The goal of this article is to examine nutritional genomics as a potential tool for individual based nutrition therapy. The genes that were studied were all heart health susceptibility genes and their common genetic variants. The specific genes that were observed in this review were methylenetetrahydrofolate reductase (MTHFR), cholesteryl ester transfer protein (CETP), lipoprotein lipase (LPL), apolipoprotein C-III (Apo C-III), and interleukin 6 (IL-6). The function, genetic variants, and dietary interactions regarding each gene are discussed. Specific dietary recommendations were alluded to, but not confirmed, depending on the type of genes that one possessed.
In order to fully understand the paper, it is important to define the difference between the two sub-categories of nutritional genomics: nutrigenomics and nutrigenetics. Nutrigenomics speaks of the functional interactions that ceratin foods have on the human genome. For instance, eicosapentaenoic acid and docosahexaenoic acid (found in fish oil) increase expression of genes that are involved in fat metabolism and energy, as well as decreasing expression of genes involved in inflammation. Nutrigenetics can be defined as how specific individuals with unique genetic makeups respond to particular foods. For example, the -13910C to T genetic variant effects lactose tolerance. The T allele allows for better metabolism of lactose, while the C allele causes lactose intolerance.
The MTHFR gene is paramount in the metabolism of homocysteine. Studies show that mildly elevated plasm total homosysteine is a risk factor for cardiovascular disease. The MTHFR gene catalyzes the reduction of 5, 10 methylenetetrahydrofolate to 5-methyltetrahydrofolate. Formation of this 5-product by MTHFR provides units for homocysteine conversion to methionine, therefore if a genetic mutation effects this efficiency of this conversion, elevated levels of homocysteine will be present in the blood. Several polymorphisms of this gene can effect the enzyme efficiency of this gene. It was found that an increase in folate intake by people with these genetic defects will decrease the chance for cardiovascular-related diseases.
The CETP gene is involved in lipid metabolism. This hydrophobic glycoprotein, which is secreted by the liver, decreases the cardioprotective HDL fraction and increases the pro-atherogenic VLDL and LDL fractions in plasma. It is therefore detrimental to increase the activity of this gene beyond normal levels, in regards to cardiovascular health. Several genetic variants, such as the Taq1B variant, cause a reduction in CETP mass and activity. People without out beneficial genetic variants of this gene would benefit from a diet that counters elevated levels of active CETP in the body. Specific dietary advice was not given in this case.
The LPL gene is also involved in lipid metabolism. Specifically, this glycoprotein is involved in the hydrolysis of the triglyceride core of circulating chylomicrons and VLDL. A more active LDL gene is correlated to lower levels of blood triglycerides, which makes it an atheroprotective enzyme. People with the 44Ser-Ter(X) SNP have a decreased risk of cardiovascular disease. The identification of any other genetic variant besides this one in a subject, therefore, is a sign for nutrigenetic companies that this person may need additional nutritional considerations. In order to increase LPL expression in individuals who do not carry favorable genetic variants, fish oil has proven to be beneficial in ramping up this genes efficiency. Mulberry, banaba, and korean ginseng have also been shown to increase expression of the LPL gene.
The Apo C-III gene is involved in regulating triglyceride metabolism by affecting lipolysis and receptor-mediated uptake of triglyceride-rich lipoproteins. Any genetic variant that increases the efficiency of this gene can cause an abnormal amount triglycerides to remain in circulation. This is a definite risk-factor for cardiovascular disease. The most recognized variant of this gene is the SstI variant, which is associated with a 38% increase in blood triglyceride levels. It was found that a diet high in monounsaturated fats is a good way to reduce plasma LDL-C, which is a product of over-expression of the Apo C-III gene. Omega-3 fatty acids (fish oil) were also found to decrease the efficiency of the Apo C-III gene in SstI variants.
Interleukin 6 genes are important in immune and inflammatory responses in the body, as well as the up-regulation in synthesis of C-reactive proteins. A functional polymorphism as position -174G to C has been associated with an altered expression of the IL-6 gene. Increased levels of IL-6 has been linked to cardiovascular disease, namely, atherosclerosis. Diets that focus on weight reduction have been shown to negate the effects of unfavorable genetic variants of the IL-6 gene. Also, fish oil, alpha-linolenic acid, and vitamin E supplementation have been shown to reduce inflammation. This is especially important for people with genetic variants that increase IL-6 because it increases bodily inflammation.
This is a great paper underlining some of the basic genes that a nutritional genetics company looks for in patients who are concerned about heart health. Specific genetic variants at each gene locus have been found to increase or decrease the risk for attaining any number of cardiovascular diseases. Fish oil seems to be the number one nutritional addition that people with increased risk factors can supplement into their diet, in order to avoid future cardiovascular problems. Its range of benefits span from decreasing the expression of unfavorable genetic variants to decreasing inflammation. As the study of the human genome continues it will be interesting to see how genetic engineering will factor into the mix. If scientists have already found out which genetic variants can increase or decrease health, genetically engineering humans to have favorable genetic variants to constitute their genome will prove to be beneficial to increasing the health of the human population as a whole. Additionally, customizing nutrition based on someone’s personal genotype will prove to be very beneficial.
-Vakili, BS. “Personalized Nutrition: Nutritional Genomics as a Potential Tool for Targeted Medical Nutrition Therapy.” Nutrition Reviews v. 65. July 2007: pg 301-315.