Jordi Casademont

Noninvasive Diagnosis of Mitochondrial Dysfunction in HAART-Related Hyperlactatemia

This study explores the role played by the welfare state in affecting women’s labor force participation and occupational achievement. Using data from 22 industrialized countries, the authors examine the consequences of state interventions for both women’s employment patterns and gender inequality in occupational attainment. The findings reveal a twofold effect: developed welfare states facilitate women’s access into the labor force but not into powerful and desirable positions. Specifically, nations characterized by progressive and developed welfare policies and by a large public service sector tend to have high levels of female labor force participation, along with a high concentration of women in female‐typed occupations and low female representation in managerial occupations. The findings provide insights into the social mechanisms underlying the relations between welfare states’ benefits to working mothers and women’s participation and achievements in the labor market.This study explores the role played by the welfare state in affecting women’s labor force participation and occupational achievement. Using data from 22 industrialized countries, the authors examine the consequences of state interventions for both women’s employment patterns and gender inequality in occupational attainment. The findings reveal a twofold effect: developed welfare states facilitate women’s access into the labor force but not into powerful and desirable positions. Specifically, nations characterized by progressive and developed welfare policies and by a large public service sector tend to have high levels of female labor force participation, along with a high concentration of women in female‐typed occupations and low female representation in managerial occupations. The findings provide insights into the social mechanisms underlying the relations between welfare states’ benefits to working mothers and women’s participation and achievements in the labor market.

Mitochondrial function in heart muscle from patients with idiopathic dilated cardiomyopathy

OBJECTIVE To study the mitochondrial respiratory chain enzyme activities in patients with idiopathic dilated cardiomyopathy (IDC). METHODS Mitochondrial respiratory chain enzyme activities were assessed spectrophotometrically in left ventricular tissue of 17 patients with IDC undergoing cardiac transplantation, as well as in two groups of controls: a group of six patients suffering from ischemic dilated cardiomyopathy (IC) also undergoing cardiac transplantation, and a group of 17 organ donors considered normal from a cardiac point of view. Cytochrome b gene from three IDC patients whose complex III activity was particularly low and from three controls was also sequenced. RESULTS We found that complex III enzymatic activity was lower not only in IDC but also in IC patients when compared with normal controls. When analysing cytochrome b gene we only found neutral polymorphisms previously described. CONCLUSIONS In view of such results, we believe that the decrease of respiratory chain complex III activity found in some cases of IDC is a secondary phenomenon, and not due to a primary mitochondrial disease.

Reduced steady-state levels of mitochondrial RNA and increased mitochondrial DNA amount in human brain with aging

The contribution of the mitochondrial genetic system in the degenerative processes of senescence remains unclear. This study deals with age-related changes in brain mtDNA expression in humans. Brain tissue from the frontal lobe cortex was obtained from autopsy of 13 humans aged between 21 and 84 years. No structural changes were detected in mtDNA, increased mtDNA content and reduced steady-state level of mitochondrial transcripts and transcription ratio (mtRNA/mtDNA) were associated with aging. These findings suggest that the increase of the mtDNA levels could be considered as an inefficient compensatory mechanism to maintain the normal levels of mtRNA transcripts. This unbalanced mitochondrial condition could play a role in the process of senescence in human brain.

Mitochondrial Effects of HIV Infection on the Peripheral Blood Mononuclear Cells of HIV-Infected Patients Who Were Never Treated with Antiretrovirals

To investigate the effects of HIV infection on mitochondrial DNA (mtDNA) content and other mitochondrial parameters, we used peripheral blood mononuclear cells (PBMCs) from 25 asymptomatic antiretroviral-naive human immunodeficiency virus (HIV)-infected patients and from 25 healthy control subjects. HIV-infected patients had significant decreases in mtDNA content (decrease, 23%; P<.05) and in the activities of mitochondrial respiratory chain (MRC) complex II (decrease, 41%; P<.001), MRC complex III (decrease, 38%; P<.001), MRC complex IV (decrease, 19%; P=.001), and glycerol-3-phosphate dehydrogenase (decrease, 22%; P<.001), along with increased lipid peroxidation of PBMC membranes (P=.007). Therefore, HIV infection is associated not only with mtDNA depletion, but also with extensive MRC disturbances and increased oxidative damage.

A nuclear defect in the 4p16 region predisposes to multiple mitochondrial DNA deletions in families with Wolfram syndrome.

Wolfram syndrome is a progressive neurodegenerative disorder transmitted in an autosomal recessive mode. We report two Wolfram syndrome families harboring multiple deletions of mitochondrial DNA. The deletions reached percentages as high as 85-90% in affected tissues such as the central nervous system of one patient, while in other tissues from the same patient and from other members of the family, the percentages of deleted mitochondrial DNA genomes were only 1-10%. Recently, a Wolfram syndrome gene has been linked to markers on 4p16. In both families linkage between the disease locus and 4p16 markers gave a maximum multipoint lod score of 3.79 at theta = 0 (P<0.03) with respect to D4S431. In these families, the syndrome was caused by mutations in this nucleus-encoded gene which deleteriously interacts with the mitochondrial genome. This is the first evidence of the implication of both genomes in a recessive disease.

Mitochondrial involvement in antiretroviral therapy-related lipodystrophy

ObjectivesThe management of HIV infection has greatly improved during recent years essentially because of the appearance of new antiretroviral drugs. Highly active antiretroviral therapy (HAART) has achieved important reductions of viraemia and significant recoveries of CD4+ cell counts in HIV-infected patients. Nonetheless, cases of HIV-infected individuals experiencing lipodystrophy (LD) are being increasingly reported. The purpose of this work was to analyse whether the presence of mitochondrial abnormalities is a frequent feature in LD, since we previously detected mitochondrial abnormalities in an HIV-patient. The second main objective was to study whether LD could be associated with a specific drug. DesignSeven HIV patients presenting LD and five HIV non-LD controls participated in the study. LD patients met the following criteria: (1) LD was their only clinical abnormality, (2) LD was clinically relevant, (3) compliance with antiretroviral treatment was higher than 90% and (4) patients did not have personal or familial history suggestive of mitochondrial disease or neuromuscular disorder. MethodsHistological stainings, histo-enzymatic reactions, enzymatic and respiratory activities of mitochondrial respiratory chain complexes, and mitochondrial DNA (mtDNA) depletion and rearrangements were examined on muscle mitochondria. ResultsStructural muscle abnormalities, mitochondrial respiratory chain dysfunction or mtDNA deletions were detected in all HIV lipodystrophic patients. ConclusionsThe mitochondrial abnormalities found suggest that mitochondrial dysfunction could play a role in the development of antiretroviral therapy-related lipodystrophy.

Reversible Inhibition of Mitochondrial Protein Synthesis during Linezolid-Related Hyperlactatemia

ABSTRACT The objective of the present study was to determine the mitochondrial toxicity mechanisms of linezolid-related hyperlactatemia. Five patients on a long-term schedule of linezolid treatment were studied during the acute phase of hyperlactatemia and after clinical recovery and lactate normalization following linezolid withdrawal. Mitochondrial studies were performed with peripheral blood mononuclear cells and consisted of measurement of mitochondrial mass, mitochondrial protein synthesis homeostasis (cytochrome c oxidase [COX] activity, COX-II subunit expression, COX-II mRNA abundance, and mitochondrial DNA [mtDNA] content), and overall mitochondrial function (mitochondrial membrane potential and intact-cell oxidative capacity). During linezolid-induced hyperlactatemia, we found extremely reduced protein expression (16% of the remaining content compared to control values [100%], P < 0.001) for the mitochondrially coded, transcribed, and translated COX-II subunit. Accordingly, COX activity was also found to be decreased (51% of the remaining activity, P < 0.05). These reductions were observed despite the numbers of COX-II mitochondrial RNA transcripts being abnormally increased (297%, P = 0.10 [not significant]) and the mitochondrial DNA content remaining stable. These abnormalities persisted even after the correction for mitochondrial mass, which was mildly decreased during the hyperlactatemic phase. Most of the mitochondrial abnormalities returned to control ranges after linezolid withdrawal, lactate normalization, and clinical recovery. Linezolid inhibits mitochondrial protein synthesis, leading to decreased mitochondrial enzymatic activity, which causes linezolid-related hyperlactatemia, which resolves upon discontinuation of linezolid treatment.

Electron transport chain defects in heart failure.

In recent years, the possibility that disorders of cardiac metabolism play a role in the mechanisms that lead to ventricular dilatation and dysfunction in heart failure has attracted much attention. Electron transport chain is constituted by a series of multimeric protein complexes, located in the inner mitochondrial membranes, whose genes are distributed over both nuclear and mitochondrial DNA. Its normal function is essential to provide the energy for cardiac function.Many studies have described abnormalities in mitochondrial DNA genes encoding for electron transport chain (ETC) in dilated cardiomyopathies. In some cases, heart failure is one more or less relevant symptom among other multisystem manifestations characteristic of mitochondrial encephalomyopathies, being heart failure imputable to a primary mitochondrial disease. In the case of idiopathic dilated cardiomyopathies (IDC), many mitochondrial abnormalities have also been described using hystological, biochemical or molecular studies. The importance of such findings is under debate. The great variability in the mitochondrial abnormalities described has prompted the proposal that mitochondrial dysfunction could be a secondary phenomenon in IDC, and not a primary one. Among other possible explanations for such findings, the presence of an increased oxidative damage due to a free radical excess has been postulated. In this setting, the dysfunction of ETC could be a consequence, but also a cause of the presence of an increased free radical damage.Independently of its origin, ETC dysfunction may contribute to the persistence and worsening of heart failure. If this hypothesis, still to be proven, was certain, the modulation of cardiac metabolism could be an interesting approach to treat IDC.The precise mechanisms that lead to ventricular dilatation and dysfunction in heart failure are still nowadays poorly understood. Circumstances such as cytotoxic insults, viral infections, immune abnormalities, contractile protein defects, ischemic factors and familial conditions have been thoroughly investigated [1]. It is possible that several mechanisms combine to produce the clinical syndrome of heart failure. In recent years the possibility that disorders of energy metabolism, either isolated or in combination with the other aforementioned factors, may play a role in the development of heart failure in susceptible patients has attracted much attention. The present paper reviews the current knowledge on mitochondrial function in the failing myocardium. We restrain our discussion to heart failure where an impaired inotropic state leads to a weakened systolic contraction (i.e. the so-called systolic heart failure). Idiopathic dilated cardiomyopathy (IDC) is the prototype of the conditions under discussion. Other circumstances where a defect in myocardial contraction is due to a chronic excessive work load (i.e., hypertension, valvular or congenital heart diseases), and states in which the principal abnormality involves impaired relaxation of the ventricle (i.e. diastolic heart failure), as well as mitochondrial defects outside the electron transport chain (i.e., defects in Krebs cycle or beta-oxidation of fatty acids) are only approached circumstantially.

Aging is associated with increased lipid peroxidation in human hearts, but not with mitochondrial respiratory chain enzyme defects

BACKGROUND Aging is associated with increased oxidative damage at multiple cellular and tissular levels. A decrease in mitochondrial function has repeatedly been advocated as a primary key event, especially on the basis of analysis of skeletal muscle mitochondria. However, some doubts on this issue have arisen when confounding variables (such as physical activity or smoking habit) have been taken into account in the analysis of mitochondrial respiratory chain (MRC) enzyme activities or when additional analytical parameters such as enzyme ratios have been considered. OBJECTIVE To determine whether oxidative damage and enzyme activities of the MRC are influenced by the aging process in human hearts. PATIENTS AND METHODS We studied cardiac muscle obtained from 59 organ donors (age: 56+/-12 years, 75% men). Oxidative membrane damage was evaluated through the assessment of lipid peroxidation. Absolute and relative enzyme activities (AEA and REA, respectively) of complex I, II, III and IV of the MRC were spectrophotometrically measured. Stoichiometric relationships among MRC complexes were also assessed through calculating MRC ratios. Linear regression analyses were employed to disclose any potential correlation between mitochondrial dysfunction and aging. RESULTS We found a progressive, significant increase of heart membrane lipid peroxidation with aging (P<0.05). Conversely, neither AEA nor REA decreased with age (P=n.s. for all complexes). Similarly to observations in other tissues, we found that stoichiometry of the MRC enzymes is maintained within a narrow range in human hearts. When the effects of aging on MRC ratios were explored, we failed again in demonstrating any subtle disarray. CONCLUSION MRC enzymes remain preserved in heart with aging, and thus they cannot be considered the main cause of the increased oxidative damage associated with aging.

Cytochrome c oxidase assay in minute amounts of human skeletal muscle using single wavelength spectrophotometers

Determination of cytochrome c oxidase (COX; EC 1.9.3.1) activity in human mitochondria presents several technical difficulties which result in a large intra- and interlaboratory variability, especially when a single wavelength spectrophotometer (SWS) is used, as is generally done in most laboratories in the context of screening procedures for the detection of respiratory chain deficiencies. We studied the experimental conditions of COX assay in human skeletal muscle mitochondria using a SWS in order to define the optimal conditions for the assay and compared these results with those obtained using a double wavelength spectrophotometer (DWS). We demonstrate that a low intra-individual variability of COX assay can be obtained with SWS by: (1) using manual stirrers to avoid the formation of bubbles in the mixture; (2) preincubating mitochondria and laurylmaltoside before the addition of cytochrome c, which prevents light scattering secondary to mitochondrial swelling; and (3) using low amounts (1-2 microg) of mitochondrial protein to extend and linearize the reaction rate. Under these experimental conditions, the concordance between SWS and DWS was very good (R=0.975).