Pancreatic uptake of radiolabeled exendin as a measure of beta cell mass in T2DM before and after bariatric surgery

Ziel/Aim The role of beta cells in type-2 diabetes mellitus (T2DM) is not clear, and might be related to T2DM remission after gatric bypass surgery (RYGB). This study aims to examine beta cell function (BCF) and mass (BCM) in patients with T2DM before and after RYGB. .

Methodik/Methods Oral glucose tolerance test (OGTT) and ⁶⁸Ga-exendin-4-PET/CT were performed pre- and one year post-RYGB. Total pancreatic uptake of ⁶⁸Ga-exendin-4 per injected activity (kBq/MBq) was measured as marker for BCM.

Ergebnisse/Results Preliminary analysis in 9 patients with complete follow-up was performed, 6 female, mean age: 54 years and mean T2DM duration: 12 years. Pre-RYGB, 6 patients had insulin therapy (104 ± 53IU/day), 3 metformin (1-2g/day). Post-RYGB, average BMI and HbA1c decreased: 39 ± 4.7 to 27 ± 3.7 kg/m² and 63 ± 10 to 47 ± 17 mmol/mol, respectively.

Pre-RYGB, pancreatic uptake of ⁶⁸Ga-exendin-4 was lower in insulin than metformin group; 1.55 [0.53-2.66] vs 2.95 [2.47-3.20] kBq/MBq (p = 0.017). Also, c-peptide response during OGTT was smaller in the insulin than the metformin group (1.1 vs 2.9 nmol/l, p = 0.015). Post-RYGB, 1 patient using insulin had complete remission (no antidiabetics, normal HbA1c), 3 patients had little improvement (insulin or sulfonylurea, unchanged HbA1c), 2 patients had improvements in between. Pancreatic uptake increased to 2.29 [1.86-3.06] kBq/MBq (p = 0.025) in the insulin group and seems to be related to the degree of improvement; relative increase was 56-340 % in 3 patients with large improvement, and 8-30 % in patients with little improvement.In the metformin group all patients had complete remission. Pancreatic uptake remained stable or decreased; relative change from -47 % to +13 %.

Schlussfolgerungen/Conclusions As could be expected, insulin dependent patients have lower BCM and BCF than non-insulin dependent patients. In the metformin group pancreatic ⁶⁸Ga-exendin-4 uptake decreased, probably reflecting reduction of beta cell hyperplasia. Insulin-dependent patients with large improvement, showed increased pancreatic uptake. This may indicate recovered BCM and has not been observed in human before. Mechanisms behind BCM recovering and ⁶⁸Ga-exendin-4 uptake need further investigation.

Publication History

Article published online:
08 April 2021