Elucidating the role of asprosin in bovine and bubaline ovarian follicular development and function

Asprosin is a novel protein released in white adipose tissues and associated with insulin resistance and polycystic ovaries, hence its role in reproduction is warranted. The objectives of this thesis were to characterize FBN1, OR4M1 (asprosin receptor) and enzyme furin mRNA abundance, and thus, protein product, asprosin in bovine and bubaline ovarian cells; to identify hormonal regulators for the expression of FBN1 and OR4M1 mRNA, and the role of asprosin in ovarian cell proliferation, steroidogenesis and follicular development. Using cell culture and gene expression analysis, results revealed that in cattle, OR4M1 mRNA levels are greatest in small-follicle granulosa cells (GC) and FBN1 mRNA is greatest in small-follicle theca cells (TC). Furin mRNA was greater in small-follicle TC than small-follicle GC. Hormonal up-regulators of both FBN1 in GC and TC were identified as TGFß1, WNT3A and FGF9, but downregulated by IGF1 in GC. While, OR4M1 mRNA was upregulated by WNT3A and GH in GC, and thus genes are developmentally and hormonally regulated in ovarian cells. In vitro studies revealed that asprosin inhibited IGF1-induced GC proliferation but stimulated FSH-induced estradiol (E2) production by GC and LH-induced androstenedione (A4) production by TC. In water buffaloes, FBN1 mRNA abundance was greater in GC of small than large follicles, but abundance of OR4M1 and CYP19A1 mRNA did not differ between the two sizes of follicles. Abundance of FBN1 mRNA was positively correlated with CYP19A1 and OR4M1 mRNA across follicle sizes, and may suggest a potential role in E2 production. Cows treated with asprosin via intra-follicular injection revealed a higher growth rate from day 0 to 2, and more asprosin-treated vs. control follicles ovulated by day 3. We conclude that FBN1 and OR4M1 mRNA abundance are developmentally regulated in GC, and that asprosin induces follicular growth in buffaloes. Asprosin may perform a paracrine and/or autocrine regulation of ovarian function by inhibiting IGF1-induced cell proliferation and stimulating LH-induced A4 production in TC, and consequently FSH-induced E2 production in GC. Overall, the developmental and hormonal regulation of FBN1 and OR4M1 mRNA in both species may affect asprosin production and its subsequent role in cell proliferation, steroidogenesis and follicular development. Understanding asprosin regulation of follicular function may lead to development of methods for improved reproductive efficiency and treatments for reproductive related disorders.