Mitochondrial antioxidative capacity regulates muscle glucose uptake in the conscious mouse: effect of exercise and diet - PubMed (original) (raw)

Mitochondrial antioxidative capacity regulates muscle glucose uptake in the conscious mouse: effect of exercise and diet

Li Kang et al. J Appl Physiol (1985). 2012.

Abstract

The objective of this study was to test the hypothesis that exercise-stimulated muscle glucose uptake (MGU) is augmented by increasing mitochondrial reactive oxygen species (mtROS) scavenging capacity. This hypothesis was tested in genetically altered mice fed chow or a high-fat (HF) diet that accelerates mtROS formation. Mice overexpressing SOD2 (sod2(Tg)), mitochondria-targeted catalase (mcat(Tg)), and combined SOD2 and mCAT (mtAO) were used to increase mtROS scavenging. mtROS was assessed by the H(2)O(2) emitting potential (JH(2)O(2)) in muscle fibers. sod2(Tg) did not decrease JH(2)O(2) in chow-fed mice, but decreased JH(2)O(2) in HF-fed mice. mcat(Tg) and mtAO decreased JH(2)O(2) in both chow- and HF-fed mice. In parallel, the ratio of reduced to oxidized glutathione (GSH/GSSG) was unaltered in sod2(Tg) in chow-fed mice, but was increased in HF-fed sod2(Tg) and both chow- and HF-fed mcat(Tg) and mtAO. Nitrotyrosine, a marker of NO-dependent, reactive nitrogen species (RNS)-induced nitrative stress, was decreased in both chow- and HF-fed sod2(Tg), mcat(Tg), and mtAO mice. This effect was not changed with exercise. Kg, an index of MGU was assessed using 2-[(14)C]-deoxyglucose during exercise. In chow-fed mice, sod2(Tg), mcat(Tg), and mtAO increased exercise Kg compared with wild types. Exercise Kg was also augmented in HF-fed sod2(Tg) and mcat(Tg) mice but unchanged in HF-fed mtAO mice. In conclusion, mtROS scavenging is a key regulator of exercise-mediated MGU and this regulation depends on nutritional state.

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Figures

Fig. 1.

Fig. 1.

Protein expression of SOD2 and catalase. Western blotting of SOD2 (A) and catalase (B) in mitochondria isolated from gastrocnemius muscle in mice after chow or high-fat diet (HF) feeding for 16 wk. Integrated intensities of bands are listed below each band and are represented as means ± SE. Data are normalized to chow-fed wild type (WT). V-DAC expression was not affected by genotype or HF feeding and was used as a loading control. N is equal to 3–8, and *P < 0.05 compared with chow-fed WT.

Fig. 2.

Fig. 2.

Antioxidant capacity in chow-fed mice. A and B: muscle mitochondrial H2O2 emitting potential (_J_H2O2) was measured in permeabilized gastrocnemius fiber bundles prepared from sedentary chow-fed WT, _sod2_Tg, _mcat_Tg, and mtAO mice. J_H2O2 was measured either in response to increasing succinate concentrations (A) or 25 μM palmitoyl-carnitine and 2 mM malate (B) during state 4 respiration (10 μg/ml oligomycin). C: GSH/GSSG ratio was determined in muscle homogenates. D: protein expression of nitrotyrosine was detected by immunohistochemistry in gastrocnemius. Representative images were displayed and the magnification of images was ×20. E: nitrotyrosine protein was quantified by the integrated intensity of staining and normalized to WT chow. Data are expressed as means ± SE and n = 3–9 for each group. ξ_P < 0.05 for genotype effect compared with WT. *P < 0.05 compared with chow-fed WT.

Fig. 3.

Fig. 3.

Metabolic responses to treadmill exercise in chow-fed mice. A and B: arterial glucose concentrations either at sedentary or during exercise were measured by a glucose meter in chow-fed mice. C: Kg was determined in gastrocnemius using the nonmetabolizable glucose analog 2-[14C]-deoxyglucose during the sedentary (Sed) or treadmill exercise (Ex) study in mice fed chow diet. D: muscle glycogen content was measured by an enzymatic assay in gastrocnemius collected immediately after the sedentary or exercise study from mice fed chow diet. E: AMPK activity was determined in gastrocnemius muscle collected immediately after the sedentary or exercise study. F: HKII and GLUT4 expression in muscle homogenates. Integrated intensities of bands are listed below each band. Data are expressed as means ± SE and n = 7–12 for blood glucose and Kg measurements, 4–5 for muscle glycogen and AMPK activity measurements, n = 3 for HKII and GLUT4 expression. *P < 0.05 compared with WT within Sed or Ex. +P < 0.05 compared with Sed within a genotype.

Fig. 4.

Fig. 4.

Antioxidant capacity in HF-fed mice. A and B: muscle mitochondrial H2O2 emitting potential (_J_H2O2) was measured in permeabilized gastrocnemius fiber bundles prepared from sedentary HF-fed WT, _sod2_Tg, _mcat_Tg, and mtAO mice. J_H2O2 was measured either in response to increasing succinate concentrations (A) or 25 μM palmitoyl-carnitine and 2 mM malate (B) during state 4 respiration (10 μg/ml oligomycin). C: GSH/GSSG ratio was determined in muscle homogenates. D: protein expression of nitrotyrosine was detected by immunohistochemistry in gastrocnemius. Representative images were displayed and the magnification of images was ×20. E: nitrotyrosine protein was quantified by the integrated intensity of staining and normalized to WT chow. Data are expressed as means ± SE and n = 3–9 for each group. ξ_P < 0.05 for genotype effect compared with WT. *P < 0.05 compared with HF-fed WT.

Fig. 5.

Fig. 5.

Metabolic responses to treadmill exercise in HF-fed mice. A and B: arterial glucose concentrations either at sedentary or during exercise were measured by a glucose meter in HF-fed mice. C: Kg was determined in gastrocnemius using the nonmetabolizable glucose analog 2-[14C]-deoxyglucose during the sedentary (Sed) or treadmill exercise (Ex) study in mice fed HF diet. D: muscle glycogen content was measured by an enzymatic assay in gastrocnemius muscle collected immediately after the sedentary or exercise study from mice fed HF diet. E: AMPK activity was determined in gastrocnemius muscle collected immediately after the sedentary or exercise study. F: HKII and GLUT4 expression in muscle homogenates. Integrated intensities of bands are listed below each band. Data are expressed as means ± SE and n = 7–12 for blood glucose and Kg measurements, 4–5 for muscle glycogen and AMPK activity measurements, n = 3 for HKII and GLUT4 expression. *P < 0.05 compared with WT within Sed or Ex. +P < 0.05 compared with Sed within a genotype.

Fig. 6.

Fig. 6.

Proposed models for how SOD2 overexpression influences mitochondrial H2O2 production in muscle of sedentary chow- and HF-fed mice. A: superoxide anion (O2˙−), predominantly generated from complex I and III of the electron transport chain (ETC) in mitochondria is removed by 3 processes: 1) reaction catalyzed by SOD2 that produces one half of H2O2 per O2˙− molecule consumed; 2) reactions that produce one or more H2O2 per O2˙−; and 3) reactions that do not produce any H2O2 molecules. H2O2 is then broken down to H2O and O2 by antioxidant enzymes, such as catalase targeted to mitochondria (mCAT) and glutathione peroxidase (GPx). A thicker line represents a greater reactivity. _k_2 and _k_3 are rate constants for reactions 2 and 3. B: as SOD2 concentration increases, the steady-state concentration of O2˙− decreases and the flux of O2˙− consumption shifts from reactions 2 and 3 to reaction 1. Dashed lines represent reduced reactions and bold lines represent increased reactions. C: on a HF diet, both steady-state levels of O2˙− and H2O2 are increased. We propose that O2˙− removal is reliant on reaction 2 in HF-fed WT mice. Enlarged fonts represent increased concentrations and reduced fonts represent decreased concentrations. D: in HF-fed _sod2_Tg mice, mitochondrial H2O2 production is reduced compared with HF-fed WT mice, attributable to the shift from reaction 2 that produces one or more H2O2 to reaction 1 that produces only one-half of H2O2 per molecule of O2˙−.

Comment in

References

    1. Abdul-Ghani MA, DeFronzo RA. Pathogenesis of insulin resistance in skeletal muscle. J Biomed Biotechnol 2010: 476279, 2010 - PMC - PubMed
    1. Anderson EJ, Lustig ME, Boyle KE, Woodlief TL, Kane DA, Lin CT, Price JW, 3rd, Kang L, Rabinovitch PS, Szeto HH, Houmard JA, Cortright RN, Wasserman DH, Neufer PD. Mitochondrial H2O2 emission and cellular redox state link excess fat intake to insulin resistance in both rodents and humans. J Clin Invest 119: 573–581, 2009 - PMC - PubMed
    1. Asha Devi S, Prathima S, Subramanyam MV. Dietary vitamin E and physical exercise: I. Altered endurance capacity and plasma lipid profile in ageing rats. Exp. Gerontol 38: 285–290, 2003 - PubMed
    1. Ayala JE, Bracy DP, Julien BM, Rottman JN, Fueger PT, Wasserman DH. Chronic treatment with sildenafil improves energy balance and insulin action in high fat-fed conscious mice. Diabetes 56: 1025–1033, 2007 - PubMed
    1. Ayala JE, Bracy DP, McGuinness OP, Wasserman DH. Considerations in the design of hyperinsulinemic-euglycemic clamps in the conscious mouse. Diabetes 55: 390–397, 2006 - PubMed

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