Adipose tissue is a specialized connective tissue consisting of lipid-rich cells called adipocytes. As it comprises about 20-25% of total body weight in healthy individuals, the main function of adipose tissue is to store energy in the form of lipids (fat). Based on its location, fat tissue is divided into parietal (under the skin) and visceral (surrounding organs). Depending on adipocyte morphology, there are two types of adipose tissue:
White adipose tissue - mainly found in adults
Brown adipose tissue - mainly found in newborns
Besides energy storing, fat tissue has several other important functions in the human body. These include thermal isolation, cushioning the organs, an endocrine role, and production of numerous bioactive factors.
Where is Adipose Tissue Located?
Adipose tissue is commonly known as body fat. It is found all over the body. It can be found under the skin (subcutaneous fat), packed around internal organs (visceral fat), between muscles, within bone marrow and in breast tissue. Men tend to store more visceral fat (fat around their internal organs), leading to obesity around the middle of their abdomen. However, women tend to store more subcutaneous fat within the buttocks and thighs. These differences are due to the sex hormones produced by males and females.
What Hormones Does Adipose Tissue Produce?
- A number of different hormones are released from adipose tissue and these are responsible for different functions within the body. Examples of these are:
- aromatase, which is involved in sex hormone metabolism
- TNF alpha, IL-6 and leptin, which are collectively termed ‘cytokines’ and are involved in sending messages between cells
- plasminogen activator inhibitor-1, which is involved in the clotting of blood
- angiotensin, which is involved in blood pressure control
- adiponectin, which improves the body’s sensitivity to insulin and so helps to protect against developing type 2 diabetes
- lipoprotein lipase and apolipoprotein E, which are involved in storage and metabolism of fat to release energy.