Skeletal muscle uncoupling protein 3 expression is a determinant of energyexpenditure in Pima Indians

The recent discovery of uncoupling protein (UCP)-2 and UCP-3? and their hig h expression in skeletal muscle, has renewed interest in a possible role fo r these proteins in underlying the variability in energy expenditure and th erefore metabolic efficiency. Using reverse transcription-polymerase chain reaction, levels of expression of UCP-2 and long and short forms of UCP-3 w ere measured in skeletal muscle of 19 nondiabetic, male Pima Indians coveri ng a wide range of body weight. Twenty-four-hour energy expenditure was mea sured ill a respiratory chamber in IG of these indi viduals. BMI was negati vely correlated with the expression levels of the long (r = -0.53, P = 0.02 5) and short (r = -0.46, P = 0.047) forms of UCP-3. BMI was not correlated with UCP-2 expression. Metabolic rate during sleep, adjusted for fat-free m ass and fat mass, was positively correlated with the long form of UCP-3 (r = 0.69, P = 0.006). These results indicate that UCP-3 may be a determinant of energy expenditure and metabolic efficiency in Pima Indians.