Trace element chromium · Briefly

Chromium was first discovered in 1797 by French chemist Nicolas-Louis Vauquelin.

In 1955, American scientists Mertz and Schwarz studied the pathological model of necrotizing hepatic degeneration in rats caused by dietary deficiency of vitamin E and factor III, and performed glucose load tests on rats with the latent stage of the disease, and found that the rate of excess blood sugar clearance in rats fed the test diet was greatly reduced (2.8% per minute in the experimental group vs. 4.0% in the control group), and this impaired glucose metabolism can be restored by supplementation with factor III.

In 1957, Schwarz and Mertz found that this impaired blood glucose metabolism was not a pathological manifestation of liver necrosis, and confirmed that selenium, the active ingredient in factor III, was the main factor in preventing liver necrosis, and selenium had no direct effect on the recovery of impaired glucose metabolism. Subsequently, they isolated another ingredient in acid-hydrolyzed porcine kidney powder and factor III crude concentrate extracted from Brewer's yeast, which was verified to not only prevent impaired glucose metabolism by oral administration, but also have therapeutic effects, and for the first time named it "glucose tolerance factor" (GTF).

In 1959 Schwarz and Mertz confirmed that trivalent chromium ions are the central active component of GTF. This discovery brought attention to the biological function of chromium.

The study found that chromium in food was mainly absorbed in the anterior segment of the small intestine of animals and transported to different tissues via transferrin. At the effect site, a chromium high-affinity small peptide LMWCr (Low molecular weight chromium-binding substance) with a molecular weight of 1.5 kDa captures 4 chromium ions to form chromium-bound small peptide holoLMWCr (also known as "Chromodulin", "chrommodulin"), and binds to the β subunit of the insulin receptor as an endogenous enhancer to make insulin receptor tyrosine kinase (Insulin). receptor tyrosine kinase (IRTK) increased the active effect on insulin by more than 8 times. Chromium mainly regulates glucose metabolism and lipid metabolism through insulin signaling pathways, and promotes protein deposition. In the subcellular components, chromium is distributed in the nucleus, organelles and cytoplasm, chromium can maintain the structure of biological macromolecules such as nucleic acids, and may also participate in cell life activities such as regulating nuclear protein function and gene expression.

The content of chromium in animal serum is reduced, and physiological manifestations such as weight loss, impaired glucose tolerance, decreased respiratory quotient, anti-insulin phenomenon, decreased anti-stress ability and nervous system damage may occur clinically. Therefore, chromium is considered an essential trace element for humans and animals.

Chromium in soil and water bodies mainly exists in oxidized form, and the absorption coefficient of chromium by plants is small, most of which accumulates in the roots and a small amount in the seed coat. The chromium content in conventional feed raw materials is low, and the absorption and utilization rate of chromium in the diet by animals is also low. Once the chromium in the animal is mobilized, it is not reabsorbed, and various stresses often cause a large amount of chromium mobilization and lead to chromium deficiency. The utilization of inorganic chromium by animals is very limited, and the utilization rate of organic chromium is more than 10 times that of inorganic chromium. Therefore, supplementing organic chromium in the diet can effectively avoid chromium deficiency or insufficient intake in animals.