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Hypoxia increases expression of selective facilitative glucose transporters (GLUT) and 2-deoxy-D-glucose uptake in human adipocytes.

Wood IS, Wang B, Lorente-Cebrián S, Trayhurn P - Biochem. Biophys. Res. Commun. (2007)

Bottom Line: Exposure of adipocytes to hypoxia (1% O(2)) for up to 24 h resulted in increases in GLUT-1 (9.2-fold), GLUT-3 (9.6-fold peak at 8 h), and GLUT-5 (8.9-fold) mRNA level compared to adipocytes in normoxia (21% O(2)).In contrast, there was no change in GLUT-4, GLUT-10 or GLUT-12 expression.The rise in GLUT-1 mRNA was accompanied by a substantial increase in GLUT-1 protein (10-fold), but there was no change in GLUT-5; GLUT-3 protein was not detected.

View Article: PubMed Central - PubMed

Affiliation: Obesity Biology Unit, School of Clinical Sciences, University Clinical Departments, Royal Liverpool University Hospital, University of Liverpool, UK. i.s.wood@liverpool.ac.uk

ABSTRACT
Hypoxia modulates the production of key inflammation-related adipokines and may underlie adipose tissue dysfunction in obesity. Here we have examined the effects of hypoxia on glucose transport by human adipocytes. Exposure of adipocytes to hypoxia (1% O(2)) for up to 24 h resulted in increases in GLUT-1 (9.2-fold), GLUT-3 (9.6-fold peak at 8 h), and GLUT-5 (8.9-fold) mRNA level compared to adipocytes in normoxia (21% O(2)). In contrast, there was no change in GLUT-4, GLUT-10 or GLUT-12 expression. The rise in GLUT-1 mRNA was accompanied by a substantial increase in GLUT-1 protein (10-fold), but there was no change in GLUT-5; GLUT-3 protein was not detected. Functional studies with [(3)H]2-deoxy-D-glucose showed that hypoxia led to a stimulation of glucose transport (4.4-fold) which was blocked by cytochalasin B. These results indicate that hypoxia increases monosaccharide uptake capacity in human adipocytes; this may contribute to adipose tissue dysregulation in obesity.

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Facilitative glucose transporter protein expression in human adipocytes in hypoxia. Adipocytes at day 14 (post-induction of differentiation) were exposed to 21% or 1% O2 for 24 h. Total cellular lysates were isolated and western blot analysis performed for (A) HIF-1α, and (B) GLUT-1 and GLUT-5. Representative blots are shown. (C) Quantification of GLUT-1 and GLUT-5 proteins by densitometry normalised to α-tubulin. The densitometry values for each protein are set relative to the respective control as =1. n = 5 per group, AU = arbitrary units. Twenty-one percent of O2 (open bars); 1% O2 (shaded bars). ∗∗∗P < 0.001, compared to adipocytes in normoxia.
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fig2: Facilitative glucose transporter protein expression in human adipocytes in hypoxia. Adipocytes at day 14 (post-induction of differentiation) were exposed to 21% or 1% O2 for 24 h. Total cellular lysates were isolated and western blot analysis performed for (A) HIF-1α, and (B) GLUT-1 and GLUT-5. Representative blots are shown. (C) Quantification of GLUT-1 and GLUT-5 proteins by densitometry normalised to α-tubulin. The densitometry values for each protein are set relative to the respective control as =1. n = 5 per group, AU = arbitrary units. Twenty-one percent of O2 (open bars); 1% O2 (shaded bars). ∗∗∗P < 0.001, compared to adipocytes in normoxia.

Mentions: In the next experiments, the effect of hypoxia on GLUT protein levels was examined. Total cellular lysates prepared from the differentiated adipocytes were examined with antibodies to those GLUT family members which showed an increase in gene expression following exposure to 1% O2. Initially, induction of HIF-1α, the inducible subunit of the hypoxia-sensitive transcription factor HIF-1, was confirmed in the adipocytes by Western blotting (Fig 2A). The GLUT protein pattern is shown in Fig. 2B. When normalised to the α-tubulin signal, an increase of over 10-fold in GLUT-1 protein abundance was found in the hypoxic cells compared to the controls (Fig. 2C). However, there was no change in the abundance of GLUT-5. Despite repeated attempts with four different antibodies, we were unable to detect an unambiguous, specific signal for GLUT-3 protein.


Hypoxia increases expression of selective facilitative glucose transporters (GLUT) and 2-deoxy-D-glucose uptake in human adipocytes.

Wood IS, Wang B, Lorente-Cebrián S, Trayhurn P - Biochem. Biophys. Res. Commun. (2007)

Facilitative glucose transporter protein expression in human adipocytes in hypoxia. Adipocytes at day 14 (post-induction of differentiation) were exposed to 21% or 1% O2 for 24 h. Total cellular lysates were isolated and western blot analysis performed for (A) HIF-1α, and (B) GLUT-1 and GLUT-5. Representative blots are shown. (C) Quantification of GLUT-1 and GLUT-5 proteins by densitometry normalised to α-tubulin. The densitometry values for each protein are set relative to the respective control as =1. n = 5 per group, AU = arbitrary units. Twenty-one percent of O2 (open bars); 1% O2 (shaded bars). ∗∗∗P < 0.001, compared to adipocytes in normoxia.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211375&req=5

fig2: Facilitative glucose transporter protein expression in human adipocytes in hypoxia. Adipocytes at day 14 (post-induction of differentiation) were exposed to 21% or 1% O2 for 24 h. Total cellular lysates were isolated and western blot analysis performed for (A) HIF-1α, and (B) GLUT-1 and GLUT-5. Representative blots are shown. (C) Quantification of GLUT-1 and GLUT-5 proteins by densitometry normalised to α-tubulin. The densitometry values for each protein are set relative to the respective control as =1. n = 5 per group, AU = arbitrary units. Twenty-one percent of O2 (open bars); 1% O2 (shaded bars). ∗∗∗P < 0.001, compared to adipocytes in normoxia.
Mentions: In the next experiments, the effect of hypoxia on GLUT protein levels was examined. Total cellular lysates prepared from the differentiated adipocytes were examined with antibodies to those GLUT family members which showed an increase in gene expression following exposure to 1% O2. Initially, induction of HIF-1α, the inducible subunit of the hypoxia-sensitive transcription factor HIF-1, was confirmed in the adipocytes by Western blotting (Fig 2A). The GLUT protein pattern is shown in Fig. 2B. When normalised to the α-tubulin signal, an increase of over 10-fold in GLUT-1 protein abundance was found in the hypoxic cells compared to the controls (Fig. 2C). However, there was no change in the abundance of GLUT-5. Despite repeated attempts with four different antibodies, we were unable to detect an unambiguous, specific signal for GLUT-3 protein.

Bottom Line: Exposure of adipocytes to hypoxia (1% O(2)) for up to 24 h resulted in increases in GLUT-1 (9.2-fold), GLUT-3 (9.6-fold peak at 8 h), and GLUT-5 (8.9-fold) mRNA level compared to adipocytes in normoxia (21% O(2)).In contrast, there was no change in GLUT-4, GLUT-10 or GLUT-12 expression.The rise in GLUT-1 mRNA was accompanied by a substantial increase in GLUT-1 protein (10-fold), but there was no change in GLUT-5; GLUT-3 protein was not detected.

View Article: PubMed Central - PubMed

Affiliation: Obesity Biology Unit, School of Clinical Sciences, University Clinical Departments, Royal Liverpool University Hospital, University of Liverpool, UK. i.s.wood@liverpool.ac.uk

ABSTRACT
Hypoxia modulates the production of key inflammation-related adipokines and may underlie adipose tissue dysfunction in obesity. Here we have examined the effects of hypoxia on glucose transport by human adipocytes. Exposure of adipocytes to hypoxia (1% O(2)) for up to 24 h resulted in increases in GLUT-1 (9.2-fold), GLUT-3 (9.6-fold peak at 8 h), and GLUT-5 (8.9-fold) mRNA level compared to adipocytes in normoxia (21% O(2)). In contrast, there was no change in GLUT-4, GLUT-10 or GLUT-12 expression. The rise in GLUT-1 mRNA was accompanied by a substantial increase in GLUT-1 protein (10-fold), but there was no change in GLUT-5; GLUT-3 protein was not detected. Functional studies with [(3)H]2-deoxy-D-glucose showed that hypoxia led to a stimulation of glucose transport (4.4-fold) which was blocked by cytochalasin B. These results indicate that hypoxia increases monosaccharide uptake capacity in human adipocytes; this may contribute to adipose tissue dysregulation in obesity.

Show MeSH
Related in: MedlinePlus