Studies Of Relationships Between The Polymorphism Of COMT Gene And Plasma Proteomic Profiling And Children’s Intelligence In High Fluoride Areas

Fluorine (F) widely exists in environment with a significant increase in body burdenaccumulation in recent years. Internal exposure to F due to diet including food, water,fluoride-containing dental products like foothpaste and fluoride supplements, is extensivelyresearched. Additionally, industrial pollution and coal burning have also been reported to bemajor sources of internal F exposure, especially in China.It is known that excessive fluoride intake over a long period of time may result in aserious public health problem called fluorosis. In addition to well-known effects offluorosis on skeleton and teeth, the neurotoxicity of F was also confirmed. Roholm et alfound that exposure to fluoride can cause bad effects on the central nervous system in rats,generate significant reduction in myelinated nerve fibers, external granμlar layer incerebellum, and increase neuronal apoptosis. In addition, alterations in the density ofneurons and in the number of undifferentiated neurons were observed in the brains offetuses therapeutically aborted in an area characterized by endemic fluorosis. It has beenindicated that the severity of the adverse effects of fluoride on the behavior of rats isdirectly correlated to the concentrations of this ion in plasma and in specific regions of thebrain. A growing number of epidemiological studies reported that the levels of mental workcapacity and the Intelligence Quotient (IQ) for children who were born and raised in theareas with endemic fluorosis were found to be lower than normals.F concentration in drinking water is long-term stable in years in a certain region.Once absorbed into the blood, fluoride readily distributes throughout the body, with the greatest amount retained in calcium-rich areas such as bone and teeth (dentine and enamel).In infants, about80-90%of the absorbed fluoride is retained; the other is excreted primarilyvia the urine. Therefore, urine F and serum F concentrations as the internal exposure indexcan systematically reflect the burden of F exposure in drinking water. In this study, wemeasured children’s intelligence quotient (IQ) using Combined Raven’s Test for RuralChina (CRT-RC) and determined fluorine concentrations of serum and urine employingfluorin ion selective electrode, and investigated the correlations between the urine F andserum F concentrations and the children’s IQ.Studies suggestd that the neurotransmitter dopamine plays an important role in humancognition. Computational modeling studies indicated that dysfunction in dopamine systemsaccounts for abnormal cognitive control in the prefrontal cortex. CatecholO-methyltransferase (COMT) is the major mammalian enzyme involved in the metabolicdegradation of released dopamine and accounts for more than60%of the metabolicdegradation of dopamine in the frontal cortex. It is therefore plausible that genetic factorsthat affect COMT function may significantly influence cognition through affectingdopaminergic function. The COMT gene contains a functional polymorphism that codes fora substitution of methionine (met) for valine (val) at codon158. The met allele isthermolabile and has one-fourth the enzymatic activity of the val allele. Egan and hiscolleagues found that there was a relationship between the COMT val158metpolymorphism and cognitive function. However, the relationship between the COMTval158met polymorphism and cognitive function of children in fluoride area has not beenreported.At present, the study of biomarkers of children with mental retardation is ralely.Studies have shown that thyroid hormone levels can be used as a sensitive indicator ofdetection of mental retardation. As direct executor of life function, proteins can directlyreflect the physiological process relative to genes. Therefore, we can make use of theproteomics approach to study changes of certain protein or peptide level in the developmentprocess of fluorosis to find the abnormal expressed proteins, so as to provide certain basisfor identifying the biological markers of fluorosis children. Part Ⅰ Drinking water of high F on children’s IQObjective: To investigate the relationships among the children’s serum F, urine F,thyroid hormone levels and children’s IQ in the high fluoride areas.Methods: we collected the samples of the drinking water, urine and blood andmeasured the F concentrations, the levels of thyroid hormone and children’s IQ using F ionselective electrode, radioimmunoassay kit (RIA) and the CRT-RC.Results: The concentrations of urine F and serum F, TSH values and IQ scores weresignificant different in children in the high fluoride group compared to those in the controlgroup (P <0.05). Spearman rank correlation analysis showed negative correlations betweenurine F, serum F concentrations and children’s IQ scores (rs=-0.206, P <0.01; rs=-0.187,P <0.05).Conclusions: The long-term intake of excessive fluoride can affect children’s IQ.Part Ⅱ The relationship between COMT gene polymorphism and children’s IQObjective: To explore the relationship between COMTval158met polymorphism andchildren’s IQ.Methods: Polymerase chain reaction (PCR) and restriction fragment lengthpolymorphism (RFLP) methods were used to discern the relationship between thefunctional polymorphism of COMT and children’s IQ.Resμlts: Children with the high-activity val/val genotype showed significantly higherIQ scores on CRT-RC Test than those with low-activity genotype.Conclusions: The val/val genotype may have a protect effect on cognitiveperformance in children.Part Ⅲ Proteomic analysis of plasma in children chronically exposed to fluorideObjective: This study was to investigate the differences in plasma proteomic profilingbetween children of high F exposure and controls.Methods:10children of high fluoride exposure and10children of normals wereselected, respectively. Plasma proteomic profiling was analyzed by formatrix assisted laserdesorption ionization-time-of-flight mass spectrometry (MALDI-TOF–TOF MS) technology.Resμlts: At the high F group, we found7differentially expressed protein spots andfive proteins were successfμlly identified, which were found to be upregμlated.Conclusions: The alterations of the plasma protein expression patterns provide certainbasis for seeking sensitive effect markers of fluorosis children.