Deletion of glucocorticoid receptors in Lepr-expressing neurons attenuates the effects of negative energy balance on female reproduction.

BACKGROUND: Negative energy balance increases glucocorticoids (GC) and inhibits reproduction; however, the neurocircuitry mediating these effects remains poorly understood. We hypothesized that GC signaling in leptin receptor (Lepr)-expressing neurons mediates reproductive disruption caused by metabolic stress. METHODS: We generated a mouse model with selective deletion of glucocorticoid receptor (GR) in Lepr-expressing cells (LeprGRKO). We characterized pubertal development, reproductive phenotype, ovarian folliculogenesis, and hypothalamic gene expression in female LeprGRKO mice and in GRlox/lox controls under both physiologic conditions and negative energy balance. In addition, we assessed the activation status of Agrp- and Pomc-expressing neurons by quantifying c-Fos co-expression in female LeprGRKO mice and GRlox/lox controls subjected to negative energy balance. RESULTS: LeprGRKO female mice had normal body weight, puberty, and reproduction in physiologic conditions. Following caloric restriction (CR), prepubertal LeprGRKO females were resistant to delayed puberty onset, compared to controls. Peri-pubertal CR was associated with reduced Pomc mRNA levels in the posterior hypothalamic region (PH) and a greater decrease in Kiss1 expression in the preoptic area (POA) of control females, compared with LeprGRKO mice. Adult LeprGRKO females were more resistant to disruption of estrous cyclicity by CR than controls. Under ad libitum feeding, LeprGRKO females had higher LH pulse frequency, amplitude, mean concentration, basal LH levels, and a normal preovulatory LH surge, compared to controls. However, both one (CR-1) and four (CR-4) days of CR were sufficient to suppress LH secretion and the preovulatory LH surge in both LeprGRKO and control females. Serum LH levels declined in controls, but not in LeprGRKO females, within 24 h of fasting. After CR-1, Pomc and Kiss1 mRNA levels were higher in the PH and POA, respectively, while Agrp expression was lower in the PH of LeprGRKO females, compared to controls. Consistent with the mRNA data, the number of Agrp- and Pomc-expressing neurons were lower and higher, respectively, in the ARC of LeprGRKO females compared with controls, and the percentage of Agrp neurons expressing c-Fos was also reduced in LeprGRKO females. After fasting for 24 h, Kiss1 mRNA levels were higher in both PH and POA, while Pdyn, Agrp, and Pomc expression were lower in the PH of LeprGRKO females, compared to controls. In addition, the number of Agrp-expressing neurons and the percentage of Agrp neurons expressing c-Fos were lower in the ARC of LeprGRKO females compared to controls. The number of Pomc-expressing neurons and the percentage of Pomc neurons expressing c-Fos did not differ between LeprGRKO and GRflox/flox females. CONCLUSIONS: Our data suggest that absence of GC signaling in Lepr-expressing cells attenuates effects of metabolic stress on disruption of reproductive function through direct regulation of Kiss1 and/or indirectly through regulation of Pomc and Agrp expression and AgRP neuronal activation.