Fatty liver disease and death of liver tissue were also confirmed in rats fed regulatory permitted and thus presumed safe doses of the weedkiller
The primary mechanism of how glyphosate herbicides kill plants is by inhibiting an enzyme called EPSPS, which is part of a biochemical pathway known as the shikimate pathway. The shikimate pathway is responsible for the synthesis of certain aromatic amino acids that are vital for the production of proteins, the building blocks of life. Thus when the synthesis of the aromatic amino acids is blocked by glyphosate inhibition of EPSPS, the plant dies.
Humans and animals do not have the shikimate pathway, so industry and regulators have claimed that glyphosate is nontoxic to humans. However, some strains of gut bacteria do have the shikimate pathway, leading to much debate about whether Roundup and glyphosate could affect the gut microbiome (bacterial populations). Imbalances in gut bacteria have been found to be linked with many diseases, including cancer, type 2 diabetes, obesity, and depression.
As many species of gut bacteria do have the shikimate pathway, scientists have hypothesised that glyphosate herbicides could inhibit the EPSPS enzyme of the shikimate pathway in these organisms, leading to imbalance in the microbiome, with potentially negative health consequences. Some have proposed that if glyphosate herbicides do disrupt the gut microbiome, EPSPS inhibition will be the primary mechanism through which this occurs.
However, proof that glyphosate herbicides can inhibit the EPSPS enzyme and the shikimate pathway in gut bacteria has been lacking. But a new study has proven beyond doubt that this does indeed happen.
The study in rats by an international team of scientists based in London, France, Italy, and the Netherlands, led by Dr Michael Antoniou of King’s College London and posted on the pre-peer-review site BioRxiv, has found that Roundup herbicide and its active ingredient glyphosate cause a dramatic increase in the levels of two substances, shikimic acid and 3-dehydroshikimic acid, in the gut, which are a direct indication that the EPSPS enzyme of the shikimic acid pathway has been severely inhibited.
In addition, the researchers found that both Roundup and glyphosate affected the microbiome at all dose levels tested, causing shifts in bacterial populations.