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

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/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).

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.