Probiotics for the management of irritable bowel syndrome: a systematic review and three-level meta-analysis.

OBJECTIVE: Previous systematic reviews demonstrated a potentially beneficial effect of probiotics on irritable bowel syndrome (IBS). However, these studies are either affected by the inclusion of insufficient trials or by the problem of dependent data across multiple outcomes, and an overall effect size has not been provided. We aimed to determine the effect of probiotics on IBS through a three-level meta-analysis and clarify potential effect moderators. METHODS: We searched MEDLINE, Embase, and Web of Science, screening for randomized controlled trials (RCTs) that examine the effect of probiotics on IBS. The primary outcome was the improvement in the severity of global IBS symptoms at the end of treatment. The secondary outcomes were the improvement in abdominal pain and the quality of life. The effect sizes of the probiotics were measured by using the standardized mean difference (SMD) and pooled by a three-level meta-analysis model. RESULTS: We included 72 RCTs in the analysis. The meta-analysis showed significantly better overall effect of probiotics than placebo on the global IBS symptoms (SMD -0.55, 95% CI -0.76 to -0.34, P <0.001), abdominal pain (SMD -0.89, 95% CI -1.29 to -0.5, P <0.001) and quality of life (SMD 0.99, 95% CI 0.45 to 1.54, P <0.001), respectively. Moderator analysis found that a treatment duration shorter than 4 weeks was associated with a larger effect size in all the outcomes, and Bacillus probiotics had better improvement on the abdominal pain. CONCLUSIONS: Probiotics had a short-term effect and a medium effect size on the global IBS symptoms. Treatment duration and types of probiotics affected the effect size of probiotics, and shorter durations and Bacillus probiotics were associated with better treatment effects. REGISTRATION: Open Science Framework.

Genetically proxied inhibition of tumor necrosis factor and the risk of colorectal cancer: A drug-target mendelian randomization study.

Background: Previous studies suggested that anti-TNF drugs might be repurposed as a preventive treatment for colorectal cancer. We aimed to examine whether genetically proxied inhibition of tumor necrosis factor receptor 1 (TNFR1) reduces the absolute risk of colorectal cancer through mendelian randomization (MR) analysis. Methods: We obtained 28 single nucleotide polymorphisms (SNPs) that were located within a ±15 kilobase window of the TNFRSF1A-the gene that encodes the TNFR1 protein, and we used genetic data from three GWAS studies of circulating levels of TNFR1, C-reactive protein (CRP), and white blood counts (WBC) to screen SNPs that proxied the inhibition of TNFR1. Positive control analyses were then performed by using another three GWAS data from the ulcerative colitis cohort (n = 45,975), Crohn's disease cohort (n = 40,266), and multiple sclerosis cohort (n = 115,803) to confirm the effect of the included SNPs. A two-sample mendelian randomization analysis was performed to examine the association between TNFR1 inhibition and the absolute risk reduction (ARR) of colorectal cancer. Results: We finally included seven SNPs to proxy the anti-TNF effect, and these SNPs caused lower levels of TNFR1, CRP, and white blood counts. In positive control analyses, the included SNPs caused lower odds ratio of ulcerative colitis and Crohn's disease but a higher odds ratio of multiple sclerosis, consistent with drug mechanistic actions and previous trial evidence. By using the inverse-variance weighted analyses to combine the effects of the seven SNPs, we found that the anti-TNF effect was associated with a 0.988 (95%CI 0.985-0.991) mg/L decrease in CRP levels and a reduction in the risk of colorectal cancer (absolute risk reduction -2.1%, 95%CI -3.8% to -0.4%, p = 0.01). Conclusion: Our study confirmed that anti-TNF drugs were associated with a risk reduction in colorectal cancer. Physicians could consider using anti-TNF drugs for the prevention of colorectal cancer, especially in patients with high risks of developing cancer.