Choline supplementation promotes hepatic insulin resistance in phosphatidylethanolamine N-methyltransferase-deficient mice via increased glucagon action

J Biol Chem. 2013 Jan 11;288(2):837-47. doi: 10.1074/jbc.M112.415117. Epub 2012 Nov 25.

Abstract

Biosynthesis of hepatic choline via phosphatidylethanolamine N-methyltransferase (PEMT) plays an important role in the development of type 2 diabetes and obesity. We investigated the mechanism(s) by which choline modulates insulin sensitivity. PEMT wild-type (Pemt(+/+)) and knock-out (Pemt(-/-)) mice received either a high fat diet (HF; 60% kcal of fat) or a high fat, high choline diet (HFHC; 4 g of choline/kg of HF diet) for 1 week. Hepatic insulin signaling and glucose and lipid homeostasis were investigated. Glucose and insulin intolerance occurred in Pemt(-/-) mice fed the HFHC diet, but not in their Pemt(-/-) littermates fed the HF diet. Plasma glucagon was elevated in Pemt(-/-) mice fed the HFHC diet compared with Pemt(-/-) mice fed the HF diet, concomitant with increased hepatic expression of glucagon receptor, phosphorylated AMP-activated protein kinase (AMPK), and phosphorylated insulin receptor substrate 1 at serine 307 (IRS1-s307). Gluconeogenesis and mitochondrial oxidative stress were markedly enhanced, whereas glucose oxidation and triacylglycerol biosynthesis were diminished in Pemt(-/-) mice fed the HFHC diet. A glucagon receptor antagonist (2-aminobenzimidazole) attenuated choline-induced hyperglycemia and insulin intolerance and blunted up-regulation of phosphorylated AMPK and IRS1-s307. Choline induces glucose and insulin intolerance in Pemt(-/-) mice through modulating plasma glucagon and its action in liver.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Choline / administration & dosage*
  • Choline / pharmacology
  • DNA Primers
  • Glucagon / physiology*
  • Gluconeogenesis / drug effects
  • Glucose Tolerance Test
  • Insulin Resistance*
  • Liver / drug effects*
  • Liver / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Phosphatidylethanolamine N-Methyltransferase / genetics
  • Phosphatidylethanolamine N-Methyltransferase / metabolism*

Substances

  • DNA Primers
  • Glucagon
  • Phosphatidylethanolamine N-Methyltransferase
  • Choline