Limits...
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

Pioglitazone treatment normalizes mitochondrial structure, respiratory function, and mitoflash activity while restoring insulin sensitivity. a In 12-week-old mt-cpYFP db/db mice, systemic insulin sensitivity was restored by pioglitazone (Pio) as indicated by the insulin tolerance test in vehicle (Veh)- and Pio-treated mt-cpYFP db/db mice (n = 6 mice for each group). b–e Pio effects on expression of Mfn2, Mfn1, Drp1, Parkin, p62, and LC3 in skeletal muscle; values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). f Maximal mitochondrial respiration was significantly improved. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). g-j Typical images (g) and statistics of Pio effects on mitoflash frequency (h), spatial area (i), and FDHM (j) (n = 4–8 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs Veh-treated db/m mice, #p < 0.05, ##p<0.01, ###p<0.001 vs Veh-treated db/db mice; values were subject to one-way ANOVA with Tukey’s post hoc analysis
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4589561&req=5

Fig6: Pioglitazone treatment normalizes mitochondrial structure, respiratory function, and mitoflash activity while restoring insulin sensitivity. a In 12-week-old mt-cpYFP db/db mice, systemic insulin sensitivity was restored by pioglitazone (Pio) as indicated by the insulin tolerance test in vehicle (Veh)- and Pio-treated mt-cpYFP db/db mice (n = 6 mice for each group). b–e Pio effects on expression of Mfn2, Mfn1, Drp1, Parkin, p62, and LC3 in skeletal muscle; values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). f Maximal mitochondrial respiration was significantly improved. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). g-j Typical images (g) and statistics of Pio effects on mitoflash frequency (h), spatial area (i), and FDHM (j) (n = 4–8 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs Veh-treated db/m mice, #p < 0.05, ##p<0.01, ###p<0.001 vs Veh-treated db/db mice; values were subject to one-way ANOVA with Tukey’s post hoc analysis

Mentions: Pioglitazone (Pio) is one of the thiazolidinediones (TZDs) that are commonly used to treat metabolic syndrome and type 2 diabetes in clinical practice [43]. A previous study has shown that rosiglitazone, another TZDs, upregulates the expression of genes involved in mitochondrial biogenesis and changes the mitochondrial structure in the adipose tissue of db/db mice [44, 45]. In obese IR mice, Pio ameliorates IR in the skeletal muscle [30]. In 12-week-old mt-cpYFP db/db mice, ITT confirmed the efficacy of Pio in restoring whole-body insulin sensitivity (Fig. 6a). Molecular profiling revealed that Mfn2 and Mfn1 were downregulated, and Drp1 was unchanged, all these dynamics-related proteins returning to or remaining at control levels (Fig. 6b, c). In terms of mitophagy-related signaling, the expression of Parkin, p62, and LC3II were also normalized (Fig. 6d, e). Functionally, the maximal mitochondrial respiration was increased by 26.4 % after Pio treatment compared to the vehicle-treated group (Fig. 6f). These results suggested that Pio treatment ameliorates the alterations in mitochondrial function, dynamics, and morphology, in good agreement with the notion that TZDs help to preserve mitochondrial function and structure in IR.Fig. 6


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)

Pioglitazone treatment normalizes mitochondrial structure, respiratory function, and mitoflash activity while restoring insulin sensitivity. a In 12-week-old mt-cpYFP db/db mice, systemic insulin sensitivity was restored by pioglitazone (Pio) as indicated by the insulin tolerance test in vehicle (Veh)- and Pio-treated mt-cpYFP db/db mice (n = 6 mice for each group). b–e Pio effects on expression of Mfn2, Mfn1, Drp1, Parkin, p62, and LC3 in skeletal muscle; values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). f Maximal mitochondrial respiration was significantly improved. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). g-j Typical images (g) and statistics of Pio effects on mitoflash frequency (h), spatial area (i), and FDHM (j) (n = 4–8 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs Veh-treated db/m mice, #p < 0.05, ##p<0.01, ###p<0.001 vs Veh-treated db/db mice; values were subject to one-way ANOVA with Tukey’s post hoc analysis
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4589561&req=5

Fig6: Pioglitazone treatment normalizes mitochondrial structure, respiratory function, and mitoflash activity while restoring insulin sensitivity. a In 12-week-old mt-cpYFP db/db mice, systemic insulin sensitivity was restored by pioglitazone (Pio) as indicated by the insulin tolerance test in vehicle (Veh)- and Pio-treated mt-cpYFP db/db mice (n = 6 mice for each group). b–e Pio effects on expression of Mfn2, Mfn1, Drp1, Parkin, p62, and LC3 in skeletal muscle; values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). f Maximal mitochondrial respiration was significantly improved. Area under curves of O2 consumption rates were calculated for comparison among groups. Values were recorded as fold change vs Veh-treated mt-cpYFP db/m littermates (n = 4 mice for each group). g-j Typical images (g) and statistics of Pio effects on mitoflash frequency (h), spatial area (i), and FDHM (j) (n = 4–8 mice for each group). Data are expressed as mean ± SEM. *p < 0.05, ***p < 0.001 vs Veh-treated db/m mice, #p < 0.05, ##p<0.01, ###p<0.001 vs Veh-treated db/db mice; values were subject to one-way ANOVA with Tukey’s post hoc analysis
Mentions: Pioglitazone (Pio) is one of the thiazolidinediones (TZDs) that are commonly used to treat metabolic syndrome and type 2 diabetes in clinical practice [43]. A previous study has shown that rosiglitazone, another TZDs, upregulates the expression of genes involved in mitochondrial biogenesis and changes the mitochondrial structure in the adipose tissue of db/db mice [44, 45]. In obese IR mice, Pio ameliorates IR in the skeletal muscle [30]. In 12-week-old mt-cpYFP db/db mice, ITT confirmed the efficacy of Pio in restoring whole-body insulin sensitivity (Fig. 6a). Molecular profiling revealed that Mfn2 and Mfn1 were downregulated, and Drp1 was unchanged, all these dynamics-related proteins returning to or remaining at control levels (Fig. 6b, c). In terms of mitophagy-related signaling, the expression of Parkin, p62, and LC3II were also normalized (Fig. 6d, e). Functionally, the maximal mitochondrial respiration was increased by 26.4 % after Pio treatment compared to the vehicle-treated group (Fig. 6f). These results suggested that Pio treatment ameliorates the alterations in mitochondrial function, dynamics, and morphology, in good agreement with the notion that TZDs help to preserve mitochondrial function and structure in IR.Fig. 6

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