Weight-reducing effects of the plasma protein encoded by the obese gene

Astrocytes of the hippocampus and responses to periprandial neuroendocrine hormones

Astrocytes have risen as stars in the field of energy homeostasis and neurocognitive function, acting as a bridge of communication between the periphery and the brain, providing metabolic support, signaling via gliotransmitters, and altering synaptic communication. Dietary factors and energy state have a profound influence on hippocampal function, and the hippocampus is critical for appropriate behavioral responses associated with feeding and internal hunger cues (being in the fasted or full state), but how the hippocampus senses periprandial status and is impacted by diet is largely unknown. Periprandial hormones act within the hippocampus to modulate processes involved in hippocampal-dependent learning and memory function and astrocytes likely play an important role in modulating this signaling. In addition to periprandial hormones, astrocytes are positioned to respond to changes in circulating nutrients like glucose. Here, we review literature investigating how astrocytes mediate changes in hippocampal function, highlighting astrocyte location, morphology, and function in the context of integrating glucose metabolism, neuroendocrine hormone action, and/or cognitive function in the hippocampus. Specifically, we discuss research findings on the effects of insulin, ghrelin, leptin, and GLP-1 on glucose homeostasis, neural activity, astrocyte function, and behavior in the hippocampus. Because obesogenic diets impact neuroendocrine hormones, astrocytes, and cognitive function, we also discuss the effects of diet and diet-induced obesity on these parameters.

Long-Acting Human PASylated Leptin Reaches the Murine Central Nervous System and Offers Potential for Optimized Replacement Therapy

Despite the multifaceted role of leptin for energy homeostasis and its broad therapeutic potential, the FDA/EMA-approved metreleptin constitutes the only leptin drug to date. To translate the promising results from previous studies on murine PASylated leptin with improved solubility and extended plasma half-life using PASylation technology─a biological alternative to PEGylation─we have developed a second-generation human leptin drug candidate and tested it rigorously in vitro and in vivo. To this end, the exposed hydrophobic Trp residue at position 100 in human leptin was replaced by Gln, which, together with the genetic fusion with a 600-residue PAS polypeptide, yielded a protein with high solubility, folding stability and receptor-stimulatory activity. In a pharmacokinetic (PK) study with wild-type mice, this modified human leptin showed an extended plasma half-life of 18.8 ± 3.6 h after subcutaneous (s.c.) injection. Furthermore, leptin-deficient mice were dosed s.c. with the modified human leptin carrying two different PAS fusion tags, PAS#1 or P/A#1, each comprising 600 residues. After only four doses, the disease phenotype, including morbid adiposity, hyperphagia, and hepatic steatosis, was completely reversed by both PASylated leptin versions, but not by the non-PASylated leptin if administered at the same dose. To assess its tissue distribution, P/A(200)-huLeptinW100Q was doubly labeled with two fluorescent dyes, which were specifically attached to the leptin and the PAS moiety, respectively. Analysis of relevant mouse organs by light sheet fluorescence microscopy after clearance revealed colocalized signals in the kidney and liver, thus indicating general stability of the PAS-leptin fusion protein in vivo. However, discrete signals were observed in the hypothalamic region, only with leptin detectable in the choroid plexus, which implies cleavage of the PAS tag during transcytosis across the physiological barriers. This study should pave the way toward a second-generation leptin drug enabling prolonged dosing intervals.

Role of Microneedles for Improved Treatment of Obesity: Progress and Challenges

Obesity is a global metabolic health epidemic characterized by excessive lipid and fat accumulation, leading to severe conditions such as diabetes, cancer, and cardiovascular disease. Immediate attention and management of obesity-related health risks are most warranted. The imbalance between fat absorption, metabolic rate, and environmental and genetic factors is responsible for obesity. Treatment typically involves lifestyle modifications, pharmacotherapy, and surgery. While lifestyle changes are crucial, effective treatment often necessitates medication as a preferred adjunct strategy. However, medications commonly used, such as oral pharmacotherapy, often show side effects due to systemic exposure and, thus, may not effectively target the intended areas, leading to drug loss. On the other hand, transdermal administration of drugs with microneedle (MN)-based technologies, a painless drug delivery approach with patient compliance, is gaining interest as an alternative obesity treatment, as it directly targets adipose tissue via local delivery, minimizing system exposure and dose reduction. This Review addresses the pathophysiology of obesity, current treatment strategies, challenges in the treatment of obesity using conventional formulations, the importance of the use of nano-based medications through transdermal delivery, and the use of MNs as a promising platform for the effective delivery of nanoparticle-based anti-obesity medications. The potential of combining MNs with stimuli-responsive and non-responsive adjuvant therapies to enhance treatment efficacy and patient outcomes is explored. In addition, the limitations and future perspectives related to the use of MNs for obesity are addressed to highlight the transformative potential of this technology for obesity management. MNs hold promise in precisely delivering anti-obesity drugs while requiring lower dosages and minimizing side effects compared to conventional oral or injectable therapies and ultimately improving the quality of life for individuals struggling with obesity and its associated comorbidities.

Hypothalamus and brainstem circuits in the regulation of glucose homeostasis

The central nervous system (CNS) senses and integrates blood glucose status, regulating its levels through communication with peripheral organs. Since traditional wisdom holds that the hypothalamus primarily controls glucose homeostasis, the brainstem, although less studied, has been emerging as a key player in blood glucose metabolism. Although the brainstem is reciprocally wired with the hypothalamus, their interactions are crucial for glucose control. Here, we focus on classic discoveries and recent advancements of hypothalamic and brainstem nodes that regulate glucose homeostasis. Based on the current progress and development for central regulation of blood sugar, we propose that the circuitry and cellular mechanisms for how hypothalamus and brainstem coordinate in blood sugar regulation are crucial; hence, a deeper understanding of both nuclei could shed light on a future cure for diabetes.

Pregnancy-induced mechanisms regulating central and peripheral leptin sensitivity: lessons from sheep

This review describes various aspects of the leptin resistance phenomenon and related physiological mechanisms that occur in pregnant sheep. Its main aim is to analyze the mechanisms that determine the occurrence of pregnancy-induced leptin resistance and to investigate the accompanying processes that affect the physiology of pregnancy and lactation in livestock. The main purpose of this analysis was to comprehensively understand the phenomenon of leptin resistance, including the causes of its emergence and its effects on nonrodent organisms.

Adipokines as Cardioprotective Factors: BAT Steps Up to the Plate

Cardiovascular disease is the leading cause of death throughout most of the industrialized world. Metabolic syndrome (MetS) and its associated pathologies are underlying factors in the etiology of cardiovascular disease, as well as a plethora of other maladies which cause excess morbidity and mortality. Adipose tissue (AT) has come to be regarded as a bona fide endocrine organ which secretes specific molecular entities constituting part of a complex web of inter-organ crosstalk that functions as a key determinant of whole-body metabolic phenotype. Brown adipose tissue (BAT) has classically been regarded as a thermogenic tissue exerting its metabolic effects primarily through its capacity to oxidize substrates decoupled from ATP resynthesis, thereby resulting in increased energy expenditure (EE) and heat production. However, in recent years, BAT has begun to receive attention as a secretory organ in its own right. The molecules secreted specifically by BAT have been termed "batokines", and currently available evidence supports the notion that batokines exert favorable metabolic effects on multiple organ systems. While maintenance of healthy body composition by conferring resistance to excessive adiposity is a rather obvious mechanism by which BAT operates via increased EE, effects on critical organs such as the heart remain unclear. This narrative review focuses on four types of batokines (FGF21, neuregulin 4, 12,13-diHOME, and BAT-derived microRNAs) for which evidence of modulation of cardiovascular function exists in the context of pathological states such as hypertension, atherosclerosis, and ischemia/reperfusion injury. Given the overwhelming burden of cardiometabolic disease, further study of the functions of BAT and its secretome is warranted and will intensify in the future.

A cellular and molecular basis of leptin resistance

Similar to most humans with obesity, diet-induced obese (DIO) mice have high leptin levels and fail to respond to the exogenous hormone, suggesting that their obesity is caused by leptin resistance, the pathogenesis of which is unknown. We found that leptin treatment reduced plasma levels of leucine and methionine, mTOR-activating ligands, leading us to hypothesize that chronic mTOR activation might reduce leptin signaling. Rapamycin, an mTOR inhibitor, reduced fat mass and increased leptin sensitivity in DIO mice but not in mice with defects in leptin signaling. Rapamycin restored leptin's actions on POMC neurons and failed to reduce the weight of mice with defects in melanocortin signaling. mTOR activation in POMC neurons caused leptin resistance, whereas POMC-specific mutations in mTOR activators decreased weight gain of DIO mice. Thus, increased mTOR activity in POMC neurons is necessary and sufficient for the development of leptin resistance in DIO mice, establishing a key pathogenic mechanism leading to obesity.

On the causes of obesity and its treatment: The end of the beginning

Over the last 30 years, our understanding of the causes of obesity has been transformed, and new, highly effective medicines for reducing weight have been developed. This remarkable progress marks an end and a beginning. By establishing that obesity is a biologic disorder amenable to scientific inquiry and rational drug development, simplistic notions about its causes and treatment should be laid to rest. The future holds the promise that additional therapeutic approaches for inducing or maintaining weight loss will be developed, and that these treatments will be tailored to different subgroups to potentially address the pathogenic mechanisms.

Hypertension prevalence in Korean adolescents according to parental hypertension: data from the Korea National Health and Nutrition Survey

The prevalence of hypertension among children and adolescents has risen to 4% globally in recent decades, presenting a significant public health challenge due to its association with increased cardiovascular risks. Existing research on the transmission of hypertension risk between parents and offspring lacks comprehensive data from general population-based samples with clinically collected measurements spanning generations. This study utilized nationally representative data to assess the risk of developing hypertension in offspring based on parental hypertension status, employing standardized blood pressure measurements rather than relying solely on historical data. A positive correlation exists between the increasing number of hypertensive parents and the risk of hypertension development in offspring. The prevalence of hypertension among individuals aged 10 to 18 years did not substantially increase with age. Adolescents whose parents were affected by hypertension exhibited a 2-fold greater prevalence of hypertension compared to the general population with the same age, with approximately a quarter of boys with both hypertensive parents having hypertension. Among nonobese individuals, the risk of hypertension associated with parental hypertension was comparable to that observed in obese subjects. Blood pressure monitoring from the early stage of life would benefit adolescents with hypertensive parents.

Leptin and Leptin Signaling in Multiple Sclerosis: A Narrative Review

Obesity, a pandemic health problem, is now considered as a chronic inflammatory state, related to many autoimmune diseases, such as multiple sclerosis. Thus, adipokines, inflammatory mediators secreted by adipose tissue, play an important role modulating the immune response. In this context, obesity, especially during adolescent age, seems to be a key factor for the development of multiple sclerosis. Leptin, the main pro-inflammatory adipokine secreted by the adipose tissue, has been found increased in patients with multiple sclerosis and is able to regulate the immune system promoting a pro-inflammatory response. Leptin signaling in both innate and adaptative immune cells might have immunomodulatory effects in the context of multiple sclerosis. In this way, leptin has been found to produce a Th1 and Th17 response, increasing M1 macrophages and decreasing regulatory T cells and Th2 response. Moreover, circulating inflammatory adipokines, such as leptin, have been found in people with multiple sclerosis. In the present work, we are reviewing literature to update the body of knowledge regarding the role of obesity and leptin in multiple sclerosis.

Neurotensin-neurotensin receptor 2 signaling in adipocytes suppresses food intake through regulating ceramide metabolism

Neurotensin (NTS) is a secretory peptide produced by lymphatic endothelial cells. Our previous study revealed that NTS suppressed the activity of brown adipose tissue via interactions with NTSR2. In the current study, we found that the depletion of Ntsr2 in white adipocytes upregulated food intake, while the local treatment of NTS suppressed food intake. Our mechanistic study revealed that suppression of NTS-NTSR2 signaling enhanced the phosphorylation of ceramide synthetase 2, increased the abundance of its products ceramides C20-C24, and downregulated the production of GDF15 in white adipose tissues, which was responsible for the elevation of food intake. We discovered a potential causal and positive correlation between serum C20-C24 ceramide levels and human food intake in four populations with different ages and ethnic backgrounds. Together, our study shows that NTS-NTSR2 signaling in white adipocytes can regulate food intake via its direct control of lipid metabolism and production of GDF15. The ceramides C20-C24 are key factors regulating food intake in mammals.

LEP rs7799039 and LEPR rs1137101 gene variants are not associated with clinical features in patients with metabolic syndrome in the Turkish population

OBJECTIVES

Genetic predisposition plays a role in the etiology of metabolic syndrome (MetS), an important health problem worldwide. Leptin (LEP), produced by adipose tissue, plays a crucial role in the development of MetS. In this study, we evaluated the effects of LEP and LEP receptor (LEPR) variants on clinical findings and risk of developing MetS in the Turkish population.

METHODS

A total of 320 patients were included in the study, of whom 150 were patients with MetS and 170 were healthy controls. DNA was extracted from blood samples. LEP rs7799039 and LEPR rs1137101 variants were genotyped using the polymerase chain reaction-based restriction fragment length polymorphism method. The genotype distributions of these variants and clinical and laboratory findings were compared.

RESULTS

The LEP rs7799039 GA and AA genotypes and A allele frequencies were higher in participants with MetS than in the control group. For LEP rs7799039, the genotype AA-GA was higher in males, and the GG genotype was higher in females. On analyzing the clinical outcomes associated with these variants, it was observed that individuals possessing LEP rs7799039 GA and AA genotypes displayed elevated levels of triglycerides. In addition, those with the AG-GG genotype of LEPR rs1137101 had lower mean hemoglobin levels.

CONCLUSION

Our results showed that the LEP rs7799039 and LEPR rs1137101 variants may be associated with both the risk of MetS development and clinical findings. Among the various contributors to MetS, a genetic predisposition is commonly recognized as the primary cause.

Regulation of energy balance by leptin as an adiposity signal and modulator of the reward system

BACKGROUND

Leptin is an adipose tissue-derived hormone that plays a crucial role in body weight, appetite, and behaviour regulation. Leptin controls energy balance as an indicator of adiposity levels and as a modulator of the reward system, which is associated with liking palatable foods. Obesity is characterized by expanded adipose tissue mass and consequently, elevated concentrations of leptin in blood. Leptin's therapeutic potential for most forms of obesity is hampered by leptin resistance and a narrow dose-response window.

SCOPE OF REVIEW

This review describes the current knowledge of the brain regions and intracellular pathways through which leptin promotes negative energy balance and restrains neural circuits affecting food reward. We also describe mechanisms that hinder these biological responses in obesity and highlight potential therapeutic interventions.

MAJOR CONCLUSIONS

Additional research is necessary to understand how pathways engaged by leptin in different brain regions are interconnected in the control of energy balance.

A Review on In-vivo and In-vitro Models of Obesity and Obesity-Associated Co-Morbidities

BACKGROUND

Obesity is becoming a global pandemic with pandemic proportions. According to the WHO estimates, there were over 1.9 billion overweight individuals and over 650 million obese adults in the globe in 2016. In recent years, scientists have encountered difficulties in choosing acceptable animal models, leading to a multitude of contradicting aspects and incorrect outcomes. This review comprehensively evaluates different screening models of obesity and obesity-associated comorbidities to reveal the advantages and disadvantages/limitations of each model while also mentioning the time duration each model requires to induce obesity.

METHODS

For this review, the authors have gone through a vast number of article sources from different scientific databases, such as Google Scholar, Web of Science, Medline, and PubMed.

RESULTS

In-vivo models used to represent a variety of obesity-inducing processes, such as diet-induced, drug-induced, surgical, chemical, stress-induced, and genetic models, are discussed. Animal cell models are examined with an emphasis on their use in understanding the molecular causes of obesity, for which we discussed in depth the important cell lines, including 3T3-L1, OP9, 3T3-F442A, and C3H10T1/2. Screening models of obesity-associated co-morbidities like diabetes, asthma, cardiovascular disorders, cancer, and polycystic ovarian syndrome (PCOS) were discussed, which provided light on the complex interactions between obesity and numerous health problems.

CONCLUSION

Mimicking obesity in an animal model reflects multifactorial aspects is a matter of challenge. Future studies could address the ethical issues surrounding the use of animals in obesity research as well as investigate newly developed models, such as non-mammalian models. In conclusion, improving our knowledge and management of obesity and related health problems will require ongoing assessment and improvement of study models.

Glp1r-Lepr coexpressing neurons modulate the suppression of food intake and body weight by a GLP-1/leptin dual agonist

Glucagon-like peptide-1 (GLP-1) and leptin signal recent feeding and long-term energy stores, respectively, and play complementary roles in the modulation of energy balance. Previous work using single-cell techniques in mice revealed the existence of a population of leptin receptor (Lepr)-containing dorsomedial hypothalamus (DMH) neurons marked by the expression of GLP-1 receptor (Glp1r; LepRGlp1r neurons) that play important roles in the control of feeding and body weight by leptin. Here, we demonstrate the existence of a population of LepRGlp1r neurons in the DMHs of nonhuman primates (NHPs), suggesting the potential translational relevance of these neurons. Consequently, we developed a GLP-1R/LepR dual agonist and demonstrated the physiological activity of both components in vivo using leptin-deficient and Lepr-deficient murine models. We further found roles for LepRGlp1r neurons in mediating the dual agonist's efficacy on food intake and body weight loss. Ablating Lepr in Glp1r-expressing neurons (LeprGlp1rKO mice) abrogated the suppression of food intake by the dual agonist. Furthermore, reactivation of Glp1r expression in Lepr neurons on an otherwise Glp1r-null background (Glp1rLeprRe mice) was sufficient to permit the suppression of food intake and body weight by the dual agonist. Hence, LepRGlp1r neurons represent targets for a GLP-1R/LepR dual agonist that potently reduces food intake and body weight.

Chronic central nervous system leptin administration attenuates kidney dysfunction and injury in a model of ischemia/reperfusion-induced acute kidney injury

In the present study, we examined whether chronic intracerebroventricular (ICV) leptin administration protects against ischemia/reperfusion (I/R)-induced acute kidney injury (AKI). Twelve-week-old male rats were implanted with an ICV cannula into the right lateral ventricle, and 8-10 days after surgery, leptin (0.021 µg/h, n = 8) or saline vehicle (0.5 µL/h, n = 8) was infused via osmotic minipump connected to the ICV cannula for 12 days. On day 8 of leptin or vehicle infusion, rats were submitted to unilateral ischemia/reperfusion (UIR) by clamping the left pedicle for 30 min. To control for leptin-induced reductions in food intake, the vehicle-treated group was pair-fed (UIR-PF) to match the same amount of food consumed by leptin-treated (UIR-Leptin) rats. On the 12th day of leptin or vehicle infusion (fourth day after AKI), single-left kidney glomerular filtration rate (GFR) was measured, blood samples were collected to quantify white blood cells, and kidneys were collected for histological assessment of injury. UIR-Leptin-treated rats showed reduced right and left kidney weights (right: 1,040 ± 24 vs. 1,281 ± 36 mg; left: 1,127 ± 71 vs. 1,707 ± 45 mg, for UIR-Leptin and UIR-PF, respectively). ICV leptin infusion improved GFR (0.50 ± 0.06 vs. 0.13 ± 0.03 mL/min/g kidney wt) and reduced kidney injury scores. ICV leptin treatment also attenuated the reduction in circulating adiponectin levels that was observed in UIR-PF rats and increased the circulating white blood cells count compared with UIR-PF rats (16.3 ± 1.3 vs. 9.8 ± 0.6 k/µL). Therefore, we show that leptin, via its actions on the central nervous system, confers significant protection against major kidney dysfunction and injury in a model of ischemia/reperfusion-induced AKI.NEW & NOTEWORTHY A major new finding of this study is that chronic activation of leptin receptors in the CNS markedly attenuates acute kidney injury and protects against severe renal dysfunction after ischemia/reperfusion, independently of leptin's anorexic effects.

Evidence from clinical studies of leptin: current and future clinical applications in humans

Leptin has been established as the prototype adipose tissue secreted hormone and as a major regulator of several human physiology functions. Here, we are primarily reviewing the findings from studies in humans involving leptin administration. We are describing the metabolic, endocrine and immunologic effects of leptin replacement in conditions of leptin deficiency, such as short-term fasting in healthy individuals, relative energy deficiency in sports (REDS), congenital leptin deficiency (CLD), generalized (GL) and partial lipodystrophy (PL), HIV-associated lipodystrophy (HIV-L) and of leptin treatment in conditions of leptin excess (common obesity, type 2 diabetes, steatotic liver disease). We are comparing the results with the findings from preclinical models and present the main conclusions regarding the role of leptin in human physiology, pathophysiology and therapeutics. We conclude that, in conditions of energy deficiency, leptin substitution effectively reduces body weight and fat mass through reduction of appetite, it improves hypertriglyceridemia, insulin resistance and hepatic steatosis (especially in GL and PL), it restores neuroendocrine function (especially the gonadotropic axis), it regulates adaptive immune system cell populations and it improves bone health. On the contrary, leptin treatment in conditions of leptin excess, such as common obesity and type 2 diabetes, does not improve any metabolic abnormalities. Strategies to overcome leptin tolerance/resistance in obesity and type 2 diabetes have provided promising results in animal studies, which should though be tested in humans in randomized clinical trials.

Leptin Activation of Dorsal Raphe Neurons Inhibits Feeding Behavior

Leptin is a homeostatic regulatory element that signals the presence of adipocyte energy stores, reduces food intake, and increases energy expenditure. Similarly, serotonin (5-HT), a signaling molecule found in both the central and peripheral nervous systems, also controls food intake. Using neuronal tract tracing, pharmacologic and optogenetic approaches, and in vivo microdialysis, combined with behavioral end points, we tested the hypothesis that leptin controls food intake not only by activating hypothalamic leptin receptors (LepRs) but also through activation of LepRs expressed by serotonergic raphe neurons that send projections to the arcuate (ARC). We showed that microinjection of leptin directly into the dorsal raphe nucleus (DRN) reduced food intake in rats. This effect was mediated by LepR-expressing neurons in the DRN, because selective optogenetic activation of these neurons at either their DRN cell bodies or their ARC terminals reduced food intake. Anatomically, we identified a unique population of serotonergic raphe neurons expressing LepRs that send projections to the ARC. Finally, by using in vivo microdialysis, we showed that leptin administration to the DRN increased 5-HT efflux into the ARC, and specific antagonism of the 5-HT2C receptors in the ARC diminished the leptin anorectic effect. Overall, this study identified a novel circuit for leptin-mediated control of food intake through a DRN-ARC pathway, identifying a new level of interaction between leptin and serotonin to control food intake. Characterization of this new pathway creates opportunities for understanding how the brain controls eating behavior and opens alternative routes for the treatment of eating disorders.

ARTICLE HIGHLIGHTS

Discover QTLs for the level of blood components in Shaoxing duck using GWAS and haplotype sharing analysis

Blood composition is indicative of health-related traits such as immunity and metabolism. The use of molecular genetics to investigate alterations in these attributes in laying ducks is a novel approach. Our objective was to employ genome - wide association studies (GWAS) and haplotype - sharing analysis to identify genomic regions and potential genes associated with 11 blood components in Shaoxing ducks. Our findings revealed 35 SNPs and 1 SNP associated with low-density lipoprotein cholesterol (LDL) and globulin (GLB), respectively. We identified 36 putative candidate genes for the LDL trait in close proximity to major QTLs and key loci. Based on their biochemical and physiological properties, TRA2A, NPY, ARHGEF26, DHX36, and AADAC are the strongest putative candidate genes. Through linkage disequilibrium analysis and haplotype sharing analysis, we identified three haplotypes and one haplotype, respectively, that were significantly linked with LDL and GLB. These haplotypes could be selected as potential candidate haplotypes for molecular breeding of Shaoxing ducks. Additionally, we utilized a bootstrap test to verify the reliability of GWAS with small experimental samples. The test can be accessed at https://github.com/xuwenwu24/Bootstrap-test.

Trapped fat: Obesity pathogenesis as an intrinsic disorder in metabolic fuel partitioning

Our understanding of the pathophysiology of obesity remains at best incomplete despite a century of research. During this time, two alternative perspectives have helped shape thinking about the etiology of the disorder. The currently prevailing view holds that excessive fat accumulation results because energy intake exceeds energy expenditure, with excessive food consumption being the primary cause of the imbalance. The other perspective attributes the initiating cause of obesity to intrinsic metabolic defects that shift fuel partitioning from pathways for mobilization and oxidation to those for synthesis and storage. The resulting reduction in fuel oxidation and trapping of energy in adipose tissue drives a compensatory increase in energy intake and, under some conditions, a decrease in expenditure. This theory of obesity pathogenesis has historically garnered relatively less attention despite its pedigree. Here, we present an updated comprehensive formulation of the fuel partitioning theory, focused on evidence gathered over the last 80 years from major animal models of obesity showing a redirection of fuel fluxes from oxidation to storage and accumulation of excess body fat with energy intake equal to or even less than that of lean animals. The aim is to inform current discussions about the etiology of obesity and by so doing, help lay new foundations for the design of more efficacious approaches to obesity research, treatment and prevention.

Seasonal food intake and energy balance: Neuronal and non-neuronal control mechanisms

Animals inhabiting temperate and high latitudes undergo drastic seasonal changes in energy storage, facilitated by changes in food intake and body mass. Those seasonal changes in the animal's biology are not mere consequences of environmental energy availability but are anticipatory responses to the energetic requirements of the upcoming season and are actively timed by tracking the annual progression in photoperiod. In this review, we discuss how photoperiod is used to control energy balance seasonally and how this is distinct from energy homeostasis. Most notably, we suggest that photoperiodic control of food intake and body mass does not originate from the arcuate nucleus, as for homeostatic appetite control, but is rather to be found in hypothalamic tanycytes. Tanycytes are specialized ependymal cells lining the third ventricle, which can sense metabolites from the cerebrospinal fluid (e.g. glucose) and can control access of circulating signals to the brain. They are also essential in conveying time-of-year information by integrating photoperiod and altering hypothalamic thyroid metabolism, a feature that is conserved in seasonal vertebrates and connects to seasonal breeding and metabolism. We also discuss how homeostatic feedback signals are handled during times of rapid energetic transitions. Studies on leptin in seasonal mammals suggest a seasonal shift in central sensitivity and blood-brain transport, which might be facilitated by tanycytes. This article is part of the Special Issue on "Food intake and feeding states".

Adipose Tissue Plasticity: A Comprehensive Definition and Multidimensional Insight

Adipose tissue is composed of adipocytes, stromal vascular fraction, nerves, surrounding immune cells, and the extracellular matrix. Under various physiological or pathological conditions, adipose tissue shifts cellular composition, lipid storage, and organelle dynamics to respond to the stress; this remodeling is called "adipose tissue plasticity". Adipose tissue plasticity includes changes in the size, species, number, lipid storage capacity, and differentiation function of adipocytes, as well as alterations in the distribution and cellular composition of adipose tissue. This plasticity has a major role in growth, obesity, organismal protection, and internal environmental homeostasis. Moreover, certain thresholds exist for this plasticity with significant individualized differences. Here, we comprehensively elaborate on the specific connotation of adipose tissue plasticity and the relationship between this plasticity and the development of many diseases. Meanwhile, we summarize possible strategies for treating obesity in response to adipose tissue plasticity, intending to provide new insights into the dynamic changes in adipose tissue and contribute new ideas to relevant clinical problems.

Adipokines in the Crosstalk between Adipose Tissues and Other Organs: Implications in Cardiometabolic Diseases

Adipose tissue was previously regarded as a dormant organ for lipid storage until the identification of adiponectin and leptin in the early 1990s. This revelation unveiled the dynamic endocrine function of adipose tissue, which has expanded further. Adipose tissue has emerged in recent decades as a multifunctional organ that plays a significant role in energy metabolism and homeostasis. Currently, it is evident that adipose tissue primarily performs its function by secreting a diverse array of signaling molecules known as adipokines. Apart from their pivotal function in energy expenditure and metabolism regulation, these adipokines exert significant influence over a multitude of biological processes, including but not limited to inflammation, thermoregulation, immune response, vascular function, and insulin sensitivity. Adipokines are pivotal in regulating numerous biological processes within adipose tissue and facilitating communication between adipose tissue and various organs, including the brain, gut, pancreas, endothelial cells, liver, muscle, and more. Dysregulated adipokines have been implicated in several metabolic diseases, like obesity and diabetes, as well as cardiovascular diseases. In this article, we attempted to describe the significance of adipokines in developing metabolic and cardiovascular diseases and highlight their role in the crosstalk between adipose tissues and other tissues and organs.

Relative Energy Deficiency in Sport (REDs): Endocrine Manifestations, Pathophysiology and Treatments

Research on lean, energy-deficient athletic and military cohorts has broadened the concept of the Female Athlete Triad into the Relative Energy Deficiency in Sport (REDs) syndrome. REDs represents a spectrum of abnormalities induced by low energy availability (LEA), which serves as the underlying cause of all symptoms described within the REDs concept, affecting exercising populations of either biological sex. Both short- and long-term LEA, in conjunction with other moderating factors, may produce a multitude of maladaptive changes that impair various physiological systems and adversely affect health, well-being, and sport performance. Consequently, the comprehensive definition of REDs encompasses a broad spectrum of physiological sequelae and adverse clinical outcomes related to LEA, such as neuroendocrine, bone, immune, and hematological effects, ultimately resulting in compromised health and performance. In this review, we discuss the pathophysiology of REDs and associated disorders. We briefly examine current treatment recommendations for REDs, primarily focusing on nonpharmacological, behavioral, and lifestyle modifications that target its underlying cause-energy deficit. We also discuss treatment approaches aimed at managing symptoms, such as menstrual dysfunction and bone stress injuries, and explore potential novel treatments that target the underlying physiology, emphasizing the roles of leptin and the activin-follistatin-inhibin axis, the roles of which remain to be fully elucidated, in the pathophysiology and management of REDs. In the near future, novel therapies leveraging our emerging understanding of molecules and physiological axes underlying energy availability or lack thereof may restore LEA-related abnormalities, thus preventing and/or treating REDs-related health complications, such as stress fractures, and improving performance.

Translational potential of mouse models of human metabolic disease

Obesity causes significant morbidity and mortality globally. Research in the last three decades has delivered a step-change in our understanding of the fundamental mechanisms that regulate energy homeostasis, building on foundational discoveries in mouse models of metabolic disease. However, not all findings made in rodents have translated to humans, hampering drug discovery in this field. Here, we review how studies in mice and humans have informed our current framework for understanding energy homeostasis, discuss their challenges and limitations, and offer a perspective on how human studies may play an increasingly important role in the discovery of disease mechanisms and identification of therapeutic targets in the future.

Leptin Is Associated with Testosterone, Nutritional Markers, and Vascular Muscular Dysfunction in Chronic Kidney Disease

Chronic kidney disease (CKD) causes specific hormonal disturbances, such as variations in leptin and testosterone levels and function. These disturbances can promote errors in signaling interaction and cellular information processing and can be implicated in the pathogenesis of atherosclerosis. This study investigates the factors that affect leptin in CKD patients and examines how leptin is related to markers of vascular disease. We conducted a cross-sectional study of 162 patients with CKD in pre-dialysis and dialysis stages. We recorded clinical and laboratory data, including leptin, testosterone, and subclinical atherosclerosis markers like brachial-ankle pulse wave velocity (ba PWV) in pre-dialysis CKD patients and flow-mediated vasodilation (FMD) and nitroglycerin-mediated vasodilation (NMD) in hemodialysis (HD) patients. Leptin was significantly correlated with testosterone in CKD pre-dialysis stages (p < 0.001) and also in HD (p = 0.026), with adipose tissue mass in pre-dialysis stages (p < 0.001), and also in HD (p < 0.001). In women HD patients, leptin correlated with NMD (p = 0.039; r = -0.379); in all HD patients, leptin correlated with C reactive protein (p = 0.007; r = 0.28) and parathormone (p = 0.039; r = -0.220). Our research emphasizes the connection between leptin, adipose tissue, and testosterone in all stages of CKD. Leptin was associated with NMD in HD women and correlated with inflammatory syndrome and parathyroid hormone in all HD patients.

The Therapeutic Potential of the Specific Intestinal Microbiome (SIM) Diet on Metabolic Diseases

Exploring the intricate crosstalk between dietary prebiotics and the specific intestinal microbiome (SIM) is intriguing in explaining the mechanisms of current successful dietary interventions, including the Mediterranean diet and high-fiber diet. This knowledge forms a robust basis for developing a new natural food therapy. The SIM diet can be measured and evaluated to establish a reliable basis for the management of metabolic diseases, such as diabetes, metabolic (dysfunction)-associated fatty liver disease (MAFLD), obesity, and metabolic cardiovascular disease. This review aims to delve into the existing body of research to shed light on the promising developments of possible dietary prebiotics in this field and explore the implications for clinical practice. The exciting part is the crosstalk of diet, microbiota, and gut-organ interactions facilitated by producing short-chain fatty acids, bile acids, and subsequent metabolite production. These metabolic-related microorganisms include Butyricicoccus, Akkermansia, and Phascolarctobacterium. The SIM diet, rather than supplementation, holds the promise of significant health consequences via the prolonged reaction with the gut microbiome. Most importantly, the literature consistently reports no adverse effects, providing a strong foundation for the safety of this dietary therapy.

Obesity-induced inflammation: connecting the periphery to the brain

Obesity is often associated with a chronic, low-grade inflammatory state affecting the entire body. This sustained inflammatory state disrupts the coordinated communication between the periphery and the brain, which has a crucial role in maintaining homeostasis through humoural, nutrient-mediated, immune and nervous signalling pathways. The inflammatory changes induced by obesity specifically affect communication interfaces, including the blood-brain barrier, glymphatic system and meninges. Consequently, brain areas near the third ventricle, including the hypothalamus and other cognition-relevant regions, become susceptible to impairments, resulting in energy homeostasis dysregulation and an elevated risk of cognitive impairments such as Alzheimer's disease and dementia. This Review explores the intricate communication between the brain and the periphery, highlighting the effect of obesity-induced inflammation on brain function.

Modeling Wound Chronicity In Vivo: The Translational Challenge to Capture the Complexity of Chronic Wounds

In an aging society with common lifestyle-associated health issues such as obesity and diabetes, chronic wounds pose a frequent challenge that physicians face in everyday clinical practice. Therefore, nonhealing wounds have attracted much scientific attention. Several in vitro and in vivo models have been introduced to deepen our understanding of chronic wound pathogenesis and amplify therapeutic strategies. Understanding how wounds become chronic will provide insights to reverse or avoid chronicity. Although choosing a suitable model is of utmost importance to receive valuable outcomes, an ideal in vivo model capturing the complexity of chronic wounds is still missing and remains a translational challenge. This review discusses the most relevant mammalian models for wound healing studies and provides guidance on how to implement the hallmarks of chronic wounds. It highlights the benefits and pitfalls of established models and maps out future avenues for research.

Leptin and ghrelin dynamics: unraveling their influence on food intake, energy balance, and the pathophysiology of type 2 diabetes mellitus

Purpose

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and impaired glucose homeostasis. In recent years, there has been growing interest in the role of hunger and satiety hormones such as ghrelin and leptin in the development and progression of T2DM. In this context, the present literature review aims to provide a comprehensive overview of the current understanding of how ghrelin and leptin influences food intake and maintain energy balance and its implications in the pathophysiology of T2DM.

Methods

A thorough literature search was performed using PubMed and Google Scholar to choose the studies that associated leptin and ghrelin with T2DM. Original articles and reviews were included, letters to editors and case reports were excluded.

Results

This narrative review article provides a comprehensive summary on mechanism of action of leptin and ghrelin, its association with obesity and T2DM, how they regulate energy and glucose homeostasis and potential therapeutic implications of leptin and ghrelin in managing T2DM.

Conclusion

Ghrelin, known for its appetite-stimulating effects, and leptin, a hormone involved in the regulation of energy balance, have been implicated in insulin resistance and glucose metabolism. Understanding the complexities of ghrelin and leptin interactions in the context of T2DM may offer insights into novel therapeutic strategies for this prevalent metabolic disorder. Further research is warranted to elucidate the molecular mechanisms underlying these hormone actions and to explore their clinical implications for T2DM prevention and management.

Neuroendocrine disturbances in women with functional hypothalamic amenorrhea: an update and future directions

Functional hypothalamic amenorrhea (FHA) is one of the most common causes of both primary and secondary amenorrhea in women of reproductive age. It is characterized by chronic anovulation and the absence of menses that appear as a result of stressors such as eating disorders, excessive exercise, or psychological distress. FHA is presumed to be a functional disruption in the pulsatile secretion of hypothalamic gonadotropin-releasing hormone, which in turn impairs the release of gonadotropin. Hypoestrogenism is observed due to the absence of ovarian follicle recruitment. Numerous neurotransmitters have been identified which play an important role in the regulation of the hypothalamic-pituitary-ovarian axis and of which the impairment would contribute to developing FHA. In this review we summarize the most recent advances in the identification of contributing neuroendocrine disturbances and relevant contributors to the development of FHA.

Leptin replacement therapy in the management of lipodystrophy syndromes

Lipodystrophy syndromes are rare diseases of genetic or acquired origin, characterized by quantitative and qualitative defects in adipose tissue. The metabolic consequences of lipodystrophy syndromes, such as insulin resistant diabetes, hypertriglyceridemia and hepatic steatosis, are frequently very difficult to treat, resulting in significant risks of acute and/or chronic complications and of decreased quality of life. The production of leptin by lipodystrophic adipose tissue is decreased, more severely in generalized forms of lipodystrophy, where adipose tissue is absent from almost all body fat depots, than in partial forms of the disease, where lipoatrophy affects only some parts of the body and can be associated with increased body fat in other anatomical regions. Several lines of evidence in preclinical and clinical models have shown that leptin replacement therapy could improve the metabolic complications of lipodystrophy syndromes. Metreleptin, a recombinant leptin analogue, was approved as an orphan drug to treat the metabolic complications of leptin deficiency in patients with generalized lipodystrophy in the USA or with either generalized or partial lipodystrophy in Japan and Europe. In this brief review, we will discuss the benefits and limitations of this therapy, and the new expectations arising from the recent development of a therapeutic monoclonal antibody able to activate the leptin receptor.

CCK-sensitive C fibers activate NTS leptin receptor-expressing neurons via NMDA receptors

The hormone leptin reduces food intake through actions in the peripheral and central nervous systems, including in the hindbrain nucleus of the solitary tract (NTS). The NTS receives viscerosensory information via vagal afferents, including information from the gastrointestinal tract, which is then relayed to other central nervous system (CNS) sites critical for control of food intake. Leptin receptors (lepRs) are expressed by a subpopulation of NTS neurons, and knockdown of these receptors increases both food intake and body weight. Recently, we demonstrated that leptin increases vagal activation of lepR-expressing neurons via increased NMDA receptor (NMDAR) currents, thereby potentiating vagally evoked firing. Furthermore, chemogenetic activation of these neurons was recently shown to inhibit food intake. However, the vagal inputs these neurons receive had not been characterized. Here we performed whole cell recordings in brain slices taken from lepRCre × floxedTdTomato mice and found that lepR neurons of the NTS are directly activated by monosynaptic inputs from C-type afferents sensitive to the transient receptor potential vanilloid type 1 (TRPV1) agonist capsaicin. CCK administered onto NTS slices stimulated spontaneous glutamate release onto lepR neurons and induced action potential firing, an effect mediated by CCKR1. Interestingly, NMDAR activation contributed to the current carried by spontaneous excitatory postsynaptic currents (EPSCs) and enhanced CCK-induced firing. Peripheral CCK also increased c-fos expression in these neurons, suggesting they are activated by CCK-sensitive vagal afferents in vivo. Our results indicate that the majority of NTS lepR neurons receive direct inputs from CCK-sensitive C vagal-type afferents, with both peripheral and central CCK capable of activating these neurons and NMDARs able to potentiate these effects.

Transient loss of satiety effects of leptin in middle-aged male mice

Extensive research is undertaken in rodents to determine the mechanism underlying obesity-induced leptin resistance. While body weight is generally tightly controlled in these studies, the effect of age of experimental animals has received less attention. Specifically, there has been little investigation into leptin regulation of food intake in middle-aged animals, which is a period of particular relevance for weight gain in humans. We investigated whether the satiety effects of leptin remained constant in young (3 months), middle-aged (12 months) or aged (18-22 months) male mice. Although mean body weight increased with age, leptin concentrations did not significantly increase in male mice beyond 12 months of age. Exogenous leptin administration led to a significant reduction in food intake in young mice but had no effect on food intake in middle-aged male mice. This loss of the satiety effect of leptin appeared to be transient, with leptin administration leading to the greatest inhibition of food intake in the aged male mice. Subsequently, we investigated whether these differences were due to changes in leptin transport into the brain with ageing. No change in leptin clearance from the blood or transport into the brain was observed, suggesting the emergence of central resistance to leptin in middle age. These studies demonstrate the presence of dynamic and age-specific changes in the satiety effects of leptin in male mice and highlight the requirement for age to be carefully considered when undertaking metabolic studies in rodents.

Hippo-YAP/TAZ signalling coordinates adipose plasticity and energy balance by uncoupling leptin expression from fat mass

Adipose tissues serve as an energy reservoir and endocrine organ, yet the mechanisms that coordinate these functions remain elusive. Here, we show that the transcriptional coregulators, YAP and TAZ, uncouple fat mass from leptin levels and regulate adipocyte plasticity to maintain metabolic homeostasis. Activating YAP/TAZ signalling in adipocytes by deletion of the upstream regulators Lats1 and Lats2 results in a profound reduction in fat mass by converting mature adipocytes into delipidated progenitor-like cells, but does not cause lipodystrophy-related metabolic dysfunction, due to a paradoxical increase in circulating leptin levels. Mechanistically, we demonstrate that YAP/TAZ-TEAD signalling upregulates leptin expression by directly binding to an upstream enhancer site of the leptin gene. We further show that YAP/TAZ activity is associated with, and functionally required for, leptin regulation during fasting and refeeding. These results suggest that adipocyte Hippo-YAP/TAZ signalling constitutes a nexus for coordinating adipose tissue lipid storage capacity and systemic energy balance through the regulation of adipocyte plasticity and leptin gene transcription.

Loss of GIPR in LEPR cells impairs glucose control by GIP and GIP:GLP-1 co-agonism without affecting body weight and food intake in mice

OBJECTIVE

The glucose-dependent insulinotropic polypeptide (GIP) decreases body weight via central GIP receptor (GIPR) signaling, but the underlying mechanisms remain largely unknown. Here, we assessed whether GIP regulates body weight and glucose control via GIPR signaling in cells that express the leptin receptor (Lepr).

METHODS

Hypothalamic, hindbrain, and pancreatic co-expression of Gipr and Lepr was assessed using single cell RNAseq analysis. Mice with deletion of Gipr in Lepr cells were generated and metabolically characterized for alterations in diet-induced obesity (DIO), glucose control and leptin sensitivity. Long-acting single- and dual-agonists at GIPR and GLP-1R were further used to assess drug effects on energy and glucose metabolism in DIO wildtype (WT) and Lepr-Gipr knock-out (KO) mice.

RESULTS

Gipr and Lepr show strong co-expression in the pancreas, but not in the hypothalamus and hindbrain. DIO Lepr-Gipr KO mice are indistinguishable from WT controls related to body weight, food intake and diet-induced leptin resistance. Acyl-GIP and the GIPR:GLP-1R co-agonist MAR709 remain fully efficacious to decrease body weight and food intake in DIO Lepr-Gipr KO mice. Consistent with the demonstration that Gipr and Lepr highly co-localize in the endocrine pancreas, including the β-cells, we find the superior glycemic effect of GIPR:GLP-1R co-agonism over single GLP-1R agonism to vanish in Lepr-Gipr KO mice.

CONCLUSIONS

GIPR signaling in cells/neurons that express the leptin receptor is not implicated in the control of body weight or food intake, but is of crucial importance for the superior glycemic effects of GIPR:GLP-1R co-agonism relative to single GLP-1R agonism.

Repeated photodynamic therapy using a chlorin e6-embedded device to prolong the therapeutic effects on obesity

OBJECTIVE

This study aimed to investigate the efficacy and safety of repeated photodynamic therapy (PDT) with a chlorin e6 (Ce6)-embedded intragastric satiety-inducing device (ISD) to maintain therapeutic effects of obesity in a juvenile pig.

METHODS

The Ce6-embedded ISD was fabricated with a dipping method. Twelve pigs were divided into four groups of three and were administered control, single, biweekly, or weekly PDT, respectively. The therapeutic effects were assessed by comparing the results of phototoxicity, endoscopy, fluoroscopy, hormone and weight changes, and histological examination.

RESULTS

The percentage of total body weight gain was significantly suppressed in PDT-treated pigs compared with control pigs (all p < 0.001). This suppression persisted in the repeated PDT groups, but percentage of total body weight gain gradually increased when PDT was stopped. Ghrelin levels in the PDT-treated groups were significantly lower and leptin levels were significantly higher than those in the control group (all p < 0.05). Inflammatory cell infiltration, collagen, TUNEL, and anti-ghrelin-positive deposition in the weekly group were significantly higher than those in the control, single, and biweekly groups (all p < 0.01).

CONCLUSIONS

Repeated and periodic PDT was technically feasible and safe and successfully maintained the therapeutic effects against obesity while eliminating the indwelling time and reducing ISD-related complications in pigs.

Novel mechanisms involved in leptin sensitization in obesity

Leptin is a hormone that is secreted by adipocytes in proportion to adipose tissue size, and that informs the brain about the energy status of the body. Leptin acts through its receptor LepRb, expressed mainly in the hypothalamus, and induces a negative energy balance by potent inhibition of feeding and activation of energy expenditure. These actions have led to huge expectations for the development of therapeutic targets for metabolic complications based on leptin-derived compounds. However, the majority of patients with obesity presents elevated leptin production, suggesting that in this setting leptin is ineffective in the regulation of energy balance. This resistance to the action of leptin in obesity has led to the development of "leptin sensitizers," which have been tested in preclinical studies. Much research has focused on generating combined treatments that act on multiple levels of the gastrointestinal-brain axis. The gastrointestinal-brain axis secretes a variety of different anorexigenic signals, such as uroguanylin, glucagon-like peptide-1, amylin, or cholecystokinin, which can alleviate the resistance to leptin action. Moreover, alternative mechanism such as pharmacokinetics, proteostasis, the role of specific kinases, chaperones, ER stress and neonatal feeding modifications are also implicated in leptin resistance. This review will cover the current knowledge regarding the interaction of leptin with different endocrine factors from the gastrointestinal-brain axis and other novel mechanisms that improve leptin sensitivity in obesity.

Central inhibition of HDAC6 re-sensitizes leptin signaling during obesity to induce profound weight loss

Leptin resistance during excess weight gain significantly contributes to the recidivism of obesity to leptin-based pharmacological therapies. The mechanisms underlying the inhibition of leptin receptor (LepR) signaling during obesity are still elusive. Here, we report that histone deacetylase 6 (HDAC6) interacts with LepR, reducing the latter's activity, and that pharmacological inhibition of HDAC6 activity disrupts this interaction and augments leptin signaling. Treatment of diet-induced obese mice with blood-brain barrier (BBB)-permeable HDAC6 inhibitors profoundly reduces food intake and leads to potent weight loss without affecting the muscle mass. Genetic depletion of Hdac6 in Agouti-related protein (AgRP)-expressing neurons or administration with BBB-impermeable HDAC6 inhibitors results in a lack of such anti-obesity effect. Together, these findings represent the first report describing a mechanistically validated and pharmaceutically tractable therapeutic approach to directly increase LepR activity as well as identifying centrally but not peripherally acting HDAC6 inhibitors as potent leptin sensitizers and anti-obesity agents.

A negative feedback loop between TET2 and leptin in adipocyte regulates body weight

Ten-eleven translocation (TET) 2 is an enzyme that catalyzes DNA demethylation to regulate gene expression by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine, functioning as an essential epigenetic regulator in various biological processes. However, the regulation and function of TET2 in adipocytes during obesity are poorly understood. In this study, we demonstrate that leptin, a key adipokine in mammalian energy homeostasis regulation, suppresses adipocyte TET2 levels via JAK2-STAT3 signaling. Adipocyte Tet2 deficiency protects against high-fat diet-induced weight gain by reducing leptin levels and further improving leptin sensitivity in obese male mice. By interacting with C/EBPα, adipocyte TET2 increases the hydroxymethylcytosine levels of the leptin gene promoter, thereby promoting leptin gene expression. A decrease in adipose TET2 is associated with obesity-related hyperleptinemia in humans. Inhibition of TET2 suppresses the production of leptin in mature human adipocytes. Our findings support the existence of a negative feedback loop between TET2 and leptin in adipocytes and reveal a compensatory mechanism for the body to counteract the metabolic dysfunction caused by obesity.

Meta-analysis investigating the impact of the LEPR rs1137101 (A>G) polymorphism on obesity risk in Asian and Caucasian ethnicities

Obesity is a chronic condition which is identified by the buildup of excess body fat caused by a combination of various factors, including genetic predisposition and lifestyle choices. rs1137101 (A > G) polymorphism in the CHR1 domain of LEPR protein linked to different diseases including obesity. Nevertheless, the connection between this polymorphism and the likelihood of developing obesity has not been determined definitively. Therefore, a meta-analysis was conducted to assess the relationship between rs1137101 and the risk of obesity. The meta-analysis included all studies meeting pre-defined criteria, found through searching databases up until February 2023. A combined odds ratio with a 95% confidence interval was estimated as overall and in continent subgroups for homozygous, heterozygous, recessive, dominant and allelic models using the fixed or the random-effects model. The meta-analysis identified 39 eligible studies with cases and controls (6099 cases/6711 controls) in 38 articles under different ethnic backgrounds. The results indicated a significant relationship between rs1137101 and the likelihood of developing obesity in each of the genetic models [the homozygous model (GG vs. AA: 95% Confidence Interval = 1.12-1.73, Odds Ratio = 1.39, P value = 0.003); the heterozygous model (AG vs. AA: 95% Confidence Interval = 1.07-1.42, Odds Ratio = 1.23, P value = 0.005); the dominant model (AG/GG vs AA: 95% Confidence Interval = 1.10-1.49, Odds Ratio = 1.28, P value = 0.001); the recessive model (GG vs AA/AG: 95% Confidence Interval = 1.02-1.45, Odds Ratio = 1.21, P value = 0.03); and the allelic model (G vs A; 95% Confidence Interval = 1.07-1.33, Odds Ratio = 1.19, P value = 0.002)] tested. Additionally, with an FDR <0.05, all genotypic models demonstrated statistical significance. The association remained significant among subgroups of Asian and Caucasian populations, although analysis in some genetic models did not show a significant association. Begg's and Egger's tests did not show publication biases. In sensitivity analysis, one particular study was found to have an impact on the Recessive model's significance, but other models remained unaffected. The current meta-analysis found significant indications supporting the association between rs1137101 and obesity. To avail a deeper understanding of this association, future research should include large-scale studies conducted in diverse ethnic populations.

The role of adiposity, adipokines and polymorphisms of leptin and adiponectin in myelodysplastic syndromes

The aim of the present study was to investigate the relationship between leptin and adiponectin gene polymorphisms, circulating levels of leptin and adiponectin, adiposity and clinical markers in patients with myelodysplastic syndrome (MDS). This cross-sectional study was conducted with 102 adults and elderly MDS patients and 102 age- and sex-matched controls. Clinical characteristics, co-morbidities, anthropometric data, laboratory evaluation and genetic analysis (polymorphisms -2548G > A/rs7799039 of the LEP gene and +276G > T/rs1501299 of the ADIPOQ gene) were investigated. Serum leptin was higher and adiponectin lower in MDS when compared with controls. There was a significant positive correlation between serum leptin levels and BMI (r = 0·264, P = 0·025), waist circumference (r = 0·235, P = 0·047), body fat percentage (BF %) (r = 0·373, P = 0·001) and the fat mass index (FMI) (r = 0·371, P < 0·001). A lower mean adiponectin was found among patients with high BF %, higher visceral adiposity index and metabolic syndrome. A significant association was found between the AA genotype (mutant) of the LEP polymorphism rs7799039 and male sex and blast excess (≥ 5 %). In addition, a significant association was observed between the TT genotype (mutant) of the ADIPOQ rs1501299 polymorphism and Fe overload. These results demonstrate the importance of a comprehensive and systematic evaluation in patients with MDS in order to identify and control negative factors not related to the disease at an early stage.

AMP-activated protein kinase activation suppresses leptin expression independently of adipogenesis in primary murine adipocytes

Adipogenesis, defined as the development of mature adipocytes from stem cell precursors, is vital for the expansion, turnover and health of adipose tissue. Loss of adipogenic potential in adipose stem cells, or impairment of adipogenesis is now recognised as an underlying cause of adipose tissue dysfunction and is associated with metabolic disease. In this study, we sought to determine the role of AMP-activated protein kinase (AMPK), an evolutionarily conserved master regulator of energy homeostasis, in adipogenesis. Primary murine adipose-derived stem cells were treated with a small molecule AMPK activator (BI-9774) during key phases of adipogenesis, to determine the effect of AMPK activation on adipocyte commitment, maturation and function. To determine the contribution of the repression of lipogenesis by AMPK in these processes, we compared the effect of pharmacological inhibition of acetyl-CoA carboxylase (ACC). We show that AMPK activation inhibits adipogenesis in a time- and concentration-dependent manner. Transient AMPK activation during adipogenic commitment leads to a significant, ACC-independent, repression of adipogenic transcription factor expression. Furthermore, we identify a striking, previously unexplored inhibition of leptin gene expression in response to both short-term and chronic AMPK activation irrespective of adipogenesis. These findings reveal that in addition to its effect on adipogenesis, AMPK activation switches off leptin gene expression in primary mouse adipocytes independently of adipogenesis. Our results identify leptin expression as a novel target of AMPK through mechanisms yet to be identified.

Animal models for type 1 and type 2 diabetes: advantages and limitations

Diabetes mellitus, commonly referred to as diabetes, is a group of metabolic disorders characterized by chronic elevation in blood glucose levels, resulting from inadequate insulin production, defective cellular response to extracellular insulin, and/or impaired glucose metabolism. The two main types that account for most diabetics are type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM), each with their own pathophysiological features. T1D is an autoimmune condition where the body's immune system attacks and destroys the insulin-producing beta cells in the pancreas. This leads to lack of insulin, a vital hormone for regulating blood sugar levels and cellular glucose uptake. As a result, those with T1D depend on lifelong insulin therapy to control their blood glucose level. In contrast, T2DM is characterized by insulin resistance, where the body's cells do not respond effectively to insulin, coupled with a relative insulin deficiency. This form of diabetes is often associated with obesity, sedentary lifestyle, and/or genetic factors, and it is managed with lifestyle changes and oral medications. Animal models play a crucial role in diabetes research. However, given the distinct differences between T1DM and T2DM, it is imperative for researchers to employ specific animal models tailored to each condition for a better understanding of the impaired mechanisms underlying each condition, and for assessing the efficacy of new therapeutics. In this review, we discuss the distinct animal models used in type 1 and type 2 diabetes mellitus research and discuss their strengths and limitations.

Role of Leptin in Obesity, Cardiovascular Disease, and Type 2 Diabetes

Diabetes mellitus (DM) is a highly prevalent disease worldwide, estimated to affect 1 in every 11 adults; among them, 90-95% of cases are type 2 diabetes mellitus. This is partly attributed to the surge in the prevalence of obesity, which has reached epidemic proportions since 2008. In these patients, cardiovascular (CV) risk stands as the primary cause of morbidity and mortality, placing a substantial burden on healthcare systems due to the potential for macrovascular and microvascular complications. In this context, leptin, an adipocyte-derived hormone, plays a fundamental role. This hormone is essential for regulating the cellular metabolism and energy balance, controlling inflammatory responses, and maintaining CV system homeostasis. Thus, leptin resistance not only contributes to weight gain but may also lead to increased cardiac inflammation, greater fibrosis, hypertension, and impairment of the cardiac metabolism. Understanding the relationship between leptin resistance and CV risk in obese individuals with type 2 DM (T2DM) could improve the management and prevention of this complication. Therefore, in this narrative review, we will discuss the evidence linking leptin with the presence, severity, and/or prognosis of obesity and T2DM regarding CV disease, aiming to shed light on the potential implications for better management and preventive strategies.

Metabolic Water As a Route for Water Acquisition in Vertebrates Inhabiting Dehydrating Environments

Vertebrates have expanded their habitats during evolution, which accompanies diversified routes for water acquisition. Water is acquired by oral intake and subsequent absorption by the intestine in terrestrial and marine animals which are subjected to constant dehydration, whereas most water is gained osmotically across body surfaces in freshwater animals. In addition, a significant amount of water, called metabolic water, is produced within the body by the oxidation of hydrogen in organic substrates. The importance of metabolic water production as a strategy for water acquisition has been well documented in desert animals, but its role has attracted little attention in marine animals which also live in a dehydrating environment. In this article, the author has attempted to reevaluate the role of metabolic water production in body fluid regulation in animals inhabiting desiccating environments. Because of the exceptional ability of their kidney, marine mammals are thought to typically gain water by drinking environmental seawater and excreting excess NaCl in the urine. On the other hand, it is established that marine teleosts drink seawater to enable intestinal water and ion absorption, and the excess NaCl is excreted by branchial ionocytes. In addition to the oral route, we suggest through experiments using eels that water production by lipid metabolism is an additional route for water acquisition when they encounter seawater. It seems that metabolic water production contributes to counteract dehydration before mechanisms for water regulation are reversed from excretion in freshwater to acquisition in seawater.

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.