Techniques for the measurement of white adipose tissue metabolism: a practical guide.

A number of old and new techniques to study various aspects of white adipose tissue metabolism in vivo and in vitro are discussed. It is possible to determine lipolysis rates in vivo with tracer techniques using glycerol or fatty acids labelled with stable or radioactive isotopes. These methods allow the determination of whole body lipolysis rates but are not valuable for the investigations of regional variations in lipolysis. When combined they permit a calculation of the rate of re-esterification of free fatty acids. The vein draining abdominal subcutaneous adipose tissue can be cannulated in humans. By this method substrate turnover can be determined in vivo over the cannulated adipose region. With microdialysis it is possible to study local metabolism in vivo in different adipose tissue regions. At the same time it is possible to locally manipulate the tissue with metabolically active pharmacological substances. A number of in vitro methods to determine glucose transport in isolated fat cells are developed. The most accurate one uses 3-O-methyl glucose as tracer. These methods can be combined with studies of the further metabolism of glucose to lipids, lactate and carbon dioxide using simple (usually radioactive) methods. Lipolysis as well as release and re-esterification of free fatty acids can be investigated in detailed in vitro with sensitive techniques based on luminescence. Finally, triglyceride turnover and partial metabolism of acylglycerols can be investigated in vitro with a double isotope technique.