Jason Lui, HK BioTek Intern Nutritionist
After the completion of Human Genome Project (HGP), scientists started thinking how to do with the genes discovered. Later, they coined a new term for their studies, nutrigenomics. This field of study focuses on the relationship between nutrition and genetics. Hot research areas include gene expression and genetic variation in response to diet.
Gene expression is the process by which a gene is used to make protein. This process is regulated by some transcription factors (TF) which control the rate of protein synthesis. Some nutrients can turn on or off one or more specific genes because they can act as an accelerator or a decelerator on transcription factors. The gene is said to be turning on when the protein is being made at a very high rate. It is said to be turning off when only very little or no protein is being made. Have you ever met an identical twin which looks unlike? It is because they have different diets, thus turning on and off different genes.
Nutrigenomics allows us to turn on or off our genes by ourselves. Soybean contains a lot of genistein which belongs to the category of isoflavones. Genistein is proven to be capable to turn on p16 and p21 tumor suppressor genes so as to inhibit the cancer progression in vitro. p16 and p21 can drastically decelerate cell division cycle. Therefore, cancer cells can no longer keep dividing uncontrollably.
Genetic Variation in response to Diet
Genetic variation exists among individuals. Macroscopically, it causes us to look different. Microscopically, it allows us to make proteins with different sequences. For example, the majority of population can make functional protein A1 with sequence CDEFGHI which catalyzes the reaction form compound B to C. Some individuals may make protein A2 with sequence CDELGHI. In this case, if protein A2 is not as efficient as protein A1, more attention should be paid to the diet because the normal way of nutrient metabolism has been changed.
Phenylketonuria (PKU) is an inherited disorder in which phenylalanine (Phe) cannot be metabolized into tyrosine (Tyr). Phe and Tyr are amino acids which constitute protein molecules. PKU patient does not have phenylalanine hydroxylase (PAH), a protein which catalyzes Phe into Tyr. PKU may lead to mental retardation, seizures, stunted growth and so on. Nutrigenomics allows early diagnosis of PKU in infants and thus planning of low-Phe diet so as to prevent damages when they grow up.