title: Impact of prolonged leucine supplementation on protein synthesis and lean growth in neonatal pigs.
abstract: Most low-birth weight infants experience extrauterine growth failure due to reduced nutrient intake as a result of feeding intolerance. The objective of this study was to determine whether prolonged enteral leucine supplementation improves lean growth in neonatal pigs fed a restricted protein diet. Neonatal pigs (n = 14-16/diet, 5 days old, 1.8 ± 0.3 kg) were fed by gastric catheter a whey-based milk replacement diet with either a high protein (HP) or restricted protein (RP) content or RP supplemented with leucine to the same level as in the HP diet (RPL). Pigs were fed 40 ml·kg body wt(-1)·meal(-1) every 4 h for 21 days. Feeding the HP diet resulted in greater total body weight and lean body mass compared with RP-fed pigs (P < 0.05). Masses of the longissimus dorsi muscle, heart, and kidneys were greater in the HP- than RP-fed pigs (P < 0.05). Body weight, lean body mass, and masses of the longissimus dorsi, heart, and kidneys in pigs fed the RPL diet were intermediate to RP- and HP-fed pigs. Protein synthesis and mTOR signaling were increased in all muscles with feeding (P < 0.05); leucine supplementation increased mTOR signaling and protein synthesis rate in the longissimus dorsi (P < 0.05). There was no effect of diet on indices of protein degradation signaling in any tissue (P > 0.05). Thus, when protein intake is chronically restricted, the capacity for leucine supplementation to enhance muscle protein accretion in neonatal pigs that are meal-fed milk protein-based diets is limited.
authors.affiliation: United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Columbus
authors.affiliation: United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Julia
authors.initials: J
authors.lastname: Steinhoff-Wagner
authors.affiliation: United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Agus
authors.initials: A
authors.lastname: Suryawan
authors.affiliation: United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Hanh V
authors.initials: HV
authors.lastname: Nguyen
authors.affiliation: United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Adriana
authors.initials: A
authors.lastname: Hernandez-Garcia
authors.affiliation: United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: Marta L
authors.initials: ML
authors.lastname: Fiorotto
authors.affiliation: United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas tdavis@bcm.edu.
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Davis
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight / Q000187:drug effects*; D018753:Diet, Protein-Restricted; D019587:Dietary Supplements; D002149:Energy Intake; D006321:Heart / Q000187:drug effects* / Q000254:growth & development; D007668:Kidney / Q000187:drug effects* / Q000254:growth & development; D007930:Leucine / Q000494:pharmacology*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000254:growth & development; D009929:Organ Size / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects*; D011897:Random Allocation; D015398:Signal Transduction / Q000187:drug effects; D034421:Sus scrofa; D058570:TOR Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism
chemical_list: D058570:TOR Serine-Threonine Kinases; D007930:Leucine
keywords: mammalian target of rapamycin; muscle; newborn; protein degradation; protein synthesis