Proposed regulation of gene expression by glucose in rodent heart.
BACKGROUND
During pressure overload-induced hypertrophy, unloading-induced atrophy, and diabetes mellitus, the heart induces 'fetal' genes (e.g. myosin heavy chain beta; mhc beta).


OBJECTIVE
We propose that altered glucose homeostasis within the cardiomyocyte acts as a central mechanism for the regulation of gene expression in response to environmental stresses. The evidence is as follows.


RESULTS
Forced glucose uptake both ex vivo and in vivo results in mhc isoform switching. Restricting dietary glucose prevents mhc isoform switching in hearts of both GLUT1-Tg mice and rats subjected to pressure overload-induced hypertrophy. Thus, glucose availability correlates with mhc isoform switching under all conditions investigated. A potential mechanism by which glucose affects gene expression is through O-linked glycosylation of specific transcription factors. Glutamine:fructose-6-phosphate amidotransferase (GFAT) catalyzes the flux generating step in UDP-N-acetylglucosamine biosynthesis, the rate determining metabolite in protein glycosylation. Ascending aortic constriction increased intracellular levels of UDP-N-acetylglucosamine, and the expression of gfat2, but not gfat1, in the rat heart.


CONCLUSIONS
Collectively, the results strongly suggest glucose-regulated gene expression in the heart, and the involvement of glucose metabolites in isoform switching of sarcomeric proteins characteristic for the fetal gene program.
Young
Martin E
ME
USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas, USA.
Yan
Jie
J
Razeghi
Peter
P
Cooksey
Robert C
RC
Guthrie
Patrick H
PH
Stepkowski
Stanislaw M
SM
McClain
Donald A
DA
Tian
Rong
R
Taegtmeyer
Heinrich
H