Genetic Basis for Variation in the Renal Elimination of Metformin

Phase 4

Completed

Conditions: Other Conditions That May Be A Focus of Clinical Attention

Interventions: Drug: Metformin

Registration Number: NCT00187720

Lead Sponsor: University of California, San Francisco

Brief Summary: The current study is part of a large multi-investigator grant to look at the pharmacogenetics of a number of membrane transporters. We will study individuals with particular genotypes of the human organic cation transporter, (hOCT2), to test the hypothesis that genetic variation in hOCT2 is associated with variation in the renal clearance of the antidiabetic agent, metformin.

Detailed Description: The drug, which is used in the treatment of Type II diabetes, has a narrow therapeutic range. Its net renal clearance by secretion (i.e., renal clearance minus filtration clearance) ranges from approximately 100 ml/min to 800ml/min in normal, healthy subjects. Although many factors may contribute to inter-individual variation in renal secretory clearance, initial estimates of heritability (greater than 0.6) suggest that genetic factors play an important role in the renal secretion of metformin. Available evidence supports the idea that hOCT2 is the primary transporter involved in the first-step of renal secretion of metformin, i.e., uptake from the blood to the tubule cell across the basolateral membrane. In particular, (a) hOCT2 is the primary organic cation transporter on the basolateral membrane of the human kidney; and (b) metformin interacts with and is translocated by hOCT2 in heterologous expression systems.

In recent studies, we identified four variants (M165I, A270S, R400C, and K432Q) with ethnic-specific allele frequencies ≥1% \[6\] that have altered function in studies in heterologous expression systems. In addition, we identified a common haplotype of hOCT2 and one haplotype that contain the non-synonymous cSNP, A270S. We will determine whether variability in the renal secretory clearance of the model organic cation, metformin, in healthy individuals is associated with genetic variation in hOCT2. In particular, we will determine whether the renal clearance of metformin differs in individuals who are homozygous for the common haplotype of OCT2 (OCT2\*1) and those who are heterozygous for the less common haplotype OCT2\*3D, which we have identified in a comprehensive screen of ethnically identified DNA samples. We will also determine whether individuals who are heterozygous for the less common OCT2 variants, M165I, R400C and K432Q, have reduced renal clearances of metformin.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 23

Inclusion Criteria

Subjects have previously participated in the Study Of Pharmacogenetics In Ethnically Diverse Populations (SOPHIE) study.
18-40 years old
Possess a pre-specified genotype for OCT2

Exclusion Criteria

Taking any regular 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 or breastfeeding

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
OCT2-variant Group	Metformin	Subjects with OCT2-variant genotype will be given a single oral dose of 850 mg of metformin.
OCT2-reference Group	Metformin	Subjects with OCT2-reference genotype will be given a single oral dose of 850 mg of metformin.

Primary Outcome Measures

Name	Time	Method
Renal Clearance of Metformin	0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 and 24 hours	To test whether individuals with genetic variants of the human organic cation transporter, OCT2, exhibit altered renal elimination of metformin we will measure the difference in renal clearance between reference and variant groups.

Secondary Outcome Measures