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Hepatic PPARα dysfunction in porcine sepsis

ABSTRACT: Despite decades of research, sepsis remains one of the most urgent unmet medical needs. Clinical trials in sepsis have mainly focused on targeting the inflammatory pathway, however, recent data indicate that sepsis should also be seen as a metabolic disease. Targeting metabolic dysregulations that take place in sepsis might uncover novel therapeutic opportunities to treat human sepsis patients. The role of PPARα in liver dysfunction during sepsis has recently been described, and restoring PPARα signaling proves to be successful in murine sepsis. To find out whether this therapy might also be helpful in human sepsis patients, we analyzed metabolic perturbations in liver of a porcine fecal peritonitis model. Resuscitation with fluids, antimicrobial therapy and abdominal drainage were applied to the pigs in order to mimic human clinical care. By using RNA-seq, we detected problems with PPARα signaling in the livers of septic pigs and reduced PPARα levels correlated well with disease severity. As PPARα regulates the expression of many genes involved in FA oxidation, reduced expression of these target genes concomitant with increased FFAs in plasma and ectopic lipid deposition in the liver was observed. The results obtained in pigs are in agreement with earlier observations in mice and support the potential of targeting defective PPARα signaling in the clinic.

ORGANISM(S): Sus scrofa

PROVIDER: GSE218636 | GEO | 2022/11/28

REPOSITORIES: GEO

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Project description:Nuclear receptor activation in liver leads to coordinated alteration of the expression of multiple gene products with attendant phenotypic changes of hepatocytes. Peroxisome proliferators including endogenous fatty acids, environmental chemicals, and drugs induce a multi-enzyme metabolic response that affects lipid and fatty acid processing. We studied the signaling network for the peroxisome proliferator-associated receptor alpha (PPARα) in primary human hepatocytes using the selective PPARα ligand, GW7647. We measured gene expression over multiple concentrations and times and conducted ChIP-seq studies at 2 and 24 hours to assess genomic binding of PPARα. Over all treatments there were 192 genes differentially expressed. Of these only 51% showed evidence of PPARα binding – either directly at PPARα response elements or via alternative mechanisms. Almost half of regulated genes had no PPARα binding. We then developed two novel bioinformatics methods to visualize the dose-dependent activation of both the transcription factor circuitry for PPARα and the downstream metabolic network in relation to functional annotation categories. Available databases identified several key transcription factors involved with the non-genomic targets after GW7647 treatment, including SP1, STAT1, ETS1, ERα, and HNF4α. The linkage from PPARα binding through gene expression likely requires intermediate protein kinases to activate these transcription factors. We found enrichment of functional annotation categories for organic acid metabolism and cell lipid metabolism among the differentially expressed genes. Lipid transport processes showed enrichment at the highest concentration of GW7647 (10μM). While our strategy for mapping transcriptional networks is evolving, these approaches are necessary in moving from toxicogenomic methods that derive signatures of activity to methods that establish pathway structure, showing the coordination of the activated nuclear receptor with other signaling pathways. Primary hepatocytes from four donors were exposed to 0, 0.001, 0.01, 0.1, 1.0, or 10.0μM GW7647 for 2, 6, 12, 24, or 72 hours.

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Hepatic PPARα dysfunction in porcine sepsis

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