Assessment of Glyphosate Induced Epigenetic Transgenerational Inheritance of Pathologies and Sperm Epimutations: Generational Toxicology

Abstract

Ancestral environmental exposures to a variety of factors and toxicants have been shown to promote the epigenetic transgenerational inheritance of adult onset disease. One of the most widely used agricultural pesticides worldwide is the herbicide glyphosate (N-(phosphonomethyl)glycine), commonly known as Roundup. There are an increasing number of conflicting reports regarding the direct exposure toxicity (risk) of glyphosate, but no rigorous investigations on the generational actions. The current study using a transient exposure of gestating F0 generation female rats found negligible impacts of glyphosate on the directly exposed F0 generation, or F1 generation offspring pathology. In contrast, dramatic increases in pathologies in the F2 generation grand-offspring, and F3 transgenerational great-grand-offspring were observed. The transgenerational pathologies observed include prostate disease, obesity, kidney disease, ovarian disease, and parturition (birth) abnormalities. Epigenetic analysis of the F1, F2 and F3 generation sperm identified differential DNA methylation regions (DMRs). A number of DMR associated genes were identified and previously shown to be involved in pathologies. Therefore, we propose glyphosate can induce the transgenerational inheritance of disease and germline (e.g. sperm) epimutations. Observations suggest the generational toxicology of glyphosate needs to be considered in the disease etiology of future generations.

Pesticides and transgenerational inheritance of pathologies: Designing, analysing and reporting rodent studies

“…Unfortunately, these methods are rarely applied and analysis problems are exacerbated by a lack of transparency about details of the design such as treatment allocation protocols and procedures for dealing with missing data at each stage. Re-analyses of a series of five studies [2][3][4][5][6] has filled a substantial gap in the literature by providing estimates of litter effects and how they can modify conclusions about treatment effects. We see, for example, that over 80% of all the variation in a puberty outcome in fourth generation rats (F3) can be attributed to 16 variation between the mothers at F2.…”

“…(iii) To generate F2 offspring, F1 rodents from all the experimental groups are either mated with rodents from different litters but from the same F0 experimental group ('dual breeding') [2][3][4][5][6], or exposed females are mated with unexposed males from outside the study ('matriline') [9], or exposed males are mated with unexposed females from outside the study ('patriline') [16]. All or some of these offspring are measured.…”

“…Turning to the design of the WSU studies [2][3][4][5][6], a careful reading of them indicates that they did not use random assignment; there is an imbalance between the numbers of treatment and control rats at F1 and some controls appear in the same three studies (S1 Table, note 5). This overlap between the control groups -and the fact that each of the five studies address essentially the same research question in the same way -means that it is both reasonable and efficient to combine the five studies into a single re-analysis with a set of outcomes defined in S1 Appendix.…”

“…-not estimable from the model as no observed problems at F3. (6) Treatment effect set to zero if z-statistic < 1.…”

“…An important, and widely ignored, issue in the analysis of these studies is the lack of independence between observational units after the first generation, an occurrence which is often referred to as the 'litter effect'. This is addressed by reanalysing data from five papers from the Center for Reproductive Biology, Washington State University (WSU), USA [2][3][4][5][6]. Each of these WSU papers analyses, in essentially the same way, epigenetic transgenerational inheritance after rats have been exposed to a pesticide (two herbicides, two insecticides and one fungicide).…”