1,25(OH)D up-regulated mitochondrial dynamics and biogenesis to modulate steroidogenesis in the scent glands of muskrats (Ondatra zibethicus).

Vitamin D plays a crucial regulatory role in steroid hormone production, but the specific mechanism remains not fully understood. In this study, we investigated the expression and distribution patterns of Vitamin D receptor (VDR), vitamin D metabolic enzymes (CYP2R1, CYP27B1 and CYP24A1), mitochondrial dynamics and biogenesis (proteins and genes), and steroidogenic enzymes in the scent glands of muskrats during the breeding and non-breeding periods. VDR, vitamin D metabolic enzymes, mitochondrial dynamics and biogenesis-related proteins, and steroidogenic enzymes were immunolocalized in the scent glandular cells in both breeding and non-breeding seasons, with stronger immunostaining in the breeding season. The mRNA expression levels of Cyp27b1, Cyp24a1, Vdr, Mfn1, Opa1, Vdac, Tfam, Pgc1b, Star, Cyp11a1, Cyp17a1, and Cyp19a1 were higher in the scent glands during the breeding season than those of the non-breeding season. 1,25(OH)₂D₃ concentration were positively correlated with the mean mRNA expression levels of mitochondrial dynamics and biogenesis marker genes and steroidogenic enzymes in the scent glands. The concentrations of circulating testosterone (T) and 17β-estradiol (E), and 1,25(OH)₂D₃ of the scent glands were also significantly higher in the breeding season. Additionally, the addition of 1,25(OH)D to the primary scent glandular cells in vitro increased the expression levels of mitochondrial dynamics and biogenesis-related genes and steroidogenic enzymes in the scent glands of muskrats. These findings suggested that 1,25(OH)₂D₃ might promote the secretion of steroid hormones by upregulating the mitochondrial dynamics and biogenesis in the scent glands of muskrats.