Brown fat

Nicholls, D. G., and Rial, E., 1984. Brown fat mitochondria. Trends Biochemical Sciences 9 489—491. 

One of Alphapharm s witnesses further buttressed the court s conclusion, "acknowledging that [compound (2)] had the negative side effects of increased body weight and brown fat" and that "a compound with such side effects would presumably not be a suitable candidate for treatment of Type II diabetes [36]."... 

Thermogenin is a natural uncoupler found in the mitochondria of brown fat in hibernating animals and infants. 

Despite the high sensitivity of [ F]-FDG-PET false-positive findings—due to physiological processes such as brown fat, colonic and gynecologic activity, infectious and inflammatory processes and rebound thymic hyperplasia—pose a major challenge. 

Thermogenin In brown fat, forms proton-conducting pores in inner mitochondrial... 

There is a remarkable and instructive exception to the general rule that respiration slows when the ATP supply is adequate. Most newborn mammals, including humans, have a type of adipose tissue called brown fat in which fuel oxidation serves not to produce ATP but to generate heat to keep the newborn warm. This specialized adipose tissue is brown because of the presence of large numbers of mitochondria and thus large amounts of... 

FIGURE 19-30 Heat generation by uncoupled mitochondria. The uncoupling protein (thermogenin) of brown fat mitochondria, by providing an alternative route for protons to reenter the mitochondrial matrix, causes the energy conserved by proton pumping to be dissipated as heat. 

The mitochondria of brown fat are like those of other mammalian cells in all respects, except that they have a unique protein in their inner membrane. Thermogenin, also called the uncoupling protein (Table 19-4), provides a path for protons to return to the matrix without passing through the F0Fx complex (Fig. 19-30). 

As a result of this short-circuiting of protons, the energy of oxidation is not conserved by ATP formation but is dissipated as heat, which contributes to maintaining the body temperature of the newborn. Hibernating animals also depend on uncoupled mitochondria of brown fat to generate heat during their long dormancy (see Box 17-1). 

In brown fat, which is specialized for the production of metabolic heat, electron transfer is uncoupled from ATP synthesis and the energy of fatty acid oxidation is dissipated as heat. 

Human infants, and many hibernating animals, have adipose tissue called brown fat, which is specialized to generate heat rather than ATP during oxidation of fatty acids. Adult humans have very little brown fat tissue. 

The uncoupling protein is affected by several control mechanisms. It is inhibited by nucleotides such as GDP, GTP, ADP, and ATP which may bind at a site corresponding to that occupied by ATP or ADP in the ADP/ATP carrier.1 Uncoupling is stimulated by noradrenaline/ which causes a rapid increase in heat production by brown fat tissues, apparently via activation of adenylate cyclase. Uncoupling is also stimulated by fatty acids.) Recently UCP1 and related uncoupling proteins have been found to require both fatty acids and ubiquinone for activity.)) )k... 

Ernster, L. (ed.), Bioenergetics. Amsterdam Elsevier, 1984. A collection of reviews covering electron transport, the ATP-synthase, translocation of ions across the mitochondrial inner membrane, thermogenesis in brown fat, and other topics in bioenergetics. 

There have been repeated reports of epidural lipomatosis, which can lead to spinal cord compression (48,49) or spinal fracture (50) in one instance, the excised lipomata contained brown fat, a phenomenon that may prove to be not unusual in glucocorticoid-induced lipomata (SEDA-16, 451). 

Brown fat, however, can actually produce heat. This heat production is called thermogenesis. Brown fat cells contain a lot of mitochondria, also known as a cell s "power plant" because they are the primary source of energy in cells. The energy is produced during respiration. The presence of so many mitochondria within brown fat cells is the key to tissue s ability to produce heat. 

Palmer, Michael. Brown Fat Tissue. Metabolism. University of Waterloo. Available online. URL http //watcut.uwaterloo.ca/ webnotes/Metabolism/page-10.2.6.html. Accessed Dec. 17,2006. 

Mice fed a diet containing 0.05% of Glu-P-1 or Glu-P-2, or 0.08% of MeAaC, mainly developed hepatic tumors and hemangio-sarcomas In the brown fat tissue of the Interscapula (39). The Incidence of hepatic tumors produced by these three compounds was higher in females than in males, but the incidence of hemangio-sarcoma in males and females was similar. AaC also induced hepatic tumors and hemagiosarcomas by feeding. 

Nicotine is irritating to the digestive tract. Salivation increases, and the strength of stomach contractions decreases. Nausea and vomiting may occur. Appetite is suppressed, particularly in females for sweet food. Metabolism is increased and brown fat is stimulated, which along with appetite suppression can lead to weight loss. 

Brown fat is a form of adipose tissue found under the skin on the backs of many young animals. Mitochondria from this tissue have a P/O ratio of less than 1 for ATP synthesis arising from oxidation of NADH. What may be the physiological function of brown fat tissue ... 

From the above P/O ratio, it is clear that ATP synthesis in brown fat mitochondria is naturally uncoupled from electron transport. Hence, protons extruded from the mitochondria during electron transport must reenter without concomitant ATP synthesis. The energy released as heat during this reentry may help to keep the young animals warm. Such small organisms have a high surface-to-volume ratio and therefore readily lose heat through convective and radiative processes. 

Newborn babies contain brown fat in their necks and upper backs that serves the function of nonshivering thermogenesis. Muscle contractions that take place in the process of shivering use ATP and produce heat, but nonshivering thermogenesis is a hormonal stimulus for heat generation without the associated muscle contractions of shivering. 

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