Monosodium glutamate-mediated Ca2+-dependent intestinal epithelial ion transports in health and IBS-D in male mice.

Despite the ubiquitous use of monosodium glutamate (MSG) as a food additive, its specific effects on intestinal health and disease remain largely unclear. Here we found mucosal application of MSG induced an upward intestinal short-circuit current (Isc) in the murine ileum, which was significantly reduced by extracellular Cl-, Na+, and Ca2+ removal. Mechanistically, MSG-induced Isc was significantly attenuated by pharmacological inhibition of key transporters (NCX, SGLT1, NKA) and secretory channels (CaCC, CFTR, IKCa). Furthermore, disrupting intracellular Ca2+ homeostasis via endoplasmic reticulum (ER) chelation or blockade of IP3R, RyR, SOCE/CRAC, and VGCC significantly suppressed both the ileal Isc and MSG-stimulated Ca2+ signaling in IECs. Importantly, MSG triggered a simultaneous elevation in intracellular Ca2+ and a reduction in Na+, which were abolished by the blockers of NCX and SGLT1. In vivo, MSG-induced Ca2+-dependent ion transports were significantly reduced in irritable bowel syndrome with diarrhea (IBS-D) mice. Our findings indicate that MSG drives Ca2+-dependent intestinal ion transports through a complex network orchestrated by SGLT1 and NCX under healthy state, which is markedly attenuated in IBS-D. This study provides novel insights into the gastrointestinal impact of dietary MSG in both health and bowel disease.