Deficiency in Apoptosis-Inducing Factor Recapitulates Chronic Kidney Disease via Aberrant Mitochondrial Homeostasis

Mechanistic Insights into 1,2-bis(2,4,6-tribromophenoxy)ethane-Induced Male Reproductive Toxicity in Zebrafish

The novel brominated flame retardant, 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), has increasingly been detected in environmental and biota samples. However, limited information is available regarding its toxicity, especially at environmentally relevant concentrations. In the present study, adult male zebrafish were exposed to varying concentrations of BTBPE (0, 0.01, 0.1, 1, and 10 μg/L) for 28 days. The results demonstrated underperformance in mating behavior and reproductive success of male zebrafish when paired with unexposed females. Additionally, a decline in sperm quality was confirmed in BTBPE-exposed male zebrafish, characterized by decreased total motility, decreased progressive motility, and increased morphological malformations. To elucidate the underlying mechanism, an integrated proteomic and phosphoproteomic analysis was performed, revealing a predominant impact on mitochondrial functions at the protein level and a universal response across different cellular compartments at the phosphorylation level. Ultrastructural damage, increased expression of apoptosis-inducing factor, and disordered respiratory chain confirmed the involvement of mitochondrial impairment in zebrafish testes. These findings not only provide valuable insights for future evaluations of the potential risks posed by BTBPE and similar chemicals but also underscore the need for further research into the impact of mitochondrial dysfunction on reproductive health.

Urinary podocyte markers in diabetic kidney disease

Podocytes are involved in maintaining kidney function and are a major focus of research on diabetic kidney disease (DKD). Urinary biomarkers derived from podocyte fragments and molecules have been proposed for the diagnosis and monitoring of DKD. Various methods have been used to detect intact podocytes and podocyte-derived microvesicles in urine, including centrifugation, visualization, and molecular quantification. Quantification of podocyte-specific protein targets and messenger RNA levels can be performed by Western blotting or enzyme-linked immunosorbent assay and quantitative polymerase chain reaction, respectively. At present, many of these techniques are expensive and labor-intensive, all limiting their widespread use in routine clinical tests. While the potential of urinary podocyte markers for monitoring and risk stratification of DKD has been explored, systematic studies and external validation are lacking in the current literature. Standardization and automation of laboratory methods should be a priority for future research, and the added value of these methods to routine clinical tests should be defined.

Huangkui capsule attenuates diabetic kidney disease through the induction of mitophagy mediated by STING1/PINK1 signaling in tubular cells

BACKGROUND

Mitochondria is critic to tubulopathy, especially in diabetic kidney disease (DKD). Huangkui capsule (HKC; a new ethanol extract from the dried corolla of Abelmoschus manihot) has significant clinical effect on DKD. Previous studies have shown that HKC protects kidney by regulating mitochondrial function, but its mechanism is still unclear. The latest research found that the stimulator of interferon genes (STING1) signal pathway is closely related to mitophagy. However, whether HKC induces mitophagy through targeting STING1/PTEN-Induced putative kinase (PINK1) in renal tubular remains elusive.

OBJECTIVE

This study aims to clarify the therapeutic effect of HKC on renal tubular mitophagy in DKD and its potential mechanism in vivo and in vitro.

METHODS

Forty male C57BL/6 mice were randomly divided into 5 groups: CON group, DKD group, HKC-L (1.0 g/kg/day, by gavage), HKC-H (2.0 g/kg/day), and LST group. Diabetes model was induced by high-fat diet (HFD) combined with intraperitoneal injection of Streptozotocin (STZ). LST (losartan) is used as a positive control drug. Then, the glomeruli, renal tubular lesions, mitochondrial morphology and function of renal tubular cells and mitophagy levels were detected in mice. In addition, a high glucose injury model was established using HK2 human renal tubular cells. Pretreate HK2 cells with HKC or LST and detect mitochondrial function, mitophagy level, and autophagic flux. In addition, small interfering RNAs (siRNAs) of STING1 and PINK1 and overexpressing pcDNA3.1 plasmids were transfected into HK-2 cells to validate the mitophagy mechanism regulated by STING1/PINK1 signaling.

RESULTS

The ratio of urinary albumin to creatinine (ACR), fasting blood glucose, body weight in the early DKD mice model was increased, with damage to the glomerulus and renal tubules, mitochondrial structure and dysfunction in the renal tubules, and inhibition of STING1/PINK1 mediated mitophagy. Although the fasting blood glucose, body weight and serum creatinine levels were hardly ameliated, high dose HKC (2.0 g/kg/day) treatment significantly reduced ACR in the DKD mice to some extent, improved renal tubular injury, accurately upregulated STING1/PINK1 signaling mediated mitophagy levels, improved autophagic flux, and restored healthy mitochondrial pools. In vitro, an increase in mitochondrial fragments, fusion to fission, ROS and apoptosis, and a decrease in respiratory function, mtDNA, and membrane potential were observed in HK2 cells exposed to high glucose. HKC treatment significantly protected mitochondrial dynamics and function, which is consistent with in vivo results. Further research has shown that HKC can increase the level of mitophagy mediated by STING1/PINK1 in HK2 cells.

CONCLUSIONS

Our results suggest that HKC ameliorates renal tubulopathy in DKD and induces mitophagy partly through the up-regulation of the STING1/PINK1 pathway. These findings may provide an innovative therapeutic basis for DKD treatment.

Natural compounds targeting mitochondrial dysfunction: emerging therapeutics for target organ damage in hypertension

Hypertension generally causes target organ damage (TOD) in the heart, brain, kidney, and blood vessels. This can result in atherosclerosis, plaque formation, cardiovascular and cerebrovascular events, and renal failure. Recent studies have indicated that mitochondrial dysfunction is crucial in hypertensive target organ damage. Consequently, mitochondria-targeted therapies attract increasing attention. Natural compounds are valuable resources for drug discovery and development. Many studies have demonstrated that natural compounds can ameliorate mitochondrial dysfunction in hypertensive target organ damage. This review examines the contribution of mitochondrial dysfunction to the development of target organ damage in hypertension. Moreover, it summarizes therapeutic strategies based on natural compounds that target mitochondrial dysfunction, which may be beneficial for preventing and treating hypertensive target organ damage.

In vivo longitudinal 920 nm two-photon intravital kidney imaging of a dynamic 2,8-DHA crystal formation and tubular deterioration in the adenine-induced chronic kidney disease mouse model

Chronic kidney disease (CKD) is one of the most common renal diseases manifested by gradual loss of kidney function with no symptoms in the early stage. The underlying mechanism in the pathogenesis of CKD with various causes such as high blood pressure, diabetes, high cholesterol, and kidney infection is not well understood. In vivo longitudinal repetitive cellular-level observation of the kidney of the CKD animal model can provide novel insights to diagnose and treat the CKD by visualizing the dynamically changing pathophysiology of CKD with its progression over time. In this study, using two-photon intravital microscopy with a single 920 nm fixed-wavelength fs-pulsed laser, we longitudinally and repetitively observed the kidney of an adenine diet-induced CKD mouse model for 30 days. Interestingly, we could successfully visualize the 2,8-dihydroxyadenine (2,8-DHA) crystal formation with a second-harmonics generation (SHG) signal and the morphological deterioration of renal tubules with autofluorescence using a single 920 nm two-photon excitation. The longitudinal in vivo two-photon imaging results of increasing 2,8-DHA crystals and decreasing tubular area ratio visualized by SHG and autofluorescence signal, respectively, were highly correlated with the CKD progression monitored by a blood test showing increased cystatin C and blood urea nitrogen (BUN) levels over time. This result suggests the potential of label-free second-harmonics generation crystal imaging as a novel optical technique for in vivo CKD progression monitoring.

Pharmacological Targeting of Mitochondria in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) in the United States and many other countries. DKD occurs through a variety of pathogenic processes that are in part driven by hyperglycemia and glomerular hypertension, leading to gradual loss of kidney function and eventually progressing to ESRD. In type 2 diabetes, chronic hyperglycemia and glomerular hyperfiltration leads to glomerular and proximal tubular dysfunction. Simultaneously, mitochondrial dysfunction occurs in the early stages of hyperglycemia and has been identified as a key event in the development of DKD. Clinical management for DKD relies primarily on blood pressure and glycemic control through the use of numerous therapeutics that slow disease progression. Because mitochondrial function is key for renal health over time, therapeutics that improve mitochondrial function could be of value in different renal diseases. Increasing evidence supports the idea that targeting aspects of mitochondrial dysfunction, such as mitochondrial biogenesis and dynamics, restores mitochondrial function and improves renal function in DKD. We will review mitochondrial function in DKD and the effects of current and experimental therapeutics on mitochondrial biogenesis and homeostasis in DKD over time. SIGNIFICANCE STATEMENT: Diabetic kidney disease (DKD) affects 20% to 40% of patients with diabetes and has limited treatment options. Mitochondrial dysfunction has been identified as a key event in the progression of DKD, and pharmacologically restoring mitochondrial function in the early stages of DKD may be a potential therapeutic strategy in preventing disease progression.

GDF11, a target of miR-32-5p, suppresses high-glucose-induced mitochondrial dysfunction and apoptosis in HK-2 cells through PI3K/AKT signaling activation

PURPOSE

To investigate the role and underlying mechanism of GDF11 on diabetic nephropathy (DN)-related mitochondrial dysfunction and apoptosis.

METHODS

A DN model of rats was established in this study. Human Kidney-2 (HK-2) cells were cultured under high-glucose (HG) condition with or without recombinant GDF11 (rGDF11). Mitochondrial morphology of HK-2 cells was analyzed by transmission electron microscope and MitoTracker Red CMXRos staining. Mitochondrial membrane potential (MMP) and ROS production were monitored using JC-1 assay kit and MitoSOX staining, respectively. Cell apoptosis was detected by TUNEL or flow cytometry assays.

RESULTS

Herein, we observed that GDF11 was down-regulated in renal cortex and serum of DN rats, which was accompanied by renal mitochondrial morphological abnormalities. In line with the findings in vivo, HK-2 cells exposed to HG presented with mitochondrial morphological alterations and further apoptosis accompanied by GDF11 reduction. In addition, HG promoted a decrease in MMP while an increase in mitochondrial ROS production. Conversely, rGDF11 treatment significantly alleviated these HG-induced mitochondrial defects in HK-2 cells. Meanwhile, HK-2 cell apoptosis induced by HG was simultaneously suppressed by rGDF11. Mechanistically, the decreased levels of p-AKT induced by HG were attenuated after rGDF11 administration. Inhibition of the PI3K/AKT pathway resisted the effects of rGDF11 on the MMP and apoptosis of HK-2 cells. In addition, we identified that GDF11 is a target of miR-32-5p. Up-regulation of miR-32-5p could inhibit the expression of GDF11.

CONCLUSION

rGDF11 treatment rescued HG-induced HK-2 cell mitochondrial dysfunction and apoptosis, which may be dependent on the activation of the PI3K/AKT pathway.

Common gene signatures and molecular mechanisms of diabetic nephropathy and metabolic syndrome

Background

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. Multiple metabolic toxicities, redox stress, and endothelial dysfunction contribute to the development of diabetic glomerulosclerosis and DN. Metabolic syndrome (MetS) is a pathological state in which the body's ability to process carbohydrates, fats, and proteins is compromised because of metabolic disorders, resulting in redox stress and renal remodeling. However, a causal relationship between MetS and DN has not been proven. This study aimed to provide valuable information for the clinical diagnosis and treatment of MetS with DN.

Methods

Here, transcriptome data of DN and MetS patients were obtained from the Gene Expression Omnibus database, and seven potential biomarkers were screened using bioinformatics analysis. In addition, the relationship between these marker genes and metabolism and immune infiltration was explored. Among the identified marker genes, the relationship between PLEKHA1 and the cellular process, oxidative phosphorylation (OXPHOS), in DN was further investigated through single-cell analysis.

Results

We found that PLEKHA1 may represent an important biomarker that perhaps initiates DN by activating B cells, proximal tubular cells, distal tubular cells, macrophages, and endothelial cells, thereby inducing OXPHOS in renal monocytes.

Conclusion

Overall, our findings can aid in further investigation of the effects of drug treatment on single cells of patients with diabetes to validate PLEKHA1 as a therapeutic target and to inform the development of targeted therapies.

Mitochondrial Dysfunction in Individuals with Diabetic Kidney Disease: A Systematic Review

Mitochondrial dysfunction is implicated in the pathogenesis of diabetic kidney disease (DKD). Compared to the vast body of evidence from preclinical in vitro and in vivo studies, evidence from human studies is limited. In a comprehensive search of the published literature, findings from studies that reported evidence of mitochondrial dysfunction in individuals with DKD were examined. Three electronic databases (PubMed, Embase, and Scopus) were searched in March 2022. A total of 1339 articles were identified, and 22 articles met the inclusion criteria. Compared to non-diabetic controls (NDC) and/or individuals with diabetes but without kidney disease (DC), individuals with DKD (age ~55 years; diabetes duration ~15 years) had evidence of mitochondrial dysfunction. Individuals with DKD had evidence of disrupted mitochondrial dynamics (11 of 11 articles), uncoupling (2 of 2 articles), oxidative damage (8 of 8 articles), decreased mitochondrial respiratory capacity (1 of 1 article), decreased mtDNA content (5 of 6 articles), and decreased antioxidant capacity (3 of 4 articles) compared to ND and/or DC. Neither diabetes nor glycemic control explained these findings, but rather presence and severity of DKD may better reflect degree of mitochondrial dysfunction in this population. Future clinical studies should include individuals closer to diagnosis of diabetes to ascertain whether mitochondrial dysfunction is implicated in the development of, or is a consequence of, DKD.

Crocodile Oil Disrupts Mitochondrial Homeostasis and Exacerbates Diabetic Kidney Injury in Spontaneously Diabetic Torii Rats

Diabetic nephropathy is currently the leading cause of end-stage renal disease (ESRD) in type 2 diabetes. Studies have suggested that supplementation with some fatty acids might reduce the risk and delay the progression to ESRD in patient with chronic kidney disease. Crocodile oil (CO) contains a variety of fatty acids, especially omega-3, -6 and -9, that have been reported to be beneficial to human health. This study examined the impact of long-term CO supplementation on the development of diabetic nephropathy in spontaneously diabetic Torii (SDT) rats. After diabetic verification, SDT rats were assigned to receive vehicle or CO at 500 and 1000 mg/kg BW, respectively, by oral gavage. Age-matched nondiabetic Sprague–Dawley rats were given vehicle or high-dose CO. After 28 weeks of intervention, CO failed to improve hyperglycemia and pancreatic histopathological changes in SDT rats. Unexpectedly, CO dose-dependently exacerbated the impairment of kidney and mitochondrial functions caused by diabetes. CO also disturbed the expressions of proteins involved in mitochondrial biogenesis, dynamics, and mitophagy. However, no significant alterations were observed in nondiabetic rats receiving high-dose CO. The findings reveal that CO has deleterious effects that aggravate diabetic kidney injury via disrupting mitochondrial homeostasis, possibly due to its improper omega-6: omega-3 ratio.

Tubular Mitochondrial Dysfunction, Oxidative Stress, and Progression of Chronic Kidney Disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected conditions, and CKD is projected to become the fifth leading global cause of death by 2040. New therapeutic approaches are needed. Mitochondrial dysfunction and oxidative stress have emerged as drivers of kidney injury in acute and chronic settings, promoting the AKI-to-CKD transition. In this work, we review the role of mitochondrial dysfunction and oxidative stress in AKI and CKD progression and discuss novel therapeutic approaches. Specifically, evidence for mitochondrial dysfunction in diverse models of AKI (nephrotoxicity, cytokine storm, and ischemia-reperfusion injury) and CKD (diabetic kidney disease, glomerulopathies) is discussed; the clinical implications of novel information on the key role of mitochondria-related transcriptional regulators peroxisome proliferator-activated receptor gamma coactivator 1-alpha, transcription factor EB (PGC-1α, TFEB), and carnitine palmitoyl-transferase 1A (CPT1A) in kidney disease are addressed; the current status of the clinical development of therapeutic approaches targeting mitochondria are updated; and barriers to the clinical development of mitochondria-targeted interventions are discussed, including the lack of clinical diagnostic tests that allow us to categorize the baseline renal mitochondrial dysfunction/mitochondrial oxidative stress and to monitor its response to therapeutic intervention. Finally, key milestones for further research are proposed.

Podocyte Injury in Diabetic Kidney Disease: A Focus on Mitochondrial Dysfunction

Podocytes are a crucial cellular component in maintaining the glomerular filtration barrier, and their injury is the major determinant in the development of albuminuria and diabetic kidney disease (DKD). Podocytes are rich in mitochondria and heavily dependent on them for energy to maintain normal functions. Emerging evidence suggests that mitochondrial dysfunction is a key driver in the pathogenesis of podocyte injury in DKD. Impairment of mitochondrial function results in an energy crisis, oxidative stress, inflammation, and cell death. In this review, we summarize the recent advances in the molecular mechanisms that cause mitochondrial damage and illustrate the impact of mitochondrial injury on podocytes. The related mitochondrial pathways involved in podocyte injury in DKD include mitochondrial dynamics and mitophagy, mitochondrial biogenesis, mitochondrial oxidative phosphorylation and oxidative stress, and mitochondrial protein quality control. Furthermore, we discuss the role of mitochondria-associated membranes (MAMs) formation, which is intimately linked with mitochondrial function in podocytes. Finally, we examine the experimental evidence exploring the targeting of podocyte mitochondrial function for treating DKD and conclude with a discussion of potential directions for future research in the field of mitochondrial dysfunction in podocytes in DKD.

Mitochondrial Pathophysiology on Chronic Kidney Disease

In healthy kidneys, interstitial fibroblasts are responsible for the maintenance of renal architecture. Progressive interstitial fibrosis is thought to be a common pathway for chronic kidney diseases (CKD). Diabetes is one of the boosters of CKD. There is no effective treatment to improve kidney function in CKD patients. The kidney is a highly demanding organ, rich in redox reactions occurring in mitochondria, making it particularly vulnerable to oxidative stress (OS). A dysregulation in OS leads to an impairment of the Electron transport chain (ETC). Gene deficiencies in the ETC are closely related to the development of kidney disease, providing evidence that mitochondria integrity is a key player in the early detection of CKD. The development of novel CKD therapies is needed since current methods of treatment are ineffective. Antioxidant targeted therapies and metabolic approaches revealed promising results to delay the progression of some markers associated with kidney disease. Herein, we discuss the role and possible origin of fibroblasts and the possible potentiators of CKD. We will focus on the important features of mitochondria in renal cell function and discuss their role in kidney disease progression. We also discuss the potential of antioxidants and pharmacologic agents to delay kidney disease progression.

Reversing mitochondrial defects in aged hearts: role of mitochondrial calpain activation

Aging chronically increases endoplasmic reticulum (ER) stress that contributes to mitochondrial dysfunction. Activation of calpain 1 (CPN1) impairs mitochondrial function during acute ER stress. We proposed that aging-induced ER stress led to mitochondrial dysfunction by activating CPN1. We posit that attenuation of the ER stress or direct inhibition of CPN1 in aged hearts can decrease cardiac injury during ischemia-reperfusion by improving mitochondrial function. Male young (3 mo) and aged mice (24 mo) were used in the present study, and 4-phenylbutyrate (4-PBA) was used to decrease the ER stress in aged mice. Subsarcolemmal (SSM) and interfibrillar mitochondria (IFM) were isolated. Chronic 4-PBA treatment for 2 wk decreased CPN1 activation as shown by the decreased cleavage of spectrin in cytosol and apoptosis inducing factor (AIF) and the α1 subunit of pyruvate dehydrogenase (PDH) in mitochondria. Treatment improved oxidative phosphorylation in 24-mo-old SSM and IFM at baseline compared with vehicle. When 4-PBA-treated 24-mo-old hearts were subjected to ischemia-reperfusion, infarct size was decreased. These results support that attenuation of the ER stress decreased cardiac injury in aged hearts by improving mitochondrial function before ischemia. To challenge the role of CPN1 as an effector of the ER stress, aged mice were treated with MDL-28170 (MDL, an inhibitor of calpain 1). MDL treatment improved mitochondrial function in aged SSM and IFM. MDL-treated 24-mo-old hearts sustained less cardiac injury following ischemia-reperfusion. These results support that age-induced ER stress augments cardiac injury during ischemia-reperfusion by impairing mitochondrial function through activation of CPN1.

Calpain-mediated protein targets in cardiac mitochondria following ischemia-reperfusion

Calpain 1 and 2 (CPN1/2) are calcium-dependent cysteine proteases that exist in cytosol and mitochondria. Pharmacologic inhibition of CPN1/2 decreases cardiac injury during ischemia (ISC)-reperfusion (REP) by improving mitochondrial function. However, the protein targets of CPN1/2 activation during ISC-REP are unclear. CPN1/2 include a large subunit and a small regulatory subunit 1 (CPNS1). Genetic deletion of CPNS1 eliminates the activities of both CPN1 and CPN2. Conditional cardiomyocyte specific CPNS1 deletion mice were used in the present study to clarify the role of CPN1/2 activation in mitochondrial damage during ISC-REP with an emphasis on identifying the potential protein targets of CPN1/2. Isolated hearts from wild type (WT) or CPNS1 deletion mice underwent 25 min in vitro global ISC and 30 min REP. Deletion of CPNS1 led to decreased cytosolic and mitochondrial calpain 1 activation compared to WT. Cardiac injury was decreased in CPNS1 deletion mice following ISC-REP as shown by the decreased infarct size compared to WT. Compared to WT, mitochondrial function was improved in CPNS1 deletion mice following ischemia-reperfusion as shown by the improved oxidative phosphorylation and decreased susceptibility to mitochondrial permeability transition pore opening. H2O2 generation was also decreased in mitochondria from deletion mice following ISC-REP compared to WT. Deletion of CPNS1 also resulted in less cytochrome c and truncated apoptosis inducing factor (tAIF) release from mitochondria. Proteomic analysis of the isolated mitochondria showed that deletion of CPNS1 increased the content of proteins functioning in regulation of mitochondrial calcium homeostasis (paraplegin and sarcalumenin) and complex III activity. These results suggest that activation of CPN1 increases cardiac injury during ischemia-reperfusion by impairing mitochondrial function and triggering cytochrome c and tAIF release from mitochondria into cytosol.

Renoprotective Roles of Curcumin

The use of herb-based therapies is increasing over the past decades. These agents have been reported to provide many beneficial effects in many experimental and clinical studies. Curcumin is one of these agents which has potent pharmacological effects enabling it for the prevent and treatment of many diseases and pathologies such as renal disorders, hyperglycemia, oxidative stress, hypertension, and dyslipidemia. However, the exact molecular mechanisms mediating these renoprotective effects of curcumin are not well established. So, in the current study, we surveyed for possible renoprotective roles of curcumin and concluded how curcumin protects against renal injuries.

Mitochondrial dynamics and diabetic kidney disease: Missing pieces for the puzzle of therapeutic approaches

Diabetic kidney disease (DKD) is a common microvascular complication among diabetic patients. Once the DKD has developed, most of the patients inevitably progress to the end‐stage renal disease (ESRD). Although many new therapeutic strategies have attempted to demolish the root of the pathogenesis of DKD, the residual risks of ESRD still remained. Alteration of mitochondrial dynamics towards mitochondrial fission concurrent with the mitochondrial dysfunction is the characteristic that is usually seen in various diseases, including DKD. It has been proposed that those perturbation and their cooperative networks could be responsible for the residual risk of ESRD in DKD patients. In this review, the collective evidence of alteration in mitochondrial dynamics and their associations with the mitochondrial function from in vitro, in vivo and clinical reports of DKD are comprehensively summarized and discussed. In addition, both basic and clinical reports regarding the pharmacological interventions that showed an impact on the mitochondrial dynamics, and the correlation with the renal parameters in DKD is presented. Understanding these complex mechanisms in combination with the existing therapeutic modalities could bring a new opportunity to overcome the unresolvable problem of DKD.

Mitochondrial Regulation of Diabetic Kidney Disease

The role and nature of mitochondrial dysfunction in diabetic kidney disease (DKD) has been extensively studied. Yet, the molecular drivers of mitochondrial remodeling in DKD are poorly understood. Diabetic kidney cells exhibit a cascade of mitochondrial dysfunction ranging from changes in mitochondrial morphology to significant alterations in mitochondrial biogenesis, biosynthetic, bioenergetics and production of reactive oxygen species (ROS). How these changes individually or in aggregate contribute to progression of DKD remain to be fully elucidated. Nevertheless, because of the remarkable progress in our basic understanding of the role of mitochondrial biology and its dysfunction in DKD, there is great excitement on future targeted therapies based on improving mitochondrial function in DKD. This review will highlight the latest advances in understanding the nature of mitochondria dysfunction and its role in progression of DKD, and the development of mitochondrial targets that could be potentially used to prevent its progression.

Genetic mapping of renal glutathione suggests a novel regulatory locus on the murine X chromosome and overlap with hepatic glutathione regulation

Glutathione (GSH) is a critical cellular antioxidant that protects against byproducts of aerobic metabolism and other reactive electrophiles to prevent oxidative stress and cell death. Proper maintenance of its reduced form, GSH, in excess of its oxidized form, GSSG, prevents oxidative stress in the kidney and protects against the development of chronic kidney disease. Evidence has indicated that renal concentrations of GSH and GSSG, as well as their ratio GSH/GSSG, are moderately heritable, and past research has identified polymorphisms and candidate genes associated with these phenotypes in mice. Yet those discoveries were made with in silico mapping methods that are prone to false positives and power limitations, so the true loci and candidate genes that control renal glutathione remain unknown. The present study utilized high-resolution gene mapping with the Diversity Outbred mouse stock to identify causal loci underlying variation in renal GSH levels and redox status. Mapping output identified a suggestive locus associated with renal GSH on murine chromosome X at 51.602 Mbp, and bioinformatic analyses identified apoptosis-inducing factor mitochondria-associated 1 (Aifm1) as the most plausible candidate. Then, mapping outputs were compiled and compared against the genetic architecture of the hepatic GSH system, and we discovered a locus on murine chromosome 14 that overlaps between hepatic GSH concentrations and renal GSH redox potential. Overall, the results support our previously proposed model that the GSH redox system is regulated by both global and tissue-specific loci, vastly improving our understanding of GSH and its regulation and proposing new candidate genes for future mechanistic studies.

T-Cell Expression and Release of Kidney Injury Molecule-1 in Response to Glucose Variations Initiates Kidney Injury in Early Diabetes

Half of the mortality in diabetes is seen in individuals <50 years of age and commonly predicted by the early onset of diabetic kidney disease (DKD). In type 1 diabetes, increased urinary albumin-to-creatinine ratio (uACR) during adolescence defines this risk, but the pathological factors responsible remain unknown. We postulated that early in diabetes, glucose variations contribute to kidney injury molecule-1 (KIM-1) release from circulating T cells, elevating uACR and DKD risk. DKD risk was assigned in youth with type 1 diabetes (n = 100; 20.0 ± 2.8 years; males/females, 54:46; HbA_1c 66.1 [12.3] mmol/mol; diabetes duration 10.7 ± 5.2 years; and BMI 24.5 [5.3] kg/m²) and 10-year historical uACR, HbA_1c, and random blood glucose concentrations collected retrospectively. Glucose fluctuations in the absence of diabetes were also compared with streptozotocin diabetes in apolipoprotein E ^-/- mice. Kidney biopsies were used to examine infiltration of KIM-1-expressing T cells in DKD and compared with other chronic kidney disease. Individuals at high risk for DKD had persistent elevations in uACR defined by area under the curve (AUC; uACR_AUC0-10yrs, 29.7 ± 8.8 vs. 4.5 ± 0.5; P < 0.01 vs. low risk) and early kidney dysfunction, including ∼8.3 mL/min/1.73 m² higher estimated glomerular filtration rates (modified Schwartz equation; P_adj < 0.031 vs. low risk) and plasma KIM-1 concentrations (∼15% higher vs. low risk; P < 0.034). High-risk individuals had greater glycemic variability and increased peripheral blood T-cell KIM-1 expression, particularly on CD8⁺ T cells. These findings were confirmed in a murine model of glycemic variability both in the presence and absence of diabetes. KIM-1⁺ T cells were also infiltrating kidney biopsies from individuals with DKD. Healthy primary human proximal tubule epithelial cells exposed to plasma from high-risk youth with diabetes showed elevated collagen IV and sodium-glucose cotransporter 2 expression, alleviated with KIM-1 blockade. Taken together, these studies suggest that glycemic variations confer risk for DKD in diabetes via increased CD8⁺ T-cell production of KIM-1.

NADH/NAD+ Redox Imbalance and Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a common and severe complication of diabetes mellitus. If left untreated, DKD can advance to end stage renal disease that requires either dialysis or kidney replacement. While numerous mechanisms underlie the pathogenesis of DKD, oxidative stress driven by NADH/NAD⁺ redox imbalance and mitochondrial dysfunction have been thought to be the major pathophysiological mechanism of DKD. In this review, the pathways that increase NADH generation and those that decrease NAD⁺ levels are overviewed. This is followed by discussion of the consequences of NADH/NAD⁺ redox imbalance including disruption of mitochondrial homeostasis and function. Approaches that can be applied to counteract DKD are then discussed, which include mitochondria-targeted antioxidants and mimetics of superoxide dismutase, caloric restriction, plant/herbal extracts or their isolated compounds. Finally, the review ends by pointing out that future studies are needed to dissect the role of each pathway involved in NADH-NAD⁺ metabolism so that novel strategies to restore NADH/NAD⁺ redox balance in the diabetic kidney could be designed to combat DKD.

Excessively Enlarged Mitochondria in the Kidneys of Diabetic Nephropathy

Diabetic nephropathy (DN) is the most serious complication of diabetes and a leading cause of kidney failure and mortality in patients with diabetes. However, the exact pathogenic mechanisms involved are poorly understood. Impaired mitochondrial function and accumulation of damaged mitochondria due to increased imbalance in mitochondrial dynamics are known to be involved in the development and progression of DN. Accumulating evidence suggests that aberrant mitochondrial fission is involved in the progression of DN. Conversely, studies linking excessively enlarged mitochondria to DN pathogenesis are emerging. In this review, we summarize the current concepts of imbalanced mitochondrial dynamics and their molecular aspects in various experimental models of DN. We discuss the recent evidence of enlarged mitochondria in the kidneys of DN and examine the possibility of a therapeutic application targeting mitochondrial dynamics in DN.

Update on the Mechanisms of Tubular Cell Injury in Diabetic Kidney Disease

Increasing evidence supports a role of proximal tubular (PT) injury in the progression of diabetic kidney disease (DKD), in patients with or without proteinuria. Research on the mechanisms of the PT injury in DKD could help us to identify potential new biomarkers and drug targets for DKD. A high glucose transport state and mismatched local hypoxia in the PT of diabetes patients may be the initiating factors causing PT injury. Other mechanism such as mitochondrial dysfunction, reactive oxygen species (ROS) overproduction, ER stress, and deficiency of autophagy interact with each other leading to more PT injury by forming a vicious circle. PT injury eventually leads to the development of tubulointerstitial inflammation and fibrosis in DKD. Many downstream signaling pathways have been demonstrated to mediate these diseased processes. This review focuses mostly on the novel mechanisms of proximal renal tubular injury in DKD and we believe such review could help us to better understand the pathogenesis of DKD and identify potential new therapies for this disease.

Mitochondrion-driven nephroprotective mechanisms of novel glucose lowering medications

Therapy for diabetic kidney disease (DKD) is undergoing a revolution with the realization that some glucose-lowering drugs have nephroprotective actions that may be intrinsic to the drugs and not dependent on the impact on diabetes control, as demonstrated with the sodium glucose co-transporter-2 (SGLT-2) inhibitors. Mitochondria are a critical factor required for the maintenance of kidney function, given its high energy demanding profile, with extensive use of adenosine triphosphate (ATP). Consequently, deficiency of the master regulator of mitochondrial biogenesis peroxisome proliferator-activated receptor gamma coactivator 1α predisposes to kidney disease. Perhaps as a result of key role of mitochondria in fundamental cellular functions, mitochondrial dysfunction may play a role in the pathogenesis of common conditions such as DKD. Finding pharmacological agents to influence this pathway could therefore lead to early implementation of therapy. Importantly, glucose-lowering drugs such as glucagon-like peptide-1 receptor activators and SGLT2 inhibitors have kidney and/or cardioprotective actions in patients with diabetes. Accumulating evidence from preclinical studies has suggested a protective effect of these drugs that is in part mediated by normalizing mitochondrial function. We now critically review this evidence and discuss studies needed to confirm mitochondrial protective benefits across a range of clinical studies.

Processed foods drive intestinal barrier permeability and microvascular diseases

Intake of processed foods has increased markedly over the past decades, coinciding with increased microvascular diseases such as chronic kidney disease (CKD) and diabetes. Here, we show in rodent models that long-term consumption of a processed diet drives intestinal barrier permeability and an increased risk of CKD. Inhibition of the advanced glycation pathway, which generates Maillard reaction products within foods upon thermal processing, reversed kidney injury. Consequently, a processed diet leads to innate immune complement activation and local kidney inflammation and injury via the potent proinflammatory effector molecule complement 5a (C5a). In a mouse model of diabetes, a high resistant starch fiber diet maintained gut barrier integrity and decreased severity of kidney injury via suppression of complement. These results demonstrate mechanisms by which processed foods cause inflammation that leads to chronic disease.

Expression pattern of apoptosis-inducing factor in the kidneys of streptozotocin-induced diabetic rats

BACKGROUND

It is believed that tubulo-interstitial fibrosis and atrophy in diabetic patients are directly associated with the progression of chronic kidney disease, CKD. AIF is one of the crucial factors responsible for mitochondrial apoptosis, however, it can also promote cell survival independently from its role in apoptosis, and therefore can be potentially used as a tool in prevention of the onset of CKD in diabetic patients. Our aim was to investigate the significance of AIF expression in the development of CKD by observing the expression of AIF in 2 weeks' and 2 months' kidneys of diabetic rats compared to their controls.

METHODS

Male Sprague-Dawley rats were treated with 55 mg/kg streptozotocin (model of type 1 diabetes mellitus; DM group) or citrate buffer (control). After 2 weeks and 2 months kidney samples were collected and analysed in different renal areas.

RESULTS

Characteristic morphologic changes were found between the 2 months' control and 2 months' diabetic groups. Those changes, including fibrosis and possible replacement of podocytes with connective tissue were mainly present in the glomeruli. AIF expression was seen in the both cortex, and in the collecting ducts of the medulla. Strong intensity of AIF expression was seen in proximal and distal convoluted tubules in both diabetic groups. In the control groups the glomeruli showed no AIF staining but moderate staining was seen in both diabetic groups. Overall, the percentage of AIF positive cells in the glomeruli was the lowest. The greatest rise in cell positivity was displayed from the 2 weeks' control group to 2 weeks' diabetes group (38 %) in glomeruli. The cell positivity of the 2 weeks' diabetic group is significantly reduced to 18 % in the 2 months' diabetic group in glomeruli. A similar pattern was seen in the proximal tubular cells (92 % positivity 2 weeks diabetic groups; 89 % positivity 2 months diabetic groups), as well as in the distal tubules. The highest percentage of AIF positive cells was seen in the collecting ducts, more than 80 % in all groups.

CONCLUSIONS

Our study provides insight into AIF expression pattern during short term diabetes model, confirming possible dual role of AIF, not only in apoptosis but also in cell function and homeostasis, and proving AIF as potential therapeutic target and marker of advancement of CKD.

Apoptosis inducing factor and mitochondrial NADH dehydrogenases: redox-controlled gear boxes to switch between mitochondrial biogenesis and cell death

The mitochondrial complex I serves as entry point for NADH into the electron transport chain. In animals, fungi and plants, additional NADH dehydrogenases carry out the same electron transfer reaction, however they do not pump protons. The apoptosis inducing factor (AIF, AIFM1 in humans) is a famous member of this group as it was the first pro-apoptotic protein identified that can induce caspase-independent cell death. Recent studies on AIFM1 and the NADH dehydrogenase Nde1 of baker's yeast revealed two independent and experimentally separable activities of this class of enzymes: On the one hand, these proteins promote the functionality of mitochondrial respiration in different ways: They channel electrons into the respiratory chain and, at least in animals, promote the import of Mia40 (named MIA40 or CHCHD4 in humans) and the assembly of complex I. On the other hand, they can give rise to pro-apoptotic fragments that are released from the mitochondria to trigger cell death. Here we propose that AIFM1 and Nde1 serve as conserved redox switches which measure metabolic conditions on the mitochondrial surface and translate it into a binary life/death decision. This function is conserved among eukaryotic cells and apparently used to purge metabolically compromised cells from populations.

Shaping Up Mitochondria in Diabetic Nephropathy

Mitochondrial medicine has experienced significant progress in recent years and is expected to grow significantly in the near future, yielding many opportunities to translate novel bench discoveries into clinical medicine. Multiple lines of evidence have linked mitochondrial dysfunction to a variety of metabolic diseases, including diabetic nephropathy (DN). Mitochondrial dysfunction presumably precedes the emergence of key histologic and biochemical features of DN, which provides the rationale to explore mitochondrial fitness as a novel therapeutic target in patients with DN. Ultimately, the success of mitochondrial medicine is dependent on a better understanding of the underlying biology of mitochondrial fitness and function. To this end, recent advances in mitochondrial biology have led to new understandings of the potential effect of mitochondrial dysfunction in a myriad of human pathologies. We have proposed that molecular mechanisms that modulate mitochondrial dynamics contribute to the alterations of mitochondrial fitness and progression of DN. In this comprehensive review, we highlight the possible effects of mitochondrial dysfunction in DN, with the hope that targeting specific mitochondrial signaling pathways may lead to the development of new drugs that mitigate DN progression. We will outline potential tools to improve mitochondrial fitness in DN as a novel therapeutic strategy. These emerging views suggest that the modulation of mitochondrial fitness could serve as a key target in ameliorating progression of kidney disease in patients with diabetes.

Exploring the role of the metabolite-sensing receptor GPR109a in diabetic nephropathy

Alterations in gut homeostasis may contribute to the progression of diabetic nephropathy. There has been recent attention on the renoprotective effects of metabolite-sensing receptors in chronic renal injury, including the G protein-coupled receptor (GPR)109a, which ligates the short-chain fatty acid butyrate. However, the role of GPR109a in the development of diabetic nephropathy, a milieu of diminished microbiome-derived metabolites, has not yet been determined. The present study aimed to assess the effects of insufficient GPR109a signaling, via genetic deletion of GPR109a, on the development of renal injury in diabetic nephropathy. Gpr109a^-/- mice or their wild-type littermates (Gpr109a^+/+) were rendered diabetic with streptozotocin. Mice received a control diet or an isocaloric high-fiber diet (12.5% resistant starch) for 24 wk, and gastrointestinal permeability and renal injury were determined. Diabetes was associated with increased albuminuria, glomerulosclerosis, and inflammation. In comparison, Gpr109a^-/- mice with diabetes did not show an altered renal phenotype. Resistant starch supplementation did not afford protection from renal injury in diabetic nephropathy. While diabetes was associated with alterations in intestinal morphology, intestinal permeability assessed in vivo using the FITC-dextran test was unaltered. GPR109a deletion did not worsen gastrointestinal permeability. Furthermore, 12.5% resistant starch supplementation, at physiological concentrations, had no effect on intestinal permeability or morphology. The results of this study indicate that GPR109a does not play a critical role in intestinal homeostasis in a model of type 1 diabetes or in the development of diabetic nephropathy.

Increased mitochondrial fission of glomerular podocytes in diabetic nephropathy

AIMS

Previous studies showed that abnormal mitochondrial structure and function were involved in the pathological process of diabetic nephropathy (DN). The dynamic mitochondrial processes, including fusion and fission, maintain the mass and quantity of mitochondria. Podocyte injury is a critical factor in the development and progression of DN. The present study evaluated the mitochondrial fission of podocytes in patients with DN.

METHODS

We recruited 31 patients with biopsy-confirmed DN. A quantitative analysis of the mitochondrial morphology was conducted with electron microscopy using a computer-assisted morphometric analysis application to calculate the aspect ratio values. Immunofluorescence assays were used to evaluate protein colocalization in the glomeruli of patients.

RESULTS

The urine protein level was significantly increased in DN patients compared to non-DN patients (P < 0.001), and the mitochondria in the podocytes from DN patients were more fragmentated than those from patients without DN. The mitochondrial aspect ratio values were negatively correlated with the proteinuria levels (r = -0.574, P = 0.01), and multiple regression analysis verified that the mitochondrial aspect ratio was significantly and independently associated with the urine protein level (β = -0.519, P = 0.007). In addition, Drp1, a mitochondrial fission factor, preferentially combines with AKAP1, which is located in the mitochondrial membrane.

CONCLUSIONS

In the podocytes of DN patients, mitochondrial fragmentation was increased, and mitochondrial aspect ratio values were correlated with the proteinuria levels. The AKAP1-Drp1 pathway may contribute to mitochondrial fission in the pathogenesis of DN.

Genetic Susceptibility to Chronic Kidney Disease - Some More Pieces for the Heritability Puzzle

Chronic kidney disease (CKD) is a major global health problem with an increasing prevalence partly driven by aging population structure. Both genomic and environmental factors contribute to this complex heterogeneous disease. CKD heritability is estimated to be high (30-75%). Genome-wide association studies (GWAS) and GWAS meta-analyses have identified several genetic loci associated with CKD, including variants in UMOD, SHROOM3, solute carriers, and E3 ubiquitin ligases. However, these genetic markers do not account for all the susceptibility to CKD, and the causal pathways remain incompletely understood; other factors must be contributing to the missing heritability. Less investigated biological factors such as telomere length; mitochondrial proteins, encoded by nuclear genes or specific mitochondrial DNA (mtDNA) encoded genes; structural variants, such as copy number variants (CNVs), insertions, deletions, inversions and translocations are poorly covered and may explain some of the missing heritability. The sex chromosomes, often excluded from GWAS studies, may also help explain gender imbalances in CKD. In this review, we outline recent findings on molecular biomarkers for CKD (telomeres, CNVs, mtDNA variants, sex chromosomes) that typically have received less attention than gene polymorphisms. Shorter telomere length has been associated with renal dysfunction and CKD progression, however, most publications report small numbers of subjects with conflicting findings. CNVs have been linked to congenital anomalies of the kidney and urinary tract, posterior urethral valves, nephronophthisis and immunoglobulin A nephropathy. Information on mtDNA biomarkers for CKD comes primarily from case reports, therefore the data are scarce and diverse. The most consistent finding is the A3243G mutation in the MT-TL1 gene, mainly associated with focal segmental glomerulosclerosis. Only one GWAS has found associations between X-chromosome and renal function (rs12845465 and rs5987107). No loci in the Y-chromosome have reached genome-wide significance. In conclusion, despite the efforts to find the genetic basis of CKD, it remains challenging to explain all of the heritability with currently available methods and datasets. Although additional biomarkers have been investigated in less common suspects such as telomeres, CNVs, mtDNA and sex chromosomes, hidden heritability in CKD remains elusive, and more comprehensive approaches, particularly through the integration of multiple -"omics" data, are needed.

The effect of Tmem135 overexpression on the mouse heart

Tissues with high-energy demand including the heart are rich in the energy-producing organelles, mitochondria, and sensitive to mitochondrial dysfunction. While alterations in mitochondrial function are increasingly recognized in cardiovascular diseases, the molecular mechanisms through which changes in mitochondria lead to heart abnormalities have not been fully elucidated. Here, we report that transgenic mice overexpressing a novel regulator of mitochondrial dynamics, transmembrane protein 135 (Tmem135), exhibit increased fragmentation of mitochondria and disease phenotypes in the heart including collagen accumulation and hypertrophy. The gene expression analysis showed that genes associated with ER stress and unfolded protein response, and especially the pathway involving activating transcription factor 4, are upregulated in the heart of Tmem135 transgenic mice. It also showed that gene expression changes in the heart of Tmem135 transgenic mice significantly overlap with those of aged mice in addition to the similarity in cardiac phenotypes, suggesting that changes in mitochondrial dynamics may be involved in the development of heart abnormalities associated with aging. Our study revealed the pathological consequence of overexpression of Tmem135, and suggested downstream molecular changes that may underlie those disease pathologies.

Effects and Mechanisms of Taurine as a Therapeutic Agent

Taurine is an abundant, β-amino acid with diverse cytoprotective activity. In some species, taurine is an essential nutrient but in man it is considered a semi-essential nutrient, although cells lacking taurine show major pathology. These findings have spurred interest in the potential use of taurine as a therapeutic agent. The discovery that taurine is an effective therapy against congestive heart failure led to the study of taurine as a therapeutic agent against other disease conditions. Today, taurine has been approved for the treatment of congestive heart failure in Japan and shows promise in the treatment of several other diseases. The present review summarizes studies supporting a role of taurine in the treatment of diseases of muscle, the central nervous system, and the cardiovascular system. In addition, taurine is extremely effective in the treatment of the mitochondrial disease, mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), and offers a new approach for the treatment of metabolic diseases, such as diabetes, and inflammatory diseases, such as arthritis. The review also addresses the functions of taurine (regulation of antioxidation, energy metabolism, gene expression, ER stress, neuromodulation, quality control and calcium homeostasis) underlying these therapeutic actions.

Mitochondrial dysfunction in diabetic kidney disease

Globally, diabetes is the leading cause of chronic kidney disease and end-stage renal disease, which are major risk factors for cardiovascular disease and death. Despite this burden, the factors that precipitate the development and progression of diabetic kidney disease (DKD) remain to be fully elucidated. Mitochondrial dysfunction is associated with kidney disease in nondiabetic contexts, and increasing evidence suggests that dysfunctional renal mitochondria are pathological mediators of DKD. These complex organelles have a broad range of functions, including the generation of ATP. The kidneys are mitochondrially rich, highly metabolic organs that require vast amounts of ATP for their normal function. The delivery of metabolic substrates for ATP production, such as fatty acids and oxygen, is altered by diabetes. Changes in metabolic fuel sources in diabetes to meet ATP demands result in increased oxygen consumption, which contributes to renal hypoxia. Inherited factors including mutations in genes that impact mitochondrial function and/or substrate delivery may also be important risk factors for DKD. Hence, we postulate that the diabetic milieu and inherited factors that underlie abnormalities in mitochondrial function synergistically drive the development and progression of DKD.

RNA-sequencing reveals genome-wide long non-coding RNAs profiling associated with early development of diabetic nephropathy

Background

Diabetic nephropathy (DN) seriously threatens the lives of patients, and the mechanism of DN remains largely unknown because of the complex regulation between long non-coding RNA (lncRNA) and protein-coding genes. In early development of diabetic nephropathy (DN), pathogenesis remains largely unknown.

Results

We used RNA-sequencing to profile protein-coding and lncRNA gene transcriptome of mouse kidney proximal tubular cells during early stage of DN at various time points. Over 7000 protein-coding and lncRNA genes were differentially expressed, and most of them were time-specific. Nearly 40% of lncRNA genes overlapped with functional element signals using CHIP-Seq data from ENCODE database. Disease progression was characterized by lncRNA expression patterns, rather than protein-coding genes, indicating that the lncRNA genes are potential biomarkers for DN. For gene ontologies related to kidney, enrichment was observed in protein-coding genes co-expressed with neighboring lncRNA genes. Based on protein-coding and lncRNA gene profiles, clustering analysis reveals dynamic expression patterns for kidney, suggesting that they are highly correlated during disease progression. To evaluate translation of mouse model to human conditions, we experimentally validated orthologous genes in human cells in vitro diabetic model. In mouse model, most gene expression patterns were repeated in human cell lines.

Conclusions

These results define dynamic transcriptome and novel functional roles for lncRNAs in diabetic kidney cells; these roles may result in lncRNA-based diagnosis and therapies for DN.

Targeted mitochondrial therapy using MitoQ shows equivalent renoprotection to angiotensin converting enzyme inhibition but no combined synergy in diabetes

Mitochondrial dysfunction is a pathological mediator of diabetic kidney disease (DKD). Our objective was to test the mitochondrially targeted agent, MitoQ, alone and in combination with first line therapy for DKD. Intervention therapies (i) vehicle (D); (ii) MitoQ (DMitoQ;0.6 mg/kg/day); (iii) Ramipril (DRam;3 mg/kg/day) or (iv) combination (DCoAd) were administered to male diabetic db/db mice for 12 weeks (n = 11–13/group). Non-diabetic (C) db/m mice were followed concurrently. No therapy altered glycaemic control or body weight. By the study end, both monotherapies improved renal function, decreasing glomerular hyperfiltration and albuminuria. All therapies prevented tubulointerstitial collagen deposition, but glomerular mesangial expansion was unaffected. Renal cortical concentrations of ATP, ADP, AMP, cAMP, creatinine phosphate and ATP:AMP ratio were increased by diabetes and mostly decreased with therapy. A higher creatine phosphate:ATP ratio in diabetic kidney cortices, suggested a decrease in ATP consumption. Diabetes elevated glucose 6-phosphate, fructose 6-phosphate and oxidised (NAD+ and NADP+) and reduced (NADH) nicotinamide dinucleotides, which therapy decreased generally. Diabetes increased mitochondrial oxygen consumption (OCR) at complex II-IV. MitoQ further increased OCR but decreased ATP, suggesting mitochondrial uncoupling as its mechanism of action. MitoQ showed renoprotection equivalent to ramipril but no synergistic benefits of combining these agents were shown.

Melatonin, mitochondria and hypertension

Melatonin, due to its multiple means and mechanisms of action, plays a fundamental role in the regulation of the organismal physiology by fine tunning several functions. The cardiovascular system is an important site of action as melatonin regulates blood pressure both by central and peripheral interventions, in addition to its relation with the renin-angiotensin system. Besides, the systemic management of several processes, melatonin acts on mitochondria regulation to maintain a healthy cardiovascular system. Hypertension affects target organs in different ways and cellular energy metabolism is frequently involved due to mitochondrial alterations that include a rise in reactive oxygen species production and an ATP synthesis decrease. The discussion that follows shows the role played by melatonin in the regulation of mitochondrial physiology in several levels of the cardiovascular system, including brain, heart, kidney, blood vessels and, particularly, regulating the renin-angiotensin system. This discussion shows the putative importance of using melatonin as a therapeutic tool involving its antioxidant potential and its action on mitochondrial physiology in the cardiovascular system.

SOCS-1 is involved in TNF-α-induced mitochondrial dysfunction and apoptosis in renal tubular epithelial cells

Tumor necrosis factor-α (TNF-α) is suggested to induce mitochondrial dysfunction and apoptosis of renal tubular epithelial cells that possibly exacerbates renal function in chronic kidney disease (CKD). Here we investigated whether suppressor of cytokine signaling-1 (SOCS-1), an inhibitor of cytokine signaling, was involved in TNF-α-induced human renal tubular epithelial cells (HKCs) oxidative stress and apoptosis. TNF-α promoted the protein and mRNA expression of SOCS-1 in a time and dose dependent manner, along with increased cell apoptosis and activation of apoptosis signal regulating kinase-1(ASK1) in HKCs. Furthermore, overexpression of SOCS-1 in HKCs reduced TNF-α-mediated oxidative stress and apoptosis. Meanwhile, We also found that overexpression of SOCS-1 could regulate the activity of JAK/STAT signaling pathway. In addition, a specific JAK2 inhibitor, AG490, that both attenuated TNF-α-induced oxidative stress, also reduced apoptosis. Taken together, overexpression of SOCS-1 prevented TNF-α-mediated cell oxidative stress and apoptosis may be via suppression of JAK/STAT signaling pathway activation in HKCs.

Development of Therapeutics That Induce Mitochondrial Biogenesis for the Treatment of Acute and Chronic Degenerative Diseases

Mitochondria have various roles in cellular metabolism and homeostasis. Because mitochondrial dysfunction is associated with many acute and chronic degenerative diseases, mitochondrial biogenesis (MB) is a therapeutic target for treating such diseases. Here, we review the role of mitochondrial dysfunction in acute and chronic degenerative diseases and the cellular signaling pathways by which MB is induced. We then review existing work describing the development and application of drugs that induce MB in vitro and in vivo. In particular, we discuss natural products and modulators of transcription factors, kinases, cyclic nucleotides, and G protein-coupled receptors.