Isocitrate dehydrogenase 2 deficiency aggravates prolonged high-fat diet intake-induced hypertension

Tricarboxylic Acid Cycle Regulation of Metabolic Program, Redox System, and Epigenetic Remodeling for Bone Health and Disease

Imbalanced osteogenic cell-mediated bone gain and osteoclastic remodeling accelerates the development of osteoporosis, which is the leading risk factor of disability in the elderly. Harmonizing the metabolic actions of bone-making cells and bone resorbing cells to the mineralized matrix network is required to maintain bone mass homeostasis. The tricarboxylic acid (TCA) cycle in mitochondria is a crucial process for cellular energy production and redox homeostasis. The canonical actions of TCA cycle enzymes and intermediates are indispensable in oxidative phosphorylation and adenosine triphosphate (ATP) biosynthesis for osteogenic differentiation and osteoclast formation. Knockout mouse models identify these enzymes' roles in bone mass and microarchitecture. In the noncanonical processes, the metabolites as a co-factor or a substrate involve epigenetic modification, including histone acetyltransferases, DNA demethylases, RNA m6A demethylases, and histone demethylases, which affect genomic stability or chromatin accessibility for cell metabolism and bone formation and resorption. The genetic manipulation of these epigenetic regulators or TCA cycle intermediate supplementation compromises age, estrogen deficiency, or inflammation-induced bone mass loss and microstructure deterioration. This review sheds light on the metabolic functions of the TCA cycle in terms of bone integrity and highlights the crosstalk of the TCA cycle and redox and epigenetic pathways in skeletal tissue metabolism and the intermediates as treatment options for delaying osteoporosis.

Common and divergent molecular mechanisms of fasting and ketogenic diets

Intermittent short-term fasting (ISTF) and ketogenic diets (KDs) exert overlapping but not identical effects on cell metabolism, function, and resilience. Whereas health benefits of KD are largely mediated by the ketone bodies (KBs), ISTF engages additional adaptive physiological responses. KDs act mainly through inhibition of histone deacetylases (HDACs), reduction of oxidative stress, improvement of mitochondria efficiency, and control of inflammation. Mechanisms of action of ISTF include stimulation of autophagy, increased insulin and leptin sensitivity, activation of AMP-activated protein kinase (AMPK), inhibition of the mechanistic target of rapamycin (mTOR) pathway, bolstering mitochondrial resilience, and suppression of oxidative stress and inflammation. Frequent switching between ketogenic and nonketogenic states may optimize health by increasing stress resistance, while also enhancing cell plasticity and functionality.

Integrative Placental Multi-Omics Analysis Reveals Perturbed Pathways and Potential Prognostic Biomarkers in Gestational Hypertension

BACKGROUND

Gestational hypertension (GH) is a severe complication that occurs after 20 weeks of pregnancy; however, its molecular mechanisms are not yet fully understood.

OBJECTIVE

Through this case-control discovery phase study, we aimed to find disease-specific candidate placental microRNAs (miRNAs) and metabolite markers for differentiating GH by integrating next-generation sequencing and metabolomics multi-omics analysis of placenta. Using small RNA sequencing and metabolomics of placental tissues of healthy pregnant (HP, n = 24) and GH subjects (n = 20), the transcriptome and metabolome were characterized in both groups.

RESULTS

The study identified a total of 44 downregulated placental miRNAs which includes three novel, three mature and 38 precursor miRNAs. Six miRNAs including three mature (hsa-miR-181a-5p, hsa-miR-498-5p, and hsa-miR-26b-5p) and three novel (NC_000016.10_1061, NC_000005.10_475, and NC_000001.11_53) were considered for final target prediction and functional annotation. Integrative analysis of differentially expressed miRNAs and metabolites yielded five pathways such as purine, glutathione, glycerophospholipid, inositol phosphate and β-alanine to be significantly perturbed in GH. We present fourteen genes (LPCAT1, LPCAT2, DGKH, PISD, GPAT2, PTEN, SACM1L, PGM2, AMPD3, AK7, AK3, CNDP1, IDH2, and ODC1) and eight metabolites (xanthosine, xanthine, spermine, glycine, CDP-Choline, glyceraldehyde 3-phosphate, β-alanine, and histidine) with potential to distinguish GH and HP.

CONCLUSION

The differential expression of miRNAs, their target genes, altered metabolites and metabolic pathways in GH patients were identified for the first time in our study. Further, the altered miRNAs and metabolites were integrated to build their inter-connectivity network. The findings obtained from our study may be used as a valuable source to further unravel the molecular pathways associated with GH and also for the evaluation of prognostic markers.

The Effects of Ketogenic Diet on Insulin Sensitivity and Weight Loss, Which Came First: The Chicken or the Egg?

The ketogenic diet (KD) is, nowadays, considered an interesting nutritional approach for weight loss and improvement in insulin resistance. Nevertheless, most of the studies available in the literature do not allow a clear distinction between its effects on insulin sensitivity per se, and the effects of weight loss induced by KDs on insulin sensitivity. In this review, we discuss the scientific evidence on the direct and weight loss mediated effects of KDs on glycemic status in humans, describing the KD's biochemical background and the underlying mechanisms.

TCA cycle metabolites associated with adverse outcomes after acute coronary syndrome: mediating effect of renal function

Aims

To examine relationships of tricarboxylic acid (TCA) cycle metabolites with risk of cardiovascular events and mortality after acute coronary syndrome (ACS), and evaluate the mediating role of renal function in these associations.

Methods

This is a prospective study performed among 309 ACS patients who were followed for a mean of 6.7 years. During this period 131 patients developed major adverse cardiovascular events (MACE), defined as the composite of myocardial infarction, hospitalization for heart failure, and all-cause mortality, and 90 deaths were recorded. Plasma concentrations of citrate, aconitate, isocitrate, succinate, malate, fumarate, α-ketoglutarate and d/l-2-hydroxyglutarate were quantified using LC-tandem MS. Multivariable Cox regression models were used to estimate hazard ratios, and a counterfactual-based mediation analysis was performed to test the mediating role of estimated glomerular filtration rate (eGFR).

Results

After adjustment for traditional cardiovascular risk factors and medications, positive associations were found between isocitrate and MACE (HR per 1 SD, 1.25; 95% CI: 1.03, 1.50), and between aconitate, isocitrate, d/l-2-hydroxyglutarate and all-cause mortality (HR per 1 SD, 1.41; 95% CI: 1.07, 1.84; 1.58; 95% CI: 1.23, 2.02; 1.38; 95% CI: 1.14, 1.68). However, these associations were no longer significant after additional adjustment for eGFR. Mediation analyses demonstrated that eGFR is a strong mediator of these associations.

Conclusion

These findings underscore the importance of TCA metabolites and renal function as conjunctive targets in the prevention of ACS complications.

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.

Epoxyeicosatrienoic acid administration or soluble epoxide hydrolase inhibition attenuates renal fibrogenesis in obstructive nephropathy

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites with biological effects, including antiapoptotic, anti-inflammatory, and antifibrotic functions. Soluble epoxide hydrolase (sEH)-mediated hydrolysis of EETs to dihydroxyeicosatrienoic acids (DHETs) attenuates these effects. Recent studies have demonstrated that inhibition of sEH prevents renal tubulointerstitial fibrosis and inflammation in the chronic kidney disease model. Given the pathophysiological role of the EET pathway in chronic kidney disease, we investigated if administration of EET regioisomers and/or sEH inhibition will promote antifibrotic and renoprotective effects in renal fibrosis following unilateral ureteral obstruction (UUO). EETs administration abolished tubulointerstitial fibrogenesis, as demonstrated by reduced fibroblast activation and collagen deposition after UUO. The inflammatory response was prevented as demonstrated by decreased neutrophil and macrophage infiltration and expression of cytokines in EET-administered UUO kidneys. EET administration and/or sEH inhibition significantly reduced M1 macrophage markers, whereas M2 macrophage markers were highly upregulated. Furthermore, UUO-induced oxidative stress, tubular injury, and apoptosis were all downregulated following EET administration. Combined EET administration and sEH inhibition, however, had no additive effect in attenuating inflammation and renal interstitial fibrogenesis after UUO. Taken together, our findings provide a mechanistic understanding of how EETs prevent kidney fibrogenesis during obstructive nephropathy and suggest EET treatment as a potential therapeutic strategy to treat fibrotic diseases.NEW & NOTEWORTHY Epoxyeicosatrienoic acids (EETs) are cytochrome P-450-dependent antihypertensive and anti-inflammatory derivatives of arachidonic acid, which are highly abundant in the kidney and considered renoprotective. We found that EET administration and/or soluble epoxide hydrolase inhibition significantly attenuates oxidative stress, renal cell death, inflammation, macrophage differentiation, and fibrogenesis following unilateral ureteral obstruction. Our findings provide a mechanistic understanding of how EETs prevent kidney fibrogenesis during obstructive nephropathy and suggest that EET treatment may be a potential therapeutic strategy to treat fibrotic diseases.

Prenatal PM2.5 exposure contributes to neuronal tau lesion in male offspring mice through mitochondrial dysfunction-mediated insulin resistance

The epidemiological evidence has linked prenatal exposure to fine particulate matter (PM_2.5) pollution with neurological diseases in offspring. However, the biological process and toxicological mechanisms remain unclear. Tau protein is a neuronal microtubule-associated protein expressed in fetal brain and plays a critical role in mediating neuronal development. Aberrant expression of tau is associated with adverse neurodevelopmental outcomes. To study whether prenatal exposure to PM_2.5 pollution induce tau lesion in mice offspring and elucidate the underlying pathogenic mechanism, we exposed pregnant mice to PM_2.5 (3 mg/kg b.w.) by oropharyngeal aspiration every other day. The results indicate that prenatal PM_2.5 exposure induced hyperphosphorylation of tau in the cortex of postnatal male offspring, which was accompanied by insulin resistance through the IRS-1/PI3K/AKT signaling pathway. Importantly, we further found that prenatal PM_2.5 exposure induced mitochondrial dysfunction by disrupting mitochondrial ultrastructure and decreasing the expression of rate-limiting enzymes (CS, IDH2 and FH) in the Krebs cycle and the subunits of mitochondrial complex IV and V (CO1, CO4, ATP6, and ATP8) during postnatal neurodevelopment. The findings suggest that prenatal PM_2.5 exposure could induce tauopathy-like changes in male offspring, in which mitochondrial dysfunction-induced insulin resistance might play an important role.

Hepatic and proximal tubule angiotensinogen play distinct roles in kidney dysfunction, glomerular and tubular injury, and fibrosis progression

Components of the renin-angiotensin system, including angiotensinogen (AGT), are critical contributors to chronic kidney disease (CKD) development and progression. However, the specific role of tissue-derived AGTs in CKD has not been fully understood. To define the contribution of liver versus kidney AGT in the CKD development, we performed 5/6 nephrectomy (Nx), an established CKD model, in wild-type (WT), proximal tubule (PT)- or liver-specific AGT knockout (KO) mice. Nx significantly elevated intrarenal AGT expression and elevated blood pressure (BP) in WT mice. The increase of intrarenal AGT protein was completely blocked in liver-specific AGT KO mice with BP reduction, suggesting a crucial role for liver AGT in BP regulation during CKD. Nx-induced glomerular and kidney injury and dysfunction, as well as fibrosis, were all attenuated to a greater extent in liver-specific AGT KO mice compared with PT-specific AGT KO and WT mice. However, the suppression of interstitial fibrosis in PT- and liver-specific AGT KO mouse kidneys was comparable. Our findings demonstrate that liver AGT acts as a critical contributor in driving glomerular and tubular injury, renal dysfunction, and fibrosis progression, whereas the role of PT AGT was limited to interstitial fibrosis progression in chronic renal insufficiency. Our results provide new insights for the development of tissue-targeted renin-angiotensin system intervention in the treatment of CKD.NEW & NOTEWORTHY Chronic kidney disease (CKD) is a major unmet medical need with no effective treatment. Current findings demonstrate that hepatic and proximal tubule angiotensinogen have distinct roles in tubular and glomerular injury, fibrogenesis, and renal dysfunction during CKD development. As renin-angiotensin system components, including angiotensinogen, are important targets for treating CKD in the clinic, the results from our study may be applied to developing better tissue-targeted treatment strategies for CKD and other fibroproliferative diseases.

miR204 potentially promotes non-alcoholic fatty liver disease by inhibition of cpt1a in mouse hepatocytes

Non-alcoholic fatty liver disease (NAFLD) is associated with hepatic metabolism dysfunction. However, the mechanistic role of miR204 in the development of NAFLD is unknown. We investigate the functional significance of miR204 in the evolution of NAFLD. IDH2 KO mice feed a normal diet (ND) or HFD increased body weight, epididymal fat-pad weight, lipid droplet in liver, blood parameter and inflammation compared to WT mice fed a ND or HFD. Moreover, the expression of miR204 is increased in mice with IDH2 deficiency. Increased miR204 by IDH2 deficiency regulates carnitine palmitoyltransferase 1a (cpt1a) synthesis, which inhibits fatty acid β-oxidation. Inhibition of miR204 prevents the disassembly of two fatty acid-related genes by activating CPT1a expression, which decreases lipid droplet in liver, inflammatory cytokines, epididymal fat pad weight, blood parameters. Increased miR204 by IDH2 deficiency promotes the pathogenesis of HFD-induced NAFLD by regulating hepatic fatty acid metabolism and inflammation.

miR204 is found to inhibit cpt1a in mouse hepatocytes, which could play a role in promoting non-alcoholic fatty liver disease.

Mitochondrial adaptation in cancer drug resistance: prevalence, mechanisms, and management

Drug resistance represents a major obstacle in cancer management, and the mechanisms underlying stress adaptation of cancer cells in response to therapy-induced hostile environment are largely unknown. As the central organelle for cellular energy supply, mitochondria can rapidly undergo dynamic changes and integrate cellular signaling pathways to provide bioenergetic and biosynthetic flexibility for cancer cells, which contributes to multiple aspects of tumor characteristics, including drug resistance. Therefore, targeting mitochondria for cancer therapy and overcoming drug resistance has attracted increasing attention for various types of cancer. Multiple mitochondrial adaptation processes, including mitochondrial dynamics, mitochondrial metabolism, and mitochondrial apoptotic regulatory machinery, have been demonstrated to be potential targets. However, recent increasing insights into mitochondria have revealed the complexity of mitochondrial structure and functions, the elusive functions of mitochondria in tumor biology, and the targeting inaccessibility of mitochondria, which have posed challenges for the clinical application of mitochondrial-based cancer therapeutic strategies. Therefore, discovery of both novel mitochondria-targeting agents and innovative mitochondria-targeting approaches is urgently required. Here, we review the most recent literature to summarize the molecular mechanisms underlying mitochondrial stress adaptation and their intricate connection with cancer drug resistance. In addition, an overview of the emerging strategies to target mitochondria for effectively overcoming chemoresistance is highlighted, with an emphasis on drug repositioning and mitochondrial drug delivery approaches, which may accelerate the application of mitochondria-targeting compounds for cancer therapy.

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

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

SIRT3-mediated deacetylation protects inner hair cell synapses in a H2O2-induced oxidative stress model in vitro

Oxidative stress is considered a driving event in the damage to inner hair cell (IHC) synapses. Mitochondrial deacetylase Sirtuin 3 (SIRT3) is an important regulator of reactive oxygen species (ROS) production. However, the effect of SIRT3 on IHC synapses remains elusive. In this study, we treated cochlear basilar membrane (CBM) with hydrogen peroxide (H₂O₂) to establish an oxidative stress model in vitro. The H₂O₂-induced CBM exhibited decreased the number of IHC synapses with low levels of ATP and mitochondrial membrane potential. Additionally, H₂O₂-incuded CBM showed markedly reduced levels of forkhead box protein O 3a (FOXO3a), superoxide dismutase 2 (SOD2), and isocitrate dehydrogenase 2 (IDH2), thereby increasing ROS generation. SIRT3 overexpression via administrating nicotinamide riboside in the H₂O₂-induced CBM protected IHC synapses against oxidative stress and inhibited hair cell apoptosis. We further demonstrated that SIRT3 overexpression led to upregulation of IDH2, and hypoacetylation of several proteins, such as FOXO3a and SOD2, which in turn reduced the levels of ROS and improved mitochondrial function. Collectively, these findings reveal that SIRT3 may be a potential therapeutic approach for damaged IHC synapses induced by oxidative stress.

Short-term control of diet affects cisplatin-induced acute kidney injury through modulation of mitochondrial dynamics and mitochondrial GSH

Obesity affects acute kidney injury (AKI) induced by various clinical settings, including transplantation and cisplatin-cancer therapy. However, the effect of short-term food intake change remains to be defined. Here, we investigated the effects of short-term high-fat diet intake and food restriction on cisplatin-induced AKI. Mice were fed either a high-fat diet (HFD) or a low-fat diet (LFD) for 11 days or were not fed for 40 hh (fasting), before cisplatin administration. Cisplatin-induced functional and structural damages to kidneys in both HFD- and LFD-fed mice, with greater damages in HFD-fed mice than LFD-fed mice. HFD decreased mitochondrial total glutathione (tGSH) level, along with increases in the plasma and kidney cholesterol levels. Cisplatin caused the increase of kidney cholesterol levels and oxidative stress, along with the decrease of mitochondrial tGSH levels. In addition, cisplatin-induced mitochondrial damage and apoptosis of tubular cells in both HFD- and LFD-fed mice. An increase of Fis1 (mitochondria fission 1 protein), whereas a decrease of Opa1 (mitochondria fusion 1 protein) occurred by cisplatin. These cisplatin effects were greater in HFD-fed mice than in LFD-fed mice. Administration of mitochondria-specific antioxidant treatment during HFD feeding inhibited these cisplatin-induced changes. Fasting for 40 h also significantly reduced the cisplatin-induced changes mentioned above. These data demonstrate that short-term HFD intake worsens cisplatin-induced oxidative stress by the reduction of mitochondrial tGSH, resulting in increased cisplatin-induced nephrotoxicity. These data newly indicate that the control of calorie intake, even for a short period, affects kidney susceptibility to injury. Although most studies described the effects of a long-term high-fat diet on the kidneys, in this study, we found that even if a high-fat diet was consumed for a short-term, physiological changes and mitochondria tGSH decrease in the kidneys, and consequently increased cisplatin-nephrotoxic susceptibility. These data suggest the association of calorie intake with kidney susceptibility to cisplatin.

Biology of IDH mutant cholangiocarcinoma

Isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) are the most frequently mutated metabolic genes across human cancers. These hotspot gain-of-function mutations cause the IDH enzyme to aberrantly generate high levels of the oncometabolite, R-2-hydroxyglutarate, which competitively inhibits enzymes that regulate epigenetics, DNA repair, metabolism, and other processes. Among epithelial malignancies, IDH mutations are particularly common in intrahepatic cholangiocarcinoma (iCCA). Importantly, pharmacological inhibition of mutant IDH (mIDH) 1 delays progression of mIDH1 iCCA, indicating a role for this oncogene in tumor maintenance. However, not all patients receive clinical benefit, and those who do typically show stable disease rather than significant tumor regressions. The elucidation of the oncogenic functions of mIDH is needed to inform strategies that can more effectively harness mIDH as a therapeutic target. This review will discuss the biology of mIDH iCCA, including roles of mIDH in blocking cell differentiation programs and suppressing antitumor immunity, and the potential relevance of these effects to mIDH1-targeted therapy. We also cover opportunities for synthetic lethal therapeutic interactions that harness the altered cell state provoked by mIDH1 rather than inhibiting the mutant enzyme. Finally, we highlight key outstanding questions in the biology of this fascinating and incompletely understood oncogene.

Cisplatin induces lung cell cilia disruption and lung damage via oxidative stress

BACKGROUND

Cisplatin (cis-diamminedichloroplatinum II) is widely used for the treatment of cancer, but its cellular toxicity, especially in the form of oxidative stress, limits its use in multiple organs including the lungs. As a cellular organelle, cilia play an important role in cellular function and can be damaged by oxidative stress. However, the effect of cisplatin-induced lung toxicity on cilia has not yet been defined. Herein, we investigated the association of cilia and oxidative stress with cisplatin-induced lung damage.

METHODS

Mice were administered with cisplatin. Some mice were treated with 2-(2,2,6,6-Tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride (Mito-TEMPO, a mitochondria-specific antioxidant) before the administration of cisplatin. Disruption of cilia was evaluated by the detection of ciliary proteins and fragments in the bronchoalveolar lavage fluid (BALF).

RESULTS

Cisplatin caused the thickening of interalveolar septa, infiltration of immune cells into the interalveolar septa, and increased protein concentration and total cell number in the BALF. Cisplatin also increased ciliary fragments and proteins in the BALF. In the lungs, cisplatin increased the production of hydrogen peroxide, lipid peroxidation, and apoptosis, while decreasing manganese superoxide dismutase, isocitrate dehydrogenase 2, and catalase expression. Treatment with Mito-TEMPO prevented cisplatin-induced lung damage, ciliary fragmentation, oxidative stress, and apoptosis.

CONCLUSION

By increasing oxidative stress in the lung, cisplatin induces lung cell damage, disruption of cilia, and release of disrupted cilia into the BALF. This suggests that cisplatin-induced lung damage can damage the cilia, manifesting as increased ciliary proteins in the BALF.

Hypertrophic preconditioning attenuates post-myocardial infarction injury through deacetylation of isocitrate dehydrogenase 2

Ischemic preconditioning induced by brief periods of coronary occlusion and reperfusion protects the heart from a subsequent prolonged ischemic insult. In this study we investigated whether a short-term nonischemic stimulation of hypertrophy renders the heart resistant to subsequent ischemic injury. Male mice were subjected to transient transverse aortic constriction (TAC) for 3 days followed aortic debanding on D4 (T3D4), as well as ligation of the left coronary artery to induce myocardial infarction (MI). The TAC preconditioning mice showed markedly improved contractile function and significantly reduced myocardial fibrotic area and apoptosis following MI. We revealed that TAC preconditioning significantly reduced MI-induced oxidative stress, evidenced by increased NADPH/NADP ratio and GSH/GSSG ratio, as well as decreased mitochondrial ROS production. Furthermore, TAC preconditioning significantly increased the expression and activity of SIRT3 protein following MI. Cardiac-specific overexpression of SIRT3 gene through in vivo AAV-SIRT3 transfection partially mimicked the protective effects of TAC preconditioning, whereas genetic ablation of SIRT3 in mice blocked the protective effects of TAC preconditioning. Moreover, expression of an IDH2 mutant mimicking deacetylation (IDH2 K413R) in cardiomyocytes promoted myocardial IDH2 activation, quenched mitochondrial reactive oxygen species (ROS), and alleviated post-MI injury, whereas expression of an acetylation mimic (IDH2 K413Q) in cardiomyocytes inactivated IDH2, exacerbated mitochondrial ROS overload, and aggravated post-MI injury. In conclusion, this study identifies TAC preconditioning as a novel strategy for induction of an endogenous self-defensive and cardioprotective mechanism against cardiac injury. Therapeutic strategies targeting IDH2 are promising treatment approaches for cardiac ischemic injury.

Hypertrophic preconditioning attenuates myocardial ischemia/reperfusion injury through the deacetylation of isocitrate dehydrogenase 2

To test the hypothesis that transient nonischemic stimulation of hypertrophy would render the heart resistant to subsequent ischemic stress, short-term transverse aortic constriction (TAC) was performed in mice and then withdrawn for several days by aortic debanding, followed by subsequent myocardial exposure to ischemia/reperfusion (I/R). Following I/R injury, the myocardial infarct size and apoptosis were markedly reduced, and contractile function was significantly improved in the TAC preconditioning group compared with the control group. Mechanistically, hypertrophic preconditioning remarkably alleviated I/R-induced oxidative stress, as evidenced by the increased reduced nicotinamide adenine dinucleotide phosphate (NADPH)/nicotinamide adenine dinucleotide phosphate (NADP) ratio, increase in the reduced glutathione (GSH)/oxidized glutathione (GSSH) ratio, and reduced mitochondrial reactive oxygen species (ROS) production. Moreover, TAC preconditioning inhibited caspase-3 activation and mitigated the mitochondrial impairment by deacetylating isocitrate dehydrogenase 2 (IDH2) via a sirtuin 3 (SIRT3)-dependent mechanism. In addition, the expression of a genetic deacetylation mimetic IDH2 mutant (IDH2 K413R) in cardiomyocytes, which increased IDH2 enzymatic activity and decreased mitochondrial ROS production, and ameliorated I/R injury, whereas the expression of a genetic acetylation mimetic (IDH2 K413Q) in cardiomyocytes abolished these protective effects of hypertrophic preconditioning. Furthermore, both the activity and expression of the SIRT3 protein were markedly increased in preconditioned mice exposed to I/R. Treatment with an adenovirus encoding SIRT3 partially emulated the actions of hypertrophic preconditioning, whereas genetic ablation of SIRT3 in mice blocked the cardioprotective effects of hypertrophic preconditioning. The present study identifies hypertrophic preconditioning as a novel endogenous self-defensive and cardioprotective strategy for cardiac I/R injury that induces IDH2 deacetylation through a SIRT3-dependent mechanism. A therapeutic strategy targeting IDH2 may be a promising treatment for cardiac ischemic injury.

Proximal tubule cyclophilin D mediates kidney fibrogenesis in obstructive nephropathy

The proximal tubule (PT) is highly vulnerable to acute injury, including ischemic insult and nephrotoxins, and chronic kidney injury. It has been established that PT injury is a primary cause of the development of chronic kidney disease, but the underlying molecular mechanism remains to be defined. Here, we tested whether PT cyclophilin D (CypD), a mitochondrial matrix protein, is a critical factor to cause kidney fibrosis progression. To define the role of CypD in kidney fibrosis, we used an established mouse model for kidney fibrosis: the unilateral ureteral obstruction (UUO) model in global and PT-specific CypD knockout (KO). Global CypD KO blunted kidney fibrosis progression with inhibition of myofibroblast activation and fibrosis. UUO-induced tubular atrophy was suppressed in kidneys of global CypD KO but not tubular dilation or apoptotic cell death. PT cell cycle arrest was highly increased in wild-type UUO kidneys but was markedly attenuated in global CypD KO UUO kidneys. The number of macrophages and neutrophils was less in UUO kidneys of global CypD KO than those of wild-type kidneys. Proinflammatory and profibrotic factors were all inhibited in global CypD KO. In line with those of global CypD KO, PT-specific CypD KO also blunted kidney fibrosis progression, along with less tubular atrophy, renal parenchymal loss, cell cycle arrest in PT, and inflammation, indicating a critical role for PT CypD in fibrogenesis. Collectively, our data demonstrate that CypD in the PT is a critical factor contributing to kidney fibrosis in UUO, providing a new paradigm for mitochondria-targeted therapeutics of fibrotic diseases.NEW & NOTEWORTHY It has been established that renal proximal tubule (PT) injury is a primary cause of the development of chronic kidney disease, but the underlying molecular mechanism remains to be defined. Here, we show that cyclophilin D, a mitochondrial matrix protein, in the PT causes kidney fibrogenesis in obstructive nephropathy. Our data suggest that targeting PT cyclophilin D could be beneficial to prevent fibrosis progression.

Involvement of Tricarboxylic Acid Cycle Metabolites in Kidney Diseases

Mitochondria are complex organelles that orchestrate several functions in the cell. The primary function recognized is energy production; however, other functions involve the communication with the rest of the cell through reactive oxygen species (ROS), calcium influx, mitochondrial DNA (mtDNA), adenosine triphosphate (ATP) levels, cytochrome c release, and also through tricarboxylic acid (TCA) metabolites. Kidney function highly depends on mitochondria; hence mitochondrial dysfunction is associated with kidney diseases. In addition to oxidative phosphorylation impairment, other mitochondrial abnormalities have been described in kidney diseases, such as induction of mitophagy, intrinsic pathway of apoptosis, and releasing molecules to communicate to the rest of the cell. The TCA cycle is a metabolic pathway whose primary function is to generate electrons to feed the electron transport system (ETS) to drives energy production. However, TCA cycle metabolites can also release from mitochondria or produced in the cytosol to exert different functions and modify cell behavior. Here we review the involvement of some of the functions of TCA metabolites in kidney diseases.

Hepatoprotective Effect of Lactobacillus plantarum HFY09 on Ethanol-Induced Liver Injury in Mice

Lactobacillus plantarum is a bacterial strain that is used as a probiotic with health-promoting effects. Our study investigated the hepatoprotective effect of Lactobacillus plantarum HFY09 (LP-HFY09) in mice with ethanol-induced liver injury. The protection afforded by LP-HFY09 was evaluated by observing the morphology of hepatic tissue and measuring liver lipid indexes and function indexes, levels of anti-oxidative enzymes, and anti-inebriation enzymes, as well as oxidative metabolism-related gene expression. Gavage administration of LP-HFY09 [1 × 10⁹ CFU/kg body weight (bw)] limited the loss of bw, alcohol damage to the liver, and maintained the normal hepatic tissue morphology. Lactobacillus plantarum HFY09 intervention in ethanol-induced mice led to decreases in serum triglyceride (TG), total cholesterol (TC), aspartic transaminase, alanine transaminase, hyaluronidase (HAase), and precollagen III (PC III), and increases in liver alcohol dehydrogenase (ADH), and acetaldehyde dehydrogenase (ALDH). Lactobacillus plantarum HFY09 assisted with alleviating inflammation by elevating the level of interleukin 10 (IL-10) and decreasing the levels of pro-inflammatory factors [IL-6, IL-1β, and tumor necrosis factor-α (TNF)-α]. Lactobacillus plantarum HFY09 significantly elevated hepatic levels of superoxide dismutase (SOD) and glutathione (GSH), and decreased liver malondialdehyde (MDA) from 3.45 to 1.64 nmol/mg protein. Lactobacillus plantarum HFY09 exhibited an overall strong regulatory effect on liver protection when compared to that of commercial Lactobacillus delbrueckii subsp. bulgaricus. The hepatoprotective effect of LP-HFY09 was reflected by the upregulated expression of peroxisome proliferator activated-receptors α, SOD1, SOD2, glutathione peroxidase (GSH-Px), nicotinamide adenine dinucleotide phosphate (NADPH), and catalase (CAT), and the downregulated expression of cyclooxygenase-1 (COX1), c-Jun N-terminal kinase (JNK), and extracellular regulated protein kinases (ERK). Administration of LP-HFY09 at a concentration of 1.0 × 10⁹ CFU/kg bw could be a potential intervention, for people who frequently consume alcohol.

Isobaric Peptide Labeling on Digital Microfluidics for Quantitative Low Cell Number Proteomics

Digital microfluidics (DMF) is a technology suitable for bioanalytical applications requiring miniaturized, automated, and multiplexed liquid handling. Its use in LC-MS-based proteomics, however, has so far been limited to qualitative proteome analyses. This is mainly due to the need for detergents that enable facile, reproducible droplet movement, which are compatible with organic solvents commonly used in targeted chemical modifications of peptides. Aiming to implement isobaric peptide labeling, a widely applied technique allowing multiplexed quantitative proteome studies, on DMF devices, we tested different commercially available detergents. We identified the maltoside-based detergent 3-dodecyloxypropyl-1-β-d-maltopyranoside (DDOPM) to enable facile droplet movement and show micelle formation even in the presence of organic solvent, which is necessary for isobaric tandem mass tag (TMT) labeling. The detergent is fully compatible with reversed phase LC-MS, not interfering with peptide identification. Tryptic digestion in the presence of DDOPM was more efficient than without detergent, resulting in more protein identifications. Using this detergent, we report the first on-DMF chip isobaric labeling strategy, with TMT-labeling efficiency comparable to conventional protocols. The newly developed labeling protocol was evaluated in the multiplexed analyses of a protein standard digest spiked into 25 cells. Finally, using only 75 cells per biological replicate, we were able to identify 39 proteins being differentially abundant after treatment of Jurkat T cells with the anticancer drug doxorubicin. In summary, we demonstrate an important step toward multiplexed quantitative proteomics on DMF, which, in combination with larger chip arrays and optimized hardware, could enable high throughput low cell number proteomics.

Isolation and identification of three water-soluble selenoproteins in Se-enriched Agaricus blazei Murrill

Selenoproteins in selenium (Se)-enriched vegetables play an important role in human health. In this study, three water-soluble selenoproteins PR-Se-1, PR-Se-2 and PR-Se-3 in Agaricus blazei Murrill (ABM) were isolated by anion exchange chromatography, gel filtration chromatography and SDS-PAGE. Sequence analyses performed by HPLC-MS/MS showed that PR-Se-1, a 114024 Da selenoprotein with 1019 amino acids (AAs), is an isoenzyme of isocitrate dehydrogenase. PR-Se-2, a 53983 Da selenoprotein with 508 AAs, is a kind of dihydrolipoyl dehydrogenase. PR-Se-3, a 47179 Da selenoprotein with 415 AAs, is a kind d-proline reductase. Se content is high at 26.1 μg/g, and selenocystine is the predominant Se unit in the three selenoproteins. Se content of ABM is 9.15 μg/g, and the organic form of Se accounts for ~81% of total Se content. ABM could be a promising source of Se in Se-poor regions.