Supplementary Material for: Exploring the Relationship Between Primary Sarcopenia and Intestinal Barrier Dysfunction in Geriatric Patients: Insights from SARC-F, Serum DAO, Zonulin, LPS, and I-FABP Levels

Introduction: The objective of this study is to assess the correlation between serum levels of DAO (Diamine oxidase), LPS (Lipopolysaccharide), I-FABP (Intestinal Fatty Acid Binding Protein), and Zonulin with primary sarcopenia in elderly patients, and to compare the diagnostic performance of these biomarkers with the SARC-F score. Methods: The study included 88 patients aged 65 and above. Comorbidities and geriatric syndromes were assessed, and those with secondary sarcopenia were excluded. The EWGSOP2 criteria were applied for diagnosing sarcopenia, while the SARC-F questionnaire was utilized to identify individuals at risk of sarcopenia. Serum levels of DAO, Zonulin, LPS, and I-FABP were measured using ELISA. Results: No significant differences were observed between the two groups regarding age and gender. SARC-F, serum DAO, and Zonulin concentrations were notably higher in the sarcopenia group than in the non-sarcopenia group (p<0.001). Statistically significant parameters were analyzed using stepwise multiple regression. In stepwise multivariate logistic regression analysis, both DAO and Zonulin scores were found to be associated with sarcopenia [Odds ratio (OR) 1.041, (95%) confidence interval (CI) 1.020-1.063, p<0.001; OR 1.108, (95%) CI 1.018-1.206, p=0.018, subsequently]. ROC curve analysis revealed that the area under the curve (AUC) for DAO, Zonulin, and SARC-F was 0.807 (p<0.001), 0.723 (p<0.001), and 0.943 (p<0.001), subsequently. The Spearman correlation test revealed a significant, low-correlation between serum Zonulin and the SARC-F score (r = 0.3583, p=0.0006), and a moderate-correlation between serum DAO and the SARC-F score (r = 0.4384, p<0.0001). Conclusion: This study is the first to show a connection between primary sarcopenia and intestinal barrier dysfunction. While the findings support the use of the SARC-F questionnaire in routine practice, serum levels of DAO and Zonulin could serve as an alternative when the SARC-F questionnaire is not applicable.