Background: Narrower retinal arterioles and wider venules are linked to adverse cardiovascular outcomes. The mitochondrial adaptor p66Shc is a major source of ageing-induced generation of reactive oxygen species. Promoter DNA methylation inhibits p66Shc gene transcription. This cross-sectional study was designed to investigate the link between physical activity, retinal vessel diameters and p66Shc expression in active and sedentary ageing subjects.
Design/methods: Altogether 158 subjects were included in the study (mean age 59.4 ± 7.0 years). Thirty-eight subjects were healthy active, 36 were healthy sedentary and 84 were sedentary with ≥2 cardiovascular risk factors. Retinal arteriolar and venular diameters were measured by means of a retinal vessel analyser. As a marker of oxidative stress, plasma 3-nitrotyrosine was determined by enzyme-linked immunosorbent assay. Gene expression of p66Shc and DNA methylation were assessed in mononuclear cells by real-time quantitative polymerase chain reaction and methylated-DNA capture (MethylMiner Enrichment kit) coupled with quantitative polymerase chain reaction, respectively.
Results: Wider retinal arterioles (179 ± 14 vs 172 ± 11 and 171 ± 14 µm; p < 0.05 and narrower venules (204 ± 17 vs 209 ± 11 and 218 ± 16 µm; p < 0.001) were observed in healthy active subjects compared with healthy sedentary subjects and sedentary subjects with ≥2 cardiovascular risk factors, respectively. Furthermore, healthy active subjects had blunted p66Shc expression and lower 3-nitrotyrosine plasma levels compared with healthy sedentary and sedentary subjects with ≥2 cardiovascular risk factors. Accordingly, hypomethylation of p66Shc promoter observed in healthy sedentary and sedentary subjects with ≥2 cardiovascular risk factors was not found in healthy active subjects.
Conclusion: Long-term physical activity-induced DNA methylation of p66Shc may represent a putative mechanistic link whereby active lifestyle promotes healthy microvascular ageing.
Keywords: Ageing; DNA methylation; oxidative stress; p66Shc; retinal microcirculation.