Aging Reduces Estradiol Protection Against Neural but Not Metabolic Effects of Obesity in Female 3xTg-AD Mice

Abstract

Vulnerability to Alzheimer's disease (AD) is increased by several risk factors, including midlife obesity, female sex, and the depletion of estrogens in women as a consequence of menopause. Conversely, estrogen-based hormone therapies have been linked with protection from age-related increases in adiposity and dementia risk, although treatment efficacy appears to be affected by the age of initiation. Potential interactions between obesity, AD, aging, and estrogen treatment are likely to have significant impact on optimizing the use of hormone therapies in postmenopausal women. In the current study, we compared how treatment with the primary estrogen, 17β-estradiol (E2), affects levels of AD-like neuropathology, behavioral impairment, and other neural and systemic effects of preexisting diet-induced obesity in female 3xTg-AD mice. Importantly, experiments were conducted at chronological ages associated with both the early and late stages of reproductive senescence. We observed that E2 treatment was generally associated with significantly improved metabolic outcomes, including reductions in body weight, adiposity, and leptin, across both age groups. Conversely, neural benefits of E2 in obese mice, including decreased β-amyloid burden, improved behavioral performance, and reduced microglial activation, were observed only in the early aging group. These results are consistent with the perspective that neural benefits of estrogen-based therapies require initiation of treatment during early rather than later phases of reproductive aging. Further, the discordance between E2 protection against systemic versus neural effects of obesity across age groups suggests that pathways other than general metabolic function, perhaps including reduced microglial activation, contribute to the mechanism(s) of the observed E2 actions. These findings reinforce the potential systemic and neural benefits of estrogen therapies against obesity, while also highlighting the critical role of aging as a mediator of estrogens' protective actions.

High-fat diet exacerbates cognitive decline in mouse models of Alzheimer's disease and mixed dementia in a sex-dependent manner

“…Generally, estrogen can protect the brain through its vasodilatory, anti-apoptotic, antioxidant, and anti-inflammatory actions [ 15 , 64 ]. Rodent studies have also shown protective effects of estrogen against Aβ [ 59 , 65 , 66 ]. A limitation of our work is that menopause is not taken into consideration.…”

Sexual dimorphism of gut microbiota at different pubertal status

“…Furthermore, reduced E2 levels during the menopause transition have been linked to increased risk of type 2 diabetes [ 36 ]. In this study, levels of E2 impacted bacteria carbohydrate metabolic pathways, which may account for the protective metabolic effects of E2 which wane during aging [ 10 , 37 ].…”

Roles of traditional chinese medicine regulating neuroendocrinology on AD treatment

“…Recent studies have shown that imbalances in various neuroendocrine related systems, such as the HPA axis, HPG axis, insulin and brain-gut axis, can be observed in people with early stage AD, while related hormone therapy has been proved to achieve better results only in the early stages of aging ( 84 , 85 ). This suggests that the intervention of AD through the neuroendocrine related axis needs to be carried out before the irreversible accumulation of neurotoxic substances, and there is still a large gap in the relevant early drug treatment in western medicine intervention.…”