P. Schrauwen et al., A novel polymorphism in the proximal UCP3 promoter region: effect on skeletal muscle UCP3 mRNA expression and obesity in male nondiabetic Pima Indians, INT J OBES, 23(12), 1999, pp. 1242-1245
OBJECTIVE: UCP2 and UCP3 are newly discovered uncoupling proteins, which ar
e thought to underlie the variability in energy metabolism in humans. Mutat
ions in the UCP2 and/or UCP3 gene have been associated with sleeping metabo
lic rate. Recently we reported that skeletal muscle UCP3 mRNA expression wa
s positively correlated with sleeping metabolic rate in Pima Indians. To st
udy whether genetic variation in the promoter region of UCP3 contributed to
the variation in expression of UCP3, we screened part of the proximal prom
oter region for polymorphisms.
METHODS: In the first part of the study, the proximal promoter region of UC
P3 was screened by direct sequencing in 24 non-diabetic Pima Indians (range
body mass index (BMI): 18- 47 kg/m(2)) (Schrauwen et al. Diabetes 1999; 48
: 146-149) and skeletal muscle UCP3 mRNA expression was measured by RT-PCR.
In the second part of the study, we typed the polymorphism found in the fi
rst part of the study in 67 Pima Indians (32 males, 35 females) from the up
per and lower extremes of the BMI distribution.
RESULTS: We identified a novel C to T substitution in the UCP3 promoter, 6b
p upstream of the putative TATA signal, and 55bp upstream of the transcript
ion starting site, Among 18 male subjects, skeletal muscle UCP3 mRNA expres
sion was significantly higher in the C/T & T/T group compared to the C/C ho
mozygotes (P < 0.02). However, in the group of 67 Pima Indians genotype fre
quencies were not different in the obese and lean groups.
CONCLUSION: We identified a novel polymorphism in the proximal promoter reg
ion of UCP3, which was associated with increased skeletal muscle expression
of UCP3 in male non-diabetic Pima Indians. Considering the suggested role
of UCP3 in energy metabolism, this polymorphism might be of physiological i
mportance in the regulation of energy balance.