Diet Intervention and GEnetic STudy (DIGEST-Pilot)

Not Applicable

• Conditions: Blood Pressure; Hyperglycemia; Cardiovascular Diseases; Inflammation; Dyslipidemias
• Interventions: Other: Typical Western Diet; Other: Prudent Diet

• Registration Number: NCT01658137
• Lead Sponsor: McMaster University

Brief Summary

Genetic factors contribute to risk factors for cardiovascular disease, such as blood lipids, blood pressure, obesity, diabetes, and may also influence dietary choices, physical activity, and responses to stress. The most robust genetic variant associated with myocardial infarction (MI) is the 9p21 variant, which may raise the risk of MI by up to 40% in those who carry 2 copies of the gene. The investigators recently found that among those who carry the 9p21 variant, the risk of MI may be "turned off" if individuals eat a diet high in fruits and vegetables. The investigators seek to determine how a "prudent" or "anti-inflammatory" diet interacts with the 9p21 risk allele to alter the risk of MI.

Detailed Description

Cardiovascular disease (CVD) is the leading cause of death globally. The majority of CVD is explained by conventional risk factors including cigarette smoking, abnormal lipids, high blood pressure, obesity, diabetes, and health behaviours including dietary intake, physical activity, and psychosocial stressors. Genetic factors contribute to the development of these risk factors, and directly to CVD through other novel pathways. Since the advent of high throughput chip-based genotyping, more than 30 genetic variants have been found to be associated with myocardial infarction. The most robust genetic variant which has been consistently associated with myocardial infarction and other forms of arterial disease is the 9p21 variant. This genetic variant located on Chromosome 9 is common in the population, with 50% of people carrying one copy of the risk allele, and an additional 25% of the population carrying two copies of the risk allele. Compared with those with no copies of the risk allele, the risk of myocardial infarction with one copy of the risk allele is 15-20% higher, and the increased risk among carriers of 2 risk alleles is 20-40%. To date the exact mechanism by which the 9p21 variant increases the risk of myocardial infarction is unknown, although some data suggests that other genes and pathways associated with cell proliferation and inflammation are involved. Recently we made the observation that among carriers of the 9p21 variant, the risk of MI may be "turned off" if individuals consumed a diet high in fruits and vegetables. However the "mechanism" underlying this interaction is unknown. We seek to discover how a "Prudent" (i.e. anti-inflammatory) diet interacts with the 9p21 risk allele(s) to alter the risk of myocardial infarction.

We postulate that a "Prudent" diet (i.e. a diet high in fruits, vegetables, whole grains, non-processed foods) in comparison to a "Western" or "inflammatory diet" (eg, a typical North American diet high in saturated fats and processed foods) will differentially alter the gene expression (measured by RNA) of the 9p21 locus, change the epigenetic marks in this region, and alter several inflammatory markers suspected to mediate the effect of 9p21 on CVD risk (eg, hs-CRP, IF-alpha21, IFN-γ , interleukin 1-alpha, interleukin 1-beta, and interleukin 6) among people with one or two copies of the risk allele compared to people without the risk allele.

The proposed study offers an unique approach to studying dietary relationships with endpoints believed to be influenced by 9p21 gene variants. Rather than testing nutritional supplements, our results will be generalizable to the setting of most dietary counseling practices, which aim to alter dietary patterns, not specific nutrients. This trial will help us to unravel the basis for gene-diet interactions and gain a greater understanding of how inflammation is linked to the development of atherosclerosis, CVD, and possibly some cancers.

Study Timeline

• Study Start: 2012-07
• Study First Submitted: 2012-07-28
• Study First Submitted QC: 2012-08-01
• Study First Posted: 2012-08-06
• Status Verified: 2016-06
• Last Update Submitted: 2016-06-05
• Last Update Posted: 2016-06-07
• Primary Completion: 2016-12
• Study Completion: 2016-12

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: All
• Target Recruitment: 84

Inclusion Criteria

• 18-80 years old
• non-smokers
• Body-Mass-Index <=30 kg/m^2
• willing and able to cook, prepare, and eat provided study foods

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Exclusion Criteria

• Aged below 18 years or above 80 years
• current tobacco smoking
• Body mass index above 30 kg/m2
• Unwillingness or inability to cook, prepare and eat provided study foods (e.g. for medical, philosophical, or religious reasons)
• Excessive use of alcohol (>14 drinks/week in men; >7 drinks/week in women)
• Significant morbidity that would interfere with participation or assessment, including :
• Cancer
• HIV
• chronic renal disease
• renal failure
• Hepatitis/Jaundice
• Liver Disease
• Chronic Obstructive Pulmonary Disease
• Inflammatory bowel disease (Crohn's / Colitis)
• High blood or urine sugar/diabetes
• High blood cholesterol or triglycerides
• Angina/Heart attack/Coronary artery disease
• Heart failure
• Other heart disease
• Angioplasty (balloon opening of an artery) or coronary bypass surgery
• Medications or nutritional supplements (including multivitamins) that could affect outcome measurements. Excluded medications would include:
• Lipid/cholesterol lowering pills
• Insulin/oral hypoglycemic agents
• Medication for stroke
• Antibiotics
• oral contraceptives
• hormone replacement therapy
• non-steroidal anti-inflammatory drugs
• corticosteroids
• unwillingness to stop nutritional supplements 1 week prior to and for duration of intervention
• anticipated difficulties maintaining body weight (e.g. athletic training)

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Typical Western Diet	Typical Western Diet	The comparator dietary pattern ("Typical Western Diet") approximates the inflammatory dietary pattern typically consumed by North Americans. It contains refined grains, processed foods, dairy fat, meats, sugar and high glycemic index foods, and few fruits, nuts, legumes, and vegetables. The fruits and vegetables are highly processed (e.g. juices) and lower in micronutrients than those in the intervention diet. The saturated fat content of this diet does not meet national guidelines for health. The polyunsaturated fat:saturated fat ratio is \~0.5 (low).
Prudent Diet	Prudent Diet	The experimental dietary pattern ("Prudent Diet") is based on intakes of foods hypothesized to have beneficial effects on inflammation and long-term health. This dietary pattern includes micronutrient and macronutrient levels consistent with healthy eating in epidemiological studies and randomized controlled trials. The diet is constructed with low-fat dairy products, fish, chicken, and lean meats to minimize saturated fat and increase protein and calcium. The diet is rich in fruits, vegetables, whole grains, nuts, legumes, and seeds that are good sources of potassium, magnesium, and dietary fiber. This diet provides a 'favorable' macronutrient profile that is low in saturated fat, has a polyunsaturated/saturated fat ratio of \~1.0 (high), and low in high glycemic index carbohydrates.

Primary Outcome Measures

Name	Time	Method
gene expression measuring ANRIL production	baseline and 2 weeks
epigenetic marks	baseline and 2 weeks

Secondary Outcome Measures

Name	Time	Method
diastolic blood pressure	baseline and 2 weeks	mmHg
high-sensitivity C-reactive protein	baseline and 2 weeks	Biomarker of inflammation
interferon-alpha-21	baseline and 2 weeks	Biomarker of inflammation
high-density lipoprotein-cholesterol	baseline and 2 weeks	lipid risk factor for cardiovascular disease
interferon-gamma	baseline and 2 weeks	Biomarker of inflammation
interleukin-1-alpha	baseline and 2 weeks	Biomarker of inflammation
total cholesterol	baseline and 2 weeks	lipid risk factor for cardiovascular disease
low-density lipoprotein-cholesterol	baseline and 2 weeks	lipid risk factor for cardiovascular disease
apolipoprotein-B	baseline and 2 weeks	lipid risk factor for cardiovascular disease
systolic blood pressure	baseline and 2 weeks	mmHg
interleukin-6	baseline and 2 weeks	Biomarker of inflammation
fasting glucose	baseline and 2 weeks	indicator of insulin resistance

Trial Locations

Locations (1)

McMaster University; 🇨🇦 Hamilton, Ontario, Canada