S100A4 Gene is Crucial for Methionine-Choline-Deficient Diet-Induced Non-Alcoholic Fatty Liver Disease in Mice

PURPOSE

To explore the influence of S100 calcium binding protein A4 (S100A4) knockout (KO) on methionine-choline-deficient (MCD) diet-induced non-alcoholic fatty liver disease (NAFLD) in mice.

MATERIALS AND METHODS

S100A4 KO mice (n=20) and their wild-type (WT) counterparts (n=20) were randomly divided into KO/MCD, Ko/methionine-choline-sufficient (MCS), WT/MCD, and WT/MCS groups. After 8 weeks of feeding, blood lipid and liver function-related indexes were measured. HE, Oil Red O, and Masson stainings were used to observe the changes of liver histopathology. Additionally, expressions of S100A4 and proinflammatory and profibrogenic cytokines were detected by qRT-PCR and Western blot, while hepatocyte apoptosis was revealed by TUNEL staining.

RESULTS

Serum levels of aminotransferase, aspartate aminotransferase, triglyceride, and total cholesterol in mice were increased after 8-week MCD feeding, and hepatocytes performed varying balloon-like changes with increased inflammatory cell infiltration and collagen fibers; however, these effects were improved in mice of KO/MCD group. Meanwhile, total NAFLD activity scores and fibrosis were lower compared to WT+MCD group. Compared to WT/MCS group, S100A4 expression in liver tissue of WT/MCD group was enhanced. The expression of proinflammatory (TNF-α, IL-1β, IL-6) and profibrogenic cytokines (TGF-β1, COL1A1, α-SMA) in MCD-induced NAFLD mice were increased, as well as apoptotic index (AI). For MCD group, the expressions of proinflammatory and profibrogenic cytokines and AI in KO mice were lower than those of WT mice.

CONCLUSION

S100A4 was detected to be upregulated in NAFLD, while S100A4 KO alleviated liver fibrosis and inflammation, in addition to inhibiting hepatocyte apoptosis.

Choline Deficiency Is Associated With Increased Risk for Venous Catheter Thrombosis

BACKGROUND

Patients with intestinal failure who require long-term parenteral nutrition (PN) develop catheter thrombosis as a complication. This patient group may also develop choline deficiency because of a defect in the hepatic transsulfuration pathway in the setting of malabsorption. This study was undertaken to determine whether choline deficiency is a risk factor for development of catheter thrombosis.

METHODS

Plasma free and phospholipid-bound choline concentrations were measured in a group of 41 patients that required long-term PN. Episodes of catheter thrombosis from onset of PN to the time of blood testing were recorded.

RESULTS

Sixteen (39%) patients developed catheter thrombosis, and 5 of these had recurrent catheter thrombosis. Plasma free choline was 7.7 +/- 2.7 nmol/mL in patients with no history of catheter thrombosis and 6.2 +/- 1.7 nmol/mL in patients with previous catheter thrombosis (p = .076 by Wilcoxon rank-sum test). The partial correlation between plasma free choline concentration and the frequency of clots after controlling for catheter duration was r = -0.33 (p = .038). The relative risk for catheter thrombosis in subjects with a plasma free choline concentration <8 nmol/mL was 10.0, 95% confidence interval (1.134-88.167). Plasma phospholipid-bound choline concentration was 2191.7 +/- 679.0 nmol/mL in patients with previous catheter thrombosis and 2103.3 +/- 531.2 nmol/mL in patients without history of catheter thrombosis (p = NS).

CONCLUSION

Choline deficiency is a significant risk factor for development of catheter thrombosis in patients with intestinal failure who require PN.

Morphological and functional characterization of non-alcoholic fatty liver disease induced by a methionine-choline-deficient diet in C57BL/6 mice

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), including non-alcoholic steatohepatitis (NASH), appears to be increasingly common worldwide. Its histopathology and the effects of nutrition on liver function have not been fully determined.

AIM

To elucidate the cellular mechanisms of NAFLD induced by a methionine-choline-deficient (MCD) diet in mice. Particular focus was placed on the role of phagocytic cells.

METHODS

Male C57BL/6 mice were fed an MCD diet for 30 weeks. A recovery model was also established wherein a normal control diet was provided for 2 weeks after a period of 8, 16, or 30 weeks.

RESULTS

Mice fed the MCD diet for ≥ 2 weeks exhibited severe steatohepatitis with elevated serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Steatohepatitis was accompanied by the infiltration of CD68-positive macrophages (Kupffer cells). The severity of steatohepatitis increased in the first 16 weeks but was seen to lessen by week 30. Fibrosis began to develop at 10 weeks and continued thereafter. Steatohepatitis and elevated serum hepatic enzyme concentrations returned to normal levels after switching the diet back to the control within the first 16 weeks, but fibrosis and CD68-positive macrophages remained.

CONCLUSIONS

The histopathological changes and irreversible fibrosis seen in this model were caused by prolonged feeding of an MCD diet. These results were accompanied by changes in the activity of CD68-positive cells with temporary elevation of CCL-2, MMP-13, and MMP-9 levels, all of which may trigger early steatohepatitis and late fibrosis through phagocytosis-associated MMP induction.

Melatonin ameliorates methionine- and choline-deficient diet-induced nonalcoholic steatohepatitis in rats

Nonalcoholic steatohepatitis (NASH) may progress to advanced fibrosis and cirrhosis. Mainly, oxidative stress and excessive hepatocyte apoptosis are implicated in the pathogenesis of progressive NASH. Melatonin is not only a powerful antioxidant but also an anti-inflammatory and anti-apoptotic agent. We aimed to evaluate the effects of melatonin on methionine- and choline-deficient diet (MCDD)-induced NASH in rats. Thirty-two male Wistar rats were divided into four groups. Two groups were fed with MCDD while the other two groups were fed a control diet, pair-fed. One of the MCDD groups and one of the control diet groups were administered melatonin 50 mg/kg/day intraperitoneally, and the controls were given a vehicle. After 1 month the liver tissue oxidative stress markers, proinflammatory cytokines and hepatocyte apoptosis were studied by commercially available kits. For grading and staging histological lesions, Brunt et al.'s system was used. Melatonin decreased oxidative stress, proinflammatory cytokines and hepatocyte apoptosis. The drug ameliorated the grade of NASH. The present study suggests that melatonin functions as a potent antioxidant, anti-inflammatory and antiapoptotic agent in NASH and may be a therapeutic option.

Protective effect of soy isoflavones and activity levels of plasma paraoxonase and arylesterase in the experimental nonalcoholic steatohepatitis model

Nonalcoholic steatohepatitis (NASH) is characterized by diffuse fatty infiltration in the liver and ballooning degeneration and inflammation in hepatocytes. We aimed to study the protective effect of soy isoflavones on experimental NASH and their effects on plasma paraoxanese and arylesterase levels in rats. Twenty-eight male rats were divided into four groups: Group 1 (n=7) received an isocaloric normal diet for 8 weeks, Group 2 (n=7) was fed an isocaloric basal diet plus oral soy isoflavone for 8 weeks (100 mg/kg in diet), Group 3 (n=7) received a special diet that was methionine and choline deficient (MCD) and rich in fat for 8 weeks, and Group 4 (n=7) was fed a special diet that was MCD and rich in fat plus oral soy isoflavone for 8 weeks (100 mg/kg in diet). Blood samples were collected to measure plasma malondialdehyde (MDA), paraoxanese, and arylesterase and biochemical parameters. Tissue samples were duly taken for histopathological examination and measurement of tissue MDA levels. Plasma MDA levels were higher in Group 3 than in Groups 1, 2, and 4 (P <0.01, P <0.05, and P <0.05 respectively). Liver tissue MDA levels were also significantly higher in Group 3 compared to Groups 1, 2, and 4 (P <0.001, P <0.001, and P <0.05 respectively). A significant decrease was found in the plasma and liver tissue MDA levels in Group 4 compared to Group 3 (P <0.05 and P <0.05, respectively). The activity levels of plasma paraoxanase and arylesterase were significantly higher in Group 2 than in Groups 1 and 3 (P <0.05 and P <0.01, respectively). Also, the plasma paraoxanase and arylesterase levels were significantly higher in Group 4 compared to Groups 1 and 3 (P <0.05 and P <0.01, respectively). A significant reduction was observed in Group 4 in steatosis, inflammation, necrosis, and fibrosis compared to Group 3 (P <0.05 for each). We conclude that soy isoflavones seem to be effective in preventing liver damage by decreasing lipid peroxidation in the NASH model induced by a MCD diet. They stimulate and increase the activity of the antioxidative paraoxanase enyzme while decreasing the total cholesterol and triglyceride levels.

Lymphocyte gene expression in subjects fed a low-choline diet differs between those who develop organ dysfunction and those who do not

BACKGROUND

Some humans fed a low-choline diet develop hepatosteatosis, liver and muscle damage, and lymphocyte apoptosis. The risk of developing such organ dysfunction is increased by the presence of single-nucleotide polymorphisms (SNPs) in genes involved in folate and choline metabolism.

OBJECTIVE

We investigated whether these changes that occur in the expression of many genes when humans are fed a low-choline diet differ between subjects who develop organ dysfunction and those who do not. We also investigated whether expression changes were dependent on the presence of the SNPs of interest.

DESIGN

Thirty-three subjects aged 20-67 y were fed for 10 d a baseline diet containing the recommended adequate intake of choline. They then were fed a low-choline diet for up to 42 d or until they developed organ dysfunction. Blood was collected at the end of each phase, and peripheral lymphocytes were isolated and used for genotyping and for gene expression profiling with the use of microarray hybridization.

RESULTS

Feeding a low-choline diet changed the expression of 259 genes, and the profiles of subjects who developed and those who did not develop signs of organ dysfunction differed. Group clustering and gene ontology analyses found that the diet-induced changes in gene expression profiles were significantly influenced by the SNPs of interest and that the gene expression phenotype of the variant gene carriers differed significantly even with the baseline diet.

CONCLUSION

These findings support our hypothesis that a person's susceptibility to organ dysfunction when fed a low-choline diet is modulated by specific SNPs in genes involved in folate and choline metabolism.

Evidence of choline depletion and reduced betaine and dimethylglycine with increased homocysteine in plasma of children with cystic fibrosis

Cystic fibrosis (CF) is associated with many clinical complications including steatosis for which the relation to defective CF transmembrane conductance regulator protein is unclear. Choline deficiency results in hepatic steatosis. Choline is the precursor of betaine, which donates methyl groups for remethylation of homocysteine to methionine and dimethylglycine. Previously, we have shown phospholipid malabsorption and increased plasma homocysteine in children with CF. In these studies we used normal phase HPLC with tandem mass spectrometry to determine plasma choline, betaine, and dimethylglycine in children with CF (n = 34) and healthy control children without CF (n = 15). Plasma choline, betaine, and dimethylglycine were significantly lower in children with CF (means +/- SEM, 6.48 +/- 0.35, 23.8 +/- 1.49, 1.49 +/- 0.13 mumol/L, respectively) than in children without CF (8.98 +/- 0.46, 37.3 +/- 1.84, 3.01 +/- 0.17 mumol/L, respectively). Plasma choline (r = 0.373, P = 0.007) and betaine (r = 0.399, P = 0.005) were positively related to methionine, and choline was inversely related to homocysteine (r = -0.316, P = 0.03). Choline, betaine, and dimethylglycine were all significantly and positively related to the plasma S-adenosylmethionine:S-adenosylhomocysteine (SAM:SAH) ratio (r = 0.294, r = 0.377, r = 0.442, respectively; P < 0.05). The plasma choline:betaine and betaine:dimethylglycine ratios did not differ between the children with CF and the control children, suggesting no increase in betaine synthesis, or betaine-dependent remethylation of homocysteine. These studies suggest that choline depletion may contribute to increased homocysteine in children with CF. Choline depletion and altered thiol metabolism may contribute to the clinical complications associated with CF.

Distinct effects of folate and choline deficiency on plasma kinetics of methionine and homocysteine in rats

Both folate and betaine, a choline metabolite, play essential roles in the remethylation of homocysteine to methionine. We have studied the effects of folate and choline deficiency on the plasma kinetics of methionine, especially remethylation of homocysteine to methionine, by means of stable isotope methodology. After a bolus intravenous administration of [(2)H(7)]methionine (5 mg/kg body weight) into the rats fed with folate-, choline-, folate + choline-deficient or control diets, the plasma concentrations of [(2)H(7)]methionine, demethylated [(2)H(4)]homocysteine, and remethylated [(2)H(4)]methionine were determined simultaneously with endogenous methionine and homocysteine by gas chromatography-mass spectrometry-selected ion monitoring. The total plasma clearance of [(2)H(7)]methionine was not significantly different among groups, suggesting that the formation of [(2)H(4)]homocysteine from [(2)H(7)]methionine was not influenced by deficiencies of folate and choline. The area under concentration-time curve of [(2)H(4)]homocysteine significantly increased in the folate- and folate + choline-deficient group as compared with the control, but not in the choline-deficient group. The time profile of plasma concentrations of [(2)H(4)]methionine in the folate-deficient group was the same as the control group, whereas the appearance of [(2)H(4)]methionine in plasma was delayed in the choline- and folate + choline-deficient group. These results suggested plasma levels of remethylated methionine were influenced by choline deficiency rather than folate deficiency.

Mouse livers with macrosteatosis are more susceptible to normothermic ischemic injury than those with microsteatosis

BACKGROUND/AIMS

Fatty livers are increasingly used for transplantation due to the dramatic organ shortage. While steatosis is an established risk factor for post-operative complications, the impact of macro- vs. microvesicular steatosis on ischemic injury is unclear.

METHODS

The effects of ischemia and reperfusion were tested in two different models of steatotic mice: ob/ob as a model disclosing predominantly macrovesicular steatosis and choline deficient diet having mainly microvesicular steatosis. Steatotic and lean livers were subjected to 45 min of ischemia. Serial markers of hepatocellular injury, animal survival were measured. Hepatic tissue blood flow and portal vein perfusion were assessed.

RESULTS

Ob/ob mice had a significantly lower tolerance to hepatic ischemia. with increased AST release and decreased survival in comparison to the choline deficient mice. No difference in ATP content was found between both steatosis models, but hepatic perfusion and portal vein flow were significantly lower after reperfusion in the ob/ob mice when compared to the choline deficient animals. Ischemic pre-conditioning significantly improved liver reperfusion and injury in both models of steatosis.

CONCLUSIONS

Livers with macrovesicular steatosis have a lower tolerance to ischemic injury than those with microvesicular steatosis. Low intrahepatic and portal vein perfusion in macrovesicular fatty livers is, at least partially, responsible for the poorer outcome.

Rodent nutritional model of steatohepatitis: effects of endotoxin (lipopolysaccharide) and tumor necrosis factor alpha deficiency

BACKGROUND AND AIMS

Intestinal endotoxin (lipopolysaccharide) is thought to contribute to liver injury in both alcoholic and nonalcoholic steatohepatitis (NASH). Tumor necrosis factor alpha (TNFalpha) is an important mediator of this process and is considered central to the inflammatory response in NASH. This study aimed to investigate the effects of lipopolysaccharide on liver injury in the methionine choline deficient (MCD) nutritional model of NASH, and to determine if TNFalpha is required for the development of steatohepatitis in this model.

METHOD

Male C57/BL6 mice received a MCD diet for 4 weeks, whilst a control group received an identical diet supplemented with 0.2% choline bitartrate and 0.3% methionine. At 4 weeks, mice received either an intraperitoneal injection of lipopolysaccharide (0.5 microg/g body mass) or sterile saline, and were killed 24 h thereafter. In a separate study, TNFalpha knockout and wild type C57BL/6 mice received either MCD or control diets for 4 weeks. Serum transaminase levels, liver histology (steatosis, inflammation and apoptosis), hepatic triglyceride concentration and hepatic lipid peroxidation products (conjugated dienes, lipid hydroperoxides and thiobarbituric reactive substances, free and total) were evaluated.

RESULTS

Intraperitoneal administration of lipopolysaccharide augmented serum alanine aminotransferase (ALT) levels (P<0.02), hepatic inflammation (P<0.025), apoptosis (P<0.01) and free thiobarbituric acid reactive substances (P<0.025) in MCD mice. TNFalpha knockout mice fed the MCD diet developed steatohepatitis with histological and biochemical changes similar to those seen in wild type counterparts.

CONCLUSIONS

Lipopolysaccharide augments liver injury in MCD mice, and TNFalpha is not required for the development of steatohepatitis in MCD mice.

Liver inflammation and cytokine production, but not acute phase protein synthesis, accompany the adult liver progenitor (oval) cell response to chronic liver injury

Oval cells are facultative liver progenitor cells, which are invoked during chronic liver injury in order to replenish damaged hepatocytes and bile duct cells. Previous studies have observed inflammation and cytokine production in the liver during chronic injury. Further, it has been proposed that inflammatory growth factors may mediate the proliferation of oval cells during disease progression. We have undertaken a detailed examination of inflammation and cytokine production during a time course of liver injury and repair, invoked by feeding mice a choline-deficient, ethionine-supplemented (CDE) diet. We show that immediately following initial liver injury, B220-expressing leucocytes transiently infiltrate the liver. This inflammatory response occurred immediately before oval cell numbers began to expand in the liver, suggesting that the two events may be linked. Two waves of liver cytokine production were observed during the CDE time course. The first occurred shortly following commencement of the diet, suggesting that it may represent a hepatic acute phase response. However, examination of acute phase marker expression in CDE-fed mice did not support this hypothesis. The second wave of cytokine expression correlated with the expansion of oval cell numbers in the liver, suggesting that these factors may mediate oval cell proliferation. No inflammatory signalling was detected following withdrawal of the injury stimulus. In summary, our results document a close correlation between inflammation, cytokine production and the expansion of oval cells in the liver during experimental chronic injury.

Choline deficiency in mice and humans is associated with increased plasma homocysteine concentration after a methionine load

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 <or=42 d. A methionine load was administered at the end of each dietary phase.

RESULTS

Two hours after the methionine load, choline-deficient mice had plasma homocysteine concentrations twice those of choline-fed mice. Four hours after the methionine load, clinically choline-depleted men had plasma homocysteine concentrations that were 35% greater than those in men not choline depleted.

CONCLUSION

These results suggest that choline, like folate, plays an important role in the metabolism of homocysteine in humans and that response to a methionine load may be useful when assessing choline nutriture.

Free choline and phospholipid-bound choline concentrations in serum and dialysate during peritoneal dialysis in children and adults

OBJECTIVES

This study tested whether continuous ambulatory peritoneal dialysis (CAPD) changes free or phospholipid-bound choline concentrations in serum or peritoneal dialysis fluid of patients with end stage renal disease (ESRD).

DESIGN AND METHODS

Serum and dialysate choline and phospholipid-bound choline were measured before, during and after 6 h CAPD.

RESULTS

Serum choline concentrations were higher in patients with ESRD compared with age-matched controls. CAPD lowered serum choline concentrations significantly although it did not influence phospholipid-bound choline. Choline accumulated in the dialysate, reaching 28.4 +/- 2.7 microM in children and 18.2 +/- 1.4 microM in adults, during six hours CAPD; phospholipid-bound choline increased to 22.9 +/- 2.5 microM and 10.8 +/- 1.4 microM in children and adults, respectively. The total daily loss of choline into the dialysate was 181 +/- 20 micromoles in children and 260 +/- 18 micromoles in adults.

CONCLUSION

CAPD causes a substantial loss of choline into peritoneal dialysates and reduces serum choline concentrations significantly.

Changes of plasma free choline and choline-containing compounds' concentrations and choline loss during hemodialysis in ESRD patients

OBJECTIVES

This study was undertaken to determine the changes in plasma free choline and choline-containing compounds in end stage renal disease (ESRD) and to determine if they were lost into the dialysate during hemodialysis.

DESIGN AND METHODS

Plasma and dialysate free choline, phosphocholine and phospholipid-, phosphatidylcholine-, sphingomyelin-bound choline were measured before, during and after hemodialysis.

RESULTS

Plasma free and bound choline concentrations (mean +/- standard error of the mean) were 12.9 +/- 0.6 and 2697 +/- 57 microM or 37.3 +/- 0.9 and 2792 +/- 98 microM in controls or in ESRD patients, respectively. Free choline concentrations were correlated (r = 0.598; p < 0.001) with the time the patients were subjected to hemodialysis. Plasma free choline and phosphocholine concentrations are decreased by a total of -8.1 +/- 0.6 micromol/L and -88 +/- 8 micromol/L, respectively; phospholipid-, phosphatidylcholine- and sphingomyelin-bound choline are increased, during hemodialysis. Patients lost about 350 micromoles of choline into the dialysate during hemodialysis.

CONCLUSION

Plasma free choline concentrations are elevated in ESRD, and a considerable amount of choline is lost into the hemodialysate.

Choline and vitamin B12 deficiencies are interrelated in folate-replete long-term total parenteral nutrition patients

BACKGROUND

Choline has recently been recognized as an essential nutrient, in part based on deficiency data in long-term home total parenteral nutrition (TPN) patients. Choline, a methyl donor in the metabolism of homocysteine, is intricately related to folate status, but little is known about choline and vitamin B12 status. Long-term TPN patients are also subject to vitamin B12 deficiency.

OBJECTIVE

The objective of the study was to evaluate any interaction between choline, vitamin B12, and folate in patients with severe malabsorption syndromes, requiring long-term TPN.

DESIGN

Plasma free choline, serum and red blood cell (RBC) folate, serum vitamin B12 methylmalonic acid, B6, and plasma total homocysteine concentrations were assayed by standard methods. Low choline was defined as values that fall 1 to < or =3 and marked low choline concentration as >3 SD below the control mean.

RESULTS

Both low choline concentrations (52% were marked low, 33% low, 14% normal) and elevated methylmalonic acid concentrations (47%) were prevalent. Choline concentration was significantly lower and RBC folate higher in patients with elevated methylmalonic acid. Total homocysteine elevations were rare (3 of 21) and mild.

CONCLUSIONS

These data suggest a strong interaction between vitamin B12 and choline deficiencies and folate status in this population, which may be due in part to variations in vitamin and choline delivery by TPN. Folate adequacy may increase B12 use for homocysteine metabolism, thus limiting B12 availability for methylmaIonic acid metabolism. Choline use may also increase, and choline deficiency may worsen if choline substitutes when the vitamin B12 side of the homocysteine metabolic pathway cannot be used.

Increased uracil misincorporation in lymphocytes from folate-deficient rats

The development of certain human cancers has been linked with inadequate intake of folates. The effects of folate deficiency in vivo on DNA stability (strand breakage, misincorporated uracil and oxidative base damage) in lymphocytes isolated from rats fed a diet deficient in folic acid was determined. Because the metabolic pathways of folate and other methyl donors are closely coupled, the effects of methionine and choline deficiency alone or in combination with folate deficiency were determined. Feeding male Hooded Lister rats a folate-free diet for 10 weeks created a moderate folate deficiency (25-50% (approx.) decrease in plasma, red blood cell and hepatic folate concentrations (P < 0.05) and a 20% rise in plasma homocysteine (P < 0.05)). Lymphocyte DNA strand breakage was increased successively in all groups after 4 weeks and 8 weeks on the diet (50-100% (approx.) after 8 weeks). Only low folate specifically and progressively induced uracil misincorporation throughout the study (100% (approx.) after 8 weeks). Neither folate deficiency nor choline/methionine deficiency altered oxidative DNA base damage. In summary, moderate folate deficiency in vivo is associated with a decrease in DNA stability, measured as increased DNA strand breakage and misincorporated uracil.

Decreased serum choline concentrations in humans after surgery, childbirth, and traumatic head injury

The serum levels of choline decreased by approximately 50% in patients having a surgery under general as well as epidural anesthesia. The decrease is lasts for two days after surgery. Intravenous administration of succinylcholine, either by a single bolus injection or by a slow continuous infusion, increased the serum choline levels several folds during surgery. In these patients, a significant decrease in the serum choline levels was observed one and two days after surgery. In 16 pregnant women at the term, serum choline levels were higher than the value observed in 19 nonpregnant women. The serum choline levels decreased by about 40% or 60% after having a childbirth either by vaginal delivery or caesarean section, respectively. Serum choline levels in blood obtained from 9 patients with traumatic head injury were significantly lower than the observed levels in blood samples obtained from healthy volunteers. These observations show that serum choline levels increase during pregnancy and decrease during stressful situations in humans.

A possible role for rat intestinal surfactant-like particles in transepithelial triacylglycerol transport

To further examine whether surfactant-like particles (DeSchryver-Kecskemeti, K., R. Eliakim, S. Carroll, W. F. Stenson, M. A. Moxley, and D. H. Alpers. 1989. J. Clin. Invest. 84:1355-1361) were involved in the transepithelial transport of lipid, alkaline phosphatase activity and surfactant-like particle content were measured in apical mucosal scrapings, enterocytes, lamina propria, and serum after inhibition of chylomicron transport. Serum triacylglycerol levels were decreased 60-76% by Pluronic L-81, fenfluramine, and choline deficiency compared with fat-fed controls. 5 h after triacylglycerol feed, alkaline phosphatase activity in all three experimental groups was decreased compared with controls by 52-69% in mucosal scrapings and by 33-72% in serum. A parallel decline (60%) in alkaline phosphatase activity occurred in the lamina propria of Pluronic-treated animals. Total particle content (measured by an ELISA using antiserum against purified particle) after Pluronic treatment was decreased in mucosal scrapings, lamina propria, and serum by 16, 22, and 29% at 3 h and by 33, 40, and 8%, respectively, at 5 h after fat feeding. In contrast, particle content was increased in enterocytes by 29% 3 h and by 8% 5 h after fat feeding. By electron microscopy, enterocytes from Pluronic- and fenfluramine-treated animals exhibited a two- to threefold increase in large intracellular cytoplasmic lipid globules and the appearance of lamellae in apposition, with a marked decrease in the number of surfactant-like particles overlying the brush border. These changes, produced by inhibition of chylomicron transport, in the distribution of surfactant-like particles and particle-bound alkaline phosphatase are consistent with a role for these particles in transepithelial triacylglycerol transport across and out of the enterocyte.

Effects of alcohol, carbon tetrachloride, and choline deficiency on iron metabolism in the rat

The effects of alcohol on hepatic iron uptake and intestinal iron transport were studied in rats fed a nutritionally replete liquid diet containing varying quantities of ethanol. Results were compared with those from animals exposed to carbon tetrachloride (CCl4) to produce hepatocellular necrosis or a choline-deficient diet to produce steatosis and cirrhosis. A high ethanol intake for 4 or 10 weeks produced hepatic steatosis. CCl4 produced hepatocellular necrosis. Choline deficiency was associated with steatosis +/- cirrhosis. Intestinal iron transport was unaffected by ethanol, CCl4, or choline deficiency. Hepatic iron uptake was significantly depressed in rats consuming 11.7 g/kg/day ethanol (p < 0.01) for 4 weeks. Choline-deficient animals studied at 14 weeks also had significantly decreased hepatic iron uptake (p < 0.01); results were similar in the cirrhotic and noncirrhotic animals. Conversely, CCl4 exposure produced a significant 5-fold increase in hepatic iron uptake (p < 0.001). Results suggest that ethanol consumption, fatty liver, and cirrhosis are not responsible for any increase in iron absorption or of hepatic iron uptake in the rat model. Acute hepatocellular injury is followed by increased hepatic iron uptake.

Liver phosphatidylcholine hydroperoxidation provoked by ethionine-containing choline-deficient diet in mice

It is shown that peroxidation of phosphatidylcholine (PC) is enhanced in liver of mice fed a hepatocarcinogenic choline-deficient diet containing 0.1% w/w ethionine. Mice were divided into 4 groups and fed for 4 weeks one of the following diets: choline-supplemented; choline-supplemented containing ethionine; choline-deficient; and choline-deficient containing ethionine. Phosphatidylcholine hydroperoxide (PCOOH) of liver lipids was measured by high performance liquid chromatography using a chemiluminescence detector. Mice fed a choline-deficient diet containing ethionine showed 6-fold higher PCOOH levels than the choline-supplemented control mice: the PCOOH/PC molar ratios of liver lipids were 32.3 X 10(-5) and 5.6 X 10(-5), respectively. In addition to this remarkable degree of lipid peroxidation in liver of mice fed the choline-deficient diet containing ethionine, we also observed a significant liver fatty infiltration, a decrease in plasma and liver alpha-tocopherol, and an increase in liver injury-indicative enzyme activities. Also, marker enzymes for hepatocarcinogenesis, glucose-6-phosphatase and gamma-glutamyl transpeptidase were affected. These data suggest that enhanced hydroperoxidation of phosphatidylcholine may participate in hepatocarcinogenesis provoked by choline deficiency in the presence of ethionine.

Reduction in VLDL, but not HDL, in plasma of rats deficient in choline

We have analyzed plasma lipoprotein levels in young male rats fed a choline-deficient diet for 3 days. We confirmed previous studies that choline deficiency promotes 6.5-fold accumulation of triacyglycerol in the liver (23.9 +/- 6.0 versus 3.69 +/- 0.92 mumol/g liver) and reduction of triacylglycerol concentration in plasma by 60% (0.17 +/- 0.04 versus 0.46 +/- 0.10 mumol/mL plasma). Agarose gel electrophoresis showed that the plasma very low density lipoprotein (VLDL) levels were reduced in choline-deficient rats, but the concentration of plasma high density lipoproteins (HDL) was not affected. Sodium dodecyl sulfate - polyacrylamide gel electrophoresis of fractionated plasma lipoproteins revealed that the concentrations of apolipoproteins (apo) BH, BL, and E in VLDL from choline-deficient rats were 37.1, 11.0, and 37.2% of normal levels, respectively. In contrast, the amount of apo A-I, the major one in HDL, was almost unchanged. Correspondingly, there were decreased lipid (mainly phosphatidylcholine and triacylglycerol) levels in VLDL from choline-deficient rats, but no change in the levels of phosphatidylcholine, cholesterol, and cholesterol ester in HDL. There were similar levels of apo B and E (components of VLDL) in homogenates of livers from normal and choline-deficient rats, as determined by immunoblotting. These results support the hypothesis that choline deficiency causes reduction of VLDL, but not HDL, levels in plasma as a consequence of impaired hepatic VLDL secretion.

Choline may be an essential nutrient in malnourished patients with cirrhosis

Elemental diets designed for nutritional support in protein-calorie malnutrition are often deficient in choline, a nonessential nutrient. Previously, malnourished patients on these diets were found to be at risk of developing plasma choline deficiency. We have now estimated the prevalence of this deficiency by determining fasting plasma levels of choline among cirrhotic and noncirrhotic malnourished male subjects maintained on regular hospital mixed food or elemental parenteral and enteral formulas. Plasma choline concentrations (microM, average +/- SD) were as follows: (i) mixed foods, 11.3 +/- 4.3 for cirrhotic (n = 22) and 9.3 +/- 2.4 for noncirrhotic (n = 12) patients; (ii) parenteral formula, 5.3 +/- 1.6 for cirrhotic (n = 5) and 8.6 +/- 5.2 for noncirrhotic (n = 16) subjects; and (iii) enteral formula, 6.1 +/- 1.2 for cirrhotic (n = 5) and 11.7 +/- 1.9 for noncirrhotic (n = 4) subjects. The level for healthy normal subjects eating mixed foods was 12.0 +/- 2.2. The prevalence of plasma choline deficiency, i.e., plasma levels greater than or equal to 2 SD below the normal average, was as follows: parenteral formula, all cirrhotic and 10 of 16 noncirrhotic subjects; enteral formula, all cirrhotic and none of the noncirrhotic subjects. The reversibility of choline deficiency was examined in a longitudinal study of three phases involving 10 patients--5 with alcoholic cirrhosis (all on enteral formula); 5 noncirrhotic (1 on enteral and 4 on parenteral formula). During phase 1 (3-day equilibration period; ad libitum regular hospital diet), plasma choline levels were within the normal range for all subjects. During phase 2 (2 wk, choline depletion phase, elemental formulas), choline levels were subnormal in all cirrhotic subjects (5.1 +/- 2.0 microM) on enteral formula and all noncirrhotic patients on parenteral formula (5.9 +/- 1.3 microM). During phase 3 (2 wk, choline repletion phase, elemental formula + 6 g choline/day), the levels normalized in all patients (cirrhotic 11.4 +/- 3.1 microM and noncirrhotic 11.9 +/- 3.2 microM). Analyses of abdominal computed tomographic scans and plasma liver chemistries in the cirrhotic subjects during the three phases suggested a correlation between plasma choline deficiency and hepatic steatosis and abnormal liver enzyme levels in some patients. Therefore, choline may be an essential nutrient in malnourished cirrhotic patients and its deficiency may be associated with adverse hepatic effects.

The relationship of choline and carnitine in the choline deficient rat

Levels of carnitine in choline deficient and choline supplemented rats were measured in heart, skeletal muscle, plasma, and liver after various treatments. A decreased hepatic concentration of carnitine was shown to be closely correlated to the deficiency in dietary choline. No change in the concentration of plasma ketone bodies after a 48 hour fast was observed in the choline deficient rats when compared to choline supplemented controls, even though the level of hepatic carnitine subsequent to the fast was lower in the deficient rats. The concentration of hepatic carnitine was increased to normal values 1.5 hours after a single injection of 100 mumoles of choline, but was not affected by other "methyl" donors. From experiments presented in this communication it is concluded that the increase in hepatic carnitine is probably due to increased transport and uptake of this compound into the liver rather than by "de novo" synthesis.

Factors influencing lipoprotein lipase activity in choline deficiency

Subcutaneous injections of the lipotropic agent, ethyl trichloracetate, to rats with established choline deficiency raised their plasma triglycerides by 60% and completely removed the hyperglyceridaemic response of Triton WR 1339. The plasma triglyceride levels of choline-supplemented rats were depressed slightly by ethyl trichloracetate administration, which was effective in abolishing response to Triton WR 1339. Lipoprotein lipase activity of epididymal fat pad was stimulated 60% while plasma lipoprotein was not stimulated by ethyl trichloracetate. The increased peripheral removal of low-density lipoprotein-triglyceride complex, allowing greater use to be made of existing apo-proteins, may explain the lipotropic character of the ester.

Alterations in lipid metabolism produced by ethyl trichloracetate

Rats maintained on a choline deficient diet and treated with subcutaneous doses of ethyl trichloracetate responded by increasing plasma beta-lipoprotein and plasma triglyceride levels while excess triglyceride was being removed from the liver. There was a transient depression in plasma phospholipid at the beginning of the treatment. Continued administration of ethyl trichloracetate raised plasma triglyceride in choline depleted rats and raised hepatic phospholipid concentration in both choline deficient and supplemented rats. It is suggested that the lipotropic action of ethyl trichloracetate occurs through hepatic triglyceride being removed by the altered plasma lipids and not by inhibition of hepatic triglyceride synthesis.

Choline loss during hemodialysis: homeostatic control of plasma choline concentrations

Endogenous concentrations of free choline in plasma were measured in azotemic subjects receiving repetitive hemodialysis and excretion of free choline into the dialysate was determined. Chemical choline in plasma and dialysate was measured by adding choline kinase and measuring the production of radiolabelled phosphorycholine in the presence of radiolabelled adenosine triphosphate (ATP). Mean free choline concentration in plasma of azotemic subjects receiving hemodialysis was found to be 37 muM, which is about twice that of normal persons. The total excretion of choline into the dialysate during 360 min averaged 730 mumoles +/- 69 (SEM). Levels of free choline in plasma fell during hemodialysis at two hours but recovered toward predialysis values at six hours. The return of plasma choline concentrations toward control values during dialysis suggests that a feedback mechanism exists which was activated rapidly to produce homeostasis of plasma choline concentrations. In these patients, the degree of peripheral neuropathy as judged by measurement of nerve conduction velocities showed a significant inverse correlation with levels of free choline in plasma.

Lipd profiles of plasma lipoproteins of fasted and fed normal and choline-deficient rats

Three major density classes of lipoproteins and a residual protein (d greater than 1.21) were isolated by ultracentrifugation from plasma of fasted, fed normal, and choline-deficient rats. Lipid extracts were obtained from total plasma and the various density classes of lipoproteins, and each extract was examined in detail by thin layer and gas chromatographies. The results indicated essentially identical compositions of molecular species of phosphatidyl choline, which suggested their rapid equilibration among the different plasma lipoprotein classes. In contrast, the molecular species of the triacylglycerols and cholesteryl esters showed significant differences among the chylomicrons, very low and low, and high density lipoproteins, which excluded the possibility of their ready equilibration in vivo. Omission of choline from diet resulted in a sharp and statistically significant decrease in all lipid components of the very low and low density lipoproteins with 2 days. After 10 days of choline deficiency, the lipid levels of chylomicrons and very low and low density lipoproteins were ca. one-half the levels found in the choline supplemented animals, and there were discernible distortions in their lipid composition. Reintroduction of choline led to a prompt return to normal levels and lipid composition of both chylomicron and very low and low density lipoprotein fractions. The lack of equilibration of the triacylglycerols among the lipoprotein classes under normal conditions and in choline deficiency demonstrates an as yet unrecgnized source of compartmentation of plasma lipids.

[Blood serum and liver phospholipids in rats with chronic choline-protein deficiency]

Serum and liver phospholipids were studied in rats at different stages of pathological processes induced by a diet with a high fat content, but deficient in protein and choline. Such cirrhosogenic diet caused fatty infiltration, fibrosis and nodular liver cirrhosis in rats, depending on the period of its administration. This diet resulted in a considerable decrease of the phospholipid content in the liver and the serum of experimental rats. Addition of choline to the cirrhosogenic diet prevented formation of fatty infilitration in rats, but failed to protect completely from a fall of phospholipids in the liver.

Choline-deficiency fatty liver: impaired release of hepatic triglycerides

After intravenous injection of palmitate-1-(14)C to rats fed a choline-deficient (CD) or choline-supplemented (CS) diet for 15-18 hr, liver triglycerides became labeled very rapidly. In CS, but not in CD rats, there was a considerable loss, with time, of radioactivity from liver triglycerides. At the same time, significantly less radioactivity appeared in plasma triglycerides of CD rats than of CS animals. No difference was seen in the triglyceride content of microsomes isolated from the liver of rats fed the two diets. The lower radioactivity in plasma triglycerides of CD rats was essentially due to a lower level and specific activity of very low density lipoprotein triglycerides. After intravenous injection of Triton and labeled palmitate, considerably less radioactivity accumulated in plasma triglycerides and phospholipids of CD rats than of CS animals. Post-Triton hyperphospholipidemia was also less pronounced in CD rats. It was concluded that the fatty liver observed in CD rats results from an impaired release of hepatic triglycerides into plasma.