Diabetes-specific genetic effects on obesity traits in American Indian populations: the Strong Heart Family Study (original) (raw)
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Scientific Reports
Obesity, parental history (PH) of type 2 diabetes (T2D), and genes play an important role in T2D development. However, the influence of each factor on T2D variability is unclear. This study aimed to investigate the influence of obesity (body mass index [BMI], waist/hip ratio), PH, and 16 singlenucleotide polymorphisms (SNPs) associated with T2D on T2D variability in Mexico, comparing 1234 non-diabetic controls and 1219 diabetic patients. To replicate the data, a case-control (n = 2904) and a cross-sectional (n = 1901) study were also included. In a multivariate logistic regression model, all factors accounted for only 27.3% of T2D variability: SNPs (8.4%); PH (11.8%) and obesity (7.1%). These factors contributed more in men (33.2%) than in women (25%), specifically when the disease was diagnosed before the age of 46 (46.7% vs. 30%). Genes played a substantially more important role in men than in women (14.9% vs. 5.5%), while obesity and PH played a similar role in both genders. Genes and PH appeared to play a greater role than obesity in T2D. However, obesity contribution was calculated at the time of recruitment and may be underestimated in patients because the BMI decreased linearly with the number of years with the disease. The data suggest that sexual hormones may play important roles in genes that are associated with T2D. The aetiology of type 2 diabetes (T2D) includes factors such as genes, genetic predisposition, ethnicity, poor nutrition, sedentary lifestyle, obesity, and dyslipidaemia 1. Several family-based studies of disease heritability have indicated that T2D is strongly heritable 2-4 , and the heritability is on average 25% 5. However, insufficient information exists on the heritability of T2D in non-twin families, and little is known regarding how much of this heritability is due to genes and other heritable factors, such as epigenetic factors 6. Historical studies of linkage, candidate genes, and genome-wide association studies (GWAS) have discovered more than 100 variants of genes associated with T2D 7,8. However, the influence of these genes on the disease is unclear. Based on their low individual odds ratios (ORs), most genes have very little influence on the development of the disease 8. According to the results of a European case-control study, only approximately 10% of the T2D variability can be explained by T2D-susceptible loci 9-11. Obesity is a modifiable factor that is clearly associated with the development of the disease. It is well known that the risk of T2D increases linearly as the body mass index (BMI) increases 12. In fact, obesity has been promoted as the main risk factor for diabetes 13. However, the relationship between T2D and
Variance-Component Analysis of Obesity in Type 2 Diabetes Confirms Loci on Chromosomes 1q and 11q
Obesity, 2003
VAN TILBURG, JONATHAN H.O., LODEWIJK A. SANDKUIJL, ERIC STRENGMAN, PETER L. PEARSON, TIMON W. VAN HAEFTEN, AND CISCA WIJMENGA. Variance-component analysis of obesity in type 2 diabetes confirms loci on chromosomes 1q and 11q. Obes Res. 2003;11:1290 -1294 To study genetic loci influencing obesity in nuclear families with type 2 diabetes, we performed a genome-wide screen with 325 microsatellite markers that had an average spacing of 11 cM and a mean heterozygosity of ϳ75% covering all 22 autosomes. Genotype data were obtained from 562 individuals from 178 families from the Breda Study Cohort. These families were determined to have at least two members with type 2 diabetes. As a measure of obesity, the BMI of each diabetes patient was determined. The genotypes were analyzed using variance components (VCs) analysis implemented in GENEHUNTER 2 to determine quantitative trait loci influencing BMI. The VC analysis revealed two genomic regions showing VC logarithm of odds (LOD) scores Ն1.0 on chromosome 1 and chromosome 11. The regions of interest on both chromosomes were further investigated by fine-mapping with additional markers, resulting in a VC LOD score of 1.5 on chromosome 1q and a VC LOD of 2.4 on chromosome 11q. The locus on chromosome 1 has been implicated previously in diabetes. The locus on chromosome 11 has been implicated previously in diabetes and obesity. Our study to determine linkage for BMI confirms the presence of quantitative trait loci influencing obesity in subjects with type 2 diabetes on chromosomes 1q31-q42 and 11q14-q24.
Diabetes care, 2015
Abdominal obesity is a major risk factor for type 2 diabetes (T2D). We aimed to examine the association between the genetic predisposition to central obesity, assessed by the waist-to-hip ratio (WHR) genetic score, and T2D risk. The current study included 2,591 participants with T2D and 3,052 participants without T2D of European ancestry from the Nurses' Health Study (NHS) and the Health Professionals Follow-up Study (HPFS). Genetic predisposition to central obesity was estimated using a genetic score based on 14 established loci for the WHR. We found that the central obesity genetic score was linearly related to higher T2D risk. Results were similar in the NHS (women) and HPFS (men). In combined results, each point of the central obesity genetic score was associated with an odds ratio (OR) of 1.04 (95% CI, 1.01-1.07) for developing T2D, and the OR was 1.24 (1.03-1.45) when comparing extreme quartiles of the genetic score after multivariate adjustment. The data indicate that gen...
Genetic determinants of obesity heterogeneity in type II diabetes
Nutrition & Metabolism, 2020
Background Although obesity is considered as the main cause of Type II diabetes (T2DM), non-obese individuals may still develop T2DM and obese individuals may not. Method The mRNA expression of PI3K/AKT axis from 100 non-obese and obese participants with insulin sensitivity and insulin resistance states were compared in this study toward the understanding of obesity heterogeneity molecular mechanism. Result In present study, there was no statistically significant difference in gene expression levels of IRS1 and PTEN between groups, whereas PI3K, AKT2 and GLUT4 genes were expressed at a lower level in obese diabetic group compared to other groups and were statistically significant. PDK1 gene was expressed at a higher level in non-obese diabetic group compared to obese diabetic and non-obese non-diabetics groups. No statistically significant difference was identified in gene expression pattern of PI3K/AKT pathway between obese non-diabetics and non-obese non-diabetics. Conclusion The ...
Diabetes, 2006
To localize quantitative trait loci for insulin metabolism and obesity, genome scans/linkage analyses were performed on >900 members of 32 extended families participating in phase 3 of the Strong Heart Study, an investigation of the genetic and environmental determinants of cardiovascular disease in American-Indian populations from Arizona, Oklahoma, and North and South Dakota. Linkage analyses of fasting insulin and two obesity-related phenotypes, BMI and percent fat mass, were performed independently in each of the three populations. For log fasting insulin, we found a genome-wide maximum, robust logarithm of odds (LOD) score of 3.42 at 51 cM on chromosome 2p in the Dakotas. Bivariate linkage analyses of log fasting insulin with both BMI and fat mass indicate a situation of incomplete pleiotropy, as well as several significant bivariate LOD scores in the Dakotas. FIG. 2. Bivariate linkage signals for log fasting insulin in relation to obesity-related phenotypes from the Dakotas center. Dashed line, log fasting insulin plus BMI; solid line, log fasting insulin plus fat mass.
The American Journal of Human Genetics, 2000
Individual genetic admixture estimates (IA) from European Americans (EAs) were computed in 7,996 members of the Gila River Indian Community (Arizona). Parental populations for the analysis were European Americans and full-heritage Pima Indians. A logistic regression was performed on 7,796 persons, to assess association of IA with type 2 diabetes. The odds ratio, comparing diabetes risk in full-heritage EAs with fullheritage Pima Indians, was 0.329 (95% confidence interval [CI] 0.225-0.482). Proportional-hazards analysis was performed on 5,482 persons who were nondiabetic at their first examination and 1,215 subjects who developed diabetes during the study. The hazard risk ratio for IA was 0.455 (95% CI 0.301-0.688). Nondiabetic persons had significantly more European IA. In nondiabetic Pimans, multivariate linear regressions of quantitative predictors of type 2 diabetes mellitus, including fasting plasma glucose, 2-h post-load plasma glucose, and body-mass index, showed significant inverse relations with IA when controlled for sex and age. These results illustrate the ongoing evolution of populations by the mechanism of gene flow and its effect on disease risk in the groups with admixture. When the two parental populations differ in disease prevalence, higher or lower risk is associated with admixture, depending on the origin of the admixed alleles and the relative magnitude of the disease prevalence in the parental populations. These data also illustrate the strong genetic components in type 2 diabetes and are consistent with one susceptibility locus common to obesity and diabetes.
Annals of Epidemiology, 2003
PURPOSE: Insulin resistance and visceral adiposity are associated with increased risk of type 2 diabetes. In this report, we describe the methods of the IRAS Family Study, which was designed to identify the genetic and environmental risk factors for insulin resistance and visceral adiposity. METHODS: Families from two ethnic groups (African American and Hispanic) have been recruited from three clinical sites. Blood samples for DNA as well as other standard measures were collected. A CT scan (visceral adiposity) and a frequently sampled glucose tolerance test (insulin resistance) were performed. Preliminary estimates of heritability for indirect measures related to insulin resistance and visceral adiposity were obtained using a variance components approach in the first 93 families (approximately 1000 individuals). RESULTS: Estimates of heritability ranged from low (0.08) for fasting insulin and HOMA, to moderate (0.28) for fasting glucose, to high (0.54) for BMI. After adjustment for age, gender and ethnicity, all heritability estimates were significantly greater than zero ( p Ͻ 0.05). CONCLUSIONS: These results are consistent with the expectation that intermediate measures of insulin resistance and visceral adiposity are heritable, and that the IRAS Family Study has statistical power to detect these intermediate phenotypes of type 2 diabetes and atherosclerosis.