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Mitoflash altered by metabolic stress in insulin-resistant skeletal muscle.

Ding Y, Fang H, Shang W, Xiao Y, Sun T, Hou N, Pan L, Sun X, Ma Q, Zhou J, Wang X, Zhang X, Cheng H - J. Mol. Med. (2015)

Bottom Line: In conjunction with in vivo imaging of skeletal muscles, we uncovered a progressive increase of mitoflash frequency along with its morphological changes.Interestingly, enhanced mitochondrial networking occurred at 12 weeks of age, and this was followed by mitochondrial fragmentation at 34 weeks.Mechanistic study revealed that the mitoflash remodeling was associated with altered expression of proteins involved in mitochondrial dynamics and quality control.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Medicine, Peking University, Beijing, China.

ABSTRACT

Unlabelled: Central to bioenergetics and reactive oxygen species (ROS) signaling, the mitochondrion plays pivotal roles in the pathogenesis of metabolic diseases. Recent advances have shown that mitochondrial flash ("mitoflash") visualized by the biosensor mt-cpYFP affords a frequency-coded, optical readout linked to mitochondrial ROS production and energy metabolism, at the resolution of a single mitochondrion. To investigate possible mitoflash responses to metabolic stress in insulin resistance (IR), we generated an mt-cpYFP-expressing db/db mouse model with the obesity and IR phenotypes unaltered. In conjunction with in vivo imaging of skeletal muscles, we uncovered a progressive increase of mitoflash frequency along with its morphological changes. Interestingly, enhanced mitochondrial networking occurred at 12 weeks of age, and this was followed by mitochondrial fragmentation at 34 weeks. Pioglitazone treatment normalized mitoflash frequency and morphology while restored mitochondrial respiratory function and insulin sensitivity in 12 weeks mt-cpYFP db/db mice. Mechanistic study revealed that the mitoflash remodeling was associated with altered expression of proteins involved in mitochondrial dynamics and quality control. These findings indicate that mitoflash activity may serve as an optical functional readout of the mitochondria, a robust and sensitive biomarker to gauge IR stresses and their amelioration by therapeutic interventions.

Key message: • In vivo detection of mitochondrial flashes in mt-cpYFP-expressing db/db mouse. • Mitoflash frequency increased progressively with disease development. • Mitoflash morphology revealed a biphasic change in mitochondrial networking. • Mitoflash abnormalities and mitochondrial defects are restored by pioglitazone. • Mitoflash may serve as a unique biomarker to gauge metabolic stress in insulin resistance.

No MeSH data available.


Related in: MedlinePlus

Altered expression of proteins for mitochondrial dynamics and mitophagy, and deficient mitochondrial respiration in IR skeletal muscle. a–d Representative Western blots (a, c) and statistics (b, d) show that the expression of essential proteins involved in mitochondrial dynamics and quality control changed during IR progression; values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). e Representative Western blots and statistics show that the expression of master regulator of mitochondrial oxidative phosphorylation, PGC1α. Values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). f Using the XF24 Extracellular Flux Analyzer (Seahorse Bioscience), isolated FDB muscles from each group were sequentially treated with oligomycin (1 μM) and FCCP (1 μM) to assess the maximal respiration capacity of mitochondria. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs 12-week-old mt-cpYFP db/m littermates (n = 4 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; values were subject to Student’s t test. &&&p < 0.001 vs age-matched mt-cpYFP db/m, #p < 0.05 vs 12-week-old mt-cpYFP db/db; values were subject to two-way ANOVA with Tukey’s post hoc analysis
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Fig5: Altered expression of proteins for mitochondrial dynamics and mitophagy, and deficient mitochondrial respiration in IR skeletal muscle. a–d Representative Western blots (a, c) and statistics (b, d) show that the expression of essential proteins involved in mitochondrial dynamics and quality control changed during IR progression; values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). e Representative Western blots and statistics show that the expression of master regulator of mitochondrial oxidative phosphorylation, PGC1α. Values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). f Using the XF24 Extracellular Flux Analyzer (Seahorse Bioscience), isolated FDB muscles from each group were sequentially treated with oligomycin (1 μM) and FCCP (1 μM) to assess the maximal respiration capacity of mitochondria. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs 12-week-old mt-cpYFP db/m littermates (n = 4 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; values were subject to Student’s t test. &&&p < 0.001 vs age-matched mt-cpYFP db/m, #p < 0.05 vs 12-week-old mt-cpYFP db/db; values were subject to two-way ANOVA with Tukey’s post hoc analysis

Mentions: We next investigated the possible molecular basis of these morphologic changes at different stages in the development of IR. We found that the levels of Mfn2 and Mfn1, which promotes mitochondrial fusion, were significantly increased at 12 weeks, coincident with enhanced mitochondrial networking and enlargement at that time. However, these upregulations disappeared at 34 weeks, when fragmentation of mitochondrial network was evident. Pro-fission protein Drp1 only manifested a significant reduction at 34 weeks (Fig. 5a, b).Fig. 5


Mitoflash altered by metabolic stress in insulin-resistant skeletal muscle.

Ding Y, Fang H, Shang W, Xiao Y, Sun T, Hou N, Pan L, Sun X, Ma Q, Zhou J, Wang X, Zhang X, Cheng H - J. Mol. Med. (2015)

Altered expression of proteins for mitochondrial dynamics and mitophagy, and deficient mitochondrial respiration in IR skeletal muscle. a–d Representative Western blots (a, c) and statistics (b, d) show that the expression of essential proteins involved in mitochondrial dynamics and quality control changed during IR progression; values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). e Representative Western blots and statistics show that the expression of master regulator of mitochondrial oxidative phosphorylation, PGC1α. Values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). f Using the XF24 Extracellular Flux Analyzer (Seahorse Bioscience), isolated FDB muscles from each group were sequentially treated with oligomycin (1 μM) and FCCP (1 μM) to assess the maximal respiration capacity of mitochondria. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs 12-week-old mt-cpYFP db/m littermates (n = 4 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; values were subject to Student’s t test. &&&p < 0.001 vs age-matched mt-cpYFP db/m, #p < 0.05 vs 12-week-old mt-cpYFP db/db; values were subject to two-way ANOVA with Tukey’s post hoc analysis
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Related In: Results  -  Collection

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Fig5: Altered expression of proteins for mitochondrial dynamics and mitophagy, and deficient mitochondrial respiration in IR skeletal muscle. a–d Representative Western blots (a, c) and statistics (b, d) show that the expression of essential proteins involved in mitochondrial dynamics and quality control changed during IR progression; values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). e Representative Western blots and statistics show that the expression of master regulator of mitochondrial oxidative phosphorylation, PGC1α. Values were recorded as fold change vs age-matched mt-cpYFP db/m littermates (n = 4–6 mice). f Using the XF24 Extracellular Flux Analyzer (Seahorse Bioscience), isolated FDB muscles from each group were sequentially treated with oligomycin (1 μM) and FCCP (1 μM) to assess the maximal respiration capacity of mitochondria. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs 12-week-old mt-cpYFP db/m littermates (n = 4 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; values were subject to Student’s t test. &&&p < 0.001 vs age-matched mt-cpYFP db/m, #p < 0.05 vs 12-week-old mt-cpYFP db/db; values were subject to two-way ANOVA with Tukey’s post hoc analysis
Mentions: We next investigated the possible molecular basis of these morphologic changes at different stages in the development of IR. We found that the levels of Mfn2 and Mfn1, which promotes mitochondrial fusion, were significantly increased at 12 weeks, coincident with enhanced mitochondrial networking and enlargement at that time. However, these upregulations disappeared at 34 weeks, when fragmentation of mitochondrial network was evident. Pro-fission protein Drp1 only manifested a significant reduction at 34 weeks (Fig. 5a, b).Fig. 5

Bottom Line: In conjunction with in vivo imaging of skeletal muscles, we uncovered a progressive increase of mitoflash frequency along with its morphological changes.Interestingly, enhanced mitochondrial networking occurred at 12 weeks of age, and this was followed by mitochondrial fragmentation at 34 weeks.Mechanistic study revealed that the mitoflash remodeling was associated with altered expression of proteins involved in mitochondrial dynamics and quality control.

View Article: PubMed Central - PubMed

Affiliation: Institute of Molecular Medicine, Peking University, Beijing, China.

ABSTRACT

Unlabelled: Central to bioenergetics and reactive oxygen species (ROS) signaling, the mitochondrion plays pivotal roles in the pathogenesis of metabolic diseases. Recent advances have shown that mitochondrial flash ("mitoflash") visualized by the biosensor mt-cpYFP affords a frequency-coded, optical readout linked to mitochondrial ROS production and energy metabolism, at the resolution of a single mitochondrion. To investigate possible mitoflash responses to metabolic stress in insulin resistance (IR), we generated an mt-cpYFP-expressing db/db mouse model with the obesity and IR phenotypes unaltered. In conjunction with in vivo imaging of skeletal muscles, we uncovered a progressive increase of mitoflash frequency along with its morphological changes. Interestingly, enhanced mitochondrial networking occurred at 12 weeks of age, and this was followed by mitochondrial fragmentation at 34 weeks. Pioglitazone treatment normalized mitoflash frequency and morphology while restored mitochondrial respiratory function and insulin sensitivity in 12 weeks mt-cpYFP db/db mice. Mechanistic study revealed that the mitoflash remodeling was associated with altered expression of proteins involved in mitochondrial dynamics and quality control. These findings indicate that mitoflash activity may serve as an optical functional readout of the mitochondria, a robust and sensitive biomarker to gauge IR stresses and their amelioration by therapeutic interventions.

Key message: • In vivo detection of mitochondrial flashes in mt-cpYFP-expressing db/db mouse. • Mitoflash frequency increased progressively with disease development. • Mitoflash morphology revealed a biphasic change in mitochondrial networking. • Mitoflash abnormalities and mitochondrial defects are restored by pioglitazone. • Mitoflash may serve as a unique biomarker to gauge metabolic stress in insulin resistance.

No MeSH data available.


Related in: MedlinePlus