OBJECTIVETo observe the effects of metformin on epididymal sperm quality and antioxidant function of the testis in diet-induced obesity rats.

METHODSThirty-two male SD rats were fed on high-fat food for 8 weeks to make obesity models, and another 8 were included as normal controls. Twenty-four of the model rats were equally randomized into a model control group to be fed continuously on high-fat food, a metformin group to be fed on normal food with metformin, and a normal food group. By the end of the 12th week, all the rats were killed for the determination of Lee's index, the organ coefficients of the testis and epididymis, epididymal sperm concentration, sperm motility, grade a + b sperm percentage, and the contents of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) in the testicular homogenate.

RESULTSLee's index was significantly increased in the model control group (P < 0.01) as compared with the other three. Lee's index was markedly higher in the normal control than in the metformin group (P < 0.05). The organ coefficients of the testis and epididymis were significantly decreased in the model control group (P < 0.01) as compared with the other three. Sperm concentration and motility and the percentage of a + b sperm were significantly decreased in the model control in comparison with the other three groups (P < 0.05 or P < 0.01). Sperm concentration was remarkably higher in the normal control than in the metformin and normal food groups (P < 0.05). The content of SOD (U/mg prot) was significantly lower in the model control (90.92 +/- 4.06) than in the normal control and metformin groups (101.69 +/- 8.49 and 102.04 +/- 10.67) (P < 0.05); that of GSH-Px (U) obviously higher in the normal control (28.32 +/- 2.28) than in the model control (23.49 +/- 1.08, P < 0.01), the metformin (25.73 +/- 2.14, P < 0.05) and the normal food group (25.77 +/- 2.19, P < 0.05), but evidently lower in the model control than in the metformin group (P < 0.05); and that of MDA (nmol/mg prot) significantly higher in the model control (2.68 +/- 0.76) than in the normal control (1.84 +/- 0.31, P < 0.01), the metformin (1.88 +/- 0.33, P < 0.01), and the normal food group (2.14 +/- 0.35, P < 0.05).

CONCLUSIONMetformin therapy and improved diet could improve sperm quality and promote the antioxidant ability of the testis in diet-induced obesity rats.