Similarities and differences in the transcriptional regulation of the leptin gene promoter in gastric and adipose cells

AbstractThe stomach was reported to synthesize and secrete leptin mainly in the gastric lumen. Gastric leptin release is markedly increased after food intake, by vagal cholinergic stimulation and by cholecystokinin and secretin. Here we show that human gastric MKN-74 cells produce leptin that increases upon challenge with cholecystokinin, insulin, glucocorticoids and all-trans retinoic acid through activation of the leptin gene promoter. In addition, we demonstrate that forskolin and BRL37344 which increased cAMP levels, fail to affect the activity of leptin gene promoter in MKN74 expressing β3-adrenoceptor cells but, induce a 2-fold decrease in this activity in adipose 3T3-L1 cells. These data described for the first time, similarities and more interestingly, differences in the regulation of the leptin gene promoter in gastric cells as compared to adipocytes

Luminal leptin inhibits L-glutamine transport in rat small intestine: involvement of ASCT2 and B0AT1.

L-glutamine is the primary metabolic fuel for enterocytes. Glutamine from the diet is transported into the absorptive cells by two sodium-dependent neutral amino acid transporters present at the apical membrane: ASCT2/SLC1A5 and B(0)AT1/SLC6A19. We have demonstrated that leptin is secreted into the stomach lumen after a meal and modulates the transport of sugars after binding to its receptors located at the brush border of the enterocytes. The present study was designed to address the effect of luminal leptin on Na(+)-dependent glutamine (Gln) transport in rat intestine and identify the transporters involved. We found that 0.2 nM leptin inhibited uptake of Gln and phenylalanine (Phe) (substrate of B(0)AT1) using everted intestinal rings. In Ussing chambers, 10 mM Gln absorption followed as Na(+)-induced short-circuit current was inhibited by leptin in a dose-dependent manner (maximum inhibition at 10 nM; I(C50) = approximately 0.1 nM). Phe absorption was also decreased by leptin. Western blot analysis after 3-min incubation of the intestinal loops with 10 mM Gln, showed marked increase of ASCT2 and B(0)AT1 protein in the brush-border membrane that was reduced by rapid preincubation of the intestinal lumen with 1 nM leptin. Similarly, the increase in ASCT2 and B(0)AT1 gene expression induced by 60-min incubation of the intestine with 10 mM Gln was strongly reduced after a short preincubation period with leptin. Altogether these data demonstrate that, in rat, leptin controls the active Gln entry through reduction of both B(0)AT1 and ASCT2 proteins traffic to the apical plasma membrane and modulation of their gene expression

Positive Regulatory Control Loop between Gut Leptin and Intestinal GLUT2/GLUT5 Transporters Links to Hepatic Metabolic Functions in Rodents

International audienceBACKGROUND AND AIMS: The small intestine is the major site of absorption of dietary sugars. The rate at which they enter and exit the intestine has a major effect on blood glucose homeostasis. In this study, we determine the effects of luminal leptin on activity/expression of GLUT2 and GLUT5 transporters in response to sugars intake and analyse their physiological consequences. METHODOLOGY: Wistar rats, wild type and AMPKalpha(2) (-/-) mice were used. In vitro and in vivo isolated jejunal loops were used to quantify transport of fructose and galactose in the absence and the presence of leptin. The effects of fructose and galactose on gastric leptin release were determined. The effects of leptin given orally without or with fructose were determined on the expression of GLUT2/5, on some gluconeogenesis and lipogenic enzymes in the intestine and the liver. PRINCIPAL FINDINGS: First, in vitro luminal leptin activating its receptors coupled to PKCbetaII and AMPKalpha, increased insertion of GLUT2/5 into the brush-border membrane leading to enhanced galactose and fructose transport. Second in vivo, oral fructose but not galactose induced in mice a rapid and potent release of gastric leptin in gastric juice without significant changes in plasma leptin levels. Moreover, leptin given orally at a dose reproducing comparable levels to those induced by fructose, stimulated GLUT5-fructose transport, and potentiated fructose-induced: i) increase in blood glucose and mRNA levels of key gluconeogenesis enzymes; ii) increase in blood triglycerides and reduction of mRNA levels of intestinal and hepatic Fasting-induced adipocyte factor (Fiaf) and iii) increase in SREBP-1c, ACC-1, FAS mRNA levels and dephosphorylation/activation of ACC-1 in liver. CONCLUSION/SIGNIFICANCE: These data identify for the first time a positive regulatory control loop between gut leptin and fructose in which fructose triggers release of gastric leptin which, in turn, up-regulates GLUT5 and concurrently modulates metabolic functions in the liver. This loop appears to be a new mechanism (possibly pathogenic) by which fructose consumption rapidly becomes highly lipogenic and deleterious

Inhibitory Effect of Ursodeoxycholic Acid on Clostridium difficile Germination Is Insufficient to Prevent Colitis: A Study in Hamsters and Humans

Introduction: Bile acids (BA) influence germination and growth of Clostridium difficile. Ursodeoxycholic acid (UDCA), a BA minor in human, used for cholestatic liver diseases, inhibits germination and growth of C. difficile in vitro, but was never tested in vivo with an infectious challenge versus control. We hypothesized that UDCA could prevent CDI. We evaluated the effects of UDCA on C. difficile in vitro and in hamsters, with pharmacokinetics study and with an infectious challenge. Then, we studied CDI incidence in UDCA–treated patients.Methods: We evaluated germination and growth of C. difficile, with 0.01, 0.05, and 0.1% UDCA. We analyzed fecal BA of hamsters receiving antibiotics and UDCA (50 mg/kg/day), antibiotics, or UDCA alone. Then, we challenged with spores of C. difficile at D6 hamsters treated with UDCA (50 mg/kg/day) from D1 to D13, versus control. In human, we analyzed the database of a cohort on CDI in acute flares of inflammatory bowel disease (IBD). As PSC-IBD patients were under UDCA treatment, we compared PSC-IBD patients to IBD patients without PSC.Results:In vitro, UDCA inhibited germination and growth of C. difficile at 0.05 and 0.1%, competing with 0.1% TCA (with 0.1%: 0.05% ± 0.05% colony forming unit versus 100% ± 0%, P < 0.0001). In hamsters, UDCA reached high levels only when administered with antibiotics (43.5% UDCA at D5). Without antibiotics, UDCA was in small amount in feces (max. 4.28%), probably because of UDCA transformation into LCA by gut microbiota. During infectious challenge, mortality was similar in animals treated or not with UDCA (62.5%, n = 5/8, P = 0.78). UDCA percentage was high, similar and with the same kinetics in dead and surviving hamsters. However, dead hamsters had a higher ratio of primary over secondary BA compared to surviving hamsters. 9% (n = 41/404) of IBD patients without PSC had a CDI, versus 25% (n = 4/12) of PSC-IBD patients treated with UDCA.Conclusion: We confirmed the inhibitory effect of UDCA on growth and germination of C. difficile in vitro, with 0.05 or 0.1% UDCA. However, in our hamster model, UDCA was inefficient to prevent CDI, despite high levels of UDCA in feces. Patients with PSC-IBD treated with UDCA did not have less CDI than IBD patients

Régulation des transports entérocytaires de sucres par la leptine digestive (impact sur l'homéostasie glucidique et énergétique)

Les signaux moléculaires produits en réponse au repas le long du tractus gastro-intestinal ont été largement impliqués dans le contrôle de l homéostasie énergétique. La leptine produite par l estomac fait partie de ces signaux car elle contrôle à court terme les apports énergétiques via les afférences du nerf vague et via l absorption des nutriments. Mes travaux avaient pour buts: d étudier les effets de la leptine digestive sur l activité et l expression des transporteurs GLUT2/5, puis de déterminer l impact de cette régulation sur l homéostasie glucidique et énergétique. Nous avons d abord démontré que la leptine augmente l absorption de fructose dépendante de GLUT5. Les mécanismes intracellulaires mettent en jeu l activation de l AMPK alpha 2 et de PKC ßII dans l intestin grêle. Cet effet était retrouvé in vivo chez la souris, après une administration orale de leptine sur l activité et la transcription de GLUT2/5. Nous avons ensuite étendu ce contrôle au nouveau transporteur de fructose/glucose GLUT7. L augmentation de l absorption de fructose par la leptine orale, était accompagnée d une hyperglycémie, hypertriglycéridémie et d une augmentation du contenu hépatique en fructose. Dans le foie, l induction par le fructose du facteur de transcription SREBP1c hépatique, d ACC-1 et de FAS est potentialisée lorsque la leptine est ingérée avec le fructose. Ces travaux nous ont permis d identifier pour la première fois une boucle de régulation positive entre la leptine et le fructose dans laquelle: le fructose augmente la sécrétion de leptine favorisant son absorption spécifique par GLUT5, avec pour conséquence une élévation péjorative des lipides disponiblesPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Tractus gastro-intestinal et tissu adipeux brun (identification de nouvelles fonctions biologiques de la leptine)

La leptine, produit du gène ob cloné en 1994, est une protéine circulante impliquée dans la régulation de la balance énergétique. Hormone adipocytaire, elle constituerait le maillon essentiel de la chaîne contrôlant l'homéostasie qui conduit des réserves adipeuses au comportement prandial. Cependant, la leptine serait impliquée également dans la régulation de fonctions aussi diverses que la reproduction, les réponses immunitaires et inflammatoires, le remodelage osseux, la cancérogenèse. Bien que le tissu adipeux blanc demeure la source majeure de leptine, le statut de protéine exclusivement adipocytaire doit être nuancé puisque d'autres sites de synthèse dont le muscle squelettique, le placenta et l'estomac ont été décrits. Cette thèse s'insrit dans le cadre de l'étude de la caractérisation et de l'identification de rôles physiologiques de la leptine du tissu adipeux brun et de l'estomac...PARIS-BIUP (751062107) / SudocSudocFranceF

Assessment of cowpea and groundnut contributions to soil fertility and succeeding sorghum yields in the Guinean savannah zone of Burkina Faso (West Africa)

Atmospheric biological nitrogen fixation (BNF) by cowpea (Vigna unguiculata) and groundnut (Arachis hypogea) was evaluated using a 2-year (2000–2001) experiment with different fertilizer treatments. The 15N isotopic dilution method with a nonfixing cowpea as test reference crop was used. The effects of the two legumes on soil N availability and succeeding sorghum (Sorghum bicolor) yields were measured. Groundnut was found to fix 8 to 23 kg N ha-1 and the percentage of N derived from the atmosphere varied from 27 to 34%. Cowpea fixed 50 to 115 kg N ha?1 and the percentage of N derived from the atmosphere varied from 52 to 56%. Compared to mineral NPK fertilizer alone, legumes fixed more N from the atmosphere when dolomite or manure was associated with mineral fertilizers. Compared to soluble phosphate, phosphate rock increased BNF by cowpea. Significant correlation (p<0.05, R 2=0.94) was observed between total N yields of legumes and total N derived from the atmosphere. Compared to monocropping of sorghum, the soils of cowpea–sorghum and groundnut–sorghum rotations increased soil mineral N from 15 and 22 kg N ha?1, respectively. Cowpea–sorghum and groundnut–sorghum rotations doubled N uptake and increased succeeding sorghum yields by 290 and 310%, respectively. Results suggested that, despite their ability to fix atmospheric nitrogen, N containing fertilizers (NPK) are recommended for the two legumes. The applications of NPK associated with dolomite or cattle manure or NK fertilizer associated with phosphate rock were the better recommendations that improved BNF, legumes, and succeeding sorghum yields

Quel rôle pour le glucagon-like peptide 1 produit par l’estomac ?

International audienceNo abstract availabl

Reply to Pattou et al. GASTRO-D-16-00421

International audienceWe thank Pattou, Daoudi and Baud for their interest in our work 1 , as well as for their complementary work 2 , on intestinal absorption of ingested glucose after Roux-en-Y Gastric Bypass (RYGB). Based on their recent data obtained with a minipig model of RYGB, they claim this bariatric surgery to affect postprandial glucose metabolism primarily by modulating sodium-glucose intestinal cotransport. They further propose this hypothesis as an " alternative explanation " of our previous data obtained in a rat model and in human subjects who underwent RYGB surgery. First of all, and contrary to what is stated in the above Letter, we never concluded in Cavin et al. 1 that " RYGB does not modify the uptake of ingested glucose ". Our ex vivo studies on intestinal transport revealed that greater amounts of ingested glucose remain within the Roux limb mucosa, as shown by increased luminal glucose uptake and increased SGLT-1 activity when compared to sham rats 1. In vivo, such a retention may result in a reduced transfer of ingested glucose to the blood

Intestinal Adaptations after Bariatric Surgery: Consequences on Glucose Homeostasis

International audienceThe gastrointestinal (GI) tract can play a direct role in glucose homeostasis by modulating the digestion and absorption of carbohydrates and by producing the incretin hormones. In recent years, numerous studies have focused on intestinal adaptation following bariatric surgeries. Changes in the number of incretin- (GLP-1, GIP) producing cells have been reported which could result in the modified hormonal response seen after surgery. Additionally, the rate of absorption and the intestinal regions exposed to sugars may affect the time course of appearance of glucose in the blood. This review gives new insights into the direct role of the GI tract in the metabolic outcomes of bariatric surgery, in the context of glucose homeostasis