mtDNA Copy Number In Patients Research Articles

#1868 Dapagliflozin reduces urinary kidney injury biomarkers in chronic kidney disease irrespective of albuminuria level

Abstract Background and Aims The beneficial effects of Sodium-Glucose Cotransporter 2(SGLT2) inhibitor in patients with chronic kidney disease (CKD) with low albuminuria levels have not been established. In this study, we aimed to compare the effects of dapagliflozin on kidney injury biomarkers in patients with CKD stratified by albuminuria level. Method We prospectively enrolled healthy volunteers (HVs) (n = 20) and patients with CKD (n = 54) with and without diabetes mellitus (DM). Patients with CKD were divided into two subgroups by age- and sex-matched according to urinary albumin-creatinine ratio (uACR) levels (<300 mg/g and ≥300 mg/g). The CKD group received dapagliflozin 10 mg per day. Urine samples were collected before treatment and after 3 months and 6 months of dapagliflozin. Urinary kidney injury molecule-1 (KIM-1), interleukin-1β (IL-1β), and mitochondrial DNA nicotinamide adenine dinucleotide dehydrogenase subunit-1 (mtND1) copy number were measured. Results The estimated glomerular filtration rate (eGFR) of patients with CKD was lower than that of HVs (p < 0.001). During the study period, eGFR decreased and uACR did not change in the CKD group. Kidney injury markers were significantly elevated in patients with CKD compared with those in HVs. Dapagliflozin reduced urinary KIM-1, IL-1β and mtDNA copy number in patients with CKD after 6 months of treatment. In further, the levels of urinary KIM-1 and IL-1β, patients with CKD decreased after 6 months of dapagliflozin treatment regardless of albuminuria level. Conclusion In this study, dapagliflozin reduced urinary kidney injury biomarkers in patients with CKD, regardless of albuminuria level. These findings suggest that SGLT2i may also attenuate the progression of low albuminuric CKD.

Dapagliflozin Reduces Urinary Kidney Injury Biomarkers in Chronic Kidney Disease Irrespective of Albuminuria Level.

The beneficial effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors in patients with chronic kidney disease (CKD) with low albuminuria levels have not been established. This study aimed to compare the effects of dapagliflozin on kidney injury biomarkers in patients with CKD stratified by albuminuria level. We prospectively enrolled healthy volunteers (HVs; n = 20) and patients with CKD (n = 54) with and without diabetes mellitus. Patients with CKD were divided into two age-matched and sex-matched subgroups according to urinary albumin-creatinine ratio (uACR) levels (<300 mg/g and ≥300 mg/g). The CKD group received dapagliflozin (10 mg/day). Urine samples were collected before treatment and after 3 and 6 months of dapagliflozin. Urinary kidney injury molecule-1 (KIM-1), interleukin-1β (IL-1β), and mitochondrial DNA nicotinamide adenine dinucleotide dehydrogenase subunit-1 (mtND1) copy number were measured. The estimated glomerular filtration rate (eGFR) of patients with CKD was lower than that of HVs (P < 0.001). During the study period, eGFR decreased and uACR did not change in the CKD group. Kidney injury markers were significantly elevated in patients with CKD compared with those in HVs. Dapagliflozin reduced urinary KIM-1, IL-1β, and mtDNA copy number in patients with CKD after 6 months of treatment. In further, the levels of urinary KIM-1 and IL-1β, patients with CKD decreased after 6 months of dapagliflozin treatment regardless of albuminuria level. Dapagliflozin reduced urinary kidney injury biomarkers in patients with CKD, regardless of albuminuria level. These findings suggest that SGLT2 inhibitors may also attenuate the progression of low albuminuric CKD.

Comparison between D-loop methylation and mtDNA copy number in patients with Aicardi-Goutières Syndrome.

Aicardi-Goutières Syndrome (AGS) is a rare encephalopathy with early onset that can be transmitted in both dominant and recessive forms. Its phenotypic covers a wide range of neurological and extraneurological symptoms. Nine genes that are all involved in nucleic acids (NAs) metabolism or signaling have so far been linked to the AGS phenotype. Recently, a link between autoimmune or neurodegenerative conditions and mitochondrial dysfunctions has been found. As part of the intricate system of epigenetic control, the mtDNA goes through various alterations. The displacement (D-loop) region represents one of the most methylated sites in the mtDNA. The term "mitoepigenetics" has been introduced as a result of increasing data suggesting that epigenetic processes may play a critical role in the control of mtDNA transcription and replication. Since we showed that RNASEH2B and RNASEH2A-mutated Lymphoblastoid Cell Lines (LCLs) derived from AGS patients had mitochondrial alterations, highlighting changes in the mtDNA content, the main objective of this study was to examine any potential methylation changes in the D-loop regulatory region of mitochondria and their relationship to the mtDNA copy number in peripheral blood cells of AGS patients with mutations in various AGS genes and healthy controls. We collected blood samples from 25 AGS patients and we performed RT-qPCR to assess the mtDNA copy number and pyrosequencing to measure DNA methylation levels in the D-loop region. Comparing AGS patients to healthy controls, D-loop methylation levels and mtDNA copy number increased significantly. We also observed that in AGS patients, the mtDNA copy number increased with age at sampling, but not the D-loop methylation levels, and there was no relationship between sex and mtDNA copy number. In addition, the D-loop methylation levels and mtDNA copy number in the AGS group showed a non-statistically significant positive relation. These findings, which contradict the evidence for an inverse relationship between D-loop methylation levels and mtDNA copy number, show that AGS patients have higher D-loop methylation levels than healthy control subjects. Additional research is needed to identify the function of these features in the etiology and course of AGS.

Mitochondrial DNA copy number as a diagnostic marker and indicator of degree of severity in alopecia areata

ABSTRACT Alopecia areata (AA) is a disorder with several etiologies. The evidence suggests that the absolute copy number of mitochondrial deoxyribonucleic acid (mtDNA), as well as proportion of mutated mtDNA copies, determines disease onset. This study aims to quantify the relative index of the mtDNA copy number in patients with AA and healthy controls and correlate the results with the existing clinical ‎information. This case-control study included 50 patients with AA and 50 age- and sex-coordinated healthy persons as controls. The severity of AA was weighed using the Severity of Alopecia Tool and Kavak’s classification. The relative index of the mtDNA copy number was measured by real-time qPCR. Significant statistical difference was observed between cases and controls regarding mean mtDNA copy number, p < .001. There was significant positive correlation with SALT score (p = 0.001). A cutoff value of >1.619 N/µL could significantly diagnose AA cases (p < .001), and a cutoff value of > 1.36 N/µL could discriminate mild AA cases from those with moderate AA (p = 0.007). The relative index of mtDNA copy number is significantly elevated in AA cases and could be helpful in diagnosing and evaluating AA severity.

Mitochondrial DNA Copy Number in Rett Syndrome Caused by Methyl-CpG-Binding Protein-2 Variants

To determine changes in mitochondrial DNA (mtDNA) copy number in peripheral blood in Rett syndrome caused by methyl-CpG-binding protein-2 (MECP2) variants and explore the mechanism of mitochondrial dysfunction in Rett syndrome. Female patients who were diagnosed with Rett syndrome and had an MECP2 variant (n=142) were recruited in this study, along with the same number of age- and sex-matched healthy controls. MtDNA copy number was quantified by real-time quantitative polymerase chain reaction with TaqMan probes. The differences in mtDNA copy number between the Rett syndrome group and the control group were analyzed using the independent-samples t test. Linear regression, biserial correlation analysis, and one-way ANOVA were applied for the correlations between mtDNA copy number and age, clinical severity, variant types, functional domains, and hot-spot variants. MtDNA copy number was found to be significantly increased in the patients with Rett syndrome with MECP2 gene variants compared with the control subjects. Age, clinical severity, variant types, functional domains, and hot-spot variants were not related to mtDNA copy number in patients with Rett syndrome. MtDNA copy number is increased significantly in patients with Rett syndrome, suggesting that changes in mitochondrial function in Rett syndrome trigger a compensatory increase in mtDNA copy number and providing new possibilities for treating Rett syndrome, such as mitochondria-targeted therapies.

Next generation sequencing-based analysis of mitochondrial DNA characteristics in plasma extracellular vesicles of patients with hepatocellular carcinoma.

Emerging evidence has revealed that mitochondrial DNA (mtDNA) is encapsulated in plasma extracellular vesicles (EVs). However, the characteristics of mtDNA in EVs from patients with cancer remain largely unexplored, which greatly limits its clinical application. Whole genome and capture-based sequencing found that EV mtDNA covered the whole mitochondrial genome. The medium fragment size in EV mtDNA was significantly larger compared with that in cell-free mtDNA [cfmtDNA; 159 vs. 109 base pairs (bp); P<0.001]. EV DNA appeared to have a higher mtDNA copy number compared with cfDNA. Of note, patients with hepatitis had >300-bp fragments in EV mtDNA compared with patients with hepatocellular carcinoma (HCC) and healthy controls. EV mtDNA fragments >300 bp in length exhibited a significantly higher proportion of EV mtDNA fragment ends than those that were ≤300 bp in length in patients with hepatitis. The EV mtDNA copy number in patients with HCC and hepatitis were significantly lower compared with those in healthy controls. Furthermore, inconsistencies in the mtDNA heteroplasmic variant were observed among HCC tissues, plasma and EVs. In conclusion, EV mtDNA exhibited different characteristics among patients with HCC, hepatitis and healthy controls, indicating the potential value of EV mtDNA as a diagnostic biomarker that complements cfmtDNA.

Mitochondrial DNA Depletion in Respiratory Chain-Deficient Parkinson Disease Neurons.

ObjectiveTo determine the extent of respiratory chain abnormalities and investigate the contribution of mtDNA to the loss of respiratory chain complexes (CI–IV) in the substantia nigra (SN) of idiopathic Parkinson disease (IPD) patients at the single‐neuron level.MethodsMultiple‐label immunofluorescence was applied to postmortem sections of 10 IPD patients and 10 controls to quantify the abundance of CI–IV subunits (NDUFB8 or NDUFA13, SDHA, UQCRC2, and COXI) and mitochondrial transcription factors (TFAM and TFB2M) relative to mitochondrial mass (porin and GRP75) in dopaminergic neurons. To assess the involvement of mtDNA in respiratory chain deficiency in IPD, SN neurons, isolated with laser‐capture microdissection, were assayed for mtDNA deletions, copy number, and presence of transcription/replication‐associated 7S DNA employing a triplex real‐time polymerase chain reaction (PCR) assay.ResultsWhereas mitochondrial mass was unchanged in single SN neurons from IPD patients, we observed a significant reduction in the abundances of CI and II subunits. At the single‐cell level, CI and II deficiencies were correlated in patients. The CI deficiency concomitantly occurred with low abundances of the mtDNA transcription factors TFAM and TFB2M, which also initiate transcription‐primed mtDNA replication. Consistent with this, real‐time PCR analysis revealed fewer transcription/replication‐associated mtDNA molecules and an overall reduction in mtDNA copy number in patients. This effect was more pronounced in single IPD neurons with severe CI deficiency.InterpretationRespiratory chain dysfunction in IPD neurons not only involves CI, but also extends to CII. These deficiencies are possibly a consequence of the interplay between nDNA and mtDNA‐encoded factors mechanistically connected via TFAM. ANN NEUROL 2016;79:366–378

Abstract 32: Mitochondrial DNA Copy Number and Oxidative Stress in Patients with Chronic Kidney Disease

Cardiovascular mortality increases with progressive decline in kidney function. Oxidative stress is a risk factor for cardiovascular complications in patients with chronic kidney disease (CKD). Oxidative stress also increases as renal function declines. Dysfunctional mitochondria are a main source of oxidative stress and may contribute to the pathogenesis of cardiovascular disease in patients with CKD. In this study we tested the hypothesis that mitochondrial function decreases with the progression of CKD by assessing mitochondrial DNA (mtDNA) copy number from blood mononuclear cells (PBMCs) and plasma isofurans. Isofurans formation is favored over F2-Isoprostanes when oxygen tissue tension is high, as observed in mitochondrial dysfunction. Eighty three subjects were separated in 3 groups based on eGFR: CKD stage 1-2, CKD stage 3-4, and CKD stage 5 (hemodialysis). Groups were comparable in age, gender, BMI and prevalence of hypertension. Estimated marginal mean (after controlling for BMI) of mtDNA copy number in patients with CKD stage 5 was 1.72 (95% CI 0.10-3.34), lower than in patients with CKD stage 3-4 (3.44, 95% CI 0.98-5.90, p=0.02) and CKD stage 1-2 (6.56, 95% CI 4.57-8.54, p=0.008). F2-Isoprostanes were not different among CKD groups, whereas isofurans were higher in patients with CKD stage 5 (median 59.72; IQR 43.13-91.03) compared to CKD stages 3-4 (median 48.41; IQR 30.93-66.19, p=0.01), and CKD stage 1-2 (median 39.00; IQR 26.22-67.03, p=0.005). These results suggest that progressive kidney disease is associated with mitochondrial dysfunction. Further studies are required to evaluate in vivo mitochondrial function in patients with different CKD stages.

Impaired Activity of Mitochondrial Respiratory Chain Enzyme Complexes and Mitochondrial Genomic Aberrations in Leukemia Cells from Patients with Acute Myeloid Leukemia.

Background: Mitochondrial DNA (mtDNA) was particularly susceptible to oxidative damage and mutation because of the high rate of reactive oxygen species (ROS) generation and inefficient mtDNA repair system. Somatic mutations of mtDNA lead to errors in the mtDNA-encoded polypeptide chains belonging to the proton-translocating complexes of the mitochondrial inner membrane. Therefore, we investigated level of ROS, mitochondrial genomic aberrations (mitochondrial genomic instability, mtGI) and the change in enzyme activity of mitochondrial respiratory chain complexes I–IV and in acute myeloid leukemia (AML) cells.Methods: Forty-eight AML bone marrow samples and 57 control blood samples were used after receiving informed consent. The intracellular ROS generation of cells can be investigated using the 2′,7′-dichlorfl uorescein-diacetate and flow cytometry. The results were expressed as mean fluorescence intensity (MFI). We sequenced the mtDNA control region, the tRNA leucine 1 gene plus part of NADH dehydrogenase (ND) 1, and cytochrome b (CYTB) directly and checked the activity of mitochondrial respiratory chain enzyme complexes I to IV using a spectrophotometric kinetic assay. To investigate mtGI, we also examined six mtGI repeats (303 poly C, 16184 poly C, 514CA repeats, 3566 poly C, 12385 poly C and 12418 poly A) using size-based PCR product separation with capillary electrophoresis. mtGI was further confirmed by cloning and sequencing. The mtDNA molecules were analyzed quantitatively using real-time PCR.Results: MFI in AML cells (4,435±709) was significantly higher than those in control blood cells (1,562±141) (P<0.05). Many polymorphisms, as well as new mtDNA variants in the control region and ND1 and CYTB genes were detected in this study. A total of 606 mtDNA sequence variants were identified. Of these, 15 mtDNA variants were identified as novel mutations that were absent from control subjects and established mtDNA polymorphism databases. There were profound alterations of mtGI in the 303 poly C, 16184 poly C, and 514 CA repeats. Seven patients (15%) had leukemia cell-specific mtDNA substitution mutations in the ND1 and CYTB genes. The enzyme activities of AML cells compared with control subjects were 0.828±2.72 vs. −2.48±3.18 for complex I, 0.03±0.08 vs. 0.144±1.72 for complex II/III, and 0.244±0.16 vs. 0.505±0.73 for complex IV. The AML cells showed decreased enzyme activity in respiratory chain complexes I, II, and III. The AML cells had an approximately two-fold decrease in mtDNA copy number compared with the results for control subjects.Conclusion: Mitochondrial genomic aberrations were commonly observed in primary AML cells. High level of ROS in these cells might be an injury to the mitochondrial genome. These mtDNA alterations may impair the activity of mitochondrial respiratory chain enzyme complexes and reduce the mtDNA copy number in patients with AML.