Laboratory assessment of nutritional metabolic bone disease in infants

Interference of Parenteral Nutrition Components in Silicon-Mediated Protection Against Aluminum Bioaccumulation

Aluminum and silicon are contaminants found in formulations used to prepare parenteral nutrition. Both elements are leached from glass containers, mainly during the heating cycle for sterilization. Insoluble and biologically inactive species of hydroxyaluminosilicates have been shown to form in solutions containing Al and Si. Therefore, this interaction may play an important role in protecting the body against Al toxicity. In this study, the bioavailability of Al in the presence of Si, calcium gluconate (Gluc.), and potassium phosphate (Phosf.) was investigated in rats. The rats were divided into 10 groups of 5 animals each: control, Al, Si, Al + Si, Gluc, Gluc + Al, Gluc + Al + Si, Phosf, Phosf + Al, and Phosf + Al + Si. The doses, consisting of 0.5 mg/kg/day Al and 2 mg/kg/day Si in the presence or absence of Gluc. or Phosf., were intraperitoneally administered for 3 months. Tissues were analyzed for Al and Si content. Al accumulated in the liver, kidneys, and bones, and the simultaneous administration of Si decreased Al accumulation in these tissues. The presence of Si reduced the amount of Al present by 72% in the liver, by 45% in the kidneys, and by 16% in bone. This effect was lees pronounced in the presence of parenteral nutrition compounds though. Si tissue accumulation was also observed, mainly when administered together with phosphate. These results suggest that Si may act as a protector against Al toxicity, by either reducing Al absorption or increasing its excretion, probably through hydroxyaluminosilicates formation. The presence of calcium gluconate and potassium phosphate decreases or inhibits this effect.

Calcium and Phosphorous in Pediatric Parenteral Nutrition

Calcium (Ca) and phosphorus (P) are essential for various systemic functions, including bone mineralization. Adequate provision of Ca and P in pediatric parenteral nutrition (PN) solutions is necessary for skeletal growth and for the prevention of metabolic bone disease. The provision of adequate doses of Ca and P in pediatric PN solutions is complicated by the increased needs in preterm and term infants, solubility limitations, and venous access. Clinicians should be aware of the evidence that supports the optimal use of Ca and P in pediatric PN solutions, including studies that have evaluated dosing and solubility. The aim of this article is to review relevant literature and practices for the use of these two minerals in pediatric PN solutions. The vitamin D endocrine system, a critical component for Ca homeostasis and bone mineralization, is discussed, as well as clinical manifestations of metabolic bone disease and methods for its prevention, assessment, and treatment in pediatric patients receiving PN.

Metabolic bone disease of prematurity: report of four cases

Osteopenia of prematurity has become a common problem recently because of improved survival rates of infants with very low birth weight (VLBW). The incidence of neonatal osteopenia is inversely correlated with gestational age and birth weight. Herein, we present four cases of preterm osteopenia that were referred to the pediatric endocrinology outpatient clinic with diverse clinical and laboratory findings and we discuss the clinical course of these infants with regard to bone disease after discharge from the neonatal intensive care unit (NICU). This report highlights the importance of enteral calcium, phosphorus and vitamin D support at adequate doses following discharge from NICU for preterm infants with VLBW who are at risk of metabolic bone disease.

Metabolic bone disease of prematurity and secondary hyperparathyroidism

AIM

To illustrate, via case histories, the importance of laboratory investigations for the early diagnosis and management of metabolic bone disease (MBD).

METHODS

We report three cases of extreme premature infants with MBD.

RESULTS

These three infants had several risk factors for MBD of prematurity: very low birthweight, delayed enteral feeds, cholestatic liver disease, intolerance of fortification, the use of glucocorticoids and diuretics. Serum alkaline phosphatase and parathyroid hormone (PTH) were elevated despite relatively normal calcium and phosphate levels. These parameters were corrected with additional supplementation of calcium, phosphate and vitamin D.

CONCLUSIONS

Infants born extremely prematurely have significant calcium and phosphate depletion by the time they reach full term compared with the normal fetal accretion rate. This is exacerbated if there is poor tolerability to feeds where extra calcium and phosphate could not be added either by additives or via human milk fortifier. Serum calcium and phosphate levels may be normal despite inadequate intake or stores due to the counter-regulatory effect of PTH. In infants at risk of MBD, testing serum alkaline phosphatase, vitamin D and PTH with calcium and phosphate may assist in the monitoring and management of MBD.

Ion-exchange and potentiometric characterization of Al–cystine and Al–cysteine complexes

The interaction between aluminium and cysteine and cystine was evaluated by means of ion-exchange experiments and potentiometry. Ion-exchange experiments included other ligands with affinity for aluminium and two kinds of resins, either a Na+ -form or an Al3+ -form exchanger. The ability of the ligands to keep aluminium in solution in the presence of the Na+ exchanger or to withdraw it from the Al3+ -form resin was evaluated. Aluminium quantification was carried out by either graphite-furnace or flame atomic absorption spectrometry. Aluminium extraction isotherms were linearised using the Scatchard plot, and stability constants were obtained from the curves' slopes. The experiments showed that the ability of the ligands to withdraw aluminium from the Al3+ -form resin increased following the order cysteine < oxalate < citrate = cystine < nitrilotriacetic acid < ethylenediaminetetraacetic acid. Potentiometric titrations, carried out in aqueous solution with constant ionic strength and temperature, showed that the predominant species in solution have a metal-ligand proportion of 1:1 for both amino acids. The main species are Al(OH)3L, with log K of 6.2 for cysteine, and AlL and Al(OH)L, with log K of 10.3 and 1.7, respectively, for cystine. Stability constants obtained from the Scatchard plots showed a linear correlation with the stability constants obtained by potentiometry for cystine and cysteine in this work and those collected from the literature for the other ligands. These results show that cysteine and cystine extract and maintain aluminium in solution, which may explain elevated concentrations of aluminium in parenteral nutrition solutions containing these amino acids.

Effect of consumption of food cooked in aluminium or stainless-steel pots on Bangladeshi children with calcium-deficient rickets: an eight month trial

The putative role of aluminium intake in young Bangladeshi children (1.5 to 4 years of age) with calcium-deficient rickets was evaluated in a non randomised controlled eight month trial. The effects of aluminium or stainless-steel cooking pots on bone metabolism were assessed by measuring blood calcium, phosphorus, alkaline phosphatase, parathyroid hormone, 1,25 dihydroxy vitamin D, aminoterminal propeptide of type 1 collagen (PINP), cross-linked carboxyterminal telopeptide of type 1 collagen (ICTP), aluminium and albumin, and by analysis of wrist radiographs. In both groups, blood alkaline phosphatase, 1,25 dihydroxy vitamin D and aluminium decreased significantly, white serum albumin increased (p < 0.01). These results suggest that the nutrition may well be of major importance, whereas the role of aluminium appears to be insignificant.

Calcium and bone health in infants

Osteopenia, rickets, and fractures from nutrient deficiencies can occur during infancy, particularly in preterm infants. Bone mass accretion during the first year of life is equal to or greater than that achieved at any other stage of life, including adolescence. Optimizing calcium and bone status during infancy can have immediate benefits in maintaining calcium homeostasis and preventing disturbances in bone mineralization and can provide long-term benefits by helping infants to later reach their maximum genetic potential for peak bone mass, a prerequisite for the prevention of osteoporosis and its complications. Dietary calcium requirements during infancy generally reflect the need to achieve normal growth and bone mineralization because 99 percent of total body calcium is present in the skeleton. Knowledge of physiologic factors that determine infant calcium requirements and the bioavailability of calcium from various dietary sources is important to ensuring bone health during infancy. Also key are the practical issues related to optimizing calcium nutriture in infants born at term and prematurely.

Influence of the glass packing on the contamination of pharmaceutical products by aluminium. Part III: Interaction container-chemicals during the heating for sterilisation

The interaction of chemicals with the container materials during heating for sterilisation was investigated, storing the components of parenteral nutrition solutions individually in sealed glass ampoules and in contact with a rubber stopper, and heating the system at 121 degrees C for 30 min. Subsequently, the aluminium content of the solutions was measured by atomic absorption spectrometry (AAS). The assay was also carried out with acids, alkalis and some complexing agents for Al. The containers were decomposed and also assayed for aluminium. 30 different commercial solutions for parenteral nutrition, stored either in glass or in plastic containers, were assayed measuring the aluminium present in the solutions and in the container materials. The results of all investigated container materials revealed an aluminium content of 1.57% Al in glass, 0.05% in plastic and 4.54% in rubber. The sterilisation procedure showed that even pure water was able to extract Al from glass and rubber, 22.5 +/- 13.3 microg/L and 79.4 +/- 22.7 microg/L respectively, while from plastic the aluminium leached was insignificant. The Al released from glass ampoules laid between 20 microg/L for leucine, ornithine and lysine solutions and 1500 microg/L for solutions of basic phosphates and bicarbonate; from rubber stoppers it reached levels over 500 microg/L for cysteine, aspartic acid, glutamic acid and cystine solutions. Ion-exchange properties and influence of pH can explain the interaction of glass with some chemicals (salts, acids and alkalis), but only an affinity for aluminium could explain the action of some amino acids and other chemicals, as albumin and heparin, on glass and rubber, considering the aluminium release. Experiments with complexing agents for Al allowed to conclude that the higher the stability constant of the complex, the higher the Al release from the container material.

Influence of the glass packing on the contamination of pharmaceutical products by aluminium. Part II: amino acids for parenteral nutrition

The presence of aluminium in amino acids parenteral nutrition solutions can be related to the affinity of the amino acids for aluminium present in glass containers used for storage. For this study solutions of 19 amino acids used in parenteral nutrition were stored individually in glass flasks and the aluminium measured at determined time intervals. Solutions of complexing agents for aluminium, as ethylene-diaminetetraacetic acid, nitrilotriacetic acid, citrate, oxalate and fluoride ions were also stored in the same flasks and the aluminium measured during the same time interval. The measurements were made by electrothermal atomic absorption spectrometry. The aluminium content of the glass containers was also measured. The results showed that the glasses have from 0.6% to 0.8% Al. Only solutions of cysteine, cystine, aspartic acid and glutamic acid became contaminated by aluminium. As the same occurred with the complexing agents, aluminum can be released from glass due to an affinity of the substances for aluminium. Comparing the action of complexing agents and amino acids for which the stability constants of aluminium complex are known, it is possible to relate the magnitude of the stability constant with the aluminium leached from glass, the higher the stability constant, the higher the aluminium released. The analysis of commercial formulations with and without cysteine, cystine, glutamic acid or aspartic acid stored in glass containers confirms that the presence of these amino acids combined with the age of the soLution are, at least partially, responsible for the aluminium contamination. The resuLts demonstrated that the contamination is an ongoing process due to the presence of aluminium in glass combined with the affinity of some amino acids for this element.

Do sweat calcium losses affect bone mass during firefighter training?

Although participation in vigorous exercise is associated with increased bone mass, recent evidence suggests that loss of calcium in sweat may result in a negative calcium balance and, ultimately, a decrease in bone mass. Anthropometric characteristics, habitual physical activity levels, dietary calcium intake, bone mineral content, and bone turnover markers were measured in 42 male recruits before and after 4 months of firefighter training. During two strenuous mid-training sessions, sweat calcium concentrations were measured; they averaged 1.1 mM. Whole body and total hip bone mineral content increased significantly, as did one marker of bone formation, and were not associated with sweat calcium concentration. This study demonstrates that intense physical training sessions that produce high sweat rates do not have an adverse effect on the bone mineral content of healthy young men.