ABSTRACT
BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) has become the leading cause of chronic liver disease worldwide and the determinants driving its severity remain to be elucidated. Perfluoroalkyl substances (PFAS) are synthetic chemical compounds. They are used in commonplace products and persistent in water, soil and the human body. In vitro and animal studies suggest a pathogenic role for PFAS in metabolic diseases such as NAFLD. OBJECTIVES: We aimed to evaluate the association between NAFLD severity and serum PFAS concentrations in humans. METHODS: One hundred biopsy-proven NAFLD patients were included with a well-balanced distribution between the different stages of severity: 25 patients with simple steatosis, 25 with early non-alcoholic steatohepatitis (NASH and F0-F1 fibrosis), 33 with fibrotic NASH (NASH and F2-F3 fibrosis), and 17 with cirrhotic NASH (NASH and F4 fibrosis). Liver histological features were evaluated according to the NASH Clinical Research Network classification. Seventeen PFAS were measured by high-performance liquid chromatography coupled with tandem mass spectrometry on serum samples stored at -80 °C. RESULTS: The median age was 60 years, 61 % of patients were male, 46 % had diabetes and the median body mass index (BMI) was 32 kg/m2. Long-chain PFAS were associated with steatosis grade (p = 0.03). Among the nine PFAS detected in > 50 % of the patients, Perfluoro-n-heptanoic acid (PFHpA) showed significantly higher concentrations in grade 3 steatosis versus grade 1 (p = 0.02). Perfluoro-n-dodecanoic acid (PFDoA) concentrations were higher in patients with significant fibrosis (p = 0.04) and PFHpA in patients with advanced fibrosis (p = 0.02). The association between PFHpA and steatosis grade remained significant in multivariate analysis adjusted for age, gender, BMI, diabetes presence and dyslipidemia (p = 0.004). DISCUSSION: Our study showed a significant association between PFHpA and liver steatosis in NAFLD. According to data available in the literature, PFHpA could be implicated in liver steatosis through ß-oxidation and biosynthesis of fatty acids.
ABSTRACT
BACKGROUND: The reconstruction of metagenome-assembled genomes (MAGs) has emerged as a powerful approach for combining the taxonomic and functional content of microbial populations. AIM: To use this new approach to highlight mechanisms linking gut microbiota to NAFLD severity METHODS: Stool samples were collected from 96 NAFLD patients on the day of liver biopsy. Shotgun DNA sequencing of the gut microbiota was performed on an Illumina HiSeq3000 system. Contigs were binned into MAGs according to their co-abundances and tetranucleotide frequencies using Metabat v.0.32.4. Predicted protein-coding genes were clustered in orthologous groups (OGs) with DIAMOND against the EggNOG v4.5 database. Liver biopsies were read in accordance with the NASH CRN classification. RESULTS: Fifty-four patients had NASH and 44 had significant fibrosis (F ≥ 2). Sequencing of DNA extracted from stools resulted in 13.8 + 3.2 million paired-end reads per sample. Of the 4,000 reconstructed MAGs, 220 in NASH patients, 192 in non-NASH patients, 203 in F ≥ 2 patients and 230 in F0-1 patients had > 70% completeness and < 5% contamination. Within these MAGs, 28 OGs were associated with NASH, 33 with significant fibrosis, and seven with both NASH and significant fibrosis. The study of MAGs showed associations between NAFLD severity and some gut bacteria with microbiota functions related to hydrogen sulfide production, citrate transport, hemicellulose degradation, aldehyde production and vitamin B12 synthesis. CONCLUSION: Using new metagenomics methods, our study unveils potential mechanisms by which certain bacteria from the gut microbiota could protect or contribute to the development of NASH and liver fibrosis in NAFLD.
