Interrelationships of nutrition, metabolic hormones and reproduction of female sheep

摘要

Regulation of ovarian activity is an integrated process involving extra-ovarian signals and intrafollicular factors. Positive effects of nutrition on reproduction have been described in sheep, particularly as related to ovulation rate. However, interactions between nutrition, metabolic hormones and reproduction have not been sufficiently described. This paper addresses the response of the reproductive axis to nutritional changes and metabolic status in the light of recent studies. The interaction between nutrition and reproduction has important implications for the reproductive development of sheep. Nutrition stimulates folliculogenesis and can also affect mRNA expression of the ovarian IGF system to regulate follicle sensitivity and response to gonadotropins. These changes are associated with intrafollicular alterations of glucose-insulin, IGF, and leptin metabolic system. Intrafollicular activation of these systems allows to suppress follicle estradiol production. Metabolic hormones also regulate steroidogenesis: glucose and insulin infusions decrease it, while IGF-I infusion increases it. Leptin antagonizes the stimulating effect of insulin on steroidogenesis of theca cells, allowing decreased estradiol secretion. In conclusion, these data suggest that local ovarian nutrients play a role in folliculogenesis.