Interaction Between The Genetic Polymorphism Of CTR And Environmental Exposure And Susceptibility To Coal-burning Borne Endemic Fluorosis

Endemic fluorosis is a typical biogeochemical disease, closely relatedto the natural environment. It happened is due to the people who livinglong in the high fluoride environment and in-taking daily consumption ofan amount of fluoride exceeding the safety threshold, resulting in majorproblems with human health. In recent years, the incidence of fluorosis inendemic fluorosis areas in China has tended to decline, while some areasare still heavier. It was associated with a variety of complex factors. Studiesof the epidemiological of endemic fluorosis have demonstrated that therewere the differences between individual illness or not and the degree ofdisease, although it is living the same area and exposuring to the same levelof fluorine.It suggested that genetic susceptibility may play an importantrole in the development and progression of fluorosis in addition toenvironmental factors in the process of the body of the damage.Chongqing is one of the popular serious coal-fired polluted of China.The main reason is that (Fluorosis has been attributed to fluoride-rich coal or to clay in mixed coal used as indoor fuel sources)most local residentsused without smoke facilities open type kitchen oven, heating and bakingfood, making indoor air and food polluted by fluoride. The prevalence offluorosis in some areas polluted by coal burning has reportedly increasedeven after preventive measures (such as changing stoves and furnaces toimprove kitchen techniques, reducing and removing fluoride, and changingdietary habits etc.) were implemented and the main source of fluorideexposure was controlled. The popularity of polluting coal-fired is not onlydamage to the physical health of the local people, but also hindered thelocal economic development. Fluorosis is still a major public healthproblem and an increasing disease burdening in China. The causes offluorosis was already very clear, while its pathological mechanism is notvery clear. In the same living environment, the same level of fluorineexposure, individuals are sick or not and how sick are different. It suggeststhat the differences may be due to the individual susceptibility or toleranceto fluorine is different. Therefore, it is necessary to discuss the relationshipbetween genetic susceptibility of fluorine and the health of human. Thesetypes of studies could help to identify high-risk subjects and could aid inpatient prognoses and preventive measures.ObjectiveUsing a case-control methods to investigate the regularity of singlenucleotide polymorphism distribution of calcitonin receptor gene1377C/T polymorphism and the relationship between polymorphism of thecalcitonin receptor gene and endemic fluorosis in han nationality ofChongqing. Find the susceptibility genes of endemic fluorosis disease, andfurther explore the interactions of gene-environment under the samecondition of fluorine exposure. Present research provides etiological onfluorosis and promotes a certain prevention measures for the further study.Materials and Methods1. Selection of investigation area and subjects: The study wasconducted in fluoride areas (Wushan and Fengjie counties) andnon-fluoride areas (Yubei qu county) in Chongqing, China. The case groupconsisted of100children (8-12years of age) with a confirmed diagnosis ofdental fluorosis. Subjects were selected using a stratified random method.The internal control group consisted of100children（8-12-year-old）without dental fluorosis. Subjects in the case and internal control groupswere matched by age, gender, and living condition (according to region),with a1:1pair-wise matching.50external control subjects fromnon-epidemic areas were matched to members of the case group(patients) by age and gender. All subjects were diagnosed by twoexperienced dentists and two epidemiologists. In addition,30adult patientswith skeletal fluorosis were selected from Wushan county.30internalcontrol subjects were matched with patients by age (±3years), gender,and living condition, and30external control subjects were matched by age (±3years) and gender with patients. All subjects were diagnosed by oneorthopedist, one radiologist, and two epidemiologists.2. Children,s dental fluorosis and Skeletal fluorosis inspection: Dentalfluorosis was assessed in all permanent teeth using Dean s Fluorosis Index.;Skeletal fluorosis was confirmed by clinical criteria （GB16398-1996）.3. Genotype analysis: The amplification of target fragments by usingPCR method and the detection of the Alu I polymorphism in the CTR geneby using restricted fragment length polymorphisms method.4. Data analysis: All analyses were performed using the SPSSsoftware,version17.0. Major methods: chi-square test, unconditionallogistic regression, conditional logistic regression and Hardy-WeinbergEquilibrium test. A P-value of less than0.05was considered statisticallysignificant.Results1. The frequencies distribution of Alu I alleles and genotypes in thisstudy followed the Hardy-Weinberg equilibrium(P>0.05). The frequencydistribution of genotypes CC、CT and TT were67.91%、27.10%and4.89%.There was statistically significant difference between the three groups inthe genotype of CTR gene and allele frequency distribution, and there wasstatistically significant between case group and in-control group in CTRgenotypes distribution, which suggests that individuals had a geneticsusceptibility differences of fluorosis though living in the same environment and the same fluoride exposure condition.2. We observed differences in the distribution of genotypes in the FG,NFG, and CG; the TT genotype was more frequent in the FG comparedwith the NFG (9.09%vs.3.85%, respectively). We hypothesized thatfluorosis may be influenced by the TT polymorphism of the CTR genotype.3. By analyzing the CTR allele frequency distribution of case andcontrol groups, we found that carrying the C allele reduced the risk offluorosis (OR=0.531vs. OR=0.578, respectively); therefore, this allelemay have a protective effect against fluorosis. Thus, our data suggested thatthe C allele of the Alu I gene polymorphism may be a sensitive biomarkerfor the detection of early stages of fluorosis.4. Analysis of logistic regression showed that Urinary fluoride≥0.95mg/L was the environmental risk factors of fluorosis. OReg value of5.530(95%CI:1.1443-21.191), γ value of2.457>1, suggested that there was apositive interaction between the CT+TT genotypes in CTR and theenvironment(Urinary fluoride≥0.95mg/L) of the fluorosis people, whichis the synergy. There was an amplification effects between the urinaryfluoride level and the CTR genotype in the role of fluorosis.Conclusion1. The CC genotype of CTR is the most common types, TT genotypemay be the susceptible genotype in the sampling region.2. With the T allele has a higher risk of fluorosis, compared with the people who carrying the C allele.3. Thus, our data suggested that the C allele of the Alu I genepolymorphism may be a sensitive biomarker for the detection of earlystages of fluorosis.4. There may be some interaction between the CTR genotypes andenvironmental risk factors(urinary fluoride level≥0.95mg/L). In general,incidence of the fluorosis in Chongqing is not only associated with genepolymorphism, but also related to the environmental factors.