TO THE EDITOR
Nonalcoholic fatty liver disease (NAFLD), now referred to as metabolic dysfunction-associated steatotic liver disease, is a public health concern of increasing significance[1]. It is associated with substantial liver-related and non-liver-related morbidity and mortality[2]. In the early stages of NAFLD, immune cells are dysregulated. Targeting these immune cells in the liver may represent an effective approach for treating nonalcoholic steatohepatitis (NASH). Thus, we read with great interest that the study explored the presence of autoantibodies in patients with NAFLD across different histological stages by Zhu et al.[3]. While we commend the authors for their substantial contributions, we offer several constructive suggestions for further refinement and depth of the research.
The present study investigated the potential association between autoimmunity and the progression of NAFLD, particularly in NASH, while considering the possibility that some cases may exhibit overlapping features without a direct causal relationship. The authors offered interesting insights into the relationship between autoimmunity and NAFLD, but it also raises several methodological and interpretive concerns that deserve further discussion. First, the study’s retrospective design limits control over potential confounding factors, such as variations in lifestyle, dietary habits, and other autoimmune markers, which could skew the findings. Although the authors excluded cases of autoimmune hepatitis, alcoholic liver disease, drug-induced liver disease, and viral hepatitis, there may be other comorbidities, particularly those related to metabolic syndrome (e.g., diabetes, hypertension, and dyslipidemia), that could still impact immune responses and potentially confound the results. For example, insulin resistance has been shown to promote inflammatory pathways that may mimic autoimmune phenomena, complicating the interpretation of immune markers in these patients[4]. A prospective design with a well-matched control group would have strengthened the causal inferences made in this study.
The autoimmune markers were a significant concern. While antinuclear antibodies (ANA) and anti-smooth muscle antibodies are commonly tested to assess autoimmune responses, the chosen antibody panel may not adequately reflect the immunological complexities associated with NAFLD[5]. For example, the relatively high positivity rate of ANA (48.1%) in this cohort could indicate a nonspecific immune response rather than an accurate autoimmune mechanism[6,7]. Since low titers of ANA can also be found in healthy individuals or those with metabolic syndrome, interpreting ANA positivity as evidence of autoimmune involvement in NAFLD could be misleading without thoroughly validating its clinical significance[8,9].
Another notable area for improvement was the categorization of NAFLD stages without considering potential age- and sex-related effects on antibody profiles and disease progression. The demographics showed a significant age difference among the groups, with cirrhosis patients being older on average. This age disparity could affect immune status and antibody production independently of NAFLD[10,11]. It would be beneficial to stratify or adjust for age in the statistical analysis to clarify whether the observed differences in antibody levels are due to disease progression or demographic factors. In addition, though the study started with a 1:40 dilution titer, it did not include specific titer values, categorizing results simply as “positive” or “negative”. This approach limits the granularity of antibody detection and may overlook variations in antibody levels that could be clinically significant[12].
Notably, it is important to include comprehensive potential confounding factors. The authors have commendably adjusted for baseline covariates. While the statistical methods used were appropriate, incorporating additional multivariate analyses could improve the adjustment for confounding variables such as body mass index and comorbidities like diabetes and hypertension. The observed associations between body mass index and controlled attenuation parameters across different stages of NAFLD could influence autoantibody positivity if not adequately controlled. Conducting a regression analysis that accounts for these factors would clarify whether the autoimmune markers are independent of these known risk factors[13]. In addition, the pathological progression of NAFLD encompasses a range of stages, from simple steatosis to NASH, and in some cases, can lead to cirrhosis. While the transition from simple steatosis to NASH is generally well-recognized, there are notable variations in the understanding of these stages across different countries, particularly regarding the prevalence of metabolic syndrome. In certain regions, advanced imaging techniques allow for the earlier diagnosis of NASH, while in others, individuals may remain undiagnosed until the disease has progressed to more severe stages[14,15].
Finally, the authors found no statistically significant difference in autoantibody positivity across NAFLD stages, yet they report substantial variability in autoantibody profiles (such as ANA, anti-smooth muscle antibodies, and AMA) among groups. It would be insightful for the authors to explore the biological plausibility of these findings, as the hypothesis that autoimmunity plays a role in NAFLD progression remains speculative. The selected markers are particularly relevant to autoimmune liver diseases; however, it is essential to recognize that a wider array of antibodies may be necessary to adequately reflect the immunological complexity associated with NAFLD. Recent research has indicated that incorporating additional markers, such as anti-liver kidney microsomal antibodies, could improve the comprehensiveness of the immunological profile for more effective assessment and diagnosis[16]. Future studies might consider examining cytokine profiles or other inflammatory markers that could bridge the observed associations and mechanistic pathways.
CONCLUSION
In conclusion, this recent study by Zhu et al[3] provided significant insights into the immunological aspects of NAFLD. However, to improve its findings’ credibility and clinical relevance, it is important to address the methodological and interpretive challenges identified. Future research that uses rigorous prospective designs, a broader spectrum of immune markers, larger sample sizes, comprehensive antibody panels, and controls for confounding factors may lead to a better understanding of the role of autoimmunity in NAFLD. The complexity and severity of NAFLD highlight the critical need for ongoing research in this area. Our suggestions were aimed at improving already impressive research, and we look forward to more insightful contributions from these authors in the future.
