To find out whether high fluoride exposure could affect the bone morphogenetic protein 2 (BMP-2) expression in human serum.

In the typical brick tea-type fluorosis areas of Guoluo Autonomous Prefecture of Qinghai Province, Hulunbeir City of Inner Mongolia Autonomous Region and Altay Prefecture of Xinjiang Autonomous Region, 73 patients with skeletal fluorosis in the typical brick-tea type fluorosis districts were selected. Accordingly, 73 age (difference not more than 3 years old), sex and nationality matched healthy controls were selected. The volunteers were investigated by questionnaire, and brick-tea water (or buttered tea), urine and peripheral blood samples were collected. Forearm, lumbar and pelvic joints were taken X-rays. The fluoride concentrations in brick-tea water (or buttered tea) and urine were determined by fluoride ion selective electrode method (WS/T 89-2006). The concentration of BMP-2 in human serum was quantified by enzyme linked immunosorbent assay (ELISA). The respondents were divided into 4 groups according to average daily fluoride intake, urine fluoride quartiles and different conditions of skeletal fluorosis, and further study was conducted.

Totally 146 subjects were investigated. The concentrations of BMP-2 in human serum among the groups with different ages were not significantly different (χ² = 2.95, P > 0.05). The concentrations of BMP-2 in human serum between female and male population were not significantly different (U = 2148.50, P > 0.05 ). However, compared with the concentration of BMP-2 in Kazakans' serum (median: 73.96 ng/L), the concentration of BMP-2 in Tibetans' serum was significantly higher (median: 109.91 ng/L, χ² = 36.28, P < 0.01). The average daily fluoride intake of brick-tea water was not significantly different between Tibetans and Kazakans (median: 7.69 vs. 7.05 ng/L, U = 674.00, P > 0.05). However, the urine fluoride concentration in Kazakans was significantly higher compared with that in Tibetans (median:3.42 vs. 2.23 ng/L, U = 672.00, P < 0.01). There were no significant differences of BMP-2 in human serum between different fluoride exposure and urine fluoride concentrations (χ² = 7.34, 1.94, all P > 0.05), and there were no spearman correlations between BMP-2, urine fluoride and urine fluoride concentrations (r = -0.037, -0.015, all P > 0.05). There was no significant difference in serum BMP-2 level between the patient and the control groups (Z = -1.78, P > 0.05). The difference of BMP-2 in human serum among different conditions of skeletal fluorosis was not significant (χ² = 2.83, P > 0.05).

Compared with the urine fluoride concentration in Kazakans, the urine fluoride concentration in Tibetans is significantly lower. However, compared with the concentration of BMP-2 in Kazakans' serum, the concentration of BMP-2 in Tibetans' serum is significantly higher.

Fluoride; Skeleton; Bone morphogenetic protein 2; Serum