Methyl-group donors cannot prevent apoptotic death of rat hepatocytes induced by choline-deficiency

Abstract

Choline-deficiency causes liver cells to die by apoptosis, and it has not been clear whether the effects of choline-deficiency are mediated by methyl-deficiency or by lack of choline moieties. SV40 immortalized CWSV-1 hepatocytes were cultivated in media that were choline-sufficient, choline-deficient, choline-deficient with methyl-donors (betaine or methionine), or choline-deficient with extra folate/vitamin B12. Choline-deficient CWSV-1 hepatocytes were not methyl-deficient as they had increased intracellular S-adenosylmethionine concentrations (132% of control; P < 0.01). Despite increased phosphatidylcholine synthesis via sequential methylation of phosphatidylethanol-amine, choline-deficient hepatocytes had significantly decreased (P < 0.01) intracellular concentrations of choline (20% of control), phosphocholine (6% of control), glycerophosphocholine (15% of control), and phosphatidylcholine (55% of control). Methyl-supplementation in choline-deficiency enhanced intracellular methyl-group availability, but did not correct choline-deficiency induced abnormalities in either choline metabolite or phospholipid content in hepatocytes. Methyl-supplemented, choline-deficient cells died by apoptosis. In a rat study, 2 weeks of a choline deficient diet supplemented with betaine did not prevent the occurrence of fatty liver and the increased DNA strand breakage induced by choline-deficiency. Though dietary supplementation with betaine restored hepatic betaine concentration and increased hepatic S-adenosylmethionine/S-adenosylhomocysteine ratio, it did not correct depleted choline (15% of control), phosphocholine (6% control), or phosphatidylcholine (48% of control) concentrations in deficient livers. These data show that decreased intracellular choline and/or choline metabolite concentrations, and not methyl deficiency, are associated with apoptotic death of hepatocytes.

PKCδ Is Activated in a Dietary Model of Steatohepatitis and Regulates Endoplasmic Reticulum Stress and Cell Death

“…It has been shown in long term (24 -72 h) culture with medium deficient in choline or methonine that protein and phospholipid synthesis are reduced (17,18). Long term culture with medium deficient in choline or methonine also results in programmed cell death (17,18), suggesting that depletion of intracellular pools of methyl group donors and choline moieties is detrimental for long term cell survival.…”

Dietary Choline, Betaine, Methionine, and Epigenetic Mechanisms Influencing Brain Development

“…Also, choline deficiency was associated with liver damage (elevated serum aminotransferases) Albright et al, 1996Albright et al, , 2005Albright and Zeisel, 1997). Liver cells died by apoptosis when placed in a choline-deficient medium (Albright et al, 1996;James et al, 1997;Shin et al, 1997) and choline-deprived rats had increased hepatocyte turnover (Goshal et al, 1983;Goshal and Farber, 1984), perhaps explaining why liver cells died and leaked enzymes into blood in choline-deficient humans. In humans, there are common SNPs in genes of 1-carbon metabolism that predicted risk for developing fatty liver, liver and muscle damage that is associated with choline deficiency (Kohlmeier et al, 2005;Da Costa et al, 2006).…”

Altered mitochondrial function and overgeneration of reactive oxygen species precede the induction of apoptosis by 1‐O‐octadecyl‐2‐methyl‐rαc‐grycero‐3‐phosphocholine in p53‐defective hepatocytes

“…We show that the anti-cancer drug ET-18-OCH 3 inhibits PC synthesis and induces generation of ROS, resulting in apoptotic cell death in p53-defective hepatocytes; these observations are similar to those described in acute CD (4,5,28). Previous reports showed that ET-18-OCH 3 inhibited PC synthesis in nonhepatocyte-type cells resulting in an inhibition of cell proliferation (1) and increased apoptosis (29).…”