Organic Cation Transporter 1 (OCT1), on Response to Metformin in Healthy Subjects

December 6, 2012 updated by: University of California, San Francisco

Effect of Genetic Variants in the Xenobiotic Transporter, OCT1, on Response to Metformin in Healthy Subjects

Specific Objectives:

  • To determine if individuals who carry a decreased or non-functional variant of OCT1 exhibit differences in the pharmacokinetics of metformin in comparison to individuals who carry the common allele.
  • To determine if individuals who carry the decreased or non-functional variants exhibit differences in the response to metformin in comparison to individuals who carry the common allele.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

In the proposed studies, we will address two questions:

•Do individuals who carry one of OCT1 variants with reduced or no function exhibit differences in the pharmacokinetics of metformin in comparison to individuals who carry the common allele?

Compared to wild type mice, Oct1-/- mice have reduced metformin distribution to the liver and intestine. We expect a similar pattern between persons who carry the variant OCT1 allele and those who carry the common allele. This effect might be reflected by a difference of Tmax or Cmax after oral administration of metformin. Other differences in metformin pharmacokinetic properties such as volume of distribution, half life and clearance may also be evident.

•Do individuals who carry the decreased or non-functional variants exhibit differences in the response to metformin in comparison to individuals who carry the common allele? Specially, we will test the hypothesis that the OCT1-expressing tissues are target organs for metformin, and that individuals with the variant transporters may have reduced metformin uptake into these sites (is this the correct meaning?) and therefore a reduced drug response to metformin.

In this study, we will evaluate metformin pharmacokinetics and glucose metabolic effects in healthy subjects rather than in patients with type 2 diabetes. Our rationale is as follows. The hepatic glucose production in diabetic patients is abnormally increased. Metformin decreases fasting blood glucose concentration by reducing hepatic glucose production and improving glucose utilization. However, the fasting blood glucose concentration is not decreased by metformin in non-diabetics who have a normal hepatic glucose production. It was suggested that the glucose-lowering effect of metformin was difficult to demonstrate in non-diabetics unless glucose concentrations were artificially raised. Although there are studies showing that metformin improves the glucose tolerance both in non-diabetics and diabetics, the results for non-diabetics have been inconsistent, depending on the variable experimental condition. Variation in OCT1 expression and activity may be one of those variables, and the time points for blood sampling after drug and glucose (meal) intakes may also be important to observe the glucose-lowering effect [16]. In this study, we employ a similar study design as that reported [16] to observe the glucose-lowering effect by metformin in healthy subjects. Before and after metformin administration, oral glucose tolerance test (OGTT) will be conducted. We expect a difference of glucose tolerance between different OCT1 genotypes, under the hypothesis that individuals with different OCT1 genotypes have different metformin concentrations in the target tissues, and hence have different glucose uptakes into (and so utilization in) the target tissues (primary muscle and liver).

In non-diabetic healthy subjects, metformin significantly attenuated the rise in immediate postprandial insulin levels. In this study, we will also determine insulin levels after glucose administration. With metformin treatment, we expect to observe significant difference in post-glucose-administration insulin levels between individuals with different OCT1 genotypes.

When mice were given metformin, the blood lactate concentration significantly increased in the wild-type mice, whereas only a slight increase was observed in Oct1-/- mice. This is consistent with our hypothesis that OCT1 is a determinant of metformin effect on glucose utilization. It will be interesting to compare plasma lactate concentrations after metformin treatment between individuals with different OCT1 genotypes.

Metformin can improve lipid metabolism in obese and diabetics patients, which is reflected by the reduced plasma levels of free fatty acid, cholesterol, and triglycerides. However, in this study with a single dose of metformin, it may not be possible to observe those effects in healthy subjects, although the corresponding concentrations will be measured.

Study Type

Interventional

Enrollment (Actual)

20

Phase

  • Phase 4

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 Francsico, 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

16 years to 38 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Previous participation in the Study Of Pharmacogenetics In Ethnically Diverse Populations (SOPHIE) study.
  • Between the ages of 18 and 40.
  • Possess a specific OCT1 genotype.

Exclusion Criteria:

  • Taking any medications other than vitamins
  • 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)
  • Pregnant at time of 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

  • Allocation: Non-Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: OCT1-variant Group
Subjects with OCT1-variant alleles will be dosed with 2 doses of Metformin
Drug: Metformin
2 doses of Metformin Day 1 1000mg, Day 2 850 mg
Other Names:
  • Glucophage
  • Dimethylguanylguanidine
Experimental: OCT1-reference Group
Subjects with OCT1-reference alleles will be dosed with 2 doses of Metformin
Drug: Metformin
2 doses of Metformin Day 1 1000mg, Day 2 850 mg
Other Names:
  • Glucophage
  • Dimethylguanylguanidine

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Area Under the Curve (AUC) of Blood Concentration-time of Metformin
Time Frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, 8, 10, 12, and 24 hours
To test whether individuals with genetic variants of human organic cation transporter, OCT1, exhibit altered pharmacokinetics of metformin, the difference in AUC of blood concentration-time of metformin between reference and variant groups will be measured.
0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, 8, 10, 12, and 24 hours
Glucose Lowering Response to Metformin
Time Frame: 0 to 180 minutes
To test whether individuals with genetic variants of human organic cation transporter, OCT1, exhibit altered glucose lowering response to metformin we will measure the difference in area under the glucose concentrations-time curve (Glucose AUC) following oral glucose tolerance test.
0 to 180 minutes

Collaborators and Investigators

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

Sponsor

University of California, San Francisco

Investigators

  • Principal Investigator: Kathleen M Giacomini, PhD, 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

July 1, 2003

Primary Completion (Actual)

March 1, 2008

Study Completion (Actual)

March 1, 2008

Study Registration Dates

First Submitted

September 13, 2005

First Submitted That Met QC Criteria

September 13, 2005

First Posted (Estimate)

September 16, 2005

Study Record Updates

Last Update Posted (Estimate)

January 8, 2013

Last Update Submitted That Met QC Criteria

December 6, 2012

Last Verified

December 1, 2012

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 865

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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