Food-derived Opioid Peptides Research Articles

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.

Food-Derived Opioid Peptides in Human Health: A Review.

World Health Organization data suggest that stress, depression, and anxiety have a noticeable prevalence and are becoming some of the most common causes of disability in the Western world. Stress-related disorders are considered to be a challenge for the healthcare system with their great economic and social impact. The knowledge on these conditions is not very clear among many people, as a high proportion of patients do not respond to the currently available medications for targeting the monoaminergic system. In addition, the use of clinical drugs is also associated with various side effects such as vomiting, dizziness, sedation, nausea, constipation, and many more, which prevents their effective use. Therefore, opioid peptides derived from food sources are becoming one of the safe and natural alternatives because of their production from natural sources such as animals and plant proteins. The requirement for screening and considering dietary proteins as a source of bioactive peptides is highlighted to understand their potential roles in stress-related disorders as a part of a diet or as a drug complementing therapeutic prescription. In this review, we discussed current knowledge on opioid endogenous and exogenous peptides concentrating on their production, purification, and related studies. To fully understand their potential in stress-related conditions, either as a drug or as a therapeutic part of a diet prescription, the need to screen more dietary proteins as a source of novel opioid peptides is emphasized.

Rubiscolins: Biologically active peptides of plant origin

Two food-derived opioid peptides with high δ-opioid receptor affinity and selectivity, rubiscolin-5 and rubiscolin-6, were isolated from spinach leaves in 2001. Ribulose 1,5-bisphosphate carboxylase/oxygenase [EC 4.1.1.39 (RuBisCO)], digested by pepsin, is known as a precursor for them. The most important advantage of rubiscolins is their oral bioavailability. Both peptides produced analgesia not only after intracerebroventricular administration, but also orally. Moreover, rubiscolin-6 enhanced memory consolidation, influenced the processes of learning and memory, and reduced anxiety. In an animal model of acute stress, rubiscolin-6 induced an antidepressive-like effect. Moreover, this peptide regulated food intake, stimulated appetite in mice fed a balanced diet and suppressed food intake in case of high-fat diet. This review summarizes various biological activities of rubiscolins and recent developments on the structure-activity relationship of rubiscolin analogs, aimed at improving their pharmacological properties. Naturally occurring opioids, such as rubiscolins, can serve as the basis of new therapeutics or functional foods.

Role of food-derived opioid peptides in the central nervous and gastrointestinal systems.

Opioid receptors are widely distributed in central nervous system and peripheral tissues. Endogenous opioid receptor ligands are involved in many physiological processes. Exogenous peptides, derived from food proteins with gastrointestinal proteases, also exert opioid-like activities, and they include gluten exorphins (wheat), casomorphins (milk), rubiscolins (spinach), and soymorphins (soybean). Milk-derived opioid peptides play both agonistic and antagonistic roles, and most of the opioid peptides exert regulatory functions in the central nervous system, related to nociception, emotion and memory after oral, intracerebroventricular, or intraperitoneal administration. This indicates that the peptides may have crossed the blood-brain barrier or acted peripherally. Furthermore, some food-derived opioid peptides influence gastrointestinal functions such as gut motility, hormone release, appetite, mucus production, and local immunity. In healthy states, food-derived opioid peptides could benefit both the nervous and digestive systems, whereas in pathological conditions, the gastrointestinal permeability change and opioid excess may contribute to pathogenesis of some disorders. PRACTICAL APPLICATIONS: Opioid receptors are important biological targets for the treatment of multiple diseases. Traditional opiate compounds, such as alkaloids, are demonstrated to exert numerous side effects, thereby limiting their clinical effectiveness. It is thought that food-derived opioid peptides may be safer than the alkaloids, and therefore can be applied in functional food development. In this review, we summarized the already discovered food opioid peptides from different sources, and elaborated their physiological functions on the central nervous and gastrointestinal systems. These effects support further exploration of the opioid peptides as therapeutic agents or as functional food ingredient for human health promotion.

Hydrolysis of food-derived opioids by dipeptidyl peptidase IV from Lactococcus lactis spp. lactis

Food-derived opioid peptides that are released from proteins by digestion, fermentation, or food production processes lead to several health problems. The opioids are generally resistant to hydrolyze by proteases, except the dipeptidyl peptidase IV (DPPIV, EC 3.4.14.5) enzyme, because of proline amino acid. β-casomorphin (BCM) from milk casein, gluteomorphin (GM) from wheat gluten, and soymorphin (SM) from the soybean β-conglycinin β-subunit are natural substrates of DPPIV because of their amino acid sequences and proline location. In the present study, DPPIV from Lactococcus lactis spp. lactis was purified and characterized by mass spectrometry. Purified DPPIV was added to standard BCM, GM, and SM, and hydrolysis percentages of morphins were measured by HPLC analysis. The results indicated that DPPIV enzyme hydrolyzed food-derived opioids (from 0.1 mM to 2 mM), BCM (33.42% for 2 mM), SM (83.81% for 2 mM), and GM (45.73% for 2 mM) in vitro. Hydrolysis percentages of SM were considerably higher than the same concentrations with BCM and GM. For dietary supplements to be promising for reducing the adverse effects of food derived opioids, this must be supported by in vivo studies of DPPIV use in the human body.

Degradation of food-derived opioid peptides by bifidobacteria.

Some food-derived opioid peptides have been reported to cause diseases, such as gastrointestinal inflammation, celiac disease, and mental disorders. Bifidobacterium is a major member of the dominant human gut microbiota, particularly in the gut of infants. In this study, we evaluated the potential of Bifidobacterium in the degradation of food-derived opioid peptides. All strains tested showed some level of dipeptidyl peptidase activity, which is thought to be involved in the degradation of food-derived opioid peptides. However, this activity was higher in bifidobacterial strains that are commonly found in the intestines of human infants, such as Bifidobacterium longum subsp. longum, B. longum subsp. infantis, Bifidobacterium breve and Bifidobacterium bifidum, than in those of other species, such as Bifidobacterium animalis and Bifidobacterium pseudolongum. In addition, some B. longum subsp. infantis and B. bifidum strains showed degradative activity in food-derived opioid peptides such as human and bovine milk-derived casomorphin-7 and wheat gluten-derived gliadorphin-7. A further screening of B. bifidum strains revealed some bifidobacterial strains that could degrade all three peptides. Our results revealed the potential of Bifidobacterium species in the degradation of food-derived opioid peptides, particularly for species commonly found in the intestine of infants. Selected strains of B. longum subsp. infantis and B. bifidum with high degradative capabilities can be used as probiotic microorganisms to eliminate food-derived opioid peptides and contribute to host health.

Bioactivities of hemorphins released from bovine haemoglobin gastrointestinal digestion: Dual effects on intestinal hormones and DPP-IV regulations

Food-derived hemorphins were studied for their interactions with intestinal cells in relation to food intake regulations. LLVV-H4, LVV-H4, VV-H4, VV-H7 and H7 were identified in the 2h-intestinal hydrolysate of haemoglobin simulated gastrointestinal digestion and synthesised. These food-derived hemorphins showed secretagogue properties of the anorexigenic hormones cholecystokinin (CCK) and glucagon-like peptide 1 (GLP-1) when in contact with murine STC-1 cells. They did not show significant modulatory effect on the corresponding prohormones mRNA levels. However, they downregulated the enzyme PC1 that processes proglucagon into GLP-1 specifically in the intestine. Moreover, VV-H4, VV-H7 & H7 were potent inhibitors of the GLP-1 inactivating dipeptidyl-peptidase IV (DPP-IV) and transiently upregulated its mRNA in human Caco-2 cells. These results suggest that food-derived hemorphins display dual luminal effects that participate at different levels in food intake and glycaemia regulation and add to the known roles of the special class of food-derived opioid peptides, the hemorphins.

Food Proteins as Source of Opioid Peptides-A Review.

Traditional opioids, mainly alkaloids, have been used in the clinical management of pain for a number of years but are often associated with numerous side-effects including sedation, dizziness, physical dependence, tolerance, addiction, nausea, vomiting, constipation and respiratory depression which prevent their effective use. Opioid peptides derived from food provide significant advantages as safe and natural alternative due to the possibility of their production using animal and plant proteins as well as comparatively less side-effects. This review aims to discuss the current literature on food-derived opioid peptides focusing on their production, methods of detection, isolation and purification. The need for screening more dietary proteins as a source of novel opioid peptides is emphasized in order to fully understand their potential in pain management either as a drug or as part of diet complementing therapeutic prescription.

Epigenetic effects of casein-derived opioid peptides in SH-SY5Y human neuroblastoma cells.

BackgroundCasein-free, gluten-free diets have been reported to mitigate some of the inflammatory gastrointestinal and behavioral traits associated with autism, but the mechanism for this palliative effect has not been elucidated. We recently showed that the opioid peptide beta-casomorphin-7, derived from bovine (bBCM7) milk, decreases cysteine uptake, lowers levels of the antioxidant glutathione (GSH) and decreases the methyl donor S-adenosylmethionine (SAM) in both Caco-2 human GI epithelial cells and SH-SY5Y human neuroblastoma cells. While human breast milk can also release a similar peptide (hBCM-7), the bBCM7 and hBCM-7 vary greatly in potency; as the bBCM-7 is highly potent and similar to morphine in it's effects. Since SAM is required for DNA methylation, we wanted to further investigate the epigenetic effects of these food-derived opioid peptides. In the current study the main objective was to characterize functional pathways and key genes responding to DNA methylation effects of food-derived opioid peptides.MethodsSH-SY5Y neuroblastoma cells were treated with 1 μM hBCM7 and bBCM7 and RNA and DNA were isolated after 4 h with or without treatment. Transcriptional changes were assessed using a microarray approach and CpG methylation status was analyzed at 450,000 CpG sites. Functional implications from both endpoints were evaluated via Ingenuity Pathway Analysis 4.0 and KEGG pathway analysis was performed to identify biological interactions between transcripts that were significantly altered at DNA methylation or transcriptional levels (p < 0.05, FDR <0.1).ResultsHere we show that hBCM7 and bBCM7, as well as morphine, cause epigenetic changes affecting gene pathways related to gastrointestinal disease and inflammation. These epigenetic consequences exhibited the same potency order as opiate inhibition of cysteine uptake insofar as hBCM7 was less potent than bBCM7, which was less potent than morphine.ConclusionOur findings indicate that epigenetic effects of milk-derived opiate peptides may contribute to GI dysfunction and inflammation in sensitive individuals. While the current study was performed using SH-SY5Y neuronal cellular models, similar actions on other cells types might combine to cause symptoms of intolerance. These actions may provide a potential contributing mechanism for the beneficial effects of a casein-free diet in alleviating gastrointestinal symptoms in neurological conditions including autism and other conditions. Lastly, our study also contributes to the evolving awareness of a “gut-brain connection”.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-015-0050-1) contains supplementary material, which is available to authorized users.

Differential neurogenic effects of casein-derived opioid peptides on neuronal stem cells: implications for redox-based epigenetic changes

Food-derived peptides, such as β-casomorphin BCM7, have potential to cross the gastrointestinal tract and blood–brain barrier and are associated with neurological disorders and neurodevelopmental disorders. We previously established a novel mechanism through which BCM7 affects the antioxidant levels in neuronal cells leading to inflammatory consequences. In the current study, we elucidated the effects of casein-derived peptides on neuronal development by using the neurogenesis of neural stem cells (NSCs) as an experimental model. First, the transient changes in intracellular thiol metabolites during NSC differentiation (neurogenesis) were investigated. Next, the neurogenic effects of food-derived opioid peptides were measured, along with changes in intracellular thiol metabolites, redox status and global DNA methylation levels. We observed that the neurogenesis of NSCs was promoted by human BCM7 to a greater extent, followed by A2-derived BCM9 in contrast to bovine BCM7, which induced increased astrocyte formation. The effect was most apparent when human BCM7 was administered for 1day starting on 3days postplating, consistent with immunocytochemistry. Furthermore, neurogenic changes regulated by bovine BCM7 and morphine were associated with an increase in the glutathione/glutathione disulfide ratio and a decrease in the S-adenosylmethionine/S-adenosylhomocysteine ratio, indicative of changes in the redox and the methylation states. Finally, bovine BCM7 and morphine decreased DNA methylation in differentiating NSCs. In conclusion, these results suggest that food-derived opioid peptides and morphine regulated neurogenesis and differentiation of NSCs through changes in the redox state and epigenetic regulation.

Food-derived opioid peptides inhibit cysteine uptake with redox and epigenetic consequences

Dietary interventions like gluten-free and casein-free diets have been reported to improve intestinal, autoimmune and neurological symptoms in patients with a variety of conditions; however, the underlying mechanism of benefit for such diets remains unclear. Epigenetic programming, including CpG methylation and histone modifications, occurring during early postnatal development can influence the risk of disease in later life, and such programming may be modulated by nutritional factors such as milk and wheat, especially during the transition from a solely milk-based diet to one that includes other forms of nutrition. The hydrolytic digestion of casein (a major milk protein) and gliadin (a wheat-derived protein) releases peptides with opioid activity, and in the present study, we demonstrate that these food-derived proline-rich opioid peptides modulate cysteine uptake in cultured human neuronal and gastrointestinal (GI) epithelial cells via activation of opioid receptors. Decreases in cysteine uptake were associated with changes in the intracellular antioxidant glutathione and the methyl donor S-adenosylmethionine. Bovine and human casein-derived opioid peptides increased genome-wide DNA methylation in the transcription start site region with a potency order similar to their inhibition of cysteine uptake. Altered expression of genes involved in redox and methylation homeostasis was also observed. These results illustrate the potential of milk- and wheat-derived peptides to exert antioxidant and epigenetic changes that may be particularly important during the postnatal transition from placental to GI nutrition. Differences between peptides derived from human and bovine milk may contribute to developmental differences between breastfed and formula-fed infants. Restricted antioxidant capacity, caused by wheat- and milk-derived opioid peptides, may predispose susceptible individuals to inflammation and systemic oxidation, partly explaining the benefits of gluten-free or casein-free diets.

Food-Derived Peptides Stimulate Mucin Secretion and Gene Expression in Intestinal Cells

In this study, the hypothesis that food-derived opioid peptides besides β-casomorphin 7 might modulate the production of mucin via a direct action on epithelial goblet cells was investigated in HT29-MTX cells used as a model of human colonic epithelium. Seven milk whey or casein peptides, a human milk peptide, and a wheat gluten-derived peptide with proved or probable ability to bind μ- or δ-opioid receptors were tested on the cell culture. Significantly increased secretion of mucins was found after exposure to six of the assayed peptides, besides the previously described β-casomorphin 7, as measured by an enzyme-linked lectin assay (ELLA). Human β-casomorphin 5 and α-lactorphin were selected to study the expression of mucin 5AC gene (MUC5AC), the HT29-MTX major secreted mucin gene. α-Lactorphin showed increased expression of MUC5AC from 4 to 24 h (up to 1.6-fold over basal level expression), although differences were statistically different only after 24 h of exposure. However, this increased expression of MUC5AC did not reach significance after cell treatment with human β-casomorphin 5. In conclusion, six food-derived peptides have been identifed with described or probable opioid activity that induce mucin secretion in HT29-MTX cells. Concretely, α-lactorphin is able to up-regulate the expression of the major secreted mucin gene encoded by these cells.

Nutropioids, Hedonism in the Gut?

The opioid system plays a pivotal role in how our brain regulates hedonic components of ingestive behavior. Duraffourd etal. (2012) add the gut to this opioid landscape, demonstrating direct activation of periportal μ-opioid receptors by food-derived opioid peptides (nutropioids), and a gut-brain feedback spiral that culminates in enhanced satiety.

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.

Role of food-derived opioid peptides in regulation of thermosensitivity of Periplaneta americana cockroach

The ability of exorphines (relative δ-selective opioid fragments of food-derived peptides) to change the defense response of American cockroaches Periplaneta americana placed in a hot chamber (T= 50°C) was studied. It was found that the ED50 for a fragment of D-ribulose-1,5-bisphosphate carboxylase rubiscolin-5 (YPLDL) doubling the stay time for the insects in the hot chamber was 340 nM/g. The ED50 for wheat gluten exorphine C (YPISL) was 573 nM/g. Cytochropin-4, a fragment of cytochrome B, did not have a significant effect. Comparison of the obtained data with the results of previous experiments with μ-selective exorphines—milk β-casein fragments—led to the conclusion that opioid receptors of various types are equally involved in regulation of cockroach protective behavior. The significance of phytogenous exorphines in formation of the opioid system of insects in the course of evolution is discussed.

Delayed effect of exorphins on learning of albino rat pups

The delayed effect of food-derived opioid peptides (exorphins) after chronic administration on postnatal days 1-14 on the learning of albino rat pups has been studied. Heptapeptide YPFPGPI (beta-casomorphin-7), pentapeptide YPLDL (rubiscolin-5) and pentapeptide YPISL (exorphin C) improved the development of the conditioned foraging reflex in a complex maze. Hexapeptide PFPGPI lacking the N-terminal tyrosine proved inefficient. Only beta-casomorphin-7 had an effect (negative) on passive avoidance conditioning. The obtained data confirm that exorphins (particularly, milk-derived beta-casomorphins) can have significant and long-term effects on the environmental adaptation of young mammals.

P.4.035 Influence of food-derived opioid peptides on behaviour and learning ability of white rat pups

P.4.035 Influence of food-derived opioid peptides on behaviour and learning ability of white rat pups

Effects of oral casokefamide on plasma levels, tolerance, and intestinal transit in man

Food-derived opioid peptides such as β-casomorphins are of interest for treatment of chronic diarrhea. The β-casomorphin analog casokefamide was administered orally at doses of 5.5, 8.0, and 16.0 mg to 10 healthy male volunteers, respectively. Dose-dependent increases of plasma levels with a maximum of 350 fmol/l were determined. No side-effects due to casokefamide has been observed. In comparison to placebo, casokefamide showed a trend toward prolongation of oro-caecal transit time. Orally applied casokefamide is well tolerated and may represent a useful tool for treatment of diarrhea in the future.