Changes of beta-casomorphin content in human milk during lactation

Human milk: From complex tailored nutrition to bioactive impact on child cognition and behavior

Human milk is a highly complex liquid food tailor-made to match an infant's needs. Beyond documented positive effects of breastfeeding on infant and maternal health, there is increasing evidence that milk constituents also impact child neurodevelopment. Non-nutrient milk bioactives would contribute to the (long-term) development of child cognition and behavior, a process termed 'Lactocrine Programming'. In this review we discuss the current state of the field on human milk composition and its links with child cognitive and behavioral development. To promote state-of-the-art methodologies and designs that facilitate data pooling and meta-analytic endeavors, we present detailed recommendations and best practices for future studies. Finally, we determine important scientific gaps that need to be filled to advance the field, and discuss innovative directions for future research. Unveiling the mechanisms underlying the links between human milk and child cognition and behavior will deepen our understanding of the broad functions of this complex liquid food, as well as provide necessary information for designing future interventions.

Insights into the Research Trends on Bovine Colostrum: Beneficial Health Perspectives with Special Reference to Manufacturing of Functional Foods and Feed Supplements

Bovine colostrum (BC) is the initial mammary secretion after parturition, which is nature's bountiful source consisting of nutritional and bioactive components present in a highly concentrated low-volume format. All mammalian newborns require colostrum to enhance physiological processes such as lifelong immunity, gastrointestinal development, and resistance to microbial infections. The genetic, environmental, and processing methods can all have an impact on the biochemical contents of BC and its supplements. BC and its derivatives have been intensively researched for their potential use in functional foods, medicines, and animal feed. Evidence from clinical studies suggests that BC products are well-tolerated, nontoxic, and safe for human ingestion. Functional foods, feed, and pharmaceutical formulations based on bovine colostrum are playing noteworthy roles in the development of innovative products for promoting health and the prevention of chronic illnesses. This systematic review sheds light on recent research on (a) the effects of processing techniques on BC components, (b) emerging techniques used in the isolation and identification of novel components, (c) BC-based functional foods for human consumption and animal feed supplements, and (d) the role of BC in current drug delivery, as well as future recommendations.

Neuromodulatory peptides: Orally active anxiolytic-like and antidepressant-like peptides derived from dietary plant proteins

Mental disorders are a severe health problem, and the number of patients is growing worldwide. Increased anxiety and decreased motivation due to excessive mental stress further accelerated the severity of the problem. Enzymatic digestion of food proteins produces bioactive peptides with various physiological functions, some of which exhibit neuromodulatory effects with oral administration. Recently, studies reported that some peptides produced from plant proteins such as soybeans, leaves, and grains exhibit emotional regulatory functions such as strong anxiolytic-like and antidepressant-like effects comparable to pharmaceuticals. Conventionally, researchers investigated bioactive peptides by fractionation of protein hydrolysates and structure-activity relationship. As a novel methodology for analyzing bioactive peptides, the information obtained by peptidomics simultaneous analysis of the digested fractions of proteins using mass spectrometry has been effectively utilized. Some small-sized peptides such as dipeptides and tripeptides released food-derived proteins show emotional regulating effects. Moreover, some middle-sized peptides produced after intestinal digestion may exhibit the emotional regulating effect via the vagus nerve, and the importance of the gut-brain axis is also focused. As the central mechanism of emotional regulation, it has been found that these plant-derived peptides regulated monoamine neurotransmitter signaling and hippocampal neurogenesis.

Casomorphins and Gliadorphins Have Diverse Systemic Effects Spanning Gut, Brain and Internal Organs

Food-derived opioid peptides include digestive products derived from cereal and dairy diets. If these opioid peptides breach the intestinal barrier, typically linked to permeability and constrained biosynthesis of dipeptidyl peptidase-4 (DPP4), they can attach to opioid receptors. The widespread presence of opioid receptors spanning gut, brain, and internal organs is fundamental to the diverse and systemic effects of food-derived opioids, with effects being evidential across many health conditions. However, manifestation delays following low-intensity long-term exposure create major challenges for clinical trials. Accordingly, it has been easiest to demonstrate causal relationships in digestion-based research where some impacts occur rapidly. Within this environment, the role of the microbiome is evidential but challenging to further elucidate, with microbiome effects ranging across gut-condition indicators and modulators, and potentially as systemic causal factors. Elucidation requires a systemic framework that acknowledges that public-health effects of food-derived opioids are complex with varying genetic susceptibility and confounding factors, together with system-wide interactions and feedbacks. The specific role of the microbiome within this puzzle remains a medical frontier. The easiest albeit challenging nutritional strategy to modify risk is reduced intake of foods containing embedded opioids. In future, constituent modification within specific foods to reduce embedded opioids may become feasible.

Bioactive Compounds in Infant Formula and Their Effects on Infant Nutrition and Health: A Systematic Literature Review

Infant formulas are an alternative to replace or supplement human milk when breastfeeding is not possible. The knowledge of human milk's bioactive compounds and their beneficial effects has attracted the interest of researchers in the field of infant nutrition, as well as researchers of technology and food sciences that seek to improve the nutritional characteristics of infant formulas. Several scientific studies evaluate the optimization of infant formula composition. The bioactive compound inclusion has been used to upgrade the quality and nutrition of infant formulas. In this context, the purpose of this systematic literature review is to assess the scientific evidence of bioactive compounds present in infant formulas (α-lactalbumin, lactoferrin, taurine, milk fat globule membrane, folates, polyamines, long-chain polyunsaturated fatty acids, prebiotics, and probiotics) and their effects on infant nutrition and health. Through previously determined criteria, studies published in the last fifteen years from five different databases were included to identify the advances in the optimization of infant formula composition. Over the last few years, there has been optimization of the infant formula composition, not only to increase the similarities in their content of macro and micronutrients but also to include novel bioactive ingredients with potential health benefits for infants. Although the infant food industry has advanced in the last years, there is no consensus on whether novel bioactive ingredients added to infant formulas have the same functional effects as the compounds found in human milk. Thus, further studies about the impact of bioactive compounds in infant nutrition are fundamental to infant health.

The protective effects of human milk-derived peptides on the pancreatic islet biology

Several epidemiological studies support the protective role of breastfeeding in reducing the risk for type 1 diabetes. Human breast milk is the perfect nutrition for infants and contains many complex proteins, lipids and carbohydrates. In this study, we examined the physiological effects of human milk-derived opioid peptides, β-casomorphins (BCM), and compared them with bovine-milk-derived opioid peptides on pancreatic hormone regulation and β-cell regeneration. Exposure of wild-type zebrafish embryos to 50 µg/ml of human BCM-5 and -7 from 3 days post fertilisation until 6 days post fertilisation resulted in an increased insulin domain of expression while exposure to bovine BCM-5 and -7 significantly reduced the insulin domain of expression as analysed by whole-mount in situ hybridisation. These changes may be accounted for by reduced insulin expression or β-cell number and were mitigated by the µ-opioid receptor antagonist, naloxone. The effect of BCM on β-cell regeneration was assessed following ablation of β-cells in Tg (ins: CFP-NTR) zebrafish from 3 days post fertilisation to 4 days post fertilisation, followed by exposure of bovine and human BCM-5 and -7 (50 µg/ml) from 4 days post fertilisation until 7 days post fertilisation. The regenerative capacity of β-cells was not impeded following exposure to human BCM-5 and -7, whereas the capacity of β-cells to regenerate following bovine BCM-5 and -7 exposure was reduced. Our data suggest that human BCM-5 and -7 may promote β-cell development and enable the regeneration of β-cells, while the bovine-milk-derived peptides, BCM-5 and -7, play an opposite role. These data may provide some biological explanation for the protective effect of breastfeeding on the development of type 1 diabetes.

Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein

This is the first systematic review, to our knowledge, of published studies investigating the gastrointestinal effects of A1-type bovine β-casein (A1) compared with A2-type bovine β-casein (A2). The review is relevant to nutrition practice given the increasing availability and promotion in a range of countries of dairy products free of A1 for both infant and adult nutrition. In vitro and in vivo studies (all species) were included. In vivo studies were limited to oral consumption. Inclusion criteria encompassed all English-language primary research studies, but not reviews, involving milk, fresh-milk products, β-casein, and β-casomorphins published through 12 April 2017. Studies involving cheese and fermented milk products were excluded. Only studies with a specific gastrointestinal focus were included. However, inclusion was not delimited by specific gastrointestinal outcome nor by a specific mechanism. Inclusion criteria were satisfied by 39 studies. In vivo consumption of A1 relative to A2 delays intestinal transit in rodents via an opioid-mediated mechanism. Rodent models also link consumption of A1 to the initiation of inflammatory response markers plus enhanced Toll-like receptor expression relative to both A2 and nonmilk controls. Although most rodent responses are confirmed as opioid-mediated, there is evidence that dipeptidyl peptidase 4 stimulation in the jejunum of rodents is via a nonopioid mechanism. In humans, there is evidence from a limited number of studies that A1 consumption is also associated with delayed intestinal transit (1 clinical study) and looser stool consistency (2 clinical studies). In addition, digestive discomfort is correlated with inflammatory markers in humans for A1 but not A2. Further research is required in humans to investigate the digestive function effects of A1 relative to A2 in different populations and dietary settings.

Study protocol: An investigation of mother-infant signalling during breastfeeding using a randomised trial to test the effectiveness of breastfeeding relaxation therapy on maternal psychological state, breast milk production and infant behaviour and growth

Background

The physiological and psychological signalling between mother and infant during lactation is one of the prominent mother-infant factors that may influence breastfeeding outcomes. The infant can ‘signal’ his needs through vocalisation, and the mother can respond by allowing or restricting nipple access, which might alter the breast milk composition or volume. This may lead to parent-offspring conflict during the lactation period. Challenging infant behaviour has also been associated with maternal psychological distress, which might affect breastfeeding performance. Most attempts to improve breastfeeding rates focus on providing additional support, yet many aspects of the breastfeeding process are poorly understood. Thus, our objective is to investigate mother-infant signalling during breastfeeding by manipulating maternal psychological state using a relaxation therapy intervention. The study will test the hypothesis that mothers who listen to the therapy will be more relaxed/less stressed and this will favourably alter breast milk composition and/or affect milk volume and hence influence infant outcomes.

Methods

A randomised controlled trial will be conducted in first-time breastfeeding mothers and their new-born infants. Pregnant mothers will be recruited at antenatal clinics in Selangor, Malaysia, and four home visits will be carried out at 2, 6, 12 and 14 weeks postnatally. Participants will be randomised into a control and an intervention group in the early post-partum period. Mothers from the intervention group will be asked to listen daily to an audio recording with relaxation therapy during breastfeeding. Maternal psychological state, breastfeeding practices and infant behaviour will be assessed using validated questionnaires. Milk volume will be measured using stable isotopes. Breast milk samples will be collected to measure macronutrient content and hormone levels. Anthropometric measurements (weight, length and head circumference) will be performed during all home visits, including body composition at week 14.

Discussion

The main outcomes will be the effect of the intervention on maternal psychological state, milk production, cortisol levels, and infant behaviour and growth. Secondary outcomes will be associations between breast milk composition and infant appetite and growth. This study aims to provide a greater understanding of maternal-infant factors which influence breastfeeding outcomes and which may be useful targets for future interventions.

Trial registration

ClinicalTrials.gov identifier: NCT01971216.

Formation and Degradation of Beta-casomorphins in Dairy Processing

Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from β-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B β-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzyme-linked immunosorbent assay (ELISA) has been used to analyze BCMs in dairy products. BCMs have been detected in raw cow's milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown.

Milk Intolerance, Beta-Casein and Lactose

True lactose intolerance (symptoms stemming from lactose malabsorption) is less common than is widely perceived, and should be viewed as just one potential cause of cows’ milk intolerance. There is increasing evidence that A1 beta-casein, a protein produced by a major proportion of European-origin cattle but not purebred Asian or African cattle, is also associated with cows’ milk intolerance. In humans, digestion of bovine A1 beta-casein, but not the alternative A2 beta-casein, releases beta-casomorphin-7, which activates μ-opioid receptors expressed throughout the gastrointestinal tract and body. Studies in rodents show that milk containing A1 beta-casein significantly increases gastrointestinal transit time, production of dipeptidyl peptidase-4 and the inflammatory marker myeloperoxidase compared with milk containing A2 beta-casein. Co-administration of the opioid receptor antagonist naloxone blocks the myeloperoxidase and gastrointestinal motility effects, indicating opioid signaling pathway involvement. In humans, a double-blind, randomized cross-over study showed that participants consuming A1 beta-casein type cows’ milk experienced statistically significantly higher Bristol stool values compared with those receiving A2 beta-casein milk. Additionally, a statistically significant positive association between abdominal pain and stool consistency was observed when participants consumed the A1 but not the A2 diet. Further studies of the role of A1 beta-casein in milk intolerance are needed.

μ-Opioid receptor gene (OPRM1) polymorphism in patients with breast cancer

Structure-dependent μ-opioid receptor (MOR) activity is an important element in cancer opioid analgesic effectiveness. It is widely accepted that guanine (G) substitution for adenine (A) at OPRM1 gene sequence position 118 changes receptor glycosylation pattern. This is associated with decreased binding ability in both exogenous and endogenous opioids, resulting in increased human pain resistance. The endogenous opioid system's function in body homeostasis maintenance is considered mainly regulatory, so its participation in breast tumor formation and progression is identified herein. We examine the association of the most frequent MOR (A118G) gene polymorphism on breast cancer risk in a Northeastern Polish population by PCR-RFLP comparison of A and G allele frequency at OPRM1 gene A118G polymorphic site in breast cancer-diagnosed patients with healthy control group frequencies. Our results highlight a strong association between G allele presence at μ-opioid receptor A118G and increased breast cancer incidence (OR = 3.3, 95 % CI 2.2-5.0, p < 0.0001) and female gender (OR = 2.0, 95 % CI 1.4-2.9, p = 0.0004). Consequently, OPRM1 G allele presence at that site is a highly significant risk factor in breast cancer development.

Glucose and calcium ions may modulate the efficiency of bovine β-casomorphin-7 permeability through a monolayer of Caco-2 cells

Milk and dairy products provide a lot of valuable nutritive elements. They are also sources of biologically active peptides, including β-casomorphins that manifest the properties of morphine. An activity of DPPIV seems to be most crucial factor decreasing the efficiency of the β-casomorphin-7 (BCM7) transport. The increase of BCM7 concentration in blood may intensify symptoms of apparent life threatening events (ALTE), autism, schizophrenia, and allergy. This study aimed at identifying the influence of several selected substances on a transport efficiency of bovine BCM7 through an intestinal monolayer in a Caco-2 cell model system. Applying the ELISA method, the permeability coefficient of BCM7 through the Caco-2 monolayer was calculated. TEER values were used to evaluate the integrity of Caco-2 cell monolayers. An increase of glucose and Ca(2+) concentrations in the culture medium was accompanied by an increase of the BCM7 transport efficiency. The lowest permeability coefficients of BCM7 were observed for the membranes with high electrical resistances. The transport was enhanced in the presence of milk infant formulas, whereas no changes were observed when using μ-opioid receptor antagonist (casoxin-6). The results may be useful in understanding the pathogenesis of inflammation and food allergy in infants.

Health-promoting properties of bioactive peptides derived from milk proteins in infant food: a review

Milk proteins have attracted extensive interest in terms of their bioavailability following ingestion. Enzymatic digestion of dairy products generates numerous peptides with various biological activities. Both human milk and infant formulas based on cow's milk are potential sources of bioactive peptides. This review aims to present current knowledge on the formation and fate of bioactive peptides from milk feeds intended for infants. Emphasis is placed on the source of the bioactive peptides with the nutritional impact of human milk and cow milk-based formulas on infant health being critically discussed from that perspective. Furthermore, the effect of processing and in vitro or in vivo digestion on the release and availability of peptides with bioactive sequences is evaluated. Considerable differences with respect to bioavailability and metabolic effects between the biologically active fragments generated following ingestion of human milk and infant formulas are documented. Peptides from milk protein of bovine origin could be a valuable supplement to human milk as multiple health-promoting properties are attributed to peptide fractions identified in standard cow milk-based infant formulas.

Changes in PACAP immunoreactivity in human milk and presence of PAC1 receptor in mammary gland during lactation

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide with widespread occurrence in the nervous system and peripheral organs, including the mammary gland. Previously, we have shown that PACAP38 is present in the human milk at higher levels than in respective blood samples. However, it is not known how PACAP levels and the expression of PAC1 receptor change during lactation. Therefore, the aim of our study was to investigate PACAP38-like immunoreactivity (PACAP38-LI) in human colostrums and transitional and mature milk during lactation and to compare the expression of PAC1 receptors in lactating and non-lactating mammary glands. We found that PACAP38-LI was significantly higher in human colostrum samples than in the transitional and mature milk. PACAP38-LI did not show any significant changes within the first 10-month period of lactation, but a significant increase was observed thereafter, up to the examined 17th month. Weak expression of PAC1 receptors was detected in non-lactating sheep and human mammary glands, but a significant increase was observed in the lactating sheep samples. In summary, the present study is the first to show changes of PACAP levels in human milk during lactation. The presence of PACAP in the milk suggests a potential role in the development of newborn, while the increased expressions of PAC1 receptors on lactating breast may indicate a PACAP38/PAC1 interaction in the mammary gland during lactation.

The exogenous opioid peptides and DPPIV serum activity in infants with apnoea expressed as apparent life threatening events (ALTE)

Casein-derived peptides have been suggested to play a role in sudden infant death syndrome (SIDS). In this study, we have determined the content of bovine β-casomorphin-7 (bBCM-7) and the activity of dipeptidyl peptidase-IV (DPPIV) in sera of infants with apparent life threatening events (ALTE syndromes, 'near miss SIDS'). We have found that the sera of some infants after an apnoea event contained more β-casomorphin-7 than that of the healthy infants in the same age. In all the children after an apnoea event, however, a lowered DPPIV was detected. We suspect that the low activity of that peptidase may be responsible for opioid-induced respiratory depression, induced by bBCM-7 in the general circulation.

The influence of μ-opioid receptor agonist and antagonist peptides on peripheral blood mononuclear cells (PBMCs)

Milk is one of the main source of biologically-active peptides that may function as regulatory substances called food hormones. After passing the gut-blood barrier, the μ-opioid receptor agonist and antagonist peptides may become the new factors influencing various functions of the human organism. The aim of the conducted research was to determine the influence of μ-opioid receptor agonist peptides: human and bovine β-casomorphin-7 (h/bBCM-7) and antagonistic peptides: casoxin-6 and- D (CXN-6/D) on proliferation and cytokine secretion of human peripheral blood mononuclear cells (PBMCs). The PBMCs proliferation was measured by the use of the BrdU test, which assesses the DNA synthesis activity and the WST-1 test which assesses the activity of mitochondrial dehydrogenase enzymes. The influence of all the investigated peptides on secretion of IL-4, IL-8, IL-13 and IFN-γ was determined by the use of the ELISA tests. Incubating the cells with the peptides has not caused any changes to their enzymatic activity, which has been proved by a WST-1 test. When using a BrdU test, however, it has been observed that there appear changes to proliferation of PBMCs correlated to amounts of bromodeoxyuridine incorporated into the cellular DNA. Moreover, changes to secretion of IL-4 and IL-13 by the cells under the influence of agonists were detected, as well as changes to secretion of IFN-gamma under the influence of all the examined substances. The obtained results provide information on immunomodulatory effects of food-derived opioid peptides, which may be of clinical significance especially in the case of allergic diseases in newborns.

Beta-casomorphins-7 in infants on different type of feeding and different levels of psychomotor development

Casomorphins are the most important during the first year of life, when postnatal formation is most active and milk is the main source of both nutritive and biologically active material for infants. This study was conducted on a total of 90 infants, of which 37 were fed with breast milk and 53 were fed with formula containing cow milk. The study has firstly indicated substances with immunoreactivity of human (irHCM) and bovine (irBCM) beta-casomorphins-7 in blood plasma of naturally and artificially fed infants, respectively. irHCM and irBCM were detected both in the morning before feeding (basal level), and 3h after feeding. Elevation of irHCM and irBCM levels after feeding was detected mainly in infants in the first 3 months of life. Chromatographic characterization of the material with irBCM has demonstrated that it has the same molecular mass and polarity as synthetic bovine beta-casomorphin-7. The highest basal irHCM was observed in breast-fed infants with normal psychomotor development and muscle tone. In contrast, elevated basal irBCM was found in formula-fed infants showing delay in psychomotor development and heightened muscle tone. Among formula-fed infants with normal development, the rate of this parameter directly correlated to basal irBCM. The data indicate that breast feeding has an advantage over artificial feeding for infants' development during the first year of life and support the hypothesis for deterioration of bovine casomorphin elimination as a risk factor for delay in psychomotor development and other diseases such as autism.

Type 1 diabetes, the A1 milk hypothesis and vitamin D deficiency

The 'A1' genetic variant of beta-casein in milk has been linked to type 1 diabetes (T1D). The keystone piece of supporting evidence is an ecological study positively correlating the incidence of T1D with amount of A1 beta-casein consumption per capita. Of relevance, A1 beta-casein consumption is also positively correlated with latitude, itself implicated in T1D through vitamin D deficiency. Ecological and biological evidence convincingly implicate vitamin D deficiency in T1D. Latitude is a confounder of the ecological data that underpin the hypothesis that A1 beta-casein in cow's milk is a causative factor in T1D.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Transport of micro-opioid receptor agonists and antagonist peptides across Caco-2 monolayer

Milk is the source of beta-casomorphins--biologically active peptides with opioid activity--which are suspected to play various roles in the human body. The local influence of exogenous opioid peptides on gastrointestinal functions has been widely reported. After passing the gut barrier, beta-casomorphins may affect the functions of immunological system, as well as dopaminergic, serotoninergic and GABA-ergic systems in brain, regulate the opioid receptor development and elicit behavioral effects. However, possibilities and mechanisms of the intestinal transport of beta-casomorphins in human body in vivo have not been reported so far. In our research, the transepithelial transport of micro-opioid receptor agonists--human beta-casomorphin-5 and 7(BCM5, BCM7) and antagonist--lactoferroxin A (LCF A) have been investigated using Caco-2 monolayer. In order to determine the pathway of investigated peptide transport across Caco-2 monolayer, two directions of the transport (apical to basolateral and basolateral to apical) have been studied. All investigated peptides were transported across the human intestinal cell line Caco-2 and the curves of cumulative amount of transported peptides in time were linear in each case. In addition, the hydrolysis of beta-casomorphins during 60 min of experiment by dipeptidyl peptidase IV was observed. The data suggest the possibility of transport of opioid peptides derived from food across human intestinal mucosa.