Hypothalamic mTOR signaling regulates food intake

The correlation between obesity and leptin signaling pathways

Obesity is a global epidemic associated with increased morbidity and mortality. It is a major risk factor for the development of chronic diseases such as type 2 diabetes mellitus, cardiovascular diseases, and certain cancers, primarily due to excessive fat accumulation in the body. Both environmental and genetic factors contribute to the development of obesity. A key pathophysiological feature of obesity is resistance to the metabolic hormones leptin and ghrelin, which play critical roles in neuroendocrine regulation of energy homeostasis. Leptin, a proinflammatory peptide hormone encoded by the obese (ob) gene, is primarily secreted by white adipose tissue. It functions as an anti-obesity hormone by suppressing appetite, reducing food intake, and increasing energy expenditure. Leptin resistance, resulting from altered expression of leptin (LEP) and its receptor (LEP-R), impairs its regulatory effects on energy balance. Additionally, aberrant leptin signaling and genetic mutations in the leptin gene or its receptor are associated with morbid obesity and other related diseases. The treatment of obesity using leptin-based therapeutics may be one of the methods to treat obesity. The present review aimed to explore the molecular mechanisms of leptin signaling, leptin resistance in obesity, and the potential of leptin-based therapies as novel interventions in obesity management.

Unraveling the Interplay Between Metabolism and Neurodevelopment in Health and Disease

BACKGROUND

Neurodevelopment is a multifaceted and tightly regulated process essential for the formation, maturation, and functional specialization of the nervous system. It spans critical stages, including cellular proliferation, differentiation, migration, synaptogenesis, and synaptic pruning, which collectively establish the foundation for cognitive, behavioral, and emotional functions. Metabolism serves as a cornerstone for neurodevelopment, providing the energy and substrates necessary for biosynthesis, signaling, and cellular activities.

RESULTS

Key metabolic pathways, including glycolysis, lipid metabolism, and amino acid metabolism, support processes such as cell proliferation, myelination, and neurotransmitter synthesis. Crucial signaling pathways, such as insulin, mTOR, and AMPK, further regulate neuronal growth, synaptic plasticity, and energy homeostasis. Dysregulation of these metabolic processes is linked to a spectrum of neurodevelopmental disorders, including autism spectrum disorders (ASDs), intellectual disabilities, and epilepsy.

CONCLUSIONS

This review investigates the intricate interplay between metabolic processes and neurodevelopment, elucidating the molecular mechanisms that govern brain development and the pathogenesis of neurodevelopmental disorders. Additionally, it highlights potential avenues for the development of innovative strategies aimed at enhancing brain health and function.

Acyl-CoA binding protein (ACBP) in Siberian sturgeon (Acipenser baerii Brandt): Characterization, synthesis and orexigenic function

Acyl-CoA binding protein (ACBP) exhibits the activity of autophagy and lipid metabolism regulation in mammals, but its indispensable role in appetite regulation has received great attention in recent years. However, its feeding regulation function in fish is unclear. In this study, we cloned the acbp gene of Siberian Sturgeon (Abacbp) which possesses high homology with those of other vertebrate species and extremely high expression in duodenum and hypothalamus. Interestingly, Abacbp mRNA was significantly increased by short-term fasting but decreased after long-term fasting and recovered after refeeding, suggesting its latent ability in appetite regulation and compensatory growth (CG). Moreover, intraperitoneal injection of Siberian sturgeon ACBP protein (AbACBP) promoted food intake and the expressions of anorexigenic factors were down-regulated and the orexigenic factors were up-regulated. In addition, the specific receptor of ACBP regulating feeding has yet to be identified. Still, our present study found that peripheral AbACBP caused the upregulation of cb1r and the inhibition of the PI3K-AKT-mTOR-S6k signal pathway in the hypothalamus. In conclusion, the research first explored the appetite-stimulating function and mechanism of ACBP. It is of great value to construct the expression strain to produce the appetite-promoting protein ACBP in large quantities for promoting the appetite of farmed animals.

The Metabolic Programming of Pubertal Onset

BACKGROUND

There is increasing evidence that maternal factors such as nutritional status (both under and over-nutrition) and diabetes, alongside prenatal exposure to endocrine disrupting chemicals (EDCs), are associated with early pubertal onset in offspring. Such children are also at increased risk of the metabolic syndrome during adolescence and young adulthood.

AIM

This literature review focuses on the role of the prenatal environment in programming pubertal onset, and the impact of prenatal metabolic stressors on the declining average age of puberty.

METHOD

A review of all relevant literature was conducted in PubMed by the authors.

OUTCOME

The mechanism for this appears to be mediated through metabolic signals, such as leptin and insulin, on the kisspeptin-neuronal nitric oxide-gonadotropin releasing hormone (KiNG) axis. Exposed children have an elevated risk of childhood obesity and display a phenotype of hyperinsunlinaemia and hyperleptinaemia. These metabolic changes permit an earlier attainment of the nutritional "threshold" for puberty. Unfortunately, this cycle may be amplified across subsequent generations, however early intervention may help "rescue" progression of this programming.

Understanding the Role of Adipokines in Cardiometabolic Dysfunction: A Review of Current Knowledge

Cardiometabolic risk and associated dysfunctions contribute largely to the recent rise in mortality globally. Advancements in multi-omics in recent years promise a better understanding of potential biomarkers that enable an early diagnosis of cardiometabolic dysfunction. However, the molecular mechanisms driving the onset and progression of cardiometabolic disorders remain poorly understood. Adipokines are adipocyte-specific cytokines that are central to deleterious cardiometabolic alterations. They exhibit both pro-inflammatory and anti-inflammatory effects, complicating their association with cardiometabolic disturbances. Thus, understanding the cardiometabolic association of adipokines from a molecular and signaling perspective assumes great importance. This review presents a comprehensive outline of the most prominent adipokines exhibiting pro-inflammatory and/or anti-inflammatory functions in cardiometabolic dysfunction. The review also presents an insight into the pathophysiological implications of such adipokines in different cardiometabolic dysfunction conditions, the status of adipokine druggability, and future studies that can be undertaken to address the existing scientific gap. A clear understanding of the functional and mechanistic role of adipokines can potentially improve our understanding of cardiovascular disease pathophysiology and enhance our current therapeutic regimen in the years to come.

Resting metabolic rate in obesity

The prevalence of obesity has continued to rise, and obesity and its attendant metabolic disorders are major global health threat factors. Among the current interventions for obesity, none have demonstrated sustained efficacy in achieving long-term outcomes. So, the identification of therapeutic targets is of paramount importance in the advancement and sustainability of obesity. Resting metabolic rate (RMR) constitutes 60%-75% of total energy expenditure and serves a crucial function in maintaining energy balance. Nevertheless, there exists considerable heterogeneity in RMR among individuals. Low RMR is associated with weight gain, elevating the susceptibility to obesity-related ailments. Hence, RMR will be the main focus of interest in the study of obesity treatment. In this review, we will elucidate the influence factors and mechanisms of action of RMR in obesity, with particular emphasis on the effects of obesity treatment on RMR and the alterations and influence factors of RMR in special types of populations with obesity.

Poria cocos Polysaccharide Delays Aging by Enhancing the Antioxidant Ability and Suppressing the Expression of the Branched-Chain Amino Acid Transferase-Encoding Gene in Drosophila melanogaster

Poria cocos polysaccharides (PCP), the main component of Poria cocos, possess a variety of biological activities, including antitumor, immunomodulatory, and antioxidant effects. However, whether PCP has an antiaging effect remains unclear. Here, we studied the beneficial effects and the mechanism of PCP on delaying aging using the Drosophila model. The results showed that the dietary supplementation of PCP significantly extended the lifespan, improved the climbing ability, attenuated intestinal barrier dysfunction, alleviated gastrointestinal acid-base imbalance, and prevented intestinal stem cells (ISCs) hyperproliferation. In addition, PCP notably increased the activities of SOD and CAT and reduced the content of MDA. Furthermore, RNA-Seq showed that PCP supplementation led to the differential expression of 638 genes. KEGG analysis revealed that these differentially expressed genes were strongly enriched in the signaling pathway of cofactor biosynthesis. Among these genes, the expression of the branched-chain amino acid transferase-encoding gene (bcat) was significantly downregulated. The bcat-knockdown prolonged the flies' lifespan, while bcat-overexpression reduced the lifespan. Interestingly, PCP addition can rescue the flies' lifespan in the background of bcat-overexpression. Taken together, our data indicate that PCP delays aging by enhancing the antioxidant ability and suppressing the expression of the bcat gene in Drosophila.

From Clinic to Mechanisms: Multi-Omics Provide New Insights into Cerebrospinal Fluid Metabolites and the Spectrum of Psychiatric Disorders

Cerebrospinal fluid (CSF) is crucial in maintaining brain homeostasis by facilitating waste clearance, nutrient transport, and immune signaling. However, the links between CSF metabolites and psychiatric disorders, as well as the underlying mechanisms, remain largely unexamined. We conducted a bidirectional two-sample Mendelian randomization analysis to investigate potential causal relationships between CSF metabolites and 12 psychiatric disorders. Summary data for psychiatric disorders were sourced from the Psychiatric Genomics Consortium, while information on CSF metabolites was derived from two studies within the Wisconsin Alzheimer's Disease cohort. Causal estimates and pleiotropy were assessed using several robust methods, including inverse-variance-weighted (IVW) analysis, weighted median analysis, MR-Egger regression, and the MR-Egger test. Furthermore, a transcriptome-wide association study was conducted to explore potential mechanisms and shared etiologies between CSF metabolites and psychiatric disorders. The genetic risk of eating disorders (ED) can be increased by leucine (OR = 1.55, 95% CI: 1.21-1.97, P = 4.35 × 10⁻4), salicylate (OR = 1.03, 95% CI: 1.01-1.04, P = 4.95 × 10⁻4), and 1-methylnicotinamide (OR = 1.06, 95% CI: 1.03-1.09, P = 6.94 × 10⁻6), while methylmalonate may reduce ED risk (OR = 0.95, 95% CI: 0.93-0.98, P = 1.31 × 10⁻4). Similarly, the risk of schizophrenia (SCZ) may be reduced by threonate (OR = 0.93, 95% CI: 0.89-0.97, P = 1.98 × 10⁻4), oxalate (OR = 0.94, 95% CI: 0.90-0.97, P = 3.15 × 10⁻4), phenyllactate (OR = 0.96, 95% CI: 0.94-0.98, P = 2.23 × 10⁻4), N-acetylglucosamine (OR = 0.98, 95% CI: 0.97-0.99, P = 3.57 × 10⁻5), and citramalate (OR = 0.98, 95% CI: 0.98-0.99, P = 5.78 × 10⁻4). Conversely, SCZ may upregulate gamma-glutamylleucine (β = 0.08, P = 1.97 × 10⁻4) and O-sulfo-L-tyrosine (β = 0.06, P = 1.25 × 10⁻4), while downregulating gamma-glutamylphenylalanine (β = - 0.50, P = 1.16 × 10⁻4). Signal pathways related to the mechanistic target of the rapamycin (mTOR), post-translational protein modifications, and immune regulation may mediate the causal relationship of CSF metabolites on ED and SCZ. We identified a casual genetic causal relationship between CSF metabolites and both ED and schizophrenia SCZ, which is potentially mediated by pathways related to energy metabolism, post-translational modifications, and immune regulation.

A cellular and molecular basis of leptin resistance

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

Transcriptome and DNA methylation analyses provide insight into the heterosis of growth-related traits in hybrid yellow croaker

BACKGROUND

Interspecific hybrid combinations of Larimichthys crocea × Larimichthys polyactis exhibit heterosis in terms of growth traits; however, the molecular regulatory mechanism underlying this phenomenon remains unclear. DNA methylation plays a pivotal role in regulating gene expression and is involved in growth and development processes. In this study, we comprehensively investigated intricate regulatory processes by integrating transcriptome and methylome datasets from brain, liver, and muscle tissues.

RESULTS

We analyzed a total of 72 sequence datasets, including transcriptome and genome-wide DNA methylome data, from 36 tissue samples using LC, LP, LPC and LCP. We elucidated the distinct expression patterns of these four populations and examined their interactions with DNA methylation. Our findings revealed diverse DNA methylation profiles and demonstrated a greater number of hypo-DMRs in hybrid yellow croakers than in their parental lines. The majority (86 ~ 92%) of these DMRs were observed within the CG context. Moreover, we found that most DMRs were located within promoter regions as well as exons and introns. A total of 1288 DMEGs were identified through correlation analysis between DNA methylation and transcriptional activity. Functional enrichment analysis revealed that most of the DMEGs were significantly enriched in pathways related to the protein export pathway, proteasome, terpenoid backbone biosynthesis, ubiquitin-mediated proteolysis, autophagy-other pathway. Furthermore, we screened candidate growth-related genes, such as stat2, capn2, akt1, mTOR, and mef2aa. Among these, the expression levels of capn2, mTOR, and akt1 exhibited a positive correlation with DNA methylation levels, whereas the expression levels of stat2 and mef2aa showed a negative correlation. These findings suggest that alterations in DNA methylation patterns may promote growth advantages in hybrid yellow croaker by modulating the expression of these genes.

CONCLUSIONS

Epigenetic changes exert distinct influences on genes related to growth heterosis. The presented data establish a foundation for comprehending the epigenetic and transcriptomic alterations underlying the growth of hybrid yellow croaker, thereby providing preliminary insights into the molecular mechanisms of growth heterosis. These findings have significant implications for breeding programs aimed at enhancing yellow croaker production.

Valine deficiency has a greater impact on broiler growth and bone health than isoleucine deficiency

Valine and isoleucine are not only two of the indispensable amino acids (AAs) in chickens but also have special mechanisms with leucine within the branched-chain AA (BCAA) category. Therefore, we aimed to investigate how valine or isoleucine deficiency could specifically affect growth performance in broilers through various analyses. A total of 252 seven-day (d)-old male Cobb 500 broilers were allotted to three treatments with six replicates and reared until d 21. The three treatments were as follows: (1) Control group (CON; 1.31 leucine:lysine ratio), (2) valine deficiency group (-VAL; 0.62 valine:lysine ratio and 85% valine level compared to the CON group), and (3) isoleucine deficiency group (-ILE; 0.54 isoleucine:lysine ratio and 85% isoleucine level compared to the CON group). The -VAL group had significantly decreased d 7, 14, and 21 body weight (BW), BW gain (BWG), feed intake (FI), and feed efficiency from d 7 to 21 compared to the CON and -ILE groups (P < 0.001). The -ILE group showed no difference in d 14 and 18 BW; however, they showed significantly reduced BW and BWG at d 21 and feed efficiency from d 7 to 21 compared to the CON group (P < 0.001). Daily FI in the -VAL group significantly decreased from the beginning compared to the two groups, and this gap further expanded until d 21. The -VAL group also had significantly decreased breast muscle weight, total tissue weight, bone mineral density, bone mineral content, and walking ability (P < 0.01). The expression levels of mechanistic target of rapamycin and BCAA catabolism-related genes were highest in the -VAL group (P < 0.05), whereas the -ILE group did not show any difference compared to the CON group (P > 0.05). In conclusion, about 85% valine deficiency is accompanied by a substantial reduction in chicken growth, which has a much greater effect than isoleucine. Valine deficiency can also lead to increased utilization of leucine, which may result in BCAA antagonism.

Effects of deficiency or supplementation of riboflavin on energy metabolism: a systematic review with preclinical studies

CONTEXT

Riboflavin (vitamin B2) is a water-soluble micronutrient considered to be a precursor of the nucleotides flavin adenine dinucleotide and flavin mononucleotide. This vitamin makes up mitochondrial complexes and participates as an enzymatic cofactor in several mechanisms associated with energy metabolism.

OBJECTIVE

This systematic review collected and discussed the most relevant results on the role of riboflavin in the energy metabolism of lipids, proteins, and carbohydrates.

DATA SOURCES

A systematic search was carried out in the PubMed-Medline, Scopus, Embase, and Web of Science databases using the PICOS (Population, Intervention, Comparison, Outcome, Study design) strategy.

DATA EXTRACTION

The screening of studies went through 2 stages following predefined eligibility criteria. The information extracted covered reference details, study design, population characteristics, experimental model, treatment parameters and dosage, route of administration, duration of treatment, and results found.

DATA ANALYSIS

The risk of bias was assessed using the SYRCLE Risk of Bias (RoB) tool for in vivo studies and the QUIN tool adapted for in vitro studies, utilizing 10 domains, including selection bias, performance bias, detection bias, attrition bias, reporting bias, and other biases, to evaluate the methodological quality of the included studies.

CONCLUSION

This review concludes that riboflavin regulates energy metabolism by activating primary metabolic pathways and is involved in energy balance homeostasis.

Leptin and Associated Neural Pathways Underlying Obesity-Induced Hypertension

Obesity rates have surged to pandemic levels, placing tremendous burden on our society. This chronic and complex disease is related to the development of many life-threatening illnesses including cardiovascular diseases. Hypertension caused by obesity increases the risk for cardiovascular mortality and morbidity by promoting stroke, myocardial infarction, congestive heart failure, and end-stage renal disease. Overwhelming evidence supports neural origins for obesity-induced hypertension and pinpoints the adipose-derived hormone, leptin, and the sympathetic nervous system as major causal factors. Hyperleptinemia in obesity is associated with selective leptin resistance where leptin's renal sympathoexcitatory and pressor effects are preserved while the metabolic actions are impaired. Understanding the mechanisms driving this phenomenon is critical for developing effective therapeutics. This review describes the neural mechanisms of obesity-induced hypertension with a focus on the molecular and neuronal substrates of leptin action.

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.

Primary Roles of Branched Chain Amino Acids (BCAAs) and Their Metabolism in Physiology and Metabolic Disorders

Leucine, isoleucine, and valine are collectively known as branched chain amino acids (BCAAs) and are often discussed in the same physiological and pathological situations. The two consecutive initial reactions of BCAA catabolism are catalyzed by the common enzymes referred to as branched chain aminotransferase (BCAT) and branched chain α-keto acid dehydrogenase (BCKDH). BCAT transfers the amino group of BCAAs to 2-ketoglutarate, which results in corresponding branched chain 2-keto acids (BCKAs) and glutamate. BCKDH performs an oxidative decarboxylation of BCKAs, which produces their coenzyme A-conjugates and NADH. BCAT2 in skeletal muscle dominantly catalyzes the transamination of BCAAs. Low BCAT activity in the liver reduces the metabolization of BCAAs, but the abundant presence of BCKDH promotes the metabolism of muscle-derived BCKAs, which leads to the production of glucose and ketone bodies. While mutations in the genes responsible for BCAA catabolism are involved in rare inherited disorders, an aberrant regulation of their enzymatic activities is associated with major metabolic disorders such as diabetes, cardiovascular disease, and cancer. Therefore, an understanding of the regulatory process of metabolic enzymes, as well as the functions of the BCAAs and their metabolites, make a significant contribution to our health.

Different dietary branched-chain amino acid ratios, crude protein levels, and protein sources can affect the growth performance and meat yield in broilers

Balanced ratios of branched-chain amino acids (BCAAs) can enhance chicken growth, immunity, and muscle synthesis. However, these ratios can be affected by changes in crude protein (CP) levels or the substitution of protein sources, leading to BCAA antagonism. This, in turn, can have a negative impact on chicken growth. In Experiment 1, a total of 960 0-d-old male Cobb 500 broilers were divided into 6 treatments with 8 replicates. Three different BCAA ratios were used in High or Low CP diets as follows: 1) Low Leu group (Low level of leucine with increased valine and isoleucine levels), 2) Med Leu group, and 3) High Leu group (High level of leucine with reduced valine and isoleucine levels) for a total of 6 diets. In Experiment 2, a total of 640 0-d-old male Cobb 500 broilers were divided into 4 treatments with 8 replicates. The four diets had either High or Low CP and one of two protein sources with the same medium levels of BCAAs: 1) the soybean meal (SBM) group, which had SBM as the main protein source (protein bound AA), and 2) the wheat middlings with non-bound AAs (WM+AA) group (non-bound AA), which had additional non-bound AAs to replace SBM. The High Leu diet had a negative effect on overall growth performance, carcass weight, breast muscle weight, and body mineral composition compared to the Low Leu and Med Leu groups, particularly in the High CP diet (P < 0.05). The SBM group showed increased growth performance, breast muscle weight, expression levels of genes promoting muscle growth, and improved bone mineral composition compared to the WM+AA group, and the High CP group intensified the negative effect of the WM+AA diet (P < 0.05). In summary, balanced BCAA ratios and SBM-based diets have positive effects on chicken growth and muscle accretion, whereas excessive leucine and non-bound AA levels in the diets may negatively affect growth performance and meat yield in chickens.

Sex-dimorphic effects of glucose transporter-2 gene knockdown on hypothalamic primary astrocyte phosphoinositide-3-kinase (PI3K)/protein kinase B (PKB/Akt)/mammalian target of rapamycin (mTOR) cascade protein expression and phosphorylation

Glucose transporter-2 (GLUT2), a unique high capacity/low affinity, highly efficient membrane transporter and sensor, regulates hypothalamic astrocyte glucose phosphorylation and glycogen metabolism. The phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway participates in glucose homeostasis, but its sensitivity to glucose-sensory cues is unknown. Current research used a hypothalamic astrocyte primary culture model to investigate whether glucoprivation causes PI3K/Akt/mTOR pathway activation in one or both sexes by GLUT2-dependent mechanisms. Glucoprivation did not alter astrocyte PI3K levels, yet up-regulated both phosphorylated derivatives in female and down-regulated male p60 phosphoprotein expression. GLUT2 siRNA pretreatment diminished glucoprivic patterns of PI3K and phospho-PI3K expression in each sex. Astrocyte Akt and phospho-Akt/Thr308 proteins exhibited divergent, sex-contingent responses to GLUT2 gene knockdown or glucoprivation. GLUT2 siRNA pretreatment exacerbated glucoprivic-associated Akt diminution in the female, and either amplified (male) or reversed (female) glucoprivic regulation of phospho-Akt/Thr308 expression. GLUT2 gene silencing down- (male) or up-(female) regulated mTOR protein, and phospho-mTOR protein in male. Male astrocyte mTOR and phospho-mTOR profile were refractory to glucoprivation, but glucose-deprived females showed GLUT2-independent mTOR inhibition and GLUT2-dependent phospho-mTOR up-augmentation. Results identify a larger number of glucoprivic-sensitive PI3K/Akt/mTOR pathway proteins in female versus male astrocytes, and document divergent responses of common glucose-sensitive targets. GLUT2 stimulates phosphoPI3K protein expression in each sex, but imposes differential control of PI3K, Akt, phospho-Akt/Thr308, mTOR, and phospho-mTOR profiles in male versus female. Data implicate GLUT2 as a driver of distinctive pathway protein responses to glucoprivation in female, but not male.

Differential Efficacy of Weight Loss Interventions in Patients with Versus Without Diabetes

Obesity is both a major risk factor for diabetes and a serious comorbidity of the condition. The twin epidemics of obesity and diabetes have spread globally over the past few decades. Treatment of obesity in patients with diabetes provides a host of clinical benefits that encompass virtually all body systems. Despite this, multiple lines of evidence suggest that the efficacy of most therapies for weight loss is significantly reduced among patients with diabetes. With this background, we summarize the evidence of a differential effect of lifestyle, pharmacological, and surgical treatments for obesity in patients with existing diabetes, and explore the potential mechanisms involved in this phenomenon. This information is then used to formulate strategies to improve weight loss outcomes for patients with diabetes.

Sestrin2 in POMC neurons modulates energy balance and obesity related metabolic disorders via mTOR signaling

Sestrin2 is a highly conserved protein that can be induced under various stress conditions. Researches have revealed that the signaling pathway of the mammalian target of rapamycin (mTOR) is essential in modulating both glucose and lipid metabolism. However, the precise involvement of Sestrin2 in the hypothalamus, particularly in pro-opiomelanocortin (POMC) neurons, in control of energy homeostasis remains uncertain. In this study, we aimed to investigate the functional role of Sestrin2 in hypothalamic POMC neurons in regulation of energy balance, as well as revealing the underlying mechanisms. Therefore, cre-dependent AAV virus encoding or silencing Sestrin2 was injected into the hypothalamic ARC of pomc-cre transgenic mice. The results demonstrated that Sestrin2 overexpression in POMC neurons ameliorated high-fat diet (HFD)-induced obesity and increased energy expenditure. Conversely, Sestrin2 deficiency in POMC neurons predisposed mice to HFD induced obesity. Additionally, the thermogenesis of brown adipose tissue and lipolysis of inguinal white adipose tissue were both enhanced by the increased sympathetic nerve innervation in Sestrin2 overexpressed mice. Further exploration revealed that Sestrin2 overexpression inhibited the mTOR signaling pathway in hypothalamic POMC neurons, which may account for the alleviation of systematic metabolic disturbance induced by HFD in these mice. Collectively, our findings demonstrate that Sestrin2 in POMC neurons plays a pivotal role in maintaining energy balance in a context of HFD-induced obesity by inhibiting the mTOR pathway, providing new insights into how hypothalamic neurons respond to nutritional signals to protect against obesity-associated metabolic dysfunction.

Dietary supplementation of valine, isoleucine, and tryptophan may overcome the negative effects of excess leucine in diets for weanling pigs containing corn fermented protein

BACKGROUND

Diets with high inclusion of corn co-products such as corn fermented protein (CFP) may contain excess Leu, which has a negative impact on feed intake and growth performance of pigs due to increased catabolism of Val and Ile and reduced availability of Trp in the brain for serotonin synthesis. However, we hypothesized that the negative effect of using CFP in diets for weanling pigs may be overcome if diets are fortified with crystalline sources of Val, Trp, and (or) Ile.

METHODS

Three hundred and twenty weanling pigs were randomly allotted to one of 10 dietary treatments in a completely randomized design, with 4 pigs per pen and 8 replicate pens per treatment. A corn-soybean meal diet and 2 basal diets based on corn and 10% CFP or corn and 20% CFP were formulated. Seven additional diets were formulated by fortifying the basal diet with 20% CFP with Ile, Trp, Val, Ile and Val, Ile and Trp, Trp and Val, or Ile, Trp and Val. A two-phase feeding program was used, with d 1 to 14 being phase 1 and d 15 to 28 being phase 2. Fecal scores were recorded every other day. Blood samples were collected on d 14 and 28 from one pig per pen. On d 14, fecal samples were collected from one pig per pen in 3 of the 10 treatments to determine volatile fatty acids, ammonium concentration, and microbial protein. These pigs were also euthanized and ileal tissue was collected.

RESULTS

There were no effects of dietary treatments on any of the parameters evaluated in phase 1. Inclusion of 10% or 20% CFP in diets reduced (P < 0.05) final body weight on d 28, and average daily gain (ADG) and average daily feed intake (ADFI) in phase 2 and for the entire experimental period. However, pigs fed the CFP diet supplemented with Val, Ile, and Trp had final body weight, ADFI, ADG and gain to feed ratio in phase 2 and for the entire experiment that was not different from pigs fed the control diet. Fecal scores in phase 2 were reduced (P < 0.05) if CFP was used.

CONCLUSIONS

Corn fermented protein may be included by up to 20% in diets for weanling pigs without affecting growth performance, gut health, or hindgut fermentation, if diets are fortified with extra Val, Trp, and Ile. Inclusion of CFP also improved fecal consistency of pigs.

Emerging roles of lipid and metabolic sensing in the neuroendocrine control of body weight and reproduction

The hypothalamus lies at the intersection of brain and hormonal mechanisms governing essential bodily functions, including metabolic/body weight homeostasis and reproduction. While metabolism and fertility are precisely regulated by independent neuroendocrine axes, these are tightly connected, as reflection of the bidirectional interplay between the energy status of the organisms and their capacity to reproduce; a connection with important pathophysiological implications in disorders affecting these two crucial systems. Beyond the well-characterized roles of key hormones (e.g., leptin, insulin, ghrelin) and neuropeptides (e.g., melanocortins, kisspeptins) in the integral control of metabolism and reproduction, mounting evidence has pointed out a relevant function of cell energy sensors and lipid sensing mechanisms in the hypothalamic control of metabolism, with prominent roles also for metabolic sensors, such as mTOR, AMPK and SIRT1, in the nutritional regulation of key aspects of reproduction, such as pubertal maturation. We provide herein a synoptic overview of these novel regulatory pathways, with a particular focus on their putative function in the metabolic control of puberty, and delineate new avenues for further exploration of the intricate mechanisms whereby metabolism and reproduction are tightly connected.

Unraveling the Mystery of Energy-Sensing Enzymes and Signaling Pathways in Tumorigenesis and Their Potential as Therapeutic Targets for Cancer

Cancer research has advanced tremendously with the identification of causative genes, proteins, and signaling pathways. Numerous antitumor drugs have been designed and screened for cancer therapeutics; however, designing target-specific drugs for malignant cells with minimal side effects is challenging. Recently, energy-sensing- and homeostasis-associated molecules and signaling pathways playing a role in proliferation, apoptosis, autophagy, and angiogenesis have received increasing attention. Energy-metabolism-based studies have shown the contribution of energetics to cancer development, where tumor cells show increased glycolytic activity and decreased oxidative phosphorylation (the Warburg effect) in order to obtain the required additional energy for rapid division. The role of energy homeostasis in the survival of normal as well as malignant cells is critical; therefore, fuel intake and expenditure must be balanced within acceptable limits. Thus, energy-sensing enzymes detecting the disruption of glycolysis, AMP, ATP, or GTP levels are promising anticancer therapeutic targets. Here, we review the common energy mediators and energy sensors and their metabolic properties, mechanisms, and associated signaling pathways involved in carcinogenesis, and explore the possibility of identifying drugs for inhibiting the energy metabolism of tumor cells. Furthermore, to corroborate our hypothesis, we performed meta-analysis based on transcriptomic profiling to search for energy-associated biomarkers and canonical pathways.

Fasting-induced miR-7a-5p in AgRP neurons regulates food intake

OBJECTIVE

The molecular control of feeding after fasting is essential for maintaining energy homeostasis, while overfeeding usually leads to obesity. Identifying non-coding microRNAs (miRNAs) that control food intake could reveal new oligonucleotide-based therapeutic targets for treating obesity and its associated diseases. This study aims to identify a miRNA modulating food intake and its mechanism in neuronal regulation of food intake and energy homeostasis.

METHODS

A comprehensive genome-wide miRNA screening in the arcuate nucleus of the hypothalamus (ARC) of fasted mice and ad libitum mice was performed. Through stereotactic virus injections, intracerebroventricular injections, and miRNA sponge technology, miR-7a-5p was inhibited specifically in AgRP neurons and the central nervous system, and metabolic phenotypes were monitored. Quantitative real-time PCR, Western blotting, immunofluorescence, whole-cell patch-clamp recording, and luciferase reporter assay were used to investigate the mechanisms underlying miR-7a-5p's regulation of food intake.

RESULTS

We found a significant increase in miR-7a-5p levels after fasting. miR-7a-5p was highly expressed in the ARC, and inhibition of miR-7a-5p specifically in AgRP neurons reduced food intake and body weight gain. miR-7a-5p inhibited S6K1 gene expression by binding to its 3'-UTR. Furthermore, the knockdown of ribosomal S6 kinase 1 (S6K1) in AgRP neurons can partially reverse the effects caused by miR-7a-5p inhibition. Importantly, intracerebroventricular administration of the miR-7a-5p inhibitor could also reduce food intake and body weight gain.

CONCLUSION

Our findings suggest that miR-7a-5p responds to energy deficit and regulates food intake by fine-tuning mTOR1/S6K1 signaling in the AgRP neurons, which could be a promising oligonucleotide-based therapeutic target for treating obesity and its associated diseases.

A LAT1-Like Amino Acid Transporter Regulates Neuronal Activity in the Drosophila Mushroom Bodies

The proper functioning of neural circuits that integrate sensory signals is essential for individual adaptation to an ever-changing environment. Many molecules can modulate neuronal activity, including neurotransmitters, receptors, and even amino acids. Here, we ask whether amino acid transporters expressed by neurons can influence neuronal activity. We found that minidiscs (mnd), which encodes a light chain of a heterodimeric amino acid transporter, is expressed in different cell types of the adult Drosophila brain: in mushroom body neurons (MBs) and in glial cells. Using live calcium imaging, we found that MND expressed in α/β MB neurons is essential for sensitivity to the L-amino acids: Leu, Ile, Asp, Glu, Lys, Thr, and Arg. We found that the Target Of Rapamycin (TOR) pathway but not the Glutamate Dehydrogenase (GDH) pathway is involved in the Leucine-dependent response of α/β MB neurons. This study strongly supports the key role of MND in regulating MB activity in response to amino acids.

The interaction of the FTO gene and age interferes with macronutrient and vitamin intake in women with morbid obesity

Fat mass and obesity-related (FTO) gene single nucleotide polymorphisms (SNPs) interferes with food preferences that impact macronutrient intake. Few studies have investigated the relationship of this polymorphisms with the intake of micronutrients. Moreover, studies have shown multiple micronutrient deficiencies in patients with obesity. This work evaluated the effect of the FTO rs9939609 gene polymorphism on dietary nutritional quality and food intake of macronutrients and vitamins in of women with obesity candidates for metabolic surgery. The study included 106 women (24 to 60 years old) with BMIs of 36.1 to 64.8 kg/m2. A food frequency questionnaire validated for the local population was applied to obtain information about food intake. The Index of Nutritional Quality (INQ) was used to assess the adequacy of macronutrient and vitamin intake. Energy, protein and lipid intakes were higher in carriers of the A allele compared to TT in the younger age groups but were similar in the class of subjects aged ≥45 years. The INQ for protein was higher in carriers of the A allele than in carriers of the TT allele. The INQs for protein, carbohydrate, vitamins B2, B3 and B6 decreased, whereas the INQ for vitamin C increased with advancing age. The INQ for vitamin A was lower in AA than in TT, regardless of age, whereas vitamin E was higher in younger AA than in older AA. The INQ for vitamin B9 was higher in younger women than in older women. In conclusion, the FTO gene contributed to the intake of more energy, protein and lipids and interfered with the intake of vitamins B9, A and E. With the exception of vitamin A, the effect of the genotype was attenuated with ageing.

Dietary Valine Requirement of Juvenile Olive Flounder (Paralichthys olivaceus)

This study was conducted to estimate dietary valine (Val) requirement for juvenile olive flounder (Paralichthys olivaceus). In a feeding trial, a total of 540 fish (initial body weight: 23.0 ± 0.2 g) were stocked into 18 tanks (210 L). Six experimental diets containing graded levels of Val (4, 8, 12, 16, 20, and 24 g/kg, dry matter basis) were fed to the fish in triplicate groups for 13 weeks. The lowest growth, feed utilization, and survival were observed in 4 g/kg Val group (P < 0.05). Dietary Val deficiency resulted in significant decreases (P < 0.05) in whole-body protein and Val concentrations, hepatosomatic index, condition factor and plasma protein and cholesterol levels. Nonspecific immunity and antioxidant activities were significantly lower (P < 0.05) in 4 g/kg Val group than in other groups. Dietary Val deficiency upregulated the expression of proinflammatory cytokines and downregulated the expression of anti-inflammatory cytokines and intestinal tight junction protein (occludin) (P < 0.05). Mucosal fold height and submucosa and muscularis thickness of fish intestine were significantly lower (P < 0.05) in fish fed 4 g/kg Val diet. Relatively lower lipid droplet in hepatic cell was observed in 4 g/kg Val group. Our findings suggested that dietary Val requirements for juvenile olive flounder would be 17.7-18.9 g Val/kg (35.4-37.8 g/kg on the basis of crude protein), estimated by quadratic regression analysis based on the weight gain, protein efficiency ratio, and protein retention efficiency.

Molecular insights into Sertoli cell function: how do metabolic disorders in childhood and adolescence affect spermatogonial fate?

Male infertility is a major public health concern globally with unknown etiology in approximately half of cases. The decline in total sperm count over the past four decades and the parallel increase in childhood obesity may suggest an association between these two conditions. Here, we review the molecular mechanisms through which obesity during childhood and adolescence may impair future testicular function. Several mechanisms occurring in obesity can interfere with the delicate metabolic processes taking place at the testicular level during childhood and adolescence, providing the molecular substrate to hypothesize a causal relationship between childhood obesity and the risk of low sperm counts in adulthood.

The role of branched-chain amino acids and their downstream metabolites in mediating insulin resistance

Elevated levels of circulating branched-chain amino acids (BCAAs) and their associated metabolites have been strongly linked to insulin resistance and type 2 diabetes. Despite extensive research, the precise mechanisms linking increased BCAA levels with these conditions remain elusive. In this review, we highlight the key organs involved in maintaining BCAA homeostasis and discuss how obesity and insulin resistance disrupt the intricate interplay among these organs, thus affecting BCAA balance. Additionally, we outline recent research shedding light on the impact of tissue-specific or systemic modulation of BCAA metabolism on circulating BCAA levels, their metabolites, and insulin sensitivity, while also identifying specific knowledge gaps and areas requiring further investigation. Finally, we summarize the effects of BCAA supplementation or restriction on obesity and insulin sensitivity.

An integrative framework to prioritize genes in more than 500 loci associated with body mass index

Obesity is a major risk factor for a myriad of diseases, affecting >600 million people worldwide. Genome-wide association studies (GWASs) have identified hundreds of genetic variants that influence body mass index (BMI), a commonly used metric to assess obesity risk. Most variants are non-coding and likely act through regulating genes nearby. Here, we apply multiple computational methods to prioritize the likely causal gene(s) within each of the 536 previously reported GWAS-identified BMI-associated loci. We performed summary-data-based Mendelian randomization (SMR), FINEMAP, DEPICT, MAGMA, transcriptome-wide association studies (TWASs), mutation significance cutoff (MSC), polygenic priority score (PoPS), and the nearest gene strategy. Results of each method were weighted based on their success in identifying genes known to be implicated in obesity, ranking all prioritized genes according to a confidence score (minimum: 0; max: 28). We identified 292 high-scoring genes (≥11) in 264 loci, including genes known to play a role in body weight regulation (e.g., DGKI, ANKRD26, MC4R, LEPR, BDNF, GIPR, AKT3, KAT8, MTOR) and genes related to comorbidities (e.g., FGFR1, ISL1, TFAP2B, PARK2, TCF7L2, GSK3B). For most of the high-scoring genes, however, we found limited or no evidence for a role in obesity, including the top-scoring gene BPTF. Many of the top-scoring genes seem to act through a neuronal regulation of body weight, whereas others affect peripheral pathways, including circadian rhythm, insulin secretion, and glucose and carbohydrate homeostasis. The characterization of these likely causal genes can increase our understanding of the underlying biology and offer avenues to develop therapeutics for weight loss.

A bird's-eye overview of molecular mechanisms regulating feed intake in chickens-with mammalian comparisons

In recent decades, a lot of research has been conducted to explore poultry feeding behavior. However, up to now, the processes behind poultry feeding behavior remain poorly understood. The review generalizes modern expertise about the hormonal regulation of feeding behavior in chickens, focusing on signaling pathways mediated by insulin, leptin, and ghrelin and regulatory pathways with a cross-reference to mammals. This overview also summarizes state-of-the-art research devoted to hypothalamic neuropeptides that control feed intake and are prime candidates for predictors of feeding efficiency. Comparative analysis of the signaling pathways that mediate the feed intake regulation allowed us to conclude that there are major differences in the processes by which hormones influence specific neuropeptides and their contrasting roles in feed intake control between two vertebrate clades.

Recent Research on Mechanisms of Feeding Regulation in Chicks

Food intake affects poultry productivity. A complete understanding of these regulatory mechanisms provides new strategies to improve productivity. Food intake is regulated by complex mechanisms involving many factors, including the central nervous system, gastrointestinal tract, hormones, and nutrients. Although several studies have been conducted to elucidate regulatory mechanisms in chickens, the mechanisms remain unclear. To update the current knowledge on feeding regulation in chickens, this review focuses on recent findings that have not been summarized in previous reviews, including spexins, adipokines, neurosecretory proteins GL and GM, and central intracellular signaling factors.

Betaine improves appetite regulation and glucose-lipid metabolism in mandarin fish (Siniperca chuatsi) fed a high-carbohydrate-diet by regulating the AMPK/mTOR signaling

Diets with high carbohydrate (HC) was reported to have influence on appetite and intermediary metabolism in fish. To illustrate whether betaine could improve appetite and glucose-lipid metabolism in aquatic animals, mandarin fish (Siniperca chuatsi) were fed with the HC diets with or without betaine for 8 weeks. The results suggested that betaine enhanced feed intake by regulating the hypothalamic appetite genes. The HC diet-induced downregulation of AMPK and appetite genes was also positively correlated with the decreased autophagy genes, suggesting a possible mechanism that AMPK/mTOR signaling might regulate appetite through autophagy. The HC diet remarkably elevated transcriptional levels of genes related to lipogenesis, while betaine alleviated the HC-induced hepatic lipid deposition. Additionally, betaine supplementation tended to store the energy storage as hepatic glycogen. Our findings proposed the possible mechanism for appetite regulation through autophagy via AMPK/mTOR, and demonstrated the feasibility of betaine as an aquafeed additive to regulate appetite and intermediary metabolism in fish.

Assessing malathion residue impact on poultry health, human safety, and production performance

Over the past decade, food safety has become a major concern due to the intensive use of pesticides. Pesticide contamination has been observed in poultry products when seeds are coated with pesticides or when stored products are exposed to pesticides in warehouses. In this experiment, the residue levels of malathion transferred from corn grain to the different parts of the chicken product, its transfer factors (TFs) and the human dietary risk for consumers were evaluated. Growth performance and carcass parameters of the chicken samples were also determined after different doses of malathion exposure. Malathion residues from different parts of chicken meat (breast, thigh, wing, liver and skin) were extracted by the QuEChERS method and analyzed by liquid chromatography-mass spectrophotometry (LC-MS/MS). A deterministic approach was used to calculate the acute and chronic risk assessment. Body weight, feed conversion ratio and feed intake decreased with increasing malathion dose. In addition to reduced feed intake, cold carcass and liver weights of the chicks were also decreased. The highest residues were found in the skin of the chicken followed by the breast, thigh, wing and liver. The TFs of malathion varied between 0.00 and 0.05 according to the different doses applied (4 mg/kg, 8 mg/kg, 16 mg/kg, 32 mg/kg). The chronic exposure assessment (HQ) showed that consumers of all ages and genders consumed 0.008-0.604% of the acceptable daily intake (0.3 mg/kg body weight (bw)/day) of malathion from chicken products. The acute intake assessment (aHQ) of consumers ranged from 0.00015 to 0.0135% of the acute reference dose (0.3 mg/kg bw). In conclusion the results suggest that the risk associated with the malathion residues in chicken meat was found to be low but the residue levels in meat should not be ignored.

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

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

mTORC1 in energy expenditure: consequences for obesity

In eukaryotic cells, the mammalian target of rapamycin complex 1 (sometimes referred to as the mechanistic target of rapamycin complex 1; mTORC1) orchestrates cellular metabolism in response to environmental energy availability. As a result, at the organismal level, mTORC1 signalling regulates the intake, storage and use of energy by acting as a hub for the actions of nutrients and hormones, such as leptin and insulin, in different cell types. It is therefore unsurprising that deregulated mTORC1 signalling is associated with obesity. Strategies that increase energy expenditure offer therapeutic promise for the treatment of obesity. Here we review current evidence illustrating the critical role of mTORC1 signalling in the regulation of energy expenditure and adaptive thermogenesis through its various effects in neuronal circuits, adipose tissue and skeletal muscle. Understanding how mTORC1 signalling in one organ and cell type affects responses in other organs and cell types could be key to developing better, safer treatments targeting this pathway in obesity.

Effects of a high-fat and high-carbohydrate diet on appetite regulation and central AMPK in the hypothalamus of blunt snout bream (Megalobrama amblycephala)

Adenosine monophosphate-activated protein kinase (AMPK) is a sensor of cellular energy changes and controls food intake. This study investigates the effect of a high-calorie diet (high fat diet [HFD], high carbohydrate diet [HCD] and high energy diet [HED]) on appetite and central AMPK in blunt snout bream. In the present study, fish (average initial weight 45.84 ± 0.07 g) were fed the control, HFD, HCD and HED in four replicates for 12 weeks. At the end of the feeding trial, the result showed that body mass index, specific growth rate, feed efficiency ratio and feed intake were not affected (p > 0.05) by dietary treatment. However, fish fed the HFD obtained a significantly higher (p < 0.05) lipid productive value, lipid gain and lipid intake than those fed the control diet, but no significant difference was attributed to others. Also, a significantly higher (p < 0.05) energy intake content was found in fish-fed HFD, HCD and HED than those given the control diet. Long-term HFD and HCD feeding significantly increased (p < 0.05) plasma glucose, glycated serum protein, advanced glycation end product, insulin and leptin content levels than the control group. Moreover, a significantly lower (p < 0.05) complex 1, 2 and 3 content was found in fish-fed HFD and HCD than in the control, but no differences (p > 0.05) were attributed to those in HED. Fish-fed HED significantly upregulated (p < 0.05) hypothalamic ampα 1 and ampα 2 expression, whereas the opposite trend was observed in the hypothalamic mammalian target of rapamycin than those in HFD and HCD compared to the control. However, hypothalamic neuropeptide y, peroxisome proliferator-activated receptor α (pparα), acetyl-coa oxidase and carnitine palmitoyltransferase 1 were significantly upregulated (p < 0.05) in the HCD group, while the opposite was seen in cholecystokinin expression compared to those in the control group. Our findings indicated that the central AMPK signal pathway and appetite were modulated according to the diet's energy level to regulate nutritional status and maintain energy homoeostasis in fish.

Excess dietary Lys reduces feed intake, stimulates jejunal CCK secretion and alters essential and non-essential blood AA profile in pigs

BACKGROUND

Commercial diets are frequently formulated to meet or exceed nutrient levels including those of limiting essential amino acids (AA) covering potential individual variations within the herd. However, the provision of dietary excess of AA, such as Lys, may lead to reduced appetite and growth in pigs. The mechanisms modulating these responses have not been extensively investigated. This study evaluated the effect of Lys dietary excesses on performance and satiety biomarkers in post weaning pigs.

METHODS

Twenty-four pigs aged 21 d and weighing 6.81 ± 0.12 kg (mean ± SEM) were individually housed and offered 1 of 4 dietary treatments for 3 weeks: a diet containing a standardized ileal digestible Lys reaching 100% (T0), 120% (T1), 150% (T2) or 200% (T3) of the NRC (2012) requirements. At the end of the experiment, blood samples from the cephalic vein of the T0 and T3 groups were obtained for AA analysis. In addition, primary intestinal cultures from T0 pigs were used, following their humane killing, to evaluate the effect of Lys on gut hormone secretion and AA sensors gene expression under ex vivo conditions.

RESULTS

Feed intake was linearly reduced (P < 0.001) and the weight gain to feed ratio reduced (P < 0.10) with increased dietary levels of Lys during the third- and first-week post weaning, respectively. Cholecystokinin concentration (P < 0.05) and the metabotropic glutamate receptor 1 and the solute carrier family 7 member 2 (P < 0.10) gene expression was enhanced in proximal jejunum tissues incubated with Lys at 20 mmol/L when compared to the control (Lys 0 mmol/L). Plasma Lys and Glu (P < 0.05) concentration increased in the T3 compared to T0 pigs. In contrast, plasma levels of His, Val, Thr, Leu (P < 0.05) and Gln (P < 0.10) were lower in T3 than T0 pigs.

CONCLUSION

The present results confirm that excess dietary Lys inhibits hunger in pigs. Moreover, the results provide evidence of pre- and post-absorptive mechanisms modulating these responses. Lys dietary excesses should be narrowed, when possible, to avoid negative effects of the AA on appetite in pigs.

Regulation of autophagy by perilysosomal calcium: a new player in β-cell lipotoxicity

Autophagy is an essential quality control mechanism for maintaining organellar functions in eukaryotic cells. Defective autophagy in pancreatic beta cells has been shown to be involved in the progression of diabetes through impaired insulin secretion under glucolipotoxic stress. The underlying mechanism reveals the pathologic role of the hyperactivation of mechanistic target of rapamycin (mTOR), which inhibits lysosomal biogenesis and autophagic processes. Moreover, accumulating evidence suggests that oxidative stress induces Ca2+ depletion in the endoplasmic reticulum (ER) and cytosolic Ca2+ overload, which may contribute to mTOR activation in perilysosomal microdomains, leading to autophagic defects and β-cell failure due to lipotoxicity. This review delineates the antagonistic regulation of autophagic flux by mTOR and AMP-dependent protein kinase (AMPK) at the lysosomal membrane, and both of these molecules could be activated by perilysosomal calcium signaling. However, aberrant and persistent Ca2+ elevation upon lipotoxic stress increases mTOR activity and suppresses autophagy. Therefore, normalization of autophagy is an attractive therapeutic strategy for patients with β-cell failure and diabetes.

Developmental metformin exposure does not rescue physiological impairments derived from early exposure to altered maternal metabolic state in offspring mice

OBJECTIVE

The incidence of gestational diabetes mellitus (GDM) and metabolic disorders during pregnancy are increasing globally. This has resulted in increased use of therapeutic interventions such as metformin to aid in glycemic control during pregnancy. Even though metformin can cross the placental barrier, its impact on offspring brain development remains poorly understood. As metformin promotes AMPK signaling, which plays a key role in axonal growth during development, we hypothesized that it may have an impact on hypothalamic signaling and the formation of neuronal projections in the hypothalamus, the key regulator of energy homeostasis. We further hypothesized that this is dependent on the metabolic and nutritional status of the mother at the time of metformin intervention. Using mouse models of maternal overnutrition, we aimed to assess the effects of metformin exposure on offspring physiology and hypothalamic neuronal circuits during key periods of development.

METHODS

Female C57BL/6N mice received either a control diet or a high-fat diet (HFD) during pregnancy and lactation periods. A subset of dams was fed a HFD exclusively during the lactation. Anti-diabetic treatments were given during the first postnatal weeks. Body weights of male and female offspring were monitored daily until weaning. Circulating metabolic factors and molecular changes in the hypothalamus were assessed at postnatal day 16 using ELISA and Western Blot, respectively. Hypothalamic innervation was assessed by immunostaining at postnatal days 16 and 21.

RESULTS

We identified alterations in weight gain and circulating hormones in male and female offspring induced by anti-diabetic treatment during the early postnatal period, which were critically dependent on the maternal metabolic state. Furthermore, hypothalamic agouti-related peptide (AgRP) and proopiomelanocortin (POMC) neuronal innervation outcomes in response to anti-diabetic treatment were also modulated by maternal metabolic state. We also identified sex-specific changes in hypothalamic AMPK signaling in response to metformin exposure.

CONCLUSION

We demonstrate a unique interaction between anti-diabetic treatment and maternal metabolic state, resulting in sex-specific effects on offspring brain development and physiological outcomes. Overall, based on our findings, no positive effect of metformin intervention was observed in the offspring, despite ameliorating effects on maternal metabolic outcomes. In fact, the metabolic state of the mother drives the most dramatic differences in offspring physiology and metformin had no rescuing effect. Our results therefore highlight the need for a deeper understanding of how maternal metabolic state (excessive weight gain versus stable weight during GDM treatment) affects the developing offspring. Further, these results emphasize that the interventions to treat alterations in maternal metabolism during pregnancy need to be reassessed from the perspective of the offspring physiology.

Chronic triclosan exposure induce impaired glucose tolerance by altering the gut microbiota

Triclosan (TCS) is an antimicrobial compound incorporated into more than 2000 consumer products. This compound is frequently detected in the human body and causes ubiquitous contamination in the environment, thereby raising concerns about its impact on human health and environmental pollution. Here, we demonstrated that 20 weeks' exposure of TCS drove the development of glucose intolerance by inducing compositional and functional alterations in intestinal microbiota in rats. Fecal-transplantation experiments corroborated the involvement of gut microbiota in TCS-induced glucose-tolerance impairment. 16S rRNA gene-sequencing analysis of cecal contents showed that TCS disrupted the gut microbiota composition in rats and increased the ratio of Firmicutes to Bacteroidetes. Cecal metabolomic analyses detected that TCS altered host metabolic pathways that are linked to host glucose and amino acid metabolism, particularly branched-chain amino acid (BCAA) biosynthesis. BCAA measurement confirmed the increase in serum BCAAs in rats exposed to TCS. Western blot and immunostaining results further confirmed that elevated BCAAs stimulated mTOR, a nutrient-sensing complex, and following IRS-1 serine phosphorylation, resulted in insulin resistance and glucose intolerance. These results suggested that TCS may induce glucose metabolism imbalance by regulating BCAA concentration by remodeling the gut microbiota.

The Unrestrained Overeating Behavior and Clinical Perspective

Obesity-related co-morbidities decrease life quality, reduce working ability, and lead to early death. In the adult population, eating addiction manifests with excessive food consumption and the unrestrained overeating behavior, which is associated with increased risk of morbidity and mortality and defined as the binge eating disorder (BED). This hedonic intake is correlated with fat preference and the total amount of dietary fat consumption is the most potent risk factor for weight gain. Long-term BED leads to greater sensitivity to the rewarding effects of palatable foods and results in obesity fatefully. Increased plasma concentrations of non-esterified free fatty acids and lipid-overloaded hypertrophic adipocytes may cause insulin resistance. In addition to dietary intake of high-fat diet, sedentary lifestyle leads to increased storage of triglycerides not only in adipose tissue but also ectopically in other tissues. Lipid-induced apoptosis, ceramide accumulation, reactive oxygen species overproduction, endoplasmic reticulum stress, and mitochondrial dysfunction play role in the pathogenesis of lipotoxicity. Food addiction and BED originate from complex action of dopaminergic, opioid, and cannabinoid systems. BED may also be associated with both obesity and major depressive disorder. For preventing morbidity and mortality, as well as decreasing the impact of obesity-related comorbidities in appropriately selected patients, opiate receptor antagonists and antidepressant combination are recommended. Pharmacotherapy alongside behavioral management improves quality of life and reduces the obesity risk; however, the number of licensed drugs is very few. Thus, stereotactic treatment is recommended to break down the refractory obesity and binge eating in obese patient. As recent applications in the field of non-invasive neuromodulation, transcranial magnetic stimulation and transcranial direct current stimulation are thought to be important in image-guided deep brain stimulation in humans. Chronic overnutrition most likely provides repetitive and persistent signals that up-regulate inhibitor of nuclear factor kappa B (NF-κB) kinase beta subunit/NF-κB (IKKβ/NF-κB) in the hypothalamus before the onset of obesity. However, how the mechanisms of high-fat diet-induced peripheral signals affect the hypothalamic arcuate nucleus remain largely unknown.

The Mechanism of Leptin Resistance in Obesity and Therapeutic Perspective

Leptin resistance is induced via leptin signaling blockade by chronic overstimulation of the leptin receptor and intracellular signaling defect or increased hypothalamic inflammation and suppressor of cytokine signaling (SOCS)-3 expression. High-fat diet triggers leptin resistance induced by at least two independent causes: first, the limited ability of peripheral leptin to activate hypothalamic signaling transducers and activators of transcription (STAT) signaling and secondly a signaling defect in leptin-responsive hypothalamic neurons. Central leptin resistance is dependent on decreased leptin transport efficiency across the blood brain barrier (BBB) rather than hypothalamic leptin insensitivity. Since the hypothalamic phosphorylated STAT3 (pSTAT3) represents a sensitive and specific readout of leptin receptor-B signaling, the assessment of pSTAT3 levels is the gold standard. Hypertriglyceridemia is one of important factors to inhibit the transport of leptin across BBB in obesity. Mismatch between high leptin and the amount of leptin receptor expression in obesity triggers brain leptin resistance via increasing hypothalamic inflammation and SOCS-3 expression. Therapeutic strategies that regulate the passage of leptin to the brain include the development of modifications in the structure of leptin analogues as well as the synthesis of new leptin receptor agonists with increased BBB permeability. In the hyperleptinemic state, polyethylene glycol (PEG)-modified leptin is unable to pass through the BBB. Peripheral histone deacetylase (HDAC) 6 inhibitor, tubastatin, and metformin increase central leptin sensitization. While add-on therapy with anagliptin, metformin and miglitol reduce leptin concentrations, the use of long-acting leptin analogs, and exendin-4 lead to the recovery of leptin sensitivity. Contouring surgery with fat removal, and bariatric surgery independently of the type of surgery performed provide significant improvement in leptin concentrations. Although approaches to correcting leptin resistance have shown some success, no clinically effective application has been developed to date. Due to the impairment of central and peripheral leptin signaling, as well as the extensive integration of leptin-sensitive metabolic pathways with other neurons, the effectiveness of methods used to eliminate leptin resistance is extremely limited.

The SLC6A15-SLC6A20 Neutral Amino Acid Transporter Subfamily: Functions, Diseases, and Their Therapeutic Relevance

The neutral amino acid transporter subfamily that consists of six members, consecutively SLC6A15-SLC620, also called orphan transporters, represents membrane, sodium-dependent symporter proteins that belong to the family of solute carrier 6 (SLC6). Primarily, they mediate the transport of neutral amino acids from the extracellular milieu toward cell or storage vesicles utilizing an electric membrane potential as the driving force. Orphan transporters are widely distributed throughout the body, covering many systems; for instance, the central nervous, renal, or intestinal system, supplying cells into molecules used in biochemical, signaling, and building pathways afterward. They are responsible for intestinal absorption and renal reabsorption of amino acids. In the central nervous system, orphan transporters constitute a significant medium for the provision of neurotransmitter precursors. Diseases related with aforementioned transporters highlight their significance; SLC6A19 mutations are associated with metabolic Hartnup disorder, whereas altered expression of SLC6A15 has been associated with a depression/stress-related disorders. Mutations of SLC6A18-SLCA20 cause iminoglycinuria and/or hyperglycinuria. SLC6A18-SLC6A20 to reach the cellular membrane require an ancillary unit ACE2 that is a molecular target for the spike protein of the SARS-CoV-2 virus. SLC6A19 has been proposed as a molecular target for the treatment of metabolic disorders resembling gastric surgery bypass. Inhibition of SLC6A15 appears to have a promising outcome in the treatment of psychiatric disorders. SLC6A19 and SLC6A20 have been suggested as potential targets in the treatment of COVID-19. In this review, we gathered recent advances on orphan transporters, their structure, functions, related disorders, and diseases, and in particular their relevance as therapeutic targets. SIGNIFICANCE STATEMENT: The following review systematizes current knowledge about the SLC6A15-SLCA20 neutral amino acid transporter subfamily and their therapeutic relevance in the treatment of different diseases.

Mammalian target of rapamycin inhibition impacts energy homeostasis and induces sex-specific body weight loss in humans

BACKGROUND

Previous data from a 2-year randomized controlled trial (CRAD001ADE12) indicated that mammalian target of rapamycin (mTOR) inhibition by everolimus slowed cyst growth in patients with autosomal-dominant polycystic kidney disease (ADPKD). During the trial, we noted body weight loss in some patients, particularly in women. We hypothesized that everolimus causes body weight reduction by reduced food intake and/or metabolic changes, which could lead to cachexia.

METHODS

Within a sub-analysis of the CRAD001ADE12 trial, body weight course was investigated regarding sex-specific differences in 433 adult ADPKD patients (everolimus, n = 215; placebo, n = 218). One hundred four out of 111 patients who participated in the clinical trial centre in Berlin were evaluated under everolimus/placebo therapy (on drug: everolimus, n = 48; placebo, n = 56) and after therapy (off drug: everolimus, n = 15; placebo, n = 18). Eating habits and nutrient/caloric intake were evaluated by validated questionnaires. Systemic and local metabolism was evaluated in four patients after an oral glucose load (OGL) by using calorimetry and adipose/muscle tissue microdialysis.

RESULTS

Within the 2-year CRAD001ADE12 trial, a significant body weight loss was observed in female patients on everolimus versus placebo (P = 0.0029). Data of the Berlin Cohort revealed that weight loss was greater in women on everolimus versus men (P < 0.01). After 9 months, women and men had lost 2.6 ± 3.8 and 0.8 ± 1.5 kg (P < 0.05) in body weight, respectively, and after 21 months, they had lost 4.1 ± 6.6 and 1.0 ± 3.3 kg (P < 0.05), respectively. On everolimus, caloric intake was significantly lower in women versus men (1510 ± 128 vs. 2264 ± 216 kcal/day, P < 0.05), caused mainly by a lower fat and protein intake in women versus men. Cognitive restraints, disinhibition and hunger remained unchanged. In a subgroup of patients resting metabolic rate was unchanged whereas OGL-induced thermogenesis was reduced (7 ± 2 vs. 11 ± 2 kcal, P < 0.05). Fasting and OGL-induced fat oxidation was increased (P < 0.05) on versus off everolimus. In adipose tissue, fasting lipolytic activity was increased, but lipolytic activity was inhibited similarly after the OGL on versus off everolimus, respectively. In skeletal muscle, postprandial glucose uptake and aerobic glycolysis was reduced in patients on everolimus.

CONCLUSIONS

mTOR inhibition by everolimus induces body weight reduction, specifically in female patients. This effect is possibly caused by a centrally mediated reduced food (fat and protein) intake and by centrally/peripherally mediated increased fat oxidation (systemic) and mobilization (adipose tissue). Glucose uptake and oxidation might be reduced in skeletal muscle. This could lead to cachexia and, possibly, muscle wasting. Therefore, our results have important implications for patients recieving immune-suppressive mTOR inhibition therapy.

Hepatic Vagal Afferents Convey Clock-Dependent Signals to Regulate Circadian Food Intake

Circadian desynchrony induced by shiftwork or jetlag is detrimental to metabolic health, but how synchronous/desynchronous signals are transmitted among tissues is unknown. Here we report that liver molecular clock dysfunction is signaled to the brain via the hepatic vagal afferent nerve (HVAN), leading to altered food intake patterns that are corrected by ablation of the HVAN. Hepatic branch vagotomy also prevents food intake disruptions induced by high-fat diet feeding and reduces body weight gain. Our findings reveal a previously unrecognized homeostatic feedback signal that relies on synchrony between the liver and the brain to control circadian food intake patterns. This identifies the hepatic vagus nerve as a therapeutic target for obesity in the setting of chrono-disruption.

One Sentence Summary

The hepatic vagal afferent nerve signals internal circadian desynchrony between the brain and liver to induce maladaptive food intake patterns.

Branched-chain amino acids prevent obesity by inhibiting the cell cycle in an NADPH-FTO-m6A coordinated manner

Obesity has become a major health crisis in the past decades. Branched-chain amino acids (BCAA), a class of essential amino acids, exerted beneficial health effects with regard to obesity and its related metabolic dysfunction, although the underlying reason is unknown. Here, we show that BCAA supplementation alleviates high-fat diet (HFD)-induced obesity and insulin resistance in mice and inhibits adipogenesis in 3T3-L1 cells. Further, we find that BCAA prevent the mitotic clonal expansion (MCE) of preadipocytes by reducing cyclin A2 (CCNA2) and cyclin-dependent kinase 2 (CDK2) expression. Mechanistically, BCAA decrease the concentration of nicotinamide adenine dinucleotide phosphate (NADPH) in adipose tissue and 3T3-L1 cells by reducing glucose-6-phosphate dehydrogenase (G6PD) expression. The reduced NADPH attenuates the expression of fat mass and obesity-associated (FTO) protein, a well-known m6A demethylase, to increase the N6-methyladenosine (m6A) levels of Ccna2 and Cdk2 mRNA. Meanwhile, the high m6A levels of Ccna2 and Cdk2 mRNA are recognized by YTH N6-methyladenosine RNA binding protein 2 (YTHDF2), which results in mRNA decay and reduction of their protein expressions. Overall, our data demonstrate that BCAA inhibit obesity and adipogenesis by reducing CDK2 and CCNA2 expression via an NADPH-FTO-m6A coordinated manner in vivo and in vitro, which raises a new perspective on the role of m6A in the BCAA regulation of obesity and adipogenesis.

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.

Metabolomic analysis of serum short-chain fatty acid concentrations in a mouse of MPTP-induced Parkinson's disease after dietary supplementation with branched-chain amino acids

The gut microbiota and microbial metabolites influence the enteric nervous system and the central nervous system via the microbial-gut-brain axis. Increasing body of evidence suggests that disturbances in the metabolism of peripheral branched-chain amino acids (BCAAs) can contribute to the development of neurodegenerative diseases through neuroinflammatory signaling. Preliminary research has shown that longitudinal changes in serum amino acid levels in mouse models of Parkinson's disease (PD) are negatively correlated with disease progression. Therefore, the aim of the present study was to determine the changes in serum levels of short-chain fatty acids (SCFAs) in a mouse model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD after dietary BCAA supplementation. In our research, gas chromatography-mass spectrometry was used to detect serum SCFA concentrations. The data were then analyzed with principal component analysis and orthogonal partial least squares discriminant analysis. Finally, the correlations of serum SCFA levels with gut and motor function in MPTP-induced PD mice were explored. Propionic acid, acetic acid, butyric acid, and isobutyric acid concentrations were elevated in MPTP + H-BCAA mice compared with MPTP mice. Propionic acid concentration was increased the most, while the isovaleric acid concentration was decreased. Propionic acid concentration was positively correlated with fecal weight and water content and negatively correlated with the pole-climbing duration. In conclusion, these results not only suggest that propionic acid may be a potential biomarker for PD, but also indicate the possibility that PD may be treated by altering circulating levels of SCFA.

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.

Glucagon-like peptide-1 receptor activation stimulates PKA-mediated phosphorylation of Raptor and this contributes to the weight loss effect of liraglutide

The canonical target of the glucagon-like peptide-1 receptor (GLP-1R), Protein Kinase A (PKA), has been shown to stimulate mechanistic Target of Rapamycin Complex 1 (mTORC1) by phosphorylating the mTOR-regulating protein Raptor at Ser791 following β-adrenergic stimulation. The objective of these studies is to test whether GLP-1R agonists similarly stimulate mTORC1 via PKA phosphorylation of Raptor at Ser791 and whether this contributes to the weight loss effect of the therapeutic GLP-1R agonist liraglutide. We measured phosphorylation of the mTORC1 signaling target ribosomal protein S6 in Chinese Hamster Ovary cells expressing GLP-1R (CHO-Glp1r) treated with liraglutide in combination with PKA inhibitors. We also assessed liraglutide-mediated phosphorylation of the PKA substrate RRXS*/T* motif in CHO-Glp1r cells expressing Myc-tagged wild-type (WT) Raptor or a PKA-resistant (Ser791Ala) Raptor mutant. Finally, we measured the body weight response to liraglutide in WT mice and mice with a targeted knock-in of PKA-resistant Ser791Ala Raptor. Liraglutide increased phosphorylation of S6 and the PKA motif in WT Raptor in a PKA-dependent manner but failed to stimulate phosphorylation of the PKA motif in Ser791Ala Raptor in CHO-Glp1r cells. Lean Ser791Ala Raptor knock-in mice were resistant to liraglutide-induced weight loss but not setmelanotide-induced (melanocortin-4 receptor-dependent) weight loss. Diet-induced obese Ser791Ala Raptor knock-in mice were not resistant to liraglutide-induced weight loss; however, there was weight-dependent variation such that there was a tendency for obese Ser791Ala Raptor knock-in mice of lower relative body weight to be resistant to liraglutide-induced weight loss compared to weight-matched controls. Together, these findings suggest that PKA-mediated phosphorylation of Raptor at Ser791 contributes to liraglutide-induced weight loss.