U exposurein mice was found to induce cognitive impairment in ApoE-deficient(ApoE–/−) males, together with some changes in cholesterollevels and metabolism.103,104 This is consistentwith the ApoEε4 allele of the ApoE gene being a risk factorfor mercury toxicity105,106 and with ApoE-deficient miceshowing increased iron accumulation in tissue over time.107 It therefore appears likely that the ApoE proteinis involved in regulating metal homeostasis. This evidence concerns the gene APOE and Cognitive impairment.