Functional characterization of a putative disaccharide membrane transporter in crustacean intestine

Abstract

Mechanisms of transepithelial absorption of dietary sucrose in the American lobster, Homarus americanus, were investigated to determine if disaccharide sugars can be transported across an animal gut intact. Intestines were mounted in a perfusion chamber to measure mucosal to serosal (MS) 14C‐sucrose transport. MS sucrose transport was a hyperbolic function of luminal sugar concentration, suggesting the presence of carrier‐mediated transport. Sodium‐dependent glucose transport inhibitor, phloridzin, partially decreased MS 14C‐sucrose transport, suggesting hydrolysis of 14C‐sucrose to glucose during transport. Phloretin, an inhibitor of Na+‐independent basolateral glucose transport, partially decreased MS 14C‐sucrose transport, suggesting that some 14C‐sucrose radioactivity may be transported to the blood as 14C‐glucose. Decreased MS 14C‐sucrose transport also occurred in the presence of the disaccharide trehalose. Thin‐layer chromatography (TLC) was used to identify the chemical nature of radioactively‐labeled sugars in the bath following transport and revealed that 14C‐sucrose was transported across the intestine largely as an intact molecule. Results suggest that disaccharide sugars may be transported intact across crustacean intestine and provide support for the occurrence of a disaccharide membrane transporter that has not previously been functionally characterized. Grant Funding Source: This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2010‐65

Fructose and Sucrose Intake Increase Exogenous Carbohydrate Oxidation during Exercise

“…Sucrose combines glucose and fructose monomers, and its hydrolysis is typically not rate-limiting for intestinal absorption [ 15 , 17 ]. In addition, recent work suggests that intact sucrose can also be transported as a disaccharide across the intestinal membrane [ 18 ]. Therefore, sucrose may represent an (even more) effective dietary source of fructose co-ingestion.…”