Chromium and genomic stability.

Many metals serve as micronutrients which protect against genomic instability. Chromium is most abundant in its trivalent and hexavalent forms. Trivalent chromium has historically been considered an essential element, though recent data indicate that while it can have pharmacological effects and value, it is not essential. There is no data indicating that trivalent chromium promotes genomic stability and, instead may promote genomic instability. Hexavalent chromium is widely accepted as highly toxic and carcinogenic with no nutritional value. Recent data indicate that it causes genomic instability and also has no role in promoting genomic stability.

Combination of Soy Protein, Amylopectin, and Chromium Stimulates Muscle Protein Synthesis by Regulation of Ubiquitin-Proteasome Proteolysis Pathway after Exercise.

The present study was undertaken to investigate the effect of the combination of soy protein, amylopectin, and chromium (SAC) on muscle protein synthesis and signal transduction pathways involved in protein synthesis (mTOR pathways, IGF-1, and AktSer473) and proteolysis (FOXO1Ser256; MURF1, MAFbx) after exercise. Thirty-five Wistar rats were randomly divided into five groups: (1) control (C); (2) exercise (E); (3) exercise + soy protein (3.1 g/kg/day) (E + S); (4) exercise + soy protein + chromium (E + S + Cr); (5) exercise + soy protein + amylopectin + chromium (E + S + A + Cr). Post-exercise ingestion of SAC significantly increased the fractional rate of protein synthesis (FSR), insulin, glycogen, and amino acid levels with the highest effect observed in E + S + A + Cr group (P Ë‚ 0.05). However, SAC supplementation decreased the lactic acid concentration (P Ë‚ 0.05). A reduction in forkhead box protein O1 (FOXO1) and forkhead box protein O3 (FOXO3) (regulators of ubiquitin-related proteolysis) and muscle atrophy F-box (MAFbx) levels was noted after treatment with SAC (P < 0.05). Insulin-like growth factor 1(IGF-1) level was increased in the E + S, E + S + Cr, and E + S + A + Cr groups (P < 0.05). While the phosphorylation of 4E-BP1Thr37/46, AktSer473, mTORSer2448, and S6K1Thr389 levels increased after SAC supplementation, phosphorylated muscle ring finger 1 (MuRF-1, an E3-ubiquitin ligase gene) was found to be significantly lower compared with the E group (P Ë‚ 0.05). These results indicate that SAC supplementation improves FSR, insulin, and glycogen levels after exercise. SAC improves protein synthesis by inhibiting the ubiquitin-proteasome pathway and inducing anabolic metabolism.

Chromium.

Two oxidation states of chromium are considered to be biologically and environmentally relevant based on their stability in the presence of water and oxygen. Compounds containing chromium(6 + ) are mutagenic and carcinogenic when inhaled and potentially when ingested orally in large quantity as well. Chromium as the trivalent will be the focus of this work as it was proposed to be an essential element for mammals ∼60 y ago; however, in the last 2 decades its status has been questioned. Chromium has been postulated to be involved in regulating carbohydrate and lipid (and potentially also protein) metabolism by enhancing insulin's efficacy (1). However, in 2014, the European Food Safety Authority found no convincing evidence that chromium is an essential element (2). Dietary chromium apparently is absorbed via passive diffusion and the extent of absorption is low (∼1%). Chromium is maintained in the bloodstream bound to the protein transferrin. It is generally believed to be delivered to tissues by transferrin via endocytosis (1). No unambiguous animal model of chromium deficiency has been established (2). One limitation in characterizing chromium deficiency in humans is the lack of an accepted biomarker of chromium nutritional status. Attempts to identify a glucose tolerance factor have not provided a chemically defined functional compound that conforms with the proposed physiologic role of chromium as a facilitator of insulin action in vivo.

DNA damage induced by a chromium(III) Schiff base complex is reversible under physiological condition.

[Cr(naphen)(H2O)(2)]+, where naphen is 1,2-bis(naphthylideneamino)ethane having the basic salen moiety, has been characterized structurally. [Cr(naphen)(H2O)(2)]+, which has an extended aromatic system and binds with calf thymus DNA (CT DNA) intercalatively, has been found to promote DNA cleavage in the presence of biological reductant such as ascorbate and oxidant like hydrogen peroxide. Results of electron paramagnetic resonance (EPR) experiments suggest involvement of hydroxyl radicals in the oxidative cleavage of DNA in the presence of the Cr(III) complex and hydrogen peroxide. The cell viability study on nicked DNA by [Cr(naphen)(H2O)(2)]+ has shown that the damage brought about to DNA could be repaired by Escherichia coli DNA repair enzymes.

Chromium deficiency and cardiovascular risk.

Recent measurements have demonstrated that plasma chromium levels in patients with coronary artery disease are very much lower than in normal subjects. A review of the literature concerning the physiological functions of chromium (or GTF) shows it to be implicated in most of the known factors of cardiovascular risk, via its effect on insulin levels and activities. Chromium deficiency leads to impaired lipid and glucide metabolism and results in high circulating insulin levels, the probable consequences of which suggest that chromium deficiency may be a primary risk factor in cardiovascular disease.

Chromium in the prevention and control of diabetes.

Chromium is an essential nutrient involved in the metabolism of glucose, insulin and blood lipids. Suboptimal dietary intake of chromium is associated with increased risk factors associated with diabetes and cardiovascular diseases. Within the past five years, chromium has been shown to improve glucose and related variables in subjects with glucose intolerance and type 1, type 2, gestational and steroid-induced diabetes. Severe neuropathy and glucose intolerance of a patient on total parenteral nutrition, who was receiving currently recommended levels of chromium, were reversed by additional supplemental chromium. Chromium increases insulin binding to cells, insulin receptor number and activates insulin receptor kinase leading to increased insulin sensitivity. Additional studies are urgently needed to elucidate the mechanism of action of chromium and its role in the prevention and control of diabetes.

The potential value and toxicity of chromium picolinate as a nutritional supplement, weight loss agent and muscle development agent.

The element chromium apparently has a role in maintaining proper carbohydrate and lipid metabolism in mammals. As this role probably involves potentiation of insulin signalling, chromium dietary supplementation has been postulated to potentially have effects on body composition, including reducing fat mass and increasing lean body mass. Because the supplement is absorbed better than dietary chromium, most studies have focused on the use of chromium picolinate [Cr(pic)(3)]. Cr(pic)(3) has been amazingly popular with the general public, especially with athletes who may have exercise-induced increased urinary chromium loss; however, its effectiveness in manifesting body composition changes has been an area of intense debate in the last decade. Additionally, claims have appeared that the supplement might give rise to deleterious effects. However, over a decade of human studies with Cr(pic)(3) indicate that the supplement has not demonstrated effects on the body composition of healthy individuals, even when taken in combination with an exercise training programme. Recent cell culture and in vivo rat studies have indicated that Cr(pic)(3) probably generates oxidative damage of DNA and lipids and is mutagenic, although the significance of these results on humans taking the supplement for prolonged periods of time is unknown and should be a focus for future investigations. Given that in vitro studies suggest that other forms of chromium used as nutritional supplements, such as chromium chloride, are unlikely to be susceptible to generating this type of oxidative damage, the use of these compounds, rather than Cr(pic)(3), would appear warranted. Potential neurological effects (both beneficial and deleterious) from Cr(pic)(3) supplementation require further study.

The relationship of chromium to the glucose tolerance factor. II.

After incubation with CrCl3 X 6H2O (or 51CrCl3 X 6H2O) for 25 days, a sterile growth medium, whole yeast cells harvested after growth on a similar chromium-containing medium for the same period, and the spent growth medium remaining after removal of the yeast were each subjected to the separation procedure reported previously [S. J. Haylock. P. D. Buckley and L. F. Blackwell, J. Inorg. Biochem., in press]. The results obtained showed that most of the eleven chromium-containing fractions isolated previously were artifacts formed as a result of direct reaction between the chromium and components of the medium. An anionic complex (which was the major chromium-containing fraction isolated) was identified as a chromium-glucose complex, but one possessing no biological activity. The biologically active chromium-containing fractions (P-3 and P-4) that were only present after yeast had been grown in the medium were further purified, however, during the purification steps, the biological activity was cleanly separated from the chromium material for both P-3 and P-4. Fraction P-4 was subsequently shown to consist of approximately 90% tyramine, but pure tyramine was not active in the yeast bioassay. Although the structure of the glucose tolerance factor-active component in fraction P-3 could not be determined due to the presence of high concentrations of salt that could not be separated on gel filtration columns, the results show that the glucose tolerance factor from brewer's yeast can no longer be regarded as a chromium complex.

A scientific review: the role of chromium in insulin resistance.

Chromium is an essential mineral that appears to have a beneficial role in the regulation of insulin action and its effects on carbohydrate, protein and lipid metabolism. Chromium is an important factor for enhancing insulin activity. Studies show that people with type 2 diabetes have lower blood levels of chromium than those without the disease. Insulin resistance is the common denominator in a cluster of cardiovascular disease risk factors. One out of every five Americans has metabolic syndrome. It affects 40% of people in their 60s and 70s. Insulin resistance, with or without the presence of metabolic syndrome, significantly increases the risk of cardiovascular disease. Insulin resistance is present in two serious health problems in women; polycystic ovarian syndrome (PCOS) and gestational diabetes. Several studies have now demonstrated that chromium supplements enhance the metabolic action of insulin and lower some of the risk factors for cardiovascular disease, particularly in overweight individuals. Chromium picolinate, specifically, has been shown to reduce insulin resistance and to help reduce the risk of cardiovascular disease and type 2 diabetes. Dietary chromium is poorly absorbed. Chromium levels decrease with age. Supplements containing 200-1,000 mcg chromium as chromium picolinate a day have been found to improve blood glucose control. Chromium picolinate is the most efficacious form of chromium supplementation. Numerous animal studies and human clinical trials have demonstrated that chromium picolinate supplements are safe.

Nutritional role of chromium.

Chromium is an essential trace element required for normal carbohydrate metabolism. The biological function of chromium is closely associated with that of insulin and most chromium-stimulated reactions are also insulin dependent. Proper chromium nutrition leads to a decreased requirement for insulin and also an improved blood lipid profile. Most fresh foods and minimally processed foods are good sources of dietary chromium. Inorganic chromium does not potentiate insulin action and must be converted to an organic biologically active form. An organic form of chromium capable of potentiating insulin has been isolated from brewer's yeast and was shown to contain: Cr, nicotinic acid and a combination of amino acids. Synthetic insulin potentiating organic chromium complexes containing chromium, nicotinic acid, glycine, cysteine, and glutamic acid or chromium, nicotinic acid and glutathione have been prepared. These complexes have not been purified to homogeneity since they dissociate during purification. Suitable analytical bioassays are available to measure total chromium and the organic biologically-active forms of chromium, respectively.

Chromium, glucose tolerance, and diabetes.

Chromium functions in maintaining normal glucose tolerance primarily by regulating insulin action. In the presence of optimal amounts of biologically active chromium, much lower amounts of insulin are required. Glucose intolerance, related to insufficient dietary chromium, appears to be widespread. Improved chromium nutrition leads to improved sugar metabolism in hypoglycemics, hyperglycemics, and diabetics.

[Chromium as an essential element]. / Chrom jako biogenní prvek.

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.

[Micronutrients and diabetes, the case of minerals]. / Micronutrientes y diabetes, el caso de los minerales.

Minerals are essential nutrients for the body, are of inorganic nature which gives them the characteristic of being resistant to heat, are involved in a lot of chemical reactions in metabolism, regulating electrolyte balance, in maintaining bone, in the process of blood clotting and the transmission of nerve impulses, particularly its role as enzyme cofactors confers a key role in various physiological processes. Glucose homeostasis involves a fine coordination of events where hormonal control by insulin plays a key role. However, the role of minerals like magnesium, zinc, chromium, iron and selenium in the diabetes is less obvious and in some cases may be controversial. This review shows the knowledge of these five elements and their correlation with diabetes.

Los minerales son nutrientes esenciales para el organismo, de naturaleza inorgánica que les confiere, entre otras características, ser resistentes al calor, participan en diversas reacciones químicas del metabolismo en donde regulan el equilibrio hidroelectrolítico, el mantenimiento óseo, en la trasmisión de los impulsos nerviosos, y durante el proceso de coagulación sanguínea, particularmente por su función como cofactores enzimáticos, tienen un papel clave en varios procesos fisiológicos. La homeostasis de la glucosa involucra una fina coordinación de eventos en donde el control hormonal por la insulina tiene un papel primordial. Sin embargo, la función de los minerales, como el magnesio, el zinc, el cromo, el hierro y el selenio en la diabetes es menos evidente y puede ser, en algún caso, controversial. Esta revisión muestra el conocimiento acerca de estos cinco elementos y su correlación con la diabetes.

[Re-evaluation of the fundamentals of trace elements].

The roles of trace elements have been extensively studied for decades. However, recent advances in both molecular and epidemiological studies on trace elements have provided new information and concepts on the actions of trace elements. Some of our fundamental knowledge on the roles of trace elements based on classical data should be replaced by new concept based on new findings. This series of "Re-evaluation of the Fundamentals of Trace Elements" aims to provide new fundamentals on trace elements by reviewing rapidly advancing knowledge in this study area. The first article is a critical review on the role of chromium in human nutrition.

[Is chromium an essential trace element in human nutrition?].

It has been recognized that chromium is an essential trace element associated with carbohydrate metabolism, and chromium deficiency causes an impaired glucose tolerance. Recently, however, Vincent et al. have reported that chromium is not an essential trace element. In the present report, the author evaluated the nutritional essentiality of chromium by reviewing several previous reports. In almost all previous reports, the chromium concentration in the animal feed used was higher than 0.1 µg/g, and it is difficult to consider that the experimental animals were in a low-chromium state. In addition, the amount of chromium administered to the animals for the improvement of glucose tolerance was at a pharmacological level, and corresponded to a level that far exceeded the human daily chromium intake (20 to 80 µg/day). On the other hand, recent research has clearly shown that feeding with a severely low-chromium diet (0.016 µg/g) does not impair glucose tolerance. The amount of chromium absorbed in humans estimated from chromium intake (20 to 80 µg/day), chromium absorption rate (1%), and urinary chromium excretion (<1 µg/day) is less than 1 µg/day, which is much lower than those of other essential trace elements. In addition, because there is an inconsistency between the chromium concentration in food and chromium intake, chromium intake seems to be dependent on chromium contamination during food processing and cooking. It is concluded that there is a high possibility that chromium is not an essential trace element.