Copper:caeruloplasmin ratio

Non-Ceruloplasmin Copper Identifies a Subtype of Alzheimer’s Disease (CuAD): Characterization of the Cognitive Profile and Case of a CuAD Patient Carrying an RGS7 Stop-Loss Variant

Alzheimer’s disease (AD) is a type of dementia whose cause is incompletely defined. Copper (Cu) involvement in AD etiology was confirmed by a meta-analysis on about 6000 participants, showing that Cu levels were decreased in AD brain specimens, while Cu and non-bound ceruloplasmin Cu (non-Cp Cu) levels were increased in serum/plasma samples. Non-Cp Cu was advocated as a stratification add-on biomarker of a Cu subtype of AD (CuAD subtype). To further circumstantiate this concept, we evaluated non-Cp Cu reliability in classifying subtypes of AD based on the characterization of the cognitive profile. The stratification of the AD patients into normal AD (non-Cp Cu ≤ 1.6 µmol/L) and CuAD (non-Cp Cu > 1.6 µmol/L) showed a significant difference in executive function outcomes, even though patients did not differ in disease duration and severity. Among the Cu-AD patients, a 76-year-old woman showed significantly abnormal levels in the Cu panel and underwent whole exome sequencing. The CuAD patient was detected with possessing the homozygous (c.1486T > C; p.(Ter496Argext*19) stop-loss variant in the RGS7 gene (MIM*602517), which encodes for Regulator of G Protein Signaling 7. Non-Cp Cu as an add-on test in the AD diagnostic pathway can provide relevant information about the underlying pathological processes in subtypes of AD and suggest specific therapeutic options.

Non-Ceruloplasmin Copper as a Stratification Biomarker of Alzheimer's Disease Patients: How to Measure and Use It

Alzheimer's disease (AD) is a type of dementia very common in the elderly. A growing body of recent evidence has linked AD pathogenesis to copper (Cu) dysmetabolism in the body. In fact, a subset of patients affected either by AD or by its prodromal form known as Mild Cognitive Impairment (MCI) have been observed to be unable to maintain a proper balance of Cu metabolism and distribution and are characterized by the presence in their serum of increased levels of Cu not bound to ceruloplasmin (non-ceruloplasmin Cu). Since serum non-ceruloplasmin Cu is a biomark- er of Wilson's disease (WD), a well-known condition of Cu-driven toxicosis, in this review, we pro- pose that in close analogy with WD, the assessment of non-ceruloplasmin Cu levels can be exploit- ed as a cost-effective stratification and susceptibility/risk biomarker for the identification of some AD/MCI individuals. The approach can also be used as an eligibility criterion for clinical trials aim- ing at investigating Cu-related interventions against AD/MCI.

Copper Imbalance in Alzheimer's Disease: Meta-Analysis of Serum, Plasma, and Brain Specimens, and Replication Study Evaluating ATP7B Gene Variants

Evidence indicates that patients with Alzheimer's dementia (AD) show signs of copper (Cu) dyshomeostasis. This study aimed at evaluating the potential of Cu dysregulation as an AD susceptibility factor. We performed a meta-analysis of 56 studies investigating Cu biomarkers in brain specimens (pooled total of 182 AD and 166 healthy controls, HC) and in serum/plasma (pooled total of 2929 AD and 3547 HC). We also completed a replication study of serum Cu biomarkers in 97 AD patients and 70 HC screened for rs732774 and rs1061472 ATP7B, the gene encoding for the Cu transporter ATPase7B. Our meta-analysis showed decreased Cu in AD brain specimens, increased Cu and nonbound ceruloplasmin (Non-Cp) Cu in serum/plasma samples, and unchanged ceruloplasmin. Serum/plasma Cu excess was associated with a three to fourfold increase in the risk of having AD. Our replication study confirmed meta-analysis results and showed that carriers of the ATP7B AG haplotype were significantly more frequent in the AD group. Overall, our study shows that AD patients fail to maintain a Cu metabolic balance and reveals the presence of a percentage of AD patients carrying ATP7B AG haplotype and presenting Non-Cp Cu excess, which suggest that a subset of AD subjects is prone to Cu imbalance. This AD subtype can be the target of precision medicine-based strategies tackling Cu dysregulation.

Single nucleotide polymorphisms in the human ATP7B gene modify the properties of the ATP7B protein

Single nucleotide polymorphisms (SNPs) are the largest source of sequence variation in the human genome. However, their functional significance is not well understood. We show that SNPs in the Wilson disease gene, ATP7B, that produce amino-acid substitutions K832R and R952K, modulate ATP7B properties in vitro and influence serum copper (Cu) status in vivo. The presence of R832 is associated with a lower ATP7B abundance and a diminished trafficking in response to elevated Cu. The K832R substitution alters surface exposure of amino acid residues in the actuator domain and increases its conformational flexibility. All SNP-related ATP7B variants (R832/R952, R832/K952, K832/K952, and K832/R952) have Cu-transport activity. However, the activity of ATP7B-K832/K952 is lower compared to other variants. In humans, the presence of K952 is associated with a higher fraction of exchangeable Cu in serum. Thus, SNPs may modulate the properties of ATP7B and the organism Cu status.

Serum Copper is not Altered in Frontotemporal Lobar Degeneration

Meta-analyses show copper dyshomeostasis in Alzheimer's disease. However, a study evaluating copper changes in other neurodegenerative forms of dementia has not yet been performed. In this study, we assessed copper, ceruloplasmin, copper not bound to ceruloplasmin, and copper to ceruloplasmin ratio in 85 patients affected by frontotemporal lobar degeneration (FTLD) and 55 healthy controls. Data were analyzed through multivariate ANOVA models taking into account age and sex as covariates and the stratification for FTLD variants, after calculating power analysis to ensure the reliability of the conclusions drawn. The study revealed no difference between the groups.

Oxidative Stress Related to Iron Metabolism in Relapsing Remitting Multiple Sclerosis Patients With Low Disability

Oxidative status may play a role in chronic inflammation and neurodegeneration which are considered critical etiopathogenetic factors in Multiple Sclerosis (MS), both in the early phase of the disease and in the progressive one. The aim of this study is to explore oxidative status related to iron metabolism in peripheral blood of stable Relapsing-Remitting MS with low disability. We studied 60 Relapsing-Remitting MS patients (age 37.2 ± 9.06, EDSS median 1.0), and 40 healthy controls (age 40.3 ± 10.86). We measured total hydroperoxides (dROMs test) and Total Antioxidant Status (TAS), along with the iron metabolism biomarkers: Iron (Fe), ferritin (Ferr), transferrin (Tf), transferrin saturation (Tfsat), and ceruloplasmin (Cp) panel biomarkers [concentration (iCp) and enzymatic activity (eCp), copper (Cu), ceruloplasmin specific activity (eCp:iCp), copper to ceruloplasmin ratio (Cu:Cp), non-ceruloplasmin copper (nCp-Cu)]. We computed also the Cp:Tf ratio as an index of oxidative stress related to iron metabolism. We found lower TAS levels in MS patients than in healthy controls (CTRL) and normal reference level and higher dROMs and Cp:Tf ratio in MS than in healthy controls. Cp and Cu were higher in MS while biomarkers of iron metabolism were not different between patients and controls. Both in controls and MS, dROMs correlated with iCp (CTRL r = 0.821, p < 0.001; MS r = 0.775 p < 0.001) and eCp (CTRL r = 0.734, p < 0.001; MS r = 0.820 p < 0.001). Moreover, only in MS group iCp correlated negatively with Tfsat (r = -0.257, p = 0.047). Dividing MS patients in “untreated” group and “treated” group, we found a significant difference in Fe values [F(2, 97) = 10.136, p < 0.001]; in particular “MS untreated” showed higher mean values (mean = 114.5, SD = 39.37 μg/dL) than CTRL (mean 78.6, SD = 27.55 μg/dL p = 0.001) and “MS treated” (mean = 72.4, SD = 38.08 μg/dL; p < 0.001). Moreover, “MS untreated” showed significantly higher values of Cp:Tf (mean = 10.19, SD = 1.77^∗10^-2; p = 0.015), than CTRL (mean = 9.03, SD = 1.46 ^∗10^-2). These results suggest that chronic oxidative stress is relevant also in the remitting phase of the disease in patients with low disability and short disease duration. Therefore, treatment with antioxidants may be beneficial also in the early stage of the disease to preserve neuronal reserve.

Copper dyshomeostasis in Wilson disease and Alzheimer's disease as shown by serum and urine copper indicators

Abnormal handling of copper is the cause of Wilson disease (WD), a rare disorder typified by increased levels in plasma copper not-bound to ceruloplasmin (nCp-Cu, also known as 'free' copper). In Alzheimer's disease (AD), meta-analyses show that copper decreases in brain but increases in serum, due to the nCp Cu component increase. Despite the similarities, a direct comparison of copper biological status in the two diseases has never been carried out. To fill this gap, we evaluated serum copper, ceruloplasmin, nCp-Cu and Cu:Cp in 385 CE and 336 healthy controls previously investigated that were compared with 9 newly diagnosed WD patients. We then assessed 24h copper urinary excretion in 24 WD patients under D-penicillamine (D-pen) treatment and in 35 healthy controls, and compared results with those of AD patients participating to a D-pen phase II clinical trial previously published. After adjusting for sex and age, serum nCp-Cu and Cu:Cp resulted higher in AD and in WD than in healthy controls (both p<0.001). While nCp-Cu was similar between AD and WD, Cu:Cp was higher in WD (p<0.016). 24h urinary copper excretion in AD patients (12.05μg/day) was higher than in healthy controls (4.82μg/day; p<0.001). 77.8% of the AD patients under D-pen treatment had a 24h urinary excretion higher than 200μg/day, suggestive of a failure of copper control. This study provides new insight into the pathophysiology of copper homeostasis in AD, showing a failure of copper control and the Cu:Cp ratio as an eligible marker.

Caeruloplasmin oxidase activity: measurement in serum by use of o-dianisidine dihydrochloride on a microplate reader

Background The enzymatic method of caeruloplasmin measurement is based on copper-dependent oxidase activity. The advantage of the oxidase determination is that it has a much lower detection limit compared with immunoassay-based methods. It has found its application in both the diagnosis of Wilson's disease and also in the monitoring of patients' response to treatment. Methods The method previously described in literature was adapted for use on a 96-well plate. Caeruloplasmin oxidase activity results were derived from the equation: caeruloplasmin oxidase activity = (A₁₅-A₅) × 185 U/L. Results Repeatability (intra-batch) imprecision ranged from 6 to 15% and intermediate (inter-batch) imprecision varied from 7 to 16% for caeruloplasmin oxidative activities of 14, 29, 45 and 99 U/L. Between 3 and 92 U/L, the assay appeared linear with a regression coefficient R²= 0.9958. The lower limit of quantification was 4 U/L. Samples were stable over a five-week period at 4℃ and for at least four freeze-thaw cycles. There was a statistically significant difference between the areas under ROC curve for copper-to-caeruloplasmin ratios between caeruloplasmin oxidative activity and immunoassay-based methods ( P < 0.0171). The reference interval for caeruloplasmin activity was determined to be 12-166 U/L. Conclusions Using the oxidative assay provides a cost-effective means of estimating caeruloplasmin concentrations. The method is easily adaptable to a 96-well plate format that facilitates high throughput of samples in a busy laboratory. The enzymatic method is more sensitive and specific for differentiating between Wilson's and non-Wilson's when compared with immunoassay-based methods.

Measurement of urinary copper excretion after 48-h d-penicillamine cessation as a compliance assessment in Wilson's disease

Treatment of Wilson's disease (WD) with anti-copper agents is effective in most compliant patients. During long-term treatment with chelating agents, a two-day interruption of the treatment should result in normal urinary copper concentrations (<50 μg/dl). The aim of this study was to establish the usefulness of this method as a compliance assessment in these patients. We examined consecutive patients treated with d-penicillamine (DPA) undergoing routine follow-up studies at our center. We performed 24-h urinary copper excretion analysis 48 h after interruption of chelating therapy. Thirty-two patients were enrolled. After DPA cessation, normalization of copper excretion was observed in 91% of reportedly compliant patients. The specificity and sensitivity values of this test were 87% and 77%, respectively. Measurement of 24-h urinary copper excretion after a 48-h interruption of DPA therapy in patients with WD is a reliable method for confirming patients' compliance.

The effect of copper from water and food: changes of serum nonceruloplasmin copper and brain's amyloid-beta in mice

Copper is an essential element and also produces adverse health consequences when overloaded. Food and water are the main sources of copper intake, however few studies have been conducted to investigate the difference between the ways of its intake in water and food in animals. In this study, copper was fed to mice with food as well as water (two groups: water and diet) for three months at concentrations of 6, 15 and 30 ppm. The copper concentration in water was adjusted for keeping the same amount during its intake in food. The experimental studies show a slow growth rate, lower hepatic reduced glutathione (GSH)/superoxide dismutase (SOD) activity and higher serum 'free' copper in the water group. The brain's soluble amyloid-beta 1-42 (Aβ42) of the water group was significantly higher than that of the diet group at the levels of 6 and 15 ppm. In conclusion, copper in the water group significantly increased the soluble Aβ42 in the brain and the 'free' copper in the serum, decreased the growth rate and hepatic GSH/SOD activity. The research studies carried out suggest that the copper in water is more 'toxic' than copper in diet and may increase the risk of Alzheimer's disease (AD).

Erythrocyte indices, microminerals and ratios, antioxidants and lipids in Centrum Materna diet-supplemented Omani mothers

Venous (maternal) and cord blood (neonatal) samples of Omani women who had a daily supplement of Centrum Materna multivitamin and multimineral tablet throughout pregnancy were investigated at late preterm (n=37) and at term (n=37) delivery for erythrocyte indices, micromineral, antioxidant, and lipid values. Hemoglobin (Hb), hematocrit (HCT), mean cell volume (MCV), red cell distribution width (RDW), copper (Cu), zinc (Zn), ceruloplasmin, erythrocyte Cu-Zn superoxide dismutase (Cu-Zn SOD), cholesterol, apolipoprotein (apo) A-I and apo B were measured by appropriate analytical systems. Cu/zinc and Cu/ceruloplasmin ratios were calculated. The erythrocyte indices were normal in neonatal blood but showed borderline anemia in maternal blood of both groups. There were significantly decreased values of Cu (P=0.012), Zn (P=0.001), apo A-I (P=0.029), and Cu/ceruloplasmin ratio (P=0.032) in late preterm compared to term mothers. Significantly decreased values of Cu (P=0.003), ceruloplasmin (P<0.0001), apo A-I (P=0.024), and Cu/Zn ratio (P=007) were observed in late preterm relative to term neonates. Late preterm mothers were significantly younger (P=0.027) than term mothers. Maternal age correlated positively with apo A-I (r=0.424, P=0.012) and negatively with Cu/Zn ratio (r=-0.353, P=0.040). The findings suggest that with daily dietary Centrum Materna supplementation throughout pregnancy, hematological indices were maintained within normal in mothers and neonates, but the levels of microminerals and micromineral ratios were subnormal in late preterm mothers and their neonates.

The relationship between serum copper and ceruloplasmin in routine clinical practice

INTRODUCTION

The biochemical assessment of copper status is not easy when investigating deficient and excess states. Most clinicians request copper and ceruloplasmin and assume that the results provided by their local laboratory are comparable with data in the literature.

AIMS AND METHODS

We decided to obtain paired copper and ceruloplasmin values retrospectively from the laboratory information systems from three different hospital laboratories to see how the relationships compared. Descriptive statistics and the relationship between caeruloplasmin and copper were obtained.

RESULTS

Our data shows differences in the relationship (slope, intercept and correlation co-efficient) between copper and ceruloplasmin; this is especially the case at the clinical cut-off of a ceruloplasmin concentration of 200 mg/l.

CONCLUSION

Differing methods or populations may be contributing to the differences between the data sets. We therefore recommend that local cut-offs are derived for the investigation of copper deficiency and excess states.