Fatty acid specificity for the synthesis of triacylglycerol and phosphatidylcholine and for the secretion of very-low-density lipoproteins and lysophosphatidylcholine by cultures of rat hepatocytes.

1. The synthesis and secretion of glycerolipids by monolayer cultures of rat hepatocytes was measured by using radioactive choline, glycerol and fatty acids and by measuring the concentration of triacylglycerols in the cells. 2. The incorporation of glycerol into triacylglycerol and the accumulation of this lipid in hepatocytes showed little specificity for fatty acids, except for eicosapentaenoate, which stimulated least. Oleate was more effective at stimulating triacylglycerol secretion than were palmitate, stearate, arachidonate and eicosapentaenoate. 3. Linoleate, linolenate, arachidonate and eicosapentaenoate stimulated the incorporation of glycerol and choline into phosphatidylcholine that was secreted into the medium. By contrast, palmitate and stearate produced relatively high incorporations into the phosphatidylcholine that remained in the cells. 4. The incorporation of glycerol and choline into lysophosphatidylcholine in the medium was stimulated 2-3-fold by all of the unsaturated fatty acids tested, whereas palmitate and stearate failed to stimulate if the acids were added separately. When 1 mM-stearate was added with 1 mM-linoleate, the incorporation of linoleate into lysophosphatidylcholine was about 4 times higher than that of stearate. 5. It is proposed that the secretion of lysophosphatidylcholine by the liver could provide a transport system for choline and essential unsaturated fatty acids to other organs.     

Evidence that remodeling of the fatty acids of phosphatidylcholine is regulated in isolated rat hepatocytes and involves both the sn-1 and sn-2 positions

The remodeling of the fatty acyl moieties of phosphatidylcholine (PC) has been studied in choline-deficient and choline-supplemented hepatocytes prepared from a choline-deficient rat. Choline-deficient hepatocytes were prelabeled with [Me-3H]choline for 30 min and subsequently incubated for up to 12 h in the presence or absence of choline. Analysis of the molecular species of PC from choline-deficient cells showed that, at the end of the pulse, approx. 75% of the label was incorporated into palmitate-containing species and only approx. 16% of the labeled species contained stearate. During the chase period there was a redistribution of label and after 12 h approx. 56% of the total radioactivity was associated with palmitate containing species and 37% was recovered in stearate-containing species. A similar distribution of radioactivity was observed in choline-supplemented cells. Measurement of the specific radioactivity of the major molecular species of PC was consistent with a precursor-product relationship between palmitate-containing species and stearate-containing species with arachidonate or linoleate on the sn-2 position. A model is presented which takes into account remodeling of both the sn-1 and sn-2 positions of PC.     

Influence of tauroursodeoxycholic and taurodeoxycholic acids on hepatic metabolism and biliary secretion of phosphatidylcholine in the isolated rat liver

Studies were carried out using an isolated rat liver system to define: the contribution of exogenous phosphatidylcholine (PC) to biliary phospholipid secretion; and its hepatic metabolism during perfusion of the livers with conjugated bile salts with different hydrophilic/hydrophobic properties. A tracer dose of sn-1-palmitoyl-sn-2-[14C]linoleoylPC was injected as a bolus into the recirculating liver perfusate, under constant infusion of 0.75 mumol/min of tauroursodeoxycholate or taurodeoxycholate. The effects on bile flow, biliary lipid secretion, 14C disappearance from the perfusate and its appearance in bile, as well as hepatic and biliary biotransformation were determined. With both the bile salts, about 40% of the [14C]PC was taken up by the liver from the perfusate over 100 min. During the same period less than 2% of the given radioactivity was secreted into bile. More than 95% of the 14C recovered in bile was located within the identical injected PC molecular species. The biliary secretion of labeled as well as unlabeled PC, however, was significantly higher in livers perfused with taurodeoxycholate than tauroursodeoxycholate, while the reverse was observed with respect to bile flow and total bile salt secretion. The exogenous PC underwent extensive hepatic metabolization which appeared to be influenced by the type of bile salt perfusing the liver. After 2 h perfusion, the liver radioactivity was found, in decreasing order, in PC, triacylglycerol, phosphatidylethanolamine and diacylglycerol. In addition, the specific activity of triacylglycerol was significantly higher in tauroursodeoxycholate than in taurodeoxycholate-perfused livers (P less than 0.025), while the reverse was true for the specific activity of hepatic PC (P less than 0.01). Because taurodeoxycholate and tauroursodeoxycholate showed opposite effects on both biliary lipid secretion and hepatic PC biotransformations, we conclude that the hepatic metabolism of glycerolipids is influenced by the physiochemical properties of bile salts.     

The synthesis of phosphatidylcholine by adult rat lung alveolar type II epithelial cells in primary culture

1. The formation of phosphatidylcholine from radioactive precursors was studied in adult rat lung alveolar type II epithelial cells in primary culture. 2. The incorporation of [Me-14C]choline into total lipids and phosphatidylcholine was stimulated by addition of palmitate, whereas the incorporation of [U-14C]glucose into phosphatidylcholine and disaturated phosphatidylcholine was stimulated by addition of choline. Addition of glucose decreased the absolute rate of incorporation of [1(3)-3H]glycerol into total lipids, phosphatidylcholine and disaturated phosphatidylcholine, decreased the percentage [1(3)-3H]glycerol recovered in phosphatidylcholine, but increased the percentage phosphatidylcholine label in the disaturated species. 3. At saturating substrate concentrations, the percentages of phosphatidylcholine radioactivity found in disaturated phosphatidylcholine after incubation with [1-(14)C]acetate (in the presence of glucose) [1-(14)C]palmitate (in the presence of glucose), [Me-14C]choline (in the presence of glucose and palmitate) and [U-14C]glucose (in the presence of choline and palmitate) were 78, 75, 74 and 90%, respectively. 4. Fatty acids stimulated the incorporation of [U-14C]glucose into the glycerol moiety of phosphatidylcholine. The degree of unsaturation of the added fatty acids was reflected in the distribution of [U-14C]glucose label among the different molecular species of phosphatidylcholine. It is suggested that the glucose concentration in the blood as related to the amount of available fatty acids and their degree of unsaturation may be factors governing the synthesis of surfactant lipids.     

Short-term energy deficit causes net accumulation of linoleoyl-enriched triacylglycerols in rat liver

Energy depletion by reduced food intake over 4 days resulted in a 73% reduction in total rat liver triacylglycerols (TG). In liver TG of energy-depleted rats, dilinoleoyl oleoyl glycerol (OLL) and trilinoleoyl glycerol (LLL)) were quantitatively increased by 85% and 147%, respectively. The net increase in linoleoyl-enriched species could be quantitatively accounted for by the release of linoleate from monolinoleoyl species and its subsequent reacylation into dilinoleoyl species and trilinolein during energy depletion. Hence while palmitate, oleate and some linoleate are being hydrolyzed, presumably for oxidation some linoleate is retained and contributes to the remodelling of hepatic triacylglycerols during energy deficit.     

A role for high density lipoproteins in hepatic phosphatidylcholine homeostasis

Choline is (95%) found largely in the biosphere as a component of phosphatidylcholine (PC) which is made from choline via the CDP-choline pathway. Animals obtain choline from both the diet and via endogenous biosynthesis that involves the conversion of phosphatidylethanolamine into PC by phosphatidylethanolamine N-methyltransferase (PEMT), followed by PC catabolism. We have uncovered a striking gender-specific conservation of choline in female mice that does not occur in male mice. Female Pemt(-/-) mice maintained hepatic PC/total choline levels during the first day of choline deprivation and escaped liver damage whereas male Pemt(-/-) mice did not. Plasma PC levels in high-density lipoproteins (HDLs) were higher in male Pemt(-/-) mice than those in females before choline deprivation. Interestingly, after choline deprivation for 1 day, female, but not male, Pemt(-/-) mice increased HDL-PC levels. Glybenclamide, an inhibitor of PC efflux mediated by ABC transporters, eliminated this response to choline deprivation in females. These data suggest that (i) increased PC efflux from extra-hepatic tissues to HDLs in the circulation provided sufficient choline for the liver and compensated for loss of hepatic PC during the initial stages of choline deprivation in female, but not male, Pemt(-/-) mice, and (ii) plasma HDL in female mice has an important function in maintenance of hepatic PC as an acute response to severe choline deprivation.     

Hepatic lipase-mediated hydrolysis versus liver uptake of HDL phospholipids and triacylglycerols by the perfused rat liver

Hepatic triacylglycerol-lipase-mediated hydrolysis and liver uptake of high-density lipoprotein (HDL) lipid components were studied in a recirculating rat liver perfusion, a situation where the enzyme is physiologically expressed and active at the vascular bed. Human native HDL were labelled with tri-[3H]oleoylglycerol, [N-methyl-3H]dipalmitoylphosphatidylcholine (DPPC), 1-palmitoyl,2-[14C]linoleoylphosphatidylcholine (PLPC), 1-palmitoyl,2-[14C]linoleoylphosphatidyl-ethanolamine (PLPE) and 1-palmitoyl,2-[14C]palmitoylphosphatidylethanolamine (DPPE). (1) Relative degradation rates of phosphatidylethanolamine molecular species were 2- to 10-fold higher than those of phosphatidylcholine. Considering [14C] PLPC and [14C] PLPE as representative of HDL phosphatidylcholine and phosphatidylethanolamine, respectively, the amounts of lysophosphatidylcholine and lysophosphatidylethanolamine generated after a 60 min perfusion were comparable. The enzyme showed a clear preference for the molecular species bearing an unsaturated fatty acid at the 2 position of glycerol; this was the most pronounced in the case of phosphatidylethanolamine molecular species. (2) Relative liver uptake of HDL-phosphatidylethanolamine was 4- to 5-fold higher than that of HDL-phosphatidylcholine, irrespective of the constitutive fatty acids. Nevertheless, mass estimation indicated that 3 times more molecules of phosphatidylcholine than of phosphatidylethanolamine were transferred. No correlation could be found between the relative degradation rates of phospholipids and their relative liver uptake, indicating a dissociation between the two processes. (3) Perfusate decay and relative liver uptake of labelled HDL-triacylglycerol were higher than that of any phospholipid class. No circulating radiolabelled free fatty acids accumulated in the perfusate, but they were found acylated into liver cell phospholipids and triacylglycerols. (4) A prior 10-12-min washout of the liver vascular bed with heparin removed over 80% of the hepatic lipase activity, as assessed by specific immunoinhibition. Hepatic lipase-depleted liver displayed impaired phospholipid hydrolysis and triacyglycerol uptake, whereas the transfer of HDL phospholipids to liver tissue was unaffected.     

Turnover of the fatty acid and glycerol moieties of acylglycerols and phosphoglycerides during development of Ceratitis capitata

• 1.1. Labelling of free fatty acids, diacylglycerols, triacylglycerols, phosphatidylethanolamine, phosphatidylcholine and their lysoderivatives was followed during the development of Ceratitis capitata after feeding larvae with mixtures of either (³H)glycerol and (¹⁴C)palmitate or (³H)glycerol and (¹⁴C)linoleate. Both, specific activity and dpm/individual were plotted vs the time of development.
• 2.2. Palmitate and linoleate moieties of the diacylglycerol fraction had two exponential components with a similar initial rapid decay component. The turnover times corresponding to the slow decay components were different for both acids in the free form and acylating diacylglycerols.
• 3.3. Triacylglycerols exhibited a monophasic behaviour with different half-life values for either palmitate or linoleate.
• 4.4. Palmitate and linoleate show different turnover in the phosphoglycerides phosphatidylethanolamine and phosphatidylcholine. Palmitate exhibited a monophasic decay curve whereas linoleate exhibited a biphasic decay for both phospholipid classes.

     

Comparison of linoleate,palmitate and acetate metabolism in rat ventral prostate

Rat ventral prostate incorporated (1-¹⁴C)acetate, (1-¹⁴C)palmitate and (1-¹⁴C)linoleate into different phospholipids in a time-dependent process. The rate of incorporation into total phospholipids was higher with linoleate (10.0 nmol/g) than with either palmitate (5.8 nmol/g) or acetate (4.7 nmol/g). Predominant labelling with all the radioactive substrates assayed was found in choline glycerophospholipids (PC). The radioactive profiles for linoleate in the other ventral prostate phospholipids differed from those obtained with palmitate and acetate. Specifically linoleate was incorporated into inositol glycerophospholipids plus lysoethanolamine glycerophospholipids (PI+LPE) and not into sphingomyelin (SM), while palmitate and acetate incorporated into SM but not into PI+LPE. Acetate showed the highest oxidation to CO₂ whereas no differences were observed in the radioactivity incorporated into CO₂ from a saturated (palmitate) or an essential unsaturated fatty acid (linoleate). These studies also show zinc-dependence by the acetate to CO₂ oxidation.Abbreviations PL total phospholipids - PC choline glycerophospholipids - PE ethanolamine glycerophospholipids - PI+LPE inositol glycerophospholipids plus lysoethanolamine glycerophospholipids - PS serine glycerophospholipids - SM sphingomyelin     

The enterohepatic recycling of bile choline in sheep

1. Measurement of unesterified choline in blood samples taken from five conscious multi-cannulated sheep indicated a significant production of unesterified choline by the alimentary tract, as judged by the portal venous minus arterial difference and significant uptake by the liver, as judged from the portal venous minus hepatic venous and arterial minus hepatic venous differences. 2. A mean liver blood flow rate of 1.68 +/- 0.22 1/min for the five sheep was determined by bromosulphophthalein clearance and, combined with the differences in unesterified choline across organs, gave a production rate of free choline of 9.1 mmol/day by the alimentary tract and an uptake by the liver of 13.2 mmol/day. 3. Infusion of [methyl-3H]choline chloride into the portal vein of a sheep over 1 hr and subsequent isolation of the bile for several days showed over 70% cumulative recovery of the radioactivity in the choline moiety of bile phosphatidylcholine over a 120 hr period. 4. Subsequent infusion 17 days later of bile lipid [3H]choline via a duodenal fistula also gave approx. 70% cumulative recovery of radioactivity in the choline moiety of newly secreted bile phosphatidylcholine in 120 hr. 5. These results show a very extensive enterohepatic recirculation of bile choline in the sheep, which is in contrast to the situation in monogastric animals.     

The Effect of Overnight Fasting on the Synthesis of Glycerolipids by Liver Slice

The uptake by liver slices of radioactive acetate, palmitate, stearate, linoleate and glycerol into glycerolipids was compared in fed and fasted (overnight, 16 hr) rats.

The incorporation of l-¹⁴C-acetate into long-chain fatty acids and glycerolipids was depressed by fasting. There was a considerable decrease in the incorporation of 1-¹⁴C-palmitate into triglyceride (TG) and that of l-¹⁴C-stearate into phosphatidylcholine (PC) in fasted liver slices. No such differences were observed with l-¹⁴C-linoleate. The incorporation of l-¹⁴C-glycerol into TG was slightly decreased, whereas that into PC and phosphatidylethanolamine (PE) was increased by fasting.

These observations, together with those with the incorporation of the precursors into molecular species of TG, PC and PE, suggested that the changes in the fatty acid composition of glycerolipids by fasting may be governed by the changes in the availability of acyl moieties as well as in the relative balance of the pathways participating to formation of TG and phospholipids.     

Stearoyl-CoA desaturase 1 deficiency increases CTP:choline cytidylyltransferase translocation into the membrane and enhances phosphatidylcholine synthesis in liver

Stearoyl-CoA desaturase (SCD) is the rate-limiting enzyme in monounsaturated fatty acid synthesis. Previously, we showed that Scd1 deficiency reduces liver triglyceride accumulation and considerably decreases synthesis of very low density lipoprotein and its secretion in both lean and obese mice. In the present study, we found that Scd1 deficiency significantly modulates hepatic glycerophospholipid profile. The content of phosphatidylcholine (PC) was increased by 40% and the activities of CTP:choline cytidylyltransferase (CCT), the rate-limiting enzyme in de novo PC synthesis, and choline phosphotransferase were increased by 64 and 53%, respectively, in liver of Scd1-/- mice. In contrast, the protein level of phosphatidylethanolamine N-methyltransferase, an enzyme involved in PC synthesis via methylation of phosphatidylethanolamine, was decreased by 80% in the liver of Scd1-/- mice. Membrane translocation of CCT is required for its activation. Immunoblot analyses demonstrated that twice as much CCTalpha was associated with plasma membrane in livers of Scd1-/- compared with wild type mice, suggesting that Scd1 mutation leads to an increase in CCT membrane affinity. The incorporation of [(3)H]glycerol into PC was increased by 2.5-fold in Scd1-/- primary hepatocytes compared with those of wild type mice. Furthermore, mitochondrial glycerol-3-phosphate acyltransferase activity was reduced by 42% in liver of Scd1-/- mice; however, the activities of microsomal glycerol-3-phosphate acyltransferase, diacylglycerol acyltransferase, and ethanolamine phosphotransferase were not affected by Scd1 mutation. Our study revealed that SCD1 deficiency specifically increases CCT activity by promoting its translocation into membrane and enhances PC biosynthesis in liver.     

Phospholipid composition of reconstituted high density lipoproteins influences their ability to inhibit endothelial cell adhesion molecule expression

The ability of different phosphatidylcholine (PC) species to inhibit cytokine-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in human umbilical vein endothelial cells (HUVECs) was investigated. PC species containing palmitoyl- in the sn-1 position and palmitoyl- (DPPC), arachidonyl- (PAPC), linoleoyl- (PLPC) or oleoyl- (POPC) in the sn-2 position were compared. These PC species were studied as components of reconstituted high density lipoproteins (rHDL) (containing apolipoprotein A-I [apoA-I] as the sole protein) or as small unilamellar vesicles (SUVs). The rHDL containing PLPC and PAPC inhibited VCAM-1 expression in activated HUVECs by 95 and 70%, respectively, at an apoA-I concentration of 16 micrometer. At this concentration of apoA-I, POPC rHDL inhibited by only 16% and DPPC rHDL did not inhibit at all. These differences could not be explained by differential binding of the rHDL to HUVECs. The same hierarchy of inhibitory activity was observed when these PC species were presented to the cells as SUVs but only when the SUVs also contained an antioxidant. It was concluded that rHDL PC is responsible for their inhibitory activity and that this varies widely with different PC species.     

Phospholipid Biosynthesis in Synchronous Plasmodium falciparum Cultures1

The metabolism of phospholipids in synchronous Plasmodium falciparum-infected erythrocytes was studied over one cycle of 48 h by the incorporation of labeled palmitate, serine, choline, and myo-inositol into cellular lipids. The rates of incorporation of palmitate and serine into total phospholipids and of choline into phosphatidylcholine (PC) were linear with the maturation of the parasite, increasing by a factor of 2–5.6 according to the precursors. The rate of inositol incorporation into phosphatidylinositol was 9.6 times higher at the schizont stage than at the ring stage, with a marked increase in the second half of the cycle. A significant incorporation of palmitate into triglycerides also occurred during the schizont stage of the parasite. The incorporations of serine and palmitate into phosphatidylethanolamine (PE) and PC showed a net increase at approximately the twentieth hour of the cycle, while the radioactivities recovered in phosphatidylserine (PS) had already reached a maximum by this time. These findings indicate an instantaneous transformation of PS into PE and PC through a decarboxylation of PS into PE, then a methylation of PE into PC during the second half of the cycle. Although PS is a minor component of the Plasmodium parasite, our findings demonstrate the important role of this phospholipid as a precursor of PE and PC, which are major constituents of parasite phospholipids.     

Direct evidence of the role of propionate in choline synthesis in rats

Wistar rats were injected with 2-14C-propionate in a dose of 30 mu Ci/100 g bw, 2 h after food intake. Two hours after isotope injection the rats were decapitated to determine specific radioactivity (SR) in liver and brain lipids, in liver phosphatidylcholine (PC) and its structural components. The label was incorporated in liver lipids in a far greater amount. In liver PC, SR appeared the highest in glycerin and less higher in the fraction of higher fatty acids. The least amount of the label from 2-14C-propionate was incorporated in choline. The fact of the label incorporation in choline was recorded for the first time.     

Glycerol as a substrate for phospholipid biosynthesis in type II pneumocytes isolated from streptozotocin-diabetic rats

Glycerol and glucose utilization for phospholipid biosynthesis was examined in type II pneumocytes isolated from normal and streptozotocin-diabetic rats. In cells from diabetic rats, incorporation of [1,3-14C]glycerol into total phosphatidylcholine (PC), disaturated phosphatidylcholine (DSPC), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) occurred to a greater degree by the glycerol 3-phosphate pathway as opposed to the dihydroxyacetone phosphate pathway. Total incorporation of glycerol into each of the major cellular phospholipids was increased up to 6-fold in cells from diabetic rats, while the total incorporation of glucose into the same lipids was decreased 2-fold. While the percentage of both glucose and glycerol carbons incorporated into the backbone of DSPC was increased in cells from diabetic rats, the percentage of carbons from both substrates incorporated into the fatty acid moieties was decreased. As a measure of DSPC synthesis, choline incorporation into DSPC was significantly decreased in type II cells from diabetic animals if the cells were incubated in the presence of glucose, palmitate and choline but not glycerol. Addition of 0.1 or 0.3 mM glycerol to the incubation medium restored choline incorporation to the control value in cells from diabetic rats, but did not affect the rate of choline incorporation into DSPC in cells from normal rats. These results suggest that exogenous glycerol can compensate for reduced glucose metabolism in type II cells of diabetic animals to maintain a constant rate of DSPC synthesis.     

Origin of biliary phosphatidylcholines studied by coenzyme labelling with [1,1-2H2]ethanol

The labelling of individual molecular species of phosphatidylcholines in bile and liver was measured in bile fistula rats given [1,1-2H2]ethanol immediately after the cannulation of the bile duct. Corresponding species in liver and bile were labelled to the same extent, the deuterium excess in the glycerol moiety (at C-2) of biliary molecules with rapid turnover possibly being slightly higher in the bile than in liver. The labelling of different positions and the half-life times of different molecular species were about the same as previously found 48 h after the cannulation. The only exception was the 1-stearoyl-2-linoleoyl species, which had a half-life time 5-7 times longer immediately after operation than after 48 h of biliary drainage. The results support our previous conclusion that the molecular species of phosphatidylcholines in liver and bile represent the same, or very similar, pool(s) of molecules.     

Reduction of various lipid hydroperoxides by rat liver homogenate

Rates of disappearance of hydroperoxy groups of various lipid peroxides added to rat liver homogenate differed from each other. The hydroperoxy group of linoleic acid disappeared rapidly, while those of L-3-phosphatidyl choline dilinoleoyl and trilinolenin disappeared slowly. The hydroperoxy groups of cholesterol linoleate were stable in the homogenate. Most of the conjugated dienes of these lipid peroxides remained. The hydroperoxy groups of the unsaturated fatty acids of the phosphatidyl choline were found to be changed to hydroxy groups as analyzed by high-performance liquid chromatography.     

Identification and analysis of products formed from phospholipids in the free radical oxidation of human low density lipoproteins

Phospholipids reside in the surface layer of LDLs and constitute approximately 20-25% of the particle by weight. We report a study of the primary products generated from the most abundant molecular species of phosphatidylcholines present in LDL during in vitro free radical oxidations. The 13-hydroperoxides of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC) and 1-stearoyl-2-linoleoyl-sn-glycero-phosphocholine (SLPC) and the 15-hydroperoxides of 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphocholine (PAPC) and 1-stearoyl-2-arachidonoyl-sn-glycero-phosphocholine (SAPC) were found to increase in a time-dependent manner and in significant amounts even in the presence of alpha-tocopherol. Phospholipid alcohols also formed during the course of the oxidations. Early in the LDL oxidations, while alpha-tocopherol was still present, the thermodynamically favored trans,trans products of PLPC and SLPC were found to form in significantly larger quantities than those formed from cholesteryl linoleate. Additionally, quantities of PAPC 11-hydroperoxide (11-OOH) decreased over time relative to PAPC 15-OOH, even while alpha-tocopherol was still present in the oxidation, presumably as a result of further oxidation of PAPC 11-OOH to form cyclic peroxide oxidation products. These results suggest that alpha-tocopherol is more closely associated with the inner cholesteryl ester-rich hydrophobic core of an LDL particle and is not as effective as an antioxidant in the outer phospholipid layer as it is in the lipid core.     

Dietary choline prevents high fat-induced disorder of hepatic cholesterol metabolism through SREBP-2/HNF-4α/CYP7A1 pathway in a freshwater teleost yellow catfish Pelteobagrus fulvidraco

Lipid overload-induced hepatic cholesterol accumulation is a major public health problem worldwide, and choline has been reported to ameliorate cholesterol accumulation, but its mechanism remains unclear. Our study found that choline prevented high-fat diet (HFD)-induced cholesterol metabolism disorder and enhanced choline uptake and phosphatidylcholine synthesis in the liver tissues; choline incubation prevented fatty acid (FA)-induced cholesterol accumulation and FA-induced inhibition of bile acid synthesis. Moreover, compared to single FA incubation, choline incubation or FA + choline co-incubation increased the mRNA abundances and protein levels of HNF4α and up-regulated the degradation of cholesterol into bile acids. Mechanistically, choline prevented the FA-induced accumulation of SREBP2 protein and the interaction between SREBP2 and HNF4α, thereby enhancing the DNA binding capacity of the HNF4α to the CYP7A1 promoter, and promoting the degradation of cholesterol into bile acids. Our study elucidated the novel regulatory mechanisms of choline preventing HFD-induced cholesterol accumulation and increasing bile acid synthesis by SREBP-2/HNF-4α/CYP7A1 pathway.