Sodium/glucose co-transporter

Non-ruminants possess several intestinal Na+-dependent saturable transport systems. These include the well-known sodium-glucose co-transporter (SGLT1), responsible for the active uptake of glucose, and it appears to be specific for cinnamic and ferulic acid and possibly for other hydroxy-cinammic acids [112]. 

Ader, R, Block, M., Pietzsch, S., Wolffram, S. (2001). Interaction of quercetin glucosides with the intestinal sodium/glucose co-transporter (SGLT-1). Cancer Lett., 162, 175-180. 

Scheen AJ (2015) Pharmacodynamics, efficacy and safety of sodium-glucose co-transporter type 2 (SGLT2) inhibitors for the treatment of type 2 diabetes mellitus. Drugs 75 33-59 Scheen AJ (2015) SGLT2 inhibition efficacy and safety in type 2 diabetes treatment. Expert Opin Drug Saf 14 1879-1904... 

Jabbour SA, Goldstein BJ. Sodium glucose co-transporter 2 inhibitors blocking renal tubular reabsorption of glucose to improve glycaemic control in patients with diabetes. Int J Chn Pract 2008 62(8) 1279-84. 

Exceptions from Lipinski s rule, i.e., molecules of PSA values > 140 A2 are found to be actively absorbed by carrier-mediated transport systems (Wessel et al. 1998), as shown in Fig. 3. IB. As further detailed in Fig. 3.2, the intestinal epithelium expresses a number of such transport systems for amino acids, organic anions and cations, nucleosides, and hexoses. Among these systems are the apical sodium-dependent bile acid transporter (ASBT Annaba et al. 2007), the monocarboxylate transporter (MCT Halestrap and Price 1999), the sodium-D-glucose co-transporter (SFGT1 Kipp et al. 2003), and the nucleotide transporter SPNT1 (Balimane and Sinko 1999). In addition, the expression of a specialized transporter system for small peptides has been found in the intestinal epithelium with the di/tripeptide transporter, PepTl (Tsuji 2002), after previous functional studies by Hu et al. (1989), and the cloning of PepTl... 

Historically important as an example of flux coupling, and one that was investigated in detail becoming a paradigm for coupled transport, was the sodium coupled glucose transport system of the small intestine and kidney (see below). This was a symport (or co-transport) rather than an antiport, normally carrying glucose into the cell coupled to a flow of sodium ions in the same direction. 

Fructose is not co-transported with sodium it enters the cell on a GLUTS transporter. Glucose, galactose and fructose are transported out of the enterocyte through the GLUT2 transporter in the basolateral membrane. 

FIGURE 2.49 An absorptive cell of the viUus. The part of the plasma membrane facing the lumen is the apical membrane, whereas that facing the blood supply is the basal and lateral (basolateral) membrane. The membrane-bound proteins used to mediate the uptake of a variety of nutrients requires the simultaneous co-transport of sodium ions. The diagram reveals that the transport of glucose cind amino acids is dependent on sodium ions. Sodium-independent transport systems also exist for many nutrients. The sodium depicted in the figure is supplied by intestinal secretions and need not be supplied by any particular diet. 

Effect Co-transport of glucose and sodium induces a bloodward osmotic fbw of water, which drags along additional ions. ORT exactly replaces water, sodium and other ions bst from the blood but does not reduce the extent or duration of diarrhoea. 

Together with substrates such as glucose and amino acids, thus providing a mechanism for net accumulation of these substrates, driven by the sodium gradient, which in turn has been created by the proton gradient produced by the hydrolysis of ATE This is a co-transport mechanism as the sodium ions and substrates travel in the same direction across the cell membrane ... 

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