Branched-chain amino acid and lysine deficiencies exert different effects on mammary translational regulation.
Deficiencies and imbalances of specific group II essential amino acids (EAA) were created in lactating cows by an infusion subtraction protocol to explore effects on milk production and abundance and phosphorylation state of regulators of mRNA translation in the mammary glands. Five lactating cows on a diet of 11.2% crude protein were infused abomasally for 5d with saline, 563 g/d of a complete EAA mix, or EAA mixes without the branched-chain amino acids (BCAA), Leu, or Lys in a 5 × 5 Latin square design. Milk protein yield was stimulated by EAA infusion and returned to saline levels upon subtraction of BCAA, Leu, or Lys. Mammary abundance of phosphorylated S6K1 was measured as an indicator of mammalian target of rapamycin complex 1 (mTORC1) activity and was found not to be affected by the complete EAA mix but was increased by the mixture lacking Lys. Total S6K1 abundances in mammary tissue were elevated by complete and BCAA-lacking infusions. All of the EAA treatments except the one lacking BCAA upregulated mammary eIF2Bε and eIF2α abundances, which is stimulatory to global mRNA translation. Phosphorylation state of eIF2Bε tended to decrease when complete or Lys-lacking EAA mixtures were infused. Phosphorylation state of eIF2α was not affected by treatment. We detected a correlation of 0.62 between phosphorylation state of S6K1 and total eIF2Bε abundance, and a correlation of 0.58 between phosphorylation state of S6K1 and total eIF2α abundance, suggesting that mTORC1 activation may have upregulated eIF2Bε and eIF2α expression. Despite maintenance of mammary eIF2Bε and eIF2α abundances during Leu and Lys deficiencies, milk protein yield declined, suggesting that other factors are responsible for mediating effects of Lys and Leu. A deficiency of all 3 BCAA may impair milk protein yield through deactivation of mTORC1-mediated upregulation of eIF2Bε and eIF2α abundances.
Nutreco Canada Agresearch, Guelph, Ontario, N1G 4T2 Canada. Electronic address: john.doelman@nutreco.ca.
John
J
Doelman
Department of Animal BioSciences, University of Guelph, Guelph, Ontario, N1G 2W1 Canada.
Julie J M
JJ
Kim
Nutreco Canada Agresearch, Guelph, Ontario, N1G 4T2 Canada.
Michelle
M
Carson
Nutreco Canada Agresearch, Guelph, Ontario, N1G 4T2 Canada.
John A
JA
Metcalf
Department of Animal BioSciences, University of Guelph, Guelph, Ontario, N1G 2W1 Canada.
John P
JP
Cant
D000018:Abomasum / Q000378:metabolism; D000597:Amino Acids, Branched-Chain / Q000172:deficiency*; D000601:Amino Acids, Essential / Q000008:administration & dosage; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000008:administration & dosage; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics; D020717:Eukaryotic Initiation Factor-2B / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D007774:Lactation / Q000502:physiology; D008239:Lysine / Q000172:deficiency*; D008321:Mammary Glands, Animal / Q000737:chemistry / Q000378:metabolism*; D000076222:Mechanistic Target of Rapamycin Complex 1; D008892:Milk / Q000737:chemistry; D008894:Milk Proteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D046912:Multiprotein Complexes / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000235:genetics*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000032:analysis; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
D000597:Amino Acids, Branched-Chain; D000601:Amino Acids, Essential; D004044:Dietary Proteins; D015852:Eukaryotic Initiation Factor-2; D020717:Eukaryotic Initiation Factor-2B; D008894:Milk Proteins; D046912:Multiprotein Complexes; D000076222:Mechanistic Target of Rapamycin Complex 1; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; D008239:Lysine
amino acid; branched-chain amino acids; mammary gland; milk protein; translation