Opioid peptides and psychiatric illness

In the 10 years since Hughes et al (1975) identified from porcine brain two related pentapeptides with potent opiate activity, abnormalities of endorphin and enkephalin production or metabolism have been postulated in many disease states. The possibility of an advance in our understanding of the aetiology of functional psychiatric illness has led to a considerable body of research, which is discussed in this paper.     

牛奶来源蛋白及活性肽降压效果的研究进展

高血压是21世纪的全球公共卫生问题。高血压与饮食密切相关,牛奶富含蛋白质,主要为酪蛋白和乳清蛋白。关于牛奶来源蛋白及其活性肽是否能通过抑制血管紧张素转化酶(ACE)降低血压,未能得出一致的结论。本文系统介绍近年来相关的动物实验和人群研究,以期全面评价牛奶来源蛋白及活性肽与血压的关系,为基础研究、临床实践和乳品加工提供科学依据。     

Immunoregulatory peptides in bovine milk

Bovine milk is known to contain a number of peptide fractions that can affect immune function. The vast majority of immunoregulatory peptides that have been characterised are hydrolysate derivatives of major milk proteins. Recent research has also indicated that the metabolic activity of probiotic lactic acid bacteria can generate de novo immunoregulatory peptides from milk, via enzymatic degradation of parent milk protein molecules. In contrast, relatively little is known of endogenous, preformed immunoregulatory peptides in milk that may be relevant to modulating human health. The natural in vivo role of preformed and enzymatically derived peptides is likely to be one of regulation of the neonatal (bovine) gastrointestinal tract immune system, in order to modulate immune function with respect to the development of immunocompetence and avoidance of undesirable immunological responses (e.g. tolerance, and hypersensitivity to nutrients). There is scope for the further characterisation of both the origin and function of milk-derived immunoregulatory peptides, so that their potential to influence human health can be fully appraised. This review highlights our current knowledge of milk-derived immunoregulatory peptides, and outlines areas that are of relevance for further research.     

Angiotensin converting enzyme inhibitory peptides from a lactotripeptide-enriched milk beverage are absorbed intact into the circulation

Food products containing angiotensin converting enzyme (ACE) inhibitory peptides reportedly play a role in treatment of mild hypertension. The aim of this placebo-controlled crossover study was to assess the bioavailability of Ile-Pro-Pro and 7 other ACE-inhibiting peptides present in a lactotripeptide (LTP)-enriched yogurt beverage and whether meal intake affects Ile-Pro-Pro bioavailability. Six male and female subjects randomly consumed an LTP-enriched yogurt beverage or a placebo in the fasted state and an LTP-enriched yogurt beverage in the fed or fasted state. The area under the curve (AUC) of Ile-Pro-Pro after the LTP treatment in the fasted state was 2.1-fold of that after the placebo treatment (P < 0.001). The maximum peptide plasma concentration (C(max)) value was greater after consumption of the LTP-enriched beverage (897 +/- 157 pmol/L) than after the placebo treatment (555 +/- 0.09 pmol/L; P < 0.001) with a greater time after ingestion when reaching C(max) (T(max)) in the placebo treatment. Plasma concentrations of the peptides Leu-Trp, Phe-Tyr, Ile-Tyr, and Leu-Pro-Pro increased compared with baseline (P < 0.05) in the LTP-enriched and placebo treatment when consumed in the fasted state. However, DeltaC(max) values differed significantly between the placebo and LTP-enriched treatment only for Leu-Pro-Pro. Meal intake affected Ile-Pro-Pro concentrations. When the beverage was consumed after a meal, the AUC of Ile-Pro-Pro was 1.3-fold (P < 0.05) of the AUC derived from premeal intake. This was due to an increase in the plasma elimination half-life (P < 0.05); C(max) and T(max) were not affected by meal intake. In summary, this is the first demonstration, to our knowledge, that the tripeptide Ile-Pro-Pro selectively escapes from intestinal degradation and reaches the circulation undegraded.     

Hypotensive peptides from milk proteins

Hypertension is the major controllable risk factor associated with cardiovascular disease (CVD) events such as myocardial infarction, stroke, heart failure, and end-stage diabetes. A 5 mm Hg decrease in blood pressure has been equated with approximately 16% decrease in CVD. In the U.S. alone current annual antihypertensive drug costs are approximately dollars 15 billion. The renin-angiotensin-aldosterone system is a target for blood pressure control. Cleavage of angiotensinogen by renin produces angiotensin I which is subsequently hydrolyzed by angiotensin-I-converting enzyme (ACE) to angiotensin II (a potent vasoconstrictor). Various side effects are associated with the use of ACE inhibitory drugs in the control of blood pressure including hypotension, increased potassium levels, reduced renal function, cough, angioedema, skin rashes, and fetal abnormalities. Milk proteins, both caseins and whey proteins, are a rich source of ACE inhibitory peptides. Several studies in spontaneously hypertensive rats show that these casokinins and lactokinins can significantly reduce blood pressure. Furthermore, a limited number of human studies have associated milk protein-derived peptides with statistically significant hypotensive effects (i.e., lower systolic and diastolic pressures). The advent of effective milk protein based functional food ingredients/nutraceuticals for the prevention/control of blood pressure therefore has the potential to significantly reduce global healthcare cost.     

Postpartum changes in pattern of gastrointestinal regulatory peptides in human milk

Concentrations of gastrointestinal neuropeptides in serial human milk samples from 28 women were determined over the first 6 postpartum mo. All gut neuropeptides were present during the first postpartum week. Gastric inhibitory peptide (GIP) concentration remained constant but the others decreased by 6 wk. Bombesin concentration in breast milk was threefold greater than concurrent plasma concentration (p less than 0.001); all other neuropeptides were at the same or lower concentrations in milk than in plasma. At 36 wk gestation plasma concentrations of GIP were lower and concentrations of vasoactive intestinal peptide were higher than concentrations in age-matched control subjects. Concentrations of gastrin and cholecystokinin, bombesin, peptide histidine methionine, peptide YY, and neurotensin in plasma were similar in pregnant and nonpregnant women. These gut neuropeptides in milk may be important for growth and maturation of the gastrointestinal system in neonates. Bombesin may contribute to neonatal hypergastrinemia.     

牛奶及奶粉中蛋白质的快速测定法

目的:建立一种牛奶及奶粉中蛋白质的快速测定方法。方法:在试管中以双氧水-硫酸加热,快速消解牛奶及奶粉中的蛋白质,使用纳氏试剂比色法测定。结果:快速消解只需5分钟即可完成。两个品种牛奶中蛋白质各测定8次,相对标准偏差分别为3.9%和1.3%,用甘氨酸标准溶液做回收试验,回收率99.4%。用本法测定奶粉标准物质(GBW10017)6次,与标准值比较结果无显著性差异。结论:该方法操作简单,结果可靠。     

Vitamin K1 binding protein in milk

Cow's milk has been shown to contain a protein complex which is able to bind vitamin K1 in a reversible manner. This binding property has been investigated by the celite method which consists in creating a dynamic equilibrium between the adsorbent, the celite and the protein complex for the ligand (vitamin K1). Based on competition experiment, the binding is specific and the vitamin K1 binding protein complex has a molecular weight equal to or higher than 7.5 X 10(2) KD.     

Splenectomised and spleen intact Aotus monkeys' immune response to Plasmodium vivax MSP-1 protein fragments and their high activity binding peptides

Two E. coli expressed recombinant polypeptides (rPvMSP-1(14) and rPvMSP-1(20)) contained in the 33kDa fragment, located within Plasmodium vivax merozoite surface protein (PvMSP-1) 42kDa C-terminal region, and a cocktail of high reticulocyte binding synthetic peptides located within these fragments, were evaluated for immunogenicity and protective immune responses in splenectomised and spleen intact Aotus nancymaae monkeys. Thirty splenectomised monkeys who had been previously immunised with either rPvMSP-1(14), rPvMSP-1(20), or a mixture of both recombinant fragments were intravenously challenged with the heterologous P. vivax VCG-1 strain (as determined by DNA sequencing); full protection was observed in five monkeys and low parasitaemia levels were obtained in eight more monkeys. Splenectomised control monkey group rapidly developed high parasitaemia levels, while no significant parasitaemia was obtained in the non-splenectomised control group. Although PvMSP-1 42 and 33kDa fragments were recognised by Western Blot and whole parasites by IFAT when tested with immune monkey sera, no correlation between protection and antibody titres by IFAT and ELISA was observed, suggesting that protection is not being solely mediated by a humoral immune response. This data showed that partial protection against a heterologous strain challenge was best achieved when immunising with a rPvMSP-1(14)-rPvMSP-1(20) mixture (2 were fully protected and 4 with low parasitaemia out of 12) suggesting for the first time, that these fragments could be good candidates for inclusion in a P. vivax multi-stage, multi-antigen vaccine.     

Review: Production and functionality of active peptides from milk

In recent years, research on the production of active peptides obtained from milk and their potential functionality has grown, to a great extent. Bioactive peptides have been defined as specific protein fragments that have a positive impact on body functions or conditions, and they may ultimately have an influence on health. Individual proteins of casein or milk-derived products such as cheese and yogurt have been used as a protein source to study the isolation and activity of peptides with several applications. Currently, the milk whey waste obtained in the production of cheese also represents a protein source from which active peptides could be isolated with potential industrial applications. The active properties of milk peptides and the results found with regard to their physiological effects have led to the classification of peptides as belonging to the group of ingredients of protein nature, appropriate for use in functional foods or pharmaceutical formulations. In this study, the main peptides obtained from milk protein and the past research studies about its production and biological activities will be explained. Second, an analysis will be made on the methods to determinate the biological activities, the separation of bioactive peptides and its structure identification. All of these form the base required to obtain synthetic peptides. Finally, we explain the experimental animal and human trials done in the past years. Nevertheless, more research is required on the design and implementation of equipment for the industrial production and separation of peptides. In addition, different authors suggest that more emphasis should therefore be given to preclinical studies, proving that results are consistent and that effects are demonstrated repeatedly by several research human groups.     

Detection of genetically modified DNA sequences in milk from the Italian market

The possible transfer and accumulation of novel DNA and/or proteins in food for human consumption derived from animals receiving genetically modified (GM) feed is at present the object of scientific dispute. A number of studies failed to identify GM DNA in milk, meat, or eggs derived from livestock receiving GM feed ingredients. The present study was performed in order to: (i) develop a valid protocol by PCR and multicomponent analysis for the detection of specific DNA sequences in milk, focused on GM maize and GM soybean; (ii) assess the stability of transgenic DNA after pasteurization treatment and (iii) determine the presence of GM DNA sequences in milk samples collected from the Italian market. Results from the screening of 60 samples of 12 different milk brands demonstrated the presence of GM maize sequences in 15 (25%) and of GM soybean sequences in 7 samples (11.7%). Our screening methodology shows a very high sensitivity and the use of an automatic identification of the amplified products increases its specificity and reliability. Moreover, we demonstrated that the pasteurization process is not able to degrade the DNA sequences in spiked milk samples. The detection of GM DNA in milk can be interpreted as an indicator of fecal or airborne contamination, respectively, with feed DNA or feed particles, although an alternative source of contamination, possibly recognizable in the natural environment can be suggested. Further studies, performed on a larger number of milk samples, are needed to understand the likely source of contamination of milk collected from the Italian market.     

紫外分光光度法快速测定液体奶、奶粉中蛋白质含量

目的：建立非蛋白质类含氮物质对测定结果无干扰的乳与乳制品中蛋白质的快速测定方法。方法：在280 nm波长处,分别测定乳品标样应用液与样品稀释液的吸光度值,基于测定液中蛋白质含量与其吸光度值呈正比关系,计算出样品中蛋白质的含量。结果：乳与乳制品中蛋白质浓度在0.1～1.0 mg/ml范围内标准应用曲线呈线性关系,曲线的回归方程为：Y=0.874X-0.002,相关系数r=0.9994,加标回收率96.0%～104.1%。结论：紫外分光光度法适用于液体奶、奶粉中蛋白质的快速检验和掺伪检验。     

Compartmentalization and quantitation of protein in human milk

Human milk protein was determined by three colorimetric methods and by Kjeldahl analysis. The distribution of nitrogen (N) and protein was determined within various milk compartments. Total N, whey, casein, nonprotein nitrogen (NPN), cell N and N in the fat fraction were analyzed by micro-Kjeldahl analysis after a series of centrifugation and ultracentrifugation separations. Fresh milk samples (colostrum, transitional milk and mature milk) were centrifuged at 500 X g to separate milk cells and at 5000 X g to skim the milk. Decelled milk and skimmed milk were ultracentrifuged at 189,000 X g to separate fat and casein micelles from whey. NPN was analyzed after trichloroacetic acid precipitation. Whole milk, decelled milk, skimmed milk and whey were analyzed for protein with the Lowry method, modified for fat-containing samples, the Bradford dye-binding assay (Bio-Rad) and the Pierce bicinchoninic acid (BCA) assay. Cell nitrogen had a tendency to be lower in mature milk than in colostrum. Colostrum contained only 6% casein protein, whereas mature milk contained 13%. Fat from skimming was lower in N than fat from ultracentrifugation. Average NPN levels were similar for milk from all three lactation periods, and constituted 10% of colostrum N and 25% of mature milk N. Protein determined by the Bio-Rad method on whole milk samples had the lowest variability (square root MSE) when correlated to Kjeldahl values. All three assays had lower variability when analyzing whey and skimmed milk than when analyzing whole milk. The Lowry method and the Bio-Rad method had low variability for whey and skimmed milk samples, but the Lowry method yielded analytical values closest to Kjeldahl protein values. The BCA method consistently overestimated Kjeldahl protein by 30%.     

A fermented milk high in bioactive peptides has a blood pressure-lowering effect in hypertensive subjects

BACKGROUND: Angiotensin-converting enzyme (ACE; EC 3.4.15.1) plays a dual role in the regulation of hypertension: it catalyzes the production of the vasoconstrictor angiotensin II and it inactivates the vasodilator bradykinin. By inhibiting these processes, ACE inhibitors have antihypertensive effects. Peptides derived from milk proteins can have ACE-inhibiting properties and may thus be used as antihypertensive components. OBJECTIVE: We evaluated the long-term blood pressure-lowering effect of milk fermented by Lactobacillus helveticus LBK-16H in hypertensive subjects. DESIGN: In a randomized placebo-controlled study, 39 hypertensive patients received 150 mL/d of either L. helveticus LBK-16H fermented milk or a control product for 21 wk after a 2-wk run-in period. During the run-in period, the average baseline diastolic and systolic blood pressure values were 155 and 97 mm Hg, respectively, in the test product group and 152 and 96 mm Hg, respectively, in the control group. After the run-in period, blood pressure was measured at home on the same day every week with the use of an automatic blood pressure recorder. RESULTS: There was a mean difference of 6.7 +/- 3.0 mm Hg in systolic blood pressure (P = 0.030) and of 3.6 +/- 1.9 mm Hg (P = 0.059) in diastolic blood pressure between the test product and control groups. Demographic factors had no significant effect on the responses. CONCLUSION: L. helveticus LBK-16H fermented milk containing bioactive peptides in normal daily use has a blood pressure-lowering effect in hypertensive subjects.     

Identification of peptides present in sour milk whey that ameliorate scopolamine-induced memory impairment in mice

Cognitive impairment is treated with cholinesterase inhibitors that slow cognitive decline but cause significant adverse effects. Functional foods that improve memory without such effects would therefore be valuable. We reported that unidentified components of sour milk whey produced by fermentations using Lactobacillus helveticus and Saccharomyces cerevisiae improved memory in a mouse model of scopolamine-induced memory impairment. Here, we show that casein-derived peptides were the most active components of orally administered fractions of this milk product. Of five peptides tested, β-casein (residues 73–91) was the most effective for ameliorating scopolamine-induced cognitive deficits, as indicated by a significantly higher percentage of alternations of mice orally administered 0.05?nmol/kg peptide (58.0?±?9.3%) versus vehicle (51.0?±?5.8%). This orally active peptide may improve cognitive function of patients with dementia.     

Mineral-binding milk proteins and peptides; occurrence, biochemical and technological characteristics

Minerals and trace elements in cow's milk occur as inorganic ions and salts or form complexes with proteins and peptides, carbohydrates, fats and small molecules. The main mineral binder or chelators of calcium are the caseins, alphas1-casein, alphas2-casein, beta-casein and kappa-casein, but also whey proteins and lactoferrin bind specific minerals like calcium, magnesium, zinc, iron, sodium and potassium. Less documented is the binding of trace elements. Peptides obtained by in vitro or in vivo hydrolysis act as mineral trappers through specific and non-specific binding sites. They may then function as carriers, chelators, of various minerals and thus enhance or inhibit bioavailability. Peptides from milk proteins have found interesting new applications in the food industry as products with improved functionality or as ingredients of dietary products, or used in pharmaceutical industry. Fortification of foods with minerals in a low concentration has for a long time been used in some countries to overcome mineral deficiency, which is an increasing problem in humans. These types of foods are being used to create a new generation of super foods in the industry today.     

奶粉中蛋白质的快速滴定法

食品中蛋白质的测定常选用国家标准《食品卫生检验方法·理化部分(一)》(GB/T5009.5-2003)中第一法凯氏定氮法,该法繁琐费时。参考有关资料,通过实验发现用十二烷基硫酸钠(SDS)直接滴定酸化稀释后的奶粉中的蛋白质,方法简便且与凯氏法测得结果无显著差异。1原理当SDS溶液缓慢滴入蛋白质溶液时,在酸性介质中,可溶性蛋白质会突然沉淀出来,且SDS的消耗量与蛋白质含量成正比。2试剂2.1 2g/LSDS溶液称取干燥24h的SDS 20.00g用蒸馏水溶解,并定容至1000m l。2.2 0.1 mol/L盐酸2.3标定用的试剂与仪器同凯氏法3方法吸取奶样1.00 m l~2.00 m l…     

乳粉中蛋白质测定条件的改进

目的对乳粉中蛋白质测定条件进行改进,以便于实验的操作和控制。方法参照中华人民共和国国家标准《食品中蛋白质的测定》（GB／T5009．5—2003）对《婴幼儿配方食品和乳粉蛋白质的测定》（GB／T5413．1—1997）中的试样前处理和消化液的蒸馏2个重要步骤用同一乳粉进行蛋白质含量的测定比对。结果测定条件改进前后所测同一乳粉中蛋白质含量结果无差异性。结论改进后的测定条件在乳粉中蛋白质测定时容易操作和控制,不易导致测定实验失败。