Mitochondrial Function In Patients Research Articles

Mitochondrial function in patients affected with fibromyalgia syndrome is impaired and correlates with disease severity

Fibromyalgia is a musculoskeletal syndrome characterized by chronic widespread pain that is often associated with systemic manifestations. Since mitochondria are the main source of cellular energy, we hypothesized that fibromyalgia syndrome (FMS) could be linked to mitochondrial impairment. Aim was to study mitochondrial dysfunction in peripheral blood mononuclear cells isolated from 50 patients with primary FMS and 20 apparently healthy controls. Although no differences in mitochondrial basal respiration were observed between patients with primary FMS and healthy controls, a lower median bioenergetic health index (BHI; − 22.1%, p = 0.03), a proxy of mitochondrial function, was found in patients. According to fibromyalgia severity score (FSS), a composite of widespread pain index and symptom severity scale, a lower median BHI (− 18.7%) was found in patients with a FSS ≥ 20 compared to those with a FSS < 20. Negative moderate correlations were found only between BHI and FSS (r = − 0.36) and widespread pain index (r = − 0.38). We demonstrated that patients with FMS had an impaired mitochondrial function. Additionally, we found a mild correlation between the widespread pain index and the BHI, possibly indicating that the altered mitochondrial function, in these patients, narrows musculoskeletal rather than central nervous system involvement.

Atrial pacing improves mitochondrial function in peripheral blood mononuclear cells in patients with cardiac implantable electronic devices.

Mitochondrial dysfunction contributes significantly to the development of atrial fibrillation (AF). Conflicting data regarding the atrial pacing and the risk of AF existed, and the impact of atrial pacing on mitochondrial function remains unknown. Therefore, we sought to examine the association between atrial pacing percentage and mitochondrial function in patients with cardiovascular implantable electronic devices (CIEDs) with atrial pacing capability. This is a cross-sectional study involving 183 patients with CIEDs with atrial pacing capability. The oxidative stress and mitochondrial function were determined in peripheral blood mononuclear cells (PBMCs). Among 183 patients, 55.7% had permanent pacemakers, 7.7% had defibrillators, and 36.6% had cardiac resynchronization therapy. Mean age was 67.5 ± 14.7 yr with 51% being male. Mean left ventricular ejection fraction (LVEF) was 53.9 ± 16.8%. We demonstrated that the presence of atrial pacing above 50% correlated with higher levels of mitochondrial spared respiratory capacity (P = 0.043) and coupling efficiency (P = 0.045). After adjusting with multiple linear regression for age, sex, LVEF, history of AF, sick sinus syndrome, comorbidities, estimated glomerular filtration rate (eGFR), cardiac resynchronization therapy (CRT), and percentage of ventricular pacing, our findings revealed a statistically significant association between a higher percentage of atrial pacing and increased spared respiratory capacity (β, 0.217, P = 0.046), lower nonmitochondrial respiration (β, -0.230; P = 0.023), and proton leak (β, -0.247; P = 0.022). We demonstrated that atrial pacing enhances mitochondrial performance in PBMCs and left ventricular contractile performance in patients with CIEDs. This observation may serve as an additional support for the preventive effect of atrial pacing in the prevention of atrial arrhythmia.NEW & NOTEWORTHY Atrial pacing enhances mitochondrial spare respiratory capacity and reduces proton leak. This finding may provide further evidence supporting the preventive role of atrial pacing in reducing the risk of atrial fibrillation in patients with cardiac implantable electronic devices.

Preoperative Increases in T2-Weighted Fat-Suppressed Magnetic Resonance Imaging Signal Intensities Associated With Advanced Tissue Degeneration and Mitochondrial Dysfunction in Rotator Cuff Tears

PurposeThe purpose of this study was to investigate the relationship between magnetic resonance imaging (MRI) signal intensities and mitochondrial function in patients undergoing arthroscopic rotator cuff repair, assessed through histological and genetic profiling of tendon tissue. MethodsThis study, conducted between April 2022 and January 2023, included 20 patients undergoing rotator cuff repair for atraumatic/degenerative tears. Rotator cuff tendon edge samples were obtained during arthroscopic rotator cuff repair. Patients were classified based on signal intensity from preoperative T2-weighted fat suppressed MRI. Specifically, they were categorized as having either high or low signal intensity at the rotator cuff tendon edge, with the deltoid muscle serving as a reference. Comparative analyses specifically compared the histological features and genetic profiles of the tendon tissue at the rotator cuff tendon edge. Histological evaluation of harvested tendon specimens during arthroscopic rotator cuff repair employed the modified Bonar score. Real-time polymerase chain reaction was used to assess expression of various mitochondrial and apoptosis-related genes. The mitochondrial morphology of the rotator cuff torn site was examined using electron microscopy. ResultsThe higher signal intensity group showed significantly higher modified Bonar scores (p=0.0068), decreased mitochondrial gene expression, increased TUNEL-positive cells (p=0.032), lower SOD activity (p=0.011), reduced ATP5A (p=0.031), and increased cleaved caspase-9 activity (p=0.026) when compared to the lower signal intensity group. Electron microscopy revealed fewer mitochondrial cristae in the higher signal intensity group. ConclusionOur results suggest correlations between high MRI signal intensities and the presence of degeneration, mitochondrial dysfunction, and increased apoptosis in rotator cuff tissues. This underscores the utility of MRI signal intensity as an indicator of tissue condition. Clinical RelevanceBuilding on the established premise that elevated preoperative MRI signal intensities may indicate higher rates of postoperative rotator cuff re-tears, the current study substantiates these findings from a mitochondrial function perspective.

Effects of sodium glucose co-transporter-2 inhibitor on atrial tachyarrhythmia burden in patients with cardiovascular implantable electronic device

Abstract Introduction Previous studies showed that sodium glucose co-transporter-2 inhibitors (SGLT2i) were associated with a lower atrial fibrillation (AF) incidence. Purpose Since mitochondrial dysfunction has been linked with AF, we aimed to examine the effects of SGLT2i on AF burden and mitochondrial function in patients with cardiovascular implantable electronic device (CIED). Methods Patients with CIED were randomly assigned to receive either dapagliflozin 10 mg daily or placebo for 3 months. The AF burden was measured as atrial high-rate episodes (AHRE) via CIED interrogations, and data were collected at baseline and 3-months post-treatment. Oxidative stress and mitochondrial function were determined in peripheral blood mononuclear cells (PBMCs). Results The study enrolled 54 CIED patients. There were 9 (16.7%) patients with diabetes mellitus and 36 (66.7%) patients with history of clinical AF. The changes of AHRE burden after 3-month treatments did not differ between dapagliflozin and placebo groups. However, in those with clinical AF, dapagliflozin significantly decreased the number of AHRE per month as compared to placebo (-2.2 vs. +0.6 episodes per month, p=0.048) (Table 1). Mitochondrial spare respiratory capacity (SRC) percentage was significantly increased after treatment with dapagliflozin (162.1% to 203.2%, p=0.003), whereas this was not found in the placebo group (Figure 1). In the subgroup analysis of patients with clinical AF, dapagliflozin showed significant improvement in both the SRC percentage (165.7 to 201.7%, p=0.016) and a reduction in cellular oxidative stress (26,840.5 to 18,164.0 arbitrary unit, p=0.049). Conclusions Dapagliflozin significantly reduced the number of AHRE per month in patients with history of clinical AF. The improvement in PBMC’s mitochondrial function and reduced cellular oxidative stress among dapagliflozin users could be the mechanisms responsible for its anti-atrial arrhythmic effect.Table 1Figure 1

A Mitochondrial Targeted Ubiquinol (MitoQ) Improves Immune Cell Bioenergetics in Patients with Heart Failure with Preserved Ejection Fraction

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is a proinflammatory syndrome. Mitochondrial dysfunction that is characteristic of HFpEF could alter immunometabolism, attenuating the functional reserve of immune cells. In addition, immune cell mitochondrial respiration is a biomarker of systemic mitochondrial health. The aim of this study was to assess the impact of a chronic oral mitochondrial targeted ubiquinol (MitoQ) on the immune cell bioenergetic profile in patients with HFpEF. We hypothesized that MitoQ administration in patients with HFpEF, would improve mitochondrial respiration in peripheral blood mononuclear cells (PBMC’s). METHODS: In this double-blind, crossover trial 8 patients with a clinical diagnosis of HFpEF (6 female, 2 male; 6 African American/Black, 2 white; mean ± SEM, Age, 58±5 years; BMI, 37±1 kg/m2) received a 4 week oral dose of MitoQ (MTQ, 20 mg/day) and placebo (PLB) in random order separated by a 2 week wash out period. Following completion of each trial arm, a venous blood sample was obtained and PBMCs were isolated using density gradient centrifugation. High resolution respirometry coupled with modulators of cellular respiration was performed to obtain basal respiration, ATP-linked respiration, maximal respiration, and spare respiratory capacity of the immune cells. Paired samples t-tests were used to compare variables between conditions. RESULTS: MitoQ was safe, well tolerated, and compliance was high (MTQ, 99 ± 1%; PLB, 89±4%). Basal respiration (MTQ, 106.4 ± 11.5 pmol/min; PLB, 66.5±5.9 pmol/min; p=0.002), ATP-linked respiration (MTQ, 41.4± 16.9 pmol/min; PLB, 16.3±6.7 pmol/min; p=0.04), maximal respiration (MTQ, 323.9 ± 50.0 pmol/min; PLB, 65.4±23.1 pmol/min; p=0.01), spare respiratory capacity (MTQ, 217.5 ± 39.6 pmol/min; PLB, 149.6 ±18.2 pmol/min; p=0.02), were higher following MTQ compared to PLB. CONCLUSIONS: In patients with HFpEF, administration of a mitochondrial targeted ubiquinol improved the immune cell mitochondrial respiration capacity and effciency. An increase in spare respiratory capacity following MTQ reflects an improvement in functional reserve that would augment the ability to respond to an acute stressor. These findings have positive implications for the ability to target and improve mitochondrial function in patients with HFpEF. Future work should investigate if the observed improvements in immune cell mitochondrial function are mirrored in other tissues. Supported by AHA 19CDA3474002. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Yiqigubiao pill treatment regulates Sirtuin 5 expression and mitochondrial function in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a heterogeneous group of pathophysiological bases of airway inflammation and its anti-inflammatory response. Aberrant mitochondrial signaling and mitochondrial dysfunction underlie the pathomechanisms leading to COPD. This study aims to investigate the effects of the Yiqigubiao (YQGB) pill, a traditional Chinese medicine (TCM), on Sirtuin 5 (SIRT5) and mitochondrial function in patients with COPD. Thirty-four patients with COPD were randomized into oral YQGB or placebo groups concurrent with a 24-week routine treatment. The pulmonary function was assessed by examining the levels of forced expiratory volume in one second (FEV1)/forced vital capacity (FVC), FEV1, and FVC. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were used to detect SIRT5 expression in mitochondria isolated from peripheral blood. Flow cytometry was used to detect changes in mitochondrial membrane potential and reactive oxygen species (ROS) in peripheral blood lymphocytes. Human bronchial epithelial (HBE) cells stimulated by cigarette smoke extract (CSE) were treated with YQGB. After SIRT5 was knocked down in cells, the changes in mitochondrial membrane potential, levels of adenosine triphosphate (ATP), and ROS were detected. YQGB treatment significantly improved lung function in patients with COPD. The expression of SIRT5 and the mitochondrial membrane potential significantly increased and ROS decreased in patients with COPD after YQGB treatment. The CSE decreased cell proliferation and SIRT5 expression, which was alleviated after YQGB treatment. Furthermore, SIRT5 was knocked down in CSE-stimulated HBE cells, and its expression was elevated upon YQGB treatment. The knockdown of SIRT5 significantly altered the CSE-stimulation-induced dysregulation of mitochondrial membrane potential, ATP levels, and ROS. This was also restored after YQGB treatment. YQGB treatment can elevate SIRT5 expression, restore mitochondrial function in COPD, and exert protective effects.

FRI029 Chronic Free Fatty Acid Elevation Is Associated With An Overcompensatory Increase In Hepatic Mitochondrial Function In Patients With Overweight Or Obesity

Abstract Disclosure: F. Bril: None. S. Kalavalapalli: None. K. Cusi: None. The obesity epidemic has resulted in a significant increase in the prevalence of nonalcoholic fatty liver disease (NAFLD). Some patients with NAFLD progress to more severe forms of the disease, such as nonalcoholic steatohepatitis (NASH) and cirrhosis. Our central hypothesis is that the inability of hepatic mitochondria to enhance nutrient oxidation in the setting of nutrient oversupply plays a key role in the progression of NAFLD. Specifically, the aim of this study was to assess if free fatty acid (FFA) excess contributes to hepatic mitochondrial dysfunction in patients with overweight or obesity. Patients with BMI ≥ 25kg/m2, without diabetes were included in the study. Patients underwent a 2-hour oral glucose tolerance test (OGTT) and a liver proton magnetic resonance spectroscopy (1H-MRS) to measure liver fat. In vivo hepatic mitochondrial ATP levels were measured by phosphorus (31P)-MRS every 30 minutes during a 2-hour oral fructose challenge (OFC). Due to unregulated phosphorylation of fructose upon entering hepatocytes, the OFC provides a dynamic measurement of hepatic ATP consumption and re-synthesis. Hepatic ATP levels were estimated as β-ATP/total phosphorus. A total of 37 patients were recruited for this study (age: 54 ± 11 years; sex: 43% male/57% female; BMI: 34.4 ± 6.3 kg/m2; A1c: 5.7 ± 0.4%; NAFLD: 51%). No differences were found in hepatic ATP levels in patients with or without NAFLD (0.019 ± 0.015 vs. 0.016 ± 0.012, p=0.44). Patients were then divided in three groups (tertiles) based on fasting FFA levels. We did not observe any significant differences among these three groups in key clinical variables, such as age, sex, BMI, A1c or prevalence of NAFLD. At baseline (pre OFC), we did not observe any difference in hepatic ATP levels (i.e., β-ATP/total phosphorus) among FFA tertiles (0.020 ± 0.015, 0.020 ± 0.012, and 0.012 ± 0.012, p=0.25). During the OFC, we estimated changes over time in hepatic ATP levels as the decremental area under the curve (AUROC) of β-ATP/total phosphorus. We observed that the decremental AUROC of hepatic ATP levels during OFC was significantly different among groups (0.57 ± 0.86, 0.14 ± 0.59, -0.40 ± 0.54, p=0.006). Patients in the highest tertile of FFAs showed no consumption of ATP after the OFC, but rather an overall increase in ATP AUROC over time. Plasma FFA levels correlated well with hepatic ATP AUROC during the OFC (-0.47, p =0.007). Conclusion: Chronic elevations in FFA levels are associated with changes in hepatic mitochondrial ATP synthesis, which were unmasked after an oral fructose challenge. While long-term, FFA elevations may impair mitochondrial function, in our study we observed an overcompensatory response in patients with high plasma FFA, characterized by an increase in hepatic ATP levels over time after fructose consumption. At what point this compensation is overwhelmed leading to inflammation and cellular lipotoxicity remains to be determined. Presentation: Friday, June 16, 2023

Abstract P373: Nuclear Receptor 4As (NR4A) Expression In Patients With Chronic Kidney Disease

Background: Nuclear Receptor 4As (NR4A1, NR4A2, and NR4A3) play important metabolic, immune, and cardiovascular functions. These receptors also play a role in mitochondrial function. Patients with chronic kidney disease (CKD) have impaired mitochondrial function and biogenesis. Thus, in this study, we hypothesize that NR4As are downregulated in muscles in patients with CKD. Methods: In a cross-sectional study, we performed RNA sequencing in skeletal muscle biopsies from three groups; controls (n=13), patients with CKD 3-5 not yet on hemodialysis (n=13), and patients on maintenance hemodialysis (MHD, n=10). Total RNA was extracted to construct libraries for total RNA sequencing using Illumina NovaSeq 6000 system. Differentially expressed genes were identified with a false discovery rate (FDR) &lt;0.05 and fold change &gt; 2. We focused our analysis on genes involved in mitochondrial biogenesis. Results: Groups were matched by gender, body mass index, and history of diabetes and hypertension. There was no difference in markers of mitochondrial biogenesis between controls and patients with CKD 3-5. We only found a significant decrease in NR4A1 and NR4A3 gene expression in patients on MHD ( Figure 1 ) compared to control (p=0.006 and p= 0.02; NR4A1 and NR4A3, respectively) and to patients with CKD 3-5 (p=8.85E-05 and p=0.005; NR4A1 and NR4A3, respectively). Conclusions: NR4A1 and NR4A3 were downregulated in muscle biopsies from patients on MHD. These findings may explain the reduced mitochondrial content and impaired mitochondrial function in patients with CKD. Further studies should evaluate the benefit of NR4As-targeted therapies to prevent mitochondrial dysfunction in CKD.

Identification of peripheral vascular function measures and circulating biomarkers of mitochondrial function in patients with mitochondrial disease.

The development of pharmacological therapies for mitochondrial diseases is hampered by the lack of tissue-level and circulating biomarkers reflecting effects of compounds on endothelial and mitochondrial function. This phase 0 study aimed to identify biomarkers differentiating between patients with mitochondrial disease and healthy volunteers (HVs). In this cross-sectional case-control study, eight participants with mitochondrial disease and eight HVs matched on age, sex, and body mass index underwent study assessments consisting of blood collection for evaluation of plasma and serum biomarkers, mitochondrial function in peripheral blood mononuclear cells (PBMCs), and an array of imaging methods for assessment of (micro)circulation. Plasma biomarkers GDF-15, IL-6, NT-proBNP, and cTNI were significantly elevated in patients compared to HVs, as were several clinical chemistry and hematology markers. No differences between groups were found for mitochondrial membrane potential, mitochondrial reactive oxygen production, oxygen consumption rate, or extracellular acidification rate in PBMCs. Imaging revealed significantly higher nicotinamide-adenine-dinucleotide-hydrogen (NADH) content in skin as well as reduced passive leg movement-induced hyperemia in patients. This study confirmed results of earlier studies regarding plasma biomarkers in mitochondrial disease and identified several imaging techniques that could detect functional differences at the tissue level between participants with mitochondrial disease and HVs. However, assays of mitochondrial function in PBMCs did not show differences between participants with mitochondrial disease and HVs, possibly reflecting compensatory mechanisms and heterogeneity in mutational load. In future clinical trials, using a mix of imaging and blood-based biomarkers may be advisable, as well as combining these with an in vivo challenge to disturb homeostasis.

O008 The impact of home-based exercise prehabilitation on skeletal muscle mitochondrial function in patients awaiting curative surgery for cancer

Abstract Introduction Cancer cachexia is associated with poor surgical outcomes, including increased length of stay, morbidity and mortality. Cachexia is a complex multi-faceted pathological process consistently associated with energy imbalance via hypermetabolism. Beyond this, pre-clinical animal models suggest mitochondrial dysfunction to be an important component of cachexia, although this is unconfirmed in humans. This study aimed to investigate the mitochondrial function of pre-surgical cancer patients, and the impact of exercise prehabilitation on this. Methods This study was approved by an NHS research ethics committee (IRAS: 275264). Male patients awaiting surgery with curative intent for colorectal and prostate cancer were eligible, with healthy volunteers recruited for comparison. Muscle biopsies of vastus lateralis were taken before and after 4-weeks home-based exercise (3x/wk). Mitochondrial oxidative phosphorylation (OXPHOS) was analysed using high-resolution respirometry (Oroboros Instruments). Results Eleven cancer patients and 6 healthy volunteers were recruited. Cancer patients had significantly lower maximal coupled (44.49pmol/(s*mg) vs. 74.81pmol/(s*mg), p=0.004) and uncoupled (55.82pmol/(s*mg) vs. 100.00pmol/(s*mg), p&amp;lt;0.001) OXPHOS capacity compared to healthy controls. Exercise training significantly increased maximal coupled (44.10pmol/(s*mg) vs. 54.64pmol/(s*mg), p=0.045) and uncoupled (56.20pmol/(s*mg) vs. 71.96pmol/(s*mg), p=0.001) OXPHOS capacity in this cancer cohort. Conclusion Declines in mitochondrial function appear to play a role in cancer cachexia. Short-term exercise training, in keeping with target timeframes for surgery (i.e., &amp;lt;31-days from decision-to-treat), appears to attenuate these declines. Further work is needed to determine if declines in mitochondrial function are causative or reactive, and to identify optimal exercise regimes to mitigate these declines.

Mitochondrial TXNRD2 and ME3 Genetic Risk Scores Are Associated with Specific Primary Open-Angle Glaucoma Phenotypes

Genetic variants in regions that include the mitochondrial genes thioredoxin reductase 2 (TXNRD2) and malic enzyme 3 (ME3) are associated with primary open-angle glaucoma (POAG) in genome-wide association studies (GWASs). To assess their clinical impact, we investigated whether TXNRD2 and ME3 genetic risk scores (GRSs) are associated with specific glaucoma phenotypes. Cross-sectional study. A total of 2617 patients with POAG and 2634 control participants from the National Eye Institute Glaucoma Human Genetics Collaboration Hereditable Overall Operational Database (NEIGHBORHOOD) consortium. All POAG-associated single nucleotide polymorphisms (SNPs) in the TXNRD2 and ME3 loci were identified using GWAS data (P < 0.05). Of these, 20 TXNRD2 and 24 ME3 SNPs were selected after adjusting for linkage disequilibrium. The correlation between SNP effect size and gene expression levels was investigated using the Gene-Tissue Expression database. Genetic risk scores were constructed for each individual using the unweighted sum of TXNRD2, ME3, and TXNRD2 + ME3 combined risk alleles. Age- and sex-adjusted odds ratios (ORs) for POAG diagnosis were calculated per decile for each GRS. Additionally, the clinical features of patients with POAG in the top 1%, 5%, and 10% of each GRS were compared with those in the bottom 1%, 5%, and 10%, respectively. Primary open-angle glaucoma OR per GRS decile, maximum treated intraocular pressure (IOP), and prevalence of paracentral visual field loss among patients with POAG with high versus low GRSs. A larger SNP effect size strongly correlated with higher TXNRD2 and lower ME3 expression levels (r= 0.95 and r= -0.97, respectively; P < 0.05 for both). Individuals in decile 10 of the TXNRD2 + ME3 GRS had the highest odds of POAG diagnosis (OR, 1.79 compared with decile 1; 95% confidence interval, 1.39-2.30; P<0.001). Patients with POAG in the top 1% of the TXNRD2 GRS showed higher mean maximum treated IOP compared with the bottom 1% (19.9 mmHg vs. 15.6 mmHg; adjusted P= 0.03). Patients with POAG in the top 1% of the ME3 and TXNRD2 + ME3 GRS showed a higher prevalence of paracentral field loss than the bottom 1% (72.7% vs. 14.3% for ME3 GRS and 88.9% vs. 33.3% for TXNRD2+ME3 GRS; adjusted P= 0.03 for both). Patients with POAG with higher TXNRD2 and ME3 GRSs showed higher treated IOP and a greater prevalence of paracentral field loss. Functional studies exploring how these variants impact mitochondrial function in patients with glaucoma are warranted. Proprietary or commercial disclosure may be found after the references.

Abstract 13472: Physical Incapacity in Heart Failure Patients is Associated With Skeletal Muscle Mitochondrial Dysfunction

Introduction: The role of skeletal muscle mitochondrial dysfunction in exercise intolerance in heart failure patients is unknown. Therefore, this study aimed to identify the relationship between physical capacity and skeletal muscle mitochondrial function in patients with heart failure and reduced ejection fraction (HFrEF). Methods A total of 53 HFrEF patients and 20 age- and sex-matched controls underwent dual-energy X-ray absorptiometry to assess muscle mass by the appendicular lean mass index (ALMI), cardiopulmonary exercise testing (peakVO2), 6-minute walking test (6MWD) and maximal isometric knee-extensor strength test. In skeletal muscle biopsies from vastus lateralis, mitochondrial respiratory capacity was measured by high resolution respirometry. We performed Pearson correlations to examine the relationships between physical capacity tests and mitochondrial function. Results Mean age of the study cohort was 71.7 ±7.0 years. Compared with healthy controls, HFrEF patients had a lower peakVO2 (14.6 ±4.1 vs. 26.2 ±8.0 mL/kg/min, p &lt;0.001) and a shorter 6MWD (429 ±106 vs. 581 ±93 m, p &lt;0.001). HFrEF patients had a lower ALMI (0.74 ±0.15 vs. 0.86 ±0.16 kg/(kg/m 2 ), p = 0.005). Maximal coupled mitochondrial respiration was decreased in HFrEF patients compared with healthy controls (59.1 ±19.0 vs. 92.6 ±38.8 ρmol O 2 *s -1 mg -1 , p &lt;0.001) as well as the respiratory control ratio (7.2 ±2.5 vs. 9.7 ±3.1). Maximal coupled mitochondrial respiration was correlated to peakVO2 (r = 0.58, p &lt;0.001) and 6MWD (r = 0.44, p &lt;0.001), but not to muscle mass or maximal knee-extensor strength. Conclusions HFrEF patients had a lower peakVO2, shorter 6MWD and impaired skeletal muscle mitochondrial function as compared with controls. Maximal coupled mitochondrial respiration was correlated with physical capacity across the population of HFrEF patients and healthy controls establishing an association between skeletal muscle mitochondrial dysfunction and physical incapacity.

Reversible Thiol Oxidation Increases Mitochondrial Electron Transport Complex Enzyme Activity but Not Respiration in Cardiomyocytes from Patients with End-Stage Heart Failure.

Cardiomyocyte dysfunction in patients with end-stage heart failure with reduced ejection fraction (HFrEF) stems from mitochondrial dysfunction, which contributes to an energetic crisis. Mitochondrial dysfunction reportedly relates to increased markers of oxidative stress, but the impact of reversible thiol oxidation on myocardial mitochondrial function in patients with HFrEF has not been investigated. In the present study, we assessed mitochondrial function in ventricular biopsies from patients with end-stage HFrEF in the presence and absence of the thiol-reducing agent dithiothreitol (DTT). Isolated mitochondria exposed to DTT had increased enzyme activity of complexes I (p = 0.009) and III (p = 0.018) of the electron transport system, while complexes II (p = 0.630) and IV (p = 0.926) showed no changes. However, increased enzyme activity did not carry over to measurements of mitochondrial respiration in permeabilized bundles. Oxidative phosphorylation conductance (p = 0.439), maximal respiration (p = 0.312), and ADP sensitivity (p = 0.514) were unchanged by 5 mM DTT treatment. These results indicate that mitochondrial function can be modulated through reversible thiol oxidation, but other components of mitochondrial energy transfer are rate limiting in end-stage HFrEF. Optimal therapies to normalize cardiac mitochondrial respiration in patients with end-stage HFrEF may benefit from interventions to reverse thiol oxidation, which limits complex I and III activities.

The Mitochondrial Epigenome: An Unexplored Avenue to Explain Unexplained Myopathies?

Mutations in either mitochondrial DNA (mtDNA) or nuclear genes that encode mitochondrial proteins may lead to dysfunctional mitochondria, giving rise to mitochondrial diseases. Some mitochondrial myopathies, however, present without a known underlying cause. Interestingly, methylation of mtDNA has been associated with various clinical pathologies. The present study set out to assess whether mtDNA methylation could explain impaired mitochondrial function in patients diagnosed with myopathy without known underlying genetic mutations. Enhanced mtDNA methylation was indicated by pyrosequencing for muscle biopsies of 14 myopathy patients compared to four healthy controls, at selected cytosines in the Cytochrome B (CYTB) gene, but not within the displacement loop (D-loop) region. The mtDNA methylation patterns of the four healthy muscle biopsies were highly consistent and showed intriguing tissue-specific differences at particular cytosines with control skin fibroblasts cultured in vitro. Within individual myopathy patients, the overall mtDNA methylation pattern correlated well between muscle and skin fibroblasts. Despite this correlation, a pilot analysis of four myopathy and five healthy fibroblast samples did not reveal a disease-associated difference in mtDNA methylation. We did, however, detect increased expression of solute carrier family 25A26 (SLC25A26), encoding the importer of S-adenosylmethionine, together with enhanced mtDNA copy numbers in myopathy fibroblasts compared to healthy controls. To confirm that pyrosequencing indeed reflected DNA methylation and not bisulfite accessibility, mass spectrometry was employed. Although no myopathy-related differences in total amount of methylated cytosines were detected at this stage, a significant contribution of contaminating nuclear DNA (nDNA) was revealed, and steps to improve enrichment for mtDNA are reported. In conclusion, in this explorative study we show that analyzing the mitochondrial genome beyond its sequence opens novel avenues to identify potential molecular biomarkers assisting in the diagnosis of unexplained myopathies.

Influence of Immune Cell Subtypes on Mitochondrial Measurements in Peripheral Blood Mononuclear Cells From Children with Sepsis.

Peripheral blood mononuclear cells (PBMCs) are commonly used to compare mitochondrial function in patients with versus without sepsis, but how these measurements in this mixed cell population vary by composition of immune cell subtypes is not known, especially in children. We determined the effect of changing immune cell composition on PBMC mitochondrial respiration and content in children with and without sepsis. PBMC mitochondrial respiration and citrate synthase (CS) activity, a marker of mitochondrial content, were measured in 167 children with sepsis at three timepoints (day 1-2, 3-5, and 8-14) and once in 19 nonseptic controls. The proportion of lymphocytes and monocytes and T, B, and NK cells was measured using flow cytometry. More specific CD4+ and CD8+ T cell subsets were measured from 13 sepsis patients and 6 controls. Spearman's correlation and simple and mixed effects linear regression were used to determine the association of PBMC mitochondrial measures with proportion of immune cell subtypes. PBMC mitochondrial respiration and CS activity were correlated with proportion of monocytes, lymphocytes, T B, and NK cells in controls, but not in sepsis patients. PBMC mitochondrial respiration was correlated with CD4+ and CD8+ T cell subsets in both groups. After controlling for differences in immune cell composition between groups using linear regression models, PBMC respiration and CS activity remained lower in sepsis patients than controls. Mitochondrial measurements from PBMCs varied with changes in immune cell composition in children with and without sepsis. However, differences in PBMC mitochondrial measurements between sepsis patients and controls were at least partially attributable to the effects of sepsis rather than solely an epiphenomena of variable immune cell composition.

283-OR: Inadequate Hepatic Mitochondrial Adaptation in Patients with NASH Is Related to the Severity of Steatohepatitis and Fibrosis Stage

Dysfunctional mitochondrial function plays an important role in the progression of nonalcoholic steatohepatitis (NASH). Mitochondrial (mt) respiratory function assessed by oxidative phosphorylation/ OXPHOS (activated respiration with mt complex I [OXPHOS CI] and mt complex I + II [OXPHOS CI+II] substrates) and electron transport system capacity [ETC] were measured using high-resolution respirometry (Oroboros Oxygraph 2k). The aim of this study was to assess mitochondrial function in patients a) with vs. without NASH, and b) NASH with vs. without fibrosis. Liver tissue was obtained from 40 patients (age: 52 ± 12 yrs; BMI: 39.4 ± 8.4 kg/m2; HbA1c: 6.9 ± 1.5%) with NAFLD and obesity or T2DM either by percutaneous liver biopsy (n=28) or during bariatric surgery (n=12). Patients with vs. without NASH (n=20 in each group) were more insulin resistant/ IR (HOMA-IR: 8.1 ± 4.2 vs. 4.5 ± 2.7 mg/dl x μU/ml; Adipo-IR: 10.4 ± 7.2 vs. 6.2 ± 3.8 mmol/L x µU/mL) and had higher OXPHOS CI+II (all p&amp;lt;0.05), likely an adaptation to IR and higher FFA flux to the liver. We then compared those with worse steatohepatitis (necroinflammation score/ NIS), divided as mild (n=16), moderate (n=15) or severe (n=9). Patients with moderate vs. mild NIS had increased mitochondrial respiration, expressed as pmol/(s x mg wet weight) (OXPHOS CI: 20.8 ± 4.8 vs. 16.4 ± 4.6; OXPHOS CI+II: 46.0 ± 11.4 vs. 31.3 ± 9.8; ETC: 60.5 ± 17.1 vs. 46.4 ± 15.2; all p&amp;lt;0.05). There was a trend for these parameters to decline with the most severe disease activity, that was significant when patients with NASH also had significant fibrosis vs. mild or no fibrosis (OXPHOS CI+II: 38.6 ± 7.8 vs. 49.8 ± 12.5, p=0.04; ETC: 50.3 ± 12.9 vs. 67.5 ± 16.1; p=0.02). Conclusion: In patients with NASH vs. simple steatosis, there is an early hepatic mitochondrial adaptation to severe insulin resistance. This adaptation is impaired when disease activity worsens, being most evident once patients develop steatohepatitis with significant fibrosis. Disclosure S. Kalavalapalli: None. D. Poulton: None. L. Mansour: None. S. Shrestha: None. F. Bril: None. S. K. Subbarayan: None. S. Kadiyala: None. K. Cusi: None. D. Barb: None. E. Godinez: None. R. Lomonaco: None. J. Friedman: Consultant; Self; Ethicon, Inc. S. Wohlgemuth: None. N. Fanous: None. R. E. Dillard: None. T. M. Cowan: None.

Mitochondrial Disorders in Stroke and Chronic Brain Ischemia

Stroke is the leading cause of disability and death in the adult population. Modern methods of treating patients with acute ischemic stroke include thrombolytic therapy with a narrow therapeutic window and endovascular thrombectomy. The development of other methods of treatment of brain hypoxia in the penumbra zone is relevant. Mitochondria, which are involved in immediate and delayed molecular mechanisms of adaptation to hypoxic stress in the cerebral cortex, primarily respond to hypoxia. Hypoxia induces reprogramming of the mitochondrial respiratory chain function and switching from oxidation of substrates of the respiratory chain complex I to succinate oxidation (complex II). The brain's need for succinate increases. Clinical studies have shown a positive effect of drugs containing succinates on the course of stroke. The study of mitochondrial function is carried out mainly in an experiment. In the present study of mitochondrial disorders in stroke and chronic brain ischemia in adult patients, the quantitative method proposed by A. G. Pearse was used to assess the activity of mitochondrial enzymes of peripheral blood lymphocytes, which are referred to as the enematic mirror of tissues. In acute cerebral ischemia, a compensatory increase in the activity of succinate dehydrogenase was observed on the first day, indicating the tension (increased activity) of the second complex of the mitochondrial respiratory chain.. These data confirm the need to prescribe succinic acid in the acute phase of stroke. At the same time, the dose of 250 mg per day is not sufficient for patients with increased body weight. The standard dose of the drug should be higher, taking into account the different body weight of patients. In patients with stroke, there was also a decrease in the activity of α-glycerophosphate dehydrogenase, which is involved in the fat metabolism of mitochondria, which is an indication for the appointment of carnitine. In chronic brain ischemia, the activity of succinate dehydrogenase and α-glycerophosphate dehydrogenase decreased, indicating indications for the appointment of idebenone and carnitine along with vasodilator therapy and endovascular thrombectomy. Thus, the results of a study of mitochondrial function in patients with acute and chronic brain ischemia are presented. Violations of complex II in the respiratory chain cycle and violation of fat metabolism were revealed, indicating indications for the appointment of energotropic therapy.

Palmitate but Not Oleate Exerts a Negative Effect on Oxygen Utilization in Myoblasts of Patients with the m.3243A&gt;G Mutation: A Pilot Study

It is known that exposure to excess saturated fatty acids, especially palmitate, can trigger cellular stress responses interpreted as lipotoxicity. The effect of excessive free fatty acids on oxidative phosphorylation capacity in myoblasts of patients with the m.3243A>G mutation was evaluated with the mitochondrial (Mito) stress test using a Seahorse XF96 analyzer. ß-oxidation, measured with the Seahorse XF96 analyzer, was similar in patients and controls, and reduced in both patients and controls at 40 °C compared to 37 °C. Mito stress test in the absence of fatty acids showed lower values in patients compared to controls. The mitochondrial activity and ATP production rates were significantly reduced in presence of palmitate, but not of oleate in patients, showing a negative effect of excessive palmitate on mitochondrial function in patients. Diabetes mellitus is a frequent symptom in patients with m.3243A>G mutation. It can be speculated that the negative effect of palmitate on mitochondrial function might be related to diacylglycerols (DAG) and ceramides (CER) mediated insulin resistance. This might contribute to the elevated risk for diabetes mellitus in m.3243A>G patients.

Inter-organelle Communication in the Pathogenesis of Mitochondrial Dysfunction and Insulin Resistance.

Impairments in mitochondrial function in patients with insulin resistance and type 2 diabetes have been disputed for decades. This review aims to briefly summarize the current knowledge on mitochondrial dysfunction in metabolic tissues and to particularly focus on addressing a new perspective of mitochondrial dysfunction, the altered capacity of mitochondria to communicate with other organelles within insulin-resistant tissues. Organelle interactions are temporally and spatially formed connections essential for normal cell function. Recent studies have shown that mitochondria interact with various cellular organelles, such as the endoplasmic reticulum, lysosomes and lipid droplets, forming inter-organelle junctions. We will discuss the current knowledge on alterations in these mitochondria-organelle interactions in insulin resistance and diabetes, with a focus on changes in mitochondria-lipid droplet communication as a major player in ectopic lipid accumulation, lipotoxicity and insulin resistance.

Changes in mitochondrial function in patients with neuromyelitis optica; correlations with motor and cognitive disabilities.

BackgroundNeuromyelitis Optica (NMO) is an inflammatory demyelinating disease that mainly affects optic nerves and spinal cord. Besides, loss of motor and cognitive function has been reported as important symptoms of disease.ObjectiveHere we investigated the mitochondrial dysfunction and metabolic alterations in NMO patients and evaluate their correlation with disease progress, disability and cognitive impairment.MethodsThe individuals (12 controls and 12 NMO) were assessed for disease severity by expanded disease status scale (EDSS), cognitive function via symbol digit modalities test (SDMT) and fine motor disability by 9-hole peg test (9-HPT). We have measured Sirtuin 1 (SIRT1), SIRT3, mitochondrial complex I, complex IV, aconitase and α-ketoglutarate dehydrogenase (α-KGD) activity in peripheral blood mononuclear cells (PBMCs). Furthermore, SIRT1, pyruvate, lactate and cytochrome c (Cyt c) were determined in plasma.ResultsOur results exhibited increased 9-HPT time in NMO patients. 9-HPT results correlated with EDSS; and SDMT negatively correlated with disease duration and number of attacks in patients. Investigation of PBMCs of NMO patients exhibited a decrease of mitochondrial complex I and IV activity that was significant for complex IV. Besides, complex I activity was negatively correlated with 9-HPT time in NMO group. In the plasma samples, a correlation between pyruvate to lactate ratio and EDSS in NMO patients was found and a negative correlation between Cyt c concentration and SDMT was detected.ConclusionOur data support the hypothesis that mitochondrial dysfunction occurred in the CNS and the peripheral blood may contribute to disease progress, disability level and the cognitive impairment in NMO patients.