Integrative neurocircuits that control metabolism and food intake

GPR40 signaling in agouti-related peptide neurons mediates fat preference

AIMS

Fat preference is mediated by fatty acid receptors in the oral, intestinal, and central nervous systems, but their central nervous system roles remain unclear. Here, we investigated how GPR40, a medium- and long-chain fatty acid receptor, regulates fat preference via agouti-related peptide (AgRP) neurons in the hypothalamic arcuate nucleus (ARC).

MATERIALS AND METHODS

AgRP neuron-specific Gpr40 knockout mice were generated to investigate the role of GPR40 in dietary fat preference. Behavioral tests were conducted to assess dietary preferences, and metabolic analyses were performed after starvation. We also measured the activity of AgRP neurons and the expression levels of AgRP and neuropeptide Y (NPY) to explore the mechanisms.

KEY FINDINGS

Our results indicate that GPR40 is a novel signaling pathway that regulates fat preference in hypothalamic AgRP neurons, but not in pro-opiomelanocortin (POMC) neurons. AgRP-specific Gpr40 knockout mice displayed a reduced preference for fat. This alteration in dietary preference was not associated with behavioral anomalies such as anxiety, depression, or deficits in short-term memory. Additionally, Gpr40 deletion in ARC AgRP neurons resulted in a diminished metabolic state, increased AgRP neuronal activity, and elevated levels of AgRP and NPY peptides following starvation, leading to reduced fat intake and increased carbohydrate intake. Inhibition of AgRP neuronal activity in AgRP-specific Gpr40 knockout mice rescued the observed changes in fat preference.

SIGNIFICANCE

GPR40 signaling in AgRP neurons plays a critical role in regulating fat preference by modulating neuronal activity and the expression of AgRP and NPY peptides.

Tanycytes in the nexus of hypothalamic inflammation, appetite control, and obesity

Hypothalamic inflammation has been identified as a critical factor driving the development of obesity and associated metabolic disorders. This inflammation-related disruption of energy balance relies on alterations in metabolic cues sensing and hypothalamic cellular functions, together leading to overeating and weight gain. Within the hypothalamic cellular networks controlling energy balance, recent studies have highlighted the significance of glial dysfunction in these processes, suggesting that these cells could provide new avenues for weight loss therapies. Glia rapidly activates following the consumption of a high-fat diet, even after a very short exposure, and contributes to the disruption of the entire system through inflammatory crosstalk. This review explores recent progress in understanding the molecular interactions between glial cells and neurons in hypothalamic inflammation related to obesity, diabetes, and associated complications. Notably, it highlights specialized ependymal cells called tanycytes, whose role is still underestimated in hypothalamic inflammation, and examines the potential for targeting this cell type as a treatment strategy for metabolic disorders.

Exploring adipose tissue-derived extracellular vesicles in inter-organ crosstalk: Implications for metabolic regulation and adipose tissue function

Intercellular and inter-organ communication systems are vital for tissue homeostasis and disease development, utilizing soluble bioactive molecules for signaling. The field of extracellular vesicle (EV) biology has rapidly expanded in recent decades, highlighting EVs as effective bioactive nanovectors for cell-to-cell communication in various physiological and pathological contexts. Numerous studies indicate that adipocyte-derived EVs are crucial components of the adipose secretome, playing a key role in autocrine and paracrine interactions within adipose tissue, as well as in endocrine signaling. This review aims to present an updated perspective on EVs as mediators of communication between adipose tissue and other organs, while also examining their therapeutic potential in the light of recent advancements in EV biology research.

Genetic etiology and clinical features of non-syndromic pediatric obesity in the Chinese population: a large cohort study

BACKGROUND

This study aimed to investigate the genetic etiology and clinical features of non-syndromic pediatric obesity in a large Chinese cohort, providing insights into the genetic profile and its correlation with clinical phenotypes.

METHODS

We enrolled 391 children, aged 7-14 years, diagnosed with non-syndromic pediatric obesity at Jiangxi Provincial Children's Hospital from January 2020 to June 2022. Whole-exome sequencing was employed to identify potential genetic causes, focusing on 79 candidate genes associated with obesity. Multivariate logistic regression analysis was performed on the clinical data of the non-syndromic obesity gene-positive group and the gene-negative group.

RESULTS

Among the 391 patients, 32 (8.2%) carried 18 non-syndromic obesity genes, with UCP3 and MC4R being the most common. Seven cases (1.8%) were rated as likely pathogenic by the American College of Medical Genetics and Genomics (ACMG). Clinical phenotype and genetic correlation analysis revealed that urinary microalbumin, fT4, GGT, uric acid, serum phosphorus, paternal weight, family history, impaired glucose tolerance (IGT), non-HDL cholesterol (non-HDL-C), and metabolic syndrome (MetS) showed significant statistical differences (P < 0.05). Serum phosphorus is an independent risk factor associated with genetic predispositions to obesity in children and adolescents (P < 0.05).

CONCLUSION

Our findings highlight the genetic heterogeneity of non-syndromic pediatric obesity and identify UCP3 and MC4R as potential hotspot genes in the Chinese population. The study underscores the potential of genetic testing for early diagnosis and personalized management of pediatric obesity.

The gut-brain axis mechanism of normal appetite induced by kynurenic acid

Feeding is essential for both host-organism survival and gut-microbiota maintenance. Our research focuses on how kynurenic acid (KYNA), a gut-microbiota metabolite, regulates appetite during fasting. We find that fasting significantly raises KYNA levels in the intestine, which increases short-term food intake by inhibiting vagal afferent nerve in the nodose ganglion (NG) and activating AgRP neurons in arcuate nucleus (ARCAgRP). The orexigenic effects of KYNA are abolished by subdiaphragmatic vagotomy (sdVx), chemogenetic activation/inhibition of glutamatergic NG/ARCAgRP neurons, inhibiting the nucleus of the solitary tract (NTS) to ARCAgRP inputs, or knockdown of GPR35 (a KYNA receptor) in the intestinal vagal afferent nerve. Our data support a model in which KYNA acts through the GPR35 receptor to inhibit vagal afferent signaling and subsequently activate ARCAgRP neurons, which leads to increased food intake. These findings reveal a mechanism by which gut microbiota controls appetite during fasting, highlighting the complex relationship between microbial and host feeding behavior.

Modulated regulation of the stress-feeding-growth neuroendocrine cascade in Chinese sea bass (Lateolabrax maculatus) under temperature and salinity changes

Temperature and salinity are among the most important factors affecting food-intake, metabolism, and growth of aquatic animals through their neuroendocrine systems. However, how the regulation of feeding, metabolism and growth are integrated under thermo-saline interaction is still unclear. In this study, modulated transcriptomic responses to temperature and salinity changes were investigated in Chinese sea bass (Lateolabrax maculatus), the economically important fish in East Asia that can adapt to diverse thermo-saline environments. L. maculatus were acclimated at different temperatures (14 °C, 21 °C, 28 °C) and salinities (freshwater and seawater) for 30 days, and their growth rate was better at 21 °C than 14 °C/28 °C (2.76-3.22 times), with mild difference between seawater and freshwater. An interaction between temperature and salinity on L. maculatus growth was detected, and low salinity (0 ppt) may mitigate the temperature (28 °C) effect. Weighted gene co-expression network analysis for L. maculatus brain transcriptomes identified growth-related temperature-salinity responsive modules, revealing the neuroendocrine gene cascade for stress-feeding-growth functions in L. maculatus. Specifically, stress-induced heat shock proteins (hspe1 and hsp30l) may stimulate the hypothalamic-pituitary-interrenal (HPI) axis (crhb and pomc), further activate anorexic genes (cart and prlh) and growth inhibiting somatostatin (sst), which was further verified through both in vitro brain culture and individual feeding test. These results revealed modulated regulation of the stress-feeding-growth cascade in L. maculatus under thermo-saline changes, which may regulate feeding behavior and ultimately control growth. These findings may provide vital guidance for the development of fast-growing L. maculatus in diverse thermo-saline environments like seawater cages, freshwater ponds, or even alkaline waters.

Rapid modulation of gut microbiota composition by hypothalamic circuits in mice

In recent years, the gut microbiota and derived metabolites have emerged as relevant players in modulating several brain functions, including energy balance control1-3. This form of distant communication mirrors that of metabolic hormones (for example, leptin, ghrelin), which convey information about the organism's energy status by exerting effects on diverse brain regions, including the master homeostatic centre, the hypothalamus4. However, whether the hypothalamus is also able to influence gut microbiota composition remains enigmatic. Here we present a study designed to unravel this challenging question. To this aim, we used chemogenetics5 (to selectively activate or inhibit hypothalamic pro-opiomelanocortin or agouti-related peptide neurons) or centrally administered leptin or ghrelin to male mice. Subsequently, we conducted microbiota composition analysis throughout the gut using 16S rRNA gene sequencing. Our results showed that these brain interventions significantly changed the gut microbiota in an anatomical and short-term (2-4 h) fashion. Transcriptomic analysis indicated that these changes were associated with the reconfiguration of neuronal and synaptic pathways in the duodenum concomitant with increased sympathetic tone. Interestingly, diet-induced obesity attenuated the brain-mediated changes triggered by leptin in gut microbiota communities and sympathetic activation. Our findings reveal a previously unanticipated brain-gut axis that acutely attunes microbiota composition on fast timescales, with potential implications for meal-to-meal adjustments and systemic energy balance control.

Hypothalamic PNOC/NPY neurons constitute mediators of leptin-controlled energy homeostasis

Leptin acts in the brain to suppress appetite, yet the responsible neurocircuitries underlying leptin's anorectic effect are incompletely defined. Prepronociceptin (PNOC)-expressing neurons mediate diet-induced hyperphagia and weight gain in mice. Here, we show that leptin regulates appetite and body weight via PNOC neurons, and that loss of leptin receptor (Lepr) expression in PNOC-expressing neurons in the arcuate nucleus of the hypothalamus (ARC) causes hyperphagia and obesity. Restoring Lepr expression in PNOC neurons on a Lepr-null obese background substantially reduces body weight. Lepr inactivation in PNOC neurons increases neuropeptide Y (Npy) expression in a subset of hypothalamic PNOC neurons that do not express agouti-related peptide (Agrp). Selective chemogenetic activation of PNOC/NPY neurons promotes feeding to the same extent as activating all PNOCARC neurons, and overexpression of Npy in PNOCARC neurons promotes hyperphagia and obesity. Thus, we introduce PNOC/NPYARC neurons as an additional critical mediator of leptin action and as a promising target for obesity therapeutics.

Potential downsides of calorie restriction

Although the potential benefits of calorie restriction on human lifespan remain uncertain, it is currently one of the most extensively researched non-genetic approaches to extending both lifespan and healthspan in animals. Calorie restriction offers numerous health benefits, including a reduced incidence of age-related diseases. However, calorie restriction also produces a range of negative effects, which are not fully documented and require further investigation, particularly in humans. As the viability of calorie restriction in humans will depend on the balance of benefits and detrimental effects, it is crucial to understand the nature of these negative effects and what drives them. In this Review, we summarize the effects of calorie restriction on wound healing, hunger, cold sensitivity, bone health, brain size, cognition, reproductive performance and infection, primarily based on studies of rodents with some data from other species and from humans. Overall, the detrimental effects of calorie restriction seem to stem directly from prioritization of vital functions and downregulation or suppression of energy-demanding processes, which helps preserve survival but can also lead to impaired physiological performance and increased vulnerability to stressors. The exact mechanisms underlying these effects remain unclear. Whether it might be possible to engage in calorie restriction but avoid these negative effects remains uncertain.

Vagal Splenic-Dependent Effects Influence Glucose Homeostasis, Insulin Secretion, and Histopathology of the Endocrine Pancreas in Hypothalamic Obese Male Rats: Vagus Nerve and Spleen Interactions Affect the Endocrine Pancreas

Vagus nerve (VN) and spleen dysfunctions are often associated with obesity (Ob). Aim: We evaluated the effects of VN and spleen ablation on adiposity, metabolism, and insulin secretion in hypothalamic obese male rats. Methods: Ob was induced by neonatal subcutaneous injection of monosodium glutamate (4 g/kg). At 60 days of life, Ob animals were randomly distributed into four groups (n = 16 rats/group): sham operation (SHAM), vagotomy (VAG), splenectomy (SPL), and VAG + SPL. Body weight and food intake were monitored for 8 weeks postsurgery. Intraperitoneal glucose tolerance test (ipGTT) and intraperitoneal pyruvate tolerance test (ipPTT) were performed at 148 days of life, and VN activity was recorded at 150 days. After euthanasia (150 days), adiposity, plasma biochemical parameters, glucose-induced insulin secretion (GIIS), and cholinergic and adrenergic islet responsiveness were evaluated. The pancreas was submitted for histopathological analysis, and the protein content of OXPHOS and IL-10 was evaluated in isolated pancreatic islets. Results: Decreased VN activity was confirmed in the Ob-VAG groups, associated with lower visceral adiposity, triglycerides, and plasma insulin, together with improved insulin sensibility and pyruvate tolerance, compared to Ob-SHAM rats. Spleen absence reduced VN activity and cholinergic insulinotropic responses, with deleterious effects on the endocrine pancreas. Furthermore, Ob-VAG + SPL rats presented greater reductions in GIIS and more severe endocrine pancreas histopathology, compared to the Ob-SHAM group, without altered islet size or number or protein content of OXPHOS or IL-10. Conclusion: Vagal and splenic interactions contribute to glucose homeostasis control in hypothalamic obese rats, modulating insulin secretion and pancreas histology.

Hypothalamic control of heart rate and body temperature by thyroid hormones

As evidenced by the clinical symptoms in hyper- or hypothyroidism, thyroid hormones have strong effects on cardiovascular and metabolic functions. While these actions had been initially attributed to direct molecular mechanisms in the respective peripheral tissues such as heart, muscle or adipose tissue, a recent paradigm shift has occurred with accumulating observations that demonstrated important indirect effects via the brain on these systems. However, the individual contributions of the peripheral versus central thyroid hormone actions for the well-known phenotypical symptoms are still not entirely understood. Similarly, the neuroanatomical substrates for these central actions have remained largely enigmatic, although many studies point to the hypothalamus as a major target of thyroid hormone action. This review critically discusses the role of the central actions of thyroid hormone for the regulation of heart rate, body temperature, energy expenditure and food intake, and integrates some novel findings to summarize the current state of the field.

Preventing and correcting polycystic ovary syndrome by targeting anti-Müllerian hormone signaling in minipuberty and adulthood in mice

Polycystic ovary syndrome (PCOS), the most common endocrinopathy in women, causes significant reproductive and metabolic comorbidities, with no current cure. Gestational androgen and anti-Müllerian hormone (AMH) excess are linked to PCOS, and prenatal aberrant exposure to these hormones induces PCOS-like traits in animal models. However, whether the AMH effects on PCOS programming could extend to early postnatal life remains unknown. Clinical observations showed higher AMH levels during minipuberty in infants of mothers with PCOS, but whether this contributes to PCOS development is uncertain. Here, we show that exposure to high AMH levels during minipuberty in mice causes PCOS-like reproductive and metabolic defects in both sexes. A neutralizing antibody targeting AMH receptor 2 (AMHR2) prevented these defects when administered during minipuberty and alleviated symptoms when given in adulthood. These findings highlight the causal role of elevated AMH in PCOS and suggest AMHR2-targeting therapy as a potential preventive or curative approach.

Childhood obesity: The threatening apprentice of the adiposity empire

Childhood obesity is a global health problem, with its prevalence having tripled since 1975. The increase in its prevalence has been predominantly in developing countries, but also in those with high economic status. Nowadays, there are multiple obesity definitions, however, one of the most accurate is the one which defines obesity as the accumulation of excessive body adiposity and not as an body weight excess. Nevertheless, the body mass index (BMI) is the most frequently used tool for its classification, according to the cut-off points established by the Center for Disease Control and World Health Organization tables. In children and adolescents an adiposity excess is related to the appearance of cardiovascular disease in adulthood and with many comorbidities such as metabolic syndrome, insulin resistance, type 2 diabetes, hypertension and metabolic dysfunction-associated steatotic liver disease, among others. Currently, there is still controversy about which is the ideal indicator for measuring overweight and obesity. BMI is still used as a standardized measure but may miss cases in which body composition is pathological despite a BMI within the normal-weight category. An adequate knowledge of the impact on health of dysfunctional adiposity as well as its accurate diagnosis will allow health professionals to address this condition in a more precise and comprehensive manner, and substantially improve the associated cardiometabolic risk and prognosis.

Brain sensing of metabolic state regulates circulating monocytes

Changes in energy availability alter the dynamics of circulating immune cells. The existing view is that these effects are due to altered nutrient levels affecting peripheral tissue metabolism. Here, using mice and genetic approaches to manipulate the activity of distinct molecularly defined neurons, we show that the brain's perception of hunger and satiety alone is sufficient to drive these immune changes. Hunger-promoting Agouti-related peptide (AgRP) neurons in the hypothalamus were both sufficient and necessary to reduce circulating Ly6CHi classical monocytes during fasting. Mechanistically, these neurons suppressed hepatic mammalian target of rapamycin signaling via sympathetic regulation, decreasing circulating chemokine ligand 2 and monocyte numbers. AgRP neuron-induced corticosterone release and glucocorticoid receptor activation played a permissive role in this process. These changes in monocyte dynamics can occur independently of actual nutrient levels, revealing an unexpected brain-mediated control of peripheral immunity in response to perceived variation in energy state.

Integrating the COM-B model into behavioral neuroscience: A framework for understanding animal behavior

In light of the intricate nature of animal behavior regulation, a theoretical model is proposed, grounded in the COM-B (Capability, Opportunity, Motivation - Behavior) framework, which has gained considerable traction in the domain of human behavioral intervention. When extending the COM-B model to behavioral neuroscience, we first discuss the utility of the model in animal research, particularly its capacity to integrate environmental and social factors, and enhance cross-species comparisons, including animal-to-human translations and evolutionary considerations. The subsequent discussion then summarizes the advantages of utilizing the COM-B model in neuroscience are summarized, including the facilitation of a systems-level understanding of behavior and the establishment of a link between neural mechanisms and specific behavioral components. The experimental design for the application of the COM-B model in neuroscience is proposed to elucidate the brain regulatory processes that govern behavior. Finally, three specific examples are provided to illustrate the theoretical considerations, namely feeding and social behavior, and the role of neuromodulators in the control of behavior.

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.

Neuronal Regulation of Feeding and Energy Metabolism: A Focus on the Hypothalamus and Brainstem

In the face of constantly changing environments, the central nervous system (CNS) rapidly and accurately calculates the body's needs, regulates feeding behavior, and maintains energy homeostasis. The arcuate nucleus of the hypothalamus (ARC) plays a key role in this process, serving as a critical brain region for detecting nutrition-related hormones and regulating appetite and energy homeostasis. Agouti-related protein (AgRP)/neuropeptide Y (NPY) neurons in the ARC are core elements that interact with other brain regions through a complex appetite-regulating network to comprehensively control energy homeostasis. In this review, we explore the discovery and research progress of AgRP neurons in regulating feeding and energy metabolism. In addition, recent advances in terms of feeding behavior and energy homeostasis, along with the redundant neural mechanisms involved in energy metabolism, are discussed. Finally, the challenges and opportunities in the field of neural regulation of feeding and energy metabolism are briefly discussed.

Connecting the dots: Understanding and addressing the metabolic impact of antipsychotic and antidepressant medications

Serious mental disorders such as schizophrenia and major depression are associated with considerable morbidity and mortality, resulting in much shorter life expectancies in those affected. The discovery of antipsychotic medications ushered in improved health outcomes for people with serious mental disorders but also brought about increased morbidity due to their metabolic side effects, including obesity and diabetes mellitus. Antidepressant medications have a more favorable metabolic side effect profile, but some can still cause weight gain and hyperglycemia. In this narrative review, we discuss antipsychotic and antidepressant medications' mechanisms of action, their respective effectiveness in treating psychosis and depression, and their metabolic side effects. In addition, we present therapeutic strategies for minimizing cardiometabolic health risks in patients treated with these medications by applying a comprehensive, biopsychosocial approach.

A Complex Network of Obesity-Risk Genes Revealed by Systematic Bioinformatics and Single-Cell Transcriptomic Analyses

The development of obesity is closely linked to genetic factors. Despite the identification of numerous genes associated with an increased risk of obesity in humans, a comprehensive understanding of their biological roles has not been achieved. In our extensive bioinformatics study, we identified 802 core genes implicated in obesity. Our protein-protein interaction (PPI) network analysis revealed that these genes form a tightly connected functional network primarily involved in neurological and metabolic regulatory processes. Moreover, our in-depth analysis of single-cell transcriptomic datasets from the human hypothalamus, pancreatic islets, adipose tissue, and liver has shed light on the distinct expression profiles of these obesity-linked genes across various tissue and cell types. This analysis also highlighted the biological processes they influence and the upstream transcriptional regulatory networks involved. Our study not only uncovers the complicated regulatory role of genetic factors in the pathogenesis and progression of obesity but also establishes a close link between the expression patterns and functional roles of these obesity-associated genes. This study provides crucial insights for advancing our understanding of the genetic mechanisms underlying obesity.

Bromocriptine improves glucose tolerance in obese mice via central dopamine D2 receptor-independent mechanism

Bromocriptine, generally regarded as a dopamine D2 receptor agonist, has been used to treat patients with type 2 diabetes in the USA; however, its mechanisms of action including the receptors that mediate its anti-diabetic effects remain unclear. Therefore, we herein conducted pharmacological and genetic knockout experiments to investigate how bromocriptine improves glucose metabolism under type 2 diabetic conditions. Bromocriptine transiently increased blood glucose levels in both wild-type and dopamine D2 receptor-deficient mice. This glucose-elevating effect was blocked by the α2-adrenergic receptor antagonist yohimbine. On the other hand, when bromocriptine was administered daily for two weeks, glucose tolerance improved in wild-type mice fed a high-fat diet. Similar anti-diabetic effects of bromocriptine were observed in dopamine D2 receptor-deficient, dopamine D1 receptor-deficient, and orexin-deficient mice under the diet-induced obese condition as well as in genetically obese db/db mice. Bromocriptine-induced improvements in glucose tolerance were not affected by a pretreatment with the autonomic ganglion blocker hexamethonium, which suggested the involvement of the peripheral effects of bromocriptine. Given the biphasic properties of bromocriptine, we examined the drug effect on hepatic endoplasmic reticulum (ER) stress that dually regulates glucose metabolism. In the livers of diet-induced obese mice, the levels of ER stress markers, including C/EBP homologous protein (CHOP), were reduced by the daily administration of bromocriptine. In human hepatoma HepG2 cells, increases in CHOP expression by thapsigargin, a potent inducer of ER stress, were prevented by a pretreatment with low concentrations of bromocriptine, whereas high concentrations induced CHOP expression. These results suggest that low concentrations of bromocriptine caused beneficial ER stress preconditioning, which protected against subsequent severe ER stress in the liver. Therefore, bromocriptine may prevent obesity-induced glucose intolerance via peripheral mechanisms including promotion of hepatic ER homeostasis, but not central dopamine D2 receptor-mediated mechanisms.

Neural and hormonal mechanisms of appetite regulation during eating

Numerous animal and clinical studies have demonstrated that the arcuate nucleus of the hypothalamus, a central regulator of appetite, plays a significant role in modulating feeding behavior. However, current research primarily focuses on long-term dietary changes and their effects on the body, with limited investigation into neuroendocrine dynamics during individual meals across diverse populations. In contrast to long-term dietary adjustments, directives for dietary behavior during a specific meal are more actionable, potentially enhancing patient adherence and achieving better outcomes in dietary behavior interventions. This review aimed to explore the neural pathways and endocrine changes activated by gastrointestinal expansion and variations in blood nutrient levels during a single meal, with the goal of informing dietary behavior guidance.

Dynamic profiling of Cell-free DNA fragmentation uncovers postprandial metabolic and immune alterations

BACKGROUND

Food intake affects body homeostasis and significantly changes circulating cell-free DNA (cfDNA). However, the source and elimination of postprandial cfDNA is difficult to trace, and it is unknown whether these changes can be revealed by cfDNA fragmentomics based on liquid biopsy.

METHODS

We performed shallow whole-genome sequencing of 30 plasma samples from 10 healthy individuals at fasting and postprandial (30-min and 2-h time points). We assessed the effect of postprandial states on cfDNA fragment size distribution and utilized deconvolutional analysis of end motifs to determine the potential roles of DNA nucleases in cfDNA fragmentation. We correlated the fragmentation index (defined as the ratio of short-to-long fragments) with gene expression to estimate the relative contribution of various cellular and tissue sources to cfDNA.

RESULTS

Compared to the fasting state, we observed a significant increase in short cfDNA fragments (70-150 bp) and a decrease in long fragments (151-250 bp) at the 30-minute postprandial state, followed by an inverse trend two hours later. Deconvolutional analysis of cfDNA end motifs showed that DNASE1L3 activity decreased at the 30-minute postprandial state, while DNASE1 and DFFB activities increased at the 2-hour postprandial state. We found that the expression of genes related to cellular metabolism and immune responses was upregulated at the postprandial state. Meanwhile, the contribution of cells and tissues involved in metabolic and immune progress to circulating plasma cfDNA was increased.

CONCLUSIONS

The fragmentation of cfDNA is considerably influenced by postprandial states, highlighting the significance of taking postprandial effects into account when evaluating cfDNA as a biomarker. Furthermore, our study reveals the potential application of cfDNA fragmentation features in monitoring metabolic and immune status changes.

Function of Amino Acids and Neuropeptides in Feeding Behavior in Chicks

Regulation of food intake, especially during the neonatal period, is important to ensure optimal nutrition and meet the metabolic requirements of growing and healthy animals. However, many problems associated with neonatal chicks remain unsolved. Feeding behavior during the neonatal stage is characterized by short resting periods between very brief times spent taking up food. Accordingly, neuropeptides, which take time to synthesize and release, as well as nutrients that are taken up via feeding, may be involved in feeding regulation. The present review summarizes current knowledge about the role of amino acids and their interaction with neuropeptides on the regulation of food intake in neonatal chicks with special emphasis on L-arginine metabolism and neuropeptide Y. Fasting and subsequent short-term refeeding influence amino acid metabolism in the brain. Short-term refeeding induces a rapid increase in the concentrations of several amino acids, which may contribute to satiety signals in the neonatal chick brain. The function of L-arginine is related to its metabolite, L-ornithine, which acts as an innate satiety signal in the control of food intake. Co-injection with L-ornithine attenuates the orexigenic effect of neuropeptide Y in a dose-dependent manner. This implies a potent interaction in the brain between the regulation of food intake by neuropeptide Y and acute satiety signals by L-ornithine. The roles of other amino acids in feeding and their relationship with the stress response are also discussed in this review. In conclusion, endogenous neuropeptides and endogenous and/or exogenous nutrients such as amino acids are believed to coordinate the feeding behavior of neonatal chicks.

Integrated transcriptomic hypothalamic-pituitary-ovarian axis network analysis reveals the role of energy availability on egg production in layers

Energy is a crucial component for maintaining egg production in layers. The hypothalamic-pituitary-ovarian (HPO) axis is an energy-sensitive functional axis for follicle development, synthesis, and secretion of reproductive hormones, and plays a key role in modulating sustained ovulation in layers. To investigate the mechanism of integrated network regulation of the HPO axis under energy fluctuation, ninety Hy-line brown layers (265-day-old, 1.92 ± 0.02 kg) were randomly divided into three groups for a 17-day experiment: a control group (Con group) fed ad libitum from days 1 to 17, an energy-deprived group (ED group) that was fed ad libitum from days 1 to 12 and then underwent a fasting period from days 13 to 17 to induce a pause in laying, and a re-fed group (Rf group) that fasted for seven days (specifically, days 1 to 5, day 7, and day 9), had ad libitum access to feed on days 6 and 8, and was continuously fed from days 10 to 17. Each treatment consisted of 10 replicates with 3 birds per replicate. The study found that energy deprivation significantly decreased reproductive performance such as egg laying rate, ovarian index, number of small yellow follicles (SYF), and normal hierarchical follicles (NHIE) (P < 0.05), which recovered after refeeding, indicating the importance of energy availability for sustained ovulation in layers. In addition, estradiol (E2), estradiol to progesterone (E2/P4) ratio, and luteinizing hormone (LH) displayed changes similar to follicle number, whereas follicle-stimulating hormone (FSH) exhibited a contrasting pattern. Transcriptome analysis revealed that energy deprivation downregulated genes related to energy and appetite-regulated neurotransmitter receptors and neuropeptides in the hypothalamus. These signals combined to inhibit gonadotropin-releasing hormone (GnRH) secretion and subsequently downregulated the crucial genes responsible for synthesizing gonadotropins, gonadotropin-releasing hormone receptor (GnRHR), and glycoprotein hormones alpha chain (CGA). Consequently, this suppression of the hypothalamus and pituitary affected ovarian function through ovarian steroidogenesis and the extracellular matrix (ECM)-receptor interaction. These findings suggest that energy deprivation inhibits the function of the HPO axis, leading to impaired follicle development and reduced egg production, and that refeeding can partially restore these indicators.

Investigating the common genetic architecture and causality of metabolic disorders with neurodegenerative diseases

BACKGROUND

The co-occurrence of metabolic dysfunction and neurodegenerative diseases suggests a genetic link, yet the shared genetic architecture and causality remain unclear. We aimed to comprehensively characterise these genetic relationships.

METHODS

We investigated genetic correlations among four neurodegenerative diseases and seven metabolic dysfunctions, followed by bidirectional Mendelian randomisation (MR) to assess potential causal relationships. Pleiotropy analysis (PLACO) was used to detect the pleiotropic effects of genetic variants. Significant pleiotropic loci were refined and annotated using functional mapping and annotation (FUMA) and Bayesian colocalisation analysis. We further explored mapped genes with tissue-specific expression and gene set enrichment analyses.

RESULTS

We identified significant genetic correlations in nine out of 28 trait pairs. MR suggested causal relationships between specific trait pairs. Pleiotropy analysis revealed 25 931 significant single-nucleotide polymorphisms, with 246 pleiotropic loci identified via FUMA and 55 causal loci through Bayesian colocalisation. These loci are involved in neurotransmitter transport and immune response mechanisms, notably the missense variant rs41286192 in SLC18B1. The tissue-specific analysis highlighted the pancreas, left ventricle, amygdala, and liver as critical organs in disease progression. Drug target analysis linked 74 unique genes to existing therapeutic agents, while gene set enrichment identified 189 pathways related to lipid metabolism, cell differentiation and immune responses.

CONCLUSION

Our findings reveal a shared genetic basis, pleiotropic loci, and potential causal relationships between metabolic dysfunction and neurodegenerative diseases. These insights highlight the biological connections underlying their phenotypic association and offer implications for future research to reduce the risk of neurodegenerative diseases.

The promise of glucagon-like peptide 1 receptor agonists (GLP-1RA) for the treatment of obesity: a look at phase 2 and 3 pipelines

INTRODUCTION

GLP-1-based therapies have changed the treatment of overweight/obesity. Liraglutide 3.0 mg daily, the first GLP-1 RA approved for treatment of overweight, induced a weight loss of 6-8%, Semaglutide 2.4 mg once weekly improved weight loss to about 12-15%, while the dual GIP/GLP-1 receptor agonist tirzepatide once weekly has induced a weight loss of about 20% in obese people without diabetes.

AREAS COVERED

This review describes results obtained with GLP-1 mono-agonists, GLP-1/GIP dual agonists, GLP-1/glucagon co-agonists, and the triple agonist retatrutide (GIP/GLP-1/glucagon), which have shown beneficial effect both on body weight and steatotic liver disease. A combination of semaglutide (a GLP-1 agonist) and cagrilintide (a long-acting amylin analogue) for weekly administration is currently in phase III development, and so is oral semaglutide and several non-peptide small molecule GLP-1 agonists for oral administration. The adverse events with the GLP-1-based therapies are primarily gastrointestinal and include nausea, vomiting, obstipation, or diarrhea, which often can be mitigated by slow up titration.

EXPERT OPINION

The GLP-1-based therapies will change the treatment of obesity and its comorbidities including steatotic liver disease in the future. Outstanding question is maintenance of the weight loss, possibly pharmacological treatment needs to be life-long.

AgRP neurons shape the sperm small RNA payload

Paternal dietary patterns and obesity can affect offspring through epigenetic signals in sperm RNA. By activating hypothalamic Agouti-related peptide (AgRP) neurons in mice to simulate obesity's effects, we observed changes in the small noncoding RNA payload of sperm. These alterations, particularly in transfer RNA-derived small RNAs (tsRNAs), are similar to those induced by short-term high-fat diets, suggesting a common upstream regulatory mechanism involving AgRP neurons that affects metabolic epigenetic inheritance.

Polyzwitterion-branched polycholic acid nanocarriers based oral delivery insulin for long-term glucose and metabolic regulation in diabetes mellitus

Diabetes represents a global health crisis that necessitates advancements in prevention, treatment, and management. Beyond glucose regulation, addressing weight management and associated complications is imperative. This study introduces an oral nanoparticle formulation designed to simultaneously control blood glucose, obesity, and metabolic dysfunction. These nanoparticles, based on poly (zwitterion-cholic acid), incorporate a polyzwitterion component to enhance permeation through the mucus layer and prolong drug residence. Furthermore, bile acid polymers not only regulate lipid metabolism but also ameliorate obesity-associated inflammation in adipose and liver tissues. In vivo experiments demonstrated significant hypoglycemic effects in healthy, type I diabetic, and type II diabetic mice. Notably, the nanocarriers significantly reduced body weight gain, ameliorated inflammation in adipose and liver tissues, and modulated lipid metabolism in the liver of db/db mice. Our study elucidates a comprehensive strategy for addressing glycemic control and diabetes-related complications, offering a promising approach for diabetes prevention and treatment.

GPCRs in hypothalamic neurons and their roles in controlling food intake and metabolism

G-protein coupled receptor (GPCR) subtypes within the hypothalamus play a pivotal role in maintaining body homeostasis, particularly in the regulation of food intake and energy metabolism. This review provides an overview of classical loss and gain-of-function studies on GPCRs related to feeding and metabolism, with a focus on emerging cell-type-specific investigations. These studies reveal that diverse GPCR-expressing neuronal populations are intricately linked to feeding and energy balance. We also discuss recent findings that highlight the interaction of distinct peptide-GPCR systems in modulating complex feeding behaviors.

Neurobiological mechanisms of nicotine's effects on feeding and body weight

Nicotine, a neuroactive substance in tobacco products, has been widely studied for its effects on feeding and body weight, mostly focusing on the involvement of nervous system, metabolism, hormones, and gut microbiota. To elucidate the action mechanism of nicotine on feeding and body weight, especially the underlying neurobiological mechanisms, we reviewed the studies on nicotine's effects on feeding and body weight by the regulation of various nerve systems, energy expenditure, peripheral hormones, gut microbiota, etc. The role of neuronal signaling molecules such as AMP-activated protein kinase (AMPK) and kappa opioid receptor (κOR) were specialized in the nicotine-regulating energy expenditure. The energy homeostasis-related neurons, pro-opiomelanocortin (POMC), agouti-related peptide (AgRP), prolactin-releasing hormone (Prlh), etc, were discussed about the responsibility for nicotine's effects on feeding. Nicotine's actions on hypothalamus and its related neural circuits were described in view of peripheral nervous system, reward system, adipose browning, hormone secretion, and gut-brain axis. Elucidation of neurobiological mechanism of nicotine's actions on feeding and body weight will be of immense value to the therapeutic strategies of smoking, and advance the medicine research for the therapy of obesity.

Neuroimmune axis: Linking environmental factors to pancreatic β-cell dysfunction in Diabetes

Pancreatic β-cells are specialized in secreting insulin in response to circulating nutrients, mainly glucose. Diabetes is one of the most prevalent endocrine-metabolic diseases characterized by an imbalance in glucose homeostasis, which result mainly from lack of insulin production (type 1 diabetes) or insufficient insulin and peripheral insulin resistance (type 2 diabetes), both influenced by genetic and environmental components. Pancreatic β-cell dysfunction and islet inflammation are common characteristics of both types of the disease. Pancreatic islets are a highly innervated tissue whose function can be influenced by the brain, either directly through the autonomic nervous system or indirectly via neuroendocrine mechanisms. In addition, it is well-established that there is a fine-tuned communication between the immune and neuroendocrine tissues in maintaining endocrine pancreas homeostasis. Various psycho-social, physico-chemical and lifestyle environmental factors have been associated with diabetes risk. In this review, I briefly comment on certain aspects of the psycho-neuro-immune interactions that link environmental factors and the endocrine pancreas, leading to metabolic health or diabetes. Interdisciplinary research, embracing new and broader perspectives, should be conducted to explore strategies for preventing or slowing down the constant increase in diabetes worldwide.

Preliminary exploration of the C-3 galloyl group and the B-5' hydroxyl group enhance the biological activity of catechins in alleviating obesity induced by high-fat diet in mice

Catechins, among the most active components in tea, effectively alleviate obesity. Catechins are primarily classified into four types based on the presence or absence of the C-3 galloyl group and the B-5' hydroxyl group. However, the impact of conformation on the anti-obesity properties of catechins remains unclear. Findings indicate that the C-3 galloyl group and the B-5' hydroxyl group significantly enhance the biological activity of catechins, aiding in obesity alleviation, regulating glycolipid metabolism, reducing hepatic steatosis, lowering serum lipopolysaccharide (LPS) levels, and promoting the proliferation of Akkermansia muciniphila. Further investigation revealed that Akkermansia muciniphila may modulate LPS/insulin resistance to protect glycolipid metabolic homeostasis, attenuate liver tissue damage, and promote catechin metabolism to generate new bioactive components. Overall, the C-3 galloyl group and the B-5' hydroxyl group may modulate the gut-liver axis through the bidirectional interplay between catechins and Akkermansia muciniphila, thereby enhancing the anti-obesity activity of catechins.

Neural mechanisms and health implications of food cravings during pregnancy

Food cravings, an intense desire to consume specific foods, are a complex interplay of cognitive, emotional, behavioral, physiological, and cultural factors. Although prevalent across genders, food cravings are more frequent and intense in women, with hormonal fluctuations-particularly during the menstrual cycle and pregnancy-playing a significant role. Pregnancy, marked by profound hormonal and physiological shifts, often heightens cravings, likely as a response to the increased metabolic needs of both mother and fetus. However, the tendency to crave high-calorie, palatable foods during this time can lead to excessive weight gain, presenting potential risks to both maternal and fetal health. This chapter examines the neural mechanisms underlying altered eating behaviors during pregnancy and their role in triggering food cravings. We discuss the health implications of disrupted eating patterns in pregnancy, emphasizing the need for further research to advance understanding of female-specific neurobiology and to develop targeted interventions that support healthy eating behaviors, ultimately improving maternal and offspring health outcomes.

Binding Kinetics, Bias, Receptor Internalization and Effects on Insulin Secretion in vitro and in vivo of a Novel GLP-1R/GIPR Dual Agonist, HISHS-2001

The use of incretin analogues has emerged in recent years as an effective approach to achieve both enhanced insulin secretion and weight loss in type 2 diabetes (T2D) patients. Agonists which bind and stimulate multiple receptors have shown particular promise. However, off target effects, including nausea and diarrhoea, remain a complication of using these agents, and modified versions with optimized pharmacological profiles and/or biased signaling at the cognate receptors are increasingly sought. Here, we describe the synthesis and properties of a molecule which binds to both glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptors (GLP-1R and GIPR) to enhance insulin secretion. HISHS-2001 shows increased affinity at the GLP-1R, as well as a tendency towards reduced internalization and recycling at this receptor versus FDA-approved dual GLP-1R/GIPR agonist tirzepatide. HISHS-2001 also displayed significantly greater bias towards cAMP generation versus β-arrestin 2 recruitment compared to tirzepatide. In contrast, Gαs recruitment was lower versus tirzepatide at the GLP-1R, but higher at the GIPR. Administered to obese hyperglycaemic db/db mice, HISHS-2001 increased circulating insulin whilst lowering body weight and HbA1c with similar efficacy to tirzepatide at substantially lower doses. Thus, HISHS-2001 represents a novel dual receptor agonist with an improved pharmacological profile.

Thalamic opioids from POMC satiety neurons switch on sugar appetite

High sugar-containing foods are readily consumed, even after meals and beyond fullness sensation (e.g., as desserts). Although reward-driven processing of palatable foods can promote overeating, the neurobiological mechanisms that underlie the selective appetite for sugar in states of satiety remain unclear. Hypothalamic pro-opiomelanocortin (POMC) neurons are principal regulators of satiety because they decrease food intake through excitatory melanocortin neuropeptides. We discovered that POMC neurons not only promote satiety in fed conditions but concomitantly switch on sugar appetite, which drives overconsumption. POMC neuron projections to the paraventricular thalamus selectively inhibited postsynaptic neurons through mu-opioid receptor signaling. This opioid circuit was strongly activated during sugar consumption, which was most notable in satiety states. Correspondingly, inhibiting its activity diminished high-sugar diet intake in sated mice.

Immuno-metabolic depression: from concept to implementation

Major depressive disorder is a common, disabling mental disorder characterized by extensive etiological and phenotypic heterogeneity. This heterogeneity makes treatment approaches imprecise and often ineffective. Insight into the underlying biological mechanisms underpinning depression and its subtypes may enable more personalized treatments. In this review, we provide an overview of immuno-metabolic depression and illustrate that significant immuno-metabolic dysregulations are present in about 20-30% of people with depression. Such immuno-metabolic depression is characterized by the clustering of 1) atypical, energy-related depressive symptoms such as hypersomnia, fatigue, hyperphagia, and possibly anhedonia, 2) systemic low-grade inflammation with elevated levels of e.g., C-reactive protein, cytokines and glycoprotein acetyls, and 3) metabolic abnormalities involving e.g., obesity, dyslipidaemia, insulin and leptin resistance. Persons with immuno-metabolic depression are at a higher risk for cardiometabolic diseases and seem to respond less well to standard antidepressant treatment. Interventions targeting inflammation, metabolism or lifestyle may be more effective treatment options for individuals with immuno-metabolic depression, in line with principles of precision psychiatry.

TGR5 receptors in SF1-expressing neurons of the ventromedial hypothalamus regulate glucose homeostasis

OBJECTIVE

Steroidogenic factor-1 (SF1) neurons of the ventromedial hypothalamus play key roles in the regulation of food intake, body weight and glucose metabolism. The bile acid receptor Takeda G protein-coupled receptor 5 (TGR5) is expressed in the hypothalamus, where it determines some of the actions of bile acids on food intake and body weight through still poorly defined neuronal mechanisms. Here, we examined the role of TGR5 in SF1 neurons in the regulation of energy balance and glucose metabolism.

METHODS

We used a genetic approach combined with metabolic phenotyping and molecular analyses to establish the effect of TGR5 deletion in SF1 neurons on meal pattern, body weight, body composition, energy expenditure and use of energy substrates as well as on possible changes in glucose handling and insulin sensitivity.

RESULTS

Our findings reveal that TGR5 in SF1 neurons does not play a major role in the regulation of food intake or body weight under standard chow, but it is involved in the adaptive feeding response to the acute exposure to cold or to a hypercaloric, high-fat diet, without changes in energy expenditure. Notably, TGR5 in SF1 neurons hinder glucose metabolism, since deletion of the receptor improves whole-body glucose uptake through heightened insulin signaling in the hypothalamus and in the brown adipose tissue.

CONCLUSIONS

TGR5 in SF1 neurons favours satiety by differently modifying the meal pattern in response to specific metabolic cues. These studies also reveal a novel key function for TGR5 in SF1 neurons in the regulation of whole-body insulin sensitivity, providing new insight into the role played by neuronal TGR5 in the regulation of metabolism.

Hypothalamic obesity: from basic mechanisms to clinical perspectives

Despite the diverse nature of obesity, there is compelling genetic, clinical, and experimental evidence that endorses the important contribution of brain circuits to this condition. The hypothalamus contains major regulatory circuits for bodyweight homoeostasis, the deregulation of which can lead to obesity. Although functional perturbation of hypothalamic pathways could lie at the basis of common forms of obesity, the term hypothalamic obesity has been created to define those rare forms of severe obesity where a clear hypothalamic substrate can be identified, either of genetic or acquired origin. An in-depth understanding of the pathogenesis, clinical presentation, and therapeutic targets of hypothalamic obesity relies on the comprehension of the physiological basis of hypothalamic pathways governing bodyweight control, the mechanisms (either genetic or acquired) whereby they are perturbed, and the consequences of such perturbation. In this Review, we provide a synoptic overview of hypothalamic obesity, from basic mechanisms to clinical perspectives, with a major focus on current developments and new avenues for the diagnosis and precise treatment of these rare forms of obesity.

Ceramides in the central control of metabolism

Central ceramides regulate energy metabolism by impacting hypothalamic neurons. This allows ceramides to integrate endocrine signals - such as leptin, ghrelin, thyroid hormones, or estradiol - and to modulate the central control of puberty. In this forum article we discuss recent evidence suggesting that specific ceramide species and neuronal populations are involved in these effects.

Quantitative analysis of the caloric restriction versus isocaloric diets models based on macronutrients composition: impacts on body weight regulation, anthropometric, and bioimpedance parameters in women with obesity

Introduction

Obesity is a growing public health issue, especially among young adults, with long-term management strategies still under debate. This prospective study compares the effects of caloric restriction and isocaloric diets with different macronutrient distributions on body composition and anthropometric parameters in obese women during a 12-week weight loss program, aiming to identify the most effective dietary strategies for managing obesity-related health outcomes.

Methods

A certified clinical nutritionist assigned specific diets over a 12-week period to 150 participants, distributed as follows: hypocaloric diets-low-energy diet (LED, 31 subjects) and very low-energy diet (VLED, 13 subjects); isocaloric diets with macronutrient distribution-low-carbohydrate diet (LCD, 48 subjects), ketogenic diet (KD, 23 subjects), and high-protein diet (HPD, 24 subjects); and isocaloric diet without macronutrient distribution-time-restricted eating (TRE, 11 subjects). Participants were dynamically monitored using anthropometric parameters: body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR) and bioelectrical impedance analysis (BIA) using the TANITA Body Composition Analyzer BC-418 MA III (T5896, Tokyo, Japan) at three key intervals-baseline, 6 weeks, and 12 weeks. The following parameters were evaluated: body weight, basal metabolic rate (BMR), percentage of total body fat, trunk fat, muscle mass, fat-free mass, and hydration status.

Results

All diets led to weight loss, but differences emerged over time. The TRE model resulted in significantly less weight loss compared to LED at the final follow-up (6.30 kg, p < 0.001), similar to the VLED (4.69 kg, p < 0.001). Isocaloric diets with varied macronutrient distributions showed significant weight loss compared to LED (p < 0.001). The KD reduced waist circumference at both 6 and 12 weeks (-4.08 cm, p < 0.001), while significant differences in waist-to-hip ratio reduction were observed across diet groups at 12 weeks (p = 0.01). Post-hoc analysis revealed significant fat mass differences at 12 weeks, with HPD outperforming IF (p = 0.01) and VLED (p = 0.003). LCD reduced trunk fat at 6 weeks (-2.36%, p = 0.001) and 12 weeks (-3.79%, p < 0.001). HPD increased muscle mass at 12 weeks (2.95%, p = 0.001), while VLED decreased it (-2.02%, p = 0.031). TRE showed a smaller BMR reduction at 12 weeks compared to LED.

Conclusion

This study highlights the superior long-term benefits of isocaloric diets with macronutrients distribution over calorie-restrictive diets in optimizing weight, BMI, body composition, and central adiposity.

Sympathetic NPY ignites adipose tissue

The established view of hypothalamic neuropeptide Y (NPY) is its orexigenic and weight-promoting effect. A recent article published in Nature by Domingos and colleagues1 demonstrates that NPY produced by sympathetic neurons protects against obesity by promoting thermogenesis and energy expenditure.

Interplay between the brain and adipose tissue: a metabolic conversation

The central nervous system and adipose tissue interact through complex communication. This bidirectional signaling regulates metabolic functions. The hypothalamus, a key homeostatic brain region, integrates exteroceptive and interoceptive signals to control appetite, energy expenditure, glucose, and lipid metabolism. This regulation is partly achieved via the nervous modulation of white (WAT) and brown (BAT) adipose tissue. In this review, we highlight the roles of sympathetic and parasympathetic innervation in regulating WAT and BAT activities, such as lipolysis and thermogenesis. Adipose tissue, in turn, plays a dual role as an energy reservoir and an endocrine organ, secreting hormones that influence brain function and metabolic health. In addition, this review focuses on recently uncovered communication pathways, including extracellular vesicles and neuro-mesenchymal units, which add new layers of regulation and complexity to the brain-adipose tissue interaction. Finally, we also examine the consequences of disrupted communication between the brain and adipose tissue in metabolic disorders like obesity and type-2 diabetes, emphasizing the potential for new therapeutic strategies targeting these pathways to improve metabolic health.

Molecular connectomics reveals a glucagon-like peptide 1-sensitive neural circuit for satiety

Liraglutide and other glucagon-like peptide 1 receptor agonists (GLP-1RAs) are effective weight loss drugs, but how they suppress appetite remains unclear. One potential mechanism is by activating neurons that inhibit the hunger-promoting Agouti-related peptide (AgRP) neurons of the arcuate hypothalamus (Arc). To identify these afferents, we developed a method combining rabies-based connectomics with single-nucleus transcriptomics. Here, we identify at least 21 afferent subtypes of AgRP neurons in the mouse mediobasal and paraventricular hypothalamus, which are predicted by our method. Among these are thyrotropin-releasing hormone (TRH)+ Arc (TRHArc) neurons, inhibitory neurons that express the Glp1r gene and are activated by the GLP-1RA liraglutide. Activating TRHArc neurons inhibits AgRP neurons and feeding, probably in an AgRP neuron-dependent manner. Silencing TRHArc neurons causes overeating and weight gain and attenuates liraglutide's effect on body weight. Our results demonstrate a widely applicable method for molecular connectomics, comprehensively identify local inputs to AgRP neurons and reveal a circuit through which GLP-1RAs suppress appetite.

Rheumatic diseases and metabolism: where centre and periphery meet

Over the past few decades, the connection between metabolism and various inflammatory and rheumatic diseases has been an area of active investigation. Nonetheless, the precise mechanisms underlying these relationships remain a topic of ongoing debate, owing in part to conflicting data. This discrepancy can be attributed to the predominant focus on peripheral mechanisms in research into the metabolic consequences of rheumatic diseases. However, a wealth of evidence supports the notion that the central nervous system, specifically the hypothalamus, has an important influence on metabolic homeostasis. Notably, links have been established between crucial hypothalamic mechanisms responsible for regulating energy balance (including food intake, thermogenesis, and glucose and lipid metabolism), such as AMP-activated protein kinase, and the pathophysiology of rheumatoid arthritis. This Review aims to comprehensively examine the current understanding of central metabolic control in rheumatic diseases and explore potential therapeutic options that target this pathophysiological mechanism.

Konjac glucomannan Inhibits Appetite of Obese Mice by Suppressing Hypothalamic Inflammatory Response and Agrp/Npy Neuron Expression

Konjac glucomannan (KGM) is used for appetite management. However, KGM's regulation of appetite through hypothalamic neurons and gut microbiota, particularly in nonobese populations, is required to be investigated. This study investigated the differential effects of KGM on appetite and energy metabolism in obese and nonobese mice. In obese mice, KGM inhibited food intake, hypothalamic inflammation, and increased energy expenditure. Conversely, in nonobese mice, KGM maintained food intake and energy expenditure but increased hypothalamic inflammation. KGM downregulated hypothalamic Agrp, Npy, and Orx expression and upregulated Cart in obese mice, while it had no effect on orexigenic genes and downregulated Cart in nonobese mice. Additionally, KGM reshaped gut microbiota and increased Short-chain fatty acids (SCFAs) formation of obese mice, where Alistipes, Bifidobacterium, and Lactobacillus, as well as SCFAs, correlated with suppressed appetite. In nonobese mice, KGM has no significant effect on SCFAs but microbes such as Blautia, Alistipes, and Flavonifractor levels were negatively correlated with hypothalamic inflammation. KGM maintains appetite and was linked to liver-derived phosphatidylcholine, countering increased hypothalamic inflammation. The differential regulation of appetite by KGM between obese and nonobese mice is associated with hypothalamic inflammatory, neuronal, and KGM-induced personalized reshaping of gut microbiota. KGM may regulate energy intake and expenditure through the microbiota-gut-brain axis.

From Mammals to Insects: Exploring the Genetic and Neural Basis of Eating Behavior

Obesity and anorexia are life-threatening diseases that are still poorly understood at the genetic and neuronal levels. Patients suffering from these conditions experience disrupted regulation of food consumption, leading to extreme weight gain or loss and, in severe situations, death from metabolic dysfunction. Despite the development of various behavioral and pharmacological interventions, current treatments often yield limited and short-lived success. To address this, a deeper understanding of the genetic and neural mechanisms underlying food perception and appetite regulation is essential for identifying new drug targets and developing more effective treatment methods. This review summarizes the progress of past research in understanding the genetic and neural mechanisms controlling food consumption and appetite regulation, focusing on two key model organisms: the fruit fly Drosophila melanogaster and the mouse Mus musculus. These studies investigate how the brain senses energy and nutrient deficiency, how sensory signals trigger appetitive behaviors, and how food intake is regulated through interconnected neural circuits in the brain.