Biochemical and Oxidative Changes in High Fat Diet/Streptozotocin-induced Diabetic Rats Treated with Metformin and the Polyherbal Diawell

Diabetes mellitus is an epidemic, with a huge disease burden on the patients. This has led to an increase in the use of herbal remedies and combination therapies to reduce this burden.

Aim: This study evaluates the biochemical and oxidative changes in type 2 diabetic rats, treated with metformin and the polyherbal drug diawell.

Methodology: A total of 35 male Wistar albino rats weighing between 120-220 g were used for this study. The rats were placed on high fat diet, and diabetes was induced by a single intraperitoneal injection of freshly prepared streptozotocin (STZ) (45 mg/kg body wt). Fasting plasma glucose (FPG) was determined using the glucose oxidase method. Fasting plasma insulin (FPI), total oxidant status (TOS), total antioxidant status (TAS) and superoxide dismutase (SOD) levels were quantitatively determined by a rat-specific sandwich-enzyme linked immunosorbent assay (ELISA) method. Insulin resistance (IR) was determined using the homeostatic model assessment for insulin resistance (HOMA-IR) method. Oxidative stress index (OSI) was determined by the ratio of TOS to TAS. Phytochemical analysis was also done on the herbal tablet.

Results: Mean FPG levels were significantly lower (p˂0.05) in all groups, except the group administered diawell, which was not significantly different (p>0.05), compared to the diabetic control. Mean FPG levels were significantly higher (p˂0.05) in the metformin group, diawell group, but showed no significant difference (p>0.05) in the combination group, compared to the negative control. HOMA-IR was significantly higher (p<0.05) in the diabetic control compared to the negative control and treatment groups. The metformin and diawell groups had significantly higher (p˂0.05) HOMA-IR values, whereas the combination (metformin + diawell) showed no significant difference (p>0.05) when compared to the negative control. TOS was significantly higher (p<0.05) in the diabetic control compared to the negative control and treatment groups. The metformin and diawell groups had significantly higher (p˂0.05) TOS values, whereas the combination (metformin + diawell) showed no significant difference (p>0.05) when compared to the negative control. There was significantly lower (p˂0.05) TAS levels in the diabetic and treatment groups, compared to the negative control. OSI values were significantly lower (p˂0.05) in all groups when compared to the diabetic control. Also, OSI values were significantly higher (p˂0.05) in the treatment groups compared to the negative control.

Conclusion: There was depletion of antioxidant parameters and an increase in oxidative stress in the diabetic rats. Administration of metformin and the polyherbal tablet diawell individually, were not effective in correcting the pathological and biochemical changes associated with diabetes. However, the combination treatment produced a better glycaemic response and attenuated the oxidant status in the rats. Antioxidant therapy should be incorporated in diabetes management, and anti-diabetic herbals properly evaluated.