High-Fat Diet-Induced Obesity Primes Impaired Fatty Acid β-Oxidation and Consequent Ovarian Dysfunction During Early Pregnancy

Abstract

Background: Obesity is associated with many adverse effects on female fertility. Obese women are more likely to have ovulatory dysfunction due to dysregulation of the hypothalamic-pituitary-ovarian axis. However, ovarian function in obese women during early pregnancy still needs further assessment. Methods: Obesity was induced in C57BL6/J mice using high-fat diets (HFD) for 12 weeks; In vitro high-fat model was established with KGN cells treated with Oleate acid and Palmitic acid. Ovarian morphology of obese mice in early pregnancy was assessed by Hematoxylin and Eosin staining and its function was assessed using ELISA, Western blotting and Immunohistochemistry. The Oil Red O staining and Transmission electron microscopy were used to detect fatty acid accumulation and specific markers relating to ovarian functional mechanism were assessed by Real time PCR, Western blotting, Lactate detection, ATP detection, Biochemical analyses and ELISA.Results: The results of this study showed that during early pregnancy, the number of corpus luteum, serum estradiol and progesterone levels, and the expression of genes CYP19A1, CYP11A1 and StAR, which are related to steroid biosynthesis, were significantly increased in HFD female mice. HFD-fed mice also showed a significant increase in ovarian lipid accumulation on day 7 of pregnancy. Genes involved in fatty acid synthesis (Acsl4 and Elovl5) and fatty acid uptake and transport (Slc27a4), together with the β-oxidation rate-limiting enzyme (Cpt1a) were significantly upregulated in HFD-fed mice. Specifically, there was abnormal elevation of ATP level and aberrant expression of tricarboxylic acid cycle (TCA) and electron transport chain related genes in the ovary of HFD pregnant mice. Treatment of KGN cells with etomoxir targeting β-oxidation of fatty acid, showed decrease tricarboxylic acid cycle and electron transport chain. The elevated ATP level and the increased estradiol and progesterone levels were reversed. Conclusions: This study indicated that during early pregnancy, high-fat diet and induced-obesity increased fatty acid β-oxidation, which in turn increase the tricarboxylic acid cycle and the electron transport chain, and consequently increases ATP production and ovarian dysfunction.