Nutrigenomics provides us with an expanded perspective on the prevention and treatment of cardiovascular disease. In cardiovascular management, nutrigenomics encompasses genetic testing, metabolomics, the identification of single nucleotide polymorphisms (SNPs) and nutrient-genetic interactions, and the newest concept, gene expression testing. These tests provide indication of whether or not your patients’ genetics are expressed and their risk of cardiovascular disease.
Most genetic expression is driven by inflammation, and the majority of the genes, once turned on, promote an inflammatory response. Most of the loci on genes associated with myocardial infarction (MI), Coronary Heart Disease (CHD), and Congestive Heart Failure (CHF) are expressed through inflammation, oxidative stress, and immune-vascular dysfunction. This dynamic starts in the vascular endothelium and vascular smooth muscle and cardiomyocytes leading to angina, coronary artery vasospasm, obstructive coronary heart disease, diastolic and systolic dysfunction and cardiomyopathy. Regardless of the type of insult, blood vessels respond to insults via these same three mechanisms: inflammation, oxidative stress, and immune-vascular dysfunction.
Consequently, the inflammatory pathways have become the primary focus in the management of genetic expression and of genetic risk for CVD.
Nutritional factors provide information that determines whether our genes are turned on or turned off, with a corresponding beneficial or detrimental outcome. One change in a single ubiquitous nutrient such as magnesium may cause 300 or 400 different changes in downstream metabolic pathways and cardiovascular function and health.
There are several issues we want to define when we initially examine patients. One is their genetic profile, the genes they were dealt. There are also epigenetic influences that are not genetic such as DNA methylation, histone modification, and non-coded messenger RNA. The final aspect is gene expression, as genes express themselves in response to nourishment or insults from different types of information coming in from the environment. Genetics have become important in determining not only dietary intake, but also medication intake in many patients, based on their genetic profile.
There are more than 400 known risk factors for cardiovascular disease. They all ultimately result in the same three finite responses in the body: inflammation, oxidative distress, and/or immune dysfunction. These risk factors ultimately translate into vascular disease.
Genes Relevant to Cardiovascular Risk
One of the primary genes we are now measuring is the 9p21 gene, which increases the risk of atherosclerosis and coronary heart disease. Patients who have a heterozygote SNP for 9p21 have a risk for MI that is increased by 50%. When a patient has a homozygote SNP, risk goes up to approximately 100%, so this is one of the top genetic risks that we measure for CHD and MI.
Apo E4 Genotype
The Apo E genotype is not new information, but we must remind ourselves that this genotype increases risk for CVD and people with the genotype have varied responses, particularly to different types of fats in their diet.
One of the newest genes that we’re looking at is COMT (catechol-O-methyltransferase) which provides instructions for the breakdown of norepinephrine and epinephrine. If this genetic SNP is present, the patient will have higher levels of norepinephrine and epinephrine and increased risk of hypertension and coronary heart disease. There is a variation in response depending on which of the specific COMPT SNPs the patient carries; for example, aspirin or vitamin E may be beneficial for patients with one type of COMT SNP, but detrimental if one of the other SNPs is present.
The risk of myocardial infarction can be increased by 71% if a SNP affecting glutathione metabolism (GSH-Px) is present. This selenium-dependent enzyme expresses different capacities to neutralise hydroxyl radicals and other oxidative molecules related to increases in oxidative stress and CVD. For these patients, glutathione peroxidase and selenium levels would be key measurements to track for the risk of CVD.
There is a whole host of genetic influences on blood pressure, probably 30 different genes that we have recognised to date, all of which are helpful in determining both risk for hypertension and risk for cardiovascular target organ damage, as well as response to nutrients, caffeine, medications, and various types of diets.
We know, for example, that someone who consumes large amounts of caffeine and has the SNP, cytochrome P-450-1A2, will increase their risk of tachycardia, hypertension, aortic stiffness, and myocardial infarction. Of course, one could have the right type of SNP for caffeine detoxification and that will reduce their risk. Approximately 60% of the population has cytochrome P-450-1A2FF, which is the wrong kind of gene to have, because they are slow metabolisers and their risk for CHD and MI actually go up with caffeine consumption.
Before you tell patients it’s okay to be drinking caffeine, you need to check the gene for cytochrome P-450 function.
Genetic assessments can play a role in both undertanding and mitigating risks associated with cardiovascular disease. This is an emerging field of medicine, and one that will shape the way we practice in the future.
Dr Houston’s Early Detection and Prevention Checklist for Cardiovascular Disease
- Genetic Expression Scoring and Testing: Corus CAD.
- Top five CHD Risk Factors treated to new goals
- Hypertension: 24 hour ambulatory blood pressure monitor (ABM)
- Dyslipidaemia: Advanced lipid testing.
- Dysglycaemia: FBS, 2h GTT, HbA1c, insulin, proinsulin, C-peptide.
- Obesity: BW, BMI, WC, WHR, body impedance analysis (BIA)
- **Tobacco: stop all forms.