Five-year change in visceral adipose tissue quantity in a minority cohort: the Insulin Resistance Atherosclerosis Study (IRAS) family study

OBJECTIVE To describe the 5-year change in visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) areas. RESEARCH DESIGN AND METHODS Absolute change in VAT and SAT measured by abdominal computed tomography scans has been obtained at a 5-year interval from African Americans (n = 389) and Hispanic Americans (n = 844), aged 20-69 years, in 10-year age-groups. RESULTS Mean 5-year increases in VAT areas in women were 18, 7, 4, 0.4, and -3 cm(2) for African Americans and 13, 7, 3, 1, and -15 cm(2) for Hispanics, across the 5 age decades (trend not significant). Mean 5-year increases in SAT areas in women were 88, 46, 19, 17, and 14 cm(2) for African Americans and 53, 20, 17, 12, and 1 cm(2) for Hispanics, across the 5 age decades (P < 0.05 for both). Similar trends have been observed in men. CONCLUSIONS Accumulation of abdominal fat is greatest in young adulthood. These data may be useful in identifying subgroups at risk of type 2 diabetes.

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.

Correlates and heritability of nonalcoholic fatty liver disease in a minority cohort

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and insulin resistance. The condition disproportionately affects Hispanic Americans. The aims of this study were to examine the risk factors and heritability of NAFLD in 795 Hispanic American and 347 African-American adults participating in the Insulin Resistance Atherosclerosis Study (IRAS) Family Study. Computed tomography (CT) scans of the abdomen were evaluated centrally for measures of liver-spleen (LS) density ratio and abdominal fat distribution. Other measures included insulin sensitivity (SI) calculated from a frequently sampled intravenous glucose tolerance test and various laboratory measures. Statistical models which adjust for familial relationships were estimated separately for the two ethnic groups. Heritability was calculated using a variance components approach. The mean age of the cohort was 49 years (range 22-84); 66% were female. NAFLD (LS ratio<1) was more common in Hispanic Americans (24%) than African Americans (10%). NAFLD was independently associated with SI and visceral adipose tissue (VAT) area in both ethnic groups, although the proportion of explained variance was considerably higher in the Hispanic models. Adiponectin contributed significantly in the African-American models whereas triglycerides (TGs) and plasminogen activator inhibitor 1 (PAI-1) contributed only in the Hispanic models. Liver density was modestly heritable in both ethnic groups (h2 approximately 0.35). In summary, the prevalence of NAFLD was twofold greater in Hispanic than African Americans. Certain correlates of NAFLD were similar between the ethnic groups, whereas others were distinct. NAFLD was modestly heritable. These findings suggest that NAFLD may have a differing environmental and/or genetic basis in these ethnic groups.

Prediction of type 2 diabetes using alternate anthropometric measures in a multi-ethnic cohort: the insulin resistance atherosclerosis study

OBJECTIVE

To compare different anthropometric measures in terms of their ability to predict type 2 diabetes and to determine whether predictive ability was modified by ethnicity.

RESEARCH DESIGN AND METHODS

Anthropometry was measured at baseline for 1,073 non-Hispanic white (nHW), African American (AA), and Hispanic (HA) subjects, of whom 146 developed type 2 diabetes after 5.2 years. Logistic regression models were used with areas under the receiver operator characteristic curve (AROCs) comparing the prediction of models.

RESULTS

Waist-to-height ratio (AROC 0.678) was the most predictive measure, followed by BMI (AROC 0.674). Results were similar in nHW and HA subjects, although in AA subjects, central adiposity measures appeared to best predict type 2 diabetes.

CONCLUSIONS

Measures of central and overall adiposity predicted type 2 diabetes to a similar degree, except in AA subjects, for whom results suggested that central measures were more predictive.

Measurement characteristics of the ankle-brachial index: results from the Action for Health in Diabetes study

Many protocols have been used in clinical and research settings for collecting systolic blood pressure (SBP) measurements to calculate the ankle-brachial index (ABI); however, it is not known how useful it is to replicate measurements and which measures best reflect cardiovascular risk. Standardized measurements of ankle and arm SBP from 5140 overweight or obese individuals with type 2 diabetes were used to estimate sources of variation. Measurement characteristics of leg-specific ABI, as calculated using a standard algorithm based on the highest SBP of the dorsalis pedis or posterior tibial arteries, were projected using simulations. Coefficients of variability ranged from 2% to 3% when single SBP measurements were used and ABI was overestimated by 2-3%. Taking two SBP measurements at each site reduced standard errors and bias each by 30-40%. The sensitivity of detecting low ABI ranges exceeded 90% for ABI within 0.05 of the 0.90 clinical cut-point. The average and the minimum of the two (i.e. right and left) leg-specific ABI values had similar U-shaped relationships with Framingham risk scores; however, the average leg ABI had slightly greater precision. Replicating SBP measurements reduces the error and bias of ABI. Averaging leg-specific values may increase power for characterizing cardiovascular disease risk.

Diabetes, abdominal adiposity, and atherogenic dyslipoproteinemia in women compared with men

OBJECTIVE

To understand why atherogenic risk differs more between diabetic and nondiabetic women than between diabetic and nondiabetic men.

RESEARCH DESIGN AND METHODS AND RESULTS

Measures of cardiovascular risk, body composition, and serum hormones from the baseline examinations of the Insulin Resistance Atherosclerosis Study on 524 nondiabetic women, 258 diabetic women, 421 nondiabetic men, and 220 diabetic men were compared to detect greater adverse differences in women than in men. Systolic blood pressure; apolipoprotein B (apoB); total cholesterol; apoB-to-apoA-I ratio; non-HDL cholesterol; LDL particle count, small LDL, and intermediate-density lipoprotein by nuclear magnetic resonance; and C-reactive protein exhibited significant diabetes-sex interaction (P < 0.05). ApoB exhibited the most significant interaction (P = 0.0005). Age- and ethnicity-adjusted apoB means were lower in nondiabetic women than nondiabetic men (102.4 vs. 106.8 mg/dl, P < 0.05) but higher in diabetes (115.7 vs. 110.2 mg/dl, P < 0.01). Plotted against BMI, waist circumference was 6% higher and hip circumference 10% lower in diabetic than nondiabetic women (both P < 0.05), whereas the circumference measures did not differ conspicuously between diabetic and nondiabetic men.

CONCLUSIONS

In diabetic women, an elevated level of atherogenic particles, as manifested by apoB and LDL particle count, which may result from abdominal adiposity, represents a major treatable cardiovascular risk factor.

Hepatic steatosis and subclinical cardiovascular disease in a cohort enriched for type 2 diabetes: the Diabetes Heart Study

OBJECTIVES

To explore mechanisms whereby hepatic steatosis may be associated with cardiovascular risk, we investigated cross-sectional relationships between hepatic steatosis, regional fat accumulation, inflammatory biomarkers, and subclinical measures of atherosclerosis in the Diabetes Heart Study.

METHODS

The Diabetes Heart Study is a family study of sibling pairs concordant for type 2 diabetes. A subset of 623 randomly selected participants was evaluated for hepatic steatosis, defined as a liver:spleen attenuation ratio of <1.0 by computed tomography. We quantified visceral fat, subcutaneous fat, coronary, aortic, and carotid artery calcium by computed tomography; and carotid atherosclerosis by ultrasound. Associations between the liver:spleen attenuation ratio and these factors were expressed as Spearman correlations.

RESULTS

After adjustment for age, race, gender, body mass index, and diabetes status, the liver:spleen attenuation ratio correlated with visceral fat (r =-0.22, P < 0.0001) and subcutaneous fat (r =-0.13, P= 0.031). Hepatic steatosis was associated with lower high-density lipoprotein (r = 0.21, P < 0.0001), higher triglycerides (r =-0.25, P < 0.0001), higher C-reactive protein (r =-0.095, P= 0.004), and lower serum adiponectin (r = 0.34, P < 0.0001). There were no significant associations between the liver:spleen attenuation ratio and coronary, aortic, or carotid calcium, or carotid intimal thickness.

CONCLUSIONS

This suggests that hepatic steatosis is less likely a direct mediator of cardiovascular disease and may best be described as an epiphenomenon. The strong correlations between pro-atherogenic biomarkers, visceral fat, and elements of the metabolic syndrome suggest that hepatic steatosis reflects more than general adiposity, but represents a systemic, inflammatory, pro-atherogenic adipose state.

Genetic and environmental determinants of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels in Hispanic and African Americans

CONTEXT

Vitamin D deficiency is associated with many adverse health outcomes, yet little is known about the genetic epidemiology of vitamin D or its metabolites.

OBJECTIVE

Our objective was to examine the relationship among three vitamin D-related genes and levels of 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] in Hispanics (HAs) and African Americans (AAs).

DESIGN AND SETTING

The cross-sectional Insulin Resistance Atherosclerosis Family Study recruited and examined subjects in: Los Angeles, California (AAs; 513 individuals from 42 families); San Luis Valley (SLV), Colorado (HAs; 513 individuals from 30 families); and San Antonio (SA), Texas (HAs; 504 individuals from 58 families).

MAIN OUTCOME MEASURES

Plasma levels of 25(OH)D and 1,25(OH)2D were measured.

RESULTS

Levels of 25(OH)D were highest in SLV-HAs [18.3 +/- 7.7 ng/ml (45.7 +/- 19.2 nmol/liter)], lower in SA-HAs [14.6 +/- 6.4 ng/ml (36.4 +/- 16.0 nmol/liter)], and lowest in AAs [11.0 +/- 5.4 ng/ml (27.5 +/- 13.5 nmol/liter)]. Levels of 1,25(OH)2D were similar in AAs [43.5 +/- 13.9 pg/ml (113.1 +/- 36.1 pmol/liter)] and SLV-HAs [43.2 +/- 13.3 pg/ml (112.3 +/- 34.6 pmol/liter)], but higher in SA-HAs [48.6 +/- 17.0 pg/ml (126.4 +/- 44.2 pmol/liter)]. After adjusting for gender and age within the site, two single nucleotide polymorphisms (SNPs) in the vitamin D binding protein gene (DBP), rs4588 and rs7041, were associated with 25(OH)D, and one SNP in the DBP, rs4588, was associated with 1,25(OH)2D at all three study centers.

CONCLUSIONS

SNPs in the DBP are associated with levels of 25(OH)D and 1,25(OH)2D in HA and AA participants in the Insulin Resistance Atherosclerosis Family Study.

Genome-wide admixture mapping for coronary artery calcification in African Americans: the NHLBI Family Heart Study

Coronary artery calcification (CAC) is an important measure of subclinical coronary atherosclerosis and an independent predictor of coronary heart disease. To identify the genetic loci contributing to CAC, we conducted a genome-wide scan with 374 microsatellite markers by applying admixture mapping to 618 African American participants in the US National Heart, Lung, and Blood Institute Family Heart Study, in which 868 European American participants from family heart study and 157 Africans genotyped by the Marshfield Medical Genetics Center were used as the two reference founding populations for the African Americans, and a computer program based on a Markov Chain Monte Carlo algorithm, STRUCTURE 2.1, was used to estimate European and African ancestries among African Americans. A permutation test for random repeated sampling regression of CAC score on marker specific African ancestry found 22 markers statistically significant at the 0.05 level and four markers, D10S189 at 10p14, D20S159 at 20q13, D12S1294 at 12q14, and D6S1053 at 6q12, significant at the 0.01 level. D10S189 and D6S1053 were further confirmed at the 0.05 significance level by regression of CAC on allelic copy number, in which individual ancestry was used as a genetic background covariate to control possible stratification in African Americans. On the basis of the results from this and other independent studies, the location of D6S1053 at 80cM on chromosome 6 (6q12) seems to harbor a highly promising quantitative trait loci for atherosclerosis.

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.

Quantitative trait analysis of type 2 diabetes susceptibility loci identified from whole genome association studies in the Insulin Resistance Atherosclerosis Family Study

OBJECTIVE

Evaluate type 2 diabetes susceptibility variants identified from genome-wide association studies in Hispanic Americans and African Americans from the Insulin Resistance Atherosclerosis Family Study (IRAS-FS) for association with quantitative measures of glucose homeostasis and determine their biological role in vivo.

RESEARCH DESIGN AND METHODS

Seventeen type 2 diabetes-associated single nucleotide polymorphisms (SNPs) were genotyped in 1,268 Hispanic- and 581 African-American participants from the IRAS-FS. SNPs were tested for association with quantitative measures of glucose homeostasis, including insulin sensitivity index (S(I)), acute insulin response (AIR), and disposition index.

RESULTS

Previously identified risk variants in cyclin-dependent kinase 5 regulatory subunit associated protein 1-like 1 (CDKAL1) were associated with reduced AIR (P < 0.0046) in Hispanic Americans. Additionally in Hispanic Americans, the variant in a hypothetical gene (chromosome 11; LOC387761) was significantly associated with AIR (P = 0.0046) with the risk allele showing protective effects, i.e., increased AIR. In both Hispanic- and African-American populations, risk variants at the solute carrier family 30, member 8 (SLC30A8) locus were nominally associated with decreased disposition index (P < 0.078). Risk variants in the insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) locus were associated with a decreased disposition index (P = 0.011) exclusively in Hispanic Americans.

CONCLUSIONS

These data indicate a distinct, limited number of diabetes-related genes, more specifically the SNPs in the genes identified in European-derived populations, with modest evidence for association with glucose homeostasis traits in Hispanic Americans and African Americans. We observe evidence that diabetes risk for CDKAL1, SLC30A8, IGF2BP2, and LOC387761 is specifically mediated through defects in insulin secretion. The mechanisms of other predisposing genes remain to be elucidated.

Association of arachidonate 12-lipoxygenase genotype variation and glycemic control with albuminuria in type 2 diabetes

BACKGROUND

Glycemic exposure activates 12-lipoxygenase (12LO) expression and formation of arachidonic acid-derived products. These products can induce cell hypertrophy, cell proliferation, and extracellular matrix deposition, potentially leading to diabetic nephropathy.

STUDY DESIGN

Cross-sectional study.

SETTINGS & PARTICIPANTS

955 European-American siblings from 369 Diabetes Heart Study families. Participants were categorized as nondiabetic, diabetic with hemoglobin A(1c) level less than 6.5%, and diabetic with hemoglobin A(1c) level greater than 6.5% (uncontrolled type 2 diabetes mellitus).

PREDICTOR

Four haplotype-tagging variants in the arachidonate 12LO gene (ALOX12), glycemic control, and other covariates.

OUTCOMES & MEASUREMENTS

Albuminuria measured by means of urinary albumin-creatinine ratio (ACR).

RESULTS

Median ACR was 11.9 mg/g (interquartile range, 5.6 to 39.1). The overall test of the Arg261Gln genotypic association with ACR was significant (P = 0.009). Compared with 261Arg allele carriers, adjusted mean ACR was 42% greater in the 189 carriers of two 261Gln alleles (95% confidence interval, 10 to 83; P = 0.007). This association was confined to the group with uncontrolled type 2 diabetes mellitus (N = 623) with the greatest ACRs (P < 0.001). Adjustments for additional determinants of ACR yielded similar results.

LIMITATIONS

Urine ACR was measured in duplicate on only a single occasion. This study was limited to European Americans.

CONCLUSIONS

Consistent with animal and cellular studies, these results provide additional evidence of the importance of the 12LO pathway in the pathogenesis of human diabetic nephropathy.

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.

Calcified atherosclerotic plaque and bone mineral density in type 2 diabetes: the diabetes heart study

The purpose of the present study was to determine the relationships between atherosclerotic calcified plaque (CP) and bone mineral density (BMD) in subjects with type 2 diabetes mellitus (DM2). CP in the coronary arteries, carotid bifurcation, and abdominal aorta was measured using computed tomography (CT) in 1023 diabetic subjects from 453 families. Trabecular volumetric BMD in thoracic (T-vBMD) and lumbar (L-vBMD) spine was measured with quantitative CT (QCT), while areal BMD (aBMD) in the lumbar spine and hip was measured by dual X-ray absorptiometry (DXA). Correlation coefficients were computed to assess the magnitude of associations and generalized estimating equations (GEE1) were used to make statistical inferences while accounting for familial correlation. Subjects were 53.8% female, 85% European American (EA) and 15% African American (AA). After adjustment for age, significant inverse associations between CP and vBMD persisted in EA men (correlations between -0.11 and -0.16, all p<0.05 with the exception of carotid CP vs. T-vBMD, p=0.076) and in AA women, excluding aortic CP (correlations between -0.16 and -0.25, all p<0.05). Estrogen use in AA but not EA women was consistently associated with an inverse relation between CP and vBMD. Significant inverse relationships between CP and vBMD were observed in EA men and AA women with DM2 after adjusting for age and other covariates. QCT determined vBMD was more strongly related to CP than aBMD by DXA. The relation between CP and BMD in diabetes is influenced by age, sex, and ethnicity, with further effect modification by hormone replacement therapy.

Kidney volume associations with subclinical renal and cardiovascular disease: the Diabetes Heart Study

BACKGROUND

The prognostic significance of total kidney volume (TKV) in subjects with type 2 diabetes mellitus (T2DM) is unknown.

METHODS

One hundred and seventy unrelated Caucasians with T2DM underwent multidetector-row computed tomography of the neck, chest, and abdomen to measure calcified plaque in the coronary artery (CorCP), carotid artery (CarCP), and infrarenal aorta (AorCP). Spearman's rank correlation coefficients were used to assess associations between TKV and subclinical renal and cardiovascular disease. Partial correlation coefficients were computed to adjust for the potential confounding effects of age, sex, body mass index, glomerular filtration rate (GFR), diabetes duration, and hemoglobin A(1c). Values are expressed as mean +/- SD (median in parentheses).

RESULTS

The study group (51% female) had a mean age of 62.9 +/- 8.5 (62.3) years, a T2DM duration of 11.5 +/- 6.8 (10.0) years, a urinary albumin:creatinine ratio of 109.9 +/- 396 (17.6) mg/g, a GFR of 63.8 +/- 12.8 (63.2) ml/min, a TKV of 272.4 +/- 69.7 (261.9) cm(3), CorCP 2,170 +/- 3,394 (653), CarCP 374 +/- 673 (104), AorCP 14,569 +/- 17,480 (8,370), and a carotid artery intima-media thickness of 0.70 +/- 0.14 (0.68) mm. Adjusting for age, sex, body mass index, diabetes duration, GFR, and hemoglobin A(1c), the TKV was significantly associated with AorCP (r = 0.20, p = 0.016), but not with CorCP, CarCP, or carotid artery intima-media thickness (all p >or= 0.25). No significant associations were detected between TKV and blood pressure or albuminuria.

CONCLUSIONS

In Caucasians with T2DM, TKV and calcified atherosclerotic plaque in the infrarenal abdominal aorta are positively associated. Common mechanisms linking renal matrix deposition with aortic atherosclerosis may underlie this association and require further study.

A comparison of risk factors for calcified atherosclerotic plaque in the coronary, carotid, and abdominal aortic arteries: the diabetes heart study

The extent of shared risk factors for calcified atherosclerotic plaque (CAP) of the coronary, carotid, and abdominal aortic arteries is unknown. CAP was measured by computed tomography in 1,125 individuals in families affected with diabetes. Statistical methods adjusted for the lack of independence between observations. CAP scores were standardized, and tests of interaction were conducted to compare risk factor relations across vascular beds. The average age of the cohort was 61 years, and 84% had diabetes. The correlation in CAP scores across vascular beds ranged from 0.59 to 0.72. Age, albumin/creatinine ratio, hemoglobin A1c, diabetes, hypertension, and lipid-lowering therapy were correlated with quantity of CAP in all vascular beds (all p<0.05); no differences in the strength of these relations were noted. In contrast, other significant correlates differed in the strength of their relations with CAP. The risk factor pack-years of smoking was most strongly correlated with CAP in the abdominal aorta (p<0.005). Male gender, previous myocardial infarction, and coronary revascularization were most strongly correlated with CAP in the coronary arteries (p<0.0001). In summary, CAPs of the coronary, carotid, and abdominal aortic arteries generally share common risk factors, even though several of these factors have a greater impact on CAP in one vascular bed than another.

Associations of adiponectin with body fat distribution and insulin sensitivity in nondiabetic Hispanics and African-Americans

CONTEXT

Hypoadiponectinemia has emerged as an independent risk factor for type 2 diabetes and cardiovascular disease. Although associations of adiponectin with central obesity and insulin resistance have been reported, very little data are available from studies using detailed measures of insulin sensitivity (S(I)) and/or body fat distribution in ethnic groups at high risk for metabolic disease.

OBJECTIVE

The aim of the study was to identify the correlates of adiponectin in 1636 nondiabetic Hispanics and African-Americans.

DESIGN

A cross-sectional analysis of participants in the Insulin Resistance Atherosclerosis Family Study was conducted. S(I) was determined from frequently sampled iv glucose tolerance tests with minimal model analysis. Subcutaneous and visceral adipose tissues (SAT, VAT, respectively) were determined with computed tomography. Triglyceride, high-density lipoprotein, C-reactive protein, and adiponectin were measured in fasting samples. Generalized estimating equation (GEE) models were used to identify factors associated with adiponectin concentration.

SETTING

A multicenter study using a family-based design was conducted.

PARTICIPANTS

A total of 1636 nondiabetic Hispanic and African-American subjects participated.

MAIN OUTCOME MEASURES

Circulating adiponectin concentration was measured.

RESULTS

Age, female gender, high-density lipoprotein, SAT, and S(I) were positive independent correlates of adiponectin, whereas glucose, CRP, and VAT were negative independent correlates (all P < 0.05). Ethnicity was not an independent correlate of adiponectin in this model (P = 0.27); however, an ethnicity by VAT interaction term was retained, indicating a stronger negative association of VAT with adiponectin in African-Americans compared with Hispanics.

CONCLUSION

Directly measured S(I), VAT, and SAT were independently correlated with adiponectin in Hispanic and African-American subjects. The inverse association of VAT with adiponectin was stronger in African-Americans compared with Hispanics, a finding that suggests possible ethnic differences in the effects of visceral obesity.

Alanine aminotransferase and directly measured insulin sensitivity in a multiethnic cohort: the Insulin Resistance Atherosclerosis Study

OBJECTIVE

The objective of the present analysis was to evaluate the association of alanine aminotransferase (ALT) with directly measured insulin sensitivity (S(i)) in a large, multiethnic cohort of U.S. adults and to determine whether ALT adds to existing metabolic risk definitions in identifying subjects with insulin resistance.

RESEARCH DESIGN AND METHODS

S(i) was directly measured from frequently sampled intravenous glucose tolerance tests among 999 nondiabetic African-American, Hispanic, and non-Hispanic white subjects aged 40-69 years who were participating in the Insulin Resistance Atherosclerosis Study. Subjects also received an oral glucose tolerance test, and fasting insulin, ALT, and alcohol intake were determined.

RESULTS

ALT was associated with S(i) after adjustment for age, sex, ethnicity, impaired fasting glucose, triglycerides, HDL, blood pressure, and waist (clinical model) (P < 0.0001). The association remained significant after further adjustment for fasting insulin and impaired glucose tolerance (P = 0.004). In logistic regression analysis, elevated ALT (upper quartile) was associated with insulin resistance (lowest quartile of S(i)) after adjustment for age, sex, and ethnicity (odds ratio 3.0 [95% CI 2.2-4.1]). Elevated ALT was independently associated with insulin resistance when included in models with waist circumference, National Cholesterol Education Program criteria for metabolic syndrome, hypertriglyceridemic waist, elevated triglyceride-to-HDL ratio, or homeostasis model assessment of insulin resistance (HOMA-IR) (all P < 0.01). Finally, the addition of elevated ALT improved classification of insulin resistance by area under the receiver operating characteristic curve criteria for all models except HOMA-IR.

CONCLUSIONS

ALT was associated with insulin resistance independently of conventional and more detailed metabolic measures. These findings suggest that the addition of ALT to existing clinically based metabolic risk definitions is an inexpensive way to improve the identification of subjects with insulin resistance.

Whole-grain intake and carotid artery atherosclerosis in a multiethnic cohort: the Insulin Resistance Atherosclerosis Study

BACKGROUND

Whole-grain intake has been shown to be inversely associated with cardiovascular events, but an association with atherosclerosis is less well established.

OBJECTIVE

We sought to evaluate the association of whole-grain intake with carotid intimal medial thickness (IMT) and IMT progression in a multiethnic cohort.

DESIGN

This study evaluated 1178 participants in the Insulin Resistance Atherosclerosis Study. Baseline whole-grain intake was estimated on the basis of intake of dark breads, cooked cereals, and high-fiber cereals assessed with a validated food-frequency questionnaire. Bilateral carotid IMT was evaluated ultrasonographically, yielding 16 IMT measures at baseline and year 5. Multivariate models evaluated the independent association of whole-grain intake with common carotid artery (CCA) and internal carotid artery (ICA) IMT and IMT progression.

RESULTS

The cohort had a mean (+/-SD) age of 55.2 +/- 8.4 y and was 56% female. The baseline median whole-grain intake was 0.79 servings/d. Whole-grain intake was inversely associated with CCA IMT (beta +/- SE: -0.043 +/- 0.013, P = 0.005) and IMT progression (beta +/- SE: -0.019 +/- 0.011, P = 0.09) in models adjusted for demographics, energy intake, energy expenditure, cardiovascular disease risk factors, and medication use. This association was less significant for ICA IMT (beta +/- SE: -0.049 +/- 0.023, P = 0.05) and not significant for ICA IMT progression (beta +/- SE: -0.013 +/- 0.014, P = 0.35). The relation between whole-grain intake and CCA IMT remained significant after adjustment for mediating pathways (lipids, adiposity, and insulin resistance), nutrient constituents, and a principal components-derived healthy dietary pattern.

CONCLUSIONS

Whole-grain intake is inversely associated with CCA IMT, and this relation is not attributable to individual risk intermediates, single nutrient constituents, or larger dietary patterns.

Haplotypes in the lipoprotein lipase gene influence fasting insulin and discovery of a new risk haplotype

CONTEXT

Prior studies of Mexican Americans described association of lipoprotein lipase (LPL) gene haplotypes with insulin sensitivity/resistance and atherosclerosis. The most common haplotype (haplotype 1) was protective, whereas the fourth most common haplotype (haplotype 4) conferred risk for insulin resistance and atherosclerosis.

OBJECTIVE

In this study of Hispanics in the Insulin Resistance Atherosclerosis Study Family Study, we sought to replicate LPL haplotype association with insulin sensitivity/resistance.

DESIGN

LPL haplotypes based on 12 single nucleotide polymorphisms were analyzed for association with indexes of insulin sensitivity and other metabolic and adiposity measures.

SETTING

This study was conducted in the general community of San Antonio, Texas, and San Luis Valley, Colorado.

PARTICIPANTS

Participants in this study were 978 members of 86 Hispanic families.

MAIN OUTCOME MEASURES

LPL haplogenotype, metabolic phenotypes, and adiposity were measured in this study.

RESULTS

The haplotype structure was identical with that observed in prior studies. Among 978 phenotyped subjects, haplotype 1 was associated with decreased fasting insulin (P = 0.01), and haplotype 4 was associated with increased fasting insulin (P = 0.02) and increased visceral fat mass (P = 0.002). Insulin sensitivity, derived from iv glucose tolerance testing, tended (P > 0.1) to be higher with haplotype 1 (S(I) = 1.72) and lower with haplotype 4 (S(I)=1.38). Haplotype 2 was associated with increases in fasting insulin, triglycerides (TGs), TG to high-density lipoprotein-cholesterol ratio, and apolipoprotein B (P = 0.01-0.04).

CONCLUSIONS

This study independently replicates our prior results of LPL haplotypes 1 and 4 as associated with measures of insulin sensitivity and resistance, respectively. Haplotype 4 may confer insulin resistance by increasing visceral fat. Haplotype 2 was identified as a new risk haplotype, suggesting the complex nature of LPL's effect on features of the insulin resistance syndrome.

Heritability and expression of C-reactive protein in type 2 diabetes in the Diabetes Heart Study

Elevated C-reactive protein (CRP) levels are associated with both prevalent and incident cardiovascular disease. In this study, familial aggregation was estimated, and we tested for association between serum CRP levels and polymorphisms within the CRP and APOE genes in sib-ships with type 2 diabetes mellitus, a population at increased risk for cardiovascular disease. CRP levels were determined in 461 diabetes-affected subjects from 224 sibships from the Diabetes Heart Study (DHS). Heritability estimates of CRP levels were obtained using variance component models. Genetic influence on serum CRP levels by single nucleotide polymorphisms (SNPs) in the CRP and APOE genes was evaluated by association analysis using mixed models. Subjects were Caucasian American (84%) and African-American (16%), 53% female, and had an average age of 62.2 +/- 9.2 years. The median CRP level was 3.3 mg/L (range 0 to 59.3 mg/L), and estimated heritability for CRP was approximately 40%. Estimates of heritability were significantly greater than zero (P < 0.0001) and relatively constant, despite adjustments for important modifiers (age, sex, ethnicity, diabetes duration, statin-use and anti-inflammatory use) of CRP. There was no significant evidence for association of CRP levels with CRP gene SNPs; however, consistent with previous reports, there was significant evidence of association of CRP levels with polymorphisms within the APOE gene. These data indicate CRP levels are significantly influenced by genetic (and/or environmental) factors that are shared within DHS families. While the APOE locus shows evidence of contributing to CRP levels, no evidence of CRP gene polymorphism association with CRP levels was observed.

Serum Uric Acid Predicts Incident Hypertension in a Biethnic Cohort

Serum uric acid has been positively associated with incident hypertension, but previous studies have had limited ability to explore this relationship across sex and ethnic strata. We sought to evaluate this association in a biethnic cohort of middle-aged men and women. Participants in the Atherosclerosis Risk in Communities (ARIC) study who were free of hypertension at baseline (N=9104) were evaluated for hypertension at 3-year intervals over 4 examinations. Adjusted Cox proportional hazards models evaluated risk of incident hypertension or progression of blood category for each SD higher baseline serum uric acid. At baseline, the mean age was 53.3 years (range: 45 to 64 years), with a mean (SD) systolic blood pressure of 113.8 (12.2) mm Hg, mean diastolic blood pressure of 70.2 (8.6) mm Hg, and mean serum uric acid of 5.7 (1.4). Higher serum uric acid was associated with greater risk of hypertension in the overall cohort (hazard ratio for each SD of higher uric acid [95% CI]: 1.10 [1.04 to 1.15]) and in subgroup analyses (black men: 1.32 [1.14 to 1.54]; black women: 1.16 [1.03 to 1.31]; white men: 1.01 [0.94 to 1.09]; white women: 1.04 [0.96 to 1.11]), after adjustment for age, baseline blood pressure, body mass index, renal function, diabetes, and smoking. The pattern was similar when modeling blood pressure progression (overall: 1.10 [1.05 to 1.14]; black men: 1.26 [1.11 to 1.42]; black women: 1.18 [1.06 to 1.31]; white men: 1.05 [0.99 to 1.11]; white women: 1.05 [1.00 to 1.12]). In conclusion, serum uric acid was positively associated with incident hypertension over 9 years of follow-up, and this relationship was stronger in blacks than in whites. More research is warranted concerning the physiological and clinical consequences of hyperuricemia, especially in blacks.

Metabolic Syndrome and Cardiovascular Disease in Older People: The Cardiovascular Health Study

OBJECTIVES

To assess the prospective association between metabolic syndrome (MetS) and cardiovascular disease (CVD) in older people and to evaluate the effect of lowering the threshold for impaired fasting glucose (IFG) on the prevalence of IFG and MetS and the risk of CVD.

DESIGN

Prospective cohort study.

SETTING

Four field centers in U.S. communities.

PARTICIPANTS

Three thousand five hundred eighty-five subjects in the Cardiovascular Health Study free of diabetes mellitus and CVD at baseline (mean age 72, 62% female, 14% black).

MEASUREMENTS

Baseline measures of MetS components and adjudicated incident CVD events. MetS (2001) was defined first using the original criteria from the Third Adult Treatment Panel Report of the National Cholesterol Education Program (> or =3 of the following: large waist circumference (women >88 cm, men >102 cm), elevated triglycerides (> or =1.70 mmol/L), low high-density lipoprotein cholesterol (men <1.04 mmol/L, women <1.30 mmol/L), elevated fasting glucose (6.1-6.9 mmol/L), and high blood pressure (> or =130/85 mmHg or self-reported use of medications for hypertension). Subjects were also classified according to the revised definition of the MetS (2005) that applies the lower threshold for fasting glucose (5.6-6.9 mmol/L).

RESULTS

During follow-up (median 11 years), 818 coronary heart disease (CHD), 401 stroke, and 554 congestive heart failure (CHF) events occurred. Age- and race-adjusted hazard ratios (HRs) for CHD, stroke, and CHF were 1.30 (95% confidence interval (CI) = 1.07-1.57), 0.94 (95% CI = 0.73-1.21), and 1.40 (95% CI = 1.12-1.76) for women and 1.35 (95% CI = 1.10-1.66), 1.51 (95% CI = 1.08-2.12), and 1.47 (95% CI = 1.14-1.90) for men, respectively. Overall, women and men with MetS (2005) were 20% to 30% more likely to experience any CVD event than subjects without MetS (2005). Using the lower cut-point for IFG resulted in a near tripling in IFG prevalence (16% to 46%) and an additional 9% classified with MetS (2005) but HRs similar to those estimated from the original MetS (2001) criteria. High blood pressure was the component most strongly associated with incident CHD.

CONCLUSION

Results from this study of an elderly, population-based cohort provide support for earlier investigations in primarily middle-aged populations that link the presence of MetS with the development of CVD and further underscore the importance of recognizing and treating its individual components, particularly high blood pressure.

A functional polymorphism in the lymphotoxin-alpha gene is associated with carotid artery wall thickness: the Diabetes Heart Study

BACKGROUND

The lymphotoxin-alpha (LTA) gene has been implicated in the pathogenesis of atherosclerosis. We tested for an association between a functional polymorphism, LTA 252A/G, and common carotid artery intima-media thickness in 1088 siblings from 435 Diabetes Heart Study families.

METHODS

Intima-media thickness was measured by high-resolution B-mode carotid ultrasonography. A MassARRAY system (Sequenom Inc., San Diego, California, USA) was used for genotyping.

RESULTS

The LTA 252G allele was positively associated with increased intima-media thickness (the odds ratio for the G allele carriers being in the top tertile of the intima-media thickness distribution was 1.41, P=0.04).

CONCLUSIONS

The LTA 252A/G polymorphism is moderately associated with sub-clinical atherosclerosis.

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.

Coincident linkage of type 2 diabetes, metabolic syndrome, and measures of cardiovascular disease in a genome scan of the diabetes heart study

Cardiovascular disease (CVD) is a major contributor to morbidity and mortality in type 2 diabetes, but the relationship between CVD and type 2 diabetes is not well understood. The Diabetes Heart Study is a study of type 2 diabetes-enriched families extensively phenotyped for measures of CVD, type 2 diabetes, and metabolic syndrome. A total of 977 Caucasian subjects from 358 pedigrees (575 type 2 diabetic relative pairs) with at least two individuals with type 2 diabetes and, where possible, unaffected siblings were included in a genome scan. Qualitative traits evaluated in this analysis are with or without the presence of coronary calcified plaque (CCP) and with or without carotid calcified plaque (CarCP) measured by electrocardiogram-gated helical computed tomography. In addition, prevalent CVD was measured using two definitions: CVD1, based on self-reported history of clinical CVD (393 subjects), and CVD2, defined as CVD1 and/or CCP >400 (606 subjects). These discrete traits (type 2 diabetes, metabolic syndrome, CVD1, CVD2, CCP, and CarCP) frequently coincide in the same individuals with concordance ranging from 42.9 to 99%. Multipoint nonparametric linkage analysis revealed evidence for coincident mapping of each trait (type 2 diabetes, metabolic syndrome, CVD1, CVD2, CCP, and CarCP) to three different genomic regions: a broad region on chromosome 3 (70-160 cM; logarithm of odds [LOD] scores ranging between 1.15 and 2.71), chromosome 4q31 (peak LOD 146 cM; LOD scores ranging between 0.90 and 2.41), and on chromosome 14p (peak LOD 23 cM; LOD scores ranging between 1.43 and 2.31). Ordered subset analysis (OSA) suggests that the linked chromosome 3 region consists of at least two separate loci on 3p and 3q. In addition, OSA based on lipid measures and other traits identify family subsets with significantly stronger evidence of linkage (e.g., CVD2 on chromosome 3 at 87 cM subsetting on low HDL with an initial LOD of 2.19 is maximized to an LOD of 7.04 in a subset of 25% of the families and CVD2 on chromosome 14 at 22 cM subsetting on high triglycerides with an initial LOD of 1.99 maximized to an LOD of 4.90 in 44% of the families). When subjects are defined as affected by the presence of each trait (type 2 diabetes, metabolic syndrome, CVD1, and CCP), significant evidence for linkage to the 3p locus is observed with a peak LOD of 4.13 at 87 cM. While the correlated nature of the traits makes it unclear whether these loci represent distinct type 2 diabetes, metabolic syndrome, or CVD loci or single loci with pleiotropic effects, the coincident linkage suggests that identification of the underlying genes may help clarify the relationship of diabetes, metabolic syndrome, and 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.

Genome-wide linkage of plasma adiponectin reveals a major locus on chromosome 3q distinct from the adiponectin structural gene: the IRAS family study

Adiponectin (APM1) is an adipocyte-derived peptide that contributes to glucose, lipid, and energy homeostasis. We assessed the genetic basis of plasma adiponectin in Hispanic-American and African-American families enrolled through the Insulin Resistance Atherosclerosis Study Family Study. A 10-cM genome scan was performed in two batches: an original set (set 1) consisting of 66 families (45 Hispanic American and 21 African American) and a replication set (set 2) consisting of 66 families (45 Hispanic American and 21 African American). Adiponectin levels were measured by radioimmunoassay in 1,727 individuals from 131 of 132 families. Linkage analysis was carried out in Hispanic Americans and African Americans separately in set 1, set 2, and the pooled set (set 1 plus set 2), with and without diabetic subjects. A major gene was mapped to 3q27 with a logarithm of odds (LOD) score of 8.21 in the Hispanic-American sample. Ninety-six unrelated individuals were screened for polymorphisms in the APM1 gene, and 18 single nucleotide polymorphisms (SNPs) were genotyped in the Hispanic-American sample. Plasma adiponectin level was modestly associated with two SNPs and their accompaning haplotypes. Incorporating each or both SNPs in the linkage analysis, however, did not significantly reduce the LOD score. Therefore, a quantitative trait locus at 3q27, likely distinct from the APM1 gene, contributes to the variation of plasma adiponectin levels in the Hispanic-American population.

Physical activity, insulin sensitivity, and hypertension among US adults: findings from the Insulin Resistance Atherosclerosis Study

Although regular physical activity is associated with less hypertension and improved insulin sensitivity, there is debate regarding the role of insulin sensitivity in hypertension. Thus, in this cross-sectional study, the authors investigated whether physical activity and insulin sensitivity were associated with hypertension. The sample consisted of 1,599 persons aged 40-69 years who participated in the Insulin Resistance Atherosclerosis Study. The outcome measure was hypertension as measured by a standard protocol. Energy expended in vigorous physical activity was calculated from a recall interview on past-year physical activity. Descriptive statistics revealed that 590 (37%) participants had prevalent hypertension. In adjusted logistic regression analysis, participants expending >or=150 kcal/day in vigorous physical activity had an odds ratio for hypertension of 0.73 (95% confidence interval (CI): 0.55, 0.98) in comparison with participants who were sedentary. Further adjustment for insulin sensitivity resulted in attenuation of the effect of vigorous physical activity on hypertension (odds ratio = 0.97, 95% CI: 0.71, 1.33), while the effect of insulin sensitivity was significant (odds ratio = 0.33, 95% CI: 0.26, 0.41). These results suggest that longitudinal studies are warranted to determine whether insulin sensitivity is a mediator of the relation between physical activity and hypertension.

Progression of Plasminogen Activator Inhibitor-1 and Fibrinogen Levels in Relation to Incident Type 2 Diabetes

Background— Several studies have shown that fibrinolytic and coagulation abnormalities as well as low-grade inflammation predict cardiovascular disease and type 2 diabetes. We studied in the Insulin Resistance Atherosclerosis Study the relation of incident diabetes to dynamic changes of plasminogen activator inhibitor-1 (PAI-1) and fibrinogen.

Methods and Results— After a follow-up of 5.2 years, diabetes developed in 140 (16.6%) of 843 individuals (57% women; mean age [range], 54.7 [40, 69] years) (converters versus nonconverters). Baseline and follow-up levels of PAI-1 and fibrinogen (demographically and smoking adjusted) were higher in converters versus nonconverters (mean [SE]): at baseline, 23.7 ng/mL (1.5) versus 14.5 (0.4) and 286.2 mg/dL (4.8) versus 273.6 (2.1); at follow-up, 45.3 ng/mL (3.2) versus 25.9 (0.8) and 292.0 mg/dL (5.6) versus 275.2 (2.5); all P <0.05. In a demographically and smoking-adjusted logistic regression model, the change in PAI-1 was related to incident diabetes (OR for a 1-SD change [CI], 1.75 [1.37, 2.22]; P <0.001) after adjusting for baseline PAI-1 levels. After further adjusting for insulin sensitivity (S I ) or waist, change in PAI-1 remained significantly related to incident diabetes (OR, 1.66 [1.28, 2.15], and 1.64 [1.28, 2.10]; P <0.001). In contrast, change in fibrinogen was not significantly related to incident diabetes.

Conclusions— Progression of PAI-1 levels over time, in addition to high baseline PAI-1 levels, is associated with incident diabetes. PAI-1 levels (but not fibrinogen) further increase with the rising glucose levels and the development of diabetes. These findings extend the current knowledge on the relation of fibrinolysis and coagulation abnormalities to the development of type 2 diabetes.

The natural course of beta-cell function in nondiabetic and diabetic individuals: the Insulin Resistance Atherosclerosis Study

Data from the UKPDS (U.K. Prospective Diabetes Study) indicate a continuous decline in beta-cell function in patients with type 2 diabetes. We studied longitudinal changes in beta-cell function (follow-up of 5.2 years) in subjects with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and type 2 diabetes, using acute insulin response (AIR) and insulin sensitivity index (S(i)) from a frequently sampled intravenous glucose tolerance test among African-American, Hispanic, and non-Hispanic white subjects aged 40-69 years. At baseline, decreasing levels of both S(i) and AIR (either unadjusted or adjusted for S(i)) mirrored deteriorating glucose tolerance status at baseline and at follow-up. A different pattern was found with respect to longitudinal changes; S(i) declined in each glucose tolerance category, ranging from -0.81 x10(-4) min(-1) x muU(-1) x ml(-1) in NGT at baseline and NGT at follow-up (NGT/NGT) to -1.06 x10(-4) in NGT/diabetes, whereas the directional change in AIR principally determined the glucose tolerance status at follow-up. In NGT/NGT S(i) decreased by 35% and AIR increased by 34%. Results were similar in each of the three ethnic groups. These data shed light on the natural course of beta-cell function; over 5.2 years, mean insulin sensitivity declined in each glucose tolerance category. The change in AIR, however, principally determined glucose tolerance status at follow-up; NGT was maintained by a compensatory increase in insulin secretion. Failure to increase insulin secretion led to IGT, and a decrease in insulin secretion led to overt diabetes. This data may have important implications for the prevention and treatment of type 2 diabetes.

Genetic mapping of disposition index and acute insulin response loci on chromosome 11q. The Insulin Resistance Atherosclerosis Study (IRAS) Family Study

Glucose homeostasis, a defining characteristic of physiological glucose metabolism, is the result of complex feedback relationships with both genetic and environmental determinants that influence insulin sensitivity and beta-cell function. Relatively little is known about the genetic basis of glucose homeostasis phenotypes or their relationship to risk of diabetes. Our group previously published a genome scan for glucose homeostasis traits in 284 African-American subjects from 21 pedigrees in the Insulin Resistance Atherosclerosis Study Family Study (IRASFS) and presented evidence for linkage to disposition index (DI) on chromosome 11q with a logarithm of odds (LOD) of 3.21 at 81 cM flanked by markers D11S2371 and D11S2002 (support interval from 71 to 96 cM). In this study, genotyping and analysis of an additional 214 African-American subjects in 21 pedigrees from the IRASFS yielded independent evidence of linkage to DI. When these two datasets were combined, a DI linkage peak was observed with an LOD of 3.89 at 78 cM (support interval from 67 to 89 cM). Fine mapping with 15 additional microsatellite markers in this 11q region for the entire 42 pedigrees resulted in an LOD score of 4.80 at 80 cM near marker D11S937 (support interval from 76 to 84 cM). In these 42 pedigrees, there was also suggestive evidence for linkage to acute insulin response (AIR) at two separate locations flanking the DI peak (64 cM, LOD 2.77, flanked by markers D11S4076 and D11S981; and 85 cM, LOD 2.54, flanked by markers D11S4172 and D11S2002). No evidence of linkage to the insulin sensitivity index (S(i)) was observed. Nine positional candidate genes were evaluated for association to DI and AIR. Among these candidates, single nucleotide polymorphisms (SNPs) in muscle glycogen phosphorylase showed evidence of association with DI (P < 0.011). In addition, SNPs in the pyruvate carboxylase gene showed evidence of association (P < 0.002) with AIR. Further analysis of these candidate genes, however, did not provide evidence that these SNPs accounted for the evidence of linkage to either DI or AIR. These detailed genetic analyses provide strong evidence of a DI locus on 11q in African-American pedigrees, with additional suggestive evidence of independent AIR loci in the same region.

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.

Variants of the CD40 gene but not of the CD40L gene are associated with coronary artery calcification in the Diabetes Heart Study (DHS)

BACKGROUND

CD40/CD40L signaling is known to play an important role in immune response. The proteins are expressed in a variety of cell types and ligation causes cells to produce inflammatory cytokines and cellular adhesion molecules. These processes are implicated in the development and progression of atherosclerosis. Animal models demonstrate that interruption of CD40/CD40L signaling produces a more fibrous and stable atherosclerotic lesion.

METHODS

We investigated the role of genetic variation in CD40 and CD40L genes in subclinical atherosclerosis assessed by coronary artery calcification (CAC) and carotid intima-media thickness in 620 individuals from 230 families in the DHS.

RESULTS

Two single nucleotide polymorphisms in the CD40 gene (rs1535045 and rs3765459) were significantly associated with decreased CAC (P < or = .02) in this population. CD40L single nucleotide polymorphisms were not significantly associated. In addition, no associations with carotid intima-media thickness, carotid artery calcification, or C-reactive protein levels were detected for either gene.

CONCLUSION

Genetic variation in the CD40 gene is associated with CAC in diabetic families.

Prediction of type 2 diabetes mellitus with alternative definitions of the metabolic syndrome: the Insulin Resistance Atherosclerosis Study

BACKGROUND

In addition to predicting cardiovascular disease (CVD) morbidity and mortality, the metabolic syndrome is strongly associated with the development of type 2 diabetes mellitus (DM), itself an important risk factor for CVD. Our objective was to compare the ability of various metabolic syndrome criteria (including those recently proposed by the International Diabetes Federation), markers of insulin resistance (IR) and inflammation, and impaired glucose tolerance (IGT) in the prediction of DM and to determine whether various proposed modifications to the National Cholesterol Education program (NCEP) metabolic syndrome definition improved predictive ability.

METHODS AND RESULTS

We examined 822 subjects in the Insulin Resistance Atherosclerosis Study aged 40 to 69 years who were nondiabetic at baseline. After 5.2 years, 148 individuals had developed DM. IGT, metabolic syndrome definitions, and IR markers all significantly predicted DM, with odds ratios ranging from 3.4 to 5.4 (all P<0.001), although there were no significant differences in the areas under the receiver operator characteristic (AROC) curves between the definitions. Modifying or requiring obesity, glucose, or IR components in NCEP-defined metabolic syndrome did not significantly alter the predictive ability of the definition under AROC curve criteria (all P>0.05). Similarly, although IR and inflammation variables were significantly associated with incident DM when included in multivariate models with NCEP-defined metabolic syndrome (all P<0.01), expanding the definition by adding these variables as components did not significantly alter the predictive ability of the definition under AROC curve criteria (all P>0.05).

CONCLUSIONS

The International Diabetes Federation and NCEP metabolic syndrome definitions predicted DM at least as well as the World Health Organization definition, despite not requiring the use of oral glucose tolerance testing or measures of IR or microalbuminuria. Modifications or additions to the NCEP metabolic syndrome definition had limited impact on the prediction of DM.

Nuclear magnetic resonance lipoprotein abnormalities in prediabetic subjects in the Insulin Resistance Atherosclerosis Study

BACKGROUND

Subjects with type 2 diabetes have smaller LDL and HDL particles in addition to higher levels of triglycerides and lower HDL cholesterol. Elevated insulin resistance, blood pressure, and dyslipidemia (including small dense LDL) predicted incident diabetes. In the Insulin Resistance Atherosclerosis Study (IRAS) we studied nuclear magnetic resonance (NMR) lipoprotein particle measures in prediabetic individuals, considering potentially modifying covariates, including insulin resistance, as directly measured using a frequently sampled intravenous glucose tolerance test.

METHODS AND RESULTS

Of 830 subjects who were nondiabetic at baseline, 130 (15.7%) developed diabetes after a mean follow-up of 5.2 years. Various lipoprotein abnormalities were found in prediabetic subjects compared with subjects who stayed nondiabetic at follow-up. In logistic regression analyses (demographically adjusted), VLDL particles, large VLDL, LDL particles, small LDL, large HDL, small HDL, VLDL size, LDL size, and HDL size were related to incident diabetes. The relation of VLDL size and small HDL to incident diabetes was independent of waist (odds ratio [OR] [95% CI], 1.43 [1.18 to 1.73] and 1.23 [1.01 to 1.51] for VLDL size and small HDL, respectively) and independent of conventionally (chemically) measured triglycerides and HDL cholesterol (OR [95% CI], 1.45 [1.18 to 1.78] and 1.30 [1.06 to 1.60], respectively). Insulin sensitivity attenuated the relation to incident diabetes of VLDL size (OR [95% CI], 1.25 [1.01 to 1.53]) but not of small HDL particles (OR [95% CI], 1.25 [1.02 to 1.54]).

CONCLUSIONS

We have shown a range of lipoprotein abnormalities in prediabetic individuals, including compositional changes in HDL and VLDL. These findings extend previous work indicating a proatherogenic state in healthy, nondiabetic subjects who subsequently develop diabetes.

Cross-sectional correlates of fasting hyperinsulinaemia in post-menopausal women of different ethnic origin

AIMS

In a large ethnically diverse nationwide sample of post-menopausal women we explored the relationship between fasting insulin levels, ethnicity, and a wide range of anthropometric, socio-economic, and lifestyle factors.

METHODS

Subjects were post-menopausal women aged 50-79 years without diagnosed diabetes mellitus comprising a subsample (n = 3500) of the Women's Health Initiative (WHI) Clinical Trial and Observational Study. In a cross-sectional survey at baseline, we analysed the association between ethnicity and fasting insulin using analysis of covariance procedures and identified independent correlates of hyperinsulinaemia, defined by the 75th percentile cut point for each ethnic group.

RESULTS

Fasting insulin levels were higher among African-American and Hispanic women than among non-Hispanic White or Asian women. These differences persisted after adjustment for age, educational attainment, total and central body obesity, adult weight change, family history of diabetes, smoking status, alcohol consumption, use of menopausal hormone therapy and physical activity. Higher levels of body mass index, waist-hip ratio, adult weight gain, and lower levels of total and moderate or strenuous recreational activity were independent correlates of fasting hyperinsulinaemia. Habitual walking was also inversely associated with fasting insulin.

CONCLUSIONS

In this cross-sectional analysis, fasting insulin levels were higher among African-American and Hispanic post-menopausal women as compared with non-Hispanic White and Asian women. In addition, obesity, adult weight gain, and low levels of moderate or strenuous physical activity were independently associated with hyperinsulinaemia.

Attempted control of hyperglycemia during cardiopulmonary bypass fails to improve neurologic or neurobehavioral outcomes in patients without diabetes mellitus undergoing coronary artery bypass grafting

OBJECTIVE

Hyperglycemia worsens outcomes in critical illness. This randomized, double-blind, placebo-controlled clinical trial tested whether insulin treatment of hyperglycemia during cardiopulmonary bypass would reduce neurologic, neuro-ophthalmologic, and neurobehavioral outcomes after coronary artery bypass grafting.

METHODS

Three hundred eighty-one nondiabetic patients undergoing isolated coronary artery bypass grafting were given infusions of insulin or placebo when their blood glucose concentration exceeded 100 mg/dL during cardiopulmonary bypass. The primary outcome measure was the combined incidence of new neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death observed at 4 to 8 days postoperatively. This same measure was assessed secondarily at 6 weeks and 6 months. Length of hospital stay was also compared as a secondary assessment.

RESULTS

The 2 groups were well matched at baseline. The insulin-treated group had significantly lower blood glucose concentrations during bypass. Sixty-six percent of subjects in the insulin-treated group and 67% of subjects in the control group demonstrated a new or worsening neurologic, neuro-ophthalmologic, or neurobehavioral deficit or neurologic death at the 4- to 8-day assessment. Outcomes were also similar in the 2 groups at 6 weeks (37% and 39% incidence, respectively) and 6 months (30% and 25%, respectively). Median lengths of stay were 7 and 6 days, respectively, in the treatment and control groups. None of these outcome differences was statistically significant.

CONCLUSION

Attempted control of hyperglycemia during cardiopulmonary bypass had no significant effect on the combined incidence of neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death and failed to shorten the length of hospital stay. These results do not contradict those of other studies showing that aggressive control of hyperglycemia in the postoperative period will improve outcome.

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.

The relationship between C-reactive protein and subclinical cardiovascular disease in the Diabetes Heart Study (DHS)

BACKGROUND

Epidemiological studies suggest that levels of C-reactive protein (CRP) predict cardiovascular disease (CVD). We have evaluated the relationship between CRP and subclinical CVD in a study cohort at high risk of CVD.

METHODS

The DHS is a single-center, family-based study of the genetic and environmental components of CVD in type 2 diabetes mellitus (T2DM). We evaluated 666 subjects (551 T2DM affected and 115 unaffected) with an average age of 61 years. Measures of coronary artery calcium (CAC), intimal-medial thickness (IMT) of the common carotid artery, and CRP were obtained on all subjects.

RESULTS

C-reactive protein is positively and significantly associated with female sex, body mass index, and smoking and is negatively and significantly associated with age and statin use. Generalized estimating equations were used to test whether CRP was associated with each subclinical CVD measure (presence/absence of CAC, quantity of CAC, and IMT) adjusting for covariates and correlation among siblings. Stratified analyses were conducted to examine whether these associations differed across sex and statin use. In the overall analysis, CRP was not significantly associated with IMT or presence of CAC but was negatively and significantly associated with quantity of CAC (P = .01). When covariates were added, the relationship was no longer significant. Similar patterns were observed in stratified analyses based on sex, statin use, and diabetes status: weak but negative association of CAC with CRP, which became nonsignificant with adjustment for covariates.

CONCLUSIONS

In a population at high risk for CVD, there was no evidence of incremental association of CRP levels with measures of subclinical CVD.

Liver markers and development of the metabolic syndrome: the insulin resistance atherosclerosis study

Nonalcoholic fatty liver disease (NAFLD) is emerging as a component of the metabolic syndrome, although it is not known whether markers of NAFLD, including elevated concentrations of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALK), predict the development of metabolic syndrome. Our objective was to investigate the associations of elevated AST, ALT, and other liver markers, including C-reactive protein (CRP), with incident National Cholesterol Education Program-defined metabolic syndrome among 633 subjects in the Insulin Resistance Atherosclerosis Study who were free of metabolic syndrome at baseline. Insulin sensitivity (Si) and acute insulin response (AIR) were directly measured from the frequently sampled intravenous glucose tolerance test among African-American, Hispanic, and non-Hispanic white subjects aged 40-69 years. After 5.2 years, 127 individuals had developed metabolic syndrome. In separate logistic regression models adjusting for age, sex, ethnicity, clinic, and alcohol consumption, subjects in the upper quartiles of ALT, ALK, and CRP were at significantly increased risk of incident metabolic syndrome compared with those in the lowest quartile: ALT, odds ratio 2.50 (95% CI 1.38-4.51); ALK, 2.28 (1.24-4.20); and CRP, 1.33 (1.09-1.63). Subjects in the upper quartile of the AST-to-ALT ratio were at significantly reduced metabolic syndrome risk (0.40 [0.22-0.74]). After further adjustment for waist circumference, Si, AIR, and impaired glucose tolerance, the associations of ALT and the AST-to-ALT ratio with incident metabolic syndrome remained significant (ALT, 2.12 [1.10-4.09]; the AST-to-ALT ratio, 0.48 [0.25-0.95]). These associations were not modified by ethnicity or sex, and they remained significant after exclusion of former and heavy drinkers. In conclusion, NAFLD markers ALT and the AST-to-ALT ratio predict metabolic syndrome independently of potential confounding variables, including directly measured Si and AIR.

P-selectin gene haplotype associations with albuminuria in the Diabetes Heart Study

BACKGROUND

Adhesion molecules, such as P-selectin, play a pivotal role in leukocyte adhesion to the endothelium during inflammation. We investigated the relationship between P-selectin gene polymorphisms and albuminuria in 565 European American siblings (84% with type 2 diabetes) from 227 families participating in the Diabetes Heart Study (DHS).

METHODS

Three common missense P-selectin polymorphisms (S290N, N562D, and T715P) were genotyped. Albuminuria was defined as an albumin:creatinine ratio (ACR) > or = 17 mg/g in males, and > or = 25 mg/g in females. Tests of association were based on generalized estimating equations (GEE1) and tests of linkage disequilibrium were based on the quantitative pedigree disequilibrium test (QPDT).

RESULTS

Each copy of the 290Asn (S290N) allele was associated with a 45% absolute increase in ACR (P= 0.007), and a higher risk for the presence of albuminuria [odds ratio (OR), 1.71 for each 290A sn allele] (P= 0.002). Adjustment for other determinants of ACR, including stratification by age, gender, and presence of diabetes, did not alter these results. Haploytpe analyses using both GEE1 and QPDT methods revealed that the N-N-T haplotype, containing asparagine codons at sites S290N and N562D, was associated with an increased risk of albuminuria (OR 1.77) (P= 0.005, for each additional copy of the N-N-T haplotype).

CONCLUSION

The 290Asn (S290N) variant of P-selectin was associated with a higher prevalence and greater degree of albuminuria in European American siblings of type 2 diabetic families.

Smoking and incidence of diabetes among U.S. adults: findings from the Insulin Resistance Atherosclerosis Study

OBJECTIVE

The objective of this study was to determine the association between smoking and incident diabetes among U.S. adults.

RESEARCH DESIGN AND METHODS

The Insulin Resistance Atherosclerosis Study (IRAS) was a prospective study of the associations of insulin sensitivity and cardiovascular risk factors. We examined the relationship between smoking status categories (never, former, and current) and incident 5-year type 2 diabetes among 906 participants free of diabetes at baseline. We also considered the effect of pack-year categories (never, former <20 pack-years, former > or = 20 pack-years, current <20 pack-years, and current > or = 20 pack-years) upon diabetes incidence.

RESULTS

Of current smokers, 96 (25%) developed diabetes at 5 years, compared with 60 (14%) never smokers. After multivariable adjustment, current smokers exhibited increased incidence of diabetes compared with never smokers (odds ratio [OR] 2.66, P = 0.001). Similar results were found among current smokers with > or = 20 pack-years with normal glucose tolerance (5.66, P = 0.001).

CONCLUSIONS

Smoking shares a robust association with incident diabetes, supporting the current Surgeon General's warnings against cigarette smoking.

The impact of pedigree structure on heritability estimates for pulse pressure in three studies

OBJECTIVES

Pulse pressure (PP) is a measure of large artery stiffness and has been shown to be an important predictor of cardiovascular morbidity and mortality. The aims of the present study were to investigate the heritability of PP in three studies, the Diabetes Heart Study (DHS), the Insulin Resistance Atherosclerosis Family Study (IRAS FS), and the NHLBI Family Heart Study (FHS), to estimate the residual heritability after inclusion of a common set of covariates, and to investigate the impact of pedigree structure on estimating heritability.

METHODS AND RESULTS

DHS is primarily a sibling pair nuclear family study design, while both IRAS FS and FHS have large pedigrees. Heritability estimates of log-transformed PP were obtained using variance component models. After adjusting for age, gender, ethnicity/center, height, diabetes status, and mean arterial pressure (MAP), heritability estimates of PP were 0.40 +/- 0.08 , 0.22 +/- 0.05, and 0.19 +/- 0.03 in DHS, IRAS FS, and FHS, respectively. The heritability estimate from DHS was significantly different from both IRAS FS and FHS (both p values <0.05). A random re-sampling technique (modified bootstrap) was used to explore the heritability in the IRAS FS and FHS data when these pedigrees were trimmed to mimic the DHS pedigree structure. The re-sampling method (mimicking a sibling pair nuclear family design in all studies) yielded PP heritability estimates of 0.37, 0.34, and 0.27 in DHS, IRAS FS, and FHS, respectively. There was no significant difference among the heritability estimates from the three studies based on the re-sampling method.

CONCLUSION

We have shown that PP has a moderately heritable component in three different studies. These data illustrate the influence of pedigree structure can have on estimating heritability. Thoughtful comparisons of heritability estimates must consider study design factors such as pedigree structure.

Cosegregation of albuminuria and blood pressure: the Insulin Resistance Atherosclerosis (IRAS) family study

BACKGROUND

Albuminuria was shown to be heritable and to share common genetic determinants with blood pressure (BP) in individuals of white ethnicity. Our aim in this study was to examine the familial aggregation of albuminuria and its phenotypic, genetic, and environmental correlations with BP in nondiabetic individuals of Hispanic (HA) and African American (AA) ethnicity.

METHODS

The study included 129 large HA and AA families, providing 1405 nondiabetic individuals; those on antihypertensive medications were excluded. The albumin/creatinine ratio (ACR) in a random urine sample was used as a measure of albuminuria. A variance component approach was used in the analysis.

RESULTS

After adjusting for age, sex, and body mass index (BMI), the heritabilities of ACR, systolic BP (SBP) and diastolic BP (DBP) were 11%, 26%, and 28%. The phenotypic correlations between ACR and each of SBP and DBP in HA (r = 0.17 and r = 0.16 respectively) and AA (r = 0.26 and r = 0.16) were significant. When partitioned into genetic and environmental factors, the genetic correlations between ACR and each of SBP and DBP were significant in HA (r(g) = 0.49 for each), whereas the environmental correlations were not. Conversely, the genetic correlations between ACR and SBP/DBP were not significant in AA (although with DBP it was not significantly different from that of HA), whereas a significant environmental correlation was observed between ACR and SBP (r(e) = 0.28, P < .001).

CONCLUSIONS

Both albuminuria and BP exhibit familial aggregation in nondiabetic HA and AA. In HA, but not in AA, ACR and especially SBP share common genetic determinants. The mechanism of this ethnic heterogeneity is unclear but merits further investigation.

The Relationship Between Albuminuria and Hormone Therapy in Postmenopausal Women

BACKGROUND

Elevated urinary albumin excretion and hormone therapy (HT) are associated with increased risk for cardiovascular events. We assessed the relationship between albuminuria and the use of hormonal preparations in postmenopausal women.

METHODS

Data from the Insulin Resistance Atherosclerosis Study were obtained at baseline and 5-year follow-up for analysis. The generalized estimating equation procedure accounting for repeated measures was used for this analysis. HT was the main predictor variable, and log(e) urine albumin-creatinine ratio (ACR) was the main outcome variable.

RESULTS

Four hundred ninety-one menopausal women were included in the analysis, 36% (n = 179) of whom received HT (either oral estrogen, progesterone, or combination therapy). At baseline, abnormal albuminuria (ACR > or = 25 mg/g) was present in 11% of women on HT and 17% not on HT (P = 0.02). After adjusting for demographics, the presence of diabetes and hypertension, and kidney function, HT was associated with a 19% reduction in ACR (P = 0.008) and an odds ratio of 0.67 (95% confidence interval, 0.43 to 1.01; P = 0.06) for the presence of abnormal albuminuria. Other predictors of abnormal albuminuria included diabetes, blood pressure, and triglyceride level.

CONCLUSION

Results of this study suggest that HT is associated with a reduction in urinary albumin excretion in postmenopausal women.

Relation of the metabolic syndrome to calcified atherosclerotic plaque in the coronary arteries and aorta

The metabolic syndrome is a clustering of low levels of high-density lipoprotein cholesterol, hyperglycemia, high waist circumference, hypertension, and elevated triglycerides, and is associated with cardiovascular disease. Calcified atherosclerotic plaque in the coronary arteries (CAC), measured by cardiac tomographic scans, is a marker for atherosclerosis and relates to mortality. The investigators examined the relation of the metabolic syndrome, and each of its components, to the prevalence of CAC, measured from 2002 to 2004 in 3,166 white and African-American subjects in the National Heart, Lung, & Blood Institute Family Heart Study. Adjusting for age, race, center, smoking, and alcohol consumption, odds ratios and 95% confidence intervals (CI) for a CAC score >100 for subjects with metabolic syndrome were 1.7 (95% CI 1.3 to 2.3) for men and 1.6 (95% CI 1.2 to 2.1) for women. Associations were found for most of the components of the metabolic syndrome with CAC. Associations with the metabolic syndrome were similar for calcified atherosclerotic plaque in the abdominal aorta among 3,173 subjects, with adjusted odds ratios for a score >1,000 of 2.1 (95% CI 1.5 to 3.1) for men and 1.8 (95% CI 1.4 to 2.4) for women. We conclude that the metabolic syndrome and most of its components are associated with a higher prevalence of calcified atherosclerotic plaque in the coronary arteries and abdominal aorta in white and African-American men and women.