The determination of the effect(s) of solute carrier family 22-member 2 (SLC22A2) haplotype variants on drug binding via molecular dynamic simulation systems.

Single nucleotide polymorphisms detected in the solute carrier member family-22 has been shown to result in a variable response in the treatment of type 2 diabetes mellitus with Metformin. This study predicted a three-dimensional protein structure for the SLC22A2 protein sequence using AlphaFold 2 and modelled five haplotypes within SLC22A2 protein structure observed in the Xhosa population of South Africa. The protein models were used to determine the effect(s) of haplotype variations on the transport function of Metformin and 10 other drugs by the SLC22A2 protein. Molecular dynamic simulation studies, molecular docking and interaction analysis of the five SLC22A2 haplotypes were performed in complex with the ligand 5RE in a POPC lipid bilayer to understand the mechanism of drug binding. Weakest binding free energy was found between 5RE and haplotype 1. Molecular docking studies indicated the top binding ligands as well as Metformin to bind inside the transport channel in all haplotypes increasing the probability of Metformin inhibition during co-administration of drugs. Metformin showed reduced binding affinity and number of interactions compared to the top four binding molecules. Molecular dynamic simulation analysis indicated that haplotypes 1, 3 and 4 were less stable than 2 and 5. The findings suggest haplotypes 4 and 5 having stronger preference for large inhibitor molecule binding in the active site and this could result in haplotypes 4 and 5 demonstrating reduced Metformin clearance via the SLC22A2 transporter during co-administration of drugs. The current study is the first to investigate the potential effect(s) of haplotype variation on the protein structure of SLC22A2 to assess its ability to transport Metformin in an indigenous South African population.

Promoter haplotype structure of solute carrier 22 member 2 (SLC22A2) in the Xhosa population of South Africa and their differential effect on gene expression.

SLC22A2 is abundantly expressed in the kidney and facilitates the transport of endogenous and exogenous cationic compounds. It plays a pivotal role in the transport of pharmacologically important compounds such as metformin, cisplatin, lamivudine and cimetidine. Polymorphisms within SLC22A2 could potentially contribute to the inter-individual variable response to drugs. The SLC22A2 gene is known to show polymorphism variability amongst populations of different ethnicities. The present study was undertaken to characterize the promoter haplotype structure of the SLC22A2 gene in the Xhosa population of South Africa. In addition to this, we also investigate the effects of the observed promoter haplotypes on gene expression levels in vitro. We identified six known single nucleotide polymorphisms in the promoter region, namely rs60249401 (G424A), rs113150889 (G289A), rs55920607 (C246T), rs59695691 (A195G), rs572296424 (G156A), rs150063153 (A95C/G) and one novel SNP at location 6:160258967 (A209T). While these polymorphisms appeared in other African and non-African populations, their minor allele frequencies differed considerably from the non-African populations and could be considered to be African specific. A total of nine promoter haplotypes were characterized and the functional significance of each haplotype on promoter activity was determined using a luciferase reporter assay system. Amongst the nine observed haplotypes, three haplotypes (i.e. haplotypes 7, 8 and 9) displayed a significant decrease in expression level when compared to the wild-type with p -values of: 0.0317, <0.0001 and 0.0013 respectively. The data presented here shows African specific promoter haplotypes to cause a decrease in SLC22A2 gene expression levels, which in turn may have an impact on the pharmacokinetic profiles of cationic drugs.

Evaluation of the suitability of 19 pharmacogenomics biomarkers for individualized metformin therapy for type 2 diabetes patients.

Objectives Type 2 Diabetes mellitus is a progressive metabolic disease characterized by relative insulin insufficiency and insulin resistance resulting in hyperglycemia. Despite the widespread use of metformin, there is considerable variation in treatment response; with approximately one-third of patients failing to achieve adequate glycemic control. Studies have reported the involvement of single nucleotide polymorphisms and their interactions in genetic pathways i.e., pharmacodynamics and pharmacokinetics. This study aims to investigate the association between 19 pharmacogenetics biomarkers and response to metformin treatment. Methods MassARRAY panels were designed and optimized by Inqaba Biotechnical Industries, to genotype 19 biomarkers for 140 type 2 diabetic outpatients. Results The CT genotype of the rs12752688 polymorphism was significantly associated with increased response to metformin therapy after correction (OR=0.33, 95% CI [0.16-0.68], p-value=0.006). An association was also found between the GA genotype of SLC47A2 rs12943590 and a decreased response to metformin therapy after correction (OR=2.29, 95% CI [1.01-5.21], p-value=0.01). Conclusions This is the first study investigating the association between genetic variants and responsiveness to medication for diabetic patients from the indigenous Nguni population in South Africa. It is suggested that rs12752688 and rs12943590 be included in pharmacogenomics profiling systems to individualize metformin therapy for diabetic patients from African populations.

Socio-demographic and modifiable risk factors of diabetes and hypertension among resource constrained patients from rural areas in Mdantsane Township in South Africa.

BACKGROUND: Recently, developing countries have shown a dramatic increase in non-communicable diseases (NCDs). The burden of NCDs in South Africa has increased over the past years resulting in an estimated 37% of all- cause mortality and 16% of disability-adjusted life years. Currently, diabetes mellitus (DM) and hypertension (HTN) are the two most prevalent NCDs associated with the rapid increase in mortality. OBJECTIVE: To demonstrate the socio-demographic and modifiable risk factors of diabetes mellitus (DM) and hypertension (HTN) among South African adults. METHODS: A cross-sectional analytical study was conducted in the Cecilia Makiwane Hospital serving the residents of Mdantsane. Relevant socio-demographic data, anthropometric measurements, triplicate blood pressure, fasting blood glucose and lipogram analysis were obtained from 265 outpatients. RESULTS: Multivariate anlysis shows that; salt intake, smoking, elevated triglycerides and decreased high-density lipoprotein levels were significantly associated with DM with adjusted odds ratio of 0.18 (p=0.002), 0.26 (p=0.048), 2.19 (p=0.006) and 0.38 (p=0.001), respectively. Overweight and obesity were significantly associated with hypertension with odds ratio of 0.03 (p=0.01) and 0.06 (p=0.006), respectively. CONCLUSION: The burden of DM and HTN on society can be drastically reduced with simple lifestyle changes, development of preventative strategies, large-scale screening and better disease management in South Africa.

Evaluation of the suitability of 19 pharmacogenomics biomarkers for individualized metformin therapy for type 2 diabetes patients.

Objectives Type 2 Diabetes mellitus is a progressive metabolic disease characterized by relative insulin insufficiency and insulin resistance resulting in hyperglycemia. Despite the widespread use of metformin, there is considerable variation in treatment response; with approximately one-third of patients failing to achieve adequate glycemic control. Studies have reported the involvement of single nucleotide polymorphisms and their interactions in genetic pathways i.e., pharmacodynamics and pharmacokinetics. This study aims to investigate the association between 19 pharmacogenetics biomarkers and response to metformin treatment. Methods MassARRAY panels were designed and optimized by Inqaba Biotechnical Industries, to genotype 19 biomarkers for 140 type 2 diabetic outpatients. Results The CT genotype of the rs12752688 polymorphism was significantly associated with increased response to metformin therapy after correction (OR=0.33, 95% CI [0.16-0.68], p-value=0.006). An association was also found between the GA genotype of SLC47A2 rs12943590 and a decreased response to metformin therapy after correction (OR=2.29, 95% CI [1.01-5.21], p-value=0.01). Conclusions This is the first study investigating the association between genetic variants and responsiveness to medication for diabetic patients from the indigenous Nguni population in South Africa. It is suggested that rs12752688 and rs12943590 be included in pharmacogenomics profiling systems to individualize metformin therapy for diabetic patients from African populations.

Effect of the African-specific promoter polymorphisms on the SLC22A2 gene expression levels.

BACKGROUND: Single nucleotide polymorphisms in promoter regions have been shown to alter the transcription of genes. Thus, SNPs in SLC22A2 can result in inter-individual variable response to medication. METHODS: The objective of the study was to investigate the effect of the African-specific promoter polymorphisms on the SLC22A2 gene expression levels in vitro. These included rs572296424 and rs150063153, which have been previously identified in the Xhosa population of South Africa. The promoter region (300 bp) for the two haplotypes was cloned into the pGLOW promoterless GFP reporter vector. The GFP expression levels of each haplotype was determined in the HEK293 cells using a GlowMax Multi-Detection E7031 luminometer in the form of light emission. RESULTS: The relative promoter activity suggests that no significant variation exists between the expression levels of the WT and -95 haplotypes and the -95 and -156 haplotypes (p=0.498). However, the relative promoter activity of the WT haplotype in comparison to the -156 haplotype displayed a significant difference in expression level (p=0.016). CONCLUSIONS: The data presented here show that the African-specific promoter polymorphisms can cause a decrease in the SLC22A2 gene expression levels in vitro, which in turn, may influence the pharmacokinetic profiles of cationic drugs.