Heritability of carotid artery intima-medial thickness in type 2 diabetes

Heritability of carotid intima-media thickness and inflammatory factors of atherosclerosis in a Chinese population

Carotid intima-media thickness (cIMT), a marker of subclinical atherosclerosis, has been found to be associated with incident stroke. High-sensitivity C-reactive protein (CRP) and fibrinogen have been demonstrated to be associated with atherosclerosis. Previous studies on heritability estimates of IMT, CRP, and fibrinogen among Chinese populations are limited. This study aims to estimate the heritability of these risk factors in residents who participated in the Taichung Community Health Study (TCHS) and their family members. A total of 2671 study subjects from 805 families were enrolled in the study, selected from a random sample of TCHS participants and their family members. CRP, and fibrinogen were obtained from each participant, and a questionnaire interview was conducted. cIMT was measured by high-resolution B-mode ultrasound and expressed as the mean of the maximum. Heritability estimates and the familial correlation of cIMT, CRP, and fibrinogen among family pairs were determined with SAGE software. With multivariate adjustments, significant heritability was found for cIMT (h2 = 0.26, P < 0.001), CRP (h2 = 0.34, P < 0.001), and fibrinogen (h2 = 0.48, P < 0.001). The intrafamilial correlation coefficients for the three indexes in the parent-offspring pairs were significant (P < 0.001) and ranged from 0.17 to 0.41. The full sibship correlations were also significant (P < 0.001) for the three indexes and ranged from 0.19 to 0.47. This study indicates that a moderate proportion of the variability in CRP, fibrinogen, and cIMT can be attributed to genetic factors in Chinese populations. The findings suggest that CRP is associated with cIMT, whereas no significant association exists between fibrinogen and cIMT.

Influence of Race and High Laminar Shear Stress on TNFR1 Signaling in Endothelial Cells

Tumor necrosis factor (TNF) binding to endothelial TNF receptor-I (TNFR-I) facilitates monocyte recruitment and chronic inflammation, leading to the development of atherosclerosis. In vitro data show a heightened inflammatory response and atherogenic potential in endothelial cells (ECs) from African American (AA) donors. High laminar shear stress (HSS) can mitigate some aspects of racial differences in endothelial function at the cellular level. We examined possible racial differences in TNF-induced monocyte adhesion and TNFR1 signaling complex expression/activity, along with the effects of HSS. Tohoku Hospital Pediatrics-1 (THP-1) monocytes were used in a co-culture system with human umbilical vein ECs (HUVECs) from Caucasian American (CA) and AA donors to examine racial differences in monocyte adhesion. An in vitro exercise mimetic model was applied to investigate the potential modulatory effect of HSS. THP-1 adherence to ECs and TNF-induced nuclear factor kappa B (NF-κB) DNA binding were elevated in AA ECs compared to CA ECs, but not significantly. We report no significant racial differences in the expression of the TNFR-I signaling complex. Application of HSS significantly increased the expression and shedding of TNFR-I and the expression of TRAF3, and decreased the expression of TRAF5 in both groups. Our data does not support TNF-induced NF-κB activation as a potential mediator of racial disparity in this model. Other pathways and associated factors activated by the TNFR1 signaling complex are recommended targets for future research.

Systematic Heritability and Heritability Enrichment Analysis for Diabetes Complications in UK Biobank and ACCORD Studies

Diabetes-related complications reflect longstanding damage to small and large vessels throughout the body. In addition to the duration of diabetes and poor glycemic control, genetic factors are important contributors to the variability in the development of vascular complications. Early heritability studies found strong familial clustering of both macrovascular and microvascular complications. However, they were limited by small sample sizes and large phenotypic heterogeneity, leading to less accurate estimates. We take advantage of two independent studies-UK Biobank and the Action to Control Cardiovascular Risk in Diabetes trial-to survey the single nucleotide polymorphism heritability for diabetes microvascular (diabetic kidney disease and diabetic retinopathy) and macrovascular (cardiovascular events) complications. Heritability for diabetic kidney disease was estimated at 29%. The heritability estimate for microalbuminuria ranged from 24 to 60% and was 41% for macroalbuminuria. Heritability estimates of diabetic retinopathy ranged from 6 to 33%, depending on the phenotype definition. More severe diabetes retinopathy possessed higher genetic contributions. We show, for the first time, that rare variants account for much of the heritability of diabetic retinopathy. This study suggests that a large portion of the genetic risk of diabetes complications is yet to be discovered and emphasizes the need for additional genetic studies of diabetes complications.

Multiethnic Genome-Wide Association Study of Subclinical Atherosclerosis in Individuals With Type 2 Diabetes

BACKGROUND

Coronary artery calcification (CAC) and carotid artery intima-media thickness (cIMT) are measures of subclinical atherosclerosis in asymptomatic individuals and strong risk factors for cardiovascular disease. Type 2 diabetes (T2D) is an independent cardiovascular disease risk factor that accelerates atherosclerosis.

METHODS

We performed meta-analyses of genome-wide association studies in up to 2500 T2D individuals of European ancestry (EA) and 1590 T2D individuals of African ancestry with or without exclusion of prevalent cardiovascular disease, for CAC measured by cardiac computed tomography, and 3608 individuals of EA and 838 individuals of African ancestry with T2D for cIMT measured by ultrasonography within the CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) Consortium.

RESULTS

We replicated 2 loci (rs9369640 and rs9349379 near PHACTR1 and rs10757278 near CDKN2B) for CAC and one locus for cIMT (rs7412 and rs445925 near APOE-APOC1) that were previously reported in the general EA populations. We identified one novel CAC locus (rs8000449 near CSNK1A1L/LINC00547/POSTN at 13q13.3) at P=2.0×10-8 in EA. No additional loci were identified with the meta-analyses of EA and African ancestry. The expression quantitative trait loci analysis with nearby expressed genes derived from arterial wall and metabolic tissues from the Genotype-Tissue Expression project pinpoints POSTN, encoding a matricellular protein involved in bone formation and bone matrix organization, as the potential candidate gene at this locus. In addition, we found significant associations (P<3.1×10-4) for 3 previously reported coronary artery disease loci for these subclinical atherosclerotic phenotypes (rs2891168 near CDKN2B-AS1 and rs11170820 near FLJ12825 for CAC, and rs7412 near APOE for cIMT).

CONCLUSIONS

Our results provide potential biological mechanisms that could link CAC and cIMT to increased cardiovascular disease risk in individuals with T2D.

Detection of Early Vascular Atherosclerosis in Type 2 Diabetes Mellitus Using Ultrasound Radiofrequency-Data Technique

OBJECTIVES

To quantitatively evaluate changes in vascular elasticity and intima-media thickness (IMT) of the common carotid artery (CCA) with Ultrasound radiofrequency (RF)-data technology in asymptomatic patients with type-2 diabetes mellitus (T2DM) and controls.

MATERIALS AND METHODS

Thirty-seven T2DM patients and 39 controls were enrolled. Arterial elasticity and CCA-IMT were quantitatively assessed by RF-data technology. The CCA diameters in the diastolic and systolic phases, carotid distensibility (CD), IMT, values of stiffness (β) and local pulse wave velocity (PWVβ) were measured and compared between the two groups.

RESULTS

The T2DM group had significantly larger CCA diastolic and systolic diameter, lower CD values, higher IMT measurements (all p < 0.001), and higher values of β and PWVβ (all P < 0.05) than the controls. Significant differences were not revealed in the mean values of IMT, β, PWVβ and CD across both sides of the CCA (all P > 0.05).

CONCLUSIONS

Higher IMT measurement and lower arterial elasticity of the CCA are significantly pronounced in asymptomatic T2DM patients and may suggest atherosclerotic changes, and the ultrasound RF-data technique may be used as a potential approach for detection of early-stage atherosclerosis.

An Early-Onset Subgroup of Type 2 Diabetes: A Multigenerational, Prospective Analysis in the Framingham Heart Study

OBJECTIVE

To assess the relation of type 2 diabetes occurring earlier (age <55 years) versus later in life to the risk of cardiovascular death and to diabetes in offspring.

RESEARCH DESIGN AND METHODS

In the Framingham Heart Study, a community-based prospective cohort study, glycemic status was ascertained at serial examinations over six decades among 5,571 first- and second-generation participants with mortality data and 2,123 second-generation participants who initially did not have diabetes with data on parental diabetes status. We assessed cause of death in a case (cardiovascular death)-control (noncardiovascular death) design and incident diabetes in offspring in relation to parental early-onset diabetes.

RESULTS

Among the participants in two generations (N = 5,571), there were 1,822 cardiovascular deaths (including 961 coronary deaths). The odds of cardiovascular versus noncardiovascular death increased with decreasing age of diabetes onset (P < 0.001 trend). Compared with never developing diabetes, early-onset diabetes conferred a 1.81-fold odds (95% CI 1.10-2.97, P = 0.02) of cardiovascular death and 1.75-fold odds (0.96-3.21, P = 0.07) of coronary death, whereas later-onset diabetes was not associated with greater risk for either (P = 0.09 for cardiovascular death; P = 0.51 for coronary death). In second-generation participants, having a parent with early-onset diabetes increased diabetes risk by 3.24-fold (1.73-6.07), whereas having one or both parents with late-onset diabetes increased diabetes risk by 2.19-fold (1.50-3.19).

CONCLUSIONS

Our findings provide evidence for a diabetes subgroup with an early onset, a stronger association with cardiovascular death, and higher transgenerational transmission.

Genetics of diabetes mellitus and diabetes complications

Diabetes is one of the fastest growing diseases worldwide, projected to affect 693 million adults by 2045. Devastating macrovascular complications (cardiovascular disease) and microvascular complications (such as diabetic kidney disease, diabetic retinopathy and neuropathy) lead to increased mortality, blindness, kidney failure and an overall decreased quality of life in individuals with diabetes. Clinical risk factors and glycaemic control alone cannot predict the development of vascular complications; numerous genetic studies have demonstrated a clear genetic component to both diabetes and its complications. Early research aimed at identifying genetic determinants of diabetes complications relied on familial linkage analysis suited to strong-effect loci, candidate gene studies prone to false positives, and underpowered genome-wide association studies limited by sample size. The explosion of new genomic datasets, both in terms of biobanks and aggregation of worldwide cohorts, has more than doubled the number of genetic discoveries for both diabetes and diabetes complications. We focus herein on genetic discoveries for diabetes and diabetes complications, empowered primarily through genome-wide association studies, and emphasize the gaps in research for taking genomic discovery to the next level.

Targeted sequencing of linkage region in Dominican families implicates PRIMA1 and the SPATA7-PTPN21-ZC3H14-EML5-TTC8 locus in carotid-intima media thickness and atherosclerotic events

Carotid intima-media thickness (cIMT) is a subclinical marker for atherosclerosis. Previously, we reported a quantitative trait locus (QTL) for total cIMT on chromosome 14q and identified PRiMA1, FOXN3 and CCDC88C as candidate genes using a common variants (CVs)-based approach. Herein, we further evaluated the genetic contribution of the QTL to cIMT by resequencing. We sequenced all exons within the QTL and genomic regions of PRiMA1, FOXN3 and CCDC88C in Dominican families with evidence for linkage to the QTL. Unrelated Dominicans from the Northern Manhattan Study (NOMAS) were used for validation. Single-variant-based and gene-based analyses were performed for CVs and rare variants (RVs). The strongest evidence for association with CVs was found in PRiMA1 (p = 8.2 × 10⁻⁵ in families, p = 0.01 in NOMAS at rs12587586), and in the five-gene cluster SPATA7-PTPN21-ZC3H14-EML5-TTC8 locus (p = 1.3 × 10⁻⁴ in families, p = 0.01 in NOMAS at rs2274736). No evidence for association with RVs was found in PRiMA1. The top marker from previous study in PRiMA1 (rs7152362) was associated with fewer atherosclerotic events (OR = 0.67; p = 0.02 in NOMAS) and smaller cIMT (β = −0.58, p = 2.8 × 10⁻⁴ in Family). Within the five-gene cluster, evidence for association was found for exonic RVs (p = 0.02 in families, p = 0.28 in NOMAS), which was enriched among RVs with higher functional potentials (p = 0.05 in NOMAS for RVs in the top functional tertile). In summary, targeted resequencing provided validation and novel insights into the genetic architecture of cIMT, suggesting stronger effects for RVs with higher functional potentials. Furthermore, our data support the clinical relevance of CVs associated with subclinical atherosclerosis.

Leveraging Genetics to Improve Cardiovascular Health in Diabetes: The 2018 Edwin Bierman Award Lecture

The past decade has witnessed an exponential increase in our ability to search the genome for genetic factors predisposing to cardiovascular disease (CVD) and in particular coronary heart disease (CHD). Identifying these genes could lead to the development of innovative strategies to prevent the cardiovascular complications of diabetes by allowing us to 1) create predictive algorithms for the identification of patients at especially high risk of CVD so that these individuals can undergo preventive interventions early in the natural history of the disease; 2) discover as yet unknown disease pathways linking diabetes to atherosclerosis, which can be used as targets for the development of new CVD-preventing drugs specifically directed at subjects with diabetes; and 3) devise personalized programs increasing the cost-effectiveness of preventive interventions by tailoring them to the genetic background of each patient. Substantial progress has been made in each of these three areas as exemplified by the recent development of a CHD genetic risk score improving CHD prediction among subjects with type 2 diabetes, the discovery of a diabetes-specific CHD locus on 1q25 pointing to glutamine synthase (GLUL) and the γ-glutamyl cycle as key regulators of CHD risk in diabetes, and the identification of two genetic loci allowing the selection of patients with type 2 diabetes who may especially benefit from intensive glycemic control. Translating these discoveries into clinical practice will not be without challenges, but the potential rewards, from the perspective of public health as well as that of persons with diabetes, make this goal worth pursuing.

Genetic determinants of blood pressure traits are associated with carotid arterial thickening and plaque formation in patients with type 2 diabetes

OBJECTIVES

The aim of this study is to explore the contribution of genetically driven cardiometabolic risk factors for development of carotid arterial thickening in patients with type 2 diabetes.

METHODS

In total, 12 genetic risk scores for blood pressure, blood lipids and glycaemic traits were constructed. The genetic risk scores were tested for association with carotid intima-media thickness and plaques in patients with type 2 diabetes ( n = 401) and in non-diabetic individuals ( n = 648) and for association with glucose levels in two population-based cohorts ( n = 1328 and n = 6161).

RESULTS

In patients with type 2 diabetes, the genetic risk scores for pulse pressure were positively associated with plaque formation ( β = 0.036 ± 0.01 standard deviation/allele, p = 0.003). The genetic risk score for diastolic blood pressure was negatively associated with carotid intima-media thickness ( β = -0.037 ± 0.01 standard deviation/allele, p = 0.005), although not significant after correction for multiple testing ( p < 0.0042). In a meta-analysis of individuals with and without type 2 diabetes, the high-density lipoprotein genetic risk scores showed a trend towards an inverse association with carotid intima-media thickness and plaques, while the low-density lipoprotein genetic risk scores showed a trend towards a positive association with plaque formation but did reach the statistical threshold.

CONCLUSION

Genetic loci for pulse pressure are associated with plaque formation among patients with type 2 diabetes, suggesting an underlying genetic contribution to arterial stiffening and atherosclerosis.

Thermodynamic Modeling of the Statistics of Cell Spreading on Ligand-Coated Elastic Substrates

Biological spread cells exist in a perpetually fluctuating state and therefore cannot be described in terms of a unique deterministic system. For modeling approaches to provide novel insight and uncover new mechanisms that drive cell behavior, a framework is required that progresses from traditional deterministic methods (whereby simulation of an experiment predicts a single outcome). In this study, we implement a new, to our knowledge, modeling approach for the analysis of cell spreading on ligand-coated substrates, extending the framework for nonequilibrium thermodynamics of cells developed by Shishvan et al. to include active focal adhesion assembly. We demonstrate that the model correctly predicts the coupled influence of surface collagen density and substrate stiffness on cell spreading, as reported experimentally by Engler et al. Low surface collagen densities are shown to result in a high probability that cells will be restricted to low spread areas. Furthermore, elastic free energy induced by substrate deformation lowers the probability of observing a highly spread cell, and, consequentially, lower cell tractions affect the assembly of focal adhesions. Experimentally measurable observables such as cell spread area and aspect ratio can be directly postprocessed from the computed homeostatic ensemble of (several million) spread states. This allows for the prediction of mean and SDs of such experimental observables. This class of cell mechanics modeling presents a significant advance on conventional deterministic approaches.

Precision medicine in diabetes prevention, classification and management

Diabetes has become a major burden of healthcare expenditure. Diabetes management following a uniform treatment algorithm is often associated with progressive treatment failure and development of diabetic complications. Recent advances in our understanding of the genomic architecture of diabetes and its complications have provided the framework for development of precision medicine to personalize diabetes prevention and management. In the present review, we summarized recent advances in the understanding of the genetic basis of diabetes and its complications. From a clinician's perspective, we attempted to provide a balanced perspective on the utility of genomic medicine in the field of diabetes. Using genetic information to guide management of monogenic forms of diabetes represents the best-known examples of genomic medicine for diabetes. Although major strides have been made in genetic research for diabetes, its complications and pharmacogenetics, ongoing efforts are required to translate these findings into practice by incorporating genetic information into a risk prediction model for prioritization of treatment strategies, as well as using multi-omic analyses to discover novel drug targets with companion diagnostics. Further research is also required to ensure the appropriate use of this information to empower individuals and healthcare professionals to make personalized decisions for achieving the optimal outcome.

Carotid Artery Atherosclerosis: A Review on Heritability and Genetics

Carotid atherosclerosis (CAS) is associated with increased cardiovascular risk, and therefore, assessing the genetic versus environmental background of CAS traits is of key importance. Carotid intima-media-thickness and plaque characteristics seem to be moderately heritable, with remarkable differences in both heritability and presence or severity of these traits among ethnicities. Although the considerable role of additive genetic effects is obvious, based on the results so far, there is an important emphasis on non-shared environmental factors as well. We aimed to collect and summarize the papers that investigate twin and family studies assessing the phenotypic variance attributable to genetic associations with CAS. Genes in relation to CAS markers were overviewed with a focus on genetic association studies and genome-wide association studies. Although the role of certain genes is confirmed by studies conducted on large populations and meta-analyses, many of them show conflicting results. A great focus should be on future studies elucidating the exact pathomechanism of these genes in CAS in order to imply them as novel therapeutic targets.

Carotid Plaque Characterization with Contrast-Enhanced Ultrasound Imaging and its Histological Validation

Introduction

Better methods are needed to determine the course of intervention in patients with atherosclerosis; therefore, plaque characterization is increasing in importance. Current guidelines suggest that the degree of stenosis and symptoms are the only criteria for the selection of the surgical intervention. However, there remain some challenges. The characterization of plaque morphology may help determine the best course of therapy. Magnetic resonance imaging and computed tomography are current standard techniques to evaluate plaque morphology, but they are expensive and unsuitable for long term surveillance and monitoring.

Objective

In this research, an ultrasound-based methodology for the characterization of carotid plaques is shown. This technique requires the injection of a small volume (approximately 1.5 mL) of contrast agent and the acquisition of postcontrast images. The rationale of this technique is that poorly perfused tissues (such as lipids) show a lower contrast enhancement with respect to highly perfused tissues (such as fibrous and muscular tissue).

Methods

The technique consists of two steps. First, the plaque region is automatically segmented by a completely user-independent algorithm. Then, the portion of the wall corresponding to the plaque is analyzed and color-coded intensity is assigned to a specific tissue. Performance evaluation was performed against histology. Twenty plaque specimens were sent to pathology for reporting. Correlation of the histology report and of the contrast-enhanced ultrasound analysis was performed.

Results

Plaque components that could be effectively identified were thrombi, lipids, fibrous/muscular tissue, and calcium. Overall the errors on 20 plaques between automated classification and histology were: 3.1 ± 1.1% for thrombus, 4.2 ± 1.5% for lipids, 5 ± 3.4% for fibrous/muscular tissue, and 3.2 ± 1.0% for calcium.

Conclusion

Despite the need for further investigation and a quantitative evaluation of the results, this methodology showed encouraging results. This analysis architecture is undergoing validation in a neurology division and is aimed at being used for the follow-up of patients and quantification of drug therapy effects.

HMGA1 Mediated High-Glucose-Induced Vascular Smooth Muscle Cell Proliferation in Diabetes Mellitus: Association Between PI3K/Akt Signaling and HMGA1 Expression

High-mobility group protein A1 (HMGA1), an architectural transcription factor, was found to regulate multiple gene expression in mammals. Recent studies firmly indicate an association between HMGA1 and type 2 diabetes. However, the presence and function of HMGA1 in diabetic vasculopathy has not been substantiated. in this study, we first determined the HMGA1 changes in aorta tissue of diabetic rats. In streptozotocin-induced diabetic rats, a higher level of blood glucose and plasma lipids, an increase of intima-media thickness, and a significant upregulation and accumulation of HMGA1, mainly in the nucleus and around the nuclear membrane of vascular smooth muscle cells (VSMCs), were detected. In vitro, high glucose increased HMGA1 expression and promoted proliferation of VSMCs, which could be blunted by Wortmannin and LY294002, inhibitors of PI3K/Akt pathway, and specificity protein 1 (SP1) siRNA. Moreover, knockdown of HMGA1 could weaken the upregulation of cyclin D1 accompanied by high-glucose-induced HMGA1 in VSMCs. Taken together, these findings demonstrate the vital role of PI3K/Akt-SP1-HMGA1 pathway in high-glucose-induced VSMCs proliferation.

Genetic basis of diabetic kidney disease and other diabetic complications

Diabetic kidney disease and other long-term complications are common in diabetes, and comprise the main cause of co-morbidity and premature mortality in individuals with diabetes. While familial clustering and heritability have been reported for all diabetic complications, the genetic background and the molecular mechanisms remain poorly understood. In recent years, genome-wide association studies have identified a few susceptibility loci for the renal complications as well as for diabetic retinopathy, diabetic cardiovascular disease and mortality. As for many complex diseases, the genetic factors increase the risk of complications in concert with the environment, and certain associations seem specific for particular conditions, for example, SP3-CDCA7 associated with end-stage renal disease only in women, or MGMT and variants on chromosome 5q13 associated with cardiovascular mortality only under tight glycaemic control. The characterization of the phenotypes is one of the main challenges for genetic research on diabetic complications, in addition to an urgent need to increase the number of individuals with diabetes with high quality phenotypic data to be included in future genetic studies.

Progress in Defining the Genetic Basis of Diabetic Complications

PURPOSE OF REVIEW

Diabetic complications affecting the kidneys, retina, nerves, and the cardiovasculature are the major causes of morbidity and mortality in diabetes. This paper aims to review the current understanding of the genetic basis of these complications, based on recent findings especially from genome-wide association studies.

RECENT FINDINGS

Variants in or near AFF3, RGMA-MCTP2, SP3-CDCA7, GLRA3, CNKSR3, and UMOD have reached genome-wide significance (p value <5 × 10^-8) for association with diabetic kidney disease, and recently, GRB2 was reported to be associated at genome-wide significance with diabetic retinopathy. While some loci affecting cardiovascular disease in the general population have been replicated in diabetes, GLUL affects the risk of cardiovascular disease specifically in diabetic subjects. Genetic findings are emerging for diabetic complications, although the studies remain relatively small compared to those for type 1 and type 2 diabetes. In addition to pinpointing specific loci, the studies also reveal biological information on correlated traits and pathways.

Rare Variants in NOD1 Associated with Carotid Bifurcation Intima-Media Thickness in Dominican Republic Families

Cardiovascular disorders including ischemic stroke (IS) and myocardial infarction (MI) are heritable; however, few replicated loci have been identified. One strategy to identify loci influencing these complex disorders is to study subclinical phenotypes, such as carotid bifurcation intima-media thickness (bIMT). We have previously shown bIMT to be heritable and found evidence for linkage and association with common variants on chromosome 7p for bIMT. In this study, we aimed to characterize contributions of rare variants (RVs) in 7p to bIMT. To achieve this aim, we sequenced the 1 LOD unit down region on 7p in nine extended families from the Dominican Republic (DR) with strong evidence for linkage to bIMT. We then performed the family-based sequence kernel association test (famSKAT) on genes within the 7p region. Analyses were restricted to single nucleotide variants (SNVs) with population based minor allele frequency (MAF) <5%. We first analyzed all exonic RVs and then the subset of only non-synonymous RVs. There were 68 genes in our analyses. Nucleotide-binding oligomerization domain (NOD1) was the most significantly associated gene when analyzing exonic RVs (famSKAT p = 9.2x10^-4; number of SNVs = 14). We achieved suggestive replication of NOD1 in an independent sample of twelve extended families from the DR (p = 0.055). Our study provides suggestive statistical evidence for a role of rare variants in NOD1 in bIMT. Studies in mice have shown Nod1 to play a role in heart function and atherosclerosis, providing biologic plausibility for a role in bIMT thus making NOD1 an excellent bIMT candidate.

Hepatic steatosis is associated with cardiometabolic risk in a rural Indian population: A prospective cohort study

BACKGROUND/OBJECTIVES

While adiposity and hepatic steatosis are linked to cardiovascular risk in developed countries, their prevalence and impact in low-income countries are poorly understood. We investigated the association of anthropomorphic variables and hepatic steatosis with cardiometabolic risk profiles and subclinical cardiovascular disease (CVD) in a large rural Indian cohort.

METHODS

In 4691 individuals in the Birbhum Population Project in West Bengal, India, we performed liver ultrasonography, carotid ultrasound and biochemical and clinical profiling. We assessed the association of hepatic steatosis and anthropomorphic indices (BMI, waist circumference) with CVD risk factors (dysglycemia, dyslipidemia, hypertension) and subclinical CVD (by carotid intimal-medial thickness).

RESULTS

Rural Indians exhibited a higher visceral adiposity index and pro-atherogenic dyslipidemia at a lower BMI than Americans. Individuals with any degree of hepatic steatosis by ultrasound had a greater probability of dysglycemia (adjusted odds ratio, OR=1.67, 95% CI 1.31-2.12, P<0.0001) and pro-atherogenic dyslipidemia (OR=1.33, 95% CI 1.07-1.63, P=0.009). We observed a positive association between liver fat, adiposity and carotid intimal-medial thickness (CIMT) in an unadjusted model (β=0.02, P=0.0001); the former was extinguished after adjustment for cardiometabolic risk factors.

CONCLUSIONS

In a large population of rural Indians, hepatic steatosis and waist circumference were associated with prevalent cardiometabolic risk and subclinical CVD at lower BMI relative to multi-ethnic Americans, though the association of the former with subclinical CVD was extinguished after adjustment. These results underscore the emerging relevance of hepatic steatosis and adiposity in the developing world, and suggest efforts to target these accessible phenotypes for cardiometabolic risk prevention.

A Report of the Women's Health Congress Workshop on The Health of Women of Color: A Critical Intersection at the Corner of Sex/Gender and Race/Ethnicity

Women of color face unique health challenges that differ significantly from those of other women and men of color. To bring these issues to light, the National Institutes of Health (NIH) Office of Research on Women's Health sponsored a preconference workshop at the 23rd Annual Women's Health Congress, which was held in Washington, DC, in April 2015. The workshop featured presentations by NIH intramural and extramural scientists who provided insight on the disparities of a wide range of conditions, including cancer, cardiovascular disease, the risk of HIV infection, and disability in an aging population. In this study, we highlight the major points of each presentation and the ensuing discussion.

Analysis of advanced glycation end products in the DHS Mind Study

AIMS

Human studies of links between advanced glycation end-products (AGEs) and disease phenotypes are less common than studies of animal and cell models. Here, we examined the association of total AGEs with diabetes risk factors in a predominately type 2 diabetes (T2D) affected cohort.

METHODS

AGEs were measured using an enzyme linked immunosorbant assay in 816 individuals from the DHS Mind Study (n=709 T2D affected), and association analyses were completed.

RESULTS

Total AGEs were associated with estimated glomerular filtration rate (p=0.0054; β=-0.1291) and coronary artery calcification (p=0.0352; β=1.1489) in the entire cohort. No significant associations were observed when individuals with T2D were analyzed separately. In individuals without T2D, increased circulating AGEs were associated with increased BMI (p=0.02, β=0.138), low density lipoproteins (p=0.046, β=17.07) and triglycerides (p=0.0004, β=0.125), and decreased carotid artery calcification (p=0.0004, β=-1.2632) and estimated glomerular filtration rate (p=0.0018, β=-0.1405). Strong trends were also observed for an association between AGEs and poorer cognitive performance on the digit symbol substitution test (p=0.046, β=-6.64) and decreased grey matter volume (p=0.037, β=-14.87).

CONCLUSIONS

AGEs may play an important role in a number of phenotypes and diseases, although not necessarily in interindividual variation in people with T2D. Further evaluation of specific AGE molecules may shed more light on these relationships.

Sequencing of candidate genes in Dominican families implicates both rare exonic and common non-exonic variants for carotid intima-media thickness at bifurcation

Through linkage and tagSNP-based association studies in 100 Dominican Republic (DR) families, we previously identified ANLN and AOAH (7p14.3) as candidate genes for carotid intima-media thickness at bifurcation (bIMT). Introns, exons, and flanking regions of ANLN and AOAH were re-sequenced in 151 individuals from nine families with evidence for linkage at 7p14.3. For common variants [CV, minor allele frequency (MAF) ≥5 %], single variant-based analysis was performed. For rare variants (RV, MAF < 5 %), gene-based analysis aggregating all RVs within a gene was performed. CV analysis revealed the strongest signal at rs3815483 (P = 0.0003) in ANLN and rs60023210 (P = 0.00005) in AOAH. In ANLN, RV analysis found suggestive evidence for association with exonic RVs (P = 0.08), and in particular non-synonymous RVs (P = 0.04) but not with all RVs (P = 0.15). The variant alleles of all non-synonymous RVs segregated with the major allele of rs3815483 and were associated with lower bIMT while a novel synonymous RV segregated with the minor allele of rs3815483 and was associated with greater bIMT. Additional analysis in 561 DR individuals found suggestive evidence for association with all ANLN non-synonymous RVs (P = 0.08). In AOAH, no evidence for association with RVs was detected. Instead, conditional analysis revealed that multiple independent intronic CVs are associated with bIMT in addition to rs60023210. We demonstrate the utility of using family-based studies to evaluate the contribution of RVs. Our data suggest two modes of genetic architecture underlying the linkage and association at ANLN (multiple exonic RVs) and AOAH (multiple intronic CVs with uncharacterized functions).

Genetics of cardiovascular and renal complications in diabetes

The development of debilitating complications represents a major heathcare burden associated with the treatment of diabetes. Despite advances in new therapies for controlling hyperglycemia, the burden associated with diabetic complications remains high, especially in relation to cardiovascular and renal complications. Furthermore, an increasing proportion of patients develop type 2 diabetes at a younger age, putting them at higher risk of developing complications as a result of the increased exposure to hyperglycemia. Diabetes has become the main contributing cause to end‐stage renal disease in most countries. Although there has been important breakthroughs in our understanding of the genetics of type 1 and type 2 diabetes, bringing important insights towards the pathogenesis of diabetes, there has been comparatively less progress in our understanding of the genetic basis of diabetic complications. Genome‐wide association studies are beginning to expand our understanding of the genetic architecture relating to diabetic complications. Improved understanding of the genetic basis of diabetic cardiorenal complications might provide an opportunity for improved risk prediction, as well as the development of new therapies.

Infrequent TRIB3 coding variants and coronary artery disease in type 2 diabetes

OBJECTIVE

Genes that modulate insulin sensitivity may also be involved in shaping the risk of coronary artery disease (CAD). The relatively common TRIB3 Q84R polymorphism (rs2295490) has been associated with abnormal insulin signaling, endothelial dysfunction, insulin resistance, and pro-atherogenic phenotypes. The aim of our study was to investigate the association between low-frequency TRIB3 coding variants and CAD in patients with type 2 diabetes (T2D).

METHODS

Three case-control studies for CAD from Italy and US were analyzed, for a total of 1565 individuals, all with type 2 diabetes. Infrequent variants were identified by re-sequencing TRIB3 exons in 140 "extreme cases" and 140 "super-controls" and then genotyped in all study subjects.

RESULTS

TRIB3 infrequent variants (n = 8), considered according to a collapsing rare variants framework, were significantly associated with CAD in diabetic patients from Italy (n = 700, OR = 0.43, 95% CI 0.20-0.91; p = 0.027), but not from the US (n = 865, OR = 1.22, 95% CI 0.69-2.18; p = 0.49). In the Italian sets, the association was especially strong among individuals who also carried the common R84 variant.

CONCLUSION

Although preliminary, our finding suggests a role of TRIB3 low-frequency variants on CAD among Italian patients with T2D. Further studies are needed to address the role of TRIB3 infrequent variants in other populations of both European and non-European ancestries.

Genetic Variant at the GLUL Locus Predicts All-Cause Mortality in Patients With Type 2 Diabetes

Single nucleotide polymorphism (SNP) rs10911021 at the glutamate-ammonia ligase (GLUL) locus has been associated with an increased risk of coronary heart disease in individuals with type 2 diabetes. The effect of this SNP on mortality was investigated among 1,242 white subjects with type 2 diabetes from the Joslin Kidney Study (JKS) (n = 416) and the Gargano Mortality Study (GMS) (n = 826). During a mean follow-up of 12.8 ± 5.8 and 7.5 ± 2.2 years, respectively, a total of 215 and 164 deaths were observed in the two studies. In both cohorts, the all-cause mortality rate significantly increased with the number of rs10911021 risk alleles, with allelic hazard ratios (HRs) of 1.32 (95% CI 1.07-1.64, P = 0.01), 1.30 (1.10-1.69, P = 0.04), and 1.32 (1.12-1.55, P = 0.0011), respectively, in the JKS, the GMS, and the two studies combined. These associations were not affected by adjustment for possible confounders. In the JKS, for which data on causes of death were available, the HR for cardiovascular mortality was 1.51 (1.12-2.04, P = 0.0077) as opposed to 1.15 (0.84-1.55, P = 0.39) for mortality from noncardiovascular causes. These findings point to SNP rs10911021 as an independent modulator of mortality in patients with type 2 diabetes and, together with the previous observation, suggest that this results from an effect of this variant on cardiovascular risk.

Genetic variants in LEKR1 and GALNT10 modulate sex-difference in carotid intima-media thickness: a genome-wide interaction study

BACKGROUND

There is an established sex-difference in carotid artery intima-media thickness (cIMT), a recognized marker of subclinical atherosclerosis. However, the genetic underpinnings of sex-differences in gene-IMT associations are largely unknown.

METHODS

With a multistage design using 731,037 single nucleotide polymorphisms (SNP), a genome wide interaction study was performed in a discovery sample of 931 unrelated Hispanics, followed by replication in 153 non-Hispanic whites and 257 non-Hispanic blacks. Assuming an additive genetic model, we tested for sex-SNP interactions on cIMT using regression analysis.

RESULTS

We did not identify any genome-wide significant SNPs but identified 14 loci with suggestive significance. Specifically, SNP-by-sex interaction was found for rs7616559 within LEKR1 gene (P = 3.5E-06 in Hispanic discovery sample, P = 0.018 in White, and P = 1.3E-06 in combined analysis) and for rs2081015 located within GALNT10 gene (P = 4.5E-06 in Hispanic discovery sample, P = 0.042 in Blacks, and P = 5.3E-07 in combined analysis). For rs7616559 within LEKR1, men had greater cIMT than women in G allele carriers (beta ± SE: 0.044 ± 0.007, P = 4.2E-09 in AG carriers; beta ± SE: 0.064 ± 0.007, P = 6.2E-05 in GG carriers). For rs2081015 within GALNT10, men had greater cIMT than women in C allele carriers (beta ± SE: 0.022 ± 0.007, P = 0.002 in CT carriers; beta ± SE: 0.051 ± 0.008, P = 3.1E-10 in CC carriers).

CONCLUSIONS

Our genome-wide interaction analysis reveals multiple loci that may modulate sex difference in cIMT. Of them, genetic variants on LEKR1 and GALNT10 genes have been associated with control of adiposity and weight. Given the consistent findings across different-ethnic groups, further studies are warranted to perform investigations of functional genetic variants in these regions.

Human genetics of diabetic retinopathy

There is evidence demonstrating that genetic factors contribute to the risk of diabetic retinopathy (DR). Genetics variants, structural variants (copy number variation, CNV) and epigenetic changes play important roles in the development of DR. Genetic linkage and association studies have uncovered a number of genetic loci and common genetic variants susceptibility to DR. CNV and interactions of gene by environment have also been detected by association analysis. Apart from nucleus genome, mitochondrial DNA plays critical roles in regulation of development of DR. Epigenetic studies have indicated epigenetic changes in chromatin affecting gene transcription in response to environmental stimuli, which provided a large body of evidence of regulating development of diabetes mellitus. Identification of genetic variants and epigenetic changes contributed to risk or protection of DR will benefit uncovering the complex mechanism underlying DR. This review focused on the current knowledge of the genetic and epigenetic basis of DR.

Heritability and genetic association analysis of neuroimaging measures in the Diabetes Heart Study

Patients with type 2 diabetes are at increased risk of age-related cognitive decline and dementia. Neuroimaging measures such as white matter lesion volume, brain volume, and fractional anisotropy may reflect the pathogenesis of these cognitive declines, and genetic factors may contribute to variability in these measures. This study examined multiple neuroimaging measures in 465 participants from 238 families with extensive genotype data in the type 2 diabetes enriched Diabetes Heart Study-Mind cohort. Heritability of these phenotypes and their association with candidate single-nucleotide polymorphisms (SNPs), and SNP data from genome- and exome-wide arrays were explored. All neuroimaging measures analyzed were significantly heritable (ĥ(2) = 0.55-0.99 in unadjusted models). Seventeen candidate SNPs (from 16 genes/regions) associated with neuroimaging phenotypes in prior studies showed no significant evidence of association. A missense variant (rs150706952, A432V) in PLEKHG4B from the exome-wide array was significantly associated with white matter mean diffusivity (p = 3.66 × 10(-7)) and gray matter mean diffusivity (p = 2.14 × 10(-7)). This analysis suggests genetic factors contribute to variation in neuroimaging measures in a population enriched for metabolic disease and other associated comorbidities.

Cross-sectional analysis of calcium intake for associations with vascular calcification and mortality in individuals with type 2 diabetes from the Diabetes Heart Study

BACKGROUND

The use of calcium supplements to prevent declines in bone mineral density and fractures is widespread in the United States, and thus reports of elevated cardiovascular disease (CVD) risk in users of calcium supplements are a major public health concern. Any elevation in CVD risk with calcium supplement use would be of particular concern in individuals with type 2 diabetes (T2D) because of increased risks of CVD and fractures observed in this population.

OBJECTIVE

In this study, we examined associations between calcium intake from diet and supplements and measures of subclinical CVD (calcified plaque in the coronary artery, carotid artery, and abdominal aorta) and mortality in individuals affected by T2D.

DESIGN

We performed a cross-sectional analysis in individuals affected by T2D from the family-based Diabetes Heart Study (n = 720).

RESULTS

We observed no significant associations of calcium from diet or supplements with any of our measures of calcified plaque, and no greater mortality risk was observed with increased calcium intake. Instead, calcium supplement use was modestly associated with reduced all-cause mortality in women (HR: 0.62; 95% CI: 0.42, 0.92; P = 0.017).

CONCLUSION

Our results do not support a substantial association between calcium intake from diet or supplements and CVD risk in individuals with T2D.

Contributors to mortality in high-risk diabetic patients in the Diabetes Heart Study

OBJECTIVE

Not all individuals with type 2 diabetes and high coronary artery calcified plaque (CAC) experience the same risk for adverse outcomes. This study examined a subset of high-risk individuals based on CAC >1,000 mg (using a total mass score) and evaluated whether differences in a range of modifiable cardiovascular disease (CVD) risk factors provided further insights into risk for mortality.

RESEARCH DESIGN AND METHODS

We assessed contributors to all-cause mortality among 371 European American individuals with type 2 diabetes and CAC >1,000 from the Diabetes Heart Study (DHS) after 8.2 ± 3.0 years (mean ± SD) of follow-up. Differences in known CVD risk factors, including modifiable CVD risk factors, were compared between living (n = 218) and deceased (n = 153) participants. Cox proportional hazards regression models were used to quantify risk for all-cause mortality.

RESULTS

Deceased participants had a longer duration of type 2 diabetes (P = 0.02) and reduced use of cholesterol-lowering medications (P = 0.004). Adjusted analyses revealed that vascular calcified plaque scores were associated with increased risk for mortality (hazard ratio 1.31-1.63; 3.89 × 10(-5) < P < 0.03). Higher HbA1c, lipids, and C-reactive protein and reduced kidney function also were associated with a 1.1- to 1.5-fold increased risk for mortality (3.45 × 10(-6) < P < 0.03) after adjusting for confounding factors.

CONCLUSIONS

Even in this high-risk group, vascular calcification and known CVD risk factors provide useful information for ongoing assessment. The use of cholesterol-lowering medication seemed to be protective for mortality.

Intima modifier locus 2 controls endothelial cell activation and vascular permeability

Carotid intima formation is a significant risk factor for cardiovascular disease. C3H/FeJ (C3H/F) and SJL/J (SJL) inbred mouse strains differ in susceptibility to immune and vascular traits. Using a congenic approach we demonstrated that the Intima modifier 2 (Im2) locus on chromosome 11 regulates leukocyte infiltration. We sought to determine whether inflammation was due to changes in circulating immune cells or activation of vascular wall cells in genetically pure Im2 (C3H/F.SJL.11.1) mice. Complete blood counts showed no differences in circulating monocytes between C3H/F and C3H/F.SJL.11.1 compared with SJL mice. Aortic vascular cell adhesion molecule-1 (VCAM-1) total protein levels were dramatically increased in SJL and C3H/F.SJL.11.1 compared with C3H/F mice. Immunostaining of aortic endothelial cells (EC) showed a significant increase in VCAM-1 expression in SJL and C3H/F.SJL.11.1 compared with C3H/F under steady flow conditions. Immunostaining of EC membranes revealed a significant decrease in EC size in SJL and C3H/F.SJL.11.1 vs. C3H/F in regions of disturbed flow. Vascular permeability was significantly higher in C3H/F.SJL.11.1 compared with C3H/F. Our results indicate that Im2 regulation of leukocyte infiltration is mediated by EC inflammation and permeability. RNA sequencing and pathway analyses comparing genes in the Im2 locus to C3H/F provide insight into candidate genes that regulate vascular wall inflammation and permeability highlighting important genetic mechanisms that control vascular intima in response to injury.

Analysis of common and coding variants with cardiovascular disease in the Diabetes Heart Study

Background

Type 2 diabetes mellitus (T2DM) is a major cardiovascular disease (CVD) risk factor. Identification of genetic risk factors for CVD is important to understand disease risk. Two recent genome-wide association study (GWAS) meta-analyses in the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium detected CVD-associated loci.

Methods

Variants identified in CHARGE were tested for association with CVD phenotypes, including vascular calcification, and conventional CVD risk factors, in the Diabetes Heart Study (DHS) (n = 1208; >80% T2DM affected). This included 36 genotyped or imputed single nucleotide polymorphisms (SNPs) from DHS GWAS data. 28 coding SNPs from 14 top CHARGE genes were also identified from exome sequencing resources and genotyped, along with 209 coding variants from the Illumina HumanExome BeadChip genotype data in the DHS were also tested. Genetic risk scores (GRS) were calculated to evaluate the association of combinations of variants with CVD measures.

Results

After correction for multiple comparisons, none of the CHARGE SNPs were associated with vascular calcification (p < 0.0014). Multiple SNPs showed nominal significance with calcification, including rs599839 (PSRC1, p = 0.008), rs646776 (CELSR2, p = 0.01), and rs17398575 (PIK3CG, p = 0.009). Additional COL4A2 and CXCL12 SNPs were nominally associated with all-cause or CVD-cause mortality. Three SNPs were significantly or nominally associated with serum lipids: rs3135506 (Ser19Trp, APOA5) with triglycerides (TG) (p = 5×10⁻⁵), LDL (p = 0.00070), and nominally with high density lipoprotein (HDL) (p = 0.0054); rs651821 (5′UTR, APOA5) with increased TGs (p = 0.0008); rs13832449 (splice donor, APOC3) associated with decreased TGs (p = 0.0015). Rs45456595 (CDKN2A, Gly63Arg), rs5128 (APOC3, 3′UTR), and rs72650673 (SH2B3, Glu400Lys) were nominally associated with history of CVD, subclinical CVD, or CVD risk factors (p < 0.010). From the exome chip, rs3750103 (CHN2, His204Arg/His68Arg) with carotid intima-medial thickness (IMT) (p = 3.9×10⁻⁵), and rs61937878 (HAL, Val549Met) with infra-renal abdominal aorta CP (AACP) (p = 7.1×10⁻⁵). The unweighted GRS containing coronary artery calcified plaque (CAC) SNPs was nominally associated with history of prior CVD (p = 0.033; OR = 1.09). The weighted GRS containing SNPs was associated with CAC and myocardial infarction (MI) was associated with history of MI (p = 0.026; OR = 1.15).

Conclusions

Genetic risk factors for subclinical CVD in the general population (CHARGE) were modestly associated with T2DM-related risk factors and CVD outcomes in the DHS.

Differences in vascular nitric oxide and endothelium-derived hyperpolarizing factor bioavailability in blacks and whites

OBJECTIVE

Abnormalities in nitric oxide (NO) bioavailability have been reported in blacks. Whether there are differences in endothelium-derived hyperpolarizing factor (EDHF) in addition to NO between blacks and whites and how these affect physiological vasodilation remain unknown. We hypothesized that the bioavailability of vascular NO and EDHF, at rest and with pharmacological and physiological vasodilation, varies between whites and blacks.

APPROACH AND RESULTS

In 74 white and 86 black subjects without known cardiovascular disease risk factors, forearm blood flow was measured using plethysmography at rest and during inhibition of NO with N(G)-monomethyl-L-arginine and of K(+) Ca channels (EDHF) with tetraethylammonium. The reduction in resting forearm blood flow was greater with N(G)-monomethyl-L-arginine (P=0.019) and similar with tetraethylammonium in whites compared with blacks. Vasodilation with bradykinin, acetylcholine, and sodium nitroprusside was lower in blacks compared with whites (all P<0.0001). Inhibition with N(G)-monomethyl-L-arginine was greater in whites compared with blacks with bradykinin, acetylcholine, and exercise. Inhibition with tetraethylammonium was lower in blacks with bradykinin, but greater during exercise and with acetylcholine.

CONCLUSIONS

The contribution to both resting and stimulus-mediated vasodilator tone of NO is greater in whites compared with blacks. EDHF partly compensates for the reduced NO release in exercise and acetylcholine-mediated vasodilation in blacks. Preserved EDHF but reduced NO bioavailability and sensitivity characterizes the vasculature in healthy blacks.

CLINICAL TRIAL REGISTRATION URL

http://clinicaltrials.gov/. Unique identifier: NCT00166166.

Genome-wide interaction study identifies RCBTB1 as a modifier for smoking effect on carotid intima-media thickness

OBJECTIVE

Carotid intima-media thickness (cIMT), a marker for atherosclerosis, is affected by smoking and has substantial interindividual variation. We sought to identify the genetic moderators influencing the effect of smoking on cIMT.

APPROACH AND RESULTS

With a multistage design using 722 379 single nucleotide polymorphisms (SNP), a genome-wide interaction study was performed in a discovery sample of 669 Hispanics, followed by replication in 589 subjects (264 Hispanics, 172 non-Hispanic blacks, 153 non-Hispanic whites). Assuming an additive genetic model, regression analysis was performed to test for smoking-SNP interaction on cIMT while controlling for age, sex, and the top 3 principal components of ancestry. The strongest interaction in Hispanics was found with a synonymous splicing SNP (rs3751383) in exon 9 of RCBTB1 (P=2.5e(-6) in discovery sample; P=0.01 in the Hispanic replication sample; P<8.8e(-9) in the combined Hispanic sample). Stratification analysis in the combined Hispanic sample showed that smoking had no effect on cIMT among rs3751383 G homozygote (P=0.15), a moderate effect among rs3751383 heterozygote (P=0.01), and a strong effect among rs3751383 A homozygote (P=2.1e(-7)). A consistent trend was observed in the non-Hispanic white and black data sets, leading to an interaction effect of P<2.9e(-9) in the meta-analysis of all 1258 subjects.

CONCLUSIONS

Our study represents the first genome-wide smoking-SNP interaction study of cIMT and identifies RCBTB1 as a modifier of the smoking effect on cIMT. Testing for gene-environment interactions can help uncover genetic factors that contribute to the interindividual variation in response to the same environmental exposure.

Variants in adiponectin signaling pathway genes show little association with subclinical CVD in the diabetes heart study

OBJECTIVE

Understanding the interplay between adiposity, inflammation, and cardiovascular complications in type 2 diabetes mellitus (T2DM) remains a challenge. Signaling from adipocytes is considered important in this context. Adiponectin is the most abundant adipocytokine and has been associated with various measures of cardiovascular disease (CVD). This study examines the relationships between genetic variants in the adiponectin (ADIPOQ) and adiponectin-related signaling pathway genes and measures of subclinical CVD (vascular calcified plaque and carotid intima-media thickness), plasma lipids, and inflammation in T2DM.

DESIGN AND METHODS

Single-nucleotide polymorphisms (SNPs) in ADIPOQ (n = 45), SNPs tagging ADIPOR1 (n = 6), APIPOR2 (n = 8), APPL1 (n = 6) and known rare coding variants in KNG1 (n = 3) and LYZL1 (n = 3) were genotyped in 1220 European Americans from the family-based Diabetes Heart Study. Associations between SNPs and phenotypes of interest were assessed using a variance components analysis with adjustment for age, sex, T2DM-affected status, and body mass index.

RESULTS

There was minimal evidence of association between SNPs in the adiponectin signaling pathway genes and measures of calcified plaque; eight of the 71 SNPs showed evidence of association with subclinical CVD (P = 0.007-0.046) but not with other phenotypes examined. Nine additional SNPs were associated with at least one of the plasma lipid measures (P = 0.008-0.05).

CONCLUSION

Findings from this study do not support a significant role for variants in the adiponectin signaling pathway genes in contributing to risk for vascular calcification in T2DM. However, further understanding the interplay between adiposity, plasma lipids, and inflammation may prove important in the prediction and management of cardiovascular complications in T2DM.

Impact of HDL genetic risk scores on coronary artery calcified plaque and mortality in individuals with type 2 diabetes from the Diabetes Heart Study

Background

Patients with type 2 diabetes (T2D) are at elevated risk for cardiovascular disease (CVD) events and mortality. Recent studies have assessed the impact of genetic variants affecting high-density lipoprotein cholesterol (HDL) concentrations on CVD risk in the general population. This study examined the utility of HDL-associated single nucleotide polymorphisms (SNPs) for CVD risk prediction in European Americans with T2D enrolled in the Diabetes Heart Study (DHS).

Methods

Genetic risk scores (GRS) of HDL-associated SNPs were constructed and evaluated for potential associations with mortality and with coronary artery calcified atherosclerotic plaque (CAC), a measure of subclinical CVD strongly associated with CVD events and mortality. Two sets of SNPs were used to construct GRS; while all SNPs were selected primarily for their impacts on HDL, one set of SNPs had pleiotropic effects on other lipid parameters, while the other set lacked effects on low-density lipoprotein cholesterol (LDL) or triglyceride concentrations.

Results

The GRS were specifically associated with HDL concentrations (4.90 × 10^-7 < p < 0.02) in models adjusted for age, sex, and body mass index (BMI), but were not associated with LDL or triglycerides. Cox proportional hazards regression analysis suggested the HDL-associated GRS had no impact on risk of CVD-mortality (0.48 < p < 0.99) in models adjusted for other known CVD risk factors. However, associations between several of the GRS and CAC were observed (3.85 × 10^-4 < p < 0.03) in models adjusted for other known CVD risk factors.

Conclusions

The GRS analyzed in this study provide a tool for assessment of HDL-associated SNPs and their impact on CVD risk in T2D. The observed associations between several of the GRS and CAC suggest a potential role for HDL-associated SNPs on subclinical CVD risk in patients with T2D.

Polymorphisms in the Selenoprotein S gene and subclinical cardiovascular disease in the Diabetes Heart Study

Selenoprotein S (SelS) has previously been associated with a range of inflammatory markers, particularly in the context of cardiovascular disease (CVD). The aim of this study was to examine the role of SELS genetic variants in risk for subclinical CVD and mortality in individuals with type 2 diabetes mellitus (T2DM). The association between 10 polymorphisms tagging SELS and coronary (CAC), carotid (CarCP) and abdominal aortic calcified plaque, carotid intima media thickness and other known CVD risk factors was examined in 1220 European Americans from the family-based Diabetes Heart Study. The strongest evidence of association for SELS SNPs was observed for CarCP; rs28665122 (5' region; β = 0.329, p = 0.044), rs4965814 (intron 5; β = 0.329, p = 0.036), rs28628459 (3' region; β = 0.331, p = 0.039) and rs7178239 (downstream; β = 0.375, p = 0.016) were all associated. In addition, rs12917258 (intron 5) was associated with CAC (β = -0.230, p = 0.032), and rs4965814, rs28628459 and rs9806366 were all associated with self-reported history of prior CVD (p = 0.020-0.043). These results suggest a potential role for the SELS region in the development subclinical CVD in this sample enriched for T2DM. Further understanding the mechanisms underpinning these relationships may prove important in predicting and managing CVD complications in T2DM.

Usefulness of biventricular volume as a predictor of mortality in patients with diabetes mellitus (from the Diabetes Heart Study)

Patients with type 2 diabetes mellitus are at increased risk for cardiovascular disease (CVD) and mortality. Beyond traditional CVD risk factors, novel measures reflecting additional aspects of disease pathophysiology, such as biventricular volume (BiVV), may be useful for risk stratification. The aim of this study was to examine the relationship between BiVV and risk for mortality in European Americans with type 2 diabetes mellitus from the Diabetes Heart Study (DHS). BiVV was calculated from 771 noncontrast computed tomographic scans performed to image coronary artery calcified plaque. Relationships between BiVV and traditional CVD risk factors were examined. Cox proportional-hazards regression was performed to determine risk for mortality (all-cause and CVD mortality) associated with increasing BiVV. Area under the curve analysis was used to assess BiVV utility in risk prediction models. During 8.4 ± 2.4 years of follow-up, 23% of the patients died. In unadjusted analyses, BiVV was significantly associated with increasing body mass index, height, coronary artery calcified plaque, history of hypertension, and previous myocardial infarction (p <0.0001 to 0.012). BiVV was significantly associated with all-cause (hazard ratio 2.45, 95% confidence interval 1.06 to 5.67, p = 0.036) and CVD (hazard ratio 4.36, 95% confidence interval 1.36 to 14.03, p = 0.014) mortality in models adjusted for other known CVD risk factors. Area under the curve increased from 0.76 to 0.78 (p = 0.04) and from 0.74 to 0.77 (p = 0.02) for all-cause and CVD mortality with the inclusion of BiVV. In conclusion, in the absence of echocardiography or other noninvasive imaging modalities to assess ventricular volumes, or when such methods are contraindicated, BiVV from computed tomography may be considered a tool for the stratification of high-risk patients, such as those with type 2 diabetes mellitus.

Vascular channel reserves in patients with systemic atherosclerosis and type 2 diabetes mellitus

Aims. To determine vascular channel reserves in patients with systemic atherosclerosis and type 2 diabetes mellitus (T2DM). Materials and Methods. Study included 143 patients with systemic atherosclerosis, 40 of them also suffered from T2DM. We applied laser Doppler flowmetry (LDF) to evaluate vascular channel reserves and transcranial spectrometry to assess cerebral oxygenation status. Results. We found that 60% of patients with systemic atherosclerosis and T2DM show microcirculation parameters below critical level, which indicates failure of collateral circulation. This group also showed lower efficiency of cerebral perfusion and more pronounced vascular constriction in response to functional load as compared to diabetes-negative controls. Conclusion. Patients with T2DM, accompanied with systemic atherosclerosis showed lower circulation efficiency and more pronounced autonomous dysregulation of cerebral circulation against patients without diabetes mellitus.

Genetic analysis of haptoglobin polymorphisms with cardiovascular disease and type 2 diabetes in the Diabetes Heart Study

Background

Haptoglobin (HP) is an acute phase protein that binds to freely circulating hemoglobin. HP exists as two distinct forms, HP1 and HP2. The longer HP2 form has been associated with cardiovascular (CVD) events and mortality in individuals with type 2 diabetes (T2DM).

Methods

This study examined the association of HP genotypes with subclinical CVD, T2DM risk, and associated risk factors in a T2DM-enriched sample. Haptoglobin genotypes were determined in 1208 European Americans (EA) from 473 Diabetes Heart Study (DHS) families via PCR. Three promoter SNPs (rs5467, rs5470, and rs5471) were also genotyped.

Results

Analyses revealed association between HP2-2 duplication and increased carotid intima-media thickness (IMT; p = 0.001). No association between HP and measures of calcified arterial plaque were observed, but the HP polymorphism was associated with triglyceride concentrations (p = 0.005) and CVD mortality (p = 0.04). We found that the HP2-2 genotype was associated with increased T2DM risk with an odds ratio (OR) of 1.49 (95% CI 1.18-1.86, p = 6.59x10^-4). Promoter SNPs were not associated with any traits.

Conclusions

This study suggests association between the HP duplication and IMT, triglycerides, CVD mortality, and T2DM in an EA population enriched for T2DM. Lack of association with atherosclerotic calcified plaque likely reflect differences in the pathogenesis of these CVD phenotypes. HP variation may contribute to the heritable risk for CVD complications in T2DM.

Genetic prediction of common diseases. Still no help for the clinical diabetologist!

Genome-wide association studies (GWAS) have identified several loci associated with many common, multifactorial diseases which have been recently used to market genetic testing directly to the consumers. We here addressed the clinical utility of such GWAS-derived genetic information in predicting type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD) in diabetic patients. In addition, the development of new statistical approaches, novel technologies of genome sequencing and ethical, legal and social aspects related to genetic testing have been also addressed. Available data clearly show that, similarly to what reported for most common diseases, genetic testing offered today by commercial companies cannot be used as predicting tools for T2DM and CAD. Further studies taking into account the complex interaction between genes as well as between genetic and non-genetic factors, including age, obesity and glycemic control which seem to modify genetic effects on the risk of T2DM and CAD, might mitigate such negative conclusions. Also, addressing the role of relatively rare variants by next generation sequencing may help identify novel and strong genetic markers with an important role in genetic prediction. Finally, statistical tools concentrated on reclassifying patients might be a useful application of genetic information for predicting many common diseases. By now, prediction of such diseases, including those of interest for the clinical diabetologist, have to be pursued by using traditional clinical markers which perform well and are not costly.

The 9p21 coronary artery disease locus and kidney dysfunction in patients with Type 2 diabetes mellitus

BACKGROUND

We investigated whether the coronary artery disease (CAD) locus on chromosome 9p21 (as represented by single nucleotide polymorphism rs2383206) is associated with low estimated glomerular filtration rate (eGFR) or increased urinary albumin excretion in patients with Type 2 diabetes mellitus (T2DM).

METHODS

Four samples, including a total of 3167 patients, were studied. The presence of low eGFR (<60 mL/min/1.73m(2)) was estimated from serum creatinine by means of the Modification of Diet in Renal Disease Study equation. Increased urinary albumin excretion was defined as an albumin-creatinine ratio (ACR) ≥2.5 mg/mmol in men and ≥3.5 mg/mmol in women.

RESULTS

No association was found between rs2383206 and low eGFR or increased ACR in each sample as well as in a pooled analysis (overall odds ratio = 1.07, 95% confidence interval 0.94-1.22, P = 0.31 and overall odds ratio = 1.00, 95% confidence interval 0.90-1.12, P = 0.95, respectively). No interaction was observed between rs2383206 and poor glycemic control [HbA1c was above the median in the pooled sample (7.7%) in modulating eGFR or ACR (P for interaction = 0.42 and 0.90, respectively)].

CONCLUSION

Variability at the 9p21 CAD locus is unlikely to play a role in modulating susceptibility to kidney dysfunction in patients with T2DM.

Genetic and environmental factors associated with type 2 diabetes and diabetic vascular complications

Faced with a global epidemic of type 2 diabetes (T2D), it is critical that researchers improve our understanding of the pathogenesis of T2D and related vascular complications. These findings may ultimately lead to novel treatment options for disease prevention or delaying progression. Two major paradigms jointly underlie the development of T2D and related coronary artery disease, diabetic nephropathy, and diabetic retinopathy. These paradigms include the genetic risk variants and behavioral/environmental factors. This article systematically reviews the literature supporting genetic determinants in the pathogenesis of T2D and diabetic vasculopathy, and the functional implications of these gene variants on the regulation of beta-cell function and glucose homeostasis. We update the discovery of diabetes and diabetic vasculopathy risk variants, and describe the genetic technologies that have uncovered them. Also, genomic linkage between obesity and T2D is discussed. There is a complementary role for behavioral and environmental factors modulating the genetic susceptibility and diabetes risk. Epidemiological and clinical data demonstrating the effects of behavioral and novel environmental exposures on disease expression are reviewed. Finally, a succinct overview of recent landmark clinical trials addressing glycemic control and its impact on rates of vascular complications is presented. It is expected that novel strategies to exploit the gene- and exposure-related underpinnings of T2D will soon result.

Haptoglobin genotype and its role in diabetic cardiovascular disease

Over the past decade, several longitudinal epidemiological studies have brought attention to the haptoglobin genotype and its importance in determining diabetic vascular disease risk. This manuscript presents an overview of the biology of the haptoglobin genotype and reviews the literature concerning its role in the development of cardiovascular disease among individuals with diabetes mellitus.

Fine mapping study reveals novel candidate genes for carotid intima-media thickness in Dominican Republican families

BACKGROUND

Carotid intima-media thickness (CIMT) is a subclinical measure for atherosclerosis. Previously, we have mapped quantitative trait loci (QTLs) for CIMT to chromosomes 7p (maximum logarithm of odds=3.1) and to 14q (maximum logarithm of odds=2.3). We sought to identify the underlying genetic variants within those QTLs.

METHODS AND RESULTS

Using the 100 extended Dominican Republican (DR) families (N=1312) used in the original linkage study, we fine mapped the QTLs with 2031 tagging single nucleotide polymorphisms (SNPs). Promising SNPs in the family data set were examined in an independent population-based subcohort comprised of DR individuals (N=553) from the Northern Manhattan Study. Among the families, evidence for association (P<0.001) was found in multiple genes (ANLN, AOAH, FOXN3, CCDC88C, PRiMA1, and an intergenic SNP rs1667498), with the strongest association at PRiMA1 (P=0.00007, corrected P=0.047). Additional analyses revealed that the association at these loci, except PRiMA1, was highly significant (P=0.00004≈0.00092) in families with evidence for linkage, but not in the rest of families (P=0.13≈0.80) and the population-based cohort, suggesting the genetic effects at these SNPs are limited to a subgroup of families. In contrast, the association at PRiMA1 was significant in both families with and without evidence for linkage (P=0.002 and 0.019, respectively) and the population-based subcohort (P=0.047), supporting a robust association.

CONCLUSIONS

We identified several candidate genes for CIMT in DR families. Some of the genes manifest genetic effects within a specific subgroup and others were generalized to all groups. Future studies are needed to further evaluate the contribution of these genes to atherosclerosis.

The SH2B1 obesity locus is associated with myocardial infarction in diabetic patients and with NO synthase activity in endothelial cells

OBJECTIVE

Obesity and cardiovascular disease recognize a common metabolic soil and may therefore share part of their genetic background. Genome-wide association studies have identified variability at the SH2B1 locus as a predictor of obesity. We investigated whether SNP rs4788102, which captures the entire SH2B1 variability, is associated with coronary artery disease (CAD) and/or myocardial infarction (MI) in patients with type 2 diabetes mellitus (T2DM).

DESIGN AND SETTING

SNP rs4788102 was typed in 2015 White subjects with T2DM from three CAD case-control studies [n=740 from the Gargano Hearth Study (GHS, Italy); n=818 from the Joslin Hearth Study (JHS, Boston); n=457 from the University of Catanzaro (CZ, Italy)].

RESULTS

SNP rs4788102 (G/A) was not associated with CAD (overall allelic OR=1.06, 95% CI=0.93-1.21; p=0.37). On the contrary, it was associated with MI in GHS (1.42, 1.12-1.81; p=0.004) and in the three samples analyzed together (1.21, 1.04-1.41; p=0.016). Insulin stimulated nitric oxide synthase (NOS) activity in human vein endothelial cells from G/G (n=4, p=0.03) but not the G/A (n=5, p=0.83) genotype. Of the SNPs in perfect LD with rs4788102, one (rs7498665) affects amino acid polarity (Ala484Thr) and falls into a highly conserved protein segment of SH2B1 containing a class II SH3 domain binding site.

CONCLUSIONS

Variability at the SH2B1 obesity locus is associated with MI in diabetic patients and with reduced insulin-stimulated NOS activity in human endothelial cells. Further studies are needed to replicate this association and dissect the biology underlying this finding.