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Publication
Control of exercise-stimulated muscle glucose uptake by GLUT4 is dependent on
glucose phosphorylation capacity in the conscious mouse.
Authors Fueger PT, Hess HS, Posey KA, Bracy DP, Pencek RR, Charron MJ, Wasserman DH
Submitted By David Wasserman on 11/6/2007
Status Published
Journal The Journal of biological chemistry
Year 2004
Date Published
Volume : Pages 279 : 50956 - 50961
PubMed Reference 15456776
Abstract Previous work suggests that normal GLUT4 content is sufficient for increases in
muscle glucose uptake (MGU) during exercise because GLUT4 overexpression does
not increase exercise-stimulated MGU. Instead of glucose transport, glucose
phosphorylation is a primary limitation of exercise-stimulated MGU. It was
hypothesized that a partial ablation of GLUT4 would not impair
exercise-stimulated MGU when glucose phosphorylation capacity is normal but
would do so when glucose phosphorylation capacity was increased. Thus, C57BL/6J
mice with hexokinase II (HKII) overexpression (HK(Tg)), a GLUT4 partial
knock-out (G4(+/-)), or both (HK(Tg) + G4(+/-)) and wild-type (WT) littermates
were implanted with carotid artery and jugular vein catheters for sampling and
infusions at 4 months of age. After a 7-day recovery, 5-h fasted mice remained
sedentary or ran on a treadmill at 0.6 mph for 30 min (n = 9-12 per group) and
received a bolus of 2-deoxy[3H]glucose to provide an index of MGU (Rg). Arterial
blood glucose and plasma insulin concentrations were similar in WT, G4(+/-),
HKTg, and HKTg + G4(+/-) mice. Sedentary Rg values were the same in all
genotypes in all muscles studied, confirming that glucose transport is a
significant barrier to basal glucose uptake. Gastrocnemius and soleus Rg were
greater in exercising compared with sedentary mice in all genotypes. During
exercise, G4(+/-) mice had a marked increase in blood glucose that was corrected
by the addition of HK II overexpression. Exercise Rg (micromol/100g/min) was not
different between WT and G4(+/-) mice in the gastrocnemius (24 +/- 5 versus 21
+/- 2) or the soleus (54 +/- 6 versus 70 +/- 7). In contrast, the enhanced
exercise Rg observed in HKTg mice compared with that in WT mice was absent in
HKTg + G4(+/-) mice in both the gastrocnemius (39 +/- 7 versus 22 +/- 6) and the
soleus (98 +/- 13 versus 65 +/- 13). Thus, glucose transport is not a
significant barrier to exercise-stimulated MGU despite a 50% reduction in GLUT4
content when glucose phosphorylation capacity is normal. However, when glucose
phosphorylation capacity is increased by HK II overexpression, GLUT4
availability becomes a marked limitation to exercise-stimulated MGU.




Strains
StrainDevelopment StatusCreation MethodOptions
C57BL/6J-Slc2a4+/- Tg(Hk)Not Applicableknockout
View
C57BL/6J-Slc2a4tm1Mch/+ Tg(OE-Hk2)Not Applicableknockout
View
C57BL/6J-Slc2a4tm1Mch Tg(Hk2)Phenotyping ongoingtransgenic
View
C57BL/6J-Slc2a4tm1Mch Tg(OE-Hk2)Phenotyping ongoingknockout
View


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