A mixed meal tolerance test predicts onset of type 2 diabetes in Southwestern Indigenous adults.

Background/objective: To identify predictors of incident type 2 diabetes using a mixed meal tolerance test (MMTT).

Methods: Adult Indigenous Americans without diabetes (n = 501) from a longitudinal cohort underwent at baseline a 4-h MMTT, measures of body composition, an oral glucose tolerance test, an intravenous glucose tolerance test for acute insulin response (AIR), and a hyperinsulinemic-euglycemic clamp for insulin action (M). Plasma glucose responses from the MMTT were quantified by the total and incremental area under the curve (AUC/iAUC).

Results: At follow-up (median time 9.6 [inter-quartile range: 5.6-13.5] years), 169 participants were diagnosed with diabetes. Unadjusted Cox proportional hazards models, glucose AUC_180-min (HR: 1.98, 95% CI: 1.67, 2.34, p < 0.0001), AUC_240-min (HR: 1.93, 95% CI: 1.62, 2.31, p < 0.0001), and iAUC_180-min (HR: 1.43, 95% CI: 1.20, 1.71, p < 0.0001) were associated with an increased risk of diabetes. After adjustment for covariates (age, sex, body fat percentage, M, AIR, Indigenous American heritage) in three subsequent models, AUC_180-min (HR: 1.44, 95% CI: 1.10, 1.88, p = 0.007) and AUC_240-min (HR: 1.41, 95% CI: 1.09, 1.84, p < 0.01) remained associated with increased risk of diabetes.

Conclusions: Glucose responses to a mixed meal predicted the development of type 2 diabetes. This indicates that a mixed nutritional challenge provides important information on disease risk.

Clinical trial registry: ClinicalTrials.gov identifier : NCT00340132, NCT00339482.