Background A recent study based on blood metabolomics analysis revealed inflammation‐associated mitochondrial dysfunction as a potential mechanism underlying acute‐on‐chronic liver failure (ACLF) in cirrhotic patients. Serine, glycine, and methionine serve to maintain a healthy immune system and adequately sustain mitochondrial functionality in hepatocytes for regulating redox homeostasis through the production of antioxidant glutathione (GSH). Based on this, we hypothesized that the circulatory levels of serine, glycine and methionine will be altered in ACLF patients due to acute worsening of hepatic function and may provide novel insights into the mitochondrial dysfunction as well. Methods The circulatory concentrations of serine, glycine, and methionine were estimated in the sera of 40 ACLF patients and 49 normal controls (NC) subject using 1D 1H‐CPMG NMR spectra recorded at 800 MHz NMR spectrometer. The resulting metabolite concentrations were compared using unpaired Student t‐test and p‐value < 0.05 was considered as the criterion of statistical significance. The diagnostic potential and statistical correlations were established using receiver‐operating‐characteristic (ROC) curve analysis and Pearson‐r method, respectively. Results Circulating levels of serine and glycine were significantly decreased in ACLF patients (Ser = 23.06 ± 1.67 µM and Gly = 83.11±7.52 µM) compared to NC subjects (Ser = 55.61 ± 2.28 µM and Gly = 156.9±7.16 µM) with p‐value < 0.0001, whereas those of methionine were significantly increased in ACLF (22.60 ± 2.49 µM) compared to NC subjects (=14.63 ± 0.85 µM) with p‐value < 0.0015. Further, the ROC analysis yielded satisfactory sensitivity and specificity for serine, glycine, and methionine‐to‐glycine ratio (MGR) with area under ROC (AUROC) curve values equal to: 0.95 [95%CI = 0.91‐0.99] for Ser; 0.87 [95%CI = 0.79‐0.95] for Gly; and 0.90 [95%CI = 0.83‐0.97] for MGR. Conclusion Compared to NC subjects, the sera of ACLF patients were characterized by hypermethioninemia and aberrantly decreased levels of serine and glycine suggesting mitochondrial dysfunction as the possible mechanism for disturbed redox homeostasis and therefore depressed immune system in ACLF.

Objectives: Acute-on-chronic liver failure (ACLF), which develops in patients with underlying alcoholic liver disease (ALD), is characterized by acute deterioration of liver function and organ failures are secondary to that. The clear understanding of metabolic pathways perturbed in ALD-ACLF patients can greatly decrease the mortality and morbidity of patients through predicting outcome, guiding treatment, and monitoring response to treatment. The purpose of this study was to investigate the metabolic disturbances associated with ACLF using nuclear magnetic resonance (NMR)-based serum metabolomics approach and further to assess if the serum metabolic alterations are affected by the severity of hepatic impairment. Materials and Methods: The serum-metabolic profiles of 40 ALD-ACLF patients were compared to those of 49 age and sex-matched normal-control (NC) subjects making composite use of both multivariate and univariate statistical tests. Results: Compared to NC, the sera of ACLF patients were characterized by significantly decreased serum levels of several amino acids (except methionine and tyrosine), lipid, and membrane metabolites suggesting a kind of nutritional deficiency and disturbed metabolic homeostasis in ACLF. Twelve serum metabolic entities (including BCAA, histidine, alanine, threonine, and glutamine) were found with AUROC (i.e., area under ROC curve) value >0.9 suggesting their potential in clinical diagnosis and surveillance. Conclusion: Overall, the study revealed important metabolic changes underlying the pathophysiology of ACLF and those related to disease progression would add value to standard clinical scores of severity to predict outcome and may serve as surrogate endpoints for evaluating treatment response.

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