Assessment of lipid peroxidation in newborn infants and rabbits by measurements of expired ethane and pentane: influence of parenteral lipid infusion

Peroxidation of the unsaturated fatty acid constituents of tissue is one proposed mechanism of in vivo oxidant damage. Products of unsaturated fatty acid peroxidation include the volatile hydrocarbons ethane and pentane. These volatile hydrocarbons are eliminated in expired air and reflect in vivo lipid peroxidation. Newborn infants excrete 16 pmol of ethane per kilogram body weight per minute and 15 pmol of pentane per kilogram body weight per minute. This compares with 1.4 pmol of ethane per kilogram body weight per minute and 1.3 pmol of pentane per kilogram body weight per minute in healthy adult men. Infants receiving total parenteral nutrition including intravenous lipid emulsion excrete more than 100 pmol of pentane per kilogram body weight per minute. Newborn rabbits, delivered at term, also excrete more pentane while receiving lipid emulsion infusion. In the newborn rabbit, the amount of pentane exhaled increases linearly with the dose of lipid emulsion. Blood and tissue thiobarbituric acid reactants are also increased in newborn rabbits after administration of lipid emulsion. These results indicate that lipid peroxidation is quantitatively greater in infants than in adult humans and can be significantly increased by parenteral administration of lipid emulsion.     

Parenteral fat emulsions based on olive and soybean oils: a randomized clinical trial in preterm infants

OBJECTIVE: To evaluate in premature infants a new parenteral lipid emulsion based on olive and soybean oils (ratio 4:1), with less polyunsaturated fatty acids (PUFA) and more alpha-tocopherol than standard soybean oil emulsion. STUDY DESIGN: Premature infants (gestational age, 28-<37 weeks) were randomized to receive one of the two emulsions within the first 72 hours of life. The triglyceride dose was increased to 2 g/kg/day within 3 days. Plasma phospholipid fatty acids, alpha-tocopherol/lipid ratio, and urinary malondialdehyde (MDA) excretion were determined at baseline and after 7 days. RESULTS: Of 45 recruited infants, 33 completed the study per protocol (15 soybean oil, 18 olive oil emulsion). At study end, groups did not differ in plasma phospholipid arachidonic acid, total n-6 and n-3 metabolites, but the olive oil group showed higher values of the PUFA intermediates C18:3n-6 (0.19% +/- 0.01% vs. 0.13% +/- 0.02%, P < 0.05) and C20:3n-6 (2.92% +/- 0.12% vs. 2.21% +/- 0.17%, P = 0.005). The plasma alpha-tocopherol/total lipd ratio was higher in the olive oil group (2.45 +/- 0.27 micromol/mmol vs. 1.90 +/- 0.08 micromol/mmol, P = 0.001), whereas urinary MDA excretion did not differ. CONCLUSION: The lower PUFA supply with the olive/soybean oil emulsion appears to enhance linoleic acid conversion. The reduced PUFA content, combined with a higher antioxidant intake in the olive oil group, results in an improved vitamin E status. The olive oil-based emulsion is a valuable alternative for parenteral feeding of preterm infants who are often exposed to oxidative stress, while their antioxidative defense is weak.     

Lipid peroxidation in newborn rabbits: effects of oxygen, lipid emulsion, and vitamin E

The extent of in vivo lipid peroxidation and the in vivo antioxidant effects of alpha-tocopherol and alpha-tocopheryl acetate were studied in newborn rabbits exposed to one of two oxidant stresses: hyperoxia (FIO2 greater than 0.9) or parenteral lipid emulsion infusion. Lipid peroxidation was monitored by measurement of expired ethane and pentane, tissue thiobarbituric acid (TBA) reactants, and tissue lipid peroxides. Seventy-two h of hyperoxia did not increase any of the parameters of lipid peroxidation although mortality was higher in oxygen exposed animals. alpha-Tocopherol (100 mg/kg, intravenous) lowered expired hydrocarbons and tissue TBA reactants, but raised liver lipid peroxides in both air and hyperoxia exposed pups. Infusion of soybean oil emulsion increased production of ethane and pentane, liver TBA reactants, and lung lipid peroxides. Both alpha-tocopherol and alpha-tocopheryl acetate prevented the soybean oil emulsion induced increase in volatile hydrocarbons. alpha-Tocopherol (100 mg/kg, intravenous) administration also prevented the increase in liver TBA reactants and lung lipid peroxides. In identically treated animals, alpha-tocopheryl acetate administration decreased liver TBA reactants but had no effect on lung lipid peroxides. We conclude that alpha-tocopherol reduces lipid peroxidation in newborn rabbits including animals exposed to hyperoxia or infused with lipid emulsions. alpha-Tocopheryl acetate results in lower tissue alpha-tocopherol concentrations and is less effective as an antioxidant in lipid emulsion infused rabbits.     

Free-radical-induced lipid peroxidation during the early neonatal period

The effect of gestational age on postnatal free-radical-mediated lipid peroxidation was studied in 19 term (gestational age 37–42 weeks) and 21 healthy preterm (gestational age 31–36 weeks) infants by measurement of expired ethane and pentane during the first 7 days of life. Ethane (11.9 versus 5.7 pmol/kg/min; p = 0.0001) and pentane (11.4 versus 7.5 pmol/kg/min; p = 0.01) were significantly higher in preterm than in term infants. Correlations were found between gestational age and ethane ( r = 0.60, p = 0.0001) for days 1–7 and pentane ( r = 0.54, p = 0.0003) for days 3–7; and between birth weight and ethane ( r = 0.58, p = 0.0001) and pentane (r = 0.55, p = 0.0003). These results indicate that during the postnatal period, immaturity is a major factor determining the rate of free-radial-mediated lipid peroxidation.     

Generation of free radicals in lipid emulsion used in parenteral nutrition

Lipid emulsions used in parenteral nutrition are prone to peroxidation that may be an important feature of oxygen-associated tissue damage. Incubation of lipid emulsion [Intralipid (IL)] with H2O2 and FeCl2 increased lipid peroxidation, measurable as increased production of pentane, from 0.39 +/- 0.33 to 0.99 +/- 0.18 microM (p less than 0.0001). Malondialdehyde was increased from 0.010 +/- 0.005 mM to 0.380 +/- 0.025 mM (p less than 0.001). Superoxide dismutase and catalase (each 100 U/mL) or vitamin C (10 mM) inhibited pentane and malondialdehyde production (p less than 0.0001). Incubation of human erythrocytes in the presence of FeCl2 caused 11.0 +/- 3.2% hemolysis (control 0.95 +/- 0.14%). Addition of 0.44% IL increased hemolysis to 66.5 +/- 3.4%, whereas further addition of vitamin E or C significantly inhibited hemolysis to 16.4 +/- 8.1 and 38.9 +/- 7.1%, respectively (p less than 0.0001). IL was administered i.v. to eight preterm infants. It increased 3- to 28-fold (p less than 0.001) the amount of pentane in expired breath. Partly, this increase was due to pentane dissolved in IL as a result of lipid peroxidation during storage. After discontinuing IL infusion, the elimination of pentane was nonexponential, consisting of a rapid and a slow component. According to our results, IL undergoes peroxidation causing free-radical-dependent damage to human cells. We propose that the adverse effects of parenteral IL are partially caused by free oxygen radicals generated by lipid peroxidation.     

Soybean oil emulsion administration during parenteral nutrition in the preterm infant: effect on essential fatty acid, lipid, and glucose metabolism

To examine the effect of a soybean oil emulsion on essential fatty acid, lipid, and glucose metabolism, preterm infants were randomized to receive 0.5 g/kg/d lipid for 5 days (n = 10, group 1) or 0.5 increased to 2.0 g/kg/d over 5 days (n = 11, group 2). Triene/tetraene ratios did not change in group 1, but decreased in group 2. In both groups, plasma phospholipid linoleate (percent and micrograms per milliliter) increased, the increase being greater in group 2. In both groups, percent content of arachidonate and 5,8,11-eicosatrienoate decreased, and that of oleate remained unchanged. In contrast, absolute content of arachidonate and oleate tended to increase, and that of 5,8,11-eicosatrienoate remained unchanged. At a lipid intake of 0.5 g/kg/d, no infants had hyperlipemia. When lipid intake exceeded 1.0 g/kg/d, the frequency of hypertriglyceridemia (triglycerides greater than 200 mg/dL) and free fatty acidemia, with the free fatty acid/molar albumin ratio exceeding 6:1, increased. Plasma glycerol increased slightly, but was substantially less than the rise in enzymatically determined triglycerides. Hyperglycemia was self-limiting and did not require alteration in dextrose intake. Thus, (1) infusion of a soybean oil emulsion at 0.5 to 2.0 g/kg/d maintains essential fatty acid status and phospholipid arachidonate concentrations; (2) significant hyperlipemia occurs when lipid intake exceeds 1.0 g/kg/d; (3) hyperglycemia associated with lipid infusion tends to be self-limiting and may not require alteration in lipid or dextrose intake; and (4) enzymatically determined triglycerides may be used to monitor lipid tolerance, provided that allowance is made for a small but systematic overestimation resulting from the rise in plasma glycerol.     

Parenteral glycerol enhances gluconeogenesis in very premature infants

We have previously demonstrated that very premature infants receiving total parenteral nutrition maintain normoglycemia primarily by glucose produced via gluconeogenesis and that the lipid emulsion is most important in supporting gluconeogenesis. It is, however, not clear whether this is a result of the glycerol or the fatty acid constituent. The purpose of the present study was to determine the effect of intravenous supplemental glycerol alone on glucose production and gluconeogenesis. Twenty infants (birth weight, 1014 +/- 32 g; gestational age, 27 +/- 1 wk) were studied on d 4 +/- 1 (mean +/- SE). All infants received glucose at 17 micromol/kg x min for 9 h (after an initial study hour with 33 micromol/kg x min). Eight infants received no additional substrate during the study, and 12 infants received supplemental glycerol at 5 (n = 6) or 10 micromol/kg x min (n = 6) over the last 5 h of study. In infants receiving glucose alone, between period 1 (study hours 4-5) and period 2 (study hours 9-10), rates of glucose production ([U-13C]glucose) decreased from 12.9 +/- 1.2 to 7.4 +/- 0.9 micromol/kg x min (p < 0.01). This was the result of decreased glycogenolysis but no change in gluconeogenesis ([U-13C]glucose mass isotopomer distribution analysis) (5.1 +/- 0.6 versus 5.7 +/- 0.4 micromol/kg x min) (ns). Glycerol infusion at 5 and 10 micromol/kg x min, respectively, maintained glucose production (despite comparable decrease in glycogenolysis) by increasing gluconeogenesis from 4.3 +/- 0.2 to 6.3 +/- 0.5 (p < 0.03), and 6.0 +/- 0.7 to 8.8 +/- 0.8 micromol/kg/min (p < 0.01). In very premature infants, parenteral glycerol enhances gluconeogenesis and attenuates time dependent decrease in glucose production.     

多种油脂肪乳在超低出生体重儿中应用的疗效分析

目的 分析多种油脂肪乳(SMOF)在超低出生体重(ELBW)儿中应用的疗效.方法 回顾性选取2018年1月1日至2020年7月30日收治的ELBW儿49例为研究对象,入院时日龄≤14 d,接受胃肠外营养时间>14 d.根据应用的脂肪乳剂种类,分为SMOF组(n=26)和中长链脂肪乳(MCT/LCT)组(n=23),比较...     

Comparison of lipid emulsions on antioxidant capacity in preterm infants receiving parenteral nutrition

Background: Although a variety of different lipid emulsions with varying fatty acid contents have been developed, there are some concerns about the administration of these lipid emulsions because of potential adverse effects, including oxidative stress‐related morbidity. The aim of the present study was to evaluate and compare the effects of the standard soybean oil‐based and olive oil‐based i.v. lipid emulsions (ILE) on oxidative stress, determined by total antioxidant capacity (TAC), and to investigate the safety of the use of these two emulsions in terms of biochemical indices. Methods: In this prospective study, premature infants were randomly assigned to two groups, each group consisting of 32 patients who received parenteral ILE of either 20% olive oil or 20% soybean oil. They were given ILE for 7 days and then were evaluated with regard to TAC. Results: No statistically significant difference was observed between the groups in terms of routine biochemical parameters. TAC for both groups on day 7 was significantly lower compared with that on day 0. Although the decrease in TAC within 7 days of ILE administration was greater in the soybean group compared with that in the olive oil group, it was not statistically significant. Conclusions: Olive oil‐based ILE exhibit similar antioxidant activity and can be used as an alternative to soybean oil‐based ILE. TAC significantly decreased in infants following administration of either lipid emulsion, and premature infants tolerated either ILE well, both biochemically and clinically.     

The metabolic effects of two different lipid emulsions used in parenterally fed premature infants--a randomized comparative study

Objective

To compare the effects of two different lipid emulsions, based on soybean oil and olive oil respectively on plasma lipid concentrations and acylcarnitine profile of very low birth weight infants.

Design

Randomized comparative study.

Patients and methods

Forty very low birth weight infants, ≤ 32 weeks of gestational age and receiving at least 40% of the calorie taken by parenteral nutrition from lipid solution at 14th day of life were evaluated. Group I (n = 20) received soybean oil based lipid emulsion (Intralipid®) and Group II (n = 20) received olive oil based lipid emulsion (Clinoleic®).

Main outcome measures

Plasma lipid concentrations and acylcarnitine profile were assessed.

Results

Triglyceride, cholesterol, high and low density lipoprotein levels, liver function tests were similar between two groups whereas very low density lipoprotein level was statistically lower in Group I (p < 0.05). Free carnitine levels were 15.73 ± 10.67 in Group I and 34.25 ± 22.18 μM in Group II (p = 0.012) and hexanoyl carnitine levels 2.18 ± 2.10 in Group I and 0.38 ± 0.12 μM in Group II, respectively (p = 0.005). Plasma medium chain acylcarnitine levels were significantly higher in Group I.

Conclusions

Low levels of very low density lipoprotein in Group I may be a way of hemostasis to keep the serum triglyceride within normal levels. Lower free carnitine levels in soybean oil-based group is the result of carnitine need during the mitochondrial transport of long chain fatty acids. In Group I, due to the inefficient transport of medium chain fatty acids into the mitochondria, medium chain acylcarnitines accumulate in plasma. This may be the reason of lower carnitine levels in Group I. We suggest that higher levels of hexanoyl carnitine, reflecting defective mitochondrial transport of hexanoyl which leads immunsupression, may be the cause of higher sepsis risk in Group I.     

Adherence of medium-chain fatty acids to feeding tubes of premature infants fed formula fortified with medium-chain triglyceride.

Adherence of medium-chain triglyceride (MCT) oil to feeding tubes during gavage feeding of Enfamil formula was quantitated. Infants were fed similar volumes of either unfortified formula (n = 11) or MCT oil-fortified formula (0.5 ml/oz); either the MCT oil was mixed with the formula before feeding (n = 11) or the MCT oil was delivered into the feeding tube and then was followed by formula (n = 11). The fat residue in the feeding sets was quantitated by gravimetry, and individual fatty acids were characterized by gas-liquid chromatography. The data show that only trace amounts of lipid (0.23 +/- 0.04%) adhered to feeding sets during feeding of unfortified formula. Significantly more lipid (p less than 0.0005) adhered when formula was fortified with MCT oil, and the method of feeding greatly affected lipid adherence, i.e., 1.52 +/- 0.21% when the MCT oil was followed by formula versus 10.20 +/- 1.76% when the MCT oil was mixed with formula before feeding. Analysis of the fat residue of fortified formula showed that greater than 90% was composed of C8:0 and C10:0, the major fatty acid components of MCT oil. We suggest that care be exercised when fortifying infant formula with MCT oil.     

Determination of the oxidation rate of medium-chain triglycerides in newborn infants with the 13C trioctanoin breath test

Up to the present time medium chain triglycerides (MCT) have been applied solely for the enteral nutrition of newborn infants. Results of the oxidative utilization of parenterally applicated MCT have not yet been published. We therefore investigated the MCT oxidation with the 13C trioctanoin breath test in neonates. The patients received parenterally 10 mg/kg MCT (1-13C3 trioctanoin) enriched with the stable isotope 13C and emulsified with MCT/LCT 10%. The expired 13CO2 resulting from fat oxidation was determined by a ratio-mass-spectrometer. The 13C content of exhaled air represents the rate of fatty acid oxidation. Within the test period the fatty acid oxidation showed a clear dependency on the simultaneous carbohydrate supply. The oxidation rates of MCT were about twice als high as those of long chain triglycerides (LCT). On account of their high energetic level, MCT-containing emulsions are, in principle, also suitable for the parenteral nutrition of newborn infants.     

Effect of heparin dose and infusion rate on lipid clearance and bilirubin binding in premature infants receiving intravenous fat emulsions

The effect of heparin dose and infusion rate on plasma lipids, lipases, and unbound bilirubin was investigated in 22 premature infants with physiologic jaundice. Infants were randomly assigned to receive low or high intravenous doses (24 vs 137.3 U/day) of heparin. Each patient then received 2 g/kg/day of 10% Intralipid on 2 successive days: one day during a 15-hour period and the other day over 24 hours, with the order assigned randomly. The results demonstrate a significantly greater change in serum-free fatty acids in infants receiving the high heparin dose during the 15-hour lipid infusion period. Lipoprotein lipase activity rose more with the high heparin dose and equally at either infusion rate. We conclude that lipid infusions of 2 g/kg/day with low heparin dosage infused over 24 hours resulted in less elevation in serum-free fatty acids. There were no adverse effects on unbound bilirubin at either infusion rate or heparin dosage.     

Quantitation of oxidation of medium-chain triglycerides in preterm infants

Medium-chain triglycerides, with a chain length of eight and 10 carbon atoms, form up to 50% of the total fat content in some preterm infant formulas. In 20 small preterm infants (birthwt: 1153 +/- 227 g; mean +/- SD) fed a special formula containing 40% MCT, a primed constant oral infusion study of 1-13C-potassium octanoate was conducted to quantify the oxidation of MCT. A plateau in 13C enrichment in breath CO2 was reached in all patients within 1-3 h. Simultaneously, substrate utilization was measured using a closed system indirect calorimeter. No significant difference was found between appropriate for gestational age (n = 8) and small for gestational age (n = 12) infants in the percentage of the administered tracer that was oxidized (44.9 +/- 9.1% versus 48.5 +/- 11.0%). In all patients, the recovery was calculated to be 47.1 +/- 10.2%, which is less than previously estimated and corresponds to a mean MCT oxidation of 1.26 +/- 0.27 g/kg/d. With indirect calorimetry, a total fat oxidation of 1.42 +/- 0.84 g/kg/d in appropriate for gestational age and 2.00 +/- 0.85 g/kg/d in small for gestational age infants was found, indicating that MCT accounted for around 85% of the total fat oxidation in appropriate for gestational age versus 65% in small for gestational age infants.     

Plasma metabolites after a lipid load in infants with congenital heart disease

Growth retardation is common in infants with congenital heart defects. The aim of this study was to investigate whether growth retardation or type of heart defect in infants with congenital heart defects is related to disturbances in lipid metabolism. Sixteen infants with ventricular septal defects and six infants with transposition of the great arteries were given an intravenous load of lipid emulsion (Intralipid^® 20 mg/ml) corresponding to 0.5 g fat/kg body weight for 5 min after fasting for 8 h. Blood samples were drawn immediately before the infusion and 3, 20, 60, 120 and 240 min after the infusion was completed. Plasma concentrations of triglycerides (TG), free fatty acids (FFA), ketones, lactate, pyruvate, alanine, glycerol and glucose were determined. The fatty acid patterns in the TG and FFA fractions were measured using gas chromatography. Severe growth retardation in infants with defects of these kinds was correlated to higher fasting and maximum levels of linoleic acid in plasma FFA. The maximum levels of linoleic acid in the TG fraction were positively correlated to weight SD score, and maximum glycerol levels were higher in the most growth-retarded infants, indicating faster intravascular lipolysis. Linoleic acid in the TG fraction was still elevated at 120 and 240 min after the lipid load. Some differences between the cyanotic and VSD groups could be noted. These indicate decreased metabolic capacity to utilize released FFA in the cyanotic group. Infants with cyanotic heart defects also had higher lactate and alanine levels compared to infants with VSD. Our results support the hypothesis that lipid metabolism is disturbed in infants with congenital heart defects.     

Effects of parenteral soybean oil lipid emulsion on the long-chain polyunsaturated fatty acid profile in very-low-birth-weight infants

Aim: Conventional soybean lipid emulsions contain no docosahexaenoic acid (DHA) or arachidonic acid (AA). We investigated the relationship between blood DHA and AA status in 27 very‐low‐birth‐weight (VLBW) infants with or without parenteral lipid emulsion. Methods: Sixteen infants received parenteral lipid emulsion, and 11 infants were control group. The fatty acid composition of the erythrocyte membrane was analysed at birth and at 2 weeks of age. Results: No significant difference in AA levels was observed in the lipid emulsion group between the two time points, whereas the AA levels at 2 weeks were significantly lower than at birth in the control group. The DHA levels in both groups at 2 weeks were significantly lower than at birth, but no group differences were observed at both time points. Conclusion: The use of parenteral soybean oil lipid emulsions in VLBW infants in the postnatal period may prevent the decline in the AA level but does not appear to influence the DHA level.     

Total parenteral nutrition in the newborn: energy substrates and plasma total fatty acids

Carbohydrate and lipid intakes have both been found to modulate the metabolism of long-chain fatty acids. To define the respective influence of these two energy substrates on plasma fatty acid concentrations, 32 studies were performed in 16 parenterally fed newborn infants (mean +/- SEM, birth wt: 2.15 +/- 0.1 kg, age: 10 +/- 1 d). In a paired cross-over design, the infants received for a given level of energy (60 versus 80 kcal/kg/d) two 6-d isonitrogenous and isocaloric regimens constructed so that the level of fat intake, 1 or 3 g/kg/d varied inversely with that of glucose. Total plasma fatty acid levels did not reflect the composition of the emulsion and varied with energy substrates. Plasma levels of three fatty acids rose inversely to the lipid intake, during the high glucose regimen: 16:1w7, 20:3w9 biologic markers of essential fatty acid deficiency, and 20:3w6 a derivative of 18:2w6. Glucose intake could exert its influence on 20:3w9 and 20:3w6 via insulin, an activator of delta 6 desaturase. Both glucose and fat should be taken into account when evaluating plasma fatty acid profile.     

Metabolic and clinical consequences of changing from high-glucose to high-fat regimens in parenterally fed newborn infants

To evaluate the metabolic and clinical consequences of changing from high-glucose to high-fat regimens during initiation of parenteral nutrition, we performed 22 studies in 11 newborn infants (birth weight (mean +/- SD) 2.54 +/- 0.54 kg, gestational age 37 +/- 3 weeks, postnatal age 8 +/- 3 days) maintained in a constant thermal environment. In a paired design, two isoproteinic (2.4 +/- 0.2 gm/kg/day) and isocaloric (64 +/- 6 kcal/kg/day) regimens differing by source of energy (high glucose vs high lipid) were infused on consecutive days. Environmental and body temperatures were recorded during a 4-hour period, and 24-hour urinary excretions of catecholamines, nitrogen, and C peptide were measured. Despite constant incubator and average skin temperatures, the rectal and interscapular temperatures rose significantly when the high-glucose regimen was changed to a high-lipid regimen. The specific locations of these changes in body temperature suggested brown fat activation. A significant drop in nitrogen retention (63 +/- 9% vs 56 +/- 10%) during the lipid infusion could be further evidence of a metabolic adaptation to the rapid change in energy substrates.     

Total parenteral nutrition with intralipid in premature infants receiving TPN with heparin: effect on plasma lipolytic enzymes, lipids, and glucose

Plasma lipolytic activity (lipoprotein lipase and hepatic lipase), free fatty acids (FFA), triglycerides, cholesterol, and glucose levels were measured in 21 premature infants [gestational age 26-37 weeks (mean +/- SEM 30.4 +/- 0.63 weeks), aged 1-8 days (mean +/- SEM 3.00 +/- 0.35 days)]. All infants were maintained on total parenteral nutrition with heparin (1 U/ml) and were given Intralipid, 1, 2, and 3 g/kg/day, over 15 h on days 1, 2, and 3, respectively. Blood samples were drawn before and at the end of Intralipid administration. Baseline plasma lipolytic activity, before the start of lipid infusion, was 1.54 +/- 0.24 U/ml (1 U = 1 mumol [3H]oleic acid released from tri[3H]olein/h). Lipolytic activity increased after lipid infusion to 4.04 +/- 0.96, 4.32 +/- 0.63, and 6.09 +/- 1.00 U/ml on days 1, 2, and 3 of the study. Hepatic lipase amounted to 38-47% of total lipolytic activity. During the 3 days of lipid infusion, there were dose-dependent increases in plasma FFA, triglyceride, and cholesterol. Whereas FFA and triglyceride concentrations returned to prelipid infusion levels 9 h after stopping the infusion of Intralipid, 1, 2, or 3 g/kg, there was a cumulative increase in plasma cholesterol and glucose concentrations. The close correlation between FFA concentrations and plasma lipolytic activity (r = 0.655, p less than 0.001) suggests considerable intravascular lipolysis. The positive correlation between plasma FFA and triglycerides (r = 0.632, p less than 0.001) and FFA and cholesterol (r = 0.582, p less than 0.001) indicate, however, that intravascular lipolysis does not prevent the lipemia associated with Intralipid infusion to low birth weight infants.(ABSTRACT TRUNCATED AT 250 WORDS)     

Daily metabolic rate in healthy infants

BACKGROUND: Previous estimates of daily metabolic rate in infants were based on short-term unstandardized measurements of energy expenditure (EE). OBJECTIVE: Determine 24-hour metabolic profiles in infants. METHODS: Energy expenditure (kcal/min by indirect calorimetry) and physical activity (oscillations in weight/min/kg body weight) were measured in 10 healthy infants (5.0+/-0.8 months, 68+/-3 cm, 7.3+/-0.8 kg) for 24 hours in the Enhanced Metabolic Testing Activity Chamber while allowing parental interaction. Energy intake, 24-hour EE, resting metabolic rate (RMR), and sleeping metabolic rate (SMR) (kcal/kg/day) were determined. In addition, extrapolated 24-hour EE, RMR, and SMR from the first 4 and 6 hours of data were compared with 24-hour measurements. RESULTS: Twenty-four-hour energy intake, EE, RMR, and SMR (mean+/-SD) were 78.2+/-17.6, 74.7+/-3.8, 65.1+/-3.5, and 60.3+/-3.9, respectively. EE and physical activity showed a decrease at 11:30 pm and a return to daytime levels by 5:30 am, suggesting a metabolic circadian rhythm. Extrapolated 24-hour EE, RMR, and SMR from the first 4 hours (72.2+/-6.6, 65.9+/-8.7, and 64.9+/-6.4) and 6 hours (74.8+/-6.7, 65.8+/-6.6, and 64.8+/-5.6) were similar to 24-hour measurements. CONCLUSIONS: An apparent circadian rhythm in metabolic rate and physical activity was detected by 24-hour measurements. Furthermore, shorter-term measurements of the variables were comparable with 24-hour values.