Oligosaccharides in human milk during different phases of lactation

Twenty-one oligosaccharides of human milk were quantified by high-performance anion-exchange chromatography. Milk samples were collected from 18 mothers during the first 3 mo of lactation. The data show that the highest amount of all oligosaccharides is present at day 4 postpartum (20 g l(-1)) and then decreases by about 20% at day 30 of lactation. The protective role played by these substances against different infectious agents, in different organs and systems of the breastfed baby, is emphasized.     

Variations in oligosaccharides and lactose in human milk during the first week of lactation

Variations in oligosaccharides and lactose in human milk were studied in 15 mothers during the first week of lactation. The neuraminyloligosaccharides and heavy neutral oligosaccharides increased slightly from days 2 to 5 postpartum and appeared to decrease until day 7. The lacto-N-difucohexaoses, lacto-N-fucopentaoses, and lacto-N-tetraose increased until day 5 and then decreased. Lactodifucotetraose and the fucosidolactoses decreased substantially until day 5 (p less than 0.05) and appeared to stablize in the following days. Lactose increased until day 5 (p less than 0.05) and continued to increase thereafter. Lactose was negatively correlated with total oligosaccharides (p less than 0.10). The fluctuations observed in total oligosaccharides from days 2 to 5 postpartum and their subsequent stabilization and regular decrease during lactation confirm the hypothesis of Kulski and Hartmann that mammary secretion occurs in three periods: colostrum for the first 36 h postpartum, transitional milk from days 2 to 5 postpartum, and mature milk after day 5. The oligosaccharide variations we found corresponded to those of other milk constituents observed by other authors. The significance of the oligosaccharide variations is discussed.     

Oligosaccharides in colostrum of Italian and Burkinabe women

Human milk contains a large number of compounds to provide nutrition and defense for the newborn. Among these, oligosaccharides are present in concentrations up to 12 g/L, and their composition varies during lactation. Colostrum from 53 Burkinabe women were collected at the maternity department of St Camille Medical Centre in Ouagadougou (Burkina Faso, West Africa). Colostrum from 50 Italian women were collected at the maternity department of St Bambino Hospital in Catania (Catania, East Sicily, Italy). All mothers spontaneously delivered at term. Italian mothers received an injection of the ergot derivative ergotamine after delivery. Ergotamine, notoriously, delays breastfeeding initiation up to 2 to 3 days. Chromatographic separation of colostrum from both Burkinabe and Italian women showed a progressive appearance of oligosaccharides in the first 3 days. Burkinabe women showed high concentrations of 2-fucosyllactose and lower concentrations of lacto-N-fucopentaose I. By contrast, Italian women showed inverted behaviour. A comparable percentage of the secretor genotype for the Lewis blood group phenotype in both Burkinabe and Italian women was found. According to the different ethnicity, different milk oligosaccharide profiles were documented in the present study. 2-Fucosyllactose in milk should be biologically significant for Burkinabe infants because of the high levels found in their mothers' colostrum after the second day of lactation.     

The impact of peripartum factors on the onset and duration of lactation

Knowledge of peripartum indicators of those mother-infant pairs that are at increased risk of early failure of lactation may improve specific support of breastfeeding. Mode of delivery, labor complications, hyperbilirubinemia, milk intake and weight development were evaluated in healthy term infants in a hospital (n = 338). Delayed onset of lactation was observed in primiparae and in study participants with peripartum complications. The quantitative intake of human milk, assessed by test weighing 0-24 h and 24-48 h after the onset of lactation, was not significantly different between these groups. In addition, volume intake, weight gain and lactation success were tracked in 77 infants. Partial feeding of infant formula or an intake of <150 g of human milk per day 24-48 h after the onset of lactation was linked to weaning within 4 weeks. Ninety-one percent of the infants were exclusively breastfed at discharge; this value had declined to 49, 35 and 20% at 4, 12 and 20 weeks, respectively. Peripartum factors may contribute to early lactation failure; the long-term success of breastfeeding was predominantly determined outside the hospital.     

Breast milk volume and composition during late lactation (7-20 months)

Breast milk composition of 119 samples collected by 46 women during months 7-20 of lactation was compared with composition of 101 samples collected at 4-6 months. Breast milk intake of 10 infants was determined by test-weighing for 1 or more months during months 7-16 of lactation. Longitudinal decreases in milk concentrations of zinc, copper, and potassium, previously documented for the first 6 months, continued into the second 6 months, while protein, iron, and sodium concentrations showed no further decline. Lactose, fat, calcium, and magnesium concentrations were similar to those in earlier stages of lactation. Weaning was associated with significant changes in milk composition: When milk volume fell below 300 ml/day, there was an increase in protein and sodium and a decrease in lactose, calcium, and zinc. Breast milk intake of infants not supplemented with cow's milk or formula averaged 875 ml/day (93% of total energy intake) at 7 months and 550 ml/day (50% of total energy intake) at 11-16 months. Total energy intake increased from 610 to 735 kcal/day, but energy intake per kilogram remained constant at a relatively low 70-79 kcal/kg/day. Our results suggest the need for further studies of nutrient intake and requirements of breast-fed infants during late lactation.     

Characterization of carbohydrates in commercial infant formulae

Human milk has always been the reference parameter for the preparation of commercial formulae. The advent of more advanced technologies has enabled increasingly precise information on the composition of human milk to be obtained. Our knowledge in the field of carbohydrates also has improved considerably in the last few years following the pioneering studies of Montreuil (1, 2). From a quantitative point of view it has been demonstrated that in the different phases of lactation, in addition to lactose, human milk contains a consistent amount of oligosaccharides (about 20 g/1 in colostrum and 10–13 g/l in mature milk) (3, 4), whereas monosaccharides make up only about 1% of the total carbohydrates (4). More than 100 different types of oligosaccharides have been identified so far in human milk (5–7), mostly tri-octasaccharides (8). From a biochemical point of view, oligosaccharides are constituted by glucose, galactose, N -acetyl-glucosamine, fucose and sialic acid, and present a linear or branching structure (5). Little is known yet about their physiological role or metabolic fate (9); nevertheless, it has been demonstrated that, in addition to their nutritional function, they participate also in the regulation of the intestinal ecosystem, encouraging the growth of bifid flora (10) and contributing to the defense mechanisms against pathogens in various organs (11–13).     

Plasma leptin levels in rat mother and offspring during pregnancy and lactation

The profiles of plasma leptin levels in pregnant and lactating rats and their offspring were determined. The plasma leptin levels increased on days 12 and 20 of gestation and declined on day 21 of gestation, remaining at this level during lactation. These changes were similar for lumbar adipose tissue weight, and a significant correlation was found when both variables were plotted with individual values. During the last 2 days of intrauterine life, the plasma leptin levels in the fetuses were in the same range as in their mothers, declining from day 20 to day 21. On the 1st day of life, the leptin levels increased to decline in suckling newborns after 4 days, remaining stable until day 20 of life. The enhancement in maternal white adipose tissue mass that takes place during pregnancy and its decline around parturition and lactation are proposed to contribute actively to the changes in the plasma leptin profile detected at these stages. Besides the contribution of placental leptin for the fetus and milk leptin for the suckling newborn, it is proposed that brown adipose tissue, which is the first form of adipose tissue that appears during development in the rat, is responsible for most of the changes in plasma leptin levels seen around birth, whereas its later decline could be mediated by the hormonal changes occurring after birth.     

The effect of neutral and acidic oligosaccharides on stool viscosity, stool frequency and stool pH in preterm infants

Aim: To determine the effect of neutral oligosaccharides [small‐chain galacto‐oligosaccharides/long‐chain fructo‐oligosaccharides (scGOS/lcFOS)] in combination with acidic oligosaccharides (pAOS) on stool viscosity, stool frequency and stool pH in preterm infants. Methods: In this explorative RCT, preterm infants with gestational age <32 weeks and/or birth weight <1500 g received enteral supplementation with scGOS/lcFOS/pAOS or placebo (maltodextrin) between days 3 and 30 of life. Stool samples were collected at day 30 after birth. Results: In total, 113 infants were included. Baseline and nutritional characteristics were not different between both groups. Stool viscosity at day 30 was lower in the prebiotics group (16.8N) (3.9–67.8) compared with the placebo group (26.3N) (1.3–148.0) (p = 0.03; 95% CI ?0.80 to 0.03). There was a trend towards higher stool frequency in the prebiotics group (3.1 ± 0.8) compared with the placebo group (2.8 ± 0.7) (p = 0.15; 95% CI ?0.08 to 0.52). Stool pH at day 30 was lower in the in the prebiotics group (5.9 ± 0.6) compared with the placebo group (6.2 ± 0.3) (p = 0.009; 95% CI 0.08 to 0.53). Conclusions: Enteral supplementation of a prebiotic mixture consisting of neutral (scGOS/lcFOS) and acidic oligosaccharides (pAOS) decreases stool viscosity and stool pH with a trend towards increased stool frequency in preterm infants. The inclusion of pAOS in a formula containing a mixture of scGOS/lcFOS does not add specific advantages to the formula in terms of stool viscosity, frequency, pH as well as feeding tolerance.     

Maternal protein restriction increases hepatic glycogen storage in young rats

This study aimed to determine whether maternal protein restriction alters hepatic glycogen metabolism. Mated female rats were fed diets containing 20% protein throughout pregnancy and lactation (CONT), 8% protein throughout pregnancy and lactation (LP), or 8% protein during the last week of pregnancy only and lactation (LLP). Weights and lengths were reduced in the LLP and LP offspring compared with the CONT offspring. The LLP and LP offspring demonstrated reduced insulin concentrations at both 10 and 26 d and also failed to show the increase in insulin seen with time in the CONT offspring. Serum glucose and leptin levels increased with time but were not different among the groups; however, in relation to adiposity leptin levels were greater in the LLP and LP offspring at 26 d. The LLP and LP offspring had increased hepatic glycogen at day 10 (CONT, 75.1 +/- 9.8; LLP, 103.4 +/- 11.0; LP, 116.0 +/- 18.4 glucose residues/g tissue) and d 26 (CONT, 183.1 +/- 38.9; LLP, 395.3 +/- 16.8; LP, 396.6 +/- 15.1 glucose residues/g tissue). Glycogen synthase expression was increased in the LLP and LP offspring at 10 d but not 26 d; glucose transporter 2 and glycogen phosphorylase expressions were not different at either time. At 26 d glycogen synthase activity was not different; however, glycogen phosphorylase a activity was reduced. The enhanced capacity to store glycogen despite reductions in insulin secretion suggests increased insulin sensitivity possibly acting with an alternative non-insulin-dependent glycogen storage mechanism.     

Dietary prebiotic oligosaccharides are detectable in the faeces of formula-fed infants

Human milk oligosaccharides are not digested during intestinal passage and can be detected in stools. In this study it was investigated whether a prebiotic mixture of low-molecular-weight galacto-oligosaccharides (GOS) and high-molecular-weight fructo-oligosaccharides (FOS) can be detected in stool samples of formula-fed infants. The test formula was supplemented with 0.8 g/dl oligosaccharides (GOS+FOS). In the control formula, maltodextrins were used as placebo. Fecal flora was assessed at the beginning (day 1) and at the end of a 28-d feeding period (day 2). At day 2 the content of galacto- and fructo-oligosaccharides in the stool samples were measured. On study day 1, the number of bifidobacteria was not different among the groups (supplemented group: 7.7 (6.2) CFU/g; placebo group: 8.0 (6.0) CFU/g). At the end of the 28-d feeding period, the number of bifidobacteria was significantly higher in the group fed the supplemented formula when compared to placebo (supplemented group: 9.8 (0.7) CFU/g stool; placebo group: 7.1 (4.7) CFU/g stool; p<0.001). In all infants fed the supplemented formula, GOS and FOS could be identified in the stool samples. That was not the case in infants fed the non-supplemented formula. CONCLUSION: The present data confirm the bifidogenicity of oligosaccharides and indicate that dietary galacto-oligosaccharides and long chain fructo-oligosaccharides remain during the whole passage in the lumen of the gastrointestinal tract, similarly to human milk oligosaccharides.     

Dietary prebiotic oligosaccharides are detectable in the faeces of formula-fed infants

Human milk oligosaccharides are not digested during intestinal passage and can be detected in stools. In this study it was investigated whether a prebiotic mixture of low-molecular-weight galacto-oligosaccharides (GOS) and high-molecular-weight fructo-oligosaccharides (FOS) can be detected in stool samples of formula-fed infants. The test formula was supplemented with 0.8 g/dl oligosaccharides (GOS+FOS). In the control formula, maltodextrins were used as placebo. Fecal flora was assessed at the beginning (day 1) and at the end of a 28-d feeding period (day 2). At day 2 the content of galacto- and fructo-oligosaccharides in the stool samples were measured. On study day 1, the number of bifidobacteria was not different among the groups (supplemented group: 7.7 (6.2) CFU/g; placebo group: 8.0 (6.0) CFU/g). At the end of the 28-d feeding period, the number of bifidobacteria was significantly higher in the group fed the supplemented formula when compared to placebo (supplemented group: 9.8 (0.7) CFU/g stool; placebo group: 7.1 (4.7) CFU/g stool; p <0.001). In all infants fed the supplemented formula, GOS and FOS could be identified in the stool samples. That was not the case in infants fed the non-supplemented formula.
Conclusion: The present data confirm the bifidogenicity of oligosaccharides and indicate that dietary galacto-oligosaccharides and long chain fructo-oligosaccharides remain during the whole passage in the lumen of the gastrointestinal tract, similarly to human milk oligosaccharides.     

Variability of human milk neutral oligosaccharides in a diverse population

BACKGROUND: A complex array of free oligosaccharides is a distinctive compositional feature of human milk. Although these oligosaccharides have been studied for several years, their variability and distribution have not been systematically studied, and their nutritional and functional roles have not been elucidated. This report describes a study in which a large number of human milk samples were analyzed for the presence and content of nine neutral oligosaccharides. The resultant data were used to probe for distribution trends by donor groups and stage of lactation. METHODS: Milk samples from 435 women residing in 10 countries were analyzed using a simple preparation procedure, gel filtration, and high-performance anion-exchange chromatography. RESULTS: All samples contained structures based on lacto-N-neotetraose and lacto-N-tetraose. This contrasts with the fucosyloligosaccharides tested, none of which was detected in 100% of the samples. Unexpected distribution trends were observed. For example, 100% of the samples from Mexico (n = 156) contained 2'-fucosyllactose, whereas only 46% of the samples from the Philippines (n = 22) contained this structure. Concentration ranges for the analyzed oligosaccharides revealed quantitative and qualitative distribution trends. CONCLUSIONS: The oligosaccharide composition of human milk varied among samples. The geographical origin of the donors was one of the factors that accounted for this variability. This can be explained by genetically determined traits that are not uniformly distributed. Results indicated that further systematic studies are needed to ascertain the effect of other factors, such as lactation stage or diet.     

Chronic caffeine intake by rat dams during gestation and lactation affects various parts of the neonatal brain

Timed-pregnant rats were randomly divided into 2 groups on day 13 of gestation. Group 1 received a 20% protein diet. Group 2 was pair-fed to group 1 with a 20% protein diet containing caffeine (1 mg/100 g body weight). At parturition, the dams of each group were continued on their respective diets until day 22 postpartum. At the time of weaning (day 22), only male rats were continued in the study. At this time, rats from both groups were fed the control diet containing 20% protein. On day 57 and 58, rats were killed, the brains divided into six areas, and DNA, RNA and protein contents were measured. In certain areas of the brain, weight, cholesterol, DNA, RNA and protein contents were different even long after returning to the caffeine-free control diet. The present study demonstrates that even if a relatively small amount of caffeine is taken during gestation and lactation, a time during which the growth rate is greater than in any other period of life, certain areas of the brain may be affected. These findings suggest that future central nervous system impairment may be expressed later in life in these offspring.     

Dose-related and other effects of maternal cimetidine pretreatment during lactation on drug metabolism in mouse dams and pups

The effects of maternal cimetidine pretreatment at different dose levels during lactation, on drug metabolism, were investigated in mouse dams and recently weaned pups. Aminopyrine N-demethylase, aniline hydroxylase and pentobarbitone metabolism were inhibited in both dams and pups in a dose-dependent manner (15, 25 and 50 mg/kg/day, i.p.). Pretreatment at a dose level of 50 mg/kg/day resulted in comparable levels of inhibition of drug metabolism in dams and female pups while male pups were less affected. Of the three indices studied, aniline hydroxylase was the least influenced by cimetidine pretreatment. Thus, the effects of maternal cimetidine pretreatment on drug metabolism in the nursing pair varied with the dose, sex and substrate. The possible implications of these results for man are discussed.     

Re-evaluation of the whey protein/casein ratio of human milk

Total casein subunits as well as whey proteins were quantitated in human milk samples during lactation. Two independent methods were used: precipitation at pH 4.3 in the presence of Ca2+ followed by Kjeldahl analysis and polyacrylamide gradient gel electrophoresis (PAGGE) followed by densitometric scanning. Both methods yielded similar results: casein synthesis is low or absent in early lactation, then increases rapidly and subsequently decreases. The concentration of whey proteins decreases from early lactation and continues to fall. These changes result in a whey protein/casein ratio of about 90:10 in early lactation, 60:40 in mature milk and 50:50 in late lactation. These observations indicate that the synthesis and/or secretion of caseins and whey proteins is regulated by different mechanisms. In addition, the relative proportion of the different beta- and kappa-casein subunits was found to vary throughout lactation.     

Effects of maternal hypocaloric diet feeding on neonatal rat brown adipose tissue

Hypocaloric diet (control diet diluted 1:1 with cellulose) feeding during pregnancy caused a reduction in the body weight of rat pups at birth whereas the main parameters of brown adipose tissue composition and thermogenic activity were unaffected. When prenatally underfed rat pups were nursed by untreated dams eating control diet during lactation, early (day 4 of life) and late (day 13 of life) neonatal body weight was rehabilitated and brown adipose tissue remained essentially unchanged. When prenatally underfed rat pups were nursed by dams that were fed with the hypocaloric diet during lactation, neonatal body weight continued lower at the two mentioned days of life and the overall thermogenic capacity of brown fat (GDP binding/g body weight) was substantially depressed. The reduction of the brown fat thermogenic capacity in these pups is mainly due to a hypotrophy of the mitochondrial component of the tissue as indicated by the lowered cytochrome oxidase activity. Results indicate that mild maternal underfeeding during lactation may depress brown adipose tissue thermogenic function in neonates whereas similar hypocaloric intakes during pregnancy did not alter brown fat thermogenic capacity.     

Zinc Concentrations in Human Milk During Lactation: a 6-month Longitudinal Study in Southern Brazil

Human milk zinc concentrations from women of low socioeconomic status in Ribeirao Preto, Southern Brazil, were studied. A group of 23 mothers, 17 multiparae and six primiparae aged from 17 to 39 years, were included in a 6-month longitudinal study. A total of 192 samples were collected starting from colostrum and then at 15-day intervals until the end of the sixth month of lactation. Initial zinc values (0.47 +/- 0.10 mg/dl) fell by about 40 per cent during the second week of lactation to 0.28 +/- 0.06 mg/dl, the decrease progressively increasing up to the 24th week (0.11 +/- 0.03 mg/dl). Zinc values were significantly higher in the colostrum than in any of the later collections (P less than 0.05). The values obtained at 15 days were significantly higher (P less than 0.05) than those obtained later, except for those obtained on the 30th day, which were higher than all of those, obtained later (P less than 0.05). The values obtained after 75 days of nursing, although steadily decreasing, were not statistically different. The data of the present study demonstrate a significant reduction in zinc levels during lactation, the amount of zinc provided by breast-milk being lower than those recommended by the recommended dietary allowance in the United States.     

Consequences of the composition of human milk for the nutrition of low-birth-weight neonates. III. Sodium and potassium

The concentrations of sodium and potassium were studied in the 24 hour pooled human milk of 37 mothers delivered preterm (PTM) and of 19 mothers delivered at term (TM) from the second to the eighth postnatal day and in addition in the PTM during the third week of lactation. During the 4th week of life the sodium balance was estimated in 31 very low birth weight infants fed a human milk formula enriched with NaCl (n = 11) or NaH2PO4 (n = 11) and in 9 infants fed the same formula without supplementary sodium. The concentrations of sodium decrease significantly during the first week of lactation. The values are significantly higher in PTM than in TM during the first 3 days but decrease in both milks to values between 1 and 2 mmol/100 ml. The concentrations of potassium increase up to the 4th day of lactation and fall to approximately 1.5 mmol/100 ml at the end of the first week of lactation. There are no differences between PTM and TM. In all three balance groups the sodium balance are positive. But only in the infants fed a sodium-supplemented human milk formula the weight gain was adequate according to the protein and caloric intakes. No signs of a pathological sodium retention could be observed during the balance period. The data suggest that a sodium intake of more than 2.5 mmol/kg/day is necessary for optimal growth. Thus, the phosphorus supplementation should be done generally as 1 mmol NaH2PO4/100 ml human milk in very low birth weight infants.     

大鼠食管下端括约肌肌间神经及肌层发育研究

目的 探讨食管下端括约肌(LES)肌间内神经及肌层的发育规律与小儿胃食管反流发生的可能关系.方法 分别取孕18 d(E18)、孕20 d(E20)胎鼠,出生后1 d(P1)、7 d(P7)、14d(P14)、21 d(P21)、30 d(P30)、成年鼠(A)的LES及食管体(EB),应用常规HE染色法及蛋白基因产物9.5(PGP9.5)免疫组化法,结合图像分析技术,定性、定量研究LES肌间内神经与肌层的发育变化.结果 随日龄的增加,LES和EB的肌间神经元、神经丛密度均逐渐下降,神经元胞体增大、胞浆着色加深,在哺乳期前后神经元成熟度达成年水平.在各个日龄组LES肌间内神经元密度和神经丛密度均较EB稠密.LES肌层出生后发育迅速,成年后各肌层继续增厚,环肌层发育总是优于纵肌层.结论 LES肌间内神经及肌层发育不一致,神经发育以哺乳期变化最为显著,至生后30 d基本发育成熟.     

Epidermal growth factor in human milk: daily production and diurnal variation during early lactation in mothers delivering at term and at premature gestation

Epidermal growth factor is a polypeptide that stimulates proliferation and differentiation of a variety of cell types, including the developing intestinal epithelium; it is the agent in human milk that induces mitosis in human fibroblast culture. We systematically evaluated the EGF content of milk from 20 women delivering prematurely and from 11 women delivering at term. In preterm mothers, the concentration of EGF was 70 +/- 5 ng/ml (mean +/- SEM), with no significant change during seven weeks of lactation. EGF concentration in milk of term mothers was 68 +/- 19 ng/ml (mean +/- SEM). No diurnal variation in the concentration was found. Total EGF content was closely correlated with the volume of milk expressed, suggesting a passive transport from the circulation. These observations confirm that a substantial amount of EGF is present in human milk and that EGF concentrations are not affected by duration of gestation, time of day, or duration of lactation.