title: Soy protein reduces triglyceride levels and triglyceride fatty acid fractional synthesis rate in hypercholesterolemic subjects.
abstract: To examine the effects of protein source and isoflavones on triglyceride (TG) fatty acid (TGFA) and cholesterol biosynthesis, subjects (>50 years, LDL cholesterol >130 mg/dl) underwent a four-phase randomized cross-over feeding trial. Diets contained either isolated soy protein or common sources of animal protein (25 g/1000 kcal), without or with isoflavones (49 mg/1000 kcal) and were each fed for 6 weeks. Blood samples from 20 hyperlipidemic subjects (6M, 14F, 62 +/- 9 years, BMI 26 +/- 3 kg/m(2), LDL cholesterol >160 mg/dl after feeding animal protein without isoflavones) were selected to measure TGFA fractional synthetic rate (TGFA-FSR) and free cholesterol fractional synthetic rate (FC-FSR) over 24h as deuterium oxide uptake into TGFA and free cholesterol. Soy protein reduced TG by 12.4% (P < 0.0001), total cholesterol by 4.4% (P < 0.001), and LDL cholesterol by 5.7% (P = 0.003) compared to animal protein. The TGFA-FSR was reduced by 13.3% (P = 0.018) and FC-FSR was increased by 7.6% (P = 0.017) after the soy protein relative to the animal protein. Isoflavones had no significant effect on TG and TGFA-FSR. Isoflavones reduced total cholesterol levels by 3.1% (P = 0.009) but had no significant effect on LDL, HDL cholesterol levels, or FC-FSR. These data demonstrate that dietary protein type modulates circulating TG and cholesterol levels in hypercholesterolemic individuals by distinct mechanisms.
authors.affiliation: School of Dietetics and Human Nutrition, Macdonald Campus of McGill University, Ste-Anne-de-Bellevue, QE, Canada H9X 3V.
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Wang
authors.forename: Peter J H
authors.initials: PJ
authors.lastname: Jones
authors.forename: Lynne M
authors.initials: LM
authors.lastname: Ausman
authors.forename: Alice H
authors.initials: AH
authors.lastname: Lichtenstein
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D005227:Fatty Acids / Q000096:biosynthesis*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006937:Hypercholesterolemia / Q000175:diagnosis / Q000628:therapy*; D007529:Isoflavones / Q000008:administration & dosage*; D008075:Lipoproteins, HDL / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011336:Probability; D012016:Reference Values; D012720:Severity of Illness Index; D030262:Soybean Proteins / Q000008:administration & dosage*; D016896:Treatment Outcome; D014280:Triglycerides / Q000096:biosynthesis*
chemical_list: D005227:Fatty Acids; D007529:Isoflavones; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D030262:Soybean Proteins; D014280:Triglycerides