Insulin Sensitivity and β-Cell Function Improve after Gastric Bypass in Severely Obese Adolescents

Abstract

Objective: To test the hypothesis that insulin secretion and insulin sensitivity would be improved in adolescents after Roux-en-Y gastric bypass (RYGB).

Study design: A longitudinal study of 22 adolescents and young adults without diabetes undergoing laparoscopic RYGB (mean age 17.1 ± 1.42 years; range 14.5-20.1; male/female 8/14; Non-Hispanic White/African American 17/5) was conducted. Intravenous glucose tolerance tests were done to obtain insulin sensitivity (insulin sensitivity index), insulin secretion (acute insulin response to glucose ), and the disposition index as primary outcome variables. These variables were compared over the 1 year of observation using linear mixed modeling.

Results: In the 1-year following surgery, body mass index fell by 38% from a mean of 61 ± 12.3 to 39 ± 8.0 kg/m(2) (P < .01). Over the year following surgery, fasting glucose and insulin values declined by 54% and 63%, respectively. Insulin sensitivity index increased 300% (P < .01), acute insulin response to glucose decreased 56% (P < .01), leading to a nearly 2-fold increase in the disposition index (P < .01). Consistent with improved β-cell function, the proinsulin to C-peptide ratio decreased by 21% (P < .01).

Conclusions: RYGB reduced body mass index and improved both insulin sensitivity and β-cell function in severely obese teens and young adults. These findings demonstrate that RYGB is associated with marked metabolic improvements in obese young people even as significant obesity persists.

Trial registration: ClinicalTrials.gov: NCT00360373.

Conflict of interest statement

Conflict of interest information is available at www.jpeds.com (Appendix).

Copyright © 2015 Elsevier Inc. All rights reserved.

Figures

Figure 1

A, Mean ±SD glucose during IVGTT (n = 15). “G,” glucose bolus administration at time zero. B, Mean ± SD insulin values during IVGTT. “AIRG,” acute insulin response to IV glucose. To enhance the sensitivity of the analysis, an intravenous insulin challenge was administered at 20 minutes, leading to a spike in insulin concentrations.

Figure 2

Disposition index for 15 individuals with baseline and 1 year data. Median values of 718 and 1370 for baseline and 1 year are plotted as the heavy lines (P = 0.01).