Familial Hypercholesterolaemia in the Era of Genetic Testing

How registers could enhance knowledge and characterization of genetic dyslipidaemias: The experience of the LIPIGEN in Italy and of other networks for familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a common genetic disorder of lipid metabolism, still underdiagnosed and undertreated in the general population. Pathology registers could play a crucial role in the creation of a comprehensive and integrated global approach to cover all aspects of this disease. Systematic data collection of patients affected by FH has increased dramatically worldwide in the past few years. Moreover, results from registers already established for the longest time showed their potentialities in the implementation of the knowledge of FH, comparing country-specific approaches and providing real-world data about identification, management and treatment of FH individuals in the clinical practice. The potential fields of research through registers are related to the deepening of the genetic basis of disease, the study of genotype-phenotype correlation, the local adaption and implementation of diagnostic algorithms, the comparison of pharmacological approaches and treatment gaps in real-life clinical practice, the evaluation of specific subpopulations, and the identification of factors modifying cardiovascular disease risk. Registers could become also a valid resource for other rare dyslipidaemias, contributing towards the evidence-based enhancement in the worldwide care of uncommon diseases.

Replacement of cysteine at position 46 in the first cysteine-rich repeat of the LDL receptor impairs apolipoprotein recognition

Background and aims

Pathogenic mutations in the Low Density Lipoprotein Receptor gene (LDLR) cause Familial Hypercholesterolemia (FH), one of the most common genetic disorders with a prevalence as high as 1 in 200 in some populations. FH is an autosomal dominant disorder of lipoprotein metabolism characterized by high blood cholesterol levels, deposits of cholesterol in peripheral tissues such as tendon xanthomas and accelerated atherosclerosis. To date, 2500 LDLR variants have been identified in the LDLR gene; however, only a minority of them have been experimentally characterized and proven to be pathogenic. Here we investigated the role of Cys46 located in the first repeat of the LDL receptor binding domain in recognition of apolipoproteins.

Methods

Activity of the p.(Cys46Gly) LDLR variant was assessed by immunoblotting and flow cytometry in CHO-ldlA7 expressing the receptor variant. Affinity of p.(Cys46Gly) for LDL and VLDL was determined by solid-phase immunoassays and in silico analysis was used to predict mutation effects.

Results and conclusion

Functional characterization of p.(Cys46Gly) LDLR variant showed impaired LDL and VLDL binding and uptake activity. Consistent with this, solid-phase immunoassays showed the p.(Cys46Gly) LDLR variant has decreased binding affinity for apolipoproteins. These results indicate the important role of Cys46 in LDL receptor activity and highlight the role of LR1 in LDLr activity modulation. This study reinforces the significance of in vitro functional characterization of LDL receptor activity in developing an accurate approach to FH genetic diagnosis. This is of particular importance because it enables clinicians to tailor personalized treatments for patients’ mutation profile.

Genetics of Dyslipidemia and Ischemic Heart Disease

PURPOSE OF REVIEW

Genetic dyslipidemias contribute to the prevalence of ischemic heart disease. The field of genetic dyslipidemias and their influence on atherosclerotic heart disease is rapidly developing and accumulating increasing evidence. The purpose of this review is to describe the current state of knowledge in regard to inherited atherogenic dyslipidemias. The disorders of familial hypercholesterolemia (FH) and elevated lipoprotein(a) will be detailed. Genetic technology has made rapid advancements, leading to new discoveries in inherited atherogenic dyslipidemias, which will be explored in this review, as well as a description of possible future developments. Increasing attention has come upon the genetic disorders of familial hypercholesterolemia and elevated lipoprotein(a).

RECENT FINDINGS

This review includes new knowledge of these disorders including description of these disorders, their method of diagnosis, their prevalence, their genetic underpinnings, and their effect on the development of cardiovascular disease. In addition, it discusses major advances in genetic technology, including the completion of the human genome sequence, next-generation sequencing, and genome-wide association studies. Also discussed are rare variant studies with specific genetic mechanisms involved in inherited dyslipidemias, such as in the proprotein convertase subtilisin/kexin type 9 (PCSK9) enzyme. The field of genetics of dyslipidemia and cardiovascular disease is rapidly growing, which will result in a bright future of novel mechanisms of action and new therapeutics.