Abstract:
INTRODUCTION: Intestinal gluconeogenesis exerts metabolic benefits in energy homeostasis via the neural sensing of portal glucose. OBJECTIVE: The aim of this work was to determine central mechanisms involved in the effects of intestinal gluconeogenesis (IGN) on the control of energy homeostasis. METHODS: We investigated the effects of glucose infusion into the portal vein, at a rate that mimics IGN, in conscious wild-type, leptin-deficient ob/ob and CGRP-/- mice. RESULTS: We report that portal glucose infusion decreases food intake and plasma glucose and induces in the hypothalamic arcuate nucleus (ARC) the phosphorylation of STAT3, the classic intracellular messenger of leptin signaling. This notably takes place in POMC-expressing neurons. STAT3-phosphorylation does not require leptin, since portal glucose effects are observed in leptin-deficient (ob/ob) mice. We hypothesized that the portal glucose effects could require calcitonin gene-related peptide (CGRP), a neuromediator previously suggested to suppress hunger. In line with this hypothesis, neither the metabolic benefits nor the phosphorylation of STAT3 in the ARC take place upon portal glucose infusion in CGRP-deficient mice. Moreover, intracerebroventricular injection of CGRP activates hypothalamic phosphorylation of STAT3 in mice, and CGRP does the same in hypothalamic cells. Finally, no metabolic benefit of dietary fibers (known to depend on the induction of IGN), takes place in CGRP deficient mice. CONCLUSIONS: CGRP-induced phosphorylation of STAT3 in the ARC is part of the neural chain determining the hunger-modulating and glucose-lowering effects of IGN/portal glucose. CONCLUSIONS: CGRP-induced phosphorylation of STAT3 in the ARC is part of the neural chain determining the hunger-modulating and glucose-lowering effects of IGN/portal glucose.

Abstract:
An unfavorable lipid profile and being overweight are known mediators in the development of cardiovascular disease (CVD) risk. The effect of diet, particularly high in protein, remains under discussion. Therefore, this study examines the effects of a high-protein (HP) diet on cardiometabolic health and vascular function (i.e., endothelial function, arterial stiffness, and retinal microvascular structure), and the possible association with plasma endocannabinoids and endocannabinoid-related compounds in overweight participants. Thirty-eight participants (64.5 +/- 5.9 (mean +/- SD) years; body mass index (BMI) 28.9 +/- 4.0 kg/m(2)) were measured for 48 h in a respiration chamber after body-weight maintenance for approximately 34 months following weight reduction. Diets with either a HP (n = 20) or moderate protein (MP; n = 18) content (25%/45%/30% vs. 15%/55%/30% protein/carbohydrate/fat) were provided in energy balance. Validated markers for cardiometabolic health (i.e., office blood pressure (BP) and serum lipoprotein concentrations) and vascular function (i.e., brachial artery flow-mediated vasodilation, pulse wave analysis and velocity, and retinal microvascular calibers) were measured before and after those 48 h. Additionally, 24 h ambulatory BP, plasma anandamide (AEA), 2-arachidonoylglycerol (2-AG), oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and pregnenolone (PREG) were analyzed throughout the day. Office and ambulatory BP, serum lipoprotein concentrations, and vascular function markers were not different between the groups. Only heart rate (HR) was higher in the HP group. HR was positively associated with OEA, while OEA and PEA were also positively associated with total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol concentrations. Vascular function markers were not associated with endocannabinoids (or endocannabinoid-related substances). In conclusion, the HP diet did not affect cardiometabolic health and vascular function in overweight participants after completing a weight-loss intervention. Furthermore, our data indicate a possible association between OEA and PEA with TC and LDL cholesterol.

Abstract:
CONTEXT: Endocannabinoids are suggested to play a role in energy balance regulation. OBJECTIVE: We aimed to investigate associations of endocannabinoid concentrations during the day with energy balance and adiposity and interactions with 2 diets differing in protein content in participants in the post-obese phase with pre-diabetes. DESIGN AND PARTICIPANTS: Participants (n=38) were individually fed in energy balance with a medium protein (MP: 15:55:30% of energy from Protein:Carbohydrate:Fat) or high protein diet (HP: 25:45:30% energy from P:C:F) for 48-hours in a respiration chamber. MAIN OUTCOME MEASURES: Associations between energy balance, energy expenditure, RQ and endocannabinoid concentrations during the day were assessed. RESULTS: Plasma-concentrations of anandamide (AEA), oleoylethanolamide (OEA), palmitoyethanolamide (PEA), and pregnenolone (PREG) significantly decreased during the day. This decrease was inversely related to BMI (AEA) or body-fat (%) (PEA; OEA). The lowest RQ value, before lunch, was inversely associated with concentrations of AEA and PEA before lunch. AUC of concentrations of AEA, 2-AG, PEA, and OEA were positively related to body-fat% (p<0.05). The HP and MP groups showed no differences in concentrations of AEA, OEA, PEA, and PREG, but the AUC of 2-arachidonoylglycerol (2-AG) was significantly higher in the HP vs. the MP group. CONCLUSIONS: In energy balance, only the endocannabinoid 2-AG changed in relation to protein level of the diet, while the endocannabinoid AEA, and endocannabinoid-related compounds OEA and PEA reflected the gradual energy intake matching energy expenditure over the day.

Abstract:
Pharmacological blockers of the cannabinoid receptor type-1 (CB1) have been considered for a long time as the holy grail of obesity pharmacotherapy. These agents were hastily released in the clinical setting, due to their clear-cut therapeutic efficacy. However, the first generation of these drugs, which were able to target both the brain and peripheral tissues, had serious neuropsychiatric effects, leading authorities to ban their clinical use. New peripherally restricted CB1 blockers, characterized by low brain penetrance, have been developed over the past 10 years. In preclinical studies, these molecules seem to overcome the neuropsychiatric negative effects previously observed with brain-penetrant CB1 inhibitors, while retaining or even outperforming their efficacy. The mechanisms of action of these peripherally restricted compounds are only beginning to emerge, and a balanced discussion of the risk/benefits ratio associated to their possible clinical use is urgently needed, in order to avoid repeating past mistakes. Here, we will critically discuss the advantages and the possible hidden threats associated with the use of peripheral CB1 blockers for the pharmacotherapy of obesity and its associated metabolic complications. We will address whether this novel pharmacological approach might 'compete' with current pharmacotherapies for obesity and diabetes, while also conceptualizing future CB1-based pharmacological trends that may significantly lower the risk/benefits ratio associated with the use of these drugs.

Abstract:
One important lesson from the last decade of studies in the field of systemic energy metabolism is that obesity is first and foremost a brain disease. Hypothalamic neurons dysfunction observed in response to chronic metabolic stress is a key pathogenic node linking consumption of hypercaloric diets with body weight gain and associated metabolic sequelae. A key hypothalamic neuronal population expressing the neuropeptide Pro-opio-melanocortin (POMC) displays altered electrical activity and dysregulated neuropeptides production capacity after long-term feeding with hypercaloric diets. However, whether such neuronal dysfunction represents a consequence or a mechanism of disease, remains a subject of debate. Here, we will review and highlight emerging pathogenic mechanisms that explain why POMC neurons undergo dysfunctional activity in response to caloric overload, and critically address whether these mechanisms may be causally implicated in the physiopathology of obesity and of its associated co-morbidities.

Abstract:
Favorable effects of a high-protein/moderate-carbohydrate (HP/MCHO) diet after weight loss on body weight management have been shown. To extend these findings, associations between perception of hunger and satiety with endocannabinoids, and with glucagon-like peptide-1 (GLP-1) and polypeptide YY (PYY) were assessed. At approximately 34 months after weight loss, 22 female and 16 male participants (mean age 64.5 +/- 5.9 years; body mass index (BMI) 28.9 +/- 3.9 kg/m(2)) completed a 48 h respiration chamber study. Participants were fed in energy balance with a HP/MCHO diet with 25%:45%:30% or a moderate-protein/high-carbohydrate (MP/HCHO) diet with 15%:55%:30% of energy from protein:carbohydrate:fat. Endocannabinoids and related compounds, relevant postprandial hormones (GLP-1, PYY), hunger, satiety, and ad libitum food intake were assessed. HP/MCHO versus MP/HCHO reduced hunger perception. The lower decremental area under the curve (dAUC) for hunger in the HP/MCHO diet (-56.6% compared to MP, p < 0.05) was associated with the higher AUC for 2-arachidonoylglycerol (2-AG) concentrations (p < 0.05). Hunger was inversely associated with PYY in the HP/MCHO group (r = -0.7, p < 0.01). Ad libitum food intake, homeostatic model assessment for insulin resistance (HOMA-IR) and incremental AUCs for gut peptides were not different between conditions. HP/MCHO versus MP/HCHO diet-induced reduction in hunger was present after 34 months weight maintenance in the post-obese state. HP/MCHO diet-induced decrease of hunger is suggested to interact with increased 2-AG and PYY concentrations.

Abstract:
OBJECTIVE: The hypothalamic paraventricular nucleus (PVN) is a key target of the melanocortin system, which orchestrates behavioral and metabolic responses depending on energy availability. The mechanistic target of rapamycin complex 1 (mTORC1) and the endocannabinoid type 1 receptor (CB1R) pathways are two key signaling systems involved in the regulation of energy balance whose activity closely depends upon energy availability. Here we tested the hypothesis that modulation of mTORC1 and CB1R signaling regulates excitatory glutamatergic inputs onto the PVN. METHODS: Patch-clamp recordings in C57BL/6J mice, in mice lacking the mTORC1 component Rptor or CB1R in pro-opio-melanocortin (POMC) neurons, combined with pharmacology targeting mTORC1, the melanocortin receptor type 4 (MC4R), or the endocannabinoid system under chow or a hypercaloric diet. RESULTS: Acute pharmacological inhibition of mTORC1 in C57BL/6J mice decreased glutamatergic inputs onto the PVN via a mechanism requiring modulation of MC4R, endocannabinoid 2-AG mobilization by PVN parvocellular neurons, and retrograde activation of presynaptic CB1R. Further electrophysiology studies using mice lacking mTORC1 activity or CB1R in POMC neurons indicated that the observed effects involved mTORC1 and CB1R-dependent regulation of glutamate release from POMC neurons. Finally, energy surfeit caused by hypercaloric high-fat diet feeding, rapidly and time-dependently altered the glutamatergic inputs onto parvocellular neurons and the ability of mTORC1 and CB1R signaling to modulate such excitatory activity. CONCLUSIONS: These findings pinpoint the relationship between mTORC1 and endocannabinoid-CB1R signaling in the regulation of the POMC-mediated glutamatergic inputs onto PVN parvocellular neurons and its rapid alteration in conditions favoring the development of obesity.

Abstract:
Glial cells have emerged as key players in the central control of energy balance and etiology of obesity. Astrocytes play a central role in neural communication via the release of gliotransmitters. Acyl-CoA binding protein (ACBP)-derived endozepines are secreted peptides that modulate the GABAA receptor. In the hypothalamus, ACBP is enriched in arcuate nucleus (ARC) astrocytes, ependymocytes and tanycytes. Central administration of the endozepine octadecaneuropeptide (ODN) reduces feeding and improves glucose tolerance, yet the contribution of endogenous ACBP in energy homeostasis is unknown. We demonstrated that ACBP deletion in GFAP+ astrocytes, but not in Nkx2.1-lineage neural cells, promoted diet-induced hyperphagia and obesity in both male and female mice, an effect prevented by viral rescue of ACBP in ARC astrocytes. ACBP-astrocytes were observed in apposition with proopiomelanocortin (POMC) neurons and ODN selectively activated POMC neurons through the ODN-GPCR but not GABAA, and supressed feeding while increasing carbohydrate utilization via the melanocortin system. Similarly, ACBP overexpression in ARC astrocytes reduced feeding and weight gain. Finally, the ODN-GPCR agonist decreased feeding and promoted weight loss in ob/ob mice. These findings uncover ACBP as an ARC gliopeptide playing a key role in energy balance control and exerting strong anorectic effects via the central melanocortin system.

Abstract:
BACKGROUND: Spinal reactive astrocytes and microglia are known to participate to the initiation and maintenance of neuropathic pain. However, whether reactive astrocytes and microglia in thalamic nuclei that process sensory-discriminative aspects of pain play a role in pain behavior remains poorly investigated. Therefore, the present study evaluated whether the presence of reactive glia (hypertrophy, increased number and upregulation of glial markers) in the ventral posterolateral thalamic nucleus (VPL) correlates with pain symptoms, 14 and 28 days after unilateral L5/L6 spinal nerve ligation (SNL) in rats. METHODS: Mechanical allodynia and hyperalgesia (von Frey filament stimulation) as well as ambulatory pain (dynamic weight bearing apparatus) were assessed. Levels of nine glial transcripts were determined by quantitative real-time PCR on laser microdissected thalamic nuclei, and levels of proteins were assessed by Western blot. We also studied by immunohistofluorescence the expression of glial markers that label processes (GFAP for astrocytes and iba-1 for microglia) and cell body (S100beta for astrocytes and iba-1 for microglia) and quantified the immunostained surface and the number of astrocytes and microglia (conventional counts and optical dissector method of stereological counting). RESULTS: Differential, time-dependent responses were observed concerning microglia and astrocytes. Specifically, at day 14, iba-1 immunostained area and number of iba-1 immunopositive cells were decreased in the VPL of SNL as compared to naive rats. By contrast, at day 28, GFAP-immunostained area was increased in the VPL of SNL as compared to naive rats while number of GFAP/S100beta immunopositive cells remained unchanged. Using quantitative real-time PCR of laser microdissected VPL, we found a sequential increase in mRNA expression of cathepsin S (day 14), fractalkine (day 28), and fractalkine receptor (day 14), three well-known markers of microglial reactivity. Using Western blot, we confirmed an increase in protein expression of fractalkine receptor at day 14. CONCLUSIONS: Our results demonstrate a sequential alteration of microglia and astrocytes in the thalamus of animals with lesioned peripheral nerves. Furthermore, our data report unprecedented concomitant molecular signs of microglial activation and morphological signs of microglial decline in the thalamus of these animals.

Abstract:
OBJECTIVE: The aim of this study was to determine whether downstream [peroxisome proliferator-activated-receptor alpha (PPARalpha) and the G-protein coupled receptor, GPR119] and upstream (a fatty acid translocase, CD36) signaling targets of N-oleoylethanolamide (OEA) were necessary for weight loss, metabolic improvements, and diet preference following vertical sleeve gastrectomy (VSG). SUMMARY BACKGROUND DATA: OEA is an anorectic N-acylethanolamine produced from dietary fats within the intestinal lumen that can modulate lipid metabolism, insulin secretion, and energy expenditure by activating targets such as PPARalpha and GPR119. METHODS: Diet-induced obese mice, including wild-type or whole body knockout (KO) of PPARalpha, GPR119, and CD36, were stratified to either VSG or sham surgery before body weight, body composition, diet preference, and glucose and lipid metabolic endpoints were assessed. RESULTS: We found increased duodenal production of OEA and expression of both GPR119 and CD36 were upregulated in wild-type mice after VSG. However, weight loss and glucose tolerance were improved in response to VSG in PPARalphaKO, GPR119KO, and CD36KO mice. In fact, VSG corrected hepatic triglyceride dysregulation in CD36KO mice, and circulating triglyceride and cholesterol levels in PPARalphaKO mice. Lastly, we found PPARalpha-mediated signaling contributes to macronutrient preference independent of VSG, while removal of CD36 signaling blunts the VSG-induced shift toward carbohydrate preference. CONCLUSIONS: In the search for more effective and less invasive therapies to help reverse the global acceleration of obesity and obesity-related disease OEA is a promising candidate; however, our data indicate that it is not an underlying mechanism of the effectiveness of VSG.