Idebenone is a cytoprotective insulin sensitizer whose mechanism is Shc inhibition

P46Shc Inhibits Mitochondrial ACAA2 Thiolase, Exacerbating Mitochondrial Injury and Inflammation in Aging Livers

Mitochondrial maladaptation and dysfunction contribute to the progression of metabolic dysfunction-associated steatohepatitis (MASH). The authors recently implicated the induction of Shc in progressive MASH during aging and the cytoplasmic p52Shc isoform in the activation of redox enzyme NOX2. The mitochondrial Shc isoform p46Shc was shown to repress acetyl-coenzyme A acyltransferase 2 (ACAA2) in vitro. ACAA2 is a key enzyme for lipid β-oxidation; however, the metabolic consequences of in vivo p46Shc induction were unknown. The authors generated p46Shc-inducible mice; these and littermate controls were aged and fed chow or fast-food diet (high-fat and high-fructose). p46Shc induction increased liver injury, inflammation, and lipid peroxidation. p46Shc overexpression did not significantly change liver triglycerides. On electron microscopy studies, mitochondria were swollen with aberrant cristae. p46Shc induction reduced mitochondrial oxygen consumption as measured by Oroboros, as well as suppressed the production of β-hydroxybutyrate, the central metabolite of therapeutic ketosis. Mitochondria exhibited increased production of reactive oxidative species. By contrast, the expression of dominant negative p46Shc reduced ACAA2 thiolase activity, improved β-oxidation, and reduced lipid peroxidation and production of reactive oxidative species. In summary, these studies support the concept that p46Shc induction in aging represses ACAA2, resulting in decreased mitochondrial β-oxidation and increased lipid peroxidation. Maintaining β-oxidation and ketogenesis could prevent liver injury, and targeting Shc-related maladaptive responses could be a successful therapeutic strategy in aging/MASH.

GLP-1R mediates idebenone-reduced blood glucose in mice

GLP-1 receptor agonists (GLP-1RAs) are an innovative class of drugs with significant therapeutic value for type 2 diabetes mellitus (T2DM). The GLP-1RAs currently available on the market are biologic macromolecular peptide agents that are expensive to treat and not easy to take orally. Therefore, the development of small molecule GLP-1RAs is becoming one of the most sought-after research targets for hypoglycemic drugs. In this study, we sought to find a potential oral small molecule GLP-1RA and to evaluate its effect on insulin secretion in rat pancreatic β cells and on blood glucose in mice. We downloaded the mRNA expression profiles of GSE102194 and GSE37936 from the Gene Expression Omnibus database. Subsequently, the small molecule compound idebenone was screened through the connectivity map database. The results of molecular docking, biolayer interferometry, and cellular thermal shift assay indicated that idebenone could bind potently with GLP-1R. Furthermore, ibebenone elevated intracellular cAMP levels. The radioimmunoassay data showed that idebenone enhanced glucose-stimulated insulin secretion via agonism of GLP-1R. Moreover, the results of oral glucose tolerance tests in C57BL/6, Glp-1r-/-, and hGlp-1r mice demonstrated that the glucose-lowering effects of idebenone were mediated by GLP-1R and that there were no species differences in the agonistic effect of idebenone on GLP-1R. In summary, idebenone reduces blood glucose in mice by promoting insulin release through agonism of GLP-1R, suggesting that idebenone is probably a potential GLP-1RA, which is expected to provide a new therapeutic strategy for the prevention and treatment of metabolic diseases such as T2DM.

Idebenone ameliorates statin-induced myotoxicity in atherosclerotic ApoE-/- mice by reducing oxidative stress and improving mitochondrial function

Statins are the first line of choice for the treatment for atherosclerosis, but their use can cause myotoxicity, a common side effect that may require dosage reduction or discontinuation. The exact mechanism of statin-induced myotoxicity is unknown. Previous research has demonstrated that the combination of idebenone and statin yielded superior anti-atherosclerotic outcomes. Here, we investigated the mechanism of statin-induced myotoxicity in atherosclerotic ApoE-/- mice and whether idebenone could counteract it. After administering simvastatin to ApoE-/- mice, we observed a reduction in plaque formation as well as a decrease in their exercise capacity. We observed elevated levels of lactic acid and creatine kinase, along with a reduction in the cross-sectional area of muscle fibers, an increased presence of ragged red fibers, heightened mitochondrial crista lysis, impaired mitochondrial complex activity, and decreased levels of CoQ9 and CoQ10. Two-photon fluorescence imaging revealed elevated H2O2 levels in the quadriceps, indicating increased oxidative stress. Proteomic analysis indicated that simvastatin inhibited the tricarboxylic acid cycle. Idebenone treatment not only further reduced plaque formation but also ameliorated the impaired exercise capacity caused by simvastatin. Our study represents the inaugural comprehensive investigation into the mechanisms underlying statin-induced myotoxicity. We have demonstrated that statins inhibit CoQ synthesis, impair mitochondrial complex functionality, and elevate oxidative stress, ultimately resulting in myotoxic effects. Furthermore, our research marks the pioneering identification of idebenone's capability to mitigate statin-induced myotoxicity by attenuating oxidative stress, thereby safeguarding mitochondrial complex functionality. The synergistic use of idebenone and statin not only enhances the effectiveness against atherosclerosis but also mitigates statin-induced myotoxicity.

Genetic variants affecting NQO1 protein levels impact the efficacy of idebenone treatment in Leber hereditary optic neuropathy

Idebenone, the only approved treatment for Leber hereditary optic neuropathy (LHON), promotes recovery of visual function in up to 50% of patients, but we can neither predict nor understand the non-responders. Idebenone is reduced by the cytosolic NAD(P)H oxidoreductase I (NQO1) and directly shuttles electrons to respiratory complex III, bypassing complex I affected in LHON. We show here that two polymorphic variants drastically reduce NQO1 protein levels when homozygous or compound heterozygous. This hampers idebenone reduction. In its oxidized form, idebenone inhibits complex I, decreasing respiratory function in cells. By retrospectively analyzing a large cohort of idebenone-treated LHON patients, classified by their response to therapy, we show that patients with homozygous or compound heterozygous NQO1 variants have the poorest therapy response, particularly if carrying the m.3460G>A/MT-ND1 LHON mutation. These results suggest consideration of patient NQO1 genotype and mitochondrial DNA mutation in the context of idebenone therapy.

Idebenone Exerts anti-Triple Negative Breast Cancer Effects via Dual Signaling Pathways of GADD45 and AMPK

Idebenone, a mitochondrial regulator, has exhibited anti-cancer activity in neurogenic and prostate tumor cells; however, its efficacy and specific targets in the treatment of triple-negative breast cancer (TNBC) remain unclear. This study aims to evaluate the potential of Idebenone as a therapeutic agent for TNBC. TNBC cell lines and Xenograft mouse models were used to assess the effect of Idebenone on TNBC both in vitro and in vivo. To investigate the underlying mechanism of Idebenone's effect on TNBC, cell viability assay, transwell invasion assay, cell cycle analysis, apoptosis assay, mitochondrial membrane potential assay, immunofluorescence staining, and transcriptome sequencing were utilized. The results showed that Idebenone impeded the proliferation, colony formation, migration, and invasion of TNBC cells, suppressed apoptosis, and halted the cell cycle in the G2/M phase. The inhibitory effect of Idebenone on TNBC was associated with the GADD45/CyclinB/CDK1 signaling pathway. By disrupting the mitochondrial membrane potential (MMP) and promoting mitophagy, Idebenone promoted cell autophagy through the AMPK/mTOR pathway, thus further suppressing the proliferation of TNBC cells. Furthermore, we found that Idebenone inhibited the development of TNBC in vivo. In conclusion, Idebenone may be a promising therapeutic option for TNBC as it is capable of inducing autophagy and apoptosis.

When a calorie is not just a calorie: Diet quality and timing as mediators of metabolism and healthy aging

An epidemic of obesity has affected large portions of the world, increasing the risk of developing many different age-associated diseases, including cancer, cardiovascular disease, and diabetes. In contrast with the prevailing notion that "a calorie is just a calorie," there are clear differences, within and between individuals, in the metabolic response to different macronutrient sources. Recent findings challenge this oversimplification; calories from different macronutrient sources or consumed at different times of day have metabolic effects beyond their value as fuel. Here, we summarize discussions conducted at a recent NIH workshop that brought together experts in calorie restriction, macronutrient composition, and time-restricted feeding to discuss how dietary composition and feeding schedule impact whole-body metabolism, longevity, and healthspan. These discussions may provide insights into the long-sought molecular mechanisms engaged by calorie restriction to extend lifespan, lead to novel therapies, and potentially inform the development of a personalized food-as-medicine approach to healthy aging.

Coenzyme Q-related compounds to maintain healthy mitochondria during aging

Mitochondrial dysfunction is one of the main factors that affects aging progression and many age-related diseases. Accumulation of dysfunctional mitochondria can be driven by unbalanced mito/autophagy or by decrease in mitochondrial biosynthesis and turnover. Coenzyme Q is an essential component of the mitochondrial electron transport chain and a key factor in the protection of membrane and mitochondrial DNA against oxidation. Coenzyme Q levels decay during aging and this can be considered an accelerating factor in mitochondrial dysfunction and aging progression. Supplementation with coenzyme Q is successful for some tissues and organs but not for others. For this reason, the role of coenzyme Q in systemic aging is a complex picture that needs different strategies depending on the organ considered the main objective to be addressed. In this chapter we focus on the different effects of coenzyme Q and related compounds and the probable strategies to induce endogenous synthesis to maintain healthy aging.

Shc Is Implicated in Calreticulin-Mediated Sterile Inflammation in Alcoholic Hepatitis

BACKGROUND & AIMS

Src homology and collagen (Shc) proteins are major adapters to extracellular signals, however, the regulatory role of Shc isoforms in sterile inflammatory responses in alcoholic hepatitis (AH) has not been fully investigated. We hypothesized that in an isoform-specific manner Shc modulates pre-apoptotic signals, calreticulin (CRT) membrane exposure, and recruitment of inflammatory cells.

METHODS

Liver biopsy samples from patients with AH vs healthy subjects were studied for Shc expression using DNA microarray data and immunohistochemistry. Shc knockdown (hypomorph) and age-matched wild-type mice were pair-fed according to the chronic-plus-binge alcohol diet. To analyze hepatocyte-specific effects, adeno-associated virus 8-thyroxine binding globulin-Cre (hepatocyte-specific Shc knockout)-mediated deletion was performed in flox/flox Shc mice. Lipid peroxidation, proinflammatory signals, redox radicals, reduced nicotinamide adenine dinucleotide/oxidized nicotinamide adenine dinucleotide ratio, as well as cleaved caspase 8, B-cell-receptor-associated protein 31 (BAP31), Bcl-2-associated X protein (Bax), and Bcl-2 homologous antagonist killer (Bak), were assessed in vivo. CRT translocation was studied in ethanol-exposed p46ShcẟSH2-transfected hepatocytes by membrane biotinylation in conjunction with phosphorylated-eukaryotic initiation factor 2 alpha, BAP31, caspase 8, and Bax/Bak. The effects of idebenone, a novel Shc inhibitor, was studied in alcohol/pair-fed mice.

RESULTS

Shc was significantly induced in patients with AH (P < .01). Alanine aminotransferase, reduced nicotinamide adenine dinucleotide/oxidized nicotinamide adenine dinucleotide ratios, production of redox radicals, and lipid peroxidation improved (P < .05), and interleukin 1β, monocyte chemoattractant protein 1, and C-X-C chemokine ligand 10 were reduced in Shc knockdown and hepatocyte-specific Shc knockout mice. In vivo, Shc-dependent induction, and, in hepatocytes, a p46Shc-dependent increase in pre-apoptotic proteins Bax/Bak, caspase 8, BAP31 cleavage, and membrane translocation of CRT/endoplasmic reticulum-resident protein 57 were seen. Idebenone protected against alcohol-mediated liver injury.

CONCLUSIONS

Alcohol induces p46Shc-dependent activation of pre-apoptotic pathways and translocation of CRT to the membrane, where it acts as a damage-associated molecular pattern, instigating immunogenicity. Shc inhibition could be a novel treatment strategy in AH.

p66Shc in Cardiovascular Pathology

p66Shc is a widely expressed protein that governs a variety of cardiovascular pathologies by generating, and exacerbating, pro-apoptotic ROS signals. Here, we review p66Shc’s connections to reactive oxygen species, expression, localization, and discuss p66Shc signaling and mitochondrial functions. Emphasis is placed on recent p66Shc mitochondrial function discoveries including structure/function relationships, ROS identity and regulation, mechanistic insights, and how p66Shc-cyt c interactions can influence p66Shc mitochondrial function. Based on recent findings, a new p66Shc mitochondrial function model is also put forth wherein p66Shc acts as a rheostat that can promote or antagonize apoptosis. A discussion of how the revised p66Shc model fits previous findings in p66Shc-mediated cardiovascular pathology follows.

Idebenone-Activating Autophagic Degradation of α-Synuclein via Inhibition of AKT-mTOR Pathway in a SH-SY5Y-A53T Model of Parkinson's Disease: A Network Pharmacological Approach

Background

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, which currently lacks disease-modifying therapy to slow down its progression. Idebenone, a coenzyme Q10 (CQ10) analogue, is a well-known antioxidant and has been used to treat neurological disorders. However, the mechanism of Idebenone on PD has not been fully elucidated. This study aims to predict the potential targets of Idebenone and explore its therapeutic mechanism against PD.

Method

We obtained potential therapeutic targets through database prediction, followed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Next, we constructed and analyzed a protein-protein interaction network (PPI) and a drug-target-pathway-disease network. A molecular docking test was conducted to identify the interactions between Idebenone and potential targets. Lastly, a PD cell line of SH-SY5Y overexpressing mutant α-synuclein was used to validate the molecular mechanism.

Result

A total of 87 targets were identified based on network pharmacology. The enrichment analysis highlighted manipulation of MAP kinase activity and the PI3K-AKT signaling pathway as potential pharmacological targets for Idebenone against PD. Additionally, molecular docking showed that AKT and MAPK could bind tightly with Idebenone. In the cell model of PD, Idebenone activated autophagy and promoted α-synuclein degradation by suppressing the AKT/mTOR pathway. Pretreating cells with chloroquine (CQ) to block autophagic flux could diminish the pharmacological effect of Idebenone to clear α-synuclein.

Conclusion

This study demonstrated that Idebenone exerts its anti-PD effects by enhancing autophagy and clearance of α-synuclein, thus providing a theoretical and experimental basis for Idebenone therapy against PD.

Bistability in fatty-acid oxidation resulting from substrate inhibition

In this study we demonstrated through analytic considerations and numerical studies that the mitochondrial fatty-acid β-oxidation can exhibit bistable-hysteresis behavior. In an experimentally validated computational model we identified a specific region in the parameter space in which two distinct stable and one unstable steady state could be attained with different fluxes. The two stable states were referred to as low-flux (disease) and high-flux (healthy) state. By a modular kinetic approach we traced the origin and causes of the bistability back to the distributive kinetics and the conservation of CoA, in particular in the last rounds of the β-oxidation. We then extended the model to investigate various interventions that may confer health benefits by activating the pathway, including (i) activation of the last enzyme MCKAT via its endogenous regulator p46-SHC protein, (ii) addition of a thioesterase (an acyl-CoA hydrolysing enzyme) as a safety valve, and (iii) concomitant activation of a number of upstream and downstream enzymes by short-chain fatty-acids (SCFA), metabolites that are produced from nutritional fibers in the gut. A high concentration of SCFAs, thioesterase activity, and inhibition of the p46Shc protein led to a disappearance of the bistability, leaving only the high-flux state. A better understanding of the switch behavior of the mitochondrial fatty-acid oxidation process between a low- and a high-flux state may lead to dietary and pharmacological intervention in the treatment or prevention of obesity and or non-alcoholic fatty-liver disease.

Shc inhibitor idebenone ameliorates liver injury and fibrosis in dietary NASH in mice

Shc expression rises in human nonalcoholic steatohepatitis (NASH) livers, and Shc-deficient mice are protected from NASH-thus Shc inhibition could be a novel therapeutic strategy for NASH. Idebenone was recently identified as the first small-molecule Shc inhibitor drug. We tested idebenone in the fibrotic methionine-choline deficient (MCD) diet and the metabolic fast food diet (FFD) mouse models of NASH. In the fibrotic MCD NASH model, idebenone reduced Shc expression and phosphorylation in peripheral blood mononuclear cells and Shc expression in the liver; decreased serum alanine aminotransferase and aspartate aminotransferase; and attenuated liver fibrosis as observed by quantitative polymerase chain reaction (qPCR) and hydroxyproline quantification. In the metabolic FFD model, idebenone administration improved insulin resistance, and reduced inflammation and fibrosis shown with qPCR, hydroxyproline measurement, and histology. Thus, idebenone ameliorates NASH in two mouse models. As an approved drug with a benign safety profile, Idebenone could be a reasonable human NASH therapy.

Src homolog and collagen homolog1 isoforms in acute and chronic liver injuries

Src homolog and collagen homolog (SHC) proteins are adaptor proteins bound to cell surface receptors that play an important role in signal transduction and related diseases. As an important member of the SHC protein family, SHC1 regulates cell proliferation and apoptosis, reactive oxygen species (ROS) production, and oxidative stress. Three isomeric proteins namely, p46shc, p52shc, and p66shc, are produced from the same SHC1 gene locus. All the three proteins are found in the liver, and are widely expressed in various hepatic cells. SHC1 has been proven to be associated with acute and chronic liver injuries of different etiologies, and plays important roles in liver fibrosis and hepatocellular carcinoma (HCC). Therefore, this review summarizes recent studies that discuss and explore the role of SHC1 in the occurrence and progression of liver diseases. We also provide a theoretical basis for future studies.

Novel Short-Chain Quinones to Treat Vision Loss in a Rat Model of Diabetic Retinopathy

Diabetic retinopathy (DR), one of the leading causes of blindness, is mainly diagnosed based on the vascular pathology of the disease. Current treatment options largely focus on this aspect with mostly insufficient therapeutic long-term efficacy. Mounting evidence implicates mitochondrial dysfunction and oxidative stress in the central etiology of DR. Consequently, drug candidates that aim at normalizing mitochondrial function could be an attractive therapeutic approach. This study compared the mitoprotective compounds, idebenone and elamipretide, side-by-side against two novel short-chain quinones (SCQs) in a rat model of DR. The model effectively mimicked type 2 diabetes over 21 weeks. During this period, visual acuity was monitored by measuring optokinetic response (OKR). Vision loss occurred 5–8 weeks after the onset of hyperglycemia. After 10 weeks of hyperglycemia, visual function was reduced by 65%. From this point, the right eyes of the animals were topically treated once daily with the test compounds. The left, untreated eye served as an internal control. Only three weeks of topical treatment significantly restored vision from 35% to 58–80%, while visual acuity of the non-treated eyes continued to deteriorate. Interestingly, the two novel SCQs restored visual acuity better than idebenone or elamipretide. This was also reflected by protection of retinal pathology against oxidative damage, retinal ganglion cell loss, reactive gliosis, vascular leakage, and retinal thinning. Overall, mitoprotective and, in particular, SCQ-based compounds have the potential to be developed into effective and fast-acting drug candidates against DR.

Idebenone: When an antioxidant is not an antioxidant

Idebenone is a well described drug that was initially developed against dementia. The current literature widely portrays this molecule as a potent antioxidant and CoQ₁₀ analogue. While numerous papers seem to support this view, a closer look indicates that the pharmacokinetics of idebenone do not support these claims. A major discrepancy between achievable tissue levels, especially in target tissues such as the brain, and doses required to show the proposed effects, significantly questions our current understanding. This review explains how this has happened and highlights the discrepancies in the current literature. More importantly, based on some recent discoveries, a new framework is presented that can explain the mode of action of this molecule and can align formerly contradictory results. Finally, this new appreciation of the molecular activities of idebenone provides a rational approach to test idebenone in novel indications that might have not been considered previously for this drug.

Novel idebenone analogs block Shc's access to insulin receptor to improve insulin sensitivity

There has been little innovation in identifying novel insulin sensitizers. Metformin, developed in the 1920s, is still used first for most Type 2 diabetes patients. Mice with genetic reduction of p52Shc protein have improved insulin sensitivity and glucose tolerance. By high-throughput screening, idebenone was isolated as the first small molecule 'Shc Blocker'. Idebenone blocks p52Shc's access to Insulin Receptor to increase insulin sensitivity. In this work the avidity of 34 novel idebenone analogs and 3 metabolites to bind p52Shc, and to block the interaction of p52Shc with the Insulin receptor was tested. Our hypothesis was that if an idebenone analog bound and blocked p52Shc's access to insulin receptor better than idebenone, it should be a more effective insulin sensitizing agent than idebenone itself. Of 34 analogs tested, only 2 both bound p52Shc more tightly and/or blocked the p52Shc-Insulin Receptor interaction more effectively than idebenone. Of those 2 only idebenone analog #11 was a superior insulin sensitizer to idebenone. Also, the long-lasting insulin-sensitizing potency of idebenone in rodents over many hours had been puzzling, as the parent molecule degrades to metabolites within 1 h. We observed that two of the idebenone's three metabolites are insulin sensitizing almost as potently as idebenone itself, explaining the persistent insulin sensitization of this rapidly metabolized molecule. These results help to identify key SAR = structure-activity relationship requirements for more potent small molecule Shc inhibitors as Shc-targeted insulin sensitizers for type 2 diabetes.

Comparative In Vitro Toxicology of Novel Cytoprotective Short-Chain Naphthoquinones

Short-chain quinones (SCQs) have been identified as potential drug candidates against mitochondrial dysfunction, which largely depends on the reversible redox characteristics of the active quinone core. We recently identified 11 naphthoquinone derivatives, 1–11, from a library of SCQs that demonstrated enhanced cytoprotection and improved metabolic stability compared to the clinically used benzoquinone idebenone. Since the toxicity properties of our promising SCQs were unknown, this study developed multiplex methods and generated detailed toxicity profiles from 11 endpoint measurements using the human hepatocarcinoma cell line HepG2. Overall, the toxicity profiles were largely comparable across different assays, with simple standard assays showing increased sensitivity compared to commercial toxicity assays. Within the 11 naphthoquinones tested, the L-phenylalanine derivative 4 consistently demonstrated the lowest toxicity across all assays. The results of this study not only provide useful information about the toxicity features of SCQs but will also enable the progression of the most promising drug candidates towards their clinical use.

Anti-Inflammatory and General Glucocorticoid Physiology in Skeletal Muscles Affected by Duchenne Muscular Dystrophy: Exploration of Steroid-Sparing Agents

In Duchenne muscular dystrophy (DMD), the activation of proinflammatory and metabolic cellular pathways in skeletal muscle cells is an inherent characteristic. Synthetic glucocorticoid intake counteracts the majority of these mechanisms. However, glucocorticoids induce burdensome secondary effects, including hypertension, arrhythmias, hyperglycemia, osteoporosis, weight gain, growth delay, skin thinning, cushingoid appearance, and tissue-specific glucocorticoid resistance. Hence, lowering the glucocorticoid dosage could be beneficial for DMD patients. A more profound insight into the major cellular pathways that are stabilized after synthetic glucocorticoid administration in DMD is needed when searching for the molecules able to achieve similar pathway stabilization. This review provides a concise overview of the major anti-inflammatory pathways, as well as the metabolic effects of glucocorticoids in the skeletal muscle affected in DMD. The known drugs able to stabilize these pathways, and which could potentially be combined with glucocorticoid therapy as steroid-sparing agents, are described. This could create new opportunities for testing in DMD animal models and/or clinical trials, possibly leading to smaller glucocorticoids dosage regimens for DMD patients.

A New Pathway Promotes Adaptation of Human Glioblastoma Cells to Glucose Starvation

Adaptation of glioblastoma to caloric restriction induces compensatory changes in tumor metabolism that are incompletely known. Here we show that in human glioblastoma cells maintained in exhausted medium, SHC adaptor protein 3 (SHC3) increases due to down-regulation of SHC3 protein degradation. This effect is reversed by glucose addition and is not present in normal astrocytes. Increased SHC3 levels are associated to increased glucose uptake mediated by changes in membrane trafficking of glucose transporters of the solute carrier 2A superfamily (GLUT/SLC2A). We found that the effects on vesicle trafficking are mediated by SHC3 interactions with adaptor protein complex 1 and 2 (AP), BMP-2-inducible protein kinase and a fraction of poly ADP-ribose polymerase 1 (PARP1) associated to vesicles containing GLUT/SLC2As. In glioblastoma cells, PARP1 inhibitor veliparib mimics glucose starvation in enhancing glucose uptake. Furthermore, cytosol extracted from glioblastoma cells inhibits PARP1 enzymatic activity in vitro while immunodepletion of SHC3 from the cytosol significantly relieves this inhibition. The identification of a new pathway controlling glucose uptake in high grade gliomas represents an opportunity for repositioning existing drugs and designing new ones.

Metabolic Stability of New Mito-Protective Short-Chain Naphthoquinones

Short-chain quinones (SCQs) have been identified as potential drug candidates against mitochondrial dysfunction, which is largely dependent on their reversible redox characteristics of the active quinone core. We recently synthesized a SCQ library of > 148 naphthoquinone derivatives and identified 16 compounds with enhanced cytoprotection compared to the clinically used benzoquinone idebenone. One of the major drawbacks of idebenone is its high metabolic conversion in the liver, which significantly restricts its therapeutic activity. Therefore, this study assessed the metabolic stability of the 16 identified naphthoquinone derivatives 1–16 using hepatocarcinoma cells in combination with an optimized reverse-phase liquid chromatography (RP-LC) method. Most of the derivatives showed significantly better stability than idebenone over 6 hours (p < 0.001). By extending the side-chain of SCQs, increased stability for some compounds was observed. Metabolic conversion from the derivative 3 to 5 and reduced idebenone metabolism in the presence of 5 were also observed. These results highlight the therapeutic potential of naphthoquinone-based SCQs and provide essential insights for future drug design, prodrug therapy and polytherapy, respectively.