The study looked at people with a lung infection caused by non‑tuberculous mycobacteria and measured vitamin D levels, the antimicrobial peptide LL‑37, and related genes. They found that while the genes that make LL‑37 were more active in patients, the actual amount of LL‑37 in the blood didn’t change, and vitamin D levels didn’t predict LL‑37 or other immune markers. In short, boosting vitamin D isn’t likely to raise LL‑37 levels or help with this lung disease.

Little information is available regarding vitamin D-associated factors in patients with non-tuberculous mycobacteria (NTM) lung disease. To determine the association between vitamin D-related factors and susceptibility to NTM lung disease. The relative gene expression levels of cathelicidin (CAMP), defensin (DEFB4), vitamin D receptor (VDR) and 1-hydroxylase (CYP27B1), as well as the serum levels of 25-hydroxyvitamin D (25[OH]D), cathelicidin (LL-37), defensin (hBD-2) and vitamin D-binding protein (DBP) from 82 patients with NTM lung disease and 28 control subjects were analysed. Gene expression of CAMP and DEFB4 was significantly higher, and gene expression of VDR and CYP27B1 was significantly lower, in NTM patients than controls. Serum LL-37 and hBD-2 levels were not significantly different between NTM patients and controls; however, the serum DBP level was higher in NTM patients than controls. The serum vitamin D status of patients did not correlate with serum LL-37, hBD-2, or DBP concentration or gene expression of CAMP, DEFB4, VDR or CYP27B1. A higher level of gene expression for antimicrobial peptide is more likely to be associated with NTM lung disease than serum vitamin D status.