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

Abstract

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 caused by Diamine Oxidase (DAO) deficiency – case report

“…The colour changes when a peroxidase substrate is used and an acid is added to complete the reaction [7]. The colour change obtained enables assessment of the DAO concentration in the serum [8]. Despite the controversy regarding the possibility of making a diagnosis based on the above-mentioned test, some authors suggest that these tests may be helpful in identifying people with histamine intolerance, including in the case of suspected genetic background, which is likely in the case of the patient described [5].…”

Usefulness of DAO biomarker in difficult allergy. Consideration based on own typical cases

“…chorobami alergicznymi, chorobami jelit, przewlekłymi infekcjami i mastocytozą [4,3]. Więcej danych na ten temat podają inne publikacje, w tym polskie [8,10,[23][24][25][26].…”

“…Przykładowo Beltrán-Ortiz i wsp. [25], stwierdzili statystycznie istotne różnice w stężeniu i aktywności DAO między pacjentami z NH a grupą kontrolną. Dlatego pomiar stężenia i aktywności DAO jest dobrą strategią diagnostyczną dla podejrzanych przypadków.…”

“…Dlatego pomiar stężenia i aktywności DAO jest dobrą strategią diagnostyczną dla podejrzanych przypadków. Jednoczesne stosowanie obu testów pozwala zmniejszyć liczbę wyników pozytywnie i negatywnie fałszywych, na przykład u pacjentów z prawidłowymi poziomami DAO, u których stwierdza się dysfunkcję w aktywności tego enzymu [25]. Dlatego stężenie i aktywność DAO mogą być stosowane jako metoda diagnostyczna dla NH [4].…”

Electrochemical (Bio)Sensing Devices for Human Microbiome Related Biomarkers

“…This is particularly relevant in humans affected by Crohn's disease where mucosal DAO activity is near 50% lower compared to healthy counterparts [60]. Moreover, this enzyme has an essential role for degradation of exogenous histamine in the intestine, a good correlation existing between histamine intolerance and a low concentration and/or activity of DAO [61]. Furthermore, iALP is involved in several physiological roles in the gastrointestinal tract, such as dephosphorylation of bacterial lipopolysaccharides (LPS) and regulation of lipid absorption, thus playing a protective role against both LPS-induced inflammation and Type 2 diabetes in humans [62].…”