PROBALIDY: moving closer to a treatment for liver diseases
The PROBALIDY project originated at the Inflammation, Microbiome and Immunosurveillance Laboratory (MI2 - Univ. Paris-Saclay, Inserm), whose Microbiome in liver diseases: from susceptibility to treatment team has identified several bacteria in the gut microbiota that help to improve NASH-Non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD). NAFLD, often referred to as soda disease, and ALD are the two largest malnutrition-related liver diseases in the world, for which there are no treatments. The first is associated with obesity and the second with excessive alcohol consumption. Both diseases share common features in their early stages and the use of a probiotic, potentially made from health-promoting bacteria, could improve patient management. PROBALIDY is currently being developed by SATT Paris-Saclay.
"How can we not be interested in intestinal microbiota when we work on the liver?" is the question Anne-Marie Cassard, Inserm Research Director and Co-Director of the Microbiome in liver diseases: from susceptibility to treatment team at the MI2 laboratory, and Gabriel Perlemuter, Professor - Hospital Practitioner (PU-PH) and current Head of the Gastroenterology and Nutrition Department at the Antoine Béclère hospital in Clamart, France, have been asking themselves since 2006. Research on microbiota was just beginning at that time and research on alcoholism- and obesity-related liver diseases was rare and difficult to finance.
In 2008, the team received its first funding from the European Foundation for Alcohol Research (ERAB) for a research project based on the cohort of patients in the gastroenterology department of Antoine Béclère hospital. The team first highlighted differences in microbiota and then showed that there is an individual susceptibility to developing liver damage when drinking alcohol. Among patients with an equivalent amount and duration of alcohol consumption, some did not develop any serious liver pathology, while others developed cirrhosis or liver cancer. Could this be due to the observed differences in microbiota? This is what the team is trying to understand using pre-clinical models.
In search of protective bacteria
"When the microbiota of individuals with liver damage were administered to mice that consumed alcohol, their damage was aggravated, unlike the mice that had received the ‘good" microbiota’," describes Anne-Marie Cassard, who therefore wondered whether there are beneficial bacteria. Vanessa Liévin-Le Moal, a lecturer at the Faculty of Pharmacy of Université Paris-Saclay and a microbiologist, joined the team in 2016 to observe these bacteria up close. In addition to molecular analysis by sequencing, she put them in culture, which provides more information. It showed different strains of bacteria in alcoholic subjects who did not have liver damage. "These are lactic acid bacteria, those found in milk or cheese, which have the benefit of being harmless to humans," explains Anne-Marie Cassard.
The team then sought to isolate these bacteria from an in vitro screening in an individual with excessive alcohol consumption but no liver damage. "Lactic acid bacteria are known to inhibit the growth of potentially harmful enterobacteria. The best known example is Escherichia Coli, which is present in our digestive tract and certain pathogenic strains of which can cause disorders of varying degrees of severity."
The question then arose as to which of the isolated lactic acid bacteria strains are the most effective and capable of preventing the proliferation of enterobacteria once in the intestinal environment. In people who drink alcohol, there is a ratio between liver damage and the number of enterobacteria present: the more enterobacteria, the more severe the liver damage. Over the course of 2018, the team finally selected seven relevant lactic acid bacteria strains from the 120 strains isolated from the microbiota.
A double whammy treatment
It turned out that NAFLD and ALD have common mechanisms and that liver damage evolves in the same way, although ALD can also cause acute hepatitis with a short-term vital risk. "It became clear to us that there were similar deleterious and beneficial bacteria in both conditions." The researchers used the more easily classified cohort of patients with heavy drinking to discover these beneficial bacteria. "We differentiated species from strains. We identified identical species with different strains among our seven candidate lactic acid bacteria. Because they did not carry the same genetic makeup, they did not have the same functional capabilities."
From discovery to development
There is currently no treatment for alcohol-related liver disease. According to Gabriel Perlemuter, there is little hope for people with severe alcoholic hepatitis, for whom anti-inflammatory treatment with corticosteroids allows just half to survive for months after hospitalisation. Administering the bacteria before the disease reaches an early stage could avoid the aggravation of liver damage.
At the end of 2018, Anne-Marie Cassard submitted a dossier to SATT Paris-Saclay, which pre-selected it for a six-month co-construction with Mathieu Gutmann, Health Project Manager. At the end of 2019, the project was selected for substantial funding that allowed the recruitment of two patent engineers and support from SATT Paris-Saclay and INSERM Transfert.
Bacteria and fibres, together
The researchers used pectin, a soluble and consumable fibre, during their work, which led them to make another discovery. "Pectin can modify the metabolism of pre-clinical models with liver damage," says Anne-Marie Cassard. Two clinical trials have now been launched to confirm the therapeutic role of pectin. The first, financed by the French National Research Agency (ANR), should provide evidence of liver improvement through the effect of pectin, via the microbiota, on bile acids and tryptophan metabolites. These two families of metabolites are partly produced by the microbiota and play a role in the immune mechanism. The second trial, carried out by the French Institute for Public Health Research (IReSP), aimes to prove the effectiveness of a fibre blend in alcohol withdrawal. These fibres modify the microbiota. They bring food to the bacteria and allow them to produce metabolites, some of which influence either the enteric nervous system (part of the autonomic nervous system that controls the digestive system) or the synthesis of neuromediators.
Will it eventually be possible to mix bacteria and fibres to create a drug? "Why not! I can imagine our bacteria and fibres in yoghurt, for example. We still have to find someone able to do this," concludes the researcher.
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