Restoration of Euglycemia and Normal Acute Insulin Response to Glucose in Obese Subjects With Type 2 Diabetes Following Bariatric Surgery

Abstract

Insulin resistance and loss of glucose-stimulated acute insulin response (AIR) are the two major and earliest defects in the course of type 2 diabetes. We investigated whether weight loss after bariatric surgery in patients with morbid obesity and type 2 diabetes could restore euglycemia and normal AIR to an intravenous glucose tolerance test (IVGTT). We studied 25 morbidly obese patients—12 with type 2 diabetes, 5 with impaired glucose tolerance, and 8 with normal glucose tolerance (NGT)—before and after a biliopancreatic diversion (BPD) with Roux-en-Y gastric bypass (RYGBP). Twelve individuals with normal BMI served as control subjects. Twelve months after surgery, in the diabetes group, BMI decreased from 53.2 ± 2.0 to 29.2 ± 1.7 kg/m², fasting glucose decreased from 9.5 ± 0.83 to 4.5 ± 0.13 mmol/l, and fasting insulin decreased from 168.4 ± 25.9 to 37.7 ± 4.4 pmol/l (mean ± SE; P < 0.001). AIR, the mean of insulin concentration at 2, 3, and 5 min over basal in the IVGTT, increased by 770 and 935% at 3 and 12 months after surgery, respectively (from 24.0 ± 22.7 to 209 ± 43.4 and 248 ± 33.1 pmol/l, respectively; P < 0,001). Conversely, in the NGT group, the AIR decreased by 40.5% (from 660 ± 60 to 393 ± 93 pmol/l; P = 0.027) 12 months after surgery. BPD with RYGBP performed in morbidly obese patients with type 2 diabetes leads to significant weight loss, euglycemia, and normal insulin sensitivity; but most importantly, it restores a normal β-cell AIR to glucose and a normal relationship of AIR to insulin sensitivity. This is the first study to demonstrate that the lost glucose-induced AIR in patients with type 2 diabetes of mild or moderate severity is a reversible abnormality.