Sialic Acid In Milk Research Articles

Concentration and distribution of sialic acid in human milk and its correlation with dietary intake.

PurposeThis study evaluates the content, distribution, and changing trend of sialic acid in human milk and the correlation between dietary intake of sialic acid and that in human milk.MethodsThe study included 33 mothers of full-term and exclusively breastfed infants. At least 2 ml of milk was collected on the 3rd, 8th, 30th, and 90th day after delivery, and 24-h diet recalls of the lactating mothers were obtained each time. The correlation of human milk sialic acid concentration with lactating women's dietary sialic acid intake during lactation was analyzed by statistical analysis software SPSS.ResultsThe average concentration of sialic acid in colostrum, transition, and 1 and 3 months were 1,670.74 ± 94.53, 1,272.19 ± 128.74, 541.64 ± 55.2, and 297.65 ± 20.78 mg/L, respectively. The total sialic acid concentration in colostrum was about 5.6 times higher than that at 3 months (P < 0.001). The average dietary sialic acid intake of lactating mothers on the 2nd, 7th, 30th, and 90th day after delivery were 106.06 ± 7.51, 127.64 ± 8.61, 120.34 ± 10.21, and 95.40 ± 6.34 mg/day, respectively. The intake of sialic acid was relatively high on the 7th day, and there was no significant difference in dietary intake of sialic acid on different days (P < 0.05). In addition, there was no correlation between the intake of dietary sialic acid and the content of total sialic acid and various forms of sialic acid in milk (P < 0.05).ConclusionDuring the lactation period, the distribution of sialic acid in breast milk is relatively stable and its content fluctuates greatly, which may not be affected by the mother's diet, but mainly depends on the self-regulation oft physiological needs.

Distribution and Influencing Factors of the Sialic Acid Content in the Breast Milk of Preterm Mothers at Different Stages.

Background and AimsThis study aimed to detect breast milk sialic acid (SA) content and the changing pattern, to understand the various stages of breastfeeding SA secretion, and the influence factors of the human milk SA content.MethodsWe recruited mothers and their infants as our subjects. At days 7, 14, 30, 120, and 365 after delivery, the contents of SA in breast milk were collected and detected through Fluorescence Detector-High Performance Liquid Chromatography. The participants completed the baseline questionnaire at ≤day 7 and were followed up at days 30, 120, and 365.ResultsA total of 95 mothers with 122 infants were included in the analysis, including 22 mothers with 22 term infants, 25 mothers with 35 late preterm infants, 31 mothers with 39 very preterm infants, and 17 mothers with 26 extremely preterm infants. Similar to previous findings, the results of the study showed that, compared with breast milk of term mothers at the same period, breast milk of preterm mothers contained more SA at each time node, and the content of SA in breast milk increased with decreasing gestational weeks. Moreover, maternal age, pre-pregnancy BMI, and delivery mode had significant effects on total SA in breast milk, especially for the preterm infant breast milk. Significant negative associations occurred between SA contents and infant growth status, especially in preterm infants.ConclusionsWe have confirmed the previous observations showing that with the prolongation of lactation time, the content of SA in breast milk gradually decreased, and the content of SA in the breast milk of preterm mothers was higher than that of term mothers. In addition, SA content was associated with maternal age, pre-pregnancy BMI, and delivery mode.

A spectrophotometric procedure for sialic acid determination in milk employing a flow-batch analysis system with direct heating

The quantitative determination of sialic acid can indicate the addition of cheese whey to milk. This work describes an automated procedure to determine sialic acid in milk samples using a flow-batch system analysis with direct heating. The sialic acid quantification was based on a reaction between the sialic acid and acid ninhydrin producing a stable compound with maximum absorption at 470 nm. The flow-batch system was designed using heating and spectrophotometric detection in the reaction chamber. Under the optimum experimental conditions, a linear response ranging from 1.0 to 10.0 mg L−1 sialic acid (R = 0.99 and n = 7), a detection (3σ criterion) and quantification (10σ criterion) limit estimated at 0.239 and 0.726 mg L−1, respectively, a relative standard deviation of 1.90% (n = 10) for a reference solution of 4.0 mg L−1 sialic acid and a sampling rate of 7 determinations per hour were achieved. Analysis of eleven milk samples, application of the t-test to the results found, and comparison with the official method provided no significant differences at a 95% confidence level. Compared to the official method, the proposed system reduced reaction time by 50%, temperature of the reaction by 30%, and diminished the consumption of reagents and samples by 90%. Thus, the use of the proposed system is an economically viable and environmentally friendly option for the determination of sialic acid in milk.

Variable sialic acid content in milk of Indian cattle and buffalo across different stages of lactation.

The aim of this Research Communication was to contribute to the knowledge of milk sialic acid concentration of bovines with specific focus on India. Sialic acids (SA) are important constituents of mammalian milks. Buffaloes are the main milk producing species in India, therefore, our research focused on both cow and buffalo. Two Indian cattle (Bos indicus) breeds (Sahiwal, Tharparkar), one cross bred cattle - Karan Fries (Tharparkar × Holstein Friesian) and a buffalo breed (Murrah) were selected. Systematic comparisons of the total, free and bound form of SA and also its distribution over the course of lactation- colostrums and mature milk (120-140 d) was generated. Animal management, sample collection and methodology of SA estimation were identical for the different groups. Colostrum had the highest concentration of SA, which declined with the progress of lactation in all the groups. Majority of the SA existed in bound form. No significant (P &lt; 0.05) difference was recorded in the total, bound or free SA across all the groups. However, differences were obvious in the total and bound SA level in the mature milk. Indian cattle, Sahiwal and Tharparkar were equivalent, but had higher concentration of total and bound SA than crossbred cattle. Milk of buffalo had SA equivalent to that of crossbred cattle. The mean (se) levels of total SA was 23.4 (0.8), 25.8 (2.4), 20.3 (0.6) and 20.2 (1.2) in Sahiwal, Tharparkar, cross bred and Murrah buffalo, respectively. The findings suggested that milk of indigenous cattle may be a potential source of SA, a bioactive compound with beneficial effect on human health and a potential functional ingredient in foods. Results add value to the currently declining indigenous cattle of India.

Analysis of sialic acid in infant formulas using ultra performance liquid chromatography-triple quadrupole mass spectrometry

The method for analysing sialic acid in infant formulas by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) has been established. Sialic acid in milk was released via acid hydrolysis, and purified by an HLB solid phase extraction cartridge. The UPLC separation was performed on an ACQUITY UPLC BEH HILIC column (50 mm x 2.1 mm, 1.7 microm) utilizing a gradient elution program of acetonitrile and water (containing 0.1% formic acid) as the mobile phases at a flow rate of 0.25 mL/min. Injection volume and column temperature were set at 5 microL and 30 degrees C, respectively. The identification and quantification were achieved by using electrospray ionisation (ESI)-MS/MS in positive ion mode and multiple reaction monitoring (MRM) mode. The linear range was from 0.05 to 5.0 mg/L for sialic acid and the correlation coefficient (R(2)) was greater than 0.99. The average recoveries spiked at the four concentration levels of 0.1, 0.5, 2.5 and 5.0 mg/L ranged between 84.3% and 98.9% with the relative standard deviations from 4.9% to 8.2%. The limit of detection was 0.01 mg/L. Therefore, this method has the characteristics of simple operation, high reproducibility and sensitivity. It can be widely applied to determine the total contents of sialic acid in infant formula, cow milk and human milk.

The Relationship between Dietary Vitamin A Intake and the Levels of Sialic Acid in the Breast Milk of Lactating Women

Sialic acid (SA) is an important nutrient but few studies have examined the link between dietary intake and breast milk sialic acid. The purpose of this observational study was to assess the potential relationship between human breast milk sialic acid levels and dietary nutrition intake 40 d postpartum. The study population included 90 healthy women who were lactating. Human breast milk SA concentrations were measured using fluorescence detector-high performance liquid chromatography (HPLC-FLD) analysis and nutritional intake was estimated by a computerized validated food frequency questionnaire. SA in human breast milk was bound to free oligosaccharides (82.35%), protein (15.27%) and free sialic acid (2.37%). The findings of this study indicate that subjects with higher milk SA levels showed statistically higher levels of vitamin A compared with subjects with lower SA levels (423.48±172.29 vs. 602.22±126.46 μg/d, p=0.000). In addition, there was a certain association (standardized coefficients=0.713; p=0.000) between breast milk SA and vitamin A intake in healthy young subjects. This study demonstrated that dietary vitamin A intake has a certain relationship with breast milk SA concentrations. This may be attributed to the influence of vitamin A on sialic acid glycoprotein and sialic acid mucopolysaccharide in the human body or the common food sources for vitamin A and sialic acid. Additional study is required to further investigate this relationship.

Direct estimation of sialic acid in milk and milk products by fluorimetry and its application in detection of sweet whey adulteration in milk

Sialic acid, being a biologically active compound, is recognised as an important component of milk and milk products. Almost all the sialic acid estimation protocols in milk require prior hydrolysis step to release the bound sialic acid followed by its estimation. The objective of this work was to estimate sialic acid in milk and milk products by fluorimetric assay which does not require a prior hydrolysis step thus decreasing the estimation time. The recovery of added sialic acid in milk was 91·6 to 95·8%. Sialic acid in milk was found to be dependent on cattle breed and was in the range of 1·68-3·93g/kg (dry matter basis). The assay was further extended to detect adulteration of milk with sweet whey which is based on the detection of glycomacropeptide (GMP) bound sialic acid in adulterated milk. GMP is the C-terminal part of κ-casein which is released into the whey during cheese making. For detection of adulteration, selective precipitation of GMP was done using trichloroacetic acid (TCA). TCA concentration in milk was first raised to 5% to precipitate milk proteins, especially κ-casein, followed by raising the TCA concentration to 14% to precipitate out GMP. In the precipitates GMP bound sialic acid was estimated using fluorimetric method and the fluorescence intensity was found to be directly proportional to the level of sweet whey in adulterated milk samples. The method was found to detect the presence of 5% sweet whey in milk.

Sialic Acid Utilization

Early postnatal development encounters milk as a key environmental variable and yet the sole nutrient source. One evolutionary conserved constituent of milk is sialic acid, which is generally displayed on glycoconjugates and free glycans. During early postnatal development, high sialic acid need was proposed to be unmet by the endogenous sialic acid synthetic capacity. Hence, milk sialic acid was proposed to serve as a conditional nutrient for the newborn. In the elderly, at the other end of ontogeny, decreased sialylation in the brain, saliva, and immune system is observed. Analogous to the neonatal situation, the endogenous synthetic capacity may be unable to keep up with the need in this age group. The data discussed here propose a functional dietary role of sialic acid as a building block for sialylation and beyond.

Sialic Acid Utilisation and Synthesis in the Neonatal Rat Revisited

BackgroundMilk is the sole source of nutrients for neonatal mammals and is generally considered to have co-evolved with the developmental needs of the suckling newborn. One evolutionary conserved constituent of milk and present on many glycoconjugates is sialic acid. The brain and colon are major sites of sialic acid display and together with the liver also of synthesis.Methodology/Principal FindingsIn this study we examined in rats the relationship between the sialic acid content of milk and the uptake, utilization and synthesis of sialic acid in suckling pups. In rat milk sialic acid was found primarily as 3′sialyllactose and at highest levels between 3 and 10 days postpartum and that decreased towards weaning. In the liver of suckling pups sialic acid synthesis paralleled the increase in milk sialic acid reaching and keeping maximum activity from postnatal day 5 onwards. In the colon, gene expression profiles suggested that a switch from sialic acid uptake and catabolism towards sialic acid synthesis and utilization occurred that mirrored the change of sialic acid in milk from high to low expression. In brain sialic acid related gene expression profiles did not change to any great extent during the suckling period.Conclusions/SignificanceOur results support the views that (i) when milk sialic acid levels are high, in the colon this sialic acid is catabolized to GlcNAc that in turn may be used as such or used as substrate for sialic acid synthesis and (ii) when milk sialic acid levels are low the endogenous sialic acid synthetic machinery in colon is activated.

Determination of Sialic Acid in Milk and Products Using High Performance Anion-Exchange Chromatography Coupled with Pulsed Amperometric Detection

A resolved succinct environmental-friendly chromatographic method was developed for the determination of N-acetylneuraminic acid ( Neu5AC ) and N-glycolylneuraminic acid ( Neu5Gc ) in bovine milk and products using high-performance anion exchange chromatography coupled with pulsed amperometric detection. The conditions affecting the separation, detection and sialic acid release from milk were optimized. The separation was carried out on CarboPac PA20 anion-exchange column using 100 mmol/L NaOH, 20 - 300 mmol/L NaAc gradient eluting in 20 min at the flow rate of 0. 5 mL/min. The separation and detection temperature were both at 30 degrees C. The detection was carried out on a gold working electrode. The detection limits were 3. 0 and 1. 8 mu g/L and the linear range of 5 to 500 mu g/L was obtained (25. 0 mu L injection, three times of the baseline noise). The spiked recovery of Neu5AC and Neu5Gc in milk was 88% - 115%.

Concentration and distribution of sialic acid in human milk and infant formulas

In animal studies, sialic acid supplementation is associated with increases of gangliosides in the brain and improved learning ability. Only limited data are available on the sialic acid content of human milk and infant formulas. We compared the concentrations of oligosaccharide-bound, protein-bound, and free sialic acid in milk from mothers of full-term and preterm infants and in a range of infant formulas. The milk from 20 and 14 mothers of full-term and preterm infants (mean gestational age: 31 +/- 3 wk), respectively, was collected at 4 stages of lactation (colostrum, transition, 1 mo, and 3 mo) and compared with 21 different infant formulas. Total sialic acid concentrations were highest in colostrum (x +/- SEM: 5.04 +/- 0.21 mmol/L in full term) and decreased by nearly 80% over the next 3 mo. Human milk from mothers of preterm infants contained 13-23% more sialic acid than did milk from mothers of full-term infants at 3 of the 4 lactation stages (P < 0.02). The sialic acid content of most formulas was <25% of that found in mature human milk (P < 0.01). Most of the sialic acid in the formulas ( approximately 70%) was bound to glycoproteins, whereas in human milk most sialic acid was bound to free oligosaccharides. Human milk, including milk from mothers of preterm infants, is a rich source of oligosaccharide-bound sialic acid, which contrasts with the relatively small amounts found in infant formulas. The nutritional significance of sialic acid is presently unknown, but it is plausible that it is a conditional nutrient that contributes to sialic acid accretion in the brain.

A colorimetric assay for the enzymic determination of sialic acid in milk

A colorimetric assay for routine enzymic determination of free sialic acid in milk is proposed. Sialic acid is cleaved intoN-acetyl-d-mannosamine and pyruvate byN-acetylneuraminic acid aldolase; the pyruvate content is measured by lactate dehydrogenase in the presence of NADH, as a change of absorbance at 340 nm. The proposed method showed good correlation with the chemical method (r=0.988), high recovery (98.0%) and repeatability (S r =0.5–0.6 mg/L) as well as high accuracy (S y,x =0.28 mg/L). The assay may be useful for routine analysis of milk, as an indicator for the quality of the raw material to be used for production of UHT milk. The normal value range is 9.0±4.0 mg/L (mean±standard deviation;n=41). Conclusions about the initial concentration of the free sialic acid in the raw material, in order to obtain an idea of the quality, cannot readily be drawn from determinations in UHT milk without knowledge of the severity of the heating process.

牛乳のシアル酸

カゼインにレンネットを作用させると,蛋白質給合性シアル酸が遊離するが,本実験ではシァル酸の遊離に際し,そのpH,温度等の影響を調べた.同時に遊離するNPNの含量も測定し比較検討した,なお電気泳動およびDEAE-セルロースカラムクロマトグラフィによつてレンネット作用をうけたカゼインの変化をみた.試料は脱脂乳,精製した酸カゼイン,初乳の酸カゼインおよびHILLの方法によつて分割したk-richカゼインを用いた.遊離したシァル酸含量は,一定量の試料にレンネットを添加し,一定温度で一定時間反応させた後,最終濃度12% TCAを加え遠心ろ過し,そのろ液中に含まれている量を測定,百分率で示した.結果は次の通りである.1. 60分間のレンネット作用によつて,常乳の酸カゼイン,脱脂乳,初乳の酸カゼインおよびk-richカゼインから遊離したシアル酸含量はそれぞれ37.0%,46.0%,51.56%および66.92%であつた.2. 常乳の酸カゼイン,脱脂乳,初乳の酸カゼインおよびk-richカゼインから遊離したNPN含量はそれぞれ1.5%,1.85%,2.70%および6.96%であつた.3. レンネットの初期反応において,蛋白質結合性シアル酸遊離のための至適pHは4.8～5.5であつた.4. 0～40°Cの範囲内で遊離したシアル酸およびNPNから求めた活性化エネルギーは10,960±800cal/molであつた.5. レンネット作用をうけたカゼインは,電気泳動図において,常乳の酸カゼインの場合はα-カゼインに相当する峰に,初乳の酸カゼインではα-およびβ-カゼインに相当する峰に開裂が生じた.6. DEAE-セルロースカラムクロマトグラフィにおいて,レンネット作用後常乳の酸カゼインはフラクション10および11,初乳の酸カゼインではフラクション10,11および12が消失した.

牛乳のシアル酸

牛乳のシアル酸