Dietary protein intake and stage of lactation differentially modulate amino acid transporter mRNA abundance in porcine mammary tissue
J Pérez Laspiur, JL Burton, PSD Weber, J Moore, RN Kirkwood, and NL Trottier, 2009, Journal of Nutrition, 139: 1677–1684.
23-Jun-2010 (15 years 11 months 13 days ago)Sow dietary AA supply below the requirement level depresses milk protein yield and subsequent neonatal pig growth. Likewise, excessive dietary AA supply depresses piglet growth and does so to a greater extent than that of dietary AA deficiency. These changes are accompanied by what seems to be some adaptive mechanisms whereby the mammary gland modulates the extraction rates of circulating AA in response to dietary AA availability. Therefore, to test the hypothesis that under restricted and surfeit protein intake the mammary gland undergoes adaptive regulation, changes in mammary tissue mRNA abundance of cationic amino acid (AA) transporter (CAT)-1, CAT-2B, alanine/serine/ cysteine/threonine transporter 1 (ASCT1), and broad specificity transporter for neutral and cationic AA (ATB0,+), and CAT- 1 protein abundance were investigated at 2 stages of lactation.
Eighteen sows were allocated to a 2 x 3 randomized incomplete block design with 2 stages of lactation (early and peak) and 3 protein levels: deficient (D), adequate (A), or in excess (E) of lactation requirement. In early lactation, compared with A, sows fed E had lower (P = 0.05) piglet growth rate and sows fed D or E had lower (P<0.05) casein yield. In early lactation, piglet growth rate and milk protein and casein yield increased from D to A and decreased from A to E (quadratic, P = 0.095, P < 0.05, and P<0.01, respectively). Protein intake did not affect CAT-1, ASCT1, ATB0,+ mRNA abundance, or CAT-1 protein level. Overall, CAT-2B mRNA abundance decreased linearly with increasing protein intake (P<0.05). Compared with A, E decreased CAT-2B mRNA abundance (P<0.05). Compared with early lactation, peak lactation did not increase CAT-1 mRNA abundance or relative CAT-1 protein content, but increased abundance of ASCT1 and ATB0,+ mRNA (P<0.01). Mammary CAT-2B appears to be adaptively regulated in vivo at the transcription level, whereas ASCT1 and ATB0,+ mRNA abundances are associated only with stage of lactation.
Neither protein intake nor stage of lactation affects porcine mammary CAT-1 gene expression in vivo.
Eighteen sows were allocated to a 2 x 3 randomized incomplete block design with 2 stages of lactation (early and peak) and 3 protein levels: deficient (D), adequate (A), or in excess (E) of lactation requirement. In early lactation, compared with A, sows fed E had lower (P = 0.05) piglet growth rate and sows fed D or E had lower (P<0.05) casein yield. In early lactation, piglet growth rate and milk protein and casein yield increased from D to A and decreased from A to E (quadratic, P = 0.095, P < 0.05, and P<0.01, respectively). Protein intake did not affect CAT-1, ASCT1, ATB0,+ mRNA abundance, or CAT-1 protein level. Overall, CAT-2B mRNA abundance decreased linearly with increasing protein intake (P<0.05). Compared with A, E decreased CAT-2B mRNA abundance (P<0.05). Compared with early lactation, peak lactation did not increase CAT-1 mRNA abundance or relative CAT-1 protein content, but increased abundance of ASCT1 and ATB0,+ mRNA (P<0.01). Mammary CAT-2B appears to be adaptively regulated in vivo at the transcription level, whereas ASCT1 and ATB0,+ mRNA abundances are associated only with stage of lactation.
Neither protein intake nor stage of lactation affects porcine mammary CAT-1 gene expression in vivo.