Conceptual Model of Lean Body Mass in Pediatric Inflammatory Bowel Disease

Bone marrow adiposity in pediatric Crohn's disease

Patients with Crohn's disease often have low bone mineral density and an increased risk of osteoporosis. Although decreased bone formation can be seen at diagnosis, the underlying pathophysiology of suboptimal bone accrual remains poorly understood. We sought to evaluate a novel mechanism affecting osteogenesis in patients with Crohn's disease. In this case series, we evaluated bone marrow composition at the distal femur and proximal tibia of the left knee measured via magnetic resonance (MR) spectroscopy and relaxometry in five adolescents with the diagnosis of Crohn's disease. The subjects were enrolled prospectively between 2011 and 2013 at Boston Children's Hospital. Additional clinical information, including DXA scans to evaluate bone mineral density and body composition, and Crohn's disease history, such as glucocorticoid use and disease duration, were assessed. Healthy adolescents have persistent hematopoietic marrow with only 40 to 50 % fat in the long bone metaphyses. The current participants with Crohn's disease had increased marrow adiposity, with a mean fat fraction of 67.8 %. There appeared to be a trend towards higher fat fraction with shorter disease duration, while participants with the longest disease duration had the lowest fat fraction. Participants also had decreased bone density, increased fat mass, and lower lean mass, as assessed by DXA and compared to pediatric reference data. Our MRI results demonstrate increased marrow adiposity in children with Crohn's disease, especially early in the course of the disease. DXA may better demonstrate longer-term effects on bone. Additional studies are needed to evaluate bone marrow composition in these patients and to elucidate further the inverse relationship between marrow adipocytes and osteogenesis, as well as the relationship between bone marrow adiposity and body composition.

Moderate-to-Vigorous Physical Activity Is Associated With Higher Bone Mineral Density in Children With Inflammatory Bowel Disease

OBJECTIVES

Decreased mineral bone density (BMD) and reduced lean body mass (LBM) are common amongst children with inflammatory bowel disease (IBD). The aim of our cross-sectional, observational study was to evaluate the relationship between BMD, body composition and physical activity (PA) in children with IBD in remission.

METHODS

Total body less head (TLBH) dual energy X-ray absorptiometry (DXA) was used to measure BMD, fat mass (FM) and lean body mass (LBM). Triaxial accelerometer for five consecutive days was used to objectivize PA.

RESULTS

Forty pediatric IBD patients in clinical remission (24 boys; age 15.3 ± 0.4 years; Crohn disease [CD], n = 20, ulcerative colitis [UC], n = 18, inflammatory bowel disease-unclassified [IBD-U], n = 2) were recruited. Mean BMD was 0.940 g/cm2 and mean BMD z score was -0.42 ± 0.14. Patients with CD had significantly lower BMD than UC counterparts (P < 0.001). Average time spent in PA was 247.24 ± 16.71 min/day with 45.73 ± 8.22 min/day spent in moderate-to-vigorous PA (MVPA). We observed a significant positive correlation between the time spent in MVPA and BMD z score (P = 0.003) and LBM z score (P = 0.026). Multivariate analysis confirmed that the positive correlation of MVPA and BMD z score. There was no significant correlation between daily protein intake and BMD. Cumulative glucocorticoid dose negatively correlated with LBM z score (P = 0.003), but not with BMD z score (P = 0.069).

CONCLUSIONS

This study points to a strong positive relationship between MVPA, LBM and BMD. Longitudinal studies are required in order to elucidate the modifiable processes that determine body health and favorable body composition.

Adults with Crohn's disease exhibit elevated gynoid fat and reduced android fat irrespective of disease relapse or remission

Crohn’s disease (CD) is a debilitating inflammatory bowel condition of unknown aetiology that is growing in prevalence globally. Large-scale studies have determined associations between female obesity or low body mass index (BMI) with risk of CD at all ages or 8– < 40 years, respectively. For males, low BMI entering adult life is associated with increased incidence of CD or ulcerative colitis up to 40 years later. Body composition analysis has shown that combinations of lean tissue loss and high visceral fat predict poor CD outcomes. Here, we assessed dietary intake, physical activity and whole or regional body composition of patients with CD relapse or remission. This anthropometric approach found people with CD, irrespective of relapse or remission, differed from a large representative healthy population sample in exhibiting elevated gynoid fat and reduced android fat. CD is associated with mesenteric adipose tissue, or “creeping fat”, that envelops affected intestine exclusive of other tissue; that fat is localised to the android region of the body. In this context, CD mesenteric adiposity represents a stark juxtaposition of organ-specific and regional adiposity. Although our study population was relatively small, we suggest tentatively that there is a rationale to refer to Crohn’s disease as a fatty intestine condition, akin to fatty liver conditions. We suggest that our data provide early insight into a subject that potentially warrants further investigation across a larger patient cohort.

Bone Health in Pediatric Patients with IBD: What Is New?

PURPOSE OF THE REVIEW

Patients with inflammatory bowel disease (IBD) have increased bone fragility, demonstrated by increased fracture risk, and often have low bone density and altered bone geometry, but the underlying pathophysiology remains poorly understood.

RECENT FINDINGS

Children and adolescents with IBD appear to have decreased bone formation, at diagnosis, which frequently improves with treatment of their underlying IBD. There is a growing body of evidence regarding how the immune system interacts with bone metabolism. There are likely multi-factorial etiologies that contribute to suboptimal bone accrual and subsequent lack of peak bone mass attainment in growing patients with IBD. There appears to be differential effects dependent upon IBD sub-type and bone compartment. Pediatric patients with IBD require recognition of several risk factors that may adversely impact their bone accrual. Future studies are necessary to further delineate the effects of IBD on pediatric bone health.

Morphometric Changes in Children With Small Bowel Crohn Disease During Induction of Therapy: A Pilot Study

OBJECTIVE

Children and adolescents with Crohn disease (CD) commonly gain weight during treatment induction, which is thought to be a marker of better health. Body composition is, however, rarely assessed at diagnosis, and changes during early treatment are not often quantified. Therefore, it is unknown if these gains are truly healthy. We sought to evaluate skeletal muscle changes during initial treatment for CD by using routine imaging.

METHODS

Single-center prospective study. Pediatric patients diagnosed with small bowel CD underwent serial magnetic resonance enterography (MRE) imaging, laboratory testing, and disease-activity assessment, at diagnosis, 1 and 6 months of treatment. MRE-based cross-sectional morphometry was used to measure psoas muscle cross sectional area (CSA). Psoas CSA z-scores were calculated using normative data.

RESULTS

We enrolled 30 children (ages 9--17 years). Twenty-eight of 30 (93%) received anti-tumor necrosis factor therapy and 4 required surgical resection. Children with below-average psoas CSA and body mass index (BMI) z-scores at diagnosis were much more likely to fail treatment or undergo surgery by 6 months compared with those with higher z-scores (55% vs 0%; P = 0.001). Children with no activity limitations at diagnosis had significantly larger muscle gains in the first month, compared with those whose activity was limited at diagnosis (P = 0.012). Most patients had higher psoas CSA z-scores by 6 months, and these increases were associated with weight and BMI z-score increases.

CONCLUSIONS

Skeletal muscle growth contributes to weight gain during treatment induction in most patients with CD. Psoas muscle CSA on diagnostic imaging may have prognostic value in children with CD.

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.