Sitosterolemia is a rare, autosomal recessive inherited sterol storage disease associated with high tissue and serum plant sterol concentrations, caused by mutations in the adenosine triphosphate-bind-ing cassette (ABC) transporter ABCG5 or ABCG8 genes. Markedly increased serum concentration of plant sterols. such as sitosterol and campesterol, cause premature atherosclerosis and massive xanthomas. Hitherto known treatments for sitosterolemia, including a low-sterol diet, bile-salt binding resins, ileal bypass surgery and low density lipoprotein (LDL) apheresis have not yielded sufficient reduction of serum plant sterol levels and many patients show a sustained elevation of plant sterol levels, subsequently developing premature atherosclerotic cardiovascular diseases. Ezetimibe, an inhibitor of intestinal cholesterol absorption through its binding to Niemann-Pick C1-like 1 (NPC1L1), has been widely used for decreasing serum LDL-cholesterol levels in patients with hypercholesterolemia. Ezetimibe also reduces the gastrointestinal absorption of plant sterols, thereby also lowering the serum concentrations of plant sterols. This pharmacological property of ezetimibe shows its potential as a novel effective therapy for sitosterolemia. In the current review, we discuss the current therapy for patients with sitosterolemia and present two Japanese adolescent patients with this disease, one of whom underwent percutaneous coronary intervention for accelerated coronary atherosclerosis. Ezetimibe administration in addition to conventional drug therapy successfully reduced serum sitosterol levels by 51.3% and 48.9%, respectively, in the two patients, demonstrating ezetimibe as a novel and potent treatment agent for sitosterolemia that could work additively with conventional drug therapy.
Aim: Gambogic acid (GA) is the major active compound of Gamboge, a brownish or orange resin exuded from Garcinia hanburryi tree in Southeast Asia. Previous studies have demonstrated that GA exhibits potent anticancer effects by inducing cell cycle arrest or apoptosis in many types of cancer cell lines and blocking angiogenesis via inhibition of vascular endothelial cell proliferation and migration. Proliferation and migration of vascular smooth muscle cells (VSMCs) are critical steps in the progress of atherosclerosis and restenosis after angioplasty. In the present study, we investigated whether GA has an inhibitory effect on the proliferation and migration of VSMCs and its possible mechanism. Methods: The inhibitory effect of GA on the proliferation induced by PDGF-BB and EGF was measured by using Cell number counting assay and [3H]-thymidine incorporation. The effects of GA on the cell cycle progression and viability stimulated by PDGF-BB and EGF were also analyzed by flow cytometry analysis. The inhibitory effect of GA on the migration stimulated by PDGF-BB was measured by transwell chamber assay. The effect of GA on the Cell cycle regulatory molecules (cyclinD1, cyclinE, CDK2, CDK4), PDGFR and its downstream signaling molecules including ERK1/2, PLCγ1, AKT and JNK was measured by western blotting. The effect of GA on the Rac1 activity was measured by using GST-pulldown assay. The effects of GA on the tyrosine phosphorylation stimulated by PDGF-BB and EGF and the capacity of GA binding with PDGF-BB and EGF were also measured. Results: We found that GA significantly inhibited proliferation, migration and DNA synthesis in primary cultured rat aortic VSMCs at concentrations of 0.25, 0.5, 1.0 and 2.0 μmol/L after stimulation of 50 μg/L platelet-derived growth factor-BB (PDGF-BB). GA induced G0/G1 phase arrest in the cell cycle progression of VSMCs. No obvious necrosis or apoptosis was found with GA treatment. The expressions of CDK2, CDK4, cyclin D1 and cyclin E, cell cycle regulatory molecules, were significantly suppressed by GA treatment in a concentration-dependent manner. The phosphorylation of PDGF receptor β (PDGFR-β) and the activities of downstream intracellular signaling molecules including phospho-ERK, phospho-PLCγ1, phospho-AKT, phospho-JNK and GTP-Rac1 were also inhibited by GA pretreatment. GA inhibited PDGFR-β phosphorylation through inhibiting the activity of tyrosine directly, rather than indirectly via binding PDGF-BB. Conclusions: The results of this study provide preliminary evidence that the inhibitory effects of GA on VSMCs proliferation and migration may be mediated through multiple signal pathways controlled by PDGF-Rβ activation and its downstream intracelluar signaling.
Aim: Postprandial hypertriglyceridemia (PHTG) has been shown repeatedly to be associated with metabolic syndrome and atherosclerotic cardiovascular diseases. We have recently reported that ezetimibe inhibits PHTG in patients with type IIb hyperlipidemia. Ezetimibe was also reported to atten-uate PHTG in combination with low-dose statins in patients with obesity or metabolic syndrome. We reported CD36-deficient (CD36KO) mice as a new model for PHTG, in which the synthesis of chylomicron (CM) in the small intestines is enhanced. In the current study, we investigated the effect of ezetimibe on PHTG in this mouse model of metabolic syndrome. Methods: Wild-type (WT) mice fed a western diet, and CD36KO mice fed a normal chow diet, respectively, were treated for 3 weeks with and without ezetimibe, followed by an evaluation of triglyceride (TG) concentrations by enzymatic method and by high performance liquid chromatogra-phy (HPLC) as well as those of and apolipoprotein (Apo) B-48 in plasma and intestinal lymph after oral fat loading with olive oil. Intestinal mucosa was also harvested to evaluate the transcriptional regulation of the genes involved in the intestinal production of ApoB-containing lipoproteins. Results: Ezetimibe dramatically reduced PHTG in both WT and CD36KO mice. HPLC analysis of plasma showed that the decrease in TG content in CM and CM remnants-sized particles contributed to this suppression, suggesting that CM production in the small intestines might be reduced after ezetimibe treatment. Intestinal lymph was collected after oral fat loading in ezetimibe-treated and non-treated mice. Both TG content and ApoB-48 mass were decreased in ezetimibe-treated mice. The quantitative RT-PCR of intestinal mucosa showed down-regulation of the mRNA expression of FATP4 and ApoB in both groups along with FABP2, DGAT1, DGAT2 and SCD1 in WT mice at postprandial state after ezetimibe treatment. Conclusion: Ezetimibe alone reduces PHTG by blocking both the absorption of cholesterol and the intracellular trafficking and metabolism of long-chain fatty acids in enterocytes, resulting in the reduction of the formation of ApoB-48 which is necessary for the ApoB48-containing lipoprotein production in the small intestines.
Aim: Fetuin-A, also known as alpha2-Heremans Schmid glycoprotein, is an abundant plasma protein synthesized predominantly in the liver. Fetuin-A inhibits insulin receptor autophosphorylation, which is mediated by its intrinsic tyrosine kinase activity. In this study, we examined the association between the serum fetuin-A level and insulin resistance in Japanese men. Methods: We recruited 300 unrelated Japanese men without known chronic diseases, such as diabetes mellitus, or a history of regular drug use, and who underwent health examinations. From a 75-g oral glucose tolerance test, the study population included 194 individuals with normal glucose tolerance, 91 with impaired glucose tolerance and/or impaired fasting glucose, and 15 with diabetes mellitus. Serum fetuin-A concentrations were measured using an ELISA kit. Results: Serum fetuin-A concentrations were positively correlated with fasting insulin levels (r=0.269, p<0.001), HOMA-IR (r=0.274, p<0.001) and LDL-cholesterol (r=0.172, p<0.01), and nega-tively correlated with HDL-cholesterol concentrations (r=-0.191, p<0.001). Fetuin-A concentra-tions were also positively correlated with serum leptin (r=0.150, p<0.01) and negatively with adi-ponectin concentrations (r=-0.208, p<0.001). Stepwise regression analyses confirmed that the fetuin-A concentration was independently associated with the fasting insulin level and HOMA-IR, as were body mass index, triglyceride, LDL-cholesterol, leptin and adiponectin concentrations. Conclusion: Our data suggest that increased serum fetuin-A levels constitute an independent marker of insulin resistance and an atherogenic lipid profile in Japanese men.
Aim: We investigated the individual and population impacts of mild abnormalities associated with metabolic syndrome (blood pressure, lipids and glucose) and abdominal obesity, for which lifestyle modification is initially applicable, on cardiovascular disease risk. Methods: Using a cohort study of 2,685 Japanese men aged 35 to 59 years with an 11-year follow-up period, we calculated the relative risks for cardiovascular diseases due to mild metabolic abnormalities that included at least one of the following three conditions: 1) systolic blood pressure 130-139 mmHg and/or diastolic blood pressure 85-89 mmHg; 2) triglycerides 150-299 mg/dL and/or high-density lipoprotein cholesterol 35-39 mg/dL; and 3) fasting plasma glucose 110-125 mg/dL and/or abdominal obesity. Participants with a mild metabolic abnormality were compared to participants with no metabolic abnormality or abdominal obesity. The population attributable fraction of these abnormalities for cardiovascular diseases was also estimated. Results: At baseline, 9.8% and 21.8% of the total population had a mild metabolic abnormality with or without abdominal obesity, respectively, while 7.5% had isolated abdominal obesity without any metabolic abnormality. A mild metabolic abnormality with or without abdominal obesity and isolated abdominal obesity increased the risk of cardiovascular disease by 2.68-fold, 1.49-fold, and 2.36-fold, respectively. Approximately 20% of cardiovascular diseases in the total population were attributable to either mild metabolic abnormalities or isolated abdominal obesity. Conclusion: The importance of lifestyle modification should be acknowledged, especially in cases of mild metabolic abnormality and/or abdominal obesity, which may contribute to approximately 20% of the population burden for cardiovascular diseases.
Aim: We questioned whether the ratio of C-reactive protein to high-molecular-weight adiponectin (C/A ratio), compared to each value alone, is more useful to predict insulin resistance and/or metabolic syndrome. Methods: We measured serum CRP and HMW adiponectin levels in 841 Japanese men who had participated in an annual health checkup. Correlations of the C/A ratio with metabolic parameters were assessed, and its predictive values for insulin resistance and MetS were compared with CRP or HMW adiponectin alone. Results: The C/A ratio was higher in subjects with MetS (n=114) than in those without MetS (0.46±0.67 vs. 0.23±0.39, p<0.0001). The C/A ratio was correlated with a larger number of metabolic parameters than CRP, but the correlation was comparable to HMW adiponectin. Likewise, the area under the curve of the C/A ratio in receiver operator characteristic analysis for MetS was greater than that of CRP, but comparable to that of HMW adiponectin. However, the AUC of the C/A ratio in ROC analysis for insulin resistance (HOMA-IR >2.5) was greater than that of CRP or HMW adiponectin alone. Conclusion: While the C/A ratio provided little advantage to predict MetS, it might be more useful to predict insulin resistance than CRP or HMW adiponectin alone.
Aim: Serum high molecular weight (HMW) adiponectin improves insulin sensitivity, and a decreased level of serum HMW adiponectin has been reported as a risk factor for the development of diabetes and coronary heart disease. This association may be further confounded by the alcohol drinking status, which is involved in the development of liver dysfunction. The aim of this study was to determine whether the alcohol drinking status is associated with serum HMW adiponectin levels in community-dwelling Japanese men. Methods: A cross-sectional study was carried out in 2002. Study participants without a clinical history of diabetes (747 men aged 60±14 (mean±standard deviation) (range, 20-89) years) were randomly recruited from a single community at the time of their annual health examination. They were classified into never drinkers, light drinkers (< 1 unit/day), moderate drinkers (1-1.9 units/day), and heavy drinkers (≥ 2 units/day). We examined the effects of alcohol consumption on serum HMW adiponectin. Results: Overall, mean serum HMW adiponectin levels were significantly lower in the group with higher alcohol consumption, and there were inter-group differences in the alcohol drinking status. Moreover, age-adjusted mean serum HMW adiponectin levels were significantly lower in the group with higher alcohol consumption. Multiple linear regression analysis showed that the alcohol drinking status was significantly and independently associated with serum adiponectin as well as age, smoking status, TG, HDL-C, LDL-C, serum ALT, and HOMA-IR. Multivariate-adjusted mean serum HMW adiponectin levels were also significantly lower in the group with higher alcohol consumption. Conclusion: The alcohol drinking status is negatively associated with serum HMW adiponectin levels in Japanese community-dwelling men.
Aim: Homocysteine is associated with increased arterial resistance and eventually causes luminal reduction. The purpose of the present study was to evaluate an association between the plasma concentration of total homocysteine (tHcy) and stenosis or occlusion of the internal carotid artery (ICA) in patients with ischemic stroke. Methods: In total, 391 patients with ischemic stroke were evaluated from March 2007 to February 2008. The criterion for ICA stenosis or occlusion was set at greater than 50% luminal narrowing or complete obstruction in at least one ICA. Patients were assigned to one of three groups: normal ICA, ICA stenosis, and ICA occlusion. Results: ICA stenosis was found in 71 patients, whereas ICA occlusion in 22 patients (18.2% and 5.6%, respectively). Plasma tHcy was significantly higher in groups with ICA stenosis/occlusion with the highest value of ICA occlusion (14.6±1.0 μmol/L, p=0.025). A 1 μmol/L increase of tHcy showed an adjusted odds ratio of 1.12 (95% confidence intervals, 1.03-1.24, p=0.008) for ICA occlusion in a multivariate logistic model adjusted for all possible confounders, including age, sex, vascular risk factors, and stroke classifications. Conclusion: Elevated levels of tHcy were significantly associated with the ICA occlusion, independent of vascular risk factors and stroke subtypes.
Aim: Silencing information regulator (SirT1), a NAD-dependent histone deacetylase, is an essential mediator of longevity in normal cells by calorie restriction. SirT1 has many biological functions, including transcription regulation, cell differentiation inhibition, cell cycle regulation, and anti-apoptosis. Resveratrol (RV)-induced SirT1 activation also improves endothelial dysfunction and suppresses vascular inflammation. In this study, we investigated the roles of RV-induced SirT1 activation in endothelial cells under oxidative stress. Methods: SirT1 mRNA expression levels were examined in the endothelium layer (endothelial cells) of cardiac coronary vessels from patients receiving coronary artery bypass graft surgery (CABG) surgery and aged rats using reverse transcriptase polymerase chain reaction (RT-PCR). To further explore the effect of SirT1 activation on oxidative stress-induced aging, senescence-associated β-galactosidase (SA-β-gal) expression in RV-treated human umbilical vein endothelial cells (HUVECs) with or without H2O2 treatment was evaluated. Results: SirT1 expression was decreased in aged and atherosclerotic vessels in vivo, and significantly reduced in endothelial cells purified from vessel tissues. Furthermore, SirT1 levels were dose-dependently increased in RV-treated HUVECs. The SA-β gal assay showed that RV inhibited the senescent phenotype of H2O2-treated HUVECs. Reactive oxygen species (ROS) production and the percentage of cells positive for SA-β gal were significantly increased in siRNA-SirT1 (knockdown of SirT1 expression)-treated HUVEC cells. Importantly, the treatment effect of RV was significantly abolished in the oxidative effects of H2O2-treated HUVECs by siRNA-SirT1. Conclusion: Our data suggested that SirT1 could be a crucial factor involved in the endothelial cells of atherosclerotic CAGB patients and aging rats. RV is a potential candidate for preventing oxidative stress-induced aging in endothelial cells. RV may also prevent ROS-induced damage via increased endothelial SirT1 expression.
Aim: Kefiran is an exopolysaccharide produced by Lactobacillus kefiranofaciens, and has been proposed to have many health-promoting properties. We investigated the antiatherogenic effect of kefiran on rabbits fed a high-cholesterol diet. Methods: Male New Zealand White rabbits were fed a 0.5% cholesterol diet without (control group, n=7) or with kefiran (kefiran group, n=8) for eight weeks. The aorta was analyzed by histochemistry and atherosclerotic lesions were quantified. Lipids and sugars in serum were measured. Foam cell formation of RAW264.7 by βVLDL derived from both groups of rabbits was also investigated. Results: Cholesterol, triglyceride and phospholipids levels of serum and lipoprotein fractions were not significantly different between these groups. Atherosclerotic lesions of the aorta in the kefiran group were statistically lower than those of the control group, with marked differences in the abdominal aorta. T-lymphocytes were not detectable in the aorta of the kefiran group. Cholesterol contents in stools were almost identical in both groups. Cholesterol content in the liver of the kefiran group was statistically lower than in the control group. Galactose content of βVLDL derived from the kefiran group was higher, and the lipid peroxidation level was much lower than in the control group. RAW264.7 macrophages treated with βVLDL from the kefiran group showed a more spherical shape and accumulated statistically lower cholesterol than macrophages treated with βVLDL from the control group. Conclusion: Orally derived kefiran is absorbed in the blood. Kefiran prevents the onset and development of atherosclerosis in hypercholesterolemic rabbits by anti-inflammatory and anti-oxidant actions.
Aim: Recently, there has been an increase in the prevalence of coronary risk factors, such as diabetes and dyslipidemia, in Japan; however, it is unclear whether this has resulted in an increased incidence of acute myocardial infarction (AMI). We investigated the relationship between risk factors changes and AMI incidence in a Japanese population. Methods: Trends in AMI incidence (per 100,000 person-years) were examined using data from the Yamagata AMI Registry from 1993 to 2007. We included 6,222 patients with a first-ever AMI (4175 men). The prevalence of coronary risk factors was investigated in three age groups of AMI patients (<65, 65-74, and ≥75 years) for the periods 1993-1997, 1998-2002, and 2003-2007. Coronary risk factors were further compared between recently registered AMI patients and 2,400 age-matched controls. Results: The age-adjusted incidence of AMI increased significantly in men, but not in women. Younger men particularly showed a significant increase in the incidence of AMI. The prevalence of hypertension and diabetes increased in both genders; however, the prevalence of treatment for risk factors was significantly lower in men than women. Younger men showed significant increases in obesity and hypertriglyceridemia. Consequently, risk factors associated with the metabolic syndrome had accumulated among younger men. We revealed that hypertension, diabetes, hypercholesterolemia and current smoking were independent risk factors for AMI. Conclusions: The incidence rate for AMI increased significantly in men, especially younger men. Preventive care for risk factors associated with metabolic syndrome, in addition to conventional risk factors, may be required in younger men.
The coexistence of obstructive sleep apnea (OSA) may impose an additional risk on aortic dissection due to the possible increase in aortic transmural pressure. Thus, effective treatment for OSA, such as noninvasive positive pressure ventilation (NPPV), is thought to decrease the risk in patients with aortic dissection. We experienced one case of an OSA patient with aortic dissection who was successfully treated with continuous positive airway pressure (CPAP), resting and antihypertensive therapy. Few reports of this kind are available in the medical literature. A 55-year old Japanese man with sudden chest and back pain was admitted to this hospital. Acute aortic dissection De Bakey type 3b was observed by radiography and the patient was treated success-fully. In cases with a high likelihood of OSA with aortic dissection, application of CPAP treatment should be considered promptly along with resting and antihypertensive therapy, except if there are complications such as comorbidities or withholding of consent.