Body Weight Regulation Research Articles

Mechanisms of Action of Bariatric Surgery on Body Weight Regulation.

Bariatric surgery is an effective treatment modality for obesity and obesity-associated complications. Weight loss after bariatric surgery was initially attributed to anatomic restriction or reduced energy absorption, but now it is understood that surgery treats obesity by influencing the subcortical areas of the brain to lower adipose tissue mass. There are three major phases of this process: initially the weight loss phase, followed by a phase where weight loss is maintained, and in a subset of patients a phase where weight is regained. These phases are characterized by altered appetitive behavior together with changes in energy expenditure. The mechanisms associated with the rearrangement of the gastrointestinal tract include central appetite control, release of gut peptides, change in microbiota and bile acids. However, the exact combination and timing of signals remain largely unknown.

Relationship between Body Condition Score, Reproductive Indicators, and Leptin and Erythropoietin Hormone Levels in Iraqi Awassi Ewes

The experiment was conducted using 35 Awassi ewes with an average body weight 52±2.5 kg. The females were divided into three groups according to the body condition score 3 (overweight, medium, lean) represented by groups 1, 2, and 3 respectively. The medium was the highest percentage, as it reached 71.42% of the total number of animals. This percentage was in accordance with a high pregnancy rate compared to lean and overweight animals, as the pregnancy rate reached ewes from the examination. The first and second examinations were 64% and 24% respectively. The concentration of leptin and erythropoietin were measured in ewes before, during and after applying the vaginal sponges. Barrenness rate had (100%, 24.13% and 100%) in group 1,2 and 3 respectively. The results were high in leptin hormone in the Body Condition Score (BCS) group. 2, especially after withdrawing the vaginal sponges. While there was no significant increase (P>0.05) in erythropoietin hormone before and during applying vaginal sponges. Body Condition Score (BCS 2) ewes had a higher conception rate than Body Condition Score (BCS) 1 and 3 ewes. Leptin and progesterone both play important roles in the regulation of sheep body weight, with higher levels of progesterone resulting in higher levels of leptin.

Food reward associations with motivational eating behavior traits and body mass index in Portuguese former elite athletes.

Motivational eating behavior traits (i.e. eating motivations and intuitive eating) have an important role in body weight regulation, as do food reward processes. Their associations might help explain different responses to food stimulus in the current environment but have never been explored. This study's primary goal was to investigate food reward associations with eating motivations, intuitive eating dimensions and body mass index in former Portuguese elite athletes with overweight/obesity. As a first step, a cultural adaptation of the Leeds Food Preference Questionnaire (LFPQ) was created and validated in an online-surveyed Portuguese sample. Step 1: Analysis from an online survey (N = 348; 69.8% female) conducted to validate the food images from the cultural adaptation of the LFPQ showed that most food images were properly recognized in terms of their fat and sweet content by the Portuguese population, except for some savory items. Step 2: Regarding our primary analysis in 94 former elite athletes with overweight/obesity, self-determined motivations to regulate eating and (to a lower extent) more body-food congruent choices (both markers for healthier eating behaviors) were associated with more favorable food reward outcomes, as opposed to non-self-determined motivations. Less emotional (more intuitive) eaters presented higher implicit wanting for low-fat sweet foods compared to more emotional eaters. These findings suggest LFPQ usefulness to evaluate food preferences and detect relevant associations between food reward and motivational eating behavior traits in former elite athletes with overweight/obesity. Health professionals are encouraged to create need-supportive environments that foster self-determined motivations and help individuals make healthier food choices. © 2023 Society of Chemical Industry.

Neurodevelopmental Programming of Adiposity: Contributions to Obesity Risk.

This review analyzes the published evidence regarding maternal factors that influence the developmental programming of long-term adiposity in humans and animals via the central nervous system (CNS). We describe the physiological outcomes of perinatal underfeeding and overfeeding and explore potential mechanisms that may mediate the impact of such exposures on the development of feeding circuits within the CNS-including the influences of metabolic hormones and epigenetic changes. The perinatal environment, reflective of maternal nutritional status, contributes to the programming of offspring adiposity. The in utero and early postnatal periods represent critically sensitive developmental windows during which the hormonal and metabolic milieu affects the maturation of the hypothalamus. Maternal hyperglycemia is associated with increased transfer of glucose to the fetus driving fetal hyperinsulinemia. Elevated fetal insulin causes increased adiposity and consequently higher fetal circulating leptin concentration. Mechanistic studies in animal models indicate important roles of leptin and insulin in central and peripheral programming of adiposity, and suggest that optimal concentrations of these hormones are critical during early life. Additionally, the environmental milieu during development may be conveyed to progeny through epigenetic marks and these can potentially be vertically transmitted to subsequent generations. Thus, nutritional and metabolic/endocrine signals during perinatal development can have lifelong (and possibly multigenerational) impacts on offspring body weight regulation.

POMC Neuron BBSome Regulation of Body Weight is Independent of its Ciliary Function.

The BBSome, a complex of several Bardet-Biedl syndrome (BBS) proteins including BBS1, has emerged as a critical regulator of energy homeostasis. Although the BBSome is best known for its involvement in cilia trafficking, through a process that involve BBS3, it also regulates the localization of cell membrane receptors underlying metabolic regulation. Here, we show that inducible Bbs1 gene deletion selectively in proopiomelanocortin (POMC) neurons cause a gradual increase in body weight, which was associated with higher fat mass. In contrast, inducible deletion of Bbs3 gene in POMC neurons failed to affect body weight and adiposity. Interestingly, loss of BBS1 in POMC neurons led to glucose intolerance and insulin insensitivity, whereas BBS3 deficiency in these neurons is associated with slight impairment in glucose handling, but normal insulin sensitivity. BBS1 deficiency altered the plasma membrane localization of serotonin 5-HT2C receptor (5-HT2CR) and ciliary trafficking of neuropeptide Y2 receptor (NPY2R).In contrast, BBS3 deficiency, which disrupted the ciliary localization of the BBSome, did not interfere with plasma membrane expression of 5-HT2CR, but reduced the trafficking of NPY2R to cilia. We also show that deficiency in BBS1, but not BBS3, alters mitochondria dynamics and decreased total and phosphorylated levels of dynamin-like protein 1 (DRP1) protein. Importantly, rescuing DRP1 activity restored mitochondria dynamics and localization of 5-HT2CR and NPY2R in BBS1-deficient cells. The contrasting effects on energy and glucose homeostasis evoked by POMC neuron deletion of BBS1 versus BBS3 indicate that BBSome regulation of metabolism is not related to its ciliary function in these neurons.

Age-Dependent Changes in the Effects of Androgens on Female Metabolic and Body Weight Regulation Systems in Humans and Laboratory Animals

In recent years, the effects of androgens on metabolic and body weight regulation systems and their underlying mechanisms have been gradually revealed in females. In women and experimental animals of reproductive age, androgen excess can adversely affect metabolic functioning, appetite, and body weight regulation. In addition, excess androgens can increase the risk of metabolic disorders, such as obesity, insulin resistance, and diabetes. These unfavorable effects of androgens are induced by alterations in the actions of hypothalamic appetite-regulatory factors, reductions in energy expenditure, insulin resistance in skeletal muscle, and β-cell dysfunction. Interestingly, these unfavorable effects of androgens on metabolic and body-weight regulation systems are neither observed nor evident in ovariectomized animals and post-menopausal women, indicating that the adverse effects of androgens might be dependent on the estrogen milieu. Recent findings may provide novel sex- and age-specific strategies for treating metabolic diseases.

Lactobacillus and Allobaculum mediates the improvement of vascular endothelial dysfunction during hypertension with TaohongSiwu decoction combined with Dubosiella newyorkensis

BackgroundPrevious study confirmed that both TaohongSiwu decoction (THSWD) and Dubosiella newyorkensis improved hypertension-induced endothelial dysfunction. However, the mechanism of THSWD combined with Dubosiella newyorkensis remains unclear. Purpose: We aimed to investigate the microecological mechanism underlying the THSWD combined with Dubosiella newyorkensis for the prevention of hypertensive vascular endothelial dysfunction. MethodsEight percent high-salt diet was applied to induce hypertension in a mouse model for 4 weeks. THSWD, Dubosiella newyorkensis and THSWD combined with Dubosiella newyorkensis were used to intervene in the model mice to observe the changes of systolic blood pressure (SBP), body weight, blood routine, endothelial function, gut contents microbiota and bile acid metabolites. ResultsResults revealed that THSWD combined with Dubosiella newyorkensis significantly restored blood pressure and regulated body weight, and markedly downregulating serum and vascular levels of endothelin-1 (ET-1), thrombin regulatory protein (TM), vascular hemophilia factor (vWF) and vascular endothelial growth factor (VEGF), and upregulating nitric oxide (NO) levels compared with the model group. Notably, It altered the diversity and community structure of gut contents microbiota in mice. Lactobacillus and Allobaculum was enormously up-regulated at the genus level. Serum bile acid differential metabolites cholic acid and chenodeoxycholic acid were markedly altered. Futhermore, there was a close relationship between Lactobacillus, Allobaculum and endothelial function indexes in mice. ConclusionLactobacillus and Allobaculum play important roles in the prevention of vascular endothelial dysfunction in hypertension during the THSWD combined with Dubosiella newyorkensis.

Association between body mass index (BMI) and [123I]Ioflupane (DaTSCAN) availabilities in patients with parkinsonism using single-photon emission computed tomography–computed tomography (SPECT-CT)

Aim[123I]Ioflupane (DaTSCAN) has a high binding affinity to the dopamine (DA) transporter (DaT) and tenfold less affinity to serotonin (5-HT) transporter (SERT). Both neurotransmitters are considered to contribute to body weight regulation. This study assesses the association between body mass index (BMI) and DaTSCAN availability in brain.MethodScans from 74 consecutive patients who had undergone DaTSCAN single-photon emission computed tomography–computed tomography (SPECT-CT) were used to obtain semi- and absolute quantitative data in several volumes of interest (VOIs). Relative semi-quantitative specific binding ratios (SBRs) from Chang attenuated SPECT were obtained from GE DaTQUANT. Absolute normalised concentration (NC) was calculated from attenuation/scatter corrected SPECT-CT images, using an adapted version of the EARL Ltd (European Association of Nuclear Medicine (EANM) Research 4 Life) template. Scans were subdivided into either degenerative parkinsonism (abnormal = 49), borderline (n = 14) or scan without evidence of dopaminergic deficit (SWEDD = 11) using visual assessment and SBR values by two nuclear medicine consultants.ResultsSBRs did not correlate with BMI. However, NC values correlated negatively in the entire cohort, with the strongest correlation in the frontal (r = − 0.649. p = 0.000), occipital (r = − 0.555, p = 0.000) regions and pons (r = − 0.555, p = 0.000). In the abnormal (n = 49) and SWEDD group (n = 11), NC of the frontal region was the most correlated with BMI (r = − 0.570, p = 0.000; r = − 0.813, p = 0.002, respectively). In the borderline group (n = 14), the left posterior putamen displayed the strongest correlation (r = − 0.765, p = 0.001).ConclusionAbsolute NC values demonstrate a strong inverse correlation with BMI, strongest in the extrastriatal regions. Due to the predominately non-overlapping distribution of DaT and SERT, this study suggests greater involvement of SERT in obesity with possible interplay with DA transmission.

Mechanisms underlying the combination effect of arsenite and high-fat diet on aggravating liver injury in mice.

Arsenic (As) is a highly toxic metalloid that can be found in insufficiently purified drinking water and exerts adverse effects on the physiology of living organisms that can negatively affect human health after subchronic exposure, causing several diseases, such as liver damage. A high-fat diet, which is increasing in frequency worldwide, can aggravate hepatic pathology. However, the mechanisms behind liver injury caused by the combinatory effects of As exposure and a high-fat diet remain unclear. In this study, we investigated such underlying mechanisms by focusing on three different aspects: As biotransformation, pathological liver damage, and differential expression of signaling pathway components. We employed mice that were fed a regular diet or a high-fat diet and exposed them to a range of arsenite concentrations (As(III), 0.05-50 mg/L) for 12 weeks. Our results showed that a high-fat diet increased the absorption of As into the liver and enhanced liver toxicity, which became progressively more severe as the As concentration increased. Co-exposure to a high-fat diet and As(III) activated PI3K/AKT and PPAR signaling as well as fatty acid metabolism pathways. In addition, the expression of proteins related to lipid cell function, lipid metabolism, and the regulation of body weight was also affected. Our study provides insights into the mechanisms that contribute to liver injury from subchronic combinatory exposure to As and a high-fat diet and showcases the importance of a healthy lifestyle, which may be of particular benefit to people living in areas with high As(III) concentrations, as a means to reduce or prevent aggravated liver damage.

Smith-Magenis syndrome protein RAI1 regulates body weight homeostasis through hypothalamic BDNF-producing neurons and neurotrophin downstream signalling.

Retinoic acid-induced 1 (RAI1) haploinsufficiency causes Smith-Magenis syndrome (SMS), a genetic disorder with symptoms including hyperphagia, hyperlipidemia, severe obesity, and autism phenotypes. RAI1 is a transcriptional regulator with a pan-neural expression pattern and hundreds of downstream targets. The mechanisms linking neural Rai1 to body weight regulation remain unclear. Here we find that hypothalamic brain-derived neurotrophic factor (BDNF) and its downstream signalling are disrupted in SMS (Rai1+/-) mice. Selective Rai1 loss from all BDNF-producing cells or from BDNF-producing neurons in the paraventricular nucleus of the hypothalamus (PVH) induced obesity in mice. Electrophysiological recordings revealed that Rai1 ablation decreased the intrinsic excitability of PVHBDNF neurons. Chronic treatment of SMS mice with LM22A-4 engages neurotrophin downstream signalling and delayed obesity onset. This treatment also partially rescued disrupted lipid profiles, insulin intolerance, and stereotypical repetitive behaviour in SMS mice. These data argue that RAI1 regulates body weight and metabolic function through hypothalamic BDNF-producing neurons and that targeting neurotrophin downstream signalling might improve associated SMS phenotypes.

Smith–Magenis syndrome protein RAI1 regulates body weight homeostasis through hypothalamic BDNF-producing neurons and neurotrophin downstream signalling

Retinoic acid-induced 1 (RAI1) haploinsufficiency causes Smith–Magenis syndrome (SMS), a genetic disorder with symptoms including hyperphagia, hyperlipidemia, severe obesity, and autism phenotypes. RAI1 is a transcriptional regulator with a pan-neural expression pattern and hundreds of downstream targets. The mechanisms linking neural Rai1 to body weight regulation remain unclear. Here we find that hypothalamic brain-derived neurotrophic factor (BDNF) and its downstream signalling are disrupted in SMS (Rai1+/-) mice. Selective Rai1 loss from all BDNF-producing cells or from BDNF-producing neurons in the paraventricular nucleus of the hypothalamus (PVH) induced obesity in mice. Electrophysiological recordings revealed that Rai1 ablation decreased the intrinsic excitability of PVHBDNF neurons. Chronic treatment of SMS mice with LM22A-4 engages neurotrophin downstream signalling and delayed obesity onset. This treatment also partially rescued disrupted lipid profiles, insulin intolerance, and stereotypical repetitive behaviour in SMS mice. These data argue that RAI1 regulates body weight and metabolic function through hypothalamic BDNF-producing neurons and that targeting neurotrophin downstream signalling might improve associated SMS phenotypes.

Glucose-dependent insulinotropic polypeptide regulates body weight and food intake via GABAergic neurons in mice

The development of single-molecule co-agonists for the glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) is considered a breakthrough in the treatment of obesity and type 2 diabetes. But although GIPR–GLP-1R co-agonism decreases body weight with superior efficacy relative to GLP-1R agonism alone in preclinical1–3 and clinical studies4,5, the role of GIP in regulating energy metabolism remains enigmatic. Increasing evidence suggests that long-acting GIPR agonists act in the brain to decrease body weight through the inhibition of food intake3,6–8; however, the mechanisms and neuronal populations through which GIP affects metabolism remain to be identified. Here, we report that long-acting GIPR agonists and GIPR–GLP-1R co-agonists decrease body weight and food intake via inhibitory GABAergic neurons. We show that acyl-GIP decreases body weight and food intake in male diet-induced obese wild-type mice, but not in mice with deletion of Gipr in Vgat(also known as Slc32a1)-expressing GABAergic neurons (Vgat-Gipr knockout). Whereas the GIPR–GLP-1R co-agonist MAR709 leads, in male diet-induced obese wild-type mice, to greater weight loss and further inhibition of food intake relative to a pharmacokinetically matched acyl-GLP-1 control, this superiority over GLP-1 vanishes in Vgat-Gipr knockout mice. Our data demonstrate that long-acting GIPR agonists crucially depend on GIPR signaling in inhibitory GABAergic neurons to decrease body weight and food intake.

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

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

The human-derived novel gut commensal Luoshenia tenuis regulates body weight and food intake in mice

Many studies have revealed that gut microbes modulate host metabolism. In this study, we characterized the therapeutic effects of a novel gut commensal Luoshenia tenuis against host metabolic disorders. First, by in silico analysis, we demonstrated that the L. tenuis was prevalent in the gut microbiomes of healthy humans but were depleted specifically in obesity cohorts. Further in vitro cultivation revealed that L. tenuis produced short chain fatty acids that were verified to modulate host metabolism and some other volatile metabolites to benefit hosts by anti-inflammation and anti-tumor. Second, gavage of the L. tenuis significantly decreased the body weight gain and food intake of high-fat diet-feeding C57BL/6J mice, which was in parallel with the changed expression level of genes related to satiety and feeding behavior. We then performed the gavage trial using diet induced obese mice, and it revealed that the administration of L. tenuis alleviated significantly the abnormal glucose and lipid metabolisms and reduced the inflammatory response. In summary, this study revealed a previously-unknown human gut commensal microbe that benefited host metabolism, and set the stage for the development of novel next-generation probiotic applicable for treatment of obesity and related metabolic disorders.

Maternal High Fat Diet in Lactation Impacts Hypothalamic Neurogenesis and Neurotrophic Development, Leading to Later Life Susceptibility to Obesity in Male but Not Female Mice.

Early life nutrition can reprogram development and exert long-term consequences on body weight regulation. In mice, maternal high-fat diet (HFD) during lactation predisposed male but not female offspring to diet-induced obesity when adult. Molecular and cellular changes in the hypothalamus at important time points are examined in the early postnatal life in relation to maternal diet and demonstrated sex-differential hypothalamic reprogramming. Maternal HFD in lactation decreased the neurotropic development of neurons formed at the embryo stage (e12.5) and impaired early postnatal neurogenesis in the hypothalamic regions of both males and females. Males show a larger increased ratio of Neuropeptide Y (NPY)to Pro-opiomelanocortin (POMC) neurons in early postnatal neurogenesis, in response to maternal HFD, setting an obese tone for male offspring. These data provide insights into the mechanisms by which hypothalamic reprograming by early life overnutrition contributes to the sex-dependent susceptibility to obesity in adult life in mice.

Ahdc1 is a potent regulator of obesity and energy metabolism.

AT-hook DNA-binding motif-containing protein 1 (AHDC1) is a causal gene of intellectual disability/developmental delay in humans. The biological role of AHDC1 is unclear. Recently, some clues from AHDC1 mutation carriers hinted that AHDC1 may participate in body-weight regulation. In this first metabolic phenotype study of Ahdc1 deficiency, we generated a Ahdc1-deficienct mouse line and found that Ahdc1 deficiency in both male and female mice led to adiposity from weaning and obesity characterized by reduced energy expenditure and respiratory quotient, with progressive development of hyperleptinemia, insulin resistance, abnormal glycolipid metabolism, and fatty liver. Our findings show that Ahdc1 is a novel key regulator of obesity and energy metabolism, which provides new insight into the physiological mechanisms of obesity.NEW & NOTEWORTHY In this first metabolic phenotype study of Ahdc1 deficiency, we generated a survivable Ahdc1-deficient mouse line. We found that Ahdc1 deficiency in both male and female mice resulted in adiposity from weaning and obesity characterized by reduced energy expenditure and respiratory quotient. Additionally, there was a progressive development of hyperleptinemia, insulin resistance, abnormal glycolipid metabolism, and fatty liver. These findings demonstrate that Ahdc1 is a novel key regulator of obesity and energy metabolism.

Prevention and management of postinterventional weight regain

Decreasing levels of patient motivation or compliance are far from being the only causes of postinterventional weight regain after lifestyle, psychological, pharmacological and surgical interventions. Weight regain originates from acomplex and individually varying set of central and peripheral mechanisms, with the overall purpose of increasing food intake by both stimulating hunger and reducing satiety (mediated by gastrointestinal hormones) and decreasing the body's energy demands (via metabolic adaption). These mechanisms counteract any attempts to reduce or maintain body weight in today's increasingly prevalent adipogenic environments. The knowledge about the biological mechanisms of body weight regulation should be taken into consideration when planning treatment programs for long-term weight reduction, including follow-up treatment for the prevention and individualized treatment of postinterventional weight regain. Therapeutic measures as well as the frequency of medical follow-ups should be based on the extent of weight regain.

Multifaceted Roles of ALK Family Receptors and Augmentor Ligands in Health and Disease: A Comprehensive Review.

This review commemorates the 10-year anniversary of the discovery of physiological ligands Augα (Augmentor α; ALKAL2; Fam150b) and Augβ (Augmentor β; ALKAL1; Fam150a) for anaplastic lymphoma kinase (ALK) and leukocyte tyrosine kinase (LTK), previously considered orphan receptors. This manuscript provides an in-depth review of the biophysical and cellular properties of ALK family receptors and their roles in cancer, metabolism, pain, ophthalmology, pigmentation, central nervous system (CNS) function, and reproduction. ALK and LTK receptors are implicated in the development of numerous cancers, and targeted inhibition of their signaling pathways can offer therapeutic benefits. Additionally, ALK family receptors are involved in regulating body weight and metabolism, modulating pain signaling, and contributing to eye development and pigmentation. In the CNS, these receptors play a role in synapse modulation, neurogenesis, and various psychiatric pathologies. Lastly, ALK expression is linked to reproductive functions, with potential implications for patients undergoing ALK inhibitor therapy. Further research is needed to better understand the complex interactions of ALK family receptors and Aug ligands and to repurpose targeted therapy for a wide range of human diseases.

THU127 Deletion Of VGLUT2 In MCH Neurons Induces Sex-Specific Changes In Metabolic And Reproductive Function

Abstract Disclosure: B.G. Beekly: None. MCH neurons have a well-established role in metabolism and energy balance. MCH-knockout (“MCH-KO”) mice, which lack the MCH peptide itself, are hyperactive, hypophagic, and lean. However, MCH neurons express numerous genes involved in the synthesis, packaging, and release of the classical neurotransmitters GABA and glutamate, which are the central nervous system’s predominant inhibitory and excitatory neurotransmitters, respectively. These genes are also critical for normal metabolism, as the conditional deletion of glutamatergic signaling from MCH neurons also affects energy balance in ways that both mirror and differ from MCH-KO. When the metabolic phenotypes of MCH neuronal ablation (diphtheria toxin), MCH-KO, and transgenic Pmch-Cre;Slc17a6fl/fl mice (which lack VGLUT2 in MCH neurons) are compared, all three experimental groups exhibit decreased body weight and adiposity, increased locomotor activity, late-onset hypophagia, attenuated weight gain on high-fat diet, and reductions in circulating leptin. These data point to some functional redundancy between MCH and glutamate release from MCH neurons in the context of energy balance. By contrast, specific indicators of glucose sensing and handling differ between groups: MCH neuronal ablation and conditional VGLUT2 deletion in MCH neurons, but not global MCH-KO, result in reduced sucrose preference and improved glucose tolerance. These data suggest a role for MCH peptide in body weight regulation, but also a glutamate-dependent mechanism by which MCH neurons contribute to glucose homeostasis. Given the findings related to MCH peptide action on pancreatic islet cells and its effects on insulin resistance, it appears that MCH and glutamatergic signaling from MCH neurons must work synergistically for optimal regulation of energy balance. Importantly, all research to date on the metabolic effect of VGLUT2 deletion from MCH neurons has been in male mice. This constitutes a significant gap in the field’s understanding of these phenomena, particularly because of documented sex differences in glucose handling and associated metabolic disorders like diabetes. To address these gap, we generated Pmch-Cre;Slc17a6fl/fl mice, which lack functional VGLUT2 in MCH neurons. Body weight was measured from weaning until 20 weeks of age and the mice were subjected to comprehensive metabolic testing including oral glucose tolerance testing. We were able to recapitulate some, but not all, of the published findings in males, a fact which may in large part be due to strain differences in metabolism and glucose handling. Notably, several sexually dimorphic phenotypes were also observed, reaffirming the importance of incorporating biological sex variables into metabolic studies. Presentation: Thursday, June 15, 2023

SAT027 Novel Obesity-Associated Melanocortin 4 Receptor Variants Modulate Signaling Differently

Abstract Disclosure: A.V. Rodriguez Rondon: None. M.S. Welling: None. E.L. van den Akker: None. E.F. van Rossum: None. P.J. Delhanty: None. J.A. Visser: None. Melanocortin-4 receptor (MC4R) is a G-protein-coupled receptor expressed in the hypothalamus regulating appetite and energy expenditure. Extensive evidence from genetic and biological studies show that MC4R is a key player in the homeostatic regulation of body weight. MC4R loss of function (LoF) variants are the most common cause of monogenic obesity. We have identified 1 homozygous and 16 heterozygous MC4R variants in patients with obesity at our academic Obesity Center CGG, Erasmus MC. The impact of these variants on MC4R signaling and the association with obesity are unknown. Here, we functionally characterized these variants by analyzing four different aspects of MC4R signaling. HEK293 cells were transiently transfected with expression plasmids encoding wild type (WT) or variant MC4R and stimulated with melanocyte stimulating hormone. Cyclic AMP response (cAMP) was measured using GloSensor cAMP bioluminescence assay, and β-arrestin-2 recruitment (βarr2) was measured using NanoBiT complementation luminescence assay. Furthermore, HiBiT Detection System was used to measure cell surface expression, and serum response element (SRE) reporter assay was used to measure extracellular signal-regulated kinase (ERK) activation. Variants were classified according to the percent of maximum response (Emax) relative to WT: complete LoF (cLoF): 0-20%; partial LoF (pLoF): 20-80%; WT: 80-120%; gain of function (GoF): >120%. The MC4R variants were identified by sequencing the MC4R gene of adult and pediatric patients with obesity using an obesity gene panel. Eleven of these variants have not been functionally studied previously. The median age of onset obesity for all patients is 3 years (range 0 – 6). Furthermore, the median BMI of the adult patients was 48.8 kg/m2 (range 36 - 58.8) and the median BMI-SDS of the pediatric patients was +4.2 SDS (range +3 – 7). Twelve out of 17 patients presented with hyperphagia. MC4R variants had differential effects on signaling. In 7 out of 17 variants, cLoF for cAMP was observed. This could be explained in 6 out of 7 of these variants due to lack of cell surface expression. Intriguingly, five out of 17 variants had a normal or GoF cAMP response and normal ERK activation. However, three out of these 5 variants showed cLoF or pLoF for βarr2, indicating a disrupted desensitization mechanism. In addition, the remaining five variants displayed pLoF for most studied pathways. We show that these MC4R variants identified in our patients with obesity affect signaling differently, through modulation of cAMP, βarr2, cell surface expression, and ERK pathways. This demonstrates the value of examining different aspects of MC4R signaling to understand possible biased effects of variants on these pathways. Overall, our results show the clinical importance of assessing the effect of MC4R variants on a range of molecular signaling mechanisms to determine their association with obesity. Presentation: Saturday, June 17, 2023