Salivary dysbiosis and the clinical spectrum in anti-Ro positive mothers of children with neonatal lupus

Mothers giving birth to children with manifestations of neonatal lupus (NL) represent a unique population at risk for the development of clinically evident pathologic autoimmunity since many are asymptomatic and only become aware of anti-SSA/Ro positivity (anti-Ro+) based on heart block in their fetus. Accordingly, we hypothesized that the microbiome in saliva is associated with the development of autoreactivity and in some cases the progression in health status from benign to overt clinical disease including Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE). The study comprised a clinical spectrum of anti-Ro+ mothers, all of whom gave birth to a child with NL: 9 were asymptomatic or had an undifferentiated autoimmune disease (Asym/UAS) and 16 fulfilled criteria for SS and/or SLE. Microbial diversity was reduced across all levels from kingdom to species for the anti-Ro+ mothers vs healthy controls; however, there were no significant differences between Asym/UAS and SS/SLE mothers. Relative abundance of Proteobacteria and more specifically class Betaproteobacteria decreased with clinical severity (healthy controls < Asym/UAS < SS/SLE). These ordered differences were maintained through the taxonomic hierarchy to three genera (Lautropia, Comamonas, and Neisseria) and species within these genera (L. mirabilis, N. flavescens and N. oralis). Biometric analysis comparing von Willebrand Factor domains present in human Ro60 with L. mirabilis proteins support the hypothesis of molecular mimicry. These data position the microbiome in the development of anti-Ro reactivity and subsequent clinical spectrum of disease.

Fine-mapping the MHC locus in juvenile idiopathic arthritis (JIA) reveals genetic heterogeneity corresponding to distinct adult inflammatory arthritic diseases

Objectives

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases, comprising seven categories. Genetic data could potentially be used to help redefine JIA categories and improve the current classification system. The human leucocyte antigen (HLA) region is strongly associated with JIA. Fine-mapping of the region was performed to look for similarities and differences in HLA associations between the JIA categories and define correspondences with adult inflammatory arthritides.

Methods

Dense genotype data from the HLA region, from the Immunochip array for 5043 JIA cases and 14 390 controls, were used to impute single-nucleotide polymorphisms, HLA classical alleles and amino acids. Bivariate analysis was performed to investigate genetic correlation between the JIA categories. Conditional analysis was used to identify additional effects within the region. Comparison of the findings with those in adult inflammatory arthritic diseases was performed.

Results

We identified category-specific associations and have demonstrated for the first time that rheumatoid factor (RF)-negative polyarticular JIA and oligoarticular JIA are genetically similar in their HLA associations. We also observe that each JIA category potentially has an adult counterpart. The RF-positive polyarthritis association at HLA-DRB1 amino acid at position 13 mirrors the association in adult seropositive rheumatoid arthritis (RA). Interestingly, the combined oligoarthritis and RF-negative polyarthritis dataset shares the same association with adult seronegative RA.

Conclusions

The findings suggest the value of using genetic data in helping to classify the categories of this heterogeneous disease. Mapping JIA categories to adult counterparts could enable shared knowledge of disease pathogenesis and aetiology and facilitate transition from paediatric to adult services.

Genetic association of CD247 (CD3ζ) with SLE in a large-scale multiethnic study

A classic T-cell phenotype in systemic lupus erythematosus (SLE) is the downregulation and replacement of the CD3ζ chain that alters T-cell receptor signaling. However, genetic associations with SLE in the human CD247 locus that encodes CD3ζ are not well established and require replication in independent cohorts. Our aim was therefore to examine, localize and validate CD247-SLE association in a large multiethnic population. We typed 44 contiguous CD247 single-nucleotide polymorphisms (SNPs) in 8922 SLE patients and 8077 controls from four ethnically distinct populations. The strongest associations were found in the Asian population (11 SNPs in intron 1, 4.99 × 10(-4) < P < 4.15 × 10(-2)), where we further identified a five-marker haplotype (rs12141731-rs2949655-rs16859085-rs12144621-rs858554; G-G-A-G-A; P(hap) = 2.12 × 10(-5)) that exceeded the most associated single SNP rs858554 (minor allele frequency in controls = 13%; P = 4.99 × 10(-4), odds ratio = 1.32) in significance. Imputation and subsequent association analysis showed evidence of association (P < 0.05) at 27 additional SNPs within intron 1. Cross-ethnic meta-analysis, assuming an additive genetic model adjusted for population proportions, showed five SNPs with significant P-values (1.40 × 10(-3) < P< 3.97 × 10(-2)), with one (rs704848) remaining significant after Bonferroni correction (P(meta) = 2.66 × 10(-2)). Our study independently confirms and extends the association of SLE with CD247, which is shared by various autoimmune disorders and supports a common T-cell-mediated mechanism.

Genetic analysis of the pathogenic molecular sub-phenotype interferon-alpha identifies multiple novel loci involved in systemic lupus erythematosus

Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disorder characterized by inflammation of multiple organ systems and dysregulated interferon responses. SLE is both genetically and phenotypically heterogeneous, greatly reducing the power of case-control studies in SLE. Elevated circulating interferon alpha (IFN-α) is a stable, heritable trait in SLE, which has been implicated in primary disease pathogenesis. 40–50% of patients have high IFN-α, and high levels correspond with clinical differences. To study genetic heterogeneity in SLE, we performed a case-case study comparing patients with high vs. low IFN-α in over 1550 SLE cases, including GWAS and replication cohorts. In meta-analysis, the top associations in European ancestry were PRKG1 rs7897633 (P_Meta=2.75 × 10⁻⁸) and PNP rs1049564 (P_Meta=1.24 × 10⁻⁷). We also found evidence for cross-ancestral background associations with the ANKRD44 and PLEKHF2 loci. These loci have not been previously identified in case-control SLE genetic studies. Bioinformatic analyses implicated these loci functionally in dendritic cells and natural killer cells, both of which are involved in IFN-α production in SLE. As case-control studies of heterogeneous diseases reach a limit of feasibility with respect to subject number and detectable effect size, the study of informative pathogenic subphenotypes becomes an attractive strategy for genetic discovery in complex disease.

GWAS identifies novel SLE susceptibility genes and explains the association of the HLA region

In a Genome Wide Association Study (GWAS) of individuals of European ancestry afflicted with Systemic Lupus Erythematosus (SLE) the extensive utilization of imputation, stepwise multiple regression, lasso regularization, and increasing study power by utilizing False Discovery Rate (FDR) instead of a Bonferroni multiple test correction enabled us to identify 13 novel non-human leukocyte antigen (HLA) genes and confirmed the association of 4 genes previously reported to be associated. Novel genes associated with SLE susceptibility included two transcription factors (EHF, and MED1), two components of the NFκB pathway (RASSF2 and RNF114), one gene involved in adhesion and endothelial migration (CNTN6), and two genes involved in antigen presentation (BIN1 and SEC61G). In addition, the strongly significant association of multiple single nucleotide polymorphisms (SNPs) in the HLA region was assigned to HLA alleles and serotypes and deconvoluted into four primary signals. The novel SLE-associated genes point to new directions for both the diagnosis and treatment of this debilitating autoimmune disease.

Analysis of FTO gene variants with obesity and glucose homeostasis measures in the multiethnic Insulin Resistance Atherosclerosis Study cohort

OBJECTIVE

Previous studies have replicated the association of variants within FTO (fat mass- and obesity-associated) intron 1 with obesity and adiposity quantitative traits in populations of European ancestry. Non-European populations, however, have not been so intensively studied. The goal of this investigation was to examine the association of FTO single-nucleotide polymorphisms (SNPs), prominent in the literature in a multiethnic sample of non-Hispanic White American (n=458), Hispanic American (n=373) and African American (n=288) subjects from the Insulin Resistance Atherosclerosis Study (IRAS). This cohort provides the unique ability to evaluate how variation within FTO influences measures of adiposity and glucose homeostasis in three different ethnicities, which were ascertained and examined using a common protocol.

DESIGN

A total of 26 FTO SNPs were genotyped, including those consistently associated in the literature (rs9939609, rs8050136, rs1121980, rs1421085, rs17817449 and rs3751812), and tested for association with adiposity and glucose homeostasis traits.

RESULTS

For the adiposity phenotypes, these and other SNPs were associated with body mass index (BMI) in both non-Hispanic Whites (P-values ranging from 0.015 to 0.048) and Hispanic Americans (P-values ranging from 7.1 × 10(-6) to 0.027). In Hispanic Americans, four other SNPs (rs8047395, rs10852521, rs8057044 and rs8044769) still showed evidence of association after multiple comparisons adjustment (P-values ranging from 5.0 × 10(-5) to 5.2 × 10(-4)). The historically associated BMI SNPs were not associated in the African Americans, but rs1108102 was associated with BMI (P-value of 5.4 × 10(-4)) after accounting for multiple comparisons. For glucose homeostasis traits, associations were seen with acute insulin response in non-Hispanic Whites and African Americans. However, all associations with glucose homeostasis measures were no longer significant after adjusting for multiple comparisons.

CONCLUSION

These results replicate the association of FTO intron 1 variants with BMI in non-Hispanic Whites and Hispanic Americans but show little evidence of association in African Americans, suggesting that the effect of FTO variants on adiposity phenotypes shows genetic heterogeneity dependent on ethnicity.

Candidate loci for insulin sensitivity and disposition index from a genome-wide association analysis of Hispanic participants in the Insulin Resistance Atherosclerosis (IRAS) Family Study

AIMS/HYPOTHESIS

The majority of type 2 diabetes genome-wide association studies (GWAS) to date have been performed in European-derived populations and have identified few variants that mediate their effect through insulin resistance. The aim of this study was to evaluate two quantitative, directly assessed measures of insulin resistance, namely insulin sensitivity index (S(I)) and insulin disposition index (DI), in Hispanic-American participants using an agnostic, high-density single nucleotide polymorphism (SNP) scan, and to validate these findings in additional samples.

METHODS

A two-stage GWAS was performed in Hispanic-American samples from the Insulin Resistance Atherosclerosis Family Study. In Stage 1, 317,000 SNPs were assessed using 229 DNA samples. SNPs with evidence of association with glucose homeostasis and adiposity traits were then genotyped on the entire set of Hispanic-American samples (n = 1,190). This report focuses on the glucose homeostasis traits: S(I) and DI.

RESULTS

Although evidence of association did not reach genome-wide significance (p = 5 x 10(-7)), in the combined analysis SNPs had admixture-adjusted p values of p (ADD) = 0.00010-0.0020 with 8 to 41% differences in genotypic means for S(I) and DI.

CONCLUSIONS/INTERPRETATION

Several candidate loci were identified that are nominally associated with S(I) and/or DI in Hispanic-American participants. Replication of these findings in independent cohorts and additional focused analysis of these loci is warranted.

Association of 25-hydroxyvitamin D with blood pressure in predominantly 25-hydroxyvitamin D deficient Hispanic and African Americans

BACKGROUND

Several observational studies have recently suggested an inverse association of circulating levels of vitamin D with blood pressure. These findings have been based mainly on Caucasian populations; whether this association also exists among Hispanic and African Americans has yet to be definitively determined. This study investigates the association of 25-hydroxyvitamin D (25[OH]D) with blood pressure in Hispanic and African Americans.

METHODS

The data source for this study is the Insulin Resistance Atherosclerosis Family Study (IRASFS), which consists of Hispanic- and African-American families from three US recruitment centers (n =1,334). A variance components model was used to analyze the association of plasma 25[OH]D levels with blood pressure.

RESULTS

An inverse association was found between 25[OH]D and both systolic (beta for 10 ng/ml difference = -2.05; P < 0.01) and diastolic (beta for 10 ng/ml difference = -1.35; P < 0.001) blood pressure in all populations combined, after adjusting for age, sex, ethnicity, and season of blood draw. Further adjustment for body mass index (BMI) weakened this association (beta for 10 ng/ml difference = -0.94; P = 0.14 and beta for 10 ng/ml difference = -0.64; P = 0.09, respectively).

CONCLUSIONS

25[OH]D levels are significantly inversely associated with blood pressure in Hispanic and African Americans from the IRASFS. However, this association was not significant after adjustment for BMI. Further research is needed to determine the role of BMI in this association. Large, well-designed prospective studies of the effect of vitamin D supplementation on blood pressure may be warranted.

A genome-wide association scan for acute insulin response to glucose in Hispanic-Americans: the Insulin Resistance Atherosclerosis Family Study (IRAS FS)

AIMS/HYPOTHESIS

This study sought to identify genes and regions in the human genome that are associated with the acute insulin response to glucose (AIRg), an important predictor of type 2 diabetes, in Hispanic-American participants from the Insulin Resistance Atherosclerosis Family Study (IRAS FS).

METHODS

A two-stage genome-wide association scan (GWAS) was performed in IRAS FS Hispanic-American samples. In the first stage, 317K single nucleotide polymorphisms (SNPs) were assessed in 229 Hispanic-American DNA samples from 34 families from San Antonio, TX, USA. SNPs with the most significant associations with AIRg were genotyped in the entire set of IRAS FS Hispanic-American samples (n = 1,190). In chromosomal regions with evidence of association, additional SNPs were genotyped to capture variation in genes.

RESULTS

No individual SNP achieved genome-wide levels of significance (p < 5 x 10(-7)); however, two regions (chromosomes 6p21 and 20p11) had multiple highly ranked SNPs that were associated with AIRg. Additional genotyping in these regions supported the initial evidence of variants contributing to variation in AIRg. One region resides in a gene desert between PXT1 and KCTD20 on 6p21, while the region on 20p11 has several viable candidate genes (ENTPD6, PYGB, GINS1 and RP4-691N24.1).

CONCLUSIONS/INTERPRETATION

A GWAS in Hispanic-American samples identified several candidate genes and loci that may be associated with AIRg. These associations explain a small component of variation in AIRg. The genes identified are involved in phosphorylation and ion transport, and provide preliminary evidence that these processes are important in beta cell response.

Complement receptor 2 polymorphisms associated with systemic lupus erythematosus modulate alternative splicing

Genetic factors influence susceptibility to systemic lupus erythematosus (SLE). A recent family-based analysis in Caucasian and Chinese populations provided evidence for association of single-nucleotide polymorphisms (SNPs) in the complement receptor 2 (CR2/CD21) gene with SLE. Here we confirmed this result in a case-control analysis of an independent European-derived population including 2084 patients with SLE and 2853 healthy controls. A haplotype formed by the minor alleles of three CR2 SNPs (rs1048971, rs17615, rs4308977) showed significant association with decreased risk of SLE (30.4% in cases vs 32.6% in controls, P=0.016, OR=0.90 (0.82-0.98)). Two of these SNPs are in exon 10, directly 5' of an alternatively spliced exon preferentially expressed in follicular dendritic cells (FDC), and the third is in the alternatively spliced exon. Effects of these SNPs and a fourth SNP in exon 11 (rs17616) on alternative splicing were evaluated. We found that the minor alleles of these SNPs decreased splicing efficiency of exon 11 both in vitro and ex vivo. These findings further implicate CR2 in the pathogenesis of SLE and suggest that CR2 variants alter the maintenance of tolerance and autoantibody production in the secondary lymphoid tissues where B cells and FDCs interact.

Variation in the ATP-binding cassette transporter 2 gene is a separate risk factor for systemic lupus erythematosus within the MHC

The ATP-binding cassette transporter (TAP) proteins are functionally relevant candidates for predisposition to systemic lupus erythematosus (SLE) by virtue of their role in autoantigen presentation and location in the major histocompatibility complex (MHC). We tested if variation in the TAP genes (TAP1 and TAP2) is associated with SLE. We genotyped tag single nucleotide polymorphisms (SNPs) and performed family-based association analysis on 390 Caucasian pedigrees. We found significant evidence of association between TAP2 and SLE (rs241453, P=1.33 x 10(-6)). Conditional logistic regression analysis suggests that this TAP2 effect is separate from the HLA-DRB1 alleles. Our analyses show that both rs241453 (P=1.6 x 10(-4)) and HLA-DRB1*03xx (P=2.3 x 10(-4)) have significant autonomous effects not due to linkage disequilibrium. Moreover, these loci exhibit a significant statistical interaction (P<1.0 x 10(-6)), demonstrated by an increase in the odds ratio for the TAP2 association from OR=2.00 (95% confidence interval (CI)=1.17-3.42) in HLA-DRB1*03xx-negative subjects to OR=4.29 (CI=1.88-9.76) in the subjects with at least one HLA-DRB1*03xx allele group. We report the largest association study of the TAP genes with SLE to date, and the first to test for its separate effect and interaction with the HLA alleles consistently associated with SLE.

Genetic associations of LYN with systemic lupus erythematosus

We targeted LYN, a src-tyosine kinase involved in B-cell activation, in case-control association studies using populations of European-American, African-American and Korean subjects. Our combined European-derived population, consisting of 2463 independent cases and 3131 unrelated controls, shows significant association with rs6983130 in a female-only analysis with 2254 cases and 2228 controls (P=1.1 x 10(-4), odds ratio (OR)=0.81 (95% confidence interval: 0.73-0.90)). This single nucleotide polymorphism (SNP) is located in the 5' untranslated region within the first intron near the transcription initiation site of LYN. In addition, SNPs upstream of the first exon also show weak and sporadic association in subsets of the total European-American population. Multivariate logistic regression analysis implicates rs6983130 as a protective factor for systemic lupus erythematosus (SLE) susceptibility when anti-dsDNA, anti-chromatin, anti-52 kDa Ro or anti-Sm autoantibody status were used as covariates. Subset analysis of the European-American female cases by American College of Rheumatology classification criteria shows a reduction in the risk of hematological disorder with rs6983130 compared with cases without hematological disorders (P=1.5 x 10(-3), OR=0.75 (95% CI: 0.62-0.89)). None of the 90 SNPs tested show significant association with SLE in the African American or Korean populations. These results support an association of LYN with European-derived individuals with SLE, especially within autoantibody or clinical subsets.

Variants in intron 13 of the ELMO1 gene are associated with diabetic nephropathy in African Americans

Variants in the engulfment and cell motility 1 (ELMO1) gene are associated with nephropathy due to type 2 diabetes mellitus (T2DM) in a Japanese cohort. We comprehensively evaluated this gene in African American (AA) T2DM patients with end-stage renal disease (ESRD). Three hundred and nine HapMap tagging SNPs and 9 reportedly associated SNPs were genotyped in 577 AA T2DM-ESRD patients and 596 AA non-diabetic controls, plus 43 non-diabetic European American controls and 45 Yoruba Nigerian samples for admixture adjustment. Replication analyses were conducted in 558 AA with T2DM-ESRD and 564 controls without diabetes. Extension analyses included 328 AA with T2DM lacking nephropathy and 326 with non-diabetic ESRD. The original and replication analyses confirmed association with four SNPs in intron 13 (permutation p-values for combined analyses = 0.001-0.003), one in intron 1 (P = 0.004) and one in intron 5 (P = 0.002) with T2DM-associated ESRD. In a subsequent combined analysis of all 1,135 T2DM-ESRD cases and 1,160 controls, an additional 7 intron 13 SNPs produced evidence of association (P = 3.5 x 10(-5)- P = 0.05). No associations were seen with these SNPs in those with T2DM lacking nephropathy or with ESRD due to non-diabetic causes. Variants in intron 13 of the ELMO1 gene appear to confer risk for diabetic nephropathy in AA.

Heterogeneity in gene loci associated with type 2 diabetes on human chromosome 20q13.1

Human chromosome 20q12-q13.1 has been linked to type 2 diabetes mellitus (T2DM) in multiple studies. We screened a 5.795-Mb region for diabetes-related susceptibility genes in a Caucasian cohort of 310 controls and 300 cases with T2DM and end-stage renal disease (ESRD), testing 390 SNPs for association with T2DM-ESRD. The most significant SNPs were found in the perigenic regions: HNF4A (hepatocyte nuclear factor 4alpha), SLC12A5 (potassium-chloride cotransporter member 5), CDH22 (cadherin-like 22), ELMO2 (engulfment and cell motility 2), SLC13A3 (sodium-dependent dicarboxylate transporter member 3), and PREX1 (phosphatidylinositol 3,4,5-triphosphate-dependent RAC exchanger 1). Haplotype analysis found six haplotype blocks globally associated with disease (p<0.05). We replicated the PREX1 SNP association in an independent case-control T2DM population and inferred replication of CDH22, ELMO2, SLC13A3, SLC12A5, and PREX1 using in silico perigenic analysis of two T2DM Genome-Wide Association Study data sets. We found substantial heterogeneity between study results.

Genetic epidemiology of subclinical cardiovascular disease in the diabetes heart study

A genome-wide linkage scan of 357 European American (EA) and 72 African American (AA) pedigrees multiplex for type 2 diabetes mellitus (T2DM) was performed with multipoint nonparametric QTL linkage analysis. Four subclinical measures of cardiovascular disease (CVD): coronary artery (CCP), carotid artery (CarCP), and abdominal aortic calcified plaque (AACP) and carotid artery intima-media thickness (IMT) were mapped. Analyses were adjusted for age, gender, body mass index, and (if appropriate) ethnicity and diabetes status. Evidence for linkage was observed in EA T2DM subjects to CarCP near 16p13 (LOD=4.39 at 8.4 cM; P = 0.00001). When all EA subjects were included, the LOD score was 2.52, suggesting an amplification of the linkage by diabetes. Linkage analysis of a principal components measure of vascular calcium (LOD = 3.85 at 9.3 cM on 16p in EA T2DM subjects) and bivariate analysis of CarCP X IMT (LOD = 3.77 at 9.3 cM on 16p in EA T2DM subjects) were consistent with this linkage. In addition, evidence for linkage was observed with CCP near D15S1515 (LOD = 2.34) in EAs. Additional loci on chromosomes 1, 2, 7, 10, 13, and 21 had LODs > 2.0. The identification of trait-determining polymorphisms underlying these linkages will help delineate risk factors for CVD in T2DM and the general population.

Genome-wide linkage scans for renal function and albuminuria in Type 2 diabetes mellitus: the Diabetes Heart Study

AIMS/HYPOTHESIS

Glomerular filtration rate (GFR), end-stage renal disease and albuminuria are highly heritable. We performed a genome-wide linkage scan in 416 Diabetes Heart Study (DHS) families to detect loci that contributed to renal function and albuminuria.

MATERIALS AND METHODS

A total of 1067 individuals (900 with Type 2 diabetes mellitus) from 348 European American and 68 African American DHS families had measures of urine albumin : creatinine ratio (ACR), serum creatinine concentration and Modification of Diet in Renal Disease estimated GFR (eGFR). Variance components quantitative trait linkage analysis (using SOLAR) was computed.

RESULTS

Participants had mean +/- sd age 61.4 +/- 9.4 years; diabetes duration 10.5 +/- 7.4 years; eGFR 1.15 +/- 0.32 ml/sec; and urine ACR 15.8 +/- 67.2 mmol/l (median 1.4). In all families, significant evidence for linkage of GFR was observed on chromosome 2p16 (log of the odds; LOD = 4.31 at 72.0 cM, ATA47C04P/D2S1352) and 1p36 (LOD = 3.81 at 45.0 cM, D1S3669/D1S3720), with suggestive evidence on 7q21 (LOD = 2.42 at 99.0 cM, D7S820/D7S821) and 13q13 (LOD = 2.28 at 28.0 cM, D13S1493/D13S894). The evidence for linkage to ACR was far weaker, on 13q21-q22 (LOD = 1.84 at 50 cM, D13S1807/D13S800), 3p24-p23 (LOD = 1.81 at 58 cM, D3S3038/D3S2432) and 10p11 (LOD = 1.78 at 71.0 cM, D10S1208/D10S1221).

CONCLUSIONS/INTERPRETATIONS

The eGFR linkage peaks on 2p16, 7q21 and 13q13 closely overlap with nephropathy peaks identified in family studies enriched for severe kidney disease. These diabetes-enriched families provide an opportunity to map genes regulating renal function, potentially leading to the identification of genes producing nephropathy susceptibility in subjects with Type 2 diabetes.

Association of genes of lipid metabolism with measures of subclinical cardiovascular disease in the Diabetes Heart Study

BACKGROUND

Dyslipidaemia is a well known risk factor for cardiovascular disease (CVD). Lipid metabolism is affected by a range of genes and proteins. This study investigated whether some of these genes are associated with measures of subclinical CVD.

METHODS

Polymorphisms of paraoxonase 1 and 2, cholesteryl ester transfer protein, hepatic lipase, and lipoprotein lipase were tested for associations with measures of subclinical CVD including carotid intima-media thickness measured by B-mode ultrasound and carotid and coronary arterial calcification measured by computed tomography. Analysis was performed in 620 European American participants in the Diabetes Heart Study, 83% of whom had type 2 diabetes mellitus. Associations of genotypes with subclinical CVD were tested by computing a series of generalised estimating equations.

RESULTS

The Q192R variant of paraoxonase 1 and rs285 of lipoprotein lipase were associated with carotid artery calcium (p values = 0.002 and 0.005, respectively). Paraoxonase 2 S311C was associated with coronary artery calcium (p value = 0.037).

CONCLUSIONS

There is evidence for modest, but significant, association of multiple single nucleotide polymorphisms in lipid genes with measures of subclinical CVD.

Hormone replacement therapy is associated with increased C-reactive protein in women with Type 2 diabetes in the Diabetes Heart Study

AIMS

Increased levels of inflammatory biomarkers, especially C-reactive protein (CRP), are associated with increased risk for cardiovascular disease (CVD) events, such as myocardial infarction, stroke, peripheral vascular disease, and sudden cardiac death. Medical interventions that increase CRP levels, such as hormone replacement therapy (HRT) in post-menopausal women, are under increasing scrutiny. The effect of HRT on CRP levels in women with Type 2 diabetes (T2DM) is not well documented, and conflicting conclusions have been reported. The aim of this study was to determine the influence of HRT on women with diabetes in a large cross-sectional study.

METHODS

Three hundred and twenty-seven post-menopausal women with T2DM from the Diabetes Heart Study participated. Current use of HRT was determined and serum CRP levels were measured using a high-sensitivity ELISA kit. Generalized estimating equation methods were used to assess the relationship of multiple clinical and lifestyle (e.g. smoking) measures on CRP levels including differences between women taking HRT (HRT+) and not taking HRT (HRT-).

RESULTS

Overall serum CRP levels were strongly associated with body mass index (P < 0.0001) and age (P < 0.0001). Of the women, 243 were not using HRT and 84 were using HRT. HRT+ and HRT- women did not differ significantly in measures of clinical traits, with the exception of higher mean low-density lipoprotein cholesterol in HRT- women (P = 0.004). In all models tested, HRT+ women had significantly higher circulating CRP levels, with P-values ranging from 0.0045 to 0.010.

CONCLUSIONS

In this study of serum CRP concentration as a function of HRT in women with Type 2 diabetes, there was consistent evidence for increased circulating CRP levels in women receiving oestrogen-containing HRT. Whether HRT-induced increases in CRP can account for the adverse cardiovascular effects of HRT remains to be established; however, based on these data, there is little reason to believe that diabetic women would be spared from such an effect.

Familial aggregation and linkage analysis of autoantibody traits in pedigrees multiplex for systemic lupus erythematosus

Autoantibodies are clinically relevant biomarkers for numerous autoimmune disorders. The genetic basis of autoantibody production in systemic lupus erythematosus (SLE) and other autoimmune diseases is poorly understood. In this study, we characterized autoantibody profiles in 1,506 individuals from 229 multiplex SLE pedigrees. There was strong familial aggregation of antinuclear antibodies (ANAs), anti-double-stranded DNA (dsDNA), anti-La/SSB, anti-Ro/SSA, anti-Sm, anti-nRNP (nuclear ribonucleoprotein), IgM antiphospholipid (aPL) antibodies (Abs) and rheumatoid factor (RF) across these families enriched for lupus. We performed genome-wide linkage analyses in an effort to map genes that contribute to the production of the following autoantibodies: Ro/SSA, La/SSB, nRNP, Sm, dsDNA, RF, nuclear and phospholipids. Using an approach to minimize false positives and adjust for multiple comparisons, evidence for linkage was found to anti-La/SSB Abs on chromosome 3q21 (adjusted P=1.9 x 10(-6)), to anti-nRNP and/or anti-Sm Abs on chromosome 3q27 (adjusted P=3.5 x 10(-6)), to anti-Ro/SSA and/or anti-La/SSB Abs on chromosome 4q34-q35 (adjusted P=3.4 x 10(-4)) and to anti-IgM aPL Abs on chromosome 13q14 (adjusted P=2.3 x 10(-4)). These results support the hypothesis that autoantibody production is a genetically complex trait. Identification of the causative alleles will advance our understanding of critical molecular mechanisms that underlie SLE and perhaps other autoimmune diseases.

Genetic mapping of a 17q chromosomal region linked to obesity phenotypes in the IRAS family study

OBJECTIVE

Obesity is widely accepted to be influenced by both environmental and genetic factors. Several recent studies have used the positional cloning approach in an attempt to discover genes contributing to obesity. In the IRAS Family Study a genomewide scan was performed on 1425 individuals of Hispanic descent (90 extended pedigree families) to identify regions of the genome linked to obesity phenotypes.

METHODS

Nonparametric QTL linkage analysis was performed using a variance components approach. The genome scan was performed in two phases: an initial genome scan in 45 families and a replication scan in 45 families. Fine mapping and candidate gene analyses were also performed. General estimating equations (GEE1) and quantitative pedigree disequilibrium tests (QPDT) were used for association analysis of single SNP and haplotype data.

RESULTS

Evidence for linkage to obesity traits was observed in each scan on the long arm of chromosome 17. When data from both scans was combined, a region on chromosome 17q was identified with evidence of linkage to visceral adipose tissue (VAT; LOD 3.11), waist circumference (WAIST) (LOD 2.5) and body mass index (BMI) (LOD 2.81). Nine additional microsatellite markers were identified and genotyped on all Hispanic individuals, with a mean marker density of approximately 1 marker/3 cM. Evidence of linkage remained significant with LOD 3.05 for VAT, LOD 2.44 for BMI and LOD 1.92 for WAIST. Fine mapping analyses suggest the possibility of two different obesity loci. In addition, the LOD - 1 interval of the major VAT peak decreased from 83-108 to 95-111 cM. Three positional candidate genes under the peak: somatostatin receptor 2 (SSTR2), galanin receptor 2 (GALR2), and growth hormone bound protein receptor 2 (GRB2) were chosen for detailed evaluation. Multiple polymorphisms within each candidate were genotyped and tested for association with the obesity phenotypes. Little evidence of association was detected between polymorphisms and obesity traits.

CONCLUSION

In conclusion, replication of linkage and fine mapping suggest that a region on chromosome 17q contains a gene (or genes) that contributes to the genetic etiology of obesity with the strongest evidence for linkage to VAT. Candidate genes in the region do not appear to account for the evidence of linkage. Additional studies are necessary to identify the obesity-related polymorphisms.

Association analysis of genes in the renin-angiotensin system with subclinical cardiovascular disease in families with Type 2 diabetes mellitus: the Diabetes Heart Study

AIMS

Cardiovascular disease (CVD) is a major complication of Type 2 diabetes mellitus. The renin-angiotensin system (RAS) and nitric oxide production are both important regulators of vascular function and blood pressure. Genes encoding proteins involved in these pathways are candidates for a contribution to CVD in diabetic patients. We have investigated variants of the angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin type 1 receptor (AT1R) and endothelial nitric oxide synthase (NOS3) genes for association with subclinical measures of CVD in families with Type 2 diabetes mellitus (T2DM).

METHODS

Atherosclerosis was measured by carotid intima-media thickness and calcification of the carotid and coronary arteries in 620 European Americans and 117 African Americans in the Diabetes Heart Study. Because of the role of these systems in blood pressure regulation, blood pressure was also investigated.

RESULTS

Compelling evidence of association was not detected with any of the SNPs with any outcome measures after adjustments for covariates despite sufficient power to detect relatively small differences in traits for specific genotype combinations.

CONCLUSIONS

Genetic variation of the RAS and NOS3 genes do not appear to strongly influence subclinical cardiovascular disease or blood pressure in this diabetic population.

Loci contributing to adult height and body mass index in African American families ascertained for type 2 diabetes

Height and body mass index (BMI) have high heritability in most studies. High BMI and reduced height are well-recognized as important risk factors for a number of cardiovascular diseases. We investigated these phenotypes in African American families originally ascertained for studies of linkage with type 2 diabetes using self-reported height and weight. We conducted a genome wide scan in 221 families containing 580 individuals and 672 relative pairs of African American descent. Estimates of heritability and support for linkage were assessed by genetic variance component analyses using SOLAR software. The estimated heritabilities for height and BMI were 0.43 and 0.64, respectively. We have identified major loci contributing to variation in height on chromosomes 15 (LOD = 2.61 at 35 cM, p = 0.0004), 3 (LOD = 1.82 at 84 cM, p = 0.0029), 8 (LOD = 1.92 at 135 cM, p = 0.0024) and 17 (LOD = 1.70 at 110 cM, p = 0.0044). A broad region on chromosome 4 supported evidence of linkage to variation in BMI, with the highest LOD = 2.66 at 168 cM (p = 0.0005). Two height loci and two BMI loci appear to confirm the existence of quantitative trait loci previously identified by other studies, providing important replicative data to allow further resolution of linkage regions suitable for positional cloning of these cardiovascular disease risk loci.

The impact of ethnicity and sex on subclinical cardiovascular disease: the Diabetes Heart Study

AIMS/HYPOTHESIS

African-Americans with type 2 diabetes and access to adequate healthcare are at lower risk of clinical coronary artery disease than are white diabetic patients. We evaluated whether ethnic differences in subclinical cardiovascular disease, coronary and carotid artery calcified plaque and carotid artery intima-medial thickness (IMT) were present in members of The Diabetes Heart Study families.

SUBJECTS AND METHODS

In a bi-racial cohort of 1,180 individuals from families enriched for members with type 2 diabetes, we calculated coronary and carotid artery calcified plaque using fast-gated helical computed tomography, and measured carotid artery IMT and clinical risk factor profiles. Generalised estimating equations were used to test for an association between measures of subclinical cardiovascular disease and ethnicity and sex.

RESULTS

After adjustment for age, ethnicity and kidney function, African-Americans had significantly lower amounts of coronary artery calcified plaque (mean+/-SE) (866+/-158 vs 1,915+/-135, respectively; p=0.0466) and carotid artery calcified plaque (179+/-51 vs 355+/-27, respectively; p=0.0240) relative to whites, despite having increased carotid IMT (0.71+/-0.01 vs 0.67+/-0.004 cm, respectively; p=0.0007), and higher blood pressure, albuminuria and HbA1c. Sex-specific analyses revealed that African-American men had significantly lower coronary and carotid artery calcified atheroma than white men. In women, ethnic differences in calcified carotid artery plaque, but not coronary artery plaque, were observed.

CONCLUSIONS/INTERPRETATION

In families enriched for members with type 2 diabetes, African-American men had markedly lower levels of coronary and carotid artery calcified plaque than white men, despite increased carotid artery IMT and conventional risk factors. These findings suggest that susceptibility to subclinical cardiovascular disease differs markedly according to ethnicity and sex.

Quantitative trait loci for abdominal fat and BMI in Hispanic-Americans and African-Americans: the IRAS Family study

OBJECTIVE

To conduct linkage analysis for body mass index (BMI, kg/m2), waist-to-hip ratio (WHR), visceral adipose tissue mass (VAT, cm2) and subcutaneous adipose tissue mass (SAT, cm2) using a whole genome scan.

DESIGN

Cross-sectional family study.

STUDY SUBJECTS

African-American families from Los Angeles (AA, n=21 extended pedigrees) and Hispanic-American families (HA) from San Antonio, TX (HA-SA, n=33 extended pedigrees) and San Luis Valley, CO (HA-SLV, n=12 extended pedigrees), totaling 1049 individuals in the Insulin Resistance and Atherosclerosis (IRAS) Family Study.

MEASUREMENTS

VAT and SAT were measured using a computed tomography scan obtained at the fourth and fifth lumbar vertebrae. All phenotypes were adjusted for age, gender, and study center. VAT, SAT, and WHR were analyzed both unadjusted and adjusted for BMI.

RESULTS

Significant linkage to BMI was found at D3S2387 (LOD=3.67) in African-Americans, and at D17S1290 in Hispanic-Americans (LOD=2.76). BMI-adjusted WHR was linked to 12q13-21 (D12S297 (LOD=2.67) and D12S1052 (LOD=2.60)) in Hispanic-Americans. The peak LOD score for BMI-adjusted VAT was found at D11S2006 (2.36) in Hispanic families from San Antonio. BMI-adjusted SAT was linked to D5S820 in Hispanic families (LOD=2.64). Evidence supporting linkage of WHR at D11S2006, VAT at D17S1290, and SAT at D1S1609, D3S2387, and D6S1056 was dependent on BMI, such that the LOD scores became nonsignificant after adjustment of these phenotypes for BMI.

CONCLUSIONS

Our findings both replicate previous linkage regions and suggest novel regions in the genome that may harbor quantitative trait locis contributing to variation in measures of adiposity.

Single-nucleotide polymorphisms in the C-reactive protein (CRP) gene promoter that affect transcription factor binding, alter transcriptional activity, and associate with differences in baseline serum CRP level

To investigate whether functional polymorphisms exist in the C-reactive protein (CRP) gene, i.e., ones that contribute directly to differences in baseline CRP among individuals, we sequenced a 1,156-nucleotide-long stretch of the CRP gene promoter in 287 ostensibly healthy people. We identified two single-nucleotide polymorphisms (SNPs), a bi-allelic one at nucleotide -409 (G-->A), and a tri-allelic one at -390 (C-->T-->A), both resident within the hexameric core of transcription factor binding E-box elements. Electrophoretic mobility shift assays confirmed that the SNP within the sequence (-412)CACGTG(-407) (E-box 1) modulates transcription factor binding, and that the one within (-394)CACTTG(-389) (E-box 2) supports transcription factor binding only when the -390 T allele is present. The commonest of four E-box 1/E-box 2 haplotypes (-409G/-390T) identified in the population supported highest promoter activity in luciferase reporter assays, and the rarest one (-409A/-390T) supported the least. Importantly, serum CRP in people with these haplotypes reproduced this rank order, i.e., people with the -409G/-390T haplotype had the highest baseline serum CRP (mean +/- SEM 10.9 +/- 2.25 microg/ml) and people with the -409A/-390T haplotype had the lowest (5.01 +/- 1.56 microg/ml). Furthermore, haplotype-associated differences in baseline CRP were not due to differences in age, sex, or race, and were still apparent in people with no history of smoking. At least two other SNPs in the CRP promoter lie within E-box elements (-198 C-->T, E-box 4, and -861 T-->C, E-box 3), indicating that not only is the quality of E-box sites in CRP a major determinant of baseline CRP level, but also that the number of E-boxes may be important. These data confirm that the CRP promoter does encode functional polymorphisms, which should be considered when baseline CRP is being used as an indicator of clinical outcome. Ultimately, development of genetic tests to screen for CRP expression variants could allow categorization of healthy people into groups at high versus low future risk of inflammatory disease.

Association of adipose tissue deposition and beta-2 adrenergic receptor variants: the IRAS family study

OBJECTIVE

Adipose tissue distribution (visceral vs subcutaneous) has been shown to be an important predictor of insulin resistance, diabetes and cardiovascular disease, independent of body mass index. The beta-2 adrenergic receptor is a major lipolytic receptor in human fat cells and the gene that codes for this protein is an important candidate gene for measures of adiposity and fat deposition. We examined whether two common polymorphisms in codons 16 (Arg16Gly) and 27 (Gln27Glu) are associated with measures of fat distribution in participants of the IRAS Family Study.

METHODS

We recruited African-American (AA) and Hispanic-American (HA) families from Los Angeles, CA, USA (18 pedigrees, 272 AA individuals), San Antonio, TX, USA (33 pedigrees, 448 HA individuals) and San Luis Valley, CO, USA (12 pedigrees, 272 HA individuals). We estimated adipose tissue distribution via computed tomography. To test for an association between adiposity measures and these polymorphisms, we used generalized estimating equations, adjusting for age, gender, clinical site (ethnicity), body mass index, and familial correlation.

RESULTS

Of the 992 individuals genotyped for these polymorphisms, 57% were female and 15% had been diagnosed with type 2 diabetes mellitus. The mean age was 42.7+/-14.6 y. The Glu27 allele of the Gln27Glu polymorphism was positively associated with (P-value for recessive model): body mass index (0.025), visceral adipose tissue (<0.0001) and visceral-to-subcutaneous adipose ratio (0.009), but not with subcutaneous adipose tissue (0.952). The Arg16Gly polymorphism was not associated with any of the adiposity measures.

CONCLUSIONS

These findings suggest that genetic variation in the beta-2 adrenergic receptor gene influences fat deposition and body size in AAs and HAs. In particular, these results support a role for the gene in the distribution of visceral adipose tissue but not subcutaneous adipose tissue.

Fine mapping chromosome 16q12 in a collection of 231 systemic lupus erythematosus sibpair and multiplex families

Systemic lupus erythematosus (SLE) is a chronic, autoimmune disorder influenced by multiple genetic and environmental factors. Linkage of SLE to chromosome 16q12-13 (LOD score=3.85) was first identified in pedigrees collected at the University of Minnesota, and has been replicated in several independent SLE collections. We performed fine mapping using microsatellites to further refine the susceptibility region(s), and the best evidence for linkage was identified at marker D16S3396 (LOD=2.28, P=0.0006). Evidence of association was suggested in the analysis of all families (D16S3094, P=0.0516) and improved to the level of significance (P=0.0106) when only the Caucasian families were analyzed. Subsets of pedigrees were then selected on the basis of clinical manifestations, and these subsets showed evidence for association with several markers: GATA143D05 (renal, P=0.0064), D16S3035 (renal, P=0.0418), D16S3117 (renal, P=0.0366), D16S3071 (malar rash, P=0.03638; neuropsychiatric, P=0.0349; oral ulcers, P=0.0459), D16S3094 (hematologic, P=0.0226), and D16S3089 (arthritis, P=0.0141). Together, these data provide further evidence that an important susceptibility gene(s) for SLE is located at 16q12.

Genome scan for loci linked to mite sensitivity: the Collaborative Study on the Genetics of Asthma (CSGA)

Mite sensitivity has been reported to be a major risk factor for asthma. As part of the Collaborative Study on the Genetics of Asthma (CSGA), a genome scan using mite reactivity (Dermatophagoides Pteronyssinus (Der p) and Dermatophagoides farinae (Der f)) as the phenotype was conducted. In 287 CSGA families, 122 were informative for linkage. Evidence supporting linkage was observed for regions on chromosome 19 (D19S591, lod=2.43, P=0.0008; D19S1037, lod=1.57, P=0.007) and chromosome 20 (D20S473/D20S604, lod=1.41, P=0.01). All three ethnic groups appeared to contribute to the evidence for linkage on chromosome 20. African-American families gave strongest support for linkage on chromosomes 3 (D3S2409, lod=1.33, P=0.01), 12 (D12S373, lod=1.51, P=0.008) and 18 (ATA82B02, lod=1.32, P=0.01). Caucasian families showed strong evidence for linkage on chromosome 19 (D19S591, lod=3.51, P=0.00006). Hispanic families supported linkage on chromosomes 11 (D11S1984, lod=1.56, P=0.007), 13 (D13S787, lod=1.30, P=0.01) and 20 (D20S470, lod=1.71, P=0.005). These results suggest that multiple genes may be involved in controlling skin reactivity to Dermatophoigoies.

Heritability of spinal trabecular volumetric bone mineral density measured by QCT in the Diabetes Heart Study

The heritability of trabecular volumetric bone mineral density (BMD) determined by quantitative computed tomography (QCT) has not yet been reported. The purpose of this study was to investigate the heritability of BMD as determined by QCT and DXA in 124 women and 120 men (age 39-83 years, BMI 17-75, 84% type 2 diabetics) from 101 families (232 sibling pairs) in the Diabetes Heart Study. Volumetric BMD had a heritability (h2) estimate of 0.73 (SE = 0.15, P < 0.0001) at the lumbar spine and 0.71 (SE = 0.15, P < 0.0001) at the thoracic spine. Areal BMD heritability estimates were 0.56 for PA spine, 0.43 for total hip, 0.43 for femoral neck, 0.45 for distal radius, 0.42 for mid-radius, and 0.52 for whole body (all P < 0.01). After accounting for familial correlation using generalized estimating equations, volumetric BMD was inversely associated with age (r = -0.52, P < 0.0001) and duration of diabetes (r = -0.24, P < 0.01) and positively associated with body weight (r = 0.25, P < 0.01). In multivariate analysis, adjustment for age, sex, and race lowered the h2 estimates for volumetric BMD at the lumbar (h2 = 0.41, P < 0.01) and thoracic (h2 = 0.48, P < 0.001) spine, increased the h2 estimate for areal BMD at the mid radius (h2 = 0.58, P < 0.0001), and had little effect on the h2 estimate for areal BMD at other sites (h2 = 0.41-0.55, all P < 0.01). Additional adjustment for BMI, duration of diabetes, and physical activity had little effect on the h2 estimates for volumetric BMD or areal BMD except at the hip where they were lowered (h2 = 0.31-0.33, all P < 0.05). These data suggest that, like areal BMD, volumetric BMD is highly heritable and may be used in designing linkage studies to locate genes governing bone metabolism.

Adiponectin as a novel determinant of bone mineral density and visceral fat

Growing evidence suggests that positive associations between fat mass (FM) and bone mineral density (BMD) are mediated by not only biomechanical but also biochemical factors. Adiponectin is a novel adipocyte-derived hormone that regulates energy homeostasis and has anti-inflammatory and anti-atherogenic effects. Unlike other adipokines such as leptin, adiponectin levels decrease in obesity and type 2 diabetes. The purpose of our study was to investigate associations of serum adiponectin with BMD (DXA and QCT), FM (DXA and QCT), and serum leptin and soluble leptin receptor levels in 38 women and 42 men (age 39-81, BMI 17-55, 86% with type 2 diabetes). After adjusting for age, gender, race, smoking, and diabetes status, serum adiponectin was inversely associated with areal BMD (r = -0.20 to -0.3, all P < 0.01), volumetric BMD (r = -0.35 to -0.44, all P < 0.01), and visceral fat volume (r = -0.30, P < 0.01). These associations remained significant after adjusting for whole body fat mass. The associations of adiponectin with subcutaneous fat volume, whole body FM, and serum leptin level were not significant (all P > 0.1). These data suggest that adiponectin may play a role in the protective effects of visceral fat on BMD.

Nonparametric linkage regression. I: Combined Caucasian CSGA and German genome scans for asthma

In this paper we applied the nonparametric linkage (NPL) regression approach to the combined Caucasian genome scan data from the Collaborative Study on the Genetics of Asthma (CSGA) and German family studies to search for regions of the genome that exhibit evidence for linkage to putative asthma-predisposing genes. The multipoint single-locus model identified three regions of the genome with LOD scores of approximately two or greater. These regions were on 6p near D6S291 (LOD = 2.78), 2p near D2S2298 (LOD = 2.11), and 1p near D1S1597 (LOD = 1.92). Modeling multiple loci together and testing for interactions among loci yielded stronger evidence for linkage in these regions. We observed a potential epistatic interaction between 2p and 14p (p = 0.0003) and conditional LOD scores of 2.75 on 1p, 3.89 on 6p, 1.64 on 7p, and 1.64 on 15q.

Multilocus linkage analysis of the German asthma data

We analyzed data from the German Asthma Genetics Group with three methods that utilize pedigree-specific nonparametric linkage scores to facilitate the search for multiple independent and interacting susceptibility loci. The three methods included a conditional analysis, logistic regression, and neural networks. Although there were differences, the three methods identified many of the same susceptibility loci. The most consistent evidence was provided for loci on chromosomes 1, 2, 6, 9, and 15. Both the conditional and the logistic regression analyses suggested an epistatic relationship between loci on chromosomes 2 and 9. The logistic regression analysis further revealed evidence for locus heterogeneity between loci on chromosomes 6 and 15. Finally, the neural network analysis identified a potential locus on chromosome 17 that was not identified in the other analyses.

Nonparametric linkage regression. II: Identification of influential pedigrees in tests for linkage

We applied case-deletion-based diagnostics to the combined Caucasian genome scan data for asthma and IgE from the Collaborative Study on the Genetics of Asthma (CSGA) and German family studies in order to identify influential pedigrees in tests for linkage. These methods identified 12 pedigrees whose data appear not to fit the asthma linkage model and for whom alternative genetic and nongenetic explanations can be explored. The methods also identified four pedigrees for chromosome 1 and two pedigrees for chromosome 2 that provide strong evidence for linkage at their respective loci. Similarly, these methods helped identify four pedigrees that strongly influenced the linkage tests for IgE. From these data, we can construct an enriched subset of pedigrees to be used in further analysis for mapping region-specific putative trait predisposing loci.

Familial aggregation of coronary artery calcium in families with type 2 diabetes

Type 2 diabetes is widely recognized as a major risk factor for atherosclerotic cardiovascular disease, including subclinical atherosclerosis as measured by noninvasive procedures. However, the role of genetic factors that contribute to various measures of subclinical atherosclerosis is largely unknown. We hypothesize that subclinical atherosclerosis, measured as coronary artery calcification (CAC), will be extensive in individuals with type 2 diabetes and that its presence depends on both genetic and environmental factors. The genetic factors should result in the familial aggregation of CAC. To determine the extent of familial aggregation of CAC in the presence of type 2 diabetes, we studied 122 individuals with type 2 diabetes (mean age 60 years) and 13 individuals without diabetes in 56 families. CAC was measured by fast-gated helical computed tomography. Other measured factors included blood pressure, body size, lipids, HbA1c, and self-reported medical history. To test for an association between CAC and these factors while accounting for the potential familial correlation of CAC, generalized estimating equations were used. CAC was detectable in 80% of individuals with diabetes (median score 84, range 0-5,776). Extent of CAC, adjusted for age, was positively associated with male sex (P = 0.0003), reduced HDL (P = 0.02), albumin-to-creatinine ratio (P = 0.008), and cigarette pack-years (P = 0.03). CAC was also positively associated with a history of angina, myocardial infarction, stroke, and vascular procedures (all P < 0.01). HbA1c and fasting glucose were positively, but nonsignificantly, associated with the extent of CAC (P = 0.14 and 0.08, respectively). CAC, adjusted for age, sex, race, and diabetes status, was heritable (h2 = 0.50; P = 0.009). In multivariate analysis with additional adjustment for HDL, BMI, hypertension, and smoking, h2 = 0.40 (P = 0.038). These results suggest that strong (independent) genetic factors as well as environmental factors contribute to the variance of CAC in individuals with type 2 diabetes. In these data, CAC seems heritable and may serve as an important feature in designing studies to map genes contributing to both atherosclerosis and type 2 diabetes.

Further evidence for a susceptibility locus for type 2 diabetes on chromosome 20q13.1-q13.2

We previously reported suggestive linkage between type 2 diabetes and markers in a region on chromosome 20q using data from a collection of 29 Caucasian families in which type 2 diabetes with middle-age-onset was segregated as an autosomal-dominant disorder. To map more precisely the susceptibility locus (or loci) within this broad region, we increased the family collection and genotyped all families for additional markers, both within the critical region and spaced over the rest of chromosome 20. Altogether 526 individuals (including 241 with diabetes) from the total collection of 43 families were included in the study. All individuals were genotyped for 23 highly polymorphic markers. Positive evidence for linkage was found for a 10-cM region on the long arm of chromosome 20q13.1-q13.2 between markers D20S119 and D20S428. The strongest evidence in two-point as well as multipoint linkage analysis (P = 1.8 x 10(-5)) occurred at the position corresponding to marker D20S196. The individuals with diabetes in the seven most strongly linked families had high serum insulin levels during fasting and 2-h post-glucose load periods. We did not find any evidence for linkage between type 2 diabetes and any other region on chromosome 20. In conclusion, our larger and more comprehensive study showed very strong evidence for a susceptibility gene for insulin-resistant type 2 diabetes located on the long arm of chromosome 20 around marker D20S196.

The polymorphic exon 1 androgen receptor CAG repeat in men with a potential inherited predisposition to prostate cancer

Recent studies have provided epidemiological evidence in support of a possible prostate cancer susceptibility locus on the X chromosome. The androgen receptor (AR) gene, located at Xq11-12, has been implicated as a risk factor for the development of prostate cancer. To examine the potential role of the AR locus in prostate cancer susceptibility, the AR CAG repeat length was measured in 270 Caucasian men with prostate cancer from 133 unrelated families. Each of these families has two or more confirmed cases of prostate cancer occurring in first- and/or second-degree relatives. No evidence for linkage of the AR gene to prostate cancer was observed. We tested for the previously reported association of short CAG alleles with prostate cancer using t tests, Pearson's chi2 tests, and logistic regression; analyses were subsequently repeated to incorporate only men with moderate- to high-grade prostate cancer. No association between AR CAG allele length and prostate cancer was detected when either a subset of unrelated patients or a subset of unrelated patients with moderate- to high-grade cancer was compared with a set of unrelated controls. We failed to detect an association between short AR CAG alleles and early age of prostate cancer diagnosis. Once specific hereditary prostate cancer genes have been identified, future studies can more carefully delineate the potential role of this AR polymorphism as a modifier locus in high-risk families.

Type 2 diabetes: evidence for linkage on chromosome 20 in 716 Finnish affected sib pairs

We are conducting a genome scan at an average resolution of 10 centimorgans (cM) for type 2 diabetes susceptibility genes in 716 affected sib pairs from 477 Finnish families. To date, our best evidence for linkage is on chromosome 20 with potentially separable peaks located on both the long and short arms. The unweighted multipoint maximum logarithm of odds score (MLS) was 3.08 on 20p (location, chi = 19.5 cM) under an additive model, whereas the weighted MLS was 2.06 on 20q (chi = 57 cM, recurrence risk,lambda(s) = 1. 25, P = 0.009). Weighted logarithm of odds scores of 2.00 (chi = 69.5 cM, P = 0.010) and 1.92 (chi = 18.5 cM, P = 0.013) were also observed. Ordered subset analyses based on sibships with extreme mean values of diabetes-related quantitative traits yielded sets of families who contributed disproportionately to the peaks. Two-hour glucose levels in offspring of diabetic individuals gave a MLS of 2. 12 (P = 0.0018) at 9.5 cM. Evidence from this and other studies suggests at least two diabetes-susceptibility genes on chromosome 20. We have also screened the gene for maturity-onset diabetes of the young 1, hepatic nuclear factor 4-a (HNF-4alpha) in 64 affected sibships with evidence for high chromosomal sharing at its location on chromosome 20q. We found no evidence that sequence changes in this gene accounted for the linkage results we observed.

The W64R variant of the beta3-adrenergic receptor is not associated with type II diabetes or obesity in a large Finnish sample

Recent studies have suggested an association between Type II (non-insulin-dependent) diabetes mellitus-related phenotypes and a cytosine-to-thymidine substitution that results in the replacement of tryptophan by arginine at codon 64 (Trp64Arg or W64R) of the beta3-adrenergic receptor gene. Here, we present the results of possibly the largest association study to date on the variant in a sample of 526 families with a total of 1725 subjects, 1053 of whom had Type II diabetes. Preliminary calculations suggested that we had excellent power to detect the moderate associations which were reported in previous studies. No associations were found between the W64R variant and the following phenotypes in our sample: Type II diabetes, age at diagnosis for Type II diabetes, measures of obesity, fasting glucose, fasting insulin, minimal model variables, and systolic and diastolic blood pressures. In the analysis of plasma lipids, we detected an association between the variant and HDL ratios (HDL cholesterol/total cholesterol) (p = 0.013), which remained significant even after adjusting for sex, affection status and age. Since W64R homozygotes (n = 11) had the highest HDL ratios, however, heterozygotes had the lowest and the wild-type subjects had intermediate values, we conclude that the W64R variant is unlikely to reduce HDL ratios in a dose-dependent, pathogenic manner.

Mapping genes for NIDDM. Design of the Finland-United States Investigation of NIDDM Genetics (FUSION) Study

OBJECTIVE

To map and identify susceptibility genes for NIDDM and for the intermediate quantitative traits associated with NIDDM.

RESEARCH DESIGN AND METHODS

We describe the methodology and sample of the Finland-United States Investigation of NIDDM Genetics (FUSION) study. The whole genome search approach is being applied in studies of several different ethnic groups to locate susceptibility genes for NIDDM. Detailed description of the study materials and designs of such studies are important, particularly when comparing the findings in these studies and when combining different data sets.

RESULTS

Using a careful selection strategy, we have ascertained 495 families with confirmed NIDDM in at least two siblings and no history of IDDM among the first-degree relatives. These families were chosen from more than 22,000 NIDDM patients, representative of patients with NIDDM in the Finnish population. In a subset of families, a spouse and offspring were sampled, and they participated in a frequently sampled intravenous glucose tolerance test (FSIGT) analyzed with the Minimal Model. An FSIGT was completed successfully for at least two nondiabetic offspring in 156 families with a confirmed nondiabetic spouse and no history of IDDM in first-degree relatives.

CONCLUSIONS

Our work demonstrates the feasibility of collecting a large number of affected sib-pair families with NIDDM to provide data that will enable a whole genome search approach, including linkage analysis.

Genetic association mapping based on discordant sib pairs: the discordant-alleles test

Family-based tests of association provide the opportunity to test for an association between a disease and a genetic marker. Such tests avoid false-positive results produced by population stratification, so that evidence for association may be interpreted as evidence for linkage or causation. Several methods that use family-based controls have been proposed, including the haplotype relative risk, the transmission-disequilibrium test, and affected family-based controls. However, because these methods require genotypes on affected individuals and their parents, they are not ideally suited to the study of late-onset diseases. In this paper, we develop several family-based tests of association that use discordant sib pairs (DSPs) in which one sib is affected with a disease and the other sib is not. These tests are based on statistics that compare counts of alleles or genotypes or that test for symmetry in tables of alleles or genotypes. We describe the use of a permutation framework to assess the significance of these statistics. These DSP-based tests provide the same general advantages as parent-offspring trio-based tests, while being applicable to essentially any disease; they may also be tailored to particular hypotheses regarding the genetic model. We compare the statistical properties of our DSP-based tests by computer simulation and illustrate their use with an application to Alzheimer disease and the apolipoprotein E polymorphism. Our results suggest that the discordant-alleles test, which compares the numbers of nonmatching alleles in DSPs, is the most powerful of the tests we considered, for a wide class of disease models and marker types. Finally, we discuss advantages and disadvantages of the DSP design for genetic association mapping.

Controlled prospective randomized comparison of high-frequency jet ventilation and conventional ventilation in neonates with respiratory failure and persistent pulmonary hypertension

OBJECTIVE

The objective of this study was to evaluate the efficacy and safety of high-frequency jet ventilation in near-term and term neonates with persistent pulmonary hypertension.

STUDY DESIGN

Subjects for this prospective, randomized, controlled comparison study were recruited from neonates treated in a level-three neonatal intensive care unit that accepts referrals for extracorporeal membrane oxygenation.

RESULTS

In patients treated with high-frequency jet ventilation (n = 11) acute improvement in oxygenation (p = 0.008), ventilation (p < 0.001), and oxygen indices (p < or = 0.01) was demonstrated while stable peak and mean airway pressures were maintained. Control group patients receiving high-frequency positive pressure ventilation with a conventional ventilator required increasingly higher peak inspiratory pressures (p = 0.005) to maintain oxygenation, ventilation, and oxygen indices. There were no significant differences in survival without use of extracorporeal membrane oxygenation, nor were there differences in duration of oxygen therapy, ventilation, and hospitalization; need for extracorporeal membrane oxygenation; or incidence of chronic lung disease.

CONCLUSIONS

High-frequency jet ventilation acutely improves oxygenation and ventilation without significantly increasing morbidity. Therefore high-frequency jet ventilation may be a useful adjunct for stabilization of the conditions of neonates with severe persistent pulmonary hypertension. Conclusions about the efficacy of high-frequency jet ventilation in improving survival without the need for extracorporeal membrane oxygenation await multicentered, collaborative investigations with large cohorts of patients.

Some techniques for the analysis of work sampling data

Work sampling is an observational technique that produces counts representing the number of times that an individual has been observed performing each of several tasks. These data are collected using either systematic or random times of observation, and typically exhibit correlation between repeated observations on the same individual, with the degree of correlation being a function of the amount of time elapsed between measurements. Using several recently developed statistical techniques, we illustrate how it is possible to carry out analyses of these nominal outcomes that account for the correlation between repeated outcomes. We use description of a work sampling study to motivate the techniques and we compare empirically results from analyses based on several different underlying assumptions.

Behavioral intervention to increase condom use among high-risk female adolescents

OBJECTIVE

To determine whether condom use among high-risk female adolescents could be increased by a behavioral intervention, with the use of infection with Chlamydia trachomatis as a biomarker of condom practices.

DESIGN

Prospective, randomized, controlled intervention.

SETTING

Urban family planning and sexually transmitted disease clinics.

PARTICIPANTS

Two hundred nine female adolescents, aged 15 through 19 years, who were treated for C. trachomatis genitourinary infection, were randomly assigned to standard (control) or experimental (behavioral intervention) groups. One hundred twelve subjects returned for follow-up 5 to 7 months after enrollment and comprise the study subjects.

MEASUREMENTS

Subjects completed a multiinstrument questionnaire measuring sexual behavior, condom practices, attitudes and beliefs, cognitive complexity, sociodemographics, and motivation at enrollment and follow-up. Endourethral and endocervical sites were sampled for C. trachomatis.

RESULTS

Among the 112 subjects who returned for repeated examination, those who had received the experimental intervention reported increased use of condoms by their sexual partners for protection against sexually transmitted diseases (odds ratio = 2.4; p = 0.02) and for vaginal intercourse (odds ratio = 3.1; p = 0.005) at the 6-month follow-up. Multivariable logistic regression analysis controlling for condom use at enrollment demonstrated that the experimental intervention (odds ratio = 2.8; p = 0.03) and the higher cognitive complexity (odds ratio = 4.6; p = 0.02) independently contributed to greater condom use at follow-up. Despite greater use of condoms among the group who had received the intervention, use remained inconsistent and rates of reinfection with C. trachomatis were not significantly different (26% vs 17%; p = 0.3).

CONCLUSION

Although a brief behavioral intervention among high-risk female adolescents can increase condom use by their sexual partners, incident infection does not appear to be reduced, because condom use remained inconsistent.

Primary care physician productivity: the physician factor

OBJECTIVES

To model physician productivity as a function of clinic (support system) characteristics and physician characteristics and to model the time a physician spends with the patient as a function of patient characteristics.

DESIGN

Observational study.

SETTING

A general medicine clinic of a university-affiliated Veterans Affairs medical center.

PATIENTS

A cohort of 2,520 patients having 2,721 consecutive outpatient visits to 56 physicians.

MAIN OUTCOME MEASURES

Physician productivity defined as patients seen/physician/hour and time (minutes) spent with the patient.

RESULTS

Physicians saw a mean (+/- SD) of 1.62 +/- 0.68 patients/hour. Clinic characteristics explained 8.2% of the variability of session-specific physician productivity. Controlling for clinic characteristics, a factor representing the physician explained an additional 55.4%. A model for overall physician productivity, using physician characteristics, explained 84.9% of the variance, and time spent with the patient was an important predictor. Modeling physician time with patients, patient characteristics accounted for only 7% of the variability. Controlling for patient characteristics, the individual physician again provided the greatest explanatory power, an additional 22.8% of the variability.

CONCLUSIONS

Physicians' practice patterns, rather than clinic or patient characteristics, may account for most of the variation in physician productivity. Given the magnitude of the influence of individual practice patterns, interventions to increase productivity need to consider methods to affect physician behavior.

Patterns of referral and examination for retinopathy in pregnant women with diabetes by primary care physicians

PURPOSE

Family practice (FP), General Practice (GP) and obstetrics-gynecology (OB/GYN) physicians were surveyed to determine whether they routinely referred pregnant patients with diabetes to an ophthalmologist, looked into the patient's eyes to screen for retinopathy, and dilated the eyes for fundi examination.

METHODS

Hospitals providing obstetrical services were contacted to identify primary-care physicians. Physicians identified as having obstetrical privileges were surveyed by mail to determine if they were actively providing obstetrical care. Physicians who provided both obstetrical and diabetes care were mailed a survey.

RESULTS

Of 668 physicians surveyed, 429 responded: 224 FPS, 184 OB/GYNS and 21 GPS. A relatively small percentage (27%) of physicians in both groups routinely refer all of their pregnant patients with pre-existing diabetes to an ophthalmologist. Family practice physicians were more likely to perform an eye exam to screen for retinopathy in patients with both pre-existing and gestational diabetes than OB/GYNS (p < .0005). Only 11% of FPS and no OB/GYNS reported that they dilated the eyes when performing a fundus examination (p = .04).

CONCLUSION

The physicians surveyed under-utilize recommended strategies for eye care of pregnant women with pre-existing diabetes. Based upon these results, we call for a recommitment to partnership of primary-care physicians and ophthalmologists in the detection and treatment of diabetic retinopathy during pregnancy.