Plasma vitamin B₁₂ and folate alter the association of blood lead and cadmium and total urinary arsenic levels with chronic kidney disease in a Taiwanese population

Heavy metals causing chronic nephrotoxicity may play a key role in the pathogenesis of chronic kidney disease (CKD). This study hypothesized that plasma folate and vitamin B₁₂ would modify the association of CKD with total urinary arsenic and blood lead and cadmium levels. We recruited 220 patients with CKD who had an estimated glomerular filtration rate of <60 mL/min/1.73 m² for ≥3 consecutive months and 438 sex-and age-matched controls. We performed inductively coupled plasma mass spectrometry to measure blood cadmium and lead levels. The urinary arsenic level was determined using a high-performance liquid chromatography– hydride generator–atomic absorption spectrometry. Plasma vitamin B₁₂ and folate levels were measured through the SimulTRAC-SNB radioassay. Compared with patients with plasma vitamin B₁₂ ≤ 6.27 pg/mL, the odds ratio (OR) and 95% confidence interval of CKD for patients with plasma vitamin B₁₂ > 9.54 pg/mL was 2.02 (1.15–3.55). However, no association was observed between plasma folate concentration and CKD. A high level of plasma vitamin B₁₂ combined with high levels of blood lead and cadmium level and total urinary arsenic tended to increase the OR of CKD in a dose-response manner, but the interactions were nonsignificant. This is the first study to demonstrate that patients with high plasma vitamin B₁₂ level exhibit increased OR of CKD related to high levels of blood cadmium and lead and total urinary arsenic.