title: Body weight and energy homeostasis was not affected in C57BL/6 mice fed high whey protein or leucine-supplemented low-fat diets.
abstract: BACKGROUND
  Leucine is suggested to act as nutrient signal of high-protein diets regulating pathways associated with an alleviation of metabolic syndrome parameters. However, the subject remains controversial.
  
  
  OBJECTIVE
  The aim of this study was to assess and to compare the effects of high-protein diets with dietary leucine supplementation in mice, particularly on energy homeostasis, body composition, and expression of uncoupling protein (UCP), which are suggested to decrease food energy efficiency.
  
  
  METHODS
  Male C57BL/6 mice were exposed for 14 weeks to semi-synthetic diets containing either 20% (adequate protein content, AP) or 50% whey protein (high-protein content, HP). A third group was fed the AP diet supplemented with L-leucine (AP + L) corresponding to the leucine content of the HP diet. The total fat content was 5% (w/w).
  
  
  RESULTS
  Body weight gain, body composition, energy expenditure, and protein expression of UCP1 in brown adipose tissue, and UCP3 in skeletal muscle were not different between groups. In HP-fed mice, a stronger increase in blood glucose levels was detected during glucose tolerance tests compared to AP and AP + L, whereas plasma insulin was similar in all groups. Leucine supplementation did not affect glucose tolerance. Plasma cholesterol was significantly decreased in HP and AP + L when compared to AP. Plasma triglyceride concentrations were increased twofold in HP-fed mice when compared to AP + L and AP groups. Liver and skeletal muscle triglyceride and glycogen concentrations were similar in all groups. Postabsorptive plasma concentrations of branched-chain amino acids were not significantly increased after exposure to HP and AP + L diets, whereas those of lysine were decreased in HP and AP + L mice when compared to AP (P < 0.001). Plasma methionine concentrations were lower after HP intake when compared to AP and AP + L (P < 0.05).
  
  
  CONCLUSIONS
  We suggest that an exposure of mice to HP diets or a corresponding leucine supplementation has no significant effect on energy homeostasis and UCP expression compared with AP diets when feeding a low-fat diet. The use of high-quality whey protein might at least in part explain the results obtained.
authors.affiliation: German Institute of Human Nutrition in Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Noatsch
authors.forename: Klaus J
authors.initials: KJ
authors.lastname: Petzke
authors.forename: Marion K
authors.initials: MK
authors.lastname: Millrose
authors.forename: Susanne
authors.initials: S
authors.lastname: Klaus
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D018752:Diet, Fat-Restricted; D019587:Dietary Supplements; D004734:Energy Metabolism; D018149:Glucose Intolerance / Q000209:etiology / Q000517:prevention & control; D006706:Homeostasis; D006937:Hypercholesterolemia / Q000209:etiology / Q000517:prevention & control; D007473:Ion Channels / Q000378:metabolism; D007930:Leucine / Q000627:therapeutic use*; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D051379:Mice; D008810:Mice, Inbred C57BL; D008894:Milk Proteins / Q000008:administration & dosage / Q000627:therapeutic use*; D024101:Mitochondrial Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D011897:Random Allocation; D000071256:Uncoupling Protein 1; D000071247:Uncoupling Protein 3; D000067816:Whey Proteins
chemical_list: D001786:Blood Glucose; D007473:Ion Channels; D008894:Milk Proteins; D024101:Mitochondrial Proteins; C000604371:UCP1 protein, human; C000604392:UCP3 protein, human; C000604372:Ucp1 protein, mouse; C000604393:Ucp3 protein, mouse; D000071256:Uncoupling Protein 1; D000071247:Uncoupling Protein 3; D000067816:Whey Proteins; D007930:Leucine