Exogenous Glucose Oxidation Breath Test (EGOBT)

The purpose of this study is to determine if oxidation of 13C glucose to 13CO2 is changed in type 2 diabetic patients.

Recruitment - Non diabetic participants will be recruited from within the National University of Ireland, Galway student and staff community. Diabetic patients will be recruited from University College Hospital, Galway in collaboration with their hospital consultant. Test- day - They will undergo two separate, identical and simultaneous Oral Glucose Tolerance test and 13C-glucose breath tests on two separate occasions after an overnight fast of 12 hours starting at 8pm. On arrival their heart rate, blood pressure, height and weight will be recorded. Following a resting period of 10 minutes, samples will be obtained for fasting glucose and breath enrichment values (at t = -20 and -10mins). At t = 0 min, participants will consume a standard glucose solution. This glucose solution will consist of 150mg of 13C-glucose, 74.85g of glucose and 200ml of water and 25ml of orange flavoring. Breath samples will be obtained immediately after consumption of test solution and repeated every 15 min over a 4-h interval. Blood glucose concentrations will be taken every 15 min starting at t = 15 min, over a 2-h interval and every 30 min for another 2-h interval. Participants will remain at rest throughout the study. Sample size assessment - Target recruitment is 40 non-diabetics and 40 diabetic participants. This study will use a Student's t-test to determine difference, or otherwise, in glucose oxidation in breath 13CO2, in 2 different groups of individuals. With power arbitrarily set at 0.8, effect size of 1.21 reduction in breath, and Alpha set at 0.01 a final number of 35 participants is required for each group. The n=40 for each group is set to allow a 5 participant drop out in each group Dillon et al (2009).

Simultaneous oral glucose tolerance test and exogenous 13C-glucose breath test following a 12hr overnight fast. Fasting samples were obtained for plasma glucose, insulin, c-peptide, leptin, adiponectin, resistin, HbA1c and two breath 13CO2 abundance values (at t = -15 and -5min). At t = 0min, each subject drank a 75g glucose solution (Thornton & Ross, UK) containing 0.15g of 1-13C glucose. Further breath samples (every 15 min over a 240min interval) and further plasma blood glucose, insulin and c-peptide samples (90,120,180min) were also taken.

The peak enrichment of 13CO2 in breath is calculated by identifying the highest abundance breath sample and subtracting the base line abundance from it.

at 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195, 210, 225, 240 minutes after glucose ingestion.

Fasting plasma glucose and glucose tolerance at 120min, as defined by plasma glucose concentrations. Also measured Leptin/Adiponectin concentrations, Fasting insulin, calculated homeostatic model assessment and and quantitative insulin sensitivity check index.

Inclusion Criteria: All research participants must be between 18 and 65 years Non-diabetic participants must not be taking any medication for diabetes Participants must speak English or Irish proficiently All participants must be males All participants must live within Galway City Type 2 diabetic participants must have been diagnosed within the last five years Type 2 diabetic participants must be treated by Metformin alone for their diabetes All participants must provide written informed consent to comply with every aspect of the study Exclusion Criteria: Females

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