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Disposition of soy isoflavones in normal human breast tissue

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Abstract
Background: Despite decades of research on the relation between soy and breast cancer, questions regarding the absorption, metabolism, and distribution of isoflavones in breast tissue largely remain unanswered. Objective: We evaluated the potential health effects of isoflavone consumption on normal breast tissue; isoflavone concentrations, metabolites, and biodistribution were investigated and compared with 17 beta-estradiol exposure. Design: In this dietary intervention study, healthy women were randomly allocated to a soy milk (n = 11; 16.98-mg genistein and 5.40-mg daidzein aglycone equivalents per dose), soy supplement (n = 10; 5.27-mg genistein and 17.56-mg daidzein aglycone equivalents per dose), or control (n = 10) group. After a run-in period >= 4 d, 3 doses of soy milk or soy supplements were taken daily for 5 d before an esthetic breast reduction. Blood and breast biopsies were collected during surgery and analyzed with liquid chromatography-tandem mass spectrometry. Results: After soy administration, genistein and total daidzein concentrations, which were expressed as aglycone equivalents, ranged from 135.1 to 2831 nmol/L and 105.1 to 1397 nmol/L, respectively, in hydrolyzed serum and from 92.33 to 493.8 pmol/g and 22.15 to 770.8 pmol/g, respectively, in hydrolyzed breast tissue. The major metabolites identified in nonhydrolyzed samples were genistein-7-O-glucuronide and daidzein-7-O-glucuronide, with an overall glucuronidation of 98%. Total isoflavones showed a breast adipose/glandular tissue distribution of 40: 60, and their mean (+/- SEM) derived 17 beta-estradiol equivalents toward estrogen receptor beta were 21 +/- 4-fold and 40 +/- 10-fold higher than the 17 beta-estradiol concentrations in adipose (0.283 +/- 6 0.089 pmol/g, P < 0.001) and glandular (0.246 +/- 0.091 pmol/g, P = 0.001) fractions, respectively. Conclusion: After intake of soy milk and soy supplements, isoflavones reach exposure levels in breast tissue at which potential health effects may occur.
Keywords
MAMMARY-GLAND, MCF-7 TUMORS, STIMULATE GROWTH, AROMATASE ACTIVITIES, IN-VITRO, POSTMENOPAUSAL WOMEN, ESTROGEN-RECEPTOR-ALPHA, CANCER TUMORS, HUMAN URINE, PHYTOESTROGENS

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Chicago
Bolca, Selin, Mireia Urpi-Sarda, Phillip Blondeel, NATHALIE ROCHE, Lynn Vanhaecke, Sam Possemiers, Nawaf Al-Maharik, et al. 2010. “Disposition of Soy Isoflavones in Normal Human Breast Tissue.” American Journal of Clinical Nutrition 91 (4): 976–984.
APA
Bolca, S., Urpi-Sarda, M., Blondeel, P., ROCHE, N., Vanhaecke, L., Possemiers, S., Al-Maharik, N., et al. (2010). Disposition of soy isoflavones in normal human breast tissue. AMERICAN JOURNAL OF CLINICAL NUTRITION, 91(4), 976–984.
Vancouver
1.
Bolca S, Urpi-Sarda M, Blondeel P, ROCHE N, Vanhaecke L, Possemiers S, et al. Disposition of soy isoflavones in normal human breast tissue. AMERICAN JOURNAL OF CLINICAL NUTRITION. 2010;91(4):976–84.
MLA
Bolca, Selin, Mireia Urpi-Sarda, Phillip Blondeel, et al. “Disposition of Soy Isoflavones in Normal Human Breast Tissue.” AMERICAN JOURNAL OF CLINICAL NUTRITION 91.4 (2010): 976–984. Print.
@article{980671,
  abstract     = {Background: Despite decades of research on the relation between soy and breast cancer, questions regarding the absorption, metabolism, and distribution of isoflavones in breast tissue largely remain unanswered.
Objective: We evaluated the potential health effects of isoflavone consumption on normal breast tissue; isoflavone concentrations, metabolites, and biodistribution were investigated and compared with 17 beta-estradiol exposure.
Design: In this dietary intervention study, healthy women were randomly allocated to a soy milk (n = 11; 16.98-mg genistein and 5.40-mg daidzein aglycone equivalents per dose), soy supplement (n = 10; 5.27-mg genistein and 17.56-mg daidzein aglycone equivalents per dose), or control (n = 10) group. After a run-in period {\textrangle}= 4 d, 3 doses of soy milk or soy supplements were taken daily for 5 d before an esthetic breast reduction. Blood and breast biopsies were collected during surgery and analyzed with liquid chromatography-tandem mass spectrometry.
Results: After soy administration, genistein and total daidzein concentrations, which were expressed as aglycone equivalents, ranged from 135.1 to 2831 nmol/L and 105.1 to 1397 nmol/L, respectively, in hydrolyzed serum and from 92.33 to 493.8 pmol/g and 22.15 to 770.8 pmol/g, respectively, in hydrolyzed breast tissue. The major metabolites identified in nonhydrolyzed samples were genistein-7-O-glucuronide and daidzein-7-O-glucuronide, with an overall glucuronidation of 98\%. Total isoflavones showed a breast adipose/glandular tissue distribution of 40: 60, and their mean (+/- SEM) derived 17 beta-estradiol equivalents toward estrogen receptor beta were 21 +/- 4-fold and 40 +/- 10-fold higher than the 17 beta-estradiol concentrations in adipose (0.283 +/- 6 0.089 pmol/g, P {\textlangle} 0.001) and glandular (0.246 +/- 0.091 pmol/g, P = 0.001) fractions, respectively.
Conclusion: After intake of soy milk and soy supplements, isoflavones reach exposure levels in breast tissue at which potential health effects may occur.},
  author       = {Bolca, Selin and Urpi-Sarda, Mireia and Blondeel, Phillip and Roche, Nathalie and Vanhaecke, Lynn and Possemiers, Sam and Al-Maharik, Nawaf and Botting, Nigel and De Keukeleire, Denis and Bracke, Marc and Heyerick, Arne and Manach, Claudine and Depypere, Herman},
  issn         = {0002-9165},
  journal      = {AMERICAN JOURNAL OF CLINICAL NUTRITION},
  keyword      = {MAMMARY-GLAND,MCF-7 TUMORS,STIMULATE GROWTH,AROMATASE ACTIVITIES,IN-VITRO,POSTMENOPAUSAL WOMEN,ESTROGEN-RECEPTOR-ALPHA,CANCER TUMORS,HUMAN URINE,PHYTOESTROGENS},
  language     = {eng},
  number       = {4},
  pages        = {976--984},
  title        = {Disposition of soy isoflavones in normal human breast tissue},
  url          = {http://dx.doi.org/10.3945/ajcn.2009.28854},
  volume       = {91},
  year         = {2010},
}

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