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Study Description

The Punjabi Sikh population is a well-defined, carefully collected homogeneous sample from northern India and the US. It has unique characteristics, which are ideal for genetic studies. Sikhs are strictly a non-smoking population and about 50% of participants are life-long vegetarians. All subjects included in the genome-wide association studies (GWAS) were recruited from one geographical location. Our population demonstrates a strong familial clustering of type 2 diabetes and related cardio-metabolic disorders that may be genetic and we believe that the contribution of alleles at specific loci are likely to be unique to Punjabi Asians compared to Europeans. Our group first showed that the association of a common variant at rs9939609 in the FTO (fat mass and obesity) gene in South Asians was independent of BMI (PMID:18598350) in contrast to Europeans where the association of same variant with T2D is mediated through obesity (PMID:17434869). These findings were later confirmed in an independent sample of South Indians (PMID:19005641), Pakistanis (PMID:21294771), and even East and South Asians in a large meta-analyses study comprising 96,551 individuals (PMID: 22109280). Earlier reported association of MTNR1B with fasting glucose concentrations and type 2 diabetes in European GWAS could not be confirmed in our Sikh cohort. On the other hand, our study revealed, for the first time, a significant protective association of another less common variant in MTNR1B with fasting glucose levels that was modulated by obesity. Ours was the first report that suggested that the low CETP activity was associated with higher CAD risk (PMID:22143414) in South Asians and that the genetic effects are significantly modulated by environmental factors (alcohol consumption). Our recent GWAS on type 2 diabetes has identified a novel locus at chromosome 13q12 in the SGCG gene (p=1.82x10-8) associated with type 2 diabetes (PMID:23300278) in Punjabi Sikhs. From these findings, we are optimistic that our resource will provide new insights to gene functions in the diabetic pathway and better help researchers to understand and translate these insights to novel therapeutic treatment and early prevention to T2D that may be important beyond Indians.

  • Study Weblink: OUHSC.edu
  • Study Type: Case-Control
  • dbGaP estimated ancestry components using GRAF-pop
  • Number of study subjects that have individual level data available through Authorized Access: 1616

Authorized Access
Publicly Available Data (Public ftp)

Connect to the public download site. The site contains release notes and manifests. If available, the site also contains data dictionaries, variable summaries, documents, and truncated analyses.

Study Inclusion/Exclusion Criteria

Inclusion:

The study sample consists of individuals who self-reported no South Indian (Dravidian) admixture and membership in the North Indian Punjabi Sikh community. Punjabi families originating from Punjab (Pakistan or India), Haryana, Jammu and Kashmir were included. Only individuals who reported that all four grandparents were Punjabi Sikhs of North Indian origin, who had Punjabi surnames and who spoke the Punjabi language, were included.

Exclusion:

Excluded from the sample were half-siblings, adopted individuals, and individuals with type I diabetes (T1DM) or a family member with T1DM, the rare form of T2DM subtype (MODY), or secondary diabetes (e.g., hemochromatosis, pancreatitis). The selection of controls was based on a fasting glucose of <100.8 mg/dL or a 2h glucose <141.0 mg/dL. Subjects with impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) were excluded when data were analyzed for association of variants with T2D.

Molecular Data
TypeSourcePlatformNumber of Oligos/SNPsSNP Batch IdComment
Whole Genome Genotyping Illumina Human660W-Quad_v1_A 592839 1048965
Study History

Funding for data collection with PhenX variables has been provided by the NHGRI PhenX RISING program.

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