Dietary Protein Sources and Atherogenic Dyslipidemia
Dietary Protein Sources and Atherogenic Dyslipidemia
There is growing epidemiological evidence that consumption of red meat is associated with
 greater incidence of Cardiovascular Disease (CVD) than either white meat or non-meat foods.
 Research from our group has shown that a high saturated fat (SF) diet with a moderate red
 meat content selectively increases intermediate density lipoproteins (IDL) and larger low
 density lipoproteins (LDLs), which are more weakly associated with CVD risk than smaller
 LDLs. In contrast, the investigators have found that with a similar intake of SF, high beef
 consumption results in a preferential increase in small and medium LDL particles that are
 strongly related to CVD. To date, no studies have directly compared the lipoprotein effects
 of red meat with that of other food sources of protein in the context of both high and low
 saturated fat intake.

 The overall objective of this project is to test the hypothesis that the effects of SF on
 lipoprotein markers of CVD risk are influenced by sources of dietary protein. The
 investigators hypothesize that adverse effects of SF on plasma levels of LDL-cholesterol (C),
 apolipoprotein B (apo B), and atherogenic LDL particles are greater in a diet with a high
 content of red meat than in diets in which the major proteins are from white meat (poultry)
 or non-meat sources. The investigators propose a clinical trial in which 180 healthy men and
 women will be randomized to high SF or low SF diet groups, and within each group, consume
 diets with equivalent amounts of protein from red meat, white meat, and non-meat sources for
 4 wks each in random order. Specifically, the investigators will test whether: (1) With high
 SF, the red meat diet, compared to the other protein sources, will result in higher levels of
 LDL-C, apoB, small and medium LDL, and total/high density lipoprotein (HDL)C; (2) With low
 SF, dietary protein source will not be related to any of these measurements; (3) With both
 the white meat and non-meat protein diets, increased LDL-C with high vs. low SF will be due
 primarily to increases in large LDL, whereas with red meat the additional increase in small
 and medium LDL will result in greater increases in plasma apoB and total LDL particle number.
 Aim 4 will test hypotheses that increases in small and medium LDL with high SF plus red meat
 are related to increased activity of hepatic lipase, a key determinant of small LDL
 production, and that increases in large LDL induced by high SF are related to suppression of
 LDL receptors. The investigators will also assess the effects of protein source and saturated
 fat content on markers of insulin resistance, inflammation and endothelial function.
Clinic Visits:

 Participants will visit the clinic a total of 11 times from screen to completion of study.
 This will include weekly visits with the nutritionist and 9 visits requiring blood draws (at
 screen and on 2 consecutive visits after each dietary period). At each visit, participants
 will be weighed, waist and hip circumference will be measured and blood pressure will be
 monitored. The total amount of blood collected during the course of the study will be 455 mL.

 Screening visit (SV: 1 hour):

 Recruiters will initially determine eligibility through review of a screening questionnaire
 and a telephone or personal interview. If a potential subject is eligible and interested, an
 orientation package will be mailed that will include written information about the study
 requirements. Interested individuals passing pre-screening will be scheduled for a screening
 blood draw visit to determine final eligibility. At the screening visit (SV), participants
 will give informed consent, review their medical history with a registered nurse, and have
 their blood pressure, weight, height, and waist and hip circumference measured. Thirty ml of
 blood will be drawn for measurement of plasma triglycerides (TG), total-C, LDL-C, HDL-C,
 glucose and thyroid stimulating hormone (TSH). Women of childbearing potential will be given
 a beta-Human Chorionic Gonadotropin (b-hCG) urine pregnancy test. Participants will be
 contacted within 2 weeks to notify them of their eligibility.

 Nutritionist Visits (Initial: 1 hr):

 Participants will meet weekly with a nutritionist to receive counseling including weight
 management and diet review. At these meetings, participants will receive a week's worth of
 frozen entrees and study foods, as well as standardized menus with check lists. During the
 washout period (weeks 6-8; weeks 12-14), subjects will continue to refrain from alcohol but
 will consume their usual home diet for 14 days.

 Post-diet Visits Requiring Blood Draws (A visits: 1.5 hr, B visits: 2.5 hr):

 Participants will visit the clinic on two separate days following completion of each diet to
 provide blood samples. Duplicate sampling reduces biological variability, and hence improves
 the power of the study to detect significant diet-induced changes in measurement. On the
 penultimate day of each diet (visits 1A, 2A, 3A, 4A) a fasting blood draw (45 mL) will be
 taken for plasma measurements (TG, total-C, LDL-C, HDL-C, lipoprotein subfractions, glucose,
 insulin, apolipoproteins AI, AII, B, and CIII, and inflammatory markers). On the last day of
 each dietary period (visits 1B, 2B, 3B, 4B) participants will provide a second fasting blood
 sample (for lipids and lipoproteins as above). Lipoprotein lipase and hepatic lipase
 activities will also be measured in plasma (20mL) collected 15 minutes after intravenous
 heparin (75 units/kg).

 Clinical Procedures:

 Clinical measurements: Blood pressure will be measured 3 times in a sitting position and the
 last 2 values averaged. Anthropometric measurements include height, weight, waist and hip
 circumference, and % body fat by bioimpedance (Tanita scale). Waist circumference is measured
 two times at the iliac crest and hip circumference is measured at the widest point of the
 hips.

 Standard Blood sampling: Using standard blood collection procedures, blood samples will be
 collected from participants after a 12-14 hour fast. The blood will be collected into tubes
 containing the following preservative solution: 3.0 gms EDTA (dipotassium), 1.7 mg P-Pack,
 0.15 gms gentamycin sulfate, 0.15 gms chloramphenicol, 5.96 mls aprotinin (Sigma A-6279), and
 0.30 gms sodium azide all of which are diluted to 20mls with doubly deionized water. Plasma
 is separated by immediate centrifugation at 4°C. Lipid and lipoprotein measurements are
 performed and aliquots of plasma are frozen for future analyses.

 Post-heparin Blood Sampling: A blood sample (20ml) will be drawn 15 minutes after intravenous
 administration of a heparin bolus (75 U/kg, see Risk section for justification) for the
 analysis of plasma lipase activity. Prior to administration, participants will be interviewed
 for family history of clotting disorders or personal contraindications including use of
 anticoagulants, history of bleeding or bruising abnormalities or other diseases, allergies,
 or recent dental work. Following administration, participants will remain in clinic for 2
 hours under observation. They will also be provided with an information sheet regarding
 heparin and the procedure.

 Measurement of endothelial function: Endothelial function will be assessed in the fasting
 state by finger reactive hyperemia peripheral arterial tonometry (RH-PAT, Endo-Pat2000,
 Itamar Medical, Israel) and expressed as RH-PAT index. Participants will rest in a supine
 position in a quiet, temperature-controlled room for 30 min. prior to PAT measurements and
 will abstain from caffeine for 6 hours and from water for 2 hours prior to the test, per
 manufacturer's guidelines.
Inclusion Criteria:

 -  30-65 years old

 -  Non-smoking

 -  Agrees to abstain from alcohol and dietary supplements during the study

 -  Willing to consume all study foods as instructed

 Exclusion Criteria:

 -  History of heart disease, cerebrovascular disease, peripheral vascular disease,
 bleeding disorder, liver or renal disease, lung disease, diabetes, Human
 immunodeficiency virus (HIV), or cancer (other than skin cancer) in the last 5 years

 -  Body mass index (BMI) > 35 kg/m2 or < 20 kg/m2

 -  Not weight stable

 -  Abnormal thyroid stimulating hormone

 -  Blood pressure > 150/90

 -  Fasting blood sugar >126 mg/dl

 -  Fasting triglyceride levels >500 mg/dl

 -  Total- and LDL cholesterol >95th percentile for age and sex

 -  Pregnant or breastfeeding

 -  Taking hormones or drugs known to affect lipid metabolism