Genetic epidemiological study of blood pressure in a sedentary rural agricultural population of West Bengal, India

Burden of Type 2 Diabetes and Associated Cardiometabolic Traits and Their Heritability Estimates in Endogamous Ethnic Groups of India: Findings From the INDIGENIUS Consortium

To assess the burden of type 2 diabetes (T2D) and its genetic profile in endogamous populations of India given the paucity of data, we aimed to determine the prevalence of T2D and estimate its heritability using family-based cohorts from three distinct Endogamous Ethnic Groups (EEGs) representing Northern (Rajasthan [Agarwals: AG]) and Southern (Tamil Nadu [Chettiars: CH] and Andhra Pradesh [Reddys: RE]) states of India. For comparison, family-based data collected previously from another North Indian Punjabi Sikh (SI) EEG was used. In addition, we examined various T2D-related cardiometabolic traits and determined their heritabilities. These studies were conducted as part of the Indian Diabetes Genetic Studies in collaboration with US (INDIGENIUS) Consortium. The pedigree, demographic, phenotypic, covariate data and samples were collected from the CH, AG, and RE EEGs. The status of T2D was defined by ADA guidelines (fasting glucose ≥ 126 mg/dl or HbA1c ≥ 6.5% and/or use of diabetes medication/history). The prevalence of T2D in CH (N = 517, families = 21, mean age = 47y, mean BMI = 27), AG (N = 530, Families = 25, mean age = 43y, mean BMI = 27), and RE (N = 500, Families = 22, mean age = 46y, mean BMI = 27) was found to be 33%, 37%, and 36%, respectively, Also, the study participants from these EEGs were found to be at increased cardiometabolic risk (e.g., obesity and prediabetes). Similar characteristics for the SI EEG (N = 1,260, Families = 324, Age = 51y, BMI = 27, T2D = 75%) were obtained previously. We used the variance components approach to carry out genetic analyses after adjusting for covariate effects. The heritability (h2) estimates of T2D in the CH, RE, SI, and AG were found to be 30%, 46%, 54%, and 82% respectively, and statistically significant (P ≤ 0.05). Other T2D related traits (e.g., BMI, lipids, blood pressure) in AG, CH, and RE EEGs exhibited strong additive genetic influences (h2 range: 17% [triglycerides/AG and hs-CRP/RE] - 86% [glucose/non-T2D/AG]). Our findings highlight the high burden of T2D in Indian EEGs with significant and differential additive genetic influences on T2D and related traits.

AGT genetic variation, plasma AGT, and blood pressure: An analysis of the Utah Genetic Reference Project pedigrees

BACKGROUND

Much remains unknown about the genetic factors that contribute to essential hypertension. The Utah Genetic Reference Project (UGRP) large pedigree collection provides new opportunities to study quantitative relationships between genetic variation, endophenotypes, and blood pressure.

METHODS

We analyzed the relationship between common single-nucleotide polymorphisms (SNPs) and haplotypes spanning the angiotensinogen (AGT) gene and promoter region, plasma AGT levels, and systolic (SBP) and diastolic blood pressure (DBP) in 424 individuals from 41 two-generation UGRP families.

RESULTS

Plasma AGT levels are significantly correlated among UGRP family members. Correlations are higher for males than for females. Parent-offspring correlations for plasma AGT (0.30) are higher than those for SBP (0.26) and DBP (0.17) (all P values <0.01). The additive heritability (h(2)) for plasma AGT is high (0.74) and substantially exceeds heritability estimates for SBP (0.26) and DBP (0.16) (all P values <0.01). Significant linkage (logarithm of the odds (LOD) >3) is found between six AGT SNPs and plasma AGT. A model that utilizes three AGT haplotype groups produces the best LOD score (5.1) that exceeds the best single SNP LOD score (3.8). Plasma AGT and blood pressure were not significantly correlated.

CONCLUSIONS

Plasma AGT levels demonstrate high heritability in 41 UGRP families. Locus-specific heritability estimates for AGT SNPs and haplotypes approach 67%, indicating that variation at AGT accounts for a large percentage of the heritability of plasma AGT. A three-way haplotype model outperforms single SNPs for quantitative linkage analysis to plasma AGT. In these predominantly normotensive individuals, plasma AGT did not correlate significantly with blood pressure.

Major gene effects in systolic and diastolic blood pressure in families receiving a health examination in Taiwan

BACKGROUND

Genetic factors play an important role in determining blood pressure values. Strong familial aggregation and estimated heritability values around 0.4-0.6 were reported in a white population.

OBJECTIVES

To investigate the genetic components and mode of inheritance of blood pressure in Taiwan.

DESIGN

A cross-sectional family study based on an adult population undergoing a health examination.

SETTING AND PARTICIPANTS

A total of 1313 adults and their spouses or first-degree relatives, or both, underwent a health examination in a tertiary university hospital from August 1998 to September 1999.

MAIN OUTCOME MEASURES

Genetic analyses, including comingling analysis, familial correlation and complex segregation analysis, were used to detect the genetic components and the mode of inheritance of blood pressures.

RESULTS

In both systolic and diastolic blood pressure, the comingling analyses demonstrated that a more than one-component distribution provided the best fit for the data. The familial correlation coefficients showed significant parent-offspring and sibling correlation. Complex segregation analyses showed major gene effects in controlling systolic and diastolic blood pressure.

CONCLUSIONS

There were significant genetic components in blood pressure among Taiwanese. Further investigation of genomic loci for the control of blood pressure is indicated.

Geographic variation in vascular mortality in Eurasia: spatial autocorrelation analysis of mortality variables and risk factors

The geographic variation patterns of vascular mortality and their major risk factors from 68 samples in Eurasia are described in this work. The goodness-of-fit tests and analysis of variance indicate significant differences in incidence of mortality from the studied diseases, as well as in risk factors among the various geographic regions in four age groups. Correlation analysis points out the two general tendencies for the majority of studied traits: (a) significant positive association with latitude and (b) significant negative correlation with longitude. In turn, one-dimensional correlograms showed no specific geographic pattern at least up to 3000 km for all studied variables. However, at the large geographic scale a long-distance differentiation pattern was indicated for total serum cholesterol and body mass index; regional patches--for total death rate, mortality rate from cardiovascular and ischaemic heart diseases, systolic and diastolic blood pressure; and a local patches pattern was detected for mortality rate from stroke. Two-dimensional correlograms uncovered three distinct and significant patterns of variation: (a) a north-south trend for total mortality rate, for death rate from cardiovascular and ischaemic heart diseases, for diastolic and systolic blood pressure and for body mass index; (b) a northwest-southeast pattern for mortality rate from cerebrovascular disease; and (c) local patches for total serum cholesterol.

Genetic and nongenetic determinants of blood pressure in a southern Brazilian sample

A probabilistic sample representative of the adult population of Rio Grande do Sul, Brazil, was studied to estimate the genetic and nongenetic determinants of blood pressure. Four thousand five hundred and sixty-five individuals, 20 to 74 years old, from 2050 households, were examined. The genetic determination of the SBP (systolic blood pressure) and DBP (diastolic blood pressure) was evaluated in 557 families extracted from this sample. The analysis was performed first with no adjustments for other influencing factors, and then adjusting for the effects of the two significant covariates, age and Quetelet's index, identified through a multiple stepwise regression analysis with nine independent variables. Higher heritability estimates were obtained for DBP (raw data: 0.40; residuals: 0.45) than for SBP (raw data: 0.22; residuals: 0.26). The significant correlation coefficients varied from 0.13 (for father-offspring raw data, total sample), to 0.36 (for siblings, adjusted data, untreated sample). Slight differences were observed between the total and pharmacologically untreated samples in relation to correlation and heritability estimates.