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First published online August 8, 2008
Journal of Experimental Biology 211, 2689-2699 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.013714
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Effects of dietary polyunsaturated fatty acids on mitochondrial metabolism in mammalian hibernation

Alexander R. Gerson*, Jason C. L. Brown, Raymond Thomas, Mark A. Bernards and James F. Staples

Department of Biology, University of Western Ontario, London, Ontario, Canada, N6A 5B8


Figure 1
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  		Fig. 1. Typical output from a TPP+-sensitive electrode during calibration and the measurement of membrane potential of liver mitochondria isolated from a summer active ground squirrel. Mitochondria (1 mg protein) were incubated with rotenone (5 µmoll–1), nigericin (80 ng ml–1) and oligomycin (1 µg ml–1) after which TPP+ electrodes were calibrated by five additions of TPP+, each of which raised [TPP+] by 1 µmoll–1. Addition of succinate initiated nonphosphorylating respiration, which was subsequently inhibited with five additions of malonate (0.5 µmoll–1). Oxygen consumption was monitored simultaneously. FCCP was added at the conclusion of the assay to uncouple respiration completely, releasing unbound TPP+ from the mitochondrial matrix and allowing for correction of electrode drift.

 

Figure 2
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  		Fig. 2. The effect of temperature and dietary PUFA on liver mitochondrial state 3 respiration rates from hibernating and summer active Spermophilus tridecemlineatus. (A) 16 mg g–1 18:2 (hibernating N=8, summer active N=6), (B) 22mgg–1 18:2 (hibernating N=8, summer active N=6), (C) 35 mg g–1 18:2 (hibernating N=8, summer active N=5) and (D) 55 mg g–1 18:2 (hibernating N=6, summer active N=4). * indicates a significant difference between hibernation and summer active at the same assay temperature. Values are means ± s.e.m.

 

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  		Fig. 3. The effect of temperature and dietary PUFA on liver mitochondrial state 4 respiration rates from hibernating and summer active Spermophilus tridecemlineatus. (A) 16 mg g–1 18:2 diet (hibernating N=8, summer active N=6), (B) 22 mg g–1 18:2 diet (hibernating N=8, summer active N=6) (C) 35 mg g–1 18:2 diet (hibernating N=8, summer active N=5) and (D) 55 mg g–1 18:2 diet (hibernating N=6, summer active N=4). No significant differences were evident. Values are means ± s.e.m.

 

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  		Fig. 4. The effect of hibernation and dietary 18:2 on the kinetics of proton leak in liver mitochondria. * indicates significant differences in maximal membrane potential (no malonate; the upper-right point of each curve). (A) 16 mg g–1 18:2 diet (hibernating N =8, summer active N =6), (B) 22 mg g–1 18:2 diet (hibernating N=8, summer active N=6), (C) 35 mg g–1 18:2 diet (hibernating N=8, summer active N=5) and (D) 55 mg g–1 18:2 diet (hibernating N=6, summer active N=4). Values are means ± s.e.m.

 

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  		Fig. 5. Estimated liver mitochondrial proton conductance at a membrane potential of 130 mV. Proton conductance was determined as proton leak rate mV–1 at 130 mV. Two-way ANOVA showed a significant difference between summer active and hibernating animals (indicated by *). No significant differences were found among diet groups within the summer active and hibernating states. Values are means ± s.e.m. Number of individuals is the same as for Fig. 4.

 

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  		Fig. 6. Correlations between mitochondrial membrane conductance and the quantity of a specific mitochondrial phospholipid fatty acid. Unfilled circles indicate samples from hibernating animals; filled circles indicate samples from summer active animals. Lines represent a statistically significant relationship within hibernators.

 

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  		Fig. 7. Substrate oxidation generates the proton motive force ({Delta}P), which can then be utilized to power reactions related to the phosphorylation of ADP under state 3 conditions or to drive the leak of protons through the inner mitochondrial membrane under conditions of low ATP turnover (state 4).

 

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© The Company of Biologists Ltd 2008