Energy reserves and cellular energy allocation studies: Should food supply be provided?

Under stressful conditions (toxicity), organisms often try to detoxify by mobilizing available energy sources with costs to various metabolic functions, such as growth or reproduction. Cellular energy allocation (CEA) is a methodology used to evaluate the energetic status and which relates with organisms’ overall condition and response to toxic stress. It consists of the integration of the energy reserves available (Ea) and energy consumption (Ec). The effects of different sublethal concentrations (0.828, 0.0828, and 0.00828 mg/l) of cadmium (Cd) was evaluated on the total energy budget of African catfish (Clarias gariepinus) juveniles over 56-day period of exposure. A total of 180 C. gariepinus were exposed under the static renewal assay, and parameters measured were the total energy reserves available (protein, carbohydrate and lipid budgets) and the energy consumption (based on electron transport system activity assay) being further integrated to obtain the CEA. The Bradford method, Phenol-sulphuric acid method and Bligh and Dyer method were used to evaluate the protein, carbohydrate, and lipid contents, respectively of the test animals. Significant changes (p<0.05) in energy reserves and energy consumption were observed upon Cd exposure. Among the three energy reserves obtained, carbohydrate offered the least energy fraction (0.23%), and followed by protein (20.27%). The highest energy fraction was offered by lipid (79.50%). The effect of cadmium brought about a tremendous decrease in Carbohydrate (from 0.04 kj/g in day 7 to 0.01 kj/g in day 28). Lipid always stepped up (from 9.84 kj/g on day 7 to 34.48 jk/g on day 28) to compliment energy loss whenever carbohydrate was exhausted. Protein was least affected (from 1.78 kj/g on day 7 to 1.23 kj/g on day 28) with mild reduction in its reserve. Increased energy consumption was recorded amongst the exposed groups, with the highest concentration (0.828 mg/l) offering the most Ec of 58.54 kj/g on day 56. Significant reduction in CEA occurred across the exposed groups as Ea and Ec dwindled.  These results have shown the adverse effects of Cd on the energy status of C. gariepinus and the sensitive effectiveness of CEA technique in assessing the toxic effects of metallic pollutants on freshwater animals. Key words: Clarias gariepinus, cellular energy allocation, energy available, electron transport system, biomarker, energy metabolism. &nbsp

Event Abstract Back to Event Oxidative stress responses and cellular energy allocation changes in microalgae following exposure to different human antibiotics Adeolu O. Aderemi1*, Sara C. Novais2, Luís M. Alves2, Marco F. Lemos2 and Colin Hunter1 1 School of Engineering and Built Environment, Glasgow Caledonian University, United Kingdom 2 MARE – Marine and Environmental Sciences Centre, ESTM, Instituto Politécnico de Leiria, Portugal The continuous discharge of pharmaceutical residues into the aquatic environment has become a growing concern due to the threat they represent to non-target organisms. Green algae as primary producers are vital for the sustenance of the aquatic ecosystem. In an effort to assess the individual effect of selected human antibiotics on microalgae, Raphidocelis subcapitata was exposed to sublethal levels of erythromycin, clarithromycin, ciprofloxacin, and sulfamethoxazole for 120 h. The effects were assessed by analyzing cell yield and several biochemical parameters related with: 1) antioxidant capacity and oxidative damage by measuring superoxide dismutase (SOD) enzyme activity and lipid peroxidation (LPO) levels; and 2) cellular energy allocation (CEA) by quantifying the content in energy reserves (total lipid, carbohydrate and protein), which represents the energy available (Ea), and the electron transport system activity that represents a measure of oxygen and energy consumption (Ec). Growth inhibitory concentrations of sulfamethoxazole (18-30%) and clarithromycin (28.7%) were found to elicit a considerable increase in energy consumption, thereby causing a significant decrease in the cellular energy allocation. The elevated Ec can be a result of the need to respond to oxidative stress occurring under those conditions since a significant increase in SOD activity was observed for both drugs at these levels. However, with sulfamethoxazole the antioxidant response does not seem to be enough to cope with the reactive oxygen species and prevent oxidative damage, given the elevated LPO levels observed. Regarding erythromycin, a significant concentration dependent decrease in the total carbohydrate content was observed, along with a significant increase in Ec, decrease in CEA and induction of SOD activity, at concentrations inhibiting growth by 17% and 39%. Ciprofloxacin, at the highest concentration tested, caused 28% inhibition of cell yield accompanied by a reduction in CEA. Moreover, at the lowest concentrations of this drug, a stimulatory effect on growth was observed (up to 16%), which was also highly correlated with the increase in the net energy budget (CEA). By revealing stress effects of R. subcapitata at the cellular level, induced at sublethal concentrations of the tested antibiotic drugs, this study suggests CEA as a reliable indicator of the organisms’ physiological status. Acknowledgements This study had the support of the Fundação para a Ciência e a Tecnologia (FCT) Strategic Project UID/MAR/04292/2013 granted to MARE. Sara C. Novais wish to acknowledge the financial support given by FCT (SFRH/BPD/94500/2013). Adeolu Aderemi was supported by a PhD studentship from SEBE, GCU. Keywords: Ecotoxicology, pharmaceuticals, Microalgae, biomarkers, Growth inhibition Conference: IMMR | International Meeting on Marine Research 2016, Peniche, Portugal, 14 Jul - 15 Jul, 2016. Presentation Type: Poster presentation Topic: Biodiversity, Conservation and Coastal Management Citation: Aderemi AO, Novais SC, Alves LM, Lemos MF and Hunter C (2016). Oxidative stress responses and cellular energy allocation changes in microalgae following exposure to different human antibiotics. Front. Mar. Sci. Conference Abstract: IMMR | International Meeting on Marine Research 2016. doi: 10.3389/conf.FMARS.2016.04.00005 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 14 May 2016; Published Online: 12 Jul 2016. * Correspondence: Mr. Adeolu O Aderemi, School of Engineering and Built Environment, Glasgow Caledonian University, Glasgow, United Kingdom, Adeolu.Aderemi@gcu.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Adeolu O Aderemi Sara C Novais Luís M Alves Marco F Lemos Colin Hunter Google Adeolu O Aderemi Sara C Novais Luís M Alves Marco F Lemos Colin Hunter Google Scholar Adeolu O Aderemi Sara C Novais Luís M Alves Marco F Lemos Colin Hunter PubMed Adeolu O Aderemi Sara C Novais Luís M Alves Marco F Lemos Colin Hunter Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Under stressful conditions, organisms often try to detoxify by mobilizing certain energy sources with costs to various functions, e.g. growth or reproduction. Cellular energy allocation (CEA) is a commonly used methodology to evaluate the energetic status of an organism. In the present study, the effects of copper (Cu) and silver (Ag) were evaluated on the total energy budget of Enchytraeus crypticus (Oligochaeta) over periods of exposure (0-2, 2-4 and 4-8days). The parameters measured were the total energy reserves available (protein, carbohydrate and lipid budgets) and the energy consumption (based on electron transport system activity) being further integrated to obtain the CEA. Results showed that Enchytraeids responded differently to Ag and Cu, mobilizing lipids and proteins in response to Ag and carbohydrates and proteins in response to Cu. Overall, it was possible to distinguish between effect concentrations (reproduction effect concentrations-EC10 and EC50), with EC10 causing an increase in energy consumption (Ec); while for the EC50, the increase in Ec is followed by a steep decrease in Ec, with a corresponding decrease in CEA in the longer exposure periods. These results could be linked with effects at higher levels of biological organization (effects on reproduction) providing evidences that CEA can be used as faster and sensitive endpoints towards metal exposure in E. crypticus.

Seasonal and spatial patterns in cellular energy allocation in the estuarine mysid Neomysis integer (Crustacea: Mysidacea) of the Scheldt estuary (The Netherlands)

Cellular energy allocation (CEA) is a methodology developed to evaluate the effects of toxic stress on the metabolic balance of organisms. It consists of the integration of the energy reserves available (Ea; total carbohydrate, protein and lipid content) and energy consumption (Ec) estimated by measuring electron transport system (ETS) activity. The main goal of the present study was to evaluate the effects on the energy budget of the soil invertebrate Enchytraeus albidus (Oligochaeta) after exposure to dimethoate, atrazine, and carbendazim (by testing the reproduction 10% effective concentration, 20% effective concentration, 50% effective concentration and 90% effective concentration) over periods of time from 0 d to 2 d, 4 d, and 8 d. Significant changes in energy reserves were observed with all pesticides, together with effects on energy consumption. Carbohydrates were the first energy source to be used, and clear depletions occurred with all pesticides. Energy consumption increased generally over longer exposures and with higher concentrations of the pesticides. Although clear changes were seen in the individual energy reserve budgets and on Ec, CEA was only significantly reduced with atrazine exposures longer than 4 d. The nearly absent effects on CEA at concentrations known to affect reproduction indicate that the reduction in reproduction is not likely to be caused by a reduction in the total energy budget during the first 8 d of exposure. The present study showed the importance of complementing CEA interpretation with the individual Ea and Ec parameters, in particular if these show opposite balances. The Ea and Ec results were in good agreement with gene transcription results from a parallel study, hence suggesting translation and showing the advantage of combining various effect levels to advance the understanding of mechanisms.

Thermal stress effects on energy resource allocation and oxygen consumption rate in the juvenile sea cucumber, Holothuria scabra (Jaeger, 1833)

Chapter 8 - Cellular Energy Allocation

Exposure of Enchytraeus albidus to Cd and Zn – Changes in cellular energy allocation (CEA) and linkage to transcriptional, enzymatic and reproductive effects

Effects of nickel and copper on Enchytraeus albidus (Oligochaeta) were investigated using the cellular energy allocation approach. This methodology is used to evaluate the energetic status of an organism and is indicative of its overall condition. Enchytraeids were exposed to the reproduction Effect Concentrations (EC50 and EC90), and the parameters measured were the total energy reserves available (protein, carbohydrate and lipid budgets) and the energy consumption [based on electron transport system activity] which were further integrated to obtain the cellular energy allocation over different periods of exposure (0-2, 2-4 and 4-8 days). Carbohydrates (in comparison to lipids and proteins) were the only energy source mobilized in the case of nickel within 8 days of exposure. For copper exposure, protein budgets were also strongly reduced. Energy consumption increased in a time and dose-dependent way for copper and in the longer exposure period (4-8 days) at the EC90 for Ni exposure, indicating that this is a good biomarker for effects of short-time metal exposure, while cellular energy allocation was only significantly reduced for the EC90 of copper (4-8 days) and EC50 of nickel (2-4 days). The effects of nickel at concentrations causing 50 and 90 % decrease in reproduction were likely not due to the changes in cellular energy allocation within 8 days of exposure.

The cellular energy allocation (CEA) methodology was used to assess the adverse effects of toxic stress on the energy budget of test organisms. This biochemical assay is quantified by determining changes in the available energy reserves, Ea (total carbohydrate, protein, and lipid content) and the energy consumption, Ec (electron transport activity). The CEA methodology was fully explored by using neonates of Daphnia magna exposed for 96 h to six model toxicants (CdCl2, K2Cr2O7, tributyltin chloride, linear alkylbenzene sulfonic acid, sodium pentachlorophenolate, and 2,4-dichlorophenoxyacetic acid). To evaluate the ecological relevance of the CEA parameter, we compared the suborganismal responses with population-level parameters (obtained from 21-d life-table experiments) such as the intrinsic rate of natural increase (rm) and the mean total offspring per female. The observed reductions in CEA values were both the result of a decrease in Ea and an increase in Ec. From all individual CEA components analyzed, the lipid reserve criterion was the most sensitive endpoint studied. Both the CEA-based lowest-observed-adverse-effect concentration (LOAEC) values and the effective concentration of 10% (EC10) values were significantly (p < 0.05) and linearly correlated with the chronic (21-d) LOAEC and EC10 values based on growth, survival, and reproduction. This relationship demonstrates the usefulness of the methodology to predict long-term effects. Furthermore, significant (p < 0.0001) sigmoid relationships between the 96-h CEA value (expressed as percentage relative to the control) and population-level effects were observed.

Freshwater mussel populations are declining worldwide, but the causes and mechanisms of these declines are poorly understood. Biomarkers that reflect the health or fitness of individual mussels are needed for understanding causes of mussel declines, but existing approaches each have weaknesses. We conducted two laboratory experiments to examine the utility of the cellular energy allocation (CEA) model for assessing juvenile mussel responses to stress induced by food limitation. The CEA assesses the energetic status of an organism as CEA = Ea/Ec, where Ea is available energy reserves (total carbohydrates, protein, and lipids) and Ec is energy consumption, estimated using electron transport system (ETS) activity as a proxy for respiration rate and metabolic demands. Experiment 1 evaluated the effects of food abundance (fed and unfed) on CEA and its component biomarkers at a single temperature (mean = 26.8°C) over 23 days. Experiment 2 evaluated the response of ETS activity to food abundance (unfed, low food, high food) in relation to temperature (20, 25, 30°C) over 27 days. In Experiment 1, most constituent biomarkers were lower in unfed mussels, but CEA did not differ between treatments because Ea and Ec declined by similar magnitudes. In Experiment 2, ETS declined with decreasing food abundance, but only at 25 and 30°C, and ETS was affected by temperature only in the unfed treatment. The ETS enzyme assay can be an informative biomarker of stress, but it requires accounting for confounding factors such as food, temperature, and species identity, as well as the lag time in response of ETS relative to respiration rate. Despite its value as a robust, holistic stress biomarker in other organisms, CEA may have limited usefulness for bivalves because of their tendency to reduce feeding and energy consumption under stress, which results in a simultaneous decline in Ea and Ec.

Oxidative stress responses and cellular energy allocation changes in microalgae following exposure to widely used human antibiotics

Plasticity of energy reserves and metabolic performance of discus fish (Symphysodon aequifasciatus) exposed to low-temperature stress

Evaluation of cadmium toxicity in Penaeus monodon using ecotoxicological tools: A foundational step for deriving seawater quality criteria.

Long-term exposure of the isopod Porcellionides pruinosus to nickel: Costs in the energy budget and detoxification enzymes