Liver ERα regulates AgRP neuronal activity in the arcuate nucleus of female mice

Role of Estrogen Receptor α in Aging and Chronic Disease

Estrogen receptor alpha (ERα) plays a crucial role in reproductive function in both sexes. It also mediates cellular responses to estrogens in multiple nonreproductive organ systems, many of which regulate systemic metabolic homeostasis and inflammatory processes in mammals. The loss of estrogens and/or ERα agonism during aging is associated with the emergence of several comorbid conditions, particularly in females undergoing the menopausal transition. Emerging data also suggests that male mammals likely benefit from ERα agonism if done in a way that circumvents feminizing characteristics. This has led us, and others, to speculate that tissue-specific ERα agonism may hold therapeutic potential for curtailing aging and chronic disease burden in males and females that are at high-risk of cancer and/or cardiovascular events with traditional estrogen replacement therapies. In this mini-review, we emphasize the role of ERα in the brain and liver, summarizing recent evidence that indicates these two organs systems mediate the beneficial effects of estrogens on metabolism and inflammation during aging. We also discuss how 17α-estradiol administration elicits health benefits in an ERα-dependent manner, which provides proof-of-concept that ERα may be a druggable target for attenuating aging and age-related disease burden.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

Renoprotective potential of myo-inositol on diabetic kidney disease: Focus on the role of the PINK1/Parkin pathway and mitophagy receptors

Recent studies have emphasized the role of mitochondria in renal function as well as in renal injury. Poor mitochondrial quality control mechanisms including mitochondrial fusion, fission and mitophagy are major contributors for progression of diabetic renal injury. The current study is aimed to evaluate the protective role of myo-inositol (MI) against diabetic nephropathy (DN) by utilizing high glucose exposed NRK 52E cell and streptozotocin (STZ) induced DN model. MI supplementation (at doses 37.5 and 75 mg/kg) ameliorated albuminuria and enhanced the renal function as indicated significant improvement in urinary creatinine and urea levels. On the other hand, the western blot analysis of both in vitro and in vivo studies has revealed poor mitophagy in renal cells which was reversed upon myo-inositol treatment. Apart from targeting the canonical PINK1/Parkin pathway, we also focused on the role mitophagy receptors prohibitin (PHB) and NIP3-like protein (NIX). A significant reduction in expression of NIX and PHB2 was observed in renal tissue of diabetic control rats and high glucose exposed NRK 52E cells. Myo-inositol treatment resulted in positive modulation of PINK1/Parkin pathway as well as PHB2 and NIX. Myo-inositol also enhanced the mitochondrial biogenesis in renal tissue of diabetic rat by upregulating Nrf2/SIRT1/PGC-1α axis. The current study thus underlines the renoprotective effect myo-inositol, upregulation of mitophagy proteins and mitochondrial biogenesis upon myo-inositol treatment.

Running the Female Power Grid Across Lifespan Through Brain Estrogen Signaling

The role of central estrogen in cognitive, metabolic, and reproductive health has long fascinated the lay public and scientists alike. In the last two decades, insight into estrogen signaling in the brain and its impact on female physiology is beginning to catch up with the vast information already established for its actions on peripheral tissues. Using newer methods to manipulate estrogen signaling in hormone-sensitive brain regions, neuroscientists are now identifying the molecular pathways and neuronal subtypes required for controlling sex-dependent energy allocation. However, the immense cellular complexity of these hormone-sensitive brain regions makes it clear that more research is needed to fully appreciate how estrogen modulates neural circuits to regulate physiological and behavioral end points. Such insight is essential for understanding how natural or drug-induced hormone fluctuations across lifespan affect women's health.

Rolling out physical exercise and energy homeostasis: Focus on hypothalamic circuitries

Energy balance is the fine regulation of energy expenditure and energy intake. Negative energy balance causes body weight loss, while positive energy balance promotes weight gain. Modern societies offer a maladapted way of life, where easy access to palatable foods and the lack of opportunities to perform physical activity are considered the roots of the obesity pandemic. Physical exercise increases energy expenditure and, consequently, is supposed to promote weight loss. Paradoxically, physical exercise acutely drives anorexigenic-like effects, but the mechanisms are still poorly understood. Using an evolutionary background, this review aims to highlight the potential involvement of the melanocortin system and other hypothalamic neural circuitries regulating energy balance during and after physical exercise. The physiological significance of these changes will be explored, and possible signalling agents will be addressed. The knowledge discussed here might be important for clarifying obesity aetiology as well as new therapeutic approaches for body weight loss.

Obesity induced by estrogen deficiency is associated with hypothalamic inflammation

Occurrence of obesity during the postmenopausal period is closely associated with inflammatory processes in multiple peripheral organs that are metabolically active. Hypothalamic inflammation has been recognized as one of the major underlying causes of various metabolic disorders, including obesity. The association between menopause-related obesity and hypothalamic inflammation remains poorly understood. We observed an elevation in hypothalamic inflammation in the ovariectomized mice, which displayed altered metabolic phenotypes and visceral obesity. Furthermore, we confirmed that ovariectomized mice displayed microglial activation accompanied by the upregulation of multiple genes involved in the inflammatory responses in hypothalamic microglia. Collectively, the current findings suggest that hypothalamic inflammation associated with microglial functioning could be a major pathogenic element in disruption of energy homeostasis during the postmenopausal period.

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Estrogen deficiency induces hypothalamic inflammation.

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Estrogen deficiency leads to inflammatory responses in hypothalamic microglia.

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Hypothalamic inflammation is associated with obesity pathogenesis during the postmenopausal period.

Conditional inactivation of Npy1r gene in mice induces sex-related differences of metabolic and behavioral functions

Sex hormone-driven differences in gene expression have been identified in experimental animals, highlighting brain neuronal populations implicated in dimorphism of metabolic and behavioral functions. Neuropeptide Y-Y1 receptor (NPY-Y1R) system is sexually dimorphic and sensitive to gonadal steroids. In the present study we compared the phenotype of male and female conditional knockout mice (Npy1r^rfb mice), carrying the inactivation of Npy1r gene in excitatory neurons of the brain limbic system. Compared to their male control (Npy1r^2lox) littermates, male Npy1r^rfb mice exhibited hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis that is associated with anxiety and executive dysfunction, reduced body weight growth, after-fasting refeeding, white adipose tissue (WAT) mass and plasma leptin levels. Conversely, female Npy1r^rfb mice displayed an anxious-like behavior but no differences in HPA axis activity, executive function and body weight, compared to control females. Moreover, conditional inactivation of Npy1r gene induced an increase of subcutaneous and gonadal WAT weight and plasma leptin levels and a compensatory decrease of Agouti-related protein immunoreactivity in the hypothalamic arcuate (ARC) nucleus in females, compared to their respective control littermates. Interestingly, Npy1r mRNA expression was reduced in the ARC and in the paraventricular hypothalamic nuclei of female, but not male mice. These results demonstrated that female mice are resilient to hormonal and metabolic effects of limbic Npy1r gene inactivation, suggesting the existence of an estrogen-dependent relay necessary to ensure the maintenance of the homeostasis, that can be mediated by hypothalamic Y1R.

Hepatic ERα accounts for sex differences in the ability to cope with an excess of dietary lipids

Objective

Among obesity-associated metabolic diseases, non-alcoholic fatty liver disease (NAFLD) represents an increasing public health issue due to its emerging association with atherogenic dyslipidemia and cardiovascular diseases (CVDs). The lower prevalence of NAFLD in pre-menopausal women compared with men or post-menopausal women led us to hypothesize that the female-inherent ability to counteract this pathology might strongly rely on estrogen signaling.

In female mammals, estrogen receptor alpha (ERα) is highly expressed in the liver, where it acts as a sensor of the nutritional status and adapts the metabolism to the reproductive needs. As in the male liver this receptor is little expressed, we here hypothesize that hepatic ERα might account for sex differences in the ability of males and females to cope with an excess of dietary lipids and counteract the accumulation of lipids in the liver.

Methods

Through liver metabolomics and transcriptomics we analyzed the relevance of hepatic ERα in the metabolic response of males and females to a diet highly enriched in fats (HFD) as a model of diet-induced obesity.

Results

The study shows that the hepatic ERα strongly contributes to the sex-specific response to an HFD and its action accounts for opposite consequences for hepatic health in males and females.

Conclusion

This study identified hepatic ERα as a novel target for the design of sex-specific therapies against fatty liver and its cardio-metabolic consequences.

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Hepatic ERα contributes to sex-specific response to a fat-enriched diet.

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Hepatic ERα action accounts for contrasting consequences in males and females.

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In males, hepatic ERα action does not prevent liver lipid accumulation.

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The lack of ERα is responsible for an altered plasma lipid profile in males.

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In females, liver ERα controls lipid catabolism and counteracts NAFLD development.

Sex-Specific Features of Microglia from Adult Mice

Sex has a role in the incidence and outcome of neurological illnesses, also influencing the response to treatments. Neuroinflammation is involved in the onset and progression of several neurological diseases, and the fact that estrogens have anti-inflammatory activity suggests that these hormones may be a determinant in the sex-dependent manifestation of brain pathologies. We describe significant differences in the transcriptome of adult male and female microglia, possibly originating from perinatal exposure to sex steroids. Microglia isolated from adult brains maintain the sex-specific features when put in culture or transplanted in the brain of the opposite sex. Female microglia are neuroprotective because they restrict the damage caused by acute focal cerebral ischemia. This study therefore provides insight into a distinct perspective on the mechanisms underscoring a sexual bias in the susceptibility to brain diseases.

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Transcriptome sequencing indicates sexual differentiation in adult murine microglia

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Female microglia show a neuroprotective phenotype, independent from hormonal cues

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Female microglia phenotype is retained after transfer into male brains

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The presence of female microglia protects male brains from ischemic stroke

The capacity for oestrogen to influence obesity through brown adipose tissue thermogenesis in animal models: A systematic review and meta-analysis

Pharmacological interventions to aid weight loss have historically targeted either appetite suppression or increased metabolic rate. Brown adipose tissue (BAT) possesses the capacity to expend energy in a futile cycle, thus increasing basal metabolic rate. In animal models, oestrogen has been implicated in the regulation of body weight, and it is hypothesized that oestrogen is acting by modulating BAT metabolism. A systematic search was performed, to identify research articles implementing in vivo oestrogen-related interventions and reporting outcome measures that provide direct or indirect measures of BAT metabolism. Meta-analyses were conducted where sufficient data were available. The final library of 67 articles were predominantly in rodent models and provided mostly indirect measures of BAT metabolism. Results of this review found that oestrogen's effects on body weight, in rats and possibly mice, are likely facilitated by both metabolic and appetitive mechanisms but are largely only found in ovariectomized models. There is a need for further studies to clarify the potential effects of oestrogen on BAT metabolism in gonad-intact and castrated male animal models.

Sexual differentiation of microglia

Sex plays a role in the incidence and outcome of neurological illnesses, also influencing the response to treatments. Despite sexual differentiation of the brain has been extensively investigated, the study of sex differences in microglia, the brain's resident immune cells, has been largely neglected until recently. To fulfill this gap, our laboratory developed several tools, including cellular and animal models, which bolstered in-depth studies on sexual differentiation of microglia and its impact on brain physiology, as well as on the onset and progression of neurological disorders. Here, we summarize the current status of knowledge on the sex-dependent function of microglia, and report recent evidence linking these cells to the sexual bias in the susceptibility to neurological brain diseases.