Aldose Reductase and AGE-RAGE Pathways: Key Players in Myocardial Ischemic Injury

Glycoxidation of mammalian whole histone generates highly immunogenic aggregates: Sera of SLE patients contain autoantibodies against aggregates

Non-enzymatic glycation and oxidation of self-proteins, causing formation and accumulation of advanced glycation end products (AGEs), have been reported in an array of pathologies, including systemic lupus erythematosus (SLE). Such modifications may generate neo-epitopes, break immunological tolerance, and induce antibody response. In this study, we have first analysed the structural modifications of whole histone in the presence of deoxyribose followed by oxidation with hydroxyl radicals. Changes in the secondary and tertiary structure of the whole histone were determined by spectroscopic techniques and biochemical assays. Fluorescence spectroscopy and UPLC-MS showed the generation of AGEs such as carboxymethyl lysine and pentosidine, while DLS and TEM indicated the presence of amorphous AGE-aggregates. Moreover, rabbits immunized with these histone-AGEs exhibited enhanced immunogenicity and ELISA and western immunoblot of IgG antibodies from SLE patients' sera showed a significantly higher specificity towards modified histone-AGEs than the native histone.

The role of glycolytic metabolic pathways in cardiovascular disease and potential therapeutic approaches

Cardiovascular disease (CVD) is a major threat to human health, accounting for 46% of non-communicable disease deaths. Glycolysis is a conserved and rigorous biological process that breaks down glucose into pyruvate, and its primary function is to provide the body with the energy and intermediate products needed for life activities. The non-glycolytic actions of enzymes associated with the glycolytic pathway have long been found to be associated with the development of CVD, typically exemplified by metabolic remodeling in heart failure, which is a condition in which the heart exhibits a rapid adaptive response to hypoxic and hypoxic conditions, occurring early in the course of heart failure. It is mainly characterized by a decrease in oxidative phosphorylation and a rise in the glycolytic pathway, and the rise in glycolysis is considered a hallmark of metabolic remodeling. In addition to this, the glycolytic metabolic pathway is the main source of energy for cardiomyocytes during ischemia-reperfusion. Not only that, the auxiliary pathways of glycolysis, such as the polyol pathway, hexosamine pathway, and pentose phosphate pathway, are also closely related to CVD. Therefore, targeting glycolysis is very attractive for therapeutic intervention in CVD. However, the relationship between glycolytic pathway and CVD is very complex, and some preclinical studies have confirmed that targeting glycolysis does have a certain degree of efficacy, but its specific role in the development of CVD has yet to be explored. This article aims to summarize the current knowledge regarding the glycolytic pathway and its key enzymes (including hexokinase (HK), phosphoglucose isomerase (PGI), phosphofructokinase-1 (PFK1), aldolase (Aldolase), phosphoglycerate metatase (PGAM), enolase (ENO) pyruvate kinase (PKM) lactate dehydrogenase (LDH)) for their role in cardiovascular diseases (e.g., heart failure, myocardial infarction, atherosclerosis) and possible emerging therapeutic targets.

Advanced glycation end products: Key mediator and therapeutic target of cardiovascular complications in diabetes

The incidence of type 2 diabetes mellitus is growing in epidemic proportions and has become one of the most critical public health concerns. Cardiovascular complications associated with diabetes are the leading cause of morbidity and mortality. The cardiovascular diseases that accompany diabetes include angina, myocardial infarction, stroke, peripheral artery disease, and congestive heart failure. Among the various risk factors generated secondary to hyperglycemic situations, advanced glycation end products (AGEs) are one of the important targets for future diagnosis and prevention of diabetes. In the last decade, AGEs have drawn a lot of attention due to their involvement in diabetic patho-physiology. AGEs can be derived exogenously and endogenously through various pathways. These are a non-homogeneous, chemically diverse group of compounds formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amino groups of protein, lipids, and nucleic acid. AGEs mediate their pathological effects at the cellular and extracellular levels by multiple pathways. At the cellular level, they activate signaling cascades via the receptor for AGEs and initiate a complex series of intracellular signaling resulting in reactive oxygen species generation, inflammation, cellular proliferation, and fibrosis that may possibly exacerbate the damaging effects on cardiac functions in diabetics. AGEs also cause covalent modifications and cross-linking of serum and extracellular matrix proteins; altering their structure, stability, and functions. Early diagnosis of diabetes may prevent its progression to complications and decrease its associated comorbidities. In the present review, we recapitulate the role of AGEs as a crucial mediator of hyperglycemia-mediated detrimental effects in diabetes-associated complications. Furthermore, this review presents an overview of future perspectives for new therapeutic interventions to ameliorate cardiovascular complications in diabetes.

Molecular Characteristics of RAGE and Advances in Small-Molecule Inhibitors

Receptor for advanced glycation end-products (RAGE) is a member of the immunoglobulin superfamily. RAGE binds and mediates cellular responses to a range of DAMPs (damage-associated molecular pattern molecules), such as AGEs, HMGB1, and S100/calgranulins, and as an innate immune sensor, can recognize microbial PAMPs (pathogen-associated molecular pattern molecules), including bacterial LPS, bacterial DNA, and viral and parasitic proteins. RAGE and its ligands stimulate the activations of diverse pathways, such as p38MAPK, ERK1/2, Cdc42/Rac, and JNK, and trigger cascades of diverse signaling events that are involved in a wide spectrum of diseases, including diabetes mellitus, inflammatory, vascular and neurodegenerative diseases, atherothrombosis, and cancer. Thus, the targeted inhibition of RAGE or its ligands is considered an important strategy for the treatment of cancer and chronic inflammatory diseases.

AGE-RAGE Stress, Stressors, and Antistressors in Health and Disease

Adverse effects of advanced glycation end-products (AGEs) on the tissues are through nonreceptor- and receptor-mediated mechanisms. In the receptor-mediated mechanism, interaction of AGEs with its cell-bound receptor of AGE (RAGE) increases generation of oxygen radicals, activates nuclear factor-kappa B, and increases expression and release of pro-inflammatory cytokines resulting in the cellular damage. The deleterious effects of AGE and AGE-RAGE interaction are coined as "AGE-RAGE stress." The body is equipped with defense mechanisms to counteract the adverse effects of AGE and RAGE through endogenous enzymatic (glyoxalase 1, glyoxalase 2) and AGE receptor-mediated (AGER1, AGER2) degradation of AGE, and through elevation of soluble receptor of AGE (sRAGE). Exogenous defense mechanisms include reduction in consumption of AGE, prevention of AGE formation, and downregulation of RAGE expression. We have coined AGE and RAGE as "stressors" and the defense mechanisms as "anti-stressors." AGE-RAGE stress is defined as a shift in the balance between stressors and antistressors in the favor of stressors. Measurements of stressors or antistressors alone would not assess AGE-RAGE stress. For true assessment of AGE-RAGE stress, the equation should include all the stressors and antistressors. The equation for AGE-RAGE stress, therefore, would be the ratio of AGE + RAGE/sRAGE + glyoxalase1 + glyoxalase 2 + AGER1 +AGER2. This is, however, not practical in patients. AGE-RAGE stress may be assessed simply by the ratio of AGE/sRAGE. A high ratio of AGE/sRAGE indicates a relative shift in stressors from antistressors, suggesting the presence of AGE-RAGE stress, resulting in tissue damage, initiation, and progression of the diseases and their complications.

Advanced glycation end-product (AGE)-albumin from activated macrophage is critical in human mesenchymal stem cells survival and post-ischemic reperfusion injury

Post-ischemic reperfusion injury (PIRI) triggers an intense inflammatory response which is essential for repair but is also implicated in pathogenesis of post-ischemic remodeling in several organs in human. Stem cell therapy has recently emerged as a promising method for treatment of PIRI in human. However, satisfactory results have not been reported due to severe loss of injected stem cells in PIRI including critical limb ischemia (CLI). For investigating the advanced glycation end-product-albumin (AGE-albumin) from activated macrophages is critical in both muscle cell and stem cell death, we evaluated the recovery of PIRI-CLI by injection of human bone marrow derived mesenchymal stem cells (hBD-MSCs) with or without soluble receptor for AGEs (sRAGE). Our results showed that activated M1 macrophages synthesize and secrete AGE-albumin, which induced the skeletal muscle cell death and injected hBD-MSCs in PIRI-CLI through RAGE increase. Combined injection of sRAGE and hBD-MSCs resulted in enhanced survival of hBD-MSCs and angiogenesis in PIRI-CLI mice. Taken together, AGE-albumin from activated macrophages is critical for both skeletal muscle cell and hBD-MSCs death in PIRI-CLI. Therefore, the inhibition of AGE-albumin from activated macrophages could be a successful therapeutic strategy for treatment of PIRI including CLI with or without stem cell therapy.

The Initial Months of Antiretroviral Therapy and Its Influence on AGEs, HMGB1, and sRAGE Levels in Asymptomatic HIV-Infected Individuals

The development of the typical comorbidities of aging which currently affects people living with HIV/AIDS (PLWHA) can be partially ascribed to the persistent immune activation and chronic inflammation characterizing these individuals. The aim of this study was to analyze the effect exerted by combined antiretroviral therapy (cART) administration on plasma levels of HMGB1 (high mobility group box protein-1), AGEs (advanced glycation end products), their soluble receptor sRAGE, cytokines, C-reactive protein (CRP), and some metabolic markers in asymptomatic PLWHA. Analyses were performed longitudinally in 30 PLWHA, before and about 6–12 months after cART initiation. We observed that lower levels of AGEs in post-cART group were accompanied by an increase of CRP and triglyceride levels already in the early months of therapy. Because of the current ever-earlier recommendations to start cART and its prolonged use, these and other markers should be investigated in order to monitor and postpone the appearance of non-AIDS comorbidities in PLWHA.

Moringa oleifera aqueous leaf extract inhibits reducing monosaccharide-induced protein glycation and oxidation of bovine serum albumin

Advanced glycation end products (AGEs) play an important factor for pathophysiology of diabetes and its complications. Moringa oleifera is one of the medicinal plants that have anti-hyperglycemic activity. However, anti-glycation property of Moringa oleifera leaf extract on the different types of reducing monosaccharides-induced protein glycation has not been investigated. Therefore, the aim of this study was to examine the protective effect of Moringa oleifera aqueous leaf extract (MOE) on reducing sugars-induced protein glycation and protein oxidation. Total phenolic content of MOE was measured using the Folin–Ciocalteu method. Bovine serum albumin was incubated with 0.5 M of reducing sugars (glucose or fructose) with or without MOE (0.5–2.0 mg/mL) for 1, 2, 3 and 4 weeks. The results found that total phenolic content was 38.56 ± 1.50 mg gallic acid equivalents/g dry extract. The formation of fluorescent and non-fluorescent AGEs [N^ε-(carboxymethyl) lysine (CML)] and the level of fructosamine were determined to indicate protein glycation, whereas the level of protein carbonyl content and thiol group were examined for protein oxidation. MOE (0.5–2.0 mg/mL) significantly inhibited the formation of fluorescent, N^ε-CML and markedly decreased fructosamine level (P < 0.05). Moreover, MOE significantly prevented protein oxidation manifested by reducing protein carbonyl and the depletion of protein thiol in a dose-dependent manner (P < 0.05). Thus, the findings indicated that polyphenols containing in MOE have high potential for decreasing protein glycation and protein oxidation that may delay or prevent AGE-related diabetic complications.

Effects of the New Aldose Reductase Inhibitor Benzofuroxane Derivative BF-5m on High Glucose Induced Prolongation of Cardiac QT Interval and Increase of Coronary Perfusion Pressure

This study investigated the effects of the new aldose reductase inhibitor benzofuroxane derivative 5(6)-(benzo[d]thiazol-2-ylmethoxy)benzofuroxane (BF-5m) on the prolongation of cardiac QT interval and increase of coronary perfusion pressure (CPP) in isolated, high glucose (33.3 mM D-glucose) perfused rat hearts. BF-5m was dissolved in the Krebs solution at a final concentration of 0.01 μM, 0.05 μM, and 0.1 μM. 33.3 mM D-glucose caused a prolongation of the QT interval and increase of CPP up to values of 190 ± 12 ms and 110 ± 8 mmHg with respect to the values of hearts perfused with standard Krebs solution (11.1 mM D-glucose). The QT prolongation was reduced by 10%, 32%, and 41%, respectively, for the concentration of BF-5m 0.01 μM, 0.05 μM, and 0.1 μM. Similarly, the CPP was reduced by 20% for BF-5m 0.05 μM and by 32% for BF-5m 0.1 μM. BF-5m also increased the expression levels of sirtuin 1, MnSOD, eNOS, and FOXO-1, into the heart. The beneficial actions of BF-5m were partly abolished by the pretreatment of the rats with the inhibitor of the sirtuin 1 activity EX527 (10 mg/kg/day/7 days i.p.) prior to perfusion of the hearts with high glucose + BF-5m (0.1 μM). Therefore, BF-5m supplies cardioprotection from the high glucose induced QT prolongation and increase of CPP.

Effect of PKC-β Signaling Pathway on Expression of MCP-1 and VCAM-1 in Different Cell Models in Response to Advanced Glycation End Products (AGEs)

Advanced glycation end products (AGEs) are compounds classified as uremic toxins in patients with chronic kidney disease that have several pro-inflammatory effects and are implicated in the development of cardiovascular diseases. To explore the mechanisms of AGEs–endothelium interactions through the receptor for AGEs (RAGE) in the PKC-β pathway, we evaluated the production of MCP-1 and VCAM-1 in human endothelial cells (HUVECs), monocytes, and a coculture of both. AGEs were prepared by albumin glycation and characterized by absorbance and electrophoresis. The effect of AGEs on cell viability was assessed with an MTT assay. The cells were also treated with AGEs with and without a PKC-β inhibitor. MCP-1 and VCAM-1 in the cell supernatants were estimated by ELISA, and RAGE was evaluated by immunocytochemistry. AGEs exposure did not affect cell viability, but AGEs induced RAGE, MCP-1, and VCAM-1 expression in HUVECs. When HUVECs or monocytes were incubated with AGEs and a PKC-β inhibitor, MCP-1 and VCAM-1 expression significantly decreased. However, in the coculture, exposure to AGEs and a PKC-β inhibitor produced no significant effect. This study demonstrates, in vitro, the regulatory mechanisms involved in MCP-1 production in three cellular models and VCAM-1 production in HUVECs, and thus mimics the endothelial dysfunction caused by AGEs in early atherosclerosis. Such mechanisms could serve as therapeutic targets to reduce the harmful effects of AGEs in patients with chronic kidney disease.

The inhibition of aldose reductase attenuates hepatic ischemia-reperfusion injury through reducing inflammatory response

OBJECTIVE

We aim to investigate the role of aldose reductase (AR) in hepatic ischemia-reperfusion injury (IRI) of normal and fatty livers and to explore the underlying mechanisms.

BACKGROUND

Hepatic IRI is a typical inflammatory response during liver surgery. It contributes to liver graft failure or nonfunction after transplantation. Increasing evidence implicates that AR plays a key role in a number of inflammatory diseases. However, the role of AR in hepatic IRI is still unknown.

METHODS

Intragraft AR expression profile and the association with liver graft injury were investigated in both human and rat liver transplantation using normal or fatty graft. The direct role of AR in hepatic IRI was studied in the AR knockout mice IRI model with or without fatty liver. They were further validated by the simulated IRI in vitro model using fatty LO2 cells with or without AR inhibitor zopolrestat and primary peritoneal macrophages isolated from AR knockout and wild-type mice. Gene expression of inflammatory cytokines/chemokines, the infiltration of macrophages/neutrophils, and NF-κB pathway activation were compared among different groups.

RESULTS

AR was overexpressed in liver graft after human and rat liver transplantation and correlated with consequent liver injuries. The knockout of AR significantly attenuated hepatic sinusoidal damage and apoptosis in both normal and fatty livers after IRI. The expression of proinflammatory cytokines/chemokines and neutrophil chemoattractants, infiltration of macrophage and neutrophil, and activation of inflammation-associated NF-κB and JNK pathway were downregulated in AR knockout mice. Furthermore, the inhibition of AR effectively suppressed macrophage migration and decreased lipopolysaccharide (LPS)-induced production of proinflammatory cytokines/chemokines in isolated macrophages.

CONCLUSIONS

The deficiency of AR attenuated hepatic IRI in both normal and fatty livers by reducing liver inflammatory responses.

Asiatic acid and maslinic acid protected heart via anti-glycative and anti-coagulatory activities in diabetic mice

The cardiac protective effects of asiatic acid (AA) and maslinic acid (MA) in diabetic mice were examined.

The role of advanced glycation end products in various types of neurodegenerative disease: a therapeutic approach

Protein glycation is initiated by a nucleophilic addition reaction between the free amino group from a protein, lipid or nucleic acid and the carbonyl group of a reducing sugar. This reaction forms a reversible Schiff base, which rearranges over a period of days to produce ketoamine or Amadori products. The Amadori products undergo dehydration and rearrangements and develop a cross-link between adjacent proteins, giving rise to protein aggregation or advanced glycation end products (AGEs). A number of studies have shown that glycation induces the formation of the β-sheet structure in β-amyloid protein, α-synuclein, transthyretin (TTR), copper-zinc superoxide dismutase 1 (Cu, Zn-SOD-1), and prion protein. Aggregation of the β-sheet structure in each case creates fibrillar structures, respectively causing Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, familial amyloid polyneuropathy, and prion disease. It has been suggested that oligomeric species of glycated α-synuclein and prion are more toxic than fibrils. This review focuses on the pathway of AGE formation, the synthesis of different types of AGE, and the molecular mechanisms by which glycation causes various types of neurodegenerative disease. It discusses several new therapeutic approaches that have been applied to treat these devastating disorders, including the use of various synthetic and naturally occurring inhibitors. Modulation of the AGE-RAGE axis is now considered promising in the prevention of neurodegenerative diseases. Additionally, the review covers several defense enzymes and proteins in the human body that are important anti-glycating systems acting to prevent the development of neurodegenerative diseases.

Role of red grape polyphenols as antidiabetic agents

The worldwide incidence of diabetes mellitus has reached alarming proportions. Persistent hyperglycemia due to impaired insulin activity and/or insulin resistance inversely affects the retina, cerebrovascular system, kidney, peripheral limbs, and other parts of the body, which leads to life-threatening complications. The causal role of oxidative stress in the development and progression of diabetic complications has been emphasized. Polyphenols present in natural products have gained much attention in recent decades in preventive studies against diabetes-associated pathologies. In the present review, we provide a comparative update on the role of quercetin, myricetin, and resveratrol—the major polyphenols present in red grapes—in intervening with diabetic complications, and a brief highlight on the molecular mechanisms underlying oxidative stress mediated hyperglycemia.

Prevalence of peripheral vascular disease and its association with carotid intima-media thickness and arterial stiffness in type 2 diabetes: the Chennai urban rural epidemiology study (CURES 111)

We investigated the prevalence of peripheral vascular disease (PVD) and its association with preclinical atherosclerotic markers [intima-media thickness (IMT)] and arterial stiffness among 1755 urban south Indian type 2 diabetic subjects recruited from the Chennai Urban Rural Epidemiology Study (CURES). Doppler studies were performed, and PVD was defined as ankle-brachial index (ABI) of ≤0.9. IMT of the common carotid artery was determined using high-resolution B-mode ultrasonography, and augmentation index (AGI) was measured using the Sphygmocor apparatus. The overall prevalence of PVD was 8.3% (age-standardized 6.5%). The prevalence of PVD was higher among known diabetic subjects (n = 1401) compared to newly detected diabetic subjects (n = 354) (8.6% vs 6.8%, p = 0.250). The mean IMT and AGI in subjects with PVD were significantly higher compared to subjects without PVD (IMT: 0.99 ± 0.26 mm vs 0.83 ± 0.19 mm; AGI: 28.1 ± 9.6% vs 25.7 ± 9.8%, respectively). IMT was independently associated with PVD even after adjusting for age [odds ratio (OR) = 2.9 (1.2-6.7), p = 0.016 for second tertile and OR = 3.9 (1.7-9.3), p = 0.002 for third tertile compared to first tertile]. AGI was also associated with PVD in the unadjusted model [OR = 1.8 (1.1-3.1), p = 0.027 for second tertile compared to first tertile]. However, when adjusted for age, the significance was lost. In conclusion, among urban south Indian type 2 diabetic subjects, the prevalence of PVD is 8.3% and IMT is more strongly associated with PVD than AGI.

Kinetics and molecular docking studies of an anti-diabetic complication inhibitor fucosterol from edible brown algae Eisenia bicyclis and Ecklonia stolonifera

In the present study, we investigated the anti-diabetic potential of fucosterol by evaluating the ability of this compound to inhibit rat lens aldose reductase (RLAR), human recombinant aldose reductase (HRAR), protein tyrosine phosphatase 1B (PTP1B), and α-glucosidase. Fucosterol displayed moderate inhibitory activity against RLAR, HRAR, and PTP1B. However, it showed weak or no activity against AGE formation and α-glucosidase. In addition, our kinetic study revealed that fucosterol showed a mixed type inhibition against RLAR and HRAR, while it noncompetitively inhibited PTP1B. Since fucosterol inhibited aldose reductase (AR), it holds great promise for use in the treatment of diabetic complications. Therefore, we predicted the 3D structure of AR in rat and human using the Autodock program to simulate binding between AR and fucosterol and evaluate the binding site-directed inhibition of AR by fucosterol. Results of the docking simulations of fucosterol demonstrated negative binding energies (-8.2 kcal/mol for RLAR and -8.5 kcal/mol for HRAR), which indicated a higher affinity and tighter binding capacity of fucosterol for the active site of the enzyme. In particular, the hydrophobic ring system and the aliphatic side chain of fucosterol were found to be tightly bound in a specificity pocket through apolar amino acid residues on AR, while the anion binding site on AR interacts with the 3-hydroxyl group and the double bond on the side chain of fucosterol. The results of the present study clearly demonstrated the potential of using fucosterol for the management and treatment of diabetes and diabetes-associated complications.

The NAD ratio redox paradox: why does too much reductive power cause oxidative stress?

The reductive power provided by nicotinamide adenine dinucleotides is invaluable for several cellular processes. It drives metabolic reactions, enzymatic activity, regulates genetic expression and allows for the maintenance of a normal cell redox status. Therefore, the balance between the oxidized (NAD(+)) and the reduced (NADH) forms is critical for the cell's proper function and ultimately, for its survival. Being intimately associated with the cells' metabolism, it is expected that alterations to the NAD(+)/NADH ratio are to be found in situations of metabolic diseases, as is the case of diabetes. NAD(+) is a necessary cofactor for several enzymes' activity, many of which are related to metabolism. Therefore, a decrease in the NAD(+)/NADH ratio causes these enzymes to decrease in activity (reductive stress), resulting in an altered metabolic situation that might be the first insult toward several pathologies, such as diabetes. Here, we review the importance of nicotinamide adenine dinucleotides in the liver cell and its fluctuations in a state of type 2 diabetes mellitus.

Anti-inflammatory and cardioprotective effects of tadalafil in diabetic mice

Background

Insulin resistance impairs nitric oxide (NO) bioavailability and obesity promotes a state of chronic inflammation and damages the vascular endothelium. Phosphodiesterase-5 inhibitors restore NO signaling and may reduce circulating inflammatory markers, and improve metabolic parameters through a number of mechanisms. We hypothesized that daily administration of the PDE-5 inhibitor, tadalafil (TAD) will attenuate inflammation, improve fasting plasma glucose and triglyceride levels, body weight, and reduce infarct size after ischemia/reperfusion injury in obese, diabetic mice.

Methods

Twenty leptin receptor null (db/db) mice underwent treatment with TAD (1 mg/Kg) or 10% DMSO for 28 days. Body weight and fasting plasma glucose levels were determined weekly. Upon completion, hearts were isolated and subjected to 30 min global ischemia followed by 60 min reperfusion in a Langendorff model. Plasma samples were taken for cytokine analysis and fasting triglyceride levels. Infarct size was measured using computer morphometry of tetrazolium stained sections. Additionally, ventricular cardiomyocytes were isolated and subjected to 40 min of simulated ischemia and reoxygenation. Necrosis was determined using trypan blue exclusion and LDH release assay and apoptosis was assessed by TUNEL assay after 1 h or 18 h of reoxygenation, respectively.

Results

Treatment with TAD caused a reduction in infarct size in the diabetic heart (23.2±1.5 vs. 47.8±3.7%, p<0.01, n = 6/group), reduced fasting glucose levels (292±31.8 vs. 511±19.3 mg/dL, p<0.001) and fasting triglycerides (43.3±21 vs. 129.7±29 mg/dL, p<0.05) as compared to DMSO, however body weight was not significantly reduced. Circulating tumor necrosis factor-α and interleukin-1β were reduced after treatment compared to control (257±16.51 vs. 402.3±17.26 and 150.8±12.55 vs. 264±31.85 pg/mL, respectively; P<0.001) Isolated cardiomyocytes from TAD-treated mice showed reduced apoptosis and necrosis.

Conclusion

We have provided the first evidence that TAD therapy ameliorates circulating inflammatory cytokines and chemokines in a diabetic animal model while improving fasting glucose levels and reducing infarct size following ischemia-reperfusion injury in the heart.

Angiotensin-converting enzyme inhibition and food restriction in diabetic mice do not correct the increased sensitivity for ischemia-reperfusion injury

Background

The number of patients with diabetes or the metabolic syndrome reaches epidemic proportions. On top of their diabetic cardiomyopathy, these patients experience frequent and severe cardiac ischemia-reperfusion (IR) insults, which further aggravate their degree of heart failure. Food restriction and angiotensin-converting enzyme inhibition (ACE-I) are standard therapies in these patients but the effects on cardiac IR injury have never been investigated. In this study, we tested the hypothesis that 1° food restriction and 2° ACE-I reduce infarct size and preserve cardiac contractility after IR injury in mouse models of diabetes and the metabolic syndrome.

Methods

C57Bl6/J wild type (WT) mice, leptin deficient ob/ob (model for type II diabetes) and double knock-out (LDLR-/-;ob/ob, further called DKO) mice with combined leptin and LDL-receptor deficiency (model for metabolic syndrome) were used. The effects of 12 weeks food restriction or ACE-I on infarct size and load-independent left ventricular contractility after 30 min regional cardiac ischemia were investigated. Differences between groups were analyzed for statistical significance by Student’s t-test or factorial ANOVA followed by a Fisher’s LSD post hoc test.

Results

Infarct size was larger in ob/ob and DKO versus WT. Twelve weeks of ACE-I improved pre-ischemic left ventricular contractility in ob/ob and DKO. Twelve weeks of food restriction, with a weight reduction of 35-40%, or ACE-I did not reduce the effect of IR.

Conclusion

ACE-I and food restriction do not correct the increased sensitivity for cardiac IR-injury in mouse models of type II diabetes and the metabolic syndrome.

An update on advanced glycation endproducts and atherosclerosis

Advanced glycation endproducts (AGEs) are a group of modified molecular species formed by nonenzymatic reactions between the aldehydic group of reducing sugars with proteins, lipids, or nucleic acids. Formation and accumulation of AGEs are related to the aging process and are accelerated in diabetes. AGEs are generated in hyperglycemia, but their production also occurs in settings characterized by oxidative stress and inflammation. These species promote vascular damage and acceleration of atherosclerotic plaque progression mainly through two mechanisms: directly, altering the functional properties of vessel wall extracellular matrix molecules, or indirectly, through activation of cell receptor-dependent signaling. Interaction between AGEs and the key receptor for AGEs (RAGE), a transmembrane signaling receptor which is present in all cells relevant to atherosclerosis, alters cellular function, promotes gene expression, and enhances the release of proinflammatory molecules. The importance of the AGE-RAGE interaction and downstream pathways, leading to vessel wall injury and plaque development, has been amply established in animal studies. Moreover, the deleterious link of AGEs with diabetic vascular complications has been suggested in many human studies. Blocking the vicious cycle of AGE-RAGE axis signaling may be essential in controlling and preventing cardiovascular complications. In this article, we review the pathogenetic role of AGEs in the development, progression and instability of atherosclerosis, and the potential targets of this biological system for the prevention and treatment of cardiovascular disease.

Aldose reductase and cardiovascular diseases, creating human-like diabetic complications in an experimental model

Hyperglycemia and reduced insulin actions affect many biological processes. One theory is that aberrant metabolism of glucose via several pathways including the polyol pathway causes cellular toxicity. Aldose reductase (AR) is a multifunctional enzyme that reduces aldehydes. Under diabetic conditions AR converts glucose into sorbitol, which is then converted to fructose. This article reviews the biology and pathobiology of AR actions. AR expression varies considerably among species. In humans and rats, the higher level of AR expression is associated with toxicity. Flux via AR is increased by ischemia and its inhibition during ischemia reperfusion reduces injury. However, similar pharmacological effects are not observed in mice unless they express a human AR transgene. This is because mice have much lower levels of AR expression, probably insufficient to generate toxic byproducts. Human AR expression in LDL receptor knockout mice exacerbates vascular disease, but only under diabetic conditions. In contrast, a recent report suggests that genetic ablation of AR increased atherosclerosis and increased hydroxynonenal in arteries. It was hypothesized that AR knockout prevented reduction of toxic aldehydes. Like many in vivo effects found in genetically manipulated animals, interpretation requires the reproduction of human-like physiology. For AR, this will require tissue specific expression of AR in sites and at levels that approximate those in humans.

Aldose reductase inhibition ameliorates the detrimental effect of estrogen replacement therapy on neuropathology in diabetic rats subjected to transient forebrain ischemia

Estrogen replacement therapy (ERT) elicits a deleterious, instead of protective, effect on neuropathology in diabetic ovariectomized (OVX) rats subjected to cerebral ischemia. This transformation may be linked to an estrogen-associated increase in function of the receptor for advanced glycation end-products (RAGE). Moreover, under diabetic conditions, advanced glycation end-products (AGEs) are excessively generated through the aldose reductase (AR)-polyol pathway. As such, in diabetic rats given ERT, a RAGE-related exacerbation of post-ischemic brain injury can occur. Thus, in the present study, we evaluated the contribution of AR in estrogen's detrimental effect on diabetic animals subjected to transient forebrain ischemia (TFI). Streptozotocin- and 17-beta estradiol-treated OVX female rats were divided into two groups, where AR activity was blocked using epalrestat; or AGEs production was restricted, via administrating the protein glycation crosslink breaker, ALT-711. In all animals, ERT was initiated approximately 10days before TFI. Pial venular leukocyte adhesion was evaluated over 10h post-TFI using a cranial window/intravital microscopy technique. In vehicle-treated control groups, a significant increase in leukocyte adhesion was observed post-TFI. Leukocyte extravasation, starting at approximately 6h post-TFI, was detected in most of the control animals. Chronic administration of either epalrestat or ALT-711 was associated with a marked decrease in post-TFI leukocyte adhesion, and the complete prevention of leukocyte extravasation. Animals receiving either epalrestat or ALT-711 exhibited a significant improvement in neurologic function, at 72h post-ischemia, compared to vehicle-treated controls. Post-ischemic (72h) histopathology was significantly reduced by epalrestat. Compared to the non-diabetic (ND) controls, diabetic OVX rats in the absence or presence of ERT showed a significant 2-fold or 3-fold increase in cortical AR mRNA levels, respectively. In contrast, only a modest increase in AR protein expression, relative to ND control, was detected in the two diabetic groups. The present findings suggest that AR participates in estrogen's deleterious action on post-ischemic neuropathology in diabetics by promoting inflammation. Targeting the AR-controlled polyol pathway may be a clinically promising strategy to restore the neuroprotection of ERT in diabetic females.

Aldose reductase inhibition prevents lipopolysaccharide-induced glucose uptake and glucose transporter 3 expression in RAW264.7 macrophages

Macrophages which play a central role in the injury, infection and sepsis, use glucose as their primary source of metabolic energy. Increased glucose uptake in inflammatory cells is well known to be one of the responsible processes that cause inflammatory response and cytotoxicity. We have shown recently that the inhibition of aldose reductase (AR) prevents bacterial endotoxin, lipopolysaccharide (LPS)-induced cytotoxicity and inflammatory response in macrophages. However, it is not known how AR inhibition prevents LPS-induced inflammation. Here in, we examined the effect of AR inhibition on LPS-induced glucose uptake and the expression of glucose transporter 3 (GLUT-3) in RAW264.7 murine macrophages. Stimulation of macrophages with LPS-increased glucose uptake as measured by using C(14) labeled methyl-d-glucose and inhibition of AR prevented it. Similarly, ablation of AR by using AR-siRNA also prevented the LPS-induced glucose uptake in macrophages. Further, AR inhibition also prevented the LPS-induced up-regulation of GLUT-3 expression, cyclic adenosine monophosphate (cAMP) accumulation and protein kinase A (PKA) activation in RAW264.7 cells. Moreover, LPS-induced down-regulation of cAMP response element modulator (CREM), phosphorylation of cAMP response element-binding protein (CREB) and DNA-binding of CREB were also prevented by AR inhibition. Further, inhibition of AR or PKA also prevented the LPS-induced levels of GLUT-3 protein as well as mRNA in macrophages. These results indicate that AR mediates LPS-induced glucose uptake and expression of glucose transporter-3 via cAMP/PKA/CREB pathway and thus represents a novel mechanism by which AR regulates LPS-induced inflammation.

Inhibitory activities of prenylated flavonoids from Sophora flavescens against aldose reductase and generation of advanced glycation endproducts

Important targets for the prevention and treatment of diabetic complications include aldose reductase (AR) inhibitors (ARIs) and inhibitors of advanced glycation endproduct (AGE) formation. Here we evaluate the inhibitory activities of prenylated flavonoids isolated from Sophora flavescens, a traditional herbal medicine, on rat lens AR (RLAR), human recombinant AR (HRAR) and AGE formation. Among the tested compounds, two prenylated chalcones — desmethylanhydroicaritin (1) and 8-lavandulylkaempferol (2) — along with five prenylated flavanones — kurarinol (8), kurarinone (9), (2S)-2′-methoxykurarinone (10), (2S)-3β,7,4′-trihydroxy-5-methoxy-8-(γ,γ-dimethylally)-flavanone (11), and kushenol E (13) were potent inhibitors of RLAR, with IC50 values of 0.95, 3.80, 2.13, 2.99, 3.77, 3.63 and 7.74 μM, respectively, compared with quercetin (IC50 7.73 μM). In the HRAR assay, most of the prenylated flavonoids tested showed marked inhibitory activity compared with quercetin (IC50 2.54 μM). In particular, all tested prenylated flavonols, such as desmethylanhydroicaritin (1, IC50 0.45 μM), 8-lavandulylkaempferol (2, IC50 0.79 μM) and kushenol C (3, IC50 0.85 μM), as well as a prenylated chalcone, kuraridin (5, IC50 0.27 μM), and a prenylated flavanone, (2S)-7,4′-dihydroxy-5-methoxy-8-(γ,γ-dimethylally)-flavanone (12, IC50 0.37 μM), showed significant inhibitory activities compared with the potent AR inhibitor epalrestat (IC50 0.28 μM). Interestingly, prenylated flavonoids 1 (IC50 104.3 μgmL−1), 2 (IC50 132.1 μgmL−1), 3 (IC50 84.6 μgmL−1) and 11 (IC50 261.0 μgmL−1), which harbour a 3-hydroxyl group, also possessed good inhibitory activity toward AGE formation compared with the positive control aminoguanidine (IC50 115.7 μgmL−1). Thus, S. flavescens and its prenylated flavonoids inhibit the processes that underlie diabetic complications and related diseases and may therefore have therapeutic benefit.

Novel role for aldose reductase in mediating acute inflammatory responses in the lung

Exaggerated inflammatory responses and the resultant increases in alveolar-capillary permeability underlie the pathogenesis of acute lung injury during sepsis. This study examined the functions of aldose reductase (AR) in mediating acute lung inflammation. Transgenic mice expressing human AR (ARTg) were used to study the functions of AR since mice have low intrinsic AR activity. In a mild cecal ligation and puncture model, ARTg mice demonstrated an enhanced AR activity and a greater inflammatory response as evaluated by circulating cytokine levels, neutrophil accumulation in the lungs, and activation of Rho kinase in lung endothelial cells (ECs). Compared with WT lung cells, ARTg lung cells produced more IL-6 and showed augmented JNK activation in response to LPS stimulation ex vivo. In human neutrophils, AR activity was required for fMLP-included CD11b activation and up-regulation, respiratory burst, and shape changes. In human pulmonary microvascular ECs, AR activity was required for TNF-alpha-induced activation of the Rho kinase/MKK4/JNK pathway and IL-6 production, but not p38 activation or ICAM-1 expression. Importantly, AR activity in both human neutrophils and ECs was required for neutrophil adhesion to TNF-alpha-stimulated ECs. These data demonstrate a novel role for AR in regulating the signaling pathways leading to neutrophil-EC adhesion during acute lung inflammation.

Clinical, historical and diagnostic findings associated with right ventricular dysfunction in patients with central and non-massive pulmonary embolism

Right ventricular dysfunction during acute pulmonary embolism (PE) predisposes to hemodynamic instability and cardiogenic shock. Aim of this case-control study was to determine the clinical, historical and diagnostic findings associated with right ventricular dysfunction in patients with acute PE involving the main or segmental pulmonary arteries (central PE) and without hemodynamic instability on admission to the Emergency Department (ED) (non-massive PE). From January 1, 2002 to December 31, 2005, 211 patients with central PE were admitted to the Department of Emergency Medicine of the "Antonio Cardarelli" Hospital (Naples, Italy). One hundred eighteen of them had echocardiographic evidence of right ventricular dysfunction on admission to the ED. A history of type 2 diabetes mellitus and chronic obstructive pulmonary disease were significantly associated with an increased risk of this PE-related complication. Compared to patients without right ventricular dysfunction, those with right ventricular dysfunction showed higher levels of markers of cardiac damage, and a significant impairment of respiratory function. Echocardiographic evidence of right ventricular dysfunction on admission to the ED was significantly associated with the occurrence of hemodynamic instability and cardiogenic shock during the PE clinical course. The study results indicate that a history of type 2 diabetes mellitus and chronic obstructive pulmonary disease are significantly associated with the occurrence of right ventricular dysfunction in patients with non-massive and central PE independent of age, gender and other historical and clinical variables detectable on admission to the ED.

Polyol pathway and RAGE: a central metabolic and signaling axis in diabetic complications

There are multiple metabolic and molecular consequences of hyperglycemia. This review will focus on the roles of the polyol pathway and the receptor for advanced glycation end products (RAGE) in the pathogenesis of diabetic complications. The lead enzyme of the polyol pathway, aldose reductase, transduces maladaptive effects of hyperglycemia by multiple mechanisms, at least in part via the generation of the products of nonenzymatic glycation of proteins, the advanced glycation end products (AGEs). Furthermore, seminal shifts in metabolic flux in the intracellular space stimulated by aldose reductase action activate signal transduction pathways, which alter gene expression and change cellular phenotype. Among the ligands of the multi-ligand receptor RAGE are the AGEs. AGE-RAGE stimulation mediates vascular and target cell dysfunction. The intersection and interdependence of the polyol pathway-RAGE connection suggest that targeting this axis may provide benefit in reducing the complications of diabetes.

Estrogen replacement therapy in diabetic ovariectomized female rats potentiates postischemic leukocyte adhesion in cerebral venules via a RAGE-related process

In this study, we tested the hypothesis that the documented transformation of 17beta-estradiol (E2) from a counterinflammatory hormone in nondiabetic (ND) rats to a proinflammatory agent in rats with diabetes mellitus (DM) is due to an enhanced contribution from the receptor for advanced glycation end products (RAGE). Rhodamine 6G-labeled leukocytes were observed through a closed cranial window in rats. In vivo pial venular leukocyte adherence and infiltration were measured over 10 h reperfusion after transient forebrain ischemia in DM (streptozotocin) versus ND intact, ovariectomized (OVX), and E2-replaced (for 7-10 days) OVX (OVE) females. The role of RAGE was examined in two ways: 1) RAGE knockdown via topical application of RAGE antisense versus missense oligodeoxynucleotide or 2) intracerebroventricular injection of the RAGE decoy inhibitor, soluble RAGE. Among diabetic rats, the lowest levels of cortical RAGE mRNA and immunoreactivity of the RAGE ligand, AGE, were seen in OVX females, with significantly higher levels exhibited in intact and OVE females. However, results from the analysis of cortical RAGE protein only partially tracked those findings. When comparing ND to DM rats, cortical AGE immunoreactivity was significantly lower in OVE and intact females but similar in OVX rats. In DM rats, the level of postischemic leukocyte adhesion and infiltration (highest to lowest) was OVE>intact>>untreated OVX. In NDs, adhesion was highest in the untreated OVX group. Leukocyte extravasation was observed at >6 h postischemia but only in diabetic OVE and intact females and in ND OVX (untreated) rats. Pretreatment with RAGE antisense-oligodeoxynucleotide or soluble RAGE attenuated postischemic leukocyte adhesion and prevented infiltration but only in the diabetic OVE and intact groups. These results indicate that the exacerbation of postischemic leukocyte adhesion by chronic E2 replacement therapy in diabetic OVX females involves a RAGE-related mechanism. Targeting RAGE may restore the neuroprotective effect of E2 replacement therapy in diabetic females.

Diabetes and the peripheral nerve

Diabetes-induced damage to peripheral nerve culminates in development of peripheral diabetic neuropathy (PDN), one of the most devastating complications of diabetes mellitus and a leading cause of foot amputation. The pathogenesis of PDN occurs as a consequence of complex interactions among multiple hyperglycemia-initiated mechanisms, impaired insulin signaling, inflammation, hypertension, and disturbances of fatty acid and lipid metabolism. This review describes experimental new findings in animal and cell culture models as well as clinical data suggesting the importance of 1) previously established hyperglycemia-initiated mechanisms such as increased aldose reductase activity, non-enzymatic glycation/glycooxidation, activation of protein kinase C, 2) oxidative-nitrosative stress and poly(ADP-ribose) polymerase activation; 3) mitogen-activated protein kinase and cyclooxygenase-2 activation, impaired Ca(++) homeostasis and signaling, and several other mechanisms, in PDN.

S100A8 and S100A9 mediate endotoxin-induced cardiomyocyte dysfunction via the receptor for advanced glycation end products

Cardiovascular dysfunction as a result of sepsis is the leading cause of death in the critically ill. Cardiomyocytes respond to infectious pathogens with a Toll-like receptor-initiated proinflammatory response in conjunction with a decrease in contractility, although the downstream events linking Toll-like receptor activation and reduced cardiac contractility remain to be elucidated. Using microarray analysis of cardiac tissue exposed to systemic lipopolysaccharide (LPS), we discovered that 2 small calcium-regulating proteins (S100A8 and S100A9) are highly upregulated. HL-1 cardiomyocytes, isolated primary cardiomyocytes, and live mice were exposed to LPS, whereas beating HL-1 cells had S100A8 and S100A9 overexpressed and their calcium flux quantified. Using in vivo microbubble technology, we delivered S100A8 and S100A9 to normal mouse hearts; using the same technology, we inhibited S100A9 production in mouse hearts and subsequently exposed them to LPS. Coimmunoprecipitation of S100A8 and S100A9 identified interaction with RAGE (the receptor for advanced glycation end products), the cardiac function and postreceptor signaling of which were investigated. HL-1 cardiomyocytes, isolated primary cardiomyocytes, and whole hearts exposed to LPS have large increases in S100A8 and S100A9. Cardiac overexpression of S100A8 and S100A9 led to a RAGE-dependent decrease in calcium flux and, in the intact mouse, to a decreased cardiac ejection fraction, whereas knockdown of S100A9 attenuated LPS-induced cardiac dysfunction. Cardiomyocytes exposed to LPS express S100A8 and S100A9, leading to a RAGE-mediated decrease in cardiomyocyte contractility. This finding provides a novel mechanistic link between circulating pathogen-associated molecular products and subsequent cardiac dysfunction.

High-fat diet induced neuropathy of pre-diabetes and obesity: effects of "healthy" diet and aldose reductase inhibition

OBJECTIVE

Subjects with dietary obesity and pre-diabetes have an increased risk for developing both nerve conduction slowing and small sensory fiber neuropathy. Animal models of this type of neuropathy have not been described. This study evaluated neuropathic changes and their amenability to dietary and pharmacological interventions in mice fed a high-fat diet (HFD), a model of pre-diabetes and alimentary obesity.

RESEARCH DESIGN AND METHODS

Female C57BL6/J mice were fed normal diets or HFDs for 16 weeks.

RESULTS

HFD-fed mice developed obesity, increased plasma FFA and insulin concentrations, and impaired glucose tolerance. They also had motor and sensory nerve conduction deficits, tactile allodynia, and thermal hypoalgesia in the absence of intraepidermal nerve fiber loss or axonal atrophy. Despite the absence of overt hyperglycemia, the mice displayed augmented sorbitol pathway activity in the peripheral nerve, as well as 4-hydroxynonenal adduct nitrotyrosine and poly(ADP-ribose) accumulation and 12/15-lipoxygenase overexpression in peripheral nerve and dorsal root ganglion neurons. A 6-week feeding with normal chow after 16 weeks on HFD alleviated tactile allodynia and essentially corrected thermal hypoalgesia and sensory nerve conduction deficit without affecting motor nerve conduction slowing. Normal chow containing the aldose reductase inhibitor fidarestat (16 mg x kg(-1) x day (-1)) corrected all functional changes of HFD-induced neuropathy.

CONCLUSIONS

Similar to human subjects with pre-diabetes and obesity, HFD-fed mice develop peripheral nerve functional, but not structural, abnormalities and, therefore, are a suitable model for evaluating dietary and pharmacological approaches to halt progression and reverse diabetic neuropathy at the earliest stage of the disease.

Pyridine nucleotide redox abnormalities in diabetes

In addition to hyperglycemia, diabetes is associated with increased levels of circulating free fatty acids, lactate, and branched chain amino acids, all of which produce an excessive reduced form of pyridine nucleotides NADH (reductive stress) in the cytosol and mitochondria. Our studies suggest that cytosolic NADH reductive stress under high glucose is largely caused by increased flux of glucose through polyol (sorbitol) pathway consisting of aldose reductase and sorbitol dehydrogenase. Inhibition of aldose reductase that blocks the polyol pathway has been shown to ameliorate diabetic neuropathy in humans. Cytosolic NADH reductive stress is predicted to increase production of diglycerides, reactive oxygen species, and methylglyoxal. Recent studies indicate that increasing NADH affects gene expression through the NADH activating transcriptional co-repressor, C-terminal binding protein (CtBP). In addition, it has been shown that the NADH utilizing enzyme, glyceraldehyde-3-phosphate dehydrogenase, participates as transcriptional regulator. These findings testify to the importance of NADH redox balance in cell biology and pathogenesis of diabetes and its complications. For example, through CtBP, the high NADH to NAD(+) ratio decreases an expression of SirT1, the protein inducing longevity and anti-apoptosis. This review covers metabolic cascades causing reductive stress and oxidative stress in diabetes after a brief introduction of the redox concept.

Glycotoxins in the diet promote diabetes and diabetic complications

Oxidant stress underlies diabetes and diabetic complications, including cardiovascular, renal, and retinal disease. Advanced glycation end products (AGEs), or glycotoxins, are a significant contributor to oxidant stress in diabetes. The diet is a major, unrecognized source of AGEs. Importantly, reduction of dietary AGEs decreases circulating inflammatory markers in both diabetic patients and prediabetic patients and complications in animal models. This beneficial outcome requires only a 50% decrease in dietary AGEs, making this necessary intervention practical and inexpensive.

Mechanisms linking diabetes mellitus to the development of atherosclerosis: a role for endoplasmic reticulum stress and glycogen synthase kinase-3

Recent decades have seen a significant increase in the incidence of diabetes mellitus. The number of individuals with diabetes is projected to reach 300 million by the year 2025. Diabetes is a leading cause of blindness, renal failure, lower limb amputation, and an independent risk factor for atherosclerotic cardiovascular disease (CVD)--a leading cause of death in Western society. Understanding the molecular and cellular mechanisms by which diabetes mellitus promotes atherosclerosis is essential to developing methods to treat and prevent diabetes-associated CVD. This review summarizes our current knowledge of the mechanisms by which diabetes may promote atherogenesis and specifically focuses on a novel pathway linking these 2 conditions. We hypothesize that the accumulation of intracellular glucosamine observed in conditions of chronic hyperglycaemia may promote atherogenesis via a mechanism involving dysregulated protein folding, activation of endoplasmic reticulum (ER) stress, and increased glycogen synthase kinase (GSK)-3 activity. The identification of this novel mechanism provides a promising hypothesis and multiple new targets for potential therapeutic intervention in the treatment of diabetes mellitus and accelerated atherosclerosis.

Role of changes in cardiac metabolism in development of diabetic cardiomyopathy

In patients with diabetes, an increased risk of symptomatic heart failure usually develops in the presence of hypertension or ischemic heart disease. However, a predisposition to heart failure might also reflect the effects of underlying abnormalities in diastolic function that can occur in asymptomatic patients with diabetes alone (termed diabetic cardiomyopathy). Evidence of cardiomyopathy has also been demonstrated in animal models of both Type 1 (streptozotocin-induced diabetes) and Type 2 diabetes (Zucker diabetic fatty rats and ob/ob or db/db mice). During insulin resistance or diabetes, the heart rapidly modifies its energy metabolism, resulting in augmented fatty acid and decreased glucose consumption. Accumulating evidence suggests that this alteration of cardiac metabolism plays an important role in the development of cardiomyopathy. Hence, a better understanding of this dysregulation in cardiac substrate utilization during insulin resistance and diabetes could provide information as to potential targets for the treatment of cardiomyopathy. This review is focused on evaluating the acute and chronic regulation and dysregulation of cardiac metabolism in normal and insulin-resistant/diabetic hearts and how these changes could contribute toward the development of cardiomyopathy.