Dataset Information

Genome-wide association study of type 2 diabetes in a sample from Mexico City and a meta-analysis of a Mexican-American sample from Starr County, Texas.

ABSTRACT:

Aims/hypothesis

We report a genome-wide association study of type 2 diabetes in an admixed sample from Mexico City and describe the results of a meta-analysis of this study and another genome-wide scan in a Mexican-American sample from Starr County, TX, USA. The top signals observed in this meta-analysis were followed up in the Diabetes Genetics Replication and Meta-analysis Consortium (DIAGRAM) and DIAGRAM+ datasets.

Methods

We analysed 967 cases and 343 normoglycaemic controls. The samples were genotyped with the Affymetrix Genome-wide Human SNP array 5.0. Associations of genotyped and imputed markers with type 2 diabetes were tested using a missing data likelihood score test. A fixed-effects meta-analysis including 1,804 cases and 780 normoglycaemic controls was carried out by weighting the effect estimates by their inverse variances.

Results

In the meta-analysis of the two Hispanic studies, markers showing suggestive associations (p < 10(-5)) were identified in two known diabetes genes, HNF1A and KCNQ1, as well as in several additional regions. Meta-analysis of the two Hispanic studies and the recent DIAGRAM+ dataset identified genome-wide significant signals (p < 5 × 10(-8)) within or near the genes HNF1A and CDKN2A/CDKN2B, as well as suggestive associations in three additional regions, IGF2BP2, KCNQ1 and the previously unreported C14orf70.

Conclusions/interpretation

We observed numerous regions with suggestive associations with type 2 diabetes. Some of these signals correspond to regions described in previous studies. However, many of these regions could not be replicated in the DIAGRAM datasets. It is critical to carry out additional studies in Hispanic and American Indian populations, which have a high prevalence of type 2 diabetes.

SUBMITTER: Parra EJ

PROVIDER: S-EPMC3818640 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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Publications

Genome-wide association study of type 2 diabetes in a sample from Mexico City and a meta-analysis of a Mexican-American sample from Starr County, Texas.

Parra E J EJ Below J E JE Krithika S S Valladares A A Barta J L JL Cox N J NJ Hanis C L CL Wacher N N Garcia-Mena J J Hu P P Shriver M D MD Kumate J J McKeigue P M PM Escobedo J J Cruz M M

Diabetologia 20110515 8

<h4>Aims/hypothesis</h4>We report a genome-wide association study of type 2 diabetes in an admixed sample from Mexico City and describe the results of a meta-analysis of this study and another genome-wide scan in a Mexican-American sample from Starr County, TX, USA. The top signals observed in this meta-analysis were followed up in the Diabetes Genetics Replication and Meta-analysis Consortium (DIAGRAM) and DIAGRAM+ datasets.<h4>Methods</h4>We analysed 967 cases and 343 normoglycaemic controls. ...[more]

PMID: 21573907

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Project description:<p>An initial observation in the 1970s that Starr County, Texas, had the highest diabetes-specific mortality of any of the 254 Texas counties led to the establishment of a field office in Rio Grande City, Texas (the county seat of Starr County) and the initiation of a series of studies to understand the epidemiology and genetics of type 2 diabetes, its complications and related conditions in this predominantly (97%) Mexican American population. The field office opened in February 1981 and has operated continuously since then. During this time, three systematic surveys of the population have been conducted as well as family and longitudinal studies. Culturally sensitive diabetes education programs have been developed and implemented and also a weight loss intervention. In total, more than 23,000 Mexican American individuals have been examined with more than 200,000 aliquots of biological specimens stored. Collectively, these studies are known as the Starr County Health Studies.</p> <p>The present Genetics of Diabetes Study has the goal of identifying loci/alleles that underlie susceptibility to type 2 diabetes in this high risk population using genome wide markers and association testing. The study makes use of two primary resources that have been developed in order to identify 1,000 type 2 diabetes cases and 1,000 disease free controls. In the first instance we have identified a subset of unrelated cases from the total cases that we have identified. Where multiply affected sibships were available, the youngest onset case with detailed phenotyping (including assessment of diabetic retinopathy) was selected. Controls came from a recent survey to establish a representative sample of the Starr County population. Blocks were randomly selected, households on selected blocks enumerated and one individual randomly selected from each household for a detailed examination. The examination included an oral glucose tolerance test. Those included as controls are those with no prior diagnosis of diabetes and a negative oral glucose tolerance test.</p> <p>This collection of cases and controls provides the opportunity to identify susceptibility loci for type 2 diabetes and its complications, specifically diabetic retinopathy and albuminuria. The data set also allows the examination of impaired fasting glucose and impaired glucose tolerance. The samples are split between those born in the United States and those born in Mexico and this gives a natural contrast for examining genotype and environmental interactions. It is anticipated that the understanding that will come will lead to strategies for delaying and preventing the onset of diabetes and its complications.</p>

Project description:BackgroundMost large, prospective studies of the effects of diabetes on mortality have focused on high-income countries where patients have access to reasonably good medical care and can receive treatments to establish and maintain good glycemic control. In those countries, diabetes less than doubles the rate of death from any cause. Few large, prospective studies have been conducted in middle-income countries where obesity and diabetes have become common and glycemic control may be poor.MethodsFrom 1998 through 2004, we recruited approximately 50,000 men and 100,000 women 35 years of age or older into a prospective study in Mexico City, Mexico. We recorded the presence or absence of previously diagnosed diabetes, obtained and stored blood samples, and tracked 12-year disease-specific deaths through January 1, 2014. We accepted diabetes as the underlying cause of death only for deaths that were due to acute diabetic crises. We estimated rate ratios for death among participants who had diabetes at recruitment versus those who did not have diabetes at recruitment; data from participants who had chronic diseases other than diabetes were excluded from the main analysis.ResultsAt the time of recruitment, obesity was common and the prevalence of diabetes rose steeply with age (3% at 35 to 39 years of age and >20% by 60 years of age). Participants who had diabetes had poor glycemic control (mean [±SD] glycated hemoglobin level, 9.0±2.4%), and the rates of use of other vasoprotective medications were low (e.g., 30% of participants with diabetes were receiving antihypertensive medication at recruitment and 1% were receiving lipid-lowering medication). Previously diagnosed diabetes was associated with rate ratios for death from any cause of 5.4 (95% confidence interval [CI], 5.0 to 6.0) at 35 to 59 years of age, 3.1 (95% CI, 2.9 to 3.3) at 60 to 74 years of age, and 1.9 (95% CI, 1.8 to 2.1) at 75 to 84 years of age. Between 35 and 74 years of age, the excess mortality associated with previously diagnosed diabetes accounted for one third of all deaths; the largest absolute excess risks of death were from renal disease (rate ratio, 20.1; 95% CI, 17.2 to 23.4), cardiac disease (rate ratio, 3.7; 95% CI, 3.2 to 4.2), infection (rate ratio, 4.7; 95% CI, 4.0 to 5.5), acute diabetic crises (8% of all deaths among participants who had previously diagnosed diabetes), and other vascular disease (mainly stroke). Little association was observed between diabetes and mortality from cirrhosis, cancer, or chronic obstructive pulmonary disease.ConclusionsIn this study in Mexico, a middle-income country with high levels of obesity, diabetes was common, glycemic control was poor, and diabetes was associated with a far worse prognosis than that seen in high-income countries; it accounted for at least one third of all deaths between 35 and 74 years of age. (Funded by the Wellcome Trust and others.).

Project description:Mexican Americans have a high prevalence of diabetes and burden of diabetes-related complications, highlighting the need for novel preventive strategies and noninvasive predictors of diabetes risk tailored to this population. Changes in the gut microbiome have the potential to predict diabetes. Here, we aimed to identify alterations in the gut microbiome associated with diabetes in the high-risk population of Mexican Americans in South Texas. Stool samples were collected from 216 subjects from the population-based Cameron County Hispanic Cohort. Among them, 75 had type 2 diabetes. Taxonomic and functional profiling of the stool samples were assessed by 16S and shotgun metagenomic sequencing, and the influence of genetic factors was explored. The gut microbiome of subjects with diabetes was enriched with proinflammatory Proteobacteria members (Enterobacteriaceae, Escherichia-Shigella) and depleted of butyrate-producing Clostridiales members (Faecalibacterium prausnitzii, Peptostreptococcaceae, and Clostridium sensu stricto 1). The accompanying metagenomic changes in subjects with diabetes suggested dysregulated amino acid metabolism, reduced galacturonate and glucuronate catabolism (correlating with Faecalibacterium prausnitzii abundance), and enriched heme biosynthesis (correlating with Enterobacteriaceae abundance). Polymorphism rs7129790 near MMP27 was strongly associated with high Proteobacteria abundance and was more frequent in this cohort and in individuals of Mexican ancestry than in Europeans. In conclusion, Mexican Americans in South Texas with diabetes display distinct gut microbiome and metagenomic signatures. These signatures may have utility in risk modeling and disease prevention in this high-risk population. IMPORTANCE The gut microbiome composition varies across ethnicities and geographical locations, yet studies on diabetes-associated microbiome changes specific to high-risk Mexican Americans are lacking. Here, we aimed to identify specific alterations associated with diabetes in this population, as well as host genetic factors that may explain increased disease susceptibility in this ethnic group. Using samples from a population-based cohort of Mexican Americans with a high prevalence of obesity and diabetes, we confirmed findings from studies on other ethnicities that suggested promotion of a chronic proinflammatory environment, loss of butyrate production, and compromised intestinal barrier integrity. High abundance of proinflammatory Proteobacteria was associated with a polymorphism that was more frequent in this cohort and in individuals of Mexican ancestry than in Europeans. Validation of microbiome-based risk models for diabetes should be evaluated in prospective cohort studies.

Dataset Information

Genome-wide association study of type 2 diabetes in a sample from Mexico City and a meta-analysis of a Mexican-American sample from Starr County, Texas.

Aims/hypothesis

Methods

Results

Conclusions/interpretation

Publications

Genome-wide association study of type 2 diabetes in a sample from Mexico City and a meta-analysis of a Mexican-American sample from Starr County, Texas.

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