Abstract
Objective 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.
Methods Insulin sensitivity in individuals with obesity undergoing RYGB was studied with DISST and a euglycaemic hyperinsulinaemic clamp.
Results Eleven participants, including nine females, mean (SD) age 51.2 (12.1) yrs, with a preoperative BMI of 48.7 (9.5) kg/m(2) 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 x 10(-4) (2.18)L.pmol(-1).min(-1) preoperatively and 2.36 x 10(-4) (0.78) L.pmol(-1).min(-1) postoperatively (p = 0.37). The mean (SD) clamp ISI was 2.14 x 10(-2) (1.80) mg.L.kg(-1).min(-1).pmol(-1) and 2.00 x 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 x 10(-2).mg.L.kg(-1).min(-1).pmol(-1) (95 %CI-2.24 to 0.32).
Conclusions 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.