Palmitic acid in HDL is associated to low apo A-I fractional catabolic rates in vivo.
BACKGROUND
HDL becomes enriched with non-esterified fatty acids (NEFAs) in some pathologies, such as nephrotic syndrome, as well as after aerobic exercise. However, little is known about the impact of NEFAs on HDL metabolism. We investigated the effects of one NEFA, the palmitic acid, on HDL structure and catabolism.


METHODS
HDL enrichment with palmitic acid (HDLPal) was performed by fusing phosphatidyl choline small unilamellar vesicles containing the NEFA with human HDL isolated from a pool of 5 normolipidemic plasma. HDL enriched only with phosphatidyl choline (HDLPhl) and native HDL (HDLCtrl) were included as controls.


RESULTS
As expected, HDLPal surface charge density was higher than HDLPhl and HDLCtrl (2014.4+/-164.8 vs. 1682.7+/-149.5 and 1758.2+/-124.3-esu/cm2, respectively, p<0.05). Both, HDLPal and HDLPhl were better substrates for cholesteryl esters transfer protein (CETP) than HDLCtrl (% of transfer, 13.02+/-3.8 and 12.7+/-4.5 vs. 7.8+/-2.7% in 16 h, respectively, p<0.05). HDLPal apo A-I catabolism in vivo, as performed in New Zealand white rabbits by exogenous radiolabeling, was markedly lower than that of HDLPhl and HDLCtrl (fractional catabolic rate, 0.019+/-0.008 vs. 0.030+/-0.005 and 0.047+/-0.003 h-1, respectively, p<0.001), suggesting that negative charge is inversely related to HDL-apo A-I catabolism.


CONCLUSIONS
Enrichment with palmitic acid increases the negative electric charge of HDL at physiological pH, contributes to decrease their catabolism, and is associated to an enhanced lipid transfer by CETP that has been related to the atherogenic process.
Pérez-Méndez
Oscar
O
Department of Physiology, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico. opmendez@yahoo.com
Alvarez-Salcedo
Paris
P
Carreón Torres
Elizabeth
E
Luc
Gérald
G
Arce Fonseca
Minerva
M
de la Peña
Aurora
A
Cruz Robles
David
D
García
José J
JJ
Vargas-Alarcón
Gilberto
G
D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism*; D053480:Cholesterol Ester Transfer Proteins / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000032:analysis; D006801:Humans; D008075:Lipoproteins, HDL / Q000032:analysis / Q000737:chemistry*; D019308:Palmitic Acid / Q000032:analysis*; D011817:Rabbits
D016632:Apolipoprotein A-I; D053480:Cholesterol Ester Transfer Proteins; D005230:Fatty Acids, Nonesterified; D008075:Lipoproteins, HDL; D019308:Palmitic Acid