Bile acid control of metabolism and inflammation in obesity, type 2 diabetes, dyslipidemia and NAFLD Short title: Bile acids in meta-inflammatory disorders

Oscar Chávez-Talavera MD and Anne Tailleux PhD contributed equally.International audienceBile acids are signaling molecules, which coordinately regulate metabolism and inflammation via the nuclear farnesoid X receptor (FXR) and the Takeda G protein-coupled receptor 5 (TGR5). These receptors activate transcriptional networks and signaling cascades controlling the expression and activity of genes involved in bile acid, lipid and carbohydrate metabolism, energy expenditure, and inflammation by acting predominantly in entero-hepatic tissues, but also in peripheral organs. In this review, we discuss the most recent findings on the inter-organ signaling and interplay with the gut microbiota of bile acids and their receptors in meta-inflammation, with a focus on their pathophysiological roles in obesity, type 2 diabetes, dyslipidemia and non-alcoholic steatohepatitis and their potential therapeutic applications

Title: Bile acid alterations in non-alcoholic fatty liver disease, obesity, insulin resistance and type 2 diabetes: what do the human studies tell?

International audienceDisclosure: The authors declare no conflict of interest. 2 Abstract Purpose of review: To discuss the influence of obesity, insulin resistance, type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD) on bile acid (BA) metabolism and analyze whether these findings reinforce current beliefs about the role of BAs in the pathophysiology of these diseases. Recent findings: Discordant results on plasma BA alterations in NAFLD patients have been reported. Obesity, insulin resistance and T2D, common co-morbidities of NAFLD, have been associated with BA changes, but the individual BA species variations differ between studies (summarized in this review), perhaps due to clinico-biological differences between the studied patient populations and the heterogeneity of statistical analyses applied. Summary: The regulatory role of BAs in metabolic and cellular homeostasis render BAs attractive candidates as players in the pathophysiology of NAFLD. However, considering the comple

Bile acids associate with glucose metabolism, but do not predict conversion from impaired fasting glucose to diabetes

International audienceObjective: Bile acids (BAs) are signaling molecules controlling lipid and glucose metabolism. Since BA alterations are associated with obesity and insulin resistance, plasma BAs have been considered candidates to predict type 2 diabetes (T2D) risk. We aimed to determine (1) the association of BAs with glucose homeostasis parameters and (2) their predictive association with the risk of conversion from prediabetes to new-onset diabetes (NOD) in a prospective cohort study.Design: 205 patients with impaired fasting glucose (IFG) were followed each year during 5 years in the IT-DIAB cohort study. Twenty-one BA species and 7α-hydroxy-4-cholesten-3-one (C4), a marker of BA synthesis, were quantified by LC/MS-MS in plasma from fasted patients at baseline. Correlations between plasma BA species and metabolic parameters at baseline were assessed by Spearman's coefficients and the association between BAs and NOD was determined using Cox proportional-hazards models.Results: Among the analyzed BA species, total hyocholic acid (HCA) and the total HCA/total chenodeoxycholic acid (CDCA) ratio, reflecting hepatic BA 6α-hydroxylation activity, negatively correlated with BMI and HOMA-IR. The total HCA/total CDCA ratio also correlated negatively with HbA1C. Conversion from IFG to NOD occurred in 33.7% of the participants during the follow-up. Plasma BA species were not independently associated with the conversion to NOD after adjustment with classical T2D risk factors.Conclusions: Fasting plasma BAs are not useful clinical biomarkers for predicting NOD in patients with IFG. However, an unexpected association between 6α-hydroxylated BAs and glucose parameters was found, suggesting a role for this specific BA pathway in metabolic homeostasis. IT-DIAB study registry number: NCT01218061

NASH-related increases in plasma bile acid levels depend on insulin resistance

International audienceIntroduction: Plasma bile acids (BA) have been extensively studied as pathophysiological actors in Non-Alcoholic Steatohepatitis (NASH). However, results from clinical studies are often complicated by the association of NASH with type 2 diabetes (T2D), obesity and insulin resistance (IR). Here, we sought to dissect the relationship between NASH, T2D and plasma BA levels in a large patient cohort. Materials and Methods: Four groups of patients from the ABOS cohort (Clin Trials NCT01129297) were included based on presence or absence of histologically evaluated NASH with or without coincident T2D. Patients were matched for BMI, HOMA2-assessed IR, HbA 1c , age and gender. To study the effect of IR and BMI on the association of plasma BA and NASH, patients from the Hepadip study were included. In both cohorts, fasting plasma BA concentrations were measured. Results: Plasma BA concentrations were higher in NASH compared to No-NASH patients both in T2D and NoT2D patients from the ABOS cohort. As we previously reported that plasma BA levels were unaltered in NASH patients of the Hepadip cohort, we assessed the impact of BMI and IR on the association of NASH and BA on the combined BA datasets. Our results revealed that NASH-associated increases in plasma total cholic acid (CA) concentrations depend on the degree of HOMA2-assessed systemic IR, but not on -cell function nor on BMI

Adipocyte-specific FXR-deficiency protects adipose tissue from oxidative stress and insulin resistance and improves glucose homeostasis

Objective: Obesity is associated with metabolic dysfunction of white adipose tissue (WAT). Activated adipocytes secrete pro-inflammatory cytokines resulting in the recruitment of pro-inflammatory macrophages, which contribute to WAT insulin resistance. The bile acid (BA)-activated nuclear Farnesoid X Receptor (FXR) controls systemic glucose and lipid metabolism. Here, we studied the role of FXR in adipose tissue function. Methods: We first investigated the immune phenotype of epididymal WAT (eWAT) from high fat diet (HFD)-fed whole-body FXR-deficient (FXR−/−) mice by flow cytometry and gene expression analysis. We then generated adipocyte-specific FXR-deficient (Ad-FXR−/−) mice and analyzed systemic and eWAT metabolism and immune phenotype upon HFD feeding. Transcriptomic analysis was done on mature eWAT adipocytes from HFD-fed Ad-FXR−/− mice. Results: eWAT from HFD-fed whole-body FXR−/− and Ad-FXR−/− mice displayed decreased pro-inflammatory macrophage infiltration and inflammation. Ad-FXR−/− mice showed lower blood glucose concentrations, improved systemic glucose tolerance and WAT insulin sensitivity and oxidative stress. Transcriptomic analysis identified Gsta4, a modulator of oxidative stress in WAT, as the most upregulated gene in Ad-FXR−/− mouse adipocytes. Finally, chromatin immunoprecipitation analysis showed that FXR binds the Gsta4 gene promoter. Conclusions: These results indicate a role for the adipocyte FXR-GSTA4 axis in controlling HFD-induced inflammation and systemic glucose homeostasis

The nuclear receptor FXR inhibits Glucagon-Like Peptide-1 secretion in response to microbiota-derived Short-Chain Fatty Acids.

The gut microbiota participates in the control of energy homeostasis partly through fermentation of dietary fibers hence producing short-chain fatty acids (SCFAs), which in turn promote the secretion of the incretin Glucagon-Like Peptide-1 (GLP-1) by binding to the SCFA receptors FFAR2 and FFAR3 on enteroendocrine L-cells. We have previously shown that activation of the nuclear Farnesoid X Receptor (FXR) decreases the L-cell response to glucose. Here, we investigated whether FXR also regulates the SCFA-induced GLP-1 secretion. GLP-1 secretion in response to SCFAs was evaluated ex vivo in murine colonic biopsies and in colonoids of wild-type (WT) and FXR knock-out (KO) mice, in vitro in GLUTag and NCI-H716 L-cells activated with the synthetic FXR agonist GW4064 and in vivo in WT and FXR KO mice after prebiotic supplementation. SCFA-induced GLP-1 secretion was blunted in colonic biopsies from GW4064-treated mice and enhanced in FXR KO colonoids. In vitro FXR activation inhibited GLP-1 secretion in response to SCFAs and FFAR2 synthetic ligands, mainly by decreasing FFAR2 expression and downstream Gαq-signaling. FXR KO mice displayed elevated colonic FFAR2 mRNA levels and increased plasma GLP-1 levels upon local supply of SCFAs with prebiotic supplementation. Our results demonstrate that FXR activation decreases L-cell GLP-1 secretion in response to inulin-derived SCFA by reducing FFAR2 expression and signaling. Inactivation of intestinal FXR using bile acid sequestrants or synthetic antagonists in combination with prebiotic supplementation may be a promising therapeutic approach to boost the incretin axis in type 2 diabetes

Beyond the Rule of 5: Impact of PEGylation with Various Polymer Sizes on Pharmacokinetic Properties, Structure–Properties Relationships of mPEGylated Small Agonists of TGR5 Receptor

International audiencePEGylation of therapeutic agents is known to improve the pharmacokinetic behavior of macromolecular drugs and nanoparticles. In this work, we performed the conjugation of polyethylene glycols (220-5000 Da) to a series of non-steroidal small agonists of the bile acids receptor TGR5. A suitable anchoring position on the agonist was identified to retain full agonistic potency with the conjugates. We describe herein an extensive structure-properties relationships study allowing us to finely describe the non-linear effects of the PEG length on the physicochemical as well as the in vitro and in vivo pharmacokinetic properties of these compounds. When appending a PEG of suitable length to the TGR5 pharmacophore, we were able to identify either systemic or gut lumen-restricted TGR5 agonists