Inhibition of nitric oxide synthase enhances contractile response of ventricular myocytes from streptozotocin-diabetic rats

Vitamin D attenuates endothelial dysfunction in streptozotocin induced diabetic rats by reducing oxidative stress

Diabetes mellitus (DM) is associated with micro- and macrovascular complications and increased cardiovascular risk. Vitamin D deficiency is the most common nutrient deficiency in the world. This study aimed to examine the effects of diabetes on the endothelial function and the role of vitamin D supplementation. Male Wistar rats (n = 30) were randomly assigned to three groups; control untreated, diabetic untreated, and diabetic groups treated with vitamin D at a dose of 12.5 μg/kg body weight, dissolved in 0.3 ml olive oil orally for 10 weeks. Compared to the control group, the serum glucose, serum asymmetric dimethylarginine (ADMA), aortic malondialdehyde (MDA) levels, endothelin-1 (ET-1) level, inducible nitric oxide synthase (iNOS) activity in diabetic rats were increased, whereas aortic superoxide dismutase (SOD) activity, nitric oxide (NO) levels, and constitutive NOS (cNOS) activity were decreased. Administration of vitamin D to diabetic rats resulted in a decrease of serum glucose, serum ADMA, a decrease of aortic MDA levels, ET-1 and iNOS activity, an increase of aortic SOD activity, NO levels, and cNOS activity. Vitamin D administration attenuated diabetic induced endothelial dysfunction by reducing oxidative stress. These results indicate that chronic vitamin D treatment might be useful in preventing diabetic vascular complications associated with endothelial dysfunction.

Cardiac Microvascular Endothelial Enhancement of Cardiomyocyte Function Is Impaired by Inflammation and Restored by Empagliflozin

The positive findings of the EMPA-REG OUTCOME trial (Randomized, Placebo-Controlled Cardiovascular Outcome Trial of Empagliflozin) on heart failure (HF) outcome in patients with type 2 diabetes mellitus suggest a direct effect of empagliflozin on the heart. These patients frequently have HF with preserved ejection fraction (HFpEF), in which a metabolic risk-related pro-inflammatory state induces cardiac microvascular endothelial cell (CMEC) dysfunction with subsequent cardiomyocyte (CM) contractility impairment. This study showed that CMECs confer a direct positive effect on contraction and relaxation of CMs, an effect that requires nitric oxide, is diminished after CMEC stimulation with tumor necrosis factor-α, and is restored by empagliflozin. Our findings on the effect of empagliflozin on CMEC-mediated preservation of CM function suggests that empagliflozin can be used to treat the cardiac mechanical implications of microvascular dysfunction in HFpEF.

Lycopene attenuates endothelial dysfunction in streptozotocin-induced diabetic rats by reducing oxidative stress

CONTEXT

Diabetes mellitus is characterized by oxidative stress, which in turn induces endothelial dysfunction. As a potent antioxidant compound, lycopene might rescue diabetic endothelial dysfunction by reducing oxidative stress.

OBJECTIVE

The present study investigated whether lycopene could lower oxidative stress and attenuate endothelial dysfunction in diabetic rats.

METHODS

Different doses of lycopene (10, 30, and 60 mg/kg/day, p.o.) were administered for 30 days to streptozotocin (STZ) (60 mg/kg)-induced diabetic rats. Biochemical parameters and aortic malondialdehyde (MDA) content, superoxidase dismutase (SOD) activity, nitric oxide (NO) levels, constitutive NOS (cNOS) activity, and inducible NOS (iNOS) activity were determined. Endothelium-dependent and endothelium-independent vasorelaxation were measured in aortas for estimating endothelial function.

RESULTS

Compared with normal controls, endothelial function was significantly reduced in diabetic rats and the blunted endothelial function was dependently ameliorated with lycopene treatment. Compared with normal controls, the serum oxidized low-density lipoprotein (ox-LDL) levels, the aortic MDA levels, and iNOS activity in diabetic rats were increased by 113, 197, and 100%, respectively, whereas aortic SOD activity, NO levels, and cNOS activity were decreased by 73, 53, and 65%, respectively. Exogenous administration of lycopene to diabetic rats caused a dose-dependent decrease of serum glucose and ox-LDL levels, an increase of aortic SOD activity, NO levels, and cNOS activity, and a decrease of aortic MDA levels and iNOS activity.

CONCLUSION

Chronic lycopene treatment could attenuate endothelial dysfunction by reducing oxidative stress in STZ-induced diabetic rats. These results indicate that chronic lycopene treatment might be useful in preventing diabetic vascular complications associated with endothelial dysfunction.

Glycoxidative stress and cardiovascular complications in experimentally-induced diabetes: effects of antioxidant treatment

Diabetes mellitus (DM) is a common metabolic disease, representing a serious risk factor for the development of cardiovascular complications, such as coronary heart disease, peripheral arterial disease and hypertension. Oxidative stress (OS), a feature of DM, is defined as an increase in the steady-state levels of reactive oxygen species (ROS) and may occur as a result of increased free radical generation and/or decreased anti-oxidant defense mechanisms. Increasing evidence indicates that hyperglycemia is the initiating cause of the tissue damage in DM, either through repeated acute changes in cellular glucose metabolism, or through long-term accumulation of glycated biomolecules and advanced glycation end products (AGEs). AGEs are formed by the Maillard process, a non-enzymatic reaction between ketone group of the glucose molecule or aldehydes and the amino groups of proteins that contributes to the aging of proteins and to the pathological complications of DM. In the presence of uncontrolled hyperglycemia, the increased formation of AGEs and lipid peroxidation products exacerbate intracellular OS and results in a loss of molecular integrity, disruption in cellular signaling and homeostasis, followed by inflammation and tissue injury such as endothelium dysfunction, arterial stiffening and microvascular complications. In addition to increased AGE production, there is also evidence of multiple pathways elevating ROS generation in DM, including; enhanced glucose auto-oxidation, increased mitochondrial superoxide production, protein kinase C-dependent activation of NADPH oxidase, uncoupled endothelial nitric oxide synthase (eNOS) activity, increased substrate flux through the polyol pathway and stimulation of eicosanoid metabolism. It is, therefore, not surprising that the correction of these variables can result in amelioration of diabetic cardiovascular abnormalities. A linking element between these phenomena is cellular redox imbalance due to glycoxidative stress (GOS). Thus, recent interest has focused on strategies to prevent, reverse or retard GOS in order to modify the natural history of diabetic cardiovascular abnormalities. This review will discuss the links between GOS and diabetes-induced cardiovascular disorders and the effect of antioxidant therapy on altering the development of cardiovascular complications in diabetic animal models.

Reactive nitrogen species: molecular mechanisms and potential significance in health and disease

Reactive nitrogen species (RNS) are various nitric oxide-derived compounds, including nitroxyl anion, nitrosonium cation, higher oxides of nitrogen, S-nitrosothiols, and dinitrosyl iron complexes. RNS have been recognized as playing a crucial role in the physiologic regulation of many, if not all, living cells, such as smooth muscle cells, cardiomyocytes, platelets, and nervous and juxtaglomerular cells. They possess pleiotropic properties on cellular targets after both posttranslational modifications and interactions with reactive oxygen species. Elevated levels of RNS have been implicated in cell injury and death by inducing nitrosative stress. The aim of this comprehensive review is to address the mechanisms of formation and removal of RNS, highlighting their potential cellular targets: lipids, DNA, and proteins. The specific importance of RNS and their paradoxic effects, depending on their local concentration under physiologic conditions, is underscored. An increasing number of compounds that modulate RNS processing or targets are being identified. Such compounds are now undergoing preclinical and clinical evaluations in the treatment of pathologies associated with RNS-induced cellular damage. Future research should help to elucidate the involvement of RNS in the therapeutic effect of drugs used to treat neurodegenerative, cardiovascular, metabolic, and inflammatory diseases and cancer.