Analysis of human leukocyte antigen allele polymorphism in patients with non alcoholic fatty liver disease

Myeloid cell MHC I expression drives CD8+ T cell activation in nonalcoholic steatohepatitis

Background & aims

Activated CD8+ T cells are elevated in Nonalcoholic steatohepatitis (NASH) and are important for driving fibrosis and inflammation. Despite this, mechanisms of CD8+ T cell activation in NASH are largely limited. Specific CD8+ T cell subsets may become activated through metabolic signals or cytokines. However, studies in NASH have not evaluated the impact of antigen presentation or the involvement of specific antigens. Therefore, we determined if activated CD8+ T cells are dependent on MHC class I expression in NASH to regulate fibrosis and inflammation.

Methods

We used H2Kb and H2Db deficient (MHC I KO), Kb transgenic mice, and myeloid cell Kb deficient mice (LysM Kb KO) to investigate how MHC class I impacts CD8+ T cell function and NASH. Flow cytometry, gene expression, and histology were used to examine hepatic inflammation and fibrosis. The hepatic class I immunopeptidome was evaluated by mass spectrometry.

Results

In NASH, MHC class I isoform H2Kb was upregulated in myeloid cells. MHC I KO demonstrated protective effects against NASH-induced inflammation and fibrosis. Kb mice exhibited increased fibrosis in the absence of H2Db while LysM Kb KO mice showed protection against fibrosis but not inflammation. H2Kb restricted peptides identified a unique NASH peptide Ncf2 capable of CD8+ T cell activation in vitro. The Ncf2 peptide was not detected during fibrosis resolution.

Conclusion

These results suggest that activated hepatic CD8+ T cells are dependent on myeloid cell MHC class I expression in diet induced NASH to promote inflammation and fibrosis. Additionally, our studies suggest a role of NADPH oxidase in the production of Ncf2 peptide generation.

Liraglutide + PYY3-36 Combination Therapy Mimics Effects of Roux-en-Y Bypass on Early NAFLD Whilst Lacking-Behind in Metabolic Improvements

Background: Treatment options for NAFLD are still limited. Bariatric surgery, such as Roux-en-Y gastric bypass (RYGB), has been shown to improve metabolic and histologic markers of NAFLD. Glucagon-like-peptide-1 (GLP-1) analogues lead to improvements in phase 2 clinical trials. We directly compared the effects of RYGB with a treatment using liraglutide and/or peptide tyrosine tyrosine 3-36 (PYY_3-36) in a rat model for early NAFLD. Methods: Obese male Wistar rats (high-fat diet (HFD)-induced) were randomized into the following treatment groups: RYGB, sham-operation (sham), liraglutide (0.4 mg/kg/day), PYY_3-36 (0.1 mg/kg/day), liraglutide+PYY_3-36, and saline. After an observation period of 4 weeks, liver samples were histologically evaluated, ELISAs and RNA sequencing + RT-qPCRs were performed. Results: RYGB and liraglutide+PYY_3-36 induced a similar body weight loss and, compared to sham/saline, marked histological improvements with significantly less steatosis. However, only RYGB induced significant metabolic improvements (e.g., adiponectin/leptin ratio 18.8 ± 11.8 vs. 2.4 ± 1.2 in liraglutide+PYY_3-36- or 1.4 ± 0.9 in sham-treated rats). Furthermore, RNA sequencing revealed a high number of differentially regulated genes in RYGB treated animals only. Conclusions: The combination therapy of liraglutide+PYY_3-36 partly mimics the positive effects of RYGB on weight reduction and on hepatic steatosis, while its effects on metabolic function lack behind RYGB.

Phenome-wide association study of the major histocompatibility complex region in the Korean population identifies novel association signals

Human leukocyte antigen (HLA) gene variants in the major histocompatibility complex (MHC) region are associated with numerous complex human diseases and quantitative traits. Previous phenome-wide association studies (PheWAS) for this region demonstrated that HLA association patterns to the phenome have both population-specific and population-shared components. We performed MHC PheWAS in the Korean population by analyzing associations between phenotypes and genetic variants in the MHC region using the Korea Biobank Array project data samples from the Korean Genome and Epidemiology Study (KoGES) cohorts. Using this single-population dataset, we curated and analyzed 82 phenotypes for 125 673 Korean individuals after imputing HLA using CookHLA, a recently developed imputation framework. More than one-third of these phenotypes showed significant associations, confirming 56 known associations and discovering 13 novel association signals that were not reported previously. In addition, we analyzed heritability explained by the variants in the MHC region and genetic correlations among phenotypes based on the MHC variants.

Major Histocompatibility Complex Class I-Related Chain A Alleles and Histology of Nonalcoholic Fatty Liver Disease

Major histocompatibility complex class I-related chain A (MICA) is a highly polymorphic gene that modulates immune surveillance by binding to its receptor on natural killer cells, and its genetic polymorphisms have been associated with chronic immune-mediated diseases. The progressive form of nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), is characterized by accumulation of fat and inflammatory cells in the hepatic parenchyma, potentially leading to liver cell injury and fibrosis. To date, there are no data describing the potential role of MICA in the pathogenesis of NAFLD. Therefore, our aim was to assess the association between MICA polymorphism and NASH and its histologic features. A total of 134 subjects were included. DNA from patients with biopsy-proven NAFLD were genotyped using polymerase chain reaction-sequence-specific oligonucleotide for MICA alleles. Liver biopsies were assessed for histologic diagnosis of NASH and specific pathologic features, including stage of fibrosis and grade of inflammation. Multivariate analysis was performed to draw associations between MICA alleles and the different variables; P ≤ 0.05 was considered significant. Univariate analysis showed that MICA*011 (odds ratio [OR], 7.14; 95% confidence interval [CI], 1.24-41.0; P = 0.04) was associated with a higher risk for histologic NASH. Multivariate analysis showed that MICA*002 was independently associated with a lower risk for focal hepatocyte necrosis (OR, 0.24; 95% CI, 0.08-0.74; P = 0.013) and advanced fibrosis (OR, 0.11; 95% CI, 0.02-0.70; P = 0.019). MICA*017 was independently associated with a higher risk for lymphocyte-mediated inflammation (OR, 5.12; 95% CI, 1.12-23.5; P = 0.035). Conclusion: MICA alleles may be associated with NASH and its histologic features of inflammation and fibrosis. Additional research is required to investigate the potential role of MICA in increased risk or protection against NAFLD.

Significance of autoantibody seropositivity in children with obesity and non-alcoholic fatty liver disease

BACKGROUND

Autoantibodies are frequently positive in adults with nonalcoholic fatty liver disease (NAFLD) without concurrent autoimmune hepatitis (AIH). The clinical significance of this is unknown in children.

OBJECTIVE

To determine the prevalence of autoantibody positivity in pediatric NAFLD and to evaluate its association with disease severity.

METHODS

Multicenter, retrospective study of patients ≤18 years of age with biopsy-confirmed NAFLD. Descriptive statistics were used and groups were compared using Wilcoxon-Mann Whitney or χ² testing, and multivariable logistic regression was used for binary or ordinal outcomes.

RESULTS

One hundred and thirty six patients with a median age of 14 years were included. The median body mass index Z-score was 2.5 (interquartile range 2.2, 2.6). Positive antinuclear antibody (ANA), anti-smooth muscle antibody (ASMA), anti-liver-kidney microsomal antibody, or any combination of autoantibodies were observed in 22%, 14%, 0%, and 33% of patients, respectively. The proportion of patients with a steatosis score ≥2 was significantly higher in those with positive ANA (P = .045). In the multivariable regression analysis, positive ANA was associated with increased odds of steatosis score ≥2 (odds ratio, 5.91; 95% confidential interval, 1.50-23.26), after controlling for potential confounders. No other significant histology differences were seen between the groups.

CONCLUSIONS

Positive ANA and ASMA are common in children with NAFLD; however, anti-LKM positivity is not. ANA positivity is associated with more severe steatosis.

From fatty hepatocytes to impaired bile flow: Matching model systems for liver biology and disease

A large variety of model systems are used in hepatobiliary research. In this review, we aim to provide an overview of established and emerging models for specific research questions. We specifically discuss the value and limitations of these models for research on metabolic associated fatty liver disease (MAFLD), (previously named non-alcoholic fatty liver diseases/non-alcoholic steatohepatitis (NAFLD/NASH)) and cholestasis-related diseases such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). The entire range of models is discussed varying from immortalized cell lines, mature or pluripotent stem cell-based models including organoids/spheroids, to animal models and human ex vivo models such as normothermic machine perfusion of livers and living liver slices. Finally, the pros and cons of each model are discussed as well as the need in the scientific community for continuous innovation in model development to better mimic the human (patho)physiology.

Genome-Wide Association Study of Lean Nonalcoholic Fatty Liver Disease Suggests Human Leukocyte Antigen as a Novel Candidate Locus

Nonalcoholic fatty liver disease (NAFLD) is supposed to manifest its metabolic phenotype in the liver, but it is common to have lean individuals diagnosed with NAFLD, known as lean NAFLD. We conducted a two-stage analysis to identify NAFLD-associated loci in Japanese patients. In stage I, 275 metabolically healthy normal-weight patients with NAFLD were compared with 1,411 non-NAFLD controls adjusted for age, sex, and alcohol consumption by a genome-wide association study (GWAS). In stage II, human leukocyte antigen (HLA) in chromosome 6 (chr6) (P = 6.73E-08), microRNA (MIR) MIR548F3 in chr7 (P = 4.25E-07), myosin light chain 2 (MYL2) in chr12 (P = 4.39E-07), and glycoprotein precursor (GPC)6 in chr13 (P = 5.43E-07), as suggested by the GWAS, were assessed by single nucleotide polymorphism (SNP) association analysis of whole NAFLD against non-NAFLD in 9,726 members of the general population. A minor allele of the secondary lead SNP in chr6, rs2076529, was significantly associated (odds ratio [OR], 1.19; 95% confidence interval [CI], 1.11-1.28; P = 2.10E-06) and the lead SNP in chr7 was weakly associated (OR 1.15; 95% CI, 1.04-1.27; P = 6.19E-03) with increased NAFLD risk. Imputation-based typing of HLA showed a significant difference in the distribution of HLA-B, HLA-DR-beta chain 1 (DRB1), and HLA-DQ-beta chain 1 (DQB1) alleles in lean NAFLD GWAS. Next-generation sequence-based typing of HLA in 5,649 members of the general population replicated the significant difference of HLA-B allele distribution and the significant increase of the HLA-B*54:01 allele in whole NAFLD. Fecal metagenomic analysis of 3,420 members of the general population showed significant dissimilarity in beta-diversity analysis of rs2076529 and HLA-B*54:01 allele carriers from noncarriers. Veillonellaceae was increased but Verrucomicrobia was decreased in rs2076529 minor allele and HLA-B*54:01 allele carriers as in NAFLD. Conclusion: HLA was identified as a novel locus associated with NAFLD susceptibility, which might be affected by the alteration of gut microbiota.