GLP-1 analogues are a new treatment for type 2 diabetes, which have recently been shown to have beneficial effects on weight, glycaemic control and postprandial triglyceride concentrations. Postprandial hypertriglyceridaemia, which is associated with an increased risk of cardiovascular disease, is a feature of type 2 diabetes. Hypertriglyceridaemia is due to excess triglyceride-rich lipoproteins (TRL) which consist of very low-density lipoproteins, (VLDL) synthesised by the liver which contain the higher molecular weight form of apolipoproteinB (apoB), apoB-100, and chylomicrons which are synthesised in the intestine in response to an intake of dietary fat and contain the lower molecular weight form of apoB, apoB-48. A recent study has shown that GLP-1 receptor signalling is required for the control of postprandial lipoprotein synthesis and secretion in hamsters and mice. GLP-1 was shown to reduce apoB-48 TRL production while a GLP-1 receptor antagonist increased apoB-48 TRL production.~This study will investigate the effect of the GLP-1 analogue lixisenatide compared with placebo, in a double blind crossover study, on postprandial triglyceride metabolism in 12 patients with type 2 diabetes. Chylomicron and VLDL production and clearance rates will be measured in a repeated meal study (Visits 4 and 8) by labelling apoB-100 and apoB-48 with 1-13C leucine (infusion for 8 hours) and by labelling triglycerides with [1,1,2,3,3-2H5 ]glycerol (as a bolus injection) and 13C triolein. Blood samples will be taken for 4 hours prior to during the 8 hr isotopic infusion to measure the enrichment of apoB-100 and apoB-48 with 1-13C leucine by gas chromatography mass spectrometry.~At Visits 3 and 7, glucose flux in response to a mixed fluid meal containing U-13C glucose will be investigated. Endogenous glucose production will also be measured by infusing [6,6-2H2] glucose for 6hours.~Gastric emptying will be measured by acetaminophen (1000 mg) absorption. Patients will also receive heparin (50U/kg) at the end of the study after 15 minutes a blood sample will be taken to determine post heparin lipoprotein lipase (LPL) activity.~During the study the patients will be asked to monitor their blood glucose for three days with continuous glucose monitoring and to fill in a 7 day food diary.~The hypothesis is that i] lixisenatide will lower postprandial glycaemia due to a decrease in endogenous glucose output and an increase in glucose clearance by peripheral tissues as a result of an improvement in insulin sensitivity.~ii] lixisenatide will reduce postprandial triglycerides due to a decrease in chylomicron production as a result of a direct effect on enterocyte chylomicron assembly and will also reduce VLDL secretion from the liver as a result of an improvement in insulin sensitivity.
Glucagon-like-peptide-1 (GLP-1) analogues are a new treatment for type 2 diabetes, which have recently been shown to have beneficial effects on weight, glycaemic control and postprandial triglyceride concentrations. Postprandial hypertriglyceridaemia, which is associated with an increased risk of cardiovascular disease, is a feature of type 2 diabetes. Hypertriglyceridaemia is due to excess triglyceride-rich lipoproteins (TRL) which consist of very low-density lipoproteins, (VLDL) synthesised by the liver which contain the higher molecular weight form of apolipoproteinB (apoB), apoB-100, and chylomicrons which are synthesised in the intestine in response to an intake of dietary fat and contain the lower molecular weight form of apoB, apoB-48. A recent study has shown that GLP-1 receptor signalling is required for the control of postprandial lipoprotein synthesis and secretion in hamsters and mice. GLP-1 was shown to reduce apoB-48 TRL production while a GLP-1 receptor antagonist increased apoB-48 TRL production.~This study will investigate the effect of the GLP-1 analogue lixisenatide compared with placebo, in a double blind crossover study, on postprandial triglyceride metabolism in 12 patients with type 2 diabetes. Chylomicron and VLDL production and clearance rates will be measured in a repeated meal study by labelling apoB-100 and apoB-48 and by labelling triglycerides using stable isotope methodology. Glucose flux in response to a mixed fluid meal will also be investigated using stable isotope methodology. Gastric emptying and post heparin LPL activity will be measured.~The hypothesis is that i] lixisenatide will lower postprandial glycaemia due to a decrease in endogenous glucose output and an increase in glucose clearance by peripheral tissues as a result of an improvement in insulin sensitivity.