Diabetes and the accompanying hyperglycemia impairs cardiomyocyte calcium cycling through increased nuclear O-GlcNAcylation.
Diabetic cardiomyopathy is characterized by impaired cardiac contractility leading to poor myocardial performance. We investigated the role that the hexosamine pathway, and especially altered nuclear O-Glc-NAcylation, plays in the development of diabetic cardiomyopathy. Incubating neonatal rat cardiomyocytes in high glucose (25 mM) resulted in prolonged calcium transients when compared with myocytes incubated in normal glucose (5.5 mM), which is consistent with delayed myocardial relaxation. High glucose-treated myocytes also exhibited reduced sarcoendoplasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) mRNA and protein expression, decreased SERCA2a promoter activity, and increased O-GlcNAcylation of nuclear proteins compared with myocytes treated with normal glucose. Exposure of myocytes to 8 mM glucosamine or an adenovirus expressing O-GlcNAc-transferase (OGT) resulted in prolonged calcium transient decays and significantly reduced SERCA2a protein levels, whereas treatment with an adenovirus encoding O-GlcNAcase (GCA) resulted in improved calcium transients and SERCA2a protein levels in myocytes exposed to high glucose. Effects of elevated glucose or altered O-GlcNAcylation were also observed on essential transcription factors involved in cardiomyocyte function. High glucose-treated myocytes (with or without OGT adenovirus) exhibited increased levels of O-GlcNAcylated specificity protein 1 compared with control myocytes, whereas infecting high glucose-treated myocytes with GCA adenovirus reduced the degree of specificity protein 1 Glc-NAcylation. Treatment of myocytes with 25 mM glucose, 8 mM glucosamine, or OGT adenovirus also significantly reduced levels of myocytes enhancer factor-2A protein compared with control myocytes, whereas infection with GCA adenovirus resulted in improved myocytes enhancer factor-2 expression. Our results suggest that the hexosamine pathway, and O-GlcNAcylation in particular, is important in impaired cardiac myocyte function and the development of diabetic cardiomyopathy.
Clark
Raymond J
RJ
Department of Medicine, University of California San Diego, La Jolla, California 92093, USA.
McDonough
Patrick M
PM
Swanson
Eric
E
Trost
Susanne U
SU
Suzuki
Misa
M
Fukuda
Minoru
M
Dillmann
Wolfgang H
WH
D000118:Acetylglucosaminidase / Q000235:genetics / Q000378:metabolism; D000215:Acylation; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000032:analysis / Q000235:genetics; D009202:Cardiomyopathies / Q000209:etiology / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000032:analysis; D003921:Diabetes Mellitus, Experimental / Q000150:complications / Q000378:metabolism*; D005456:Fluorescent Dyes; D015870:Gene Expression; D005822:Genetic Vectors; D005944:Glucosamine / Q000378:metabolism* / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D006031:Glycosylation; D006595:Hexosamines / Q000378:metabolism; D051548:Histone Acetyltransferases; D006943:Hyperglycemia / Q000378:metabolism*; D007211:Indoles; D064326:MEF2 Transcription Factors; D009097:Multienzyme Complexes; D009206:Myocardium / Q000378:metabolism / Q000648:ultrastructure*; D018006:Myogenic Regulatory Factors; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D016329:Sp1 Transcription Factor / Q000032:analysis; D014157:Transcription Factors / Q000032:analysis; D014162:Transfection; D014530:Uridine Diphosphate / Q000032:analysis; D001619:beta-N-Acetylhexosaminidases
D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; D006595:Hexosamines; D007211:Indoles; D064326:MEF2 Transcription Factors; D009097:Multienzyme Complexes; D018006:Myogenic Regulatory Factors; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D014530:Uridine Diphosphate; D051548:Histone Acetyltransferases; D017351:N-Acetylglucosaminyltransferases; C449880:O-GlcNAc transferase; C110628:hexosaminidase C; D000118:Acetylglucosaminidase; D001619:beta-N-Acetylhexosaminidases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D005947:Glucose; D005944:Glucosamine; C048960:indo-1; D002118:Calcium