Degree of Preoperative Insulin Resistance Predicts Whether Gastric Bypass Will Lead to Improved or Worsened Insulin Glucose Homeostasis in the Severely Obese

Richard A Perugini, Gordie K Kaban, Steven H Quarfordt, Donald R Czerniach, Dariush Elahi, Dana K Andersen, Demetrius EM Litwin, John J Kelly
University of Massachusetts Medical Center, Worcester, MA

Objective:
We studied early changes in insulin-glucose homeostasis following laparoscopic gastric bypass (LGB).
Design:
Inception cohort
Setting:
Tertiary care medical center
Patients:
Thirty-six consecutive patients meeting NIH criteria for bariatric surgery
Interventions:
LGB consisted of a 15-30 ml gastric pouch, an antecolic, antegastric 120 cm Roux limb, and a gastrojejunal anastomosis performed with a 25 mm circular stapler.
Main Outcome Measures:
Fasting insulin and glucose levels were drawn on day 0 and two weeks postoperatively. Homeostasis model assessment estimated insulin resistance (HOMA-IR) and beta cell efficiency (HOMA-B). We performed a multivariate analysis to study whether postoperative changes in insulin resistance could be predicted by age, gender, weight, BMI, preoperative HOMA-IR, presence of comorbid conditions (hypertension, diabetes, sleep apnea, hypercholesterolemia), and % excess body weight lost at two weeks postoperatively.
Results:
Multivariate analysis identified preoperative HOMA-IR as the only factor predictive of change in insulin sensitivity (correlation coefficient -0.66, p < 0.001). ROC curve analysis confirmed HOMA-IR was highly predictive of postoperative change in insulin resistance (auc = 0.941), and suggested a HOMA-IR of 3.8 as a cut-point maximizing sensitivity and specificity. In patients with preoperative HOMA-IR > 3.8 (58% of total population), 96% improved postoperatively. In contrast, in patients with HOMA-IR < 3.8 (42% of total population), 87% worsened postoperatively.
Conclusions:
Insulin resistant obese patients have improved insulin sensitivity within two weeks of LGB, in direct proportion to their initial degree of insulin resistance. Patients with more normal insulin sensitivity have worsened insulin-glucose homeostasis postoperatively.

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