Difference between revisions of "McFarlane 2017 Am J Physiol Regul Integr Comp Physiol"
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{{Publication | {{Publication | ||
|title=McFarlane SV, Mathers KE, Staples JF (2017) Reversible temperature-dependent differences in brown adipose tissue respiration during torpor in a mammalian hibernator. Am J Physiol Regul Integr Comp Physiol 312:R434-42. | |title=McFarlane SV, Mathers KE, Staples JF (2017) Reversible temperature-dependent differences in brown adipose tissue respiration during torpor in a mammalian hibernator. Am J Physiol Regul Integr Comp Physiol 312:R434-42. | ||
|info=[https://www.ncbi.nlm.nih.gov/pubmed/28077390] | |info=[https://www.ncbi.nlm.nih.gov/pubmed/28077390 PMID: 28077390] | ||
|authors=McFarlane SV, Mathers KE, Staples JF | |authors=McFarlane SV, Mathers KE, Staples JF | ||
|year=2017 | |year=2017 | ||
|journal=Am J Physiol Regul Integr Comp Physiol | |journal=Am J Physiol Regul Integr Comp Physiol | ||
|abstract=Although seasonal modifications of brown adipose tissue (BAT) in hibernators are well documented, we know little about functional regulation of BAT in different phases of hibernation. In the 13-lined ground squirrel, liver mitochondrial respiration is suppressed by up to 70% during torpor. This suppression is reversed during arousal and interbout euthermia (IBE), and corresponds with patterns of maximal activities of electron transport system ( | |abstract=Although seasonal modifications of brown adipose tissue (BAT) in hibernators are well documented, we know little about functional regulation of BAT in different phases of hibernation. In the 13-lined ground squirrel, liver mitochondrial respiration is suppressed by up to 70% during torpor. This suppression is reversed during arousal and interbout euthermia (IBE), and corresponds with patterns of maximal activities of electron transport system (ET-pathway) enzymes. Uncoupling of BAT mitochondria is controlled by free fatty acid release stimulated by sympathetic activation of adipocytes, so we hypothesized that further regulation at the level of the ET-pathway would be of little advantage. As predicted, maximal ET-pathway enzyme activities of isolated BAT mitochondria did not differ between torpor and IBE. In contrast to this pattern, respiration rates of mitochondria isolated from torpid individuals were suppressed by ~60% compared with rates from IBE individuals when measured at 37°C. At 10°C, however, mitochondrial respiration rates tended to be greater in torpor than IBE. As a result, the temperature sensitivity (Q10) of mitochondrial respiration was significantly lower in torpor (~1.4) than IBE (~2.4), perhaps facilitating energy savings during entrance into torpor and thermogenesis at low body temperatures. Despite the observed differences in isolated mitochondria, norepinephrine-stimulated respiration rates of isolated BAT adipocytes did not differ between torpor and IBE, perhaps because the adipocyte isolation requires lengthy incubation at 37°C, potentially reversing any changes that occur in torpor. Such changes may include remodeling of BAT mitochondrial membrane phospholipids, which could change ''in situ'' enzyme activities and temperature sensitivities. | ||
Copyright © 2017 the American Physiological Society. | Copyright © 2017 the American Physiological Society. | ||
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|preparations=Intact cells, Isolated mitochondria | |preparations=Intact cells, Isolated mitochondria | ||
|enzymes=Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase | |enzymes=Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase | ||
|topics=Temperature | |||
|couplingstates=LEAK, ROUTINE, OXPHOS | |couplingstates=LEAK, ROUTINE, OXPHOS | ||
|pathways=F, N | |pathways=F, N | ||
|instruments=Oxygraph-2k | |instruments=Oxygraph-2k | ||
}} | }} |
Latest revision as of 09:56, 29 November 2017
McFarlane SV, Mathers KE, Staples JF (2017) Reversible temperature-dependent differences in brown adipose tissue respiration during torpor in a mammalian hibernator. Am J Physiol Regul Integr Comp Physiol 312:R434-42. |
McFarlane SV, Mathers KE, Staples JF (2017) Am J Physiol Regul Integr Comp Physiol
Abstract: Although seasonal modifications of brown adipose tissue (BAT) in hibernators are well documented, we know little about functional regulation of BAT in different phases of hibernation. In the 13-lined ground squirrel, liver mitochondrial respiration is suppressed by up to 70% during torpor. This suppression is reversed during arousal and interbout euthermia (IBE), and corresponds with patterns of maximal activities of electron transport system (ET-pathway) enzymes. Uncoupling of BAT mitochondria is controlled by free fatty acid release stimulated by sympathetic activation of adipocytes, so we hypothesized that further regulation at the level of the ET-pathway would be of little advantage. As predicted, maximal ET-pathway enzyme activities of isolated BAT mitochondria did not differ between torpor and IBE. In contrast to this pattern, respiration rates of mitochondria isolated from torpid individuals were suppressed by ~60% compared with rates from IBE individuals when measured at 37°C. At 10°C, however, mitochondrial respiration rates tended to be greater in torpor than IBE. As a result, the temperature sensitivity (Q10) of mitochondrial respiration was significantly lower in torpor (~1.4) than IBE (~2.4), perhaps facilitating energy savings during entrance into torpor and thermogenesis at low body temperatures. Despite the observed differences in isolated mitochondria, norepinephrine-stimulated respiration rates of isolated BAT adipocytes did not differ between torpor and IBE, perhaps because the adipocyte isolation requires lengthy incubation at 37°C, potentially reversing any changes that occur in torpor. Such changes may include remodeling of BAT mitochondrial membrane phospholipids, which could change in situ enzyme activities and temperature sensitivities.
Copyright © 2017 the American Physiological Society. • Keywords: Q10, Electron transport system, Hibernation, Mitochondria, Uncoupled thermogenesis • Bioblast editor: Kandolf G • O2k-Network Lab: CA London Staples JF
Labels: MiParea: Respiration, Comparative MiP;environmental MiP
Stress:Temperature Organism: Other mammals Tissue;cell: Fat Preparation: Intact cells, Isolated mitochondria Enzyme: Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase Regulation: Temperature Coupling state: LEAK, ROUTINE, OXPHOS Pathway: F, N HRR: Oxygraph-2k