Mitochondrial aldehyde dehydrogenase obliterates insulin resistance-induced cardiac dysfunction through deacetylation of PGC-1α

Ginsenoside Rh4 Ameliorates Cisplatin-Induced Intestinal Toxicity via PGC-1[Formula: see text]-Mediated Mitochondrial Autophagy and Apoptosis Pathways

Cisplatin-evoked profound gastrointestinal symptomatology is one of the most common side effects of chemotherapy drugs, causing further gastrointestinal cell and intestinal mucosal injury. Ginsenoside Rh4 (G-Rh4), an active component extracted from red ginseng, possesses beneficial anti-oxidative and anti-apoptosis effects. This study aimed to assess the effectiveness of pharmacological intervention with G-Rh4 mitigating intestinal toxicity evoked by cisplatin in a murine model and in IEC-6 cells in vitro. Following oral administration for 10 days, G-Rh4 (10[Formula: see text]mg/kg and 20[Formula: see text]mg/kg) significantly increased the indicators of diamine oxidase (DAO) affected by cisplatin (20[Formula: see text]mg/kg) in mice, and histopathological analysis further indicated that G-Rh4 could effectively improve intestinal tissue morphology, as well as the expression of peroxisome proliferator-activated receptor-gamma coactivator 1 [Formula: see text] (PGC-1[Formula: see text] pathway and autophagy-related proteins. Moreover, in vitro experiments demonstrated that G-Rh4 exerted a concentration-dependent increase in cell viability, while also inhibiting cytotoxicity and abnormal rise of reactive oxygen species (ROS). Notably, ROS also activate PGC-1[Formula: see text] protein and mediate the occurrence of mitochondrial autophagy and apoptosis pathways. The molecular docking approach was employed to dock G-Rh4 with PGC-1[Formula: see text] and AMPK, revealing a binding energy of [Formula: see text]7.3[Formula: see text]kcal/mol and [Formula: see text]8.1[Formula: see text]kcal/mol and indicating a tight interaction between the components and the target. G-Rh4 could reduce the expression of autophagy-related protein p62/p53, reduce the accumulation of autophagy products, and promote the flow of autophagy. In conclusion, G-Rh4 exerted protective effects against cisplatin-induced intestinal toxicity, at least partially through PGC-1[Formula: see text]-mediated autophagy and apoptosis.

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

The effects of resveratrol and melatonin on biochemical and molecular parameters in diabetic old female rat hearts

The roles of melatonin and resveratrol-enhanced activation of SIRT1 (silent information regulator 1), GLUT4 (glucose transporter type 4), and PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) in mediating the protective effects on the heart in aged female rats with streptozotocin-induced diabetes were investigated. 16-month-old 48 Wistar female rats were separated into 8 groups with equal numbers. Group 1: Control, Group 2: Resveratrol Control, Group 3: Melatonin Control, Group 4: Resveratrol and Melatonin Control, Group 5: Diabetes, Group 6: Diabetes Resveratrol, Group 7: Diabetes Melatonin, Group 8: Diabetes Resveratrol and Melatonin. A single dose of 40 mg/kg intraperitoneal streptozotocin was injected into the rats of Groups 5, 6, 7, and 8 to induce experimental diabetes. Blood glucose levels were measured from the tail veins of the animals six days after the injections, using a diagnostic glucose kit. Rats with a blood glucose levels ≥300 mg/dl were considered diabetic. 5 mg/kg/day of resveratrol (intraperitoneal) and melatonin (subcutaneous) were administered for four weeks. At the end of the applications, SIRT1, GLUT4, PGC-1α gene expression as well as MDA and GSH levels in the heart tissues were determined by the PCR method from heart tissue samples taken under general anesthesia. The findings of our study show that suppressed antioxidant activity and decreased GLUT4, SIRT1, and PGC-1α gene expression in heart tissue can be reversed by the combination of resveratrol, melatonin, and resveratrol + melatonin in a diabetic aged female rat model. Resveratrol and melatonin supplementation may have a protective effect on cardiac functions in the diabetic aged female rat model.

Mitochondrial aldehyde dehydrogenase (ALDH2) rescues cardiac contractile dysfunction in an APP/PS1 murine model of Alzheimer's disease via inhibition of ACSL4-dependent ferroptosis

Alzheimer's disease (AD) is associated with high incidence of cardiovascular events but the mechanism remains elusive. Our previous study reveals a tight correlation between cardiac dysfunction and low mitochondrial aldehyde dehydrogenase (ALDH2) activity in elderly AD patients. In the present study we investigated the effect of ALDH2 overexpression on cardiac function in APP/PS1 mouse model of AD. Global ALDH2 transgenic mice were crossed with APP/PS1 mutant mice to generate the ALDH2-APP/PS1 mutant mice. Cognitive function, cardiac contractile, and morphological properties were assessed. We showed that APP/PS1 mice displayed significant cognitive deficit in Morris water maze test, myocardial ultrastructural, geometric (cardiac atrophy, interstitial fibrosis) and functional (reduced fractional shortening and cardiomyocyte contraction) anomalies along with oxidative stress, apoptosis, and inflammation in myocardium. ALDH2 transgene significantly attenuated or mitigated these anomalies. We also noted the markedly elevated levels of lipid peroxidation, the essential lipid peroxidation enzyme acyl-CoA synthetase long-chain family member 4 (ACSL4), the transcriptional regulator for ACLS4 special protein 1 (SP1) and ferroptosis, evidenced by elevated NCOA4, decreased GPx4, and SLC7A11 in myocardium of APP/PS1 mutant mice; these effects were nullified by ALDH2 transgene. In cardiomyocytes isolated from WT mice and in H9C2 myoblasts in vitro, application of Aβ (20 μM) decreased cell survival, compromised cardiomyocyte contractile function, and induced lipid peroxidation; ALDH2 transgene or activator Alda-1 rescued Aβ-induced deteriorating effects. ALDH2-induced protection against Aβ-induced lipid peroxidation was mimicked by the SP1 inhibitor tolfenamic acid (TA) or the ACSL4 inhibitor triacsin C (TC), and mitigated by the lipid peroxidation inducer 5-hydroxyeicosatetraenoic acid (5-HETE) or the ferroptosis inducer erastin. These results demonstrate an essential role for ALDH2 in AD-induced cardiac anomalies through regulation of lipid peroxidation and ferroptosis.

Mitochondrial proteins in heart failure: The role of deacetylation by SIRT3

Heart failure (HF) is still the leading cause of death worldwide, occurring with a variety of complex mechanisms. However, most intervention for HF do not directly target the pathological mechanisms underlying cell damage in failing cardiomyocytes. Mitochondria are involved in many physiological processes, which is an important guarantee for normal heart function. Mitochondrial dysfunction is considered to be the critical node of the development of HF. Strict modulation of the mitochondrial function can ameliorate the myocardial injury and protect cardiac function. Acetylation plays an important role in mitochondrial protein homeostasis, and SIRT3, the most important deacetylation protein in mitochondria, is involved in the maintenance of mitochondrial function. SIRT3 can delay the progression of HF by improving mitochondrial function. Herein we summarize the interaction between SIRT3 and proteins related to mitochondrial function including oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO), mitochondrial biosynthesis, mitochondrial quality control. In addition, we also sum up the effects of this interaction on HF and the research progress of treatments targeting SIRT3, so as to find potential HF therapeutic for clinical use in the future.

Therapeutic potential of targeting oxidative stress in diabetic cardiomyopathy

Even in the absence of coronary artery disease and hypertension, diabetes mellitus (DM) may increase the risk for heart failure development. This risk evolves from functional and structural alterations induced by diabetes in the heart, a cardiac entity termed diabetic cardiomyopathy (DbCM). Oxidative stress, defined as the imbalance of reactive oxygen species (ROS) has been increasingly proposed to contribute to the development of DbCM. There are several sources of ROS production including the mitochondria, NAD(P)H oxidase, xanthine oxidase, and uncoupled nitric oxide synthase. Overproduction of ROS in DbCM is thought to be counterbalanced by elevated antioxidant defense enzymes such as catalase and superoxide dismutase. Excess ROS in the cardiomyocyte results in further ROS production, mitochondrial DNA damage, lipid peroxidation, post-translational modifications of proteins and ultimately cell death and cardiac dysfunction. Furthermore, ROS modulates transcription factors responsible for expression of antioxidant enzymes. Lastly, evidence exists that several pharmacological agents may convey cardiovascular benefit by antioxidant mechanisms. As such, increasing our understanding of the pathways that lead to increased ROS production and impaired antioxidant defense may enable the development of therapeutic strategies against the progression of DbCM. Herein, we review the current knowledge about causes and consequences of ROS in DbCM, as well as the therapeutic potential and strategies of targeting oxidative stress in the diabetic heart.

Formononetin Ameliorates Cognitive Disorder via PGC-1α Pathway in Neuroinflammation Conditions in High-Fat Diet-Induced Mice

BACKGROUND

Alzheimer's disease is one of the most common neurodegenerative diseases in many modern societies. The core pathogenesis of Alzheimer's disease includes the aggregation of hyperphosphorylated Tau and abnormal Amyloid-β generation. In addition, previous studies have shown that neuroinflammation is one of the pathogenesis of Alzheimer's disease. Formononetin, an isoflavone compound extracted from Trifolium pratense L., has been found to have various properties including anti-obesity, anti-inflammation, and neuroprotective effects. But there are very few studies on the treatment of Alzheimer's disease with Formononetin.

OBJECTIVE

The present study focused on the protective activities of Formononetin on a high-fat dietinduced cognitive decline and explored the underlying mechanisms.

METHODS

Mice were fed with HFD for 10 weeks and intragastric administrated daily with metformin (300 mg/kg) and Formononetin (20 and 40 mg/kg).

RESULTS

We found that Formononetin (20, 40 mg/kg) significantly attenuated the learning and memory deficits companied by weight improvement and decreased the levels of blood glucose, total cholesterol and triglyceride in high-fat diet-induced mice. Meanwhile, we observed high-fat diet significantly caused the Tau hyperphosphorylation in the hippocampus of mice, whereas Formononetin reversed this effect. Additionally, Formononetin markedly reduced the levels of inflammation cytokines IL-1β and TNF-α in high-fat diet-induced mice. The mechanism study showed that Formononetin suppressed the pro-inflammatory NF-κB signaling and enhanced the anti-inflammatory Nrf-2/HO-1 signaling, which might be related to the regulation of PGC-1α in the hippocampus of high-fat diet -induced mice.

CONCLUSION

Taken together, our results showed that Formononetin could improve the cognitive function by inhibiting neuroinflammation, which is attributed to the regulation of PGC-1α pathway in HFD-induced mice.

SIRT3 deficiency exacerbates fatty liver by attenuating the HIF1α-LIPIN 1 pathway and increasing CD36 through Nrf2

Background

Deficiency of mitochondrial sirtuin 3 (SIRT3), a NAD⁺-dependent protein deacetylase that maintains redox status and lipid homeostasis, contributes to hepatic steatosis. In this study, we investigated additional mechanisms that might play a role in aggravating hepatic steatosis in Sirt3-deficient mice fed a high-fat diet (HFD).

Methods

Studies were conducted in wild-type (WT) and Sirt3^−/− mice fed a standard diet or a HFD and in SIRT3-knockdown human Huh-7 hepatoma cells.

Results

Sirt3^−/− mice fed a HFD presented exacerbated hepatic steatosis that was accompanied by decreased expression and DNA-binding activity of peroxisome proliferator-activated receptor (PPAR) α and of several of its target genes involved in fatty acid oxidation, compared to WT mice fed the HFD. Interestingly, Sirt3 deficiency in liver and its knockdown in Huh-7 cells resulted in upregulation of the nuclear levels of LIPIN1, a PPARα co-activator, and of the protein that controls its levels and localization, hypoxia-inducible factor 1α (HIF-1α). These changes were prevented by lipid exposure through a mechanism that might involve a decrease in succinate levels. Finally, Sirt3^−/− mice fed the HFD showed increased levels of some proteins involved in lipid uptake, such as CD36 and the VLDL receptor. The upregulation in CD36 was confirmed in Huh-7 cells treated with a SIRT3 inhibitor or transfected with SIRT3 siRNA and incubated with palmitate, an effect that was prevented by the Nrf2 inhibitor ML385.

Conclusion

These findings demonstrate new mechanisms by which Sirt3 deficiency contributes to hepatic steatosis.

ALDH2 contributes to melatonin-induced protection against APP/PS1 mutation-prompted cardiac anomalies through cGAS-STING-TBK1-mediated regulation of mitophagy

Ample clinical evidence suggests a high incidence of cardiovascular events in Alzheimer's disease (AD), although neither precise etiology nor effective treatment is available. This study was designed to evaluate cardiac function in AD patients and APP/PS1 mutant mice, along with circulating levels of melatonin, mitochondrial aldehyde dehydrogenase (ALDH2) and autophagy. AD patients and APP/PS1 mice displayed cognitive and myocardial deficits, low levels of circulating melatonin, ALDH2 activity, and autophagy, ultrastructural, geometric (cardiac atrophy and interstitial fibrosis) and functional (reduced fractional shortening and cardiomyocyte contraction) anomalies, mitochondrial injury, cytosolic mtDNA buildup, apoptosis, and suppressed autophagy and mitophagy. APP/PS1 mutation downregulated cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) levels and TBK1 phosphorylation, while promoting Aβ accumulation. Treatment with melatonin overtly ameliorated unfavorable APP/PS1-induced changes in cardiac geometry and function, apoptosis, mitochondrial integrity, cytosolic mtDNA accumulation (using both immunocytochemistry and qPCR), mitophagy, and cGAS-STING-TBK1 signaling, although these benefits were absent in APP/PS1/ALDH2-/- mice. In vitro evidence indicated that melatonin attenuated APP/PS1-induced suppression of mitophagy and cardiomyocyte function, and the effect was negated by the nonselective melatonin receptor blocker luzindole, inhibitors or RNA interference of cGAS, STING, TBK1, and autophagy. Our data collectively established a correlation among cardiac dysfunction, low levels of melatonin, ALDH2 activity, and autophagy in AD patients, with compelling support in APP/PS1 mice, in which melatonin rescued myopathic changes by promoting cGAS-STING-TBK1 signaling and mitophagy via an ALDH2-dependent mechanism.

Acetylation in cardiovascular diseases: Molecular mechanisms and clinical implications

Acetylation belongs to a class of post-translational modification (PTM) processes that epigenetically regulate gene expression and gene transcriptional activity. Reversible histone acetylation on lysine residues governs the interactions between DNA and histones to mediate chromatin remodeling and gene transcription. Non-histone protein acetylation complicates cellular function whereas acetylation of key mitochondrial enzymes regulates bioenergetic metabolism. Acetylation and deacetylation of functional proteins are essential to the delicated homeostatic regulation of embryonic development, postnatal maturation, cardiomyocyte differentiation, cardiac remodeling and onset of various cardiovascular diseases including obesity, diabetes mellitus, cardiometabolic diseases, ischemia-reperfusion injury, cardiac remodeling, hypertension, and arrhythmias. Histone acetyltransferase (HATs) and histone deacetylases (HDACs) are essential enzymes mainly responsible for the regulation of lysine acetylation levels, thus providing possible drugable targets for therapeutic interventions in the management of cardiovascular diseases.

Altered mitochondrial metabolism in the insulin-resistant heart

Obesity-induced insulin resistance and type 2 diabetes mellitus can ultimately result in various complications, including diabetic cardiomyopathy. In this case, cardiac dysfunction is characterized by metabolic disturbances such as impaired glucose oxidation and an increased reliance on fatty acid (FA) oxidation. Mitochondrial dysfunction has often been associated with the altered metabolic function in the diabetic heart, and may result from FA-induced lipotoxicity and uncoupling of oxidative phosphorylation. In this review, we address the metabolic changes in the diabetic heart, focusing on the loss of metabolic flexibility and cardiac mitochondrial function. We consider the alterations observed in mitochondrial substrate utilization, bioenergetics and dynamics, and highlight new areas of research which may improve our understanding of the cause and effect of cardiac mitochondrial dysfunction in diabetes. Finally, we explore how lifestyle (nutrition and exercise) and pharmacological interventions can prevent and treat metabolic and mitochondrial dysfunction in diabetes.

Smooth Muscle Contact Drives Endothelial Regeneration by BMPR2-Notch1-Mediated Metabolic and Epigenetic Changes

RATIONALE

Maintaining endothelial cells (EC) as a monolayer in the vessel wall depends on their metabolic state and gene expression profile, features influenced by contact with neighboring cells such as pericytes and smooth muscle cells (SMC). Failure to regenerate a normal EC monolayer in response to injury can result in occlusive neointima formation in diseases such as atherosclerosis and pulmonary arterial hypertension.

OBJECTIVE

We investigated the nature and functional importance of contact-dependent communication between SMC and EC to maintain EC integrity.

METHODS AND RESULTS

We found that in SMC and EC contact cocultures, BMPR2 (bone morphogenetic protein receptor 2) is required by both cell types to produce collagen IV to activate ILK (integrin-linked kinase). This enzyme directs p-JNK (phospho-c-Jun N-terminal kinase) to the EC membrane, where it stabilizes presenilin1 and releases N1ICD (Notch1 intracellular domain) to promote EC proliferation. This response is necessary for EC regeneration after carotid artery injury. It is deficient in EC-SMC Bmpr2 double heterozygous mice in association with reduced collagen IV production, decreased N1ICD, and attenuated EC proliferation, but can be rescued by targeting N1ICD to EC. Deletion of EC- Notch1 in transgenic mice worsens hypoxia-induced pulmonary hypertension, in association with impaired EC regenerative function associated with loss of precapillary arteries. We further determined that N1ICD maintains EC proliferative capacity by increasing mitochondrial mass and by inducing the phosphofructokinase PFKFB3 (fructose-2,6-bisphosphatase 3). Chromatin immunoprecipitation sequencing analyses showed that PFKFB3 is required for citrate-dependent H3K27 acetylation at enhancer sites of genes regulated by the acetyl transferase p300 and by N1ICD or the N1ICD target MYC and necessary for EC proliferation and homeostasis.

CONCLUSIONS

Thus, SMC-EC contact is required for activation of Notch1 by BMPR2, to coordinate metabolism with chromatin remodeling of genes that enable EC regeneration, and to maintain monolayer integrity and vascular homeostasis in response to injury.

PGC-1α activation: a therapeutic target for type 2 diabetes?

Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) has gained popularity as a very attractive target for diabetic therapies due to its role in lipid and glucose metabolism. Pharmacological activation of PGC-1α is thought to elicit health benefits. However, this notion has been questioned by increasing evidence, which suggests that insulin resistant is exacerbated when PGC-1α expression is far beyond normal physiological limits and is prevented under the condition of PGC-1α deficiency. This narrative review suggests that PGC-1α, as a master metabolic regulator, exerts roles in insulin sensitivity in a tissue-specific manner and in a physical activity/age-dependent fashion. When using PGC-1α as a target for therapeutic strategies against insulin resistance and T2DM, we should take these factors into consideration.Level of evidence: Level V, narrative review.

Aldehyde Dehydrogenase (ALDH) 2 in Diabetic Heart Diseases

A major pathophysiological mechanism behind the development of diabetic heart diseases is oxidative stress mediated by toxic reactive aldehydes such as 4-hydroxynonenal (4HNE). Aldehyde dehydrogenase (ALDH) 2 is a mitochondrial enzyme that has been found to detoxify these deleterious aldehydes and thereby mitigate cardiac damage. Furthermore, its protective role in cellular signaling reverses aberrations caused by hyperglycemia, thereby protecting cardiac function. This chapter assesses the role of ALDH2 in diabetic heart diseases by examining preclinical studies where ALDH2 activity is perturbed in both decreased and increased directions. In doing so, issues in improving ALDH2 activity in select human populations are elucidated, and further research directions are discussed.

Blossoming 20: The Energetic Regulator's Birthday Unveils its Versatility in Cardiac Diseases

The peroxisome proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α) was first identified in 1998 as a PGC-1 family member that regulates adaptive thermogenesis and mitochondrial function following cold exposure in brown adipose tissue. The PGC-1 family has drawn widespread attention over the past two decades as the energetic regulator. We recently summarized a review regarding PGC-1 signaling pathway and its mechanisms in cardiac metabolism. In this review, we elaborate upon the PGC-1 signaling network and highlight the recent progress of its versatile roles in cardiac diseases, including myocardial hypertrophy, peripartum and diabetic cardiomyopathy, and heart failure. The information reviewed here may be useful in future studies, which may increase the potential of this energetic regulator as a therapeutic target.

MD1 Deficiency Promotes Inflammatory Atrial Remodelling Induced by High-Fat Diets

BACKGROUND

Myeloid differentiation protein 1 (MD1) is expressed in various tissues, including the heart. However, the role of MD1 in obesity-related atrial remodelling remains incompletely understood. Here, this study intends to determine the regulatory role and underlying mechanisms of MD1 in obesity-related atrial remodelling.

METHODS

A high-fat diet (HFD) feeding was performed in 6-week-old MD1-knockout (MD1-KO) mice and wild-type (WT) littermates for 20 weeks. Morphological, biochemical, functional, histological, and electrophysiological studies were conducted at the age of 26 weeks.

RESULTS

Our results revealed that the MD1 expression levels were downregulated in the atrium of the HFD-fed induced obesity mice. An increase in body weight, glucose intolerance, hyperlipidemia, and adverse atrial remodelling, such as atrial inflammation and fibrosis, were induced by HFD feeding in WT mice. Vulnerability to atrial fibrillation (AF) was also significantly increased by HFD feeding in WT mice. In addition, these adverse effects caused by HFD-fed induced obesity were further exaggerated in MD1-KO mice compared with WT mice. Mechanistically, MD1-KO activated TLR4/NF-κB signaling pathways, which led to atrial remodelling in mice fed by HFD by increasing the phosphorylation of p65 and IκBα.

CONCLUSIONS

Our data suggested that MD1 deficiency played an important role in accelerating the development of inflammatory atrial fibrosis and increasing vulnerability to AF in mice with HFD-fed induced obesity, providing an essential target for improving HFD-induced atrial remodelling.

Beneficial Autophagic Activities, Mitochondrial Function, and Metabolic Phenotype Adaptations Promoted by High-Intensity Interval Training in a Rat Model

The effects of high-intensity interval (HIIT) and moderate-intensity continuous training (MICT) on basal autophagy and mitochondrial function in cardiac and skeletal muscle and plasma metabolic phenotypes have not been clearly characterized. Here, we investigated how 10-weeks HIIT and MICT differentially modify basal autophagy and mitochondrial markers in cardiac and skeletal muscle and conducted an untargeted metabolomics study with proton nuclear magnetic resonance (¹H NMR) spectroscopy and multivariate statistical analysis of plasma metabolic phenotypes. Male Sprague–Dawley rats were separated into three groups: sedentary control (SED), MICT, and HIIT. Rats underwent evaluation of exercise performance, including exercise tolerance and grip strength, and blood lactate levels were measured immediately after an incremental exercise test. Plasma samples were analyzed by ¹H NMR. The expression of autophagy and mitochondrial markers and autophagic flux (LC3II/LC3-I ratio) in cardiac, rectus femoris, and soleus muscle were analyzed by western blotting. Time to exhaustion and grip strength increased significantly following HIIT compared with that in both SED and MICT groups. Compared with those in the SED group, blood lactate level, and the expression of SDH, COX-IV, and SIRT3 significantly increased in rectus femoris and soleus muscle of both HIIT and MICT groups. Meanwhile, SDH and COX-IV content of cardiac muscle and COX-IV and SIRT3 content of rectus femoris and soleus muscle increased significantly following HIIT compared with that following MICT. The expression of LC3-II, ATG-3, and Beclin-1 and LC3II/LC3-I ratio were significantly increased only in soleus and cardiac muscle following HIIT. These data indicate that HIIT was more effective for improving physical performance and facilitating cardiac and skeletal muscle adaptations that increase mitochondrial function and basal autophagic activities. Moreover, ¹H NMR spectroscopy and multivariate statistical analysis identified 11 metabolites in plasma, among which fine significantly and similarly changed after both HIIT and MICT, while BCAAs isoleucine, leucine, and valine and glutamine were changed only after HIIT. Together, these data indicate distinct differences in specific metabolites and autophagy and mitochondrial markers following HIIT vs. MICT and highlight the value of metabolomic analysis in providing more detailed insight into the metabolic adaptations to exercise training.

ALDH2 protects against high fat diet-induced obesity cardiomyopathy and defective autophagy: role of CaM kinase II, histone H3K9 methyltransferase SUV39H, Sirt1, and PGC-1α deacetylation

BACKGROUND AND AIMS

Uncorrected obesity contributes to cardiac remodeling and contractile dysfunction although the underlying mechanism remains poorly understood. Mitochondrial aldehyde dehydrogenase (ALDH2) is a mitochondrial enzyme with some promises in a number of cardiovascular diseases. This study was designed to evaluate the impact of ALDH2 on cardiac remodeling and contractile property in high fat diet-induced obesity.

METHODS

Wild-type (WT) and ALDH2 transgenic mice were fed low (10% calorie from fat) or high (45% calorie from fat) fat diet for 5 months prior to the assessment of cardiac geometry and function using echocardiography, IonOptix system, Lectin, and Masson Trichrome staining. Western blot analysis was employed to evaluate autophagy, CaM kinase II, PGC-1α, histone H3K9 methyltransferase SUV39H, and Sirt-1.

RESULTS

Our data revealed that high fat diet intake promoted weight gain, cardiac remodeling (hypertrophy and interstitial fibrosis, p < 0.0001) and contractile dysfunction (reduced fractional shortening (p < 0.0001), cardiomyocyte function (p < 0.0001), and intracellular Ca²⁺ handling (p = 0.0346)), mitochondrial injury (elevated O₂^- levels, suppressed PGC-1α, and enhanced PGC-1α acetylation, p < 0.0001), elevated SUV39H, suppressed Sirt1, autophagy and phosphorylation of AMPK and CaM kinase II, the effects of which were negated by ALDH2 (p ≤ 0.0162). In vitro incubation of the ALDH2 activator Alda-1 rescued against palmitic acid-induced changes in cardiomyocyte function, the effect of which was nullified by the Sirt-1 inhibitor nicotinamide and the CaM kinase II inhibitor KN-93 (p < 0.0001). The SUV39H inhibitor chaetocin mimicked Alda-1-induced protection again palmitic acid (p < 0.0001). Examination in overweight human revealed an inverse correlation between diastolic cardiac function and ALDH2 gene mutation (p < 0.05).

CONCLUSIONS

Taken together, these data suggest that ALDH2 serves as an indispensable factor against cardiac anomalies in diet-induced obesity through a mechanism related to autophagy regulation and facilitation of the SUV39H-Sirt1-dependent PGC-1α deacetylation.

The potential of aldehyde dehydrogenase 2 as a therapeutic target in cardiovascular disease

INTRODUCTION

Mitochondrial aldehyde dehydrogenase (ALDH-2) plays a major role in the ethanol detoxification pathway by removing acetaldehyde. Therefore, ALDH-2 inhibitors such as disulfiram represent the first therapeutic targeting of ALDH-2 for alcoholism therapy. Areas covered: Recently, ALDH-2 was identified as an essential bioactivating enzyme of the anti-ischemic organic nitrate nitroglycerin, bringing ALDH-2 again into the focus of clinical interest. Mechanistic studies on the nitroglycerin bioactivation process revealed that during bioconversion of nitroglycerin and in the presence of reactive oxygen and nitrogen species the active site thiols of ALDH-2 are oxidized and the enzyme activity is lost. Thus, ALDH-2 activity represents a useful marker for cardiovascular oxidative stress, a concept, which has been meanwhile supported by a number of animal disease models. Mechanistic studies on the protective role of ALDH-2 in different disease processes identified the detoxification of 4-hydroxynonenal by ALDH-2 as a fundamental process of cardiovascular, cerebral and antioxidant protection. Expert opinion: The most recent therapeutic exploitation of ALDH-2 includes activators of the enzyme such as Alda-1 but also cell-based therapies (ALDH-bright cells) that deserve further clinical characterization in the future.

SIRT3: A New Regulator of Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading causes of death worldwide, and defects in mitochondrial function contribute largely to the occurrence of CVDs. Recent studies suggest that sirtuin 3 (SIRT3), the mitochondrial NAD⁺-dependent deacetylase, may regulate mitochondrial function and biosynthetic pathways such as glucose and fatty acid metabolism and the tricarboxylic acid (TCA) cycle, oxidative stress, and apoptosis by reversible protein lysine deacetylation. SIRT3 regulates glucose and lipid metabolism and maintains myocardial ATP levels, which protects the heart from metabolic disturbances. SIRT3 can also protect cardiomyocytes from oxidative stress-mediated cell damage and block the development of cardiac hypertrophy. Recent reports show that SIRT3 is involved in the protection of several heart diseases. This review discusses the progress in SIRT3-related research and the role of SIRT3 in the prevention and treatment of CVDs.

Resveratrol alleviates diabetic cardiomyopathy in rats by improving mitochondrial function through PGC-1α deacetylation

Recent evidence shows that resveratrol (RSV) may ameliorate high-glucose-induced cardiac oxidative stress, mitochondrial dysfunction and myocardial fibrosis in diabetes. However, the mechanisms by which RSV regulates mitochondrial function in diabetic cardiomyopathy have not been fully elucidated. Mitochondrial dysfunction contributes to cardiac dysfunction in diabetic patients, which is associated with dysregulation of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α). In this study we examined whether resveratrol alleviated cardiac dysfunction in diabetes by improving mitochondrial function via SIRT1-mediated PGC-1α deacetylation. T2DM was induced in rats by a high-fat diet combined with STZ injection. Diabetic rats were orally administered RSV (50 mg·kg^-1·d^-1) for 16 weeks. RSV administration significantly attenuated diabetes-induced cardiac dysfunction and hypertrophy evidenced by increasing ejection fraction (EF%), fraction shortening (FS%), ratio of early diastolic peak velocity (E velocity) and late diastolic peak velocity (A velocity) of the LV inflow (E/A ratio) and reducing expression levels of pro-hypertrophic markers ANP, BNP and β-MHC. Furthermore, manganese superoxide dismutase (SOD) activity, ATP content, mitochondrial DNA copy number, mitochondrial membrane potential and the expression of nuclear respiration factor (NRF) were all significantly increased in diabetic hearts by RSV administration, whereas the levels of malondialdehvde (MDA) and uncoupling protein 2 (UCP2) were significantly decreased. Moreover, RSV administration significantly activated SIRT1 expression and increased PGC-1α deacetylation. H9c2 cells cultured in a high glucose (HG, 30 mmol/L) condition were used for further analyzing the role of SIRT1/PGC-1α pathway in RSV regulation of mitochondrial function. RSV (20 μmol/L) caused similar beneficial effects in HG-treated H9c2 cells in vitro as in diabetic rats, but these protective effects were abolished by addition of a SIRT1 inhibitor sirtinol (25 μmol/L) or by SIRT1 siRNA transfection. In H9c2 cells, RSV-induced PGC-1α deacetylation was dependent on SIRT1, which was also abolished by a SIRT1 inhibitor and SIRT1 siRNA transfection. Our results demonstrate that resveratrol attenuates cardiac injury in diabetic rats through regulation of mitochondrial function, which is mediated partly through SIRT1 activation and increased PGC-1α deacetylation.

Regulation of Sirtuin-Mediated Protein Deacetylation by Cardioprotective Phytochemicals

Modulation of posttranslational modifications (PTMs), such as protein acetylation, is considered a novel therapeutic strategy to combat the development and progression of cardiovascular diseases. Protein hyperacetylation is associated with the development of numerous cardiovascular diseases, including atherosclerosis, hypertension, cardiac hypertrophy, and heart failure. In addition, decreased expression and activity of the deacetylases Sirt1, Sirt3, and Sirt6 have been linked to the development and progression of cardiac dysfunction. Several phytochemicals exert cardioprotective effects by regulating protein acetylation levels. These effects are mainly exerted via activation of Sirt1 and Sirt3 and inhibition of acetyltransferases. Numerous studies support a cardioprotective role for sirtuin activators (e.g., resveratrol), as well as other emerging modulators of protein acetylation, including curcumin, honokiol, oroxilyn A, quercetin, epigallocatechin-3-gallate, bakuchiol, tyrosol, and berberine. Studies also point to a cardioprotective role for various nonaromatic molecules, such as docosahexaenoic acid, alpha-lipoic acid, sulforaphane, and caffeic acid ethanolamide. Here, we review the vast evidence from the bench to the clinical setting for the potential cardioprotective roles of various phytochemicals in the modulation of sirtuin-mediated deacetylation.

ALDH2 restores exhaustive exercise-induced mitochondrial dysfunction in skeletal muscle

BACKGROUND

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is highly expressed in heart and skeletal muscles, and is the major enzyme that metabolizes acetaldehyde and toxic aldehydes. The cardioprotective effects of ALDH2 during cardiac ischemia/reperfusion injury have been recognized. However, less is known about the function of ALDH2 in skeletal muscle. This study was designed to evaluate the effect of ALDH2 on exhaustive exercise-induced skeletal muscle injury.

METHODS

We created transgenic mice expressing ALDH2 in skeletal muscles. Male wild-type C57/BL6 (WT) and ALDH2 transgenic mice (ALDH2-Tg), 8-weeks old, were challenged with exhaustive exercise for 1 week to induce skeletal muscle injury. Animals were sacrificed 24 h post-exercise and muscle tissue was excised.

RESULTS

ALDH2-Tg mice displayed significantly increased treadmill exercise capacity compared to WT mice. Exhaustive exercise caused an increase in mRNA levels of the muscle atrophy markers, Atrogin-1 and MuRF1, and reduced mitochondrial biogenesis and fusion in WT skeletal muscles; these effects were attenuated in ALDH2-Tg mice. Exhaustive exercise also enhanced mitochondrial autophagy pathway activity, including increased conversion of LC3-I to LC3-II and greater expression of Beclin1 and Bnip3; the effects of which were mitigated by ALDH2 overexpression. In addition, ALDH2-Tg reversed the increase of an oxidative stress biomarker (4-hydroxynonenal) and decreased levels of mitochondrial antioxidant proteins, including manganese superoxide dismutase and NAD(P)H:quinone oxidoreductase 1, in skeletal muscle induced by exhaustive exercise.

CONCLUSION

ALDH2 may reverse skeletal muscle mitochondrial dysfunction due to exhaustive exercise by regulating mitochondria dynamic remodeling and enhancing the quality of mitochondria.