<![CDATA[BACKGROUND: Intestinal tuberculosis (ITB) is a type of tuberculosis (TB) that affects the gastrointestinal tract. Cathelicidin, an antimicrobial peptide, contributes to defense against Mycobacterium tuberculosis, which causes TB. Its expression is tightly regulated by vitamin D through vitamin D receptor signaling and autophagy pathways. Despite the increasing evidence on TB, studies exploring the correlation between cathelicidin and vitamin D in the ITB remain poorly characterized and almost exclusively derived from pulmonary TB. Therefore, the present study was conducted to compare serum cathelicidin and vitamin D levels between subjects with ITB and without ITB, and to determine the correlation between these two biomarkers.METHODS: This comparative cross-sectional study utilized stored serum samples obtained from participants enrolled in a previous ITB project. Twenty-two ITB and 22 non-ITB subjects aged >18 years who had undergone colonoscopy, histopathological examinations, and fulfilled predefined clinical and diagnostic criteria were included. Serum cathelicidin and vitamin D levels were measured using sandwich enzyme-linked immunosorbent assay (ELISA) and chemiluminescent microparticle immunoassay (CMIA), respectively.RESULTS: Significantly higher levels of serum cathelicidin were identified in ITB subjects, with a median level of 3.67 (2.27‒5.95) ng/mL, compared with non-ITB subjects with a median level of 2.04 (1.66‒2.46) ng/mL (p<0.0001). Although the difference was not statistically significant (p=0.091), vitamin D level tended to be lower in subjects with ITB, with a median level of 11.05 (6.80‒25.25) ng/mL, compared to non-ITB subjects with a median level of 17.95 (12.13‒23.63) ng/mL. A significant moderate negative correlation was found between cathelicidin and vitamin D (r=-0.485, p=0.001).CONCLUSION: The ITB is associated with elevated cathelicidin levels and a tendency toward lower vitamin D levels. The inverse correlation suggests a complex relationship between vitamin D status and cathelicidin expression, highlighting immunological mechanisms involved in ITB pathogenesis.KEYWORDS: antimicrobial peptide, cathelicidin, innate immunity, intestinal tuberculosis, vitamin D]]>
