Metabolite Profiling to Monitor Organochlorine Pesticide Exposure in HepG2 Cell Culture

Type 2 Diabetes Induced by Changes in Proteomic Profiling of Zebrafish Chronically Exposed to a Mixture of Organochlorine Pesticides at Low Concentrations

Effect of organochlorine pesticides (OCPs) mixtures on development of type 2 diabetes mellitus (T2DM) and the underlying mechanism, especially at protein levels, are largely unknown. We exposed a mixture of five OCPs to zebrafish at concentrations of 0, 0.05, 0.25, 2.5, and 25 μg/L for 12 weeks. Differentially expressed proteins (DEPs) were quantitatively identified in female zebrafish livers, and its functional study was conducted. The significantly high glucose and low insulin levels were observed only at 0.05 μg/L, linking to the different pattern of DEPs than other concentrations. A total of 1082 proteins was quantified, of which 321 proteins formed 6 clusters in protein dynamics analysis. The enriched pathways in cluster 3 showing distinct pattern of DEPs could explain the nonlinear response at 0.05 μg/L, indicating that OCP mixtures adversely affected proteins associated with mitochondrial function and energy metabolism. We proposed a feasible mechanism that decrease in expression of aldehyde dehydrogenase led to abnormal accumulation of aldehydes, reducing expression of glyceraldehyde 3-phosphate dehydrogenase, and resulting in disruption of glucose homeostasis. Our findings help to better understand the causality of T2DM by exposure to OCP mixtures and to identify biomarkers in the protein expression level.

Exposure to a low concentration of mixed organochlorine pesticides impairs glucose metabolism and mitochondrial function in L6 myotubes and zebrafish

More realistic effects on glucose metabolic dysfunction can be evaluated by applying organochlorine (OCP) mixtures than individual OCPs. We formulated an equal ratio mixture of five OCPs (chlordane, heptachlor, p,p'-dichlorodiphenyltrichloroethane, β-hexachlorocyclohexane, and hexachlorobenzene) and treated L6 myotubes with this OCP mixture to investigate effects on glucose uptake and the underlying mechanism. Exposure to the OCP mixture reduced 2-NBDG staining, representing glucose uptake, and stimulated the excessive production of reactive oxygen species (ROS). Reduced 2-NBDG uptake and ROS overproduction were compensated by insulin treatment. The expression of proteins such as IRβ, PI3K, and AKT was downregulated, indicating that ROS overproduction contributed to the inhibition of insulin-dependent glucose uptake. Reduction in mitochondria quantity and decreased expression levels of PGC-1α, PDH, and GLUT4 proteins were observed, suggesting that mitochondrial dysfunction played a causative role in the disruption of glucose uptake. The inhibition of glucose uptake and ROS overproduction caused by the OCP mixture were also found in zebrafish as an in vivo model. We demonstrated that exposure to the OCP mixture, even at the lowest concentration, perturbed glucose uptake, which was associated with mitochondrial dysfunction, suggesting that an OCP mixture could be a potential environmental factor in type 2 diabetes-related effects on skeletal muscles.

Investigation of steatosis profiles induced by pesticides using liver organ-on-chip model and omics analysis

Several studies have reported a correlation between pesticides exposure and metabolic disorders. Dichlorodiphenyltrichloroethane (DDT) and permethrin (PMT), two pesticides highly prevalent in the environment, have been associated to dysregulation of liver lipids and glucose metabolisms and non-alcoholic fatty liver disease (NAFLD). However, the effects of DDT/PMT mixtures and mechanisms mediating their action remain unclear. Here, we used multi-omic to investigate the liver damage induced by DDT, PMT and their mixture in rat liver organ-on-chip. Organ-on-chip allow the reproduction of in vivo-like micro-environment. Two concentrations, 15 and 150 μM, were used to expose the hepatocytes for 24 h under perfusion. The transcriptome and metabolome analysis suggested a dose-dependent effect for all conditions, with a profile close to control for pesticides low-doses. The comparison between control and high-doses detected 266/24, 256/24 and 1349/30 genes/metabolites differentially expressed for DDT150, PMT150 and Mix150 (DDT150/PMT150). Transcriptome modulation reflected liver inflammation, steatosis, necrosis, PPAR signaling and fatty acid metabolism. The metabolome analysis highlighted common signature of three treatments including lipid and carbohydrates production, and a decrease in amino acids and krebs cycle intermediates. Our study illustrates the potential of organ-on-chip coupled to multi-omics for toxicological studies and provides new tools for chemical risk assessment.

The use of non-targeted metabolomics to assess the toxicity of bifenthrin to juvenile Chinook salmon (Oncorhynchus tshawytscha)

An increase in urban and agricultural application of pyrethroid insecticides in the San Francisco Bay Estuary and Sacramento San Joaquin Delta has raised concern for the populations of several salmonids, including Chinook salmon (Oncorhynchus tshawytscha). Bifenthrin, a type I pyrethroid, is among the most frequently detected pyrethroids in the Bay-Delta watershed, with surface water concentrations often exceeding chronic toxicity thresholds for several invertebrate and fish species. To better understand the mechanisms of bifenthrin-induced neurotoxicity, juvenile Chinook salmon were exposed to concentrations of bifenthrin previously measured in the Delta. Non-targeted metabolomic profiles were used to identify transcriptomic changes in the brains of bifenthrin-exposed fish. Pathway analysis software predicted increased apoptotic, inflammatory, and reactive oxygen species (ROS) responses in Chinook following exposure to 0.15 and 1.50 μg/L bifenthrin for 96 h. These responses were largely driven by reduced levels of inosine, hypoxanthine, and guanosine. Subsequently, in the brain, the expression of caspase 3, a predominant effector for apoptosis, was significantly upregulated following exposure to 1.50 μg/L bifenthrin. This data suggests that metabolites involved in inflammatory and apoptotic responses, as well as those involved in maintaining proper neuronal function may be disrupted following sublethal exposure to bifenthrin and further suggests that additional population studies should focus on behavioral responses associated with impaired brain function.

Concentrations of legacy and new contaminants are related to metabolite profiles in Hudson Bay polar bears

There are very few metabolomics assessments based on field accumulated, uncontrolled contaminant exposures in wildlife, particularly in the Arctic. In the present study, targeted metabolomics and contaminant data were analyzed together to assess potential influences of contaminant exposure on the hepatic metabolome of male polar bears (n = 29) from the southern and western Hudson Bay (SHB and WHB respectively), Canada. The 29 metabolites identified as important in the differentiation of the two subpopulations after partial least squares discriminant analysis (PLS-DA) included phosphatidylcholines (PCs), acylcarnitines (ACs; involved in β-oxidation of fatty acids), and the fatty acid (FA) arachidonic acid (ARA). Perfluorinated alkyl substances, polybrominated diphenyl ethers, dichlorodiphenyldichloroethylene (p,p'-DDE) and some highly chlorinated ortho-polychlorinated biphenyl congeners were greater in the SHB bears and were consistently inversely correlated with discriminating ACs and PCs between the subpopulations. The concentrations of discriminatory, legacy organochlorine pesticides along with one tetrachlorobiphenyl were greater in the WHB and were directly correlated with the VIP-identified ACs and PCs. ARA, glycerophospholipid and several amino acid metabolic pathways were identified as different between subpopulations and/or were impacted. ARA is an important, conditionally essential, dietary n-6 FA and is also part of the inflammation response, and elevated concentrations in the SHB could be related to differences in chronic contaminant exposure and/or differences in diet and/or season, among a number of possible explanations. Dietary tracers (stable isotopes of carbon and nitrogen) were correlated with some discriminatory metabolites, supporting the hypothesis that dietary variation was also an important factor in the differentiation of the subpopulations. The results suggest linkages between contaminant exposure in Hudson Bay polar bears and elements of the hepatic metabolome, particularly those related to lipid metabolism.

Effects of DDT and permethrin on rat hepatocytes cultivated in microfluidic biochips: Metabolomics and gene expression study

Dichlorodiphenyl-trichloroethane (DDT) and permethrin (PMT) are amongst most prevalent pesticides in the environment. Although their toxicity has been extensively studied, molecular mechanisms and metabolic effects remain unclear, including in liver where their detoxification occurs. Here, we used metabolomics, coupled to RT-qPCR analysis, to examine effects of DDT and PMT on hepatocytes cultivated in biochips. At 150 μM, DDT caused cell death, cytochrome P450 induction and modulation of estrogen metabolism. Metabolomics analysis showed an increase in some lipids and sugars after 6 h, and a decrease in fatty acids (tetradecanoate, octanoate and linoleate) after 24 h exposure. We also found a change in expression associated with genes involved in hepatic estrogen, lipid, and sugar metabolism. PMT at 150 μM perturbed lipid/sugar homeostasis and estrogen signaling pathway, between 2 and 6 h. After 24 h, lipids and sugars were found to decrease, suggesting continuous energy demand to detoxify PMT. Finally, at 15 μM, DDT and PMT appeared to have a small effect on metabolism and were detoxified after 24 h. Our results show a time-dependent perturbation of sugar/lipid homeostasis by DDT and PMT at 150 μM. Furthermore, DDT at high dose led to cell death, inflammatory response and oxidative stress.