Glucevia®, a Fraxinus angustifolia Vahl extract, is able to modify the gut microbiota composition and those effects are correlated with steatosis severity in obese and diabetic mice

Abstract

Nonalcoholic fatty liver disease (NAFLD) is a condition defined by excessive fat (triglycerides) accumulation (> 5%) in the liver that could evolve to nonalcoholic steatohepatitis (NASH) with liver cell injury and inflammation and increased risks of cirrhosis, liver failure, and hepatocellular carcinoma. NASH is widely considered to be the liver expression of the metabolic syndrome and it is now estimated that about 30% of all adults have NAFLD and 2%–6% of adults have NASH in the US and Western countries and that NAFLD is affecting up to 70–80% of obese individuals. Alteration of the ecologic organization of the gut microbiota, named dysbiosis, have been found to be related with several clinical conditions such as obesity, diabetes and NAFLD. We have previously demonstrated that Glucevia®, a Fraxinus angustifolia Vahl samara extract, is able to improve glucose tolerance in healthy humans and also to improve fasting blood glucose, circulating triglycerides and steatosis in diabetic animals. Here, we aimed to investigate the impact of Glucevia consumption on the gut microbiota and its correlation with steatosis in obese and diabetic mice. Nine‐week‐old adult male C57BL/6 mice (n=20/groups) were fed with a high‐fat diet (HFD, 60% energy from fat) supplemented or not with Glucevia (200 mg/kg bw/day) for 12 weeks. Glucevia treatment was able to reduce body weight gain and fat mass (evaluated by NMR) and to reduce glucose intolerance in mice fed the HFD as shown by the significantly reduced blood glucose concentration 30 and 60 minutes after a glycemic load (p<0.05) and by the reduction of the area under the (glycaemia versus time) curve (AUC) (p=0.07). The HFD induced a high level of fat deposit into the liver in control mice (35.2%) whereas Glucevia was able to significantly reduce the severity of steatosis (fat content: 22.8%; – 35%; p= 0.004). According to the World Gastroenterology Organization histological scoring system (Grade 0: <5%, Grade 1: 5–33%, Grade 2: 34–66%, Grade 3: >67%), Glucevia warranted the reduction of steatosis severity from grade 2 to grade 1. In order to evaluate gut microbiota modifications induced by Glucevia, a 16S rDNA metagenomics study was performed on the murine fecal samples at the beginning (4 weeks) and after 12 weeks of HFD consumption (n=10/group). Bacterial populations contained in the samples were determined using next generation high throughput sequencing of variable regions (V3–V4) of the 16S rDNA bacterial gene. LefSe analysis revealed that, at the genus or OTU levels, there was enrichment of different taxonomic groups (Burkholderiales, Sutterellacae, Parasutterella, Betaproteobacteria, Enterorhabdus and other OTUs) in mice treated with Glucevia in comparison to untreated mice. Conversely, Prevotellaceae, Flavonifractor, Clostridium_IV, Butyricicoccus and other taxonomic groups were less represented in mice treated with Glucevia in comparison to untreated mice. Correlation between microbiota analysis and steatosis severity was analyzed by using the Random Forest Analysis methodology. The relative abundance of several taxonomic groups at the family or the genus level were significantly correlated with the steatosis severity (p<0.05), clearly showing that Glucevia was able to modify the gut microbiota and particularly the relative abundance of some families or genus (i.e. Coriobacteriaceae, Lactobacillaceae, Rikenellaceae) and that these modifications could be linked to the reduction of steatosis progression.Support or Funding InformationNaturex provided the extract and financial support for this study