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Proton leak and hydrogen peroxide production in liver mitochondria from energy-restricted rats

¹Department of Molecular Biosciences, University of California, Davis, California 95616; ²Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5; and ³Department of Medicine, University of Wisconsin, Madison, Wisconsin 53606

Submitted 23 June 2003 ; accepted in final form 10 September 2003

Energy restriction (ER), without malnutrition, is the only environmental intervention that consistently increases maximum life span in laboratory rodents. One theory proposes that a reduction in energy expenditure and reactive oxygen species production is the mechanism responsible for this action of ER. To further test this theory, proton leak, H₂O₂ production, lipid peroxidation, and protein carbonyls were measured in mitochondria from FBNF₁ rats fed either a control or 40% ER diet (onset at 6 mo of age). Liver mitochondria were isolated at 7 and 12 mo of age. Liver weight decreased 25 and 36% at 1 and 6 mo of ER, respectively (P < 0.05). ER resulted in an increase (P < 0.05) in percent total polyunsaturates, n-6 polyunsaturates, and total unsaturates (6 mo only) in mitochondrial lipids. These changes, however, were not associated with significant alterations in mitochondrial function. State 4 respiration and membrane potential were not different (P > 0.05) between groups at either assessment period. Similarly, proton leak kinetics were not different between control and ER animals. Top-down metabolic control analysis and its extension, elasticity analysis, were used at the 6-mo assessment and revealed no difference in control of the oxidative phosphorylation system between control and ER rats. H₂O₂ production with either succinate or pyruvate/malate substrates was also not different (P > 0.05) between groups at either time point. In conclusion, ER did not alter proton leak or H₂O₂ production at this age or stage of restriction in liver.

calorie restriction; energy expenditure; mitochondrial lipids; aging; oxidative stress

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