Himalaya Livline | Vol 6 | No. 5 | Sep–Dec 2023 | 15 The Liver and the Body Nonalcoholic Fatty Liver Disease Increases the Risk of Irritable Bowel Syndrome: Decoding the Liver–Gut Interaction Nonalcoholic fatty liver disease (NAFLD) and irritable bowel syndrome (IBS) are 2 highly prevalent clinical conditions with overlapping pathophysiologies. NAFLD and IBS (Rome III or Rome IV diagnostic criteria) have been found to have common etiologic factors such as unhealthy dietary pattern and obesity, gut dysbiosis, and uncontrolled immune responses. Both NAFLD and IBS significantly affect the quality of life. Various preclinical studies reveal a high prevalence of IBS in patients with NAFLD. The plausible association between NAFLD and IBS may be because of the following factors: Expression of Proinflammatory Cytokines Proinflammatory cytokines have been reported to play an important role in the development of IBS symptoms mediated by toll-like receptors. • Increased expression of tumor necrosis factor-α influences the peripheral and central nervous systems to become hypersensitive and the gut to become hypomotile. • Increased expressions of interleukin (IL)-6 affects the stimulation of gut submucosal neurons and intestinal barrier integrity. • Increased levels of IL-1β and IL-6 and decreased level of IL-10 influence gut homeostasis. Cross-Talk of the Liver–Brain–Gut Neural Arc The communication between the gut and liver is relayed from the liver to the brain by the autonomic nervous system. Such communication mediated by the peripheral regulatory T-cells is necessary for maintaining immune homeostasis and preventing uncontrolled inflammatory responses. Gut Dysbiosis The bile salts and antimicrobial molecules are generally transported from the liver to the intestinal lumen through the biliary tract. This safe passage controls unrestricted bacterial overgrowth and ensures gut eubiosis. In NAFLD, the ineffective clearance of microbial byproducts and inhibition of bacterial overgrowth leads to gut dysbiosis. These alterations in the gut microbiota eventually affect intestinal permeability, intestinal motility, and visceral hypersensitivity, and result in IBS. Thus, it is imperative to evaluate the presence of the clinical features of IBS in patients with NAFLD and ensure timely medical intervention. Sources: Purssell H, et al. World J Hepatol. 2021;13(12):1816–1827. Wu S, et al. BMC Med. 2022;20:262.
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