in Diabetic Rats

Lujain A. Ashoor and Safaa Y. Qusti*

Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah - 21551 Saudi Arabia.

ABSTRACT: Cinnamon has a beneficial role in improving the symptoms of type 2 diabetes. Concurrent use of cinnamon and the antidiabetic drug “metformin” could have undesirable effects on glucose metabolism. Therefore, the present study investigated the proposed undesirable effect of cinnamon through the interaction between two doses of cinnamon extract and metformin through studying the biochemical parameters related to diabetic syndrome in rats. Ninety male Wistar rats were divided into nine groups. Cinnamon extracts were administered in doses of zero, 300 (low), 600 (high) mg/kg/day to three groups of each, normal, diabetic and metformin-diabetic rats. In normal animals, the high dose of cinnamon extract was able to decrease serum glucose level by 13%, while the two doses of cinnamon did not effect the insulin level. The greatest level of hypoglycemia and the lowest level of serum insulin were obtained with metformin-diabetic rats which received the high dose of cinnamon. Moreover, it is likely that cinnamon extract had similar effects as metformin in lowering the serum lipids of diabetic animals. The combination of metformin with cinnamon extract increased the serum level of HDL-Cholesterol significantly, more than metformin alone and the two doses of cinnamon decreased serum total cholesterol and LDL-C levels. In diabetic rats, the two doses of cinnamon had almost similar reducing effects in ALT, AST and LDH as metformin while the greatest activities were observed with diabetic and metformin-diabetic rats which received high dose of cinnamon. Cinnamon interaction with metformin in diabetic rats might induce DNA damage in hepatocytes, with greater damage being detected at high dose of cinnamon than the low dose. This result could be due to increase in oxidative stress together with poor glycemic control. In conclusion, this study would support the beneficial effect of cinnamon in diabetic rats. While in metformin-diabetic rats, cinnamon would have a synergistic activity compared to the metformin alone which leads to adverse effects on glucose metabolism.

KEYWORDS: Cinnamon; metformin; interactions; type 2 diabetes

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