[Chromium as an essential element]

Abstract

Chromium was known for many years to be an element causing allergic reactions and having neurotoxic and carcinogenic effects. These effects can be observed especially in the case of hexavalent chromium. Only a little more than four decades ago trivalent chromium has been known as an essential element with relation to glycide and lipid metabolism. And only during several last years this chromium function has been revealed on a molecular level. After absorption in the gastrointestinal tract, chromium is most likely transported to cells bound to the plasma protein transferrin. 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 amplifying the insulin signalling effect. After binding to insulin-activated receptor, chromodulin increases tyrosine kinase activity by one order. This enzyme forms a part of intracellular portion of insulin receptor. Chromium supplementation in people with chromium deficiency can improve glucose tolerance and some lipid metabolism parameters. The supplementation is indicated in persons with impaired glucose tolerance both in preclinical and manifested stadium of type 2 diabetes mellitus where increased lost of chromium in urine was documented. In these patients, chromium deficiency can participate in insulin resistance and hyperlipidaemia. Chromium is usually applied in the form of organic compounds: yeast extract or chromium(III) picolinate. Cr(III) picolinate can be reduced to compounds of Cr(II) in the cells which can then produce free hydroxyl radical in the so called Fenton reaction.