The Gut Microbiome's Influence on Hormones and Fertility in Zebrafish

One in eight couples of reproductive age will experience difficulties conceiving and having children. A woman's fertility is largely contributed to by estrogen production. Recent research indicates that the composition of the gut microbiome may contribute to estrogen levels and thus play a role in reproductive health and fertility. However, currently there is little to no work connecting the microbiome to the hormonal imbalances associated with infertility. This study investigates the effects of gut microbiome modulation on hormones in the hypothalamic‐pituitary‐gonadal (HPG) axis and fertility. Total bacterial DNA in the gut, expression of GnRH receptor, and expression of estrogen receptor were examined via qRT‐PCR in three groups of fish: untreated, antibiotic‐treated with zero‐day reacclimation period, and antibiotic‐treated with 14‐day reacclimation period. There was over a 50% reduction in bacterial abundance in antibiotic treated fish (n=4, p< 0.05). In females, this corresponded to a 17‐fold increase of GnRH receptor expression in antibiotic treated fish with a 14‐day reacclimation (n= 6, p< 0.05) while estrogen receptor expression showed no significant differences in any groups. Collectively, these data indicate the gut microbiota may play a role in modulation of reproductive hormones, thus influencing fertility in zebrafish.