Appearance and Characterization of Lipoprotein X during Continuous Intralipid Infusions in the Neonate

Abstract

A B S T R A C T The development of hyperphospholipidemia and hypercholesterolemia was studied in infants that required total parenteral nutrition and given a continuous infusion of Intralipid, (1)(2)(3)(4) g/kg body wt per 24 h. Detailed studies were carried out on infusion periods lasting 1-10 d. After 24 h there was a marked increase in plasma free cholesterol (68%) and phospholipid (77%) concentrations. Based on the amount of cholesterol in Intralipid, and the rate of infusion, it was estimated that at least 50% of the plasma cholesterol increment during 64-h infusions was derived from endogenous sources. By contrast, the hyperphospholipidemia could be attributed to the Intralipid as the rise in plasma was calculated to be equivalent to only 16% of the exogenous phospholipid infused. Approximately 10% of the phospholipid in Intralipid was in a triglyceride-free mesophase form with a free cholesterol:phospholipid molar ratio of 0.063. There were no systematic changes in plasma concentrations of cholesterol ester or triglyceride during Intralipid infusions. The increase in free cholesterol and phospholipid was localized in the low density lipoproteins (d = 1.006-1.063 g/ml). The presence of lipoprotein X (Lp-X) 2 Detailed analyses of Intralipid (three preparations) revealed the presence of free cholesterol (4 mg/g Intralipid triglyceride) as well as plant sterols (2 mg/g Intralipid triglyceride). Two Intralipid preparations were subjected to ultracentrifugation at saline density (1.6 x 106 g min). Analysis of the supematant and infranatant fractions obtained after tube slicing revealed that 8-12% of the total phospholipid and free cholesterol was associated with the infranatant fraction as a triglyceride-free micelle. The molar ratio of free cholesterol:phospholipid in the triglyceride-rich supernatant and the infranatant mesophase was 0.063.3Griffin, E. A., M. H. Bryan, and A. Angel. Intralipid tolerance tests and continuous infusion in neonates. Manuscript submitted for publication. cellulose nitrate centrifuge tubes. Plasma (0.6-1.0 ml) was overlayered with saline, pH 7.4 (d = 1.006 g/ml) and centrifuged at 106,000 g for 18 h. A supematant fraction (0.8 ml) and an infranatant fraction (1.2 ml) were quantitatively collected by tube slicing. The infranatant fraction was adjusted to d 1.063 and centrifuged at 106,000 g for 24 h to obtain low density lipoproteins (LDL) in the supernatant fraction. For studies involving protein analyses, LDL was washed once. The infranatant was adjusted to d = 1.21 g/ml and centrifuged for 42 h at 106,000 g to obtain high density lipoproteins (HDL).The lipoproteins ofd 1.006-1.063 were further resolved by hydroxylapatite column chromatography as described by Kostner et al. (14) for the isolation of lipoprotein X (Lp-X) from cholestatic patients. In these studies, columns were eluted at 0.1 M phosphate buffer (pH 6.8) to obtain Lp-X and at 0.65 M phosphate (pH 6.8) to obtain "residual LDL." Because initial studies demonstrated that the elution profiles monitored by optical den...

Plasma Cholesterol and Lathosterol Levels in Term Infants in the Early Neonatal Period

“…Finally, plasma mevalonate analysis would also require verificaiton for use in the neonate. In support of the lathosterol methodology, our data from preterm infants (34) show elevated plasma lathosterol levels coincident with administration of 10% Intralipid, which is predicted to be a stimulant of cholesterol synthesis (35).…”

Short-Term Exposure to Exogenous Lipids in Premature Infants and Long-Term Changes in Aortic and Cardiac Function

“…Further work is needed to determine how this alteration in lipid profile and subsequent clearance by the neonate results in long-term changes in cardiac and vascular pathophysiology. 8 We studied aortic PWV as our primary end point as a gold standard measurement of global aortic stiffness. 11 Aortic PWV is known to be relevant to later cardiovascular outcome and improve cardiovascular risk prediction when combined with other cardiovascular risk factors.…”

“…7 Hypercholesterolemia secondary to Intralipid use is well described, likely driven by endogenous cholesterol synthesis as a result of delayed lipid clearance. [7][8][9] Because fatty streaks first appear in the aorta, 5 and in animal models arterial stiffness is the first pathophysiological change that occurs during this process, 10 we studied global aortic stiffness in early adulthood, measured as pulse wave velocity (PWV), a measure known to be relevant to later cardiovascular outcome in large-scale studies. 11 We used cardiovascular magnetic resonance imaging, 12 which, as it images the aorta directly, also allowed us to study regional variation in aortic stiffness.…”

Low Levels of Apolipoprotein A1 Are Not Contributors to the Low Lecithin-Cholesterol Acyl Transferase Activity in Premature Newborn Infants

“…borns, Intralipid overload leads to phospholipid accumulation and hyperlipemia (3)(4)(5)(6)(7)(8) that could be due to low LCAT activity. Indeed, LCAT activity was found to be lower at birth than in adults (9)(10)(11)(12).…”