DNA is the hereditary material, which is identical in all cells of our body. A gene is a DNA fragment or a ‘building block’ that acts as instructions to make proteins. Human genome contains approximately 20,000 to 25,000 genes. Genes contain information about where and when to produce necessary proteins and they also determine the protein composition, which lays ground to difference in protein structure and function and thus entire functionality of the body.
DNA consists of nucleotides (A, T, C, and G) and DNA fragments of two different individuals may contain a difference in a single nucleotide, e.g. GCCTGA and GCTTGA, respectively. Such differences arise from SNPs (pronounced snips) or single nucleotide polymorphisms or variations in DNA sequence. SNPs occur on average once in every 1000 nucleotides and their differences are responsible for genetic uniqueness of every individual (except for identical twins who share the same genotype). Thus, SNPs account for approximately 90% of the genetic differences between individuals (Brookes, 1999). Each human cell has two copies of chromosomes and thus we receive from our parents either two different or two identical copies of each SNP.
SNPs do not generally cause diseases, but they may help to determine the probability of developing an illness. Such DNA sequence variations may also determine individual response to pathogens, chemicals, drugs, vaccines, and also to various nutrients (e.g. whether weight gain is more likely in case of excessive consumption of carbohydrates), and the amount of physical exercise required to maintain normal weight or to become a successful athlete.
|Genes analysed in the genetic test for weight management:|| Genes
analysed in the genetic test of athletic abilities: |
The genetic test for weight management analyses eight SNP-s in seven genes
FTO gene has shown the strongest association with the occurrence of overweight and obesity (Scuteri, Sanna et al. 2007; Speliotes, Willer et al. 2010). FTO also participates in regulation of appetite and satiety. People with risk alleles in FTO gene are at 70% higher risk of becoming overweight in comparison to those without risk alleles. Occurrence of one risk allele increases the risk of becoming overweight by 30%.
MC4R gene and FTO gene regulate the mechanism behind hunger and satiety. MC4R collects the hunger and satiety signals and instructs the body to either eat or stop eating (Fani, Bak et al. 2013). Satiety does not occur easily in individuals with risk alleles in MC4R gene and thus, they may overeat and constantly snack between meals. This may lead to overweight and obesity (Lubrano- Berthelier, Cavazos et al. 2003; Speliotes, Willer et al. 2010).
TMEM18 gene has also strong association with gaining excess weight (Thorleifsson, Walters et al. 2009; Willer, Speliotes etal. 2009; Speliotes, Willer et al. 2010). Persons with TMEM18 risk alleles have significantly elevated risk of developing type 2 diabetes, which manifests if they are/become overweight (Kalnina, Zaharenko et al. 2013).
FABP2 gene takes part in intracellular fatty acid transportation
to adipocytes and regulates fat uptake in epithelial cells of the small
intestine (Baier, Sacchettini et
al. 1995). Studies have shown that the
presence of risk allele is incidental to increased binding of fatty acids and
is therefore associated with both increased body mass index, body fat percentage,
visceral fat, and excess weight (Baier, Sacchettini et
PPARG gene plays an important role in adipogenesis (Lowell 1999), lipid metabolism and
breaking down fatty acids. Individuals with risk alleles in PPARG gene are more
susceptible to fatty food, they find it harder to lose weight and thus, they
are at higher risk of gaining excess weight. When consuming fatty food, PPARG
stores fat and makes small adipocytes to grow in size (Kubota, Terauchi et al.
ADRB2 and ADRB3 genes have important role in regulating energy balance, contributing to lipolysis and generation of body heat. Our test analyses two different SNPs in ADRB2 gene. Occurrence of risk alleles in ADRB2 (I) reduces lipolysis (Macho-Azcarate, Marti et al. 2003) and increases BMI, body fat, adipocyte size, and waist-to-hip ratio (Large, Hellstrom et al. 1997).
In people with risk allele in ADRB2 (II) gene, the fat burning is not as efficient as in people without relevant risk allele. Additionally, individuals with risk allele have increased risk of obesity in case of high-carb diet, which arises from elevated insulin release and changes in breaking down carbs and fats. Decomposition of carbohydrates increases, while decomposition of fatty acids reduces significantly and they are stored as body fat (Martinez et al. 2003).
ADRB3 is located on the surface of abdominal cavity and brown fat cells, stimulating lipolysis and thermogenesis by releasing noradrenaline when subject to low temperature, eating, and exercise (Tappy 1996). The impact of ADRB3 gene on obesity depends on the level of physical activity. The presence of risk alleles in ADRB3 causes reduced lipolysis in fat cells (Umekawa, Yoshida et al. 1999). Thus, the occurrence of ADRB3 risk alleles may lead to obesity due to reduced energy consumption in adipose tissue. Individuals with risk alleles have increased BMI in case of sedentary lifestyle. To reduce the risk of excess weight, people with risk alleles are recommended to be physically active for more than 10 active hours a week. People with A allele lose weight more easily and even lower physical activity is enough to lower the risk of overweight.
The genetic test of athletic abilities analyses six SNPs in six genes
ACE gene is involved in producing physiologically active angiotensin II. Angiotensin II regulates both constriction of blood vessels and water-salt balance. ACE also regulates erythropoiesis (production of red blood cells), is responsible for supplying tissues with oxygen, and adjusts the efficiency of skeletal muscles (Montgomery, Clarkson et al. 1999; Zhang, Budker et al. 2001; Jones, Montgomery et al. 2002).
Actin proteins represent main components in superstructure that causes contraction inside the muscle fibres (MacArthur and North 2004; Vincent, De Bock et al. 2007). ACTN3 gene encodes α-actinin-3 protein found in fast-twitch muscle fibres and it generates the force necessary for successful power athletes (Yang, MacArthur et al. 2003).
AMPD1 gene regulates muscle metabolism and energy supply during exercise (Gross, Rotzer etal. 2002).
IGF1 is expressed locally in many tissues including muscle cells and is a major regulator of muscle mass during development, due to its effect on myogenic cell proliferation and differentiation (Schiaffino and Mammucari 2011).
T allele in NOS3 gene indicates predisposition towards
achieving better results in power sports (Gómez-Gallego et al.
2009). Nitric oxide is a gas
produced in the body, required for “communication” between the cells, relaxation
of blood vessels, and supplying muscles and skin with blood. Nitric oxide has
an important role in healing and regeneration of the myocardial tissue (Otani 2009). Regular exercise increases
NO production, thus also improving the performance capacity. Regulation of
blood supply is particularly important for athletes engaged in high-endurance
sports, because training a muscle requires additional oxygen.
Hypersensitivity or intolerance against certain foods continues to be controversial topic. What is the mechanism behind it, whether and how to determine it, how to proceed after receiving test results?
Have you felt more forgetful and less focused after a sleepless night? Have you noticed that some of your friends are active already early in the morning, while others would sleep till noon and prefer to work late at night? These are but a few examples of the effect sleep may have on us, our productivity and even our health.
Sports Gene helped junior swimmer Kregor Zirk to determine his athletic predisposition and food intolerance. On 11 May, daily newspaper Postimees published an article that discusses in detail the expectations of Kregor and his coach Kaja Haljaste regarding the genetic test and practical use of the results in planning Kregor’s future career.