Estrogen Metabolites in Premenopausal Women with High versus Average Aerobic Fitness

Abstract

1990 Physical activity is suggested to alter estrogen metabolism, a proposed biomarker of breast cancer risk, by causing a shift towards higher 2-OHE1 and lower 16a-OHE1 levels. PURPOSE: To investigate the association between aerobic fitness and estrogen metabolites, 2-OHE1 and 16a-OHE1. METHODS: An extreme-groups split design was used to compare 2-OHE1 and 16a-OHE1 profiles in women with high aerobic fitness (n = 17; VO2max = 48 ml × kg × min−1) to women with average aerobic fitness (n = 13; VO2max = 40 ml × kg × min−1). Participants were healthy, regularly menstruating Caucasian women, aged 20 to 42 years, with a normal body mass index (BMI) of 18–24, who were not using pharmacologic contraceptives, or tobacco products, and were not vegetarian. Height, weight, and sum of four skinfolds, were obtained prior to completing an incremental exercise test to exhaustion on a cycle ergometer to determine maximal aerobic fitness (VO2max). A single blood and urine sample was collected during the follicular and luteal phase of the following menstrual cycle for estradiol and estrogen metabolite determination, respectively. Saliva samples were collected daily during the luteal phase for progesterone determination. RESULTS: No significant differences were found between average and high fit women for 2- OHE1, 16a-OHE1, or the 2:16a-OHE1 ratio in either the follicular or luteal phase. In ancillary analyses, a higher sum of skinfolds was associated with significantly higher luteal 16-OHE1 levels (r = .39, P = 0.03) and lower luteal phase 2:16 OHE ratio (r = −.41, P = 0.02). Higher BMI was associated with lower follicular phase 2-OHE1 (r = −.37, p = 0.038) and lower follicular 2:16 OHE1 ratio (r = −40, P = 0.03). Estradiol levels were not different between groups. CONCLUSIONS: This is the first study to investigate the relationship between estrogen metabolites and aerobic fitness using metabolic parameters. This exploratory study failed to find an association between aerobic fitness and 2-OHE1 and 16a-OHE1 but found that body composition was positively associated with 2-OHE1 and 16a-OHE1 levels. Supported by EFF Support for the Advancement of Scholarship from the University of Alberta, and a Grant from the National Cancer Institute of Canada (NCIC) with funds from the Canadian Cancer Society (CCS) and the CCS/NCIC Sociobehavioural Cancer Research Network.