Physical activity, metabolites, and breast cancer associations.

Background: The effects of usual physical activity on physiology and disease prevention are not fully understood. We examined the associations between physical activity, metabolites, and breast cancer risk.

Methods: Physical activity levels were assessed using doubly labeled water, accelerometers, and 24-hr recalls in the IDATA study (N = 707 participants, ages 50-74 years, 51% women), with 1-6 assessments over 12 months and two blood sample collections. Partial Spearman correlations were used to estimate associations between physical activity and 843 serum metabolites, corrected for multiple testing. Conditional logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of metabolites with postmenopausal breast cancer in a nested case-control study (621 cases, 621 controls), all statistical tests were 2-sided.

Results: Physical activity was associated with 164 metabolites spanning numerous pathways, including amino acid and fatty acid metabolism. Twelve of these metabolites were also associated with breast cancer risk, ten of which supported a protective role of physical activity. Notably, higher physical activity was associated with lower 16alpha-hydroxy DHEA 3-sulfate (androgen) and adipoylcarnitine (fatty acid), both of which were associated with increased breast cancer risk (OR per 1 standard deviation (SD)=1.34, 95% CI = 1.16-1.55 and 1.26,1.11-1.42, respectively). Higher physical activity energy expenditure was also associated with lower sphingomyelin (d18:1/20:1, d18:2/20:0), which was associated with a reduced breast cancer risk (0.82,0.73-0.93).

Conclusion: Physical activity is associated with a broad range of metabolites, many of which are consistent with a protective effect against breast cancer. Our findings highlight potential metabolic pathways for cancer prevention.