Ryota Kawase

Adiponectin prevents atherosclerosis by increasing cholesterol efflux from macrophages.

Plasma high density lipoprotein (HDL)-cholesterol levels are inversely correlated to the risk of atherosclerotic cardiovascular diseases. Reverse cholesterol transport (RCT) is one of the major protective systems against atherosclerosis, in which HDL particles play a crucial role to carry cholesterol derived from peripheral tissues to the liver. Recently, ATP-binding cassette transporters (ABCA1, ABCG1) and scavenger receptor (SR-BI) have been identified as important membrane receptors to generate HDL by removing cholesterol from foam cells. Adiponectin (APN) secreted from adipocytes is one of the important molecules to inhibit the development of atherosclerosis. Epidemiological studies have revealed a positive correlation between plasma HDL-cholesterol and APN concentrations in humans, although its mechanism has not been clarified. Therefore, in the present study, we investigated the role of APN on RCT, in particular, cellular cholesterol efflux from human monocyte-derived and APN-knockout (APN-KO) mice macrophages. APN up-regulated the expression of ABCA1 in human macrophages, respectively. ApoA-1-mediated cholesterol efflux from macrophages was also increased by APN treatment. Furthermore, the mRNA expression of LXRalpha and PPARgamma was increased by APN. In APN-KO mice, the expression of ABCA1, LXRalpha, PPARgamma, and apoA-I-mediated cholesterol efflux was decreased compared with wild-type mice. In summary, APN might protect against atherosclerosis by increasing apoA-I-mediated cholesterol efflux from macrophages through ABCA1-dependent pathway by the activation of LXRalpha and PPARgamma.

Deletion of progranulin exacerbates atherosclerosis in ApoE knockout mice

AIMS Progranulin (PGRN) is a multifunctional protein known to be involved in inflammation. However, the relation between PGRN and atherosclerosis remains elusive. The aim of this study was to define the role of PGRN in the development of atherosclerosis. METHODS AND RESULTS First, we checked the expression levels of PGRN in human atherosclerotic plaques. Immunohistochemical analysis showed that PGRN is strongly expressed in foam cells of atherosclerotic plaques. We also found that PGRN is expressed more abundantly in macrophages than in the smooth muscle cells of atherosclerotic lesions in ApoE(-/-) mice fed a high-fat diet for 12 weeks. Next, PGRN(-/-)ApoE(-/-) mice were generated to investigate the effect of PGRN on the development of atherosclerosis. PGRN(-/-)ApoE(-/-) mice exhibited severe atherosclerotic lesions compared with PGRN(+/+)ApoE(-/-) mice, despite their anti-atherogenic lipid profile. These results are partly due to enhanced expression of inflammatory cytokines, adhesion molecules, and decreased expression of endothelial nitric oxide synthase. In addition, lack of PGRN leads to accumulate excessive cholesterol in the macrophages and alter HDL-associated proteins. CONCLUSION PGRN seems to be involved in the pathogenesis of atherosclerosis, possibly by various anti-atherogenic effects, including modulation of local and/or systemic inflammation.

Serum apolipoprotein B-48 levels are correlated with carotid intima-media thickness in subjects with normal serum triglyceride levels

BACKGROUND Postprandial hyperlipidemia (PPHL) is an independent risk factor for coronary heart disease (CHD) which is based on the accumulation of chylomicrons (CM) and CM remnants containing apolipoprotein B-48 (apoB-48). Since atherosclerotic cardiovascular diseases are frequently observed even in subjects with normal serum triglyceride (TG) level, the correlation between fasting apoB-48 containing lipoproteins and carotid intima-media thickness (IMT) was analyzed in subjects with normal TG levels. METHODS From subjects who took their annual health check at the Osaka Police Hospital (n=245, male), one-hundred and sixty-four male subjects were selected to take part in this study; the excluding factors were: systolic blood pressure ≥ 140 mmHg, intake of antihypertensive or antihyperlipidemic drugs, or age >65 years. The association between biochemical markers and IMT was analyzed and independent predictors of max-IMT were determined by multiple regression analysis in all subjects and in groups N-1 (TG<100mg/dl, n=58), N-2 (100 ≤ TG<150 mg/dl, n=53) and H (150 ≤ TG mg/dl, n=53), respectively. RESULTS Fasting total cholesterol, LDL-cholesterol, HDL-cholesterol, apoB-100 and lnRemL-C (remnant lipoprotein-cholesterol) levels were not correlated with max-IMT, but lnTG and lnapoB-48 were significantly correlated with max-IMT in all subjects. LnapoB-48 and apoB-48/TG ratio were significantly correlated with max-IMT in group N-2. By multiple regression analysis, age and lnapoB-48 were independent variables associated with max-IMT in group N-2. CONCLUSION Serum apoB-48 level might be a good marker for the detection of early atherosclerosis in middle-aged subjects with normal-range levels of blood pressure and TG.

Serum adiponectin level is correlated with the size of HDL and LDL particles determined by high performance liquid chromatography

OBJECTIVE Adiponectin (APN) improves insulin resistance and prevents atherosclerosis, and HDL removes cholesterol from atherosclerotic lesions. We have demonstrated that serum HDL-cholesterol (HDL-C) and APN concentrations are positively correlated and that APN accelerates reverse cholesterol transport (RCT) by increasing HDL synthesis in the liver and cholesterol efflux from macrophages. We previously reported that APN reduced apolipoprotein (apo) B secretion from the liver. It is well-known that insulin resistance influences the lipoprotein profile. In this study, we investigated the clinical significance of APN levels and insulin resistance in lipoprotein metabolism. MATERIAL/METHOD We investigated the correlation between serum APN concentration, HOMA-R, the lipid concentrations and lipoprotein particle size by high-performance liquid chromatography (HPLC) in 245 Japanese men during an annual health checkup. RESULTS Serum APN level was positively correlated with the cholesterol content in large LDL and HDL particles, but inversely correlated with the cholesterol content in large VLDL and small LDL particles. HOMA-R was negatively correlated with the cholesterol content in large LDL and HDL particles and positively correlated with the cholesterol content in large VLDL and small LDL particles. By multivariate analysis, APN was correlated with the particle size of LDL-C and HDL-C independently of age, BMI and HOMA-R. CONCLUSIONS APN may be associated with the formation of both HDL and LDL particles, reflecting the enhancement of RCT and the improvement in TG-rich lipoprotein metabolism and insulin resistance.

Establishment of chemiluminescence enzyme immunoassay for apolipoprotein B-48 and its clinical applications for evaluation of impaired chylomicron remnant metabolism

BACKGROUND Apolipoprotein B-48 (apoB-48) is a constituent of chylomicron remnants synthesized in the small intestines. The serum concentration of apoB-48 at fasting has been reported to be a marker of postprandial hyperlipidemia, a presumed risk factor for atherosclerosis. METHODS We evaluated the basal performance of a recently developed chemiluminescent enzyme immunoassay (CLEIA). We also examined the correlations between serum apoB-48 concentrations and other lipid concentrations or life style patterns, including smoking and drinking. We analyzed the data of 273 clinical samples by multiple regression analysis to examine the influence of other serum lipid values, age, sex, smoking, drinking status and BMI on serum apoB-48 values. RESULTS Within-run and between-run precision was obtained with 1.7-2.7% and 1.2-7.3%, respectively. The correlativity of enzyme-linked immunosorbent assay was correlation coefficient r=0.953, and regression y=1.02×-1.59. Serum apoB-48 concentrations were higher in males than in females, and were correlated with the status of smoking as well as with remnant-like particle-cholesterol (RLP-C) concentrations. Patients with the metabolic syndrome showed higher values of serum apoB-48 compared with control subjects. CONCLUSION Serum apoB-48 measurement by CLEIA was satisfactory for clinical use to assess abnormalities in the chylomicron remnant metabolism.

Progranulin plays crucial roles in preserving bone mass by inhibiting TNF-α-induced osteoclastogenesis and promoting osteoblastic differentiation in mice.

A close correlation between atherosclerosis, inflammation, and osteoporosis has been recognized, although the precise mechanism remains unclear. The growth factor progranulin (PGRN) is expressed in various cells such as macrophages, leukocytes, and chondrocytes. PGRN plays critical roles in a variety of diseases, such as atherosclerosis and arthritis by inhibiting Tumor Necrosis Factor-α (TNF-α) signaling. The purpose of this study was to investigate the effect of PGRN on bone metabolism. Forty-eight-week old female homozygous PGRN knockout mice (PGRN-KO) (n = 8) demonstrated severe low bone mass in the distal femur compared to age- and sex-matched wild type C57BL/6J mice (WT) (n = 8) [BV/TV (%): 5.8 vs. 16.6; p < 0.001, trabecular number (1/mm): 1.6 vs. 3.8; p < 0.001]. In vitro, PGRN inhibited TNF-α-induced osteoclastogenesis from spleen cells of PGRN-KO mice. Moreover, PGRN significantly promoted ALP activity, osteoblast-related mRNA (ALP, osteocalcin) expression in a dose-dependent manner and up-regulated osteoblastic differentiation by down-regulating phosphorylation of ERK1/2 in mouse calvarial cells. In conclusion, PGRN may be a promising treatment target for both atherosclerosis and inflammation-related osteoporosis.

Differential reactivities of four homogeneous assays for LDL-cholesterol in serum to intermediate-density lipoproteins and small dense LDL: comparisons with the Friedewald equation.

BACKGROUND In routine clinical laboratory testing and numerous epidemiological studies, LDL-cholesterol (LDL-C) has been estimated commonly using the Friedewald equation. We investigated the relationship between the Friedewald equation and 4 homogeneous assays for LDL-C. METHODS LDL-C was determined by 4 homogeneous assays [liquid selective detergent method: LDL-C (L), selective solubilization method: LDL-C (S), elimination method: LDL-C (E), and enzyme selective protecting method: LDL-C (P)]. Samples with discrepancies between the Friedewald equation and the 4 homogeneous assays for LDL-C were subjected to polyacrylamide gel electrophoresis and the beta-quantification method. RESULTS The correlations between the Friedewald equation and the 4 homogeneous LDL-C assays were as follows: LDL-C (L) (r=0.962), LDL-C (S) (r=0.986), LDL-C (E) (r=0.946) and LDL-C (P) (r=0.963). Discrepancies were observed in sera from type III hyperlipoproteinemia patients and in sera containing large amounts of midband and small dense LDL on polyacrylamide gel electrophoresis. LDL-C (S) was most strongly correlated with the beta-quantification method even in sera from patients with type III hyperlipoproteinemia. CONCLUSIONS Of the 4 homogeneous assays for LDL-C, LDL-C (S) exhibited the closest correlation with the Friedewald equation and the beta-quantification method, thus reflecting the current clinical databases for coronary heart disease.

Myocardial energy provision is preserved by increased utilization of glucose and ketone bodies in CD36 knockout mice

AIMS CD36 is an important transporter of long-chain fatty acids (LCFAs) in the myocardium. As we have reported previously, CD36-deficient patients demonstrate a marked reduction in myocardial uptake of (123)I-15-(p-iodophenyl)-(R, S)-methyl pentadecanoic acid (BMIPP), which is an analog of LCFAs, while myocardial (18)F-fluorodeoxy-glucose (FDG) uptake is increased. However, it has not been clarified whether energy provision is preserved in patients with CD36 deficiency. The aims of the current study were to investigate the myocardial uptake of glucose and alterations in myocardial metabolites in wild-type (WT) and CD36 knockout (KO) mice. METHODS AND RESULTS High-resolution positron emission tomography (PET) demonstrated markedly enhanced glucose uptake in KO mouse hearts compared with those of WT mice in real-time. The myocardial protein expression of glucose transporter protein 1 (GLUT1) was significantly enhanced in KO mice compared to WT mice, whereas that of GLUT4 was not altered. While the myocardial expression of genes involved in fatty acid metabolism did not increase in KO mice, that of genes related to glucose utilization compensatorily increased in KO mice. The metabolomic analysis of cardiac tissues revealed that the myocardial concentrations of ATP and phosphocreatine were maintained, even in KO mice. The concentration of 3-hydroxybutyric acid and mRNA expression of hydroxybutyrate dehydrogenase in the heart were significantly higher in KO than in WT mice. CONCLUSION These data suggest that high-energy phosphate might be preserved by the increased utilization of glucose and ketone bodies in CD36KO mouse hearts under conditions of deficient LCFA uptake.

Establishment of a Novel Murine Model of Ischemic Cardiomyopathy with Multiple Diffuse Coronary Lesions

Objectives Atherosclerotic lesions of the coronary arteries are the pathological basis for myocardial infarction and ischemic cardiomyopathy. Progression of heart failure after myocardial infarction is associated with cardiac remodeling, which has been studied by means of coronary ligation in mice. However, this ligation model requires excellent techniques. Recently, a new murine model, HypoE mouse was reported to exhibit atherogenic Paigen diet-induced coronary atherosclerosis and myocardial infarction; however, the HypoE mice died too early to make possible investigation of cardiac remodeling. Therefore, we aimed to modify the HypoE mouse model to establish a novel model for ischemic cardiomyopathy caused by atherosclerotic lesions, which the ligation model does not exhibit. Methods and Results In our study, the sustained Paigen diet for the HypoE mice was shortened to 7 or 10 days, allowing the mice to survive longer. The 7-day Paigen diet intervention starting when the mice were 8 weeks old was adequate to permit the mice to survive myocardial infarction. Our murine model, called the “modified HypoE mouse”, was maintained until 8 weeks, with a median survival period of 36 days, after the dietary intervention (male, n = 222). Echocardiography demonstrated that the fractional shortening 2 weeks after the Paigen diet (n = 14) significantly decreased compared with that just before the Paigen diet (n = 6) (31.4±11.9% vs. 54.4±2.6%, respectively, P<0.01). Coronary angiography revealed multiple diffuse lesions. Cardiac remodeling and fibrosis were identified by serial analyses of cardiac morphological features and mRNA expression levels in tissue factors such as MMP-2, MMP-9, TIMP-1, collagen-1, and TGF-β. Conclusion Modified HypoE mice are a suitable model for ischemic cardiomyopathy with multiple diffuse lesions and may be considered as a novel and convenient model for investigations of cardiac remodeling on a highly atherogenic background.

Methods for Studying the Function of Progranulin in Atherosclerosis Using Both Knockout Mice Models and In Vitro Studies

Progranulin (PGRN) has been reported to be associated with cell proliferation, cell growth, wound healing, and inflammation. PGRN mutations are known to be related to dementia. However, the association between PGRN and atherosclerosis remains to be elucidated. Therefore, we generated PGRN-/-ApoE-/- mice to analyze the effect of PGRN on the development of atherosclerosis.