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. 2009 Feb;322(1-2):81-6.
doi: 10.1007/s11010-008-9942-y. Epub 2008 Nov 14.

Munc18c is not rate-limiting for glucose and long-chain fatty acid uptake in the heart

Daphna D J Habets  1 , Debbie C Thurmond, Will A Coumans, Arend Bonen, Jan F C Glatz, Joost J F P Luiken
Affiliations

Munc18c is not rate-limiting for glucose and long-chain fatty acid uptake in the heart

Daphna D J Habets et al. Mol Cell Biochem. 2009 Feb.

Abstract

The role of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)- and SNARE-associated proteins have not yet been assessed in regulation of cardiac glucose uptake, nor in the regulation of long-chain fatty acid (LCFA) uptake in any tissue. Munc18c is a SNARE-associated protein that regulates GLUT4 translocation in skeletal muscle and adipose tissue. Using cardiomyocytes from Munc18c(-/+) mice (with 56% reduction of Munc18c protein expression), we investigated whether this syntaxin4-associated protein is involved in regulation of cardiac substrate uptake. Basal, insulin- and oligomycin (a 5' AMP-activated protein kinase-activating agent)-stimulated glucose and LCFA uptake were not altered significantly in Munc18c(-/+) cardiomyocytes compared to wild-type cells. We conclude, therefore, that Munc18c is not rate-limiting for cardiac substrate uptake, neither under basal conditions nor when maximally stimulated metabolically.

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Figures

Fig. 1
Fig. 1
Effects of oligomycin and insulin on GLUT4 and CD36 expression at the sarcolemma. Cardiomyocytes (n = 4) from WT mice were incubated for 20 min in the absence (Ctrl) or presence of 1 µmol/l oligomycin (Oli) or 100 nmol/l insulin (Ins) whereafter biotin-labeled (cell surface) GLUT4 and CD36, and total cellular GLUT4 and CD36 were determined. A representative Western Blot is displayed
Fig. 2
Fig. 2
Munc18c, GLUT4, and CD36 expression in cardiomyocytes from WT and Munc18c−/+ mice and the effects of oligomycin and insulin treatment on phosphorylation of AMPK, ACC, and PKB. WT and Munc18c−/+ cardiomyocytes were used to determine Munc18c, and GAPDH (loading control) expression (panel a), and after incubation for 20 min in the absence (Ctrl) or presence of 1 µmol/l oligomycin (Oli) or 100 nmol/l insulin (Ins) phospho-AMPK (Thr172), phospho-ACC (Ser79), phospho-PKB (Ser473) (panel b) by Western blotting. A representative Western blot is presented out of five experiments with different cardiomyocyte preparations
Fig. 3
Fig. 3
Effects of oligomycin and insulin stimulation on deoxyglucose and palmitate uptake in cardiomyocytes from WT and Munc18c−/+ mice. WT (□) and Munc18c−/+ cardiomyocytes (■) were incubated for 20 min in the absence (Ctrl) or presence of 1 µmol/l oligomycin (Oli) or 100 nmol/l insulin (Ins) whereafter uptake rates of 3H-deoxyglucose (panel a) and 14C-palmitate (panel b) and were measured. Data are means ± SEM for 10 experiments carried out with different cardiomyocyte preparations. *Significantly different from Ctrl (P < 0.05)
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References

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