Muscle torque relative to cross-sectional area and the functional muscle-bone unit in children and adolescents with chronic disease

Scoping review on health-related physical fitness in patients with inflammatory bowel disease: Assessment, interventions, and future directions

BACKGROUND

Reaching the Selecting Therapeutic Targets in Inflammatory Bowel Disease-II (STRIDE-II) therapeutic targets for inflammatory bowel disease (IBD) requires an interdisciplinary approach. Lifestyle interventions focusing on enhancing and preserving health-related physical fitness (HRPF) may aid in improving subjective health, decreasing disability, or even controlling inflammation. However, ambiguity remains about the status and impact of HRPF (i.e. body composition, cardiorespiratory fitness, muscular strength, muscular endurance, and flexibility) in IBD patients, hindering the development of physical activity and physical exercise training guidelines.

AIM

To review HRPF components in IBD patients and the impact of physical activity and physical exercise training interventions on HRPF.

METHODS

A systematic search in multiple databases was conducted for original studies that included patients with IBD, assessed one or more HRPF components, and/or evaluated physical activity or physical exercise training interventions.

RESULTS

Sixty-eight articles were included. No study examined the complete concept of HRPF, and considerable heterogeneity existed in assessment methods, with frequent use of non-validated tests. According to studies that used gold standard tests, cardiorespiratory fitness seemed to be reduced, but findings on muscular strength and endurance were inconsistent. A limited number of studies that evaluated physical activity or physical exercise training interventions reported effects on HRPF, overall showing a positive impact.

CONCLUSION

We performed a scoping review using a systematic and iterative approach to identify and synthesize an emerging body of literature on health-related physical fitness in patients with IBD, highlighting several research gaps and opportunities for future research. Findings of this review revealed a gap in the literature regarding the accurate assessment of HRPF in patients with IBD and highlighted important methodological limitations of studies that evaluated physical activity or physical exercise training interventions. This scoping review is a step towards performing studies and systematic reviews in the future, which was not possible at present given the heterogeneity in endpoints and designs of the available studies on this topic. Future well-designed studies are required to determine the optimal training paradigm for improving HRPF in patients with IBD before guidelines can be developed and integrated into the therapeutic strategy.

Malnutrition Patterns in Children with Chronic Kidney Disease

Malnutrition is frequent in children with chronic kidney disease (CKD). Apart from undernutrition and protein energy wasting (PEW), overnutrition prevalence is rising, resulting in fat mass accumulation. Sedentary behavior and unbalanced diet are the most important causal factors. Both underweight and obesity are linked to adverse outcomes regarding renal function, cardiometabolic risk and mortality rate. Muscle wasting is the cornerstone finding of PEW, preceding fat loss and may lead to fatigue, musculoskeletal decline and frailty. In addition, clinical data emphasize the growing occurrence of muscle mass and strength deficits in patients with fat mass accumulation, attributed to CKD-related wasting processes, reduced physical activity and possibly to obesity-induced inflammatory diseases, leading to sarcopenic obesity. Moreover, children with CKD are susceptible to abdominal obesity, resulting from high body fat distribution into the visceral abdomen compartment. Both sarcopenic and abdominal obesity are associated with increased cardiometabolic risk. This review analyzes the pathogenetic mechanisms, current trends and outcomes of malnutrition patterns in pediatric CKD. Moreover, it underlines the importance of body composition assessment for the nutritional evaluation and summarizes the advantages and limitations of the currently available techniques. Furthermore, it highlights the benefits of growth hormone therapy and physical activity on malnutrition management.

Persistent Musculoskeletal Deficits in Pediatric, Adolescent and Young Adult Survivors of Allogeneic Hematopoietic Stem-Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a common therapy for pediatric hematologic malignancies. With improved supportive care, addressing treatment-related late effects is at the forefront of survivor long-term health and quality of life. We previously demonstrated that alloHSCT survivors had increased adiposity, decreased lean mass, and lower bone density and strength, 7 years (median) from alloHSCT compared to their healthy peers. Yet it is unknown whether these deficits persist. Our longitudinal study characterized changes in muscle and bone over a period of 3.4 (range, 2.0 to 4.9) years in 47 childhood alloHSCT survivors, age 5-26 years at baseline (34% female). Tibia cortical bone geometry and volumetric density and lower leg muscle cross-sectional area (MCSA) were assessed via peripheral quantitative computed tomography (pQCT). Anthropometric and pQCT measurements were converted to age, sex, and ancestry-specific standard deviation scores, adjusted for leg length. Muscle-specific force was assessed as strength relative to MCSA adjusted for leg length (strength Z-score). Measurements were compared to a healthy reference cohort (n = 921), age 5-30 years (52% female). At baseline and follow-up, alloHSCT survivors demonstrated lower height Z-scores, weight Z-scores, and leg length Z-scores compared to the healthy reference cohort. Deficits in MCSA, trabecular volumetric bone density, and cortical bone size and estimated strength (section modulus) were evident in survivors (all p < 0.05). Between the two study time points, anthropometric, muscle, and bone Z-scores did not change significantly in alloHSCT survivors. Approximately 15% and 17% of alloHSCT survivors had MCSA and section modulus Z-score < -2.0, at baseline and follow-up, respectively. Furthermore, those with a history of total body irradiation compared to those without demonstrated lower MCSA at follow-up. The persistent muscle and bone deficits in pediatric alloHSCT survivors support the need for strategies to improve bone and muscle health in this at-risk population. © 2022 American Society for Bone and Mineral Research (ASBMR).

Treatment of cystic fibrosis related bone disease

The advent of highly effective CFTR modulator therapies has slowed the progression of pulmonary complications in people with cystic fibrosis. There is increased interest in cystic fibrosis bone disease (CFBD) due to the increasing longevity of people with cystic fibrosis. CFBD is a complex and multifactorial disease. CFBD is a result of hypomineralized bone leading to poor strength, structure and quality leading to susceptibility to fractures. The development of CFBD spans different age groups. The management must be tailored to each group with nuance and based on available guidelines while balancing therapeutic benefits to risks of long-term use of bone-active medication. For now, the mainstay of treatment includes bisphosphonates. However, the long-term effects of bisphosphonate treatment in people with CF are not fully understood. We describe newer agents available for osteoporosis treatment. Still, the lack of data behooves trials of monoclonal antibodies treatments such as Denosumab and Romozosumab and anabolic bone therapy such as teriparatide and Abaloparatide. In this review, we also summarize screening and non-pharmacologic treatment of CFBD and describe the various options available for the pharmacotherapy of CFBD. We address the prospect of CFTR modulators on bone health while awaiting long-term trials to describe the effects of these medications on bone health.

Skeletal muscle deficits are associated with worse exercise performance in pediatric pulmonary hypertension

BACKGROUND

Skeletal muscle deficits are associated with worse exercise performance in adults with pulmonary hypertension (PH) but the impact is poorly understood in pediatric PH.

OBJECTIVE

To study muscle deficits, physical inactivity, and performance on cardiopulmonary exercise test (CPET) and exercise cardiac magnetic resonance (eCMR) in pediatric PH.

METHODS

Youth 8-18 years participated in a prospective, cross-sectional study including densitometry (DXA) for measurement of leg lean mass Z-score (LLMZ), handheld dynamometer with generation of dominant and non-dominant handgrip Z-scores, Physical Activity Questionnaire (PAQ), CPET, and optional eCMR. CPET parameters were expressed relative to published reference values. CMR protocol included ventricular volumes and indexed systemic flow at rest and just after supine ergometer exercise. Relationships between LLMZ, PAQ score, and exercise performance were assessed by Pearson correlation and multiple linear regression.

RESULTS

There were 25 participants (13.7 ± 2.8 years, 56% female, 64% PH Group 1, 60% functional class I); 12 (48%) performed both CPET and eCMR. Mean LLMZ (-0.96 ± 1.14) was associated with PAQ score (r = 50, p = 0.01) and with peak oxygen consumption (VO₂) (r = 0.74, p = < 0.001), VO₂ at anaerobic threshold (r = 0.65, p < 0.001), and peak work rate (r = 0.64, p < 0.01). Higher handgrip Z-scores were associated with better CPET and eCMR performance. On regression analysis, LLMZ and PAQ score were positively associated with peak VO₂, while handgrip Z-score and PAQ score were positively associated with peak work rate.

CONCLUSION

Muscle mass and strength are positively associated with exercise performance in pediatric PH. Future studies should determine the effect of rehabilitation programs on muscle properties and exercise performance.

Marked skeletal muscle deficits are associated with 6-minute walk distance in paediatric pulmonary hypertension

BACKGROUND

Poor growth is common in children with pulmonary hypertension; however, skeletal muscle deficits have not been described and the association between muscle deficits and functional status is unknown.

METHODS

Patients aged 8-18 years with pulmonary hypertension (diagnostic Groups 1, 2, or 3) and World Health Organization functional class I or II underwent dual-energy absorptiometry to measure leg lean mass Z-score (a surrogate for skeletal muscle). Muscle strength was assessed using dynamometry. Physical activity questionnaires were administered. Clinical data, including 6-minute walk distance, were reviewed. Relationships between skeletal muscle, physical activity score, and 6-minute walk distance were assessed by correlations and linear regression.

RESULTS

Sixteen patients (12.1 ± 3.2 years, 50% female, 56% Group 1, 56% functional class II) were enrolled. Leg lean mass Z-score was significantly less than reference data (-1.40 ± 1.12 versus 0.0 ± 0.9, p < 0.001) and worse in those with functional class II versus I (-2.10 ± 0.83 versus -0.50 ± 0.73, p < 0.01). Leg lean mass Z-score was positively associated with right ventricular systolic function by tricuspid annular plane systolic Z-score (r = 0.54, p = 0.03) and negatively associated with indexed pulmonary vascular resistance (r = -0.78, p < 0.001). Leg lean mass Z-score and forearm strength were positively associated with physical activity score. When physical activity score was held constant, leg lean mass Z-score independently predicted 6-minute walk distance (R2 = 0.39, p = 0.03).

CONCLUSIONS

Youth with pulmonary hypertension demonstrate marked skeletal muscle deficits in association with exercise intolerance. Future studies should investigate whether low leg lean mass is a marker of disease severity or an independent target that can be improved.

Sarcopenia and preserved bone mineral density in paediatric survivors of high-risk neuroblastoma with growth failure

BACKGROUND

Survival from paediatric high-risk neuroblastoma (HR-NBL) has increased, but cis-retinoic acid (cis-RA), the cornerstone of HR-NBL therapy, can cause osteoporosis and premature physeal closure and is a potential threat to skeletal structure in HR-NBL survivors. Sarcopenia is associated with increased morbidity in survivors of paediatric malignancies. Low muscle mass may be associated with poor prognosis in HR-NBL patients but has not been studied in these survivors. The study objective was to assess bone density, body composition and muscle strength in HR-NBL survivors compared with controls.

METHODS

This prospective cross-sectional study assessed areal bone mineral density (aBMD) of the whole body, lumbar spine, total hip, femoral neck, distal 1/3 and ultradistal radius and body composition (muscle and fat mass) using dual-energy X-ray absorptiometry (DXA) and lower leg muscle strength using a dynamometer. Measures expressed as sex-specific standard deviation scores (Z-scores) included aBMD (adjusted for height Z-score), bone mineral apparent density (BMAD), leg lean mass (adjusted for leg length), whole-body fat mass index (FMI) and ankle dorsiflexion peak torque adjusted for leg length (strength-Z). Muscle-specific force was assessed as strength relative to leg lean mass. Outcomes were compared between HR-NBL survivors and controls using Student's t-test or Mann-Whitney U test. Linear regression models examined correlations between DXA and dynamometer outcomes.

RESULTS

We enrolled 20 survivors of HR-NBL treated with cis-RA [13 male; mean age: 12.4 ± 1.6 years; median (range) age at therapy initiation: 2.6 (0.3-9.1) years] and 20 age-, sex- and race-matched controls. Height-Z was significantly lower in HR-NBL survivors compared with controls (-1.73 ± 1.38 vs. 0.34 ± 1.12, P < 0.001). Areal BMD-Z, BMAD-Z, FMI-Z, visceral adipose tissue and subcutaneous adipose tissue were not significantly different in HR-NBL survivors compared with controls. Compared with controls, HR-NBL survivors had lower leg lean mass-Z (-1.46 ± 1.35 vs. - 0.17 ± 0.84, P < 0.001) and strength-Z (-1.13 ± 0.86 vs. - 0.15 ± 0.71, P < 0.001). Muscle-specific force was lower in HR-NBL survivors compared with controls (P < 0.05).

CONCLUSIONS

Bone mineral density and adiposity are not severely impacted in HR-NBL survivors with growth failure, but significant sarcopenia persists years after treatment. Future studies are needed to determine if sarcopenia improves with muscle-specific interventions in this population of cancer survivors.

Quantitative Evaluation of Hip Muscle Atrophy in Patients with Unilateral Slipped Capital Femoral Epiphysis Based on Magnetic Resonance Imaging

RATIONALE AND OBJECTIVES

Hip muscle atrophy commonly occurs in patients with unilateral slipped capital femoral epiphysis (SCFE), its effect in patients with unilateral SCFE is worthy of further investigation. This study aimed to investigate the relationship between hip muscle cross-sectional area (M-CSA) and unilateral SCFE using magnetic resonance imaging.

MATERIALS AND METHODS

Overall, 32 unilateral SCFE patients (SCFE group) and 15 asymptomatic subjects (control group) were evaluated. All patients underwent magnetic resonance imaging and frog-leg lateral radiograph examinations. M-CSA and Southwick angle were evaluated to calculate the M-CSA ratio of the affected side over the healthy side (A/H) ratio in the SCFE group and the control group. Associations between the A/H ratio, Southwick angle, and the disease time course were investigated with Spearman correlation test. An independent sample t-test, one-way analysis of variance tests, and intraclass correlation coefficients were also applied.

RESULTS

A/H ratios of the control group were significantly higher than those of the SCFE group (anterior muscles group: 1.09 ± 0.14 vs 0.86 ± 0.12, medial muscles group: 1.02 ± 0.15 vs 0.82 ± 0.18, posterior muscles group: 1.03 ± 0.07 vs 0.84 ± 0.11, all p < 0.01). A/H ratios of the medial and posterior muscle groups were significantly correlated with severity of SCFE (r = -0.504, p = 0.003, and r = -0.438, p = 0.012, respectively).

CONCLUSION

Hip muscle atrophy is associated with SCFE severity in patients with unilateral SCFE. The A/H ratio can reflect the patients' prognosis and rehabilitation status. Maintenance of hip muscle morphology and function may be beneficial to clinical performance and prognosis of patients with unilateral SCFE.

Muscle and bone parameters in underprivileged Indian children and adolescents with T1DM

BACKGROUND

The incidence of Type 1 diabetes mellitus (T1DM) is increasing and sarcopenia and osteoporosis have been reported to be associated with long standing diabetes. There is scarcity of data on bone health status of children with T1DM. Our aim was to assess bone health parameters [by Dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT)] and muscle strength (by hand grip) in underprivileged Indian children with T1DM.

MATERIAL AND METHODS

A cross sectional, observational study was conducted in underprivileged children with diabetes attending the out patient clinic for T1DM at a tertiary care hospital. Children with T1DM with disease duration more than 1 year were included in the study. Age and gender matched controls were also enrolled. Data on age, gender, disease duration, anthropometric parameters and HbA1c were collected. Bone mineral density (BMD) was assessed by dual energy X-ray absorptiometry (Lunar iDXA) and peripheral quantitative computed tomography (pQCT, Stratec XCT 2000) and muscle strength by handgrip. Data were analysed using SPSS 25.0.

RESULTS

251 children with T1DM and 250 age gender matched controls were studied. Mean age of T1DM children was 10.8 ± 4.3yrs (controls 10.3 ± 3.6). Mean HbA1C was 9.7 ± 2.1%. The total body less head areal BMD (TBLH aBMD) and lumbar spine bone mineral apparent density (LSBMAD) Z-scores were significantly lower in children with T1DM (-1.5 ± 1.3, -1.3 ± 1.6 respectively) as compared to controls (-0.5 ± 1.3, -0.64 ± 1.5 respectively) (p < 0.05 for both). Z-scores for trabecular and total density (vBMD) were significantly lower in patients with T1DM (-0.7 ± 1.0, -0.7 ± 1.0 respectively) than controls (-0.15 ± 1.2, -0.31 ± 1.1), (p <  0.05) and trabecular density was lower at distal radius with increasing disease duration. Hand-grip strength Z-score was lower in children with T1DM (-3.0 ± 0.5) as compared to controls (-2.8 ± 0.5). Trabecular density and HbA1C concentrations were negatively correlated (R = -0.18, p < 0.05) as was muscle area and HbA1C concentrations (R = -0.17, p < 0.05,).

CONCLUSION

Bone and muscle health were affected in children with poorly controlled T1DM. With increasing disease duration, attention is required for optimising musculoskeletal health.

Quantitative analysis of modified functional muscle-bone unit and back muscle density in patients with lumbar vertebral fracture in Chinese elderly men: a case-control study

OBJECTIVES

Bone mineral density (BMD) is associated with muscle mass and quality, but little research has been done on functional muscle-bone unit and back muscle density in patients with lumbar vertebral fracture. This study used the "modified functional muscle-bone unit" concept and measured back muscle density to investigate muscle-bone interaction difference between the fracture and control group.

METHODS

This was a case-control study. A total of 52 elderly male patients (mean age 75 years) with lumbar vertebral fracture (cases) and 52 control healthy subjects were enrolled. Cross-sectional area (CSA) and density of paravertebral muscle were measured in quantitative computed tomography (QCT) images to represent the muscle mass, while the bone mineral density measured by QCT was used to represent the bone mass. The modified functional muscle-bone unit was calculated as the value of volumetric BMD divided by muscle area.

RESULTS

People with vertebral fractures reported significantly lower values in the cross-sectional area and density of paravertebral muscle compared to control group. In the multivariate analysis, BMD (odds ratio, OR = 0.929; 95% confidence intervals, CIs 0.888-0.971), erector muscle density (OR = 0.698; 95% CI 0.547-0.892), and summated muscle CSA (OR = 0.963; 95% CI 0.93-0.991) were independent protective factors for the presence of a fracture. BMD resulted significantly and moderately associated with cross-sectional area and density of paravertebral muscle (r = 0.329-0.396).

CONCLUSIONS

There were significant differences between the modified functional muscle-bone unit and back muscle density between the fracture group and control group in elderly men. Lower BMD, loss of muscle mass and density are associated with increased presence of the lumbar vertebral fracture.

Low muscle mass and strength in pediatrics patients: Why should we care?

Skeletal muscle plays major roles in metabolism and overall health across the lifecycle. Emerging evidence indicates that prenatal (maternal diet during pregnancy and genetic defects) and postnatal factors (physical activity, hormones, dietary protein, and obesity) influence muscle mass acquisition and strength early in life. As a consequence, low muscle mass and strength contributes to several adverse health outcomes during childhood. Specifically, studies demonstrated inverse associations of muscle mass and strength to single and clustered metabolic risk factors. The literature also consistently reports that low muscle mass and strength are associated with reduced bone parameters during growth, increasing the risk of osteoporosis in old age. Furthermore, muscle mass gains are associated with improved neurodevelopment in the first years of life. Given these negative implications of low muscle mass and strength on health, it is crucial to track muscle mass and strength development from childhood to adolescence. Several body composition techniques are currently available for estimation of muscle mass, all with unique advantages and disadvantages. The value of ultrasound as a technique to measure muscle mass is emerging in pediatric research with potential for translating the research findings to clinical settings. For the assessment of muscle strength, the handgrip strength test has been widely employed but without a standardized protocol. Although further research is needed to define normative data and cut points for the low muscle mass and strength phenotype, the use of such non-invasive medical monitoring is a promising strategy to identify early abnormalities and prevent low muscle mass in adulthood.

The Association of Diet and Exercise With Body Composition in Pediatric Crohn's Disease

BACKGROUND

In pediatric Crohn's disease, fat mass improves over time with treatment, but lean mass deficits persist. This observational study of the associations of physical activity and dietary intake with lean mass and muscle strength in children with Crohn's disease was ancillary to a previously reported randomized clinical trial of an intervention to improve bone health.

METHODS

In this study, 138 participants were followed at baseline and at 6, 12, and 24 months with evaluation of lean and fat mass using DXA, muscle strength (peak torque), Crohn's characteristics, dietary intake, time in moderate to vigorous physical activity (MVPA), and serum insulin-like growth factor-1 (IGF-1) and tumor necrosis factor-alpha (TNF-α). Race- and sex-specific Z-scores for leg lean mass and whole body fat mass were generated. Quasi least square regression evaluated determinants of changes in body composition and muscle strength.

RESULTS

Leg lean mass and muscle strength were positively associated with time in MVPA (P < 0.05) and negatively associated with increasing clinical disease activity (P < 0.05). Both leg lean mass and strength were positively associated with IGF-1 Z-score (P ≤ 0.03) but negatively associated with serum TNF-α (P ≤ 0.04). Neither lean mass nor muscle strength was associated with caloric or protein intake.

CONCLUSIONS

Persistence of lean mass deficits was related to ongoing Crohn's disease activity but improved with greater time spent in moderate to vigorous physical activity. Future trials are needed to evaluate the efficacy of physical activity in improving lean mass in pediatric Crohn's disease.

Frailty and the Quality of Life in Hemodialysis Patients: The Importance of Waist Circumference

OBJECTIVE

Frailty among the end-stage renal disease (ESRD) population is highly prevalent and has been associated with mortality. Little is known about the relation of different aspects of body composition, a modifiable risk factor, with the risk of frailty in ESRD population.

DESIGN AND METHODS

One hundred and fifty-one patients including 85 men and 66 women, aged ≥18 years with ESRD who had been receiving conventional maintenance hemodialysis (HD) for at least 3 months were included. Body fat and muscle mass from both bioimpedance spectroscopy and skin-fold thickness and waist circumference as a surrogate of abdominal obesity were measured. Frailty was defined based on Fried's criteria. Health-related quality of life was collected using the RAND version of the Kidney Disease Quality of Life (KDQOL-36) Survey.

RESULTS

We performed single and multiple predictor logistic regression analyses to determine factors associated with frailty. After adjustment for age, sex, and comorbidities, fat mass (both by bioimpedance spectroscopy and anthropometry) and waist circumference, but not muscle mass remained the main predictors of frailty. The odds ratio of frailty in the third tertile compared with the first was 4.97 (1.70-14.55) and 3.84 (1.39-10.61) for fat mass and waist circumference, respectively (P for trends for both <.05). The scores of physical health and kidney disease effect component of quality of life were lower in frail compared with nonfrail patients (40.7 ± 9.2 vs. 33.7 ± 10.2, P < .01 and 66.8 ± 22.4 vs. 51.6 ± 25.7, P < .05 for physical health and effects of disease, respectively).

CONCLUSIONS

Frailty, which is associated with poor outcomes in chronic HD patients, is common and predicted by fat mass and waist circumference but not by body mass index and muscle mass. Interventions to modify abdominal obesity, reflected by waist circumference, could potentially lower the incidence of frailty and hence improve the quality of life in the HD population.

Muscle-Bone Interactions in Pediatric Bone Diseases

PURPOSE

Here, we review the skeletal effects of pediatric muscle disorders as well as muscle impairment in pediatric bone disorders.

RECENT FINDINGS

When starting in utero, muscle disorders can lead to congenital multiple contractures. Pediatric-onset muscle weakness such as cerebral palsy, Duchenne muscular dystrophy, spinal muscular atrophy, or spina bifida typically are associated with small diameter of long-bone shafts, low density of metaphyseal bone, and increased fracture incidence in the lower extremities, in particular, the distal femur. Primary bone diseases can affect muscles through generic mechanisms, such as decreased physical activity or in disease-specific ways. For example, the collagen defect underlying the bone fragility of osteogenesis imperfecta may also affect muscle force generation or transmission. Transforming growth factor beta released from bone in Camurati Engelman disease may decrease muscle function.

FUTURE DIRECTIONS

Considering muscle-bone interactions does not only contribute to the understanding of musculoskeletal disorders but also can identify new targets for therapeutic interventions.

Effect of Low-Magnitude Mechanical Stimuli on Bone Density and Structure in Pediatric Crohn's Disease: A Randomized Placebo-Controlled Trial

Pediatric Crohn's Disease (CD) is associated with low trabecular bone mineral density (BMD), cortical area, and muscle mass. Low-magnitude mechanical stimulation (LMMS) may be anabolic. We conducted a 12-month randomized double-blind placebo-controlled trial of 10 minutes daily exposure to LMMS (30 Hz frequency, 0.3 g peak-to-peak acceleration). The primary outcomes were tibia trabecular BMD and cortical area by peripheral quantitative CT (pQCT) and vertebral trabecular BMD by QCT; additional outcomes included dual-energy X-ray absorptiometry (DXA) whole body, hip and spine BMD, and leg lean mass. Results were expressed as sex-specific Z-scores relative to age. CD participants, ages 8 to 21 years with tibia trabecular BMD <25th percentile for age, were eligible and received daily cholecalciferol (800 IU) and calcium (1000 mg). In total, 138 enrolled (48% male), and 121 (61 active, 60 placebo) completed the 12-month trial. Median adherence measured with an electronic monitor was 79% and did not differ between arms. By intention-to-treat analysis, LMMS had no significant effect on pQCT or DXA outcomes. The mean change in spine QCT trabecular BMD Z-score was +0.22 in the active arm and -0.02 in the placebo arm (difference in change 0.24 [95% CI 0.04, 0.44]; p = 0.02). Among those with >50% adherence, the effect was 0.38 (95% CI 0.17, 0.58, p < 0.0005). Within the active arm, each 10% greater adherence was associated with a 0.06 (95% CI 0.01, 1.17, p = 0.03) greater increase in spine QCT BMD Z-score. Treatment response did not vary according to baseline body mass index (BMI) Z-score, pubertal status, CD severity, or concurrent glucocorticoid or biologic medications. In all participants combined, height, pQCT trabecular BMD, and cortical area and DXA outcomes improved significantly. In conclusion, LMMS was associated with increases in vertebral trabecular BMD by QCT; however, no effects were observed at DXA or pQCT sites. © 2016 American Society for Bone and Mineral Research.

Update on Bone Health in Pediatric Chronic Disease

Children and adolescents with chronic disease are predisposed to impaired bone health. Pediatric illness, including type 1 diabetes mellitus, celiac disease, and cystic fibrosis, have significant risk of low bone mineralization and fracture due to underlying inflammation, malabsorption, lack of physical activity, and delayed puberty. Dual-energy x-ray absorptiometry is the primary imaging method to assess bone health in this population. The purpose of this review is to update readers about the assessment and management of bone health in children with common pediatric chronic illnesses and review recent advances in the prevention and treatment of impaired bone health.

Physical activity and screen time in adolescents in the chronic kidney disease in children (CKiD) cohort

BACKGROUND

Self-reported physical activity (PA) and screen time exposure in adolescents with chronic kidney disease (CKD) has not been evaluated.

METHODS

We performed a cross-sectional analysis of PA and screen time in 224 adolescents at entry into the Chronic Kidney Disease in Children (CKiD) cohort. We compared proportions of CKiD vs. healthy 2012 National Health and Nutrition Examination Survey (NHANES) participants reporting the recommended 60 min of PA 7 days/week or ≤ 2 h/day of entertainment screen time (binomial probability test). Within CKiD, we assessed correlates of PA and screen time using multivariable logistic and linear regression and examined longitudinal data for 136 participants.

RESULTS

Median age of CKiD participants was 15 years, and 60 % were male. Median estimated glomerular filtration rate (eGFR) was 41.3 (IQR 30.8, 52.3) ml/min/1.73 m(2). Only 13 % of CKiD participants met recommendations for PA vs. 25 % of NHANES (p < 0.001), while 98 % in CKiD exceeded the recommended screen time vs. 73 % in NHANES (p < 0.001). Within CKiD, obesity (p = 0.04) and lower eGFR (p = 0.02) were independently associated with greater screen time.

CONCLUSIONS

Adolescents with CKD engage in significantly less PA and greater screen time than healthy youth in the United States, and this may worsen over time.

Body composition estimation using skinfolds in children with and without health conditions affecting growth and body composition

BACKGROUND

Body composition prediction equations using skinfolds are useful alternatives to advanced techniques, but their utility across diverse paediatric populations is unknown.

AIM

To evaluate published and new prediction equations across diverse samples of children with health conditions affecting growth and body composition.

SUBJECTS AND METHODS

Anthropometric and dual-energy X-ray absorptiometry (DXA) body composition measures were obtained in children with Down syndrome (n = 59), Crohn disease (n = 128), steroid-sensitive nephrotic syndrome (n = 67) and a healthy reference group (n = 835). Published body composition equations were evaluated. New equations were developed for ages 3-21 years using the healthy reference sample and validated in other groups and national survey data.

RESULTS

Fat mass (FM), fat-free mass (FFM) and percentage body fat (%BF) from published equations were highly correlated with DXA-derived measures (r = 0.71-0.98), but with poor agreement (mean difference = 2.4 kg, -1.9 kg and 6.3% for FM, FFM and %BF). New equations produced similar correlations (r = 0.85-1.0) with improved agreement for the reference group (0.2 kg, 0.4 kg and 0.0% for FM, FFM and %BF, respectively) and in sub-groups.

CONCLUSIONS

New body composition prediction equations show excellent agreement with DXA and improve body composition estimation in healthy children and those with selected conditions affecting growth.

Reduced skeletal muscle function is associated with decreased fiber cross-sectional area in the Cy/+ rat model of progressive kidney disease

BACKGROUND

The combination of skeletal muscle wasting and compromised function plays a role in the health decline commonly observed in chronic kidney disease (CKD) patients, but the pathophysiology of muscle mass/strength changes remains unclear. The purpose of this study was to characterize muscle properties in the Cy/+ rat model of spontaneously progressive CKD.

METHODS

Leg muscle function and serum biochemistry of male Cy/+ (CKD) rats and their nonaffected littermates (NLs) were assessed in vivo at 25, 30 and 35 weeks of age. Architecture and histology of extensor digitorum longus (EDL) and soleus (SOL) muscles were assessed ex vivo at the conclusion of the experiment. We tested the hypothesis that animals with CKD have progressive loss of muscle function, and that this functional deficit is associated with loss of muscle mass and quality.

RESULTS

Thirty-five-week-old CKD rats produced significantly lower maximum torque in ankle dorsiflexion and shorter time to maximum torque, and longer half relaxation time in dorsiflexion and plantarflexion compared with NL rats. Peak dorsiflexion torque (but not plantarflexion torque) in CKD remained steady from 25 to 35 weeks, while in NL rats, peak torque increased. Mass, physiologic cross-sectional area (CSA) and fiber-type (myosin heavy chain isoform) proportions of EDL and SOL were not different between CKD and NL. However, the EDL of CKD rats showed reduced CSAs in all fiber types, while only MyHC-1 fibers were decreased in area in the SOL.

CONCLUSIONS

The results of this study demonstrate that muscle function progressively declines in the Cy/+ rat model of CKD. Because whole muscle mass and architecture do not vary between CKD and NL, but CKD muscles show reduction in individual fiber CSA, our data suggest that the functional decline is related to increased muscle fiber atrophy.

Improvements in Bone Density and Structure during Anti-TNF-α Therapy in Pediatric Crohn's Disease

CONTEXT

Pediatric Crohn's Disease (CD) is associated with deficits in trabecular bone mineral density (BMD) and cortical structure, potentially related to TNF-α effects to decrease bone formation and promote bone resorption.

OBJECTIVE

This study aimed to examine changes in bone density and structure in children and adolescents with CD following initiation of anti-TNF-α therapy.

DESIGN AND PARTICIPANTS

Participants (n = 74; age 5-21 years) with CD completed a 12-month prospective cohort study.

MAIN OUTCOME MEASURES

Tibia peripheral quantitative computed tomography scans were obtained at initiation of anti-TNF-α therapy and 12 months later. Musculoskeletal outcomes were expressed as sex-and race-specific z scores relative to age, based on >650 reference participants.

RESULTS

At baseline, CD participants had lower height, trabecular BMD, cortical area (due to smaller periosteal and larger endocortical circumferences), and muscle area z scores, compared with reference participants (all P < .01). Pediatric CD activity index decreased during the 10-week induction (P < .001), in association with subsequent gains in height, trabecular BMD, cortical area (due to recovery of endocortical bone), and muscle area z scores over 12 months (height P < .05; others P < .001). Bone-specific alkaline phosphatase levels, a biomarker of bone formation, increased a median of 75% (P < .001) during induction with associated 12-month improvements in trabecular BMD and cortical area z scores (both P < .001). Younger age was associated with greater increases in trabecular BMD z scores (P < .001) and greater linear growth with greater recovery of cortical area (P < .001).

CONCLUSIONS

Anti-TNF-α therapy was associated with improvements in trabecular BMD and cortical structure. Improvements were greater in younger and growing participants, suggesting a window of opportunity for treatment of bone deficits.

Muscle wasting in end-stage renal disease promulgates premature death: established, emerging and potential novel treatment strategies

Muscle wasting (or sarcopenia) is a common feature of the uremic phenotype and predisposes this vulnerable patient population to increased risk of comorbid complications, poor quality of life, frailty and premature death. The old age of dialysis patients is in addition a likely contributor to loss of muscle mass. As recent evidence suggests that assessment of muscle strength (i.e. function) is a better predictor of outcome and comorbidities than muscle mass, this opens new screening, assessment and therapeutic opportunities. Among established treatment strategies, the benefit of resistance exercise and endurance training are increasingly recognized among nephrologists as being effective and should be promoted in sedentary chronic kidney disease patients. Testosterone and growth hormone replacement appear as the most promising among emerging treatments strategies for muscle wasting. As treatment of muscle wasting is difficult and seldom successful in this often old, frail, sedentary and exercise-hesitant patient group, novel treatment strategies are urgently needed. In this review, we summarize recent studies on stimulation of mitochondrial biogenesis, myogenic stem (satellite) cells and manipulation of transforming growth factor family members, all of which hold promise for more effective therapies to target muscle mass loss and function in the future.

Tibia and radius bone geometry and volumetric density in obese compared to non-obese adolescents

Childhood obesity is associated with biologic and behavioral characteristics that may impact bone mineral density (BMD) and structure. The objective was to determine the association between obesity and bone outcomes, independent of sexual and skeletal maturity, muscle area and strength, physical activity, calcium intake, biomarkers of inflammation, and vitamin D status. Tibia and radius peripheral quantitative CT scans were obtained in 91 obese (BMI>97th percentile) and 51 non-obese adolescents (BMI>5th and <85th percentiles). Results were converted to sex- and race-specific Z-scores relative to age. Cortical structure, muscle area and muscle strength (by dynamometry) Z-scores were further adjusted for bone length. Obese participants had greater height Z-scores (p<0.001), and advanced skeletal maturity (p<0.0001), compared with non-obese participants. Tibia cortical section modulus and calf muscle area Z-scores were greater in obese participants (1.07 and 1.63, respectively, both p<0.0001). Tibia and radius trabecular and cortical volumetric BMD did not differ significantly between groups. Calf muscle area and strength Z-scores, advanced skeletal maturity, and physical activity (by accelerometry) were positively associated with tibia cortical section modulus Z-scores (all p<0.01). Adjustment for muscle area Z-score attenuated differences in tibia section modulus Z-scores between obese and non-obese participants from 1.07 to 0.28. After multivariate adjustment for greater calf muscle area and strength Z-scores, advanced maturity, and less moderate to vigorous physical activity, tibia section modulus Z-scores were 0.32 (95% CI -0.18, 0.43, p=0.06) greater in obese, vs. non-obese participants. Radius cortical section modulus Z-scores were 0.45 greater (p=0.08) in obese vs. non-obese participants; this difference was attenuated to 0.14 with adjustment for advanced maturity. These findings suggest that greater tibia cortical section modulus in obese adolescents is attributable to advanced skeletal maturation and greater muscle area and strength, while less moderate to vigorous physical activities offset the positive effects of these covariates. The impact of obesity on cortical structure was greater at weight bearing sites.