The IGF1 gene influences circulating levels of the IGF1 hormone which is necessary for muscle growth and development. Variants have been associated with benefits for strength performance. We test for two variations of the IGF1 gene (IGF1 and IGF1_2), which code for the same protein, but have a slightly different effect on the protein’s function, and ultimately on the physical trait of performance. Your FitnessGenes result will identify how your circulating IGF1 levels are affected and how this impacts on these traits.
Global population distribution:
Source: 1000 Genome Project. Global averages for both sexes
More about IGF1
THE IGF1 GENE
This gene codes for the hormone insulin-like growth factor 1 (IGF1). We test for two variations of the IGF1 gene (IGF1 and IGF1-2), which code for the same protein, but have a slightly different effect on the protein’s function, and ultimately on the physical trait of performance. The expression of this hormone regulates the release of growth hormone which is involved in cell growth, proliferation, differentiation, cell survival, and the regulation of glucose, fat and protein metabolism. One of the key roles of IGF1 is stimulating the production of nitric oxide (NO) – a vasodilator (widening of the blood vessels). This aids the delivery of nutrients and transport of waste products such as metabolites and carbon dioxide, which will facilitate the other functions of IGF1. Although produced in a number of tissues, IGF1 is most abundantly found within the blood stream where is it bound to IGF binding protein (IGFBP). When bound to IGFBP, IGF1 is broken down at a slower rate which prolongs the impact of this hormone. With age, there is a decline in IGF1 expression. This has been implicated as a mechanism behind the loss of muscle mass and the onset of sarcopenia (loss of skeletal muscle and strength with ageing) in older, sedentary adults.
Since IGF1 has multiple roles in many processes and tissues, elucidating the influence of the polymorphisms of the IGF1 gene have been an important topic in science. For example, IGF1 was found to be associated with cardiovascular risk, because of its stimulation of NO. Within skeletal muscle, IGF1 was found to trigger hypertrophic signalling and the switch to glycolytic metabolism. Different genetic variants of the IGF1 gene may influence strength gains and responses to resistance training. Genetic variants have also been associated with fasting blood glucose levels. Finally, studies also showed that administration of external IGF1 improves insulin sensitivity in type 2 diabetics.
Nutrition can also influence circulating levels of IGF1. This demonstrates the importance of lifestyle factors, in addition to genetic influences. Caloric restriction seems to lower hepatic IGF1 expression, while a high protein diet can increase levels of IGF1. Thus, a high-protein diet may be good for those with lower circulating IGF1 levels, provided that genetic variances and other health markers are taken into consideration.