The Antisecretory Factor (AF), a protein endogenous to the body with an important role in secretory and inflammatory diseases by regulating cellular fluid and ion transport over cell membranes in various organs of the body.
How Protein AF works
Chemistry and biology
In the early 1990’s Ivar Lönnroth concentrated on chemical and biological characterisation of the AF protein. This work was completed in the mid 1990’s. The protein is of medium size, 41 kDa, comprised of 380 amino acids with the active region located as a peptide of 38 amino acid length in the terminal N-region of the protein.
The purified protein was administered to rabbits and used to produce antibodies, in turn used to clone the protein coding gene. It is now possible to produce highly purified protein through microbiological methods as well as chemical synthesis.
The antisecretory effect is present in both the protein and the peptide, which is unusual. It acts mainly by stimulating the nerves in the intestine and by affecting the nerve signals regulating fluid transport. The protein has its own pharmacological effect and initiates production of endogenous defence mechanisms against secretion and inflammation.
AF is the most potent anti-diarrhoeal substance known and it has been proven to inhibit secretion caused not only by cholera, but also by a number of other known toxins, i.e. E.coli, Campylobacter, Clostridium difficile and okadaic acid, the blue mussel toxin.
Within a couple of hours the plasma level of AF rises quickly following exposure to diarrhoea stimulation. In healthy subjects AF is inactive and not of vital importance. It will however become activated upon stimulation from bacterial toxins. An elevated synthesis of AF can also be achieved by the ingestion of AF-inducing specially processed cereals, SPC-Flakes® .
Evidence suggests that the body has a biological memory of AF stimulation. This has been studied in healthy subjects. When given 1 g/kg bodyweight per day of AF inducing cereals, SPC-Flakes®, administered 2-3 times daily one can expect to see significant elevation of AF levels. After 10-15 days of administration, levels will reach 1 AF-unit/ml plasma. Depending on the length of cereal intake the level will remain for a corresponding amount of time. A three-month break in the intake will cause a return to low AF levels. If the intake of AF-enhancing cereals is resumed, the levels will reach significant values again already after 2-3 days.
AF regulates the fluid and ion transport over cell membranes in different organs of the body, probably by regulating the permeability in the channels responsible for water and ion transport. Thus, AF has a fundamental influence over diseases where secretion is of importance. It has effect in regulating fluid transport over the intestinal wall in e.g. Crohn’s disease and fluid pressure in the inner ear in Ménière’s disease, as well as in other conditions caused by an imbalance in the fluid regulation in bodily tissues.
Aside from the highly potent antisecretory activity, the AF protein also has important anti-inflammatory effects. The clinical significance of this activity has been shown in rheumatoid arthritis, inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn’s disease, as well as other situations where inflammation plays an important role, e.g. in mastitis, common in breastfeeding women.
In 2001 the collected experiences from research and clinical trials was published in the renowned journal International Review of Cytology (Lange and Lönnroth, 2001).
There is broad international interest for protein AF and in 2010 an international review article was published (Ulgheri, Paganini och Rossi, Nutrition Research Reviws)
AF in the body
AF is present in most tissues in the body. With immunohistochemistry techniques it has been demonstrated that AF is present in most tissues in the body. Eva Jennische, at the Department of Anatomy and Cell Biology at Gothenburg University, has in her studies shown that AF protein is located in three cell types; epithelial cells, lymphatic cells, especially leukocytes, and nervous cells. AF is expressed in the mucosal epithelium of the gastrointestinal tract, the respiratory organs, the urogenital organs and in pituitary cells, mainly endocrine cells in the pituitary gland. Under certain conditions also other white blood cells can express AF, i.e. during inflammatory response. AF protein has further been identified in central and peripheral nervous tissue, in neuronal cells and synaptic nerve terminals.
As a result of the positive clinical effects of AF treatment of Ménière’s disease, immunohistochemical analyses have been performed showing that AF can be localized to the Purkinje cells of the cerebellum, which probably are of importance for inhibitory vestibular functions. AF has also been found in the peripheral receptor organs, cochlea and the vestibular apparatus. These findings have later been confirmed by Chinese researchers.
Research is ongoing to identify a true classical receptor for AF
(So far, two binding proteins of interest have been identified, flottilin-1 and vestibule-1, which possibly can interact with AF. The researchers also believe that the GABAA receptor can interact partially with AF.)
In a bioassay model developed by Professor Stefan Lange (Lange, 1982) one can measure the concentration of AF in different tissues achieved by measuring hypersecretion in the rat intestine by the sectioning of a 10-15 cm segment. The AF activity in man is measured by injecting a purified plasma sample intravenously in a rat stimulated with cholera toxin. An AF concentration that inhibits 50% of the secretion in the loop is given an AF value of 1.0. The clinical studies have shown that an AF value exceeding 0.5 is correlated to an influence on diarrhoea.
There is ongoing intensive research to find a direct method for determining the blood concentration of AF in humans, thereby avoiding indirect measurements in rat. Such a method would easily determine which AF level a certain person has. Monoclonal antibodies have been developed for measuring AF-activity (Johansson et al, Journal of Immunological Methods, 2009 se link).
It is probable that a low AF level can be found in several diseases, whereas a high level is found in healthy subjects. A patient with a low concentration of protein AF could thereby start the treatment with a suitable AF product, and this without having to change his other medication.