Impaired insulin sensitivity (IS) is a major risk factor for cardiovascular disease and type 2 diabetes. Metabolomic profiling during an oral glucose tolerance test (OGTT) can reveal early pathogenic alterations in healthy individuals. Our aim was to identify IS biomarkers and gain new pathophysiologic insights by applying untargeted metabolomics to repeated OGTT plasma samples in association with a hyperinsulinemic-euglycemic clamp assessment. We studied 192 metabolites identified by non-targeted liquid chromatography/mass spectrometry in plasma samples taken at 0, 30, and 120 min during an OGTT in 470 non-diabetic 71-yr-old men. Insulin sensitivity was associated with 35 metabolites at one or more time points in multivariable-adjusted linear regression. The trajectories of nine metabolites during the OGTT were related to IS, six of which (oleic and palmitoleic acid, decanoyl- and dodecanoylcarnitine, deoxycholate-glycine and hexose) showed no associations with IS in the baseline fasting state. The strongest effects were detected for medium-chain acylcarnitines, which increased between 30-120 min in insulin-resistant individuals compared to those with normal IS. In this large community sample, we identified novel associations between clamp-measured IS and metabolite profiles that became apparent only after an oral glucose challenge. Associations of differential medium-chain acylcarnitine and monounsaturated fatty acid trajectories with IS provide new insights into the pathogenesis of insulin resistance.
Tove Fall and Erik Ingelsson has contributed equally to this work.