Central nervous system control of food intake

Obesogenic effects of six classes of emerging contaminants

There is growing concern about the concept that exposure to environmental chemicals may be contributing to the obesity epidemic. However, there is no consensus on the obesogenic effects of emerging contaminants from a toxicological and environmental perspective. The potential human exposure and experimental evidence for obesogenic effects of emerging contaminants need to be systematically discussed. The main objective of this review is to provide recommendations for further subsequent policy development following a critical analysis of the literature for humans and experimental animals exposed to emerging contaminants. This article reviews human exposure to emerging contaminants (with a focus on antimicrobials, preservatives, water and oil repellents, flame retardants, antibiotics and bisphenols) and the impact of emerging contaminants on obesity. These emerging contaminants have been widely detected in human biological samples. Epidemiological studies provide evidence linking exposure to emerging contaminants to the risks of obesity in humans. Studies based on animal models and adipose cells show the obesogenic effects of emerging contaminants and identify modes of action by which contaminants may induce changes in body fat accumulation and lipid metabolic homeostasis. Some knowledge gaps in this area and future directions for further investigation are discussed.

Postnatal undernutrition increases estradiol plasma levels and sexual receptivity and disrupts the kisspeptin-GnRH pathway in adult female rats

Undernutrition has increased worldwide in recent years and it is known that environmental factors to which individuals are exposed in early life can result in metabolic and reproductive changes that remain in adult life. In this context, the litter size expansion is a classic model used to induce undernutrition early in development. Thus, this study aimed to evaluate the effects of neonatal undernutrition induced by the litter size expansion on metabolic and reproductive parameters of female rats. At birth, litter size was adjusted to large (LL - 16 pups) and normal (NL - 10 pups) litters. After weaning, the feed was offered ad libitum and the animals were euthanized from postnatal day 90, when in proestrus. Neonatal undernutrition resulted in lower body weight from weaning to adulthood, although food intake remained higher in the LL group in this period. These animals exhibited a delayed onset of puberty, demonstrated by a late first estrus, increased values of circulating estradiol, luteinizing hormone, follicle-stimulating hormone, and number of antral follicles in the ovaries, associated with higher sexual receptivity, without differences in maternal behavior. The LL group also exhibited decreased messenger RNA (mRNA) expression of kisspeptin and gonadotropin-releasing hormone (GnRH) in the preoptic area, without changes in the mRNA expression of GnRH receptor in the pituitary. These results demonstrate that moderate undernutrition in the lactational period promotes metabolic changes associated with impairments in the kisspeptin-GnRH pathway, without compromising maternal behavior and peripheral reproductive functions such as estrous cyclicity, sexual receptivity, and fertility.

Activation of glutamatergic neurons in the organum vasculosum of the lamina terminalis induces thirst-driven sniffing

Sniffing is a specialized respiratory behavior that enables rodents to localize and track objects in their environment. The organum vasculosum of the lamina terminalis (OVLT) is critically involved in the regulation of thirst and water intake, yet its role in controlling thirst-driven exploratory sniffing behaviors remains unclear. This study demonstrates that hypertonic stimulation significantly increases sniffing and activates OVLT glutamatergic (OVLTGlut) neurons. Photostimulation of both OVLTGlut neurons and their axon terminals within the paraventricular nucleus of the hypothalamus (PVN) induces robust sniffing. Furthermore, ablation of PVN neurons projecting to the preBötzinger complex not only reduces the sniffing time induced by photostimulation of OVLTGlut neurons projecting to the PVN but also prolongs the drinking latency. These findings identify the OVLTGlut-PVN-preBötzinger complex circuit as a pivotal regulator of thirst-driven sniffing, providing insights into the neural mechanisms underlying thirst and exploratory behavior.

Sex-dependent effects of a high-fat diet on the hypothalamic response in mice

Sex differences in rodent models of diet-induced obesity are still poorly documented, particularly regarding how central mechanisms vary between sexes in response to an obesogenic diet. Here, we wanted to determine whether obese phenotype and hypothalamic response to a high-fat diet (HFD) differed between male and female C57Bl/6J mice. Mice were exposed to either a 60% HFD or a standard diet first for both a long- (14 weeks) and shorter-periods of time (3, 7, 14 and 28 days). Analysis of the expression profile of key neuronal, glial and inflammatory hypothalamic markers was performed using RT-qPCR. In addition, astrocytic and microglial morphology was examined in the arcuate nucleus. Monitoring of body weight and composition revealed that body weight and fat mass gain appeared earlier and was more pronounced in male mice. After 14 weeks of HFD exposure, normalized increase of body weight reached similar levels between male and female mice. Overall, both sexes under HFD displayed a decrease of orexigenic neuropeptides expression while an increase in Pomc gene expression was observed only in female mice. In addition, changes in the expression of hypothalamic inflammatory markers were relatively modest. We also reported that the glial cell markers expression and morphology were affected by HFD in a sex- and time dependent manner, suggesting a more pronounced glial cell activation in female mice. Taken together, these data show that male and female mice responded differently to HFD exposure, both on short- and long-term and suggest that a strong inflammatory hypothalamic profile is not systematically present in diet-induced obesity models. Nevertheless, in addition to these present data, the underlying mechanisms should be deciphered in further investigations.

Quantitative Analysis of Neuropeptide Y (NPY) and C-Terminal Glycine-Extended NPY by Mass Spectrometry and Their Localization in the Developing and Sexual Adult Mouse Brains

Neuropeptide Y (NPY), a central stimulator of food intake and an energy balance controlling hormone, was quantitatively analyzed in developing brains at birth using microflow liquid chromatography (LC) and triple-quadrupole tandem mass spectrometry (MS/MS). We detected and identified endogenous C-terminal glycine-extended NPY (NPY-Gly 1-37) first, an intermediate of NPY before amidation in the mouse brain using high-resolution Fourier-transform Orbitrap MS and MS/MS. NPY-Gly was present in the fetal brain (E16) at almost the same levels as NPY of 1.92 pmol/g-brain tissue. After birth, NPY in postnatal 2-day brains (P2) was elevated drastically at 11.02 pmol/g-brain (p < 0.05 vs E16) and remained at a high level for the first 10 postnatal days, an important period for the formation of the NPY neural circuit in the brain. Immunohistochemistry unexpectedly showed that the localizations of NPY and NPY-Gly in the hypothalamus were completely different: NPY was localized in the arcuate nucleus, whereas NPY-Gly was already located at pars tuberalis during brain development from a fetus to a neonate to a sexual adult.

Obesity and Atherosclerotic Cardiovascular Disease: A Review of Social and Biobehavioral Pathways

In the United States, two out of every five adults have obesity. The obesity epidemic is a significant public health concern and a major risk factor for atherosclerotic cardiovascular disease (ASCVD), contributing to its development through a complex interplay of social, biologic and behavioral mechanisms. It exacerbates traditional cardiovascular risk factors such as dyslipidemia, hypertension, and type 2 diabetes, while visceral and epicardial fat deposition promotes inflammation and insulin resistance, thereby accelerating atherosclerosis. Beyond traditional pathophysiologic pathways, social determinants of health (SDoH) significantly contribute to obesity-related disparities, particularly among racial and ethnic minorities. SDoH factors such as socioeconomic status, access to health care, and limited availability of nutritious food and safe spaces for physical activity not only increase obesity prevalence but also exacerbate its psychological toll, including stress and anxiety, which further elevate cardiovascular risk. Environmental factors, such as limited green spaces and air pollution, further promote obesogenic behaviors and worsen cardiovascular outcomes. In this review, we explore the association between obesity and ASCVD and key mediating pathways including the role of SDoH and environmental risk factors. We also discuss potential strategies-including patient education, community engagement to address SDoH, and establishment of dedicated cardiometabolic and cardiovascular prevention clinics-to mitigate the population burden of obesity and improve downstream cardiovascular outcomes.

Reduction of Neuroinflammation as a Common Mechanism of Action of Anorexigenic and Orexigenic Peptide Analogues in the Triple Transgenic Mouse Model of Alzheimer´s Disease

Alzheimer's disease (AD) is the most common form of dementia. Characterized by progressive neurodegeneration, AD typically begins with mild cognitive decline escalating to severe impairment in communication and responsiveness. It primarily affects cerebral regions responsible for cognition, memory, and language processing, significantly impeding the functional independence of patients. With nearly 50 million dementia cases worldwide, a number expected to triple by 2050, the need for effective treatments is more urgent than ever. Recent insights into the association between obesity, type 2 diabetes mellitus, and neurodegenerative disorders have led to the development of promising treatments involving antidiabetic and anti-obesity agents. One such novel promising candidate for addressing AD pathology is a lipidized analogue of anorexigenic peptide called prolactin-releasing peptide (palm11-PrRP31). Interestingly, anorexigenic and orexigenic peptides have opposite effects on food intake regulation, however, both types exhibit neuroprotective properties. Recent studies have also identified ghrelin, an orexigenic peptide, as a potential neuroprotective agent. Hence, we employed both anorexigenic and orexigenic compounds to investigate the common mechanisms underpinning their neuroprotective effects in a triple transgenic mouse model of AD (3xTg-AD mouse model) combining amyloid-beta (Aβ) pathology and Tau pathology, two hallmarks of AD. We treated 3xTg-AD mice for 4 months with two stable lipidized anorexigenic peptide analogues - palm11-PrRP31, and liraglutide, a glucagon-like peptide 1 (GLP-1) analogue - as well as Dpr3-ghrelin, a stable analogue of the orexigenic peptide ghrelin, and using the method of immunohistochemistry and western blot demonstrate the effects of these compounds on the development of AD-like pathology in the brain. Palm11-PrRP31, Dpr3-ghrelin, and liraglutide reduced intraneuronal deposits of Aβ plaque load in the hippocampi and amygdalae of 3xTg-AD mice. Palm11-PrRP31 and Dpr3-ghrelin reduced microgliosis in the hippocampi, amygdalae, and cortices of 3xTg-AD mice. Palm11-PrRP31 and liraglutide reduced astrocytosis in the amygdalae of 3xTg-AD mice. We propose that these peptides are involved in reducing inflammation, a common mechanism underlying their therapeutic effects. This is the first study to demonstrate improvements in AD pathology following the administration of both orexigenic and anorexigenic compounds, highlighting the therapeutic potential of food intake-regulating peptides in neurodegenerative disorders.

Identification of Differentially Expressed Genes in the Hypothalamus of Broilers Under Heat Stress Using Transcriptome Analysis

The hypothalamus is the advanced center that regulates visceral activities under the cerebral cortex. It plays some key roles, such as regulating body temperature, assessing feed intake, and balancing blood glucose and endocrine gland activities. Heat stress is known to trigger a series of detrimental consequences, prominently featuring a reduction in feed intake, an elevation in body temperature, and other related phenomena. To understand the mechanisms of how heat stress affects the function of the hypothalamus, broilers were allocated to three groups: the normal control (NC) group, the heat-stress (HS) group, and the pair-fed (PF) group. The PF group was established with the aim of eliminating the confounding effect of reduced feed intake. The trial lasted for two weeks, from the age of 28 to 42 d. A total of 280 differential expressed genes (DEGs) were identified (padj < 0.05, |log2(FC)| ≥ 1) among three groups, including 3 up-regulated and 112 down-regulated genes in the HS group compared to the NC group, and 3 up-regulated and 13 down-regulated genes between the PF and NC groups. Compared with the HS group, a total of 149 genes were identified in the PF group, of which 125 genes were up-regulated and 24 genes were down-regulated. Gene Ontology enrichment indicated that a subset of DEGs was involved in brain development, the central nervous system (CNS), nerve signal transduction, and calcium homeostasis. The solute carrier family 1 member A6 and solute carrier family 6 member 13, identified as down-regulated genes (padj < 0.05) in the HS group, were considered as key genes in Gamma-aminobutyric acid (GABA) transportation, the normal expression of which ensures that extracellular GABA is maintained at a certain level and provides the amino acids needed for metabolism. Simultaneously, the solute carrier family 13 member 4 and solute carrier family 16 member 8 were also identified as down-regulated, which indicated that heat stress resulted in disorder and physiologic derangement in the hypothalamus. Meanwhile, the anorexigenic part of pro-opiomelanocortin genes was up-regulated significantly in the HS group. The transcriptome sequencing results can help us understand the regulatory mechanism of feed intake decline in broilers under heat stress at the genetic level.

Central and Peripheral Roles of Salt-inducible Kinases in Metabolic Regulation

Salt-inducible kinases (SIKs), a member of the serine/threonine protein kinase family, have recently garnered considerable research interest as one of the emerging key regulators of metabolism. The 3 SIK isoforms-SIK1, SIK2, and SIK3-exhibit diverse roles both in central and peripheral physiological processes. While early studies focused on their role in inflammation, spurring the development of SIK inhibitors for chronic inflammatory diseases currently in clinical trials, emerging evidence highlights their broader functions in metabolism. In this review, we will summarize the current state of research on the central roles of SIKs in the brain, particularly in regulating energy balance and glucose homeostasis, alongside their peripheral functions in critical metabolic tissues such as the liver, adipose tissue, and pancreas. By integrating insights into their central and peripheral roles, this review underscores the importance of SIKs in maintaining metabolic homeostasis and highlights their therapeutic potential as novel targets for metabolic disease.

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.

The MC4R agonist, setmelanotide, is associated with an improvement in hypercapnic chemosensitivity and weight loss in male mice

Obesity increases the risk of respiratory diseases that reduce respiratory chemosensitivity, such as Obesity Hypoventilation Syndrome and sleep apnea. Recent evidence suggests that obesity-related changes in the brain, including alterations in melanocortin signaling via the melanocortin-4 receptor (MC4R), may underly altered chemosensitivity. Setmelanotide, an MC4R agonist, causes weight loss in both humans and animal models. However, it is unknown the extent to which setmelanotide affects respiratory chemosensitivity independent of body weight loss. The present study uses diet-induced obese, male C57bl/6 J mice to determine the extent to which acute setmelanotide treatment affects the hypercapnic ventilatory response (HCVR). We find that ten days of daily setmelanotide treatment at 1 mg/kg, but not 0.2 mg/kg, is sufficient to cause weight loss and increase HCVR. In a separate group of animals, we find that we can emulate setmelanotide's effect on weight loss by restricting daily calories to match the hypophagia triggered by setmelanotide. These pair-fed animals exhibit improvements in HCVR similar to those who receive setmelanotide. We conclude that acute treatment with setmelanotide is as effective as weight loss at improving respiratory hypercapnic chemosensitivity.

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.

Serotonin neurons integrate GABA and dopamine inputs to regulate meal initiation

Obesity is a growing global health epidemic with limited orally administered therapeutics. Serotonin (5-HT) is one neurotransmitter which remains an excellent target for new weight-loss therapies, but a gap remains in understanding the mechanisms involved in 5-HT produced in the dorsal Raphe nucleus (DRN) and its involvement in meal initiation. Using an optogenetic feeding paradigm, we showed that the 5-HTDRN➔arcuate nucleus (ARH) circuit plays a role in meal initiation. Incorporating electrophysiology and ChannelRhodopsin-2-Assisted Circuit Mapping, we demonstrated that 5-HTDRN neurons receive inhibitory input partially from GABAergic neurons in the DRN, and the 5-HT response can be enhanced by hunger. Additionally, deletion of the GABAA receptor subunit in 5-HT neurons inhibits meal initiation with no effect on the satiation process. Finally, we identified the role of dopaminergic inputs via dopamine receptor D2 in enhancing the response to GABA-induced feeding. Thus, our results indicate that 5-HTDRN neurons are inhibited by synergistic inhibitory actions of GABA and dopamine, for the initiation of a meal.

Mechanisms and pharmacotherapy of cancer cachexia-associated anorexia

Cachexia is a multifactorial metabolic syndrome characterized by weight and skeletal muscle loss caused by underlying illnesses such as cancer, heart failure, and renal failure. Inflammation, insulin resistance, increased muscle protein degradation, decreased food intake, and anorexia are the primary pathophysiological drivers of cachexia. Cachexia causes physical deterioration and functional impairment, loss of quality of life, lower response to active treatment, and ultimately morbidity and mortality, while the difficulties in tackling cachexia in its advanced phases and the heterogeneity of the syndrome among patients require an individualized and multidisciplinary approach from an early stage. Specifically, strategies combining nutritional and exercise interventions as well as pharmacotherapy that directly affect the pathogenesis of cachexia, such as anti-inflammatory, metabolism-improving, and appetite-stimulating agents, have been proposed, but none of which have demonstrated sufficient evidence to date. Nevertheless, several agents have recently emerged, including anamorelin, a ghrelin receptor agonist, growth differentiation factor 15 neutralization therapy, and melanocortin receptor antagonist, as candidates for ameliorating anorexia associated with cancer cachexia. Therefore, in this review, we outline cancer cachexia-associated anorexia and its pharmacotherapy, including corticosteroids, progesterone analogs, cannabinoids, anti-psychotics, and thalidomide which have been previously explored for their efficacy, in addition to the aforementioned novel agents, along with their mechanisms.

Differences in GIP Receptor Expression by Feeding Status in the Mouse Brain

Gastric inhibitory polypeptide (GIP) contributes to energy metabolism regulation. We investigated differences in GIP receptor expression in the brain by feeding status among lean and obese mice and the effect of acute central GIP administration on the expression of appetite-regulating hypothalamic neuropeptides. We divided the mice into four groups: fed/lean, fasted/lean, fed/obese, and fasted/obese. The arcuate nucleus (ARC), paraventricular nucleus of the hypothalamus, and nucleus of the solitary tract in the brainstem were harvested. GIP (6 nmol) or saline was injected for the acute intracerebroventricular administration test, followed by the collection of hypothalamic tissue after 2 h. Fed/obese mice had higher ARC GIP receptor mRNA levels than fasted/obese and lean mice. This difference was not observed among lean mice by feeding status. Obese mice had higher blood GIP levels than lean mice. Fed/obese mice had higher blood GIP levels than fasted/obese mice. This difference was not observed among lean mice by feeding status. GIP administration significantly increased proopiomelano-cortin (Pomc) mRNA levels (GIP: 7.59 ± 0.14; saline: 3.44 ± 1.38 arbitrary units; p = 0.030). Increased GIP receptor expression in the ARC in obese mice indicates its central nervous system involvement in energy balance regulation. GIP potentially regulates POMC-mediated appetite regulation in the hypothalamus. It is possible that POMC neurons are targets of GIP action in the brain.

The BDNF Protein is Associated With Glucose Homeostasis and Food Intake in Carriers of Common BDNF Gene Variants

CONTEXT

Brain-derived neurotrophic factor (BDNF) concentrations may differ between BDNF genotype carriers. These changes occur in individuals with metabolic and mental disorders.

OBJECTIVE

The aim of this study was to assess the associations of glucose homeostasis parameters and the frequency of food consumption with BDNF protein concentrations based on BDNF single nucleotide polymorphisms (SNPs).

METHODS

Among the 439 participants, some common rs10835211 BDNF gene variants were analyzed. We evaluated BDNF concentrations, and measured glucose and insulin after fasting and during oral glucose tolerance tests. Anthropometric measurements, body composition, and body fat distribution were assessed, and a 3-day food intake diary and food frequency questionnaire were completed.

RESULTS

We observed significant differences in BDNF concentration between AA and AG genotype rs10835211 carriers (P = .018). The group of AA genotype holders were older, and positive correlation was found between age and BDNF in the whole study population (P = .012) and in the GG genotype carriers (P = .023). Moreover, BDNF protein correlated with fasting insulin (P = .015), HOMA-IR (P = .031), HOMA-B (P = .010), and the visceral/subcutaneous adipose tissue (VAT/SAT) ratio (P = .026) in the GG genotype individuals. Presence of the GG genotype was negatively correlated with nut and seed (P = .047) and lean pork consumption (P = .015), and the BDNF protein. Moreover, we observed correlations between the frequency of chicken (P = .028), pasta (P = .033), and sweet food intake (P = .040) with BDNF concentration in the general population. Among carriers of the AA genotype, we observed a positive correlation between the consumption of rice (P = .048) and sweet food (P = .028) and the BDNF protein level.

CONCLUSION

Peripheral BDNF may be associated with VAT content and insulin concentrations in GG genotype carriers and may vary with particular food intake, which warrants further investigation.

Early maternal undernutrition induces sex-related metabolic changes in adult offspring

Nutritional status during the developmental periods leads to predisposition to several diseases and comorbidities, highlighting metabolic and reproductive changes throughout adult life, and in the next generations. One of the experimental models used to induce undernutrition is litter size expansion, which decreases the availability of breast milk to pups and delays development. This work evaluated the effects of maternal undernutrition induced by litter size expansion, a maternal undernutrition preconception model, on the metabolic and reproductive alterations of the offspring. For this, metabolic and reproductive parameters were evaluated in male and female offspring of female rats reared in normal (NL - 10 pups: 5 males and 5 females) and large (LL - 16 pups: 8 males and 8 females) litters. Male and female offspring of LL mothers presented higher food intake than the offspring of NL mothers. Male offspring from undernourished females showed reduced body weight from lactation to adulthood, nasoanal distance in childhood, increased nasoanal distance, and decreased Lee index in adult life, while female offspring showed decreased nasoanal distance in childhood. The male offspring from LL mothers showed increased insulin plasma levels and glucose tolerance, and reduced triglycerides plasma levels, without changes in the female offspring. These results indicate that neonatal undernutrition in females predisposes their male and female offspring to develop metabolic alterations, without reproductive repercussions, and male offspring seems to be more susceptible to present these metabolic changes than females. Thus, there are sexual differences in the metabolic responses of the offspring elicited by maternal preconceptional undernutrition.

Perspectives on obesity imaging: [18F]2FNQ1P a specific 5-HT6 brain PET radiotracer

BACKGROUND

Estimates suggest that approximatively 25% of the world population will be overweight in 2025. Better understanding of the pathophysiology of obesity will help to develop future therapeutics. Serotonin subtype 6 receptors (5-HT6) have been shown to be critically involved in appetite reduction and weight loss. However, it is not known if the pathological cascade triggered by obesity modifies the density of 5-HT6 receptors in the brain.

METHODS

Influence of diet-induced obesity (DIO) in Wistar rats was explored using MRI (whole-body fat) and PET ([18F]2FNQ1P as a specific 5-HT6 radiotracer). The primary goal was to monitor the 5-HT6 receptor density before and after a 10-week diet (DIO group). The secondary goal was to compare 5-HT6 receptor densities between DIO group, Wistar control diet group, Zucker rats (with genetic obesity) and Zucker lean strain rats.

RESULTS

Wistar rats fed with high-fat diet showed higher body fat gain than Wistar control diet rats on MRI. [18F]2FNQ1P PET analysis highlighted significant clusters of voxels (located in hippocampus, striatum, cingulate, temporal cortex and brainstem) with increased binding after high-fat diet (p < 0.05, FWE corrected).

CONCLUSION

This study sheds a new light on the influence of high-fat diet on 5-HT6 receptors. This study also positions [18F]2FNQ1P PET as an innovative tool to explore neuronal consequences of obesity or eating disorder pathophysiology.

Insulin activates parasympathetic hepatic-related neurons of the paraventricular nucleus of the hypothalamus through mTOR signaling

Integration of autonomic and metabolic regulation, including hepatic function, is a critical role played by the brain's hypothalamic region. Specifically, the paraventricular nucleus of the hypothalamus (PVN) regulates autonomic functions related to metabolism, such as hepatic glucose production. Although insulin can act directly on hepatic tissue to inhibit hepatic glucose production, recent evidence implicates that central actions of insulin within PVN also regulate glucose metabolism. However, specific central circuits responsible for insulin signaling with relation to hepatic regulation are poorly understood. As a heterogeneous nucleus essential to controlling parasympathetic motor output with notable expression of insulin receptors, PVN is an appealing target for insulin-dependent modulation of parasympathetic activity. Here, we tested the hypothesis that insulin activates hepatic-related PVN (PVNhepatic) neurons through a parasympathetic pathway. Using transsynaptic retrograde tracing, labeling within PVN was first identified 24 h after its expression in the dorsal motor nucleus of the vagus (DMV) and 72 h after hepatic injection. Critically, nearly all labeling in medial PVN was abolished after a left vagotomy, indicating that PVNhepatic neurons in this region are part of a central circuit innervating parasympathetic motor neurons. Insulin also significantly increased the firing frequency of PVNhepatic neurons in this subregion. Mechanistically, rapamycin pretreatment inhibited insulin-dependent activation of PVNhepatic neurons. Therefore, central insulin signaling can activate a subset of PVNhepatic neurons that are part of a unique parasympathetic network in control of hepatic function. Taken together, PVNhepatic neurons related to parasympathetic output regulation could serve as a key central network in insulin's ability to control hepatic functions.NEW & NOTEWORTHY Increased peripheral insulin concentrations are known to decrease hepatic glucose production through both direct actions on hepatocytes and central autonomic networks. Despite this understanding, how (and in which brain regions) insulin exerts its action is still obscure. Here, we demonstrate that insulin activates parasympathetic hepatic-related PVN neurons (PVNhepatic) and that this effect relies on mammalian target of rapamycin (mTOR) signaling, suggesting that insulin modulates hepatic function through autonomic pathways involving insulin receptor intracellular signaling cascades.

Estrogens impair hypophagia and hypothalamic cell activation induced by vasoactive intestinal peptide, but not by pituitary adenylate cyclase-activating polypeptide

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) act in arcuate (ARC) and paraventricular (PVN) hypothalamic nuclei, reducing food intake and changing plasma parameters. Estrogens (E) also regulate energy homeostasis, and loss of ovarian function leads to hyperphagia and body weight gain. This study aimed to evaluate the effects of estradiol (E) in a postmenopausal rat model, ovariectomy (OVX), on PAC1 and VPAC2 receptors in the PVN and ARC, as well as on food intake, plasma parameters, and PVN and ARC cell activation in response to intracerebroventricular microinjection of VIP and PACAP. For this, the rats underwent intracerebroventricular and OVX surgeries, being treated daily with subcutaneous injections of 0.2 mL of corn oil or 10 μg/0.2 mL of estradiol cypionate, comprising the OVX+O and OVX+E groups, respectively. OVX+E showed reduced VPAC2 mRNA expression in the PVN. PACAP reduced food intake in both groups, and VIP-induced hypophagia was not observed in OVX+E. VIP increased plasma glucose in both groups, and PACAP increased plasma glucose only in OVX+O. VIP decreased free fatty acids in OVX+E. Furthermore, PACAP increased ARC cell activation in both groups, and in the PVN only in OVX+O. Cell activation induced by VIP in ARC and PVN was blocked by estradiol. Therefore, estrogens disrupted the hypophagia induced by VIP, but not by PACAP, and these differences seem to be, at least in part, due to an impairment of the activation of the ARC-PVN pathway.

The Impact of Gastric Leptin and Leptin Receptor Expression on Metabolic Outcomes Post Laparoscopic Sleeve Gastrectomy

PURPOSE

Obesity is a growing global crisis, with predictions that nearly half of the world's population will be overweight or with severe obesity by 2030. Metabolic bariatric surgery, effective for those unable to lose weight through conventional methods, results in significant weight loss and alleviates associated medical problems. This study investigates changes in gastric leptin (LE) and leptin receptor (LER) expression following laparoscopic sleeve gastrectomy (LSG) and explores their metabolic contributions to surgical outcomes.

MATERIALS AND METHODS

Immunohistochemical staining for LE and LER was performed on gastric tissue biopsies from 54 patients pre- and post-LSG. Expression levels were scored for each epithelium and connective tissue component. Changes in these scores post-LSG were analyzed and correlated with body mass index (BMI), total weight loss (TWL), blood hemoglobin A1c, blood cholesterol, and triglyceride levels. Statistical analysis included paired t-tests, Pearson correlation coefficients, and one-way ANOVA.

RESULTS

Significant decreases in LE and LER receptor expression were observed post-LSG, correlating with reductions in BMI, blood hemoglobin A1c, total cholesterol, and triglyceride levels. The mean BMI decreased from 46.82 kg/m2 pre-surgery to 32.45 kg/m2 at 1 year post-surgery (p < 0.001). Hemoglobin A1c levels reduced from 7.8% to 5.9% (p < 0.001). Total cholesterol and triglyceride levels showed significant reductions, with cholesterol decreasing from 220 mg/dL to 180 mg/dL (p < 0.001) and triglycerides from 180 mg/dL to 120 mg/dL (p < 0.001). Pearson correlation coefficients demonstrated strong negative correlations between LE expression and BMI (r = -0.65, p < 0.001) and between LER expression and hemoglobin A1c (r = -0.60, p < 0.001).

CONCLUSIONS

Beyond weight reduction, the decreased expression of gastric LE and LER post-LSG contributes metabolically to weight loss and improved associated metabolic parameters following the metabolic bariatric surgery.

Insulin and leptin acutely modulate the energy metabolism of primary hypothalamic and cortical astrocytes

Astrocytes constitute a heterogeneous cell population within the brain, contributing crucially to brain homeostasis and playing an important role in overall brain function. Their function and metabolism are not only regulated by local signals, for example, from nearby neurons, but also by long-range signals such as hormones. Thus, two prominent hormones primarily known for regulating the energy balance of the whole organism, insulin, and leptin, have been reported to also impact astrocytes within the brain. In this study, we investigated the acute regulation of astrocytic metabolism by these hormones in cultured astrocytes prepared from the mouse cortex and hypothalamus, a pivotal region in the context of nutritional regulation. Utilizing genetically encoded, fluorescent nanosensors, the cytosolic concentrations of glucose, lactate, and ATP, along with glycolytic rate and the NADH/NAD+ redox state were measured. Under basal conditions, differences between the two populations of astrocytes were observed for glucose and lactate concentrations as well as the glycolytic rate. Additionally, astrocytic metabolism responded to insulin and leptin in both brain regions, with some unique characteristics for each cell population. Finally, both hormones influenced how cells responded to elevated extracellular levels of potassium ions, a common indicator of neuronal activity. In summary, our study provides evidence that insulin and leptin acutely regulate astrocytic metabolism within minutes. Additionally, while astrocytes from the hypothalamus and cortex share similarities in their metabolism, they also exhibit distinct properties, further underscoring the growing recognition of astrocyte heterogeneity.

Rare variants in the melanocortin 4 receptor gene (MC4R) are associated with abdominal fat and insulin resistance in youth with obesity

BACKGROUND

Rare variants in melanocortin 4 receptor gene (MC4R) result in a severe form of early-onset obesity; however, it is unclear how these variants may affect abdominal fat distribution, intrahepatic fat accumulation, and related metabolic sequelae.

METHODS

Eight hundred seventy-seven youth (6-21 years) with overweight/obesity, recruited from the Yale Pediatric Obesity Clinic in New Haven, CT, underwent genetic analysis to screen for functionally damaging, rare variants (MAF < 0.01) in MC4R. Participants were assigned to a Pathogenic Variant or No Pathogenic Variant group and completed a 10-timepoint 180-min oral glucose tolerance test (OGTT) and abdominal MRI.

RESULTS

Compared to the No Pathogenic Variant group, the Pathogenic Variant group demonstrated significantly greater glucose concentrations (AUCtot: 24.7 ± 1.22 g/dL × 180 min vs. 21.9 ± 1.41 g/dL × 180 min; p = 0.001), insulin levels (AUCtot: 57.4 ± 11.5 mU/mL × 180 min vs. 35.5 ± 8.90 mU/mL × 180 min; p = 0.002), and lower insulin sensitivity (WBISI: 1.01 ± 0.137 vs. 1.85 ± 0.036; p = 0.0008) during the OGTT. The Pathogenic Variant group also presented with greater visceral adipose tissue (VAT) (85.1 cm2 ± 10.3 vs. 56.1 cm2 ± 1.64; p = 0.003) and intrahepatic fat content (HFF%) (19.4% ± 4.94 vs. 8.21% ± 0.495; p = 0.012) than the No Pathogenic Variant group despite the two groups having similar BMI z-scores (p = 0.255), subcutaneous adipose tissue (SAT) (p = 0.643), and total body fat (p = 0.225).

CONCLUSIONS

Pathogenic variants in MC4R are associated with increased VAT, HFF%, and insulin resistance, independent from the degree of obesity in youth.

Chronic sleep deprivation disturbs energy balance modulated by suprachiasmatic nucleus efferents in mice

BACKGROUND

Epidemiologic researches show that short sleep duration may affect feeding behaviors resulting in higher energy intake and increased risk of obesity, but the further mechanisms that can interpret the causality remain unclear. The circadian rhythm is fine-tuned by the suprachiasmatic nucleus (SCN) as the master clock, which is essential for driving rhythms in food intake and energy metabolism through neuronal projections to the arcuate nucleus (ARC) and paraventricular nucleus (PVN).

RESULTS

We showed that chronic SD-induced aberrant expressions of AgRP/NPY and POMC attributed to compromised JAK/STAT3 signals and reduced energy expenditure in the mice, which can be rescued with AAV-genetic overexpression of BMAL1 into SCN. The potential mechanism may be related to the disruptions of SCN efferent mediated by BMAL1.

CONCLUSIONS

Chronic SD impairs energy balance through directly dampening BMAL1 expression, probably in the transcription level, in the SCN, which in turn affects the neuron projections to ARC and PVN. Remarkably, we provide evidence that may explain the causal mechanisms associated with sleep curtailment and obesity in adolescents.

Obesogens and Energy Homeostasis: Definition, Mechanisms of Action, Exposure, and Adverse Effects on Human Health

BACKGROUND

Obesity is a major risk factor for noncommunicable diseases and is associated with a reduced life expectancy of up to 20 years, as well as with other consequences such as unemployment and increased economic burden for society. It is a multifactorial disease, and physiopathology of obesity involves dysregulated calorie utilization and energy balance, disrupted homeostasis of appetite and satiety, lifestyle factors including sedentary lifestyle, lower socioeconomic status, genetic predisposition, epigenetics, and environmental factors. Some endocrine-disrupting chemicals (EDCs) have been proposed as "obesogens" that stimulate adipogenesis leading to obesity. In this review, definition of obesogens, their adverse effects, underlying mechanisms, and metabolic implications will be updated and discussed.

SUMMARY

Disruption of lipid homeostasis by EDCs involves multiple mechanisms including increase in the number and size of adipocytes, disruption of endocrine-regulated adiposity and metabolism, alteration of hypothalamic regulation of appetite, satiety, food preference and energy balance, and modification of insulin sensitivity in the liver, skeletal muscle, pancreas, gastrointestinal system, and the brain. At a cellular level, obesogens can exert their endocrine disruptive effects by interfering with peroxisome proliferator-activated receptors and steroid receptors. Human exposure to chemical obesogens mainly occurs by ingestion and, to some extent, by inhalation and dermal uptake, usually in an unconscious manner. Persistent pollutants are lipophilic features; thus, they bioaccumulate in adipose tissue.

KEY MESSAGES

Although there are an increasing number of reports studying the effects of obesogens, their mechanisms of action remain to be elucidated. In addition, epidemiological studies are needed in order to evaluate human exposure to obesogens.

The vices and virtues of medical models of obesity

Despite numerous public health organizations supporting the pathologization of obesity and considering recent obesity rates a health crisis, many researchers in the humanities, social sciences, and even in the health sciences remain unconvinced. In this paper, we address a set of arguments coming from these academic fields that criticize medical models of obesity for their supposedly flawed diagnostic categories that shift focus onto individuals and support moralizing judgements. Clarifying some key claims in these models and explicating the view of obesity in terms of energy dysregulation, we aim to tease apart misunderstandings and argue that not only do these models not say what they are often accused of saying, but their apparent vices may actually be virtues in helping to combat stigma. Building on the social psychology of stigma and disease labeling, we then suggest that current medical models are largely supportive of many moral and political aims promoted by critics of these models.

History and future of leptin: Discovery, regulation and signaling

The cloning of leptin 30 years ago in 1994 was an important milestone in obesity research. Prior to the discovery of leptin, obesity was stigmatized as a condition caused by lack of character and self-control. Mutations in either leptin or its receptor were the first single gene mutations found to cause severe obesity, and it is now recognized that obesity is caused mostly by a dysregulation of central neuronal circuits. Since the discovery of the leptin-deficient obese mouse (ob/ob) the cloning of leptin (ob aka lep) and leptin receptor (db aka lepr) genes, we have learned much about leptin and its action in the central nervous system. The first hope that leptin would cure obesity was quickly dampened because humans with obesity have increased leptin levels and develop leptin resistance. Nevertheless, leptin target sites in the brain represent an excellent blueprint to understand how neuronal circuits control energy homeostasis. Our expanding understanding of leptin function, interconnection of leptin signaling with other systems and impact on distinct physiological functions continues to guide and improve the development of safe and effective interventions to treat metabolic illnesses. This review highlights past concepts and current emerging concepts of the hormone leptin, leptin receptor signaling pathways and central targets to mediate distinct physiological functions.

A new target for treating intervertebral disk degeneration: gut microbes

Intervertebral disk degeneration (IDD) is a common clinical spinal disease and one of the main causes of low back pain (LBP). Generally speaking, IDD is considered a natural degenerative process with age. However, with the deepening of research, people have discovered that IDD is not only related to age, but also has many factors that can induce and accelerate its progression. In addition, the pathogenesis of IDD remains unclear, resulting in limited traditional treatment methods that cannot effectively prevent and treat IDD. Conservative treatment may lead to patients' dependence on drugs, and the pain relief effect is not obvious. Similarly, surgical treatment is highly invasive, with a longer recovery time and a higher recurrence rate. With the deepening of exploration, people have discovered that intestinal microorganisms are an important symbiotic microbial community in the human body and are closely related to the occurrence and development of various diseases. Changes in intestinal microorganisms and their metabolites may affect the body's inflammatory response, immune regulation, and metabolic processes, thereby affecting the health of the intervertebral disk. In this context, the gut microbiota has received considerable attention as a potential target for delaying or treating IDD. This article first introduces the impact of gut microbes on common distal organs, and then focuses on three potential mechanisms by which gut microbes and their metabolites influence IDD. Finally, we also summarized the methods of delaying or treating IDD by interfering with intestinal microorganisms and their metabolites. Further understanding of the potential mechanisms between intestinal microorganisms and IDD will help to formulate reasonable IDD treatment strategies to achieve ideal therapeutic effects.

A biological rhythm in the hypothalamic system links sleep-wake cycles with feeding-fasting cycles

The hypothalamus senses the appetite-regulating hormones and also coordinates the metabolic function in alignment with the circadian rhythm. This alignment is essential to maintain the physiological conditions that prevent clinically important comorbidities, such as obesity or type-2 diabetes. However, a complete model of the hypothalamus that relates food intake with circadian rhythms and appetite hormones has not yet been developed. In this work, we present a computational model that accurately allows interpreting neural activity in terms of hormone regulation and sleep-wake cycles. We used a conductance-based model, which consists of a system of four differential equations that considers the ionotropic and metabotropic receptors, and the input currents from homeostatic hormones. We proposed a logistic function that fits available experimental data of insulin hormone concentration and added it into a short-term ghrelin model that served as an input to our dynamical system. Our results show a double oscillatory system, one synchronized by light-regulated sleep-wake cycles and the other by food-regulated feeding-fasting cycles. We have also found that meal timing frequency is highly relevant for the regulation of the hypothalamus neurons. We therefore present a mathematical model to explore the plausible link between the circadian rhythm and the endogenous food clock.

"OMICS" in Human Milk: Focus on Biological Effects on Bone Homeostasis

Human milk (HM) is a complex biofluid rich in nutrients and bioactive compounds essential for infant health. Recent advances in omics technologies-such as proteomics, metabolomics, and transcriptomics-have shed light on the influence of HM on bone development and health. This review discusses the impact of various HM components, including proteins, lipids, carbohydrates, and hormones, on bone metabolism and skeletal growth. Proteins like casein and whey promote calcium absorption and osteoblast differentiation, supporting bone mineralization. Long-chain polyunsaturated fatty acids like docosahexaenoic acid (DHA) contribute to bone health by modulating inflammatory pathways and regulating osteoclast activity. Additionally, human milk oligosaccharides (HMOs) act as prebiotics, improving gut health and calcium bioavailability while influencing bone mineralization. Hormones present in HM, such as insulin-like growth factor 1 (IGF-1), leptin, and adiponectin, have been linked to infant growth, body composition, and bone density. Research has shown that higher IGF-1 levels in breast milk are associated with increased weight gain, while leptin and adiponectin influence fat mass and bone metabolism. Emerging studies have also highlighted the role of microRNAs (miRNAs) in regulating key processes like adipogenesis and bone homeostasis. Furthermore, microbiome-focused techniques reveal HM's role in establishing a balanced infant gut microbiota, indirectly influencing bone development by enhancing nutrient absorption. Although current findings are promising, comprehensive longitudinal studies integrating omics approaches are needed to fully understand the intricate relationships among maternal diet, HM composition, and infant bone health. Bridging these gaps could offer novel dietary strategies to optimize skeletal health during infancy, advancing early-life nutrition science.

Sexual dimorphism and the impact of aging on ball rolling-associated locomotor behavior in Drosophila

Insects exhibit a remarkable ability to interact with inanimate objects to facilitate essential behaviors such as foraging, reproduction, shelter building, and defense. In this study, we assessed whether Drosophila interacted with inanimate objects when they were suspended on their wings and provided with a thermocol ball (foam ball). Drosophila indeed exhibited ball rolling behavior. We further examined the sexual dimorphism in this ball rolling-associated locomotor behavior. We carried out a ball rolling assay using 3-day-old male and female w1118 flies and measured the duration for which the flies could roll the ball without dropping it within a 10 min period. The ball was returned to the flies whenever they dropped it, and we calculated the number of times the ball was dropped within the 10 min duration. Females exhibited a longer ball holding duration than males. We also observed a decrease in ball holding duration and an increase in the number of times the ball was dropped by 15-day-old male and female flies than their younger counterparts. These results suggest sexual dimorphism and age-dependent alterations in Drosophila ball rolling-associated locomotor behavior.

Consumption of Plant-Derived Phenolic Acids Modulates Hunger and Satiety Responses Due to Chemical Interactions with Enteroendocrine Mediators

Energy-dense foods are commonly rich in fat and simple sugars and poor in dietary fiber and micronutrients; regularly consuming them decreases the concentration and/or effect of anorexigenic hormones and may increase that of orexigenic ones, thereby decreasing satiety. In contrast, plant-derived phenolic-rich foods exert positive effects on satiety. In silico, in vitro, and in vivo investigations on some of most representative phenolic acids like chlorogenic acid (CGA), gallic acid (GA), ferulic acid (FA), and protocatechuic acid (PCA) have shown that they are able to modulate various hunger and satiety processes; however, there are few studies that show how their chemical structure contributes to achieve such effects. The objective of this review is to summarize how these phenolic acids can favorably modulate hormones and other satiety mediators, with emphasis on the chemical interactions exerted between the core of these compounds and their biological targets. The evidence suggests that they form interactions with certain hormones, their receptors, and/or enzymes involved in regulating hunger and satiety, which are attributed to their chemical structure (such as the position of hydroxyl groups). Further research is needed to continue understanding these molecular mechanisms of action and to utilize the knowledge in the development of health-promoting foods.

Global hotspots and trends in tea anti-obesity research: a bibliometric analysis from 2004 to 2024

Background

The prevalence of obesity and its related ailments is on the rise, posing a substantial challenge to public health. Tea, widely enjoyed for its flavors, has shown notable potential in mitigating obesity. Yet, there remains a lack of exhaustive bibliometric studies in this domain.

Methods

We retrieved and analyzed multidimensional data concerning tea and obesity studies from January 2004 to June 2024, using the Web of Science Core Collection database. This bibliometric investigation utilized tools such as Bibliometrix, CiteSpace, and VOSviewer to gather and analyze data concerning geographical distribution, leading institutions, prolific authors, impactful journals, citation patterns, and prevalent keywords.

Results

There has been a significant surge in publications relevant to this field within the last two decades. Notably, China, Hunan Agricultural University, and the journal Food and Function have emerged as leading contributors in terms of country, institution, and publication medium, respectively. Zhonghua Liu of Hunan Agricultural University has the distinction of most publications, whereas Joshua D. Lambert of The State University of New Jersey is the most cited author. Analyses of co-citations and frequently used keywords have identified critical focus areas within tea anti-obesity research. Current studies are primarily aimed at understanding the roles of tea components in regulating gut microbiota, boosting fat oxidation, and increasing metabolic rate. The research trajectory has progressed from preliminary mechanism studies and clinical trials to more sophisticated investigations into the mechanisms, particularly focusing on tea's regulatory effects on gut microbiota.

Conclusion

This study offers an intricate overview of the prevailing conditions, principal focus areas, and developmental trends in the research of tea's role against obesity. It delivers a comprehensive summary and discourse on the recent progress in this field, emphasizing the study's core findings and pivotal insights. Highlighting tea's efficacy in obesity prevention and treatment, this study also points out the critical need for continued research in this area.

Intermittent access to sugary drinks associated with fasting induces overeating and depressive-like behavior in female C57BL/6J mice

Binge eating disorder is the most prevalent eating disorder, affecting both sexes but more commonly found in women. Given the frequent co-occurrence of psychiatric disorders, this study aimed to establish a standardized experimental intermittent protocol to investigate overeating associated with depression. A 10-day protocol induced uncontrolled eating behavior in C57BL/6J female mice. The first experiment included the following groups: naive group (chow ad libitum), control group (chow and sucrose solution ad libitum), and fasting groups (16 and 20 h) exposed to an intermittent sucrose solution (10 %) and chow regimen. Subsequently, the feeding test, open field test, elevated plus maze test, tail suspension test, and light/dark conflict test were conducted. Furthermore, monoamine oxidase (MAO) A and B activities in brain structures and plasma corticosterone levels were assessed. Food overconsumption and depressive-like behavior were observed in both sucrose fasting groups, while risk-taking behaviors were specifically observed in the 20-hour fasting sucrose group. While both fasting sucrose groups caused reduced hippocampal MAO-A activity, only the F20 sucrose group inhibited MAO-B in the cortex and hypothalamus. Moreover, both fasting sucrose groups exhibited elevated corticosterone levels. In a separate design (Experiment 2), groups with 16 and 20 h of fasting alone (without sucrose) did not show the same behavioral results as the intermittent fasting sucrose groups, thus avoiding fasting bias. Based on these results, the 20-hour sucrose fasting group was chosen as the ideal protocol for mimicking overeating behavior associated with depression to investigate future therapeutic approaches for this comorbidity.

Spinal afferent neurons: emerging regulators of energy balance and metabolism

Recent advancements in neurophysiology have challenged the long-held paradigm that vagal afferents serve as the primary conduits for physiological signals governing food intake and energy expenditure. An expanding body of evidence now illuminates the critical role of spinal afferent neurons in these processes, necessitating a reevaluation of our understanding of energy homeostasis regulation. This comprehensive review synthesizes cutting-edge research elucidating the multifaceted functions of spinal afferent neurons in maintaining metabolic equilibrium. Once predominantly associated with nociception and pathological states, these neurons are now recognized as integral components in the intricate network regulating feeding behavior, nutrient sensing, and energy balance. We explore the role of spinal afferents in food intake and how these neurons contribute to satiation signaling and meal termination through complex gut-brain axis pathways. The review also delves into the developing evidence that spinal afferents play a crucial role in energy expenditure regulation. We explore the ability of these neuronal fibers to carry signals that can modulate feeding behavior as well as adaptive thermogenesis in adipose tissue influencing basal metabolic rate, and thereby contributing to overall energy balance. This comprehensive analysis not only challenges existing paradigms but also opens new avenues for therapeutic interventions suggesting potential targets for treating metabolic disorders. In conclusion, this review highlights the need for a shift in our understanding of energy homeostasis, positioning spinal afferent neurons as key players in the intricate web of metabolic regulation.

Impact of Sleeve Gastrectomy on Body Weight and Food Intake Regulation in Diet-Induced Obese Mice

The epidemic of obesity has increased worldwide and is associated with comorbidities such as diabetes and cardiovascular disease. In this context, strategies that modulate body weight and improve glycemic metabolism have increased, and bariatric surgeries such as Sleeve Gastrectomy (SG) have been highlighted in obesity treatment. However, the mechanism by which SG reduces body weight and improves glycemic control remains unknown. Thus, in this study, we aimed to evaluate food intake and the expression of hypothalamic genes involved with the regulation of this process in diet-induced obese mice submitted to SG. For this, we used C57BL/6 mice submitted to a 10-week high-fat diet protocol and submitted to SG. Food intake, fed and fasted glycemia, as well as hypothalamic anorexigenic and orexigenic gene expression were evaluated 4 weeks after the surgical procedure. First, we observed that SG reduces body weight (44.19 ± 0.47 HFD, 43.51 ± 0.71 HFD-SHAM, and 38.22 ± 1.31 HFD-SG), fasting glycemia (115.0 ± 4.60 HFD, 122.4 ± 3.48 HFD-SHAM, and 93.43 ± 4.67 HFD-SG), insulinemia (1.77 ± 0.15 HFD, 1.92 ± 0.27 HFD-SHAM, and 0.93 ± 0.05 HFD-SG), and leptinemia (5.86 ± 1.38 HFD, 6.44 ± 1.51 HFD-SHAM, and 1.43 ± 0.35 HFD-SG) in obese mice. Additionally, SG reduces food (5.15 ± 0.18 HFD, 5.49 ± 0.32, HFD-SHAM, and 3.28 ± 0.26 HFD-SG) and total (16.88 ± 0.88 HFD, 17.05 ± 0.42, HFD-SHAM, and 14.30 ± 0.73 HFD-SG) calorie intake without alterations in anorexigenic and orexigenic gene expression. In conclusion, these data indicate that SG improves obesity-associated alterations at least in part by a reduction in food intake. This effect is not associated with the canonical food intake pathway in the hypothalamus, indicating the involvement of non-canonical pathways in this process.

Pathophysiological significance and modulation of the transient receptor potential canonical 3 ion channel

Transient receptor potential canonical 3 (TRPC3) protein belongs to the TRP family of nonselective cation channels. Its activation occurs by signaling through a G protein-coupled receptor (GPCR) and a phospholipase C-dependent (PLC) pathway. Perturbations in the expression of TRPC3 are associated with a plethora of pathophysiological conditions responsible for disorders of the cardiovascular, immune, and central nervous systems. The recently solved cryo-EM structure of TRPC3 provides detailed inputs about the underlying mechanistic aspects of the channel, which in turn enables more efficient ways of designing small-molecule modulators. Pharmacologically targeting TRPC3 in animal models has demonstrated great efficacy in treating diseases including cancers, neurological disorders, and cardiovascular diseases. Despite extensive scientific evidence supporting some strong correlations between the expression and activity of TRPC3 and various pathophysiological conditions, therapeutic strategies based on its pharmacological modulations have not led to clinical trials. The development of small-molecule TRPC3 modulators with high safety, sufficient brain penetration, and acceptable drug-like profiles remains in progress. Determining the pathological mechanisms for TRPC3 involvement in human diseases and understanding the requirements for a drug-like TRPC3 modulator will be valuable in advancing small-molecule therapeutics to future clinical trials. In this review, we provide an overview of the origin and activation mechanism of TRPC3 channels, diseases associated with irregularities in their expression, and new development in small-molecule modulators as potential therapeutic interventions for treating TRPC3 channelopathies.

Rikkunshito improves anorexia through ghrelin- and orexin-dependent activation of the brain hypothalamus and mesolimbic dopaminergic pathway in rats

BACKGROUND

Rikkunshito (RKT), a traditional Japanese medicine, can relieve epigastric discomfort and anorexia in patients with functional dyspepsia. RKT enhances the orexigenic hormone, ghrelin. Ghrelin regulates food motivation by stimulating the appetite control center in the hypothalamus and the brain mesolimbic dopaminergic pathway (MDPW). However, the effect of RKT on MDPW remains unclear. Here, we aimed to investigate the central neural mechanisms underlying the orexigenic effects of RKT, focusing on the MDPW.

METHODS

We examined the effects of RKT on food intake and neuronal c-Fos expression in restraint stress- and cholecystokinin octapeptide-induced anorexia in male rats.

KEY RESULTS

RKT treatment significantly restored stress- and cholecystokinin octapeptide-induced decreased food intake. RKT increased c-Fos expression in the ventral tegmental area (VTA), especially in tyrosine hydroxylase-immunoreactive neurons, and nucleus accumbens (NAc). The effects of RKT were suppressed by the ghrelin receptor antagonist [D-Lys3]-GHRP-6. RKT increased the number of c-Fos/orexin-double-positive neurons in the lateral hypothalamus (LH), which project to the VTA. The orexin receptor antagonist, SB334867, suppressed RKT-induced increase in food intake and c-Fos expression in the LH, VTA, and NAc. RKT increased c-Fos expression in the arcuate nucleus and nucleus of the solitary tract of the medulla, which was inhibited by [D-Lys3]-GHRP-6.

CONCLUSIONS & INFERENCES

RKT may restore appetite in subjects with anorexia through ghrelin- and orexin-dependent activation of neurons regulating the brain appetite control network, including the hypothalamus and MDPW.

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

Study on the Function of Leptin Nutrient Acquisition and Energy Metabolism of Zebrafish (Danio rerio)

Leptin plays an indispensable role in energy homeostasis, and its involvement in metabolic activities has been extensively explored in fish. We generated mutant lines of leptina (-5 bp) and leptinb (+8 bp) in zebrafish using CRISPR/Cas9 technology to explore the metabolic characteristics of lepa and lepb mutant zebrafish in response to high glucose nutritional stress induced by high levels of carbohydrates. The results were as follows: the body weight and food intake of adult zebrafish of the two mutant species were increased; the visceral fat accumulation, whole-body crude lipid, and crude protein contents of lepb-/- were increased; and the visceral fat accumulation and crude lipid in lepa-/- zebrafish were decreased. The blood glucose levels of the two mutant zebrafish were increased, the mRNA expression levels of glycolytic genes pk and gck were decreased in the two mutant zebrafish, and there were differences between lepa-/- and lepb-/- zebrafish. The expressions of glycogen synthesis and decomposition genes were inhibited and promoted, respectively. The expression of adipose synthesis genes in the liver and muscle was stimulated in lepb-/- zebrafish but suppressed in lepa-/- zebrafish. Lipolysis and oxidation genes were also stimulated in lepa-/- zebrafish livers, while the livers of lepb-/- zebrafish were stimulated but muscle was inhibited. In conclusion, the results indicate that lepa plays a major role in glucose metabolism, which is conducive to promoting glucose utilization and lipogenesis, while lepb mainly promotes lipolysis and oxidation, regulates protein generation, and plays a minor role in glucose metabolism.

Biomarker identification and risk assessment of cardiovascular disease based on untargeted metabolomics and machine learning

Cardiovascular disease (CVD) is the leading cause of mortality, disability, and healthcare costs, with a significant impact on the elderly and contributing to premature deaths across various age groups, including those below age 70. Despite decades of transformative discoveries and clinical efforts, the challenges of diagnosis, prevention, and treatment of CVD persist on a massive scale. This study aimed to unravel potential CVD-associated biomarkers and establish a machine learning model for the risk assessment of CVD. Untargeted metabolic assay with ultra-high performance liquid chromatography-tandem mass spectrometry and routine clinical biochemistry test were undertaken on the fasting venous blood specimens from 57 subjects. Four relevant clinical traits and 164 CVD-associated metabolites were identified, especially those related to glycerophospholipid metabolism and biosynthesis of unsaturated fatty acids. The machine learning model achieved from an integrated biomarker panel of palmitic amide, oleic acid, 138-pos (the 138th detected metabolomic feature in positive ion mode), phosphatidylcholine, linoleic acid, age, direct bilirubin, and inorganic phosphate, was able to improve the accuracy of CVD risk assessment up to a high satisfactory value of 0.91. The findings indicate that disorders in the metabolic processes of biological membranes and energy are significantly associated with increased risk of vascular damage in CVD patients. With machine learning methods, the pivotal metabolites and clinical biomarkers offer a promising potential for the efficient risk assessment and diagnosis of CVD.

Repetitive transcranial magnetic stimulation elicits weight loss and improved insulin sensitivity in type 2 diabetic rats

BACKGROUND

Type 2 diabetes (T2D) accounts for the majority of diabetes incidences and remains a widespread global chronic disorder. Apart from early lifestyle changes, intervention options for T2D are mainly pharmaceutical.

METHODS

Repetitive transcranial magnetic stimulation (rTMS) has been approved by the FDA as a therapeutic intervention option for major depressive disorders, with further studies also indicating its role in energy metabolism and appetite. Considering its safe and non-invasive properties, we evaluated the effects of rTMS on systemic metabolism using T2D rats.

RESULTS

We observed that rTMS improved glucose tolerance and insulin sensitivity in T2D rats after a 10-day exposure. Improved systemic insulin sensitivity was maintained after a 21-day treatment period, accompanied by modest yet significant weight loss. Circulating serum lipid levels, including those of cholesteryl ester, tryglyceride and ceramides, were also reduced following rTMS application. RNA-seq analyses further revealed a changed expression profile of hepatic genes that are related to sterol production and fatty acid metabolism. Altered expression of hypothalamic genes that are related to appetite regulation, neural activity and ether lipid metabolism were also implicated.

CONCLUSION

In summary, our data report a positive impact of rTMS on systemic insulin sensitivity and weight management of T2D rats. The underlying mechanisms via which rTMS regulates systemic metabolic parameters partially involve lipid utilization in the periphery as well as central regulation of energy intake and lipid metabolism.

Canonical transient receptor potential channels and hypothalamic control of homeostatic functions

Recent molecular biological and electrophysiological studies have identified multiple transient receptor potential (TRP) channels in hypothalamic neurons as critical modulators of homeostatic functions. In particular, the canonical transient receptor potential channels (TRPCs) are expressed in hypothalamic neurons that are vital for the control of fertility and energy homeostasis. Classical neurotransmitters such as serotonin and glutamate and peptide neurotransmitters such as kisspeptin, neurokinin B and pituitary adenylyl cyclase-activating polypeptide signal through their cognate G protein-coupled receptors to activate TPRC 4, 5 channels, which are essentially ligand-gated calcium channels. In addition to neurotransmitters, circulating hormones like insulin and leptin signal through insulin receptor (InsR) and leptin receptor (LRb), respectively, to activate TRPC 5 channels in hypothalamic arcuate nucleus pro-opiomelanocortin (POMC) and kisspeptin (arcuate Kiss1 [Kiss1ARH]) neurons to have profound physiological (excitatory) effects. Besides its overt depolarizing effects, TRPC channels conduct calcium ions into the cytoplasm, which has a plethora of downstream effects. Moreover, not only the expression of Trpc5 mRNA but also the coupling of receptors to TRPC 5 channel opening are regulated in different physiological states. In particular, the mRNA expression of Trpc5 is highly regulated in kisspeptin neurons by circulating estrogens, which ultimately dictates the firing pattern of kisspeptin neurons. In obesity states, InsRs are "uncoupled" from opening TRPC 5 channels in POMC neurons, rendering them less excitable. Therefore, in this review, we will focus on the critical role of TRPC 5 channels in regulating the excitability of Kiss1ARH and POMC neurons in different physiological and pathological states.

Risk factors, prevention and treatment of weight gain associated with the use of antidepressants and antipsychotics: a state-of-the-art clinical review

INTRODUCTION

People with severe mental illness have poor cardiometabolic health. Commonly used antidepressants and antipsychotics frequently lead to weight gain, which may further contribute to adverse cardiovascular outcomes.

AREAS COVERED

We searched MEDLINE up to April 2023 for umbrella reviews, (network-)meta-analyses, trials and cohort studies on risk factors, prevention and treatment strategies of weight gain associated with antidepressants/antipsychotics. We developed 10 clinical recommendations.

EXPERT OPINION

To prevent, manage, and treat antidepressant/antipsychotic-related weight gain, we recommend i) assessing risk factors for obesity before treatment, ii) monitoring metabolic health at baseline and regularly during follow-up, iii) offering lifestyle interventions including regular exercise and healthy diet based on patient preference to optimize motivation, iv) considering first-line psychotherapy for mild-moderate depression and anxiety disorders, v)choosing medications based on medications' and patient's weight gain risk, vi) choosing medications based on acute vs long-term treatment, vii) using effective, tolerated medications, viii) switching to less weight-inducing antipsychotics/antidepressants where possible, ix) using early weight gain as a predictor of further weight gain to inform the timing of intervention/switch options, and x) considering adding metformin or glucagon-like peptide-1 receptor agonists, or topiramate(second-line due to potential adverse cognitive effects) to antipsychotics, or aripiprazole to clozapine or olanzapine.

Leptin gene expression in the brain is associated with the physiological onset of estivation in western sand lance Ammodytes japonicus

Dormancy is an essential ecological characteristic for the survival of organisms that experience harsh environments. Although factors that initiate dormancy vary, suppression or cessation of feeding activities are common among taxa. To distinguish between extrinsic and intrinsic causes of metabolic reduction, we focused on estivation, which occurs in summer when the feeding activity is generally enhanced. Sand lances (genus Ammodytes) are a unique marine fish with a long estivation period from early summer to late autumn. In the present study, we aimed to elucidate the control mechanisms of estivation in western sand lance (A. japonicus), and firstly examined behavioral changes in 8 months including a transition between active and dormant phases. We found that swimming/feeding behavior gradually decreased from June, and completely disappeared by late August, indicating all individuals had entered estivation. Next, we focused on leptin, known as a feeding suppression hormone in various organisms, and examined leptin-A gene (AjLepA) expression in the brain that may regulate the seasonal behavioral pattern. AjLepA expression decreased after 7 days of fasting, suggesting that leptin has a function to regulate feeding in this species. The monthly expression dynamics of AjLepA during the feeding (active) and non-feeding (estivation) periods showed that the levels gradually increased with the onset of estivation and reached its peak when all the experimental fish had estivated. The present study suggests that the suppression of feeding activity by leptin causes shift in the physiological modes of A. japonicus before estivation.

Behavioral tests of the insulin-cholinergic-dopamine link in nucleus accumbens and inhibition by high fat-high sugar diet in male and female rats

It was previously shown in striatal slices obtained from male rats that insulin excites cholinergic interneurons and increases dopamine (DA) release via α4β2 nicotinic receptors on DA terminals. The effect of insulin on DA release was blocked either by maintaining rats on a high sugar-high fat (HS-HF) diet that induced hyperinsulinemia and nucleus accumbens (NAc) insulin receptor insensitivity, or applying the α4β2 antagonist DHβE. In vivo, NAc shell insulin inactivation decreased a glucose lick microstructure parameter indicative of hedonic impact in male and female rats, and prevented flavor-nutrient learning, tested only in males. The HS-HF diet decreased hedonic impact in males but not females, and prevented flavor-nutrient learning, tested only in males. The present study extends testing to more fully assess the translation of brain slice results to the behaving rat. Insulin inactivation by antibody microinjection in NAc shell was found to decrease the number of lick bursts emitted and average lick burst size, measures of incentive motivation and hedonic impact respectively, for a wide range of glucose concentrations in male and female rats. In contrast, the HS-HF diet decreased these lick parameters in males but not females. Follow-up two-bottle choice tests for 10 % versus 40 % glucose showed decreased intake of both concentrations by males but increased intake of 40 % glucose by females. In a further set of experiments, it was predicted that α4β2 receptor blockade would induce the same behavioral effects as insulin inactivation. In females, DHβE microinjection in NAc shell decreased both lick parameters for glucose as predicted, but in males only the number of lick bursts emitted was decreased. DHβE also decreased the number of lick bursts emitted for saccharin by females but not males. Finally, DHβE microinjection in NAc shell decreased flavor-nutrient learning in both sexes. The few discrepancies seen with regard to the hypothesized insulin-nicotinic-dopaminergic regulation of behavioral responses to nutritive sweetener, and its inhibition by HS-HF diet, are discussed with reference to sex differences in DA dynamics, female resistance to diet-induced metabolic morbidities, and extra-striatal cholinergic inputs to NAc.

IGF-1 and insulin receptors in LepRb neurons jointly regulate body growth, bone mass, reproduction, and metabolism

Leptin receptor (LepRb)-expressing neurons are known to link body growth and reproduction, but whether these functions are mediated via insulin-like growth factor 1 receptor (IGF1R) signaling is unknown. IGF-1 and insulin can bind to each other's receptors, permitting IGF-1 signaling in the absence of IGF1R. Therefore, we created mice lacking IGF1R exclusively in LepRb neurons (IGF1RLepRb mice) and simultaneously lacking IGF1R and insulin receptor (IR) in LepRb neurons (IGF1R/IRLepRb mice) and then characterized their body growth, bone morphology, reproductive and metabolic functions. We found that IGF1R and IR in LepRb neurons were required for normal timing of pubertal onset, while IGF1R in LepRb neurons played a predominant role in regulating adult fertility and exerted protective effects against reproductive aging. Accompanying these reproductive deficits, IGF1RLepRb mice and IGF1R/IRLepRb mice had transient growth retardation. Notably, IGF1R in LepRb neurons was indispensable for normal trabecular and cortical bone mass accrual in both sexes. These findings suggest that IGF1R in LepRb neurons is involved in the interaction among body growth, bone development, and reproduction. Though only mild changes in body weight were detected, simultaneous deletion of IGF1R and IR in LepRb neurons caused dramatically increased fat mass composition, decreased lean mass composition, lower energy expenditure, and locomotor activity in both sexes. Male IGF1R/IRLepRb mice exhibited impaired insulin sensitivity. These findings suggest that IGF1R and IR in LepRb neurons jointly regulated body composition, energy balance, and glucose homeostasis. Taken together, our studies identified the sex-dependent complex roles of IGF1R and IR in LepRb neurons in regulating body growth, reproduction, and metabolism.

Role of the intestinal microbiota in contributing to weight disorders and associated comorbidities

SUMMARYThe gut microbiota is a major factor contributing to the regulation of energy homeostasis and has been linked to both excessive body weight and accumulation of fat mass (i.e., overweight, obesity) or body weight loss, weakness, muscle atrophy, and fat depletion (i.e., cachexia). These syndromes are characterized by multiple metabolic dysfunctions including abnormal regulation of food reward and intake, energy storage, and low-grade inflammation. Given the increasing worldwide prevalence of obesity, cachexia, and associated metabolic disorders, novel therapeutic strategies are needed. Among the different mechanisms explaining how the gut microbiota is capable of influencing host metabolism and energy balance, numerous studies have investigated the complex interactions existing between nutrition, gut microbes, and their metabolites. In this review, we discuss how gut microbes and different microbiota-derived metabolites regulate host metabolism. We describe the role of the gut barrier function in the onset of inflammation in this context. We explore the importance of the gut-to-brain axis in the regulation of energy homeostasis and glucose metabolism but also the key role played by the liver. Finally, we present specific key examples of how using targeted approaches such as prebiotics and probiotics might affect specific metabolites, their signaling pathways, and their interactions with the host and reflect on the challenges to move from bench to bedside.

Maid gene dysfunction promotes hyperobesity via the reduction of adipose tissue inflammation in Mc4r gene-deficient mice

The onset and progression mechanisms of metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH) are being studied. We developed and analyzed a new mouse model of obesity by combining maternal Id-like molecule (Maid) and melanocortin-4 receptor (Mc4r) gene deletions. Four mice, each at 12 and 28 weeks of age, were analyzed for each genotype: Maid gene knockout, Mc4r gene knockout, combined Mc4r and Maid gene knockout, and Mc4r gene knockout with a high-fat diet. Mice with a combined deficiency of Mc4r and Maid gene showed significantly more severe obesity compared to all other genotypes, but no liver fibrosis or a decline in metabolic status were observed. In visceral white adipose tissue, Maid and Mc4r gene knockout mice had fewer CD11c-positive cells and lower mRNA expression of both inflammatory and anti-inflammatory cytokines. Furthermore, Maid and Mc4r gene knockout mice showed lower expression of adipocytokines in visceral white adipose tissue and uncoupling protein-1 in scapular brown adipose tissue. The expression of adipocytokines and uncoupling protein-1 is regulated by sympathetic nerve signaling that contribute severe obesity in Maid and Mc4r gene knockout mice. These mechanisms contribute hyperobesity in Maid and Mc4r gene knockout mice.

Differentiating monogenic and syndromic obesities from polygenic obesity: Assessment, diagnosis, and management

Background

Obesity is a multifactorial neurohormonal disease that results from dysfunction within energy regulation pathways and is associated with increased morbidity, mortality, and reduced quality of life. The most common form is polygenic obesity, which results from interactions between multiple gene variants and environmental factors. Highly penetrant monogenic and syndromic obesities result from rare genetic variants with minimal environmental influence and can be differentiated from polygenic obesity depending on key symptoms, including hyperphagia; early-onset, severe obesity; and suboptimal responses to nontargeted therapies. Timely diagnosis of monogenic or syndromic obesity is critical to inform management strategies and reduce disease burden. We outline the physiology of weight regulation, role of genetics in obesity, and differentiating characteristics between polygenic and rare genetic obesity to facilitate diagnosis and transition toward targeted therapies.

Methods

In this narrative review, we focused on case reports, case studies, and natural history studies of patients with monogenic and syndromic obesities and clinical trials examining the efficacy, safety, and quality of life impact of nontargeted and targeted therapies in these populations. We also provide comprehensive algorithms for diagnosis of patients with suspected rare genetic causes of obesity.

Results

Patients with monogenic and syndromic obesities commonly present with hyperphagia (ie, pathologic, insatiable hunger) and early-onset, severe obesity, and the presence of hallmark characteristics can inform genetic testing and diagnostic approach. Following diagnosis, specialized care teams can address complex symptoms, and hyperphagia is managed behaviorally. Various pharmacotherapies show promise in these patient populations, including setmelanotide and glucagon-like peptide-1 receptor agonists.

Conclusion

Understanding the pathophysiology and differentiating characteristics of monogenic and syndromic obesities can facilitate diagnosis and management and has led to development of targeted pharmacotherapies with demonstrated efficacy for reducing body weight and hunger in the affected populations.