Development Of Diabetic Cardiovascular Complications Research Articles

N-Acetylcysteine Enhances the Recovery of Ischemic Limb in Type-2 Diabetic Mice

Critical limb ischemia (CLI) is a severe complication of diabetes mellitus that occurs without effective therapy. Excessive reactive oxygen species (ROS) production and oxidative stress play critical roles in the development of diabetic cardiovascular complications. N-acetylcysteine (NAC) reduces ischemia-induced ROS production. The present study aimed to investigate the effect of NAC on the recovery of ischemic limb in an experimental model of type-2 diabetes. TALLYHO/JngJ diabetic and SWR/J non-diabetic mice were used for developing a CLI model. For NAC treatment, mice received NAC (1 mg/mL) in their drinking water for 24 h before initiating CLI, and continuously for the duration of the experiment. Blood flow, mechanical function, histology, expression of antioxidant enzymes including superoxide dismutase (SOD)-1, SOD-3, glutathione peroxidase (Gpx)-1, catalase, and phosphorylated insulin receptor substrate (IRS)-1, Akt, and eNOS in ischemic limb were evaluated in vivo or ex vivo. Body weight, blood glucose, plasma advanced glycation end-products (AGEs), plasma insulin, insulin resistance index, and plasma TNF-a were also evaluated during the experiment. NAC treatment effectively attenuated ROS production with preserved expressions of SOD-1, Gpx-1, catalase, phosphorylated Akt, and eNOS, and enhanced the recovery of blood flow and function of the diabetic ischemic limb. NAC treatment also significantly decreased the levels of phosphorylated IRS-1 (Ser307) expression and plasma TNF-α in diabetic mice without significant changes in blood glucose and AGEs levels. In conclusion, NAC treatment enhanced the recovery of blood flow and mechanical function in ischemic limbs in T2D mice in association with improved tissue redox/inflammatory status and insulin resistance.

A Cross-sectional Study on the Development of Diabetic Cardiovascular Complications in Type 2 Diabetes Mellitus in a South Indian Tertiary Care Hospital

Background: Diabetic cardiovascular complication is a familiar macrovascular complication of Type 2 Diabetes mellitus (T2DM). Cardiovascular disease (CVD) is the major cause of morbidity and mortality for people with diabetes.
 Objective: The aim of this study was to evaluate the parameters related to diabetic cardiovascular complication in patients with T2DM.
 Methodology: This study was conducted on 530 subjects (171 with or 359 without diabetic cardiovascular complication). Prevalence of diabetic cardiovascular complication was measured, risk factors for diabetic cardiovascular complications, and drug utilization pattern was assessed.
 Results: Cardiovascular complication was significantly higher in the subjects who are poorly educated, nature of work (house wives) and risk factors were pre-existing conditions (Hypertension, Cardiac, endocrine and other diseases), habit of smoking (past smoker), tea/coffee (twice without sugar), poor glycemic control, elevated triglyceride levels, elevated creatinine levels, duration of diabetes (5-10 years; >10 years).
 Conclusion: Combination of Glimepiride and Metformin (35.10%), Metformin (34.04%), combination of insulin isophane and insulin regular (23.40%), Insulin Regular (11.70%) were the anti-diabetic drugs widely prescribed to the T2DM patients with cardiovascular complications. Significant risk factors for development of diabetic cardiovascular complication were multiple.

Improved Endothelium-Dependent Relaxation of Thoracic Aorta in Niclosamide-Treated Diabetic Rats.

Diabetes-induced endothelial dysfunction is critical for the development of diabetic cardiovascular complications. The aim of this study was to investigate the effect of niclosamide (Nic) on vascular endothelial dysfunction in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were injected with a single intraperitoneal injection of STZ (75mg/kg) to induce type 1 diabetes, and Nic (10mg/kg) was intraperitoneally administered per day for 4weeks. Endothelial function was evaluated as carbachol (CCh, an endothelium-dependent vasodilator)-evoked relaxation in the experiments performed on isolated thoracic aortas. The changes in the protein expressions of phosphorylated eNOS at serine 1177 (p-eNOSSer1177) and phosphorylated VASP at serine 239 (p-VASPSer239) of the rat aortas were analyzed by western blotting to determine whether NO/cGMP signaling is involved in the mechanism of Nic. STZ-injected rats had higher fasting blood glucose and less body weight compared to control rats (p < 0.05). Nic treatment did not affect blood glucose levels or body weights of the rats. CCh-induced endothelium-dependent relaxation of the aortic rings was significantly decreased in diabetic rats compared to control (Emax = 66.79 ± 7.41% and 90.28 ± 5.55%, respectively; p < 0.05). CCh-induced relaxation response was greater in Nic-treated diabetic rats compared to diabetic rats (Emax = 91.56 ± 1.20% and 66.79 ± 7.41%, respectively; p < 0.05). Phosphorylation of eNOS and VASP in aortic tissues was significantly reduced in diabetic rats, which were markedly increased by Nic treatment (p < 0.05). We demonstrated that Nic improved endothelial dysfunction possibly through the activation of NO/cGMP signaling without affecting hyperglycemia in diabetic rats. Our results suggesting that Nic has potential of repurposing for diabetic cardiovascular complications.

Can Metformin Exert as an Active Drug on Endothelial Dysfunction in Diabetic Subjects?

Cardiovascular mortality is a major cause of death among in type 2 diabetes (T2DM). Endothelial dysfunction (ED) is a well-known important risk factor for the development of diabetes cardiovascular complications. Therefore, the prevention of diabetic macroangiopathies by preserving endothelial function represents a major therapeutic concern for all National Health Systems. Several complex mechanisms support ED in diabetic patients, frequently cross-talking each other: uncoupling of eNOS with impaired endothelium-dependent vascular response, increased ROS production, mitochondrial dysfunction, activation of polyol pathway, generation of advanced glycation end-products (AGEs), activation of protein kinase C (PKC), endothelial inflammation, endothelial apoptosis and senescence, and dysregulation of microRNAs (miRNAs). Metformin is a milestone in T2DM treatment. To date, according to most recent EASD/ADA guidelines, it still represents the first-choice drug in these patients. Intriguingly, several extraglycemic effects of metformin have been recently observed, among which large preclinical and clinical evidence support metformin’s efficacy against ED in T2DM. Metformin seems effective thanks to its favorable action on all the aforementioned pathophysiological ED mechanisms. AMPK pharmacological activation plays a key role, with metformin inhibiting inflammation and improving ED. Therefore, aim of this review is to assess metformin’s beneficial effects on endothelial dysfunction in T2DM, which could preempt development of atherosclerosis.

Regulation of NLRP3 inflammasome by CD38 through cADPR-mediated Ca2+ release in vascular smooth muscle cells in diabetic mice

Aims: NLR family pyrin domain containing 3 (NLRP3) inflammasome activation contributes to the development of diabetic cardiovascular complications. CD38 regulates vascular inflammation through cyclic ADP-ribose (cADPR)-mediated Ca2+ signaling in vascular smooth muscle cells (VSMCs). Ca2+ mobilization may modulate inflammasome activation by impacting mitochondrial function. However, it remains unclear whether CD38 regulates NLRP3 inflammasome activation in VSMCs through cADPR-dependent Ca2+ release under diabetic condition.Main methods and key findings: In VSMCs, we observed that high glucose (HG, 30 mM) enhanced CD38 protein expression and ADP ribosyl cyclase activity. Moreover, along with less abundance of NLRP3, apoptosis-associated speck-like protein containing CARD (ASC) and their colocalization, the expression of active caspase-1(p20) and IL-1β were significantly inhibited by CD38 gene deficiency with siRNA transfection in VSMCs. Further, CD38 regulated the release of intracellular cADPR-mediated Ca2+ and mitochondrial DNA (mtDNA) to the cytosol, which was associated with NLRP3 inflammasome activation and VSMCs proliferation and collagen I synthesis. Finally, we found that CD38 inhibitors, nicotinamide and telmisartan significantly improved the endothelium-independent contraction and vascular remodeling, which was also associated with the inhibition of NLRP3 inflammasome in the aorta media in the diabetic mice.Significance: Our data suggested that CD38/cADPR-mediated Ca2+ signaling contributed to the mitochondrial damage, consequently released mtDNA to the cytosol, which was related with NLRP3 inflammasome activation and VSMCs remodeling in diabetic mice.

Metabolic Stress and Cardiovascular Disease in Diabetes Mellitus: The Role of Protein O-GlcNAc Modification.

Mammalian cells metabolize glucose primarily for energy production, biomass synthesis, and posttranslational glycosylation; and maintaining glucose metabolic homeostasis is essential for normal physiology of cells. Impaired glucose homeostasis leads to hyperglycemia, a hallmark of diabetes mellitus. Chronically increased glucose in diabetes mellitus promotes pathological changes accompanied by impaired cellular function and tissue damage, which facilitates the development of cardiovascular complications, the major cause of morbidity and mortality of patients with diabetes mellitus. Emerging roles of glucose metabolism via the hexosamine biosynthesis pathway (HBP) and increased protein modification via O-linked β-N-acetylglucosamine (O-GlcNAcylation) have been demonstrated in diabetes mellitus and implicated in the development of diabetic cardiovascular complications. This review will discuss the biological outcomes of the glucose metabolism via the hexosamine biogenesis pathway and protein O-GlcNAcylation in regulating cellular homeostasis, and highlight the regulations and contributions of elevated O-GlcNAcylation to the pathogenesis of diabetic cardiovascular disease.

Pyrrolidine dithiocarbamate ameliorates endothelial dysfunction in thoracic aorta of diabetic rats by preserving vascular DDAH activity.

ObjectiveEndothelial dysfunction plays a pivotal role in the development of diabetic cardiovascular complications. Accumulation of endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) and inhibition of dimethylarginine dimethylaminohydrolase (DDAH) activity have been involved in diabetic endothelial dysfunction. This study was to investigate the effect of pyrrolidine dithiocarbamate (PDTC) on impairment of endothelium-dependent vasodilatation in diabetic rats and its potential mechanism.MethodsDiabetic rats were induced by a single intraperitoneal injection of streptozotocin (60mg/kg), and PDTC (10mg/kg) was given in drinking water for 8 weeks. Blood glucose and serum ADMA concentrations were measured in experimental rats. Recombinant adenovirus encoding human DDAH2 gene were constructed and ex vivo transferred to isolated rat aortas. The maximal relaxation (Emax) and half maximal effective concentration (EC50) of aortic rings response to accumulative concentrations of acetylcholine and vascular DDAH activity were examined before and after gene transfection.ResultsDiabetic rats displayed significant elevations of blood glucose and serum ADMA levels compared to control group (P<0.01). Vascular DDAH activity and endothelium-dependent relaxation of aortas were inhibited, as expressed by the decreased Emax and increased EC50 in diabetic rats compared to control rats (P<0.01). Treatment with PDTC not only decreased blood glucose and serum ADMA concentration (P<0.01) but also restored vascular DDAH activity and endothelium-dependent relaxation, evidenced by the higher Emax and lower EC50 in PDTC-treated diabetic rats compared to untreated diabetic rats (P<0.01). Similar restoration of Emax, EC50 and DDAH activity were observed in diabetic aortas after DDAH2-gene transfection.ConclusionsThese results indicate that PDTC could ameliorate impairment of endothelium-dependent relaxation in diabetic rats. The underlying mechanisms might be related to preservation of vascular DDAH activity and consequent reduction of endogenous ADMA in endothelium via its antioxidant action. This study highlights the therapeutic potential of PDTC in impaired vasodilation and provides a new strategy for treatment of diabetic cardiovascular complications.

Sphingosine-1-phosphate receptor 2 mediates endothelial cells dysfunction by PI3K-Akt pathway under high glucose condition

Endothelial dysfunction is believed the early stage of development of diabetic cardiovascular complications. Sphingosine-1-phosphate (S1P) regulates various biological activities by binding to sphingosine-1-phosphate receptors (S1PRs) including S1PR1-S1PR5. In the present study, the role of S1P receptors in S1P-induced human coronary artery endothelial cells (HCAECs) dysfunction under high glucose condition was investigated and the underlying mechanism was explored. S1PR1-S1PR5 mRNA levels were detected by quantitative Real-time PCR. NO level and polymorphonuclear neutrophils (PMN)-endothelial cells adhesion were measured by nitrate reductase and myeloperoxidase colorimetric method, respectively. Protein levels of endothelial nitric oxide synthase (eNOS), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1(ICAM-1), phosphatidylinositol 3-kinase (PI3K) and Akt were measured by Western blot analysis. S1PR2 were found the predominant S1P receptor expressed in HCAECs exposed to high glucose. NO level and eNOS activity were remarkably decreased, while PMN adhesion, VCAM-1 and ICAM-1 protein levels were increased significantly by S1P treatment in HCAECs exposed to high glucose and normal glucose. Blockage of S1PR2 with specific antagonist JTE-013 and small interfering RNA (siRNA) resulted in enhanced NO level and eNOS activity as well as decreased PMN adhesion, reduced protein levels of VCAM-1 and ICAM-1 induced by S1P. Furthermore, Phosphor-PI3K and phosphor-Akt level were markedly increased by S1PR2 blockade in S1P-treated cells exposed to high glucose, which were suppressed by PI3K inhibitor wortmannin. In conclusion, S1P/S1PR2 mediated endothelial dysfunction partly by inhibiting PI3K/Akt signaling pathway under high glucose condition. S1PR2 blockage could ameliorate endothelial dysfunction which might provide a potential therapeutic strategy for diabetic vascular complications.

Acute restraint stress increases carotid reactivity in type-I diabetic rats by enhancing Nox4/NADPH oxidase functionality

Hyperglycemia increases the generation of reactive oxygen species and affects systems that regulate the vascular tone including renin–angiotensin system. Stress could exacerbate intracellular oxidative stress during Diabetes upon the activation of angiotensin AT1/NADPH oxidase pathway, which contributes to the development of diabetic cardiovascular complications. For this study, type-I Diabetes was induced in Wistar rats by intraperitoneal injection of streptozotocin. 28 days after streptozotocin injection, the animals underwent to acute restraint stress for 3h. Cumulative concentration–response curves for angiotensin II were obtained in carotid rings pre-treated or not with Nox or cyclooxygenase inhibitors. Nox1 or Nox4 expression and activity were assessed by Western blotting and lucigenin chemiluminescence, respectively. The role of Nox1 and Nox4 on reactive oxygen species generation was evaluated by flow cytometry and Amplex Red assays. Cyclooxygenases expression was assessed by real-time polymerase chain reaction. The contractile response evoked by angiotensin II was increased in diabetic rat carotid. Acute restraint stress increased this response in this vessel by mechanisms mediated by Nox4, whose local expression and activity in generating hydrogen peroxide are increased. The contractile hyperreactivity to angiotensin II in stressed diabetic rat carotid is also mediated by metabolites derived from cyclooxygenase-2, whose local expression is increased. Taken together, our findings suggest that acute restraint stress exacerbates the contractile hyperreactivity to angiotensin II in diabetic rat carotid by enhancing Nox4-driven generation of hydrogen peroxide, which evokes contractile tone by cyclooxygenases-dependent mechanisms. Finally, these findings highlight the harmful role played by acute stress in modulating diabetic vascular complications.

GW24-e2480 Ginkgo biloba attenuates oxidative DNA damage of human umbilical vein endothelial cells induced by intermittent high glucose

ObjectivesIntermittent high glucose, one general and important phenomenon existed in patients with diabetes, has greater effect than sustained high glucose on development of diabetic cardiovascular complications, in which endothelial dysfunction...

Exogenous hydrogen sulfide protects H9c2 cardiac cells against high glucose-induced injury by inhibiting the activities of the p38 MAPK and ERK1/2 pathways

Hyperglycemia is a risk factor for the development of diabetic cardiovascular complications, which are associated with the activation of the mitogen-activated protein kinase (MAPK) signaling pathway. In this study, we demonstrate the inhibitory effects of exogenous hydrogen sulfide (H₂S) on the activation of the MAPK pathway. The aim of the present study was to determine whether exogenous H₂S prevents high glucose (HG)-induced injury by inhibiting the activation of the p38 MAPK and extracellular signal-regulated kinase (ERK)1/2 (members of MAPK) pathways in cardiomyoblasts (H9c2 cells). The findings of the present study demonstrated that the treatment of H9c2 cells with HG (35 mM glucose) for 24 h not only significantly induced injury, including cytotoxicity, apoptosis, overproduction of reactive oxygen species (ROS) and the loss of mitochondrial membrane potential (MMP), but also upregulated the expression levels of phosphorylated (p)-p38 MAPK and p-ERK1/2. The increased expression levels of p-p38 MAPK and p-ERK1/2 were markedly reduced by pre-treatment of the H9c2 cells with 400 µM sodium hydrogen sulfide (NaHS; a donor of H2S) prior to exposure to 35 mM glucose. Importantly, pre-treatment of the cells with 400 µM NaHS or 3 µM SB203580 (a selective inhibitor of p38 MAPK) or 15 µM U0126 (a selective inhibitor of ERK1/2) attenuated the HG-induced cardiomyocyte injury, leading to an increase in cell viability and a decrease in the number of apoptotic cells, preventing ROS generation, as well as the loss of MMP. In addition, pre-treatment of the cells with 1,000 µM N‑acetyl‑L‑cysteine (a ROS scavenger) prior to exposure to HG ameliorated the HG-induced cytotoxicity. Taken together, the data from the present study demonstrate for the first time, to our knowledge, that exogenous H2S exerts a protective effect against HG‑induced injury by inhibiting the activation of the p38 MAPK and ERK1/2 pathways and preventing oxidative stress in H9c2 cells.

Застосування Ліпофлавону® для фармакологічної корекції ендотеліальної дисфункції у щурів за умов цукрового діабету

It is known that endothelial dysfunction is one of the major factors in development of diabetic cardio-vascular complications. Besides, pathophysiological linkages between high concentration of glucose and vascular dysfunction remain not fully established. The aim of this study was to investigate acetylcholine-induced endothelium-dependent dilation of vascular segments obtained from healthy rats and incubated in hyperglycemic solution and vascular segments from diabetic rats before and after quercetin-filled phosphatidylcholine liposomes (Lipoflavon®) treatment in both in vitro and in vivo conditions. Changes in vascular tone were registered in isometric mode. Data are presented as mean ± SEM with “n” indicating the number of vascular preparations tested. On the day of the experiment diabetic rats showed four times higher blood glucose level and decreased dilation responses to acetylcholine (ACh, 1 nM–10 mM) of aortic rings precontracted with noradrenaline (NA, 1 mM)as compared to controls. Incubation of vascular rings under hyperglycemic (25 mM/L glucose) conditions led to time-dependent impairment of dilation responses as compared to normoglycemic (5.5 mM/L glucose) conditions. Lipoflavon® (3 µg/mL of quercetin) application to the organ bath with diabetic rats precontracted vascular rings resulted in a significant reduction in vascular tension. Being added on the plateau of Lipoflavon® relaxation, ACh showed increased dilation responses in comparison to diabetic tissues without Lipoflavon® application. Intravenous Lipoflavon® injections to diabetic rats in concentrations 15 mg/kg or 50 mg/kg of phosphatidylcholine restored dilatation responses up to the control level. In conclusion, we confirmed that hyperglycemia is one of the main factors leading to impairment of endothelium-dependent vasodilation. Quercetin-filled phosphatidylcholine liposomes significantly improve endothelium-dependent relaxation of isolated vascular rings from diabetic rats. We assume that Lipoflavon® is perspective in treatment of diabetic angiopathies. Keywords: diabetic vascular complications, endothelial disfunction, quercetin, Lipoflavon®.

Diabetic CVD – Soluble Epoxide Hydrolase as A Target

The incidence of cardiovascular diseases remains high in diabetic patients despite the optimization of blood glucose control and the therapeutic management of risk factors. One emerging promising pharmacological approach that may help to prevent the development of diabetic cardiovascular complications is to improve endothelial function through the restoration of the bioavailability of epoxyeicosatrienoic acids (EETs). EETs are crucial eicosanoid signaling molecules synthesized by cytochrome P450 epoxygenases in the vascular endothelium and in pancreatic islets. EETs promote vasodilatation and display attractive anti-inflammatory and anti-aggregating actions together with potent effects on insulin release and sensitivity. In animal models of insulin-resistance and diabetes, a decrease in EET availability has been reported, and is a deleterious mechanism that probably contributes to multiple metabolic, cardiovascular and renal disorders in this setting. Moreover, increasing experimental evidence suggest that the use of soluble epoxide hydrolase (sEH) inhibitors, which prevent EET degradation, is a promising pharmacological approach to prevent endothelial dysfunction and to protect against target organ damage in metabolic diseases. This review presents evidence that the EET pathway is disturbed from the early stages of metabolic diseases, and analyzes the potential contribution of EETs impairment to the progression of cardiovascular diseases associated with diabetes. Pathophysiological and therapeutic perspectives are thereafter discussed, including the necessity to demonstrate the role of EET pathway alterations in endothelial dysfunction associated with diabetes in human, and the interest of sEH inhibitors to prevent the development of diabetic cardiovascular complications, with the expected result of improving patients' health.

PKCβ inhibition with ruboxistaurin reduces oxidative stress and attenuates left ventricular hypertrophy and dysfuntion in rats with streptozotocin-induced diabetes

Oxidative stress plays critical roles in the development of diabetic cardiovascular complications, including myocardial hypertrophy. The β isoform of PKC (protein kinase C) is preferentially overexpressed in the myocardium of diabetic subjects accompanied with increased activation of the pro-oxidant enzyme NADPH oxidase, which may exacerbate oxidative stress. We hypothesized that myocardial PKCβ is a major upstream mediator of oxidative stress in diabetes and that PKCβ inhibition can attenuate myocardial hypertrophy and dysfunction. Control or streptozotocin-induced diabetic rats were treated with the selective PKCβ inhibitor RBX (ruboxistaurin; 1mg/kg of body weight per day) or the antioxidant NAC (N-acetylcysteine) for 4weeks. LV (left ventricular) dimensions and functions were detected by echocardiography. 15-F2t-isoprostane (a specific index of oxidative stress) and myocardial activities of superoxide dismutase as well as protein levels of NADPH oxidase were assessed by immunoassay or Western blotting. Echocardiography revealed that the LV mass/body weight ratio was significantly increased in diabetic rats (P<0.01 compared with the control group) in parallel with the impaired LV relaxation. A significant increase in cardiomyocyte cross-sectional area was observed in diabetic rats accompanied by an increased production of O2- (superoxide anion) and 15-F2t-isoprostane (all P<0.05 compared with the control group). RBX normalized these changes with concomitant inhibition of PKCβ2 activation and prevention of NADPH oxidase subunit p67phox membrane translocation and p22phox overexpression. The effects of RBX were comparable with that of NAC, except that NAC was inferior to RBX in attenuating cardiac dysfunction. It is concluded that RBX can ameliorate myocardial hypertrophy and dysfunction in diabetes, which may represent a novel therapy in the prevention of diabetic cardiovascular complications.

High glucose (HG)‐induced angiotensin‐converting enzyme 2 (ACE2) and angiotensin (1–7) [Ang (1–7)] decrease is prevented by captopril, losartan and insulin in rat vascular smooth muscle cells (VSMCs)

Ang (1–7) prevents the development of diabetic cardiovascular complications. In VSMCs ACE2 is a major source of Ang (1–7). ACE2 expression is PKCβII dependent and it is decreased by exposure to HG via Nox1‐derived superoxides. In diabetic animal models captopril and losartan restore circulating Ang (1–7) levels. This study was conducted to determine if in rat VSMCs these agents and insulin prevent HG‐induced ACE2 and Ang (1–7) decrease. Cells were maintained in normal glucose (NG) or HG (~4.1 mmol/l and ~23.1 mmol/l, accordingly) for up to 72 hours and exposed to captopril, losartan, insulin or angiotensin II (Ang II). The cell lysates were subjected to Western blot, RTQ‐PCR and Ang (1–7) radioimmunoassay. HG‐induced ACE2 and Ang (1–7) decrease was prevented by captopril, losartan and insulin. Ang II alone reduced ACE2 expression in the presence of NG, which was prevented by captopril and losartan, and partially by insulin. HG‐induced Nox1 increase was diminished by captopril, losartan and insulin, whereas Ang II‐induced Nox1 increase was reversed by captopril and losartan but not insulin. HG deceased PKCβII level that was blocked by captopril, losartan and insulin. These data suggest that these agents prevent HG‐induced ACE2 and Ang (1–7) decrease by diminishing HG‐induced Nox‐1 expression and by restoring PKCβII level in VSMCs (Supported by NIH grant 079109‐03 from the HLBI).

+647 A/C and +1245 MT1A polymorphisms in the susceptibility of diabetes mellitus and cardiovascular complications

Diabetes mellitus is a chronic disease characterized by an overproduction of reactive oxygen species, which perturbs zinc metabolism and promotes the onset of cardiovascular disease (CVD) in diabetic patients. Metallothioneins (MT) are cysteine-rich metal-binding proteins which, by means of their antioxidant and zinc-buffering properties, might prevent the development of diabetic cardiovascular complications. A recent investigation shows that a polymorphism (+647 A/C) in the human MT-1A gene, affects the intracellular zinc ion release (iZnR) from the proteins and is associated with longevity in Italian population. The aim of the present study is to assess the involvement of +647 A/C and +1245 A/G MT1A polymorphisms with the susceptibility to type 2 diabetes (DM2) and cardiovascular complications. The study included 694 old individuals: 242 old healthy controls, 217 DM2 patients without clinical evidence of CVD (DNC) and 235 diabetic patients with diagnosis of CVD (DCVD). +647 A/C MT1A polymorphism, but not the second SNP, was associated with DM2. C allele carriers were more prevalent in DNC and DCVD patients than in control group (OR = 1.37, p = 0.034; OR = 1.54, p = 0.002, respectively). C+ carriers was associated with higher glycemia and glycosylated hemoglobin in DCVD patients, but not in DNC or control subjects. No differences in plasma zinc, but a modulation of MT levels and iZnR in PBMCs were observed in DCVD cohort when related to +647 A/C MT1A polymorphism. In summary, this work provides novel evidence on the association of the +647 A/C MT1A polymorphism with DM2. Moreover, C+ carriers in DCVD patients presented a worse glycemic control, a reduced iZnR and a higher MT levels, suggesting a possible role of MT in diabetic cardiovascular complications.

Lipid Disorders in Diabetes Mellitus and Current Management

Lipid disorders are common in diabetes mellitus (DM), and play crucial roles in the development of diabetic cardiovascular complications. Diabetic dyslipidemia is characterized by hypertriglyceridemia, increased levels of very low density lipoproteins (VLDL), small dense low density lipoprotein (LDL), and decreased levels of high density lipoprotein (HDL)-cholesterol. The activity of lipoprotein lipase is reduced in diabetic patients, which attenuates the lipolysis of triglyceride-rich lipoproteins and the uptake of free fatty acids. The increased uptake of triglycerides in liver promotes the production of VLDL. Hypertriglyceridemia promotes the exchange of cholesteryl ester from HDL to VLDL or LDL for triglycerides. Obesity or nephropathy deteriorates the dyslipidemia in DM patients. The initial management of lipid disorders in diabetic patients without cardiovascular disease is lifestyle intervention and glucose control. The abnormalities in the metabolism of LDL or HDL in diabetic patients often require pharmacological intervention. Target of LDL-cholesterol (LDL-c) is more restrict in diabetic patients than in non-diabetic subjects. Treatment with HMG-CoA reductase inhibitors (statins) effectively reduces LDL-c and cardiac events, and that was associated with moderately increases in HDL-c. The combination of ezetimibe with a statin helps to achieve LDL-c target in patients with unsatisfactory cholesterol lowering by statin alone. Fibrates (PPAR-α agonists) or PPAR-γ agonists reduce the levels of triglycerides and moderately elevate HDL-c. PPAR-γ agonists also improve insulin sensitivity. Cholesteryl ester transfer protein inhibitors may dramatically increase HDL-c. Lipid management has been considered as an effective approach to reduce cardiovascular risk in diabetes.

High Dose Ramipril Inhibits Connective Tissue Growth Factor Expression and Fibrosis in Type 2 Diabetic Rat Heart

Background and Objectives:Connective tissue growth factor (CTGF) is a profibrotic cytokine, which may play an important role in the development of diabetic cardiovascular complications. ACE inhibition significantly prevents cardiovascular events in diabetics, although the mechanism remains obscure. The purpose of this study was to explore the effect of ACE inhibitors on the expression of CTGF and oxidative stress in the diabetic heart, and determine the effects of long term treatment with ACE inhibitors on diabetic cardiomyopathy. Materials and Methods:Thirty OLETF (Otsuka Long Evans Tokushima Fatty) diabetic and thirty LETO (Long Evans Tokushima Otsuka) nondiabetic control rats were randomized into four groups for 24 weeks of treatment with either ramipril (5 mg/kg/day, n=15, each groups) or saline (n=15, each groups). Results:The OLETF diabetic rats had prominent perivascular fibrosis, as shown by picrosirius red stains, compared to the LETO nondiabetic rats. ACE inhibition significantly prevented perivascular fibrosis in OLETF rats (p<0.01). Immunohistochemi- cal stains were used to detect proteins for the receptors of advanced glycation end products (RAGE), CTGF, collagen III and nitrotyrosine. Although there were no significant differences in the myocardiac collagen contents, as found by measuring the hydroxyproline concentration among the four groups, the OLFTF diabetic rats had significantly increased cardiac CTGF and collagen III protein expression compared with the nondiabetic rats. The ACE inhibitor attenuated the increases in RAGE (-50.3%; p<0.01), CTGF (-37.5%; p<0.01) and collagen III (-52.3%; p<0.01) expression in the diabetic heart microvascular area. The OLFTF rats showed marked an increment in cardiac nitrotyrosine, a marker of protein oxidation. Ramipril also inhibited the expression of cardiac nitrotyrosine (-78.3%; p<0.01). Conclusion:The present study shows a possible role of RAGE/nitrotyrosine/ CTGF in the diabetic cardiomyopathy of OLETF rats. The long term treatment of high dose ACE inhibitors may have beneficial effects on the diabetic heart through both antioxidant and antifibrotic mechanisms. (Korean Circulation J 2006;36:635-643)

Cardiac Metallothionein Synthesis in Streptozotocin-Induced Diabetic Mice, and Its Protection against Diabetes-Induced Cardiac Injury

Oxidative stress is involved in the pathogenesis of diabetes and its cardiovascular complications. Metallothionein (MT), a stress-response protein, is significantly increased in the liver and kidney of diabetic animals. We examined whether diabetes also induces cardiac MT synthesis through oxidative damage and whether MT overexpression protects the heart from injury. Diabetes was induced in mice by single injection of streptozotocin (STZ), and cardiac MT mRNA and protein levels were measured 2 weeks and 2 months after STZ treatment. Diabetes significantly increased cardiac MT synthesis 2 weeks and 2 months after STZ treatment, with no change in cardiac metals including zinc, copper, and iron. Serum and cardiac vasopeptide endothelin and inflammatory cytokine tumor necrosis factor-alpha were also significantly increased in diabetic hearts, as were the ratio of oxidized to reduced glutathione and the immunohistochemical staining of 3-nitrotyrosine and 4-hydroxynonenal. To explore the biological importance of increased MT synthesis in the heart, MT-overexpressing transgenic mice were treated with STZ and then examined 2 months later. A loss of inotropic reserve, uncovered during beta-adrenergic stimulation, and the presence of cardiac fibrosis, shown by increased Sirius red staining of collagen, were evident in the wild-type diabetic mice but not in the MT-overexpressing transgenic diabetic mice. These results suggest that diabetes-induced cardiac MT expression likely associates with systemic increases in endothelin-1 and tumor necrosis factor-alpha and the resulting cardiac oxidative stress. Overexpressing cardiac MT significantly protects the heart from diabetes-induced injury.

Biochemical, histological and echocardiographic changes during experimental cardiomyopathy in STZ-induced diabetic rats

Diabetes mellitus is associated with an increased susceptibility to cardiovascular disease and it has been suggested that alterations in myocardial function may contribute to the development of diabetic cardiovascular complications. The objective of the present study is to examine the left ventricular (LV) function in streptozotocin (STZ)-induced diabetic rats in a definite course of time by non-invasive methods, i.e. M-mode and Doppler echocardiography. From the results, it was found that treatment of animals with STZ resulted in increase in blood glucose, triglycerides, cholesterol, low density lipoproteins (LDL) and decrease in serum total protein levels. Echocardiographic studies revealed that LV internal dimension (mm) during systole was significantly increased after 12 weeks of diabetes when compared to base line data of the same animals and with control animals 6.50±0.13 versus 4.25±0.17, versus 4.34±0.25 ( P<0.05), however there was no significant change after 4–8 weeks of diabetes. Also LV internal dimension (mm) during end diastole increased significantly only after 12 weeks of diabetes than to base line data of the same animals and with control animals 7.71±0.34 versus 6.18±0.25, versus 6.25±0.18 ( P<0.05). Fractional shortening (%), 15.69±5.1 versus 31.22±1.7, versus 30.56±2.1 ( P<0.05), and ejection fraction (%) 37±2.31 versus 68.18±2.8, versus 60.32±3.5 ( P<0.05), differ significantly after 12 weeks of diabetes when compared to base line data of the same animals and with control animals. E-wave (cm/s) was significantly decreased after 12 weeks of diabetes 21.11±1.5 versus 35.19±4.5, versus 32.75±3.0 ( P<0.05), and A-wave (cm/s) was significantly increased after 12 weeks of diabetes 34.88±4.2 versus 19.21±2.8, versus 20.59±2.1 ( P<0.05); thus, diabetic animals after 12 weeks had an inversed E/ A ratio. Histological studies revealed that after 8 weeks of diabetes, necrosis was minimal, but after 12 weeks of diabetes extensive focal endomyocardial necrosis was observed. From this study, we conclude that overt LV systolic and diastolic dysfunction was fully visible at 12 weeks of diabetes on echocardiography and this non-invasive technique of echocardiography is useful in diagnosing LV dysfunction in diabetic rats without the need of invasive histopathological procedures.