Age-related divergence of lipid dysregulation in Chinese patients with Wilson’s disease

To the Editor: Wilson’s disease (WD) is an autosomal recessive disorder characterized by mutations in the ATP7B gene.[1] The ATP7B gene encodes a protein functioning as a copper-transporting P-type ATPase, which plays a critical role in two key physiological processes: the incorporation of copper into apoceruloplasmin to form holoceruloplasmin and the facilitation of biliary excretion of excess copper. Loss or reduction of ATPase copper transporting beta (ATP7B) function disrupts copper homeostasis, leading to toxic intracellular copper accumulation. Hepatic impairment is the most common manifestation of WD, with the liver playing a central role in lipid metabolism.[2] Proper regulation of lipid biosynthesis, transport, and storage is essential for maintaining cellular and systemic homeostasis. Recent studies suggest that copper plays a significant role in lipid metabolism, yet the mechanisms underlying copper-lipid interactions in WD remain unclear. Previous investigations into lipid metabolism in WD have reported inconsistent findings, largely due to heterogeneity in study design. Patients across different disease stages, treatment statuses, and ages at enrollment were often analyzed together, leading to unreliable results. In our clinical practice, we have observed a high prevalence of lipid metabolism abnormalities among patients with WD, particularly in pediatric patients under 7 years of age. Notably, some children with WD can develop hepatic steatosis as early as 3 years of age. Moreover, the specific characteristics and clinical implications of lipid alterations in patients with WD across different age groups remain poorly defined. Therefore, in the present study, we investigated lipid metabolism profiles in a large cohort of patients with genetically confirmed WD, focusing on age-related differences. Between March 2015 and June 2025, 220 patients with WD were enrolled at the Second Affiliated Hospital of Zhejiang University School of Medicine. The cohort included 98 adults (group 1, ≥18 years) and 122 pediatric patients, including 70 aged 7–18 years (group 2) and 52 aged ≤7 years (group 3). All patients met the established diagnostic criteria for WD, exhibited good nutritional status, and were confirmed to carry pathogenic ATP7B variants on both alleles. Patients with a history of major systemic diseases, earlier exposure to potentially hepatotoxic medications, or previous metal chelation therapy were excluded. Age- and sex-matched healthy controls were recruited from individuals undergoing routine physical examinations between 2023 and 2024 and were selected using propensity score matching (n = 76 for group 1, 58 for group 2, and 45 for group 3). The study protocol was approved by the Ethics Committee of the Second Affiliated Hospital of Zhejiang University School of Medicine (No. 2015-048). Written informed consent was obtained from all participants or their legal guardians. Clinical data were extracted from electronic medical records using a standardized case report form. Collected information included age, sex, clinical phenotype, mutation sites, physical examination findings, serum ceruloplasmin levels, 24-hour urinary copper excretion, and slit-lamp assessment of Kayser–Fleischer rings. Biochemical parameters related to lipid metabolism, including total cholesterol (TCHO), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), were measured from fasting venous blood samples obtained at admission. Three milliliters of fasting venous blood were centrifuged at 3500 rpm (radius 16 cm) for 5 minutes, and the resulting serum was stored at −80°C until analysis. Lipid levels were determined enzymatically using an ADVIA 2400 automated biochemical analyzer (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA). Reference ranges were as follows: TCHO 3.00–5.70 mmol/L; TG <1.70 mmol/L; HDL-C 0.90–2.19 mmol/L; and LDL-C <3.36 mmol/L. Patients were further categorized according to clinical phenotype and ATP7B genotype. Based on predominant symptoms at diagnosis, patients were classified as having asymptomatic, hepatic, or neurological phenotypes. Regarding genotype, the ATP7B variants p.R778L and p.P992L, along with truncating mutations, are the most frequent mutations in Chinese patients and have been associated with severe clinical manifestations.[3] Accordingly, patients were subdivided into three genotypic categories: (1) both R778L/P992L/x: both alleles carry p.R778L, p.P992L, or truncating mutations; (2) one R778L/P992L/x: one allele carries p.R778L, p.P992L, or a truncating mutation, and the other allele carries a different variant; (3) no R778L/P992L/x: neither allele carries p.R778L, p.P992L, or a truncating mutation. Data normality was assessed using the Shapiro–Wilk test. Continuous variables with normal distribution were expressed as mean ± standard deviation and compared using Student’s t-test, whereas nonnormally distributed variables were expressed as median (interquartile range [IQR]) and compared using the Mann–Whitney U test. Categorical variables were presented as counts and percentages (%). Comparisons among three or more groups were performed using Welch’s analysis of variance or the Kruskal–Wallis test, as appropriate, followed by Bonferroni correction and the Benjamini–Hochberg procedure for multiple comparisons. Statistical significance was defined as P <0.05. All analyses were performed using GraphPad Prism version 8.4.0 (GraphPad Software, La Jolla, CA, USA). The baseline clinical characteristics of patients with WD are summarized in Supplementary Table 1, https://links.lww.com/CM9/C900. Among adult patients with WD (group 1), the median age at diagnosis was 29 (IQR: 22–36) years, and in pediatric groups 2 (patients aged 7–18 years) and group 3 (patients ≤7 years), the median ages were 14 (IQR: 12–16) and 4 (IQR: 3–6) years, respectively. In group 1, the majority (65/98, 66%) presented with a neurological phenotype, followed by 28 (29%) who exhibited a hepatic phenotype, and 5 (5%) who were asymptomatic. In group 2, the neurological phenotype predominated (37/70, 53%), followed by 18 (26%) asymptomatic and 15 (21%) hepatic cases. Conversely, the distribution pattern in group 3 differed markedly: most children (37/52, 71%) were asymptomatic, 14 (27%) had hepatic phenotype, and only one presented with neurological symptoms. Compared with age- and sex-matched controls, adult (group 1) and pediatric (group 2) patients with WD exhibited significantly reduced lipid levels in TCHO and LDL-C, whereas younger pediatric patients (group 3) demonstrated marked elevation [Supplementary Table 2, https://links.lww.com/CM9/C900]. In group 1, median TCHO was 3.69 (IQR: 3.33–4.27) mmol/L, significantly lower than controls (4.59 mmol/L, IQR: 4.07–5.34 mmol/L; P <0.0001). LDL-C was also decreased (1.72 mmol/L, IQR: 1.39–2.13 mmol/L vs. 2.37 mmol/L, IQR: 1.98–2.91 mmol/L; P <0.0001) [Supplementary Figure 1A, https://links.lww.com/CM9/C900]. Similarly, group 2 showed reduced lipid levels: TCHO was 3.66 (IQR: 3.23–4.27) mmol/L vs. 4.16 mmol/L in controls (IQR: 3.61–4.66 mmol/L; P = 0.0022), and LDL-C was 1.69 (IQR: 1.36–2.17) mmol/L vs. 1.99 mmol/L in controls (IQR: 1.77–2.42 mmol/L; P = 0.0004) [Supplementary Figure 1B, https://links.lww.com/CM9/C900]. In contrast, group 3 exhibited significantly higher TG, TCHO, and LDL-C levels compared with controls (P <0.0001 for all). Median TG, TCHO, and LDL-C levels were 1.41 (IQR: 1.17–1.77) mmol/L, 5.08 (IQR: 4.52–5.58) mmol/L, and 2.75 (IQR: 2.29–2.97) mmol/L, respectively, compared with 0.75 (IQR: 0.58–0.93) mmol/L, 4.20 (IQR: 3.90–4.60) mmol/L, and 1.99 (IQR: 1.53–2.38) mmol/L in controls [Supplementary Figure 1C, https://links.lww.com/CM9/C900]. To further explore potential clinical and genetic influences, lipid levels were analyzed according to patients’ phenotype and mutation type [Supplementary Tables 3 and 4, https://links.lww.com/CM9/C900]. In adult patients (group 1), no significant differences in TG, TCHO, HDL-C, or LDL-C levels were observed between the hepatic and neurological subgroups [Supplementary Figure 1D, https://links.lww.com/CM9/C900]. In group 2, TG levels were significantly higher in asymptomatic patients than those with the neurological phenotype or controls (P <0.05) [Supplementary Figure 1E, https://links.lww.com/CM9/C900]. Among younger children (group 3), the predominant phenotypes were hepatic and asymptomatic. TG, TCHO, and LDL-C levels were significantly lower in the hepatic phenotype than the asymptomatic phenotype (P <0.05). Specifically, TG, TCHO, and LDL-C were 1.03 (IQR: 0.66–1.52) mmol/L, 4.65 (IQR: 4.22–5.38) mmol/L, and 2.51 (IQR: 2.14–2.89) mmol/L in hepatic cases, vs. 1.43 (IQR: 1.28–1.74) mmol/L, 5.36 (IQR: 4.76–5.76) mmol/L, and 2.85 (IQR: 2.47–3.08) mmol/L in asymptomatic cases. Both subgroups exhibited higher lipid levels in TG, TCHO, and LDL-C than matched controls, consistent with the overall group 3 trend [Supplementary Figure 1F, https://links.lww.com/CM9/C900]. Patients were categorized into three mutation-based subgroups associated with severe clinical manifestations (“Both R778L/P992L/x”, “One R778L/P992L/x”, and “No R778L/P992L/x”). No significant differences in lipid parameters were detected among mutation subgroups in any of the three age-defined groups [Supplementary Table 4, https://links.lww.com/CM9/C900]. Over the past decades, several research groups have investigated lipid metabolism in WD. However, the findings have remained inconsistent and inconclusive, largely due to heterogeneity in study design. By applying stricter inclusion criteria and stratifying patients by age, our study provides a more reliable characterization of lipid dysregulation in patients with WD and identifies opposite lipid trends between adults and young children. In our WD cohort, children under 7 years exhibited elevated TG, TCHO, and LDL-C levels, whereas adult and older pediatric patients showed reduced TCHO and LDL-C levels. This pattern likely reflects the dynamic interplay between copper overload and hepatic lipid metabolism. Notably, patients with WD under 7 years with hepatic manifestations exhibited lower lipid levels than asymptomatic individuals, although both subgroups still showed higher lipid levels than controls. This finding further supports the notion that hepatic copper accumulation exerts a suppressive effect on lipid synthesis once the threshold for copper toxicity is reached. Together, these results suggest that hepatic copper burden determines the direction and extent of lipid dysregulation in WD, transitioning from early compensatory accumulation to chronic suppression with disease advancement. Studies have revealed that copper is intricately linked to lipid metabolism through multiple molecular pathways. A previous study revealed that the chaperone synthesis of cytochrome C oxidase 1 (SCO1) senses copper and activates AMP-activated protein kinase (AMPK) to enhance lipid catabolism.[4] Additionally, the markedly altered oxysterol profile observed in WD suggests that copper dyshomeostasis interferes with multiple steps of cholesterol synthesis, transport, and efflux.[5] Future studies should use in vivo models, such as Atp7b-knockout mice, to elucidate the impact of hepatic copper overload on lipid metabolic pathways. Integrating longitudinal clinical data with metabolomic and transcriptomic profiling will facilitate a deeper understanding of the temporal dynamics of lipid dysregulation in WD. Such investigations may help identify potential therapeutic targets and refine clinical monitoring strategies. Funding This study was supported by grants from the National Natural Science Foundation of China (Nos. 81125009 and 82502246) and the Research Foundation for Distinguished Scholars of Zhejiang University (No. 188020-193810101/089).