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Obesity in a model of gpx4 haploinsufficiency uncovers a causal role for lipid-derived aldehydes in human metabolic disease and cardiomyopathy.

Katunga LA, Gudimella P, Efird JT, Abernathy S, Mattox TA, Beatty C, Darden TM, Thayne KA, Alwair H, Kypson AP, Virag JA, Anderson EJ - Mol Metab (2015)

Bottom Line: Biochemical and immuno-histological analysis was performed in heart and liver at termination of study, and mitochondrial function was analyzed in heart.Mitochondrial dysfunction manifesting as decreased fat oxidation capacity and increased reactive oxygen species was also present in obese GPx4(+/-) but not WT hearts, along with up-regulation of pro-inflammatory and pro-fibrotic genes.Patients with diabetes and hyperglycemia exhibited significantly less GPx4 enzyme and greater HNE-adducts in their hearts, compared with age-matched non-diabetic patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology & Toxicology, East Carolina University, Greenville, NC, United States ; Department of Public Health, East Carolina University, Greenville, NC, United States.

ABSTRACT

Objective: Lipid peroxides and their reactive aldehyde derivatives (LPPs) have been linked to obesity-related pathologies, but whether they have a causal role has remained unclear. Glutathione peroxidase 4 (GPx4) is a selenoenzyme that selectively neutralizes lipid hydroperoxides, and human gpx4 gene variants have been associated with obesity and cardiovascular disease in epidemiological studies. This study tested the hypothesis that LPPs underlie cardio-metabolic derangements in obesity using a high fat, high sucrose (HFHS) diet in gpx4 haploinsufficient mice (GPx4(+/-)) and in samples of human myocardium.

Methods: Wild-type (WT) and GPx4(+/-) mice were fed either a standard chow (CNTL) or HFHS diet for 24 weeks, with metabolic and cardiovascular parameters measured throughout. Biochemical and immuno-histological analysis was performed in heart and liver at termination of study, and mitochondrial function was analyzed in heart. Biochemical analysis was also performed on samples of human atrial myocardium from a cohort of 103 patients undergoing elective heart surgery.

Results: Following HFHS diet, WT mice displayed moderate increases in 4-hydroxynonenal (HNE)-adducts and carbonyl stress, and a 1.5-fold increase in GPx4 enzyme in both liver and heart, while gpx4 haploinsufficient (GPx4(+/-)) mice had marked carbonyl stress in these organs accompanied by exacerbated glucose intolerance, dyslipidemia, and liver steatosis. Although normotensive, cardiac hypertrophy was evident with obesity, and cardiac fibrosis more pronounced in obese GPx4(+/-) mice. Mitochondrial dysfunction manifesting as decreased fat oxidation capacity and increased reactive oxygen species was also present in obese GPx4(+/-) but not WT hearts, along with up-regulation of pro-inflammatory and pro-fibrotic genes. Patients with diabetes and hyperglycemia exhibited significantly less GPx4 enzyme and greater HNE-adducts in their hearts, compared with age-matched non-diabetic patients.

Conclusion: These findings suggest LPPs are key factors underlying cardio-metabolic derangements that occur with obesity and that GPx4 serves a critical role as an adaptive countermeasure.

No MeSH data available.


Related in: MedlinePlus

Cardiac mitochondrial GPx4 and functional parameters. A representative immunoblot of GPx4 protein A and HNE-adducts B along with corresponding COX IV loading control are shown of isolated cardiac mitochondria obtained from mice used in this study. In C are maximal ADP-stimulated rates of mitochondrial respiration (JO2) supported by palmitoyl-l-carnitine in permeabilized cardiac myofibers from these mice. Shown in D are rates of mitochondrial H2O2 emission (mito-JH2O2) in phosphorylating state supported by palmitoyl-l-carnitine + 100 μM ADP, in the absence (−) and presence (+) of the TxnRd2 inhibitor Auranofin. Data shown in C & D are means ± S.E.M, N = 4–6 per group. *P < 0.05 vs. all other groups for each respiratory state, †P < 0.05 vs. WT-HFHS, §P < 0.05 vs. GPx4+/--CNTL, #P < 0.05 for Auranofin effect within group.
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fig4: Cardiac mitochondrial GPx4 and functional parameters. A representative immunoblot of GPx4 protein A and HNE-adducts B along with corresponding COX IV loading control are shown of isolated cardiac mitochondria obtained from mice used in this study. In C are maximal ADP-stimulated rates of mitochondrial respiration (JO2) supported by palmitoyl-l-carnitine in permeabilized cardiac myofibers from these mice. Shown in D are rates of mitochondrial H2O2 emission (mito-JH2O2) in phosphorylating state supported by palmitoyl-l-carnitine + 100 μM ADP, in the absence (−) and presence (+) of the TxnRd2 inhibitor Auranofin. Data shown in C & D are means ± S.E.M, N = 4–6 per group. *P < 0.05 vs. all other groups for each respiratory state, †P < 0.05 vs. WT-HFHS, §P < 0.05 vs. GPx4+/--CNTL, #P < 0.05 for Auranofin effect within group.

Mentions: Mitochondrial dysfunction, as characterized by decreased ATP and/or respiration combined with increased ROS, has been linked to several obesity-related pathologies, including insulin resistance and cardiomyopathy, and recent studies have implicated a role for mitochondrial protein carbonylation in mediating this dysfunction [51–53]. Parameters of mitochondrial function in permeabilized LV myofibers were examined to assess the relationship between GPx4 deficiency, carbonyl stress, and mitochondria in the obese myocardium. GPx4 enzyme content was measured in the mitochondrial fraction isolated from whole hearts. GPx4 increased in cardiac mitochondria of WT mice with HFHS diet, while total levels of GPx4 were lower and remained that way following HFHS diet in the GPx4+/− mice (Figure 4A and Supplemental Figure 2A).


Obesity in a model of gpx4 haploinsufficiency uncovers a causal role for lipid-derived aldehydes in human metabolic disease and cardiomyopathy.

Katunga LA, Gudimella P, Efird JT, Abernathy S, Mattox TA, Beatty C, Darden TM, Thayne KA, Alwair H, Kypson AP, Virag JA, Anderson EJ - Mol Metab (2015)

Cardiac mitochondrial GPx4 and functional parameters. A representative immunoblot of GPx4 protein A and HNE-adducts B along with corresponding COX IV loading control are shown of isolated cardiac mitochondria obtained from mice used in this study. In C are maximal ADP-stimulated rates of mitochondrial respiration (JO2) supported by palmitoyl-l-carnitine in permeabilized cardiac myofibers from these mice. Shown in D are rates of mitochondrial H2O2 emission (mito-JH2O2) in phosphorylating state supported by palmitoyl-l-carnitine + 100 μM ADP, in the absence (−) and presence (+) of the TxnRd2 inhibitor Auranofin. Data shown in C & D are means ± S.E.M, N = 4–6 per group. *P < 0.05 vs. all other groups for each respiratory state, †P < 0.05 vs. WT-HFHS, §P < 0.05 vs. GPx4+/--CNTL, #P < 0.05 for Auranofin effect within group.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

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fig4: Cardiac mitochondrial GPx4 and functional parameters. A representative immunoblot of GPx4 protein A and HNE-adducts B along with corresponding COX IV loading control are shown of isolated cardiac mitochondria obtained from mice used in this study. In C are maximal ADP-stimulated rates of mitochondrial respiration (JO2) supported by palmitoyl-l-carnitine in permeabilized cardiac myofibers from these mice. Shown in D are rates of mitochondrial H2O2 emission (mito-JH2O2) in phosphorylating state supported by palmitoyl-l-carnitine + 100 μM ADP, in the absence (−) and presence (+) of the TxnRd2 inhibitor Auranofin. Data shown in C & D are means ± S.E.M, N = 4–6 per group. *P < 0.05 vs. all other groups for each respiratory state, †P < 0.05 vs. WT-HFHS, §P < 0.05 vs. GPx4+/--CNTL, #P < 0.05 for Auranofin effect within group.
Mentions: Mitochondrial dysfunction, as characterized by decreased ATP and/or respiration combined with increased ROS, has been linked to several obesity-related pathologies, including insulin resistance and cardiomyopathy, and recent studies have implicated a role for mitochondrial protein carbonylation in mediating this dysfunction [51–53]. Parameters of mitochondrial function in permeabilized LV myofibers were examined to assess the relationship between GPx4 deficiency, carbonyl stress, and mitochondria in the obese myocardium. GPx4 enzyme content was measured in the mitochondrial fraction isolated from whole hearts. GPx4 increased in cardiac mitochondria of WT mice with HFHS diet, while total levels of GPx4 were lower and remained that way following HFHS diet in the GPx4+/− mice (Figure 4A and Supplemental Figure 2A).

Bottom Line: Biochemical and immuno-histological analysis was performed in heart and liver at termination of study, and mitochondrial function was analyzed in heart.Mitochondrial dysfunction manifesting as decreased fat oxidation capacity and increased reactive oxygen species was also present in obese GPx4(+/-) but not WT hearts, along with up-regulation of pro-inflammatory and pro-fibrotic genes.Patients with diabetes and hyperglycemia exhibited significantly less GPx4 enzyme and greater HNE-adducts in their hearts, compared with age-matched non-diabetic patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology & Toxicology, East Carolina University, Greenville, NC, United States ; Department of Public Health, East Carolina University, Greenville, NC, United States.

ABSTRACT

Objective: Lipid peroxides and their reactive aldehyde derivatives (LPPs) have been linked to obesity-related pathologies, but whether they have a causal role has remained unclear. Glutathione peroxidase 4 (GPx4) is a selenoenzyme that selectively neutralizes lipid hydroperoxides, and human gpx4 gene variants have been associated with obesity and cardiovascular disease in epidemiological studies. This study tested the hypothesis that LPPs underlie cardio-metabolic derangements in obesity using a high fat, high sucrose (HFHS) diet in gpx4 haploinsufficient mice (GPx4(+/-)) and in samples of human myocardium.

Methods: Wild-type (WT) and GPx4(+/-) mice were fed either a standard chow (CNTL) or HFHS diet for 24 weeks, with metabolic and cardiovascular parameters measured throughout. Biochemical and immuno-histological analysis was performed in heart and liver at termination of study, and mitochondrial function was analyzed in heart. Biochemical analysis was also performed on samples of human atrial myocardium from a cohort of 103 patients undergoing elective heart surgery.

Results: Following HFHS diet, WT mice displayed moderate increases in 4-hydroxynonenal (HNE)-adducts and carbonyl stress, and a 1.5-fold increase in GPx4 enzyme in both liver and heart, while gpx4 haploinsufficient (GPx4(+/-)) mice had marked carbonyl stress in these organs accompanied by exacerbated glucose intolerance, dyslipidemia, and liver steatosis. Although normotensive, cardiac hypertrophy was evident with obesity, and cardiac fibrosis more pronounced in obese GPx4(+/-) mice. Mitochondrial dysfunction manifesting as decreased fat oxidation capacity and increased reactive oxygen species was also present in obese GPx4(+/-) but not WT hearts, along with up-regulation of pro-inflammatory and pro-fibrotic genes. Patients with diabetes and hyperglycemia exhibited significantly less GPx4 enzyme and greater HNE-adducts in their hearts, compared with age-matched non-diabetic patients.

Conclusion: These findings suggest LPPs are key factors underlying cardio-metabolic derangements that occur with obesity and that GPx4 serves a critical role as an adaptive countermeasure.

No MeSH data available.


Related in: MedlinePlus