Synthesis of phospholipids and triglycerides in human liver slices. 3. Influence of bile acids, choline, and linoleic acid

Lecithin and cardiovascular health: a comprehensive review

BACKGROUND

Cardiovascular diseases are one of the prime causes of mortality globally. Therefore, concerted efforts are made to prevent or manage disruptions from normal functioning of the cardiovascular system. Disruption in lipid metabolism is a major contributor to cardiovascular dysfunction. This review examines how lecithin impacts lipid metabolism and cardiovascular health. It emphasizes lecithin's ability to reduce excess low-density lipoproteins (LDL) while specifically promoting the synthesis of high-density lipoprotein (HDL) particles, thus contributing to clearer understanding of its role in cardiovascular well-being. Emphasizing the importance of lecithin cholesterol acyltransferase (LCAT) in the reverse cholesterol transport (RCT) process, the article delves into its contribution in removing surplus cholesterol from cells. This review aims to clarify existing literature on lipid metabolism, providing insights for targeted strategies in the prevention and management of atherosclerotic cardiovascular disease (ASCVD). This review summarizes the potential of lecithin in cardiovascular health and the role of LCAT in cholesterol metabolism modulation, based on articles from 2000 to 2023 sourced from databases like MEDLINE, PubMed and the Scientific Electronic Library Online.

MAIN BODY

While studies suggest a positive correlation between increased LCAT activities, reduced LDL particle size and elevated serum levels of triglyceride-rich lipoprotein (TRL) markers in individuals at risk of ASCVD, the review acknowledges existing controversies. The precise nature of LCAT's potential adverse effects remains uncertain, with varying reports in the literature. Notably, gastrointestinal symptoms such as diarrhea and nausea have been sporadically documented.

CONCLUSIONS

The review calls for a comprehensive investigation into the complexities of LCAT's impact on cardiovascular health, recognizing the need for a nuanced understanding of its potential drawbacks. Despite indications of potential benefits, conflicting findings warrant further research to clarify LCAT's role in atherosclerosis.

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.

Lipid composition in jaundiced rat liver by radio-thin-layer chromatography and photodensitometry

In vitro hepatic synthesis of lipids starting from (1-14C)acetate was investigated for 14 days in rats with biliary obstruction by ligation of the common bile duct using radio-thin-layer chromatography (radio-TLC). This study was correlated with a quantitative assay of the various hepatic lipids using TLC correlated with photodensitometry. Hepatic total lipid synthesis increased progressively with time. With concern to the single fractions, the major modifications were verified on the 3rd day with a decreased incorporation of the labelled acetate into the triglycerides. On the other hand, using photodensitometry, they demonstrated a percentage increase. These variations can be justified by the presence of a feedback mechanism. The syntheses of cholesterol and the other fractions were maximum during this period. Histologic examination revealed, especially on the 3rd day, a neoformation of biliary ductules and on the 14th day, a regression of these histological changes.

Gallstones. The present and future of medical dissolution

Adequate concentrations of bile acids and phospholipids are necessary to keep cholesterol in solution in bile. When the amount of cholesterol exceeds the capacity of bile acids and phospholipids to keep the cholesterol in micellar solution, bile becomes supersaturated; then, under appropriate conditions, cholesterol crystals form and gallstones may develop. Current dissolution therapy is aimed at desaturating the bile, thereby shifting the equilibrium of cholesterol from a crystalline phase back toward a micellar state, thus permitting gallstones to dissolve. Chenodeoxycholic acid is the drug being most extensively tested for efficacy in dissolution; at present, it is successful in about 60 per cent of cases. The primary mechanism of action appears to be suppression of biliary secretion of cholesterol. Further experience is needed to confirm the safety of chenodeoxycholic acid, to gain more precision in patient selection, and to determine ideal dose. The role of chenodeoxycholic acid in prophylaxis and in prevention of recurrence needs further study. Other potential agents for dissolution also deserve investigation.

Influence of cholic and chenodeoxycholic acid on biliary cholesterol secretion in man

The interrelationships between biliary bile acid, lecithin and cholesterol secretion rates were studied druing depletion of the bile acid pool and during duodenal administration of cholic or chenodeoxycholic acid in thirteen patients 7-12 days after operation for uncomplicated gallstone disease. The mean lecithin secretion rate was signigicantly higher during cholic acid than during chenodeoxycholic acid infusion. The relationship between bile acid and cholesterol secretion rates was curvilinear, y = x/(a + bx) during bile acid pool depletion and during duodenal cholic acid infusion. At low bile acid secretion rates, during bile acid pool depletion and during cholic acid infusion, the lecithin secretion rate was significantly correlated to the cholesterol secreation rate. The bile acid and cholesterol secretion rates were not significantly correlated during chenodeoxycholic acid infusion. However, under this experimental condition a significant curvilinear relationship between lecithin and cholesterol secretion rates was found. The hepatic bile became unsaturated in cholesterol at significantly lower bile acid secretion rate during chenodeoxycholic acid infusion (10.7 +/- 0.3 mumol min-1) than during cholic acid infusion (15.6 +/- 0.5 mumol min-1).