Clicerio González Villalpando

Genetic Basis of Variation in Carotid Artery Wall Thickness

BACKGROUND AND PURPOSE Other than the documented associations of risk factors and carotid artery wall thickness, the genetic basis of variation in carotid artery intimal-medial thickness (IMT) is unknown. The purpose of this study was to examine the extent to which variation in common carotid artery (CCA) IMT and internal carotid artery (ICA) IMT are under genetic control. METHODS The sibship data used for this analysis were part of an epidemiological survey in Mexico City. The CCA and ICA analyses were based on 46 and 44 sibships of various sizes, respectively. The CCA and ICA IMTs were measured with carotid ultrasonography. Using a robust variance decomposition method, we performed genetic analyses of CCA IMT and ICA IMT measurements with models incorporating several cardiovascular risk factors (eg, lipids, diabetes, blood pressure, and smoking) as covariates. RESULTS After accounting for the effects of covariates, we detected high heritabilities for CCA IMT (h2 = 0.92 +/- 0.05, P = .001) and ICA IMT (h2 = 0.86 +/- 0.13, P = .029). Genes accounted for 66.0% of the total variation in CCA IMT, whereas 27.7% of variation was attributable to covariates. For ICA IMT, genes explained a high proportion (74.9%) of total phenotypic variation. The covariates accounted for 11.5% of variation in ICA IMT. CONCLUSIONS Our results suggest that substantial proportions of phenotypic variance in CCA IMT and ICA IMT are attributable to shared genetic factors.

Elevated Carotid Artery Intima-Media Thickness Levels in Individuals Who Subsequently Develop Type 2 Diabetes

Objective—We examined whether B-mode ultrasound–detected carotid artery intima-media thickness (IMT) was elevated before the onset of clinical diabetes. Methods and Results—The study population for these analyses included 1127 nondiabetic participants, 66 prediabetic participants, and 303 diabetic participants with a mean age of 49.8 years who participated in the Mexico City Diabetes Study, a prospective cohort study. Common carotid artery (CCA) and internal carotid artery (ICA) IMTs were measured bilaterally by B-mode ultrasound. Age- and sex-adjusted mean ICA and CCA IMTs were both significantly higher among prediabetic individuals {0.81 mm [95% confidence interval (CI), 0.75–0.88] and 0.72 mm [95% CI, 0.69–0.75], respectively} than in individuals who remained free of diabetes [0.71 mm (95% CI, 0.69–0.72) and 0.69 mm (95% CI, 0.68–0.69), respectively]. However, after adjustment for established cardiovascular risk factors, ICA IMT, but not CCA IMT, remained significantly higher among prediabetic individuals [0.81 mm (95% CI, 0.75–0.88) and 0.71 mm (95% CI, 0.68–0.74)] than in individuals who remained free of diabetes [0.71 mm (95% CI, 0.69–0.72) and 0.69 mm (95% CI, 0.68–0.70)]. Conclusions—The present study provides direct evidence at the vascular level that atherosclerosis levels are elevated before the clinical onset of diabetes.

Myocardial Infarction and Cardiovascular Risk Factors in Mexico City and San Antonio, Texas

Because the epidemiology of cardiovascular disease in Mexico is largely unknown, we examined the prevalence of cardiovascular risk factors and myocardial infarction (MI) in adults from low-income colonias in Mexico City. Data were collected as part of the Mexico City Diabetes Study, a population-based survey of diabetes and cardiovascular disease conducted between 1987 and 1992. Results were compared with those obtained from a comparable survey conducted previously among low-income Mexican Americans in San Antonio, Tex. A total of 2271 individuals between the ages of 35 and 64 years from Mexico City and 1143 adults of the same age range from San Antonio were studied. Despite being leaner and having lower levels of total cholesterol, Mexicans in Mexico City had markedly higher levels of triglycerides (P < .001) and lower levels of HDL cholesterol (P < .001) than Mexican Americans in San Antonio. MI was assessed by Minnesota-coded electrocardiograms and by a self-reported history of physician-diagnosed heart attack. In men, the prevalence of self-reported heart attack was significantly higher in San Antonio than in Mexico City (odds ratio, 5.85; P < .001), and in women, the prevalence of electrocardiogram-documented MI was significantly higher in San Antonio than Mexico City (odds ratio, 2.51; P < .001). The apparent excess of MI in San Antonio relative to Mexico City could be due to higher case-fatality in Mexico City or to a higher incidence in San Antonio.

Moderate-to-Severe Diabetic Retinopathy Is More Prevalent in Mexico City Than in San Antonio, Texas

OBJECTIVE To compare the prevalence of diabetic retinopathy (DR) between low-income Mexicans from Mexico City and Mexican-Americans from San Antonio, Texas. RESEARCH DESIGN AND METHODS We designed a cross-sectional population-based study in low-income neighborhoods of Mexico City and San Antonio. The men and non-pregnant women included in the study had NIDDM and were between 35 and 64 years of age. Ophthalmologic evaluation was performed in 414 patients, 204 in San Antonio and 210 in Mexico City. Seven field standard stereophotographs of each eye were obtained, adapting the Early Treatment Diabetic Retinopathy Study protocol, and graded at the Fundus Photograph Reading Center of the University of Wisconsin. RESULTS Early nonproliferative DR occurred in 37 (17.6%) and 39 (19.1%) patients in Mexico City and San Antonio, respectively. Moderate-to-severe nonproliferative DR occurred in 55 (26.2%) and 37 (18.1%) patients in Mexico City and San Antonio, respectively, and proliferative DR occurred in 12 (5.7%) and 7 (3.4%) patients in Mexico City and San Antonio, respectively. Using univariate and multivariate logistic regression analysis with DR as the dependent variable, age, duration of disease, and fasting glucose concentration were positively and significantly associated with retinopathy, whereas city, systolic blood pressure, and other selected metabolic variables were not. We defined moderate-to-severe DR to include the categories of moderate-to-severe nonproliferative and proliferative DR. For this combined category, Mexico City patients with diabetes had a significantly higher prevalence (P < 0.01) than those from San Antonio when analyzed by multiple logistic regression analysis (odds ratio for Mexico City/San Antonio, 1.72; 95% CI 1.10–2.70). CONCLUSIONS Overall prevalence of DR is similar in both cities. However, moderate-to-severe DR is significantly higher in Mexico City.