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A brown fat cell. Yellow adipose tissue in paraffin. White fat cells contain a single large lipid droplet surrounded by a layer of cytoplasm, and are known as unilocular. The nucleus is flattened and pushed to the periphery. A typical fat cell is 0.1 um in diameter [2] with some being twice that
Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. [ 1 ] [ 2 ] It also contains the stromal vascular fraction ( SVF ) of cells including preadipocytes , fibroblasts , vascular endothelial cells and a variety of immune cells such as adipose tissue macrophages .
The adipokines, or adipocytokines (Greek adipo-, fat; cytos-, cell; and -kinos, movement) are cytokines (cell signaling proteins) secreted by adipose tissue.Some contribute to an obesity-related low-grade state of inflammation or to the development of metabolic syndrome, a constellation of diseases including, but not limited to, type 2 diabetes, cardiovascular disease and atherosclerosis. [1]
Lipid metabolism is often considered the digestion and absorption process of dietary fat; however, there are two sources of fats that organisms can use to obtain energy: from consumed dietary fats and from stored fat. [5] Vertebrates (including humans) use both sources of fat to produce energy for organs such as the heart to function. [6]
Although regulation of fat stores is deemed to be the primary function of leptin, it also plays a role in other physiological processes, as evidenced by its many sites of synthesis other than fat cells, and the many cell types beyond hypothalamic cells that have leptin receptors. Many of these additional functions are yet to be fully defined.
Common lipid signaling molecules: lysophosphatidic acid (LPA) sphingosine-1-phosphate (S1P) platelet activating factor (PAF) anandamide or arachidonoyl ethanolamine (AEA). Lipid signaling, broadly defined, refers to any biological cell signaling event involving a lipid messenger that binds a protein target, such as a receptor, kinase or phosphatase, which in turn mediate the effects of these ...
Epinephrine binds to a beta-adrenergic receptor in the cell membrane of the adipocyte, which causes cAMP to be generated inside the cell. The cAMP activates a protein kinase, which phosphorylates and thus, in turn, activates a hormone-sensitive lipase in the fat cell. This lipase cleaves free fatty acids from their attachment to glycerol in the ...
These include sphingosine-1-phosphate, a sphingolipid derived from ceramide that is a potent messenger molecule involved in regulating calcium mobilization, [71] cell growth, and apoptosis; [72] diacylglycerol and the phosphatidylinositol phosphates (PIPs), involved in calcium-mediated activation of protein kinase C; [73] the prostaglandins ...