Cellular mechanism by which estradiol protects female ovariectomized mice from high-fat diet-induced hepatic and muscle insulin resistance

Gut microbiome-driven regulation of sex hormone homeostasis: a potential neuroendocrine connection

The gut microbiome is known to have a bidirectional relationship with sex hormone homeostasis; however, its role in mediating interactions between the primary regulatory axes of sex hormones and their productions is yet to be fully understood. We utilized both conventionally raised and gnotobiotic mouse models to investigate the regulatory role of the gut microbiome on the hypothalamic-pituitary-gonadal (HPG) axis. Male and female conventionally raised mice underwent surgical modifications as follows: (1) hormonally intact controls; (2) gonadectomized males and females; (3) gonadectomized males and females supplemented with testosterone and estrogen, respectively. Fecal samples from these mice were used to colonize sex-matched, intact, germ-free recipient mice through fecal microbiota transplant (FMT). Serum gonadotropins, gonadal sex hormones, cecal microbiota, and the serum global metabolome were assessed. FMT recipients of gonadectomized-associated microbiota showed lower circulating gonadotropin levels than recipients of intact-associated microbiota, opposite to that of FMT donors. FMT recipients of gonadectomized-associated microbiota also had greater testicular weights compared to recipients of intact-associated microbiota. The gut microbiota composition of recipient mice differed significantly based on the FMT received, with the male microbiota having a more concerted impact in response to changes in the HPG axis. Network analyses showed that multiple metabolically unrelated pathways may be involved in driving differences in serum metabolites due to sex and microbiome received in the recipient mice. In sum, our findings indicate that the gut microbiome responds to the HPG axis and subsequently modulates its feedback mechanisms. A deeper understanding of interactions between the gut microbiota and the neuroendocrine-gonadal system may contribute to the development of therapies for sexually dimorphic diseases.

Hepatic Inactivation of Carnitine Palmitoyltransferase 1a Lowers ApoB-Containing Lipoproteins in Mice

BACKGROUND

Genome- and epigenome-wide association studies have associated variants and methylation status of CPT1a (carnitine palmitoyltransferase 1a) to reductions in VLDL (very low-density lipoprotein) cholesterol and triglyceride levels. The objective of this study was to determine the mechanisms by which CPT1a-dependent mitochondrial fatty acid oxidation influences hepatic and lipoprotein metabolism.

METHODS

Eight-week-old male and female Cpt1a-floxed mice (Cpt1afl/fl) and Cpt1a-floxed mice expressing the human apo B100 transgene (Cpt1afl/fl/B100Tg) were administered control adeno-associated virus or adeno-associated virus encoding Cre-recombinase under control of a liver-specific promoter (TBG-Cre). Control and liver-specific knockout mice were placed on a low-fat control or western-type diet (42% kcal fat, 0.2% cholesterol) for 16 weeks. Livers were collected and used for histological and lipid analysis, while gene and protein expression were measured by bulk RNA-sequencing and immunoblotting, respectively. Lipoprotein composition in plasma was determined by size exclusion chromatography and nuclear magnetic resonance. Rates of VLDL-triglyceride secretion were quantified after lipase inhibition with poloxamer 407. Liquid and gas chromatography-mass spectrometry were used to measure bile acid species and fecal neutral sterols, respectively.

RESULTS

We report significant associations between the presence of CPT1a SNPs and reductions in plasma cholesterol, as well as positive associations between hepatic Cpt1a expression and plasma cholesterol levels across inbred mouse strains. Mechanistic studies show that both wild-type and human apo B100 (apoB)-transgenic mice with liver-specific deletion of Cpt1a (liver-specific knockout) display lower circulating apoB levels consistent with reduced LDL (low-density lipoprotein)-cholesterol and LDL particle number. Despite a reduction in steady-state plasma lipids, VLDL-triglyceride and VLDL cholesterol secretion rates are increased, suggesting accelerated clearance of apoB-LPs (apoB-containing lipoproteins) in liver-specific knockout mice. Mechanistic approaches show greater PPARα (peroxisome proliferator-activated receptor α) signaling which favors enhanced lipoprotein lipase-mediated metabolism of apoB-LPs, including increases in apo AIV and apo CII and reductions in apo CIII and Angptl3.

CONCLUSIONS

These studies provide mechanistic insight linking genetic variants and methylation status of CPT1a to reductions in circulating apoB-LPs in humans.

G Protein Coupled Estrogen Receptor Signaling Maintains β Cell Identity in Female Mice

Type 2 diabetes (T2D) arises in the context of obesity and overnutrition; however, additional demographic features including age and biological sex contribute to T2D risk. Estradiol (E2) is thought to play a protective metabolic role that may govern sex differences in the development of T2D. The mechanisms by which E2 exerts these effects and the impact of reduced E2 signaling in β cells during menopause remain incompletely understood. We analyzed publicly available whole islet transcriptome datasets from female and male cadaveric donors and showed significant age-related modulation of gene expression, including changes in pathways related to β cell function, in islets from female donors. Importantly, these patterns were not observed in islets from male donors. To test the in vivo relationship between E2 signaling and β cell function, 10-week- old female C57BL6/J mice underwent an ovariectomy (OVX) or sham (CTR) surgery, followed by 4 weeks of high-fat diet (HFD) treatment. HFD-OVX mice exhibited obesity-induced glucose intolerance, increased α cell mass, and reduced expression of β cell identity markers. Furthermore, ex vivo treatment of islets with the G protein coupled estrogen receptor (GPER)- specific agonist G-1 restored β cell identity gene expression. Together, these data identify a novel connection between GPER signaling and β cell identity and suggest that menopausal loss of E2 signaling through GPER may be linked with loss of β cell identity.

Metabolic effects of late-onset estradiol replacement in high-fat-fed ovariectomized mice

Background

Decreased estrogen levels in postmenopausal women negatively impact metabolic health. It is known that estradiol (E2) replacement can reverse this condition. However, there is no consensus on whether the effects mediated by E2 depend on the starting time of E2 replacement after menopause. We aimed to investigate the effects of different onset E2 treatments on glucose tolerance and metabolic parameters in high-fat-fed ovariectomized mice.

Material and methods

Eight-week-old female C57BL/6J mice were divided into three groups: SHAM, OVX, and E2, to evaluate three different time points of E2 replacement after ovariectomy: early (after 4 weeks), intermediate (after 12 weeks), and late replacement (after 20 weeks). E2 groups received treatment through subcutaneous pellets.

Results

E2 replacement improved the parameters analyzed independently of the time since ovariectomy, reducing body weight gain and fat mass, as well as increasing the percentage of lean mass. Glucose intolerance, fasting insulin, HOMA-IR, and cholesterol levels were also reduced after treatment with E2. In the liver, there was a decrease in triacylglycerol (TAG) deposition, with no difference in the expression of SREBP1 and ERα proteins. In the muscle, there was a decrease in TAG deposition. In periuterine adipose tissue, there was an increase in the expression of SREBP1, FASN, and SCD, with no difference in the expression of ERα.

Conclusions

Our findings reinforce the critical role of E2 in regulating both glucose and lipid metabolism and indicate that E2 action on metabolic health was not dependent on time since ovariectomy for the parameters analyzed.

A cost-effective predictive tool for AFP-negative focal hepatic lesions of retrospective study: enhancing clinical triage and decision-making

Background

Identifying alpha-fetal protein (AFP)-negative focal hepatic lesions presents a significant challenge, particularly in China. We sought to develop an economically portable tool for the diagnosis of benign and malignant liver lesions with AFP-negative status, and explore its clinical diagnostic efficiency.

Methods

A retrospective study was conducted at Peking University Shenzhen Hospital from January 2017 to February 2023, including a total of 348 inpatients with AFP-negative liver space-occupying lesions. The study used a training set of 252 inpatients from January 2017 to September 2021 to establish a diagnostic model for differentiating benign and malignant AFP-negative liver space-occupying lesions. Additionally, a validation cohort of 96 inpatients from October 2021 to February 2023 was used to confirm the diagnostic performance of the model. From January 2017 to February 2023, patients at JingNing People's Hospital, Gansu Province were assigned to the external cohort (n = 78).

Results

A predictive tool was established by screening age, gender, hepatitis B virus (HBV)/hepatitis C virus (HCV) infected, single lesion, alanine amino transferase (ALT), and lymphocyte-to-monocyte ratio (LMR) using multivariate logistic regression analysis and clinical practice. The area under the curve (AUC) of the model was 0.911 (95% CI [0.873-0.949]) in the training set and 0.882 (95% CI [0.815-0.949]) in the validation cohort. In addition, the model achieved an area under the curve of 0.811 (95% CI [0.687-0.935]) in the external validation cohort.

Conclusion

Our results demonstrated that the predictive tool has the characteristics of good diagnostic efficiency, economy and convenience, which is helpful for the clinical triage and decision-making of AFP-negative liver space-occupying lesions.

Hepatic Inactivation of Carnitine Palmitoyltransferase 1a Lowers Apolipoprotein B Containing Lipoproteins in Mice

Genome- and epigenome-wide association studies have associated variants and methylation status of carnitine palmitoyltransferase 1a (CPT1a) to reductions in very low-density lipoprotein (VLDL) cholesterol and triglyceride levels. We report significant associations between the presence of CPT1a SNPs and reductions in plasma cholesterol, as well as positive associations between hepatic Cpt1a expression and plasma cholesterol levels across inbred mouse strains. Mechanistic studies show that both wild type and human apolipoprotein B100 (apoB)-transgenic mice with liver-specific deletion of Cpt1a (LKO) display lower circulating apoB levels consistent with reduced LDL-cholesterol (LDL-C) and LDL particle number. Despite a reduction in steady-state plasma lipids, VLDL-triglyceride (VLDL-TG) and cholesterol (VLDL-C) secretion rates are increased, suggesting accelerated clearance of apoB-containing lipoproteins (apoB-LPs) in LKO mice. Mechanistic approaches show greater peroxisome proliferator activated receptor α (PPARα) signaling which favors enhanced lipoprotein lipase-mediated metabolism of apoB-LPs, including increases in ApoCII and ApoAIV and reductions in ApoCIII & Angptl3. These studies provide mechanistic insight linking genetic variants and methylation status of CPT1a to reductions in circulating apoB-LPs in humans.

HIGHLIGHTS

Loss-of-function SNPs in CPT1a associate with reductions in plasma cholesterol in humans Hepatic Cpt1a expression positively associates with plasma cholesterol levels across inbred strains of miceLiver-specific Cpt1a deficiency lowers circulating apoB, plasma cholesterol, LDL-C, and LDL particle numberCpt1a ablation activates PPARα and favors clearance of apoB-containing lipoproteins.

Sex-specific thermoregulatory effects of estrogen signaling in Reprimo lineage cells

Menopause affects over a million individuals annually and is characterized by variable and declining ovarian hormones. Decreasing estrogen levels impact energy homeostasis and increases the risk of metabolic disorders. Energy expenditure is largely directed towards thermoregulation, which is modulated in part by estrogen receptor (ER) α expressing neurons in the hypothalamus. Whether specific sub-populations of ERα+ neurons control the effects of estrogens on thermogenesis remains poorly understood. This study investigates the function of ERα in neurons that express Rprm (Reprimo), a gene we previously linked to thermoregulation in females. Here, we use a novel ReprimoCre mouse to selectively knock out ERα in Rprm lineage neurons (Reprimo-specific estrogen receptor α KO; RERKO) and report changes in core temperature in female mice, with no changes in body weight, body composition, or food intake. RERKO females have elevated brown adipose tissue (BAT) temperature and lower tail temperature relative to controls, suggesting increased heat production and impaired heat dissipation, respectively. Developmental expression of Rprm was detected in the brain, but not in BAT or white adipose tissue suggesting temperature changes may be mediated by the nervous system. Thus, we next ablated Rprm expressing neurons in the ventrolateral area of the ventromedial nucleus of the hypothalamus (VMHvl) and observed a reduction in core temperature and increased fat mass in ablated female mice relative to controls. Taken together, these results show that estrogen signaling in Rprm expressing cells and VMHvl Rprm neurons are critical for thermoregulation, mainly through the modulation of brown adipose tissue thermogenesis in female, but not male mice.

The musculoskeletal syndrome of menopause

Fifty-one percent of humans are born with ovaries. As the ovarian production of estrogen diminishes in midlife and ultimately stops, it is estimated that more than 47 million women worldwide enter the menopause transition annually. More than 70% will experience musculoskeletal symptoms and 25% will be disabled by them through the transition from perimenopause to postmenopause. This often-unrecognized collective of musculoskeletal symptoms, largely influenced by estrogen flux, includes arthralgia, loss of muscle mass, loss of bone density and progression of osteoarthritis, among others. In isolation, it can be difficult for clinicians and patients to adequately appreciate the substantial role of decreasing estrogen, anticipate the onset of related symptoms and actively treat to mitigate future detrimental processes. Thus, in this review we introduce a new term, the musculoskeletal syndrome of menopause, to describe the collective musculoskeletal signs and symptoms associated with the loss of estrogen. Given the significant effects of these processes on quality of life and the associated personal and financial costs, it is important for clinicians and the women they care for to be aware of this terminology and the constellation of musculoskeletal processes for which proper risk assessment and prophylactic management are of consequence.

Estrogen receptor-α signaling in tanycytes lies at the crossroads of fertility and metabolism

BACKGROUND

Estrogen secretion by the ovaries regulates the hypothalamic-pituitary-gonadal axis during the reproductive cycle, influencing gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion, and also plays a role in regulating metabolism. Here, we establish that hypothalamic tanycytes-specialized glia lining the floor and walls of the third ventricle-integrate estrogenic feedback signals from the gonads and couple reproduction with metabolism by relaying this information to orexigenic neuropeptide Y (NPY) neurons.

METHODS

Using mouse models, including mice floxed for Esr1 (encoding estrogen receptor alpha, ERα) and those with Cre-dependent expression of designer receptors exclusively activated by designer drugs (DREADDs), along with viral-mediated, pharmacological and indirect calorimetric approaches, we evaluated the role of tanycytes and tanycytic estrogen signaling in pulsatile LH secretion, cFos expression in NPY neurons, estrous cyclicity, body-weight changes and metabolic parameters in adult females.

RESULTS

In ovariectomized mice, chemogenetic activation of tanycytes significantly reduced LH pulsatile release, mimicking the effects of direct NPY neuron activation. In intact mice, tanycytes were crucial for the estrogen-mediated control of GnRH/LH release, with tanycytic ERα activation suppressing fasting-induced NPY neuron activation. Selective knockout of Esr1 in tanycytes altered estrous cyclicity and fertility in female mice and affected estrogen's ability to inhibit refeeding in fasting mice. The absence of ERα signaling in tanycytes increased Npy transcripts and body weight in intact mice and prevented the estrogen-mediated decrease in food intake as well as increase in energy expenditure and fatty acid oxidation in ovariectomized mice.

CONCLUSIONS

Our findings underscore the pivotal role of tanycytes in the neuroendocrine coupling of reproduction and metabolism, with potential implications for its age-related deregulation after menopause.

SIGNIFICANCE STATEMENT

Our investigation reveals that tanycytes, specialized glial cells in the brain, are key interpreters of estrogen signals for orexigenic NPY neurons in the hypothalamus. Disrupting tanycytic estrogen receptors not only alters fertility in female mice but also impairs the ability of estrogens to suppress appetite. This work thus sheds light on the critical role played by tanycytes in bridging the hormonal regulation of cyclic reproductive function and appetite/feeding behavior. This understanding may have potential implications for age-related metabolic deregulation after menopause.

Role of the type 3 cytokines IL-17 and IL-22 in modulating metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) comprises a spectrum of liver diseases that span simple steatosis, metabolic dysfunction-associated steatohepatitis (MASH) and fibrosis and may progress to cirrhosis and cancer. The pathogenesis of MASLD is multifactorial and is driven by environmental, genetic, metabolic and immune factors. This review will focus on the role of the type 3 cytokines IL-17 and IL-22 in MASLD pathogenesis and progression. IL-17 and IL-22 are produced by similar adaptive and innate immune cells such as Th17 and innate lymphoid cells, respectively. IL-17-related signaling is upregulated during MASLD resulting in increased chemokines and proinflammatory cytokines in the liver microenvironment, enhanced recruitment of myeloid cells and T cells leading to exacerbation of inflammation and liver disease progression. IL-17 may also act directly by activating hepatic stellate cells resulting in increased fibrosis. In contrast, IL-22 is a pleiotropic cytokine with a dominantly protective signature in MASLD and is currently being tested as a therapeutic strategy. IL-22 also exhibits beneficial metabolic effects and abrogates MASH-related inflammation and fibrosis development via inducing the production of anti-oxidants and anti-apoptotic factors. A sex-dependent effect has been attributed to both cytokines, most importantly to IL-22 in MASLD or related conditions. Altogether, IL-17 and IL-22 are key effectors in MASLD pathogenesis and progression. We will review the role of these two cytokines and cells that produce them in the development of MASLD, their interaction with host factors driving MASLD including sexual dimorphism, and their potential therapeutic benefits.

Alleviation of Menopausal Symptoms by Yam (Dioscorea japonica Thunb.) and Gromwell (Lithospermum erythrorhizon Sieb. Et Zucc.) Extracts in Ovariectomized Mice

SCOPE

The decline in estrogen during menopause contributes to a variety of menopausal symptoms, for which hormone replacement therapy (HRT) has been extensively applied. Regarding side effects and limited effectiveness of HRT for specific individuals, there is a growing interest in safe alternatives such as phytoestrogens which are structurally analogous to estrogens. This study aims to investigate the efficacy of yam and gromwell extracts, rich in bioactive compounds, and the synergistic effect of extracts on symptoms induced by estrogen deficiency in ovariectomized (OVX) mice.

METHODS AND RESULTS

OVX mice receive dietary intervention of either yam, gromwell extract, or their mixture for 14 weeks. Sham-operated mice and E2-injected OVX mice serve as positive controls. Following 14 weeks of oral administration, blood, adipose tissue, vagina, uterus, femurs, and tibias are harvested for further investigation. Consequently, yam and gromwell extracts ameliorate menopausal conditions such as weight gain, glucose intolerance, dyslipidemia, and osteoporosis in estrogen-deficient OVX mice. In addition, the mixture of yam and gromwell extracts synergistically aids in the relief of the indications.

CONCLUSION

These results indicate the potential use of yam and gromwell extracts, as well as their mixture, for the development of healthy functional foods to modulate menopausal symptoms.

The Role of Estrogen across Multiple Disease Mechanisms

Estrogen is a significant hormone that is involved in a multitude of physiological and pathological processes. In addition to its pivotal role in the reproductive system, estrogen is also implicated in the pathogenesis of a multitude of diseases. Nevertheless, previous research on the role of estrogen in a multitude of diseases, including Alzheimer's disease, depression, cardiovascular disease, diabetes, osteoporosis, gastrointestinal diseases, and estrogen-dependent cancers, has concentrated on a single disease area, resulting in a lack of comprehensive understanding of cross-disease mechanisms. This has brought some challenges to the current treatment methods for these diseases, because estrogen as a potential therapeutic tool has not yet fully developed its potential. Therefore, this review aims to comprehensively explore the mechanism of estrogen in these seven types of diseases. The objective of this study is to describe the relationship between each disease and estrogen, including the ways in which estrogen participates in regulating disease mechanisms, and to outline the efficacy of estrogen in treating these diseases in clinical practice. By studying the role of estrogen in a variety of disease mechanisms, it is hoped that a more accurate theoretical basis and clinical guidance for future treatment strategies will be provided, thus promoting the effective management and treatment of these diseases.

Strength Training Protects High-Fat-Fed Ovariectomized Mice against Insulin Resistance and Hepatic Steatosis

Menopause is characterized by a reduction in sex hormones in women and is associated with metabolic changes, including fatty liver and insulin resistance. Lifestyle changes, including a balanced diet and physical exercise, are necessary to prevent these undesirable changes. Strength training (ST) has been widely used because of the muscle and metabolic benefits it provides. Our study aims to evaluate the effects of ST on hepatic steatosis and insulin resistance in ovariectomized mice fed a high-fat diet (HFD) divided into four groups as follows: simulated sedentary surgery (SHAM-SED), trained simulated surgery (SHAM-EXE), sedentary ovariectomy (OVX-SED), and trained ovariectomy (OVX-EXE). They were fed an HFD for 9 weeks. ST was performed thrice a week. ST efficiently reduced body weight and fat percentage and increased lean mass in OVX mice. Furthermore, ST reduced the accumulation of ectopic hepatic lipids, increased AMPK phosphorylation, and inhibited the de novo lipogenesis pathway. OVX-EXE mice also showed a better glycemic profile, associated with greater insulin sensitivity identified by the euglycemic-hyperinsulinemic clamp, and reduced markers of hepatic oxidative stress compared with sedentary animals. Our data support the idea that ST can be indicated as a non-pharmacological treatment approach to mitigate metabolic changes resulting from menopause.

Brown adipose tissue metabolism in women is dependent on ovarian status

In rodents, loss of estradiol (E2) reduces brown adipose tissue (BAT) metabolic activity. Whether E2 impacts BAT activity in women is not known. BAT oxidative metabolism was measured in premenopausal (n = 27; 35 ± 9 yr; body mass index = 26.0 ± 5.3 kg/m2) and postmenopausal (n = 25; 51 ± 8 yr; body mass index = 28.0 ± 5.0 kg/m2) women at room temperature and during acute cold exposure using [11C]acetate with positron emission tomography coupled with computed tomograph. BAT glucose uptake was also measured during acute cold exposure using 2-deoxy-2-[18F]fluoro-d-glucose. To isolate the effects of ovarian hormones from biological aging, measurements were repeated in a subset of premenopausal women (n = 8; 40 ± 4 yr; BMI = 28.0 ± 7.2 kg/m2) after 6 mo of gonadotropin-releasing hormone agonist therapy to suppress ovarian hormones. At room temperature, there was no difference in BAT oxidative metabolism between premenopausal (0.56 ± 0.31 min-1) and postmenopausal women (0.63 ± 0.28 min-1). During cold exposure, BAT oxidative metabolism (1.28 ± 0.85 vs. 0.91 ± 0.63 min-1, P = 0.03) and net BAT glucose uptake (84.4 ± 82.5 vs. 29.7 ± 31.4 nmol·g-1·min-1, P < 0.01) were higher in premenopausal than postmenopausal women. In premenopausal women who underwent gonadotropin-releasing hormone agonist, cold-stimulated BAT oxidative metabolism was reduced to a similar level (from 1.36 ± 0.66 min-1 to 0.91 ± 0.41 min-1) to that observed in postmenopausal women (0.91 ± 0.63 min-1). These results provide the first evidence in humans that reproductive hormones are associated with BAT oxidative metabolism and suggest that BAT may be a target to attenuate age-related reduction in energy expenditure and maintain metabolic health in postmenopausal women.NEW & NOTEWORTHY In rodents, loss of estrogen reduces brown adipose tissue (BAT) activity. Whether this is true in humans is not known. We found that BAT oxidative metabolism and glucose uptake were lower in postmenopausal compared to premenopausal women. In premenopausal women who underwent ovarian suppression to reduce circulating estrogen, BAT oxidative metabolism was reduced to postmenopausal levels. Thus the loss of ovarian function in women leads to a reduction in BAT metabolic activity independent of age.

The 100 top-cited articles in menopausal syndrome: a bibliometric analysis

BACKGROUND

Significant scientific research has been conducted concerning menopausal syndrome(MPS), yet few bibliometric analyses have been performed. Our aim was to recognise the 100 most highly cited published articles on MPS and to analytically evaluate their key features.

METHODS

To identify the 100 most frequently cited articles, a search was conducted on Web of Science using the term 'menopausal syndrome'. Articles that matched the predetermined criteria were scrutinised to obtain the following data: citation ranking, year of publication, publishing journal, journal impact factor, country of origin, academic institution, authors, study type, and keywords.

RESULTS

The publication period is from January 1, 2000, to August 31, 2022. The maximum number of citations was 406 and in 2012. The median citations per year was 39.70. Most of the articles focused on treatment and complications. These articles were published in 36 different journals, with the Journal of MENOPAUSE having published the greatest number (14%). Forty-eight articles (48%) were from the United States, with the University of Pittsburgh being the leading institute (9%). Joann E. Manson was the most frequent first author (n = 6). Observational studies were the most frequently conducted research type (n = 53), followed by experimental studies (n = 33). Keyword analysis identified classic research topics, including genitourinary syndrome of menopause, bone mineral density (BMD), and anti-mullerian hormone (AMH) loci.

CONCLUSION

Using bibliometrics, we conducted an analysis to identify the inadequacies, traditional focal points, and potential prospects in the study of MPS across current scientific areas. Treatment and complications are at the core of MPS research, whereas prediction and biomarkers have less literature of high quality. There is a necessity for innovative analytical metrics to measure the real effect of these papers with a high level of citation on clinical application.

Role of human Kallistatin in glucose and energy homeostasis in mice

OBJECTIVE

Kallistatin (KST), also known as SERPIN A4, is a circulating, broadly acting human plasma protein with pleiotropic properties. Clinical studies in humans revealed reduced KST levels in obesity. The exact role of KST in glucose and energy homeostasis in the setting of insulin resistance and type 2 diabetes is currently unknown.

METHODS

Kallistatin mRNA expression in human subcutaneous white adipose tissue (sWAT) of 47 people with overweight to obesity of the clinical trial "Comparison of Low Fat and Low Carbohydrate Diets With Respect to Weight Loss and Metabolic Effects (B-SMART)" was measured. Moreover, we studied transgenic mice systemically overexpressing human KST (hKST-TG) and wild type littermate control mice (WT) under normal chow (NCD) and high-fat diet (HFD) conditions.

RESULTS

In sWAT of people with overweight to obesity, KST mRNA increased after diet-induced weight loss. On NCD, we did not observe differences between hKST-TG and WT mice. Under HFD conditions, body weight, body fat and liver fat content did not differ between genotypes. Yet, during intraperitoneal glucose tolerance tests (ipGTT) insulin excursions and HOMA-IR were lower in hKST-TG (4.42 ± 0.87 AU, WT vs. 2.20 ± 0.27 AU, hKST-TG, p < 0.05). Hyperinsulinemic euglycemic clamp studies with tracer-labeled glucose infusion confirmed improved insulin sensitivity by higher glucose infusion rates in hKST-TG mice (31.5 ± 1.78 mg/kg/min, hKST-TG vs. 18.1 ± 1.67 mg/kg/min, WT, p < 0.05). Improved insulin sensitivity was driven by reduced hepatic insulin resistance (clamp hepatic glucose output: 7.7 ± 1.9 mg/kg/min, hKST-TG vs 12.2 ± 0.8 mg/kg/min, WT, p < 0.05), providing evidence for direct insulin sensitizing effects of KST for the first time. Insulin sensitivity was differentially affected in skeletal muscle and adipose tissue. Mechanistically, we observed reduced Wnt signaling in the liver but not in skeletal muscle, which may explain the effect.

CONCLUSIONS

KST expression increases after weight loss in sWAT from people with obesity. Furthermore, human KST ameliorates diet-induced hepatic insulin resistance in mice, while differentially affecting skeletal muscle and adipose tissue insulin sensitivity. Thus, KST may be an interesting, yet challenging, therapeutic target for patients with obesity and insulin resistance.

Maternal preconception stress produces sex-specific effects at the maternal:fetal interface to impact offspring development and phenotypic outcomes†

Entering pregnancy with a history of adversity, including adverse childhood experiences and racial discrimination stress, is a predictor of negative maternal and fetal health outcomes. Little is known about the biological mechanisms by which preconception adverse experiences are stored and impact future offspring health outcomes. In our maternal preconception stress (MPS) model, female mice underwent chronic stress from postnatal days 28-70 and were mated 2 weeks post-stress. Maternal preconception stress dams blunted the pregnancy-induced shift in the circulating extracellular vesicle proteome and reduced glucose tolerance at mid-gestation, suggesting a shift in pregnancy adaptation. To investigate MPS effects at the maternal:fetal interface, we probed the mid-gestation placental, uterine, and fetal brain tissue transcriptome. Male and female placentas differentially regulated expression of genes involved in growth and metabolic signaling in response to gestation in an MPS dam. We also report novel offspring sex- and MPS-specific responses in the uterine tissue apposing these placentas. In the fetal compartment, MPS female offspring reduced expression of neurodevelopmental genes. Using a ribosome-tagging transgenic approach we detected a dramatic increase in genes involved in chromatin regulation in a PVN-enriched neuronal population in females at PN21. While MPS had an additive effect on high-fat-diet (HFD)-induced weight gain in male offspring, both MPS and HFD were necessary to induce significant weight gain in female offspring. These data highlight the preconception period as a determinant of maternal health in pregnancy and provides novel insights into mechanisms by which maternal stress history impacts offspring developmental programming.

Sex difference in liver diseases: How preclinical models help to dissect the sex-related mechanisms sustaining NAFLD and hepatocellular carcinoma

Only a few preclinical findings are confirmed in the clinic, posing a critical issue for clinical development. Therefore, identifying the best preclinical models can help to dissect molecular and mechanistic insights into liver disease pathogenesis while being clinically relevant. In this context, the sex relevance of most preclinical models has been only partially considered. This is particularly significant in NAFLD and HCC, which have a higher prevalence in men when compared to pre-menopause women but not to those in post-menopausal status, suggesting a role for sex hormones in the pathogenesis of the diseases. This review gathers the sex-relevant findings and the available preclinical models focusing on both in vitro and in vivo studies and discusses the potential implications and perspectives of introducing the sex effect in the selection of the best preclinical model. This is a critical aspect that would help to tailor personalized therapies based on sex.

Endocrine aspects of metabolic dysfunction-associated steatotic liver disease (MASLD): Beyond insulin resistance

While the association of metabolic dysfunction-associated steatotic liver disease (MASLD) with obesity and insulin resistance is widely appreciated, there are a host of complex interactions between the liver and other endocrine axes. While it can be difficult to definitively distinguish direct causal relationships and those attributable to increased adipocyte mass, there is substantial evidence of the direct and indirect effects of endocrine dysregulation on the severity of MASLD, with strong evidence that low levels of growth hormone, sex hormones, and thyroid hormone promote the development and progression of disease. The impact of steroid hormones, e.g. cortisol and dehydroepiandrosterone, and adipokines is much more divergent. Thoughtful assessment, based on individual risk factors and findings, and management of non-insulin endocrine axes is essential in the evaluation and management of MASLD. Multiple therapeutic options have emerged that leverage various endocrine axes to reduce the fibroinflammatory cascade in MASH.

Neurolysin Knockout Mice in a Diet-Induced Obesity Model

Neurolysin oligopeptidase (E.C.3.4.24.16; Nln), a member of the zinc metallopeptidase M3 family, was first identified in rat brain synaptic membranes hydrolyzing neurotensin at the Pro-Tyr peptide bond. The previous development of C57BL6/N mice with suppression of Nln gene expression (Nln-/-), demonstrated the biological relevance of this oligopeptidase for insulin signaling and glucose uptake. Here, several metabolic parameters were investigated in Nln-/- and wild-type C57BL6/N animals (WT; n = 5-8), male and female, fed either a standard (SD) or a hypercaloric diet (HD), for seven weeks. Higher food intake and body mass gain was observed for Nln-/- animals fed HD, compared to both male and female WT control animals fed HD. Leptin gene expression was higher in Nln-/- male and female animals fed HD, compared to WT controls. Both WT and Nln-/- females fed HD showed similar gene expression increase of dipeptidyl peptidase 4 (DPP4), a peptidase related to glucagon-like peptide-1 (GLP-1) metabolism. The present data suggest that Nln participates in the physiological mechanisms related to diet-induced obesity. Further studies will be necessary to better understand the molecular mechanism responsible for the higher body mass gain observed in Nln-/- animals fed HD.

Ovarian aging in humans: potential strategies for extending reproductive lifespan

Ovarian reserve is a term used to estimate the total number of immature follicles present in the ovaries. Between birth and menopause, there is a progressive decrease in the number of ovarian follicles. Ovarian aging is a continuous physiological phenomenon, with menopause being the clinical mark of the end of ovarian function. Genetics, measured as family history for age at the onset of menopause, is the main determinant. However, physical activity, diet, and lifestyle are important factors that can influence the age of menopause. The low estrogen levels after natural or premature menopause increased the risk for several diseases, resulting in increased mortality risk. Besides that, the decreasing ovarian reserve is associated to reduced fertility. In women with infertility undergoing in vitro fertilization, reduced markers of ovarian reserve, including antral follicular count and anti-Mullerian hormone, are the main indicators of reduced chances of becoming pregnant. Therefore, it becomes clear that the ovarian reserve has a central role in women's life, affecting fertility early in life and overall health later in life. Based on this, the ideal strategy for delaying ovarian aging should have the following characteristics: (1) be initiated in the presence of good ovarian reserve; (2) maintained for a long period; (3) have an action on the dynamics of primordial follicles, controlling the rate of activation and atresia; and (4) safe use in pre-conception, pregnancy, and lactation. In this review, we therefore discuss some of these strategies and its feasibility for preventing a decline in the ovarian reserve.

Downregulation of mTORC1 and Mcl-1 by lipid-oversupply contributes to islet β-cell apoptosis and dysfunction

Pancreatic β-cell apoptosis is a key feature of diabetes and can be induced by chronic exposure to saturated fatty acids (FAs). However, the underlying mechanisms remain poorly understood. We presently evaluated the role of Mcl-1 and mTOR in mice fed with high-fat-diet (HFD) and β-cells exposed to the overloaded palmitic acid (PA). Compared with normal-chow-diet (NCD)-fed mice, HFD group showed impaired glucose tolerance after two months. Along with the diabetes progression, pancreatic islets first became hypertrophic and then atrophic, the ratio of β-cell:α-cell increased in the islets of four months HFD-fed mice while decreased after six months. This process was accompanied by significantly increased β-cell apoptosis and AMPK activity, and decreased Mcl-1 expression and mTOR activity. Consistently, glucose-induced insulin secretion dropped. In terms of mechanism, PA with lipotoxic dose could activate AMPK, which in turn inhibited ERK-stimulated Mcl-1Thr163 phosphorylation. Meanwhile, AMPK blocked Akt activity to release Akt inhibition on GSK3β, followed by GSK3β-initiated Mcl-1Ser159 phosphorylation. The context of Mcl-1 phosphorylation finally led to its degradation by ubiquitination. Also, AMPK inhibited the activity of mTORC1, resulting in a lower level of Mcl-1. Suppression of mTORC1 activity and Mcl-1 expression positively related to β-cell failure. Alteration of Mcl-1 or mTOR expression rendered different tolerance of β-cell to different dose of PA. In conclusion, lipid oversupply-induced dual modulation of mTORC1 and Mcl-1 finally led to β-cell apoptosis and impaired insulin secretion. The study may help further understand the pathogenesis of β-cell dysfunction in case of dyslipidemia, and provide promising therapeutic targets for diabetes.

Estradiol Protects Female ApoE KO Mice against Western-Diet-Induced Non-Alcoholic Steatohepatitis

The prevalence of non-alcoholic fatty liver disease (NAFLD) and its severe form, non-alcoholic steatohepatitis (NASH), is higher in men than in women of reproductive age, and postmenopausal women are especially susceptible to developing the disease.

AIM

we evaluated if female apolipoprotein E (ApoE) KO mice were protected against Western-diet (WD)-induced NASH.

METHODS

Female ovariectomized (OVX) ApoE KO mice or sham-operated (SHAM) mice were fed either a WD or a regular chow (RC) for 7 weeks. Additionally, OVX mice fed a WD were treated with either estradiol (OVX + E2) or vehicle (OVX).

RESULTS

Whole-body fat, plasma glucose, and plasma insulin were increased and associated with increased glucose intolerance in OVX mice fed a WD (OVX + WD). Plasma and hepatic triglycerides, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) hepatic enzymes were also increased in the plasma of OVX + WD group, which was associated with hepatic fibrosis and inflammation. Estradiol replacement in OVX mice reduced body weight, body fat, glycemia, and plasma insulin associated with reduced glucose intolerance. Treatment also reduced hepatic triglycerides, ALT, AST, hepatic fibrosis, and inflammation in OVX mice.

CONCLUSIONS

These data support the hypothesis that estradiol protects OVX ApoE KO mice from NASH and glucose intolerance.

Butyrate mitigates metabolic dysfunctions via the ERα-AMPK pathway in muscle in OVX mice with diet-induced obesity

The higher prevalence of metabolic syndrome (MetS) in women after menopause is associated with a decrease in circulating 17β-oestradiol. To explore novel treatments for MetS in women with oestrogen deficiency, we studied the effect of exogenous butyrate on diet-induced obesity and metabolic dysfunctions using ovariectomized (OVX) mice as a menopause model. Oral administration of sodium butyrate (NaB) reduced the body fat content and blood lipids, increased whole-body energy expenditure, and improved insulin sensitivity. Additionally, NaB induced oestrogen receptor alpha (ERα) expression, activated the phosphorylation of AMPK and PGC1α, and improved mitochondrial aerobic respiration in cultured skeletal muscle cells. In conclusion, oral NaB improves metabolic parameters in OVX mice with diet-induced obesity. Oral supplementation with NaB might provide a novel therapeutic approach to treating MetS in women with menopause. Video Abstract.

Progesterone Has No Impact on the Beneficial Effects of Estradiol Treatment in High-Fat-Fed Ovariectomized Mice

In recent decades, clinical and experimental studies have revealed that estradiol contributes enormously to glycemic homeostasis. However, the same consensus does not exist in women during menopause who undergo replacement with progesterone or conjugated estradiol and progesterone. Since most hormone replacement treatments in menopausal women are performed with estradiol (E2) and progesterone (P4) combined, this work aimed to investigate the effects of progesterone on energy metabolism and insulin resistance in an experimental model of menopause (ovariectomized female mice-OVX mice) fed a high-fat diet (HFD). OVX mice were treated with E2 or P4 (or both combined). OVX mice treated with E2 alone or combined with P4 displayed reduced body weight after six weeks of HFD feeding compared to OVX mice and OVX mice treated with P4 alone. These data were associated with improved glucose tolerance and insulin sensitivity in OVX mice treated with E2 (alone or combined with P4) compared to OVX and P4-treated mice. Additionally, E2 treatment (alone or combined with P4) reduced both hepatic and muscle triglyceride content compared with OVX control mice and OVX + P4 mice. There were no differences between groups regarding hepatic enzymes in plasma and inflammatory markers. Therefore, our results revealed that progesterone replacement alone does not seem to influence glucose homeostasis and ectopic lipid accumulation in OVX mice. These results will help expand knowledge about hormone replacement in postmenopausal women associated with metabolic syndrome and non-alcoholic fatty liver disease.

Sexual Dimorphism in Lipid Metabolism and Gut Microbiota in Mice Fed a High-Fat Diet

The gut microbiome plays an essential role in regulating lipid metabolism. However, little is known about how gut microbiome modulates sex differences in lipid metabolism. The present study aims to determine whether gut microbiota modulates sexual dimorphism of lipid metabolism in mice fed a high-fat diet (HFD). Conventional and germ-free male and female mice were fed an HFD for four weeks, and lipid absorption, plasma lipid profiles, and apolipoprotein levels were then evaluated. The gut microbiota was analyzed by 16S rRNA gene sequencing. After 4-week HFD consumption, the females exhibited less body weight gain and body fat composition and significantly lower triglyceride levels in very-low-density lipoprotein (VLDL) and cholesterol levels in high-density lipoprotein (HDL) compared to male mice. The fecal microbiota analysis revealed that the male mice were associated with reduced gut microbial diversity. The female mice had considerably different microbiota composition compared to males, e.g., enriched growth of beneficial microbes (e.g., Akkermansia) and depleted growth of Adlercreutzia and Enterococcus. Correlation analyses suggested that the different compositions of the gut microbiota were associated with sexual dimorphism in body weight, fat mass, and lipid metabolism in mice fed an HFD. Our findings demonstrated significant sex differences in lipid metabolism and the microbiota composition at baseline (during LFD), along with sex-dependent responses to HFD. A comprehensive understanding of sexual dimorphism in lipid metabolism modulated by microbiota will help to develop more sex-specific effective treatment options for dyslipidemia and metabolic disorders in females.

Sex differences in glycolipidic disorders after exposure to maternal hyperglycemia during early development

PURPOSE

The aim of this review was to summarize sex differences in glycolipid metabolic phenotypes of human and animal models after exposure to maternal hyperglycemia and overview the underlying mechanisms, providing a new perspective on the maternal hyperglycemia-triggered risk of glycolipidic disorders in offspring.

METHODS

A comprehensive literature search within PubMed was performed. Selected publications related to studies on offspring exposed to maternal hyperglycemia investigating the sex differences of glycolipid metabolism were reviewed.

RESULTS

Maternal hyperglycemia increases the risk of glycolipid metabolic disorders in offspring, such as obesity, glucose intolerance and diabetes. Whether with or without intervention, metabolic phenotypes have been shown to exhibit sex differences between male and female offspring in response to maternal hyperglycemia, which may be related to gonadal hormones, organic intrinsic differences, placenta, and epigenetic modifications.

CONCLUSION

Sex may play a role in the different incidences and pathogenesis of abnormal glycolipid metabolism. More studies investigating both sexes are needed to understand how and why environmental conditions in early life affect long-term health between male and female individuals.

Estradiol-mediated protection against high-fat diet induced anxiety and obesity is associated with changes in the gut microbiota in female mice

Decreased estrogens during menopause are associated with increased risk of anxiety, depression, type 2 diabetes and obesity. Similarly, depleting estrogens in rodents by ovariectomy, combined with a high-fat diet (HFD), increases anxiety and adiposity. How estrogens and diet interact to affect anxiety and metabolism is poorly understood. Mounting evidence indicates that gut microbiota influence anxiety and metabolism. Here, we investigated the effects of estradiol (E) and HFD on anxiety, metabolism, and their correlation with changes in gut microbiota in female mice. Adult C57BL/6J mice were ovariectomized, implanted with E or vehicle-containing capsules and fed a standard diet or HFD. Anxiety-like behavior was assessed and neuronal activation was measured by c-fos immunoreactivity throughout the brain using iDISCO. HFD increased anxiety-like behavior, while E reduced this HFD-dependent anxiogenic effect. Interestingly, E decreased neuronal activation in brain regions involved in anxiety and metabolism. E treatment also altered gut microbes, a subset of which were associated with anxiety-like behavior. These findings provide insight into gut microbiota-based therapies for anxiety and metabolic disorders associated with declining estrogens in menopausal women.

Brown Adipose Tissue-A Translational Perspective

Brown adipose tissue (BAT) displays the unique capacity to generate heat through uncoupled oxidative phosphorylation that makes it a very attractive therapeutic target for cardiometabolic diseases. Here, we review BAT cellular metabolism, its regulation by the central nervous and endocrine systems and circulating metabolites, the plausible roles of this tissue in human thermoregulation, energy balance, and cardiometabolic disorders, and the current knowledge on its pharmacological stimulation in humans. The current definition and measurement of BAT in human studies relies almost exclusively on BAT glucose uptake from positron emission tomography with 18F-fluorodeoxiglucose, which can be dissociated from BAT thermogenic activity, as for example in insulin-resistant states. The most important energy substrate for BAT thermogenesis is its intracellular fatty acid content mobilized from sympathetic stimulation of intracellular triglyceride lipolysis. This lipolytic BAT response is intertwined with that of white adipose (WAT) and other metabolic tissues, and cannot be independently stimulated with the drugs tested thus far. BAT is an interesting and biologically plausible target that has yet to be fully and selectively activated to increase the body's thermogenic response and shift energy balance. The field of human BAT research is in need of methods able to directly, specifically, and reliably measure BAT thermogenic capacity while also tracking the related thermogenic responses in WAT and other tissues. Until this is achieved, uncertainty will remain about the role played by this fascinating tissue in human cardiometabolic diseases.

Apolipoprotein C3 is negatively associated with estrogen and mediates the protective effect of estrogen on hypertriglyceridemia in obese adults

BACKGROUND

Both estrogen and apolipoprotein C3 (ApoC3) play crucial roles in lipid metabolism. But the link between them remains unclear, and it is unknown whether estrogen regulates triglyceride (TG) levels via ApoC3. Researchers hypothesized that estrogen exerts a regulatory effect on ApoC3 metabolism, and that this regulation could play a significant role in lipid metabolism. To explore this potential link, the present investigation aimed to examine the associations between estradiol (E2), ApoC3, and TG levels in both males and females.

METHODS

A total of 519 obese people (133 males and 386 premenopausal females) were recruited. Based on their TG levels, the participants were split into two groups [hypertriglyceridemia (HTG) group: TG ≥ 1.7 mmol/L; control group: TG < 1.7 mmol/L]. Serum ApoC3, E2, and TG levels were measured and compared in those two groups for both sexes separately. To ascertain the connection among E2, ApoC3, and TG, linear regression and mediation analysis were used.

RESULTS

Participants in the HTG group presented higher levels of ApoC3 (P < 0.001). In contrast, they tend to have lower E2 levels than the control. Linear regression analysis proposed that in both sexes, E2 was negatively associated with ApoC3 levels. The relationship remained significant after adjustment for confounding factors (male: standardized β = -0.144, t = -2.392, P < 0.05; female: standardized β = -0.077, t = -2.360, P < 0.001). Furthermore, mediation analysis revealed the relationship between reduced E2 levels and elevated TG levels is directly mediated by ApoC3.

CONCLUSIONS

In obese men and premenopausal women, ApoC3 was negatively and linearly correlated with serum E2 levels. The findings showed that estrogen may suppress ApoC3 expression and thus lower TG levels.

Sex difference in effects of intermittent heat exposure on hepatic lipid and glucose metabolisms

Global climate warming has drawn worldwide attention. However, the health impact of heat exposure is still controversial. This study aimed to explore the exact effects and sex differential vulnerability under intermittent heat exposure (IHE) patterns and tried to elucidate the potential mechanisms by which IHE modulated hepatic lipid and glucose homeostasis. Both female and male C57BL/6 N mice were randomly allocated to control group (22 ± 1 °C) or intermittent heat group (37 ± 1 °C for 6 h) for 9 consecutive days followed by 4-day recovery at 22 ± 1 °C in a whole-body exposure chamber. Male mice, but not female, being influenced by IHE with decreased body weight, improved insulin sensitivity and glucose tolerance. Next, the levels of hepatic triglyceride (TG) were decreased and free fatty acid (FFA) increased in male mice exposed to intermittent heat, accompanied with upregulated expression of anti-oxidative enzymes in the liver. In addition, IHE led to enhanced lipid catabolism in male mice by inducing fatty acid uptake, lipid lipolysis, mitochondrial/peroxisomal fatty acid oxidation and lipid export. And glycolysis and glucose utilization were induced by IHE in male mice as well. Mechanically, heat shock protein 70 (HSP70)/insulin receptor substrate 1 (IRS1)/AMPKα pathways were activated in response to IHE. These findings provide new evidence that IHE sex-dependently enhanced the metabolism of lipid and glucose in male mice through HSP70/IRS1/AMPKα signaling.

Oral combined contraceptives induce liver mitochondrial reactive oxygen species and whole-body metabolic adaptations in female mice

Compared to age-matched men, pre-menopausal women show greater resilience against cardiovascular disease (CVD), hepatic steatosis, diabetes and obesity - findings that are widely attributed to oestrogen. However, meta-analysis data suggest that current use of oral combined contraceptives (OC) is a risk factor for myocardial infarction, and OC use further compounds with metabolic disease risk factors to increase CVD susceptibility. While mitochondrial function in tissues such as the liver and skeletal muscle is an emerging mechanism by which oestrogen may confer its protection, effects of OC use on mitochondria and metabolism in the context of disease risk remain unexplored. To answer this question, female C57Bl/6J mice were fed a high fat diet and treated with vehicle or OCs for 3, 12 or 20 weeks (n = 6 to 12 per group) at a dose and ratio that mimic the human condition of cycle cessation in the low oestrogen, high progesterone stage. Liver and skeletal muscle mitochondrial function (respiratory capacity, H₂ O₂ , coupling) was measured along with clinical outcomes of cardiometabolic disease such as obesity, glucose tolerance, hepatic steatosis and aortic atherosclerosis. The main findings indicate that regardless of treatment duration, OCs robustly increase hepatic mitochondrial H₂ O₂ levels, likely due to diminished antioxidant capacity, but have no impact on muscle mitochondrial H₂ O₂ . Furthermore, OC-treated mice had lower adiposity and hepatic triglyceride content compared to control mice despite reduced wheel running, spontaneous physical activity and total energy expenditure. Together, these studies describe tissue-specific effects of OC use on mitochondria as well as variable impacts on markers of metabolic disease susceptibility. KEY POINTS: Oestrogen loss in women increases risk for cardiometabolic diseases, a link that has been partially attributed to negative impacts on mitochondria and energy metabolism. To study the effect of oral combined contraceptives (OCs) on hepatic and skeletal muscle mitochondria and whole-body energy metabolism, we used an animal model of OCs which mimics the human condition of cessation of hormonal cycling in the low oestrogen, high progesterone state. OC-treated mice have increased hepatic mitochondrial oxidative stress and decreased physical activity and energy expenditure, despite displaying lower adiposity and liver fat at this time point. These pre-clinical data reveal tissue-specific effects of OCs that likely underlie the clinical findings of increased cardiometabolic disease in women who use OCs compared to non-users, when matched for obesity.

Augmenting Skeletal Muscle Estrogen Does not Prevent or Rescue Obesity-linked Metabolic Impairments in Female Mice

AIMS

We developed a novel mouse model with increased skeletal muscle estrogen content via inducible, skeletal-muscle-specific aromatase overexpression (SkM-Arom↑). We proposed to examine the effect that increased skeletal muscle estrogen both in gonadally intact and ovariectomized (OVX) female mice has on preventing or rescuing high-fat diet (HFD)-induced obesity.

METHODS

In the prevention experiment, gonadally intact and OVX SkM-Arom↑ mice and littermate controls were fed a low-fat diet (LFD) or HFD for 13 weeks. SkM-Arom↑ was induced at the initiation of dietary treatment. In the intervention experiment, gonadally intact and OVX SkM-Arom↑ mice and littermate controls were fed an HFD for 14 weeks before induction of SkM-Arom↑ for 6 weeks. Glucose tolerance, insulin action, adipose tissue inflammation, and body composition were assessed. Liquid chromatography-mass spectrometry was used to determine circulating and skeletal muscle steroid content.

RESULTS

SkM-Arom↑ significantly increased skeletal muscle 17β-estradiol (E2) and estrone (E1) in both experiments. Interestingly, this resulted in leakage of estrogens into circulation, producing a physiologically relevant E2 concentration. Consequently, bone mineral density (BMD) was enhanced and adipose tissue inflammation was reduced in the prevention experiment only. However, no benefits were seen with respect to changes in adiposity or metabolic outcomes.

CONCLUSION

We show that increasing skeletal muscle estrogen content does not provide a metabolic benefit in gonadally intact and OVX female mice in the setting of obesity. However, a chronic physiological concentration of circulating E2 can improve BMD and reduce adipose tissue inflammation independently of a metabolic benefit or changes in adiposity.

Peroxisome Proliferator-Activated Receptor α Has a Protective Effect on Fatty Liver Caused by Excessive Sucrose Intake

Sterol regulatory element binding protein (SREBP)-1c is a transcription factor that regulates lipid synthesis from glucose in the liver. It is activated by sucrose, which activates the fatty acid synthesis pathway. On the other hand, peroxisome proliferator-activated receptor (PPAR) α regulates the transcription of several genes encoding enzymes involved in fatty acid β-oxidation in the liver. To evaluate the beneficial effects of PPARα on fatty liver caused by excessive sucrose intake, we investigated the molecular mechanisms related to the development of fatty liver in PPARα-deficient mice that were fed a high-sucrose diet (Suc). The SREBP-1c target gene expression was increased by sucrose intake, leading to the development of fatty liver. Furthermore, PPARα−/− mice developed severe fatty liver. Male and female PPARα−/− mice fed Suc showed 3.7- and 3.1-fold higher liver fat content than Suc-fed male and female wild-type mice, respectively. Thus, PPARα may work to prevent the development of fatty liver caused by excessive sucrose intake. Liver TG accumulation differed between male and female PPARα−/− mice. A possible explanation is that male mice show the increased expression of Pparγ, which usually contributes to triglyceride synthesis in the liver, to compensate for Pparα deficiency. In contrast, female wild-type mice inherently have low Pparα levels. Thus, Pparα deficiency has less pronounced effects in female mice. A diet that activates PPARα may be effective for preventing the development of fatty liver due to excessive sucrose intake.

Research Centers Collaborative Network Workshop on Sex and Gender Differences in Aging

Aging affects men and women differently; however, the impact of sex and gender on the aging process is not well understood. Moreover, these 2 concepts are often conflated, which further contributes to a lack of clarity on this important issue. In an effort to better understand the relevance of sex and gender in aging research, the Research Centers Collaborative Network sponsored a 1.5-day conference on sex and gender differences in aging that brought together key thought leaders from the 6 National Institute on Aging center programs. The meeting included sessions on comparing males and females, pathophysiological differences, sex/gender in clinical care, and gender and health in the social context. Presenters from a wide array of disciplines identified opportunities for multidisciplinary research to address current gaps in the field and highlighted the need for a more systematic approach to understanding the how and why of sex/gender differences, as well as the health implications of these differences and the sex/gender biases that affect clinical treatment and outcomes. This article summarizes the proceedings of the workshop and provides several recommendations to move the field forward, such as better data collection tools to assess the intersection of sex and gender in epidemiological research; a life course perspective with attention to fetal/developmental origins and key life stages; innovative animal models to distinguish contributions from sex hormones versus sex chromosomes; and integration of sex/gender into teaching and clinical practice. Ultimately, successful implementation of these recommendations will require thoughtful investigations across the translational spectrum and increased collaborations among those with expertise in sex and gender differences.

Ovariectomy Affects Acute Pancreatitis in Mice

BACKGROUND

Serum estradiol levels in severe acute injury are correlated with in hospital mortality. In acute pancreatitis, serum estradiol levels are strong predictors of disease severity. Studies of whether changes in estradiol levels play a causative role in acute pancreatitis severity are limited. The ovariectomized mouse model has been used to study the effects of estradiol in health and disease.

AIMS

We assessed whether the ovariectomized mouse model could be used to assess the effects of estradiol on pancreatitis severity.

METHODS

C57BL/6 mice with their ovaries removed were used to simulate low circulating estradiol conditions. Ovariectomized mice were treated with six hourly injections of cerulein to induce mild acute pancreatitis and compared to ovariectomized mice pre-treated with subcutaneous estradiol injections.

RESULTS

Findings suggest ovariectomized model is a problematic preparation to study pancreatitis. At baseline, ovariectomy leads to prominent acinar cell ultrastructure changes as well as changes in other select morphologic and biomarkers of pancreatitis. In addition, ovariectomy changed select acute pancreatitis responses that were only partially rescued by estradiol pre-treatment.

CONCLUSIONS

These findings suggest that the ovariectomized mouse as a model of estradiol depletion should be used with caution in pancreatic studies. Future studies should explore whether derangements in other female hormones produced by the ovaries can lead to changes in pancreatic studies.

Estradiol (E2) Improves Glucose-Stimulated Insulin Secretion and Stabilizes GDM Progression in a Prediabetic Mouse Model

Female New Zealand obese (NZO) mice are an established model of preconceptional (pc.) prediabetes that progresses as gestational diabetes mellitus (GDM) during gestation. It is known that NZO mice show improvement in insulin sensitivity and glucose-stimulated insulin secretion (GSIS) during gestation in vivo. The latter is no longer detectable in ex vivo perifusion experiments in isolated islets of Langerhans, suggesting a modulation by extrapancreatic factors. Here, we demonstrated that plasma 17β-estradiol (E2) levels increased markedly in NZO mice during gestation. The aim of this work was to determine whether these increased E2 levels are responsible for the improvement in metabolism during gestation. To achieve this goal, we examined its effects in isolated islets and primary hepatocytes of both NZO and metabolically healthy NMRI mice. E2 increased GSIS in the islets of both strains significantly. Hepatic glucose production (HGP) failed to be decreased by insulin in NZO hepatocytes but was reduced by E2 in both strains. Hepatocytes of pregnant NZO mice showed significantly lower glucose uptake (HGU) compared with NMRI controls, whereby E2 stimulation diminished this difference. Hepatocytes of pregnant NZO showed reduced glycogen content, increased cyclic adenosine monophosphate (cAMP) levels, and reduced AKT activation. These differences were abolished after E2 stimulation. In conclusion, our data indicate that E2 stabilizes and prevents deterioration of the metabolic state of the prediabetic NZO mice. E2 particularly increases GSIS and improves hepatic glucose utilization to a lower extent.

Hepatic adropin is regulated by estrogen and contributes to adverse metabolic phenotypes in ovariectomized mice

OBJECTIVE

Menopause is associated with visceral adiposity, hepatic steatosis and increased risk for cardiovascular disease. As estrogen replacement therapy is not suitable for all postmenopausal women, a need for alternative therapeutics and biomarkers has emerged.

METHODS

9-week-old C57BL/6 J female mice were subjected to ovariectomy (OVX) or SHAM surgery (n = 10 per group), fed a standard diet and sacrificed 6- & 12 weeks post-surgery.

RESULTS

Increased weight gain, hepatic triglyceride content and changes in hepatic gene expression of Cyp17a1, Rgs16, Fitm1 as well as Il18, Rares2, Retn, Rbp4 in mesenteric visceral adipose tissue (VAT) were observed in OVX vs. SHAM. Liver RNA-sequencing 6-weeks post-surgery revealed changes in genes and microRNAs involved in fat metabolism in OVX vs. SHAM mice. Energy Homeostasis Associated gene (Enho) coding for the hepatokine adropin was significantly reduced in OVX mice livers and strongly inversely correlated with weight gain (r = -0.7 p < 0.001) and liver triglyceride content (r = -0.4, p = 0.04), with a similar trend for serum adropin. In vitro, Enho expression was tripled by 17β-estradiol in BNL 1 ME liver cells with increased adropin in supernatant. Analysis of open-access datasets revealed increased hepatic Enho expression in estrogen treated OVX mice and estrogen dependent ERα binding to Enho. Treatment of 5-month-old OVX mice with Adropin (i.p. 450 nmol/kg/twice daily, n = 4,5 per group) for 6-weeks reversed adverse adipokine gene expression signature in VAT, with a trended increase in lean body mass and decreased liver TG content with upregulation of Rgs16.

CONCLUSIONS

OVX is sufficient to induce deranged metabolism in adult female mice. Hepatic adropin is regulated by estrogen, negatively correlated with adverse OVX-induced metabolic phenotypes, which were partially reversed with adropin treatment. Adropin should be further explored as a potential therapeutic target and biomarker for menopause-related metabolic derangement.

The Ameliorating Effects of Apple Polyphenol Extract on High-Fat-Diet-Induced Hepatic Steatosis Are SIRT1-Dependent: Evidence from Hepatic-Specific SIRT1 Heterozygous Mutant C57BL/6 Mice

Apple polyphenol extract (APE) has been reported to possess protective effects against hepatic steatosis. To explore whether APE-induced alleviation of hepatic steatosis is SIRT1-dependent, the present study was carried out using wild-type and hepatic SIRT1 heterozygous mutant (Sirt1^+/-) C57BL/6 mice. On consideration of the sex disparity related to hepatic steatosis morbidity, both male and female mice were included in the study. Six to eight week old mice were fed a high-fat diet (HFD) and randomly assigned to one of the following groups: (1) wild-type mice (wt+HFD), (2) Sirt1^+/- mice (Sirt1^+/-+HFD), and (3) Sirt1^+/- mice with 500 mg/(kg·bw·d) APE intragastric administration (Sirt1^+/-+HAP). HFD-induced weight gain and triglyceride accumulation was more prominent in Sirt1^+/- mice in comparison to wild-type mice. Following APE treatment, these effects were significantly reduced along with the alleviation of hepatic steatosis via upregulated expression of SIRT1 at the protein and mRNA levels in both male and female mice. However, APE differentially regulated the genes related to lipid metabolism (Lkb1, Ampk, Hsl, Srebp-1c, Abcg1, and Cd36) in a sex-specific manner. Moreover, APE treatment altered gut microbiota composition, with an increased relative abundance of Akkermansia and a decreased Firmicutes/Bacterodetes ratio. Thus, our study provided new evidence supporting our hypothesis that APE-induced alleviation of hepatic steatosis is SIRT1-dependent.

Ethnic and sex differences in hepatic lipid content and related cardiometabolic parameters in lean individuals

BackgroundNonalcoholic fatty liver affects 25% to 30% of the US and European populations; is associated with insulin resistance (IR), type 2 diabetes, and increased cardiovascular risk; and is defined by hepatic triglyceride (HTG) content greater than 5.56%. However, it is unknown whether HTG content less than 5.56% is associated with cardiometabolic risk factors and whether there are ethnic (Asian Indian, AI, versus non-AI) and/or sex differences in these parameters in lean individuals.MethodsWe prospectively recruited 2331 individuals and measured HTG, using 1H magnetic resonance spectroscopy, and plasma concentrations of triglycerides, total cholesterol, LDL-cholesterol, HDL-cholesterol, and uric acid. Insulin sensitivity was assessed using Homeostatic Model Assessment of Insulin Resistance and the Matsuda Insulin Sensitivity Index.ResultsThe 95th percentile for HTG in lean non-AI individuals was 1.85%. Plasma insulin, triglycerides, total cholesterol, LDL-cholesterol, and uric acid concentrations were increased and HDL-cholesterol was decreased in individuals with HTG content > 1.85% and ≤ 5.56% compared with those individuals with HTG content ≤ 1.85%, and these altered parameters were associated with increased IR. Mean HTG was lower in lean non-AI women compared with lean non-AI men, whereas lean AI men and women had a 40% to 100% increase in HTG when compared with non-AI men and women, which was associated with increased cardiometabolic risk factors.ConclusionWe found that the 95th percentile of HTG in lean non-AI individuals was 1.85% and that HTG concentrations above this threshold were associated with IR and cardiovascular risk factors. Premenopausal women were protected from these changes whereas young, lean AI men and women manifested increased HTG content and associated cardiometabolic risk factors.FundingGrants from the United States Department of Health and Human Resources (NIH/National Institute of Diabetes and Digestive and Kidney Diseases): R01 DK113984, P30 DK45735, U24 DK59635, and UL1 RR024139; and the Novo Nordisk Foundation (NNF18CC0034900).

Estradiol replacement improves high-fat diet-induced insulin resistance in ovariectomized rats

The role of 17β-estradiol (E2) in high-fat diet (HFD)-induced alteration of the protein kinase B (Akt) signaling pathway in ovariectomized (OVX) rats is unclear. Therefore, we examined whether chronic estrogen replacement restores HFD-induced impairment in insulin sensitivity by its effects concomitant with alterations in the Akt isoform 2 (Akt2) and Akt substrate of 160 kDa (AS160) phosphorylation in muscles of OVX rats. Nine-week-old female Wistar rats underwent ovariectomy under anesthesia; after 4 weeks, subcutaneous implantation of either E2 or placebo (PL) pellets was performed, and HFD feeding was initiated. Intravenous glucose tolerance tests were performed to assess insulin sensitivity. Following insulin injection into rats' portal vein, the liver and gastrocnemius muscle were dissected for insulin signaling analysis. We observed that HFD increased energy intake and body weight in the PL group; however, it was temporarily decreased in the E2 group. Adipose tissue accumulation was larger in HFD-fed rats than in normal chow diet (NCD)-fed rats in the PL group; however, this difference was not observed in the E2 group. HFD reduced insulin sensitivity in the PL group only. In vivo insulin stimulation increased Akt2 phosphorylation in the muscles of NCD-fed rats in both groups. In contrast, HFD affected insulin-stimulated phosphorylation of Akt2 and AS160 in the muscles of rats in the PL group but not in the E2 group. Our data suggest that E2 replacement improves HFD-induced insulin resistance, and this effect is accompanied by the alterations in the Akt2 and AS160 phosphorylation in insulin-stimulated muscles of OVX rats.

Body composition and cardiometabolic health across the menopause transition

Every year, 2 million women reach menopause in the United States, and they may spend 40% or more of their life in a postmenopausal state. In the years immediately preceding menopause-known as the menopause transition (or perimenopause)-changes in hormones and body composition increase a woman's overall cardiometabolic risk. In this narrative review, we summarize the changes in weight, body composition, and body fat distribution, as well as the changes in energy intake, energy expenditure, and other cardiometabolic risk factors (lipid profile, glucose metabolism, sleep health, and vascular function), that occur during the menopause transition. We also discuss the benefits of lifestyle interventions in women in the earlier stages of menopause before these detrimental changes occur. Finally, we discuss how to include perimenopausal women in research studies so that women across the life-span are adequately represented.

Traffic-generated air pollution - Exposure mediated expression of factors associated with demyelination in a female apolipoprotein E-/- mouse model

Epidemiology studies suggest that exposure to ambient air pollution is associated with demyelinating diseases in the central nervous system (CNS), including multiple sclerosis (MS). The pathophysiology of MS results from an autoimmune response involving increased inflammation and demyelination in the CNS, which is higher in young (adult) females. Exposure to traffic-generated air pollution is associated with neuroinflammation and other detrimental outcomes in the CNS; however, its role in the progression of pathologies associated with demyelinating diseases has not yet been fully characterized in a female model. Thus, we investigated the effects of inhalation exposure to mixed vehicle emissions (MVE) in the brains of both ovary-intact (ov+) and ovariectomized (ov-) female Apolipoprotein (ApoE^-/-) mice. Ov + and ov- ApoE^-/- mice were exposed via whole-body inhalation to either filtered air (FA, controls) or mixed gasoline and diesel vehicle emissions (MVE: 200 PM μg/m³) for 6 h/d, 7 d/wk., for 30 d. We then analyzed MVE-exposure mediated alterations in myelination, the presence of CD4+ and CD8+ T cells, reactive oxygen species (ROS), myelin oligodendrocyte protein (MOG), and expression of estrogen (ERα and ERβ) and progesterone (PROA/B) receptors in the CNS. MVE-exposure mediated significant alterations in myelination across multiple regions in the cerebrum, as well as increased CD4+ and CD8+ staining. There was also an increase in ROS production in the CNS of MVE-exposed ov- and ov + ApoE^-/- mice. Ov- mice displayed a reduction in cerebral ERα mRNA expression, compared to ov + mice; however, MVE exposure resulted in an even further decrease in ERα expression, while ERβ and PRO A/B were unchanged across groups. These findings collectively suggest that inhaled MVE-exposure may mediate estrogen receptor expression alterations associated with increased CD4+/CD8+ infiltration, regional demyelination, and ROS production in the CNS of female ApoE^-/- mice.

Fibroblast Growth Factor 21 (FGF21) Administration Sex-Specifically Affects Blood Insulin Levels and Liver Steatosis in Obese Ay Mice

FGF21 is a promising candidate for treating obesity, diabetes, and NAFLD; however, some of its pharmacological effects are sex-specific in mice with the A^y mutation that evokes melanocortin receptor 4 blockade, obesity, and hepatosteatosis. This suggests that the ability of FGF21 to correct melanocortin obesity may depend on sex. This study compares FGF21 action on food intake, locomotor activity, gene expression, metabolic characteristics, and liver state in obese A^y males and females. A^y mice were administered FGF21 for seven days, and metabolic parameters and gene expression in different tissues were assessed. Placebo-treated females were more obese than males and had lower levels of blood insulin and liver triglycerides, and higher expression of genes for insulin signaling in the liver, white adipose tissue (WAT) and muscles, and pro-inflammatory cytokines in the liver. FGF21 administration did not affect body weight, and increased food intake, locomotor activity, expression of Fgf21 and Ucp1 in brown fat and genes related to lipolysis and insulin action in WAT regardless of sex; however, it decreased hyperinsulinemia and hepatic lipid accumulation and increased muscle expression of Cpt1 and Irs1 only in males. Thus, FGF21’s beneficial effects on metabolic disorders associated with melanocortin obesity are more pronounced in males.

Estrogenic and Antioxidant Activities of Pterocarpus soyauxii (Fabaceae) Heartwood Aqueous Extract in Bilateral Oophorectomized Wistar Rat

Phytoestrogens are used to ease postmenopausal symptoms, a property probably due to estrogenic and antioxidant effects. Pterocarpus soyauxii (P. soyauxii) is empirically used in Cameroon to treat among others primary and secondary amenorrhea. The aim of this study is to evaluate estrogenic and antioxidant activities of P. soyauxii heartwood aqueous extract in bilateral oophorectomized Wistar rats. Firstly, a characterization of the extract was carried out. For that, flavonoids, phenols, and tannins levels in P. soyauxii extract were evaluated by colorimetric assays and UHPLC-MS analysis was realized. In vitro antioxidant analysis of P. soyauxii was conducted using DPPH, ABTS, and FRAP assays. Secondly, 2 sets of pharmacologic tests were carried out. The results revealed that P. soyauxii aqueous extract contains, respectively, 229.42 ± 3.62 mg EAG/g, 63.42 ± 2.16 mg EQ/g, and 27.88 ± 0.23 mg ETA/g of polyphenols, flavonoids, and tannins. UHPLC-MS enabled identifying seven components including mono(2-ethylhexyl) phthalate, cembrene, 3′,5′-dimethoxy-4-stilbenol, and linoleic acid. DPPH, ABTS, and FRAP assays revealed that P. soyauxii extract possessed a high antioxidant activity with IC₅₀ value of 730.20 µg/mL, 892.90 µg/mL, and 765.75 mEAG/g of extract, respectively. In the uterotrophic assay, P. soyauxii extract induced significant increase of fresh uterine weight, uterine and vaginal epithelial size, and mammary glands differentiation compared to Ovx control. In the postmenopausal model, compared to the sham control, vagina and uterine dystrophies were observed in Ovx rats treated with distilled water. P. soyauxii aqueous extract expressed estrogenic-like effects on vagina and did not affect uterine epithelial height compared with vehicle groups. On the back of these vaginotrophic effects, the extract displayed antiatherogenic properties by reducing (p < 0.001) AI and LDL cholesterol level as compared to Ovx control group. The extract at 200 mg/kg significantly prevented the increase of MDA (p < 0.01) level and decreased nitrites (p < 0.001) and GSH (p < 0.01) levels compared to Ovx rats. These beneficial effects are related at least in part to the presence of compound such as mono(2-ethylhexyl) phthalate, 3′,5′-dimethoxy-4-stilbenol, and linoleic acid. Overall, P. soyauxii aqueous extract exhibits estrogenic and antioxidant effects which can inhibit postmenopausal symptoms by providing vaginal stratification, improving lipid profile and insulin sensitivity, and reducing oxidative stress without side effects on the endometrium and mammary gland in 84-day Ovx rats.

Dietary Intake and Energy Expenditure in Breast Cancer Survivors: A Review

Many breast cancer survivors (BCS) gain fat mass and lose fat-free mass during treatment (chemotherapy, radiation, surgery) and estrogen suppression therapy, which increases the risk of developing comorbidities. Whether these body composition alterations are a result of changes in dietary intake, energy expenditure, or both is unclear. Thus, we reviewed studies that have measured components of energy balance in BCS who have completed treatment. Longitudinal studies suggest that BCS reduce self-reported energy intake and increase fruit and vegetable consumption. Although some evidence suggests that resting metabolic rate is higher in BCS than in age-matched controls, no study has measured total daily energy expenditure (TDEE) in this population. Whether physical activity levels are altered in BCS is unclear, but evidence suggests that light-intensity physical activity is lower in BCS compared to age-matched controls. We also discuss the mechanisms through which estrogen suppression may impact energy balance and develop a theoretical framework of dietary intake and TDEE interactions in BCS. Preclinical and human experimental studies indicate that estrogen suppression likely elicits increased energy intake and decreased TDEE, although this has not been systematically investigated in BCS specifically. Estrogen suppression may modulate energy balance via alterations in appetite, fat-free mass, resting metabolic rate, and physical activity. There are several potential areas for future mechanistic energetic research in BCS (e.g., characterizing predictors of intervention response, appetite, dynamic changes in energy balance, and differences in cancer sub-types) that would ultimately support the development of more targeted and personalized behavioral interventions.

Distinct Changes in Gut Microbiota Are Associated with Estradiol-Mediated Protection from Diet-Induced Obesity in Female Mice

A decrease in ovarian estrogens in postmenopausal women increases the risk of weight gain, cardiovascular disease, type 2 diabetes, and chronic inflammation. While it is known that gut microbiota regulates energy homeostasis, it is unclear if gut microbiota is associated with estradiol regulation of metabolism. In this study, we tested if estradiol-mediated protection from high-fat diet (HFD)-induced obesity and metabolic changes are associated with longitudinal alterations in gut microbiota in female mice. Ovariectomized adult mice with vehicle or estradiol (E2) implants were fed chow for two weeks and HFD for four weeks. As reported previously, E2 increased energy expenditure, physical activity, insulin sensitivity, and whole-body glucose turnover. Interestingly, E2 decreased the tight junction protein occludin, suggesting E2 affects gut epithelial integrity. Moreover, E2 increased Akkermansia and decreased Erysipleotrichaceae and Streptococcaceae. Furthermore, Coprobacillus and Lactococcus were positively correlated, while Akkermansia was negatively correlated, with body weight and fat mass. These results suggest that changes in gut epithelial barrier and specific gut microbiota contribute to E2-mediated protection against diet-induced obesity and metabolic dysregulation. These findings provide support for the gut microbiota as a therapeutic target for treating estrogen-dependent metabolic disorders in women.

Estradiol treatment or modest exercise improves hepatic health and mitochondrial outcomes in female mice following ovariectomy

We recently reported that compared with males, female mice have increased hepatic mitochondrial respiratory capacity and are protected against high-fat diet-induced steatosis. Here, we sought to determine the role of estrogen in hepatic mitochondrial function, steatosis, and bile acid metabolism in female mice and investigate potential benefits of exercise in the absence or presence of estrogen via ovariectomy (OVX). Female C57BL mice (n = 6 per group) were randomly assigned to sham surgery (sham), ovariectomy (OVX), or OVX plus estradiol replacement therapy (OVX + Est). Half of the mice in each treatment group were sedentary (SED) or had access to voluntary wheel running (VWR). All mice were fed a high-fat diet (HFD) and were housed at thermoneutral temperatures. We assessed isolated hepatic mitochondrial respiratory capacity using the Oroboros O2k with both pyruvate and palmitoylcarnitine as substrates. As expected, OVX mice presented with greater hepatic steatosis, weight gain, and fat mass gain compared with sham and OVX + Est animals. Hepatic mitochondrial coupling (basal/state 3 respiration) with pyruvate was impaired following OVX, but both VWR and estradiol treatment rescued coupling to levels greater than or equal to sham animals. Estradiol and exercise also had different effects on liver electron transport chain protein expression depending on OVX status. Markers of bile acid metabolism and excretion were also impaired by ovariectomy but rescued with estradiol add-back. Together our data suggest that estrogen depletion impairs hepatic mitochondrial function and liver health, and that estradiol replacement and modest exercise can aid in rescuing this phenotype.NEW & NOTEWORTHY OVX induces hepatic steatosis in sedentary mice which can be prevented by modest physical activity (VWR) and/or estradiol treatment. Estrogen impacts hepatic mitochondrial coupling in a substrate-specific manner. OVX mice have impaired fecal bile acid excretion, which was rescued with estradiol treatment.

Pancreastatin mediated regulation of UCP-1 and energy expenditure in high fructose fed perimenopausal rats

AIMS

Pancreastatin (PST) is a crucial bioactive peptide derived from chromogranin A (CHGA) proprotein that exhibits an anti-insulin effect on adipocytes. Herein, we investigated the effects of PST on brown adipose tissues (BAT) and white adipose tissue (WAT) in connection with uncoupling protein-1 (UCP-1) regulated energy expenditure in high fructose diet (HFrD) fed and vinylcyclohexenediepoxide (VCD) induced perimenopausal rats.

MATERIAL AND METHODS

We administered VCD in rats for 17 consecutive days and fed HFrd for 12 weeks. After 12 weeks estradiol and progesterone levels were detected. Furthermore, detection of glucose tolerance, insulin sensitivity, and body composition revealed impaired glucose homeostasis and enhanced PST levels. Effects of enhanced PST on UCP-1 level in BAT and WAT of perimenopausal rats were further investigated.

KEY FINDINGS

Reduced serum estradiol, progesterone, and attenuated insulin response confirmed perimenopausal model development. Furthermore, enhanced PST serum level and its increased expression in BAT and WAT downregulated the UCP-1 expression. Subsequently, impaired ATP level, NADP/NADPH ratio, citrate synthase activity, enhanced mitochondrial reactive oxygen species (ROS) generation and perturbed mitochondrial membrane potential, further exacerbated mitochondrial dysfunction, cellular ROS production, and promoted apoptosis. Interestingly, PST inhibition by PST inhibitor peptide-8 (PSTi8) displayed a favorable impact on UCP-1 and energy expenditure.

SIGNIFICANCE

The aforementioned outcomes indicated the substantial role of PST in altering the UCP-1 expression and associated energy homeostasis. Hence our results corroborate novel avenues to unravel the quest deciphering PST's role in energy homeostasis and its association with perimenopause.