A Sodium Glucose Cotransporter 2 Inhibitor Fails to Improve Perivascular Adipose Tissue-Mediated Modulation of Vasodilation and Cardiac Function in Rats With Metabolic Syndrome

Arterial perivascular adipose tissue (PVAT) can elicit vasodilator signals complementary to those elicited by the endothelium in SHRSP.Z-Lepr^fa/IzmDmcr (SHRSP.ZF) rats, an animal model of metabolic syndrome (MetS). Here, we tested whether a glucose cotransporter 2 inhibitor (SGLT2-i; tofogliflozin) increased this PVAT effect to prevent the deterioration of cardiac function in aging SHRSP.ZF rats. Tofogliflozin treatments (1 or 10 mg/kg/day) or vehicle (control) were administered for 10 weeks by oral gavage to SHRSP.ZF rats, starting at 13 weeks of age. At 23 weeks of age, glucose levels in the serum and urine (24 h after the last administration) were determined using commercial kits. Vasodilator responsiveness of PVAT-surrounded or PVAT-free superior mesenteric arteries was determined using acetylcholine with organ-bath methods. Cardiac ventricular function and coronary flow were determined using Langendorff heart preparations. Serum and urine glucose levels in SGLT2-i treatment groups did not differ from those in the controls, but the ratios of glycated to non-glycated albumin were lower than those in the controls. Tofogliflozin treatments did not alter relaxations in the presence of PVAT or affect relaxations of PVAT-free arteries. Left ventricular systolic pressures, maximum rate of pressure decline, and coronary flow in ex vivo hearts did not differ among the treatment groups. PVAT effects and cardiac dysfunction were not altered by tofogliflozin treatment in SHRSP.ZF rats with MetS. These results do not provide strong evidence to support the use of SGLT2-i as a cardiovascular protective therapy in MetS, which occurs prior to the onset of type 2 diabetes.

Activation of protease-activated receptor 2 is associated with blood pressure regulation and proteinuria reduction in metabolic syndrome

Metabolic syndrome (MetS) increases the risk of kidney disease. In SHRSP.Z-Leprfa /IzmDmcr (SHRSP.ZF) rats with MetS, protease-activated receptor 2 (PAR2)-mediated vasorelaxation is preserved in the aorta at 20 weeks of age (weeks) via enhancement of nitric oxide production but impaired at 30 weeks by oxidative stress. However, impairment of PAR2-mediated vasorelaxation of renal arteries and its possible implications for kidney disease are unclear. We used organ baths to assess PAR2-mediated vasorelaxation of isolated renal arteries, colorimetric methods to measure urinary protein levels as an index of renal function, and western blot to determine expression of PAR2 and nephrin proteins in the kidneys of SHRSP.ZF rats at 10, 20, and 30 weeks. We assessed renal arteries and kidney function for effects of orally administered GB88, a pathway-dependent PAR2 antagonist, from 10 to 18 weeks, and azilsartan, an angiotensin II type 1 receptor blocker, from 13 to 23 weeks. PAR2-mediated vasorelaxation was slightly lower at 20 weeks and attenuated significantly at 30 weeks compared with those at 10 weeks. Urinary protein levels were increased at 20 and 30 weeks. Decreased protein expression of PAR2 and nephrin in the kidney were observed at 30 weeks. Administration of GB88 increased blood pressure (BP) and proteinuria. Azilsartan reduced the high BP and the impaired PAR2-mediated vasorelaxation, but did not restore the increase in urinary protein levels and decreased PAR2 and nephrin protein expression in the kidney. PAR2 activation in the kidney may be associated with maintenance of BP and urinary protein excretion in MetS.

Non-alcoholic steatohepatitis aggravates nitric oxide synthase inhibition-induced arteriosclerosis in SHRSP5/Dmcr rat model

Non-alcoholic steatohepatitis (NASH) is linked to increased cardiovascular risk, independent of the broad spectrum of metabolic syndrome risk factors. Stroke-prone (SP) spontaneously hypertensive rats (SHRSP5/Dmcr) fed a high-fat and high-cholesterol (HFC) diet developed hepatic lesions similar to those in human NASH pathology. These rats simultaneously developed lipid deposits in the mesenteric arteries, cardiac fibrosis, endothelial dysfunction and left ventricle (LV) diastolic dysfunction. However, the intermediary factors between NASH and cardiovascular disease are still unknown. We investigated whether NASH aggravates nitric oxide (NO) synthase inhibition-induced arteriosclerosis in SHRSP5/Dmcr rats. Wistar Kyoto and SHRSP5/Dmcr rats were divided into 4 groups of 5 and fed the stroke-prone (SP) or HFC diets for 8 weeks. To induce NO synthase inhibition, N^ω -nitro-L-arginine methyl ester hydrochloride (L-NAME) mixed with drinking water was administered in the final 2 weeks. The NASH+L-NAME group demonstrated the following characteristics related to arteriosclerosis and myocardial ischaemia: (a) LV systolic dysfunction with asynergy, (b) replacement fibrosis caused by the shedding of cardiomyocytes and (c) arterial lipid deposition and coronary occlusion secondary to endothelial dysfunction. These characteristics were not observed in the NASH or non-NASH+L-NAME groups. The SHRSP5/Dmcr rat model demonstrates that NASH significantly aggravates cardiovascular risk.

Modeling heart failure risk in diabetes and kidney disease: limitations and potential applications of transverse aortic constriction in high-fat-fed mice

There is an increased incidence of heart failure in individuals with diabetes mellitus (DM). The coexistence of kidney disease in DM exacerbates the cardiovascular prognosis. Researchers have attempted to combine the critical features of heart failure, using transverse aortic constriction, with DM in mice, but variable findings have been reported. Furthermore, kidney outcomes have not been assessed in this setting; thus its utility as a model of heart failure in DM and kidney disease is unknown. We generated a mouse model of obesity, hyperglycemia, and mild kidney pathology by feeding male C57BL/6J mice a high-fat diet (HFD). Cardiac pressure overload was surgically induced using transverse aortic constriction (TAC). Normal diet (ND) and sham controls were included. Heart failure risk factors were evident at 8-wk post-TAC, including increased left ventricular mass (+49% in ND and +35% in HFD), cardiomyocyte hypertrophy (+40% in ND and +28% in HFD), and interstitial and perivascular fibrosis (Masson's trichrome and picrosirius red positivity). High-fat feeding did not exacerbate the TAC-induced cardiac outcomes. At 11 wk post-TAC in a separate mouse cohort, echocardiography revealed reduced left ventricular size and increased left ventricular wall thickness, the latter being evident in ND mice only. Systolic function was preserved in the TAC mice and was similar between ND and HFD. Thus combined high-fat feeding and TAC in mice did not model the increased incidence of heart failure in DM patients. This model, however, may mimic the better cardiovascular prognosis seen in overweight and obese heart failure patients.

A High-Fat and High-Cholesterol Diet Induces Cardiac Fibrosis, Vascular Endothelial, and Left Ventricular Diastolic Dysfunction in SHRSP5/Dmcr Rats

AIM

Non-alcoholic steatohepatitis (NASH) increases cardiovascular risk regardless of risk factors in metabolic syndrome. However, the intermediary factors between NASH and vascular disease are still unknown because a suitable animal model has never been established. The stroke-prone (SP) spontaneously hypertensive rat, SHRSP5/Dmcr, simultaneously develops hypertension, acute arterial lipid deposits in mesenteric arteries, and NASH when feed with a high-fat and high-cholesterol (HFC) diet. We investigated whether SHRSP5/Dmcr affected with NASH aggravates the cardiac or vascular dysfunction.

METHOD

Wister Kyoto and SHRSP5/Dmcr rats were divided into 4 groups of 5 rats each, and fed with a SP or HFC diet. After 8 weeks of HFC or SP diet feeding, glucose and insulin resistance, echocardiography, blood biochemistry, histopathological staining, and endothelial function in aorta were evaluated.

RESULTS

We demonstrate that SHRSP5/Dmcr rats fed with a HFC diet presented with cardiac and vascular dysfunction caused by cardiac fibrosis, endothelial dysfunction, and left ventricular diastolic dysfunction, in association with NASH and hypertension. These cardiac and vascular dysfunctions were aggravated and not associated with the presence of hypertension, glucose metabolism disorder, and/or obesity.

CONCLUSIONS

SHRSP5/Dmcr rats may be a suitable animal model for elucidating the organ interaction between NASH and cardiac or vascular dysfunction.

Time-Dependent Differences in the Influence of Perivascular Adipose Tissue on Vasomotor Functions in Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) facilitates the development of cardiovascular disease due to atherosclerosis, which is accelerated by defects of the vascular endothelium. Vascular dysfunction in response to nitric oxide (NO) occurs in the mesenteric arteries of an animal model of MetS, SHRSP.Z-Lepr^fa/IzmDmcr (SHRSP.ZF) rats. Vascular responses to vasodilators are affected by perivascular adipose tissue (PVAT) that surrounds the outsides of arteries. In this study, we assessed the role of PVAT in vascular dysfunction observed in SHRSP.ZF.

METHODS

To determine the effects of PVAT on vasodilators in SHRSP.ZF and control Wistar-Kyoto (WKY) rats, we used organ bath bioassay techniques to assay acetylcholine and nitroprusside-induced relaxations of isolated mesenteric arterial ring preparations with PVAT intact or removed.

RESULTS

A PVAT-mediated enhancement of relaxations induced by acetylcholine and nitroprusside occurred in SHRSP.ZF at 20 weeks of age, but not at 10 and 30 weeks, and did not occur in WKY. Furthermore, the enhancing effects of PVAT from SHRSP.ZF at 20 weeks could not be substituted by replacement with PVAT from either WKY or 30-week-old SHRSP.ZF, was inhibited by NO synthase inhibitor, and abolished by removal of the arteries' endothelium. Cyclic guanosine monophosphate (cGMP) accumulation elicited by nitroprusside was higher in SHRSP.ZF arteries with PVAT than arteries without PVAT at 20 weeks, but the enhancement of cGMP accumulation did not occur at 30 weeks.

CONCLUSIONS

PVAT may regulate arterial tone by releasing diffusible vasorelaxing factor(s), which, through endothelium-derived NO production, compensates for impaired vasodilations at early stages of MetS.

Panax notoginseng saponins ameliorate impaired arterial vasodilation in SHRSP.Z-Lepr(fa) /lzmDmcr rats with metabolic syndrome

Panax notoginseng saponins (PNS) are major components of Panax notoginseng, a herb with established clinical efficacy against vascular diseases. SHRSP.Z-Lepr(fa) /IzmDmcr (SHRSP.ZF) rats, a new animal model for metabolic syndrome, display an impaired vasorelaxation response in aortas and mesenteric arteries that is mediated by nitric oxide (NO). This study investigated whether PNS and its components can ameliorate this vascular dysfunction in SHRSP.ZF rats. In an in vitro study, in the presence or absence of PNS and its components, vasodilation in response to nitroprusside was determined from myographs under isometric tension conditions in aortas and mesenteric arteries from male SHRSP.ZF rats at 18-20 weeks of age. In an in vivo study, PNS (30 mg/kg per day) was orally administered to SHRSP.ZF rats from 8 to 20 weeks of age. In vitro treatment with PNS and Ginsenoside Rb1 increased nitroprusside-induced relaxation of aortas and mesenteric arteries in SHRSP.ZF rats. The PNS-induced increase was not affected by a nitric oxide (NO) synthase inhibitor or endothelium denudation. Relaxation in response to a cell-permeable cGMP analogue was increased by PNS, but cGMP accumulation by nitroprusside was not altered. In vivo treatment with PNS in SHRSP.ZF rats lowered blood pressure and increased relaxation and the expression of soluble guanylyl cyclase protein in arteries, without affecting metabolic abnormalities. These results indicate that PNS causes an increase in vasodilation in response to NO and a decrease in blood pressure, resulting in protection against vascular dysfunction in SHRSP.ZF rats. PNS might be beneficial in alleviating impaired vasodilation in metabolic syndrome.

APOE*3Leiden.CETP transgenic mice as model for pharmaceutical treatment of the metabolic syndrome

AIMS

This study aimed to investigate systematically (i) the appropriate dietary conditions to induce the features of the MetS in APOE*3Leiden.humanCholesteryl Ester Transfer Protein (E3L.CETP) mice and (ii) whether the response of this model to different antidiabetic and hypolipidemic drugs is similar as in humans.

METHODS

Male obese, IR and dyslipidemic E3L.CETP mice were treated with antidiabetic drugs rosiglitazone, liraglutide or an experimental 11β-hydroxysteroid-dehydrogenase-1 (HSD-1) inhibitor, or with hypolipidemic drugs atorvastatin, fenofibrate or niacin for 4-6 weeks. The effects on bw, IR and plasma and liver lipids were assessed.

RESULTS

Rosiglitazone, liraglutide and HSD-1 inhibitor significantly decreased glucose and insulin levels or IR. Liraglutide and HSD-1 inhibitor also decreased bw. Atorvastatin, fenofibrate and niacin improved the dyslipidemia and fenofibrate and niacin increased high-density lipoprotein (HDL) cholesterol. In addition, hepatic triglycerides were significantly decreased by treatment with rosiglitazone and liraglutide, while hepatic cholesterol esters were significantly decreased by rosiglitazone and atorvastatin.

CONCLUSIONS

We conclude that the E3L.CETP mouse is a promising novel translational model to investigate the effects of new drugs, alone or in combination, that affect IR, diabetic dyslipidemia and non-alcoholic fatty liver disease (NAFLD).

Establishment of a model of spontaneously-running-Tokushima-shikoku rats with left atrial thrombosis

Studies that investigate the underlying mechanisms of disease and treatment options typically require the use of a suitable animal model. Few suitable animal models exist for left atrial thrombosis. Here, we demonstrated that the Spontaneously-Running-Tokushima-Shikoku (SPORTS) rat — a Wistar strain known for its running ability—is predisposed to the development of thrombi in the left atrium. We investigated the incidence of left atrial thrombosis in male (n = 16) and female (n = 17) SPORTS rats and observed organized atrial thrombosis in 57% and 38% of males and female rats, respectively. In the male rats, systolic blood pressures and heart rates were significantly higher in SPORTS rats than in control Wistar rats. We could not find any evidence of arrhythmias, such as atrial fibrillation, during electrocardiographic examination of SPORTS rats. We believe that the SPORTS rat could serve as a new research model for left atrial thrombosis; further, it may be suitable for research investigating the development of new antithrombotic approaches for the control of atrial thrombosis or familial thrombophilia in humans.

Abnormal amounts of intracellular calcium regulatory proteins in SHRSP.Z-Leprfa/IzmDmcr rats with metabolic syndrome and cardiac dysfunction

Metabolic syndrome is known to increase the risk of abnormal cardiac structure and function, which are considered to contribute to increased incidence of cardiovascular disease and mortality. We previously demonstrated that ventricular hypertrophy and diastolic dysfunction occur in SHRSP.Z-Leprfa/IzmDmcr (SHRSP fatty) rats with metabolic syndrome. The aim of this study was to investigate the possible mechanisms underlying abnormal heart function in SHRSP fatty rats. The amount of sarcoplasmic reticulum Ca2+-ATPase (SERCA) 2a, phospholamban (PLB) protein, and Ser16-phosphorylated PLB was decreased in cardiomyocytes from SHRSP fatty rats compared with those from control Wistar–Kyoto rats at 18 weeks of age, and the PLB-to-SERCA2a ratio was increased. Left ventricular developed pressure was unchanged, and coronary flow rate and maximum rate of left ventricular pressure decline (−dP/dt) was decreased in SHRSP fatty rats. Treatment with telmisartan reversed the abnormalities of PLB amount, coronary flow rate, and −dP/dt in SHRSP fatty rats. These results indicate that abnormal amounts of intracellular Ca2+ regulatory proteins in cardiomyocytes, leading to reduced intracellular Ca2+ reuptake into the sarcoplasmic reticulum, may play a role in the diastolic dysfunction in SHRSP fatty rats and that these effects are partially related to decreased coronary circulation. Telmisartan may be beneficial in protecting against disturbances in cardiac function associated with metabolic syndrome.

Telmisartan provides protection against development of impaired vasodilation independently of metabolic effects in SHRSP.Z-Lepr(fa)/IzmDmcr rats with metabolic syndrome

Metabolic syndrome is known to facilitate the development of cardiovascular disease. We have demonstrated that mesenteric arteries of SHRSP.Z-Lepr(fa)/IzmDmcr (SHRSP-fatty) rats with metabolic syndrome display an impaired vasorelaxation response mediated by nitric oxide. We examined whether the condition could be alleviated by treatment with telmisartan, an angiotensin II type 1 (AT1) receptor antagonist with PPAR-γ-activating properties and compared the results with those from pioglitazone, a PPAR-γ agonist. Telmisartan (5 mg·kg(-1)·day(-1)) or pioglitazone (2.5 mg·kg(-1)·day(-1)) was orally administered to male SHRSP-fatty rats for 8 weeks. Serum triglyceride and cholesterol levels were determined, and the oral glucose tolerance test was performed to evaluate insulin resistance. Vasodilations in response to acetylcholine and nitroprusside were determined by wire myographs under isometric tension conditions, protein expressions of soluble guanylyl cyclase in mesenteric arteries by Western blotting, and the contents of 3-nitrotyrosine in aortas by high-performance liquid chromatography with electrochemical detection. Telmisartan exerted antihypertensive effects, while pioglitazone ameliorated metabolic abnormalities in SHRSP-fatty rats. Telmisartan increased acetylcholine- and nitroprusside-induced relaxation and soluble guanylyl cyclase protein expression in mesenteric arteries and reduced 3-nitrotyrosine content in aortas. Pioglitazone displayed no such alleviating effects on vascular functions. These findings indicate that telmisartan protects against vasodilation disturbance through anti-oxidative and -nitrative stress independently of metabolic effects in SHRSP-fatty rats with metabolic syndrome.