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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Brown adipose tissue (BAT) is a major site of nonshivering thermogenesis (NST) during cold acclimation for most mammals. Repetitive nonthermal stress such as immobilization has been shown to enhance the capacity of NST as cold acclimation. In the present study, the effects of running training, another type of nonthermal stress, were investigated on in vitro thermogenesis and the cellularity of interscapular BAT in rats. The rats were subjected to treadmill running for 30 min daily at 30m/min under 8 degrees inclination for 4-5 weeks. In vitro thermogenesis was then measured in minced tissue blocks incubated in a Krebs-Ringer phosphate buffer containing glucose and albumin at 37 degrees C, using a Clark type oxygen electrode. The trained rats showed less body weight gain during the experiment. The weights of BAT and epididymal white adipose tissue were smaller in the trained rats. Noradrenaline- and glucagon-stimulated oxygen consumption were also significantly smaller in the trained rats. The tissue DNA level was greater in the trained rats, but the DNA content per tissue pad did not significantly differ. The results indicate that running training reduces BAT thermogenesis, possibly as an adaptation to conserve energy substrates for physical work.
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PMID:Effects of running training on in vitro brown adipose tissue thermogenesis in rats. 163 84

Brown adipose tissue (BAT) glucagon level was higher in cold-acclimated rats (CA) than in warm controls (WC). Noradrenaline (NA) injection increased BAT glucagon levels in both WC and CA with increases in plasma glucagon levels. The magnitude of increase was significantly greater in CA for plasma glucagon, while it did not differ for BAT between groups. However, BAT glucagon was kept at a higher level in CA after NA injection than in WC.
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PMID:Noradrenaline-induced changes in rat brown adipose tissue glucagon. 276 Nov 24

Resting oxygen consumption was elevated by 30% in young rats fed a cafeteria diet compared with their chow-fed controls and by 22% in cafeteria-fed, adrenalectomized (ADX) rats compared with the ADX chow-fed group, but injection of propranolol reduced oxygen consumption in the cafeteria-fed animals and abolished these differences. Brown adipose tissue (BAT) mass was increased by cafeteria feeding, and the activity of the mitochondrial proton conductance pathway (assessed from purine nucleotide binding) was enhanced by adrenalectomy and by cafeteria feeding. Norepinephrine turnover in BAT (determined from the time-dependent loss of tissue [3H]norepinephrine specific activity) was increased by 105% in sham-operated, cafeteria-fed rats, by 142% in chow-fed ADX rats, and by 400% in cafeteria-fed ADX rats, compared with chow-fed controls. Cardiac norepinephrine turnover was elevated by 80% in sham-operated, cafeteria-fed rats, but unaffected by adrenalectomy. These data indicate that the enhanced thermogenesis and BAT activity induced by adrenalectomy in chow- or cafeteria-fed rats is due to increased sympathetic activity in the tissue.
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PMID:Thermogenesis and sympathetic activity in BAT of overfed rats after adrenalectomy. 345 37

Brown adipocytes from cold-adapted guinea-pigs (C-cells) are more sensitive to uncoupling by exogenous palmitate than are cells from warm-adapted animals (W-cells) with much less uncoupling protein. Half-maximal respiratory stimulation of C-cells requires 80 nM free palmitate. Noradrenaline-stimulated lipolysis is not rate-limiting for the respiration of either C-cells or W-cells. Half-maximal stimulation of fatty acid oxidation by mitochondria from warm-adapted guinea-pigs (W-mitochondria) and cold-adapted guinea-pigs (C-mitochondria) both require 12 nM free palmitate. Palmitate uncouples C-mitochondria much more readily than M-mitochondria, paralleling its action on the adipocytes. The uncoupling is partially saturable, about 100 nM free palmitate being required for half-maximal response of C-mitochondria. W- and C-mitochondria show identical binding characteristics for palmitate. The respiratory increase of mitochondria is calculated as a function of bound palmitate. After correcting for the residual uncoupling protein present in W-mitochondria, palmitate is estimated to be almost ineffective as an uncoupler of brown fat mitochondria in the absence of the protein. It is concluded that fatty acids display characteristics required of a necessary and sufficient physiological activator of the uncoupling protein.
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PMID:Quantification of fatty acid activation of the uncoupling protein in brown adipocytes and mitochondria from the guinea-pig. 370 41

1. Exposure of new-born rabbits to the cold leads to an increase in the incorporation of [(14)C]glucose into the glycerol of brown-fat triglyceride, but has no effect on [(14)C]glucose incorporation into triglyceride of white fat or liver. The effect of cold exposure on brown-fat triglyceride is abolished by cutting the cervical sympathetic nerve. 2. Brown fat incorporates very little [(14)C]glucose into triglyceride fatty acids, either in vivo or in vitro. 3. Noradrenaline added to incubations of brown fat from new-born rabbits stimulates O(2) consumption, CO(2) output and incorporation of glucose into triglyceride glycerol. The effects of noradrenaline in vitro are therefore consistent with the hypothesis that noradrenaline mediates the response of the brown fat of new-born rabbits to cold exposure. 4. Glycerokinase is present in the brown fat of new-born rabbits, but its activity is much less than that of the glycerokinase in the brown fat of adult rats. 5. Insulin has no effect on O(2) consumption, CO(2) output or glucose uptake in brown fat of new-born rabbits. 6. It is concluded that the thermogenic response of new-born rabbits to cold exposure is accompanied by a selective acceleration of the triglyceride cycle in brown fat. However, resynthesis of triglyceride would not account for more than 1% of the O(2) consumed in vitro by new-born rabbit brown fat in the presence of noradrenaline if respiration remains coupled to phosphorylation.
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PMID:A comparison between the effects of cold exposure in vivo and of noradrenaline in vitro on the metabolism of the brown fat of new-born rabbits. 548 44

An investigation of the mechanisms of norepinephrine action and heat production in brown adipose tissue from newborn rabbits has been carried out. Data obtained with the use of biochemical techniques has been correlated with morphological data from electron microscopy. Norepinephrine was found to stimulate the respiration of brown fat in vitro. Inhibitors of glycolysis abolish this effect, whereas inhibitors of oxidative phosphorylation do not, at least not to the same extent. Brown fat is readily permeable to added Krebs cycle intermediates. Substrate level phosphorylation, but no electron transport-coupled phosphorylation, could be demonstrated in isolated mitochondria. It is suggested that the rate of fatty acid oxidation is limited by the availability of phosphate acceptor systems which break down ATP formed at the substrate level and thus provide ADP for further substrate level phosphorylation. The theory of respiratory control by the action of reesterification of fatty acids is discussed in the light of these findings. Under the electron microscope, brown fat mitochondria are characterized by their large size, tightly packed cristae, and by the different types of granules in the matrix. No elementary particles are seen when the mitochondria are examined by the negative-staining technique. The absence of electron transport-coupled phosphorylation together with the apparent absence of elementary particles seems to be of particular significance.
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PMID:Studies of the mitochondrial energy-transfer system of brown adipose tissue. 603 37

To determine the effects of cafeteria feeding on brown (BAT) and white (WAT) adipose tissue cellularity, thermogenesis and body composition, male Sprague-Dawley rats were fed a cafeteria or a Purina chow diet for 52 days postweaning. Interscapular BAT (IBAT) was removed from subgroups of rats on each diet, and the animals continued on the same regimens. The IBAT weight of rats fed cafeteria diets was 160% of controls after 3 days and 220% after 52 days of the dietary regimens, and brown adipocyte numbers were 130 and 300% those of stock diet-fed rats, respectively, during the same period. Brown adipocyte diameters were initially greater in rats fed cafeteria diet than in rats fed stock diet but were similar after 52 days. Norepinephrine-stimulated thermogenesis was greater in rats fed cafeteria diets than in rats fed stock diet and was intermediate between the two in the IBAT-lipectomized group fed cafeteria diet. Surgical reduction of IBAT resulted in hypertrophy of WAT and an improved efficiency of weight gain, whereas body composition, WAT cellularity, and the efficiency of weight gain of similarly operated rats fed stock diet were unaltered from those of unoperated animals fed stock diet. These results are consistent with the development of a nutritionally induced hyperplasia and/or differentiation of BAT similar to that which follows cold acclimatization. BAT may play an active role in the expenditure of excess energy during periods of overnutrition, and thereby influence an animal's propensity for fatness.
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PMID:Effect of cafeteria feeding on brown and white adipose tissue cellularity, thermogenesis, and body composition in rats. 714 7

Two modes of heat production exist which are involved in body temperature regulation with decreasing environmental temperature: shivering thermogenesis and more efficient nonshivering thermogenesis (NST). Enhanced NST is mediated by the activated sympathetic nervous activity and increased secretions of hormonal factors such as glucagon through an enhanced lipid utilization. Moreover, cold acclimation causes an increased responsiveness of the organism to these factors. Noradrenaline-induced secretion of glucagon is also enhanced by cold acclimation. Chronic administration of glucagon simulates cold acclimation, resulting in an improved cold tolerance by an increased NST. Brown adipose tissue (BAT) is a major site for nonshivering thermogenesis (NST) during metabolic cold acclimation. Cold acclimation causes a hyperplasia as well as an enhanced metabolic capacity of BAT cell. BAT function is mainly regulated by sympathetic noradrenaline and several hormonal factors such as glucagon. BAT possesses rich blood supply by which its high thermogenic capacity and an efficient transfer of heat are maintained. Noradrenaline and glucagon increases not only heat production, but also blood flow in BAT. Nitric oxide (NO), endothelium-derived relaxing factor, is involved in noradrenaline-, glucagon- and cold-induced increases of blood flow through BAT. Noradrenaline-induced BAT thermogenesis is suggested to be mediated by NO. NO synthase occurs in BAT cell in addition to endothelium of BAT vessel. These findings indicate that NO may be a signalling molecule for an enhanced NST during cold acclimation. Moreover, BAT contributes to adaptation to overfeeding, nonthermal stress and fever by means of producing heat, playing a role as adaptive organ in overall energy metabolism.
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PMID:[Regulation of thermoregulatory thermogenesis]. 774 60

The uncoupling protein (UCP) or thermogenin is a 33 kDa inner-membrane mitochondrial protein exclusive to brown adipocytes in mammals that functions as a proton transporter, allowing the dissipation as heat of the proton gradient generated by the respiratory chain and thereby uncoupling oxidative phosphorylation. Thermogenesis (heat production) in brown adipose tissue, which is activated in response to cold exposure or chronic overeating, depends largely on UCP activity. Norepinephrine, released from sympathetic terminals and acting via beta-adrenoceptors and cAMP, is the main positive regulator of both UCP synthesis and activity. Brown fat thermogenesis plays a critical role in thermoregulation and in overall energy balance, at least in rodents. Manipulation of thermogenesis, whether through UCP or through analogous uncoupling proteins, could be an effective strategy against obesity.
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PMID:The uncoupling protein, thermogenin. 959 49

We aimed to investigate whether infra red thermography (IRT) can be used to measure and quantify non-shivering thermogenesis (NST) in the short-tailed field vole Microtus agrestis, by directly comparing it with a standard method, i.e. metabolic response following Noradrenaline injection (NA). Mean skin surface temperature overlying Brown adipose tissue (BAT) depot was 0.82 degrees C higher than mean surface temperature that did not overly BAT. The difference in temperature increased by 1.26 degrees C after NA was administered. Mean skin surface temperature overlying BAT increased by 0.32 degrees C after NA was administered; however, surface temperature decreased by 1.32 degrees C after saline was administered. Mean skin surface temperature overlying BAT did not change significantly between warm and cold acclimated voles; in contrast metabolic peak following NA injection significantly increased in cold acclimated voles. There was no significant correlation between change in surface temperature after NA injection and metabolic peak following NA injection. The results of this study suggest that IRT is not a sensitive enough method to measure changes in NST capacity in BAT following NA injection, or to detect changes in NST capacity induced by cold acclimation. However, IRT can distinguish between skin surfaces overlying BAT and skin surfaces that do not.
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PMID:Can non-shivering thermogenesis in brown adipose tissue following NA injection be quantified by changes in overlying surface temperatures using infrared thermography? 1116 23


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