Introduction

In the older subject and in the adult, the role of the brown adipose tissue is not clearly defined. However, multilocular cells typical of the brown adipose tissue persist in the adult. The brown adipose tissue belongs to the so-called “primary formation” type of fat; this first appears during fetal development. The increased penetration of glucose into the adipose cell enhances lipogenesis by promoting fatty acid synthesis and by producing the a-glycero-phosphate necessary to the esterification or reesterification of the intracellular fatty acids in triglycerides. The hydrolysis of intracellular triglycerides into glycerol and fatty acids is controlled by a lipase. The changes in metabolic activity with age and the variations in fatty acid composition of stored triglycerides will be discussed in detail further. Most of the fatty acids remain in the cell: part is oxidized into CO₂ and H₂O, and the rest is resynthesized into triglycerides.