title: A soy, whey and caseinate blend extends postprandial skeletal muscle protein synthesis in rats.
abstract: OBJECTIVE
  Blends of dairy and soy protein are used in commercial sports nutrition products; however, no studies have systematically compared blends to isolated protein sources and their effects on muscle protein synthesis (MPS). Dairy whey protein (WP), soy protein isolate (SP), and two blends (Blend 1 and Blend 2) consisting of ratios of 50:25:25 and 25:50:25 for whey:caseinate:soy, respectively, were evaluated for their ability to affect MPS.
  
  
  METHODS
  Male Sprague-Dawley rats were trained to eat 3 meals/day: a 4 g meal at 0700-0720 hours followed by ad lib feeding at 1300-1400 hours and 1800-1900 hours. After ~5 days of training, fasted rats were administered their respective 4 g meal at 0700-0720 hours and an intravenous flooding dose of (2)H5-phenylalanine 10 min prior to euthanasia. Individual rats were euthanized at designated postprandial time points. Blood and gastrocnemius samples were collected and the latter was used to measure mixed muscle protein fractional synthetic rates (FSR).
  
  
  RESULTS
  Plasma leucine concentrations peaked in all groups at 90 min and were still above baseline at 300 min post-meal. FSR tended to increase in all groups post-meal but initial peaks of FSR were different times (45, 90 and 135 min for WP or SP, Blend 1 and Blend 2, respectively). Blend 2 had a significantly higher FSR compared to WP alone at 135 min (P < 0.05).
  
  
  CONCLUSIONS
  Single source proteins and protein blends all enhance skeletal MPS after a meal, however, Blend 2 had a delayed FSR peak which was significantly higher than whey protein at 135 min.
authors.affiliation: Solae, LLC, Global Nutrition, 4300 Duncan Ave, St Louis, MO 63110, USA. DButteig@solae.com
authors.forename: D N
authors.initials: DN
authors.lastname: Butteiger
authors.forename: M
authors.initials: M
authors.lastname: Cope
authors.forename: P
authors.initials: P
authors.lastname: Liu
authors.forename: R
authors.initials: R
authors.lastname: Mukherjea
authors.forename: E
authors.initials: E
authors.lastname: Volpi
authors.forename: B B
authors.initials: BB
authors.lastname: Rasmussen
authors.forename: E S
authors.initials: ES
authors.lastname: Krul
mesh_terms: D061605:Administration, Intravenous; D000818:Animals; D002364:Caseins / Q000008:administration & dosage; D007930:Leucine / Q000097:blood; D008297:Male; D008894:Milk Proteins / Q000008:administration & dosage*; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D010649:Phenylalanine / Q000008:administration & dosage / Q000097:blood; D019518:Postprandial Period / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D030262:Soybean Proteins / Q000008:administration & dosage*; D000067816:Whey Proteins
chemical_list: D002364:Caseins; D008894:Milk Proteins; D009124:Muscle Proteins; D030262:Soybean Proteins; D000067816:Whey Proteins; D010649:Phenylalanine; D007930:Leucine