Lipoproteins are large complexes of molecules that transport lipids (primarily triglycerides and cholesterol) through the blood. The intestine has traditionally been viewed as a ‘passive’ organ with respect to lipoprotein production, with intestinal lipoprotein production rates responding mainly to fat ingestion and absorption. We have recently demonstrated in animal models that there is a overproduction of intestinal lipoproteins in both the fasted and the fed state. We have also recently demonstrated that an elevation of plasma free fatty acids (FFA) stimulates intestinal lipoprotein in the hamster. It is not known whether intestinal lipoprotein production can be acutely stimulated by an elevation of plasma FFAs in humans. Hypothesis: Intestinal lipoprotein particle production in humans can be stimulated by an acute elevation of plasma free fatty acids.

Condition	Intervention
Intestinal lipoprotein production Insulin Resistance	Drug: Intralipid  Drug: leucine, glycerol

Further Study Details: 

Primary Outcomes: To determine if the elevation of plasma FFAs by infusing intralipid and heparin stimulates intestinal lipoprotein production.
Expected Total Enrollment:  10

This study proposes to use a published stable isotope method to study the kinetics of apoB48 and apoB100 in the constant fed state in healthy subjects. These studies will be performed in 10 healthy, lean men and women aged 18 to 65 yrs of age. Each subject will serve as their own control and will undergo 3 separate lipoprotein turnover studies, in random order, 4 to 6 weeks apart. Since the infusion of intralipid (a synthetic triglyceride emulsion that provides a source of fatty acids) and heparin (to activate lipoprotein lipase) raises both FFAs and glycerol, two control studies will be performed, one with saline and one with glycerol infusion. Apo B48-containing lipoprotein particle production will be determined as outlined above but for this study in the fasted state, in response to the following interventions; 1. Intralipid (20% solution @ 40ml/hr) and heparin (250 u/hr) infusion to achieve an ~2-fold elevation of plasma FFAs (as previously shown), starting 90 minutes prior to and continuing throughout the lipoprotein turnover experiment, 2. saline infusion control study and 3. Glycerol control study in which glycerol will be infused at a rate of 2.25g/hr to simulate the infusion of glycerol contained in Intralipid (61).

Stable isotope infusion protocol. Following a 14-h overnight fast, an IV will be inserted into a superficial vein in each forearm, one for infusion and one for sampling. At 7 am, a fasting blood sample will be drawn and the subject will begin to ingest the first of 15 identical small hourly meals, each equivalent to 1/15th of their daily food intake. This will be achieved by giving the patient the drink BOOST (Mead Johnson Nutritionals, Ottawa, On) and, using the Harris Benedict Equation (HBE) to determine the number of total energy requirements (formula for the HBE included in the appendix). This is based on height, weight, age and activity factors. The subject will have nothing else to eat until the end of the study. At the same time an IV infusion with either heparin plus intralipid or saline or glycerol as indicated above will be started. At 10 am (3 hours after starting the ingestion of hourly feeds), a primed-constant infusion of deuterium-labeled leucine ([D3]L-leucine 98%, Cambridge Isotope Laboratories, MA) will be started, as previously described (0.6 mg/kg as an initial injection and then 0.6 mg/kg.hr thereafter). In addition, an IV bolus of d5-glycerol (100 mmol/kg) will be administered. These are standard techniques used for the assessment of lipoprotein metabolism in humans . Leucine, an amino acid and glycerol, an intermediary metabolite, are used by cells in the body as building blocks for proteins, fats and for energy. The form of leucine that will be administered is deuterated leucine (chemical formula L-[5,5,5-2H3]) and the form of glycerol is d5-glycerol, which have been enriched with the naturally occurring isotope (chemical variant) of hydrogen (2H). Deuterated leucine and glycerol are stable isotopes that occur naturally in the environment and in the body, and there are no health/safety issues regarding the infusion of the amounts of deuterated leucine and glycerol indicated above. The solutions are prepared using sterile techniques and are monitored for contamination prior to administration. Blood samples will be collected prior to and at the following time points after administration of the stable isotopes: 1hr, 2hr, 3hr, 5hr, 7hr, 9hr, 10hr, 11 hr and 12hr. A total of 340 ml of blood will be drawn.

Ages Eligible for Study:  18 Years   -   65 Years,  Genders Eligible for Study:  Both

Accepts Healthy Volunteers

Criteria

Inclusion Criteria:

- non-diabetic men and women aged 18-65 years:

1. Written informed consent obtained
2. Body mass index (BMI < 27kg/m2
3. Fasting triglycerides < 2 .5mmol/l
4. Waist circumference < 90 cm
5. Fasting blood glucose < 6 mmol/l
6. Haemoglobin above 130g/L.

Exclusion Criteria:

1. Patient has a history of hepatitis/hepatic disease that has been active within the previous 2 years.
2. Any significant active (over the past 12 months) disease of the gastrointestinal, pulmonary, neurological, renal (Cr > 1.5 mg/dL) genitourinary, hematological systems, or has severe uncontrolled treated or untreated hypertension (sitting diastolic BP > 100 or systolic > 180) or proliferative retinopathy
3. Fasting blood glucose > 6 mmol/l or known diabetes.
4. Any history of a MI or clinically significant, active, cardiovascular history including a history of arrhythmia’s or conduction delays on ECG, unstable angina, or decompensated heart failure.
5. Any laboratory values: AST > 2x ULN; ALT > 2x ULN TSH > 6 mU/l
6. Known or suspected allergy to the medication or a history of multiple and/or severe allergies to drugs or foods or a history of severe anaphylactic reactions.
7. Current addiction to alcohol or substances of abuse as determined by the investigator.
8. Mental incapacity, unwillingness or language barrier precluding adequate understanding or cooperation
9. Any lipid lowering of hypoglycemic agents
10. Will not donate blood three months before start or three months after completing study.
11. Thrombocytopenia -

Please refer to this study by ClinicalTrials.gov identifier  NCT00152945

Pat S Harley, RN      416-340-4800  Ext. 8886    pat.harley@uhn.on.ca
Gary F Lewis, MD      416-340-4270    gary.lewis@uhn.on.ca

Canada, Ontario
      University Health Network, Toronto,  Ontario,  M5G 2c4,  Canada; Recruiting

Study chairs or principal investigators

Gary F Lewis, MD,  Principal Investigator,  University Health Network, Toronto, Ontario, Canada   

Study ID Numbers:  04-0575-B; CIHR Grant 777509574
Last Updated:  September 8, 2005
Record first received:  September 8, 2005
ClinicalTrials.gov Identifier:  NCT00152945
Health Authority: Canada: Canadian REB
ClinicalTrials.gov processed this record on 2005-09-13