Altered DNA methylation pattern characterizes the peripheral immune cells of patients with autoimmune hepatitis

PNPLA3 I148 M genetic variant in autoimmune hepatitis characterises advanced disease at diagnosis and reduced survival free of cirrhotic events and liver-related mortality

Background

Autoimmune hepatitis (AIH) is a relatively rare autoimmune disease with a strong genetic background. The patatin-like phospholipase domain-containing protein 3 (PNPLA3) I148 M (rs738409 C/G) variant has been associated with hepatic inflammation and fibrosis in chronic hepatic diseases beyond metabolic dysfunction-associated steatotic liver disease (MASLD).

Aim

Our aim was to investigate the significance of PNPLA3 I148 M variant in AIH.

Method

Two hundred AIH patients, followed in our centre, were evaluated while 100 healthy subjects served as controls. Genotyping was performed with allelic discrimination end-point polymerase chain reaction (PCR).

Results

The I148 M variant was present in 95/200 (47.5 %) AIH patients compared to 47/100 (47 %) healthy controls (p = 1.000). Patients with GG/CG genotypes were more likely to present with decompensated cirrhosis at diagnosis (GG/CG 6.3 % vs. CC 1 %, p = 0.039). Comorbidity with cardiometabolic risk factors and concurrence of MASLD was similar across genotypes. Simple steatosis was present in 37/186 (19.9 %) and steatohepatitis in 14/186 (7.5 %) patients with available liver biopsy without correlation with PNPLA3 genotype. Fibrosis stage and grade of inflammation were not correlated with any genotype. Response to treatment was also independent of the presence of the I148 M variant, even though a longer time was needed to achieve complete biochemical response in those carrying the GG/CG genotypes (p = 0.07). On Kaplan Meier analysis homozygosity for the G allele corelated with reduced survival free of decompensation (p = 0.006), cirrhotic events (decompensation, liver transplantation, hepatocellular carcinoma; p = 0.001) and liver-related death or liver transplantation (p = 0.011) in treated patients.

Conclusions

The PNPLA3 I148 M variant in AIH patients is associated with increased risk of advanced disease at diagnosis and reduced survival free of cirrhotic events and liver-related death or liver transplantation, regardless of the presence of MASLD. This signifies a potential role for the PNPLA3 I148 M variant as a new AIH biomarker allowing to identify patients at increased risk of disease progression.

Missing Causality and Heritability of Autoimmune Hepatitis

BACKGROUND

Autoimmune hepatitis has an unknown cause and genetic associations that are not disease-specific or always present. Clarification of its missing causality and heritability could improve prevention and management strategies.

AIMS

Describe the key epigenetic and genetic mechanisms that could account for missing causality and heritability in autoimmune hepatitis; indicate the prospects of these mechanisms as pivotal factors; and encourage investigations of their pathogenic role and therapeutic potential.

METHODS

English abstracts were identified in PubMed using multiple key search phases. Several hundred abstracts and 210 full-length articles were reviewed.

RESULTS

Environmental induction of epigenetic changes is the prime candidate for explaining the missing causality of autoimmune hepatitis. Environmental factors (diet, toxic exposures) can alter chromatin structure and the production of micro-ribonucleic acids that affect gene expression. Epistatic interaction between unsuspected genes is the prime candidate for explaining the missing heritability. The non-additive, interactive effects of multiple genes could enhance their impact on the propensity and phenotype of autoimmune hepatitis. Transgenerational inheritance of acquired epigenetic marks constitutes another mechanism of transmitting parental adaptations that could affect susceptibility. Management strategies could range from lifestyle adjustments and nutritional supplements to precision editing of the epigenetic landscape.

CONCLUSIONS

Autoimmune hepatitis has a missing causality that might be explained by epigenetic changes induced by environmental factors and a missing heritability that might reflect epistatic gene interactions or transgenerational transmission of acquired epigenetic marks. These unassessed or under-evaluated areas warrant investigation.

Diagnosis and management of autoimmune hepatitis

Autoimmune hepatitis is an inflammatory disease of the liver of unknown cause that may progress to liver cirrhosis and end stage liver failure if diagnosis is overlooked and treatment delayed. The clinical presentation is often that of acute hepatitis, sometimes very severe; less frequently, it can be insidious or completely asymptomatic. The disease can affect people of any age and is more common in women; its incidence and prevalence seem to be on the rise worldwide. An abnormal immune response targeting liver autoantigens and inducing persistent and self-perpetuating liver inflammation is the pathogenic mechanism of the disease. A specific set of autoantibodies, increased IgG concentrations, and histological demonstration of interface hepatitis and periportal necrosis are the diagnostic hallmarks of autoimmune hepatitis. Prompt response to treatment with corticosteroids and other immunomodulatory drugs is almost universal and supports the diagnosis. The aims of treatment are to induce and maintain long term remission of liver inflammation. Treatment can often even reverse liver fibrosis, thus preventing progression to advanced cirrhosis and its complications. Most patients need lifelong maintenance therapy, and repeated follow-up in experienced hands improves the quality of care and quality of life for affected patients.