Genetics of Low Density Lipoprotein Subclasses in Hypercholesterolemia

February 8, 2016 updated by: University of Washington
To perform genetic studies of low density lipoprotein (LDL) subclasses in 160 families in whom the probands had metabolically defined hypercholesterolemia.

Study Overview

Status

Completed

Conditions

Detailed Description

BACKGROUND:

Low density lipoprotein cholesterol has been convincingly established as a major coronary heart disease risk factor by many epidemiologic studies, clinical trials, and experimental studies. A strong inverse association exists between high density lipoprotein cholesterol and coronary heart disease. However, the status of very low density lipoprotein (VLDL) cholesterol and plasma triglyceride levels as independent risk factors for cardiovascular disease is less clear. Case control studies have shown a positive association between coronary heart disease and plasma levels of apoprotein B, the major protein on LDL particles, and an inverse relationship with apoprotein AI, the primary protein constituent of HDL particles. In fact, it has been proposed that plasma levels of the apoproteins may be stronger risk factors than lipid levels. Thus, understanding the mechanisms underlying variations in both lipoprotein and apoprotein levels among individuals is essential to elucidating the etiology of coronary heart disease in the general population.

Cardiovascular disease is also known to cluster in families, and this may be related to the clustering of lipid and lipoprotein levels among family members. A review suggested that the familial aggregation of heart disease may be primarily a reflection of the familial aggregation of known risk factors, including cholesterol levels. The work of Goldstein and Brown on familial hypercholesterolemia demonstrated that genetic control of lipoprotein metabolism can play a causative role in the development of atherosclerosis. However, familial hypercholesterolemia is a relatively rare disorder: the prevalence of heterozygotes is estimated to be 1 in 500, homozygotes 1 in a million. In 1987, little was understood about more common genetic contributions to lipid and lipoprotein abnormalities leading to the familial aggregation of coronary heart disease.

DESIGN NARRATIVE:

The design was that of a cross-sectional family study. The recruitment and screening of probands were conducted over a four-year period at the University of Texas at Dallas under separate funding. The recruitment and screening of first-degree relatives were carried out at Berkeley. Blood samples were obtained from relatives for LDL subclass analysis and for lipid and apoprotein determination. An interview was conducted to obtain demographic information and information on behavioral and environmental risk factors such as smoking, exercise, and diet. The data were used to determine whether LDL subclasses were genetically controlled in families with hypercholesterolemia due to overproduction of LDL or defective clearance of LDL particles. Segregation analysis of LDL subclasses in these two types of families was performed to search for a single major genetic locus and to simultaneously test for the influence of polygenes and environmental effects. The relationships between the LDL subclass phenotype characterized by a predominance of small, dense LDL and overproduction of apoprotein B and LDL clearance defects were investigated in family members. A determination was made as to whether an age-of-onset effect existed for the expression of LDL subclass phenotypes. Genetic-environmental interactions were also studied.

Study Type

Observational

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

No older than 100 years (Child, Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

Male

Description

No eligibility criteria

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Collaborators and Investigators

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Sponsor

University of Washington

Collaborators

National Heart, Lung, and Blood Institute (NHLBI)

Investigators

  • Melissa Austin, University of Washington

Publications and helpful links

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General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

July 1, 1987

Study Completion

June 1, 1992

Study Registration Dates

First Submitted

May 25, 2000

First Submitted That Met QC Criteria

May 25, 2000

First Posted (Estimate)

May 26, 2000

Study Record Updates

Last Update Posted (Estimate)

February 10, 2016

Last Update Submitted That Met QC Criteria

February 8, 2016

Last Verified

August 1, 2004

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1082
  • R29HL038760 (U.S. NIH Grant/Contract)

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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