Genomics of type 2 diabetes mellitus: implications for the clinician

Differentiation-Promoting Effects of Okeaniamides A and B from an Okeania sp. Marine Cyanobacterium on Preadipocytes

The linear lipopeptides okeaniamide A (1) and okeaniamide B (2) were isolated from an Okeania sp. marine cyanobacterium collected in Okinawa. The structures of these compounds were established by spectroscopic analyses, and the absolute configurations were elucidated based on a combination of chemical degradations, Marfey's analysis, and derivatization reactions. Okeaniamide A (1) and okeaniamide B (2) dose-dependently promoted the differentiation of mouse 3T3-L1 preadipocytes in the presence of insulin.

Differential contribution of alpha and beta cell dysfunction to impaired fasting glucose and impaired glucose tolerance

AIMS/HYPOTHESIS

People with isolated impaired fasting glucose (IFG) have normal beta cell function. We hypothesised that an increased glucose threshold for beta cell secretion explains IFG.

METHODS

We used graded glucose infusion to examine the relationship of insulin secretion rate (ISR) and glucagon secretion rate (GSR) with rising glucose. We studied 39 non-diabetic individuals (53 ± 2 years, BMI 30 ± 1 kg/m2), categorised by fasting glucose and glucose tolerance status. After an overnight fast, a variable insulin infusion was used to maintain glucose at ~4.44 mmol/l (07:00 to 08:30 hours). At 09:00 hours, graded glucose infusion commenced at 1 mg kg-1 min-1 and doubled every 60 min until 13:00 hours. GSR and ISR were calculated by nonparametric deconvolution from concentrations of glucagon and C-peptide, respectively.

RESULTS

The relationship of ISR with glucose was linear and the threshold for insulin secretion in isolated IFG did not differ from that in people with normal fasting glucose and normal glucose tolerance. GSR exhibited a single-exponential relationship with glucose that could be characterised by G50, the change in glucose necessary to suppress GSR by 50%. G50 was increased in IFG compared with normal fasting glucose regardless of the presence of impaired or normal glucose tolerance.

CONCLUSIONS/INTERPRETATION

These data show that, in non-diabetic humans, alpha cell dysfunction contributes to the pathogenesis of IFG independently of defects in insulin secretion. We also describe a new index that quantifies the suppression of glucagon secretion by glucose.

Clinically Relevant Circulating Protein Biomarkers for Type 1 Diabetes: Evidence From a Two-Sample Mendelian Randomization Study

OBJECTIVE

To identify circulating proteins influencing type 1 diabetes susceptibility using Mendelian randomization (MR).

RESEARCH DESIGN AND METHODS

We used a large-scale two-sample MR study, using cis genetic determinants (protein quantitative trait loci [pQTL]) of up to 1,611 circulating proteins from five large genome-wide association studies, to screen for causal associations of these proteins with type 1 diabetes risk in 9,684 case subjects with type 1 diabetes and 15,743 control subjects. Further, pleiotropy-robust MR methods were used in sensitivity analyses using both cis and trans-pQTL.

RESULTS

We found that a genetically predicted SD increase in signal regulatory protein gamma (SIRPG) level was associated with increased risk of type 1 diabetes risk (MR odds ratio [OR] 1.66 [95% 1.36-2.03]; P = 7.1 × 10-7). The risk of type 1 diabetes increased almost twofold per genetically predicted standard deviation (SD) increase in interleukin-27 Epstein-Barr virus-induced 3 (IL27-EBI3) protein levels (MR OR 1.97 [95% CI 1.48-2.62]; P = 3.7 × 10-6). However, an SD increase in chymotrypsinogen B1 (CTRB1) was associated with decreased risk of type 1 diabetes (MR OR 0.84 [95% CI 0.77-0.90]; P = 6.1 × 10-6). Sensitivity analyses using MR methods testing for pleiotropy while including trans-pQTL showed similar results. While the MR-Egger suggested no pleotropic effect (P value MR-Egger intercept = 0.31), there was evidence of pleiotropy in MR-PRESSO (P value global test = 0.006).

CONCLUSIONS

We identified three novel circulating protein biomarkers associated with type 1 diabetes risk using an MR approach. These biomarkers are promising targets for development of drugs and/or of screening tools for early prediction of type 1 diabetes.

A Bittersweet Response to Infection in Diabetes; Targeting Neutrophils to Modify Inflammation and Improve Host Immunity

Chronic and recurrent infections occur commonly in both type 1 and type 2 diabetes (T1D, T2D) and increase patient morbidity and mortality. Neutrophils are professional phagocytes of the innate immune system that are critical in pathogen handling. Neutrophil responses to infection are dysregulated in diabetes, predominantly mediated by persistent hyperglycaemia; the chief biochemical abnormality in T1D and T2D. Therapeutically enhancing host immunity in diabetes to improve infection resolution is an expanding area of research. Individuals with diabetes are also at an increased risk of severe coronavirus disease 2019 (COVID-19), highlighting the need for re-invigorated and urgent focus on this field. The aim of this review is to explore the breadth of previous literature investigating neutrophil function in both T1D and T2D, in order to understand the complex neutrophil phenotype present in this disease and also to focus on the development of new therapies to improve aberrant neutrophil function in diabetes. Existing literature illustrates a dual neutrophil dysfunction in diabetes. Key pathogen handling mechanisms of neutrophil recruitment, chemotaxis, phagocytosis and intracellular reactive oxygen species (ROS) production are decreased in diabetes, weakening the immune response to infection. However, pro-inflammatory neutrophil pathways, mainly neutrophil extracellular trap (NET) formation, extracellular ROS generation and pro-inflammatory cytokine generation, are significantly upregulated, causing damage to the host and perpetuating inflammation. Reducing these proinflammatory outputs therapeutically is emerging as a credible strategy to improve infection resolution in diabetes, and also more recently COVID-19. Future research needs to drive forward the exploration of novel treatments to improve infection resolution in T1D and T2D to improve patient morbidity and mortality.

Insulin exacerbated high glucose-induced epithelial-mesenchymal transition in prostatic epithelial cells BPH-1 and prostate cancer cells PC-3 via MEK/ERK signaling pathway

As two most common progressive diseases of aging, type 2 diabetes mellitus (T2DM) and benign prostatic hyperplasia (BPH) were all characterized by endocrine and metabolic disorders. Here, our clinical study showed that there were significant differences in fasting blood glucose (FBG), fasting insulin (FINS), insulin resistance index (HOMA-IR) and prostate volume (PV) between simple BPH patients and BPH complicated with T2DM patients. Further analysis showed that HOMA-IR was positively correlated with PV in BPH complicated with T2DM patients. The in vitro experiment results showed that high glucose (HG) promoted EMT process in a glucose-dependent manner in human prostate hyperplasia cells (BPH-1) and prostate cancer cells (PC-3), and this pathological process was exacerbated by co-culture with insulin. Mechanistically, insulin-induced exacerbation of EMT was depended on the activation of MEK/ERK signaling pathway, and we suggested that insulin and its analogs should be used very carefully for the clinical antihyperglycemic treatment of BPH complicated with T2DM patients.

Development and validation of a predictive model for incident type 2 diabetes in middle-aged Mexican adults: the metabolic syndrome cohort

BACKGROUND

Type 2 diabetes mellitus (T2D) is a leading cause of morbidity and mortality in Mexico. Here, we aimed to report incidence rates (IR) of type 2 diabetes in middle-aged apparently-healthy Mexican adults, identify risk factors associated to ID and develop a predictive model for ID in a high-risk population.

METHODS

Prospective 3-year observational cohort, comprised of apparently-healthy adults from urban settings of central Mexico in whom demographic, anthropometric and biochemical data was collected. We evaluated risk factors for ID using Cox proportional hazard regression and developed predictive models for ID.

RESULTS

We included 7636 participants of whom 6144 completed follow-up. We observed 331 ID cases (IR: 21.9 per 1000 person-years, 95%CI 21.37-22.47). Risk factors for ID included family history of diabetes, age, abdominal obesity, waist-height ratio, impaired fasting glucose (IFG), HOMA2-IR and metabolic syndrome. Early-onset ID was also high (IR 14.77 per 1000 person-years, 95%CI 14.21-15.35), and risk factors included HOMA-IR and IFG. Our ID predictive model included age, hypertriglyceridemia, IFG, hypertension and abdominal obesity as predictors (Dxy = 0.487, c-statistic = 0.741) and had higher predictive accuracy compared to FINDRISC and Cambridge risk scores.

CONCLUSIONS

ID in apparently healthy middle-aged Mexican adults is currently at an alarming rate. The constructed models can be implemented to predict diabetes risk and represent the largest prospective effort for the study metabolic diseases in Latin-American population.

Ypaoamides B and C, Linear Lipopeptides from an Okeania sp. Marine Cyanobacterium

Two new pyrrolinone-containing lipopeptides, ypaoamides B (1) and C (2), were isolated from an Okeania sp. marine cyanobacterium collected in Okinawa. Their structures were determined by spectroscopic analysis and Marfey's analysis of acid hydrolysates. Ypaoamides B (1) and C (2) stimulated glucose uptake in cultured rat L6 myotubes. In particular, ypaoamide B (1) showed potent activity and activated AMP-activated protein kinase.

Kringle IV Type 2, Not Low Lipoprotein(a), as a Cause of Diabetes: A Novel Genetic Approach Using SNPs Associated Selectively with Lipoprotein(a) Concentrations or with Kringle IV Type 2 Repeats

BACKGROUND

Low plasma lipoprotein(a) concentrations are associated with type 2 diabetes. Whether this is due to low lipoprotein(a) concentrations per se or to a large number of kringle IV type 2 (KIV-2) repeats remains unclear. We therefore aimed to identify genetic variants associated selectively with lipoprotein(a) concentrations or with the number of KIV-2 repeats, to investigate which of these traits confer risk of diabetes.

METHODS

We genotyped 8411 individuals from the Copenhagen City Heart Study for 778 single-nucleotide polymorphisms (SNPs) in the proximity of the LPA gene, and examined the association of these SNPs with plasma concentrations of lipoprotein(a) and with KIV-2 number of repeats. SNPs that were selectively associated with lipoprotein(a) concentrations but not with KIV-2 number of repeats, or vice versa, were included in a Mendelian randomization study.

RESULTS

We identified 3 SNPs (rs12209517, rs12194138, and rs641990) that were associated selectively with lipoprotein(a) concentrations and 3 SNPs (rs1084651, rs9458009, and rs9365166) that were associated selectively with KIV-2 number of repeats. For SNPs selectively associated with lipoprotein(a) concentrations, an allele score of 4-6 vs 0-2 had an odds ratio for type 2 diabetes of 1.03 (95% CI, 0.86-1.23). In contrast, for SNPs selectively associated with KIV-2 number of repeats, an allele score of 4-6 vs 0-2 had an odds ratio for type 2 diabetes of 1.42 (95% CI, 1.17-1.69).

CONCLUSIONS

Using a novel genetic approach, our results indicate that it is a high number of KIV-2 repeats that are associated causally with increased risk of type 2 diabetes, and not low lipoprotein(a) concentrations per se. This is a reassuring finding for lipoprotein(a)-lowering therapies that do not increase the KIV-2 number of repeats.

The association between leptin receptor gene polymorphisms and type 2 diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

Several case-control studies have demonstrated a relationship between leptin receptor (LEPR) gene polymorphism and type 2 diabetes mellitus (T2DM) risk, though the results have not always been consistent among diverse populations. This meta-analysis was designed to assess a more accurate association between LEPR polymorphism and T2DM.

METHODS

Eight electronic databases were consulted and researchers searched for Chinese and English peer-reviewed articles, published between 2000 and 2015, that referred to the association between LEPR polymorphism and T2DM. Pooled odds ratios (OR) with a 95% confidence interval (CI) were calculated in allele contrast, recessive, dominant and additive genetic models to assess this association.

RESULTS

Four repeatedly reviewed polymorphisms, taken from 22 studies on Arg109Lys, Asn656Lys, Gln223Arg and Pro1019Pro with 31,260 controls and 25,560 cases, were included in the meta-analysis model. The meta-result demonstrated that only the Pro1019Pro polymorphism was substantially associated with T2DM risk-G vs. A: OR with 95% CI 0.58 (0.43-0.79), Z=3.51, p=0.0005; GG vs. AG+AA: 0.57 (0.42-0.77), Z=3.66, p=0.0002; GG+AG vs. AA: 0.55 (0.37-0.81), Z=3.01, p=0.003; GG vs. AA: 0.51 (0.37-0.69), Z=4.24, p<0.001.

CONCLUSIONS

Our meta-analysis suggested a significant association between the LEPR Pro1019Pro polymorphism and T2DM risk. Thus, targeted healthcare should be strengthened with regard to this gene carrier in order to prevent T2DM.

Overview of genetic research in anorexia nervosa: The past, the present and the future

BACKGROUND

Even though the evidence supporting the presence of a heritable component in the aetiology of anorexia nervosa (AN) is strong, the underlying genetic mechanisms remain poorly understood. The recent publication of a genome-wide association study (GWAS) of AN (Boraska, Mol Psychiatry, 2014) was an important step in genetic research in AN.

OBJECTIVE

To briefly sum up strengths and weaknesses of candidate-gene and genome-wide approaches, to discuss the genome-wide association studies of AN and to make predictions about the genetic architecture of AN by comparing it to that of schizophrenia (since the diseases share some similarities and genetic research in schizophrenia is more advanced).

METHOD

Descriptive literature review.

RESULTS

Despite remarkable efforts, the gene-association studies in AN did not advance our knowledge as much as had been hoped, although some results still await replication.

DISCUSSION

Continuous effort of participants, clinicians and researchers remains necessary to ensure that genetic research in AN follows a similarly successful path as in schizophrenia. Identification of genetic susceptibility loci provides a basis for follow-up studies.

The Human Genome Project, and recent advances in personalized genomics

The language of “personalized medicine” and “personal genomics” has now entered the common lexicon. The idea of personalized medicine is the integration of genomic risk assessment alongside other clinical investigations. Consistent with this approach, testing is delivered by health care professionals who are not medical geneticists, and where results represent risks, as opposed to clinical diagnosis of disease, to be interpreted alongside the entirety of a patient’s health and medical data. In this review we consider the evidence concerning the application of such personalized genomics within the context of population screening, and potential implications that arise from this. We highlight two general approaches which illustrate potential uses of genomic information in screening. The first is a narrowly targeted approach in which genetic profiling is linked with standard population-based screening for diseases; the second is a broader targeting of variants associated with multiple single gene disorders, performed opportunistically on patients being investigated for unrelated conditions. In doing so we consider the organization and evaluation of tests and services, the challenge of interpretation with less targeted testing, professional confidence, barriers in practice, and education needs. We conclude by discussing several issues pertinent to health policy, namely: avoiding the conflation of genetics with biological determinism, resisting the “technological imperative”, due consideration of the organization of screening services, the need for professional education, as well as informed decision making and public understanding.

Pancreatic gene variants potentially associated with dipeptidyl peptidase-4 inhibitor treatment response in Type 2 diabetes

In the adult pancreas, the expression of the genes PAX4, KCNQ1, TCF7L2, KCNJ11, ABCC8, MTNR1B and WFS1 are mainly restricted to β cells to maintain glucose homeostasis. We have identified these genes as the main regulators of incretin-mediated actions, and therefore they may potentially influence the response of DPP-4 inhibitors. This review represents the first detailed exploration of pancreatic β-cell genes and their variant mechanisms, which could potentially affect the response of DPP-4 inhibitors in Type 2 diabetes. We have focused on the signaling pathways of these genes to understand their roles in gastrointestinal incretin-mediated effects; and finally, we sought to associate gene mechanisms with their Type 2 diabetes risk variants to predict the responses of DPP-4 inhibitors for this disease.

Role of rs6923761 gene variant in glucagon-like peptide 1 receptor in basal GLP-1 levels, cardiovascular risk factor and serum adipokine levels in naïve type 2 diabetic patients

BACKGROUND

Role of GLP-1 variants on basal GLP-1 levels, body weight and cardiovascular risk factors remains unclear in patients with diabetes mellitus type 2.

OBJECTIVE

Our aim was to analyze the effects of rs6923761 GLP-1 receptor polymorphism on body weight, cardiovascular risk factors, basal GLP-1 levels and serum adipokine levels in naïve patients with diabetes mellitus type 2.

DESIGN

A sample of 104 naïve patients with diabetes mellitus type 2 was enrolled in a prospective way. Basal fasting glucose, c-reactive protein (CRP), insulin, insulin resistance (HOMA), total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides concentration, basal GLP-1, HbA1c and adipokines (leptin, adiponectin, resistin) levels were determined. Weights, body mass index, waist circumference, fat mass by bioimpedance and blood pressure measures were measured.

RESULTS

Forty-nine patients (47.1%) had the genotype GG and 55 (52.9%) diabetic subjects had the next genotypes; GA (44 patients, 42.3%) or AA (11 study subjects, 10.6%) (second group). In A allele carriers, basal GLP-1 levels were higher than non-carriers (2.9 ± 2.1 ng/ml; p < 0.05). No differences were detected between both genotype groups.

CONCLUSION

Our cross-sectional study revealed an association between the rs6923761 GLP-1 receptor polymorphism (A allele carriers) and basal GLP-1 levels in naïve patients with diabetes mellitus type 2.

Relation of the rs6923761 gene variant in glucagon-like peptide 1 receptor to metabolic syndrome in obese subjects

BACKGROUND

The role of glucagon-like peptide 1 (GLP-1) variants in metabolic syndrome (MS) and its components remains unclear in obese subjects.

OBJECTIVE

The aim of our study was to evaluate the relationship of rs6923761 with MS and its components in obese subjects.

DESIGN

A population of 1,122 obese subjects was analyzed in a cross-sectional survey. To estimate the prevalence of MS, we considered the definitions of the Adult Treatment Panel III.

RESULTS

Five hundred and forty-eight patients (48.8%) had the GG genotype (wild-type group), whereas 487 patients (43.4%) had the GA genotype and 87 patients (7.8%) the AA genotype. The mean age was 48.9 ± 12.8 years. The prevalence of MS was 47.4% (532 patients), and 52.6% of patients had no MS (n = 590). The odds ratio of MS for the wild-type versus the mutant genotype was 1.02, with a 95% confidence interval of 0.88-1.12. Body mass index, weight, fat mass, waist circumference, and waist to hip ratio were lower in the mutant than in the wild-type group in patients with and without MS.

CONCLUSION

The GLP-1 receptor variant rs6923761 was found to be associated with decreased weight and anthropometric parameters in A allele carriers with and without MS. MS or its components were not associated with this polymorphism in obese adults.

Computer-supported indirect-form lifestyle-modification support program using Lifestyle Intervention Support Software for Diabetes Prevention (LISS-DP) for people with a family history of type 2 diabetes in a medical checkup setting: a randomized controlled trial

AIMS

To investigate the effect of a computer-supported indirect-form lifestyle-modification program using Lifestyle Intervention Support Software for Diabetes Prevention (LISS-DP), as a clinically feasible strategy for primary prevention, on diet and physical activity habits in adults with a family history of type 2 diabetes.

METHODS

This was a two-arm, randomized controlled trial: (1) lifestyle intervention (LI) group (n=70); (2) control (n=71). Healthy adults aged 30-60 years with a history of type 2 diabetes among their first-degree relatives were recruited. LI group received three times of lifestyle intervention using LISS-DP during six-month intervention period via mail.

RESULTS

Lifestyle intervention group showed significantly greater decrease in energy intake six months after baseline, compared to control (-118.31 and -24.79 kcal/day, respectively, p=0.0099, Cohen's d=0.22), though the difference disappeared 1 year after from baseline. No difference was found in physical activity energy expenditure.

CONCLUSIONS

A computer-based, non-face-to-face lifestyle intervention was effective on dietary habits, only during the intervention period. Further examination of the long-term effects of such intervention and physical activity is required.

An explained variance-based genetic risk score associated with gestational diabetes antecedent and with progression to pre-diabetes and type 2 diabetes: a cohort study

OBJECTIVE

To determine whether an explained-variance genetic risk score (GRS), with 36 single nucleotide polymorphisms (SNPs) previously associated with type 2 diabetes (T2D), is also associated with gestational diabetes mellitus (GDM), and with the progression to pre-diabetes and T2D among women with prior GDM.

DESIGN

A cohort study.

SETTING

Clinical investigation unit of Laval University, Quebec, Canada.

POPULATION

A cohort of 214 women with prior GDM and 82 controls recruited between 2009 and 2012.

METHODS

Associations between the GRS and GDM.

MAIN OUTCOMES MEASURES

GDM and prevalence of pre-diabetes and T2D.

RESULTS

Women with prior GDM had a higher GRS compared with controls (38.6 ± 3.9, 95% CI 38.1-39.1, versus 37.4 ± 3.2, 95% CI 36.7-38.1; P < 0.0001). In women with prior GDM, the explained-variance GRS was higher for pre-diabetic women compared with women who remained normoglucotolerant at testing (1.21 ± 0.18, 95% CI 1.18-1.23, versus 1.17 ± 0.15, 95% CI 1.13-1.20; P < 0.0001). Similarly, women with T2D had a higher explained-variance GRS compared with women with prior GDM who remained normoglucotolerant (1.20 ± 0.18, 95% CI 1.14-1.25, versus 1.17 ± 0.17, 95% CI 1.13-1.20; P < 0.0001). The predictive effects of the explained-variance GRS, age, and body mass index (BMI), or the additive effects of the three variables, were tested for pre-diabetes and T2D. We observed an area under the curve of 0.6269 (95% CI 0.5638-0.6901) for age and BMI, and adding the explained-variance GRS into the model increased the area to 0.6672 (95% CI 0.6064-0.7281) for the prediction of pre-diabetes.

CONCLUSIONS

An explained-variance GRS is associated with both GDM and progression to pre-diabetes and T2D in women with prior GDM.

Cytokine gene polymorphism among Indigenous Australians

The health profile of Indigenous Australians is characterised by high rates of classic 'lifestyle' diseases. Potential roles of inflammation in pathophysiology of these diseases requires investigation. It is not clear if genetic regulation of inflammation in Indigenous Australians is similar to other populations. This study characterised frequencies of single nucleotide polymorphisms (SNPs) for eight cytokine genes for 100 individuals from a remote Indigenous Australian community and assessed novel genetic variants in four cytokine genes. We used a commercially-available allelic discrimination assay for SNP genotyping; re-sequencing was undertaken by standard Sanger sequencing methodologies for 26 samples. Frequencies of cytokine gene SNPs differed significantly from the Caucasian population (P < 0.001-0.044). Twenty-five novel variants were identified across four re-sequenced genes; frequencies ranged from <5% to 100%. Genotype frequencies observed in Indigenous Australians did not consistently resemble reported HapMap frequencies in Northern and Western European populations, Yoruba Nigerian or Han Chinese. Our findings indicate Indigenous Australians might have an inherited propensity for strong inflammatory responses. Preliminary evidence of novel genetic variants highlights the need to catalogue the extent of genetic variation in specific population groups. Improved understanding of differences in genetic variation between specific population groups could assist in assessment of risk for lifestyle diseases.

Relation of the rs6923761 gene variant in glucagon-like peptide 1 receptor with weight, cardiovascular risk factor, and serum adipokine levels in obese female subjects

BACKGROUND

Studies of the glucagon-like peptide 1 (GLP-1) receptor have been directed at identifying polymorphisms in the GLP-1 receptor gene that may be a contributing factor in the pathogenesis of diabetes mellitus and cardiovascular risk factors. Nevertheless, the role of GLP-1 variants on body weight, cardiovascular risk factors, and adipokines remains unclear in obese patients.

OBJECTIVE

Our aim was to analyze the effects of rs6923761 GLP-1 receptor polymorphism on body weight, cardiovascular risk factors, and serum adipokine levels in nondiabetic obese females.

DESIGN

A sample of 645 obese nondiabetic Caucasian females was enrolled in a prospective way. Basal fasting glucose, c-reactive protein (CRP), insulin, insulin resistance (homeostasis model assessment (HOMA)), total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides concentration, and adipokines were measured. Weights, body mass index (BMI), waist circumference, fat mass by bioimpedance, and blood pressure measures were measured.

RESULTS

Three hundred and twenty-seven participants (50.7%) had the genotype GG and 318 (49.3%) study subjects had the next genotypes; GA (270 study subjects, 41.9%) or AA (48 study subjects, 7.4%) (second group). In wild group (GG genotype), BMI (1.8 ± 2.3 kg/m(2) ; P < 0.05), weight (3.1 ± 1.3 kg; P < 0.05), fat mass (2.4 ± 1.1 kg; P < 0.05), waist circumference (2.7 ± 1.9 cm; P < 0.05), triglyceride levels (10.4 ± 5.3 mg/dl; P < 0.05), interleukin 6 (IL-6) (1.5 ± 0.9 ng/dl; P < 0.05), resistin (1.1 ± 0.3 ng/dl; P < 0.05), and leptin (30.1 ± 10.3 ng/dl; P < 0.05) levels were higher than mutant group (GA + AA).

CONCLUSION

Data from our study revealed an association with decreased metabolic and cardiovascular markers in obese females. BMI weight, fat mass, waist circumference, triglycerides, leptin, resistin, and IL-6 serum levels were lower in subjects with A allele than non-A allele subjects.

Risk factors for periodontal disease

Risk factors play an important role in an individual's response to periodontal infection. Identification of these risk factors helps to target patients for prevention and treatment, with modification of risk factors critical to the control of periodontal disease. Shifts in our understanding of periodontal disease prevalence, and advances in scientific methodology and statistical analysis in the last few decades, have allowed identification of several major systemic risk factors for periodontal disease. The first change in our thinking was the understanding that periodontal disease is not universal, but that severe forms are found only in a portion of the adult population who show abnormal susceptibility. Analysis of risk factors and the ability to statistically adjust and stratify populations to eliminate the effects of confounding factors have allowed identification of independent risk factors. These independent but modifiable, risk factors for periodontal disease include lifestyle factors, such as smoking and alcohol consumption. They also include diseases and unhealthy conditions such as diabetes mellitus, obesity, metabolic syndrome, osteoporosis, and low dietary calcium and vitamin D. These risk factors are modifiable and their management is a major component of the contemporary care of many periodontal patients. Genetic factors also play a role in periodontal disease and allow one to target individuals for prevention and early detection. The role of genetic factors in aggressive periodontitis is clear. However, although genetic factors (i.e., specific genes) are strongly suspected to have an association with chronic adult periodontitis, there is as yet no clear evidence for this in the general population. It is important to pursue efforts to identify genetic factors associated with chronic periodontitis because such factors have potential in identifying patients who have a high susceptibility for development of this disease. Many of the systemic risk factors for periodontal disease, such as smoking, diabetes and obesity, and osteoporosis in postmenopausal women, are relatively common and can be expected to affect most patients with periodontal disease seen in clinics and dental practices. Hence, risk factor identification and management has become a key component of care for periodontal patients.

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.

Global O-GlcNAc Levels Modulate Transcription of the Adipocyte Secretome during Chronic Insulin Resistance

Increased flux through the hexosamine biosynthetic pathway and the corresponding increase in intracellular glycosylation of proteins via O-linked β-N-acetylglucosamine (O-GlcNAc) is sufficient to induce insulin resistance (IR) in multiple systems. Previously, our group used shotgun proteomics to identify multiple rodent adipocytokines and secreted proteins whose levels are modulated upon the induction of IR by indirectly and directly modulating O-GlcNAc levels. We have validated the relative levels of several of these factors using immunoblotting. Since adipocytokines levels are regulated primarily at the level of transcription and O-GlcNAc alters the function of many transcription factors, we hypothesized that elevated O-GlcNAc levels on key transcription factors are modulating secreted protein expression. Here, we show that upon the elevation of O-GlcNAc levels and the induction of IR in mature 3T3-F442a adipocytes, the transcript levels of multiple secreted proteins reflect the modulation observed at the protein level. We validate the transcript levels in male mouse models of diabetes. Using inguinal fat pads from the severely IR db/db mouse model and the mildly IR diet-induced mouse model, we have confirmed that the secreted proteins regulated by O-GlcNAc modulation in cell culture are likewise modulated in the whole animal upon a shift to IR. By comparing the promoters of similarly regulated genes, we determine that Sp1 is a common cis-acting element. Furthermore, we show that the LPL and SPARC promoters are enriched for Sp1 and O-GlcNAc modified proteins during insulin resistance in adipocytes. Thus, the O-GlcNAc modification of proteins bound to promoters, including Sp1, is linked to adipocytokine transcription during insulin resistance.

Lipoprotein(a) concentrations, isoform size, and risk of type 2 diabetes: a Mendelian randomisation study

BACKGROUND

Low concentrations of lipoprotein(a) in plasma are associated with increased risk of type 2 diabetes, but whether this association is causal is unclear. Variations in the LPA gene affect lipoprotein(a) isoform size and concentrations in plasma. We therefore did a Mendelian randomisation study to investigate whether large isoform size, low concentrations in plasma, or both, are causally associated with type 2 diabetes.

METHODS

We assessed data for adults from the Danish general population enrolled in the Copenhagen City Heart Study and the Copenhagen General Population Study, with and without type 2 diabetes. Eligible participants had data for lipoprotein(a) concentrations in plasma, LPA kringle IV type 2 (KIV-2) sums of repeats (affecting both isoform size and plasma concentrations), and carrier status for the LPA single-nucleotide polymorphism rs10455872 (mainly affecting concentrations in plasma).

FINDINGS

77,901 individuals had lipoprotein(a) data, of whom 28,567 (36·7%) had all three measurements. Low concentrations of lipoprotein(a) in plasma were associated with risk of type 2 diabetes, with adjusted odds ratios of 1·26 (1·09-1·45), 1·17 (1·01-1·36), 1·04 (0·90-1·21), and 1·05 (95% CI 0·90-1·22), respectively, for quintiles 1-4, compared with quintile 5 concentrations. High KIV-2 sums of repeats were associated with risk of type 2 diabetes (adjusted odds ratio 1·16, 95% CI 1·05-1·28) for KIV-2 quintile 5 versus quintiles 1-4 combined. Being a carrier of rs10455872 did not affect risk of type 2 diabetes. For a halving of lipoprotein(a) concentrations, the instrumental variable estimate of the causal odds ratio for type 2 diabetes was 1·15 (95% CI 1·05-1·27) for KIV-2 sum of repeats and 0·99 (0·95-1·03) for rs10455872 genotype.

INTERPRETATION

Low lipoprotein(a) concentrations alone seem not to be causally associated with type 2 diabetes, but a causal association for large lipoprotein(a) isoform size cannot be excluded.

FUNDING

Danish Heart Foundation, Danish Council for Independent Research-Medical Sciences, IMK Almene Fund, and Johan and Lise Boserup's Fund.

Gene variants associated with antisocial behaviour: a latent variable approach

OBJECTIVE

The aim of this study was to determine if a latent variable approach might be useful in identifying shared variance across genetic risk alleles that is associated with antisocial behaviour at age 15 years.

METHODS

Using a conventional latent variable approach, we derived an antisocial phenotype in 328 adolescents utilizing data from a 15-year follow-up of a randomized trial of a prenatal and infancy nurse-home visitation programme in Elmira, New York. We then investigated, via a novel latent variable approach, 450 informative genetic polymorphisms in 71 genes previously associated with antisocial behaviour, drug use, affiliative behaviours and stress response in 241 consenting individuals for whom DNA was available. Haplotype and Pathway analyses were also performed.

RESULTS

Eight single-nucleotide polymorphisms (SNPs) from eight genes contributed to the latent genetic variable that in turn accounted for 16.0% of the variance within the latent antisocial phenotype. The number of risk alleles was linearly related to the latent antisocial variable scores. Haplotypes that included the putative risk alleles for all eight genes were also associated with higher latent antisocial variable scores. In addition, 33 SNPs from 63 of the remaining genes were also significant when added to the final model. Many of these genes interact on a molecular level, forming molecular networks. The results support a role for genes related to dopamine, norepinephrine, serotonin, glutamate, opioid and cholinergic signalling as well as stress response pathways in mediating susceptibility to antisocial behaviour.

CONCLUSIONS

This preliminary study supports use of relevant behavioural indicators and latent variable approaches to study the potential 'co-action' of gene variants associated with antisocial behaviour. It also underscores the cumulative relevance of common genetic variants for understanding the aetiology of complex behaviour. If replicated in future studies, this approach may allow the identification of a 'shared' variance across genetic risk alleles associated with complex neuropsychiatric dimensional phenotypes using relatively small numbers of well-characterized research participants.

The 2010 ESPEN Sir David Cuthbertson Lecture: new and old proteins: clinical implications

The past century had witnessed vast advances in biomedical research, particularly in the fields of genomics and proteomics, yet the translation of these discoveries into clinical practice has been hindered by gaps in mechanistic understanding of variability governing disease susceptibility and pathogenesis. Among the greatest challenges are the dynamic nature of the proteome and the imperfect methodologies currently available to study it. Here, we review key recently developed proteomic techniques that have allowed for dynamic characterization of protein quality, as well as quantity, and discuss their potential applications in understanding aging and metabolic disorders including diabetes. These methodologies revealed that senescence is characterized, in part, by decreased rates of de novo protein synthesis and potentially also degradation, in addition to concomitantly increased levels of oxidative stress, ultimately resulting in excessive accumulation of damaged and dysfunctional proteins. Insulin may be a key mediator in these pathologies, as hyperinsulinemia has been shown to hinder protein degradation while transient insulin deficiency may accelerate oxidative damage. We also discuss two interventions that have been proposed to delay, and possibly reverse, senescence by augmenting protein degradation: chronic caloric restriction and aerobic exercise.

Dual peroxisome proliferator-activated receptor α/δ agonist GFT505 improves hepatic and peripheral insulin sensitivity in abdominally obese subjects

OBJECTIVE

The development of new insulin sensitizers is an unmet need for the treatment of type 2 diabetes. We investigated the effect of GFT505, a dual peroxisome proliferator-activated receptor (PPAR)-α/δ agonist, on peripheral and hepatic insulin sensitivity.

RESEARCH DESIGN AND METHODS

Twenty-two abdominally obese insulin-resistant males (homeostasis model assessment of insulin resistance>3) were randomly assigned in a randomized crossover study to subsequent 8-week treatment periods with GFT505 (80 mg/day) or placebo, followed by a two-step hyperinsulinemic-euglycemic insulin clamp with a glucose tracer to calculate endogenous glucose production (EGP). The primary end point was the improvement in glucose infusion rate (GIR). Gene expression analysis was performed on skeletal muscle biopsy specimens.

RESULTS

GFT505 improved peripheral insulin sensitivity, with a 21% (P=0.048) increase of the GIR at the second insulin infusion period. GFT505 also enhanced hepatic insulin sensitivity, with a 44% (P=0.006) increase of insulin suppression of EGP at the first insulin infusion period. Insulin-suppressed plasma free fatty acid concentrations were significantly reduced on GFT505 treatment (0.21±0.07 vs. 0.27±0.11 mmol/L; P=0.006). Neither PPARα nor PPARδ target genes were induced in skeletal muscle, suggesting a liver-targeted action of GFT505. GFT505 significantly reduced fasting plasma triglycerides (-21%; P=0.003) and LDL cholesterol (-13%; P=0.0006), as well as liver enzyme concentrations (γ-glutamyltranspeptidase: -30.4%, P=0.003; alanine aminotransferase: -20.5%, P=0.004). There was no safety concern or any indication of PPARγ activation with GFT505.

CONCLUSIONS

The dual PPARα/δ agonist GFT505 is a liver-targeted insulin-sensitizer that is a promising drug candidate for the treatment of type 2 diabetes and nonalcoholic fatty liver disease.

The polymorphism in the let-7 targeted region of the Lin28 gene is associated with increased risk of type 2 diabetes mellitus

Genetic polymorphisms in the miRNAs pathway of the pathogenesis of disease might contribute to the risk of disease. However, it is unclear whether these polymorphisms about miRNAs are associated with the risk of type 2 diabetes mellitus (T2DM). We performed a case-control study to investigate two polymorphisms in the let-7/Lin28 pathway based on 588 T2DM patients and 588 age and sex matched controls. The results showed that the rs3811463 polymorphism was associated with increased risk of T2DM (odds ratio (OR)=1.47, 95% confidence inference (95%CI)=1.13-1.93, P=0.005), while the rs3811464 not (OR=1.04, 95%CI=0.79-1.36, P=0.78). For the rs3811463 polymorphism, the variant genotypes were associated with increased risk of disease in females; statistically differences were observed in the clinical features of age at diagnosis, hypertension and peripheral neuropathy for the variant and wild genotype of the rs3811463 in T2DM. In summary, the results indicated that the rs3811463 polymorphism in the let-7/Lin28 pathway could significantly increase the risk of T2DM.

Osteocalcin and the Regulation of Glucose Metabolism

Uncarboxylated osteocalcin enhances insulin and adiponectin release and improves glucose tolerance in mice. Data in humans do not unequivocally support a role for osteocalcin in glucose homeostasis. Changes in the amount of uncarboxylated osteocalcin induced by vitamin K or warfarin treatment are not associated with changes in glucose and insulin concentrations. Interventional studies in humans, designed to detect small changes in insulin secretion and action attributable to changes in uncarboxylated osteocalcin, will be required to reliably detect effects of osteocalcin on glucose metabolism and to better understand its interaction with adiposity and adipokines.

Associations between UCP1 -3826A/G, UCP2 -866G/A, Ala55Val and Ins/Del, and UCP3 -55C/T polymorphisms and susceptibility to type 2 diabetes mellitus: case-control study and meta-analysis

Background

Some studies have reported associations between five uncoupling protein (UCP) 1–3 polymorphisms and type 2 diabetes mellitus (T2DM). However, other studies have failed to confirm the associations. This paper describes a case-control study and a meta-analysis conducted to attempt to determine whether the following polymorphisms are associated with T2DM: -3826A/G (UCP1); -866G/A, Ala55Val and Ins/Del (UCP2) and -55C/T (UCP3).

Methods

The case-control study enrolled 981 T2DM patients and 534 nondiabetic subjects, all of European ancestry. A literature search was run to identify all studies that investigated associations between UCP1–3 polymorphisms and T2DM. Pooled odds ratios (OR) were calculated for allele contrast, additive, recessive, dominant and co-dominant inheritance models. Sensitivity analyses were performed after stratification by ethnicity.

Results

In the case-control study the frequencies of the UCP polymorphisms did not differ significantly between T2DM and nondiabetic groups (P>0.05). Twenty-three studies were eligible for the meta-analysis. Meta-analysis results showed that the Ala55Val polymorphism was associated with T2DM under a dominant model (OR = 1.27, 95% CI 1.03–1.57); while the -55C/T polymorphism was associated with this disease in almost all genetic models: allele contrast (OR = 1.17, 95% CI 1.02–1.34), additive (OR = 1.32, 95% CI 1.01–1.72) and dominant (OR = 1.18, 95% CI 1.02–1.37). However, after stratification by ethnicity, the UCP2 55Val and UCP3 -55C/T alleles remained associated with T2DM only in Asians (OR = 1.25, 95% CI 1.02–1.51 and OR = 1.22, 95% CI 1.04–1.44, respectively; allele contrast model). No significant association of the -3826A/G, -866G/A and Ins/Del polymorphisms with T2DM was observed.

Conclusions

In our case-control study of people with European ancestry we were not able to demonstrate any association between the UCP polymorphisms and T2DM; however, our meta-analysis detected a significant association between the UCP2 Ala55Val and UCP3 -55C/T polymorphisms and increased susceptibility for T2DM in Asians.

Therapeutic potential of VIP vs PACAP in diabetes

Type 2 diabetes (T2D) is characterized by chronic insulin resistance and a progressive decline in beta-cell function. Although rigorous glucose control can reduce morbidity and mortality associated with diabetes, achieving optimal long-term glycemic control remains to be accomplished in many diabetic patients. As beta-cell mass and function inevitably decline in T2D, exogenous insulin administration is almost unavoidable as a final outcome despite the use of oral antihyperglycemic agents in many diabetic patients. Pancreatic islet cell death, but not the defect in new islet formation or beta-cell replication, has been blamed for the decrease in beta-cell mass observed in T2D patients. Thus, therapeutic approaches designed to protect islet cells from apoptosis could significantly improve the management of T2D, because of its potential to reverse diabetes not just ameliorate glycemia. Therefore, an ideal beta-cell-preserving agent is expected to protect beta cells from apoptosis and stimulate postprandial insulin secretion along with increasing beta-cell replication and/or islet neogenesis. One such potential agent, the islet endocrine neuropeptide vasoactive intestinal peptide (VIP) strongly stimulates postprandial insulin secretion. Because of its broad spectrum of biological functions such as acting as a potent anti-inflammatory factor through suppression of Th1 immune response, and induction of immune tolerance via regulatory T cells, VIP has emerged as a promising therapeutic agent for the treatment of many autoimmune diseases including diabetes.

IRS1 gene variants, dysglycaemic metabolic changes and type-2 diabetes risk

BACKGROUND AND AIMS

A recent genome-wide association study identified rs2943641C > T, 500 kb from the insulin receptor substrate-1 gene (IRS1), as a type-2 diabetes (T2D) susceptibility locus. We aimed to replicate this association by meta-analysis and examine whether common variants within IRS1, present on the HumanCVD BeadChip, were associated with T2D risk.

METHODS AND RESULTS

We genotyped rs2943641 in 2389 prevalent or incident T2D patients and 6494 controls from two prospective and three case studies based in UK and in the European Atherosclerosis Research Study-II (EARSII; n = 714). Thirty-three IRS1 variants had been genotyped in the prospective Whitehall-II study (n = 4752) using the HumanCVD BeadChip. In a fixed-effects meta-analysis of the UK study cohorts rs2943641T allele was associated with 6% lower risk of T2D (p = 0.18), with T-allele carriers having an odds ratio (OR) of 0.89 (95% confidence interval [CI]: 0.80-1.00, p = 0.056) compared to CC subjects. The T-allele was also associated with lower fasting insulin and homeostasis model assessment index of insulin resistance in Whitehall-II and with lower post-load insulin after an oral glucose tolerance test in EARSII (all p < 0.05). None of the IRS1 variants on the chip showed linkage disequilibrium with rs2943641. In silico analysis with follow-up genotyping (total n = 9313) identified that the rare allele of the IRS1 promoter variant rs6725556A > G showed association with reduced T2D risk (OR per G-allele: 0.82, 95%CI: 0.69-0.96, p = 0.015).

CONCLUSIONS

We confirm the association of rs2943641T with T2D protection. There is a possible independent effect on risk of a putative IRS1 promoter variant.

Type 2 diabetes in Asians: prevalence, risk factors, and effectiveness of behavioral intervention at individual and population levels

This review summarizes the current data on diabetes risk factors, prevalence, and prevention efforts in Asia and Asian migrant populations. Studies indicate that type 2 diabetes mellitus is a large and growing threat to public health in Asian populations. Furthermore, Asian subgroups (e.g., South Asians/Asian Indians, Chinese) have unique risk factor profiles for developing diabetes, which differ from other populations and between Asian ethnic groups. Lifestyle intervention programs are effective in preventing diabetes in Asians, as with other ethnicities. The strength of these findings is lessened by the lack of systematically collected data using objective measurements. Large epidemiologic studies of diabetes prevalence and risk factor profiles and translational trials identifying sustainable and culturally acceptable lifestyle programs for Asian subgroups are needed.

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.

African ancestry and its correlation to type 2 diabetes in African Americans: a genetic admixture analysis in three U.S. population cohorts

The risk of type 2 diabetes is approximately 2-fold higher in African Americans than in European Americans even after adjusting for known environmental risk factors, including socioeconomic status (SES), suggesting that genetic factors may explain some of this population difference in disease risk. However, relatively few genetic studies have examined this hypothesis in a large sample of African Americans with and without diabetes. Therefore, we performed an admixture analysis using 2,189 ancestry-informative markers in 7,021 African Americans (2,373 with type 2 diabetes and 4,648 without) from the Atherosclerosis Risk in Communities Study, the Jackson Heart Study, and the Multiethnic Cohort to 1) determine the association of type 2 diabetes and its related quantitative traits with African ancestry controlling for measures of SES and 2) identify genetic loci for type 2 diabetes through a genome-wide admixture mapping scan. The median percentage of African ancestry of diabetic participants was slightly greater than that of non-diabetic participants (study-adjusted difference = 1.6%, P<0.001). The odds ratio for diabetes comparing participants in the highest vs. lowest tertile of African ancestry was 1.33 (95% confidence interval 1.13-1.55), after adjustment for age, sex, study, body mass index (BMI), and SES. Admixture scans identified two potential loci for diabetes at 12p13.31 (LOD = 4.0) and 13q14.3 (Z score = 4.5, P = 6.6 × 10(-6)). In conclusion, genetic ancestry has a significant association with type 2 diabetes above and beyond its association with non-genetic risk factors for type 2 diabetes in African Americans, but no single gene with a major effect is sufficient to explain a large portion of the observed population difference in risk of diabetes. There undoubtedly is a complex interplay among specific genetic loci and non-genetic factors, which may both be associated with overall admixture, leading to the observed ethnic differences in diabetes risk.

Common genetic variants differentially influence the transition from clinically defined states of fasting glucose metabolism

AIMS/HYPOTHESIS

Common genetic variants have been associated with type 2 diabetes. We hypothesised that a subset of these variants may have different effects on the transition from normal fasting glucose (NFG) to impaired fasting glucose (IFG) than on that from IFG to diabetes.

METHODS

We identified 16 type 2 diabetes risk variants from the Illumina Broad Candidate-gene Association Resource (CARe) array genotyped in 26,576 CARe participants. Participants were categorised at baseline as NFG, IFG or type 2 diabetic (n = 16,465, 8,017 or 2,291, respectively). Using Cox proportional hazards and likelihood ratio tests (LRTs), we compared rates of progression by genotype for 4,909 (NFG to IFG) and 1,518 (IFG to type 2 diabetes) individuals, respectively. We then performed multinomial regression analyses at baseline, comparing the risk of assignment to the NFG, IFG or diabetes groups by genotype.

RESULTS

The rate of progression from NFG to IFG was significantly greater in participants carrying the risk allele at MTNR1B (p = 1 × 10(-4)), nominally greater at GCK and SLC30A8 (p < 0.05) and nominally smaller at IGF2BP2 (p = 0.01) than the rate of progression from IFG to diabetes by the LRT. Results of the baseline, multinomial regression model were consistent with these findings.

CONCLUSIONS/INTERPRETATION

Common genetic risk variants at GCK, SLC30A8, IGF2BP2 and MTNR1B influence to different extents the development of IFG and the transition from IFG to type 2 diabetes. Our findings may have implications for understanding the genetic contribution of these variants to the development of IFG and type 2 diabetes.

Personal genome testing: test characteristics to clarify the discourse on ethical, legal and societal issues

Background

As genetics technology proceeds, practices of genetic testing have become more heterogeneous: many different types of tests are finding their way to the public in different settings and for a variety of purposes. This diversification is relevant to the discourse on ethical, legal and societal issues (ELSI) surrounding genetic testing, which must evolve to encompass these differences. One important development is the rise of personal genome testing on the basis of genetic profiling: the testing of multiple genetic variants simultaneously for the prediction of common multifactorial diseases. Currently, an increasing number of companies are offering personal genome tests directly to consumers and are spurring ELSI-discussions, which stand in need of clarification. This paper presents a systematic approach to the ELSI-evaluation of personal genome testing for multifactorial diseases along the lines of its test characteristics.

Discussion

This paper addresses four test characteristics of personal genome testing: its being a non-targeted type of testing, its high analytical validity, low clinical validity and problematic clinical utility. These characteristics raise their own specific ELSI, for example: non-targeted genetic profiling poses serious problems for information provision and informed consent. Questions about the quantity and quality of the necessary information, as well as about moral responsibilities with regard to the provision of information are therefore becoming central themes within ELSI-discussions of personal genome testing. Further, the current low level of clinical validity of genetic profiles raises questions concerning societal risks and regulatory requirements, whereas simultaneously it causes traditional ELSI-issues of clinical genetics, such as psychological and health risks, discrimination, and stigmatization, to lose part of their relevance. Also, classic notions of clinical utility are challenged by the newer notion of 'personal utility.'

Summary

Consideration of test characteristics is essential to any valuable discourse on the ELSI of personal genome testing for multifactorial diseases. Four key characteristics of the test - targeted/non-targeted testing, analytical validity, clinical validity and clinical utility - together determine the applicability and the relevance of ELSI to specific tests. The paper identifies and discusses four areas of interest for the ELSI-debate on personal genome testing: informational problems, risks, regulatory issues, and the notion of personal utility.

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.

Deep congenic analysis identifies many strong, context-dependent QTLs, one of which, Slc35b4, regulates obesity and glucose homeostasis

Although central to many studies of phenotypic variation and disease susceptibility, characterizing the genetic architecture of complex traits has been unexpectedly difficult. For example, most of the susceptibility genes that contribute to highly heritable conditions such as obesity and type 2 diabetes (T2D) remain to be identified despite intensive study. We took advantage of mouse models of diet-induced metabolic disease in chromosome substitution strains (CSSs) both to characterize the genetic architecture of diet-induced obesity and glucose homeostasis and to test the feasibility of gene discovery. Beginning with a survey of CSSs, followed with genetic and phenotypic analysis of congenic, subcongenic, and subsubcongenic strains, we identified a remarkable number of closely linked, phenotypically heterogeneous quantitative trait loci (QTLs) on mouse chromosome 6 that have unexpectedly large phenotypic effects. Although fine-mapping reduced the genomic intervals and gene content of these QTLs over 3000-fold, the average phenotypic effect on body weight was reduced less than threefold, highlighting the "fractal" nature of genetic architecture in mice. Despite this genetic complexity, we found evidence for 14 QTLs in only 32 recombination events in less than 3000 mice, and with an average of four genes located within the three body weight QTLs in the subsubcongenic strains. For Obrq2a1, genetic and functional studies collectively identified the solute receptor Slc35b4 as a regulator of obesity, insulin resistance, and gluconeogenesis. This work demonstrated the unique power of CSSs as a platform for studying complex genetic traits and identifying QTLs.

D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms interact in the modulation of insulin resistance in type 2 diabetic patients

Type 2 deiodinase (D2) converts T4 into its active metabolite T3, an essential step in thyroid metabolism. A Thr92Ala polymorphism in the gene encoding D2 has been inconsistently associated with insulin resistance (IR). Recently, it was reported that the D2 Thr92Ala (rs225014) and the peroxisome proliferator-activated receptor (PPAR) γ2 Pro12Ala (rs1801282) polymorphisms interact in the modulation of metabolic syndrome in nondiabetic subjects. Here, we investigated the effect of both polymorphisms, isolated or in combination, on IR in patients with type 2 diabetes mellitus (DM2). The D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms were genotyped in 721 DM2 patients. IR was evaluated using the homeostasis model assessment-IR (HOMA(IR)) index in a subgroup of 246 DM2 subjects. The frequencies of D2 Ala92 and PPARγ2 Ala12 variants were 0.390 and 0.074, respectively. Patients carrying D2 Ala/Ala genotype had a higher fasting plasma insulin and HOMA(IR) index as compared to patients carrying Thr/Ala or Thr/Thr genotypes (P = 0.022 and P = 0.001, respectively). A significant synergistic effect was observed between D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms on HOMA(IR) index, with carriers of both D2 Ala/Ala genotype and PPARγ2 Ala12 allele showing the highest HOMA(IR) values, after adjusting for age, gender, BMI, and use of medication for DM2 (P = 0.010). In conclusion, DM2 patients harboring both D2 Ala/Ala genotype and PPARγ2 Ala12 allele seem to present more severe IR than those with other D2/PPARγ2 genotype combinations. These findings suggest that these polymorphisms interact in the IR modulation, which may constitute a potential therapeutic target.

Updated genetic score based on 34 confirmed type 2 diabetes Loci is associated with diabetes incidence and regression to normoglycemia in the diabetes prevention program

OBJECTIVE

Over 30 loci have been associated with risk of type 2 diabetes at genome-wide statistical significance. Genetic risk scores (GRSs) developed from these loci predict diabetes in the general population. We tested if a GRS based on an updated list of 34 type 2 diabetes-associated loci predicted progression to diabetes or regression toward normal glucose regulation (NGR) in the Diabetes Prevention Program (DPP).

RESEARCH DESIGN AND METHODS

We genotyped 34 type 2 diabetes-associated variants in 2,843 DPP participants at high risk of type 2 diabetes from five ethnic groups representative of the U.S. population, who had been randomized to placebo, metformin, or lifestyle intervention. We built a GRS by weighting each risk allele by its reported effect size on type 2 diabetes risk and summing these values. We tested its ability to predict diabetes incidence or regression to NGR in models adjusted for age, sex, ethnicity, waist circumference, and treatment assignment.

RESULTS

In multivariate-adjusted models, the GRS was significantly associated with increased risk of progression to diabetes (hazard ratio [HR] = 1.02 per risk allele [95% CI 1.00-1.05]; P = 0.03) and a lower probability of regression to NGR (HR = 0.95 per risk allele [95% CI 0.93-0.98]; P < 0.0001). At baseline, a higher GRS was associated with a lower insulinogenic index (P < 0.001), confirming an impairment in β-cell function. We detected no significant interaction between GRS and treatment, but the lifestyle intervention was effective in the highest quartile of GRS (P < 0.0001).

CONCLUSIONS

A high GRS is associated with increased risk of developing diabetes and lower probability of returning to NGR in high-risk individuals, but a lifestyle intervention attenuates this risk.

The emergence of human-evolutionary medical genomics

In this review, I describe how evolutionary genomics is uniquely suited to spearhead advances in understanding human disease risk, owing to the privileged position of genes as fundamental causes of phenotypic variation, and the ability of population genetic and phylogenetic methods to robustly infer processes of natural selection, drift, and mutation from genetic variation at the levels of family, population, species, and clade. I first provide an overview of models for the origins and maintenance of genetically based disease risk in humans. I then discuss how analyses of genetic disease risk can be dovetailed with studies of positive and balancing selection, to evaluate the degree to which the 'genes that make us human' also represent the genes that mediate risk of polygenic disease. Finally, I present four basic principles for the nascent field of human evolutionary medical genomics, each of which represents a process that is nonintuitive from a proximate perspective. Joint consideration of these principles compels novel forms of interdisciplinary analyses, most notably studies that (i) analyze tradeoffs at the level of molecular genetics, and (ii) identify genetic variants that are derived in the human lineage or in specific populations, and then compare individuals with derived versus ancestral alleles.

Type 2 diabetes (T2D) associated polymorphisms regulate expression of adjacent transcripts in transformed lymphocytes, adipose, and muscle from Caucasian and African-American subjects

CONTEXT

Genome-wide association scans (GWAS) have identified novel single nucleotide polymorphisms (SNPs) that increase T2D susceptibility and indicated the role of nearby genes in T2D pathogenesis.

OBJECTIVE

We hypothesized that T2D-associated SNPs act as cis-regulators of nearby genes in human tissues and that expression of these transcripts may correlate with metabolic traits, including insulin sensitivity (S(I)).

DESIGN, SETTINGS, AND PATIENTS

Association of SNPs with the expression of their nearest transcripts was tested in adipose and muscle from 168 healthy individuals who spanned a broad range of S(I) and body mass index (BMI) and in transformed lymphocytes (TLs). We tested correlations between the expression of these transcripts in adipose and muscle with metabolic traits. Utilizing allelic expression imbalance (AEI) analysis we examined the presence of other cis-regulators for those transcripts in TLs.

RESULTS

SNP rs9472138 was significantly (P = 0.037) associated with the expression of VEGFA in TLs while rs6698181 was detected as a cis-regulator for the PKN2 in muscle (P = 0.00027) and adipose (P = 0.018). Significant association was also observed for rs17036101 (P = 0.001) with expression of SYN2 in adipose of Caucasians. Among 19 GWAS-implicated transcripts, expression of VEGFA in adipose was correlated with BMI (r = -0.305) and S(I) (r = 0.230). Although only a minority of the T2D-associated SNPs were validated as cis-eQTLs for nearby transcripts, AEI analysis indicated presence of other cis-regulatory polymorphisms in 54% of these transcripts.

CONCLUSIONS

Our study suggests that a small subset of GWAS-identified SNPs may increase T2D susceptibility by modulating expression of nearby transcripts in adipose or muscle.

Genome-wide association studies of atrial fibrillation: past, present, and future

Genome-wide association studies (GWAS) for atrial fibrillation (AF) have identified three distinct genetic loci on chromosomes 1q21, 4q25, and 16q22 that are associated with the arrhythmia. Susceptibility loci also have been identified by GWAS for PR interval duration, a quantitative phenotype related to AF. In this review article, we have sought to summarize the latest findings for population-based genetic studies of AF, to highlight ongoing functional studies, and to explore the future directions of genetic research on AF.

Genetic risk factors for stroke in the genome-wide association era

IMPORTANCE OF THE FIELD

Recent genome-wide association studies (GWASs) have renewed interest in genetic determinants of a wide range of complex traits and disorders, including stroke.

AREAS COVERED IN THIS REVIEW

This paper reviews the current knowledge of genes that contribute to rare monogenic forms of stroke as well as more common 'garden variety' forms, focusing on the results of GWASs. Potential clinical pharmacogenetic and diagnostic applications of this information are considered. Publications from 1990 to September 2010 were identified through a Medline search using terms 'human stroke' and 'genetics', 'monogenic', 'familial', 'mutation', 'genome-wide association study', 'polymorphism', or 'genotype'.

WHAT THE READER WILL GAIN

The review synthesizes and collates the current understanding of genes that are involved across a range of stroke subphenotypes.

TAKE HOME MESSAGE

The complexity of stroke will make translation of genetic findings into new diagnostic or therapeutic tools relatively more challenging than for some other conditions and tempers the authors' enthusiasm for the eventual clinical utility of this information.