Bone turnover in malnourished children

Children with severe acute malnutrition have high rates of bone resorption: A cross-sectional comparative study

Malnutrition in under-5 children (i.e., children younger than age 5 years) remains a major public health problem. Because of the reductive adaptation in children with severe acute malnutrition (SAM), changes in bone health are often subtle. We hypothesized that children with SAM have higher rates of bone resorption than bone formation, which can be assessed using bone turnover markers. In this cross-sectional comparative study, we evaluated the status of bone turnover markers, serum osteocalcin and serum tartrate-resistant acid phosphatase-5b (TRAP-5b) in under-5 children with SAM. Thirty children (6-59 months) with SAM (defined as per World Health Organization criteria) were enrolled as cases and another 30 children (age and sex matched) with normal nutritional status (weight for height -1 standard deviation [SD] to +1 SD) were enrolled for comparison of bone turnover markers. Serum TRAP-5b concentrations were significantly higher in children with SAM compared with children with normal nutritional status (mean [SD] 22.6 [15.3] vs. 11.3 [9.6], P = .009), whereas serum osteocalcin concentrations were comparable between the 2 groups (mean [SD] 40.6 [17.9] vs. 36.0 [12.5], P = .344). Frequency of hypocalcemia and vitamin D deficiency were also significantly high in children with SAM (P < .05). An inverse correlation was found between serum calcium and serum osteocalcin (r = -0.383, P < .05). Our results indicate that children with SAM have a higher bone resorption rate than children with normal nutrition status indicating compromised bone health.

Bone Turnover Markers in Children: From Laboratory Challenges to Clinical Interpretation

Bone turnover markers (BTMs) have been developed many years ago to study, in combination with imaging techniques, bone remodeling in adults. In children and adolescents, bone metabolism differs from adults since it implies both growth and bone remodeling, suggesting an age- and gender-dependent BTM concentration. Therefore, specific studies have evaluated BTMs in not only physiological but also pathological conditions. However, in pediatrics, the use of BTMs in clinical practice is still limited due to these many children-related specificities. This review will discuss about physiological levels of BTMs as well as their modifications under pathological conditions in children and adolescents. A focus is also given on analytical and clinical challenges that restrain BTM usefulness in pediatrics.

Bone biochemical markers for assessment of bone responses to differentiated phosphorus supply in growing-finishing pigs

Phosphorus (P) is essential for building and maintaining a healthy and strong skeleton. Moreover, dietary P supply may play a role for bone turnover, and the excretion of bone turnover metabolites may be useful as markers for sufficient dietary P supply. The objective was to study the long-term effects of low, medium, and high dietary P supply on bone metabolism in terms of serum concentration and urinary excretion of bone turnover components and metabolites in healthy growing-finishing pigs compared with bone mineral content (BMC) and bone mineral density (BMD) of humerus and femur. Pigs were fed diets containing low [LP; 4.1 g/kg dry matter (DM)], medium (MP; 6.2 g/kg DM), or high dietary P (HP; 8.9 g/kg DM) from 39.7 kg body weight (BW) until slaughter at 110 kg BW. Urine and blood were collected at 40, 70, and 110 kg BW while bones were collected at slaughter. Serum was analyzed for osteocalcin (OC), bone alkaline phosphatase (BAP), and C-terminal telopeptides of type I collagen (CTX-I), whereas urine was analyzed for pyridinoline (PYD), deoxypyridinoline (DPD), CTX-I, hydroxylysine (HYL), galactosyl-hydroxylysine (GAL-HYL), glycosyl-galactosyl-hydroxylysine (GLC-GAL-HYL), and hydroxyproline (HYP). Humerus and femur were analyzed for BMC and BMD. The LP diet caused reduced OC and increased BAP and CTX-I concentrations in serum. Furthermore, BAP was increased in response to the HP diet. Urine metabolites of bone resorption were all increased in pigs fed the LP diet, but only a few responses were obtained in response to the HP diet. Furthermore, age-related decreases were identified for BAP, HYL, GAL-HYL, and GLC-GAL-HYL. Bone mineral content and BMD were markedly lowered in pigs fed the LP diet but were not affected in pigs fed the HP diet. In conclusion, OC, BAP, and CTX-I in serum have proved useful for P adequacy in growing-finishing pigs. In addition, urine bone resorption metabolites have also proved useful for P adequacy and analysis of PYD, DPD, and CTX-I was considered to be the most relevant markers due to their specificity for bone and their negative correlation with BMD, BMC, ash, calcium (Ca), and P contents. Finally, DPD may be the preferred marker in long-term P feeding assessments.

Nutrition and growth: assessing the impact of regional nutritional intake on childhood development and metacarpal parameters

Measuring skeletal development throughout juvenile growth can provide a greater understanding into the health, hormonal function and genetics of children. The metacarpals have been of interest for their potential to provide insights into healthy juvenile skeletal development. This study investigated the growth patterns of developing females from isolated communities who had varied diets. Anthropometrical measurements and hand-wrist X-rays were taken of 353 juvenile females from three populations: Pari Coastal Village and Bundi Highlands Village, Papua New Guinea (PNG); and Brisbane, Australia between 1968 to 1983. Radiographs were digitized, and the length and width of the second and third metacarpals compared to each subject's height and weight. As subject heights increased, metacarpal length and width increased. However, stature and second metacarpal length indicated the strongest correlation (P<0.01), compared to third metacarpal length (P<0.01) or width. From 11 to 13 years of age, Brisbane subjects were significantly heavier and taller in comparison to subjects from PNG, and coastal females were heavier and taller than the highland females. A prominent difference between the two PNG populations was the regional intake of protein in their diets. The second metacarpal presents particularly accurate measurements when determining the height or development of a child. Nutritional intake appears to have a major influence normal childhood growth, with a potential for protein deficiency to strongly inhibit growth. Any delayed growth is particularly evident in the child's stature, as well as in the development of the metacarpal long bones of the hand.

Cereals and pulse-based ready-to-use therapeutic food as an alternative to the standard milk- and peanut paste-based formulation for treating severe acute malnutrition: a noninferiority, individually randomized controlled efficacy clinical trial

BACKGROUND

The cost of current standard ready-to-use therapeutic food (RUTF) is among the major obstacles to scaling up community-based management of acute malnutrition (CMAM), an important child survival strategy. Identifying a cheaper alternative is a global public health priority.

OBJECTIVE

We sought to compare the efficacy of soya-maize-sorghum RUTF (SMS-RUTF) with that of standard peanut paste-based RUTF (P-RUTF).

DESIGN

We used a nonblinded, parallel-group, simple randomized controlled trial along with a day care approach that enrolled 2 groups of children aged 6-23 and 24-59 mo, respectively, with severe acute malnutrition (SAM).

RESULTS

Intention-to-treat (ITT) and per-protocol (PP) analyses showed noninferiority of SMS-RUTF compared with P-RUTF for the recovery rate [ITT: Δ = -2.0% (95% CI: -7.6%, 3.6%); PP: -1.9% (95% CI: -5.3%, 1.4%)], weight gain [Δ = -0.7 g · kg(-1)· d(-1)(95% CI: -1.3, 0.0 g · kg(-1)· d(-1))], and length of stay [Δ = 2.0 d (95% CI: -1.7, 5.8 d)] in children ≥24 mo of age. In children ≤23 mo of age, the recovery rate of SMS-RUTF was inferior to that of P-RUTF [ITT: Δ = -20.8% (95% CI: -29.9%, -11.7%); PP: -17.2% (95% CI: -25.6%, -8.7%)]. Treatment with SMS-RUTF resulted in a greater increase in hemoglobin [0.670 g/dL (95% CI: 0.420, 0.921 g/dL);P< 0.001]. Treatment with both RUTFs resulted in the replenishment of all of the amino acids tested except for methionine. There were no differences at discharge between RUTF groups in fat mass [Δ = 0.3 kg (95% CI: -0.6, 1.6 kg);P= 0.341] or fat mass index [Δ = 0.4 kg/m(2)(95% CI: -0.3, 1.1 kg/m(2));P= 0.262]. By contrast, comparisons of fat-free mass indicated lower concentrations than the community controls after treatment with either of the 2 RUTFs [Δ = -1.3 kg (95% CI: -2.4, -0.1 kg) andP= 0.034 for comparison between community controls and the SMS-RUTF group; Δ = -1.8 kg (95% CI: -2.9, -0.6 kg) andP= 0.003 for comparison between community controls and the P-RUTF group].

CONCLUSION

SMS-RUTF can be used to treat SAM in children aged ≥24 mo to reduce the costs of CMAM programs. More research is required to optimize SMS-RUTF for younger children. This trial was registered in the Pan African Clinical Trial Registry as PACTR201303000475166.

Comparison of the effectiveness of a milk-free soy-maize-sorghum-based ready-to-use therapeutic food to standard ready-to-use therapeutic food with 25% milk in nutrition management of severely acutely malnourished Zambian children: an equivalence non-blinded cluster randomised controlled trial

Community-based Management of Acute Malnutrition using ready-to-use therapeutic food (RUTF) has revolutionised the treatment of severe acute malnutrition (SAM). However, 25% milk content in standard peanut-based RUTF (P-RUTF) makes it too expensive. The effectiveness of milk-free RUTF has not been reported hitherto. This non-blinded, parallel group, cluster randomised, controlled, equivalence trial that compares the effectiveness of a milk-free soy-maize-sorghum-based RUTF (SMS-RUTF) with P-RUTF in treatment of children with SAM, closes the gap. A statistician randomly assigned health centres (HC) either to the SMS-RUTF (n = 12; 824 enrolled) or P-RUTF (n = 12; 1103 enrolled) arms. All SAM children admitted at the participating HCs were enrolled. All the outcomes were measured at individual level. Recovery rate was the primary outcome. The recovery rates for SMS-RUTF and P-RUTF were 53.3% and 60.8% for the intention-to-treat (ITT) analysis and 77.9% and 81.8% for per protocol (PP) analyses, respectively. The corresponding adjusted risk difference (ARD) and 95% confidence interval, were -7.6% (-14.9, 0.6%) and -3.5% (-9,6., 2.7%) for ITT (P = 0.034) and PP analyses (P = 0.257), respectively. An unanticipated interaction (interaction P < 0.001 for ITT analyses and 0.0683 for PP analyses) between the study arm and age group was observed. The ARDs were -10.0 (-17.7 to -2.3)% for ITT (P = 0.013) and -4.7 (-10.0 to 0.7) for PP (P = 0.083) analyses for the <24 months age group and 2.1 (-10.3,14.6)% for ITT (P = 0.726) and -0.6 (-16.1, 14.5) for PP (P = 0.939) for the ≥24 months age group. In conclusion, the study did not confirm our hypothesis of equivalence between SMS-RUTF and P-RUTF in SAM management.

Proposed Recommended Nutrient Densities for Moderately Malnourished Children

Recommended Nutrient Intakes (RNIs) are set for healthy individuals living in clean environments. There are no generally accepted RNIs for those with moderate malnutrition, wasting, and stunting, who live in poor environments. Two sets of recommendations are made for the dietary intake of 30 essential nutrients in children with moderate malnutrition who require accelerated growth to regain normality: first, for those moderately malnourished children who will receive specially formulated foods and diets; and second, for those who are to take mixtures of locally available foods over a longer term to treat or prevent moderate stunting and wasting. Because of the change in definition of severe malnutrition, much of the older literature is pertinent to the moderately wasted or stunted child. A factorial approach has been used in deriving the recommendations for both functional, protective nutrients (type I) and growth nutrients (type II).

A Mediterranean dietary style improves calcium utilization in healthy male adolescents

OBJECTIVE

To examine the effects of consuming a diet based on the Mediterranean patterns on calcium availability and metabolism in male adolescents.

DESIGN

A longitudinal study divided into two periods: a 3-day basal period, during which the subjects (n = 20; 12.9 +/- 1.14 years) consumed their usual diet (basal diet, BD), and a 28-day nutritional intervention period, in which an intervention Mediterranean-type diet - was consumed (ID).

METHODS

Dietary calcium utilization was assessed by means of calcium intake in food and calcium output in feces and urine as measured by flame absorption spectrophotometry. In addition, markers of calcium metabolism (serum Ca, parathyroid hormone and total alkaline phosphatase) and bone resorption (urine deoxypiridinoline) were measured.

RESULTS

No differences in total calcium intake were found between the two diets, but food sources of dietary calcium varied significantly. Compared with the BD, the consumption of the ID resulted in significant increases in calcium absorption (approximately 40%, p = 0.04) and retention (approximately 80%, p = 0.008), and a considerable decrease in urinary calcium excretion (approximately 40%, p = 0.01).The variations observed in bone markers reflected a higher bone turnover rate after the ID consumption.

CONCLUSIONS

A varied diet based on Mediterranean diet patterns during adolescence greatly improves dietary calcium utilization, which may help to maximize the peak bone mass and prevent related diseases, such as osteoporosis.

A new method of monitoring osteomyelitis

Chronic infections of bone such as osteomyelitis are frequent events, especially in immunocompromised or diabetic patients, and costly on a national level. Incorrect treatment or delayed diagnosis may lead to loss of the affected extremity or mandible. The aim of this study was to assess the possible value of urinary lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) concentrations in the monitoring of mandibular osteomyelitis. Patients were assigned to the following groups: group 1 (n=85), control; group 2a (n=38), patients with active disease; group 2b (n=25), patients of group 2a 6 months after successful treatment; group 2c (n=7), patients of group 2a with ongoing osteomyelitis 6 months after treatment. The range and upper limit of normal values (HP(max) and LP(max)) were determined in group 1. Levels of LP and HP were measured by high-performance liquid chromatography and fluorescence detection. There was a significant decrease (mean 45.43% for HP and 32.12% for LP) in samples of group 2b compared to 2a (P<0.001 for HP and LP). There was a significant increase in HP values in samples from group 2c compared to 2a (P=0.018). The urinary concentrations of HP and LP appear to act as a marker of disease activity, with a decrease reflecting treatment success and an increase or stable values indicating persistent disease. An inexpensive tool (US$5 per analysis) for the monitoring of osteomyelitis is described.

Vitamin C status and collagen cross-link ratios in Gambian children

Vitamin C (ascorbate) is essential for hydroxylation of prolyl and lysyl residues in nascent collagen, the failure of which leads to connective tissue lesions of scurvy. Of the pyridinium-type cross-links in mature collagen, pyridinoline requires more hydroxylysyl residues than does deoxypyridinoline. Our study tested the hypothesis that pyridinoline:deoxypyridinoline ratios in urinary degradation products may vary with ascorbate status in man. These ratios were compared between British and Gambian prepubertal boys, mean age 8.3 years, and in Gambian boys between two seasons with contrasting ascorbate availability. The mean cross-links ratio in 216 British boys was 4.36 (SD 0.71), significantly greater (P<0.0001) than in sixty-two Gambian boys: 3.83 (SD 0.52). In the Gambians the cross-links ratio was significantly higher in the dry season (with high ascorbate intake and status) than in the rains (with low intake and status). A 7-week controlled intervention was carried out in Gambian boys during the rainy season (the 'hungry' season, when vitamin C-containing foods are virtually unavailable): 100 mg ascorbate/d was given to one group of thirty-two Gambian boys and placebo to another group. The intervention did not, however, significantly alter the cross-link ratio, possibly because the response time and/or intervention-response delay is >7 weeks. If confirmed, the putative association between ascorbate and collagen cross-link ratios in man could become the basis for a functional test for adequacy of ascorbate status.

Dietary protein intake and risk of osteoporotic hip fracture in elderly residents of Utah

The role of protein intake in osteoporosis is unclear. In a case-control study in Utah (n = 2501), increasing level of protein intake was associated with a decreased risk of hip fracture in men and women 50-69 years of age but not in those 70-89 years of age. Protein intake may be important for optimal bone health.

INTRODUCTION

Protein is an important component of bone, but the role of dietary protein intake in osteoporosis and fracture risk remains controversial.

MATERIAL AND METHODS

The role of dietary protein intake in osteoporotic hip fracture was evaluated in a statewide case-control study in Utah. Patients, 50-89 years of age, with hip fracture (cases) were ascertained through surveillance of 18 Utah hospitals during 1997-2001. Age- and gender-matched controls were randomly selected. Participants were interviewed in their place of residence, and diet was assessed using a picture-sort food frequency questionnaire previously reported to give a useful measure of usual dietary intake in the elderly Utah population. The association between protein intake and risk of hip fracture was examined across quartiles of protein intake and stratified by age group for 1167 cases (831 women, 336 men) and 1334 controls (885 women, 449 men).

RESULTS

In logistic regression analyses that controlled for gender, body mass index, smoking status, alcohol use, calcium, vitamin D, potassium, physical activity, and estrogen use in women, the odds ratios (OR) of hip fracture decreased across increasing quartiles of total protein intake for participants 50-69 years of age (OR: 1.0 [reference]; 0.51 [95% CI: 0.30-0.87]; 0.53 [0.31-0.89]; 0.35 [0.21-0.59]; p < 0.001). No similar associations were observed among participants 70-89 years of age. Results from analyses stratified by low and high calcium and potassium intake did not differ appreciably from the results presented above.

CONCLUSION

Higher total protein intake was associated with a reduced risk of hip fracture in men and women 50-69 years of age but not in men and women 70-89 years of age. The association between dietary protein intake and risk of hip fracture may be modified by age. Our study supports the hypothesis that adequate dietary protein is important for optimal bone health in the elderly 50-69 years of age.

Differential enhancement of collagen crosslink excretion in cases of osteosarcoma and chondrosarcoma

Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are markers of collagen absorption and LP is specific for collagen type I in bone. In the present study we evaluated the concentration of HP and LP in urine of patients with osteosarcoma ( n=20; age range 16-49 years) and chondrosarcoma ( n=15; age range 18-70 years). The values were compared with those obtained from 74 healthy controls (age range 16-83 years). The range and upper limit of normal values (HP(max) and LP(max)) were measured in our control group. High performance liquid chromatography (HPLC) was used to determine concentrations of HP and LP (nmol/mmol creatinine). The average urinary HP concentrations were significantly increased in patients with osteosarcoma ( p=0.001) and chondrosarcoma ( p<0.001), whereas HP remained within the normal range in approximately half of the patients. The average urinary LP concentrations were not increased in osteosarcoma and chondrosarcoma patients as compared with the control group. Further studies in a large group of patients are necessary to evaluate whether HP might be a valuable marker of prognosis, and if its urinary concentration can be correlated to tumour burden.

Comparison of vitamin C deficiency with food restriction on collagen cross-link ratios in bone, urine and skin of weanling guinea-pigs

Mild-to-moderate vitamin C depletion in weanling guinea-pigs affects pyridinoline:deoxypyridinoline (collagen cross-link) ratios in femur shaft and urine, attributed to impairment of hydroxylation of collagen lysine. We investigated: (1). whether the picture at two time points is compatible with progressive accumulation of abnormal collagen; (2). whether any changes are seen in skin, where little deoxypyridinoline occurs; (3). whether total food restriction has similar effects. Male weanling Dunkin-Hartley guinea-pigs were fed diets containing either 0.5 (vitamin C-restricted) or 160.0-320.0 (vitamin C-adequate) mg vitamin C/d. Two groups receiving the vitamin C-adequate diet received it ad libitum. Two other groups received the vitamin C-adequate diet in a restricted amount, limited to that which permitted nearly the same growth rate as in the vitamin C-restricted groups. Animals were fed for 4 or 8 weeks; urine was collected, and vitamin C and collagen indices were measured. In the femur shaft, the hydroxyproline content per unit weight was unaffected by vitamin C restriction or by total food restriction. Deoxypyridinoline was increased and the pyridinoline:deoxypyridinoline ratio was decreased in vitamin C-restricted groups, but not in food-restricted groups. Changes in the value of the ratio were greater after 8 than after 4 weeks. Urine indices mirrored bone indices. In skin, the main effect of vitamin C restriction was to reduce hydroxyproline. Here, the cross-link ratios changed less markedly than in bone, and there was less deoxypyridinoline. We conclude that the picture at two time points is compatible with a progressive accumulation of pyridinoline-enriched collagen in vitamin C-deprived animals, that the picture in skin differs from that of bone and urine, and that cross-link changes are not produced by total food restriction.

Assessment and Recommendations on Factors Contributing to Preanalytical Variability of Urinary Pyridinoline and Deoxypyridinoline

Background: Pyridinoline (PYD) and deoxypyridinoline (DPD) are two of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. We reviewed factors contributing to preanalytical variation of pyridinium cross-links in urine.

Methods: We searched four databases for English-language reports on PYD and/or DPD in urine. Searches were restricted to humans, except for studies of stability, when the search was expanded to other species. The 599 identified articles were supplemented with references from those articles and with articles known to the authors.

Results: The mean reported within-day variability was 71% for PYD (range, 57–78%) and 67% for DPD (range, 53–75%). The mean interday variability was 16% for both DPD and PYD (range for PYD, 12–21%; range for DPD, 5–24%). The mean intersubject variabilities across studies were 26% for PYD (range, 12–63%) and 34% for DPD (range, 8–98%) for healthy premenopausal women and 36% (range, 22–61%) and 40%, (range, 27–54%) for postmenopausal women, respectively. Specimen instability and errors in creatinine measurements were additional sources of variability.

Conclusions: Intra- and intersubject variability can be reduced by collecting specimens at a specific time of the day and by maintaining similar patient status at each specimen collection regarding factors such as medications and dietary supplements.

Urinary excretion of pyridinium crosslinks in short children treated with growth hormone

The aim of this study was to evaluate the effect of growth hormone (GH) treatment on bone resorption in children with GH deficiency and those with idiopathic short stature. The study population included seven children with subnormal spontaneous GH secretion and 13 children with idiopathic short stature, all of them pre-pubertal. Anthropometric measurements, free, protein-bound and total urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd), serum GH, and serum immunoreactive PTH were measured at baseline and months 1, 3, 6 and 12 of GH treatment. The urinary excretion of total Pyd and Dpd, standardized by the cube of height (m3) in overnight, 24-hour urine collections was not different from age-matched healthy controls at baseline in either group of patients. During treatment with human recombinant GH, both pyridinium crosslinks increased above normal values, reaching a peak after one month in children with GH deficiency and later (after 3-6 months) in children with short stature. Free and total crosslink forms were correlated, and GH treatment did not affect the proportion of free to bound crosslinks. Serum concentrations of iPTH showed a moderate but not statistically significant increase. This study provides no evidence of reduced bone resorption in untreated GH deficiency or in idiopathic short stature. GH treatment induced a marked, but temporary, increase of bone resorption in both groups of patients.

Collagen cross-links and early postnatal growth in newborns with intrauterine growth retardation

This study assessed growth and skeletal metabolism in full-term newborns with intrauterine growth retardation (IUGR) and determined the value of the urinary excretion of collagen cross-links in predicting postnatal catch-up growth. We studied 38 newborns (16 females) born at term with a birth weight less than the 10th centile of the reference and a ponderal index ([PI] 100 x weight in g/length in cm3) of 2.27 +/- 0.19. The sample was divided into 23 children with proportionate ([P] PI > or = 10th centile of the reference) and 15 with nonproportionate ([NP] PI < 10th centile of the reference) IUGR. The weight, head circumference, length, and knee-heel length of the newborns at days 7, 14, 30, 60, and 90 were measured. The height of 23 of the 38 children was also assessed at 27 +/- 6 months of life. Urinary collagen cross-links were analyzed by high-performance liquid chromatography at day 14 and day 60. Most of the infants (68%) underwent catch-up growth, and the growth performance at 3 months was independent of the proportions at birth. Children who did not show catch-up growth in the first trimester of life failed to normalize in height in the following 2 years. The urinary excretion of pyridinoline (Pyd) was not related to the anthropometric measurements. In P children, urinary excretion of deoxypiridinoline (Dpd) at day 14 significantly correlated with the gain in length during the first 3 months, accounting for 25% of the variance. In NP children, these correlations between urinary Dpd and the gain in length were not significant. The evaluation of urinary Dpd excretion at 2 weeks of age might help to determine the therapeutic regimen in IUGR children.

Bone metabolism and mineral density following renal transplantation

AIM

To study bone turnover following renal transplantation using a panel of biochemical markers and to correlate the results with both areal and volumetric bone mineral density (BMD).

PATIENTS

A total of 31 patients aged 18.1 years were transplanted 5.4 years before this study. Control patients (n = 31) were age and gender matched.

METHODS

In addition to measurement of biochemical markers, BMD was measured by single photon absorptiometry and peripheral quantitative computed tomography on the non-dominant radius.

RESULTS

Patients had reduced glomerular filtration rate, raised concentrations of serum phosphate, serum procollagene type I carboxy terminal propeptide, osteocalcin, and serum procollagene type I cross linked carboxy terminal telopeptide. The differences were still significant if only patients with normal intact parathyroid hormone were considered. BMD single photon absorptiometry Z score for age was significantly decreased. Following standardisation for height the differences were no longer present. With volumetric techniques patients had normal trabecular but decreased cortical and total BMD compared to age matched controls, but there was no difference from height matched controls.

CONCLUSION

Markers of bone turnover are increased following renal transplantation. However, the biochemical analysis did not allow conclusions to be drawn on the bone mineral content. BMD single photon absorptiometry Z score corrected for height and BMD measured by quantitative computed tomography compared to height matched controls were normal in paediatric renal transplantation patients. Height matched controls should be used in both areal and volumetric BMD measurements in states of growth failure.

Circulating biochemical markers of bone remodeling in uremic patients

Chronic renal failure is often associated with bone disorders, including secondary hyperparathyroidism, aluminum-related low-turnover bone disease, osteomalacia, adynamic osteopathy, osteoporosis, and skeletal beta2-microglobulin amyloid deposits. In spite of the enormous progress made during the last few years in the search of noninvasive methods to assess bone metabolism, the distinction between high- and low-turnover bone diseases in these patients still frequently requires invasive and/or costly procedures such as bone biopsy after double tetracycline labeling, scintigraphic-scan studies, computed tomography, and densitometry. This review is focused on the diagnostic value of several new serum markers of bone metabolism, including bone-specific alkaline phosphatase (bAP), procollagen type I carboxy-terminal extension peptide (PICP), procollagen type I cross-linked carboxy-terminal telopeptide (ICTP), pyridinoline (PYD), osteocalcin, and tartrate-resistant acid phosphatase (TRAP) in patients with chronic renal failure. Most of the observations made by several groups converge to the conclusion that serum bAP is the most sensitive and specific marker to evaluate the degree of bone remodeling in uremic patients. Nonetheless, PYD and osteocalcin, in spite of their retention and accumulation in the serum of renal insufficient patients, are also excellent markers of bone turnover. The future generalized use of these markers, individually or in combination with other methods, will undoubtedly improve the diagnosis and the treatment of the complex renal osteodystrophy.

Prospective study of dietary protein intake and risk of hip fracture in postmenopausal women

BACKGROUND

The role of dietary protein intake in osteoporosis remains controversial. Protein is an important structural component of bone and protein supplementation improves the medical outcome of hip fracture patients, but it is unknown whether protein intake can reduce the incidence risk of hip fracture.

OBJECTIVE

The relation between intake of protein and other nutrients and subsequent incidence of hip fracture was evaluated.

DESIGN

Nutrient intake was assessed with a food-frequency questionnaire in a cohort of Iowa women aged 55-69 y at baseline in 1986. Incident hip fractures were ascertained through follow-up questionnaires mailed to participants in 1987 and 1989 and verified by physician reports.

RESULTS

Forty-four cases of incident hip fractures were included in the analyses of 104338 person-years (the number of subjects studied times the number of years of follow-up) of follow-up data. The risk of hip fracture was not related to intake of calcium or vitamin D, but was negatively associated with total protein intake. Animal rather than vegetable sources of protein appeared to account for this association. In a multivariate model with inclusion of age, body size, parity, smoking, alcohol intake, estrogen use, and physical activity, the relative risks of hip fracture decreased across increasing quartiles of intake of animal protein as follows: 1.00 (reference), 0.59 (95% CI: 0.26, 1.34), 0.63 (0.28, 1.42), and 0.31 (0.10, 0.93); P for trend = 0.037.

CONCLUSION

Intake of dietary protein, especially from animal sources, may be associated with a reduced incidence of hip fractures in postmenopausal women.

Dissociation of bone turnover in anorexia nervosa

Biochemical markers were measured to assess bone turnover in a cross-sectional study of 43 patients with anorexia nervosa; 28 were at their first assessment (untreated) with a body mass index (BMI) (median interquartile range) of 13.3 (2) kg/m2. A second group of 15 patients undergoing treatment (treated) had a median BMI of 17.6 (2.8) kg/m2. The median, interquartile range of urinary deoxypyridinoline (DPyd), a bone resorption marker, was raised in both groups compared with an age-matched control population [DPyd = 17.8 (15.2), 17.5 (16.4) and 9.2 (4.0) nmol/mmol creatinine, respectively]. Serum type 1 collagen carboxyterminal propeptide (P1CP), a marker of bone formation, was similar to controls in the untreated patients [112 (29) and 112 (78.5) ng/ml, respectively], but was significantly raised in the treated patients [163 (219) ng/ml, P < 0.05]. A second group of 21 patients was followed prospectively, on admission and during 8 weeks of intensive inpatient care (BMI on admission and after 8 weeks was 13.0 (2) and 16.7 (3) kg/m2, respectively). The resorption marker, serum type 1 collagen carboxyterminal telopeptide (1CTP) was raised on admission and remained high during treatment. P1CP and osteocalcin levels were similar to control levels on admission but increased with treatment, and after 8 weeks were 40% and 63% higher respectively than on admission. These findings suggest that in untreated anorexia nervosa there was uncoupling of bone turnover as bone resorption markers were raised without a concomitant increase in bone formation markers. As the condition was treated and patients gained weight, the formation markers also increased, leading to a more balanced, although higher, bone turnover.

Exercise before puberty may confer residual benefits in bone density in adulthood: studies in active prepubertal and retired female gymnasts

Exercise during growth may contribute to the prevention of osteoporosis by increasing peak bone mineral density (BMD). However, exercise during puberty may be associated with primary amenorrhea and low peak BMD, while exercise after puberty may be associated with secondary amenorrhea and bone loss. As growth before puberty is relatively sex hormone independent, are the prepubertal years the time during which exercise results in higher BMD? Are any benefits retained in adulthood? We measured areal BMD (g/cm2) by dual-energy X-ray absorptiometry in 45 active prepubertal female gymnasts aged 10.4 +/- 0.3 years (mean +/- SEM), 36 retired female gymnasts aged 25.0 +/- 0.9 years, and 50 controls. The results were expressed as a standardized deviation (SD) or Z score adjusted for bone age in prepubertal gymnasts and chronological age in retired gymnasts. In the cross-sectional analyses, areal BMD in the active prepubertal gymnasts was 0.7-1.9 SD higher at the weight-bearing sites than the predicted mean in controls (p < 0.01). The Z scores increased as the duration of training increased (r = 0.32-0.48, p ranging between <0.04 and <0.002). During 12 months, the increase in areal BMD (g/cm2/year) of the total body, spine, and legs in the active prepubertal gymnasts was 30-85% greater than in prepubertal controls (all p < 0.05). In the retired gymnasts, the areal BMD was 0.5-1.5 SD higher than the predicted mean in controls at all sites, except the skull (p ranging between <0.06 and <0.0001). There was no diminution across the 20 years since retirement (mean 8 +/- 1 years), despite the lower frequency and intensity of exercise. The prepubertal years are likely to be an opportune time for exercise to increase bone density. As residual benefits are maintained into adulthood, exercise before puberty may reduce fracture risk after menopause.

Procollagen propeptide and pyridinium cross-links as markers of type I collagen turnover: sex- and age-related changes in healthy children

The correlations among age, gender, body size parameters, and type I collagen metabolism were evaluated in 183 healthy infants, aged 8.5-27.5 months. Collagen formation was assessed by measuring serum type I collagen carboxy-terminal propeptide, and degradation was determined by urinary pyridinoline and deoxypyridinoline (measured by high performance liquid chromatography) and cross-linked N- and C-terminal telopeptides of type I collagen (measured by NTx and CrossLaps assays). A new RIA specific for deoxypyridinoline was also evaluated. The results provide reference values at 10 months and 2 yr of age, including cross-linked C-terminal telopeptides (1492 +/- 685 and 1510 +/- 446 in boys; 1705 +/- 612 and 1849 +/- 611 micrograms/mmol creatinine in girls; mean +/- 1 SD). There was a good correlation between the high performance liquid chromatography and RIA data for deoxypyridinoline, showing that the RIA method is suitable for use in healthy children. Some correlations were found among peptide-bound cross-links, serum type I collagen carboxy-terminal propeptide, and the anthropometric parameters, suggesting that these peptides reflect bone resorption and also overall body type I collagen. Finally, there were age- and sex-related differences in the urinary excretion of the collagen degradation markers, suggesting that, unlike boys, girls maintain a high degree of collagen degradation up to the age of 24 months despite a decrease in their rate of collagen formation.

Very low rate of type I collagen synthesis and degradation in newly diagnosed children with acute lymphoblastic leukemia

In children with acute lymphoblastic leukemia (ALL), the metabolism of type I collagen, the major collagen of bones, may be changed at diagnosis and during early chemotherapy. In the present study, bone formation and degradation rates were evaluated longitudinally in 35 children with ALL, using two serum markers of bone collagen formation: the amino-terminal (PINP) and carboxyterminal (PICP) propeptides; and a marker of degradation: the carboxyterminal telopeptide of type I collagen (ICTP). These serum markers were determined at diagnosis, during induction treatment (at 1, 4, and 6 weeks), and during consolidation treatment (at 8 and 12 weeks). The changes in the serum markers suggested that, at diagnosis, type I collagen turnover (i.e., both synthesis and degradation) was remarkably low. The median serum levels of PINP, PICP, and ICTP were -2.6 SDS (standard deviation score), -1.5 SDS, and -2.5 SDS, respectively. The PICP and PINP levels declined further during the first week of therapy (p < 0.001), whereas the ICTP levels had risen by end of the induction phase (p < 0.05). By the end of the 12 week interval, the concentrations of the formation and degradation markers had returned to normal (p < 0.01). Our findings suggest that ALL is accompanied by low turnover of bone collagen. The abnormalities are at first aggravated, but then corrected, by treatment.

Urinary immunoreactive deoxypyridinoline in children and adolescents: variations with age, sex and growth velocity

The collagen cross-linking compound deoxypyridinoline (DPD) has been shown to be a marker of bone resorption and skeletal growth in children. However, the original method for the determination of total (i.e. free and peptide-bound) DPD (tDPD) in urine samples is technically demanding. The recent development of a simple enzyme-linked immunosorbent assay for the quantification of immunogenic DPD (iDPD) in urine samples might be a more convenient technique. Yet, it is unclear at present whether iDPD is equal to tDPD as an index of bone resorption and skeletal growth. Therefore, using 24-h urines from 144 healthy children and adolescents aged 4-19 years, we established reference ranges for the daily urinary excretion of iDPD. A close correlation was found between the daily urinary excretion of iDPD and tDPD related to body weight (r = 0.87, p < 0.001). In 72 subjects aged 4-18 years, the daily excretion of iDPD normalized to body weight was highly significantly correlated with growth velocity (r = 0.70, p < 0.001). We conclude that the enzyme-linked immunosorbent assay for urinary iDPD appears to provide a good index of bone resorption and growth in healthy children.

Effects of weight loss on bone mineral density in rats

OBJECTIVE

To evaluate the effects of weight loss on bone mineral density (BMD).

METHODS

Eight-week-old female rats were divided into 4 groups: Those in Group A received a restricted diet for 4 weeks; those in Group B received a restricted diet and were treated with estrogen; those in Group C were castrated; and those in Group D underwent sham operations. The rat's body weight (BW) and vaginal smears were checked, and their femoral BMD was measured.

RESULTS

The BW and BMD at 12 weeks were lower in Groups A and B than in Groups C and D; thereafter, however, these values increased for Groups A and B, but were still lower than those in Group D even at 20 weeks. In Group C, the BMD did not decrease, but it was significantly lower than that in Group D at 16 and 20 weeks. Group A showed continuous diestrus 2 weeks after dietary restriction began, but recovered to a 4-day cycle 2 weeks after the initiation of free food consumption.

CONCLUSION

Weight loss had a greater effect on BMD than hypoestrogenism.

Urinary excretion of pyridinium cross-links of collagen in infancy

This cross-sectional study evaluated urinary excretion of pyridinium cross-links of collagen, specific markers of ongoing bone resorption, in infants aged 1 week to 7 months and examined the relationship between urinary cross-links and individual renal function. Spot urines from a total of 100 infants were analyzed. The collagen cross-links, pyridinoline (Pyd) and deoxypyridinoline (D-Pyd), were assayed by fluorescence detection after high-performance liquid chromatography (HPLC). Beta2-Microglobulin (beta2M), an index of renal tubular function, was determined by radioimmunoassay. In healthy term infants, urinary collagen cross-links were several times higher than the reported data for older children, with peak values seen at 1 month of age. Excretion of Pyd and D-Pyd was also markedly elevated in 1-month-old preterm infants, despite poor somatic growth. Such high excretion of collagen cross-links probably reflects the state of accelerated bone turnover in infancy. The postnatal change in the cross-links was different from that in urinary beta2M, and the values obtained did not correlate with beta2M in either term or preterm infants. These results indicate that cross-link excretion is not influenced directly by individual renal function.

Bone and collagen turnover during treatment with inhaled dry powder budesonide and beclomethasone dipropionate

OBJECTIVES

To assess bone and collagen turnover in asthmatic children treated with dry powder budesonide from the Turbuhaler and dry powder beclomethasone dipropionate from the Diskhaler in a dose of 800 micrograms/day.

SUBJECTS

Thirteen prepubertal children with asthma.

DESIGN

Open crossover study with two treatment periods and treatment free run-in and wash-out periods. All periods were of two weeks' duration. At day 14 in each period blood samples were taken for assessment of serum osteocalcin, the carboxyterminal propeptide of type I collagen (PICP), and the aminoterminal propeptide of type III collagen (PIIINP). At the same time urine was collected for assessment of creatinine corrected pyridinoline (uPYR/cr) and deoxypyridinoline (udPYR/cr) crosslinks.

RESULTS

Osteocalcin concentrations were not influenced by any of the treatments. During budesonide treatment mean (SEM) PICP was reduced by 18% (8%) (p = 0.03), PIIINP by 24% (3%) (p = 0.0002), uPYR/cr by 16% (6%) (p = 0.03), and udPYR/cr by 21% (13%) (p = 0.12). During treatment with beclomethasone dipropionate mean (SEM) PICP was reduced by 20% (6%) (p = 0.01), PIIINP by 36% (3%) (p = 0.0002), uPYR/cr by 18% (4%) (p = 0.004), and udPYR by 13% (5%) (p = 0.02). The suppressive effect of beclomethasone dipropionate on PIIINP was more marked than that of budesonide (p = 0.001).

CONCLUSION

Treatment with dry powder budesonide and beclomethasone dipropionate 800 micrograms/day is associated with suppression of bone and collagen turnover. The suppression seems to be more marked during treatment with beclomethasone dipropionate. Long term effects and effects of lower doses of budesonide and beclomethasone dipropionate on bone and collagen markers needs further study.

Serum levels of the pyridinoline crosslinked carboxyterminal telopeptide of type I collagen (ICTP) and osteocalcin in rachitic children in Nigeria

OBJECTIVES

We measured the levels of the pyridinoline crosslinked carboxyterminal telopeptide of type I collagen (ICTP) and osteocalcin (OC) in the serum of 12 rachitic and 27 healthy Nigerian children, and compared the performance of these relatively new markers of bone metabolism with established laboratory parameters of skeletal disease.

DESIGN AND METHODS

Active rickets was diagnosed on the basis of clinical and biochemical criteria. Serum calcium and phosphorus concentration and alkaline phosphatase activity were determined using clinically accepted methods. Radioimmunoassay was performed to quantify parathyroid hormone, 1-,25-dihydroxyvitamin D, OC, and ICTP.

RESULTS

The rachitic children had statistically significant serum elevations of ICTP and osteocalcin as compared with age- and sex-matched controls. Serum levels of ICTP correlated with alkaline phosphate activity.

CONCLUSIONS

As a marker of abnormal bone metabolism, ICTP performs at least as well as alkaline phosphate. ICTP and OC are valuable additions to the growing repertoire of bone markers.

Effects of rhIGF-I administration on bone turnover during short-term fasting

Insulin-like growth factor-I (IGF-I) is a nutritionally dependent bone trophic hormone which stimulates osteoblast function and collagen synthesis in vivo and in vitro. We hypothesized that in the fasting state, IGF-I levels would decline significantly and would establish a model in which we could investigate the effects of IGF-I administration on bone turnover. We therefore studied 14 normal women ages 19-33 (mean, 24 +/- 4 [SD] years) during a complete 10-d fast. After 4 d of fasting, subjects were randomized to receive rhIGF-I or placebo subcutaneously twice a day for 6 d. Bone turnover was assessed using specific markers of formation (osteocalcin and type I procollagen carboxyl-terminal propeptide [PICP]) and resorption (pyridinoline, deoxypyridinoline, type I collagen crosslinked N-telopeptide [N-telopeptide] and hydroxyproline). Serum levels of PICP and osteocalcin decreased from 143 +/- 52 to 60 +/- 28 ng/ml (P = 0.001) and from 7.6 +/- 5.4 to 4.2 +/- 3.1 ng/ml (P = 0.001) respectively with 4 d of fasting. Urinary excretion of pyridinoline and deoxypyridinoline decreased from 96 +/- 63 to 47 +/- 38 nmol/mmol creatinine (P < 0.05) and from 28 +/- 17 to 14 +/- 11 nmol/mmol creatinine (P < 0.05) respectively. Mean IGF-I levels decreased from 310 +/- 81 to 186 +/- 78 ng/ml (P = 0.001). In the second part of the experimental protocol, serum osteocalcin and PICP levels increased 5- and 3-fold, respectively with rhIGF-I administration and were significantly elevated compared with the placebo group at the end of treatment (20.9 +/- 17.3 vs. 5.9 +/- 6.4 ng/ml for osteocalcin [P < 0.05] and 188 +/- 45 vs. 110 +/- 37 ng/ml for PICP [P < 0.05]). In contrast, all four markers of bone resorption, including urinary pyridinoline, deoxypyridinoline, N-telopeptide and hydroxyproline were unchanged with rhIGF-I administration. This report is the first to demonstrate that bone turnover falls rapidly with acute caloric deprivation in normal women. RhIGF-I administration uncouples bone formation in this setting by significantly increasing bone formation, but not resorption. These data suggest a novel use of rhIGF-I to selectively stimulate bone formation in states of undernutrition and low bone turnover.

Serum pyridinoline as a specific marker of collagen breakdown and bone metabolism in hemodialysis patients

Type I collagen represents more than 90% of bone matrix. Quantitative analysis of collagen cross-link molecules such as pyridinoline (PYD) provides valuable information on bone resorption rate. We have studied 37 hemodialysis patients who underwent a systematic transiliac bone biopsy for histomorphometry study. Eighteen of them had tetracycline double labeling, allowing to determine dynamic, in addition to static bone parameters. Measurement of serum-free PYD was performed using a new competitive enzyme immunoassay. Serum PYD values were compared with those of three other serum markers of bone metabolism, namely intact PTH (iPTH), bone-specific alkaline phosphatase (bAP), and osteocalcin, for the correlations with bone histomorphometric parameters. Serum PYD levels (mean +/- SD) were significantly higher in dialysis patients than in normal individuals, 90.6 +/- 99.6 nM versus 1.9 +/- 0.4 nM, respectively. Patients with high turnover bone disease had significantly higher serum PYD levels than patients with normal or low bone turnover, 108.8 +/- 108.0 nM versus 34.1 +/- 12.8 nM, respectively. Serum PYD levels were positively correlated with bone resorption parameters including osteoclast surface (r = 0.59, p < 0.0001) and osteoclast number/mm2 (r = 0.61, p < 0.0001), and also with bone formation parameters, osteoblast surface (r = 0.43, p < 0.008), double-labeled surface (r = 0.81, p < 0.001), and BFR (r = 0.91, p < 0.0001). The BFR was better correlated with serum PYD levels than with either serum iPTH or osteocalcin concentrations. However, correlation with serum bAP was comparable.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased urinary excretion of collagen crosslinks in girls with Ullrich-Turner syndrome

Skeletal abnormalities and "osteoporosis" are frequent features of Ullrich-Turner syndrome (UTS), but their cause remains largely unknown. In this study, we compared the urinary excretion of hydroxyproline (OHP), pyridinoline (PYD) and deoxypyridinoline (DPD) in 28 girls (bone age 3.5-11.0 years, mean 7.4 years) with UTS and 30 healthy prepubertal children (chronological age 3.9-10.9 years, mean 7.6 years). Expressed relative to the square of the height, the excretion of both collagen crosslinks was significantly higher in UTS than in controls (23.4% for PYD, 33.6% for DPD, p < 0.05). In contrast, no significant difference was found for OHP. The molar PYD/DPD ratio was significantly lower in UTS children than in controls (mean (+/- SD) 3.4 (+/- 0.41) versus 3.8 (+/- 0.55); p = 0.004). While the higher excretion of collagen crosslinks reflects enhanced bone resorptive activity in UTS, the lower PYD/DPD ratio might be due to structural alterations in collagen.

Direct, enzyme-linked immunoassay for urinary deoxypyridinoline as a specific marker for measuring bone resorption

Several studies in recent years have shown that the pyridinium crosslinks of collagen provide good urinary markers of collagen degradation, primarily reflecting bone resorption. Most studies, however, were based on time-consuming HPLC assays of the crosslinks. We now describe the development of an immunoassay (ELISA) based on a monoclonal antibody for free deoxypyridinoline (Dpd) and its use in healthy individuals and patients with bone-related disorders to measure the urinary excretion of Dpd as an improved assessment of bone resorption rate. The Dpd antibody exhibited less than 1% cross-reaction with free pyridinoline and was shown to react only with free Dpd in urine, having no significant interaction with peptide forms of the crosslinks. The intra- and interassay variations were less than 10 and 15%, respectively. A total of 402 urine samples from patients and healthy volunteers were analyzed by both the immunoassay and HPLC. The ELISA results were highly correlated with those for total Dpd measured by HPLC over the full range of sample groups (r = 0.95). In normal adults, the excretion of Dpd (mean +/- SD) was 4.7 +/- 1.6 nmol/mmol creatinine, with about fivefold higher excretion rates in children. For 31 osteoporotic patients, the ELISA Dpd values (median 6.7; range 3.0-13.5 nmol/mmol Cr) were significantly higher (p < 0.0001) than the corresponding values for age- and sex-matched controls (median 4.0; range 1.8-7.4). The difference between the groups was similar for total Dpd by HPLC (osteoporotic: mean 12.8, range 4.8-30.7; controls: 6.6, range 3.0-18.1; p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)