Stability and absorption of chromium and absorption of chromium histidinate complexes by humans

Increased intake of chromium (Cr) often leads to improvements in glucose, insulin, lipids, and related variables in studies involving humans and experimental and farm animals. However, the results are often variable, depending not only on the selection of subjects but also dietary conditions and the form of supplemental Cr used. Our objective was to find a Cr supplement suitable for humans that was absorbed better than any of those available. Chromium absorption by six adult subjects, three males and three females, was determined based on the amount of Cr excreted in the urine in the initial 2 d following intake of 200 μg of Cr of the various forms of chromium tested. The absorption of the newly synthesized complexes was greatest for those containing histidine. Urinary Cr losses for six control subjects consuming 200 μg of Cr as Cr histidinate increased from basal levels of 256±48 to 3670±338 ng/d compared with 2082±201 ng for Cr picolinate, the currently most popular nutrient supplement, in the 48h following Cr consumption. Chromium histidinate complexes were stable and absorption was similar to the initial values after more than 2 yr. Mixing of some of the complexes with starch, which was postulated to improve Cr absorption, was shown to essentially block Cr absorption within 1 mo. These data demonstrate that urinary Cr losses need to be determined because stability and absorption of the Cr complexes varies widely and could be responsible for the variability in some of the Cr supplementation studies. Chromium ***DIRECT SUPPORT *** A02Q2015 00003 histidinate complexes are absorbed better than any of the Cr complexes currently available and need to be evaluated as Cr nutritional supplements.     

Nutritional supplement chromium picolinate generates chromosomal aberrations and impedes progeny development in Drosophila melanogaster

Chromium picolinate, [Cr(pic)₃], is a popular nutritional supplement found in a variety of consumer products. Despite its popularity, safety concerns over its use have arisen. The supplement has been shown to generate clastogenic damage, mitochondrial damage, oxidative damage, and mutagenic effects in cultured cells and oxidative DNA damage and lipid peroxidation in rats. Recently [Cr(pic)₃] has been demonstrated to generate heritable genetic change and delays in progeny development in Drosophila melanogaster. Based on the damage to chromosomes of cultured cells and of animal models, similar chromosome damage appeared to be a likely source of the mutagenic effects of the supplement in Drosophila. The current three-part study examines the effects of several chromium-containing supplements and their components on hatching and eclosion rates and success of development of first generation progeny of adult Drosophila fed food containing these compounds. It further examines the effects of the compounds on longevity of virgin male and female adults. Finally, the chromosomes in the salivary glands of Drosophila late in the third instar larval stage, which were the progeny of Drosophila whose diets were supplemented with nutritional levels of [Cr(pic)₃], are shown to contain on average over one chromosomal aberration per two identifiable chromosomal arms. No aberrations were observed in chromosomes of progeny of untreated flies. The results suggest that human consumption of the supplement should be a matter of concern and continued investigation to provide insight into the requirements of chromium-containing supplements to give rise to genotoxic effects.     

A newly synthetic chromium complex--chromium(phenylalanine)3 improves insulin responsiveness and reduces whole body glucose tolerance

Low-molecular-weight organic chromium complexes such as chromium picolinate are often used as dietary supplements to improve insulin sensitivity and to correct dyslipidemia. However, toxicity associated with such chromium compounds has compromised their therapeutic value. The aim of this study was to evaluate the impact of a newly synthesized complex of chromium with phenylalanine, Cr(pa)3 on insulin-signaling and glucose tolerance. Cr(pa)3 was synthesized by chelating chromium(III) with D-phenylalanine ligand in aqueous solution. In mouse 3T3-adipocytes, Cr(pa)3 augmented insulin-stimulated glucose-uptake as assessed by a radioactive-glucose uptake assay. At the molecular level, Cr(pa)3 enhanced insulin-stimulated phosphorylation of Akt in a time- and concentration-dependent manner without altering the phosphorylation of insulin receptor. Oral treatment with Cr(pa)3 (150 microg/kg/d, for six weeks) in ob/ob+/+ obese mice significantly alleviated glucose tolerance compared with untreated obese mice. Unlike chromium picolinate, Cr(pa)3 does not cleave DNA under physiological reducing conditions. Collectively, these data suggest that Cr(pa)3 may represent a novel, less-toxic chromium supplement with potential therapeutic value to improve insulin sensitivity and glycemic control in type II diabetes.     

Absorption of the biomimetic chromium cation triaqua-μ3-oxo-μ-hexapropionatotrichromium(III) in rats

The cation [Cr₃O(O₂CCH₂CH₃)₆(H₂O)₃]⁺ has been shown in vitro to mimic to the oligopeptide chromodulin’s ability to stimulate the tyrosine kinase activity of insulin receptor and shown in healthy and type 2 diabetic model rats to increase insulin sensitivity and decrease plasma total and low-density lipoprotein cholesterol and triglycerides concentrations. However, the degree to which the complex is absorbed after gavage administration to rats had not been previously determined. The biomimetic cation at nutritional supplement levels is absorbed with greater than 60% efficiency, and at pharmacological levels, it is absorbed with greater than 40% efficiency, an order of magnitude greater absorption than that of CrCl₃, Cr nicotinate, or Cr picolinate, currently marketed nutritional supplements. The difference in degree of absorption is readily explained by the stability and solubility of the cation.     

Beneficial effects of chromium in people with type 2 diabetes, and urinary chromium response to glucose load as a possible indicator of status

No reliable method for the estimation of chromium (Cr) status is available yet. The aim of this study is to investigate the possibility of using urinary Cr response to glucose load as an indicator of Cr status. Seventy-eight non-insulin-dependent diabetes mellitus patients were divided randomly into two groups and given Cr supplements as brewer’s yeast and CrCl₃ sequentially with placebo in between, in a double-blind, crossover design of four stages, each lasting 8 wk. At the beginning and end of each stage, subjects were weighed, their dietary data and drug dosage recorded, and blood and urine samples collected for analysis of glucose and urinary chromium (fasting and 2 h post-75-g glucose load) and fructosamine. The mean urinary Cr after the glucose load was significantly higher than the fasting mean at zero time (p<0.01). However, only 52 of the patients showed an obvious increase; the others showed a slight decrease or no change. Both supplements caused a significant increase in the means of urinary Cr and a significant decrease in the means of glucose and fructosamine. Only those subjects responding to Cr supplement by improved glucose control showed an increase in post-glucose-load urinary Cr over fasting level, after the supplement but not at zero time. Therefore, it was concluded that urinary Cr response to glucose load could be used as an indicator of Cr status.     

Mass Spectrometric and Spectroscopic Studies of the Nutritional Supplement Chromium(III) Nicotinate

Despite chromium nicotinate’s popular use as a chromium nutritional supplement, the structure and composition of chromium nicotinate have only been poorly described. As solid chromium nicotinate is intractable, being insoluble or unstable in common solvents, studies on the solid have been limited, and studies of the solution from which the “compound” precipitates have additionally provided little additional data. The results of mass spectrometric and spectroscopic investigations designed to further elucidate the structure and composition of chromium nicotinate are described. The results demonstrated that the three common methods for producing “chromium nicotinate” all yield different compounds, all of which are polymers of Cr(III), oxygen-bound nicotinate, hydroxide, and water. Implications for interpreting results of nutritional studies of “chromium nicotinate” are discussed.     

Safety of trivalent chromium complexes: no evidence for DNA damage in human HaCaT keratinocytes

Several studies have demonstrated beneficial effects of supplemental trivalent Cr in subjects with reduced insulin sensitivity with no documented signs of toxicity. However, recent studies have questioned the safety of supplemental trivalent Cr complexes. The objective of this study was to evaluate the cytotoxic and genotoxic potential of the Cr(III) complexes (histidinate, picolinate, and chloride) used as nutrient supplements compared with Cr(VI) dichromate. The cytotoxic and genotoxic effects of the Cr complexes were assessed in human HaCaT keratinocytes. The concentrations of Cr required to decrease cell viability were assessed by determining the ability of a keratinocyte cell line (HaCaT) to reduce tetrazolium dye, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. DNA damage using the Comet assay and the production of 8-hydroxy-2′-deoxyguanosine were also determined with and without hydrogen peroxide-induced stress. The LC50 for human cultured HaCaT keratinocytes was 50 μM for hexavalent sodium dichromate and more than 120-fold higher for Cr chloride (6 mM) and Cr histidinate (10 mM). For Cr picolinate at saturating concentration (120 μM) the LC50 was not attained. High Cr(III) concentrations, 250 μM Cr as Cr chloride and Cr histidinate and 120 μM Cr picolinate (highest amount soluble in the system), not only did not result in oxidative DNA damage but exhibited protective antioxidant effects when cells were exposed to hydrogen peroxide-induced oxidative stress. These data further support the low toxicity of trivalent Cr complexes used in nutrient supplements.     

Kinetic and equilibrium studies on the interaction of reduced flavoprotein D-amino acid oxidase with pyridine carboxylates

The equilibrium constants and the rate constants (binding and dissociation constants) between reduced D-amino acid oxidase and pyridine carboxylates were obtained at various pH values (from pH 6.0 to 8.3). The pH dependence of the constants is consistent with the previous conclusion from a resonance Raman study that pyridine carboxylates in the form of a cation protonated at the N atom can bind to the reduced enzyme, but those in the neutral form cannot bind, showing that the positive charge of cationic pyridine carboxylates interacts with the negative charge of the anionic reduced flavin in the reduced enzyme. The binding rate constants of picolinate and nicotinate in the cationic form for the reduced enzyme were quite similar to each other, but the dissociation rate constant of picolinate is several times smaller than that of nicotinate. Thus, it is concluded that the difference in affinity of picolinate and nicotinate for the reduced enzyme is derived from the difference of the dissociation rate constants.     

Chromium picolinate increases membrane fluidity and rate of insulin internalization.

The effects of chromium chloride, chromium nicotinate, and chromium picolinate on insulin internalization in cultured rat skeletal muscle cells was examined. Insulin internalization was markedly increased in cells cultured in a medium that contained chromium picolinate and the increased internalization rate was accompanied by a marked increase in the uptake of both glucose and leucine. The effect was specific for chromium picolinate since neither zinc picolinate nor any of the other forms of chromium tested was effective. The increased insulin internalization rate may result from an increase in membrane fluidity since chromium picolinate and to a lesser extent, chromium nicotinate, increased the membrane fluidity of synthetic liposomal membranes.     

Ultrastructural damage in chromium picolinate-treated cells: a TEM study

Chromium picolinate (CrPic) is a human dietary supplement that provides a bioavailable form of chromium(III). Its mechanism of action is unknown, and a number of toxic endpoints have been attributed to its use. Understanding the cellular effects of CrPic is important for confirmation or dismissal of these potential toxic effects. The purpose of this work was to characterize morphological damage caused by CrPic, picolinic acid, and chromic chloride in Chinese hamster ovary AA8 cells. A 48-h exposure to 80 micro g/cm(2) CrPic (0.44 mg/mL CrPic) produced 45% survival by colony formation. Transmission electron microscopy (TEM) showed 83% of analyzed cells having swollen mitochondria with degraded cristae. Apoptosis was identified by nuclear convolution and fragmentation, and cytoplasmic blebbing. Apoptosis was quantified by fluorescence microscopy with acridine orange/ethidium bromide staining. At the 80 micro g/cm(2) dose of CrPic, 37% of the cells were apoptotic cells at 48 h. An equivalent dose of picolinate, 3 mM, was much more cytotoxic and thus there was an inadequate cell number for TEM analysis. However, a lower dose of 1.5 mM induced 49% cell survival, and damaged 86% of the mitochondria, with 51% of the cells undergoing apoptosis. A dose of 1 mM chromic chloride produced 71% cell survival, and damaged 86% of the mitochondria, with 22% of the cells undergoing apoptosis. The amount of apoptosis correlated with overall cell survival by colony formation, but not with the amount of mitochondrial damage. The coordination of Cr(III) by picolinate ligands may alter the cellular chemistry of Cr(III) to make chromium picolinate a toxic form of Cr(III).     

Untersuchungen über die Qualität des Futtereiweißes bei Legehennen

An experiment with 40 female growing pigs from 27.4 to 106.5 kg body weight (BW) in individual pens was conducted to evaluate the effect of different chromium supplements (Cr‐chloride, Cr‐yeast and Cr‐picoli‐nate) according to 0.5 ppm Cr in the diet compared with a control diet without any additional chromium. The influence on growth performance and carcass as well as meat composition was studied.

In comparison with the control diet body weight gain and feed conversion ratio in the finishing period (60 to 106.5 kg BW) were significant increased and lowered respectively in the treatment with Cr‐chloride and with the other Cr supplements tendentially. The results of the carcass composition as well as the fatty acid profile of neutral and complex lipids in the muscle (M. longissimus dorsi) at the 10th rib did not indicate a statistically significant effect of the Cr supplements. Furthermore energy utilization on the base of digestibility was not affected. Concerning the Longissimus muscle area and the intramuscular fat content there were positive tendencies of the investigated Cr supplements.     

Comparing metabolic effects of six different commercial trivalent chromium compounds

Recent reports provide cogent evidence that the average individual becomes chromium deficient with age. Unfortunately, chromium deficiency is strongly associated with many aspects of the Metabolic Syndrome, including insulin resistance and type 2 diabetes. Since replacement of chromium, per os, often ameliorates many deleterious manifestations associated with insulin resistance and diabetes, it is not surprising that many different, commercial trivalent chromium compounds are available on the market. However, previous reports have shown that the form of trivalent chromium (negative charges) can influence effectiveness markedly. We compared various commercial forms of trivalent chromium commonly used alone or in formulations, to examine whether they are equally effective and non-toxic. In the first study, five different chromium products were examined - citrate, amino acid chelate (AAC), chelavite, polynicotinate (NBC), and nicotinate. In the second study, effects of NBC and picolinate were assessed. Results demonstrated that only chelavite and NBC improved insulin sensitivity, and only NBC decreased systolic blood pressure (SBP) significantly. In the second study, both picolinate and NBC significantly decreased SBP compared to control. NBC and picolinate decreased malonyldialdehyde concentrations (free radical formation) and DNA fragmentation in hepatic and renal tissues. No evidence of adverse effects was noted with any of the compounds tested. In conclusion, while all the trivalent chromium compounds tested seem safe, only three enhanced insulin sensitivity (NBC, chelavite, and picolinate) and only two decreased SBP significantly (NBC and picolinate). Furthermore, both NBC and picolinate were protective in lessening free radical formation and DNA damage in the liver and kidneys.     

Effects of Pre- and Postnatal Exposure to Chromium Picolinate or Picolinic Acid on Neurological Development in CD-1 Mice

Chromium picolinate, Cr(pic)3, a popular dietary supplement marketed as an aid in fat loss and lean muscle gain, has also been suggested as a therapy for women with gestational diabetes. The current study investigated the effects of maternal exposure to Cr(pic)3 and picolinic acid during gestation and lactation on neurological development of the offspring. Mated female CD-1 mice were fed diets from implantation through weaning that were either untreated or that contained Cr(pic)3 (200 mg kg(-1) day(-1)) or picolinic acid (174 mg kg(-1) day(-1)). A comprehensive battery of postnatal tests was administered, including a modified Fox battery, straight-channel swim, open-field activity, and odor-discrimination tests. Pups exposed to picolinic acid tended to weigh less than either control or Cr(pic)3-exposed pups, although the differences were not significant. Offspring of picolinic acid-treated dams also appeared to display impaired learning ability, diminished olfactory orientation ability, and decreased forelimb grip strength, although the differences among the treatment groups were not significant. The results indicate that there were no significant effects on the offspring with regard to neurological development from supplementation of the dams with either Cr(pic)3 or picolinic acid.     

Tissue and subcellular distribution of chromium picolinate with time after entering the bloodstream

Chromium picolinate, [Cr(pic)(3)], is a popular nutritional supplement; however, the fate of the complex in vivo has not previously been established. Consequently, rats were administered [51Cr(pic)(3)] intravenously and the fate of the radiolabel in the urine, blood plasma, tissues, and subcellular components of hepatocytes was followed for the first 24 h after injection. The supplement leaves the blood stream rapidly appearing in the urine and entering tissue cells intact. Kidney, muscle, and liver possess most of the absorbed radiolabel. In hepatocytes, the radiolabel appears most rapidly in the nucleus and mitochondria, then in the cytosol, and finally in the lysosomes and microsomes. Thus, while the lifetime of the supplement in vivo is brief, it enters cells rapidly intact. The significance of the lifetime and distribution of [Cr(pic)(3)] in relationship to recent reported potential DNA damage from the supplement is discussed.     

Nutritional supplement chromium picolinate generates chromosomal aberrations and impedes progeny development in Drosophila melanogaster

Chromium picolinate, [Cr(pic)(3)], is a popular nutritional supplement found in a variety of consumer products. Despite its popularity, safety concerns over its use have arisen. The supplement has been shown to generate clastogenic damage, mitochondrial damage, oxidative damage, and mutagenic effects in cultured cells and oxidative DNA damage and lipid peroxidation in rats. Recently [Cr(pic)(3)] has been demonstrated to generate heritable genetic change and delays in progeny development in Drosophila melanogaster. Based on the damage to chromosomes of cultured cells and of animal models, similar chromosome damage appeared to be a likely source of the mutagenic effects of the supplement in Drosophila. The current three-part study examines the effects of several chromium-containing supplements and their components on hatching and eclosion rates and success of development of first generation progeny of adult Drosophila fed food containing these compounds. It further examines the effects of the compounds on longevity of virgin male and female adults. Finally, the chromosomes in the salivary glands of Drosophila late in the third instar larval stage, which were the progeny of Drosophila whose diets were supplemented with nutritional levels of [Cr(pic)(3)], are shown to contain on average over one chromosomal aberration per two identifiable chromosomal arms. No aberrations were observed in chromosomes of progeny of untreated flies. The results suggest that human consumption of the supplement should be a matter of concern and continued investigation to provide insight into the requirements of chromium-containing supplements to give rise to genotoxic effects.     

Potential of Chromium(III) Picolinate for Reproductive or Developmental Toxicity Following Exposure of Male CD-1 Mice Prior to Mating

Chromium(III) picolinate, [Cr(pic)₃], is a commonly used nutritional supplement in humans, which has also been approved for use in animals. Health concerns have arisen over the use of [Cr(pic)₃]. At high [Cr(pic)₃] doses, developmental toxicity tests in female mice have shown a higher litter incidence of split cervical arch in exposed fetuses, but this was not consistently reproducible. In the current study, male CD-1 mice were used to further assess the potential for reproductive or developmental toxicity. Four weeks prior to mating, the males were fed a diet providing 200 mg/kg/day [Cr(pic)₃] for comparison with untreated controls. Females were not treated. Each male was mated with two females, which were sacrificed on gestation day 17, and their litters were examined for adverse effects. Mating and fertility indices were not significantly altered by treatment. Male exposure to [Cr(pic)₃] also had no effect on prenatal mortality, fetal weight, or gross or skeletal morphology. These results suggest that paternal dietary exposure to chromium(III) picolinate has little potential for adverse reproductive effects, even at exposure levels considerably higher than expected human exposures from nutritional supplements (1 mg of Cr per day or less).     

EDTA chelation therapy does not selectively increase chromium losses

Chelation therapy and supplemental Cr have both been shown to lead to improved blood glucose, lipids, and insulin activity. Chelation therapy leads to the removal of toxic as well as essential metals. To determine if chelation therapy leads to increased urinary Cr losses and altered Cr homeostasis, 2 groups of subjects (1 group that had undergone only 1 or no chelation therapy and 1 group in which all subjects had undergone at least 19 chelation sessions) were evaluated for differences in possible Cr homeostasis based on urinary Cr losses. There were no significant differences in urinary Cr losses between the two groups of subjects and there were no significant increases in urinary Cr losses resulting from chelation therapy. Increases in urinary Cr losses were strongly influenced by supplementation but not chelation therapy.     

The effect of the high-fat diet supplemented with various forms of chromium on rats body composition,liver metabolism and organ histology Cr in liver metabolism and histology of selected organs

BackgroundIn the present study, we hypothesized that feeding rats a high-fat diet negatively affects liver metabolism and function and disturbs the histology of some internal organs. We also postulated that there is a form of chromium whose administration alleviates the negative effects of a high-fat diet in rats.MethodsTo verify the hypotheses, we tested the effect of various forms of chrome (picolinate – Cr-Pic, Chromium(III)-methionine complex – Cr-Met, and chrome nanoparticles – Cr-NPs) applied in the recommended amount of 0.3 mg/kg of BW on growth parameters, body fat, liver metabolism and functional disorders, and histological parameters of selected internal organs in rats fed a standard (S) or high-fat diet (F). The experiment was conducted on 56 male outbred Wistar rats (Rattus norvegicus. Cmdb:WI) randomly divided into eight experimental groups. For eight weeks the rats received a standard or high-fat diet, without Cr or with Cr at 0.3 mg/kg diet in the form of Cr-Pic, Cr-Met or Cr-NPs.Results and conclusionThe use of a F diet disrupted the lipid-carbohydrate profile, worsened liver metabolism and function, reduced the expression of hepatic PPAR-α and leaded to negative changes in the histological image of internal organs - liver, kidneys and pancreas. The 8-week use of an chromium supplement in a F diet, regardless of the form used, did not improve the ratio of fat tissue to lean tissue, worsened liver function and negatively affected on the histological image of the liver, kidneys and pancreas. However, the most negative changes in lipid-carbohydrate metabolism and liver functioning were observed with CrNPs supplementation.     

The Efficacy of Chromium as a Growth Enhancer for Mirror Carp (Cyprinus carpio L): An Integrated Study Using Biochemical, Genetic, and Histological Responses

A growth trial was conducted on juvenile mirror carp (Cyprinus carpio L.) for 8 weeks to compare the efficacy of three chromium (Cr) compounds (Cr chloride, Cr picolinate, and Cr yeast) at a level 0.5 mg/kg as a potential growth enhancer. In addition, a high level of Cr (2.0 mg/kg) as Cr chloride has also been added in parallel for comparison. All Cr fortified diets at a level 0.5 mg/kg produced superior growth for carp compared to the control group and the group fed the high level of Cr chloride (2.0 mg/kg). Metabolic indicators measured included two of the key liver enzymes (hexokinase, HK) and (glucose-6-phosphate dehydrogenase, G6PD) activity. The results validated the positive effect of Cr at a level 0.5 mg/kg on enzyme activity and carbohydrate utilization producing significantly better growth performance for mirror carp. The study also included measurement of DNA strand breaks in the erythrocytes using the comet assay which revealed significantly (P < 0.05) increased DNA damage in fish fed on high level of Cr chloride (2.0 mg/kg) but the other treatments were not significantly different (P > 0.05) from the control groups. The concentration of Cr in the liver, gut, and whole fish tissues increased with increasing dietary Cr supplementation. Overall, Cr supplementation at a level 0.5 mg/kg from different sources may affect growth performance in carp by activation of some key liver enzymes (HK and G6PD).     

Effects of Dietary Chromium Picolinate and Ascorbic Acid Supplementation on Egg Production,Egg Quality and Some Serum Metabolites of Laying Hens Reared under a Low Ambient Temperature (6 °C)

This experiment was conducted to evaluate the effects of chromium (chromium picolinate, Cr Pic) and vitamin C (L-ascorbic acid) supplementation on egg production and egg quality in laying hens (Hy-Line) kept at 18 °C (at thermo-neutral zone) or 6 °C (cold stress) in temperature-controlled rooms. One hundred and fifty laying hens (32 week-old) were divided into 5 groups, 30 hens per group. The laying hens kept at 6 °C temperature were fed either a basal diet (low temperature-basal diet, LTB group) or the basal diet supplemented with either 400 µg of Cr per kg diet (Cr group), 250mg of L-ascorbic acid per kg diet (Vit C group) or 400 µg of Cr plus 250mg of L-ascorbic acid per kg diet (Vit C + Cr group) while hens kept at 18 °C fed a basal diet (thermo-neutral-basal diet, TNB group). Performance and egg quality were significantly reduced in LTB group compared with TNB group. Supplemental chromium and vitamin C significantly increased live weight change, egg production, and improved feed efficiency in cold-stressed hens compared with group fed the basal diet at 6 °C brought up to the values of the group reared under thermoneutral conditions (18 °C). Egg production and egg weight were also greater in each supplemental group compared with the LTB group. Separately or as a combination, supplemental chromium and vitamin C increased serum insulin but decreased corticosterone, glucose and cholesterol concentrations. Results of the present study show that supplementing vitamin C and chromium, particularly as a combination, improved the performance of cold-stressed hens. Such a combination of supplement can offer a potential protective management practice in preventing cold stress-related losses in performance of laying hens.