Antioxidant capacity

The body's antioxidant defense system, especially the enzymes glutathione peroxidase and catalase, are responsible for keeping the levels of reactive oxygen species (ROS) low to avoid a physiological state of oxidative stress.

Reactive oxygen species (ROS) are by-products of normal cellular activity. They are produced in many cellular compartments and play an important role in signaling pathways.

However, overproduction of ROS disrupts the body's antioxidant defense system and can lead to oxidative stress. This situation is associated with the development of several human diseases (such as cancer, cardiovascular, neurodegenerative and metabolic disorders), inflammation and aging.

Antioxidant mechanisms protect cells against ROS-induced oxidative damage. The body's antioxidant defense system has been reported to consist of SOD (manganese superoxide dismutase), CAT (catalase), GST (glutathione S-transferase) and GSH (glutathione) activity. SOD catalyzes the breakdown of endogenous cytotoxic superoxide radicals into H2O2, which is degraded by CAT. Therefore, they play a crucial role in the maintenance of physiological O2 and H2O2 levels. On the other hand, GSH, together with GST, has a basic role in cellular defense against deleterious free radicals and other oxidative species. GST catalyzes the conjugation of the thiol group of glutathione to electrophilic substrates and thus detoxifies endogenous compounds such as peroxidized lipids.

Its activity and ability to protect cells and tissues from ROS and their harmful products are influenced by polymorphisms in antioxidant genes.

The activity of enzymes responsible for combating oxidative damage from reactive oxygen species (ROSS) can be affected by factors such as diet, drug intake or polymorphisms affecting genes involved in antioxidant function. Several studies have identified some mutations that affect the activity of antioxidant enzymes. These mutations have been identified in genes such as the CAT gene and the GPX1 gene.

The CAT gene codes for the enzyme catalase, which is responsible for the control of the most important endogenous enzymatic antioxidants. It catalyzes the decomposition of 2 molecules of hydrogen peroxide into 1 molecule of oxygen and 2 molecules of water, and is therefore responsible for hydrogen peroxide concentrations.

In turn, the GPX1 gene produces the enzyme glutathione peroxidase, which is a selenium-dependent enzyme. This enzyme is important because it is responsible for protecting red blood cells from hemoglobin by reducing peroxides and lipoperoxides, using glutathione as a substrate. Disruption of GPx-1 activity leads to increased levels of peroxides and lipoperoxides (inducers of oxidative stress). Its affinity for oxygen peroxide is higher than that of the enzyme catalase, making the enzyme glutathione peroxidase the main antioxidant of oxygen peroxides.

Reduced antioxidant enzyme activity can lead to the accumulation of reactive oxygen species and promote the development of diseases such as obesity, encephalopathies, renal failure, diabetes, cervical cancer and prostate cancer.

Number of observed variants

13.5 million variants

Number of variants analyzed in the study

2 variants

Bibliography

Chen J., Cao Q., et al. GPx-1 polymorphism (rs1050450) contributes to tumor susceptibility: evidence from meta-analysis. J Cancer Res Clin Oncol. 2011 Oct;137(10):1553-61.

Bastaki M., Huen K., et al. Genotype-activity relationship for Mn-superoxide dismutase, glutathione peroxidase 1 and catalase in humans. Pharmacogenet Genomics. 2006 Apr;16(4):279-86.

Liu K., Liu X., et al. Two common functional catalase gene polymorphisms (rs1001179 and rs794316) and cancer susceptibility: evidence from 14,942 cancer cases and 43,285 controls. Oncotarget. 2016 Sep 27;7(39):62954-62965.

Minlikeeva A.N., Browne R.W., et al. Single-Nucleotide Polymorphisms and Markers of Oxidative Stress in Healthy Women. PLoS One. 2016 Jun 7;11(6):e0156450.

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