Nutrition and bone growth in pediatrics

The Effects of Nutrition on Linear Growth

Linear growth is a complex process and is considered one of the best indicators of children’s well-being and health. Genetics, epigenetics and environment (mainly stress and availability of nutrients) are the main regulators of growth. Nutrition exerts its effects on growth throughout the course of life with different, not completely understood mechanisms. Cells have a sophisticated sensing system, which allows growth processes to occur in the presence of an adequate nutrient availability. Most of the nutritional influence on growth is mediated by hormonal signals, in turn sensitive to nutritional cues. Both macro- and micro-nutrients are required for normal growth, as demonstrated by the impairment of growth occurring when their intake is insufficient. Clinical conditions characterized by abnormal nutritional status, including obesity and eating disorders, are associated with alterations of growth pattern, confirming the tight link between growth and nutrition. The precise molecular mechanisms connecting nutrition to linear growth are far from being fully understood and further studies are required. A better understanding of the interplay between nutrients and the endocrine system will allow one to develop more appropriate and effective nutritional interventions for optimizing child growth.

Metabolic-endocrine disruption due to preterm birth impacts growth, body composition, and neonatal outcome

Despite optimized nutrition, preterm-born infants grow slowly and tend to over-accrete body fat. We hypothesize that the premature dissociation of the maternal-placental-fetal unit disrupts the maintenance of physiological endocrine function in the fetus, which has severe consequences for postnatal development. This review highlights the endocrine interactions of the maternal-placental-fetal unit and the early perinatal period in both preterm and term infants. We report on hormonal levels (including tissue, thyroid, adrenal, pancreatic, pituitary, and placental hormones) and nutritional supply and their impact on infant body composition. The data suggest that the premature dissociation of the maternal-placental-fetal unit leads to a clinical picture similar to panhypopituitarism. Further, we describe how the premature withdrawal of the maternal-placental unit, neonatal morbidities, and perinatal stress can cause differences in the levels of growth-promoting hormones, particularly insulin-like growth factors (IGF). In combination with the endocrine disruption that occurs following dissociation of the maternal-placental-fetal unit, the premature adaptation to the extrauterine environment leads to early and fast accretion of fat mass in an immature body. In addition, we report on interventional studies that have aimed to compensate for hormonal deficiencies in infants born preterm through IGF therapy, resulting in improved neonatal morbidity and growth. IMPACT: Preterm birth prematurely dissociates the maternal-placental-fetal unit and disrupts the metabolic-endocrine maintenance of the immature fetus with serious consequences for growth, body composition, and neonatal outcomes. The preterm metabolic-endocrine disruption induces symptoms resembling anterior pituitary failure (panhypopituitarism) with low levels of IGF-1, excessive postnatal fat mass accretion, poor longitudinal growth, and failure to thrive. Appropriate gestational age-adapted nutrition alone seems insufficient for the achievement of optimal growth of preterm infants. Preliminary results from interventional studies show promising effects of early IGF-1 supplementation on postnatal development and neonatal outcomes.

Recent research on the growth plate: Impact of inflammatory cytokines on longitudinal bone growth

Children with inflammatory diseases usually display abnormal growth patterns as well as delayed puberty. This is a result of several factors related to the disease itself, such as malnutrition, hypercortisolism, and elevated levels of pro-inflammatory cytokines. These factors in combination with glucocorticoid treatment contribute to growth retardation during chronic inflammation by systemically affecting the major regulator of growth, the GH/IGF1 axis. However, recent studies have also shown evidence of a direct effect of these factors at the growth plate level. In conditions of chronic inflammation, pro-inflammatory cytokines are upregulated and released into the circulation. The most abundant of these, tumor necrosis factor α, interleukin 1β (IL1β), and IL6, are all known to directly act on growth plate cartilage to induce apoptosis and thereby suppress bone growth. Both clinical and experimental studies have shown that growth retardation can partly be rescued when these cytokines are blocked. Therefore, therapy modulating the local actions of these cytokines may be effective for preventing growth failure in patients with chronic inflammatory disorders. In this review, we report the current knowledge of inflammatory cytokines and their role in regulating bone growth.

Growth in children with chronic kidney disease: role of nutrition, growth hormone, dialysis, and steroids

PURPOSE OF REVIEW

Children with chronic kidney disease (CKD) have impaired growth that leads to short stature in adulthood. The problem persists even with successful transplantation and steroid withdrawal protocols. The aim of this review is to provide an overview of the pressing issues related to growth failure in children with CKD both before and after transplantation.

RECENT FINDINGS

Although great strides have been made in dialysis and transplantation, the incidence of abnormal adult height in children growing up with CKD remains as high as 45-60%. The lack of catch-up growth and resultant short stature is a critical issue for self-esteem and quality of life in many children with CKD. Aggressive daily dialysis, improved nutrition, treatment of metabolic bone disease, and the use of recombinant human growth hormone provide some hope for catch-up growth in select patients.

SUMMARY

The causes of growth failure in the setting of CKD are multifactorial. Attention to all the details by optimizing nutritional, bone and mineral metabolism, correcting metabolic acidosis and anemia, achieving excellent blood pressure control, reversing cardiovascular complications such as left ventricular hypertrophy, and minimizing the use of corticosteroids is the current standard of care. Aggressive daily dialysis can reverse many of the uremic derangements. For patients not yet on dialysis or for those after renal transplant, early institution of recombinant human growth hormone can promote growth. Improved understanding of the mechanisms of hormone resistance may offer novel targets or measurements of treatment effectiveness.

Slipped capital femoral epiphysis and its association with endocrine, metabolic and chronic diseases: a systematic review of the literature

PURPOSE

Puberty, obesity, endocrine and chronic systemic diseases are known to be associated with slipped capital femoral epiphysis (SCFE). The mechanical insufficiency of the physis in SCFE is thought to be the result of an abnormal weakening of the physis. However, the mechanism at the cellular level has not been unravelled up to now.

METHODS

To understand the pathophysiology of endocrine and metabolic factors acting on the physis, we performed a systematic review focussing on published studies reporting on hormonal, morphological and cellular abnormalities of the physis in children with SCFE. In addition, we looked for studies of the effects of endocrinopathies on the human physis which can lead to cause SCFE and focussed in detail on hormonal signalling, hormone receptor expression and extracellular matrix (ECM) composition of the physis. We searched in the PubMed, EMBASE.com and The Cochrane Library (via Wiley) databases from inception to 11th September 2012. The search generated a total of 689 references: 382 in PubMed, 232 in EMBASE.com and 75 in The Cochrane Library. After removing duplicate papers, 525 papers remained. Of these, 119 were selected based on titles and abstracts. After excluding 63 papers not related to the human physis, 56 papers were included in this review.

RESULTS

Activation of the gonadal axis and the subsequent augmentation of the activity of the growth hormone-insulin-like growth factor 1 (GH-IGF-1) axis are important for the pubertal growth spurt, as well as for cessation of the physis at the end of puberty. The effects of leptin, thyroid hormone and corticosteroids on linear growth and on the physis are also discussed. Children with chronic diseases suffer from inflammation, acidosis and malnutrition. These consequences of chronic diseases affect the GH-IGF-1 axis, thereby, increasing the risk of the development of SCFE. The risk of SCFE and avascular necrosis in children with chronic renal insufficiency, growth hormone treatment and renal osteodystrophy remains equivocal.

CONCLUSIONS

SCFE is most likely the result of a multi-factorial event during adolescence when height and weight increase dramatically and the delicate balance between the various hormonal equilibria can be disturbed. Up to now, there are no screening or diagnostic tests available to predict patients at risk.