Soy protein with isoflavones, but not an isoflavone-rich supplement, improves arterial low-density lipoprotein metabolism and atherogenesis.
OBJECTIVE
We sought to determine if arterial LDL metabolism contributes to the decreased atherosclerosis seen with soy and if isolated isoflavones would have similar effects.


RESULTS
Ovariectomized monkeys were fed an atherogenic diet for 20 weeks with a protein source of (1) casein/lactalbumin (CAS, n=20), (2) soy protein isolate (SOY, n=20), or (3) casein/lactalbumin with isolated soy isoflavones (ISO, n=17). Plasma lipoprotein concentrations were improved with SOY but not ISO. Arterial LDL metabolism was characterized with one subset (n=12/group) injected with dual-labeled tyramine-cellobiose (TC)-LDL (125I-TC-131I-LDL) 24 hours before necropsy to determine LDL degradation and accumulation, while another subset (n=8/group) was injected with 125I-TC-LDL 1 hour before necropsy to determine LDL permeability and delivery.


CONCLUSIONS
Coronary artery LDL degradation was reduced by 50% (P=0.02) with SOY but not with ISO compared with CAS. Neither treatment altered arterial permeability. Reduced LDL degradation with SOY was due to decreased arterial LDL delivery (P=0.02). Carotid artery cholesterol ester was also decreased with SOY, but not with ISO. Plasma isoprostanes or plasma markers of inflammation did not differ among treatment groups. Thus, the decreased arterial LDL delivery and subsequent LDL degradation may explain, in part, the atheroprotective effects of soy.
Wake Forest University Medical Center, Winston-Salem, NC, USA. jwagner@wfubmc.edu
Janice D
JD
Wagner
Dawn C
DC
Schwenke
Kathryn A
KA
Greaves
Li
L
Zhang
Mary S
MS
Anthony
Robert M
RM
Blair
Melanie K
MK
Shadoan
J Koudy
JK
Williams
D000818:Animals; D001161:Arteriosclerosis / Q000178:diet therapy / Q000517:prevention & control*; D015415:Biomarkers / Q000097:blood; D002784:Cholesterol / Q000097:blood; D019587:Dietary Supplements; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology; D005260:Female; D007529:Isoflavones / Q000008:administration & dosage* / Q000378:metabolism / Q000627:therapeutic use*; D028421:Isoprostanes / Q000097:blood; D008055:Lipids / Q000097:blood; D008074:Lipoproteins / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood* / Q000378:metabolism*; D008252:Macaca fascicularis; D030262:Soybean Proteins / Q000627:therapeutic use*
D015415:Biomarkers; D007529:Isoflavones; D028421:Isoprostanes; D008055:Lipids; D008074:Lipoproteins; D008077:Lipoproteins, LDL; D030262:Soybean Proteins; C065753:isoflavanone; D002784:Cholesterol