The Impact of Glucotoxicity on Gastric Emptying in Chinese Patients With Newly Diagnosed Type 2 Diabetes

Gastric emptying is now recognized as a major determinant of the blood glucose response to carbohydrate in both health and type 2 diabetes (T2D). While patients with longstanding diabetes exhibit a high prevalence of delayed gastric emptying, i.e. gastroparesis, patients with fewer complications are often associated with accelerated gastric emptying, which exacerbates postprandial glycaemic excursions. Moreover, gastric emptying appears to be more rapid in Han Chinese patients with T2D, as compared to Caucasian patients with T2D.

The proposed study will (i) compare the rate of gastric emptying in newly diagnosed, Chinese patients with T2D to non-diabetic controls, (ii) evaluate the relationship between gastric emptying and glycaemic indices, including measures of glucose variability, and (iii) determine whether gastric emptying is altered by glucose-lowering therapies.

A total of 100 newly diagnosed Han Chinese patients with type 2 diabetes will be recruited into the study through the Department of Endocrinology, Nanjing first Hospital. Following enrolment, patients will receive either an intensive insulin pump therapy for a months, or a combination of oral glucose-lowering agents (including metformin, DPP-4 inhibitors and/or sodium-glucose co-transporter-2 inhibitors), or a combination of oral glucose-lowering agents and injectable glucagon-like peptide-1 (GLP-1) receptor agonists for 3 months. Before the commencement of the therapy and on days 30 and 90, patients will attend the hospital for continuous glucose monitoring over 24 hours and measurement of gastric emptying using a 75 g oral glucose tolerance test (OGTT).

During their hospital stay, patients will consume 3 standard meals (i.e. breakfast, lunch and dinner) provided by the Department of Clinical Nutrition, with their glucose levels tracked by continuous glucose monitoring system (CGMS). Following the dinner, subjects will be asked to fast from solids and liquids (other than water) until the following morning, when they will be subjected to an OGTT at \~0900h. An intravenous cannula will be placed into a vein on the forearm. Subjects will be asked to consume a glucose drink containing 75 g glucose and 150mg 13C-acetate, within 5 min for the assessment of gastric emptying, postprandial glycemic and hormonal responses. Breath samples will be collected immediately before, and every 15 minutes after the drink for 3 hours for the measurement of gastric emptying. Venous blood samples will be taken at t = 0, 30, 60, 90, 120, 150 and 180 min for the measurements of plasma glucose, serum insulin, C-peptide, glucagon, total GLP-1, GIP and bile acids concentrations. Blood pressure and heart rate will be measured before and every 15 min after the drink for 3 hours.

Eligibility Criteria:
Inclusion Criteria:

1. Patients newly diagnosed of type 2 diabetes as defined by published Criteria of World Health Organization in 1999; with HbA1c ≥ 7%, age ≥ 18 years of age and ≤ 80 years old, and willing to receive anti-diabetic treatments,
2. Non-diabetic controls, with BMI and age matched to patients with type 2 diabetes

Exclusion Criteria:

1. Patients with a fasting blood glucose ≤ 3.9mmol/L;
2. Patients with insulin allergy;
3. Patients with severe gastrointestinal symptoms and diseases;
4. Patients with gastrointestinal surgery history;
5. Use of any medication that may influence gastrointestinal motor function, body weight or appetite (opiates, anticholinergics, levodopa, clonidine, nitrates, tricyclic antidepressants, selective serotonin re-uptake inhibitors, phosphodiesterase type 5 inhibitors, sumatriptan, metoclopramide, domperidone, cisapride, prucalopride, or erythromycin);
6. Patients with major cardiovascular disease event (e.g., stroke, symptomatic peripheral artery disease, myocardial infarction, percutaneous coronary or peripheral artery angioplasty or coronary artery bypass surgery) in the previous 6 months;
7. Patients with liver dysfunction (aspartate aminotransferase or alanine aminotransferase level of more than two times the upper limit of normal range) or renal dysfunction (creatinine \> 150 μmol/L or GFR \< 60 mL/min/1.73m2);
8. Patients with severe anemia and hemoglobin disorders (Hb \< 60 g/L);
9. Patients with infected injection site or coagulation disorders;
10. Patients who are pregnant.