Endothelial cell-derived oxysterol ablation attenuates experimental autoimmune encephalomyelitis.

The vasculature is a key regulator of leukocyte trafficking into the central nervous system (CNS) during inflammatory diseases including multiple sclerosis (MS). However, the impact of endothelial-derived factors on CNS immune responses remains unknown. Bioactive lipids, in particular oxysterols downstream of Cholesterol-25-hydroxylase (Ch25h), promote neuroinflammation but their functions in the CNS are not well-understood. Using floxed-reporter Ch25h knock-in mice, we trace Ch25h expression to CNS endothelial cells (ECs) and myeloid cells and demonstrate that Ch25h ablation specifically from ECs attenuates experimental autoimmune encephalomyelitis (EAE). Mechanistically, inflamed Ch25h-deficient CNS ECs display altered lipid metabolism favoring polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC) expansion, which suppresses encephalitogenic T lymphocyte proliferation. Additionally, endothelial Ch25h-deficiency combined with immature neutrophil mobilization into the blood circulation nearly completely protects mice from EAE. Our findings reveal a central role for CNS endothelial Ch25h in promoting neuroinflammation by inhibiting the expansion of immunosuppressive myeloid cell populations.

Prebiotic dietary fibre intervention improves fecal markers related to inflammation in obese patients: results from the Food4Gut randomized placebo-controlled trial.

PURPOSE: Inulin-type fructans (ITF) are prebiotic dietary fibre (DF) that may confer beneficial health effects, by interacting with the gut microbiota. We have tested the hypothesis that a dietary intervention promoting inulin intake versus placebo influences fecal microbial-derived metabolites and markers related to gut integrity and inflammation in obese patients. METHODS: Microbiota (16S rRNA sequencing), long- and short-chain fatty acids (LCFA, SCFA), bile acids, zonulin, and calprotectin were analyzed in fecal samples obtained from obese patients included in a randomized, placebo-controlled trial. Participants received either 16 g/d native inulin (prebiotic n = 12) versus maltodextrin (placebo n = 12), coupled to dietary advice to consume inulin-rich versus inulin-poor vegetables for 3 months, in addition to dietary caloric restriction. RESULTS: Both placebo and prebiotic interventions lowered energy and protein intake. A substantial increase in Bifidobacterium was detected after ITF treatment (q = 0.049) supporting our recent data obtained in a larger cohort. Interestingly, fecal calprotectin, a marker of gut inflammation, was reduced upon ITF treatment. Both prebiotic and placebo interventions increased the ratio of tauro-conjugated/free bile acids in feces. Prebiotic treatment did not significantly modify fecal SCFA content but it increased fecal rumenic acid, a conjugated linoleic acid (cis-9, trans-11 CLA) with immunomodulatory properties, that correlated notably to the expansion of Bifidobacterium (p = 0.031; r = 0.052). CONCLUSIONS: Our study demonstrates that ITF-prebiotic intake during 3 months decreases a fecal marker of intestinal inflammation in obese patients. Our data point to a potential contribution of microbial lipid-derived metabolites in gastro-intestinal dysfunction related to obesity. CLINICALTRIALS. GOV IDENTIFIER: NCT03852069 (February 22, 2019 retrospectively, registered).

The gut microbiota metabolite indole alleviates liver inflammation in mice.

The gut microbiota regulates key hepatic functions, notably through the production of bacterial metabolites that are transported via the portal circulation. We evaluated the effects of metabolites produced by the gut microbiota from aromatic amino acids (phenylacetate, benzoate, p-cresol, and indole) on liver inflammation induced by bacterial endotoxin. Precision-cut liver slices prepared from control mice, Kupffer cell (KC)-depleted mice, and obese mice ( ob/ ob) were treated with or without LPS and bacterial metabolites. We observed beneficial effects of indole that dose-dependently reduced the LPS-induced up-regulation of proinflammatory mediators at both mRNA and protein levels in precision-cut liver slices prepared from control or ob/ ob mice. KC depletion partly prevented the antiinflammatory effects of indole, notably through a reduction of nucleotide-binding domain and leucine-rich repeat containing (NLR) family pyrin domain-containing 3 (NLRP3) pathway activation. In vivo, the oral administration of indole before an LPS injection reduced the expression of key proteins of the NF-κB pathway and downstream proinflammatory gene up-regulation. Indole also prevented LPS-induced alterations of cholesterol metabolism through a transcriptional regulation associated with increased 4ß-hydroxycholesterol hepatic levels. In summary, indole appears as a bacterial metabolite produced from tryptophan that is able to counteract the detrimental effects of LPS in the liver. Indole could be a new target to develop innovative strategies to decrease hepatic inflammation.-Beaumont, M., Neyrinck, A. M., Olivares, M., Rodriguez, J., de Rocca Serra, A., Roumain, M., Bindels, L. B., Cani, P. D., Evenepoel, P., Muccioli, G. G., Demoulin, J.-B., Delzenne, N. M. The gut microbiota metabolite indole alleviates liver inflammation in mice.

Identification and in vivo detection of side-chain hydroxylated metabolites of 4ß-hydroxycholesterol.

Oxysterols are oxidized derivatives of cholesterol that are formed by enzymatic processes or through the action of reactive oxygen species. Several of these bioactive lipids have been shown to be affected and/or play a role in inflammatory processes. 4ß-hydroxycholesterol is one of the major oxysterols in mice and humans and its levels are affected by inflammatory diseases. However, apart from its long half-life, little is known about its catabolism. By incubating 4ß-hydroxycholesterol with mouse mitochondria-enriched liver fractions, as well as 25-hydroxycholesterol and 27-hydroxycholesterol with recombinant CYP3A4, we identified 4ß,25-dihydroxycholesterol and 4ß,27-dihydroxycholesterol as 4ß-hydroxycholesterol metabolites. Supporting the biological relevance of this metabolism, we detected both metabolites after incubation of J774, primary mouse peritoneal macrophages and PMA-differentiated THP-1 cells with 4ß-hydroxycholesterol. Across our experiments, the incubation of cells with lipopolysaccharides differentially affected the levels of the 25- and 27-hydroxylated metabolites of 4ß-hydroxycholesterol. Finally, 4ß,27-dihydroxycholesterol was also detected in mice liver and plasma after intraperitoneal administration of 4ß-hydroxycholesterol. To our knowledge, this is the first report of the in vitro and in vivo detection and quantification of 4ß-hydroxycholesterol metabolites.

Pediatric Autoimmune or Primary Sclerosing Cholangitis: Metronidazole Effectiveness on Biochemical Data, Bile Acid Profile, and Gut Microbiota: A Pilot Study.

Objectives: Autoimmune hepatitis and primary sclerosing cholangitis (PSC) can both be present, resulting in autoimmune sclerosing cholangitis (ASC). PSC physiopathology could be based on the cross-talk between gut microbiota and bile acids (BAs); antibiotics are an innovative therapy. This pilot study assesses metronidazole (MTZ)'s effectiveness in ASC or PSC patients according to the stage of the disease, and its effects on biochemical parameters, BA profiles, and gut microbiota. Methods: ASC or PSC patients from Cliniques universitaires Saint-Luc's pediatric hepato-gastroenterology division were enrolled retrospectively and prospectively; both datasets were merged. MTZ was administered over at least 14 days on top of standard treatment (ursodeoxycholic acid, azathioprine, and steroids). Fecal and blood samples were collected before (T0) and at MTZ day 14 (T14). Sustained biochemical remission was defined by the reduction of transaminases (AST and ALT), gamma-glutamyl transferase (GGT), and CRP until 12 months post-MTZ. Results: A total of 18 patients (mean age, 13.2 ± 4.5 years) were enrolled (13 ASC and 5 PSC), and divided in remission or relapse patients. CRP, AST, ALT, and GGT levels decreased post-MTZ in both groups (excepting GGT in relapse patients), with decreases between T0 and T14 being significant for AST and ALT. Relapse patients were older (P = 0.0351) and in late-disease stage, with mainly large-duct PSC (P = 0.0466). In remission patients, the mean plasma relative abundance of hydrophilic BA increased by +6.3% (P = 0.0391) after MTZ. Neither at baseline nor T14, there were significant differences in gut microbiota recorded. Conclusion: These data are likely indicative of long-term benefits following MTZ therapy at early-stage ASC or PSC, with increased hydrophilic BA abundance. Multicenter prospective studies are needed.

Inulin increases the beneficial effects of rhubarb supplementation on high-fat high-sugar diet-induced metabolic disorders in mice: impact on energy expenditure, brown adipose tissue activity, and microbiota.

Consumption of prebiotics and plant-based compounds have many beneficial health effects through modulation of gut microbiota composition and are considered as promising nutritional strategy for the treatment of metabolic diseases. In the present study, we assessed the separated and combined effects of inulin and rhubarb on diet-induced metabolic disease in mice. We showed that supplementation with both inulin and rhubarb abolished the total body and fat mass gain upon high-fat and high-sucrose diet (HFHS) as well as several obesity-associated metabolic disorders. These effects were associated with increased energy expenditure, lower whitening of the brown adipose tissue, higher mitochondria activity and increased expression of lipolytic markers in white adipose tissue. Despite modifications of intestinal gut microbiota and bile acid compositions by inulin or rhubarb alone, combination of both inulin and rhubarb had minor additional impact on these parameters. However, the combination of inulin and rhubarb increased the expression of several antimicrobial peptides and higher goblet cell numbers, thereby suggesting a reinforcement of the gut barrier. Together, these results suggest that the combination of inulin and rhubarb in mice potentiates beneficial effects of separated rhubarb and inulin on HFHS-related metabolic disease and could be considered as nutritional strategy for the prevention and treatment of obesity and related pathologies.

EBI2 is a negative modulator of brown adipose tissue energy expenditure in mice and human brown adipocytes.

Pharmacological activation of brown adipose tissue (BAT) is an attractive approach for increasing energy expenditure to counteract obesity. Given the side-effects of known activators of BAT, we studied inhibitors of BAT as a novel, alternative concept to regulate energy expenditure. We focused on G-protein-coupled receptors that are one of the major targets of clinically used drugs. Here, we identify GPR183, also known as EBI2, as the most highly expressed inhibitory G-protein-coupled receptor in BAT among the receptors examined. Activation of EBI2 using its endogenous ligand 7α,25-dihydroxycholesterol significantly decreases BAT-mediated energy expenditure in mice. In contrast, mice deficient for EBI2 show increased energy dissipation in response to cold. Interestingly, only thermogenic adipose tissue depots - BAT and subcutaneous white adipose tissue -respond to 7α,25-dihydroxycholesterol treatment/EBI2 activation but not gonadal white fat, which has the lowest thermogenic capacity. EBI2 activation in brown adipocytes significantly reduces norepinephrine-induced cAMP production, whereas pharmacological inhibition or genetic ablation of EBI2 results in an increased response. Importantly, EBI2 significantly inhibits norepinephrine-induced activation of human brown adipocytes. Our data identify the 7α,25-dihydroxycholesterol/EBI2 signaling pathway as a so far unknown BAT inhibitor. Understanding the inhibitory regulation of BAT might lead to novel pharmacological approaches to increase the activity of thermogenic adipose tissue and whole body energy expenditure in humans.

GPR183 Is Dispensable for B1 Cell Accumulation and Function, but Affects B2 Cell Abundance, in the Omentum and Peritoneal Cavity.

B1 cells constitute a specialized subset of B cells, best characterized in mice, which is abundant in body cavities, including the peritoneal cavity. Through natural and antigen-induced antibody production, B1 cells participate in the early defense against bacteria. The G protein-coupled receptor 183 (GPR183), also known as Epstein-Barr virus-induced gene 2 (EBI2), is an oxysterol-activated chemotactic receptor that regulates migration of B cells. We investigated the role of GPR183 in B1 cells in the peritoneal cavity and omentum. B1 cells expressed GPR183 at the mRNA level and migrated towards the GPR183 ligand 7α,25-dihydroxycholesterol (7α,25-OHC). GPR183 knock-out (KO) mice had smaller omenta, but with normal numbers of B1 cells, whereas they had fewer B2 cells in the omentum and peritoneal cavity than wildtype (WT) mice. GPR183 was not responsible for B1 cell accumulation in the omentum in response to i.p. lipopolysaccharide (LPS)-injection, in spite of a massive increase in 7α,25-OHC levels. Lack of GPR183 also did not affect B1a- or B1b cell-specific antibody responses after vaccination. In conclusion, we found that GPR183 is non-essential for the accumulation and function of B1 cells in the omentum and peritoneal cavity, but that it influences the abundance of B2 cells in these compartments.

Chitin-glucan supplementation improved postprandial metabolism and altered gut microbiota in subjects at cardiometabolic risk in a randomized trial.

Chitin-glucan (CG), an insoluble dietary fiber, has been shown to improve cardiometabolic disorders associated with obesity in mice. Its effects in healthy subjects has recently been studied, revealing its interaction with the gut microbiota. In this double-blind, randomized, cross-over, twice 3-week exploratory study, we investigated the impacts of CG on the cardiometabolic profile and gut microbiota composition and functions in 15 subjects at cardiometabolic risk. They consumed as a supplement 4.5 g of CG daily or maltodextrin as control. Before and after interventions, fasting and postprandial metabolic parameters and exhaled gases (hydrogen [H2] and methane [CH4]) were evaluated. Gut microbiota composition (16S rRNA gene sequencing analysis), fecal concentrations of bile acids, long- and short-chain fatty acids (LCFA, SCFA), zonulin, calprotectin and lipopolysaccharide binding protein (LBP) were analyzed. Compared to control, CG supplementation increased exhaled H2 following an enriched-fiber breakfast ingestion and decreased postprandial glycemia and triglyceridemia response to a standardized test meal challenge served at lunch. Of note, the decrease in postprandial glycemia was only observed in subjects with higher exhaled H2, assessed upon lactulose breath test performed at inclusion. CG decreased a family belonging to Actinobacteria phylum and increased 3 bacterial taxa: Erysipelotrichaceae UCG.003, Ruminococcaceae UCG.005 and Eubacterium ventriosum group. Fecal metabolites, inflammatory and intestinal permeability markers did not differ between groups. In conclusion, we showed that CG supplementation modified the gut microbiota composition and improved postprandial glycemic response, an early determinant of cardiometabolic risk. Our results also suggest breath H2 production as a non-invasive parameter of interest for predicting the effectiveness of dietary fiber intervention.

Bile Acid Dysregulation Is Intrinsically Related to Cachexia in Tumor-Bearing Mice.

Bile acids exert diverse actions on host metabolism and immunity through bile acid-activated receptors, including Takeda G protein-coupled receptor 5 (TGR5). We have recently evidenced an alteration in bile acids in cancer cachexia, an inflammatory and metabolic syndrome contributing to cancer death. This current study aims to further explore the links emerging between bile acids and cancer cachexia. First, we showed that bile flow is reduced in cachectic mice. Next, comparing mice inoculated with cachexia-inducing and with non-cachexia-inducing C26 colon carcinoma cells, we demonstrated that alterations in the bile acid pathways and profile are directly associated with cachexia. Finally, we performed an interventional study using ursodeoxycholic acid (UDCA), a compound commonly used in hepatobiliary disorders, to induce bile acid secretion and decrease inflammation. We found that UDCA does not improve hepatic inflammation and worsens muscle atrophy in cachectic mice. This exacerbation of the cachectic phenotype upon UDCA was accompanied by a decreased TGR5 activity, suggesting that TGR5 agonists, known to reduce inflammation in several pathological conditions, could potentially counteract cachectic features. This work brings to light major evidence sustaining the emerging links between bile acids and cancer cachexia and reinforces the interest in studying bile acid-activated receptors in this context.

ß-arrestin2 recruitment at the ß2 adrenergic receptor: A luciferase complementation assay adapted for undergraduate training in pharmacology.

In the context of pharmacology teaching, hands-on activities constitute an essential complement to theoretical lectures. Frequently, these activities consist in exposing fresh animal tissues or even living animals to selected drugs and qualitatively or quantitatively evaluating functional responses. However, technological advancements in pharmacological research and the growing concerns for animal experimentation support the need for innovative and flexible in vitro assays adapted for teaching purposes. We herein report the implementation of a luciferase complementation assay (LCA) enabling to dynamically monitor ß-arrestin2 recruitment at the ß2 adrenergic receptor in the framework of pharmacological training at the faculty of Pharmacy and Biomedical Sciences. The assay allowed students to quantitatively characterize the competitive antagonism of propranolol, and to calculate pEC50 , pKB , and pA2 values after a guided data analysis session. Moreover, the newly implemented workshop delivered highly reproducible results and were generally appreciated by students. As such, we report that the luciferase complementation-based assay proved to be a straightforward, robust, and cost-effective alternative to experiments performed on animal tissues, constituting a useful and flexible tool to enhance and update current hands-on training in the context of pharmacological teaching.

Canagliflozin protects against sepsis capillary leak syndrome by activating endothelial α1AMPK.

Sepsis capillary leak syndrome (SCLS) is an independent prognostic factor for poor sepsis outcome. We previously demonstrated that α1AMP-activated protein kinase (α1AMPK) prevents sepsis-induced vascular hyperpermeability by mechanisms involving VE-cadherin (VE-Cad) stabilization and activation of p38 mitogen activated protein kinase/heat shock protein of 27 kDa (p38MAPK/HSP27) pathway. Canagliflozin, a sodium-glucose co-transporter 2 inhibitor, has recently been proven to activate AMPK in endothelial cells. Therefore, we hypothesized that canagliflozin could be of therapeutic potential in patients suffering from SCLS. We herein report that canagliflozin, used at clinically relevant concentrations, counteracts lipopolysaccharide-induced vascular hyperpermeability and albumin leakage in wild-type, but not in endothelial-specific α1AMPK-knockout mice. In vitro, canagliflozin was demonstrated to activate α1AMPK/p38MAPK/HSP27 pathway and to preserve VE-Cad's integrity in human endothelial cells exposed to human septic plasma. In conclusion, our data demonstrate that canagliflozin protects against SCLS via an α1AMPK-dependent pathway, and lead us to consider novel therapeutic perspectives for this drug in SCLS.

Novel insights into the genetically obese (ob/ob) and diabetic (db/db) mice: two sides of the same coin.

BACKGROUND: Leptin-deficient ob/ob mice and leptin receptor-deficient db/db mice are commonly used mice models mimicking the conditions of obesity and type 2 diabetes development. However, although ob/ob and db/db mice are similarly gaining weight and developing massive obesity, db/db mice are more diabetic than ob/ob mice. It remains still unclear why targeting the same pathway-leptin signaling-leads to the development of two different phenotypes. Given that gut microbes dialogue with the host via different metabolites (e.g., short-chain fatty acids) but also contribute to the regulation of bile acids metabolism, we investigated whether inflammatory markers, bacterial components, bile acids, short-chain fatty acids, and gut microbes could contribute to explain the specific phenotype discriminating the onset of an obese and/or a diabetic state in ob/ob and db/db mice. RESULTS: Six-week-old ob/ob and db/db mice were followed for 7 weeks; they had comparable body weight, fat mass, and lean mass gain, confirming their severely obese status. However, as expected, the glucose metabolism and the glucose-induced insulin secretion were significantly different between ob/ob and db/db mice. Strikingly, the fat distribution was different, with db/db mice having more subcutaneous and ob/ob mice having more epididymal fat. In addition, liver steatosis was more pronounced in the ob/ob mice than in db/db mice. We also found very distinct inflammatory profiles between ob/ob and db/db mice, with a more pronounced inflammatory tone in the liver for ob/ob mice as compared to a higher inflammatory tone in the (subcutaneous) adipose tissue for db/db mice. When analyzing the gut microbiota composition, we found that the quantity of 19 microbial taxa was in some way affected by the genotype. Furthermore, we also show that serum LPS concentration, hepatic bile acid content, and cecal short-chain fatty acid profiles were differently affected by the two genotypes. CONCLUSION: Taken together, our results elucidate potential mechanisms implicated in the development of an obese or a diabetic state in two genetic models characterized by an altered leptin signaling. We propose that these differences could be linked to specific inflammatory tones, serum LPS concentration, bile acid metabolism, short-chain fatty acid profile, and gut microbiota composition. Video abstract.

Inflammation-induced cholestasis in cancer cachexia.

BACKGROUND: Cancer cachexia is a debilitating metabolic syndrome contributing to cancer death. Organs other than the muscle may contribute to the pathogenesis of cancer cachexia. This work explores new mechanisms underlying hepatic alterations in cancer cachexia. METHODS: We used transcriptomics to reveal the hepatic gene expression profile in the colon carcinoma 26 cachectic mouse model. We performed bile acid, tissue mRNA, histological, biochemical, and western blot analyses. Two interventional studies were performed using a neutralizing interleukin 6 antibody and a bile acid sequestrant, cholestyramine. Our findings were evaluated in a cohort of 94 colorectal cancer patients with or without cachexia (43/51). RESULTS: In colon carcinoma 26 cachectic mice, we discovered alterations in five inflammatory pathways as well as in other pathways, including bile acid metabolism, fatty acid metabolism, and xenobiotic metabolism (normalized enrichment scores of -1.97, -2.16, and -1.34, respectively; all Padj < 0.05). The hepatobiliary transport system was deeply impaired in cachectic mice, leading to increased systemic and hepatic bile acid levels (+1512 ± 511.6 pmol/mg, P = 0.01) and increased hepatic inflammatory cytokines and neutrophil recruitment to the liver of cachectic mice (+43.36 ± 16.01 neutrophils per square millimetre, P = 0.001). Adaptive mechanisms were set up to counteract this bile acid accumulation by repressing bile acid synthesis and by enhancing alternative routes of basolateral bile acid efflux. Targeting bile acids using cholestyramine reduced hepatic inflammation, without affecting the hepatobiliary transporters (e.g. tumour necrosis factor α signalling via NFκB and inflammatory response pathways, normalized enrichment scores of -1.44 and -1.36, all Padj < 0.05). Reducing interleukin 6 levels counteracted the change in expression of genes involved in the hepatobiliary transport, bile acid synthesis, and inflammation. Serum bile acid levels were increased in cachectic vs. non-cachectic cancer patients (e.g. total bile acids, +5.409 ± 1.834 µM, P = 0.026) and were strongly correlated to systemic inflammation (taurochenodeoxycholic acid and C-reactive protein: ρ = 0.36, Padj = 0.017). CONCLUSIONS: We show alterations in bile acid metabolism and hepatobiliary secretion in cancer cachexia. In this context, we demonstrate the contribution of systemic inflammation to the impairment of the hepatobiliary transport system and the role played by bile acids in the hepatic inflammation. This work paves the way to a better understanding of the role of the liver in cancer cachexia.

High Dose Versus Low Dose Syngeneic Hepatocyte Transplantation in Pex1-G844D NMRI Mouse Model is Safe but Does Not Achieve Long Term Engraftment.

Genetic alterations in PEX genes lead to peroxisome biogenesis disorder. In humans, they are associated with Zellweger spectrum disorders (ZSD). No validated treatment has been shown to modify the dismal natural history of ZSD. Liver transplantation (LT) improved clinical and biochemical outcomes in mild ZSD patients. Hepatocyte transplantation (HT), developed to overcome LT limitations, was performed in a mild ZSD 4-year-old child with encouraging short-term results. Here, we evaluated low dose (12.5 million hepatocytes/kg) and high dose (50 million hepatocytes/kg) syngeneic male HT via intrasplenic infusion in the Pex1-G844D NMRI mouse model which recapitulates a mild ZSD phenotype. HT was feasible and safe in growth retarded ZSD mice. Clinical (weight and food intake) and biochemical parameters (very long-chain fatty acids, abnormal bile acids, etc.) were in accordance with ZSD phenotype but they were not robustly modified by HT. As expected, one third of the infused cells were detected in the liver 24 h post-HT. No liver nor spleen microchimerism was detected after 7, 14 and 30 days. Future optimizations are required to improve hepatocyte engraftment in Pex1-G844D NMRI mouse liver. The mouse model exhibited the robustness required for ZSD liver-targeted therapies evaluation.

Chemical Compositional Changes in Over-Oxidized Fish Oils.

A recent study has reported that the administration during gestation of a highly rancid hoki liver oil, obtained by oxidation through sustained exposure to oxygen gas and incident light for 30 days, causes newborn mortality in rats. This effect was attributed to lipid hydroperoxides formed in the omega-3 long-chain polyunsaturated fatty acid-rich oil, while other chemical changes in the damaged oil were overlooked. In the present study, the oxidation condition employed to damage the hoki liver oil was replicated, and the extreme rancidity was confirmed. A detailed analysis of temporal chemical changes resulting from the sustained oxidative challenge involved measures of eicosapentaenoic acid/docosahexaenoic acid (EPA/DHA) omega-3 oil oxidative quality (peroxide value, para-anisidine value, total oxidation number, acid value, oligomers, antioxidant content, and induction time) as well as changes in fatty acid content, volatiles, isoprostanoids, and oxysterols. The chemical description was extended to refined anchovy oil, which is a more representative ingredient oil used in omega-3 finished products. The present study also analyzed the effects of a different oxidation method involving thermal exposure in the dark in contact with air, which is an oxidation condition that is more relevant to retail products. The two oils had different susceptibility to the oxidation conditions, resulting in distinct chemical oxidation signatures that were determined primarily by antioxidant protection as well as specific methodological aspects of the applied oxidative conditions. Unique isoprostanoids and oxysterols were formed in the over-oxidized fish oils, which are discussed in light of their potential biological activities.

Hepatic NAPE-PLD Is a Key Regulator of Liver Lipid Metabolism.

Diverse metabolic disorders have been associated with an alteration of N-acylethanolamine (NAE) levels. These bioactive lipids are synthesized mainly by N-acylphosphatidylethanolamine-selective phospholipase D (NAPE-PLD) and influence host metabolism. We have previously discovered that NAPE-PLD in the intestine and adipose tissue is connected to the pathophysiology of obesity. However, the physiological function of NAPE-PLD in the liver remains to be deciphered. To study the role of liver NAPE-PLD on metabolism, we generated a new mouse model of inducible Napepld hepatocyte-specific deletion (Napepld∆Hep mice). In this study, we report that Napepld∆Hep mice develop a high-fat diet-like phenotype, characterized by an increased fat mass gain, hepatic steatosis and we show that Napepld∆Hep mice are more sensitive to liver inflammation. We also demonstrate that the role of liver NAPE-PLD goes beyond the mere synthesis of NAEs, since the deletion of NAPE-PLD is associated with a marked modification of various bioactive lipids involved in host homeostasis such as oxysterols and bile acids. Collectively these data suggest that NAPE-PLD in hepatocytes is a key regulator of liver bioactive lipid synthesis and a dysregulation of this enzyme leads to metabolic complications. Therefore, deepening our understanding of the regulation of NAPE-PLD could be crucial to tackle obesity and related comorbidities.

Longitudinal study of Pex1-G844D NMRI mouse model: A robust pre-clinical model for mild Zellweger spectrum disorder.

Zellweger spectrum disorders (ZSD) are inborn errors of metabolism caused by mutations in PEX genes that lead to peroxisomal biogenesis disorder (PBD). No validated treatment is able to modify the dismal progression of the disease. ZSD mouse models used to develop therapeutic approaches are limited by poor survival and breeding restrictions. To overcome these limitations, we backcrossed the hypomorphic Pex1 p.G844D allele to NMRI background. NMRI mouse breeding restored an autosomal recessive Mendelian inheritance pattern and delivered twice larger litters. Mice were longitudinally phenotyped up to 6 months of age to make this model suitable for therapeutic interventions. ZSD mice exhibited growth retardation and relative hepatomegaly associated to progressive hepatocyte hypertrophy. Biochemical studies associated with RNA sequencing deciphered ZSD liver glycogen metabolism alterations. Affected fibroblasts displayed classical immunofluorescence pattern and biochemical alterations associated with PBD. Plasma and liver showed very long-chain fatty acids, specific oxysterols and C27 bile acids intermediates elevation in ZSD mice along with a specific urine organic acid profile. With ageing, C26 fatty acid and phytanic acid levels tended to normalize in ZSD mice, as described in patients reaching adulthood. In conclusion, our mouse model recapitulates a mild ZSD phenotype and is suitable for liver-targeted therapies evaluation.

Metabolite profiling reveals the interaction of chitin-glucan with the gut microbiota.

Dietary fibers are considered beneficial nutrients for health. Current data suggest that their interaction with the gut microbiota largely contributes to their physiological effects. In this context, chitin-glucan (CG) improves metabolic disorders associated with obesity in mice, but its effect on gut microbiota has never been evaluated in humans. This study explores the effect of a 3-week intervention with CG supplementation in healthy individuals on gut microbiota composition and bacterial metabolites. CG was given to healthy volunteers (n = 15) for three weeks as a supplement (4.5 g/day). Food diary, visual analog and Bristol stool form scales and a "quality of life" survey were analyzed. Among gut microbiota-derived metabolites, bile acids (BA), long- and short-chain fatty acids (LCFA, SCFA) profiling were assessed in stool samples. The gut microbiota (primary outcome) was analyzed by Illumina sequencing. A 3-week supplementation with CG is well tolerated in healthy humans. CG induces specific changes in the gut microbiota composition, with Eubacterium, Dorea and Roseburia genera showing the strongest regulation. In addition, CG increased bacterial metabolites in feces including butyric, iso-valeric, caproic and vaccenic acids. No major changes were observed for the fecal BA profile following CG intervention. In summary, our work reveals new potential bacterial genera and gut microbiota-derived metabolites characterizing the interaction between an insoluble dietary fiber -CG- and the gut microbiota.