New Role of the Serotonin as a Biomarker of Gut-Brain Interaction

Abstract

Serotonin (5-hydroxytryptamine: 5-HT), a neurotransmitter that regulates mood in the brain and signaling in the gut, has receptors throughout the body that serve various functions, especially in the gut and brain. Selective serotonin reuptake inhibitors (SSRIs) are used to treat depression, but their efficacy is uncertain. Depression is often associated with early gastrointestinal symptoms. Gut disorders such as functional dyspepsia (FD), irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), are linked to elevated serotonin levels. In this review, we would like to discuss the approach of using serotonin as a biomarker for gut-brain, and body-wide organ communication may lead to the development of preventive and innovative treatments for gut-brain disorders, offering improved visibility and therapeutic monitoring. It could also be used to gauge stress intensity for self-care and mental health improvement.

Keywords: biomarker; cancer; functional dyspepsia (FD); gut homeostasis; gut–brain interaction; inflammatory bowel disease (IBD); irritable bowel syndrome (IBS); mood; serotonin.

Figure 1

5-HT receptors and primary functions and SERT mechanism. (A) 5-HT in the deficient state; (B) 5-HT in the excess state; (C) (serotonin transporter) mechanism for 5-HT signaling and SERT function become abnormal.

Figure 2

Parkinson’s disease developed 20 years ago in Gut. Dopamine receptors (D₁, D₂, D₃, D₄, and D₅): D₁, D₂, and D₅ receptors are expressed in the GI tract, and D₁, D₂, D₄ receptors are expressed in the brain.

Figure 3

Role of serotonin in carcinogenesis. (A) 5-HT involved in carcinogenesis; (B) mechanism: elevated 5-HT increases cancer mortality risk; (C) therapeutic strategy: 5-HT receptor antagonists and/or SSRIs stop cancer cells from growing.

Figure 4

Good communication between patient and doctor.