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BACKGROUND: Human milk is frequently heat treated in hospitals to reduce bacterial contamination, particularly in banked milk fed to preterm infants. Pasteurization and sterilization may induce oxidative losses of unsaturated lipids and vitamins and may inactivate enzymes and immunologic factors. This study was designed to examine the effects of pasteurization and sterilization on milk fat content available to the recipient infant and on fatty acid composition. METHODS: In fresh, pasteurized (62.5 degrees C for 30 minutes), and sterilized (120 degrees C for 30 minutes) milk samples (5 ml) of 12 mothers (days 5-35 of lactation), fat content was determined gravimetrically and the contribution of 30 fatty acids was determined by gas-liquid chromatography. RESULTS: The coefficients of variation for measurements of milk fat content were 0.7% and of fatty acids accounting for more than 0.09% of weight, 0.1-3.0%. Available fat content was 3.1+/-1.4 g/dl (mean +/- SD) in fresh human milk and 3.1+/-1.4 g/dl (not significant) in pasteurized human milk. Fat content declined to 2.7+/-1.1 g/dl (p < 0.001 vs. fresh) in sterilized human milk, because of increased fat adherence to the container surface after sterilization. The percentage composition of saturated, monounsaturated, and polyunsaturated fatty acids of the n-6 (C18:3, C20:2, C20:3, and C22:4) and the n-3 series (C18:3 C20:5, C22:5, and C22:6) was not affected by thermal treatment. Milk sterilization caused a slight decrease of linoleic (-0.7% vs. fresh milk; p = 0,006) and arachidonic (-2,6%; p = 0.045) acids. CONCLUSIONS: Pasteurization of human milk does not influence fat content and composition, but sterilization may reduce available fat content by more than 10%, whereas there are only slight changes in fatty acid composition.
The rapid growth of young infants is supported by a high dietary fat intake close to 50% of the energy intake, resulting in a high dietary energy density. The adequacy of diets with low fat content during the second half year of life with respect to supporting growth has recently been studied. The digestion of dietary lipids is initiated by gastric lipolysis, which may provide an important contribution to total fat digestion in premature infants. The supply, metabolism and biological effects of long-chain polyunsaturated fatty acids during early development has been the subject of intensive research in recent years in view of potential effects on growth and functional development of visual and neural tissues. Intravenous lipid emulsions are an indispensable part of parenteral nutrition of young children, and efforts are being made to improve the parenteral feeding regimens to meet the metabolic needs for this sensitive group of patients.
BACKGROUND/AIM: Previous studies in vitro and in animals in vivo found that alpha-linolenic acid (C18:3omega3) may enhance oxidative damage of essential amino acids. We investigated whether the addition of the long-chain polyunsaturated fatty acids (LCPUFA) arachidonate (C20:4omega-6; AA) and docosahexaenoate (C22:6-omega3; DHA) in the form of egg phospholipids to infant formula affects plasma amino acid concentrations and indices of protein metabolism in term infants. METHODS: In a double-blind, randomized clinical trial, healthy infants were fed from day 5 of life formula with or without preformed LCPUFA (n = 10 and 12, respectively). At the age of 5 days and 1, 2, 3 and 4 months, blood samples were obtained and analyzed for plasma amino acids by high-performance liquid chromatography and for plasma phospholipid fatty acid composition by gas chromatography. RESULTS: At the age of 3 months, plasma threonine concentrations were significantly lower in infants receiving dietary LCPUFA than in controls (124 +/- 16 vs. 216 +/- 28 micromol/l, p < 0.05). Values of other plasma essential amino acids, total protein, albumin, creatinine and urea nitrogen did not differ between the two feeding groups throughout the study. At the age of 5 days, plasma phospholipid AA and DHA concentrations were inversely correlated with histidine concentrations (AA: r = -0.60, p = 0.01; DHA: r = -0.53, p < 0.05). At the age of 3 months, DHA concentrations were inversely related to plasma histidine, methionine and threonine concentrations (r = -0.66, -0.62, and -0.64, respectively, p < 0.05). CONCLUSIONS: The dietary LCPUFA supplementation of infant formula used in this study has no adverse effects on infant plasma amino acid concentrations and indicators of protein metabolism. Nonetheless, the apparent interaction of LCPUFA with some amino acids in formula-fed infants warrants further investigation.
Long chain polyunsaturated fatty acids are nutritionally important constituents of breast milk. The origin of these fatty acids in milk has not been clearly identified. We studied the contribution of maternal endogenous conversion of linoleic acid to milk dihomo-gamma-linolenic and arachidonic acids, using stable isotope techniques. Six lactating women ingested 1 mg of [U-13C]linoleic acid/kg body weight in the 2nd, 6th, and 12th week of lactation. Before and at several times during a 5-day period after tracer intake, samples of breath and milk were collected and the volume of daily milk production was recorded. Nutrient intakes were assessed with dietary protocols. The estimated oxidized proportion of the ingested labeled linoleic acid did not differ significantly with duration of lactation (2nd week: 18.9+/-4.5%, 6th week: 24.0+/-3.8%, 12th week: 17.7+/-3.5%, mean +/- SE), nor did transfer into milk as linoleic acid (12.7+/-1.4%, 13.1+/-2.5%, 11.7+/-2.7%, respectively). About 0.2% of the tracer appeared in milk as dihomo-gamma-linolenic acid and 0.02% as arachidonic acid. There were no statistically significant changes with time. We estimate that about 30% of milk linoleic acid is directly transferred from the diet, whereas about 11% of milk dihomo-gamma-linolenic acid and 1.2% of milk arachidonic acid originate from direct endogenous conversion of dietary linoleic acid.
Dietary lipids are the major energy source for infants and young children. Tissue lipid accretion in growing infants is very high and contributes 90% of all energy deposited in the body during the first 6 months of life. To meet these demands, a relatively high dietary fat intake is desirable for young infants, because the capacity for endogenous fat synthesis appears to be limited and would also require an increased energy intake. For sick infants with malnutrition or fat malabsorption, the physiological advantages of a high intake of metabolisable fat for growth are even greater. Technological advantages have made higher fat contents in therapeutical semielemental diets feasible, which appears to be of significant advantage for some of the recipient infants. With respect to fat quality, particular attention is currently directed at the optimal content of polyunsaturated fatty acids and their long-chain metabolites (LC-PUFA). The results of several studies suggest potential improvements of visual and mural functions in infants receiving dietary preformed LC-PUFA. Further research is required to study in more detail the metabolic effects, functional outcomes and safety of different forms of LC-PUFA supply for infants.
A method for the simultaneous determination of low concentrations of retinol and tocopherols from 100 microliters plasma using isocratic reversed-phase HPLC is described. Retinol is quantified with a programmable UV-Vis detector, whereas tocopherols are quantified by fluorescence detection using tocol as the internal standard. Intra- and inter-assay precision are 3.7 and 4.3% for retinol and 2.3 and 6.1% for alpha-tocopherol, respectively. The accuracy as determined with standard material from the US National Institute of Standards and Technology with low, medium and high concentrations is in the range of 0.2-6.0% bias for retinol and of -3.0 to 5.5% for alpha-tocopherol, respectively. This method is highly sensitive and selective and has a good precision and accuracy for measuring low concentrations of vitamins in small plasma volumes.
UNLABELLED: The increased employment of stable isotope tracers for diagnostic and research purposes frequently raises questions on potential risks associated with their use, which is of particular importance in the paediatric age group. Biological effects and the potential of adverse events has been evaluated in a large number of animal and, in part, also human studies. Possible differences in physical, chemical and biochemical behaviour resulting in kinetic and thermodynamic isotope effects between stable isotopes of the same element are related to the relative differences in atomic weight. Deuterium (2H), which differs markedly in mass from the predominant hydrogen isotope 1H, may induce serious side-effects at high concentrations in body fluids. The threshold dose for the occurrence of side-effects lies well above the usual tracer dosages for clinical use. In contrast to deuterium, heavier stable isotopes such as 13C, 15N or 18O that differ relatively little in mass from the predominant isotopes such as 12C, does not show any adverse biological effects even at highest enrichments. CONCLUSION: The doses of stable isotope tracer substances that are used for clinical diagnostic and research purposes appear safe and without any adverse effects. Stable isotope tracers should only be used in children if the trace is safe at the doses applied, and tracer is chemically pure and stable. In the case of intravenous application, the tracer preparation must also be sterile and pyrogen free.
UNLABELLED: Dynamic processes are of great interest in the study of lipid and fatty acid metabolism. Their in vivo investigation is now possible with the use of stable isotope tracers and the available sensitive analytical technology. We present some examples demonstrating the assessment of lipid oxidation as well as modulating factors by analysis of the tracer appearance in breath CO2 by isotope ratio mass spectrometry (IRMS). In a child with severe hypertriglycendaemia due to decreased cleavage of chylomicrons, medium-chain triglycerides were oxidised normally, whereas utilisation of long-chain triglycerides was severely disturbed. In another patient with primary carnitine deficiency, the beneficial effect of carnitine supplementation on fat oxidation could be demonstrated. In combination with gas chromatography, the high sensitivity of IRMS may be used for the detection of tracer materials in various plasma metabolites. In a pilot study, we applied C-13C labelled linoleic and alpha-linolenic acids to infants aged 2 weeks and 11 months, respectively. In these subjects, we could show a relative decrease of the conversion of these essential fatty acids to their longer chain polyunsaturated derivatives with age. The ability of term infants aged 19 days to convert linoleic into arachidonic acid was evaluated by using small natural differences in 13C abundance between different foods. Stable isotopes are also suitable for elucidation of new metabolic pathways. As an example, we could show in rats that linoleic and alpha-linolenic acids, which are usually considered to be essential substrates, can be synthesized endogenously from C16 precursors. CONCLUSION: IRMS is well suitable for the clinical investigation of lipid metabolism with stable isotopes in children. With different sample preparation devices, breath CO2 as well as specific plasma components can be analysed. While breath tests are already applied in clinical routing testing, GC-C-IRMS is a promising tool for research.
UNLABELLED: The fatty acid composition of human breast milk was determined longitudinally after term and preterm delivery by high resolution gas liquid chromatography. Milk samples were obtained at days 5, 10, 20 and 30 after term (n = 38) or preterm (n = 19) delivery. The saturated fatty acids C10:0 and C12:0 and the polyunsaturates linoleic acid (C18:2 omega-6) and alpha-linolenic acid (C18:3 omega-3) increased significantly from day 5 to day 10, whereas arachidonic acid (C20:4 omega-6), total omega-6 long-chain polyunsaturates (LCP), docosahexaenoic acid (C22:6 omega 3) and total omega-3 LCP decreased significantly. Term and preterm milk did not differ in percentage content of linoleic acid, alpha-linolenic acid and LCP at any time point. Preterm milk contained significantly more medium and intermediate chain fatty acids (C10:0, C12:0 and C14:0) than term milk on days 5 (12.28 vs 9.78%; P > 0.05), 10 (16.25 vs 12.62%; P > 0.05) and 20 (17.29 vs 13.47%; P > 0.005). CONCLUSION: The milk of mothers of preterm infants is not better suited to meet the high LCP requirements of their infants during the first weeks after birth. The slightly higher proportion of medium and intermediate chain fatty acids in preterm milk during the 1st month after birth might be advantageous for the fat and calcium absorption of preterm infants.
UNLABELLED: Recent data indicate that supplementation of infant formula with omega-3 and omega-6 long-chain polyunsaturated fatty acids might offer developmental benefits for full term infants. We investigated biochemical consequences of feeding formula supplemented with egg lipids to provide long-chain polyunsaturated fatty acids and compared triglyceride, cholesterol, lipoprotein cholesterol (HDL2-cholesterol, HDL3-cholesterol, non-HDL-cholesterol) and apolipoprotein A-I, A-II and B concentrations in full term infants fed either conventional formula (n = 10) or a formula supplemented with omega-3 and omega-6 long-chain polyunsaturated fatty acids and cholesterol in amounts similar to those found in mature human milk (n = 12). At the age of 5 days, cholesterol, non-HDL-cholesterol and triglyceride concentrations were significantly higher in infants fed supplemented than in those receiving conventional formula. At the age of 30 days, triglyceride concentrations were significantly higher with supplemented than with conventional formula. Thereafter throughout the study, no significant differences were seen between the two groups. CONCLUSION: Full term infants fed formula supplemented with omega-3 and omega-6 long-chain polyunsaturated fatty acids and cholesterol showed significantly higher plasma cholesterol and triglyceride concentrations than infants receiving conventional formula on day 5 and on days 5 and 30, respectively. Thereafter no appreciable effect of diet on plasma phospholipid, triglyceride, cholesterol, lipoprotein cholesterol and apolipoprotein concentrations were seen.
Our objective was to develop a suitable probe to study metabolism of polyunsaturated fatty acids by 13C nuclear magnetic resonance (NMR) in the suckling rat pup. [3-13C] gamma-Linolenic acid was chemically synthesized, and a 20 mg (Experiment 1) or 5 mg (Experiment 2) dose was injected into the stomachs of 6-10-day-old suckling rat pups that were then killed over a 192 h (8 d) time course. 13C NMR showed that 13C in gamma-linolenate peaked in liver total lipids by 12-h post-dosing and that [5-13C]-arachidonic acid peaked in both brain and liver total lipids 48-96 h post-dosing. 13C enrichment in brain gamma-linolenic acid was not detected by NMR, but gas chromatography-combustion-isotope ratio mass spectrometry showed that its mass enrichment in brain phospholipids at 48-96 h post-dosing was 1-2% of that in brain arachidonic acid. 13C was present in liver and brain cholesterol and in perchloric acid-extractable water-soluble metabolites in the brain, liver and carcass. We conclude that low but measurable amounts of exogenous gamma-linolenic acid do access the suckling rat brain in vivo. The slow time course of [5-13C] arachidonic acid appearance in the brain suggests most of it was probably transported there after synthesis elsewhere, probably in the liver. Some carbon from gamma-linolenic acid is also incorporated into lipid products other than n-6 long-chain polyunsaturated fatty acids.
The liver plays a central role in the metabolism of polyunsaturated fatty acids. We studied the relationship between essential fatty acid (EFA) status and indicators of liver function in 15 children with chronic cholestasis aged 9 months to 3.4 years (median, 1.3 years). Compared with 13 control children, the patients studied had low percentage values of phospholipid EFAs, particularly of the omega-6 fatty acids linoleic acid (18:2omega-6) and arachidonic acid (20:4omega-6). Fatty acid values exhibited an inverse relationship to serum bile acids, as well as to serum bilirubin. Bilirubin values were unrelated to the EFA precursors linoleic acid and alpha-linolenic acid but correlated inversely with the long-chain metabolites arachidonic acid (r = -0.75; p = 0.001), docosapentaenoic acid (22:5omega-3; r = -0.63; p = 0.01), and docosahexaenoic acid (22:6omega-3; r = 0.72; p = 0.002). We conclude that children with chronic cholestasis are at a high risk for EFA deficiency, which increases with progressive elevation of serum bilirubin. Hepatic conversion of essential precursor fatty acids into their long-chain metabolites may be increasingly impaired with advancing severity of liver disease.
Plasma alpha-tocopherol and beta-carotene concentrations were significantly lower in obese boys than in control subjects (medians: 3.41 versus 7.46 mg/L and 0.038 versus 0.078 mg/L, respectively, p < 0.05). The differences remained significant after correction for lipidemia. These reduced plasma concentrations of the major lipid-soluble antioxidants in obese children may add to the increased risk of cardiovascular disease in obesity.
The consumption of trans isomers of unsaturated fatty acids has been associated withuntoward metabolic effects. Several clinical investigations demonstrated that trans fatty acids increase plasma LDL-cholesterol and lipoprotein (a) and reduce HDL-cholesterol concentrations. These alterations of plasma lipid profiles indicate an atherogenic effect of trans fatty acids. Both in preterm infants and in healthy children aged 1-15 years, we found blood plasma arachidonic acid (C20:4omega-6) levels and the product/substrate ratios of arachidonic acid synthesis (C20:4omega-6/C18:2omega-6) inversely correlated to the level of the principal trans fatty acid, trans octadecaenoic acid (C18:1omega-9/7, trans), which is compatible with a dose-dependent inhibition of arachidonic acid synthesis by trans fatty acids. Moreover, in premature infants trans fatty acids in blood plasma correlated inversely with birth weight in an observational study, indicating that trans fatty acids may impair early human growth. It appears desirable to limit the dietary intake of trans fatty acids. The major dietary sources of trans fatty acids are partially hydrogenated vegetable and fish oils. Refinement of the industrial technology of partial hydrogenation and appropriate food labelling may lead to a considerably decrease of human exposure to trans fatty acids.
The fatty acid compositions of serum phospholipids and cholesterol esters and direct bilirubinemia were determined in 11 children with cholestasis due to extrahepatic biliary atresia. The levels of the different fatty acids in these lipid classes were compared with those of 22 appropriate controls and correlations with conjugated bilirubinemia were calculated. Significant differences were found in the levels of several fatty acids in these lipid classes, some of which were related to conjugated bilirubinemia. Relationships between fatty acids in phospholipids and cholesterol esters which exist in the control group were either absent or different in the patient group. The results found are compatible with the concept that malabsorption, overflow in blood of phospholipids, which are excreted in bile in healthy individuals, and liver disease per se contribute to the deviating fatty acid compositions. They suggest that administration in the diet may be required of preformed long chain polyunsaturated fatty acids in an easily absorbable form.
Disturbances of fatty acid metabolism with accumulation of odd-chain fatty acids have been reported in propionic acidaemia (PA). It is not known whether the synthesis of long-chain polyunsaturated fatty acids (LCPUFA) is also affected. In five clinically stable children with PA (median age 8 years, range 3.5-9.5 years; median percentage fibroblast propionyl-CoA carboxylase activity 0.8, range 0.8-1.5), we determined the fatty acid composition of plasma phospholipids, triglycerides and sterol esters and compared the results with those of 18 age-matched healthy controls. Odd-numbered fatty acids were found in all samples of PA patients but in controls median values were zero. Percentage contributions of substrate (linoleic acid, C18:2 omega-6) and principal product (arachidonic acid, C20:4 omega-6) of omega-6 LCPUFA synthesis did not differ between patients and controls. Similarly, there were no differences between both groups in the substrate (alpha-linolenic acid, C18:3 omega-3) and principal product (docosahexaenoic acid, C22:6 omega-3) of omega-3 LCPUFA formation. We conclude that disturbances of fatty acid metabolism in clinically stable children with PA do not affect LCPUFA synthesis.
BACKGROUND: Treatment of vitamin E-deficient cholestatic children with water-soluble alpha-tocopherol polyethylene glycol succinate (TPGS) was previously shown to normalize vitamin E status and to improve neurological outcome. METHODS: Because vitamin E plays an important role as a free-radical scavenger, we studied the effects of long-term TPGS supplementation on lipid peroxidation and polyunsaturated fatty acid status in 15 children ages 9 months-3.4 years (median, 1.3 years) with chronic cholestasis with low serum vitamin E concentrations [1.95 (0.8-3.7) mg/L; median (1st-3rd quartile)]. The previous supplementation of alpha-tocopherol was replaced by a 20% solution of TPGS in one daily dose of 20 IU/kg. Serum alpha-tocopherol, plasma lipid peroxides expressed as thiobarbiturate reactive substance concentration (TBARS) and plasma phospholipid fatty acid profile were estimated at baseline and again after 1 month in all 15 patients, and after 1 year of TPGS therapy in 11 patients. RESULTS: alpha-Tocopherol was significantly increased after 1 month [6.9 (4.4-8.4) mg/L; p = 0.008] and rose further after 1 year [9.7 (7.2-14.9) mg/L]; similar results were obtained for the ratio vitamin E/total lipids. TBARS concentrations were significantly higher in cholestatic children at baseline [2.9 (1.5-3.32) nmol/ml] than in a control group [1.2 (1.1-1.3) nmol/ml; p = 0.0006], but were not changed significantly during TPGS therapy [after 1 year 2.34 (1.9-3.0) nmol/ml]. Compared with controls, the contributions of polyunsaturated fatty acids to total phospholipid fatty acids were markedly decreased in cholestatic patients at baseline [27.7 (22.4-31.5)% versus 36.9 (34.5-39.0)%; p = 0.001] and did not show major changes after 1 year of TPGS supplementation. CONCLUSIONS: We conclude that oral TPGS supplementation of cholestatic children can quickly normalize serum vitamin E levels but does not improve the increased lipid peroxidation and poor polyunsaturated fatty acid status.