Background and Purpose: Luminal glucose enhances intestinal Ca 2+ absorption through apical Ca v 1.3 channels necessary for GLUT2-mediated glucose absorption. As these reciprocal mechanisms are not well understood, we investigated the regulatory mechanisms of intestinal [Ca 2+ ] cyt and SGLT1-mediated Na +-glucose co-transports. Experimental Approach: Glucose absorption and channel expression were examined in mouse upper jejunal epithelium using an Ussing chamber, immunocytochemistry and Ca 2+ and Na + imaging in single intestinal epithelial cells. Key Results: Glucose induced jejunal I sc via Na +-glucose cotransporter 1 (SGLT1) operated more efficiently in the presence of extracellular Ca 2+. A crosstalk between luminal Ca 2+ entry via plasma Ca v 1.3 channels and the ER Ca 2+ release through ryanodine receptor (RYR) activation in small intestinal epithelial cell (IEC) or Ca 2+-induced Ca 2+ release (CICR) mechanism was involve in Ca 2+-mediated jejunal glucose absorption. The ER Ca 2+ release through RyR triggered basolateral Ca 2+ entry or store-operated Ca 2+ entry (SOCE) mechanism and the subsequent Ca 2+ entry via Na + /Ca 2+ exchanger 1 (NCX1) were found to be critical in Na +-glucose cotransporter-mediated glucose absorption. Blocking RyR, SOCE and NCX1 inhibited glucose induced [Na + ] cyt and [Ca 2+ ] cyt in single IEC and protein expression and co-localization of STIM1/Orai1, RyR1 and NCX1 were detected in IEC and jejunal mucosa. Conclusion and Implications: Luminal Ca 2+ influx through Ca v 1.3 triggers the CICR through RyR1 to deplete the ER Ca 2+ , which induces the basolateral STIM1/Orai1-mediated SOCE mechanism and the subsequent Ca 2+ entry via NCX1 to regulate intestinal glucose uptake via Ca 2+ signalling. Targeting these mechanisms in IEC may help to modulate blood glucose and sodium in the metabolic disease. Abbreviations: [Ca 2+ ]cyt, cytosolic Ca 2+ concentration; [Na + ]cyt, cytosolic Na + concentration; 2-APB, 2-aminoethoxydiphenyl borate; CICR, Ca 2+-induced Ca 2+ release; CIRC, calcium-induced calcium release; ER, endoplasmic reticulum; IEC, intestinal epithelial cells; I sc , short-circuit current; NCX1, Na + /Ca 2+ exchanger 1; RyR, ryanodine receptor; SOCE, store-operated Ca 2+ entry; STIM1, stromal interaction molecule 1; TPEN, N,N,N 0 ,N 0-tetrakis(2-pyridylmethyl) ethylenediamine. Fenglian Zhang and Hanxing Wan equally contributed to this work.

No abstract

Oral glutamine (Gln) has been widely used in gastrointestinal (GI) clinical practice, but it is unclear if Ca2+ regulates intestinal Gln transport, although both of them are essential nutrients for mammals. Chambers were used to determine Gln (25 mM)-induced Isc through Na+/Gln co-transporters in the small intestine in the absence or the presence of selective activators or blockers of ion channels and transporters. Luminal but not serosal application of Gln induced marked intestinal Isc, especially in the distal ileum. Lowering luminal Na+ almost abolished the Gln-induced ileal Isc, in which the calcium-sensitive receptor (CaSR) activation were not involved. Ca2+ removal from both luminal and serosal sides of the ileum significantly reduced Gln- Isc. Blocking either luminal Ca2+ entry via the voltage-gated calcium channels (VGCC) or endoplasmic reticulum (ER) release via inositol 1,4,5-triphosphate receptor (IP3R) and ryanodine receptor (RyR) attenuated the Gln-induced ileal Isc, Likewise, blocking serosal Ca2+ entry via the store-operated Ca2+ entry (SOCE), TRPV1/2 channels, and Na+/Ca2+ exchangers (NCX) attenuated the Gln-induced ileal Isc. In contrast, activating TRPV1/2 channels enhanced the Gln-induced ileal Isc. We concluded that Ca2+ signaling is critical for intestinal Gln transport, and multiple plasma membrane Ca2+-permeable channels and transporters play roles in this process. The Ca2+ regulation of ileal Na+/Gln transport expands our understanding of intestinal nutrient uptake and may be significant in GI health and disease.