|
Brown adipose tissue (BAT) or brown fat is one of two types of fat or adipose tissue (the other being white adipose tissue, or white fat) found in mammals. It is especially abundant in newborns and in hibernating mammals. Its primary function is to generate body heat in animals or newborns that do not shiver. In contrast to white adipocytes (fat cells), which contain a single lipid droplet, brown adipocytes contain numerous smaller droplets and a much higher number of (iron-containing) mitochondria, which make it brown. Brown fat also contains more capillaries than white fat, since it has a greater need for oxygen than most tissues. ==Development== Brown fat cells and muscle cells both seem to be derived from the same stem cells in the embryo. Both have the same marker on their surface (myogenic factor 5 (Myf5), which white fat cells do not have).〔 Brown fat cells and muscle cells both come from the middle embryo layer. The three layers of the embryo during the gastrulation stage are ectoderm, mesoderm, endoderm. Mesoderm is the source of myocytes (muscle cells), adipocytes, and chondrocytes (cartilage cells). Adipocytes give rise to white fat cells and brown fat cells. Researchers found that both muscle and brown fat cells expressed the same muscle factor Myf5, whereas white fat cells did not. This suggested that muscle cells and brown fat cells were both derived from the same type of stem cell. Furthermore, muscle cells that were cultured with the transcription factor PRDM16 were converted into brown fat cells, and brown fat cells without PRDM16 were converted into muscle cells.〔 However, there may be two types of brown fat cells—with and without Myf5. The other type, without Myf5, may share the same origin as white fat cells. They both seem to be derived from pericytes, the cells which surround the blood vessels that run through white fat tissue.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Brown adipose tissue」の詳細全文を読む スポンサード リンク
|