Choline and methionine differentially alter methyl carbon metabolism in bovine neonatal hepatocytes

PLoS One. 2017 Feb 2;12(2):e0171080. doi: 10.1371/journal.pone.0171080. eCollection 2017.

Abstract

Intersections in hepatic methyl group metabolism pathways highlights potential competition or compensation of methyl donors. The objective of this experiment was to examine the expression of genes related to methyl group transfer and lipid metabolism in response to increasing concentrations of choline chloride (CC) and DL-methionine (DLM) in primary neonatal hepatocytes that were or were not exposed to fatty acids (FA). Primary hepatocytes isolated from 4 neonatal Holstein calves were maintained as monolayer cultures for 24 h before treatment with CC (61, 128, 2028, and 4528 μmol/L) and DLM (16, 30, 100, 300 μmol/L), with or without a 1 mmol/L FA cocktail in a factorial arrangement. After 24 h of treatment, media was collected for quantification of reactive oxygen species (ROS) and very low-density lipoprotein (VLDL), and cell lysates were collected for quantification of gene expression. No interactions were detected between CC, DLM, or FA. Both CC and DLM decreased the expression of methionine adenosyltransferase 1A (MAT1A). Increasing CC did not alter betaine-homocysteine S-methyltranferase (BHMT) but did increase 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR) and methylenetetrahydrofolate reductase (MTHFR) expression. Increasing DLM decreased expression of BHMT and MTR, but did not affect MTHFR. Expression of both phosphatidylethanolamine N-methyltransferase (PEMT) and microsomal triglyceride transfer protein (MTTP) were decreased by increasing CC and DLM, while carnitine palmitoyltransferase 1A (CPT1A) was unaffected by either. Treatment with FA decreased the expression of MAT1A, MTR, MTHFR and tended to decrease PEMT but did not affect BHMT and MTTP. Treatment with FA increased CPT1A expression. Increasing CC increased secretion of VLDL and decreased the accumulation of ROS in media. Within neonatal bovine hepatocytes, choline and methionine differentially regulate methyl carbon pathways and suggest that choline may play a critical role in donating methyl groups to support methionine regeneration. Stimulating VLDL export and decreasing ROS accumulation suggests that increasing CC is hepato-protective.

MeSH terms

  • Animals
  • Animals, Newborn
  • Carbon / metabolism
  • Cattle
  • Cells, Cultured
  • Choline / metabolism*
  • Choline / pharmacology
  • Fatty Acids / metabolism
  • Fatty Acids / pharmacology
  • Gene Expression / drug effects
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism*
  • Lipid Metabolism / drug effects
  • Lipid Metabolism / genetics
  • Lipoproteins, VLDL / metabolism
  • Metabolic Networks and Pathways / drug effects
  • Metabolic Networks and Pathways / genetics
  • Methionine / metabolism*
  • Methionine / pharmacology
  • Methylation
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Reactive Oxygen Species / metabolism

Substances

  • Fatty Acids
  • Lipoproteins, VLDL
  • RNA, Messenger
  • Reactive Oxygen Species
  • Carbon
  • Methionine
  • Choline

Grants and funding

This research was supported by funding provided through the Real Science Initiative Grant by Balchem Corporation, New Hampton, NY (http://www.balchem.com/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.