Effects of Delta-Aminolevulinic Acid Dehydratase Polymorphisms on Susceptibility to Lead in Han Subjects from Southwestern China

Yuelin Yang,Pin Sun,Jin Wu

doi:10.3390/ijerph9072326

Abstract

This study is to determine the distribution of the delta-aminolevulinic acid dehydratase (ALAD) polymorphism among Han subjects of the Chinese population and to study whether the polymorphism in the ALAD gene modifies the toxicity of lead in lead-exposed workers. For this purpose we conducted a cross-sectional study on 156 Chinese workers who were exposed to lead in lead-acid battery and electric-flex manufacturing plants. The authors found that the allele frequencies of ALAD1 and ALAD2 were 0.9679 and 0.0321, respectively. Workers with the ALAD 1-1 genotype were associated with higher blood lead levels than those with the ALAD 1-2 genotype. Blood and urine lead levels were much higher in storage battery workers than in cable workers. The self-conscious symptom survey showed that the incidences of debilitation, amnesia and dreaminess were much higher in those had more than five years of tenure or contact with lead on the job within the ALAD 1-1 genotype subgroup. Laboratory examinations showed that serum iron and zinc levels in workers’ with the ALAD 1-2 genotype were higher than those with the ALAD 1-1 genotype, especially in storage-battery workers. Correlation analysis indicated that the blood lead level negatively correlated with serum calcium, iron and zinc level. The data of this study suggest that the ALAD gene polymorphism and serum ion levels may modify the kinetics of lead in blood. Therefore, the authors recommend that an adequate intake of dietary calcium, iron, and zinc or the calcium, iron, and zinc supplementation should be prescribed to Chinese lead exposed workers.

Highlights

Lead is a known toxicant and remains a persistent environmental health threat [1]
The distribution of genotypes for the aminolevulinic acid dehydratase (ALAD) polymorphism showed no deviation from the Hardy-Weinberg equilibrium (P > 0.05)
ALAD 1-1 genotype was found in 50 males and in 96 females; the ALAD 1-2 genotype was found in one male and nine females

Summary

Introduction

Lead is a known toxicant and remains a persistent environmental health threat [1]. Occupational exposure to lead is most often encountered at lead smelters and battery manufacturing facilities.Exposure to lead can result in significant adverse health effects to multiple organ systems. Lead is a known toxicant and remains a persistent environmental health threat [1]. Occupational exposure to lead is most often encountered at lead smelters and battery manufacturing facilities. Exposure to lead can result in significant adverse health effects to multiple organ systems. One of lead's primary effects is hematotoxicity, inhibition of heme synthesis. Lead inhibits three enzymes in the heme biosynthesis pathway: delta-aminolevulinic acid dehydratase (ALAD), coporphyrinogen oxidase, and ferrochelatase, but its effects on ALAD are most profound [2]. ALAD catalyses the second step of heme synthesis and is encoded by a gene located on chromosome 9q34 [3]

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