Recent advances in the biochemistry of chromium(III)

The biochemistry of chromium(III) [Cr(III)] has been a poorly understood field of endeavor; studies of the biochemistry of none of the other transition metals have been as problematic. Despite four decades of investigation, only recently has a clear picture of the role of Cr potentially been defined. The biologically important form is the trivalent ion. Cr(III) apparently is required for proper carbohydrate and lipid metabolism in mammals, although Cr deficiency is difficult to achieve. Conditions that increase circulating glucose and insulin concentrations increase urinary chromium output. Chromium is excreted after an insulin challenge, probably in the form of the oligopeptide chromodulin. Chromodulin may be the key to understanding the role of chromium at a molecular level as the molecule has been found to bind to activated insulin receptor, stimulating its kinase activity. A mechanism for the action of chromodulin has recently been proposed; this mechanism can serve as a potential framework for further studies to test the role of chromium in metabolism. An examination of the use of chromium picolinate, [Cr(pic)(3)], illustrates the difficulties associated with biochemical studies dealing with Cr(III).