Copper deficiency alters plasma pool size, percent composition and concentration of lipoprotein components in rats

Copper status and its relation to abdominal obesity indices and liver function in non-alcoholic fatty liver disease: a case-control study

OBJECTIVE

This study investigated copper (Cu) status in relation to abdominal obesity indices and liver function in patients with non-alcoholic fatty liver disease (NAFLD). This case-control study was carried out on 80 overweight/obese patients with NAFLD and 80 apparently healthy age, sex, and body mass index (BMI)-matched controls. A validated and reliable 168-item semi-quantitative food frequency questionnaire was completed for each subject and fasting serum levels of liver aminotransferases, ferritin, Cu and ceruloplasmin were assessed.

RESULTS

Mean intakes of energy and carbophydrate were significantly lower in patients with NAFLD than the control group while mean protein intake was highre (p < 0.05). Although mean Cu intake was greater in cases than controls, low dietary intake of Cu was found in 7.5% and 32.5% of the cases and controls, respectively. Apart from serum levels of liver aminotransferases (p < 0.001) and ferritin (p = 0.010), no significant differences were found in serum levels of Cu and ceruloplasmin. Serum and dietary Cu were positively correlated with obesity indices and serum ceruloplasmin was correlated with waist to height ratio and ferritin only in cases (p < 0.05). Low Cu intake (< 0.95 mg/day) was more likely to increase the odds of NAFLD (p for trend = 0.002), after adjusting for potential confounders.

Intermittent hypoxia exacerbates metabolic dysfunction-associated fatty liver disease by aggravating hepatic copper deficiency-induced ferroptosis

Intermittent hypoxia (IH) is an independent risk factor for metabolic dysfunction-associated fatty liver disease (MAFLD). Copper deficiency can disrupt redox homeostasis, iron, and lipid metabolism. Here, we investigated whether hepatic copper deficiency plays a role in IH-associated MAFLD and explored the underlying mechanism(s). Male C57BL/6 mice were fed a western-type diet with adequate copper (CuA) or marginally deficient copper (CuD) and were exposed separately to room air (RA) or IH. Hepatic histology, plasma biomarkers, copper-iron status, and oxidative stress were assessed. An in vitro HepG2 cell lipotoxicity model and proteomic analysis were used to elucidate the specific targets involved. We observed that there were no differences in hepatic phenotypes between CuA-fed and CuD-fed mice under RA. However, in IH exposure, CuD-fed mice showed more pronounced hepatic steatosis, liver injury, and oxidative stress than CuA-fed mice. IH induced copper accumulation in the brain and heart and exacerbated hepatic copper deficiency and secondary iron deposition. In vitro, CuD-treated cells with IH exposure showed elevated levels of lipid accumulation, oxidative stress, and ferroptosis susceptibility. Proteomic analysis identified 360 upregulated and 359 downregulated differentially expressed proteins between CuA and CuD groups under IH; these proteins were mainly enriched in citrate cycle, oxidative phosphorylation, fatty acid metabolism, the peroxisome proliferator-activated receptor (PPAR)α pathway, and ferroptosis. In IH exposure, CuD significantly upregulated the ferroptosis-promoting factor arachidonyl-CoA synthetase long chain family member (ACSL)4. ACSL4 knockdown markedly eliminated CuD-induced ferroptosis and lipid accumulation in IH exposure. In conculsion, IH can lead to reduced hepatic copper reserves and secondary iron deposition, thereby inducing ferroptosis and subsequent MAFLD progression. Insufficient dietary copper may worsen IH-associated MAFLD.

Exploring the Regulatory Effect of LPJZ-658 on Copper Deficiency Combined with Sugar-Induced MASLD in Middle-Aged Mice Based on Multi-Omics Analysis

Globally, metabolic dysfunction-associated steatotic liver disease (MASLD), previously termed nonalcoholic fatty liver disease (NAFLD), is one of the most common liver disorders and is strongly associated with copper deficiency. To explore the potential effects and mechanisms of Lactiplantibacillus plantarum LPJZ-658, copper deficiency combined with a high-sugar diet-induced MASLD mouse model was utilized in this study. We fed 40-week-old (middle-aged) male C57BL/6 mice a copper-deficient and high-sugar diet for 16 weeks (CuDS), with supplementary LPJZ-658 for the last 6 weeks (CuDS + LPJZ-658). In this study, we measured body weight, liver weight, and serum biochemical markers. Lipid accumulation, histology, lipidomics, and sphingolipid metabolism-related enzyme expression were investigated to analyze liver function. Untargeted metabolomics was used to analyze the serum and the composition and abundance of intestinal flora. In addition, the correlation between differential liver lipid profiles, serum metabolites, and gut flora at the genus level was measured. The results show that LPJZ-658 significantly improves abnormal liver function and hepatic steatosis. The lipidomics analyses and metabolic pathway analysis identified sphingolipid, retinol, and glycerophospholipid metabolism as the most relevant metabolic pathways that characterized liver lipid dysregulation in the CuDS group. Consistently, RT-qPCR analyses revealed that the enzymes catalyzing sphingolipid metabolism that were significantly upregulated in the CuDS group were downregulated by the LPJZ-658 treatment. In addition, the serum metabolomics results indicated that the linoleic acid, taurine and hypotaurine, and ascorbate and aldarate metabolism pathways were associated with CuDS-induced MASLD. Notably, we found that treatment with LPJZ-658 partially reversed the changes in the differential serum metabolites. Finally, LPJZ-658 effectively regulated intestinal flora abnormalities and was significantly correlated with differential hepatic lipid species and serum metabolites. In conclusion, we elucidated the function and potential mechanisms of LPJZ-658 in alleviating copper deficiency combined with sugar-induced middle-aged MASLD and hope this will provide possible treatment strategies for improving MASLD.

Effect of High Molybdenum Diet on Copper Status, Growth Performance, Blood Metabolites, Select Liver and Kidney Minerals, and Immune Responses of Boer Crosses

This study examined the effects of elevated molybdenum (Mo) in goat diets on the growth, blood parameters, and immune responses in goats. Eighteen Boer crosses goats (BW = 25.6 ± 1.03 kg) were randomly assigned to three treatment groups: (1) control (no additional Mo), (2) 5 ppm Mo, and (3) 10 ppm Mo as ammonium molybdate was added to the grain mix. Animals were fed a 50:50 hay:grain diet ad libitum twice daily. Daily feed refusals were monitored, and intake was adjusted weekly. Body weights were recorded every 14 days and blood samples were collected on the second week of every month to determine Cu, Mo, Fe, Zn, and other blood metabolites. After 85 days, animals were humanely euthanized and carcass traits were measured. Liver, longissimus muscle area, and kidney samples were collected postmortem. Liver Cu (p < 0.003), blood triacylglycerides (p < 0.03), and serum total protein (p < 0.03) levels were reduced; the liver (p = 0.07) and kidney (p < 0.001) Mo concentrations were increased; and the immune response was decreased linearly (p < 0.01) with additional Mo. Low levels of Cu with increasing Mo levels in the diet did not negatively impact animal performance or blood metabolites, in the duration of this study (85 days); however, it lowered the liver Cu, Fe, and immune responses in goats.

A cross-sectional analysis of zinc and copper levels and their relationship to cardiovascular disease risk markers in Qatar biobank participants

Cardiovascular diseases (CVD) are the leading cause of mortality and morbidity worldwide. Dietary intake, particularly zinc (Zn) and copper (Cu) has been strongly associated with CVD. These trace elements play a crucial role in human enzyme activity, suppressing inflammation, catalyzing lipid metabolism enzymes, reducing oxidative stress, and regulating glucose metabolism. However, imbalances in these elements are linked to cardiovascular disturbances. Thus, this study aimed to investigate the association between circulating levels of Zn, Cu, and Zn/Cu ratio with CVD risk factors in the Qatari population. Bivariate logistic regression, adjusted for age, nationality, gender, and education was performed to examine the impact of Zn, Cu, and Zn/Cu ratio (as independent variables) on major CVD risk markers (as dependent variables). Participants in the highest Zn tertiles (T2 and T3) were at greater odds ratio (OR) of unfavorable metabolic functions such as elevated HbA1C [OR = 2.5, p = 0.015 (T2) and OR = 3.2, p = 0.002 (T3)], triglycerides [OR = 2.17, p = 0.015 (T2), and TyG index [OR = 2.21, p = 0.004 (T2), and OR = 2.67, p < 0.001 (T3)] compared to T1. Conversely, they had significantly lower ORs for prolonged prothrombin time [OR = 0.37, p = 0.001 (T3)]. Higher levels of Cu (T2 and T3) had higher OR for elevated HDL-C levels [OR = 1.69, p = 0.046 (T2), and OR = 2.27, p = 0.002 (T3)] and lower OR for elevated levels of triglycerides (OR = 0.4, p = 0.009, T3), diastolic blood pressure [OR = 0.41, p = 0.024 (T2), and OR = 0.47, p = 0.049 (T3)], and creatinine kinase (OR = 0.27, p = 0.014, T3) compared to T1. Higher levels of Cu (T2 and T3) were associated with a higher risk for elevated fibrinogen levels [OR = 3.1, p = 0.035 (T2), and OR = 5.04, p = 0.002 (T3)]. Additionally, higher Zn/Cu ratio (T2 and T3) were associated with lower ORs for elevated fibrinogen levels [OR = 0.3, p = 0.005 (T2), and OR = 0.27, p = 0.005 (T3)] compared to T1, indicating a lower risk of developing CVD. The study reveals a link between Zn, Cu, and the Zn/Cu ratio and cardiovascular disease risk. A higher Zn/Cu ratio may protect against CVD, while elevated Cu levels are linked to obesity, fibrinogen levels, and HbA1C. Maintaining optimal levels of these trace elements, either through diet or supplementation, may help reduce CVD risk.

BMI Modifies the Association Between Depression Symptoms and Serum Copper Levels

Depression is one of the most common mental disorders which dramatically threatens public health and wellness. Copper has been known to be involved in many biological processes that could help explaining the occurrence of depression. However, studies focusing on its effect have yielded mixed results. The present study aims to evaluate the association between serum copper levels and depression symptoms. It also investigates the effect of modification of BMI (body mass index) on depression symptoms. A total of 5419 US adults aged 20 years or older from the National Health and Nutrition Examination Survey (NHANES) 2011-2016 participated in the cross-sectional study. Logistic regression models were applied using depression levels as the outcome and serum cooper/selenium/zinc categories as the main predictor, with the adjustments of gender, age, marital status, race, education, family income level, alcohol drinking, cigarette smoking, diabetes, pressure, stroke, and BMI. The interaction terms for copper levels and other covariates were further incorporated into the model to assess their roles in predicting depression symptoms. The prevalence of depression symptoms was significantly higher in samples with a high copper level. Among the levels of serum copper, selenium, and zinc, only the association between depression symptoms and serum copper levels was observed to be significant in the unadjusted model (P = 0.002). Individuals with a high copper level (114-134 μg/dL) and a very high copper level (≥ 134 μg/dL) had 1.85 (95% CI 1.24, 2.77)- and 1.72 (95% CI 1.21, 2.44)-fold higher odds ratio of depression symptoms, respectively, compared to those with a normal serum copper level. Although the association was not significant in the adjusted models, in which confounders were added, the interaction of copper level, including high and very high copper levels, and obesity (BMI ≥ 30 kg/m²) exhibited significantly higher odds ratio (4.12 (95% CI 1.38, 12.27) and 4.53 (95% CI 1.87, 10.96)) of having depression symptoms. The concentration of serum copper was positively associated with the prevalence of depression symptoms. Obesity exacerbated the risk of having depression symptoms in people with high serum copper levels.

Serum copper, ceruloplasmin, and their relations to metabolic factors in nonalcoholic fatty liver disease: a cross-sectional study

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) characterized by excessive intrahepatic fat accumulation is increasing worldwide. This study aimed to investigate serum copper (Cu) and ceruloplasmin (Cer) levels and their relations to metabolic factors in NAFLD.

METHODS

This cross-sectional study was conducted on 141 subjects with NAFLD diagnosed using abdominal ultrasonography. Personal information, anthropometric measures, glucose and lipid profile, and serum levels of liver enzymes were assessed. Fasting serum levels of Cu and Cer were determined using colorimetry and nephelometry assay, respectively. Odds ratios (ORs) were used to examine the associations of serum Cu and Cer levels with NAFLD risk.

RESULTS

The results on 85 patients with NAFLD and 56 apparently healthy participants showed that all NAFLD cases and 53.6% of the healthy subjects were overweight or obese. More than half of the patients (58.8%) showed mild NAFLD. Age, weight, BMI, lipid profile, uric acid, and ferritin were significantly higher in NAFLD patients than the healthy cases. No significant differences were found in the concentrations of Cu and Cer between the groups. Only 7.4% of the healthy subjects and 2.4% of the patients were Cu deficient (<70 µg/dl). No association was found between the risk of NAFLD and serum Cu [OR: 0.994; 95% confidence interval (CI): 0.981-1.006] and Cer levels (OR: 0.414; 95% CI: 0.001-123.604) after adjusting for the confounders.

CONCLUSION

Our findings revealed no association between Cu deficiency and NAFLD risk. Further human studies with larger sample sizes are required to investigate how Cu and Cer status may affect NAFLD.

An Emerging Role of Defective Copper Metabolism in Heart Disease

Copper is an essential trace metal element that significantly affects human physiology and pathology by regulating various important biological processes, including mitochondrial oxidative phosphorylation, iron mobilization, connective tissue crosslinking, antioxidant defense, melanin synthesis, blood clotting, and neuron peptide maturation. Increasing lines of evidence obtained from studies of cell culture, animals, and human genetics have demonstrated that dysregulation of copper metabolism causes heart disease, which is the leading cause of mortality in the US. Defects of copper homeostasis caused by perturbed regulation of copper chaperones or copper transporters or by copper deficiency resulted in various types of heart disease, including cardiac hypertrophy, heart failure, ischemic heart disease, and diabetes mellitus cardiomyopathy. This review aims to provide a timely summary of the effects of defective copper homeostasis on heart disease and discuss potential underlying molecular mechanisms.

Dietary Cholesterol Supplements Disturb Copper Homeostasis in Multiple Organs in Rabbits: Aorta Copper Concentrations Negatively Correlate with the Severity of Atherosclerotic Lesions

Dietary cholesterol causes atherosclerosis along with a reduction of copper concentrations in the atherosclerosis wall. This study was to determine the relationship between aorta copper concentrations and the severity of atherosclerotic lesions as well as copper homeostasis in multiple organs in cholesterol-fed rabbits. Male New Zealand white rabbits, 10-week-old and averaged 2.0 kg, were fed a diet containing 1% (w/w) cholesterol or the same diet without cholesterol as controls. Twelve weeks after the feeding, aortic atherosclerotic lesions, serum cholesterol, and multiple organ copper concentrations were measured. Compared to controls, rabbits fed cholesterol-supplemented diet displayed higher serum cholesterol levels and developed atherosclerosis. Copper concentrations in the cholesterol-fed rabbits were increased in the serum and kidney but decreased in the atherosclerosis wall and multiple organs, including heart, liver, spleen, and lung. Furthermore, aorta copper concentrations negatively correlated, respectively, with the severity of the atherosclerotic lesion (r = - 0.64, p = 0.01), the microscope atherosclerotic lesion area (r = - 0.60, p = 0.02), and the stenosis of the lumen (r = - 0.54, p = 0.04). Dietary cholesterol not only causes atherosclerosis but also disturbs copper homeostasis in multiple organ systems. The negative correlation between aorta copper concentrations and the severity of atherosclerotic lesions suggests a vicious cycle between copper reduction and the pathogenesis of atherosclerosis. These changes in copper homeostasis would be additive to atherosclerosis as a risk factor for cardiovascular disease in humans.

The Association between Zinc and Copper Circulating Levels and Cardiometabolic Risk Factors in Adults: A Study of Qatar Biobank Data

Cardiometabolic risk (CMR) factors increase the likelihood of developing cardiovascular diseases (CVD). In Qatar, 24% of the total deaths are attributed to CVDs. Several nutritional disturbances have been linked to high risk of CVD. Many studies have discussed the effects of zinc (Zn) and copper (Cu) on CMR factors; however, evidence has been controversial. This investigated the association between CMR factors and the status of Zn and Cu, in addition to Zn/Cu ratio. A total of 575 Qatari men and women aged 18 years and older were obtained from Qatar Biobank. Plasma levels of Zn and Cu were determined using inductively coupled plasma mass spectrometry (ICP-MS). Anthropometric data and CMR factors were determined using standard methods. Adjusted associations between trace minerals and CMR were estimated by logistic regression. Partial correlation was performed to test the strength of the associations. Zn was not strongly correlated (p-value ˃ 0.01) or significantly associated with CMR factors and metabolic syndrome (MetS). Cu levels correlated positively with body mass index (BMI) (0.23; p ˂ 0.001), pulse rate (PR) (0.18; p ˂ 0.001), total cholesterol (0.13; p = 0.01), and high-density lipoproteins (HDL) (0.27; p ˂ 0.001); and negatively with diastolic blood pressure (DBP) (−0.13; p = 0.01). High plasma Cu significantly decreased the risk of metabolic syndrome (MetS) (0.121; p ˂ 0.001). Furthermore, Zn/Cu ratio positively correlated with waist circumference (0.13; p = 0.01), systolic blood pressure (0.13; p ˂ 0.01), and DBP (0.14; p ˂ 0.01); and negatively with BMI (−0.19; p ˂ 0.001), PR (−0.17; p ˂ 0.001), and HDL (−0.27; p ˂ 0.001). High Zn/Cu ratio increased the prevalence of low HDL (4.508; p ˂ 0.001) and MetS (5.570; p ˂ 0.01). These findings suggest that high plasma Cu levels are associated with a protective effect on DBP, HDL and MetS and that high plasma Zn/Cu ratio is associated with the risk of having low HDL and MetS.

DISTINCT PHENOTYPE OF NON-ALCOHOLIC FATTY LIVER DISEASE IN PATIENTS WITH LOW LEVELS OF FREE COPPER AND OF CERULOPLASMIN

BACKGROUND

Copper deficiency has been linked to alterations in lipid metabolism and hepatic steatosis. Oxidative stress plays a role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). One of the enzymes that neutralize oxidative stress is Cu/Zn superoxide dismutase, which depends on the availability of adequate amounts of copper.

OBJECTIVE

Correlate the levels of ceruloplasmin and of non-ceruloplasmin-bound copper (NCBC) with clinical, biochemical and histological parameters of non-alcoholic fatty liver disease (NAFLD) patients.

METHODS

Data from 95 consecutively admitted NAFLD patients who underwent liver biopsy composed the groups based on ceruloplasmin levels lower than 25 mg/dL and on negative NCBC. The risk factors for NAFLD in each group were compared.

RESULTS

Body mass index was lower in patients with ceruloplasmin <25 mg/dL (29.1±3.47 vs 32.8±6.24 kg/m2; P=0.005) as were the levels of LDL, HDL and total cholesterol, when compared with their counterparts with ceruloplasmin >25 mg/dL (101±38 vs 116±35 mg/dL, P=0.05; 43±9 vs 51±16 mg/dL, P=0.01; 174±43 vs 197±39 mg/dL, P=0.01, respectively). Mean serum ferritin levels were higher in the ceruloplasmin <25 mg/dL group (343±327 vs 197±190 ng/mL; P=0.02). Otherwise, patients with negative NCBC had higher HOMA-IR (8.2±14.7 vs 4.6±3.7; P=0.03). Age, gender, hypertension and diabetes showed no statistical difference.

CONCLUSION

Patients with NAFLD had different clinical and biochemical markers according to the levels of NCBC and ceruloplasmin.

Dietary Copper Plays an Important Role in Maintaining Intestinal Barrier Integrity During Alcohol-Induced Liver Disease Through Regulation of the Intestinal HIF-1α Signaling Pathway and Oxidative Stress

Impaired intestinal barrier function and oxidative stress injury play critical roles in the pathogenesis of alcoholic liver disease (ALD), and recent investigations have revealed a role for dietary copper in the liver and intestinal barrier function. Therefore, the current study investigates the mechanisms and role of dietary copper in alcohol induced liver diseases. C57BL/6 mice were used to create an alcoholic liver disease model with a Lieber-DeCarli diet containing 5% alcohol and were fed with different concentrations of dietary copper of adequate (6 ppm, CuA), marginal (1.5 ppm, CuM), or supplemental (20 ppm, CuS) amounts. Caco-2 cells were also exposed to ethanol and different concentrations of copper. Damages of the liver and intestine were evaluated by transaminases, histology staining, and protein and mRNA level, as well as cell proliferation, oxidative stress, and mitochondrial membrane potential. In animal experiments, the results indicate that an alcohol diet causes liver injury and disruption of intestinal barrier function as well as decreasing the expression of genes such as HIF-1α, occludin, SOD1, and GPX1. Supplemental dietary copper can revert these changes except for SOD1, but marginal dietary copper can worsen these changes. The in vitro cell experiments showed that proper copper supplementation can promote cell growth and reduce reactive oxygen species (ROS) production. In conclusion, supplemental dietary copper has beneficial effects on alcohol-induced intestine and liver injury, and marginal dietary copper shows detrimental effects on these parameters.

Adipocyte-specific disruption of ATPase copper transporting α in mice accelerates lipoatrophy

AIMS/HYPOTHESIS

ATPase copper transporting α (ATP7A), also known as Menkes disease protein, is a P-type ATPase that transports copper across cell membranes. The critical role of ATP7A-mediated copper homeostasis has been well recognised in various organs, such as the intestine, macrophages and the nervous system. However, the importance of adipocyte ATP7A-mediated copper homeostasis on fat metabolism is not well understood. Here, we sought to reveal the contribution of adipose ATP7A to whole-body fat metabolism in mice.

METHODS

We generated adipocyte-specific Atp7a-knockout (ASKO) mice using the Cre/loxP system, with Cre expression driven by the adiponectin promoter. ASKO mice and littermate control mice were aged on a chow diet or fed with a high-fat diet (HFD); body weight, fat mass, and glucose and insulin metabolism were analysed. Histological analysis, transmission electron microscopy and RNA-sequencing (RNA-Seq) analysis of white adipose tissue (WAT) were used to understand the physiological and molecular changes associated with loss of copper homeostasis in adipocytes.

RESULTS

Significantly increased copper concentrations were observed in adipose tissues of ASKO mice compared with control mice. Aged or HFD-fed ASKO mice manifested a lipoatrophic phenotype characterised by a progressive generalised loss of WAT. Dysfunction of adipose tissues in these ASKO mice was confirmed by decreased levels of both serum leptin and adiponectin and increased levels of triacylglycerol and insulin. Systemic metabolism was also impaired in these mice, as evidenced by a pronounced glucose intolerance, insulin resistance and hepatic steatosis. Moreover, we demonstrate a significant induction of lipolysis and DNA-damage signalling pathways in gonadal WAT from aged and HFD-fed ASKO mice. In vitro studies suggest that copper overload is responsible for increased lipolysis and DNA damage.

CONCLUSIONS/INTERPRETATION

Our results show a previously unappreciated role of adipocyte Atp7a in the regulation of ageing-related metabolic disease and identify new metallophysiologies in whole-body fat metabolism.

DATA AVAILABILITY

The datasets generated during the current study are available in the Genome Sequence Archive in BIG Data Center, Beijing Institute of Genomics (BIG), Chinese Academy of Sciences, under accession number CRA001769 (http://bigd.big.ac.cn/gsa).

Low hair copper concentration is related to a high risk of nonalcoholic fatty liver disease in adults

Copper, an essential micronutrient, is required for lipid metabolism, mitochondrial function, iron metabolism, and antioxidant defense. Copper deficiency has been linked to alterations in lipid metabolism and various metabolic processes of the liver, including nonalcoholic fatty liver disease (NAFLD); however, most of these studies relied on copper measurements in the blood or tissues. In this study, we investigated the association between hair copper concentration and NAFLD in Korean adults, independent of metabolic syndrome status. Clinical and laboratory parameters, including factors of metabolic syndrome, were analyzed in 751 Korean adults divided into quintiles, according to hair copper concentration. Lower hair copper concentration was significantly correlated with higher body mass index, waist circumference, blood pressure, and lower levels of high-density lipoprotein cholesterol. Subjects with NAFLD showed significantly lower hair copper concentrations, and the risk of NAFLD was significantly higher for the lower hair copper quintile groups even after adjusting for metabolic syndrome-related factors. Overall, this study suggests that lower hair copper concentration could be associated with NAFLD, independent of metabolic syndrome factors.

Triggering and resolution of inflammation in NASH

Nonalcoholic steatohepatitis (NASH) is considered the progressive form of nonalcoholic fatty liver disease (NAFLD) and is characterized by liver steatosis, inflammation, hepatocellular injury and different degrees of fibrosis. A central issue in this field relates to the identification of those factors that trigger inflammation, thus fuelling the transition from nonalcoholic fatty liver to NASH. These triggers of liver inflammation might have their origins outside the liver (such as in adipose tissue or the gut) as well as inside the organ (for instance, lipotoxicity, innate immune responses, cell death pathways, mitochondrial dysfunction and endoplasmic reticulum stress), both of which contribute to NASH development. In this Review, we summarize the currently available information on the key upstream triggers of inflammation in NASH. We further delineate the mechanisms by which liver inflammation is resolved and the implications of a defective pro-resolution process. A better knowledge of these mechanisms should help to design targeted therapies able to halt or reverse disease progression.

Low Hepatic Tissue Copper in Pediatric Nonalcoholic Fatty Liver Disease

OBJECTIVE

Animal models and studies in adults have demonstrated that copper restriction increases severity of liver injury in nonalcoholic fatty liver disease (NAFLD). This has not been studied in children. We aimed to determine if lower tissue copper is associated with increased NAFLD severity in children.

METHODS

This was a retrospective study of pediatric patients who had a liver biopsy including a hepatic copper quantitation. The primary outcome compared hepatic copper concentration in NAFLD versus non-NAFLD. Secondary outcomes compared hepatic copper levels against steatosis, fibrosis, lobular inflammation, balloon degeneration, and NAFLD activity score (NAS).

RESULTS

The study analysis included 150 pediatric subjects (102 with NAFLD and 48 non-NAFLD). After adjusting for age, body mass index z score, gamma glutamyl transferase, alanine aminotransferase, and total bilirubin, NAFLD subjects had lower levels of hepatic copper than non-NAFLD (P = 0.005). In addition, tissue copper concentration decreased as steatosis severity increased (P < 0.001). Copper levels were not associated with degree of fibrosis, lobular inflammation, portal inflammation, or balloon degeneration.

CONCLUSIONS

In this cohort of pediatric subjects with NAFLD, we observed decreased tissue copper levels in subjects with NAFLD when compared with non-NAFLD subjects. In addition, tissue copper levels were lower in subjects with nonalcoholic steatohepatitis, a more severe form of the disease, when compared with steatosis alone. Further studies are needed to explore the relationship between copper levels and NAFLD progression.

Copper regulates cyclic-AMP-dependent lipolysis

Cell signaling relies extensively on dynamic pools of redox-inactive metal ions such as sodium, potassium, calcium and zinc, but their redox-active transition metal counterparts such as copper and iron have been studied primarily as static enzyme cofactors. Here we report that copper is an endogenous regulator of lipolysis, the breakdown of fat, which is an essential process in maintaining body weight and energy stores. Using a mouse model of genetic copper misregulation, in combination with pharmacological alterations in copper status and imaging studies in a 3T3-L1 white adipocyte model, we found that copper regulates lipolysis at the level of the second messenger, cyclic AMP (cAMP), by altering the activity of the cAMP-degrading phosphodiesterase PDE3B. Biochemical studies of the copper-PDE3B interaction establish copper-dependent inhibition of enzyme activity and identify a key conserved cysteine residue in a PDE3-specific loop that is essential for the observed copper-dependent lipolytic phenotype.

The Potential Role of Iron and Copper in Pediatric Obesity and Nonalcoholic Fatty Liver Disease

Obesity is a rapidly growing health problem and is paralleled by a multitude of comorbidities, including nonalcoholic fatty liver disease (NAFLD). NAFLD has become the most common chronic liver disease in both adults and children. The current understanding of NAFLD is still fragmentary. While simple steatosis is characterized by the interplay between excessive free fatty acid accumulation and hepatic insulin resistance, the progression to NASH has been related to oxidative stress and a proinflammatory state with dysbalanced adipokine, cytokine levels, and endotoxin-mediated immune response. In addition, oxidative stress has been suggested to play a central role for the sequelae leading to NASH. Trace elements are critical in regulatory, immunologic, and antioxidant functions resulting in protection against inflammation and peroxidation and consequently against the known comorbidities of obesity. Disruptions of the metal detoxification processes located in the liver are plausibly related to NAFLD development via oxidative stress. Perturbations of iron and copper (Cu) homeostasis have been shown to contribute to the pathogenesis of NAFLD. This review presents current data from pediatric studies. In addition, data from adult studies are summarized where clinical relevance may be extrapolated to pediatric obesity and NAFLD.

A role for low hepatic copper concentrations in nonalcoholic Fatty liver disease

OBJECTIVES

Copper has a role in antioxidant defense, lipid peroxidation, and mitochondrial function, and copper deficiency has been linked to atherogenic dyslipidemia. We aimed to investigate the potential role of copper availability in the pathogenesis of nonalcoholic fatty liver disease (NAFLD).

METHODS

Patients with NAFLD (n=124) were compared to patients with chronic hepatitis C (n=50), hemochromatosis (n=35), alcoholic liver disease (n=13), autoimmune hepatitis (n=11), and control subjects (n=27). We determined liver and serum copper concentrations with correlation to clinical, histological, and biochemical parameters in humans. The effect of dietary copper restriction on liver histology and intermediary metabolism in rats was investigated.

RESULTS

Hepatic copper concentrations in patients with NAFLD were lower than in control subjects (17.9+/-8.4 vs. 31.4+/-8.2 microg/g; P<0.001) and in patients with other liver diseases (P<0.05 for all liver diseases). In patients with NAFLD, lower liver copper was correlated with more pronounced hepatic steatosis (R=-0.248; P=0.010), fasting glucose (R=-0.245; P=0.008), and components of the metabolic syndrome (MetS; R=0.363; P<0.001). Patients with nonalcoholic steatohepatitis (NASH; n=31) had lower hepatic copper concentrations than those with simple steatosis (n=93; P=0.038). Restriction of dietary copper in rats induced hepatic steatosis and insulin resistance (IR).

CONCLUSIONS

Reduced hepatic copper concentrations are found in human NAFLD and are associated with more pronounced hepatic steatosis, NASH, and components of the MetS. The development of hepatic steatosis and IR in response to dietary copper restriction in rats suggests that copper availability may be involved in the development of NAFLD.

Copper availability contributes to iron perturbations in human nonalcoholic fatty liver disease

BACKGROUND & AIMS

Iron perturbations are frequently observed in nonalcoholic fatty liver disease (NAFLD). We aimed to investigate a potential association of copper status with disturbances of iron homeostasis in NAFLD.

METHODS

We retrospectively studied 140 NAFLD patients and 25 control subjects. Biochemical and hepatic iron and copper parameters were analyzed. Hepatic expression of iron regulatory molecules was investigated in liver biopsy specimens by reverse-transcription polymerase chain reaction and Western blot analysis.

RESULTS

NAFLD patients had lower hepatic copper concentrations than control subjects (21.9 +/- 9.8 vs 29.6 +/- 5.1 microg/g; P = .002). NAFLD patients with low serum and liver copper concentrations presented with higher serum ferritin levels (606.7 +/- 265.8 vs 224.2 +/- 176.0 mg/L; P < .001), increased prevalence of siderosis in liver biopsy specimens (36/46 vs 10/47 patients; P < .001), and with elevated hepatic iron concentrations (1184.4 +/- 842.7 vs 319.9 +/- 451.3 microg/g; P = .020). Lower serum concentrations of the copper-dependent ferroxidase ceruloplasmin (21.7 +/- 4.1 vs 30.4 +/- 6.4 mg/dL; P < .001) and decreased liver ferroportin (FP-1; P = .009) messenger RNA expression were found in these patients compared with NAFLD patients with high liver or serum copper concentrations. Accordingly, in rats, a reduced dietary copper intake was paralleled by a decreased hepatic FP-1 protein expression.

CONCLUSIONS

A significant proportion of NAFLD patients should be considered copper deficient. Our results indicate that copper status is linked to iron homeostasis in NAFLD, suggesting that low copper bioavailability causes increased hepatic iron stores via decreased FP-1 expression and ceruloplasmin ferroxidase activity thus blocking liver iron export in copper-deficient subjects.

Normolipidemic effect of antioxidants in low cholesterol-modified poultry eggPsi on Zn-induced dyslipidemia and liver pathology in Wistar rats

A low cholesterol (CH)-modified poultry egg (ME Psi) containing more vitamin E, lenolenic acid, and minerals Cu and Mg but low total lipid (TL) and Zn contents than the conventional egg evaluated to reduce the severity of dyslipidemia induced by excessive Zn in the diet. The experimental data was recorded on male rats fed on normolipidemic (NL) semi-synthetic basal diet containing 20 mg Zn/kg diet in control group I, Zn supplemented dyslipidemic diet-A (Zn-DL-A) and B (Zn-DL-B) containing 40 and 80 mg Zn/kg diet in groups II and III, and ME Psi-mixed Test diet-A (Zn-DL-A + 4 ME Psi) and Test diet-B (Zn-DL-B + 4 ME Psi) in groups IIEM and IIIEM, respectively, for 180 and 90 days. Data recorded on liver and blood lipid profiles showed reduction in the concentration of TL, CH, triglycerides, and glycogen (GG) in liver consequently leading to their rise in blood serum including rise in VLDL-c and LDL-c but fall in HDL-c in groups II and III rats that reversed after ME Psi treatment resulting in rise of their levels in the liver and fall in the blood of groups IIEM and IIIEM rats, respectively. Mineral status in the liver showed a rise in Zn but fall in Cu and Mg levels in groups II and III that was reversed after ME Psi treatment resulting in fall in Zn and rise in Cu and Mg concentration in the liver of groups IIEM and IIIEM rats. Hepatopathogical studies showed reduction in the dilatation of long citernal profile of endoplasmic reticulum and increase in GG and TL granules in the cytoplasm of hepatocytes of groups IIEM and IIIEM after ME Psi treatment than those of groups II and III rats. It was concluded that the inclusion of ME Psi would be helpful in reducing dyslipidemia by correcting the ionic imbalance generated by excessive Zn intake in rats or by drugs, even in chronic diseased conditions without aggravating risk factors for heart diseases in humans that need further studies.

How reliable and robust are current biomarkers for copper status?

Cu is an essential nutrient for man, but can be toxic if intakes are too high. In sensitive populations, marginal over- or under-exposure can have detrimental effects. Malnourished children, the elderly, and pregnant or lactating females may be susceptible for Cu deficiency. Cu status and exposure in the population can currently not be easily measured, as neither plasma Cu nor plasma cuproenzymes reflect Cu status precisely. Some blood markers (such as ceruloplasmin) indicate severe Cu depletion, but do not inversely respond to Cu excess, and are not suitable to indicate marginal states. A biomarker of Cu is needed that is sensitive to small changes in Cu status, and that responds to Cu excess as well as deficiency. Such a marker will aid in monitoring Cu status in large populations, and will help to avoid chronic health effects (for example, liver damage in chronic toxicity, osteoporosis, loss of collagen stability, or increased susceptibility to infections in deficiency). The advent of high-throughput technologies has enabled us to screen for potential biomarkers in the whole proteome of a cell, not excluding markers that have no direct link to Cu. Further, this screening allows us to search for a whole group of proteins that, in combination, reflect Cu status. The present review emphasises the need to find sensitive biomarkers for Cu, examines potential markers of Cu status already available, and discusses methods to identify a novel suite of biomarkers.

High Copper Selectively Alters Lipid Metabolism and Cell Cycle Machinery in the Mouse Model of Wilson Disease

Copper is essential for human physiology, but in excess it causes the severe metabolic disorder Wilson disease. Elevated copper is thought to induce pathological changes in tissues by stimulating the production of reactive oxygen species that damage multiple cell targets. To better understand the molecular basis of this disease, we performed genome-wide mRNA profiling as well as protein and metabolite analysis for Atp7b-/- mice, an animal model of Wilson disease. We found that at the presymptomatic stages of the disease, copper-induced changes are inconsistent with widespread radical-mediated damage, which is likely due to the sequestration of cytosolic copper by metallothioneins that are markedly up-regulated in Atp7b-/- livers. Instead, copper selectively up-regulates molecular machinery associated with the cell cycle and chromatin structure and down-regulates lipid metabolism, particularly cholesterol biosynthesis. Specific changes in the transcriptome are accompanied by distinct metabolic changes. Biochemical and mass spectroscopy measurements revealed a 3.6-fold decrease of very low density lipoprotein cholesterol in serum and a 33% decrease of liver cholesterol, indicative of a marked decrease in cholesterol biosynthesis. Consistent with low cholesterol levels, the amount of activated sterol regulatory-binding protein 2 (SREBP-2) is increased in Atp7b-/- nuclei. However, the SREBP-2 target genes are dysregulated suggesting that elevated copper alters SREBP-2 function rather than its processing or re-localization. Thus, in Atp7b-/- mice elevated copper affects specific cellular targets at the transcription and/or translation levels and has distinct effects on liver metabolic function, prior to appearance of histopathological changes. The identification of the network of specific copper-responsive targets facilitates further mechanistic analysis of human disorders of copper misbalance.

Copper deficiency induces hepatic fatty acid synthase gene transcription in rats by increasing the nuclear content of mature sterol regulatory element binding protein 1

Dietary copper (Cu) deficiency results in an accelerated rate of hepatic fatty acid synthase gene transcription and an enhanced rate of hepatic lipid synthesis. Because the nuclear transcription factor sterol regulatory element binding protein-1 (SREBP-1) is a strong enhancer of fatty acid synthase promoter activity, it was hypothesized that Cu deficiency induces fatty acid synthase gene transcription by increasing the nuclear localization of mature SREBP-1. Male weanling rats were pair-fed a Cu-adequate (6.0 mg/kg) or Cu-deficient (0.6 mg/kg) diet (AIN-93) for 28 d. DNase I hypersensitivity site mapping of the hepatic fatty acid synthase gene revealed the presence of four major hypersensitivity sites located at -8700 to -8600, -7300 to -6900, -600 to -400 and -100 to +50. Although Cu deficiency did not change the hypersensitivity site pattern or intensity, in vitro footprinting of the region between -100 and +50 indicated that Cu deficiency enhanced DNA protein interactions within this region. The sequence between -68 and -58 contains the DNA recognition sequence for SREBP-1 and upstream stimulatory element-1 (USF-1). Western blot analysis revealed that the dietary Cu deficiency increased the hepatic nuclear content of mature SREBP-1 by 150% (P: < 0.05), and it concomitantly decreased the membrane content of precursor SREBP-1 by 45% (P: < 0.05). Changes in the hepatic distribution of SREBP-1 associated with Cu deficiency were not accompanied by changes in SREBP-1 mRNA. The nuclear content of USF-1 was unaffected by dietary Cu status. The hepatic increase in mature SREBP-1 of Cu-deficient rats was accompanied by a 400% increase and an 80% decrease in the abundance of fatty acid synthase and cholesterol 7-alpha hydroxylase mRNA, respectively. hepatic These data indicate that a Cu deficiency stimulates hepatic lipogenic gene expression by increasing the hepatic translocation of mature SREBP-1.

Plasma diamine oxidase activity is greater in copper-adequate than copper-marginal or copper-deficient rats

The object of this study was to determine whether serum diamine oxidase activity could distinguish among adequate, marginal and deficient copper status in rats. Male weanling Sprague-Dawley rats (n = 21) were randomly assigned to one of three dietary regimens, with copper concentrations of 0.52, 1.73 and 6.7 mg/kg diet. On completion of the study, body weights were significantly different among dietary groups, with copper-marginal rats displaying the highest mean weight and copper-deficient rats the lowest. Copper-deficient rats ate significantly less food than the other two groups. Rats fed the three diets had significantly different liver copper concentrations. Liver and heart superoxide dismutase and cytochrome c oxidase activities, and plasma ceruloplasmin and erythrocyte superoxide dismutase activities were significantly lower in the copper-deficient rats than in the other two groups. Plasma diamine oxidase activity was lower in both copper-deficient (0.18 +/- 0.11 U/L) and marginal (0.21 +/- 0.11 U/L) rats compared with copper-adequate rats (3.35 +/- 0.28 U/L). Of the biochemical indices measured, only liver copper concentration (-20%) and plasma diamine oxidase activity (-94%) differed between rats fed copper-marginal and copper-adequate diets. Plasma diamine oxidase activity, therefore, may be a sensitive functional biomarker of suboptimal copper status.

Cardiac hypertrophy in copper-deficient rats is owing to increased mitochondria

Dietary copper depletion results in cardiac hypertrophy and ultrastructural alterations. The objective of this study was to determine the components that contribute to cardiac enlargement. Two groups (n = 4) of male, weaning, Sprague-Dawley rats were fed ad libitum with copper-adequate or copper-deficient diets for five weeks. Cross sectional transmission electron micrographs from both groups were evaluated using image analysis to quantify absolute area occupied by myocyte, mitochondria, myofibril, and other intracellular material. Copper-deficient rats had larger myocytes, increased area of mitochondria, and increased ratio of mitochondria:myofibril as well as mitochondria:myocyte. Copper deficiency did not change the absolute area occupied by myofibrils. These data suggested that increase in the absolute mitochondria area is the major contributory factor to the cardiac hypertrophy in copper deficiency. Under the conditions used, myofibril has minimal role toward contributing to the hypertrophic state. The pathology reported resembles human forms of genetic mitochondrial cardiomyopathies. The copper-deficient rat may be a useful model to investigate the underlying biochemical or molecular responses when peptides of enzymes are deleted.

Regulation of apolipoprotein A-I gene expression in Hep G2 cells depleted of Cu by cupruretic tetramine

Studies were designed to examine the regulation of apolipoprotein (apo) A-I gene expression in Cu-depleted Hep G2 cells. The cupruretic chelator N,N'-bis(2-aminoethyl)-1,3-propanediamine 4 HCl (2,3,2-tetramine or TETA) was used to maintain a 77% reduction in cellular Cu in Hep G2 cells. After two passages of TETA treatment, the relative abundance of apoA-I mRNA was elevated 52%. In TETA-treated cells, the rate of apoA-I mRNA decay measured by an actinomycin D chase study was accelerated 108%, and the synthesis of apoA-I mRNA determined by a nuclear runoff assay was enhanced 2.5-fold in TETA-treated cells. All of those changes could be reverted toward the control values with Cu supplementation for only 2 days. In transient transfection assays, a 26.7% increase in chloramphenicol O-acetyltransferase (CAT) activity for the reporter construct -256AI-CAT was observed in the treated cells. However, the ability of apoA-I regulatory protein 1 (ARP-1) to repress the CAT activity was not affected by the depressed Cu status. In addition, gel retardation experiments demonstrated that Cu depletion enhanced the binding of hepatocyte nuclear factor 4 (HNF-4) and other undefined nuclear factors to oligonucleotides containing site A, one of three regulatory sites of the apoA-I gene promoter. Moreover, the relative abundance of HNF-4 mRNA was increased 58% in the Cu-depleted cells. Thus the observed increase in apoA-I gene transcription may be mediated mostly by an elevated level of the regulatory factor, HNF-4. In summary, the present findings established the mechanism by which a depressed cellular Cu status can enhance apoA-I mRNA production and subsequently increase apoA-I synthesis.

The possible role of copper ions in atherogenesis: the Blue Janus

It has been proposed that the oxidative modification of low density lipoprotein (LDL) is a key event in human atherogenesis. Copper ions can catalyse the oxidative modification of LDL in vitro and there is some evidence that they may also participate in the oxidation of LDL within the arterial wall. However, copper ions also form an intrinsic constituent of superoxide dismutase and caeruloplasmin, enzymes that may be involved in preventing oxidative injury. Atherosclerotic lesions frequently contain considerable quantities of extracellular matrix molecules. These may contribute to the expansion of the arterial neointima, causing luminal narrowing. They may also play a beneficial role by stabilising the plaque. Copper is an essential component of lysyl oxidase, an enzyme involved in the biosynthesis of collagen, which is a major constituent of the extracellular matrix. The impact of alterations in body copper status on atherogenesis is therefore difficult to predict. Experimental and epidemiological data are conflicting and therefore do not provide a clear resolution of this issue. We have reviewed the biochemical and cellular effects of copper ions that may play a role in atherogenesis.

Copper deficiency increases hepatic apolipoprotein B secretion and mRNA editing in rats

Male weanling Sprague-Dawley rats were assigned to copper-deficient (9.0 mumol Cu/kg diet) or copper-adequate (102 mumol Cu/kg diet) dietary treatments for 6 wk. Pulse-chase studies using freshly isolated rat liver parenchymal cells demonstrated that apolipoprotein B (apoB)-48 and apoB-100 syntheses were not altered, but secretion was increased twofold in hepatocytes derived from copper-deficient rats. Both plasma apoB-48 and apoB-100 levels were increased by copper deficiency, but only the apoB-48 increase was significant. Hepatic apoB mRNA editing, expressed as a ratio of apoB-48 mRNA to apoB-48 plus apoB-100 mRNA, was significantly increased from 60.8% in copper-adequate to 70.2% in copper-deficient rats. Moreover, hepatic apoB mRNA abundance was not significantly altered by copper deficiency. Thus the increased amount of nascent apoB-48 secreted into the medium as well as the enhanced apoB mRNA editing may have contributed to the differential increase in plasma apoB-48 over apoB-100 level in copper-deficient rats.

Increased hepatic synthesis and accumulation of plasma apolipoprotein B100 in copper-deficient rats does not result from modification in apolipoprotein B mRNA editing

Experimentally induced copper deficiency in the rat results in increased plasma apolipoprotein B100 (apo B100) concentration in association with increased hepatic apo B100 synthesis. This enhancement of apo B100 synthesis and plasma accumulation accounts for the rise of plasma low density lipoprotein in these animals. In the present study, we have investigated if the selective increase in hepatic apo B100 synthesis is accounted for by changes in apo B mRNA editing. Reverse transcription coupled with polymerase chain reaction amplification and primer extension analysis of apo B cDNA revealed no differences in apo B mRNA editing in either the liver or small intestine between control and copper-deficient rats. We speculate that the increase in apo B100 synthesis in the liver of copper-deficient rats reflects posttranslational alterations in gene expression accompanying changes in very low density lipoprotein assembly and secretion.

Apolipoprotein A-I, A-IV and E synthesis in the liver of copper-deficient rats

Copper deficiency induces hypercholesterolemia in the rat. This hypercholesterolemia is mainly due to an increase in apo E-rich high density lipoproteins (HDL1). The present study was undertaken to determine whether the HDL increase could be explained by altered low-molecular weight apolipoprotein (apo) synthesis in the liver. The effect of copper deficiency on apo A-I, apo A-IV and apo E concentrations in plasma, as well as on respective mRNA levels and synthesis in the liver, were therefore investigated. We observed that the increased HDL1 levels in the plasma of copper-deficient rats were associated with a significant rise in plasma apo E concentrations; however, plasma apo A-I and apo A-IV concentrations remained unchanged. Liver apo synthesis and respective apo mRNA levels were not significantly altered in copper-deficient animals when compared to control rats. No changes in apo E mRNA levels in various tissues from copper-deficient, as compared to control rats, were noted. Based on the data obtained, it was concluded that the observed changes in plasma lipoprotein and apo concentrations are not related to changes in low-molecular weight apo synthesis in the liver. The mechanisms of the impaired catabolism of HDL1 should be further evaluated to possibly explain the observed increase in this fraction in copper-deficient rats.

Hepatic apolipoprotein B synthesis in copper-deficient rats

The present study was designed to examine if induction of apolipoprotein B synthesis is associated with hypercholesterolemia in copper-deficient rats. This hypercholesterolemia mainly resides in an increase in the HDL-1 and LDL and is associated with a significant increase in plasma apoB concentration. Liver apoB mRNA levels were not significantly modified in deficient animals as compared to control rats. Studies on liver apolipoprotein synthesis indicated that apoB100 synthesis was increased in deficient animals whereas apoB48 synthesis was unchanged. Thus, it appears that the increase in apoB synthesis in the liver of copper-deficient rats occurs at the posttranscriptional level. The selective increase in apoB100 synthesis indicates the possible impact of this deficiency on the editing of apoB. An increase in apoB100 synthesis by the liver in copper-deficient rats may significantly contribute to the increase in plasma concentration of LDL.