Cold-induced changes in the energy coupling and the UCP3 level in rodent skeletal muscles

Simonyan, Ruben A.; Jiménez, María; Ceddia, Rolando B.; Giacobino, Jean‐Paul; Muzzin, Patrick; Vp, Skulachev

doi:10.1016/s0005-2728(01)00168-2

Cited by 53 publications

(44 citation statements)

References 35 publications

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“…3A'), thus suggesting that, under this experimental condition, PUCP may be insensitive to ATP in DWM from stressed seedlings (see also Trono et al 2006). At this regard, lower UCP sensitivity to nucleotides as a result of stress has been already observed in mitochondria from cold-stressed rat skeletal muscle (Simonyan et al 2001) and dehydrated slices of Jerusalem artichoke tubers (Paventi et al 2006). In the light of this, it appears unlikely that any change of ATP concentration occurring under stress conditions may modulate PUCP, whereas one can assume that the loss of sensitivity to ATP is the key factor for PUCP activation.…”

Section: Determination Of Cef-atp Contentmentioning

confidence: 72%

A new simple fluorimetric method to assay cytosolic ATP content: application to durum wheat seedlings to assess modulation of mitochondrial potassium channel and uncoupling protein activity under hyperosmotic stress

et al. 2013

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Abstract:The assays commonly used to determine ATP content in biological samples generally measure total cellular ATP content, but not the different subcellular pools. In this study a new simple method for measuring ATP content in a cytosol-enriched fraction (CEF) was developed, based on a rapid cytosolic ATP extraction (by an isotonic grinding medium that preserves organelle integrity) and its detection monitoring the NADPH fluorescence generated via hexokinase/glucose-6-phosphate dehydrogenase coupled reactions. Four protocols, differing for timing of NADPH generation and for either the presence or absence of some inhibitors of ATP and NADPH metabolism, were compared by determining CEF-ATP, as well as total ATP, in durum wheat (Triticum durum Desf.) etiolated seedlings. The best protocol was the one adopting both simultaneous NADPH generation and use of inhibitors during tissue homogenization. This protocol also showed higher performance than the classical trichloroacetic acid extraction. Using the new method, CEF-ATP content was assessed in control, salt-and osmotic-stressed seedlings, resulting 2.68 ± 0.04, 1.69 ± 0.12 (−40%) and 1.35 ± 0.16 (−50%) µmol/g dry weight, respectively. Finally, the effects of this stress-dependent decrease of cytosolic ATP were evaluated with respect to a possible modulation of two mitochondrial energy-dissipating systems, the uncoupling protein (PUCP) and the K + channel (PmitoKATP), both inhibited by cytosolic ATP. Experiments carried out at different physiological ATP concentrations suggest that the decreased cytosolic ATP content occurring under hyperosmotic stress may contribute to attenuate inhibition of PmitoKATP, thus promoting its activity (up to about 90%), but not of PUCP, that appears to lose ATP sensitivity under stress condition.

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Section: Determination Of Cef-atp Contentmentioning

confidence: 72%

A new simple fluorimetric method to assay cytosolic ATP content: application to durum wheat seedlings to assess modulation of mitochondrial potassium channel and uncoupling protein activity under hyperosmotic stress

et al. 2013

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“…It is possible that this thermogenesis is caused by an increased amount of UCP3 that, through its uncoupling action, is responsible for the heat production. Indeed, it has consistently been found that acute hyperthyroidism is associated with an increased level of UCP3 mRNA and UCP3 protein in muscle (Gong et al 1997;Larkin et al 1997;Lanni et al 1999;Barbe et al 2001;de Lange et al 2001;Short et al 2001;Simonyan et al 2001), and there is evidence of altered mitochondrial parameters (increased mitochondrial membrane permeability, i.e. 'uncoupling') in muscle mitochondria from hyperthyroid animals (Lanni et al 1999;de Lange et al 2001).…”

Section: Ucp2/ucp3 Are the Mediators Of Thyroid Thermogenesismentioning

confidence: 99%

The ‘Novel’‘Uncoupling’ Proteins UCP2 and UCP3: What Do They Really do? Pros and Cons for Suggested Functions

Nedergaard¹,

Cannon

2003

Experimental Physiology

207

150

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The scientifically novel, but evolutionarily ancient, so‐called uncoupling proteins 2 and 3 (UCP2, UCP3) are structually similar to the archetypical uncoupling protein UCP1. A series of suggestions have been forwarded for their physiological function. We discuss systematically here the pros and cons for these suggestions. We conclude that the novel UCPs do not seem to be physiologically relevant uncoupling proteins; the uncoupling property was apparently a late introduction into the subfamily through the evolution of UCP1. Physiological functions ascribed to UCP2 and UCP3 based on their purported uncoupling property may have to be revised (i.e. any type of thermogenesis, including protection against obesity, protection against the formation of reactive oxygen species and thermogenic involvement in the fever response). The presence of a mixed genetic background in most published studies of UCP2 or UCP3 gene‐ablated mice also means that data concerning marked differences in diabetes propensity, infection sensitivity and production of reactive oxygen species may require confirmation in backcrossed mice. The increased expression of UCP2 and UCP3 under conditions of increased fatty acid metabolism implies an as yet undefined role in lipid metabolism. Thus, the novel UCPs should probably be considered as mitochondrial carriers, and the challenge now is to identify the transported molecule.

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“…A natural candidate for such a role would be OE itself, which is well known as a weak mitochondrial uncoupler (34). To test this hypothesis, we titrated mitochondrial membrane potential in the control and OE-exposed permeabilized MIN6 cells with OE (35,36). Typical titration kinetics (Fig.…”

Section: Effect Of Oleate Exposure On Insulin Secretion-incubationmentioning

confidence: 99%

Mitochondrial Functional State in Clonal Pancreatic β-Cells Exposed to Free Fatty Acids

Koshkin

Wang

Scherer

et al. 2003

Journal of Biological Chemistry

115

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Excessive free fatty acid (FFA) exposure represents a potentially important diabetogenic condition that can impair insulin secretion from pancreatic ␤-cells. Because mitochondrial oxidative phosphorylation is a main link between glucose metabolism and insulin secretion, in the present work we investigated the effects of the FFA oleate (OE) on mitochondrial function in the clonal pancreatic ␤-cell line, MIN6. Both the long term (72 h) and short term (immediately after application) impact of OE exposure on ␤-cells was investigated. After 72 h of exposure to OE (0.4 mM, 0.5% bovine serum albumin) cells were washed and permeabilized, and mitochondrial function (respiration, phosphorylation, membrane potential formation, production of reactive oxygen species) was measured in the absence or presence of OE. MIN6 cells exposed to OE for 72 h showed impaired glucose-stimulated insulin secretion and decreased cellular ATP. Mitochondria in OE-exposed cells retained normal functional characteristics in FFA-free medium; however, they were significantly more sensitive to the acute uncoupling effect of OE treatment. The mitochondria of OE-exposed cells displayed increased depolarization caused by acute OE treatment, which is attributable to the elevation in the FFA-transporting function of uncoupling protein 2 and the dicarboxylate carrier. These cells also had an increased production of reactive oxygen species in complex I of the mitochondrial respiratory chain that could be activated by FFA. A high level of reduction of respiratory complex I augmented acute FFA-induced uncoupling in a way compatible with activation of mitochondrial uncoupling protein by intramitochondrial superoxide. A stronger augmentation was observed in OE-exposed cells. Together, these events may underlie FFA-induced depression of the ATP/ADP ratio in ␤-cells, which accounts for the defective glucose-stimulated insulin secretion associated with lipotoxicity.Chronic elevation of circulating free fatty acids (FFAs) 1 is associated with obesity and type 2 diabetes. Long term exposure of insulin-secreting pancreatic ␤-cells to elevated concentrations of FFAs alters glucose-induced insulin secretion and is considered as an important factor in the pathogenesis of diabetes (1-3). In pancreatic ␤-cells, mitochondrial oxidative phosphorylation is a crucial intermediate between glucose metabolism and insulin secretion (4, 5), and thus the effect of fatty acids on the functional state of mitochondria in this cell type is an important area of investigation.Previous work demonstrated that fatty acids applied for 48 -72 h cause partial uncoupling of oxidative phosphorylation (decreased mitochondrial membrane potential and ATP content and increased respiration) (1, 6). Although fatty acids are natural weak uncouplers of oxidative phosphorylation, a direct uncoupling effect of fatty acids on ␤-cell mitochondria was considered as unlikely since these effects were observed after long term (48 -72 h) but not short term (15 min-2 h) application (1, 6). Instead, alteration...

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Cold-induced changes in the energy coupling and the UCP3 level in rodent skeletal muscles

Cited by 53 publications

References 35 publications

A new simple fluorimetric method to assay cytosolic ATP content: application to durum wheat seedlings to assess modulation of mitochondrial potassium channel and uncoupling protein activity under hyperosmotic stress

A new simple fluorimetric method to assay cytosolic ATP content: application to durum wheat seedlings to assess modulation of mitochondrial potassium channel and uncoupling protein activity under hyperosmotic stress

The ‘Novel’‘Uncoupling’ Proteins UCP2 and UCP3: What Do They Really do? Pros and Cons for Suggested Functions

Mitochondrial Functional State in Clonal Pancreatic β-Cells Exposed to Free Fatty Acids

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