Lixisenatide-The Effects on Glucose and Lipid Metabolism in Type 2 Diabetes

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.

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.

Eligibility Criteria:
Inclusion Criteria:

* Subjects with type 2 diabetes inadequately controlled by metformin.
* Stable diabetes management over last 3 months: metformin dose unchanged. HbA1c not known to have changed by \>0.5% over 3 months.
* Caucasian
* Male
* 40-65 years (inclusive)
* HbA1c 7.5-9.5% (inclusive)
* BMI 27-40 kg/m2 (inclusive)
* Able and willing to self-administer placebo/lixisenatide injection
* Able and willing to perform self-blood glucose monitoring.
* Able and willing to wear a Continuous Glucose Monitoring System (CGMS) for 3 days

Exclusion Criteria:

* Subjects treated with insulin, any oral hypoglycaemic agents (OHA) (other than metformin), any insulin secretagogue or Thiazolidinediones (TZDs)
* A history of heavy alcohol use (\>12 to 15 g of alcohol per day)
* Arteriopathy

  * History of significant coronary artery disease (myocardial infarction, surgical or percutaneous \[balloon and/or stent\] coronary revascularization procedure, or coronary angiography showing at least one stenosis ≥ 50% in a major epicardial artery or branch vessel)
  * Ischemic cerebrovascular disease, including:

    * History of ischemic stroke.
    * History of carotid arterial disease as documented by ≥ 50 % stenosis documented by carotid ultrasound, magnetic resonance imaging or angiography, with or without neurological sequelae.
  * Atherosclerotic peripheral arterial disease, as documented by history of amputation due to vascular disease; history of surgical or percutaneous revascularization procedure; current symptoms of intermittent claudication confirmed by an ankle-brachial pressure index less than 0.9
* Hepatic disease: alanine transaminase (ALT) \>3 times upper limit of normal (ULN)
* Renal disease: estimated glomerular filtration rate (Cockroft-Gault equation) less than 40ml/minute.
* Subjects receiving fibrates or weight reducing drugs
* Mental incapacity
* Unwillingness or a language barrier precluding adequate understanding or co-operation
* Fasting plasma triglycerides \>4.0 mmol/l
* Systolic blood pressure \>160 mmHg on 2 occasions, measured at least 10-minutes apart
* Screening amylase and/or lipase \> 3 times ULN or P-calcitonin ≥20 pg/ml (5.9 pmol/L).
* Personal or immediate family history of medullary thyroid cancer (MTC) or genetic condition that predisposes to MTC (e.g. multiple endocrine neoplasia syndromes).
* History of unexplained pancreatitis, chronic pancreatitis, pancreatectomy.
* Any stomach/gastric surgery other than minor endoscopic procedures such as peptic ulcer injection
* Allergic reaction to any GLP-1 receptor agonist or to metacresol.
* Clinically relevant history of gastrointestinal disease associated with prolonged nausea and vomiting.
* Current smokers
* Subject enrolled in another experimental protocol which involves the use of an investigational drug or device