Expression Analysis of Solute Carrier (SLC2A) Genes in Milk Derived Mammary Epithelial Cells during Different Stages of Lactation in Sahiwal (Bos indicus) Cows

Abstract

Solute carriers (SLC2A/ GLUT) are one of the major types of transporter superfamily that have been predominantly involved in active transport of glucose across the plasma membrane. Glucose uptake by mammary epithelial cells (MECs) is an important step in the milk synthesis during lactation, and hence directly influences the milk yield. Use of MEC isolated from milk has been speculated to be a good alternative to mammary gland tissues in order to understand the expression profile of important genes associated with lactation , in particular large dairy animals where obtaining biopsies is sometimes difficult. The present study was therefore undertaken in milk purified MECs to assess relative mRNA expression of major solute carriers/glucose transporters (SLC2A/GLUTs) viz., SLC2A1(GLUT1), SLC2A(GLUT4), SLC2A8(GLUT8), SLC2A12(GLUT12) and hexokinase (HK2) genes during; early(10-20 days), peak (30-50 days), mid (100-140 days) and late (215-245 days) lactation stages of Sahiwal cows . MECs were isolated from fresh milk, using Dyna Beads coated with anticytokeratin 18 antibodies. For normalization of qPCR expression data, 10 known housekeeping genes (HKGs) from different functional classes were evaluated. A panel of four best stable HKGs; eukaryotic translation elongation factor 1 alpha (EEF1A1), ribosomal protein L4(RPL4), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin-beta (ACTB) were identified through ge Norm, Norm Finder and Best Keeper analysis. Expression level of SLC2A1 was significantly (P<0.05) higher during peak/mid lactation period as compared to late lactation period. Similarly, SLC2A8 mRNA expression was relatively higher during mid-lactation stages than other stages of lactation. In contrast, SLC2A4 expression level was relatively higher during the late lactation stages. The SLC2A12 mRNA on the other hand was undetectable, indicating its expression to be either very low or absent in MEC of Sahiwal cows. Our expression data indicated SLC2A1, SLC2A4 and SLC2A8 to be the major solute carriers in Sahiwal MEC. Further, HK2 expression was significantly (P<0.05) higher during early and mid-lactation stages. The stage specific expression about of major SLC2A/GLUT and HK2 genes indicate their functional role in regulating glucose uptake in MECs of Sahiwal cows.

Genomewide Association Analyses of Lactation Persistency and Milk Production Traits in Holstein Cattle Based on Imputed Whole-Genome Sequence Data

“…SLC4A4 is a solute transporter, belonging to one of the major transporter superfamilies mostly involved in the active transport of glucose. Glucose uptake by mammary epithelial cells is a crucial stage in milk synthesis, and therefore, directly influences MILK [76]. Furthermore, NIM1K and ZNF131 have been reported to prolong lactation period culminating in higher milk production levels in Canadian dairy cattle [36].…”

Mammary fat globules as a source of mRNA to model alterations in the expression of some milk component genes during lactation in bovines

“…However, Mann et al [ 50 ] reported the same level of GLUT1 expression in both stages of lactation (early, peak). On the other hand, Pradeep et al [ 51 ] showed that GLUT1 gene expression was highest during the cows' peak lactation stage and lowest during the cows' early lactation stage. Compared to buffalo, GLUT1 gene expression was found to be higher in cows, as reported by both Yadav et al [ 30 ] and Pradeep et al [ 51 ].…”

“…On the other hand, Pradeep et al [ 51 ] showed that GLUT1 gene expression was highest during the cows' peak lactation stage and lowest during the cows' early lactation stage. Compared to buffalo, GLUT1 gene expression was found to be higher in cows, as reported by both Yadav et al [ 30 ] and Pradeep et al [ 51 ]. Since the quantity of milk produced is directly proportional to the amount of glucose absorbed by the alveolar epithelial cells of the mammary gland Pradeep et al [ 51 ], and since GLUT1 is the predominant glucose transporter that is responsible for glucose transmission in the mammary gland, the GLUT1 expression would be correlated with milk production throughout the two stages of lactation.…”