Associations of lead biomarkers and delta-aminolevulinic acid dehydratase and vitamin D receptor genotypes with hematopoietic outcomes in Korean lead workers.

OBJECTIVES: This study compares and contrasts associations of dimercaptosuccinic acid (DMSA)-chelatable lead, tibia lead, and blood lead with five hematopoietic outcomes and evaluates the effect modification of these relations by polymorphisms in the delta-aminolevulinic acid dehydratase (ALAD) and vitamin D receptor (VDR) genes. METHODS: A cross-sectional study of 798 lead workers and 135 unexposed referents was performed. RESULTS: The DMSA-chelatable lead, tibia lead, and blood lead levels ranged in the lead (Pb) workers from 4.8 to 2103 g, -7 to 338 g Pb/g bone mineral, and 4 to 86 g/dl, respectively. The mean of the hemoglobin, hematocrit, zinc protoporphyrin (ZPP), and urinary (ALAU) and plasma (ALAP) delta-aminolevulinic acid levels of the lead workers were 14.2 (SD 1.4) g/dl, 42.4 (SD 4.4)%, 80.2 (SD 63.5) g/dl, 2.1 (SD 3.7) mg/l, and 17.7 (20.6) g/ml, respectively. After adjustment for the covariates, tibia lead was associated with all five hematopoietic outcomes, while blood lead and DMSA-chelatable lead were associated only with ZPP, ALAP, and ALAU. A comparison of the regression coefficients, total model adjusted R2 values, and delta R2 values revealed that blood lead was the best predictor of ZPP, ALAP, and ALAU. Only tibia lead was significantly associated with hemoglobin and hematocrit levels, but the additional variance explained by tibia lead was (<1%). No clear effect modification of the relations between the lead biomarkers and hematopoietic outcomes studied was caused by ALAD or VDR genotype. CONCLUSIONS: Lead must have a chronic, cumulative effect on hemoglobin and hematocrit levels, and any speculated mechanism cannot merely involve short-term plasma or target organ lead levels.     

Interaction of blood lead and delta-aminolevulinic acid dehydratase genotype on markers of heme synthesis and sperm production in lead smelter workers.

The gene that encodes gamma-aminolevulinic acid dehydratase (ALAD) has a polymorphism that may modify lead toxicokinetics and ultimately influence individual susceptibility to lead poisoning. To evaluate the effect of the ALAD polymorphism on lead-mediated outcomes, a cross-sectional study of male employees from a lead-zinc smelter compared associations between blood lead concentration and markers of heme synthesis and semen quality with respect to ALAD genotype. Male employees were recruited via postal questionnaire to donate blood and urine for analysis of blood lead, zinc protoporphyrin (ZPP), urinary coproporphyrin (CPU), and ALAD genotype, and semen samples for semen analysis. Of the 134 workers who had ALAD genotypes completed, 114 (85%) were ALAD1-1 (ALAD1) and 20 (15%) were ALAD1-2 (ALAD2). The mean blood lead concentrations for ALAD1 and ALAD2 were 23.1 and 28.4 microg/dl (p = 0.08), respectively. ZPP/heme ratios were higher in ALAD1 workers (68.6 vs. 57.8 micromol/ml; p = 0.14), and the slope of the blood lead ZPP linear relationship was greater for ALAD1 (2.83 vs. 1.50, p = 0.06). No linear relationship between CPU and blood lead concentration was observed for either ALAD1 or ALAD2. The associations of blood lead concentration with ZPP, CPU, sperm count, and sperm concentration were more evident in workers with the ALAD1 genotype and blood lead concentrations >/= 40 microg/dl. The ALAD genetic polymorphism appears to modify the association between blood lead concentration and ZPP. However, consistent modification of effects were not found for CPU, sperm count, or sperm concentration.     

Different behaviors of erythrocyte delta-aminolevulinic acid dehydratase. A comparison study between lead workers and normals.

Different characteristics of erythrocyte delta-aminolevulinic acid dehydratase (ALA-D1) between the workers with the history of occupational lead exposure and normals are described. In the blood of lead workers, when the hemolysates are heated at 60 C for five minutes, the activity of the erythrocytes ALA-D increases up to about 3.6-fold of an initial level, and as a result of heating the optimum in pH-activity curvee changes from pH 6.0 to pH 6.6, which is similar to the optimum pH of normal ALA-D. On the contrary, in normal blood, the optimum in the pH-activity curve is but little changed, even though the erythrocyte ALA-D activity is increased up to about 1.3-fold of the initial level by heating the hemolysates at 60 C for five minutes.     

Polymorphism of delta-aminolevulinic acid dehydratase and its effect on blood lead levels in Thai workers

To determine the prevalence of delta-aminolevulinic acid dehydratase (ALAD) polymorphism and its effects on blood lead levels (BLLs) in Thai workers, the authors performed a cross-sectional analysis of 389 Thai workers who were exposed to lead in a battery plant. The authors collected blood for BLLs and genotypic study, and they found that the allele frequencies of ALAD1 and ALAD2 were 0.98 and 0.02, respectively. They made a comparison of BLLs between genotype by dividing the levels into 2 categories of lead exposure (high and medium magnitude of exposure) and using length of employment as a covariance. Their results showed no significant difference of BLLs between the ALAD1-1 and ALAD1-2/ALAD2-2 groups in both levels of exposure. The frequency of ALAD2 in Thai workers was low; the authors found that ALAD polymorphism had a small or only modest effect on BLLs.     

δ-氨基乙酰丙酸脱水酶基因多态性与血铅和锌原卟啉的关系

目的　探讨δ 氨基乙酰丙酸脱水酶 (ALAD)基因多态性与血铅和锌原卟啉之间的关系。方法　采样分析 370名严重铅污染区儿童的血铅、锌原卟啉和ALAD基因型。结果　ALAD1 2 / 2 2 基因型的血铅水平 (2 6 2 1± 0 5 6 1) μmol/L高于ALAD1 1基因型 (2 36 0± 0 5 96 ) μmol/L ;而锌原卟啉水平也增高 ,前者 (13 0 7± 9 38) μmol/L ,后者 (9 90± 6 30 ) μmol/L。 结论　在同样的高铅暴露条件下 ,ALAD1 2 / 2 2 基因型可影响儿童体内铅负荷水平以及铅所致血液毒性效应     

Association of renal function and delta-aminolevulinic acid dehydratase polymorphism among Vietnamese and Singapore workers exposed to inorganic lead

Objectives

To investigate the effect of δ‐aminolevulinic acid dehydratase (ALAD) polymorphisms on the association between blood lead and renal function among Vietnamese and Singaporean workers who were exposed to low to medium levels of inorganic lead, and to study the distribution of ALAD polymorphism among Vietnamese, Chinese, Malays and Indians.

Methods

A total of 459 male and female workers were studied. Blood and urine were collected for each worker in order to determine ALAD genotype, blood lead, and urinary δ‐aminolevulinic acid (ALAU). Renal function tests included urine albumin (Ualb), urine β2 microglobulin (Uβ2m), urinary α1 microglobulin (Uα1m), N‐acetyl‐glucosaminidas (NAG), and urine retinol blinding protein (RBP). A multiple regression model with interaction term was applied to fit the entire data and to explore the modifying effect of ALAD polymorphism on the relation of blood lead to each renal function parameter.

Results

ALAD1‐1 was the predominant genotype for all the ethnic groups while ALAD2‐2 was the rarest. The frequency of ALAD2 allele was higher among Malays (8.8%) and Indians (10.6%) compared to the Chinese (5.0%) and Vietnamese (4.3%). The geometric mean of blood lead for all workers was 19.0 μg/dl. The models for Uβ2m, Uα1m, and NAG showed that the ALAD1‐2/2‐2 group had higher β coefficients than the ALAD1‐1 group. Corresponding to 10 μg/dl blood lead, ALAD1‐1 homozygotes had an increment of 1.288 μg/g Cr, 1.175 mg/g Cr, and 1.995 U/g Cr for Uβ2m, Uα1m, and NAG, respectively. ALAD1‐2/2‐2 subjects had higher increments of 3.802 μg/g Cr, 2.138 mg/g Cr, and 3.89 U/g Cr for Uβ2m, Uα1m, and NAG, respectively.

Conclusion

The frequency of the ALAD2 allele is as low in Vietnamese workers as in Chinese. Workers with the ALAD2 allele appeared more susceptible to the effects of lead (especially at higher levels) on renal function.     

Blood lead and erythrocyte delta-aminolevulinic acid dehydratase levels in Manchester taxi drivers.

Among 40 Manchester taxi drivers the mean blood lead was 1.10 mumol/1 (22.8 mug per 100 ml). The mean erythrocyte delta-aminolevulinic acid dehydratase (ALAD) activity among 34 of them was 30.1 units. No significant association was found between the blood lead levels and erythrocyte ALAD activity in these 34 men. No significant association was found between either blood lead elvels or erythrocyte ALAD activity and duration of service or weekly mileage as a taxi driver or with drinking or smoking habits, or age. The mean blood lead of those with homes in the north east quadrant of the city was higher than of those living elsewhere but the difference was not statistically significant. Although there was no correlation between blood lead levels and the source of domestic water, the mean blood lead of those with lead domestic plumbing was appreciably higher than the level of those with copper plumbing. There was no indication that, by virtue of their occupation, the taxi drivers were liable to greater lead absorption than their fellow-citizens.     

Blood lead and erythrocyte delta-aminolevulinic acid dehydratase levels in Manchester taxi drivers.

Among 40 Manchester taxi drivers the mean blood lead was 1.10 mumol/1 (22.8 mug per 100 ml). The mean erythrocyte delta-aminolevulinic acid dehydratase (ALAD) activity among 34 of them was 30.1 units. No significant association was found between the blood lead levels and erythrocyte ALAD activity in these 34 men. No significant association was found between either blood lead elvels or erythrocyte ALAD activity and duration of service or weekly mileage as a taxi driver or with drinking or smoking habits, or age. The mean blood lead of those with homes in the north east quadrant of the city was higher than of those living elsewhere but the difference was not statistically significant. Although there was no correlation between blood lead levels and the source of domestic water, the mean blood lead of those with lead domestic plumbing was appreciably higher than the level of those with copper plumbing. There was no indication that, by virtue of their occupation, the taxi drivers were liable to greater lead absorption than their fellow-citizens.     

Antagonistic effects of zinc and aluminum on lead inhibition of delta-aminolevulinic acid dehydratase

In vitro and in vivo studies regarding the influence of metals on delta-aminolevulinic acid dehydratase activity in erythrocytes indicate that a lead concentration of 4 micrometer/l completely inhibits the enzyme. Zinc activates the enzyme both in vitro and in vivo at concentrations greater than 76 micrometer/l. Aluminum has an inhibitory effect at all concentrations in vitro whereas it activates the enzyme in vivo. Zinc and aluminum together activate the enzyme in vivo. The in vitro activation of zinc is inhibited by increasing concentrations of aluminum. Aluminum and lead together depress the enzyme activity in an additive way that can be reactivated by the addition of zinc.     

Effect modification by delta-aminolevulinic acid dehydratase, vitamin D receptor, and nitric oxide synthase gene polymorphisms on associations between patella lead and renal function in lead workers

Genetic polymorphisms that affect lead toxicokinetics or toxicodynamics may be important modifiers of risk for adverse outcomes in lead-exposed populations. We recently reported associations between higher patella lead, which is hypothesized to represent a lead pool that is both bioavailable and cumulative, and adverse renal outcomes in current and former Korean lead workers. In the present study, we assessed effect modification by polymorphisms in the genes encoding for delta-aminolevulinic acid dehydratase (ALAD), the vitamin D receptor (VDR), and endothelial nitric oxide synthase on those associations. Similar analyses were conducted with three other lead biomarkers. Renal function was assessed via blood urea nitrogen, serum creatinine, measured and calculated creatinine clearances, urinary N-acetyl-beta-D-glucosaminidase, and retinol-binding protein. Mean (SD) blood, patella, tibia, and dimercaptosuccinic acid-chelatable lead values were 30.9 (16.7) microg/dl, 75.1 (101.1)and 33.6 (43.4) microg Pb/g bone mineral, and 0.63 (0.75) microg Pb/mg creatinine, respectively, in 647 lead workers. Little evidence of effect modification by genotype on associations between patella lead and renal outcomes was observed. The VDR polymorphism did modify associations between the other lead biomarkers and the serum creatinine and calculated creatinine clearance. Higher lead dose was associated with worse renal function in participants with the variant B allele. Models in two groups, dichotomized by median age, showed that this effect was present in the younger half of the population. Limited evidence of effect modification by ALAD genotype was observed; higher blood lead levels were associated with higher calculated creatinine clearance among participants with the ALAD(1-2) genotype. In conclusion, VDR and/or ALAD genotypes modified associations between all the lead biomarkers, except patella lead, and the renal outcomes.     

Relationships between blood lead concentration and aminolevulinic acid dehydratase in alcoholics and workers industrially exposed to lead

Blood lead concentration (Pb-B), aminolevulinic acid dehydratase (ALAD), and gamma-GT were measured in 265 workers industrially exposed to lead and in 184 patients with liver disease resulting from alcohol consumption. The first group was divided according to alcohol use, i.e., nondrinkers, moderate drinkers, and heavy drinkers. The second group was divided according to the following criteria: hepatopatic without cirrhosis, hepatopatic with compensated cirrhosis, and hepatopatic with decompensated cirrhosis. Heavy drinkers who were industrially exposed had the highest Pb-B (40.4 +/- 14.6 micrograms/dl) and the lowest ALAD (22.2 +/- 9.1 U/L). The correlations between Pb-B and ALAD show no significant change with the increase of Pb-B. In the alcoholic group, 76 patients with alcoholic liver disease without cirrhosis had the highest Pb-B (40.3-9.1 micrograms/dl) and ALAD the lowest (18.6 +/- 7.7 U/L). The negative correlation between Pb-B and log ALAD disappeared completely in individuals with Pb-B that exceeded 50 micrograms/dl, independent from the seriousness of illness.     

Erythrocyte delta-aminolevulinic acid dehydratase genotype and other mechanisms affecting workers' susceptibility to lead.

In this study, the role of delta-aminolevulinic acid dehydratase (ALAD) variants in lead susceptibility was examined. The study subjects comprised 223 male workers, and the relationship between their blood lead level and erythrocyte ALAD activity or plasma/urine delta-aminolevulinic acid level was studied. Leukocyte specimens from 11 workers, whose erythrocyte ALAD activities were as low as one-fifth that of the other normal workers, were subjected to analyses of their ALAD and ALAD alleles. Further, the entire exon fragment of the ALAD gene was analyzed by polymerase chain reaction, and the reaction product was used as a target for direct DNA sequencing. Genomic DNA analysis revealed that all 11 workers had the ALAD allele, whereas the entire ALAD gene analysis failed to indicate other variants, except for the Rsa I site. The depletion in erythrocyte ALAD activity was not found to be caused by the ALAD allele.     

Influence of the delta-aminolevulinic acid dehydratase (ALAD) polymorphism on biomarkers of lead exposure in Turkish storage battery manufacturing workers

BACKGROUND: The relationship between delta-aminolevulinic acid dehydratase polymorphism (ALAD) and biomarkers of exposure was investigated in Turkish lead workers in this study. METHODS: Seventy two male lead battery manufacturing workers were selected for the study. Blood lead (BPb) and urinary lead (UPb) concentrations were determined by atomic absorption spectrometry. Erythrocyte ALAD activity and urinary 5-aminolevulinic acid (UALA) were measured spectrophotometrically. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to determine the genotype of the ALAD gene. RESULTS: In total, 51 workers (70.8%) had the ALAD 1-1 genotype, whereas 21 workers (29.2%) had the ALAD 1-2 genotype. No significant relationships were found between the two genotypes and BPb, UPb, and ALAD activity. ALAD1 homozygotes showed significantly higher levels of UALA in comparison with those ALAD2 carriers. CONCLUSIONS: ALAD 1-1 individuals might be an increased risk compared to ALAD2 carriers to disturbance in heme biosynthetic pathway in high lead exposure.     

Associations of uric acid with polymorphisms in the delta-aminolevulinic acid dehydratase, vitamin D receptor, and nitric oxide synthase genes in Korean lead workers

Recent research suggests that uric acid may be nephrotoxic at lower levels than previously recognized and that it may be one mechanism for lead-related nephrotoxicity. Therefore, in understanding mechanisms for lead-related nephrotoxicity, it would be of value to determine whether genetic polymorphisms that are associated with renal outcomes in lead workers and/or modify associations between lead dose and renal function are also associated with uric acid and/or modify associations between lead dose and uric acid. We analyzed data on three such genetic polymorphisms: delta-aminolevulinic acid dehydratase (ALAD), endothelial nitric oxide synthase (eNOS), and the vitamin D receptor (VDR). Mean (+/- SD) tibia, blood, and dimercaptosuccinic acid-chelatable lead levels were 37.2 +/- 40.4 microg/g bone mineral, 32.0+/- 15.0 g/dL, and 0.77+/- 0.86 microg/mg creatinine, respectively, in 798 current and former lead workers. Participants with the eNOSAsp allele had lower mean serum uric acid compared with those with the Glu/Glu genotype. Among older workers (age > or = median of 40.6 years), ALAD genotype modified associations between lead dose and uric acid levels. Higher lead dose was significantly associated with higher uric acid in workers with the ALAD1-1 genotype; associations were in the opposite direction in participants with the variant ALAD1-2 genotype. In contrast, higher tibia lead was associated with higher uric acid in those with the variant VDRB allele; however, modification was dependent on participants with the bb genotype and high tibia lead levels. We conclude that genetic polymorphisms may modify uric acid mediation of lead-related adverse renal effects.     

Improved method for the determination of urinary delta-aminolevulinic acid in lead workers

An improved method for the determination of urinary delta-aminolevulinic acid (ALA) as an indicator of lead absorption is described. It is a modification of the analytical procedure described by Tomokuni and Ogata in 1972. In the present method, the spot urine from lead-exposed workers which was diluted 3-fold with distilled water beforehand was used as the sample to eliminate as much as possible the urinary matrix interference. In addition, methyl acetoacetate was used as the condensation reagent for ALA-pyrrole, because the color intensity of ALA-pyrrole was higher with the use of methyl acetoacetate than that with ethyl acetoacetate which was used in the original method. The urinary ALA value determined by the present method was similar to that measured using an internal-standard addition method. This method is suitable as a rapid and inexpensive screening procedure for the routine quantitative analysis of urinary ALA.