Mitochondrial Dynamics in Type 2 Diabetes and Cancer

Inhibition of Mitochondrial Fission Protein Drp1 Ameliorates Myopathy in the D2-mdx Model of Duchenne Muscular Dystrophy

Although current treatments for Duchenne Muscular Dystrophy (DMD) have proven to be effective in delaying myopathy, there remains a strong need to identify novel targets to develop additional therapies. Mitochondrial dysfunction is an early pathological feature of DMD. A fine balance of mitochondrial dynamics (fission and fusion) is crucial to maintain mitochondrial function and skeletal muscle health. Excessive activation of Dynamin-Related Protein 1 (Drp1)-mediated mitochondrial fission was reported in animal models of DMD. However, whether Drp1-mediated mitochondrial fission is a viable target for treating myopathy in DMD remains unknown. Here, we treated a D2-mdx model of DMD (9-10 weeks old) with Mdivi-1, a selective Drp1 inhibitor, every other day (i.p. injection) for 5 weeks. We demonstrated that Mdivi-1 effectively improved skeletal muscle strength and reduced serum creatine kinase concentration. Mdivi-1 treatment also effectively inhibited mitochondrial fission regulatory protein markers, Drp1(Ser616) phosphorylation and Fis1 in skeletal muscles from D2-mdx mice, which resulted in reduced content of damaged and fragmented mitochondria. Furthermore, Mdivi-1 treatment attenuated lipid peroxidation product, 4-HNE, in skeletal muscle from D2-mdx mice, which was inversely correlated with muscle grip strength. Finally, we revealed that Mdivi-1 treatment downregulated Alpha 1 Type I Collagen (Col1a1) protein expression, a marker of fibrosis, and Interleukin-6 (IL-6) mRNA expression, a marker of inflammation. In summary, these results demonstrate that inhibition of Drp1-mediated mitochondrial fission by Mdivi-1 is effective in improving muscle strength and alleviating muscle damage in D2-mdx mice. These improvements are associated with improved skeletal muscle mitochondrial integrity, leading to attenuated lipid peroxidation.

Phosphocreatine ameliorates hepatocellular apoptosis mediated by protecting mitochondrial damage in liver ischemia/reperfusion injury through inhibiting TLR4 and Agonizing Akt Pathway

Hepatic ischemia/reperfusion (HI/R) presents significant challenges in surgical liver transplantation and hepatic ischemic shock, with few effective clinical preventive measures available. This study explores the potential protective effects and underlying mechanisms of phosphocreatine (PCr) in the context of HI/R. We established an in vitro ischemia/reperfusion model using hepatocellular carcinoma HepG2 cells and normal liver L02 cells. For in vivo assessments, C57BL/6 mice were subjected to the HI/R model to evaluate the impact of PCr on liver protection. PCr pretreatment significantly improved liver cell survival rates, maintained mitochondrial membrane potential (MMP), reduced apoptosis, and alleviated oxidative damage and inflammatory responses. Importantly, PCr exerted its protective effects by downregulating TLR4 and activating the Akt signaling pathway, which suppressed inflammation, mitigated oxidative stress, inhibited apoptosis, and modulated key biomarkers, including ALT, AST, IL-6, IL-1β, TNF-α, SOD, MDA, and reactive oxygen species (ROS). Western blot analyses demonstrated PCr's anti-inflammatory effects through the regulation of UCP2, Cyp-D, Cyt-C, and PGC-1α, thereby preserving mitochondrial structure and function, maintaining MMP, and regulating membrane pores. Transmission electron microscopy further highlighted PCr's role in sustaining mitochondrial integrity. In conclusion, our findings suggest that PCr helps maintain mitochondrial homeostasis by intervening in the TLR4 inflammatory pathway and activating the Akt signaling pathway, ultimately reducing liver injury. This study offers new insights and potential treatment strategies for HI/R, providing valuable guidance for future clinical applications.

Isotoosendanin inhibits triple-negative breast cancer metastasis by reducing mitochondrial fission and lamellipodia formation regulated by the Smad2/3-GOT2-MYH9 signaling axis

Triple-negative breast cancer (TNBC) is incurable and prone to widespread metastasis. Therefore, identification of key targets for TNBC progression is urgently needed. Our previous study revealed that isotoosendanin (ITSN) reduced TNBC metastasis by targeting TGFβR1. ITSN is currently used as an effective chemical probe to further discover the key molecules involved in TNBC metastasis downstream of TGFβR1. The results showed that GOT2 was the gene downstream of Smad2/3 and that ITSN decreased GOT2 expression by abrogating the activation of the TGF-β-Smad2/3 signaling pathway through directly binding to TGFβR1. GOT2 was highly expressed in TNBC, and its knockdown decreased TNBC metastasis. However, GOT2 overexpression reversed the inhibitory effect of ITSN on TNBC metastasis both in vitro and in vivo. GOT2 interacted with MYH9 and hindered its binding to the E3 ubiquitin ligase STUB1, thereby reducing MYH9 ubiquitination and degradation. Moreover, GOT2 also enhanced the translocation of MYH9 to mitochondria and thus induced DRP1 phosphorylation, thereby promoting mitochondrial fission and lamellipodia formation in TNBC cells. ITSN-mediated inhibition of mitochondrial fission and lamellipodia formation was associated with reduced GOT2 expression. In conclusion, ITSN prevented MYH9-regulated mitochondrial fission and lamellipodia formation in TNBC cells by enhancing MYH9 protein degradation through a reduction in GOT2 expression, thus contributing to its inhibition of TNBC metastasis.

Voluntary Exercise Attenuates Tumor Growth in a Preclinical Model of Castration-Resistant Prostate Cancer

Purpose

To examine the effects of voluntary exercise training on tumor growth and explore the underlying intratumoral molecular pathways and processes responsible for the beneficial effects of VWR on tumor initiation and progression in a mouse model of Castration-Resistant Prostate Cancer (CRPC).

Methods

Male immunodeficient mice (SCID) were castrated and subcutaneously inoculated with human CWR-22RV1 cancer cells to construct CRPC xenograft model before randomly assigned to either voluntary wheel running (VWR) or sedentary (SED) group (n=6/group). After three weeks, tumor tissues were collected. Tumor size was measured and calculated. mRNA expression of markers of DNA replication, Androgen Receptor (AR) signaling, and mitochondrial dynamics was determined by RT-PCR. Protein expression of mitochondrial content and dynamics was determined by western blotting. Finally, RNA-sequencing analysis was performed in the tumor tissues.

Results

Voluntary wheel running resulted in smaller tumor volume at the initial stage and attenuated tumor progression throughout the time course (P < 0.05). The reduction of tumor volume in VWR group was coincided with lower mRNA expression of DNA replication markers ( MCM2 , MCM6 , and MCM7 ), AR signaling ( ELOVL5 and FKBP5 ) and regulatory proteins of mitochondrial fission (Drp1 and Fis1) and fusion (MFN1 and OPA1) when compared to the SED group (P<0.05). More importantly, RNA sequencing data further revealed that pathways related to pathways related to angiogenesis, extracellular matrix formation and endothelial cell proliferation were downregulated.

Conclusions

Three weeks of VWR was effective in delaying tumor initiation and progression, which coincided with reduced transcription of DNA replication, AR signaling targets and mitochondrial dynamics. We further identified reduced molecular pathways/processes related to angiogenesis that may be responsible for the delayed tumor initiation and progression by VWR.

Cuproptosis: potential new direction in diabetes research and treatment

Cuproptosis, a recently discovered form of cell death, stems from an overabundance of copper ions infiltrating mitochondria. These ions directly engage lipoylated proteins, prompting their oligomerization and subsequent loss of iron-sulfur clusters. This sequence induces proteotoxic stress, ultimately culminating in cell death. Type 2 diabetes, a chronic metabolic disorder resulting from a complex interplay of genetic and environmental factors, has not yet been fully understood in terms of its etiology and pathogenesis. Intricately, it is linked to various modalities of cell death, including mitochondrial autophagy, apoptosis, pyroptosis, and ferroptosis. Studies have discovered impaired copper metabolism in individuals with Type 2 diabetes, hinting at a unique role for copper homeostasis in the progression of the disease. To this end, the present research aims to delineate the potential correlation between cuproptosis and Type 2 diabetes by exhaustively reviewing the existing literature. By synthesizing relevant research on cuproptosis, the paper intends to lay the groundwork for a thorough exploration of the pathogenesis of Type 2 diabetes and the development of targeted therapeutic interventions. The ultimate objective is to facilitate a deeper understanding of Type 2 diabetes and to identify novel therapeutic strategies associated with cuproptosis.

Promoting mitochondrial dynamics by inhibiting the PINK1-PRKN pathway to relieve diabetic nephropathy

Diabetes is a metabolic disorder characterized by high blood glucose levels and is a leading cause of kidney disease. Diabetic nephropathy has been attributed to dysfunctional mitochondria. However, many questions remain about the exact mechanism. The structure, function and molecular pathways are highly conserved between mammalian podocytes and Drosophila nephrocytes; therefore, we used flies on a high-sucrose diet to model type 2 diabetic nephropathy. The nephrocytes from flies on a high-sucrose diet showed a significant functional decline and decreased cell size, associated with a shortened lifespan. Structurally, the nephrocyte filtration structure, known as the slit diaphragm, was disorganized. At the cellular level, we found altered mitochondrial dynamics and dysfunctional mitochondria. Regulating mitochondrial dynamics by either genetic modification of the Pink1-Park (mammalian PINK1-PRKN) pathway or treatment with BGP-15, mitigated the mitochondrial defects and nephrocyte functional decline. These findings support a role for Pink1-Park-mediated mitophagy and associated control of mitochondrial dynamics in diabetic nephropathy, and demonstrate that targeting this pathway might provide therapeutic benefits for type 2 diabetic nephropathy.

Mitochondrial quality control in health and cardiovascular diseases

Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

Tacrolimus Improves Therapeutic Efficacy of Umbilical Cord Blood-Derived Mesenchymal Stem Cells in Diabetic Retinopathy by Suppressing DRP1-Mediated Mitochondrial Fission

Diabetic retinopathy (DR) is a leading cause of blindness in diabetic patients. Umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) are emerging as a promising new drug for degenerative disease associated with diabetes. Recent studies have shown that high glucose-increased excessive calcium levels are a major risk factor for mitochondrial reactive oxygen species (mtROS) accumulation and apoptosis. This study aimed to investigate the role of high glucose-induced NFATC1 signaling in mitochondrial oxidative stress-stimulated apoptosis and the effect of tacrolimus on the therapeutic efficacy of subconjunctival transplantation of UCB-MSCs in a DR rat model. High glucose increased mtROS and cleaved caspase-9 expression in UCB-MSCs. High glucose conditions increased O-GlcNAcylated protein expression and nuclear translocation of NFATC1. Tacrolimus pretreatment recovered high glucose-induced mtROS levels and apoptosis. In the DR rat model, subconjunctival transplantation of tacrolimus-pretreated MSCs improved retinal vessel formation, retinal function, and uveitis. In high glucose conditions, tacrolimus pretreatment reduced protein and mRNA expression levels of DRP1 and inhibited mitochondrial fission. In conclusion, we demonstrated that high glucose-induced O-GlcNAcylation activates NFATC1 signaling, which is important for DRP1-mediated mitochondrial fission and mitochondrial apoptosis. Finally, we proposed NFATC1 suppression by tacrolimus as a promising therapeutic strategy to improve the therapeutic efficacy of UCB-MSC transplantation for DR treatment.

Mitochondrial Fission as a Therapeutic Target for Metabolic Diseases: Insights into Antioxidant Strategies

Mitochondrial fission is a crucial process in maintaining metabolic homeostasis in normal physiology and under conditions of stress. Its dysregulation has been associated with several metabolic diseases, including, but not limited to, obesity, type 2 diabetes (T2DM), and cardiovascular diseases. Reactive oxygen species (ROS) serve a vital role in the genesis of these conditions, and mitochondria are both the main sites of ROS production and the primary targets of ROS. In this review, we explore the physiological and pathological roles of mitochondrial fission, its regulation by dynamin-related protein 1 (Drp1), and the interplay between ROS and mitochondria in health and metabolic diseases. We also discuss the potential therapeutic strategies of targeting mitochondrial fission through antioxidant treatments for ROS-induced conditions, including the effects of lifestyle interventions, dietary supplements, and chemicals, such as mitochondrial division inhibitor-1 (Mdivi-1) and other mitochondrial fission inhibitors, as well as certain commonly used drugs for metabolic diseases. This review highlights the importance of understanding the role of mitochondrial fission in health and metabolic diseases, and the potential of targeting mitochondrial fission as a therapeutic approach to protecting against these conditions.

Investigating the Link between Ketogenic Diet, NAFLD, Mitochondria, and Oxidative Stress: A Narrative Review

Together with the global rise in obesity and metabolic syndrome, the prevalence of individuals who suffer from nonalcoholic fatty liver disease (NAFLD) has risen dramatically. NAFLD is currently the most common chronic liver disease and includes a continuum of liver disorders from initial fat accumulation to nonalcoholic steatohepatitis (NASH), considered the more severe forms, which can evolve in, cirrhosis, and hepatocellular carcinoma. Common features of NAFLD includes altered lipid metabolism mainly linked to mitochondrial dysfunction, which, as a vicious cycle, aggravates oxidative stress and promotes inflammation and, as a consequence, the progressive death of hepatocytes and the severe form of NAFLD. A ketogenic diet (KD), i.e., a diet very low in carbohydrates (<30 g/die) that induces "physiological ketosis", has been demonstrated to alleviate oxidative stress and restore mitochondrial function. Based on this, the aim of the present review is to analyze the body of evidence regarding the potential therapeutic role of KD in NAFLD, focusing on the interplay between mitochondria and the liver, the effects of ketosis on oxidative stress pathways, and the impact of KD on liver and mitochondrial function.

MitoTEMPOL modulates mitophagy and histopathology of Wistar rat liver after streptozotocin injection

OBJECTIVES

This study aims to explore the effect of mitoTEMPOL on histopathology, lipid droplet, and mitophagy gene expression of Wistar rat's liver after injection of streptozotocin (STZ).

MATERIALS AND METHODS

Twenty male Wistar rats were divided into 4 groups: Control (n=5); 100 mg/kg BW/day mitoTEMPOL orally (n=5); 50 mg/kg BW STZ intraperitoneal injection (n=5); and mitoTEMPOL+STZ (n=5). STZ was given a single dose, while mitoTEMPOL was given for 5 weeks after 1 week of STZ injection. Histopathological appearance, lipid droplets, mitophagy, and autophagy gene expression were examined after the mitoTEMPOL treatment.

RESULTS

We found metabolic zone shifting that might be correlated with the liver activity of fatty acid oxidation in the STZ group, a decrease of lipid droplets in mitoTEMPOL and mitoTEMPOL + STZ compared with Control and STZ groups were found in this study. We also found significant changes in PINK1, Parkin, BNIP3, Mfn1, and LC3 gene expression, but no difference in Opa1, Fis1, Drp1, and p62 gene expression, suggesting a change of mitochondrial fusion rather than mitochondrial fission correlated with mitophagy.

CONCLUSION

All this concluded that mitoTEMPOL could act as a modulator of mitophagy and metabolic function of the liver, thus amplifying its crucial role in preventing mitochondrial damage in the liver in the early onset of diabetes mellitus.

Ginger Root Extract Improves GI Health in Diabetic Rats by Improving Intestinal Integrity and Mitochondrial Function

Background Emerging research suggests hyperglycemia can increase intestinal permeability. Ginger and its bioactive compounds have been reported to benefit diabetic animals due to their anti-inflammatory and antioxidant properties. In this study, we revealed the beneficial effect of gingerol-enriched ginger (GEG) on intestinal health (i.e., barrier function, mitochondrial function, and anti-inflammation) in diabetic rats. Methods Thirty-three male Sprague Dawley rats were assigned to three groups: low-fat diet (control group), high-fat-diet (HFD) + streptozotocin (single low dose 35 mg/kg body weight (BW) after 2 weeks of HFD feeding) (DM group), and HFD + streptozotocin + 0.75% GEG in diet (GEG group) for 42 days. Glucose tolerance tests (GTT) and insulin tolerance tests (ITT) were conducted at baseline and prior to sample collection. Total pancreatic insulin content was determined by ELISA. Total RNA of intestinal tissues was extracted for mRNA expression using qRT-PCR. Results Compared to the DM group, the GEG group had improved glucose tolerance and increased pancreatic insulin content. Compared to those without GEG (DM group), GEG supplementation (GEG group) increased the gene expression of tight junction (Claudin-3) and antioxidant capacity (SOD1), while it decreased the gene expression for mitochondrial fusion (MFN1), fission (FIS1), biogenesis (PGC-1α, TFAM), mitophagy (LC3B, P62, PINK1), and inflammation (NF-κB). Conclusions Ginger root extract improved glucose homeostasis in diabetic rats, in part, via improving intestinal integrity and mitochondrial dysfunction of GI health.

The Role of Mitochondrial Quality Control in Anthracycline-Induced Cardiotoxicity: From Bench to Bedside

Cardiotoxicity is the major side effect of anthracyclines (doxorubicin, daunorubicin, epirubicin, and idarubicin), though being the most commonly used chemotherapy drugs and the mainstay of therapy in solid and hematological neoplasms. Advances in the field of cardio-oncology have expanded our understanding of the molecular mechanisms underlying anthracycline-induced cardiotoxicity (AIC). AIC has a complex pathogenesis that includes a variety of aspects such as oxidative stress, autophagy, and inflammation. Emerging evidence has strongly suggested that the loss of mitochondrial quality control (MQC) plays an important role in the progression of AIC. Mitochondria are vital organelles in the cardiomyocytes that serve as the key regulators of reactive oxygen species (ROS) production, energy metabolism, cell death, and calcium buffering. However, as mitochondria are susceptible to damage, the MQC system, including mitochondrial dynamics (fusion/fission), mitophagy, mitochondrial biogenesis, and mitochondrial protein quality control, appears to be crucial in maintaining mitochondrial homeostasis. In this review, we summarize current evidence on the role of MQC in the pathogenesis of AIC and highlight the therapeutic potential of restoring the cardiomyocyte MQC system in the prevention and intervention of AIC.

In Vitro Effect of Mitochondria-Targeted Triphenylphosphonium-Based Compounds (Honokiol, Lonidamine, and Atovaquone) on the Platelet Function and Cytotoxic Activity

Introduction: Obtaining triphenylphosphonium salts derived from anticancer compounds to inhibit mitochondrial metabolism is of major interest due to their pivotal role in reactive oxygen species (ROS) production, calcium homeostasis, apoptosis, and cell proliferation. However, the use of this type of antitumor compound presents a risk of bleeding since the platelet activation is especially dependent on the mitochondrial function. In this study, we evaluated the in vitro effect of three triphenylphosphonium-based compounds, honokiol (HNK), lonidamine (LDN), and atovaquone (ATO), on the platelet function linked to the triphenylphosphonium cation by a lineal 10-carbon alkyl chain and also the decyltriphenylphosphonium salt (decylphos).

Methods: Platelets obtained by phlebotomy from healthy donors were exposed in vitro to different concentrations (0.1–10 μM) of the three compounds; cellular viability, exposure of phosphatidylserine, the mitochondrial membrane potential (∆Ψm), intracellular calcium release, and intracellular ROS generation were measured. Platelet activation and aggregation were induced by agonists (adenosine diphosphate, thrombin receptor-activating peptide-6, convulxin, or phorbol-12-myristate-13-acetate) and were evaluated by flow cytometry and light transmission, respectively.

Results: The three compounds showed a slight cytotoxic effect from 1 μM, and this was concomitant with a decrease in ∆Ψm and intracellular calcium increase. Only ATO produced a modest but significant increase in intra-platelet ROS. Also, the three compounds increased the exposure to phosphatidylserine in platelets expressed in platelets positive for annexin V. None of the compounds had an inhibitory effect on the aggregation or activation markers of platelets stimulated with three different agonists. Similar results were obtained with decylphos.

Conclusion: Triphenylphosphonium derivatives showed slight platelet toxicity below 1 μM, probably associated with their effect on ∆Ψm and exposure to phosphatidylserine, but no significant effect on platelet activation and aggregation, making them an antitumoral alternative with a low risk of bleeding. However, future assays on animal models and human trials are required to evaluate if their effects with a low risk for hemostasis are replicated in vivo.

Mitochondrial Fission and Fusion in Tumor Progression to Metastasis

Mitochondria are highly dynamic organelles which can change their shape, via processes termed fission and fusion, in order to adapt to different environmental and developmental contexts. Due to the importance of these processes in maintaining a physiologically healthy pool of mitochondria, aberrant cycles of fission/fusion are often seen in pathological contexts. In this review we will discuss how dysregulated fission and fusion promote tumor progression. We focus on the molecular mechanisms involved in fission and fusion, discussing how altered mitochondrial fission and fusion change tumor cell growth, metabolism, motility, and invasion and, finally how changes to these tumor-cell intrinsic phenotypes directly and indirectly impact tumor progression to metastasis. Although this is an emerging field of investigation, the current consensus is that mitochondrial fission positively influences metastatic potential in a broad variety of tumor types. As mitochondria are now being investigated as vulnerable targets in a variety of cancer types, we underscore the importance of their dynamic nature in potentiating tumor progression.

The Imbalance of Mitochondrial Fusion/Fission Drives High-Glucose-Induced Vascular Injury

Emerging evidence shows that mitochondria fusion/fission imbalance is related to the occurrence of hyperglycemia-induced vascular injury. To study the temporal dynamics of mitochondrial fusion and fission, we observed the alteration of mitochondrial fusion/fission proteins in a set of different high-glucose exposure durations, especially in the early stage of hyperglycemia. The in vitro results show that persistent cellular apoptosis and endothelial dysfunction can be induced rapidly within 12 hours’ high-glucose pre-incubation. Our results show that mitochondria maintain normal morphology and function within 4 hours’ high-glucose pre-incubation; with the extended high-glucose exposure, there is a transition to progressive fragmentation; once severe mitochondria fusion/fission imbalance occurs, persistent cellular apoptosis will develop. In vitro and in vivo results consistently suggest that mitochondrial fusion/fission homeostasis alterations trigger high-glucose-induced vascular injury. As the guardian of mitochondria, AMPK is suppressed in response to hyperglycemia, resulting in imbalanced mitochondrial fusion/fission, which can be reversed by AMPK stimulation. Our results suggest that mitochondrial fusion/fission’s staged homeostasis may be a predictive factor of diabetic cardiovascular complications.

Pardaxin Activates Excessive Mitophagy and Mitochondria-Mediated Apoptosis in Human Ovarian Cancer by Inducing Reactive Oxygen Species

Most ovarian cancer (OC) patients are diagnosed with stage III or higher disease, resulting in a poor prognosis. Currently, paclitaxel combined with carboplatin shows the best treatment outcome for OC. However, no effective drug is available for patients that do not respond to treatment; thus, new drugs for OC are needed. We evaluated the antimicrobial peptide, pardaxin, in PA-1 and SKOV3 cells. Pardaxin induced apoptosis as determined by MTT and TUNEL assays, as well as activation of caspases-9/3, Bid, t-Bid, and Bax, whereas Bcl-2 was downregulated. The IC₅₀ values for pardaxin were 4.6-3.0 μM at 24 and 48 h. Mitochondrial and intracellular reactive oxygen species (ROS) were overproduced and associated with disrupted mitochondrial membrane potential and respiratory capacity. Additionally, the mitochondrial network was fragmented with downregulated fusogenic proteins, MFN1/2 and L-/S-OPA1, and upregulated fission-related proteins, DRP1 and FIS1. Autophagy was also activated as evidenced by increased expression of autophagosome formation-related proteins, Beclin, p62, and LC3. Enhanced mitochondrial fragmentation and autophagy indicate that mitophagy was activated. ROS-induced cytotoxicity was reversed by the addition of N-acetylcysteine, confirming ROS overproduction as a contributor. Taken together, pardaxin demonstrated promising anticancer activity in OC cells, which warrants further preclinical development of this compound.

Nicotine Causes Mitochondrial Dynamics Imbalance and Apoptosis Through ROS Mediated Mitophagy Impairment in Cardiomyocytes

Nicotine contained in traditional cigarettes, hookahs, and e-cigarettes is an important risk factor for cardiovascular disease. Our previous study showed that macroautophagic flux impairment occurred under nicotine stimulation. However, whether nicotine influences mitochondrial dynamics in neonatal rat ventricular myocytes (NRVMs) is unclear. The purpose of this study was to explore the effects and potential mechanism of nicotine on mitophagy, mitochondrial dynamics, apoptosis, and the relationship between these processes in NRVMs. Our results showed that nicotine exposure increased mitochondria-derived superoxide production, decreased mitochondrial membrane potential, and impaired PINK1/Parkin-mediated mitophagic flux in NRVMs. Interestingly, nicotine significantly promoted dynamin-related protein 1 (Drp1)-mediated mitochondrial fission and suppressed mitofusin (MFN)-mediated fusion, which was also observed in the bafilomycin A1-treated group. These results suggest that mitophagic flux impairment may contribute to Drp-1-mediated mitochondrial fission. Finally, nicotine caused excessive mitochondrial fission and contributed to apoptosis, which could be alleviated by mdivi-1, an inhibitor of Drp1. In addition to CTSB, as we previously reported, the enzyme activity of cathepsin L (CTSL) was also decreased in lysosomes after stimulation with nicotine, which may be the main cause of the hindered mitophagic flux induced by nicotine in NRVMs. Pretreatment with Torin 1, which is an inhibitor of mTOR, activated CTSL and ameliorated nicotine-induced mTOR activation and mitophagy impairment, decreased mitochondria-derived superoxide production, and blunted mitochondrial fission and apoptosis. Pretreatment with the ROS scavenger N-acetyl-cysteine (NAC) or inhibitors of p38 and JNK, which could also alleviate mitophagy impairment, exhibited similar effects as Torin1 on mitochondria. Taken together, our study demonstrated that nicotine treatment may lead to an increase in Drp1-mediated mitochondrial fission by blocking mitophagic flux by weakening the enzyme activity of CTSL and activating the ROS/p38/JNK signaling pathway. Excessive mitochondrial fission induced by nicotine ultimately leads to apoptosis. Torin1 restored the decreased CTSL enzyme activity by removing excessive ROS and alleviated the effects of nicotine on mitophagic flux, mitochondrial dynamics, and apoptosis. These results may provide new evidence on the relationship between mitophagic flux and mitochondrial dynamics and new perspectives on nicotine’s effects on mitochondrial dynamics in cardiomyocytes.

The mechanisms of mitochondrial dysfunction and glucose intake decrease induced by Microcystin-LR in ovarian granulosa cells

Microcystin-LR (MC-LR) is a cyclic heptapeptide; it is an intracellular toxin released by cyanobacteria that exhibits strong reproductive toxicity. Previous studies have demonstrated that MC-LR induces oxidative stress in granulosa cells by damaging the mitochondria, which eventually leads to follicle atresia and female subfertility. In the present study, granulosa cells were exposed to 0, 0.01, 0.1 and 1 μM MC-LR. After 24 h, we observed changes in mitochondrial cristae morphology and dynamics by analyzing the results of mitochondrial transmission electron microscopy and detecting the expression of DRP1. We also evaluated glucose intake using biochemical assays and expression of glucose transport related proteins. MC-LR exposure resulted in mitochondrial fragmentation and glucose intake decrease in granulosa cells, as shown by increasing mitochondrial fission via dynamin-related protein 1 (DRP1) upregulation and decreasing glucose transporter 1 and 4 (GLUT1 and GLUT4). Furthermore, the expression levels of forkhead box protein M1 (FOXM1) significantly increased due to the overproduction of reactive oxygen species (ROS) after MC-LR exposure. Our results proved that MC-LR exposure causes mitochondrial fragmentation and glucose intake decrease in granulosa cells, which provides new insights to study the molecular mechanism of female reproductive toxicity induced by MC-LR.

Mitochondrial Dysfunction and Mitophagy Closely Cooperate in Neurological Deficits Associated with Alzheimer's Disease and Type 2 Diabetes

Alzheimer's disease (AD) and type 2 diabetes (T2D) are known to be correlated in terms of their epidemiology, histopathology, and molecular and biochemical characteristics. The prevalence of T2D leading to AD is approximately 50-70%. Moreover, AD is often considered type III diabetes because of the common risk factors. Uncontrolled T2D may affect the brain, leading to memory and learning deficits in patients. In addition, metabolic disorders and impaired oxidative phosphorylation in AD and T2D patients suggest that mitochondrial dysfunction is involved in both diseases. The dysregulation of pathways involved in maintaining mitochondrial dynamics, biogenesis and mitophagy are responsible for exacerbating the impact of hyperglycemia on the brain and neurodegeneration under T2D conditions. The first section of this review describes the recent views on mitochondrial dysfunction that connect these two disease conditions, as the pathways are observed to overlap. The second section of the review highlights the importance of different mitochondrial miRNAs (mitomiRs) involved in the regulation of mitochondrial dynamics and their association with the pathogenesis of T2D and AD. Therefore, targeting mitochondrial biogenesis and mitophagy pathways, along with the use of mitomiRs, could be a potent therapeutic strategy for T2D-related AD. The last section of the review highlights the known drugs targeting mitochondrial function for the treatment of both disease conditions.

Mitochondrial Fission Protein 1: Emerging Roles in Organellar Form and Function in Health and Disease

Mitochondrial fission protein 1 (Fis1) was identified in yeast as being essential for mitochondrial division or fission and subsequently determined to mediate human mitochondrial and peroxisomal fission. Yet, its exact functions in humans, especially in regard to mitochondrial fission, remains an enigma as genetic deletion of Fis1 elongates mitochondria in some cell types, but not others. Fis1 has also been identified as an important component of apoptotic and mitophagic pathways suggesting the protein may have multiple, essential roles. This review presents current perspectives on the emerging functions of Fis1 and their implications in human health and diseases, with an emphasis on Fis1's role in both endocrine and neurological disorders.

Quality Matters? The Involvement of Mitochondrial Quality Control in Cardiovascular Disease

Cardiovascular diseases are one of the leading causes of death and global health problems worldwide. Multiple factors are known to affect the cardiovascular system from lifestyles, genes, underlying comorbidities, and age. Requiring high workload, metabolism of the heart is largely dependent on continuous power supply via mitochondria through effective oxidative respiration. Mitochondria not only serve as cellular power plants, but are also involved in many critical cellular processes, including the generation of intracellular reactive oxygen species (ROS) and regulating cellular survival. To cope with environmental stress, mitochondrial function has been suggested to be essential during bioenergetics adaptation resulting in cardiac pathological remodeling. Thus, mitochondrial dysfunction has been advocated in various aspects of cardiovascular pathology including the response to ischemia/reperfusion (I/R) injury, hypertension (HTN), and cardiovascular complications related to type 2 diabetes mellitus (DM). Therefore, mitochondrial homeostasis through mitochondrial dynamics and quality control is pivotal in the maintenance of cardiac health. Impairment of the segregation of damaged components and degradation of unhealthy mitochondria through autophagic mechanisms may play a crucial role in the pathogenesis of various cardiac disorders. This article provides in-depth understanding of the current literature regarding mitochondrial remodeling and dynamics in cardiovascular diseases.

Mst1 Knockout Alleviates Mitochondrial Fission and Mitigates Left Ventricular Remodeling in the Development of Diabetic Cardiomyopathy

The disruption of mitochondrial dynamics is responsible for the development of diabetic cardiomyopathy (DCM). However, the mechanisms that regulate the balance of mitochondrial fission and fusion are not well-understood. Wild-type, Mst1 transgenic and Mst1 knockout mice were induced with experimental diabetes by streptozotocin injection. In addition, primary neonatal cardiomyocytes were isolated and cultured to simulate diabetes to explore the mechanisms. Echocardiograms and hemodynamic measurements revealed that Mst1 knockout alleviated left ventricular remodeling and cardiac dysfunction in diabetic mice. Mst1 knockdown significantly decreased the number of TUNEL-positive cardiomyocytes subjected to high-glucose (HG) medium culture. Immunofluorescence study indicated that Mst1 overexpression enhanced, while Mst1 knockdown mitigated mitochondrial fission in DCM. Mst1 participated in the regulation of mitochondrial fission by upregulating the expression of Drp1, activating Drp1^S616 phosphorylation and Drp1^S637 dephosphorylation, as well as promoting Drp1 recruitment to the mitochondria. Furthermore, Drp1 knockdown abolished the effects of Mst1 on mitochondrial fission, mitochondrial membrane potential and mitochondrial dysfunction in cardiomyocytes subjected to HG treatment. These results indicated that Mst1 knockout inhibits mitochondrial fission and alleviates left ventricular remodeling thus prevents the development of DCM.

Persulfide Signaling in Stress-Initiated Calmodulin Kinase Response

Significance: Calcium ion (Ca²⁺)/calmodulin (CaM)-dependent protein kinases (CaMKs) are activated by phosphorylation of a crucial threonine residue either by itself (CaMKII) or by upstream kinases, CaMK kinases (CaMKKs) (CaMKI and CaMKIV). CaMKs, present in most mammalian tissues, can phosphorylate many downstream targets, thereby regulating numerous cellular functions. Recent Advances: Aside from canonical post-translational modifications, cysteine-based redox switches in CaMKs affect their enzyme activities. In addition to reactive oxygen species (ROS) and reactive nitrogen species (RNS), reactive sulfur species (RSS) are also recognized as key signaling molecules, regulating protein function through polysulfidation, formation of polysulfides [-S-(S)_n-H] on their reactive cysteine residues. To comprehend the biological significance of RSS signaling-related CaMK regulation, here we introduce a novel concept defining CaMKs as RSS targets in stress responses. The stress responses include an irreversible electrophile attack for CaMKI, inflammation for CaMKII, and endoplasmic reticulum stress for CaMKIV. Critical Issues: Development of various human diseases is associated with increased ROS, RNS, and RSS generation. Therefore, depending on specific pathophysiology, RSS could have very particular effects on CaMK functions. Future Directions: How multiple sources and mutual reactions of ROS, RNS, and RSS are coordinated is obscure. Elucidating the mechanisms through applications of enzymology, chemical biology, and mass spectrometry enables to uncover the complexities of redox regulation of CaMK cascades.

Oxidative Stress Orchestrates MAPK and Nitric-Oxide Synthase Signal

Reactive oxygen species (ROS) are not only harmful to cell survival but also essential to cell signaling through cysteine-based redox switches. In fact, ROS triggers the potential activation of mitogen-activated protein kinases (MAPKs). The 90 kDa ribosomal S6 kinase 1 (RSK1), one of the downstream mediators of the MAPK pathway, is implicated in various cellular processes through phosphorylating different substrates. As such, RSK1 associates with and phosphorylates neuronal nitric oxide (NO) synthase (nNOS) at Ser847, leading to a decrease in NO generation. In addition, the RSK1 activity is sensitive to inhibition by reversible cysteine-based redox modification of its Cys223 during oxidative stress. Aside from oxidative stress, nitrosative stress also contributes to cysteine-based redox modification. Thus, the protein kinases such as Ca²⁺/calmodulin (CaM)-dependent protein kinase I (CaMKI) and II (CaMKII) that phosphorylate nNOS could be potentially regulated by cysteine-based redox modification. In this review, we focus on the role of post-translational modifications in regulating nNOS and nNOS-phosphorylating protein kinases and communication among themselves.

Estrogen Regulation of mTOR Signaling and Mitochondrial Function in Invasive Lobular Carcinoma Cell Lines Requires WNT4

Simple Summary

Invasive lobular carcinoma (ILC) is a common but understudied breast cancer subtype. ILC is presumed to be a low-risk disease in part because nearly all ILCs contain the estrogen receptor (ER). However, we previously showed that ER has unique functions in ILC cells, including driving expression of the Wnt ligand WNT4. WNT4 signaling is required for ILC cell proliferation and survival, but the mechanisms and targets of WNT4 signaling in ILC is unknown. We found that WNT4 regulates mTOR signaling via S6 kinase, and controls levels of MCL-1 protein, ultimately regulating mitochondrial function and cellular metabolism. These findings offer new insight into a novel Wnt signaling pathway and identify new targets to inhibit WNT4 signaling as potential treatments against ILC cells.

Abstract

Invasive lobular carcinoma of the breast (ILC) is strongly estrogen-driven and represents a unique context for estrogen receptor (ER) signaling. In ILC, ER controls the expression of the Wnt ligand WNT4, which is critical for endocrine response and anti-estrogen resistance. However, signaling mediated by WNT4 is cell type- and tissue-specific, and has not been explored in ILC. We utilized reverse phase protein array (RPPA) to characterize ER and WNT4-driven signaling in ILC cells and identified that WNT4 mediates downstream mTOR signaling via phosphorylation of S6 Kinase. Additionally, ER and WNT4 control levels of MCL-1, which is associated with regulation of mitochondrial function. In this context, WNT4 knockdown led to decreased ATP production and increased mitochondrial fragmentation. WNT4 regulation of both mTOR signaling and MCL-1 were also observed in anti-estrogen resistant models of ILC. We identified that high WNT4 expression is associated with similar mTOR pathway activation in ILC and serous ovarian cancer tumors, suggesting that WNT4 signaling is active in multiple tumor types. The identified downstream pathways offer insight into WNT4 signaling and represent potential targets to overcome anti-estrogen resistance for patients with ILC.

The antimicrobial peptide tilapia piscidin 3 induces mitochondria-modulated intrinsic apoptosis of osteosarcoma cells

Osteosarcoma (OS) is the most common solid tumor of the bone that most often affects adolescents. The introduction of chemotherapy for the treatment of OS has largely improved the survival rates of patients with localized tumors. However, the 5-year survival rate of OS patients with relapsed or metastatic disease is only 10 to 20%. In this study, the antimicrobial peptide tilapia piscidin 3 (TP3), isolated from Nile tilapia (Oreochromis niloticus), was treated to OS MG63 cells. Our findings showed that TP3 concentration as low as 1 μM induced significant inhibition of cell viability and increased DNA fragmentation, as determined by the MTT and TUNEL assays, respectively. The protein expression levels of cleaved caspases 3/9 were increased. An in situ live-cell time-lapse video and cell tomographic microscopy images showed cellular blebbing, shrinkage, nuclear fragmentation, and chromatin condensation, with the formation of beaded apoptopodia. Moreover, there were significant increase in the production of TP3-induced mitochondrial and cellular reactive oxygen species (ROS), as well as down-regulated mitochondrial oxygen consumption and extracellular acidification rates. Additionally, TP3 enhanced mitochondrial fission, whereas fusion was attenuated. Furthermore, after administration of the mitochondria targeted antioxidant mitoTempo, TP3-induced ROS oxidant levels and alterations in cleaved caspases 3/9 expression were rescued. TP3 promoted mitochondria-modulated intrinsic apoptosis through the induction of ROS production, activation of caspases 3/9, and the down-regulation of mitochondrial oxygen consumption and extracellular acidification rates, suggesting that TP3 has potential as an innovative alternative for OS treatment.

HmtVar: a new resource for human mitochondrial variations and pathogenicity data

Interest in human mitochondrial genetic data is constantly increasing among both clinicians and researchers, due to the involvement of mitochondrial DNA (mtDNA) in a number of physiological and pathological processes. Thanks to new sequencing technologies and modern databases, the large amount of information on mtDNA variability may be exploited to gain insights into the relationship between mtDNA variants, phenotypes and diseases. To facilitate this process, we have developed the HmtVar resource, a variant-focused database that allows the exploration of a dataset of over 40 000 human mitochondrial variants. Mitochondrial variation data, initially gathered from the HmtDB platform, are integrated with in-house pathogenicity assessments based on various evaluation criteria and with a set of additional annotations from third-party resources. The result is a comprehensive collection of information of crucial importance for human mitochondrial variation studies and investigation of common and rare diseases in which the mitochondrion may be involved. HmtVar is accessible at https://www.hmtvar.uniba.it and data may be retrieved using either a web interface through the Query page or a state-of-the-art API for programmatic access.

Mechanisms of mitochondrial DNA escape and its relationship with different metabolic diseases

It is well-known that mitochondrial DNA (mtDNA) can escape to intracellular or extracellular compartments under different stress conditions, yet understanding their escape mechanisms remains a challenge. Although Bax/Bak pores and VDAC oligomers are the strongest possibilities, other mechanisms may be involved. For example, mitochondria permeability transition, altered mitophagy, and mitochondrial dynamics are associated with intracellular mtDNA escape, while extracellular traps and extracellular vesicles can participate in extracellular mtDNA escape. The evidence suggests that mtDNA escape is a complex event with more than one mechanism involved. In addition, once the mtDNA is outside the mitochondria, the effects can be complex. Different danger signal sensors recognize the mtDNA as a damage-associated molecular pattern, triggering an innate immune inflammatory response that can be observed in multiple metabolic diseases characterized by chronic inflammation, including autoimmune diseases, diabetes, cancer, and cardiovascular disorders. For these reasons, we will review the most recent evidence regarding mtDNA escape mechanisms and their impact on different metabolic diseases.

Conditional knockout of pyruvate dehydrogenase in mouse pancreatic β‑cells causes morphological and functional changes

Diabetes mellitus is a metabolic disorder predominantly caused by the dysfunction of pancreatic β-cells. This dysfunction is partly caused by the dysregulation of pyruvate dehydrogenase (PDH), which acts as an important mediator of pyruvate oxidation after glycolysis and fuels the tricarboxylic acid cycle. Previous studies have reported decreased PDH expression in rodent models and humans with type 2 diabetes mellitus (T2DM), suggesting that PDH may play an important role in the development of T2DM. However, the mechanism by which PDH affects insulin secretion and β-cell development is poorly understood. Using immunofluorescence staining, the present study found that the expression of pyruvate dehydrogenase E1-α subunit (PDHA1; encoded by the PDHA1 gene) in the islets of type 2 diabetic mice (db/db mice) was lower than in wild-type mice, which indicated the possible association between PDHA1and diabetes. To further understand this mechanism, an inducible, islet-specific PDHA1 knockout mouse (βKO) model was established. The phenotype was authenticated, and the blood glucose levels and islet function between the βKO and control mice were compared. Though no changes were found in food intake, development status, fasting blood glucose or weight between the groups, the level of insulin secretion at 30 min after glucose injection in the βKO group was significantly lower compared with the control group. Furthermore, the performed of the βKO mice on the intraperitoneal glucose tolerance test was visibly impaired when compared with the control mice. Pancreatic tissues were collected for hematoxylin and eosin staining, immunohistochemical and confocal laser-scanning microscopy analysis. Examination of the islets from the βKO mouse model indicated that abolishing the expression of PDH caused a compensatory islet enlargement and impaired insulin secretion.

Two-stage Bayesian GWAS of 9576 individuals identifies SNP regions that are targeted by miRNAs inversely expressed in Alzheimer's and cancer

INTRODUCTION

We compared genetic variants between Alzheimer's disease (AD) and two age-related cancers-breast and prostate -to identify single-nucleotide polymorphisms (SNPs) that are associated with inverse comorbidity of AD and cancer.

METHODS

Bayesian multinomial regression was used to compare sex-stratified cases (AD and cancer) against controls in a two-stage study. A ±500 KB region around each replicated hit was imputed and analyzed after merging individuals from the two stages. The microRNAs (miRNAs) that target the genes involving these SNPs were analyzed for miRNA family enrichment.

RESULTS

We identified 137 variants with inverse odds ratios for AD and cancer located on chromosomes 19, 4, and 5. The mapped miRNAs within the network were enriched for miR-17 and miR-515 families.

DISCUSSION

The identified SNPs were rs4298154 (intergenic), within TOMM40/APOE/APOC1, MARK4, CLPTM1, and near the VDAC1/FSTL4 locus. The miRNAs identified in our network have been previously reported to have inverse expression in AD and cancer.

Pro-renin receptor suppresses mitochondrial biogenesis and function via AMPK/SIRT-1/ PGC-1α pathway in diabetic kidney

Abnormal mitochondrial biogenesis and function has been linked to multiple diseases including diabetes. Recently, we demonstrated the role of renal (Pro)renin receptor (PRR) in the dysregulation of mitochondria. We hypothesized that PRR contributes to the reduction of mitochondrial biogenesis and function in diabetic kidney via PGC-1α/AMPK/SIRT-1 signaling pathway. In vivo and in vitro studies were conducted in C57BL/6 mouse and mouse renal mesangial cells (mRMCs). Control and streptozotocin-induced diabetic mice were injected with scramble or PRR shRNA and followed for a period of eight weeks. PRR mRNA and protein expression increased by 44% and 39% respectively (P<0.05) in kidneys of diabetic mice, and in mRMCs exposed to high glucose by 43 and 61% respectively compared to their respective controls. These results were accompanied by reduced mRNA and protein expressions of PGC-1α (67% and 75%), nuclear respiratory factors (NRF-1, 48% and 53%), mitochondrial transcriptional factor A (mtTFA, 56% and 40%), mitochondrial DNA copy number by 75% (all, P<0.05), and ATP production by 54%, respectively in diabetic kidneys and in mRMCs exposed to high glucose. Compared to non-diabetic control mice, PRR knockdown in diabetic mice and in mRMCs, not only attenuated the PRR mRNA and protein expression but also normalized mRNA and protein expressions of PGC-1α, NRF-1, mtTFA, mitochondrial DNA copy number, and ATP production. Treatment with AMPK inhibitor, Compound C, or SIRT-1 inhibitor, EX-527, alone, or combined with PRR siRNA caused marked reduction of mRNA expression of PGC-1α, NRF-1 and mtTFA, and ATP production in mRMCs exposed to high glucose. In conclusion, our study demonstrated the contribution of the PRR to the reduction of mitochondrial biogenesis and function in diabetic kidney disease via decreasing AMPK/SIRT-1/ PGC-1α signaling pathway.

Intersections and Clinical Translations of Diabetes Mellitus with Cancer Promotion, Progression and Prognosis

The association between cancer and dysglycemia has been well documented. It is underappreciated, however, that sustained dysglycemia could potentially be a catalyst toward a pro-cancer physiologic milieu and/or increase the burden of cancer. Hyperglycemia, hyperinsulinemia and energy metabolism at large impact a cascade of growth pathways, epi/genetic modifications, and mitochondrial changes that could feasibly link to tumor processes. Oxidative stress is a recurring motif in cell dysfunction: in diabetes, oxidative stress and reactive oxygen species (ROS) feature prominently in the damage and demise of pancreatic beta cells, as well as cell damage contributing to diabetes-related complications. Oxidative stress may be one intersection at which metabolic and oncogenic processes cross paths with deleterious results in the development of precancer, cancer, and cancer progression. This would augur for tight glucose control. Regrettably, some medical societies have recently relaxed hemoglobin A1c targets. A framework for the hyperglycemic state is presented that helps account and translate the full scope of effects of dysglycemia to ultimately improve clinical best practices.

Mitochondrial Structural Changes in the Pathogenesis of Diabetic Retinopathy

At the core of proper mitochondrial functionality is the maintenance of its structure and morphology. Physical changes in mitochondrial structure alter metabolic pathways inside mitochondria, affect mitochondrial turnover, disturb mitochondrial dynamics, and promote mitochondrial fragmentation, ultimately triggering apoptosis. In high glucose condition, increased mitochondrial fragmentation contributes to apoptotic death in retinal vascular and Müller cells. Although alterations in mitochondrial morphology have been detected in several diabetic tissues, it remains to be established in the vascular cells of the diabetic retina. From a mechanistic standpoint, our current work supports the notion that increased expression of fission genes and decreased expression of fusion genes are involved in promoting excessive mitochondrial fragmentation. While mechanistic insights are only beginning to reveal how high glucose alters mitochondrial morphology, the consequences are clearly seen as release of cytochrome c from fragmented mitochondria triggers apoptosis. Current findings raise the prospect of targeting excessive mitochondrial fragmentation as a potential therapeutic strategy for treatment of diabetic retinopathy. While biochemical and epigenetic changes have been reported to be associated with mitochondrial dysfunction, this review focuses on alterations in mitochondrial morphology, and their impact on mitochondrial function and pathogenesis of diabetic retinopathy.

Mitochondrial ROS-induced lysosomal dysfunction impairs autophagic flux and contributes to M1 macrophage polarization in a diabetic condition

Macrophage polarization toward the M1 phenotype and its subsequent inflammatory response have been implicated in the progression of diabetic complications. Despite adverse consequences of autophagy impairment on macrophage inflammation, the regulation of macrophage autophagy under hyperglycemic conditions is incompletely understood. Here, we report that the autophagy-lysosome system and mitochondrial function are impaired in streptozotocin (STZ)-induced diabetic mice and high glucose (HG)-stimulated RAW 264.7 cells. Mitochondrial dysfunction promotes reactive oxygen species (ROS) production and blocks autophagic flux by impairing lysosome function in macrophages under hyperglycemic conditions. Conversely, inhibition of mitochondrial ROS by Mito-TEMPO prevents HG-induced M1 macrophage polarization, and its effect is offset by blocking autophagic flux. The role of mitochondrial ROS in lysosome dysfunction and M1 macrophage polarization is also demonstrated in mitochondrial complex I defective RAW 264.7 cells induced by silencing NADH:ubiquinone oxidoreductase subunit-S4 (Ndufs4). These findings prove that mitochondrial ROS plays a key role in promoting macrophage polarization to inflammatory phenotype by impairing autophagy-lysosome system, which might provide clue to a novel treatment for diabetic complications.

Mitochondrial dynamics and their potential as a therapeutic target

Mitochondrial dynamics shape the mitochondrial network and contribute to mitochondrial function and quality control. Mitochondrial fusion and division are integrated into diverse cellular functions and respond to changes in cell physiology. Imbalanced mitochondrial dynamics are associated with a range of diseases that are broadly characterized by impaired mitochondrial function and increased cell death. In various disease models, modulating mitochondrial fusion and division with either small molecules or genetic approaches has improved function. Although additional mechanistic understanding of mitochondrial fusion and division will be critical to inform further therapeutic approaches, mitochondrial dynamics represent a powerful therapeutic target in a wide range of human diseases.

Targeting acidity in cancer and diabetes

While cancer is commonly described as "a disease of the genes", it is also a disease of metabolism. Indeed, carcinogenesis and malignancy are highly associated with metabolic re-programming, and there is clinical evidence that interrupting a cancer's metabolic program can improve patients' outcomes. Notably, many of the metabolic adaptations observed in cancer are similar to the same perturbations observed in diabetic patients. For example, metformin is commonly used to reduce hyperglycemia in diabetic patients, and has been demonstrated to reduce cancer incidence. Treatment with PI3K inhibitors can induce hyperinsulinemia, which can blunt therapeutic efficacy if unchecked. While commonalities between metabolism in cancer and diabetes have been extensively reviewed, here we examine a less explored and emergent convergence between diabetic and cancer metabolism: the generation of lactic acid and subsequent acidification of the surrounding microenvironment. Extracellular lactic acidosis is integral in disease manifestation and is a negative prognostic in both disease states. In tumors, this results in important sequela for cancer progression including increased invasion and metastasis, as well as inhibition of immune surveillance. In diabetes, acidosis impacts the ability of insulin to bind to its receptor, leading to peripheral resistance and an exacerbation of symptoms. Thus, acidosis may be a relevant therapeutic target, and we describe three approaches for targeting: buffers, nanomedicine, and proton pump inhibitors.

The role of dihydrosphingolipids in disease

Dihydrosphingolipids refer to sphingolipids early in the biosynthetic pathway that do not contain a C4-trans-double bond in the sphingoid backbone: 3-ketosphinganine (3-ketoSph), dihydrosphingosine (dhSph), dihydrosphingosine-1-phosphate (dhS1P) and dihydroceramide (dhCer). Recent advances in research related to sphingolipid biochemistry have shed light on the importance of sphingolipids in terms of cellular signalling in health and disease. However, dihydrosphingolipids have received less attention and research is lacking especially in terms of their molecular mechanisms of action. This is despite studies implicating them in the pathophysiology of disease, for example dhCer in predicting type 2 diabetes in obese individuals, dhS1P in cardiovascular diseases and dhSph in hepato-renal toxicity. This review gives a comprehensive summary of research in the last 10-15 years on the dihydrosphingolipids, 3-ketoSph, dhSph, dhS1P and dhCer, and their relevant roles in different diseases. It also highlights gaps in research that could be of future interest.

Mitochondrial dysfunction in type 2 diabetes mellitus: an organ-based analysis

Type 2 diabetes mellitus (T2DM) is a systemic disease characterized by hyperglycemia, hyperlipidemia, and organismic insulin resistance. This pathological shift in both circulating fuel levels and energy substrate utilization by central and peripheral tissues contributes to mitochondrial dysfunction across organ systems. The mitochondrion lies at the intersection of critical cellular pathways such as energy substrate metabolism, reactive oxygen species (ROS) generation, and apoptosis. It is the disequilibrium of these processes in T2DM that results in downstream deficits in vital functions, including hepatocyte metabolism, cardiac output, skeletal muscle contraction, β-cell insulin production, and neuronal health. Although mitochondria are known to be susceptible to a variety of genetic and environmental insults, the accumulation of mitochondrial DNA (mtDNA) mutations and mtDNA copy number depletion is helping to explain the prevalence of mitochondrial-related diseases such as T2DM. Recent work has uncovered novel mitochondrial biology implicated in disease progressions such as mtDNA heteroplasmy, noncoding RNA (ncRNA), epigenetic modification of the mitochondrial genome, and epitranscriptomic regulation of the mtDNA-encoded mitochondrial transcriptome. The goal of this review is to highlight mitochondrial dysfunction observed throughout major organ systems in the context of T2DM and to present new ideas for future research directions based on novel experimental and technological innovations in mitochondrial biology. Finally, the field of mitochondria-targeted therapeutics is discussed, with an emphasis on novel therapeutic strategies to restore mitochondrial homeostasis in the setting of T2DM.

Mitochondrial Stability in Diabetic Retinopathy: Lessons Learned From Epigenetics

Diabetic retinopathy remains the leading cause of acquired blindness in working-age adults. While the cutting-edge research in the field has identified many molecular, functional, and structural abnormalities, the exact molecular mechanism of this devastating disease remains obscure. Diabetic environment drives dysfunction of the power generator of the cell and disturbs the homeostasis of mitochondrial dynamic. Mitochondrial DNA (mtDNA) is damaged, the transcription of mtDNA-encoded genes is impaired, and the electron transport chain is compromised, fueling into a vicious cycle of free radicals. The hyperglycemic milieu also alters the epigenetic machinery, and mtDNA and other genes associated with mitochondrial homeostasis are epigenetically modified, further contributing to the mitochondrial damage. Thus, mitochondria appear to have a significant role in the development of diabetic retinopathy, and unraveling the mechanism responsible for their damage as well as the role of epigenetic modifications in mitochondrial homeostasis should identify novel therapeutic targets. This will have a major impact on inhibiting/halting diabetic retinopathy and preventing the loss of vision.