Functions and Signaling Pathways of Amino Acids in Intestinal Inflammation

Abstract

Intestine is always exposed to external environment and intestinal microorganism; thus it is more sensitive to dysfunction and dysbiosis, leading to intestinal inflammation, such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and diarrhea. An increasing number of studies indicate that dietary amino acids play significant roles in preventing and treating intestinal inflammation. The review aims to summarize the functions and signaling mechanisms of amino acids in intestinal inflammation. Amino acids, including essential amino acids (EAAs), conditionally essential amino acids (CEAAs), and nonessential amino acids (NEAAs), improve the functions of intestinal barrier and expressions of anti-inflammatory cytokines and tight junction proteins but decrease oxidative stress and the apoptosis of enterocytes as well as the expressions of proinflammatory cytokines in the intestinal inflammation. The functions of amino acids are associated with various signaling pathways, including mechanistic target of rapamycin (mTOR), inducible nitric oxide synthase (iNOS), calcium-sensing receptor (CaSR), nuclear factor-kappa-B (NF-κB), mitogen-activated protein kinase (MAPK), nuclear erythroid-related factor 2 (Nrf2), general controlled nonrepressed kinase 2 (GCN2), and angiotensin-converting enzyme 2 (ACE2).

Serum amino acid profile in 51 dogs with immunosuppressant-responsive enteropathy (IRE): a pilot study on clinical aspects and outcomes

“…The CD included 8 mixed breeds and the following breeds: Dachshund (3), Labrador (2), Golden Retriever (2), English Setter (2), Jack Russel Terrier (2), Border Collie (1), Bernese Mountain Dog (1), Whippet (1), Maremma Shepherd (1), Cocker Spaniel (1), Poodle (1), and Lagotto Romagnolo (1). The median BCS was 4.5 (range [4][5][6]. No difference in age and sex between the two study populations (IRE and CD) was found (p = 0.89 and p = 0.21, respectively).…”

“…In human inflammatory bowel disease (IBD), specific alterations in the metabolism of AAs can result from the pathophysiological process caused by bowel inflammation and can influence the progression of IBD [2,3]. AAs have various functions, and can reduce oxidative stress, contribute to the restoration of mucosal homeostasis, balance inflammatory and proinflammatory cytokines production and increase immune regulatory cytokine concentration [1,4,5]. The microbiota synthesizes the different proteins and a variety of metabolites originating from AAs, which thus play an important role in the nutrition and physiology of the host [6].…”

Plasma amino acid profiles in dogs with inflammatory bowel disease

“…Tryptophan supplementation ameliorates clinical signs, improves feed conversion ratio, ameliorates histologic signs of colonic inflammation, and reduces gut permeability and the expression of several pro‐inflammatory cytokines in animal models of dextran sodium sulfate‐induced colitis . Recently, interest in amino acids, including tryptophan, has been focused on the relationship between intestinal inflammation and their therapeutic potential in IBD . Therefore, oral supplementation with tryptophan might represent a novel therapeutic strategy for dogs with IBD, especially in IBD dogs with PLE.…”

Effects of IRW and IQW on Oxidative Stress and Gut Microbiota in Dextran Sodium Sulfate-Induced Colitis

“…In addition to this anti-inflammatory effect, the observed advantages of these peptides have included antioxidant effects [16]. The capacity for dietary constituents to function as modulators for intestinal inflammatory disease has been demonstrated by previous work examining nutritional regulation by amino acids [17][18][19]. This study examines the impacts of the presence of dietary IRW or IQW on oxidative stress and colon microbiota in dextran sodium sulfate (DSS) induced colitis.…”