Prevalence of Brick Tea-Type Fluorosis in the Tibet Autonomous Region

Regulating effect of miR-132-3p on the changes of MAPK pathway in rat brains and SH-SY5Y cells exposed to excessive fluoride by targeting expression of MAPK1

BACKGROUND

Although the changes of mitogen-activated protein kinase (MAPK) pathway in the central nervous system (CNS) induced by excessive fluoride has been confirmed by our previous findings, the underlying mechanism(s) of the action remains unclear. Here, we investigate the possibility that microRNAs (miRNAs) are involved in the aspect.

METHODS

As a model of chronic fluorosis, SD rats received different concentrations of fluoride in their drinking water for 3 or 6 months and SH-SY5Y cells were exposed to fluoride. Literature reviews and bioinformatics analyses were used to predict and real-time PCR to measure the expression of 12 miRNAs; an algorithm-based approach was applied to identify multiply potential target-genes and pathways; the dual-luciferase reporter system to detect the association of miR-132-3p with MAPK1; and fluorescence in situ hybridization to detect miR-132-3p localization. The miR-132-3p inhibitor or mimics or MAPK1 silencing RNA were transfected into cultured cells. Expression of protein components of the MAPK pathway was assessed by immunofluorescence or Western blotting.

RESULTS

In the rat hippocampus exposed with high fluoride, ten miRNAs were down-regulated and two up-regulated. Among these, miR-132-3p expression was down-regulated to the greatest extent and MAPK1 level (selected from the 220 genes predicted) was corelated with the alteration of miR-132-3p. Furthermore, miR-132-3p level was declined, whereas the protein levels MAPK pathway components were increased in the rat brains and SH-SY5Y cells exposed to high fluoride. MiR-132-3p up-regulated MAPK1 by binding directly to its 3'-untranslated region. Obviously, miR-132-3p mimics or MAPK1 silencing RNA attenuated the elevated expressions of the proteins components of the MAPK pathway induced by fluorosis in SH-SY5Y cells, whereas an inhibitor of miR-132-3p just played the opposite effect.

CONCLUSION

MiR-132-3p appears to modulate the changes of MAPK signaling pathway in the CNS associated with chronic fluorosis.

Drinking brick tea containing high fluoride increases the prevalence of osteoarthritis in Tibetan, China

The prevalence of osteoarthritis (OA) in Tibetans is higher than that in Han, while Tibetans have a habit of drinking brick tea with high fluoride. A cross-sectional study was conducted to explore the association between fluoride exposure in drinking brick tea and OA. All subjects were divided into four groups by the quartiles (Q) of tea fluoride (TF) and urine fluoride (UF). ROC was plotted and OR were obtained using logistic regression model. The prevalence of OA in the Q3 and Q4 group of TF were 2.2 and 2.7 times higher than in the Q1 group, and the prevalence of OA in the Q2, Q3 and Q4 group of UF were 3.2, 3.5, and 4.1 times higher than in the Q1 group. ROC analysis showed the cutoff values were 4.523 mg/day (TF) and 1.666 mg/L (UF). In conclusion, excessive fluoride in drinking brick tea could be a risk factor for developing OA.

Fluoride Exposure and Skeletal Fluorosis: a Systematic Review and Dose-response Meta-analysis

PURPOSE OF REVIEW

We performed a systematic review and meta-analysis on the relation between fluoride exposure and skeletal fluorosis (SF) using a novel statistical methodology for dose-response modeling.

RECENT FINDINGS

Skeletal fluorosis, a major health issue that is endemic in some regions, affects millions of people worldwide. However, data regarding the dose-response relation between fluoride exposure and SF are limited and outdated. We included twenty-three studies in the meta-analysis. When comparing the highest versus the lowest fluoride category, the summary risk ratio (RR) for SF prevalence was 2.05 (95% CI 1.60; 2.64), with a value of 2.73 (95% CI 1.92; 3.90) for drinking water and 1.40 (95% CI 0.90; 2.17) for urinary fluoride. The RR by the risk of bias (RoB) was 2.37 (95% CI 1.56; 3.58) and 1.78 (95% CI 1.34; 2.36) for moderate and high RoB studies, respectively. The dose-response curve based on a one-stage cubic spline regression model showed an almost linear positive relation between exposure and SF occurrence starting from relatively low concentrations up to 5 mg/L and 2.5 mg/L, respectively, for water and urinary fluoride, with no substantial increase above this threshold. The RR for developing moderate-severe forms increases at 5.00 mg/L and 2.5 mg/L of water and urinary fluoride, respectively. Better-quality studies are needed to confirm these results, but greater attention should be given to water fluoride levels to prevent SF, in addition to the other potential adverse effects of fluoride exposure.

Relatively low fluoride in drinking water increases risk of knee osteoarthritis (KOA): a population-based cross-sectional study in China

Previous studies indicate that fluoride in drinking water has a toxic effect on cartilage and skeleton, which triggers osteoarthritis (OA) of which the most frequent is knee OA (KOA). A cross-sectional study was conducted to assess the association between fluoride exposure and KOA among 1128 subjects. Water fluoride (WF) and urinary fluoride (UF) were chosen as external exposure (internal exposure) of fluoride. Logistic regression analysis showed that an increased fluoride exposure was a risk factor for KOA (WF: OR = 1.318, 95% CI 1.162-1.495, p < 0.001; UF: OR = 1.210, 95% CI 1.119-1.310, p < 0.001). After adjusting for covariates, the risk of KOA in the 4th quartile (Q) of WF was twice that of the 1st Q (OR = 2.079, 95% CI 1.448-2.986, p < 0.001). The risks of KOA in the 2nd Q, 3rd Q and 4th Q of UF were 1.6, 1.5, and 2.9 times higher than in the 1stQ (OR = 1.597, 95% CI 1.066-2.393, p = 0.023; OR = 1.560, 95% CI 1.043-2.333, p = 0.030; OR = 2.897, 95% CI 1.957-4.288, p < 0.001). The population aged < 60 exposed to the 4th Q of WF (or UF) had a higher risk than the population exposed to the 1st Q of WF (or UF) (ORWF = 1.958, 95% CI 1.249-3.070, p = 0.003; ORUF = 2.923, 95% CI 1.814-4.711, p < 0.001). With increasing UF by Q, the male had a risk of KOA. In conclusion, excessive fluoride dose in drinking water could increase the risk of KOA. Especially, the population with aged < 60, male and obesity more likely to having KOA when they exposed to same higher fluoride.

Factors influencing the spatial distribution and individual variation in urinary fluoride levels in Tibet, China

Nowadays, fluorosis is the most prevalent endemic disease in Tibet and one of the most concerned public health problems in China; urinary fluoride is a common diagnostic indicator of endemic fluorosis. However, the spatial distribution and influencing factors of urinary fluoride content in Tibet remain unclear. This study aims to bridge this gap by geographically weighted regression (GWR), analyses of variance (ANOVAs), Geodetector, and stepwise multiple linear regression (MLR). To achieve this goal, this study first investigated fluoride levels in the fasting urine among 637 Tibetan residents from 73 counties in Tibet, the urinary fluoride level was chosen as an indicator of fluorosis, which can reflect the health impairment. Then we identified the potential factors that could influence the spatial distribution and individual variation of urinary fluoride levels from physical environmental and socioeconomic perspective, respectively. The results showed that urinary fluoride levels in Tibet were slightly exceeding the average value for adult urinary fluoride in China, and that residents with high urinary fluoride were mainly found in the west and east; those with low urinary fluoride were mainly found in the central-southern regions. And the urinary fluoride levels had a significantly positive correlation with water fluoride and a significantly negative correlation with average annual temperature. Urinary fluoride levels increased until age 60 and followed an inverted "U"-shaped trajectory according to annual household income (80,000 renminbi (RMB) was the inflection point); pastoralists had greater exposure to fluoride than farmers. Furthermore, the Geodetector and MLR showed that the urinary fluoride level was influenced by both physical environmental and socioeconomic factors. The socioeconomic factors such as age, annual household income and occupation had a greater impact than the physical environment on urinary fluoride concentration. These findings can provide scientific basis for preventing and controlling endemic fluorosis in the Tibetan Plateau and adjacent areas.

Effects of aqueous extract from Baiyedancong-Oolong tea on cytochrome P450 enzymes activities, P-gp and OATs transport abilities and transcription levels in mice

Introduction

Recent studies have been conducted on its influence on drug metabolism and its potential mechanisms, among which the most studies have been focused on CYP3A enzymes.

Methods

In this study, Baiyedancong Oolong tea (BOT) was processed by freeze- and hot air-drying techniques separately to obtain the aqueous extracts of freeze-and hot-dried BOT (FBOT and HBOT, respectively). High and low doses of FBOT (1463.7 and 292.74 mg/kg/d, respectively) and HBOT (1454.46 mg/kg/d, 290.89, respectively) were administered to mice for 7 days.

Results

Aqueous extracts from BOT simultaneously improved liver CYP3A, CYP2E1, and CYP2C37 activities and weakened the transport ability of P-gp and OATs in a dose-dependent manner, thus affecting multiple links of oral drug metabolism in liver, intestinal absorption and metabolism, and renal excretion. Moreover, aqueous extracts from BOT significantly increased the mRNA expressions of liver CYP3A11 and CYP2C37 as well as intestinal CYP3A11. Decreased transcription levels of MDR1 encoding P-gp in small intestine and renal OAT1 and OAT3, which was in the same direction as the regulation of the above enzyme activities and transport capacities. Besides, the transcription level of liver CYP2E1 was weakened, which was inconsistent with its corresponding enzyme activity, suggesting that the increased CYP2E1 activity may be caused by other mechanisms.

Conclusion

Daily consumption or high dose administration of BOT and its related products may affect drug absorption, metabolisms, and excretion.

Characteristics, sources, and risk assessment of thallium and associated with metal(loid)s in the Yarlung Tsangpo River Basin, southern Tibetan Plateau

The Tibetan Plateau (TP) is known as the water tower of Asia, and the water quality has long been a focus of public concern, especially in the Yarlung Tsangpo River Basin (YTRB), a unique area that is climate-sensitive, geologically complex, eco-fragile, and densely populated. Thallium (Tl) is a typical metal that is more toxic than Pb, Cd, and As and often occurs in sulfide minerals. Although large-scale polymetallic sulfide mineralization developed in the YTRB, the geochemical dispersion and potential risk of Tl in aquatic environments of the YTRB remain poorly understood. In this study, the concentration, distribution, source, and health risk of Tl and associated metal(loid)s in the hot springs and surface water in the YTRB were systematically analyzed. The results showed that the trace elements (Cd, Cr, Zn, Cu, Al, Sr, Ni, Co, Mn, Pb) in water environments are within the recommended limits, except for Tl and As. Principal component analysis (PCA) and correlation analysis (CA) showed that the elements of Tl and As were positively related to each other in either both hot spring water and surface water, indicating their common origin. Spatial variations suggested that high levels of Tl and As observed in the north YTRB, which may be relevant to the reduction-dissolution of Tl (As)-bearing minerals and the magmatic hydrothermal system formed in the shallow part of the northern YTRB. Furthermore, source apportionment identified natural sources of Cu, Ni, Cr, Co, Mn, Zn, and Cd and anthropogenic inputs of Al and Pb. Exposure assessment studies have found that ingestion is the primary route of As and Tl exposure to local population, and balneological and bathing purposes do not constitute a human health concern. This study offers valuable insights into the risk of naturally occurring Tl enrichment being hidden in As-rich hydrosphere in the YTRB and other regions with similar geoenvironmental contexts.

Brick tea consumption and its relationship with fluorosis in Tibetan areas

Brick tea-type fluorosis (BTF) due to a high intake of brick tea is possible in Tibetan populations, and dental fluorosis (DF) and skeletal fluorosis (SF) are its primary manifestations. To determine the prevalence of DF and SF and their relationships with brick tea intake in Tibetan populations, a literature review was conducted for studies published between 1994 and 2021. The available evidence revealed that brick tea may be produced from older stems and leaves of the tea plant and that the fluoride content of brick tea exceeds the national standard. The harsh environment of the plateau has led to limited food sources for the local Tibetan people who form the habit of drinking tea leaves as a satiation solution to digest greasy food and replenish vitamins, and regular consumption of brick tea leads to excessive exposure of Tibetan residents to fluoride. Studies in Tibet showed that the prevalence of DF in children was 14.06-75.93% in different districts, and the overall pooled prevalence of DF was 26.08%. The prevalence of SF in adults was 19.90-74.77% in different Tibetan districts, and the overall pooled prevalence of SF was 33.84%. The analysis of risk factors showed that the prevalence of BTF may be related to high-altitude and different working and living conditions, and BTF in children may be associated with fluoride intake during mothers' pregnancy and lactation. With the development of bioinformatics research, gene polymorphisms were suspected to be related to susceptibility to fluorosis in Tibetan populations. The study of BTF in Tibetan people needs to be further investigated and standardized, and additional studies evaluating the pathogenesis and preventive measures of BTF are warranted.

Association of Tibetan Habitual Food and Metabolic Syndrome Among Tibetan People in China: A Cross-Sectional Study

Background

The association between habitual food intake in Tibet and metabolic syndrome (MetS) is largely unclear.

Objective

To examine the association between Tibetan habitual food intake and MetS among Tibetan adults.

Methods

A population-based cross-sectional study, named the China Multi-Ethnic Cohort (CMEC) study, was conducted between 2018 and 2019. We used data from all Tibetans in the CMEC in the current study. The participants, 1,954 men and 3,060 women aged 18–79 years, were from Lhasa, Tibet Autonomous Region, Tibet. The habitual dietary intake was assessed using a food frequency questionnaire (FFQ). MetS was defined according to ATP III guidelines. Multivariate logistic regression was used to estimate the association between five Tibetan habitual foods and MetS.

Results

Tsampa, butter tea, and Qing cha intake were associated with reduced prevalence of MetS. Compared with the lowest quartile of each food, odds ratios (ORs) and their 95% confidence intervals (95% CIs) of medium and high Tsampa intake were 0.59 (0.41–0.85) and 0.53 (0.36–0.77), ORs (95% CIs) of butter tea were 0.67 (0.52–0.88) and 0.61 (0.46–0.81), and Qing cha were 0.85 (0.71–1.03) and 0.75 (0.60–0.93), respectively. When exploring the joint effects of these three foods on MetS, the adjusted ORs and their 95% CIs were 0.65 (0.49–0.87) for the middle intake group and 0.59 (0.42–0.83) for the high intake group as compared with the never/rarely group (p = 0.022 for trend). Associations of MetS with Tibetan noodles and raw beef were not observed.

Conclusion

Tsampa, butter tea, and Qing cha were negatively associated with MetS. The recommendation of increasing the intake of these foods may be beneficial for MetS prevention.

A critical review of Fuzhuan brick tea: processing, chemical constituents, health benefits and potential risk

Fuzhuan brick tea (FBT) is a traditional popular beverage in the border regions of China. Nowadays, FBT has been attracted great attention due to its uniquely flavor and various health-promoting functions. An increasing number of efforts have been devoted to the studies on health benefits and chemistry of FBT over the last decades. However, FBT was still received much less attention than green tea, oolong tea and black tea. Therefore, it is necessary to review the current encouraging findings about processing, microorganisms, chemical constituents, health benefits and potential risk of FBT. The fungus fermentation is the key stage for processing of FBT, which is involved in a complex and unique microbial fermentation process. The fungal community in FBT is mainly dominated by "golden flower" fungi, which is identified as Aspergillus cristatus. A great diversity of novel compounds is formed and identified after a series of biochemical reactions during the fermentation process of FBT. FBT shows various biological activities, such as antioxidant, anti-inflammatory, anti-obesity, anti-bacterial, and anti-tumor activities. Furthermore, the potential risk of FBT was also discussed. It is expected that this review could be useful for stimulating further research of FBT.

Progress of Signaling Pathways, Stress Pathways and Epigenetics in the Pathogenesis of Skeletal Fluorosis

Fluorine is widely dispersed in nature and has multiple physiological functions. Although it is usually regarded as an essential trace element for humans, this view is not held universally. Moreover, chronic fluorosis, mainly characterized by skeletal fluorosis, can be induced by long-term excessive fluoride consumption. High concentrations of fluoride in the environment and drinking water are major causes, and patients with skeletal fluorosis mainly present with symptoms of osteosclerosis, osteochondrosis, osteoporosis, and degenerative changes in joint cartilage. Etiologies for skeletal fluorosis have been established, but the specific pathogenesis is inconclusive. Currently, active osteogenesis and accelerated bone turnover are considered critical processes in the progression of skeletal fluorosis. In recent years, researchers have conducted extensive studies in fields of signaling pathways (Wnt/β-catenin, Notch, PI3K/Akt/mTOR, Hedgehog, parathyroid hormone, and insulin signaling pathways), stress pathways (oxidative stress and endoplasmic reticulum stress pathways), epigenetics (DNA methylation and non-coding RNAs), and their inter-regulation involved in the pathogenesis of skeletal fluorosis. In this review, we summarised and analyzed relevant findings to provide a basis for comprehensive understandings of the pathogenesis of skeletal fluorosis and hopefully propose more effective prevention and therapeutic strategies.

Application of BRAFO-tiered approach for health benefit-risk assessment of dark tea consumption in China

Dark tea, a unique tea fermented primarily in China, has numerous potential beneficial effects. However, harmful substances present in dark tea have provoked significant concern. To conduct a quantitative benefit-risk assessment of dark tea for Chinese residents and provide guidance on rational consumption, a framework of Benefit-Risk Analysis for Foods (BRAFO) and meta-analysis was applied to construct a disability-adjusted life year (DALY). Based on the BRAFO-tiered approach, a reference scenario (no intake) and an alternative scenario (intake of 3 cups/day) were determined. The overall health impacts of dark tea were simulated by comparing the risks of fluoride and AF with benefits of reduced-risk to coronary heart disease (CHD) and diabetes in different scenarios. Three cups of fermented tea consumed per day decreased risks of CHD and diabetes by 8.16% and 12.77% respectively. After quantitative integration of information, the ultimate net health effect was found to be -1958.827 illustrating that the benefits of drinking three cups of dark tea per day outweigh the risks. However, considering the uncertainties in the process, decision-makers should proceed with caution, consulting additional well-conducted studies and further managing harmful substances in dark tea.

Meta-analysis and risk assessment of fluoride contamination in groundwater

This study aimed to carry out a systematic review of meta-analysis and risk assessment of the global pooled concentration of fluoride and identify the influencing factors of fluoride loads in groundwater. The study extracted data from 36 most prevalent regions of 20 countries in the world through various search engines using keywords as well as Boolean operators and follows the PRISMA statement in every phase of literature searching. The study illustrated the pooled concentration of fluoride in the selected 20 countries was 2.1267 mg/L (1.650, 2.604) at 95% confidence interval, which was higher than the WHO standards limit of 1.5 mg/L. The results of the meta-analysis suggested that pH, Na, HCO₃ and rainfall was significantly positively correlated (r = ~0.4; p ˂ 0.05) to fluoride and has a weak correction with the other parameters such as local temperature, altitude, water depth, EC, Ca, and Mg (r = -0.064 to +0.214; p ˂ 0.05). Concerning, the risk assessment through oral and dermal route exposure revealed that the consumers in most of the regions were at considerable risk, and the children were more vulnerable than the adults (THQ > 1). The study findings would help to take measures for safe water supply in the affected areas. PRACTITIONER POINTS: The calculated pooled concentration of fluoride was 2.1267 mg/L (1.650, 2.604) at 95% CI in groundwater of the study areas. Climatic conditions and lithological composition are the key controlling factors for groundwater fluoride contamination. Semi-arid and arid regions are significantly affected by fluoride rather than humid areas. Regarding fluorosis in selected regions, children (78%) are more vulnerable than adults (23%).

Plasma and water fluoride levels and hyperuricemia among adolescents: A cross-sectional study of a nationally representative sample of the United States for 2013-2016

Exposure to excessive fluoride has been associated with a number of adverse health outcomes; however, there is a lack of evidence on the relation between fluoride exposure and serum uric acid levels, especially in human populations. The present study examined a potential relationship between fluoride exposure, measured as both plasma and water fluoride concentrations, and uric acid levels in an adolescent population. A nationally representative subsample of 1933 adolescents, aged 12-19 years, in the 2013-2016 National Health and Nutrition Examination Survey was analyzed for the association of fluoride concentrations with serum uric acid levels using multivariate general linear and logistic regression models, adjusting for potential confounders. Since uric acid levels change during development, hyperuricemia was defined in this study as over the mean plus one standard deviation for each sex and age group of adolescents. Of the study participants, 276 adolescents (weighted prevalence, 16.56%) had hyperuricemia. A significant and dose-dependent increase in prevalence of hyperuricemia was seen among the participants cross increasing quartiles of plasma fluoride (p-trend = 0.0017). After adjusting for potential confounders, we found that adolescents in the higher quartiles of plasma fluoride (≥0.32 µmol/L) and in the highest quartile of water fluoride (≥0.73 mg/L) had significantly increased odds of hyperuricemia compared with those in the lowest quartile. A 1.95-fold increased odds (95% CI: 1.37, 2.77) of hyperuricemia was also observed when analyzing plasma fluoride concentrations as continuous variable. A general linear model revealed that a 1 µmol/L increase in ln-plasma fluoride was associated with a 0.212 mg/dL (p < 0.0001) increased serum uric acid level. Furthermore, a positive relationship was observed between water and plasma fluoride concentrations (β = 0.1907; p < 0.0001). Our study demonstrates a potential relation between fluoride exposure and hyperuricemia in adolescents. Further studies are warranted to overcome the limitations of this study to examine the impact of long-term exposure to low levels of fluoride during development on hyperuricemia and its related health outcomes.

High Altitude and Its Effects on Oral Health: A Review of Literature

Health deterioration at high altitudes is related to many pathophysiological processes. The literature contains much evidence describing the multiple factors responsible for this deterioration, including hypoxia, decreased oxygen saturation, and decreased barometric pressure. An increase in the levels of oxidative stress at high altitudes can lead to many serious health events, although the human body may be able to adapt to such changes in the case of people who are accustomed to living at a high altitude. The pathophysiological processes at high altitudes also have adverse effects on oral tissue health. The aim of this review is to summarize the major published findings about oral health deterioration of living in and travelling to high-altitude areas.

Most studies have noted the adverse effects of prolonged exposure to hypoxia at high altitudes on oral tissues, including the salivary gland, periodontal tissue, gingival crevicular fluids, and jawbone. These changes include increases in the levels of inflammatory mediators and periodontal inflammation parameters. In addition, the incidence and severity of dental fluorosis is higher in residents of high-altitude areas. Abrupt changes in barometric pressure in people who travel to high altitudes may cause dental barotrauma and appear to increase sensitivity to pain (barodontalgia). In conclusion, it is important to consider that travelling to and living in high-altitude areas is a possible risk factor for multiple oral diseases.

Excision of Prominent Bony Mass due to Skeletal Fluorosis: A Case Report

CASE

A 72-year-old man presented for evaluation of bony prominences over extremities. Radiographic imaging demonstrated masses of varying sizes extending from the cortical surfaces without medullary continuity. The patient had a history of Freon inhalation abuse and was diagnosed with skeletal fluorosis due to elevated serum fluoride levels. He underwent an uncomplicated excision of a left fibular mass that was threatening skin breakdown.

CONCLUSIONS

This is the first reported surgical case of skeletal fluorosis demonstrating continued enlargement of bony prominences throughout the body. Skeletal fluorosis not only causes diffuse mineralization but may also lead to protruding lesions throughout the body.

Enhanced fluoride adsorption of aluminum humate and its resistance on fluoride accumulation in tea leaves

Tea trees (Camellia sinensis) can take in fluorine from soil and the content of fluorine in tea increases with maturity, leading to high content of fluoride in tea leaves and tea products. Long-term consumption of high fluoride tea products could result in chronic fluoride intoxication. Confining the fluoride in the earth with absorbents to reduce the fluoride accumulation of the tea trees during the growth period which could radically control the fluoride level in tea product. Humic acid (HA), a kind of organic matter in the earth was used as raw material to prepare adsorbent aluminum humate (HAA) by aluminum modification. The HAA absorbent presented excellent absorption performance to the fluoride in a wide pH range (4-10), and the maximum adsorptive capacity can reach to 62.5 mg/g. The absorption isotherm demonstrated the adsorption of fluoride was the monomolecular adsorption and the absorption was in accordance with the pseudo-second order kinetic equation. Fluoride content in real soil solution decreased significantly by 53.03% by using the HAA absorbent. The utilization of HAA adsorbent in the culture and field plots experiments also obviously adsorb the soluble fluoride in solution and soil, which could significantly suppress the fluoride accumulation in tea leaves. In September, the fluoride accumulation in tea leaves has been reduced 74.29% in the field plots experiments.

Factors influencing the relationship between fluoride in drinking water and dental fluorosis: a ten-year systematic review and meta-analysis

The relationship between naturally fluoridated groundwater and dental fluorosis has received large attention from researchers around the world. Despite recognition that several factors influence this relationship, there is a lack of systematic studies analyzing the heterogeneity of these results. To fill such a gap, this study performs a systematic review and meta-analysis to understand which factors influence this relationship and how. Selected studies were sampled between 2007 and 2017 from Web of Science, PubMed, Google Scholar and Scopus using keywords and Boolean operators. Results of the systematic review show that dental fluorosis affects individuals of all ages, with the highest prevalence below 11, while the impact of other factors (gender, environmental conditions, diet and dental caries) was inconclusive. Meta-regression analysis, based on information collected through systematic review, indicates that both fluoride in drinking water and temperature influence dental fluorosis significantly and that these studies might be affected by publication bias. Findings show that fluoride negatively affects people's health in less developed countries. The conclusions discuss policy tools and technological innovations that could reduce fluoride levels below that of the World Health Organization (WHO) (<1.5 mg/L).

Brick tea consumption is a risk factor for dental caries and dental fluorosis among 12-year-old Tibetan children in Ganzi

Brick tea contains high concentration of fluoride. The aim of the present work was to explore whether and how the brick tea is a risk factor for dental caries and dental fluorosis among Tibetan children in Ganzi. A cross-sectional study was conducted with 368 12-year-old Tibetan children in Ganzi. Dental caries was measured by DMFT index, and dental fluorosis severity was measured by Dean's Index. Community Fluorosis Index was used to estimate public health significance of dental fluorosis. Oral health-related behaviors and awareness, dietary habits and socioeconomic status were determined by a questionnaire. Bivariate and multivariate analyses were used to determine risk factors associated with dental caries and dental fluorosis. Dental caries prevalence was 37.50%, mean DMFT was 0.84 ± 1.53, while dental fluorosis prevalence was 62.23%. Community Fluorosis Index was 1.35, indicating a medium prevalent strength of dental fluorosis. Dental fluorosis was associated with mother's regular consumption of brick tea and residence altitude, and dental caries was associated with mother's regular consumption of brick tea. Mother's regular consumption of brick tea was a risk factor for both dental fluorosis and dental caries among children. Reducing mother's brick tea consumption during pregnancy and lactation may improve oral health status of their children.

Differential Expression of miRNAs in the Hippocampi of Offspring Rats Exposed to Fluorine Combined with Aluminum during the Embryonic Stage and into Adulthood

A previous study from our team found that continuous exposure to fluorine combined with aluminum (FA) impaired the neurobehavioral reflexes, spatial learning, and memory of offspring rats. To date, the specific mechanisms for these changes are unclear. Here, high-throughput sequencing was utilized to analyze the microRNA (miRNA) profile of the hippocampi in the offspring of rats exposed to FA during the embryonic stage and into adulthood through tap water supplemented with NaF and AlCl₃ at concentrations of (0, 0); (60, 600); (120, 600); and (240, 600) mg/L, respectively. qRT-PCR was performed to validate the reliability of the sequence data. Twenty differentially expressed miRNAs were selected for further analysis using bioinformatics tools. Several genes related to neuromodulation were found to be regulated by miR-10a-5p, miR-34b-5p, and miR-182, which might be harmful to normal nerve function. The protein levels of brain-derived neurotrophic factor (BDNF) and tyrosine receptor kinase B (TrkB) in hippocampus were markedly downregulated. These data suggest that miR-10a-5p, miR-34b-5p, and miR-182 and BDNF-TrkB signaling pathway are involved in mechanisms of hippocampal damage in the offspring of rats exposed to FA. HIGHLIGHTS: • Multiple miRNAs were significantly differentially expressed in offspring rat hippocampus after fluorine combined with aluminum (FA) exposure. • Twenty differentially expressed miRNAs might mediate FA-induced developmental neurotoxicity. • MiR-10a-5p, miR-34b-5p, and miR-182 were closely related to neurotoxic signaling of FA. • The BDNF-TrkB learning and memory-associated pathway was downregulated in the hippocampus after FA exposure.

Protective effects of melatonin against fluoride-induced oxidative stress in rats at high altitude

This study was conducted to evaluate the protective effects of melatonin against fluoride-induced oxidative stress-mediated haematological and biochemical changes in rat at high altitude. Adult male Wistar rats (6) were given the basal diet and drinking water ad lib. for first 7-days which was considered as the control period. Thereafter, they were exposed to NaF (@ 50 ppm) per-oral through drinking water for the next 14 days followed by melatonin treatment (@ 15 mg/kg BW, p.o.) for the next 14 days. The result showed induction of oxidative stress during NaF treatment alone, which caused significant increase in alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activity, and % inhibition of DPPH, MDA, and water intake. Whereas, total antioxidant capacity (FRAP) and body weight gain were significantly reduced during NaF exposure. Haemogram analysis indicated significant decrease in haemoglobin, packed cell volume, erythrocytes, lymphocytes, platelets count, whereas increase in MCH, monocytes, neutrophil, and eosinophil during NaF exposure. However, melatonin administration after 14 days of fluoride treatment resulted in significant amelioration of adverse changes occurred in different blood-biochemical parameters and also increased the total antioxidant status. Notably, the body weight gain improved during melatonin administration. These findings indicated induction of oxidative stress-mediated adverse change in haematology and biochemical parameters, and amelioration effect of oral dose of melatonin in rats under high altitude stress condition. Hence it can be concluded that melatonin acts as a potent antioxidant agent, which may be orally supplemented for amelioration of fluoride-mediated oxidative stress even under prevalent high altitude stress.

The effect of elemental content on the risk of dental fluorosis and the exposure of the environment and population to fluoride produced by coal-burning

Endemic fluorosis is a geochemical disease that affects thousands of people. Growing evidence from domestic and foreign studies indicate that fluorosis is associated with an abnormal level of the elements (such as F, Ca, Fe, Mg, Cu, Zn, P) in the environment and a population exposed to fluoride. To study the effect of the elemental content on the risk of dental fluorosis, the content of 25 elements in the environment produced by coal-burning and a population exposed to fluoride was determined. The results show that an abnormal level of various elements (including F, Al, Se, Zn, Cu, Fe, Mo, Mn, B, V, Ca, Mg, and P) in the population exposed to fluoride, which is related to the increasing or decreasing of the corresponding elements in the environment. Subsequent univariate and multivariate regression analyses show that high levels of F, Al, As, Pb and Cr were a risk factor for dental fluorosis, but not Se, Zn, Cu, B, Ca and P which were a protective factor for dental fluorosis. This study can provide a scientific basis for a further understanding of the causes of health damage caused by fluoride and the improvement of targeted prevention strategies.

Biomarkers of chronic fluoride exposure in groundwater in a highly exposed population

This study examined the relation between fluoride (F-) concentrations in fingernail clippings and urine and the prevalence and severity of enamel fluorosis (EF) among Ethiopian Rift Valley populations exposed to high levels of F- in drinking water. The utility of fingernail clippings as a biomarker for F- exposure and EF was also assessed for the first time in a high-F- region. The study recorded the EF status of 386 individuals (10 to 50years old), who consume naturally contaminated groundwater with widely varying F- concentration (0.6-15mg/L). The mean F- concentrations among residents of communities with primary reliance on groundwater were 5.1mg/kg (range: 0.5-34mg/kg) in fingernails and 8.9mg/L (range: 0.44-34mg/L) in urine. We show strong positive correlations between F- in drinking water and 12-hour urinary excretion (r=0.74, p<0.001, n=287), fingernail F- content (r=0.6, p<0.001, n=258), and mean individual measures of EF severity as measured using the Thylstrup and Fejerskov (TF) Index (r=0.42, p<0.001, n=316). The data indicate that both fingernail and urine measures are good biomarkers for F- exposure and EF outcomes, the latter being slightly more sensitive. Cases of moderate/severe EF were significantly more common among younger subjects (10 to 15years old) than older subjects (mostly >25years old) (p<0.001), consistent with their greater exposure to F- during early childhood, which is the only period of life the enamel is at risk of fluorosis. In this younger population, EF may be useful as a biomarker for identifying individuals with other potential health effects that depend on a specific age window of susceptibility. The finding of exceptionally high F- concentrations in water, fingernail clippings and urine in this region should motivate further investigations of other potential health consequences such as bone disease and abnormalities in the function of the neurological and endocrine systems.

Prolactin rs1341239 T allele may have protective role against the brick tea type skeletal fluorosis

Objective

Prolactin (PRL) has been reported to be associated with increased bone turnover, and increased bone turnover is also a feature of skeletal fluorosis (SF). Autocrine/paracrine production of PRL is regulated by the extrapituitary promoter and a polymorphism in the extrapituitary PRL promoter at -1149 (rs1341239) is associated with disturbances of bone metabolism in other diseases. Here, we have investigated the possibility that the rs1341239 polymorphism is associated with SF, which results from the consumption of brick tea.

Design

We conducted a cross-sectional study in Sinkiang, Qinghai, Inner Mongolia in China. Demography survey questionnaires were completed and physical examination and X-ray diagnoses were used to diagnose SF. Brick tea water fluoride intake (IF) and urinary fluoride (UF) were tested by an F-ion selective electrode method. A Sequenom MassARRAY system was used to determine PRL gene polymorphisms.

Results

Subjects who were younger than 45 years of age and carried the T allele had a significantly decreased risk of SF [OR = 0.279 (95%CI, 0.094–0.824)] compared to those carrying the homozygous G allele. This phenomenon was only observed in Kazakh subjects [OR = 0.127 (95%CI, 0.025–0.646)]. Kazakh females who carried T alleles has a decreased risk of SF [OR = 0.410 (95%CI, 0.199–0.847)]. For Kazakh subjects which IF is less than 3.5 mg/d, a decreased risk of SF was observed among the participants who carried T alleles [OR = 0.118 (95%CI, 0.029–0.472)]. Overall, subjects with 1.6–3.2 mg/L UF and carried T alleles had a significantly decreased risk of SF [OR = 0.476 (95%CI, 0.237–0.955)] compared to homozygous G allele carriers. This phenomenon was only observed in Kazakh subjects [OR = 0.324 (95%CI, 0.114–0.923)].

Conclusions

Our results suggested that the PRL rs1341239 T allele decreases the risk of brick tea SF.

Matrix Metallopeptidase-2 Gene rs2287074 Polymorphism is Associated with Brick Tea Skeletal Fluorosis in Tibetans and Kazaks, China

Brick tea skeletal fluorosis is still a public health issue in the north-western area of China. However its pathogenesis remains unknown. Our previous study reveals that the severity of skeletal fluorosis in Tibetans is more serious than that in Kazaks, although they have similar fluoride exposure, suggesting the onset of brick tea type skeletal fluorosis might be genetically influenced. Here we show that MMP-2 rs2287074 SNP (G/A), but not rs243865, was associated with Brick tea type fluorosis in Tibetans and Kazaks, China. The trend test reveals a decline in probability for skeletal fluorosis with increasing number of A alleles in Tibetans. After controlling potential confounders, AA genotype had about 80 percent lower probability of developing skeletal fluorosis than GG genotype in Tibetans (odds ratio = 0.174, 95% CI: 0.053, 0.575), and approximately 53 percent lower probability in Kazaks (odds ratio = 0.462, 95% CI: 0.214, 0.996). A meta-analysis shows that the AA genotype had approximately 63 percent lower odds (odds ratio = 0.373, 95% CI: 0.202, 0.689) compared with GG genotype within the two ethnicities. A significant correlation was also found between the genotype of MMP2 rs2287074 and skeletal fluorosis severity. Therefore, the A allele of MMP2 rs2287074 could be a protective factor for brick tea skeletal fluorosis.