Satoshi Iimuro

The GPCR modulator protein RAMP2 is essential for angiogenesis and vascular integrity

Adrenomedullin (AM) is a peptide involved both in the pathogenesis of cardiovascular diseases and in circulatory homeostasis. The high-affinity AM receptor is composed of receptor activity-modifying protein 2 or 3 (RAMP2 or -3) and the GPCR calcitonin receptor-like receptor. Testing our hypothesis that RAMP2 is a key determinant of the effects of AM on the vasculature, we generated and analyzed mice lacking RAMP2. Similar to AM-/- embryos, RAMP2-/- embryos died in utero at midgestation due to vascular fragility that led to severe edema and hemorrhage. Vascular ECs in RAMP2-/- embryos were severely deformed and detached from the basement membrane. In addition, the abnormally thin arterial walls of these mice had a severe disruption of their typically multilayer structure. Expression of tight junction, adherence junction, and basement membrane molecules by ECs was diminished in RAMP2-/- embryos, leading to paracellular leakage and likely contributing to the severe edema observed. In adult RAMP2+/- mice, reduced RAMP2 expression led to vascular hyperpermeability and impaired neovascularization. Conversely, ECs overexpressing RAMP2 had enhanced capillary formation, firmer tight junctions, and reduced vascular permeability. Our findings in human cells and in mice demonstrate that RAMP2 is a key determinant of the effects of AM on the vasculature and is essential for angiogenesis and vascular integrity.

Angiogenic Effects of Adrenomedullin in Ischemia and Tumor Growth

Adrenomedullin (AM) is a novel vasodilating peptide involved in the regulation of circulatory homeostasis and implicated in the pathophysiology of cardiovascular disease. We tested the hypothesis that AM also possesses angiogenic properties. Using laser Doppler perfusion imaging, we found that AM stimulated recovery of blood flow to the affected limb in the mouse hind-limb ischemia model. AM exerted this effect in part by promoting expression of vascular endothelial growth factor (VEGF) in the ischemic limb, and immunostaining for CD31 showed the enhanced flow to reflect increased collateral capillary density. By enhancing tumor angiogenesis, AM also promoted the growth of subcutaneously transplanted sarcoma 180 tumor cells. However, heterozygotic AM knockout mice (AM+/−) showed significantly less blood flow recovery with less collateral capillary development and VEGF expression than their wild-type littermates. Similarly, mice treated with AM22-52, a competitive inhibitor of AM, showed reduced capillary development, and growth of sarcoma 180 tumors was inhibited in AM+/− and AM22-52–treated mice. Notably, administration of VEGF or AM rescued blood flow recovery and capillary formation in AM+/− and AM22-52–treated mice. In cocultures of endothelial cells and fibroblasts, AM enhanced VEGF-induced capillary formation, whereas in cultures of endothelial cells AM enhanced VEGF-induced Akt activation. These results show that AM possesses novel angiogenic properties mediated by its ability to enhance VEGF expression and Akt activity. This may make AM a useful therapeutic tool for relieving ischemia; conversely, inhibitors of AM could be useful for clinical management of tumor growth.

Serum Level of Triglycerides Is a Potent Risk Factor Comparable to LDL Cholesterol for Coronary Heart Disease in Japanese Patients with Type 2 Diabetes: Subanalysis of the Japan Diabetes Complications Study (JDCS)

CONTEXT Risk factors for cardiovascular complications in Japanese patients with diabetes have not been fully elucidated. OBJECTIVE Our objective was to determine incidence of and risk factors for coronary heart disease (CHD) and stroke in Japanese diabetic patients. DESIGN AND SETTINGS We conducted a prospective study at 59 hospitals throughout Japan. PATIENTS Patients included 940 men and 831 women with type 2 diabetes (mean age, 58.2 yr) without a history of cardiovascular complications who were followed for a median of 7.86 yr. INTERVENTION This was an observational study. MAIN OUTCOME MEASURES Incidence of CHD and stroke was evaluated. RESULTS Incidences of CHD and stroke per 1000 person-years were 9.59 and 7.45, respectively, whereas those of myocardial and brain infarctions were 3.84 and 6.29, respectively. Multivariate Cox analysis revealed that the serum log-transformed triglyceride level was a potent and independent predictor of CHD [hazard ratio (HR) = 1.54; 95% confidence interval (CI) = 1.22-1.94 per 1 sd increase), comparable to low-density lipoprotein (LDL) cholesterol (HR = 1.49; 95% CI = 1.25-1.78 per 1 sd increase). Triglycerides and LDL cholesterol linearly and continuously increased CHD risk, and subjects in the top third for both had markedly high risks of CHD, and their effects were possibly additive. However, serum triglycerides worked independently of blood pressure levels. Systolic blood pressure was the only significant predictor for stroke except for age (HR = 1.31; 95% CI = 1.04-1.65, per 1 sd increase). CONCLUSIONS In Japanese patients with type 2 diabetes, the serum triglyceride level was a leading predictor of CHD, comparable to LDL cholesterol. Because the serum triglyceride level is not a leading predictor of CHD in diabetic subjects in Western countries, ethnic group-specific strategies for prevention of diabetic macroangiopathy may be indicated.

Protective Effects of Endogenous Adrenomedullin on Cardiac Hypertrophy, Fibrosis, and Renal Damage

BACKGROUND Adrenomedullin (AM) is a novel vasodilating peptide thought to have important effects on cardiovascular function. The aim of this study was to assess the activity of endogenous AM in the cardiovascular system using AM knockout mice. METHODS AND RESULTS Mice heterozygous for an AM-null mutation (AM+/-) and their wild-type littermates were subjected to aortic constriction or angiotensin II (Ang II) infusion. The resultant cardiovascular stress led to increases in heart weight/body weight ratios, left ventricular wall thickness, and perivascular fibrosis, as well as expression of genes encoding angiotensinogen, ACE, transforming growth factor-beta, collagen type I, brain natriuretic peptide, and c-fos. In addition, renal damage characterized by decreased creatinine clearance with glomerular sclerosis was noted. In all cases, the effects were significantly more pronounced in AM+/- mice. Hearts from adult mice subjected to aortic constriction showed enhanced extracellular signal-regulated kinase (ERK) activation, as did cardiac myocytes from neonates treated acutely with Ang II. Again the effect was more pronounced in AM+/- mice, which showed increases in cardiac myocyte size, protein synthesis, and fibroblast proliferation. ERK activation was suppressed by protein kinase C inhibition to a greater degree in AM+/- myocytes. In addition, treatment of cardiac myocytes with recombinant AM suppressed Ang II-induced ERK activation via a protein kinase A-dependent pathway. CONCLUSIONS Endogenous AM exerts a protective effect against stress-induced cardiac hypertrophy via protein kinase C- and protein kinase A-dependent regulation of ERK activation. AM may thus represent a useful new tool for the treatment of cardiovascular disease.

Chronic Kidney Disease Japan Cohort (CKD-JAC) Study: Design and Methods

The prevalence and incidence of end-stage renal disease (ESRD) in Japan are the highest and the third highest, respectively, in the world, while the incidence of cardiac death in Japan is the lowest among developed countries. A recent study showed that the prevalence of chronic kidney disease (CKD), defined as an estimated glomerular filtration rate (GFR) of less than 60 mL/min/1.73 m2, is extremely high in Japan, about 20% of the adult population. However, the risk of ESRD and cardiovascular disease (CVD) in the CKD population has not been determined nationwide. For this observational study, we will establish a Chronic Kidney Disease Japan Cohort (CKD-JAC) by enrolling 3,000 patients with CKD in 17 clinical centers around Japan, which will be used to determine the incidence of ESRD and CVD in Japanese CKD patients. Risk factors associated with the development of CVD will also be examined. Comorbidity of diabetes in CKD patients will be analyzed to determine whether it is a risk for rapid progression of CKD and high incidence of CVD. In addition, we will study whether the burden of CKD decreases the QOL of patients, and increases hospitalization or health resource utilization. Insights from the CKD-JAC study will provide a basis for future interventional trials focused on reducing the burden of ESRD and CVD in patients with CKD in Japan.

Age-Associated Increase in Abdominal Obesity and Insulin Resistance, and Usefulness of AHA/NHLBI Definition of Metabolic Syndrome for Predicting Cardiovascular Disease in Japanese Elderly with Type 2 Diabetes Mellitus

Background: Management of metabolic syndrome (MetS) seems to constitute an efficient strategy to attain successful ageing. Although the clinical entity of MetS in patients with diabetes mellitus has been discussed, there is very little information on MetS-type cardiometabolic risk factor clustering in diabetic elderly. Objective: To determine the relationship among age-associated changes in obesity, insulin resistance, and clustering of MetS-type risk factors, in association with vascular complications, in Japanese elderly with type 2 diabetes. Methods: A cross-sectional study was conducted of 812 diabetic elderly enrolled in the Japanese Elderly Diabetes Intervention Trial. Information on diabetes, blood examinations and complications was obtained. Abdominal obesity, insulin resistance and prevalence of MetS risk factor clustering, defined by three sets of criteria from the International Diabetes Federation (IDF), the Japanese Society of Internal Medicine (JSIM), and the American Heart Association and the National Heart, Lung, and Blood Institute (AHA/NHLBI), were analyzed. Results: Waist circumference and insulin resistance estimated by homeostasis model assessment insulin resistance (HOMA-IR) increased with age, followed by a partial decrease at age 80 and over. Prevalence of IDF-MetS and JSIM-MetS also increased with age at least until the age of 80, whereas the incidence of AHA/NHLBI-MetS did not show any apparent age changes. There was a significant crude linear association between waist circumference and HOMA-IR, which was highly elevated in IDF and AHA/NHLBI overlapping with MetS, and also elevated in AHA/NHLBI without abdominal obesity. Although IDF-MetS and JSIM-MetS, which specify abdominal obesity, did not always appear to be associated with cardiovascular diseases, AHA/NHLBI-MetS, comprising both abdominal obesity and non-abdominal obesity, independently correlated with coronary heart disease and stroke after adjustment for other risk factors of atherosclerotic diseases. Conclusion: There was an age-associated increase in the prevalence of abdominal obesity and insulin resistance in elderly diabetic Japanese subjects, with a clear relationship between waist circumference and insulin resistance. However, insulin resistance was elevated not only in cases with but also in those without abdominal obesity if accompanied by clustering of metabolic disorders. The AHA/NHLBI definition of MetS proved to be the most useful to predict cardiovascular disease in the diabetic elderly.

Taming the chronic kidney disease epidemic: a global view of surveillance efforts

Chronic kidney disease is now recognized to be a worldwide problem associated with significant morbidity and mortality and there is a steep increase in the number of patients reaching end-stage renal disease. In many parts of the world, the disease affects younger people without diabetes or hypertension. The costs to family and society can be enormous. Early recognition of CKD may help prevent disease progression and the subsequent decline in health and longevity. Surveillance programs for early CKD detection are beginning to be implemented in a few countries. In this article, we will focus on the challenges and successes of these programs with the hope that their eventual and widespread use will reduce the complications, deaths, disabilities, and economic burdens associated with CKD worldwide.

Long-term multiple risk factor interventions in Japanese elderly diabetic patients: the Japanese Elderly Diabetes Intervention Trial--study design, baseline characteristics and effects of intervention.

Aim:  To evaluate long‐term, multiple risk factor intervention on physical, psychological and mental prognosis, and development of complications and cardiovascular disease in elderly type 2 diabetes patients.

Predicting Macro- and Microvascular Complications in Type 2 Diabetes: The Japan Diabetes Complications Study/the Japanese Elderly Diabetes Intervention Trial risk engine

OBJECTIVE To develop and validate a risk engine that calculates the risks of macro- and microvascular complications in type 2 diabetes. RESEARCH DESIGN AND METHODS We analyzed pooled data from two clinical trials on 1,748 Japanese type 2 diabetic patients without diabetes complications other than mild diabetic retinopathy with a median follow-up of 7.2 years. End points were coronary heart disease (CHD), stroke, noncardiovascular mortality, overt nephropathy defined by persistent proteinuria, and progression of retinopathy. We fit a multistate Cox regression model to derive an algorithm for prediction. The predictive accuracy of the calculated 5-year risks was cross-validated. RESULTS Sex, age, HbA1c, years after diagnosis, BMI, systolic blood pressure, non-HDL cholesterol, albumin-to-creatinine ratio, atrial fibrillation, current smoker, and leisure-time physical activity were risk factors for macro- and microvascular complications and were incorporated into the risk engine. The observed-to-predicted (O/P) ratios for each event were between 0.93 and 1.08, and Hosmer-Lemeshow tests showed no significant deviations between observed and predicted events. In contrast, the UK Prospective Diabetes Study (UKPDS) risk engine overestimated CHD risk (O/P ratios: 0.30 for CHD and 0.72 for stroke). C statistics in our Japanese patients were high for CHD, noncardiovascular mortality, and overt nephropathy (0.725, 0.696, and 0.767) but moderate for stroke and progression of retinopathy (0.636 and 0.614). By combining macro- and microvascular risks, the classification of low- and high-risk patients was improved by a net reclassification improvement of 5.7% (P = 0.02). CONCLUSIONS The risk engine accurately predicts macro- and microvascular complications and would provide helpful information in risk classification and health economic simulations.

Synthetic Retinoid Am80 Reduces Scavenger Receptor Expression and Atherosclerosis in Mice by Inhibiting IL-6

Background—Macrophage scavenger receptors facilitate the uptake of modified low-density lipoprotein (LDL), formation of foam cells, and development of atherosclerosis. Given that proinflammatory cytokines, including IL-6, can modulate the macrophage foaming process, the aim of the present study was to determine whether the synthetic retinoic acid receptor-α/β-specific agonist Am80, which is also an IL-6 inhibitor, can modulate macrophage lipid accumulation and foam cell formation. Methods and Results—Am80 suppressed IL-6 production induced by 12-myristate 13-acetate (PMA) or angiotensin II in mouse Raw264 macrophages. It also suppressed expression of the 2 major scavenger receptors (scavenger receptor-A [SR-A] and CD36), in part by inhibiting IL-6, and inhibited macrophage foam cell formation. Systemic administration of Am80 led to reductions in the areas of atherosclerotic lesions and foam cell accumulation in the aortas of apolipoprotein E (apoE)-deficient mice and reduced serum concentrations of IL-6 and IL-1β without affecting body weights, serum lipid profiles or IL-10 levels. Conclusions—Am80 suppresses scavenger receptor expression and macrophage foam cell formation in vitro and prevents atherogenesis in apoE-deficient mice in vivo. This suggests Am80 is a novel candidate agent that could be highly useful in the prevention and treatment of atherosclerosis.