Substitution of mixed amino acids resembling soy protein for mixed amino acids resembling casein in the diet reduces plasma cholesterol in slowly, but not rapidly fed nor fasted baboons.
Studies of cholesterol and triglyceride metabolism were conducted under steady-state conditions in conscious restrained female baboons to ascertain whether the cholesterol- and triglyceride-lowering effects of soy protein v casein in nonrodents can be explained by differences in amino acid composition between the two proteins and whether the lipid-lowering effects of soy protein are influenced by fasting or the rate of feeding, ie, the nutritional state. The metabolic changes underlying the changes in serum cholesterol and triglyceride concentration were also investigated. Isocaloric diets consisting of 45% mixed amino acids (soy or casein type), 50% glucose and 5% corn oil, including all nutritional requirements, were infused intraduodenally for five days. There were no differences in lipid levels between the soy and casein diets in fasting baboons (days 4 or 5) or when the daily diet (calculated to equal 24 hours of energy utilization) was given rapidly by constant intraduodenal infusion over seven hours (day 4). During rapid feeding there was, unexpectedly, no significant change in plasma cholesterol concentration, but the estimated rate of cholesterol oxidation to bile acids fell significantly by 38 +/- 6% (from 39 +/- 4 to 24 +/- 3 mg/d). Significant differences between the soy and casein diets were observed only in the fed state produced by the slow constant isocaloric intraduodenal infusions of the diets [5.8 mg mixed amino acids (soy or casein type) plus 7.2 mg glucose/min/kg body wt0.75] on day 5. These diets were calculated to equal the simultaneous rate of energy utilization.(ABSTRACT TRUNCATED AT 250 WORDS)
D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002364:Caseins / Q000494:pharmacology*; D002784:Cholesterol / Q000097:blood*; D004044:Dietary Proteins / Q000494:pharmacology*; D005215:Fasting; D005260:Female; D007441:Intubation, Gastrointestinal; D009752:Nutritional Status; D010215:Papio; D014674:Plant Proteins, Dietary / Q000494:pharmacology*; D030262:Soybean Proteins; D014280:Triglycerides / Q000097:blood
D000596:Amino Acids; D001786:Blood Glucose; D002364:Caseins; D004044:Dietary Proteins; D014674:Plant Proteins, Dietary; D030262:Soybean Proteins; D014280:Triglycerides; D002784:Cholesterol