Adipose tissue plays critical roles in energy homeostasis, endocrine function, and the regulation of metabolic processes. It consists mainly of adipocytes but also includes a variety of other cell types such as preadipocytes, macrophages, and endothelial cells. The heterogeneity of adipose tissue is crucial for its functionality and is influenced by factors such as location (subcutaneous vs. visceral), hormonal signaling, and metabolic state.
Classification of Adipose Tissue
In mammals, there are two main types of adipose tissue: brown adipose tissue (BAT) and white adipose tissue (WAT).
- Brown Adipose Tissue (BAT): BAT develops from Myf5- and Pax7-expressing precursor cells in the mesoderm, which also contribute to skeletal muscle and some white adipocytes. Brown adipocytes are primarily located in the interscapular region and are characterized by multilocular lipid droplets and a high number of mitochondria, functioning mainly to dissipate energy as heat. While BAT was once thought to be limited to infants and adults exposed to extreme cold, recent findings indicate that brown adipocytes, as well as "beige" or "brite" adipocytes (which exhibit traits of both brown and white fat), may be more prevalent in adults than previously recognized.
- White Adipose Tissue (WAT): The majority of adipose tissue in mammals, including adult humans, is WAT, which is primarily composed of large adipocytes that harbor a single lipid droplet and markedly fewer mitochondria than brown adipocytes.
Functions of Adipose Tissue
The use of human frozen tissue sections has opened new avenues for research in adipose biology:
- Understanding Metabolic Regulation
- Investigating Adipocyte Differentiation
- Evaluating Therapeutic Targets
