Influence of OCTN2 Variants on Carnitine Status and Plasma Triglycerides

September 11, 2012 updated by: University of California, San Francisco
The current study is part of a large multi-investigator grant to look at the pharmacogenetics of a number of membrane transporters. Previously, the investigators have recruited a cohort of healthy volunteers (Studies of Pharmacogenetics in Ethnically-Diverse Populations, or SOPHIE) and have resequenced the coding region of a number of membrane transporter genes to identify genetic polymorphisms in these genes. Subjects in this cohort have agreed to be called back for recruitment in further studies based on their own genetic sequence, allowing the investigators the possibility to prospectively study the influence of genetic polymorphisms on particular phenotypes (i.e., genotype-to-phenotype studies). The investigators plan to take a genotype-to-phenotype approach to study the influence of specific polymorphisms in the novel organic cation transporter 2 (OCTN2) gene on carnitine and lipid metabolism in healthy subjects.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Although OCTN2 is fairly well studied in its relationship with SCD, little is known about the carrier frequency of disease-causing alleles of OCTN2, or of more common functional polymorphisms in this gene. To address these issues, we screened for genetic variants in the OCTN2 coding region by direct sequencing of the exons and flanking intronic region of OCTN2 in a large sample (n = 276) of ethnically diverse subjects. In addition, we established lymphoblastoid cell lines from subjects homozygous for either allele of the previously identified promoter region variant, -207G>C. We found eight amino acid sequence variants of OCTN2, of which three (Phe17Leu, Leu144Phe, and Pro549Ser) were polymorphic in at least one ethnic group. When assayed for functional activity by expression in human embryonic kidney 293 cells, using as probes both the endogenous substrate (l-carnitine) and the organic cation tetraethylammonium, three variants showed functional differences from the reference OCTN2 (Phe17Leu, Tyr449Asp, Val481Phe; p < 0.05). Further studies of the Phe17Leu polymorphism showed a reduced V(max) for l-carnitine transport to approximately 50% of the reference OCTN2. Confocal microscopy studies using an OCTN2-GFP fusion protein showed that Phe17Leu had distinct subcellular localization from the reference OCTN2, with diffuse cytoplasmic retention of Phe17Leu, in contrast to reference OCTN2, which localized specifically to the plasma membrane. Lymphoblasts from subjects homozygous for the -207G allele showed increased l-carnitine transport compared with the -207C/C homozygotes (p < 0.05). This study suggests that although loss-of-function mutations in OCTN2 are likely to be rare, common variants of OCTN2 found in healthy populations may contribute to variation in the disposition of carnitine and some clinically used drugs.

Study Type

Observational

Enrollment (Actual)

16

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • California
      • San Francisco, California, United States, 94143
        • San Francisco General Hospital

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

18 years to 40 years (ADULT)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

Healthy individuals per screening laboratory results and health questionnaire

Description

Inclusion Criteria:

  • Previous participation in the "SOPHIE" study
  • Between the ages of 18 and 40 years old
  • Have a pre-selected genotype for OCTN1 and OCTN2
  • Have been selected as healthy by medical history questionnaire and screening blood work (complete blood count [CBC], comprehensive metabolic panel).

Exclusion Criteria:

  • Pregnant at the time of the study
  • Have a new history indicating they are no longer healthy
  • Taking a medication that could confound study results
  • Individuals with anemia (hemoglobin < 12 g/dL), an elevation in liver enzymes to higher than double the respective normal value, or elevated creatinine concentrations (males ≥ 1.5 mg/dL, females ≥ 1.4 mg/dL).
  • Do not consent to participate in the study.

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?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Fasting
Other: Fasting blood and urine collection
Other: Fasting blood and urine collection
Not applicable no drugs dispensed

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of California, San Francisco

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

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

January 1, 2005

Primary Completion (ACTUAL)

February 1, 2008

Study Completion (ACTUAL)

February 1, 2008

Study Registration Dates

First Submitted

September 14, 2005

First Submitted That Met QC Criteria

September 14, 2005

First Posted (ESTIMATE)

September 16, 2005

Study Record Updates

Last Update Posted (ESTIMATE)

September 13, 2012

Last Update Submitted That Met QC Criteria

September 11, 2012

Last Verified

September 1, 2012

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 1005

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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