The female reproductive system provides several functions. These include ovulation, pregnancy and childbirth. The incidence of diabetes mellitus (DM) is increasing rapidly worldwide and it is associated with reproductive complications. Metformin is an oral hypoglycaemic drug used in the management of DM. The present study determined the effect of metformin on some reproductive function in alloxan-induced diabetic female Sprague-Dawley rats.
Rats were divided into four groups; (1) Untreated non-diabetic control (drug vehicle), (2) Untreated diabetic (drug vehicle), (3) Treated non-diabetic (metformin 100 mg/kg); and (4) Treated diabetic (metformin 100 mg/kg). Diabetes was induced with alloxan in the rats followed by a six-week treatment with metformin. The pattern of the oestrous cycle, followed by the ova count were observed and recorded. Plasma levels of oestradiol, progesterone, follicle stimulating hormone and luteinizing hormone were measured. Oxidative stress parameters and expression of oestrogen receptors (ERβ) in the ovaries were also determined.
Diabetes caused a significant increase (P<0.05) in the frequency of proestrus, oestrus, ova count, and expression of ERβ receptor. In the ovary, the levels of antioxidant enzymes - catalase and glutathione were reduced. However, after metformin treatment, expression of the receptor was increased. Metformin treatment also increase the ova count, frequency of the proestrus and oestrous phases, with a significant decrease in the diestrus phase in the treated diabetic group. Plasma level of reproductive hormones (oestrogen, LH and FSH) were unchanged after metformin treatment of diabetic rats except for progesterone that was returned to control level. In addition, there was an improved antioxidant status in diabetic rats following metformin treatment.
In conclusion, the result of the present study showed that metformin can improve on some reproductive function in the diabetic state; and so, more consideration should be given to its non-hypoglycaemic effects and its use in the management of reproductive complications associated with DM.