Acute improvement in insulin resistance after laparoscopic Roux-en-Y gastric bypass: is 3 days enough to correct insulin metabolism?

Background: Although medium- to long-term improvement in insulin resistance and T2DM after Roux-en-Y gastric bypass (RYGB) is well documented, few studies have analyzed the acute effects after surgery. Understanding these effects might help explain the physiologic adjustments after surgery and help in managing insulin resistance and controlling the hypoglycemic treatment for bariatric patients.

Methods: We recruited a prospective cohort of 55 consecutive female patients that underwent primary laparoscopic RYGB between January and June/2011. Blood samples were collected preoperatively and at the first, third, and fifth post-operative days after an overnight fast.

Results: There was a significant increase in homeostasis model assessment for insulin resistance (HOMA-IR) on day 1 (2.36 vs 3.12; p = 0.032), followed by a rapid decrease from day 3 onward (3.12 vs 1.70; <0.001). We found a statistically significant difference (p < 0.05) at all time points compared with baseline. HOMA-IR levels at POD5 were 47 % lower than baseline values and were not significantly different from values at 6 months (1.24 vs 0.93; p = 0.09). The blood levels of glucose and insulin closely matched those of HOMA-IR.

Conclusions: RYGB results in a rapid improvement in insulin resistance and a clinically significant decrease in fasting glucose and insulin levels. This improvement is significant at the 3rd post-operative day, and by the 5th day, patients express insulin resistance levels that are similar to those expressed at 6 months after surgery. This work highlights the acute metabolic impact of surgery. Understanding the behavior of insulin and glucose after surgery might improve our knowledge of the pathophysiology of diabetes and lead to novel therapies and tailored surgical approaches.