THE EFFECT OF ISOLATED SOY PROTEIN ON PLASMA BIOMARKERS IN ELDERLY MEN WITH ELEVATED SERUM PROSTATE SPECIFIC ANTIGEN
Abstract
Purpose:
We performed a randomized double-blind crossover pilot study in elderly men with elevated prostate specific antigen (PSA) on the effects of the daily consumption of 2 soy beverages, each containing 20 gm. of isolated soy protein, on the isoflavone concentration in blood and urine, and on the 3 serum biomarkers cholesterol, PSA and the soluble p105 component of the p185erbB-2 proto-oncogene.
Materials and Methods:
A total of 34 men supplemented their diet by consuming 1 of 2 soy protein beverages assigned randomly twice daily for a 6-week period. In a second 6-week period they consumed the other soy protein beverage. The beverage ISP+ provided 42 mg. of genistein and 27 mg. of daidzein daily, whereas the other beverage, ISP−, provided only 2.1 and 1.3 mg. of these isoflavones daily, respectively. Blood and 24-hour urine samples were obtained before the study, at 2-week intervals during the study and 2 weeks after study completion.
Results:
ISP+ and to a lesser extent ISP− substantially increased the serum concentration and urinary output of the isoflavones and their metabolites. Serum cholesterol was significantly decreased by ISP+ irrespective of the order in which the 2 soy beverages were administered and in apparent correlation with the total isoflavone concentration. There was no significant effect of the soy beverages on serum PSA and p105erbB-2 values.
Conclusions:
This study reveals that short-term exposure of elderly men with elevated serum PSA values to soy protein containing isoflavones decreases serum cholesterol but not the serum biomarkers PSA and p105erbB-2.
References
- 1 : Cancer statistics, 1996. CA Cancer J Clin,1996; 65: 5. Google Scholar
- 2 : A prospective study of demographics, diet and prostate cancer among men of Japanese ancestry in Hawaii. Cancer Res,1989; 49: 1857. Google Scholar
- 3 : A case-control study of prostatic cancer with reference to dietary habits. Prostate,1988; 12: 179. Google Scholar
- 4 : Genistein, daidzein, and their β-glycoside conjugates: antitumor isoflavones in soybean foods from American and Asian diets. J Agric Food Chem,1993; 41: 1461. Google Scholar
- 5 :
Adenocarcinoma of the prostate . In: . Edited by . Philadelphia: W. B. Saunders1992: 1159. Google Scholar - 6 : Soy intake and cancer risk: a review of in vitro and in vivo data. Nutr Cancer,1994; 21: 113. Google Scholar
- 7 : Genistein inhibits the growth of human-patient BPH and prostate cancer in histoculture. Prostate,1998; 34: 75. Google Scholar
- 8 : Genistein, a component of soy, inhibits the expression of the EGF and ErbB/Neu receptors in the rat dorsolateral prostate. Prostate,1998; 37: 36. Google Scholar
- 9 : Influence of isoflavones in soy protein isolates on development of induced prostate-related cancers in L-W rats. Nutr Cancer1997; 28: 41. Google Scholar
- 10 : Genistein and biochanin A inhibit the growth of human prostate cancer cells, but not epidermal growth factor receptor tyrosine auto-phosphorylation. Prostate1993; 22: 333. Google Scholar
- 11 : Isoflavones and their conjugates in soy foods: extraction conditions and analysis by HPLC-mass spectrometry. J Agric Food Chem1994; 42: 2466. Google Scholar
- 12 : Elevated serum levels of p105erbb-2 in patients with advanced stage prostatic adenocarcinoma. Int J Cancer (Pred Oncol),1996; 69: 398. Google Scholar
- 13 Synchron LX Systems Chemistry Information Manual. XXX. Google Scholar
- 14 : Analysis of plasma isoflavones by reversed-phase hplc-multiple reaction ion monitoring-mass spectrometry. Clin Chim Acta,1996; 247: 121. Google Scholar
- 15 : HPLC-mass spectrometry analysis of isoflavones. Proc Soc Exp Biol Med1998; 217: 254. Google Scholar
- 16 : Nonparametic Statistics for the Behavioral Sciences. New York: McGraw-Hill1988. Google Scholar
- 17 : Meta-analysis of the effects of soy protein intake on serum lipids. New Engl J Med1995; 333: 276. Google Scholar
- 18 : A randomized trial comparing the effect of casein with that of soy protein containing varying amounts of isoflavones on plasma concentrations of lipids and lipoproteins. Arch Intern Med,1999; 159: 2070. Google Scholar
- 19 : Total serum cholesterol and ischemic heart disease risk in clinical trials and observational studies. Am J Prevent Med1985; 1: 18. Google Scholar
- 20 : Isoflavones reduce plasma cholesterol and atherosclerosis in C57BL/6 mice but not LDL receptor-deficient mice. J Nutr,1998; 128: 954. Google Scholar
- 21 : Role of isoflavones in the cholesterol reduction by soy proteins in the clinic. Am J Clin Nutr,1997; 65: 166. Google Scholar
- 22 : Intake of soy protein and soy protein extracts influences lipid metabolism and hepatic gene expression in gerbils. J Nutr,1998; 128: 839. Google Scholar
- 23 : Soy protein and cardiovascular disease: the impact of bioactive components in soy. Nutr Rev1998; 56: 231. Google Scholar
- 24 : Effects of soybean isoflavones on cell growth and apoptosis of the human prostatic cancer cell line LNCaP. Jpn J Clin Oncol,1998; 28: 360. Google Scholar
- 25 : Soybean phytochemicals inhibit the growth of transplantable human prostate carcinoma and tumor angiogenesis in mice. J Nutr,1999; 129: 1628. Google Scholar
- 26 : Phytoestrogens and prostate cancer: possible preventive role. Med J Austr1997; 167: 138. Google Scholar
From the Division of Urology, Departments of Surgery, Pathology and Pharmacology and Toxicology, and Biostatistics Unit and Mass Spectrometry Shared Facility, Comprehensive Cancer Center, University of Alabama at Birmingham and Pharmacy Department, University of Alabama Hospital, Birmingham, Alabama
