Defining the genetic contribution of type 2 diabetes mellitus

Association of polymorphisms within P2RX4 with type 2 diabetes mellitus: a preliminary case-control study

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is a complex heterogenic metabolic with a wide range of etiology. Purinergic receptors have pivotal roles in different processes and are hypothesized to have roles in the pathogenesis of T2DM.

MATERIALS AND METHODS

Three hundred subjects affected by T2DM and 300 healthy subjects were genotyped by amplification refractory mutation system polymerase chain reaction (ARMS-PCR). SPSS V16.0 was recruited for statistical analysis.

RESULTS

The findings showed that the G allele of rs25644A > G increases the risk of T2DM in our population statistically (OR = 1.51, 95% CI = 1.14-1.99, p = 0.003). This allele in some genotype models, including the dominant model, caused an increase in the risk of T2DM. The interaction of genotypes between studied variants in the P2XR4 gene increased the risk of T2DM. Haplotype analysis showed that Ars1169727/Grs25644 haplotype caused an increase in the risk of T2DM.

CONCLUSIONS

The findings suggest that rs25644A > G plays a role in our population's increased risk of T2DM.

Association of Genetic polymorphisms of EDN1 gene and Endothelin-1 level in patients with type 2 diabetes mellitus in the Jordanian population

Endothelin-1 (ET-1) is one of the most potent vasoconstrictors, encoded by the endothelin-1 (EDN1) gene. It has been shown to play an important role in different diseases including Diabetes Mellitus (DM). Various single nucleotide polymorphisms (SNPs) in the EDN1 gene are related to microvascular complications of type 2 diabetes mellitus (T2DM) such as retinopathy, neuropathy and nephropathy. This study aims to determine the association between two selected EDN1 gene polymorphisms (rs2071942 G > A, rs5370 G > T) and T2DM in the Jordanian population, also to measure the level of ET-1 in T2DM. The samples were collected from the National Center of Diabetes, Endocrinology, and Genetics- Amman, Jordan, including 97 patients with T2DM and 80 healthy individuals. PCR-RFLP was used for SNPs genotyping. ET-1 level was determined using IQELISA kits. The univariate analysis for both SNPs didn't show statistically significant differences in the genotype or allele frequencies among T2DM cases as well as in controls. The same results were obtained regarding ET-1 concentration. The subgroup analysis by sex showed that the genotype and allelic frequencies of rs5370, rs2071942 G/A polymorphisms were not significantly different in males and females. Multivariate Analysis adjusted for various confounders didn't express statistical significance difference for occurrences of both SNPs. However, height and gender showed to be significant risk factors for occurrences of heterozygote alleles in both SNPs. On the other hand, the duration of diabetes has appeared to be related to the recessive allele in rs5370.

The prevalence of diabetes and associated risk factors among adult population in a Turkish population (Trabzon city)

OBJECTIVE

The objectives of this study were to determine the prevalence of diagnosed and undiagnosed diabetes mellitus (DM) and prediabetes, and to evaluate the associated risk factors in a sample of adult Turkish population.

METHODS

A total of 4000 eligible study subjects, aged 20 years or older, chosen by multistage sampling on a field were considered. Of those 3721 subjects (2139 women and 1582 men) participated in the study.

RESULTS

The prevalence of prediabetes and DM were found to be as 6.4% and 10.4% (3.6% being newly diagnosed by this study), respectively. In multivariate logistic regression analysis, advanced age (OR:26.7, p < 0.0005 in the group 70 years and over), marriage (OR:2.05, p = 0.047), housewives (OR:1.34, p = 0.003), family history of diabetes (OR:2.84, p < 0.0005), overweight (OR:1.61, p = 0.026), obesity (OR:2.25, p < 0.0005), hypertension (OR:1.42, p = 0.007) and dyslipidemia (OR:1.38, p = 0.028) were independent risk factors for being diabetic.

CONCLUSIONS

DM is an important health problem in the adult population of Trabzon city. Newly diagnosed diabetic patients who were unaware of their status are at high risk. To control DM and associated risk factors, effective public health education and taking urgent steps are needed.

The Link between Type 2 Diabetes Mellitus and the Polymorphisms of Glutathione-Metabolizing Genes Suggests a New Hypothesis Explaining Disease Initiation and Progression

The present study investigated whether type 2 diabetes (T2D) is associated with polymorphisms of genes encoding glutathione-metabolizing enzymes such as glutathione synthetase (GSS) and gamma-glutamyl transferase 7 (GGT7). A total of 3198 unrelated Russian subjects including 1572 T2D patients and 1626 healthy subjects were enrolled. Single nucleotide polymorphisms (SNPs) of the GSS and GGT7 genes were genotyped using the MassArray-4 system. We found that the GSS and GGT7 gene polymorphisms alone and in combinations are associated with T2D risk regardless of sex, age, and body mass index, as well as correlated with plasma glutathione, hydrogen peroxide, and fasting blood glucose levels. Polymorphisms of GSS (rs13041792) and GGT7 (rs6119534 and rs11546155) genes were associated with the tissue-specific expression of genes involved in unfolded protein response and the regulation of proteostasis. Transcriptome-wide association analysis has shown that the pancreatic expression of some of these genes such as EDEM2, MYH7B, MAP1LC3A, and CPNE1 is linked to the genetic risk of T2D. A comprehensive analysis of the data allowed proposing a new hypothesis for the etiology of type 2 diabetes that endogenous glutathione deficiency might be a key condition responsible for the impaired folding of proinsulin which triggered an unfolded protein response, ultimately leading to beta-cell apoptosis and disease development.

MS-275, a class 1 histone deacetylase inhibitor augments glucagon-like peptide-1 receptor agonism to improve glycemic control and reduce obesity in diet-induced obese mice

Given its glycemic efficacy and ability to reduce the body weight, glucagon-like peptide 1 receptor (GLP-1R) agonism has emerged as a preferred treatment for diabetes associated with obesity. We here report that a small-molecule Class 1 histone deacetylase (HDAC) inhibitor Entinostat (MS-275) enhances GLP-1R agonism to potentiate glucose-stimulated insulin secretion and decrease body weight in diet-induced obese (DIO) mice. MS-275 is not an agonist or allosteric activator of GLP-1R but enhances the sustained receptor-mediated signaling through the modulation of the expression of proteins involved in the signaling pathway. MS-275 and liraglutide combined therapy improved fasting glycemia upon short-term treatment and a chronic administration causes a reduction of obesity in DIO mice. Overall, our results emphasize the therapeutic potential of MS-275 as an adjunct to GLP-1R therapy in the treatment of diabetes and obesity.

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.

Heritability and Genetics of Type 2 Diabetes Mellitus in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

OBJECTIVES

Sub-Saharan Africa (SSA) is observing an accelerating prevalence rate of type 2 diabetes mellitus (T2DM) influenced by gene-environment interaction of modifiable and nonmodifiable factors. We conducted a systematic review and meta-analysis on the heritability and genetic risk of T2DM in SSA.

METHODS

We reviewed all published articles on T2DM in SSA between January 2000 and December 2019 and available in PubMed, Scopus, and Web of Science. Studies that reported on the genetics and/or heritability of T2DM or indicators of glycaemia were included. Data extracted included the study design, records of family history, pattern and characteristics of inheritance, genetic determinants, and effects estimates.

RESULTS

The pattern and characteristics of T2DM heritability in SSA are preference for maternal aggregation, higher among first degree compared to second-degree relatives; early age-onset (<50 years), and inherited abnormalities of beta-cell function/mass. The overall prevalence of T2DM was 28.2% for the population with a positive family history (PFH) and 11.2% for the population with negative family history (NFH). The pooled odds ratio of the impact of PFH on T2DM was 3.29 (95% CI: 2.40-4.52). Overall, 28 polymorphisms in 17 genes have been investigated in relation with T2DM in SSA. Almost all studies used the candidate gene approach with most (45.8%) of genetic studies published between 2011 and 2015. Polymorphisms in ABCC8, Haptoglobin, KCNJ11, ACDC, ENPP1, TNF-α, and TCF7L2 were found to be associated with T2DM, with overlapping effect on specific cardiometabolic traits. Genome-wide studies identified ancestry-specific signals (AGMO-rs73284431, VT11A-rs17746147, and ZRANB3) and TCF7L2-rs7903146 as the only transferable genetic risk variants to SSA population. TCF7L2-rs7903146 polymorphism was investigated in multiple studies with consistent effects and low-moderate statistical heterogeneity. Effect sizes were modestly strong [odds ratio = 6.17 (95% CI: 2.03-18.81), codominant model; 2.27 (95% CI: 1.50-3.44), additive model; 1.75 (95% CI: 1.18-2.59), recessive model]. Current evidence on the heritability and genetic markers of T2DM in SSA populations is limited and largely insufficient to reliably inform the genetic architecture of T2DM across SSA regions.

Deep learning for clustering of multivariate clinical patient trajectories with missing values

BACKGROUND

Precision medicine requires a stratification of patients by disease presentation that is sufficiently informative to allow for selecting treatments on a per-patient basis. For many diseases, such as neurological disorders, this stratification problem translates into a complex problem of clustering multivariate and relatively short time series because (i) these diseases are multifactorial and not well described by single clinical outcome variables and (ii) disease progression needs to be monitored over time. Additionally, clinical data often additionally are hindered by the presence of many missing values, further complicating any clustering attempts.

FINDINGS

The problem of clustering multivariate short time series with many missing values is generally not well addressed in the literature. In this work, we propose a deep learning-based method to address this issue, variational deep embedding with recurrence (VaDER). VaDER relies on a Gaussian mixture variational autoencoder framework, which is further extended to (i) model multivariate time series and (ii) directly deal with missing values. We validated VaDER by accurately recovering clusters from simulated and benchmark data with known ground truth clustering, while varying the degree of missingness. We then used VaDER to successfully stratify patients with Alzheimer disease and patients with Parkinson disease into subgroups characterized by clinically divergent disease progression profiles. Additional analyses demonstrated that these clinical differences reflected known underlying aspects of Alzheimer disease and Parkinson disease.

CONCLUSIONS

We believe our results show that VaDER can be of great value for future efforts in patient stratification, and multivariate time-series clustering in general.

Sugar in mind: Untangling a sweet and sour relationship beyond type 2 diabetes

It is widely recognised that type 2 diabetes (T2D) represents a major disease burden but it is only recently that its role in neurodegeneration has attracted more attention. This research has shown that T2D is associated with impaired cerebral health, cognitive decline and dementia. However, the impact on the brain of progressive metabolic changes associated with the pre-clinical development of the disease is less clear. The aim of this review is to comprehensively summarise how the emergence of risk factors and co-morbid conditions linked to the development of T2D impact cerebral health. Particular attention is directed at characterising how normal but elevated blood glucose levels in individuals without T2D contribute to neurodegenerative processes, and how the main risk factors for T2D including obesity, physical activity and diet modulate these effects. Where available, evidence from the animal and human literature is contrasted, and sex differences in risk and outcomes are highlighted.

The genetic side of type 2 diabetes - A review

AIM

Type 2 diabetes (T2DM) is a complex disease. Interactions between genetic susceptible variants and environmental cues results in the development of this heterogenous disease. Having an understanding of the genetics of T2DM may lead to a better perspective and management of the pathogenesis contributing to T2DM.

MATERIALS AND METHODS

Published primary and secondary sources were reviewed covering the keywords "genetics + type 2 diabetes" using PubMed and Google Scholar as the main databases. Full articles were considered when the title and the abstract was found to be sufficiently related to the review's aim.

RESULTS

Various genetic aspects of T2DM were summarised including a general understanding of the heritability and heterogeneity of T2DM. Furthermore, an explanation of the different genetic modalities that can be used to identify T2DM susceptible genes was provided.

CONCLUSION

In this day and era, researchers and healthcare professionals working in the field of metabolic disorders should have an understanding of T2DM genetics. The future lies in preventive and management action plans targeting the combination of genetics and environmental risk factors for a better health outcome.

Metabolic syndrome: an update on diagnostic criteria, pathogenesis, and genetic links

Metabolic syndrome (MetS), today a major global public health problem, is a cluster of clinical, metabolic, and biochemical abnormalities, such as central adiposity, hypertension, insulin resistance, and dyslipidemias. These MetS-related traits significantly increase the risk of type 2 diabetes mellitus, adverse cardiac events, stroke, and hepatic steatosis. The pathogenesis of MetS is multifactorial, with the interplay of environmental, nutritional, and genetic factors. Chronic low-grade inflammation together with visceral adipose tissue, adipocyte dysfunction, and insulin resistance plays a major role in the progression of the syndrome by impairing lipid and glucose homeostasis in insulin-sensitive tissues, such as the liver, muscle, and adipocytes. Adipose-derived inflammatory cytokines and non-esterified fatty acids establish the link between central obesity IR, inflammation, and atherogenesis. Various studies have reported an association between MetS and related traits with single-nucleotide polymorphisms of different susceptibility genes. Modulation of cytokine levels, pro-oxidants, and disturbed energy homeostasis, in relation to the genetic variations, is described in this review of the recent literature, which also provides updated data regarding the epidemiology, diagnostic criteria, and pathogenesis of MetS.

Long-term Impact of Cardiorespiratory Fitness on Type 2 Diabetes Incidence: A Cohort Study of Japanese Men

BACKGROUND

We sought to examine the association between cardiorespiratory fitness (CRF) and incidence of type 2 diabetes considering the follow-up period in a cohort of Japanese men with a maximum follow-up period of 23 years.

METHODS

This study enrolled 7,804 male workers free of diabetes in 1986. CRF was measured using a cycle ergometer, and maximal oxygen uptake was estimated. During 1986-2009, participants were followed for development of type 2 diabetes, which was diagnosed using fasting blood tests, self-administered questionnaires, or oral glucose tolerance tests after urinary tests from annual health checkups. Hazard ratios for the incidence of type 2 diabetes were estimated using Cox proportional hazards models.

RESULTS

During the follow-up period, 1,047 men developed type 2 diabetes. In analyses by follow-up periods (1986-1993, 1994-2001, and 2002-2009), there was an inverse dose-response relationship between CRF and the development of type 2 diabetes for all three follow-up periods (P for trend 0.019, <0.001, and 0.001, respectively), and the association between CRF at baseline and the incidence of type 2 diabetes did not weaken with longer follow-up period. Compared with the lowest CRF group, hazard ratios of developing type 2 diabetes were 0.69 (95% confidence interval [CI], 0.49-0.97) for the highest CRF group in 1986-1993, 0.57 (95% CI, 0.42-0.79) for the highest CRF in 1994-2001, and 0.47 (95% CI, 0.30-0.74) for the highest CRF in 2002-2009.

CONCLUSION

High CRF is associated with a lower risk of the incidence of type 2 diabetes over an extended period of >20 years among men.

Patient Preference for Once-Weekly Dosing in Type 2 Diabetes Mellitus in Japan

Background: Among several factors that impair adherence to available therapies in type 2 diabetes mellitus (T2DM) is the complexity of the dosing regimen. Moreover, the value of a once-weekly (QW) administration of oral medications for T2DM compared to once, twice, or thrice daily (QD, BID, TID) regimens is unclear. This study aims to identify subgroups and patient characteristics correlated with a preference for QW dosing compared to daily dosing using survey-based methods. Methods: This was a cross-sectional online survey study among patients with T2DM in Japan. Patients with T2DM were categorized into one of the three groups: (1) patients on treatment with oral hypoglycemic agent(s) only, (2) patients on combination treatment with oral hypoglycemic agent(s) and insulin, and (3) patients diagnosed with or suspected to have T2DM with no current or past experience with T2DM drug treatment (treatment naïve). Preliminary logistic regressions and classification and regression tree analysis (QW/QD dosing preferences as the dependent variable) were conducted to identify key predictors of dosing preference, followed by an evaluation of frequencies and trends in dosing preferences by the identified factors (subgroups). Results: Current treatment regimen, age, and work status were identified as the major demographic factors that were most predictive of QW preference. While, overall, 55.5% preferred QD and 33.3% preferred QW, the preference toward QW is higher in a specific cohort of patients that is treatment naïve (i.e., patients diagnosed with T2DM and/on diet/exercise therapy with no current or past experience with T2DM drug treatment) than who are on treatment, younger (age ≤64 years old), working full-time than part-time, and/or currently taking 0 or 1 drugs or more than 6 drugs (68.67% versus 30.12%). The most commonly cited reasons for QW preference were (1) "less burdensome because they didn't have to take it every day" (47.8%), (2) "less psychological burden" (14.6%), and (3) "forget to take it less often"(12.5%). Conclusion: Patients with T2DM vary in terms of preference for dosing regimens. Daily dosing was preferred over QW dosing in the overall population, however, preference for QW was higher in younger, full-time working, treatment naïve subjects, who are/or currently taking 0 or 1 drugs or more than 6 drugs.

High-fat-diet induced development of increased fasting glucose levels and impaired response to intraperitoneal glucose challenge in the collaborative cross mouse genetic reference population

Background

The prevalence of Type 2 Diabetes (T2D) mellitus in the past decades, has reached epidemic proportions. Several lines of evidence support the role of genetic variation in the pathogenesis of T2D and insulin resistance. Elucidating these factors could contribute to developing new medical treatments and tools to identify those most at risk. The aim of this study was to characterize the phenotypic response of the Collaborative Cross (CC) mouse genetic resource population to high-fat diet (HFD) induced T2D-like disease to evluate its suitability for this purpose.

Results

We studied 683 mice of 21 different lines of the CC population. Of these, 265 mice (149 males and 116 females) were challenged by HFD (42 % fat); and 384 mice (239 males and145 females) of 17 of the 21 lines were reared as control group on standard Chow diet (18 % fat). Briefly, 8 week old mice were maintained on HFD until 20 weeks of age, and subsequently assessed by intraperitoneal glucose tolerance test (IPGTT). Biweekly body weight (BW), body length (BL), waist circumstance (WC), and body mass index (BMI) were measured. On statistical analysis, trait measurements taken at 20 weeks of age showed significant sex by diet interaction across the different lines and traits. Consequently, males and females were analyzed, separately. Differences among lines were analyzed by ANOVA and shown to be significant (P <0.05), for BW, WC, BMI, fasting blood glucose, and IPGTT-AUC. We use these data to infer broad sense heritability adjusted for number of mice tested in each line; coefficient of genetic variation; genetic correlations between the same trait in the two sexes, and phenotypic correlations between different traits in the same sex.

Conclusions

These results are consistent with the hypothesis that host susceptibility to HFD-induced T2D is a complex trait and controlled by multiple genetic factors and sex, and that the CC population can be a powerful tool for genetic dissection of this trait.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0321-x) contains supplementary material, which is available to authorized users.

16S gut community of the Cameron County Hispanic Cohort

BACKGROUND

Obesity and type 2 diabetes (T2D) are major public health concerns worldwide, and their prevalence has only increased in recent years. Mexican Americans are disproportionately afflicted by obesity and T2D, and rates are even higher in the United States-Mexico border region. To determine the factors associated with the increased risk of T2D, obesity, and other diseases in this population, the Cameron County Hispanic Cohort was established in 2004.

RESULTS

In this study, we characterized the 16S gut community of a subset of 63 subjects from this unique cohort. We found that these communities, when compared to Human Microbiome Project subjects, exhibit community shifts often observed in obese and T2D individuals in published studies. We also examined microbial network relationships between operational taxonomic units (OTUs) in the Cameron County Hispanic Cohort (CCHC) and three additional datasets. We identified a group of seven genera that form a tightly interconnected network present in all four tested datasets, dominated by butyrate producers, which are often increased in obese individuals while being depleted in T2D patients.

CONCLUSIONS

Through a combination of increased disease prevalence and relatively high gut microbial homogeneity in the subset of CCHC members we examined, we believe that the CCHC may represent an ideal community to dissect mechanisms underlying the role of the gut microbiome in human health and disease. The lack of CCHC subject gut community segregation based on all tested metadata suggests that the community structure we observe in the CCHC likely occurs early in life, and endures. This persistent 'disease'-related gut microbial community in CCHC subjects may enhance existing genetic or lifestyle predispositions to the prevalent diseases of the CCHC, leading to increased attack rates of obesity, T2D, non-alcoholic fatty liver disease, and others.

Reference values for cardiorespiratory fitness and incidence of type 2 diabetes

BACKGROUND

In "Physical Activity Reference for Health Promotion 2013" the Japan Ministry of Health, Labour and Welfare publication gives reference values for cardiorespiratory fitness (CRF) required for good health. We examined the associations between the CRF reference values and incidence of type 2 diabetes.

METHODS

This prospective cohort study enrolled 4633 nondiabetic Japanese men aged 20 to 39 years at baseline. CRF was measured using the cycle ergometer test, and maximal oxygen uptake was estimated. On the basis of the CRF reference value, participants were classified into 2 groups: those with values less than the reference value (under-RV) and those with values equal to or greater than reference value (over-RV). Hazard ratios (HRs) and 95% CIs for incident type 2 diabetes were estimated using a Cox proportional hazards model.

RESULTS

A total of 266 participants developed type 2 diabetes during the 14 years of follow-up. As compared with the under-RV group, the over-RV group had a significantly lower multivariable-adjusted HR for type 2 diabetes (HR 0.67; 95% CI, 0.51-0.89). In receiver operating characteristic analysis, the optimal CRF cut-off value for predicting incident type 2 diabetes was 10.8 metabolic equivalents (sensitivity, 0.64; specificity, 0.64), which was close to the CRF reference value of 11.0 metabolic equivalents.

CONCLUSIONS

The reference CRF value appears to be reasonably valid for prevention of type 2 diabetes, especially among Japanese men younger than 40 years. Development of type 2 diabetes can be prevented by maintaining a CRF level above the reference value.

Quantitative assessment of the variation in IGF2BP2 gene and type 2 diabetes risk

Insulin-like growth factor 2 mRNA-binding protein 2 (IFG2BP2) belongs to an mRNA-binding protein family involved in the development and stimulation of insulin action, which has attracted considerable attention as a candidate gene for type 2 diabetes (T2D) since it was first identified through genome-wide association approach. The relationship between IFG2BP2 and T2D has been reported in various ethnic groups; however, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of 35 studies involving a total of 175,965 subjects for two wildly studied polymorphisms (rs4402960 and rs1470579) of the IFG2BP2 to evaluate the effect of IFG2BP2 on genetic susceptibility for T2D. An overall random-effects per-allele OR of 1.13 (95% CI: 1.12-1.15; P < 10(-5)) and 1.09 (95% CI: 1.07-1.12; P < 10(-5)) was found for the two variants, respectively. Significant results were also observed using dominant or recessive genetic model. No significant results between study heterogeneity were found in most of the comparison. In the subgroup analysis by ethnicity, sample size, diagnostic criterion and mean age and BMI of cases, significantly increased risks were found for these polymorphisms in almost all genetic models. This meta-analysis demonstrated that these two common polymorphisms is a risk factor for developing T2D, but these associations vary in different ethnic populations.

The association between KCNQ1 gene polymorphism and type 2 diabetes risk: a meta-analysis

BACKGROUND

KCNQ1 (potassium voltage-gated channel KQT-like sub-family, member 1) encodes a pore-forming subunit of a voltage-gated K(+) channel (KvLQT1) that plays a key role for the repolarization of the cardiac action potential as well as water and salt transport in epithelial tissues. Recently, genome-wide association studies have identified KCNQ1 as a type 2 diabetes (T2D) susceptibility gene in populations of Asian descent. After that, a number of studies reported that the rs2237892 and rs2237895 polymorphism in KCNQ1 has been implicated in T2D risk. However, studies on the association between these polymorphism and T2D remain conflicting. To investigate this inconsistency, we performed this meta-analysis.

METHODS

Databases including Pubmed, EMBASE, Web of Science and China National Knowledge Infrastructure (CNKI) were searched to find relevant studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. Potential sources of heterogeneity were also assessed by subgroup analysis and meta-regression.

RESULTS

A total of 25 articles involving 70,577 T2D cases and 99,068 controls were included. Overall, the summary odds ratio of C allele for T2D was 1.32 (95% CI 1.26-1.38; P<10-5) and 1.24 (95% CI: 1.20-1.29; P<10-5) for KCNQ1 rs2237892 and rs2237895 polymorphisms, respectively. Significant results were also observed using co-dominant, dominant and recessive genetic models. After stratifying by ethnicity, sample size, and diagnostic criteria, significant associations were also obtained.

CONCLUSIONS

This meta-analysis suggests that the rs2237892 and rs2237895 polymorphisms in KCNQ1 are associated with elevated type 2 diabetes susceptibility.

High fat diet induced insulin resistance and glucose intolerance are gender-specific in IGF-1R heterozygous mice

Interactions between genes and environment play a critical role in the pathogenesis of type 2 diabetes. Low birth weight, due to genetic and environmental variables affecting fetal growth, is associated with increased susceptibility to the development of type 2 diabetes and metabolic disorders in adulthood. Clinical studies have shown that polymorphisms in the Insulin-like growth factor 1 (IGF-1) gene or heterozygous mutations in IGF-1 and IGF-1 receptor (IGF-1R) genes, resulting in reduced IGF-1 action, are associated with low birth weight and post-natal growth. Mice lacking one of the IGF-1R alleles (Igf1r(+/-)) exhibit a 10% reduction in post-natal growth, and develop glucose intolerance (males) and insulin resistance (males and females) as they age. To investigate whether adverse environmental factors could accelerate the onset of the metabolic syndrome, we conducted a short duration intervention of high fat diet (HFD) feeding in male and female Igf1r(+/-) and wild-type (WT) control mice. The HFD resulted in insulin resistance, hyperglycemia, and impaired glucose tolerance in males of both genotypes whereas in females exacerbated diabetes was observed only in the Igf1r(+/-) genotype, thus suggesting a sexual dimorphism in the influence of obesity on the genetic predisposition to diabetes caused by reduced IGF-1 action.

A hospital-based observational study of type 2 diabetic subjects from Gujarat, India

The aim of this observational study was to describe the profile of subjects with type 2 diabetes mellitus from Gujarat, India. The study was performed with newly-diagnosed 622 type 2 diabetic subjects who attended the Department of Diabetology, All India Institute of Diabetes and Research and Yash Diabetes Specialties Centre (Swasthya), Ahmedabad, during August 2006-January 2009. The subjects completed an interviewer-administered questionnaire. The questionnaire included variables, such as sociodemographic factors, presenting symptoms, risk profile (hypertension, obesity, dyslipidaemia, and glycaemic status), family history of diabetes, physical activity, and behavioural profile. Blood pressure, body mass index (BMI), glycosylated haemoglobin levels, and fasting lipid profile were measured. Descriptive and bivariate analyses were carried out using the SPSS software (version 11.5). In total; 622 type 2 diabetes mellitus (T2DM) cases with mean age of 47.7 +/- 10.9 years were studied. Of the 622 subjects, 384 (62%) were male. The majority (68%) of the T2DM subjects were obese, and 67% had a positive family history of diabetes. Renal dysfunctions and vision impairment were, respectively, found in 10% (n=62) and 9% (n=57) of the 622 T2DM subjects. The mean HbAlc level was 9.02 +/- 1.67%, and good glycaemic control (HbAlc level <7%) was achieved only in 7.4% of the T2DM subjects. Results of chi-square analysis showed that higher BMI (> or =25 kg/m2) was significantly associated with hypertension among the T2DM subjects (p < 0.01). There were significant differences (p < 0.05) between male and female subjects with respect to mean age, BMI, waist- and hip-circumference, and mean low-density lipoprotein (LDL) level. The results revealed that many factors, such as obesity, family history of diabetes, dyslipidaemia, uncontrolled glycaemic status, sedentary lifestyles, and hypertension were prevalent among the T2DM subjects. The characterization of this risk profile will contribute to designing more effective and specific strategies for screening and controlling T2DM in Gujarat, India.

Saxagliptin: the evidence for its place in the treatment of type 2 diabetes mellitus

INTRODUCTION

The worldwide prevalence of type 2 diabetes mellitus (T2DM) is high, and the chronically poor metabolic control that can result from T2DM is associated with a high risk for microvascular and macrovascular complications. Because of the progressive pathophysiology of T2DM, oral antidiabetic agents often fail to provide sustained glycemic control, indicating the need for new therapies. Saxagliptin (Onglyza™; Bristol-Myers Squibb Company, Princeton, NJ, USA; AstraZeneca Pharmaceuticals LP, Wilmington, DE, USA) is an oral dipeptidyl peptidase-4 inhibitor, recently approved for the treatment of T2DM.

EVIDENCE REVIEW

Saxagliptin significantly improves glycemic control vs placebo, as demonstrated by decreasing glycated hemoglobin, fasting plasma glucose, and postprandial plasma glucose levels when used as monotherapy; in initial combination with metformin; and as add-on therapy with metformin, sulfonylurea (SU), or thiazolidinedione (TZD). Saxagliptin also significantly improves β-cell function, is weight neutral, has a low risk for hypoglycemia, and has been shown to have cardiovascular safety.

PLACE IN THERAPY

The clinical profile for saxagliptin indicates that it is useful as an adjunct to diet and exercise as first-line monotherapy and in combination with metformin; or as add-on treatment for patients who cannot achieve glycemic control with a combination of diet and lifestyle changes and metformin, SU, or TZD.

IGF2BP1, IGF2BP2 and IGF2BP3 genotype, haplotype and genetic model studies in metabolic syndrome traits and diabetes

OBJECTIVE

Genetic variation at the insulin-like binding protein 2 (IGF2BP2) gene has been associated with type 2 diabetes (T2D) by genome-wide association studies and by replication analyses. Our aim was to explore the underlying genetic model and mechanism of action, factors accounting for non-replications of the associations, and the effect of variation from pathway-related genes IGF2BP1 and IGF2BP3.

METHOD

We analysed here the association between T2D (and related traits) and rs4402960 and rs1470579 in IGF2BP2, and rs46522 and rs6949019 (marking IGF2BP1 and IGF2BP3 respectively) from the Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study (N approximately 2500 aged 65-96 years). We undertook a retrospective analysis of the deviations from the multiplicative model in previous studies and the present study.

RESULTS

We replicated an association between rs4402960 and T2D status, and reported significant associations with anthropometric traits, fasting insulin, HOMA-IR and HOMA-%B. These associations were also observed for rs1470579, but not for the SNPs marking IGF2BP1 and IGF2BP3.

CONCLUSIONS

The lower fasting insulin levels and the impaired beta-cell function associated with IGF2BP2 SNPs are independent of obesity phenotypes. The action of these SNPs on T2D may result from an effect on beta-cell function. This could lead to lower insulin levels, the association with anthropometric traits being secondary. We discuss possible mechanisms of action relating IGF2BP2 with T2D traits. The occurrence of null alleles, the inclusion of T2D patients in analyses of metabolic syndrome risk traits and the genetic model, are possible factors accounting for non-replications of IGF2BP2 associations with T2D.

Association of endothelial nitric oxide synthase promoter region (T-786C) gene polymorphism with acute coronary syndrome and coronary heart disease

BACKGROUND

Nitric oxide (NO) is an endothelium derived relaxing factor (EDRF) which has an important role for regulating the heart-vessel physiology. The objective of this study was to evaluate the effects of the eNOS T-786C polymorphism on lipid parameters and the development of acute coronary syndrome (ACS) and coronary heart disease (CHD) for the first time in a Turkish study group. We have analyzed the genotype frequencies of the T-786C polymorphism of the eNOS gene in 10 ACS patients (5 men, 5 women), 20 CHD patients (14 men, 6 women), and 31 controls (10 men, 21 women), who were angiographically proven to have normal coronaries.

RESULTS

The demographic, biochemical and left ventricule systolic dysfunction data of the ACS, CHD patients and controls were analyzed as a function of eNOS T-786C genotypes. The eNOS gene T-786C polymorphism frequencies for T/T, C/T and C/C genotypes were respectively 10%, 40%, 50% in subjects with ACS; 75%, 20%, 5% in subjects with CHD and 67.7%, 25.8%, 6.5% in the control group. Significant difference was observed in genotype frequencies between the study groups for T-786C polymorphism (p = 0.001). The CC genotype frequency was found to be the most prevalent in ACS group in comparison to CHD and control groups (p = 0.001). TT was the most frequently observed genotype in both CHD patients and controls (p = 0.001). Left ventricule systolic dysfunction frequency was found to be highest in C/T genotype carriers (66.7%) in patients (ACS+CHD). None of the patients with LVSD were carrying the normal genotype (T/T). The eNOS T-786C polymorphism was not found to be effective over any analyzed lipid variable in patients (ACS+CHD). The HDL-cholesterol levels were found to be lower in CHD group were compared to controls (p < 0.01), whereas glucose and leucocyte levels of the ACS and CHD groups were both higher than controls (p < 0.001).

CONCLUSION

The significantly high frequency of eNOS -786C/C genotype in ACS patients than in those of controls, indicate the genotype association with ACS. The finding of significantly high frequency of T/T genotype in the CHD group, may support the relationship of CC genotype with ACS without CHD. The high frequency of the mutant (C/C) and heterozygous (C/T) genotypes found may be linked to left ventricule remodeling after MI.

Anthropometry, carbohydrate and lipid metabolism in the East Flanders Prospective Twin Survey: heritabilities

AIMS/HYPOTHESIS

We determined the genetic contribution of 18 anthropometric and metabolic risk factors of type 2 diabetes using a young healthy twin population.

METHODS

Traits were measured in 240 monozygotic (MZ) and 138 dizygotic (DZ) twin pairs aged 18 to 34 years. Twins were recruited from the Belgian population-based East Flanders Prospective Twin Survey, which is characterised by its accurate zygosity determination and extensive collection of perinatal and placental data, including information on chorionicity. Heritability was estimated using structural equation modelling implemented in the Mx software package.

RESULTS

Intra-pair correlations of the anthropometric and metabolic characteristics did not differ between MZ monochorionic and MZ dichorionic pairs; consequently heritabilities were estimated using the classical twin approach. For body mass, BMI and fat mass, quantitative sex differences were observed; genetic variance explained 84, 85 and 81% of the total variation in men and 74, 75 and 70% in women, respectively. Heritability estimates of the waist-to-hip ratio, sum of four skinfold thicknesses and lean body mass were 70, 74 and 81%, respectively. The heritability estimates of fasting glucose, fasting insulin, homeostasis model assessment of insulin resistance and beta cell function, as well as insulin-like growth factor binding protein-1 levels were 67, 49, 48, 62 and 47%, in that order. Finally, for total cholesterol, LDL-cholesterol, HDL-cholesterol, total cholesterol:HDL-cholesterol ratio, triacylglycerol, NEFA and leptin levels, genetic factors explained 75, 78, 76, 79, 58, 37 and 53% of the total variation, respectively.

CONCLUSIONS/INTERPRETATION

Genetic factors explain the greater part of the variation in traits related to obesity, glucose intolerance/insulin resistance and dyslipidaemia.

Blood gene expression profiling in liver transplant recipients with hepatitis C virus and posttransplantation diabetes mellitus

BACKGROUND

Hepatitis C virus (HCV) is a risk factor for developing posttransplantation diabetes mellitus (PTDM) after liver transplantation; little is known about the biological mechanisms involved with this risk. This study investigated gene expression differences to provide insight into potential mechanisms.

PATIENTS AND METHODS

Gene expression profiles of blood samples obtained from 6 HCV+ liver transplant recipients were determined using Affymetrix U133 Plus 2.0 microarrays. Differential gene expression was assessed between HCV+ recipients with PTDM (n = 3) and without PTDM (n = 3) using the GeneSpring 7.3 software package. The Welch t test was used to identify significant differences (P < .05) between groups. Gene expression profiles for 6 HCV- liver transplant recipients (with PTDM = 3, without PTDM = 3) were used as a blind test set to evaluate a subset of genes to predict PTDM.

RESULTS

Expression levels of 347 genes were significantly different between recipients with PTDM and those without PTDM. Seventy-four genes were up-regulated and 270 were down-regulated in PTDM. Genes were categorized into functional classes: apoptosis (n = 69 genes); immune function (n = 110); diabetes (n = 17); hepatitis C (n = 12); liver transplant (n = 69). The expression profile of a subset of genes was evaluated for predicting PTDM in 6 HCV- transplant recipients. We accurately predicted the presence or absence of PTDM in 5/6 recipients.

CONCLUSIONS

PTDM in HCV+ liver transplant recipients was associated with down-regulated expression of a large number of genes. A subset of these genes was useful to predict PTDM in HCV- recipients. Most genes were associated with apoptosis and immune function. HCV may act as a primer by affecting a group of genes involved in developing diabetes.

The genetic landscape of type 2 diabetes in mice

Inbred mouse strains provide genetic diversity comparable to that of the human population. Like humans, mice have a wide range of diabetes-related phenotypes. The inbred mouse strains differ in the response of their critical physiological functions, such as insulin sensitivity, insulin secretion, beta-cell proliferation and survival, and fuel partitioning, to diet and obesity. Most of the critical genes underlying these differences have not been identified, although many loci have been mapped. The dramatic improvements in genomic and bioinformatics resources are accelerating the pace of gene discovery. This review describes how mouse genetics can be used to discover diabetes-related genes, summarizes how the mouse strains differ in their diabetes-related phenotypes, and describes several examples of how loci identified in the mouse may directly relate to human diabetes.

The impact of family history of diabetes and lifestyle factors on abnormal glucose regulation in middle-aged Swedish men and women

AIMS/HYPOTHESIS

We investigated associations between abnormal glucose regulation and family history of diabetes, separately and in combination with lifestyle risk factors.

SUBJECTS AND METHODS

This cross-sectional study comprised 3,128 men and 4,821 women, aged 35-56 years, half with a family history of diabetes. Oral glucose tolerance testing identified subjects with previously undiagnosed prediabetes (IFG, IGT) and type 2 diabetes. Information on lifestyle factors was obtained by questionnaire. Biological interaction was measured with the synergy index.

RESULTS

A family history of diabetes conferred a higher odds ratio (OR) for type 2 diabetes in men (OR=3.1, 95% CI 1.7-5.6) than in women (OR=1.7, 95% CI 1.0-3.0), and the synergy index was 2.8 (95% CI 0.9-9.0), suggesting interaction between a family history of diabetes and sex. For prediabetes and diabetes combined, the synergy index was 1.7 (1.0-2.8). Exposure to only one lifestyle risk factor (obesity, physical inactivity, smoking or low sense of coherence [a psychosocial index]) increased the risk to a similar extent in men and women. Combined exposure to a family history of diabetes and lifestyle-related risk factors had a greater effect on type 2 diabetes than any of these factors alone, especially in men. However, analysis of interaction between a family history of diabetes and the lifestyle factors did not indicate any interaction for diabetes, but did indicate interaction for a family history of diabetes and obesity in women with prediabetes.

CONCLUSIONS/INTERPRETATION

Our data suggest a more pronounced effect of a family history of diabetes on the risk of type 2 diabetes in men than in women. While both a family history of diabetes and lifestyle risk factors had effects on type 2 diabetes, irrespective of sex, these effects did not appear to interact.

Computational disease gene identification: a concert of methods prioritizes type 2 diabetes and obesity candidate genes

Genome-wide experimental methods to identify disease genes, such as linkage analysis and association studies, generate increasingly large candidate gene sets for which comprehensive empirical analysis is impractical. Computational methods employ data from a variety of sources to identify the most likely candidate disease genes from these gene sets. Here, we review seven independent computational disease gene prioritization methods, and then apply them in concert to the analysis of 9556 positional candidate genes for type 2 diabetes (T2D) and the related trait obesity. We generate and analyse a list of nine primary candidate genes for T2D genes and five for obesity. Two genes, LPL and BCKDHA, are common to these two sets. We also present a set of secondary candidates for T2D (94 genes) and for obesity (116 genes) with 58 genes in common to both diseases.

Detection of single nucleotide polymorphisms by minisequencing on a polypyrrole DNA chip designed for medical diagnosis

With the increasing availability of genetic information and its relationship to human diseases, there is a growing need in the medical diagnostic field for technologies that can proceed to the parallel genotyping of multiple markers. In this paper, we report the development of a new flexible microarray-based method that aims to be inexpensive, accurate, and adapted to routine analysis. The construction of the MICAM (MICrosystem for Analysis in Medicine) DNA chip is based on the controlled electro-synthesis of a conducting polymer film bearing oligonucleotide probes on gold electrodes. First, accessible 3'OH-ends of grafted probes are directly used to conduct single template-dependent nucleotide extension reactions with fluorescence-labeled chain terminators. Then, the fluorescence of incorporated dideoxynucleotides on controls and probes of interest are recorded to assess base calling. Here, we present the development of the methodology to assign the genotype of TP53 (tumor protein p53) codon 72 polymorphism and its application to analysis of genomic DNA from cell lines and from human colorectal samples. The genotyping results obtained by mini-sequencing on the polypyrrole DNA chip were 100% concordant with data obtained by polymerase chain reaction-restriction fragment length polymorphism and direct sequencing. Moreover, the developed probe array assay has been successfully applied to the detection of TP53 loss of heterozygosity.

Functional polymorphisms in the vascular endothelial growth factor gene are associated with development of end-stage renal disease in males

This study elucidates the genetic role of vascular endothelial growth factor (VEGF) as a predisposing factor for progression of chronic kidney disease. Single-nucleotide polymorphisms were genotyped and haplotype structures were determined in the 3' untranslated region (UTR) of VEGF gene, and the distribution of each haplotype in male patients with ESRD (n=101) and healthy male control subjects (n=189) was examined. The 936C/T and 1451C/T polymorphisms in the 3' UTR were in nearly absolute linkage disequilibrium, and haplotype analysis demonstrated that they were the primary responsible single-nucleotide polymorphisms. The distribution of the 936CC-1451CC genotype was significantly more frequent among patients with ESRD than among the age-matched healthy control subjects. In addition to case-control association study, the 936CC-1451CC genotype was also associated with significantly higher plasma VEGF levels in healthy individuals, but a significant association was found only in males, not in females. We also examined the effect of the 936C-1451C haplotype on mRNA stability. Consistent with the results of plasma VEGF levels, mRNA carrying 936C-1451C haplotype showed higher stability. The 936CC-1451CC genotype in the 3' UTR showed not only susceptibility for ESRD but also higher plasma VEGF levels and mRNA stability, indicating the contribution of VEGF to chronic kidney disease progression, especially in males.

Genome Wide Expression Analysis of White Blood Cells and Liver of Pre-diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) Rats Using a cDNA Microarray

In a prior study, we reported on a significant decrease in calpain10 gene expression in white blood cells (WBC) as well as the major insulin-target tissues including liver and adipose tissue, before the onset of diabetes in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. In this study, we extended our hypothesis that some type 2 diabetes mellitus (NIDDM) susceptible genes are up/down-regulated before the onset in WBC of OLETF rats, reflecting their up/down-regulation in major insulin-target tissues, such as the liver. We tested this hypothesis using rat cDNA microarrays. The findings show that 1080 genes are up/down-regulated by more than 2-fold compared to the controls, Long-Evans Tokushima Otsuka rats, before the onset in WBC and liver under fasted or insulin administered condition. Fifty-seven of the 1080 genes were up/down-regulated in both WBC and the liver. More than half have been reported to NIDDM susceptible genes and the remainder have not been reported to be related to NIDDM. These results indicate that there some NIDDM related genes are up/down-regulated in WBC before the onset of diabetes.

Target gene discovery in extended families with type 2 diabetes mellitus

Type 2 diabetes mellitus is a polygenic, multifactorial disease. Multiple attempts have been made to identify genes that predispose to development of diabetes using both the candidate gene approach and whole genome scanning. However, in spite of substantial financial commitment, very few targets have been identified. Identification of predisposing genes is complicated by several factors. Diabetic patients demonstrate a variety of gene defect combinations. Identification of predisposing genomic regions is thus impeded if data are collected from a heterogeneous population. In addition, the diseased phenotype may only manifest when the net effect of the predisposing factors exceeds a certain "threshold". The effects of predisposing genetic and environmental factors thus appear to be additive, and this also complicates target gene discovery. Using the traditional approach, significant associations between genomic regions and disease are rarely observed unless data are acquired from hundreds of individuals. In contrast, results from whole genome scans performed in homogeneous and consanguineous populations with a high incidence of type 2 diabetes have demonstrated that highly significant associations can be obtained using data from a small number of subjects belonging to the same extended family. Such populations offer the promise of substantial progress in type 2 diabetes genomics research.

Human blood genomics: distinct profiles for gender, age and neurofibromatosis type 1

Application of gene expression profiling to human diseases will be limited by availability of tissue samples. It was postulated that germline genetic defects affect blood cells to produce unique expression patterns. This hypothesis was addressed by using a test neurological disease-neurofibromatosis type 1 (NF1), an autosomal dominant genetic disease caused by mutations of the NF1 gene at chromosome 17q11.2. Oligonucleotide arrays were used to survey the blood gene expression pattern of 12 NF1 patients compared to 96 controls. A group of genes related to tissue remodeling, bone development and tumor suppression were down-regulated in NF1 blood samples. In addition, there were blood genomic patterns for gender and age: Y chromosome genes showing higher expression in males, indicating a gene-dosage effect; and genes related to lymphocyte functions showing higher expression in children. The results suggest that genetic mutations can be manifested at the transcriptional level in peripheral blood cells and blood gene expression profiling may be useful for studying phenotypic differences of human genetic diseases and possibly providing diagnostic and prognostic markers.

Schizophrenia, the metabolic syndrome and diabetes

The prevalence of diabetes is increased in patients with schizophrenia. Although many reasons, including hereditary and lifestyle factors, contribute to this association, recently there has been heightened interest in the subject because of the link between the use of the newer atypical anti-psychotic drugs and the development of diabetes. These drugs cause significant weight gain and this may be one of the mechanisms by which they increase incident diabetes. The increased prevalence of diabetes among people with schizophrenia has implications for the delivery of care by psychiatrists, diabetologists and primary care.

Anthropometric parameters and type 2 diabetes: a case-control study in a Guadeloupean population

OBJECTIVE

The aim of this study was to quantify the association between three anthropometric parameters and type 2 diabetes in an adult population in Guadeloupe and to evaluate the effect of age on these associations.

DESIGNS AND METHODS

We conducted a case-control study in a population recruited in an Health Center of Guadeloupe in Year 2000. A total of 309 subjects with documented type 2 diabetes were matched on sex and age (+/- 2 Years) with controls free of any glycemic abnormality. Student t-test was used and conditional logistic regressions were performed separately for men and women to quantify the association between type 2 diabetes and the explanatory variables, body mass index (BMI), waist to hip ratio (WHR) and waist circumference (WC).

RESULTS

Mean (SD) WC was 89.0 cm (0.9) in non diabetics men and 97.3 cm (1.1) in diabetics ones, p<10-4. In women, it was 87.7 (0.8) cm for non diabetics and 96.3 cm (0.9) for diabetics. This difference was persistent for any tertile of age in each sex. It was discordant for BMI and WHR at higher tertile for men and women. In the multivariate analysis, Odds ratio[CI95%] for WC was 9.67 [2.32-40.20] in men and 2.97 [1.70-5.19] in women. It was 2.94 [0.99-8.74] in men and 6.15 [3.11-12.17] in women for WHR. Results for BMI were non significant in both sex.

CONCLUSION

Differences between WC and WHR over age groups and sex in predicting type 2 diabetes should be taken into account when using these parameters routinely in medical practice.

Genome-wide screen in obese pedigrees with type 2 diabetes mellitus from a defined Dutch population

A genome scan was performed in obese type 2 diabetes mellitus pedigrees to identify susceptibility loci involved in obesity-driven type 2 diabetes mellitus. We studied the 20% most obese diabetes pedigrees from a confined Dutch population from around the town of Breda. Previously we, and others, have already shown that a susceptibility locus influencing obesity in diabetes may reside on chromosome 18p11. We now report evidence to also suggest linkage for type 2 diabetes in these obese pedigrees on chromosome regions 11p (genome-wide P-value </= 0.061) and 12q (genome-wide P-value </= 0.029), thereby confirming previous findings from corresponding regions. The linkage found in the Breda Cohort of type 2 diabetes patients is influenced by obesity. This supports the notion that a genetic predisposition to obesity is probably intertwined with a genetic predisposition to type 2 diabetes. Further efforts should address the question of how, on a genetic level, these two factors interact.

The functions of insulin signaling: size isn't everything, even in Drosophila

Mammalian insulin and insulin-like growth factors (IGFs) signal through several receptors with different ligand specificities to regulate metabolism and growth. This regulation is defective in diabetes and in a wide variety of human tumors. Recent analysis in Drosophila melanogaster has revealed that insulin-like molecules (known as DILPs in flies) also control growth and metabolism, but probably do so by signaling through a single insulin receptor (InR). The intracellular signaling molecules regulated by this receptor are highly evolutionarily conserved. Work in flies has helped to dissect the network of InR-regulated intracellular signaling pathways and identify some of the critical players in these pathways and in interacting signaling cascades. Surprisingly, these studies have shown that DILPs control tissue and body growth primarily by regulating cell growth and cell size. Changes in cell growth produced by these molecules may subsequently modulate the rate of cell proliferation in a cell type-specific fashion. At least part of this growth effect is mediated by two small groups of neurons in the Drosophila brain, which secrete DILPs into the circulatory system at levels that are modulated by nutrition. This signaling center is also involved in DILP-dependent control of the fly's rate of development, fertility, and life span. These surprisingly diverse functions of InR signaling, which appear to be conserved in all higher animals, reflect a central role for this pathway in coordinating development, physiology, and properly proportioned growth of the organism in response to its nutritional state. Studies in flies are providing important new insights into the biology of this system, and the identification of novel components in the InR-regulated signaling cascade is already beginning to inform the development of new therapeutic strategies for insulin-linked diseases in the clinic.

Early disturbances in insulin secretion in the development of type 2 diabetes mellitus

After a short description of normal glucose homeostasis, recent findings in relation to insulin release in three groups with a high risk of future development of type 2 diabetes are described. Hyperglycemic clamps in subjects with impaired glucose tolerance (IGT) clearly indicate that pancreatic beta cell function is decreased, in addition to the decreased insulin sensitivity. In women with former gestational diabetes mellitus (GDM), insulin release is also lower than in controls. In Caucasian first-degree relatives (FDRs) with normal glucose tolerance, various studies have shown that beta cell function is lower than in controls, while on the average insulin sensitivity is normal. This implies that beta cell function is disturbed earlier in subjects at risk of developing diabetes than is often appreciated. In the near future, the genetic studies currently underway will presumably unravel the pathogenesis of disturbances both in insulin secretion and in insulin action, in type 2 diabetes mellitus.

Genetically defined pancreatic beta cell failure

The major subtypes of diabetes mellitus (DM) are complex diseases in which the interactions between genetic susceptibility and metabolic, immunologic and environmental factors ultimately lead to the clinical phenotype. The unraveling of these factors and the study of their contribution to the pathogenesis of DM is a process of unimaginable complexity. As a result, despite the individual differences in DM phenotype, most patients with DM receive treatment according to generalized treatment protocols, only discriminating between Type 1 and Type 2 DM and not related to the individual genetic background of the patients. Nevertheless, in recent years, much progress has been made in the search for genetic factors in DM. As an example, the recognition of monogenetic defects in beta cell function has lead to the definition of novel DM subtypes, which have important implications for the individual therapeutic approach for these patients and the understanding of the etiology of DM.