Histamine intolerance occurs when there is an imbalance between histamine production and the capacity for histamine degradation. Diamine oxidase (DAO) is the main enzyme for the catabolism of ingested histamine degradation in the gastrointestinal tract and its deficiency has been linked to allergy-like symptoms. Psychostimulant drugs are commonly used to treat Attention Deficit Hyperactivity Disorder (ADHD), but their interaction with DAO is not well characterized. In this work, we evaluated the effects of psychostimulant drugs (methylphenidate and lisdexamfetamine) on in vitro DAO activity and in the human cell line of enterocytes (Caco-2), evaluating DAO expression (mRNA and protein) and DAO activity. Methylphenidate and lisdexamfetamine did not repress the in vitro DAO activity. In addition, in Caco-2 cells, lisdexamfetamine promoted a strong upregulation of DAO mRNA levels, whereas methylphenidate tended to induce DAO activity. To sum up, methylphenidate and lisdexamfetamine treatments do not reduce DAO activity. These findings could be useful for physicians prescribing these two drugs to ADHD patients affected by DAO deficiency.
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Diamine oxidase (DAO) supplements have gained increasing attention in recent years due to their potential to support DAO deficiency, histamine intolerance and related symptoms. However, choosing a reliable and trustworthy DAO supplement can be a challenging task for patients and Healthcare practitioners. One of the main concerns is the lack of regulatory oversight on dietary supplements, which may result in misleading or incomplete labelling, incorrect dosages, and inadequate quality control. Such situations may lead to patients consuming supplements with insufficient amounts of active enzyme or with questionable purity, potentially resulting in undesired health outcomes. Thus, we tested the DAO activity of a variety of already in-the-market supplements and compared them with one another and against the specified activity, if any, by the manufacturer. Our results show a great discrepancy in most of the products and significant differences in DAO activity between different manufacturers.
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