Letter: Attempted Validation of Villin‐1 as a Gut Barrier Marker in Decompensated Cirrhosis—Potential Confounding by Tubular Injury and Aetiology

We read with great interest the study by Tornai et al. [1] proposing serum villin-1 as a marker of gut barrier damage and predictor of mortality in acute decompensation (AD) and acute-on-chronic liver failure (ACLF). The authors deserve recognition for addressing this unmet clinical need [2]. However, gut barrier biomarker validation in liver disease requires careful evaluation across disease stages, as regulation is often stage-dependent and frequently confounded by hepatic synthesis capacity, extrahepatic organ failure or portal congestion [3]. Tornai et al. [1] describe a bimodal trajectory of serum villin-1, reduced in stable AD, increasing with disease progression and substantially elevated in ACLF. However, the derivation cohort included only 22 patients with ACLF, and the validation cohort contained just seven ACLF patients, limiting statistical power for mortality prediction in patients at highest risk. The study also lacked a control group of patients with compensated cirrhosis, and optimal cut-offs varied widely between discovery and validation cohorts. Thus, we investigated villin-1 serum concentrations in an independent cohort of 237 patients (compensated: n = 36; decompensated with ascites: n = 201, including n = 65 with ACLF) recruited at Jena University Hospital and University Hospital RWTH Aachen using the same ELISA (Fine Test; Wuhan, Hubei, China, Cat no. EH3957). Baseline characteristics of the cohort are provided in Table S1. Our data reveal a different regulation pattern from that observed by Tornai et al. [1]. Villin-1 levels were highest in compensated cirrhosis compared to AD or ACLF, contradicting the reported elevation in ACLF (Figure 1A). We observed no progressive increase across ACLF grades, with grade 2 showing the lowest levels (Figure 1B). Stratification by ACLF grade revealed that villin-1 was elevated in ACLF grade 1a (defined by isolated kidney failure) compared to AD, whilst ACLF ≥ 1b showed no significant difference from AD (Figure 1C). This aligns with the known physiological expression of villin-1 in proximal renal tubule brush borders and its temporal release following renal ischemia–reperfusion injury [5]. Regarding other potential confounders, villin-1 did not correlate with bilirubin or aminotransferase levels, arguing against a significant hepatic source (Figure 1D). However, regulation differed between alcohol-related and non-alcohol-related liver disease (Figure 1E), with highest concentrations in decompensated patients with probable alcoholic hepatitis [4] (Figure 1F) suggesting confounding effects of alcohol use on villin-1 release. Despite these associations, villin-1 showed no significant differences between 90-day survivors and non-survivors after hospitalisation for AD (Figure 1G). Several factors may explain the discrepancy between our findings and those of Tornai et al. [1], including differences in cohort composition and assay performance. Clinical implementation of a novel biomarker requires assay stability, distinct stage-dependent regulation, and reproducible prognostic stratification. In our cohort, villin-1 did not meet these criteria. Further characterization of release kinetics and cellular sources, direct correlation with functional gut permeability measures, and assessment of the impact of renal dysfunction remain essential before villin-1 can be considered for clinical risk stratification in advanced chronic liver disease. Frederic Haedge: conceptualization, data curation, investigation, writing – original draft, methodology, visualization, formal analysis. Mohamad Murad: data curation, writing – review and editing. Majda El-Hassani: writing – review and editing, data curation. Stefanie Quickert: data curation, writing – review and editing. Karsten Große: data curation, writing – review and editing. Johanna Reißing: methodology, writing – review and editing, data curation, formal analysis. Mick Frissen: data curation, methodology, writing – review and editing, formal analysis. Philipp A. Reuken: writing – review and editing, funding acquisition, data curation, resources. Tony Bruns: conceptualization, investigation, resources, supervision, project administration, writing – original draft, funding acquisition, visualization. This study was funded by the German Research Foundation (DFG) project ID 403224013 (B07). The authors declare no conflicts of interest. This article is linked to Tornai et al. paper. To view this article, visit https://doi/10.1111/apt.70481. The data that support the findings of this study are available from the corresponding author upon reasonable request. Table S1: Baseline characteristics of patients with cirrhosis. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.