Micro-organic basis of functional gastrointestinal (GI) disorders: Role of microRNAs in GI pacemaking cells

MicroRNA-29a Compromises Hepatic Adiposis and Gut Dysbiosis in High Fat Diet-Fed Mice via Downregulating Inflammation

SCOPE

miR-29a expression patterns influence numerous physiological phenomena. Of note, upregulation of miR-29a ameliorates high-fat diet (HFD)-induced liver dysfunctions in mice. However, the miR-29a effect on gut microbiome composition and HFD-induced gut microbiota changes during metabolic disturbances remains unclear. The study provides compelling evidence for the protective role of miR-29a in gut barrier dysfunction and steatohepatitis.

METHODS AND RESULTS

miR-29a overexpressed mice (miR-29aTg) are bred to characterize intestinal, serum biochemical, and fecal microbiota profiling features compared to wild-type mice (WT). Mice are fed an HFD for 8 months to induce steatohepatitis, and intestinal dysfunction is determined via histopathological analysis. miR-29aTg has better lipid metabolism capability that decreases total cholesterol and triglyceride levels in serum than WT of the same age. The study further demonstrates that miR-29aTg contributes to intestinal integrity by maintaining periodic acid Schiff positive cell numbers and diversity of fecal microorganisms. HFD-induced bacterial community disturbance and steatohepatitis result in more severe WT than miR-29aTg. Gut microorganism profiling reveals Lactobacillus, Ruminiclostridium_9, and Lachnoclostridium enrichment in miR-29aTg and significantly decreases interleukin-6 expression in the liver and intestinal tract.

CONCLUSION

This study provides new evidence that sheds light on the host genetic background of miR-29a, which protects against steatohepatitis and other intestinal disorders.

Functional Implications and Clinical Potential of MicroRNAs in Irritable Bowel Syndrome: A Concise Review

MicroRNAs (miRNAs) are tiny (20-24 nucleotides long), non-coding, highly conserved RNA molecules that play a crucial role within the post-transcriptional regulation of gene expression via sequence-specific mechanisms. Since the miRNA transcriptome is involved in multiple molecular processes needed for cellular homeostasis, its altered expression can trigger the development and progression of several human pathologies. In this context, over the last few years, several relevant studies have demonstrated that dysregulated miRNAs affect a wide range of molecular mechanisms associated with irritable bowel syndrome (IBS), a common gastrointestinal disorder. For instance, abnormal miRNA expression in IBS patients is related to the alteration of intestinal permeability, visceral hyperalgesia, inflammatory pathways, and pain sensitivity. Besides, specific miRNAs are differentially expressed in the different subtypes of IBS, and therefore, they might be used as biomarkers for precise diagnosis of these pathological conditions. Accordingly, miRNAs have noteworthy potential as theragnostic targets for IBS. Hence, in this current review, we present an overview of the recent discoveries regarding the clinical relevance of miRNAs in IBS, which might be useful in the future for the development of miRNA-based drugs against this disorder.

Enterochromaffin Cells-Gut Microbiota Crosstalk: Underpinning the Symptoms, Pathogenesis, and Pharmacotherapy in Disorders of Gut-Brain Interaction

Disorders of gut-brain interaction (DGBIs) are common conditions in community and clinical practice. As specialized enteroendocrine cells, enterochromaffin (EC) cells produce up to 95% of total body serotonin and coordinate luminal and basolateral communication in the gastrointestinal (GI) tract. EC cells affect a broad range of gut physiological processes, such as motility, absorption, secretion, chemo/mechanosensation, and pathologies, including visceral hypersensitivity, immune dysfunction, and impaired gastrointestinal barrier function. We aim to review EC cell and serotonin-mediated physiology and pathophysiology with particular emphasis on DGBIs. We explored the knowledge gap and attempted to suggest new perspectives of physiological and pathophysiological insights of DGBIs, such as (1) functional heterogeneity of regionally distributed EC cells throughout the entire GI tract; (2) potential pathophysiological mechanisms mediated by EC cell defect in DGBIs; (3) cellular and molecular mechanisms characterizing EC cells and gut microbiota bidirectional communication; (4) differential modulation of EC cells through GI segment-specific gut microbiota; (5) uncover whether crosstalk between EC cells and (i) luminal contents; (ii) enteric nervous system; and (iii) central nervous system are core mechanisms modulating gut-brain homeostasis; and (6) explore the therapeutic modalities for physiological and pathophysiological mechanisms mediated through EC cells. Insights discussed in this review will fuel the conception and realization of pathophysiological mechanisms and therapeutic clues to improve the management and clinical care of DGBIs.

Current Treatment Options and Therapeutic Insights for Gastrointestinal Dysmotility and Functional Gastrointestinal Disorders

Functional gastrointestinal disorders (FGIDs) have been re-named as disorders of gut-brain interactions. These conditions are not only common in clinical practice, but also in the community. In reference to the Rome IV criteria, the most common FGIDs, include functional dyspepsia (FD) and irritable bowel syndrome (IBS). Additionally, there is substantial overlap of these disorders and other specific gastrointestinal motility disorders, such as gastroparesis. These disorders are heterogeneous and are intertwined with several proposed pathophysiological mechanisms, such as altered gut motility, intestinal barrier dysfunction, gut immune dysfunction, visceral hypersensitivity, altered GI secretion, presence and degree of bile acid malabsorption, microbial dysbiosis, and alterations to the gut-brain axis. The treatment options currently available include lifestyle modifications, dietary and gut microbiota manipulation interventions including fecal microbiota transplantation, prokinetics, antispasmodics, laxatives, and centrally and peripherally acting neuromodulators. However, treatment that targets the pathophysiological mechanisms underlying the symptoms are scanty. Pharmacological agents that are developed based on the cellular and molecular mechanisms underlying pathologies of these disorders might provide the best avenue for future pharmaceutical development. The currently available therapies lack long-term effectiveness and safety for their use to treat motility disorders and FGIDs. Furthermore, the fundamental challenges in treating these disorders should be defined; for instance, 1. Cause and effect cannot be disentangled between symptoms and pathophysiological mechanisms due to current therapies that entail the off-label use of medications to treat symptoms. 2. Despite the knowledge that the microbiota in our gut plays an essential part in maintaining gut health, their exact functions in gut homeostasis are still unclear. What constitutes a healthy microbiome and further, the precise definition of gut microbial dysbiosis is lacking. More comprehensive, large-scale, and longitudinal studies utilizing multi-omics data are needed to dissect the exact contribution of gut microbial alterations in disease pathogenesis. Accordingly, we review the current treatment options, clinical insight on pathophysiology, therapeutic modalities, current challenges, and therapeutic clues for the clinical care and management of functional dyspepsia, gastroparesis, irritable bowel syndrome, functional constipation, and functional diarrhea.

Role of microRNAs in Disorders of Gut-Brain Interactions: Clinical Insights and Therapeutic Alternatives

Disorders of gut–brain interactions (DGBIs) are heterogeneous in nature and intertwine with diverse pathophysiological mechanisms. Regular functioning of the gut requires complex coordinated interplay between a variety of gastrointestinal (GI) cell types and their functions are regulated by multiple mechanisms at the transcriptional, post-transcriptional, translational, and post-translational levels. MicroRNAs (miRNAs) are small non-coding RNA molecules that post-transcriptionally regulate gene expression by binding to specific mRNA targets to repress their translation and/or promote the target mRNA degradation. Dysregulation of miRNAs might impair gut physiological functions leading to DGBIs and gut motility disorders. Studies have shown miRNAs regulate gut functions such as visceral sensation, gut immune response, GI barrier function, enteric neuronal development, and GI motility. These biological processes are highly relevant to the gut where neuroimmune interactions are key contributors in controlling gut homeostasis and functional defects lead to DGBIs. Although extensive research has explored the pathophysiology of DGBIs, further research is warranted to bolster the molecular mechanisms behind these disorders. The therapeutic targeting of miRNAs represents an attractive approach for the treatment of DGBIs because they offer new insights into disease mechanisms and have great potential to be used in the clinic as diagnostic markers and therapeutic targets. Here, we review recent advances regarding the regulation of miRNAs in GI pacemaking cells, immune cells, and enteric neurons modulating pathophysiological mechanisms of DGBIs. This review aims to assess the impacts of miRNAs on the pathophysiological mechanisms of DGBIs, including GI dysmotility, impaired intestinal barrier function, gut immune dysfunction, and visceral hypersensitivity. We also summarize the therapeutic alternatives for gut microbial dysbiosis in DGBIs, highlighting the clinical insights and areas for further exploration. We further discuss the challenges in miRNA therapeutics and promising emerging approaches.

Gut microbiota dysbiosis in functional gastrointestinal disorders: Underpinning the symptoms and pathophysiology

Functional gastrointestinal disorders (FGIDs), currently known as disorders of gut-brain interaction, are emerging microbiota-gut-brain abnormalities that are prevalent worldwide. The pathogenesis of FGIDs is heterogeneous and is intertwined with gut microbiota and its derived molecule-modulated mechanisms, including gut dysmotility, visceral hypersensitivity, gut immune abnormalities, abnormal secretion, and impaired barrier function. There has been phenomenal progress in understanding the role of gut microbiota in FGIDs by underpinning the species alternations between healthy and pathological conditions such as FGIDs. However, the precise gut microbiota-directed cellular and molecular pathogeneses of FGIDs are yet enigmatic. Determining the mechanistic link between the gut microbiota and gastrointestinal (GI) diseases has been difficult due to (i) the lack of robust animal models imitating the various aspects of human FGID pathophysiology; (ii) the absence of longitudinal human and/or animal studies to unveil the interaction of the gut microbiota with FGID-relevant pathogenesis; (iii) uncertainty about connections between human and animal studies; and (iv) insufficient data supporting a holistic view of disease-specific pathophysiological changes in FGID patients. These unidentified gaps open possibilities to explore pathological mechanisms directed through gut microbiota dysbiosis in FGIDs. The current treatment options for dysbiotic gut microbiota are limited; dietary interventions, antibiotics, probiotics, and fecal microbiota transplantation are the front-line clinical options. Here, we review the contribution of gut microbiota and its derived molecules in gut homeostasis and explore the possible pathophysiological mechanisms involved in FGIDs leading to potential therapeutics options.