Effect of nutrition on plasma lipid profile and mRNA levels of ovarian genes involved in steroid hormone synthesis in Hu sheep during luteal phase

Ovarian steroid hormones regulate follicular growth and atresia. This study aims to determine whether key ovarian sterol-regulatory genes are differentially expressed in Hu sheep under different short-term nutritional regimens. Estrus was synchronized using intravaginal progestagen sponges. The ewes were assigned randomly to 3 groups. On d 6 to 12 of their estrous cycle, the control (CON) group received a maintenance diet (1.0 x M), the supplemented (SUP) group received 1.5 x M, and the restricted (R) group received 0.5 x M. On d 7 to 12, blood samples were taken. The sheep were slaughtered at the end of the treatment, and their organs and ovaries were collected. The plasma concentrations of urea (P < 0.01), total cholesterol (P < 0.01), low-density lipoprotein cholesterol (P < 0.01), NEFA (P < 0.01), FSH (P < 0.05), and estradiol (P < 0.05) increased with decreasing dietary intake, whereas plasma triglyceride (P < 0.01) and triiodothyronine (T3) concentrations decreased (P < 0.05). The ewes in the R group had higher spleen weight and percentage of spleen to BW and lower liver and small intestine weights and percentage of liver/stomach to BW than the SUP group ewes (P < 0.05). Nutritional restriction decreased the cytochrome p450 (CYP17A1) and estrogen receptor 1 (ESR1) mRNA expression (P < 0.05) and increased the cytochrome p450 aromatase (CYP19A1) mRNA expression (P < 0.05) in follicles > 2.5 mm. Follicle size affected the mRNA expression of very low density lipoprotein receptor (VLDLR), estrogen receptor 2 (ESR2), FSH receptor (FSHR), CYP17A1, and CYP19A1 (P < 0.05). In conclusion, we suggest that a potential mechanism by which short-term negative energy balance inhibits follicular growth may involve responses to disrupted reproductive hormone concentrations and influenced the intrafollicular expression of CYP17A1, CYP19A1, and ESR1. This result may be due to increased plasma urea and lipid concentrations.