Zinc-rs13266634 and the arrival of diabetes pharmacogenetics: the "zinc mystique"

Genetically-Guided Medical Nutrition Therapy in Type 2 Diabetes Mellitus and Pre-diabetes: A Series of n-of-1 Superiority Trials

Type 2 diabetes mellitus (T2DM) is a heterogeneous metabolic disorder of multifactorial etiology that includes genetic and dietary influences. By addressing the latter, medical nutrition therapy (MNT) contributes to the management of T2DM or pre-diabetes toward achieving glycaemic control and improved insulin sensitivity. However, the clinical outcomes of MNT vary and may further benefit from personalized nutritional plans that take into consideration genetic variations associated with individual responses to macronutrients. The aim of the present series of n-of-1 trials was to assess the effects of genetically-guided vs. conventional MNT on patients with pre-diabetes or T2DM. A quasi-experimental, cross-over design was adopted in three Caucasian adult men with either diagnosis. Complete diet, bioclinical and anthropometric assessment was performed and a conventional MNT, based on the clinical practice guidelines was applied for 8 weeks. After a week of “wash-out,” a precision MNT was prescribed for an additional 8-week period, based on the genetic characteristics of each patient. Outcomes of interest included changes in body weight (BW), fasting plasma glucose (FPG), and blood pressure (BP). Collectively, the trials indicated improvements in BW, FPG, BP, and glycosylated hemoglobin (HbA1c) following the genetically-guided precision MNT intervention. Moreover, both patients with pre-diabetes experienced remission of the condition. We conclude that improved BW loss and glycemic control can be achieved in patients with pre-diabetes/T2DM, by coupling MNT to their genetic makeup, guiding optimal diet, macronutrient composition, exercise and oral nutrient supplementation in a personalized manner.

SLC30A8 gene polymorphism rs13266634 associated with increased risk for developing type 2 diabetes mellitus in Jordanian population

BACKGROUND

Several genome-wide association studies (GWAS) have identified the single nucleotide polymorphism (SNP) rs13266634 in the Solute carrier family 30 member 8 (SLC30A8) gene as a risk factor to type 2 diabetes mellitus (T2DM). Nevertheless, other studies reported controversial findings of no significant association between the rs13266634 with T2DM. In this study, we aimed to investigate the association of this SNP with T2DM among Jordanian population in addition to define its corresponding allelic and genotypic frequencies.

METHOD

This case-control study enrolled 358 T2DM patients and 326 healthy controls who fulfilled the inclusion criteria. Blood samples were collected from all participants and were used for the rs13266634 SNP genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique.

RESULTS

We demonstrated a significant association between the C/T rs13266634 SNP and T2DM among Jordanian population. A significant difference was found between the cases and controls regarding the allelic (P = 0.003) distribution. Compared to people having T allele, those with C allele had higher risk of T2DM (OR = 1.47 ; 95% CI: 1.14 - 1.89; P = 0.003). Having a CC genotype versus TT genotype was significantly associated with increased risk to T2DM (OR = 2.44; 95% CI: 1.16 - 5.12; P = 0.019) after adjusting for age, gender, and BMI. Under the recessive model, subjects with CC genotype were more likely to have T2DM compared to those with CT or TT genotypes, (OR = 1.64; 95% CI: 1.18 - 2.26; P = 0.003) after adjusting for age, gender and BMI.

CONCLUSION

The rs13266634 SNP is significantly associated with T2DM susceptibility among Jordanian Population.

Zinc transporters and insulin resistance: therapeutic implications for type 2 diabetes and metabolic disease

BACKGROUND

Zinc is a metal ion that is essential for growth and development, immunity, and metabolism, and therefore vital for life. Recent studies have highlighted zinc's dynamic role as an insulin mimetic and a cellular second messenger that controls many processes associated with insulin signaling and other downstream pathways that are amendable to glycemic control.

MAIN BODY

Mechanisms that contribute to the decompartmentalization of zinc and dysfunctional zinc transporter mechanisms, including zinc signaling are associated with metabolic disease, including type 2 diabetes. The actions of the proteins involved in the uptake, storage, compartmentalization and distribution of zinc in cells is under intense investigation. Of these, emerging research has highlighted a role for several zinc transporters in the initiation of zinc signaling events in cells that lead to metabolic processes associated with maintaining insulin sensitivity and thus glycemic homeostasis.

CONCLUSION

This raises the possibility that zinc transporters could provide novel utility to be targeted experimentally and in a clinical setting to treat patients with insulin resistance and thus introduce a new class of drug target with utility for diabetes pharmacotherapy.

Pharmacogenomics of glinides

Glinides, including repaglinide, nateglinide and mitiglinide, are a type of fasting insulin secretagogue that could help to mimic early-phase insulin release, thus providing improved control of the postprandial glucose levels. Glinides stimulate insulin secretion by inhibiting ATP-sensitive potassium channels in the pancreatic β-cell membrane. Although glinides have been widely used clinically and display excellent safety and efficacy, the response to glinides varies among individuals, which is partially due to genetic factors involved in drug absorption, distribution, metabolism and targeting. Several pharmacogenomic studies have demonstrated that variants of genes involved in the pharmacokinetics or pharmacodynamics of glinides are associated with the drug response. Polymorphisms of genes involved in drug metabolism, such as CYP2C9, CYP2C8 and SLCO1B1, may influence the efficacy of glinides and the incidence of adverse effects. In addition, Type 2 diabetes mellitus susceptibility genes, such as KCNQ1, PAX4 and BETA2, also influence the efficacy of glinides. In this article, we review and discuss current pharmacogenomics researches on glinides, and hopefully provide useful data and proof for clinical application.