New insight in understanding the contribution of SGLT1 in cardiac glucose uptake: evidence for a truncated form in mice and humans.
(2021) American journal of physiology. Heart and circulatory physiology — Vol. 320, n° 2, p. H838-H853 (2021)
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Bultot, Laurent 
- Abstract
- Although sodium-glucose co-transporter 1 (SGLT1) has been identified as one of the major SGLT isoforms expressed in the heart, its exact role remains elusive. Evidences using phlorizin, the most common inhibitor of SGLTs, suggested its role in glucose transport. However, phlorizin could also affect classical facilitated diffusion via glucose transporters (GLUTs), bringing into question the relevance of SGLT1 in overall cardiac glucose uptake. Accordingly, we assessed the contribution of SGLT1 in cardiac glucose uptake using the SGLT1 knock-out mouse model, which lacks exon 1. Glucose uptake was similar in cardiomyocytes isolated from SGLT1 knock-out (KO) and control littermate (WT) mice, either under basal state, insulin, or hyperglycemia. Similarly, in vivo basal and insulin-stimulated cardiac glucose transport measured by micro-PET scan technology did not differ between WT and KO mice. Micromolar concentrations of phlorizin had no impact on glucose uptake in either isolated WT or KO-derived cardiomyocytes. However, higher concentrations (1mM) completely inhibited insulin-stimulated glucose transport without affecting insulin signaling nor GLUT4 translocation, independently from cardiomyocyte genotype. Interestingly, we discover that mouse and human hearts expressed a shorter slc5a1 transcript, leading to SGLT1 protein lacking transmembrane domains and residues involved in glucose and sodium bindings. In conclusion, cardiac SGLT1 does not contribute to overall glucose uptake, probably due to the expression of slc5a1 transcript variant. The inhibitory effect of phlorizin on cardiac glucose uptake is SGLT1-independent and can be explained by GLUT transporter inhibition. These data open new perspectives in understanding the role of SGLT1 in the heart.
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Ferté, L., Marino, A., Battault, S., Bultot, L., Van Steenbergen, A., Bol, A., Cumps, J., Ginion, A., Koepsell, H., Dumoutier, L., Hue, L., Horman, S., Bertrand, L., & Beauloye, C. (2021). New insight in understanding the contribution of SGLT1 in cardiac glucose uptake: evidence for a truncated form in mice and humans. American journal of physiology. Heart and circulatory physiology, 320(2), H838-H853. https://doi.org/10.1152/ajpheart.00736.2019 (Original work published 2021)