Glyphosate: Interaction with Genetics

RoundUp is the most widely used herbicide in the world. It is made by Monsanto, which is now owned by Bayer. Glyphosate is the active ingredient in RoundUp, and it will kill most broadleaf plants and grasses. [ref]

Glyphosate works by blocking the shikimate pathway, which is a vital enzyme pathway in plants and some microorganisms. The shikimate pathway is the process by which plants, bacteria, archaea, fungi, and algae make folates and certain amino acids (tryptophan, tyrosine, and phenylalanine). Without those amino acids, the plants and microorganisms die.

The shikimate pathway isn’t found in animals, and the amino acids that it makes are ones that we must get from our diet (essential amino acids for humans). Thus, RoundUp doesn’t kill us outright like it does plants.

Why is RoundUp the most popular kid on the herbicide block? The creation of RoundUp Ready genetically modified crops has increased the use of RoundUp by 100-fold since the 1970s. These RoundUp Ready crops can be sprayed with glyphosate and not die. Thus, farmers can spray their RoundUp Ready soybean field, killing all the weeds and leaving their crop standing tall.

The EPA says that ‘there are no risks to public health why glyphosate is used in accordance with its current label and that glyphosate is not a carcinogen’.[ref]

On the other hand, the International Agency for Research on Cancer (IARC) lists glyphosate as a ‘probable carcinogen’ and several recent lawsuits have successfully shown the link between glyphosate and non-Hodgkin’s lymphoma. [ref]

Genetic variant impacted by glyphosate:

A study came out a couple of weeks ago showing that some people are more affected by glyphosate than others. [ref]

The study found that people with CYP1A1 genetic variants are more likely to have problems with acetylcholinesterase inhibition from glyphosate.

Glyphosate has been shown in animal studies to affect acetylcholinesterase a little bit.  Acetylcholinesterase is the enzyme that breaks down acetylcholine, which is an important neurotransmitter. Acetylcholine transfers the signal between the nerves that control your muscles (and also neurons in the brain). Think of it as the on switch for a muscle nerve which causes a contraction. For every ‘on’ impulse, you need to stop the signal with an ‘off switch’ — that would be acetylcholinesterase.

The animal studies show that glyphosate inhibits acetylcholinesterase (a little).[ref][ref] If you totally inhibit acetylcholinesterase, it can lead to paralysis, convulsions, and death due to asphyxiation (i.e. not being able to move the muscles around the lungs to breath). This is how nerve gas, such as Sarin gas, works in chemical warfare. Not pretty… but, also nothing like the very low levels that we are talking about here.

Serum cholinesterase can also be used as a marker of herbicide poisoning because it is decreased when liver function is damaged.[ref]

Getting back to glyphosate and how it affects people…

The recent study[ref] was done on people whose job it was to make glyphosate (in China). Those people were exposed to only to glyphosate (no other pesticides), and their blood was tested to see what their serum acetylcholinesterase levels were. These pesticide manufacturers were exposed to glyphosate through their work. (Experiments cannot be done on humans by making them consume glyphosate – that would not be cool. Instead, researchers look at people that have already been exposed to higher than normal levels.)

The study showed that people with the CYP1A1 rs1048943 A/G or G/G genotype were more likely to have lower acetylcholinesterase levels due to glyphosate exposure. This variant alters CYP1A1 expression.  Lower acetylcholinesterase was assumed to be a marker of liver damage.

Check your genetic data for rs1048943 (23andMe v4 only):

  • T/T: normal
  • C/T: more likely to have low acetylcholinesterase due to glyphosate exposure, especially in women
  • C/C: more likely to have low acetylcholinesterase due to glyphosate exposure, especially in women[ref]

 

A couple of take-aways from this study:

First, there is an effect from glyphosate on acetylcholinesterase levels, especially at higher exposure levels. This isn’t necessarily a big problem for most people, but it is interesting. Most of the  EPA information says that glyphosate passes through people without being metabolized — which apparently isn’t completely accurate.

Second, the urinary glyphosate metabolite levels of these Chinese glyphosate manufacturer workers were not extraordinarily high. A recent study of children in Mexico showed similar average concentrations to that of the Chinese workers. [ref]

Third, why on earth are there not more genetic related studies on glyphosate? It is something that almost all of us are exposed to on a regular basis.

 

 

 



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