No effect of copper supplementation on biochemical markers of bone metabolism in healthy adults

Re-evaluation of the existing health-based guidance values for copper and exposure assessment from all sources

Copper is an essential micronutrient and also a regulated product used in organic and in conventional farming pest management. Both deficiency and excessive exposure to copper can have adverse health effects. In this Scientific Opinion, the EFSA 2021 harmonised approach for establishing health-based guidance values (HBGVs) for substances that are regulated products and also nutrients was used to resolve the divergent existing HBGVs for copper. The tightly regulated homeostasis prevents toxicity manifestation in the short term, but the development of chronic copper toxicity is dependent on copper homeostasis and its tissue retention. Evidence from Wilson disease suggests that hepatic retention is indicative of potential future and possibly sudden onset of copper toxicity under conditions of continuous intake. Hence, emphasis was placed on copper retention as an early marker of potential adverse effects. The relationships between (a) chronic copper exposure and its retention in the body, particularly the liver, and (b) hepatic copper concentrations and evidence of toxicity were examined. The Scientific Committee (SC) concludes that no retention of copper is expected to occur with intake of 5 mg/day and established an Acceptable Daily Intake (ADI) of 0.07 mg/kg bw. A refined dietary exposure assessment was performed, assessing contribution from dietary and non-dietary sources. Background copper levels are a significant source of copper. The contribution of copper from its use as plant protection product (PPP), food and feed additives or fertilisers is negligible. The use of copper in fertilisers or PPPs contributes to copper accumulation in soil. Infant formula and follow-on formula are important contributors to dietary exposure of copper in infants and toddlers. Contribution from non-oral sources is negligible. Dietary exposure to total copper does not exceed the HBGV in adolescents, adults, elderly and the very elderly. Neither hepatic copper retention nor adverse effects are expected to occur from the estimated copper exposure in children due to higher nutrient requirements related to growth.

Bone Turnover Markers: Basic Biology to Clinical Applications

Bone turnover markers (BTMs) are used widely, in both research and clinical practice. In the last 20 years, much experience has been gained in measurement and interpretation of these markers, which include commonly used bone formation markers bone alkaline phosphatase, osteocalcin, and procollagen I N-propeptide; and commonly used resorption markers serum C-telopeptides of type I collagen, urinary N-telopeptides of type I collagen and tartrate resistant acid phosphatase type 5b. BTMs are usually measured by enzyme-linked immunosorbent assay or automated immunoassay. Sources contributing to BTM variability include uncontrollable components (e.g., age, gender, ethnicity) and controllable components, particularly relating to collection conditions (e.g., fasting/feeding state, and timing relative to circadian rhythms, menstrual cycling, and exercise). Pregnancy, season, drugs, and recent fracture(s) can also affect BTMs. BTMs correlate with other methods of assessing bone turnover, such as bone biopsies and radiotracer kinetics; and can usefully contribute to diagnosis and management of several diseases such as osteoporosis, osteomalacia, Paget's disease, fibrous dysplasia, hypophosphatasia, primary hyperparathyroidism, and chronic kidney disease-mineral bone disorder.

Copper nutrition and biochemistry and human (patho)physiology

The essential trace mineral copper plays important roles in human physiology and pathophysiology. Disruption of copper homeostasis may underlie the development of ischemic heart disease, and connective tissue and neurodegenerative disorders. Copper also likely participates in the host response to bacterial infection and is further implicated more broadly in regulating immunity. Recent studies further associate copper with disruption of lipid homeostasis, as is frequently seen in, for example, non-alcoholic fatty liver disease (NAFLD). Moreover, continuing investigation of copper chaperones has revealed new roles for these intracellular copper-binding proteins. Despite these (and many other) significant advances, many questions related to copper biology remain unanswered. For example, what are the most sensitive and specific biomarkers of copper status, and which ones are useful in marginal (or "sub-clinical" copper deficiency)? Further research on this topic is required to inform future investigations of copper metabolism in humans (so the copper status of study participants can be fully appreciated). Also, are current recommendations for copper intake adequate? Recent studies suggest that overt copper deficiency is more common than once thought, and further, some have suggested that the copper RDAs for adults may be too low. Additional human balance and interventional studies are necessary and could provide the impetus for reconsidering the copper RDAs in the future. These and myriad other unresolved aspects of copper nutrition will undoubtedly be the focus of future investigation.

Dietary Zinc Supplementation to Prevent Chronic Copper Poisoning in Sheep

Simple Summary

Sheep are susceptible to copper toxicosis, a deadly disease that usually occurs when the animals ingest large amounts of this mineral. Considering that the susceptibility of sheep to copper accumulation varies widely among breeds and from animal to animal., we evaluate whether Zn supplementation could be an option as a preventive measure to protect against hepatic Cu accumulation in sheep. Zn at 300 mg/kg dry matter (DM) is useful for preventing excessive hepatic Cu accumulation. Hepatic Cu accumulation is lower in animals receiving the Zn supplementation.

Abstract

The aim of this study was to evaluate whether zinc (Zn) supplementation protects against hepatic copper (Cu) accumulation in copper-loaded sheep. Forty cross-bred lambs were assigned to five experimental groups. These included the control group (C) and four treatment groups that received Cu and/or Zn supplementation (dry matter (DM) basis) over 14 weeks, as follows: Cu (450 mg Cu/kg); Zn-35 (450 mg Cu + 35 mg Zn/kg); Zn-150 (450 mg Cu + 150 mg Zn/kg); and Zn-300 (450 mg Cu + 300 mg Zn/kg). Blood, liver, and bile samples were obtained for mineral determination by inductively coupled plasma optical emission spectrometry (ICP–OES). The hepatic metallothionein (MT) concentrations were also determined. At the end of the experiment, hepatic Cu concentrations were higher in all Cu-supplemented groups than in C. Hepatic Cu accumulation was lower in the groups receiving the Zn supplementation than in the Cu group, although the difference was only statistically significant (66%) in the Zn-300 group. The MT concentrations tended to be higher (almost two-fold) in the Zn groups (but were not dose related) than in the C and Cu groups, and they were related to hepatic Zn concentrations. Zn supplementation at 300 mg/kg DM is useful for preventing excessive hepatic Cu accumulation in sheep exposed to high dietary concentrations of Cu.

Corrosion and biological performance of biodegradable magnesium alloys mediated by low copper addition and processing

Mg-Cu alloys were designed by introducing the well-known antibacterial property of copper into magnesium alloy to solve the infection problem especially under the neutralised environment in vitro. In this paper, the Mg-Cu alloys with further processing by solution and extrusion were studied to optimise the corrosion-related performance for their future application. It was shown that the differences in the property profile of Mg-Cu alloys are dependent on different compositions as well as on different microstructures that are obtained by the different processing routes. Galvanic corrosion can be significantly relieved by solution treatment and extrusion due to decrease and well distribution of cathodic Mg₂Cu phases. Negligible cytotoxicity were observed with rBMSCs incubation. Antibacterial assays proved that the alloys reduced the viability of Staphylococcus aureus by high alkalinity and copper ions releasing, especially in comparison with pure magnesium. Finally, the as-solutionized Mg-0.1Cu alloy showed the optimal corrosion properties and promising antibacterial activity, which warranted its potentials as antibacterial biodegradable implant materials.

Biodegradable Mg-Cu alloys with enhanced osteogenesis, angiogenesis, and long-lasting antibacterial effects

A series of biodegradable Mg-Cu alloys is designed to induce osteogenesis, stimulate angiogenesis, and provide long-lasting antibacterial performance at the same time. The Mg-Cu alloys with precipitated Mg2Cu intermetallic phases exhibit accelerated degradation in the physiological environment due to galvanic corrosion and the alkaline environment combined with Cu release endows the Mg-Cu alloys with prolonged antibacterial effects. In addition to no cytotoxicity towards HUVECs and MC3T3-E1 cells, the Mg-Cu alloys, particularly Mg-0.03Cu, enhance the cell viability, alkaline phosphatase activity, matrix mineralization, collagen secretion, osteogenesis-related gene and protein expressions of MC3T3-E1 cells, cell proliferation, migration, endothelial tubule forming, angiogenesis-related gene, and protein expressions of HUVECs compared to pure Mg. The favorable osteogenesis and angiogenesis are believed to arise from the release of bioactive Mg and Cu ions into the biological environment and the biodegradable Mg-Cu alloys with osteogenesis, angiogenesis, and long-term antibacterial ability are very promising in orthopedic applications.

Building healthy bones throughout life: an evidence-informed strategy to prevent osteoporosis in Australia

Osteoporosis imposes a tremendous burden on Australia: 1.2 million Australians have osteoporosis and 6.3 million have osteopenia. In the 2007–08 financial year, 82 000 Australians suffered fragility fractures, of which > 17 000 were hip fractures. In the 2000–01 financial year, direct costs were estimated at $1.9 billion per year and an additional $5.6 billion on indirect costs. Osteoporosis was designated a National Health Priority Area in 2002; however, implementation of national plans has not yet matched the rhetoric in terms of urgency. Building healthy bones throughout life, the Osteoporosis Australia strategy to prevent osteoporosis throughout the life cycle, presents an evidence-informed set of recommendations for consumers, health care professionals and policymakers. The strategy was adopted by consensus at the Osteoporosis Australia Summit in Sydney, 20 October 2011. Primary objectives throughout the life cycle are: to maximise peak bone mass during childhood and adolescence to prevent premature bone loss and improve or maintain muscle mass, strength and functional capacity in healthy adults to prevent and treat osteoporosis in order to minimise the risk of suffering fragility fractures, and reduce falls risk, in older people. The recommendations focus on three affordable and important interventions — to ensure people have adequate calcium intake, vitamin D levels and appropriate physical activity throughout their lives. Recommendations relevant to all stages of life include: daily dietary calcium intakes should be consistent with Australian and New Zealand guidelines serum levels of vitamin D in the general population should be above 50nmol/L in winter or early spring for optimal bone health regular weight-bearing physical activity, muscle strengthening exercises and challenging balance/mobility activities should be conducted in a safe environment.

An exposure-response curve for copper excess and deficiency

There is a need to define exposure-response curves for both Cu excess and deficiency to assist in determining the acceptable range of oral intake. A comprehensive database has been developed where different health outcomes from elevated and deficient Cu intakes were assigned ordinal severity scores to create common measures of response. A generalized linear model for ordinal data was used to estimate the probability of response associated with dose, duration and severity. The model can account for differences in animal species, the exposure medium (drinking water and feed), age, sex, and solubility. Using this model, an optimal intake level of 2.6 mg Cu/d was determined. This value is higher than the current U.S. recommended dietary intake (RDI; 0.9 mg/d) that protects against toxicity from Cu deficiency. It is also lower than the current tolerable upper intake level (UL; 10 mg/d) that protects against toxicity from Cu excess. Compared to traditional risk assessment approaches, categorical regression can provide risk managers with more information, including a range of intake levels associated with different levels of severity and probability of response. To weigh the relative harms of deficiency and excess, it is important that the results be interpreted along with the available information on the nature of the responses that were assigned to each severity score.

Methods of assessment of copper status in humans: a systematic review

BACKGROUND

The assessment of dietary adequacy of copper is constrained by the absence of recognized copper status biomarkers.

OBJECTIVES

The objectives were to systematically review the usefulness of copper status biomarkers and identify those that reflected changes in status over > or =4 wk.

DESIGN

The methods included a structured search on Ovid MEDLINE, EMBASE (Ovid), and Cochrane databases to October 2007, followed by the use of formal inclusion/exclusion criteria, data extraction, validity assessment, and meta-analysis.

RESULTS

A total of 16 studies (288 participants) were included in the review, with data on 16 possible copper biomarkers. All of the included studies were small and at high risk of bias. Data for serum copper suggested its value as a biomarker, reflecting changes in status in both depleted and replete individuals, although these changes were smaller in the latter. Total ceruloplasmin protein is related to copper status but reflects changes in highly depleted individuals only. Erythrocyte superoxide dismutase and urinary deoxypyridinoline are not useful biomarkers, but there were insufficient data to draw firm conclusions about plasma, erythrocyte, and platelet copper; leukocyte superoxide dismutase; erythrocyte, platelet, and plasma glutathione peroxidase; platelet and leukocyte cytochrome-c oxidase; total glutathione; diamine oxidase; and urinary pyridinoline. The paucity of data prevented detailed subgroup analysis.

CONCLUSIONS

Despite limited data, serum copper appears to be a useful biomarker of copper status at the population level. Further large studies with low risk of bias are needed to explore the effectiveness of other biomarkers of copper status and the relation between biomarker responsiveness, dose, and period of supplementation.

CCS and SOD1 mRNA are reduced after copper supplementation in peripheral mononuclear cells of individuals with high serum ceruloplasmin concentration

The limits of copper homeostatic regulation in humans are not known, making it difficult to define the milder effects of early copper excess. Furthermore, a robust assay to facilitate the detection of early stages of copper excess is needed. To address these issues, we assessed changes in relative mRNA abundance of methallothionein 2A (MT2A), prion (PrP), amyloid precursor-like protein 2 (APLP2), Cu/Zn superoxide dismutase (SOD1) and its copper chaperone (CCS) in peripheral mononuclear cells (PMNCs) from healthy adults representing the 5% highest and lowest extremes in the distribution curve of serum ceruloplasmin (Cp) concentrations of 800 individuals. The intracellular Cu content was also determined. PMNCs were isolated from individuals before and after exposure to a single daily dose of 10 mg Cu (as CuSO(4)) for 2 months. Results showed that although there were fluctuations in serum Cp values of the samples assessed before copper exposure, no significant differences were observed in cell copper content or in the relative abundance of MT2A, PrP and APLP2 transcripts in PMNCs. Also, these values were not modified after copper supplementation. However, CCS and SOD1 mRNA levels were reduced in PMNCs after copper supplementation in the individuals with the high Cp values, suggesting that they should be further explored as biomarkers of moderate copper overload in humans.

Assessment of some blood parameters as potential markers of hepatic copper accumulation in cattle

The increasing frequency of copper (Cu) toxicosis episodes in cattle in recent years, mainly associated with excess Cu supplementation, underscores the need to identify animals in the clinically silent phase of hepatic Cu accumulation. The aim of the study reported here was to evaluate the suitability of various blood parameters as potential early markers of hepatic Cu accumulation in cattle. Paired liver and blood samples from 70 calves aged 6 to 10 months were obtained at slaughter in a region in northwestern Spain where animals usually have hepatic Cu concentration higher than safe values. Neither serum Cu concentration nor ceruloplasmin (CP) concentration, the 2 parameters most commonly used for diagnosis of Cu deficiency, were significantly associated with hepatic Cu concentration. However, whole-blood Cu concentration had a slight but significant correlation with hepatic Cu concentration (r = 0.269, P = 0.026). The use of calculated blood parameters, such as the serum or whole-blood non-CP Cu fraction, or the CP-to-serum Cu ratio, increased the correlation with the hepatic Cu concentration (r = 0.393, P = 0.001, in the case of whole-blood, non-CP Cu concentration), but the strength of the association remained insufficient for accurate prediction of hepatic Cu values. Likewise, hepatic enzyme (aspartate transaminase and gamma-glutamyltransferase) activities were significantly or nearly correlated significantly with hepatic Cu concentration, but the strength of the association remained too low for accurate prediction. It is concluded that direct analysis of Cu concentration in liver biopsy specimens--preferably postmortem liver samples obtained at slaughter--is the best technique currently available for detecting chronic subclinical Cu accumulation in cattle at risk for supraoptimal Cu exposure.

The immune system as a physiological indicator of marginal copper status?

Cu appears to have many important functional roles in the body that apparently relate, among others, to the maintenance of immune function, bone health and haemostasis. Some have suggested a role for long-term marginal Cu deficiency in the aetiology of a number of degenerative diseases. Accurate diagnosis of marginal Cu deficiency, however, has remained elusive despite an increased understanding of the biochemistry of Cu and its physiological roles in the body. Traditional markers of Cu status, such as serum Cu and caeruloplasmin protein concentrations are insensitive to subtle changes in Cu status. Cu-containing enzymes, such as Cu–Zn-superoxide dismutase, cytochromecoxidase and diamine oxidase, may be more reliable but evidence to date is not conclusive. Development of markers sensitive to marginal Cu status is essential before conclusions can be drawn concerning the risks of long-term intake of suboptimal dietary Cu. As Cu appears to be essential for maintenance of immune function, activities of specific immunological markers, altered in Cu deficiency, offer alternatives. This review evaluates a selection of immunological markers that could be considered potentially sensitive markers of marginal Cu status. The indices of immune function reviewed are neutrophil function, interleukin 2 production, blastogenic response to mitogens and lymphocyte subset phenotyping.

Effect of copper supplementation on indices of copper status and certain CVD risk markers in young healthy women

Western diets containing suboptimal Cu concentrations could be widespread. A link between marginal Cu deficiency and CVD has been suggested. The objective of the present study was to investigate the effect of Cu supplementation on both Cu status and CVD risk factors in healthy young women. Sixteen women with a mean age of 24 (sd 2) years participated in a randomised crossover study of three 4-week periods with 3-week washouts between periods. During each intervention period, subjects received 0, 3 or 6 mg elemental Cu/d as CuSO4in addition to their habitual diet. Blood samples were taken to assess the effect of supplementation on putative markers of Cu status. The content of plasma lipids, lipoprotein (a), apo and certain haemostatic factors, as putative indices of CVD, was also analysed. Daily supplementation with 3 mg Cu significantly increased (P<0·05) serum Cu concentration and the activity of erythrocyte superoxide dismutase, although there was no further significant increase after an intake of 6 mg Cu/d. The concentration of the fibrinolytic factor plasminogen activator inhibitor type 1 was significantly reduced (P<0·05) by about 30% after supplementation with 6 mg Cu/d. No other marker of Cu status or CVD risk factor was affected by Cu supplementation. The results indicate that supplementation with 3 or 6 mg Cu/d may improve Cu status in these healthy young women. Increased Cu intake could reduce the risk of CVD and atherosclerosis in man by promoting improved fibrinolytic capacity.

In Long-Term Bedridden Elderly Patients with Dietary Copper Deficiency, Biochemical Markers of Bone Resorption Are Increased with Copper Supplementation during 12 Weeks

BACKGROUND

Although the effect of copper on bone has been tested in animals and healthy subjects, no studies concerning the effect of copper supplementation on bone metabolism in patients with copper deficiency have been reported because of the rarity of these patients. This study was conducted to investigate the effect of copper supplementation on bone metabolism in copper-deficient patients.

METHOD

This study included 10 patients (83.7 +/- 8.3 years) with dietary copper deficiency under long-term bed rest for more than 12 months. They had their diets supplemented with copper sulfate (3 mg/day) over 12 weeks in addition to their diet of only one kind of enteral food with a low concentration of copper. Serum copper and ceruloplasmin, urinary deoxypyridinoline (DPD) and collagen-type 1 N-telopeptide (NTX) (biomarkers of bone resorption), serum osteocalcin (OC) and bone-specific alkaline phosphatase (Bone ALP) (biomarkers of bone formation) were analyzed at baseline, 4 and 12 weeks after copper supplementation.

RESULTS

DPD and NTX excretion were significantly increased 4 weeks after copper supplementation (p = 0.009 and p = 0.013, respectively). Serum bone ALP and OC were not significantly changed 12 weeks after copper supplementation (p = 0.051 and p = 0.594).

CONCLUSIONS

In patients with nutritional copper deficiency, bone resorption markers are increased with copper supplementation.

Osteoporosis: the role of micronutrients

Osteoporosis and low bone mass are currently estimated to be a major public health threat. Adequate nutrition plays a major role in the prevention and treatment of osteoporosis; the micronutrients of greatest importance are calcium and vitamin D. Calcium has been shown to have beneficial effects on bone mass at all ages, although the results are not always consistent. Higher doses than the current US recommendation (600 IU) of vitamin D in the elderly (age > or = 65 y) may actually be required for optimal bone health (800-1000 IU/d). The elderly can clearly benefit from increased vitamin D intakes; however, the potential importance of vitamin D in peak bone mass is just being investigated. Vitamin D has been related to falls, with supplementation reducing the number of falls. There are clear fracture benefits demonstrated in randomized clinical trials of calcium and vitamin D supplementation. The other micronutrient needs for optimizing bone health can be easily met by a healthy diet that is high in fruits and vegetables to ensure adequate intakes for magnesium, potassium, vitamin C, vitamin K, and other potentially important nutrients. Healthcare professionals need to be aware of the importance of adequate calcium and vitamin D intakes (easily monitored by serum 25(OH)D) for optimal bone health, as well as the prevention of falls and fractures. In addition, a healthy diet that includes 5 servings a day of fruits and vegetables should optimize the intake of micronutrients required for bone health.

No effect of copper supplementation on biochemical markers of bone metabolism in healthy young adult females despite apparently improved copper status

OBJECTIVE

To investigate the effects of increasing Cu intakes, above the usual dietary intake, on biomarkers of bone metabolism in healthy young adult females (aged 21-28 y) over a 4 week period.

DESIGN

A double-blind, placebo-controlled randomised repeat crossover Cu supplementation trial.

SETTING

The study was conducted at the Royal Veterinary and Agricultural University (RVAU), Copenhagen, Denmark.

SUBJECTS

Sixteen healthy young adult females aged 20-28 y were recruited from among students at the RVAU.

INTERVENTION

During the 4 week intervention periods in this randomised, crossover trial (3x4 weeks with a minimum 3 week wash-out period), each subject received, in addition to their usual diet, either 3 or 6 mg elemental Cu/day as CuSO4 or a matching placebo. On the last 3 days of each dietary period 24 h urines were collected. In addition, blood was collected on the last day of each dietary period.

RESULTS

Serum Cu and erythrocyte superoxide dismutase (but not caeruloplasmin protein concentration or activity (putative indices of Cu status)) were significantly increased (P<0.05) after daily Cu supplementation with 3 and 6 mg/day for 4 weeks. Serum osteocalcin (biomarker of bone formation), urinary creatinine (Cr) concentration, urinary pyridinoline (Pyr)/Cr or deoxypyridinoline (Dpyr)/Cr excretion, or daily urinary Pyr or Dpyr excretion (biomarkers of bone resorption) were unaffected by Cu supplementation.

CONCLUSION

Copper supplementation of the usual diet in healthy young adult females, while apparently improving Cu status, had no effect on biochemical markers of bone formation or bone resorption over 4 week periods.

SPONSORSHIP

Funding from the European Commission.