Impact of high-dose cholecalciferol (vitamin D3) and inulin prebiotic on intestinal and airway microbiota in adults with cystic fibrosis: A 2 × 2 randomized, placebo-controlled, double-blind pilot study

Abstract

Background: Cystic fibrosis (CF) is a multi-organ disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). Individuals with CF often have gastrointestinal (GI) dysbiosis due to chronic inflammation and antibiotic use. Previous studies suggested a role for vitamin D in reversing the GI dysbiosis found in CF.

Objective: To explore the potential role of a combination of high-dose oral cholecalciferol (vitamin D₃) and fermentable dietary fiber, inulin, to impact bacterial composition, richness, and diversity of intestinal and airway microbiota in adults with CF.

Methods: This was a 2 × 2 factorial, double-blinded, placebo-controlled, randomized, pilot clinical trial in which adults with CF received oral cholecalciferol (vitamin D₃) (50,000 IU/week) and/or inulin (12 g/day) for 12 weeks. Thus, there were 4 study groups (n = 10 subjects per group); 1) placebo 2) vitamin D₃ 3) inulin 4) vitamin D₃ plus inulin. Stool and sputum samples were collected at baseline (just before) and after the intervention and were analysed using 16S ribosomal RNA gene sequencing for gut and airway microbiota composition. Statistical analyses assessed alpha and beta diversity to evaluate microbial community changes.

Results: Of a total of 254 screened participants, 40 eligible participants were randomized to one of the 4 treatment arms. Participants receiving vitamin D₃ plus inulin exhibited greater changes in microbiome indexes in both intestinal and airway relative to those in the other study groups. Specific taxonomic changes supported the potential beneficial influence of this combination to mitigate both intestinal and airway dysbiosis in adults with CF.

Conclusion: This pilot study established that the combination of oral vitamin D₃ and the prebiotic inulin was well tolerated over 12 weeks in adults with CF and altered gut and airway bacterial communities. Future research appear warranted to define clinical outcomes and the role of microbiota changes therein with this approach.

Keywords: Cholecalciferol; Cystic fibrosis; Inulin; Microbiome; Prebiotics; Vitamin D; vitamin D deficiency.

Fig. 1

CONSORT diagram of completed Vitamin D₃ and Prebiotics for Intestinal Health in Cystic Fibrosis (Pre-D) clinical trial.

Fig. 2

Beta diversity of intestinal microbiota. PCoA plot of Bray-Curtis distance before (A) and after (B) the intervention. PERMANOVA was done to determine the difference between groups; p-values were p = 0.02 (A) and p = 0.01 (B). The adjusted p-values of multiple comparisons were as follows: (A) all pairs not significant; (B) p = 0.052 for Placebo vs Vitamin D; p = 0.052 for Vitamin D vs Inulin; p = 0.052 for Inulin vs (Vitamin D& Inulin), the other pairs not significant. (C) Box plot of bray-Curtis distance of each subject between time points. Two-tailed unpaired Welch’s t-test was done to determine difference between groups (p < 0.05).

Fig. 2

Beta diversity of intestinal microbiota. PCoA plot of Bray-Curtis distance before (A) and after (B) the intervention. PERMANOVA was done to determine the difference between groups; p-values were p = 0.02 (A) and p = 0.01 (B). The adjusted p-values of multiple comparisons were as follows: (A) all pairs not significant; (B) p = 0.052 for Placebo vs Vitamin D; p = 0.052 for Vitamin D vs Inulin; p = 0.052 for Inulin vs (Vitamin D& Inulin), the other pairs not significant. (C) Box plot of bray-Curtis distance of each subject between time points. Two-tailed unpaired Welch’s t-test was done to determine difference between groups (p < 0.05).

Fig. 3

Beta diversity of airway microbiota. PCoA plot of Bray-Curtis distance before (A) and after (B) the intervention. PERMANOVA was done to determine the difference between groups; p-values were p = 0.37 (A) and p = 0.06 (B). The adjusted p-values of multiple comparisons were as follows: (A) all pairs not significant; (B) p = 0.02 for VitaminD vs (Vitamin D& Inulin), the other pairs not significant. C) Box plot of bray-Curtis distance of each subject between time points. Two-tailed unpaired Welch’s t-test was done to determine difference between groups (p < 0.05).

Fig. 3

Beta diversity of airway microbiota. PCoA plot of Bray-Curtis distance before (A) and after (B) the intervention. PERMANOVA was done to determine the difference between groups; p-values were p = 0.37 (A) and p = 0.06 (B). The adjusted p-values of multiple comparisons were as follows: (A) all pairs not significant; (B) p = 0.02 for VitaminD vs (Vitamin D& Inulin), the other pairs not significant. C) Box plot of bray-Curtis distance of each subject between time points. Two-tailed unpaired Welch’s t-test was done to determine difference between groups (p < 0.05).