Study of insulin resistance in cybrid cells harboring diabetes-susceptible and diabetes-protective mitochondrial haplogroups

Functional analysis of the novel mitochondrial tRNATrp and tRNASer(AGY) variants associated with type 2 diabetes mellitus

BACKGROUND

Mutations in mitochondrial tRNA (mt-tRNA) genes that result in mitochondrial dysfunction play important roles in type 2 diabetes mellitus (T2DM). We pre-viously reported a large Chinese pedigree with maternally inherited T2DM that harbors novel mt-tRNA Trp A5514G and tRNA Ser(AGY) C12237T variants, however, the effects of these mt-tRNA variants on T2DM progression are largely unknown.

AIM

To assess the potential pathogenicity of T2DM-associated m.A5514G and m.C12237T variants at genetic, molecular, and biochemical levels.

METHODS

Cytoplasmic hybrid (cybrid) cells carrying both m.A5514G and m.C12237T variants, and healthy control cells without these mitochondrial DNA (mtDNA) variants were generated using trans-mitochondrial technology. Mitochondrial features, including mt-tRNA steady-state level, levels of adenosine triphosphate (ATP), mitochondrial membrane potential (MMP), reactive oxygen species (ROS), mtDNA copy number, nicotinamide adenine dinucleotide (NAD+)/NADH ratio, enzymatic activities of respiratory chain complexes (RCCs), 8-hydroxy-deo-xyguanine (8-OhdG), malondialdehyde (MDA), and superoxide dismutase (SOD) were examined in cell lines with and without these mt-tRNA variants.

RESULTS

Compared with control cells, the m.A5514G variant caused an approximately 35% reduction in the steady-state level of mt-tRNA Trp (P < 0.0001); however, the m.C12237T variant did not affect the mt-tRNA Ser(AGY) steady-state level (P = 0.5849). Biochemical analysis revealed that cells with both m.A5514G and m.C12237T variants exhibited more severe mitochondrial dysfunctions and elevated oxidative stress than control cells: ATP, MMP, NAD+/NADH ratio, enzyme activities of RCCs and SOD levels were markedly decreased in mutant cells (P < 0.05 for all measures). By contrast, the levels of ROS, 8-OhdG and MDA were significantly increased (P < 0.05 for all measures), but mtDNA copy number was not affected by m.A5514G and m.C12237T variants (P = 0.5942).

CONCLUSION

The m.A5514G variant impaired mt-tRNA Trp metabolism, which subsequently caused mitochondrial dysfunction. The m.C12237T variant did not alter the steady-state level of mt-tRNA Ser(AGY), indicating that it may be a modifier of the m.A5514G variant. The m.A5514G variant may exacerbate the pathogenesis and progression of T2DM in this Chinese pedigree.

Thyroid Cancer-Associated Mitochondrial DNA Mutation G3842A Promotes Tumorigenicity via ROS-Mediated ERK1/2 Activation

Mitochondrial DNA (mtDNA) mutations have been identified in various human cancers, including thyroid cancer. However, the relationship between mtDNA and thyroid cancer remains unclear. Previous studies by others and us strongly suggested that mtDNA mutations in complex I may participate in thyroid cancer processes according to sequencing results of thyroid cancer tissue, although the associated pathogenic processes remain unknown. Here, to investigate whether mtDNA mutations contribute to thyroid cancer, we reanalyzed our sequencing results and characterized thyroid cancer-associated mutations in the mitochondrial complex. The results identified the highest mutation frequencies in nicotinamide adenine dinucleotide hydride (NADH) dehydrogenase subunit 4 gene (ND4) and cytochrome c oxidase subunit 1 gene (COI), which also harbored the highest rates of $\text{G}>\text{A}$ substitutions, with most of the mutations resulting in changes in the polarity of amino acids. We then established cybrids containing the G3842A mutation identified in papillary thyroid carcinoma, which revealed it as a mutation in NADH dehydrogenase subunit 1 gene (ND1) and is previously reported in follicular thyroid carcinoma, thereby suggesting a possibly pathogenic role in thyroid carcinoma. Additionally, we found that the G3842A mutation accelerates tumorigenicity and decreases the abundance and activity of mitochondrial complex I, the oxygen consumption rate, and adenosine triphosphate levels. By contrast, the levels of reactive oxygen species (ROS) were increased to activate extracellular signal-regulated kinase (ERK1/2) signaling, which contributed to tumorigenicity. These findings suggest for the first time that mtDNA mutations help drive tumor development and that G3842A may represent a new risk factor for thyroid cancer. Furthermore, our findings indicate that drugs targeting ROS and ERK1/2 may serve as a viable therapeutic strategy for thyroid cancer.

Mitochondrial haplogroups have a better correlation to insulin requirement than nuclear genetic variants for type 2 diabetes mellitus in Taiwanese individuals

AIMS/INTRODUCTION

Identifying diabetes-susceptible genetic variants will help to provide personalized therapy for the management of type 2 diabetes. Previous studies have reported a genetic risk score (GRS), computed by the sum of nuclear DNA (nDNA) risk alleles, that may predict the future requirement for insulin therapy. Although mitochondrial dysfunction has a close association with insulin resistance (IR), there are few studies investigating whether genetic variants of mitochondrial DNA (mtDNA) will affect the clinical characteristics of type 2 diabetes.

MATERIALS AND METHODS

Mitochondrial haplogroups were determined using mtDNA whole genome next generation sequencing and 13 single nucleotide polymorphisms (SNPs) in nDNA susceptibility loci of 13 genes in 604 Taiwanese subjects with type 2 diabetes. A GRS of nDNA was computed by summation of the number of risk alleles. The correlation between the mtDNA haplogroup and the clinical characteristics of type 2 diabetes was assessed by logistic regression analysis. The results were compared with the GRS subgroups for the risk of insulin requirement.

RESULTS

Mitochondrial haplogroups modulate the clinical characteristics of type 2 diabetes, in which patients harboring haplogroup D4, compared with those harboring non-D4 haplotypes, were less prone to require insulin treatment, after adjusting for age, gender, and diabetes duration. However, there was no association between insulin requirement and GRS calculated from nuclear genetic variants.

CONCLUSIONS

Mitochondrial haplogroups, but not nuclear genetic variants, have a better association with the insulin requirement. The results highlight the role of mitochondria in the management of common metabolic diseases.

The Role of Mitochondria in Immune-Cell-Mediated Tissue Regeneration and Ageing

During tissue injury events, the innate immune system responds immediately to alarms sent from the injured cells, and the adaptive immune system subsequently joins in the inflammatory reaction. The control mechanism of each immune reaction relies on the orchestration of different types of T cells and the activators, antigen-presenting cells, co-stimulatory molecules, and cytokines. Mitochondria are an intracellular signaling organelle and energy plant, which supply the energy requirement of the immune system and maintain the system activation with the production of reactive oxygen species (ROS). Extracellular mitochondria can elicit regenerative effects or serve as an activator of the immune cells to eliminate the damaged cells. Recent clarification of the cytosolic escape of mitochondrial DNA triggering innate immunity underscores the pivotal role of mitochondria in inflammation-related diseases. Human mesenchymal stem cells could transfer mitochondria through nanotubular structures to defective mitochondrial DNA cells. In recent years, mitochondrial therapy has shown promise in treating heart ischemic events, Parkinson's disease, and fulminating hepatitis. Taken together, these results emphasize the emerging role of mitochondria in immune-cell-mediated tissue regeneration and ageing.

Mitophagy: An Emerging Target in Ocular Pathology

Mitochondrial function is essential for the viability of aerobic eukaryotic cells, as mitochondria provide energy through the generation of adenosine triphosphate (ATP), regulate cellular metabolism, provide redox balancing, participate in immune signaling, and can initiate apoptosis. Mitochondria are dynamic organelles that participate in a cyclical and ongoing process of regeneration and autophagy (clearance), termed mitophagy specifically for mitochondrial (macro)autophagy. An imbalance in mitochondrial function toward mitochondrial dysfunction can be catastrophic for cells and has been characterized in several common ophthalmic diseases. In this article, we review mitochondrial homeostasis in detail, focusing on the balance of mitochondrial dynamics including the processes of fission and fusion, and provide a description of the mechanisms involved in mitophagy. Furthermore, this article reviews investigations of ocular diseases with impaired mitophagy, including Fuchs endothelial corneal dystrophy, primary open-angle glaucoma, diabetic retinopathy, and age-related macular degeneration, as well as several primary mitochondrial diseases with ocular phenotypes that display impaired mitophagy, including mitochondrial encephalopathy lactic acidosis stroke, Leber hereditary optic neuropathy, and chronic progressive external ophthalmoplegia. The results of various studies using cell culture, animal, and human tissue models are presented and reflect a growing awareness of mitophagy impairment as an important feature of ophthalmic disease pathology. As this review indicates, it is imperative that mitophagy be investigated as a targetable mechanism in developing therapies for ocular diseases characterized by oxidative stress and mitochondrial dysfunction.

African and Asian Mitochondrial DNA Haplogroups Confer Resistance Against Diabetic Stresses on Retinal Pigment Epithelial Cybrid Cells In Vitro

Diabetic retinopathy (DR) is the most common cause of blindness for individuals under the age of 65. This loss of vision can be due to ischemia, neovascularization, and/or diabetic macular edema, which are caused by breakdown of the blood-retina barrier at the level of the retinal pigment epithelium (RPE) and inner retinal vasculature. The prevalence of diabetes and its complications differ between Caucasian-Americans and certain minority populations, such as African-Americans and Asian-Americans. Individuals can be classified by their mitochondrial haplogroups, which are collections of single nucleotide polymorphisms (SNPs) in mitochondrial DNA (mtDNA) representing ancient geographic origins of populations. In this study, we compared the responses of diabetic human RPE cybrids, cell lines containing identical nuclei but mitochondria from either European (maternal European) or maternal African or Asian individuals, to hypoxia and high glucose levels. The African and Asian diabetic ([Afr+Asi]/DM) cybrids showed (1) resistance to both hyperglycemic and hypoxic stresses; (2) downregulation of pro-apoptotic indicator BAX; (3) upregulation of DNA methylation genes, such as DNMT3A and DNMT3B; and (4) resistance to DNA demethylation by the methylation inhibitor 5-Aza-2'-deoxycytidine (5-Aza-dC) compared to European diabetic (Euro/DM) cybrids. Our findings suggest that mitochondria from African and Asian diabetic subjects possess a "metabolic memory" that confers resistance against hyperglycemia, hypoxia, and demethylation, and that this "metabolic memory" can be transferred into the RPE cybrid cell lines in vitro.

The Causal Role of Mitochondrial Dynamics in Regulating Innate Immunity in Diabetes

Background: Plenty of evidence suggested that chronic low-grade inflammation triggered by innate immunity activation contributes to the pathogenesis of type 2 diabetes (T2D). Using the trans-mitochondrial cybrid cell model, we have demonstrated that mitochondria independently take part in the pathological process of insulin resistance (IR) and pro-inflammatory phenotype in cybrid cells harboring mitochondrial haplogroup B4, which are more likely to develop T2D. The mitochondrial network is more fragmented, and the expression of fusion-related proteins is low in Cybrid B4. We also discovered the causal role of mitochondrial dynamics (mtDYN) proteins in regulating IR in this cybrid model, and the bidirectional interaction between mtDYN and mitochondrial oxidative stress is considered etiologically important. In this study, we further investigated whether mtDYN bridges the gap between nutrient excess and chronic inflammation in T2D. Methods: Trans-mitochondrial cybrid cells derived from the 143B human osteosarcoma cell line were cultured in a medium containing glucose (25 mM) with or without saturated fatty acid (0.25 mM BSA-conjugated palmitate), and the expression of innate immunity/inflammasome molecules was compared between cybrid B4 (the major T2D-susceptible haplogroup among the Chinese population) and cybrid D4 (the major T2D-resistant haplogroup among the Chinese population). We investigated the causal relationship between mtDYN and nutrient excess-induced inflammation in cybrid B4 by genetic manipulation of mtDYN and by pharmacologically inhibiting mitochondrial fission using the Drp1 inhibitor, mdivi-1, and metformin. Results: Under nutrient excess with high fatty acid, cybrid B4 presented increased mitochondrial pro-fission profiles and enhanced chronic inflammation markers (RIG-I, MDA5, MAVS) and inflammasome (NLRP3, Caspase-1, IL-1β), whereas the levels in cybrid D4 were not or less significantly altered. In cybrid B4 under nutrient excess, overexpression of fusion proteins (Mfn1 or Mfn2) significantly repressed the expression of innate immunity/inflammasome-related molecules, while knockdown had a less significant effect. On the contrary, knockdown of fission proteins (Drp1 or Fis1) significantly repressed the expression of innate immunity/inflammasome-related molecules, while overexpression had a less significant effect. In addition, Drp1 inhibitor mdivi-1 and metformin inhibited mitochondrial fission and attenuated the pro-inflammation expression as well. Conclusion: Our results discovered the causal relationship between mtDYN and nutrient excess-induced chronic inflammation in a diabetes-susceptible cell model. Targeting mtDYN by direct interfering pro-fission can be a therapeutic intervention for chronic inflammation in T2D.

Mitochondrial DNA variation and the pathogenesis of osteoarthritis phenotypes

Mitochondria and mitochondrial DNA (mtDNA) variation are now recognized as important factors in the development of osteoarthritis (OA). Mitochondria are the energy powerhouses of the cell, and also regulate different processes involved in the pathogenesis of OA including inflammation, apoptosis, calcium metabolism and the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Mitochondria contain their own genetic material, mtDNA, which evolved through the sequential accumulation of mtDNA variants to enable humans to adapt to different climates. The ROS and reactive metabolic intermediates that are by-products of mitochondrial metabolism are regulated in part by mtDNA and are among the signals that transmit information between mitochondria and the nucleus. These signals can alter nuclear gene expression and, when disrupted, affect a number of cellular processes and metabolic pathways, leading to disease. mtDNA variation influences OA-associated phenotypes, including those related to metabolism, inflammation and even ageing, as well as nuclear epigenetic regulation. This influence also enables the use of specific mtDNA haplogroups as complementary diagnostic and prognostic biomarkers of OA.

The Causal Role of Mitochondrial Dynamics in Regulating Insulin Resistance in Diabetes: Link through Mitochondrial Reactive Oxygen Species

Background

Mitochondrial dynamics (mtDYN) has been proposed as a bridge between mitochondrial dysfunction and insulin resistance (IR), which is involved in the pathogenesis of type 2 diabetes (T2D). Our previous study has identified that mitochondrial DNA (mtDNA) haplogroup B4 is a T2D-susceptible genotype. Using transmitochondrial cybrid model, we have confirmed that haplogroup B4 contributes to cellular IR as well as a profission mtDYN, which can be reversed by antioxidant treatment. However, the causal relationship between mtDYN and cellular IR pertaining to T2D-susceptible haplogroup B4 remains unanswered.

Methods

To dissect the mechanisms between mtDYN and IR, knockdown or overexpression of MFN1, MFN2, DRP1, and FIS1 was performed using cybrid B4. We then examined the mitochondrial network and mitochondrial oxidative stress (mtROS) as well as insulin signaling IRS-AKT pathway and glucose transporters (GLUT) translocation to plasma membrane stimulated by insulin. We employed Drp1 inhibitor, mdivi-1, to interfere with endogenous expression of fission to validate the pharmacological effects on IR.

Results

Overexpression of MFN1 or MFN2 increased mitochondrial network and reduced mtROS, while knockdown had an opposing effect. In contrast, overexpression of DRP1 or FIS1 decreased mitochondrial network and increased mtROS, while knockdown had an opposing effect. Concomitant with the enhanced mitochondrial network, activation of the IRS1-AKT pathway and GLUT translocation stimulated by insulin were improved. On the contrary, suppression of mitochondrial network caused a reduction of the IRS1-AKT pathway and GLUT translocation stimulated by insulin. Pharmacologically inhibiting mitochondrial fission by the Drp1 inhibitor, mdivi-1, also rescued mitochondrial network, reduced mtROS, and improved insulin signaling of diabetes-susceptible cybrid cells.

Conclusion

Our results discovered the causal role of mtDYN proteins in regulating IR resulted from diabetes-susceptible mitochondrial haplogroup. The existence of a bidirectional interaction between mtDYN and mtROS plays an important role. Direct intervention to reverse profission in mtDYN provides a novel therapeutic strategy for IR and T2D.

mtDNA Haplogroup N9a Increases the Risk of Type 2 Diabetes by Altering Mitochondrial Function and Intracellular Mitochondrial Signals

Mitochondrial DNA (mtDNA) haplogroups have been associated with the incidence of type 2 diabetes (T2D); however, their underlying role in T2D remains poorly elucidated. Here, we report that mtDNA haplogroup N9a was associated with an increased risk of T2D occurrence in Southern China (odds ratio 1.999 [95% CI 1.229-3.251], P = 0.005). By using transmitochondrial technology, we demonstrated that the activity of respiratory chain complexes was lower in the case of mtDNA haplogroup N9a (N9a1 and N9a10a) than in three non-N9a haplogroups (D4j, G3a2, and Y1) and that this could lead to alterations in mitochondrial function and mitochondrial redox status. Transcriptome analysis revealed that OXPHOS function and metabolic regulation differed markedly between N9a and non-N9a cybrids. Furthermore, in N9a cybrids, insulin-stimulated glucose uptake might be inhibited at least partially through enhanced stimulation of ERK1/2 phosphorylation and subsequent TLR4 activation, which was found to be mediated by the elevated redox status in N9a cybrids. Although it remains unclear whether other signaling pathways (e.g., Wnt pathway) contribute to the T2D susceptibility of haplogroup N9a, our data indicate that in the case of mtDNA haplogroup N9a, T2D is affected, at least partially through ERK1/2 overstimulation and subsequent TLR4 activation.

Generation and Bioenergetic Profiles of Cybrids with East Asian mtDNA Haplogroups

Human mitochondrial DNA (mtDNA) variants and haplogroups may contribute to susceptibility to various diseases and pathological conditions, but the underlying mechanisms are not well understood. To address this issue, we established a cytoplasmic hybrid (cybrid) system to investigate the role of mtDNA haplogroups in human disease; specifically, we examined the effects of East Asian mtDNA genetic backgrounds on oxidative phosphorylation (OxPhos). We found that mtDNA single nucleotide polymorphisms such as m.489T>C, m.10398A>G, m.10400C>T, m.C16223T, and m.T16362C affected mitochondrial function at the level of mtDNA, mtRNA, or the OxPhos complex. Macrohaplogroup M exhibited higher respiratory activity than haplogroup N owing to its higher mtDNA content, mtRNA transcript levels, and complex III abundance. Additionally, haplogroup M had higher reactive oxygen species levels and NAD⁺/NADH ratios than haplogroup N, suggesting difference in mitonuclear interactions. Notably, subhaplogroups G2, B4, and F1 appeared to contribute significantly to the differences between haplogroups M and N. Thus, our cybrid-based system can provide insight into the mechanistic basis for the role of mtDNA haplogroups in human diseases and the effect of mtDNA variants on mitochondrial OxPhos function. In addition, studies of mitonuclear interaction using this system can reveal predisposition to certain diseases conferred by variations in mtDNA.

Mitochondrial DNA haplogroups influence the risk of incident knee osteoarthritis in OAI and CHECK cohorts. A meta-analysis and functional study

Objective

To evaluate the influence of the mitochondrial DNA (mtDNA) haplogroups in the risk of incident knee osteoarthritis (OA) and to explain the functional consequences of this association to identify potential diagnostic biomarkers and therapeutic targets.

Methods

Two prospective cohorts contributed participants. The osteoarthritis initiative (OAI) included 2579 subjects of the incidence subcohort, and the cohort hip and cohort knee (CHECK) included 635, both with 8-year follow-up. The analysis included the association of mtDNA haplogroups with the rate of incident knee OA in subjects from both cohorts followed by a subsequent meta-analysis. Transmitochondrial cybrids harbouring haplogroup J or H were constructed to detect differences between them in relation to physiological features including specific mitochondrial metabolic parameters, reactive oxygen species production, oxidative stress and apoptosis.

Results

Compared with H, the haplogroup J associates with decreased risk of incident knee OA in subjects from OAI (HR=0.680; 95% CI 0.470 to 0.968; p<0.05) and CHECK (HR=0.728; 95% CI 0.469 to 0.998; p<0.05). The subsequent meta-analysis including 3214 cases showed that the haplogroup J associates with a lower risk of incident knee OA (HR=0.702; 95% CI 0.541 to 0.912; p=0.008). J cybrids show a lower free radical production, higher cell survival under oxidative stress conditions, lower grade of apoptosis as well as lower expression of the mitochondrially related pro-apoptotic gene BCL2 binding component 3 (BBC3). In addition, J cybrids also show a lower mitochondrial respiration and glycolysis leading to decreased ATP production.

Conclusions

The physiological effects of the haplogroup J are beneficial to have a lower rate of incident knee OA over time. Potential drugs to treat OA could focus on emulating the mitochondrial behaviour of this haplogroup.

Altered mitochondrial dynamics and response to insulin in cybrid cells harboring a diabetes-susceptible mitochondrial DNA haplogroup

The advantage of using a cytoplasmic hybrid (cybrid) model to study the genetic effects of mitochondria is that the cells have the same nuclear genomic background. We previously demonstrated the independent role of mitochondria in the pathogenesis of insulin resistance (IR) and pro-inflammation in type 2 diabetes. In this study, we compared mitochondrial dynamics and related physiological functions between cybrid cells harboring diabetes-susceptible (B4) and diabetes-protective (D4) mitochondrial haplogroups, especially the responses before and after insulin stimulation. Cybrid B4 showed a more fragmented mitochondrial network, impaired mitochondrial biogenesis and bioenergetics, increased apoptosis and ineffective mitophagy and a low expression of fusion-related molecules. Upon insulin stimulation, increases in network formation, mitochondrial DNA (mtDNA) content, and ATP production were observed only in cybrid D4. Insulin promoted a pro-fusion dynamic status in both cybrids, but the trend was greater in cybrid D4. In cybrid B4, the imbalance of mitochondrial dynamics and impaired biogenesis and bioenergetics, and increased apoptosis were significantly improved in response to antioxidant treatment. We concluded that diabetes-susceptible mtDNA variants are themselves resistant to insulin.

Mitochondrial DNA variants can mediate methylation status of inflammation, angiogenesis and signaling genes

Mitochondrial (mt) DNA can be classified into haplogroups representing different geographic and/or racial origins of populations. The H haplogroup is protective against age-related macular degeneration (AMD), while the J haplogroup is high risk for AMD. In the present study, we performed comparison analyses of human retinal cell cybrids, which possess identical nuclei, but mtDNA from subjects with either the H or J haplogroups, and demonstrate differences in total global methylation, and expression patterns for two genes related to acetylation and five genes related to methylation. Analyses revealed that untreated-H and -J cybrids have different expression levels for nuclear genes (CFH, EFEMP1, VEGFA and NFkB2). However, expression levels for these genes become equivalent after treatment with a methylation inhibitor, 5-aza-2'-deoxycytidine. Moreover, sequencing of the entire mtDNA suggests that differences in epigenetic status found in cybrids are likely due to single nucleotide polymorphisms (SNPs) within the haplogroup profiles rather than rare variants or private SNPs. In conclusion, our findings indicate that mtDNA variants can mediate methylation profiles and transcription for inflammation, angiogenesis and various signaling pathways, which are important in several common diseases.

Mitochondrial transfer from Wharton's jelly-derived mesenchymal stem cells to mitochondria-defective cells recaptures impaired mitochondrial function

Adult mesenchymal stem cell (MSC)-conducted mitochondrial transfer has been recently shown to rescue cellular bioenergetics and prevent cell death caused by mitochondrial dysfunction. Wharton's jelly-derived MSCs (WJMSCs) harvested from postpartum umbilical cords are an accessible and abundant source of stem cells. This study aimed to determine the capability of WJMSCs to transfer their own mitochondria and rescue impaired oxidative phosphorylation (OXPHOS) and bioenergetics caused by mitochondrial DNA defects. To do this, WJMSCs were co-cultured with mitochondrial DNA (mtDNA)-depleted ρ(0) cells and the recapture of mitochondrial function was evaluated. WJMSCs were shown to be capable of transferring their own mitochondria into ρ(0) cells and underwent interorganellar mixture within these cells. Permissive culture media (BrdU-containing and pyruvate- and uridine-free) sieved out a survival cell population from the co-cultured WJMSCs (BrdU-sensitive) and ρ(0) cells (pyruvate/uridine-free). The survival cells had mtDNA identical to that of WJMSCs, whereas they expressed cellular markers identical to that of ρ(0) cells. Importantly, these ρ(0)-plus -WJMSC-mtDNA (ρ(+W)) cells recovered the expression of mtDNA-encoded proteins and exhibited functional oxygen consumption and respiratory control, as well as the activity of electron transport chain (ETC) complexes I, II, III and IV. In addition, ETC complex V-inhibitor-sensitive ATP production and metabolic shifting were also recovered. Furthermore, cellular behaviors including attachment-free proliferation, aerobic viability and OXPHOS-reliant cellular motility were also regained after mitochondrial transfer by WJMSCs. The therapeutic effect of WJMSCs-derived mitochondrial transfer was able to stably sustain for at least 45 passages. In conclusion, this study suggests that WJMSCs may serve as a potential therapeutic strategy for diseases linked to mitochondrial dysfunction through the donation of healthy mitochondria to cells with genetic mitochondrial defects.

Mitochondrial DNA haplogroups and risk of new-onset diabetes among tacrolimus-treated renal transplanted patients

BACKGROUND AND AIMS

Tacrolimus (Tac) is an immunosuppressive drug widely used to avoid organ rejection. New-onset diabetes after transplantation (NODAT) is a major complication among transplanted patients who receive Tac. The increased risk for NODAT could be partly mediated by the effect of Tac on mitochondria from pancreatic beta-cells. Common and rare mitochondrial DNA variants have been linked to the risk of diabetes. Our aim was to determine whether mtDNA polymorphisms/haplogroups were associated with NODAT in Tac-treated kidney transplanted.

METHODS

Seven polymorphisms that define the common European haplogroups were determined in 115 NODAT and 197 no-NODAT patients.

RESULTS

Haplogroup H was significantly more frequent in the NODAT group (50% vs. 35%; p=0.01, OR=1.82). There was no difference between patients without and with (n=106) D2M prior to the transplant.

CONCLUSIONS

Mitochondrial haplogroup H was associated with the risk for NODAT among Tac-treated transplanted patients. The reported differences between the mtDNA variants could explain the increased NODAT-risk among H-patients.