Acute effects of intravenous glutamine supplementation on protein metabolism in very low birth weight infants: a stable isotope study.

Although very low birth weight infants are subjected to severe stress and glutamine is now considered a conditionally essential amino acid that may attenuate stress-induced protein wasting in adults, current amino acid solutions designed for neonatal parenteral nutrition do not contain glutamine. To determine whether a short-term supplementation with i.v. glutamine would affect protein metabolism in very low birth weight infants, 13 preterm neonates (gestational age, 28-30 wk; birth weight, 820-1610 g) receiving parenteral nutrition supplying 1.5 g x kg(-1) x d(-1) amino acids and approximately 60 nonprotein kcal x kg(-1) x d(-1) were randomized to receive an i.v. supplement made of either 1) natural L-glutamine (0.5 g x kg(-1) x d(-1); glutamine group), or 2) an isonitrogenous glutamine-free amino acid mixture (control group), for 24 h starting on the third day of life. On the fourth day of life, they received a 2-h infusion of NaH(13)CO(3) to assess the recovery of (13)C in breath, immediately followed by a 3-h L-[1-(13)C]leucine infusion. Plasma ammonia did not differ between the groups. Glutamine supplementation was associated with 1) higher plasma glutamine (629 +/- 94 versus 503 +/- 83 microM, mean +/- SD; p < 0.05, one-tailed unpaired t test), 2) lower rates of leucine release from protein breakdown (-16%, p < 0.05) and leucine oxidation (-35%, p < 0.05), 3) a lower rate of nonoxidative leucine disposal, an index of protein synthesis (-20%, p < 0.05), and 4) no change in protein balance (nonoxidative leucine disposal - leucine release from protein breakdown, NS). We conclude that although parenteral glutamine failed to enhance rates of protein synthesis, glutamine may have an acute protein-sparing effect, as it suppressed leucine oxidation and protein breakdown, in parenterally fed very low birth weight infants.     

Minimum protein intake for the preterm neonate determined by protein and amino acid kinetics

Lower limits of protein needs in prematurely born neonates have not been adequately studied, yet providing protein in amounts maximizing accretion without excess is a goal in these infants' nutritional care. We hypothesized that with the use of amino acid oxidation methodology, it would be possible to define minimum protein requirement. Our objective was to investigate protein kinetics during short-term changes in protein intake by measurement of nitrogen balance and amino acid flux and oxidation using [(15)N]glycine, [(13)C]phenylalanine, and [(13)C]leucine tracers. Protein kinetics were examined in 21 preterm infants (gestational age: 29 +/- 3 wk; birth weight: 1091 +/- 324 g) at five protein intakes (1.0, 1.5, 2.0, 2.5, and 3.0 g x kg(-1) x d(-1)) with 1 d of adaptation to the test intakes. From nitrogen balance data, a protein need of 0.74 g x kg(-1 x -1) was estimated to achieve zero balance. For all three amino acids, flux and oxidation estimates were not different across protein intakes. Whole-body protein synthesis and breakdown estimates from [(15)N]ammonia data were 14.6 +/- 3.4 and 14.4 +/- 4.1 g x kg(-1) x d(-1), respectively. Glycine flux (680 +/- 168 micromol x kg(-1) x h(-1)) was greater than leucine flux (323 +/- 115 micromol x kg(-1) x h(-1)), which was greater than phenylalanine flux (84.3 +/- 35.2 micromol x kg(-1) x h(-1)). Leucine oxidation (36.7 +/- 15.6 micromol x kg(-1) x h(-1)) was also greater than phenylalanine oxidation (6.64 +/- 4.41 micromol x kg(-1) x h(-1)). Infants in our study were able to adapt to short-term changes in protein intake with little consequence to the overall whole-body protein economy, as measured by the three test amino acids.     

Leucine kinetics during feeding in normal newborns

To examine how leucine and protein metabolism is affected by feeding, leucine kinetics were determined in 11 normal term newborns during feeding using a prime constant tracer infusion of 1-13C leucine combined with respiratory calorimetry. Fed newborns were compared with previously studied fasting newborns. Feeding and fasting newborns had similar rates of leucine oxidation (34 +/- 3 mumol/kg/h versus 31 +/- 4 mumol/kg/h) and leucine release from existing protein (156 +/- 16 mumol/kg/h versus 164 +/- 8 mumol/kg/h). In contrast, nonoxidative disposal rates of leucine (a reflection of protein synthesis) were significantly greater in feeding newborns (170 +/- 13 mumol/kg/h versus 129 +/- 9 mumol/kg/h). A significant positive correlation between birth weight and leucine flux was demonstrated in both feeding and fasting newborns. These results suggest that 1) newborns may accomplish protein accretion primarily by increases in protein synthesis rather than suppression of protein breakdown; 2) an estimate can be made of the minimal leucine intake required to replace irreversible leucine oxidative losses (816 mumol/kg/d, 107 mg/kg/d); and 3) the positive correlation between birth weight and leucine flux in both feeding and fasting newborns may be a result of differences in previous protein and energy supplies.     

Effect of two amino acid solutions on leucine turnover in preterm infants

OBJECTIVE: To assess the effect of two different parenteral amino acid mixtures, Trophamine and Primene, on leucine turnover in preterm infants. METHOD: Leucine kinetics were measured with [5,5,5 D3]leucine tracer in 15 infants receiving Trophamine (group 'T') (mean birth weight 1,263 g) and 22 who received Primene (group 'P') (mean birth weight 1,336 g) during two study periods, within a few hours after birth but before introduction of parenteral amino acid solution, and again at postnatal day 7. The rate of appearance of leucine was calculated from the enrichment of alpha-ketoisocaproic acid in plasma. RESULTS: There were no significant differences in leucine turnover within a few hours after birth in the two groups. In the infants who received Primene leucine turnover on day 7 was significantly lower than in those who received Trophamine (269 +/- 43 vs. 335 +/- 27, p < 0.05). Despite a higher intake of leucine in the Trophamine group (108 +/- 10 vs. 77 +/- 8 micromol.kg(-1).h(-1)), leucine released from proteins at day 7 was higher in this group compared to Primene (227 +/- 27 vs. 192 +/- 42 micromol.kg(-1).h(-1)). CONCLUSIONS: Primene administration results in lower leucine released from proteins, an estimate of protein breakdown, than Trophamine in preterm infants. Increases in whole body leucine turnover in response to administration of i.v. amino acids is influenced by the composition of the amino acid mixture. The factors responsible for this difference remain to be elucidated.     

Whole body protein turnover measured with 13C-leucine and energy expenditure in preterm infants

Our study was undertaken in preterm infants to examine the relationship of whole body protein kinetics with protein intake and energy expenditure. Leucine kinetics were determined in seven low birth wt preterm infants fed human milk or human milk enriched with protein (2.5 to 4.3 g protein/kg.d). The infants received a short (4-h) constant infusion of L-[1-13C]leucine and leucine turnover and oxidation were calculated from 13C-plasma leucine and expired 13CO2 enrichments measured by mass spectrometry. Energy expenditure was measured by indirect calorimetry. Nonoxidative leucine disposal (an estimate of protein synthesis) and leucine derived from protein (an estimate of protein breakdown) were, respectively, 2.98 +/- 0.82 and 2.06 +/- 0.74 mumol/kg.min. Whole body protein turnover and deposition, derived from leucine kinetics, were 8.22 +/- 2.31 and 2.17 +/- 0.50 g/kg.d, whereas energy expenditure was 56.3 kcal/kg.day. Protein turnover was correlated with protein intake but not with protein deposition. Energy expenditure was correlated with protein turnover, synthesis, and breakdown but not with protein deposition. These data are in agreement with the fact that protein deposition depends upon protein intake, but they also suggest that an elevated protein deposition is not necessarily the result of a rapid protein turnover or associated with an elevated energy expenditure.     

Glutamine supplement with parenteral nutrition decreases whole body proteolysis in low birth weight infants

OBJECTIVES: To examine the effect of supplemental glutamine (0.6 g.kg -1 .d -1 ) on whole body protein/nitrogen and glutamine kinetics in low birth weight (LBW) infants receiving parenteral nutrition in the immediate neonatal period. STUDY DESIGN: Premature infants < or =32 weeks gestation with a birth weight from 694 to 1590 g were randomly assigned to either a glutamine-supplemented group (n = 10) or to a control group (n = 10). Tracer isotope studies were performed when the infants were 6 to 7 days old and had been receiving an amino acid intake of approximately 3.0 g.kg -1 .d -1 for at least 3 days. Whole body glutamine and nitrogen kinetics were measured with [5-15N]glutamine, [2H5]phenylalanine, [1-13C, 15 N]leucine, [15N2]urea, and GC-mass spectrometry. RESULTS: Supplemental glutamine was associated with a lower rate of appearance of glutamine ( P = .003), phenylalanine ( P = .001), and leucine C ( P = .003). There was no significant difference in leucine N turnover, urea turnover and plasma cortisol, and C-reactive protein levels in the 2 groups. CONCLUSION: Parenteral glutamine supplement in LBW infants was associated with lower whole-body protein breakdown. Because the decrease in whole body proteolysis is associated with protein accretion, parenteral glutamine supplement may be beneficial in selected populations of LBW infants.     

Supplementation of pooled human milk with casein hydrolysate: energy and nitrogen balance and weight gain composition in very low birth weight infants

Growth and nitrogen and energy balances were studied with a combined technique of nutrient balance and indirect calorimetry measurement in two groups of eight very low birth weight infants fed pooled pasteurized human milk (HM) or cow's milk casein hydrolysate supplemented HM (HM-Pr). There was no difference in the amount of energy absorbed (91 +/- 17 kcal/kg/day with HM-Pr versus 95 +/- 8 with HM-P) or in the growth rate. The infants fed HM-Pr had a higher nitrogen intake (602 +/- 80 versus 395 +/- 64 mg/kg/day; p less than 0.001), urinary nitrogen excretion (160 +/- 64 versus 78 +/- 16 mg/kg/day; p less than 0.005) and nitrogen retention (326 +/- 32 versus 252 +/- 48 mg/kg/day; p less than 0.01). They also had increased plasma concentrations of essential amino acids, urea nitrogen, and total protein without metabolic imbalance. Energy expenditure was higher (58 versus 49 kcal/kg/day; p less than 0.005) and energy storage lower (33 versus 47 kcal/kg/day; p less than 0.05) with HM-Pr. In percent of weight gain, protein and fat accretion represented 12 and 14% in HM-Pr group versus 10 and 27% in HM group. Very low birth weight infants fed casein hydrolysate supplemented pooled HM achieved a growth rate and a weight gain composition similar to the fetus.     

Changes in protein turnover after the introduction of parenteral nutrition in premature infants: comparison of breast milk and egg protein-based amino acid solutions.

Rates of protein turnover were measured in 20 infants receiving either Vamin Infant (group A) or Vamin 9 glucose (group B) as the amino acid source in total parenteral nutrition. A constant infusion of L-[1-13C]leucine was used to measure whole body leucine flux, and leucine oxidation rates were derived from measurements of total urinary nitrogen excretion. Infants were first studied when receiving only i.v. glucose and again on each of the next 4 d as total parenteral nutrition was gradually increased to a maximum of 430 mg nitrogen/kg/d and 90 nonprotein kcal/kg/d. Net protein gain and protein synthesis and breakdown rates increased progressively for all infants taken together over the study period as i.v. nutrition was increasing (p less than 0.001). There were no differences between groups in the changes in net protein gain and rates of protein synthesis and breakdown throughout the study period. Nitrogen retention on d 5 for the two groups was similar (60 +/- 16% and 67 +/- 11% in groups A and B, respectively). In a subgroup of infants, measurements were repeated on d 8, when the intake had been constant for 3 d. Protein retention was the same as on d 5, but both synthesis and breakdown were increased. It is concluded that rates of protein turnover increase significantly in response to increasing i.v. nutrition and that this elevation was not influenced by the composition of the amino acid mixture given.     

Effect of minimal enteral feeding on splanchnic uptake of leucine in the postabsorptive state in preterm infants

We conducted a controlled, randomized trial to study the effect of minimal enteral feeding on leucine uptake by splanchnic tissues, as an indicator of maturation of these tissues, in preterm infants in the first week of life. Within a few hours after birth, while receiving only glucose, a primed constant infusion of [1-(13)C]-leucine was started and continued for 5 h via the nasogastric tube, whereas 5,5,5 D3-leucine was infused intravenously (for both tracers, priming dose 2 mg/kg, continuous infusion 2 mg/kg/h). Patients were thereafter randomized to receive solely parenteral nutrition (C), parenteral nutrition and 20 mL breast milk/kg/d (BM), or parenteral nutrition and 20 mL formula/kg/d (F). On d 7, the measurements were repeated, after discontinuing the oral intake for 5 h. Fourteen infants were included in group C, 12 in group BM, and 12 in group F. There was no difference in energy intake or nitrogen balance at any time. On d 1, plasma enrichment for the nasogastric tracer was lower than for the intravenous tracer for all three groups, both for leucine and for alpha-keto-isocaproic acid. On d 7, the enrichment for leucine and alpha-keto-isocaproic acid for the nasogastric tracer was lower than for the intravenous tracer for the groups BM and F (BM: 3.65 +/- 1.20 nasogastric versus 4.64 +/- 0.64 i.v.; F: 4.37 +/- 1.14 nasogastric versus 5.21 +/- 0.9 i.v.). In the control group, there was no difference between tracers. The lower plasma enrichment for the nasogastric tracer compared with the intravenous tracer suggests uptake of leucine by the splanchnic tissues. We conclude that minimal enteral feeding--even in low volumes of 20 mL/kg/d--increases the leucine uptake by the splanchnic tissue. We speculate that this reflects a higher protein synthesis of splanchnic tissues in the groups receiving enteral nutrition.     

Effect of preeclampsia in the mother on the leucine metabolism in the newborn infant.

The leucine turnover in newborn infants is influenced by factors such as nutritional state and corticosteroid treatment. Little is known about maternal factors influencing the leucine turnover in the newborn. In order to approach the effect of preeclampsia in the mother on neonatal protein turnover, we studied the leucine turnover in preterm infants soon after birth and again after 7 days. Ten infants from preeclamptic mothers (birth weight 1,280 +/- 240 g, gestational age 31 +/- 2 weeks) and 15 control patients (birth weight 1,320 +/- 210 g, gestational age 30 +/- 2 weeks) were enrolled. The leucine turnover was measured using a primed constant 5-hour intravenous infusion of [1-(13)C]leucine within the first 24 h after delivery and again on day 7 of life. The turnover (leucine flux; micromol.kg(-1).h(-1)) was calculated from the enrichment in alpha-ketoisocaproic acid in plasma. The leucine turnover on day 1 was 300 +/- 65 in the preeclampsia group and 358 +/- 70 in the controls (ANOVA, p < 0.05). The values on day 7 were 474 +/- 73 in the preeclampsia group and 485 +/- 80 in the control group (n.s.). To conclude, the leucine turnover on day 1 is lower in infants of preeclamptic mothers as compared with controls. This difference has disappeared on day 7 of life after receiving the same protein and energy intake.     

Leucine kinetics during simultaneously administered insulin and dexamethasone in preterm infants with severe lung disease

The objective of this study was to determine whether insulin administration would prevent the well-documented catabolic effect of dexamethasone given to preterm infants with chronic lung disease. We studied leucine metabolism in 11 very-low-birth-weight infants before dexamethasone treatment and on d 2, 4, and 7 thereafter. During the first 4 d of dexamethasone, insulin was administered i.v. at a dose of 0.5 (n = 7) or 1.0 (n = 5) IU/kg/d. Leucine turnover was not significantly different between d 0 (337 +/- 41.3 micromol leucine/kg/h), d 2 (288 +/- 27.2 micromol leucine/kg/h), d 4 (302 +/- 22.1 micromol leucine/kg/h), and d 7 (321 +/- 21.2 micromol leucine/kg/h), and neither was leucine breakdown (272 +/- 21.9 micromol leucine/kg/h on d 0, 225 +/- 21.5 micromol leucine/kg/h on d 2, 231 +/- 21 micromol leucine/kg/h on d 4, and 242 +/- 17.6 micromol leucine/kg/h on d 7). Weight gain rates were significantly lower during the first week of dexamethasone treatment compared with the week before treatment or the second and third week. We conclude that during insulin and corticosteroid administration in very-low-birth-weight infants, no changes were observed in leucine kinetics in contrast to previous studies. The decrease in weight gain was not reversed.     

Amino acids, glutamine, and protein metabolism in very low birth weight infants

Glutamine has been proposed to be conditionally essential for premature infants, and the currently used parenteral nutrient mixtures do not contain glutamine. De novo glutamine synthesis (DGln) is linked to inflow of carbon into and out of the tricarboxylic acid (TCA) cycle. We hypothesized that a higher supply of parenteral amino acids by increasing the influx of amino acid carbon into the TCA cycle will enhance the rate of DGln. Very low birth weight infants were randomized to receive parenteral amino acids either 1.5 g/kg/d for 20 h followed by 3.0 g/kg/d for 5 h (AA1.5) or 3.0 g/kg/d for 20 h followed by 1.5 g/kg/d for 5 h (AA3.0). A third group of babies received amino acids 1.5 g/kg/d for 20 h followed by 3.0 g/kg/d for 20 h (AA-Ext). Glutamine and protein/nitrogen kinetics were examined using [5-(15)N]glutamine, [2H5]phenylalanine, [1-(13)C,15N]leucine, and [15N2]urea tracers. An acute increase in parenteral amino acid infusion for 5 h (AA1.5) resulted in decrease in rate of appearance (Ra) of phenylalanine and urea, but had no effect on glutamine Ra. Infusion of amino acids at 3.0 g/kg/d for 20 h resulted in increase in DGln, leucine transamination, and urea synthesis, but had no effect on Ra phenylalanine (AA-Ext). These data show an acute increase in parenteral amino acid-suppressed proteolysis, however, such an effect was not seen when amino acids were infused for 20 h and resulted in an increase in glutamine synthesis.     

Weight gain composition in preterm infants with dual energy X-ray absorptiometry

Whole body composition was investigated using dual energy x-ray absorptiometry in 54 healthy preterm infants, birth weight < 1750 g, who were fed fortified human milk (n = 20) and preterm formula (n = 34) when full enteral feeding was attained and then again 3 wk later at around the time of discharge. Weight gain composition was calculated from the difference between the earlier and later measurement. The minimal detectable changes in whole body composition over time according to the variance of the population (within groups of 20 infants) and the minimal detectable changes according to the dietary intervention (between two groups of 20 infants) were determined at 5% significance and 80% power. Whole body composition was similar in the two groups at the initial measurement, but all the measured variables differed at the time of the second measurement. Formula-fed infants showed a greater weight gain (19.9 +/- 3.2 versus 15.9 +/- 2.2 g.kg(-1).d(-1), p < 0.05), fat mass deposition (5.1 +/- 1.9 versus 3.3 +/- 1.3 g.kg(-1).d(-1), p < 0.05), bone mineral content gain (289 +/- 99 versus 214 +/- 64 mg.kg(-1).d(-1), p < 0.05), and increase in bone area (1.6 +/- 0.4 versus 1.3 +/- 0.3 cm(2).kg(-1).d(-1), p < 0.05) compared with the fortified human milk group. From these data, a minimal increase from the first measurement of 111 g lean body mass, 68 g fat mass, and 3. 1 g bone mineral content is needed to be detectable in a longitudinal study that includes 20 infants. For significance between two groups of 20 infants around the time of discharge, dietary intervention needs to achieve minimal differences of 160 g lean body mass, 86 g fat mass, and 4.1 g bone mineral content. With respect to weight gain composition, the minimal differences required to reach significance are 2.1 g.kg(-1).d(-1) for gain in lean body mass, 1.2 g.kg(-1).d(-1) for gain in fat mass, and 76 mg.kg(-1). d(-1) for gain in bone mineral content. We conclude that dual energy x-ray absorptiometry allows evaluation of the effects of dietary intervention on whole body and weight gain composition in preterm infants during the first weeks of life.     

Zinc absorption, distribution, excretion, and retention by healthy preterm infants

Zinc (Zn) is an essential nutrient for growth, but little is known about Zn absorption, distribution, excretion, and retention in preterm infants. Nine infants with gestational age 32+/-1 wk (mean+/-SE), birth weight 1.44+/-0.08 kg, postnatal age 14+/-3 d, on Zn intake of 23+/-3 micromol/kg per d via enteral feeding of preterm formula were studied. A stable Zn isotope (70Zn) was administered orally or i.v., and plasma, red blood cells, urine, and feces were sampled for up to 30 d. Samples were analyzed for Zn by inductively coupled plasma atomic emission spectrometry and for isotope enrichment by inductively coupled plasma mass spectrometry. Data were analyzed by compartmental analysis using the Simulation Analysis and Modeling program, and absorption, distribution, excretion, and retention were calculated. Absorption was 36+/-5% or 7+/-1 micromol/kg per d; distribution in plasma was 15+/-1 micromol Zn/L and in RBC was 41+/-4 micromol Zn/L; excretion in urine was 0.55+/-0.03 micromol Zn/kg per d and in feces was 17+/-3 micromol Zn/kg per d and retention was 5+/-1 microl/kg per d. Results show that healthy preterm infants with Zn intake of 23 micromol/kg per d and expected growth rates (> 15 g/kg per d) absorb and retain Zn at rates comparable to in utero accretion. The values for absorption, distribution, and excretion by this population of healthy preterm infants provide a normal range for future studies, although further studies are required to determine endogenous excretion rates in healthy preterm infants. We speculate that these values can be used to determine whether Zn kinetics are abnormal in sick infants or in infants with slow growth.     

Increased parenteral amino acid administration to extremely low-birth-weight infants during early postnatal life

BACKGROUND: Early administration of parenteral amino acids to infants with extremely low birth weight (birth weight < or = 1,000 g) has been encouraged to foster growth. However, excessive intravenous intake of amino acids may cause metabolic acidosis and uremia in extremely low birth weight infants. The hypothesis for this study was that extremely low birth weight infants would tolerate slightly increased early postnatal parenteral amino acid administration and benefit. METHODS: The peak daily parenteral amino acid dosage was increased from 3 g/kg (standard group) to 4 g/kg (modified group). The corrected parenteral amino acid dosage was computed to account for enteral protein intake and keep the combined daily intravenous amino acid and enteral protein intake at or below 3 g . kg -1 . d -1 in the standard group and 4 g . kg -1 . d -1 in the modified group. The primary outcome measure was plasma bicarbonate concentration as an indicator of acid-base status. Data were collected for patient demographics, nutritional intake, serum bicarbonate and serum urea nitrogen concentrations, and outcome. RESULTS: The corrected parenteral amino acid intake of the modified group was 16% greater at postnatal week 1 (3.30 +/- 0.83 g . kg -1 . d -1; mean, +/-1 SD) and 18% greater (3.86 +/- 0.94 g . kg -1 . d -1 ) at postnatal week 2 than the parenteral amino acid intake of the standard group. In the modified group, the mean serum bicarbonate concentration was 19.1 +/- 1.8 mEq/dL at week 1 and 23.9 +/- 2.9 mEq/dL at week 2, with no difference between the groups. At week 1, serum urea nitrogen concentrations were the same in both groups. The mean serum urea nitrogen concentration of the modified group at postnatal week 2 (18.2 +/- 8.8 mg/dL) was unchanged from postnatal week 1, but was greater than that of the standard group at postnatal week 2. Weight gain was the same in both groups. Corrected parenteral amino acid intake at postnatal week 1 correlated directly with weight gain from birth to postnatal week 2 ( P < 0.03) in both groups. CONCLUSIONS: Infants with extremely low birth weight tolerated parenteral amino acid intake of approximately 4 g . kg -1 . d -1. Mild increases of mean serum urea nitrogen concentration and mean weight gain were associated with increased parenteral amino acid administration without significant acidosis.     

Postnatal weight gain and serum total protein and albumin levels in very low birthweight (less than or equal to 1500 g) preterm infants

Postnatal weight gain during the first 8 weeks of life of 20 very low birthweight preterm infants (gestational age: 28.9 +/- 1.7 weeks, birthweight: 1098 +/- 199 g, mean +/- SD) was compared to the in utero weight gain of theoretical control fetuses. By the end of the study period preterm infants gained significantly less weight than their controls (155 +/- 15 vs 221 +/- 16%, p less than 0.001). During the first 6 weeks of life daily additional weight gain of the preterm infants was less than that of the controls, but after that time no significant difference was seen (7th-8th week: 12.0 +/- 3.6 vs 13.7 +/- 3.9 g/kg/day, study infants vs controls, ns). During the 7th-8th weeks of life positive correlation was found between calorie intake and weight gain (r = 0.33, F = 2.17, p less than 0.05). The changes in serum total protein and albumin levels, including an initial increase by the age of 2 weeks, were statistically not significant.     

影响极低出生体重儿体重增长的多因素分析

目的探讨影响极低出生体重儿(VLBW)体重增长的相关因素。方法对1998年7月—2004年3月重庆医科大学儿童医院新生儿病房收治的51例VLBW进行回顾性分析。结果单因素分析发现,早开奶、热卡摄入量和蛋白质摄入量对体重增长有显著性影响(P<0·05)。多元逐步回归分析结果示,热卡摄入量和蛋白质摄入量是影响体重增长的显著因素,回归方程为Y(体重增长)=-6·426+0·120X1(热卡摄入量)+3·737X2(蛋白质摄入量)(P<0·01)。达到体重增长目标对象中单纯胃肠内营养组和部分胃肠外营养组热卡摄入量分别为(520·62±21·59)kJ/(kg·d)[(124·43±5·16)kcal/(kg·d)]、(451·49±68·41)kJ/(kg·d)[(107·98±16·35)kcal/(kg·d)],差异有统计学意义(P<0·05)。早开奶组出生体重恢复时间、住院时间和胃肠外营养液体量占总液量比例>75%时间平均秩分别为18·58、20·24、20·11,晚开奶组分别为33·00、32·48、31·83,差异有统计学意义(P<0·05)。结论VLBW在生后应保证足量热卡和蛋白质的供给,对于小于胎龄儿和有严重并发症的患儿更应该加强营养的补充,对VLBW应尽早喂养,同时需要胃肠外营养作为肠内营养的补充。     

Growth of very low birth weight infants on varying amounts of human milk protein

In a double-blind, randomized study, 28 healthy, growing very low birth wt, appropriate-for-gestational-age infants were fed human milk, preferably mother's own, fortified daily with human milk protein and/or human milk fat. The infants entered the study when they were stable on complete enteral intakes of 170 mL/kg/d (mean age = 19 d). The study lasted for a mean of 4 wk. Samples from all the milks were collected daily, and intakes of protein, fat, carbohydrates, energy, and electrolytes were calculated weekly during the whole study period. Protein intakes ranged from 1.7 to 3.9 g/kg/d, and energy intakes from 100 to 150 kcal/kg/d. Wt and length gain in the nonprotein-enriched groups were 15.6 +/- 2.7 g/kg/d (mean +/- SD) and 0.88 +/- 0.17 cm/wk; the corresponding figures for the protein-enriched groups were 20.2 +/- 2.1 g/kg/d and 1.24 +/- 0.14 cm/wk. There was a strong correlation between protein intake and growth in wt and length up to an intake of about 3 g/kg/d; more protein did not result in increased growth. The same was true for energy intake, with a maximal growth rate at an intake of about 120 kcal/kg/d. A protein intake of more than 3 g/kg/d resulted in a growth rate equal to or higher than the estimated intrauterine growth rate. Some infants fed mature banked human milk alone had a poor growth. Sodium intake was low, ranging from 1.5 to 2.6 mmol/kg/d. No correlation was found between sodium intake and growth rates.     

Whole-body leucine kinetics and the acute phase response during acute infection in marasmic Malawian children

This study compared leucine kinetics and acute-phase protein and cytokine concentrations in three groups of Malawian children who were fed an isoenergetic, isonitrogenous diet: children with marasmus with (n = 25) and without (n = 17) infection and well-nourished children with infection (n =13). The hypotheses tested were that whole-body leucine kinetics will be less in marasmic acutely infected children than in well-nourished acutely infected children but greater than in marasmic uninfected children. Children were studied after 24 h of therapy using standard (13)C-leucine stable isotope tracer techniques. Well-nourished children with acute infection had greater leucine kinetic rates than did marasmic children with acute infection; nonoxidative leucine disposal was 153 +/- 31 versus 118 +/- 43 micromol leucine. kg(-1). h(-1), leucine derived from whole-body proteolysis was 196 +/- 34 versus 121 +/- 47, and leucine oxidation was 85 +/- 31 versus 45 +/- 13 (p < 0.01 for all comparisons). Leucine kinetic rates were similar in marasmic children with and without acute infection. Well-nourished children with acute infection increased their serum concentration of five of six acute-phase proteins during the first 24 h, whereas marasmic children with infection did not have any increases. The serum concentrations of IL-6 were elevated in well-nourished and marasmic children with infection. These data suggest that the cytokine stimulus for the acute-phase protein kinetic response to acute infection is present in marasmic children but that the acute-phase protein metabolic response is blunted by malnutrition.     

Relationship between protein and energy in the feeding of preterm infants during the first month of life

Energy and protein quantity and quality in the diet are factors regulating the rate of growth in the preterm infant. In the present study twenty infants 31-36 weeks of gestational age were fed with identical test formulas which varied only in the content of energy. One formula (F-81) contained 3.1 g protein (60 bovine whey: 40 bovine caseins) and 81 kcal per dl. The second formula (F-94) contained the same amount of protein but 94 kcal per dl. At an intake of 150 ml/kg/d the infants received 4.6 g protein/kg/d and either 121 or 141 kcal/kg/d. The infants on F-94 had a significantly higher rate of weight gain, but growth of length and head circumference was equal in the two groups. Significant differences were found in the plasma concentrations of glutamine and alanine between the two feeding groups. The other plasma amino acids were not statistically different in the two groups of infants. Urine excretion of threonine, serine, glycine, alanine, histidine, tyrosine, glutamine and cystathionine was significantly increased in the high caloric, F-94-group. The results indicate that increasing the caloric intake above 120 kcal/kg/d in preterm infants on a relatively high protein intake does not increase linear growth but does produce increased weight gain. The biochemical results provide indirect evidence that this weight increase is the result of increased fat accretion.