Regulation Of Feeding Behavior Research Articles

Glial cell changes in the corpus callosum in chronically-starved mice

Anorexia nervosa (AN) is characterized by emaciation, hyperactivity, and amenorrhea. Imaging studies in AN patients have revealed reductions in grey and white matter volume, which correlate with the severity of neuropsychological deficits. However, the cellular basis for the observed brain atrophy is poorly understood. Although distinct hypothalamic centers, including the arcuate nucleus (ARC) are critically involved in regulating feeding behavior, little is known about potential hypothalamic modifications in this disorder. Since glia e.g. astrocytes and microglia influence neuronal circuits, we investigated the glial changes underlying pathophysiology of starvation in the corpus callosum (CC) and hypothalamus. Female mice were given a limited amount of food once a day and had unlimited access to a running wheel until a 20% weight reduction was achieved (acute starvation). This weight reduction was maintained for two weeks to mimic chronic starvation. Immunohistochemistry was used to quantify the density of astrocytes, microglia, oligodendrocytes, and the staining intensity of neuropeptide Y (NPY), a potent orexigenic peptide. Chronic starvation induced a decreased density of OLIG2+ oligodendrocytes, GFAP+ astrocytes, and IBA1+ microglia in the CC. However, the densities of glial cells remained unchanged in the ARC following starvation. Additionally, the staining intensity of NPY increased after both acute and chronic starvation, indicating an increased orexigenic signaling. Chronic starvation induced glial cell changes in the CC in a mouse model of AN suggesting that glia pathophysiology may play a role in the disease.

Characterization of expression response in post-prandial situation of food sensing system in rainbow trout (Oncorhynchus mykiss) fed a plant-based diet: Focus on free fatty acid receptors and their signaling pathways

Recently identified and characterized in rainbow trout (Oncorhynchus mikyss), the main gustatory receptors for fatty acid, known as free fatty acids receptor (FFAR) 1 and 2, may play a crucial role in nutrient detection and regulation of feeding behavior. However, our understanding of their post-prandial roles remains limited. This study investigates the impact of a single meal (acute effect) with an alternative plant-based diet (vegetal diet, V diet devoid of fish meal and fish oil) on the food detection mechanisms in trout. After 30 days of feeding with commercial-like diet (C diet made up of a mix of fish meal, fish oil and plant ingredients) followed 5 days of fasting, we conducted a post-prandial kinetic experiment after single meal with C or V diet. We assessed the expression pattern of ffar genes, their associated signaling pathways (calcium and indolamine pathways) in the tongue along with the expression pattern of appetite-regulating neuropeptides in the hypothalamus. Additionally, we evaluated central activity through brain activity markers in the telencephalon of trout at various post-meal time points, including 20 min, 2, 6, 10 and 24 h. Our results revealed that the diet nature (C vs V) influences the expression of ffar genes, while some paralogs of ffar2 (ffar2a2 and ffar2b1.2) were early up-regulated by V diet, ffar2b1.1 and ffar1 were latter up-regulated by C diet. Differential regulations in the tongues of V diet fish were also observed on calcium signaling and an early alteration in serotonin turnover. The expression increase of neuropeptide npya from 6 to 10 h after meal, could suggest a greater sensation of hunger in fish fed the C diet. Finally, our findings suggest that rainbow trout exhibit a keen ability to detect a novel feed after a single meal with V diet at the brain level, particularly in areas associated with decision-making and behavior control. Altogether, results not only show that the integrative feeding response appears to be dysregulated by V diet, but also highlight the noteworthy sensitivity of nutrient detection mechanisms in rainbow trout to new food sources. FFARs may play a role in finely discerning diets with varying levels of ω-3 LC-PUFAs in rainbow trout. This heightened detection sensitivity holds the potential to significantly influence the regulation of feeding behavior and food detection in farmed fish.

Progesterone-Induced Hyperphagia is Attenuated by <i>Myrica nagi</i> through Dopaminergic and Serotonergic Modulation in Female Mice

Regulation of feeding behavior to control obesity is an alternative line of research for the treatment of obesity and diabetes. Compared to other models of obesity, the progesterone-induced obesity model is more specific to the female population; it focuses on the eating behavior and behavioral and emotional changes associated with progesterone. We aimed to study the changes in feeding behavior upon progesterone administration and the effects of Myrica nagi Thunb (Myricaceae) extracts on these changes. Further, this study aimed to provide insights into the progesterone-induced hyperphagia modulated by serotonergic and dopaminergic systems. In this study, experimental obesity was induced in female mice by treating with a high dose of progesterone for 28 days (sub-chronic study) followed by the assessment of parameters such as food consumption behavior, behavioral parameters including ambulatory movements, rearing, and grooming, and biochemical parameters such as lipid profile (total cholesterol, triglycerides, high-density lipoprotein, and low-density lipoprotein), liver parameters (alkaline phosphatase and serum glutamic pyruvic transaminase), serotonin and dopamine levels, and liver histopathology. The sub-chronic administration of progesterone, via the subcutaneous route, induced significant hyperphagia and promoted fat accumulation. Even though we did not find significant differences in food intake between mice in the control group and progesterone-treated groups, the final weight in the progesterone-administered groups increased, signifying the impact of this progesterone-induced obesity model. Treatment with MEMN extract reversed the progesterone-induced effects suggesting that herbal extracts can be exploited as serotonergic and dopaminergic agents for the treatment of progesterone-induced eating disorders, especially in the female population.

Ginkgo biloba extract modulates astrocytic and microglial recruitment in the hippocampus and hypothalamus of menopause-induced ovariectomized rats

BackgroundChanges in steroid hormone levels associated with menopause are known to affect body composition, with increased accumulation of visceral fat and impaired actions of appetite-regulating neuropeptides. Anti-obesogenic, antioxidant, anti-inflammatory and neuromodulatory properties have been attributed to Ginkgo biloba extract (GbE) oral supplementation. Hypothesis/purposeWe investigated in menopause-induced ovariectomized rats the effects of GbE oral supplementation on microglial reactivity and astrocyte recruitment in hippocampal and hypothalamic subregions involved in the regulation of feeding behavior and energy homeostasis. Study design/methodsOvariectomy (Ovx) or false-Ovx (Sham) surgery were performed in 2-month-old female Wistar rats. Sixty days after surgery, Ovx rats were gavaged daily for 14 days with either saline (Ovx + Veh) or GbE 500 mg/Kg (Ovx + GbE). Rats were subsequently sacrificed, brains harvested and subjected to immunohistochemistry and immunofluorescence analyses. ResultsOvx increased microglial reactivity in CA1, CA3 and dentate gyrus (DG) in the dorsal hippocampal formation (dHF), as well as in DG in the ventral hippocampal formation (vHF).Additionally, Ovx reduced astrocyte count in dHF CA3. The disturbances found in Ovx + Veh versus Sham were not found in Ovx + GbE versus Sham. Furthermore, higher astrocyte counts in DG of both dHF and vHF were found in Ovx + GbE as compared to Ovx + Veh. In the hypothalamus, Ovx + Veh showed reduced microglial reactivity in the arcuate (ARC) and ventromedial (VMH) nuclei as compared to Ovx + GbE. Ovx + GbE rats presented higher astrocyte counts in ARC compared to Sham rats. ConclusionOur results show for the first time in a rodent model of menopause that GbE supplementation modulates astrocyte and microglial recruitment and reactivity in hippocampal and hypothalamic subregions involved in feeding behavior and energy homeostasis. Future research employing other experimental models may further elucidate whether GbE supplementation possesses therapeutic properties upon glial cell reactivity to potentially alleviate changes in energy homeostasis associated with menopause.

Sublethal concentrations of pymetrozine reduce Sogatella furcifera transmission of Southern rice black-streaked dwarf virus.

The transmission of plant viruses is closely associated with the specific probing behaviors of the vectors. Pymetrozine is a pyridine azomethine insecticide that interferes with nervous regulation of feeding behavior of piercing-sucking insects. This study aimed to evaluate the potential of sublethal concentrations of pymetrozine in reducing the transmission of Southern rice black-streaked dwarf virus (SRBSDV) by the planthopper Sogatella furcifera. Laboratory assays showed that both acquisition and inoculation rates of SRBSDV decreased significantly in the planthoppers feeding on plants treated with lethal concentrations 10% and 50% (LC10 and LC50 ) pymetrozine compared with the insects feeding on the control plants, for which significant effects of pymetrozine concentration and time post-treatment were detected. Honeydew excretion of the planthoppers showed significant reduction with increasing concentration of the insecticide but no significant association with time post-treatment. Electrical penetration graph recordings revealed that total durations of each waveform in both acquisition and inoculation were significantly affected by pymetrozine treatment, with total durations of non-probing (NP), penetration initiation (N1), and extracellular activity (N3) elongated whereas those of salivation (N2) and phloem-related activities (N4-a and N4-b) shortened. Additionally, both acquisition and inoculation rates were significantly lower at 168 h than at 6 h post-treatment. The results indicate that sublethal concentrations of pymetrozine reduce SRBSDV transmission, which is associated with reduction in feeding and alteration in probing behaviors characterized by the prolonged non-probing, penetration initiation and extracellular activity and shortened salivation and phloem-related activities. © 2023 Society of Chemical Industry.

CRH neurons in the lateral hypothalamic area regulate feeding behavior of mice

Food cues serve as pivotal triggers for eliciting physiological responses that subsequently influence food consumption. The magnitude of response induced by these cues stands as a critical determinant in the context of obesity risk. Nonetheless, the underlying neural mechanism that underpins how cues associated with edible food potentiate feeding behaviors remains uncertain. In this study, we revealed that corticotropin-releasing hormone (CRH)-expressing neurons in the lateral hypothalamic area played a crucial role in promoting consummatory behaviors in mice, shedding light on this intricate process. By employing an array of diverse assays, we initially established the activation of these neurons during feeding. Manipulations using optogenetic and chemogenetic assays revealed that their activation amplified appetite and promoted feeding behaviors, whereas inhibition decreased them. Additionally, our investigation identified downstream targets, including the ventral tegmental area, and underscored the pivotal involvement of the CRH neuropeptide itself in orchestrating this regulatory network. This research casts a clarifying light on the neural mechanism underlying the augmentation of appetite and the facilitation of feeding behaviors in response to food cues. VIDEO ABSTRACT.

CD8 cytotoxic T-cell infiltrates and cellular damage in the hypothalamus in human obesity

Rare cases of paraneoplastic obesity in children suggest sporadic obesity might also arise from an adaptive immune cell-mediated mechanism. Since the hypothalamus is a central regulator of feeding behavior and energy expenditure, we quantified lymphocytic inflammation in this region in a cohort of obese and non-obese human post-mortem brains. We report that CD8-positive cytotoxic T-cells are increased in hypothalamic median eminence/arcuate nucleus (ME/Arc) and bed nucleus of the stria terminalis in 40% of obese compared to non-obese patients, but not in other hypothalamic nuclei or brain regions. CD8 T-cells were most abundant in individuals with concurrent obesity and diabetes. Markers of cytotoxic T-cell induced damage, activated caspase 3 and poly-ADP ribose, were also elevated in the ME/Arc of obese patients. To provoke CD8 cytotoxic T-cell infiltrates in ventromedial region of hypothalamus in mice we performed stereotactic injections of an adeno-associated virus expressing immunogenic green fluorescent protein or saline. AAV but not saline injections triggered hypothalamic CD8 T-cell infiltrates associated with a rapid weight gain in mice recapitulating the findings in human obesity. This is the first description of the neuropathology of human obesity and when combined with its reconstitution in a mouse model suggests adaptive immunity may drive as much as 40% of the human condition.

Brain-derived neurotrophic factor (BDNF) activates PI3K-AKT-mTOR signaling via hypothalamic TrkB receptors to reduce feeding in Siberian sturgeon (Acipenser baerii)

Although Brain-derived neurotrophic factor (BDNF) has been identified as an orexigenic peptide in zebrafish, its role in regulating feeding behavior in other fish species is still unclear. This study aimed to investigate the regulatory role of BDNF in feeding behavior of Siberian sturgeon (Acipenser baerii). The bdnf and its receptor TrkB genes (Abbdnf and AbTrkB) of Siberian sturgeon were cloned and found to be most highly expressed in the hypothalamus. Short- and long-term fasting experiments showed that Abbdnf and AbTrkB mRNA levels decreased in the hypothalamus after fasting, but increased after refeeding, consistent with the pattern observed for anorexigenic peptides. The NGF(nerve growth factor) structural domain has an important role in mediating the binding of BDNF to the TrkB receptor. To explore the feeding regulatory role of BDNF, recombinant AbBDNFNGF protein was expressed using prokaryotic expression system. Intraperitoneal injection of AbBDNFNGF suppressed cumulative food intake at 1 h, 3 h, and 6 h after administration, and resulted in upregulation of anorexigenic peptides (pomc and leptin) mRNA and downregulation of orexigenic peptides (npy and agrp) mRNA in both central and peripheral tissues. Additionally, AbBDNFNGF injection led to activation of TrkB receptors and pi3k-akt-mtor signaling pathway in the hypothalamus. Overall, this study confirms the anorexigenic effect of BDNF in Siberian sturgeon.

Food-induced brain activity in adult obesity: a quantitative electroencephalographic study

BACKGROUND Obesity may be associated with declined food consumption control through neurological and behavioral processes, as well as heightened responsiveness of the brain’s reward systems. Performing neuroimaging and neurophysiological methods such as electroencephalography (EEG) can examine the connection between brain function and behavior. This study aimed to identify brain regulation of feeding behavior to food cues, which could be a potential neuromodulatory intervention target in adult obesity.
 METHODS This cross-sectional study was conducted at Cipto Mangunkusumo Hospital, Jakarta, involving 40 adults with obesity. EEG analysis was performed to measure electrophysiological brain activity during eyes-open condition and during exposure to high-calorie food cues. Student’s t-tests were performed to identify any significant differences between the groups (p<0.05).
 RESULTS Beta waves in the frontal (channel F7) and gamma waves in the central (channels C3 and C4) and parietal (channels P3 and P4) regions were significantly increased during food cues compared to resting state/eyes-open condition without stimulation. Theta waves in the frontal (channels F7 and F8), central (channel C3), and parietal (channels P3 and P4) regions and alpha waves in the central (channels C3 and C4) and parietal (channels P3 and P4) regions were significantly decreased during food cues compared with resting state.
 CONCLUSIONS In adults with obesity, increased beta activity in the frontal and gamma in the central and parietal regions suggested increased food-cue awareness and heightened attentional focus toward food stimuli. Additionally, decreased alpha and theta activities in frontal regions could underline deficits in executive functions and higher motivation.

Transcriptomics analysis unveils key potential genes associated with brain development and feeding behavior in the hypothalamus of L-citrulline-fed broiler chickens

High ambient temperature is a major environmental stressor affecting poultry production, especially in the tropical and subtropical regions of the world. Nutritional interventions have been adopted to combat thermal stress in poultry, including the use of amino acids. L-citrulline is a nonessential amino acid that is involved in nitric oxide generation and thermoregulation, however, the molecular mechanisms behind L-citrulline's regulation of body temperature are still unascertained. This study investigated the global gene expression in the hypothalamus of chickens fed either basal diet or L-citrulline-supplemented diets under different housing temperatures. Ross 308 broilers were fed with basal diet (CON) or 1% L-citrulline diet (LCT) from day-old, and later subjected to 2 environmental temperatures in a 2 by 2 factorial arrangement as follows; basal diet-fed chickens housed at 24°C (CON-TN); L-citrulline diet-fed chickens housed at 24°C (LCT-TN); basal diet-fed chickens housed at 35°C (CON-HS), and L-citrulline diet-fed chickens housed at 35°C (LCT-HS) from 22 to 42 d of age. At 42-days old, hypothalamic tissues were collected for mRNA analyses and RNA sequencing. A total of 1,019 million raw reads were generated and about 82.59 to 82.96% were uniquely mapped to genes. The gene ontology (GO) term between the CON-TN and LCT-TN groups revealed significant enrichments of pathways such as central nervous system development, and Wnt signaling pathway. On the other hand, GO terms between the CON-HS and LCT-HS groups revealed enrichments in the regulation of corticosteroid release, regulation of feeding behavior, and regulation of inflammatory response. Several potential candidate genes were identified to be responsible for central nervous system development (EMX2, WFIKKN2, SLC6A4 Wnt10a, and PHOX2B), and regulation of feed intake (NPY, AgRP, GAL, POMC, and NMU) in chickens. Therefore, this study unveils that L-citrulline can influence transcripts associated with brain development, feeding behavior, energy metabolism, and thermoregulation in chickens raised under different ambient temperatures.

Family connectedness and sexual minority Asian Americans' eating behavior regulation

To date, psychosocial and interpersonal protective factors such as family connectedness have received little attention in studies of eating behaviors among sexual minority Asian Americans. Therefore, we investigated associations of family connectedness and two types of eating behavior regulation motives and the moderating role of individualism in these associations among 134 sexual minority Asian American young adults. Linear regression models assessed the main and interaction effects of family connectedness and individualism on introjected and identified eating behavior regulation motives. We observed a significant interaction effect between family connectedness and individualism only on introjected regulation. For participants with low levels of individualism, those who reported high levels of family connectedness had lower scores for introjected regulation of eating behavior. The findings of this study highlight the importance of examining strengths related to sexual minority Asian Americans by demonstrating the important role family connectedness plays in eating behavior regulation motives, particularly for those with lower individualism.

ATP-sensitive inward rectifier potassium channels regulate secretion of pro-feeding salivary proteins in the lone star tick (Amblyomma americanum)

Understanding the physiological and molecular regulation of tick feeding is necessary for developing intervention strategies to curb disease transmission by ticks. Pharmacological activation of ATP-gated inward rectifier potassium (KATP) channels reduced fluid secretion from isolated salivary gland and blood feeding in the lone star tick, Amblyomma americanum, yet the temporal expression pattern of KATP channel proteins remained unknown. KATP channels were highly expressed in type II and III acini in off-host stage and early feeding phase ticks, yet expression was reduced in later stages of feeding. We next assessed KATP channel regulation of the secreted proteome of tick saliva. LC-MS/MS analysis identified 40 differentially secreted tick saliva proteins after exposure to KATP activators or inhibitors. Secretion of previously validated tick saliva proteins that promote tick feeding, AV422, AAS27, and AAS41 were significantly reduced by upwards of 8 log units in ticks exposed to KATP channel activators when compared to untreated ticks. Importantly, activation of KATP channels inhibited tick feeding and vice versa for KATP channel inhibitors. Data indicate KATP channels regulate tick feeding biology by controlling secretion of pro-feeding proteins that are essential during early feeding phases, which provides insights into physiological and molecular regulation of tick feeding behavior.

Unraveling the periprandial changes in brain serotonergic activity and its correlation with food intake-related neuropeptides in rainbow trout Oncorhynchus mykiss.

This study explored changes in brain serotonin content and activity together with hypothalamic neuropeptide mRNA abundance around feeding time in rainbow trout, as well as the effect of one-day fasting. Groups of trout fed at two (ZT2) and six (ZT6) hours after lights on were sampled from 90 minutes before to 240 minutes after feeding, while additional groups of non-fed trout were also included in the study. Changes in brain amine and metabolite contents were measured in hindbrain, diencephalon and telencephalon, while in the diencephalon the mRNA abundance of tryptophan hydroxylase (tph1, tph2), serotonin receptors (5htr1a, 5htr1b and 5htr2c) and several neuropeptides (npy, agrp1, cartpt, pomca1, crfb) involved in the control of food intake were also assessed. The results showed changes in the hypothalamic neuropeptides that were consistent with the expected role for each in the regulation of food intake in rainbow trout. Serotonergic activity increased rapidly at the time of food intake in the diencephalon and hindbrain and remained high for much of the postprandial period. This increase in serotonin abundance was concomitant with elevated levels of pomca1 mRNA in the diencephalon, suggesting that serotonin might act on brain neuropeptides to promote a satiety profile. Furthermore, serotonin synthesis and neuronal activity appear to increase already before the time of feeding, suggesting additional functions for this amine before and during food intake. Exploration of serotonin receptors in the diencephalon revealed only small changes for gene expression of 5htr1b and 5htr2c receptors during the postprandial phase. Therefore, the results suggest that serotonin may play a relevant role in the regulation of feeding behavior in rainbow trout during periprandial time, but a better understanding of its interaction with brain centers involved in receiving and processing food-related signals is still needed.

The role of functional and structural properties of the nucleus accumbens subregions in eating behavior regulation of bulimia nervosa.

Although studies have demonstrated the involvement of the nucleus accumbens (NAc) in the neurobiology of eating disorders, its alterations in bulimia nervosa (BN) remain largely unknown. This study investigated the structural and functional properties of NAc in patients with BN. Based on the resting-state functional MRI and high-resolution anatomical T1-weighted imaging data acquired from 43 right-handed BN patients and 40 sex-, age- and education-matched right-handed healthy controls (HCs), the group differences in gray matter volume (GMV) and fractional amplitude of low-frequency fluctuation (fALFF) in slow-4 and -5 bands and functional connectivity (FC) of NAc subregions (core and shell) were compared. The relationships between MRI and clinical data were explored in the BN group. Compared with HCs, BN patients showed preserved GMV, decreased fALFF in slow-5 band of the left NAc core and shell, decreased FC between left NAc core and right caudate, and increased FC between all NAc subregions and frontal regions, between all NAc subregions (except the right NAc core) and the supramarginal gyrus (SMG), and between right NAc shell and left middle temporal gyrus. FC between the NAc and SMG was correlated with emotional eating behaviors. Our study revealed preserved GMV, local neuronal activity reduction and functional network reorganization of the NAc in BN. The functional network reorganization of the NAc mainly occurred in the frontal cortex and was correlated with emotional eating behavior. These findings may provide novel insights into the BN using NAc as an entry point. Although studies have demonstrated the involvement of the nucleus accumbens (NAc) in the neurobiology of eating disorders, its alterations in bulimia nervosa (BN) remain largely unknown. We used a multimodal MRI technique to systematically investigate structural and functional alterations in NAc subregions of BN patients and explored the associations between such alterations and maladaptive eating behaviors, hoping to provide novel insights into BN.

Regulation of feeding and energy homeostasis by clock-mediated Gart in Drosophila

Feeding behavior is essential for growth and survival of animals; however, relatively little is known about its intrinsic mechanisms. Here, we demonstrate that Gart is expressed in the glia, fat body, and gut and positively regulates feeding behavior via cooperation and coordination. Gart in the gut is crucial for maintaining endogenous feeding rhythms and food intake, while Gart in the glia and fat body regulates energy homeostasis between synthesis and metabolism. These roles of Gart further impact Drosophila lifespan. Importantly, Gart expression is directly regulated by the CLOCK/CYCLE heterodimer via canonical E-box, in which the CLOCKs (CLKs) in the glia, fat body, and gut positively regulate Gart of peripheral tissues, while the core CLK in brain negatively controls Gart of peripheral tissues. This study provides insight into the complex and subtle regulatory mechanisms of feeding and lifespan extension in animals.

352-OR: Regulation of Melanocortin Receptor 4 (MC4R) Ciliary Trafficking

The primary cilium, a hair-like projection at the surface of nearly every cell, functions as a signaling antenna in processes as diverse as vision and body weight homeostasis. Obesity is a cardinal symptom of many ciliopathies including Bardet-Biedl Syndrome (BBS). While we are beginning to understand how cilia participate in body weight homeostasis, the molecular pathway that leads to obesity in BBS patients remains unclear. We now know that the melanocortin receptor 4, a GPCR that regulates feeding behavior, localizes to cilia in hypothalamic neurons. Meanwhile, most BBS proteins assemble or regulate the BBSome, a protein complex that removes activated signaling receptors from cilia. To characterize the stimuli and mechanisms that regulate MC4R trafficking in and out of cilia, we recapitulated MC4R trafficking in ciliated cell lines amenable to rapid manipulation. Surprisingly, levels of MC4R in cilia remain under the detection limit in most cells unless treated with an inverse agonist of MC4R. In addition, interference with BBSome function also increases ciliary MC4R levels in all cells. Thus, the tonic activity of MC4R promotes the constitutive clearance of MC4R from cilia via BBSome-mediated exit. These results suggest that artificially increasing the ciliary levels of MC4R may augment its signaling activity. To selectively recognize activated GPCRs, the BBSome relies on specific ubiquitin chains linked at lysine 63 (K63Ub chains) that become attached onto activated GPCRs via β-arrestin-associated ubiquitin ligases. Depletion of β-arrestin blocked the constitutive exit of MC4R from cilia and mutation of ubiquitin acceptor lysines from MC4R and MRAP2 results in a measurable increase in the ciliary levels of MC4R. In addition, targeting a protease that specifically cleaves K63Ub chains to cilia completely blocks the exit of MC4R from cilia. We conclude that the tonically active MC4R is ubiquitinated in cilia and actively removed by the BBSome. Disclosure M.Nachury: None. Funding American Diabetes Association (1-20-VSN-03)

Whole-brain monosynaptic inputs and outputs of leptin receptor b neurons of the nucleus tractus solitarii in mice

The nucleus tractus solitarii (NTS) is the primary central station that integrates visceral afferent information and regulates respiratory, gastrointestinal, cardiovascular, and other physiological functions. Leptin receptor b (LepRb)-expressing neurons of the NTS (NTSLepRb neurons) are implicated in central respiration regulation, respiratory facilitation, and respiratory drive enhancement. Furthermore, LepRb dysfunction is involved in obesity, insulin resistance, and sleep-disordered breathing. However, the monosynaptic inputs and outputs of NTSLepRb neurons in whole-brain mapping remain to be elucidated. Therefore, the exploration of its whole-brain connection system may provide strong support for comprehensively understanding the physiological and pathological functions of NTSLepRb neurons. In the present study, we used a cell type-specific, modified rabies virus and adeno-associated virus with the Cre-loxp system to map monosynaptic inputs and outputs of NTSLepRb neurons in LepRb-Cre mice. The results showed that NTSLepRb neurons received inputs from 48 nuclei in the whole brain from five brain regions, including especially the medulla. We found that NTSLepRb neurons received inputs from nuclei associated with respiration, such as the pre-Bötzinger complex, ambiguus nucleus, and parabrachial nucleus. Interestingly, some brain areas related to cardiovascular regulation—i.e., the ventrolateral periaqueductal gray and locus coeruleus—also sent a small number of inputs to NTSLepRb neurons. In addition, anterograde tracing results demonstrated that NTSLepRb neurons sent efferent projections to 15 nuclei, including the dorsomedial hypothalamic nucleus and arcuate hypothalamic nucleus, which are involved in regulation of energy metabolism and feeding behaviors. Quantitative statistical analysis revealed that the inputs of the whole brain to NTSLepRb neurons were significantly greater than the outputs. Our study comprehensively revealed neuronal connections of NTSLepRb neurons in the whole brain and provided a neuroanatomical basis for further research on physiological and pathological functions of NTSLepRb neurons.

1608-P: Phenotype of Liver-Specific MC3R Knockout Mice

The melanocortin 3 receptor (MC3R) is a key regulator of energy homeostasis and feeding behavior. Global Mc3r knockout mice exhibit greater fat mass and reduced lean mass. Our previous research has found that Mc3r transcripts can be detected in liver and the MC3R deficiency phenotype is partially reversed in liver-specific MC3R recovery mice on a chow diet, in both male and female mice, and high fat diet, in females only. To further examine the role of hepatic MC3R, we produced a liver-specific Mc3r knockout model by crossing mice expressing albumin-Cre recombinase (Alb-Cre+/+) to mice with a floxed Mc3r gene (LoxP+/+), and placed them on a 45 kcal% energy from fat diet for 12 weeks. Female liver-specific Mc3r-deficient mice with diet-induced obesity displayed nonsignificant trends towards worsened glucose tolerance during a glucose tolerance test (glucose AUC Lox+/+, Alb-Cre+/+: n=10, 24036±1644; Alb-Cre+/+: n=10, 19745±1364; BL/6: n=11, 21072±1152 min*mg/dL, p=0.059) and insulin resistance during a glucose tolerance test (glucose AUC LoxP+/+, Alb-Cre+/+: n=10, 14938±812.2;Alb-Cre+/+: n=14, 13062±850; BL/6: n=11, 11725±1024 min*mg/dL, p=0.12), but no differences in morning serum C-peptide (LoxP+/+, Alb-Cre+/+: n=8, 0.74±0.07; Alb-Cre+/+: n=4, 0.55±0.15; BL/6: n=8, 0.29±0.05 ng/mL, p=0.32). Similar patterns were observed for total food consumption (LoxP+/+, Alb-Cre+/+: n=10, 37.2±1.2; Alb-Cre+/+: n=15, 34.5±0.7; BL/6: n=10, 35.7±1.4 g/15 days, p=0.082), with no differences in feeding efficiency (LoxP+/+, Alb-Cre+/+: n=10, 0.027±0.008; Alb-Cre+/+: n=15, 0.009±0.011; BL/6: n=10, 0.017±0.025 g/kcal, p=0.19). No notable trends were observed in male mice. These data suggest that hepatic Mc3r deficiency alone is at most a minor contributor to the obesity phenotypes associated with HFD-treated Mc3r-deficient mice. Additional analysis of tissue samples from these mice and future studies examining Mc3r function in the liver will further elucidate the role of hepatic MC3R. Disclosure J.Chen: None. J.K.Elmquist: Research Support; Regeneron Pharmaceuticals Inc. J.A.Yanovski: Research Support; Hikma Pharmaceuticals, Rhythm Pharmaceuticals, Inc., Soleno Therapeutics, Inc., Versanis Bio Inc. T.P.Patel: None. A.Jain: None. D.Elizondo: None. E.K.Altman: None. N.Tugarinov: None. M.Hollis: None. R.Roberson: None. A.Caron: None.

Azelaic acid induces cholecystokinin secretion and reduces fat-rich food preference via activation of Olfr544

Olfactory receptor 544 (Olfr544) is expressed in extra-nasal tissues and has been shown to reduce adiposity and shift fuel preference to fats. Here, we investigated whether Olfr544 regulates feeding behavior. Azelaic acid increased cholecystokinin (CCK) secretion ex vivo and in vivo by Olfr544 dependently. In a two-food choice study, oral administration of azelaic acid reduced high fat diet (HFD) intake and increased normal diet (ND) intake, which was abolished in Olfr544-knockout mice. In a two-bottle preference test, the oral administration of azelaic acid reduced the intake of linoleic acid solution while increasing the intake of control solution (xanthan gum) and the effect of azelaic acid disappeared in Olfr544-knockout mice. Intraperitoneal injection of proglumide, a CCK-1/2 receptor antagonist, negated the effect of azelaic acid in reducing fat preference. Collectively, our findings suggested that Olfr544 activation by azelaic acid reduced calorie-rich high-fat food intake mediated, at least in part, by CCK secretion.

The cholinergic pathway transmits signals of neuropeptide F to regulate feeding of Ostrinia furnacalis larvae.

Feeding is the basis of animal survival and reproduction. In insects, the neuropeptide F (NPF), a homologous polypeptide of NPY in vertebrates, plays an important role in regulation of feeding behavior. However, relatively little has been known about the molecular mechanism of feeding. In this study, we show that the cholinergic pathway is very important in signaling transmission of NPF feeding regulation in Ostrinia furnacalis larvae, in which the choline acetyltransferase (ChAT), the vesicular acetylcholine transporter (vAChT) in presynaptic membrane and the nicotinic acetylcholine receptor (nAChR) in postsynaptic membrane are positively regulated by NPF, while the ace1 and ace2 encoding the acetylcholinesterase (AChE) are negatively regulated by NPF, leading to a balance of acetylcholine (ACh)-the excitatory transmitter. More, the cholinergic pathway further transmits signaling to the downstream pathways of the phosphoInositide-3 kinase (PI3K) and the cAMP responsive element binding protein (CREB), respectively. The cholinergic transmission, positively regulated by NPF, is involved in feeding of O. furnacalis larvae via downstream PI3K and the CREB pathways, respectively. The deexcitation of cell cholinergic pathway or inhibition of PI3K and CREB lead to decreases of larval feeding amount. © 2023 Society of Chemical Industry.