Effects of Xhosa specific solute carrier family 22-member 2 haplotypes on the cellular uptake of metformin and cimetidine.

Background: Studies have shown that solute carrier transporters play an important role in the transport and distribution of metformin, and that genetic variation(s) in solute carrier genes have play a role in the variation of metformin efficacy and disposition observed in populations. This study aimed to determine the cellular uptake efficiency of metformin in SLC22A2 coding haplotypes of an indigenous South African population.

Methods and results: To determine metformin and cimetidine cellular uptake in transfected HEK-293 cells, ultra high-performance liquid chromatography was used to quantitate substrate concentration(s). Haplotypes 3 and 4 showed decreased metformin uptake, and haplotypes 2 and 5 displayed increased metformin uptake in comparison to haplotype 1 (i.e. wildtype haplotype). Haplotypes 2-5 showed decreased uptake of cimetidine in comparison to haplotype 1, implying a reduced sensitivity to the inhibition of cimetidine. In all haplotypes, no significant transport was observed for metformin and cimetidine. Passive permeability of metformin was favoured in haplotypes 3 and 5, whilst the remaining haplotypes demonstrate higher passive permeability ratios in favour of cimetidine.

Conclusion: Haplotype 4, which is characterised by the non-synonymous single nucleotide polymorphisms rs316019 and rs8177517, demonstrates potential impaired metformin transport.