Ethics committee approval
A group of five patients undergoing BPD was considered sufficient for the aims of this pilot study. Inclusion criteria were type 2 diabetes according to the American Diabetes Association criteria , HbA1c >7.5%, BMI between 26 and 33 kg/m2 and age between 30 and 60 years. Exclusion criteria were: type 1 diabetes, renal or hepatic failure, major psychological disorders, pregnancy and previous abdominal surgery. Neither gastric complications nor major side effects occurred following the surgical procedure. All patients received oral vitamin and iron supplementation and dietary suggestions. A matched group of type 2 diabetes patients (three women and four men) was selected from a large database including patients before and 1 month after a daily energy deficit of 2,090–4,180 kJ/day, calculated as resting energy expenditure × 1.4 (measured by indirect calorimetry with a Deltatrac II Metabolic Monitor [Datex-Ohmeda Instrumentarium Corp., Helsinki, Finland]). Weight loss was 0.5–1.0 kg/week. The studies were approved by the Institutional Review Board and Ethics Committee of the Catholic University—Policlinico Gemelli (Rome, Italy). All patients gave written consent.
BPD was used since this is the standard of care for bariatric patients at our Institution. An open BPD was performed , although the majority of centres worldwide currently perform bariatric surgery using a laparoscopic approach to minimise risks. The procedure included a distal, horizontal gastrectomy which leaves behind a 300–400 cm3 sized upper stomach. This remnant stomach is anastomosed to the distal 250 cm of the small intestine (alimentary limb). The excluded small intestine (including the duodenum, jejunum and part of the ileum) carries the bile and pancreatic secretions (biliary limb) and is connected to the alimentary limb at 100 cm proximal to the ileocaecal valve to create the ‘common limb’, the only segment where bile and nutrients mix.
Body weight was measured to the nearest 0.1 kg by a beam scale, and height to the nearest 0.5 cm using a stadiometer (Holtain, Crymych, UK). Body composition was estimated by isotopic dilution . HbA1c levels were measured before and 1, 3, 6, 12 and 18 months after surgery and 1 month after the diet.
OGTT and chemical analyses
A 75 g OGTT was performed in each patient at baseline and at 1 month after surgery or diet (blood sampling at 0, 30, 60, 90, 120 and 180 min). Glycaemia was measured by the glucose oxidase method (Beckman, Fullerton, CA, USA). Insulinaemia was assayed by microparticle enzyme immunoassay (Abbott, Pasadena, CA, USA) with a sensitivity of 6 pmol/l and an intra-assay CV of 6.6%. C-peptide was assayed by RIA (MYRIA; Technogenetics, Milan, Italy) with a minimal detectable concentration of 17 pmol/l and inter- and intra-assay CV values of 3.3–5.7% and 4.6–5.3%, respectively. Fasting and total insulin secretion rate (ISR) after the OGTT were calculated by deconvolution of C-peptide concentrations  and expressed in nmol min−1 m−2 body surface area. Total ISR was computed as the integral over the 3 h of the ISR after the OGTT. Insulin sensitivity was calculated from the OGTT by the oral glucose insulin sensitivity (OGIS), which provides an index that is analogous to the index of insulin sensitivity obtained from the glucose clamp .
Peripheral insulin sensitivity was evaluated by a euglycaemic–hyperinsulinaemic clamp (EHC). Prior to the clamp, plasma glycaemia was maintained in a physiological range by an overnight insulin infusion. Whole-body glucose uptake was calculated with respect to fat-free mass (FFM) as the M value (µmol kgFFM
−1 min−1) calculated during the last 40 min period of the steady-state insulin infusion.
Data (means ± SEM) were analysed by SPSS statistical software (version 13; SPSS, Chicago, IL, USA). The Wilcoxon signed-rank test was performed to compare data from the same patients before and after the interventions. ANOVA with repeated measures was used to detect glucose and insulin changes over time during the OGTT. Two-way ANOVA was performed to compare the BPD with the diet group. p < 0.05 was set as significant.