Impact of OCT1 on Metformin Tolerance

Summary

Metformin is the first-line treatment for medical management of Type 2 Diabetes. Up to 25% of patients experience significant gastrointestinal symptoms and in approximate 5%, side-effects result in the discontinuation of metformin. It would be of great clinical significance if the underlying cause of this intolerance was identified. Recent data has highlighted a metformin transporter in the gut - Organic Cation Transporter 1(OCT1) - as a potential culprit for the variability in metformin tolerance. Across a diabetic population, up to one in four people were shown to have a single reduced function allele for OCT1, with approximately 8% having two reduced function alleles. This may increase the risk of the individual experiencing metformin-associated side-effects, potentially due to accumulation within the cells lining the intestine. The investigators aim to show that loss of function of OCT1, either due to genetic variation or drug inhibition of OCT1, may lead to an increase in the symptoms associated with metformin intolerance. The study is being undertaken at the Clinical Research Centre in Ninewells Hospital, Dundee. The investigators will recruit participants from the GoDARTS study (Genetics of Diabetes and Audit Research Tayside Study). The participants will be healthy controls, i.e. non-diabetic, and recruited according to their genotype of OCT1 (information from GoDARTS). The volunteers will then enter a matched cross-over study with two treatment periods. Metformin is taken during both treatment periods alongside either Omeprazole (a proton pump inhibitor used to prevent excess stomach acid, known to interact with OCT1) or placebo. The metformin dose is increased gradually during each period, to a maximum tolerated dose. The investigators expect to see a lower maximum tolerated dose in individuals with loss of function genotype, or in those taking concurrent omeprazole compared to placebo. The study will last approximately 9 weeks. Volunteers have 3 visits to the CRC, and weekly phone call interviews.

Timeline

Start

2016-03

Primary completion

2018-04-09

Completion

2018-04-09

Publications

• Background Koehler MR, Wissinger B, Gorboulev V, Koepsell H, Schmid M. The two human organic cation transporter genes SLC22A1 and SLC22A2 are located on chromosome 6q26. Cytogenet Cell Genet. 1997;79(3-4):198-200. doi: 10.1159/000134720.
• Background Koepsell H, Endou H. The SLC22 drug transporter family. Pflugers Arch. 2004 Feb;447(5):666-76. doi: 10.1007/s00424-003-1089-9. Epub 2003 Jul 19.
• Background Han TK, Proctor WR, Costales CL, Cai H, Everett RS, Thakker DR. Four cation-selective transporters contribute to apical uptake and accumulation of metformin in Caco-2 cell monolayers. J Pharmacol Exp Ther. 2015 Mar;352(3):519-28. doi: 10.1124/jpet.114.220350. Epub 2015 Jan 6.
• Background Proctor WR, Bourdet DL, Thakker DR. Mechanisms underlying saturable intestinal absorption of metformin. Drug Metab Dispos. 2008 Aug;36(8):1650-8. doi: 10.1124/dmd.107.020180. Epub 2008 May 5.
• Background Muller J, Lips KS, Metzner L, Neubert RH, Koepsell H, Brandsch M. Drug specificity and intestinal membrane localization of human organic cation transporters (OCT). Biochem Pharmacol. 2005 Dec 5;70(12):1851-60. doi: 10.1016/j.bcp.2005.09.011. Epub 2005 Nov 2.
• Background Han TK, Everett RS, Proctor WR, Ng CM, Costales CL, Brouwer KL, Thakker DR. Organic cation transporter 1 (OCT1/mOct1) is localized in the apical membrane of Caco-2 cell monolayers and enterocytes. Mol Pharmacol. 2013 Aug;84(2):182-9. doi: 10.1124/mol.112.084517. Epub 2013 May 16.
• Background Dujic T, Zhou K, Donnelly LA, Tavendale R, Palmer CN, Pearson ER. Association of Organic Cation Transporter 1 With Intolerance to Metformin in Type 2 Diabetes: A GoDARTS Study. Diabetes. 2015 May;64(5):1786-93. doi: 10.2337/db14-1388. Epub 2014 Dec 15.
• Background Stage TB, Brosen K, Christensen MM. A Comprehensive Review of Drug-Drug Interactions with Metformin. Clin Pharmacokinet. 2015 Aug;54(8):811-24. doi: 10.1007/s40262-015-0270-6.
• Background Christensen MM, Brasch-Andersen C, Green H, Nielsen F, Damkier P, Beck-Nielsen H, Brosen K. The pharmacogenetics of metformin and its impact on plasma metformin steady-state levels and glycosylated hemoglobin A1c. Pharmacogenet Genomics. 2011 Dec;21(12):837-50. doi: 10.1097/FPC.0b013e32834c0010.
• Background Christensen MMH, Hojlund K, Hother-Nielsen O, Stage TB, Damkier P, Beck-Nielsen H, Brosen K. Steady-state pharmacokinetics of metformin is independent of the OCT1 genotype in healthy volunteers. Eur J Clin Pharmacol. 2015 Jun;71(6):691-697. doi: 10.1007/s00228-015-1853-8. Epub 2015 May 5.

Drugs

Indications

No indication recorded.