The involvement of the histamine degradation pathway by diamine oxidase in manifest gastrointestinal allergies

Association of anhedonia with brain-derived neurotrophic factor and interleukin-10 in major depressive disorder

BACKGROUND

Anhedonia, a core symptom of major depressive disorder (MDD), manifests in two forms: anticipatory and consummatory, reflecting a diminished capacity to anticipate or enjoy pleasurable activities. Prior studies suggest that brain-derived neurotrophic factor (BDNF) and interleukin-10 (IL-10) may play key roles in the emergence of anhedonia in MDD. The specific relationships between these biomarkers and the two forms of anhedonia remain unclear. This study investigated the potential links between BDNF, IL-10, and both forms of anhedonia in MDD patients.

METHODS

This study included 43 participants diagnosed with MDD and 58 healthy controls. It involved detailed assessments of depression and anxiety levels, anticipatory and consummatory pleasure, cognitive functions, and a broad spectrum of plasma biomarkers, such as C-reactive protein, various interleukins, and BDNF. Using partial correlation, variables related to pleasant experiences were identified. Stepwise multiple linear regression analysis was applied to pinpoint the independent predictors of anhedonia in the MDD group.

RESULTS

Demographically, both groups were comparable in terms of age, sex, body mass index, educational year, and marital status. Individuals with MDD displayed markedly reduced levels of anticipatory and consummatory pleasure, higher anxiety, and depression scores compared to healthy controls. Additionally, cognitive performance was notably poorer in the MDD group. These patients also had lower plasma diamine oxidase levels. Analysis linked anhedonia to impaired delayed memory. Regression results identified IL-10 and BDNF as independent predictors of anticipatory and consummatory anhedonia, respectively.

CONCLUSION

These findings demonstrate that anticipatory and consummatory anhedonia are influenced by independent factors, thereby providing critical insights into the distinct neuroimmunological mechanisms that underlie various forms of anhedonia. Clinicl Trial Registration Number: NCT03790085.

Cumulative effect of AOC1 gene variants on symptoms and pathological conditions in adult women with fibromyalgia: a pilot study

Introduction: The amine oxidase copper-containing 1 (AOC1) gene encodes for the diamine oxidase (DAO) enzyme. DAO is an enzyme that catabolizes some molecules, including histamine, and is the degradative enzyme in the polyamine catabolic pathway that is active in intestinal mucosal cells. Variants of AOC1 are associated with reduced DAO activity, resulting in accumulation of high levels of histamine and causing a wide range of neurological, gastrointestinal, and epidermal disorders, which are present in people with fibromyalgia. This study aimed to evaluate the impact of four AOC1 gene variants, namely, rs10156191, rs1049742, rs1049793, and rs2052129, on fibromyalgia symptoms measured by the Fibromyalgia Impact Questionnaire (FIQ), such as sleep disorders, atopic dermatitis, migraine, gastrointestinal (GI) disorders, allergies, and intolerances, in adult women with fibromyalgia. Methods: The sample consisted of 100 unrelated women with fibromyalgia between 33 and 60 years of age (48.48 years ±7.35), whose were diagnosed by a rheumatologist based on symptoms such as pain, stiffness, and fatigue. Single-nucleotide polymorphisms (SNPs) of AOC1 were identified using oral mucosa samples collected following a standard hygiene protocol. DNA was extracted, and gene variants of interest were analyzed using multiplex single-nucleotide primer extension (SNPE). Clinical data were collected using the FIQ and a series of variables that quantified the intensity and frequency of the symptoms. Results: The minor allele frequencies of rs10156191, rs1049742, rs1049793, and rs2052129 were 31.5, 10, 32.5, and 27%, respectively. Each variant was found to be in Hardy-Weinberg equilibrium, but partial linkage disequilibrium between AOC1 SNPs is suspected. The results show that fibromyalgia symptoms measured using the FIQ tend to increase with the number of risk alleles and that the intensity of dry skin and low stool consistency may be associated with an increase in the number of these alleles. Conclusion: This study constitutes the first step in investigating associations between fibromyalgia symptoms and candidate variants of the AOC1 gene in DAO enzyme activity. Identification of reduced DAO activity may improve the quality of life and treatment of symptoms in fibromyalgia patients.

Histamine Intolerance in Children: A Narrative Review

Histamine intolerance is defined as a disequilibrium of accumulated histamine and the capacity for histamine degradation. This clinical term addresses a non-immunologically mediated pathology when histamine ingested with food is not particularly high, however its degradation is decreased. This paper aims to provide a narrative review on etiopathology, epidemiology, possible diagnostic algorithms and diagnostic challenges of histamine intolerance in children. The clinical picture of histamine intolerance in children is similar to that observed in adults apart from male predominance found in paediatric patients. Both in children and adults, a histamine-reduced diet is typically the treatment of choice. Diamine oxidase supplementation offers another treatment option. There is no symptom or test pathognomonic for histamine intolerance. Nevertheless, manifestations of chronic gastrointestinal symptoms, measurements of diamine oxidase deficits, positive results of histamine provocation tests and improvement in symptoms with histamine-reduced diet considerably increase the probability of histamine intolerance diagnosis. These factors have been included in the proposed diagnostic algorithm for histamine intolerance. In children histamine intolerance most likely co-occurs with allergies and bowel diseases, which creates an additional diagnostic challenge. As the evidence for children is poor further research is needed the determine epidemiology, validate diagnostic algorithms and establish possible treatment options regarding histamine intolerance.

Standardization of a colorimetric technique for determination of enzymatic activity of diamine oxidase (DAO) and its application in patients with clinical diagnosis of histamine intolerance

Background

Diamine Oxidase (DAO) has an essential role for degradation of exogenous histamine in the intestine; thus, histamine intolerance (HI) mainly has been correlated to a low concentration and/or activity of this enzyme. The objective of the study was to standardize a colorimetric technique to measure the enzymatic activity (function) of hDAO to then apply it to a series of 22 patients with a clinical diagnosis of HI.

Methods

For the standardization variables such as volume and type of sample, incubation time, wavelength of maximum absorption, types of substrates, and concentration of oxidized ascorbate were evaluated. Then the activity and concentration of DAO was determined in 22 patients diagnosed with HI and 22 healthy subjects.

Results

The mean of serum DAO concentration in the 22 patients was of 9.268 ± 1.124 U/mL. The mean of serum DAO concentration in the 22 controls was of 20.710 ± 2.509 U/mL, being significantly higher (P value 0.0002) the mean of the samples. The mean of serum DAO activity of the patients was of 1.143 ± 0.085 U/L and the controls was 1.533 ± 0.119 U/L, significantly greater than the patients (P value 0.011). In addition, the sensitivity of both techniques was 0.63. In the measuring of DAO concentration the specificity was 0.9, constituting a good diagnostic test, especially to rule out the true negatives. The determination of DAO activity had a specificity of 0.68.

Conclusions

Although we used a small number of patients and controls and the absorbance values were lower than expected, statistically significant differences were found in the levels of concentration and DAO activity between the patients with histamine intolerance and the controls. Therefore, the measuring of DAO concentration and DAO activity is a good diagnostic strategy for study suspect cases of HI. The simultaneous use of both assays allows to reduce positive and negative false results, for example, patients with normal DAO levels that could present a dysfunction in the activity of this enzyme.

Histamine Intolerance: The Current State of the Art

Histamine intolerance, also referred to as enteral histaminosis or sensitivity to dietary histamine, is a disorder associated with an impaired ability to metabolize ingested histamine that was described at the beginning of the 21st century. Although interest in histamine intolerance has considerably grown in recent years, more scientific evidence is still required to help define, diagnose and clinically manage this condition. This article will provide an updated review on histamine intolerance, mainly focusing on its etiology and the existing diagnostic and treatment strategies. In this work, a glance on histamine intoxication will also be provided, as well as the analysis of some uncertainties historically associated to histamine intoxication outbreaks that may be better explained by the existence of interindividual susceptibility to ingested histamine.

Zymographic approach to determine the intrinsic enzyme specific activity of diamine oxidase in presence of interfering enzymes

The purpose of this investigation was to elaborate a fast zymographic assay of oxidase enzymes in the presence of interfering enzymes as catalase (which disturbs current dosages based on H₂O₂ detection). This method also allows the determination of intrinsic specific activity (ISA) of oxidases, such as diamine oxidase (DAO) or glucose oxidase (GOD). The SDS-PAGE gels with entrapped peroxidase have been obtained by polymerization of acrylamide and bis-acrylamide in the presence of horse-radish peroxidase. The entrapped peroxidase was uniformly distributed in the PolyacrylAmide (PAA) material and did not migrate during electrophoresis. The obtained PAA gels allow the electrophoretic separation of various oxidases from contaminating proteins. As an example, to reveal DAO, the resulting PAA-gel should be incubated after the electrophoretic run in the developing solution containing putrescine (a DAO substrate) and o-phenylenediamine (a HRP substrate) to give coloured bands on the gel in the presence of DAO-generated H₂O₂. The results showed that is possible to determine the DAO in the presence of interfering catalase because they migrate differently. Thus, the H₂O₂ released in situ by DAO is no more decomposed by catalase because of its different mobility. It was also found that the same electrophoretic gel, after zymography, can be restained by Coomassie Blue for quantitation of proteins corresponding to the zymographic bands. With the obtained enzyme units and protein concentration it is also possible to calculate the intrinsic specific activity of DAO directly from the intensities of enzyme bands in zymography and from those of protein bands (Coomassie Blue staining), quantified by densitometry.

Diamine Oxidase from White Pea (Lathyrus sativus) Combined with Catalase Protects the Human Intestinal Caco-2 Cell Line from Histamine Damage

Diamine oxidase (DAO) administration has been proposed to treat certain gastrointestinal dysfunctions induced by histamine, an immunomodulator, signaling, and pro-inflammatory factor. However, H₂O₂ resulting from the oxidative deamination of histamine by DAO may be toxic. The purpose of this study was to investigate to which extent DAO from white pea (Lathyrus sativus), alone or in combination with catalase, may modulate histamine toxicity in the human intestinal Caco-2 cell line. The results show that histamine at concentrations higher than 1 mM is toxic to the Caco-2 cells, independently of the cell differentiation status, with a LC₅₀ of ≅ 10 mM following a 24-h exposure. Depending on its concentration, DAO increased histamine toxicity to a greater extent in differentiated cells compared to undifferentiated cultures. In the presence of catalase, the DAO-induced increase in histamine toxicity was completely abolished in the undifferentiated cells and only partially decreased in differentiated cells, showing differences in the sensitivity of Caco-2 cells to the products resulting from histamine degradation by DAO (H₂O₂, NH₃, or imidazole aldehyde). It appears that treatment of food histaminosis using a combination of vegetal DAO and catalase would protect against histamine toxicity and prevent H₂O₂-induced damage that may occur during histamine oxidative deamination.

Carboxymethyl starch/alginate microspheres containing diamine oxidase for intestinal targeting

The association of carboxymethyl starch (CMS) and alginate is proposed as a novel matrix for the entrapment of bioactive agents in microspheres affording their protection against gastrointestinal degradation. In this study, the enzyme diamine oxidase (DAO) from white pea (Lathyrus sativus) was immobilized by inclusion in microspheres formed by ionotropic gelation of CMS/alginate by complexation with Ca(2+) . The association of CMS to alginate generated a more compact structure presenting a lesser porosity, thus decreasing the access of gastric fluid inside the microspheres and preventing the loss of entrapped enzyme. Moreover, the immobilized enzyme remained active and was able to oxidize the polyamine substrates even in the presence of degrading proteases of pancreatin. The inclusion yield in terms of entrapped protein was of about 82%-95%. The DAO entrapped in calcium CMS/alginate beads retained up to 70% of its initial activity in simulated gastric fluid (pH 2.0). In simulated intestinal fluid (pH 7.2) with pancreatin, an overall retention of 65% of activity for the immobilized DAO was observed over 24 H, whereas in similar conditions the free enzyme was totally inactivated. Our project proposes the vegetal DAO as an antihistaminic agent orally administered to treat food histaminosis and colon inflammation.

Dietary Renaissance in IBS: Has Food Replaced Medications as a Primary Treatment Strategy?

OPINION STATEMENT

The medical community has only recently started to focus attention on the role of food in the pathogenesis of irritable bowel syndrome (IBS), though the association between food and gastrointestinal (GI) symptoms has been recognized by patients for decades. Health care providers receive little formal training in the dietary management of IBS and have traditionally viewed dietary interventions with skepticism. There is mounting evidence that links food to changes in motility, visceral sensation, microbiome, permeability, immune activation, and brain-gut interactions-all key elements in the pathogenesis of IBS. The role of specific dietary modification in the management of IBS has not been rigorously investigated until recently. There is now credible evidence suggesting that targeted dietary carbohydrate exclusion provides clinical benefits to IBS patients. There is emerging evidence to suggest that proteins such as gluten, as well as food chemicals, may play a role in IBS.

Amine oxidase copper-containing 1 (AOC1) is a downstream target gene of the Wilms tumor protein, WT1, during kidney development

Amine oxidase copper-containing 1 (AOC1; formerly known as amiloride-binding protein 1) is a secreted glycoprotein that catalyzes the degradation of putrescine and histamine. Polyamines and their diamine precursor putrescine are ubiquitous to all organisms and fulfill pivotal functions in cell growth and proliferation. Despite the importance of AOC1 in regulating polyamine breakdown, very little is known about the molecular mechanisms that control its expression. We report here that the Wilms tumor protein, WT1, which is necessary for normal kidney development, activates transcription of the AOC1 gene. Expression of a firefly luciferase reporter under control of the proximal AOC1 promoter was significantly enhanced by co-transfection of a WT1 expression construct. Binding of WT1 protein to a cis-regulatory element in the AOC1 promoter was confirmed by electrophoretic mobility shift assay and chromatin immunoprecipitation. Antisense inhibition of WT1 protein translation strongly reduced Aoc1 transcripts in cultured murine embryonic kidneys and gonads. Aoc1 mRNA levels correlated with WT1 protein in several cell lines. Double immunofluorescent staining revealed a co-expression of WT1 and AOC1 proteins in the developing genitourinary system of mice and rats. Strikingly, induced changes in polyamine homeostasis affected branching morphogenesis of cultured murine embryonic kidneys in a developmental stage-specific manner. These findings suggest that WT1-dependent control of polyamine breakdown, which is mediated by changes in AOC1 expression, has a role in kidney organogenesis.

Lack of association of plasma histamine with diamine oxidase in chronic idiopathic urticaria

BACKGROUND

Chronic idiopathic urticaria (CIU) is considered a complex and multifactorial disease. Excessive histamine intake may induce an attack of urticaria. The main enzyme for histamine metabolism is diamine oxidase (DAO).

OBJECTIVE

Plasma histamine concentrations and DAO activities were evaluated to determine whether there are abnormalities in the histamine metabolism of CIU patients.

METHODS

Seventy-five CIU patients and twenty-five healthy control subjects were included in the study. Blood was taken from all subjects to measure plasma levels of the histamine and DAO.

RESULTS

Mean plasma histamine levels were significantly higher in CIU patients (11.59±10.98 nM) than in the control subjects (8.75±2.55 nM) (p=0.04). Mean DAO activities were lower in patients of CIU (80.86±26.81 histamine degrading unit [HDU]/ml) than in the controls (81.60±9.67 HDU/ml), but without significant difference. In 15 CIU patients with gastrointestinal symptoms, the mean histamine concentration was higher (12.43±7.97 nM) and DAO activity was lower (77.93±27.53 HDU/ml) than in the remaining 60 CIU patients without gastrointestinal symptoms (11.38±11.67 nM and 81.58±26.82 HDU/ml), without significant difference. The relationship between DAO activity and plasma histamine concentrations showed a significant negative linear value (p=0.001). There were no significant relationships between plasma histamine concentrations and symptom severity score.

CONCLUSION

In CIU patients, a high plasma histamine concentration may not be explained by DAO activity. CIU patients with gastrointestinal (GI) symptoms showed no significantly lower DAO activity. Larger group studies are required to elucidate the relationship between plasma histamine concentrations and DAO activity, especially of CIU patients with GI symptomsto understand the difference in CIU patients with and without GI symptoms.

Allergic predisposition, histamine and histamine receptor expression (H1R, H2R) are associated with complicated courses of sigmoid diverticulitis

BACKGROUND

We aimed to evaluate our hypothesis that allergic predisposition and expression of histamine receptors might contribute to complicated courses of sigmoid diverticulitis.

METHODS

Expression of histamine and histamine receptors (H1R, H2R) was analysed on protein level (immunohistochemistry/immunofluorescence (IF)) as well as mRNA level (reverse transcription-PCR (RT-PCR) in surgical specimen of patients (n = 101) having undergone resection for sigmoid diverticulits (n = 57 complicated diverticulitis/n = 44 non-complicated diverticulitis).

RESULTS

The mean number of comorbid diseases per patient was 1.76 ± 1.25. Thirty-nine of 101 patients (38.6%) exhibited allergic predisposition (grass poll, food, drug, pets, etc.). Comorbid diseases were significantly associated with complicated diverticulitis (p = 0.027). Complicated sigmoid diverticulitis was significantly associated with high H1R and H2R expression (p < 0.001). Furthermore, an association of complicated diverticulitis with allergic predisposition was found (odds ratio = 3.2, p = 0.0097). IF double-labelling experiments showed a strong correlation of increased histamine expression with expression of H1R and H2R on intestinal enterocytes (histamine/H1R, rho = 0.841, p < 0.0001 and histamine/H2R, rho = 0.806, p < 0.0001). The results of increased H1R and H2R expression in complicated sigmoid diverticulitis were also detected on mRNA level in a subset of patients (RT-PCR, p = 0.009).

CONCLUSIONS

Our findings suggest that allergic predisposition might be another important risk factor for complicated courses of acute sigmoid diverticulitis and linked with histamine receptor expression. Supportive therapies with antihistaminic drugs might become an option. Allergic predisposition might be worth considering when indicating surgery for sigmoid diverticulitis.

Association of single nucleotide polymorphisms in the diamine oxidase gene with diamine oxidase serum activities

BACKGROUND

Histamine intolerance (HIT) is associated with an excess of histamine because of an impaired function of the histamine-degrading enzyme diamine oxidase (DAO). The genetic background of HIT is unknown yet.

METHODS

Case-control association study of all haplotype tagging and four previously reported DAO SNPs and one HNMT Single nucleotide polymorphism with symptoms of HIT and DAO serum activity in 484 German individuals including 285 patients with clinical symptoms of HIT and 199 controls.

RESULTS

Diamine oxidase serum activity was significantly associated with seven SNPs within the DAO gene. The minor allele at rs2052129, rs2268999, rs10156191 and rs1049742 increased the risk for a reduced DAO activity whereas showing a moderate protective effect at rs2071514, rs1049748 and rs2071517 in the genotypic (P = 2.1 × 10(-8) , 7.6 × 10(-10) , 8.3 × 10(-10) , 0.009, 0.005, 0.00001, 0.006, respectively) and allelic genetic model (P = 2.5 × 10(-11) , 5.4 × 10(-13) , 8.9 × 10(-13) , 0.00002, 0.006, 0.0003, 0.005, respectively). Reporter gene assays at rs2052129 revealed a lower promoter activity (P = 0.016) of the minor allele. DAO mRNA expression in peripheral blood mononuclear cells of homozygous carriers of the minor allele at rs2052129, rs2268999, rs10156191 was lower (P = 0.002) than homozygous carriers of the major allele. Diamine oxidase variants were not associated with the HIT phenotype per se, only with DAO activity alone and the subgroup of HIT patients displaying a reduced DAO activity.

CONCLUSIONS

DAO gene variants strongly influence DAO expression and activity but alone are not sufficient to fully effectuate the potentially associated disease state of HIT, suggesting an interplay of genetic and environmental factors.

[Histamine intolerance mimics anorexia nervosa]

Histamine intolerance is a clinically heterogeneous disease. We present a woman who suffered from weight loss, diarrhea, abdominal pain, headache, flushing and bronchial asthma for several years. When placed on a histamine-poor diet, she experienced weight gain and improvement of other all signs and symptoms, supporting the diagnosis of histamine intolerance. Therefore, this disease should be included in the differential diagnosis of anorexia nervosa.

Correlation of active site metal content in human diamine oxidase with trihydroxyphenylalanine quinone cofactor biogenesis

Copper-containing amine oxidases (CAOs) require a protein-derived topaquinone cofactor (TPQ) for activity. TPQ biogenesis is a self-processing reaction requiring the presence of copper and molecular oxygen. Recombinant human diamine oxidase (hDAO) was heterologously expressed in Drosophila S2 cells, and analysis indicates that the purified hDAO contains substoichiometric amounts of copper and TPQ. The crystal structure of a complex of an inhibitor, aminoguanidine, and hDAO at 2.05 Å resolution shows that the aminoguanidine forms a covalent adduct with the TPQ and that the site is ∼75% occupied. Aminoguanidine is a potent inhibitor of hDAO with an IC(50) of 153 ± 9 nM. The structure indicates that the catalytic metal site, normally occupied by copper, is fully occupied. X-ray diffraction data recorded below the copper edge, between the copper and zinc edges, and above the zinc edge have been used to show that the metal site is occupied approximately 75% by copper and 25% by zinc and the formation of the TPQ cofactor is correlated with copper occupancy.

A new crystal form of human diamine oxidase

Copper amine oxidases (CAOs) are ubiquitous in nature and catalyse the oxidative deamination of primary amines to the corresponding aldehydes. Humans have three viable CAO genes (AOC1-3). AOC1 encodes human diamine oxidase (hDAO), which is the frontline enzyme for histamine metabolism. hDAO is unique among CAOs in that it has a distinct substrate preference for diamines. The structure of hDAO in space group P2(1)2(1)2(1) with two molecules in the asymmetric unit has recently been reported. Here, the structure of hDAO refined to 2.1 A resolution in space group C222(1) with one molecule in the asymmetric unit is reported.

Structure and inhibition of human diamine oxidase

Humans have three functioning genes that encode copper-containing amine oxidases. The product of the AOC1 gene is a so-called diamine oxidase (hDAO), named for its substrate preference for diamines, particularly histamine. hDAO has been cloned and expressed in insect cells and the structure of the native enzyme determined by X-ray crystallography to a resolution of 1.8 A. The homodimeric structure has the archetypal amine oxidase fold. Two active sites, one in each subunit, are characterized by the presence of a copper ion and a topaquinone residue formed by the post-translational modification of a tyrosine. Although hDAO shares 37.9% sequence identity with another human copper amine oxidase, semicarbazide sensitive amine oxidase or vascular adhesion protein-1, its substrate binding pocket and entry channel are distinctly different in accord with the different substrate specificities. The structures of two inhibitor complexes of hDAO, berenil and pentamidine, have been refined to resolutions of 2.1 and 2.2 A, respectively. They bind noncovalently in the active-site channel. The inhibitor binding suggests that an aspartic acid residue, conserved in all diamine oxidases but absent from other amine oxidases, is responsible for the diamine specificity by interacting with the second amino group of preferred diamine substrates.

The polyamine and histamine metabolic interplay in cancer and chronic inflammation

PURPOSE OF REVIEW

To provide an update on the major research contributing to deciphering the metabolic interplay of polyamines/histamine and its impact in cancer and chronic inflammation.

RECENT FINDINGS

The most recent and relevant findings that might reflect a link between the polyamines/histamine metabolic interplay and the development of cancer and chronic inflammation-related diseases include: the observation that histamine catabolism is downregulated in the colonic mucosa of patients with colonic adenoma; the finding that some polyamine and histamine-related metabolites are different between a breast cancer cell line and a reference mammary epithelial cell line; and the demonstration of the critical role that mast cells (a cell type in which the polyamine/histamine metabolic interplay has been confirmed) play in the development of pancreatic tumors. There is still, however, a lack of specific studies elucidating the exact contribution of the polyamine/histamine metabolic interplay in these clinical settings.

SUMMARY

In mammalian cells, a polyamine/histamine metabolic interplay has been extensively proven; however, its ultimate effect on human health largely depends on the cell type and environment. Information on this topic is currently fragmented in the literature. In order to develop efficient intervention strategies, it will be necessary to establish an integrated and holistic view of the role of the polyamine/histamine metabolic interplay in each pathological state.

Decreased histamine catabolism in the colonic mucosa of patients with colonic adenoma

INTRODUCTION

Alterations in mucosal histamine degradation play an important role in various gastrotinestinal diseases including colonic adenoma. In humans, histamine can be catabolized either by oxidative deamination by diamine oxidase (DAO) or by ring methylation by histamine N-methyltransferase (HNMT). The significance of HNMT in this context was investigated for the first time in this project.

METHODS

About 94 colonic biopsies were endoscopically obtained from 23 patients suffering from colonic adenoma and 26 biopsies from six healthy individuals. Each sample was mechanically homogenized, homogenates were cleared by centrifugation and used for determination of protein and histamine concentrations and enzyme activities of DAO and HNMT by radiometric assay.

RESULTS

In adenoma patients DAO activities were slightly and HNMT activities were significantly decreased in normal mucosa compared to controls. Activities of both enzymes were significantly lower in adenoma tissue than in healthy mucosa in the same patients. A significant correlation was found between HNMT and DAO in all investigated samples. Histamine concentrations were elevated in adenoma patients.

CONCLUSIONS

Histamine catabolism is decreased in the colonic mucosa of patients with colonic adenoma.

Histamine in food: is there anything to worry about?

Biogenic mono-, di- and poly-amines are widely distributed among living organisms. The amines fulfil many important functions in the human body both in the periphery and brain. Some authors suggest that foods rich in biogenic amines, especially histamine, present high health hazards for consumers. However, this is conditional on a range of other factors. The alimentary tract is well equipped with enzymes that inactivate amines and the blood-brain barrier prevents them entering the brain from the circulation. Oxidative deamination, methylation, acetylation and transglutamylation are the degradation pathways which operate efficiently in the stomach, intestines and liver. Particularly important is oxidative deamination. Food histamine poisoning or cheese reaction, manifested itself in patients treated with drugs that inhibit amine oxidases or in patients showing an enterocytic diamine oxidase deficit. It is rather food allergy, which should worry us more, as endogenous histamine release from mast cells is more dangerous. Preventive measures should be undertaken against increases in food allergies.

Histamine and histamine intolerance

Histamine intolerance results from a disequilibrium of accumulated histamine and the capacity for histamine degradation. Histamine is a biogenic amine that occurs to various degrees in many foods. In healthy persons, dietary histamine can be rapidly detoxified by amine oxidases, whereas persons with low amine oxidase activity are at risk of histamine toxicity. Diamine oxidase (DAO) is the main enzyme for the metabolism of ingested histamine. It has been proposed that DAO, when functioning as a secretory protein, may be responsible for scavenging extracellular histamine after mediator release. Conversely, histamine N-methyltransferase, the other important enzyme inactivating histamine, is a cytosolic protein that can convert histamine only in the intracellular space of cells. An impaired histamine degradation based on reduced DAO activity and the resulting histamine excess may cause numerous symptoms mimicking an allergic reaction. The ingestion of histamine-rich food or of alcohol or drugs that release histamine or block DAO may provoke diarrhea, headache, rhinoconjunctival symptoms, asthma, hypotension, arrhythmia, urticaria, pruritus, flushing, and other conditions in patients with histamine intolerance. Symptoms can be reduced by a histamine-free diet or be eliminated by antihistamines. However, because of the multifaceted nature of the symptoms, the existence of histamine intolerance has been underestimated, and further studies based on double-blind, placebo-controlled provocations are needed. In patients in whom the abovementioned symptoms are triggered by the corresponding substances and who have a negative diagnosis of allergy or internal disorders, histamine intolerance should be considered as an underlying pathomechanism.

Evidence for a reduced histamine degradation capacity in a subgroup of patients with atopic eczema

BACKGROUND

A diminished histamine degradation based on a reduced diaminoxidase activity is suspected as a reason for non-IgE-mediated food intolerance caused by histamine. Atopic eczema (AE) is often complicated by relapses triggered by IgE-mediated allergy to different kinds of food. However, in a subgroup of patients with AE, allergy testing proves negative, although these patients report a coherence of food intake and worsening of AE and describe symptoms that are very similar to histamine intolerance (HIT).

OBJECTIVES

It was the aim of our study to evaluate symptoms of HIT in combination with diaminoxidase levels in a total of 360 individuals consisting of patients with AE (n = 162) in comparison with patients with HIT (n = 124) without AE and healthy control volunteers (n = 85).

METHODS

Histamine plasma level was determined with an ELISA and diaminoxidase serum activity with the help of radio extraction assays using [3H]-labeled putrescine-dihydrochloride as a substrate. Detailed clinical evaluations of characteristic features of AE and HIT were performed.

RESULTS

Reduced diaminoxidase serum levels leading to occurrence of HIT symptoms like chronic headache, dysmenorrhea, flushing, gastrointestinal symptoms, and intolerance of histamine-rich food and alcohol were significantly more common in patients with AE than in controls. Reduction of both symptoms of HIT and Severity Scoring of Atopic Dermatitis could be achieved by a histamine-free diet in the subgroup of patients with AE and low diaminoxidase serum levels.

CONCLUSION

Higher histamine plasma levels combined with a reduced histamine degradation capacity might influence the clinical course of a subgroup of patients with AE.

CLINICAL IMPLICATIONS

As HIT emerges in a subgroup of patients with AE, a detailed anamnestic evaluation of food intolerance and HIT symptoms complemented by an allergological screening for food allergy, a diet diary, and, in confirmed suspicion of HIT, measurement of diaminoxidase activity and a histamine-free diet should be undertaken.

Immunoglobulin E production in chronic pancreatitis

OBJECTIVES

Serum immunoglobulin E (IgE) was investigated in patients with chronic pancreatitis in order to elucidate possible disease mechanisms linking pancreatitis, adverse reaction to foods and allergy.

DESIGN AND METHODS

Serum IgE was analysed in 86 non-atopic patients with advanced chronic pancreatitis and 54 non-atopic controls. IgE detection was performed by enzyme-linked immunofluorescence.

RESULTS

Mean IgE levels (+/- standard error of mean) in chronic pancreatitis patients (286.1+/-49 kU/l) were found to be significantly elevated compared to controls (67.7+/-11 kU/l; P<0.0001). Normal IgE levels (<100 kU/l) were present in 40/54 control patients (74.1%), but only 39/86 pancreatitis patients (45.3%). Of the patients with chronic pancreatitis, 47/86 (54.6%) had clearly elevated IgE levels of >100 kU/l and their IgE values did not show a Gaussian distribution. However, nine-fold higher IgE levels were found in chronic pancreatitis patients with alcohol consumption of >25 g/day and exocrine insufficiency (915.5+/-240 kU/l) than in pancreatitis patients with normal exocrine function and no alcohol consumption (103.4+/-43 kU/l; P<0.001). Moreover, acute episodes of chronic pancreatitis were found to increase serum IgE levels.

CONCLUSIONS

In patients with chronic pancreatitis, serum IgE production is markedly enhanced, especially during acute inflammatory episodes or when alcohol is consumed. Since abstinence from alcohol and pancreatic enzyme substitution are associated with clearly lower IgE levels, it may be concluded that pancreatic insufficiency with reduced nutrient digestion and alcohol consumption stimulate IgE production. This finding gives rise to the speculation that, apart from pancreatic inflammation, cross-linking of IgE with alimentary or other antigens might be involved in the pathophysiology of a sub-population of patients with chronic pancreatitis and manifest pancreatic insufficiency.