Catalase alleviates cardiomyocyte dysfunction in diabetes: role of Akt, Forkhead transcriptional factor and silent information regulator 2

Vasodilator reactive oxygen species ameliorate perturbed myocardial oxygen delivery in exercising swine with multiple comorbidities

Multiple common cardiovascular comorbidities produce coronary microvascular dysfunction. We previously observed in swine that a combination of diabetes mellitus (DM), high fat diet (HFD) and chronic kidney disease (CKD) induced systemic inflammation, increased oxidative stress and produced coronary endothelial dysfunction, altering control of coronary microvascular tone via loss of NO bioavailability, which was associated with an increase in circulating endothelin (ET). In the present study, we tested the hypotheses that (1) ROS scavenging and (2) ETA+B-receptor blockade improve myocardial oxygen delivery in the same female swine model. Healthy female swine on normal pig chow served as controls (Normal). Five months after induction of DM (streptozotocin, 3 × 50 mg kg-1 i.v.), hypercholesterolemia (HFD) and CKD (renal embolization), swine were chronically instrumented and studied at rest and during exercise. Sustained hyperglycemia, hypercholesterolemia and renal dysfunction were accompanied by systemic inflammation and oxidative stress. In vivo ROS scavenging (TEMPOL + MPG) reduced myocardial oxygen delivery in DM + HFD + CKD swine, suggestive of a vasodilator influence of endogenous ROS, while it had no effect in Normal swine. In vitro wire myography revealed a vasodilator role for hydrogen peroxide (H2O2) in isolated small coronary artery segments from DM + HFD + CKD, but not Normal swine. Increased catalase activity and ceramide production in left ventricular myocardial tissue of DM + HFD + CKD swine further suggest that increased H2O2 acts as vasodilator ROS in the coronary microvasculature. Despite elevated ET-1 plasma levels in DM + HFD + CKD swine, ETA+B blockade did not affect myocardial oxygen delivery in Normal or DM + HFD + CKD swine. In conclusion, loss of NO bioavailability due to 5 months exposure to multiple comorbidities is partially compensated by increased H2O2-mediated coronary vasodilation.

Mitochondrial aldehyde dehydrogenase rescues against diabetic cardiomyopathy through GSK3β-mediated preservation of mitochondrial integrity and Parkin-mediated mitophagy

Mitochondrial aldehyde dehydrogenase (ALDH2) offers proven cardiovascular benefit, although its impact on diabetes remains elusive. This study examined the effects of ALDH2 overexpression and knockout on diabetic cardiomyopathy and the mechanism involved with a focus on mitochondrial integrity. Mice challenged with streptozotocin (STZ, 200 mg/kg, via intraperitoneal injection) exhibited pathological alterations, including reduced respiratory exchange ratio, dampened fractional shortening and ejection fraction, increased left ventricular end-systolic and diastolic diameters, cardiac remodeling, cardiomyocyte contractile anomalies, intracellular Ca2+ defects, myocardial ultrastructural injury, oxidative stress, apoptosis, and mitochondrial damage, which were overtly attenuated or accentuated by ALDH2 overexpression or knockout, respectively. Diabetic patients also exhibited reduced plasma ALDH2 activity, cardiac remodeling, and diastolic dysfunction. In addition, STZ challenge altered expression levels of mitochondrial proteins (PGC-1α and UCP2) and Ca2+ regulatory proteins (SERCA, Na+-Ca2+ exchanger, and phospholamban), dampened autophagy and mitophagy (LC3B ratio, TOM20, Parkin, FUNDC1, and BNIP3), disrupted phosphorylation of Akt, GSK3β, and Foxo3a, and elevated PTEN phosphorylation, most of which were reversed or worsened by ALDH2 overexpression or knockout, respectively. Furthermore, the novel ALDH2 activator torezolid, as well as the classical ALDH2 activator Alda-1, protected against STZ- or high glucose-induced in vivo or in vitro cardiac anomalies, which was nullified by inhibition of Akt, GSK3β, Parkin, or mitochondrial coupling. Our data discerned a vital role for ALDH2 in diabetic cardiomyopathy possibly through regulation of Akt and GSK3β activation, Parkin mitophagy, and mitochondrial function.

Cardiac-specific overexpression of catalase attenuates lipopolysaccharide-induced cardiac anomalies through reconciliation of autophagy and ferroptosis

Lipopolysaccharide (LPS) from Gram-negative bacteria is a major contributor to cardiovascular failure, but the signaling mechanisms underlying its stress response are not fully understood. This study aimed to investigate the effect of the antioxidant enzyme catalase on LPS-induced cardiac abnormalities and the mechanisms involved, with particular focus on the interplay between autophagy, ferroptosis, and apoptosis. Cardiac-specific catalase (CAT) overexpression and wild-type (WT) mice were stimulated with LPS (6 mg/kg, intravenous injection), and cardiac morphology and function were evaluated. Oxidative stress, ferroptosis, apoptosis, and mitochondrial status were monitored, and survival curves were plotted based on the results of LPS stimulation. The results showed that, compared with WT mice, mice overexpressing catalase had a higher survival rate under LPS stimulation. Ultrasound echocardiography, cardiomyocyte characteristics, and Masson's trichrome staining showed that LPS inhibited cardiac function and caused cardiac fibrosis, while catalase alleviated these adverse effects. LPS increased apoptosis (TUNEL, caspase-3 activation, cleaved caspase-3), increased O₂^·- production, induced inflammation (TNF-α), autophagy, iron toxicity, and carbonyl damage, and significantly damaged mitochondria (mitochondrial membrane potential, mitochondrial proteins, and ultrastructure). These effects were significantly alleviated by catalase. Interestingly, the antioxidant N-acetylcysteine, autophagy inhibitor 3-methyladenine, and ferroptosis inhibitor lipostatin-1 all eliminated the LPS-induced contraction dysfunction and ferroptosis (using lipid peroxidation). Induction of ferroptosis could eliminate the cardioprotective effect of NAC. In conclusion, catalase rescues LPS-induced cardiac dysfunction by regulating oxidative stress, autophagy, ferroptosis, apoptosis, and mitochondrial damage in cardiomyocytes.

Energy substrate metabolism and oxidative stress in metabolic cardiomyopathy

Metabolic cardiomyopathy is an emerging cause of heart failure in patients with obesity, insulin resistance, and diabetes. It is characterized by impaired myocardial metabolic flexibility, intramyocardial triglyceride accumulation, and lipotoxic damage in association with structural and functional alterations of the heart, unrelated to hypertension, coronary artery disease, and other cardiovascular diseases. Oxidative stress plays an important role in the development and progression of metabolic cardiomyopathy. Mitochondria are the most significant sources of reactive oxygen species (ROS) in cardiomyocytes. Disturbances in myocardial substrate metabolism induce mitochondrial adaptation and dysfunction, manifested as a mismatch between mitochondrial fatty acid oxidation and the electron transport chain (ETC) activity, which facilitates ROS production within the ETC components. In addition, non-ETC sources of mitochondrial ROS, such as β-oxidation of fatty acids, may also produce a considerable quantity of ROS in metabolic cardiomyopathy. Augmented ROS production in cardiomyocytes can induce a variety of effects, including the programming of myocardial energy substrate metabolism, modulation of metabolic inflammation, redox modification of ion channels and transporters, and cardiomyocyte apoptosis, ultimately leading to the structural and functional alterations of the heart. Based on the above mechanistic views, the present review summarizes the current understanding of the mechanisms underlying metabolic cardiomyopathy, focusing on the role of oxidative stress.

Cardiac Acetylation in Metabolic Diseases

Lysine acetylation is a highly conserved mechanism that affects several biological processes such as cell growth, metabolism, enzymatic activity, subcellular localization of proteins, gene transcription or chromatin structure. This post-translational modification, mainly regulated by lysine acetyltransferase (KAT) and lysine deacetylase (KDAC) enzymes, can occur on histone or non-histone proteins. Several studies have demonstrated that dysregulated acetylation is involved in cardiac dysfunction, associated with metabolic disorder or heart failure. Since the prevalence of obesity, type 2 diabetes or heart failure rises and represents a major cause of cardiovascular morbidity and mortality worldwide, cardiac acetylation may constitute a crucial pathway that could contribute to disease development. In this review, we summarize the mechanisms involved in the regulation of cardiac acetylation and its roles in physiological conditions. In addition, we highlight the effects of cardiac acetylation in physiopathology, with a focus on obesity, type 2 diabetes and heart failure. This review sheds light on the major role of acetylation in cardiovascular diseases and emphasizes KATs and KDACs as potential therapeutic targets for heart failure.

Genes and Longevity of Lifespan

Aging is a complex process indicated by low energy levels, declined physiological activity, stress induced loss of homeostasis leading to the risk of diseases and mortality. Recent developments in medical sciences and an increased availability of nutritional requirements has significantly increased the average human lifespan worldwide. Several environmental and physiological factors contribute to the aging process. However, about 40% human life expectancy is inherited among generations, many lifespan associated genes, genetic mechanisms and pathways have been demonstrated during last decades. In the present review, we have evaluated many human genes and their non-human orthologs established for their role in the regulation of lifespan. The study has included more than fifty genes reported in the literature for their contributions to the longevity of life. Intact genomic DNA is essential for the life activities at the level of cell, tissue, and organ. Nucleic acids are vulnerable to oxidative stress, chemotherapies, and exposure to radiations. Efficient DNA repair mechanisms are essential for the maintenance of genomic integrity, damaged DNA is not replicated and transferred to next generations rather the presence of deleterious DNA initiates signaling cascades leading to the cell cycle arrest or apoptosis. DNA modifications, DNA methylation, histone methylation, histone acetylation and DNA damage can eventually lead towards apoptosis. The importance of calorie restriction therapy in the extension of lifespan has also been discussed. The role of pathways involved in the regulation of lifespan such as DAF-16/FOXO (forkhead box protein O1), TOR and JNK pathways has also been particularized. The study provides an updated account of genetic factors associated with the extended lifespan and their interactive contributory role with cellular pathways.

The Mystery of Diabetic Cardiomyopathy: From Early Concepts and Underlying Mechanisms to Novel Therapeutic Possibilities

Diabetic patients are predisposed to diabetic cardiomyopathy, a specific form of cardiomyopathy which is characterized by the development of myocardial fibrosis, cardiomyocyte hypertrophy, and apoptosis that develops independently of concomitant macrovascular and microvascular diabetic complications. Its pathophysiology is multifactorial and poorly understood and no specific therapeutic guideline has yet been established. Diabetic cardiomyopathy is a challenging diagnosis, made after excluding other potential entities, treated with different pharmacotherapeutic agents targeting various pathophysiological pathways that need yet to be unraveled. It has great clinical importance as diabetes is a disease with pandemic proportions. This review focuses on the potential mechanisms contributing to this entity, diagnostic options, as well as on potential therapeutic interventions taking in consideration their clinical feasibility and limitations in everyday practice. Besides conventional therapies, we discuss novel therapeutic possibilities that have not yet been translated into clinical practice.

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.

SUMOylation is essential for Sirt2 tumor-suppressor function in neuroblastoma

SUMOylation is an important post-translational modification that participates in a variety of cellular physiological and pathological processes in eukaryotic cells. Sirt2, a NAD⁺-dependent deacetylase, usually exerts a tumor-suppressor function. However, the role of SUMOylation in cancer cells is not fully known. In this study, we found that SUMOylation can occur in the Sirt2 protein at both lysine 183 and lysine 340 sites. SUMOylation did not affect Sirt2 localization or stability but was involved in P38-mTORC2-AKT cellular signal transduction via direct deacetylation on a new substrate MAPK/P38. SUMOylation-deficient Sirt2 lost the capability of suppressing tumor processes and showed resistance to the Sirt2-specific inhibitor AK-7 in neuroblastoma cells. Here, we revealed the important function of Sirt2-SUMOylation, which is closely associated with cellular signal transduction and is essential for suppressing tumorigenesis in neuroblastoma.

Diabetic Cardiomyopathy: From Mechanism to Management in a Nutshell

Diabetic cardiomyopathy (DCM) is a significant complication of diabetes mellitus characterized by gradually failing heart with detrimental cardiac remodelings, such as fibrosis and diastolic and systolic dysfunction, which is not directly attributable to coronary artery disease. Insulin resistance and resulting hyperglycemia is the main trigger involved in the initiation of diabetic cardiomyopathy. There is a constellation of many pathophysiological events, such as lipotoxicity, oxidative stress, inflammation, inappropriate activation of the renin-angiotensin-aldosterone system, dysfunctional immune modulation promoting increased rate of cardiac cell injury, apoptosis, and necrosis, which ultimately culminates into interstitial fibrosis, cardiac stiffness, diastolic dysfunction, initially, and later systolic dysfunction too. These events finally lead to clinical heart failure of DCM. Herein, The pathophysiology of DCM is briefly discussed. Furthermore, potential therapeutic strategies currently used for DCM are also briefly mentioned.

MicroRNA-140-5p aggravates hypertension and oxidative stress of atherosclerosis via targeting Nrf2 and Sirt2

In the present study, the function of microRNA (miR)-140-5p on oxidative stress in mice with atherosclerosis was investigated. A reverse transcription-quantitative polymerase chain reaction assay was used to determine the expression of miR-140-5p. Oxidative stress kits and reactive oxygen species (ROS) kits were used to analyze alterations in oxidative stress and ROS levels. The alterations in protein expression were determined using western blot analysis and an immunofluorescence assay. miR-140-5p expression was increased in mice with atherosclerosis with hypertension. Consistently, miR-140-5p expression was also increased in mice with atherosclerosis. Upregulation of miR-140-5p increased oxidative stress and ROS levels by suppressing the protein expression of nuclear factor erythroid 2-related factor 2 (Nrf2), sirtuin 2 (Sirt2), Kelch-like enoyl-CoA hydratase-associated protein 1 (Keap1) and heme oxygenase 1 (HO-1) in vitro. By contrast, downregulation of miR-140-5p decreased oxidative stress and ROS levels by activating the protein expression of Nrf2, Sirt2, Keap1 and HO-1 in vitro. Sirt2 agonist or Nrf2 agonist inhibited the effects of miR-140-5p on oxidative stress in vitro. Collectively, these results suggested that miR-140-5p aggravated hypertension and oxidative stress of mice with atherosclerosis by targeting Nrf2 and Sirt2.

Pathophysiology of cardiovascular disease in diabetes mellitus

Diabetes mellitus elicits cellular, epigenetic, and post-translational changes that directly or indirectly affect the biology of the vasculature and other metabolic systems resulting in the apparition of cardiovascular disease. In this review, we provide a current perspective on the most recent discoveries in this field, with particular focus on hyperglycemia- induced pathology in the cardiovascular system. We also provide perspective on the clinical importance of molecular targeting of cardiovascular and diabetes mellitus therapies to treat hyperglycemia, inflammation, thrombosis, dyslipidemia, atherosclerosis, and hypertension.

Amelioration of streptozotocin‑induced pancreatic β cell damage by morin: Involvement of the AMPK‑FOXO3‑catalase signaling pathway

Pancreatic β cells are sensitive to oxidative stress, which is one of the predominant causes of cell damage and the emergence of diabetes. The identification of effective therapeutic strategies to protect pancreatic cells from oxidative stress has increased interest in the screening of antioxidants from natural products. The present study aimed to investigate the protective effects of morin against streptozotocin (STZ)‑induced cell damage in a rat insulinoma cell line (RINm5F pancreatic β cells) and to identify the underlying mechanisms. The results indicated that morin inhibited the increase in intracellular reactive oxygen species, attenuated the activity of poly (ADP‑ribose) polymerase, restored intracellular nicotinamide adenine dinucleotide levels and reduced the apoptotic cell death of STZ‑treated pancreatic β cells. Treatment with morin significantly upregulated catalase in pancreatic β cells, and ameliorated the STZ‑induced loss of catalase at the genetic, protein and enzymatic level. In further experiments, morin induced the phosphorylation of 5' adenosine monophosphate‑activated protein kinase (AMPK), which subsequently promoted the translocation of forkhead box O3 (FOXO3) to the nucleus. Specific small interfering RNAs (siRNAs) against AMPK and FOXO3 suppressed morin‑induced catalase expression. Furthermore, catalase‑specific siRNA abolished the protective effects of morin against STZ‑stimulated cell death. Taken together, these results indicated that morin protected RINm5F cells from STZ‑induced cell damage by triggering the phosphorylation of AMPK, thus resulting in subsequent activation of FOXO3 and induction of catalase.

Inhibition of advanced glycation endproduct (AGE) rescues against streptozotocin-induced diabetic cardiomyopathy: Role of autophagy and ER stress

Diabetes mellitus leads to oxidative stress and contractile dysfunction in the heart. Although several rationales have been speculated, the precise mechanism behind diabetic cardiomyopathy remains elusive. This study was designed to assess the role of inhibition of advanced glycation endproducts (AGE) in streptozotocin (STZ)-induced diabetic cardiac dysfunction. Cardiac contractile function was assessed in normal C57BL/6 and STZ (200mg/kg, single injection and maintained for 2 wks)-induced diabetic mice treated with or without the AGE inhibitor aminoguanidine (50mg/kg/d in drinking water) for 2 weeks using echocardiography and IonOptix MyoCam techniques. Diabetes compromised cardiac contractile function shown as reduced fractional shortening and ejection fraction, enlarged left ventricular end systolic/diastolic diameters, decreased peak shortening, maximal velocity of shortening/relengthening, prolonged shortening and relengthening duration as well as impaired intracellular Ca²⁺ homeostasis, the effects of which were alleviated or reversed by aminoguanidine treatment. Diabetes also inhibited autophagy, increased ER stress and phosphorylation of pro-hypertrophic signaling molecules Akt and mTOR, the effect of which was reversed by aminoguanidine. In vitro study revealed that methylglyoxal-derived AGE (MG-AGE) incubation in isolated cardiomyocytes promoted oxidation of sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA2a) and production of superoxide, the effects of which were negated by the autophagy inducer rapamycin, the ER stress chaperone TUDCA or the antioxidant N-acetylcysteine. Taken together, these data revealed that inhibition of AGE formation rescues against experimental diabetes-induced cardiac remodeling and contractile dysfunction possible through regulation of autophagy and ER stress.

Antioxidants: Friend or foe?

Reactive oxygen species are the intermediates that are formed during the normal metabolic process which are effectively neutralized by the antioxidant system of the body. Any imbalance in this neutralization process causes oxidative stress which has been implicated as one of the cause in diseases such as Alzheimer's disease, cardiovascular disorders, cancer etc. Research has enabled the use of antioxidants as therapeutic agents in the treatment of various diseases. Literature also puts forth the negative effects of using antioxidants in the treatment of diseases. This review is a compilation of both the beneficial and detrimental effects of use of antioxidants in the treatment of diseases such as cancer, cardiovascular diseases, diabetes and oral diseases.

Catalase, a remarkable enzyme: targeting the oldest antioxidant enzyme to find a new cancer treatment approach

This review is centered on the antioxidant enzyme catalase and will present different aspects of this particular protein. Among them: historical discovery, biological functions, types of catalases and recent data with regard to molecular mechanisms regulating its expression. The main goal is to understand the biological consequences of chronic exposure of cells to hydrogen peroxide leading to cellular adaptation. Such issues are of the utmost importance with potential therapeutic extrapolation for various pathologies. Catalase is a key enzyme in the metabolism of H2O2 and reactive nitrogen species, and its expression and localization is markedly altered in tumors. The molecular mechanisms regulating the expression of catalase, the oldest known and first discovered antioxidant enzyme, are not completely elucidated. As cancer cells are characterized by an increased production of reactive oxygen species (ROS) and a rather altered expression of antioxidant enzymes, these characteristics represent an advantage in terms of cell proliferation. Meanwhile, they render cancer cells particularly sensitive to an oxidant insult. In this context, targeting the redox status of cancer cells by modulating catalase expression is emerging as a novel approach to potentiate chemotherapy.

Glucose variability aggravates cardiac fibrosis by altering AKT signalling path

OBJECTIVE

To study the effect of blood glucose variability on cardiac fibrosis and its mechanism in a model of diabetic cardiomyopathy.

METHODS

A total of 45 Sprague Dawley rats were randomly divided into three groups: control, control diabetes mellitus and fluctuated blood glucose groups. Fluctuated blood glucose was induced by daily subcutaneous insulin and intraperitoneal glucose injections at different time points. Blood lipids and glycosylated haemoglobin A1c were assessed. Super oxide dismutase activity and malondialdehyde level in rat heart homogenates were determined by assay kit. Structural cardiac tissue changes were observed by haematoxylin and eosin staining and Masson's trichrome staining. Collagen type 3, fibronectin, phosphorylated Ser/Thr protein kinase, phosphorylated glycogen synthase kinase-3 beta, glycogen synthase kinase-3 beta, nuclear factor kappa-light-chain-enhancer of activated B cells, cleaved-cysteinyl aspartate-specific proteinase-3 (caspase-3) and tumour necrosis factor-α levels were determined by western blot.

RESULTS

Compared with the control group, cardiac fibrosis and oxidative stress in heart tissue were aggravated in diabetic rats, which were more pronounced in glucose variability rats. However, the expression levels of AKT and glycogen synthase kinase-3 beta were not significantly different in three groups, but the expression levels of phosphorylated Ser/Thr protein kinase and phosphorylated glycogen synthase kinase-3 beta were significantly decreased in the control diabetes mellitus and fluctuated blood glucose groups compared to control group, and levels in the fluctuated blood glucose group were significantly less than in the control diabetes mellitus group. In addition, the expression levels of nuclear factor kappa B and caspase-3 in both the control diabetes mellitus and fluctuated blood glucose groups were higher than in the control group, with the highest levels measured in the fluctuated blood glucose group.

CONCLUSION

Blood glucose variability can aggravate heart tissue fibrosis, possibly involving oxidative stress by inhibiting AKT signalling path.

Metabolic Remodeling in Diabetic Cardiomyopathy

Diabetes is a risk factor for heart failure and cardiovascular mortality with specific changes to myocardial metabolism, energetics, structure, and function. The gradual impairment of insulin production and signalling in diabetes is associated with elevated plasma fatty acids and increased myocardial free fatty acid uptake and activation of the transcription factor PPARα. The increased free fatty acid uptake results in accumulation of toxic metabolites, such as ceramide and diacylglycerol, activation of protein kinase C, and elevation of uncoupling protein-3. Insulin signalling and glucose uptake/oxidation become further impaired, and mitochondrial function and ATP production become compromised. Increased oxidative stress also impairs mitochondrial function and disrupts metabolic pathways. The diabetic heart relies on free fatty acids (FFA) as the major substrate for oxidative phosphorylation and is unable to increase glucose oxidation during ischaemia or hypoxia, thereby increasing myocardial injury, especially in ageing female diabetic animals. Pharmacological activation of PPARγ in adipose tissue may lower plasma FFA and improve recovery from myocardial ischaemic injury in diabetes. Not only is the diabetic heart energetically-impaired, it also has early diastolic dysfunction and concentric remodelling. The contractile function of the diabetic myocardium negatively correlates with epicardial adipose tissue, which secretes proinflammatory cytokines, resulting in interstitial fibrosis. Novel pharmacological strategies targeting oxidative stress seem promising in preventing progression of diabetic cardiomyopathy, although clinical evidence is lacking. Metabolic agents that lower plasma FFA or glucose, including PPARγ agonism and SGLT2 inhibition, may therefore be promising options.

Diabetes-Induced Reactive Oxygen Species: Mechanism of Their Generation and Role in Renal Injury

Diabetes induces the onset and progression of renal injury through causing hemodynamic dysregulation along with abnormal morphological and functional nephron changes. The most important event that precedes renal injury is an increase in permeability of plasma proteins such as albumin through a damaged glomerular filtration barrier resulting in excessive urinary albumin excretion (UAE). Moreover, once enhanced UAE begins, it may advance renal injury from progression of abnormal renal hemodynamics, increased glomerular basement membrane (GBM) thickness, mesangial expansion, extracellular matrix accumulation, and glomerulosclerosis to eventual end-stage renal damage. Interestingly, all these pathological changes are predominantly driven by diabetes-induced reactive oxygen species (ROS) and abnormal downstream signaling molecules. In diabetic kidney, NADPH oxidase (enzymatic) and mitochondrial electron transport chain (nonenzymatic) are the prominent sources of ROS, which are believed to cause the onset of albuminuria followed by progression to renal damage through podocyte depletion. Chronic hyperglycemia and consequent ROS production can trigger abnormal signaling pathways involving diverse signaling mediators such as transcription factors, inflammatory cytokines, chemokines, and vasoactive substances. Persistently, increased expression and activation of these signaling molecules contribute to the irreversible functional and structural changes in the kidney resulting in critically decreased glomerular filtration rate leading to eventual renal failure.

Association study of polymorphisms in FOXO3, AKT1 and IGF-2R genes with human longevity in a Han Chinese population

FOXO3, AKT1 and IGF-2R are critical members of the insulin/IGF-1 signaling pathway. Previous studies showed that polymorphisms (SNPs) in FOXO3, AKT1 and IGF-2R were associated with human longevity in Caucasian population. However, the association of these SNPs in different ethnic groups is often inconsistent. Here, we investigated the association of genetic variants in three genes with human longevity in Han Chinese population. Twelve SNPs from FOXO3, AKT1 and IGF-2R were selected and genotyped in 1202 long-lived individuals (nonagenarians and centenarians) and younger individuals. Rs9486902 of FOXO3 was found to be associated with human longevity in both genders combined in this study (allelic P = 0.002, corrected P = 0.024). The other eleven SNPs were not significantly associated with human longevity in Han Chinese population. The haplotypes TTCTT, CCTTC and CTCCT of FOXO3 as well as GGTCGG and GGTCAG of AKT1 were shown to have a significant difference between case and control (P =0.006, 2.78×10-5, 4.68×10-6, 0.003,0.005, respectively). The estimated prevalence of diabetes and prediabetes in long-lived individuals was significantly lower than in common adult populations (P = 0.001, 2.3×10-26) .Therefore, the search for longevity-associated genes provides the identification of new potential targets beneficial for the treatment of diabetes.

Estrogen receptor ERα plays a major role in ethanol-evoked myocardial oxidative stress and dysfunction in conscious female rats

Our previous studies showed that ethanol elicited estrogen (E2)-dependent myocardial oxidative stress and dysfunction. In the present study we tested the hypothesis that E2 signaling via the estrogen receptor (ER), ERα, mediates this myocardial detrimental effect of alcohol. To achieve this goal, conscious female rats in proestrus phase (highest endogenous E2 level) received a selective ER antagonist (200 μg/kg; intra-venous [i.v.]) for ERα (MPP), ERβ (PHTPP) or GPER (G15) or saline 30 min before ethanol (1 g/kg; i.v.) or saline infusion. ERα blockade virtually abrogated ethanol-evoked myocardial dysfunction and hypotension, while ERβ blockade had little effect on the hypotensive response, but caused delayed attenuation of the ethanol-evoked reductions in left ventricular developed pressure and the rate of left ventricle pressure rise. GPER blockade caused delayed attenuation of all cardiovascular effects of ethanol. All three antagonists attenuated the ethanol-evoked increases in myocardial catalase and ALDH2 activities, Akt, ERK1/2, p38, eNOS, and nNOS phosphorylation, except for a lack of effect of PHTPP on p38. Finally, all three ER antagonists attenuated ethanol-evoked elevation in myocardial ROS, but this effect was most notable with ERα blockade. In conclusion, ERα plays a greater role in, and might serve as a molecular target for ameliorating, the E2-dependent myocardial oxidative stress and dysfunction caused by ethanol.

Antioxidant plants and diabetes mellitus

The incidence of diabetes mellitus (DM) is increasing rapidly and it is expected to increase by 2030. Other than currently available therapeutic options, there are a lot of herbal medicines, which have been recommended for its treatment. Herbal medicines have long been used for the treatment of DM because of the advantage usually having no or less side-effects. Most of these plants have antioxidant activities and hence, prevent or treat hard curable diseases, other than having the property of combating the toxicity of toxic or other drugs. In this review other than presenting new findings of DM, the plants, which are used and have been evaluated scientifically for the treatment of DM are introduced.

Cardiac-specific overexpression of catalase prevents diabetes-induced pathological changes by inhibiting NF-κB signaling activation in the heart

Catalase is an antioxidant enzyme that specifically catabolizes hydrogen peroxide (H2O2). Overexpression of catalase via a heart-specific promoter (CAT-TG) was reported to reduce diabetes-induced accumulation of reactive oxygen species (ROS) and further prevent diabetes-induced pathological abnormalities, including cardiac structural derangement and left ventricular abnormity in mice. However, the mechanism by which catalase overexpression protects heart function remains unclear. This study found that activation of a ROS-dependent NF-κB signaling pathway was downregulated in hearts of diabetic mice overexpressing catalase. In addition, catalase overexpression inhibited the significant increase in nitration levels of key enzymes involved in energy metabolism, including α-oxoglutarate dehydrogenase E1 component (α-KGD) and ATP synthase α and β subunits (ATP-α and ATP-β). To assess the effects of the NF-κB pathway activation on heart function, Bay11-7082, an inhibitor of the NF-κB signaling pathway, was injected into diabetic mice, protecting mice against the development of cardiac damage and increased nitrative modifications of key enzymes involved in energy metabolism. In conclusion, these findings demonstrated that catalase protects mouse hearts against diabetic cardiomyopathy, partially by suppressing NF-κB-dependent inflammatory responses and associated protein nitration.

How exercise may amend metabolic disturbances in diabetic cardiomyopathy

SIGNIFICANCE

Over-nutrition and sedentary lifestyle has led to a worldwide increase in obesity, insulin resistance, and type 2 diabetes (T2D) associated with an increased risk of development of cardiovascular disorders. Diabetic cardiomyopathy, independent of hypertension or coronary disease, is induced by a range of systemic changes and may through multiple processes result in functional and structural cardiac derangements. The pathogenesis of this cardiomyopathy is complex and multifactorial, and it will eventually lead to reduced cardiac working capacity and increased susceptibility to ischemic injury.

RECENT ADVANCES

Metabolic disturbances such as altered lipid handling and substrate utilization, decreased mechanical efficiency, mitochondrial dysfunction, disturbances in nonoxidative glucose pathways, and increased oxidative stress are hallmarks of diabetic cardiomyopathy. Interestingly, several of these disturbances are found to precede the development of cardiac dysfunction.

CRITICAL ISSUES

Exercise training is effective in the prevention and treatment of obesity and T2D. In addition to its beneficial influence on diabetes/obesity-related systemic changes, it may also amend many of the metabolic disturbances characterizing the diabetic myocardium. These changes are due to both indirect effects, exercise-mediated systemic changes, and direct effects originating from the high contractile activity of the heart during physical training.

FUTURE DIRECTIONS

Revealing the molecular mechanisms behind the beneficial effects of exercise training is of considerable scientific value to generate evidence-based therapy and in the development of new treatment strategies.

Oxidative stress and autonomic dysregulation contribute to the acute time-dependent myocardial depressant effect of ethanol in conscious female rats

BACKGROUND

The molecular mechanisms of the acute hypotensive and indirectly assessed cardiac depressant effect of ethanol (EtOH)-evoked myocardial depression and hypotension in female rats are not known. We tested the hypothesis that a time-dependent myocardial depression caused by EtOH is initiated by its direct and indirect (cardiac vagal dominance) effects and is exacerbated by gradual development of oxidative stress.

METHODS

In conscious female rats, we directly measured left ventricular developed pressure (LVDP), the maximal rise of ventricular pressure over time (dP/dtmax ), blood pressure (BP), heart rate (HR), and sympathovagal activity following intragastric EtOH (1 g/kg) or water over 90 minutes. Catalytic activity of acetaldehyde (ACA)-generating (alcohol dehydrogenase [ADH] and catalase) and eliminating aldehyde dehydrogenase [ALDH2] enzymes along with mediators of oxidative stress were measured in myocardial tissues collected at 30, 60, or 90 minutes after EtOH or water.

RESULTS

EtOH reduced myocardial function (LVDP and dP/dtmax ) within 5 to 10 minutes before the steady fall in BP in conscious proestrus rats. Further, EtOH shifted the sympathovagal balance, analyzed by spectral analysis of high frequency and low frequency of interbeat intervals, toward vagal dominance. Prior vagal blockade (atropine) or antioxidant (tempol) treatment attenuated EtOH-evoked myocardial depression and hypotension. Ex vivo studies revealed time-dependent: (i) enhancement of ADH, but not ALDH2 activity (indicative of elevated ACA levels), (ii) increases in phosphorylated Akt and ERK1/2, NADPH-oxidase activity, reactive oxygen species, malondialdehyde, and 4-hydroxy-2-nonenal-modified proteins. These molecular responses along with reduced myocardial catalase activity were most evident at 90 minutes post-EtOH when the reductions in cardiac function and BP reached their nadir.

CONCLUSIONS

Vagal dominance and time-dependent myocardial oxidative stress along with the accumulation of cardiotoxic aldehydes mediate EtOH-evoked myocardial dysfunction and hypotension in conscious proestrus female rats.

Activation of Wnt/β-catenin/GSK3β signaling during the development of diabetic cardiomyopathy

BACKGROUND

As Wnt/β-catenin/glycogen synthase kinase 3β (GSK3β) signaling has been implicated in myocardial injury and diabetic cardiomyopathy (DCM) is a major part of diabetic cardiovascular complications, we therefore investigated the alterations of Wnt/β-catenin/GSK3β signaling during the development of DCM.

METHODS

The rat model of diabetes mellitus (DM) was established using a single intraperitoneal injection of streptozotocin (STZ, 60 mg/kg). The alterations of Wnt/β-catenin/GSK3β signaling were determined 4, 8, and 12 weeks following DM using Western blotting, immunohistochemistry, and quantitative real-time reverse transcriptase polymerase chain reaction. Cardiac pathology changes were evaluated using hematoxylin and eosin, Masson trichromatic, and terminal dUTP nick-end labeling staining.

RESULTS

Histological analyses revealed that DM induced significant myocardial injury and progressive cardiomyocyte apoptosis. The protein and mRNA levels of Wnt2, β-catenin, and c-Myc were progressively increased 4, 8, and 12 weeks following DM. The expression of T-cell factor 4 and phosphorylated of GSK3β on Ser9 were progressively increased. However, the expression of the endogenous Wnt inhibitor Dickkopf-1 was increased after STZ injection and then decreased as DCM developed.

CONCLUSION

Wnt/β-catenin/GSK3β signaling pathway is activated in the development of DCM. Further investigation into the role of Wnt signaling during DCM will functionally find novel therapeutic target for DCM.

A novel protective mechanism for mitochondrial aldehyde dehydrogenase (ALDH2) in type i diabetes-induced cardiac dysfunction: role of AMPK-regulated autophagy

Mitochondrial aldehyde dehydrogenase (ALDH2) is known to offer myocardial protection against stress conditions including ischemia-reperfusion injury, alcoholism and diabetes mellitus although the precise mechanism is unclear. This study was designed to evaluate the effect of ALDH2 on diabetes-induced myocardial injury with a focus on autophagy. Wild-type FVB and ALDH2 transgenic mice were challenged with streptozotozin (STZ, 200mg/kg, i.p.) for 3months to induce experimental diabetic cardiomyopathy. Diabetes triggered cardiac remodeling and contractile dysfunction as evidenced by cardiac hypertrophy, decreased cell shortening and prolonged relengthening duration, the effects of which were mitigated by ALDH2. Lectin staining displayed that diabetes promoted cardiac hypertrophy, the effect of which was alleviated by ALDH2. Western blot analysis revealed dampened autophagy protein markers including LC3B ratio and Atg7 along with upregulated p62 following experimental diabetes, the effect of which was reconciled by ALDH2. Phosphorylation level of AMPK was decreased and its downstream signaling molecule FOXO3a was upregulated in both diabetic cardiac tissue and in H9C2 cells with high glucose exposure. All these effect were partly abolished by ALDH2 overexpression and ALDH2 agonist Alda1. High glucose challenge dampened autophagy in H9C2 cells as evidenced by enhanced p62 levels and decreased levels of Atg7 and LC3B, the effect of which was alleviated by the ALDH2 activator Alda-1. High glucose-induced cell death and apoptosis were reversed by Alda-1. The autophagy inhibitor 3-MA and the AMPK inhibitor compound C mitigated Alda-1-offered beneficial effect whereas the autophagy inducer rapamycin mimicked or exacerbated high glucose-induced cell injury. Moreover, compound C nullified Alda-1-induced protection against STZ-induced changes in autophagy and function. Our results suggested that ALDH2 protects against diabetes-induced myocardial dysfunction possibly through an AMPK -dependent regulation of autophagy. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

Catalase expression in MCF-7 breast cancer cells is mainly controlled by PI3K/Akt/mTor signaling pathway

Catalase is an antioxidant enzyme that catalyzes mainly the transformation of hydrogen peroxide into water and oxygen. Although catalase is frequently down-regulated in tumors the underlying mechanism remains unclear. Few transcription factors have been reported to directly bind the human catalase promoter. Among them FoxO3a has been proposed as a positive regulator of catalase expression. Therefore, we decided to study the role of the transcription factor FoxO3a and the phosphatidylinositol-3 kinase (PI3K) signaling pathway, which regulates FoxO3a, in the expression of catalase. To this end, we developed an experimental model of mammary breast MCF-7 cancer cells that acquire resistance to oxidative stress, the so-called Resox cells, in which catalase is overexpressed as compared with MCF-7 parental cell line. In Resox cells, Akt expression is decreased but its phosphorylation is enhanced when compared with MCF-7 cells. A similar profile is observed for FoxO3a, with less total protein but more phosphorylated FoxO3a in Resox cells, correlating with its higher Akt activity. The modulation of FoxO3a expression by knockdown and overexpression strategies did not affect catalase expression, neither in MCF-7 nor in Resox cells. Inhibition of PI3K and mTOR by LY295002 and rapamycin, respectively, decreases the phosphorylation of downstream targets (i.e. GSK3β and p70S6K) and leads to an increase of catalase expression only in MCF-7 but not in Resox cells. In conclusion, FoxO3a does not appear to play a critical role in the regulation of catalase expression in both cancer cells. Only MCF-7 cells are sensitive and dependent on PI3K/Akt/mTOR signaling.

Diabetic cardiomyopathy: mechanisms and new treatment strategies targeting antioxidant signaling pathways

Cardiovascular disease is the primary cause of morbidity and mortality among the diabetic population. Both experimental and clinical evidence suggest that diabetic subjects are predisposed to a distinct cardiomyopathy, independent of concomitant macro- and microvascular disorders. 'Diabetic cardiomyopathy' is characterized by early impairments in diastolic function, accompanied by the development of cardiomyocyte hypertrophy, myocardial fibrosis and cardiomyocyte apoptosis. The pathophysiology underlying diabetes-induced cardiac damage is complex and multifactorial, with elevated oxidative stress as a key contributor. We now review the current evidence of molecular disturbances present in the diabetic heart, and their role in the development of diabetes-induced impairments in myocardial function and structure. Our focus incorporates both the contribution of increased reactive oxygen species production and reduced antioxidant defenses to diabetic cardiomyopathy, together with modulation of protein signaling pathways and the emerging role of protein O-GlcNAcylation and miRNA dysregulation in the progression of diabetic heart disease. Lastly, we discuss both conventional and novel therapeutic approaches for the treatment of left ventricular dysfunction in diabetic patients, from inhibition of the renin-angiotensin-aldosterone-system, through recent evidence favoring supplementation of endogenous antioxidants for the treatment of diabetic cardiomyopathy. Novel therapeutic strategies, such as gene therapy targeting the phosphoinositide 3-kinase PI3K(p110α) signaling pathway, and miRNA dysregulation, are also reviewed. Targeting redox stress and protective protein signaling pathways may represent a future strategy for combating the ever-increasing incidence of heart failure in the diabetic population.

Conundrum of pathogenesis of diabetic cardiomyopathy: role of vascular endothelial dysfunction, reactive oxygen species, and mitochondria

Diabetic cardiomyopathy and heart failure have been recognized as the leading causes of mortality among diabetics. Diabetic cardiomyopathy has been characterized primarily by the manifestation of left ventricular dysfunction that is independent of coronary artery disease and hypertension among the patients affected by diabetes mellitus. A complex array of contributing factors including the hypertrophy of left ventricle, alterations of metabolism, microvascular pathology, insulin resistance, fibrosis, apoptotic cell death, and oxidative stress have been implicated in the pathogenesis of diabetic cardiomyopathy. Nevertheless, the exact mechanisms underlying the pathogenesis of diabetic cardiomyopathy are yet to be established. The critical involvement of multifarious factors including the vascular endothelial dysfunction, microangiopathy, reactive oxygen species (ROS), oxidative stress, mitochondrial dysfunction has been identified in the mechanism of pathogenesis of diabetic cardiomyopathy. Although it is difficult to establish how each factor contributes to disease, the involvement of ROS and mitochondrial dysfunction are emerging as front-runners in the mechanism of pathogenesis of diabetic cardiomyopathy. This review highlights the role of vascular endothelial dysfunction, ROS, oxidative stress, and mitochondriopathy in the pathogenesis of diabetic cardiomyopathy. Furthermore, the review emphasizes that the puzzle has to be solved to firmly establish the mitochondrial and/or ROS mechanism(s) by identifying their most critical molecular players involved at both spatial and temporal levels in diabetic cardiomyopathy as targets for specific and effective pharmacological/therapeutic interventions.

Exposure of cardiomyocytes to angiotensin II induces over-activation of monoamine oxidase type A: implications in heart failure

Several evidences indicate that increased cardiac mitochondrial monoamine oxidase type A (MAO-A) activity associates with a failing phenotype. Till now, the mechanism underlying such relation is largely unknown. We explored the hypothesis that exposure of cardiomyocytes to AT-II caused activation of MAO-A and also of catalase and aldehyde dehydrogenase activities, enzymes involved in degrading MAO's end products. Left ventricular cardiomyocytes were isolated from normoglycemic (N) and streptozotocin-injected (50 mg/kg) rats (D) treated or not treated with losartan (20 mg/kg/day in drinking water; DLos and NLos, respectively), a type 1 receptor (AT1) antagonist, for 3 weeks. In each group of cells, MAO, catalase and aldehyde dehydrogenase activities were measured radiochemically and spectrophotometrically. The same enzymes were also measured in HL-1 immortalized cardiomyocytes not exposed and exposed to AT-II (100 nM for 18 h) in the absence and in the presence of irbesartan (1 μM), an AT1 antagonist. MAO-A catalase and aldehyde dehydrogenase activities were found significantly higher in D, than in N cells. MAO-A positively correlated with catalase activity in D cells. MAO-A and aldehyde dehydrogenase but not catalase over-activation, were prevented in DLos cells. Similarly, MAO-A activity, but not catalase and aldehyde dehydrogenase increased significantly in HL-1 cells acutely exposed to AT-II and this increase was prevented when irbesartan, an AT1 antagonist was present. Over-activation of cardiomyocyte MAO-A activity is among acute (18 h) and short-term (2-weeks of diabetes) cardiac effects of AT-II and a novel target of AT1 antagonists, first line treatments of diabetic cardiomyopathy.

Oxidative activation of Ca(2+)/calmodulin-activated kinase II mediates ER stress-induced cardiac dysfunction and apoptosis

Endoplasmic reticulum (ER) stress elicits oxidative stress and intracellular Ca(2+) derangement via activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). This study was designed to examine the role of CaMKII in ER stress-induced cardiac dysfunction and apoptosis as well as the effect of antioxidant catalase. Wild-type FVB and transgenic mice with cardiac-specific overexpression of catalase were challenged with the ER stress inducer tunicamycin (3 mg/kg ip for 48 h). Presence of ER stress was verified using the ER stress protein markers immunoglobulin binding protein (BiP) and C/EBP homologous protein (CHOP), the effect of which was unaffected by catalase overexpression. Echocardiographic assessment revealed that tunicamycin elicited cardiac remodeling (enlarged end-systolic diameter without affecting diastolic and ventricular wall thickness), depressed fractional shortening, ejection fraction, and cardiomyocyte contractile capacity, intracellular Ca(2+) mishandling, accumulation of reactive oxygen species (superoxide production and NADPH oxidase p47phox level), CaMKII oxidation, and apoptosis (evidenced by Bax, Bcl-2/Bax ratio, and TUNEL staining), the effects of which were obliterated by catalase. Interestingly, tunicamycin-induced cardiomyocyte mechanical anomalies and cell death were ablated by the CaMKII inhibitor KN93, in a manner reminiscent of catalase. These data favored a permissive role of oxidative stress and CaMKII activation in ER stress-induced cardiac dysfunction and cell death. Our data further revealed the therapeutic potential of antioxidant or CaMKII inhibition in cardiac pathological conditions associated with ER stress. This research shows for the first time that contractile dysfunction caused by ER stress is a result of the oxidative activation of the CaMKII pathway.

RETRACTED: Cardiac-specific overexpression of catalase attenuates lipopolysaccharide-induced myocardial contractile dysfunction: Role of autophagy

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. After an institutional investigation into the work of Dr. Jun Ren, University of Wyoming subsequently conducted an examination of other selected publications of Dr. Ren's under the direction of the HHS Office of Research Integrity. Based on the findings of this examination, the University of Wyoming recommended this article be retracted due to concerns regarding data irregularities inconsistent with published conclusions. Specifically, University of Wyoming found evidence of data irregularities and image reuse in Figure 2 that significantly affect the results and conclusions reported in the manuscript.

Mitochondrial aldehyde dehydrogenase (ALDH2) protects against streptozotocin-induced diabetic cardiomyopathy: role of GSK3β and mitochondrial function

BACKGROUND

Mitochondrial aldehyde dehydrogenase (ALDH2) displays some promise in the protection against cardiovascular diseases although its role in diabetes has not been elucidated.

METHODS

This study was designed to evaluate the impact of ALDH2 on streptozotocin-induced diabetic cardiomyopathy. Friendly virus B(FVB) and ALDH2 transgenic mice were treated with streptozotocin (intraperitoneal injection of 200 mg/kg) to induce diabetes.

RESULTS

Echocardiographic evaluation revealed reduced fractional shortening, increased end-systolic and -diastolic diameter, and decreased wall thickness in streptozotocin-treated FVB mice. Streptozotocin led to a reduced respiratory exchange ratio; myocardial apoptosis and mitochondrial damage; cardiomyocyte contractile and intracellular Ca2+ defects, including depressed peak shortening and maximal velocity of shortening and relengthening; prolonged duration of shortening and relengthening; and dampened intracellular Ca2+ rise and clearance. Western blot analysis revealed disrupted phosphorylation of Akt, glycogen synthase kinase-3β and Foxo3a (but not mammalian target of rapamycin), elevated PTEN phosphorylation and downregulated expression of mitochondrial proteins, peroxisome proliferator-activated receptor γ coactivator 1α and UCP-2. Intriguingly, ALDH2 attenuated or ablated streptozotocin-induced echocardiographic, mitochondrial, apoptotic and myocardial contractile and intracellular Ca2+ anomalies as well as changes in the phosphorylation of Akt, glycogen synthase kinase-3β, Foxo3a and phosphatase and tensin homologue on chromosome ten, despite persistent hyperglycemia and a low respiratory exchange ratio. In vitro data revealed that the ALDH2 activator Alda-1 and glycogen synthase kinase-3β inhibition protected against high glucose-induced mitochondrial and mechanical anomalies, the effect of which was cancelled by mitochondrial uncoupling.

CONCLUSIONS

In summary, our data revealed that ALDH2 acted against diabetes-induced cardiac contractile and intracellular Ca2+ dysregulation, possibly through regulation of apoptosis, glycogen synthase kinase-3β activation and mitochondrial function independent of the global metabolic profile.

Long-term administration of fasudil improves cardiomyopathy in streptozotocin-induced diabetic rats

Inhibition of Rho kinase (ROCK) has been shown to improve diabetic-related disorders. In this study, the cardio-protective effects and potential mechanisms of fasudil, a selective ROCK inhibitor, on diabetic cardiomyopathy were investigated in a streptozotocin (STZ)-induced diabetic rat model. Eight weeks after diabetes was induced by a single tail vein injection of 60 mg/kg STZ, rats were administered long-term fasudil or captopril as a control over a four-week period. Similar to the effect of captopril, fasudil treatment significantly protected against STZ-induced hemodynamic, histopathologic changes and decreased serum lactate dehydrogenase and creatine phosphokinase. Moreover, fasudil significantly down-regulated ROCK I mRNA expression and ROCK activity, reduced cardiac collagen deposition, and decreased the incidence of apoptosis and ratio of Bax/Bcl-2 protein expression. Additionally, fasudil potently elevated superoxide dismutase activity and suppressed the extent of lipid peroxidation in sera and hearts of diabetic rats. Our findings indicated that long-term treatment with fasudil could improve cardiac dysfunction, attenuate myocardial injury and prevent pathological changes in a rat model of diabetic cardiomyopathy. These effects could be attributed to regulation of antioxidative activities, suppression of myocardial hypertrophy, apoptosis, fibrosis and subsequent cardiac remodeling. These results may help to expand the clinical application of fasudil for diabetic cardiomyopathy.

Inhibition of NADPH oxidase alleviates experimental diabetes-induced myocardial contractile dysfunction

AIM

O(2) (-) production is implicated in cardiac dysfunction for a number of diseases including diabetes. Activation of the O(2) (-)-producing enzyme NADPH oxidase is seen in diabetes, although its role in diabetic cardiomyopathy is unclear. This study was designed to evaluate the effect of NADPH oxidase inhibition on cardiac function in diabetes.

METHODS

Experimental diabetes was induced in adult C57 mice using streptozotocin (STZ, 150 mg/kg, i.p.) prior to the administration of the NADPH oxidase inhibitor apocynin (4 mg/kg/day) for 2 weeks. Left ventricular (LV) and myocyte contractile functions were evaluated using echocardiography and edge-detection, respectively.

RESULTS

STZ elicited hyperglycaemia and reduced body weight gain, which was unaffected by apocynin. STZ significantly reduced fractional shortening, LV wall thickness, peak shortening, maximal velocity and duration of shortening or relengthening, the effects of which - with the exception of wall thickness - were significantly attenuated or ablated by apocynin. Western blot analysis revealed that the effects of comparable Akt phosphorylation, reduced AMPK phosphorylation, downregulation of sarco(endo)plasmic reticulum Ca(2+)-ATPase and lessened phosphorylation of phospholamban in diabetic myocardium were unaffected by apocynin. Both apocynin and the nitric oxide synthase (NOS) inhibitor l-arginine methyl ester (L-NAME) inhibited elevated O(2) (-) production in diabetes without any additive effect between the two, indicating the presence of endothelial nitric oxide synthase (eNOS) uncoupling. However, neither diabetes nor apocynin altered the expression of heat shock protein 90 and eNOS phosphorylation (Ser(1177)). In addition, apocynin mitigated elevated levels of nitrotyrosine and nitric oxide in diabetes.

CONCLUSION

Taken together, these data indicate the beneficial role of NADPH oxidase inhibition in diabetes-induced myocardial contractile dysfunction.

Oxidative stress: a key contributor to diabetic cardiomyopathy

Diabetes and its associated complications are major known health disorders. Diabetes mellitus increases the risk of cardiovascular morbidity and mortality by promoting cardiomyopathy. It appears to arise as a result of the diabetic state, at times independent of vascular or valvular pathology. It manifests initially as asymptomatic diastolic dysfunction, which progresses to symptomatic heart failure. The compliance of the heart wall is decreased and contractile function is impaired. The pathophysiology of diabetic cardiomyopathy is incompletely understood but appears to be multifactorial in origin. Several hypotheses have been proposed, including oxidative stress, inflammation, endothelial dysfunction, metabolic derangements, abnormalities in ion homeostasis, alterations in structural proteins, and interstitial fibrosis. Amongst these various mechanisms, an increase in reactive oxygen species, leading to oxidative stress, has received significant experimental support. This review focuses on the role of oxidative stress in the pathogenesis of diabetic cardiomyopathy and the potential of antioxidant therapy.

Macrophage migration inhibitory factor deficiency augments cardiac dysfunction in Type 1 diabetic murine cardiomyocytes

BACKGROUND

It has become evident that macrophage migration inhibitory factor (MIF) is associated with the development of Type 1 diabetes mellitus. The aim of the present study was to determine whether MIF plays a role in cardiac contractile dysfunction in T1DM mice.

METHODS

Mechanical and intracellular Ca(2+) properties were measured in cardiomyocytes isolated from wild-type (WT) and MIF-knockout (MIF-KO) mice administrated or not streptozotocin (200 mg/kg, i.p.). Relative stress signaling was evaluated using western blot analysis.

RESULTS

Peak shortening (PS) and maximal velocity of shortening/relengthening (±dL/dt) were reduced and the duration of relengthening (TR90) was prolonged in both WT and MIF-KO cardiomyocytes treated with STZ (P < 0.01 vs control), which may be associated with reduced intracellular Ca(2+) decay in both groups. However, STZ-treated WT cardiomyocytes demonstrated significantly better contractile function and intracellular Ca(2+) properties compared with STZ-treated MIF-KO cardiomyocytes (all P < 0.05). Interestingly, the physiological data clearly showed that blood glucose levels were significantly higher in STZ-treated MIF-KO mice than STZ-treated WT mice (P < 0.01). Moreover, phosphorylation of AMP-activated protein kinase (AMPK) and its direct downstream target acetyl-CoA carboxylase (ACC) was markedly lower in hearts from STZ-treated MIF-KO mice than STZ-treated WT mice (P < 0.05). There were no significant differences between untreated WT and MIF-KO control groups.

CONCLUSIONS

There is a beneficial action of MIF in the management of cardiac dysfunction in T1DM. The cardioprotective effect of MIF may be associated with AMPK signaling.

Signaling of reactive oxygen and nitrogen species in Diabetes mellitus

Disorder of physiological signaling functions of reactive oxygen species (ROS) superoxide and hydrogen peroxide and reactive nitrogen species (RNS) nitric oxide and peroxynitrite is an important feature of diabetes mellitus type 1 and type 2. It is now known that hyperglycemic conditions of cells are associated with the enhanced levels of ROS mainly generated by mitochondria and NADPH oxidase. It has been established that ROS stimulate many enzymatic cascades under normal physiological conditions, but hyperglycemia causes ROS overproduction and the deregulation of ROS signaling pathways initiating the development of diabetes mellitus. On the other hand the deregulation of RNS signaling leads basically to a decrease in NO formation with subsequent damaging disorders. In the present work we will consider the pathological changes of ROS and RNS signaling in enzyme/gene regulated processes catalyzed by protein kinases C and B (Akt/B), phosphatidylinositol 3'-kinase (PI3-kinase), extracellular signal-regulated kinase 1/2 (ERK1/2), and some others. Furthermore we will discuss a particularly important role of several ROS-regulated genes and adapter proteins such as the p66shc, FOXO3a, and Sirt2. The effects of low and high ROS levels in diabetes will be also considered. Thus the regulation of damaging ROS levels in diabetes by antioxidants and free radical scavengers must be one of promising treatment of this disease, however, because of the inability of traditional antioxidative vitamin E and C to interact with superoxide and hydrogen peroxide, new free radical scavengers such as flavonoids, quinones and synthetic mimetics of superoxide dismutase (SOD) should be intensively studied.

Temporal effects of catalase overexpression on healing after myocardial infarction

BACKGROUND

Reactive oxygen species, such as hydrogen peroxide (H(2)O(2)), contribute to progression of dysfunction after myocardial infarction (MI). However, chronic overexpression studies do not agree with acute protein delivery studies. The purpose of the present study was to assess the temporal role of cardiomyocyte-derived H(2)O(2) scavenging on cardiac function after infarction using an inducible system.

METHODS AND RESULTS

We developed a tamoxifen-inducible, cardiomyocyte-specific, catalase-overexpressing mouse. Catalase overexpression was induced either 5 days before or after MI. Mice exhibited a 3-fold increase in cardiac catalase activity that was associated with a significant decrease in H(2)O(2) levels at both 7 and 21 days. However, cardiac function improved only at the later time point. Proinflammatory and fibrotic genes were acutely upregulated after MI, but catalase overexpression abolished the increase despite no acute change in function. This led to reduced overall scar formation, with lower levels of Collagen 1A and increased contractile Collagen 3A expression at 21 days.

CONCLUSIONS

In contrast to prior studies, there were no acute functional improvements with physiological catalase overexpression before MI. Scavenging of H(2)O(2), however, reduced proinflammatory cytokines and altered cardiac collagen isoforms, associated with an improvement in cardiac function after 21 days. Our results suggest that sustained H(2)O(2) levels rather than acute levels immediately after MI may be critical in directing remodeling and cardiac function at later time points.

Genetic association of FOXO1A and FOXO3A with longevity trait in Han Chinese populations

FOXO1A and FOXO3A are two members of the FoxO family. FOXO3A has recently been linked to human longevity in Japanese, German and Italian populations. Here we tested the genetic contribution of FOXO1A and FOXO3A to the longevity phenotype in Han Chinese population. Six tagging SNPs from FOXO1A and FOXO3A were selected and genotyped in 1817 centenarians and younger individuals. Two SNPs of FOXO1A were found to be associated with longevity in women (P = 0.01-0.005), whereas all three SNPs of FOXO3A were associated with longevity in both genders (P = 0.005-0.001). One SNP from FOXO1A was found not to be associated with longevity. In haplotype association tests, the OR (95% CI) for haplotypes TTG and CCG of FOXO1A in association with female longevity were 0.72 (0.58-0.90) and 1.38 (1.08-1.76), P = 0.0033 and 0.0063, respectively. The haplotypes of FOXO3A were associated with longevity in men [GTC: OR (95% CI) = 0.67 (0.51-0.86), P = 0.0014; CGT: OR (95% CI) = 1.48 (1.12-1.94), P = 0.0035] and in women [GTC: OR (95% CI) = 0.75 (0.60-0.94), P = 0.0094; CGT: OR (95% CI) = 1.47 (1.16-1.86), P = 0.0009]. The haplotype association tests were validated by permutation analysis. The association of FOXO1A with female longevity was replicated in 700 centenarians and younger individuals that were sampled geographically different from the original population. Thus, we demonstrate that, unlike FOXO3A, FOXO1A is more closely associated with human female longevity, suggesting that the genetic contribution to longevity trait may be affected by genders.

Function of sirtuins in biological tissues

Sirtuins are protein deacetylases, which are dependent on nicotine adenine dinucleotide. They are phylogenetically conserved from bacteria to humans. Seven sirtuin proteins localized in a wide variety of subcellular locations have been identified in the human genome. The most important known function of sirtuins is their regulation of transcriptional repression, mediated through binding of a complex containing sirtuins and other proteins. Studies have shown that sirtuins have pathophysiological relevance to neurodegeneration, muscle differentiation, inflammation, obesity, and cancer. In addition, sirtuin activity extends the lifespan of several organisms. In this review, we discuss the mode(s) of action of sirtuins, and their biological role(s) in health and disease.

A newly synthetic chromium complex-chromium (D-phenylalanine)3 activates AMP-activated protein kinase and stimulates glucose transport

We synthesized the chromium (phenylalanine)(3) [Cr(D-phe)(3)] by chelating chromium(III) with D-phenylalanine ligand in aqueous solution to improve the bioavailability of chromium, and reported that Cr(D-phe)(3) improved insulin sensitivity. AMP-activated protein kinase (AMPK) is a key mediator for glucose uptake and insulin sensitivity. To address the molecular mechanisms by which Cr(d-phe)(3) increases insulin sensitivity, we investigated whether Cr(D-phe)(3) stimulates glucose uptake via activation of AMPK signaling pathway. H9c2 myoblasts and isolated cardiomyocytes were treated with Cr(D-phe)(3) (25microM). Western blotting was used for signaling determination. The glucose uptake was determined by 2-deoxy-D-glucose-(3)H accumulation. HPLC measured concentrations of AMP. The mitochondrial membrane potential (Deltapsi) was detected by JC-1 fluorescence assay. Cr(D-phe)(3) stimulated the phosphorylation of alpha catalytic subunit of AMPK at Thr(172), as well the downstream targets of AMPK, acetyl-CoA carboxylase (ACC, Ser(212)) and eNOS (Ser(1177)). Moreover, Cr(D-phe)(3) significantly stimulated glucose uptake in both H9c2 cells and cardiomyocytes. AMPK inhibitor compound C (10microM) dramatically inhibited the glucose uptake stimulated by Cr(D-phe)(3), while it did not affect insulin stimulation of glucose uptake. Furthermore, in vivo studies showed that Cr(D-phe)(3) also activated cardiac AMPK signaling pathway. The increase of cardiac AMP concentration and the decrease of mitochondrial membrane potential (Deltapsi) may contribute to the activation of AMPK induced by Cr(D-phe)(3). Cr(D-phe)(3) is a novel compound that activates AMPK signaling pathway, which contributes to the regulation of glucose transport during stress conditions that may be associated the role of AMPK in increasing insulin sensitivity.

Mechanisms and molecular probes of sirtuins

Sirtuins are critical regulators of many cellular processes, including insulin secretion, the cell cycle, and apoptosis. Sirtuins are associated with a variety of age-associated diseases such as type II diabetes, obesity, and Alzheimer's disease. A thorough understanding of sirtuin chemical mechanisms will aid toward developing novel therapeutics that regulate metabolic disorders and combat associated diseases. In this review, we discuss the unique deacetylase mechanism of sirtuins and how this information might be employed to develop inhibitors and other molecular probes for therapeutic and basic research applications. We also cover physiological regulation of sirtuin activity and how these modes of regulation may be exploited to manipulate sirtuin activity in live cells. Development of molecular probes and drugs that specifically target sirtuins will further understanding of sirtuin biology and potentially afford new treatments of several human diseases.