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FAQ
What is a histamine?
Histamine is a biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in connective tissues.
What do histamines do in your body? Are they useful?
Histamine increases the permeability of the capillaries to white blood cells and other proteins, in order to allow them to engage foreign invaders in the affected tissues. It is found in virtually all animal body cells.
Histamine [2-(4-Imidazolyl)-ethylamine] is an important mediator of many biological processes including inflammation, gastric acid secretion, neuromodulation, and regulation of immune function. Due to its potent pharmacological activity even at very low concentrations, the synthesis, transport, storage, release and degradation of histamine have to be carefully regulated to avoid undesirable reactions. Histamine is also generated by microbiological action in the course of food processing and it is therefore present in substantial amounts in many fermented foodstuffs and beverages.
What is histamine intolerance?
In general, symptoms of histamine intolerance are caused by an overload of the organism with histamines (other biogenic amines can also be involved)
It does not make any difference whether the histamine is liberated by bacterial production or by ingestion of histamine-rich food. It also does not matter, if the problem is created by a low level of Diaminoxidase (extracellular) or by a low level of N-methyltransferase (intracellular).
Does histamine intolerance mean that the body is overloaded with histamines?
Yes, although the answer is too simple. In hypoallergenic persons, even a histamine load within a ‘normal’ range, can be already a problem. It is not about the histamines, but about two enzymes, who have to eliminate excess amounts of histamines from the body: DAO (Diaminoxidase) and NMT (N-Methyltransferase).
What are the reasons for high levels of histamines or low levels of NMT?
a) congenital enzyme defect
b) gastrointestinal infections (acute and long-term)
c) other infections in parts of the body where histamines are active
d) consumption of histamine-rich foods
e) consumption of foods high in other biogenic amines (like tyramines)
f) consumption of histamine liberators (certain foods and medication)
this list will probably be getting longer over the time
What makes histaminosis so different from allergies? And can histamine intolerance life threatening?
Histamine intolerance is a Pseudo Allergy: It is not mediated by IgE, but can trigger a severe reaction, like anaphylactic shock. Because the “allergy” is not detectable makes histamine intolerance even more dangerous.
What are histamine receptors?
Four histamine receptors have been identified, all of which are G protein-coupled receptors. These different receptors are expressed on different cell types and work through different intracellular signalling mechanisms, which explains, at least at a simple level, the diverse effects of histamine in different cells and tissues. H1 to be found in smooth muscle, endothelial cells (acute allergic responses. H2 to be found in gastric parietal cells (secretion of gastric acid). H3 to be found in the central nervous system (for modulating neurotransmission). H4 to be found in mast cells, eosinophils, T cells (regulating immune responses).
What are the symptoms for histamine intolerance?
This is a major problem, because all of the following are scientific accepted symptoms of a histamine intolerance. Primary symptoms group a: hay fever, flushing, redness, wheezing, hay fever related symptoms also in winter, urticaria, asthma.
Primary symptoms group b: IBS-related symptoms, bloating, diarrhoea, constipation, abdominal miraines, nausea, unspecified food intolerances, hypersensitivity to many foods which give different and changing symptoms, allergies to pollen and cross allergies with OAS (oral allergy symptoms). Other primary symptoms (group c): low blood pressure, migraine, tension headaches, palpitation, anxiety, panic attacks, depression, over-emotional.
Should I be worried, if I have one or two of the above list?
No, but because histamine intolerance is so little researched, it might be a good idea to investigate if you have e.g. 5 – 6 symptoms of the above AND all previous investigations and treatments by medical practitioners did not find a solution or did not make you feel much better.
What does the Diaminoxidase (DAO) do?
In layman terms: Diaminoxidase (DAO) eliminates extracellular histamines from the body. In scientific terms: Diamine oxidase uses molecular oxygen to oxidatively deaminate histamine to imidazole acetaldehyde, ammonia and hydrogen peroxide DAO is a member of the class of copper-containing amine oxidases that have in their active-sites a copper ion bound by three conserved histidine residues and the cofactor 2,4,5-trihydroxyphenylalanine quinone, formed post-translationally from a conserved tyrosine residue. Mammalian DAO polypeptide sequences are highly conserved and DAO is encoded by a single gene designated ABP1 or AOC1 that has five exons. The human DAO gene is located on chromosome 7q35. Mammalian DAO is a homodimeric glycoprotein of 200 kDa consisting of two polypeptides of ca. 750 amino acid residues. At the N-terminus, DAO has a signal peptide sequence that targets the protein for secretion. DAO is expressed mainly in intestinal and kidney epithelial cells where the enzyme is stored in secretory vesicles at the basolateral plasma membrane and released into the extracellular space upon stimulation. The best characterised DAO release stimulator is heparin that is released together with histamine by activated mast cells. Apparently, DAO is released locally to inactivate the excess of extracellular histamine to terminate its action. Besides taking care of endogenously released histamine, DAO in the gut is also responsible for catabolizing dietary histamine present in considerable amounts in certain food to prevent its uptake into the circulation. In addition to histamine, DAO also deaminates other diamines with primary amino groups such as 1,4-diaminobutane (putrescine), 1,5-diaminopentane (cadaverine), and agmatine, the decarboxylation product of L-arginine.
What is the N-methyltransferase?
There are different types of N-methyltransferases and they are closely linked. Histamine N-methyltransferase (HMT) is one of two enzymes involved in the metabolism of histamine. Histamine N-methyltransferase catalyzes the methylation of histamine in the presence of S-adenosylmethionine (SAM) forming N-methylhistamine. HMT is present in most body tissues but is not present in fluid. Histamine N-methyltransferase is encoded by a single gene which has been mapped to chromosome 2.
Do histamines work totally on their own?
No… which makes things even more complicated. It seems to be, that putrescines and cadaverines are involved… |
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