Comparison Between RYGB, DS, and VSG Effect On Glucose Homeostasis: Interim Report of Prospective Study

Mitchell S Roslin, MD FACS, Yuriy Dudiy, MD, Joanne Weiskopf, PA, Paresh Shah, MD FACS, Paresh Shah, MD FACS. Lenox Hill Hospital, Northern Westchester Hospital Center

Introduction: The effect of Roux en Y gastric bypass (RYGB) on insulin resistance and resolution of diabetes has been documented. Our group has reported a high incidence of reactive hypoglycemia, following RYGB. The purpose of this study is to compare the six month response to oral glucose challenge, improvement in insulin resistance, and diabetes resolution in patients undergoing RYGB, duodenal switch (DS), and vertical sleeve gastrectomy (VSG).

Methods and procedures: Sixty patients meeting criteria for bariatric surgery are enrolled in this prospective non-randomized study. Twenty-six patients who have reached the six month mark are the basis of this report. Prior to the surgery and at six months follow-up, patients underwent blood draw to determine fasting glucose, fasting insulin, HbA1c, C peptide level. Two hours oral liquid glucose challenge test was done to evaluate glucose response. A ratio of serum glucose levels at the 1 hour and 2 hour marks was calculated. HOMA-IR was calculated using standard formula. All patients signed an informed consent and the protocol was approved by the institutional IRB.

Results: All patients underwent a successful laparoscopic bariatric procedure (VSG =12, DS =7 and RYGB = 7). Although self selected, the groups were similar except for the higher preoperative BMI of the switch patients (BMI=62.2±13.6 compare to 47.9±9.0 in VSG patients and 49.1±12.07 in RYGB patients). Preoperatively, 18 patients had increased insulin resistance based on HOMA> 2.5, 12 were diabetic or pre diabetic based on HgbA1c > 6.0%, and five had fasting blood glucose level (FBS) > 120 mg/dL. At six month follow-up, mean BMI decreased by 16.55±10.7, HgbA1c decreased by 0.39±1.43%, fasting glucose decreased by 15.8±29.3 mg/dL. 12/18 patients had HOMA < 2.5, 9/12 had HgbA1c < 6.0% (1 > 6% with each procedure), and 3/5 had FBS < 120 mg/d. Table 1 shows the results by procedure HOMA-IR decreased from a mean of 7.9 to 0.85 (RYGB), from 3.08 to 1.08 (DS) and 12.04 to 4.2 (VSG). Six month GTT 1hr/2hrs glucose ratio was 2.2(RYGB), 1.56 (DS), 1.66 (VSG).

Conclusions: Our data demonstrates that all the stapling weight loss operations improve insulin resistance and improve HgbA1c. Six month weight loss was similar between RYGB and VSG, and highest in DS. Improvement in insulin resistance, measured by HOMA-IR, did not correlate with weight loss. Higher 1hr/2hrs glucose ratio with RYGB suggests rapid absorption of nutrients with a sharper rise and fall in glucose level. The combination of rapid emptying and improved insulin sensitivity may result in hypoglycemia promoting maladaptive eating, or in the extreme, neuroglycopenia. Preserving the pyloric valve may result in a more physiologic improvement in insulin resistance, while demonstrating meaningful improvement in HgbA1. Our completed study that will include 60 patients, one year follow up with solid meal and liquid glucose challenge will hopefully clarify these issues.

Table 1.