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Variants in Pharmacokinetic Transporters and Glycemic Response to Metformin: A Metgen Meta-Analysis.

ABSTRACT: Therapeutic response to metformin, a first-line drug for type 2 diabetes (T2D), is highly variable, in part likely due to genetic factors. To date, metformin pharmacogenetic studies have mainly focused on the impact of variants in metformin transporter genes, with inconsistent results. To clarify the significance of these variants in glycemic response to metformin in T2D, we performed a large-scale meta-analysis across the cohorts of the Metformin Genetics Consortium (MetGen). Nine candidate polymorphisms in five transporter genes (organic cation transporter [OCT]1, OCT2, multidrug and toxin extrusion transporter [MATE]1, MATE2-K, and OCTN1) were analyzed in up to 7,968 individuals. None of the variants showed a significant effect on metformin response in the primary analysis, or in the exploratory secondary analyses, when patients were stratified according to possible confounding genotypes or prescribed a daily dose of metformin. Our results suggest that candidate transporter gene variants have little contribution to variability in glycemic response to metformin in T2D.

SUBMITTER: Dujic T

PROVIDER: S-EPMC5425333 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Variants in Pharmacokinetic Transporters and Glycemic Response to Metformin: A Metgen Meta-Analysis.

Dujic T T Zhou K K Yee S W SW van Leeuwen N N de Keyser C E CE Javorský M M Goswami S S Zaharenko L L Hougaard Christensen M M MM Out M M Tavendale R R Kubo M M Hedderson M M MM van der Heijden A A AA Klimčáková L L Pirags V V Kooy A A Brøsen K K Klovins J J Semiz S S Tkáč I I Stricker B H BH Palmer Cna C 't Hart L M LM Giacomini K M KM Pearson E R ER

Clinical pharmacology and therapeutics 20170203 6

Therapeutic response to metformin, a first-line drug for type 2 diabetes (T2D), is highly variable, in part likely due to genetic factors. To date, metformin pharmacogenetic studies have mainly focused on the impact of variants in metformin transporter genes, with inconsistent results. To clarify the significance of these variants in glycemic response to metformin in T2D, we performed a large-scale meta-analysis across the cohorts of the Metformin Genetics Consortium (MetGen). Nine candidate pol ...[more]

PMID: 27859023

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Project description:ObjectiveSulfonylureas, the first available drugs for the management of type 2 diabetes, remain widely prescribed today. However, there exists significant variability in glycemic response to treatment. We aimed to establish heritability of sulfonylurea response and identify genetic variants and interacting treatments associated with HbA1c reduction.Research design and methodsAs an initiative of the Metformin Genetics Plus Consortium (MetGen Plus) and the DIabetes REsearCh on patient straTification (DIRECT) consortium, 5,485 White Europeans with type 2 diabetes treated with sulfonylureas were recruited from six referral centers in Europe and North America. We first estimated heritability using the generalized restricted maximum likelihood approach and then undertook genome-wide association studies of glycemic response to sulfonylureas measured as HbA1c reduction after 12 months of therapy followed by meta-analysis. These results were supported by acute glipizide challenge in humans who were naïve to type 2 diabetes medications, cis expression quantitative trait loci (eQTL), and functional validation in cellular models. Finally, we examined for possible drug-drug-gene interactions.ResultsAfter establishing that sulfonylurea response is heritable (mean ± SEM 37 ± 11%), we identified two independent loci near the GXYLT1 and SLCO1B1 genes associated with HbA1c reduction at a genome-wide scale (P < 5 × 10-8). The C allele at rs1234032, near GXYLT1, was associated with 0.14% (1.5 mmol/mol), P = 2.39 × 10-8), lower reduction in HbA1c. Similarly, the C allele was associated with higher glucose trough levels (β = 1.61, P = 0.005) in healthy volunteers in the SUGAR-MGH given glipizide (N = 857). In 3,029 human whole blood samples, the C allele is a cis eQTL for increased expression of GXYLT1 (β = 0.21, P = 2.04 × 10-58). The C allele of rs10770791, in an intronic region of SLCO1B1, was associated with 0.11% (1.2 mmol/mol) greater reduction in HbA1c (P = 4.80 × 10-8). In 1,183 human liver samples, the C allele at rs10770791 is a cis eQTL for reduced SLCO1B1 expression (P = 1.61 × 10-7), which, together with functional studies in cells expressing SLCO1B1, supports a key role for hepatic SLCO1B1 (encoding OATP1B1) in regulation of sulfonylurea transport. Further, a significant interaction between statin use and SLCO1B1 genotype was observed (P = 0.001). In statin nonusers, C allele homozygotes at rs10770791 had a large absolute reduction in HbA1c (0.48 ± 0.12% [5.2 ± 1.26 mmol/mol]), equivalent to that associated with initiation of a dipeptidyl peptidase 4 inhibitor.ConclusionsWe have identified clinically important genetic effects at genome-wide levels of significance, and important drug-drug-gene interactions, which include commonly prescribed statins. With increasing availability of genetic data embedded in clinical records these findings will be important in prescribing glucose-lowering drugs.

Project description:Background and Aims: Metformin is the most widely-used anti-diabetic drug in the United States. However, medication management fails to achieve therapeutic goals in ~20% of patients. This study attempted to identify genetic polymorphisms associated with metformin treatment failure. We studied the associations between polymorphisms in two liver and kidney organic cation transporter genes (OCT1 & OCT2) and two kidney multidrug and toxin extrusion transporter genes, (MATE1 & MATE2K) and response to metformin monotherapy. Methods: At Kaiser Permanente Southeast and Marshfield Clinic Research Foundation we identified 304 type 2 diabetes (T2DM) patients on metformin monotherapy who: were enrolled for >=6 months prior to initiation; remained on metformin >= 90 days following initiation; and had a HgbA1c measured prior to first metformin prescription and then after initiation. From this group we selected 171 patients who had not received metformin or other anti-diabetics previously, and had baseline HbA1c levels >7.0% prior to metformin initiation. We genotyped 10 SNPs, and assessed response by measuring absolute and relative change in HbA1c after after metformin initiation. Results: Three SNPs were identified that were significantly associated with reduced response to metformin, after adjustment for baseline HbA1c, dose, and ethnicity. In a dominant model, heterozygosity or homozygosity for minor A allele in the MATE1 intronic SNP, rs2289669, resulted in a smaller absolute change in HbA1c (mean of 0.45% less reduction in absolute change in HbA1c; 95% CI 0.17 to 0.74%) compared to individuals homozygous for major G allele. In a recessive model, homozygosity for minor A allele in MATE2K 5′-UTR SNP, rs12943590, resulted in smaller absolute change in HbA1c (mean of 0.43% less reduction in absolute change in HbA1c, 95% CI 0.053 to 0.86%). The reduced function SNPs in OCT1 & OCT2 were not associated with metformin response, except for rs34059508 (G465R). This SNP showed a positive (but not statistically significant) association with smaller absolute change in HbA1c (mean of 0.49%; 95% CI −0.06354 to 1.045%). Conclusions: These three variants of metformin transporter genes may be important for personalizing treatment for patients with T2DM. A replication study in a larger population is currently being planned.

Dataset Information

Variants in Pharmacokinetic Transporters and Glycemic Response to Metformin: A Metgen Meta-Analysis.

Publications

Variants in Pharmacokinetic Transporters and Glycemic Response to Metformin: A Metgen Meta-Analysis.

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