A cooperative interaction between soy protein and its isoflavone-enriched fraction lowers hepatic lipids in male obese Zucker rats and reduces blood platelet sensitivity in male Sprague-Dawley rats.
Soy protein diets lower plasma cholesterol in hyperlipoproteinemic human subjects, as well as in animal models. We fed 7-wk-old male obese (fa/fa) and lean Zucker rats a modified AIN-76 diet (20 g protein/kg diet) containing casein (C), low isoflavone soy protein (38 mg isoflavones/kg diet; LI), or high isoflavone soy protein (578 mg isoflavones/kg diet; HI) for 70 d. In obese rats, plasma total cholesterol was 21 and 29% lower in the LI and HI groups, respectively, than in the C group (P: </= 0.004). Liver weight and liver triglyceride and cholesteryl ester concentrations were 27, 33 and 46% lower, respectively, in the LI group than in the C group (P: < 0.003). These liver measurements were 23, 24 and 57% lower, respectively, in the HI group than in the LI group (P: < 0.05). In a complementary study, 5-wk-old male Sprague-Dawley rats were fed the same C, LI and HI diets for 42 d. Thrombin-mediated platelet serotonin release in vitro was 13% lower in the HI group than in the C group (P: = 0.003). In a third study, 7-wk-old male Sprague-Dawley rats were fed either a modified AIN-76 control diet or a high fat casein-based atherogenic diet (140 g fat, 12 g cholesterol, and 2 g cholic acid/kg diet) with or without a soy isoflavones extract (983 mg isoflavones/kg diet) for 63 d. Addition of the isoflavones extract to the atherogenic diet lowered the liver triglyceride concentration by 33% relative to the atherogenic diet without isoflavones (P: = 0.0001). Our studies suggest that the hypocholesterolemic mechanism of dietary soy protein involves a cooperative interaction between the protein and isoflavone-enriched fraction that lowers hepatic lipid concentrations. We speculate that modulation of liver and plasma lipid homeostasis can also lower blood platelet sensitivity.
Peluso
M R
MR
Department of Animal Science, Food and Nutrition, Southern Illinois University, Carbondale, IL 62901, USA.
Winters
T A
TA
Shanahan
M F
MF
Banz
W J
WJ
D000704:Analysis of Variance; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D002784:Cholesterol / Q000097:blood*; D004036:Diet, Atherogenic; D004347:Drug Interactions; D007529:Isoflavones / Q000008:administration & dosage / Q000494:pharmacology*; D050356:Lipid Metabolism; D008055:Lipids / Q000097:blood; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011924:Rats, Zucker; D030262:Soybean Proteins / Q000008:administration & dosage / Q000494:pharmacology*
D007529:Isoflavones; D008055:Lipids; D030262:Soybean Proteins; D002784:Cholesterol