d Complications Trial, it was shown that severity of retinopathy was associated with increasing serum triglycerides and inversely associated with HDL-cholesterol levels. There is also evidence for the involvement of hypercholesterolemia in the formation of hard exudates in diabetic retina, with potential negative effects on disease progression. Lipid-modifying fenofibrate has been shown 24195657 to reduce the need for laser treatment of sight-threatening diabetic retinopathy, but the effect did not seem to be attributable to changes in lipid profile. Furthermore, results from the ACCORD Study Group and ACCORD Eye Study Group showed that combination therapy reduced the rate of progression of diabetic retinopathy. Despite accumulating clinical evidence, the underlying mechanisms of lipid involvement are not clear and experimental data are sparse. In the present study, we used the genetically modified apolipoprotein E deficient mouse, 
a widely used mouse model of atherosclerosis and natural hypercholesterolemia, to study the effect of dyslipidemia on endothelial VCAM-1 expression. ApoE is a structural component of astrocytes in the central nervous system and of Muller cells in the retina, and it has important lipid transport regulatory and immunologic functions. In Chlorphenoxamine site ophthalmology, the ApoE2/2 model is most frequently used in neovascular agerelated macular degeneration experiments, but is not as widely used for studies of diabetic retinopathy. Although the lipid profile of the ApoE2/2 differs somehow from that of dyslipidemic human subjects, we suggest that this model may be relevant for addressing the issue of inflammation and/or endothelial activation in diabetic retinopathy. The second aim of our study was thus to assess whether the VCAM-1 expression pattern in retinal vessels was different in dyslipidemic compared to wild type mouse, and how diabetes would influence such an expression. As a complement to genetically caused dyslipidemia, we also explored the effects of high fat diet on VCAM-1 expression in retinal vessels. There is strong evidence that tumor necrosis factor-a is involved in inflammatory processes in diabetic retinopathy. TNFa is one of the key cytokines in inflammation, but the pathways directly or indirectly activated upon TNFa engagement may vary widely and lead to different outcomes depending on celland receptor type as well as on environmental factors. Both inflammatory and anti-inflammatory TNFa actions have been described. The third aim of the present study was to evaluate the influence of TNFa on endothelial VCAM-1 expression in diabetes and/or dyslipidemia, using TNFa knockout mice. Results Effect of diabetes and high fat diet on body weight, blood glucose, triglycerides and cholesterol To investigate the effects of diabetes on VCAM-1 expression, as well as the potential role of TNFa, C57BL/6 wild-type, ApoE2/2, TNFa2/2 and ApoE2/2/TNFa2/2 mice were chowfed until 22 weeks of age, injected with STZ or vehicle once a day for 5 days and kept on chow diet for additional 8 weeks. Mean body weight, blood glucose, plasma triglycerides, total cholesterol as well as LDL- and HDL-cholesterol for the different genotypes are listed in Genotype wt control wt diabetes ApoE2/2 control ApoE2/2 diabetes TNF-a2/2 control TNF-a2/2 diabetes ApoE2/2/TNF-a2/2 control ApoE2/2/TNF-a2/2 diabetes Body weight 23.461.5 20.561.9 23.662.4 21.361.8 23.461.0 20.660.5 22.761.1 20.062.7 Blood glucose 7.160.6 16.965.9 8.860.8 18.665.4 7.161.0 14.464.3 7.761
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