title: Expression of genes involved in hepatic carnitine synthesis and uptake in dairy cows in the transition period and at different stages of lactation.
abstract: BACKGROUND
  In rodents and pigs, it has shown that carnitine synthesis and uptake of carnitine into cells are regulated by peroxisome proliferator-activated receptor α (PPARA), a transcription factor which is physiologically activated during fasting or energy deprivation. Dairy cows are typically in a negative energy balance during early lactation. We investigated the hypothesis that genes of carnitine synthesis and uptake in dairy cows are enhanced during early lactation.
  
  
  RESULTS
  mRNA abundances of PPARA and some of its classical target genes and genes involved in carnitine biosynthesis [trimethyllysine dioxygenase (TMLHE), 4-N-trimethylaminobutyraldehyde dehydrogenase (ALDH9A1), γ-butyrobetaine dioxygenase (BBOX1)] and uptake of carnitine [novel organic cation transporter 2 (SLC22A5)] as well as carnitine concentrations in liver biopsy samples of 20 dairy cows in late pregnancy (3 wk prepartum) and early lactation (1 wk, 5 wk, 14 wk postpartum) were determined. From 3 wk prepartum to 1 wk postpartum, mRNA abundances of PPARΑ and several PPARΑ target genes involved in fatty acid uptake, fatty acid oxidation and ketogenesis in the liver were strongly increased. Simultaneously, mRNA abundances of enzymes of carnitine synthesis (TMLHE: 10-fold; ALDH9A1: 6-fold; BBOX1: 1.8-fold) and carnitine uptake (SLC22A5: 13-fold) and the concentration of carnitine in the liver were increased from 3 wk prepartum to 1 wk postpartum (P < 0.05). From 1 wk to 5 and 14 wk postpartum, mRNA abundances of these genes and hepatic carnitine concentrations were declining (P < 0.05). There were moreover positive correlations between plasma concentrations of non-esterified fatty acids (NEFA) and hepatic carnitine concentrations at 1 wk, 5 wk and 14 wk postpartum (P < 0.05).
  
  
  CONCLUSIONS
  The results of this study show for the first time that the expression of hepatic genes of carnitine synthesis and cellular uptake of carnitine is enhanced in dairy cows during early lactation. These changes might provide an explanation for increased hepatic carnitine concentrations observed in 1 wk postpartum and might be regarded as a physiologic means to provide liver cells with sufficient carnitine required for transport of excessive amounts of NEFA during a negative energy balance.
authors.affiliation: Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-Universität Giessen, Giessen, Germany.
authors.forename: Gloria
authors.initials: G
authors.lastname: Schlegel
authors.forename: Janine
authors.initials: J
authors.lastname: Keller
authors.forename: Frank
authors.initials: F
authors.lastname: Hirche
authors.forename: Stefanie
authors.initials: S
authors.lastname: Geissler
authors.forename: Frieder J
authors.initials: FJ
authors.lastname: Schwarz
authors.forename: Robert
authors.initials: R
authors.lastname: Ringseis
authors.forename: Gabriele I
authors.initials: GI
authors.lastname: Stangl
authors.forename: Klaus
authors.initials: K
authors.lastname: Eder
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002331:Carnitine / Q000097:blood / Q000378:metabolism*; D002417:Cattle / Q000235:genetics* / Q000378:metabolism; D004435:Eating / Q000502:physiology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D007774:Lactation / Q000235:genetics* / Q000378:metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008892:Milk / Q000737:chemistry; D027701:Organic Cation Transport Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D047493:PPAR alpha / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D012044:Regression Analysis; D050563:gamma-Butyrobetaine Dioxygenase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism
chemical_list: D027701:Organic Cation Transport Proteins; D047493:PPAR alpha; D012333:RNA, Messenger; D050563:gamma-Butyrobetaine Dioxygenase; C023095:4-N-trimethylaminobutyraldehyde dehydrogenase; D000445:Aldehyde Oxidoreductases; D002331:Carnitine