Opioid peptides from food (the exorphins)

The effect of source of protein fed during pregnancy and lactation on the development of characteristics of metabolic syndrome in male offspring of obese Wistar rats

Gestational obesity has major negative impacts on both mothers and their offspring. More than two-thirds of women of reproductive age in the United States are overweight and/or obese. We previously reported that the source of protein in the maternal diet influences the phenotype of offspring born to normal-weight dams. However, whether it has the same effect in obese mothers was unclear. The casein- and soya protein-based diets were fed to obese pregnant Wistar rats and compared for their effects on characteristics of the metabolic syndrome in male offspring. Dams randomized to either a casein (CD) or soya protein (SD) diet (n 12). Pups were weaned to either a CD or SD for 16 weeks. Offspring of SD dams had higher birthweight (P < 0⋅01). Glucose metabolism was not altered at birth but fasting blood glucose (FBG) (P < 0⋅02), insulin (P < 0⋅0002), insulin/glucose ratio (P < 0⋅03), and HOMA-IR index (P < 0⋅0002) were higher in offspring of SD dams at week 17. The pulse rate was higher in dams (P < 0⋅03). Food intake and body weight of offspring were affected by interactive effects of time and dams' diet (P < 0⋅05). Food intake was not influenced by maternal diet, but it was higher in pups weaned to SD dams (P < 0⋅03) The results of this study indicate that although the source of protein in the maternal diet is still an influencing factor in the outcome of the pregnancy in obese mothers, gestational obesity may mask this effect possibly by imposing general detrimental effects on measured parameters regardless of the source of protein in maternal diet.

Molecular basis of the therapeutic properties of hemorphins

Hemorphins are endogenous peptides, 4-10 amino acids long, belonging to the family of atypical opioid peptides released during the sequential cleavage of hemoglobin protein. Hemorphins have been shown to exhibit diverse therapeutic effects in both human and animal models. However, the precise cellular and molecular mechanisms involved in such effects remain elusive. In this review, we summarize and propose potential mechanisms based on studies that investigated the biological activity of hemorphins of different lengths on multiple therapeutic targets. Special emphasis is given to molecular events related to renin-angiotensin system (RAS), opioid receptors and insulin-regulated aminopeptidase receptor (IRAP). This review provides a comprehensive coverage of the molecular mechanisms that underpin the therapeutic potential of hemorphins. Furthermore, it highlights the role of various hemorphin residues in pathological conditions, which could be explored further for therapeutic purposes.

The Effect of Maternal Intact Protein- and Amino Acid-Based Diets on Development of Food Intake Regulatory Systems and Body Weight in Dams and Male Offspring of Wistar Rats

The objective of this study is to examine the effect of maternal and weaning intact protein- and amino acid-based diets on regulation of food intake, intake regulatory hormones, and body weight in dams and their male offspring. Pregnant Wistar rats were allocated to two groups (n = 12) and were fed either an intact protein diet (IPD) or mixed amino acid diet (AAD) from day 3 of gestation throughout gestation and lactation. Male offspring were weaned to either an IPD or AAD for 18 weeks. Food intake (FI) and body weight (BW) were measured weekly. Results: In dams, the AAD group had lower FI and BW in the post-partum period compared with the IPD group. In pups born to AAD dams, birth weight and BW were lower. However, the percentage of fat and lean mass were not affected. Food intake was influenced by maternal diet and was higher in pups born to IPD dams throughout post-weaning. Short-term FI in response to protein preloads was lower in pups born to AAD dams in 1 h. Fasting plasma concentrations of glucose, insulin, and ghrelin were not influenced by either maternal or weaning diet. However, peptide YY (PYY) was higher in pups born to IPD dams at weaning. Conclusions: The physicochemical properties of proteins fed during pregnancy and lactation had determining effects on the body weight and development of food intake regulatory systems in offspring. Maternal AAD resulted in lower BW in dams and lower birth weight and post-weaning BWs in pups compared with maternal IPD which was consistent with their lower FI.

The effect of characteristics of proteins fed during gestation and lactation on development of metabolic syndrome in dams and male offspring of Wistar rats

Objective

The objective of the study is to examine the role of characteristics of proteins in maternal and weaning diets on risk of metabolic syndrome in male offspring.

Methods

Pregnant Wistar rats were allocated to two groups (n = 12) and were fed the AIN‐93G diets based on either intact protein‐based diet (IPD) or mixed amino acid‐based diet (AAD) from day 3 of gestation throughout gestation and lactation. Male offspring were weaned to either an IPD or AAD diet for 18 weeks.

Results

In dams, AAD group had lower body weight in post‐partum period and higher pulse rate compared with IPD group. In pups born to AAD dams, birth weight and body weight were significantly lower, and systolic blood pressure and fasting blood glucose were significantly higher compared with those born to IPD dams. Fat/weight ratio, insulin and homeostasis model assessment of insulin resistance were not influenced by either maternal or weaning diet.

Conclusions

These results indicate that the physico‐chemical structure of proteins fed to dams is important in altering risk factors of metabolic syndrome in the offspring, while weaning diets do not seem to play a role. IPD had more favourable effect than AAD. These results may also indicate that dietary recommendations during development must be updated based on physiological properties of dietary proteins that are beyond their nutritional role.

Protein Hydrolysates and Biopeptides: Production, Biological Activities, and Applications in Foods and Health Benefits. A Review

In recent years, a great deal of interest has been expressed regarding the production, characterization, and applications of protein hydrolysates and food-derived biopeptides due to their numerous beneficial health effects. In this regard, research is mainly focused on investigating the therapeutic potential of these natural compounds. Based on their amino acids composition, sequences, hydrophobicity, and length, peptides released from food proteins, beyond their nutritional properties, can exhibit various biological activities including antihypertensive, antioxidative, antithrombotic, hypoglycemic, hypocholesterolemic, and antibacterial activities among others. Protein hydrolysates are essentially produced by enzymatic hydrolysis of whole protein sources by appropriate proteolytic enzymes under controlled conditions, followed by posthydrolysis processing to isolate desired and potent bioactive peptides from a complex mixture of active and inactive peptides. Therefore, because of their human health potential and safety profiles, protein hydrolysates and biopeptides may be used as ingredients in functional foods and pharmaceuticals to improve human health and prevent diseases. In this review, we have focused on the major variables influencing the enzymatic process of protein hydrolysates production. The biological properties of protein hydrolysates will be described as well as their applications in foods and health benefits.

The Role of Maternal Dietary Proteins in Development of Metabolic Syndrome in Offspring

The prevalence of metabolic syndrome and obesity has been increasing. Pre-natal environment has been suggested as a factor influencing the risk of metabolic syndrome in adulthood. Both observational and experimental studies showed that maternal diet is a major modifier of the development of regulatory systems in the offspring in utero and post-natally. Both protein content and source in maternal diet influence pre- and early post-natal development. High and low protein dams’ diets have detrimental effect on body weight, blood pressure191 and metabolic and intake regulatory systems in the offspring. Moreover, the role of the source of protein in a nutritionally adequate maternal diet in programming of food intake regulatory system, body weight, glucose metabolism and blood pressure in offspring is studied. However, underlying mechanisms are still elusive. The purpose of this review is to examine the current literature related to the role of proteins in maternal diets in development of characteristics of the metabolic syndrome in offspring.

Milk Collected at Night Induces Sedative and Anxiolytic-Like Effects and Augments Pentobarbital-Induced Sleeping Behavior in Mice

Milk has long been known and used to promote sleep. The sleep-promoting effect of milk has been attributed to its psychological associations (i.e., the memory of a mother giving milk at bedtime) and its rich store of sleep-promoting constituents (e.g., tryptophan). Studies have shown that milk harvested at night (Night milk) contains exceptionally high amounts of tryptophan and melatonin. In the present study, we evaluated the psychopharmacological properties of Night milk, particularly its probable sleep-promoting/enhancing, and anxiolytic effects. Night milk was orally administered to ICR mice at various concentrations (100, 200, or 300 mg/kg). An hour after administration, assessment of its sedative (open-field and rotarod tests) and sedative sleep-potentiating effects (pentobarbital-induced sleeping test) was conducted. For comparison, the effects of Day milk (daytime milking) were also assessed. In addition, the effects of Night milk on anxiety behavior (elevated plus maze [EPM] test) and electroencephalographic (EEG) waves were evaluated. Night milk-treated animals exhibited decreased spontaneous locomotion (open-field test) and impaired motor balance and coordination (rotarod test). Furthermore, Night milk shortened the sleep onset and prolonged the sleep duration induced by pentobarbital sodium. These effects were comparable to that of diazepam. In addition, Night milk significantly increased the percentage of time spent and entries into the open arms of the EPM, indicating that it also has anxiolytic effects. No significant changes in EEG waves were observed. Altogether, these findings suggest that Night milk is a promising natural aid for sleep- and anxiety-related disturbances.

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.

Dietary proteins as determinants of metabolic and physiologic functions of the gastrointestinal tract

Dietary proteins elicit a wide range of nutritional and biological functions. Beyond their nutritional role as the source of amino acids for protein synthesis, they are instrumental in the regulation of food intake, glucose and lipid metabolism, blood pressure, bone metabolism and immune function. The interaction of dietary proteins and their products of digestion with the regulatory functions of the gastrointestinal (GI) tract plays a dominant role in determining the physiological properties of proteins. The site of interaction is widespread, from the oral cavity to the colon. The characteristics of proteins that influence their interaction with the GI tract in a source-dependent manner include their physico-chemical properties, their amino acid composition and sequence, their bioactive peptides, their digestion kinetics and also the non-protein bioactive components conjugated with them. Within the GI tract, these products affect several regulatory functions by interacting with receptors releasing hormones, affecting stomach emptying and GI transport and absorption, transmitting neural signals to the brain, and modifying the microflora. This review discusses the interaction of dietary proteins during digestion and absorption with the physiological and metabolic functions of the GI tract, and illustrates the importance of this interaction in the regulation of amino acid, glucose, lipid metabolism, and food intake.

Is MYO9B the missing link between schizophrenia and celiac disease?

There has long been discussion on the correlation between schizophrenia and autoimmune diseases (especially celiac disease), which makes the recently discovered celiac disease risk factor, MYO9B, an attractive functional and positional candidate gene for schizophrenia. To test this hypothesis we compared allele frequencies of three MYO9B tag SNPs in 315 schizophrenia cases and 1,624 healthy controls in a genetic association study. Highly significant differences in allele frequencies between schizophrenia cases and healthy controls were observed for SNP rs2305767 in intron 14 of MYO9B (P = 1.16 x 10(-4); OR 1.41, 95% CI 1.18-1.67). We demonstrate significant association of allelic variants in MYO9B with schizophrenia. To our knowledge, this is the first molecular genetic evidence for a correlation between autoimmune diseases and the risk of developing schizophrenia.

Milk biologically active components as nutraceuticals: review

Milk contains components that provide critical nutritive elements, immunological protection, and biologically active substances to both neonates and adults. Milk proteins are currently the main source of a range of biologically active peptides. Concentrates of these peptides are potential health-enhancing nutraceuticals for food and pharmaceutical applications. Several bioactive peptides may be used as nutraceuticals, for example, in the treatment of diarrhea, hypertension, thrombosis, dental diseases, as well as mineral malabsorption, and immunodeficiency. Minor whey proteins, such as lactoferrin, lactoperoxidase, lysozyme, and immunoglobulins, are considered antimicrobial proteins. Milk also contains some natural bioactive substances. These include oligosaccharides, fucosylated oligosaccharides, hormones, growth factors, mucin, gangliosides, and endogenous peptides, which are present in milk at secretion. Most of the claimed physiological properties of milk bioactive components have been carried out in vitro or in animal model systems, and these hypothesized properties remain to be proven in humans. Whether these milk bioactive components will replace drugs entirely in the immediate future is still unclear, but the increasing appreciation of "drug foods" or nutraceuticals plays a complementary rather than a substitutional role to the synthetic pharmacological drugs.

Effects of milk-derived bioactives: an overview

Milk contains various components with physiological functionality. Peptides derived from caseins and whey proteins including opioid peptides, antihypertensive peptides, casein phosphopeptides, alpha- and beta-lactorphins and albutensin have been shown to possess various bioactive properties. This review considers an overview of the bioactive components in milk proteins and whey and their physiological function.

Opioid peptides encrypted in intact milk protein sequences

Opioid agonistic and antagonistic peptides which are inactive within the sequence of the precursor milk proteins can be released and thus activated by enzymatic proteolysis, for example during gastrointestinal digestion or during food processing. Activated opioid peptides are potential modulators of various regulatory processes in the body. Opioid peptides can interact with subepithelial opioid receptors or specific luminal binding sites in the intestinal tract. Furthermore, they may be absorbed and then reach endogenous opioid receptors.

Biochemical properties of regulatory peptides derived from milk proteins

Biologically active peptides derived from milk proteins are inactive within the sequence of the precursor proteins but can be released by enzymatic proteolysis. Based on structure-activity studies, peptides with a defined bioactivity show common structural features. Moreover, many milk protein-derived peptides reveal multifunctional bioactivities. Bioactive peptide fragments originating from milk proteins should be taken into account as potential modulators of various regulatory processes in the body. Opioid peptides are opioid receptor ligands with agonistic or antagonistic activities. Angiotensin converting enzyme (ACE) inhibitory peptides can exert an antihypertensive effect. Immunomodulating casein peptides have been found to stimulate the proliferation of human lymphocytes and the phagocytic activities of macrophages. Antimicrobial peptides have been shown to kill sensitive microorganisms. Antithrombotic peptides inhibit the fibrinogen binding to a specific receptor region on the platelet surface and also inhibit aggregation of platelets. Casein phosphopeptides can form soluble organophosphate salts and may function as carriers for different minerals, especially calcium. In relation to their mode of action, bioactive peptides may reach target sites (e.g., receptors, enzymes) at the luminal side of the intestinal tract or after absorption, in peripheral organs. The physiological significance of bioactive peptides as exogenous regulatory substances is not yet fully understood. Nevertheless, several bioactive peptides derived from milk proteins have been shown to exert beneficial physiological effects. Milk-derived peptides were already produced on an industrial scale and as a consequence these peptides have been considered for application both as dietary supplements in "functional foods" and as drugs.

Opioid peptides derived from hemoglobin: hemorphins

Investigation of hemoglobin peptic hydrolysate has revealed the presence of biologically active peptides with affinity for opioid receptors. Two peptides, VV-hemorphin-7 and LVV-hemorphin-7, were resolved by a combination of size exclusion and reversed phase HPLC. A new spectroscopic method based on the second order derivative spectra analysis of aromatic amino acids has been developed. This method allows qualitative and quantitative evaluation of hemorphins generated by peptic hemoglobin hydrolysis. Using this method, a kinetic study of hemorphins appearance has been undertaken. In this paper, we also evidenced the generation of VV-hemorphin-7 from globin by peritoneal macrophages. In regard to this result, the putative physiological role of hemorphins is discussed.

Milk protein-derived opioid receptor ligands

Milk is mammalian characteristic and is of particular importance for humans: Mother's milk or its substitutes from cows' milk are absolutely essential nutriments for the neonate and cows' milk also represents a basic foodstuff for adults. However, in addition to their well-known nutritive role, milk constituents apparently are also able to carry specific information from the milk producer's to the milk receiver's organism: Thus, a number of milk protein fragments has been shown to behave like opioid receptor ligands able to address opioidergic systems in the adult's or in the neonate's organism. With respect to the proteins, which they are derived off these peptides have been named alpha-casein exorphins or casoxin D (alpha-casein), beta-casomorphins or beta-casorphin (beta-casein), casoxin or casoxin A, B, or C (k-casein), alpha-lactorphins (alpha-lactalbumin), beta-lactorphin (beta-lactoglobulin) or lactoferroxins (lactoferrin). Only casoxins and lactoferroxins display antagonistic properties; the other peptides behave like opioid receptor agonists. Most of the information available so far has been collected about beta-casomorphins. These peptides obviously can be released from beta-casein in the adult's or in the neonate's organism, where they might elicit opioid effects in the frame of a regulatory role as "food hormones". Several synthetic beta-casomorphin derivatives have been shown to be highly specific and potent mu-type opioid receptor ligands which frequently have been used as standard tools in opioid research.

Bioactive milk peptides: a prospectus

Bioactive peptides have been identified within the amino acid sequences of native milk proteins. Hydrolytic reactions, such as those catalyzed by digestive enzymes, result in their release. These peptides directly influence numerous biological processes evoking behavioral, gastrointestinal, hormonal, immunological, neurological, and nutritional responses. The specific bioreactions associated with each physiological class have been well characterized. Herein, we review the scientific literature and attempt to stimulate consideration of the continued use of bioactive peptides and their expanded development as a commercial product. Several applications have already evolved. For example, phosphopeptides derived from casein fractions are currently used as both dietary and pharmaceutical supplements. Potentially, the addition of bioactive peptides to food products could improve consumer safety as a result of their antimicrobial properties. Lastly, bioactive peptides may function as health care products, providing therapeutic value for either treatment of infection or prevention of disease.

VV-hemorphin-7 and LVV-hemorphin-7 released during in vitro peptic hemoglobin hydrolysis are morphinomimetic peptides

Two opioid peptides were generated by in vitro pepsin treatment of bovine hemoglobin. These peptides were identified using a GPI test and purified using HPLC chromatographic techniques. They correspond to fragments 31-40 (LVV-hemorphin-7) and 32-40 (VV-hemorphin-7) of the beta-chain of bovine hemoglobin. Binding experiments strongly confirm that VV-hemorphin-7 and LVV-hemorphin-7 are opioid peptides since they inhibited [3H]naloxone binding to rat brain membranes. Our results indicate that VV-hemorphin-7 and LVV-hemorphin-7 exhibit a lesser potency both in GPI and binding tests. Selectivity and affinity of these purified peptides and synthetic hemorphin-7 for opioid receptors is discussed.

Bioactive peptides derived from milk proteins. Structural, physiological and analytical aspects

The primary function of dietary proteins is to supply the body adequately with indispensable amino acids and organic nitrogen. Little attention has been paid up to date to milk proteins, in particular caseins, that are currently the main source of biologically active peptides, although other animal as well as vegetable proteins are known to contain potentially bioactive sequences. Such regulatory peptides can be released by enzymatic proteolysis of caseins in vitro and in vivo and may act as potential physiological modulators of metabolism during the intestinal digestion of the diet. It has been proved that bioactive peptides derived from caseins, such as beta-casomorphins and phosphopeptides, can be released during gastrointestinal passage. It is also evident that peptides originating from food proteins should be taken into account as potential modulators of various regulatory processes in the body. The possible regulatory effects concern nutrient uptake (phosphopeptides, casomorphins), postprandial hormone secretion (casomorphins), immune defense (immunopeptides, casokinins, casomorphins) and neuroendocrine information transfer (casokinins). The advances in the research field of bioactive peptides are driven by a molecular understanding of biological processes, and analytical techniques are a critical component of this understanding. Different up-to-date methods, including peptide synthesis and immunochemistry, have been applied to the chemical characterization of bioactive peptides. Especially casein derived peptides have already found interesting applications, both as dietary supplements (phosphopeptides) and as pharmaceutical preparations (phosphopeptides, beta-casomorphins). The question of 'what kinds of bioactive peptides are beneficial and desirable as food constituents or as drugs' should be always carefully examined. However, the possibilities for the design of dietary products and 'natural' drugs look promising.

Purification and characterization of enkephalin-related peptides released by in vitro peptic digestion of bovine plasma proteins

In vitro pepsin treatment of plasma proteins generates biologically active peptides such as enkephalin-related peptides. These peptides were characterized using chromatographic techniques along with a radioimmunoassay procedure involving the use of Leu-enkephalin and Met-enkephalin antisera. Serum albumin is the only existing source of Met-enkephalin-immunoreactive peptides. One of these peptides consists of nine residues with the sequence NH2-Glu-Lys-Leu-Gly-Glu-Tyr-Gly-Phe-Gln; a second immunoreactive peptide might be the hexapeptide NH2-Gly-Glu-Tyr-Gly-Phe-Gln, which has been already identified in a rat serum albumin hydrolysate. Our results indicate that immunoglobulins constitute the main source of Leu-enkephalin-immunoreactive peptides. Immunoreactive NH2-Tyr-Phe-Leu was isolated from pepsin-treated bovine immunoglobulins. Binding experiments and cyclic nucleotide measurements suggested that this peptide was an enkephalin-related peptide. Similar experiments could be carried out to identify the proteins that contain enkephalin-like peptide sequences with the view to investigating the various biological processes occurring in enzymatically treated proteins.

Symptom and personality profiles of young adults from a college student population with self-reported illness from foods and chemicals

Despite much debate over a presumptively somatic vs psychological etiology of nonatopic food and chemical sensitivities, little systematic research has addressed the issues. The present study investigated self-reported illness from several common foods (wheat, dairy, eggs) and chemicals (pesticide, car exhaust, paint, perfume, new carpet), symptom patterns, and psychological profiles of a sample of young adult college students (n = 490, age 19.4 +/- 2.4, 52% female/48% male). Subjects were divided into 4 groups on the basis of sample medians for frequency of illness from the foods (FI) and chemicals (CI); high FI with high CI (FI/CI), high FI alone, high CI alone, and NOILL (low FI and CI). FI was associated with more defensiveness (denial of negativity) while CI was linked with more shyness (avoidance of novelty). Women outnumbered men in all groups (FI/CI: 61%; FI: 80% CI: 55%) except the NOILL (40% women). Nevertheless, the FI/CI, FI, and/or CI groups still had significantly higher total symptom scores as well as more indigestion, headache, and memory trouble than did the NOILL group, even after depression, anxiety, shyness, defensiveness, and gender were covaried. The illness groups reported significantly more limitation of foods that mobilize endogenous opioids or generate exogenous opioids (sweets, fats, bread) as well as more illness from opiate drugs, small amounts of beverage alcohol, and late meals. Nasal symptoms from pollens or animals were more common in the FI/CI (42%) and CI (42%) than in FI (26%) or NOILL (28%) groups. Premenstrual tension syndrome and irritable bowel were also more common in the FI/CI group. The findings indicate that young adults outside the clinical setting who are relatively higher in FI and/or CI have distinctive symptom and psychological patterns. Covariate analyses suggest that important symptoms in FI and CI individuals such as indigestion, headache, and memory problems may occur in addition to rather than as simply part of emotional distress. The data are consistent with a previously hypothesized role of olfactory-limbic and hypothalamic pathways and with a time-dependent sensitization model for illness from foods and chemicals.

Polysymptomatic syndromes and autonomic reactivity to nonfood stressors in individuals with self-reported adverse food reactions

This study compared symptom reports and cardiovascular reactivity of a group of 24 individuals recruited from the community who reported a cognitive or emotional symptom caused by at least one food (food-sensitivity reporters, FSR) vs those of 15 controls (C) without a history of food, chemical, drug, or inhalant sensitivities. The main findings were: 1) FSR indicated sensitivities not only to foods, but also to environmental chemicals, drugs, and natural inhalants, as well as significantly more symptoms than C in multiple systems; 2) more FSR than C noted recent state depression and anxiety, as well as higher trait anxiety on the Bendig form of the Taylor Manifest Anxiety Scale; 3) however, on multiple regression analysis, not only depression, but also the number of sensitivities (foods, chemicals, drugs, inhalants), accounted for part of the variance in total number of symptoms (38 and 17%, respectively), whereas none of the affective measures accounted for any of the variance in total number of sensitivities over all subjects; 4) after controlling for depression and anxiety, FSR still showed a trend toward poorer performance on a timed mental arithmetic task (p = 0.16); and 5) FSR and C showed opposite patterns of heart rate change to two different stressful tasks (mental arithmetic and isometric exercise) (group by task interaction, p < 0.05). The data are discussed in terms of a time-dependent sensitization (TDS) process that predicts a cross-sensitizing and cross-reactive role for xenobiotic agents (e.g., foods, chemicals, drugs, and inhalants) and for salient psychological stress in the expression of psychophysiological dysfunctions of FSR. As in other chronically ill populations, negative affect in food-sensitive individuals may explain greater symptom reporting, but not necessarily account for the illness itself. For either a food or a psychological stimulus to begin to elicit sensitized responses, e.g., marked physiological differences from C, FSR may require multiple, intermittent exposures spaced over 5-28 days rather than on only 1 day.

Uptake and transport of macromolecules by the intestine: possible role in clinical disorders (an update)

The intestine is exposed to a wide variety of macromolecules. Because macromolecules are antigenic, mechanisms have evolved in the gastrointestinal tract to regulate their absorption. Macromolecular uptake can be beneficial in delivering essential factors for growth and in sampling the antigenic milieu of the gastrointestinal tract. Specific transport mechanisms exist to execute this physiological absorption. However, inappropriate and uncontrolled antigen transport may occur in disease states or as a prelude to disease states in the gastrointestinal tract. Such transport may result in immune responses that are harmful. This review examines physiological transport of macromolecules through epithelia and through M cells. It also considers uncontrolled transport and its relation to disease states. The review concludes with an examination of the interrelationship between antigen transport and an altered immune system in the establishment of gastrointestinal disease.

Could dietary proteins serve as cyclo(His-Pro) precursors?

Cyclic dipeptides or diketopiperazines are readily generated during in vitro hydrolysis of proteins and polypeptides. This led us to examine whether cyclo(His-Pro) (CHP), a diketopiperazine containing histidine and proline, could be formed in vivo from dietary proteins. The data presented here show that at least in rat, neither urinary nor plasma concentration of CHP is elevated by consumption of a diet rich in proteins. Several dietary supplements derived from casein and/or soy protein hydrolysates, however, contain high levels of CHP-LI. Oral intake of one such supplement led to a sharp increase in the plasma level of CHP-LI.