Immediate enhancement of first-phase insulin secretion and unchanged glucose effectiveness in patients with type 2 diabetes after Roux-en-Y gastric bypass
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Roux-en-Y gastric bypass surgery (RYGB) in patients with type 2 diabetes often leads to early disease remission, and it is unknown to what extent this involves improved pancreatic β-cell function per se and/or enhanced insulin- and non-insulin-mediated glucose disposal (glucose effectiveness). We studied 30 obese patients, including 10 with type 2 diabetes, 8 with impaired glucose tolerance and 12 with normal glucose tolerance, before, 1 week and 3 months after RYGB, using an intravenous glucose tolerance test to estimate first-phase insulin response, insulin sensitivity (Si) and glucose effectiveness with Bergman's minimal model. In the fasting state, insulin sensitivity was estimated by HOMA-S and β-cell function by HOMA-β. Moreover, mixed meal tests and OGTTs were performed. In patients with type 2 diabetes, glucose levels normalized after RYGB, first-phase insulin secretion in response to iv glucose increased two-fold and HOMA-β improved already 1 week postoperatively, with further enhancements at 3 months. Insulin sensitivity increased in the liver (HOMA-S) at 1 week and at 3 months in peripheral tissues (Si), whereas glucose effectiveness did not improve significantly. During oral testing, GLP-1 responses and insulin secretion increased regardless of glucose tolerance. Therefore, in addition to increased insulin sensitivity and exaggerated postprandial GLP-1 levels, diabetes remission after RYGB involves early improvement of pancreatic β-cell function per se, reflected in enhanced first-phase insulin secretion to iv glucose and increased HOMA-β. A major role for improved glucose effectiveness after RYGB was not supported by this study.
Original language | English |
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Journal | American Journal of Physiology: Endocrinology and Metabolism |
Volume | 308 |
Issue number | 6 |
Pages (from-to) | E535-44 |
Number of pages | 10 |
ISSN | 0193-1849 |
DOIs | |
Publication status | Published - 15 Mar 2015 |
ID: 132046627