Mechanistic insights into the heterogeneity of glucose response classes in youths with obesity: a latent class trajectory approach

  

Objective. In a large multiethnic cohort of youths with obesity, we analyzed pathophysiological and genetic mechanisms underlying variations in plasma glucose responses to an oral glucose tolerance test (180min-OGTT).

Research Design and Methods. Latent class trajectory analysis was used to identify different glucose response profiles to 9-point, 180min-OGTT in 2,378 participants in the “Yale Pathogenesis of youth-onset T2D” study, of whom 1,190 had available TCF7L2 genotyping and 358 had multiple OGTTs over a 5-year follow-up. Insulin sensitivity, clearance and β-cell function were estimated by C-peptide modeling. 

Results. Four latent classes were identified and numbered from 1 to 4 based on increasing areas under the glucose curves. Subjects in class 3 and 4 had the worst metabolic and genetic risk profiles, featuring impaired insulin sensitivity, clearance, and β-cell function. Model-predicted probability to be classified as class 1 and 4 increased across ages, while insulin sensitivity and clearance showed transient reductions and β-cell function progressively declined. Insulin sensitivity was the strongest determinant of class assignment at enrolment and of the longitudinal change from class 1 and 2 to higher classes. Transitions between class 3 and 4 were explained only by changes in β-cell glucose sensitivity. 

Conclusions. We identified four glucose response classes in youths with obesity with different genetic risk profiles and progressive impairment in insulin kinetics and action. Insulin sensitivity was the main determinant in the transition between lower and higher glucose classes across ages. In contrast, transitions between the two worst glucose classes were only driven by β-cell glucose sensitivity.