Lipoprotein(a) and Familial Hypercholesterolemia: A Short Review Including the Laboratory Viewpoint

Lp(a) does not affect intima media thickness in hypercholesterolemic children -a retrospective cross sectional study

PURPOSE

Combined hyperlipidaemia results in premature atherosclerosis and a high burden of cardiovascular morbidity and mortality. Early identification of highly affected subjects within this population is of utmost importance to enable informed treatment decisions. The measurement of intima media thickness (IMT) is a readily available, non-invasive method to investigate evidence of early atherosclerosis. To assess the usefulness of this method in pediatric subjects with hypercholesterolemia, we here examined a possible interaction of LDL-C and Lp(a) on IMT.

METHODS

Blood lipids (Lp(a), LDL-cholesterol, total cholesterol, triglycerides, high density lipoprotein (HDL) -cholesterol, apolipoprotein A1, apolipoprotein B), anthropometric parameters (age, height, weight, body mass index (BMI)) and possibly existing early evidence of atherosclerotic lesions measured by intima media thickness (IMT zscore).as a surrogate parameter was examined retrospectively in 113 children and adolescents (aged 1-18 years) with elevated Lp(a) and/or LDL-cholesterol (Lp(a) > 30 mg/dL, LDL>130 mg/dL). Furthermore, we compared hsCRP levels between groups.

RESULTS

There were no significant differences in IMT Zscore or hsCRP between groups. Regression analysis did not reveal a statistically significant interaction between Lp(a) and LDL-C.

CONCLUSIONS

At the age of 6-18 years, we found no significant differences in early markers of atherosclerosis between subjects with high Lp(a)- and/or high LDL-cholesterol with no detectable synergistic effects between the two lipoproteins.

Identification and Functional Characterization of a Low-Density Lipoprotein Receptor Gene Pathogenic Variant in Familial Hypercholesterolemia

We report a single-point variant of low-density lipoprotein receptor (LDLR) in a Chinese proband with a clinical diagnosis of familial hypercholesterolemia (FH) with a comprehensive functional analysis. Target exome capture-based next-generation sequencing was used for sequencing and identification of genomic variants in the LDLR gene. The expression, cellular location, and function of the mutant LDLR were analyzed. Sequencing of LDLR in FH patients indicated a point variant of single-base substitution (G < A) at a position of 2389 in the 16th exon, which led to a loss of the 16th exon in the LDLR messenger RNA. This genomic variant was found to cause exon 16 deletion in the mutant LDLR protein. Subsequent functional analyses showed that the mutant LDLR was retained in the Golgi apparatus and rarely expressed in the cellular membranes of HepG2 cells. Accordingly, the intake ability of HepG2 cells with the mutant LDLR was significantly reduced (P < 0.05). In conclusion, our results suggest that a mutant with a single-base substitution (c. 2389G > A) in the 16th exon of the LDLR gene was associated with miscleavage of messenger RNA and the retention of mutant LDLR in the Golgi apparatus, which revealed a pathogenic variant in LDLR underlying the pathogenesis of FH.