The metabolism of selenium in relation to diabetes and cancer therapies

Selenium is a trace element that supports well over 25 different selenoproteins, which are important for our energy turnover, blood sugar balance, metabolism, cell protection, and a host of other essential functions. A group of scientists from Rutgers University in New Jersey, USA, has just uncovered the mechanisms involved in getting selenium into the “engine room” of the cells, from where it is metabolized into the different selenoproteins. According to the scientists, this new insight into the metabolism of selenium may lead to new therapies that can treat a variety of diseases such as diabetes, metabolic disorders, and cancer.

The new study describes in detail the exact processes through which selenium from the diet or from supplements is first incorporated into the essential amino acid, selenocysteine, and then metabolized into the more than 25 known selenoproteins that have numerous essential functions in the body. By using a special cryo-electron microscope, the scientists were able to visualize the cellular mechanisms in a three-dimensional perspective. That way, they could clearly see the different protein structures and other molecules and even take a closer look at how these structures move and change inside the cell. Their study revealed unique selenium structures and parts of the selenoprotein metabolism that have never been observed before. According to the scientists, their study results are important for understanding the mechanisms with regard to developing new therapies for treating different diseases.

Selenium’s metabolism reflects the many functions of this trace element

The incorporation of selenium takes place deep inside the intricate “engine room” of the cell. The scientists already knew that certain molecules and RNA are involved in this process. It should be added that RNA is a nucleic acid that we have in all cells and which is involved in protein synthesis. But the scientists did not know much about the steps that follow – not until now, anyway.
In their study, they discovered that selenocysteine is bound to a special RNA molecule in the cell and then transported to the ribosome with help from a protein factor. When this happens, selenium can be incorporated into the many different selenoproteins.
Once selenium is embedded in the selenoproteins, the selenoprotein is able to carry out a host of cellular functions that are needed for growth and development and cell defense. Selenoproteins are essential for a number of specific functions, of which some of the most important are:

• Formation of cell membranes
• Formation of nucleotides that are building blocks of cellular DNA
• Utilization of Q10, a compound involved in cellular energy turnover
• Decomposition of fat for the energy turnover
• Activation of the thyroid hormones
• Fertility
• Immune defense
• Support of antioxidants that protect cells against damage caused by free radicals and oxidative stress

Selenium deficiency can cause a variety of diseases

The scientists behind the new study say that lack of selenium may cause a variety of diseases because the cells are unable to carry out their functions or to defend themselves against damage, including damage to their DNA. They mention diseases like cancer, cardiovascular disease, impaired fertility, diabetes, and thyroid disorders. By understanding the exact mechanisms involved in incorporating selenocysteine into the cells and metabolizing it into the different selenoproteins, they now have a fundamental understanding of something that can help them develop new therapies for many different diseases.
The study is published in the journal Science.

Widespread selenium deficiency and ways to compensate for it

The farmland in large parts of Europe contains very little selenium, and the selenium content in crops is therefore correspondingly low. In Denmark, the recommended daily selenium intake is 55 micrograms. However, studies show that we need around 100-150 micrograms of selenium per day in order to effectively saturate selenoprotein P that is used as a marker to gauge the body’s selenium status. In many studies of patients with cancer and thyroid disorders, selenium has been administered in doses of 200 micrograms per day.

• If the body lacks selenium, the different selenoproteins fail to function properly
• Selenium deficiency can therefore explain many types of diseases

References:

Tarek Hilal et al. Structure of the mammalian ribosome as it decodes the selenocysteine UGA codon. Science, 2022; 376 (6599): 1338 DOI: 10.1126/science.abg3875

Rutgers University. "Vital cell machinery behind the human body's incorporation of selenium observed." ScienceDaily, 20 June 2022.

Ola Brodin et al. Selenoprotein P as Biomarker of Selenium Status in Clinical Trials with Therapeutic Dosages of Selenit. Nutrients 2020 Apr 12.