Elevated heavy metals levels in cognitively impaired patients from Pakistan

The relationship between cadmium and cognition in the elderly: a systematic review

Context: The relationship between cadmium (Cd) and the cognition of the elderly is indistinct.Objective: To summarise the studies on the relationship between the cognition of the elderly and Cd.Methods: Literatures were searched in PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), and Wan fang database on April 25, 2022. The entries in the STROBE statement were used to evaluate the literature quality; all the quantitative studies that met the requirements were systematically summarised.Results: Blood Cd was negatively correlated with the cognitive ability of the elderly, corresponding to different cognitive ability assessment methods, the regression coefficients were: -0.11 (-0.20, -0.03), -0.46 (-0.71, -0.21), -0.54 (-0.90, -0.17), -0.19 (-0.37, -0.01), and -2.29 (-3.41, -1.16). The regression coefficients between urinary Cd level and cognition score were -1.42 (-2.38, -0.46), and 0.76 (-1.28, -0.23). When dietary Cd increased by 1 μg/kg, the composite z-score decreased by 3.64 (p = 0.001). There was no significant correlation between drinking water Cd, fingernail Cd and cognition (p > 0.05).Conclusion: We concluded that blood Cd (including whole blood and plasma), urine Cd and dietary Cd were negatively correlated with the cognition of the elderly, but the relationship between Cd in drinking water and fingernails and cognition was not statistically significant.

Poorer cognitive function and environmental airborne Mn exposure determined by biomonitoring and personal environmental monitors in a healthy adult population

BACKGROUND/AIM

In the Santander Bay (Cantabria, northern Spain), a ferromanganese alloy plant is located. Our objective was to characterize the Mn personal exposure of adult healthy volunteers living in this highly Mn exposed region, and to determine its association with a poorer cognitive function.

METHODS

Cross-sectional study analyzing 130 consecutive participants. Cognitive function was assessed by Stroop Color Word, Verbal Fluency tests, Trail Making Test (TMT), Digit Span (WAIS III) and Rey Osterrieth Complex Figure (ROCF) tests and crude scores were standardized according to NEURONORMA norms. Exposure to Mn was assessed in terms of source distance, by Personal Environmental Monitors (PEMs) allowing the separation of fine (PM2.5) and coarse (PM10-2.5) particles (obtaining the bioaccessible fraction by in-vitro bioaccessibility tests), and by biomarkers (blood, hair and fingernails). Age, sex, study level and number of years of residence were predefined as confounding variables and adjusted Mean Differences (MDs) were obtained.

RESULTS

Statistically significant lower scores (negative MDs) in all test were observed when living near the industrial emission source, after adjusting for the predefined variables. Regarding PEMs results, statistically significant lower scores in all Stroop parts were obtained in participants with higher levels of Total Mn in All fractions (PM10). For Verbal Fluency tests, negative MDs were obtained for both bioaccessible fractions. Digit Span Backward scores were lower for those with higher levels in the bioaccessible coarse fraction, and negative MDs were also observed for the ROCF Delayed part and the non-bioaccessible fine fraction. As regards to Mn in fingernails, adjusted MDs of -1.60; 95%CI (-2.57 to -0.64) and -1.45; 95%CI (-2.29 to -0.61) for Digit Span Forward and Backward parts were observed.

CONCLUSIONS

Our results support an association between poorer cognitive function and environmental airborne Mn exposure.

Association between blood metals mixtures concentrations and cognitive performance, and effect modification by diet in older US adults

Background:

Chronic exposure to heavy metals has been associated with adverse neurological outcomes in older adults. Inflammatory processes are suspected as an underlying pathway by which metals exert their neurotoxicity. In parallel, a diet rich in antioxidant and anti-inflammatory components may protect against chronic inflammation.

Objectives:

We examined the associations of blood concentrations of lead, cadmium, and manganese as a mixture with cognitive performance in older US adults and potential modification of these associations by diet as measured by the Healthy Eating Index 2015 (HEI-2015) and the Adapted Dietary Inflammatory Index (ADII).

Methods:

We used data on 1,777 adults ≥60 years old from the US National Health and Nutrition Examination Survey (NHANES; 2011–2014). We derived the ADII and the HEI-2015 from two nonconsecutive 24-hour diet recalls. Cognitive performance was measured by the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) Word Learning subtest, the animal fluency test, and the Digit Symbol Substitution Test (DSST). We also constructed a composite z-score reflecting overall cognitive performance. We used quantile g-computation to evaluate the joint associations of a mixture of metals with cognitive performance test scores. We also evaluated effect modification by sex and diet quality indices using Cochran Q tests.

Results:

The median (interquartile range) of blood metals were 0.38 μg/L (0.35), 14.70 μg/L (11.70), and 8.74 μg/L (4.06) for cadmium, lead, and manganese, respectively. Increasing blood concentrations of all metals by one quartile was associated with a decrease in overall cognitive performance (–0.04; 95% confidence interval [CI] = –0.09, 0.02), CERAD (–0.04; 95% CI = –0.12, 0.03), animal fluency (–0.02; 95% CI, –0.11, 0.06), and DSST (–0.05; 95% CI = –0.11, 0.02) test scores. These associations were more pronounced in adults with high pro-inflammatory or low-diet quality and null or positive though imprecise associations in participants with a high anti-inflammatory. These associations also varied by sex with inverse associations in men and positive associations in women.

Conclusions:

Our findings suggest that adherence to an antioxidant and anti-inflammatory diet may prevent blood metals adverse cognitive effects among older adults. If confirmed, strategies based on diet could provide a potential complementary and efficient approach to counteract effects of environmental pollutants.

The role of regulatory T cells on the activation of astrocytes in the brain of high-fat diet mice following lead exposure

Lead (Pb) exposure can cause damage to the central nervous system (CNS)*. Pb can accumulate in the hippocampus, leading to learning and memory impairments. Recent studies have shown that high-fat diet (HFD) is also associated with cognitive impairment. However, there are few reports on CNS damage due to HFD and Pb exposure. We aimed to investigate the effect of Pb on cognitive functions of HFD-fed mice, focusing on the role of regulatory T (Treg) cells in astrocyte activation. C57BL/6J mice were randomly divided into control, HFD, Pb, and HFD + Pb groups. TGF-β and IL-10 secreted by Treg cells and the intracellular transcription factor Foxp3 were evaluated as a measure of Treg cell function; astrocyte activation was assessed by evaluating glial fibrillary acidic protein (GFAP) expression. The learning and memory ability was significantly lower in the HFD + Pb group than in other groups. The brain Treg cell ratio was significantly decreased and the protein levels of TGF-β, IL-10, and Foxp3 were significantly lower, whereas the protein level of GFAP was higher in the HFD + Pb group. The hippocampus of the HFD + Pb group mice showed significantly higher levels of neurotoxic reactive astrocyte markers and astrogliosis was also much higher compared to HFD and Pb groups. Furthermore, all-trans retinoic acid treatment increased the brain Treg cell ratio, reversed cognitive decline, and suppressed astrocyte activation in the HFD + Pb group mice. We concluded that HFD along with Pb exposure could aggravate the activation of astrocytes in the brain, and the brain Treg cells may be involved in inhibiting astrocyte activation in HFD-fed mice exposed to Pb.

Longitudinal study of the effects of occupational aluminium exposure on workers' cognition

OBJECTIVE

To explore the effects of occupational aluminium(Al) exposure on workers' cognition through a longitudinal study.

METHODS

The study population consisted of 276 workers in an Al factory. In 2014, we used inductively coupled plasma mass spectrometry (ICP-MS) to determine the plasma aluminium (P-Al) concentration of the workers, and a combined questionnaire to test the workers' cognitive function. Followed-up in 2016, the workers were tested again for cognitive function. Generalized linear regression was used to assess the association between P-Al concentration and cognitive scores, and multivariable logistic regression was used to assess the risk of cognitive decline caused by Al exposure.

RESULTS

Generalized linear regression results showed that a non-significant association was found between the P-Al concentration and cognitive test scores (P > 0.05) in 2014. Two years later, each 10-fold increase in P-Al concentration was inversely associated with the score of Mini-Mental state examination (MMSE) (β: -0.53, 95% CI: -0.86, -0.20) and Fuld object memory evaluation (FOME) (β: -0.93, 95% CI: -1.62, -0.24). Each 10-fold increase in P-Al concentration was inversely associated with MMSE_2016-2014 (β: -0.38, 95% CI: -0.74, -0.01) and FOME_2016-2014 (β: -1.20, 95% CI: -1.95, -0.45). There was a statistically significant difference in the average annual rate of change of MMSE and FOME with the tertile of P-Al concentration increase (P < 0.05). The multivariable logistic regression results showed that as the P-Al concentration increased, the risk of a FOME score decline increased (P_trend = 0.009).

CONCLUSIONS

Continuous occupational Al exposure can damage workers' overall cognitive ability, especially episodic memory function.

Impact of Environmental Airborne Manganese Exposure on Cognitive and Motor Functions in Adults: A Systematic Review and Meta-Analysis

Background/Objective: Whether environmental exposure to Manganese (Mn) in adults is associated with poorer results in cognitive and motor function is unclear. We aimed to determine these associations through a meta-analysis of published studies. Methods: A systematic review was conducted to identify epidemiological studies on a population ≥18 years old exposed to environmental airborne Mn, and in which results on specific tests to evaluate cognitive or motor functions were reported. We consulted Medline through PubMed, Web of Science and SCOPUS databases. We also performed a manual search within the list of bibliographic references of the retrieved studies and systematic reviews. To weight Mn effects, a random effects versus fixed effect model was chosen after studying the heterogeneity of each outcome. Results. Eighteen studies met the inclusion criteria. Among them, eleven studies reported data susceptible for meta-analysis through a pooled correlation or a standardized means difference (SMD) approach between exposed and non-exposed groups. Regarding cognitive function, the results of the studies showed heterogeneity among them (I² = 76.49%, p < 0.001). The overall effect was a statistically significant negative correlation in the random effects model (pooled r = −0.165; 95%CI: −0.214 to −0.116; p < 0.001). For SMD, the results showed a lower heterogeneity with a negative SMD that did not reach statistical significance under the fixed effects model (SMD = −0.052; 95%CI −0.108 to 0.004; p = 0.068). Regarding motor function, heterogeneity (I² = 75%) was also observed in the correlation approach with a pooled r (random effect model) = −0.150; 95%CI: −0.219 to −0.079; p < 0.001. Moderate heterogeneity was observed according to the SMD approach (I² = 52.28%), with a pooled SMD = −0.136; 95%CI: −0.188 to−0.084; p < 0.001, indicating worse motor function in those exposed. Conclusions: Correlation approach results support a negative effect on cognitive and motor functions (the higher the Mn levels, the poorer the scores). Regarding the SMD approach, results also support a worse cognitive and motor functions in those exposed, although only for motor function statistical significance was obtained.

Transition Metals in Freshwater Crustaceans, Tilapia, and Inland Water: Hazardous to the Population of the Small Island Province

This paper elaborates on the potential toxicants detected in inland water, freshwater crustaceans, and tilapia in an island that experienced mining disasters in 1993 and 1996. Specimen samples were collected in six municipalities of the island province in 2019 and presence of metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were analyzed using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). Potential ecological risks analysis followed the Hakanson approach. Canonical correspondence analysis PAST Version 3.22, IBM SPSS 25.0, and Pearson correlation were employed for statistical analysis, and GIS Pro 2.5 for mapping of sampling locations and spatial distribution. Results showed that Mn and Zn concentration was highest in surface water (SW) and groundwater (GW), respectively. All metal concentration values exceeded the maximum permissible limit by regulatory international organizations. Elevated concentration of Cr, Cu, Fe, Mn, and Zn was detected in both crustaceans and tilapia. The calculated health hazard indices were greater than one, which means potential high adverse effects on public health when ingested. The municipality of Sta. Cruz and Torrijos recorded higher potential ecological risk among the six municipalities. Results of the correlation analysis suggested that metals in SW and GW have a similar origin, mutual dependence, and identical behavior during transport.

High-Fat Diet Affects Heavy Metal Accumulation and Toxicity to Mice Liver and Kidney Probably via Gut Microbiota

Previous studies proved that heavy metals could increase the risk of disease by acting on the gut microbiota. Meanwhile, gut microbiota played important roles in detoxifying heavy metals. However, the response of gut microbiota to heavy metals and which microbes dominated this detoxification processes are still unclear. This study investigated the difference of high-fat-diet (HFD) and normal-diet (ND) gut microbiota and their response to and detoxification effects on arsenic (As), cadmium (Cd), and lead (Pb) exposure. Results showed that gut microbiota of ND and HFD was significantly different and responded to As, Pb, and Cd exposure differently, too. When exposed to 100 ppm As, Cd, or Pb, HFD-fed mice accumulated more heavy metals in the liver and kidney along with more severe functional damage than ND-fed mice, indicated by a more dramatic increase of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and urinary total protein (TPU), urinary uric acid (UUA), and urinary creatinine (Ucrea) content. Among ND gut microbiota, relative abundance of Bacteroides, Lactobacillus, Butyricimonas, and Dorea was significantly increased by arsenic (As) exposure; relative abundance of Faecoccus and Lactobacillus was significantly increased by Cd exposure; relative abundance of Desulfovibrio, Plasmodium, and Roseburia were significantly increased by Pb exposure. However, among HFD gut microbiota, those microbes were not significantly changed. Bivariate association analysis found weak positive correlations between content of fecal excreted heavy metals and richness of total fecal microbiota as well as abundance of some of the heavy metal-enriched microbes. Our study concluded that HFD increased disease risk of heavy metal exposure probably via its gut microbiota which excreted less heavy metal through feces.

Disruption of essential metal homeostasis in the brain by cadmium and high-fat diet

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Whole-life exposure to cadmium leads to elevated metal levels in the brain that further increases in high-fat diet fed mice.

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Female animals accumulate more cadmium in the brain than males, under all treatment conditions.

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Cadmium exposure is associated with changes in the levels of several essential metals.

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Cadmium and high fat diet increase levels of superoxide anion in the cortex, amygdala and hippocampus.

Analyses of human cohort data support the roles of cadmium and obesity in the development of several neurocognitive disorders. To explore the effects of cadmium exposure in the brain, mice were subjected to whole life oral cadmium exposure. There were significant increases in cadmium levels with female animals accumulating more metal than males (p < 0.001). Both genders fed a high fat diet showed significant increases in cadmium levels compared to low fat diet fed mice (p < 0.001). Cadmium and high fat diet significantly affected the levels of several essential metals, including magnesium, potassium, chromium, iron, cobalt, copper, zinc and selenium. Additionally, these treatments resulted in increased superoxide levels within the cortex, amygdala and hippocampus. These findings support a model where cadmium and high fat diet affect the levels of redox-active, essential metal homeostasis. This phenomenon may contribute to the underlying mechanism(s) responsible for the development of neurocognitive disorders.

Blood-Based Biomarkers for Predictive Diagnosis of Cognitive Impairment in a Pakistani Population

Numerous studies have identified an association between age-related cognitive impairment (CI) and oxidative damage, accumulation of metals, amyloid levels, tau, and deranged lipid profile. There is a concerted effort to establish the reliability of these blood-based biomarkers for predictive diagnosis of CI and its progression. We assessed the serum levels of high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, total cholesterol, selected metals (Cu, Al, Zn, Pb, Mn, Cad), and total-tau and amyloid beta-42 protein in mild (n = 71), moderate (n = 86) and severe (n = 25) cognitively impaired patients and compared them with age-matched healthy controls (n = 90) from Pakistan. We found that a decrease in HDL cholesterol (correlation coefficient r = 0.467) and amyloid beta-42 (r = 0.451) were associated with increased severity of CI. On the other hand, an increase in cholesterol ratio (r = -0.562), LDL cholesterol (r = -0.428), triglycerides, and total-tau (r = -0.443) were associated with increased severity of CI. Increases in cholesterol ratio showed the strongest association and correlated with increases in tau concentration (r = 0.368), and increased triglycerides were associated with decreased amyloid beta-42 (r = -0.345). Increased Cu levels showed the strongest association with tau increase and increased Zn and Pb levels showed the strongest association with reduced amyloid beta-42 levels. Receiver Operating Characteristic (ROC) showed the cutoff values of blood metals (Al, Pb, Cu, Cad, Zn, and Mn), total-tau, and amyloid beta-42 with sensitivity and specificity. Our data show for the first time that blood lipids, metals (particularly Cu, Zn, Pb, and Al), serum amyloid-beta-42/tau proteins modulate each other's levels and can be collectively used as a predictive marker for CI.

Relation between cadmium body burden and cognitive function in older men: A cross-sectional study in China

Cadmium (Cd) is a known neurotoxicant and its relation with cognition has been well studied in children. However, evidence linking Cd and cognitive function among older individuals is limited. To evaluate the association between Cd exposure and cognitive function in older age, we conducted a cross-sectional study involving 375 older men aged 60-74 years (mean age: 66.0 years) in Guangxi, China. Urinary Cd concentrations were measured. Cognitive function was assessed by the Chinese version of Mini-Mental State Examination (MMSE) and cognitive impairment was identified using education-specific cutoff points of MMSE scores. General linear regression and logistic regression models were applied to evaluate the associations of urinary Cd concentrations with MMSE scores and the risk of cognitive impairment, respectively. The median urinary Cd concentration of all participants was 1.58 μg/g creatinine. Urinary Cd levels were inversely associated with MMSE scores [β = -0.76; 95% confidence interval (CI): -1.28 to -0.23 for a 2-fold increase in urinary Cd]. A 2-fold increase in urinary Cd was associated with increased risk of cognitive impairment [adjusted odds ratio (OR) = 1.46; 95% CI: 1.14 to 1.86]. When urinary Cd levels were analyzed as quartiles, higher urinary Cd levels were also significantly associated with increased risk of cognitive impairment in a dose-response manner (adjusted OR = 2.68; 95% CI: 1.33 to 5.38 for the highest vs. lowest quartile; p for trend = 0.002). Our findings suggest that long-term exposure to Cd may have adverse consequences for older men's cognitive function, but these results need further confirmation.

Characterising the spatial and temporal brain metal profile in a mouse model of tauopathy

A dysregulation in the homeostasis of metals such as copper, iron and zinc is speculated to be involved in the pathogenesis of tauopathies, which includes Alzheimer's disease (AD). In particular, there is a growing body of evidence to support a role for iron in facilitating the hyperphosphorylation and aggregation of the tau protein into neurofibrillary tangles (NFTs) - a primary neuropathological hallmark of tauopathies. Therefore, the aim of this study was to characterize the spatial and temporal brain metallomic profile in a mouse model of tauopathy (rTg(tauP301L)4510), so as to provide some insight into the potential interaction between tau pathology and iron. Using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), our results revealed an age-dependent increase in brain iron levels in both WT and rTg(tauP301L)4510 mice. In addition, size exclusion chromatography-ICP-MS (SEC-ICP-MS) revealed significant age-related changes in iron bound to metalloproteins such as ferritin. The outcomes from this study may provide valuable insight into the inter-relationship between iron and tau in ageing and neurodegeneration.

Environmental chronic exposure to metals and effects on attention and executive function in the general population

Heavy metals are neurotoxic, associated with brain dysfunction, and have been linked with cognitive decline in adults. This study was aimed to characterize chronic exposure to metals (Cd, Be, Co, Hg, Sn, V, Al, Ba, Cr, Cu, Fe, Li, Mn, Ni, Pb, and Zn) and metalloids (As, B, Sb) and assess its impact on cognitive performance of Tehran's residents, capital of Iran. Scalp hair samples gathered from 200 volunteered participants (110 men and 90 women), aged 14-70 years and quantified by inductively coupled plasma atomic emission spectroscopy (ICP-OES). Attention and executive function, two measures of cognitive performance, were characterized using the trail making test (TMT) part A and B, respectively. Mental flexibility was characterized as the Delta TMT B-A scores and cognitive efficiency or dissimulation as the ration between TMT B and A scores. A comprehensive questionnaire was used to gather information on demographic and socioeconomic as well as lifestyle and health status. The highest and lowest mean concentrations were observed for B (325 μg/g) and As (0.29 μg/g), respectively. Results indicated that chronic metal exposure measured in hair changed significantly based on gender and age (p < 0.05). The levels of Cr, Fe, Ni, Si, Hg, Pb and B were significantly higher in males' hair, whereas those of Ag and Ba were greater in females' hair (p < 0.05). The results of the cognitive TMT test were significantly different between gender and age groups (p < 0.05). Moreover, results revealed that As, Hg, Mn, and Pb levels in hair were significantly associated with poorer participants' performance scores in the TMT test (p < 0.05). Age, gender, cigarette smoking, water-pipe smoking, traffic density in the area of residence, and dental amalgam filling were significant factors affecting the TMT test scores. The results suggest that chronic exposure to metals has detrimental effects on attention, executive function, mental flexibility and cognitive efficiency.