Abstract
Background
Social disadvantage and unhealthy lifestyles may induce molecular changes associated with aging and age-related diseases. For instance, previous studies reported socioeconomic difference in DNA methylation, which in turn led to aberrant gene expression and genome instability. Socioeconomic status (SES) alone, however, does not completely explain this difference, and further studies are needed to unveil what factors contribute to it.
Methods
We conducted a cross-sectional study on 349 Italian women, aged 25-64 years, to assess SES differences in LINE-1 methylation level - a surrogate marker of global DNA methylation - and to examine the mediating effect of lifestyles (i.e. diet, smoking habits, physical activity, and weight status). Educational level was used as SES indicator. The adherence to Mediterranean diet (MD) was assessed by the Mediterranean Diet Score (MDS). Leukocyte LINE-1 methylation was assessed by pyrosequencing. Mediation analysis was conducted using the PROCESS macro for the SPSS software.
Results
We first observed that women with high educational level were more likely to be normal weight (p < 0.001) and to adhere to MD (p = 0.018), and less likely to perform physical activity (p = 0.012) than their less educated counterpart. Moreover, age-adjusted linear regression demonstrated that LINE-1 methylation level increased with increasing educational level (β = 0.016; SE = 0.003; p < 0.001). In line, mediation analysis demonstrated an indirect effect of high educational level on LINE-1 methylation through the adherence to MD (β = 0.003; 95%CI=0.001-0.006). Specifically, the mediator could account for 9.5% of the total effect. None of the other lifestyles, instead, exhibited a significant mediating effect.
Conclusions
To our knowledge, this is the first study demonstrating the mediation of diet in the relationship between SES and DNA methylation. Thus, our findings add even more value to the promotion of healthy dietary habits among social disadvantaged people.
Key messages
Social disadvantage is associated with epigenetic changes related to aging and age-related diseases. Adherence to the Mediterranean diet might mediate the association between socioeconomic status and DNA methylation.
The mediating effect of lifestyles on the association between social factors and DNA methylation
