Sexual Dimorphism and Estrogen Action in Mouse Liver.

Recent studies have demonstrated that in mice, the estrogen receptor alpha (ERα) is expressed in the liver and has a direct effect on the regulation of the hepatic genes relevant for energy metabolism and drug metabolism. The sex-related differential expression of the hepatic ERα raises the questions as to whether this receptor is responsible for the sexual differences observed in the physiopathology of the liver.

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.

Effects of Vitis vinifera L. leaves extract on UV radiation damage in human keratinocytes (HaCaT).

Vitis vinifera L. water extract from red grapevine leaves contains high levels of polyphenols in quantities similar to those found in red grape and grape seeds. Phenolic compounds are the largest group of natural antioxidants with also an anti-inflammatory activity, widely demonstrated both in vitro and in vivo. Interestingly, their antioxidant effect relies not only on the direct radical scavenging activity but also on their ability in modulating cellular signalling transduction pathways. UV radiation exerts multiple effects on skin cells inducing apoptosis, senescence and carcinogenesis. The aim of this study was to investigate the antioxidant and the DNA protective potentials of Vitis vinifera L. water extract against UV-A and UV-B radiation in HaCaT cells, a human keratinocytes cell line. Comet and É£H2AX assays were used to assess DNA damage in UV irradiated cells pre-treated or not with the extract (100 µg/mL). For UV-B, DNA damage resulted significantly increased at 40 mJ/cm2 dose determining cell cycle arrest and apoptosis. For UV-A, DNA damage was significant at 10 J/cm2 while cell cycle arrest and apoptosis were evident only at 25 J/cm2. The extract (1h of pre-treatment) highlights the antioxidant and scavenger activity on the UV-A, while the maintenance of the apoptosis with both UV-A and UV-B must be interpreted as an anti-mutagenic effect.

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.

Short-Term Fasting Reveals Amino Acid Metabolism as a Major Sex-Discriminating Factor in the Liver.

Sex impacts on liver physiology with severe consequences for energy metabolism and response to xenobiotic, hepatic, and extra-hepatic diseases. The comprehension of the biology subtending sex-related hepatic differences is therefore very relevant in the medical, pharmacological, and dietary perspective. The extensive application of metabolomics paired to transcriptomics here shows that, in the case of short-term fasting, the decision to maintain lipid synthesis using amino acids (aa) as a source of fuel is the key discriminant for the hepatic metabolism of male and female mice. Pharmacological and genetic interventions indicate that the hepatic estrogen receptor (ERα) has a key role in this sex-related strategy that is primed around birth by the aromatase-dependent conversion of testosterone into estradiol. This energy partition strategy, possibly the result of an evolutionary pressure enabling mammals to tailor their reproductive capacities to nutritional status, is most important to direct future sex-specific dietary and medical interventions.

An Essential Role for Liver ERα in Coupling Hepatic Metabolism to the Reproductive Cycle.

Lipoprotein synthesis is controlled by estrogens, but the exact mechanisms underpinning this regulation and the role of the hepatic estrogen receptor α (ERα) in cholesterol physiology are unclear. Utilizing a mouse model involving selective ablation of ERα in the liver, we demonstrate that hepatic ERα couples lipid metabolism to the reproductive cycle. We show that this receptor regulates the synthesis of cholesterol transport proteins, enzymes for lipoprotein remodeling, and receptors for cholesterol uptake. Additionally, ERα is indispensable during proestrus for the generation of high-density lipoproteins efficient in eliciting cholesterol efflux from macrophages. We propose that a specific interaction with liver X receptor α (LXRα) mediates the broad effects of ERα on the hepatic lipid metabolism.