Glyphosate, pathways to modern diseases III: Manganese, neurological diseases, and associated pathologies

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DOI: 10.4103/2152-7806.153876
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Abstract
Manganese (Mn) is an often overlooked but important nutrient, required in small amounts for multiple essential functions in the body. A recent study on cows fed genetically modified Roundup®‐Ready feed revealed a severe depletion of serum Mn. Glyphosate, the active ingredient in Roundup®, has also been shown to severely deplete Mn levels in plants. Here, we investigate the impact of Mn on physiology, and its association with gut dysbiosis as well as neuropathologies such as autism, Alzheimer’s disease (AD), depression, anxiety syndrome, Parkinson’s disease (PD), and prion diseases. Glutamate overexpression in the brain in association with autism, AD, and other neurological diseases can be explained by Mn deficiency. Mn superoxide dismutase protects mitochondria from oxidative damage, and mitochondrial dysfunction is a key feature of autism and Alzheimer’s. Chondroitin sulfate synthesis depends on Mn, and its deficiency leads to osteoporosis and osteomalacia. Lactobacillus, depleted in autism, depend critically on Mn for antioxidant protection. Lactobacillus probiotics can treat anxiety, which is a comorbidity of autism and chronic fatigue syndrome. Reduced gut Lactobacillus leads to overgrowth of the pathogen, Salmonella, which is resistant to glyphosate toxicity, and Mn plays a role here as well. Sperm motility depends on Mn, and this may partially explain increased rates of infertility and birth defects. We further reason that, under conditions of adequate Mn in the diet, glyphosate, through its disruption of bile acid homeostasis, ironically promotes toxic accumulation of Mn in the brainstem, leading to conditions such as PD and prion diseases.

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Original Article
Glyphosate, pathways to modern diseases III: Manganese,
neurological diseases, and associated pathologies
Anthony Samsel, Stephanie Seneff1
Research Scientist and Consultant, Deerfield, NH 03037, 1Spoken Language Systems Group, Computer Science and Artificial Intelligence Laboratory, MIT,
Cambridge MA 02139, USA
E-mail: Anthony Samsel - anthonysamsel@acoustictracks.net; *Stephanie Seneff - seneff@csail.mit.edu
*Corresponding author
Received: 22 September 14 Accepted: 21 January 15 Published: 24 March 15
INTRODUCTION
Glyphosate is the active ingredient in Roundup®, the
most widely used herbicide on the planet.[314] Glyphosate
enjoys widespread usage on core food crops, in large part
because of its perceived nontoxicity to humans. The
adoption of genetically engineered “Roundup®-Ready”
corn, soy, canola, cotton, alfalfa, and sugar beets has
made it relatively easy to control weeds without killing
the crop plant, but this means that glyphosate will be
present as a residue in derived foods. Unfortunately,
weeds among GM Roundup®-Ready crops are developing
ever-increasing resistance to Roundup®,[107,221] which
requires an increased rate of herbicide application.[26]
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Abstract
Manganese (Mn) is an often overlooked but important nutrient, required in small
amounts for multiple essential functions in the body. A recent study on cows fed
®
®, has also been shown to severely
deplete Mn levels in plants. Here, we investigate the impact of Mn on physiology,
and its association with gut dysbiosis as well as neuropathologies such as autism,
Alzheimer’s disease (AD), depression, anxiety syndrome, Parkinson’s disease (PD),
and prion diseases. Glutamate overexpression in the brain in association with

Mn superoxide dismutase protects mitochondria from oxidative damage, and
mitochondrial dysfunction is a key feature of autism and Alzheimer’s. Chondroitin
   
osteomalacia. Lactobacillus, depleted in autism, depend critically on Mn for
antioxidant protection. Lactobacillus probiotics can treat anxiety, which is a

leads to overgrowth of the pathogen, Salmonella, which is resistant to glyphosate
toxicity, and Mn plays a role here as well. Sperm motility depends on Mn, and
this may partially explain increased rates of infertility and birth defects. We further
reason that, under conditions of adequate Mn in the diet, glyphosate, through its
disruption of bile acid homeostasis, ironically promotes toxic accumulation of Mn
in the brainstem, leading to conditions such as PD and prion diseases.
Key Words: Autism, cholestasis, glyphosate, manganese, Parkinson’s disease
This article may be cited as:
Samsel A, Seneff S. Glyphosate, pathways to modern diseases III: Manganese, neurological diseases, and associated pathologies. Surg Neurol Int 2015;6:45.
Available FREE in open access from: http://www.surgicalneurologyint.com/text.asp?2015/6/1/45/153876
Copyright: © 2015 Samsel A. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution,
and reproduction in any medium, provided the original author and source are credited.
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
In 1987, glyphosate was the 17th most commonly used
herbicide in the United States, but, in large part due
to the introduction of glyphosate-resistant core crops,
it became the number one herbicide by 2001.[146] Its
usage has increased steadily since then, in step with the
rise in autism rates. Glyphosate’s perceived nontoxicity
is predicated on the assumption that our cells do not
possess the shikimate pathway, the biological pathway
in plants, which is disrupted by glyphosate, and whose
disruption is believed to be the most important factor in
its toxicity.
It may seem implausible that glyphosate could be toxic to
humans, given the fact that government regulators appear
nonchalant about steadily increasing residue limits, and
that the levels in food and water are rarely monitored
by government agencies, presumably due to lack of
concern. However, a paper by Antoniou et al.[12] provided
a scathing indictment of the European regulatory process
regarding glyphosate’s toxicity, focusing on potential
teratogenic effects. They identified several key factors
leading to a tendency to overlook potential toxic effects.
These include using animal studies that are too short or
have too few animals to achieve statistical significance,
disregarding in vitro studies or studies with exposures that
are higher than what is expected to be realistically present
in food, and discarding studies that examine the effects
of glyphosate formulations rather than pure glyphosate,
even though formulations are a more realistic model of
the natural setting and are often orders of magnitude
more toxic than the active ingredient in pesticides.[189]
Regulators also seemed unaware that chemicals that act
as endocrine disruptors (such as glyphosate[108]) often
have an inverted dose–response relationship, wherein very
low doses can have more acute effects than higher doses.
Teratogenic effects have been demonstrated in human
cell lines.[212] An in vitro study showed that glyphosate
in parts per trillion can induce human breast cancer cell
proliferation.[289]
Adjuvants in pesticides are synergistically toxic with
the active ingredient. Mesnage et al.[189] showed that
Roundup® was 125 times more toxic than glyphosate
by itself. These authors wrote: “Despite its relatively
benign reputation, Roundup® was among the most toxic
herbicides and insecticides tested.”[189]
The industry dictates that 3 months is a sufficiently
long time to test for toxicity in rodent studies, and as a
consequence none of the industry studies have run for
longer than 3 months. The only study we are aware of
that was a realistic assessment of the long-term effects
of GM Roundup®-Ready corn and soy feed on mammals
was the study by Séralini et al. that examined the effects
on rats fed these foods for their entire life span.[261] This
study showed increased risk to mammary tumors in
females, as well as kidney and liver damage in the males,
and a shortened lifespan in both females and males.
These effects occurred both in response to Roundup and
to the GM food alone. These effects only began to be
apparent after 4 months.
There are multiple pathways by which glyphosate could
lead to pathology.[248] A major consideration is that our
gut bacteria do have the shikimate pathway, and that we
depend upon this pathway in our gut bacteria as well as
in plants to supply us with the essential aromatic amino
acids, tryptophan, tyrosine, and phenylalanine. Methionine,
an essential sulfur-containing amino acid, and glycine,
are also negatively impacted by glyphosate. Furthermore,
many other biologically active molecules, including
serotonin, melatonin, melanin, epinephrine, dopamine,
thyroid hormone, folate, coenzyme Q10, vitamin K, and
vitamin E, depend on the shikimate pathway metabolites
as precursors. Gut bacteria and plants use exclusively the
shikimate pathway to produce these amino acids. In part
because of shikimate pathway disruption, our gut bacteria
are harmed by glyphosate, as evidenced by the fact that it
has been patented as an antimicrobial agent.[298]
Metal chelation and inactivation of cytochrome
P450 (CYP) enzymes (which contain heme) play
important roles in the adverse effects of glyphosate on
humans. A recent study on rats showed that both males
and females exposed to Roundup® had 50% reduction in
hepatic CYP enzyme levels compared with controls.[156]
CYP enzyme dysfunction impairs the liver’s ability to
detoxify xenobiotics. A large number of chemicals have
been identified as being porphyrinogenic.[77] Rossignol
et al.[242] have reviewed the evidence for environmental
toxicant exposure as a causative factor in autism, and they
referenced several studies showing that urinary excretion
of porphyrin precursors to heme is found in association
with autism, suggesting impaired heme synthesis.
Impaired biliary excretion leads to increased excretion
of heme precursors in the urine, a biomarker of multiple
chemical sensitivity syndrome.[77] We later discuss the
ability of glyphosate to disrupt bile homeostasis, which we
believe is a major source of its toxic effects on humans.
Glyphosate is a likely cause of the recent epidemic in
celiac disease.[249] Glyphosate residues are found in wheat
due to the increasingly widespread practice of staging
and desiccation of wheat right before harvest. Many of
the pathologies associated with celiac disease can be
explained by disruption of CYP enzymes.[156] Celiac
patients have a shortened life span, mainly due to an
increased risk to cancer, most especially non-Hodgkin’s
lymphoma, which has also been linked to glyphosate.[85,253]
Celiac disease trends over time match well with the
increase in glyphosate usage on wheat crops.
Glyphosate is also neurotoxic.[59] Its mammalian
metabolism yields two products: Aminomethylphosphonic
acid (AMPA) and glyoxylate, with AMPA being at least as
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
toxic as glyphosate. Glyoxylate is a highly reactive glycating
agent, which will disrupt the function of multiple proteins
in cells that are exposed.[90] Glycation has been directly
implicated in Parkinson’s disease (PD).[57] Glyphosate
has been detected in the brains of malformed piglets.[155]
In a report produced by the Environmental Protection
Agency (EPA), over 36% of 271 incidences involving acute
glyphosate poisoning involved neurological symptoms,
indicative of glyphosate toxicity in the brain and nervous
system.[122]
In the remainder of this paper, we first introduce the
link between glyphosate and manganese (Mn) dysbiosis,
and briefly describe the main biological roles of Mn.
We then describe how glyphosate’s disruption of gut
bacteria may be a major player in the recent epidemic
in antibiotic resistance. We then explain how glyphosate
can influence the uptake of arsenic and aluminum, and
propose similar mechanisms at work with Mn. In the
next section, we describe how Mn deficiency can lead
to a reduction in Lactobacillus in the gut, and we link
this to anxiety disorder. We follow with a discussion on
mitochondrial dysfunction associated with suppressed
Mn superoxide dismutase (Mn-SOD), and then a section
on implications of Mn deficiency for oxalate metabolism.
The following section explains how Mn deficiency can
lead to the overexpression of ammonia and glutamate in
many neurological diseases. The next two sections show
how Mn accumulation in the liver is linked to cholestasis
and high serum low density lipoprotein (LDL), and how
this can also induce increased susceptibility to Salmonella
poisoning. We then identify a role for Mn in chondroitin
sulfate synthesis, and the implications for osteomalacia.
The next two sections explain how glyphosate exposure
can lead to Mn toxicity in the brain, and discuss two
neurological diseases that are associated with excess
Mn, PD and prion diseases. After a section on the link
between male infertility and Mn deficiency in the testes,
we discuss evidence of exposure to glyphosate and end
with a short summary of our findings.
SUPPORTIVE EVIDENCE OF MANGANESE
DYSBIOSIS DUE TO GLYPHOSATE
Glyphosate’s disruption of the shikimate pathway is due
in part to its chelation of Mn, which is a catalyst for
enolpyruvylshikimate phosphate synthase (EPSPS), a
critical early enzyme in the pathway.[63] A recent study on
Danish dairy cattle investigated mineral composition in
serum of cattle fed Roundup®-Ready feed.[154] The study
identified a marked deficiency in two minerals: Serum
cobalt and serum Mn. All of the cattle on eight different
farms had severe Mn deficiency, along with measurable
amounts of glyphosate in their urine. In Australia,
following two seasons of high levels of stillbirths in cattle,
it was found that all dead calves were Mn deficient.[184]
Furthermore, 63% of newborns with birth defects were
found to be deficient in Mn.
Mn, named after the Greek word for “magic,” is one
of 14 essential trace elements. Mn plays essential roles
in antioxidant protection, glutamine synthesis, bone
development, and sperm motility, among other things.
Although Mn is essential, it is only required in trace
amounts. And an excess of Mn can be neurotoxic.
Remarkably, Mn deficiency can explain many of the
pathologies associated with autism and Alzheimer’s
disease (AD). The incidence of both of these conditions
has been increasing at an alarming rate in the past two
decades, in step with the increased usage of glyphosate
on corn and soy crops in the United States, as shown
in [Figures 1 and 2]. Although correlation does not
necessarily mean causation, from 1995 to 2010, the autism
rates in first grade in the public school correlates almost
perfectly (P = 0.997) with total glyphosate application on
corn and soy crops over the previous 4 years (from age 2 to
6 for each child) [Figure 1]. Such remarkable correlation
necessitates further experimental investigation. These
neurological disorders are associated with mitochondrial
impairment[197,241,243,281,316] and with excess glutamate
and ammonia in the brain,[2,109,265] leading to a chronic
low-grade encephalopathy.[256,260] As we will show later, Mn
deficiency is critically associated with these pathologies.
Thyroid dysfunction can be predicted as well, and
low maternal thyroid function predicts autism in the
fetus.[238] Furthermore, increases in bone fractures in
both children and the elderly can also be explained
by Mn deficiency, due to its critical role in bone
development.[276] Osteoporosis, which is a serious problem
Figure 1: Plots of amount of glyphosate applied to corn and soy
crops in the US over the previous 4 years (red), provided by the
US Department of Agriculture, compared with number of children
    
autism category according to the Individuals with Disabilities
Education Act (IDEA) (blue bars). (Figure courtesy of Dr. Nancy
Swanson)
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
Figure 2: Plots of amount of glyphosate applied to corn and soy
crops in the US over time, compared to the rate of death from AD.
(Figure courtesy of Dr. Nancy Swanson)
Figure 3: Plots of glyphosate usage on corn and soy crops (blue),
percent of corn and soy that is genetically engineered to be
“Roundup Ready” (red), and prevalence of diabetes (yellow bars)
in the US. (Figure courtesy of Dr. Nancy Swanson)
among the elderly today, is also likely promoted by Mn
deficiency,[247] and osteoporosis leads to increased risk to
fractures.[98,139,140]
Sprague-Dawley rats fed a Mn-deficient diet had
significantly reduced concentrations of Mn in liver,
kidney, heart, and pancreas, compared with controls.[18]
Furthermore, pancreatic insulin content was only 63%
of control levels, and insulin release following glucose
administration was also reduced. Mn deficiency not only
impairs insulin secretion in Sprague-Dawley rats, but it
also causes reduced glucose uptake in adipose tissue,[19]
so Mn deficiency could contribute to impaired glucose
metabolism in both type 1 and type 2 diabetes, which
are a growing problem worldwide.[199] Type 1 diabetes in
children is associated with a decrease in Lactobacillus
and Bifidobacterium, and an increase in Clostridium,
in the gut.[195] These same pathologies are also found in
gut bacteria from poultry fed Roundup®-Ready feed.[263]
The increased incidence of diabetes in the US is strongly
correlated with glyphosate usage on corn and soy, as
shown in [Figure 3].
Much remains elusive about Mn’s roles in cellular
metabolism, but it is clear that it is very important. For
instance, Target of Rapamycin Complex 1 (TORC1)
accelerates the aging process in cells from yeast to
mammals,[231] and Mn inhibits TORC1, but only if it is
present in the Golgi.[86] Zinc (Zn) is essential for DNA
and RNA replication and cell division. Zn deficiency leads
to greatly enhanced Mn uptake by cells, and this induces
modifications to messenger RNA such that the ratio of
guanine and cytosine nucleotides (C + G) to adenine
and thymine (A + T) is sharply increased.[100] Clearly,
more research is needed to explain the significance of
these phenomena.
We infer, paradoxically, that both Mn deficiency and
Mn toxicity, attributable to glyphosate, can occur
simultaneously. Because of glyphosate’s disruption of CYP
enzymes, the liver becomes impaired in its ability to dispose
of Mn via the bile acids, and instead it transports the Mn
via the vagus nerve to brainstem nuclei, where excess Mn
leads to PD. Recently, PD has also increased dramatically,
in step with glyphosate usage on corn and soy [Figure 4].
Ironically, while the brainstem suffers from excess
Mn, the rest of the brain incurs Mn deficiency due to
the depressed serum levels of Mn. Mn is particularly
important in the hippocampus, and deficiency there can
lead to seizures. A high incidence of seizures is found in
children with autism.[302] Seizures are also associated with
reduced serum Mn,[54,88,269] and this is consistent with the
liver’s inability to distribute Mn to the body via the bile
acids. Antibiotics have been found to induce seizures.[132]
Mn uptake in the brain is normally enhanced during
the neonatal period in rats, and proper development
Figure 4: Plots of glyphosate usage on corn and soy crops (blue),
percent of corn and soy that is genetically engineered to be
“Roundup Ready,” (red), and deaths from PD (yellow bars) in the
US. (Figure courtesy of Dr. Nancy Swanson)
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
of the hippocampus depends on Mn.[284] Soy formula
increases the risk of seizures in autism,[310] hardly
surprising when one considers that soybean crops
are now 90% Roundup®-Ready. A recent paper has
confirmed that alarmingly high glyphosate residues
appear in Roundup®-Ready soy.[35] The US Department
of Agriculture analyzed glyphosate residues in soy in
2011, and reported that 91% of the 300 samples tested
were positive for glyphosate, with 96% being positive
for AMPA, an equally toxic by-product of glyphosate
breakdown.[297] Our own analysis confirms that glyphosate
is present in infant formula. Out of several soy-based
baby formulas we tested, only one contained glyphosate
residues. We found levels of 170 ppb in Enfamil
ProSobee liquid concentrate. Further testing is underway.
Soybean product sourcing and residue testing should be
required prior to product manufacturing and is necessary
to prevent inadvertent infant exposure.
Another mechanism by which glyphosate in soy formula
could cause seizures is through bilirubin production.
Serum concentrations of bilirubin were elevated in
catfish exposed to sublethal doses of Roundup®, in a
dose-dependent relationship.[208] Neonates, due to an
immature digestive system, are unable to metabolize
bilirubin in the gut, and it can therefore build up in the
blood and even penetrate their immature blood–brain
barrier to cause seizures.[308]
GLYPHOSATE AND MICROBIAL ANTIBIOTIC
INTOLERANCE
Microbial antibiotic tolerance and resistance are a
growing problem worldwide, likely fueled by horizontal
gene transfer among different bacterial species.[106,121]
Multiple-drug resistant commensal bacteria in the
guts of both animals and humans form a reservoir of
resistance genes that can spread to pathogenic species.
Methicillin-resistant Staphylococcus aureus (MRSA),[119]
Clostridium difficile,[183] and Pseudomonas aeruguinosa[169]
are all becoming major threats, especially in the hospital
environment. A generic mechanism of upregulated efflux
through membrane pores offers broad-domain resistance
to multiple antibiotics.[169] Exposure to antibiotics early
in life can even lead to obesity as a direct consequence of
the resulting imbalance in gut bacteria.[73]
Studies have shown that increased mutation rates due to
chronic low level exposure to one antibiotic can induce
an accelerated rate of development of resistance to
diverse other antibiotics.[151] Glyphosate, patented as an
antimicrobial agent,[298] is present in steadily increasing
amounts in the GM Roundup-Ready corn and soy feed
of cows, pigs, chickens, farmed shrimp, and fish, and it is
ubiquitous in the Western diet of humans. Pseudomonas
aeruginosa can use glyphosate as a sole source of
phosphorus,[192] and it is one of a small number of resistant
bacterial species with the ability to metabolize glyphosate,
a feature that might be exploited for soil remediation.[1]
However, DNA mutations due to exposure would enhance
tolerance to glyphosate and other antibiotics, perhaps
explaining the current epidemic in multiple antibiotic
resistant P. aeruginosa infections, which have a 20%
mortality rate.[190] Antibiotic resistance sequences
engineered into GM crops may also play a role in the
current crisis concerning antibiotic resistant pathogens.
Glyphosate has also been demonstrated as a remarkable
antimicrobial synergist. It greatly increases the cidal effects
of other antimicrobials, particularly when combined as
salts of glyphosate. A concentration dependent synergy
index (SI) ranging from 0.34 to 5.13 has been recorded for
the Zn salt of glyphosate.[299] This has serious implications
for glyphosate ingested with pharmaceuticals or residues
of other widely used agricultural chemicals, such as the
herbicides Diquat, Paraquat, 2,4 D and Glufosinate, the
fungicide Chlorothalonil and the systemic neonicotinoid
insecticides Acetamiprid, Imidacloprid, Thiacloprid,
Thiamethoxam, and Clothianidin.
Glyphosate acts as a catalyst for the development of
antibiotic resistance genes in pathogens. Since both
poultry and cow manure are used as natural fertilizers
in crops, it can be expected that a vector for microbial
resistance to multiple drugs is through contamination
of fruits and vegetables. Indeed, multiple resistance
genes have been identified from diverse phyla found
in cow manure, including Proteobacteria, Firmicutes,
Bacteroidetes, and Actinobacteria, that is, in
phylogenetically diverse organisms.[311]
One of the ways in which glyphosate is toxic to plants
is through disruption of chlorophyll synthesis, due to
suppression of the activity of the first enzyme in pyrrole
synthesis.[61,69,143,319] Pyrrole is the core building block of
both chlorophyll and the porphyrin rings, including corrin
in cobalamin and heme in hemoglobin and cytochrome
enzymes. Several cofactors containing a structurally
complex tetrapyrrole-derived framework chelating a
metal ion (cobalt (Co), magnesium (Mg), iron (Fe), or
nickel (Ni)) are synthesized by gut bacteria and supplied
to the host organism, including heme and corrin.[236]
Thus, glyphosate can be expected to disrupt synthesis
of these biologically essential molecules. Pseudomonas
normally thrives in the small bowel and produces
abundant cobalamin that may be a significant source for
the human host.[6] P. aeruginosa’s successful colonization
may be due in part to its ability to produce cobalamin
despite the presence of glyphosate. Only recently has it
also been recognized that a Mn–porphyrin complex can
protect from mitochondrial overproduction of hydrogen
peroxide (H2O2) in response to ionizing radiation.[274] It
can be predicted that homeostasis of all of these minerals
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
in the gut (Co, Mn, Fe, Ni, and Mg) is impaired in
the presence of glyphosate, and this will have serious
consequences not only to the gut bacteria but also to the
impaired regulation of these minerals. The implications
of impaired heme and cobalamin synthesis will be further
addressed in a future paper.
A key component of glyphosate’s action is its ability to
chelate minerals, particularly transition metals such
as Mn. Glyphosate forms strong complexes with the
transition metals via the amino, the carboxylic, and the
phosphonic moieties in the molecule. Each of these can
coordinate separately to metal ions or in combination as
bidentate or tridentate ligands.[194,296]
ANALOGY WITH ARSENIC AND ALUMINUM
Chronic kidney disease is clearly associated with multiple
environmental toxicants.[268] There has been an epidemic
in recent years in kidney failure among young agricultural
workers in Central America, India, and Sri Lanka,
particularly those working in the sugar cane fields.[249] A
recent paper reached the unmistakable conclusion that
glyphosate plays a critical role in this epidemic.[133] A
growing practice of spraying sugar cane with glyphosate
as a ripener and desiccant right before the harvest has led
to much greater exposure to the workers in the fields. The
authors, who focused their studies on affected workers in
rice paddies in Sri Lanka, identified a synergistic effect of
arsenic, which contaminated the soil in the affected regions.
This paper is highly significant, because it proposes a
mechanism whereby glyphosate greatly increases the toxicity
of arsenic through chelation, which promotes uptake by the
gut. Glyphosate also depletes glutathione (GSH)[60,128] and
glutathione S transferase (GST) is a critical enzyme for
liver detoxification of arsenic.[295] As a consequence, excess
arsenic in the kidney causes acute kidney failure, without
evidence of other symptoms such as diabetes usually
preceding kidney failure.
Arsenic is normally disposed of by the liver through
biliary excretion. In rats exposed to arsenic, large amounts
of GSH appeared in the bile simultaneously with biliary
excretion of arsenic.[113] It was first hypothesized, and later
confirmed, that arsenic is transported in bile acids in the
form of unstable GSH complexes (monomethylarsonous
acid), which release GSH upon decomposing. Since
glyphosate disrupts CYP enzymes necessary for bile acid
formation,[248,249] as well as depleting GSH,[60,128] it can
be expected that glyphosate would disrupt the process
of biliary excretion of arsenic, thus forcing arsenic to be
redirected toward urinary excretion, leading ultimately to
kidney failure.
Glyphosate also chelates aluminum,[230] and it has been
reasoned that this enables aluminum to get past the
gut barrier more readily through direct analogy with the
situation with arsenic, which is also a 3+ cation.[193]
However, it has been demonstrated through
experimentation that glyphosate prefers divalent cations.
Thus, aluminum would enter the bloodstream via the
digestive tract's portal vein to the organs traveling with
albumin, which is known to attach and transport many
xenobiotics. It is well established that citrate also binds
aluminum and promotes its uptake past the gut barrier
through a mechanism that parallels glyphosate’s binding
to aluminum.[68,148] Both are small molecules that easily
pass through a leaky gut barrier.
Considering these observations regarding aluminum
and arsenic, it is reasonable to expect that something
similar might happen with Mn. Unlike these other two,
however, Mn plays many essential roles in the body,
and so its chelation by glyphosate would interfere with
its bioavailability in the general circulation. Just as for
arsenic, bile acids play a critical role in Mn homeostasis.
Bile is the major excretory route of injected Mn.[17]
Malecki et al. wrote: “Biliary excretion may be a major
homeostatic mechanism for preventing both deficiency
and toxicity of Mn.”[179, p. 489]
Glyphosate, a dipolar zwitterion, is toxic in part due
to its bio-transformative properties as pH varies.
We postulate that Mn, which is transported in the
blood stream bound to glyphosate, is oxidized to
Mn3+ following its release in the localized acidic
environment of sulfated glycosaminoglycans (GAGs) in
the glycocalyx lining the capillary wall.[234] As we will
later explain, Mn uniquely is able to travel along axons
and across synapses, and this results in a novel path via
the vagus nerve for brain toxicity following excess Mn
accumulation in the liver.
Mn is a transition metal, and therefore it can catalyze
oxidative reactions in neurons via the Fenton reaction.[305]
While Mn2+ is the form of Mn that catalyzes enzyme
reactions, Mn3+, similar to Al3+, is directly toxic to
neuronal membranes.[13] In vitro studies have shown
that Mn3+ complexes auto-oxidize catecholamines, and
therefore exposure to excess Mn leads to a decrease in the
bioavailability of dopamine, serotonin, and noradrenaline
in the striatum.[227]
It has been shown that glyphosate enhances the oxidation
of Mn from a 2+ oxidation state to 3+, both in solution
and on an inert surface.[21] It can be inferred, therefore,
that Mn2+ oxidation to the toxic form, Mn3+, might occur
in the artery wall following exposure to superoxide in the
presence of glyphosate. Mn3+ also enhances glyphosate
degradation to AMPA,[21] which would produce the
highly glycating by-product, glyoxylate. Glyoxylate and
Mn3+ would both cause significant arterial damage in
association with the inflammatory response.
We suggest that another route for Mn transport is the
vagus nerve, which delivers Mn from the liver to the
brainstem nuclei. When bile acid synthesis is impaired,
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the brainstem nuclei can acquire neurotoxic levels of Mn,
while serum levels are simultaneously depressed.
GUT BACTERIA DYSBIOSIS AND ANXIETY
Anxiety disorder is a comorbidity of autism,[110] AD,[288]
and PD,[235] and, in this section, we argue that disruption
of Lactobacillus due to impaired Mn bioavailability
is a likely cause. Anxiety disorder is also correlated
with glyphosate usage on corn and soy, as illustrated
in [Figure 5].
Glyphosate has been shown to severely deplete Mn
uptake by plants, both by the roots and by the shoots.[127]
Experiments on plants demonstrated that Mn applied as
fertilizer antagonizes glyphosate’s effectiveness in weed
control,[29] and this implied that Mn chelation was an
important part of glyphosate’s toxicity to plants. Electron
paramagnetic resonance (EPR) spectroscopy analyses
conducted by these authors demonstrated that glyphosate’s
binding to Mn increased with pH as pH rose from 2.8 to
7.5. The pH of plant symplast is typically 7.5, a level at
which glyphosate would be an effective chelator of Mn.
Certain species of gut bacteria, such as members of
the Lactobacillus family, utilize Mn in novel ways for
protection from oxidation damage, and, as a consequence,
their requirements for Mn are much higher than those
of other species.[13,14] Thus, Mn chelation by glyphosate
would lead to reduced numbers of these essential bacteria
in the gut. This leads directly to neurological symptoms
such as anxiety, due to the influence of the gut–brain
axis.[70,75,106] In the small intestine, the pH increases
gradually from pH 6 to pH 7.4 in the terminal ileum.[101]
At pH 7.4, Mn bioavailability can be expected to be
reduced by 50% due to glyphosate chelation.[173]
The liver regulates the amount of Mn in the general
vascular circulation, by incorporating any excess into
bile acids, which gives the gut bacteria repeated
chances to take it up. However, production of bile acids
depends upon CYP enzymes, which are disrupted by
glyphosate.[248,249] Hence, glyphosate can be expected to
lead to severe impairment of Mn bioavailability to the
gut bacteria, while at the same time allowing too much
Mn to accumulate in the liver.
Lactobacillus tends to reside in the foregut.[286] The pH
of the foregut is higher than that of the cecum,[100] so
Mn chelation by glyphosate is a bigger issue there, since
glyphosate’s chelation effects increase with increasing
pH. Mn-SOD is an important enzyme in mitochondria
for protection from oxidative damage. Most Lactobacillus
species lack Mn-SOD, but they have devised a way to
protect themselves from oxidation damage due to the
superoxide radical by using active transport of Mn in
the +2 oxidation state. Many Lactobacilli normally have
high intracellular concentrations of Mn.[14] For example,
Lactobacillus plantarum accumulates over 30 mM of
intracellular Mn (II).[13]
A recent study demonstrated that Roundup® in
concentrations lower than those recommended
in agriculture inhibited microbial growth of three
microorganisms that are widely used as starters in
fermentation of milk products,[66] including a species
of Lactobacillus. Research into genetically engineering
an Mn-SOD-encoding gene derived from Streptococcus
thermophilus into various Lactobacillus species has shown
that they can produce Mn-SOD from these heterologous
genes and use it to improve their resistance to oxidative
stress.[48]
Bruno-Bárcena et al.[48] proposed that such genetically
engineered Lactobacilli might provide benefit as
probiotics to people suffering from colitis or peptic
ulcers. Colitis is associated with increased inflammation
in the gut, which may be due to impaired function of
Mn-SOD. An experiment on a mouse model of colitis
demonstrated that Lactobacilus gasseri treatment
alleviated inflammation in the colon of Il-10 deficient
mice.[55] Genetically modified forms of L. gasseri as
described above, which overproduce Mn-SOD, showed
enhanced therapeutic effects.
Several members of the Lactobacillus family are capable of
producing the inhibitory neurotransmitter γ-aminobutyric
acid (GABA) via the enzyme glutamate decarboxylase, and
this may be a reason for their ability to improve symptoms
of anxiety. Experiments with Lactobacillus probiotics in
mice demonstrated neurochemical and behavioral effects
related to changes in GABAergic expression in regions of
the brain that control mood.[165] These effects were absent
in vagotomized mice, pointing to the vagus nerve as the
bacterial communication pathway between gut and brain.
Figure 5: Plots of glyphosate usage on corn and soy crops (blue),
provided by the US Department of Agriculture, and rates per
10,000 of phobia, anxiety disorder, and panic disorder (red) in the
US, provided by the Centers for Disease Control. (Figure courtesy
of Dr. Nancy Swanson)
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Lactobacillus have been successfully cultivated to produce
fermented food containing high levels of GABA, proposed
to be a health benefit in probiotics.[40]
Patients suffering from chronic fatigue syndrome (CFS)
often have imbalances in microbial flora,[177] along
with anxiety as a frequent comorbidity.[104] A pilot
placebo-controlled study involved daily administration
of Lactobacillus casei probiotics over a 2-month period
to CFS patients.[232] The outcome was a significant
rise in both Lactobacillus and Bifidobacteria in the
gut, along with a significant decrease in anxiety
symptoms (P = 0.01). This study reinforces the gut–
brain connection, specifically implicating Lactobacillus in
the etiology of anxiety disorder.
MN-SUPEROXIDE DISMUTASE AND
MITOCHONDRIAL DYSFUNCTION
Mitochondrial dysfunction, particularly for the
neutrophils, which perform important immune system
functions, is implicated in CFS,[196] and this could be
due to impaired Mn supply to Mn-SOD. Mn-SOD
is dramatically upregulated in association with the
inflammatory markers tumor necrosis factor α (TNF-α),
lipopolysaccharide (LPS), and interleukin-1,[301]
presumably to protect mitochondria from oxidative
damage. SOD plays an important role in antioxidant
defenses, by converting superoxide into H2O2, which
can then be further detoxified by other enzymes such
as catalase.[182] There are three major classes of SOD,
which are distinguished by the metal catalyst, which can
be copper (Cu), Zn, Mn, iron, or nickel. Eukaryotes rely
on a distinct form in the mitochondria, which depends
on Mn, whereas Cu/Zn SOD is present in the cytoplasm
and extracellularly. Many bacterial species including
Escherichia coli use Fe-SOD as well as Mn-SOD. The
adjuvants in Roundup® may play an important role
in enabling glyphosate to penetrate the mitochondrial
membrane,[215] where it can interfere with the activities of
Mn-SOD via chelation of Mn.
Recent experiments on goldfish involved exposing them
for 96 h to Roundup® at concentrations ranging from
2.5 to 20 mg/L.[174] Several metabolites were measured
from the liver, kidney, and brain. Remarkably, Roundup®
inhibited SOD activity in all three organs examined, by
51–68% in the brain, 58–67% in the liver, and 33–53% in
the kidney, and this was the most striking effect that was
observed. Unfortunately, they did not specify whether the
cytoplasmic Cu/Zn SOD or the mitochondrial Mn-SOD
was most affected. Regardless, a plausible explanation of
this effect is the chelation of Mn, Cu, and Zn, which are
essential cofactors for the two SODs.
A recent study on the fish species Anguilla anguilla
exposed to environmentally realistic levels of glyphosate
over a short time period revealed DNA strand breaks in
both liver and gills, along with a suppression of SOD
activity in the liver.[116] A plausible explanation is that
the breakdown product of glyphosate, glyoxylate, which
is a potent glycating agent, would cause DNA damage
by attacking Cu, Zn-SOD. Experiments have shown
that released Cu in combination with H2O2 produced
by glycated Cu, Zn-SOD triggers a Fenton reaction,
resulting in nuclear DNA cleavage.[138]
Aconitase, an enzyme that converts citrate to isocitrate,
is a crucial participant in Complex I of the citric acid
cycle in the mitochondria. Many neurodegenerative
diseases have been linked to decreased aconitase activity
due to oxidative stress, including Friedreich ataxia,[245,249]
Huntington’s disease,[282] progressive supranuclear palsy,[213]
autism,[239] and epilepsy.
[300] The presence of a single
unligated iron atom in the iron–sulfur cluster of aconitase
makes it uniquely sensitive to oxidative inactivation by
superoxide.[105] Aconitase inactivation has a cascade effect,
because the released iron results in ferrous iron toxicity,
further promoting cell death.[52] The pervasive herbicide
Par aqua t h as been im pli cate d i n o xid ativ e i nact iva tion of
aconitase, and this likely explains its known role in PD.[52]
A postmortem study of brains of autistic individuals
showed a striking decrease in aconitase activity in
the cerebellum associated with a similar decrease in
glutathione redox antioxidant capacity (GSH/GSSG),
with the plot producing a near 100% separation between
cases and controls.[239] Inadequate clearance of superoxide
due to Mn-SOD inactivation can easily account for this
observation. Aconitase is a crucial participant in the
citric acid cycle in the mitochondria, so this effect has
catastrophic consequences on the renewal of adenosine
triphosphate (ATP) as an energy source for the neurons.
In another study, cells from children with autism exhibited
higher oxidative stress than control cells, including a 1.6-fold
increase in reactive oxygen species (ROS) production,
1.5-fold increase in mitochondrial DNA copy number
per cell, and more deletions.[198] Furthermore, oxidative
phosphorylation capacity of granulocytes from children
with autism was 3-fold lower than in controls. These are all
indicators of oxidative stress, which could be due to SOD
inhibition by glyphosate, mediated by Mn deficiency.
OXALATE
Monsanto’s Roundup herbicide, WeatherMax® with
Transorb II Technology, is now a preferred formulation
and uses a potassium salt of glyphosate (48.8%). The
Transorb Technology, which utilizes a dual surfactant
system and adjuvants, was first introduced in 1996 as
Roundup ULTRA. In 1998, the formula was altered and
released as WeatherMAX, then further improved and
released in 2005 as the current product.
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The inert ingredients have undergone several changes
over the years to include formula variations, which
included the use of dual surfactants of siloxane
copolymers and Polyoxyethylated tallow amine (POEA).
As noted by Monsanto, “Promotion of stomatal
infiltration of glyphosate by an organosilicone surfactant
reduces the critical rainfall period,” hence the
rain-fastness of Roundup WeatherMax® with Transorb
®
2 Technology. In 1995, US Patent #5,464,806 was
issued which reflected another product formulation
improvement and move from the use of Silwet-77
siloxane surfactant due to phase separation problems,
to the use of an acetylenic diol.[142] The new formula
provides protection from herbicide loss due to rain within
30 min of application. Additional adjuvants, well known
in the paper-making industry, were used to quickly break
down cell walls and collapse the plant. These chemicals
originally included sodium sulfite with a later change
to oxalic acid (oxalate) as patented in 2006.[315] In this
patent, it was noted that “it has been discovered that
the addition of oxalic acid or salts thereof to glyphosate
compositions increases the cell membrane permeability
of plant cells or suppresses oxidative burst to increase
cellular uptake of glyphosate.”
This modification may be related to the recent increase
in health issues concerning excess serum oxalate in the
United States and elsewhere, linked to both autism
and kidney stones. A study comparing children with
autism with controls found a 3-fold increase in serum
oxalate levels in the children with autism,[152] and it was
suggested that this might be due to excess absorption
through the gut barrier, and that oxalate crystals in the
brain could potentially disrupt brain function. Calcium
oxalate crystals are responsible for up to 80% of kidney
stones, and there has been an increased incidence of
kidney stones recently in the US.[250] In a study on
prisoners in Illinois who complained of gastrointestinal
distress following a change to a high-soy diet, it was
proposed that the unusually high levels of oxalate in
the processed soy protein might be responsible for the
observed symptoms.[175]
Both the high oxalate content of the soy and the high
serum oxalate in humans could be due to impaired
oxalate metabolism. Oxalate metabolism by oxalate
oxidase in plants and by oxalate decarboxylases in
fungi and a few bacteria, such as Bacillus subtilis, are
both dependent on Mn as a cofactor.[280] Bifidobacteria,
which are highly sensitive to glyphosate,[263] possess
an oxalate-metabolizing enzyme that depends on
magnesium rather than Mn as a cofactor.[102] However,
glyphosate decreases the content of both magnesium
and Mn in plants.[50] Furthermore, gamma-glutamyl
carboxylase, a liver enzyme that metabolizes oxalate, is
catalyzed by vitamin K, which depends on the shikimate
pathway.[51] It has been shown that patients with calcium
oxalate urolithiasis have significantly reduced activity of
this enzyme in the liver.[65]
The sulfate ion transporter, Sat-1, plays an important
role not only in sulfate transport but also in oxalate
transport,[273] as evidenced by the fact that mice with a
disrupted Sat-1 gene develop urolithiasis.[252] Glyoxylate
is not only a substrate of Sat-1 but it is also a key
regulator.[252] The upregulation of SAT-1 by glyoxylate in
hepatic cells likely serves to flush oxalate and glyoxylate
from the liver, to avoid hepatotoxicity. However, this
can lead to nephrotoxicity due to glyoxylate glycation
damage and the formation of kidney stones. Due to
competition between oxalate and sulfate for transport via
Sat-1, glyoxylate, and oxalate, likely, also disrupt sulfate
homeostasis in the liver. Sulfate is critical for bile acid
formation and for detoxification of xenobiotics such as
acetaminophen.
The conversion of glyoxylate to oxalate by the enzyme
lactate dehydrogenase is inhibited by oxalate.[87] Hence
gloxylate, derived from glyphosate breakdown, would
accumulate in the presence of excess oxalate.
Aside from the obvious damaging effects of oxalate
crystals on tissues, the oxalate, whose metabolism is
impaired due to Mn deficiency, will also interfere with
the metabolism of glyphosate, likely greatly increasing
both its effectiveness as an herbicide and its toxicity
to mammals. Under oxalate stress conditions, both
superoxide and the hydroxyl radical are produced in
excess amounts.[258] Obviously, the ineffectiveness of
Mn-SOD due to Mn deficiency would further enhance
the damage due to excess oxalate. SOD activity has been
shown to be reduced in association with the urolithic
kidney, and methionine supplementation can alleviate
this problem.[257] As mentioned previously, methionine is
depleted by glyphosate.
AMMONIA, GLUTAMATE, AND
NEUROTOXICITY
In this section, we will show that both glutamate and
ammonia are implicated as neurotoxins in connection
with autism and other neurological diseases, and we will
offer the simple explanation that Mn deficiency leads
to impaired activity of glutamine synthase and arginase,
both of which utilize Mn as a cofactor. Mn deficiency can
also explain the increased risk to epilepsy found in autism,
due to the fact that Mn decreases T2 relaxation time.
Mn-deprived rats are more susceptible to convulsions.[129]
Blaylock and Strunecká[32] have proposed that
immune-glutamatergic dysfunction may be the central
mechanism of autism spectrum disorders. Ghanizadeh[109]
reported that glutamate and homocysteine are elevated in
the serum in association with autism, and that glutamine
and tryptophan are depleted. Tryptophan, which depends
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upon the shikimate pathway in plants and microbes, is
the precursor to serotonin and melatonin. An increase in
glutamate and a corresponding decrease in glutamine can
be entirely explained by an inactive glutamine synthase
enzyme. Another extensive study on children with autism
compared with controls found low serum tryptophan, high
serum glutamate and homocysteine, and significantly
reduced free sulfate, as well as high levels of oxidative
stress markers,[1] all of which are consistent with these
assertions. High serum homocysteine is one associated
consequence of folate deficiency:[76] Folate is produced
by Lactobacillus and Bifidobacteria from products of the
shikimate pathway.[240]
The neurotransmitter glutamate has been implicated as
an excitatory neurotoxin in the brain not only in autism
but also in association with multiple neurological diseases,
including AD, PD, amyotrophic lateral sclerosis (ALS),
and multiple sclerosis.[93] Ordinarily, following glutamate
release into the synaptic cleft, microglia in the brain take
up excess glutamate and convert it to glutamine, using
the enzyme glutamine synthase.[204] Glutamine is then
released into the extracellular space, taken up by neurons,
and converted in the cytoplasm to glutamate to be held
within internal vesicles in anticipation of future activity.
Conversion to glutamine for the transport stage from
microglia to neurons renders the molecule inactive as a
neurotransmitter, and therefore as a neurotoxin, when it
is out of service.
TNF-α, secreted by activated microglia in the brain, is a
major cytokine leading to neurotoxicity in association with
multiple neurological diseases. A major component of the
damaging effect of TNF-α is the autocrine induction of
the release of glutamate from microglia.[285] Experiments
exposing immature rats to Roundup®, whether via
exposure to the dam during pregnancy and lactation or
via acute exposure to the pup for 30 min, demonstrated
lipid peroxidation and NMDA receptor activation in the
hippocampus, indicative of oxidative stress and glutamate
excitotoxicity.[59] Acute exposure increased the release of
glutamate into the synaptic cleft, and depleted GSH.
Glutamine synthase depends upon Mn as a cofactor,
so depleted Mn supplies would lead to a build-up of
glutamate that cannot be returned to the neurons using
normal channels. Multiple sclerosis is associated with both
depleted Mn in the cerebrospinal fluid[185] and depleted
GSH synthase in the white matter lesions.[309] Cerebellar
brain samples taken postmortem from 10 individuals
with autism demonstrated an anomalous increase in
mRNA expression of excitatory amino acid transporter
1 and glutamate receptor AMPA 1, both involved in
the glutamate system.[226] Glutamate receptor binding
proteins were also abnormally expressed, and AMPA-type
glutamate receptor density was low. These effects could
be explained as a response to the excess bioavailability of
glutamate due to an inability to convert it to the inactive
form, glutamine.
Further confirmation of glutamate dysbiosis in autism
comes from a study on levels of 25 amino acids in
the platelet-poor plasma of high-functioning autistic
children compared with normal controls, which revealed
that only glutamate and glutamine were abnormally
expressed in the children with autism, with a highly
significant (P < 0.002) excess of glutamate and a highly
significant (P < 0.004) decrease in glutamine.[264] They
linked these findings to glutamatergic abnormalities
reported by others.
It is intriguing to us that Mn deficiency leads to a pair
of complementary pathologies – excess glutamate along
with aconitase deficiency, which together allow for the
cells to generate ATP by metabolizing glutamate instead
of glucose. Glutamate enters the citric acid cycle beyond
Complex I, thus bypassing the step that is impaired by
aconitase deficiency. This is a rather elegant regulatory
system that provides energy even in the face of Complex
I impairment.
The prevalence of epilepsy in the US is similar to that
of diabetes, making it a common disorder affecting 2
million Americans.[47] Epilepsy is associated with increased
T2 relaxation time in nagnetic resonance imaging (MRI)
signaling analysis of the hippocampus, both in the
ipsilateral sclerotic hippocampus as well as the contralateral
hippocampus and anterior temporal lobe.[42] Following
intracerebral injection of Mn, a large amount of Mn
accumulates in the hippocampal fissure, which results in a
reduction in T2 relaxation time.[78] Epilepsy may therefore
be a consequence of insufficient Mn in the hippocampus,
which could easily account for the associated increase in
T2. Autism is associated with a high risk of epilepsy,[293,162]
and the hippocampus has been the focus of many studies
on the neurological pathology of autism.[84,95]
Ammonia is a well-established neurotoxin, which
accumulates when the urea cycle is unable to keep up
with ammonia released from protein breakdown.[290]
Ammonia can induce tremor, ataxia, seizures, coma,
and death.[49] Ammonia is a highly diffusible gas
that readily crosses the blood–brain barrier, and
its detoxification depends upon the conversion
of glutamate to glutamine, which is catalyzed by
glutamine synthase, the enzyme in microglia that relies
upon Mn as a cofactor.[71] Thus, impaired function of
glutamine synthase leads to the accumulation of both
glutamate and ammonia in the brain, both of which
are established neurotoxins.
Excess ammonia due to impaired ability to detoxify excess
nitrogen via the urea cycle can lead to impaired memory,
shortened attention span, sleep–wake cycle disruption,
brain edema, intracranial hypertension, seizures, ataxia,
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and coma.[37] Arginase, the final enzyme of the urea cycle,
is ubiquitous in living systems, and depends upon Mn as
a cofactor. Therefore, Mn deficiency due to glyphosate’s
chelation of the metal would be expected to lead directly
to impaired arginase function. The excess accumulation
of ammonia due to inactive glutamine synthase combined
with the decreased ability to metabolize ammonia to urea
constitute a double-hit leading to ammonia toxicity in
the brain.
A case study of a 4-year-old girl showed that a
genetic defect in arginase could present as pervasive
developmental delay not otherwise specified (PDD-NOS)
with many similarities to autism.[112] Its manifestations
include brain edema and signs of epilepsy, as would
be expected with ammonia toxicity in the brain.
A Mn-deficient diet administered to rats induced a
reduction in hepatic arginase activity (P < 0.01), along
with a significant rise in plasma ammonia (P < 0.01).[43]
Seneff et al.[260] put forward the idea that excess ammonia
due to disrupted gut bacteria could lead to a chronic
low-grade encephalopathy that could explain much of
the pathology associated with autism. Furthermore,
glyphosate is known to induce excess ammonia
production in plants, due to overactivity of the enzyme
phenylalanine ammonia lyase (PAL).[86,117,125] This enzyme
may also be overactive in gut bacteria exposed to
glyphosate, further compounding the problem.
CHOLESTASIS AND BILIRUBINEMIA
Mn stimulates cholesterol synthesis in the liver,
presumably because bile acids, derived from cholesterol,
are needed to bind to Mn and carry it back to the gut
for recycling.[5] However, CYP enzyme inhibition will
impair the liver’s ability to oxidize cholesterol, since the
formation of oxysterols in the liver for incorporation into
bile acids depends on several CYP enzymes (members
of the CYP3, CYP7, CYP8, CYP27, CYP39, and CYP46
families).[200,217] As a result, it can be anticipated that,
when Mn supplies are plentiful, both the Mn and
the cholesterol will accumulate to toxic levels in the
liver, unless another method can be found for their
redistribution. In the case of cholesterol, this may lead to
a necessary increase in the synthesis and release of LDL
particles. People with a defective CYP7A1 gene have
significantly elevated total and LDL cholesterol levels, as
well as substantial accumulation of cholesterol in the liver
and a markedly decreased rate of bile acid excretion.[225]
Neonatal cholestasis and hypercholesterolemia (elevated
LDL) were produced in mice with a defective CYP7A1
gene fed a normal chow diet.[96] The increased serum levels
of LDL associated with heart disease risk may therefore
be a consequence of the production of cholesterol that
cannot be exported through the biliary ducts.
Studies with rats have shown that Lactobacillus
plantarum probiotic supplements lower serum LDL
levels.[166] Lactobacillus levels were reduced in chickens
exposed to antimicrobial drugs, which resulted in
reduced bile salt deconjugation in the gut.[114] Impaired
bile salt deconjugation by gut bacteria results in
significant weight gain along with elevated plasma
cholesterol and liver triglycerides in mice.[136] Thus,
glyphosate acting as an antibiotic that preferentially
kills Lactobacillus can be expected to lead to elevated
serum cholesterol and triglycerides through a similar
mechanism.
Cholestasis is a blockage of bile acid flow, which often
occurs as a side effect of various pharmaceutical
drugs.[211] Glyphosate administration to rats over a
period of 13 weeks induced increases in serum bile acids,
indicative of cholestasis.[64] Severe cholestasis can induce
bilirubinemia,[28] and glyphosate also independently
induces bilirubinemia in catfish.[208] At least two other
studies have shown bile stagnation in fish exposed to
glyphosate.[80,135]
Inflammatory bowel disease (colitis and Crohn’s disease)
has been increasing in frequency in the US over the past
20 years, in step with glyphosate usage on corn and soy
crops, as shown in [Figure 6]. According to analyses by
Cappello et al. in a hospital-based survey,[53] cholestasis is
a common feature of inflammatory bowel disease. They
observed a cholestatic pattern in 60% of patients studied,
mainly related to older age, longer duration of disease,
and hypertension. Gallstones were commonly found,
often in association with abnormal bile salt absorption,
especially in Crohn’s disease patients.
Ironically, while Mn-SOD depends upon Mn as a cofactor,
excess exposure to Mn can inhibit SOD expression.
Experiments exposing rats to excess Mn revealed several
Figure 6: Plots of glyphosate usage on corn and soy crops (blue),
    
(Crohn’s andulcerative colitis) in the US, over time. (Figure courtesy
of Dr. Nancy Swanson)
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pathological effects on the liver, including inhibition
of SOD and GSH peroxidase, as well as decreased
levels of GSH and reduced levels of sodium-potassium
ATPase activity.[126] It is striking that glyphosate has also
been shown to have these very same effects in animal
experiments,[60,174,89] and it is conceivable that these effects
may be in part mediated by excess Mn accumulation in
the liver.
Bilirubinemia in neonates is a risk factor for autism,
particularly when it is unbound and unconjugated.[10]
Glucose 6-phosphate dehydrogenase (G6PD) deficiency
can induce bilirubin toxicity in neonates,[176] due to the
fact that G6PD enables conjugation of bilirubin.[141]
Glyphosate was shown to induce a 2.67-fold reduction
in G6PD expression in E. coli.[171] Studies on goldfish
demonstrated that glyphosate significantly decreased
G6PD activity in liver, kidney, and brain.[174]
G6PD is the main enzyme responsible for regeneration
of NADPH, an essential requirement for GSH reductase
activity.[174] Cholestasis is associated with a reduction in
the supply of reduced GSH.[317] Furthermore, glyphosate
has been shown to reduce the activity of GSH reductase
in the liver.[174] Preeclampsia, affecting 4% of pregnancies,
is associated with G6PD deficiency in red blood cells
along with a reduction in reduced GSH.[3] The ratio
of oxidized to reduced GSH is consistently high in
association with autism, in plasma, immune cells, and
the brain.[239]
A mouse model of cholestasis can be induced by exposing
mice to Mn, followed shortly by exposure to bilirubin.[82]
Mn induces cholesterol synthesis in the liver, and bilirubin
disrupts 7-α oxidation of cholesterol, a crucial step in bile
acid formation.[5] Cholesterol 7-α hydroxylase is the CYP
enzyme CYP7A1 and is likely disrupted independently
by glyphosate. Therefore, excess Mn in the liver works
synergistically with glyphosate to induce cholestasis.
The incorporation of cholesterol products into
exported bile acids is crucial for regulating cholesterol
homeostasis.[205] Bile acid transport depends on ATP,[203]
so mitochondrial disruption due to oxidation damage
consequential to excess Mn could contribute to disturbed
bile acid export, leading again to cholestasis. In vitro
experiments exposing rat H9c2 cells to glyphosate
plus the surfactant TN-20, which is a polyoxyethylene
tallow amine commonly used in glyphosate herbicides,
demonstrated that the surfactant in conjunction with
glyphosate causes collapse of the mitochondrial membrane
potential, leading to necrosis and apoptosis.[147] Even
in the absence of a catastrophic death cascade, a drop
in mitochondrial membrane potential would obviously
negatively impact ATP production. The effect could
be due in part to polyoxyethylenealkylamine (POEA),
which includes polyethoxylated tallow amine surfactants
that enable glyphosate to penetrate the mitochondrial
membrane.[188] But, in addition, excess Mn, which would
accumulate due to the lack of bile flow, itself induces a
collapse in mitochondrial membrane potential.[137]
Intracellular accumulation of bile acids, associated with
cholestasis, is known to be toxic to hepatocytes. The
accumulation of bile acids in the cholestatic liver induces
oxidative stress and apoptosis, resulting in damage to
the liver parenchyma, and, ultimately, extrahepatic
tissues as well.[180] The lipophilic bile acids are much
more damaging than the hydrophilic ones,[15] and
they can induce proton leakage and the permeability
transition pore (PTP), resulting in programmed cellular
death.[237] Their toxic effect is directly due to their role as
surfactants.[180] Therefore, they enhance the effects of the
surfactants in Roundup®, acting in a cascade reaction.
On the other hand, the hydrophilic bile acid,
ursodeoxycholic acid (UDCA), is protective, and
its protective effects have been proposed to be due
to its ability to induce the expression of CYP3A4,
a bile-metabolizing enzyme, in hepatocytes.[11]
Hydroxylation, which depends on CYP enzymes, converts
lipophilic compounds into hydrophilic products. So
one can expect that, in the context of the CYP-enzyme
suppressing effects of glyphosate, [248,249] lipophilic bile
acids would accumulate in hepatocytes, and their export
would be impeded by the loss of ATP subsequent to
mitochondrial damage, in a positive feedback loop.
Another enzyme class that was discovered to be
downregulated in the liver by glyphosate in the goldfish
study is GST, an important class of enzymes. The main
function of the GST enzymes is the detoxification of
electrophilic xenobiotics by GSH conjugation.[275] Beyond
their important role in the detoxification of xenobiotics,
gene variants where the enzyme is inactive are associated
with increased risk to basal cell carcinoma, and a
gain-of-function mutation leads to decreased risk to
asthma.[275] Arsenic, whose toxicity is synergistically
enhanced by glyphosate[132] is a risk factor for basal cell
carcinoma.[62] Asthma is reaching epidemic proportions
today[91] and is associated with autism.[24,25] GST is
increasingly recognized as an important enzyme in gut
bacteria, which allows them to assist in the detoxification
of xenobiotics.[7]
One final factor in cholestasis is vitamin K deficiency,
which is associated with cholestatic liver disease.[278]
Chorismate, the intermediary in the shikimate pathway
whose synthesis is blocked by glyphosate, is a precursor
not only for the three aromatic amino acids but also
for tetrahydrofolate and phylloquinone (vitamin K1)
in plants.[294] Similarly, menaquinone (vitamin K2)
is synthesized by bacteria from chorismate.[27] Thus,
disruption of the shikimate pathway contributes to
vitamin K deficiency, which can lead to cholestasis.
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SALMONELLA INFECTION
Multiple drug-resistant strains of Salmonella are becoming
an increasing problem both in the industrialized[191] and in
the developing world.[246] This may be due in part to the
fact that Salmonella is more resistant to glyphosate than
other species. Salmonella typhimurium is among a small set
of microbes that possess phosphonatase genes that allow
it to use the commonly occurring natural phosphonate,
2-aminoethyl-phosphonate (AEPn), as a sole source of
phosphorus,[134] which likely contributes to its growth
advantage in the presence of the phosphonate, glyphosate.
Furthermore, Lactobacillus, which are especially vulnerable
to glyphosate, produce antimicrobial compounds that can
defend against Salmonella.[81] Salmonella infections often
originate from contamination of plant-based foods exposed
to manure of chickens and pigs. A study on poultry
showed that Salmonella entritidis, Salmonella galliarum,
and Salmonella typhimurium were all highly resistant to
glyphosate compared with other more benign species.[263]
Our research into the pathology of Salmonella has
uncovered a complex interplay of many factors that
may be responsible for the epidemic, which includes an
important role for Mn, as well as a role for industrial
processing of lecithin from soy, and bile acid disruption
by glyphosate. Commercial lecithin is a mixture of
phospholipids and various metabolites, often derived from
soy. In food processing, phospholipase A (PLA) is applied
enzymatically to hydrolyze phospholipids in lecithin into
lysophospholipids and fatty acids, in order to improve its
emulsification, surfactant, and lubricant properties.[97]
This may be a factor in inducing both increased virulence
and an inflammatory response to Salmonella in the gut,
contributing to inflammatory bowel disease.
Salmonella depend on cyclic adenosine
monophosphate (cAMP) for flagella formation,
and therefore for motility.[318] Salmonella possess a
lysophospholipid sensing mechanism that triggers the
synthesis of flagellin, mediated by cAMP, and this activates
toll-like receptor 5 (TLR5) in macrophages, inducing an
inflammatory response.[279] Experiments have shown, as
might be expected, that flagella, produced from flagellin,
not only enhance mobility but also protect S. typhimurium
from internal death in macrophages and enhance their
ability to multiply within an infected cell.[306]
Salmonella are remarkably resilient in an inflammatory
environment, and, in a novel strategy for survival
in a hostile environment, they take advantage of
tetrathionate produced from oxidation of thiosulfate
by ROS as a terminal electron acceptor in processing
ethanolamine derived from host lysophospholipids
as a source of energy not available to other
microbes.[8,313] They can also uniquely use a glycated
L-asparagine (fructose-asparagine, F-asn) as a source of
both carbon and nitrogen.[8] Concentrations of F-asn, an
Amadori product, are surprisingly high in heated fruits
and vegetables.[92]
It has only recently been appreciated that Mn plays
an important role in the virulence of Salmonella.[144]
Salmonella depend on Mn to resist the oxidative attack of
macrophages via Mn-SOD.[292] Since glyphosate’s chelation
of Mn makes it unavailable to gut bacteria, a mystery
arises as to how Salmonella might acquire adequate Mn
for defense against oxidative damage. Salmonella possess a
Mn uptake system based on a protein that is homologous
to eukaryotic Nramp transporters. This protein, MntH,
is a proton-dependent metal transporter that is highly
selective for Mn2+ over Fe2+,[144] or any other cation.
Intracellular Mn2+ can accumulate in millimolar amounts
even when environmental Mn2+ is scarce.
A feature unique to Salmonella is that they are especially
adept at binding to cholesterol in the gall bladder,
particularly in association with gallstones, and they also
possess adaptive responses that allow them to survive
the harsh environment of the bile acid milieu, as well as
the highly acidic environment of the stomach.[9] In fact,
studies have shown that they can survive a lower pH
environment than either Shigella flexneri or E. coli.[167]
Several different species of Salmonella can form biofilms on
human gallstones, which is dependent upon the presence
of bile.[222,74] Since bile is an excellent source of Mn, and
glyphosate’s chelation of Mn is dependent on a basic
environment, they could accumulate Mn while resident
in the bile acids present in the gallstones. Bile acids offer
antibacterial defenses, but Salmonella have developed
resistance genes to protect them from bile acids.[123] In
association with gallstones, S. typhi colonize the human
gallbladder and persist in an asymptomatic carrier state.[9,187]
Thus, impaired bile acid flow due to glyphosate would
promote both gallstones and microbial growth.
Fibrates are hypolipidemic agents that are known to
suppress bile acid synthesis via suppression of peroxisome
proliferator-activated receptor γ (PPAR-γ).[220] Studies on
humans exposed to fibrates have shown reduced activity of
cholesterol 7α-hydroxylase (CYP7A1), leading to reduced
bile acid production, and concurrent increased risk of
gallstones.[271,31] Thus, it is plausible that Salmonella are
able as well to gain a foothold on the gallstones caused by
suppression of bile-acid production by glyphosate due to
CYP enzyme inactivation, and they are able to take up Mn
in the immobilized bile acids and utilize it for Mn-SOD
production, protecting them from oxidative attack by
macrophages. The pathogen responsible for Lyme disease,
Borrelia burgdorferi, is also uniquely dependent on Mn,[4]
and the disruption of Mn homeostasis by glyphosate may
therefore play a role in its emergence.
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CHONDROITIN SULFATE, OSTEOMALACIA
AND ARTHRITIS
Vitamin D deficiency has reached epidemic proportions
in the US and increasingly around the world in recent
years.[124] In a large population study in the US, Bodnar
et al.[34] found deficient levels of vitamin D in 83% of
Black women and 92% of their newborns, as well as in
47% of White women and 66% of their newborns, despite
the fact that over 90% of the women were on prenatal
vitamins. This deficiency is associated with an increased
risk to bone fractures, likely due to impaired calcium
homeostasis.[145] It is even likely that care-takers are being
falsely accused (“Shaken Baby Syndrome”) of abusing
children in their care who suffer from bone fractures.[255]
These children are highly vulnerable to bone fractures
due to impaired bone development. Bone fractures in
the elderly due to osteoporosis have also risen sharply
recently in the industrialized world.[139] The cause of a
surging incidence of hip fractures across multiple age
groups remains a mystery to medical personnel.[140]
Samsel and Seneff[248,249] proposed that the current
vitamin D deficiency epidemic is caused by glyphosate,
due to glyphosate’s interference with CYP enzymes.
The metabolite that is usually measured, 25-hydroxy
vitamin D, is the product of activation in the liver by a
CYP enzyme that is also critical in bile acid formation.
However, there is a larger problem with bone development
due to impaired Mn homeostasis. Bone mineralization
depends critically on Mn, due to its essential role in
chondroitin sulfate synthesis.[36,158] Several enzymes
in the osteoblasts needed for this crucial step in bone
development require Mn as a cofactor, including the
polymerase, which polymerizes uridine diphosphate
N-acetyle-galactosamine (UDP-N-acetyl-galactosamine)
and UDP-glucuronic acid to form the polysaccharide,
and galactotransferase, which incorporates galactose
from UDP-galactose into the trisaccharide that links
the polysaccharide to the glycosylated protein.[157,158]
Chondroitin sulfate, together with osteocalcin, forms
the ground substance to which collagen adheres to
maintain healthy bone, ligaments and cartilage. Sulfate
uptake by GAGs in chicks fed a Mn deficient diet was
only 50% of that in control chicks, and the deficient
chicks suffered from growth retardation and skeletal
abnormalities.[36]
Osteoarthritis is another pathology likely related to Mn
deficiency, impaired chondroitin sulfate synthesis and
impaired vitamin D activation. Vitamin D deficiency is
associated with rheumatoid arthritis.[207] Mn is necessary
for the synthesis of GAGs or mucopolysaccharides,[156,254]
which provide lubrication and protection for the joints.
Rheumatoid arthritis is associated with Mn accumulation
in the liver,[72] which is consistent with impaired bile
flow. Glucosamine sulfate has been demonstrated to
be effective in treating osteoarthritis, and it may even
delay disease progression.[259] A combination therapy
of glucosamine, chondroitin sulfate, and Mn ascorbate
was shown to be effective in treating knee osteoarthritis
in a placebo-controlled study conducted on US Navy
specialists.[160]
A mysterious epidemic of a new disease, called “sea
star wasting syndrome,” is currently sweeping across
the Pacific coast of North America, affecting at least 12
different species of sea stars.[307] We highly suspect that
glyphosate plays an important role in this disease, and
that it does so by chelating Mn, and therefore disrupting
chondroitin sulfate synthesis. A likely source is Roundup®
applied to oyster beds to kill the invading sea grass,
since oysters are a common food for sea stars.[118] The
state of Massachusetts was forced to close oyster beds in
Edgartown on Cape Cod recently, due to infection with
a pathogen, Vibrio parahaemolyticus.[214] This species
synthesizes an N-acetyl transferase (NAT) protein, which
is capable of detoxifying glyphosate by acetylating the
nitrogen moiety,[58] and this could explain its overgrowth
as being linked to glyphosate contamination. An
analysis of the GAGs isolated from brittle stars showed
exceptionally high proportions of di- and trisulfated
chondroitin sulfate/dermatan sulfate disaccharides,[233]
whose synthesis would be severely impaired by Mn
deficiency due to chelation by glyphosate.
A protective layer of mucopolysaccharides called mucus
is secreted by corals, and it has been characterized as
containing sulfated glycoproteins similar to chondroitin
sulfate,[44] which play an important role in controlling
pH and the transepithelial movement of electrolytes
and water, just as is the case in vertebrate mucosa.
Mucus pathology is implicated in coral disease leading
to mortality, particularly in the Caribbean.[219] Thus, an
interesting hypothesis that should be considered is that
glyphosate chelation of Mn is a crucial factor in the
worldwide coral die-off.
PARKINSON’S DISEASE
It might be anticipated that a simple Mn mineral
supplement could correct for the problem of glyphosate’s
chelation of Mn, but this assumption is almost certainly
false. We suggest that glyphosate’s disruption of
Mn homeostasis leads to extreme sensitivity to Mn
bioavailability, making it easy to err in the direction of
either too little or too much.[103] Our investigations
into the body’s mechanisms for transporting Mn has
revealed a likely pathway from the liver to the brain
that would induce Mn toxicity in the brainstem nuclei
whenever Mn is plentiful but glyphosate is also present.
A strong clue comes from the condition, “manganism,”
closely resembling PD, which develops following
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chronic occupational exposure to airborne nanoparticles
containing Mn.[163,172,244] In addition to evidence from
direct occupational exposure, geographical studies in the
US have shown a higher incidence of PD in urban areas
with higher industrial release of Mn.[312]
The fact that death from PD has increased in the past two
decades in step with glyphosate usage on corn and soy
suggests that there may be a role for glyphosate to play
in Parkinson’s pathology [Figure 4]. A case of accidental
acute exposure to glyphosate through skin contact
showed a remarkable development of Parkinsonian
symptoms beginning just 1 month following exposure.[20]
T2-weighted images revealed a hyperintense signal in the
globus pallidus and substantia nigra. Another case study
involved a 44-year-old female who developed PD after
a 3-year period of job-related exposure at a chemical
plant.[304] Glyphosate has also been shown to induce
Parkinsonian-like effects in the worm, Caenorhabditis
elegans, characterized by damage to both GABAergic
and dopaminergic neurons.[201] The mechanism behind
this effect remains obscure. However, a Mn-containing
fungicide, MANCOZEB, ethylene bisdithio-carbamate,
also induced similar damage.
An experiment where rats were exposed to Mn via
intranasal instillation demonstrated that the Mn could
enter the brain through the olfactory bulbs by following
major neuronal pathways.[291] Mn migrated via both
secondary and tertiary olfactory pathways and beyond to
ultimately reach most parts of the brain and the spinal
cord. By contrast, cadmium was unable to pass through
synaptic junctions and was therefore limited in its
penetration. These authors concluded that the olfactory
nerve is the likely pathway by which Mn gains access to
the brain in manganism, thus circumventing the blood–
brain barrier. Autoradiographic studies tracking the
distribution of radiolabeled Mn injected into rat brain
verified that Mn is subject to widespread axonal transport
in neuronal circuits.[283]
Elder et al.[94] reinforced this idea, in a study involving
exposure of rats to ultrafine particles (UFPs) of inhaled
Mn oxide. Their conclusion sums up the situation quite
well: “We conclude from our studies that the olfactory
neuronal pathway represents a significant exposure
route of central nervous system (CNS) tissue to inhaled
solid Mn oxide UFPs. In rats, which are obligatory nose
breathers, translocation of inhaled nanosized particles
along neurons seems to be a more efficient pathway to
the CNS than via the blood circulation across the blood–
brain barrier. Given that this neuronal translocation
pathway was also demonstrated in nonhuman primates, it
is likely to be operative in humans as well.” [94, p. 1178]
Manganism is distinct from PD mainly in that it is the
locus coeruleus that is preferentially damaged rather than
the substantia nigra.[216] In the rat, at least 40% of all locus
coeruleus neurons project to the olfactory bulb.[266] Since
glyphosate likely interferes with the normal recycling
of Mn via the bile acids, the liver will need to find an
alternative route to dispose of excess Mn. Following
the example of nerve-fiber migration from the olfactory
bulb,[291] and the study on injected Mn,[283] a likely path
is the vagus nerve, which has extensive innervation in the
liver, with 10 times as many afferent nerves as efferent
nerves, and particularly concentrated on the outer surface
of the bile ducts.[30] MRI abnormalities indicative of
Mn toxicity in the globi pallidi and substantia nigra were
noted in three cases of patients with liver disease.[120] PD
is associated with nonmotor symptoms that often precede
the movement impairment aspects.[320] These include
depression and gastrointestinal disturbances.
Berthoud et al.[30] proposed that the onset of PD may
be associated with impairment of the vagus nerve, and
subsequent functional inhibition of the dopamine system.
Clinical trials have revealed pathological alteration of the
vagus nerve in PD patients.[218] The dorsal motor nucleus
of the vagus is an early site of pathology.[38] Liver failure
can lead to excessive build-up of Mn in the brainstem,
particularly the globus pallidus in the basal ganglia, which
regulates voluntary movement. This is due primarily to
decreased billiary excretion from the liver,[99,131] as bile
acids recycle Mn back to the gut, where it is taken up by
gut bacteria or disposed of. Liver cirrhosis is associated
with excess Mn in the brain and associated Parkinsonian
symptoms.[99] Mn neurotoxicity in the basal ganglia
causing Parkinsonian symptoms has also been identified in
association with chronic liver failure.[150] Despite the fact
that Mn is an essential cofactor for glutamine synthase,
excess Mn actually downregulates expression and activity
of the enzyme, causing neuropathology. Its toxicity is
linked to disruption of the cycling between astrocytes
and neurons of glutamine, glutamate, and GABA.[267] Mn
inhibits ATP-dependent calcium signaling in astrocytes,
which likely contributes to the toxic effects of excess Mn
on neurons.[277] Decreased bile flow associated with the
birth defect, biliary atresia, leads to Mn accumulation in
the liver[23] and in the globus pallidus.[130] As discussed
previously, bile acid synthesis and export are disrupted by
glyphosate and by surfactants, which is also a common
effect of many toxic chemicals whose detoxification
would be impaired by glyphosate’s disruption of CYP
enzymes.[248]
A study using MRI technology to detect Mn distribution
in the brain in marmosets and rats following Mn injections
revealed an accumulation in the basal ganglia as well
as other parts of the brain that were situated near the
ventricles, suggesting redistribution via the cerebrospinal
fluid.[33] There was also considerable liver damage,
especially in the marmosets, including hemosiderosis,
congestion, and hepatic necrosis. Marmosets were far
more susceptible than rats to Mn toxicity.
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Both the substantia nigra and the locus coeruleus are
characterized by high concentrations of neuromelanin.
While it is unclear what role neuromelanin plays,
one hypothesis is that it carries a protective action
through its unique ability to accumulate and retain
various amines and metallic cations, especially Mn.[168]
The neuromelanin produced by the substantia nigra
is closely related to dopamine, and therefore derived
from tyrosine. The locus coeruleus’ melanin is
related to noradrenaline, and therefore derived from
tryptophan. Both tyrosine and tryptophan are products
of the shikimate pathway, and are therefore likely to be
deficient in the context of glyphosate exposure to plants
and microbes. This would result in a reduced ability to
temporarily house excess Mn in the brainstem nuclei
until it can be disposed of.
Glyphosate itself likely also contributes directly to PD. PD
is caused by degeneration of dopaminergic neurons in the
substantia nigra, attributed to mitochondrial dysfunction,
oxidative stress, and protein aggregation.[79,251] PC12 cells
are a popular model cell line for investigating neurological
disease, and they produce dopamine in vesicles, as is
appropriate for cells from the substantia nigra. A study
on PC12 cells exposed to glyphosate demonstrated that
glyphosate induced cell death via autophagy pathways as
well as apoptotic pathways.[115]
A study on serum Mn levels in infants and their
association with neurodevelopment revealed a U-shaped
curve, with both too little and too much Mn leading
to impaired development.[67] This study was conducted
on children born in Mexico City between 1997 and
2000. We hypothesize that extreme sensitivity to Mn
levels can be expected in the context of glyphosate,
because it would prevent the liver from disposing of
Mn via the bile acids, and therefore cause a flooding
of the brainstem nuclei with excess Mn delivered via
the vagus nerve. At the same time, Mn uptake into
the blood stream from the gut is suppressed, both
because of glyphosate’s chelation of Mn at higher pH
and the impaired recycling to the gut from the liver.
This can lead to a paradoxical situation in which the
brainstem nuclei are overwhelmed with Mn while the
precortex and cortex are deprived because of the low
bioavailability from the blood stream. One might
postulate that seizures play a role in enhancing Mn
redistribution from the brainstem to the cortex by
mobilizing Mn transport along axons, and this effect
might therefore explain the benefit of electroconvulsive
therapy (ECT) to depression.[16]
Dopamine suppresses thyroid stimulating hormone, and
therefore dopamine insufficiency can lead to overactive
thyroid and potential burnout of the thyroid gland.[270]
This problem is compounded by the fact that thyroid
hormone itself is derived from tyrosine, one of the
three aromatic amino acids that are negatively impacted
by glyphosate through disruption of the shikimate
pathway. The thyroid gland also depends critically
on selenoproteins as antioxidants.[249] Glyphosates
depletion of both selenium and methionine will lead
to reduced bioavailability of selenoproteins. It is
conceivable that all of these factors working together can
explain the strong correlation of glyphosate application
to corn and soy with thyroid cancer [Figure 7], as well
as the association between maternal thyroid disease and
autism.[238]
PRION DISEASES AND MANGANESE
Prions are a special class of proteins that acquire
alternative conformations that can become
self-propagating. There is a class of neurological diseases
called transmissible spongiform encephalopathies that are
believed to be caused by misfolding of prion proteins,
predominantly accumulating in the gray matter in the
brain.[223] These include Creutzfeldt–Jakob disease (CJD)
in humans, scrapie in sheep, chronic wasting disease of
deer, and bovine spongiform encephalopathy or Madcow
disease.
Prion proteins have been shown to bind Cu in vivo,[46]
and this is probably an important factor in their normal
functioning. Cu protects against conversion of prions to
the pathogenic form, and studies have shown that gene
variants with extra octarepeat inserts exhibit decreased
Cu binding in association with markedly increased disease
risk.[272] A theory first proposed by Purdey[228,229] is that the
prion protein misfolds following binding to Mn instead
of Cu. The pathology is then explained by a high Mn to
Cu ratio in the diet. Brown et al.[45] investigated metal
binding properties of prion proteins, and demonstrated
that prions only bind to Cu and Mn. Furthermore, Mn
binding induces a resistance to protein degradation by
Figure 7: Plots of glyphosate usage on corn and soy crops (blue),
percent of corn and soy that is genetically engineered to be
“Roundup Ready” (red), and incidence of thyroid cancer (yellow
bars) in the US. (Figure courtesy of Dr. Nancy Swanson)
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
protease, a characteristic feature of prion diseases. Aging
of the Mn-bound version of prion proteins leads to loss
of function. A later experiment demonstrated that Mn
promotes prion protein aggregation.[161] Thus, Mn is
causal in the formation of fibrils characteristic of the
scrapie isoform of the protein in prion diseases.
The possible link between excess Mn and prion diseases
was also supported in a later study by Masánová et al.,[181]
who compared different regions of the Slovak republic
and found a correlation between an elevated Mn/Cu ratio
in core food items such as potato and bread, as well as in
the soil, and a higher incidence of CJD.
Mn-SOD-/- mice die between days 3 and 13 following
birth. They exhibit a marked dilated cardiomyopathy,
neurodegeneration and fatty liver disease.[159,164] Mn 5,
10, 15, 20-tetrakis (4-benzoic acid) porphyrin (MnTBAP)
rescues mice from this pathology and dramatically
improves their lifespan. It operates at 10% of the
efficiency of Mn-SOD to oxidize superoxide to H2O2.
However, these supplemented mice develop a spongiform
encephalopathy very similar to CJD.[186] This is most
likely caused by excess delivery of Mn to the brain by the
MnTBAP.
Purdey[227] has noted that madcow disease epidemiology
aligned with the regulatory requirement to apply the
organo phthalimido-phosphorus insecticide, phosmet, on
the backs of cattle, for the control of warble fly during
the 1980s. He maintained that phosmet chelated Cu
in the CNS, but also caused oxidation of Mn to Mn3+,
leading to its toxicity. Like glyphosate, phosmet also
disrupts CYP enzyme function,[262] which would lead to a
similar disabling of bile acids.
New experimental data support the idea that the class of
prion diseases should be expanded to include AD, PD,
and related tauopathies.[224] Indeed, it has been proposed
that Cu deficiency may be a factor in AD.[149] Glyphosate
chelates Cu down to much lower pH values than those
at which it chelates Mn [173,296] [Figure 8], and it has also
been shown to oxidize Mn to the +3 oxidation state.[21]
Thus, one can surmise that glyphosate might behave
similarly to both phosmet and MnTBAP to be causal
in prion diseases. In the pH 4 environment adjacent to
the sulfates in the glycocalyx, Mn, but not Cu, would
be released by glyphosate. Abundant bioavailability
of Mn3+ alongside Cu deficiency further aggravated
by glyphosate could set up a situation whereby excess
Mn supplied to the neurons in the cortex, bound to
glyphosate, over-competes with Cu in binding to prion
protein. One can predict that glyphosate’s tenacious
binding to Cu will render Cu systemically unavailable,
which argues for a role for glyphosate in prion diseases
through Cu binding.[45,228,229]
MN AND INFERTILITY
Multiple papers on rodent studies have indicated
disruption of the male reproductive system by glyphosate.
Acute treatment of 60-day-old male Sprague-Dawley rats
to Roundup® caused a marked increase in aromatase
mRNA in testicular tissue,[56] likely reflecting an increase
in production due to suppression of the activity of
aromatase (CYP 19), accompanied by abnormal sperm
morphology. Aromatase participates in both hormone
synthesis and metabolism. It is an important enzyme
in testes that converts testosterone to estrogen, thus
regulating the balance of sex hormones.
In vitro studies on Sertoli cells from mouse testis
demonstrated that glyphosate opens L-type
voltage-dependent calcium channels, leading to
calcium-overload cell death.[83] However, glyphosate’s
disruption of the supply of Mn to sperm may be a
more important factor leading to infertility, due to
immobilization of the sperm. Sperm are critically
dependent on Mn for their motility. Mammalian sperm
contain a distinctive form of Mn-dependent adenylate
cyclase, which first appears during development in
seminiferous tubules simultaneously with the appearance
of spermatid cells.[39] It is expressed at the highest levels
following sexual maturity. Adenylate cyclase catalyzes
the synthesis of cAMP. Bacteria such as E. coli and
Salmonella typhimurium depend on cAMP for flagella
formation, and therefore for motility.[318] cAMP-dependent
phosphorylation has been linked to activation of motility
in sperm flagella from sea squirts[209] and from dogs.[287]
Human sperm also depend on cAMP for increased flagellar
motility.[210,303] A study on zebrafish demonstrated that
glyphosate exposure at concentrations of 5 and 10 mg/L
over a 24-h time period reduced sperm motility.[170] Mn
stimulated the progressive motility of human sperm in a
time- and dose-dependent manner, and this was linked to
adenyl cyclase activity.[178] The decrease in male fertility
levels today in the industrialized world[111] may therefore
be explained by Mn deficiency.
Figure 8: Fractions of metal complexed with glyphosate as a function
of pH, for copper and manganese. Figure adapted from Lundager
Madsen et al[170]
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
EVIDENCE OF EXPOSURE
Glyphosate-containing herbicides are applied to
crops several times each season both for killing
weeds and for desiccation just prior to the harvest in
non-Roundup®-Ready crops, such as wheat and sugar
cane. It accumulates in the leaves, grains, and fruit, and
thus cannot be removed by washing and, furthermore, is
not broken down by cooking.[41] Nowell et al.[206] identified
pesticides as a leading cause for declines and deformities
among amphibians and pollinators in the United States.
A total of 100% of all water surfaces and 96% of all
examined fish contained detectable levels of pesticides. In
a recent US-based study by Battaglin et al.,[22] glyphosate
and AMPA were detected frequently in soils and sediment,
ditches and drains, rainwater, rivers, and streams.
A recently published study by Shehata et al.[264] showed
that glyphosate residues can be found in the organs and
muscles of chickens that consume glyphosate in their
feed, including the liver, spleen, lung, intestine, heart,
and kidney. All animals fed a diet contaminated by
glyphosate would be subject to such bioaccumulation
due to the molecule’s ability to act as an attaching
ligand. Feed supplementation with humic acid was able
to significantly reduce the glyphosate burden in tissues.
A recent paper by Nevison[202] investigated temporal
trends in autism since 1988 to assess to what degree
the recent observed rate increases are due to increased
diagnosis versus increased incidence. She concluded that
increased incidence accounts for 75–80% of the tracked
increase. She also investigated trend lines for a variety of
environmental toxicants potentially implicated in autism.
She wrote in the abstract: “Among the suspected toxins
surveyed, polybrominated diphenyl ethers, aluminum
adjuvants, and the herbicide glyphosate have increasing
trends that correlate positively to the rise in autism.”
As we have stated earlier, glyphosate and aluminum are
synergistically toxic.
There has been very little testing of glyphosate levels in
either humans or other mammals. Glyphosate is passed
in both the urine and the feces. Recent research from
Europe has shown that glyphosate is consistently present
in significant amounts in the urine of cows consuming
Roundup®-Ready feed, as well as in the organs and meat
of cattle.[153] Furthermore, they also detected glyphosate
in the urine of humans, and the generally healthy
population had significantly lower levels than the sick
population. Those consuming a predominantly organic
diet also had a significantly lower glyphosate burden.
Another study found detectable levels of glyphosate
in lungs, liver, kidney, brain, gut wall, and heart of
malformed euthanized 1-day-old Danish piglets, and the
authors proposed that glyphosate could be the cause of
the deformities.[155]
CONCLUSION
Glyphosate is the most widely used herbicide on the
planet, in part because of its perceived low toxicity to
humans. In this paper, we propose that glyphosate’s
chelation of Mn, working together with other known
effects of glyphosate such as CYP enzyme suppression
and depletion of derivatives of the shikimate pathway
in microorganisms, may explain the recent increase in
incidence of multiple neurological diseases and other
pathologies. We have shown that glyphosate’s disruption
of Mn homeostasis can lead to extreme sensitivity to
variations in Mn bioavailability: While Mn deficiency in
the blood leads to impairment of several Mn dependent
enzymes, in contrast, excess Mn readily accumulates in
the liver and in the brainstem due to the liver’s impaired
ability to export it in the bile acids. This pathology
can lead to liver damage and PD. Mn depletion in the
gut due to chelation by glyphosate selectively affects
Lactobacillus, leading to increased anxiety via the gut–
brain access. Both low Lactobacillus levels in the gut
and anxiety syndrome are known features of autism,
and Lactobacillus probiotic treatments have been shown
to alleviate anxiety. Increased incidence of Salmonella
poisoning can also be attributed to glyphosate,
through its impairment of bile acid synthesis. Low Mn
bioavailability from the blood supply to the brain leads to
impaired function of glutamine synthase and a build-up
of glutamate and ammonia in the brain, both of which
are neurotoxic. Excess brain glutamate and ammonia are
associated with many neurological diseases. At the same
time, impaired function of Mn-SOD in the mitochondria
results in mitochondrial damage, also a hallmark of many
neurological diseases. Mn deficiency can account for poor
sperm motility and therefore low fertilization rates, as well
as poor bone development leading to osteoporosis and
osteomalacia. Sea star wasting syndrome and the collapse
of coral reefs may in fact be an ecological consequence
of the environmental pervasiveness of the herbicide.
Many diseases and conditions are currently on the rise
in step with glyphosate usage in agriculture, particularly
on GM crops of corn and soy. These include autism, AD,
PD, anxiety disorder, osteoporosis, inflammatory bowel
disease, renal lithiasis, osteomalacia, cholestasis, thyroid
dysfunction, and infertility. All of these conditions can
be substantially explained by the dysregulation of Mn
utilization in the body due to glyphosate.
ACKNOWLEDGMENTS
This work was funded in part by Quanta Computers, Taipei,
Taiwan, under the auspices of the Qmulus Project. The authors
thank Dr. Nancy Swanson for providing the plots showing
correlations over time of multiple diseases and conditions with
glyphosate usage on corn and soy in the US.
Surgical Neurology International 2015, 6:45 http://www.surgicalneurologyint.com/content/6/1/45
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