Diseases Associated with Selenium Deficiency

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Dietary deficiency in selenium has been associated with a wide range of conditions, from the development of cardiomyopathy involved in Keshan disease to mood disorders and Parkinson's disease.25 28 Considering the role of selenium in anti-oxidant enzymes such as GPx, it is not surprising that selenium deficiency is implicated in conditions associated with oxidative stress, such as atherosclerosis.23,26,27,29 Selenium dietary supplements, sodium selenite and selenium-enriched yeast are available to counter potential deficiency and a number of excellent reviews address the consequences of inadequate selenium intake.26,27,30 Whilst both sodium selenite and selenomethionine (SeMet) (present in Se-rich yeast) are available for biosynthesis of selenoproteins, SeMet is advocated by some as a preferred source of selenium as it is the form commonly found in food and is less toxic than sodium selenite.26,31 Excess SeMet can be stored in non-specific body proteins in place of methionine; thus SeMet appears to increase selenium levels more efficiently than sodium selenite (Figure 17.1). However, selenium from SeMet is less bioavailable and SeMet stored in proteins must undergo a longer metabolic pathway to generate H2Se for use in selenoprotein synthesis than sodium selenite.26,31

17.2.1 Asthma

A symptom of asthma is lung inflammation, which has been associated with the generation of hydrogen peroxide as a by-product of increased metabolic activ-ity.32 Hydrogen peroxide activates a nuclear transcription factor for inflammatory cytokines, NF-kB.32,33 GPx appears to have a role in the regulation of NF-kB activity. Comparison of selenium-deficient and selenium-supplemented cells showed upregulation and inhibition of NF-kB, respectively. Whether these results are purely due to removal of hydrogen peroxide by GPx remains unclear.17 Studies have found evidence of a relationship between dietary selenium intake and asthma, and subjects supplemented with dietary sodium selenite showed decrease in asthma symptoms.26 Recent research by Kim and co-workers established that GPx levels increased and the activity of NF-kB was reduced in allergen-sensitized mice treated with sodium selenite. Additionally, selenium-pretreated mice were less affected by exposure to the allergen.32

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Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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