Autoimmune hepatitis displays distinctively high multi-antennary sialylation on plasma N-glycans compared to other liver diseases

Abstract

Background: Changes in plasma protein glycosylation are known to functionally affect proteins and to associate with liver diseases, including cirrhosis and hepatocellular carcinoma. Autoimmune hepatitis (AIH) is a liver disease characterized by liver inflammation and raised serum levels of IgG, and is difficult to distinguish from other liver diseases. The aim of this study was to examine plasma and IgG-specific N-glycosylation in AIH and compare it with healthy controls and other liver diseases.

Methods: In this cross-sectional cohort study, total plasma N-glycosylation and IgG Fc glycosylation analysis was performed by mass spectrometry for 66 AIH patients, 60 age- and sex-matched healthy controls, 31 primary biliary cholangitis patients, 10 primary sclerosing cholangitis patients, 30 non-alcoholic fatty liver disease patients and 74 patients with viral or alcoholic hepatitis. A total of 121 glycans were quantified per individual. Associations between glycosylation traits and AIH were investigated as compared to healthy controls and other liver diseases.

Results: Glycan traits bisection (OR: 3.78 [1.88-9.35], p-value: 5.88 × 10^{- 3}), tetraantennary sialylation per galactose (A4GS) (OR: 2.88 [1.75-5.16], p-value: 1.63 × 10^{- 3}), IgG1 galactosylation (OR: 0.35 [0.2-0.58], p-value: 3.47 × 10^{- 5}) and hybrid type glycans (OR: 2.73 [1.67-4.89], p-value: 2.31 × 10^{- 3}) were found as discriminators between AIH and healthy controls. High A4GS differentiated AIH from other liver diseases, while bisection associated with cirrhosis severity.

Conclusions: Compared to other liver diseases, AIH shows distinctively high A4GS levels in plasma, with potential implications on glycoprotein function and clearance. Plasma-derived glycosylation has potential to be used as a diagnostic marker for AIH in the future. This may alleviate the need for a liver biopsy at diagnosis. Glycosidic changes should be investigated further in longitudinal studies and may be used for diagnostic and monitoring purposes in the future.

Keywords: Autoimmune hepatitis; Biomarker; Glycome; IgG glycosylation; Liver inflammation; Plasma N-glycosylation; Tetraantennary glycans.

Fig. 1

Monosaccharide diversity, glycan types and derived traits. (A) Common monosaccharide constituents of human N-glycans. (B) The three general types of N-glycans. (C) N-glycosylation derived traits, and their abbreviations, representing common biosynthetic pathways

Fig. 2

Main associations found between AIH patients and healthy controls. (A) Volcano plot based on the 155 derived glycosylation traits. (B-E) Relative abundance differences of derived glycosylation traits: (B) IgG1 galactosylation, (C) THy, (D) CB (E) A4GS, between AIH and healthy controls and other liver disease groups. AIH is the reference group against which comparisons are shown (Wilcoxon rank-sum test). P-values, ORs and corresponding 95% CIs for the associations are shown in Table 3 and Supplementary Table 5, whereas p-values for the disease group comparisons are shown in Supplementary Tables 6–7. Boxplots represent the median and the interquartile range, whilst whiskers correspond to the first and third quartiles (25th and 75th percentiles) and extend from the hinges to the largest or smallest value no further than 1.5x the interquartile range. *, **, ***, ****: p-value < 0.05, 0.01, 0.001, 0.0001, respectively

Fig. 3

Associations between cirrhosis severity and bisection in alcoholic and viral hepatitis patients. Relative abundance differences of glycosylation traits (A) CB and (B) CirrhosisTest. Statistical tests and boxplots as described in Fig. 2

Fig. 4

Correlations between AIH disease activity and glycosylation. Relative abundance differences of derived glycosylation traits: (A) IgG1 galactosylation, (B) THy, (C) CB and (D) A4GS. Statistical tests and boxplots as described in Fig. 2

Fig. 5

Longitudinal changes associated with AIH disease activity. Relative abundance differences of glycosylation derived traits: (A) THy and (B) A4GS. A Wilcoxon signed-rank test was used to compare longitudinal samples (n = 11)