Adipocyte

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Brown fat cell

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Yellow adipose tissue in paraffin section - lipids washed out

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Lipoblast features, annotated

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Proteolytic activation of SREBF-controlled lipid biosynthesis

Adipocytes, also known as lipocytes or 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 through a process called adipogenesis. In humans, adipose tissue is located beneath the skin (subcutaneous fat), around internal organs (visceral fat), in bone marrow (yellow bone marrow), and in the breast tissue. Adipose tissue is found in specific locations, which are referred to as adipose depots. Adipocytes are crucial for energy storage, insulation, and cushioning of organs.

Structure and Function

Adipocytes contain a large lipid droplet surrounded by a thin layer of cytoplasm, with the nucleus pushed to one side by the lipid. There are two types of adipose tissue, white adipose tissue (WAT) and brown adipose tissue (BAT), which are made up of white and brown adipocytes, respectively. White adipocytes store energy in a large lipid droplet, while brown adipocytes contain numerous smaller droplets and a high number of mitochondria, enabling them to burn energy and generate heat (thermogenesis).

Adipogenesis

Adipogenesis is the process of cell differentiation by which preadipocytes become mature adipocytes. This process is regulated by a complex network of hormones and transcription factors, including PPARγ (peroxisome proliferator-activated receptor gamma) and C/EBPα (CCAAT/enhancer-binding protein alpha).

Role in Health and Disease

Adipocytes play a significant role in the body's metabolism. They not only store and release energy but also secrete various substances, including adipokines (such as leptin and adiponectin), which play roles in appetite regulation, insulin sensitivity, and inflammation. Dysregulation of adipocyte function can lead to metabolic disorders, such as obesity, type 2 diabetes, and cardiovascular disease. Obesity is characterized by an increase in the size (hypertrophy) and number (hyperplasia) of adipocytes.

Research and Clinical Implications

Understanding the function and regulation of adipocytes is crucial for developing treatments for obesity and related metabolic diseases. Research in adipocyte biology is focused on uncovering the mechanisms of adipogenesis, the effects of adipokines on the body's metabolism, and the interaction between adipocytes and other cell types.