Heritability estimates for dental caries and sucrose sweetness preference

A systematic review of caries risk in children <6 years of age

BACKGROUND

For caries risk assessment (CRA) tools for young children to be evidence-based, it is important to systematically review the literature to identify factors associated with the onset of early childhood caries (ECC).

AIM

This updated systematic review aimed to identify current evidence on caries risk in young children.

DESIGN

A comprehensive and systematic literature search of relevant databases was conducted to update a previous systematic review and identify risk factors associated with ECC. Potential risk factors were identified based on strength of association using odds ratios, hazard ratios, relative risk, etc. GRADE was used for rating quality evidence through consensus.

RESULTS

Twenty-two studies met inclusion criteria for the search from mid-2017 to 2021. Twenty-five publications from the prior systematic review, from 1997 to mid-2017, were also included. Several socioeconomic, behavioral, and clinical variables were identified as ECC risk factors. Factors included the following: age, socioeconomic status, frequency of and supervised toothbrushing, fluoride exposure, breast- and bottle-feeding, feeding habits, absence of a dental home, past caries experience, active non-cavitated lesions, visible plaque, enamel defects, and microbiome.

CONCLUSION

This study provides updated evidence of risk factors for ECC that could be included in CRA tools.

Brazilian Twin Studies: A Scoping Review

The current study was motivated by an interest in deepening understanding of Brazilian twin research, which is underrepresented internationally, in an effort to rectify this situation. Our aim was threefold: (1) to carry out a comprehensive investigation of Brazilian research on twins according to the area of knowledge; (2) to evaluate the representation of research in the field of psychology in comparison with other areas; (3) to evaluate characteristics of the research that may have contributed to its exclusion from the comprehensive meta-analysis of 50 years of twin research. A scoping review was performed according to PRISMA guidelines. Titles and abstracts were searched up to 2022 in six databases: CAPES, BDLTD, PePSIC, PubMed, Google Scholar, and SciELO, using selected keywords both in Portuguese and in English (e.g., 'twins' and 'Brazil'; 'twinning' and 'Brazil'; 'gemelaridade' [twinning], and 'gêmeos' [twins]). Three hundred and forty publications were included in the review. Approximately half (53.8‰) used the classic twin design to investigate the heritability of several traits, and the other half (46.2%) used other research designs. The scoping review showed that the number of publications doubled approximately every 10 years. Most publications were from the health area, with medicine accounting for approximately half of the studies, followed by psychology, odontology, and biology. We found that the interest in studying twins among Brazilian scientists is increasing over the years and there are reasons to be enthusiastic about the potential impact of this trend in the global scenario.

Is there an association between dental caries and genetics? Systematic review and meta-analysis of studies with twins

OBJECTIVE

This review aimed to assess the agreement of dental caries experience between monozygotic (MZ) and dizygotic (DZ) twins.

DATA RESOURCES

This systematic review was performed by reviewers in the databases Embase, MEDLINE-PubMed, Scopus, Web of Science and manual searches and gray literature Google Scholar® and Opengray. Observational studies that evaluated dental caries in twins were included. The risk of bias was analyzed using the Joanna Briggs checklist. Meta-analyses were performed to assess the pooled Odds Ratio to estimate the agreement values of dental caries experience and DMF index between pairs of twins (p < 0.05). To assess the certainty of evidence, the GRADE scale was used.

STUDY SELECTION

2533 studies were identified, of which 19 were included in the qualitative analysis, six in the quantitative synthesis, with two meta-analyses being carried out. Association between genetics and the development of the disease was observed in most studies. In the risk of bias analysis, 47.4% had moderate risk. Higher agreement of dental caries experience was observed in MZ twins than DZ in both dentitions (OR: 5.94; 95% CI: 2.00-17.57). However, there was no difference between the MZ and DZ twin groups in the analysis comparing DMF index agreement (OR: 2.86; 95%CI: 0.25-32.79). The certainty of evidence was considered low and very low for all studies included in meta-analyses.

CONCLUSION

With very low certainty of the evidence, the genetic factor seems to influence the agreement of the caries experience.

CLINICAL RELEVANCE

Understanding the genetic influence on the disease has the potential to contribute to the development of studies that may use biotechnologies for prevention and treatment as well as guide future research involving gene therapies aiming to prevent the occurrence of dental caries.

Genetic aspects of dental caries

Dental caries is a common chronic disease affecting humans in all age groups. Various factors can affect the formation of caries including demineralization and remineralization processes with oral flora; dietary and oral hygiene habits; salivary composition, flow rate, pH and buffering capacity; morphological features of the teeth; fluoride exposures, environmental and socioeconomic factors. One of the most important factors causing inter-individual variations in caries susceptibility is the host genetics. Several genes affect individual caries susceptibility. Genes play a role in immune response, development of saliva and tooth enamel. The present review aims to overview the literature focusing on the genetic features of dental caries.

Taste perception in children with different caries activity

PURPOSE

The aim of the study was to investigate whether caries-active and caries-free children differ in terms of their taste perception for sweet, sour, salty and bitter.

METHODS

The study group consisted of 100 children aged 5-10 years: 50 caries-free children and 50 children with at least four untreated carious lesions. Taste perception was analysed using two test systems. First, filter paper strips impregnated with four taste qualities (sweet, sour, salty, and bitter) at four defined intensities were used ("taste strips"). Then a tasting spray in suprathreshold concentration of the respective taste was applied. The children were asked to name the perceived taste. The parents answered a questionnaire about the children's dietary habits.

RESULTS

The children with high caries activity scored lower on average on the taste strips than the caries-free participants. For the taste sprays, the perception of the taste quality "bitter" was significantly worse in the children with caries than in caries-free children (Mann-Whitney U test p < 0.05).

CONCLUSION

The results of this study suggest that taste preferences in children are associated with increased susceptibility to tooth decay.

A Constrained Generalized Functional Linear Model for Multi-Loci Genetic Mapping

In genome-wide association studies (GWAS), efficient incorporation of linkage disequilibria (LD) among densely typed genetic variants into association analysis is a critical yet challenging problem. Functional linear models (FLM), which impose a smoothing structure on the coefficients of correlated covariates, are advantageous in genetic mapping of multiple variants with high LD. Here we propose a novel constrained generalized FLM (cGFLM) framework to perform simultaneous association tests on a block of linked SNPs with various trait types, including continuous, binary and zero-inflated count phenotypes. The new cGFLM applies a set of inequality constraints on the FLM to ensure model identifiability under different genetic codings. The method is implemented via B-splines, and an augmented Lagrangian algorithm is employed for parameter estimation. For hypotheses testing, a test statistic that accounts for the model constraints was derived, following a mixture of chi-square distributions. Simulation results show that cGFLM is effective in identifying causal loci and gene clusters compared to several competing methods based on single markers and SKAT-C. We applied the proposed method to analyze a candidate gene-based COGEND study and a large-scale GWAS data on dental caries risk.

Differences in Sweet Taste Perception and Its Association with the Streptococcus mutans Cariogenic Profile in Preschool Children with Caries

The aim of the study was to verify the hypothesis about differences in sweet taste perception in the group of preschool children with and without caries, and to determine its relationship with cariogenic microbiota and the frequency of sweets consumption in children. The study group included of 63 children aged 2–6 years: 32 with caries and 31 without caries. The study consisted of collecting questionnaire data and assessment of dental status using the decayed, missing, filled in primary teeth index (dmft) and the International Caries Detection and Assessment System (ICDAS II). The evaluation of sweet taste perception was carried out using a specific method that simultaneously assessed the level of taste preferences and the sensitivity threshold for a given taste. The microbiological analysis consisted of the assessment of the quantitative and qualitative compositions of the oral microbiota of the examined children. The sweet taste perception of children with caries was characterized by a lower susceptibility to sucrose (the preferred sucrose solution concentration was >4 g/L) compared to children without caries (in the range ≤ 4 g/L, p = 0.0015, chi-square test). A similar relationship was also observed for frequent snacking between meals (p = 0.0038, chi-square test). The analysis of studied variables showed the existence of a strong positive correlation between the perception of sweet taste and the occurrence and intensity of the cariogenic process (p = 0.007 for dmft; and p = 0.012 for ICDAS II), as well as the frequency of consuming sweets (p ≤ 0.001 for frequent and repeated consumption of sweets during the day, Spearman test) in children with caries. Additionally, children with an elevated sucrose taste threshold were more than 10-times more likely to develop S. mutans presence (OR = 10.21; 95% CI 3.11–33.44). The results of this study suggest the future use of taste preferences in children as a diagnostic tool for the early detection of increased susceptibility to caries through microbial dysbiosis towards specific species of microorganisms.

Heritability of Oral Microbiota and Immune Responses to Oral Bacteria

Maintaining a symbiotic oral microbiota is essential for oral and dental health, and host genetic factors may affect the composition or function of the oral microbiota through a range of possible mechanisms, including immune pathways. The study included 836 Swedish twins divided into separate groups of adolescents (n = 418) and unrelated adults (n = 418). Oral microbiota composition and functions of non-enzymatically lysed oral bacteria samples were evaluated using 16S rRNA gene sequencing and functional bioinformatics tools in the adolescents. Adaptive immune responses were assessed by testing for serum IgG antibodies against a panel of common oral bacteria in adults. In the adolescents, host genetic factors were associated with both the detection and abundance of microbial species, but with considerable variation between species. Host genetic factors were associated with predicted microbiota functions, including several functions related to bacterial sucrose, fructose, and carbohydrate metabolism. In adults, genetic factors were associated with serum antibodies against oral bacteria. In conclusion, host genetic factors affect the composition of the oral microbiota at a species level, and host-governed adaptive immune responses, and also affect the concerted functions of the oral microbiota as a whole. This may help explain why some people are genetically predisposed to the major dental diseases of caries and periodontitis.

Taste Perception in School Children: Is There an Association with Dental Caries?

Background/Aim: Individuals make food choices based on a number of physiological, nutritional, environmental and socioeconomic factors but sensory qualities of food namely the taste has priority as the determinant in food selection. The purpose of the study is to evaluate sweet, salty, sour and bitter taste perceptions of school children and compare them in term of caries experience.

Material and Methods: Two hundred children aged from 6-13 were included in the study. The dental examinations of children were performed using DMF(T), DMF(S), df(t) and df(s) indices. Questionnaires were presented to parents to record the socioeconomic and educational levels, oral health knowledge, child’s general health, oral health habits and fluoride exposure. Children rinsed sucrose (12g/L; 24g/L), sodium chloride (2g/L; 4g/L), citric acid (0,6g/L; 1,20g/L) and caffeine (0,27g/L; 0,54g/L) solutions randomly and the taste perception was recorded. Relationship between the taste perception and caries experience were evaluated.

Results: A significant correlation was found between 2 g/L of NaCl and age (p= 0,007, r= 0,178). When occlusal or approximal caries of the children aged from 6 to 9 were discriminated, the Spearman’s test found a weak positive correlation between occlusal caries and higher sweet taste (24 g/L sucrose) (r= 0,232; p= 0,021) and a weak negative correlation between approximal caries and higher salty taste (4 g/L NaCl) (r= –0,225; p= 0,025).

Conclusions: Age should be considered in the assessment of taste perception of children. Additionally, there is a weak relationship between taste perceptions and dental caries. These data suggest that further studies need to focus on the effect of taste preferences on dental caries.

Determinants of Sweetness Preference: A Scoping Review of Human Studies

Factors associated with sweetness preference are multi-faceted and incredibly complex. A scoping review was undertaken to identify determinants of sweetness preference in humans. Using an online search tool, ProQuest ™, a total of 99 publications were identified and subsequently grouped into the following categories of determinants: Age, dietary factors, reproductive hormonal factors, body weight status, heritable, weight loss, sound, personality, ethnicity and lifestyle, previous exposure, disease, and 'other' determinants. Methodologies amongst studies were heterogenous in nature (e.g., there was variability across studies in the sweetness concentrations tested, the number of different sweetness concentrations used to assess sweetness preference, and the methods utilized to measure sweetness preference), rendering interpretation of overall findings challenging; however, for certain determinants, the evidence appeared to support predictive capacity of greater sweetness preference, such as age during certain life-stages (i.e., young and old), being in a hungry versus satiated state, and heritable factors (e.g., similar sweetness preferences amongst family members). Recommendations for the design of future studies on sweetness preference determinants are provided herein, including an "investigator checklist" of criteria to consider.

Heritability of Caries Scores, Trajectories, and Disease Subtypes

Previous studies report that dental caries is partially heritable, but there is uncertainty in the magnitude of genetic effects and little understanding of how genetic factors might influence caries progression or caries subtypes. This study aimed to estimate the relative importance of genetic and environmental factors in the etiology of different caries outcomes using a twin-based design. Analysis included up to 41,678 twins in the Swedish Twin Register aged 7 to 97 y, and dental data were obtained from preexisting dental records. The outcome measures were 1) summary indices of caries experience, 2) parameters representing trajectory in caries progression derived from longitudinal modeling, and 3) caries scores in groups of biologically similar tooth surfaces derived from hierarchical clustering of tooth surfaces (termed caries clusters). Additive genetic factors explained between 49.1% and 62.7% of variation in caries scores and between 50.0% and 60.5% of variation in caries trajectories. Seven caries clusters were identified, which had estimates of heritability lying between 41.9% and 54.3%. Shared environmental factors were important for only some of these clusters and explained 16% of variation in fissure caries in molar teeth but little variation in other clusters of caries presentation. The genetic factors influencing these clusters were only partially overlapping, suggesting that different biological processes are important in different groups of tooth surfaces and that innate liability to some patterns of caries presentation may partially explain why groups of tooth surfaces form clusters within the mouth. These results provide 1) improved quantification of genetic factors in the etiology of caries and 2) new data about the role of genetics in terms of longitudinal changes in caries status and specific patterns of disease presentation, and they may help lay the foundations for personalized interventions in the future.

Genetic and Early-Life Environmental Influences on Dental Caries Risk: A Twin Study

OBJECTIVES

To explore the relative contributions of genetic and environmental influences on dental caries risk and to investigate fetal and developmental risk factors for dental caries.

METHODS

We recruited children from 250 twin pregnancies midgestation and collected demographic, health, and phenotypic data at recruitment, 24 and 36 weeks' gestational age, birth and 18 months, and 6 years of age. 25-hydroxyvitamin D was quantified in mothers at 28 weeks' gestation and in infants at birth. Dental caries and enamel defects were measured at six years of age. We compared concordance for the presence of any caries and advanced caries in monozygotic and dizygotic twin pairs. To investigate environmental risk factors for caries, we fitted multiple logistic regression models using generalized estimating equations to adjust for twin correlation.

RESULTS

A total of 345 twins underwent dental assessment, with 111 (32.2%) showing signs of any caries and 83 (24.1%) having advanced caries. There was no evidence of higher concordance in monozygotic twins compared with dizygotic twins, with a difference of 0.05 (95% confidence interval -0.14 to 0.25; P = .30) and 0.00 (95% confidence interval -0.26 to 0.26; P = .50) for any caries and advanced caries, respectively, suggesting that environmental factors, rather than genetics, are the predominant determinant of caries risk. After adjusting for potential confounders, lack of community water fluoridation, hypomineralized second primary molars, dichorionic placenta, and maternal obesity were associated with caries.

CONCLUSIONS

Environmental rather than genetic factors drive dental caries risk and arise as early as prenatal life.

Nutrition, dental caries and periodontal disease: a narrative review

AIM

To provide a narrative review of the role of macro- and micronutrients in relation to dental caries, gingival bleeding and destructive periodontal disease.

MATERIALS & METHODS

This review is based on systematic reviews (when available) and comparative human studies.

RESULTS

Dental caries cannot develop without the presence of dietary fermentable carbohydrates, in particular sugar. The susceptibility to develop caries in the presence of carbohydrates may be influenced by genetics and micronutrients such as vitamin D. Gingival bleeding and destructive periodontal disease are sensitive markers to both abnormalities in macronutrient content (excessive carbohydrates or poly-unsaturated fat intake, deficient protein intake) and micronutrient intake (e.g. vitamin C and B12).

CONCLUSION

Dental caries and periodontal diseases are a sensitive alarm bell for an unhealthy diet, which predicts the future onset of the diseases of civilizations.

Consortium-based genome-wide meta-analysis for childhood dental caries traits

Prior studies suggest dental caries traits in children and adolescents are partially heritable, but there has been no large-scale consortium genome-wide association study (GWAS) to date. We therefore performed GWAS for caries in participants aged 2.5-18.0 years from nine contributing centres. Phenotype definitions were created for the presence or absence of treated or untreated caries, stratified by primary and permanent dentition. All studies tested for association between caries and genotype dosage and the results were combined using fixed-effects meta-analysis. Analysis included up to 19 003 individuals (7530 affected) for primary teeth and 13 353 individuals (5875 affected) for permanent teeth. Evidence for association with caries status was observed at rs1594318-C for primary teeth [intronic within ALLC, odds ratio (OR) 0.85, effect allele frequency (EAF) 0.60, P 4.13e-8] and rs7738851-A (intronic within NEDD9, OR 1.28, EAF 0.85, P 1.63e-8) for permanent teeth. Consortium-wide estimated heritability of caries was low [h2 of 1% (95% CI: 0%: 7%) and 6% (95% CI 0%: 13%) for primary and permanent dentitions, respectively] compared with corresponding within-study estimates [h2 of 28% (95% CI: 9%: 48%) and 17% (95% CI: 2%: 31%)] or previously published estimates. This study was designed to identify common genetic variants with modest effects which are consistent across different populations. We found few single variants associated with caries status under these assumptions. Phenotypic heterogeneity between cohorts and limited statistical power will have contributed; these findings could also reflect complexity not captured by our study design, such as genetic effects which are conditional on environmental exposure.

Dental genetics in Brazil: Where we are

Dentistry constitutes the basic nucleus of professionals of higher level of health in Brazil with one of the largest concentrations of dentists per capita in the world. However, the genetic in dentistry in Brazil is explored, basically, in research field. Future actions need to be performed in order to deep the whole knowledge about diagnosis and treatment of diseases with genetic basis in dentistry, in Brazil.

Sweet Taste Perception and Dental Caries in 13- to 15-Year-Olds: A Multicenter Cross-Sectional Study

Dietary habits and, in particular, the intake frequency of sucrose are of major importance for the development of dental caries. The perception of sweet taste is believed to have an influence on sucrose intake and therefore affects the predisposition to dental caries. The aim was to study the caries experience and sweet taste perception and to further analyze the possible relationship between the 2 tested variables in 13- to 15-year-old children from 3 different geographical areas. A cross-sectional survey comprising 669 children (220 Italian, 224 Mexican, and 225 Saudi Arabian) was conducted. The children were examined in their school setting. A sweet taste perception level was determined by the sweet taste threshold (TT) and sweet taste preference (TP). The sweet test was performed with sucrose solutions varying in concentration from 1.63 to 821.52 g/L. The International Caries Detection and Assessment System (ICDAS) and DMFS indices were used to diagnose caries. The highest mean value for TT was found for Italian children followed by Saudi and Mexican. Saudi schoolchildren showed the highest mean values for TP and DMFS, followed by Italian and Mexican. A statistically significant difference for TP, TT, DMFS, and initial caries was found between the 3 countries. A weak yet positive correlation was found between taste perception (TT and TP) versus DMFS and manifest caries in all 3 countries (r = 0.137-0.313). The findings of the present study showed a variation in sweet taste perception between the 3 countries, which may influence the caries outcome of the children in the individual countries.

Precision Dentistry in Early Childhood: The Central Role of Genomics

Pediatric oral health is determined by the interaction of environmental factors and genetic influences. This is the case for early childhood caries, the most common disease of childhood. The complexity of exogenous-environmental factors interacting with innate biological predispositions results in a continuum of normal variation, as well as oral health and disease outcomes. Optimal oral health and care or precision dentistry warrants comprehensive understanding of these influences and tools enabling intervention on modifiable factors. This article reviews the current knowledge of the genomic basis of pediatric oral health and highlights known and postulated mechanistic pathways of action relevant to early childhood caries.

Variants on chromosome 4q21 near PKD2 and SIBLINGs are associated with dental caries

A recent genome-wide association study for dental caries nominated the chromosomal region 4q21 near ABCG2, PKD2 and the SIBLING gene family. In this investigation we followed-up and fine-mapped this region using a tag-SNP (single nucleotide polymorphism) approach in 13 age- and race-stratified samples from 6 independent studies (N=4,089). Participants were assessed for dental caries via intra-oral examination and 49 tag-SNPs were genotyped capturing much of the variation in the 4q21 locus. Linear models were used to test for genetic association, while adjusting for sex, age, and components of ancestry. SNPs in and near PKD2 showed significant evidence of association in individual samples of black adults (rs17013735, p-value=0.0009) and white adults (rs11938025; p-value=0.0005; rs2725270, p-value=0.003). Meta-analyses across black adult samples recapitulated the association with rs17013735 (p-value=0.003), which occurs at low frequency in non-African populations, possibly explaining the race-specificity of the effect. In addition to race-specific associations, we also observed evidence of gene-by-fluoride exposure interaction effects in white adults for SNP rs2725233 upstream of PKD2 (p=0.002). Our results show evidence of regional replication, though no single variant clearly accounted for the original GWAS signal. Therefore, while we interpret our results as strengthening the hypothesis that chromosome 4q21 may impact dental caries, additional work is needed.

Predicting Dental Caries Outcomes in Children: A "Risky" Concept

In recent years, unprecedented gains in the understanding of the biology and mechanisms underlying human health and disease have been made. In the domain of oral health, although much remains to be learned, the complex interactions between different systems in play have begun to unravel: host genome, oral microbiome with its transcriptome, proteome and metabolome, and more distal influences, including relevant behaviors and environmental exposures. A reasonable expectation is that this emerging body of knowledge can help improve the oral health and optimize care for individuals and populations. These goals are articulated by the National Institutes of Health as "precision medicine" and the elimination of health disparities. Key processes in these efforts are the discovery of causal factors or mechanistic pathways and the identification of individuals or population segments that are most likely to develop (any or severe forms of) oral disease. This article critically reviews the fundamental concepts of risk assessment and outcome prediction, as they relate to early childhood caries (ECC)-a common complex disease with significant negative impacts on children, their families, and the health system. The article highlights recent work and advances in methods available to estimate caries risk and derive person-level caries propensities. It further discusses the reasons for their limited utility in predicting individual ECC outcomes and informing clinical decision making. Critical issues identified include the misconception of defining dental caries as a tooth or surface-level condition versus a person-level disease; the fallacy of applying population-level parameters to individuals, termed privatization of risk; and the inadequacy of using frequentist versus Bayesian modeling approaches to derive individual disease propensity estimates. The article concludes with the notion that accurate caries risk assessment at the population level and "precision dentistry" at the person level are both desirable and achievable but must be based on high-quality longitudinal data and rigorous methodology.

Pyrosequencing of Plaque Microflora In Twin Children with Discordant Caries Phenotypes

Despite recent successes in the control of dental caries, the mechanism of caries development remains unclear. To investigate the causes of dental decay, especially in early childhood caries, the supragingival microflora composition of 20 twins with discordant caries phenotypes were analyzed using high-throughput pyrosequencing. In addition, the parents completed a lifestyle questionnaire. A total of 228,789 sequencing reads revealed 10 phyla, 84 genera, and 155 species of microflora, the relative abundances of these strains varied dramatically among the children, Comparative analysis between groups revealed that Veillonella, Corynebacterium and Actinomyces were presumed to be caries-related genera, Fusobacterium, Kingella and Leptotrichia were presumed to be healthy-related genus, yet this six genera were not statistically significant (P>0.05). Moreover, a cluster analysis revealed that the microbial composition of samples in the same group was often dissimilar but that the microbial composition observed in twins was usually similar. Although the genetic and environmental factors that strongly influence the microbial composition of dental caries remains unknown, we speculate that genetic factors primarily influence the individual's susceptibility to dental caries and that environmental factors primarily regulate the microbial composition of the dental plaque and the progression to caries. By using improved twins models and increased sample sizes, our study can be extended to analyze the specific genetic and environmental factors that affect the development of caries.

A common genetic influence on human intensity ratings of sugars and high-potency sweeteners

The perception of sweetness varies among individuals but the sources of this variation are not fully understood. Here, in a sample of 1,901 adolescent and young adults (53.8% female; 243 MZ and 452 DZ twin pairs, 511 unpaired individuals; mean age 16.2±2.8, range 12–26 years), we studied the variation in the perception of sweetness intensity of two monosaccharides and two high-potency sweeteners: glucose, fructose, neohesperidine dihydrochalcone (NHDC), and aspartame. Perceived intensity for all sweeteners decreased with age (2–5% per year) and increased with the history of otitis media (6–9%). Males rated aspartame slightly stronger than females (7%). We found similar heritabilities for sugars (glucose: h2=0.31, fructose: h2=0.34) and high-potency sweeteners (NHDC: h2=0.31, aspartame: h2=0.30); all were in the modest range. Multivariate modeling showed that a common genetic factor accounted for >75% of the genetic variance in the four sweeteners, suggesting that individual differences in perceived sweet intensity, which are partly due to genetic factors, may be attributed to a single set of genes. This study provided evidence of the shared genetic pathways between the perception of sugars and high-potency sweeteners.

Polymorphisms in sweet taste genes (TAS1R2 and GLUT2), sweet liking, and dental caries prevalence in an adult Italian population

The aim of the study was to assess the relationship between sweet taste genes and dental caries prevalence in a large sample of adults. In addition, the association between sweet liking and sugar intake with dental caries was investigated. Caries was measured by the decayed, missing, filled teeth (DMFT) index in 647 Caucasian subjects (285 males and 362 females, aged 18-65 years), coming from six villages in northeastern Italy. Sweet liking was assessed using a 9-point scale, and the mean of the liking given by each individual to specific sweet food and beverages was used to create a sweet liking score. Simple sugar consumption was estimated by a dietary history interview, considering both added sugars and sugar present naturally in foods. Our study confirmed that polymorphisms in TAS1R2 and GLUT2 genes are related to DMFT index. In particular, GG homozygous individuals for rs3935570 in TAS1R2 gene (p value = 0.0117) and GG homozygous individuals for rs1499821 in GLUT2 gene (p value = 0.0273) showed higher DMFT levels compared to both heterozygous and homozygous for the alternative allele. Furthermore, while the relationship sugar intake-DMFT did not achieve statistical significance (p value = 0.075), a significant association was identified between sweet liking and DMFT (p value = 0.004), independent of other variables. Our study showed that sweet taste genetic factors contribute to caries prevalence and highlighted the role of sweet liking as a predictor of caries risk. Therefore, these results may open new perspectives for individual risk identification and implementation of target preventive strategies, such as identifying high-risk patients before caries development.

Genetic susceptibility to dental caries differs between the sexes: a family-based study

Many of the factors affecting susceptibility to dental caries are likely influenced by genetics. In fact, genetics accounts for up to 65% of inter-individual variation in dental caries experience. Sex differences in dental caries experience have been widely reported, with females usually exhibiting a higher prevalence and severity of disease across all ages. The cause for this sex bias is currently uncertain, although it may be partly due to the differential effects of genetic factors between the sexes: gene-by-sex interactions. In this family based study (N = 2,663; 740 families; ages 1-93 years), we assessed dental caries via intra-oral examination and generated six indices of caries experience (DMFS, dfs, and indices of both pit-and-fissure surface caries and smooth surface caries in both primary and permanent dentitions). We used likelihood-based methods to model the variance in caries experience conditional on the expected genetic sharing among relatives in our sample. This modeling framework allowed us to test two lines of evidence for gene-by-sex interactions: (1) whether the magnitude of the cumulative effect of genes differs between the sexes, and (2) whether different genes are involved. We observed significant evidence of gene-by-sex interactions for caries experience in both the primary and permanent dentitions. In the primary dentition, the magnitude of the effect of genes was greater in males than females. In the permanent dentition, different genes may play important roles in each of the sexes. Overall, this study provides the first direct evidence that sex differences in dental caries experiences may be explained, in part, by gene-by-sex interactions.

Genome-wide two-marker linkage disequilibrium mapping of quantitative trait loci

BACKGROUND

In a natural population, the alleles of multiple tightly linked loci on the same chromosome co-segregate and are passed non-randomly from generation to generation. Capitalizing on this phenomenon, a group of mapping methods, commonly referred to as the linkage disequilibrium-based mapping (LD mapping), have been developed recently for detecting genetic associations. However, most current LD mapping methods mainly employed single-marker analysis, overlooking the rich information contained within adjacent linked loci.

RESULTS

We extend the single-marker LD mapping to include two linked loci and explicitly incorporate their LD information into genetic mapping models (tmLD). We establish the theoretical foundations for the tmLD mapping method and also provide a thorough examination of its statistical properties. Our simulation studies demonstrate that the tmLD mapping method significantly improves the detection power of association compared to the single-marker based and also haplotype based mapping methods. The practical usage and properties of the tmLD mapping method were further elucidated through the analysis of a large-scale dental caries GWAS data set. It shows that the tmLD mapping method can identify significant SNPs that are missed by the traditional single-marker association analysis and haplotype based mapping method. An R package for our proposed method has been developed and is freely available.

CONCLUSIONS

The proposed tmLD mapping method is more powerful than single marker mapping generally used in GWAS data analysis. We recommend the usage of this improved method over the traditional single marker association analysis.

Do polymorphisms in chemosensory genes matter for human ingestive behavior?

In the last decade, basic research in chemoreceptor genetics and neurobiology have revolutionized our understanding of individual differences in chemosensation. From an evolutionary perspective, chemosensory variations appear to have arisen in response to different living environments, generally in the avoidance of toxins and to better detect vital food sources. Today, it is often assumed that these differences may drive variable food preferences and choices, with downstream effects on health and wellness. A growing body of evidence indicates chemosensory variation is far more complex than previously believed. However, just because a genetic polymorphism results in altered receptor function in cultured cells or even behavioral phenotypes in the laboratory, this variation may not be sufficient to influence food choice in free living humans. Still, there is ample evidence to indicate allelic variation in TAS2R38 predicts variation in bitterness of synthetic pharmaceuticals (e.g., propylthiouracil) and natural plant compounds (e.g., goitrin), and this variation associates with differential intake of alcohol and vegetables. Further, this is only one of 25 unique bitter taste genes (TAS2Rs) in humans, and emerging evidence suggests other TAS2Rs may also contain polymorphisms that a functional with respect to ingestive behavior. For example, TAS2R16 polymorphisms are linked to the bitterness of naturally occurring plant compounds and alcoholic beverage intake, a TAS2R19 polymorphism predicts differences in quinine bitterness and grapefruit bitterness and liking, and TAS2R31 polymorphisms associate with differential bitterness of plant compounds like aristolochic acid and the sulfonyl amide sweeteners saccharin and acesulfame-K. More critically with respect to food choices, these polymorphisms may vary independently from each other within and across individuals, meaning a monolithic one-size-fits-all approach to bitterness needs to be abandoned. Nor are genetic differences restricted to bitterness. Perceptual variation has also been associated with polymorphisms in genes involved in odors associated with meat defects (boar taint), green/grassy notes, and cilantro, as well as umami and sweet tastes (TAS1R1/2/3). Here, a short primer on receptor genetics is provided, followed by a summary of current knowledge, and implications for human ingestive behavior are discussed.

Lack of association between lactotransferrin polymorphism and dental caries

OBJECTIVE

Dental caries is a complex, multifactorial disease and one of the most common illnesses worldwide. Its etiology is related to microbial, dietary and host factors. Recent evidence suggests a role of lactotransferrin (LTF) in caries. The purpose of this study was to determine the association between LTF gene polymorphism and dental caries.

METHODS

In this case-control study, 637 unrelated children, aged 11-13 years, were enrolled. The subjects were divided into two groups, i.e. caries-free (decayed/missing/filled teeth = 0) and caries-affected children (decayed/missing/filled teeth ≥ 1). The LTF rs1126478 (140A/G in exon 2, Lys/Arg) genotypes were determined by PCR with restriction analysis using the EarI enzyme.

RESULTS

Of 637 children, 155 (24.3%) were caries free. There were no statistically significant differences between caries levels and allele or genotype distributions in the total cohort. When the caries-affected group (n = 482) was stratified into low (decayed/missing/filled teeth = 1), moderate (2 ≤ decayed/missing/filled teeth ≤ 3) and high (decayed/missing/filled teeth ≥ 4) caries experience, allele and genotype frequencies were similar among all subgroups.

CONCLUSIONS

The LTF 140A/G (exon 2, Lys/Arg) polymorphism was not associated with the susceptibility to or severity of dental caries in the Czech population.

Role of TRAV locus in low caries experience

Caries is the most common chronic, multifactorial disease in the world today; and little is still known about the genetic factors influencing susceptibility. Our previous genome-wide linkage scan has identified five loci related to caries susceptibility: 5q13.3, 13q31.1, 14q11.2, 14q 24.3, and Xq27. In the present study, we fine mapped the 14q11.2 locus to identify genetic contributors to caries susceptibility. Four hundred seventy-seven subjects from 72 pedigrees with similar cultural and behavioral habits and limited access to dental care living in the Philippines were studied. An additional 387 DNA samples from unrelated individuals were used to determine allele frequencies. For replication purposes, a total of 1,446 independent subjects from four different populations were analyzed based on their caries experience (low versus high). Forty-eight markers in 14q11.2 were genotyped using TaqMan chemistry. Transmission disequilibrium test was used to detect over transmission of alleles in the Filipino families, and Chi-square, Fisher's exact and logistic regression were used to test for association between low caries experience and variant alleles in the replication data sets. We finally assessed the mRNA expression of TRAV4 in the saliva of 143 study subjects. In the Filipino families, statistically significant associations were found between low caries experience and markers in TRAV4. We were able to replicate these results in the populations studied that were characteristically from underserved areas. Direct sequencing of 22 subjects carrying the associated alleles detects one missense mutation (Y30R) that is predicted to be probably damaging. Finally, we observed higher expression in children and teenagers with low caries experience, correlating with specific alleles in TRAV4. Our results suggest that TRAV4 may have a role in protecting against caries.

Fine-mapping of 5q12.1-13.3 unveils new genetic contributors to caries

Caries is a multifactorial disease and little is still known about the host genetic factors influencing susceptibility. Our previous genome-wide linkage scan has identified the interval 5q12.1-5q13.3 as linked to low caries susceptibility in Filipino families. Here we fine-mapped this region in order to identify genetic contributors to caries susceptibility. Four hundred and seventy-seven subjects from 72 pedigrees with similar cultural and behavioral habits and limited access to dental care living in the Philippines were studied. DMFT scores and genotype data of 75 single-nucleotide polymorphisms were evaluated in the Filipino families with the Family-Based Association Test. For replication purposes, a total 1,467 independent subjects from five different populations were analyzed in a case-control format. In the Filipino cohort, statistically significant and borderline associations were found between low caries experience and four genes spanning 13 million base pairs (PART1, ZSWIM6, CCNB1, and BTF3). We were able to replicate these results in some of the populations studied. We detected PART1 and BTF3 expression in whole saliva, and the expression of BTF3 was associated with caries experience. Our results suggest BTF3 may have a functional role in protecting against caries.

Genome-wide association scan of dental caries in the permanent dentition

BACKGROUND

Over 90% of adults aged 20 years or older with permanent teeth have suffered from dental caries leading to pain, infection, or even tooth loss. Although caries prevalence has decreased over the past decade, there are still about 23% of dentate adults who have untreated carious lesions in the US. Dental caries is a complex disorder affected by both individual susceptibility and environmental factors. Approximately 35-55% of caries phenotypic variation in the permanent dentition is attributable to genes, though few specific caries genes have been identified. Therefore, we conducted the first genome-wide association study (GWAS) to identify genes affecting susceptibility to caries in adults.

METHODS

Five independent cohorts were included in this study, totaling more than 7000 participants. For each participant, dental caries was assessed and genetic markers (single nucleotide polymorphisms, SNPs) were genotyped or imputed across the entire genome. Due to the heterogeneity among the five cohorts regarding age, genotyping platform, quality of dental caries assessment, and study design, we first conducted genome-wide association (GWA) analyses on each of the five independent cohorts separately. We then performed three meta-analyses to combine results for: (i) the comparatively younger, Appalachian cohorts (N = 1483) with well-assessed caries phenotype, (ii) the comparatively older, non-Appalachian cohorts (N = 5960) with inferior caries phenotypes, and (iii) all five cohorts (N = 7443). Top ranking genetic loci within and across meta-analyses were scrutinized for biologically plausible roles on caries.

RESULTS

Different sets of genes were nominated across the three meta-analyses, especially between the younger and older age cohorts. In general, we identified several suggestive loci (P-value ≤ 10E-05) within or near genes with plausible biological roles for dental caries, including RPS6KA2 and PTK2B, involved in p38-depenedent MAPK signaling, and RHOU and FZD1, involved in the Wnt signaling cascade. Both of these pathways have been implicated in dental caries. ADMTS3 and ISL1 are involved in tooth development, and TLR2 is involved in immune response to oral pathogens.

CONCLUSIONS

As the first GWAS for dental caries in adults, this study nominated several novel caries genes for future study, which may lead to better understanding of cariogenesis, and ultimately, to improved disease predictions, prevention, and/or treatment.

Genetic and environmental factors associated with dental caries in children: the Iowa Fluoride Study

Dental caries remains the most common chronic childhood disease. Despite strong evidence of genetic components, there have been few studies of candidate genes and caries. In this analysis we tried to assess genetic and environmental factors contributing to childhood caries in the Iowa Fluoride Study. Environmental factors (age, sex, race, tooth-brushing frequencies and water fluoride level) and three dental caries scores (d(2)fs-total, d(2)fs-pit/fissure, and d(2)fs-smooth surface) were assessed in 575 unrelated children (mean age 5.2 years). Regression analyses were applied to assess environmental correlates. The Family-Based Association Test was used to test genetic associations for 23 single nucleotide polymorphism (SNP) markers in 7 caries candidate genes on 333 Caucasian parent-child trios. We evaluated the associations between caries status and the level of both single and multiple SNPs (haplotype) respectively. Permutation procedure was performed for correction of inflated type I errors due to multiple testing. Age, tooth-brushing frequency and water fluoride level were significantly correlated to at least one carious score. Caries on pit and fissure surfaces was substantially higher than on smooth surfaces (61 vs. 39%). SNPs in three genes (DSPP, KLK4 and AQP5) showed consistent associations with protection against caries. Of note, KLK4 and AQP5 were also highlighted by subsequent haplotype analysis. Our results support the concept that genes can modify the susceptibility of caries in children. Replication analysis in independent cohorts is highly needed in order to verify the validity of our findings.

Heritable patterns of tooth decay in the permanent dentition: principal components and factor analyses

Background

Dental caries is the result of a complex interplay among environmental, behavioral, and genetic factors, with distinct patterns of decay likely due to specific etiologies. Therefore, global measures of decay, such as the DMFS index, may not be optimal for identifying risk factors that manifest as specific decay patterns, especially if the risk factors such as genetic susceptibility loci have small individual effects. We used two methods to extract patterns of decay from surface-level caries data in order to generate novel phenotypes with which to explore the genetic regulation of caries.

Methods

The 128 tooth surfaces of the permanent dentition were scored as carious or not by intra-oral examination for 1,068 participants aged 18 to 75 years from 664 biological families. Principal components analysis (PCA) and factor analysis (FA), two methods of identifying underlying patterns without a priori surface classifications, were applied to our data.

Results

The three strongest caries patterns identified by PCA recaptured variation represented by DMFS index (correlation, r = 0.97), pit and fissure surface caries (r = 0.95), and smooth surface caries (r = 0.89). However, together, these three patterns explained only 37% of the variability in the data, indicating that a priori caries measures are insufficient for fully quantifying caries variation. In comparison, the first pattern identified by FA was strongly correlated with pit and fissure surface caries (r = 0.81), but other identified patterns, including a second pattern representing caries of the maxillary incisors, were not representative of any previously defined caries indices. Some patterns identified by PCA and FA were heritable (h² = 30-65%, p = 0.043-0.006), whereas other patterns were not, indicating both genetic and non-genetic etiologies of individual decay patterns.

Conclusions

This study demonstrates the use of decay patterns as novel phenotypes to assist in understanding the multifactorial nature of dental caries.

Genetic susceptibility to dental caries on pit and fissure and smooth surfaces

Carious lesions are distributed nonuniformly across tooth surfaces of the complete dentition, suggesting that the effects of risk factors may be surface-specific. Whether genes differentially affect caries risk across tooth surfaces is unknown. We investigated the role of genetics on two classes of tooth surfaces, pit and fissure surfaces (PFS) and smooth surfaces (SMS), in more than 2,600 subjects from 740 families. Participants were examined for surface-level evidence of dental caries, and caries scores for permanent and/or primary teeth were generated separately for PFS and SMS. Heritability estimates (h(2), i.e. the proportion of trait variation due to genes) of PFS and SMS caries scores were obtained using likelihood methods. The genetic correlations between PFS and SMS caries scores were calculated to assess the degree to which traits covary due to common genetic effects. Overall, the heritability of caries scores was similar for PFS (h(2) = 19-53%; p < 0.001) and SMS (h(2) = 17-42%; p < 0.001). Heritability of caries scores for both PFS and SMS in the primary dentition was greater than in the permanent dentition and total dentition. With one exception, the genetic correlation between PFS and SMS caries scores was not significantly different from 100%, indicating that (mostly) common genes are involved in the risk of caries for both surface types. Genetic correlation for the primary dentition dfs (decay + filled surfaces) was significantly less than 100% (p < 0.001), indicating that genetic factors may exert differential effects on caries risk in PFS versus SMS in the primary dentition.

Timing of colonization of caries-producing bacteria: an approach based on studying monozygotic twin pairs

Findings are presented from a prospective cohort study of timing of primary tooth emergence and timing of oral colonization of Streptococcus mutans (S. mutans) in Australian twins. The paper focuses on differences in colonization timing in genetically identical monozygotic (MZ) twins. Timing of tooth emergence was based on parental report. Colonization timing of S. mutans were established by plating samples of plaque and saliva on selective media at 3 monthly intervals and assessing colony morphology. In 25% of individuals colonization occurred prior to emergence of the first tooth. A significant proportion of MZ pairs (21%) was discordant for colonization occurring before or after first tooth emergence, suggesting a role of environmental or epigenetic factors in timing of tooth emergence, colonization by S. mutans, or both. These findings and further application of the MZ co-twin model should assist in development of strategies to prevent or delay infection with S. mutans in children.

Contribution of host genotype to the composition of health-associated supragingival and subgingival microbiomes

AIM

Periodontitis and caries are two of the most prevalent diseases to affect humans, however; the individual susceptibility to these diseases varies significantly in the population. The aim of this investigation, therefore, was to examine the influence of host genotype on the composition of health-associated supragingival and subgingival microbiomes.

MATERIALS AND METHODS

Subgingival and supragingival plaque was collected from orally and systemically healthy adult monozygotic and dizygotic twin pairs. Zygosity was determined by multiplexed PCR amplification of 13 short tandem repeats. Terminal restriction fragment length polymorphism was used for bacterial community profiling. The number of species shared by the twin pairs as well as the similarity of the microbial communities between the twins was computed and compared using two-sample t-test

RESULTS

There was no difference in the number of species shared by the twin pairs as well as the similarity of the microbial communities between the twin dyads. Age was not a modifier of genetic influence on these microbial parameters. There was no difference between monozygotic and dizygotic twin pairs in the correlation between supragingival and subgingival community similarity.

CONCLUSION

The contributory role of host genotype, if any, is not apparent on an established, health-associated oral microbial community.

Resemblance of tongue anatomy in twins

This study compared the anatomical features of the tongue in nine pairs of twins - six monozygotic and three dizygotic. The aim of the project was to determine if tongues, like any other anatomical structure, could be used to reliably predict relatedness given that tongue shape, presentation and surface can be influenced by environment. Using the method of forced choice, 30 subjects were asked to match the photographs of tongues from twins. Our data indicate that, based on visual assessment, monozygotic twins have highly similar tongues (60% matches); similarly, dizygotic twins were matched 31% of the time, which is a higher probability than would be expected from random selection. This study should help identify baseline and control data in future behavioral studies of taste, which has a genetic basis.

Taste genes associated with dental caries

Dental caries is influenced by a complex interplay of genetic and environmental factors, including dietary habits. Previous reports have characterized the influence of genetic variation on taste preferences and dietary habits. We therefore hypothesized that genetic variation in taste pathway genes (TAS2R38, TAS1R2, GNAT3) may be associated with dental caries risk and/or protection. Families were recruited by the Center for Oral Health Research in Appalachia (COHRA) for collection of biological samples, demographic data, and clinical assessment of oral health, including caries scores. Multiple single-nucleotide polymorphism (SNP) assays for each gene were performed and analyzed by transmission disequilibrium test (TDT) analysis (FBAT software) for three dentition groups: primary, mixed, and permanent. Statistically significant associations were seen in TAS2R38 and TAS1R2 for caries risk and/or protection.

Association between common variation in genes encoding sweet taste signaling components and human sucrose perception

Variation in taste perception of different chemical substances is a well-known phenomenon in both humans and animals. Recent advances in the understanding of sweet taste signaling have identified a number of proteins involved in this signal transduction. We evaluated the hypothesis that sequence variations occurring in genes encoding taste signaling molecules can influence sweet taste perception in humans. Our population consisted of unrelated individuals (n = 160) of Caucasian, African-American, and Asian descent. Threshold and suprathreshold sensitivities of participants for sucrose were estimated using a sorting test and signal detection analysis that produced cumulative R-index area under the curve (AUC) scores. Genetic association analysis revealed significant correlation of sucrose AUC scores with genetic variation occurring in the GNAT3 gene (single point P = 10(-3) to 10(-4)), which encodes the taste-specific G(alpha) protein subunit gustducin. Subsequent sequencing identified additional GNAT3 variations having significant association with sucrose AUC scores. Collectively, GNAT3 polymorphisms explain 13% of the variation in sucrose perception. Our findings underscore the importance of common genetic variants influencing human taste perception.

Genes and their effects on dental caries may differ between primary and permanent dentitions

The importance of genetic factors in the genesis of dental caries of both primary and permanent dentitions is well established; however, the degree to which genes contribute to the development of dental caries, and whether these genes differ between primary and permanent dentitions, is largely unknown. Using family-based likelihood methods, we assessed the heritability of caries-related phenotypes for both children and adults in 2,600 participants from 740 families. We found that caries phenotypes in the primary dentition were highly heritable, with genes accounting for 54-70% of variation in caries scores. The heritability of caries scores in the permanent dentition was also substantial (35-55%, all p < 0.01), although this was lower than analogous phenotypes in the primary dentition. Assessment of the genetic correlation between primary and permanent caries scores indicated that 18% of the covariation in these traits was due to common genetic factors (p < 0.01). Therefore, dental caries in primary and permanent teeth may be partly attributable to different suites of genes or genes with differential effects. Sex and age explained much of the phenotypic variation in permanent, but not primary, dentition. Further, including pre-cavitated white-spot lesions in the phenotype definition substantially increased the heritability estimates for dental caries. In conclusion, our results show that dental caries are heritable, and suggest that genes affecting susceptibility to caries in the primary dentition may differ from those in permanent teeth. Moreover, metrics for quantifying caries that incorporate white-spot lesions may serve as better phenotypes in genetic studies of the causes of tooth decay.

Genetic and Environmental Factors in Oral Health among Twins

To date, studies on the contributions of genetic factors to oral health have been inconclusive. We hypothesized that major dental diseases show a significant genetic component. The study was based on self-reported oral health among young adult twins. The data were derived from the fourth wave of the longitudinal FinnTwin16 study, in which participants completed a questionnaire in 2000-2002 enquiring about the number of filled teeth and the prevalence of gingival bleeding. We used quantitative genetic modeling, based on the genetic similarity of identical and non-identical twins, to calculate the most probable model for both filled teeth and gingival bleeding. The models revealed a strong genetic component behind the number of filled teeth, differing between males (49%) and females (68%), and a weaker genetic component affecting gingival bleeding, being similar for males and females (32%). Genetic factors contribute to inter-individual differences in oral health among young adults.

Allelic polymorphism within the TAS1R3 promoter is associated with human taste sensitivity to sucrose

Human sweet taste perception is mediated by the heterodimeric G protein-coupled receptor encoded by the TAS1R2 and TAS1R3 genes. Variation in these genes has been characterized, but the functional consequences of such variation for sweet perception are unknown. We found that two C/T single-nucleotide polymorphisms (SNPs) located at positions -1572 (rs307355) and -1266 (rs35744813) upstream of the TAS1R3 coding sequence strongly correlate with human taste sensitivity to sucrose and explain 16% of population variability in perception. By using a luciferase reporter assay, we demonstrated that the T allele of each SNP results in reduced promoter activity in comparison to the C alleles, consistent with the phenotype observed in humans carrying T alleles. We also found that the distal region of the TAS1R3 promoter harbors a composite cis-acting element that has a strong silencing effect on promoter activity. We conclude that the rs307355 and rs35744813 SNPs affect gene transcription by altering the function of this regulatory element. A worldwide population survey reveals that the T alleles of rs307355 and rs35744813 occur at lowest frequencies in European populations. We propose that inherited differences in TAS1R3 transcription account for a substantial fraction of worldwide differences in human sweet taste perception.

Reared apart Korean female twins: Genetic and cultural influences on life histories, physical and health-related measures, and behavioral traits

This paper reports physical and behavioral similarities and differences in a pair of 18-year-old monozygotic (MZA) female twins, raised apart from birth in dramatically different cultures: South Korea and the United States. The main outcome measures included life history characteristics (e.g., age at separation, age at reunion), physical and health-related traits (e.g., height, weight, body mass index, age at menarche, illnesses), and behavioral traits (e.g., IQ, special mental abilities, personality traits, dietary preferences). Similarities in some physical characteristics, as well as differences, were noted. High levels of concordance were obtained for IQ and for two special mental ability measures. Selected personality traits presented a mixed picture with respect to concordance and discordance, and dietary preferences showed some unexpected similarities. The findings are discussed with reference to genetic and cultural influences on development.

Serum level of intercellular adhesion molecule-1 in children with malignant lymphoma

OBJECTIVE

To estimate the serum levels of soluble intercellular adhesion molecule-1 (s-ICAM-1) in children newly diagnosed with lymphoma and to correlate levels of s-ICAM-1 in lymphoma patients with clinical stage, pathological types, clinical and laboratory data and patient outcome.

SUBJECTS AND METHODS

Thirty-five children with newly-diagnosed malignant lymphoma (Non-Hodgkin's lymphoma, NHL: 23), Hodgkin's disease (HD: 12), and 8 apparently healthy subjects of matched age and sex taken as a control group were studied. For the patients and control group, the following tests were performed: complete blood count, and the following biochemical investigations: liver function tests, lactate dehydrogenase (LDH), and soluble ICAM-1 estimation using ELISA. In addition, for patients, pathological examination of lymph node biopsy for pathological grading, bone marrow aspiration and biopsy were done. Patients were observed for over 12 months or until death.

RESULTS

Serum ICAM-1 increased more in HD and NHL than in the control group (p < 0.000); also s-ICAM-1 increased in advanced stages and high-grade NHL (p < 0.008, 0.04, respectively). LDH levels were higher in patients compared to controls (p < 0.000). There was a positive correlation between high levels of s-ICAM-1 and increased levels of LDH in HD (r = 0.72, p < 0.008) and a positive correlation between high levels of s-ICAM-1 and increased ALT in NHL patients. A positive correlation between s-ICAM-1 levels and the presence of B symptoms in HD and NHL, and a positive correlation between elevated s-ICAM-1 levels and worse outcome in HD and NHL were detected.

CONCLUSIONS

The data indicate that in children with malignant lymphoma, high serum levels of ICAM-1 correlated with tumor aggressiveness, and quantification of s-ICAM-1 levels may identify a subgroup of children with worse prognosis. Therefore, detection of s-ICAM-1 levels in children with malignant lymphoma might represent an additional disease-associated marker for use in the clinical management of the patients.