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Effect of the DGAT1 K232A genotype of dairy cows on the milk metabolome and proteome

Lu, Jing, Boeren, Sjef, van Hooijdonk, Toon, Vervoort, Jacques, Hettinga, Kasper
Journal of dairy science 2015 v.98 no.5 pp. 3460-3469
blood lipids, carnitine, cell membranes, choline, citrates, creatine, dairy cows, diacylglycerol acyltransferase, diacylglycerols, epithelial cells, fatty acid composition, genotype, lipid content, mammary glands, metabolites, metabolome, metabolomics, milk, milk fat, milk yield, orotic acid, phosphates, phosphocreatine, protein content, proteome, proteomics, sphingomyelins, sugars, tandem mass spectrometry, triacylglycerols, uridine diphosphate
Diglyceride O-acyltransferase 1 (DGAT1) is the enzyme that catalyzes the synthesis of triglycerides from diglycerides and acyl-coenzyme A. The DGAT1 K232A polymorphism was previously shown to have a significant influence on bovine milk production characteristics (milk yield, protein content, fat content, and fatty acid composition). The mechanism of this influence has, however, not been elucidated. In this study, metabolomics (1H-nuclear magnetic resonance) and proteomics (laser chromatography-tandem mass spectrometry) were applied to determine the serum and lipid metabolite composition and milk fat globule membrane proteome of milk samples from cows with the DGAT1 KK and AA genotypes. The milk samples from cows with the DGAT1 KK genotype contained more stomatin, sphingomyelin, choline, and carnitine, and less citrate, creatine or phosphocreatine, glycerol-phosphocholine, mannose-like sugar, acetyl sugar phosphate, uridine diphosphate (UDP)-related sugar, and orotic acid compared with milk samples from cows with the DGAT1 AA genotype. Based on these results, we propose that the differences between the DGAT1 genotypes may be related to stomatin-sphingomyelin lipid rafts as well as structural (cell membrane) differences in epithelial cells of the mammary gland. In conclusion, our study shows that, in addition to previously described changes in triglyceride composition, cows differing in DGAT1 polymorphism differ in their milk proteome and metabolome, which may help in further understanding the effect of the DGAT1 K232A polymorphism on milk production characteristics.