UCP3 regulates cardiac efficiency and mitochondrial coupling in high fat-fed mice but not in leptin-deficient mice - PubMed (original) (raw)

. 2012 Dec;61(12):3260-9.

doi: 10.2337/db12-0063. Epub 2012 Aug 21.

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UCP3 regulates cardiac efficiency and mitochondrial coupling in high fat-fed mice but not in leptin-deficient mice

Sihem Boudina et al. Diabetes. 2012 Dec.

Abstract

These studies investigate the role of uncoupling protein 3 (UCP3) in cardiac energy metabolism, cardiac O(2) consumption (MVO(2)), cardiac efficiency (CE), and mitochondrial uncoupling in high fat (HF)-fed or leptin-deficient mice. UCP3KO and wild-type (WT) mice were fed normal chow or HF diets for 10 weeks. Substrate utilization rates, MVO(2), CE, and mitochondrial uncoupling were measured in perfused working hearts and saponin-permeabilized cardiac fibers, respectively. Similar analyses were performed in hearts of ob/ob mice lacking UCP3 (U3OB mice). HF increased cardiac UCP3 protein. However, fatty acid (FA) oxidation rates were similarly increased by HF diet in WT and UCP3KO mice. By contrast, MVO(2) increased in WT, but not in UCP3KO with HF, leading to increased CE in UCP3KO mice. Consistent with increased CE, mitochondrial coupling was increased in the hearts of HF-fed UCP3KO mice. Unexpectedly, UCP3 deletion in ob/ob mice reduced FA oxidation but had no effect on MVO(2) or CE. In addition, FA-induced mitochondrial uncoupling was similarly enhanced in U3OB compared with ob/ob hearts and was associated with elevated mitochondrial thioesterase-1 protein content. These studies show that although UCP3 may mediate mitochondrial uncoupling and reduced CE after HF feeding, it does not mediate uncoupling in leptin-deficient states.

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Figures

FIG. 1.

FIG. 1.

UCP3 deletion does not alter cardiac FA oxidation but increases CE during HF feeding. A: Representative Western blot of cardiac UCP3 protein content and the corresponding densitometry normalized to Coomassie Blue staining in WT and UCP3 knockout mice fed NC or HF diet for 10 weeks. n = 4 per genotype and per feeding condition. B: Palmitate oxidation. C: MVO2. D: Percent CE. E: Cardiac power in the hearts of WT and UCP3 knockout mice fed NC or HF for 10 weeks. n = 6 per genotype for NC and n = 7–8 per genotype for HF. Data are means ± SEM. An unpaired, two-tailed Student t test was used to compare the groups in A. B–E: A two-way ANOVA was performed to analyze differences by diet and by genotype, including Bonferroni post hoc test, when significant interaction occurred. **P < 0.005 vs. diet (NC vs. HF); #P < 0.05 UCP3KOHF vs. WTHF. AU, arbitrary units; WHW, wet heart weight; DHW, dry heart weight. *P < 0.05 vs. diet (NC vs. HF).

FIG. 2.

FIG. 2.

UCP3 deletion in the heart increases mitochondrial ATP/O ratios upon HF feeding. A: Mitochondrial respiration. B: ATP synthesis rate. C: ATP/O ratios in saponin-permeabilized cardiac fibers using palmitoyl-carnitine as substrate. Mice were fed NC or HF diet for 10 weeks, and hearts were not preperfused. n = 5 per genotype for NC and n = 5–6 per genotype for HF. Data are means ± SEM. Two-way ANOVA was performed to analyze differences between diet and genotype, followed by Bonferroni post hoc test when significant interaction occurred. *P < 0.05; **P < 0.005 for diet (NC vs. HF). mgdw, milligrams dry weight.

FIG. 3.

FIG. 3.

Impact of UCP3 deletion in ob/ob mice on body weight, heart weight, and glucose homeostasis. A: Representative immunoblot and the corresponding densitometry of UCP3 protein normalized to Coomassie Blue staining. B: Body weights. C: Fasting blood glucose levels. D: Glucose tolerance tests. E: Heart weights of WT, UCP3KO, ob/ob, and U3OB mice at 20 weeks of age. n = 4–5 per group for Western blots. n = 8 for WT, n = 13 for UCP3KO, n = 6–9 for ob/ob, and n = 6–8 for U3OB for all other measurements. *P < 0.05; **P < 0.005 vs. WT; +P < 0.05; ++P < 0.005 vs. UCP3KO; #P < 0.05; ##P < 0.005 vs. ob/ob.

FIG. 4.

FIG. 4.

UCP3 deletion in ob/ob mice reduces myocardial palmitate oxidation, cardiac power, and CE. A: Palmitate oxidation. B: MVO2. C: Cardiac power. D: Percent CE in WT, UCP3KO, ob/ob, and U3OB mice at 20 weeks of age (n = 7 per genotype). Data are means ± SEM. *P < 0.05 WT; +P < 0.05 UCP3KO; #P < 0.05 vs. ob/ob. WHW, wet heart weight.

FIG. 5.

FIG. 5.

FA-induced mitochondrial uncoupling persists in U3OB hearts. A: V0 (no ADP). B: VADP (1 mmol/L exogenous ADP). C: Voligo (1 μg/mL of the ATP synthase inhibitor oligomycin). D: ATP synthesis rate. E: ATP/O ratios in saponin-permeabilized cardiac fibers using palmitoyl-carnitine as substrate. Hearts were preperfused in the Langendorff mode with 11 mmol/L glucose and 1 mmol/L palmitate for 30 min prior to mitochondrial respiration measurements (n = 8 for WT, n = 7 for UCP3KO, n = 5 for ob/ob, and n = 9 for U3OB). Data are means ± SEM. *P < 0.05 vs. WT; +P < 0.05 vs. UCP3KO. mgdw, milligrams dry weight.

FIG. 6.

FIG. 6.

Increased MTE-1 protein expression in ob/ob and U3OB hearts. A and B: Representative Western blots of ANT and the MTE-1 in whole-heart homogenates of WT, UCP3KO, ob/ob, and U3OB mice. C and D: Densitometry relative to tubulin and Coomassie Blue staining, respectively (n = 5 per genotype for ANT blot and n = 6 per genotype for MTE-1 blot). Data are means ± SEM. *P < 0.05; **P < 0.005 vs. WT; +P < 0.05 vs. UCP3KO. AU, arbitrary units.

FIG. 7.

FIG. 7.

ROS levels and oxidative modifications in the hearts of WT and UCP3KO mice on HF diet or in the ob/ob background. A: DCF fluorescence in heart homogenates from WT and UCP3KO mice fed NC or HF diet for 10 weeks (n = 6 per group and per diet). B: Representative Western blot and the corresponding densitometry of 4-HNE adduct products normalized to Coomassie Blue staining. C: Representative Western blot and densitometry of 4-HNE abundance in heart homogenates from WT, UCP3KO, ob/ob, and U3OB mice (n = 5 per genotype). Data are means ± SEM. Two-way ANOVA was performed for A and B to analyze differences by diet and genotype, including Bonferroni post hoc test when significant interaction occurred. *P < 0.05; **P < 0.005 vs. NC of the same genotype; ##P < 0.05 for UCP3KONC vs. WTNC. AU, arbitrary units.

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