Phalangeal quantitative ultrasound in children with phenylketonuria: a pilot study

Creatine energy substrate increases bone density in the Pahenu2 classical PKU mouse in the context of phenylalanine restriction

Pathophysiology of osteopenia in phenylalanine hydroxylase (PAH) deficient phenylketonuria (PKU) is poorly characterized. The Pahenu2 mouse is universally osteopenic where dietary phenylalanine (Phe) management with amino acid defined chow does not improve bone density. We previously demonstrated Pahenu2 osteopenia owes to a skeletal stem cell (SSC) developmental deficit mediated by energy dysregulation and oxidative stress. This investigation demonstrates complexity of Pahenu2 SSC energy dysregulation. Creatine use by bone tissue is recognized. In vitro Pahenu2 SSCs in osteoblast differentiation respond to creatine with increased in situ alkaline phosphatase activity and increased intracellular ATP content. Animal studies applied a 60-day creatine regimen to Pahenu2 and control cohorts. Control cohorts include unaffected littermates (wt/wt), Pahenu2 receiving no intervention, and dietary Phe restricted Pahenu2. Experimental cohorts (Phe unrestricted Pahenu2, Phe restricted Pahenu2) were provided 1% creatine ad libitum in water. After 60 days, microcomputed tomography assessed bone metrics. Equivalent osteopenia occurs in Phe-restricted and untreated Pahenu2 control cohorts. In Phe unrestricted Pahenu2, creatine was without effect as bone density remained equivalent to Pahenu2 control cohorts. Alternatively, Phe-restricted Pahenu2 receiving creatine present increased bone density. We hypothesize small molecule dysregulation in untreated Pahenu2 disallows creatine utilization; therefore, osteopenia persisted. Dietary Phe restriction enables creatine utilization to enhance SSC osteoblast differentiation and improve in vivo bone density. PKU intervention singularly focused on Phe reduction enables residual disease including osteopenia and neurologic elements. Intervention concurrently addressing Phe homeostasis and energy dysregulation will improve disease elements refractory to standard of care Phe reduction mono-therapy.

Glutamine energy substrate anaplerosis increases bone density in the Pahenu2 classical PKU mouse in the absence of phenylalanine restriction

Osteopenia is an under-investigated clinical presentation of phenylalanine hydroxylase (PAH)-deficient phenylketonuria (PKU). While osteopenia is not fully penetrant in human PKU, the Pahenu2 mouse is universally osteopenic and ideal to study the phenotype. We determined Pahenu2 mesenchymal stem cells (MSCs) are developmentally impaired in the osteoblast lineage. Moreover, we determined energy dysregulation and oxidative stress contribute to the osteoblast developmental deficit. The MSC preferred substrate glutamine (Gln) was applied to enhance energy homeostasis. In vitro Pahenu2 MSCs, in the context of 1200 μM Phe, respond to Gln with increased in situ alkaline phosphatase activity indicating augmented osteoblast differentiation. Oximetry applied to Pahenu2 MSCs in osteoblast differentiation show Gln energy substrate increases oxygen consumption, specifically maximum respiration and respiratory reserve. For 60 days post-weaning, Pahenu2 animals received either no intervention (standard lab chow), amino acid defined chow maintaining plasma Phe at ~200 μM, or standard lab chow where ad libitum water was a 2% Gln solution. Bone density was assessed by microcomputed tomography and bone growth assessed by dye labeling. Bone density and dye labeling in Phe-restricted Pahenu2 was indistinguishable from untreated Pahenu2. Gln energy substrate provided to Pahenu2, in the context of uncontrolled hyperphenylalaninemia, present increased bone density and dye labeling. These data provide further evidence that Pahenu2 MSCs experience a secondary energy deficit that is responsive both in vitro and in vivo to Gln energy substrate and independent of hyperphenylalaninemia. Energy support may have effect to treat human PKU osteopenia and elements of PKU neurologic disease resistant to standard of care systemic Phe reduction. Glutamine energy substrate anaplerosis increased Pahenu2 bone density and improved in vitro MSC function in the context of hyperphenylalaninemia in the classical PKU range.

Mesenchymal stem cell energy deficit and oxidative stress contribute to osteopenia in the Pahenu2 classical PKU mouse

Osteopenia occurs in a subset of phenylalanine hydroxylase (PAH) deficient phenylketonuria (PKU) patients. While osteopenia is not fully penetrant in patients, the Pah^enu2 classical PKU mouse is universally osteopenic, making it an ideal model of the phenotype. Pah^enu2 Phe management, with a Phe-fee amino acid defined diet, does not improve bone density as histomorphometry metrics remain indistinguishable from untreated animals. Previously, we demonstrated Pah^enu2 mesenchymal stem cells (MSCs) display impaired osteoblast differentiation. Oxidative stress is recognized in PKU patients and PKU animal models. Pah^enu2 MSCs experience oxidative stress determined by intracellular superoxide over-representation. The deleterious impact of oxidative stress on mitochondria is recognized. Oximetry applied to Pah^enu2 MSCs identified mitochondrial stress by increased basal respiration with concurrently reduced maximal respiration and respiratory reserve. Proton leak secondary to mitochondrial complex 1 dysfunction is a recognized superoxide source. Respirometry applied to Pah^enu2 MSCs, in the course of osteoblast differentiation, identified a partial complex 1 deficit. Pah^enu2 MSCs treated with the antioxidant resveratrol demonstrated increased mitochondrial mass by MitoTracker green labeling. In hyperphenylalaninemic conditions, resveratrol increased in situ alkaline phosphatase activity suggesting partial recovery of Pah^enu2 MSCs osteoblast differentiation. Up-regulation of oxidative energy production is required for osteoblasts differentiation. Our data suggests impaired Pah^enu2 MSC developmental competence involves an energy deficit. We posit energy support and oxidative stress reduction will enable Pah^enu2 MSC differentiation in the osteoblast lineage to subsequently increase bone density.

A bone mineralization defect in the Pahenu2 model of classical phenylketonuria involves compromised mesenchymal stem cell differentiation

Osteopenia is observed in some patients affected by phenylalanine hydroxylase (PAH) deficient phenylketonuria (PKU). Bone density studies, in diverse PKU patient cohorts, have demonstrated bone disease is neither fully penetrant nor uniform in bone density loss. Biochemical assessment has generated a muddled perspective regarding mechanisms of the PKU bone phenotype where the participation of hyperphenylalaninemia remains unresolved. Osteopenia is realized in the Pahenu2 mouse model of classical PKU; although, characterization is incomplete. We characterized the Pahenu2 bone phenotype and assessed the effect of hyperphenylalaninemia on bone differentiation. Employing Pahenu2 and control animals, cytology, static and dynamic histomorphometry, and biochemistry were applied to further characterize the bone phenotype. These investigations demonstrate Pahenu2 bone density is decreased 33% relative to C57BL/6; bone volume/total volume was similarly decreased; trabecular thickness was unchanged while increased trabecular spacing was observed. Dynamic histomorphometry demonstrated a 25% decrease in mineral apposition. Biochemically, control and PKU animals have similar plasma cortisol, adrenocorticotropic hormone, and 25-hydroxyvitamin D. PKU animals show moderately increased plasma parathyroid hormone while plasma calcium and phosphate are reduced. These data are consistent with a mineralization defect. The effect of hyperphenylalaninemia on bone maturation was assessed in vitro employing bone-derived mesenchymal stem cells (MSCs) and their differentiation into bone. Using standard culture conditions, PAH deficient MSCs differentiate into bone as assessed by in situ alkaline phosphatase activity and mineral staining. However, PAH deficient MSCs cultured in 1200 μM PHE (metric defining classical PKU) show significantly reduced mineralization. These data are the first biological evidence demonstrating a negative impact of hyperphenylalaninemia upon bone maturation. In PAH deficient MSCs, expression of Col1A1 and Rankl are suppressed by hyperphenylalaninemia consistent with reduced bone formation and bone turnover. Osteopenia is intrinsic to PKU pathology in untreated Pahenu2 animals and our data suggests PHE toxicity participates by inhibiting mineralization in the course of MSC bone differentiation.

Sex differences in body composition and bone mineral density in phenylketonuria: A cross-sectional study

Background

Low bone mineral density (BMD) and subsequent skeletal fragility have emerged as a long-term complication of phenylketonuria (PKU).

Objective

To determine if there are differences in BMD and body composition between male and female participants with PKU.

Methods

From our randomized, crossover trial [1] of participants with early-treated PKU who consumed a low-phenylalanine (Phe) diet combined with amino acid medical foods (AA-MF) or glycomacropeptide medical foods (GMP-MF), a subset of 15 participants (6 males, 9 females, aged 15-50 y, 8 classical and 7 variant PKU) completed one dual energy X-ray absorptiometry (DXA) scan and 3-day food records after each dietary treatment. Participants reported lifelong compliance with AA-MF. In a crossover design, 8 participants (4 males, 4 females, aged 16-35 y) provided a 24-h urine collection after consuming AA-MF or GMP-MF for 1-3 weeks each.

Results

Male participants had significantly lower mean total body BMD Z-scores (means ± SE, males = - 0.9 ± 0.4; females, 0.2 ± 0.3; p = 0.01) and tended to have lower mean L1-4 spine and total femur BMD Z-scores compared to female participants. Only 50% percent of male participants had total body BMD Z-scores above - 1.0 compared to 100% of females (p = 0.06). Total femur Z-scores were negatively correlated with intake of AA-MF (r = - 0.58; p = 0.048). Males tended to consume more grams of protein equivalents per day from AA-MF (means ± SE, males: 67 ± 6 g, females: 52 ± 4 g; p = 0.057). Males and females demonstrated similar urinary excretion of renal net acid, magnesium and sulfate; males showed a trend for higher urinary calcium excretion compared to females (means ± SE, males: 339 ± 75 mg/d, females: 228 ± 69 mg/d; p = 0.13). Females had a greater percentage of total fat mass compared to males (means ± SE, males: 24.5 ± 4.8%, females: 36.5 ± 2.5%; p = 0.047). Mean appendicular lean mass index was similar between males and females. Male participants had low-normal lean mass based on the appendicular lean mass index.

Conclusions

Males with PKU have lower BMD compared with females with PKU that may be related to higher intake of AA-MF and greater calcium excretion. The trial was registered at www.clinicaltrials.gov as NCT01428258.

Constitutional bone impairment in Noonan syndrome

Noonan syndrome (NS) is an autosomal dominant trait characterized by genotypic and phenotypic variability. It belongs to the Ras/MAPK pathway disorders collectively named Rasopathies or neurocardiofaciocutaneous syndromes. Phenotype is characterized by short stature, congenital heart defects, facial dysmorphisms, skeletal and ectodermal anomalies, cryptorchidism, mild to moderate developmental delay/learning disability, and tumor predisposition. Short stature and skeletal dysmorphisms are almost constant and several studies hypothesized a role for the RAS pathway in regulating bone metabolism. In this study, we investigated the bone quality assessed by phalangeal quantitative ultrasound (QUS) and the metabolic bone profiling in a group of patients with NS, to determine whether low bone mineralization is primary or secondary to NS characteristics. Thirty-five patients were enrolled, including 20 males (55.6%) and 15 females (44.5%) aged 1.0-17.8 years (mean 6.4 ± 4.5, median 4.9 years). Each patients was submitted to clinical examination, estimation of the bone age, laboratory assays, and QUS assessment. Twenty-five percent of the cohort shows reduced QUS values for their age based on bone transmission time. Bone measurement were adjusted for multiple factors frequently observed in NS patients, such as growth retardation, delayed bone age, retarded puberty, and reduced body mass index, potentially affecting bone quality or its appraisal. In spite of the correction attempts, QUS measurement indicates that bone impairment persists in nearly 15% of the cohort studied. Our results indicate that bone impairment in NS is likely primary and not secondary to any of the phenotypic traits of NS, nor consistent with metabolic disturbances. © 2017 Wiley Periodicals, Inc.

Greater Calcium Intake is Associated with Better Bone Health Measured by Quantitative Ultrasound of the Phalanges in Pediatric Patients Treated with Anticonvulsant Drugs

We aimed to investigate and compare the effects of chronic antiepileptic therapy on bone health in pediatric patients using quantitative ultrasound of the phalanges (QUS) and controlling for potential confounding factors, particularly nutrient intake. The amplitude-dependent speed of sound (Ad-SoS) was measured in 33 epileptic children and 32 healthy children aged 6.5 ± 3.1 and 6.3 ± 1.1 (mean ± SD) years, respectively. There were no significant differences in the demographics such as age, weight and height between epileptic children and the control group children. None of the children in the epileptic or the treatment group were found to have a vitamin D deficiency. There were no significant differences in laboratory tests between groups. Lower QUS figures were found in the epileptic children (p = 0.001). After further adjustment for potential confounders such age, height, weight, calcium intake, vitamin D intake, physical activity and sex, the differences remained significant (p < 0.001). After further classification of the participants based on the tertile of calcium intake, no significant differences were found between patients and healthy controls in the greatest tertile of calcium intake (p = 0.217). We conclude that anticonvulsant therapy using valproate may lead to low bone mass in children and that an adequate intake of calcium might counteract such deleterious effects.

Brazilian pediatric reference data for quantitative ultrasound of phalanges according to gender, age, height and weight

Aims

To establish normative data for phalangeal quantitative ultrasound (QUS) measures in Brazilian students.

Methods

The sample was composed of 6870 students (3688 females and 3182 males), aged 6 to 17 years. The bone status parameter, Amplitude Dependent Speed of Sound (AD-SoS) was assessed by QUS of the phalanges using DBM Sonic BP (IGEA, Carpi, Italy) equipment. Skin color was obtained by self-evaluation. The LMS method was used to derive smoothed percentiles reference charts for AD-SoS according to sex, age, height and weight and to generate the L, M, and S parameters.

Results

Girls showed higher AD-SoS values than boys in the age groups 7–16 (p<0.001). There were no differences on AD-SoS Z-scores according to skin color. In both sexes, the obese group showed lower values of AD-SoS Z-scores compared with subjects classified as thin or normal weight. Age (r² = 0.48) and height (r² = 0.35) were independent predictors of AD-SoS in females and males, respectively.

Conclusion

AD-SoS values in Brazilian children and adolescents were influenced by sex, age and weight status, but not by skin color. Our normative data could be used for monitoring AD-SoS in children or adolescents aged 6–17 years.

Bone health in phenylketonuria: a systematic review and meta-analysis

Patients with Phenylketonuria (PKU) reportedly have decreased bone mineral density (BMD). The primary aim of this study was to perform a systematic review and meta-analysis to determine the extent and significance of low BMD in early treated patients with PKU. Secondary aims were to assess other bone status indicators including bone turnover markers (BTM) and to define areas for future research. Two research teams (Amsterdam, Netherlands and Atlanta, USA) performed literature searches for articles reporting data on BMD, osteopenia and osteoporosis, BTM or other bone indicators in patients with PKU. Included articles were compared between research teams and assessed for quality and risk of bias. A total of 13 unique articles were included; 11/13 articles reported BMD including a total of 360 patients. Ten out of 11 articles found BMD was significantly lower in patients with PKU. Meta-analyses for total BMD (TBMD; 3 studies; n = 133), lumbar spine BMD (LBMD; 7 studies; n = 247), and femoral neck BMD (FBMD; 2 studies; n = 78) Z-scores were performed. Overall effect sizes were: TBMD -0.45 (95% CI -0.61, -0.28); LBMD -0.70 (95% CI -0.82, -0.57); FBMD -0.96 (95% CI -1.42, -0.49). Definitions of osteopenia and osteoporosis were highly heterogeneous between studies and did not align with World Health Organization standards and the International Society for Clinical Densitometry positions on BMD measurement. Despite individual study findings of low BMD indicating higher risk of osteoporosis, pooled available data suggest reduction in BMD is not clinically important when using standard definitions of low BMD. Results from studies evaluating BTM are inconclusive. Phenylalanine concentration, vitamin D, PTH, and nutrient intake do not correlate with BMD or BTM. We recommend forthcoming studies use standard definitions of low BMD to determine clinical implications of BMD Z-scores below 0, explore cause of low BMD in the subset of patients with low BMD for chronological age (Z-score < -2) and assess fracture risk in patients with PKU.

A systematic review of bone mineral density and fractures in phenylketonuria

INTRODUCTION

Our objective was to systematically review and analyze published data on bone mineral density (BMD) and fracture rates in patients with phenylketonuria (PKU), and relationships between BMD and phenylalanine levels.

METHODOLOGY

We searched PubMed, CINAHL, and Cochrane databases from January 1966 to November 2013 for studies of spine BMD or fracture in PKU and control subjects. We excluded studies assessing skeletal health by ultrasound or peripheral quantitative computer tomography. Both authors reviewed abstracts for inclusion, and read full text papers to extract data.

RESULTS

Sixteen studies met eligibility criteria. Meta-analysis of three studies found that spine BMD was 0.100 g/cm(2) lower (95% CI, -0.110, -0.090 g/cm(2)) in 67 subjects with PKU, compared to 161 controls. Among six studies, 20% (53 of 263) of PKU subjects experienced clinical fractures. In the single study with controls, the fracture rate was 2.6 fold higher (95% CI, 1.1-6.1) after age 8 in PKU subjects, compared to healthy sibling controls. When considering a total of 12 studies in 412 subjects, nine or 75% of studies representing 71% of studied subjects reported no association between phenylalanine levels and BMD. Spine BMD is lower in PKU than control subjects, but only one study controlled for smaller body size. Existing studies suggest a clinical fracture rate of 20% among PKU subjects, but fracture rates in controls are lacking. Finally, existing data shows no consistent relationship between phenylalanine levels and BMD. Future studies are needed to clarify the etiology and health consequences of low BMD in PKU.

Phalangeal quantitative ultrasound in 1,719 children and adolescents with bone disorders

SUMMARY

We measured bone properties by phalangeal quantitative ultrasound in 1,719 pediatric patients with bone disorders, classifying them according to fracture status. Quantitative ultrasound discriminated fractured and nonfractured pediatric patients and enabled us to stratify fractured patients into classes according to the severity of the causative trauma (spontaneous, minimal trauma, appropriate trauma fractures).

INTRODUCTION

The correlation between quantitative bone measurements and fractures is poorly established in pediatric patients with bone disorders. We correlated phalangeal quantitative ultrasound (QUS) and fracture history in children and adolescents with bone disorders and evaluated the ability of QUS to recognize fractured patients.

METHODS

Amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT) were measured in 1,719 pediatric patients with bone disorders and related to fracture history. The patients were classified as (1) spontaneously (77), (2) minimal trauma (101), or (3) appropriate trauma fractured (206), and (4) nonfractured (1,335). The likelihood of fracture according to QUS was calculated as odds ratio per SD decrease (OR/SD), and the effectiveness in discriminating fractured patients was evaluated by receiver operating characteristic (ROC) analysis. The influence of age, sex, puberty, height, and BMI was explored by respective adjustments and multiple logistic regression.

RESULTS

Fractured patients showed significantly reduced AD-SoS and BTT standard deviation score (-0.32 ± 1.54 and -0.78 ± 1.49) compared to nonfractured subjects (0.43 ± 1.63 and -0.11 ± 1.34). QUS measurements paralleled the causative trauma severity, ranging from the lowest values in spontaneously fractured patients to normal values in appropriate trauma fractured subjects. The OR/SD were increasingly higher in appropriate trauma fractured, minimal trauma fractured, and spontaneously fractured patients. At ROC analysis, both parameters proved to have significant discrimination power in recognizing spontaneously and minimal trauma-fractured patients.

CONCLUSIONS

QUS identifies fractured pediatric patients with bone disorders, reflecting the severity of the causative trauma with a high discrimination power for fragility fractures.

Cross-talk between T cells and osteoclasts in bone resorption

Osteoclasts (OCs) are the exclusive bone resorptive cell, they derive from monocyte/macrophage precursors, which can circulate within the hematopoietic cell pool or be resident in a number of tissues. The maintenance of an adequate bone mass depends on the controlled and timely removal of old, damaged bone. The increase of OC activity is observed in many pathologies characterised by bone loss, such as osteoporosis, rheumatoid arthritis, bone metastasis, periprosthetic osteolysis in aseptic loosening of arthroplasty and also in pediatric diseases, such as phenilketonuria and 21-hydroxylase deficiency. During the bone resorption process there is an intense cross-talk between immune system cells and OCs. In particular, T cells release factors and cytokines, which rule osteoclastogenesis, and on the other hand, OCs produce factors that act on T cells. A primary mediator of osteoclastogenesis is the receptor activator of nuclear factor-κβ-RANK ligand-osteoprotegerin system, but also other cytokines promote OC activation according to the different pathologies. This review summarizes the main mechanisms promoting osteoclastogenesis in diseases characterised by bone loss, focusing on factors and cytokines involved in this process and on the interaction between OCs and T cells.

Bone impairment in phenylketonuria is characterized by circulating osteoclast precursors and activated T cell increase

BACKGROUND

Phenylketonuria (PKU) is a rare inborn error of metabolism often complicated by a progressive bone impairment of uncertain etiology, as documented by both ionizing and non- ionizing techniques.

METHODOLOGY

Peripheral blood mononuclear cell (PBMC) cultures were performed to study osteoclastogenesis, in the presence or absence of recombinant human monocyte-colony stimulating factor (M-CSF) and receptor activator of NFκB ligand (RANKL). Flow cytometry was utilized to analyze osteoclast precursors (OCPs) and T cell phenotype. Tumour necrosis factor α (TNF-α), RANKL and osteoprotegerin (OPG) were quantified in cell culture supernatants by ELISA. The effects of RANKFc and anti-TNF-α antibodies were also investigated to determine their ability to inhibit osteoclastogenesis. In addition, bone conditions and phenylalanine levels in PKU patients were clinically evaluated.

PRINCIPAL FINDINGS

Several in vitro studies in PKU patients' cells identified a potential mechanism of bone formation inhibition commonly associated with this disorder. First, PKU patients disclosed an increased osteoclastogenesis compared to healthy controls, both in unstimulated and M-CSF/RANKL stimulated PBMC cultures. OCPs and the measured RANKL/OPG ratio were higher in PKU patients compared to healthy controls. The addition of specific antagonist RANKFc caused osteoclastogenesis inhibition, whereas anti-TNF-α failed to have this effect. Among PBMCs isolated from PKU patients, activated T cells, expressing CD69, CD25 and RANKL were identified. Confirmatory in vivo studies support this proposed model. These in vivo studies included the analysis of osteoclastogenesis in PKU patients, which demonstrated an inverse relation to bone condition assessed by phalangeal Quantitative Ultrasound (QUS). This was also directly related to non-compliance to therapeutic diet reflected by hyperphenylalaninemia.

CONCLUSIONS

Our results indicate that PKU spontaneous osteoclastogenesis depends on the circulating OCP increase and the activation of T cells. Osteoclastogenesis correlates with clinical parameters, suggesting its value as a diagnostic tool for an early assessment of an increased bone resorption in PKU patients.

Suboptimal outcomes in patients with PKU treated early with diet alone: revisiting the evidence

BACKGROUND

The National Institute of Health (NIH) published a Consensus Statement on the screening and management of Phenylketonuria (PKU) in 2000. The panel involved in the development of this consensus statement acknowledged the lack of data regarding the potential for more subtle suboptimal outcomes and the need for further research into treatment options. In subsequent years, the approval of new treatment options for PKU and outcome data for patients treated from the newborn period by dietary therapy alone have become available. We hypothesized that a review of the PKU literature since 2000 would provide further evidence related to neurocognitive, psychosocial, and physical outcomes that could serve as a basis for reassessment of the 2000 NIH Consensus Statement.

METHODS

A systematic review of literature residing in PubMed, Scopus and PsychInfo was performed in order to assess the outcome data over the last decade in diet-alone early-treated PKU patients to assess the need for new recommendations and validity of older recommendations in light of new evidence.

RESULTS

The majority of publications (140/150) that contained primary outcome data presented at least one suboptimal outcome compared to control groups or standardized norms/reference values in at least one of the following areas: neurocognitive/psychosocial (N=60; 58 reporting suboptimal outcomes); quality of life (N=6; 4 reporting suboptimal outcomes); brain pathology (N=32; 30 reporting suboptimal outcomes); growth/nutrition (N=34; 29 reporting suboptimal outcomes); bone pathology (N=9; 9 reporting suboptimal outcomes); and/or maternal PKU (N=19; 19 reporting suboptimal outcomes).

CONCLUSIONS

Despite the remarkable success of public health programs that have instituted newborn screening and early introduction of dietary therapy for PKU, there is a growing body of evidence that suggests that neurocognitive, psychosocial, quality of life, growth, nutrition, bone pathology and maternal PKU outcomes are suboptimal. The time may be right for revisiting the 2000 NIH Consensus Statement in order to address a number of important issues related to PKU management, including treatment advancements for metabolic control in PKU, blood Phe variability, neurocognitive and psychological assessments, routine screening measures for nutritional biomarkers, and bone pathology.

Prospective bone ultrasound patterns during childhood acute lymphoblastic leukemia treatment

OBJECTIVE

Bone impairment is a well-known complication in childhood acute lymphoblastic leukemia (ALL) survivors but less is known about bone dynamics during ALL therapy. We longitudinally assessed by Quantitative Ultrasound (QUS) skeletal modifications during this treatment.

MATERIALS AND METHODS

Forty-four newly diagnosed ALL children underwent bone measurement by QUS parameters BTT (Bone Transmission Time) and AD-SoS (Amplitude-Dependent Speed of Sound), mainly reliant on bone density and cortical thickness, respectively. Measurements were performed at diagnosis, and 6, 12, and 24 months thereafter. The occurrence of skeletal complications such as fractures, vertebral collapse, osteonecrosis, and osteopenia was related to measurement outcome.

RESULTS

A rapid deterioration of bone properties measured by BTT and AD-SoS was evident in the first semester of therapy (p<0.001). Subsequently, the next measurements were characterized by progressive uncoupling of the two QUS parameters (p<0.001). These were both significantly reduced at the end of therapy (p<0.001). Twelve subjects with in-treatment skeletal complications displayed an almost two-fold decrease of both parameters (p<0.001). BTT decreasing more than 1 Standard Deviation (SD) over 6 months of therapy was able to predict skeletal complication occurrence (p<0.001).

CONCLUSION

This report represents the largest longitudinal cohort systematically submitted to bone condition assessment from the beginning to the end of therapy for childhood ALL. Bone deterioration occurs early and persists throughout therapy, consistent with bone properties uncoupling. This pattern possibly reflects an initial impairment of both mineral density and cortical thickness with a subsequent recovery of this latter. QUS permits an early detection of bone deterioration and related skeletal complications in childhood ALL.

Analysis of quantitative ultrasound graphic trace and derived variables assessed at proximal phalanges of the hand in healthy subjects and in patients with cerebral palsy or juvenile idiopathic arthritis. A pilot study

Amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT) are the quantitative ultrasound (QUS) variables usually assessed at proximal phalanges of the hand to estimate bone mineral status. The aim of the study was to provide a reference database for some additional QUS variables reflecting morphology of the ultrasound graphic trace according to gender, age, height, weight, and body mass index (BMI), and to assess their clinical usefulness. Fifty-two patients (age 3.1-20.9 years) affected by cerebral palsy with spastic tetraplegia (CPST, n=38) or polyarticular active juvenile idiopathic arthritis (JIA, n=14) were examined. In addition to AD-SoS and BTT, two QUS variables derived from the morphological analysis of ultrasound graphic trace, such as energy, extrapolated from the area under the ultrasound signal received, and weighted-slope (W-slope), derived from the angular coefficient of the regression line fitting the top point of the peaks of the ultrasound signal, were measured by phalangeal QUS (DBM Sonic, IGEA). The values of all the QUS variables measured in the patients were compared with our own sex- and age-reference values (n=1083, 587 males and 496 females, aged 3-21 years). The mean values of AD-SoS, BTT, energy, and W-slope were reduced (P<0.0001) in patients as a whole compared with normative data (-2.4+/-1.2, -2.7+/-1.5, -2.5+/-1.1, -2.5+/-1.1 Z-score, respectively). Fractured patients showed lower (P<0.001-P<0.0001) values of the QUS variables than fracture-free patients (AD-SoS, -3.3+/-1.2 and -1.8+/-0.9; BTT, -3.9+/-1.7 and -1.8+/-1.1; energy, -3.2+/-1.2 and -2.2+/-0.7; W-slope, -3.4+/-1.4 and -2.2+/-0.9 Z-score, respectively). There was no difference (P=NS) between patients with CPST and those with JIA. Age and height were positively correlated with all the QUS variables (r=0.55-0.79, P<0.01-P<0.0001). QUS variables were positively correlated among them (r=0.74-0.94, P<0.0001). Age and number of fractures were independent predictors of the QUS variables (coefficients: AD-SoS, 11.466 and -17.642; BTT, 0.049 and -0.045; energy, 1.072 and -1.303; W-slope, 0.046 and -0.067; respectively). In conclusion, measurement of QUS variables derived from the morphological analysis of the ultrasound signal could give additional information in estimating bone mineral status in children and adolescents, probably reflecting some aspect related to bone structure.

Increased spontaneous osteoclastogenesis from peripheral blood mononuclear cells in phenylketonuria

Phenylketonuria (PKU) is commonly complicated by a progressive bone impairment of uncertain aetiology. The therapeutic phenylalanine (Phe)-restricted diet and the possible noxious effects of high plasma Phe concentrations on bone have previously been suggested as possible determinant factors. Since osteoclasts are involved in bone reabsorption, they could play a role in determining bone damage in PKU. The reported increased excretion of bone resorption markers in PKU patients is consistent with this hypothesis. Although different diseases characterized by bone loss have been related to increased spontaneous osteoclastogenesis from peripheral blood mononuclear cells (PBMCs), to date there is no evidence of increased osteoclast formation in PKU. In this study, we compared the spontaneous osteoclastogenesis from PBMCs in 20 patients affected by PKU with that observed in age- and sex-matched healthy subjects. Phenylketonuric patients showed the number of osteoclasts to be almost double that observed in controls (159.9 ± 79.5 and 87.8 ± 44.7, respectively; p = 0.001). Moreover, a strict direct correlation between the spontaneous osteoclastogenesis in PKU patients and the mean blood Phe concentrations in the preceding year was observed (r = 0.576; p = 0.010). An imbalance between bone formation and bone resorption might explain, at least in part, the pathogenesis of bone loss in this disease. These findings could provide new insights into the biological mechanisms underlying bone damage in PKU.