Change in insulin resistance, beta cell function, glucagon-like peptide-1 and calcitonin levels two weeks after...

Bariatric surgery causes profound improvement in metabolic parameters by increasing plasma glucagon like peptide - 1 (GLP-1) level even few weeks after surgery. GLP-1 analogues can cause calcitonin secreting medullary thyroid carcinoma in animals. The studies relating to the mechanisms that underlie these changes are few. The objectives of the study were to measure the change in insulin resistance, beta cell function, GLP-1 and calcitonin levels before and 2 weeks after bariatric surgery.

Patients above 18 years of age who underwent either laparoscopic sleeve gastrectomy or Roux-en Y gastric bypass were recruited into the study. Measured indices were homeostatic model assessment 2 for insulin resistance (HOMA2-IR), an index for hepatic insulin resistance; Matsuda index, an index of whole body insulin sensitivity; and insulin secretion and sensitivity index (ISSI-2), a marker of beta cell secretion.

Twenty eight patients completed the study. HOMA2-IR was lower (2.72 ± 1.28 vs. 2.04 ± 0.9; P = 0.001) and ISSI-2 was higher (0.80 (0.51-1.26) vs. 1.04 (0.56-1.38); P = 0.019) at 2 weeks after surgery compared to baseline. Matsuda index also improved after surgery but was not statistically significant (2.02 (1.1-2.94) vs. 2.84 (1.56-4.12); P = 0.078). Fasting GLP-1 and calcitonin levels did not change while both peak GLP-1, and area under curve for GLP-1 were higher after surgery.

At 2 weeks following bariatric surgery, hepatic insulin resistance decreased while beta cell function improved due to increase in postprandial GLP-1 level without any change in fasting calcitonin levels.