Exercise-related alterations in MCT1 and GLUT4 expressions in the liver and pancreas of rats with STZ-induced diabetes.

Background: The liver and pancreas tissues play a central role in controlling glucose homeostasis. In patients with type I diabetes mellitus (T1DM), the function of these tissues is impaired. The positive effects of exercise have been shown in diabetic patients. To demonstrate the positive effects of exercise in T1DM, we examined the effects of moderate-intensity endurance training (MIET) on the liver enzymes and expression of MCT1 and GLUT4 genes. Methods: Male Wistar rats were allocated into 4 groups of control (C), training (T), diabetic control (DC), and diabetes + training (DT). The serum levels of liver enzymes such as alanine aminotransferase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) were determined by ELIZA. MCT1 and GLUT4 mRNA expressions in the liver and pancreas tissues were evaluated through real-time qPCR after 10 weeks of training. Results: The mRNA levels of MCT1 and GLUT4 decreased in DC group and increased in DT group. T1DM led to weight loss, but the weight loss was less in the DT group. T1DM caused an increase in liver enzymes such as ALT, AST and ALP, whereas endurance training preserved enzymatic levels. Conclusion: These results suggested that MIET increases levels of MCT1 and GLUT4 liver and pancreas in the diabetic rats and improves liver function tests. Upregulation of MCT1 and GLUT4 can probably improve the function of liver and pancreas tissues and promote glucose homeostasis in T1DM.

Interaction of Klotho and sirtuins.

OBJECTIVE: In this article, we review the articles that have reported the interaction between Klotho and sirtuins. RECENT FINDINGS: Sirtuins are a family of histone deacetylase enzymes that are considered to be the main regulators of biological processes. This family is one of the essential factors for postponing aging and increasing the life span of organisms. Sirtuins play a role in regulating the function of various cellular processes such as cellular metabolism, oxidative stress, apoptosis, and inflammation. It has also been shown that various diseases are related to these enzymes. Klotho is an anti-aging protein that exists as a membrane protein as well as a soluble circulating form. The membrane type of this protein acts as a co-receptor of the FGF endocrine family. It has been shown that the Klotho gene is related to age-related diseases, including osteoporosis, coronary artery, brain diseases, diabetes, etc. At the same time, it is difficult to separate the actions of Klotho and endocrine FGFs. Several studies have shown that Klotho and sirtuins interact with each other at different regulatory levels. However, it is necessary to carry out more in-vivo investigations to create new windows towards the treatment or prevention of various diseases.

Protamine as a barrier against the angiogenic effect of insulin: a possible role of apelin.

Insulin is proved to have angiogenic ability thereby may worsen the diabetic retinopathy (DR) progression. Insulin also triggers the expression of endogenous angiogenic peptide, apelin. Since protamine was introduced as an inhibitor of the apelin receptor, we hypothesized that use of protaminated insulin instead of non-protaminated insulin can decrease the negative role of insulin in progression of DR. Firstly, the incidence of DR was compared among three diabetic patient groups: an oral medication, non-protaminated insulin, and protaminated insulin (PIns). Proliferation and migration rate of HUVECs was measured after insulin, apelin, and protamine exposure. In clinical study, the chance of developing DR was 8.5 and 4.1 times higher in insulin group and PIns groups compared with oral group respectively. Insulin group had a chance of 9.5-folds of non-proliferative DR compared to oral group. However, the difference of non-proliferative DR between PIns and oral group wasn't significant. In-vitro tests showed that concomitant use of insulin and apelin increases viability and migratory potential of HUVECs. However, protamine could reverse this effect. Protamine present in some insulins might show a promising protective role against diabetic retinopathy. Thus, protaminated insulins may be preferable in the treatment of diabetes.

SIRT1 and Klotho expression in the heart and kidneys of rats with acute and chronic renovascular hypertension.

AIM: To evaluate Klotho and SIRT1 expression in the heart and kidneys of rats with acute and chronic renovascular hypertension. METHODS: Four and sixteen weeks after the induction of renovascular hypertension by clipping the left renal artery, systemic blood pressure, serum angiotensin II level, and the expression of Klotho and SIRT1 proteins and oxidative stress indices in the heart and kidneys were assessed. RESULTS: SIRT1 level was significantly reduced in the ischemic (left) kidney in acute and chronic phases of hypertension. In the heart, it decreased in the acute phase, but increased in the chronic phase. Klotho levels in the heart and kidneys did not change significantly in either hypertension phase. Superoxide dismutase (SOD) activity in the heart significantly decreased, and SOD, total antioxidant capacity, and malondialdehyde in the ischemic kidney significantly increased during the development of hypertension. Serum angiotensin II level significantly increased in the acute phase of hypertension. CONCLUSION: Development of renovascular hypertension was associated with a reduction of SIRT1 expression in the heart and ischemic kidney. As angiotensin II and SIRT1 counteract each other's expression, a SIRT1 reduction in the heart and kidney, along with the influence of systemic/local angiotensin II, seems to be partly responsible for hypertension development. A combination of SIRT1 agonists and angiotensin II antagonists may be considered for use in the treatment of renovascular hypertension.

PEGylated Graphene Quantum Dot Improved Cardiac Function in Rats with Myocardial Infarction: Morphological, Oxidative Stress, and Toxicological Evidences.

INTRODUCTION: The biocompatibility and potential application of graphene-based nanomaterials in biomedicine have been documented. The effects of polyethylene glycol-graphene quantum dots (GQDs-PEG) on cardiac function in rats with myocardial infarction (MI) were examined. METHODS: Wistar rats were randomly assigned to two main groups, each consisting of sham-Veh., MI-Veh., and MI+GQDs-PEG at doses of 5, 10, and 20 mg/kg. MI was induced by the closure of the left anterior descending (LAD) coronary artery. After MI, GQDs-PEG were injected at different doses IP every other day for two weeks. In the end, hemodynamic and heart contractility indices were assessed. The levels of myocardial MDA (malondialdehyde), SOD (superoxide dismutase), GPX (glutathione peroxidase), and TAC (total antioxidant capacity) were measured by the ELISA method. The serum ALP, ALT, AST, creatinine, and urea levels were measured using the photometric method. The infarct size was assessed by TTC staining. RESULTS: GQDs-PEG decreased the infarct size at doses of 10 and 20 mg/kg and recovered the MI-induced reductions of +dp/dt max and -dp/dt max in the study groups. GQDs-PEG normalized systolic blood pressure and left ventricular systolic pressure reduction at the dose of 20 mg/kg in the MI group. Heart SOD, GPX, and TAC increased in the GQDs-PEG 10 and 20 groups. Almost no signs of toxic effects due to GQDs-PEG administration were observed on the liver and kidneys. CONCLUSIONS: The results provided clear evidence that GQDs-PEG improve cardiac performance and hemodynamic parameters in rats with MI by reducing oxidative stress. GQDs-PEG is proposed as a therapeutic target for the treatment of MI.

Klotho and SIRT1 changes from pre-diabetes to diabetes and pre-hypertension to hypertension.

BACKGROUND: Hypertension and diabetes are among the most important risk factors of cardiovascular diseases. Klotho and SIRT1 are known as anti-aging factors with beneficial effects on cardiovascular system. In this study we investigated the serum Klotho and SIRT1 levels in pre-diabetic and pre-hypertensive individuals and then in diabetic and hypertensive patients to see their relationship with these diseases. METHOD: 229 individuals divided into six groups with similar gender and age distribution 1-Control (normal BP and FBS) 2-pre-diabetic (FBS between 100 and 125 mg/dl) 3-diabetic (FBS ≥ 126 mg/dl), 4-pre-hypertensive (SBP 120-139 or DBP 80-89 mm Hg) 5-hypertensive (SBP ≥ 140 or DBP ≥ 90 mm Hg), and 6-patients with combined hypertension/diabetes. Serum levels of Klotho and SIRT1 were measured by ELISA method. RESULTS: Serum Klotho and STRT1 levels decreased in pre-diabetes and returned to normal in diabetic patients. Their concentration increased in pre-hypertension and recovered to normal in hypertension. In the physiologic range of FBS there is a negative correlation between Klotho and SIRT1 with FBS. When pathologic ranges of FBS added to analysis, the negative correlation abolished/U shaped. Also an inverse U shape correlation observed between Klotho and SIRT1 with MAP in the range of normal to hypertensive BP levels. There was an overall positive relationship between the serum levels of Klotho and SIRT1 themselves. CONCLUSION: The serum levels of the anti-aging proteins Klotho and SIRT1 increases or reduces at the onset of the disease, as a compensatory mechanism, but as the disease progresses their level recovers.

Improvement of Cardiac Function in Rats With Myocardial Infarction by Low-Intensity to Moderate-Intensity Endurance Exercise Is Associated With Normalization of Klotho and SIRT1.

ABSTRACT: Exercise training (Ex) has beneficial effects on cardiovascular diseases by increasing Klotho and SIRT1. This study aimed to investigate whether the beneficial impact of Ex on myocardial infarction (MI) is mediated through Klotho and SIRT1. Fifty-six Wistar rats were divided into 4 main groups of Sham, MI, Ex, and MI + Ex. MI was induced by the closure of the left anterior descending. Animals were trained by endurance exercise for 4 weeks. In the end, hemodynamic and heart contractility indices were assessed. The levels of Klotho and SIRT1 in the serum and heart were measured by enzyme-linked immunosorbent assay and Western blot, respectively. The ADAM17 level in the heart and kidneys was assessed by enzyme-linked immunosorbent assay. The infarct size and fibrosis area were assessed by triphenyltetrazolium chloride and Masson trichrome staining, respectively. Ex recovered the reduction of dp/dt max and dp/dt min and decreased myocardial infarct size and fibrotic area in the MI group. Ex normalized the increase in heart rate, systolic blood pressure, left ventricular systolic pressure, and left ventricular end diastolic pressure in the MI group. Ex also normalized the reduction of the levels of Klotho and SIRT1 in serum and heart in the MI group. The changes of Klotho and SIRT1 in serum were positively correlated. Ex also restored ADAM17 levels in the MI group. Ex improved cardiac function in the MI group and is associated with reduction of the infarct size and normalization of Klotho and SIRT1 levels. Regarding unidirectional changes in Klotho and SIRT1, these proteins may play a role in beneficial effects of Ex on MI recovery.

Effect of apelin on cardiac contractility in acute reno-vascular hypertension: The role of apelin receptor and kappa opioid receptor heterodimerization.

OBJECTIVES: Apelin/APJ system plays an important role in the regulation of myocardial contractility (MC) and blood pressure. Opioid receptors (OPRs) are also important cardiovascular regulators and exert many of their effects through modulating the function of other systems. This study analyzed the interaction between APJ and kappa OPRs (KOR) in cardiac responsiveness to apelin in acute reno-vascular hypertension (2K1C). MATERIALS AND METHODS: MC studies were carried out on 2K1C rats. F13A (APJ blocker), Naloxone (OPR inhibitor), nor-Binaltorphiminedihydrochloride (nor-BNI; kappa OPR inhibitor), PTX (Gi path inhibitor) and chelerytrine (protein kinase C; PKC inhibitor) were administered prior to apelin 20 and 40 µg/kg. The phosphorylation of extracellular signal-regulated kinases (ERK1/2) (PERK) was also assessed. Dimerization of APJ and KOR was evaluated by immunoprecipitation. RESULTS: Both doses of apelin reduced blood pressure. Apelin 40 exerted a negative inotropic effect, which was inhibited by nor-BNI, but apelin 20 showed a positive inotropic effect, which was resistant to this inhibition. Hypertension increased heterodimerization of the APJ and KOR and this was reduced by apelin 20. F13A, naloxone and PTX significantly reduced PERK in apelin 40 group, but F13A, naloxone, and chelerytrine significantly increased PERK in the apelin 20 group. CONCLUSION: The lowering effect of apelin 40 on MC and its non-effectiveness on APJ/KOR dimerization, while augmenting the contractility and reducing the dimerization by apelin 20 implies the APJ/KOR-related effects of apelin on the MC under acute reno-vascular hypertension. This may have potential clinical applications as apelin has been introduced as a potential therapeutic agent in heart failure and opioids are being currently used in the treatment of myocardial infarction.

Opioid receptors mediate inotropic and depressor effects of apelin in rats with 2K1C-induced chronic renovascular hypertension.

Apelin receptors (APJ) cross-talk with other G-protein-coupled receptors. However, the role of APJ interaction with opioid receptors (OPR) on the cardiovascular effects of apelin in hypertension is not clear. Renovascular hypertension was induced by placing a Plexiglas clip on the left kidney of rats. After 16 weeks, F13A (an APJ antagonist), naloxone (a general OPR inhibitor), and nor-binaltorphimine dihydrochloride (nor-BNI; a selective inhibitor of KOR) were given prior to injections of apelin at doses of 40 and 60 µg/kg. The arterial systolic/diastolic blood pressure and left ventricular contractility responses were then evaluated. The arterial systolic/diastolic blood pressure in sham and 2K1C rats was 110/71 mm Hg and 171/124 mm Hg, respectively. The hypotensive effects of apelin at both doses were inhibited by F13A and naloxone. Nor-BNI completely inhibited the effects of apelin 40 on arterial pressure, and decreased the effects of 60 µg/kg. KOR inhibition also prevented the compensation for the decrease in the left ventricle +dp/dt max and -dp/dt max caused by apelin 60. The simultaneous inhibition of OPR and APJ reduced arterial pressure and increased cardiac contractility. Findings showed that the OPR, particularly KOR, mediate the inotropic, lusitropic, and depressor effects of apelin. The interaction of the OPR and APJ augments the inotropic and vasodepressor effects of apelin. This interaction may have potential clinical applications in cardiac failure since opioids are currently used in the treatment of myocardial infarction and stroke, and apelin has been introduced as a potential therapeutic agent in cardiovascular complications.

Heterodimerization of apelin and opioid receptors and cardiac inotropic and lusitropic effects of apelin in 2K1C hypertension: Role of pERK1/2 and PKC.

AIMS: Kappa Opioid receptors (KORs) change the impact of apelin on the phosphorylated ERK1/2 (pERK1/2). However, the role of interaction between KOR and apelin receptors (APJ) on the cardiac contractility effects of apelin and in regulation of pERK1/2 and PKC in the heart of renovascular hypertensive (2K1C) rats is unknown. MAIN METHODS: Hemodynamic factors, the heterodimerization of KOR and APJ, the expression of KOR mRNA and protein and pERK1/2 in the left ventricle of 2K1C rats were measured following APJ, KOR, PKC and Gi path inhibition by F13A, nor-BNI, chelerythrine and PTX respectively. KEY FINDINGS: Apelin in 40 and 60µg/kg doses increased cardiac contractility, and reduced mean arterial pressure. The cardiac impacts in both doses were reduced by F13A, nor-BNI and chelerytrine and blocked by PTX. Hypertension increased the expression of KORs and heterodimerization of APJ and KOR, and reduced pERK1/2 in the left ventricle. Apelin, in both doses reduced (normalized) heterodimerization and recovered the reduction in pERK1/2. The recovery of ERK1/2 phosphorylation was accompanied by reduction of KOR and APJ heterodimerization. SIGNIFICANCE: 2K1C hypertension increased the expression of KORs and heterodimerization of APJ and KORs. The heterodimerization was associated by reduction of ERK phosphorylation and altered the cardiac inotropic and lusitropic effects of apelin. These changes may participate in pathophysiology of cardiac dysfunction in renovascular hypertension that is associated with subnormal level of serum apelin. Apelin- induced recovery of ERK1/2 phosphorylation and KOR-APJ dimerization may nominate apelin as a therapeutic goal in treatment of this kind of hypertension.

The differential effects of low and high doses of apelin through opioid receptors on the blood pressure of rats with renovascular hypertension.

The apelin/APJ system has an important role in the regulation of vascular tone and blood pressure. Opioid receptors (OPRs) are also important cardiovascular regulators and exert many of their effects by modulating the function of other G-protein-coupled receptors. The aim of this study was to analyze the interaction of apelin and the opioid system with respect to vascular responses to apelin in rats with renovascular hypertension (two-kidney, one clip (2K1C)). Homodynamic studies were carried out in 2K1C rats. Naloxone (a nonselective OPR inhibitor) or nor-binaltorphimine dihydrochloride (norBNI, a kappa OPR inhibitor) and signaling pathway inhibitors PTX (a Gi path inhibitor) and chelerythrine (a protein kinase C (PKC) inhibitor) were administered before apelin at 20 and 40 µg kg-1. Apelin at 20 and 40 µg kg-1 decreased the systolic blood pressure by 15% and 20%, respectively (P<0.05). The pressure drop caused by apelin 20 was inhibited by naloxone, norBNI and PTX, but it was not affected by chelerythrine. The pressure drop caused by apelin 40 was augmented by naloxone and chelerythrine, and it was not affected by norBNI or PTX. The lowering effect of apelin 20 on blood pressure is exerted through OPRs and stimulation of Gi and PKC pathways. However, apelin 40 functions independently of OPRs, Gi and PKC. This dose-dependent differential effect of apelin may have potential clinical applications as opioids are currently used, and apelin has been introduced as a potential therapeutic agent in cardiovascular complications.