OttaBac® plus vitamin D could improve gut barrier function and gut microbiota composition in non-constipated IBS
Irritable bowel syndrome (IBS) is a common disorder of gut-brain interaction and its pathogenesis is not completely known. However, gut microbiota (GM) imbalance seems to play a major role in determining the disease and the possibility to modulate microbiota with probiotics has gained interest in recent decades. Similarly, vitamin D through its effect in maintaining gut barrier integrity and immune regulation, could promote IBS development when deficient. The aim of this study is to evaluate the efficacy of a new multi-strain probiotic combined with vitamin D in gut barrier function in patients with IBS- non constipation.  We performed a phase IIb double blind randomized placebo controlled, parallel group, multicenter, clinical trial. Selected patients (active group) after a 4-week screening period were treated for 12 weeks with OttaBac®, a high concentration (500 billion CFU/d) multistrain probiotic plus cholecalciferol (2000 UI/die). OttaBac® is a probiotic mixture containing eight live, freeze-dried bacterial strains: Bifidobacterium animalis subsp. lactis BL03, Streptococcus thermophilus BT01, B. animalis subsp. lactis BI04, Lactiplantibacillus plantarum BP06, Lactobacillus acidophilus BA05, Lacticaseibacillus paracasei BP07, Lactobacillus helveticus BD08 and Bifidobacterium breve BB02. Patients were then followed-up until week 16. Patients performed before and at the end of treatment: lactulose/mannitol (LaMa) test, serum zonulin, citrulline and plasmalemma vesicle–associated protein-1 (PV1); faecal sample collection was provided for GM metataxonomy, PICRUSt-based functional pathways' prediction and short chain fatty acids (SCFAs; acetate, butyrate, propionate) determinations. Symptoms were evaluated through variation of IBS-SSS questionnaire and Bristol stool scale and quality of life through SF-36 questionnaire. At week 16 the following evaluations were performed: IBS-SSS, SF-36, serum biomarkers and 16-S rRNA stool analyses. Thirty-five patients were successfully randomized (28 were included in Per Protocol Population).  Mean zonulin values showed a significant progressive reduction in active group (-10 .2 ng/ml at week 12 p=0.0375,  - 19.5 ng/ml at week 16 p=0.0002), whereas stable values were observed in placebo group (-4.25 ng/ml at week 12 p= ns, -0.47 at week 16, p=ns), with significant difference between group at week 16 in the PP population. (-19,01, p =0.0053). Vitamin D mean levels significantly increased in the active group after 12 weeks of treatment (PP 43.13 ± 14.57 vs 25.73 ± 8.62, p=0.0054 for active and placebo group, respectively. No differences were found in lactulose/mannitol ratio, IBSS-SSS and SF-36 total scores, PV-1 and citrulline between groups after treatment.. Furthermore, when evaluating the percentage of days of abnormal bowel movements, where a day with normal bowel movements is defined as a day with less or equal to 3 bowel movement per day AND Bristol stool scale less or equal than 5, in the PP population, patients in placebo group showed a trend toward improvement during treatment but without significant results and  an increase of abnormal days at week 16, numerically higher compared to baseline. Patients in the active group showed a more stable trend toward improvement, maintaining this trend also after treatment discontinuation, with a significant improvement compared to baseline at week 16 (-23.2, p=0.0265) with significant differences compared to placebo group at week 16 (mean variation compared to baseline 5.57 vs -23.2, p=0.0492)  The active treatment significantly modulated microbiome composition, with increases in Bifidobacterium animalis subsp. lactis and Streptococcus thermophilus (p < 0.05), while Lachnospira decreased (p < 0.05). SCFA analysis showed increases in lactate (p < 0.01) and acetate (p < 0.05) post-treatment. Significant changes in Actinobacteria and Proteobacteria were observed in the active group (p < 0.05). Machine learning approaches classified subjects with 85% and 80% accuracy based on treatment. Correlation analysis indicated significant associations between microbial biomarkers and clinical parameters (p < 0.05)  Probiotics supplementation combined with vitamin D in IBS could improve gut barrier function through gut microbiota modulation and reduction of intestinal permeability that continues also after treatment discontinuation.