Vitamin D status and muscle function in children with neurofibromatosis type 1 (NF1).

OBJECTIVES: The aim of this cross-sectional study was to assess the vitamin D status and muscle function in children with NF1 compared with their unaffected siblings. METHODS: NF1 children between 5 and 18 years of age and who had at least one unaffected sibling were identified. Serum concentrations of 25-hydroxyvitamin D (25(OH)D), calcium, inorganic phosphate, alkaline phosphate, parathyroid hormone and 1,25-dihydroxyvitamin D were measured. The Leonardo Mechanography Ground Reaction Force Platform (GRFP) was used to measure EFI, jump power, force and height. RESULTS: There was no significant difference in 25(OH)D between NF1 subjects and unaffected siblings. Relative jump power and force were found to be significantly different. The adjusted means (95% confidence limits) of non-NF1 and NF1 children for relative jump power (W/kg), controlling for body mass and age, were 37.31 (34.14, 40.49) and 32.51 (29.34, 35.68), respectively (P=0.054); and force (N/kg), controlling for body mass, age and gender, were 25.79 (24.28, 27.30) and 21.12 (19.61, 22.63), respectively (P<0.0001). Jumping parameters were not related to serum 25(OH)D. CONCLUSIONS: There was no significant relationship between vitamin D status and NF1 status in children. NF1 children had significantly impaired jumping power and force, when compared to their unaffected siblings.

Body composition and bone status of children born to mothers with type 1 diabetes mellitus.

BACKGROUND: Altered growth, body composition and abnormalities of skeletal mineralisation have been reported in offspring of mothers with type 1 and type 2 diabetes mellitus. AIMS: The authors hypothesised that children born to mothers with type 1 diabetes mellitus (CDM) would be taller, have higher body mass index (BMI), greater fat mass, thicker diaphyseal bone cortices and reduced trabecular bone mineral density (BMD), as compared to those born to non-diabetic mothers. METHODS: Anthropometric, body composition and bone parameters were assessed using dual-energy x-ray absorptiometry (DXA) and peripheral quantitative CT in 67 white Caucasian CDM (35 boys; age 5-18 years) and in 246 (121 boys) age-matched controls. RESULTS: CDM were taller (p<0.0001), heavier (p<0.0001) and had higher BMI (p=0.02), and had 32% more total body fat mass and 7.5% more total body lean mass than controls. At the total body and lumbar spine (L1-L4) sites, CDM had significantly higher bone area and bone mineral content compared with controls. However, areal BMD at both these sites and lumbar spine bone mineral apparent density were not significantly different in the two groups, indicating that CDM have bigger bones compared with controls but their mineral content per unit area or volume is not substantially different. The distal radial trabecular and total volumetric BMD in CDM was not demonstrably different from controls. At the mid-radius, both periosteal (2.4%; p=0.03) and endosteal circumferences (5.7%; p=0.02) were bigger in CDM compared with controls. CONCLUSION: The authors speculate that the intrauterine diabetic environment is associated with an increase in linear growth, adiposity and larger bone dimensions during childhood and adolescence.

Bone status of children aged 5-8 years, treated with dexamethasone for chronic lung disease of prematurity.

BACKGROUND: It is not known whether treatment with dexamethasone in the neonatal period may lead to reduced bone mineral density in childhood. METHODS: Anthropometric and bone densitometry measurements were taken of children aged 5-8 years who had chronic lung disease (CLD) in the neonatal period (n = 22). 15 of these children were treated with dexamethasone. A control group consisted of children born preterm who did not develop CLD (n = 29). RESULTS: Total body bone mineral content and bone mineral apparent density of the lumbar spine were lower in children whose CLD was treated with dexamethasone in the neonatal period, compared with the preterm controls. CONCLUSION: Dexamethasone treatment in the neonatal period appears to cause impairment of mineralisation which persists into childhood.

Intrauterine programming of urinary calcium and magnesium excretion in children born to mothers with insulin dependent diabetes mellitus.

BACKGROUND: Offspring of diabetic rats have reduced urinary calcium and magnesium excretion compared with offspring of controls; these differences persist up to 16 weeks after birth, a time equivalent to young adulthood in humans. OBJECTIVES: To test the hypothesis that urinary calcium and magnesium excretion would be lower in children born to mothers with insulin dependent diabetes mellitus (ChMIDDM) than those born to non-diabetic mothers. METHODS: Concentrations of calcium, magnesium, sodium, and creatinine were measured in first void spot urine samples collected from 45 (28 male; median age 9.6 years) ChMIDDM and 127 (58 male; median age 11.3 years) controls. Analysis of covariance was used to test for differences in urinary calcium to creatinine ratios (UCa/Cr), magnesium to creatinine ratios (UMg/Cr), and log sodium to creatinine ratios (logUNa/Cr) between controls and ChMIDDM after allowing for the effects of sex and age. RESULTS: UCa/Cr (difference -0.10, 95% confidence interval (CI) -0.19 to -0.01; p = 0.03) and UMg/Cr (difference -0.15, 95% CI -0.22 to -0.08; p<0.0001) were lower in ChMIDDM than controls. However, logUNa/Cr did not differ between ChMIDDM and controls (difference -0.14, 95% CI -0.33 to 0.05; p = 0.1). The daily estimated intake of magnesium, sodium, and protein were significantly higher and that of calcium non-significantly higher in ChMIDDM than controls. In ChMIDDM, UCa/Cr and UMg/Cr were not related to diabetic control of mothers. CONCLUSIONS: Results of this study provide the first evidence that in humans, as in rats, there is modification of renal Ca and Mg handling in ChMIDDM, which persists well into childhood.