Improvement in insulin sensitivity and β-cell function following ileal interposition with sleeve gastrectomy in type 2 diabetic patients: potential mechanisms.

Introduction: Bariatric surgery in morbidly obese type 2 diabetic (T2DM) patients is associated with high rates of diabetes remission. We investigated the mechanisms of the anti-diabetic effect of the laparoscopic ileal interposition with sleeve gastrectomy (LII-SG) in normal weight (NW), overweight (OW) and obese (OB) T2DM patients.

Methods: Ninety-four patients (aged 54 ± 8 years) with long-standing (median 10 years), treated diabetes (median HbA(1c) = 8.6%), who were NW (15), OW (64) or OB (15) based on BMI, underwent LII-SG. Insulin sensitivity and parameters of ß-cell function were measured from an Oral Glycaemic Tolerance Test pre- and post-operatively.

Results: At a median of 13.4 months post-operatively, weight loss averaged 9.4 ± 1.3, 16.8 ± 0.8 and 23.2 ± 1.7 kg in NW, OW and OB subjects, respectively (p < 0.0001). Insulin sensitivity was fully restored (395 [108] vs 208 [99] ml min⁻¹ m⁻²), fasting insulin secretion rate decreased (68 [52] vs 146 [120] pmol min⁻¹ m⁻²) and total insulin output increased (52 [26] vs 39 [28] nmol m⁻², all p ≤ 0.001). ß-cell glucose sensitivity doubled (37 [33] vs 18 [24] mol min⁻¹ m⁻² mM⁻¹, p < 0.0001). The only parameter predicting remission of diabetes was a lower baseline insulin sensitivity (p = 0.005).

Conclusions: LII-SG induced changes on T2DM by mechanisms in part distinct from weight loss, principally involving restoration of insulin sensitivity and improvement of ß-cell function.