Genetically inherited - and high fat diet induced - obesity differentially alters spermatogenesis in adult male rats.

Obesity is a multifactorial disorder with predominantly genetic and/or environmental causes. Thus, our aim was to delineate effects of genetically inherited and high fat diet induced obesity on fertility and spermatogenesis using two Wistar rat models: genetically inherited obese (GIO): WNIN/Ob and diet induced obese (DIO): High fat diet. The terminal body weights were similar in both GIO and DIO groups, but, there was a significant difference in metabolic and hormone profile between the two groups. Fertility assessment revealed significant decrease in the litter size due to increased pre- and post-implantation loss in DIO group, while GIO group were infertile due to lack of libido. Significant decrease in sperm counts were observed in GIO but not in DIO group despite body weights being comparable in both groups. To study the effect of obesity on spermatogenesis, enumeration of testicular cells based on ploidy and cell type specific expression markers demonstrated that both GIO and DIO affects mitosis process as spermatogonia and S phase population were increased. However, distinctive effects were observed on meiosis and spermiogenesis in both the groups. Our results indicate that the differential effects of GIO and DIO on fertility and spermatogenesis could be due to the significant difference in the white adipose tissue accumulation between the groups and not due to high body weights. The differential effects of obesity suggest that male obesity induced infertility observed in humans could be a combination of both genetic and environmental factors.