The goal of this randomized sham-controlled trial is to ivestigate efficacy and safety of G-POEM in treatment of diabetic gastroparesis and explore impact of G-POEM on glucose metabolism and incretine hormones.

Study Design The study is a single-centre double-blinded sham-controlled randomized trial. All patients have the same baseline characterization. Patients and researchers will be blinded to allocation in trial. Before randomization patients will have an additional meal test performed addressing metabolic characterization of the incretine hormones at baseline. Patients will afterwards be allocated to either the group receiving G-POEM or to the control group where a sham procedure consisting of a gastroscopy with biopsy during general anaesthesia will be done. The randomization will be carried out per-operatively. A computer-generated bloc randomization with sizes of four will be applied. The study will consist of 5 study visits, with a follow-up of 90 days after procedure. Symptoms and adverse event will be monitored 7, 30, and 90 days after intervention. During the 90-day follow-up all primary and secondary outcome will be reassessed.

G-POEM procedure is carried out in general anaesthesia in the operating theatre at the Department of Surgery, Hvidovre Hospital. Procedures will be performed by experienced surgeons from the Gastro Unit at Hvidovre Hospital,who postoperatively will have no contact with the research team or study participants. Patients will receive the same care during hospitalization.

Patients allocated to sham procedure will have 4 mucosa biopsies from antrum. All biopsies will be handled with formalin and transported to Zealand University Hospital. Here they will be formalin fixed paraffin-embedded and kept in a biobank.

Inclusion Criteria:

• The ability to give signed written informed consent,
• Patients with diabetes and gastroparesis,
• Age >18 years,
• Gastroparesis is diagnosed with technetium-scintigraphy,
• Normal gastroscopy,

Exclusion Criteria:

• Ongoing cancer treatment or other concurrent illness that will make the patient unable to attend the study on the discretion of the investigator,
• Recent gastrointestinal surgery,
• Active duodenal/gastric ulcer disease,
• Diseases in the ventricle or previously complicated upper abdominal surgery,
• Previous bariatric surgery,
• Pregnancy or breastfeeding,
• Parkinson disease,
• Persons who, in the judgement of the investigator, may be unable to follow the protocol, Use of metoclopramide, domperidone, prucalopride, ghrelin, macrolide antibiotics (eg, azithromycin, clarithromycin, erythromycin) during study period.
• drugs with an anti-cholinergic mechanism,
• Use of motility slowing agents: anticholinergic agents, calcium channel blockers, TCA, GLP-1 analogs, Lithium, diphenhydramin, glucagon, dopamine agonists, progesterone, L-dopa, calcitonine, octreotide, interferon alfa, sucralsulfate,
• botulinum toxin injections (eg, Botox®) by pyloric injection less than 4 months prior to procedure

Patients and researchers will be blinded to allocation in the trial.