ACSL1, AGPAT6, FABP3, LPIN1, and SLC27A6 are the most abundant isoforms in bovine mammary tissue and their expression is affected by stage of lactation

The lactating bovine mammary gland is a formidable triacylglycerol- synthesizing machine and, as such, represents an ideal model for studying putative functions of distinct isoforms of solute carrier family 27 transporters [(SLC27A) 1, 2, 3, 5, 6], long chain acyl-CoA synthetases [(ACSL) 1, 3, 4, 5, 6], fatty acid binding proteins [(FABP) 1, 3, 4, 5, 6], 1-acylglycerol-3- phosphate O-acyltransferases [(AGPAT) 1, 2, 3, 4, 5, 6, 7, 8], and lipins [(LPIN) 1, 2, 3]. The relative percentage of mRNA abundance and fold-changes in the expression of isoforms in mammary tissue from 6 cows each at 215, 15, 60, and 240 d relative to parturition were analyzed using quantitative PCR. Transcripts of FABP isoforms were most abundant, accounting for 78% of the 28 genes measured, and SLC27A isoforms were least abundant (<0.5% of genes measured). mRNA of AGPAT, ACSL, and LPIN accounted for ∼12, 7, or ∼2%, respectively, of all genes measured. The mRNA abundance at 60 d postpartum for FABP3, ACSL1, AGPAT6, and LPIN1 was 80-, 7-, 15-, and 20-fold greater relative to 215 d. Transcripts of these isoforms constituted the most abundant within each specific gene family. SLC27A2, SLC27A5, and SLC27A6 had peak expression at 240, 240, or 15 d relative to parturition, respectively. Results suggest that SLC27A6, ACSL1, FABP3, AGPAT6, and LPIN1 coordinately regulate the channeling of fatty acids toward copious milk fat synthesis in bovine mammary.