Yasushi Takeya

Genetic variants at the 9p21 locus contribute to atherosclerosis through modulation of ANRIL and CDKN2A/B

UNLABELLED Genome-wide association studies (GWAS) have identified genetic variants contributing to the risk of cardiovascular disease (CVD) at the chromosome 9p21 locus. The CVD-associated region is adjacent to the two cyclin dependent kinase inhibitors (CDKN)2A and 2B and the last exons of the non-coding RNA, ANRIL. It is still not clear which of or how these transcripts are involved in the pathogenesis of atherosclerosis. OBJECTIVE We assessed the hypothesis that 9p21 locus polymorphisms influence the expression of the transcripts in the region (ANRIL, CDKN2A/B) and that these transcripts contribute to atherogenesis through the modulation of proliferation in VSMC. METHODS We genotyped 18 SNPs (r(2)<0.8 and MAF>0.05) across the region of interest: CDKN2A/B and ANRIL, encompassing the CVD-associated region. RNA and DNA were extracted from the blood of 57 volunteers (69-72 years old). Carotid ultrasound was performed in 56 subjects. CDKN2A/B and ANRIL (exons 1-2 and 17-18) expression was measured employing RT-PCR. Gene expression and cell growth were evaluated in cultured VSMC after the siRNA-mediated knock-down of ANRIL. RESULTS The risk alleles for atherosclerosis-related phenotypes were consistently associated with a lower expression of ANRIL when evaluating exons 1-2. Common carotid artery stenosis was associated with a significantly lower (P<0.01) expression of ANRIL (exons 1-2). ANRIL knock-down in VSMC caused significant variation in expression of CDKN2A/B (P<0.05) and reduction of cell growth (P<0.05) in vitro. CONCLUSION Disease-associated SNPs at the 9p21 locus predominantly affect the expression of ANRIL. Overall, our results suggest that several CVD-associated SNPs in the 9p21 locus affect the expression of ANRIL, which, in turn modulate cell growth, possibly via CDKN2A/B regulation.

The impact of visit-to-visit variability in blood pressure on renal function.

Hypertension is an important risk factor for cardiovascular diseases such as chronic kidney disease. It is still not fully understood how blood pressure impacts the kidneys. In this study, we aimed to establish the significance of visit-to-visit variability in blood pressure for renal function. We analyzed 143 consecutive patients undergoing renal Doppler ultrasonography in our hospital ward and measured blood pressure at outpatient visits six or more times. We analyzed the correlation between visit-to-visit variability in blood pressure and multiple clinical parameters, including albuminuria and resistive index evaluated by renal Doppler ultrasonography, which is thought to be a good indicator of renal vascular resistance. Subjects with higher variability in systolic blood pressure showed a significantly higher prevalence rate of clinical albuminuria and microalbuminuria, and showed significantly higher resistive index. Stepwise multiple regression analysis showed that variability in systolic blood pressure was a significant risk factor for higher resistive index, independent of other renal risk factors. Visit-to-visit variability in blood pressure correlates significantly with renal function and renal arteriosclerotic change. This parameter could provide additional information about renal arteriosclerotic change independent of estimated glomerular filtration rate and albuminuria, and should be considered a therapeutic target for renal protection.

Angiogenic and antifibrotic actions of hepatocyte growth factor improve cardiac dysfunction in porcine ischemic cardiomyopathy

Impairment of cardiac function in ischemic cardiomyopathy has been postulated to be due to the decrease in blood flow and increase in collagen synthesis. Therefore, an approach to alter them directly by means of a growth factor may open up a new therapeutic concept in ischemic cardiomyopathy. From this viewpoint, hepatocyte growth factor (HGF) is a unique growth factor with angiogenic and antifibrotic effects. Thus, we examined the feasibility of gene therapy using HGF plasmid DNA for ischemic cardiomyopathy. Human HGF plasmid DNA at a dose of 0.4 or 4 mg was injected into ischemic myocardium of pigs induced by ameroid constrictor with the NOGA system. At 1 month after injection, the ischemic area was significantly reduced in the HGF group, accompanied by a significant increase in capillary density and regional myocardial perfusion in the ischemic area (P<0.01). In contrast, a significant decrease in fibrotic area was observed in the HGF group, associated with a significant decrease in collagen I, III and TGF-β synthesis as compared to the control group (P<0.01). Consistently, cardiac function was significantly improved in the 4 mg HGF group as compared to the control group (P<0.05). Overall, the present in vivo experiments demonstrated that intramyocardial injection of human HGF plasmid DNA in ischemic cardiomyopathy resulted in a significant improvement in cardiac function through an increase in blood flow and decrease in fibrosis. These favorable outcomes suggest potential utility to treat patients with ischemic heart disease using HGF gene transfer. Currently, a phase I study using human HGF plasmid DNA is ongoing to test the validity of this concept.

Klotho protein diminishes endothelial apoptosis and senescence via a mitogen-activated kinase pathway.

Aim:  Mice that carry the Klotho mutation (KL‐/‐) manifest diverse age‐related disorders similar to those observed in humans. Thus, the Klotho protein might function as an anti‐aging hormone in mammals. Recently, we reported that Klotho recombinant protein attenuated apoptosis and cellular senescence in endothelial cells, but the mechanism remained unclear. Here, we designed an in vitro study to test whether inhibitors of extracellular signal‐regulated kinase and mitogen‐activated kinase kinase could affect Klotho regulation of apoptosis and cellular senescence.

Loss of ACE2 Exaggerates High-Calorie Diet–Induced Insulin Resistance by Reduction of GLUT4 in Mice

ACE type 2 (ACE2) functions as a negative regulator of the renin-angiotensin system by cleaving angiotensin II (AII) into angiotensin 1–7 (A1–7). This study assessed the role of endogenous ACE2 in maintaining insulin sensitivity. Twelve-week-old male ACE2 knockout (ACE2KO) mice had normal insulin sensitivities when fed a standard diet. AII infusion or a high-fat, high-sucrose (HFHS) diet impaired glucose tolerance and insulin sensitivity more severely in ACE2KO mice than in their wild-type (WT) littermates. The strain difference in glucose tolerance was not eliminated by an AII receptor type 1 (AT1) blocker but was eradicated by A1–7 or an AT1 blocker combined with the A1–7 inhibitor (A779). The expression of GLUT4 and a transcriptional factor, myocyte enhancer factor (MEF) 2A, was dramatically reduced in the skeletal muscles of the standard diet–fed ACE2KO mice. The expression of GLUT4 and MEF2A was increased by A1–7 in ACE2KO mice and decreased by A779 in WT mice. A1–7 enhanced upregulation of MEF2A and GLUT4 during differentiation of myoblast cells. In conclusion, ACE2 protects against high-calorie diet–induced insulin resistance in mice. This mechanism may involve the transcriptional regulation of GLUT4 via an A1–7–dependent pathway.

Usefulness of the resistive index in renal Doppler ultrasonography as an indicator of vascular damage in patients with risks of atherosclerosis

BACKGROUND Chronic kidney disease (CKD) is caused by various risk factors of cardiovascular disease (CVD). The estimated glomerular filtration rate (eGFR) is commonly used for the evaluation of the renal function in patients with CKD; however, it is difficult to assess the pathogenesis of CKD and predict the renal prognosis accurately using only eGFR. The resistive index (RI) in renal Doppler ultrasonography (RDU) is thought to be a good indicator of renal vascular resistance caused by atherosclerosis. In the present study, we investigated whether RI could be used to evaluate the pathogenesis of renal damage and predict the renal prognosis and investigated the correlation between RI and blood pressure (BP) fluctuations in patients with or without hypertension. METHODS The total study population included 194 patients (mean age: 66.2 years), who underwent RDU in our hospital ward between February 2009 and July 2010. We investigated the correlation between RI and multiple clinical parameters, including ambulatory blood pressure monitoring (ABPM). RESULTS RI significantly correlated with age, eGFR, diastolic BP, pulse pressure and level of albuminuria. Patients with diabetes mellitus (DM) showed a significantly higher RI than patients without DM, although their eGFR was similar; thus, DM might accelerate renal vascular damage and RI could detect earlier changes of vascular damage proceeding the time eGFR is reduced. Regarding ABPM, patients with a larger morning surge [systolic blood pressure (SBP) in the early morning--lowest SBP during sleep] showed a significantly higher RI. CONCLUSIONS The present study indicated that RI might be very useful for the evaluation of very early renal damage more effectively than eGFR and that diurnal BP change might be partly due to the progression of atherosclerotic change in the kidney evaluated by RI.

The counterregulating role of ACE2 and ACE2-mediated angiotensin 1–7 signaling against angiotensin II stimulation in vascular cells

To clarify the role of endogenous angiotensin (Ang)-converting enzyme 2 (ACE2) and its cleavage product, Ang 1–7, in the atherogenic stimulation of vascular cells, we investigated the effect of pharmacological inhibition of ACE2 and Mas, an Ang 1–7 receptor, on cellular responses against Ang II stimulation. We measured extracellular signal-regulated kinase (ERK) 1/2 phosphorylation by western blot, smooth muscle cell (SMC) proliferation by WST assay and the adhesion of monocytes labeled with PKH67 to endothelial cells (ECs) by fluorescence microplate reader. Cells were pretreated with Ang 1–7, olmesartan (Ang II type 1 receptor (AT1) blocker), DX600 (ACE2 inhibitor), -Ala7-Ang1–7 (D-Ala; Mas antagonist), or combinations of treatments before the application of Ang II. Treatment with Ang II increased phosphorylated ERK 1/2 of SMC and EC, proliferation of SMC and adhesion of monocyte to EC, which were blocked by olmesartan. Pretreatment with DX600 either did not accelerate or only slightly accelerated these cellular responses. However, when Ang II signaling through AT1 was reduced by olmesartan, the additional treatment with DX600 significantly blunted some of the effect of olmesartan. Similarly, pretreatment with D-Ala reduced the inhibitory effect of olmesartan in response to Ang II stimulation. Endogenous ACE2 in vascular cells may contribute to counteracting the Ang II-mediated cellular response partly by upregulating the Ang 1–7 signaling through Mas.

Alteration of vascular function is an important factor in the correlation between visit-to-visit blood pressure variability and cardiovascular disease.

Objective: To assess how visit-to-visit variability of SBP correlates with systemic atherosclerotic change and various prognoses. Background: Visit-to-visit SBP variability correlates with cardiovascular events. However, the mechanisms underlying the impact of visit-to-visit SBP variability on prognoses are poorly understood. Methods and results: A total of 485 patients with essential hypertension from the Non-Invasive Atherosclerotic Evaluation in Hypertension (NOAH) study cohort were included. We analyzed the correlation between visit-to-visit SBP variability and multiple clinical parameters. Next, we prospectively examined the correlation of SBP variability and frequency of cardiovascular disease (CVD) and total mortality. Patients with higher SBP variability exhibited significantly higher rates of statin use, as well as higher pulse wave velocity (PWV), left-ventricular mass index (LVMI), plaque score, and resistive index of the common carotid artery; these patients also exhibited lower estimated glomerular filtration rate. Kaplan–Meier analysis demonstrated that patients with higher SBP variability have a significantly higher incidence of CVD and mortality rate. The hazard ratio of SBP variability for incidence of CVD was greatly diminished after adjustment for intima–media thickness, plaque score, and resistive index, and was slightly diminished after adjustment for PWV and LVMI. Visit-to-visit SBP variability remained an independent risk factor for mortality after adjustment. Conclusion: Visit-to-visit SBP variability correlates significantly with systemic atherosclerotic change, incidence of CVD, and mortality rate. Altered arterial functions, such as macrovascular atherosclerosis and vascular resistance, are responsible for the correlations between visit-to-visit SBP variability and incidence of CVD.

Differences between daytime and nighttime blood pressure variability regarding systemic atherosclerotic change and renal function

Recently, new parameters related to hypertension, such as variability in blood pressure and ambulatory arterial stiffness index (AASI), were demonstrated to correlate with arteriosclerotic change. In this study, we investigated the correlation between circadian variability in blood pressure/AASI and renal function. We also investigated differences in the clinical impact of 24 h, daytime and nighttime blood pressure variability on renal and systemic atherosclerotic changes. We analyzed data from 120 patients who underwent renal Doppler ultrasonography (RDU) and ambulatory blood pressure monitoring (ABPM) at our hospital ward, and investigated the correlation between circadian variability in blood pressure/AASI and renal function, including resistive index (RI) evaluated with RDU, which is thought to be a good indicator of renal vascular resistance. Subjects with higher circadian variability in systolic blood pressure (SBP) had significantly higher RI. Daytime variability in SBP correlated more strongly with RI than nighttime variability. Meanwhile, only nighttime variability, but not daytime variability, in SBP was related to carotid atherosclerosis. Similarly, AASI was significantly correlated with RI. Circadian variability in SBP and AASI were both significantly correlated with renal function. Daytime SBP s.d. was especially more strongly correlated with renal vascular resistance, and nighttime SBP s.d. was significantly correlated with intima-media thickness (IMT) and plaque score. These results indicate that evaluating both daytime and nighttime blood pressure variability enables an assessment of pathological conditions in hypertensive patients to prevent cardiovascular diseases.

Serum uric acid is an independent risk factor for cardiovascular disease and mortality in hypertensive patients.

The purpose of the study was to investigate the association of serum uric acid (UA) levels in hypertensive patients with the prognosis for cardiovascular disease (CVD) and mortality. This hospital-based cohort study included 669 patients with essential hypertension. A questionnaire was used to identify patients in whom hypertensive complications had occurred, as well as causes of death. The primary end point of this study was new onset of stroke or CVD (new onset of angina pectoris, myocardial infarction or heart failure). We evaluated the baseline characteristics of patients, including UA levels, and assessed whether UA levels could be used to predict stroke and CVD. We also classified subjects into four groups according to the serum UA levels. During a mean follow-up period of 7.1±0.1 years, 71 strokes, 58 cases of CVD and 64 deaths were recorded. Kaplan–Meier analysis revealed that subjects in the high UA group had a higher frequency of stroke and CVD (P=0.0120) and total mortality (P=0.0021). A Cox proportional hazard model determined that, after adjusting for traditional risk factors, serum UA levels were predictive of CVD (relative risk=1.30; P=0.0073), stroke and CVD (relative risk=1.19; P=0.0141), mortality (relative risk=1.23; P=0.0353) and stroke CVD and mortality (relative risk=1.19; P=0.0083), but not stroke (P=0.4268). The significant correlations were particularly marked in women. Serum UA levels may be an independent risk factor for stroke and CVD in patients with essential hypertension, particularly women.