title: Positive net movements of amino acids in the hindlimb after overnight food deprivation contribute to sustaining the elevated anabolism of neonatal pigs.
abstract: During the neonatal period, high protein breakdown rate is a metabolic process inherent to elevated rates of protein accretion in skeletal muscle. To determine the relationship between hindlimb net movements of essential and nonessential amino acids in the regulation of hindlimb protein breakdown during an overnight fasting-feeding cycle, we infused overnight-food-deprived 10- and 28-day-old piglets with [1-(13)C]phenylalanine and [ring-(2)H(4)]tyrosine over 7 h (during 3 h of fasting and then during 4 h of feeding). Extraction rates for aspartate and glutamate after an overnight fast were 15% and 51% in the 10-day-old compared with 6% and 25% in the 28-day-old (P < 0.05) piglets, suggesting an altered requirement for precursors of amino acids to shuttle nitrogen to the liver as early life progresses. This occurred simultaneously with marginal positive hindlimb net balance of essential amino acids after an overnight fast, with negative net release of many nonessential amino acids, such as alanine, asparagine, glutamine, glycine, and proline. This suggests that newborn muscle does not undergo significant protein mobilization after a short period of fasting in support of an elevated rate of protein accretion. Furthermore, tyrosine efflux from hindlimb breakdown between overnight fasting and feeding periods was not different in the 10-day-old piglets, for which tyrosine was limiting, but when tyrosine supply balanced requirements in the 28-day-old piglet, hindlimb efflux was increased (P = 0.01). The results of the present study indicate that proteolysis and net movements of amino acids are coordinated mechanisms that sustain the elevated rate of net protein accretion during overnight feeding-fasting cycles in the neonate.
authors.affiliation: Rowett Institute of Nutrition and Health, Greenburn Rd., Bucksburn, Aberdeen AB21 9SB, UK. c.thivierge@rowett.ac.uk
authors.forename: M Carole
authors.initials: MC
authors.lastname: Thivierge
authors.forename: Jill A
authors.initials: JA
authors.lastname: Bush
authors.forename: Agus
authors.initials: A
authors.lastname: Suryawan
authors.forename: Hanh V
authors.initials: HV
authors.lastname: Nguyen
authors.forename: Renan A
authors.initials: RA
authors.lastname: Orellana
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Burrin
authors.forename: Farook
authors.initials: F
authors.lastname: Jahoor
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Davis
mesh_terms: D000465:Algorithms; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D002404:Catheterization; D004435:Eating / Q000502:physiology; D005508:Food Deprivation / Q000502:physiology*; D006614:Hindlimb / Q000254:growth & development / Q000378:metabolism; D007700:Kinetics; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000378:metabolism*; D013552:Swine; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000596:Amino Acids; D014443:Tyrosine
references.citation: Am J Physiol Endocrinol Metab. 2006 Apr;290(4):E612-21
references.pmid: 16278252
references.citation: Am J Physiol Endocrinol Metab. 2005 Oct;289(4):E678-83
references.pmid: 15914508
references.citation: J Lipid Res. 2007 Nov;48(11):2396-410
references.pmid: 17673528
references.citation: J Clin Endocrinol Metab. 2000 Dec;85(12):4481-90
references.pmid: 11134097
references.citation: Am J Physiol Endocrinol Metab. 2001 Sep;281(3):E472-8
references.pmid: 11500302
references.citation: Am J Physiol Endocrinol Metab. 2001 Nov;281(5):E908-15
references.pmid: 11595645
references.citation: J Nutr. 2002 Jan;132(1):59-67
references.pmid: 11773509
references.citation: Am J Physiol Endocrinol Metab. 2002 Apr;282(4):E880-90
references.pmid: 11882508
references.citation: Am J Physiol Endocrinol Metab. 2003 Jan;284(1):E110-9
references.pmid: 12388131
references.citation: Am J Physiol Endocrinol Metab. 2003 Feb;284(2):E302-12
references.pmid: 12388127
references.citation: Br J Nutr. 2003 Feb;89(2):167-79
references.pmid: 12575901
references.citation: J Nutr. 2003 Jun;133(6 Suppl 1):2068S-2072S
references.pmid: 12771367
references.citation: Br J Nutr. 1970 Jun;24(2):557-64
references.pmid: 5452705
references.citation: Am J Physiol. 1972 Aug;223(2):447-54
references.pmid: 5046760
references.citation: J Biol Chem. 1978 May 25;253(10):3677-84
references.pmid: 649595
references.citation: J Biol Chem. 1978 May 25;253(10):3685-93
references.pmid: 649596
references.citation: Biochem J. 1984 Jan 15;217(2):507-16
references.pmid: 6199020
references.citation: Biochem J. 1985 Jul 1;229(1):19-29
references.pmid: 3899101
references.citation: Biochem J. 1986 Feb 1;233(3):621-30
references.pmid: 3085650
references.citation: Am J Physiol. 1990 Oct;259(4 Pt 1):E477-82
references.pmid: 2221049
references.citation: J Nutr. 1992 Mar;122(3):457-66
references.pmid: 1542004
references.citation: Am J Physiol. 1993 Aug;265(2 Pt 2):R334-40
references.pmid: 8368387
references.citation: Am J Physiol. 1995 Aug;269(2 Pt 1):E361-7
references.pmid: 7653553
references.citation: Pediatr Res. 1996 Jul;40(1):41-6
references.pmid: 8798244
references.citation: Am J Physiol. 1997 Apr;272(4 Pt 1):E592-9
references.pmid: 9142879
references.citation: Am J Physiol. 1997 Aug;273(2 Pt 1):E305-14
references.pmid: 9277383
references.citation: J Nutr. 1998 Feb;128(2 Suppl):347S-350S
references.pmid: 9478022
references.citation: Diabetes. 1999 May;48(5):949-57
references.pmid: 10331397
references.citation: Am J Clin Pathol. 1954 Sep;24(9):1016-24
references.pmid: 13197333
references.citation: J Nutr. 2005 Jun;135(6):1430-7
references.pmid: 15930448
references.citation: Am J Physiol Endocrinol Metab. 2006 Oct;291(4):E849-59
references.pmid: 16757550