Characterization of proteoliposomes containing apoprotein A-I: a new substrate for the measurement of lecithin: cholesterol acyltransferase activity.

Chen, C H; Albers, John J.

doi:10.1016/s0022-2275(20)38100-1

Cited by 295 publications

(23 citation statements)

References 33 publications

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“…LCAT activity was assayed by using proteoliposome substrates, prepared according to the method of Chen and Albers (27). The substrate contained PC:[4-14 C] cholesterol:apoA-I at molar ratios of 250:12.5:0.8.…”

Section: Enzyme Assaysmentioning

confidence: 99%

“…Effect of the presence of trans-fatty acid at sn-2 position of substrate PC on LCAT activity. Synthetic PCs, containing 16:0 at sn-1 position and the indicated fatty acid at sn -2, were incorporated into proteoliposome substrates (27), which contained a common 'inert' matrix (90% POPC diether and 10% test PC), in addition to labeled cholesterol and apoA-I. Cholesterol esterification was determined as described in Methods, and the esterification rate obtained in presence of the trans -PC was expressed as the % of the activity obtained with the corresponding cis isomer under identical conditions.…”

Section: Effect Of Positional Isomers Of Tufa-containing Pcsmentioning

confidence: 99%

“…Inhibition of LCAT activity, assayed with egg PC substrate, by TUFA-containing PC. Varying amounts of 16:0-18:1 t PC or 18:1t-16:0 PC were substituted for egg PC in the standard proteoliposome substrate (27) (keeping the total PC concentration constant) and activities of purified human LCAT (top) and rat LCAT (bottom) were assayed in presence of the mixed substrates. All activities are expressed as % of the activity obtained in presence of 100% egg PC.…”

Section: Competition Of Tufa-containing Pc With Egg Pc Substratementioning

confidence: 99%

“…2.Effect of the presence of trans-fatty acid at sn-1 position of substrate PC on LCAT activity. Synthetic PCs that contained the indicated fatty acid at sn-1 and 20:4 at sn -2 were incorporated into proteoliposomes(27) with 90% POPC diether matrix, as described under Fig.1. The enzyme activity obtained with trans -PC is expressed as % of the activity obtained in presence of the corresponding cis-isomer.…”

mentioning

confidence: 99%

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Trans unsaturated fatty acids inhibit lecithin: cholesterol acyltransferase and alter its positional specificity

Subbaiah

Subramanian

Liu

1998

Journal of Lipid Research

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Although dietary trans unsaturated fatty acids (TUFA) are known to decrease plasma HDL, the underlying mechanisms for this effect are unclear. We tested the hypothesis that the decreased HDL is due to an inhibition of lecithin:cholesterol acyltransferase (LCAT), the enzyme essential for the formation of HDL, by determining the activity of purified LCAT in the presence of synthetic phosphatidylcholine (PC) substrates containing TUFA. Both human and rat LCATs exhibited significantly lower activity ( ؊ 37% to ؊ 50%) with PCs containing 18:1 t or 18:2 t , when compared with the PCs containing corresponding cis isomers. TUFA-containing PCs also inhibited the enzyme activity competitively, when added to egg PC substrate. The inhibition of LCAT activity was not due to changes in the fluidity of the substrate particle. However, the inhibition depended on the position occupied by TUFA in the PC, as well as on the paired fatty acid. Thus, for human LCAT, 18:1 t was more inhibitory when present at sn -2 position of PC, than at sn -1, when paired with 16:0. In contrast, when paired with 20:4, 18:1 t was more inhibitory at sn -1 position of PC. Both human and rat LCATs, which are normally specific for the sn -2 acyl group of PC, exhibited an alteration in their positional specificity when 16:0-18:1 t PC or 16:1 t -20:4 PC was used as substrate, deriving 26-86% of the total acyl groups for cholesterol esterification from the sn -1 position. These results show that the trans fatty acids decrease high density lipoprotein through their inhibition of lecithin: cholesterol acyltransferase (LCAT) activity, and also alter LCAT's positional specificity, inducing the formation of more saturated cholesteryl esters, which are more atherogenic.-Subbaiah, P. V., V. S. Subramanian, and M. Liu. Trans unsaturated fatty acids inhibit lecithin:cholesterol acyltransferase and alter its positional specificity.

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Section: Enzyme Assaysmentioning

confidence: 99%

Section: Effect Of Positional Isomers Of Tufa-containing Pcsmentioning

confidence: 99%

Section: Competition Of Tufa-containing Pc With Egg Pc Substratementioning

confidence: 99%

mentioning

confidence: 99%

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Trans unsaturated fatty acids inhibit lecithin: cholesterol acyltransferase and alter its positional specificity

Subbaiah

Subramanian

Liu

1998

Journal of Lipid Research

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“…This method measures the esterification of endogenous cholesterol and reflects not only enzyme concentration but also the effect of substrate and inhibitor composition. In the proteoliposome assay (25), an external substrate, containing labeled cholesterol, PC, and human apoA-I, was added to 20 l of plasma, and the esterification of labeled cholesterol was determined (24). This method reflects the concentration of active enzyme in the plasma and is believed to be unaffected by endogenous substrates, activators, or inhibitors (25).…”

Section: Enzyme Assaysmentioning

confidence: 99%

Impaired function of lecithin:cholesterol acyltransferase in atherosclerosis-susceptible White Carneau pigeons: possible effects on metabolism of oxidized phospholipids

Liu

Clair

Subbaiah

1998

Journal of Lipid Research

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Although White Carneau (WC) pigeons are known to be more susceptible to atherosclerosis than Show Racer (SR) pigeons, the reasons for this difference are not fully understood. While no major differences are known in the lipoprotein composition, a difference in the cholesteryl ester (CE) composition was reported. However, there is little information on the activity or specificity of lecithin:cholesterol acyltransferase (LCAT), the major source of plasma CE. In order to determine whether the esterification of cholesterol or other functions of LCAT are compromised in WC pigeons, we studied the various reactions catalyzed by LCAT in the two groups. The cholesterol esterification was found to be significantly lower in WC pigeons, whether assayed with exogenous or endogenous substrates. Furthermore, lyso phosphatidylcholine (PC) esterification and oxidized PC hydrolysis, two other reactions carried out by LCAT, were also lower in WC. We found evidence for the presence of an active lysophospholipase in pigeon plasma, and this activity was also lower in WC compared to SR. A significant increase in the FC/PC ratio, another reported atherogenic risk factor, was found in WC plasma.Because of the absence of other hydrolytic enzymes in pigeon plasma, LCAT may play an important role in the metabolism of oxidized PC generated during lipoprotein oxidation, and therefore a decrease in its activity in White Carneau pigeons may contribute to increased risk of atherosclerosis.-Liu, M., R. W. St. Clair, and P. V. Subbaiah. Impaired function of lecithin:cholesterol acyltransferase in atherosclerosis-susceptible White Carneau pigeons: possible effects on metabolism of oxidized phospholipids.

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Effectiveness of Low-Dose Crystalline Nicotinic Acid in Men With Low High-Density Lipoprotein Cholesterol Levels

et al. 1996

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A low dose (1.5 g/d) of crystalline nicotinic acid causes an average 20% increase in HDL-C levels and significantly lowers triglyceride levels in both normolipidemic and hyperlipidemic patients with low HDL-C levels. Although the changes induced by this dose are less than those that can be achieved by a higher dose, the lower dose is better tolerated. Nicotinic acid may be useful in combined drug therapy for secondary prevention of coronary heart disease, and if higher doses cannot be tolerated, use of a lower dose should still be useful for producing a moderate rise in HDL-C levels in patients with hypoalphalipoproteinemia.

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Characterization of proteoliposomes containing apoprotein A-I: a new substrate for the measurement of lecithin: cholesterol acyltransferase activity.

Cited by 295 publications

References 33 publications

Trans unsaturated fatty acids inhibit lecithin: cholesterol acyltransferase and alter its positional specificity

Trans unsaturated fatty acids inhibit lecithin: cholesterol acyltransferase and alter its positional specificity

Impaired function of lecithin:cholesterol acyltransferase in atherosclerosis-susceptible White Carneau pigeons: possible effects on metabolism of oxidized phospholipids

Effectiveness of Low-Dose Crystalline Nicotinic Acid in Men With Low High-Density Lipoprotein Cholesterol Levels

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