Arsenic exposure associated with decreased bone mineralization in male

Abstract

Objective: Arsenic (As) exposure may cause several medical problems. There were a few studies investigated whether it has affected bone tissue in women. However, there was no study in men. The aim of this study was to evaluate associations between bone mineral density (BMD) and As exposure in men subjects.

Material and methods: We enrolled in this study 254 subjects who due to chronic As exposure suspected and 82 subjects as a control group. Hair As levels were detected by a hair analysis (Varian AA240Z Zeeman Atomic Absorption Spectrometer, USA). BMD measurements were obtained using dual-energy X-ray absorptiometry instrumentation. We investigated associations between the hair As levels and BMD measurements.

Results: The frequency of osteoporosis and osteopenia was found to be 0.8% and 54.5%, respectively, in the As exposure group. The frequency of osteoporosis was found to be 1% and osteopenia was 32.4% in control subjects. There was significant difference between two groups (p < 0.001). Hair As level has a median 1.01 (min: 0.06 and max: 25.71). There were no significant correlation between hair As levels and BMD measurements.

Conclusion: According to our observations, As exposure was associated with bone metabolism. Possible cause of osteopenia may be exposure to As. Further investigations are needed to estimate the relationship between As and bone metabolism.

• Arsenic
• body mineral density measurements
• male

Introduction

Arsenic (As) exposure is a global health problem. As is known to be carcinogenic and an element of toxic effects on different systems to humans. Exposure to As can occur in the industry or in the environment. As enters the body in several ways and may get eliminated in several pathways such as in urine and feces. As exposure can lead to acute and chronic illness. Acute exposure of As emesis causes vomiting, paralysis, febrile, cardiac arrhythmias and convulsion. While As levels decline in the liver, spleen, gastrointestinal tract approximately after one month of initial As exposure, it can begin to accumulate in the bone. Thereafter, it can lead to serious toxicities in these tissues depending on its doses and exposure duration. However, there were a few studies investigated whether it has affected bone tissue [1,2]. Late phases of As exposure accumulated in the bone, and it may remain for many years in bone [3]. As can compete with phosphorus in the oxidative phosphorylation process, and this can lead to the replacement of phosphorus in the bone [4]. However, data on the As concentration of human bones are very little. There have been very few studies that have investigated the effects of As on bone metabolism. An experimental study revealed that As alters endochondral ossification [5]. Only clinical study demonstrated that there was no relationship between As levels and patients with postmenopausal osteoporosis [6]. However, to our knowledge, bone mineral density (BMD) measurements have not investigated As exposure in men. Therefore, we investigated associations between BMD and hair As levels.

Patients and methods

Study patients

This study included patients who referred to Ankara Occupational Diseases Hospital due to chronic As exposure suspected during 2011 and 2012. We enrolled in this study a total of 274 subjects, between ages 18 and 55 years. In our study, we included subjects working in a job that involves As production or use, such as copper or lead smelting, wood treating or pesticide application. Before the subjects referred our center, all workers As levels were examined with a urine test. Patients with excess As levels in the urine test referred our hospital. We investigated As levels in hair. We considered several confounders: age, race, sex, body mass index (BMI), tobacco use, alcohol use, physical activity, calcium intake, chronic medical conditions, use of certain medications and socioeconomic status. The exclusion criteria included women, hyperthyroidism, liver disease, kidney disease and use of medications or recreational drugs that may affect bone metabolism. Height and weight were recorded in all subjects. BMI was calculated by using a formula: weight (kg)/height (m²).

Control subjects

Control subjects were selected among healthy men subjects. Some systemic diseases including diabetes mellitus, liver disease, kidney disease and use of medications or recreational drugs may affect bone metabolism.

Definition of As exposure

Hairs from the neck region were thoroughly cleaned with 0.1% Triton-X solution and then washed several times with distilled water. Specimens were dried at room temperature for 24 hours. Then, 0.1 g specimens were weighed and microwaved with high temperature-resistant Teflon tubes. Then 5 ml of 65% nitric acid (HNO₃) was added. After the burning process (CEM Mars Xpress microwave oven at 200 °C for 15 min, 1600 W power), burned hair samples were transferred to polypropylene tubes containing 15 ml. Total volume was completed to 10 ml with deionized water. Hair samples were analyzed by AA240Z Varian Zeeman Atomic Absorption Spectrometer.

Bone mineral density

The primary outcome was the mean BMD of the lumbar vertebra and femoral neck head. BMD measurements were obtained using dual-energy X-ray absorptiometry instruments (QDR 1000; Hologic, Waltham, MA) in pencil-beam model. The diagnosis was osteopenia, lowest T score −1.1 to −2.5, osteoporosis more than −2.5 SD.

Statistical methods

The results were expressed as mean ± standard deviation. As levels and BMD measurements were shown as median (minimum–maximum). Qualitative variables were analyzed with the chi-square test. Quantitative variables were analyzed with Student’s t-test and Mann–Whitney U test. The Spearman correlation coefficient was used to examine the relationship between As levels and BMD measurements. p Value under 0.05 was considered statistically significant. Statistical Package for the Social Sciences (SPSS) 15.0 software (Chicago, IL) was used for all analysis.

Results

Our study included a total of 274 As-exposure patients. Twenty patients were excluded because of liver test abnormality (five patients), anemia (seven patients), diabetes mellitus (five patients) and renal test abnormality (three patients). Two-hundred fifty-four patients were analyzed. The mean age of the patients included in the study was found to be 32.4 ± 7.6 years. Mean BMI was found to be 25.5 ± 11.5 kg/m². The rate of cigarette smoking was 38%. Any patients’ history of medical conditions was not any systemic diseases and alcohol consumption. Liver tests, whole blood measurements and levels of bone mineral metabolism markers (phosphor, ALP and Ca) are presented in Table 1. There was no significant difference between As exposure and control groups.

Table 1. Demographic and laboratory findings.

	Control group	Arsenic exposure group	p Value
Age (years)	33.4 + 6.9	32.4 ± 7.6	0.456
Body mass index (kg/m^2)	26.5 ± 7.6	25.5 ± 11.5	0.767
Smoking (%)	30.8	68	< 0.001
Arsenic levels (μg/g)	–	1.01 (min: 0.06 and max: 25.71)
Hemoglobin (g/dl)	15.1 ± 1.2	15.6 ± 1.0	0.498
White cell counts (mm^3)	8200 ± 3200	7700 ± 2900	0.431
Thrombocyte (mm^3)	243 000 ± 55 000	218 000 ± 48 000	0.536
Aspartat aminotransferase (U/L)	15.0 ± 5.1	19.9 ± 4.7	0.423
Alanine aminotransferase (U/L)	22.1 ± 6.8	20.6 ± 8.9	0.125
Alkaline phosphatase (U/L)	88 ± 20.1	82.3 ± 21.4	0.240
Gama glutamil tranferase (U/L)	23.4 ± 8.0	22.8 ± 9.1	0.127
Creatinin (mg/dl)	0.8 ± 0.2	0.9 ± 0.2	0.945
Urea (g/dl)	12.3 ± 4.1	13.1 ± 3.0	0.450
Thyroid Stimulating hormone	1.6 ± 0.3	1.7 ± 0.9	0.345
Phosphor (mg/dl)	3.5 ± 0.4	3.7 ± 0.5	0.923
Calcium (mg/dl)	9.5 ± 0.5	9.9 ± 0.4	0.825
Magnesium (mg/dl)	2.1 ± 0.2	2.0 ± 0.1	0.912

The frequency of osteoporosis and osteopenia was found to be 0.8% and 54.5 in patients with As exposure. Control subjects osteoporosis frequency was detected as 1% and osteopenia was 32.4%. Osteopenia frequency in the As-exposure group was found higher than the control group (p < 0.001). Total femur T scores and total lumbar spine scores were significantly lower in the As-exposure group compared to control subjects. Table 2 shows BMD values of patients with As-exposure and control groups. Hair As levels had median 1.01 μg/g (min: 0.06 and max: 25.71). Study subjects were further subdivided into two groups based on the recommended upper limit, 1 μg/g, of hair As concentration. BMD measurements had no significant difference among two groups (p > 0.05). Subject with greater hair As levels showed osteopenia rate of 51.8% and lesser 1% 57.3 (p = 0.382). Phosphor, alkaline phosphatase, calcium and magnesium were found to be similar in both groups. There was no correlation in hair As levels and any BMD measurements (p > 0.05).

Table 2. T scores show in control and Arsenic exposure group.

	Control group	Arsenic exposure group	p Values
Total lumbar T score	−0.2 (−1.9–2.10)	−0.7 (−3.0–2.55)	0.011
Femur neck T score	−0.6 (−1.9–2.54)	−1.0 (−2.95–1.47)	0.032

Values were showed as a median (minimum–maximum).

Discussion

As may accumulate in bone tissues and it may lead to bone marrow depression. However, there is very little knowledge regarding effects on bone metabolism. A few very old publications showed that small amount of As was detected in bone [7,8]. However, until now, only one clinical study had investigated the relationship between As and BMD [6]. This study revealed that As did not link with postmenopausal osteoporosis in woman. However, there was no study on men regarding the relationship between As levels and BMD.

Our study showed that osteoporosis frequency was similar between control and As exposure groups. However, we demonstrated higher osteopenia frequency in As exposure groups compared to control groups. But we did not show that hair As levels was not associated with any BMD measurements. However, in general, osteopenia or osteoporosis in men has been occurring in very few older than 50 years. Several risk factors lead to BMD: advanced age, glucocorticoid using, tobacco and alcohol use, low levels androgens, thyroid disorders, chronic liver and kidney diseases and low BMI. Our study included subjects who were young men and any risk factors for osteoporosis were not found. Therefore, we think that As exposure can lead to bone mineral metabolism.

Previous studies reported that As in bone replacement of phosphorus has a role of oxidative phosphorylation process [4]. A new experimental study shows As lead to decreased osteoblast differentiation and function [9]. That study showed declined BMD and trabecular bone volume of femur in As-treated rats. In cell culture, ATO decreased osteoblast mineralization by decreasing alkaline phosphatase expression, and this effect was prevented by co-addition of inorganic phosphate. Moreover, As lead to decrease of bone turnover markers of osteocalcin, procollagen type I N-terminal propeptide and C-terminal cross-linked telopeptide. Another experimental study by Odstrcil Adel C et al. showed that As leads to total growth cartilage plate thickness at the expense of the hypertrophic zone. Therefore, authors argued that AS deteriorated endochondral ossification [5].

In conclusion, our observations of As association with and bone metabolism and chronic As exposure possible caused osteopenia. Further investigations are needed to estimate the relationship between As and bone metabolism.

Declaration of interest

We certify that no party having a direct interest in the results of the research supporting this article has or will confer a benefit on us or on any organization with which we are associated.