Authors: I. Tkáč Authors‘ workplace: IV. interná klinika Lekárskej fakulty UPJŠ a UN L. Pasteura Košice, Slovenská republika, prednosta prof. MUDr. Ivan Tkáč, PhD. Published in: Vnitř Lék 2012; 58(7 a 8): 97-100 Category: 80th Birthday MUDr. Miroslav Mydlík, DrSc.
Patients with type 2 diabetes present with high variability of therapeutic responses to treatment with oral antidiabetics. This variability stems from psychological and social factors, such as treatment adherence, access to health care and prescribing habits of the physicians, as well as from biological factors. Biological factors are non-genetic and genetic. Non-genetic factors include disease duration (reflects residual function of β cells), body weight, kidney function, liver function etc. Among genetic factors, genes associated with pharmacokinetics as well as pharmacodynamics of oral antidiabetic agents have been studied. Cytochrom P450 2C9 coded by the CYP2C9 gene is the most important of the enzymes affecting pharmacokinetics of sulfonylurea. Presence of non-synonymic variants of this gene leads to slower catabolism of sulfonylurea and thus its increased effect. Of the genes associated with the effect of sulfonylurea, pharmacogenetics are affected by the KCNJ11 and ABCC8 gene variants that code the ATP-dependent potassium channel proteins (KATP). Pharmacogenomic studies in type 2 diabetes mellitus patients showed an increased effect of sulfonylurea derivatives in bearers of high risk polymorphic alleles of these genes. Other genes with proven association with the sulfonylurea effect include TCF7L2 gene, the variants of which are the most closely associated with type 2 diabetes mellitus. The effect of sulfonylurea was significantly lower in carriers of the risk allele. With respect to treatment with metformin, variants of the genes associated with pharmacokinetics of metformin are the best described. These specifically include genes coding organic cation transporters OCT1, OCT2 and MATE1, which facilitate transport of metformin into liver cells and renal tubules as well as transport of metformin from the kidneys into urine. Variants of these genes have been associated with reduced as well as increased response to metformin, depending on localization of the transporter and the effect of polymorphism on its function. Only one genome-wide association study has been performed so far and found an association between a polymorphism near the ATM gene with the effect of metformin. However, it is not clear in what way the product of this gene, involved in the process of DNA reparation, affects the effect of metformin. The presence of variants of these genes led to a different effect of various antidiabetics expressed as reduced HbA1 in a range of 0.3–0.6% depending on patient genotype (appears to be clinically significant). Therefore, future use of a panel of polymorphisms of the discussed genes for personalization of type 2 diabetes mellitus treatment cannot be ruled out.
Key words: pharmacogenetics – type 2 diabetes mellitus – sulfonylurea derivatives – metformin – personalized medicine
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