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Roundup is an endocrine disruptor in rats

Date Added to website 27th August 2015


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Roundup is an endocrine disruptor in rats
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Note: this study actually names Roundup as the chemical substance tested in the lab. The findings are of course consistent with other studies of glyphosate, which is a known endocrine disruptor. What remains unclear is the extent to which the observed effects are down to the "active substance" (glyphosate). Some of the effects might be down to the adjuvants and other components in the commercial formulation -- or the degree of disruption might simply be exacerbated. In any case, this confirms that Roundup is an extremely dangerous chemical which should be banned immediately.

Analysis of endocrine disruption effect of Roundup® in adrenal gland of male rats
Aparamita Pandey, Medhamurthy Rudraiah,
Toxicology Reports
Volume 2, 2015, Pages 1075–1085
http://www.sciencedirect.com/science/article/pii/S221475001530041X

doi:10.1016/j.toxrep.2015.07.021

Key quote: "The findings that Roundup® treatment down regulates endogenous ACTH, is similar to the condition known as adrenal insufficiency in humans. This condition manifests as fatigue, anorexia, sweating, anxiety, shaking, nausea, heart palpitations and weight loss. Chronic adrenal insufficiency could be fatal, if untreated. A progressive increase in its prevalence has been observed in humans [8], while a very few studies relating to xenobiotic exposure and adrenal insufficiency development have been reported. The present study describes one of the possible mechanisms of adrenal insufficiency due to Roundup® and suggests more systematic studies, to investigate the area further."

Abstract

The effect of Roundup® on adrenal gland steroidogenesis and signaling pathway associated with steroid production was investigated. Doses of 10, 50, 100 and 250 mg/kg bw/d Roundup® were administered for two weeks to adult male rats. The 10 mg/kg bw/d dose which reduced circulatory corticosterone levels, but did not change food consumption and body weight, was selected for further study. The expression of cholesterol receptor (low density lipoprotein receptor), de novo cholesterol synthesis enzyme (3-hydroxy-3-methylglutaryl-coenzyme A synthase), hormone-sensitive lipase, steroidogenic acute regulatory protein (StAR) mRNA and phosphorylated form was decreased. Adrenocorticotropic hormone receptor (ACTH), melanocortin-2 receptor, expression was not changed but circulatory ACTH levels and adrenal cortex protein kinase A (PKA) activity were reduced. Surprisingly, exogenous ACTH treatment rescued steroidogenesis in Roundup®-treated animals. Apoptosis was evident at 250 mg/kg bw/d, but not at 10 mg/kg bw/d dose. These results suggest that Roundup® may be inhibitory to hypothalamic–pituitary axis leading to reduction in cyclic adenosine monophosphate (cAMP)/PKA pathway, StAR phosphorylation and corticosterone synthesis in the adrenal tissue.

Extract

4. Discussion

4.1. The effect of Roundup® is demonstrable at the low dose of 10 mg/kg bw/d, while toxic effects are evident at the high dose

The present study was conducted to examine EDC effect of Roundup® on adrenal gland steroidogenesis and to determine its mechanism of action. For this purpose, after determining the effect of ranges of doses on different parameters such as food consumption, body weight etc., the lowest dose was selected which was devoid of obvious toxic effects other than the EDC effect. A dose of 50 mg/kg bw/d Roundup® manifested significant loss in body weight but not in food consumption, while doses higher than 50 mg/kg bw/d caused decrease in food consumption as well as body weight of rats in the second week of the treatment. In previous studies, it was observed that Roundup® exposure did not change body weight of male Spraque–Dawley rats at a dose of 560 mg/ kg bw Roundup® for 91 days [4], while female Spraque–Dawley pregnant rats exposed orally to Roundup® with 500 mg/kg bw/d and higher doses for 10 days of pregnancy, reduced food consumption as well as body weight [12]. The discrepancy of the effect of Roundup® observed in the present as well as in other studies may be related to the differences in strains of rats, age of rats and duration of treatment employed. In order to circumvent possible effects of Roundup® on causing stress and other toxicity related effects, the doses of Roundup® higher than 50 mg/kg were not used for studying the endocrine disrupting effect.

Further, circulatory corticosterone levels in the doses 10 and 50 mg/kg bw/d were observed to be lower compared to the vehicle treated group. To verify that the decrease in corticosterone is due to possible EDC effect of Roundup®, another steroid hormone, testosterone level was also determined. The Roundup® has previously been reported to inhibit testosterone levels and the results in present study are in agreement with others [9], [5] and [32]. The result observed suggest suitability of the dose 10 mg/kb bw to assess the EDC effect of the Roundup®.

In cancer cell line studies, Roundup® has been reported to have apoptotic effect [7] and [27]. We examined one of the makers of apoptosis and performed TUNEL assay in adrenal glands and observed evidence for increased apoptosis at higher dose of 250 mg/kg bw/d compared to vehicle but not in 10 mg/kg bw/d treated rats. Therefore, decreased corticosterone level that was seen at low dose may not be attributed to toxicity or cell death induced by Roundup® treatment.

4.2. Roundup® negatively regulates StAR in the adrenal gland via cAMP/PKA pathway

The analysis of expression of genes associated with steroidogenesis such as StAR and P450scc, revealed no change in P450scc expression, but decrease in StAR expression, both at mRNA and protein levels. Moreover, phosphorylated StAR expression showed greater degree of down regulation compared to total protein and RNA levels. The difference between total StAR and phosphorylated StAR expression levels post Roundup® treatment, suggests gene regulation at two levels; one at transcription and another at phosphorylation process. Phosphorylation of StAR at serine 194/195 enhances the cholesterol transport capacity to at least 40–50% [2]. Significant down regulation in phosphorylated StAR levels observed in the present study suggest decreased pStAR could be responsible for down regulation of steroidogenesis in the adrenal gland of Roundup®-treated rats. Interestingly, in the present study higher lipid droplet accumulation was observed in Roundup®-treated rats and this is one of the characteristic of the StAR gene knockout mice [17]. The finding that phosphorylated CREB was lower, may be correlated to StAR expression down regulation, since CREB phosphorylation is involved in StAR transcription [24]. However to what extent that CREB down regulation contributed to decrease in StAR mRNA levels, remains to be explored. It should be pointed out that in the adrenal gland, ACTH upon binding to its cognate receptor Mc2r, activates cAMP/PKA pathway leading phosphorylation of CREB and StAR proteins [2]. In the adrenal gland of Roundup®-treated rats, the lowered PKA activity was reversed post ACTH treatment confirming cAMP/PKA pathway to be disrupted in the adrenal gland of Roundup®-treated animals.

4.3. Roundup® alters cholesterol homeostasis moderately

Roundup®-treated animals did not show altered total cholesterol levels in circulation at the lowest dose i.e., 10 mg/kg bw/d, but it was observed to be moderately higher in the adrenal gland. With this observation, it can be hypothesized that the cholesterol homeostasis within gland may be altered by increased cholesterol intake and/or de novo synthesis. Interestingly, there was down regulation of genes associated with cholesterol intake (Ldlr, Srb1) and de novo synthesis (Hmgcs, Hmgcr). Also, analysis revealed higher levels of esterified or stored form of cholesterol in the adrenal gland of Roundup®-treated rats. The data taken together suggest that increased levels of stored cholesterol might be due to lowered utilization and/or lowered hydrolysis of esterified form. Hsl expression was not significantly altered in the present study. Hsl or lipe gene is involved in cholesterol ester hydrolysis [22] and reported to be regulated by cAMP/PKA pathway [20]. Therefore, Roundup® appears to act via cAMP/PKA pathway and regulate StAR phosphorylation negatively leading to decrease in cholesterol utilization and increase in cholesterol stored in adrenal glands.

Interestingly, increase in the weight of adrenal gland was observed in Roundup®-treated animals, but its significance is not clear. The study examining diethylstilbestrol effects on the adrenal gland steroidogenesis has suggested steroid metabolic changes to be the contributing factor for increased weight [16].

4.4. Roundup® acts via HPA axis

Since Roundup® treatment at a dose of 10 mg/kg bw/d decreased corticosterone levels, it became of interest to examine the responsiveness of adrenal gland to exogenous ACTH treatment. The findings that the adrenal gland was responsive to ACTH treatment in Roundup® treated animals suggest that Roundup® acts at a site higher than the adrenal gland and this indirectly suggests that ACTH synthesis and/or release may be affected. Since the adrenal gland responsiveness to external ACTH was found to be similar or higher compared to vehicle treated animals suggest that the process of steroidogenesis in the adrenal gland appears to be intact post herbicide treatment. Therefore, it can be inferred that the stimulation of adrenal gland i.e., ACTH synthesis and release appears to be impaired rather than defects in the steroidogenesis machinery of the adrenal gland. A significantly higher increase in corticosterone levels in response to supraphysiological dose of ACTH was observed in Roundup®-treated rats compared to vehicle treated rats is perhaps due to higher stored cholesterol content in the adrenal gland of Roundup®-treated animals. The mechanism of action may vary with different experimental system e.g., [33] observed higher testosterone, LH and FSH concentrations in second generation or pups of Roundup®-treated Wistar rat dams in contrast to lowered testosterone observed in the present study as well as other studies where adult rats or different cell lines have been studied. Nonetheless, the results are in agreement with a pilot study of glyphosate exposure to Jundiá fish [6]. In sum, the data suggest Roundup® appears to act at the hypothalamo-pituitary level under in vivo conditions.

4.5. Implications of the study

The recent information regarding Roundup® and its metabolites detection in food, water and in human urine [1] signifies the relevance of toxicological studies as one presented. The findings that Roundup® treatment down regulates endogenous ACTH, is similar to the condition known as adrenal insufficiency in humans. This condition manifests as fatigue, anorexia, sweating, anxiety, shaking, nausea, heart palpitations and weight loss. Chronic adrenal insufficiency could be fatal, if untreated. A progressive increase in its prevalence has been observed in humans [8], while a very few studies relating to xenobiotic exposure and adrenal insufficiency development have been reported. The present study describes one of the possible mechanisms of adrenal insufficiency due to Roundup® and suggests more systematic studies, to investigate the area further.