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Fructose transport-deficient Staphylococcus aureus reveals important role of epithelial glucose transporters in limiting sugar-driven bacterial growth in airway surface liquid.

Garnett JP, Braun D, McCarthy AJ, Farrant MR, Baker EH, Lindsay JA, Baines DL - Cell. Mol. Life Sci. (2014)

Bottom Line: However, sugar-induced growth of NE768(fruA) was significantly less when basolateral fructose rather than glucose was elevated.Therefore, we propose that the preferential uptake of glucose (compared to fructose) limits its accumulation in ASL.Pre-treatment with metformin increased transepithelial resistance and reduced the sugar-dependent growth of S. aureus.

View Article: PubMed Central - PubMed

Affiliation: Institute for Infection and Immunity, St George's, University of London, Tooting, London, SW17 0RE, UK.

ABSTRACT
Hyperglycaemia as a result of diabetes mellitus or acute illness is associated with increased susceptibility to respiratory infection with Staphylococcus aureus. Hyperglycaemia increases the concentration of glucose in airway surface liquid (ASL) and promotes the growth of S. aureus in vitro and in vivo. Whether elevation of other sugars in the blood, such as fructose, also results in increased concentrations in ASL is unknown and whether sugars in ASL are directly utilised by S. aureus for growth has not been investigated. We obtained mutant S. aureus JE2 strains with transposon disrupted sugar transport genes. NE768(fruA) exhibited restricted growth in 10 mM fructose. In H441 airway epithelial-bacterial co-culture, elevation of basolateral sugar concentration (5-20 mM) increased the apical growth of JE2. However, sugar-induced growth of NE768(fruA) was significantly less when basolateral fructose rather than glucose was elevated. This is the first experimental evidence to show that S. aureus directly utilises sugars present in the ASL for growth. Interestingly, JE2 growth was promoted less by glucose than fructose. Net transepithelial flux of D-glucose was lower than D-fructose. However, uptake of D-glucose was higher than D-fructose across both apical and basolateral membranes consistent with the presence of GLUT1/10 in the airway epithelium. Therefore, we propose that the preferential uptake of glucose (compared to fructose) limits its accumulation in ASL. Pre-treatment with metformin increased transepithelial resistance and reduced the sugar-dependent growth of S. aureus. Thus, epithelial paracellular permeability and glucose transport mechanisms are vital to maintain low glucose concentration in ASL and limit bacterial nutrient sources as a defence against infection.

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Transepithelial flux and uptake of glucose and fructose across airway epithelial monolayers. a Uptake of 14C-d-glucose and 14C-D-fructose across the apical membrane of H441 monolayers, n = 8. b Uptake of 14C-d-glucose and 14C-d-fructose across the basolateral membrane of H441 monolayers, n = 8. c Basolateral-to-apical transepithelial flux of d-glucose, d-fructose and l-glucose across H441 monolayers, measured by adding radiolabelled sugar to the basolateral surface and monitoring its appearance of the apical surface over 1 h, n = 4. d Calculated basolateral-to-apical transepithelial flux of d-glucose and d-fructose across H441 monolayers, after compensation for epithelial uptake, n = 4. *p < 0.05, **p < 0.01, ***p < 0.001
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Fig4: Transepithelial flux and uptake of glucose and fructose across airway epithelial monolayers. a Uptake of 14C-d-glucose and 14C-D-fructose across the apical membrane of H441 monolayers, n = 8. b Uptake of 14C-d-glucose and 14C-d-fructose across the basolateral membrane of H441 monolayers, n = 8. c Basolateral-to-apical transepithelial flux of d-glucose, d-fructose and l-glucose across H441 monolayers, measured by adding radiolabelled sugar to the basolateral surface and monitoring its appearance of the apical surface over 1 h, n = 4. d Calculated basolateral-to-apical transepithelial flux of d-glucose and d-fructose across H441 monolayers, after compensation for epithelial uptake, n = 4. *p < 0.05, **p < 0.01, ***p < 0.001

Mentions: A comparison of d-fructose and d-glucose uptake by H441 monolayers revealed that fructose uptake was significantly less than glucose across both apical and basolateral membranes (p < 0.01 and p < 0.001, respectively; n = 8, Fig. 4a, b).Fig. 4


Fructose transport-deficient Staphylococcus aureus reveals important role of epithelial glucose transporters in limiting sugar-driven bacterial growth in airway surface liquid.

Garnett JP, Braun D, McCarthy AJ, Farrant MR, Baker EH, Lindsay JA, Baines DL - Cell. Mol. Life Sci. (2014)

Transepithelial flux and uptake of glucose and fructose across airway epithelial monolayers. a Uptake of 14C-d-glucose and 14C-D-fructose across the apical membrane of H441 monolayers, n = 8. b Uptake of 14C-d-glucose and 14C-d-fructose across the basolateral membrane of H441 monolayers, n = 8. c Basolateral-to-apical transepithelial flux of d-glucose, d-fructose and l-glucose across H441 monolayers, measured by adding radiolabelled sugar to the basolateral surface and monitoring its appearance of the apical surface over 1 h, n = 4. d Calculated basolateral-to-apical transepithelial flux of d-glucose and d-fructose across H441 monolayers, after compensation for epithelial uptake, n = 4. *p < 0.05, **p < 0.01, ***p < 0.001
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig4: Transepithelial flux and uptake of glucose and fructose across airway epithelial monolayers. a Uptake of 14C-d-glucose and 14C-D-fructose across the apical membrane of H441 monolayers, n = 8. b Uptake of 14C-d-glucose and 14C-d-fructose across the basolateral membrane of H441 monolayers, n = 8. c Basolateral-to-apical transepithelial flux of d-glucose, d-fructose and l-glucose across H441 monolayers, measured by adding radiolabelled sugar to the basolateral surface and monitoring its appearance of the apical surface over 1 h, n = 4. d Calculated basolateral-to-apical transepithelial flux of d-glucose and d-fructose across H441 monolayers, after compensation for epithelial uptake, n = 4. *p < 0.05, **p < 0.01, ***p < 0.001
Mentions: A comparison of d-fructose and d-glucose uptake by H441 monolayers revealed that fructose uptake was significantly less than glucose across both apical and basolateral membranes (p < 0.01 and p < 0.001, respectively; n = 8, Fig. 4a, b).Fig. 4

Bottom Line: However, sugar-induced growth of NE768(fruA) was significantly less when basolateral fructose rather than glucose was elevated.Therefore, we propose that the preferential uptake of glucose (compared to fructose) limits its accumulation in ASL.Pre-treatment with metformin increased transepithelial resistance and reduced the sugar-dependent growth of S. aureus.

View Article: PubMed Central - PubMed

Affiliation: Institute for Infection and Immunity, St George's, University of London, Tooting, London, SW17 0RE, UK.

ABSTRACT
Hyperglycaemia as a result of diabetes mellitus or acute illness is associated with increased susceptibility to respiratory infection with Staphylococcus aureus. Hyperglycaemia increases the concentration of glucose in airway surface liquid (ASL) and promotes the growth of S. aureus in vitro and in vivo. Whether elevation of other sugars in the blood, such as fructose, also results in increased concentrations in ASL is unknown and whether sugars in ASL are directly utilised by S. aureus for growth has not been investigated. We obtained mutant S. aureus JE2 strains with transposon disrupted sugar transport genes. NE768(fruA) exhibited restricted growth in 10 mM fructose. In H441 airway epithelial-bacterial co-culture, elevation of basolateral sugar concentration (5-20 mM) increased the apical growth of JE2. However, sugar-induced growth of NE768(fruA) was significantly less when basolateral fructose rather than glucose was elevated. This is the first experimental evidence to show that S. aureus directly utilises sugars present in the ASL for growth. Interestingly, JE2 growth was promoted less by glucose than fructose. Net transepithelial flux of D-glucose was lower than D-fructose. However, uptake of D-glucose was higher than D-fructose across both apical and basolateral membranes consistent with the presence of GLUT1/10 in the airway epithelium. Therefore, we propose that the preferential uptake of glucose (compared to fructose) limits its accumulation in ASL. Pre-treatment with metformin increased transepithelial resistance and reduced the sugar-dependent growth of S. aureus. Thus, epithelial paracellular permeability and glucose transport mechanisms are vital to maintain low glucose concentration in ASL and limit bacterial nutrient sources as a defence against infection.

Show MeSH
Related in: MedlinePlus