Decreased thiamine and magnesium levels in the potentiation of the neurotoxicity of lead in occupational lead exposure

Effects of Sub-chronic Lead Exposure on Essential Element Levels in Mice

Lead (Pb), a corrosion-resistant heavy non-ferrous metal, is one of the most common environmental neurotoxic metals. The effects of Pb on other essential metal elements are contradictory. Therefore, this in vivo study addressed the effects of sub-chronic Pb exposure on the distribution of other divalent metals, exploring the relationships between Pb levels in blood, teeth, bones, hair, and brain tissues. Thirty-two healthy male C57BL/6 mice received intragastric administration (i.g.) with 0, 12.5, 25, and 50 mg/kg Pb acetate, once a day for 8 weeks. Levels of Pb and other metal elements [including iron(Fe), zinc (Zn), magnesium (Mg), copper (Cu), and calcium(Ca)] in the whole blood, teeth, the right thighbone, hair, and brain tissues (including cortex, hippocampus, striatum, and hypothalamus) were detected with inductively coupled plasma-mass spectrometry (ICP-MS). Pb levels in all detected organs were increased after Pb-exposed for 8 weeks. The results of relationship analysis between Pb levels in the tissues and lifetime cumulative Pb exposure (LCPE) showed that Pb levels in the blood, bone, and hair could indirectly reflect the Pb accumulation in the murine brain. These measures might serve as valuable biomarkers for chronic Pb exposure reflective of the accumulation of Pb in the central nervous system (CNS). Sub-chronic Pb exposure for 8 weeks altered Ca, Cu, Fe, and Zn levels, but no effects were noted on Mg levels in any of the analyzed tissues. Pb decreased Ca in teeth, Cu in thighbone and teeth, Zn in whole blood and hair, and Fe in hair. In contrast, Pb increased Ca levels in corpus striatum and hypothalamus, Cu levels in striatum, Zn levels in teeth, and Fe levels in hippocampus, thighbone, and teeth. The Pb-induced changes in metal ratios in various tissues may serve as valuable biomarkers for chronic Pb exposure as they are closely related to the accumulations of Pb in the murine CNS. The results suggest that altered distribution of several essential metal elements may be involved in Pb-induced neurotoxicity. Additional studies should address the interaction between Pb and essential metal elements in the CNS and other organs.

Relationship between Postural Stability, Lead Content, and Selected Parameters of Oxidative Stress

This study attempts to determine whether the increased blood lead concentration affects the posturographic test and to determine the relationship between the parameters of posture stability and selected parameters of oxidative stress. The study population consisted of 268 male employees and was divided into two equal subgroups, depending on the lead content in the blood. A posturographic examination was performed. Concentrations of lead, cadmium, zinc protoporphyrin, selected essential elements, and selected markers of oxidative stress in the blood were tested. Higher blood lead concentrations positively affected the values of the sway results: the field and the mean velocity of the center of the feet pressure in posturography. The absolute value of the proprioception ratio was similar in both subgroups. The content of malondialdehyde shows a statistically significantly higher value in a subgroup with high blood lead concentration and exhibits significant correlations only with some of the posturography parameters. The lipofuscin content in erythrocytes correlates with the results of the posturography test. Zinc protoporphyrin, total oxidant status, total antioxidant capacity, selected minerals, and metals did not correlate with the results of the posturography test. In conclusion, posturographic results correlate only with selected markers of oxidative stress, so it can be assumed that the effect on the body balance is only partial.

Association between blood lead levels and markers of calcium homeostasis: a systematic review and meta-analysis

Chronic Pb exposure associated systemic illness are partly posited to involve calcium homeostasis. Present systematic review aims to comprehensively evaluate the association between chronic lead exposure and markers of calcium homeostasis. Observational studies documenting the changes in calcium homeostasis markers (i.e. serum calcium, parathyroid hormone, vitamin D & calcitonin) between occupationally Pb exposed group and control group were systematically searched from pubmed-Medline, Scopus, and Embase digital databases since inception to September 24, 2021. The protocol was earlier registered at PROSPERO (ID: CRD42020199503) and executed adhering to PRISMA 2020 guidelines. Mean differences of calcium homeostasis markers between the groups were analysed using random-effects model. Conventional I2 statistics was employed to assess heterogeneity, while the risk for various biases were assessed using Newcastle Ottawa Scale. Sub-group, sensitivity and meta-regression analyses were performed where data permitted. Eleven studies including 837 Pb exposed and 739 controls were part of the present study. Pb exposed group exhibited higher mean blood lead level [i.e. 36.13 (with 95% CI 25.88-46.38) µg/dl] significantly lower serum calcium (i.e. - 0.72 mg/dl with 95% CI - 0.36 to - 1.07) and trend of higher parathyroid levels and lower vitamin D levels than controls. Heterogeneity was high (I2 > 90%) among the studies. Considering the cardinal role of calcium in multiple biological functions, present observations emphasis the need for periodic evaluation of calcium levels and its markers among those with known cumulative Pb exposure.

The Effect of a Short-Term Exposure to Lead on the Levels of Essential Metal Ions, Selected Proteins Related to Them, and Oxidative Stress Parameters in Humans

The present study was designed to explore the possible influence of subacute exposure to lead on the levels of selected essential metals, selected proteins related to them, and oxidative stress parameters in occupationally exposed workers. The study population included 36 males occupationally exposed to lead for 36 to 44 days. Their blood lead level at the beginning of the study was 10.7 ± 7.67 μg/dl and increased to the level of 49.1 ± 14.1 μg/dl at the end of the study. The levels of calcium, magnesium, and zinc increased significantly after lead exposure compared to baseline by 3%, 3%, and 8%, respectively, while the level of copper decreased significantly by 7%. The malondialdehyde (MDA) level and the activities of catalase (CAT) and superoxide dismutase (SOD) did not change due to lead exposure. However, the level of lipid hydroperoxides (LPH) in serum increased significantly by 46%, while the level of erythrocyte lipofuscin (LPS) decreased by 13%. The serum levels of essential metals are modified by a short-term exposure to lead in occupationally exposed workers. A short-term exposure to lead induces oxidative stress associated with elevated levels of LPH but not MDA.

Relationship of blood levels of Pb with Cu, Zn, Ca, Mg, Fe, and Hb in children aged 0 ∼ 6 years from Wuhan, China

The aim of this study was to investigate the relationship of blood lead (Pb) levels with copper (Cu), zinc (Zn), calcium (Ca), magnesium (Mg), iron (Fe), and hemoglobin (Hb) in children aged from 0-6 years in Wuhan, China. A total of 1047 children from six communities, which were randomly selected in Wuhan city and three communities, located in the urban area and others in the suburban area, were recruited for this study between November 2012 and July 2013. The levels of elements in the blood were detected using an atomic absorption spectrometer, and Hb level was tested by an automated hematology analyzer. The results showed that the mean blood lead level (BLL) is 33.72 ± 19.03 μg/L. The BLL was significantly higher among boys than girls (P < 0.05). Higher BLL was also observed in suburbs compared to that in urban areas (P < 0.05). The BLL and Zn level were gradually increased with age. The elevated rate of BLL in children was 20.9 %, while the Zn deficiency rate was 65.0 %. And, the level of Hb in higher BLL group was significantly lower. Negative correlations of the blood levels of Pb with those of Cu (r = -0.087, P = 0.005), Mg (r = -0.102, P = 0.001), and Fe (r = -0.091, P = 0.003) were observed. These data suggested that the elevated rate of BLL in children from Wuhan is still higher according to the updated reference values in the USA. The deficiency of Cu, Mg, and Fe may indicate the elevation of lead absorption. The dietary supplement of Zn, Ca, and Fe in children requires more attention.

Blood lead level and its relationship to certain essential elements in the children aged 0 to 14 years from Beijing, China

OBJECTIVE

To investigate blood lead level and its relationship to copper, zinc, calcium, magnesium and iron in the children aged 0 to 14 years old from Beijing, China.

METHODS

We classified 3181 children into one of the four groups: Group A (n=783, <1 year old); Group B (n=1538, 1-3 years old); Group C (n=443, 3-7 years old); and, Group D (n=417, 7-14 years old). All these metal elements were determined by atomic absorption spectrometry.

RESULTS

The blood lead level was 0.207±0.105 μmol/L. There was a significant gender difference for zinc (P<0.05) in Group C, and there was also a significant gender difference for copper (P<0.05) and lead (P<0.05) in Group D. Controlling for gender and age, we observed that there was a negative correlation of lead with zinc (r=-0.052, P<0.01), magnesium (r=-0.042, P<0.05) and iron (r=-0.031, P<0.05), respectively. Furthermore, in the children aged 1-7 years old, we also found there was a negative linear correlation of lead with zinc, magnesium and iron, respectively (P<0.01).

CONCLUSION

Blood lead level in children from Beijing was markedly decreased. And deficiency of zinc, magnesium and iron is related to the elevated blood lead level in the children aged 1-7 years.

Lead and essential trace element levels in school children: a cross-sectional study

BACKGROUND

Nutritional status is thought to modulate susceptibility to lead (Pb) toxicity. The type and nature of these interactions needs to be investigated.

AIM

To assess the prevalence of sub-clinical Pb toxicity (defined by ≥ 10 μ_rm;g/dL blood levels) and trace element deficiencies (Iron (Fe), Zinc (Zn), Copper (Cu) and Magnesium (Mg)) and to find out their possible relationship, if any.

SUBJECTS AND METHODS

A cross-sectional survey was carried out in a total of 195 school children residing in urban (n = 65), urban heavy traffic (n = 65) and urban industrial (n = 65) zones of Hyderabad, India. Blood Pb, trace element levels, haemoglobin and δ-aminolevulinate dehydratase (δ-ALAD) activity was measured.

RESULTS

High blood lead levels ( ≥ 10 μ_rm;g/dL) were observed in 54.3% of children while percentage prevalence of trace element deficiencies such as Fe (16.2%), Zn (68.6%), Mg (41.7%) and Cu (25%) were also high in children included in the study. Higher blood Pb levels and reduced δ-ALAD activity was observed in children residing in heavy traffic and industrial areas. Blood Pb levels but not δ-ALAD activity correlated inversely with serum Fe in heavy traffic and industrial children, respectively. Interestingly, δ-ALAD activity but not blood Pb levels correlated inversely with trace element levels only in urban children.

CONCLUSIONS

These results suggest higher prevalence of sub-clinical Pb toxicity and trace element deficiencies in urban children. Further, high blood Pb levels appear to be correlated with reduced δ-ALAD activity and iron status in Pb exposed children.

Thiamine reduces tissue lead levels in rats: mechanism of interaction

Lead (Pb) toxicity has been a serious concern in industrialized societies because of its association with functional deficits in nervous, haematopoietic and renal systems. Several studies have shown beneficial effects of thiamine on Pb toxicity. It is speculated that Pb chelation by thiamine may be a possible mechanism. However, the exact nature of these interactions remained elusive. In the present study we have characterized the interaction of Pb with thiamine using UV-Vis as well as fluorescence spectroscopic methods and studied the effect of thiamine treatment on blood and tissue Pb levels during simultaneous or post-exposure to Pb in rat model. The spectroscopic studies revealed that Pb interacts with the pyrimidine ring of thiamine, leading to its solubilization at physiological pH. Further, thiamine reduced the Pb levels in blood, kidney and bone during both simultaneous and post-exposure Pb treatment. Interestingly, thiamine appears to prevent the accumulation of Pb in bone during simultaneous treatment. Together these results suggest that pyrimidine ring of thiamine mediates its interaction with Pb, leading to the prevention of its accumulation and/or increased clearance from tissues.