Nutrient interactions with total parenteral nutrition: effect of histidine and cysteine intake on urinary zinc excretion

Because cysteine and histidine, two amino acids included in total parenteral nutrition regimens, bind zinc and increase its renal ultrafilterability, my objective was to quantify the effects of infusion of amino acids, including cysteine and histidine, on urinary zinc excretion. The effect of the infusion of high amounts of cysteine and no cysteine (100 mg/kg/day vs none) and of high and low amounts of histidine (165 vs. 95 mg/kg/day) on urinary zinc excretion was determined in 14 newborn infants receiving total parenteral nutrition who had similar zinc intakes (approximately 7 mumol/kg/day). After a 72-hour adaptation period, each infant's urine was collected for two 48-hour periods. Urinary zinc excretion during the high-dose histidine and cysteine infusion periods was significantly elevated compared with that during the no-cysteine and low-dose histidine periods. Therefore concurrent intakes of specific amino acids may have to be considered when zinc dosages are calculated.

Hepatic metallothionein as a source of zinc and cysteine during the first year of life

Metallothionein, a high cysteine-containing protein, can bind with both essential and nonessential metals and thus play an important role as a metal storage protein and also in the detoxification of toxic metals. Although in the human fetus, levels of trace minerals and metallothionein are very high, their postnatal changes are not well documented. The purpose of the present investigation, therefore, was to quantify the accumulation of metallothionein in premature and full-term infants during the first year of life and to identify factors affecting its accumulation. From 47 postmortem samples, it was determined that hepatic metallothionein levels were highest in newborn premature and full-term infants falling to levels found in older children by 4.4 months of age. Hepatic zinc levels were also highest in the youngest infants, falling with increasing postnatal age. There was a significant positive correlation between zinc and metallothionein at all ages. However, there was a negative correlation between hepatic metallothionein levels and cystathionase activity. Hepatic copper and metallothionein levels were unrelated. The renal concentration of metallothionein, zinc, and copper were significantly lower than corresponding hepatic levels. The fall in hepatic levels of zinc and metallothionein during the first months of life correspond to a period of negative zinc balance and low endogenous cysteine production in the newborn. Thus metallothionein may play an important role as a storage depot for these two essential nutrients during this critical period of active growth.

Amino acid intake and urinary zinc excretion in newborn infants receiving total parenteral nutrition

Zinc deficiency is well described in infants on total parenteral nutrition (TPN). Urinary Zn excretion is the major source of Zn loss in the parenterally fed infant; factors causing increased zincuria will predispose the infant to Zn deficiency and affect the recommended Zn intake dosage. Histidine, threonine, and lysine have been shown to bind Zn increasing its renal ultrafilterability. The effect of the infusion of high and low lysine (206 +/- 34 vs 158 +/- 38 mg.kg-1.d-1; means +/- SD), threonine (147 +/- 24 vs 113 +/- 27), and histidine (124 +/- 34 vs 85 +/- 15) on urinary Zn excretion were determined in 23 newborns on TPN who received similar Zn intakes (6.8 +/- 1.4 mumol.kg-1.d-1). After a 72-h adaptation period each infant had urine collected for two 24-h periods. Despite the significant difference in amino acid intakes, mean urinary Zn excretion was identical (1.58 +/- 0.73 vs 1.56 +/- 0.63 mumol.kg-1.d-1). Hyperzincuria, therefore, does not occur when amino acids are infused at rates appropriate for the safety and nutritional maintenance of neonates.

Relationship between the sulfur content of total parenteral nutrition and sulfoester excretion in low-birthweight infants

Inorganic sulfate is an end product of sulfur amino acid metabolism but it is also the cosubstrate for the biosynthesis of a wide array of complex sulfoesters. In vitro studies have shown that SO4 availability may be the primary determinant of sulfoconjugation rates for specific substrates but the relationship between S intake and sulfoester formation in vivo is not known. By substituting MgCl2 for MgSO4 in an amino acid infusate for parenteral nutrition, we were able to examine prospectively the effect of an altered SO4 load on S metabolism. In comparing 21 low-birthweight infants on the experimental MgC2 infusate with 14 subjects on the control MgSO4 infusate, we observed a 40% decrease in urinary excretion of free SO4 and a 31% decrease in excretion of total acid-labile sulfoesters. There was a significant correlation (r = 0.44; p less than 0.02) between total S intake and sulfoester excretion, suggesting that S intake influences sulfoconjugation in the low-birthweight infant requiring total parenteral nutrition.

Effect of amino acid containing dialysis solutions on plasma amino acid profiles in children with chronic renal failure

Our previous studies demonstrated that, over single peritoneal dialysis cycles, amino acid-based dialysis solutions (AAD) were effective in dialyzing children with chronic renal failure (CRF) and offered metabolic advantages over traditional glucose dialysis solutions. The AAD, however, resulted in undesirable elevations of certain plasma amino acids, notably methionine. To further investigate the relationship between dialysate and plasma amino acid levels, we assessed the plasma amino acid response to a new AAD with relatively low methionine content (Vamin-based) over separate 5-h cycles with 1.3 and 2.3% AAD in eight patients with CRF (age 1-9 years) on continuous ambulatory peritoneal dialysis (CAPD). There was a net absorption of 70-73% of the amino acids, the net absorption of individual amino acids corresponding with the AAD composition. Plasma amino acid levels rose with AAD, peaking by 1 h postinfusion. Although most amino acids fell to preinfusion levels at the end of the cycle (including methionine), isoleucine with the 1.3% AAD and isoleucine, leucine, phenylalanine, and tyrosine with the 2.3% AAD remained significantly elevated. Having demonstrated in children that amino acids are absorbed from the peritoneal cavity in proportion to the AAD profile, modification of the current AAD is suggested.

Zinc absorption from glucose and amino acid dialysis solutions in children on continuous ambulatory peritoneal dialysis (CAPD)

Zinc deficiency in children with chronic renal failure may be due to inadequate intake or excessive losses. To determine the effect of dialysate solute type and concentration on the net absorption or loss of zinc from the peritoneal cavity, six CAPD patients ages 9-19 years were dialyzed with 1.3% and 2.3% amino acid-containing dialysis solutions and 2.5% and 4.25% glucose-containing solutions on four separate occasions. Zinc contamination of the initial effluent dialysis solutions was quite high (17.1 +/- 7.7 micrograms/dl) but did not differ between the four solutions. Significantly higher zinc retention was documented with the glucose-containing dialysis solutions compared to the amino acid-containing solutions (99.8 +/- 32.7 vs. 28.3 +/- 51.3 micrograms, 2.5% G vs 1.3% AA, p less than 0.01; 146.0 +/- 112.6 vs. 23.0 +/- 84.3, 4.25% G vs 2.3% AA, p less than .01). Although the mechanism is unclear, results of this study confirm in children that there is significant net absorption of zinc from glucose containing dialysis solutions at both high and low glucose concentrations. Thus, CAPD does not contribute to zinc depletion. Solute concentration did not affect net zinc absorption; thus it appears that movement of zinc across the peritoneum is dependent on solute type (amino acid or glucose) and independent of the osmolality.

Effectiveness and nutritional consequences of amino acid-based vs glucose-based dialysis solutions in infants and children receiving CAPD

Excessive glucose absorption and dialysate amino acid and protein losses contribute to malnutrition in children on glucose-based continuous ambulatory peritoneal dialysis (CAPD). We used 2.5 and 4.25% glucose and 1.1 and 2.0% amino acid dialysates to assess short-term effectiveness and nutritional consequences of amino acid-based dialysis solutions. Plasma and effluent urea and creatinine concentrations were similar with amino acid and glucose dialysis although 16% less fluid was removed with amino acid dialysates. Absorption of 77.3 +/- 5.3% of dialysate amino acids exceeded losses of amino acids and protein in glucose effluent. With amino acid dialysates, fasting plasma glucose concentrations were maintained while plasma amino acid levels rose, peaked at 1 h, and, excepting methionine, isoleucine, and phenylalanine with the 2.0% solution, returned to initial levels after 5 h. Compared with glucose, amino acid dialysates provide reduced but satisfactory fluid and waste removal, maintain normoglycemia, and more than compensate for effluent losses of amino acids and protein.

Percentile estimates of reference values for total protein and albumin in sera of premature infants (less than 37 weeks of gestation)

We measured the concentrations of total protein and albumin in sera of 281 well-fed premature infants, gestational ages 22-36 weeks, and calculated reference values from the 10th to 90th percentiles. The mean serum albumin concentration (27.6 +/- 4.4 g/L, mean +/- SD) and total protein concentration (49.2 +/- 6.7 g/L) at a postnatal age of 14.5 days were lower than reference values for full-term infants. We detected a significant positive correlation between albumin concentration and gestational age (r = 0.34, p less than 0.01) and total protein concentration and gestational age (r = 0.43, p less than 0.01). Even though albumin values were low, generalized edema was not present. We conclude that values for total protein and albumin in the preterm infant are lower than in the full-term infant but are an expected physiological response to premature birth.

Percentile estimates of reference values for total protein and albumin in sera of premature infants (less than 37 weeks of gestation)

We measured the concentrations of total protein and albumin in sera of 281 well-fed premature infants, gestational ages 22-36 weeks, and calculated reference values from the 10th to 90th percentiles. The mean serum albumin concentration (27.6 +/- 4.4 g/L, mean +/- SD) and total protein concentration (49.2 +/- 6.7 g/L) at a postnatal age of 14.5 days were lower than reference values for full-term infants. We detected a significant positive correlation between albumin concentration and gestational age (r = 0.34, p less than 0.01) and total protein concentration and gestational age (r = 0.43, p less than 0.01). Even though albumin values were low, generalized edema was not present. We conclude that values for total protein and albumin in the preterm infant are lower than in the full-term infant but are an expected physiological response to premature birth.

Clearance of osteocalcin by peritoneal dialysis in children with end-stage renal disease

Osteocalcin is a bone-specific protein whose concentration in blood is a direct reflection of bone turnover. In chronic renal failure, circulating osteocalcin is elevated. This elevation is due to decreased renal clearance and, in some patients, increased bone turnover secondary to renal osteodystrophy. In children receiving continuous ambulatory peritoneal dialysis, mean serum osteocalcin concentrations are substantially lower than in similar patients on hemodyalysis (1). This difference may be due to clearance of the protein by the peritoneal membrane. To test this possibility we examined osteocalcin in 16 infants and adolescents undergoing continuous ambulatory peritoneal dialysis with two commercially available glucose-based dialysis solutions (2.5 and 4.25% Dianeal). Mass transfer of osteocalcin over 5-h dialysis exchange periods was -18.9 +/- 2.8 and -28.4 +/- 7.8 micrograms for the low and high glucose solutions, respectively. Serum levels fell over the course of single exchange periods in concert with increasing dialysate concentrations. There were significant correlations between initial blood concentrations of osteocalcin and the total amount of osteocalcin transferred (r = 0.609 and 0.642 for the high and low glucose solutions, respectively, p less than 0.05). There were also strong correlations between the mass transfers of osteocalcin and those of creatinine (p less than 0.05) and total protein (p less than 0.01) with the 4.25% glucose exchange. The relationships were weaker with the 2.5% glucose exchange. Fractionation of serum revealed a single immunoreactive peak eluting coincident with intact osteocalcin, but two or three immunoreactive peaks were identified in matching dialysate samples, suggesting that both intact osteocalcin and circulating fragments are transferred by the peritoneal membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of naltrexone, an oral beta-endorphin antagonist, in children with the Prader-Willi syndrome

Children with the Prader-Willi syndrome have severe and often intractable hyperphagia unresponsive to medical or surgical treatment. Although the effect of opioid antagonists on suppressing appetite in humans has been inconsistent, we evaluated the effectiveness of a new opioid antagonist, naltrexone, in suppressing appetite in four obese adolescents with the Prader-Willi syndrome. Data were collected during the double blind oral administration of the drug and placebo for two 7-day periods. No clinical or biochemical toxicity was apparent during the naltrexone period, and measures of attention span, alertness, and mood did not change. Nutrient intake remained excessive during both the drug and placebo periods. Thus, naltrexone was ineffective in suppressing appetite, at least during the short term.

Clearance of inorganic sulfate by peritoneal dialysis in children with chronic renal failure

The peritoneal clearance of inorganic sulfate was measured in 6 infants and 12 children with end-stage renal disease who were receiving continuous ambulatory peritoneal dialysis. Serum sulfate, which was elevated before dialysis, changed little during the 5-hour dialysis period. The dialysis sulfate concentration increased at the same rate as creatinine. Net clearance of the two metabolites was not different. It was calculated that the removal by continuous ambulatory peritoneal dialysis in 24 h is comparable to the daily excretion of SO4 in healthy children.

Unconventional eating practices and their health implications

The authors discuss a number of unconventional or faddist foods and eating practices and their health implications. Among the topics included are vegetarianism, Zen macrobiotic diets, fast foods, junk foods, megavitamins and their toxicity, health foods, fad diets in infancy, and elimination diets.

Total parenteral nutrition in children

This article first focuses on the indications for total parenteral nutrition and the effect of its use on the outcome of various nutrient-depleting diseases in infants and children. This is followed by a discussion of some of the newer nutrient additions to total parenteral nutrition regimens, such as biotin, carnitine, zinc, copper, iron, and others.

Tissue selenium accretion in premature and full-term human infants and children

Development of supplementation guidelines for formulated diets and total parenteral nutrition requires knowledge of Se tissue accretion. To this end, the total organ Se content was calculated from the Se concentrations that were measured by neutron activation analysis in postmortem samples of liver (n=56), kidney (n=11), adrenal cortex (n=9), and pancreas (n=6) from infants and children from birth to 10 yr including 17 born prematurely. Hepatic Se concentrations were similar in full-term and premature newborns, decreased from birth to 1 yr, and then increased thereafter. The total hepatic Se content was significantly greater in full-term than in preterm newborns and increased with age and liver size after 1 yr. No significant differences were found between the concentrations of Se in kidney, pancreas, and adrenal tissues. Falling hepatic Se concentrations in the full-term infant concurrent with stable total organ Se content may indicate inadequate dietary intake or may reflect a normal redistribution of the nutrient. Premature infants are born with smaller stores than full-term infants and are at greater risk of developing a deficiency.

Fat overload syndrome causing respiratory insufficiency

The fat overload syndrome developed in a 7-year-old girl who was on home TPN which included 20% Intralipid (total lipid dose 3.2 g/kg/d). Acute respiratory insufficiency developed with cough, dyspnea, tachypnea, and cyanosis. The chest x-ray revealed mild cardiomegaly and pulmonary edema. Blood gases showed profound hypoxia (PaO2 29 torr on room air). Spontaneous resolution occurred over the next seven days as the lipemia cleared.

Bleeding disorder from the "fat overload" syndrome

The fat overload syndrome developed in a 7-yr-old girl receiving total parenteral nutrition with 20% Intralipid. She developed a bleeding disorder characterized by severe hematemesis that appeared to be due to abnormal platelet function associated with platelet phagocytosis of lipid demonstrable by electron microscopy. The platelet defect and bleeding reversed when the lipemia cleared.

Intravenous nitrogen intake requirements in full-term newborns undergoing surgery

To determine the intravenous intake of nitrogen needed to duplicate the weight gain and nitrogen retention observed in healthy infants fed human milk, full-term infants had weight change and nitrogen balance measured postoperatively while they were receiving two different parenteral regimens which provided adequate energy (87 kcal/kg/d) and varying intakes of nitrogen as crystalline amino acids (290 to 579 mg/kg/d) over a six-day period. Weight change was similar to that observed in breast-fed infants (35 g/d) and was independent of nitrogen intake. A significant correlation was observed between nitrogen intake and retention (r = .71, P less than .01). Substituting the rate of nitrogen retention observed in thriving full-term infants fed human milk into the regression equation describing the relationship between nitrogen intake and retention, the nitrogen intake required by parenterally fed infants in order to duplicate the accretion rate of their milk-fed counterparts was 280 mg/kg/d. After correcting for individual variation, recommended intravenous amino acid intakes range from 2.3 to 2.7 g/kg/d depending on the commercial amino acid formulation chosen and providing that adequate amounts of energy are concurrently infused.

Meeting zinc and copper intake requirements in the parenterally fed preterm and full-term infant

To determine the intravenous zinc and copper intakes required to build up body stores in the preterm infant and achieve positive retention in full-term infants, balance studies were completed in 38 preterm, full-term, and full-term SGA infants who received complete intravenously delivered nutrient formulations excluding zinc and copper. Zinc as ZnSo4 and copper as CuCl2 were then added to individual infants' formulations, with intakes ranging from 91 to 824 micrograms/kg/day (zinc) and 8 to 92 micrograms/kg/day (copper). Samples of infusate as well as urine, stool, and aspirate were collected for 72 hours and analyzed for zinc and copper by atomic absorption spectrophotometry. Zinc and copper retention correlated significantly with intake (r = 0.89; 0.82, P less than 0.01) and were independent of gestational age, postnatal age, and birth weight. In full-term and full-term SGA infants, intakes of zinc at greater than 150 and copper at greater than 16 micrograms/kg/day were adequate to replace ongoing losses and prevent acute deficiencies. The dosage for copper is similar to the current recommendation of the American Medical Association; the zinc dosage is 50% higher. Preterm infants receiving intakes of zinc at 438 and copper at 63 micrograms/kg/day achieve in utero retention rates. These dosages are significantly higher than AMA recommendations. Both combinations can be delivered by peripheral or central line without complications.

Sulfur balances in intravenously fed infants: effects of cysteine supplementation

Sulfur balances were completed in newborn infants parenterally fed with or without cysteine. In both groups, the preservative, potassium metabisulfite, accounted for the majority of sulfur intake (32 mg S/kg/day), while methionine intakes provided an additional 27 sulfate losses accounted for approximately 95% of the sulfur excretion, with the remainder contained in amino acids. Balance data accounted for over 99% of the sulfur infused in the unsupplemented group, but only 90% of that given to the cysteine-supplemented group. Thus, urinary excretion of sulfate generally reflects input from either inorganic or amino acid sources. Of the sulfur retained in the supplemented group, 75% was calculated to be retained in lean tissue and in increases in total body sulfate, but the distribution of the remaining 25% remains unknown. The failure to account fully for the sulfate provided to the cysteine-supplemented group, however, may be due to errors in the balance technique or due to an accumulation of cysteine or sulfate in body pools undefined by this study.