THE CHARACTERIZATION AND ENERGETIC POTENTIAL OF BROWN ADIPOSE-TISSUE IN MAN

In the adult man, brown fat is detected in perinephric fat depots by visual inspection, EM and nucleotide binding to the tissue-specific uncoupling protein. The 32 kdalton uncoupling protein is functionally active, showing a nucleotide-sensitive conductance to protons and uncoupling response to fatty acids. The amount of uncoupling protein in human mitochondria is equivalent to that in a partially cold-adapted guinea pig, indicating some potential for thermogenesis. Respiratory capacity measurements indicate that the total perinephric fat in adult man can only account for 1/500 of the whole-body response to infused noradrenaline [norepinephrine]. Although brown fat was quantitatively important in animal studies, considerable caution must be exercised in extrapolating its significance to adult man.