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

Abstract

AimsInflammation 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.MethodsMacrophage-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.ResultsThe 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.ConclusionInfiltrative macrophages in atherosclerotic arteries might affect metabolic systems, and hypoxia but not classical activation might augment glycolytic and pentose phosphate pathways in macrophages.

Macrophage metabolism in atherosclerosis

“…Mass spectrometry‐based metabolomics analyses performed in rabbit arteries demonstrated that the levels of numerous metabolites derived from bioenergetic pathways are increased in arteries containing macrophage‐rich neointima, compared with uninjured arteries or smooth muscle cell‐rich neointima . In particular, metabolites from glycolysis and the PPP were markedly increased as well as citrate, fumarate and succinate, similar to what is observed in activated macrophages .…”

“…Increased metabolites from the PPP were found in rabbit atherosclerotic arteries . The few studies that focus on the role of the PPP in atherosclerosis point out a detrimental role for the PPP in lesion formation.…”

Involvement of the Warburg effect in non‐tumor diseases processes

“…Sarrazy et al () find that glucose uptake and aerobic glycolysis significantly increase in atheromatous plaques of ApoE −/− mice. Yamashita et al () also reveal that metabolite levels of aerobic glycolysis increases in rabbit atherosclerotic arteries. Thus, Warburg effect is found in atherosclerosis process.…”

Recent Advances in the Development of PET/SPECT Probes for Atherosclerosis Imaging

“…Derlin et al [15] examined the topographic relationship between arterial 11 C-acetate uptake and vascular calcification in oncology patients, and indicated that 11 C-acetate uptake may represent the early stages of disease. Although there have been few studies on the use of 11 C-acetate for the imaging of atherosclerotic plaques, in our recent metabolome study in a rabbit model, markedly increased acetyl-CoA levels were found in macrophage-rich lesions [35]. Further studies, including comparative studies with …”

“…On the other hand, it is reported that glucose metabolism and 18 F-FDG uptake in macrophages are more strongly enhanced by hypoxic stimuli than by pro-inflammatory cytokines. Indeed, 18 F-FDG uptake was positively associated with hypoxic areas in atherosclerotic arteries induced by balloon injury in rabbits fed with a high-cholesterol diet [35]. However, high 18 F-FDG uptake was also observed in nonhypoxic macrophage-rich regions of the arteries.…”