Hypothalamic POMC neurons modulate systemic energy balance and glucose homeostasis by sensing nutritional state signals. In addition to this classic regulatory mode, these neurons are also activated by the sensory perception of food. Here, we report that food-related sensory cues engage glycogen metabolism in POMC neurons. Genetic depletion of glycogen through various approaches renders POMC neurons unresponsive to food-associated sensory stimuli. This defective perception of food is linked to alterations in consummatory behaviour, hepatic adaptations and cephalic insulin release associated with a prediabetic phenotype that progresses into overweight and overt diabetes with a high-calorie diet or ageing. Collectively, our results posit glycogen as a decisive fuel resource for meeting the rapid and demanding energy requirements linked with sensory activation. Furthermore, our data delineate the biological function of food perception and provide support for the physiological relevance of neuronal glycogen.

OBJECTIVE:Intestinal gluconeogenesis (IGN), via the initiation of a gut-brain nervous circuit, accounts for the metabolic benefits linked to dietary proteins or fermentable fiber in rodents and has been positively correlated with the rapid amelioration of body weight after gastric bypass surgery in humans with obesity. In particular, the activation of IGN moderates the development of hepatic steatosis accompanying obesity. In this study, we investigated the specific effects of IGN on adipose tissue metabolism, independent of its induction by nutritional manipulation. METHODS:We used two transgenic mouse models of suppression or overexpression of G6pc1, the catalytic subunit of glucose-6 phosphatase, which is the key enzyme of endogenous glucose production specifically in the intestine. RESULTS:Under a hypercaloric diet, mice overexpressing IGN showed lower adiposity and higher thermogenic capacities than wild-type mice, featuring marked browning of white adipose tissue (WAT) and prevention of the whitening of brown adipose tissue (BAT). Sympathetic denervation restricted to BAT caused the loss of the antiobesity effects associated with IGN. Conversely, IGN-deficient mice exhibited an increase in adiposity under a standard diet, which was associated with decreased expression of markers of thermogenesis in both BAT and WAT. CONCLUSIONS:IGN is sufficient to activate the sympathetic nervous system and prevent the expansion and the metabolic alterations of BAT and WAT metabolism under a high-calorie diet, thereby preventing the development of obesity. These data increase knowledge of the mechanisms of weight reduction in gastric bypass surgery and pave the way for new approaches to prevent or cure obesity.

Introduction: Glioblastomas present intensive angiogenesis, thus anti-Vascular Endothelial Growth Factor (VEGF) antibodies (mAbs) have been proposed as promising therapies. However, the results of clinical trials reported moderate toxicity and limited effectiveness. This study evaluates the in vivo pharmacokinetics and biodistribution of these mAbs in a growing model of glioblastoma in rats using Positron Emission Tomography (PET). Material: &Methods: mAbs were radiolabeled with zirconium-89. Four days after the model induction, animals were injected with 2.33 +/- 1.3 MBq of [89Zr]-DFO-bevacizumab (n = 8) or 2.35 +/- 0.26 MBq of [89Zr]-DFO-aflibercept (n = 6). PETs were performed at 0H, 48H, 168H, 240H, and 336H post-injection. Tumor induction was confirmed using [18F]Fluorodeoxyglucose-PET and immunohistochemistry. Radiotracer uptake was estimated in all pre-defined Volumes-of-Interest. Results: Anti-VEGF mAbs showed 100 % Radiochemical-Purity. [89Zr]-DFO-bevacizumab showed a significantly higher bioavailability in whole-blood. A significant increase in the tumor uptake was detectable at 168H PET with [89Zr]-DFO-bevacizumab meanwhile with [89Zr]-DFO-aflibercept it was only detectable at 336H. [89Zr]DFO-bevacizumab tumor uptake was significantly higher than that of [89Zr]-DFO-aflibercept in all the scans. Tumor induction was confirmed in all animal models. Conclusion: MAbs detect VEGF-expression in glioblastoma models. Tumors were earlier targeted by Bevacizumab. The lower blood availability of aflibercept resulted in a lower tumor uptake than bevacizumab in all the scans.

OBJECTIVE:Free fatty acid receptor-1 (FFAR1) is a medium- and long-chain fatty acid sensing G protein-coupled receptor that is highly expressed in the hypothalamus. Here, we investigated the central role of FFAR1 on energy balance. METHODS:Central FFAR1 agonism and virogenic knockdown were performed in mice. Energy balance studies, infrared thermographic analysis of brown adipose tissue (BAT) and molecular analysis of the hypothalamus, BAT, white adipose tissue (WAT) and liver were carried out. RESULTS:Pharmacological stimulation of FFAR1, using central administration of its agonist TUG-905 in diet-induced obese mice, decreases body weight and is associated with increased energy expenditure, BAT thermogenesis and browning of subcutaneous WAT (sWAT), as well as reduced AMP-activated protein kinase (AMPK) levels, reduced inflammation, and decreased endoplasmic reticulum (ER) stress in the hypothalamus. As FFAR1 is expressed in distinct hypothalamic neuronal subpopulations, we used an AAV vector expressing a shRNA to specifically knockdown Ffar1 in proopiomelanocortin (POMC) neurons of the arcuate nucleus of the hypothalamus (ARC) of obese mice. Our data showed that knockdown of Ffar1 in POMC neurons promoted hyperphagia and body weight gain. In parallel, these mice developed hepatic insulin resistance and steatosis. CONCLUSIONS:FFAR1 emerges as a new hypothalamic nutrient sensor regulating whole body energy balance. Moreover, pharmacological activation of FFAR1 could provide a therapeutic advance in the management of obesity and its associated metabolic disorders.

There has been an intense focus to uncover the molecular mechanisms by which fasting triggers the adaptive cellular responses in the major organs of the body. Here, we show that in mice, hepatic S-adenosylmethionine (SAMe)-the principal methyl donor-acts as a metabolic sensor of nutrition to fine-tune the catabolic-fasting response by modulating phosphatidylethanolamine N-methyltransferase (PEMT) activity, endoplasmic reticulum-mitochondria contacts, 0-oxidation, and ATP production in the liver, together with FGF21-mediated lipolysis and thermogenesis in adipose tissues. Notably, we show that glucagon induces the expression of the hepatic SAMe-synthesizing enzyme methionine adeno-syltransferase a1 (MAT1A), which translocates to mitochondria-associated membranes. This leads to the production of this metabolite at these sites, which acts as a brake to prevent excessive 0-oxidation and mitochondrial ATP synthesis and thereby endoplasmic reticulum stress and liver injury. This work provides important insights into the previously undescribed function of SAMe as a new arm of the metabolic adap-tation to fasting.

Early-life determinants are thought to be a major factor in the rapid increase of obesity. However, while maternal nutrition has been extensively studied, the effects of breastfeeding by the infant on the reprogramming of energy balance in childhood and throughout adulthood remain largely unknown. Here we show that delayed weaning in rat pups protects them against diet-induced obesity in adulthood, through enhanced brown adipose tissue thermogenesis and energy expenditure. In-depth metabolic phenotyping in this rat model as well as in transgenic mice reveals that the effects of prolonged suckling are mediated by increased hepatic fibroblast growth factor 21 (FGF21) production and tanycyte-controlled access to the hypothalamus in adulthood. Specifically, FGF21 activates GABA-containing neurons expressing dopamine receptor 2 in the lateral hypothalamic area and zona incerta. Prolonged breastfeeding thus constitutes a protective mechanism against obesity by affecting long-lasting physiological changes in liver-to-hypothalamus communication and hypothalamic metabolic regulation.

Weight gain is a hallmark of decreased estradiol (E2) levels because of menopause or following surgical ovariectomy (OVX) at younger ages. Of note, this weight gain tends to be around the abdomen, which is frequently associated with impaired metabolic homeostasis and greater cardiovascular risk in both rodents and humans. However, the molecular underpinnings and the neuronal basis for these effects remain to be elucidated. The aim of this study is to elucidate whether the kappa-opioid receptor (k-OR) system is involved in mediating body weight changes associated with E2 withdrawal. Here, we document that body weight gain induced by OVX occurs, at least partially, in a k-OR dependent manner, by modulation of energy expenditure independently of food intake as assessed in Oprk1−/−global KO mice. These effects were also observed following central pharmacological blockade of the k-OR system using the k-OR-selective antagonist PF-04455242 in wild type mice, in which we also observed a decrease in OVX-induced weight gain associated with increased UCP1 positive immunostaining in brown adipose tissue (BAT) and browning of white adipose tissue (WAT). Remarkably, the hypothalamic mTOR pathway plays an important role in regulating weight gain and adiposity in OVX mice. These findings will help to define new therapies to manage metabolic disorders associated with low/null E2 levels based on the modulation of central k-OR signaling.

Data gleaned recently shows that ghrelin, a stomach derived peptide, and liver-expressed-antimicrobial peptide 2 (LEAP-2) play opposite roles on food intake. However, the data available with LEAP-2 in relation to in vivo studies are still very scanty and some key questions regarding the interplay among ghrelin and LEAP-2 remain to be answered. In this work, using rats and mice, we study fasting-induced food intake as well as testing the effect of diet exposure, e.g., standard diet and high fat diet, in terms of ghrelin-induced food intake. The anorexigenic effect of LEAP-2 on fasting induced food intake appears to be dependent on energy stores, being more evident in ob/ob than in wild type mice and also in animals exposed to high fat diet. On the other hand, LEAP-2 administration markedly inhibited ghrelin-induced food intake in lean, obese (ob/ob and DIO) mice, aged rats and GH-deficient dwarf rats. In contrast, the inhibitory effect on glucose levels can only be observed in some specific experimental models indicating that the mechanisms involved are likely to be quite different. Taken together from these data, LEAP-2 emerged as a potential candidate to be therapeutically useful in obesity.

Reciprocal interactions between endothelial cells (ECs) and adipocytes are fundamental to maintain white adipose tissue (WAT) homeostasis, as illustrated by the activation of angiogenesis upon WAT expansion, a process that is impaired in obesity. However, the molecular mechanisms underlying the crosstalk between ECs and adipocytes remain poorly understood. Here, we show that local production of polyamines in ECs stimulates adipocyte lipolysis and regulates WAT homeostasis in mice. We promote enhanced cell-autonomous angiogenesis by deleting Pten in the murine endothelium. Endothelial Pten loss leads to a WAT-selective phenotype, characterized by reduced body weight and adiposity in pathophysiological conditions. This phenotype stems from enhanced fatty acid β-oxidation in ECs concomitant with a paracrine lipolytic action on adipocytes, accounting for reduced adiposity. Combined analysis of murine models, isolated ECs and human specimens reveals that WAT lipolysis is mediated by mTORC1-dependent production of polyamines by ECs. Our results indicate that angiocrine metabolic signals are important for WAT homeostasis and organismal metabolism.

ABSTRACTObjectiveIntestinal gluconeogenesis, via the initiation of a gut-brain nervous circuit, accounts for the metabolic benefits linked to dietary proteins or fermentable fibre in rodents and has been positively correlated with the rapid amelioration of body weight after gastric bypass surgery in obese humans. In particular, the activation of intestinal gluconeogenesis moderates the development of hepatic steatosis accompanying obesity. In this study, we investigated the specific effects of intestinal gluconeogenesis on adipose tissue metabolism, independently of its induction by nutritional manipulation.MethodsWe used two transgenic mouse models of suppression or overexpression of G6PC, the catalytic subunit of glucose-6 phosphatase, the key enzyme of endogenous glucose production, specifically in the intestine.ResultsUnder a hypercaloric diet, mice with a genetic overexpression of intestinal gluconeogenesis showed a lower adiposity and higher thermogenic capacities than wild-type mice, featuring marked browning of white adipose tissue and prevention of the whitening of brown adipose tissue. Suppression of sympathetic nervous signalling in brown adipose tissue impairs the activation of thermogenesis. Conversely, mice with genetic suppression of intestinal gluconeogenesis exhibit an increase in adiposity under standard diet, associated with a decreased expression of markers of thermogenesis in both the brown and white adipose tissues.ConclusionIntestinal gluconeogenesis is sufficient in itself to activate the sympathetic nervous system and prevent the expansion and the metabolic alterations of brown and white adipose tissues metabolism under high calorie diet, thus preventing the development of obesity. These data increase knowledge of the mechanisms of weight reduction in gastric bypass surgery and pave the way of new approaches to prevent or cure obesity.

p53 regulates several signaling pathways to maintain the metabolic homeostasis of cells and modulates the cellular response to stress. Deficiency or excess of nutrients causes cellular metabolic stress, and we hypothesized that p53 could be linked to glucose maintenance. We show here that upon starvation hepatic p53 is stabilized by O -GlcNAcylation and plays an essential role in the physiological regulation of glucose homeostasis. More specifically, p53 binds to PCK1 promoter and regulates its transcriptional activation, thereby controlling hepatic glucose production. Mice lacking p53 in the liver show a reduced gluconeogenic response during calorie restriction. Glucagon, adrenaline and glucocorticoids augment protein levels of p53, and administration of these hormones to p53 deficient human hepatocytes and to liver-specific p53 deficient mice fails to increase glucose levels. Moreover, insulin decreases p53 levels, and over-expression of p53 impairs insulin sensitivity. Finally, protein levels of p53, as well as genes responsible of O- GlcNAcylation are elevated in the liver of type 2 diabetic patients and positively correlate with glucose and HOMA-IR. Overall these results indicate that the O -GlcNAcylation of p53 plays an unsuspected key role regulating in vivo glucose homeostasis.

Sirtuin 3 (SIRT3) is one of the seven mammalian sirtuin homologs of the yeast Sir2 gene that has emerged as an important player in the regulation of energy metabolism in peripheral tissues. However, its role in the hypothalamus has not been explored. Herein, we show that the genetic inhibition of SIRT3 in the hypothalamic arcuate nucleus (ARC) induced a negative energy balance and improvement of several metabolic parameters. These effects are specific for POMC neurons, because ablation of SIRT3 in POMC, but not in AgRP neurons, decreased body weight and adiposity, increased energy expenditure and brown adipose tissue (BAT) activity, and induced browning in white adipose tissue (WAT). Notably, the depletion of SIRT3 in POMC neurons caused these effects in male mice fed a chow diet but failed to affect energy balance in males fed a high fat diet and females under both type of diets. Overall, we provide the first evidence pointing for a key role of SIRT3 in POMC neurons in the regulation of energy balance.

Background and Aims G protein–coupled receptor (GPR) 55 is a putative cannabinoid receptor, and l‐α‐lysophosphatidylinositol (LPI) is its only known endogenous ligand. Although GPR55 has been linked to energy homeostasis in different organs, its specific role in lipid metabolism in the liver and its contribution to the pathophysiology of nonalcoholic fatty liver disease (NAFLD) remains unknown. Approach and Results We measured (1) GPR55 expression in the liver of patients with NAFLD compared with individuals without obesity and without liver disease, as well as animal models with steatosis and nonalcoholic steatohepatitis (NASH), and (2) the effects of LPI and genetic disruption of GPR55 in mice, human hepatocytes, and human hepatic stellate cells. Notably, we found that circulating LPI and liver expression of GPR55 were up‐regulated in patients with NASH. LPI induced adenosine monophosphate–activated protein kinase activation of acetyl–coenzyme A carboxylase (ACC) and increased lipid content in human hepatocytes and in the liver of treated mice by inducing de novo lipogenesis and decreasing β‐oxidation. The inhibition of GPR55 and ACCα blocked the effects of LPI, and the in vivo knockdown of GPR55 was sufficient to improve liver damage in mice fed a high‐fat diet and in mice fed a methionine‐choline–deficient diet. Finally, LPI promoted the initiation of hepatic stellate cell activation by stimulating GPR55 and activation of ACC. Conclusions The LPI/GPR55 system plays a role in the development of NAFLD and NASH by activating ACC.

Background and PurposeGlucagon‐like peptide‐2 (GLP‐2) is a gastrointestinal hormone released in response to nutritional intake that exerts a wide range of effects by activating GLP‐2 receptors. In addition to its intestinotrophic effects, GLP‐2 also positively influences glucose metabolism under conditions of obesity, but the mechanisms behind this remain unclear. Here, we have investigated the molecular role of the GLP‐2/GLP‐2 receptor axis in energetic metabolism, focusing on its potential modulatory effects on adipose tissue.Experimental ApproachPhysiological measurements (body weight, food intake, locomotor activity, and energy expenditure) and metabolic studies (glucose and insulin tolerance tests) were performed on lean and obese mice treated with the protease‐resistant GLP‐2 analogue teduglutide.Key ResultsAcute but not chronic centrally administered teduglutide decreased food intake and weight‐gain. By contrast, chronic activation of peripheral GLP‐2 receptors increased body weight‐independent glucose tolerance and had anti‐inflammatory effects on visceral adipose tissue. Using a gene silencing approach, we found that adipose tissue is necessary for these beneficial effects of teduglutide. Finally, teduglutide regulates the inflammatory state and acts as an anabolic signal in human adipocytes.Conclusion and ImplicationsOverall, our data identify adipose tissue as a new, clinically relevant, site of action for GLP‐2 activity in obesity.LINKED ARTICLESThis article is part of a themed issue on Cellular metabolism and diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.10/issuetoc

Our objective was to explore the physiological role of the intestinal endocannabinoids in the regulation of appetite upon short-term exposure to high-fat-diet (HFD) and understand the mechanisms responsible for aberrant gut-brain signaling leading to hyperphagia in mice lacking Napepld in the intestinal epithelial cells (IECs). We generated a murine model harboring an inducible NAPE-PLD deletion in IECs (NapepldΔIEC). After an overnight fast, we exposed wild-type (WT) and NapepldΔIEC mice to different forms of lipid challenge (HFD or gavage), and we compared the modification occurring in the hypothalamus, in the vagus nerve, and at endocrine level 30 and 60 min after the stimulation. NapepldΔIEC mice displayed lower hypothalamic levels of N-oleoylethanolamine (OEA) in response to HFD. Lower mRNA expression of anorexigenic Pomc occurred in the hypothalamus of NapepldΔIEC mice after lipid challenge. This early hypothalamic alteration was not the consequence of impaired vagal signaling in NapepldΔIEC mice. Following lipid administration, WT and NapepldΔIEC mice had similar portal levels of glucagon-like peptide-1 (GLP-1) and similar rates of GLP-1 inactivation. Administration of exendin-4, a full agonist of GLP-1 receptor (GLP-1R), prevented the hyperphagia of NapepldΔIEC mice upon HFD. We conclude that in response to lipid, NapepldΔIEC mice displayed reduced OEA in brain and intestine, suggesting an impairment of the gut-brain axis in this model. We speculated that decreased levels of OEA likely contributes to reduce GLP-1R activation, explaining the observed hyperphagia in this model. Altogether, we elucidated novel physiological mechanisms regarding the gut-brain axis by which intestinal NAPE-PLD regulates appetite rapidly after lipid exposure.

Skeletal muscle promotes metabolic balance by regulating glucose uptake and the stimulation of multiple interorgan crosstalk. We show here that the catalytic activity of Vav2, a Rho GTPase activator, modulates the signaling output of the IGF1- and insulin-stimulated phosphatidylinositol 3-kinase pathway in that tissue. Consistent with this, mice bearing a Vav2 protein with decreased catalytic activity exhibit reduced muscle mass, lack of proper insulin responsiveness and, at much later times, a metabolic syndrome-like condition. Conversely, mice expressing a catalytically hyperactive Vav2 develop muscle hypertrophy and increased insulin responsiveness. Of note, while hypoactive Vav2 predisposes to, hyperactive Vav2 protects against high fat diet-induced metabolic imbalance. These data unveil a regulatory layer affecting the signaling output of insulin family factors in muscle.

Liver metabolism follows diurnal fluctuations through the modulation of molecular clock genes. Disruption of this molecular clock can result in metabolic disease but its potential regulation by immune cells remains unexplored. Here, we demonstrated that in steady state, neutrophils infiltrated the mouse liver following a circadian pattern and regulated hepatocyte clock-genes by neutrophil elastase (NE) secretion. NE signals through c-Jun NH2-terminal kinase (JNK) inhibiting fibroblast growth factor 21 (FGF21) and activating Bmal1 expression in the hepatocyte. Interestingly, mice with neutropenia, defective neutrophil infiltration or lacking elastase were protected against steatosis correlating with lower JNK activation, reduced Bmal1 and increased FGF21 expression, together with decreased lipogenesis in the liver. Lastly, using a cohort of human samples we found a direct correlation between JNK activation, NE levels and Bmal1 expression in the liver. This study demonstrates that neutrophils contribute to the maintenance of daily hepatic homeostasis through the regulation of the NE/JNK/Bmal1 axis.

Linaclotide is a synthetic peptide approved by the FDA for the treatment of constipation-predominant irritable bowel syndrome and chronic constipation. Linaclotide binds and activates the transmembrane receptor guanylate cyclase 2C (Gucy2c). Uroguanylin (UGN) is a 16 amino acid peptide that is mainly secreted by enterochromaffin cells in the duodenum and proximal small intestine. UGN is the endogenous ligand of Gucy2c and decreases body weight in diet-induced obese (DIO) mice via the activation of the thermogenic program in brown adipose tissue. Therefore, we wanted to evaluate whether oral linaclotide could also improve DIO mice metabolic phenotype. In this study, we have demonstrated that DIO mice orally treated with linaclotide exhibited a significant reduction of body weight without modifying food intake. Linaclotide exerts its actions through the central nervous system, and more specifically, via Gucy2c receptors located in the mediobasal hypothalamus, leading to the activation of the sympathetic nervous system to trigger the thermogenic activity of brown fat stimulating energy expenditure. These findings indicate for first time that, in addition to its effects at intestinal level to treat irritable bowel syndrome with constipation and chronic constipation, linaclotide also exerts a beneficial effect in whole body metabolism.