Mitochondrial dysfunction mediates the association between mercury exposure and lipid metabolism in children and adolescents

Mercury (Hg) is a widespread environmental pollutant with known neurotoxic and cardiometabolic effects, and its influence on lipid metabolism during childhood remains insufficiently understood. Mitochondrial dysfunction is proposed as a potential mechanism linking Hg exposure to metabolic disruption. Mitochondrial DNA copy number (mtDNA-CN) is regarded as an indicator of mitochondrial biogenesis and functional capacity, where lower levels generally suggest mitochondrial damage or dysfunction. In contrast, ribosomal DNA (rDNA) and relative telomere length (RTL) reflect genomic stability and cellular aging. This study investigated the associations between blood Hg levels and serum lipid profiles in children and adolescents and assessed the mediating roles of mtDNA-CN, rDNA, and RTL. A cross-sectional study was performed among 352 children and adolescents aged 6–17 years in eastern China. Blood Hg levels were determined using inductively coupled plasma mass spectrometry (ICP-MS), and serum lipid markers, namely total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), and lipoprotein(a), were assessed along with the genomic indicators such as mtDNA-CN, rDNA, and RTL. Multivariable linear regression and mediation analyses were conducted. Higher Hg levels were significantly related with increased TC (β = 0.144, P = 0.012), LDL-C (β = 0.266, P < 0.001) and ApoB (β = 3.79, P = 0.005) and with decreased HDL-C (β = − 0.149, P < 0.001). These associations exhibited stronger in girls than in boys. mtDNA-CN was positively associated with Hg exposure and significantly mediated the relationships between Hg and HDL-C (53.8%), ApoA1 (180.6%), and LDL-C (24.7%). Hg exposure in children and adolescents is linked to an atherogenic lipid profile, potentially through mitochondrial dysfunction. MtDNA-CN appears to be a sensitive molecular mediator of Hg-induced lipid disturbances, which highlights the relevance of mitochondrial health in early-life environmental epidemiology and cardiovascular risk prevention. The findings support early prevention strategies and environmentally focused health policies that reduce toxicant exposure and thus promote long-term cardiometabolic health in young populations.