The α' subunit of β-conglycinin and various glycinin subunits of soy are not required to modulate hepatic lipid metabolism in rats.
OBJECTIVE
This study examined the effect of soy proteins with depletion of different subunits of the two major storage proteins, β-conglycinin and glycinin, on hepatic lipids and proteins involved in lipid metabolism in rats, since the bioactive component of soy responsible for lipid-lowering is unclear.


METHODS
Weanling Sprague Dawley rats were fed diets containing either 20% casein protein in the absence (casein) or presence (casein + ISF) of isoflavones or 20% alcohol-washed soy protein isolate (SPI) or 20% soy protein concentrates derived from a conventional (Haro) or 2 soybean lines lacking the α' subunit of β-conglycinin and the A1-3 (1TF) or A1-5 (1a) subunits of glycinin. After 8 weeks, the rats were necropsied and liver proteins and lipids were extracted and analysed.


RESULTS
The results showed that soy protein diets reduced lipid droplet accumulation and content in the liver compared to casein diets. The soy protein diets also decreased the level of hepatic mature SREBP-1 and FAS in males, with significant decreases in diets 1TF and 1a compared to the casein diets. The effect of the soy protein diets on female hepatic mature SREBP-1, FAS, and HMGCR was confounded since casein + ISF decreased these levels compared to casein alone perhaps muting the decrease by soy protein. A reduction in both phosphorylated and total STAT3 in female livers by ISF may account for the gender difference in mechanism in the regulation and protein expression of the lipid modulators.


CONCLUSIONS
Overall, soy protein deficient in the α' subunit of β-conglycinin and A1-5 subunits of glycinin maintain similar hypolipidemic function compared to the conventional soy protein. The exact bioactive component(s) warrant identification.
Nutrition Research Division, Food Directorate, Health Products and Food Branch, Health Canada, Banting Research Centre, 251 Sir Frederick Banting Drive, Ottawa, ON, K1A 0K9, Canada.|Ottawa Research & Development Centre, Central Experimental Farm, Agriculture and Agri-Food Canada, 960 Carling Avenue Building#21, Ottawa, ON, K1A 0C6, Canada.
Cynthia
C
Chatterjee
Nutrition Research Division, Food Directorate, Health Products and Food Branch, Health Canada, Banting Research Centre, 251 Sir Frederick Banting Drive, Ottawa, ON, K1A 0K9, Canada.
Jiajie
J
Liu
Nutrition Research Division, Food Directorate, Health Products and Food Branch, Health Canada, Banting Research Centre, 251 Sir Frederick Banting Drive, Ottawa, ON, K1A 0K9, Canada.
Carla
C
Wood
Ottawa Research & Development Centre, Central Experimental Farm, Agriculture and Agri-Food Canada, 960 Carling Avenue Building#21, Ottawa, ON, K1A 0C6, Canada.
Christine
C
Gagnon
Ottawa Research & Development Centre, Central Experimental Farm, Agriculture and Agri-Food Canada, 960 Carling Avenue Building#21, Ottawa, ON, K1A 0C6, Canada.
Elroy R
ER
Cober
Ottawa Research & Development Centre, Central Experimental Farm, Agriculture and Agri-Food Canada, 960 Carling Avenue Building#21, Ottawa, ON, K1A 0C6, Canada.
Judith A
JA
Frégeau-Reid
Ottawa Research & Development Centre, Central Experimental Farm, Agriculture and Agri-Food Canada, 960 Carling Avenue Building#21, Ottawa, ON, K1A 0C6, Canada.
Stephen
S
Gleddie
Nutrition Research Division, Food Directorate, Health Products and Food Branch, Health Canada, Banting Research Centre, 251 Sir Frederick Banting Drive, Ottawa, ON, K1A 0K9, Canada. chaowu.xiao@hc-sc.gc.ca.|Food and Nutrition Science Program, Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada. chaowu.xiao@hc-sc.gc.ca.
Chao-Wu
CW
Xiao
D000818:Animals; D052179:Antigens, Plant / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D002364:Caseins / Q000009:adverse effects; D059305:Diet, High-Fat / Q000009:adverse effects; D005260:Female; D030841:Food, Genetically Modified; D005916:Globulins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D006949:Hyperlipidemias / Q000209:etiology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D066292:Lipid Droplets / Q000378:metabolism / Q000473:pathology; D050356:Lipid Metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D010766:Phosphorylation; D014674:Plant Proteins, Dietary / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D017207:Rats, Sprague-Dawley; D050796:STAT3 Transcription Factor / Q000378:metabolism; D055314:Seed Storage Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D012727:Sex Characteristics; D030262:Soybean Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D014617:Vacuoles / Q000473:pathology; D014886:Weaning
D052179:Antigens, Plant; D002364:Caseins; D005916:Globulins; D014674:Plant Proteins, Dietary; D021122:Protein Subunits; D050796:STAT3 Transcription Factor; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C494088:Stat3 protein, rat; C013894:beta-conglycinin protein, Glycine max; C011474:glycinin
Glycinin; Lipid metabolism; Liver; Metabolic disease; Rats; Soy protein; β-Conglycinin