Significance and Functions of Silicon in Warm-Blooded Animals. Review and Outlook

Summary

Some earlier research and the developments which led to the discovery of the essentiality of silicon for warm blooded animals are reviewed, and pitfalls in the methodology of silicon determination in biological material are described with special reference to germanium as an interfering factor in the ammonium molybdate reaction. Previous work from our laboratory on the occurrence of bound silicon in connective tissue components such as glycosaminoglycans is reviewed. It was based partially on results obtained with materials which were contaminated by silica or polysilicic acid. The total amount of silicon in ground matrix and connective tissue is smaller than assumed earlier. Thus, the hypothesis that silicon acts as a cross-linking agent in the ground matrix may have to be modified. Silicic acid derivatives may function in this fashion in special organelles such as base membranes, micro-tubules, etc. In the formation of organic silic acid derivatives, i.e., silanolates or silicic acid esters, not only the hydroxyl groups of carbohydrate derivatives, but also the hydroxyamino acids or other hydroxyl groups may serve as potential carriers of the silicic acid residue. In such structures, donation of electrons by amino N, leading to penta- or hexa-coordinated derivatives may have a stabilizing effect.

A number of model compounds based primarily on bifunctional alcohols such as substituted propanediol or butanediol have been prepared. The trimethoxy and triethoxy silanes containing a silicic acid moiety at each hydroxyl group, and also the corresponding cyclic derivatives containing only one silicic acid moiety connecting both alcoholic hydroxyl groups were obtained. Some of these showed enhanced biological activity when compared to sodium metasilicate in the growth assay on rats maintained in silicon-free environmental systems. An enzyme, silicase, was discovered in pancreas, stomach and also kidney which liberates silicic acid from a synthetic substrate, trimethoxy dodecanoxy silane. The enzyme has been prepared in concentrated form and some of its properties are described. It normally occurs in membrane bound form in mitochondria and microsomes. It can be liberated by non-ionic detergents, is inactivated by removal of lipid and reactivated by treatment with appropriate triglycerides. As an example of the possible involvement of silicon in disease mechanisms, data are presented on the silicon contents of dietary fiber, and also of water samples from various areas of Finland, which support the concept that lack of silicon may be an etiological factor in atherosclerosis.

“Effects of silicic acid are destined to play a great and major role in therapy.” Louis Pasteur June 13, 1878