Decreased expression of m6A demethylase FTO in ovarian aging

N6-methyladenosine (m6A) and demethylase fat mass and obesity-associated protein (FTO) were reported to be associated with oocyte development and maturation. But the relationship between FTO and ovarian aging was still unclear. This study was aimed at investigating the FTO expression level and the m6A content during ovarian aging. The expression level of FTO and the content of m6A RNA methylation in human follicular fluid (FF), granulosa cells (GCs) and mouse ovary from different age groups were studied by ELISA, WB, qRT-PCR, IHC and m6A Colorimetric. Human FF ELISA quantified that the level of FTO protein decreased with age (P = 0.025). QRT-PCR results showed that the relative expression of FTO in human GCs was lower in the elderly group than in the young group (P = 0.012). FTO mRNA and protein expression levels were lower in the ovary of 32-week-old mice than in 3- and 8-week-old mice (P < 0.05). Immunohistochemistry showed FTO was relatively decreased in 32-week-old mice (P < 0.05). The m6A content in total RNA from old human GCs and ovary from 32-week-old mice was significantly higher compared with the younger ones. In human FF, GCs and mouse ovary, the expression of FTO decreased while the content of m6A increased with aging. However, the inner mechanism still needs further investigation.