Asprosin is a recently discovered protein encoded by the fibrillin-1 (FBN1) gene. It increases with fasting and decreases after feeding, and contributes to regulation of glucose metabolism. Elevated plasma asprosin is associated with an increased risk of developing polycystic ovary syndrome (PCOS). It directly correlates with androgen concentrations in women with PCOS who are obese, which may suggest that it has a role in regulating ovarian follicle androgen production. Asprosin and fibrillin are synthesised as a proprotein that is cleaved by the enzyme furin. Oocyte-specific deletion of furin leads to early follicle arrest and infertility in female mice, but whether asprosin has direct effects on ovarian function is unknown.

Maylem et al. assessed expression of mRNAs encoding FBN1, FURIN and OR4M1 (the putative asprosin receptor ‘olfactory receptor family 4 subfamily M member 1’) in granulosa and theca cells isolated from bovine ovaries. FBN1 and FURIN were more abundant in theca cells than in granulosa cells, whereas the abundance of OR4M1 was greater in granulosa cells, consistent with potential for paracrine asprosin signalling within follicles. Asprosin directly affected follicular function by enhancing luteinising hormone-induced androstenedione production. Asprosin also reduced insulin-like growth factor-1-induced theca cell proliferation, but did not affect progesterone production.

Together, these preliminary findings suggest asprosin signalling is present within the ovary and may contribute to regulation of follicular function.

Read the full article in Journal of Molecular Endocrinology 66 35–44