Insulin Sensitivity Index data added to the Portal

The loss of sensitivity to insulin, often termed insulin resistance, is characteristic of type 2 diabetes. Since this sensitivity is difficult to measure directly, researchers have developed an index that reflects it: the modified Stumvoll Insulin Sensitivity Index (ISI). The index is derived by a formula that combines fasting insulin levels with glucose and insulin levels measured two hours after a glucose load.

Now, the results of a study of genetic associations of variants with ISI are available in the T2D Knowledge Portal. These results are from a recent paper in Diabetes by co-first authors Geoffrey Walford, Stefan Gustafsson, Denis Rybin, and fellow members of the Meta-Analyses of Glucose and Insulin-related traits Consortium (MAGIC). (For an overview of the results, see our blog post about the paper.)

In this study, ISI was calculated for 16,753 non-diabetic individuals, and associations of their variants with ISI values were analyzed. The associations were adjusted in one of three ways: for age and sex; for age, sex, and body mass index (BMI); or according to a model that analyzed the combined influence of the genotype effect adjusted for BMI and the interaction effect between the genotype and BMI on ISI. More details about this data set and others from MAGIC may be found on our Data page.

ISI associations are a subset of the MAGIC GWAS data set. They may be viewed in the Portal by selecting one of these phenotypes:

• ISI adjusted for age-sex
• ISI adjusted for age-sex-BMI
• ISI adjusted for genotype-BMI interaction

Associations with these phenotypes can be found in these locations on Portal pages:

• On Gene Pages (see an example) in the Variants & Associations table
• On Variant Pages (see an example) in the Associations at a glance section and in the Association statistics across traits table
• Via the Variant Finder tool, for the phenotypes listed above
• A "Manhattan plot" of associations across the genome may be seen by selecting one of the phenotypes listed above in the View full genetic association results for a phenotype scroll box on the Portal home page.