Quantitative modelling of transcription factor binding sites

Abstract One of the most important issues in molecular biology is to understand regulatory mechanisms that control gene expression. Gene expression is often regulated by proteins, called transcription factors which bind to short (5 to 20 base pairs),degenerate segments of DNA. Experimental efforts towards understanding the sequence specificity of transcription factors is laborious and expensive, but can be substantially accelerated with the use of computational predictions. This thesis describes the use of algorithms and resources for transcriptionfactor binding site analysis in addressing quantitative modelling, where probabilitic models are built to represent binding properties of a transcription factor and can be used to find new functional binding sites in genomes. Initially, an open-access database(HTPSELEX) was created, holding high quality binding sequences for two eukaryotic families of transcription factors namely CTF/NF1 and LEFT/TCF. The binding sequences were elucidated using a recently described experimental procedure called HTP-SELEX, that allows generation of large number (> 1000) of binding sites using mass sequencing technology. For each HTP-SELEX experiments we also provide accurate primary experimental information about the protein material used, details of the wet lab protocol, an archive of sequencing trace files, and assembled clone sequences of binding sequences. The database also offers reasonably large SELEX libraries obtained with conventional low-throughput protocols.The database is available at http://wwwisrec.isb-sib.ch/htpselex/ and and ftp://ftp.isrec.isb-sib.ch/pub/databases/htpselex. The Expectation-Maximisation(EM) algorithm is one the frequently used methods to estimate probabilistic models to represent the sequence specificity of transcription factors. We present computer simulations in order to estimate the precision of EM estimated models as a function of data set parameters(like length of initial sequences, number of initial sequences, percentage of nonbinding sequences). We observed a remarkable robustness of the EM algorithm with regard to length of training sequences and the degree of contamination. The HTPSELEX database and the benchmarked results of the EM algorithm formed part of the foundation for the subsequent project, where a statistical framework called hidden Markov model has been developed to represent sequence specificity of the transcription factors CTF/NF1 and LEF1/TCF using the HTP-SELEX experiment data. The hidden Markov model framework is capable of both predicting and classifying CTF/NF1 and LEF1/TCF binding sites. A covariance analysis of the binding sites revealed non-independent base preferences at different nucleotide positions, providing insight into the binding mechanism. We next tested the LEF1/TCF model by computing binding scores for a set of LEF1/TCF binding sequences for which relative affinities were determined experimentally using non-linear regression. The predicted and experimentally determined binding affinities were in good correlation.

Clinical relevance of L-carnitine-supplemented total parenteral nutrition in postoperative trauma. Metabolic effects of continuous or acute carnitine administration with special reference to fat oxidation and nitrogen utilization.

Carnitine-free total parenteral nutrition (TPN) is claimed to result in a carnitine deficiency with subsequent impairment of fat oxidation. The present study was designed to evaluate the possible benefit of carnitine supplementation on postoperative fat and nitrogen utilization. Sixteen patients undergoing total esophagectomy were evenly randomized and received TPN without or with L-carnitine supplementation (74 mumol.kg-1.d-1) during 11 postoperative days. On day 11, a 4-h infusion of L-carnitine (125 mumol/kg) was performed in both groups. The effect of supplementation was evaluated by indirect calorimetry, N balance, and repeated measurements of plasma lipids and ketone bodies. Irrespective of continuous or acute supplementation, respiratory quotient and fat oxidation were similarly maintained throughout the study in both groups whereas N balance appeared to be more favorable without carnitine. We conclude that carnitine-supplemented TPN does not improve fat oxidation or promote N utilization in the postoperative phase.

Répercussions de l'agression sur le métabolisme et la composition corporelle chez l'individu obèse : Nutrition de l'obèse agressé. [Repercussions of injury on metabolic and body composition factors in obese individuals : Nutrition and obese critical patients]

La réponse métabolique de l'obèse apparemment « sainen situation d'agression aiguë (polytraumatisés, traumatisés crâniens, patients chirurgicaux, grands brûlés, opérations électives) ne se distingue pas ou peu de celle de l'individu non-obèse. Cependant, les complications médicales liées à l'agression (insuffisances respiratoire et cardiaque, bronchopneumonie, infections de plaies, thrombophlébites et embolies) demeurent plus importantes chez l'obèse morbide que chez l'individu de poids normal. Grâce à l'inflation de ses réserves énergétiques, l'obèse apparemment sain est avantagé, par rapport au sujet mince, au cours d'une agression nutritionnelle chronique telle que le jeûne prolongé. Le facteur fonctionnel limitant la survie dépend avant tout de la composition corporelle initiale et du degré d'adaptation métabolique (et comportementale) en particulier du degré de conservation de la masse maigre par rapport à la masse grasse. La mobilisation accrue de la masse grasse associée à la perte de poids chez l'obèse (par rapport à son homologue non-obèse) est favorable à une prolongation de la vie, car, en brûlant davantage de graisse corporelle, la part des protéines corporelles endogènes utilisée à des fins énergétiques est plus faible. Il s'ensuit chez l'obèse qu'un niveau de masse maigre critique pour la survie n'est atteint qu'après une réduction très marquée de ses réserves énergétiques. En revanche, le sujet mince perd davantage de masse maigre lors de l'amaigrissement et, par conséquent, son métabolisme de repos diminuera plus rapidement que celui du sujet obèse. Cela peut constituer un avantage énergétique évident en termes d'économie d'énergie consécutive à l'adaptation métabolique, mais un inconvénient majeur quant à la durée de la survie. The metabolic response of « apparently healthyobese individuals following acute injury (multiple trauma, head injury and surgical patients, extended burns, elective surgery) is not dramatically different from that of a non-obese individuals. However, the medical complications following the injury (respiratory and cardiac insufficiency, broncho-pneumonia, infections of wounds, trombophlebitis and embolism) are more prevalent in morbid obese patients than in individuals of normal body weight. Because of a large increase in their individuals energy store, "apparently healthy" obese individuals have an advantage over very lean subjects when exposed to a chronic nutritional aggression such as total fasting. The functional limiting factor for survival depends primarily on initial body composition and the magnitude of metabolic adaptation (including behavioral adaptation). The key factor is the extent to which the fat-free mass is maintained (versus to the fat mass) during weight loss. The increased proportion of body fat mobilized during weight loss in obese patients, compared with their non-obese counterparts, favors prolonged survival, because more adipose tissue is burned off, the fraction of body protein endogenously utilized for energy purpose individuals, is smaller. This implies that obese individuals do not reach a fat-free mass "critical" for their survival until their energy stores reach very low values. In contrast, lean subject tend to lose more fat-free mass during weight loss than obese subjects and, as a result, their energy expenditure drops more rapidly. This may offer a potential advantage in terms of energy economy (more energy saving) but a major disadvantage in terms of duration of survival.

Thermogenesis in obese women: effect of fructose vs. glucose added to a meal.

To assess the effect of a fructose meal on resting energy expenditure (EE), indirect calorimetry was used in 23 women (10 lean and 13 obese) for 30 min before and 6 h after the ingestion of a mixed meal containing 20% protein, 33% fat, and either 75 g glucose or 75 g fructose as carbohydrate source (47%). Expressed as a percentage of the energy content of the meal, the thermogenic response to the fructose meal was significantly greater (10.2 +/- 0.5%) than that of the glucose meal (8.4 +/- 0.4%, P less than 0.01). This difference was still apparent when the lean and obese women were considered separately. The mean respiratory quotient during the 6-h postprandial period was significantly greater (P less than 0.01) for the fructose (0.85 +/- 0.01) than for the glucose meal (0.83 +/- 0.01) in the combined subjects. In addition, cumulative carbohydrate oxidation was significantly greater after the fructose than after the glucose meal (51.1 +/- 2.3 vs. 40.9 +/- 2.0 g/6 h, respectively, P less than 0.01). Only small changes were observed in postprandial plasma levels of glucose and insulin after the fructose meal, but the plasma levels of lactate increased more with fructose than with the glucose meal. These results suggest that there might be some advantages (higher thermogenesis and carbohydrate oxidations) in using fructose as part of the carbohydrate source in diet of people with obesity and/or insulin resistance.

Ability of different adiposity indicators to identify children with elevated blood pressure.

OBJECTIVE: Body composition measured by dual-energy X-ray absorptiometry (DXA) is believed to be superior to crude measures such as BMI or waist circumference (WC) to assess health risks associated with adiposity in adults. We compared the ability of BMI, WC, waist-to-height ratio (WHtR), percentage body fat from skinfold thickness, and measures of total and central fat assessed by DXA to identify children with elevated blood pressure (BP). STUDY DESIGN: The QUALITY Study follows 630 Caucasian families (father, mother, and child originally aged 8-10 years). BP, height, weight, WC, and skinfold thickness were measured according to standardized protocols. Elevated BP was defined as systolic or diastolic BP at least 90th age, sex, and height-specific percentile. Total and central fat were determined with DXA. The area under the receiver operating characteristic (ROC) curve (AUC) statistic was computed from logistic models that adjusted for age, sex, height, Tanner stage, and physical activity. RESULTS: All adiposity indicators were highly correlated. WC and WHtR did not show superior ability over BMI to identify children with elevated SBP (P = 0.421 and 0.473). Measures of total and central fat from DXA did not show an improved ability over BMI or WC to identify children with elevated SBP (P = 0.325-0.662). CONCLUSION: Results support the use of BMI in clinical and public health settings, at least in this age group. As all indicators had a limited ability to identify children with elevated BP, results also support measurement of BP in all children of this age independent of a weight status.

Is the adiposity-associated FTO gene variant related to all-cause mortality independent of adiposity? Meta-analysis of data from 169,551 Caucasian adults.

Previously, a single nucleotide polymorphism (SNP), rs9939609, in the FTO gene showed a much stronger association with all-cause mortality than expected from its association with body mass index (BMI), body fat mass index (FMI) and waist circumference (WC). This finding implies that the SNP has strong pleiotropic effects on adiposity and adiposity-independent pathological pathways that leads to increased mortality. To investigate this further, we conducted a meta-analysis of similar data from 34 longitudinal studies including 169,551 adult Caucasians among whom 27,100 died during follow-up. Linear regression showed that the minor allele of the FTO SNP was associated with greater BMI (n = 169,551; 0.32 kg m(-2) ; 95% CI 0.28-0.32, P < 1 × 10(-32) ), WC (n = 152,631; 0.76 cm; 0.68-0.84, P < 1 × 10(-32) ) and FMI (n = 48,192; 0.17 kg m(-2) ; 0.13-0.22, P = 1.0 × 10(-13) ). Cox proportional hazard regression analyses for mortality showed that the hazards ratio (HR) for the minor allele of the FTO SNPs was 1.02 (1.00-1.04, P = 0.097), but the apparent excess risk was eliminated after adjustment for BMI and WC (HR: 1.00; 0.98-1.03, P = 0.662) and for FMI (HR: 1.00; 0.96-1.04, P = 0.932). In conclusion, this study does not support that the FTO SNP is associated with all-cause mortality independently of the adiposity phenotypes.

Vitamin D time profile based on the contribution of non-genetic and genetic factors in HIV-infected individuals of European ancestry.

BACKGROUND: Vitamin D deficiency is prevalent in HIV-infected individuals and vitamin D supplementation is proposed according to standard care. This study aimed at characterizing the kinetics of 25(OH)D in a cohort of HIV-infected individuals of European ancestry to better define the influence of genetic and non-genetic factors on 25(OH)D levels. These data were used for the optimization of vitamin D supplementation in order to reach therapeutic targets. METHODS: 1,397 25(OH)D plasma levels and relevant clinical information were collected in 664 participants during medical routine follow-up visits. They were genotyped for 7 SNPs in 4 genes known to be associated with 25(OH)D levels. 25(OH)D concentrations were analysed using a population pharmacokinetic approach. The percentage of individuals with 25(OH)D concentrations within the recommended range of 20-40 ng/ml during 12 months of follow-up and several dosage regimens were evaluated by simulation. RESULTS: A one-compartment model with linear absorption and elimination was used to describe 25(OH)D pharmacokinetics, while integrating endogenous baseline plasma concentrations. Covariate analyses confirmed the effect of seasonality, body mass index, smoking habits, the analytical method, darunavir/ritonavir and the genetic variant in GC (rs2282679) on 25(OH)D concentrations. 11% of the inter-individual variability in 25(OH)D levels was explained by seasonality and other non-genetic covariates, and 1% by genetics. The optimal supplementation for severe vitamin D deficient patients was 300,000 IU two times per year. CONCLUSIONS: This analysis allowed identifying factors associated with 25(OH)D plasma levels in HIV-infected individuals. Improvement of dosage regimen and timing of vitamin D supplementation is proposed based on those results.

Effect of GA3, KNO3, and removing of basal point of seeds on germination of sweet granadilla (Passiflora ligularis Juss) and yellow passion fruit (Passiflora edulis f. flavicarpa)

Passiflora seeds germinate erratically presenting difficulties for their handling in a greenhouse. The effect of removing of basal point of seeds (RB) and pre-imbibition of seeds of sweet granadilla and yellow passion fruit in 50, 100, 200, and 400 mg mL-1 solutions of gibberellic acid (GA3) or 0.1% KNO3 solution was studied. The experiment was conducted in greenhouses in La Plata, Colombia. Two accessions PrJ1 and PrJ2 of sweet granadilla were evaluated. There were calculated the final percentage of germination (PG), mean germination time (MGT), and the mean germination rate (MGR). The leaf area and dry mass of seedlings were measured 22 days after sowing (das); with this data, specific leaf area and relation root/shoot were calculated. In all cases, the highest germination percentages were achieved treating seeds with KNO3 (89, 92, and 87% for yellow passion fruit, PrJ2, and PrJ1, respectively), but the increase in MGR (3.3 germinated seeds per day) and the decrease in MGT (16 days) were only significant for PrJ1. RB had a significant reduction of PG in all cases (28, 12, and 33% for passion fruit, PrJ2 and PrJ1, respectively). With the increase in the concentration of GA3, PG was reduced for two accessions of sweet granadilla, for yellow passion fruit this trend was not clear, no treatment with GA3 showed significant differences with the control. Leaf area (24.07 cm2) and dry mass of seedlings (135 mg) were significantly higher than seeds previously treated with KNO3 only for PrJ1.The solution of KNO3 0,1% is recommended to improve the germination and initial growth of granadilla seedlings.

Prevalence of Ischemic Heart Disease and Management of Coronary Risk in Daily Clinical Practice: Results from a Mediterranean Cohort of HIV-Infected Patients

There are conflicting data on the prevalence of coronary events and the quality of the management of modifiable cardiovascular risk factors (CVRF) inHIV-infected patients. Methods.We performed a retrospective descriptive study to determine the prevalence of coronary events and to evaluate the management of CVRF in a Mediterranean cohort of 3760 HIV-1-infected patients from April 1983 through June 2011. Results.We identified 81 patients with a history of a coronary event (prevalence 2.15%); 83% of them suffered an acute myocardial infarction. At the time of the coronary event, CVRF were highly prevalent (60.5% hypertension, 48% dyslipidemia, and 16% diabetes mellitus).OtherCVRF, such as smoking, hypertension, lack of exercise, and body mass index, were not routinely assessed. After the coronary event, a significant decrease in total cholesterol ( � = 0.025) and LDLcholesterol ( � = 0.004) was observed. However, the percentage of patients whomaintained LDL-cholesterol > 100mg/dL remained stable (from 46% to 41%, � = 0.103). Patients using protease inhibitors associated with a favorable lipid profile increased over time ( � = 0.028). Conclusions.The prevalence of coronary events in our cohort is low. CVRF prevalence is high and theirmanagement is far from optimal. More aggressive interventions should be implemented to diminish cardiovascular risk in HIV-infected patients.

Pathomorphological and CT-angiographical characteristics of coronary atherosclerotic plaques in cases of sudden cardiac death.

The goal of this study was to assess the localization and types of thrombosed plaques in cases of sudden cardiac death attributed to coronary artery disease and to evaluate possible correlations with body mass index (BMI) and increased heart weight. This retrospective study was performed on forensic cases for which the cause of death was attributed to coronary artery disease. A complete autopsy and a multi-phase postmortem computed tomography (CT) angiography (MPMCTA) were performed in all cases. Eighty-five cases were selected (mean age, 55.18 ± 11.04 years; 72 men and 13 women). MPMCTA performed prior to autopsy enabled an evaluation of coronary artery perfusion before dissection of the body and helped therefore to guide sampling for histology. An acute coronary thrombosis was found in 57 cases, which included plaque erosion in 26 cases (mean age, 46.73 ± 8.33 years) and rupture or intra-plaque hemorrhage in 31 cases (mean age, 58.23 ± 10.62 years). Erosions were most frequently found in the left anterior descending artery (61.5 %), while only 35.48 % of ruptures were observed in this artery. Chronic coronary pathology was considered as the main cause of death in 28 cases (mean age, 59.64 ± 9.47 years). Sixty-two of the cases (72.94 %) had a BMI in the overweight category (BMI ≥25), with the highest mean BMI in patients with chronic coronary pathology without acute thrombosis found at autopsy. The heart weight was above the predicted reference values in 52 cases (61.18 %). Our results are in accordance with previously published studies on the spatial distribution of vulnerable plaques. We observed a higher percentage of eroded plaques than previously reported. Patients with coronary erosions were significantly younger than those with plaque rupture or those without an acute coronary thrombosis (p values <0.0001). BMI and heart weight were significantly higher for cases without thrombosis in comparison with those with plaque rupture (p values 0.028 and 0.003, respectively). Our results indicating that increased BMI and overweight hearts are associated with chronic ischemic heart disease are compatible with clinical studies. Performing more postmortem studies on forensic autopsies, including modern radiological examinations with MPMCTA, can enhance the detection of vulnerable plaques in living patients and prevent sudden cardiac death.

Targeting of Fn14 Prevents Cancer-Induced Cachexia and Prolongs Survival.

The cytokine TWEAK and its cognate receptor Fn14 are members of the TNF/TNFR superfamily and are upregulated in tumors. We found that Fn14, when expressed in tumors, causes cachexia and that antibodies against Fn14 dramatically extended lifespan by inhibiting tumor-induced weight loss although having only moderate inhibitory effects on tumor growth. Anti-Fn14 antibodies prevented tumor-induced inflammation and loss of fat and muscle mass. Fn14 signaling in the tumor, rather than host, is responsible for inducing this cachexia because tumors in Fn14- and TWEAK-deficient hosts developed cachexia that was comparable to that of wild-type mice. These results extend the role of Fn14 in wound repair and muscle development to involvement in the etiology of cachexia and indicate that Fn14 antibodies may be a promising approach to treat cachexia, thereby extending lifespan and improving quality of life for cancer patients.

The increase in hydric volume is associated to contractile impairment in the calf after the world's most extreme mountain ultra-marathon

BACKGROUND: Studies have recently focused on the effect of running a mountain ultra-marathon (MUM) and their results show muscular inflammation, damage and force loss. However, the link between peripheral oedema and muscle force loss is not really established. We tested the hypothesis that, after a MUM, lower leg muscles' swelling could be associated with muscle force loss. The knee extensor (KE) and the plantar flexor (PF) muscles' contractile function was measured by supramaximal electrical stimulations, potentiated low- and high-frequency doublets (PS10 and PS100) of the KE and the PF were measured by transcutaneous electrical nerve stimulation and bioimpedance was used to assess body composition in the runners (n = 11) before (Pre) and after (Post) the MUM and compared with the controls (n = 8). RESULTS: The maximal voluntary contraction of the KE and the PF significantly decreased by 20 % Post-MUM in the runners. Hydration of the non-fat mass (NF-Hyd) and extracellular water volume (Ve) were increased by 12 % Post-MUM (p < 0.001) in the runners. Calf circumference (+2 %, p < 0.05) was also increased. Significant relationships were found for percentage increases in Ve and NF-Hyd with percentage decrease in PS10 of the PF (r = -0.68 and r = -0.70, p < 0.05) and with percentage increase of calf circumference (r = 0.72 and r = 0.73, p < 0.05) in the runners. CONCLUSIONS: The present study suggests that increases in circumference and in hydric volume are associated to contractile impairment in the calf in ultra-marathon runners.

In Vivo Profiling and Distribution of Known and Novel Phase I and Phase II Metabolites of Efavirenz in Plasma, Urine, and Cerebrospinal Fluid.

Efavirenz (EFV) is principally metabolized by CYP2B6 to 8-hydroxy-efavirenz (8OH-EFV) and to a lesser extent by CYP2A6 to 7-hydroxy-efavirenz (7OH-EFV). So far, most metabolite profile analyses have been restricted to 8OH-EFV, 7OH-EFV, and EFV-N-glucuronide, even though these metabolites represent a minor percentage of EFV metabolites present in vivo. We have performed a quantitative phase I and II metabolite profile analysis by tandem mass spectrometry of plasma, cerebrospinal fluid (CSF), and urine samples in 71 human immunodeficiency virus patients taking efavirenz, prior to and after enzymatic (glucuronidase and sulfatase) hydrolysis. We have shown that phase II metabolites constitute the major part of the known circulating efavirenz species in humans. The 8OH-EFV-glucuronide (gln) and 8OH-EFV-sulfate (identified for the first time) in humans were found to be 64- and 7-fold higher than the parent 8OH-EFV, respectively. In individuals (n = 67) genotyped for CYP2B6, 2A6, and CYP3A metabolic pathways, 8OH-EFV/EFV ratios in plasma were an index of CYP2B6 phenotypic activity (P < 0.0001), which was also reflected by phase II metabolites 8OH-EFV-glucuronide/EFV and 8OH-EFV-sulfate/EFV ratios. Neither EFV nor 8OH-EFV, nor any other considered metabolites in plasma were associated with an increased risk of central nervous system (CNS) toxicity. In CSF, 8OH-EFV levels were not influenced by CYP2B6 genotypes and did not predict CNS toxicity. The phase II metabolites 8OH-EFV-gln, 8OH-EFV-sulfate, and 7OH-EFV-gln were present in CSF at 2- to 9-fold higher concentrations than 8OH-EFV. The potential contribution of known and previously unreported EFV metabolites in CSF to the neuropsychological effects of efavirenz needs to be further examined in larger cohort studies.

Rapid analysis of multiclass antibiotic residues and some of their metabolites in hospital, urban wastewater and river water by ultra-highperformance liquid chromatography coupled to quadrupole-linear ion trap tandem mass spectrometry

The present work describes the development of a fast and robust analytical method for the determination of 53 antibiotic residues, covering various chemical groups and some of their metabolites, in environmental matrices that are considered important sources of antibiotic pollution, namely hospital and urban wastewaters, as well as in river waters. The method is based on automated off-line solid phase extraction (SPE) followed by ultra-high-performance liquid chromatography coupled to quadrupole linear ion trap tandem mass spectrometry (UHPLC–QqLIT). For unequivocal identification and confirmation, and in order to fulfill EU guidelines, two selected reaction monitoring (SRM) transitions per compound are monitored (the most intense one is used for quantification and the second one for confirmation). Quantification of target antibiotics is performed by the internal standard approach, using one isotopically labeled compound for each chemical group, in order to correct matrix effects. The main advantages of the method are automation and speed-up of sample preparation, by the reduction of extraction volumes for all matrices, the fast separation of a wide spectrum of antibiotics by using ultra-high-performance liquid chromatography, its sensitivity (limits of detection in the low ng/L range) and selectivity (due to the use of tandem mass spectrometry) The inclusion of β-lactam antibiotics (penicillins and cephalosporins), which are compounds difficult to analyze in multi-residue methods due to their instability in water matrices, and some antibiotics metabolites are other important benefits of the method developed. As part of the validation procedure, the method developed was applied to the analysis of antibiotics residues in hospital, urban influent and effluent wastewaters as well as in river water samples

Predictors of trabecular bone score in school children.

UNLABELLED: Trabecular bone score (TBS) is a DXA-based tool that assesses bone texture and reflects microarchitecture. It has been shown to independently predict the risk of osteoporotic fracture in the elderly. In this study, we investigated the determinants of TBS in adolescents. INTRODUCTION: TBS is a gray-level textural measurement derived from lumbar spine DXA images. It appears to be an index of bone microarchitecture that provides skeletal information additional to the standard BMD measurement and clinical risk factors. Our objectives were to characterize the relationship between TBS and both age and pubertal stages and identify other predictors in adolescents. METHODS: We assessed TBS by reanalyzing spine DXA scan images obtained from 170 boys and 168 girls, age range 10-17 years, gathered at study entry and at 1 year, using TBS software. The results are from post hoc analyses obtained using data gathered from a prospective randomized vitamin D trial. Predictors of TBS were assessed using t test or Pearson's correlation and adjusted using regression analyses, as applicable. RESULTS: The mean age of the study population was 13.2 ± 2.1 years, similar between boys and girls. Age, height, weight, sun exposure, spine BMC and BMD, body BMC and BMD, and lean and fat mass are all significantly correlated with TBS at baseline (r = 0.20-0.75, p < 0.035). Correlations mostly noted in late-pubertal stages. However, after adjustment for BMC, age remained an independent predictor only in girls. CONCLUSIONS: In univariate exploratory analyses, age and pubertal stages were determinants of TBS in adolescents. Studies to investigate predictors of TBS and to investigate its value as a prognostic tool of bone fragility in the pediatric population are needed.