How do marine biotoxins interfere with health?
If mussels contain high levels of marine biotoxins, their consumption can lead to food poisoning. Depending on the toxin, the symptoms can vary. One of these marine biotoxins is okadaic acid. Ingestion of high concentrations leads to intestinal problems with severe diarrhoea, vomiting and abdominal pain. Apart from these acute effects, it is also known that okadaic acid can, in animal experiments, harm the intestine and liver. In addition, it is carcinogenic and embryotoxic. In the research project "Molecular characterisation of the toxicological effects of the marine biotoxin okadaic acid in in-vitro models of the human gastrointestinal barrier and the liver", scientists of the Department of Food Safety of the German Federal Institute for Risk Assessment (BfR) are investigating the toxic mechanism which leads to these health problems. "The question is whether and how okadaic acid reaches the blood stream and hence the liver from the intestine and into what substances the body transforms the acid in the process", explains BfR President Professor Dr. Dr. Andreas Hensel. There are currently great gaps in our knowledge about the extent to which okadaic acid is converted into more toxic substances which can cause damage to cells. The research project aims to close these knowledge gaps.
Marine biotoxins are metabolites from algae. Under especially good environmental conditions ("algae bloom"), they form in larger quantities. Since algae are the main source of food for water filtering mussels, this means that marine biotoxins such as okadaic acid too are ingested and accumulate in the flesh of the mussels. When humans eat mussels containing high levels of okadaic acid, this results in the typical diarrhoeic mussel poisoning which predominantly causes problems of the intestinal tract. These acute effects which are confined to the intestinal tract are well researched. What is less well researched are the carcinogenic and highly embryotoxic properties of okadaic acid. They can occur when the marine biotoxin overcomes the intestinal barrier, enters the blood stream, and additional toxic metabolites are then formed in the liver. Whether this actually occurs depends on the quantity of ingested okadaic acid. In the research project, the scientists investigated how the intestinal wall protects the body from okadaic acid in low concentrations and why in the presence of high concentrations in the intestine this barrier fails. With the help of cell cultures made up of cells from the human intestinal wall, the changes in the barrier properties of a specific layer of the intestinal mucosa under the influence of okadaic acid and the detoxification mechanism of the intestine are studied. Using human liver cells, the metabolism of this marine biotoxins are additionally investigated, i.e. the formation of metabolites of higher or lower toxicity. It is hoped that an understanding of the molecular connections of detoxification and activation of additional toxic properties will contribute to the identification of unknown toxicity mechanisms of okadaic acid which play a relevant role for the reaction of the body following the consumption of larger doses of this marine biotoxin. The BfR expects the results of this research project to supply additional data on the oral bioavailability, toxicokinetics and metabolism of okadaic acid in order to be able to assess the health risks it poses to humans more accurately. The research project is scheduled to run for three years and is sponsored by the German Research Foundation (DFG).
About the BfR
The German Federal Institute for Risk Assessment (BfR) is a scientifically independent institution within the portfolio of the Federal Ministry of Food and Agriculture (BMEL) in Germany. It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. The BfR conducts its own research on topics that are closely linked to its assessment tasks.