Kazuaki Yamasaki

Increased Metabolite Levels of Glycolysis and Pentose Phosphate Pathway in Rabbit Atherosclerotic Arteries and Hypoxic Macrophage

Aims Inflammation and possibly hypoxia largely affect glucose utilization in atherosclerotic arteries, which could alter many metabolic systems. However, metabolic changes in atherosclerotic plaques remain unknown. The present study aims to identify changes in metabolic systems relative to glucose uptake and hypoxia in rabbit atherosclerotic arteries and cultured macrophages. Methods Macrophage-rich or smooth muscle cell (SMC)-rich neointima was created by balloon injury in the iliac-femoral arteries of rabbits fed with a 0.5% cholesterol diet or a conventional diet. THP-1 macrophages stimulated with lipopolysaccharides (LPS) and interferon-γ (INFγ) were cultured under normoxic and hypoxic conditions. We evaluated comprehensive arterial and macrophage metabolism by performing metabolomic analyses using capillary electrophoresis-time of flight mass spectrometry. We evaluated glucose uptake and its relationship to vascular hypoxia using 18F-fluorodeoxyglucose (18F-FDG) and pimonidazole, a marker of hypoxia. Results The levels of many metabolites increased in the iliac-femoral arteries with macrophage-rich neointima, compared with those that were not injured and those with SMC-rich neointima (glycolysis, 4 of 9; pentose phosphate pathway, 4 of 6; tricarboxylic acid cycle, 4 of 6; nucleotides, 10 of 20). The uptake of 18F-FDG in arterial walls measured by autoradiography positively correlated with macrophage- and pimonidazole-immunopositive areas (r = 0.76, and r = 0.59 respectively; n = 69 for both; p<0.0001). Pimonidazole immunoreactivity was closely localized with the nuclear translocation of hypoxia inducible factor-1α and hexokinase II expression in macrophage-rich neointima. The levels of glycolytic (8 of 8) and pentose phosphate pathway (4 of 6) metabolites increased in LPS and INFγ stimulated macrophages under hypoxic but not normoxic condition. Plasminogen activator inhibitor-1 protein levels in the supernatant were closely associated with metabolic pathways in the macrophages. Conclusion Infiltrative macrophages in atherosclerotic arteries might affect metabolic systems, and hypoxia but not classical activation might augment glycolytic and pentose phosphate pathways in macrophages.

Study of kaempferol glycoside as an insulin mimic reveals glycon to be the key active structure.

Diabetes mellitus is increasing in prevalence with patient numbers rising throughout the world. Current treatments for diabetes mellitus focus on control of blood glucose levels. Certain kinds of flavonoids or their glycosides stimulate cells to improve glucose uptake and lower blood glucose levels. We synthesized kaempferol 3-O-neohesperidoside (1), a naturally occurring substance present in Cyathea phalerata Mart., reported to mimic the action of insulin. Synthetic 1 promoted glucose uptake in the cultured cell line, L6. Further studies to determine the core structure responsible for this activity using synthetic compounds revealed neohesperidose to be the primary pharmacophore. These findings support the use of certain saccharides as a potential novel treatment for diabetes mellitus by replacing or supporting insulin.

Altered glucose metabolism and hypoxic response in alloxan-induced diabetic atherosclerosis in rabbits

Diabetes mellitus accelerates atherosclerosis that causes most cardiovascular events. Several metabolic pathways are considered to contribute to the development of atherosclerosis, but comprehensive metabolic alterations to atherosclerotic arterial cells remain unknown. The present study investigated metabolic changes and their relationship to vascular histopathological changes in the atherosclerotic arteries of rabbits with alloxan-induced diabetes. Diabetic atherosclerosis was induced in rabbit ilio-femoral arteries by injecting alloxan (100 mg/kg), injuring the arteries using a balloon, and feeding with a 0.5% cholesterol diet. We histologically assessed the atherosclerotic lesion development, cellular content, pimonidazole positive-hypoxic area, the nuclear localization of hypoxia-inducible factor-1α, and apoptosis. We evaluated comprehensive arterial metabolism by performing metabolomic analyses using capillary electrophoresis-time of flight mass spectrometry. We evaluated glucose uptake and its relationship to vascular hypoxia using 18F-fluorodeoxyglucose and pimonidazole. Plaque burden, macrophage content, and hypoxic areas were more prevalent in arteries with diabetic, than non-diabetic atherosclerosis. Metabolomic analyses highlighted 12 metabolites that were significantly altered between diabetic and non-diabetic atherosclerosis. A half of them were associated with glycolysis metabolites, and their levels were decreased in diabetic atherosclerosis. The uptake of glucose evaluated as 18F-fluorodeoxyglucose in atherosclerotic lesions increased according to increased macrophage content or hypoxic areas in non-diabetic, but not diabetic rabbits. Despite profound hypoxic areas, the nuclear localization of hypoxia-inducible factor-1α decreased and the number of apoptotic cells increased in diabetic atherosclerotic lesions. Altered glycolysis metabolism and an impaired response to hypoxia in atherosclerotic lesions under conditions of insulin-dependent diabetes might be involved in the development of diabetic atherosclerosis.

Irbesartan Attenuates Atherosclerosis in Watanabe Heritable Hyperlipidemic Rabbits: Noninvasive Imaging of Inflammation by 18F-Fluorodeoxyglucose Positron Emission Tomography

The purpose of this study was to assess the usefulness of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in evaluating the antiatherogenic effects of irbesartan, an angiotensin II type 1 receptor blocker. Watanabe heritable hyperlipidemic rabbits were divided into the irbesartan-treated group (75 mg/kg/d; n = 14) and the control group (n = 14). After a 9-month treatment, rabbits underwent 18F-FDG PET. Using the aortic lesions, autoradiography and histologic examinations were performed. PET imaging clearly visualized the thoracic lesions of control rabbits and showed a significant decrease in the 18F-FDG uptake level of irbesartan-treated rabbits (78.8% of controls; p < .05). Irbesartan treatment significantly reduced the plaque size (43.1% of controls) and intraplaque macrophage infiltration level (48.1% of controls). The 18F-FDG uptake level in plaques positively correlated with the plaque size (r = .65, p < .05) and macrophage infiltration level (r = .57, p < .05). Noninvasive imaging by 18F-FDG PET is useful for evaluating the therapeutic effects of irbesartan and reflects inflammation, a key factor involved in the therapeutic effects.The purpose of this study was to assess the usefulness of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in evaluating the antiatherogenic effects of irbesartan, an angiotensin II type 1 receptor blocker. Watanabe heritable hyperlipidemic rabbits were divided into the irbesartan-treated group (75 mg/kg/d; n = 14) and the control group ( n = 14). After a 9-month treatment, rabbits underwent 18F-FDG PET. Using the aortic lesions, autoradiography and histologic examinations were performed. PET imaging clearly visualized the thoracic lesions of control rabbits and showed a significant decrease in the 18F-FDG uptake level of irbesartan-treated rabbits (78.8% of controls; p < .05). Irbesartan treatment significantly reduced the plaque size (43.1% of controls) and intraplaque macrophage infiltration level (48.1% of controls). The 18F-FDG uptake level in plaques positively correlated with the plaque size ( r = .65, p < .05) and macrophage infiltration level ( r = .57, p < .05). Noninvasive imaging by 18F-FDG PET is useful for evaluating the therapeutic effects of irbesartan and reflects inflammation, a key factor involved in the therapeutic effects.

Screening and Identification of Disaccharides with Insulin Mimetic Activity against L6 Cells

Insulin mimetics are considered as prospective anti-diabetic agents, and the disaccharide, neohesperidose, has been found to show insulin mimetic activity against L6 cells. We screened several other disaccharides for their insulin mimetic activity and identified three new insulin mimetic disaccharides.

In vitro uptake and metabolism of [14C]acetate in rabbit atherosclerotic arteries: biological basis for atherosclerosis imaging with [11C]acetate

INTRODUCTION Detection of vulnerable plaques is critically important for the selection of appropriate treatment and/or the prevention of atherosclerosis and ensuing cardiovascular diseases. In order to clarify the utility of [11C]acetate for atherosclerosis imaging, we determined the uptake and metabolism of acetate by in vitro studies using rabbit atherosclerotic arteries and [14C]acetate. METHODS Rabbits were fed with a conventional (n=5) or a 0.5% cholesterol diet (n=6). One side of the iliac-femoral arteries was injured by a balloon catheter. Radioactivity levels in the iliac-femoral arteries were measured after incubation in DMEM containing [1-14C]acetate for 60 min (% dpm/mg tissue). Radioactive components in the homogenized arteries were partitioned into aqueous, organic, and residue fractions by the Folch method, and analyzed by thin-layer chromatography (TLC). RESULTS The radioactivity level in the injured arteries of rabbits fed with the 0.5% cholesterol diet (atherosclerotic arteries) was significantly higher than that in either the non-injured or injured arteries of rabbits fed with the conventional diet (p<0.05) (% dpm/mg tissue: conventional diet groups; 0.022±0.005 and 0.024±0.007, cholesterol diet groups; 0.029±0.007 and 0.034±0.005 for non-injured and injured arteries). In metabolite analysis, most of the radioactivity was found in the aqueous fraction in each group (87.4-94.6% of total radioactivity in the arteries), and glutamate was a dominant component (67.4-69.7% of the aqueous fraction in the arteries). CONCLUSIONS The level of [14C]acetate-derived radioactivity into the arteries was increased by balloon injury and the burden of a cholesterol diet. Water-soluble metabolites were the dominant components with radioactivity in the atherosclerotic lesions. These results provide a biological basis for imaging atherosclerotic lesions by PET using [11C]acetate.