Effect of warm or cold exposure on GDP binding and uncoupling protein in rat brown fat

Trayhurn, Paul; Ashwell, Margaret; Jennings, G.; Richard, Denis; Stirling, Dorothy M.

doi:10.1152/ajpendo.1987.252.2.e237

Cited by 54 publications

(41 citation statements)

References 18 publications

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“…The amount of UCP determined in rat mitochondria was 2-6-times smaller as compared to earlier reports [6][7][8][9][10][11]. UCP isolated by hydroxyapatite chromatography [5] has been used as a UCP standard and as antigen to develop UCP-specific serum (6-9, 30-321.…”

Section: Resultsmentioning

confidence: 76%

Effect of acclimation temperature on the concentration of uncoupling protein and GDP binding in rat brown fat mitochondria

Feil

Rafael

1994

European Journal of Biochemistry

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The effect of the acclimation temperature on the concentration of the uncoupling protein (UCP) and specific GDP binding in rat brown adipose tissue mitochondria was investigated. UCP was measured by competition ELISA using purified UCP as a standard and antiserum developed against the C-terminus of the protein. UCP was purified by means of specific polyclonal antibodies immobilized on protein-A-agarose. It represented 2.4% of the total protein in brown fat mitochondria from rats acclimated to 4°C and 1.1% in mitochondria from rats acclimated to 29°C. No UCP was found in liver mitochondria. The molar ratio of bound GDP and UCP was 0.5 in mitochondria from warmacclimated rats and 1 .O in cold-acclimated rats. The GDPKJCP ratio was increased from 0.5 to 1 . O after a 90-min exposure to 4°C of warm-acclimated rats; it was decreased from 1.0 to 0.5, when cold-acclimated rats were transferred to 29°C for 24 h. Treatment of mitochondrial membranes from warm-acclimated rats with 3 M urea at pH 10.0 increased the GDPAJCP ratio from 0.5 to 1.0. Specific GDP binding was a direct measure of the UCP concentration during maximally activated or inactivated thermogenesis in brown adipose tissue. We suggest that variable GDP binding reflects the functional activity of UCP based on different protein conformations.The uncoupling protein (UCP) [I] in brown adipose tissue mitochondria, also called thermogenin [2], allows for a transmembrane flow of protons and thus for a chemiosmotic short circuit that uncouples respiration from ATP synthesis and dissipates chemical energy into metabolic heat. Nucleotides like ATP, ADP, GTP and GDP, which are specifically bound by UCP, inhibit the proton flow and restore respiratory control in the isolated mitochondria (reviewed in [3, 41). Nucleotide interaction with UCP is also likely to regulate the protein function in vivo. UCP, isolated with Triton X-100, has been shown to bind one nucleotide molecule/protein dimer [5]. It is, however, unclear, if this relationship applies also to UCP in the mitochondrial membrane. The molar ratio of bound GDP and UCP in rat brown adipose tissue mitochondria reported in the literature varies extensively [6-111. The relationship is made even more unclear by the altered nucleotide binding observed in mitochondria with unchanged UCP concentrations in response to acute cold or other forms of stimulation of the sympathetic nervous system (reviewed in [12]). According to the latter finding, the stoichiometry of nucleotide binding by UCP corresponds to the thermogenic activity of brown adipose tissue and thus to the activity of UCP. From this point of view, knowledge of the exact relationship between UCP and specifically bound nucleotide seemed important with respect to the molecular mechanism of UCP function. It was the purpose of this study to clarify the stoichiometry of GDP binding by UCP in mitochondria from brown adipose tissue of rats exposed to varying environmental temperatures. MATERIALS AND METHODS AnimalsTen-week-old male Sprague Dawley rats were maintain...

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Section: Resultsmentioning

confidence: 76%

Effect of acclimation temperature on the concentration of uncoupling protein and GDP binding in rat brown fat mitochondria

Feil

Rafael

1994

European Journal of Biochemistry

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“…4,5 A similar loss of functioning BAT is observed in animals that have been maintained at thermoneutrality. [6][7][8] Altogether, these results suggest that mechanisms exist whereby b-agonists have the potential to promote postnatal changes in the WAT/BAT ratio, which could possibly induce weight loss in humans as is observed in laboratory animals such as adult dogs and rhesus monkeys. 9-14 These latter two species are similar to humans in that, unlike rodents, they do not retain large discrete depots of BAT in adulthood, yet they can still exhibit mixed white and brown adipocyte populations.…”

Section: Introductionmentioning

confidence: 76%

Positive and negative control of Ucp1 gene transcription and the role of β-adrenergic signaling networks

2010

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Adrenergic receptor signaling in adipocytes controls not only the hydrolysis of triglycerides as fuel for other organs but is also a driver of brown adipocyte thermogenesis and energy consumption. As the appearance of these mitochondria-rich, thermogenically active cells in 'white' adipocyte depots is correlated with resistance to overnutrition and glucose intolerance, the molecular basis of their genesis and metabolic activity needs to be understood. b-adrenergic receptors regulate the enzymatic machinery for lipolysis and fuel utilization. They also coordinately stimulate the transcription of genes that support the specific functions of white and brown adipocytes. They accomplish this through the activation of a network of signaling pathways that include cAMP-dependent protein kinase and members of the mitogen-activated protein kinase family. In brown adipocytes, these kinases control the transcription of nuclear factors such as peroxisome proliferator-activated receptor-g coactivator-1s, as well as other molecules discovered to respond to adrenergic signals, to increase mitochondrial biogenesis and uncoupling protein-1 (UCP1) expression. However, it is also important to understand the mechanisms that may actively repress these energy-wasting processes. Toward that end, we provide evidence for an important role for the nuclear receptor LXRa as a cAMP-and oxysterol-dependent transcriptional repressor of the Ucp1 gene. Adipocytes from LXRa-null mice have increased expression of most 'markers' of brown adipocytes, increased mitochondrial mass and uncoupled respiration. These studies reveal potential new targets and directions for controlling the relative levels of white versus brown adipocytes as a means of metabolic fuel utilization in the struggle against obesity and related metabolic diseases.

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“…Isolated mitochondria were obtained from this homogenate, as described by Nedergaard and Cannon. 12 3 H-GDP (New England Nuclear, Boston, MA) binding of 3 H-GDP to isolated mitochondria was assessed according to Trayhurn et al 13 Protein concentration was assessed on an aliquot of BAT mitochondria suspension using the micro bicinchonic acid (BCA) protein assay kit (Pierce, Rockford, IL). Results of mitochondria 3 H-GDP binding were expressed per mg protein.…”

Section: Analytical Proceduresmentioning

confidence: 99%

Stimulation by leptin of 3H GDP binding to brown adipose tissue of fasted but not fed rats

Surmely

Voirol²,

Stefanoni

et al. 1998

Int J Obes

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OBJECTIVES: To assess the effects of intracerebroventricular (icv) leptin administration on rats fed ad libitum or fasted on 3 H GDP binding to brown adipose tissue (BAT). SUBJECTS: Groups of 5 ± 6 ten-week-old male Wistar rats. EXPERIMENTAL DESIGN: An icv cannula was inserted and unilateral denervation of interscapular brown adipose tissue (BAT) was performed 5 d before each study. Thereafter, leptin was infused icv during 72 h while rats were fed ad libitum or fasted. Vehicle-infused, pair-fed or fasted rats were used as controls. MEASUREMENTS: 3 H GDP binding to innervated and denervated BAT mitochondria. RESULTS: 3 H GDP binding to innervated or denervated BAT of rats fed ab libitum compared to vehicle-infused, pair-fed rats was not increased by icv leptin. 3 H GDP binding was lower in fasted than in fed rats, and the difference was larger in innervated than denervated BAT. Icv leptin increased 3 H GDP binding by 30% in innervated, and by 51% in denervated BAT (P`0.05) in fasted rats. CONCLUSIONS: Icv leptin does not increase 3 H GDP binding to BAT of rats fed ad libitum compared to pair-fed (foodrestricted) rats. In contrast, icv leptin produces a mild stimulation of 3 H GDP binding to BAT of fasted rats. This effect is not mediated by the sympathetic nervous system, because it is observed in both innervated and denervated BAT. These results are compatible with the concept that, in fasting rats, the decrease in leptin secretion contributes to the reduction in 3 H GDP binding to BAT mitochondria.

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Effect of warm or cold exposure on GDP binding and uncoupling protein in rat brown fat

Cited by 54 publications

References 18 publications

Effect of acclimation temperature on the concentration of uncoupling protein and GDP binding in rat brown fat mitochondria

Effect of acclimation temperature on the concentration of uncoupling protein and GDP binding in rat brown fat mitochondria

Positive and negative control of Ucp1 gene transcription and the role of β-adrenergic signaling networks

Stimulation by leptin of 3H GDP binding to brown adipose tissue of fasted but not fed rats

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