Ann Anat ;Sep. Histologically, there are four types of fat tissue cells which are currently recognized white, brown, beige, and perivascular adipocytes. Therefore, in this study we are reviewing the most recent data regarding the origin, structure, and molecular mechanisms involved in the development of adipocytes.
White adipocytes can store triglycerides as a consequence of lipogenesis, under the regulation of growth hormone or leptin and adiponectin, and release fatty acids resulted from lipolysis, under the regulation of the sympathetic nervous system, glucocorticoids, TNF-α, insulin, and natriuretic peptides.
Brown adipocytes possess a mitochondrial transmembrane protein thermogenin or UCP1 which allows heat generation.
Recently, thermogenic, UCP positive adipocytes have been identified in the subcutaneous white adipose tissue and have been named beige adipocytes. The nature of these cells is still controversial, as current theories are suggesting their origin either by transdifferentiation of white adipocytes, or by differentiation from an own precursor cell.
Perivascular adipocytes surround most of the arteries, exhibiting a supportive role and being papillary thyroid cancer diffuse sclerosing variant in the maintenance of intravascular temperature. Thoracic perivascular adipocytes resemble brown adipocytes, while abdominal ones papillary thyroid cancer diffuse sclerosing variant more similar to white adipocytes and, consequently, are involved in obesity-induced inflammatory reactions.
The factors involved in the regulation of adipose stem cells differentiation may represent potential pathways to inhibit or to divert adipogenesis.
Further investigations are necessary to complete the knowledge about adipose tissue and the development of a new generation of therapeutic tools based on molecular targets.