Leptin plays an important role in reproduction and development, however, its effect on follicular development and ovulation is not fully understood. We have previously shown that leptin neutralizing antibodies effects the follicular dynamics in mice (Panwar et al. 2012). In this study we examine the effects on ovulation and mRNA expression profiles of leptin, its receptors and anti mullerian hormone (amh) in the ovary.
Immature mice (3 weeks old) were divided into four groups (n=3) and given subcutaneous injections of the following treatments on day 1 and day 3 (i) saline; (ii) anti-leptin antibody (50 µg); (iii) eCG (0.5 IU); (iv) eCG (0.5 IU) + anti-leptin antibody (50 µg). Animals were sacrificed by CO2 asphyxiation 24 hours after the last injection. Ovaries and uteri were dissected out, weighed and samples were collected for RNA extraction. The numbers of eggs in the oviduct were counted. The mRNA expression for leptin, leptin receptors and amh in the ovary were determined by qPCR.
There was no difference in ovarian and uterus weights between experimental groups except for the eCG + anti-leptin group ovaries which was significantly heavier than the control ovaries. A higher number of eggs were collected from the eCG + anti-leptin (16.1 ± 1.8) group compared to control (1.12 ± 0.02), eCG (0.8 ± 0.03) anti-leptin group (2.8 ± 0.09). Leptin mRNA was increased in the eCG and eCG + anti leptin groups. There were differential responses of the leptin receptor isoforms to the treatments. Anti-leptin treatment reduced amh expression while eCG and eCG + anti leptin increased it compared to control ovaries.
In summary, reducing peripheral leptin increases the sensitivity of the ovary to gonadotrophins and induces earlier ovulation. In the meantime, this low level of leptin effects the expression of some but not all of its receptors and reduces amh expression in the ovary.