FGF21 contributes to neuroendocrine control of female reproduction

Abstract

Preventing reproduction during nutritional deprivation is an adaptive process that is conserved and essential for the survival of species. In mammals, the mechanisms that inhibit fertility during starvation are complex and incompletely understood. Here we show that exposure of female mice to fibroblast growth factor 21 (FGF21), a fasting-induced hepatokine, mimics infertility secondary to starvation. Mechanistically, FGF21 acts on the suprachiasmatic nucleus (SCN) in the hypothalamus to suppress the vasopressin-kisspeptin signaling cascade, thereby inhibiting the proestrus surge in luteinizing hormone. Mice lacking the FGF21 co-receptor, β-Klotho, in the SCN are refractory to the inhibitory effect of FGF21 on female fertility. Thus, FGF21 defines an important liver-neuroendocrine axis that modulates female reproduction in response to nutritional challenge.

Figure 1

Female Tg(Fgf21) mice are infertile. (a) Age at onset of puberty (vaginal opening) in female wild-type (WT) and Tg(Fgf21) (Tg21) mice (n = 6–7). (b) Proportion of WT and Tg(Fgf21) mice that mated with proven stud males (n = 8). (c) Representative examples of estrus cycles in WT and Tg(Fgf21) mice as determined by vaginal cytology (C: cornified cells [estrus], N: nucleated cells [proestrus], L: leukocytes [diestrus]). (d) Examples of ovarian histology from WT and Tg(Fgf21) mice (CL: corpora lutea). Bar = 500 µm. (e) Plasma FSH and LH levels measured in diestrus at ZT6–7 (n = 5). Data represent the mean ± SEM, *P < 0.05 compared to WT.

Figure 2

Female Tg(Fgf21) mice display hypothalamic hypogonadism. (a) Plasma estradiol levels in (wild-type) WT and Tg(Fgf21) (Tg21) mice (n = 7–9) treated with saline or gonadotropin from pregnant mare serum (PMSG). (b, c) Plasma LH in WT and Tg(Fgf21) mice (n = 4–6) treated with vehicle and estradiol (E2) or vehicle and the GnRH-receptor agonist leuprolide. (d) Kiss1 expression in the arcuate (Arc) and anteroventral periventricular (AVPV) nuclei, or vasopressin (Avp) expression in the suprachiasmatic nucleus (SCN) of female WT and Tg(Fgf21) mice in diestrus (n = 8). (e) Plasma LH in Tg(Fgf21) mice treated with a single i.c.v injection of vehicle (artificial cerebral spinal fluid) or kisspeptin (n = 4). (f) Plasma LH in Tg(Fgf21) mice (n = 4–6) treated with estradiol (E2) and an i.c.v injection of either vehicle (artificial cerebral spinal fluid) or vasopressin (AVP). Data represent the mean ± SEM; *P < 0.05 compared to Veh or WT controls, or as indicated in figure.

Figure 3

Klb expression in the hypothalamus is essential for FGF21-mediated effects on ovulation. (a) Hypothalamic gene expression in Klb^tm1::Tg(Fgf21) mice in the presence (+ cre) or absence (−cre) of Camk2a-Cre (n = 7–8). (b, c) Representative examples of estrus cycles and quantification of mating success in Klb^tm1::Tg(Fgf21) mice in the presence (n = 14) or absence (n = 6) of Camk2a-Cre. Data represent the mean ± SEM; *P < 0.05 compared to −cre controls.

Figure 4

Evidence that FGF21 modulates female reproduction as part of the adaptive starvation response. (a) Delayed ovulation caused by a 48 h fast in Klb^tm1 (−cre) and Klb^tm1(Camk2a) (+cre) mice (n = 6). (b) Hypothalamic gene expression in in Klb^tm1 (−cre) and Klb^tm1(Camk2a) (+cre) mice following a 48 h fast (n = 6). Cycle time (Ct) values are shown for −cre controls. (c) Plasma human FGF21 levels achieved by osmotic mini-pump infusion of vehicle (V) or hFGF21 (n = 6). (d) Effects of mini-pump administration of FGF21 on estrus cycles and (e) hypothalamic gene expression in in Klb^tm1 (−cre) and Klb^tm1(Camk2a) (+cre) mice (n = 6). Ct values are shown for vehicle (veh) controls. (f) Model of FGF21 action on the hypothalamic-pituitary-ovarian axis. Data represent the mean ± SEM; *P < 0.05 compared to −cre controls.