Obesity impairs reproductive functions through multiple mechanisms, possibly through disruption of ovarian function. We hypothesized that increased adiposity will lead to a proinflammatory gene signature and upregulation of Egr-1 protein in ovaries from obese (OB; n = 7) compared with lean (LN; n = 10) female Sprague-Dawley rats during the peri-implantation period at 4.5 days postcoitus (dpc). Obesity was induced by overfeeding (40% excess calories for 28 days) via total enteral nutrition prior to mating. OB dams had higher body weight (P < 0.001), greater fat mass (P < 0.001), and reduced lean mass (P < 0.05) and developed metabolic dysfunction with elevated serum lipids, insulin, leptin, and CCL2 (P < 0.05) compared with LN dams. Microarray analyses identified 284 differentially expressed genes between ovaries from LN vs. OB dams (±1.3 fold, P < 0.05). RT-qPCR confirmed a decrease in expression of glucose transporters GLUT4 and GLUT9 and elevation of proinflammatory genes, including CCL2, CXCL10, CXCL11, CCR2, CXCR1, and TNFα in ovaries from OB compared with LN (P < 0.05). Protein levels of PI3K and phosphorylated Akt were significantly decreased (P < 0.05), whereas nuclear levels of Egr-1 (P < 0.05) were increased in OB compared with LN ovaries. Moreover, Egr-1 was localized to granulosa cells, with the highest expression in cumulus cells of preovulatory follicles. mRNA expression of VCAN, AURKB, and PLAT (P < 0.05) correlated with %visceral fat weight (r = 0.51, -0.77, and -0.57, respectively, P ≤ 0.05), suggesting alterations in ovarian function with obesity. In summary, maternal obesity led to an upregulation of inflammatory genes and Egr-1 expression in peri-implantation ovarian tissue and a concurrent downregulation of GLUTs and Akt and PI3K protein levels.
Keywords: early growth response factor 1; gene expression; inflammation; obesity; reproduction.