Chrom jako biogenní prvek

Chromium as an Essential Element

Chromium was known for many years to be an element causing allergic reactions and having neurotoxic andcarcinogenic effects. These effects can be observed especially in the case of hexavalent chromium. Only a little morethan four decades ago trivalent chromium has been known as an essential element with relation to glycide and lipidmetabolism. And only during several last years this chromium function has been revealed on a molecular level. Afterabsorption in the gastrointestinal tract, chromium is most likely transported to cells bound to the plasma proteintransferrin. Insulin initiates chromium transport into the cells where it is bound to the oligopeptide apochromodulin.This oligopeptide combined with four chromium(III) atoms forms chromodulin, which is important for amplifyingthe insulin signalling effect.After binding to insulin-activated receptor, chromodulin increases tyrosine kinase activityby one order. This enzyme forms a part of intracellular portion of insulin receptor. Chromium supplementation inpeople with chromium deficiency can improve glucose tolerance and some lipid metabolism parameters. Thesupplementation is indicated in persons with impaired glucose tolerance both in praeclinical and manifested stadiumof type 2 diabetes mellitus where increased lost of chromium in urine was documented. In these patients, chromiumdeficiency can participate in insulin resistance and hyperlipidaemia. Chromium is usually applied in the form oforganic compounds: yeast extract or chromium(III) picolinate. Cr(III) picolinate can be reduced to compounds ofCr(II) in the cells which can then produce free hydroxyl radical in the so called Fenton reaction.

Key words:
chromium, chromodulin, diabetes mellitus, insulin, insulin resistance.