Uncoupling protein-1 mRNA expression in obese human subjects: the role of sequence variations at the uncoupling protein-1 gene locus.
Uncoupling protein-1 (UCP-1) activity in brown adipose tissue increases thermogenesis, contributes to facultative energy expenditure in humans, and has been implicated in the pathogenesis of rodent obesity. To determine genetic factors controlling UCP-1 expression in humans, we measured intra- and extraperitoneal UCP-1 mRNA abundance levels by a competitive RT-PCR method and compared expression levels with common sequence variations in the beta3-adrenergic receptor gene and the distal UCP-1 gene promoter in obese human subjects. While median and average UCP-1 mRNA levels in both the intra- and extraperitoneal tissue were lower in subjects heterozygous for the Trp64Arg mutation in the beta3-adrenergic receptor gene, this difference was not statistically significant. However, a strong association of intraperitoneal UCP-1 mRNA abundance with the UCP-1 gene polymorphism at -3826 relative to the transcription start site was observed that explained 19.3% of the interindividual variability. The minor allele imparted a dose-dependent reduction on UCP gene expression. The importance of sequence variations at the UCP-1 gene locus as a common source of UCP-1 mRNA abundance variability was supported by allele-specific expression studies utilizing a newly identified polymorphism in exon 2 of the UCP-1 gene that predicts a substitution of alanine by threonine. In four subjects heterozygous for the -3826 polymorphism, the mRNA species transcribed from the wild-type allele accounted for 63+/-6% percent of total intraperitoneal mRNA abundance. In one subject homozygous for the minor promoter allele, wild-type mRNA was also more abundant than variant mRNA. Thus, the UCP-1 polymorphism at -3826 is probably only a marker for a frequent mutation causing reduced mRNA expression.
Esterbauer
H
H
Department of Laboratory Medicine, Landeskrankenanstalten Salzburg, Austria.
Oberkofler
H
H
Liu
Y M
YM
Breban
D
D
Hell
E
E
Krempler
F
F
Patsch
W
W
D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D002352:Carrier Proteins / Q000235:genetics*; D015252:Deoxyribonucleases, Type II Site-Specific; D005260:Female; D005838:Genotype; D006801:Humans; D007473:Ion Channels; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D024101:Mitochondrial Proteins; D009767:Obesity, Morbid / Q000235:genetics*; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis*; D011943:Receptors, Adrenergic, beta / Q000235:genetics; D022702:Receptors, Adrenergic, beta-3; D000071256:Uncoupling Protein 1; D044465:White People
D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D022702:Receptors, Adrenergic, beta-3; C000604371:UCP1 protein, human; D000071256:Uncoupling Protein 1; C066171:endodeoxyribonuclease AciI; C041666:endodeoxyribonuclease BclI; D015252:Deoxyribonucleases, Type II Site-Specific