Vitamin B12 and folate decrease inflammation and fibrosis in NASH by preventing syntaxin 17 homocysteinylation

BACKGROUND & AIMS

Several recent clinical studies have shown that serum homocysteine (Hcy) levels are positively correlated, while vitamin B₁₂ (B₁₂) and folate levels are negative correlated, with non-alcoholic steatohepatitis (NASH) severity. However, it is not known whether hyperhomocysteinemia (HHcy) plays a pathogenic role in NASH.

METHODS

We examined the effects of HHcy on NASH progression, metabolism, and autophagy in dietary and genetic mouse models, patients, and primates. We employed vitamin B₁₂ (B₁₂) and folate (Fol) to reverse NASH features in mice and cell culture.

RESULTS

Serum Hcy correlated with hepatic inflammation and fibrosis in NASH. Elevated hepatic Hcy induced and exacerbated NASH. Gene expression of hepatic Hcy-metabolizing enzymes was downregulated in NASH. Surprisingly, we found increased homocysteinylation (Hcy-lation) and ubiquitination of multiple hepatic proteins in NASH including the key autophagosome/lysosome fusion protein, Syntaxin 17 (Stx17). This protein was Hcy-lated and ubiquitinated, and its degradation led to a block in autophagy. Genetic manipulation of Stx17 revealed its critical role in regulating autophagy, inflammation and fibrosis during HHcy. Remarkably, dietary B₁₂/Fol, which promotes enzymatic conversion of Hcy to methionine, decreased HHcy and hepatic Hcy-lated protein levels, restored Stx17 expression and autophagy, stimulated β -oxidation of fatty acids, and improved hepatic histology in mice with pre-established NASH.

CONCLUSIONS

HHcy plays a key role in the pathogenesis of NASH via Stx17 homocysteinylation. B₁₂/folate also may represent a novel first-line therapy for NASH.

LAY SUMMARY

The incidence of non-alcoholic steatohepatitis, for which there are no approved pharmacological therapies, is increasing, posing a significant healthcare challenge. Herein, based on studies in mice, primates and humans, we found that dietary supplementation with vitamin B₁₂ and folate could have therapeutic potential for the prevention or treatment of non-alcoholic steatohepatitis.

Validation of the Expanded Baveno-VI Criteria for Screening Gastroscopy in Asian Patients with Compensated Advanced Chronic Liver Disease

BACKGROUND

The expanded Baveno-VI criteria may further reduce the need for screening gastroscopy compared to Baveno-VI criteria.

AIM

We sought to validate the performance of these criteria in a cohort of compensated advanced chronic liver disease (cACLD) patients with predominantly hepatitis B infection.

METHODS

Consecutive cACLD patients from 2006 to 2012 with paired liver stiffness measurements and screening gastroscopy within 1 year were included. The expanded Baveno-VI criteria were applied to evaluate the sensitivity (SS), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) for the presence of high-risk varices (HRV).

RESULTS

Among 165 cACLD patients included, 17 (10.3%) had HRV. The commonest etiology of cACLD was chronic hepatitis B (36.4%) followed by NAFLD (20.0%). Application of expanded Baveno-VI criteria avoided more screening gastroscopy (43.6%) as compared to the original Baveno-VI criteria (18.8%) without missing more HRV (1 with both criteria). The overall SS, SP, PPV and NPV of the expanded Baveno-VI criteria in predicting HRV were 94.1%, 48.0%, 17.2% and 98.6%, respectively.

CONCLUSION

Application of the expanded Baveno-VI criteria can safely avoid screening gastroscopy in 43.6% of cACLD patients with an excellent ability to exclude HRV.