Improved detection of familial hypercholesterolemia by determining low density lipoprotein receptor expression in mitogen-induced proliferating lymphocytes.

Abstract

In view of the presence of some 190 mutations in the low density lipoprotein receptor (LDL-R) gene and a lack of simple detection methods, we have developed an improved assay system for detecting familial hypercholesterolemia (FH) using mitogen-induced proliferating lymphocytes. Freshly isolated mononuclear cells were cultured for 3 days in RPMI 1640 supplemented with 10% human lipoprotein-deficient serum (LPDS) and 1% phytohemagglutinin (PHA). LDL-R expression was measured by flow cytometry using a monoclonal anti-LDL-R antibody or DiI-LDL. Mitogenic responses were monitored by cell size (FSC), interleukin-2 receptor (IL2-R) expression, and stimulation index (SI). The LDL-R expression in PHA-stimulated lymphocytes was significantly higher than lymphocytes or monocytes cultured without PHA (15.2- and 3.6-fold, respectively). The gradation of the LDL-R expression was highly correlated to FSC, IL2-R expression, and SI (r > 0.9 in each case). However, no difference in FSC, IL2-R expression, or SI existed between 30 clinically diagnosed FH and 42 normolipemic control subjects. The significantly lower LDL-R expression in the FH group (45.2 +/- 15.3% versus 100 +/- 14.1%; unpaired t test, P < 0.0001) indicated the presence of genetic defects. Normocholesterolemic first degree relatives and non-FH hypercholesterolemic subjects demonstrated normal LDL-R expression as did the controls. The assay carries an efficiency of 97% and both sensitivity and specificity of 98.5%. Measurement of low density lipoprotein receptor expression in phytohemagglutinin- and lipoprotein-deficient serum-stimulated lymphocytes offers a simple method for detecting familial hypercholesterolemia with improved sensitivity.

• Authors: P C Chan, A Edwards, R Lafrenière, H G Parsons
• Journal: Journal of lipid research (J Lipid Res) Vol. 39 Issue 11 Pg. 2261-70 (Nov 1998) ISSN: 0022-2275 [Print] United States
• PMID: 9799812 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Lipopolysaccharide Receptors
• Mitogens
• Receptors, Interleukin-2
• Receptors, LDL
• Tetradecanoylphorbol Acetate

Topics

• Adolescent
• Adult
• Aged
• Cell Separation
• Child
• Female
• Flow Cytometry (methods)
• Humans
• Hyperlipoproteinemia Type II (diagnosis)
• Lipopolysaccharide Receptors (analysis)
• Lymphocyte Activation
• Lymphocytes (drug effects, metabolism)
• Male
• Middle Aged
• Mitogens (pharmacology)
• Receptors, Interleukin-2 (analysis)
• Receptors, LDL (biosynthesis)
• Tetradecanoylphorbol Acetate (pharmacology)
• Up-Regulation