Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes, osteoblasts, myocytes and other cell types through adipogenesis.
There are two types of adipose tissue, white adipose tissue (WAT) and brown adipose tissue (BAT), which are also known as white fat and brown fat, respectively, and comprise two types of fat cells. Most recently, the presence of beige adipocytes with a gene expression pattern distinct from either white or brown adipocytes has been described.
White fat cells or monovacuolar cells contain a large lipid droplet surrounded by a layer of cytoplasm. The nucleus is flattened and located on the periphery. A typical fat cell is 0.1 mm in diameter with some being twice that size and others half that size. The fat stored is in a semi-liquid state, and is composed primarily of triglycerides and cholesteryl ester. White fat cells secrete many proteins acting as adipokines such as resistin, adiponectin, leptin and apelin. An average human adult has 30 billion fat cells with a weight of 30 lbs or 13.5 kg. If excess weight is gained as an adult, fat cells increase in size about fourfold before dividing and increasing the absolute number of fat cells present
The Origin of Stem Cells The origin of stem cells includes human mesenchymal stem cells which are cells with the capacity to differentiate into, among other tissues, osteocytes, adipocytes, and chondrocytes (cartilage producing cells). The isolation and characterization of mesenchymal stem cells occurred decades ago (1966). It wasn’t much longer before scientist began to study […]