Systemic metabolic benefits of 17α-estradiol are not exclusively mediated by ERα in glutamatergic or GABAergic neurons.

Abstract

17α-Estradiol (17αE2), a less-feminising enantiomer of 17β-estradiol, has been shown to prolong lifespan and improve metabolic health in a sex-specific manner in male, but not in female mice. Recent studies have demonstrated the pivotal role of estrogen receptor α (ERα) in mediating the effects of 17αE2 on metabolic health. However, the specific tissues and/or neuronal signalling pathways that 17αE2 acts through remain to be elucidated. ERα expression in glutamatergic and GABAergic neurons (principal excitatory and inhibitory neurons respectively) in the hypothalamus is essential for estradiol signalling. Therefore, we hypothesised that knocking out ERα from one of these neuronal populations would attenuate the established beneficial metabolic effects of 17αE2 in male mice exposed to a high fat diet. To test this hypothesis we used two established brain specific ERα KO models, targeting either glutamatergic or GABAergic neurons (Vglut2/Vgat-ERαKO). We show that both of these ERα KO models exhibit a strong reduction in ERα expression in the arcuate nucleus of the hypothalamus, a control centre for metabolic regulation. Deletion of ERα from GABAergic neurons significantly diminished the effect of 17αE2 on body weight relative to controls, although these animals still show metabolic benefits with 17αE2 treatment. The response to 17αE2 was unaffected by ERα deletion in glutamatergic neurons. Our results support a benefit of 17αE2 treatment in protection against metabolic dysfunction, but these effects do not depend on exclusive ERα expression in glutamatergic and GABAergic neurons and persist when ERα expression is strongly reduced in the arcuate nucleus of the hypothalamus.