Leptin Receptor Mediates Bmal1 Regulation of Estrogen Synthesis in Granulosa Cells

Chronobiology affects female fertility in mammals. Lepr is required for leptin regulation of female reproduction. The presence of E-box elements in the Lepr promoter that are recognized and bound by clock genes to initiate gene transcription suggested that circadian systems might regulate fertility through Lepr. However, it is unclear whether Bmal1, a key oscillator controlling other clock genes, is involved in leptin regulation in hormone synthesis through Lepr. In this study, serum estradiol (E₂) concentration and the expressions of Bmal1, Lepr, Cyp19a1, and Cyp11a1 genes were found to display well-synchronized circadian rhythms. Knockdown of Bmal1 significantly reduced expression levels of Lepr, Fshr, and Cyp19a1 genes; protein production of Bmal1, Lepr, and Cyp19a1; and the E₂ concentration in granulosa cells. Knockdown of Lepr reduced the expression levels of Cyp19a1 and Cyp11a1 genes and Cyp19a1 protein, and also reduced E₂ concentration. Addition of leptin affected the expression of Cyp19a1, Cyp11a1, and Fshr genes. Bmal1 deficiency counteracted leptin-stimulated upregulation of the genes encoding E₂ synthesis in granulosa cells. These results demonstrated that Bmal1 participates in the process by which leptin acts on Lepr to regulate E₂ synthesis.