GM Maize Reduces Fertility & Deregulates Genes in Mice
Comprehensive long term studies commissioned by the Austrian government
reveal that mice fed GM maize produced fewer and smaller litters with many genes
affected compared to controls. Dr.
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Austrian scientists carried out long term studies that showed GM maize fed
to mice significantly reduced their fertility over three to four breeding
cycles within one generation . Similar effects were found in mice fed GM
maize and bred over four generations; although the results did not reach statistical
significance in any one generation, the trend was unmistakable, more pups
lost and smaller litters in the GM-fed mice.
The studies are by far the most meticulous and comprehensive
feeding trials to-date, and confirm deleterious reproductive and health impacts
obtained by scientists independent of the biotech industry and farmers’ observations
in the field. For a recent review, see  GM is Dangerous and Futile (SiS
The new research results are a landmark in the safety assessment
of GM food. Most feeding trials were short-term and restricted to a single
generation or a single breeding cycle. The “multi-generational” study widely
cited as evidence of no long term adverse impacts from GM feed is highly misleading
as the experiment did not involve trans-generational feeding,
but merely breeding mice that were not GM fed for three generations,
and carrying out a separate experiment with GM feed for each generation
 (Letter to
Nature Biotechnology: Systematic bias in favour of no adverse impacts from
GM feed, SiS 37). There were other serious flaws in that experiment,
not least the failure to ascertain by polymerase chain reaction (PCR) that
the processed GM feed used actually contained GM soya.
Targeting long term effects
The new studies were commissioned by the Austrian government several years
ago, when it became clear that proper feeding trials were very thin on the
ground, and regulators all over the world were largely dependent on companies
submitting data that were inadequate and unreliable in many ways, but which
they accepted without question  (GM Food Nightmare
Unfolding in the Regulatory Sham, ISIS scientific publication).
Alberta Velimirov at Research Institute on Biological Agriculture
(Forschungsinttitut für biologishen Landbau) and Claudia Binter and Jürgen
Zentck at the Institute for Nutrition (Institut für Ernährung) both in Vienna,
monitored changes in gross morphology, reproductive performance, and sub-microscopic
analyses of tissues and cells, as well as gene expression. (They found no
immunochemical or other microscopic differences in the tissues.)
Three series of experiments were done. The first was a multigeneration
feeding trial in which the mice were fed and bred for four successive generations,
beginning with the F0 parents that were fed on the diets from birth. The second
was a multi-cycle breeding trial lasting 20 weeks in which breeding pairs
of mice were fed beginning 1 week prior to co-habitation until the end of
experiment, and allowed to go through four breeding cycles in the same generation.
The third was a life-term trial involving feeding the mice without breeding
from conception (via the pregnant mothers) to their eventual death.
A laboratory non-inbred strain of mice was used for all experiments,
in order to avoid the effects of inbreeding, so that the results would be
more generally applicable to natural populations.
The researchers report that it was not possible to obtain a GM
test crop plus parental line from the agro-business companies, which was why
the test diets consisting of 33 percent GM maize had to be compared with a
non-GM maize variety (also at 33 percent) that was closely related to the
GM maize. Both were grown under identical conditions in the Organic Agriculture
Centre of Canada in Nova Scotia, in 2005 and 2007. The GM maize was the transgene
hybrid NK603 x MON810 containing three gene cassettes, two conveying glyphosate
herbicide tolerance and one insect resistance coding for endotoxin Cry1Ab.
The transgenic protein was estimated to be 0.11-0.24 microgram per gram of
The multigeneration study also included one group with a non-GM
maize variety cultivated in Austria.
The herbicides dicamba, atrazine and s-metalochlor were used
Maise, while glyphosate only was used with the GM maize. Contamination levels
of the maize grains with herbicides were determined to be less than 0.01 percent
of each of the herbicides. This was important to make sure that effects due
to herbicides were not confounded with those from the GM feed.
Main effects on reproduction
In the multigeneration study, the parental generation was fed since birth
with either GM or nonGM maize diet, and 4 generations were bred. Less pups
were born in successive generations in both control and GM fed mice. But the
controls tended to do better than GM fed. The average litter size and weight
as well as number of weaned pups were in favour of the non-GM maize group.
None of the differences reached statistical significance in any one generation,
although the trend was clear.
Over all generations, about twice as many pups were lost in the
GM group as compared with the control group (14.59 percent vs 7.4 percent).
More litters with 8 or more pups were seen in the control compared with GM
group. And a greater number of pups were lost at weaning in the GM fed.
Comparison of organ weights did not indicate direct dietary effects
in the multigeneration study, except for the kidneys. Kidney weight of females
in the GM-fed group were significantly lower in the F2, F3 and F4 generations
than controls; and males in the GM-fed group also had significantly lower
kidney weight than controls in the F2 generation
The electron microscope investigations revealed differences in
the liver cells indicative of reduced core metabolism in the GM-fed mice.
In addition, DNA microarray analyses showed important differences in gene
expression between both groups fed non-GM maize and the group fed GM maize.
In the multi-cycle breeding trial, the same differences between
GM-fed and controls were evident. and reached statistically significant levels
in the 3rd and 4th litters. There were clearly fewer
and smaller litters in the GM-fed mice.
The average number of pups born was always lower in the GM fed
but did not reach statistical significance before the 3 rd and 4th
deliveries. The number of pups at weaning was also always smaller in the GM-fed
group. Over all the deliveries, more pups were born in the controls than in
the GM group (1035 vs 844).
Consistent with these findings, the life-term feeding trial showed
no significant differences in the average life-span of the GM-fed mice compared
Epigenetic effects of GM maize feed
In the F3 generation of the multigeneration trial, DNA microarray analyses
were performed on the lower small intestine. This identified 2 374 genes that
were significantly abnormally expressed in GM fed compared with non GM fed
mice; with 421 of these showing a 2-fold or greater change from controls.
This was more than 3.2 percent of the total 13 034 genes expressed in the
lower small intestine. The reproductive and other effects observed could be
just the tip of the iceberg as far as the epigenetic changes are concerned.
The impacts could take more generations of GM feeding to become fully manifest.
The genes were functionally classified and found to predominate
in the pathways of protein biosynthesis and protein metabolism and modification,
interleukin signalling and cholesterol biosynthesis.
Epigenetics – the study of heritable
changes in gene expression that do not involve alterations in DNA sequence
– is a maturing discipline with growing applications in toxicology, cancer,
nutrition, and brain and behavioural sciences [5-8]. A change in our
diet as far-reaching and profound as GM food cannot be entertained without
detailed long term studies of the kind carried out by the Austrian scientists
together with analyses using DNA microarrays, proteomics,
and metabolic profiling, which are now routine in laboratory and field studies.
Velimirov A, Binter C and Zentek J. Biological effects of transgenic maize
NK603xMON810 fed in long term reproduction studies in mice. Report, Forschungsberichte
der Sektion IV, Band 3. Institut für Ernährung, and Forschungsinttitut für
biologischen Landbau, Vienna, Austria, November 2008.