Mitochondrial uncoupling proteins in energy expenditure

Four recently discovered homologues of the brown adipose tissue-specific mi tochondrial uncoupling protein (UCP1) vary from 29% to 58% in their similar ity to UCP1. Although these homologues share important structural features with UCP1 and like UCP1 can reduce the mitochondrial membrane potential whe n expressed in yeast, there is no clear evidence that they can function the rmogenically in vivo. On the other hand, evidence continues to accumulate i ndicating that the upregulation of Ucp1 reduces excessive adiposity.