High-intensity interval training modulates retinal microvascular phenotype and DNA methylation of p66^Shc gene: A randomized controlled trial (EXAMIN AGE)

Aims: Impairments of retinal vessel diameter are associated with major adverse cardiovascular (CV) events. Promoter DNA methylation is a repressor of the mitochondrial adaptor p66^Shc gene transcription, a key driver of ageing-induced reactive oxygen species. The study aimed to investigate whether high-intensity interval training (HIIT) affects retinal microvascular phenotype as well as p66^Shc expression and oxidative stress in ageing subjects with increased CV risk from the EXAMIN AGE cohort. Methods and results: Eighty-four sedentary subjects (mean age 59.4 ± 7.0 years) with ≥2 CV risk factors were randomized into either a 12-week HIIT or standard physical activity recommendations. Retinal arteriolar and venular diameters were measured by use of a retinal vessel analyser. As a marker of oxidative stress plasma 3-nitrotyrosine (3-NT) level was determined by ELISA. Gene expression of p66^Shc and DNA methylation were assessed in mononuclear cells by RT-qPCR and methylated-DNA capture (MethylMiner Enrichment Kit) coupled with qPCR, respectively. High-intensity interval training reduced body mass index, fat mass, low-density lipoprotein and increased muscle mass, as well as maximal oxygen uptake (VO₂max). Moreover, HIIT restored microvascular phenotype by inducing retinal arteriolar widening (pre: 175 ± 14 μm vs. post: 181 ± 13 μm, P = 0.001) and venular narrowing (pre: 222 ± 14 μm vs. post: 220 ± 14 μm, P = 0.007). After HIIT, restoration of p66^Shc promoter methylation (P = 0.034) reduced p66^Shc gene expression (P = 0.037) and, in turn, blunted 3-NT plasma levels (P = 0.002). Conclusion: High-intensity interval training rescues microvascular dysfunction in ageing subjects at increased CV risk. Exercise-induced reprogramming of DNA methylation of p66^Shc gene may represent a putative mechanistic link whereby exercise protects against age-related oxidative stress. Clinical trial registration: ClinicalTrials.gov: NCT02796976 (https://clinicaltrials.gov/ct2/show/NCT02796976).