Effect of occupational lead exposure on serum 1,25-dihydroxyvitamin D levels

Comparison of Vitamin B12, Vitamin D, and Folic Acid Blood Levels in Plumbism Patients and Controls in Eastern Iran

The aim of this study was to evaluate the blood levels of folic acid, vitamin B12, and 25-hydroxyvitamin D (25-OHD) in patients with lead poisoning compared with control subjects in Eastern Iran. This analytical case-control study was conducted on 40 lead-poisoned patients who were referred to Imam Reza Hospital in Birjand from 2018 to 2019. Blood samples were collected from an additional 40 individuals without lead poisoning as a control group. The results indicated that the mean vitamin B12, vitamin D, and folic acid levels for the case group were 356.5 ± 200.1 pg/ml, 24.38 ± 9.5 ng/ml, and 7.4 ± 3.7 ng/ml, respectively. Mean folic acid level in the case group was significantly lower than control group (7.4 ng/ml vs. 12.70 pg/ml, P = 0.001), whereas the mean of the vitamin D levels at the case group was significantly higher than that of the control group (24.3 ng/ml vs. 20.1 ng/ml, P = 0.03). Moreover, mean vitamin B12 levels were significantly lower in the case group in comparison with the control group (356.5 pg/ml vs. 500.8 pg/ml) (P < 0.001). In the control group, 3 patients had folic acid below normal level (< 6 ng/mL) while 12 cases had folic acid below normal (P < 0.05). Also, none of the control group had low vitamin B12 concentrations (< 180 pg/ml), while 7 cases had vitamin b12 below normal (P < 0.05). Our results suggest that lead may induce folate and vitamin B12 dysregulation. Although we found that vitamin D levels were insufficient in both case and control groups, they were significantly higher in the case group. The interpretation of this result is unclear given inconsistent literature reports on this relationship.

Impacts of lead exposure and chelation therapy on bone metabolism during different developmental stages of rats

OBJECTIVE

To explore the impacts of Pb exposure and the dimercaptosuccinic acid (DMSA) chelation therapy on bone metabolisms in young rats of different ages, as well as the potential mechanisms.

METHOD

Young rats were exposed to 0.05%-0.1% Pb acetate for 19 days, during infanthood (postnatal day, PND2-20), childhood (PND21-39) and adolescenthood (PND40-58) respectively. In each developmental stage, rats were further divided into three subgroups: lead-exposed, one-course and two-course DMSA chelation therapy subgroups. Blood/bone lead concentrations, serum calciotropic hormones concentrations, and mRNA and protein expressions of bone turnover markers in the serum and bones were measured. Bone microstructures were analyzed using Micro-CT.

RESULTS

Compared with lead-exposed during childhood and adolescenthood, increases in blood/bone lead levels, and the changes of blood/bone lead and trabecular bone microstructures after one-course DMSA chelation were most significant in rats lead-exposed during infanthood (P < .05). The serum osteocalcin (OC) concentrations, mRNA/protein expressions of OC and runt-related transcription factor 2 (RUNX2) in bones all decreased after Pb exposure, along with significant increases in serum C-terminal telopeptide of type I collagen (CTX) concentrations (P < .05). These effects were accompanied by changes of serum parathormone (PTH) and 1,25-dihydroxyvitamin D₃ (1,25-(OH₂)-D₃) concentrations. DMSA chelation partially reversed the changes of bone microarchitectures, bone formation and resorption markers, and calciotropic-hormones, and the efficiency was greatest when the therapy was provided during infanthood.

CONCLUSION

Developmental Pb exposure impaired bone microstructures and interfered bone metabolism, and the exposure effect was more obvious during infanthood than during childhood and adolescenthood. Lead effects were partially reversed by chelation therapy, and the efficacy may be most significant when the therapy was provided at younger ages.

Are Shiftwork and Indoor Work Related to D3 Vitamin Deficiency? A Systematic Review of Current Evidences

Background

Reported cases of vitamin D3 deficiency have been increasing in incidence worldwide. Although there is a lack of consensus relating to optimal levels of vitamin D, generally serum 25-(OH)D concentrations lower than 50 nmol/L (20 ng/mL) are at least considered to be detrimental to bone health.

Aim

Aim of this systematic review is to investigate if occupations, and specifically shiftworking and indoor working, may be considered as possible contributors to the increased incidence of vitamin D3 deficiency in industrialized nations.

Materials and Methods

Systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement using PubMed, Scopus, and ISI Web of Knowledge databases.

Results

Overall 90 papers were found, 23 articles through PubMed, 30 through Scopus, and 37 through ISI Web of Knowledge. Successively, 46 duplicates and 34 articles that did not respect the inclusion criteria were excluded. Finally 10 articles were selected: 9 cross-sectional studies and 1 systematic review. Results of the studies included revealed that certain occupations are either suffering from, or have a predilection to suffer from, a deficiency of this vitamin. Shiftworkers and indoor workers are consistently reported as being the occupational group most likely to suffer from a deficiency of vitamin D3. It would appear prudent to investigate the potential of providing nutritional education to workers in addition to including preventative measures in the workplace.

Vitamin D levels and deficiency with different occupations: a systematic review

Background

Vitamin D deficiency is prevalent worldwide, but some groups are at greater risk. We aim to evaluate vitamin D levels in different occupations and identify groups vulnerable to vitamin D deficiency.

Methods

An electronic search conducted in Medline, Embase, the Cochrane Central Register of Controlled Trials, and CINAHL Plus with Full Text generated 2505 hits; 71 peer-reviewed articles fulfilled the inclusion criteria. Occupations investigated included outdoor and indoor workers, shiftworkers, lead/smelter workers, coalminers, and healthcare professionals. We calculated the pooled average metabolite level as mean ± SD; deficiency/insufficiency status was described as % of the total number of subjects in a given category.

Results

Compared to outdoor workers, indoor workers had lower 25-hydroxyvitamin D (25-(OH)D) levels (40.6 ± 13.3 vs. 66.7 ± 16.7 nmol/L; p < 0.0001). Mean 25-(OH)D levels (in nmol/L) in shiftworkers, lead/smelter workers and coalminers were 33.8 ± 10.0, 77.8 ± 5.4 and 56.6 ± 28.4, respectively. Vitamin D deficiency (25-(OH)D < 50 nmol/L), was high in shiftworkers (80%) and indoor workers (78%) compared to outdoor workers (48%). Among healthcare professionals, medical residents and healthcare students had the lowest levels of mean 25-(OH)D, 44.0 ± 8.3 nmol/L and 45.2 ± 5.5 nmol/L, respectively. The mean 25-(OH)D level of practising physicians, 55.0 ± 5.8 nmol/L, was significantly different from both medical residents (p < 0.0001) and healthcare students (p < 0.0001). Nurses and other healthcare employees had 25-(OH)D levels of 63.4 ± 4.2 nmol/L and 63.0 ± 11.0 nmol/L, respectively, which differed significantly compared to practising physicians (p = 0.01), medical residents (p < 0.0001) and healthcare students (p < 0.0001).

Rates of vitamin D deficiency among healthcare professionals were: healthcare students 72%, medical residents 65%, practising physicians 46%, other healthcare employees 44%, and nurses 43%. Combined rates of vitamin D deficiency or insufficiency (25-(OH)D < 75 nmol/L) were very high in all investigated groups.

Potential confounders such as gender and body composition were not consistently reported in the primary studies and were therefore not analyzed. Furthermore, the descriptions of occupational characteristics may be incomplete. These are limitations of our systematic review.

Conclusions

Our review demonstrates that shiftworkers, healthcare workers and indoor workers are at high risk to develop vitamin D deficiency, which may reflect key lifestyle differences (e.g. sunlight exposure). This may help target health promotion and preventive efforts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-017-4436-z) contains supplementary material, which is available to authorized users.

The effect of lead intoxication on endocrine functions

Studies on the effects of lead on the endocrine system are mainly based on occupationally lead-exposed workers and experimental animal models. Although evidence is conflicting, it has been reported that accumulation of lead affects the majority of the endocrine glands. In particular, it appears to have an effect on the hypothalamic-pituitary axis causing blunted TSH, GH, and FSH/LH responses to TRH, GHRH, and GnRH stimulation, respectively. Suppressed GH release has been reported, probably caused by reduced synthesis of GHRH, inhibition of GHRH release or reduced somatotrope responsiveness. Higher levels of PRL in lead intoxication have been reported. In short-term lead-exposed individuals, high LH and FSH levels are usually associated to normal testosterone concentrations, whereas in long-term exposed individuals' low testosterone levels do not induce high LH and FSH concentrations. These findings suggest that lead initially causes some subclinical testicular damage, followed by hypothalamic or pituitary disturbance when longer periods of exposure take place. Similarly, lead accumulates in granulosa cells of the ovary, causing delays in growth and pubertal development and reduced fertility in females. In the parenchyma of adrenals histological and cytological changes are demonstrated, causing changes in plasma basal and stress-mediated corticosterone concentrations and reduced cytosolic and nuclear glucocorticoid receptor binding. Thyroid hormone kinetics are also affected. Central defect of the thyroid axis or an alteration in T4 metabolism or binding to proteins may be involved in derangements in thyroid hormone action. Lead toxicity involves alterations on calcitropic hormones' homeostasis, which increase the risk of skeletal disorders.

Associations of bone mineral density and lead levels in blood, tibia, and patella in urban-dwelling women

OBJECTIVE

The objective of this study was to evaluate the relations between bone mineral density (BMD) and lead in blood, tibia, and patella and to investigate how BMD modifies these lead biomarkers in older women.

DESIGN

In this study, we used cross-sectional analysis.

PARTICIPANTS

We studied 112 women, 50-70 years of age, including both whites and African Americans, residing in Baltimore, Maryland.

MEASUREMENTS

We measured lumbar spine BMD, blood and bone lead by dual energy X-ray absorptiometry, anodic stripping voltammetry, and (109)Cd-induced K-shell X-ray fluorescence, respectively. We measured vitamin D receptor and apolipoprotein E (APOE) genotypes using standard methods.

RESULTS

Mean (+/- SD) BMD and lead levels in blood, tibia, and patella were 1.02+/-0.16 g/cm(2), 3.3+/-2.2 microg/dL, 19.7+/-13.2 microg/g, and 5.7+/-15.3 microg/g, respectively. In adjusted analysis, higher BMD was associated with higher tibia lead levels (p=0.03). BMD was not associated with lead levels in blood or patella. There was evidence of significant effect modification by BMD on relations of physical activity with blood lead levels and by APOE genotype on relations of BMD with tibia lead levels. There was no evidence that BMD modified relations between tibia lead or patella lead and blood lead levels.

CONCLUSIONS

We believe that BMD represents the capacity of bone that can store lead, by substitution for calcium, and thus the findings may have relevance for effect-size estimates in persons with higher BMD.

RELEVANCE TO CLINICAL PRACTICE

The results have implications for changes in lead kinetics with aging, and thus the related risk of health effects associated with substantial early- and midlife lead exposure in older persons.

Seasonal changes in calcitropic hormones in Israeli men

Seasonal changes in calcitropic hormones might be expected, being that dietary calcium intake may differ with fluctuations in climate and temperature, and vitamin D is diet- and sunlight-dependent. While there are studies on elderly subjects, prospective data on younger men is limited. The objective of this study was to clarify possible seasonal changes in homeostatic regulators of calcium in Israeli men aged 25-64 years. The study was a prospective follow-up analysis of data collected during June-August 1995 and 1996 (summer) and January March 1995 and 1996 (winter). Subjects were ninety-five industrial male employees with and without occupational lead exposure. The main outcome measures were summer and winter serum concentrations of parathyroid hormone (PTH), 25-hydroxyvitamin D (25-OH-D), and 1,25-dihydroxyvitamin D (calcitriol). Summer and winter values of PTH were similar (38.2 and 39.8 ng/l, respectively). 25-OH-D levels were significantly higher in summer (32.8 ng/ml) than in winter (25.4 ng/ml) after controlling for possible confounders (p < 0.0001). Calcitriol levels were significantly higher in summer (79.1 pmol/l) than in winter (73.5 pmol/l) in univariate analyses, but not after controlling for possible confounders. We conclude that healthy men show considerable seasonal changes in 25-OH-D levels even in Israel, a relatively sunny country all the year round. Summer values of 25-OH-D, were 35% higher than in winter. These fluctuations should be taken into account during evaluation of pathological conditions and in research. Given an adequate diet and vitamin D status there are no seasonal variations in PTH or in calcitriol levels.

Association of calcitriol and blood pressure in normotensive men

The purpose of this study was to clarify the possible associations between the serum 1,25-dihydroxyvitamin D (calcitriol) level and blood pressure. Cross-sectional analysis of data was performed. Data collected included levels of serum calcitriol, parathyroid hormone, serum calcium, and blood lead; blood pressure; dietary history; and demographic and anthropometric variables. One hundred normotensive male industrial employees made up the study population. Systolic blood pressure and diastolic blood pressure were main outcome measures. After possible confounders were controlled for, multivariate analyses yielded an inverse, independent, and statistically significant association between calcitriol level and systolic blood pressure (standardized beta= -0.2704, P=.0051). A similar trend of borderline significance was found for the association between calcitriol and diastolic blood pressure (standardized beta= -0.1814, P=.0611). Parathyroid hormone, serum calcium, and blood lead levels were not associated with blood pressure. When subjects were divided into four groups by calcitriol level, those in the lowest quartile showed significantly higher systolic and diastolic blood pressures than those in the upper quartile (difference=11 mmHg, P=.007, and difference=4 mmHg, P=.071, respectively). There is an inverse association between serum calcitriol level and blood pressure. This suggests that in addition to its role in calcium homeostasis, the active metabolite of vitamin D may play a role in determining blood pressure. The differences in both systolic and diastolic blood pressures between the upper and lower quartiles of serum calcitriol were substantial and may be of clinical significance.