Aluminum loading during total parenteral nutrition

Evaluating the Toxicity and Histological Effects of Al2O3 Nanoparticles on Bone Tissue in Animal Model: A Case-Control Study

The applications of nanostructures have been limited by their different toxicities. So, the investigation of these toxicities is necessary before nanostructure application. This study aimed to evaluate the effect of aluminum oxide (Al₂O₃) nanoparticles on bone density in Wistar rat. Al₂O₃ nanoparticle was prepared by the sol-gel method. Characterization was done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Sixty-four male adult Wistar rats were divided into eight groups including six groups intravenously treated with Al₂O₃ nanoparticle at concentrations of 25, 50, 100, 250, 500, and 1000 µg/ml: one group received food and water as the control group, and one group received food and water as well as intravenously distilled water as an injection control group. After 41 days, bone density was analyzed by dual-energy X-ray absorptiometry (DEXA). According to X-ray diffraction, the average particle size for Al₂O₃ nanoparticles was 20.85 nm. The data of densitometry showed that the bone density of right and left foot was reduced in concentrations of 250, 500, and 1000 µg/ml that were statistically significant in comparison with the control group. The reduction of bone density was increased with the enhancement of nanostructures concentration. The effect of Al₂O₃ nanoparticles on bone density was similar in the left and right legs. Histopatholological assessment also showed that Al₂O₃ nanoparticles (250, 500, and 1000 µg/ml) lead to significant reduction of trabeculae. Empty lacunae are observed in these three groups. Considering that high concentrations of Al₂O₃ nanoparticles had toxicity on bone tissue, it must be used by more caution, especially its use as a coating in different devices such as implants, surgical instruments, and bone prostheses.

Determination of aluminum concentrations of parenteral nutrition solutions by HPLC

Aluminum (Al) contamination of parenteral nutrition (PN) solutions has been known for over 30 years. In particular, vascular intake of Al leads to its accumulation in tissues. In this study, 8 all-in-one PN solutions the aluminum concentration was analyzed by high-performance liquid chromatography. The mean Al concentration of the glucose solutions of the PN solutions combinations was 16.36 ± 8.31 µg/L, the mean Al concentration of the amino acid solutions was 4.96 ± 3.73 µg/L, and the mean Al concentration of the lipid solutions was 9.09 ± 11.23 µg/L. The Al concentration of the PN₅ glucose and PN₂ lipid solutions were above 25 µg/L, which is the limit set by the Food and Drug Administration (FDA). No studies in the literature have examined the Al concentrations of all-in-one PN solutions via HPLC. In two of the analyzed solutions, the Al concentration was found to be higher than the limit set by the FDA.

Metabolic bone diseases in intestinal failure

Metabolic bone diseases are a group of conditions that are common complications in patients with intestinal failure. These may occur as a result of the underlying condition, leading to intestinal failure, particularly inflammatory conditions such as Crohn's disease and their associated treatments including corticosteroids. Malabsorption, as a result of a loss of enterocyte mass or gut function, of many nutrients, including vitamin D, may further compound metabolic bone problems, and there has been historical contamination of parenteral nutrition with aluminium that has prevented normal bone metabolism contributing to osteoporosis. This review looks at the diagnosis and current management of bone health in patients with intestinal failure.

Aluminum toxicity to bone: A multisystem effect?

Aluminum (Al) is the third most abundant element in the earth's crust and is omnipresent in our environment, including our food. However, with normal renal function, oral and enteral ingestion of substances contaminated with Al, such as antacids and infant formulae, do not cause problems. The intestine, skin, and respiratory tract are barriers to Al entry into the blood. However, contamination of fluids given parenterally, such as parenteral nutrition solutions, or hemodialysis, peritoneal dialysis or even oral Al-containing substances to patients with impaired renal function could result in accumulation in bone, parathyroids, liver, spleen, and kidney. The toxic effects of Al to the skeleton include fractures accompanying a painful osteomalacia, hypoparathyroidism, microcytic anemia, cholestatic hepatotoxicity, and suppression of the renal enzyme 25-hydroxyvitamin D-1 alpha hydroxylase. The sources of Al include contamination of calcium and phosphate salts, albumin and heparin. Contamination occurs either from inability to remove the naturally accumulating Al or from leeching from glass columns used in compound purification processes. Awareness of this long-standing problem should allow physicians to choose pharmaceutical products with lower quantities of Al listed on the label as long as this practice is mandated by specific national drug regulatory agencies.

An assessment of exposure to rare earth elements among patients receiving long-term parenteral nutrition

Patients receiving long-term parenteral nutrition (PN) are exposed to potentially toxic elements, which may accumulate in bone. Bone samples collected from seven PN patients (average = 14 years) and eighteen hip/knee samples were analyzed for Al as part of a previous investigation. Yttrium was serendipitously detected in the PN bone samples, leading to the present investigation of rare earth elements (REEs). A method for quantitating fifteen REEs in digested bone was developed based on tandem ICP-MS (ICP-MS/MS) to resolve spectral interferences. The method was validated against nine biological reference materials (RMs) for which assigned values were available for most REEs. Values found in two NIST bone SRMs (1400 Bone Ash and 1486 Bone Meal) compared favorably to those reported elsewhere. Method detection limits ranged from 0.9 ng g^-1 (Tm) to 5.8 ng g^-1 (Y). Median REE values in the PN patient group were at least fifteen times higher than the "control" group, and exceeded all previously reported data for eleven REEs in human bones. REE content in PN bones normalized to the Earth's upper crust revealed anomalies for Gd in two patients, likely from exposure to Gd-containing contrast agents used in MRI studies. A retrospective review of the medical record for one patient revealed an almost certain case of nephrogenic systemic fibrosis, associated with Gd exposure. Analysis of two current PN formulations showed traces of REEs with relative abundances similar to those found in the PN bones, providing convincing evidence that PN solutions were the primary source of REEs in this population.

A Review of the Relationship Between Parenteral Nutrition and Metabolic Bone Disease

Metabolic bone disease (MBD) refers to the conditions that produce a diffuse decrease in bone density and strength because of an imbalance between bone resorption and bone formation. MBD can be a potential complication in patients receiving chronic parenteral nutrition (PN) therapy and the management of this condition presents a challenge for many clinicians. The etiology of PN-associated MBD is poorly understood, but traditional risk factors can include malnutrition, vitamin and mineral deficiencies, toxic contaminants in the PN solution, concomitant medications, and presence of certain disease states. Although additional studies are warranted to further elucidate the development and management of this condition, the following review discusses some of the important factors that may play a role in the genesis of PN-associated MBD and evaluates some potential strategies for the diagnosis and treatment of this complication.

Bone deficits in parenteral nutrition-dependent infants and children with intestinal failure are attenuated when accounting for slower growth

OBJECTIVE

The aim of the present study was to determine whether bone mineral content (BMC) and density (BMD) of infants and children with parenteral nutrition (PN)-dependent intestinal failure (IF) is lower than healthy controls, and investigate potential causes of lower BMC and BMD.

METHODS

We performed a cross-sectional study comparing infants and children with PN-dependent IF with duos of age-, sex-, and race-matched controls. Lumbar spine BMC and BMD were measured by dual-energy x-ray absorptiometry, and serum cytokines, aluminum, insulin-like growth factor-1 (IGF-1), IGF-binding protein 3 (IGF-BP3), parathyroid hormone, 25-hydroxy vitamin D, and 1,25-dihydroxy vitamin D were measured. Generalized estimating equation models accounting for matching were used for comparisons.

RESULTS

BMC was 15% and BMD was 12% lower in IF participants than in controls (P ≤ 0.004). Group differences were attenuated to 3% and 7% and were not statistically significant (P = 0.40 and P = 0.07) when adjusted for length and weight; length- and weight-for-age were lower in IF than in control participants (12.5% vs 63%; 29.5% vs 54%, P ≤ 0.03). IF participants had higher serum aluminum (23 vs 7 μg/L, P < 0.0001), IGF-1 (97 vs 64 ng/mL, P = 0.04), and 25-hydroxy vitamin D concentrations (40 vs 30 ng/mL, P = 0.0005), and lower IGF-BP3 (1418 vs 1812 ng/mL, P < 0.0001) and parathyroid hormone concentrations (51 vs 98 pg/mL, P = 0.0002) than controls. There was no difference in serum cytokine concentrations (P ≥ 0.09).

CONCLUSIONS

Growth retardation is a significant problem for patients with PN-dependent IF. Additional investigation is needed to elucidate the cause and its effect on bone mass and density, especially the role of IGF-1 resistance and aluminum toxicity.

Review article: the management of long-term parenteral nutrition

BACKGROUND

Home parenteral nutrition (HPN) is currently the management of choice for patients with chronic intestinal failure.

AIM

To summarise the major issues in delivering long-term parenteral nutrition (>3 months) and assess outcome as per complications, mortality and quality of life. To assess the evidence for the therapeutic use of trophic factors such as teduglutide and to review evolving therapeutic options in the treatment of chronic intestinal failure.

METHODS

A literature search using PubMed and MEDLINE databases was performed.

RESULTS

Safe delivery of HPN relies upon individualised formulations of parenteral nutrition administered via carefully maintained central venous catheters by trained patients or carers, supported by a skilled multidisciplinary team. Early diagnosis and treatment of complications including catheter-associated blood stream infection (reported incidence 0.14-0.83 episodes/patient-year on HPN) and central venous thrombosis (reported incidence 0.03 episodes/patient-year) is important to minimise mortality and morbidity. There is a significant variation in the reported incidence of both hepatobiliary complications (19-75%) and advanced liver disease (0-50%). Five-year survival rates in large centres are reported between 60% and 78% with survival primarily related to underlying diagnosis. Long-term survival remains higher on HPN than with intestinal transplantation. The role of intestinal lengthening procedures is yet to be validated in adults.

CONCLUSIONS

Home parenteral nutrition delivered by skilled nutrition teams has low incidences of catheter-related complications. Most deaths relate to the underlying disease. Therapies such as teduglutide and small bowel transplantation appear promising, but home parenteral nutrition appears likely to remain the bedrock of management in the near term.

Reduced aluminum contamination decreases parenteral nutrition associated liver injury

PURPOSE

Parenteral nutrition-associated cholestasis remains a significant problem, especially for the surgical neonates. Aluminum is a toxic element known to contaminate parenteral nutrition. We hypothesize that parenterally administered aluminum causes liver injury similar to that seen in parenteral nutrition-associated cholestasis.

METHODS

Twenty 3- to 6-day-old domestic pigs were divided into 5 equal groups. A control group received daily intravenous 0.9% NaCl. Each subject in experimental groups received intravenous aluminum chloride at 1500 μg kg(-1) d(-1) for 1, 2, 3, or 4 weeks. At the end of the study, blood was sampled for direct bilirubin and total bile acid levels. Liver, bile, and urine were sampled for aluminum content. Liver tissue was imaged by transmission electron microscopy for ultrastructural changes.

RESULTS

Transmission electron microscopy revealed marked blunting of bile canaliculi microvilli in all experimental subjects but not the controls. Serum total bile acids correlated with the duration of aluminum exposure. The hepatic aluminum concentration correlated with the duration of aluminum exposure.

CONCLUSIONS

Parenterally infused aluminum resulted in liver injury as demonstrated by elevated bile acids and by blunting of the bile canaliculi microvilli. These findings are similar to those reported in early parenteral nutrition-associated liver disease.

Determination of aluminium and physicochemical parameters in the palm oil estates water supply at Johor, Malaysia

The study was to determine the concentration of aluminium (Al) and study the physicochemical parameters (pH, total dissolved solids (TDS), turbidity, and residual chlorine) in drinking water supply in selected palm oil estates in Kota Tinggi, Johor. Water samples were collected from the estates with the private and the public water supplies. The sampling points were at the water source (S), the treatment plant outlet (TPO), and at the nearest houses (H1) and the furthest houses (H2) from the TPO. All estates with private water supply failed to meet the NSDWQ for Al with mean concentration of 0.99 ± 1.52 mg/L. However, Al concentrations in all public water supply estates were well within the limit except for one estate. The pH for all samples complied with the NSDWQ except from the private estates for the drinking water supply with an acidic pH (5.50 ± 0.90). The private water supply showed violated turbidity value in the drinking water samples (14.2 ± 24.1 NTU). Insufficient amount of chlorination was observed in the private water supply estates (0.09 ± 0.30 mg/L). Private water supplies with inefficient water treatment served unsatisfactory drinking water quality to the community which may lead to major health problems.

The Effects Of Sucralfate Ingestion On Serum And Specific Tissue Aluminum Concentration In Normal Rats

The effects of sucralfate ingestion on serum and specific tissue aluminum (Al) accumulation were studied in normal rats fed either a control diet or the same diet supplemented with sucralfate. Although serum Al concentrations were not significantly different between the groups, animals fed sucralfate for 8 weeks had significantly higher bone but not brain or liver Al concentrations when compared with controls. This study indicates that 8 weeks exposure to Al in sucralfate leads to an increase in bone Al concentrations, without changes in serum Al concentrations, suggesting that serum Al concentration may be a poor predictor of gastrointestinal absorption and specific tissue retention of Al.

Essential trace element provision to patients receiving home intravenous nutrition in the United Kingdom

The methods of provision of essential trace elements to patients receiving long-term home intravenous nutrition in the U.K. have been reviewed and their trace element status has been assessed. Over a 2 year period, 57 patients based on 15 hospitals throughout the country were studied. Although biochemical abnormalities of trace element status were frequent, related clinical complications were apparently rare. Zinc provision from commercial preparations generally required further supplementation. Copper requirements were variable. Manganese provision from trace element mixtures and chromium provision from contaminants of other parenteral nutrient solutions were excessive in many cases. Aluminium contamination is not significant in the nutrient solutions currently used in the U.K. The most common depletion state is for selenium which should probably be provided on a routine basis. The clinical consequences of long-term under- or over-provision of trace elements by the intravenous route requires further study.

Recent developments in aluminium contamination of products used in parenteral nutrition

PURPOSE OF REVIEW

This review evaluates recent developments concerning aluminium contamination of products used in the preparation of parenteral nutrition solutions and the failure of the pharmaceutical industry to respond to these concerns. The difficulty in meeting the intent of the recent US Food and Drug Administration mandate to reduce aluminium exposure with currently available parenteral nutrition additives is addressed. This review also summarizes the issues associated with aluminium toxicity, the patient populations at risk, treatment options, and compounding considerations.

RECENT FINDINGS

Unfortunately, the published literature detailing the toxicities seen from aluminium exposure in the parenteral nutrition patient are primarily limited to those published in the 1980s and 1990s. Recent publications refer back to these classic papers and discuss the challenges that practitioners face when trying to apply the recommendations of the recently implemented Food and Drug Administration mandate with outdated literature. Few studies have been published to validate those earlier findings.

SUMMARY

The issues surrounding aluminium toxicity are real and must be addressed. In order to make meaningful changes in clinical practice, low aluminium parenteral nutrition additives are needed and studies must be conducted using currently available products. It remains a challenge to optimize nutritional intake from parenteral nutrition and at the same time reduce aluminium exposure.

Metabolic bone disease and parenteral nutrition

Metabolic bone disease (MBD) is abnormal bone metabolism and includes the common disorders of osteoporosis and osteomalacia, which can develop in patients receiving long-term parenteral nutrition (PN). Patients who require long-term PN have significant gastrointestinal failure and malabsorption, which is generally caused by severe inflammatory bowel disease, intestinal ischemia, or malignancy. The exact cause of MBD in long-term PN patients is unknown, but its origin is thought to be multifactorial, with factors including underlying disease, effect of medications used to treat this disease (eg, corticosteroids), and various components of the PN solution. Caring for patients on long-term PN requires routine assessment and monitoring for MBD. Appropriate adjustments of the PN solution can help reduce the risk for developing PN-associated MBD and in some instances improve bone mineral density. Recent developments in pharmacologic treatment for osteoporosis show promise for patients with MBD receiving PN.

Hepatobiliary, renal and bone complications of intestinal failure

Abnormal liver function tests in patients with intestinal failure (IF) may be due to the underlying disease, IF or the treatments given (including parenteral nutrition (PN)). PN-related liver disease in children usually relates to intrahepatic cholestasis and in adults to steatosis. Steatosis may be consequent upon an excess of carbohydrate, lipid or protein, or upon a deficiency of a specific molecule. Pigment-type gallstones are common in adults and children with IF; these develop from biliary sludge that forms during periods of gallbladder stasis. Ileal disease/resection, parenteral nutrition, surgery, rapid weight loss and drugs all increase the risk of developing gallstones. Gallstone formation may be prevented by reducing gallbladder stasis (oral/enteral feeding or prokinetic agents), altering bile composition, or by means of a prophylactic cholecystectomy. Calcium oxalate renal stones are common in patients with a short bowel and retained functioning colon and are consequent upon increased absorption of dietary oxalate; they are prevented by a low-oxalate diet. An osteopathy may occur with long-term parenteral nutrition.

Aluminum contamination of parenteral nutrition and aluminum loading in children on long-term parenteral nutrition

BACKGROUND

Children who are receiving parenteral nutrition are at risk of aluminum overload, which may contribute to such side effects as osteopenic bone disease. The aim of the present study is to determine the aluminum contamination of parenteral nutrition solutions and their components, and to assess the aluminum status of children on long-term parenteral nutrition.

METHODS

Aluminum concentrations were determined by graphite furnace absorption spectroscopy in components and in final parenteral nutrition solutions. The urinary aluminum excretion and plasma aluminum concentration were determined in 10 children on long-term parenteral nutrition.

RESULTS

The mean aluminum concentration in the administered parenteral nutrition solutions was 1.6 +/- 0.9 micromol x l(-1)(mean +/- standard deviation (SD)). The resulting mean aluminum daily intake of the 10 patients was 0.08 +/- 0.03 micromol x kg(-1) x day(-1).

CONCLUSIONS

Compared to two previous studies performed in 1990 and in 1995 in our hospital, the aluminum contamination of parenteral nutrition solutions and the daily aluminum intake of the children seemed to decrease. However, the plasma aluminum concentration and daily urinary aluminum excretion of the children still remain above normal standards. The children had no clinical symptoms of bone disease but aluminum accumulation in tissue can not be excluded. To prevent this iatrogenic toxicity, the aluminum contamination of parenteral nutrition should be assessed regularly.

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.

Complications of long-term home total parenteral nutrition: their identification, prevention and treatment

The purpose of this review is to describe the most common complications of home total parenteral nutrition, their identification, treatment and prevention. Data sources were manuscripts and abstracts published in the English literature since 1968. Studies were selected for summarization in this review on the basis of clinical relevance to the practicing clinician. Home total parenteral nutrition is a relatively safe, life-saving method for nutrient delivery in patients with compromised gastrointestinal function. However, numerous complications, with associated morbidity and mortality, involving the delivery system and the gastrointestinal, renal, and skeletal systems may develop. Catheter-related complications are often preventable and treatable when they occur, although renal and bone abnormalities have elusive etiologies.

Safety evaluation of dietary aluminum

Aluminum is a nonessential metal to which humans are frequently exposed. Aluminum in the food supply comes from natural sources, water used in food preparation, food ingredients, and utensils used during food preparations. The amount of aluminum in the diet is small, compared with the amount of aluminum in antacids and some buffered analgesics. The healthy human body has effective barriers (skin, lungs, gastrointestinal tract) to reduce the systemic absorption of aluminum ingested from water, foods, drugs, and air. The small amount of aluminum (<1%) that is systemically absorbed is excreted principally in the urine and, to a lesser extent, in the feces. No reports of dietary aluminum toxicity to healthy individuals exist in the literature. Aluminum can be neurotoxic, when injected directly into the brains of animals and when accidentally introduced into human brains (by dialysis or shrapnel). A study from Canada reports cognitive and other neurological deficits among groups of workers occupationally exposed to dust containing high levels of aluminum. While the precise pathogenic role of aluminum in Alzheimer's disease (AD) remains to be defined, present data do not support a causative role for aluminum in AD. High intake of aluminum from antacid for gastrointestinal ailments has not been reported to cause any adverse effects and has not been correlated with neurotoxicity or AD. Foods and food ingredients are generally the major dietary sources of aluminum in the United States. Cooking in aluminum utensils often results in statistically significant, but relatively small, increases in aluminum content of food. Common aluminum-containing food ingredients are used mainly as preservatives, coloring agents, leavening agents, anticaking agents, etc. Safety evaluation and approval of these ingredients by the Food and Drug Administration indicate that these aluminum-containing compounds are safe for use in foods.

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.

Altered diurnal regulation of blood ionized calcium and serum parathyroid hormone concentrations during parenteral nutrition

BACKGROUND

Little is known about parathyroid gland function in patients receiving total parenteral nutrition (TPN).

OBJECTIVE

Our objective was to determine whether parathyroid gland function is abnormal in TPN recipients.

DESIGN

Six patients with a mean (+/-1 SD) age of 45.5 +/- 8.0 y who had been receiving TPN for 18.7 +/- 2. 8 y underwent bone biopsy, bone mass measurements with dual-energy X-ray absorptiometry, and dynamic tests of parathyroid gland function. Diurnal variations in blood ionized calcium (iCa(2+)) and serum parathyroid hormone (PTH) concentrations were also assessed. Results were compared with those of healthy volunteers.

RESULTS

Bone mass and bone formation were subnormal in all patients. Basal serum PTH concentrations were moderately higher in the TPN recipients than in healthy volunteers, and values obtained every 30 min over 24 h were significantly higher (P < 0.001) in TPN recipients (5.0 +/- 0.9 pmol/L) than in healthy volunteers (2.6 +/- 0.6 pmol/L). The percentage increase in serum PTH during citrate-induced hypocalcemia was lower in the TPN recipients, consistent with secondary hyperparathyroidism. Evening infusions of calcium-containing TPN eliminated the nocturnal rise in serum PTH, increased the amplitude of change for iCa(2+) and PTH over 24 h, increased the orderliness of change for iCa(2+) and PTH as measured by approximate entropy (ApEn), and enhanced the synchrony of change between iCa(2+) and PTH. Treatment for 10 d with calcium-free TPN restored the nocturnal rise in serum PTH and increased ApEn for PTH. ApEn for iCa(2+) remained low, suggesting that a component of nutrient solutions, but not calcium per se, enhances the regularity of PTH release in TPN recipients.

CONCLUSION

Parathyroid gland function is abnormal in long-term TPN recipients, which may contribute to disturbances in bone metabolism.

The application of in vitro data in the derivation of the acceptable daily intake of food additives

The acceptable daily intake (ADI) for food additives is commonly derived from the NOAEL (no-observed-adverse-effect level) in long-term animal in vivo studies. To derive an ADI a safety or uncertainty factor (commonly 100) is applied to the NOAEL in the most sensitive test species. The 100-fold safety factor is considered to be the product of both species and inter-individual differences in toxicokinetics and toxicodynamics. Although in vitro data have previously been considered during the risk assessment of food additives, they have generally had no direct influence on the calculation of ADI values. In this review 18 food additives are evaluated for the availability of in vitro toxicity data which might be used for the derivation of a specific data-derived uncertainty factor. For the majority of the food additives reviewed, additional in vitro tests have been conducted which supplement and support the short- and long-term in vivo toxicity studies. However, it was recognized that these in vitro studies could not be used in isolation to derive an ADI; only when sufficient in vivo mechanistic data are available can such information be used in a regulatory context. Additional short-term studies are proposed for the food additives which, if conducted, would provide data that could then be used for the calculation of data-derived uncertainty factors.

Longitudinal and lateral variations in the aluminum concentration of selected caprine, bovine, and human bone samples

Longitudinal and lateral variations in Al concentration in several large animal (bovine and caprine) long bones (tibia and femur) and several human clavicle bones were examined using a sensitive analytical method based on electrothermal atomization atomic absorption spectrometry with Zeeman background correction. Bone segments were carefully removed using special tools free of significant Al contamination, freeze-dried, and digested overnight at room temperature in concentrated HNO3. Bone digestates were analyzed for Al using simple aqueous calibration standards with a Ca(NO3)2 modifier. Mean bone Al concentrations were relatively low (<1 microg/g, dry weight) in bovine and caprine long bones compared to literature values for human bone samples. Longitudinal variations of Al in the animal bones examined appeared relatively uniform compared to the human clavicle bones, where, in three of five cases, Al appeared enriched at the epiphyses (joints). The Al "enrichment" was symmetrical with respect to both left and right clavicle bones. Aluminum concentrations at the mid-shaft of the clavicle bone show less variation compared to whole bone studies, but considerable scatter is evident along the bone length. The mean bone aluminum concentration in the five human subjects varied from 1 to 6 microg/g dry weight.

Bone turnover in preterm infants

Total parenteral nutrition is associated with osteopenia in preterm infants. Insufficient calcium and phosphate are likely causes: aluminum contamination is another possible contributing factor as this adversely affects bone formation and mineralization. The study was designed to evaluate changes in biochemical markers of bone turnover in 22 preterm infants receiving total parenteral nutrition in comparison with 19 term infants. We collected urine and serum samples from 22 preterm infants, mean gestational age 29 wk, within 48 h and again at 3 wk of life. We also collected urine samples from 19 term infants, mean gestational age 39 wk, during the first day of life. Bone resorption was assessed by the measurement of urinary pyridinium cross-links by HPLC and ELISA and the N-telopeptide of type I collagen by ELISA. Bone formation was assessed in premature infants by the measurement of serum osteocalcin. The N-telopeptide of type I collagen was higher in the preterm infants compared with term at baseline (p < 0.01). There was no difference between the pyridinium cross-links in the preterm and term infants. All the biochemical markers of bone turnover increased significantly in the preterm infants during the first 3 wk of life, e.g. N-telopeptide was a 153% change from baseline (p < 0.001). Aluminum in the total parenteral nutrition solutions did not cause a decrease in bone formation at the level administered (3-6 microg, 0.1-0.2 micromol x kg(-1) x d(-1)).

Aluminum in total parenteral nutrition solutions produces portal inflammation in rats

BACKGROUND

Aluminum contaminates parenteral nutrition solutions and accumulates in bone and liver of patients receiving total parenteral nutrition therapy. Although previous reports have shown that parenteral administration of aluminum in pharmacologic doses to rats results in the production of elevated total serum bile acid concentrations alone or in combination with decreased bile flow, they have failed to demonstrate any abnormalities in the histologic appearance of liver tissue. The effects of aluminum in total parenteral nutrition and of aluminum chloride on total serum bile acid concentrations, aluminum contents of the liver, and histopathologic changes in the liver were studied in rats.

METHODS

The aluminum concentrations in the aluminum chloride solution and total parenteral nutrition formula were equal (300 microg/l). They were given intraperitoneally as follows: control group, 0.9% saline for 14 days; T7 group, total parenteral nutrition for 7 days; A7 group, aluminum chloride for 7 days; A14 group, aluminum chloride for 14 days; T7A7 group, total parenteral nutrition for 7 days and aluminum chloride for the next 7 days; and T7O7 group, total parenteral nutrition for 7 days and 0.9% saline for the next 7 days. Volumes of 0.9% saline, aluminum chloride, and total parenteral nutrition given to rats were equal. During the experiment, rats were maintained on rat chow and water ad libitum. Serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, alkaline phosphatase, and bile acid concentrations and aluminum content of the liver were measured. The liver was evaluated histopathologically by light microscope, and a morphologic portal inflammation index was calculated.

RESULTS

Portal inflammation was present in all groups except the control group. The morphologic portal inflammation correlated with hepatic aluminum accumulation in all groups and was the highest in the T7A7 group. Levels of serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, and alkaline phosphatase did not correlate with the histopathologic findings, but serum bile acid concentrations correlated with morphologic portal inflammation and hepatic aluminum accumulation in all groups. Hepatic aluminum accumulation also correlated with the duration of exposure to total parenteral nutrition and aluminum chloride concentration.

CONCLUSION

Aluminum in contaminating doses, not in pharmacologic doses, accumulates in the liver and can produce hepatobiliary dysfunction characterized by portal inflammation detectable in histologic examination of liver tissue.

Metabolic bone disease of total parenteral nutrition

Parenteral nutrition-associated metabolic bone disease in children is manifested primarily as osteopenia and, on occasion, fractures. The etiology is likely multifactorial, with calcium and phosphate deficiency playing a major role in the preterm infant and with the role of aluminum toxicity yet to be clearly defined in this population. Lack of normal values of bone histomorphometry in the premature infant as well as lack of normal data for biochemical markers of bone turnover in these patients contribute to the uncertainty. Other factors that may play a role in the pathogenesis include lack of periodic enteral feeding; underlying intestinal disease, including malabsorption and inflammation; the presence of neoplasms; and drug-induced alterations in calcium and bone metabolism. The true incidence and prevalence of parenteral nutrition-associated bone abnormalities in pediatric patients remain unknown.

Aluminum exposure and metabolism

Aluminum (Al) is a nonessential, toxic metal to which humans are frequently exposed. Oral exposure to aluminum occurs through ingestion of aluminum-containing pharmaceuticals and to a lesser extent foods and water. Parenteral exposure to aluminum can occur via contaminated total parenteral nutrition (TPN), intravenous (i.v.) solutions, or contaminated dialysates. Inhalation exposure may be important in some occupational settings. The gut is the most effective organ in preventing tissue aluminum accumulation after oral exposure. Typically gastrointestinal absorption of aluminum from diets is < 1%. Although the mechanisms of aluminum absorption have not been elucidated, both passive and active transcellular processes and paracellular transport are believed to occur. Aluminum and calcium may share some absorptive pathways. Aluminum absorption is also affected by the speciation of aluminum and a variety of other substances, including citrate, in the gut milieu. Not all absorbed or parenterally delivered aluminum is excreted in urine. Low glomerular filtration of aluminum reflects that most aluminum in plasma is nonfiltrable because of complexation to proteins, predominantly transferrin. The importance of biliary secretion of aluminum is debatable and the mechanism(s) is poorly understood and appears to be saturable by fairly low oral doses of aluminum.

Effects of aluminum chloride on normal and uremic adult male rats. Tissue distribution, brain choline acetyltransferase activity, and some biological variables

Normal and uremic adult male rats were given a daily ip injection of 20 mg Al (Al chloride)/kg for 14 d. The results indicate that Al induces a significant decrease in food ingestion, weight gain, and total protein concentration in the plasma. Compared with control animals, very high increases in Al levels were found in plasma and hepatic homogenates (about 36 and 19 times, respectively). In the brain homogenates, the Al increases were lower (about 23%). The brain cholineacetyltransferase activity was reduced: 10.6 and 14.9% in normal and uremic rats, respectively. The nephrectomy and the food restriction did not affect the total protein concentrations in plasma and the cerebral cholineacetyltransferase activity. Both were only found to be reduced in the rats treated by Al chloride.

Biological indicators of exposure to total and respirable aluminium dust fractions in a primary aluminium smelter

OBJECTIVES

The study attempts to define biological indicators of aluminium uptake and excretion in workers exposed to airborne aluminium compounds in a primary aluminium smelter. Also, this study defines the total and respirable aluminium dust fractions in two different potrooms, and correlates their concentrations with biological indicators in this group of workers.

METHODS

Air was sampled at defined work sites. Non-destructive and conventional techniques were used to find total and respirable aluminium content of the dust. Blood and urine was collected from 84 volunteers employed at various work stations throughout the smelter and from two different cohorts of controls matched for sex, age, and socioeconomic status. Aluminium in serum samples and urine specimens was measured by flameless atomic absorption with a PE 4100 ZL spectrometer.

RESULTS

The correlation of aluminium concentrations in serum and urine samples with the degree of exposure was assessed for three arbitrary exposure categories; low (0.036 mg Al/m3), medium (0.35 mg Al/m3) and high (1.47 mg Al/m3) as found in different areas of the smelter. At medium and high exposure, the ratio of respirable to total aluminium in the dust samples varied significantly. At high exposure, serum aluminium, although significantly raised, was still within the normal range of an unexposed population. The workers with low exposure excreted aluminium in urine at levels significantly higher than the controls, but still within the normal range of the population. However, potroom workers with medium and high exposure had significantly higher urinary aluminium than the normal range.

CONCLUSIONS

It is concluded that only urinary aluminium constitutes a practical index of occupational exposure at or above 0.35 mg Al/m3, and that the respirable fraction of the dust may play a major role in the biological response to exposure to aluminium in a smelter environment.

Antacid-induced osteomalacia

The case of a 49-year-old woman suffering from generalized skeletal pain and multiple fractures accompanied by severe hypophosphataemia and low urinary phosphorus excretion is reported. She had been taking large amounts of antacids containing aluminum hydroxide for many years. A diagnosis of antacid-induced osteomalacia was made. It was confirmed by biological work-up, radiographs and bone biopsy. A dramatic biological, osteodensitometric, and clinical improvement was achieved by withdrawal of antacids and phosphorus administration. The literature concerning this unusual condition has been reviewed.

Trace elements in parenteral micronutrition

OBJECTIVE

To update some essential trace metals required in total parenteral nutrition.

CONCLUSION

Essential trace metals, chromium, copper, manganese, molybdenum, selenium, and zinc are added to parenteral fluids to prevent the development of deficiency syndromes. When possible, these metals should be monitored, even in patients on short-term total parenteral nutrition (TPN) to avoid deficiency or toxicity. Many of the nutrients or additives used in parenteral solutions may be contaminated with metals, such as aluminum or chromium. Such trace-metal monitoring becomes more critical in infants, and those on long-term TPN.

Harry M. Vars Research Award. Increase in lumbar spine bone mineral content in patients on long-term parenteral nutrition without vitamin D supplementation

BACKGROUND

We had previously shown that short-term withdrawal of vitamin D in patients with metabolic bone disease complicating home parenteral nutrition (HPN) corrected osteomalacia. We therefore conducted a prospective study of the effect of long term withdrawal of vitamin D in patients on home parenteral nutrition.

METHODS

Baseline measurements of bone mineral content, serum levels of calcium, phosphorus, parathormone, 25-OH and 1,25 (OH)2D; urinary calcium; and bone mineral density were measured. Then all parenteral vitamin D was withdrawn and the above parameters were followed for a mean of 4.5 years.

RESULTS

Lumbar spine bone mineral content (LSBMC) was 0.79 +/- 0.06 g/cm2 at the start of the study, well below the reference value, 1.16 +/- 0.13 g/cm2. Parathyroid hormone (PTH) (0.48 +/- 0.24 pmol/L) and 1,25-(OH)2D levels (22.8 +/- 7.9 pmol/L) were low and 25-hydroxyvitaniin D levels were normal (33.3 +/- 5.5 nmol/L) before removing vitandn D from the HPN solutions. After withdrawal of vitamin D for 4.5 +/- 0.2 years LSBMC increased from 0.79 +/- 0.06 to 0.93 0.07 g/cm2 (p < 0.005). Calcium phosphorus, magnesium and 25-hydroxyvitamin D did not change significantly, 1,25(OH)2D, and PTH levels became normal after withdrawal of vitamin D.

CONCLUSIONS

In selected patients with depressed PTH levels, long-term withdrawal of vitamin D during HPN increases LSBMC and levels of PTH and 1,25(OH)2D. There is no reduction of the mean level of 25-hydroxyvitamin D.

Abnormal trace elements in a patient on total parenteral nutrition with normal renal function

OBJECTIVE

To describe trace metal changes in a 74-year-old male patient with mesenteric fibrosis and a small bowel fistula who was maintained on total parenteral nutrition in the hospital and at home.

METHODS

Trace elements which included chromium and selenium were monitored over a 14-month period as part of his nutrient follow-up.

RESULTS

Serum chromium reached levels > 21-fold the upper reference range, and serum selenium, in contrast, was < 0.5 the lower reference range. Plasma aluminum was also measured, and found to be nearly twice the upper reference range, although the patient had normal renal function. We measured the aluminum content of the parenteral nutrients and additives, and found that replacement of calcium gluconate by calcium chloride helped to reduce the aluminum content in the final parenteral solution by 34%. Aluminum and chromium contaminants found in parenteral solutions need to be reduced or removed to avoid toxic accumulation.

CONCLUSION

This study illustrates the importance of adequately adjusting essential trace elements, and monitoring contaminants in parenteral fluids in an individual on total parenteral nutrition.