Genome-wide linkage scans for type 2 diabetes mellitus in four ethnically diverse populations-significant evidence for linkage on chromosome 4q in African Americans: the Family Investigation of Nephropathy and Diabetes Research Group.

BACKGROUND: Previous studies have shown that in addition to environmental influences, type 2 diabetes mellitus (T2DM) has a strong genetic component. The goal of the current study is to identify regions of linkage for T2DM in ethnically diverse populations. METHODS: Phenotypic and genotypic data were obtained from African American (AA; total number of individuals [N] = 1004), American Indian (AI; N = 883), European American (EA; N = 537), and Mexican American (MA; N = 1634) individuals from the Family Investigation of Nephropathy and Diabetes. Non-parametric linkage analysis, using an average of 4404 SNPs, was performed in relative pairs affected with T2DM in each ethnic group. In addition, family-based tests were performed to detect association with T2DM. RESULTS: Statistically significant evidence for linkage was observed on chromosome 4q21.1 (LOD = 3.13; genome-wide p = 0.04) in AA. In addition, a total of 11 regions showed suggestive evidence for linkage (estimated at LOD > 1.71), with the highest LOD scores on chromosomes 12q21.31 (LOD = 2.02) and 22q12.3 (LOD = 2.38) in AA, 2p11.1 (LOD = 2.23) in AI, 6p12.3 (LOD = 2.77) in EA, and 13q21.1 (LOD = . 2.24) in MA. While no region overlapped across all ethnic groups, at least five loci showing LOD > 1.71 have been identified in previously published studies. CONCLUSIONS: The results from this study provide evidence for the presence of genes affecting T2DM on chromosomes 4q, 12q, and 22q in AA; 6p in EA; 2p in AI; and 13q in MA. The strong evidence for linkage on chromosome 4q in AA provides important information given the paucity of diabetes genetic studies in this population.

Inflammation, complement factor h, and age-related macular degeneration: the Multi-ethnic Study of Atherosclerosis.

OBJECTIVE: To describe the relationship of systemic inflammatory disease, complement factor H (CFH) Y402H (1277T-->C) genotype status and age-related macular degeneration (AMD) prevalence in a multiethnic population of whites, blacks, Hispanics, and Chinese. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: We included 5887 persons aged 45 to 84 years with gradable AMD. METHODS: Digital fundus photographs were used to measure AMD. Two years earlier, biomarkers of inflammation were measured and history of inflammatory disease and use of antiinflammatory agents obtained. MAIN OUTCOME MEASURE: Prevalence of AMD. RESULTS: While controlling for age, gender, race/ethnicity, and study site, there were no associations between systemic inflammatory factors and AMD severity. Higher levels of high-sensitivity C-reactive protein (odds ratio [OR] per standard deviation [SD] increase in natural log [ln] units, 2.34; 95% confidence interval [CI], 1.33-4.13) and interleukin-6 (OR per SD in ln, 2.06; 95% CI, 1.21-3.49) were associated with geographic atrophy but not other AMD end points. History of periodontal disease (OR, 1.68; 95% CI, 1.14-2.47) was related to increased retinal pigment. A history of arthritis was associated with soft distinct drusen (OR, 1.24; 95% CI, 1.06-1.46). A history of oral steroid use was related to large drusen (OR, 2.13; 95% CI, 1.14-3.97) and soft distinct drusen (OR, 1.76; 95% CI, 1.00-3.10) and history of cyclooxygenase 2 inhibitor use were associated with large drusen (OR, 1.50; 95% CI, 1.10-2.04), soft indistinct drusen (OR, 1.84; 95% CI, 1.09-3.10), and large drusen area (OR, 1.66; 95% CI, 1.02-2.71). Whites, blacks, and Hispanics with CFH Y402H CC variant genotype had the highest frequency of early AMD compared with those with wild TT genotype. The frequency of CFH did explain some of the difference in AMD prevalence between Chinese and Hispanics compared with whites, but did not explain the difference in prevalence between whites and blacks. CONCLUSIONS: This study confirmed associations of the Y402H CFH gene variant with AMD in nonwhite populations, but neither explained the lack of association between inflammatory factors and AMD in the cohort nor the basis for the observed differences in AMD prevalence across ethnic groups.

Ethnicity and sex modify the association of serum c-reactive protein with microalbuminuria.

OBJECTIVES: To study the association between serum C-reactive protein (CRP) and urinary albumin excretion in the Multi-Ethnic Study of Atherosclerosis and to assess whether the association is modified by ethnicity, sex, or systolic blood pressure. METHODS: This was a cross-sectional study of 6675 participants who were free from macroalbuminuria and clinical cardiovascular disease (mean age 62.1 years, 53% female; 39% White, 27% African American, 22% Hispanic, and 12% Chinese). Urinary albumin excretion was measured by spot urine albumin-to-creatinine ratio (ACR). Effect modifications were tested after adjusting for age, diabetes, body mass index, smoking, use of angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker, other antihypertensive drugs, estrogens, statins, and high-density lipoprotein cholesterol and triglyceride levels. RESULTS: The association between CRP and ACR was modified by ethnicity (P=.01) and sex (P<.001), but not by systolic blood pressure. After multivariate adjustment, the association remained in Chinese, African American, and Hispanic men and African American women (P<.02 for African American men, and P<.04 for the other subgroups). CONCLUSIONS: The association between CRP and ACR was modified by ethnicity and sex; it was stronger in non-White men and African American women. These interactions have not been reported before, and future studies should consider them.

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.

Feasibility of automating insulin delivery for the treatment of type 1 diabetes.

An automated closed-loop insulin delivery system based on subcutaneous glucose sensing and subcutaneous insulin delivery was evaluated in 10 subjects with type 1 diabetes (2 men, 8 women, mean [+/-SD] age 43.4 +/- 11.4 years, duration of diabetes 18.2 +/- 13.5 years). Closed-loop control was assessed over approximately 30 h and compared with open-loop control assessed over 3 days. Closed-loop insulin delivery was calculated using a model of the beta-cell's multiphasic insulin response to glucose. Plasma glucose was 160 +/- 66 mg/dl at the start of closed loop and was thereafter reduced to 71 +/- 19 by 1:00 p.m. (preprandial lunch). Fasting glucose the subsequent morning on closed loop was not different from target (124 +/- 25 vs. 120 mg/dl, respectively; P > 0.05). Mean glucose levels were not different between the open and closed loop (133 +/- 63 vs. 133 +/- 52 mg/dl, respectively; P > 0.65). However, glucose was within the range 70-180 mg/dl 75% of the time under closed loop versus 63% for open loop. Incidence of biochemical hypoglycemia (blood glucose <60 mg/dl) was similar under the two treatments. There were no episodes of severe hypoglycemia. The data provide proof of concept that glycemic control can be achieved by a completely automated external closed-loop insulin delivery system.

Lipin deficiency impairs diurnal metabolic fuel switching.

Fatty liver is a common feature of both obesity and lipodystrophy, reflecting compromised adipose tissue function. The lipin-deficient fatty liver dystrophy (fld) mouse is an exception, as there is lipodystrophy without a fatty liver. Using a combination of indirect calorimetry and stable-isotope flux phenotyping, we determined that fld mice exhibit abnormal fuel utilization throughout the diurnal cycle, with increased glucose oxidation near the end of the fasting period and increased fatty acid oxidation during the feeding period. The mechanisms underlying these alterations include a twofold increase compared with wild-type mice in tissue glycogen storage during the fed state, a 40% reduction in hepatic glucose production in the fasted state, and a 27-fold increase in de novo fatty acid synthesis in liver during the fed state. Thus, the inability to store energy in adipose tissue in the fld mouse leads to a compensatory increase in glycogen storage for use during the fasting period and reliance upon hepatic fatty acid synthesis to provide fuel for peripheral tissues during the fed state. The increase in hepatic fatty acid synthesis and peripheral utilization provides a potential mechanism to ameliorate fatty liver in the fld that would otherwise occur as a consequence of adipose tissue dysfunction.

Decreased hepatic futile cycling compensates for increased glucose disposal in the Pten heterodeficient mouse.

Despite altered regulation of insulin signaling, Pten(+/-) heterodeficient standard diet-fed mice, approximately 4 months old, exhibit normal fasting glucose and insulin levels. We report here a stable isotope flux phenotyping study of this "silent" phenotype, in which tissue-specific insulin effects in whole-body Pten(+/-)-deficient mice were dissected in vivo. Flux phenotyping showed gain of function in Pten(+/-) mice, seen as increased peripheral glucose disposal, and compensation by a metabolic feedback mechanism that 1) decreases hepatic glucose recycling via suppression of glucokinase expression in the basal state to preserve hepatic glucose production and 2) increases hepatic responsiveness in the fasted-to-fed transition. In Pten(+/-) mice, hepatic gene expression of glucokinase was 10-fold less than wild-type (Pten(+/+)) mice in the fasted state and reached Pten(+/+) values in the fed state. Glucose-6-phosphatase expression was the same for Pten(+/-) and Pten(+/+) mice in the fasted state, and its expression for Pten(+/-) was 25% of Pten(+/+) in the fed state. This study demonstrates how intra- and interorgan flux compensations can preserve glucose homeostasis (despite a specific gene defect that accelerates glucose disposal) and how flux phenotyping can dissect these tissue-specific flux compensations in mice presenting with a "silent" phenotype.

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.

Change in body size and the risk of colorectal adenomas.

Adiposity has been recognized as a risk factor for colorectal adenoma, but the influence of weight gain, adipose tissue distribution, and possible differences between ethnic/racial and gender groups remains unanswered. The aim of this prospective study was to examine the association between adiposity and weight change and colorectal adenoma risk. Over approximately 10-year period, anthropometric measures and other risk factors were measured at three time points in the multicenter multiethnic Insulin Resistance Atherosclerosis Study cohort. Colonoscopies were then conducted on 600 cohort participants regardless of symptoms whose mean age at colonoscopy was 64 years. Multivariate logistic regression analyses were used to assess the association between colorectal adenomas and measures of adiposity and weight change over the approximately 10-year period before colonoscopy. Obesity was positively associated with risk of colorectal adenomas at the time of colonoscopy [adjusted odds ratio (OR(adj)), 2.16; 95% confidence interval (95% CI), 1.13-4.14] and was stronger in women (OR(adj), 4.42; 95% CI, 1.53-12.78) than in men (OR(adj), 1.26; 95% CI, 0.52-3.07). The risk of adenomas increased among participants who gained weight compared with those who maintained weight over the approximately 5 years (OR(adj), 2.30; 95% CI, 1.25-4.22) and approximately 10 years (OR(adj), 2.12; 95% CI, 1.25-3.62). These associations were similar for both advanced and nonadvanced adenomas. These results suggest a positive association between obesity, weight gain, and colorectal adenoma risk. Stronger associations were observed when obesity was measured at the time of colonoscopy, suggesting that obesity may be a promoting factor in the growth of colorectal adenomas.

LDL particle subclasses, LDL particle size, and carotid atherosclerosis in the Multi-Ethnic Study of Atherosclerosis (MESA).

BACKGROUND: Previous studies showing that smaller low-density lipoprotein (LDL) size is associated with greater atherosclerotic risk did not adequately control for small and large LDL particle correlation. METHODS AND RESULTS: We studied the association of lipoproteins measured by proton nuclear magnetic resonance spectroscopy with carotid intima-media thickness (IMT) in apparently healthy individuals (N = 5538, 38% White, 28% African American, 22% Hispanic, 12% Chinese). Small and large LDL particle concentrations (LDL-p) were inversely correlated (r = /-0.63, P < 0.0001). Controlling for risk factors but not for LDL subclass correlation, LDL size and small LDL-p separately were associated with IMT (-20.9 and 31.7 microm change in IMT per 1-S.D., respectively, both P < 0.001), but large LDL-p was not (4.9 microm, P = 0.27). When LDL subclasses were included in the same model, large and small LDL-p were both associated with IMT (36.6 and 52.2 microm higher IMT per 1-S.D., respectively, both P < 0.001; 17.7 and 11.6 microm per 100 nmol/L, respectively). LDL size was not significant after accounting for LDL subclasses and risk factors (P = 0.10). CONCLUSION: Both LDL subclasses were significantly associated with subclinical atherosclerosis, with small LDL confounding the association of large LDL with atherosclerosis. Future studies of LDL size should account for the strong inverse correlation of LDL subclasses.

Subclinical atherosclerotic cardiovascular disease and early age-related macular degeneration in a multiracial cohort: the Multiethnic Study of Atherosclerosis.

OBJECTIVE: To investigate the relationship of subclinical atherosclerotic cardiovascular disease (CVD) and its risk factors with age-related macular degeneration (AMD) in the Multiethnic Study of Atherosclerosis. METHODS: This study included 6176 white, black, Hispanic, and Chinese participants aged 44 to 84 years from 6 communities in the United States. Measurements of subclinical CVD were performed according to standardized protocols. Fundus images were graded using the Wisconsin Age-Related Maculopathy Grading System. RESULTS: In analyses controlled for age, sex, race/ethnicity, and study location, early AMD was associated with a higher serum high-density lipoprotein cholesterol level (odds ratio per 15 mg/dL, 1.16; 95% confidence interval, 1.01-1.36) and the presence of echolucent carotid artery plaque (odds ratio for present vs no plaque, 0.37; 95% confidence interval, 0.18-0.74) in the whole cohort. Interactions of race/ethnicity and early AMD were found for carotid intima-media thickness, increasing severity of maximum carotid artery stenosis, serum triglyceride level, subclinical CVD severity, and Agatston calcium score. CONCLUSION: Few associations were found between subclinical CVD and CVD risk factors with early AMD. The findings of associations of early AMD with some signs of subclinical atherosclerotic CVD are different among the 4 racial/ethnic groups, which suggests that care must be taken in generalizing from one racial/ethnic group to another.

The uncoupling protein 1 gene, UCP1, is expressed in mammalian islet cells and associated with acute insulin response to glucose in African American families from the IRAS Family Study.

BACKGROUND: Variants of uncoupling protein genes UCP1 and UCP2 have been associated with a range of traits. We wished to evaluate contributions of known UCP1 and UCP2 variants to metabolic traits in the Insulin Resistance and Atherosclerosis (IRAS) Family Study. METHODS: We genotyped five promoter or coding single nucleotide polymorphisms (SNPs) in 239 African American (AA) participants and 583 Hispanic participants from San Antonio (SA) and San Luis Valley. Generalized estimating equations using a sandwich estimator of the variance and exchangeable correlation to account for familial correlation were computed for the test of genotypic association, and dominant, additive and recessive models. Tests were adjusted for age, gender and BMI (glucose homeostasis and lipid traits), or age and gender (obesity traits), and empirical P-values estimated using a gene dropping approach. RESULTS: UCP1 A-3826G was associated with AIR(g) in AA (P = 0.006) and approached significance in Hispanic families (P = 0.054); and with HDL-C levels in SA families (P = 0.0004). Although UCP1 expression is reported to be restricted to adipose tissue, RT-PCR indicated that UCP1 is expressed in human pancreas and MIN-6 cells, and immunohistochemistry demonstrated co-localization of UCP1 protein with insulin in human islets. UCP2 A55V was associated with waist circumference (P = 0.045) in AA, and BMI in SA (P = 0.018); and UCP2 G-866A with waist-to-hip ratio in AA (P = 0.016). CONCLUSION: This study suggests a functional variant of UCP1 contributes to the variance of AIR(g) in an AA population; the plausibility of this unexpected association is supported by the novel finding that UCP1 is expressed in islets.

Diabetic cardiomyopathy and subclinical cardiovascular disease: the Multi-Ethnic Study of Atherosclerosis (MESA).

OBJECTIVE: Studies have demonstrated increased left ventricular mass (LVM) and diastolic dysfunction among diabetic patients without clinical cardiovascular disease (CVD), but few have assessed the potential contribution of subclinical CVD to ventricular abnormalities in diabetes. We examined whether diabetic cardiomyopathy is associated with subclinical atherosclerosis and if abnormalities are found with impaired fasting glucose (IFG). RESEARCH DESIGN AND METHODS: LVM, end-diastolic volume (EDV), and stroke volume were measured by magnetic resonance imaging (MRI), and atherosclerosis was assessed by coronary artery calcium and carotid intima-media wall thickness in 4,991 participants in the Multi-Ethnic Study of Atherosclerosis, a cohort study of adults aged 45-84 without prior CVD. Multivariable linear regression was used to analyze the association between MRI measures and glucose status. RESULTS: Increased LVM was observed in white, black, and Hispanic participants with diabetes but not among Chinese participants. After adjustment for weight, height, CVD risk factors, and subclinical atherosclerosis, ethnicity-specific differences in ventricular parameters were present. Among whites and Chinese with diabetes, LVM was similar to that in normal subjects; EDV and stroke volume were reduced. In blacks with diabetes, EDV and stroke volume were reduced, and LVM was increased (+5.6 g, P < 0.05). Among Hispanics with diabetes, EDV and stroke volume were similar to normal, but LVM was increased (+5.5 g, P < 0.05). After adjustment, IFG was associated with a decrease in EDV and stroke volume in whites and blacks only; however, no significant differences in LVM were observed. CONCLUSIONS: Ethnicity-specific differences in LVM, EDV, and stroke volume are associated with abnormal glucose metabolism and are independent of subclinical CVD.

Ethnic differences in coronary calcification: the Multi-Ethnic Study of Atherosclerosis (MESA).

BACKGROUND: There is substantial evidence that coronary calcification, a marker for the presence and quantity of coronary atherosclerosis, is higher in US whites than blacks; however, there have been no large population-based studies comparing coronary calcification among US ethnic groups. METHODS AND RESULTS: Using computed tomography, we measured coronary calcification in 6814 white, black, Hispanic, and Chinese men and women aged 45 to 84 years with no clinical cardiovascular disease who participated in the Multi-Ethnic Study of Atherosclerosis (MESA). The prevalence of coronary calcification (Agatston score >0) in these 4 ethnic groups was 70.4%, 52.1%, 56.5%, and 59.2%, respectively, in men (P<0.001) and 44.6%, 36.5%, 34.9%, and 41.9%, respectively, (P<0.001) in women. After adjustment for age, education, lipids, body mass index, smoking, diabetes, hypertension, treatment for hypercholesterolemia, gender, and scanning center, compared with whites, the relative risks for having coronary calcification were 0.78 (95% CI 0.74 to 0.82) in blacks, 0.85 (95% CI 0.79 to 0.91) in Hispanics, and 0.92 (95% CI 0.85 to 0.99) in Chinese. After similar adjustments, the amount of coronary calcification among those with an Agatston score >0 was greatest among whites, followed by Chinese (77% that of whites; 95% CI 62% to 96%), Hispanics (74%; 95% CI 61% to 90%), and blacks (69%; 95% CI 59% to 80%). CONCLUSIONS: We observed ethnic differences in the presence and quantity of coronary calcification that were not explained by coronary risk factors. Identification of the mechanism underlying these differences would further our understanding of the pathophysiology of coronary calcification and its clinical significance. Data on the predictive value of coronary calcium in different ethnic groups are needed.

A genome scan for fasting insulin and fasting glucose identifies a quantitative trait locus on chromosome 17p: the insulin resistance atherosclerosis study (IRAS) family study.

Plasma insulin and glucose concentrations are important quantitative phenotypes related to diabetes and the metabolic syndrome. Reports purporting to identify quantitative trait loci (QTLs) that contribute to the variation in fasting insulin and glucose concentrations are discrepant. As part of the Insulin Resistance Atherosclerosis Study (IRAS) Family Study, a genome scan was performed in African-American (n = 42) and Hispanic (n = 90) extended families to identify regions that may contain positional candidate genes for fasting insulin and fasting glucose (n = 1,604 subjects). There was significant evidence for linkage of fasting insulin to the short arm of chromosome 17 (logarithm of odds [LOD] = 3.30; 54 cM between D17S1294 and D17S1299, P = 1.0 x 10(-4)). The strongest evidence for linkage over all pedigrees for fasting glucose was also observed in this region (LOD = 1.44; 58 cM, P = 9.9 x 10(-3)). The results of this study provide impetus for future positional cloning of QTLs regulating insulin and glucose levels. Identifying genes in these regions should provide insight into the nature of genetic factors regulating plasma glucose and insulin concentrations.

Smoking, diabetes, and blood cholesterol differ in their associations with subclinical atherosclerosis: the Multiethnic Study of Atherosclerosis (MESA).

Previous reports suggest that low-density lipoprotein cholesterol (LDLc) is associated with atherosclerosis plaque initiation while cigarette smoking is more associated with plaque progression. The role of diabetes in plaque initiation and progression is not clear. The aim of this study was to confirm and extend these findings. Among 6384 men and women aged 45-84 free of clinical cardiovascular disease, subclinical atherosclerosis severity was classified on the basis of ultrasound measures of carotid stenosis and thickness and the ankle-brachial blood pressure index of lower extremity arterial disease. Carotid plaques were classified as echolucent or echogenic. Distensibility was calculated from the change in carotid diameter over the cardiac cycle. The smoking association with minimal, moderate, and more severe disease was progressive, estimated as equivalent to LDLc effects of 40, 85 and 238 mg/dl respectively. LDLc was relatively more associated with echolucent plaques; smoking with echogenic plaques. Diabetes was associated with carotid stiffness, whereas smoking was associated with greater distensibility. The results, together with pathological literature, suggest that LDLc may be of key importance both in plaque initiation and vulnerability to rupture, whereas smoking may relate to plaque progression to thicker, more fibrous lesions. Diabetes contributes uniquely to arterial stiffness.

Prevalence of age-related macular degeneration in 4 racial/ethnic groups in the multi-ethnic study of atherosclerosis.

OBJECTIVE: To describe the prevalence of age-related macular degeneration (AMD) in 4 racial/ethnic groups (white, black, Hispanic, and Chinese) that participated in the second examination of the Multi-ethnic Study of Atherosclerosis (MESA). DESIGN: Prospective cohort study. PARTICIPANTS: Six thousand one hundred seventy-six 45- to 85-year-old subjects selected from 6 United States communities. METHODS: Fundus images were taken using a 45 degrees digital camera through dark-adapted pupils and were graded for drusen size, type, area, increased retinal pigment, retinal pigment epithelial depigmentation, neovascular lesions, and geographic atrophy using the modified Wisconsin Age-Related Maculopathy Grading System. MAIN OUTCOME MEASURE: Age-related macular degeneration. RESULTS: Prevalences of AMD were 2.4% (black), 4.2% (Hispanic), 4.6% (Chinese), to 5.4% (white) (P<0.001 for any differences among groups). The highest prevalence of any AMD occurred in those 75 to 84 years old, varying from 7.4% in blacks to 15.8% in whites and Chinese (P = 0.03). Estimated prevalences of late AMD were 0.3% (black), 0.2% (Hispanic), 0.6% (white), and 1.0% (Chinese). These differences were marginally significant (age and gender adjusted, P = 0.08). The frequency of exudative AMD was highest in Chinese (age- and gender-adjusted odds ratio, 4.30; 95% confidence interval, 1.30-14.27) compared with whites. Differences in age, gender, pupil size, body mass index, smoking, alcohol drinking history, diabetes, and hypertension status did not explain the variability among the 4 racial/ethnic groups. CONCLUSIONS: Low prevalences of AMD were found in the MESA cohort in all groups. A lower prevalence of AMD was found in blacks compared with whites. The higher prevalence of exudative AMD in Chinese needs further study.

Association between levels of blood pressure and measures of subclinical disease multi-ethnic study of atherosclerosis.

BACKGROUND: High blood pressure (BP) is associated with the presence and severity of subclinical disease. Less is known about associations between normal levels of BP and various measures of subclinical disease. METHODS: The Multi-Ethnic Study of Atherosclerosis (MESA) enrolled 6814 participants free of clinical cardiovascular disease (38% white, 28% African American, 22% Hispanic, and 12% Asian). The baseline examination included standardized measures of BP, common carotid intimal-medial thickness determined by ultrasonography, coronary artery calcium by computed tomography, and left ventricular mass by magnetic resonance imaging. Participants with treated hypertension (n = 2173) were excluded. Statistical methods included analysis of variance, linear regression, and chi(2) tests. RESULTS: Among the 4640 participants, BP was strongly related to age and African American ethnicity. Carotid intimal-medial thickness was directly associated with systolic BP (SBP) and inversely associated with diastolic BP (DBP, P < .001 for both). For SBP in men, for instance, the adjusted regression coefficient was 0.058 mm per 1 SD (21 mm Hg; 95% CI, 0.045 to 0.070), and for SBP in women it was 0.043 (95% CI, 0.033 to 0.052). Left ventricular mass was directly related to SBP and DBP. The proportion with non-zero calcium scores increased with SBP but decreased with DBP. CONCLUSIONS: The range of BP examined in this study fell largely within the normal or prehypertension stage. In cross-sectional analysis of data from a population-based study, these untreated levels of BP were associated with a variety of measures of subclinical cardiovascular disease.

Factor analysis of metabolic syndrome using directly measured insulin sensitivity: The Insulin Resistance Atherosclerosis Study.

Factor analysis, a multivariate correlation technique, has been used to provide insight into the underlying structure of metabolic syndrome, which is characterized by physiological complexity and strong statistical intercorrelation among its key variables. The majority of previous factor analyses, however, have used only surrogate measures of insulin sensitivity. In addition, few have included members of multiple ethnic groups, and only one has presented results separately for subjects with impaired glucose tolerance. The objective of this study was to investigate, using factor analysis, the clustering of physiologic variables using data from 1,087 nondiabetic participants in the Insulin Resistance Atherosclerosis Study (IRAS). This study includes information on the directly measured insulin sensitivity index (S(I)) from intravenous glucose tolerance testing among African-American, Hispanic, and non-Hispanic white subjects aged 40-69 years at various stages of glucose tolerance. Principal factor analysis identified two factors that explained 28 and 9% of the variance in the dataset, respectively. These factors were interpreted as 1) a " metabolic" factor, with positive loadings of BMI, waist, fasting and 2-h glucose, and triglyceride and inverse loadings of log(S(I)+1) and HDL; and 2) a "blood pressure" factor, with positive loadings of systolic and diastolic blood pressure. The results were unchanged when surrogate measures of insulin resistance were used in place of log(S(I)+1). In addition, the results were similar within strata of sex, glucose tolerance status, and ethnicity. In conclusion, factor analysis identified two underlying factors among a group of metabolic syndrome variables in this dataset. Analyses using surrogate measures of insulin resistance suggested that these variables provide adequate information to explore the underlying intercorrelational structure of metabolic syndrome. Additional clarification of the physiologic characteristics of metabolic syndrome is required as individuals with this condition are increasingly being considered candidates for behavioral and pharmacologic intervention.

Evaluation of insulin sensitivity and beta-cell function indexes obtained from minimal model analysis of a meal tolerance test.

Modeling analysis of glucose, insulin, and C-peptide following a meal has been proposed as a means to estimate insulin sensitivity (S(i)) and beta-cell function from a single test. We compared the model-derived meal indexes with analogous indexes obtained from an intravenous glucose tolerance test (IVGTT) and hyperglycemic clamp (HGC) in 17 nondiabetic subjects (14 men, 3 women, aged 50 +/- 2 years [mean +/- SE], BMI 25.0 +/- 0.7 kg/m(2)). S(i) estimated from the meal was correlated with S(i) estimated from the IVGTT and the HGC (r = 0.59 and 0.76, respectively; P < 0.01 for both) but was approximately 2.3 and 1.4 times higher (P < 0.05 for both). The meal-derived estimate of the beta-cell's response to a steady-state change in glucose (static secretion index) was correlated with the HGC second-phase insulin response (r = 0.69; P = 0.002), but the estimated rate-of-change component (dynamic secretion index) was not correlated with first-phase insulin release from either the HGC or IVGTT. Indexes of beta-cell function obtained from the meal were significantly higher than those obtained from the HGC. In conclusion, insulin sensitivity and beta-cell indexes derived from a meal are not analogous to those from the clamp or IVGTT. Further work is needed before these indexes can be routinely used in clinical and epidemiological studies.