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Research on the relationship between obstructive sleep apnea and cognitive functioning has yielded conflicting results, particularly in the older population, and moderators of this association have rarely been studied. Here we investigated the cross-sectional association between obstructive sleep apnea and cognitive functioning as well as the moderating effect of age, sex, apolipoprotein E4, and obesity on this association among community-dwelling older people. We analysed data from 496 participants (71.4 ± 4.4 years; 45.6% men) of the HypnoLaus study who underwent polysomnography and a battery of neuropsychological tests. The sample was categorised as no-to-mild obstructive sleep apnea (apnea-hypopnea index 0-14.9/h; reference), moderate obstructive sleep apnea (apnea-hypopnea index 15.0-29.9/h), or severe obstructive sleep apnea (apnea-hypopnea index ≥30/h). Regression and moderation analyses were performed with adjustment for confounders. Apolipoprotein E4 and obesity moderated the association between severe obstructive sleep apnea and processing speed, whereas no moderating effects were found for age and sex. In apolipoprotein E4 carriers only, severe obstructive sleep apnea was associated with lower performance in Stroop condition 1 (B = 3.13, p = 0.024). In obese participants only, severe obstructive sleep apnea was associated with lower performance in Stroop condition 1 (B = 3.02, p = 0.025) and Stroop condition 2 (B = 3.30, p = 0.034). Severe obstructive sleep apnea was also associated with lower executive function in the whole sample according to Stroop condition 3 (B = 3.44, p = 0.020) and Stroop interference score (B = 0.24, p = 0.006). Our findings support associations of severe obstructive sleep apnea (but not moderate obstructive sleep apnea) with lower performance in processing speed and executive function in the older general population. Apolipoprotein E4 and obesity appear to be vulnerability factors that strengthen the association between severe obstructive sleep apnea and lower performance in processing speed.
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Apolipoproteína E4 , Apnea Obstructiva del Sueño , Masculino , Humanos , Anciano , Femenino , Apolipoproteína E4/genética , Estudios Transversales , Apnea Obstructiva del Sueño/complicaciones , Apnea Obstructiva del Sueño/epidemiología , Cognición , Obesidad/complicaciones , Obesidad/epidemiologíaRESUMEN
PURPOSE OF REVIEW: Obstructive sleep apnea is extremely prevalent in the elderly and may precipitate dementia. We review recent advances on gray and white matter structure in obstructive sleep apnea, the impact of treatment, and potential pathological and neurodegenerative processes underlying brain structural changes. RECENT FINDINGS: Two opposite patterns are observed in neuroimaging studies of obstructive sleep apnea. One may indicate cellular damage (gray matter atrophy, higher white matter hyperintensity burden, lower white matter fractional anisotropy, higher water diffusivities), while the other (gray matter hypertrophy, restricted white matter diffusivities) may reflect transitory responses, such as intracellular edema, reactive gliosis or compensatory structural changes. Treating obstructive sleep apnea could partly reverse these structural changes. Structural alterations related to obstructive sleep apnea may follow a multi-determined biphasic pattern depending on numerous factors (e.g. severity, symptomatology, age) that could tip the scale toward neurodegeneration and need to be investigated by longitudinal studies.
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Apnea Obstructiva del Sueño , Sustancia Blanca , Anciano , Encéfalo/diagnóstico por imagen , Sustancia Gris/diagnóstico por imagen , Humanos , Imagen por Resonancia Magnética , Apnea Obstructiva del Sueño/diagnóstico por imagen , Sustancia Blanca/diagnóstico por imagenRESUMEN
Heart failure (HF) is associated with metabolic perturbations, particularly of fatty acids (FAs), which remain to be better understood in humans. This study aimed at testing the hypothesis that HF patients with reduced ejection fraction display systemic perturbations in levels of energy-related metabolites, especially those reflecting dysregulation of FA metabolism, namely, acylcarnitines (ACs). Circulating metabolites were assessed using mass spectrometry (MS)-based methods in two cohorts. The main cohort consisted of 72 control subjects and 68 HF patients exhibiting depressed left ventricular ejection fraction (25.9 ± 6.9%) and mostly of ischemic etiology with ≥2 comorbidities. HF patients displayed marginal changes in plasma levels of tricarboxylic acid cycle-related metabolites or indexes of mitochondrial or cytosolic redox status. They had, however, 22-79% higher circulating ACs, irrespective of chain length (P < 0.0001, adjusted for sex, age, renal function, and insulin resistance, determined by shotgun MS/MS), which reflects defective mitochondrial ß-oxidation, and were significantly associated with levels of NH2-terminal pro-B-type natriuretic peptide levels, a disease severity marker. Subsequent extended liquid chromatography-tandem MS analysis of 53 plasma ACs in a subset group from the primary cohort confirmed and further substantiated with a comprehensive lipidomic analysis in a validation cohort revealed in HF patients a more complex circulating AC profile. The latter included dicarboxylic-ACs and dihydroxy-ACs as well as very long chain (VLC) ACs or sphingolipids with VLCFAs (>20 carbons), which are proxies of dysregulated FA metabolism in peroxisomes. Our study identified alterations in circulating ACs in HF patients that are independent of biological traits and associated with disease severity markers. These alterations reflect dysfunctional FA metabolism in mitochondria but also beyond, namely, in peroxisomes, suggesting a novel mechanism contributing to global lipid perturbations in human HF.NEW & NOTEWORTHY Mass spectrometry-based profiling of circulating energy metabolites, including acylcarnitines, in two cohorts of heart failure versus control subjects revealed multiple alterations in fatty acid metabolism in peroxisomes in addition to mitochondria, thereby highlighting a novel mechanism contributing to global lipid perturbations in heart failure.Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/acylcarnitines-in-human-heart-failure/.
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Carnitina/análogos & derivados , Ácidos Grasos/metabolismo , Insuficiencia Cardíaca/sangre , Trastornos del Metabolismo de los Lípidos/sangre , Mitocondrias Cardíacas/metabolismo , Anciano , Carnitina/sangre , Estudios de Cohortes , Femenino , Humanos , Masculino , Persona de Mediana Edad , Peroxisomas/metabolismo , Esfingolípidos/metabolismo , Volumen Sistólico , Disfunción Ventricular Izquierda/sangre , Disfunción Ventricular Izquierda/fisiopatologíaRESUMEN
Leigh syndrome French Canadian type (LSFC) is a recessive neurodegenerative disease characterized by tissue-specific deficiency in cytochrome c oxidase (COX), the fourth complex in the oxidative phosphorylation system. LSFC is caused by mutations in the leucine rich pentatricopeptide repeat containing gene (LRPPRC). Most LSFC patients in Quebec are homozygous for an A354V substitution that causes a decrease in the expression of the LRPPRC protein. While LRPPRC is ubiquitously expressed and is involved in multiple cellular functions, tissue-specific expression of LRPPRC and COX activity is correlated with clinical features. In this proof-of-principle study, we developed human induced pluripotent stem cell (hiPSC)-based models from fibroblasts taken from a patient with LSFC, homozygous for the LRPPRC*354V allele, and from a control, homozygous for the LRPPRC*A354 allele. Specifically, for both of these fibroblast lines we generated hiPSC, hiPSC-derived cardiomyocytes (hiPSC-CMs) and hepatocyte-like cell (hiPSC-HLCs) lines, as well as the three germ layers. We observed that LRPPRC protein expression is reduced in all cell lines/layers derived from LSFC patient compared to control cells, with a reduction ranging from â¼70% in hiPSC-CMs to undetectable levels in hiPSC-HLC, reflecting tissue heterogeneity observed in patient tissues. We next performed exploratory analyses of these cell lines and observed that COX protein expression was reduced in all cell lines derived from LSFC patient compared to control cells. We also observed that mutant LRPPRC was associated with altered expression of key markers of endoplasmic reticulum stress response in hiPSC-HLCs but not in other cell types that were tested. While this demonstrates feasibility of the approach to experimentally study genotype-based differences that have tissue-specific impacts, this study will need to be extended to a larger number of patients and controls to not only validate the current observations but also to delve more deeply in the pathogenic mechanisms of LSFC.
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BACKGROUND: The metabolic environment plays a crucial role in the development of heart failure (HF). Our prior research demonstrated that myo-inositol, a metabolite transported by the sodium-myo-inositol co-transporter 1 (SMIT-1), can induce oxidative stress and may be detrimental to heart function. However, plasmatic myo-inositol concentration has not been comprehensively assessed in large cohorts of patients with heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF). METHODS: Plasmatic myo-inositol levels were measured using mass spectrometry and correlated with clinical characteristics in no HF subjects and patients with HFrEF and HFpEF from Belgian (male, no HF, 53%; HFrEF, 84% and HFpEF, 40%) and Canadian cohorts (male, no HF, 51%; HFrEF, 92% and HFpEF, 62%). FINDINGS: Myo-inositol levels were significantly elevated in patients with HF, with a more pronounced increase observed in the HFpEF population of both cohorts. After adjusting for age, sex, body mass index, hypertension, diabetes, and atrial fibrillation, we observed that both HFpEF status and impaired kidney function were associated with elevated plasma myo-inositol. Unlike HFrEF, abnormally high myo-inositol (≥69.8 µM) was linked to unfavourable clinical outcomes (hazard ratio, 1.62; 95% confidence interval, [1.05-2.5]) in patients with HFpEF. These elevated levels were correlated with NTproBNP, troponin, and cardiac fibrosis in this subset of patients. INTERPRETATION: Myo-inositol is a metabolite elevated in patients with HF and strongly correlated to kidney failure. In patients with HFpEF, high myo-inositol levels predict poor clinical outcomes and are linked to markers of cardiac adverse remodelling. This suggests that myo-inositol and its transporter SMIT1 may have a role in the pathophysiology of HFpEF. FUNDING: BECAME-HF was supported by Collaborative Bilateral Research Program Québec - Wallonie-Brussels Federation.
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BACKGROUND: Whether obstructive sleep apnea (OSA) increases the risk of cognitive decline and how sex and age influence this association is not clear. Here, we characterized the sex- and age-specific associations between OSA risk and 3-year cognitive change in middle-aged and older adults. METHODS: We included 24,819 participants aged 45-85 (52% women) from the Canadian Longitudinal Study on Aging. OSA risk was measured at baseline using the STOP combined to body mass index (STOP-B). Neuropsychological tests assessed memory, executive functioning, and psychomotor speed at baseline and at 3-year follow-up. We conducted age- and sex-specific linear mixed models to estimate the predictive role of baseline STOP-B score on 3-year cognitive change. RESULTS: Men at high-risk for OSA aged 45-59 years showed a steeper decline in psychomotor speed (+13.2 [95% CI: -1.6, 27.9]) compared to men at low-risk. Men at high-risk for OSA aged 60-69 showed a steeper decline in mental flexibility (-1.2 [-1.9, -0.5]) and processing speed (+0.6 [0.3, 0.9]) than those at low-risk. Women at high-risk for OSA aged 45-59 showed a steeper decline in processing speed (+0.1 [-0.2, 0.4]) than women at low-risk, while women at high-risk ≥70 years had a steeper decline in memory (-0.2 [-0.6, 0.1]) and processing speed (+1.0 [0.4, 1.5]). CONCLUSIONS: Associations between OSA risk and cognitive decline over 3 years depend on age and sex. Being at high-risk for OSA is associated with a generalized cognitive decline in attention and processing speed, while a memory decline is specific to older women (≥70 years).
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Disfunción Cognitiva , Apnea Obstructiva del Sueño , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Envejecimiento , Canadá/epidemiología , Cognición , Disfunción Cognitiva/complicaciones , Estudios Longitudinales , Apnea Obstructiva del Sueño/complicaciones , Apnea Obstructiva del Sueño/epidemiología , Anciano de 80 o más AñosRESUMEN
Determining the prevalence and characteristics of individuals susceptible to present with obstructive sleep apnea (OSA) is essential for developing targeted and efficient prevention and screening strategies. We included 27,210 participants aged ≥45 years old (50.3% women) from the Canadian Longitudinal Study on Aging. Using the STOP questionnaire combined to the percentage of body fat (%BF), we estimated the prevalence of individuals at high-risk for OSA in a sex and age-specific manner, and tested the relation with comorbidities, menopause and systemic inflammation. The prevalence was 17.5%, and was lower in women (13.1%) than in men (21.9%). A high level of high-sensitivity C-reactive protein was the strongest factor associated with OSA risk and this association was 1.3-2.3 times higher in women than in men. OSA risk increased with age, cardiovascular diseases, diabetes mellitus, anxio-depressive symptoms, asthma and arthritis. In women, post-menopausal status was associated with a high OSA risk. Nearly 1 adult out of 5 older than 45 is at risk for OSA in Canada. Comorbidities, menopause and systemic inflammation, more than age, explain increased OSA prevalence. Considering this high prevalence and associations with medical and mental comorbidities, health care practitioners should incorporate systematic OSA screening in their clinical procedures.
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Apnea Obstructiva del Sueño , Anciano , Envejecimiento , Canadá/epidemiología , Femenino , Humanos , Inflamación/complicaciones , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Prevalencia , Factores de Riesgo , Apnea Obstructiva del Sueño/complicacionesRESUMEN
BACKGROUND: The association between obstructive sleep apnea and cognitive functioning is not yet fully understood and could be influenced by factors such as sex, age and systemic inflammation. We determined the sex- and age-specific association between obstructive sleep apnea risk and cognitive performance, and the influence of systemic inflammation on this association. METHODS: We included 25,899 participants from the Canadian Longitudinal Study of Aging comprehensive cohort, aged 45-85 years (51% women). We conducted sex- and age-specific (45-59; 60-69; ≥70) general linear models between obstructive sleep apnea risk and cognitive scores, and tested the moderating and mediating effects of high-sensitivity C-reactive protein levels. Obstructive sleep apnea risk was estimated by combining the STOP and whole-body fat percentage. Cognitive tests assessed episodic verbal memory, executive functions and psychomotor speed. Levels of high-sensitivity C-reactive protein were obtained through blood samples. RESULTS: Higher obstructive sleep apnea risk was associated with poorer episodic memory in women aged 45-59 years, and poorer executive function (p < 0.05 on multiple tests) in women aged 45-59 and 60-69 years. No such association was found in men. High-sensitivity C-reactive protein levels mediated some associations between obstructive sleep apnea risk and executive function in women and men aged <70 years. CONCLUSIONS: Being at high-risk for obstructive sleep apnea is associated with poorer cognition in women aged <70 years. These associations were partly mediated by systemic inflammation. These results underscore the importance of obstructive sleep apnea diagnosis, treatment and appropriate follow-up, particularly in middle-aged women who might already show signs of early cognitive impairments.
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Proteína C-Reactiva , Apnea Obstructiva del Sueño , Envejecimiento , Canadá/epidemiología , Cognición , Femenino , Humanos , Inflamación/complicaciones , Estudios Longitudinales , Masculino , Trastornos de la Memoria/complicaciones , Persona de Mediana Edad , Apnea Obstructiva del Sueño/complicaciones , Apnea Obstructiva del Sueño/diagnóstico , Apnea Obstructiva del Sueño/epidemiologíaRESUMEN
Medial temporal structures, namely the hippocampus, the entorhinal cortex and the parahippocampal gyrus, are particularly vulnerable to Alzheimer's disease and hypoxemia. Here, we tested the associations between obstructive sleep apnea (OSA) severity and medial temporal lobe volumes in 114 participants aged 55-86 years (35 % women). We also investigated the impact of sex, age, cognitive status, and free-water fraction correction on these associations. Increased OSA severity was associated with larger hippocampal and entorhinal cortex volumes in women, but not in men. Greater OSA severity also correlated with increased hippocampal volumes in participants with amnestic mild cognitive impairment, but not in cognitively unimpaired participants, regardless of sex. Using free-water corrected volumes eliminated all significant associations with OSA severity. Therefore, the increase in medial temporal subregion volumes may possibly be due to edema. Whether these structural manifestations further progress to neuronal death in non-treated OSA patients should be investigated.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Apnea Obstructiva del Sueño , Masculino , Humanos , Femenino , Imagen por Resonancia Magnética , Lóbulo Temporal/diagnóstico por imagen , Disfunción Cognitiva/diagnóstico por imagen , Apnea Obstructiva del Sueño/diagnóstico por imagen , Cognición/fisiología , AguaRESUMEN
Patients with very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency frequently present cardiomyopathy and heartbeat disorders. However, the underlying factors, which may be of cardiac or extra cardiac origins, remain to be elucidated. In this study, we tested for metabolic and functional alterations in the heart from 3- and 7-mo-old VLCAD null mice and their littermate counterparts, using validated experimental paradigms, namely, 1) ex vivo perfusion in working mode, with concomitant evaluation of myocardial contractility and metabolic fluxes using (13)C-labeled substrates under various conditions; as well as 2) in vivo targeted lipidomics, gene expression analysis as well as electrocardiogram monitoring by telemetry in mice fed various diets. Unexpectedly, when perfused ex vivo, working VLCAD null mouse hearts maintained values similar to those of the controls for functional parameters and for the contribution of exogenous palmitate to ß-oxidation (energy production), even at high palmitate concentration (1 mM) and increased energy demand (with 1 µM epinephrine) or after fasting. However, in vivo, these hearts displayed a prolonged rate-corrected QT (QTc) interval under all conditions examined, as well as the following lipid alterations: 1) age- and condition-dependent accumulation of triglycerides, and 2) 20% lower docosahexaenoic acid (an omega-3 polyunsaturated fatty acid) in membrane phospholipids. The latter was independent of liver but affected by feeding a diet enriched in saturated fat (exacerbated) or fish oil (attenuated). Our finding of a longer QTc interval in VLCAD null mice appears to be most relevant given that such condition increases the risk of sudden cardiac death.
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Acil-CoA Deshidrogenasa de Cadena Larga/deficiencia , Sistema de Conducción Cardíaco/fisiopatología , Metabolismo de los Lípidos/genética , Síndrome de QT Prolongado/enzimología , Errores Innatos del Metabolismo/enzimología , Enfermedades Mitocondriales/enzimología , Enfermedades Musculares/enzimología , Miocardio/enzimología , Acil-CoA Deshidrogenasa de Cadena Larga/genética , Factores de Edad , Envejecimiento , Análisis de Varianza , Animales , Síndromes Congénitos de Insuficiencia de la Médula Ósea , Modelos Animales de Enfermedad , Ácidos Docosahexaenoicos/metabolismo , Electrocardiografía Ambulatoria , Aceites de Pescado/administración & dosificación , Aceites de Pescado/metabolismo , Errores Innatos del Metabolismo Lipídico , Hígado/metabolismo , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/fisiopatología , Síndrome de QT Prolongado/prevención & control , Masculino , Errores Innatos del Metabolismo/complicaciones , Errores Innatos del Metabolismo/genética , Errores Innatos del Metabolismo/fisiopatología , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Ratones Noqueados , Enfermedades Mitocondriales/complicaciones , Enfermedades Mitocondriales/genética , Enfermedades Mitocondriales/fisiopatología , Enfermedades Musculares/complicaciones , Enfermedades Musculares/genética , Enfermedades Musculares/fisiopatología , Contracción Miocárdica , Oxidación-Reducción , Ácido Palmítico/metabolismo , Perfusión , Telemetría , Triglicéridos/metabolismoRESUMEN
Around 40% of dementia risk is attributable to modifiable risk factors such as physical inactivity, hypertension, diabetes and obesity. Recently, sleep disorders, including obstructive sleep apnea (OSA), have also been considered among these factors. However, despite several epidemiological studies investigating the link between OSA and cognitive decline, there is still no consensus on whether OSA increases the risk of dementia or not. Part of the heterogeneity observed in previous studies might be related to some individual characteristics that modulate the association between OSA and cognitive decline. In this narrative review, we present these individual characteristics, namely, age, sex, menopause, obesity, diabetes mellitus, hypertension, cardiovascular diseases, smoking, excessive alcohol consumption, depression, air pollution, Apolipoprotein E ε4 allele, physical activity, and cognitive reserve. To date, large cohort studies of OSA and cognitive decline tended to statistically control for the effects of these variables, but whether they interact with OSA to predict cognitive decline remains to be elucidated. Being able to better predict who is at risk of cognitive decline when they have OSA would improve clinical management and treatment decisions, particularly when patients present relatively mild OSA.
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Leigh Syndrome French Canadian (LSFC) is a rare autosomal recessive metabolic disorder characterized by severe lactic acidosis crises and early mortality. LSFC patients carry mutations in the Leucine Rich Pentatricopeptide Repeat Containing (LRPPRC) gene, which lead to defects in the respiratory chain complexes and mitochondrial dysfunction. Mitochondrial respiration modulates cellular metabolic activity, which impacts many cell types including the differentiation and function of immune cells. Hence, we postulated that, in addition to neurological and metabolic disorders, LSFC patients may show impaired immune activity. To gain insight into the quality of the immune response in LSFC patients, we examined the response to the measles, mumps and rubella (MMR) vaccine by measuring antibody titers to MMR in the plasma. In a cohort of eight LSFC patients, the response to the MMR vaccine was variable, with some individuals showing antibodies to all three viruses, while others had antibodies to two or fewer viruses. These results suggest that the mutations in the LRPPRC gene present in LSFC patients may affect the immune response to vaccines. Monitoring vaccine response in this fragile population should be considered to ensure full protection against pathogens.
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Inmunogenicidad Vacunal , Enfermedad de Leigh/inmunología , Vacuna contra el Sarampión-Parotiditis-Rubéola/inmunología , Adolescente , Adulto , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/inmunología , Niño , Femenino , Humanos , Enfermedad de Leigh/epidemiología , Enfermedad de Leigh/genética , Masculino , Proteínas de Neoplasias/genética , Quebec , Vacunación/estadística & datos numéricosRESUMEN
Mitochondrial dysfunction characterizes many rare and common age-associated diseases. The biochemical consequences, underlying clinical manifestations, and potential therapeutic targets, remain to be better understood. We tested the hypothesis that lipid dyshomeostasis in mitochondrial disorders goes beyond mitochondrial fatty acid ß-oxidation, particularly in liver. This was achieved using comprehensive untargeted and targeted lipidomics in a case-control cohort of patients with Leigh syndrome French-Canadian variant (LSFC), a mitochondrial disease caused by mutations in LRPPRC, and in mice harboring liver-specific inactivation of Lrpprc (H-Lrpprc-/-). We discovered a plasma lipid signature discriminating LSFC patients from controls encompassing lower levels of plasmalogens and conjugated bile acids, which suggest perturbations in peroxisomal lipid metabolism. This premise was reinforced in H-Lrpprc-/- mice, which compared with littermates recapitulated a similar, albeit stronger peroxisomal metabolic signature in plasma and liver including elevated levels of very-long-chain acylcarnitines. These mice also presented higher transcript levels for hepatic markers of peroxisome proliferation in addition to lipid remodeling reminiscent of nonalcoholic fatty liver diseases. Our study underscores the value of lipidomics to unveil unexpected mechanisms underlying lipid dyshomeostasis ensuing from mitochondrial dysfunction herein implying peroxisomes and liver, which likely contribute to the pathophysiology of LSFC, but also other rare and common mitochondrial diseases.
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Enfermedad de Leigh/diagnóstico , Metabolismo de los Lípidos/genética , Proteínas de Neoplasias/genética , Plasmalógenos/sangre , Adolescente , Animales , Ácidos y Sales Biliares/metabolismo , Biomarcadores/sangre , Biomarcadores/metabolismo , Carnitina/análogos & derivados , Carnitina/sangre , Carnitina/metabolismo , Estudios de Casos y Controles , Modelos Animales de Enfermedad , Femenino , Humanos , Enfermedad de Leigh/sangre , Enfermedad de Leigh/genética , Enfermedad de Leigh/metabolismo , Lipidómica , Hígado/metabolismo , Masculino , Ratones , Ratones Noqueados , Mitocondrias/metabolismo , Mutación , Proteínas de Neoplasias/metabolismo , Peroxisomas/metabolismo , Plasmalógenos/metabolismo , Estudios Prospectivos , Adulto JovenRESUMEN
Heart disease remains a major complication of diabetes, and the identification of new therapeutic targets is essential. This study investigates the role of the protein kinase MK2, a p38 mitogen-activated protein kinase downstream target, in the development of diabetes-induced cardiomyopathy. Diabetes was induced in control (MK2(+/+)) and MK2-null (MK2(-/-)) mice using repeated injections of a low dose of streptozotocin (STZ). This protocol generated in MK2(+/+) mice a model of diabetes characterized by a 50% decrease in plasma insulin, hyperglycemia, and insulin resistance (IR), as well as major contractile dysfunction, which was associated with alterations in proteins involved in calcium handling. While MK2(-/-)-STZ mice remained hyperglycemic, they showed improved IR and none of the cardiac functional or molecular alterations. Further analyses highlighted marked lipid perturbations in MK2(+/+)-STZ mice, which encompass increased 1) circulating levels of free fatty acid, ketone bodies, and long-chain acylcarnitines and 2) cardiac triglyceride accumulation and ex vivo palmitate ß-oxidation. MK2(-/-)-STZ mice were also protected against all these diabetes-induced lipid alterations. Our results demonstrate the benefits of MK2 deletion on diabetes-induced cardiac molecular and lipid metabolic changes, as well as contractile dysfunction. As a result, MK2 represents a new potential therapeutic target to prevent diabetes-induced cardiac dysfunction.
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Diabetes Mellitus Experimental/genética , Cardiomiopatías Diabéticas/genética , Eliminación de Gen , Péptidos y Proteínas de Señalización Intracelular/genética , Metabolismo de los Lípidos/genética , Proteínas Serina-Treonina Quinasas/genética , Animales , Carnitina/análogos & derivados , Carnitina/metabolismo , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/metabolismo , Cardiomiopatías Diabéticas/metabolismo , Ácidos Grasos no Esterificados/metabolismo , Hiperglucemia/genética , Insulina/sangre , Resistencia a la Insulina/genética , Cuerpos Cetónicos/metabolismo , Ratones , Contracción Muscular/genética , Estreptozocina , Triglicéridos/metabolismoRESUMEN
Mutations in LRPPRC are responsible for the French Canadian variant of Leigh Syndrome (LSFC), a severe disorder characterized biochemically by a tissue-specific deficiency of cytochrome c oxidase (COX) and clinically by the occurrence of severe and deadly acidotic crises. Factors that precipitate these crises remain unclear. To better understand the physiopathology and identify potential treatments, we performed a comprehensive analysis of mitochondrial function in LSFC and control fibroblasts. Furthermore, we have used this cell-based model to screen for conditions that promote premature cell death in LSFC cells and test the protective effect of ten interventions targeting well-defined aspects of mitochondrial function. We show that, despite maintaining normal ATP levels, LSFC fibroblasts present several mitochondrial functional abnormalities under normal baseline conditions, which likely impair their capacity to respond to stress. This includes mitochondrial network fragmentation, impaired oxidative phosphorylation capacity, lower membrane potential, increased sensitivity to Ca2+-induced permeability transition, but no changes in reactive oxygen species production. We also show that LSFC fibroblasts display enhanced susceptibility to cell death when exposed to palmitate, an effect that is potentiated by high lactate, while high glucose or acidosis alone or in combination were neutral. Furthermore, we demonstrate that compounds that are known to promote flux through the electron transport chain independent of phosphorylation (methylene blue, dinitrophenol), or modulate fatty acid (L-carnitine) or Krebs cycle metabolism (propionate) are protective, while antioxidants (idebenone, N-acetyl cysteine, resveratrol) exacerbate palmitate plus lactate-induced cell death. Collectively, beyond highlighting multiple alterations in mitochondrial function and increased susceptibility to nutrient-induced cytotoxicity in LSFC fibroblasts, these results raise questions about the nature of the diets, particularly excess fat intake, as well as on the use of antioxidants in patients with LSFC and, possibly, other COX defects.
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Fibroblastos/metabolismo , Enfermedad de Leigh/metabolismo , Mitocondrias/metabolismo , Adenosina Trifosfato/metabolismo , Adolescente , Adulto , Calcio/metabolismo , Canadá , Estudios de Casos y Controles , Permeabilidad de la Membrana Celular , Niño , Humanos , Enfermedad de Leigh/genética , Potencial de la Membrana Mitocondrial , Mitocondrias/genética , Mutación , Proteínas de Neoplasias/genética , Fosforilación Oxidativa , Fenotipo , Especies Reactivas de Oxígeno , Estrés Fisiológico , Superóxidos/metabolismo , Adulto JovenRESUMEN
A decline in mitochondrial respiration represents the root cause of a large number of inborn errors of metabolism. It is also associated with common age-associated diseases and the aging process. To gain insight into the systemic, biochemical consequences of respiratory chain dysfunction, we performed a case-control, prospective metabolic profiling study in a genetically homogenous cohort of patients with Leigh syndrome French Canadian variant, a mitochondrial respiratory chain disease due to loss-of-function mutations in LRPPRC. We discovered 45 plasma and urinary analytes discriminating patients from controls, including classic markers of mitochondrial metabolic dysfunction (lactate and acylcarnitines), as well as unexpected markers of cardiometabolic risk (insulin and adiponectin), amino acid catabolism linked to NADH status (α-hydroxybutyrate), and NAD(+) biosynthesis (kynurenine and 3-hydroxyanthranilic acid). Our study identifies systemic, metabolic pathway derangements that can lie downstream of primary mitochondrial lesions, with implications for understanding how the organelle contributes to rare and common diseases.