Leptin and the endocrine control of energy balance

Is the leptin/BMI ratio a reliable biomarker for endometriosis?

Background

The aim of this study was to analyze the concentration of leptin in peritoneal fluid and plasma and to assess their role as potential biomarkers in the diagnosis of endometriosis.

Materials & methods

Leptin adjusted for BMI (leptin/BMI ratio) was measured using surface plasmon resonance imaging (SPRI) biosensors. Patients with suspected endometriosis were included in the study. Plasma was collected from 70 cases, and peritoneal fluid from 67 cases. Based on the presence of endometriosis lesions detected during laparoscopy, patients were divided into a study group and a control group (patients without endometriosis).

Results

Leptin/BMI ratio in plasma did not differ between women with endometriosis and the control group (0.7159 ± 0.259 vs 0.6992 ± 0.273, p= 0,7988). No significant differences were observed in peritoneal leptin/BMI ratio levels in patients with and without endometriosis (0.6206 ± 0.258 vs 0.6215 ± 0.264, p= 0,9896). Plasma and peritoneal leptin/BMI ratios were significantly lower in women with endometriosis - related primary infertility compared to women with endometriosis without primary infertility (0.640 ± 0.502 vs 0.878 ± 0.623, p < 0.05). The difference was observed in case of primary infertility, but not in terms of the secondary one. No significant differences were noted between leptin/BMI ratio in the proliferative phase and the secretory phase (0.716 ± 0.252 vs 0.697 ± 0.288, p= 0,7785).

Conclusion

The results of present study do not support the relevance of leptin concentration determination as a biomarker of the endometriosis. Due to the limited number of samples in the tested group, further studies are needed to confirm its role.

Adipose Tissue Dysfunction and Energy Balance Paradigms in People Living With HIV

Over the past 4 decades, the clinical care of people living with HIV (PLWH) evolved from treatment of acute opportunistic infections to the management of chronic, noncommunicable comorbidities. Concurrently, our understanding of adipose tissue function matured to acknowledge its important endocrine contributions to energy balance. PLWH experience changes in the mass and composition of adipose tissue depots before and after initiating antiretroviral therapy, including regional loss (lipoatrophy), gain (lipohypertrophy), or mixed lipodystrophy. These conditions may coexist with generalized obesity in PLWH and reflect disturbances of energy balance regulation caused by HIV persistence and antiretroviral therapy drugs. Adipocyte hypertrophy characterizes visceral and subcutaneous adipose tissue depot expansion, as well as ectopic lipid deposition that occurs diffusely in the liver, skeletal muscle, and heart. PLWH with excess visceral adipose tissue exhibit adipokine dysregulation coupled with increased insulin resistance, heightening their risk for cardiovascular disease above that of the HIV-negative population. However, conventional therapies are ineffective for the management of cardiometabolic risk in this patient population. Although the knowledge of complex cardiometabolic comorbidities in PLWH continues to expand, significant knowledge gaps remain. Ongoing studies aimed at understanding interorgan communication and energy balance provide insights into metabolic observations in PLWH and reveal potential therapeutic targets. Our review focuses on current knowledge and recent advances in HIV-associated adipose tissue dysfunction, highlights emerging adipokine paradigms, and describes critical mechanistic and clinical insights.

Cotadutide (GLP-1/Glucagon dual receptor agonist) modulates hypothalamic orexigenic and anorexigenic neuropeptides in obese mice

The hypothalamic neuropeptides linked to appetite and satiety were investigated in obese mice treated with cotadutide (a dual receptor agonist of glucagon-like peptide 1 (GLP-1R)/Glucagon (GCGR)). Twelve-week-old male C57BL/6 mice were fed a control diet (C group, n = 20) or a high-fat diet (HF group, n = 20) for ten weeks. Each group was further divided, adding cotadutide treatment and forming groups C, CC, HF, and HFC for four additional weeks. The hypothalamic arcuate neurons were labeled by immunofluorescence, and protein expressions (Western blotting) for neuropeptide Y (NPY), proopiomelanocortin (POMC), agouti-related protein (AgRP), and cocaine- and amphetamine-regulated transcript (CART). Cotadutide enhanced POMC and CART neuropeptides and depressed NPY and AGRP neuropeptides. In addition, gene expressions (RT-qPCR) determined that Lepr (leptin receptor) and Calcr (calcitonin receptor) were diminished in HF compared to C but enhanced in CC compared to C and HFC compared to HF. Besides, Socs3 (suppressor of cytokine signaling 3) was decreased in HFC compared to HF, while Sst (somatostatin) was higher in HFC compared to HF; Tac1 (tachykinin 1) and Mc4r (melanocortin-4-receptor) were lower in HF compared to C but increased in HFC compared to HF. Also, Glp1r and Gcgr were higher in HFC compared to HF. In conclusion, the findings are compelling, demonstrating the effects of cotadutide on hypothalamic neuropeptides and hormone receptors of obese mice. Cotadutide modulates energy balance through the gut-brain axis and its associated signaling pathways. The study provides insights into the mechanisms underlying cotadutide's anti-obesity effects and its possible implications for obesity treatment.

Wiring the Brain for Wellness: Sensory Integration in Feeding and Thermogenesis: A Report on Research Supported by Pathway to Stop Diabetes

The recognition of sensory signals from within the body (interoceptive) and from the external environment (exteroceptive), along with the integration of these cues by the central nervous system, plays a crucial role in maintaining metabolic balance. This orchestration is vital for regulating processes related to both food intake and energy expenditure. Animal model studies indicate that manipulating specific populations of neurons in the central nervous system which influence these processes can effectively modify energy balance. This body of work presents an opportunity for the development of innovative weight loss therapies for the treatment of obesity and type 2 diabetes. In this overview, we delve into the sensory cues and the neuronal populations responsible for their integration, exploring their potential in the development of weight loss treatments for obesity and type 2 diabetes. This article is the first in a series of Perspectives that report on research funded by the American Diabetes Association Pathway to Stop Diabetes program.

ARTICLE HIGHLIGHTS

Adipose tissue as a therapeutic target for vascular damage in Alzheimer's disease

Adipose tissue has recently been recognized as an important endocrine organ that plays a crucial role in energy metabolism and in the immune response in many metabolic tissues. With this regard, emerging evidence indicates that an important crosstalk exists between the adipose tissue and the brain. However, the contribution of adipose tissue to the development of age-related diseases, including Alzheimer's disease, remains poorly defined. New studies suggest that the adipose tissue modulates brain function through a range of endogenous biologically active factors known as adipokines, which can cross the blood-brain barrier to reach the target areas in the brain or to regulate the function of the blood-brain barrier. In this review, we discuss the effects of several adipokines on the physiology of the blood-brain barrier, their contribution to the development of Alzheimer's disease and their therapeutic potential. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Unraveling Adipose Tissue Dysfunction: Molecular Mechanisms, Novel Biomarkers, and Therapeutic Targets for Liver Fat Deposition

Adipose tissue (AT), once considered a mere fat storage organ, is now recognized as a dynamic and complex entity crucial for regulating human physiology, including metabolic processes, energy balance, and immune responses. It comprises mainly two types: white adipose tissue (WAT) for energy storage and brown adipose tissue (BAT) for thermogenesis, with beige adipocytes demonstrating the plasticity of these cells. WAT, beyond lipid storage, is involved in various metabolic activities, notably lipogenesis and lipolysis, critical for maintaining energy homeostasis. It also functions as an endocrine organ, secreting adipokines that influence metabolic, inflammatory, and immune processes. However, dysfunction in WAT, especially related to obesity, leads to metabolic disturbances, including the inability to properly store excess lipids, resulting in ectopic fat deposition in organs like the liver, contributing to non-alcoholic fatty liver disease (NAFLD). This narrative review delves into the multifaceted roles of WAT, its composition, metabolic functions, and the pathophysiology of WAT dysfunction. It also explores diagnostic approaches for adipose-related disorders, emphasizing the importance of accurately assessing AT distribution and understanding the complex relationships between fat compartments and metabolic health. Furthermore, it discusses various therapeutic strategies, including innovative therapeutics like adipose-derived mesenchymal stem cells (ADMSCs)-based treatments and gene therapy, highlighting the potential of precision medicine in targeting obesity and its associated complications.

Circulating leptin levels in the assessment of Crohn's disease activity and its relation to nutritional status

Introduction

Objective: to evaluate leptin levels and its relation to nutritional status in Crohn's disease (CD). Methods: the study included 154 CD patients and healthy controls. Leptin level was determined before treatment. Nutrition levels were assessed using the Nutrition Risk Screening 2002 (NRS-2002) and Patient-Generated Subjective Global Assessment (PG-SGA). Indicators included body mass index (BMI), mid-arm circumference, the circumference of the upper-arm muscle, triceps skinfold thickness, and circumference of legs. Results: leptin levels differed between CD patients (1,025 ± 874 ng/ml) and controls (18,481,222 ng/ml). Significant differences were seen in NRS-2002, PG-SGA scores, BMI and other nutritional indicators. Negative correlations were observed between leptin and NRS-2002, PG-SGA scores, while positive correlations were observed with other nutritional indicators. The receiver operating characteristic (ROC) curve showed association between leptin and the diagnosis of CD, suggesting leptin concentration below 803.02 ng/ml as a threshold for CD. Conclusion: dysfunctional leptin regulation may relate to poor nutritional status associated with CD. The leptin level is thus an additional tool for evaluating CD patients, predicting disease activity and clinical response. Leptin may be a potential target for intervention in CD to improve nutritional status.

Protection against overfeeding-induced weight gain is preserved in obesity but does not require FGF21 or MC4R

Overfeeding triggers homeostatic compensatory mechanisms that counteract weight gain. Here, we show that both lean and diet-induced obese (DIO) male mice exhibit a potent and prolonged inhibition of voluntary food intake following overfeeding-induced weight gain. We reveal that FGF21 is dispensable for this defense against weight gain. Targeted proteomics unveiled novel circulating factors linked to overfeeding, including the protease  legumain (LGMN). Administration of recombinant LGMN lowers body weight and food intake in DIO mice. The protection against weight gain is also associated with reduced vascularization in the hypothalamus and sustained reductions in the expression of the orexigenic neuropeptide genes, Npy and Agrp, suggesting a role for hypothalamic signaling in this homeostatic recovery from overfeeding. Overfeeding of melanocortin 4 receptor (MC4R) KO mice shows that these mice can suppress voluntary food intake and counteract the enforced weight gain, although their rate of weight recovery is impaired. Collectively, these findings demonstrate that the defense against overfeeding-induced weight gain remains intact in obesity and involves mechanisms independent of both FGF21 and MC4R.

Mechanism of Acupuncture in Treating Obesity: Advances and Prospects

Obesity is a common metabolic syndrome that causes a significant burden on individuals and society. Conventional therapies include lifestyle interventions, bariatric surgery, and pharmacological therapies, which are not effective and have a high risk of adverse events. Acupuncture is an effective alternative for obesity, it modulates the hypothalamus, sympathetic activity and parasympathetic activity, obesity-related hormones (leptin, ghrelin, insulin, and CCK), the brain-gut axis, inflammatory status, adipose tissue browning, muscle blood flow, hypoxia, and reactive oxygen species (ROS) to influence metabolism, eating behavior, motivation, cognition, and the reward system. However, hypothalamic regulation by acupuncture should be further demonstrated in human studies using novel techniques, such as functional MRI (fMRI), positron emission tomography (PET), electroencephalogram (EEG), and magnetoencephalography (MEG). Moreover, a longer follow-up phase of clinical trials is required to detect the long-term effects of acupuncture. Also, future studies should investigate the optimal acupuncture therapeutic option for obesity. This review aims to consolidate the recent improvements in the mechanism of acupuncture for obesity as well as discuss the future research prospects and potential of acupuncture for obesity.

The Sympathetic-Immune Milieu in Metabolic Health and Diseases: Insights from Pancreas, Liver, Intestine, and Adipose Tissues

Sympathetic innervation plays a crucial role in maintaining energy balance and contributes to metabolic pathophysiology. Recent evidence has begun to uncover the innervation landscape of sympathetic projections and sheds light on their important functions in metabolic activities. Additionally, the immune system has long been studied for its essential roles in metabolic health and diseases. In this review, the aim is to provide an overview of the current research progress on the sympathetic regulation of key metabolic organs, including the pancreas, liver, intestine, and adipose tissues. In particular, efforts are made to highlight the critical roles of the peripheral nervous system and its potential interplay with immune components. Overall, it is hoped to underscore the importance of studying metabolic organs from a comprehensive and interconnected perspective, which will provide valuable insights into the complex mechanisms underlying metabolic regulation and may lead to novel therapeutic strategies for metabolic diseases.

The role of serotonin hormone on weight loss maintenance after sleeve gastrectomy: a systematic review

Surgical interventions, such as laparoscopic sleeve gastrectomy (LSG), are frequently associated with significant weight loss. However, the initiation and maintenance of this weight reduction are multifaceted processes influenced by genetic, psychological, behavioral, dietary, and metabolic factors. This review examined the role of metabolic hormones, specifically serotonin, in sustaining weight loss post-LSG. A systematic evaluation of six research articles obtained from Scopus, PubMed, and Cochrane was conducted, focusing on the role of serotonin in weight loss maintenance. We included randomized controlled trials involving adults over 18 years. Studies lacking an intensive weight regulation approach were excluded. Information was systematically extracted and analyzed from the selected studies, with data on intervention and control groups summarized in tables to compare outcomes one year post-LSG. The findings revealed a complex interplay between serotonin and its role in weight maintenance after sleeve gastrectomy. While some studies demonstrated successful weight loss maintenance with serotonin intervention, the systematic review found no association between serotonin and weight loss maintenance. Factors beyond serotonin levels, including individual motivation, behavioral strategies, and physical activity, were identified as crucial contributors to sustained weight loss. While the results may not demonstrate a recognizable association between serotonin and weight loss maintenance, the significance of this review lies in its contribution to the existing body of knowledge. By synthesizing current evidence, the study adds a nuanced perspective to understanding factors influencing post-LSG outcomes.

Excess feeding increases adipogenesis but lowers leptin transcript abundance in zebrafish larvae

Although fish exposed to municipal wastewater effluents (MWWE) show higher lipid accumulation, whether this is due to adipogenesis is unclear. The objective here was to identify molecular markers of adipogenesis in zebrafish (Danio rerio) larvae for use as high throughput screening tools for environmental contaminants, including obesogens in MWWE. Zebrafish larvae were fed a commercial diet at a maintenance level (5 % body mass) or in excess (25 or 50 % body mass) from day 6 to 30 days post-fertilization (dpf) to stimulate adipogenesis. We monitored fat accumulation and markers of lipid metabolism, including peroxisome proliferator-activated receptor γ (ppar γ), fatty acid synthase (fas), ELOVL fatty acid elongase 2 (elovl2), diacylglycerol O-acyltransferase 2 (dgat2), leptin (lepa and lepb), leptin receptor (lepr), and lipoprotein lipase (lpl). Excess feeding led to a higher growth rate, protein content and an increase in igf1 transcript abundance. Also, these larvae had higher triglyceride levels and accumulated lipids droplets in the abdominal cavity and viscera. The molecular markers of adipogenesis, including fas, elovl2, and dgat2, were upregulated, while the transcript abundance of lpl, a lipolytic gene, was transiently lower due to excess feeding. The increased adiposity seen at 30 dpf due to excess feeding coincided with a lower lep but not lepr transcript abundance in zebrafish. Our results demonstrate that excess feeding alters the developmental programming of key genes involved in lipid homeostasis, leading to excess lipid accumulation in zebrafish larvae. Overall, fas, elovl2, lpl, and dgat2, but not lep or ppar γ, have the potential to be biomarkers of adipogenesis in zebrafish larvae.

Osteocalcin of maternal and embryonic origins synergize to establish homeostasis in offspring

Many physiological osteocalcin-regulated functions are affected in adult offspring of mothers experiencing unhealthy pregnancy. Furthermore, osteocalcin signaling during gestation influences cognition and adrenal steroidogenesis in adult mice. Together these observations suggest that osteocalcin may broadly function during pregnancy to determine organismal homeostasis in adult mammals. To test this hypothesis, we analyzed in unchallenged wildtype and Osteocalcin-deficient, newborn and adult mice of various genotypes and origin maintained on different genetic backgrounds, the functions of osteocalcin in the pancreas, liver and testes and their molecular underpinnings. This analysis revealed that providing mothers are Osteocalcin-deficient, Osteocalcin haploinsufficiency in embryos hampers insulin secretion, liver gluconeogenesis, glucose homeostasis, testes steroidogenesis in adult offspring; inhibits cell proliferation in developing pancreatic islets and testes; and disrupts distinct programs of gene expression in these organs and in the brain. This study indicates that osteocalcin exerts dominant functions in most organs it influences. Furthermore, through their synergistic regulation of multiple physiological functions, osteocalcin of maternal and embryonic origins contributes to the establishment and maintenance of organismal homeostasis in newborn and adult offspring.

Leptin Reduction as a Required Component for Weight Loss

Partial leptin reduction can induce significant weight loss, while weight loss contributes to partial leptin reduction. The cause-and-effect relationship between leptin reduction and weight loss remains to be further elucidated. Here, we show that FGF21 and the glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide rapidly induced a reduction in leptin. This leptin reduction contributed to the beneficial effects of GLP-1R agonism in metabolic health, as transgenically maintaining leptin levels during treatment partially curtailed the beneficial effects seen with these agonists. Moreover, a higher degree of leptin reduction during treatment, induced by including a leptin neutralizing antibody with either FGF21 or liraglutide, synergistically induced greater weight loss and better glucose tolerance in diet-induced obese mice. Furthermore, upon cessation of either liraglutide or FGF21 treatment, the expected immediate weight regain was observed, associated with a rapid increase in circulating leptin levels. Prevention of this leptin surge with leptin neutralizing antibodies slowed down weight gain and preserved better glucose tolerance. Mechanistically, a significant reduction in leptin induced a higher degree of leptin sensitivity in hypothalamic neurons. Our observations support a model that postulates that a reduction of leptin levels is a necessary prerequisite for substantial weight loss, and partial leptin reduction is a viable strategy to treat obesity and its associated insulin resistance.

ARTICLE HIGHLIGHTS

The Combined Effects of High-Intensity Interval Exercise Training and Dietary Supplementation on Reduction of Body Fat in Adults with Overweight and Obesity: A Systematic Review

Excessive body fat is associated with various comorbidities including cardiovascular disease, type 2 diabetes mellitus and certain types of cancer. The search for effective, relatively easy to maintain body-fat reduction interventions has been ongoing. We aimed to review the current literature to assess the effectiveness of high-intensity interval training with and without dietary supplementation on body fat loss, concentration of markers of metabolic health and aerobic capacity of adults with overweight and obesity. Seventy full-text articles were assessed to determine their eligibility and thirteen were included in the review. The methodology of this systematic review was developed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Almost all studies (93%) demonstrated effectiveness of high-intensity interval training of various protocols in reducing body fat, improving metabolic health and aerobic capacity of adults with overweight and obesity. These effects were enhanced by an addition of a dietary supplement, such as green tea or ginger or other. Although combining HIIT with dietary supplementation seem to improve body composition, metabolic health and aerobic capacity in adults with overweight and obesity in some instances to a greater extent than HIIT alone, it does not seem to be necessary to combine these two interventions.

Adipokines in atopic dermatitis: the link between obesity and atopic dermatitis

Atopic dermatitis (AD) is a chronic skin condition with intense pruritus, eczema, and dry skin. The recurrent intense pruritus and numerous complications in patients with AD can profoundly affect their quality of life. Obesity is one of its comorbidities that has been confirmed to be the hazard factor of AD and also worsen its severity. Nevertheless, the specific mechanisms that explain the connection between obesity and AD remain incompletely recognized. Recent studies have built hopes on various adipokines to explain this connection. Adipokines, which are disturbed by an obese state, may lead to immune system imbalances in people with AD and promote the development of the disease. This review focuses on the abnormal expression patterns of adipokines in patients with AD and their potential regulatory molecular mechanisms associated with AD. The connection between AD and obesity is elucidated through the involvement of adipokines. This conduces to the in-depth exploration of AD pathogenesis and provides a new perspective to develop therapeutic targets.

Microbiota Implications in Endocrine-Related Diseases: From Development to Novel Therapeutic Approaches

This comprehensive review article delves into the critical role of the human microbiota in the development and management of endocrine-related diseases. We explore the complex interactions between the microbiota and the endocrine system, emphasizing the implications of microbiota dysbiosis for the onset and progression of various endocrine disorders. The review aims to synthesize current knowledge, highlighting recent advancements and the potential of novel therapeutic approaches targeting microbiota-endocrine interactions. Key topics include the impact of microbiota on hormone regulation, its role in endocrine pathologies, and the promising avenues of microbiota modulation through diet, probiotics, prebiotics, and fecal microbiota transplantation. We underscore the importance of this research in advancing personalized medicine, offering insights for more tailored and effective treatments for endocrine-related diseases.

Molecular and Cellular Mechanisms Underlying the Cardiac Hypertrophic and Pro-Remodelling Effects of Leptin

Since its initial discovery in 1994, the adipokine leptin has received extensive interest as an important satiety factor and regulator of energy expenditure. Although produced primarily by white adipocytes, leptin can be synthesized by numerous tissues including those comprising the cardiovascular system. Cardiovascular function can thus be affected by locally produced leptin via an autocrine or paracrine manner but also by circulating leptin. Leptin exerts its effects by binding to and activating specific receptors, termed ObRs or LepRs, belonging to the Class I cytokine family of receptors of which six isoforms have been identified. Although all ObRs have identical intracellular domains, they differ substantially in length in terms of their extracellular domains, which determine their ability to activate cell signalling pathways. The most important of these receptors in terms of biological effects of leptin is the so-called long form (ObRb), which possesses the complete intracellular domain linked to full cell signalling processes. The heart has been shown to express ObRb as well as to produce leptin. Leptin exerts numerous cardiac effects including the development of hypertrophy likely through a number of cell signaling processes as well as mitochondrial dynamics, thus demonstrating substantial complex underlying mechanisms. Here, we discuss mechanisms that potentially mediate leptin-induced cardiac pathological hypertrophy, which may contribute to the development of heart failure.

Role of Perturbated Hemostasis in MASLD and Its Correlation with Adipokines

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) continues to rise, making it one of the most prevalent chronic liver disorders. MASLD encompasses a range of liver pathologies, from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH) with inflammation, hepatocyte damage, and fibrosis. Interestingly, the liver exhibits close intercommunication with fatty tissue. In fact, adipose tissue could contribute to the etiology and advancement of MASLD, acting as an endocrine organ that releases several hormones and cytokines, with the adipokines assuming a pivotal role. The levels of adipokines in the blood are altered in people with MASLD, and recent research has shed light on the crucial role played by adipokines in regulating energy expenditure, inflammation, and fibrosis in MASLD. However, MASLD disease is a multifaceted condition that affects various aspects of health beyond liver function, including its impact on hemostasis. The alterations in coagulation mechanisms and endothelial and platelet functions may play a role in the increased vulnerability and severity of MASLD. Therefore, more attention is being given to imbalanced adipokines as causative agents in causing disturbances in hemostasis in MASLD. Metabolic inflammation and hepatic injury are fundamental components of MASLD, and the interrelation between these biological components and the hemostasis pathway is delineated by reciprocal influences, as well as the induction of alterations. Adipokines have the potential to serve as the shared elements within this complex interrelationship. The objective of this review is to thoroughly examine the existing scientific knowledge on the impairment of hemostasis in MASLD and its connection with adipokines, with the aim of enhancing our comprehension of the disease.

Crosstalk Between the Neuroendocrine System and Bone Homeostasis

The homeostasis of bone microenvironment is the foundation of bone health and comprises 2 concerted events: bone formation by osteoblasts and bone resorption by osteoclasts. In the early 21st century, leptin, an adipocytes-derived hormone, was found to affect bone homeostasis through hypothalamic relay and the sympathetic nervous system, involving neurotransmitters like serotonin and norepinephrine. This discovery has provided a new perspective regarding the synergistic effects of endocrine and nervous systems on skeletal homeostasis. Since then, more studies have been conducted, gradually uncovering the complex neuroendocrine regulation underlying bone homeostasis. Intriguingly, bone is also considered as an endocrine organ that can produce regulatory factors that in turn exert effects on neuroendocrine activities. After decades of exploration into bone regulation mechanisms, separate bioactive factors have been extensively investigated, whereas few studies have systematically shown a global view of bone homeostasis regulation. Therefore, we summarized the previously studied regulatory patterns from the nervous system and endocrine system to bone. This review will provide readers with a panoramic view of the intimate relationship between the neuroendocrine system and bone, compensating for the current understanding of the regulation patterns of bone homeostasis, and probably developing new therapeutic strategies for its related disorders.

Nutrition and dietary restrictions in cancer prevention

The composition and pattern of dietary intake have emerged as key factors influencing aging, regeneration, and consequently, healthspan and lifespan. Cancer is one of the major diseases more tightly linked with aging, and age-related mortality. Although the role of nutrition in cancer incidence is generally well established, we are far from a consensus on how diet influences tumour development in different tissues. In this review, we will discuss how diet and dietary restrictions affect cancer risk and the molecular mechanisms potentially responsible for their effects. We will cover calorie restriction, intermittent fasting, prolonged fasting, fasting-mimicking diet, time-restricted eating, ketogenic diet, high protein diet, Mediterranean diet, and the vegan and vegetarian diets.

Metabolic flux analysis in adipose tissue reprogramming

Obesity is a growing epidemic in the United States and worldwide and is associated with insulin resistance and cardiovascular disease, among other comorbidities. Understanding of the pathology that links overnutrition to these disease processes is ongoing. Adipose tissue is a heterogeneous organ comprised of multiple different cell types and it is likely that dysregulated metabolism within these cell populations disrupts both inter- and intracellular interactions and is a key driver of human disease. In recent years, metabolic flux analysis, which offers a precise quantification of metabolic pathway fluxes in biological systems, has emerged as a candidate strategy for uncovering the metabolic changes that stoke these disease processes. In this mini review, we discuss metabolic flux analysis as an experimental tool, with a specific emphasis on mass spectrometry with isotope tracing as this is the technique most frequently used for metabolic flux analysis in adipocytes. Furthermore, we examine existing literature that uses metabolic flux analysis to further our understanding of adipose tissue biology. Our group has a specific interest in understanding the role of white adipose tissue inflammation in the progression of cardiometabolic disease, as we know that in obesity the accumulation of pro-inflammatory adipose tissue macrophages is associated with significant morbidity, so we use this as a paradigm throughout our review for framing the application of these experimental techniques. However, there are many other biological applications to which they can be applied to further understanding of not only adipose tissue biology but also systemic homeostasis.

Hypothalamic inflammation and the development of an obese phenotype induced by high-fat diet consumption is exacerbated in alpha7 nicotinic cholinergic receptor knockout mice

Hypothalamic inflammation and metabolic changes resulting from the consumption of high-fat diets have been linked to low grade inflammation and obesity. Inflammation impairs the hypothalamic expression of α7 nicotinic acetylcholine receptor (α7nAChR). The α7nAChR is described as the main component of the anti-inflammatory cholinergic pathway in different inflammation models. To assess whether the reduction in α7nAChR expression exacerbates hypothalamic inflammation induced by a high-fat diet (HFD), were used male and female global α7nAChR knockout mouse line in normal or high-fat diet for 4 weeks. Body weight gain, adiposity, glucose homeostasis, hypothalamic inflammation, food intake, and energy expenditure were evaluated. Insulin sensitivity was evaluated in neuronal cell culture. Consumption of an HFD for 4 weeks resulted in body weight gain and adiposity in male Chrna7-/- mice and the hypothalamus of male Chrna7-/- mice showed neuroinflammatory markers, with increased gene expression of pro-inflammatory cytokines and dysregulation in the nuclear factor kappa B pathway. Moreover, male Chrna7-/- mice consuming an HFD showed alterations in glucose homeostasis and serum of Chrna7-/- mice that consumed an HFD impaired insulin signalling in neuronal cell culture experiments. In general, female Chrna7-/- mice that consumed an HFD did not show the phenotypic and molecular changes found in male mice, indicating that there is sexual dimorphism in the analysed parameters. Thus, receptor deletion resulted in increased susceptibility to hypothalamic inflammation and metabolic damage associated with HFD consumption in male mice.

Neuroendocrinological and Clinical Aspects of Leptin

Obesity is characterized by an abnormal increase in adipose tissue mass and is regarded as a neurobehavioral as well as a metabolic disorder. Increases in body fat are caused by even slight, long-term discrepancies between energy intake and energy expenditure. It is a chronic condition linked to the metabolic syndrome, a spectrum of risky conditions, such as diabetes, high blood pressure, and heart disease. With a swiftly rising prevalence, obesity has emerged as a significant global health concern. Leptin influences the brain's neuroendocrine and metabolic processes, which is important for maintaining energy homeostasis. White adipose tissue secretes the majority of leptin, and there is a positive correlation between leptin levels in the blood and body fat percentages. The central nervous system is also modulated by leptin levels to modify energy intake and usage. The idea of an obesity cure sparked excitement after it was discovered more than 25 years ago. However, the leptin medication only effectively reduces weight in patients with congenital leptin insufficiency and not in patients with typical obesity who may also have leptin resistance. Recent research has focused on the role of leptin in managing weight reduction and preventing "yo-yo dieting". This review concentrates on the neurological effects of leptin with a focus on therapeutic and diagnostic applications, particularly for childhood obesity.

The Mechanism of Leptin Resistance in Obesity and Therapeutic Perspective

Leptin resistance is induced via leptin signaling blockade by chronic overstimulation of the leptin receptor and intracellular signaling defect or increased hypothalamic inflammation and suppressor of cytokine signaling (SOCS)-3 expression. High-fat diet triggers leptin resistance induced by at least two independent causes: first, the limited ability of peripheral leptin to activate hypothalamic signaling transducers and activators of transcription (STAT) signaling and secondly a signaling defect in leptin-responsive hypothalamic neurons. Central leptin resistance is dependent on decreased leptin transport efficiency across the blood brain barrier (BBB) rather than hypothalamic leptin insensitivity. Since the hypothalamic phosphorylated STAT3 (pSTAT3) represents a sensitive and specific readout of leptin receptor-B signaling, the assessment of pSTAT3 levels is the gold standard. Hypertriglyceridemia is one of important factors to inhibit the transport of leptin across BBB in obesity. Mismatch between high leptin and the amount of leptin receptor expression in obesity triggers brain leptin resistance via increasing hypothalamic inflammation and SOCS-3 expression. Therapeutic strategies that regulate the passage of leptin to the brain include the development of modifications in the structure of leptin analogues as well as the synthesis of new leptin receptor agonists with increased BBB permeability. In the hyperleptinemic state, polyethylene glycol (PEG)-modified leptin is unable to pass through the BBB. Peripheral histone deacetylase (HDAC) 6 inhibitor, tubastatin, and metformin increase central leptin sensitization. While add-on therapy with anagliptin, metformin and miglitol reduce leptin concentrations, the use of long-acting leptin analogs, and exendin-4 lead to the recovery of leptin sensitivity. Contouring surgery with fat removal, and bariatric surgery independently of the type of surgery performed provide significant improvement in leptin concentrations. Although approaches to correcting leptin resistance have shown some success, no clinically effective application has been developed to date. Due to the impairment of central and peripheral leptin signaling, as well as the extensive integration of leptin-sensitive metabolic pathways with other neurons, the effectiveness of methods used to eliminate leptin resistance is extremely limited.

Upregulation of hypothalamic TRPV4 via S100a4/AMPKα signaling pathway promotes the development of diet-induced obesity

Obesity is associated with abnormal regulation of energy metabolism in the hypothalamus. Transient receptor potential vanilloid 4 (TRPV4) is involved in regulating osmotic pressure, temperature and mechanical force transmission, but little is known about its role in obesity. Herein, the present study aimed to elucidate the effect of hypothalamic TRPV4 on high-fat diet-induced obesity (DIO) and evaluate its potential for regulating energy metabolism. Here we show that hypothalamic TRPV4 content is increased in DIO rats. Central administration of adeno-associated virus expressing TRPV4 in these animals remarkably increased body weight and fat mass by activating the S100a4/AMPKα signaling pathway, thereby promoting positive energy metabolism. Overexpressed hypothalamic TRPV4 impaired glucose tolerance, while promoting the accumulation of fat in liver cells, resulting in hepatic steatosis. In addition, the upregulation of hypothalamic TRPV4 reduces high-fat induced central inflammation. This study provides evidence that hypothalamic TRPV4 plays a significant role in regulating homeostasis. Hypothalamic TRPV4 emerges as a target for therapeutic intervention against obesity.

Comprehensive Role of GDF15 in Inhibiting Adipogenesis and Hyperlipidemia, Enhancing Cardiovascular Health and Alleviating Inflammation in Metabolic Disorders

Growth Differentiation Factor 15 (GDF15) has emerged as a pivotal signaling molecule implicated in diverse physiological processes, spanning metabolic regulation, inflammation, and cardiovascular health. This study provides a comprehensive exploration of GDF15's multifaceted role, primarily focusing on its association with obesity-related complications and therapeutic potential. GDF15's involvement in energy homeostasis, specifically its regulation of body weight and appetite through hindbrain neuron activation and the GFRAL-RET signaling pathway, underscores its significance as an appetite-regulating hormone. GDF15's intricate modulation within adipose tissue dynamics in response to dietary changes and obesity, coupled with its influence on insulin sensitivity, highlights its critical role in metabolic health. The manuscript delves into the intricate crosstalk between GDF15 and pathways related to insulin sensitivity, macrophage polarization, and adipose tissue function, elucidating its potential as a therapeutic target for metabolic disorders associated with obesity. GDF15's association with chronic low-grade inflammation and its impact on cardiovascular health, particularly during hyperlipidemia and ischemic events, are explored. The intricate relationship between GDF15 and cardiovascular diseases, including its effects on endothelial function, cardiac hypertrophy, and heart failure, emphasizes its multifaceted nature in maintaining overall cardiovascular well-being. Challenges regarding the therapeutic application of GDF15, such as long-term safety concerns and ongoing clinical investigations, are discussed. Lastly, future research directions exploring GDF15's potential in addressing obesity-related complications and cardiovascular risks are proposed, highlighting its promising role as a therapeutic target in reshaping treatment strategies for obesity and associated health conditions.

A chromosome-level genome assembly for the Silkie chicken resolves complete sequences for key chicken metabolic, reproductive, and immunity genes

A set of high-quality pan-genomes would help identify important genes that are still hidden/incomplete in bird reference genomes. In an attempt to address these issues, we have assembled a de novo chromosome-level reference genome of the Silkie (Gallus gallus domesticus), which is an important avian model for unique traits, like fibromelanosis, with unclear genetic foundation. This Silkie genome includes the complete genomic sequences of well-known, but unresolved, evolutionarily, endocrinologically, and immunologically important genes, including leptin, ovocleidin-17, and tumor-necrosis factor-α. The gap-less and manually annotated MHC (major histocompatibility complex) region possesses 38 recently identified genes, with differentially regulated genes recovered in response to pathogen challenges. We also provide whole-genome methylation and genetic variation maps, and resolve a complex genetic region that may contribute to fibromelanosis in these animals. Finally, we experimentally show leptin binding to the identified leptin receptor in chicken, confirming an active leptin ligand-receptor system. The Silkie genome assembly not only provides a rich data resource for avian genome studies, but also lays a foundation for further functional validation of resolved genes.

Risk of metabolic abnormalities in osteoarthritis: a new perspective to understand its pathological mechanisms

Although aging has traditionally been viewed as the most important risk factor for osteoarthritis (OA), an increasing amount of epidemiological evidence has highlighted the association between metabolic abnormalities and OA, particularly in younger individuals. Metabolic abnormalities, such as obesity and type II diabetes, are strongly linked to OA, and they affect both weight-bearing and non-weight-bearing joints, thus suggesting that the pathogenesis of OA is more complicated than the mechanical stress induced by overweight. This review aims to explore the recent advances in research on the relationship between metabolic abnormalities and OA risk, including the impact of abnormal glucose and lipid metabolism, the potential pathogenesis and targeted therapeutic strategies.

Adipo-glial signaling mediates metabolic adaptation in peripheral nerve regeneration

The peripheral nervous system harbors a remarkable potential to regenerate after acute nerve trauma. Full functional recovery, however, is rare and critically depends on peripheral nerve Schwann cells that orchestrate breakdown and resynthesis of myelin and, at the same time, support axonal regrowth. How Schwann cells meet the high metabolic demand required for nerve repair remains poorly understood. We here report that nerve injury induces adipocyte to glial signaling and identify the adipokine leptin as an upstream regulator of glial metabolic adaptation in regeneration. Signal integration by leptin receptors in Schwann cells ensures efficient peripheral nerve repair by adjusting injury-specific catabolic processes in regenerating nerves, including myelin autophagy and mitochondrial respiration. Our findings propose a model according to which acute nerve injury triggers a therapeutically targetable intercellular crosstalk that modulates glial metabolism to provide sufficient energy for successful nerve repair.

Association between genetic polymorphisms of leptin receptor and preeclampsia in Chinese women

OBJECTIVE

Leptin signaling plays an important role in regulating metabolism and reproduction. In the present study, we investigated the relationship between polymorphisms of leptin receptor (LEPR) gene A223G and A668G and preeclampsia (PE) and evaluated influences of genotypes on clinical, metabolic, and oxidative stress indices in Chinese women.

METHODS

This is a case-control study including 322 patients with PE and 1295 healthy pregnant women. The two polymorphisms were genotyped by polymerase chain reaction-restriction fragments length polymorphism method. Clinical and biochemical parameters were analyzed.

RESULTS

The frequencies of the AA + AG genotypes (28.6% vs. 36.1%) and A allele (14.9% vs. 19.8%) of LEPR A223G polymorphism, and those of the AA + AG genotypes (17.7% vs. 24.6%) and A allele (9.0% vs. 12.9%) of LEPR A668G polymorphism were significantly lower in the PE group than those in the control group. The 223A and 668A alleles were protective factors against PE in the regression model, which included age and delivery body mass index as covariates (OR = 0.684, 95% CI: 0.506-0.926, p = .014; OR = 0.650, 95% CI: 0.456-0.927, p = .017, respectively). When the 668GG/223GG combined genotype served as the reference category, the 668A/223A combined allele had further enhanced the protective effect on PE (OR = 0.558, 95% CI: 0.374-0.833, p = .004). Patients possessing the LEPR 223A allele had higher total antioxidant capacity and lower oxidative stress index (p < .05), while those with the LEPR 668A allele had higher high-density lipoprotein cholesterol levels (p = .045) compared with those carrying the corresponding GG genotype.

CONCLUSIONS

The 223A and 668A alleles of LEPR polymorphisms are genetic protective factors for PE in Chinese women. The two alleles may exert a beneficial effect on oxidative stress and lipid metabolism in patients.

Reduction of body weight by increased loading is associated with activation of norepinephrine neurones in the medial nucleus of the solitary tract

We previously provided evidence supporting the existence of a novel leptin-independent body weight homeostat ("the gravitostat") that senses body weight and then initiates a homeostatic feed-back regulation of body weight. We, herein, hypothesize that this feed-back regulation involves a CNS mechanism. To identify populations of neurones of importance for the putative feed-back signal induced by increased loading, high-fat diet-fed rats or mice were implanted intraperitoneally or subcutaneously with capsules weighing ∼15% (Load) or ∼2.5% (Control) of body weight. At 3-5 days after implantation, neuronal activation was assessed in different parts of the brain/brainstem by immunohistochemical detection of FosB. Implantation of weighted capsules, both subcutaneous and intraperitoneal, induced FosB in specific neurones in the medial nucleus of the solitary tract (mNTS), known to integrate information about the metabolic status of the body. These neurones also expressed tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DbH), a pattern typical of norepinephrine neurones. In functional studies, we specifically ablated norepinephrine neurones in mNTS, which attenuated the feed-back regulation of increased load on body weight and food intake. In conclusion, increased load appears to reduce body weight and food intake via activation of norepinephrine neurones in the mNTS.

The Role of Cdc42 in the Insulin and Leptin Pathways Contributing to the Development of Age-Related Obesity

Age-related obesity significantly increases the risk of chronic diseases such as type 2 diabetes, cardiovascular diseases, hypertension, and certain cancers. The insulin-leptin axis is crucial in understanding metabolic disturbances associated with age-related obesity. Rho GTPase Cdc42 is a member of the Rho family of GTPases that participates in many cellular processes including, but not limited to, regulation of actin cytoskeleton, vesicle trafficking, cell polarity, morphology, proliferation, motility, and migration. Cdc42 functions as an integral part of regulating insulin secretion and aging. Some novel roles for Cdc42 have also been recently identified in maintaining glucose metabolism, where Cdc42 is involved in controlling blood glucose levels in metabolically active tissues, including skeletal muscle, adipose tissue, pancreas, etc., which puts this protein in line with other critical regulators of glucose metabolism. Importantly, Cdc42 plays a vital role in cellular processes associated with the insulin and leptin signaling pathways, which are integral elements involved in obesity development if misregulated. Additionally, a change in Cdc42 activity may affect senescence, thus contributing to disorders associated with aging. This review explores the complex relationships among age-associated obesity, the insulin-leptin axis, and the Cdc42 signaling pathway. This article sheds light on the vast molecular web that supports metabolic dysregulation in aging people. In addition, it also discusses the potential therapeutic implications of the Cdc42 pathway to mitigate obesity since some new data suggest that inhibition of Cdc42 using antidiabetic drugs or antioxidants may promote weight loss in overweight or obese patients.

Seeking satiety: From signals to solutions

Remedies for the treatment of obesity date to Hippocrates, when patients with obesity were directed to "reduce food and avoid drinking to fullness" and begin "running during the night." Similar recommendations have been repeated ever since, despite the fact that they are largely ineffective. Recently, highly effective therapeutics were developed that may soon enable physicians to manage body weight in patients with obesity in a manner similar to the way that blood pressure is controlled in patients with hypertension. These medicines have grown out of a revolution in our understanding of the molecular and neural control of appetite and body weight, reviewed here.

Adipokines in Rheumatoid Arthritis: Emerging Biomarkers and Therapeutic Targets

Rheumatoid arthritis (RA) is a chronic inflammatory disease manifested by joint involvement, extra-articular manifestations, and general symptoms. Adipose tissue, previously perceived as an inert energy storage organ, has been recognised as a significant contributor to RA pathophysiology. Adipokines modulate immune responses, inflammation, and metabolic pathways in RA. Although most adipokines have a pro-inflammatory and aggravating effect on RA, some could counteract this pathological process. The coexistence of RA and sarcopenic obesity (SO) has gained attention due to its impact on disease severity and outcomes. Sarcopenic obesity further contributes to the inflammatory milieu and metabolic disturbances. Recent research has highlighted the intricate crosstalk between adipose tissue and skeletal muscle, suggesting potential interactions between these tissues in RA. This review summarizes the roles of adipokines in RA, particularly in inflammation, immune modulation, and joint destruction. In addition, it explores the emerging role of adipomyokines, specifically irisin and myostatin, in the pathogenesis of RA and their potential as therapeutic targets. We discuss the therapeutic implications of targeting adipokines and adipomyokines in RA management and highlight the challenges and future directions for research in this field.

Decoding the obesity-cancer connection: lessons from preclinical models of pancreatic adenocarcinoma

Obesity is a metabolic state of energy excess and a risk factor for over a dozen cancer types. Because of the rising worldwide prevalence of obesity, decoding the mechanisms by which obesity promotes tumor initiation and early progression is a societal imperative and could broadly impact human health. Here, we review results from preclinical models that link obesity to cancer, using pancreatic adenocarcinoma as a paradigmatic example. We discuss how obesity drives cancer development by reprogramming the pretumor or tumor cell and its micro- and macro-environments. Specifically, we describe evidence for (1) altered cellular metabolism, (2) hormone dysregulation, (3) inflammation, and (4) microbial dysbiosis in obesity-driven pancreatic tumorigenesis, denoting variables that confound interpretation of these studies, and highlight remaining gaps in knowledge. Recent advances in preclinical modeling and emerging unbiased analytic approaches will aid in further unraveling the complex link between obesity and cancer, informing novel strategies for prevention, interception, and therapy in pancreatic adenocarcinoma and other obesity-associated cancers.

The dual hypothesis of homeostatic body weight regulation, including gravity-dependent and leptin-dependent actions

Body weight is tightly regulated when outside the normal range. It has been proposed that there are individual-specific lower and upper intervention points for when the homeostatic regulation of body weight is initiated. The nature of the homeostatic mechanisms regulating body weight at the lower and upper ends of the body weight spectrum might differ. Previous studies demonstrate that leptin is the main regulator of body weight at the lower end of the body weight spectrum. We have proposed that land-living animals use gravity to regulate their body weight. We named this homeostatic system the gravitostat and proposed that there are two components of the gravitostat. First, an obvious mechanism involves increased energy consumption in relation to body weight when working against gravity on land. In addition, we propose that there exists a component, involving sensing of the body weight by osteocytes in the weight-bearing bones, resulting in a feedback regulation of energy metabolism and body weight. The gravity-dependent homeostatic regulation is mainly active in obese mice. We, herein, propose the dual hypothesis of body weight regulation, including gravity-dependent actions (= gravitostat) at the upper end and leptin-dependent actions at the lower end of the body weight spectrum. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

Mice lacking triglyceride synthesis enzymes in adipose tissue are resistant to diet-induced obesity

Triglycerides (TGs) in adipocytes provide the major stores of metabolic energy in the body. Optimal amounts of TG stores are desirable as insufficient capacity to store TG, as in lipodystrophy, or exceeding the capacity for storage, as in obesity, results in metabolic disease. We hypothesized that mice lacking TG storage in adipocytes would result in excess TG storage in cell types other than adipocytes and severe lipotoxicity accompanied by metabolic disease. To test this hypothesis, we selectively deleted both TG synthesis enzymes, DGAT1 and DGAT2, in adipocytes (ADGAT DKO mice). As expected with depleted energy stores, ADGAT DKO mice did not tolerate fasting well and, with prolonged fasting, entered torpor. However, ADGAT DKO mice were unexpectedly otherwise metabolically healthy and did not accumulate TGs ectopically or develop associated metabolic perturbations, even when fed a high-fat diet. The favorable metabolic phenotype resulted from activation of energy expenditure, in part via BAT (brown adipose tissue) activation and beiging of white adipose tissue. Thus, the ADGAT DKO mice provide a fascinating new model to study the coupling of metabolic energy storage to energy expenditure.

Soluble Fiber Effect on Human Serum Leptin and Adiponectin: A Systematic Review and Dose-Response Meta-Analysis

Literature showed that soluble fiber has beneficial effects on cardiometabolic risk factors and leptin and adiponectin serum levels. Our aim in this meta-analysis was to determine the effect of soluble fiber supplementation on leptin and adiponectin serum levels. A systematic search was conducted using PubMed, Scopus, and ISI Web of Science for eligible trials up to December 2021. A random-effects model was used to pool calculated effect sizes. Our analysis showed that soluble fiber supplementation did not significantly affect adiponectin (standardized mean difference [SMD], -0.49 Hedges's, 95% confidence interval [CI], -1.20, 0.21, p value = 0.167; I2 = 95.4, p value < 0.001) and leptin (SMD, -0.8 Hedges's, 95% CI, -1.70, 0.08, p value = 0.076; I2 = 94.6, p value < 0.001) concentrations in comparison with placebo. However, in the subgroup, soluble fiber supplementation had a significant improvement in leptin concentration in overweight and obese patients (SMD, -0.22 Hedges's, 95% CI, -0.43, -0.01, p value = 0.048) and a non-significant beneficial effect in adiponectin level in female (SMD, 0.29 Hedges's, 95% CI, -0.13, 0.71, p value = 0.183) and diabetic patients (SMD, 0.32 Hedges's, 95% CI, -0.67, 1.32, p value = 0.526). A non-linear association between soluble fiber dosage and adiponectin (pnon-linearity < 0.001) was observed. Soluble fiber supplementation could not change the circulatory leptin and adiponectin levels. However, beneficial effects were seen in overweight and obese leptin, and increases in adiponectin may also be observed in female and diabetic patients. Further studies are needed to confirm this results.

Epigenetic Mechanisms in Obesity: Broadening Our Understanding of the Disease

Now recognized as more than just the result of overeating or the consumption of poor-quality foods, obesity is understood to be a multifactorial disease, strongly correlated with a variety of environment-gene interactions. In addressing the complex public health issue of obesity, medical practitioners, along with their allied healthcare counterparts, face the challenge of reducing its prevalence by utilizing and sharing with patients the current, yet incomplete, scientific knowledge concerning the disease. While continued research is required to strengthen direct cause-effect relationships, substantial evidence links post-translational modifications such as DNA methylation and histone modifications of several candidate "obesity" genes to the predilection for obesity. Additional evidence supports the influence of maternal diet during the gestational period, individual diet, and other lifestyle and genetic factors in obesity. The purpose of this review is to synthesize the current information concerning epigenetic modifications that appear to support, or result from, the development of obesity. Such mechanisms may serve as therapeutic targets for developing novel prevention and/or treatment strategies for obesity or as epigenetic biomarkers for monitoring recovery.

The role of cognitive function in the relationship between surrogate markers of visceral fat and depressive symptoms in general middle-aged and elderly population: A nationwide population-based study

BACKGROUND

The relationship between obesity and depressive symptoms is well documented, but not visceral fat, especially among Chinese adults are scarce. We aimed to investigate the association between visceral fat and depressive symptoms and the mediation of cognitive function.

METHODS

A total of 19,919 and 5555 participants from the China Health and Retirement Longitudinal Study were enrolled in the cross-sectional and follow-up analyses. Depressive symptoms were measured by the Center of Epidemiological studies depression scale (CES-D). Visceral fat measured by the waist circumference triglyceride (WT) index [calculated as waist circumference (cm)* triglyceride (mmol/L)]. The relationship between the WT index and depressive symptoms was analyzed by binary logistics and Poisson regression. The mediated role of cognitive ability was examined by intermediary analysis.

RESULTS

In the cross-sectional study, higher visceral fat was associated with a lower risk of depressive symptoms. But in the follow-up study, individuals in quintile 2 to quintile 4 of the WT index have a reduced risk of depressive symptoms after four years. Compared with the lower index, quintile 2 of the WT index protected from difficulty concentrating (RR [95%CI]: 0.90 [0.82,0.98], p = 0.023), feeling scared (RR [95%CI]: 0.86 [0.73,0.98], p = 0.030) and feeling that life could not go on (RR [95%CI]: 0.85 [0.74,0.98], p = 0.023). Moreover, cognitive ability explained 11.52 % of the association between visceral fat and depressive symptoms.

CONCLUSIONS

Our findings show that moderate visceral fat was associated with a lower risk of depressive symptoms in middle-aged and older Chinese, partly mediated by cognitive function.

A brown fat-enriched adipokine, ASRA, is a leptin receptor antagonist that stimulates appetite

The endocrine control of food intake remains incompletely understood, and whether the leptin receptor-mediated anorexigenic pathway in the hypothalamus is negatively regulated by a humoral factor is unknown. Here we identify an appetite-stimulating factor - ASRA - that acts as a leptin receptor antagonist. ASRA encodes an 8 kD protein that is abundantly and selectively expressed in adipose tissue and to a lesser extent, in liver, and is upregulated during fasting and cold. ASRA protein associates with autophagosomes and its secretion is induced by energy deficiency. Overexpression of ASRA in mice attenuates leptin receptor signaling leading to elevated blood glucose and development of severe hyperphagic obesity, whereas either adipose- or liver-specific ASRA knockout mice display increased leptin sensitivity, improved glucose homeostasis, reduced food intake, and resistance to high fat diet-induced obesity. Furthermore, ASRA is indispensable for cold-evoked feeding response. Recombinant ASRA (rASRA) protein binds to leptin receptor and suppresses leptin receptor signaling in cultured cells. In vivo, rASRA promotes food intake and increases blood glucose in a leptin receptor signaling-dependent manner. Our studies collectively show that ASRA, acting as a peripheral signal of energy deficit, stimulates appetite and regulates glucose metabolism by antagonizing leptin receptor signaling, thus revealing a previously unknown endocrine mechanism that has important implications for our understanding of leptin resistance.

Energy homeostasis from Lavoisier to control theory

The intellectual history of energy homeostasis, focusing on food intake and energy storage, is briefly reviewed. Physiological energetics was founded by Lavoisier, who in the late eighteenth century invented direct and indirect calorimetry and discovered the role of oxygen in combustion and respiration. Energy was understood well enough by the mid-nineteenth century to realize the physiological energy-balance equation, that energy intake - energy expenditure = energy storage, but this did not greatly influence physiological research for another century. Homeostasis, the concept that many vital physiological variables are actively regulated in narrow envelopes, was developed by Bernard and Cannon between approximately 1870-1940 and remains a central principle of physiology. Kennedy coined the term lipostasis in 1953 to refer to the constancy of fat mass, which Mayer argued was the mechanism regulating body weight. A parameterized control-theory model suggests that a proportional negative-feedback control system incompletely compensates weight loss during persistent negative energy balance, suggesting that Cannon's idea of constancy within a narrow envelope may not fit body-weight regulation well. This modelling encourages further application of control theory to issues in energy homeostasis, including to the development of obesity. It also sets the stage for understanding the underlying neuroendocrine mechanisms. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

Effect of C-reactive protein deficiency on insulin resistance reversal in rats with polycystic ovary syndrome through augmented leptin action

BACKGROUND

C-reactive protein(CRP), is an inflammatory marker that weaken leptin bioavailability and insulin sensitivity to disturb energy and glucose metabolism. Polycystic ovary syndrome (PCOS) exhibit a metabolic component consisting of higher plasma CRP levels, hyperinsulinemic and hyperleptinemia. The ability of leptin to regulation of hepatic glucose production (HGP) in the absence of CRP in PCOS remain unknown.

METHODS

Dehydroepiandrosterone (DHEA) was used to induce PCOS in rats. We assessed the effects of CRP gene knockout in PCOS model rats on body weight, energy expenditure glucose metabolism and insulin sensitivity. We conducted experiments involving the administration of leptin to both the peripheral and central systems in PCOS model rats with CRP knockout, and studied the effects on changes in glucose kinetics during hyperinsulinemic-euglycemic clamps.

RESULTS

In female PCOS rats, the lack of CRP resulted in decreased leptin resistance and weight gain, increased energy expenditure, and improved insulin sensitivity. Additionally, the deletion of the CRP gene strengthened the HGP-lowering effects of leptin when administered peripherally or centrally. This effect was accompanied by a decrease in the expression of hepatic gluconeogenic enzymes and an increase in hepatic insulin signaling. Finally, inhibition of glucose production was also enhanced for central leptin administration during lipid infusion in PCOS rats.

CONCLUSIONS

Our findings highlight the therapeutic potential of targeting CRP to restore glucose homeostasis and insulin sensitivity for leptin in PCOS.

Metabolic hormone action in the VTA: Reward-directed behavior and mechanistic insights

Dysfunctional signaling in midbrain reward circuits perpetuates diseases characterized by compulsive overconsumption of rewarding substances such as substance abuse, binge eating disorder, and obesity. Ventral tegmental area (VTA) dopaminergic activity serves as an index for how rewarding stimuli are perceived and triggers behaviors necessary to obtain future rewards. The evolutionary linking of reward with seeking and consuming palatable foods ensured an organism's survival, and hormone systems that regulate appetite concomitantly developed to regulate motivated behaviors. Today, these same mechanisms serve to regulate reward-directed behavior around food, drugs, alcohol, and social interactions. Understanding how hormonal regulation of VTA dopaminergic output alters motivated behaviors is essential to leveraging therapeutics that target these hormone systems to treat addiction and disordered eating. This review will outline our current understanding of the mechanisms underlying VTA action of the metabolic hormones ghrelin, glucagon-like peptide-1, amylin, leptin, and insulin to regulate behavior around food and drugs of abuse, highlighting commonalities and differences in how these five hormones ultimately modulate VTA dopamine signaling.

Recent progress in leptin signaling from a structural perspective and its implications for diseases

As a multi-potency cytokine, leptin not only plays a crucial role in controlling weight and energy homeostasis but also participates in the metabolic balance in the human body. Leptin is a small helical protein with a molecular weight of 16 kDa. It can interact with multiple subtypes of its receptors to initiate intracellular signal transduction and exerts physiological effects. Disturbances in leptin signaling may lead to obesity and a variety of metabolic diseases. Leptin was also found to be a critical factor in many diseases of the elderly. In this review, we focus on recent advances in the structural and molecular mechanisms of leptin signaling through its receptors with the aim of a deeper understanding of leptin-related diseases.

Adipokines from adipose tissue and common variable immunodeficiency: Is there any association?

Adiponectin and leptin are adipokines, secreted by white adipose tissue (WAT), which play an important role in energy homeostasis. Some evidence has shown that adipokine-producing adipose cells present in the bone marrow (BM) appear to exert an influence on hematopoiesis and B cell development. Common variable immunodeficiency (CVID) is one of the most common inborn errors of immunity in humans. In CVID, numerical and/or functional defects of B cells and their precursors result in hypogammaglobulinemia, usually Immunoglobulin (Ig) A and IgG. Manifestations of CVID include immunodeficiency, autoimmunity, inflammation and lymphoproliferation, resulting in a wide range of phenotypes. How adipokines interact and influence the pathophysiology of CVID is still unclear. In this review, we seek to summarize the aspects known so far concerning the interface between adipokines, B cells and CVID. More research is needed to fully understand these interactions; this knowledge is a potential avenue for the discovery of useful biomarkers and may provide new therapeutic targets for the treatment of patients with CVID and related diseases.

Isoform-specific disruption of the TP73 gene reveals a critical role for TAp73γ in tumorigenesis via leptin

TP73, a member of the p53 family, is expressed as TAp73 and ΔNp73 along with multiple C-terminal isoforms (α-η). ΔNp73 is primarily expressed in neuronal cells and necessary for neuronal development. Interestingly, while TAp73α is a tumor suppressor and predominantly expressed in normal cells, TAp73 is found to be frequently altered in human cancers, suggesting a role of TAp73 C-terminal isoforms in tumorigenesis. To test this, the TCGA SpliceSeq database was searched and showed that exon 11 (E11) exclusion occurs frequently in several human cancers. We also found that p73α to p73γ isoform switch resulting from E11 skipping occurs frequently in human prostate cancers and dog lymphomas. To determine whether p73α to p73γ isoform switch plays a role in tumorigenesis, CRISPR technology was used to generate multiple cancer cell lines and a mouse model in that Trp73 E11 is deleted. Surprisingly, we found that in E11-deificient cells, p73γ becomes the predominant isoform and exerts oncogenic activities by promoting cell proliferation and migration. In line with this, E11-deficient mice were more prone to obesity and B-cell lymphomas, indicating a unique role of p73γ in lipid metabolism and tumorigenesis. Additionally, we found that E11-deficient mice phenocopies Trp73-deficient mice with short lifespan, infertility, and chronic inflammation. Mechanistically, we showed that Leptin, a pleiotropic adipocytokine involved in energy metabolism and oncogenesis, was highly induced by p73γ,necessary for p73γ-mediated oncogenic activity, and associated with p73α to γ isoform switch in human prostate cancer and dog lymphoma. Finally, we showed that E11-knockout promoted, whereas knockdown of p73γ or Leptin suppressed, xenograft growth in mice. Our study indicates that the p73γ-Leptin pathway promotes tumorigenesis and alters lipid metabolism, which may be targeted for cancer management.

Hypothalamic astrocytic-BMAL1 regulates energy homeostasis in a sex-dependent manner

Here, we demonstrate that hypothalamic astrocytic BMAL1 computes cyclic metabolic information to optimize energetic resources in a sexually dimorphic manner. Knockdown of BMAL1 in female astrocytes leads to negative energy balance and alters basal metabolic cycles without affecting circadian locomotor activity. Thus, astrocytic BMAL1 contributes to the control of energy balance through the modulation of the metabolic rate, hepatic and white adipose tissue lipogenesis, and the activity of brown adipose tissue. Importantly, most of these alterations are specific to hypothalamic astrocytic BMAL1. Moreover, female mice with BMAL1 knockdown in astrocytes exhibited a "male-like" metabolic obese phenotype when fed a high-fat diet. Overall, our results suggest a sexually dimorphic effect of astrocytic BMAL1 on the regulation of energy homeostasis, which may be of interest in the physiopathology of obesity and related comorbidities.