Regulation of choline deficiency apoptosis by epidermal growth factor in CWSV-1 rat hepatocytes.
(33/288)
Previous studies show that acute choline deficiency (CD) triggers apoptosis in cultured rat hepatocytes (CWSV-1 cells). We demonstrate that prolonged EGF stimulation (10 ng/mL x 48 hrs) restores cell proliferation, as assessed by BrdU labeling, and protects cells from CD-induced apoptosis, as assessed by TUNEL labeling and cleavage of poly(ADP-ribose) polymerase. However, EGF rescue was not accompanied by restoration of depleted intracellular concentrations of choline, glycerphosphocholine, phosphocholine, or phosphatidylcholine. In contrast, we show that EGF stimulation blocks apoptosis by restoring mitochondrial membrane potential (Delta Psi(m)), as determined using the potential-sensitive dye chloromethyl-X-rosamine, and by preventing the release and nuclear localization of cytochrome c. We investigated whether EGF rescue involves EGF receptor phosphorylation and activation of the down-stream cell survival factor Akt. Compared to cells in control medium (CT, 70 micromol choline x 48 hrs), cells in CD medium (5 micromol choline) were less sensitive to EGF-induced (0-300 ng/mL x 5 min) receptor tyrosine phosphorylation. Compared to cells in CT medium, cells in CD medium treated with EGF (10 ng/mL x 5 min) exhibited higher levels of phosphatidylinositol 3-kinase (PI3K)-dependent phosphorylation of AktSer473. Inactivation of PI3K was sufficient to block EGF-stimulated activation of Akt, restoration of mitochondrial Delta Psi(m), and prevention of cytochrome c release. These studies indicate that stimulation with EGF activates a cell survival response against CD-apoptosis by restoring mitochondrial membrane potential and preventing cytochrome c release and nuclear translocation which are mediated by activation of Akt in hepatocytes. (+info)
Choline deficiency in mice and humans is associated with increased plasma homocysteine concentration after a methionine load.
(34/288)
BACKGROUND: Elevated concentrations of homocysteine in blood may be an independent risk factor for the development of atherosclerosis. Elevated homocysteine concentrations can be caused by decreased methylation of homocysteine to form methionine, as occurs in folate deficiency. A parallel pathway exists for methylation of homocysteine, in which choline, by way of betaine, is the methyl donor. OBJECTIVE: Our goal was to determine whether choline deficiency results in a decreased capacity to methylate homocysteine. DESIGN: C57BL/6J mice were fed diets containing 0, 10, or 35 mmol choline/kg diet for 3 wk. We then administered an oral methionine load to the animals and measured plasma homocysteine concentrations. Also, in a pilot study, we examined 8 men who were fed a diet providing 550 mg choline/d per 70 kg body weight for 10 d, followed by a diet providing almost no choline, until the subjects were clinically judged to be choline deficient or for +info)
Phosphatidylcholine and lysophosphatidylcholine excretion is increased in children with cystic fibrosis and is associated with plasma homocysteine, S-adenosylhomocysteine, and S-adenosylmethionine.
(35/288)
BACKGROUND: Hepatic steatosis and fat malabsorption are common in cystic fibrosis (CF). Choline deficiency results in decreased phosphatidylcholine synthesis through the cytidine diphosphocholine-choline pathway and hepatic steatosis and in increased synthesis of phosphatidylcholine from phosphatidylethanolamine using methyl groups from S-adenosylmethionine. The intestinal absorption of phosphatidylcholine in CF is unknown. OBJECTIVES: The objective was to determine whether excretion of choline phosphoglyceride (phosphatidylcholine and lysophosphatidylcholine) is increased in CF and whether loss of fecal choline phosphoglyceride is associated with altered plasma methionine cycle metabolites. DESIGN: A cross-sectional study involved 53 children with CF and 18 control children without CF. Blood was collected from all participants. A subset of 18 children with CF and 8 control children provided 72-h fecal samples and 5-d food records. RESULTS: Fat absorption was significantly lower (x+/- SEM: 86.2 +/- 1.6% and 94.1 +/- 1.2%) and excretion of fecal fat (12.9 +/- 1.7 and 3.9 +/- 0.7 g/d), phospholipid (median: 130 and 47.7 mg/d), phosphatidylcholine (19.6 and 2.1 mg/d), and lysophosphatidylcholine (60.3 and 16.9 mg/d) was significantly higher in children with CF than in control children, respectively (P < 0.05). Choline phosphoglyceride excretion was positively correlated with plasma homocysteine and S-adenosylhomocysteine and inversely related with plasma methionine (P < 0.05). CONCLUSIONS: Choline phosphoglyceride excretion is increased in children with CF and is associated with decreased plasma methionine and increased homocysteine and S-adenosylhomocysteine. These findings suggest choline depletion and an increased choline synthesis by S-adenosylmethionine-dependent methylation in CF, as well as a metabolic link between phosphatidylcholine metabolism and the methionine-homocysteine cycle in humans. (+info)
Maternal dietary choline availability alters the balance of netrin-1 and DCC neuronal migration proteins in fetal mouse brain hippocampus.
(36/288)
Alterations in maternal dietary choline availability during days 12-17 of pregnancy led to an increase in the level of immunoreactive netrin-1 and a decrease in the level of DCC protein in the developing fetal mouse brain hippocampus compared with controls. Changes in the expression of cell migration cues during development could account for some of the lifelong consequences of maternal dietary choline availability for cognitive and memory processes. (+info)
Tumour necrosis factor alpha signalling through activation of Kupffer cells plays an essential role in liver fibrosis of non-alcoholic steatohepatitis in mice.
(37/288)
BACKGROUND: While tumour necrosis factor alpha (TNF-alpha) appears to be associated with the development of non-alcoholic steatohepatitis (NASH), its precise role in the pathogenesis of NASH is not well understood. METHODS: Male mice deficient in both TNF receptors 1 (TNFR1) and 2 (TNFR2) (TNFRDKO mice) and wild-type mice were fed a methionine and choline deficient (MCD) diet or a control diet for eight weeks, maintaining isoenergetic intake. RESULTS: MCD dietary feeding of TNFRDKO mice for eight weeks resulted in attenuated liver steatosis and fibrosis compared with control wild-type mice. In the liver, the number of activated hepatic Kupffer cells recruited was significantly decreased in TNFRDKO mice after MCD dietary feeding. In addition, hepatic induction of TNF-alpha, vascular cell adhesion molecule 1, and intracellular adhesion molecule 1 was significantly suppressed in TNFRDKO mice. While in control animals MCD dietary feeding dramatically increased mRNA expression of tissue inhibitor of metalloproteinase 1 (TIMP-1) in both whole liver and hepatic stellate cells, concomitant with enhanced activation of hepatic stellate cells, both factors were significantly lower in TNFRDKO mice. In primary cultures, TNF-alpha administration enhanced TIMP-1 mRNA expression in activated hepatic stellate cells and suppressed apoptotic induction in activated hepatic stellate cells. Inhibition of TNF induced TIMP-1 upregulation by TIMP-1 specific siRNA reversed the apoptotic suppression seen in hepatic stellate cells. CONCLUSIONS: Enhancement of the TNF-alpha/TNFR mediated signalling pathway via activation of Kupffer cells in an autocrine or paracrine manner may be critically involved in the pathogenesis of liver fibrosis in this NASH animal model. (+info)
Application of proton NMR spectroscopy in the study of lipid metabolites in a rat hepatocarcinogenesis model.
(38/288)
Liver cancer is one of the most common cancers worldwide. Altered lipid metabolism in the liver is a key feature of developing liver nodules and tumors. Methods of analysis vary from the most sophisticated chromatography to the in vivo nuclear magnetic resonance (NMR) spectroscopy. In this study, we present a systematic method for the identification and quantitation of signature signals from lipid metabolites using 1D NMR proton spectroscopy. We assessed lipid metabolites in an epigenetic rat hepatocarcinogenesis model induced by treatment with a choline-deficient diet (CDAA, choline-deficient l-amino acid defined) over a period of 1 year, from the formation of steatosis, to the development of nodules and adenomas. A comparable choline-sufficient (CSAA) diet was used for the controls. The resonances of the methylene protons of the glycerol backbone in phospholipids were used to quantify the total concentration of such compounds. CDAA rat livers were found to have significantly higher levels of phospholipids, when compared to CSAA, throughout the entire carcinogenesis period. The tri-methyl protons of choline compounds serves to quantify total choline, and the vinyl and bis-allyl proton resonances can be used to not only quantify fatty acid concentrations but also to probe the number of double bonds in a fatty acid moiety. Early stages of carcinogenesis indicate a lower degree of double bonds in fatty acyl containing compounds in CDAA rat livers, when compared to CSAA. The results of this study are in agreement with those previously published in the literature on other rat hepatocarcinogenesis models. (+info)
Genetic variation of folate-mediated one-carbon transfer pathway predicts susceptibility to choline deficiency in humans.
(39/288)
Choline is a required nutrient, and some humans deplete quickly when fed a low-choline diet, whereas others do not. Endogenous choline synthesis can spare some of the dietary requirement and requires one-carbon groups derived from folate metabolism. We examined whether major genetic variants of folate metabolism modify susceptibility of humans to choline deficiency. Fifty-four adult men and women were fed diets containing adequate choline and folate, followed by a diet containing almost no choline, with or without added folate, until they were clinically judged to be choline-deficient, or for up to 42 days. Criteria for clinical choline deficiency were a more than five times increase in serum creatine kinase activity or a >28% increase of liver fat after consuming the low-choline diet that resolved when choline was returned to the diet. Choline deficiency was observed in more than half of the participants, usually within less than a month. Individuals who were carriers of the very common 5,10-methylenetetrahydrofolate dehydrogenase-1958A gene allele were more likely than noncarriers to develop signs of choline deficiency (odds ratio, 7.0; 95% confidence interval, 2.0-25; P < 0.01) on the low-choline diet unless they were also treated with a folic acid supplement. The effects of the C677T and A1298C polymorphisms of the 5,10-methylene tetrahydrofolate reductase gene and the A80C polymorphism of the reduced folate carrier 1 gene were not statistically significant. The most remarkable finding was the strong association in premenopausal women of the 5,10-methylenetetrahydrofolate dehydrogenase-1958A gene allele polymorphism with 15 times increased susceptibility to developing organ dysfunction on a low-choline diet. (+info)
Diethanolamine and phenobarbital produce an altered pattern of methylation in GC-rich regions of DNA in B6C3F1 mouse hepatocytes similar to that resulting from choline deficiency.
(40/288)
DNA methylation is an epigenetic mechanism regulating transcription, which when disrupted, can alter gene expression and contribute to carcinogenesis. Diethanolamine (DEA), a non-genotoxic alkanolamine, produces liver tumors in mice. Studies suggest DEA inhibits choline uptake and causes biochemical changes consistent with choline deficiency (CD). Rodents fed methyl-deficient diets exhibit altered methylation of hepatic DNA and an increase in liver tumors, e.g., CD causes liver tumors in B6C3F1 mice. We hypothesize that DEA-induced CD leads to altered methylation patterns which facilitates tumorigenesis. B6C3F1 hepatocytes in primary culture were grown in the presence of either 4.5 mM DEA, 3 mM Phenobarbital (PB), or CD media for 48 h. These concentrations induced comparable increases in DNA synthesis. PB, a nongenotoxic rodent liver carcinogen known to alter methylation in mouse liver, was included as a positive control. Global, average, DNA methylation status was not affected. The methylation status of GC-rich regions of DNA, which are often associated with promoter regions, were assessed via methylation-sensitive restriction digestion and arbitrarily primed PCR with capillary electrophoretic separation and detection of PCR products. DEA, PB, and CD treatments resulted in 54, 63, and 54 regions of altered methylation (RAMs), respectively, and the majority were hypomethylations. A high proportion of RAMs (72%) were identical when DEA was compared to CD. Similarly, 70% were identical between PB and CD. Altered patterns of methylation in GC-rich regions induced by DEA and PB resemble that of CD and indicate that altered DNA methylation is an epigenetic mechanism involved in the facilitation of mouse liver tumorigenesis. (+info)