Katsuya Yamazaki

Adiponectin Inhibits Endothelial Synthesis of Interleukin-8

Adiponectin is an antiatherogenic adipokine that inhibits inflammation by mechanisms that are not completely understood. We explored the effect of adiponectin on endothelial synthesis of interleukin-8 (IL-8), a pro-inflammatory chemokine that plays a role in atherogenesis. Adiponectin decreased the secretion of IL-8 from human aortic endothelial cells (HAEC) stimulated with tumor necrosis factor-&agr; (TNF-&agr;). Adiponectin also inhibited IL-8 mRNA expression induced by TNF-&agr;. Phosphorylation of I&kgr;B-&agr; was decreased by adiponectin, but phosphorylation of ERK, SAPK/JNK, and p38MAPK were unaffected. Adiponectin increased intra-cellular cAMP levels in HAEC in a dose-dependent manner; PKA activity was also increased. The inhibitory effect of adiponectin on TNF-&agr;–induced IL-8 synthesis was inhibited by pretreatment with Rp-cAMP, a PKA inhibitor. These observations suggest that adiponectin inhibits IL-8 synthesis through inhibition of a PKA dependent NF-&kgr;B signaling pathway. We also showed that adiponectin enhances Akt phosphorylation. The inhibitory effect of adiponectin on TNF-&agr;–induced IL-8 synthesis was abrogated in part by pretreatment with the PI3 kinase inhibitor LY294002 or by Akt siRNA transfection, suggesting that Akt activation might inhibit IL-8 synthesis induced by TNF-&agr;. We conclude that inhibition of NF-&kgr;B and activation of Akt phosphorylation may mediate adiponectin inhibition of atherosclerosis.

Comparison of the conversion rates of α-linolenic acid (18:3(n − 3)) and stearidonic acid (18:4(n − 3)) to longer polyunsaturated fatty acids in rats

The delta 6-desaturase reaction is regarded to be the rate-limiting step in the conversion of linoleic acid (18:2(n - 6)) to arachidonic acid (20:4(n - 6)). The same is probably also the case with the conversion of alpha-linolenic acid (18:3(n - 3)) to eicosapentaenoic acid (20:5(n - 3)). However, there are very few in vivo studies that directly compared the conversion rate between 18:3(n - 3) and stearidonic acid (18:4(n - 3)), which is the delta 6-desaturated product of 18:3(n - 3). We compared this rate by feeding rats on a lipid-free diet supplemented with lard (9%, w/w) and 18:3(n - 3) ethyl ester (1%) diet or on a diet containing lard (9%) and 18:4(n - 3) ethyl ester (1%). A lard (10%)-supplemented diet was used as the control diet. The fatty acid compositions of total phospholipids, triglycerides and free fatty acids of both liver and plasma were measured after 1 or 3 weeks on different diets. The molar ratio of 20:5(n - 3) of most lipid fractions was about 2-fold higher in rats fed the 18:4(n - 3)-supplemented diet than in rats fed the 18:3(n - 3)-supplemented diet. 18:4(n - 3) was found in the liver lipid fraction in only a very small amount, even in the 18:4(n - 3)-supplemented groups. Thus, desaturation at C-6 is suggested to be the rate-limiting step in the conversion of 18:3(n - 3) to 20:5(n - 3).

EFFECT OF EICOSAPENTAENOIC AND DOCOSAHEXAENOIC ACID ON NATURAL-KILLER-CELL ACTIVITY IN HUMAN PERIPHERAL-BLOOD LYMPHOCYTES

The effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on natural killer (NK) cell activity in human peripheral blood lymphocytes were studied. The direct addition of trieicosapentaenoyl-glycerol (EPA-TG) or tridocosahexaenoylglycerol (DHA-TG) emulsion to a cytotoxicity assay system significantly suppressed NK cell activity. The addition of lipoxygenase inhibitor AA861 also inhibited NK cell activity. The inhibition was proportional to the concentration of EPA-TG emulsion. DHA-TG emulsion, or AA861. The presence of both EPA-TG emulsion or DHA-TG emulsion and AA861 at the same time led to a greater inhibitory effect on NK cell activity than when these emulsions were used separately. The inhibitory effect caused by these lipids or lipoxygenase blockade could not be reversed by adding back exogenous leukotrienes to the assay system. Preincubation of effector cells with EPA-TG or DHA-TG emulsion resulted in a significant inhibition of their NK cell activity. NK cell activity of human lymphocytes was markedly decreased after the infusion of EPA-TG emulsion into healthy volunteers. Thus, in vivo use of EPA-TG or DHA-TG emulsion may influence immune reactivity of the host, although the mechanism has not yet been elucidated.

Comparison of pulse wave velocity of the aorta between inhabitants of fishing and farming villages in Japan

Pulse wave velocity (PWV) of the aorta was measured in 55 inhabitants of fishing villages and in 49 inhabitants of farming villages, where people normally eat less fish than in the fishing villages. The PWV was significantly slower (indicating less sclerosis) in the fishing villages than in the farming villages (P less than 0.005). This is consistent with a lower incidence of ischemic heart disease in a coastal area, which includes the fishing villages, than in a mountainous area, including the farming villages. It is reported that a long-term fish-diet slows down sclerotic changes of arteries.

Changes in oral antidiabetic prescriptions and improved glycemic control during the years 2002–2011 in Japan (JDDM32)

Six kinds of oral antidiabetic drugs (OADs), including the new dipeptidyl peptidase 4 (DPP‐4) inhibitors, are available. The present study aimed to define trends within the prescribing patterns of OADs, as well as changes in glycemic control in Japan over a 10‐year period from 2002 to 2011.

Inhibitory effect of pitavastatin (NK-104) on the C-reactive-protein-induced interleukin-8 production in human aortic endothelial cells

Recent data have indicated that CRP (C-reactive protein) plays a role in atherosclerosis, in addition to being a marker for inflammatory diseases. IL-8 (interleukin-8), a CXC chemokine, is present in human coronary atheroma and promotes monocyte-endothelial cell adhesion. In the present study, we examined the effect of pitavastatin (NK-104), a synthetic statin (3-hydroxy-3-methylglutaryl CoA reductase inhibitor), on IL-8 production induced by CRP in human AoEC (aortic endothelial cells). We also investigated whether CRP can induce IL-8 production and if the activation of signalling pathways are functionally related. The concentrations of IL-8 in the media after stimulation with CRP were measured by ELISA, and the expression of IL-8 mRNA was assessed by Northern blot. The phosphorylation of MAPKs (mitogen-activated protein kinases) was determined by Western blot. The production of IL-8 induced by CRP (10 microg/ml) was enhanced significantly and was inhibited by pitavastatin. The expression of IL-8 mRNA was increased in a dose-dependent manner after stimulation with CRP (1-100 microg/ml), whereas expression of IL-8 mRNA induced by CRP (50 microg/ml) was significantly diminished by 5 microM pitavastatin. Furthermore, specific MAPK inhibitors (PD98059, SB203580 and SP600125) inhibited the expression of IL-8 mRNA induced by CRP (50 microg/ml). The phosphorylation of all three MAPKs [ERK (extracellular-signal-regulated kinase), p38 MAPK and JNK (c-Jun N-terminal kinase)] induced by CRP (10 microg/ml) was also significantly inhibited by pitavastatin. Our results suggest that CRP may play a role in atherosclerosis via IL-8 production and pitavastatin may prevent the progression of atherosclerosis not only by lowering plasma low-density lipoprotein cholesterol levels, but also by suppressing IL-8 production in endothelial cells through the inhibition of MAPK (ERK, p38 MAPK and JNK) pathways.

Association of the polymorphisms in the 5′-untranslated region of PTEN gene with type 2 diabetes in a Japanese population

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is known to act as a lipid phosphatase hydrolyzing phosphatidylinositol (PI)(3,4,5)P3 to PI(4,5)P2. Since the PI3‐kinase product, PI(3,4,5)P3, is an important second messenger leading to the metabolic action of insulin, PTEN functions as a potent negative regulator of insulin signaling and its gene is one of the possible candidates involved in susceptibility to the development of type 2 (non‐insulin‐dependent) diabetes. In the present study, we investigated the polymorphisms of the PTEN gene in Japanese patients with type 2 diabetes and non‐diabetic control subjects. We identified three mutations of the gene in the type 2 diabetes patients. Among these mutations, the frequency of the substitution of C with G at position −9 (−9C→G) (SNP1), located in the untranslated region of exon 1, was significantly higher in type 2 diabetic patients than in control subjects. In addition, transfection of the PTEN gene with SNP1 resulted in a significantly higher expression level of PTEN protein compared with that of the wild‐type PTEN gene in Cos1 and Rat1 cells. Furthermore, insulin‐induced phosphorylation of Akt in HIRc cells was decreased more greatly by transfection of SNP1 PTEN gene than that of wild‐type PTEN gene. These findings suggest that the change of C to G at position −9 of the PTEN gene is associated with the insulin resistance of type 2 diabetes due possibly to a potentiated hydrolysis of the PI3‐kinase product.

Pravastatin suppresses the interleukin‐8 production induced by thrombin in human aortic endothelial cells cultured with high glucose by inhibiting the p44/42 mitogen activated protein kinase

3‐Hydroxy‐3‐methylglutaryl co‐enzyme A reductase inhibitors (statins) prevent the progression of atherosclerosis by lowering cholesterol. However, the effect of statins on the synthesis of pro‐inflammatory cytokines from endothelial cells has not yet been fully investigated. Here, we examined the effect of pravastatin, one of the statins, on IL‐8 synthesis induced by thrombin in human aortic endothelial cells (AoEC) cultured with high glucose concentrations. Pravastatin significantly decreased the IL‐8 synthesis induced by thrombin. Pravastatin inhibited the p44/42 MAP kinase activity induced by thrombin, but did not inhibit the p38 MAP kinase activity. Translocation of ras protein from the cytosol to plasma membrane was inhibited by pravastatin. Pravastatin inhibit the activator protein‐1 activity, but did not inhibit the activation of IκB‐α. Dominant negative ras inhibited the p44/42 MAP kinase activity induced by PMA. Our results suggest that pravastatin inhibits IL‐8 synthesis by blocking the ras‐MAP (p44/42) kinase pathway rather than nuclear factor‐κB. Pravastatin may prevent atherosclerosis not only by lowering cholesterol levels, but also by suppressing IL‐8 synthesis in AoEC through the inhibition of p44/42 MAP kinase, and this may be more beneficial in diabetic patients than in non‐diabetics.

Changes in fatty acid composition in rat blood and organs after infusion of eicosapentaenoic acid ethyl ester

An infusible emulsion of 10% eicosapentaenoic acid ethyl ester (EPA-EE, 99.2% pure) was prepared. Three ml of the emulsion was infused into tail veins of 20 Wistar rats weighing approx. 300 g. They were killed 1 h, 6 h, 24 h, 3 d and 7 d after the infusion, and fatty acid composition of various organs and plasma was analyzed along with that of control rats. There was no lipidosis in any organs of any rats. It was estimated that not less than 98% of infused EPA was cleared from plasma during the first hour after the infusion. EPA concentrations reached their peaks within 6 h after EPA infusion in plasma lipid fractions and in the phospholipid fraction of liver, heart, lung, kidney and spleen. The fatty acid composition of the phospholipid fraction of heart was very stable, and was not altered by EPA infusion except for a very slight increase in EPA at 1 h after the infusion (0.18% at 0 h to 0.56%). However, EPA concentrations increased markedly in the free fatty acid fraction of heart at 1 h after the infusion (0.15% at 0 h to 4.23%). Arachidonic acid concentrations decreased significantly within 24 h in the phospholipid fraction of organs except for heart. EPA emulsion might be useful for patients in whom a rapid increment in EPA in tissues is beneficial.

Effects of cilostazol on serum lipid concentrations and plasma fatty acid composition in type 2 diabetic patients with peripheral vascular disease.

Abstract. Cilostazol is an anti-thrombotic and vasodilating agent, reported to have both anti-thrombotic and cerebral vasodilating effects. We investigated the effects of cilostazol on serum lipid concentrations and plasma fatty acid composition in type 2 diabetic patients with peripheral vascular disease. The serum concentrations of total cholesterol, triglycerides, high-density lipoprotein-cholesterol, lipoprotein (a), remnant-like particles-cholesterol, apolipoproteins, and plasma fatty acid composition were measured in 17 diabetic patients with peripheral vascular disease before and 1, 3, and 6 months after administration of cilostazol (200 mg/day). Serum triglyceride concentrations were significantly decreased after cilostazol (from 1.31±0.17 mmol/l to 0.86±0.07 mmol/l at 6 months, P<0.01). Plasma docosahexaenoic acid levels were significantly increased after cilostazol (4.11±0.26% to 4.94±0.26% at 6 months, P<0.01). Our findings show that cilostazol can induce some beneficial changes in serum lipid profile and plasma fatty acid composition.