Keshan’s Disease

Selenium is an essential element for humans and is a constituent of selenoamino acids contained in selenoenzymes, such as glutathione peroxidases. This group of enzymes catalyzes the reduction of peroxides and thereby takes part in the anti-oxidative defense of the body. A severely low Se intake may cause heart disease (Keshan s disease). Therefore, possible adverse health effects are associated with a low intake of this element and justify the focus on the low percentile Se intake in the population. The food groups that contribute the most to the Se intake are meat (including offal) followed by bread and cereals, and fish, as shown in Figure 9.8. 

Most extreme values come from areas of human Se deficiency, such as the Keshan s disease region in China (7 p.g/day) and the chronic selenosis area in China (4900 p.g/day). Less extreme values of low dietary Se intakes (28-30 p.g/day) have been observed in Finland and New Zealand, while intakes in the United States often tend to fall within the range 50-200 p,g/day. 

Coxsackie virus strain B3, when introduced into Se-deficient mice, produces a myocarditis that is similar to that of human Keshan s disease, and this virus consistently undergoes mutation at six distinct amino acid (= nucleotide) sites in the Se-deficient but not the control animals. These mutated viruses are then able to produce myocarditis even in selenium-replete control mice. Thus, the virulence change has become permanent by mutation, and the increased virulence is no longer dependent on a simultaneous lack of selenium. Comparable selenium Hmitation-induced mutations in influenza virus have also been shown in Se-deficient mice. It is suggested that in the presence of a low selenium supply, a normally quiescent virus may become activated by increased oxidative stress and host cell apoptosis, the mutation to increased virulence being a survival strategy by the virus. 

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Se has a greatly uneven distribution in the world. For example, there are Se-deficient places with the Keshan disease due to scant Se intake in Keshan (China) while by contrast, in other places of China, the levels of Se concentration are toxic to humans and animals. The Se accumulation and distribution in plants hence varies among species, and as a function of chemical forms and concentrations of Se supplied. In general, with an elemental abundance of 0.08 J,g g in the Earth s crust and 13 4g g in the Earth s interior, the existence and speciation of Se in nature is so dispersive that it commonly does not reach a threshold abundance warranting industrial... 

Selenium has been recognized as an essential trace element in the diets of man and animals for many years (1) Another strong indication of its essentiality is the fact that it is an essential component of the enzyme glutathione peroxidase (2) Recently, scientists from the People s Republic of China demonstrated that Keshan disease (a cardiomyopathy in children) was correlated with low dietary selenium Intakes ( ) and could largely be prevented with supplementation Similarly, poor selenium nutrition in patients receiving total parenteral nutrition has been linked to muscular discomfort (4) and cardiomyopathy ( ) ... 

Johnson C. C., Ge X., Green K. A., andEiuX. (2000) Selenium distribution in the local environment of selected villages of the Keshan Disease belt, Zhangjiakou District, Hebei Province, People s Republic of China. Appl. Geochem. 15, 385-401. 

RNA genome codes for four proteins. Three of these proteins are virus capsule proteins (they coat the RNA), and one of these proteins is a viral protease. The virus can cause temporary fever and sore throats in children however, about 5% of infections in adults and children result in damage to the heart, It is thought that Keshan disease In China, which is associated with selenium-deficient populations, is due to some influence of the selenium deficiency on the activation of coxsackievirus Studies with nrtice have revealed an interesting phenomenon. One particular strain of coxsackievirus can infect mice, but does not result in much hann to the mice. However, when the mice arc raised on an Sc-deficient diet, the virus acquires mutations in its genome and produces damage to the mouse s heart (Beck t ai., 1995). 

Chen X-S (1987) Studies on Selenium and Keshan Disease in China. 2nd Nordic Symposium on Trace Elements in Human Health and Disease, Odense. Abstract Mini-Symposium No. 11 and Proceedings, pp. 72-73. Environ Health 20, WHO Regional Office for Europe, Copenhagen. 

Chen X-S, Yang G, Chen J, et al. (1980) Studies on the relations of selenium and Keshan disease. Biol Trace Elem Res 2 91-107. 

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