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Intestinal gluconeogenesis (IGN), gastric bypass (GBP) and gut microbiota positively regulate glucose homeostasis and diet-induced dysmetabolism. GBP modulates gut microbiota, whether IGN could shape it has not been investigated. We studied gut microbiota and microbiome in wild type and IGN-deficient mice, undergoing GBP or not, and fed on either a normal chow (NC) or a high-fat/high-sucrose (HFHS) diet. We also studied fecal and urine metabolome in NC-fed mice. IGN and GBP had a different effect on the gut microbiota of mice fed with NC and HFHS diet. IGN inactivation increased abundance of Deltaproteobacteria on NC and of Proteobacteria such as Helicobacter on HFHS diet. GBP increased abundance of Firmicutes and Proteobacteria on NC-fed WT mice and of Firmicutes, Bacteroidetes and Proteobacteria on HFHS-fed WT mice. The combined effect of IGN inactivation and GBP increased abundance of Actinobacteria on NC and the abundance of Enterococcaceae and Enterobacteriaceae on HFHS diet. A reduction was observed in the amounf of short-chain fatty acids in fecal (by GBP) and in both fecal and urine (by IGN inactivation) metabolome. IGN and GBP, separately or combined, shape gut microbiota and microbiome on NC- and HFHS-fed mice, and modify fecal and urine metabolome.

International audience; ABSTRACT Background The role of hepatoportal glucose sensors is poorly understood in the context of insulin resistance. Objectives We assessed the effects of glucose infusion in the portal vein on insulin tolerance in 2 rat models of insulin resistance, and the role of capsaicin sensitive nerves in this signal. Methods Male Wistar rats, 8 weeks old, weighing 250–275 g, were used. Insulin and glucose tolerance were assessed following a 4-hour infusion of either glucose or saline through catheterization in the portal vein in 3 paradigms. In experiment 1, for diet-induced insulin resistance, rats were fed either a control diet (energy content: proteins = 22.5%, carbohydrates = 64.1%, and lipids = 13.4%) or a high-fat diet (energy content: proteins = 15.3%, carbohydrates = 40.3%, and lipids =44.4%) for 4 months. In experiment 2, for centrally induced peripheral insulin resistance, catheters were inserted in the carotid artery to deliver either an emulsion of triglycerides [intralipid (IL)] or saline towards the brain for 24 hours. In experiment 3, for testing the role of capsaicin-sensitive nerves, experiment 2 was repeated following a periportal treatment with capsaicin or vehicle. Results In experiment 1, when compared to rats fed the control diet, rats fed the high-fat diet exhibited decreased insulin and glucose tolerance (P ≤ 0.05) that was restored with a glucose infusion in the portal vein (P ≤ 0.05). In experiment 2, infusion of a triglyceride emulsion towards the brain (IL rats) decreased insulin and glucose tolerance and increased hepatic endogenous production when compared to saline-infused rats (P ≤ 0.05). Glucose infusion in the portal vein in IL rats restored insulin and glucose tolerance, as well as hepatic glucose production, to controls levels (P ≤ 0.05). In experiment 3, portal infusion of glucose did not increase insulin tolerance in IL rats that received a periportal pretreatment with capsaicin. Conclusions Stimulation of hepatoportal glucose sensors increases insulin tolerance in rat models of insulin resistance and requires the presence of capsaicin-sensitive nerves.

International audience; The excessive endogenous glucose production (EGP) induced by glucagon participates in the development of type 2 diabetes. To further understand this hormonal control, we studied the short-term regulation by cyclic adenosine monophosphate (cAMP) of the glucose-6-phosphatase (G6Pase) enzyme, which catalyzes the last reaction of EGP. In gluconeogenic cell models, a 1-h treatment by the adenylate cyclase activator forskolin increased G6Pase activity and glucose production independently of any change in enzyme protein amount or G6P content. Using specific inhibitors or protein overexpression, we showed that the stimulation of G6Pase activity involved the protein kinase A (PKA). Results of site-directed mutagenesis, mass spectrometry analyses, and in vitro phosphorylation experiments suggested that the PKA stimulation of G6Pase activity did not depend on a direct phosphorylation of the enzyme. However, the temperature-dependent induction of both G6Pase activity and glucose release suggested a membrane-based mechanism. G6Pase is composed of a G6P transporter (G6PT) and a catalytic unit (G6PC). Surprisingly, we demonstrated that the increase in G6PT activity was required for the stimulation of G6Pase activity by forskolin. Our data demonstrate the existence of a post-translational mechanism that regulates G6Pase activity and reveal the key role of G6PT in the hormonal regulation of G6Pase activity and of EGP.Erratum inCorrection to "Post-Translational Regulation of the Glucose-6-Phosphatase Complex by Cyclic Adenosine Monophosphate Is a Crucial Determinant of Endogenous Glucose Production and Is Controlled by the Glucose-6-Phosphate Transporter". [J Proteome Res. 2016]PMID: 27111186 DOI: 10.1021/acs.jproteome.6b00284

International audience; MINI-ABSTRACTWe performed bile diversions matching the modified biliary flow occurring after gastric bypass (GBP)in rats. Our results strongly suggest that the only modification of bile routing mimics the mainmetabolic benefits of GBP: 1) improved glucose control, 2) decreased food intake because ofdisinterest in high calorie food.STRUCTURED ABSTRACTObjective: To evaluate the role of bile routing modification on the beneficial effects of gastric bypasssurgery on glucose and energy metabolism.Summary background data: Gastric bypass surgery (GBP) promotes early improvements in glucoseand energy homeostasis in obese diabetic patients. A suggested mechanism associates a decrease inhepatic glucose production (HGP) to an enhanced intestinal gluconeogenesis (IGN). Moreover,plasma bile acids are elevated after GBP and bile acids are inhibitors of gluconeogenesis.Methods: In male Sprague-Dawley rats, we performed bile diversions from the bile duct to the midjejunumor the mid-ileum to match the modified bile delivery in the gut occurring in GBP. Bodyweight, food intake, glucose tolerance, insulin sensitivity and food preference were analyzed. Theexpression of gluconeogenesis genes was evaluated in both the liver and the intestine.Results: Bile diversions mimicking GBP promote an increase in plasma bile acids and a markedimprovement in glucose control. Bile bioavailability modification is causal since a bile acidsequestrant suppresses the beneficial effects of bile diversions on glucose control. In agreement withthe inhibitory role of bile acids on gluconeogenesis, bile diversions promote a blunting in HGP,whereas IGN is increased in the gut segments devoid of bile. In rats fed a high fat-high sucrose diet,bile diversions improve glucose control and dramatically decrease food intake due to an acquireddisinterest in fatty food.Conclusion: This study shows that bile routing modification is a key mechanistic feature in thebeneficial outcomes of GBP.

Roux-en-Y gastric bypass (RYGB) induces remission or substantial improvement of type 2 diabetes mellitus (T2D) but underlying mechanisms are still unclear. The beneficial effects of dietary proteins on energy and glucose homeostasis are mediated by the antagonist effects of peptides toward mu-opioid receptors (MORs), which are highly expressed in the distal gut. We hypothesized that the beneficial effects of RYGB could depend at least in part on the interaction of peptides from food with intestinal MORs. Duodenal-jejunal bypass (DJB) was performed in obese and lean wild-type (WT) or MOR deficient (MOR−/−) mice. Food intake and body weight was monitored daily during 3 weeks. Glucose homeostasis was assessed from glucose and insulin tolerance tests. In obese WT and MOR−/− mice, DJB induced a rapid and sustained weight loss partly independent of food intake, and a rapid improvement in glycaemic parameters. Weight loss was a major determinant of the improvements observed. In lean WT and MOR−/− mice, DJB had no effect on weight loss but significantly enhanced glucose tolerance. We found that MORs are not essential in the metabolic beneficial effects of DJB, suggesting that protein sensing in the distal gut is not a link in the metabolic benefits of gastric surgery.

OBJECTIVE Since the pioneering work of Claude Bernard, the scientific community has considered the liver to be the major source of endogenous glucose production in all postabsorptive situations. Nevertheless, the kidneys and intestine can also produce glucose in blood, particularly during fasting and under protein feeding. The aim of this study was to better define the importance of the three gluconeogenic organs in glucose homeostasis. RESEARCH DESIGN AND METHODS We investigated blood glucose regulation during fasting in a mouse model of inducible liver-specific deletion of the glucose-6-phosphatase gene (L-G6pc−/− mice), encoding a mandatory enzyme for glucose production. Furthermore, we characterized molecular mechanisms underlying expression changes of gluconeogenic genes (G6pc, Pck1, and glutaminase) in both the kidneys and intestine. RESULTS We show that the absence of hepatic glucose release had no major effect on the control of fasting plasma glucose concentration. Instead, compensatory induction of gluconeogenesis occurred in the kidneys and intestine, driven by glucagon, glucocorticoids, and acidosis. Moreover, the extrahepatic action of glucagon took place in wild-type mice. CONCLUSIONS Our study provides a definitive quantitative estimate of the capacity of extrahepatic gluconeogenesis to sustain fasting endogenous glucose production under the control of glucagon, regardless of the contribution of the liver. Thus, the current dogma relating to the respective role of the liver and of extrahepatic gluconeogenic organs in glucose homeostasis requires re-examination.

International audience; Unlike the adjustable gastric banding procedure (AGB), Roux-en-Y gastric bypass surgery (RYGBP) in humans has an intriguing effect: a rapid and substantial control of type 2 diabetes mellitus (T2DM). We performed gastric lap-band (GLB) and entero-gastro anastomosis (EGA) procedures in C57Bl6 mice that were fed a high-fat diet. The EGA procedure specifically reduced food intake and increased insulin sensitivity as measured by endogenous glucose production. Intestinal gluconeogenesis increased after the EGA procedure, but not after gastric banding. All EGA effects were abolished in GLUT-2 knockout mice and in mice with portal vein denervation. We thus provide mechanistic evidence that the beneficial effects of the EGA procedure on food intake and glucose homeostasis involve intestinal gluconeogenesis and its detection via a GLUT-2 and hepatoportal sensor pathway.

International audience; Beneficial effects of dietary fiber on glucose and energy homeostasis have long been described, focusing mostly on the production of short-chain fatty acids by the gut commensal bacteria. However, bacterial fermentation of dietary fiber also produces large amounts of succinate and, to date, no study has focused on the role of succinate on host metabolism. Here, we fed mice a fiber-rich diet and found that succinate was the most abundant carboxylic acid in the cecum. Dietary succinate was identified as a substrate for intestinal gluconeogenesis (IGN), a process that improves glucose homeostasis. Accordingly, dietary succinate improved glucose and insulin tolerance in wild-type mice, but those effects were absent in mice deficient in IGN. Conventional mice colonized with the succinate producer Prevotella copri exhibited metabolic benefits, which could be related to succinate-activated IGN. Thus, microbiota-produced succinate is a previously unsuspected bacterial metabolite improving glycemic control through activation of IGN.

It has been recently suggested that the small intestine (SI) has the capacity to contribute to endogenous glucose production (EGP), in addition to the liver and kidney. The aim of this work was: (1) to estimate the role of SI glucose fluxes in glucose homeostasis in insulin resistance states (induced by high-fat (HF) feeding); (2) to assess the effect of metformin, an anti-diabetic molecule, on these fluxes. Rats were fed for 6 weeks on a HF-diet, supplemented or not with metformin (HF-Met) at a daily dosage of 50 mg/kg during the last week. We combined arterio-venous glucose balance measurements and isotopic dilution techniques to separate basal intestinal glucose uptake (IGU) and release (IGR). Contrary to what was observed in control starch-fed rats, IGU was negligible in HF-fed rats: 0.6 ± 2.4 μmol/kg min (mean ± S.E.M., n = 9). It was restored to a level close to that of control rats in the HF-Met group: 13.0 ± 6.7 μmol/kg min (mean ± S.E.M., n = 9, p p

To date, glyceroneogenesis has only been described in mammals but we demonstrate in this paper that it could exist in the invertebrate Schistosoma mansoni, the parasitic helminth transmitted by fresh water molluscs and responsible for the major human endemic disease, schistosomiasis. Glyceroneogenesis is a phosphoenolpyruvate carboxykinase (PEPCK)-dependent process by which glycerol can be produced from precursors like glutamine and therefore represents a truncated gluconeogenic pathway. We have previously demonstrated the possible central role of glutamine in mollusc-schistosome interactions. In this work, we show that glutamine effectively promotes in vitro survival and protein synthesis in sporocysts, the intramolluscan larval stages of S. mansoni, possibly through its role as an energy source. However, the demonstration that PEPCK is massively expressed in these larval forms as compared to adult parasites, together with the observation that 3-mercaptopicolinate, a specific inhibitor of PEPCK, significantly reduces the effect of glutamine on sporocyst growth, suggest that glutamine could also be used for glucose or glycerol production. Results of [14C] glutamine incorporation confirmed that neosynthesis of glucose and mainly of glycerol occurred in sporocysts and was dependent on PEPCK activity. Therefore, our results strongly indicate that glyceroneogenesis could exist in schistosomes. Several hypotheses can be proposed concerning the importance of glycerol for the adaptation of this helminth to its host osmotic and energetic environment.

The liver is considered the main contributor of endogenous glucose production (EGP) in the postabsorptive (PA) state in mammals. However, it has been shown that the kidney, in PA and fasting states, and the intestine, in insulinopenia states, could make significant contributions to EGP. Using glucose tracer dilution combined to a vessel ligaturing approach, we studied the respective role of these organs in glucose turnover under various nutritional conditions in the rat (Rattus norvegicus). Both organs constitute key sites of glucose disposal in all situations in the non-moving rat. The kidney makes a small (12%) contribution to EGP in the PA state (9.6+/-1.3 micromol/kg min, means+/-SEM, n=5), which is dramatically increased (p

International audience; ABSTRACTType 2 diabetes is characterized by a deterioration of glucose tolerance, which associates insulinresistance of glucose uptake by peripheral tissues and increased endogenous glucose production.Here we report that the specific suppression of hepatic glucose production positively modulateswhole-body glucose and energy metabolism. We used mice deficient in liver glucose-6 phosphatasethat is mandatory for endogenous glucose production. When they were fed a high fat/high sucrosediet, they resisted the development of diabetes and obesity due to the activation of peripheralglucose metabolism and thermogenesis. This was linked to the secretion of hepatic hormones likefibroblast growth factor 21 and angiopoietin-like factor 6. Interestingly, the deletion of hepaticglucose-6 phosphatase in previously obese and insulin-resistant mice resulted in the rapidrestoration of glucose and body weight controls. Therefore, hepatic glucose production is anessential lever for the control of whole-body energy metabolism during the development of obesityand diabetes.

International audience; Objectives: Certain nutrients positively regulate energy homeostasis via intestinalgluconeogenesis (IGN). The objective of this study was to evaluate the impact of a deficientIGN in glucose control independently of nutritional environment.Methods: We used mice deficient in the intestine glucose-6 phosphatase catalytic unit, thekey enzyme of IGN (I-G6pc-/- mice). We evaluated a number of parameters involved inenergy homeostasis, including insulin sensitivity (hyperinsulinemic euglycaemic clamp), thepancreatic function (insulin secretion in vivo and in isolated islets) and the hypothalamichomeostatic function (leptin sensitivity).Results: Intestinal-G6pc-/- mice exhibit slight fasting hyperglycaemia and hyperinsulinemia,glucose intolerance, insulin resistance and a deteriorated pancreatic function, despite normaldiet with no change in body weight. These defects evoking type 2 diabetes (T2D) derive fromthe basal activation of the sympathetic nervous system (SNS). They are corrected bytreatment with an inhibitor of α-2 adrenergic receptors. Deregulation in a key target of IGN,the homeostatic hypothalamic function (highlighted here through leptin resistance) is amechanistic link. Hence the leptin resistance and metabolic disorders in I-G6pc-/- mice arecorrected by rescuing IGN by portal glucose infusion. Finally, I-G6pc-/- mice develop thehyperglycaemia characteristic of T2D more rapidly under high fat/high sucrose diet.Conclusions: Intestinal gluconeogenesis is a mandatory function for the healthy neuralcontrol of glucose homeostasis.

Using Northern blot with a specific glucose-6-phosphatase (Glc6Pase) cDNA probe and enzymatic activity determination, we studied the effect of streptozotocininduced diabetes on Glc6Pase in rat gluconeogenic tissues. The Glc6Pase mRNA abundance was increased four to five times in both the liver and kidney of diabetic rats. This was correlated with a concomitant 130% increase in Glc6Pase catalytic subunit in both tissues. The elevated level of Glc6Pase mRNA was significantly corrected in both the liver and kidney of diabetic rats after a 12-h insulin treatment. We also studied Glc6Pase mRNA and activity in gluconeogenic tissues during the fed-fasted and fasted-refed transitions in normal rats. In the liver, the abundance of Glc6Pase mRNA was sharply increased about four times after 24 or 48 h of fasting. In the kidney, the Glc6Pase mRNA level was gradually increased some three and five times after 24 and 48 h of fasting, respectively. The increase of Glc6Pase mRNA in both organs was matched with a doubling of the activity of Glc6Pase catalytic subunit: rapid in the liver and gradual in the kidney. The liver Glc6Pase mRNA abundance in 48-h fasted rats was acutely and importantly decreased upon refeeding. The kidney Glc6Pase mRNA level was also significantly lowered under these conditions, albeit less rapidly. These data demonstrate that efficient control of Glc6Pase takes place in both gluconeogenic organs at the pretranslational level and suggest that insulin might play an important role in this control. In addition, using reverse transcription-polymerase chain reaction and Northern blot, we report that Glc6Pase mRNA is not detectable in several other tissues previously assumed to express the enzyme.

OBJECTIVE Since the pioneering work of Claude Bernard, the scientific community has considered the liver to be the major source of endogenous glucose production in all postabsorptive situations. Nevertheless, the kidneys and intestine can also produce glucose in blood, particularly during fasting and under protein feeding. The aim of this study was to better define the importance of the three gluconeogenic organs in glucose homeostasis. RESEARCH DESIGN AND METHODS We investigated blood glucose regulation during fasting in a mouse model of inducible liver-specific deletion of the glucose-6-phosphatase gene (L-G6pc−/− mice), encoding a mandatory enzyme for glucose production. Furthermore, we characterized molecular mechanisms underlying expression changes of gluconeogenic genes (G6pc, Pck1, and glutaminase) in both the kidneys and intestine. RESULTS We show that the absence of hepatic glucose release had no major effect on the control of fasting plasma glucose concentration. Instead, compensatory induction of gluconeogenesis occurred in the kidneys and intestine, driven by glucagon, glucocorticoids, and acidosis. Moreover, the extrahepatic action of glucagon took place in wild-type mice. CONCLUSIONS Our study provides a definitive quantitative estimate of the capacity of extrahepatic gluconeogenesis to sustain fasting endogenous glucose production under the control of glucagon, regardless of the contribution of the liver. Thus, the current dogma relating to the respective role of the liver and of extrahepatic gluconeogenic organs in glucose homeostasis requires re-examination.

International audience; BACKGROUND: Deregulation of hypothalamic fatty acid sensing lead to hepatic insulin-resistance which may partly contribute to further impairment of glucose homeostasis. METHODOLOGY: We investigated here whether hypothalamic nitric oxide (NO) could mediate deleterious peripheral effect of central lipid overload. Thus we infused rats for 24 hours into carotid artery towards brain, either with heparinized triglyceride emulsion (Intralipid, IL) or heparinized saline (control rats). PRINCIPAL FINDINGS: Lipids infusion led to hepatic insulin-resistance partly related to a decreased parasympathetic activity in the liver assessed by an increased acetylcholinesterase activity. Hypothalamic nitric oxide synthases (NOS) activities were significantly increased in IL rats, as the catalytically active neuronal NOS (nNOS) dimers compared to controls. This was related to a decrease in expression of protein inhibitor of nNOS (PIN). Effect of IL infusion on deregulated hepatic insulin-sensitivity was reversed by carotid injection of non selective NOS inhibitor NG-monomethyl-L-arginine (L-NMMA) and also by a selective inhibitor of the nNOS isoform, 7-Nitro-Indazole (7-Ni). In addition, NO donor injection (L-arginine and SNP) within carotid in control rats mimicked lipid effects onto impaired hepatic insulin sensitivity. In parallel we showed that cultured VMH neurons produce NO in response to fatty acid (oleic acid). CONCLUSIONS/SIGNIFICANCE: We conclude that cerebral fatty acid overload induces an enhancement of nNOS activity within hypothalamus which is, at least in part, responsible fatty acid increased hepatic glucose production.

The aim of this study was to assess in rats the effect of protein feeding on the: 1) distribution of endogenous glucose production (EGP) among gluconeogenic organs, and 2) repercussion on the insulin sensitivity of glucose metabolism. We used gene expression analyses, a combination of glucose tracer dilution and arteriovenous balance to quantify specific organ release, and hyperinsulinemic euglycemic clamps to assess EGP and glucose uptake. Protein feeding promoted a dramatic induction of the main regulatory gluconeogenic genes (glucose-6 phosphatase and phosphoenolpyruvate carboxykinase) in the kidney, but not in the liver. As a consequence, the kidney glucose release was markedly increased, compared with rats fed a normal starch diet. Protein feeding ameliorated the suppression of EGP by insulin and the sparing of glycogen storage in the liver but had no effect on glucose uptake. Combined with the previously reported induction of gluconeogenesis in the small intestine, the present work strongly suggests that a redistribution of glucose production among gluconeogenic organs might occur upon protein feeding. This phenomenon is in keeping with the improvement of insulin sensitivity of EGP, most likely involving the hepatic site. These data shed a new light on the improvement of glucose tolerance, previously observed upon increasing the amount of protein in the diet, in type 2 diabetic patients.Protein feeding increases kidney gluconeogenesis without increasing global endogenous glucose production, and improves insulin suppression of the latter, likely at the hepatic site.

Introduction De nombreuses donnees suggerent des interactions entre les systemes mu-opioide et endocannabinoide dans les domaines de la nociception et de l'addiction. Les recepteurs aux mu-opioides (MOR) et aux endocannabinoides (CB1) forment des heterodimeres in vitro et in vivo et partagent des sites d'expression dans plusieurs regions du cerveau. Nous avons pu montrer 1) que les MOR periportaux modulent la prise alimentaire en induisant la neoglucogenese intestinale, fonction peripherique connue pour ses effets de satiete ; 2) que les CB1 periportaux agissaient de maniere similaire. Nous avons emis l'hypothese que les deux systemes agiraient en synergie pour controler la prise alimentaire. Materiels et methodes Des souris sauvages sont perfusees en veine porte avec des doses combinees subefficaces d'antagonistes CB1 et/ou MOR. Leur prise alimentaire et leurs neoglucogeneses intestinale et hepatique sont evaluees. Pour etudier si l'effet de satiete dependant des MOR necessite la presence des CB1, nous avons etudie la prise alimentaire et suivi le poids de souris CB1-/- nourries avec un regime hyperproteique (qui est un effecteur MOR). Resultats Des doses combinees subefficaces d'antagonistes CB1 et MOR diminuent la prise alimentaire de 50 % chez les souris sauvages alors qu'elles n'ont aucun effet lorsqu'elles sont perfusees separement. L'activite de la glucose-6 phosphatase (G6Pase) intestinale est augmentee par les doses combinees (29,0 ± 1,1 vs 18,0 ± 2,2 U/g de proteines pour le vehicule, p vs 77,2 ± 4,6 U/g pour le vehicule, p Conclusion Les recepteurs MOR et CB1 controlent de maniere synergique la prise alimentaire via la modulation d'une fonction peripherique: la neoglucogenese intestinale. Declaration d’interet Les auteurs declarent ne pas avoir d'interet direct ou indirect (financier ou en nature) avec un organisme prive, industriel ou commercial en relation avec le sujet presente.

We have studied the effect of various phospholipids on the activity of glucose-6-phosphatase (Glc6Pase) in untreated and detergent-treated rat liver microsomes. Glc6Pase is inhibited in the presence of phosphoinositides in a dose-dependent manner within a range of concentration 0.5-10 microM. The order of efficiency in untreated microsomes is: phosphatidylinositol (PI) 3,4,5P3PI3,4P2 = PI4,5P2PI3P = PI4PPI. In contrast, Glc6Pase is not inhibited in the presence of phosphatidylserine, phosphatidylcholine, and phosphatidylethanolamine, diacylglycerol, and inositol 1,4, 5-trisphosphate at concentrations up to 100 microM. The mechanism of Glc6Pase inhibition by PI4,5P2, PI3,4P2, and PI3,4,5P3 is competitive in both untreated and detergent-treated microsomes. In untreated microsomes, the Ki for PI3,4,5P3 (1.7 +/- 0.3 microM, mean +/- S.D. n = 3) is significantly lower (p0.01) than that for PI3, 4P2 (5.0 +/- 0.8 microM) and for PI4,5P2 (4.7 +/- 0.7 microM). In detergent-treated microsomes, Glc6Pase is less sensitive to the inhibition and there is no difference anymore among the Ki values for the three compounds: 8.3 +/- 0.8, 11.1 +/- 0.5 and 8.9 +/- 0.4 microM for PI3,4,5P3, PI3,4P2, and PI4,5P2, respectively. This inhibition phenomenon might be of special importance with regards to the insulin's inhibition of hepatic glucose production.

Gluconeogenesis is induced in both the liver and intestine by increased cAMP levels. However, hepatic and intestinal glucose production can have opposite effects on glucose homeostasis. Glucose release into the portal vein by the intestine increases glucose uptake and reduces food intake. In contrast, glucose production by the liver contributes to hyperglycemia in type II diabetes. Glucose-6-phosphatase (Glc6Pase) is the key enzyme of gluconeogenesis in both the liver and intestine. Here we specify the cAMP/protein kinase A regulation of the Glc6Pase gene in the intestine compared with the liver. Similarly to the liver, the molecular mechanism of cAMP/protein kinase A regulation involves cAMP-response element-binding protein, HNF4alpha, CAAT/enhancer-binding protein, and HNF1. In contrast to the situation in the liver, we find that different isoforms of CAAT/enhancer-binding protein and HNF1 contribute to the specific regulation of the Glc6Pase gene in the intestine. Moreover, we show that cAMP-response element binding modulator specifically contributes to the regulation of the Glc6Pase gene in the intestine but not in the liver. These results allow us to identify intestine-specific regulators of the Glc6Pase gene and to improve the understanding of the differences in the regulation of gluconeogenesis in the intestine compared with the liver.

It has been recently suggested that the small intestine (SI) has the capacity to contribute to endogenous glucose production (EGP), in addition to the liver and kidney. The aim of this work was: (1) to estimate the role of SI glucose fluxes in glucose homeostasis in insulin resistance states (induced by high-fat (HF) feeding); (2) to assess the effect of metformin, an anti-diabetic molecule, on these fluxes. Rats were fed for 6 weeks on a HF-diet, supplemented or not with metformin (HF-Met) at a daily dosage of 50 mg/kg during the last week. We combined arterio-venous glucose balance measurements and isotopic dilution techniques to separate basal intestinal glucose uptake (IGU) and release (IGR). Contrary to what was observed in control starch-fed rats, IGU was negligible in HF-fed rats: 0.6 +/- 2.4 micromol/kg min (mean +/- S.E.M., n = 9). It was restored to a level close to that of control rats in the HF-Met group: 13.0 +/- 6.7 micromol/kg min (mean +/- S.E.M., n = 9, p0.05 compared to the non-treated group). Similarly, IGR was close to zero in HF-fed rats (-3.8 +/- 2.6 micromol/kg min), but was significant in HF-Met rats (7.4 +/- 4.4 micromol/kg min, p0.05 compared to non-treated rats). These data strongly suggest that the impairment of glucose uptake in the SI might be a crucial feature of insulin resistance states and that a key beneficial effect of metformin in these situations might be to restore a normal glucose metabolism in this tissue.

We studied in rats the expression of genes involved in gluconeogenesis from glutamine and glycerol in the small intestine (SI) during fasting and diabetes. From Northern blot and enzymatic studies, we report that only phospho enolpyruvate carboxykinase (PEPCK) activity is induced at 24 h of fasting, whereas glucose-6-phosphatase (G-6-Pase) activity is induced only from 48 h. Both genes then plateau, whereas glutaminase and glycerokinase strikingly rebound between 48 and 72 h. The two latter genes are fully expressed in streptozotocin-diabetic rats. From arteriovenous balance and isotopic techniques, we show that the SI does not release glucose at 24 h of fasting and that SI gluconeogenesis contributes to 35% of total glucose production in 72-h-fasted rats. The new findings are that 1) the SI can quantitatively account for up to one-third of glucose production in prolonged fasting; 2) the induction of PEPCK is not sufficient by itself to trigger SI gluconeogenesis; 3) G-6-Pase likely plays a crucial role in this process; and 4) glutaminase and glycerokinase may play a key potentiating role in the latest times of fasting and in diabetes.

This study was conducted to test the hypothesis of the activation of glucose-6-phosphatase (G-6-Pase) in situations where the liver is supposed to sustain high glucose supply, such as during the counterregulatory response to hypoglycemia. Hypoglycemia was induced by insulin infusion in anesthetized rats. Despite hyperinsulinemia, endogenous glucose production (EGP), assessed by [3-3H]glucose tracer dilution, was paradoxically not suppressed in hypoglycemic rats. G-6-Pase activity, assayed in a freeze-clamped liver lobe, was increased by 30% in hypoglycemia ( P < 0.01 vs. saline-infused controls). Infusion of epinephrine (1 μg · kg−1· min−1) in normal rats induced a dramatic 80% increase in EGP and a 60% increase in G-6-Pase activity. In contrast, infusion of dexamethasone had no effect on these parameters. Similar insulin-induced hypoglycemia experiments performed in adrenalectomized rats did not induce any stimulation of G-6-Pase. Infusion of epinephrine in adrenalectomized rats restored a stimulation of G-6-Pase similar to that triggered by hypoglycemia in normal rats. These results strongly suggest that specific activatory mechanisms of G-6-Pase take place and contribute to EGP in situations where the latter is supposed to be sustained.

Objectifs Les effets hypophagiques des antagonistes selectifs du recepteur aux endocannabinoides CB1 sont attribues a des mecanismes centraux. On trouve aussi des CB1 sur les fibres nerveuses innervant l’intestin. La neoglucogenese intestinale (NGI) induit la satiete et potentialise la suppression de la production hepatique de glucose (PHG) par l’insuline via un signal glucose portal. Nous avons emis l’hypothese que les CB1 peripheriques pourraient moduler la prise alimentaire en induisant la NGI. Methodes Des souris vigiles sauvages et invalidees pour le gene de la G6Pc dans l’intestin (I-G6Pc-/−) sont perfusees en veine porte avec un antagoniste des CB1 semblable au Rimonabant (AM251). Leur prise alimentaire, leur neoglucogenese intestinale et hepatique sont quantifiees. Un marquage c-Fos des noyaux hypothalamiques et des relais centraux des voies spinale et vagale a ete egalement realise. Resultats L’activite de la glucose-6 phosphatase (G6Pase) intestinale est augmentee par l’AM251 (34,8 ± 2,4 vs 19,4 ± 2,8 U/g de proteines avec le vehicule). Au contraire, l’activite G6Pase hepatique est diminuee par l’AM251 (43,7 ± 4,2 vs 60,8 ± 8,1 U/g de proteines avec le vehicule). La perfusion de l’AM251 est associee a une diminution de la prise alimentaire de 30 %. On constate une activation neuronale des centres de satiete ainsi que des relais centraux des voies spinale et vagale en reponse a l’inhibition des CB1 portaux. L’ensemble de ces effets est aboli chez les souris I-G6Pc-/− et par denervation portale (capsaicine). Discussion L’effet hypophagique et de diminution de la PHG de l’AM251 perfuse en veine porte sont dependants de l’induction d’une fonction peripherique : la NGI.

Introduction La chirurgie de l'obesite de type by-pass gastrique (BPG) a montre des effets spectaculaires dans l'amelioration, voire la remission, du diabete de type 2 independamment de la perte de poids. La neoglucogenese intestinale (NGGI) induit des effets benefiques sur l'homeostasie glucidique via l'emission d'un « signal glucose portal » a destination du cerveau. Nous avons teste l'hypothese selon laquelle les effets metaboliques benefiques du BPG pourraient dependre de la NGGI et donc ne pas prendre place chez des souris invalidees pour la glucose-6-phosphatase intestinale, l'enzyme essentielle de la neoglucogenese (I-G6pc-KO). Materiels et methodes Des BPG (sans reduction de la taille de l'estomac) et des laparotomies-sham ont ete realises sur des souris temoins (B6J) et I-G6pc-KO (n=5–6) nourries en regime standard a base d'amidon. Le poids, la prise alimentaire et les tolerances au glucose et a l'insuline ont ete etudies. Resultats Apres BPG, les souris B6J et I-G6pc-KO ingerent la meme quantite de nourriture que leurs temoins laparotomie. La sensibilite a l'insuline n'est modifiee apres BPG ni chez les souris B6J ni chez les souris I-G6pc-KO par rapport aux temoins laparotomie (aire sous la courbe : 624±36 vs 565±26 pour les B6J-BPG vs B6J-laparotomie, NS ; 780±54 vs 692±33 pour les I-G6pc-KO-BPG vs I-G6pc-KO-laparotomie, NS). Par contre, la tolerance au glucose est amelioree chez les souris B6J-BPG vs B6J-laparotomie (aire sous la courbe : 2 291±74 vs 2 588±72, p Conclusion Chez la souris en regime standard, la NGGI a un role causal dans l'amelioration de la tolerance au glucose induite par le BPG, en absence de perte de poids. Cet effet semble etre independant de la sensibilite a l'insuline.

Objectif Les effets hypophagiques des antagonistes selectifs du recepteur aux endocannabinoides CB1 (CB1R) sont attribues a des mecanismes centraux notamment hypothalamiques. On trouve aussi des CB1Rs sur les fibres nerveuses innervant le tractus gastro-intestinal. En induisant un signal glucose portal, la neoglucogenese intestinale (NGI) induit la satiete et potentialise la suppression de la production hepatique de glucose par l'insuline. Nous avons emis l'hypothese que les CB1Rs peripheriques pourraient initier un circuit nerveux intestin-cerveau-foie par induction de la NGI. Materiels et methodes Des souris vigiles controles et invalidees pour le gene de la G6Pc dans l'intestin (I-G6Pc-/-) sont perfusees en veine porte avec un antagoniste des CB1Rs analogue au Rimonabant (AM251). Leur prise alimentaire est etudiee. Leur neoglucogenese intestinale et hepatique est quantifiee. Un marquage c-fos des noyaux hypothalamiques et des relais centraux des voies spinales et vagales a ete egalement realise. Resultats L'activite de la glucose-6 phosphatase (G6Pase) intestinale est augmentee par l'AM251 (34,8±2,4U/g de proteines vs 19,4±2,8U/g avec le vehicule ; p Discussion Cette etude suggere que l'inhibition des CB1Rs portaux par un antagoniste selectif induirait la NGI et produirait ainsi ses effets benefiques sur la prise alimentaire et l'homeostasie glucidique hepatique. Le systeme nerveux portal serait essentiel dans l'initiation de ce circuit nerveux intestin-cerveaufoie.

PEPCK is a key enzyme of gluconeogenesis in liver and kidney. Recently, we have shown that small intestine also contributes to the endogenous glucose production in insulinopenia in rats and that glutamine is the main precursor of glucose synthesized in this tissue. The expression of the PEPCK gene in rat and human small intestine and the effect of streptozotocin-induced diabetes and fasting have been studied using reverse transcriptase-polymerase chain reaction, Northern blot analysis, and determination of enzyme activity. The PEPCK gene is expressed along the whole small intestine in adult rat and human. The abundance of PEPCK mRNA was increased approximately 30 times in the duodenum, 15 times in the jejunum, and only 3 times in the ileum from diabetic rats. PEPCK mRNA was downregulated in all parts of the tissue upon insulin treatment for 10 h. In 48-h fasted rats, the PEPCK mRNA abundance was increased 17 times in the duodenum and the jejunum and 3 times in the ileum, and it was normalized upon refeeding for 7 h. PEPCK activity was also increased 2-5 times in diabetic and fasted rats in the duodenum and jejunum but not in the ileum. We conclude that PEPCK is a crucial enzyme contributing to the induction of gluconeogenesis in small intestine, just as it is well known to be in the liver and kidney.

Background & Aims: Glucose-6 phosphatase (Glc6Pase) is the last enzyme of gluconeogenesis and glycogenolysis, previously assumed to be expressed in the liver and kidney only, conferring on both tissues the capacity to produce endogenous glucose in blood. Methods: Using Northern blotting and reverse-transcription polymerase chain reaction and a highly specific Glc6Pase assay, we studied expression of the Glc6Pase gene in human and in rat tissues (fasted and diabetic). Results: The Glc6Pase gene is expressed in the duodenum and jejunum in normal fed rats and in the duodenum, jejunum, and ileum in humans. The Glc6Pase messenger RNA (mRNA) abundance was increased eightfold and sixfold in the duodenum and jejunum of streptozotocin diabetic rats. It was normalized in both tissues after 10 hours of insulin treatment. Glc6Pase activity was increased by 300% in the duodenum and jejunum in diabetic rats compared with normal rats. The Glc6Pase mRNA abundances and enzymatic activities were increased in a similar manner in both tissues in 48-hour-fasted rats. Normalization of mRNA abundance was achieved after refeeding for 7 hours. In addition, Glc6Pase mRNA and activity were also expressed in the ileum during fasting in rats. Conclusions: These data show that the small intestine has the ability to release endogenous glucose and strongly suggest that its contribution to systemic glucose production might be increased in situations of insulinopenia (type 1 diabetes) and insulin resistance (type 2 diabetes and others). GASTROENTEROLOGY 1999;117:132-139

But Comprendre pourquoi le by-pass gastrique (BPG) (et non l’anneau gastrique) chez la souris C57Bl6 soumise au regime gras (HFD) provoque une amelioration rapide de la sensibilite a l’insuline et de la secretion d’insuline. Materiels et methodes Nous avions montre que le BPG provoquait une hausse de la concentration plasmatique de GLP-1 observable lors du test de tolerance orale au glucose (OGTT). Pour connaitre la place du GLP-1 dans les modifications metaboliques apres BPG, la prise alimentaire, le poids, la sensibilite a l’insuline et l’OGTT ont ete realisees chez des souris mâles C57Bl6 HFD avant et apres BPG avec ou sans traitement par un antagoniste du GLP-1 (exendine [9-39] amide). Par ailleurs, nous avons teste l’hypothese que les effets du BPG pouvaient s’expliquer en partie par une stimulation de la neoglucogenese intestinale. L’activite de la glucose-6 phosphatase (Glc6Pase) a ete mesuree dans les differents segments intestinaux de souris C57Bl6 HFD temoins (sham operated), BPG et anneau (n = 10 souris par groupe). Dans ces groupes, le flux de glucose portal a egalement ete mesure. Le transporteur GLUT2 a ete suggere comme sensor essentiel de la detection du glucose portal. Nous avons alors realise un BPG chez des souris KOGLUT2 soumises au regime gras. Resultats Nous montrons que l’exendine 9-39 reduit l’insulinosecretion lors de l’OGTT mais ne modifie pas les effets du BPG sur la prise alimentaire et sur sensibilite a l’insuline. Le BPG est la seule situation ou l’on observe une augmentation de l’activite de la Glc6Pase intestinale et une augmentation du flux de glucose portal. Dans ce cas, la neoglucogenese hepatique diminue et la sensibilite a l’insuline hepatique augmente. Enfin, les effets metaboliques du BPG ne sont pas observes chez les souris KOGLUT2. Conclusion Nos resultats suggerent que le GLP-1 a un role crucial dans les modifications de l’insulinosecretion apres BPG alors que les autres modifications metaboliques (prise alimentaire, sensibilite a l’insuline) semblent determinees par la stimulation de la neoglucogenese intestinale.

By using a rapid procedure of isolation of microsomes, we have shown that the liver glucose-6-phosphatase activity was lowered by about 30% (p0.001) after refeeding for 360 min rats previously unfed for 48 h, whereas the amount of glucose-6-phosphatase protein was not lowered during the same time. The amount of the regulatory subunit (p85) and the catalytic activity of phosphatidylinositol 3-kinase (PI3K) were higher by a factor of 2.6 and 2.4, respectively (p0.01), in microsomes from refed as compared with fasted rats. This resulted from a translocation process because the total amount of p85 was the same in the whole liver homogenates from fasted and refed rats. The amount of insulin receptor substrate 1 (IRS1) was also higher by a factor of 2.6 in microsomes from refed rats (p0. 01). Microsome-bound IRS1 was only detected in p85 immunoprecipitates. These results strongly suggest that an insulin-triggered mechanism of translocation of PI3K onto microsomes occurs in the liver of rats during refeeding. This process, via the lipid products of PI3K, which are potent inhibitors of glucose-6-phosphatase (Mithieux, G., Danièle, N., Payrastre, B., and Zitoun, C. (1998) J. Biol. Chem. 273, 17-19), may account for the inhibition of the enzyme and participate to the inhibition of hepatic glucose production occurring in this situation.

Introduction L’effet spectaculaire des by-pass gastriques sur l’equilibre glucidique et la sensation de faim est associe a une augmentation de la concentration plasmatique des acides biliaires (AB). Ces derniers sont des inhibiteurs de l’expression des genes de la neoglucogenese in vitro. Notre hypothese est que les AB plasmatiques diminueraient la neoglucogenese hepatique (NGH), tandis que leur absence dans l’anse alimentaire induirait la neoglucogenese intestinale (NGI, initiant satiete et sensibilite a l’insuline). Materiels et methodes Des derivations biliaires sont realisees a partir du canal choledoque soit directement dans une veine mesenterique (VM), soit au milieu du jejunum (MJ) ou de l’ileon (MI), afin de mimer differents by-pass, chez des rats mâles nourris en regime standard. Resultats Les rats ayant subi une derivation biliaire presentent, 6 jours apres l’operation, une diminution de leur poids (– 24,7 ± 6,8 g pour VM, – 28,5 ± 7,4 g pour MJ, − 12,7 ± 7,2 g pour MI versus +24,2 ± 5,2 g pour temoins, p Discussion Les changements de biodisponibilite des AB permettraient d’expliquer les modifications d’expression de la NGH et de la NGI in vivo chez le rat. Ces regulations opposees par les AB pourraient etre un facteur cle de l’amelioration du controle glucidique apres by-pass gastrique.

Introduction Les fibres alimentaires solubles, en particulier l’oligofructose (FOS), sont benefiques pour l’homeostasie glucidique, mais cet effet est encore mal compris. Ces fibres sont fermentees par les bacteries intestinales, produisant les acides gras a courte chaine (AGCC) acetate, butyrate et propionate, un substrat de la neoglucogenese. La neoglucogenese intestinale (NGI) induit la satiete et la sensibilite a l’insuline. Notre hypothese est que les AGCC exercent leurs effets benefiques via la NGI. Materiels et methodes La prise alimentaire de rats nourris avec une nourriture enrichie en FOS ou AGCC (10% des calories ingerees) pendant deux semaines est mesuree. La tolerance au glucose et a l’insuline est egalement evaluee. Les rats sont ensuite euthanasies et la NGI caracterisee. Les memes experiences sont faites chez des souris sauvages ou invalidees specifiquement pour la glucose-6-phosphatase (G6Pase) intestinale (I-G6PC-KO). Les niveaux d’ARNm des enzymes de la NGI sont caracterises par Q-PCR sur cellules Caco-2 cultivees en presence d’AGCC. Resultats L’activite de la G6Pase intestinale est augmentee par les FOS et les AGCC (propionate : 25,5 ± 1,3 U/g de proteines ; butyrate : 20,6 ± 0,8 U/g ; FOS : 24,5 ± 2,0 U/g ; temoin : 12,5 ± 1,2 U/g ; P Discussion La NGI aurait donc un role causal dans les effets benefiques des FOS et AGCC. Ces derniers agiraient comme substrats de la NGI et signaux d’induction des genes.

We have studied the role of Glc6Pase mRNA abundance in the time course of Glc6Pase activity in liver and kidney during long-term fasting in rat. Refered to the mRNA level in the fed state, Glc6Pase mRNA abundance was increased by 3.5 +/- 0.5 and 3.7 +/- 0.5 times (mean +/- S.E.M., n = 5) in the 24 h and 48 h-fasted liver, respectively. Then, the liver Glc6Pase mRNA was decreased to the level of the fed liver after 72 and 96 h of fasting (1.0 +/- 0.3 and 1.4 +/- 0.3). In the kidney, Glc6Pase mRNA abundance was increased by 2.7 +/- 1.0 and 5 +/- 1.2 times at 24 and 48 h of fasting, respectively. Then, it plateaued at the level of the 48 h fasted kidney after 72 h and 96 h of fasting (4.5 +/- 1.0 and 4.3 +/- 1.0). After 24 and 48 h-refeeding, the abundance of Glc6Pase mRNA in 48 h-fasted rats was decreased to the level found in the liver and kidney of fed rats. The time course of the activity of Glc6Pase catalytic subunit during fasting and refeeding was strikingly parallel to the time course of Glc6Pase mRNA level in respective tissues. These data strongly suggest that the differential expression of Glc6Pase activity in liver and kidney in the course of fasting may be accounted for by the respective time course of mRNA abundance in both organs.

We have studied the effects of fatty-acyl-CoA esters on the activity of glucose-6-phosphatase (Glc6Pase) in untreated and detergent-treated liver microsomes. Fatty-acyl-CoA esters with chain lengths less than or equal to nine carbons do not inhibit Glc6Pase. Medium-chain fatty-acyl-CoA esters (10-14 carbons) inhibit Glc6Pase of untreated microsomes in a dose-dependent manner in the range 1-20 microM. The inhibitory effect is also dependent on the acyl-chain length. The higher the chain length, the stronger the inhibitory effect. It is also dependent on the microsomal protein concentration. The higher the protein concentration, the lower the inhibitory effect. Fatty-acyl-CoA esters with longer chain length (equal to or higher than 16 carbons) inhibit Glc6Pase of untreated microsomes within the range 1-2 microM. However, the inhibitory effect is either partially or totally cancelled, or even changed into an activation effect at higher concentrations. This is due to the release of mannose-6-phosphatase latency. The inhibition is fully reversible in the presence of bovine serum albumin. The mechanism of the Glc6Pase inhibition in untreated microsomes is uncompetitive (Ki for myristoyl-CoA = 1.2 +/- 0.3 microM, mean +/- SD, n = 3). Glc6Pase of detergent-treated microsomes is also inhibited by fatty-acyl-CoA esters, albeit less efficiently. In this case, the mechanism is non-competitive (Ki for myristoyl-CoA = 29 +/- 3 microM).

Introduction Le diabete de type 2 est caracterise par une hyperglycemie chronique, qui engendre la production d’especes actives de l’oxygene (EAOs), generatrices de phenomenes de glucotoxicite. Cette hyperglycemie est associee a une induction paradoxale de l’expression de la sous-unite catalytique de la glucose-6-phosphatase (G6PC), enzyme cle de la neoglucogenese, concourant probablement a la deregulation de la production hepatique de glucose observee chez les diabetiques. Nous avons fait l’hypothese que le glucose regule l’activite transcriptionnelle du gene G6pc via les EAOs. Materiels et methodes La production d’EAOs induite par un traitement de 24 h avec 25 mM de glucose est mesuree dans des hepatocytes primaires de rat et la lignee HepG2. L’activite transcriptionnelle du promoteur G6pc (gene rapporteur) est etudiee dans la lignee HepG2. La liaison de facteurs de transcription au promoteur G6pc de rat est etudiee par immunoprecipitation de chromatine issue d’hepatocytes de rats. Resultats L’induction de l’activite transcriptionnelle du gene G6pc par le glucose est annulee lorsque la quantite d’EAOs est reduite par un traitement antioxydant ou lorsque l’activite transactivatrice du facteur HIF-1alpha (hypoxia inducible factor 1alpha) est annulee par la surexpression de son dominant negatif. Dans les hepatocytes, le glucose induit la stabilisation du facteur HIF-1alpha et sa liaison au promoteur G6pc. La production d’EAOs ou une forte concentration de glucose stimule l’interaction entre HIF-1alpha et le co-facteur CBP (CREB binding protein), permettant a CBP d’etre recrute sur le promoteur G6pc. Cette regulation est mise en evidence dans le foie de souris rendues obeses et diabetiques par un regime hypercalorique. Conclusion Cette etude caracterise le role des EAOs et de HIF-1alpha dans la regulation de l’activite transcriptionnelle du gene G6pc par le glucose. Elle met egalement en evidence un mecanisme graduel de regulation d’HIF-1alpha par le glucose, dependant des EAOs, semblable a celui decrit lors de l’hypoxie.

Introduction Les regimes hyperproteiques augmentent la satiete et ameliorent le controle glycemique. Ces effets sont inities par la detection du glucose produit par l’intestin dans la veine porte, signal transmis au cerveau par les afferences nerveuses peripheriques. Le transporteur GLUT2, et le catabolisme glucidique, ont ete impliques dans l’initiation de ce signal, notamment pour des perfusions de glucose equivalentes a la production endogene. Afin de proposer un modele general pour la detection portale, nous avons etudie le role eventuel de mecanismes alternatifs de detection du glucose, dans les conditions de sa production en reponse aux proteines alimentaires. Materiels et Methodes Le role de GLUT2 dans la detection du glucose issu de l’intestin a ete evalue par la mesure de la prise alimentaire de souris C57BL6/J depourvues du transporteur et soumises a un regime hyperproteique. Des rats Sprague-Dawley adultes ont recu des perfusions portales d’activateurs ou d’inhibiteurs des autres voies de detection etudiees, et leur prise alimentaire a ete mesuree pour evaluer les mecanismes du signal glucose portal. Resultats Les souris depourvues du transporteur GLUT2 recevant un regime riche en proteines diminuent leur prise alimentaire du meme ordre de grandeur que les souris sauvages (-20 %). La perfusion portale d’edulcorants (sucralose, acesulfame K) a des doses suffisantes pour activer les recepteurs au gout sucre n’a pas eu d’effet sur la prise alimentaire des animaux. La perfusion a 25umol/kg/min d’alpha-methylglucose (activateur des transporteurs couples au sodium, SGLTs), mais pas celle de 3-O-methylglucose (activateur de SGLT1), diminue la prise alimentaire des individus avec une efficacite similaire au glucose (-37 %). L’ajout de 0,2umol/kg/min de phlorizine a une perfusion de glucose annule l’effet de ce dernier sur la satiete, sans que cet inhibiteur des SGLTs ne modifie la prise alimentaire s’il est perfuse seul. Enfin, la presence de SGLT3 et GLUT2 dans la zone portale a ete confirmee par Western blot. Conclusion Nos resultats suggerent l’existence de deux mecanismes de detection du glucose dans la veine porte, qui conferent a ce site une sensibilite a la fois a des variations de glycemie importantes (via GLUT2), et plus faibles (via SGLT3).

Introduction : La production endogene de glucose est une fonction restreinte a trois tissus : le foie, le rein et l'intestin qui, seuls, expriment la glucose-6-phosphatase (G6Pase). Les souris transgeniques invalidees pour la sous-unite catalytique de la G6Pase specifiquement dans le foie (B6.g6pc ex3del .SA +/CreERT2 ) sont capables de reguler leur glycemie meme au cours du jeune grâce a leurs productions intestinale et renale de glucose. Nous avons voulu determiner le role de l'intestin dans cette regulation. Materiels et Methodes : Des souris B6.g6pc ex3lox .SA +/CreERT2 (pour l'invalidation hepatique) et des souris B6.g6pc ex3lox .Vill +/CreERT2 (pour l'invalidation intestinale) ont ete croisees pour obtenir des souris doublement invalidees (DKO) par une strategie Cre-Lox ciblee et inductible. La glycemie des souris a ete etudiee au cours du jeune. Les activites des enzymes de la neoglucogenese ont ete determinees sur des homogenats tissulaires. Resultats : La glycemie des souris DKO est fortement diminuee (61 ± 2,3 mg/dL) a 6 h de jeune, comme celle des souris invalidees dans le foie (L-g6pc-/-), en raison de l'absence de glycogenolyse hepatique. Au contraire, les souris temoins maintiennent leur glycemie (169 ± 3,9 mg/dL). Au cours du jeune prolonge, la glycemie des souris DKO reste basse (environ 60 mg/dL) alors que celle des souris L-g6pc-/- augmente des 16 h de jeune, pour atteindre environ 100 mg/dL a 48 h de jeune. A l'euthanasie des souris, les activites G6Pase et phosphoenol pyruvate carboxykinase cytosolique renales des souris DKO etaient augmentees par rapport a celles des souris temoins et comparables a celles des souris L-g6pc-/-. Conclusion : En l'absence de production hepatique et intestinale de glucose, les reins sont capables d'assurer le maintien d'une glycemie minimale, compatible avec la survie au cours du jeune. Nos resultats suggerent aussi que la neoglucogenese intestinale, lorsqu'elle s'ajoute a la neoglucogenese renale, permet le maintien d'une glycemie physiologique dans cette situation.

Introduction Les proteines induisent chez le rat l'expression des genes intestinaux et renaux des enzymes clefs de la neoglucogenese. Par ailleurs, les parametres glycemiques de patients diabetiques de type 2 sont rapidement ameliores par un regime enrichi en proteines. Nous avons voulu preciser l'impact d'un tel regime 1. sur la repartition de la production endogene de glucose (PEG) entre les differents organes neoglucogeniques 2. sur la sensibilite a l'insuline. Materiels et methodes Chez le rat nourri par un regime enrichi en proteines (50 % proteines vs. 17 % en regime standard), nous avons 1. determine la production renale de glucose (PRG) par une methode combinee de dilution de traceur et de balance glycemique arterio-veineuse, 2. estime la reponse de la PEG et du captage peripherique de glucose a l'insuline a l'aide de clamps hyperinsulinemiques euglycemiques, 3. quantifie le contenu en glycogene hepatique. Resultats La PRG est fortement induite par le regime proteique (26,0±4,7μmol/kg/mn vs 12,5±1,9μmol/kg/mn en regime standard) et porte la participation du rein dans ces conditions a 40 % de la PEG (contre 17 % en regime standard). Cette derniere est similaire chez les deux groupes de rats. Les clamps hyperinsulinemiques euglycemiques indiquent une suppression plus importante de la PEG sous regime proteique (inhibition de 50 % contre 25-30 % chez les rats temoins). Le captage de glucose n'est cependant pas affecte par le regime. L'insulinemie des rats est semblable chez les deux groupes de rats, que ce soit en basal ou apres clamp. Le contenu en glycogene hepatique est plus eleve chez les rats nourris par le regime riche en proteines que chez les rats en regime standard (18±3,5 vs 4.,7±3,2mg/g de tissus). Discussion Associes a de precedents resultats sur l'intestin, nous pouvons conclure a une redistribution de la PEG au profit du rein et de l'intestin, induite par les proteines. Ceci s'accompagne d'une amelioration de la sensibilite a l'insuline de la PEG, principalement dans le foie par le biais d'une epargne du glycogene. Conclusion Ces resultats pourraient expliquer au moins en partie l'amelioration spectaculaire des parametres glycemiques observes sous regime hyperproteique chez les patients diabetiques.

International audience; Soluble dietary fibers promote metabolic benefits on body weight and glucose control, but underlying mechanisms are poorly understood. Recent evidence indicates that intestinal gluconeogenesis (IGN) has beneficial effects on glucose and energy homeostasis. Here, we show that the short-chain fatty acids (SCFAs) propionate and butyrate, which are generated by fermentation of soluble fiber by the gut microbiota, activate IGN via complementary mechanisms. Butyrate activates IGN gene expression through a cAMP-dependent mechanism, while propionate, itself a substrate of IGN, activates IGN gene expression via a gut-brain neural circuit involving the fatty acid receptor FFAR3. The metabolic benefits on body weight and glucose control induced by SCFAs or dietary fiber in normal mice are absent in mice deficient for IGN, despite similar modifications in gut microbiota composition. Thus, the regulation of IGN is necessary for the metabolic benefits associated with SCFAs and soluble fiber.