Assessment of the Dynamic Insulin Secretion and Sensitivity Test (DISST) Pre and Post Gastric bypass Surgery

To compare the dynamic insulin secretion and sensitivity test (DISST) with the euglycaemic clamp in individuals undergoing open Roux-en-Y gastric bypass (RYGB) surgery prior-to and one month after surgery.

Insulin sensitivity in individuals with obesity undergoing RYGB was studied with DISST and a euglycaemic hyperinsulinaemic clamp.

Eleven participants, including nine females, mean(SD) age 51.2 (12.1) yrs, with a preoperative BMI of 48.7(9.5)kg/m² were studied. Weight reduced from a mean (SD) of 133.8 (29.8) kg to 123.8 (28.9) kg post-surgery (p<0.001). The mean (SD) insulin sensitivity index (ISI-DISST) was 3.07×10^-4 (2.18) L.pmol^-1.min^-1 preoperatively and 2.36 ×10^-4 (0.78)L.pmol^-1.min^-1 postoperatively (p=0.37). The mean(SD) clamp ISI was 2.14 ×10^-2 (1.80) mg.L.kg^-1.min^-1.pmol^-1 and 2.00×10^-2.(0.76) mg.L.kg^-1.min^-1.pmol^-1 postoperatively (p=0.86). Correlation between ISI-DISST and ISI-Clamp preoperatively was r=0.81(95%CI 0.37-0.95) and post-operatively r=0.47(95%CI 0-0.88). Bland-Altman analysis demonstrates systematic bias between the two tests, where DISST underestimated insulin sensitivity compared with the clamp by 0.96×10^-2.mg.L.kg^-1.min^-1.pmol^-1 (95%CI -2.24 to 0.32).

There was a strong correlation between DISST and the clamp preoperatively and DISST can be used to estimate insulin sensitivity in individuals with morbid obesity. After RYGB surgery, DISST had a weaker correlation with the clamp suggesting the fundamental physiological determinants of insulin sensitivity being measured by each method change in different ways with changes in glucose homeostasis following RYGB surgery.