Genetics of Type 2 Diabetes in West Africans
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|ClinicalTrials.gov Identifier: NCT00837122|
Recruitment Status : Recruiting
First Posted : February 5, 2009
Last Update Posted : May 25, 2023
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- Type 2 diabetes (T2D) and associated complications are major contributors to the global disease burden. T2D is already a major health threat in populations in developed countries and is rapidly taking hold in the developing world.
- It is believed that understanding the complex interplay between genetic and lifestyle characteristics in the etiology of T2D and related complications will lead to the development of better preventive and therapeutic strategies. In Addition, the results of this project will facilitate our understanding of causes of diabetes in African Americans, other US and world populations
- To conduct a genome-wide association study (GWAS) to identify susceptibility genetic variants for diabetes among the Yoruba people in Ibadan, Nigeria.
- To enroll and examine 300 unrelated cases of T2D and 300 ethnicity-matched Yoruba controls.
- To conduct resequencing of positional candidate gene/loci to identify likely functional variants in a subset of the cohort.
- To conduct replication studies of the top-100 scoring variants in three independent African and European ancestry samples.
- To investigate whether diabetes-associated variants discovered in European populations increase diabetes risk in West Africans.
- Patients 18 years of age with confirmed T2D who are newly diagnosed or on treatment of Yoruba ethnicity in Ibadan, Nigeria. Control subjects are nondiabetics ethnically matched to patients.
- The study design for both patients and controls consists of the following steps:
- Discuss informed consent process and obtain signed informed consent form. Informed consent will be administered by trained clinic staff.
- Assign study ID (barcode)
- Administer questionnaires
- Obtain spot urine sample
- Measure blood pressure
- Obtain anthropometric measurements including body composition
- Perform finger prick for blood glucose level
- Obtain venous blood samples
- Perform eye examination
- On the following day, perform confirmatory blood glucose for the small subset of participants requiring confirmation of previous test result DNA extraction of stored samples will be done at either the National Institutes of Health or the laboratory in Nigeria.
- GWAS will be conducted using publicly available software packages.
|Condition or disease|
|Study Type :||Observational|
|Estimated Enrollment :||10000 participants|
|Official Title:||Genetics of Type 2 Diabetes in Diverse Populations|
|Actual Study Start Date :||February 3, 2009|
Control subjects are nondiabetics ethnically matched to patients
Patients with confirmed T2D who are newly diagnosed or on treatment in Ibadan, Nigeria
- I [ Time Frame: ongoing ]In a subset of participants, to investigate the relationship between diets, gut microbiota, and T2D/related traits.
- H [ Time Frame: ongoing ]To investigate whether hemoglobin A1c (HbA1c) as an indicator of blood glucose control over time is reliable in the presence of the sickle cell trait (HbS), a common hemoglobinopathy in West Africa. The association between HbA1c repeated measures and changes in T2D-related traits over time will be evaluated. We will also evaluate if there is a systematic difference (bias) in the estimation of A1c in carriers of the sickle trait and non-carriers in persons with and without diabetes.
- G [ Time Frame: ongoing ]g- In a subset of participants, to investigate key tissues in the pathophysiology of T2D, we will study differences in the gene expression of skeletal muscle and adipose tissue in lean and obese individuals with and without T2D (n=100, Biopsy Substudy).
- F [ Time Frame: ongoing ]f- To conduct population genetic analyses to describe population history and to develop statistical techniques appropriate for genetic analysis of African ancestry individuals.
- E [ Time Frame: ongoing ]e-To describe these individuals epidemiologically in terms of metabolic traits and the prevalence of relevant conditions, as, for some traits, this may be the first large-scale epidemiological, population-based study of Africans with the appropriate data for such description.
- D [ Time Frame: ongoing ]d- To conduct trans-ethnic fine mapping to determine whether the reduced LD across the genome in African ancestry individuals can refine the region of interest around genetic associations discovered in populations of non-African ancestry. To conduct candidate gene resequencing, Whole Genome Sequencing (WGS), or Whole Exome Sequencing (WES), as funding allows, in participants with metabolic profiles of interest. For instance, individuals will be selected who have extreme values for serum lipids for WES. Variants identified by this resequencing will be genotyped in the larger study population for association analysis.
- C [ Time Frame: ongoing ]c- To develop a large-scale genetic epidemiological resource for the replication of findings in other studies of related traits in African ancestry and non-African ancestry individuals.
- B [ Time Frame: ongoing ]b- To investigate the contribution of gene x environment interactions in T2D risk and in influencing related traits. These investigations may be conducted on either a hypothesis-driven, locus-specific manner or agnostically, i.e. genome-wide. Environmental variants to be considered include lifestyle factors (e.g. diet, measured by food frequency questionnaires (FFQ), socioeconomic measures, and medications taken.
- A [ Time Frame: ongoing ]a- To conduct genetic association studies of T2D and related traits (including blood pressure, serum lipids, blood glucose, adiposity) in West Africans of diverse ethnic groups. Approaches will include genome-wide association studies (including exome chip data) and candidate gene/loci association analyses.
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|Ages Eligible for Study:||18 Years and older (Adult, Older Adult)|
|Sexes Eligible for Study:||All|
|Accepts Healthy Volunteers:||Yes|
|Sampling Method:||Non-Probability Sample|
- INCLUSION CRITERIA:
Cases - Men and women with confirmed type 2 diabetes mellitus that are either on treatment for diabetes or newly diagnosed with blood sugar reading on more than one occasion exceeding or equal to 126 mg/dl. These persons must be above the age of 118 years. In this regard, all newly diagnosed participants will be required to visit the clinic on the following day to perform a fasting blood glucose test to confirm previous results.
Controls Men and women with fasting plasma glucose (FPG) less than 100 mg/dl (5.6 mmol/l). Controls must be above age 18 years and should be ethnically matched to the cases. Enrolled cases and controls have to be unrelated. Therefore, only one person may be enrolled from each family unless they are husband and wife.
Attempts will be made to enroll an equal number of men and women. To ensure that ethnic distribution is maintained in each study, we are proposing to enroll ethnically-matched participants relevant to each study.
People who do not meet the above criteria (e.g., younger than 18, without the blood sugar requirements, etc). No more than one non-spouse member of each family. No prisoners, pregnant women or fetuses will be included in this study.
To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00837122
|Contact: Shirley Freeman||(301) firstname.lastname@example.org|
|Contact: Charles N Rotimi, M.D.||(301) email@example.com|
|University of Ibadan||Recruiting|
|Contact: Clement Adebamowo, M.D. (410) 706-6116 firstname.lastname@example.org|
|Principal Investigator:||Charles N Rotimi, M.D.||National Human Genome Research Institute (NHGRI)|
|Responsible Party:||National Human Genome Research Institute (NHGRI)|
|Other Study ID Numbers:||
|First Posted:||February 5, 2009 Key Record Dates|
|Last Update Posted:||May 25, 2023|
|Last Verified:||October 6, 2022|
|Individual Participant Data (IPD) Sharing Statement:|
|Plan to Share IPD:||No|
|Plan Description:||.Extensive review of the consents related to this protocol by the NHGRI IRB was conducted and it was determined that because the initial consent process did not address sharing of participants' data and the related risks and the carefully established rapport and trust with African populations and collaborators, it would not be appropriate to share participant's data. A memorandum to this effect can be provided, if necessary. We will continue to be open to making the data available through collaboration, a use of the data that was described in initial consent forms.|
|Studies a U.S. FDA-regulated Drug Product:||No|
|Studies a U.S. FDA-regulated Device Product:||No|
Glucose Metabolism Disorders
Endocrine System Diseases