Masa-aki Kawashiri

Circulating matrix metalloproteinases and their inhibitors in premature coronary atherosclerosis

Abstract To investigate the clinical significance of circulating matrix metalloproteinases (MMPs) and their tissue inhibitos (TIMPs) in patients with premature coronary atheroscrelosis, we studied 53 consecutive male patients with angiographically defined premature (<65 years) and stable coronary artery disease. Plasma levels of MMP-2, MMP-3, MMP-9, TIMP-1, and TIMP-2 were determined in peripheral blood by a sandwich enzyme immunoassay, and the results were compared with those from 133 age-matched control males. There were significant differences in all the MMPs and TIMPs (p<0.001) between patients and controls. In the patient group, the levels of MMP-9 (mean±SD (ng/ml) 27.2±15.2/21.8±15.2) and TIMP-1 (130.4±55.7/94.5±26.3) were significantly higher, and the levels of MMP-2 (632.5±191.6/727.6±171.4), MMP-3 (53.1±31.2/79.6± 29.9), and TIMP-2 (24.7±15.2/35.4±16.4) were significantly lower than those of controls. We found significant positive correlation between plasma MMP-9 levels and low-density lipoprotein (LDL)-cholesterol levels (Rs=0.168, p=0.022), and significant negative correlation between plasma MMP-9 levels and high-density lipoprotein (HDL)-cholesterol levels (Rs=−0.164, p=0.026) by Spearman rank correlation test. In contrast, plasma MMP-2 (Rs=0.181, p=0.014) and MMP-3 (Rs=0.260, p=0.0004) levels were positively correlated with HDL-cholesterol levels. TIMP-2 levels were negatively correlated with total cholesterol (Rs=−0.197, p=0.007) and LDL-cholesterol (Rs=−0.168, p=0.022) levels. These results suggest that the circulating levels of MMPs and TIMPs are altered in patients with premature coronary atherosclerosis and that plasma lipoprotein cholesterol levels correlate with these, possibly as a result of the lipoprotein-vessel wall interactions.

Impact of anti-apoptotic and anti-oxidative effects of bone marrow mesenchymal stem cells with transient overexpression of heme oxygenase-1 on myocardial ischemia

Although mesenchymal stem cells (MSCs) have therapeutic potential for tissue injury, intolerance and poor cell viability limit their reparative capability. Therefore, we examined the impact of bone marrow-derived MSCs, in which heme oxygenase-1 (HO-1) was transiently overexpressed, on the repair of an ischemic myocardial injury. When MSCs and HO-1-overexpressed MSCs (MSC(HO-1)) were exposed to serum deprivation/hypoxia or H(2)O(2)-induced oxidative stress, MSC(HO-1) exhibited increased resistance to cell apoptosis compared with MSCs (17 +/- 1 vs. 30 +/- 2%, P < 0.05) and were markedly resistant to cell death (2 +/- 1 vs. 32 +/- 2%, P < 0.05). Under these conditions, vascular endothelial growth factor (VEGF) production was 2.1-fold greater in MSC(HO-1) than in MSCs. Pretreatment of MSCs and MSC(HO-1) with phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (Akt) pathway inhibitors such as LY-294002 (50 muM) or wortmannin (100 nM) significantly decreased VEGF production. In a rat infarction model with MSCs or MSC(HO-1) (5 x 10(6) +/- 0.1 x 10(6) cells/rat) transplantation, the number of TdT-mediated dUTP nick end-labeling-positive cells was significantly lower in the MSC(HO-1) group than in the MSC group (12.1 +/- 1.0 cells/field vs. 26.5 +/- 2.6, P < 0.05) on the 4th day after cell transplantation. On the 28th day, increased capillary density associated with decreased infarction size was observed in the MSC(HO-1) group (1,415 +/- 47/mm(2) with 21.6 +/- 2.3%) compared with those in the MSCs group (1,215 +/- 43/mm(2) with 28.2 +/- 2.3%, P < 0.05), although infarction size relative to area at risk was not different in each group at 24 h after transplantation. These results demonstrate that MSC(HO-1) exhibit markedly enhanced anti-apoptotic and anti-oxidative capabilities compared with MSCs, thus contributing to improved repair of ischemic myocardial injury through cell survival and VEGF production associated with the PI 3-kinase/Akt pathway.

Apolipoprotein A-I Deficiency Results in Markedly Increased Atherosclerosis in Mice Lacking the LDL Receptor

Objective—An inverse and independent association between plasma levels of apolipoprotein (apo) A-I and coronary heart disease in humans is well established. ApoA-I is the primary protein component of HDL and is thought to play an important role in mediating several of the atheroprotective effects of HDL. However, studies of the effects of apoA-I deficiency on the development of atherosclerosis in mice have not been definitive. We examined the effects of apoA-I deficiency on plasma lipids and atherosclerosis in LDL receptor-deficient mice fed a chow diet for up to 22 months. Methods and Results—Both apoA-I-deficient (apoA-I−/−)/LDL receptor-deficient (LDLR−/−) and LDLR−/− mice had a similar moderate elevation of non-HDL cholesterol (non-HDL-C). Unlike previous studies of apoA-I deficiency in which the HDL-C levels were extremely low, the apoA-I−/−/LDLR−/− mice in this study had substantial levels of HDL-C that were similar to wild-type mice. Despite similar levels of non-HDL-C and substantial levels of HDL-C, apoA-I−/−/LDLR−/− mice develop significantly more atherosclerosis (up to a 5-fold increase) and oxidant stress (39% increase) than LDLR−/− mice. Conclusions—These results demonstrate that despite normal levels of HDL-C, apoA-I deficiency is associated with a significant loss of protection from the formation of atherosclerosis in LDLR−/− mice fed a chow diet.

Impacts of Visceral Adipose Tissue and Subcutaneous Adipose Tissue on Metabolic Risk Factors in Middle‐aged Japanese

Regional fat distribution rather than overall fat volume has been considered to be important to understanding the link between obesity and metabolic disorders. We aimed to evaluate the independent associations of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) with metabolic risk factors in apparently healthy middle‐aged Japanese. Participants were 1,119 men and 854 women aged 38–60 years who were not taking medications for diabetes, hypertension, or dyslipidemia. VAT and SAT were measured by use of computed tomography (CT) scanning. VAT and SAT were significantly and positively correlated with each other in men (r = 0.531, P < 0.001) and women (r = 0.589, P < 0.001). In multiple regression analyses, either measure of abdominal adiposity (VAT or SAT) was positively associated with blood pressure, fasting plasma glucose, and log triglyceride (P < 0.001) and inversely with high‐density lipoprotein (HDL)‐cholesterol (P < 0.001). When VAT and SAT were simultaneously included in the model, the association of VAT with triglycerides was maintained (P < 0.001) but that of SAT was lost. The same was true for HDL‐cholesterol in women. For fasting plasma glucose, the association with VAT was strong (P < 0.001) and the borderline association with SAT was maintained (P = 0.060 in men and P = 0.020 in women). Both VAT and SAT were independently associated with blood pressure (P < 0.001). Further adjustment for anthropometric indices resulted in the independent association only with VAT for all risk factors. In conclusion, impacts of VAT and SAT differed among risk factors. VAT showed dominant impacts on triglyceride concentrations in both genders and on HDL‐cholesterol in women, while SAT also had an independent association with blood pressure.

Comparison of waist circumference with body mass index for predicting abdominal adipose tissue

AIMS To compare waist circumference (WC) with body mass index (BMI) for the prediction of abdominal adipose tissues in Japanese men and women. METHODS 1432 men and 1038 women aged 38-60 years were recruited. WC, BMI, visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) using CT scans were measured. RESULTS Women had a lower mean VAT than men (79.3 cm(2) vs. 132.3 cm(2); p<0.001) and a higher mean SAT (196.2 cm(2) vs. 139.7 cm(2); p<0.001). The correlation with WC or BMI was greatest for total adipose tissue (TAT), followed by SAT, and least for VAT. The correlation coefficients were not significantly different between WC and BMI for any adipose tissue except for VAT in men (p<0.05). Age was positively correlated with VAT in both genders (p<0.001). Using multiple regression analyses on VAT, R(2) values using WC and age were 0.45 in men and 0.48 in women. For SAT, the values were 0.57 in men and 0.59 in women. CONCLUSIONS The relationship with WC or BMI was greatest for TAT and SAT, and least for VAT. WC and BMI provided essentially similar estimates of TAT, VAT, and SAT in both genders.

Effects of serum B vitamins on elevated plasma homocysteine levels associated with the mutation of methylenetetrahydrofolate reductase gene in Japanese

High plasma homocysteine, a risk factor for atherosclerosis, is frequently caused by a common mutation in the gene for the enzyme, 5,10-methylenetetrahydrofolate reductase (MTHFR), C677T (alanine to valine substitution) or low intake of B vitamins that affect the remethylation or transsulfuration pathways in homocysteine metabolism. However, the interaction of the C677T mutation and B vitamins other than folate has not been well elucidated. We conducted a cross-sectional survey of 324 men and 641 women who participated in a 1996 health examination under a hypothesis that high nutritional status of folate, vitamin B12 and vitamin B6 expressed as high serum levels, may compensate for the hyperhomocysteinemia associated with homozygosity for the C677T mutation, but not for having the mutation per se. Age-adjusted plasma homocysteine levels were higher for both men and women with the homozygous genotype for the mutation than those who were heterozygous or had no mutation. Elevated homocysteine levels in homozygous genotype was attenuated among persons with higher serum levels of vitamin B12 and folate, but not vitamin B6, and among persons with the combination of lower folate and higher vitamin B12 and of higher folate and higher vitamin B12, split by the median. These findings suggest that elevated homocysteine levels among Japanese with the homozygous genotype for the MTHFR gene mutation can be modified efficiently by dietary supplement of vitamin B12 as well as folate.

The E32K variant of PCSK9 exacerbates the phenotype of familial hypercholesterolaemia by increasing PCSK9 function and concentration in the circulation

OBJECTIVE Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates cholesterol trafficking by mediating degradation of cell-surface LDL receptors (LDLR). Gain-of-function PCSK9 mutations are known to increase plasma LDL-C levels. We attempted to find gain-of-function PCSK9 mutations in Japanese subjects and determine the frequency and impacts of these mutations, especially on circulating PCSK9 and LDL-C levels. METHODS PCR-SSCP followed by direct sequence analysis was performed for all 12 exons and intronic junctions of the PCSK9 in 55 subjects with clinically diagnosed familial hypercholesterolaemia (clinical-FH), who were confirmed to have no LDLR mutations. Among the mutations detected, PCSK9 E32K was likely to be a gain-of-function mutation, and screening was performed by PCR-RFLP in clinical-FH and general Japanese controls. The levels of PCSK9 in plasma from subjects and in media of HepG2 cells transfected with PCSK9 constructs were measured by ELISA. RESULTS We detected 7 PCSK9 variants, including E32K. The frequency of PCSK9 E32K in clinical-FH (6.42%) was significantly higher than that in controls (1.71%). Three cases representing homozygous FH phenotypes were double heterozygous for PCSK9 E32K and LDLR C183S, C292X or K790X. Two cases were true homozygous for PCSK9 E32K; to our knowledge, these are the first true homozygotes for gain-of-function PCSK9 mutations reported to date. The PCSK9 E32K mutant had over 30% increased levels of PCSK9 in plasma from the subjects and in media of transiently transfected HepG2 cells as compared with those in controls. Furthermore, LDL-C levels in the PCSK9 E32K true homozygotes and heterozygotes were 2.10- and 1.47-fold higher than those in controls with comparable circulating PCSK9 levels, respectively, suggesting enhanced function of PCSK9 E32K. CONCLUSIONS We found 2 true homozygotes for PCSK9 E32K and 3 double heterozygotes for PCSK9 E32K and LDLR mutations associated with autosomal dominant hypercholesterolaemia. This study provided evidence that PCSK9 E32K significantly affects LDL-C levels via increased mass and function of PCSK9, and could exacerbate the clinical phenotypes of patients carrying LDLR mutations.

ATP-binding cassette transporter G8 M429V polymorphism as a novel genetic marker of higher cholesterol absorption in hypercholesterolaemic Japanese subjects.

The ratio of serum plant sterols to cholesterol is positively correlated with the fractional cholesterol absorption, whereas serum precursors of cholesterol synthesis are positively correlated with cholesterol synthesis. Recently, two ABC (ATP-binding cassette) transporters, ABCG5 and ABCG8, have been described as playing an important role in the absorption and excretion of sterols. In the present study, we tested the hypothesis that genetic variation in ABCG5/ABCG8 influences the levels of serum plant sterol (sitosterol) and cholesterol precursor (lathosterol) in Japanese primary hypercholesterolaemic patients (n = 100). We identified a novel mutation [859T/C (C287R)] and a novel polymorphism [1285A/G (M429V)] at the ABCG5/ABCG8 loci, as well as four polymorphisms reported previously [1810C/G (Q604E), 161G/A (C54Y), 1199C/A (T400K) and 1895C/T (A632V)]. In carriers of the novel M429V variant, the serum level of sitosterol and the sitosterol/cholesterol ratio were significantly higher than those in non-carriers (3.64 compared with 2.56 microg/ml, and 1.45 microg/mg compared with 1.00 microg/mg respectively; P < 0.01 for both), and serum lathosterol tended to be lower (1.95 microg/ml compared with 3.03 microg/ml; P = 0.08), whereas no significant difference was observed in other lipid profiles. These four polymorphisms (1810C/G, 161G/A, 1199C/A and 1285A/G) generated six haplotypes, and the C/G/C/G haplotype was significantly associated with a higher sitosterol level and sitosterol/cholesterol ratio compared with the other five haplotypes (P < 0.05 for both). We conclude that, in 8% of patients with hypercholesterolaemia, the novel ABCG8 M429V variant was associated with higher cholesterol absorption efficiency. Future studies should investigate whether these findings have implications for the optimal cholesterol-lowering drug treatment in hypercholesterolaemic patients.

Characterization of Autosomal Dominant Hypercholesterolemia Caused by PCSK9 Gain of Function Mutations and its Specific Treatment with Alirocumab, a PCSK9 Monoclonal Antibody

Background—Patients with PCSK9 gene gain of function (GOF) mutations have a rare form of autosomal dominant hypercholesterolemia. However, data examining their clinical characteristics and geographic distribution are lacking. Furthermore, no randomized treatment study in this population has been reported. Methods and Results—We compiled clinical characteristics of PCSK9 GOF mutation carriers in a multinational retrospective, cross-sectional, observational study. We then performed a randomized placebo-phase, double-blind study of alirocumab 150 mg administered subcutaneously every 2 weeks to 13 patients representing 4 different PCSK9 GOF mutations with low-density lipoprotein cholesterol (LDL-C) ≥70 mg/dL on their current lipid-lowering therapies at baseline. Observational study: among 164 patients, 16 different PCSK9 GOF mutations distributed throughout the gene were associated with varying severity of untreated LDL-C levels. Coronary artery disease was common (33%; average age of onset, 49.4 years), and untreated LDL-C concentrations were higher compared with matched carriers of mutations in the LDLR (n=2126) or apolipoprotein B (n=470) genes. Intervention study: in PCSK9 GOF mutation patients randomly assigned to receive alirocumab, mean percent reduction in LDL-C at 2 weeks was 62.5% (P<0.0001) from baseline, 53.7% compared with placebo-treated PCSK9 GOF mutation patients (P=0.0009; primary end point). After all subjects received 8 weeks of alirocumab treatment, LDL-C was reduced by 73% from baseline (P<0.0001). Conclusions—PCSK9 GOF mutation carriers have elevated LDL-C levels and are at high risk of premature cardiovascular disease. Alirocumab, a PCSK9 antibody, markedly lowers LDL-C levels and seems to be well tolerated in these patients. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique Identifier: NCT01604824.

Current perspectives in genetic cardiovascular disorders: from basic to clinical aspects

We summarize recent advances in the clinical genetics of hypercholesterolemia, hypertrophic cardiomyopathy (HCM), and lethal arrhythmia, all of which are monogenic cardiovascular diseases being essential to understanding the heart and circulatory pathophysiology. Among the issues of hypercholesterolemia which play a pivotal role in development of vascular damages, familial hypercholesterolemia is the common genetic cardiovascular disease; in addition to identifying the gene mutation coding low-density lipoprotein receptor, lipid kinetics in autosomal recessive hypercholesterolemia as well as in proprotein convertase subtilisin/kexin 9 gene mutation were recently demonstrated. As for HCM, some gene mutations were identified to correlate with clinical manifestations. Additionally, a gene polymorphism of the renin–angiotensin system in development of heart failure was identified as a modifier gene. The lethal arrhythmias such as sudden death syndromes, QT prolongation, and Brugada syndrome were found to exhibit gene mutation coding potassium and/or sodium ion channels. Interestingly, functional analysis of these gene mutations helped to identify the role of each gene mutation in developing these cardiovascular disorders. We suggest considering the genetic mechanisms of cardiovascular diseases associated with hyperlipidemia, myocardial hypertrophy, or lethal arrhythmia in terms of not only clinical diagnosis but also understanding pathophysiology of each disease with therapeutic aspects.