Abstract
The neutral carbohydrate content of both the protein (apoB) and lipid fractions of low density lipoproteins (LDL) from subjects with a predominance of small, dense LDL (subclass pattern B) was found to be lower than in subjects with larger LDL (subclass pattern A): 45 +/- 12 versus 64 +/- 13 mg/g apoLDL, and 58 +/- 8 versus 71 +/- 8 mg/g apoLDL (P less than 0.0005 for both). Sialic acid content of LDL lipids, but not apoB, was also reduced in subclass pattern B. ApoB and glycolipid carbohydrate content of total LDL and LDL density subfractions declined with increasing LDL density and decreasing particle diameter. Moreover, in LDL subfractions from pattern B subjects, carbohydrate content of LDL apoB, but not LDL glycolipid, was significantly lower in comparison with particles of similar size from pattern A subjects. Thus, in LDL subclass pattern B, reductions in LDL carbohydrate content are associated both with reduced concentrations of larger carbohydrate-enriched LDL subclasses, and with reduced glycosylation of apoB in all LDL particles. LDL glycolipids may vary with overall lipid content of LDL particles, but variation in apoB glycosylation may indicate differences in pathways for LDL production, and reduced apoB glycosylation may reflect the altered metabolic state responsible for LDL subclass pattern B.
Highlights
The neutral carbohydrate content of both the protein and lipid fractions of low density lipoproteins (LDL)
Differences in carbohydrate content of low density lipoproteins associated with low density lipoprotein subclass patterns
Low density lipoproteins are complex macromolecules consisting of a core of esterified cholesterol surrounded by a layer of more polar lipids and a single large ( = 550 kD) glycoprotein, apolipoprotein B
Summary
BSA, resorcinol, amyl alcohol, copper sulfate, Dmannose, sialic acid, and neuraminidase (Type X) were from Sigma. Relatively small major LDL peak (251 A) and a larger diameter (264 A) secondary LDL peak. Buoyant density and relatively lower 1ipid:protein ratio than the larger LDL that predominate in subclass pattern. At least 50% of the carbohydrate on apoB is present in the form of either of two types of N-linked carbohydrate chains: a high-mannose oligosaccharide containing six mannose and two N-acetylglucosamine residues and a complex-type oligosaccharide containing two sialic acid, two galactose, five mannose, and three N-acetylglucosamine residues [22]. In this study we report on differences in the carbohydrate content of the LDL isolated from subjects with LDL subclass pattern A or B. Additional studies were carried out in a 31-year-old female with heterozygous familial hypercholesterolemia (total cholesterol 366 mgldl, HDL cholesterol 70 mg/dl, LDL cholesterol 275 mg/dl, and plasma triglycerides 107 mgldl)
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