3-nitrotyrosine and Diabetic-Cardiomyopathies

The purpose of the study is to identify potential mechanisms involved in the cardiac protective effects of sitagliptin in Zucker diabetic fatty (ZDF) rats.. Male non-diabetic lean Zucker rats (Lean) and ZDF rats treated with saline (ZDF) or sitagliptin (ZDF + sita) were used in this study. The blood pressure and lipid profiles were increased significantly in ZDF rats compared with Lean rats. ZDF + sitagliptin rats had decreased systolic blood pressure compared with ZDF rats. Sitagliptin treatment decreased total cholesterol (TC), triglycerides (TGs), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) levels. Ejection fraction (EF) and fractional shortening (FS) were decreased in ZDF rats, which improved with sitagliptin from 59.8% ± 3.0 and 34.5% ± 3.1 to 66.9% ± 3.4 and 40.9% ± 4.2, respectively. Moreover, the nitroxidative stress level was increased while autophagy levels were decreased in ZDF rats, which was reversed by the administration of sitagliptin. Treatment with sitagliptin or FeTMPyP improved the autophagy level in high-glucose cultured H9c2 cells by increasing autolysosome numbers from 15 ± 4 to 21 ± 3 and 22 ± 3, respectively. We detected a positive correlation between DPP-4 activity and 3-nitrotyrosine levels (r = 0.3903; P < 0.01), a negative correlation between Beclin-1 levels and DPP-4 activity (r = - 0.3335; P < 0.01), and a negative correlation between 3-nitrotyrosine and Beclin-1 levels (r = - 0.3794; P < 0.01) in coronary heart disease patients.. Sitagliptin alleviates diabetes-induced cardiac injury by reducing nitroxidative stress and promoting autophagy. This study indicates a novel target pathway for the treatment of cardiovascular complications in type 2 diabetes mellitus.

Topics: Animals; Autophagy; Beclin-1; Blood Glucose; Cell Line; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Dipeptidyl Peptidase 4; Dipeptidyl-Peptidase IV Inhibitors; Disease Models, Animal; Humans; Lipids; Male; Myocytes, Cardiac; Nitrosative Stress; Obesity; Rats, Zucker; Sitagliptin Phosphate; Stroke Volume; Tyrosine; Ventricular Function, Left

The aim of this study was to investigate whether 3-nitrotyrosine (3-NT) may serve as a predictive biomarker for cardiomyocyte apoptosis in a diabetic cardiomyopathic rat model. Using male Sprague-Dawley (SD) rats in a prospective, randomized, controlled study, a diabetic type II animal model was established by injection with streptozotocin. The diabetic group and the diabetic cardiomyopathy (DCM) group were administered valsartan. This study revealed the following: i) The ratio of heart/body weight increased in the DCM, diabetes administered with valsartan (D+V) and DCM+V groups compared with the N group. ii) The expression index (EI) of 3-NT correlated positively with the apoptotic index (AI) of the cardiomyocytes, whereas 3-NT in the serum did not reflect changes in the AI. iii) The AI of the DCM group was the highest of the assessed groups. The AI of the DCM group was higher than that in the D+V group, and the AI of the DCM+V group was higher than that of the N group. iv) The EI of 3-NT increased with a higher AI. The higher the EI of 3-NT, the higher the AI observed in rat cardiomyocytes. Both the EI of 3-NT and the AI of the DCM group were higher than in the other groups. However, both the EI of 3-NT and the AI in the DCM group markedly decreased for the DCM+V group. 3-NT in the myocardial tissue of rats was deemed to be a successful biomarker for predicting cardiomyocyte apoptosis in SD rats. 3-NT levels were significantly increased and related to cardiomyocyte apoptosis. Valsartan post-treatment reversed the increase of 3-NT and apoptosis in diabetic cardiomyopathy.

Topics: Animals; Apoptosis; Biomarkers; Diabetes Mellitus, Experimental; Diabetic Cardiomyopathies; Male; Myocardium; Myocytes, Cardiac; Rats; Rats, Sprague-Dawley; Tetrazoles; Tyrosine; Valine; Valsartan

1. Uncoupling of nitric oxide synthase (NOS) has been implicated in the pathogenesis of left ventricular (LV) dysfunction in diabetes mellitus. In the present study, we investigated the role of NOS uncoupling in oxidative/nitrosative stress and LV dysfunction in the diabetic mouse heart. 2. Diabetes was induced in wild-type (WT), endothelial (e) NOS knockout (eNOS(-/-)), inducible (i) NOS knockout (iNOS(-/-)) and neuronal (n) NOS knockout (nNOS(-/-)) mice by streptozotocin (STZ) treatment. 3. In the diabetic heart, iNOS, but not eNOS or nNOS, expression was increased. Levels of malondialdehyde (MDA), 4-hydroxy-noneal (HNE) and nitrotyrosine (NT), as markers of oxidative/nitrosative stress, were increased in the diabetic mouse heart, but the increase in oxidative/nitrosative stress was significantly repressed in the iNOS(-/-) diabetic mouse heart. Levels of nitrite and nitrate (NO(x)), as an index of nitric oxide, bioavailability were significantly decreased in the iNOS(-/-) diabetic mouse heart. 4. Oral administration of sepiapterin (10 mg/kg per day), a precursor of tetrahydrobiopterin (BH(4)), significantly increased BH(4) and the BH(4)/BH(2) ratio in diabetic mouse heart. Similarly, sepiapterin inhibited the formation of HNE, MDA and NT in diabetic hearts from all three genotypes, but the increase in NO(x) following sepiapterin treatment was significantly attenuated in the iNOS(-/-) diabetic mouse heart. Percentage fractional shortening (FS), evaluated by echocardiography, decreased significantly in all genotypes of diabetic mice. Sepiapterin significantly increased percentage FS in diabetic mice, except in iNOS(-/-) mice. 5. These results suggest that sepiapterin inhibits uncoupling of NOS and improves LV function presumably by increasing iNOS-derived nitric oxide in the diabetic heart.

Topics: Animals; Biopterins; Cardiotonic Agents; Coenzymes; Diabetes Mellitus, Experimental; Diabetic Cardiomyopathies; Enzyme Inhibitors; Lipid Peroxidation; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide; Nitric Oxide Synthase; Pterins; Tyrosine; Ventricular Dysfunction, Left; Ventricular Function, Left

Hyperglycemia (HG) significantly increases mortality after myocardial infarction (MI) in patients with and without established diabetes. The specific underlying mechanism remains unknown. The present study attempted to determine whether nitrative inactivation of thioredoxin-1 (Trx-1) may contribute to the exaggerated myocardial ischemia/reperfusion (I/R) injury observed in the hyperglycemic condition. Diabetes was induced by multiple intraperitoneal injections of low-dose streptozotocin (STZ) in mice. After 30 min ischemia by slip-knot ligature of the left anterior descending coronary artery, the myocardium was reperfused for 3h after knot release (for apoptosis, Trx-1-activity, and -nitration determination) or 24h (for cardiac function and infarct size determination). At 10 min before reperfusion, diabetic mice were randomized to receive vehicle, EUK134 (a peroxynitrite scavenger), recombinant human Trx-1 (rhTrx-1), or SIN-1 (a peroxynitrite donor) nitrated Trx-1 (N-Trx-1) administration. Diabetes intensified I/R-induced myocardial injury, evidenced by further enlarged infarct size, increased apoptosis, and decreased cardiac function in diabetic mice. Trx-1 nitrative inactivation was elevated in the diabetic heart before I/R and was further amplified after I/R. Treatment with EUK134 or rhTrx-1, but not N-Trx-1, before reperfusion significantly reduced Trx-1 nitration, preserved Trx-1 activity, attenuated apoptosis, reduced infarct size, and improved cardiac function in diabetic mice. Taken together, our results demonstrated that HG increased cardiac vulnerability to I/R injury by enhancing nitrative inactivation of Trx-1, suggesting that blockade of Trx-1 nitration, or supplementation of exogenous rhTrx-1, might represent novel therapies to attenuate cardiac injury after MI in diabetic patients.

Topics: Animals; Apoptosis; Blood Glucose; Cells, Cultured; Diabetes Mellitus, Experimental; Diabetic Cardiomyopathies; Heart; Hyperglycemia; Immunoblotting; Immunoprecipitation; Mice; Myocardial Reperfusion Injury; Nitrates; Nitrosation; p38 Mitogen-Activated Protein Kinases; Peroxynitrous Acid; Thioredoxins; Tyrosine