Association of Three Polymorphisms rs11614913, rs2910146, and rs3746444 in miRNA-196a2, miRNA-146a, and miRNA-499 with Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

MiR-146a (rs2910164) Gene Polymorphism and Its Impact on Circulating MiR-146a Levels in Patients with Inflammatory Bowel Diseases

MicroRNA-146a (miR-146a) has been involved in the pathophysiology of inflammatory bowel disease (IBD). However, the precise processes are still not entirely understood. Contradictory studies suggest that miR-146a expression could be influenced by the miR-146a rs2910164 C > G polymorphism. This case-control study aimed to investigate the association of miR-146a rs2910164 C > G gene polymorphism and its impact on circulating miR-146a expression levels in Egyptian IBD patients. We included 40 IBD patients and 30 matched healthy controls. Genotyping of miR-146a rs2910164 polymorphism and assessment of miR-146a expression level were done using quantitative real-time PCR in all participants. MiR-146a rs2910164 GG genotype and the G allele were reported in 47% and 70% of the IBD patient group, respectively. And they were associated with increased IBD risk. All the IBD patients with the CC genotype (100%) and most of those with the CG genotype (66.67%) had an inactive disease, while most IBD patients with the GG genotype (73.68%) had an active disease. The miR-146a expression level was the highest with the CC genotype and the lowest with the GG genotype. Also, miR-146a expression level decreased significantly in IBD patients than controls and with disease activity. Combined detection of fecal calprotectin with miR-146a expression level improved the diagnostic sensitivity and the negative predictive value in differentiating IBD patients with active disease from those inactive. Our study identified a strong association of miR-146a rs2910164 GG genotype and G allele with IBD-increased susceptibility and activity in the Egyptian population. The miR-146a rs2910164 polymorphism can reduce miR-146a expression levels in these patients as well. Further research on a larger sample size and different ethnic populations can be the key to progress in establishing this genetic association.

MiR-128-3p alleviates TNBS-induced colitis through inactivating TRAF6/NF-κB signaling pathway in rats

miR-128-3p is reported to involve in pathogenesis of several autoimmune diseases, yet the role of miR-128-3p in inflammatory bowel disease (IBD) remains unknown. To investigate miR-128-3p in IBD, experimental colitis animal model was generated by 2,4,6-Trinitrobenzenesulfonic acid solution (TNBS). miR-128-3p agomir was used to overexpress miR-128-3p in rats. Histological assessment and myeloperoxidase activity were conducted to evaluate the TNBS-induced colitis. Effect of miR-128-3p overexpression on levels of TNF-α, IL-1β, ICAM-1, and MCP-1 was tested by ELISA assay. The target of miR-128-3p was predicted and further confirmed by dual-luciferase reporter assay. The expressions of TRAF6, p-NF-κB, and NF-κB were determined by western blot. The miR-128-3p level was significantly decreased in rats with TNBS-induced colitis. miR-128-3p could alleviate TNBS-induced colitis and inhibit production of inflammatory factors. We found TRAF6 was a direct target of miR-128-3p using bioinformatics and luciferase assay. By western blot, we discovered miR-128-3p activates NF-κB by targeting TRAF6. Our data reveal a novel mechanism that a decreased miR-128-3p level in TNBS-induced colitis could inhibit production of inflammatory factors, which activates NF-κB signaling by targeting TRAF6. Our findings might provide a novel therapeutic target for drug design and development for IBD therapeutics.

Vitamin D Modulates Intestinal Microbiota in Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD) is a chronic inflammation of the gastrointestinal tract (GIT), including Crohn's disease (CD) and ulcerative colitis (UC), which differ in the location and lesion extensions. Both diseases are associated with microbiota dysbiosis, with a reduced population of butyrate-producing species, abnormal inflammatory response, and micronutrient deficiency (e.g., vitamin D hypovitaminosis). Vitamin D (VitD) is involved in immune cell differentiation, gut microbiota modulation, gene transcription, and barrier integrity. Vitamin D receptor (VDR) regulates the biological actions of the active VitD (1α,25-dihydroxyvitamin D3), and is involved in the genetic, environmental, immune, and microbial aspects of IBD. VitD deficiency is correlated with disease activity and its administration targeting a concentration of 30 ng/mL may have the potential to reduce disease activity. Moreover, VDR regulates functions of T cells and Paneth cells and modulates release of antimicrobial peptides in gut microbiota-host interactions. Meanwhile, beneficial microbial metabolites, e.g., butyrate, upregulate the VDR signaling. In this review, we summarize the clinical progress and mechanism studies on VitD/VDR related to gut microbiota modulation in IBD. We also discuss epigenetics in IBD and the probiotic regulation of VDR. Furthermore, we discuss the existing challenges and future directions. There is a lack of well-designed clinical trials exploring the appropriate dose and the influence of gender, age, ethnicity, genetics, microbiome, and metabolic disorders in IBD subtypes. To move forward, we need well-designed therapeutic studies to examine whether enhanced vitamin D will restore functions of VDR and microbiome in inhibiting chronic inflammation.

Non-coding RNAs - A primer for the laboratory scientist

Advances in molecular genetics have identified several species of RNA that fail to translate - hence the non-coding RNAs. The two major groups within this class of nucleic acids are microRNAs (miRNA) and long non-coding RNAs (lncRNA). There is growing body of evidence supporting the view that these molecules have regulatory effect on both DNA and RNA. The objective of this brief review is to explain the molecular genetic of these molecules, to summarize their potential as mediators of disease, and to highlight their value as diagnostic markers and as tools in disease management.

Association of rs2910164 polymorphism in MiR-146a gene with psoriasis susceptibility: A meta-analysis

The rs2910164 single nucleotide polymorphism (SNP) in miR-146a has been implicated in the etiology of psoriasis in different relevant studies with contradictory conclusions and limited sample size. Therefore, the aim of this study was to undertake a systematic review and meta-analysis to estimate the association between rs2910164 SNP and psoriasis. We searched the databases of PubMed, EMBASE, Web of Science, WanFang, and Chinese National Knowledge Infrastructure (CNKI) to identify relevant literatures published before July 15, 2018. Four case-control studies including 2212 cases and 2274 healthy controls from 4 different countries met the predetermined criteria. The effect size was pooled by odds ratios (ORs) and 95% confidence intervals (95%CIs). Recessive model (CC vs CG+GG) was confirmed to be the optimal model. The results indicated that rs2910164 SNP was significantly associated with psoriasis (OR = 0.74, 95%CI 0.60-0.91, P = .004), and individuals with CC-genotype were predisposed to have decreased risk of psoriasis.

Vitamin A and inflammatory bowel diseases: from cellular studies and animal models to human disease

Vitamin A (VA) and metabolites such as Retinoic Acid (RA) and all-trans-RA (at-RA) are crucial in the modulation of the immune system and may be determinative in the balance of the immune responses. Inflammatory bowel diseases (IBD) consist of chronic relapsing and heterogeneous disorders with not well-known etiology. Due to its role in inflammatory processes, VA may be helpful in the treatment of IBD. Area covered: As VA plays a significant role in the inflammatory processes, this review aims to show the potential role of this vitamin in IBD, searching for cellular studies, animal models, and studies with humans. Expert commentary: Many studies have described the importance of alternative therapeutic approaches for IBD. Due to its role in the immune system, VA may also exert an indispensable role in the IBD. Nevertheless, some authors have shown that these compounds could stimulate the release of pro-inflammatory cytokines. For these reasons, more studies should be performed to establish the precise mechanisms of VA and its metabolites in systemic and intestinal inflammation.