Insulin chromium complexes

Chromium. Chromium Ill) polentiales the action of insulin and may be considered a col actor for insulin. Chromium is thought to form a complex with insulin and insulin receptors. 

In humans and animals, chromium(III) is an essential nutrient that plays a role in glucose, fat, and protein metabolism by potentiating action of insulin. Chromium picolinate, a trivalent form of chromium complexed with picolinic acid, is used as a dietary supplement, because it is claimed to speed metabolism... 

Metabolic Functions. Chromium (ITT) potentiates the action of insulin and may be considered a cofactor for insulin (137,138). In in vitro tests of epididymal fat tissue of chromium-deficient rats, Cr(III) increases the uptake of glucose only in the presence of insulin (137). The interaction of Cr(III) and insulin also is demonstrated by experimental results indicating an effect of Cr(III) in translocation of sugars into ceUs at the first step of sugar metaboHsm. Chromium is thought to form a complex with insulin and insulin receptors (136). 

Chromium was recognized as an essential trace element in 1955.1190 Rats fed a chromium-deficient diet developed an impaired tolerance for intravenous glucose, which could be reversed by an insulin-potentiating factor present in brewer s yeast, meat and various other foods. The insulin-potentiating factor was found to be a complex of chromium(IH)1191 and such substances have been termed Glucose Tolerance Factor(s) (GTFs). Chromium was demonstrated to be essential for humans in 1975.1192 There are several reviews of the chemistry of chromium(III) and its relationship to glucose tolerance.1193-1196... 

It has been proposed that GTF is related to a dinicotinatotris(amino acid)chromium(III) complex, which forms a ternary complex at the membrane receptor with insulin. Porcine insulin binds a Cr(nic)2(glutathione) complex very tightly. 

Chromium(III) is an essential nutrient required for normal energy metabolism. The National Research Council (NRC) recommends a dietary intake of 50-200 ig/day (NRC 1989). The biologically active form of an organic chromium(ni) complex, often referred to as GTF, is believed to function by facilitating the interaction of insulin with its cellular receptor sites. The exact mechanism of this interaction is not known (Anderson 1981 Evans 1989). Studies have shown that chromium supplementation in deficient and marginally deficient subjects can result in improved glucose, protein, and lipid metabolism. 

GTE), which acts as a cofactor of insuhn in all insulin-dependent systems. Food intake is the main Cr source for humans l,l,l-Trifluoro-2,4-pentadione (tfacH) is one of the most commonly used chelating agents for the GC measurement of chromium, due to its quantitative reaction with the analyte, its volatility and thermal stability and its relative inertness towards undesirable on-column reactions. Furthermore, the exceptional sensitivity of ECD to the fluorinated complex and the ease of synthesis for calibration purposes, all these have made of tfacFI the most commonly used chelating agent for several decades . ... 

The biochemical mechanism that allows chromium to potentiate the actions of insulin receptors on cell membranes has been intensively investigated. It is now suggested that a low molecular weight intracellular octapeptide (LMWCr), also known as chromodulin, binds Cr and enhances the response of insulm receptors. Chromodufin binds four Cr ions and then locates on cell membranes near to the site of insulin receptors. The structure of chromodulin has been examined by a variety of advanced spectroscopic techniques and the complex shown to possess a unique type of multmuclear assembly, with the chromium centers having an octahedral coordination with oxygen-based ligands. ... 

Hexavalent chromium has no known essential function. However, trivalent chromium in the form of a dinicotinic acid-glutathione complex is an essential cofactor for insulin production and forms complexes with protein, amino acids, and other organic acids. 

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