Clinical and biochemical aspects of chromium deficiency

Towards prolonging ovarian reproductive life: Insights into trace elements homeostasis

Ovarian aging is marked by a reduction in the quantity and quality of ovarian follicles, leading to a decline in female fertility and ovarian endocrine function. While the biological characteristics of ovarian aging are well-established, the exact mechanisms underlying this process remain elusive. Recent studies underscore the vital role of trace elements (TEs) in maintaining ovarian function. Imbalances in TEs can lead to ovarian aging, characterized by reduced enzyme activity, hormonal imbalances, ovulatory disorders, and decreased fertility. A comprehensive understanding of the relationship between systemic and cellular TEs balance and ovarian aging is critical for developing treatments to delay aging and manage age-related conditions. This review consolidates current insights into TEs homeostasis and its impact on ovarian aging, assesses how altered TEs metabolism affects ovarian aging, and suggests future research directions to prolong ovarian reproductive life. These studies are expected to offer novel approaches for mitigating ovarian aging.

Trace elements in Ladoga ringed seal (Pusa hispida ladogensis) hair

Hair samples of two adults, eight molted pups, and four newborn Ladoga ringed seals Pusa hispida ladogensis found stranded ashore on Lake Ladoga, North-West Russia, in 2020-2021, were analyzed for concentrations of trace elements, including toxic heavy metals. Al had the highest median concentration (9.25 μg/g, range 1.26-262 μg/g) among toxic elements, followed by Hg (8.84 μg/g, range 2-12.75 μg/g), and Pb (0.16 μg/g, range 0.04-2 μg/g). The Cd concentration in lanugo compared with adult hair of young-of-the-year was significantly lower, suggesting a barrier effect of the placenta for Cd transport to the fetus. The concentrations of Co, Cr, and Zn were higher before the molt, demonstrating the role of lanugo shedding in the excretion of these metals. The concentrations of Hg, Cd, Pb, and Cu were significantly lower than in the 1990s, and lead and copper continued to decline further after the 2000s. Based on available reference trace element levels in other seal species, we found little evidence of substantially elevated levels or deficiencies in Ladoga seals. Nevertheless, since imbalance of trace elements due to contamination can cause physiological disorders, future trace element monitoring in the Ladoga seal is recommended.

Essentiality of Trace Elements in Pregnancy, Fertility, and Gynecologic Cancers-A State-of-the-Art Review

Gynecological neoplasms pose a serious threat to women's health. It is estimated that in 2020, there were nearly 1.3 million new cases worldwide, from which almost 50% ended in death. The most commonly diagnosed are cervical and endometrial cancers; when it comes to infertility, it affects ~48.5 million couples worldwide and the number is continually rising. Ageing of the population, environmental factors such as dietary habits, environmental pollutants and increasing prevalence of risk factors may affect the reproductive potential in women. Therefore, in order to identify potential risk factors for these issues, attention has been drawn to trace elements. Trace mineral imbalances can be caused by a variety of causes, starting with hereditary diseases, finishing with an incorrect diet or exposure to polluted air or water. In this review, we aimed to summarize the current knowledge regarding trace elements imbalances in the case of gynecologic cancers as well as female fertility and during pregnancy.

Effects of chromium supplementation on oxidative Stress biomarkers

Aim: This systematic review and meta-analysis aimed to evaluate the effects of chromium supplementation on oxidative stress biomarkers such as superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPX), malondialdehyde (MDA), total antioxidant status (TAS), thiobarbituric acid reactive substances (TBARS), catalase (CAT), nitric oxide (NO), total antioxidant capacity (TAC) and protein carbonyl. Methods: Relevant studies, published from inception until July 2019, were searched through PubMed/Medline, Scopus, ISI Web of Science, Embase, and Google Scholar. All randomized clinical trials investigating the effect of chromium supplementation on oxidative stress were included. Results: Out of 252 citations, 10 trials that enrolled 595 subjects were included. Chromium supplementation resulted in a significant increase in GSH (WMD: 64.79 mg/dl, 95% CI: 22.43 to 107.15; P=0.003) but no significant change in MDA, TAS, TBARS levels, SOD, CAT levels and GPX. Chromium picolinate supplementation resulted in a significant increase in TAC while failing to have a significant effect on NO. Moreover, both chromium picolinate and chromium dinicocysteinate supplementation reduced protein carbonyl levels. Conclusion: Overall, this meta-analysis demonstrated that chromium supplementation increased GSH without any significant changes in the mean of GPX, MDA, TAS, TBARS, CAT and SOD.

The effect of chromium supplementation on apolipoproteins: A systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Apos play a role in lipoprotein metabolism. Several studies have been carried out on the effect of chromium supplement in improving CVD risk factors.

OBJECTIVE

This study is a systematic review and meta-analysis that aimed to investigate the effect of chromium supplementation on Apos levels of human studies.

MATERIALS AND METHODS

We searched PubMed, Scopus up to May 2020 up to September 2019. We retrieved studies from identified articles. The studies' quality was evaluated using Cochrane Risk of Bias Tool. We estimated the effect of chromium supplementation on Apo A, Apo A1, and Apo B by pooling mean and standard deviation (SD) values.

RESULTS

We obtained six trials involving 231 participants. Chromium consumption resulted significantly decreased Apo B while the subjects were ingesting chromium picolinate. Chromium supplementation did not significantly decrease Apo A (WMD: -3.89 mg/dl; 95% CI, -11.96 to 4.18) with no significant heterogeneity (I² = 0.00%, p = 0.37). The serum level of Apo A1 did not statistically change following chromium intervention (WMD: 6.11 mg/dl; 95% CI, -7.01 to 19.23) with no significant heterogeneity (I² = 0.00%, p = 0.68). Chromium supplementation did not significantly decrease Apo B (WMD: 3.81 mg/dl; 95% CI, -5.32 to 12.94). With no significant heterogeneity (I² = 42.3%, p = 0.12).

CONCLUSIONS

The chromium supplement did not have a significant effect on the Apolipoproteins (Apo A, ApoA1 and Apo B).

Effects of Selenium- and Chromium-Enriched Diets on Growth Performance, Lipid Profile, and Mineral Concentration in Different Tissues of Growing Rabbits

The aim of this study was to investigate the effect of dietary supplementation with different sources of selenium and/or organic chromium on the growth performance, digestibility, lipid profile, and mineral content of hair, liver, and fore and hind limb of growing rabbits. A total of 150 weanling New Zealand White (NZW) male rabbits were randomly allotted to six dietary treatment groups: (1) basal diet (control group), (2) basal diet + 0.6 mg sodium selenite/kg diet, (3) basal diet + 0.6 mg selenium yeast/kg diet, (4) basal diet + 0.3 mg sodium selenite/kg diet + 0.3 mg selenium yeast/kg diet, (5) basal diet + 0.6 mg chromium yeast/kg diet + 0.6 mg selenium yeast/kg diet, (6) basal diet + 0.6 mg chromium yeast/kg diet. Only the combination between inorganic and organic selenium led to significant improvement in body weight, body weight gain, and feed conversion ratio. Carcass traits were not different in all groups. Selenium (Se) and chromium (Cr) were deposited in the tissues of rabbits fed diets supplemented with Se and Cr, respectively. Blood serum in both of selenium- and chromium-supplemented groups showed declined total cholesterol, triglycerides, and low-density lipoprotein (LDL). Group supplemented with organic chromium showed higher high-density lipoprotein (HDL) than the other groups. It could be concluded that using a mixture of inorganic and organic Se has a positive effect on the growth performance of growing rabbits. Both Se and Cr have hypocholesterolemic effect. Both of Se and Cr can be deposited in the meat and other tissues of rabbits and that improves meat quality which positively reflects on human acceptance. The combination between inorganic (0.3 mg sodium selenite/kg diet) and organic selenium (0.6 mg selenium yeast/kg diet) improved growth performance traits of growing rabbits.

Chromium Supplementation Reduces Resting Heart Rate in Patients with Metabolic Syndrome and Impaired Glucose Tolerance

Chromium (Cr) is considered as an important mineral, involved in biochemical reactions in human metabolic pathways. Organically bound Cr supplementation has been suggested to improve glycemia especially in patients with type 2 diabetes mellitus, but there are conflicting reports on efficacy. Effect of Cr is not clear in prediabetes status. Seventy patients with metabolic syndrome and impaired glucose tolerance (IGT), who are observed and treated in the Center of Preventive Cardiology of the University Hospital in Pilsen, were included in the prospective, randomized, double-blind, and placebo-controlled clinical study. Effect of Cr-enriched yeast (200 μg of elementary Cr in the morning and 100 μg in the evening) on glucose, lipid metabolism, fat tissue hormones, oxidative stress, and DNA damage markers was analyzed. There were no significant changes in glucose and lipid parameters, oxidative stress, or other laboratory markers. Only resting heart rate was significantly reduced in patients treated by Cr yeast, reflecting reduced sympathetic activity. This could represent an important cardiovascular risk reduction in patients with high cardiometabolic risk.

Selective chromo-fluorogenic detection of trivalent cations in aqueous environments using a dehydration reaction

Trivalent cations induced a dehydration reaction of a chemodosimeter in water that is coupled with colour and emission changes.

A correlation between diet and longevity characterization by means of element profiles in healthy people over 80 years from a Chinese longevous region

Monitoring the element concentrations in the human body is of critical importance for health and longevity. In order to explore the formation mechanism of longevity from the perspective of the body's element loads, this study investigated the prominent feature of element profiles in healthy people over 80 years from Bama County (China), a famous longevous region (LR). The element profiles in nails of elderly people from the LR and a non-longevous region were determined by inductively coupled plasma mass spectrometry, using orthogonal projections to latent structures discriminant analysis (OPLS-DA) for pattern recognition. As a result, four characteristic elements closely related to the healthy elderly people from LR, including Cr, Fe, Mn, and Co, were identified. The concentrations of Cr, Fe, Mn, and Co were significantly increased in the LR group (p < 0.05). The values of fold change of Cr, Fe, Mn, and Co were 3.00, 2.46, 2.24, and 2.21, respectively. These characteristic elements could provide an important material guarantee for health and longevity of elderly people in the LR. The further correlation analysis revealed significant positive correlations between the Sr (r = 0.886), Mn (r = 0.873), Ni (r = 0.786), and Co (r = 0.738) concentrations in nails of elderly people and those in drinking water. Furthermore, significant positive correlations were found between the Se (r = 0.940), Mn (r = 0.833), and Fe (r = 0.733) concentrations in nails and their dietary intake. Consequently, the observations suggested that diet could provide extraordinary reference information in terms of reflecting the feature of element profiles in healthy elderly people over 80 years from the LR.

A Chalcone-Based Highly Selective and Sensitive Chromofluorogenic Probe for Trivalent Metal Cations

A new chalcone-based probe for the chromofluorogenic sensing of trivalent (Al³⁺ , Fe³⁺ , Cr³⁺ , Ga³⁺ , In³⁺ and As³⁺ ) over mono- and divalent cations and anions is reported. In the presence of trivalent metal cations, the probe was able to display a remarkable color change from yellow to colorless that was clearly visible to the naked eye. Also, the initial strong yellow emission was gradually quenched and substituted by a weakly shifted band.

Effect of chromium supplementation on glycated hemoglobin and fasting plasma glucose in patients with diabetes mellitus

Aims

Chromium (Cr) is a trace element involved in glucose homeostasis. We aim to evaluate and quantify the effects of Cr supplementation on A1C and FPG in patients with T2DM.

Materials and methods

A systematic literature search of Pubmed, EMBASE and the Cochrane Library (from database inception to 11/2014) with no language restrictions sought RCTs or cohort studies evaluating Cr supplementation in T2DM vs control and reporting either change in glycated hemoglobin (A1C) or fasting plasma glucose (FPG). Meta-analysis was conducted on each subtype of Cr supplement separately, and was analyzed by random effects model to yield the weighted mean differences (WMD) and 95% confidence intervals (CIs). Heterogeneity was assessed by using the I² statistic.

Results

A total of 14 RCTs (n = 875 participants, mean age range: 30 to 83 years old, 8 to 24 weeks of follow-up) were identified (Cr chloride: n = 3 study, Cr picolinate: n = 5 study, brewer’s yeast: n = 4 study and Cr yeast: n = 3 study). Compared with placebo, Cr yeast, brewer’s yeast and Cr picolinate did not show statistically significant effects on A1C. Furthermore, compared to control, Cr chloride, Cr yeast and Cr picolinate showed no effect on FPG, however, brewer’s yeast showed a statistically significant decrease in FPG -19.23 mg/dL (95% CI = -35.30 to -3.16, I² = 21%, n = 137).

Conclusions

Cr supplementation with brewer’s yeast may provide marginal benefits in lowering FPG in patients with T2DM compared to placebo however it did not have any effect on A1C.

Alterations in kidney tissue following zinc supplementation to STZ-induced diabetic rats

Diabetes mellitus is a chronic disease characterized by anomalies forming in carbohydrate, lipid, protein metabolisms and the incidence of this disease varies widely throughout the world. Zinc is an important element which is essential for life and is present in nature. In this study, the animals were divided into four groups. These groups were named as untreated; zinc sulfate; streptozotocin (STZ); STZ and zinc sulfate. STZ (65 mg/kg) was dissolved in a freshly prepared 0.01 M pH 4.5 citrate buffer and given with intraperitoneal injection in a single dose. Zinc sulfate (100mg/kg) was dissolved in distilled water and given to the animals by gavage at a daily dose for 60 days. The rats were sacrificed under ether anesthesia. This study was aimed to investigate histological and biochemical changes of zinc supplementation on the kidney tissue in STZ-induced diabetic rats. In the current study, histological and histochemical observations showed that the occurred degenerative changes decreased after giving zinc in the kidney tissue of diabetic group. Kidney glutathione (GSH) levels decreased and lipid peroxidation (LPO), nonenzymatic glycosylation (NEG), urea and creatinine levels increased in diabetic rats. GSH levels increased, while LPO, NEG, urea and creatinine levels decreased in the kidney with administration of zinc to diabetic rats. As a result, we observed curative effects of zinc given to diabetic rats. We can say that zinc may be an important antioxidant for the treatment of secondary complications of diabetes in kidney tissue.

Chromium levels in healthy and newly diagnosed type 1 diabetic children

BACKGROUND

The aim of this study was to compare the chromium levels of plasma (PCL), erythrocyte (ECL) and urine (UCL) in type 1 diabetics and healthy subjects and to review the relation between metabolic parameters.

METHODS

We evaluated 165 subjects who were: newly diagnosed type 1 diabetics (group 1 [n= 29]); previously diagnosed type 1 diabetics (group 2 [n= 18]); non-diabetic control subjects who were admitted and treated for any reason in hospital (group 3 [n= 21]); and two other groups of control subjects from two schools that have different socioeconomic levels (group 4 [n= 48] and group 5 [n= 49]).

RESULTS

PCL in group 1 and group 2 subjects (7.21 ± 4.78 and 10.94 ± 3.04 mcg/L, respectively) was significantly lower than in all control groups (21.84 ± 7.87, 16.11 ± 7.44, 17.25 ± 8.58 mcg/L, respectively) (P < 0.05). A significant difference in PCL between the group 1 and group 2 subjects was present (7.21 ± 4.78 and 10.94 ± 3.04, respectively) (P= 0.021). ECL (as tissue chromium) in group 1 and group 2 subjects (13.99 ± 11.37 and 19.64 ± 12.58, respectively) was significantly lower than in all control groups (28.20 ± 7.34.25, 49 ± 12.47, 26.37 ± 9.77 mcg/L, respectively) (P= 0.05). UCL in group 1 and group 2 subjects (11.44 ± 6.88 and 15.68 ± 6.75 mcg/L, respectively) was significantly lower than in group 3 subjects (28.83 ± 9.37 mcg/L) (P < 0.05). There were significant correlations between length, bodyweight and PCL in the group 1 subjects (r = 0.42, P= 0.22 and r = 0.53, P= 0.03, respectively). There was a negative correlation between plasma glucose and UCL, which was not statistically significant in group 2 subjects (r =-0.4, P= 0.061).

CONCLUSION

There was a negative chromium balance in type 1 diabetics. This negative balance may affect the insulin function badly. If this negative balance should be confirmed by recent studies we suggest that chromium supplementation with insulin is necessary for type 1 diabetes.

The effects of chromium picolinate and chromium histidinate administration on NF-κB and Nrf2/HO-1 pathway in the brain of diabetic rats

The objective of this experiment was to investigate the effects of supplemental chromium picolinate (CrPic) and chromium histidinate (CrHis) on nuclear factor-kappa B (NF-κB p65) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling pathway in diabetic rat brain. Nondiabetic (n = 45) and diabetic (n = 45) male Wistar rats were either not supplemented or supplemented with CrPic or CrHis via drinking water to consume 8 μg elemental chromium (Cr) per day for 12 weeks. Diabetes was induced by streptozotocin injection (40 mg/kg i.p., for 2 weeks) and maintained by high-fat feeding (40 %). Diabetes was associated with increases in cerebral NF-κB and 4-hydroxynonenal (4-HNE) protein adducts and decreased in cerebral nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor, alpha (IκBα) and Nrf2 levels. Both Cr chelates were effective to decrease levels of NF-κB and 4-HNE protein adducts and to increase levels of IκBα and Nrf2 in the brain of diabetic rats. However, responses of these increases and decreases were more notable when Cr was supplemented as CrHis than as CrPic. In conclusion, Cr may play a protective role in cerebral antioxidant defense system in diabetic subjects via the Nrf2 pathway by reducing inflammation through NF-κB p65 inhibition. Histidinate form of Cr was superior to picolinate form of Cr in reducing NF-κB expression and increasing Nrf2 expression in the brain of diabetic rats.

Effect of chromium supplementation on productive and reproductive performances and some metabolic parameters in late gestation and early lactation of dairy cows

The objective of this study was to determine the effect of supplemental chromium as chromium-L-methionine (Cr-Met) on productive and reproductive performances and some metabolic parameters in late gestation and early lactation of dairy cows. Sixty multiparous Holstein dairy cows according to prior lactation, parity, body mass (682±33 kg), and expected calving date were divided equally (30 cows/treatment) and were randomly allocated to one of the two groups. One group received basal diet without Cr (control group) and another group received Cr-Met supplement added at manufacturer's recommended level (8 mg of "Cr"/head per day) from 21 days before expected calving date until 21 days of lactation. Supplemental Cr tended to increase milk yield (P=0.08) while percentage of lactose and lactose yield increased (P<0.01). Chromium supplementation decreased serum nonesterified fatty acids concentration at 7 days prepartum and 21 days postpartum. Serum insulin concentration for cows receiving Cr was higher than the control group (P=0.05). Serum cortisol concentration decreased (P<0.05) in prepartum period in supplemented group. Chromium did not affect concentrations of metabolic parameters at calving. However, serum glucose concentration increased at 21 days postpartum in the supplemented group (P<0.05). Chromium supplementation increased neutrophil and neutrophil to lymphocyte ratio in prepartum period (P<0.05). Based on serum concentrations of progesterone, days to first ovulation tended (P=0.07) to occur earlier in the supplemented group. Furthermore, days to first service and days to first estrus of the supplemented group occurred earlier than the control group (P<0.05) but days open, services per conception and conception rates at first insemination did not differ between two groups (P>0.05). Percentage of cyclic cows at 36 days postpartum and estrous behavior before AI was higher in the supplemented group.

Trace elements in glucometabolic disorders: an update

Many trace elements, among which metals, are indispensable for proper functioning of a myriad of biochemical reactions, more particularly as enzyme cofactors. This is particularly true for the vast set of processes involved in regulation of glucose homeostasis, being it in glucose metabolism itself or in hormonal control, especially insulin. The role and importance of trace elements such as chromium, zinc, selenium, lithium and vanadium are much less evident and subjected to chronic debate. This review updates our actual knowledge concerning these five trace elements. A careful survey of the literature shows that while theoretical postulates from some key roles of these elements had led to real hopes for therapy of insulin resistance and diabetes, the limited experience based on available data indicates that beneficial effects and use of most of them are subjected to caution, given the narrow window between safe and unsafe doses. Clear therapeutic benefit in these pathologies is presently doubtful but some data indicate that these metals may have a clinical interest in patients presenting deficiencies in individual metal levels. The same holds true for an association of some trace elements such as chromium or zinc with oral antidiabetics. However, this area is essentially unexplored in adequate clinical trials, which are worth being performed.

The effects of chromium histidinate on mineral status of serum and tissue in fat-fed and streptozotocin-treated type II diabetic rats

The present study was conducted to investigate the effects of chromium histidinate (CrHis) against experimentally induced type II diabetes and on chromium (Cr), zinc (Zn), selenium (Se), manganese (Mn), iron (Fe), and copper (Cu) in serum, liver, and kidney of diabetic rats. The male Wistar rats (n = 60, 8 weeks old) were divided into four groups. Group I received a standard diet (12% of calories as fat); group II were fed standard diet and received CrHis (110 mcg CrHis/kg body weight per day); group III received a high-fat diet (HFD; 40% of calories as fat) for 2 weeks and then were injected with streptozotocin (STZ) on day 14 (STZ, 40 mg/kg i.p.; HFD/STZ); group IV were treated as group III (HFD/STZ) but supplemented with 110 mcg CrHis/kg body weight per day. The mineral concentrations in the serum and tissue were determined by atomic absorption spectrometry. Compared to the HFD/STZ group, CrHis significantly increased body weight and reduced blood glucose in diabetic rats (p < 0.001). Concentrations of Cr, Zn, Se, and Mn in serum, liver, and kidney of the diabetic rats were significantly lower than in the control rats (p < 0.0001). In contrast, higher Fe and Cu levels were found in serum and tissues from diabetic versus the non-diabetic rats (p < 0.001). Chromium histidinate supplementation increased serum, liver, and kidney concentrations of Cr and Zn both in diabetic and non-diabetic rats (p < 0.001). Chromium supplementation increased Mn and Se levels in diabetic rats (p < 0.001); however, it decreased Cu levels in STZ-treated group (p < 0.001). Chromium histidinate supplementation did not affect Fe levels in both groups (p > 0.05). The results of the present study conclude that supplementing Cr to the diet of diabetic rats influences serum and tissue Cr, Zn, Se, Mn, and Cu concentrations.

Effects of chromium histidinate on renal function, oxidative stress, and heat-shock proteins in fat-fed and streptozotocin-treated rats

OBJECTIVE

Chromium is an essential element for carbohydrate, fat, and protein metabolism. The therapeutic potential of chromium histidinate (CrHis) in the treatment of diabetes has been elucidated. The present study investigated the effects of CrHis on serum parameters of renal function, on oxidative stress markers (malondialdehyde [MDA] and 8-isoprostane), and on the expression of heat-shock proteins (HSPs) in rats.

METHODS

Male Wistar rats (n=60, 8 weeks old) were divided into four groups. Group 1 received a standard diet (12% of calories as fat). Group 2 received a standard diet, plus CrHis. Group 3 received a high-fat diet (40% of calories as fat) for 2 weeks, and was then injected with streptozotocin (STZ) on day 14 (STZ, 40 mg/kg intraperitoneally). Group 4 was treated in the same way as group 3 (HFD/STZ), but was supplemented with 110 microg CrHis/kg/body weight/day. Oxidative stress in the kidneys of diabetic rats was evidenced by an elevation in levels of MDA and 8-isoprostane. Protein concentrations of HSP60 and HSP70 in renal tissue were determined by Western blot analyses.

RESULTS

Chromium histidinate supplementation lowered kidney concentrations of MDA, 8-isoprostane levels, serum urea-N, and creatinine, and reduced the severity of renal damage in the STZ-treated group (i.e., the diabetes-induced group). The expression of HSP60 and HSP70 was lower in the STZ group that received CrHis than in the group that did not. No significant effect of CrHis supplementation was detected in regard to the overall measured parameters in the control group.

CONCLUSIONS

Chromium histidinate significantly decreased lipid peroxidation levels and HSP expression in the kidneys of experimentally induced diabetic rats. This study supported the efficacy of CrHis in reducing renal risk factors and impairment because of diabetes.

Framework for metals risk assessment

EPA recognized that metals present unique risk assessment issues, and saw the need to develop a framework document that puts forth key scientific principles for metals risk assessments to help ensure consistency in metals assessments across EPA programs and regional offices. This framework, called the "Framework for Metals Risk Assessment," is a science-based document that describes basic principles that address the special attributes and behaviors of metals and metal compounds to be considered when assessing their human health and ecological risks. The Risk Assessment Forum oversaw the development of this document, including input from stakeholders and experts throughout the Agency, and obtained through several expert workshops, followed by peer review by the EPA Science Advisory Board (SAB). The Framework for Metals Risk Assessment document is intended to serve as a guide for all EPA programs and regional offices to supplement or update the policies, practices and guidance they currently use in their respective metals assessments. This framework document is not a prescriptive guide on how any particular type of assessment should be conducted within an EPA program office. Rather, it outlines key metal principles and describes how they should be considered in conducting human health and ecological risk assessments to advance our understanding of metals impact and foster consistency across EPA programs and regions. Although the audience for the framework is primarily intended to be Agency risk assessors, it also will communicate principles and recommendations for metals risk assessment to stakeholders and the public. This framework will be used in conjunction with guidance developed by the programs and regions for site-specific risk assessment, criteria derivation, ranking or categorization and other similar Agency activities related to metals. The Framework for Metals Risk Assessment document is intended to serve as a guide for all EPA programs and regional offices to supplement or update the policies, practices and guidance they currently use in their respective metals assessments. EPA assessments can vary in level of detail from simple, screening analyses to complex, definitive assessments. More complex scientific tools and metal specific methods should be applied as the complexity of the hazard assessment or risk assessment increases.

The influence of chromium chloride-containing milk to glycemic control of patients with type 2 diabetes mellitus: a randomized, double-blind, placebo-controlled trial

The aim of this study is to evaluate the effect and safety of chromium-containing milk powder in patients with type 2 diabetes mellitus. A randomized, double-blind, placebo-controlled trial was conducted in Taiwan. A total of 60 patients with type 2 diabetes mellitus, aged 30 to 75 years, and on a dose of gliclazide sulfonylurea agent (< or =160 mg/d) for at least 3 months were enrolled. Their glycosylated hemoglobin ranged from 7.5% to 12%, fasting plasma glucose (FPG) from 140 to 250 mg/dL, and body mass index from 20 to 35 kg/m(2). The subjects were divided into 2 groups, one group to receive chromium-containing milk powder (chromium 200 microg/20 g milk powder) and the other to receive placebo twice a day for 16 weeks. Frequently sampled intravenous glucose tolerance test (IVGTT) was performed before and after treatment. The chromium group demonstrated a lower FPG and fasting insulin (-38.1 +/- 9.2 vs 63 +/- 8. 5 mg/dL and -1.7 +/- 0.2 vs 1.9 +/- 0.3 microU/mL, respectively; P < .05), especially in male patients (-41 +/- 9.2 vs 85 +/- 11.7 mg/dL and -2.7 +/- 0.2 vs 3.1 +/- 0.3 microU/mL, respectively; P < .01), at the end of the study. Lower glycosylated hemoglobin was observed in chromium-treated male patients (-1.1 +/- 0. 5 vs 0.7 +/- 0. 2; P < .05). However, there were no significant changes in other metabolic parameters (lipid profiles including total cholesterol, triglyceride, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol), except improvement of insulin resistance (homeostasis model assessment for insulin resistance and insulin sensitivity index from frequently sampled intravenous glucose tolerance test) observed in male patients (-2.1 +/- 1.1 vs -0.41 +/- 1.12 and 0.18 +/- 0.11 vs -0.15 +/- 0. 2, respectively; P < .05). There were no adverse events in both groups, except for mild complaints in the chromium group on constipation (5%) and flatulence (5%). Intake of milk powder containing 400 microg/d of chromium for 16 weeks in subjects with type 2 diabetes mellitus resulted in lowering of FPG, fasting insulin, and improvement of metabolic control in male patients.

Comparison of anti-hyperglycemic effect amongst vanadium, molybdenum and other metal maltol complexes

A wide variety of vanadium-containing complexes have been tested, both in vivo and in vitro, as possible therapeutic agents for the oral treatment of type 2 diabetes mellitus. None so far has surpassed bis(maltolato)oxovanadium(IV) (BMOV) for glucose- and lipid-lowering in an orally available formulation. Ligand choice is clearly an important factor in pharmacological efficacy of vanadium compounds as insulin enhancing agents. In this study, we kept the ligand and dose the same, varying instead the metal ion bound to the maltolato ligand in a series of binary complexes of neutral charge. A requirement for vanadyl ion as the metal ion of choice was apparent; no other metal ion tested served as a suitable substitute. Amongst [MoO(2)](2+), Co(II), Cu(II), Cr(III), and Zn(II), only [MoO(2)](2+) and Co(II) showed any hypoglycemic activity at the ED(50) dose for bis(maltolato)oxovanadium(IV), 0.6 mmolkg(-1) by oral gavage in streptozotocin (STZ)-diabetic rats within 72 h of administration of compound.

Chromium as adjunctive treatment for type 2 diabetes

OBJECTIVE

To review the chemistry, pharmacology, efficacy, and safety of trivalent chromium in the treatment of type 2 diabetes and hyperlipidemia.

DATA SOURCES

The English literature was searched from 1966 through May 2002 using MEDLINE, International Pharmaceutical Abstracts, and EMBASE. The key words included chromium, glucose, lipids, and diabetes. Pertinent references from review articles and studies were used as additional sources.

DATA SYNTHESIS

Trivalent chromium is an essential nutrient and has a key role in lipid and glucose metabolism. Supplementation with chromium does not appear to reduce glucose levels in euglycemia. It may, however, have some efficacy in reducing glucose levels in hyperglycemia. The effects of chromium on lipid levels are variable. Chromium in doses <1000 microg/d appears to be safe for short-term administration. Kidney function and dermatologic changes need to be monitored.

CONCLUSIONS

Chromium appears to be a safe supplement and may have a role as adjunctive therapy for treatment of type 2 diabetes. Additional large-scale, long-term, randomized, double-blind studies examining the effect of various doses and forms of chromium are needed.

Experimental copper deficiency, chromium deficiency and additional molybdenum supplementation in goats--pathological findings

Secondary copper (Cu) deficiency, chromium (Cr) deficiency and molybdenosis (Mo) has been suggested to cause the "mysterious" moose disease in the southwest of Sweden. The present experiment was performed on goats to investigate the clinical, chemical, and pathological alterations after 20 months feeding of a semi-synthetic diet deficient in Cu and Cr. Four groups were included in the study: control group (n = 4), Cu-deficient group (group 1, n = 4), Cr-deficient group (group 2, n = 2) and Cu + Cr-deficient group (group 3, n = 3). Group 3 was additionally supplemented with tetrathiomolybdate during the last 2 months of the experiment. Main histopathological findings in groups 1 and 3 were the lesions in the liver, characterised by a severe active fibrosis, bile duct proliferation, haemosiderosis and mild necroses. Additionally, degenerative alterations of the exocrine pancreas were prominent in groups 1 and 3. Lesions in group 3 were more pronounced than in group 1. In group 3, the skin showed an atrophic dermatosis, while in group 2 a crusty dermatitis caused by Candida spp. was observed. This study shows that liver, pancreas and skin are mainly affected by a long term deficiency of copper and the findings are complicated by molybdenum application while chromium deficiency produced no histomorphological effects in our study.

Metabolite and hormonal responses to glucose or propionate infusions in periparturient dairy cows supplemented with chromium

Two studies were conducted to evaluate the effects of Cr supplementation on blood metabolite and hormonal responses of Holstein cows to glucose challenges during late pregnancy and early lactation and to propionate challenges during early lactation. Eight multiparous and 4 primiparous cows (Experiment 1) and 12 primiparous cows (Experiment 2) were assigned to one of two treatments: control and 0.5 ppm of supplemental Cr. The glucose challenges were performed at 2 wk prepartum and at 2 wk postpartum, and the propionate challenges were conducted at wk 2 and 6 postpartum. During glucose tolerance tests, Cr supplementation reduced the ratio of insulin to glucose and reduced plasma concentrations of insulin and triglycerides of primiparous cows during the prepartum period. Chromium supplementation decreased plasma Cr of primiparous cows following glucose challenge. With supplemental Cr, insulin sensitivity was reduced postpartum, particularly for primiparous cows, but insulin sensitivity was increased prepartum. Results of this study suggested that primiparous cows experienced Cr deficiency during late pregnancy and possibly during early lactation. Following propionate infusion, Cr supplementation increased the serum glucose peak, increased the area under the response curve for serum glucose, and tended to increase IGF-I concentrations. Chromium supplementation tended to reduce the ratio of insulin to glucagon. Supplementation might have enhanced gluconeogenesis or glycogenolysis. Supplemental Cr also resulted in reduced variability of most parameters during both experiments.

The clinical importance of hypochlorhydria (a consequence of chronic Helicobacter infection): its possible etiological role in mineral and amino acid malabsorption, depression, and other syndromes

In a previous paper evidence was presented to show that Helicobacter-induced chronic gastritis is the probable cause of most chronic hypochlorhydria. In this article evidence is presented for the clinical relevance of reduced stomach acid secretion. Reduced mineral absorption is fairly well documented and has sound theoretical support from basic chemistry. Impaired digestion of protein has been suggested by a few studies. Small intestinal bacterial overgrowth in hypochlorhydria probably leads to putrefactive breakdown of the metobolically useful products of protein digestion, thereby reducing their availability for certain essential pathways. The possible lowering of tryptophan, tyrosine, and phenylalanine in the blood may be a precipitating factor in depression in hypochlorhydric patients. In reduced or absent stomach acid secretion a constellation of gastrointestinal symptoms has been consistently observed and reported by clinicians in the past, and treatment of the hypochlorhydria with hydrochloric acid or its substitutes has often been observed to be effective in reducing these symptoms.

Chromium metabolism. A literature review

The trivalent state of chromium (Cr3+) is that encountered in biological milieus and is responsible for its nutritional activity. The principal route by which trivalent chromium enters the body is the digestive system. Chromium in foods is present both in the inorganic form and as organic complexes. Intestinal absorption of chromium is low (0.5-2%), and the mechanism has not yet been fully elucidated. Absorbed chromium circulates as free Cr3+, as Cr3+ bound to transferrin or other plasma proteins, or as complexes, such as glucose tolerance factor (GTF)-Cr. Circulating trivalent chromium can be taken up by tissues, and its distribution in the body depends on the species, age, and chemical form. It is excreted primarily in the urine by glomerular filtration or bound to a low-mol-wt organic transporter. Chromium metabolism is still imperfectly understood. The use of 51Cr has nevertheless furnished valuable data concerning its transport and excretion.

Clinical implications of trace elements in endocrinology

The implications of essential trace elements in endocrinological processes, mainly thyroid function, growth, gonadal function, adrenal hormones, prolactin, glucose homeostasis, calcium-phosphorus metabolism, and thymulin activity, are reviewed. Most concerned elements in this field include iodine, zinc, selenium, copper, chromium, manganese and vanadium. The minerals are powerful modulators of several physiological functions that can be considerably perturbed in deficiency states. The resulting biochemical and clinical modifications can be prevented and/or corrected by adequate supplementation. Sometimes, however, they act like pharmacological agents when their beneficial effects are not the result of a correction of a nutritional deficiency state. Their potentialities as therapeutic agents are perfectly described in many cases, but some indications deserve further investigations.

A fraction derived from brewer's yeast inhibits cholesterol synthesis by rat liver preparations in vitro

Brewer's yeast was grown on a defined medium containing tracer 51Cr with or without added chromium. The two batches of yeast contained 10 microgram/g (high-Cr) or 80 ng/g (low-Cr). Extracts were prepared and fractionated. A third batch of yeast (third batch) was grown with added Cr, and fractionated. Rats were reared on either rat cubes (normal diet) or on a low-Cr diet (low-Cr), or on rat cubes with added cholestyramine (cholestyramine diet). Preparations of rat liver, both cell-free and intact hepatocytes, incorporated acetate-carbon into fatty acids and cholesterol. These processes were inhibited by a yeast fraction containing small, neutral, water-soluble compounds. The degree of inhibition was the same whether the liver came from normal rats or rats fed on the low-Cr diet. Similarly the inhibitory effect was found with identical amounts of extracts from low- or high-Cr yeasts. Therefore, Cr compounds do not appear to account for the inhibitory effects of brewer's yeast. Use of other substrates indicated that the site of inhibition of sterol synthesis was apparently between acetyl-CoA and mevalonate. One inhibitory substance was isolated from yeast and was found to be nicotinamide riboside. This may have been produced from NAD(P) during the preparation of yeast extracts, and it may be produced from dietary yeast supplements during digestion in vivo. Nicotinamide riboside may be partly responsible for the reported effects of yeast supplements on plasma lipids in humans.

Effects of extracts of high- and low-chromium brewer's yeast on metabolism of glucose by hepatocytes from rats fed on high- or low-Cr diets

Brewer's yeast was grown on a defined medium containing glucose, ammonia, salts and vitamins plus tracer 51Cr without (low-Cr) or with (high-Cr) carrier Cr. The two batches of yeast differed by more than 100-fold in Cr content, containing 80 ng and 10 micrograms Cr/g dry yeast respectively. Extraction and fractionation procedures were designed to isolate Cr complexes with properties similar to those reported for glucose tolerance factor. After weaning, rats were reared on rat cubes (normal diet) or on a diet containing less than 0.1 microgram Cr/kg (low-Cr diet), or on the low-Cr diet supplemented with Cr (1 mg Cr/kg). Hepatocytes from these rats were incubated with [U-14C]glucose and incorporation of 14C into glycogen was measured. Incorporation of glucose-C into glycogen was enhanced by some yeast fractions in the presence of insulin, but had less effect in the absence of insulin. No difference could be detected between the responses to fractions from high- or low-Cr yeast extracts, or between responses by hepatocytes from animals fed on normal or low-Cr diets with or without Cr supplementation. Glycogen synthetase (EC 2.4.1.11) activity (total and percentage in the a form) was similar in hepatocytes isolated from animals on the normal and low-Cr diets. Those yeast fractions which enhanced the response to insulin in the 14C-incorporation experiments also enhanced the percentage of the enzyme in the a form in the presence of insulin, but not in the absence of insulin. The presence in yeast extracts of material which enhances the response to insulin by hepatocytes may help to explain the reported beneficial effects of dietary yeast supplements on glucose tolerance.

[Trace elements in artificial nutrition. Art and practice]

The trace elements known to be necessary for man are iron, zinc, copper, selenium, chromium, manganese, molybdenum, cobalt and iodine. This review article, which excludes iron, deals with the need for supplemental trace elements during artificial feeding, and the way they should be administered. The biological importance of these trace elements is argued on the basis of their biochemical involvement and the clinical pictures seen in accidental or experimental deficiency states. Assessing a patient's trace element status is rather difficult. The relative merits of different laboratory investigations is discussed: plasma, erythrocyte, capillary and urinary levels, specific enzyme activities, loading tests. The different situations when trace elements are required, assessing the amount needed and the possible toxic risks, are presented from a literature survey.

Radiochromium distribution in aged rats

Fragmentary studies suggest that tissue chromium (Cr) levels decrease with age. Regardless of the mechanism for such a decline, decreased tissue exchange with administered radiochromium (51Cr) should result. Accordingly, body retention, urinary excretion, and serum (plasma) and tissue levels of 51Cr were determined in 2-month-old male control rats and in 9-18-month-old experimental male rats 3 days after the intravenous injection of high specific activity trivalent 51Cr. The older rats retained relatively less 51Cr than the 2-month-old rats in comparison to body weight but had similar urinary excretions of 51Cr. Serum (plasma) 51Cr levels were generally higher and tissue 51Cr levels generally lower in the older rats, with the exception of spleen 51Cr content, which increased. Skeletal 51Cr content was markedly decreased, by 30-85%. These data suggest that aging alters 51Cr distribution by decreasing cellular Cr content and transport. Other mechanisms must be operative in bone since skeletal Cr is primarily extracellular.

Radiochromium distribution during saline diuresis

Free water diuresis in vasopressin-deficient Brattleboro rats does not influence body conservation of chromium (Cr+3), suggesting a proximal tubular site for renal Cr reabsorption. Other data suggest that Cr conservation is accomplished primarily by lack of glomerular filtration or by tissue binding to a specific Cr-binding substance. To provide further data, radiochromium (51Cr) retention and tissue distribution were studied in SHR and WKY rats undergoing saline diuresis. Despite high urine flows, body retention and urinary excretion of 51Cr were unchanged. Tissue content of 51Cr was minimally and not consistently influenced by saline diuresis in either rat strain. Compared to WKY rats, the SHR rats had a trend to lower serum and tissue 51Cr content but higher tissue/serum 51Cr ratios. These data fail to incriminate collecting duct reabsorption in Cr conservation but are compatible with proximal Cr reabsorption or either of the two hypotheses mentioned above. The decreased serum 51Cr content of SHR rats may be due to the mechanical effect of increased plasma and extracellular volumes. One possible explanation for the increased tissue/serum 51Cr ratios may be the presence of a factor in SHR rats promoting cellular Cr transport. However, there is no present evidence to suggest that any of the hormones believed capable of increasing Cr transport (insulin, growth hormone, thyroxine, ADH) are increased in the SHR rat.