cyclic-gmp and Diabetic-Cardiomyopathies

Hyperglycemia-induced cardiac fibrosis is one of the main causes of diabetic cardiomyopathy (DM). Chlorogenic acid (CGA) found in many foods has excellent hypoglycemic effectiveness, but it is not known whether CGA can improve DM by inhibiting cardiac fibrosis caused by hyperglycemia.. Type I diabetic mice are induced by streptozotocin, and after treatment with CGA for 12 weeks, cardiac functions and fibrosis are determined. CGA significantly attenuates hyperglycemia-induced cardiac fibrosis and improves cardiac functions. The mechanism of CGA on fibrotic inhibition is further studied by immunofluorescence, western blot and RNA interference technology in vivo and in vitro. The results show CGA exerted its anti-fibrotic effects through activating the cyclic GMP/protein kinase G pathway (cGMP/PKG) to block hyperglycemia-induced nuclear translocation of p-Smad2/3, and then inhibiting pro-fibrotic gene expression in cardiac fibroblasts without depending on its hypoglycemic function. Moreover, the data also revealed that CGA increased cGMP level and activated PKG in cardiac fibroblasts by enhancing endothelial nitric oxide synthase (eNOS) activity and NO production.. Besides lowering blood glucose, CGA also has an independent ability to inhibit cardiac fibrosis. Therefore, long-term consumption of foods rich in CGA for diabetic patients will have great benefits to improve diabetic cardiomyopathy.

Topics: Animals; Cardiotonic Agents; Cell Proliferation; Chlorogenic Acid; Collagen; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetic Cardiomyopathies; Fibroblasts; Fibrosis; Heart; Hyperglycemia; Male; Mice, Inbred C57BL; Myocardium; Nitric Oxide; Nitric Oxide Synthase Type III; Smad3 Protein

The objective of this research was to explore the effect of dioscin on myocardium in streptozotocin (STZ)-induced diabetic rats and the underlying mechanisms.. Diabetic rat model was established by a single intravenous injection of streptozocin (STZ). The rats were divided into 5 groups: control group, control+dioscin group, model group (diabetes), DDL group (diabetic rats treated with 100 μg/kg/day dioscin) and DDH group (diabetic rats treated with 200 μg/kg/day dioscin). Each group was continuously intervened for 6 weeks. Hemodynamic parameters were detected and pathological alterations of myocardium were observed by hematoxylin-eosin (HE) staining. Inflammatory response and related proteins in the NO-sGC-cGMP-PKG pathway were detected by western blot.. Dioscin treatment can increase ejection fraction (EF) and decrease left ventricular end-diastolic pressure (LVEDP) as well as time constant of left ventricular pressure decay (Tau) parameters in diabetic rats, suggesting the improvement of left ventricular function. By histopathology observation, we found that dioscin treatment can also improve myocardial histological lesions caused by diabetes. In addition, the levels of inflammatory cytokines TGF-β1, TNF-α and IL-1β of the model group were remarkably higher than those in the control group (. Dioscin may prevent the myocardial injury in diabetic rats by up-regulating NO-sGC-cGMP-PKG pathway.

Topics: Animals; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetes Mellitus, Experimental; Diabetic Cardiomyopathies; Diosgenin; Disease Models, Animal; Fibrosis; Guanylate Cyclase; Nitric Oxide; Rats; Rats, Sprague-Dawley; Signal Transduction

Cardiovascular complications contribute to the major mortality and morbidity in type 2 diabetes. Diabetic cardiomyopathy (DCM) is increasingly recognized as an important cause of heart failure. EMPA-REG OUTCOME trial has reported that empagliflozin, the sodium-glucose cotransporter 2 inhibitor, exerts cardiovascular benefits on diabetic population. However, the mechanism by which empagliflozin alleviates DCM still remains unclear. In the current study, we investigated the cardiac protective effects of empagliflozin on spontaneous type 2 diabetic db/db mice and its potential mechanism. Eight weeks of empagliflozin treatment (10 mg/kg/day) decreased body weight and blood glucose level, and increased urinary glucose excretion (UGE) in diabetic mice. Echocardiography revealed that both systolic and diastolic functions of db/db mice were also obviously improved by empagliflozin. Furthermore, empagliflozin-treated diabetic mice presented with amelioration of cardiac hypertrophy and fibrosis. In addition, diabetic hearts exhibited the deterioration of oxidative stress, apoptosis and pyroptosis, while these effects were significantly counteracted after empagliflozin treatment. Moreover, empagliflozin rescued diabetes-induced suppression of sGC (soluble guanylate cyclase enzyme)-cGMP (cyclic guanosine monophosphate)-PKG (cGMP-dependent protein kinase) pathway. However, when sGC-β expression of hearts was inhibited by transvascular delivery of small interfering RNA, cardiac dysfunction was aggravated and the advantages of empagliflozin were reversed through inhibiting sGC-cGMP-PKG pathway. Collectively, these findings indicate that empagliflozin improves cardiac function involving the inhibition of oxidative stress-induced injury via sGC-cGMP-PKG pathway and may be a promising therapeutic option for DCM.

Topics: Animals; Benzhydryl Compounds; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Glucosides; Heart; Humans; Male; Mice; Oxidative Stress; Signal Transduction; Soluble Guanylyl Cyclase

Increased titin-dependent cardiomyocyte tension is a hallmark of heart failure with preserved ejection fraction associated with type-2 diabetes mellitus. However, the insulin-related signaling pathways that modify titin-based cardiomyocyte tension, thereby contributing to modulation of diastolic function, are largely unknown.. We aimed to determine how impaired insulin signaling affects titin expression and phosphorylation and thus increases passive cardiomyocyte tension, and whether metformin or neuregulin-1 (NRG-1) can correct disturbed titin modifications and increased titin-based stiffness.. We used cardiac biopsies from human diabetic (n=23) and nondiabetic patients (n=19), cultured rat cardiomyocytes, left ventricular tissue from apolipoprotein E-deficient mice with streptozotocin-induced diabetes mellitus (n=12-22), and ZSF1 (obese diabetic Zucker fatty/spontaneously hypertensive heart failure F1 hybrid) rats (n=5-6) and analyzed insulin-dependent signaling pathways that modulate titin phosphorylation. Titin-based passive tension was measured using permeabilized cardiomyocytes. In human diabetic hearts, we detected titin hypophosphorylation at S4099 and hyperphosphorylation at S11878, suggesting altered activity of protein kinases; cardiomyocyte passive tension was significantly increased. When applied to cultured cardiomyocytes, insulin and metformin increased titin phosphorylation at S4010, S4099, and S11878 via enhanced ERK1/2 (extracellular signal regulated kinase 1/2) and PKCα (protein kinase Cα) activity; NRG-1 application enhanced ERK1/2 activity but reduced PKCα activity. In apolipoprotein E-deficient mice, chronic treatment of streptozotocin-induced diabetes mellitus with NRG-1 corrected titin phosphorylation via increased PKG (protein kinase G) and ERK1/2 activity and reduced PKCα activity, which reversed the diabetes mellitus-associated changes in titin-based passive tension. Acute application of NRG-1 to obese ZSF1 rats with type-2 diabetes mellitus reduced end-diastolic pressure.. Mechanistically, we found that impaired cGMP-PKG signaling and elevated PKCα activity are key modulators of titin-based cardiomyocyte stiffening in diabetic hearts. We conclude that by restoring normal kinase activities of PKG, ERK1/2, and PKCα, and by reducing cardiomyocyte passive tension, chronic NRG-1 application is a promising approach to modulate titin properties in heart failure with preserved ejection fraction associated with type-2 diabetes mellitus.

Topics: Animals; Cells, Cultured; Connectin; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetic Cardiomyopathies; Humans; Hypoglycemic Agents; Insulin; Metformin; Mice; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Myocytes, Cardiac; Neuregulin-1; Phosphorylation; Protein Kinase C-alpha; Protein Processing, Post-Translational; Rats; Rats, Zucker; Signal Transduction

Diabetes mellitus (DM) leads to the development of diabetic cardiomyopathy, which is associated with altered nitric oxide (NO)--soluble guanylate cyclase (sGC)--cyclic guanosine monophosphate (cGMP) signalling. Cardioprotective effects of elevated intracellular cGMP-levels have been described in different heart diseases. In the current study we aimed at investigating the effects of pharmacological activation of sGC in diabetic cardiomyopathy.. Type-1 DM was induced in rats by streptozotocin. Animals were treated either with the sGC activator cinaciguat (10 mg/kg/day) or with placebo orally for 8 weeks. Left ventricular (LV) pressure-volume (P-V) analysis was used to assess cardiac performance. Additionally, gene expression (qRT-PCR) and protein expression analysis (western blot) were performed. Cardiac structure, markers of fibrotic remodelling and DNA damage were examined by histology, immunohistochemistry and TUNEL assay, respectively.. DM was associated with deteriorated cGMP signalling in the myocardium (elevated phosphodiesterase-5 expression, lower cGMP-level and impaired PKG activity). Cardiomyocyte hypertrophy, fibrotic remodelling and DNA fragmentation were present in DM that was associated with impaired LV contractility (preload recruitable stroke work (PRSW): 49.5 ± 3.3 vs. 83.0 ± 5.5 mmHg, P < 0.05) and diastolic function (time constant of LV pressure decay (Tau): 17.3 ± 0.8 vs. 10.3 ± 0.3 ms, P < 0.05). Cinaciguat treatment effectively prevented DM related molecular, histological alterations and significantly improved systolic (PRSW: 66.8 ± 3.6 mmHg) and diastolic (Tau: 14.9 ± 0.6 ms) function.. Cinaciguat prevented structural, molecular alterations and improved cardiac performance of the diabetic heart. Pharmacological activation of sGC might represent a new therapy approach for diabetic cardiomyopathy.

Topics: Animals; Benzoates; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetic Cardiomyopathies; Disease Models, Animal; DNA Damage; Fibrosis; Heart; Immunohistochemistry; In Situ Nick-End Labeling; Myocardium; Nitric Oxide; Rats