Results from animal testing show differences between rats fed GMO versus non-GMO corn. Photo: Understanding Animal Research.
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Related studies

In an effort to gain a deeper insight into the findings of kidney and liver pathology in rats fed NK603 corn over a two-year period (Séralini et al, 2014), a full transcriptomics and metabolomics analysis was conducted of the kidneys and livers from the female animals (Mesnage et al, 2017a). Transcriptomics analysis looks at the gene expression patterns in the organs and metabolomics analysis looks at the metabolites present in the organs.

Tissues from the liver and kidneys of three groups of rats were tested:

  • Rats fed a diet consisting of 33% GMO NK603 corn that had been sprayed once with Roundup herbicide during cultivation
  • Rats fed a diet of 33% GMO NK603 corn that was not sprayed with Roundup during cultivation
  • Rats fed a control diet of 33% non-GMO corn that was the nearest available relative to the GM corn, but without the genetic modification (called the non-GMO isogenic variety).

Statistically significant changes were observed in the levels of some metabolites in test groups compared to controls; 23 in NK603 + Roundup kidneys, 51 in NK603 kidneys, 12 in NK603 + Roundup livers and 56 in NK603 livers. Several metabolites that were indicative of organ damage were found to be altered in test animals fed the GMO corn as compared with control animals fed the non-GMO isogenic corn. For example:

  • The metabolite 3-methylhistidine was found to be elevated in the kidney tissue of animals fed GMO NK603 corn, both with and without Roundup application. This is an indicator of protein catabolism (breakdown), in particular from the degradation of muscle tissue. The degradation of muscle tissues generates free 3-methylhistidine, which is slowly released into the bloodstream, from where it is filtered by the kidneys. The measurement of 3-methylhistidine provides an index of the rate of muscle protein breakdown.
  • In the liver of animals fed GMO NK603 corn, both with and without Roundup application, there was an accumulation of potentially toxic polyamines (putrescine and spermidine), which could suggest an elevated metabolic state. This state of increased metabolic activity can signal underlying health issues and/or injury to this organ. Typically, polyamines are highly active in rapidly proliferating cells, although their levels fluctuate during the cell cycle and accumulate in the regenerating liver. This suggests that the liver may have been damaged and is trying to repair itself. However, the increased levels of polyamines in the liver could also be explained by an increased dietary intake since the NK603 corn tested in this study had previously been found to contain more polyamines than its non-GMO near-isogenic counterpart (Mesnage et al, 2017a).

Statistical analysis

In spite of the above findings, when the dataset as a whole was statistically analyzed by applying a tool called the Benjamini-Hochberg correction, a high score was obtained, implying that the changes in individual metabolites could have arisen by chance (Mesnage et al, 2017a). However, it is important to note that this does not mean that the significant changes seen were not real or valid. It simply means that definitive conclusions cannot be drawn from these findings.

In addition, differences observed between individuals within a given group were greater than the metabolic effect of the different diets (Mesnage et al, 2017a).

Due to these factors, the authors of the study concluded that the biological relevance of the statistically significant differences presented in this study was unclear and that it was not possible to draw firm conclusions of harm or safety regarding the effects of consumption of this GMO corn (Mesnage et al, 2017a).

The statistical analysis suggests that the way to resolve the uncertainties regarding any toxic effects arising from consumption of GMO NK603 corn is to perform an experiment with larger numbers of animals. This would increase the statistical power of the study such that even low-level toxic effects, as may have been seen here, are highlighted.

In contrast, clear results were obtained from a similar molecular profiling analysis (Mesnage et al, 2017b) of the liver tissues of rats from the same original long-term feeding study (Séralini et al, 2014) that had been given a very low dose of Roundup in their drinking water, below regulatory permitted levels. In the molecular profiling analysis, a protein composition profile (“proteomics”) and small molecule metabolite biochemical profile (“metabolomics”) investigation of the same liver samples showed that the Roundup-fed rats suffered from non-alcoholic fatty liver disease (NAFLD). The study is unique in that it is the first to show a causative link between consumption of Roundup at a real-world environmental dose and a serious disease condition (Mesnage et al, 2017b).

EU research study

After the publication of the initial animal feeding study in which rats were fed NK603 maize and very low doses of Roundup over a long-term two-year period (Séralini et al, 2014), the EU launched a two-year carcinogenicity study with GMO NK603 corn (G-TwYST, 2014).] The research project is called G-TwYST and the results are expected to be announced in 2018.

However, the Germany-based research group Testbiotech has raised questions about the scientific integrity and independence from industry of G-TwYST and its interconnected project, GRACE (Testbiotech, 2015). In 2013 a report published by Testbiotech showed that several members of the GRACE and G-TwYST research teams had strong ties with institutions that are financed by industry, either completely or to a large extent. Amongst those institutions were the International Life Sciences Institute (ILSI) and International Society for Biosafety Research (ISBR) (Bauer-Panskus and Then, 2013).

As evidence that the industry ties of the researchers might influence their presentation and interpretation of scientific results, Testbiotech pointed to (Testbiotech, 2015) a publication by the GRACE team of the results from a feeding study on rats fed a GMO Bt corn, MON810, over 90 days (Zeljenková et al, 2014). (GMO Bt crops are engineered to express Bt toxins, which are insecticides derived from a soil bacterium.) The GMO corn-fed rats had decreased total serum protein and pancreas weight, with the latter accompanied by increased blood glucose levels. These effects were statistically significant and dose-dependent, reinforcing the strength of the findings. Nevertheless, the authors dismissed them, among other effects of the GMO diet, as toxicologically irrelevant (Zeljenková et al, 2014). It is important that the G-TwYST research team avoid such practices in reporting the NK603 results.

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