Isolation and carbohydrate composition of glycopeptides of human apo low-density lipoprotein from normal and type II hyperlipoproteinemic subjects

1976 ◽  
Vol 54 (9) ◽  
pp. 829-833 ◽  
Author(s):  
P. Lee ◽  
W. Carl Breckenridge
Keyword(s):  
Molecular Weight ◽  
Low Density Lipoprotein ◽  
Gel Filtration ◽  
Density Lipoprotein ◽  
Major Portion ◽  
Low Density ◽  
Type Ii ◽  
Carbohydrate Composition ◽  
Considerable Heterogeneity ◽  
Normal Individuals

Glycopeptides were prepared from the delipidized protein of low-density lipoprotein (LDL, d = 1.019–1.063) of three normal and three familial heterozygous type II hyperlipoproteinemic (HLP) subjects. The glycopeptides of all subjects were resolved into three groups by gel filtration on Bio-Gel P6 following papain (EC 3.4.22.2) digestion and initial purification on Bio-Gel P2. In normal individuals the component of largest molecular weight (F-1) contained mannose (Man), N-acetyl glucosamine (GlcNAc), galactose (Gal), and N-acetyl neuraminic acid (NANA) in the respective amounts of 45.9 ± 6.7, 37.3 ± 5.9, 28.6 ± 3.4, and 27.0 ± 3.9 nmol/mg original apoprotein. The group of smallest molecular weight (F-3) contained essentially only Man (25.8 ± 1.5 nmol/mg protein) and GlcNac (3.0 ± 0.4 nmol/mg protein) with traces of Gal and NANA. A group of intermediate molecular weight (F-2) exhibited considerable heterogeneity and contained Man, GlcNAc, Gal, and NANA in the amounts of45.9 ± 5.1, 18.3 ± 1.7, 11.0 ± 1.7, and 7.7 ± 1.2 nmol/mg protein. While the major portion of NANA (78%), Gal (71%), and GlcNAc (64%) was present in F-1, approximately 22% of the total Man was in F-3. No major differences were detected in the carbohydrate composition of the three glycopeptide fractions of LDL apoprotein from normal and Type II subjects.

The carbohydrate composition of human apo low density lipoprotein from normal and type II hyperlipoproteinemic subjects

1976 ◽  
Vol 54 (1) ◽  
pp. 42-49 ◽  
Author(s):  
P. Lee ◽  
W. Carl Breckenridge
Keyword(s):  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Normal Subjects ◽  
Low Density ◽  
Type Ii ◽  
Carbohydrate Composition ◽  
Acetylneuraminic Acid ◽  
Liquid Chromatographic Analysis ◽  
Liquid Chromatographic

The carbohydrate composition of the apoprotein from low density lipoprotein (LDL) of normal (average LDL cholesterol, 122 mg/100 ml) and type II hyperlipoproteinemic (average LDL cholesterol, 236 mg/100 ml) males was studied using gas–liquid chromatographic analysis of the methyl glycoside derivatives. All samples containing detectable sinking pre-beta-lipoprotein were excluded from the study.The apo LDL from both groups of subjects contained mannose, galactose, N-acetylglucosamine, and N-acetylneuraminic acid. Glucose and fucose were not found while trace quantities of galactosamine were detected. Although the quantities of galactose and N-acetylglucosamine were the same in the two groups, lower quantities of mannose [Formula: see text] and N-acetylneuraminic acid [Formula: see text] were found in the type II patients as opposed to normal subjects.

Processing and characterization of the low density lipoprotein receptor in the human colonic carcinoma cell subclone HT29-18: A potential pathway for delivering therapeutic drugs and genes

1992 ◽  
Vol 12 (6) ◽  
pp. 483-494 ◽  
Author(s):  
J. C. Mazière ◽  
C. Mazière ◽  
S. Emami ◽  
B. Noel ◽  
Y. Poumay ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Carcinoma Cell ◽  
Low Density Lipoprotein ◽  
Human Fibroblasts ◽  
Density Lipoprotein ◽  
Apparent Molecular Weight ◽  
Colonic Carcinoma ◽  
Sterol Synthesis ◽  
Low Density ◽  
Ldl Binding

Low density lipoprotein (LDL) processing has been investigated in the subcloned human colonic carcinoma cell line HT29-18. LDL binding at 4°C was a saturable process in relation to time and LDL concentration. The Kd for LDL binding was 11 μg/ml. ApoE-free HDL3 or acetylated LDL did not significantly compete with125I-LDL binding, up to 500 μg/ml.125I-LDL binding was decreased by 70% in HT29-18 cells preincubated for 24 hours in culture medium containing 100 μg/ml unlabelled LDL. Ligand blotting studies performed on HT29-18 homogenates using colloidal gold labelled LDL indicated the presence of one autoradiographic band corresponding to an apparent molecular weight of 130 kDa, which is consistent with the previously reported molecular weight of the LDL receptor in human fibroblasts. At 37°C,125I-LDL was actively internalized by HT29-18 cells and lysosomal degradation occurred as demonstrated by the inhibitory effect of chloroquine. LDL uptake and degradation by HT29-18 cells also resulted in a marked decrease in endogenous sterol synthesis. These data demonstrate that the HT29-18 human cancerous intestinal cells are able to specifically bind and internalize LDL, and that LDL processing results in down-regulation of sterol biosynthesis. Thus, intestinal epithelial cells possess specific LDL receptors that can be exploited to accomplish drug delivery and gene transfer via the receptor-mediated endocytosis pathway.

Paraoxonase-1 (PON-1) genotype and activity and in vivo oxidized plasma low-density lipoprotein in Type II diabetes

2005 ◽  
Vol 109 (2) ◽  
pp. 189-197 ◽  
Author(s):  
Mike J. Sampson ◽  
Simon Braschi ◽  
Gavin Willis ◽  
Sian B. Astley
Keyword(s):  
Type Ii Diabetes ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Paraoxonase 1 ◽  
Ldl Oxidation ◽  
Phenyl Acetate ◽  
Low Density ◽  
Type Ii

The HDL (high-density lipoprotein)-associated enzyme PON (paraoxonase)-1 protects LDL (low-density lipoprotein) from oxidative modification in vitro, although it is unknown if this anti-atherogenic action occurs in vivo. In a cross-sectional study of 58 Type II diabetic subjects and 50 controls, we examined the fasting plasma LDL basal conjugated diene concentration [a direct measurement of circulating oxLDL (oxidatively modified LDL)], lipoprotein particle size by NMR spectroscopy, PON-1 polymorphisms (coding region polymorphisms Q192R and L55M, and gene promoter polymorphisms −108C/T and −162G/A), PON activity (with paraoxon or phenyl acetate as the substrates) and dietary antioxidant intake. Plasma oxLDL concentrations were higher in Type II diabetic patients (males, P=0.048; females, P=0.009) and unrelated to NMR lipoprotein size, PON-1 polymorphisms or PON activity (with paraoxon as the substrate) in any group. In men with Type II diabetes, however, there was a direct relationship between oxLDL concentrations and PON activity (with phenyl acetate as the substrate; r=0.611, P=0.0001) and an atherogenic NMR lipid profile in those who were PON-1 55LL homozygotes. Circulating oxLDL concentrations in vivo were unrelated to PON-1 genotypes or activity, except in male Type II diabetics where there was a direct association between PON activity (with phenyl acetate as the substrate) and oxLDL levels. These in vivo data contrast with in vitro data, and may be due to confounding by dietary fat intake. Male Type II diabetic subjects with PON-1 55LL homozygosity have an atherogenic NMR lipid profile independent of LDL oxidation. These data do not support an in vivo action of PON on LDL oxidation.

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