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Obesogens beyond Vertebrates: Lipid Perturbation by Tributyltin in the Crustacean Daphnia magna.

Jordão R, Casas J, Fabrias G, Campos B, Piña B, Lemos MF, Soares AM, Tauler R, Barata C - Environ. Health Perspect. (2015)

Bottom Line: The analysis of obesogenic effects in invertebrates is limited by our poor knowledge of the regulatory pathways of lipid metabolism.TBT's disruptive effects translated into a lower fitness for offspring and adults.These findings indicate the presence of obesogenic effects in a nonvertebrate species.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA), Spanish Research Council (IDAEA, CSIC), Barcelona, Spain.

ABSTRACT

Background: The analysis of obesogenic effects in invertebrates is limited by our poor knowledge of the regulatory pathways of lipid metabolism. Recent data from the crustacean Daphnia magna points to three signaling hormonal pathways related to the molting and reproductive cycles [retinoic X receptor (RXR), juvenile hormone (JH), and ecdysone] as putative targets for exogenous obesogens.

Objective: The present study addresses the disruptive effects of the model obesogen tributyltin (TBT) on the lipid homeostasis in Daphnia during the molting and reproductive cycle, its genetic control, and health consequences of its disruption.

Methods: D. magna individuals were exposed to low and high levels of TBT. Reproductive effects were assessed by Life History analysis methods. Quantitative and qualitative changes in lipid droplets during molting and the reproductive cycle were studied using Nile red staining. Lipid composition and dynamics were analyzed by ultra-performance liquid chromatography coupled to a time-of-flight mass spectrometer. Relative abundances of mRNA from different genes related to RXR, ecdysone, and JH signaling pathways were studied by qRT-PCR.

Results and conclusions: TBT disrupted the dynamics of neutral lipids, impairing the transfer of triacylglycerols to eggs and hence promoting their accumulation in adult individuals. TBT's disruptive effects translated into a lower fitness for offspring and adults. Co-regulation of gene transcripts suggests that TBT activates the ecdysone, JH, and RXR receptor signaling pathways, presumably through the already proposed interaction with RXR. These findings indicate the presence of obesogenic effects in a nonvertebrate species.

No MeSH data available.


Quantitative assessment of lipid droplets in Daphnia magna individuals. (A) Lateral partial view under fluorescent microscopy of adolescent females just after molting and releasing the first brood of eggs across different food ration regimes (starving, low food, and high food) and treatments [control and TBT H (1 μg/L)]; top left, bright field microscopy image of a female, with the studied area indicated by a rectangle. Lipid droplets stained with Nile red are in green. (B) Nile red fluorescence [mean ± SE fluorescence units (FU); n = 5–10] in 48-hr females across starving, low, and high food rations, and (C) across TBT L and TBT H at low and high food rations. (D) Nile red fluorescence (mean ± SE; n = 5–10) measured at different time points within the adolescent instar and just after molting across TBT L and TBT H at high food rations. In B and C, different letters indicate significant (p < 0.05) differences among food levels or across food levels and TBT treatments, respectively, following ANOVA and Tukey’s post hoc tests. Further details are in the text.
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f1: Quantitative assessment of lipid droplets in Daphnia magna individuals. (A) Lateral partial view under fluorescent microscopy of adolescent females just after molting and releasing the first brood of eggs across different food ration regimes (starving, low food, and high food) and treatments [control and TBT H (1 μg/L)]; top left, bright field microscopy image of a female, with the studied area indicated by a rectangle. Lipid droplets stained with Nile red are in green. (B) Nile red fluorescence [mean ± SE fluorescence units (FU); n = 5–10] in 48-hr females across starving, low, and high food rations, and (C) across TBT L and TBT H at low and high food rations. (D) Nile red fluorescence (mean ± SE; n = 5–10) measured at different time points within the adolescent instar and just after molting across TBT L and TBT H at high food rations. In B and C, different letters indicate significant (p < 0.05) differences among food levels or across food levels and TBT treatments, respectively, following ANOVA and Tukey’s post hoc tests. Further details are in the text.

Mentions: Nile red staining of lipid droplets. The complex dynamics of lipid droplet dynamics in D. magna is summarized in Figure 1. Nile red staining showed significantly higher levels of fluorescence in females cultured at high food levels than in those reared at low food levels or starved (F2,27 = 144.1, p < 0.05; Figure 1A; the quantification of results are shown in Figure 1B). Exposure to TBT H significantly increased Nile red fluorescence in females within (F2,54 = 55.9, p < 0.05) and across (F2,54 = 22.7, p < 0.05) food levels at TBT H, such effects being more pronounced at high food levels (Figure 1A,C). The dynamics of lipid droplets during the first reproductive cycle in the presence or absence of TBT is shown in Figure 1D. In untreated females (control) or those exposed to TBT L, Nile red fluorescence increased during the intermolt period, peaked at 24 hr, and decreased just after molting and releasing of their first brood of eggs (48 hr). Exposure to TBT H significantly increased Nile red fluorescence, starting at 16 hr of exposure, reaching a maximal level at 24 hr (corresponding to twice the levels of control or TBT L samples), and remaining at this high level even after molting (48 hr). Statistical analyses showed significant (p < 0.05) effects of sampling period (F4,60 = 104.3), treatment (F2,60 = 31.5), and their interaction (F8,60 = 10.1). Whether such changes correspond to enhanced levels of TG was further studied by analyzing changes in the whole lipidome.


Obesogens beyond Vertebrates: Lipid Perturbation by Tributyltin in the Crustacean Daphnia magna.

Jordão R, Casas J, Fabrias G, Campos B, Piña B, Lemos MF, Soares AM, Tauler R, Barata C - Environ. Health Perspect. (2015)

Quantitative assessment of lipid droplets in Daphnia magna individuals. (A) Lateral partial view under fluorescent microscopy of adolescent females just after molting and releasing the first brood of eggs across different food ration regimes (starving, low food, and high food) and treatments [control and TBT H (1 μg/L)]; top left, bright field microscopy image of a female, with the studied area indicated by a rectangle. Lipid droplets stained with Nile red are in green. (B) Nile red fluorescence [mean ± SE fluorescence units (FU); n = 5–10] in 48-hr females across starving, low, and high food rations, and (C) across TBT L and TBT H at low and high food rations. (D) Nile red fluorescence (mean ± SE; n = 5–10) measured at different time points within the adolescent instar and just after molting across TBT L and TBT H at high food rations. In B and C, different letters indicate significant (p < 0.05) differences among food levels or across food levels and TBT treatments, respectively, following ANOVA and Tukey’s post hoc tests. Further details are in the text.
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4529017&req=5

f1: Quantitative assessment of lipid droplets in Daphnia magna individuals. (A) Lateral partial view under fluorescent microscopy of adolescent females just after molting and releasing the first brood of eggs across different food ration regimes (starving, low food, and high food) and treatments [control and TBT H (1 μg/L)]; top left, bright field microscopy image of a female, with the studied area indicated by a rectangle. Lipid droplets stained with Nile red are in green. (B) Nile red fluorescence [mean ± SE fluorescence units (FU); n = 5–10] in 48-hr females across starving, low, and high food rations, and (C) across TBT L and TBT H at low and high food rations. (D) Nile red fluorescence (mean ± SE; n = 5–10) measured at different time points within the adolescent instar and just after molting across TBT L and TBT H at high food rations. In B and C, different letters indicate significant (p < 0.05) differences among food levels or across food levels and TBT treatments, respectively, following ANOVA and Tukey’s post hoc tests. Further details are in the text.
Mentions: Nile red staining of lipid droplets. The complex dynamics of lipid droplet dynamics in D. magna is summarized in Figure 1. Nile red staining showed significantly higher levels of fluorescence in females cultured at high food levels than in those reared at low food levels or starved (F2,27 = 144.1, p < 0.05; Figure 1A; the quantification of results are shown in Figure 1B). Exposure to TBT H significantly increased Nile red fluorescence in females within (F2,54 = 55.9, p < 0.05) and across (F2,54 = 22.7, p < 0.05) food levels at TBT H, such effects being more pronounced at high food levels (Figure 1A,C). The dynamics of lipid droplets during the first reproductive cycle in the presence or absence of TBT is shown in Figure 1D. In untreated females (control) or those exposed to TBT L, Nile red fluorescence increased during the intermolt period, peaked at 24 hr, and decreased just after molting and releasing of their first brood of eggs (48 hr). Exposure to TBT H significantly increased Nile red fluorescence, starting at 16 hr of exposure, reaching a maximal level at 24 hr (corresponding to twice the levels of control or TBT L samples), and remaining at this high level even after molting (48 hr). Statistical analyses showed significant (p < 0.05) effects of sampling period (F4,60 = 104.3), treatment (F2,60 = 31.5), and their interaction (F8,60 = 10.1). Whether such changes correspond to enhanced levels of TG was further studied by analyzing changes in the whole lipidome.

Bottom Line: The analysis of obesogenic effects in invertebrates is limited by our poor knowledge of the regulatory pathways of lipid metabolism.TBT's disruptive effects translated into a lower fitness for offspring and adults.These findings indicate the presence of obesogenic effects in a nonvertebrate species.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA), Spanish Research Council (IDAEA, CSIC), Barcelona, Spain.

ABSTRACT

Background: The analysis of obesogenic effects in invertebrates is limited by our poor knowledge of the regulatory pathways of lipid metabolism. Recent data from the crustacean Daphnia magna points to three signaling hormonal pathways related to the molting and reproductive cycles [retinoic X receptor (RXR), juvenile hormone (JH), and ecdysone] as putative targets for exogenous obesogens.

Objective: The present study addresses the disruptive effects of the model obesogen tributyltin (TBT) on the lipid homeostasis in Daphnia during the molting and reproductive cycle, its genetic control, and health consequences of its disruption.

Methods: D. magna individuals were exposed to low and high levels of TBT. Reproductive effects were assessed by Life History analysis methods. Quantitative and qualitative changes in lipid droplets during molting and the reproductive cycle were studied using Nile red staining. Lipid composition and dynamics were analyzed by ultra-performance liquid chromatography coupled to a time-of-flight mass spectrometer. Relative abundances of mRNA from different genes related to RXR, ecdysone, and JH signaling pathways were studied by qRT-PCR.

Results and conclusions: TBT disrupted the dynamics of neutral lipids, impairing the transfer of triacylglycerols to eggs and hence promoting their accumulation in adult individuals. TBT's disruptive effects translated into a lower fitness for offspring and adults. Co-regulation of gene transcripts suggests that TBT activates the ecdysone, JH, and RXR receptor signaling pathways, presumably through the already proposed interaction with RXR. These findings indicate the presence of obesogenic effects in a nonvertebrate species.

No MeSH data available.