Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis [Chahira Snoussi, Robert Ducroc, Mohamed Hédi Hamdaoui, Karima Dhaouadi, Houda Abaidi, Francoise Cluzeaud, Corinne Nazaret, Maude Le Gall, André Bado* (Inserm UMRS1149, UFR de Médecine Paris 7, Université Paris Diderot, Sorbonne Paris Cité, Paris, France), The Journal of Nutritional Biochemistry, 2014, 25(5), 557–564].

BACKGROUND & AIMSBariatric procedures, such as Roux-en-Y gastric bypass (RYGB) or vertical sleeve gastrectomy (VSG), are the most effective approaches to resolve type 2 diabetes in obese individuals. Alimentary glucose absorption and intestinal disposal of blood glucose have not been directly compared between individuals or animals that underwent RYGB vs VSG. We evaluated in rats and humans how the gut epithelium adapts after surgery and the consequences on alimentary glucose absorption and intestinal disposal of blood glucose.METHODSObese male rats underwent RYGB, VSG, or sham (control) operations. We collected intestine segments from all rats; we performed histologic analyses and measured levels of messenger RNAs encoding the sugar transporters SGLT1, GLUT1, GLUT2, GLUT3, GLUT4, and GLUT5. Glucose transport and consumption were assayed using ex vivo jejunal loops. Histologic analyses were also performed on Roux limb sections from patients who underwent RYGB 1-5 years after surgery. Roux limb glucose consumption was assayed after surgery by positron emission and computed tomography imaging.RESULTSIn rats and humans that underwent RYGB, the Roux limb became hyperplasic, with an increased number of incretin-producing cells compared with the corresponding jejunal segment of controls. Furthermore, expression of sugar transporters and hypoxia-related genes increased and the nonintestinal glucose transporter GLUT1 appeared at the basolateral membrane of enterocytes. Ingested and circulating glucose was trapped within the intestinal epithelial cells of rats and humans that underwent RYGB. By contrast, there was no hyperplasia of the intestine after VSG, but the intestinal absorption of alimentary glucose was reduced and density of endocrine cells secreting glucagon-like peptide-1 increased.CONCLUSIONSThe intestine adapts differently to RYGB vs VSG. RYGB increases intestinal glucose disposal and VSG delays glucose absorption; both contribute to observed improvements in glycemia.

Objective: Olive mill wastewater (OMWW) is a by-product of olive oil production and contains biologically active compounds. The aim of this study was to investigate the effect of OMWW on intestinal glucose absorption in mice, a target for treating diabetes. Methods: The effect oral administration of OMWW on mice glycemia was evaluated by oral glucose tolerance tests (OGTT), and mice jejunal mucosal strips were mounted in Ussing chambers to evaluate the activity of sodium-dependent glucose transporter (SGLT-1). Western blot analysis was performed to study SGLT-1 and protein kinase C (PKC) at the brush border membranes (BBM) of mice jejunal mucosa. Results: We found that the raised glycemia in mice in response to oral glucose administration (OGTT) was decreased in presence of OMWW, being highly effective at 4 g/kg of body weight. Further, OMWW inhibited glucose induced short-circuit current (Isc) in mice jejunal, which is a marker of SGLT-1 activity. The effect was rapid, with maximal inhibition of 80 % versus control. Also, OMWW induced a strong decrease of SGLT-1 protein (60%) as well as PKC (30%), a key effector protein in BBM of mice jejunal mucosa in response to glucose. Conclusion: Our results suggest that OMWW may be beneficial for diabetes through its novel hypoglycemic effect by acting on the PKC-SGLT-1 axis.

•GTD and BTD reduced liver content of total lipids and triglycerides, plasma triglycerides, glucose and total cholesterol.•GTD and BTD reduced lipid digestion by increasing fecal lipids and triglycerides excretion.•GTD and BTD reduced adipose tissue gains, which is consistent with the reduction of circulating leptin levels.•GTD and BTD reduced body weight gain of rats fed HFD.•Although the amount of TPC was more important in GTD, the BTD is more efficient than GTD.

Diet is among the most important factors contributing to intestinal homeostasis, and basic functions performed by the small intestine need to be tightly preserved to maintain health. Little is known about the direct impact of high-fat (HF) diet on small-intestinal mucosal defenses and spatial distribution of the microbiota during the early phase of its administration. We observed that only 30 d after HF diet initiation, the intervillous zone of the ileum-which is usually described as free of bacteria-became occupied by a dense microbiota. In addition to affecting its spatial distribution, HF diet also drastically affected microbiota composition with a profile characterized by the expansion of Firmicutes (appearance of Erysipelotrichi), Proteobacteria (Desulfovibrionales) and Verrucomicrobia, and decrease of Bacteroidetes (family S24-7) and Candidatus arthromitus A decrease in antimicrobial peptide expression was predominantly observed in the ileum where bacterial density appeared highest. In addition, HF diet increased intestinal permeability and decreased cystic fibrosis transmembrane conductance regulator (Cftr) and the Na-K-2Cl cotransporter 1 (Nkcc1) gene and protein expressions, leading to a decrease in ileal secretion of chloride, likely responsible for massive alteration in mucus phenotype. This complex phenotype triggered by HF diet at the interface between the microbiota and the mucosal surface was reversed when the diet was switched back to standard composition or when mice were treated for 1 wk with rosiglitazone, a specific agonist of peroxisome proliferator-activated receptor-γ (PPAR-γ). Moreover, weaker expression of antimicrobial peptide-encoding genes and intervillous bacterial colonization were observed in Ppar-γ-deficient mice, highlighting the major role of lipids in modulation of mucosal immune defenses.

L'origine de l'amélioration rapide de l'équilibre glycémique après bypass gastrique Roux-en-Y (RYGB) est encore discutée. Nous avons analysé dans un modèle murin et chez l'homme, l'adaptation de l'intestin après RYGB et les conséquences sur le transport et/ou la consommation intestinale du glucose alimentaire et sanguin. Des rats mâles obèses et intolérants au glucose ont été opérés de RYGB. 15 jours après la chirurgie, la cinétique du transport de glucose a été mesurée sur des anses jéjunales isolées ex vivo. Des analyses histologiques et immunohistochimiques ont été réalisées et l'expression des transporteurs de sucre a été analysée dans les différents segments intestinaux remodelés. Des analyses histologiques ont également été effectuées sur des segments de muqueuse jéjunale de l'anse alimentaire de sujets obèses opérés de RYGB depuis 1 à 5 ans. Les résultats ont été comparés à la muqueuse jéjunale de sujets obèses avant opération. La consommation de glucose par l'anse alimentaire a été par objectivée par imagerie PET/CT (Tomographie par émission de positons) en utilisant du fluorodésoxyglu-cose (18F). Chez les rats et les sujets obèses qui ont subi un RYGB, l'anse alimentaire est devenue hyperplasique par rapport au jéjunum des contrôles. En outre, le transporteur de glucose non-intestinal GLUT1 est apparu à la membrane basolatérale des entérocytes. Dans le modèle de rat, la consommation de glucose alimentaire et sanguin par l'anse alimentaire est fortement accrue (P < 0,001 vs contôle). Chez l'homme, l'imagerie PET-CT montre une augmentation du captage de fluorodésoxyglucose (18F) par l'anse alimentaire après RYGB comparé au jéjunum de sujets témoins. Nous montrons chez le rat et pour la première fois chez l'homme, une augmentation de la prolifération et une réexpression de GLUT1 dans l'anse alimentaire après RYGB. Très rapidement après l'opération, les capacités de transport et de consommation des sucres par le jéjunum changent, le captage du glucose alimentaire augmente ainsi que la consommation intestinale de glucose sanguin entre les repas. Ces deux effets pourraient contribuer à l'amélioration rapide de l'homéostasie glucidique après la chirurgie.

to crypts.Aquaporins are a family of cell plasma membrane channels; AQP3 transports water, and glycerol and putatively also hydrogen peroxide (H 2 O 2 ).AQP3 is expressed on the basolateral membrane of epithelial cells lining the colon, but its exact role in intestinal function in health and disease are not known.To investigate the epithelial specific role of AQP-3 in intestinal crypt formation, we generated small intestinal and colonic enteroids from wild-type and AQP-3 null mice.AQP-3 deficient enteroids exhibited slowed crypt budding and growth on initial isolation.To measure AQP-3 dependent H 2 O 2 transport, enteriods were virally transfected with a ratiometric fluorescent H 2 O 2 sensitive YFP.Enteroids were immobilized on matrigel coated coverslips in a small volume perfusion chamber and live fluorescence imaging carried out.AQP3 deficient enterocytes exhibited slowed membrane hydrogen peroxide transport at high extracellular (>100mM) concentrations.Enteroids grown with hydrogen peroxide on isolation resulted in a change in enteroid morphology.These data suggest that AQP-3 may play a role in crypt formation in response to injury.

BACKGROUND High-fat diets induce intestinal barrier alterations and promote intestinal diseases. Little is known about the effects of long-chain fatty acids (LCFAs) on mucin 2 (MUC2) production by goblet cells, which are crucial for intestinal protection. OBJECTIVE We investigated the effects of LCFAs on the differentiation of colonic goblet cells, MUC2 expression, and colonic barrier function. METHODS Upon reaching confluence, human colonic mucus-secreting HT29-MTX cells were stimulated (21 d) with a saturated LCFA (palmitic or stearic acid), a monounsaturated LCFA (oleic acid), or a polyunsaturated LCFA (linoleic, γ-linolenic, α-linolenic, or eicosapentaenoic acid). In addition, rat pups underwent oral administration of oil (palm, rapeseed, or sunflower oil) or water (10 μL/g body weight, postnatal days 10-15). Subsequently, colon goblet cells were studied by Western blotting, reverse transcriptase-quantitative polymerase chain reaction, and immunohistochemistry and colonic transmucosal electrical resistance was measured by using Ussing chambers. RESULTS In vitro, palmitic acid enhanced MUC2 production (140% of control) and hepatocyte nuclear factor 4α expression, whereas oleic, linoleic, γ-linolenic, α-linolenic, and eicosapentaenoic acids reduced MUC2 expression (at least -50% of control). All unsaturated LCFAs decreased the expression of human atonal homolog 1, a transcription factor controlling goblet cell differentiation (at least -31% vs. control). In vivo, rats fed palm oil had higher palmitic acid concentrations (3-fold) in their colonic contents and increased mucus granule surfaces in their goblet cells (>2-fold) than did all other groups. Palm oil also increased colonic transmucosal electrical resistance (245% of control), yet had no effect on occludin and zonula occludens-1 expression. In contrast, sunflower and rapeseed oils decreased goblet cell number when compared with control (at least -10%) and palm oil (at least -14%) groups. CONCLUSIONS Palm oil in rat pups and palmitic acid in HT29-MTX cells increase the production of MUC2 and strengthen the intestinal barrier. In contrast, unsaturated LCFAs decrease MUC2 expression. These data should be taken into account in the context of preventive or therapeutic nutritional programs.

Whereas the remodeling of intestinal mucosa after bariatric surgeries has been the matter of numerous studies to our knowledge, very few reported on the remodeling of the residual gastric mucosa. In this study, we analyzed remodeling of gastric mucosa after Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) in rats. Diet-induced obese rats were subjected to RYGB, VSG or sham surgical procedures. All animals were assessed for food intake, body-weight, fasting blood, metabolites and hormones profiling, as well as insulin and glucose tolerance tests before and up to 5 weeks post-surgery. Remodeling of gastric tissues was analyzed by routine histology and immunohistochemistry studies, and qRT-PCR analyses of ghrelin and gastrin mRNA levels. In obese rats with impaired glucose tolerance, VSG and RYGB caused substantial weight loss and rats greatly improved their oral glucose tolerance. The remaining gastric mucosa after VSG and gastric pouch (GP) after RYGB revealed a hyperplasia of the mucous neck cells that displayed a strong immunoreactivity for parietal cell H+/K+-ATPase. Ghrelin mRNA levels were reduced by 2-fold in remaining fundic mucosa after VSG and 10-fold in GP after RYGB. In the antrum, gastrin mRNA levels were reduced after VSG in line with the reduced number of gastrin positive cells. This study reports novel and important observations dealing with the remaining gastric mucosa after RYGB and VSG. The data demonstrate, for the first time, a hyperplasia of the mucous neck cells, a transit cell population of the stomach bearing differentiating capacities into zymogenic and peptic cells.

Leptin is secreted into the digestive tract and contributes to the absorption of dietary molecules by regulating transporters activity. Here, we studied the effect of luminal leptin on the intestinal transport of L-glutamate, an important component of human diet. We examined the effect of leptin on L-glutamate uptake in rat intestine in vitro measuring glutamate-induced short-circuit current (Isc) in Ussing chambers and L-[3H (U)]-glutamate uptake in jejunal everted rings. Glutamate-induced Isc was only observed in Na+-free conditions. This Isc was concentration (1–60 mmol L−1) and pH dependent. Luminal leptin increased glutamate Isc (∼100 %). Dose-response curve showed a biphasic pattern, with maximal stimulations observed at 10−13 and 10−10 mmol L−1, that were sensitive to leptin receptor antagonist. In everted rings, two glutamate transport mechanisms were distinguished: a Na+-dependent, H+-independent, that was inhibited by leptin (∼20 %), and a Na+-independent but H+-dependent, that was enhanced by leptin (∼20 %), in line with data obtained in Ussing chambers. Altogether, these data reveal original non-monotonic effect of luminal leptin in the intestine and demonstrate a new role for this hormone in the modulation of L-glutamate transport, showing that luminal active gut peptides can influence absorption of amino acids.

We investigated the effects of early colonizing bacteria on the colonic epithelium. We isolated dominant bacteria, Escherichia coli, Enterococcus faecalis, Lactobacillus intestinalis, Clostridium innocuum and a novel Fusobacterium spp., from the intestinal contents of conventional suckling rats and transferred them in different combinations into germfree (GF) adult rats. Animals were investigated after various times up to 21 days. Proliferative cell markers (Ki67, proliferating cell nuclear antigen, phospho-histone H3, cyclin A) were higher in rats monocolonized with E. coli than in GF at all time points, but not in rats monocolonized with E. faecalis. The mucin content of goblet cells declined shortly after E. coli administration whereas the mucus layer doubled in thickness. Fluorescence in situ hybridization analyses revealed that E. coli resides in this mucus layer. The epithelial mucin content progressively returned to baseline, following an increase in KLF4 and in the cell cycle arrest-related proteins p21CIP1 and p27KIP1. Markers of colonic differentiated cells involved in electrolyte (carbonic anhydrase II and slc26A3) and water (aquaglyceroporin3 (aqp3)) transport, and secretory responses to carbachol were modulated after E. coli inoculation suggesting that ion transport dynamics were also affected. The colonic responses to simplified microbiotas differed substantially according to whether or not E. coli was combined with the other four bacteria. Thus, proliferation markers increased substantially when E. coli was in the mix, but very much less when it was absent. This work demonstrates that a pioneer strain of E. coli elicits sequential epithelial remodeling affecting the structure, mucus layer and ionic movements and suggests this can result in a microbiota-compliant state.

Le syndrome de grêle court (SGC) résulte d'une résection étendue de l'intestin grêle et se caractérise par une insuffisance intestinale chronique. Le patient devient dépendant ou non de la nutrition parentérale (NP), selon la longueur de grêle restant, la présence ou non du côlon et de la capacité d'adaptation interindividuelle. Parmi les mécanismes de l'adaptation colique, il existe une hyperplasie des cryptes colique. Notre objectif est de comprendre les mécanismes moléculaires et cellulaires de l'adaptation fonctionnelle au niveau du colon résiduel après résection étendue du grêle et leur contribution à l'amélioration de l'absorption. Des rats Wistar ont subi une résection de 75 % d'intestin grêle, de la valve iléo-caecale et une colectomie partielle (IR) ou une transsection intestinale (témoins). Nous avons évalué la survie, la perte de poids et prélevés les fèces des rats IR et témoins pendant 7 jours. A J7 les rats ont été sacrifiés et le colon restant a été prélevé. Une étude morphologique de l'intestin restant a été réalisée (à partir de segments fixés). La perméabilité de l'épithélium et l'activité des transporteurs de glucose (SGLT1) et d'acides gras à chaine courtes AGCC (Slc5a8) ont été évaluées en chambre de Ussing sur 2 segments coliques. L'expression génique et/ou protéique des transporteurs SGLT-1, Slc5a8 et PepT1 (transporteur de di- et tri-peptides), a été quantifiée dans les muqueuses coliques par qRT-PCR et WB (à partir de segments coliques congelés). À J5 post-opératoire, ont été étudiés les AGCC (quantification par chromatographie en phase gazeuse) et le microbiote intestinal (qPCR 16sARNr). Les résultats sont exprimés en M ± SEM et analysés par des tests non paramétriques. Le taux de survie des rats IR était de 60 % à J7 post-opératoire. Une diminution progressive de la diarrhée est observée. La profondeur des cryptes coliques est augmentée chez les rats IR (1,5x, P < 0,0001 vs témoins). Chez les rats IR, la perméabilité de l'épithélium colique est augmentée (1,9x, P < 0,01 vs témoins) avec une augmentation de l'activité de SGLT-1 (5,7x, P < 0,05 vs témoins) alors que les taux d'ARNm SGLT-1 sont inchangés. L'expression (ARNm et protéine) de PepT1 est augmentée dans le colon des rats IR (3x, P < 0,05 vs témoins). L'activité de Slc5a8 (transport de butyrate) semble diminuée (3,5x) chez les rats IR avec une réduction de concentration fécale de butyrate. L'analyse du microbiote a révélé une dysbiose chez le rat IR. Ce travail confirme l'adaptation morphologique du côlon au cours du SGC chez l'animal. Pour la première fois, il est démontré l'acquisition d'une fonction absorptive de glucose par le côlon restant chez animal SGC. L'ensemble de ces résultats suggèrent que l'acquisition par le côlon de fonctions absorptives habituellement présentes au niveau du grêle, lui confère un rôle essentiel dans l'équilibre hydrominéral et nutritionnel du SGC.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease affecting the rectum which progressively extents. Its etiology remains unknown and the number of treatments available is limited. Studies of UC patients have identified an unbalanced endoplasmic reticulum (ER) stress in the non-inflamed colonic mucosa. Animal models with impaired ER stress are sensitive to intestinal inflammation, suggesting that an unbalanced ER stress could cause inflammation. However, there are no ER stress-regulating strategies proposed in the management of UC partly because of the lack of relevant preclinical model mimicking the disease. Here we generated the IL10/Nox1dKO mouse model which combines immune dysfunction (IL-10 deficiency) and abnormal epithelium (NADPH oxidase 1 (Nox1) deficiency) and spontaneously develops a UC-like phenotype with similar complications (colorectal cancer) than UC. Our data identified an unanticipated combined role of IL10 and Nox1 in the fine-tuning of ER stress responses in goblet cells. As in humans, the ER stress was unbalanced in mice with decreased eIF2α phosphorylation preceding inflammation. In IL10/Nox1dKO mice, salubrinal preserved eIF2α phosphorylation through inhibition of the regulatory subunit of the protein phosphatase 1 PP1R15A/GADD34 and prevented colitis. Thus, this new experimental model highlighted the central role of epithelial ER stress abnormalities in the development of colitis and defined the defective eIF2α pathway as a key pathophysiological target for UC. Therefore, specific regulators able to restore the defective eIF2α pathway could lead to the molecular remission needed to treat UC.

differed between Responders and Non-Responders at the P<0.05 level.OTUs and metabolites which were found to share significant correlations (q < 0.10) are highlighted in the Figure .Conclusions: Fecal metabolite composition differed between Responders and Non-Responders to a low fermentable substrate dietary intervention and are associated with differences in microbiome composition in children with IBS.Microbial factors such as gut microbiome composition and fecal metabolites may relate to dietary intervention efficacy.Further studies are needed to investigate the potential relationship between fecal metabolites and symptom generation/amelioration.

Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT-1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis.

The importance of B-isoform of leptin receptor (LEPR-B) signaling in the hypothalamus, pancreas, or liver has been well characterized, but in the intestine, a unique site of entry for dietary nutrition into the body, it has been relatively ignored. To address this question, we characterized a mouse model deficient for LEPR-B specifically in intestinal epithelial cells (IECs). (LEPR)-L-IEC-B-knockout (KO) and wild-type (WT) mice were generated by Cre-Lox strategy and fed a normal or high-fat diet (HFD). The analyses of the animals involved histology and immunohistochemistry of intestinal mucosa, indirect calorimetric measurements, whole-body composition, and expression and activities of nutrient transporters. (LEPR)-L-IEC-B-KO mice exhibited a 2-fold increase in length of jejunal villi and have normal growth on a normal diet but were less susceptible (P<0.01) to HFD-induced obesity. No differences occurred in energy intake and expenditure between (LEPR)-L-IEC-B-WT and -KO mice, but (LEPR)-L-IEC-B-KO mice fed an HFD showed increased excreted fats (P<0.05). Activities of the Na+/glucose cotransporter SGLT-1 and GLUT2 were unaffected in LEPR-B-KO jejunum, while GLUT5-mediated fructose transport and PepT1-mediated peptide transport were substantially reduced (P<0.01). These data demonstrate that intestinal LEPR-B signaling is important for the onset of diet-induced obesity. They suggest that intestinal LEPR-B could be a potential per os target for prevention against obesity.

OBJECTIVES: In obesity, while hyperleptinemia highly correlates with excess fat mass, the status of gastric leptin remains unknown. Here, we investigated the expression of leptin in stomach biopsies of obese humans and analyzed the temporal changes of gastric leptin expression in response to diet-induced obesity and its impact on 5-hydroxytryptamine (5HT)-producing cells.METHODS: Enterochromaffin (EC) cells and expression of leptin, PAX4 (critical factor for EC specification), tryptophane hydroxylase-1 (TPH1, the peripheral rate-limiting enzyme for 5HT) and 5HT were examined by immunofluorescence, quantitative real-time PCR, radioimmunoassay, respectively, in stomach and duodenum biopsies from 19 obese and 14 normo-weighed individuals, and in mucosa scrapings from C57Bl6/J diet-induced obese mice, leptin-deficient ob/ob mice and intestine-specific leptin receptor isoform B-deficient mice.RESULTS: Gastric mucosa of obese subjects displays an increased expression of leptin (LEP mRNA by fivefold and protein by twofold, P < 0.01), TPH1 ((1.75-2.73, 95% confidence interval (CI)) vs (0.38-0.67, 95% CI); P < 0.01) and PAX4 ((1.33-2.11, 95% CI) vs (0.62-0.81, 95% CI); P < 0.01) as compared with normo-weighed individuals. In diet-induced obese mice, the overexpressions of gastric leptin, antral Pax4, Tph1 and increased EC cell number occurred before the onset of obesity and hyperleptinemia (reflect of adipocyte leptin production). In addition, leptin deficiency was associated with reduced Pax4 mRNA, whereas oral leptin treatment enhanced both Tph1 and Pax4 mRNA. Finally, mice with an intestine-specific deletion of leptin signaling exhibit significant decrease in duodenal mucosa 5HT content.CONCLUSIONS: These data demonstrate that gastric leptin is upregulated in obese individuals. Results from high-fat diet mice showed that overexpression of gastric leptin that is linked to gut '5HT pathway' occurred before the onset of obesity and expansion of fat mass. This may be relevant in the pathophysiology of obesity.