ESI-MS quantitation of increased sphingomyelin in Niemann-Pick disease type B HDL

Ching Yin Lee,Alain Lesimple,Åsmund Larsen,Orval Mamer,Jacques Genest

doi:10.1194/jlr.m500011-jlr200

Ching Yin Lee, Alain Lesimple + Show 3 more

Open Access

https://doi.org/10.1194/jlr.m500011-jlr200

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Abstract

HDLs have been proposed to have antiatherogenic properties because of their role in reverse cholesterol transport as lipid acceptors. To elucidate the phospholipid profile of these particles, we used electrospray ionization mass spectrometry to examine the phosphatidylcholine (PC) and sphingomyelin (SM) composition of HDLs purified from plasma and nascently generated in vitro from fibroblasts. We also quantitatively compared the phospholipids present in these lipoproteins between normal and Niemann-Pick disease type B (NPD-B) subjects characterized by sphingomyelinase (SMase) deficiency. We demonstrated that plasma HDLs from NPD-B were significantly enriched in SM by an average of 28%, particularly the palmitoyl SM (with an increase of 95%), which accounted for approximately 25-44% of total SM molecular species. Similarly, we observed an increase of approximately 63% in total SM levels in nascent HDLs prepared from NPD-B fibroblasts. Although PC levels in nascent HDLs were comparable between control and NPD-B cells, there was a 95% increase in total PC levels similar to that of SM in plasma HDLs extracted from NPD-B subjects. These data provide insight into the structure of HDLs and identify potential new roles for SMase in lipoprotein metabolism.

Highlights

HDLs have been proposed to have antiatherogenic properties because of their role in reverse cholesterol transport as lipid acceptors
Niemann-Pick disease type B (NPD-B) is an autosomal recessive disorder caused by mutations in the sphingomyelin phosphodiesterase 1 (SMPD-1) gene, which codes for the acid sphingomyelinase (SMase)
HDL particles are formed through a stepwise maturation process: lipidfree apolipoprotein A-I is initially lipidated with phospholipids to form disc-like pre␤ HDLs

Summary

Introduction

HDLs have been proposed to have antiatherogenic properties because of their role in reverse cholesterol transport as lipid acceptors. PC levels in nascent HDLs were comparable between control and NPD-B cells, there was a 95% increase in total PC levels similar to that of SM in plasma HDLs extracted from NPD-B subjects. These data provide insight into the structure of HDLs and identify potential new roles for SMase in lipoprotein metabolism.—Lee, C. LCAT promotes the esterification of their cholesterol content, forming spherical HDL particles with an inner core of cholesteryl esters These ␣-migrating particles absorb more lipids and mature into HDL2 particles [4, 5]. Mass spectrometry is the most sophisticated technique for assessing the phospholipid content of biological samples because of its high sensitivity and unmatched specificity, as it directly analyzes phospholipids as intact

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