Intestinal mucosal adherence and translocation of commensal bacteria at the early onset of type 2 diabetes: molecular mechanisms and probiotic treatment

A fat-enriched diet modifies intestinal microbiota and initiates a low-grade inflammation, insulin resistance and type-2 diabetes. Here, we demonstrate that before the onset of diabetes, after only one week of a high-fat diet (HFD), live commensal intestinal bacteria are present in large numbers in the adipose tissue and the blood where they can induce inflammation. This translocation is prevented in mice lacking the microbial pattern recognition receptors Nod1 or CD14, but overtly increased in Myd88 knockout and ob/ob mouse. This ‘metabolic bacteremia’ is characterized by an increased co-localization with dendritic cells from the intestinal lamina propria and by an augmented intestinal mucosal adherence of non-pathogenic Escherichia coli. The bacterial translocation process from intestine towards tissue can be reversed by six weeks of treatment with the probiotic strain Bifidobacterium animalis subsp. lactis 420, which improves the animals' overall inflammatory and metabolic status. Altogether, these data demonstrate that the early onset of HFD-induced hyperglycemia is characterized by an increased bacterial translocation from intestine towards tissues, fuelling a continuous metabolic bacteremia, which could represent new therapeutic targets

Resveratrol Increases Glucose Induced GLP-1 Secretion in Mice: A Mechanism which Contributes to the Glycemic Control

Resveratrol (RSV) is a potent anti-diabetic agent when used at high doses. However, the direct targets primarily responsible for the beneficial actions of RSV remain unclear. We used a formulation that increases oral bioavailability to assess the mechanisms involved in the glucoregulatory action of RSV in high-fat diet (HFD)-fed diabetic wild type mice. Administration of RSV for 5 weeks reduced the development of glucose intolerance, and increased portal vein concentrations of both Glucagon-like peptid-1 (GLP-1) and insulin, and intestinal content of active GLP-1. This was associated with increased levels of colonic proglucagon mRNA transcripts. RSV-mediated glucoregulation required a functional GLP-1 receptor (Glp1r) as neither glucose nor insulin levels were modulated in Glp1r-/- mice. Conversely, levels of active GLP-1 and control of glycemia were further improved when the Dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin was co-administered with RSV. In addition, RSV treatment modified gut microbiota and decreased the inflammatory status of mice. Our data suggest that RSV exerts its actions in part through modulation of the enteroendocrine axis in vivo

Brain GLP-1 Signaling Regulates Femoral Artery Blood Flow and Insulin Sensitivity Through Hypothalamic PKC-{delta}

International audienceOBJECTIVE Glucagon-like peptide 1 (GLP-1) is a gut-brain hormone that regulates food intake, energy metabolism, and cardiovascular functions. In the brain, through a currently unknown molecular mechanism, it simultaneously reduces femoral artery blood flow and muscle glucose uptake. By analogy to pancreatic β-cells where GLP-1 activates protein kinase C (PKC) to stimulate insulin secretion, we postulated that PKC enzymes would be molecular targets of brain GLP-1 signaling that regulate metabolic and vascular function. RESEARCH DESIGN AND METHODS We used both genetic and pharmacological approaches to investigate the role of PKC isoforms in brain GLP-1 signaling in the conscious, free-moving mouse simultaneous with metabolic and vascular measurements. RESULTS In normal wild-type (WT) mouse brain, the GLP-1 receptor (GLP-1R) agonist exendin-4 selectively promotes translocation of PKC-δ (but not -βII, -α, or -ε) to the plasma membrane. This translocation is blocked in Glp1r(-/-) mice and in WT mice infused in the brain with exendin-9, an antagonist of the GLP-1R. This mechanism coordinates both blood flow in the femoral artery and whole-body insulin sensitivity. Consequently, in hyperglycemic, high-fat diet-fed diabetic mice, hypothalamic PKC-δ activity was increased and its pharmacological inhibition improved both insulin-sensitive metabolic and vascular phenotypes. CONCLUSIONS Our studies show that brain GLP-1 signaling activates hypothalamic glucose-dependent PKC-δ to regulate femoral artery blood flow and insulin sensitivity. This mechanism is attenuated during the development of experimental hyperglycemia and may contribute to the pathophysiology of type 2 diabetes

Biological Role of Pazopanib and Sunitinib Aldehyde Derivatives in Drug-Induced Liver Injury

International audienceTyrosine kinase inhibitors pazopanib and sunitinib are both used to treat advanced renal cell carcinoma but expose patients to an increased risk of hepatotoxicity. We have previously identified two aldehyde derivatives for pazopanib and sunitinib (P-CHO and S-CHO, respectively) in liver microsomes. In this study, we aimed to decipher their role in hepatotoxicity by treating HepG2 and HepaRG hepatic cell lines with these derivatives and evaluating cell viability, mitochondrial dysfunction, and oxidative stress accumulation. Additionally, plasma concentrations of P-CHO were assessed in a cohort of patients treated with pazopanib. Results showed that S-CHO slightly decreased the viability of HepG2, but to a lesser extent than sunitinib, and affected the maximal respiratory capacity of the mitochondrial chain. P-CHO decreased viability and ATP production in HepG2. Traces of P-CHO were detected in the plasma of patients treated with pazopanib. Overall, these results showed that P-CHO and S-CHO affect hepatocyte integrity and could be involved in the pazopanib and sunitinib hepatotoxicity

RSV improves glucose tolerance in high fat-fed diabetic mice.

<p><b>A)</b> Glycemic profiles (mg/dL) of normal chow (circles), high fat diet-fed mice treated with vehicle (triangles) or RSV (squares) for five weeks and <b>B)</b> area under the curve for glucose (AUC); Data are presented as mean ± S.E.M, n = 8 mice per group * and *** statistically different between groups when p<0.05 and p<0.001, respectively, as analyzed by one-way ANOVA followed by Tukey test.</p

The glucose control by RSV is blunted in high fat diet-fed Glp1r^−/− mice.

<p><b>A)</b> Glycemic profiles (mg/dL) of high fat diet-fed Glp1r^−/− mice treated with vehicle (triangles) or RSV (squares) for five weeks and <b>B)</b> an index of area under the curve glucose (AUC); <b>C)</b> proglucagon mRNA levels (Relative expression level REL) of high fat diet-fed mice treated with vehicle (open bars) and RSV (closed bars) for five weeks. <b>D)</b> Glycemic profiles (mg/dL) of high fat diet-fed wild type mice (high fat diet-fed mice treated with vehicule (white triangles) or RSV (white squares)) and Glp1r^−/− mice (high fat diet-fed mice treated with vehicule (black triangles) or RSV (black squares)) after five weeks of treatment and <b>E)</b> an index of area under the curve glucose (AUC). Data are presented as mean ± S.E.M, n = 8 mice per group.</p

RSV has a prebiotic effect on gut microbiota.

<p>DGGE profiles generated from the caecal content of mice fed normal chow (NC), high fat diet and treated with vehicle (HFD±Veh), or RSV (HFD±RSV) for 5 weeks. Each number and profile corresponds to a different animal. The arrows denote a subset of bands, which have disappeared with the RSV treatment, were cloned and sequenced (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020700#s3" target="_blank">results</a> for identification).</p

Primers Used.

<p>Primers Used.</p

RSV increases levels of GLP-1 and Insulin.

<p><b>A)</b> Portal vein active GLP-1 concentrations (pM); <b>B)</b> proglucagon mRNA concentration (Relative Expression Level, REL); <b>C)</b> intestinal GLP-1 concentrations (pmol/g of tissue) and <b>D)</b> portal plasma insulin concentrations (µg/L) of normal chow (stripe bars), high fat diet-fed mice treated with vehicle (open bars) or RSV (closed bars) for five weeks. Data are presented as mean ± S.E.M, n = 8 mice per group (in fed state) *, ** and *** statistically different between groups when p<0.05, p<0.01 and p<0.001, respectively, as analyzed by one-way ANOVA followed by Tukey test.</p