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Thermogenesis is the process of heat production in organisms.It occurs in all warm-blooded animals, and also in a few species of thermogenic plants such as the Eastern skunk cabbage, the Voodoo lily (Sauromatum venosum), and the giant water lilies of the genus Victoria.
However, brown adipose tissue is highly specialized for this non-shivering thermogenesis. First, each cell has a higher number of mitochondria compared to more typical cells. Second, these mitochondria have a higher-than-normal concentration of thermogenin in the inner membrane.
Non-exercise activity thermogenesis (NEAT), also known as non-exercise physical activity (NEPA), [1] is energy expenditure during activities that are not part of a structured exercise program. NEAT includes physical activity at the workplace, hobbies, standing instead of sitting, walking around, climbing stairs, doing chores, and fidgeting .
The second is non-shivering, which occurs in brown adipose tissue. [19] Population studies have shown that the San tribe of Southern Africa and the Sandawe of Eastern Africa have reduced shivering thermogenesis in the cold, and poor cold-induced vasodilation in fingers and toes compared to that of Caucasians. [5]
The lipase converts triacylglycerols into free fatty acids, which activate UCP1, overriding the inhibition caused by purine nucleotides (GDP and ADP). During the termination of thermogenesis, thermogenin is inactivated and residual fatty acids are disposed of through oxidation, allowing the cell to resume its normal energy-conserving state.
BMP7 not only stimulates brown adipogenesis, [20] [21] it also stimulates the "browning" of brite or beige adipocytes, turning them from a white-like phenotype into a brown-like phenotype (with induction of UCP1 and able to perform non-shivering thermogenesis, which allows to disperse energy as heat).
In addition, shivering also signals the body to produce irisin, a hormone that has been shown to convert white fat to brown fat, which is used in non-shivering thermogenesis, the second type of human thermogensis. [27] Non-shivering thermogenesis occurs in the brown fat, which contains the uncoupling protein thermogenin.
Specific dynamic action (SDA), also known as thermic effect of food (TEF) or dietary induced thermogenesis (DIT), is the amount of energy expenditure above the basal metabolic rate due to the cost of processing food for use and storage. [1]