Ephedrine-Induced Thermogenesis in Man: No Role for Interscapular Brown Adipose Tissue

Abstract

The warmest interscapular skin areas were located by thermography in 6 healthy subjects during ephedrine-induced thermogenesis. In these intercapsular areas, and in lumbar control areas, the skin temperature, s.c. temperature and adipose tissue blood flow were measured before and during ephedrine-induced thermogenesis. The skin and s.c. temperatures increased in the interscapular area as well as in the lumbar area, by .apprx. 0.7.degree.-1.2.degree. C. The interscapular skin temperature remained .apprx. 1.degree. C higher than the lumbar; the s.c. temperatures in the 2 areas were identical during the experiments. Although the interscapular s.c. adipose tissue blood flow increased about 6-fold and the lumbar increased 2-fold, the absolute flows were higher in the lumbar area. The O2 uptake increased to a maximum of 30% above control level. Plasma glucose and glycerol concentrations remained unchanged, and plasma non-esterified fatty acids, lactate and noradrenaline [norepinephrine] concentrations increased slightly but significantly. Biopsies taken from the hot interscapular areas did not contain brown adipose tissue. The high interscapular skin temperature may be due to a lower insulating fat thickness and the increases in skin and s.c. temperatures during ephedrine-induced thermogenesis are caused by an increased blood flow. These observations weigh against the hypothesis that the interscapular temperature increase is due to functional, interscapular brown adipose tissue. [Implications for obesity are discussed.].