Cytochrome P450 2C9 *2 and *3 polymorphisms and the dose and effect of sulfonylurea in type II diabetes mellitus

Precision Medicine in Diabetes

Tailoring treatment or management to groups of individuals based on specific clinical, molecular, and genomic features is the concept of precision medicine. Diabetes is highly heterogenous with respect to clinical manifestations, disease progression, development of complications, and drug response. The current practice for drug treatment is largely based on evidence from clinical trials that report average effects. However, around half of patients with type 2 diabetes do not achieve glycaemic targets despite having a high level of adherence and there are substantial differences in the incidence of adverse outcomes. Therefore, there is a need to identify predictive markers that can inform differential drug responses at the point of prescribing. Recent advances in molecular genetics and increased availability of real-world and randomised trial data have started to increase our understanding of disease heterogeneity and its impact on potential treatments for specific groups. Leveraging information from simple clinical features (age, sex, BMI, ethnicity, and co-prescribed medications) and genomic markers has a potential to identify sub-groups who are likely to benefit from a given drug with minimal adverse effects. In this chapter, we will discuss the state of current evidence in the discovery of clinical and genetic markers that have the potential to optimise drug treatment in type 2 diabetes.

Pharmacogenomics of sulfonylureas in type 2 diabetes mellitus; a systematic review

Purpose

Genetic factors have a role in response to a target medication (personalized medicine). This study aimed to review available evidence about the relationship between gene variants and therapeutic response to sulfonylureas in type 2 diabetes, systematically.

Methods

An extensive search was done in Scopus, PubMed, and Web of Science with specific search strategy in the field from the beginning until the 1^st of Jan. 2021. After sending records to endnote software and removing duplicate records remained documents were screened by title and abstract. Full texts of remained documents were assessed after removing un-related records. Required data was extracted from remained documents and records were categorized according to gene/SNP studied.

Results

Finally, 26 studies with 9170 T2DM patients with a mean age of 59.47 ± 6.67 (49.7-75.2 years) remained. The most contribution was from China, Slovakia and Greece, respectively and the most genes studied were CYP2C9, KCNJ11, and both KCNQ1 and ABCC8 with 10, 7, and 4 articles, respectively. Also, rs1799853 and rs1057910 (each with seven studies), rs5219 with six studies and CYP2C9*1(with four articles), respectively were the most common variants investigated. Studies about each gene obtained different positive or negative results and were not consistent.

Conclusion

Considering heterogeneity between SFUs pharmacogenomic studies regarding the method, sample size, population, gene/variant studied, and outcome and findings, these studies are not conclusive and need further studies.

Genome-Wide Meta-analysis Identifies Genetic Variants Associated With Glycemic Response to Sulfonylureas

OBJECTIVE

Sulfonylureas, 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 METHODS

As 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.

RESULTS

After 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.

CONCLUSIONS

We 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.

Pharmacogenomics and Personalized Medicine in Type 2 Diabetes Mellitus: Potential Implications for Clinical Practice

Type 2 diabetes mellitus (T2DM) is the most common form of diabetes, and is rising in incidence with widespread prevalence. Multiple gene variants are associated with glucose homeostasis, complex T2DM pathogenesis, and its complications. Exploring more effective therapeutic strategies for patients with diabetes is crucial. Pharmacogenomics has made precision medicine possible by allowing for individualized drug therapy based on a patient's genetic and genomic information. T2DM is treated with various classes of oral hypoglycemic agents, such as biguanides, sulfonylureas, thiazolidinediones, meglitinides, DPP4 inhibitors, SGLT2 inhibitors, α-glucosidase inhibitors, and GLP1 analogues, which exhibit various pharmacogenetic variants. Although genomic interventions in monogenic diabetes have been implemented in clinical practice, they are still in the early stages for complex polygenic disorders, such as T2DM. Precision DM medicine has the potential to be effective in personalized therapy for those suffering from various forms of DM, such as T2DM. With recent developments in genetic techniques, the application of candidate-gene studies, large-scale genotyping investigations, genome-wide association studies, and "multiomics" studies has begun to produce results that may lead to changes in clinical practice. Enhanced knowledge of the genetic architecture of T2DM presents a bigger translational potential. This review summarizes the genetics and pathophysiology of T2DM, candidate-gene approaches, genome-wide association studies, personalized medicine, clinical relevance of pharmacogenetic variants associated with oral hypoglycemic agents, and paths toward personalized diabetology.

The Genetics of Adverse Drug Outcomes in Type 2 Diabetes: A Systematic Review

Background: Adverse drug reactions (ADR) are a major clinical problem accounting for significant hospital admission rates, morbidity, mortality, and health care costs. One-third of people with diabetes experience at least one ADR. However, there is notable interindividual heterogeneity resulting in patient harm and unnecessary medical costs. Genomics is at the forefront of research to understand interindividual variability, and there are many genotype-drug response associations in diabetes with inconsistent findings. Here, we conducted a systematic review to comprehensively examine and synthesize the effect of genetic polymorphisms on the incidence of ADRs of oral glucose-lowering drugs in people with type 2 diabetes.

Methods: A literature search was made to identify articles that included specific results of research on genetic polymorphism and adverse effects associated with oral glucose-lowering drugs. The electronic search was carried out on 3rd October 2020, through Cochrane Library, PubMed, and Web of Science using keywords and MeSH terms.

Result: Eighteen articles consisting of 10, 383 subjects were included in this review. Carriers of reduced-function alleles of organic cation transporter 1 (OCT 1, encoded by SLC22A1) or reduced expression alleles of plasma membrane monoamine transporter (PMAT, encoded by SLC29A4) or serotonin transporter (SERT, encoded by SLC6A4) were associated with increased incidence of metformin-related gastrointestinal (GI) adverse effects. These effects were shown to exacerbate by concomitant treatment with gut transporter inhibiting drugs. The CYP2C9 alleles, ^*2 (rs1799853C>T) and ^*3 (rs1057910A>C) that are predictive of low enzyme activity were more common in subjects who experienced hypoglycemia after treatment with sulfonylureas. However, there was no significant association between sulfonylurea-related hypoglycemia and genetic variants in the ATP-binding cassette transporter sub-family C member 8 (ABCC8)/Potassium Inwardly Rectifying Channel Subfamily J Member 11 (KCNJ11). Compared to the wild type, the low enzyme activity C allele at CYP2C8^*3 (rs1057910A>C) was associated with less weight gain whereas the C allele at rs6123045 in the NFATC2 gene was significantly associated with edema from rosiglitazone treatment.

Conclusion: In spite of limited studies investigating genetics and ADR in diabetes, some convincing results are emerging. Genetic variants in genes encoding drug transporters and metabolizing enzymes are implicated in metformin-related GI adverse effects, and sulfonylurea-induced hypoglycemia, respectively. Further studies to investigate newer antidiabetic drugs such as DPP-4i, GLP-1RA, and SGLT2i are warranted. In addition, pharmacogenetic studies that account for race and ethnic differences are required.

In Vivo Functional Effects of CYP2C9 M1L, a Novel and Common Variant in the Yup'ik Alaska Native Population

Alaska Native people are under-represented in genetic research but have unique gene variation that may critically impact their response to pharmacotherapy. Full resequencing of CYP2C9 in a cross-section of this population identified CYP2C9 Met1Leu (M1L), a novel, relatively common single nucleotide polymorphism hypothesized to confer CYP2C9 poor metabolizer phenotype by disrupting the start codon. M1L is present at a minor allele frequency of 6.3% in Yup'ik Alaska Native people and thus can contribute to the risk of an adverse drug response from narrow-therapeutic-index CYP2C9 substrates such as (S)-warfarin. This study's objective was to characterize the catalytic efficiency of the Leu1 variant enzyme in vivo by evaluating the pharmacokinetic behavior of naproxen, a probe substrate for CYP2C9 activity, in genotyped Yup'ik participants. We first confirmed the selectivity of (S)-naproxen O-demethylation by CYP2C9 using activity-phenotyped human liver microsomes and selective cytochrome P450 inhibitors and then developed and validated a novel liquid chromatography mass spectrometry method for simultaneous quantification of (S)-naproxen, (S)-O-desmethylnaproxen, and naproxen acyl glucuronide in human urine. The average ratio of (S)-O-desmethylnaproxen to unchanged (S)-naproxen in urine was 18.0 ± 8.0 (n = 11) for the homozygous CYP2C9Met1 reference group and 10.3 ± 6.6 (n = 11) for the Leu1 variant carrier group (P = 0.011). The effect of M1L variation on CYP2C9 function and its potential to alter the pharmacokinetics of drugs metabolized by the enzyme has clinical implications and should be included in a variant screening panel when pharmacogenetic testing in the Alaska Native population is warranted. SIGNIFICANCE STATEMENT: The novel CYP2C9 Met1Leu variant in Alaska Native people was recently identified. This study validated (S)-naproxen as a CYP2C9 probe substrate to characterize the in vivo functional activity of the CYP2C9 Leu1 variant. The results of this pharmacogenetic-pharmacokinetic study suggest that the CYP2C9 Leu1 variant exhibits loss of enzyme activity. This finding may be important to consider when administering narrow-therapeutic-index medications metabolized by CYP2C9 and also compels further investigation to characterize novel genetic variation in understudied populations.

Hypoglycemia and Glycemic Control With Glyburide in Women With Gestational Diabetes and Genetic Variants of Cytochrome P450 2C9 and/or OATP1B3

Glyburide is mainly metabolized by the cytochrome P450 2C9 (CYP2C9) enzyme and enters the liver via the transporter OATP1B3. The variants OATP1B3*4 (699 G>A; rs7311358) and CYP2C9*2 and *3 are known to have a significant influence on the hepatic uptake and metabolism of glyburide, with lower clearance than in the wild type. In an ancillary study of the INDAO trial, we selected 117 pregnant women with gestational diabetes treated by glyburide and assessed the role of the combined CYP2C9 and OATP1B3 genetic polymorphisms in hypoglycemia and glycemic control. Three groups were constituted: (1) the wild-type genotype group (wild-type allele genotype for both CYP2C9*1 and OATP1B3*1 (699G)), (2) the intermediate group (carriers of CYP2C9*2 allele or OATP1B3*4 (699G>A) heterozygous), and (3) the variant group (carriers of CYP2C9*3 allele and/or OATP1B3*4 (699G>A) homozygous variant). We found that the risk of hypoglycemia was significantly higher in the variant genotype at the second week of treatment: 20.0% (4/20) vs. 8.1% (3/37) in the intermediate group and 4.1% (2/49) in the wild-type genotype group (P = 0.03). The last daily dose of glyburide during pregnancy was lower for patients in the variant genotype group: 4.7 mg (SD 3.5) vs. 8.7 mg (SD 5.7) in the wild-type group and 5.7 mg (SD 3.7) in the intermediate group (P < 0.01). In conclusion, the no-function variants CYP2C9*3 and OATP1B3*4 are associated with a higher risk of hypoglycemia and a lower dose of glyburide in women with gestational diabetes treated with glyburide, which is consistent with the pharmacokinetic roles of both CYP2C9 and OATP1B3.

Diabetes and Genetics: A Relationship Between Genetic Risk Alleles, Clinical Phenotypes and Therapeutic Approaches

Unveiling human genome through successful completion of Human Genome Project and International HapMap Projects with the advent of state of art technologies has shed light on diseases associated genetic determinants. Identification of mutational landscapes such as copy number variation, single nucleotide polymorphisms or variants in different genes and loci have revealed not only genetic risk factors responsible for diseases but also region(s) playing protective roles. Diabetes is a global health concern with two major types - type 1 diabetes (T1D) and type 2 diabetes (T2D). Great progress in understanding the underlying genetic predisposition to T1D and T2D have been made by candidate gene studies, genetic linkage studies, genome wide association studies with substantial number of samples. Genetic information has importance in predicting clinical outcomes. In this review, we focus on recent advancement regarding candidate gene(s) associated with these two traits along with their clinical parameters as well as therapeutic approaches perceived. Understanding genetic architecture of these disease traits relating clinical phenotypes would certainly facilitate population stratification in diagnosing and treating T1D/T2D considering the doses and toxicity of specific drugs.

The presence of two reduced function variants in CYP2C9 influences the acute response to glipizide

AIMS

To examine whether the presence of two common missense variants in the CYP2C9 gene (rs1799853, encoding Arg144Cys and denoted as *2, and rs1057910, encoding Ile359Leu and denoted as *3) influences the acute physiological response to a single glipizide dose in individuals naïve to diabetes medications.

METHODS

In the Study to Understand the Genetics of the Acute Response to Metformin and Glipizide in Humans (SUGAR-MGH), 786 individuals genotyped for rs1799853/rs41291560 (*2) and rs1057910/rs9332214 (*3) were treated with 5 mg glipizide in the fasting state. Glucose and insulin levels were measured at baseline, 30, 60, 90, 120, 180 and 240 min for calculation of phenotypic endpoints of glipizide response. The challenge was aborted as a result of hypoglycaemia, defined as glucose <2.8 mmol/l or hypoglycaemia-related symptoms.

RESULTS

Carriers with two reduced function alleles had a 50% larger insulin area under the curve than carriers with zero or one copy (P=0.037), although this finding was primarily driven by an individual with a robust insulin response. In adjusted analyses, the risk of aborting the glipizide challenge was doubled in two-copy carriers (P=0.034). No significant findings were observed in glucose-based endpoints.

CONCLUSIONS

Carriers of two reduced function alleles in CYP2C9 may experience an increased insulin response to glipizide and be predisposed to a higher risk of hypoglycaemia, although no effect of genotype was seen in glucose-based measurements. Further studies are needed to clarify the utility of CYP2C9 genotyping to guide sulfonylurea treatment.

Diabetes: Is There a Future for Pharmacogenomics Guided Treatment?

Diabetes is a disease defined on the basis of hyperglycemia. There are monogenic forms of diabetes where defining the genetic cause has a dramatic impact on treatment—with patients being able to transition from insulin to sulfonylureas. However, the majority of diabetes is type 2 diabetes. This review outlines the robust evidence accrued to date for pharmacogenetics of metformin, sulfonylureas, thiazolidinediones, and dipeptidyl peptidase‐4 inhibitors but highlights that these variants will only be of clinical utility when the genotype is already known at the point of prescribing. The future of pharmacogenetics in diabetes and other common complex disease relies on a paradigm shift—that of preemptive panel genotyping and use of clinical decision support tools to assimilate this genetic information with other clinical phenotypic data and to present this information simply to the prescriber. Given the recent dramatic fall in genotyping costs, this future is not far off.

The Importance of Precision Medicine in Type 2 Diabetes Mellitus (T2DM): From Pharmacogenetic and Pharmacoepigenetic Aspects

BACKGROUND

Type 2 Diabetes Mellitus (T2DM) is a worldwide disorder as the most important challenges of health-care systems. Controlling the normal glycaemia greatly profit long-term prognosis and gives explanation for early, effective, constant, and safe intervention.

MATERIAL AND METHODS

Finding the main genetic and epigenetic profile of T2DM and the exact molecular targets of T2DM medications can shed light on its personalized management. The comprehensive information of T2DM was earned through the genome-wide association study (GWAS) studies. In the current review, we represent the most important candidate genes of T2DM like CAPN10, TCF7L2, PPAR-γ, IRSs, KCNJ11, WFS1, and HNF homeoboxes. Different genetic variations of a candidate gene can predict the efficacy of T2DM personalized strategy medication.

RESULTS

SLCs and AMPK variations are considered for metformin, CYP2C9, KATP channel, CDKAL1, CDKN2A/2B and KCNQ1 for sulphonylureas, OATP1B, and KCNQ1 for repaglinide and the last but not the least ADIPOQ, PPAR-γ, SLC, CYP2C8, and SLCO1B1 for thiazolidinediones response prediction.

CONCLUSION

Taken everything into consideration, there is an extreme need to determine the genetic status of T2DM patients in some known genetic region before planning the medication strategies.

Investigating the Effect of Demographics, Clinical Characteristics, and Polymorphism of MDR-1, CYP1A2, CYP3A4, and CYP3A5 on Clopidogrel Resistance

Clopidogrel is an antiplatelet agent that is indicated for cardiovascular emergencies and procedures. The drug, however, is subject to response variability leading to therapy resistance. In this research, we explored the demographic, clinical, and genetic factors associated with clopidogrel resistance. Data analysis among our 280 subjects receiving clopidogrel showed some risk factors that are significantly associated with clopidogrel resistance compared with responders. Those were: female sex (P = 0.021), advanced age (P = 0.011), obesity (P = 0.002), and higher body mass index (P = 0.008) and higher platelets count (P = 0.002). However, known polymorphisms of MDR-1, CYP1A2, CYP3A4, and CYP3A5 were not associated with treatment resistance when compared to responders to clopidogrel therapy. Knowledge about such risk factors might provide recommendation in the future about starting doses or monitoring recommendations.

Frequency of CYP2C9 (*2, *3 and IVS8-109A>T) allelic variants, and their clinical implications, among Mexican patients with diabetes mellitus type 2 undergoing treatment with glibenclamide and metformin

The majority of Mexican patients with diabetes mellitus type 2 (DMT2) (67.9-85.0%) are prescribed sulphonylureas (SUs), which are metabolized by cytochrome P450 2C9 (abbreviated as CYP2C9). SUs are a type of oral anti-diabetic compound which inhibit ATP-sensitive potassium channels, thus inducing glucose-independent insulin release by the β-pancreatic cells. The wide variability reported in SU responses has been attributed to the polymorphisms of CYP2C9. The present study aimed to describe CYP2C9 polymorphisms (*2, *3 and IVS8-109T) within a sample of Mexican patients with DMT2, while suggesting the potential clinical implications in terms of glibenclamide response variability. From a sample of 248 patients with DMT2 who initially consented to be studied, those ultimately included in the study were treated with glibenclamide (n=11), glibenclamide combined with metformin (n=112) or metformin (n=76), and were subsequently genotyped using a reverse transcription-quantitative polymerase chain reaction (PCR), end-point allelic discrimination and PCR amplifying enzymatic restriction fragment long polymorphism. Clinical data were gathered through medical record revision. The frequencies revealed were as follows: CYP2C9*1/*1, 87.5%; *1/*2, 6.5%; *1/*3, 5.2%; and CYP2C9, IVS8-109A>T, 16.1%. Glibenclamide significantly reduced the level of pre-prandial glucose (P<0.01) and the percentage of glycated hemoglobin (%HbA1c; P<0.01) for IVS8-109A>T compared with combined glibenclamide and metformin treatment. Concerning the various treatments with respect to the different genotypes, the percentages obtained were as follows: Glibenclamide A/A, HbA1c<6.5=33.3%; glibenclamide + metformin A/A, HbA1c<6.5=24.6%; glibenclamide A/T, HbA1c<6.5=33.3%; glibenclamide + metformin A/T, HbA1c<6.5=25%; glibenclamide T/T, HbA1c<6.5=100%; and glibenclamide + metformin T/T, HbA1c<6.5=12.5%. Altogether, these results revealed that, although genetically customized prescriptions remain a desirable goal to increase the chances of therapeutic success, within the studied population neither allelic variants nor dosages demonstrated a clear association with biomarker levels. A key limitation of the present study was the lack of ability to quantify either the plasma concentrations of SU or their metabolites; therefore, further, precise experimental and observational studies are required.

Pharmacogenetics of type 2 diabetes mellitus, the route toward tailored medicine

Type 2 diabetes mellitus (T2DM) is a chronic disease that has reached the levels of a global epidemic. In order to achieve optimal glucose control, it is often necessary to rely on combination therapy of multiple drugs or insulin because uncontrolled glucose levels result in T2DM progression and enhanced risk of complications and mortality. Several antihyperglycemic agents have been developed over time, and T2DM pharmacotherapy should be prescribed based on suitability for the individual patient's characteristics. Pharmacogenetics is the branch of genetics that investigates how our genome influences individual responses to drugs, therapeutic outcomes, and incidence of adverse effects. In this review, we evaluated the pharmacogenetic evidences currently available in the literature, and we identified the top informative genetic variants associated with response to the most common anti-diabetic drugs: metformin, DPP-4 inhibitors/GLP1R agonists, thiazolidinediones, and sulfonylureas/meglitinides. Overall, we found 40 polymorphisms for each drug class in a total of 71 loci, and we examined the possibility of encouraging genetic screening of these variants/loci in order to critically implement decision-making about the therapeutic approach through precision medicine strategies. It is possible then to anticipate that when the clinical practice will take advantage of the genetic information of the diabetic patients, this will provide a useful resource for the prevention of T2DM progression, enabling the identification of the precise drug that is most likely to be effective and safe for each patient and the reduction of the economic impact on a global scale.

Pharmacokinetics and metabolic elimination of tolbutamide in female rats: Comparison with male rats

As there are to be known gender differences in the expression profiles of rat hepatic CYP2C, we examined the pharmacokinetic behavior of tolbutamide (TB), a typical probe for CYP2C, and hepatic enzyme activities for metabolizing TB in female rats to compare with male rats. On the pharmacokinetic analysis of TB after intravenous administration to female rats, the elimination rate constant at the terminal phase (k_e ), total clearance (CL_tot ) and the apparent volume of distribution at steady-state (Vd_ss ) were significantly lower than in male rats. The binding rates of TB to serum protein were similar in male and female rats, indicating that the change in unbound TB concentration in serum is not associated with the difference in the pharmacokinetic disposition of TB. On metabolic examination using hepatic microsomes, the maximum reaction velocity (V_max ) of the metabolic conversion from TB to 4-hydroxytolbutamide (4-OH-TB) in female rats was lower than that in male rats, although there was no significant difference in the Michaelis constant (K_m ) between genders. Consistent with this, the V_max -to-K_m ratio (V_max /K_m ) was significantly lower in female rats than in male rats. Therefore, the low in vitro CYP2C-dependent activity for hepatic TB removal in female rats provided a clear explanation for the lower in vivo elimination clearance of TB. Our findings strongly suggest that there is a gender difference in the metabolic capacity to eliminate drugs that serve as substrates of hepatic CYP2C enzymes in rats.

Implication of critical pharmacokinetic gene variants on therapeutic response to metformin in Type 2 diabetes

Aim: Metformin, an oral hypoglycemic drug is the first line of treatment for Type 2 diabetes individuals. We studied the effect of critical gene single nucleotide polymorphisms  on the glucose lowering effect of metformin. Method: We performed a prospective study on 221 newly diagnosed, treatment-naive Type 2 diabetes subjects. Individuals were started with metformin monotherapy and followed up for 12 weeks. Results: Our association analysis revealed that SLC22A2 rs316019 and SLC47A2 rs12943590 were significantly associated with metformin drug response across co-dominant and dominant models, respectively. SLC22A2 rs316019 GG and SLC47A2 rs12943590 GA combined genotypes showed maximum average change in HbA1c level. Conclusion: The present study proposes a role of SLC22A2 rs316019 and SLC47A2 rs12943590 in the pharmacokinetic action of metformin.

Genotypic and Phenotypic Factors Influencing Drug Response in Mexican Patients With Type 2 Diabetes Mellitus

The treatment of Type 2 Diabetes Mellitus (T2DM) consists primarily of oral antidiabetic drugs (OADs) that stimulate insulin secretion, such as sulfonylureas (SUs) and reduce hepatic glucose production (e.g., biguanides), among others. The marked inter-individual differences among T2DM patients’ response to these drugs have become an issue on prescribing and dosing efficiently. In this study, fourteen polymorphisms selected from Genome-wide association studies (GWAS) were screened in 495 T2DM Mexican patients previously treated with OADs to find the relationship between the presence of these polymorphisms and response to the OADs. Then, a novel association screening method, based on global probabilities, was used to globally characterize important relationships between the drug response to OADs and genetic and clinical parameters, including polymorphisms, patient information, and type of treatment. Two polymorphisms, ABCC8-Ala1369Ser and KCNJ11-Glu23Lys, showed a significant impact on response to SUs. Heterozygous ABCC8-Ala1369Ser variant (A/C) carriers exhibited a higher response to SUs compared to homozygous ABCC8-Ala1369Ser variant (A/A) carriers (p-value = 0.029) and to homozygous wild-type genotypes (C/C) (p-value = 0.012). The homozygous KCNJ11-Glu23Lys variant (C/C) and wild-type (T/T) genotypes had a lower response to SUs compared to heterozygous (C/T) carriers (p-value = 0.039). The screening of OADs response related genetic and clinical factors could help improve the prescribing and dosing of OADs for T2DM patients and thus contribute to the design of personalized treatments.

TCF7L2 Genetic Variation Augments Incretin Resistance and Influences Response to a Sulfonylurea and Metformin: The Study to Understand the Genetics of the Acute Response to Metformin and Glipizide in Humans (SUGAR-MGH)

OBJECTIVE

The rs7903146 T allele in transcription factor 7 like 2 (TCF7L2) is strongly associated with type 2 diabetes (T2D), but the mechanisms for increased risk remain unclear. We evaluated the physiologic and hormonal effects of TCF7L2 genotype before and after interventions that influence glucose physiology.

RESEARCH DESIGN AND METHODS

We genotyped rs7903146 in 608 individuals without diabetes and recorded biochemical data before and after 1) one dose of glipizide (5 mg) on visit 1 and 2) a 75-g oral glucose tolerance test (OGTT) performed after administration of metformin 500 mg twice daily over 2 days. Incretin levels were measured in 150 of the 608 participants.

RESULTS

TT risk-allele homozygotes had 1.6 mg/dL higher baseline fasting glucose levels and 2.5 pg/mL lower glucagon levels per T allele than carriers of other genotypes at baseline. In a subset of participants, the T allele was associated with higher basal glucagon-like peptide 1 (GLP-1) levels at visit 1 (β = 1.52, P = 0.02 and β = 0.96, P = 0.002 for total and active GLP-1, respectively), and across all points of the OGTT after metformin administration. Regarding drug response, the T allele was associated with a shorter time (β = -7.00, P = 0.03) and a steeper slope (β = 0.23, P = 0.04) to trough glucose levels after glipizide administration, and lower visit 2 fasting glucose level adjusted for visit 1 fasting glucose level (β = -1.02, P = 0.04) and a greater decline in glucose level between visits (β = -1.61, P = 0.047) after metformin administration.

CONCLUSIONS

Our findings demonstrate that common variation at TCF7L2 influences acute responses to both glipizide and metformin in people without diabetes and highlight altered incretin signaling as a potential mechanism by which TCF7L2 variation increases T2D risk.

Interaction between variants in the CYP2C9 and POR genes and the risk of sulfonylurea-induced hypoglycaemia: A GoDARTS Study

Data on the association of CYP2C9 genetic polymorphisms with sulfonylurea (SU)-induced hypoglycaemia (SH) are inconsistent. Recent studies showed that variants in the P450 oxidoreductase (POR) gene could affect CYP2C9 activity. In this study, we explored the effects of POR*28 and combined CYP2C9*2 and CYP2C9*3 genotypes on SH and the efficacy of SU treatment in type 2 diabetes. A total of 1770 patients were included in the analysis of SU efficacy, assessed as the combined outcome of the HbA1c reduction and the prescribed SU daily dose. Sixty-nine patients with severe SH were compared with 311 control patients. The number of CYP2C9 deficient alleles was associated with nearly three-fold higher odds of hypoglycaemia (OR, 2.81; 95% CI, 1.30-6.09; P = .009) and better response to SU treatment (β, -0.218; SE, 0.074; P = .003) only in patients carrying the POR*1/*1 genotype. Our results indicate that interaction between CYP2C9 and POR genes may be an important determinant of efficacy and severe adverse effects of SU treatment.

Pharmacogenomics of CYP2C9: Functional and Clinical Considerations

CYP2C9 is the most abundant CYP2C subfamily enzyme in human liver and the most important contributor from this subfamily to drug metabolism. Polymorphisms resulting in decreased enzyme activity are common in the CYP2C9 gene and this, combined with narrow therapeutic indices for several key drug substrates, results in some important issues relating to drug safety and efficacy. CYP2C9 substrate selectivity is detailed and, based on crystal structures for the enzyme, we describe how CYP2C9 catalyzes these reactions. Factors relevant to clinical response to CYP2C9 substrates including inhibition, induction and genetic polymorphism are discussed in detail. In particular, we consider the issue of ethnic variation in pattern and frequency of genetic polymorphisms and clinical implications. Warfarin is the most well studied CYP2C9 substrate; recent work on use of dosing algorithms that include CYP2C9 genotype to improve patient safety during initiation of warfarin dosing are reviewed and prospects for their clinical implementation considered. Finally, we discuss a novel approach to cataloging the functional capabilities of rare 'variants of uncertain significance', which are increasingly detected as more exome and genome sequencing of diverse populations is conducted.

Effects of functional CYP2C8,CYP2C9,CYP3A5,and ABCB1 genetic variants on the pharmacokinetics of insulin sensitizer pioglitazone in Chinese Han individuals

BACKGROUND AND OBJECTIVES

Pioglitazone is a thiazolidinedione antihyperglycemic drug with insulin-sensitizing properties. We investigated whether the variant genotypes of cytochrome P450 2C8 (CYP2C8), CYP2C9, CYP3A5 and transporter ABCB1 influence the pharmacokinetic phenotype of the substrate pioglitazone in Chinese individuals.

PARTICIPANTS AND METHODS

Single-nucleotide polymorphisms were determined by the PCR-restriction fragment length polymorphism method in 244 (CYP2C8 and CYP2C9) healthy Chinese Han individuals. After a single oral dose of 30 mg pioglitazone, the plasma concentrations of the parent drug and of two major active metabolites M-III and M-IV were measured using a validated LC-MS/MS in 21 (genotyping CYP3A5 and ABCB1) of these 244 volunteers.

RESULTS

The results confirmed that the unique frequencies of CYP2C8*2 (0.0%), CYP2C8*3 (0.0%), and CYP2C9*2 (0.0%) alleles were significantly different from those reported in Whites and Africans, and there were only 10 variant CYP2C9*1/*3 heterozygous (CYP2C9*3 carriers) among 244 Chinese individuals. These results were similar to those reported in Asian ethnic populations, including the Chinese. Unexpectedly, the pioglitazone AUC0-48 in CYP2C9*3 carriers was lower (50.8%), whereas the AUC0-48 ratios of metabolites M-III/pioglitazone and M-IV/pioglitazone increased to 134.3 and 155.8%, respectively, compared with the wild-type CYP2C9*1/*1 homozygous. Moreover, this phenomenon was not observed in individuals with genetic variants of CYP3A5*3 and ABCB1 (C1236T).

CONCLUSION

The present research suggests that the CYP2C8, CYP3A5, and ABCB1 genes play no significant role in the interindividual variation of pioglitazone pharmacokinetics, whereas CYP2C9*3 carriers are likely to accelerate the metabolism of this antidiabetic drug in the Chinese Han ethnic population.

Falls: the adverse drug reaction of the elderly and the impact of pharmacogenetics

Falls is a frequent type of adverse drug reactions causing significant morbidity and mortality in the elderly. We reviewed, with which drugs the risk of falls is relevant and might depend on genomic variation. Pharmacogenetic variability may contribute to drug-induced falls for instance mediated by impaired drug elimination due to inherited deficiency in enzymes like CYP2C9, CYP2C19 and CYP2D6. The relative role of specific genes and polymorphisms in old age may differ from younger people. Biomarkers for frailty, but also genomic biomarkers might help identifying patients at high risk for drug-induced falls. Many other factors including disease and drug-drug interactions also contribute to risk of falls. Further studies analyzing the impact of genomic variation on the medication-related fall risk in the older adult are urgently needed.

Polymorphisms of the KCNQ1 gene are associated with the therapeutic responses of sulfonylureas in Chinese patients with type 2 diabetes

KCNQ1 channel is a member of the voltage-gated potassium channel KQT-like subfamily. The KCNQ1 gene has recently been identified as a susceptibility locus for type 2 diabetes mellitus (T2DM). In the present study, we examined the effects of KCNQ1 variants on the therapeutic response to modified-release gliclazide (gliclazide MR) treatment in Chinese patients newly diagnosed with T2DM. A total of 100 newly diagnosed T2DM patients without a history of any anti-diabetic medications were treated with gliclazide MR for 16 weeks, but 91 patients completed the entire study. The anthropometric parameters were determined at baseline and at the final visit, while clinical laboratory tests were performed at baseline and on weeks 2, 4, 6, 12, 16. Two SNPs, rs2237892 and rs2237895, in the region of the KCNQ1 gene were genotyped in all the participants. All calculations and statistical analyses were conducted using SPSS. The rs2237892 TT homozygotes exhibited significantly higher 2-h glucose levels at baseline (P<0.05) and a lower cumulative attainment rate of the target 2-h glucose level (Plog-rank=0.020) than the C allele carriers. Patients with greater numbers of rs2237892 T alleles exhibited larger augmentations (Δ) in the 2-h glucose levels (P=0.027); and patients with the rs2237892 TT genotype exhibited a higher Δ homeostasis model assessment of β-cell function (HOMA-β) than CC and CT genotype carriers (P=0.021 and P=0.043, respectively). Moreover, the rs2237895 C allele was associated with a greater decrement in Δ glycated hemoglobin (HbA1c) (P=0.024); and patients with the CC genotype exhibited greater variance than those with the AA and AC genotypes (P=0.005 and 0.021, respectively). Compared with the C allele, the odds ratio for treatment success among carriers of the rs2237892 T allele was 2.533 (P=0.007); and the rs2237895 C allele was associated with a 2.360-fold decrease in HbA1c compared with the A allele (P=0.009). KCNQ1 polymorphisms are associated with gliclazide MR efficacy in Chinese patients with type 2 diabetes.

Possible approaches to CYP2C9-guided prescription of sulfonylureas in Russia

AIM

To evaluate a possible role of CYP2C9 genotyping for sulfonylureas (SUs) prescription in Russia.

MATERIALS & METHODS

We have collected the current data on correlation between SUs pharmacodynamics and CYP2C9 polymorphisms. We have evaluated the frequency of CYP2C9 polymorphisms in Russia by reviewing the literature published from 2004 to 2015 on Russian CYP2C9.

RESULTS

The genotype *1/*1, which confers risk for treatment failure, has a higher frequency (81.92%) in the non-Caucasians than that (64.92%) in the Caucasians. The Caucasians have a frequency (3.58%) of the poor metabolizers (*2/*2, *2/*3 and *3/*3) eight-times higher than that (0.44%) in the non-Caucasians, predisposing an increased risk of hypoglycemia.

CONCLUSION

Considering the received data and the existed knowledge on CYP2C9 influence on SUs pharmacokinetics and pharmacodynamics, we propose a possible approach to CYP2C9-guided SUs prescription for Russians.

The Application of Genomics in Diabetes: Barriers to Discovery and Implementation

The emerging availability of genomic and electronic health data in large populations is a powerful tool for research that has drawn interest in bringing precision medicine to diabetes. In this article, we discuss the potential application of genomics to the prediction, prevention, and treatment of diabetes, and we use examples from other areas of medicine to illustrate some of the challenges involved in conducting genomics research in human populations and implementing findings in practice. At this time, a major barrier to the application of genomics in diabetes care is the lack of actionable genomic findings. Whether genomic information should be used in clinical practice requires a framework for evaluating the validity and clinical utility of this approach, an improved integration of genomic data into electronic health records, and the clinical decision support and educational resources for clinicians to use these data. Efforts to identify optimal approaches in all of these domains are in progress and may help to bring diabetes into the era of genomic medicine.

Pharmacogenetic studies update in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a silent progressive polygenic metabolic disorder resulting from ineffective insulin cascading in the body. World-wide, about 415 million people are suffering from T2DM with a projected rise to 642 million in 2040. T2DM is treated with several classes of oral antidiabetic drugs (OADs) viz. biguanides, sulfonylureas, thiazolidinediones, meglitinides, etc. Treatment strategies for T2DM are to minimize long-term micro and macro vascular complications by achieving an optimized glycemic control. Genetic variations in the human genome not only disclose the risk of T2DM development but also predict the personalized response to drug therapy. Inter-individual variability in response to OADs is due to polymorphisms in genes encoding drug receptors, transporters, and metabolizing enzymes for example, genetic variants in solute carrier transporters (SLC22A1, SLC22A2, SLC22A3, SLC47A1 and SLC47A2) are actively involved in glycemic/HbA1c management of metformin. In addition, CYP gene encoding Cytochrome P450 enzymes also play a crucial role with respect to metabolism of drugs. Pharmacogenetic studies provide insights on the relationship between individual genetic variants and variable therapeutic outcomes of various OADs. Clinical utility of pharmacogenetic study is to predict the therapeutic dose of various OADs on individual basis. Pharmacogenetics therefore, is a step towards personalized medicine which will greatly improve the efficacy of diabetes treatment.

Computational Analysis of Single Nucleotide Polymorphisms Associated with Altered Drug Responsiveness in Type 2 Diabetes

Type 2 diabetes (T2D) is one of the most frequent mortality causes in western countries, with rapidly increasing prevalence. Anti-diabetic drugs are the first therapeutic approach, although many patients develop drug resistance. Most drug responsiveness variability can be explained by genetic causes. Inter-individual variability is principally due to single nucleotide polymorphisms, and differential drug responsiveness has been correlated to alteration in genes involved in drug metabolism (CYP2C9) or insulin signaling (IRS1, ABCC8, KCNJ11 and PPARG). However, most genome-wide association studies did not provide clues about the contribution of DNA variations to impaired drug responsiveness. Thus, characterizing T2D drug responsiveness variants is needed to guide clinicians toward tailored therapeutic approaches. Here, we extensively investigated polymorphisms associated with altered drug response in T2D, predicting their effects in silico. Combining different computational approaches, we focused on the expression pattern of genes correlated to drug resistance and inferred evolutionary conservation of polymorphic residues, computationally predicting the biochemical properties of polymorphic proteins. Using RNA-Sequencing followed by targeted validation, we identified and experimentally confirmed that two nucleotide variations in the CAPN10 gene—currently annotated as intronic—fall within two new transcripts in this locus. Additionally, we found that a Single Nucleotide Polymorphism (SNP), currently reported as intergenic, maps to the intron of a new transcript, harboring CAPN10 and GPR35 genes, which undergoes non-sense mediated decay. Finally, we analyzed variants that fall into non-coding regulatory regions of yet underestimated functional significance, predicting that some of them can potentially affect gene expression and/or post-transcriptional regulation of mRNAs affecting the splicing.

Pharmacogenomics in diabetes mellitus: insights into drug action and drug discovery

Genomic studies have greatly advanced our understanding of the multifactorial aetiology of type 2 diabetes mellitus (T2DM) as well as the multiple subtypes of monogenic diabetes mellitus. In this Review, we discuss the existing pharmacogenetic evidence in both monogenic diabetes mellitus and T2DM. We highlight mechanistic insights from the study of adverse effects and the efficacy of antidiabetic drugs. The identification of extreme sulfonylurea sensitivity in patients with diabetes mellitus owing to heterozygous mutations in HNF1A represents a clear example of how pharmacogenetics can direct patient care. However, pharmacogenomic studies of response to antidiabetic drugs in T2DM has yet to be translated into clinical practice, although some moderate genetic effects have now been described that merit follow-up in trials in which patients are selected according to genotype. We also discuss how future pharmacogenomic findings could provide insights into treatment response in diabetes mellitus that, in addition to other areas of human genetics, facilitates drug discovery and drug development for T2DM.

Pharmacogenetics in type 2 diabetes: influence on response to oral hypoglycemic agents

Type 2 diabetes is one of the leading causes of morbidity and mortality, consuming a significant proportion of public health spending. Oral hypoglycemic agents (OHAs) are the frontline treatment approaches after lifestyle changes. However, huge interindividual variation in response to OHAs results in unnecessary treatment failure. In addition to nongenetic factors, genetic factors are thought to contribute to much of such variability, highlighting the importance of the potential of pharmacogenetics to improve therapeutic outcome. Despite the presence of conflicting results, significant progress has been made in an effort to identify the genetic markers associated with pharmacokinetics, pharmacodynamics, and ultimately therapeutic response and/or adverse outcomes to OHAs. As such, this article presents a comprehensive review of current knowledge on pharmacogenetics of OHAs and provides insights into knowledge gaps and future directions.

CYP2C93 variant is associated with antidiabetes efficacy of gliclazide in Chinese type 2 diabetes patients

Aims/Introduction

The objective of the present study was to investigate the effects of CYP2C9*3 polymorphisms on the therapeutic response to gliclazide in type 2 diabetes patients.

Materials and Methods

A total of 746 incident type 2 diabetes patients were included in this study. After enrolment, patients went on 4‐week gliclazide monotherapy. Fasting plasma glucose was measured before and after treatment. Hypoglycemia episodes and lifestyle information were collected by weekly follow up. Genotyping of rs1057910 was carried out using the single base primer extension method. The t‐test, analysis of variance and chisquare‐test were used to evaluate the effects of rs1057910 alleles on the therapeutic response to gliclazide.

Results

After the therapy, fasting plasma glucose decreased significantly from 11.2 ± 2.7 mmol/L to 8.0 ± 2.2 mmol/L (P < 0.001). Patients with AC/CC genotypes of rs1057910 had a greater reduction of fasting plasma glucose (3.6 vs 3.0 mmol/L, P < 0.001; 31.4 vs 24.5%, P < 0.001) and a higher rate of treatment success (54.7 vs 37.5%, P < 0.001; 51.4 vs 32.3%, P < 0.001; 71.6 vs 48.3%, P < 0.001 for criterion 1, 2 and 3, respectively).

Conclusions

The present study showed that the polymorphism at rs1057910 significantly affected the therapeutic response of gliclazide in type 2 diabetes mellitus patients. The risk allele is associated with a greater decrease of fasting blood glucose and a higher rate of treatment success with gliclazide monotherapy.

This study demonstrated that polymorphism at rs1057910 significantly affected therapeutic response of gliclazide in type 2 diabetes mellitus patients. It associated with the decrease of FPG and the rate of treatment success in the gliclazide monotherapy.

Optimal glycaemic control in elderly people with type 2 diabetes: what does the evidence say?

The global prevalence of type 2 diabetes mellitus (T2DM) is rising in an ageing population through a combination of lifestyle changes and greater longevity. However, by excluding participants aged over 70 years, most major interventional trials on which current diabetes therapeutic guidelines are based have failed to provide specific evidence to support the prescribed management of diabetes in elderly people. While diabetes per se has a significant impact on the elderly person, the side effects of medications, particularly hypoglycaemia, prevent optimisation of diabetes treatment. Hypoglycaemia is associated with significant morbidity, to which elderly people are often more vulnerable because of factors such as the effects of ageing, progressive renal impairment, frailty, polypharmacy and cognitive decline. T2DM is associated with accelerated cognitive decline in some individuals, and recurrent severe hypoglycaemia has been implicated as a potential contributory factor. Although the evidence for selection of appropriate glycaemic targets in elderly patients is sparse, it is now acknowledged that prevention of hypoglycaemia must influence individualisation of treatment goals in this vulnerable group. This should also be reflected by the choice of anti-diabetes agents that are initiated when diet and lifestyle advice is ineffective. Recently developed international guidelines, which have specifically addressed the management of diabetes in elderly people, highlight the importance of a pragmatic management approach rather than attempting to achieve a generic glycated haemoglobin goal and are summarised in this article.

Stratified medicine for the use of antidiabetic medication in treatment of type II diabetes and cancer: where do we go from here?

At present, the global diabetes epidemic is affecting 347 million individuals, 90% of whom are diagnosed with type II diabetes mellitus (T2DM). T2DM is commonly treated with more than one type of therapy, including oral antidiabetic drugs (OADs) and agents used in the treatment of diabetic complications. Several pharmacological classes of OADs are currently available for the treatment of T2DM, of which insulin secretagogues (i.e. sulphonylureas and meglitinides), insulin sensitizers [thiazolidinediones (TZDs)] and biguanides are the most commonly prescribed. Although many of these OADs have been used for more than half a century in the treatment of T2DM, the pharmacogenomic characteristics of these compounds have only recently been investigated, primarily in retrospective studies. Recent advances in pharmacogenomics have led to the identification of polymorphisms that affect the expression and function of drug-metabolizing enzymes and drug transporters, as well as drug targets and receptors. These polymorphisms have been shown to affect the therapeutic response to and side effects associated with OADs. The aim of this review was to provide an up-to-date summary of some of the pharmacogenomic data obtained from studies of T2DM treatment, with a focus on polymorphisms in genes affecting pharmacokinetics, pharmacodynamics and treatment outcome of the most commonly prescribed OADs. In addition, the implications of pharmacogenomics in the use of the OAD metformin in cancer will be briefly discussed. Finally, we will focus on recent advances in novel 'omics' technologies and discuss how these might aid in the personalized management of T2DM.

Genomic-based tools for the risk assessment, management, and prevention of type 2 diabetes

Type 2 diabetes (T2D) is a common and serious disorder and is a significant risk factor for the development of cardiovascular disease, neuropathy, nephropathy, retinopathy, periodontal disease, and foot ulcers and amputations. The burden of disease associated with T2D has led to an emphasis on early identification of the millions of individuals at high risk so that management and intervention strategies can be effectively implemented before disease progression begins. With increasing knowledge about the genetic basis of T2D, several genomic-based strategies have been tested for their ability to improve risk assessment, management and prevention. Genetic risk scores have been developed with the intent to more accurately identify those at risk for T2D and to potentially improve motivation and adherence to lifestyle modification programs. In addition, evidence is building that oral antihyperglycemic medications are subject to pharmacogenomic variation in a substantial number of patients, suggesting genomics may soon play a role in determining the most effective therapies. T2D is a complex disease that affects individuals differently, and risk prediction and treatment may be challenging for health care providers. Genomic approaches hold promise for their potential to improve risk prediction and tailor management for individual patients and to contribute to better health outcomes for those with T2D.

Pharmacogenetics of type 2 diabetes mellitus: An example of success in clinical and translational medicine

The pharmacological interventions currently available to control type 2 diabetes mellitus (T2DM) show a wide interindividual variability in drug response, emphasizing the importance of a personalized, more effective medical treatment for each individual patient. In this context, a growing interest has emerged in recent years and has focused on pharmacogenetics, a discipline aimed at understanding the variability in patients’ drug response, making it possible to predict which drug is best for each patient and at what doses. Recent pharmacological and clinical evidences indicate that genetic polymorphisms (or genetic variations) of certain genes can adversely affect drug response and therapeutic efficacy of oral hypoglycemic agents in patients with T2DM, through pharmacokinetic- and/or pharmacodynamic-based mechanisms that may reduce the therapeutic effects or increase toxicity. For example, genetic variants in genes encoding enzymes of the cytochrome P-450 superfamily, or proteins of the ATP-sensitive potassium channel on the beta-cell of the pancreas, are responsible for the interindividual variability of drug response to sulfonylureas in patients with T2DM. Instead, genetic variants in the genes that encode for the organic cation transporters of metformin have been related to changes in both pharmacodynamic and pharmacokinetic responses to metformin in metformin-treated patients. Thus, based on the individual’s genotype, the possibility, in these subjects, of a personalized therapy constitutes the main goal of pharmacogenetics, directly leading to the development of the right medicine for the right patient. Undoubtedly, this represents an integral part of the translational medicine network.

The role of CYP2C9 genetic polymorphism in carvedilol O-desmethylation in vitro

We aimed at investigating the role of CYP2C9 in carvedilol O-desmethylation and identifying the effect of 35 CYP2C9 allelic variants we found in Chinese Han population on the in vitro metabolism of carvedilol. Recombinant CYP2C9 and CYP2D6 microsomes of the wild type were used to test and verify the enzymes involved in carvedilol O-desmethylation. Recombinant CYP2C9 microsomes of distinguished genotypes were used to characterize the corresponding enzyme activity toward carvedilol. 2-100 μM carvedilol was incubated for 30 min at 37 °C. The products were detected using high-performance liquid chromatography. CYP2C9 plays a certain role in carvedilol metabolism. Compared with wild-type CYP2C9*1, the intrinsic clearance (V max/K m) values of all variants toward carvedilol O-desmethylation were significantly altered. The variants exhibited significantly decreased values (from 30 to 99.8 %) due to increased K m and/or decreased V max values. We conclude that recombinant system could be used to investigate the enzymes involved in drug metabolism and these findings complement the database where CYP2C9 polymorphism interacts with biotransformation of exogenous substances like drugs and toxins.

RS11212617 is associated with metformin treatment response in type 2 diabetes in Shanghai local Chinese population

OBJECTIVE

This study was designed to examine the relevance of single-nucleotide polymorphism (SNP) rs11212617 with treatment success in type 2 diabetes patients from Shanghai local Chinese Han population.

METHODS

We genotyped rs11212617 in incident metformin users of type 2 diabetes patients from Shanghai local Chinese Han population. Association between rs11212617 and changes in HbA1c, fasting plasma glucose and postprandial glucose level were analysed.

RESULTS

Two hundred and seventy-four incident metformin users were included in the study sample. The SNP rs11212617 was significantly associated with metformin response in Shanghai local Chinese Han population.

CONCLUSION

The rs11212617 is associated with a reduction in HbA1c, fasting plasma glucose and postprandial glucose level. These results suggest that metformin treatment may be more efficacious in Shanghai and valuable for Chinese daily clinical practice.

CYP2C9 allelic variants and frequencies in a pediatric sickle cell disease cohort: implications for NSAIDs pharmacotherapy

Nonsteroidal anti-inflammatory drugs (NSAIDs) used to treat pain in patients with sickle cell disease (SCD) are metabolized by the CYP2C9 enzyme. Racial differences in CYP2C9 allele frequencies impact NSAIDs efficacy and safety. We determined the frequencies of CYP2C9 alleles in an African American pediatric SCD cohort. Genomic DNA was isolated from blood samples of 30 patients aged between 7 and 17 years. Genotyping of nine CYP2C9 alleles (*1,*2, *3, *4, *5, *6, *8, *11, and *13) was performed using restriction fragment length polymorphism-PCR assays and the Tag-It™ Mutation Detection System. The wild type *1 allele frequency was 0.850. The most common variant allele detected was CYP2C9*8 (0.067). The combined frequency of the *2, *5, *6, *8, and *11 variants was 0.151. Seventy percent of the study cohort were predicted extensive metabolizers (*1/*1) and 30% were intermediate metabolizers due mainly to the *1/*8 genotype. Analysis of CYP2C9 using an expanded assay panel facilitated improved classification of predicted drug metabolic phenotypes in our cohort. However, the pharmacokinetic effects of the CYP2C9*5,*6,*8, and *11 alleles on NSAIDs metabolism has not been evaluated and underscores the need for studies on substrate-specific effects of variant alleles common in populations with genetic susceptibility to SCD.

Glimepiride reduces CD14 expression and cytokine secretion from macrophages

Background

Activated microglia are associated with deposits of aggregated proteins within the brains of patients with Alzheimer’s disease (AD), Parkinson’s disease (PD) and prion diseases. Since the cytokines secreted from activated microglia are thought to contribute to the pathogenesis of these neurodegenerative diseases, compounds that suppress cytokine production have been identified as potential therapeutic targets. CD14 is a glycosylphosphatidylinositol (GPI)- anchored protein that is part of a receptor complex that mediates microglial responses to peptides that accumulate in prion disease (PrP82-146), AD (amyloid-β (Aβ)₄₂) and PD (α-synuclein (αSN)). As some GPI-anchored proteins are released from cells by treatment with glimepiride, a sulphonylurea used for the treatment of diabetes, the effects of glimepiride upon CD14 expression and cytokine production from cultured macrophages were studied.

Methods

RAW 264 cells and microglial cells were treated with glimepiride or phosphatidylinositol (PI)-phospholipase C (PLC) and the expression of cell receptors was analysed by ELISA and immunoblot. Treated cells were subsequently incubated with Aβ₄₂, αSN, PrP82-146 or lipopolysaccharide (LPS) and the amounts of Toll-like receptor (TLR)-4, tumour necrosis factor (TNF), interleukin (IL)-1 and IL-6 measured.

Results

Glimepiride released CD14 from RAW 264 cells and microglial cells. Pre-treatment with glimepiride significantly reduced TNF, IL-1 and IL-6 secretion from RAW 264 and microglial cells incubated with LPS, Aβ₄₂, αSN and PrP82-146. Glimepiride also reduced the LPS, Aβ₄₂, αSN and PrP82-146-induced translocation of TLR-4 into membrane rafts that is associated with cell activation. These effects of glimepiride were also seen after digestion of RAW 264 cells with PI-phospholipase C (PLC). In addition, the effects of glimepiride were blocked by pharmacological inhibition of GPI-PLC. The cytokine production was CD14-dependent; it was reduced in microglia from CD14 knockout mice and was blocked by antiserum to CD14.

Conclusions

RAW 264 and microglial cell responses to Aβ_1–42, αSN, PrP82-146 and LPS are dependent upon CD14 expression. Glimepiride induced the shedding of CD14 from cells by activation of GPI-PLC and consequently reduced cytokine production in response to Aβ₄₂, αSN, PrP82-146 and LPS. These results suggest that glimepiride acts as a novel anti-inflammatory agent that could modify the progression of neurodegenerative diseases.

CYP2C9, KCNJ11 and ABCC8 polymorphisms and the response to sulphonylurea treatment in type 2 diabetes patients

PURPOSE

Sulphonylureas (SU) are widely used in the management of type 2 diabetes. We investigated the influence of CYP2C9, KCNJ11 and ABCC8 polymorphisms on the response to SU currently used in everyday clinical practice.

METHODS

Patients treated for type 2 diabetes with sulphonylurea in monotherapy (n = 21) or in combination with metformin (n = 135) were provided with glucose-monitoring devices and instructed to measure fasting blood glucose levels once per week and additionally at any signs and symptoms suggesting low blood glucose for a period of three months. All patients were genotyped for CYP2C9 rs1799853 and rs1057910 (*2 and *3 allele, respectively), KCNJ11 rs5219 and rs5215, and ABCC8 rs757110.

RESULTS

The average duration of diabetes in the study group was 10.6 ± 7.1 years. Most of the patients achieved relatively good blood glucose control (HbA1c 7.0 ± 0.9). In total, 76 hypoglycemia events were observed (mean 0.48 ± 1.3). No severe hypoglycemia was reported; the lowest blood glucose was 2.1 mmol/l. Although 124 (79.5 %) patients never experienced hypoglycemia, 32 (20.5 %) patients experienced from one to eight events. None of the investigated polymorphisms influenced HbA1c levels or risk for hypoglycemia episodes in the whole group of patients. CYP2C9 genotype significantly influenced the occurrence of hypoglycemia events among the elderly patients (aged 60 years and over; n = 103). Among them, carriers of two wild-type alleles suffered 0.36 ± 0.98 events, while patients with one or two polymorphic alleles had 0.79 ± 1.7 or 2.67 ± 4.6 events, respectively (p = 0.014).

CONCLUSIONS

Our results indicate that the CYP2C9 genotype may influence the risk for hypoglycemia events in elderly patients, but not in the overall population of type 2 diabetes patients.