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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 frequency and unitary properties of mitoflashes in IR skeletal muscle. a Surface plots of the frequency, amplitude, location, and spatial properties of mitoflashes in representative skeletal muscles from 12- and 34-week-old mt-cpYFP db/m and mt-cpYFP db/db mice. Vertical ticks beneath the images mark the timing of these events during a 100-s acquisition window. b Mitoflash frequency increased during disease progression in mt-cpYFP db/db mice. c, d Ensemble-averaged time courses of mitoflashes (c) and quantitation of mitoflash amplitude (∆F/F0) and kinetics (full duration at half maximum, FDHM) (d). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; ##p < 0.01, ###p < 0.001 vs 12-week-old mt-cpYFP db/db mice; values were subject to two-way ANOVA with Tukey’s post hoc analysis
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Fig2: Altered frequency and unitary properties of mitoflashes in IR skeletal muscle. a Surface plots of the frequency, amplitude, location, and spatial properties of mitoflashes in representative skeletal muscles from 12- and 34-week-old mt-cpYFP db/m and mt-cpYFP db/db mice. Vertical ticks beneath the images mark the timing of these events during a 100-s acquisition window. b Mitoflash frequency increased during disease progression in mt-cpYFP db/db mice. c, d Ensemble-averaged time courses of mitoflashes (c) and quantitation of mitoflash amplitude (∆F/F0) and kinetics (full duration at half maximum, FDHM) (d). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; ##p < 0.01, ###p < 0.001 vs 12-week-old mt-cpYFP db/db mice; values were subject to two-way ANOVA with Tukey’s post hoc analysis

Mentions: To determine whether and how mitoflash changes during the progression of IR, we acquired and characterized mitoflash events from mt-cpYFP db/m and mt-cpYFP db/db mice at 12 and 34 weeks of age (Fig. 2a). At 12 weeks, the rate of occurrence of mitoflashes showed a marginal but significant increase in mt-cpYFP db/db mice, from 0.21 ± 0.02/1000 μm2 · 100 s in mt-cpYFP db/m control mice (n = 173 files from 4 mice, 6–20 skeletal muscle cells/mouse) to 0.32 ± 0.03/1000 μm2 · 100 s (n = 240 files from 7 mice, 7–25 skeletal muscle cells/mouse), accompanied by overt obesity, hyperglycemia, hyperinsulinemia, and IR (Fig. 1d, e). At 34 weeks, the mitoflash frequency in mt-cpYFP db/db mice was significantly increased compared to that at 12 weeks and was 243 % higher than that in the age-matched mt-cpYFP db/m control group (Fig. 2b).Fig. 2


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 frequency and unitary properties of mitoflashes in IR skeletal muscle. a Surface plots of the frequency, amplitude, location, and spatial properties of mitoflashes in representative skeletal muscles from 12- and 34-week-old mt-cpYFP db/m and mt-cpYFP db/db mice. Vertical ticks beneath the images mark the timing of these events during a 100-s acquisition window. b Mitoflash frequency increased during disease progression in mt-cpYFP db/db mice. c, d Ensemble-averaged time courses of mitoflashes (c) and quantitation of mitoflash amplitude (∆F/F0) and kinetics (full duration at half maximum, FDHM) (d). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; ##p < 0.01, ###p < 0.001 vs 12-week-old mt-cpYFP db/db mice; values were subject to two-way ANOVA with Tukey’s post hoc analysis
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig2: Altered frequency and unitary properties of mitoflashes in IR skeletal muscle. a Surface plots of the frequency, amplitude, location, and spatial properties of mitoflashes in representative skeletal muscles from 12- and 34-week-old mt-cpYFP db/m and mt-cpYFP db/db mice. Vertical ticks beneath the images mark the timing of these events during a 100-s acquisition window. b Mitoflash frequency increased during disease progression in mt-cpYFP db/db mice. c, d Ensemble-averaged time courses of mitoflashes (c) and quantitation of mitoflash amplitude (∆F/F0) and kinetics (full duration at half maximum, FDHM) (d). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs age-matched mt-cpYFP db/m mice; ##p < 0.01, ###p < 0.001 vs 12-week-old mt-cpYFP db/db mice; values were subject to two-way ANOVA with Tukey’s post hoc analysis
Mentions: To determine whether and how mitoflash changes during the progression of IR, we acquired and characterized mitoflash events from mt-cpYFP db/m and mt-cpYFP db/db mice at 12 and 34 weeks of age (Fig. 2a). At 12 weeks, the rate of occurrence of mitoflashes showed a marginal but significant increase in mt-cpYFP db/db mice, from 0.21 ± 0.02/1000 μm2 · 100 s in mt-cpYFP db/m control mice (n = 173 files from 4 mice, 6–20 skeletal muscle cells/mouse) to 0.32 ± 0.03/1000 μm2 · 100 s (n = 240 files from 7 mice, 7–25 skeletal muscle cells/mouse), accompanied by overt obesity, hyperglycemia, hyperinsulinemia, and IR (Fig. 1d, e). At 34 weeks, the mitoflash frequency in mt-cpYFP db/db mice was significantly increased compared to that at 12 weeks and was 243 % higher than that in the age-matched mt-cpYFP db/m control group (Fig. 2b).Fig. 2

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