Increased adipose tissue aromatase activity improves insulin sensitivity and reduces adipose tissue inflammation in male mice

MicroRNA in cardiometabolic health and disease: The perspectives of sex, gender and personalised medicine

BACKGROUND

Personalized medicine represents a novel and integrative approach that focuses on an individual's genetics and epigenetics, precision medicine, lifestyle and exposures as key players of health status and disease phenotypes.

METHODS

In this narrative review, we aim to carefully discuss the current knowledge on gender disparities in cardiometabolic diseases, and we consider the sex- specific expression of miRNAs and their role as promising tool in precision medicine.

RESULTS

Personalised medicine overcomes the restricted care of patient based on a binomial sex approach, by enriching itself with a holistic and dynamic gender integration. Recognized as a major worldwide health emergency, cardiometabolic disorders continue to rise, impacting on health systems and requiring more effective and targeted strategies. Several sex and gender drivers might affect the onset and progression of cardiometabolic disorders in males and females at multiple levels. In this respect, distinct contribution of genetic and epigenetic mechanisms, molecular and physiological pathways, sex hormones, visceral fat and subcutaneous fat and lifestyle lead to differences in disease burden and outcomes in males and females.

CONCLUSIONS

Sex and gender play a pivotal role in precision medicine because the influence the physiology of each individual and the way they interact with environment from intrauterine life.

Estrogen restores disordered lipid metabolism in visceral fat of prediabetic mice

BACKGROUND

Visceral obesity is increasingly prevalent among adolescents and young adults and is commonly recognized as a risk factor for type 2 diabetes. Estrogen [17β-estradiol (E2)] is known to offer protection against obesity via diverse me-chanisms, while its specific effects on visceral adipose tissue (VAT) remain to be fully elucidated.

AIM

To investigate the impact of E2 on the gene expression profile within VAT of a mouse model of prediabetes.

METHODS

Metabolic parameters were collected, encompassing body weight, weights of visceral and subcutaneous adipose tissues (VAT and SAT), random blood glucose levels, glucose tolerance, insulin tolerance, and overall body composition. The gene expression profiles of VAT were quantified utilizing the Whole Mouse Genome Oligo Microarray and subsequently analyzed through Agilent Feature Extraction software. Functional and pathway analyses were conducted employing Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses, respectively.

RESULTS

Feeding a high-fat diet (HFD) moderately increased the weights of both VAT and SAT, but this increase was mitigated by the protective effect of endogenous E2. Conversely, ovariectomy (OVX) led to a significant increase in VAT weight and the VAT/SAT weight ratio, and this increase was also reversed with E2 treatment. Notably, OVX diminished the expression of genes involved in lipid metabolism compared to HFD feeding alone, signaling a widespread reduction in lipid metabolic activity, which was completely counteracted by E2 administration. This study provides a comprehensive insight into E2's local and direct protective effects against visceral adiposity in VAT at the gene level.

CONCLUSION

In conclusion, the present study demonstrated that the HFD-induced over-nutritional challenge disrupted the gene expression profile of visceral fat, leading to a universally decreased lipid metabolic status in E2 deficient mice. E2 treatment effectively reversed this condition, shedding light on the mechanistic role and therapeutic potential of E2 in combating visceral obesity.

MHO or MUO? White adipose tissue remodeling

In this review, we delve into the intricate relationship between white adipose tissue (WAT) remodeling and metabolic aspects in obesity, with a specific focus on individuals with metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO). WAT is a highly heterogeneous, plastic, and dynamically secreting endocrine and immune organ. WAT remodeling plays a crucial role in metabolic health, involving expansion mode, microenvironment, phenotype, and distribution. In individuals with MHO, WAT remodeling is beneficial, reducing ectopic fat deposition and insulin resistance (IR) through mechanisms like increased adipocyte hyperplasia, anti-inflammatory microenvironment, appropriate extracellular matrix (ECM) remodeling, appropriate vascularization, enhanced WAT browning, and subcutaneous adipose tissue (SWAT) deposition. Conversely, for those with MUO, WAT remodeling leads to ectopic fat deposition and IR, causing metabolic dysregulation. This process involves adipocyte hypertrophy, disrupted vascularization, heightened pro-inflammatory microenvironment, enhanced brown adipose tissue (BAT) whitening, and accumulation of visceral adipose tissue (VWAT) deposition. The review underscores the pivotal importance of intervening in WAT remodeling to hinder the transition from MHO to MUO. This insight is valuable for tailoring personalized and effective management strategies for patients with obesity in clinical practice.

Non-aromatizable androgens modulate the lipopolysaccharide induced expression of the P2X7 receptor in human adipocytes

Introduction: The activation of the P2X7 receptor subtype (P2X7R) has a main role in orchestrating the cellular inflammatory response in many different tissues. Obesity is characterized by dysfunctional fat deposition leading to a tissue-specific and systemic low-grade inflammation. Androgens and estrogens contribute to the whole adipose tissue inflammatory state, but the involvement of sex steroids in the purinergic signaling modulation in adipocytes is still unknown. Methods: We performed an in vitro study to evaluate the possible role of sex hormones on the P2X7R gene expression in human adipocytes, at baseline and after stimulation with bacterial lipopolysaccharide (LPS). We evaluated P2X7R gene expression during in vitro differentiation of human adipocytes, in the absence and presence of testosterone (T) and 17β-estradiol (E2) in the presence and absence of LPS. Furthermore, we analyzed the effects of incubation with dihydrotestosterone (DHT), a non-aromatizable androgen, using the co-incubation of isolated human adipocytes with T alone or in combination with anastrozole, an inhibitor of aromatase, the enzyme responsible of T conversion to E2. Results: At baseline, incubation of adipocytes with T or E2 did not significantly affect P2X7R gene expression. On the contrary, the incubation with DHT was associated with a significant reduction of P2X7R gene expression. LPS incubation significantly increased gene expression of P2X7R with respect to baseline. Interestingly, after LPS stimulation, DHT exposure showed an additional effect, markedly increasing the P2X7R gene expression. This amplificatory effect was confirmed by the incubation of adipocytes to both anastrozole and testosterone. In these experimental conditions, while no effect was observed at baseline, an amplification of the expression of the P2X7R mRNA was observed after stimulation with LPS. Discussion: The purinergic system is involved in the inflammatory response of adipocytes, and androgens may modulate its activity. In particular DHT, a non-aromatizable androgen, amplifies the LPS-induced P2X7R gene expression in human adipocytes thus showing a gender regulated response of the expression of this purinergic receptor strongly involved in the inflammatory response in adipose tissue.

The association between organophosphate esters exposure and body mass index in children and adolescents: The mediating effect of sex hormones

Organophosphate esters (OPEs), used as flame retardants and plasticizers, have been indicated to impair growth and development in toxicological studies, but current epidemiological data on their associations with body mass index (BMI) are limited and the underlying biological mechanisms remain unclear. In this study, we aim to explore the association of OPE metabolites with BMI z-score, and assess whether sex hormones mediate the relationships between OPE exposure and BMI z-score. We measured weight and height, and determined OPE metabolites in spot urine samples and sex hormones in serum samples among 1156 children and adolescents aged 6-18 years in Liuzhou city, China. The results showed that di-o-cresyl phosphate and di-pcresyl phosphate (DoCP & DpCP) levels were associated with lower BMI z-score of all participants and a similar pattern of associations were presented in prepubertal boys stratified by sex-puberty groups and male children stratified by sex-age groups. In addition, sex hormone binding globulin (SHBG) were related to reduced BMI z-score among all subgroups including prepubertal boys, prepubertal girls, pubertal boys, and pubertal girls (all P_trend<0.05). We also found that DoCP & DpCP showed positive associations with SHBG among prepubertal boys. Mediation analysis further showed that SHBG mediated 35.0% of the association between DoCP & DpCP and reduced BMI z-score in prepubertal boys. Our results indicated that OPEs may impair growth and development by disrupting the sex hormones in prepubertal boys.

Dihydrotestosterone, and Not Testosterone, Enhances the LPS-Induced Inflammatory Cytokine Gene Expression in Human Adipocytes

BACKGROUND

The development of obesity-related complications lies in the low-grade inflammatory state consequent to adipocyte dysfunction. The direct involvement of sex hormones in adipose tissue inflammation has been previously suggested, but the evidence is scarce. In this study, we evaluated the effects of sex steroids on the in-vitroexpression of inflammatory mediators in human-derived adipocytes before and after lipopolysaccharide (LPS) exposure.

METHODS

Human adipocytes were differentiated from the vascular stromal fraction of adipose tissue samples of subjects undergoing abdominoplasty. We evaluated MCP-1, IL-1β, IL-6, and TNF-α gene expression in the presence of the main sex steroids, testosterone (T), and 17β-estradiol (E). Furthermore, we analyzed the effects of adipocytes exposure to the non-aromatizable androgen dihydrotestosterone (DHT), together with the effects of adipocytes pre-incubation with the aromatase inhibitor anastrozole alone (A), and in combination with T (A/T) before incubation with LPS.

RESULTS

DHT, but not T, significantly enhanced the LPSinduction of MCP-1, IL-1β, IL-6, and TNF-α. Intriguingly, the exposure of adipocytes with A/T dramatically increased the LPS-induced expression of all considered inflammatory cytokines, even more than a hundred-fold.

CONCLUSIONS

DHT and A/T dramatically enhance LPS-induced inflammatory cytokine expression in human-derived adipocytes. These results confirm the involvement of sex hormones in adipose tissue inflammation, suggesting a specific role for non-aromatizable androgens as the amplificatory sex hormones of the inflammatory response.

Oral Administration of Lipopolysaccharide Enhances Insulin Signaling-Related Factors in the KK/Ay Mouse Model of Type 2 Diabetes Mellitus

Lipopolysaccharide (LPS), an endotoxin, induces systemic inflammation by injection and is thought to be a causative agent of chronic inflammatory diseases, including type 2 diabetes mellitus (T2DM). However, our previous studies found that oral LPS administration does not exacerbate T2DM conditions in KK/Ay mice, which is the opposite of the response from LPS injection. Therefore, this study aims to confirm that oral LPS administration does not aggravate T2DM and to investigate the possible mechanisms. In this study, KK/Ay mice with T2DM were orally administered LPS (1 mg/kg BW/day) for 8 weeks, and blood glucose parameters before and after oral administration were compared. Abnormal glucose tolerance, insulin resistance progression, and progression of T2DM symptoms were suppressed by oral LPS administration. Furthermore, the expressions of factors involved in insulin signaling, such as insulin receptor, insulin receptor substrate 1, thymoma viral proto-oncogene, and glucose transporter type 4, were upregulated in the adipose tissues of KK/Ay mice, where this effect was observed. For the first time, oral LPS administration induces the expression of adiponectin in adipose tissues, which is involved in the increased expression of these molecules. Briefly, oral LPS administration may prevent T2DM by inducing an increase in the expressions of insulin signaling-related factors based on adiponectin production in adipose tissues.

Adipocyte Metabolism and Health after the Menopause: The Role of Exercise

Postmenopausal women represent an important target population in need of preventative cardiometabolic approaches. The loss of estrogen following the menopause eliminates protections against metabolic dysfunction, largely due to its role in the health and function of adipose tissue. In addition, some studies associate the menopause with reduced physical activity, which could potentially exacerbate the deleterious cardiometabolic risk profile accompanying the menopause. Meanwhile, exercise has adipocyte-specific effects that may alleviate the adverse impact of estrogen loss through the menopausal transition period and beyond. Exercise thus remains the best therapeutic agent available to mitigate menopause-associated metabolic dysfunction and represents a vital behavioral strategy to prevent and alleviate health decline in this population.

Species Differences in Tryptophan Metabolism and Disposition

Major species differences in tryptophan (Trp) metabolism and disposition exist with important physiological, functional and toxicity implications. Unlike mammalian and other species in which plasma Trp exists largely bound to albumin, teleosts and other aquatic species possess little or no albumin, such that Trp entry into their tissues is not hampered, neither is that of environmental chemicals and toxins, hence the need for strict measures to safeguard their aquatic environments. In species sensitive to toxicity of excess Trp, hepatic Trp 2,3-dioxygenase (TDO) lacks the free apoenzyme and its glucocorticoid induction mechanism. These species, which are largely herbivorous, however, dispose of Trp more rapidly and their TDO is activated by smaller doses of Trp than Trp-tolerant species. In general, sensitive species may possess a higher indoleamine 2,3-dioxygenase (IDO) activity which equips them to resist immune insults up to a point. Of the enzymes of the kynurenine pathway beyond TDO and IDO, 2-amino-3-carboxymuconic acid-6-semialdehyde decarboxylase (ACMSD) determines the extent of progress of the pathway towards NAD⁺ synthesis and its activity varies across species, with the domestic cat (Felis catus) being the leading species possessing the highest activity, hence its inability to utilise Trp for NAD⁺ synthesis. The paucity of current knowledge of Trp metabolism and disposition in wild carnivores, invertebrates and many other animal species described here underscores the need for further studies of the physiology of these species and its interaction with Trp metabolism.

The role of the androgen receptor in the pathogenesis of obesity and its utility as a target for obesity treatments

Obesity is associated with hypothalamic-pituitary-testicular axis dysregulation in males. Here, we summarize recent evidence derived from clinical trials and studies in preclinical animal models regarding the role of androgen receptor (AR) signaling in the pathophysiology of males with obesity. We also discuss therapeutic strategies targeting the AR for the treatment of obesity and their limitations and provide insight into the future research necessary to advance this field.

The Regulation of Adipose Tissue Health by Estrogens

Obesity and its' associated metabolic diseases such as type 2 diabetes and cardiometabolic disorders are significant health problems confronting many countries. A major driver for developing obesity and metabolic dysfunction is the uncontrolled expansion of white adipose tissue (WAT). Specifically, the pathophysiological expansion of visceral WAT is often associated with metabolic dysfunction due to changes in adipokine secretion profiles, reduced vascularization, increased fibrosis, and enrichment of pro-inflammatory immune cells. A critical determinate of body fat distribution and WAT health is the sex steroid estrogen. The bioavailability of estrogen appears to favor metabolically healthy subcutaneous fat over visceral fat growth while protecting against changes in metabolic dysfunction. Our review will focus on the role of estrogen on body fat partitioning, WAT homeostasis, adipogenesis, adipocyte progenitor cell (APC) function, and thermogenesis to control WAT health and systemic metabolism.

Insights of the role of estrogen in obesity from two models of ERα deletion

Sex hormones play a pivotal role in physiology and disease. Estrogen, the female sex hormone, has been long implicated in having protective roles against obesity. However, the direct impact of estrogens in white adipose tissue (WAT) function and growth is not understood. Here, we show that the deletion of estrogen receptor alpha (ERα; Esr1) from adipocytes using Adipoq-credoes not affect adipose mass in male or female mice under normal or high-fat diet (HFD) conditions. However, loss of ERα in adipocyte precursor cells (APs) via Pdgfra-cre leads to exacerbated obesity upon HFD feeding in both male and female mice, with s.c. adipose (SWAT)-specific expansion in male mice. Further characterization of these mice revealed infertility and increased plasma levels of sex hormones, including estradiol in female mice and androgens in male mice. These findings compromise the study of estrogen signaling within the adipocyte lineage using the Pdgfra-crestrain. However, AP transplant studies demonstrate that the increased AP hyperplasia in male SWAT upon Pdgfra-cre-mediated ablation of ERα is not driven by AP-intrinsic mechanisms but is rather mediated by off-target effects. These data highlight the inherent difficulties in studying models that disrupt the intricate balance of sex hormones. Thus, better approaches are needed to study the cellular and molecular mechanisms of sex hormones in obesity and disease.

Metabolic and Epigenetic Regulation by Estrogen in Adipocytes

Sex hormones contribute to differences between males and females in body fat distribution and associated disease risk. Higher concentrations of estrogens are associated with a more gynoid body shape and with more fat storage on hips and thighs rather than in visceral depots. Estrogen-mediated protection against visceral adiposity is shown in post-menopausal women with lower levels of estrogens and the reduction in central body fat observed after treatment with hormone-replacement therapy. Estrogen exerts its physiological effects via the estrogen receptors (ERα, ERβ and GPR30) in target cells, including adipocytes. Studies in mice indicate that estrogen protects against adipose inflammation and fibrosis also before the onset of obesity. The mechanisms involved in estrogen-dependent body fat distribution are incompletely understood, but involve, e.g., increased mTOR signaling and suppression of autophagy and adipogenesis/lipid storage. Estrogen plays a key role in epigenetic regulation of adipogenic genes by interacting with enzymes that remodel DNA methylation and histone tail post-translational modifications. However, more studies are needed to map the differential epigenetic effects of ER in different adipocyte subtypes, including those in subcutaneous and visceral adipose tissues. We here review recent discoveries of ER-mediated transcriptional and epigenetic regulation in adipocytes, which may explain sexual dimorphisms in body fat distribution and obesity-related disease risk.

The prognostic roles of CYP19A1 expression in bladder cancer patients of different genders

Background

The incidence of bladder cancer (BCa) in male is approximately three to four times higher than in female, but the oncological outcomes in female patients with BCa are significantly worse than in male patients. Although many biomarkers have been identified in recent decades to predict the prognosis of BCa patients, few of them are able to distinguish the prognosis of BCa patients with gender difference. Aromatase encoded by the CYP19A1 gene catalyzes the conversion of androgens to estrogens. In this study, we investigate the prognosis significance of CYP19A1 expression considering the gender difference in BCa patients from four available public databases.

Methods

Four available public databases of BCa, including GSE13507, TCGA-BLCA, E-MTAB-4321, and E-MTAB-1803, were utilized in this analysis. The overall survival (OS) and progression-free survival (PFS) in different stages and genders were evaluated using the Kaplan-Meier analysis based on the optimal cut-off values of CYP19A1 expression. Then, Gene Set Enrichment Analysis (GSEA) were further performed to explore the potential biologic pathways by altering CYP19A1 expression in BCa patients.

Results

The results showed that patients with high CYP19A1 expression had a poorer outcome compared with those with low expression in both BCa cohorts in general. Higher CYP19A1 expression in male patients were significantly associated with shorter survival for either non-muscle-invasive bladder cancer (NMIBC) or muscle-invasive bladder cancer (MIBC). However, female NMIBC patients with high CYP19A1 expression were identified to have a better prognosis, whereas high CYP19A1 expression in female MIBC patients were significantly associated with poorer survival. The result of the GSEA showed that different outcomes in female and male patients with NMIBC were related to the interaction of CYP19A1 and the cell-cycle-related pathways.

Conclusions

These findings demonstrated that CYP19A1 expression might have a potential role in distinguishing the prognosis of female BCa patients dependent on tumor stage. Our results provide new insights for aromatase-mediated BCa therapy.

Age and Sex: Impact on adipose tissue metabolism and inflammation

Age associated chronic inflammation is a major contributor to diseases with advancing age. Adipose tissue function is at the nexus of processes contributing to age-related metabolic disease and mediating longevity. Hormonal fluctuations in aging potentially regulate age-associated visceral adiposity and metabolic dysfunction. Visceral adiposity in aging is linked to aberrant adipogenesis, insulin resistance, lipotoxicity and altered adipokine secretion. Age-related inflammatory phenomena depict sex differences in macrophage polarization, changes in T and B cell numbers, and types of dendritic cells. Sex differences are also observed in adipose tissue remodeling and cellular senescence suggesting a role for sex steroid hormones in the regulation of the adipose tissue microenvironment. It is crucial to investigate sex differences in aging clinical outcomes to identify and better understand physiology in at-risk individuals. Early interventions aimed at targets involved in adipose tissue adipogenesis, remodeling and inflammation in aging could facilitate a profound impact on health span and overcome age-related functional decline.

The Association Between Dietary Inflammatory Potential and Sex Hormones in Male Children and Adolescents Aged 6-19 Years

Aims

This study aimed to assess the relationship between dietary inflammatory index (DII) and sex hormones in male children and adolescents aged 6-19 years.

Methods

We obtained data from the 2013-2016 National Health and Nutrition Examination Survey (NHANES). Male participants aged 6-19 years old with the complete data of DII and sex hormones were included. Weighted multiple regression analysis and subgroup analysis were preformed to estimate the independent relationship between DII and sex hormones.

Results

A total of 1717 male participants with the average age of 13.02 ± 3.82 years were enrolled, of whom 41.3% (n=713) were children and 58.47% (n=1004) were adolescents. In children, mean DII was 0.18 ± 1.67, with scores ranging from -4.53 to 4.08. As for adolescents, the mean DII was 0.36 ± 1.98, mean total testosterone (TT) was 376.94 ± 206.69 ng/dl overall. A negative association between DII with TT and estradiol (E2) was observed (TT: β=-11.97, P=0.0006; E2: β=-0.45, P=0.0108) in male adolescent. Subgroup analysis and interaction test results indicated that this association was similar in male adolescents with different body mass index. No statistically significant association was observed in children.

Conclusions

Pro-inflammatory diet was associated with lower TT and E2 level in male adolescent, while no association with statistical significance between them was observed in male children. However, more studies are still needed to validate the causal relationship between DII and sex hormones.

Acetaminophen Modulates the Expression of Steroidogenesis-Associated Genes and Estradiol Levels in Human Placental JEG-3 Cells

Acetaminophen is the only medication recommended for pain and fever management during pregnancy. However, studies have reported an association between in utero acetaminophen and neurocognitive disorders later in life. Additionally, acetaminophen has been shown to have endocrine disrupting properties altering hormones critical for normal fetal development. As the placenta is an endocrine organ that produces hormones for fetal development, any attempts to elucidate the mechanism underlying in utero acetaminophen and birth outcomes must also focus on the placenta. The present study set out to examine the effect of acetaminophen on mRNA expression, protein expression, and hormone synthesis in placental JEG-3 cells. The analysis focused on genes involved in steroidogenesis and acetaminophen metabolism as well those with known roles as nuclear receptors and transporters. The results highlight that at high concentrations, acetaminophen reduced the gene expression of aromatase (CYP19A1) and type 1 3β-hydroxysteroid dehydrogenase (HSD3B1), and increased the expression of 17β-hydroxysteroid dehydrogenase (HSD17B1). Additionally, acetaminophen at high concentrations also reduced the protein expression of aromatase (CYP19A1). These effects were accompanied by a significant dose-dependent decrease in estradiol secretion. Estradiol plays an important role in the development of reproductive organs and the brain of the developing fetus. This study highlights the potential for acetaminophen to interfere with hormone regulation during pregnancy and underscores the need for additional studies aimed at understanding the endocrine disruption activity of acetaminophen during fetal development.

Sex Differences in Brown Adipose Tissue Function: Sex Hormones, Glucocorticoids, and Their Crosstalk

Excessive fat accumulation in the body causes overweight and obesity. To date, research has confirmed that there are two types of adipose tissue with opposing functions: lipid-storing white adipose tissue (WAT) and lipid-burning brown adipose tissue (BAT). After the rediscovery of the presence of metabolically active BAT in adults, BAT has received increasing attention especially since activation of BAT is considered a promising way to combat obesity and associated comorbidities. It has become clear that energy homeostasis differs between the sexes, which has a significant impact on the development of pathological conditions such as type 2 diabetes. Sex differences in BAT activity may contribute to this and, therefore, it is important to address the underlying mechanisms that contribute to sex differences in BAT activity. In this review, we discuss the role of sex hormones in the regulation of BAT activity under physiological and some pathological conditions. Given the increasing number of studies suggesting a crosstalk between sex hormones and the hypothalamic-pituitary-adrenal axis in metabolism, we also discuss this crosstalk in relation to sex differences in BAT activity.

Adipose tissue inflammation and metabolic dysfunction in obesity

Several lines of preclinical and clinical research have confirmed that chronic low-grade inflammation of adipose tissue is mechanistically linked to metabolic disease and organ tissue complications in the overweight and obese organism. Despite this widely confirmed paradigm, numerous open questions and knowledge gaps remain to be investigated. This is mainly due to the intricately intertwined cross-talk of various pro- and anti-inflammatory signaling cascades involved in the immune response of expanding adipose depots, particularly the visceral adipose tissue. Adipose tissue inflammation is initiated and sustained over time by dysfunctional adipocytes that secrete inflammatory adipokines and by infiltration of bone marrow-derived immune cells that signal via production of cytokines and chemokines. Despite its low-grade nature, adipose tissue inflammation negatively impacts remote organ function, a phenomenon that is considered causative of the complications of obesity. The aim of this review is to broadly present an overview of adipose tissue inflammation by highlighting the most recent reports in the scientific literature and summarizing our overall understanding of the field. We also discuss key endogenous anti-inflammatory mediators and analyze their mechanistic role(s) in the pathogenesis and treatment of adipose tissue inflammation. In doing so, we hope to stimulate studies to uncover novel physiological, cellular, and molecular targets for the treatment of obesity.

Hypothesized mechanisms explaining poor prognosis in type 2 diabetes patients with COVID-19: a review

PURPOSE

Epidemiological data suggest that comorbid patients, mostly those with type 2 diabetes (T2D), are predisposed to poor prognosis in Coronavirus disease 2019 (COVID-19), leading to serious healthcare concerns. The aim of the present manuscript is to review the main relevant mechanisms possibly contributing to worsen the clinical course of COVID-19 in T2D.

RESULTS

Poor glucose control, high glycaemic variability and diabetes-related comorbidities at baseline, particularly cardiovascular diseases and obesity, contribute in worsening the prognosis in the above-mentioned cluster of patients. Moreover, both a lower efficient innate immune system response and cytokine dysregulation predispose patients with T2D to impaired viral clearance and more serious pulmonary and systemic inflammation once the SARS-CoV-2 infection occurred. Inconclusive data are currently available for specifically indicate or contraindicate concurrent medications for managing T2D and its comorbidities in infected patients.

CONCLUSIONS

T2D individuals should be considered as more vulnerable to COVID-19 than general population, and thus require adequate advices about hygienic tips to protect themselves during the pandemic. A careful management of glucose levels and diabetes-related comorbidities remains essential for avoiding further complications, and patient monitoring during the pandemic should be performed also at distance by means of telemedicine. Further studies are needed to clarify whether medications normally used for managing T2D and its associated comorbidities could have a protective or detrimental effect on COVID-19 clinical course.

Age, Sex, and Depot-Specific Differences in Adipose-Tissue Estrogen Receptors in Individuals with Obesity

OBJECTIVE

The aim of this study was to examine the effects of sex and menopausal status on depot-specific estrogen signaling in white adipose tissue (AT) in age-matched men and women with morbid obesity.

METHODS

A total of 28 premenopausal women, 16 postmenopausal women, and 27 age-matched men undergoing bariatric surgery were compared for omental (OM) AT (OMAT) and abdominal subcutaneous (SQ) AT (SQAT) genes and proteins.

RESULTS

With the exception of fasting nonesterified fatty acids being higher in women (P < 0.01), no differences were found in other indicators of glucose and lipid metabolism. In OMAT, estrogen receptor (ER) beta (ERβ) levels were higher in older women than in younger women and older men (sex-age interaction, P < 0.01), and aromatase expression was higher in older men than in older women (P < 0.05). In SQAT, women had lower expression of ERβ than men (P < 0.05). Protein content of ER alpha and ERβ was highly correlated with the mitochondrial protein uncoupling protein 1 across sexes and ages (P < 0.001). Age increased SQ inflammatory gene expression in both sexes.

CONCLUSIONS

In morbid obesity, sex and age affect AT ERs, lipid metabolism, mitochondrial uncoupling protein 1, and inflammatory expression in an AT depot-dependent manner. The SQAT immunometabolic profile is heavily influenced by age and menopause status, more so than OMAT.

Worse progression of COVID-19 in men: Is testosterone a key factor?

Background

The novel severe acute respiratory syndrome coronavirus (SARS‐CoV‐2) disease 2019 (COVID‐19) seems to have a worse clinical course among infected men compared with women, thus highlighting concerns about gender predisposition to serious prognosis. Therefore, androgens, particularly testosterone (T), could be suspected as playing a critical role in driving this excess of risk. However, gonadal function in critically ill men is actually unknown, mainly because serum T concentration is not routinely measured in clinical practice, even more in this clinical context.

Objective

To overview on possible mechanisms by which serum T levels could affect the progression of COVID‐19 in men.

Methods

Authors searched PubMed/MEDLINE, Web of Science, EMBASE, Cochrane Library, Google, and institutional websites for medical subject headings terms and free text words referred to “SARS‐CoV‐2,” “COVID‐19,” “testosterone,” “male hypogonadism,” “gender” “immune system,” “obesity,” “thrombosis” until May 19th 2020.

Results

T, co‐regulating the expression of angiotensin‐converting enzyme 2 and transmembrane protease serine 2 in host cells, may facilitate SARS‐CoV‐2 internalization. Instead, low serum T levels may predispose to endothelial dysfunction, thrombosis and defective immune response, leading to both impaired viral clearance and systemic inflammation. Obesity, one of the leading causes of severe prognosis in infected patients, is strictly associated with functional hypogonadism, and may consistently strengthen the aforementioned alterations, ultimately predisposing to serious respiratory and systemic consequences.

Discussion and conclusion

T in comparison to estrogen may predispose men to a widespread COVID‐19 infection. Low serum levels of T, which should be supposed to characterize the hormonal milieu in seriously ill individuals, may predispose men, especially elderly men, to poor prognosis or death. Further studies are needed to confirm these pathophysiological assumptions and to promptly identify adequate therapeutic strategies.

TLR4 induced Wnt3a-Dvl3 restrains the intensity of inflammation and protects against endotoxin-driven organ failure through GSK3β/β-catenin signaling

BACKGROUND

Accumulating evidence suggests a regulatory role of Wnt proteins in innate immune responses. However, the effects of Wnt3a signaling on TLR4-mediated inflammatory responses are controversial and the signaling crosstalk between TLR4 and Wnt3a remains uncertain.

METHODS

Gain- and Loss- of function approaches were utilized to determine the function of Wnt3a signaling in TLR4-mediated inflammatory responses. Cytokine production at protein and mRNA levels and phosphorylation of signaling molecules were measured by ELISA, qRT-PCR, and Western Blot, respectively. Endotoxemia mouse model was employed to assess the effect of Wnt3a on systemic inflammatory cytokine levels and neutrophil infiltration.

RESULTS

LPS stimulation leads to an increase of Wnt3a expression and its downstream molecule, Dvl3, in primary monocytes. Inhibition or silence of Wnt3a or Dvl3 significantly increases the production of pro-inflammatory cytokines (IL-12, IL-6, TNFα), robustly reduces β-catenin accumulation, and enhances the phosphorylation of NF-κB P65 and its DNA binding activity. These results were confirmed by multiple gain- and loss- of function approaches including specific siRNA and ectopic expression of Dvl3, GSK3β, and β-catenin in monocytes. Moreover, in vivo relevance was established in a murine endotoxin model, in which Wnt3a inhibition enhances the inflammatory responses by augmenting the systemic pro-inflammatory cytokine levels and neutrophil infiltration.

CONCLUSIONS

TLR4 activation promotes Wnt3a-Dvl3 signaling, which acts as rheostats to restrain the intensity of inflammation through regulating GSK3β-β-catenin signaling and NF-κB activity.

GENERAL SIGNIFICANCE

Wnt3a-Dvl3-β-catenin signaling axis could be a potential interventional target for manipulating the direction and intensity of inflammatory responses.

Aromatase deficiency in hematopoietic cells improves glucose tolerance in male mice through skeletal muscle-specific effects

Estrogens are important for maintaining metabolic health in males. However, the key sources of local estrogen production for regulating energy metabolism have not been fully defined. Immune cells exhibit aromatase activity and are resident in metabolic tissues. To determine the relative contribution of immune cell-derived estrogens for metabolic health in males, C57BL6/J mice underwent bone marrow transplant with marrow from either wild-type (WT(WT)) or aromatase-deficient (WT(ArKO)) donors. Body weight, body composition, and glucose and insulin tolerance were assessed over 24 weeks with mice maintained on a regular chow diet. No differences were found in insulin sensitivity between groups, but WT(ArKO) mice were more glucose tolerant than WT(WT) mice 20 weeks after transplant, suggestive of enhanced glucose disposal (AUCglucose 6061±3349 in WT(WT) mice versus 3406±1367 in WT(ArKO) mice, p = 0.01). Consistent with this, skeletal muscle from WT(ArKO) mice showed higher expression of the mitochondrial genes Ppargc1a (p = 0.03) and Nrf1 (p = 0.01), as well as glucose transporter type 4 (GLUT4, Scl2a4; p = 0.02). Skeletal muscle from WT(ArKO) mice had a lower concentration of 17β-estradiol (5489±2189 pg/gm in WT(WT) mice versus 3836±2160 pg/gm in WT(ArKO) mice, p = 0.08) but higher expression of estrogen receptor-α (ERα, Esr1), raising the possibility that aromatase deficiency in immune cells led to a compensatory increase in ERα signaling. No differences between groups were found with regard to body weight, adiposity, or gene expression within adipose tissue or liver. Immune cells are a key source of local 17β-estradiol production and contribute to metabolic regulation in males, particularly within skeletal muscle. The respective intracrine and paracrine roles of immune cell-derived estrogens require further delineation, as do the pathways that regulate aromatase activity in immune cells specifically within metabolic tissues.

Estradiol stimulates adipogenesis and Slc2a4/GLUT4 expression via ESR1-mediated activation of CEBPA

The ability of adipose tissue to expand is dependent on adipocyte differentiation and adipose tissue glucose disposal. The CCAAT/enhancer-binding protein alpha (CEBPA) enhances the expression of the Slc2a4 gene and GLUT4 protein, which are markers of adipocyte differentiation/glucose disposal. We hypothesized estradiol (E2) facilitates adipocyte differentiation/glucose disposal by an estrogen receptor 1 (ESR1)-dependent and CEBPA-mediated mechanism. Our results suggest that E2 (10 nM) has a positive effect on 3T3-L1 adipocyte differentiation (days 2-8), lipid accumulation, Slc2a4 and Cebpa mRNA expression, total GLUT4 and nuclear CEBPA contents, and CEBP/Slc2a4-binding activity. Esr1 silencing (∼50%) in mature adipocytes abrogates the 24-h E2 effects on nuclear CEBPA content, Slc2a4/GLUT4 expression and GLUT4 translocation to the cell membrane. Thus, E2 stimulates adipocyte differentiation and Slc2a4/GLUT4 expression in an ESR1/CEBPA-mediated pathway. Our data provide mechanistic insight demonstrating E2 participates in adipose-tissue differentiation and glucose transporter expression which ultimately can improve adipose tissue expandability and glycemic control.

Androgens sensitise mice to glucocorticoid-induced insulin resistance and fat accumulation

AIMS/HYPOTHESIS

Chronic glucocorticoid therapy causes insulin resistance, dyslipidaemia, abnormal fat accumulation, loss of muscle mass and osteoporosis. Here we describe a hitherto unknown sexual dimorphism in the metabolic response to chronic glucocorticoid exposure in mice. This led us to investigate whether glucocorticoid-induced insulin resistance and obesity were dependent on sex hormones.

METHODS

Male and female CD1 mice were treated for 4 weeks with supraphysiological doses (~250 μg/day) of corticosterone, the main glucocorticoid in rodents, or equivalent volume of vehicle (drinking water without corticosterone). To investigate the effects of sex hormones, a separate group of mice were either orchidectomised or ovariectomised prior to corticosterone treatment, with or without dihydrotestosterone replacement. Body composition was determined before and after corticosterone treatment, and insulin tolerance was assessed after 7 and 28 days of treatment. Adipocyte morphology was assessed in white and brown adipose tissues by immunohistochemistry, and fasting serum concentrations of NEFA, triacylglycerols, total cholesterol and free glycerol were measured using colorimetric assays. Obesity- and diabetes-related hormones were measured using multiplex assays, and RNA and protein expression in adipose tissues were measured by RT-PCR and immunoblotting, respectively.

RESULTS

Chronic corticosterone treatment led to insulin resistance, fasting hyperinsulinaemia, increased adiposity and dyslipidaemia in male, but not female mice. In males, orchidectomy improved baseline insulin sensitivity and attenuated corticosterone-induced insulin resistance, but did not prevent fat accumulation. In androgen-deficient mice (orchidectomised males, and intact and ovariectomised females) treated with dihydrotestosterone, corticosterone treatment led to insulin resistance and dyslipidaemia. In brown adipose tissue, androgens were required for corticosterone-induced intracellular lipid accumulation ('whitening'), and dihydrotestosterone specifically exacerbated corticosterone-induced accumulation of white adipose tissue by increasing adipocyte hypertrophy. Androgens also suppressed circulating adiponectin concentrations, but corticosterone-induced insulin resistance did not involve additional suppression of adiponectin levels. In white adipose tissue, androgens were required for induction of the glucocorticoid target gene Gilz (also known as Tsc22d3) by corticosterone.

CONCLUSIONS/INTERPRETATION

In mice, androgens potentiate the development of insulin resistance, fat accumulation and brown adipose tissue whitening following chronic glucocorticoid treatment.

Obesity and male hypogonadism: Tales of a vicious cycle

Obesity prevalence, particularly in children and young adults, is perilously increasing worldwide foreseeing serious negative health impacts in the future to come. Obesity is linked to impaired male gonadal function and is currently a major cause of hypogonadism. Besides signs and symptoms directly derived from decreased circulating testosterone levels, males with obesity also present poor fertility outcomes, further evidencing the parallelism between obesity and male reproductive function. In addition, males with androgen deficiency also exhibit increased fat accumulation and reduced muscle and mineral bone mass. Thus, compelling evidence highlights a vicious cycle where male hypogonadism can lead to increased adiposity, while obesity can be a cause for male hypogonadism. On the opposite direction, sustained weight loss can attain amelioration of male gonadal function. In this scenario, a thorough evaluation of gonadal function in men with obesity is crucial to dissect the causes from the consequences in order to target clinical interventions towards maximized improvement of reproductive health. This review will address the causes and consequences of the bidirectional relationship between obesity and hypogonadism, highlighting the implicit male reproductive repercussions.

Sex hormones, aging and cardiometabolic syndrome

It is well documented that the metabolic syndrome predisposes patients to increased cardiovascular risk. Emerging data indicates that cardiovascular risk conferred by metabolic syndrome is highly dependent on sex and sex hormone status throughout the lifetime. Both male and female sex hormones, as well as sex chromosomes themselves, contribute to the development of obesity and intervene in the control of insulin homeostasis and blood pressure. Furthermore, men and women develop age-associated cardiometabolic risk in a sex-specific fashion in association with changes in these sex hormonal levels. Therefore, the current notion of the metabolic syndrome as a sex-independent diagnosis is antiquated, and novel studies and clinical trials utilizing these known sex differences in the development of metabolic dysregulation and cardiometabolic risk are warranted.

Immunometabolic Links between Estrogen, Adipose Tissue and Female Reproductive Metabolism

The current knowledge of sex-dependent differences in adipose tissue biology remains in its infancy and is motivated in part by the desire to understand why menopause is linked to an increased risk of metabolic disease. However, the development and characterization of targeted genetically-modified rodent models are shedding new light on the physiological actions of sex hormones in healthy reproductive metabolism. In this review we consider the need for differentially regulating metabolic flexibility, energy balance, and immunity in a sex-dependent manner. We discuss the recent advances in our understanding of physiological roles of systemic estrogen in regulating sex-dependent adipose tissue distribution, form and function; and in sex-dependent healthy immune function. We also review the decline in protective properties of estrogen signaling in pathophysiological settings such as obesity-related metaflammation and metabolic disease. It is clear that the many physiological actions of estrogen on energy balance, immunity, and immunometabolism together with its dynamic regulation in females make it an excellent candidate for regulating metabolic flexibility in the context of reproductive metabolism.

Androgens modulate glucocorticoid receptor activity in adipose tissue and liver

Glucocorticoid signaling is context-dependent, and in certain scenarios glucocorticoid receptors (GR) are able to engage with other members of the nuclear receptor subfamily. Glucocorticoid signaling can exert sexually dimorphic effects, suggesting a possible interaction with androgen sex hormones. We therefore set out to determine the crosstalk between glucocorticoids and androgens in metabolic tissues including white adipose tissue, liver and brown adipose tissue. Thereto we exposed male C57BL/6J mice to elevated levels of corticosterone in combination with an androgen receptor (AR) agonist or an AR antagonist. Systemic and local glucocorticoid levels were determined by mass spectrometry, tissue expression of glucocorticoid-responsive genes and protein was measured by RT-qPCR and Western blot, respectively. To evaluate crosstalk in vitro, cultured white and brown adipocytes were exposed to a combination of corticosterone and an androgen agonist. We found that AR agonism potentiated transcriptional response to GR in vitro in white and brown adipocytes and in vivo in white and brown adipose tissue. Conversely, AR antagonism substantially attenuated glucocorticoid signaling in white adipose tissue and liver. In white adipose tissue this effect could partially be attributed to decreased 11B-hydroxysteroid dehydrogenase type 1-mediated glucocorticoid regeneration upon AR antagonism. In liver, attenuated GR activity was independent of active glucocorticoid ligand levels. We conclude that androgen signaling modulates GR transcriptional output in a tissue-specific manner.

Hypogonadism and male obesity: Focus on unresolved questions

Obesity, increasing in prevalence globally, is the clinical condition most strongly associated with lowered testosterone concentrations in men and presents as one of the strongest predictors of receiving testosterone treatment. While low circulating total testosterone concentrations in modest obesity primarily reflect reduced concentrations of sex hormone binding globulin, more marked obesity can lead to genuine hypothalamic-pituitary-testicular axis (HPT) suppression. HPT axis suppression is likely mediated via pro-inflammatory cytokine and dysregulated leptin signalling and aggravated by associated comorbidities. Whether oestradiol-mediated negative hypothalamic-pituitary feedback plays a pathogenic role requires further study. Although the obesity-hypogonadism relationship is bidirectional, the effects of obesity on testosterone concentrations are more substantial than the effects of testosterone on adiposity. In markedly obese men submitted to bariatric surgery, substantial weight loss is very effective in reactivating the HPT axis. In contrast, lifestyle measures are less effective in reducing weight and generally only associated with modest increases in circulating testosterone. In randomized controlled clinical trials (RCTs), testosterone treatment does not reduce body weight, but modestly reduces fat mass and increases muscle mass. Short-term studies have shown that testosterone treatment in carefully selected obese men may have modest benefits on symptoms of androgen deficiency and body composition even additive to diet alone. However, longer term, larger RCTs designed for patient-important outcomes and potential risks are required. Until such trials are available, testosterone treatment cannot be routinely recommended for men with obesity-associated nonclassical hypogonadism. Lifestyle measures or where indicated bariatric surgery to achieve weight loss, and optimization of comorbidities remain first line.

An intracrine view of sex steroids, immunity, and metabolic regulation

Background

Over the past two decades, parallel recognition has grown of the importance of both sex steroids and immune activity in metabolic regulation. More recently, these discrete areas have been integrated in studies examining the metabolic effects of sex steroid immunomodulation. Implicit in these studies has been a traditional, endocrine model of sex steroid delivery from the gonads to target cells, including immune cells. Thus, research to date has focused on the metabolic effects of sex steroid receptor signaling in immune cells. This endocrine model, however, overlooks the extensive capacity of immune cells to generate and metabolize sex steroids, enabling the production of sex steroids for intracrine signaling – that is, sex steroid production for signaling within the cell of origin. Intracrine function allows highly cell-autonomous regulation of sex steroid exposure, and sex steroid secretion by immune cells could confer paracrine signaling effects in neighboring cells within metabolic tissues. In this review, immune cell intracrinology will denote sex steroid production within immune cells for either intracrine or paracrine signaling. This intracrine capacity of immune cells has been well established, and prior work has supported its importance in autoimmune disorders, trauma, and cancer. The potential relevance of immune cell intracrine function to the regulation of energy balance, body weight, body composition, and insulin sensitivity has yet to be explored.

Scope of review

The following review will detail findings to date regarding the steroidogenic and steroid metabolizing capacity of immune cells, the regulation of immune cell intracrine function, and the biological effects of immune-derived sex steroids, including the clinical relevance of immune cell intracrinology in fields other than metabolism. These findings will serve as the basis for a proposed model of immune cell intracrinology constituting a new frontier in metabolism research.

Major conclusions

The development of highly sensitive mass spectrometric methods for sex steroid measurement and quantitation of metabolic flux now allows unprecedented ability to interrogate sex steroid production, metabolism and secretion by immune cells. Immune cell intracrinology could reveal key mechanisms underlying immune cell-mediated metabolic regulation.

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Sex steroids exert immunomodulatory effects that may influence metabolic health.

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Immune cells can synthesize, modify, and metabolize sex steroids.

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Immune cell-derived sex steroids may play intracrine, autocrine, paracrine, and possibly even endocrine roles.

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Immune cell steroidogenesis is a largely unexplored area of metabolism research.

The Role of Sex and Sex Hormones in Regulating Obesity-Induced Inflammation

Metabolic and non-metabolic complications due to obesity are becoming more prevalent, yet our understanding of the mechanisms driving these is not. This is due to individual risk factor variability making it difficult to predict disease outcomes such as diabetes and insulin resistance. Gender is a critical factor in obesity outcomes with women having more adiposity but reduced metabolic complications compared to men. The role of immune system activation during obesity is an emerging field that links adiposity to metabolic syndrome. Furthermore, evidence from animal models suggests that sex differences exist in immune responses and, therefore, could be a possible mechanism leading to sex differences in metabolic disease. While there is still much to learn in the area of sex-differences research, this chapter will review the current knowledge and literature detailing the role of sex and sex hormones on adiposity and metabolically induced inflammation in obesity.