Irritable Bowel Syndrome: Is It Really a Functional Disorder? A New Perspective on Alteration of Enteric Nervous System

Abstract

In recent decades, we have regarded irritable bowel syndrome (IBS) as a functional disorder which means symptoms of IBS are not explained by identifiable structural or biochemical abnormalities. 1 Under the premise that the symptom of IBS originated from disturbance of function, multi-factorial etiologies have been suggested, including abnormal motility, visceral hypersensitivity, genetic predisposition, and psycho-social influences. Of these, the role of the central nervous system in terms of brain-gut interaction has been considered as an important factor for abnormal motility and visceral hypersensitivity, and has been intensively studied. For example, the corticotrophin-releasing factor, a key modulator of stress response in the brain, has been extensively investigated and the present role in the gastrointestinal tract such as decreasing gastric emptying, increasing colonic motility, and inducing visceral hypersensitivity are established. [2][3][4] Psychological comorbidities such as depression and anxiety are also more prevalent in patients with IBS compared to healthy controls and is thought to play an important role in IBS.1 However, latest medical and scientific developments have led to further investigation of organic changes in patients with IBS such as inflammatory cell infiltration, increased permeability, and changes in neuroendocrine system in the gut. 5,6 The enteric nervous system (ENS) is one of the candidates for a possible organic cause of underlying IBS pathophysiology. The ENS regulates muscular, neuro-hormonal, and secretory systems of the gastrointestinal tract to generate functionally effective patterns of various digestive states. 7The ENS can be divided into 2 major regions, the submucosal plexus (SMP) and the myenteric plexus (MP). The SMP controls absorptive and secretory functions of the mucosal epithelium, intramural blood flow, and neuroimmune interactions, while the MP regulates intestinal motility for specific digestive states.

The Role of Neuro-Immune Interaction in Chronic Pain Conditions; Functional Somatic Syndrome, Neurogenic Inflammation, and Peripheral Neuropathy

“…The role of the enteric nervous system in the pathophysiology of IBS is also not fully elucidated. The enteric nervous system consists of millions of neurons and glial cells (present in ganglia) and is sub-divided into the submucosal plexus and the myenteric plexus regulating muscular, neuro-hormonal, and secretory systems of the GIT, allowing for digestive action [ 110 ]. The findings of Ostertag, 2015, show altered neuron activity in the submucosal plexus of patients presenting with IBS, which were stimulated by immune mediators [ 111 ].…”

The enteric nervous system: “A little brain in the gut”

“…Physical or psychological stress, with its ability to disturb the hypothalamic-pituitary-adrenal axis, is a major player in IBS development and relapse (Moloney et al, 2015;Jahng and Kim, 2016). Stress induces histological and functional changes in the ENS (Li et al, 2016b).…”

The role of acupuncture on the autonomic nervous system in irritable bowel syndrome

“…Moreover, the fundamental role of the enteric nervous system (ENS), which is a subset of the ANS [10] , is to govern physiological processes and maintain homeostasis. It has independent regulatory effects on gastrointestinal motility, secretion, and blood supply, and functional gastrointestinal disorders are closely related to intestinal neuromodulation of gastrointestinal dysfunction [11] . As a result, an abnormal ANS is a significant pathophysiology that causes dysfunctional intestinal secretion and motility.…”