Genetic architecture of type 2 diabetes: recent progress and clinical implications

Genome-wide association studies: utility and limitations for research in physiology

Physiological systems are subject to interindividual variation encoded by genetics. Genome-wide association studies (GWAS) operate by surveying thousands of genetic variants from a substantial number of individuals and assessing their association to a trait of interest, be it a physiological variable, a molecular phenotype (e.g. gene expression), or even a disease or condition. Through a myriad of methods, GWAS downstream analyses then explore the functional consequences of each variant and attempt to ascertain a causal relationship to the phenotype of interest, as well as to delve into its links to other traits. This type of investigation allows mechanistic insights into physiological functions, pathological disturbances and shared biological processes between traits (i.e. pleiotropy). An exciting example is the discovery of a new thyroid hormone transporter (SLC17A4) and hormone metabolising enzyme (AADAT) from a GWAS on free thyroxine levels. Therefore, GWAS have substantially contributed with insights into physiology and have been shown to be useful in unveiling the genetic control underlying complex traits and pathological conditions; they will continue to do so with global collaborations and advances in genotyping technology. Finally, the increasing number of trans-ancestry GWAS and initiatives to include ancestry diversity in genomics will boost the power for discoveries, making them also applicable to non-European populations.

Association between RAC1 gene variation, redox homeostasis and type 2 diabetes mellitus

BACKGROUND

Increased production of reactive oxygen species (ROS) and oxidative stress are known to play a key role in the pathogenesis of type 2 diabetes (T2D); however, the relationship between genes encoding a multi-subunit ROS-generated enzyme NADPH oxidase and disease susceptibility remains unexplored.

AIMS

The present pilot study investigated whether single-nucleotide polymorphisms (SNP) at the RAC1 gene (Rac family small GTPase 1), a molecular switcher of NADPH oxidase, are associated with the risk of T2D, glucose metabolism and redox homeostasis.

MATERIALS & METHODS

DNA samples from 3206 unrelated Russian subjects (1579 T2D patients and 1627 controls) were genotyped for six common SNPs rs4724800, rs7784465, rs10951982, rs10238136, rs836478 and rs9374 of RAC1 using the MassArray-4 system.

RESULTS

SNP rs7784465 was associated with an increased risk of T2D (p = .0003), and significant differences in the RAC1 haplotypes occurred between the cases and controls (p = .005). Seventeen combinations of RAC1 genotypes showed significant associations with T2D risk (FDR <0.05). Associations of RAC1 polymorphisms with T2D were modified by environmental factors such as sedentary lifestyle, psychological stresses, a dietary deficit of fresh fruits/vegetables and increased carbohydrate intake. RAC1 polymorphisms were associated with biochemical parameters in diabetics: rs7784465 (p = .015) and rs836478 (p = .028) with increased glycated haemoglobin, rs836478 (p = .005) with increased fasting blood glucose, oxidized glutathione (p = .012) and uric acid (p = .034). Haplotype rs4724800A-rs7784465C-rs10951982G-rs10238136A-rs836478C-rs9374G was strongly associated with increased levels of hydrogen peroxide (p < .0001).

CONCLUSION

Thus, polymorphisms in the RAC1 gene represent novel genetic markers of type 2 diabetes, and their link with glucose metabolism and disease pathogenesis is associated with the changes in redox homeostasis.

Surface-Catalyzed Secondary Nucleation Dominates the Generation of Toxic IAPP Aggregates

The aggregation of the human islet amyloid polypeptide (IAPP) is associated with diabetes type II. A quantitative understanding of this connection at the molecular level requires that the aggregation mechanism of IAPP is resolved in terms of the underlying microscopic steps. Here we have systematically studied recombinant IAPP, with amidated C-terminus in oxidised form with a disulphide bond between residues 3 and 7, using thioflavin T fluorescence to monitor the formation of amyloid fibrils as a function of time and IAPP concentration. We used global kinetic analyses to connect the macroscopic measurements of aggregation to the microscopic mechanisms, and show that the generation of new aggregates is dominated by the secondary nucleation of monomers on the fibril surface. We then exposed insulinoma cells to aliquots extracted from different time points of the aggregation process, finding the highest toxicity at the midpoint of the reaction, when the secondary nucleation rate reaches its maximum. These results identify IAPP oligomers as the most cytotoxic species generated during IAPP aggregation, and suggest that compounds that target secondary nucleation of IAPP could be most effective as therapeutic candidates for diabetes type II.

Expression, purification and characterisation of large quantities of recombinant human IAPP for mechanistic studies

Malfunction and amyloid formation of the Islet Amyloid Polypeptide (IAPP) are factors contributing to Type 2 diabetes. Unravelling the mechanism of IAPP aggregate formation may forward our understanding of this process and its effect on pancreatic β-islet cell. Such mechanistic studies require access to sequence homogeneous and highly pure IAPP. Here we present a new facile protocol for the production of pure recombinant human IAPP at relatively high yield. The protocol uses a His-tagged version of the Npro mutant EDDIE, which drives expression to inclusion bodies, from which the peptide is purified using sonication, refolding and auto-cleavage, removal of EDDIE using Ni-NTA chromatography and reverse-phase HPLC. The purified material is used at multiple concentrations in aggregation kinetics measurements monitored by thioflavin-T fluorescence. Global analysis of the data implies a double nucleation aggregation mechanism including both primary and secondary nucleation.

Perception on genetic testing in Korean medicine doctors: A mobile-based survey

Background

Currently, genetic testing is widely used to understand individual characteristics. In Korea, genetic testing has been in use, but not actively in Korean Medicine (KM). To examine the perceptions of genetic testing, we performed online survey to Korean Medicine doctors (KMDs).

Methods

The survey was a mobile-based study that was developed by 6 survey specialists based on electronic database search results. The questionnaire consisted of 6 categories: general characteristics of respondents, understanding of genetic testing, demand for using genetic testing, application field and utilization level of genetic testing, limitations of genetic testing, and plans and necessary efforts to begin using genetic testing based on an 11-point Likert scale.

Results

With the response rate of 27.2% (n = 544), 46.9% of respondents answered that they understood the definition and mechanism of genetic testing. About 80% of KMDs responded that they would be willing to use genetic testing results; a notable reason for this was the need for more objective and evidence-based test results. KMDs recognized that genetic testing could not only provide personalized treatment and care, but also help communicate with patients.

Conclusions

This study observed KMDs’ perceptions of the potential clinical benefits of genetic testing. We confirmed that development of genetic testing technology, knowledge of their use, and new technology-friendly policies are essential for expanding the genetic testing technology in Korean medicine.

Genetic predisposition in type 2 diabetes: A promising approach toward a personalized management of diabetes

Diabetes mellitus, also known simply as diabetes, has been described as a chronic and complex endocrine metabolic disorder that is a leading cause of death across the globe. It is considered a key public health problem worldwide and one of four important non-communicable diseases prioritized for intervention through world health campaigns by various international foundations. Among its four categories, Type 2 diabetes (T2D) is the commonest form of diabetes accounting for over 90% of worldwide cases. Unlike monogenic inherited disorders that are passed on in a simple pattern, T2D is a multifactorial disease with a complex etiology, where a mixture of genetic and environmental factors are strong candidates for the development of the clinical condition and pathology. The genetic factors are believed to be key predisposing determinants in individual susceptibility to T2D. Therefore, identifying the predisposing genetic variants could be a crucial step in T2D management as it may ameliorate the clinical condition and preclude complications. Through an understanding the unique genetic and environmental factors that influence the development of this chronic disease individuals can benefit from personalized approaches to treatment. We searched the literature published in three electronic databases: PubMed, Scopus and ISI Web of Science for the current status of T2D and its associated genetic risk variants and discus promising approaches toward a personalized management of this chronic, non-communicable disorder.

NASH (nonalcoholic steatohepatitis), diabetes, and macrovascular disease: multiple chronic conditions and a potential treatment at the metabolic root

Introduction: NASH and type 2 diabetes (T2D) are clinical definitions that overlap and result from metabolic dysfunction caused by over-nutrition relative to metabolic need. This volume details drug development programs aimed at specific NASH pathology with a focus on liver outcomes; this commentary suggests a metabolic approach that should not be overlooked based on a new understanding of insulin sensitizers.Areas covered: The overlap of NASH and T2D with respect to metabolic syndrome is discussed in the context of new understandings of insulin sensitizers. Adverse clinical outcomes in subjects with advanced NAFLD (e.g. NASH) and advanced metabolic dysfunction (e.g., T2D) are primarily due to cardiovascular issues. Clinical evidence suggests that insulin resistance and hyperinsulinemia predict adverse cardiovascular outcomes. NALFD/NASH significantly contributes to insulin resistance and hyperinsulinemia. A new insulin sensitizer that targets the newly identified mitochondrial pyruvate carrier could provide an approach.Expert opinion: A metabolic approach is needed for the treatment of NASH. Clinical studies are underway to determine whether a new insulin sensitizer that targets pyruvate metabolism can impact NASH, T2D, and cardiovascular disease. A broader view of metabolic disease may provide a more assessable way to track therapeutic benefit.

Prevalence of Diabetes Mellitus and Associated Factors in Addis Ababa Public Health Facilities, Addis Ababa, Ethiopia, 2016

INTRODUCTION

Diabetes mellitus is one of the most public health challenges of the twenty-first century. Globally, 382 million people had diabetes by the year 2013.

PURPOSE

The purpose of this study was to determine the prevalence of diabetes mellitus and identify its associated factors at public health institutions in Addis Ababa.

PATIENTS AND METHODS

An institution-based cross-sectional study was carried out from June to July 2016. A total of 758 participants were selected using a multistage sampling technique. Data were collected with a structured interviewer-administered questionnaire; a WHO STEPwise approach of NCDs risk factors identification, and the collected data were checked for completeness immediately following data collection and the filled questionnaires were entered into Epi-Info 3.5.1, and then exported to SPSS 23 for further analysis. Descriptive statistics such as mean, percentages, standard deviation, and ranges were determined. To identify factors associated with diabetes mellitus, binary logistics regression was used.

RESULTS

The overall prevalence of diabetes mellitus was 14.8%, with a sex-specific prevalence of 18.35% and 16.62% for males and females, respectively. Older age participants had higher risks of developing diabetes mellitus than younger age individuals. Alcohol drinkers had more risks of developing diabetes mellitus than non-alcohol drinkers. Participants with plasma HDL-C ≥40mg/dl were more likely to develop diabetes mellitus than those with <40mg/dl. Participants with a higher level of plasma triglyceride ≥130mg/dl were found to be more exposed to the risks of developing diabetes mellitus than study participants with a low level of triglycerides.

CONCLUSION

A higher prevalence of diabetes mellitus was observed in Addis Ababa public health institutions. Factors such as age, alcohol drinking, HDL, triglycerides, and vagarious physical activity were associated with diabetes mellitus. Concerned bodies need to work over the ever-increasing diabetes mellitus in Addis Ababa.

The Role of Genetic Polymorphism in the Formation of Arterial Hypertension, Type 2 Diabetes and their Comorbidity

BACKGROUND

Hereditary component plays a significant role in the formation of insulin resistance (IR) - one of the pathogenetic links of arterial hypertension (AH) and type 2 diabetes mellitus (DM2). However, the genetic predisposition to IR can not be realized and does not manifest itself clinically in the absence of appropriate factors of the environment (excessive nutrition, low physical activity, etc.).

OBJECTIVE

The review summarizes the results of studies which describe the contribution of genetic polymorphism to the formation and progression of AH, DM2 and their comorbidity in various populations.

RESULTS

In many studies, it has been established that genetic polymorphism of candidate genes is influenced by the formation, course and complication of AH and DM2. According to research data, the modulating effect of polymorphism of some genetic markers of AH and DM2 on metabolism and hemodynamics has been established. The results of numerous studies have shown a higher frequency of occurrence of AH and DM2, as well as their more severe course with adverse genetic polymorphisms. At the same time, the role of genetic polymorphism in the formation of AH and DM2 differs in different populations.

CONCLUSION

Contradictory data on the influence of gene polymorphisms on the formation of AH and DM2 in different populations, as well as a small number of studies on the combined effects of several polymorphisms on the formation of comorbidity, determine the continuation of research in this direction.

A COMMENTARY ON CLASSIFICATION OF DIABETES: LATENT AUTOIMMUNE DIABETES IN ADULTS (LADA) OR INTERMEDIARY DIABETES MELLITUS (IDM)?

Diabetes Mellitus is a huge syndrome which can be detected from the first day of life until the last year of life of a centenarian. In the current classification of diabetes among the so-called "idiopathic phenotypes", apart Type 1 Diabetes (T1D) and Type 2 Diabetes (T2D) has been included provisionally term "Latent Autoimmune Diabetes in Adults" (LADA). This has unclear characterization regarding the age at onset, the presence of anti-β-cell antibodies and the level of insulin secretory function, in conformity with C-peptide levels. According to several recent publications, there are no specific biochemical or genetic markers for Latent Autoimmune Diabetes in Adults (LADA), but only a gradual transition from T1D to T2D. In addition, the word "latent" in the construction of "LADA" term is inaccurate because in this phenotype nothing is latent: both the autoimmunity and diabetes are present and are even parts of the diagnosis. So that, the best term should be what in reality this sub-phenotype is: an Intermediary Diabetes Mellitus (IDM). Some recent genetic data strongly support this designation.

Evaluating the glucose raising effect of established loci via a genetic risk score

Recent genome-wide association studies have identified several single nucleotide polymorphisms (SNPs) associated with glucose levels. We tested the hypothesis here whether the cumulative effect of glucose raising SNPs, assessed via a score, is associated with glucose levels. A total of 1,434 participants of Greek descent from the THISEAS study and 1,160 participants form the GOMAP study were included in this analysis. We developed a genetic risk score (GRS), based on the known glucose-raising loci, in order to investigate the cumulative effect of known glucose loci on glucose levels. In the THISEAS study, the GRS score was significantly associated with increased glucose levels (mmol/L) (β ± SE: 0.024 ± 0.004, P = 8.27e-07). The effect of the genetic risk score was also significant in the GOMAP study (β ± SE: 0.011 ± 0.005, P = 0.031). In the meta-analysis of the two studies both scores were significantly associated with higher glucose levels GRS: β ± SE: 0.019 ± 0.003, P = 1.41e-09. Also, variants at the SLC30A8, PROX1, MTNR1B, ADRA2A, G6PC2, LPIN3 loci indicated nominal evidence for association with glucose levels (p < 0.05). We replicate associations of the established glucose raising variants in the Greek population and confirm directional consistency of effects (binomial sign test p = 6.96e-05). We also demonstrate that the cumulative effect of the established glucose loci yielded a significant association with increasing glucose levels.

Mulberry branch bark powder significantly improves hyperglycemia and regulates insulin secretion in type II diabetic mice

This experiment, based on the previous study on R. mori, introduces whole mulberry branch powder into the diet to treat diabetic mice. Mulberry branch bark powder (MBBP) was administered orally to streptozotocin (STZ)-induced type II diabetic (T2D) mice to investigate hypoglycemic effects. After a 4-week period of diet consumption containing 5%, 10% and 20% MBBP, the fasting blood glucose, body weight and the related western blotting were measured, pathologic and immunohistochemical were observed. The 20% MBBP group showed a significant reduction in hyperglycemia and hyperinsulinemia; fasting blood glucose and insulin decreased from 25.0 to 14.8 mmol/L and 26.5 to 16.0 mU/L, respectively. Pathologic and immunohistochemical observation showed that MBBP administration lead to the repair of pancreas cells and restoration of insulin secretion. Dietary MBBP was associated with the decrease in the contents of 3, 4-methylenedioxeamphetamine, 8-OHdG, aspartate aminotransferase, and alanine aminotransferase, and the increase in antioxidative ability and glucose tolerance. Western blotting (WB) analysis suggested that MBBP decreased the TNF-α levels, thus relieving inflammation and improving liver function. It also led to the downregulation of apoptosis factor expression. WB also confirmed that MBBP enhanced the gene expression of the key enzymes: insulin receptor, insulin receptor substrate, p-AKT, GSK3β, glycogen synthase, G6Pase and phosphoenolpyruvate carboxykinase, which are related to glucose metabolism in the liver, and increase the expression of the genes PDX-1, GLUT2, MafA, and glucokinase, related to insulin secretion. Thus, oral administration of MBBP regulated insulin secretion and effectively maintained normal levels of glucose metabolism in mice, which may be done by improving the antioxidant capacity and activating insulin signaling with T2D..

Does bilirubin protect against developing diabetes mellitus?

After 25 years of evaluating bilirubin as a possible protective agent in neonatal and cardiovascular disease, interest has moved on to a exploring a possible protective role in diabetes mellitus (DM). This review finds conflicting prospective data for a protective relationship though there are retrospective, case-controlled data, that can only show association, which is not causality. Only prospective studies can show causality. Also, it would appear that the underlying biochemical assumptions do not readily translate from the animal to the human setting. Given that many factors impact on circulating bilirubin levels, it is not surprising that a clear-cut answer is not available; the jury is still out. Any relationship between DM and bilirubin might relate to intermediates in bilirubin metabolism, including relationships involving the genes for the enzymes participating in those steps. Nevertheless, the pursuit of bilirubin in disease causation is opening new avenues for research and if it is established that serum bilirubin can predict risks, much will have been achieved. The answer may have to come from molecular genetic analyses.

Association between transcription factor 7-like 2 rs7903146 polymorphism and diabetic retinopathy in type 2 diabetes mellitus: A meta-analysis

As one of the vascular complications of type 2 diabetes mellitus, the incidence of diabetes retinopathy is greatly increasing worldwide. Both genetic and environmental factors are involved in the pathologies. A meta-analysis was conducted to assess the association between transcription factor 7-like 2 polymorphism (rs7903146) and type 2 diabetic retinopathy. Published literature from PubMed, Web of Science and China National Knowledge Infrastructure were retrieved. Pooled odds ratios with 95% confidence intervals were calculated to estimate the strength of the association. Eight studies including 6422 participants were included in the final meta-analysis. Our analysis provides substantial evidence that the rs7903146 variant is significantly associated with the risk of diabetic retinopathy in Caucasian populations while not in East Asian populations. The variant of rs7903146 appeared more likely to be a promising genetic biomarker of diabetic retinopathy in Caucasians.

Continual evolution of type 2 diabetes: an update on pathophysiology and emerging treatment options

Diabetes is a complex and progressive disease that has a major societal and economic impact. The most common form of diabetes, type 2 diabetes mellitus (T2DM), is a multifactorial disease, the pathophysiology of which involves not only the pancreas but also the liver, skeletal muscle, adipose tissue, gastrointestinal tract, brain, and kidney. Novel therapies with mechanisms of action that are different from most existing drugs are emerging. One such class consists of compounds that inhibit renal sodium-glucose cotransporter 2, which is responsible for the bulk of glucose reabsorption by the kidneys. This new class of compounds improves glycemic control independently of insulin and promotes weight reduction, providing an additional tool to treat patients with T2DM. This review discusses the underlying pathophysiology of T2DM, clinical guidelines, and available and emerging treatment options, with particular emphasis on sodium-glucose cotransporter 2 inhibitors.

Significance of a common variant in the CDKAL1 gene with susceptibility to type 2 diabetes mellitus in Iranian population

Background:

Type 2 diabetes mellitus (T2DM) is a worldwide problem that threatens the public health and economies of all countries. A multifactorial etiology and interaction between environmental factors and genetic components are responsible for triggering and progression of T2DM. Recently, rs7754840 single nucleotide polymorphism (SNP) in the CDKAL1 gene was reported to be associated with T2DM in various populations. However, due to inconsistent results in various populations about the association of rs7754840 with T2DM, and lack of information in the Iranian population, we have evaluated its association with T2DM in a subset of the Iranian population from Isfahan province, central part of Iran.

Materials and Methods:

The study included 140 patients and 140 controls selected based on the World Health Organization guidelines. Genomic DNA was extracted from blood samples and the rs7754840 SNP was genotyped using a polymerase chain reaction-restriction fragment length polymorphism assay with specific primers and restriction enzyme (Ac1I).

Results:

The frequency of the C allele in the cases was higher than that in the controls (72.9% vs. 65%; P = 0.045). Using logistic regression analysis, we found a significant risk association of CC genotype with T2DM susceptibility (OR = 2.319, 95% CI = 1.436-3.744, P = 0.001). Furthermore, compared with the CC genotype, individuals with the GC genotype had a lower risk (protective association) of developing T2DM (OR = 0.332, 95% CI = 0.202-0.547, P < 0.001).

Conclusions:

We confirmed that there is a significant risk association between rs7754840 polymorphism and development of T2DM in a subset of the Iranian population from Isfahan province.

Common polymorphisms in MIR146a, MIR128a and MIR27a genes contribute to neuropathy susceptibility in type 2 diabetes

Diabetic polyneuropathy (DPN) and cardiovascular autonomic neuropathy (CAN) are common type 2 diabetes complications with a large inter-individual variability in terms of clinical manifestations and severity. Our aim was to evaluate a possible involvement of genetic polymorphisms in miRNA regions in the susceptibility to DPN and CAN. Nine polymorphisms in miRNA genes were studied in a sample of 132 type 2 diabetes patients (T2D) analysed for DPN and 128 T2D patients analysed for CAN. A genotype-phenotype correlation analysis was performed. The T allele of rs11888095 single nucleotide polymorphism (SNP) in MIR128a was significantly associated with a higher risk (ORadj = 4.89, P adj = 0.02), whereas the C allele of rs2910164 SNP in MIR146a was associated with a lower risk to develop DPN (ORadj = 0.49, P adj = 0.09), respectively. A multivariate logistic regression analysis confirmed that both SNPs contribute to DPN (p < 0.001 and p = 0.01 for MIR128a and MIR146a, respectively). MIR128a SNP significantly contributed also to DPN score (p = 0.026). Rs895819 SNP in MIR27a was significantly associated with a higher risk to develop early CAN (P adj = 0.023 and ORadj = 3.43). The rs2910164 SNP in MIR146a showed a protective effect respect to early CAN (P adj = 0.052, ORadj = 0.32) and to confirmed CAN (P adj = 0.041, ORadj = 0.13). The same SNP resulted significantly associated with a lower CAN score and a higher E/I (p = 0.002 and p = 0.003, respectively). In conclusion, we described associations of MIR128a and MIR146a SNPs with DPN susceptibility and of MIR146a and MIR27a SNPs with CAN susceptibility. This is the first study showing that genetic variability in miRNA genes could be involved in diabetic neuropathies susceptibility.

RBP4 gene variants are associated with insulin resistance in women with previous gestational diabetes

Objective. This study aimed to examine possible genetic effects of some retinol binding protein-4 (RBP4) single nucleotide polymorphisms (SNPs) on the risk of gestational diabetes mellitus (GDM). In addition, the SNPs were examined for their possible association with insulin resistance at 6 weeks after delivery. Methods. This was a prospective study of 100 women with GDM and 100 participants with normal gestation who were evaluated at gestational week 30 and 6 weeks postpartum. Three SNPs of RBP4 (rs3758539, rs116736522, and rs34571439) were genotyped using TaqMan assay. The genotype distributions between GDM patients and normal controls were analyzed using logistic regression models. In addition, differences in clinical characteristics among subjects grouped by genotype were assessed using the analysis of covariance test. Results. The frequencies of the rare alleles were not significantly different between GDM patients and controls. However, we identified two variants rs3758539 and rs34571439 associated with insulin levels and insulin resistance in women with previous GDM. Conclusion. Noncoding SNPs of the RBP4 gene are not associated with GDM, but two SNPs showed associations with insulin resistance and insulin levels in women with prior GDM. Additional studies with increased sample size will be necessary in other GDM cohorts.

The effect of genetic counseling for adult offspring of patients with type 2 diabetes on attitudes toward diabetes and its heredity: a randomized controlled trial

The aim of this study is to investigate the effect of diabetes genetic counseling on attitudes toward diabetes and its heredity in relatives of type 2 diabetes patients. This study was an unmasked, randomized controlled trial at a medical check-up center in Japan. Subjects in this study are healthy adults between 30 and 60 years of age who have a family history of type 2 diabetes in their first degree relatives. Participants in the intervention group received a brief genetic counseling session for approximately 10 min. Genetic counseling was structured based on the Health Belief Model. Both intervention and control groups received a booklet for general diabetes prevention. Risk perception and recognition of diabetes, and attitude towards its prevention were measured at baseline, 1 week and 1 year after genetic counseling. Participants who received genetic counseling showed significantly higher recognition about their sense of control over diabetes onset than control group both at 1 week and 1 year after the session. On the other hand, anxiety about diabetes did not change significantly. The findings show that genetic counseling for diabetes at a medical check center helped adults with diabetes family history understand they are able to exert control over the onset of their disease through lifestyle modification.

Glucagon gene polymorphism modifies the effects of smoking and physical activity on risk of type 2 diabetes mellitus in Han Chinese

Few genome-wide association studies have considered interactions between multiple genetic variants and environmental factors associated with disease. The interaction was examined between a glucagon gene (GCG) polymorphism and smoking, alcohol consumption and physical activity and the association with risk of type 2 diabetes mellitus (T2DM) in a case-control study of Chinese Han subjects. The rs12104705 polymorphism of GCG and interactions with environmental variables were analyzed for 9619 participants by binary multiple logistic regression. Smoking with the C-C haplotype of rs12104705 was associated with increased risk of T2DM (OR=1.174, 95% CI=1.013-1.361). Moderate and high physical activity with the C-C genotype was associated with decreased risk of T2DM as compared with low physical activity with the genotype (OR=0.251, 95% CI=0.206-0.306 and OR=0.190, 95% CI=0.164-0.220). However, the interaction of drinking and genotype was not associated with risk of T2DM. Genetic polymorphism in rs12104705 of GCG may interact with smoking and physical activity to modify the risk of T2DM.

A replication study of 19 GWAS-validated type 2 diabetes at-risk variants in the Lebanese population

AIM

Recent genome-wide association scans (GWAS) and replication studies have expanded the list of validated type 2 diabetes (T2DM) susceptibility loci. We replicated T2DM association of 19 SNPs from 15 candidate loci in Lebanese Arabs.

METHODS

Case-control association study, comprising 995 T2DM patients and 1076 control participants. We genotyped by the allelic discrimination method 19 SNPs in/near ADAM30, NOTCH2, THADA, TMEFF2, COL8A1, ADAMTS9-AS2, WFS1, JAZF1, SLC30A8, KCNQ1, LOC387761, ALX4, TSPAN8, FTO, and HNF1.

RESULTS

Allele frequencies of the tested SNPs were comparable with those of Caucasians. COL8A1 rs792837 (P=2.9 × 10(-9)), KCNQ1 rs2237892 (P=1.8 × 10(-18)) and rs2237895 (P=0.002), ALX4 rs729287 (Pc=7.5 × 10(-5)), and HNF1 rs4430796 (P=0.003) were significantly associated with T2DM, with similar effect sizes to those of Europeans. While FTO rs8050136 and rs17817449, ADAMTS9 rs4607103, and WFS1 rs10010131 were initially associated with T2DM, this was lost upon multiple testing correction. The remaining variants were not associated with T2DM, possibly resulting from insufficient power to detect smaller allele effects.

CONCLUSION

In addition to previous findings on the association of IGF2BP2, CDKAL1, TCF7L2 variants with T2DM among Lebanese, here we extend these by validating the association of five additional loci with T2DM in Lebanese Arabs.

Evaluating empirical bounds on complex disease genetic architecture

The genetic architecture of human diseases governs the success of genetic mapping and the future of personalized medicine. Although numerous studies have queried the genetic basis of common disease, contradictory hypotheses have been advocated about features of genetic architecture (for example, the contribution of rare versus common variants). We developed an integrated simulation framework, calibrated to empirical data, to enable the systematic evaluation of such hypotheses. For type 2 diabetes (T2D), two simple parameters--(i) the target size for causal mutation and (ii) the coupling between selection and phenotypic effect--define a broad space of architectures. Whereas extreme models are excluded by the combination of epidemiology, linkage and genome-wide association studies, many models remain consistent, including those where rare variants explain either little (<25%) or most (>80%) of T2D heritability. Ongoing sequencing and genotyping studies will further constrain the space of possible architectures, but very large samples (for example, >250,000 unselected individuals) will be required to localize most of the heritability underlying T2D and other traits characterized by these models.

TCF7L2 gene polymorphisms and type 2 diabetes: association with diabetic retinopathy and cardiovascular autonomic neuropathy

Type 2 diabetes (T2DM) is a complex disease resulting from the contribution of both environmental and genetic factors. Recently, the list of genes implicated in the susceptibility to T2DM has substantially grown, also as a consequence of the great development of the genome-wide association studies in the last decade. Common polymorphisms in TCF7L2 gene have shown to have a strong effect with respect to many other involved genes. The aims of our study were to confirm the role of TCF7L2 in the susceptibility to T2DM in the Italian population and to investigate whether TCF7L2 genotypes also contribute to the clinical phenotypes variability and to diabetic complications development. Three TCF7L2 polymorphisms (rs7903146, rs7901695 and rs12255372) have been analyzed by allelic discrimination assays in a cohort of 154 Italian patients with T2DM and 171 healthy controls. A case-control association study and a genotype-phenotype correlation study have been carried out. Consistent with previous studies, all three SNPs showed a strong association with susceptibility to T2DM, both at genotypic (P = 0.003, P = 0.004 and P = 0.012) and at allelic level (P = 0.0004, P = 0.0004 and P = 0.003). Moreover, we observed associations between TCF7L2 variants and the following diabetic complications: diabetic retinopathy, cardiovascular disease and coronary artery disease. We also found a strong correlation between the rs7903146 and the presence of cardiovascular autonomic neuropathy (P = 0.02 with a high OR = 8.28). In conclusion, our study, in addition to confirming the involvement of TCF7L2 gene in the T2DM susceptibility, has shown that TCF7L2 genetic variability also contributes to the development of diabetic complications such as retinopathy and cardiovascular autonomic neuropathy.

Association study of genetic variants of 17 diabetes-related genes/loci and cardiovascular risk and diabetic nephropathy in the Chinese She population

BACKGROUND

Genetic determinations are important in type 2 diabetes (T2DM) pathology. We investigated associations between genetic variants of 17 diabetes-related genes/loci, T2DM and diabetic complications in Chinese She subjects.

METHODS

A comprehensive gene-based association study was conducted using 17 single nucleotide polymorphisms in Chinese She subjects with normal glucose tolerance (n = 1119), impaired glucose regulation (n = 1767), and T2DM (n = 443). We applied major abnormal Minnesota Code findings to predict cardiovascular risk and estimated glomerular filtration rate to assess kidney function.

RESULTS

Nine variants in FTO rs8050136, WFS1 rs10010131, CDKN2A/B rs10811661, KCNJ11 rs5219, CDC123/CAMK1D rs12779790, JAZF1 rs864745, SLC30A8 rs13266634, CDKAL1 rs10946398, and HHEX/IDE rs5015480 were significantly associated with T2DM (P < 0.05). Single nucleotide polymorphisms in WFS1 rs10010131, CDKN2A/B rs10811661, CDC123/CAMK1D rs12779790, JAZF1 rs864745, FTO rs8050136, and HHEX/IDE rs5015480 were associated with T2DM and impaired glucose regulation. Risk alleles in WFS1 rs10010131, IGF2BP2 rs4402960, CDKAL1 rs10946398, FTO rs8050136, KCNQ1 rs2237897, and ADAMTS9 rs4607103 were significantly associated with decreased homeostatic model assessment (HOMA)-β (P < 0.05). After adjusting for age, gender and body mass index, genetic variants JAZF1 rs864745, FTO rs8050136, and HHEX/IDE rs5015480 were significantly related to reduced estimated glomerular filtration rate (P < 0.05). Genetic variants in WFS1 rs10010131, CDKN2A/B rs10811661, CDC123/CAMID rs12779790, JAZF1 rs864745, FTO rs80501360, CDKAL1 rs10946398, and HHEX/IDE rs5015480 correlated with abnormal major Minnesota Code findings (P < 0.05).

CONCLUSION

Variants in WFS1, CDKN2A/B, KCNJ11, CDC123/CAMK1D, JAZF1, SLC30A8, FTO, CDKAL1, and HHEX/IDE genes are significantly associated with T2DM in She Chinese subjects. JAZF1, FTO, CDKAL1, and HHEX/IDE are associated with diabetic nephropathy. WFS1, CDKN2A/B, CDC123/CAMK1D, JAZF1, FTO, CDKAL1, and HHEX/IDE are associated with cardiovascular risk.

Obesity and insulin resistance: an abridged molecular correlation

A relationship between obesity and type 2 diabetes is now generally well accepted. This relationship represents several major health hazards including morbid obesity and cardiovascular complications worldwide. Diabetes mellitus is a complex metabolic disorder characterized by impaired insulin release and insulin resistance. Lipids play an important physiological role in skeletal muscle, heart, liver and pancreas. Deregulation of fatty acid metabolism is the main culprit for developing insulin resistance and type 2 diabetes. A predominant predisposing factor to developing obesity, insulin resistance and type 2 diabetes is the permanent elevation of free fatty acids in plasma followed by impaired utilization of lipids by muscle. Diabetes-induced inflammation and oxidative stress have also vital role for development of insulin resistance in diabetic patients. The present review is intended to describe the correlation between lipids, obesity and insulin resistance based on current literature, in order to elucidate involved molecular mechanisms in depth.

Meta-analysis investigating associations between healthy diet and fasting glucose and insulin levels and modification by loci associated with glucose homeostasis in data from 15 cohorts

Whether loci that influence fasting glucose (FG) and fasting insulin (FI) levels, as identified by genome-wide association studies, modify associations of diet with FG or FI is unknown. We utilized data from 15 U.S. and European cohort studies comprising 51,289 persons without diabetes to test whether genotype and diet interact to influence FG or FI concentration. We constructed a diet score using study-specific quartile rankings for intakes of whole grains, fish, fruits, vegetables, and nuts/seeds (favorable) and red/processed meats, sweets, sugared beverages, and fried potatoes (unfavorable). We used linear regression within studies, followed by inverse-variance-weighted meta-analysis, to quantify 1) associations of diet score with FG and FI levels and 2) interactions of diet score with 16 FG-associated loci and 2 FI-associated loci. Diet score (per unit increase) was inversely associated with FG (β = -0.004 mmol/L, 95% confidence interval: -0.005, -0.003) and FI (β = -0.008 ln-pmol/L, 95% confidence interval: -0.009, -0.007) levels after adjustment for demographic factors, lifestyle, and body mass index. Genotype variation at the studied loci did not modify these associations. Healthier diets were associated with lower FG and FI concentrations regardless of genotype at previously replicated FG- and FI-associated loci. Studies focusing on genomic regions that do not yield highly statistically significant associations from main-effect genome-wide association studies may be more fruitful in identifying diet-gene interactions.

Effect of communicating genetic and phenotypic risk for type 2 diabetes in combination with lifestyle advice on objectively measured physical activity: protocol of a randomised controlled trial

BACKGROUND

Type 2 diabetes (T2D) is associated with increased risk of morbidity and premature mortality. Among those at high risk, incidence can be halved through healthy changes in behaviour. Information about genetic and phenotypic risk of T2D is now widely available. Whether such information motivates behaviour change is unknown. We aim to assess the effects of communicating genetic and phenotypic risk of T2D on risk-reducing health behaviours, anxiety, and other cognitive and emotional theory-based antecedents of behaviour change.

METHODS

In a parallel group, open randomised controlled trial, approximately 580 adults born between 1950 and 1975 will be recruited from the on-going population-based, observational Fenland Study (Cambridgeshire, UK). Eligible participants will have undergone clinical, anthropometric, and psychosocial measurements, been genotyped for 23 single-nucleotide polymorphisms associated with T2D, and worn a combined heart rate monitor and accelerometer (Actiheart(®)) continuously for six days and nights to assess physical activity. Participants are randomised to receive either standard lifestyle advice alone (control group), or in combination with a genetic or a phenotypic risk estimate for T2D (intervention groups). The primary outcome is objectively measured physical activity. Secondary outcomes include self-reported diet, self-reported weight, intention to be physically active and to engage in a healthy diet, anxiety, diabetes-related worry, self-rated health, and other cognitive and emotional outcomes. Follow-up occurs eight weeks post-intervention. Values at follow-up, adjusted for baseline, will be compared between randomised groups.

DISCUSSION

This study will provide much needed evidence on the effects of providing information about the genetic and phenotypic risk of T2D. Importantly, it will be among the first to examine the impact of genetic risk information using a randomised controlled trial design, a population-based sample, and an objectively measured behavioural outcome. Results of this trial, along with recent evidence syntheses of similar studies, should inform policy concerning the availability and use of genetic risk information.

Randomized controlled trial of the effectiveness of genetic counseling and a distance, computer-based, lifestyle intervention program for adult offspring of patients with type 2 diabetes: background, study protocol, and baseline patient characteristics

Relatives of type 2 diabetic patients are at a high risk of developing type 2 diabetes and should be regarded as target of intervention for diabetes prevention. However, it is usually hard to motivate them to implement preventive lifestyle changes, because of lack of opportunity to take advises from medical professionals, inadequate risk perception, and low priority for preventive behavior. Prevention strategy for them therefore should be highly acceptable and suited for them. The parallel, three-group trial is now being conducted to investigate the effects of genetic counseling and/or a computerized behavioral program on the prevention of type 2 diabetes in that population. The preventive strategies used in this study could provide a novel solution to the numbers of genetically high-risk individuals, if found to be effective. The objective of this paper is to describe the background, protocol, and baseline patient characteristics of the trial.

Gene-environment interactions in the development of type 2 diabetes: recent progress and continuing challenges

Type 2 diabetes (T2D) is thought to arise from the complex interplay of both genetic and environmental factors. Since the advent of genome-wide association studies (GWAS), we have seen considerable progress in our understanding of the role that genetics and gene-environment interactions play in the development of T2D. Recent work suggests that the adverse effect of several T2D loci may be abolished or at least attenuated by higher physical activity levels or healthy lifestyle, whereas low physical activity and dietary factors characterizing a Western dietary pattern may augment it. However, there still remain inconsistencies warranting further investigation. Lack of statistical power and measurement errors for the environmental factors continue to challenge our efforts for characterizing interactions. Although our recent focus on established T2D loci is reasonable, we may be overlooking many other potential loci not captured by recent T2D GWAS. Agnostic approaches to the discovery of gene and environment interactions may address this possibility, but their application to the field is currently limited and still faces conceptual challenges. Nonetheless, continued investment in gene-environment interaction studies through large collaborative efforts holds promise in furthering our understanding of the interplay between genetic and environmental factors.

Variants at the endocannabinoid receptor CB1 gene (CNR1) and insulin sensitivity, type 2 diabetes, and coronary heart disease

Inhibition of the endocannabinoid receptor CB1 improves insulin sensitivity, lowers glycemia, and slows atherosclerosis. We analyzed whether common variants in the gene encoding CB1, CNR1, are associated with insulin resistance, risk of type 2 diabetes (T2D) or coronary heart disease (CHD). We studied 2,411 participants of the Framingham Offspring Study (mean age 60 years, 52% women) for quantitative traits and CHD, and the Framingham SHARe database for T2D risk. We genotyped 19 single-nucleotide polymorphisms (SNPs) that tagged 85% (at r(2) = 0.8) of common (>5%) CNR1 SNPs. Fasting blood glucose and insulin at the 7th (1999-2001) exam were collected. We used age-, sex-, BMI-adjusted models to test additive associations of genotype with homeostasis model assessment of insulin resistance (HOMA(IR)) (linear mixed-effect models), T2D, or CHD. To account for multiple tests of SNPs, we generated empirical P values. The C allele at SNP rs806365 (frequency, 57.4%), ~4.1 kb 3' from CNR1, was associated with increased HOMA(IR) (n = 2,261, β = 0.05 per C, empirical P = 0.01), risk of T2D (674 cases, odds ratio = 1.19 per C, nominal P = 0.01) and CHD (237 cases, hazard ratio = 1.23 per C, nominal P = 0.04). The association of rs806365 with HOMA(IR) was replicated in a meta-analysis of two independent cohorts (National Health and Nutrition Examination Survey III genetic cohort (NHANES-III) plus Partners Case-Control Diabetes Study; 2,540 white individuals, β = 0.037, nominal P = 0.007), but not in the large Meta-Analyses of Glucose and Insulin-related traits Consortium (MAGIC) Consortium (n = 29,248, nominal P = 0.74). The association of rs806365 was not replicated either with T2D in Diabetes Genetics Replication and Meta-analysis (DIAGRAM) (n = 10,128, nominal P = 0.31), or with CHD in PROCARDIS (n = 13,614, nominal P = 0.37). Although supported by initial results, we found no reproducible statistical association of common variation at CNR1 with insulin resistance, T2D, or CHD.

Potassium and risk of Type 2 diabetes

The rising incidence and prevalence of Type 2 diabetes worldwide requires us to try to identify the determinants of this epidemic and to identify improved measures to prevent and treat this condition. While obesity is a major risk factor for diabetes, there are other risk factors that could potentially be corrected more easily. Potassium, both serum levels and to a lesser extent dietary intake levels, has been associated with incident diabetes. Lower levels of potassium have been found to be associated with a higher risk of diabetes in some studies. This article will review the literature available describing these associations and will help to identify where further research is needed.

Metabolic profiling in personalized medicine: bridging the gap between knowledge and clinical practice in Type 2 diabetes

Type 2 diabetes mellitus (DM2) is the most commonly diagnosed metabolic disease and its prevalence is expected to increase. Epidemiological studies clearly show excess mortality associated with DM2, as well as an increased risk of DM2-related complications. Advances in personalized medicine would greatly improve patient care in the field of diabetes and other metabolic diseases. Prediction of the disease in asymptomatic patients as well as its harsh complications in patients already diagnosed is becoming a necessity, with the considerable increase in the cost of the treatment. In the current article, we review the known clinical, molecular metabolic and genetic biomarkers that should be integrated in a future bioinformatic platform to be used at the point-of-care, and discuss the challenges we face in applying this vision of personalized medicine for diabetes into reality.

Genetics of type 2 diabetes: pathophysiologic and clinical relevance

BACKGROUND

Recent genome-wide association studies enlarged our knowledge about the genetic background of type 2 diabetes.

AIMS

This review provides an overview of the role of these novel genetic findings for the pathophysiology, prediction and treatment of type 2 diabetes.

RESULTS

The genetic susceptibility to type 2 diabetes appears to be determined by many common variants in multiple gene loci with low effect sizes. Although at least 36 diabetes-associated genes were identified, only about 10% of the heritability of type 2 diabetes can be explained. Most of the discovered gene variants have been linked to beta-cell dysfunction rather than insulin resistance, which might challenge established thinking of type 2 diabetes as a predominant disorder of insulin action. Genetic data can lead to statistically significant, but not to clinically relevant contributions to risk prediction for type 2 diabetes. Nevertheless, preliminary evidence suggests interactions between genotypes and response to lifestyle changes or drug treatment.

CONCLUSIONS

Future studies need to target the issue of hidden heritability and to detect the causal gene variants within the identified gene loci. Improved understanding of the genetic contribution to type 2 diabetes may then help addressing the questions whether genotyping is useful to predict individual diabetes risk, identifies individual responsiveness to preventive and therapeutic interventions or at least allows for breaking down type 2 diabetes into smaller, clinically meaningful subtypes.

Genetic risk profiling for prediction of type 2 diabetes

Type 2 diabetes (T2D) is a common disease caused by a complex interplay between many genetic and environmental factors. Candidate gene studies and recent collaborative genome-wide association efforts revealed at least 38 common single nucleotide polymorphisms (SNPs) associated with increased risk of T2D. Genetic testing of multiple SNPs is considered a potentially useful tool for early detection of individuals at high diabetes risk leading to improved targeting of preventive interventions.

Effect of sulphonylurea treatment on glycaemic control is related to TCF7L2 genotype in patients with type 2 diabetes

The aim of the present study was to analyse effects of sulphonylurea treatment on parameters of glycaemic control in relation to transcription factor 7-like 2 (TCF7L2) genotypes. In 87 patients with type 2 diabetes who failed to achieve glycaemic control on metformin monotherapy, effects of 6-month sulphonylurea in addition to metformin on reductions in haemoglobin A1c (HbA1c) and fasting plasma glucose (FPG) levels were evaluated. Reduction in HbA1c and FPG in response to 6-month sulphonylurea treatment was significantly higher in patients with CC genotype compared to those with the CT+TT genotype (1.16 ± 0.07 vs. 0.86 ± 0.07%, p = 0.003; 1.57 ± 0.12 vs. 1.14 ± 0.14 mmol/l, p = 0.031, respectively). In the multivariate analysis, baseline HbA1c and the TCF7L2 genotype were the only significant predictors of HbA1c reduction. In conclusion, the magnitude of HbA1c and FPG reductions after 6-month sulphonylurea treatment in addition to metformin is related to the TCF7L2 gene polymorphism.

Genetic risk reclassification for type 2 diabetes by age below or above 50 years using 40 type 2 diabetes risk single nucleotide polymorphisms

OBJECTIVE

To test if knowledge of type 2 diabetes genetic variants improves disease prediction.

RESEARCH DESIGN AND METHODS

We tested 40 single nucleotide polymorphisms (SNPs) associated with diabetes in 3,471 Framingham Offspring Study subjects followed over 34 years using pooled logistic regression models stratified by age (<50 years, diabetes cases = 144; or ≥50 years, diabetes cases = 302). Models included clinical risk factors and a 40-SNP weighted genetic risk score.

RESULTS

In people <50 years of age, the clinical risk factors model C-statistic was 0.908; the 40-SNP score increased it to 0.911 (P = 0.3; net reclassification improvement (NRI): 10.2%, P = 0.001). In people ≥50 years of age, the C-statistics without and with the score were 0.883 and 0.884 (P = 0.2; NRI: 0.4%). The risk per risk allele was higher in people <50 than ≥50 years of age (24 vs. 11%; P value for age interaction = 0.02).

CONCLUSIONS

Knowledge of common genetic variation appropriately reclassifies younger people for type 2 diabetes risk beyond clinical risk factors but not older people.

Interactions of dietary whole-grain intake with fasting glucose- and insulin-related genetic loci in individuals of European descent: a meta-analysis of 14 cohort studies

OBJECTIVE

Whole-grain foods are touted for multiple health benefits, including enhancing insulin sensitivity and reducing type 2 diabetes risk. Recent genome-wide association studies (GWAS) have identified several single nucleotide polymorphisms (SNPs) associated with fasting glucose and insulin concentrations in individuals free of diabetes. We tested the hypothesis that whole-grain food intake and genetic variation interact to influence concentrations of fasting glucose and insulin.

RESEARCH DESIGN AND METHODS

Via meta-analysis of data from 14 cohorts comprising ∼ 48,000 participants of European descent, we studied interactions of whole-grain intake with loci previously associated in GWAS with fasting glucose (16 loci) and/or insulin (2 loci) concentrations. For tests of interaction, we considered a P value <0.0028 (0.05 of 18 tests) as statistically significant.

RESULTS

Greater whole-grain food intake was associated with lower fasting glucose and insulin concentrations independent of demographics, other dietary and lifestyle factors, and BMI (β [95% CI] per 1-serving-greater whole-grain intake: -0.009 mmol/l glucose [-0.013 to -0.005], P < 0.0001 and -0.011 pmol/l [ln] insulin [-0.015 to -0.007], P = 0.0003). No interactions met our multiple testing-adjusted statistical significance threshold. The strongest SNP interaction with whole-grain intake was rs780094 (GCKR) for fasting insulin (P = 0.006), where greater whole-grain intake was associated with a smaller reduction in fasting insulin concentrations in those with the insulin-raising allele.

CONCLUSIONS

Our results support the favorable association of whole-grain intake with fasting glucose and insulin and suggest a potential interaction between variation in GCKR and whole-grain intake in influencing fasting insulin concentrations.

Invited commentary: Gene X lifestyle interactions and complex disease traits--inferring cause and effect from observational data, sine qua non

Observational epidemiology has made outstanding contributions to the discovery and elucidation of relations between lifestyle factors and common complex diseases such as type 2 diabetes. Recent major advances in the understanding of the human genetics of this disease have inspired studies that seek to determine whether the risk conveyed by bona fide risk loci might be modified by lifestyle factors such as diet composition and physical activity levels. A major challenge is to determine which of the reported findings are likely to represent causal interactions and which might be explained by other factors. The authors of this commentary use the Bradford-Hill criteria, a set of tried-and-tested guidelines for causal inference, to evaluate the findings of a recent study on interaction between variation at the cyclin-dependent kinase 5 regulatory subunit-associated protein 1-like 1 (CDKAL1) locus and total energy intake with respect to prevalent metabolic syndrome and hemoglobin A₁(c) levels in a cohort of 313 Japanese men. The current authors conclude that the study, while useful for hypothesis generation, does not provide overwhelming evidence of causal interactions. They overview ways in which future studies of gene × lifestyle interactions might overcome the limitations that motivated this conclusion.

Impact of a Booklet about Diabetes Genetic Susceptibility and Its Prevention on Attitudes towards Prevention and Perceived Behavioral Change in Patients with Type 2 Diabetes and Their Offspring

Background. Offspring of type 2 diabetic patients are at a high risk of type 2 diabetes. Information on diabetes genetic susceptibility and prevention should be supplied to the offspring. Methods. A six-page booklet on diabetes genetic susceptibility and prevention was distributed to 173 patients who ere ordered to hand it to their offspring. The patients answered a self-administered questionnaire on booklet delivery and attitudinal and behavioral changes toward diabetes and its prevention in themselves and their offspring. Results. Valid responses were obtained from 130 patients. Forty-nine patients had actually handed the booklet. Booklet induces more relief than anxiety. From the patient's view, favorable attitudinal and/or behavioral changes occurred in more than half of the offspring who were delivered the booklet. Conclusion. The booklet worked effectively on attitudes and behaviors toward diabetes and its prevention both in patients and their offspring. However, the effectiveness of patients as information deliverers was limited.

Revision of the ADA-classification of diabetes mellitus type 2 (DMT2): the importance of maturity onset diabetes (MOD), and senile diabetes (DS)

The changing social and economic conditions and the increase of the life span induced a progressive increase of the general prevalence of DMT2, particularly in the elderly population of the highly evoluted countries. Up to now 18 genetic loci have been identified, each of them consisting of several single nucleotide polymorphisms (SNPs). The evidence that the DMT2 is regulated by a high number of genes, demonstrate the pathogenetic complexity of this disease. The onset of diabetes mellitus (DM) in medium age is a consequence of the breakdown of the glycemic homeostasis in correlation with the genetic factors, such as the variants of the TCF7L2, obesity, etc., and the environmental factors, such as the life-style, the evolution of chronic-degenerative diseases, etc. In case of DM that onsets in old age we have to add the deterioration of the anti-aging defense mechanisms, characterized by the antagonistic action of the genes of longevity and aging. One can observe several clinical and therapeutic differences; therefore, the authors of this review propose the reinsertion of three forms into the DMT2 correlated with the age of onset and with the actual age of the subjects: the maturity onset diabetes (MOD), the maturity onset diabetes in elderly (MODE), and the senile diabetes (DS).

Sulfonylurea pharmacogenomics in Type 2 diabetes: the influence of drug target and diabetes risk polymorphisms

The sulfonylureas stimulate insulin release from pancreatic beta cells, and have been a cornerstone of Type 2 diabetes pharmacotherapy for over 50 years. Although sulfonylureas are effective antihyperglycemic agents, interindividual variability exists in drug response (i.e., pharmacodynamics), disposition (i.e., pharmacokinetics) and adverse effects. The field of pharmacogenomics has been applied to sulfonylurea clinical studies in order to elucidate the genetic underpinnings of this response variability. Historically, most studies have sought to determine the influence of polymorphisms in drug-metabolizing enzyme genes on sulfonylurea pharmacokinetics in humans. More recently, polymorphisms in sulfonylurea drug target genes and diabetes risk genes have been implicated as important determinants of sulfonylurea pharmacodynamics in patients with Type 2 diabetes. As such, the purpose of this review is to discuss sulfonylurea pharmacogenomics in the setting of Type 2 diabetes, specifically focusing on polymorphisms in drug target and diabetes risk genes, and their relationship with interindividual variability in sulfonylurea response and adverse effects.

Loss-of-function CYP2C9 variants: finding the correct clinical role for Type 2 diabetes pharmacogenetic testing

Continuing advances in genetic discovery have uncovered several dozen loci that are associated with Type 2 diabetes, including genetic variants that appear to modify responses to commonly prescribed diabetes medications. The use of an individual's genetic information to guide therapy choices raises the possibility of 'personalized medicine', wherein each patient's treatment plan is tailored based on genotype results. However, before such a model of care can be implemented, research is needed to more clearly quantify the association of genetic variation with treatment outcomes and adverse effects. In this article, we review a study examining the association of genetic variation in the cytochrome P450 2C9 enzyme with glycemic response to sulfonylureas in a large cohort of patients with Type 2 diabetes from the Genetics of Diabetes Audit and Research Tayside Study (Go-DARTS).

The contribution of enteroinsular hormones to the pathogenesis of type 2 diabetes mellitus

The gastrointestinal hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), termed incretins, are essential regulators of normal glucose homeostasis. Research indicates that the incretin effect is impaired in type 2 diabetes, and this seems to be a consequence rather than a cause of type 2 diabetes. This review describes the defects in the incretin system seen in diabetic patients and discusses the potential roles of GIP and GLP-1 in the pathogenesis of type 2 diabetes. In addition, new information on clinical applications that exploit the enteroinsular axis to control blood glucose is discussed.

Gene-gene interactions lead to higher risk for development of type 2 diabetes in an Ashkenazi Jewish population

Background

Evidence has accumulated that multiple genetic and environmental factors play important roles in determining susceptibility to type 2 diabetes (T2D). Although variants from candidate genes have become prime targets for genetic analysis, few studies have considered their interplay. Our goal was to evaluate interactions among SNPs within genes frequently identified as associated with T2D.

Methods/Principal Findings

Logistic regression was used to study interactions among 4 SNPs, one each from HNF4A[rs1884613], TCF7L2[rs12255372], WFS1[rs10010131], and KCNJ11[rs5219] in a case-control Ashkenazi sample of 974 diabetic subjects and 896 controls. Nonparametric multifactor dimensionality reduction (MDR) and generalized MDR (GMDR) were used to confirm findings from the logistic regression analysis. HNF4A and WFS1 SNPs were associated with T2D in logistic regression analyses [P<0.0001, P<0.0002, respectively]. Interaction between these SNPs were also strong using parametric or nonparametric methods: the unadjusted odds of being affected with T2D was 3 times greater in subjects with the HNF4A and WFS1 risk alleles than those without either (95% CI = [1.7–5.3]; P≤0.0001). Although the univariate association between the TCF7L2 SNP and T2D was relatively modest [P = 0.02], when paired with the HNF4A SNP, the OR for subjects with risk alleles in both SNPs was 2.4 [95% CI = 1.7–3.4; P≤0.0001]. The KCNJ11 variant reached significance only when paired with either the HNF4A or WFSI SNPs: unadjusted ORs were 2.0 [95% CI = 1.4–2.8; P≤0.0001] and 2.3 [95% CI = 1.2-4.4; P≤0.0001], respectively. MDR and GMDR results were consistent with the parametric findings.

Conclusions

These results provide evidence of strong independent associations between T2D and SNPs in HNF4A and WFS1 and their interaction in our Ashkenazi sample. We also observed an interaction in the nonparametric analysis between the HNF4A and KCNJ11 SNPs (P≤0.001), demonstrating that an independently non-significant variant may interact with another variant resulting in an increased disease risk.

The clinical application of genetic testing in type 2 diabetes: a patient and physician survey

AIMS/HYPOTHESIS

Advances in type 2 diabetes genetics have raised hopes that genetic testing will improve disease prediction, prevention and treatment. Little is known about current physician and patient views regarding type 2 diabetes genetic testing. We hypothesised that physician and patient views would differ regarding the impact of genetic testing on motivation and adherence.

METHODS

We surveyed a nationally representative sample of US primary care physicians and endocrinologists (n = 304), a random sample of non-diabetic primary care patients (n = 152) and patients enrolled in a diabetes pharmacogenetics study (n = 89).

RESULTS

Physicians and patients favoured genetic testing for diabetes risk prediction (79% of physicians vs 80% of non-diabetic patients would be somewhat/very likely to order/request testing, p = 0.7). More patients than physicians (71% vs 23%, p < 0.01) indicated that a 'high risk' result would be very likely to improve motivation to adopt preventive lifestyle changes. Patients favoured genetic testing to guide therapy (78% of patients vs 48% of physicians very likely to request/recommend testing, p < 0.01) and reported that genetic testing would make them 'much more motivated' to adhere to medications (72% vs 18% of physicians, p < 0.01). Many physicians (39%) would be somewhat/very likely to order genetic testing before published evidence of clinical efficacy.

CONCLUSIONS/INTERPRETATION

Despite the paucity of current data, physicians and patients reported high expectations that genetic testing would improve patient motivation to adopt key behaviours for the prevention or control of type 2 diabetes. This suggests the testable hypothesis that 'genetic' risk information might have greater value to motivate behaviour change compared with standard risk information.