Peroxisome Deficiency Dysregulates Fatty Acid Oxidization and Exacerbates Lipotoxicity in β Cells

The peroxisome: an update on mysteries 3.0

Peroxisomes are highly dynamic, oxidative organelles with key metabolic functions in cellular lipid metabolism, such as the β-oxidation of fatty acids and the synthesis of myelin sheath lipids, as well as the regulation of cellular redox balance. Loss of peroxisomal functions causes severe metabolic disorders in humans. Furthermore, peroxisomes also fulfil protective roles in pathogen and viral defence and immunity, highlighting their wider significance in human health and disease. This has sparked increasing interest in peroxisome biology and their physiological functions. This review presents an update and a continuation of three previous review articles addressing the unsolved mysteries of this remarkable organelle. We continue to highlight recent discoveries, advancements, and trends in peroxisome research, and address novel findings on the metabolic functions of peroxisomes, their biogenesis, protein import, membrane dynamics and division, as well as on peroxisome-organelle membrane contact sites and organelle cooperation. Furthermore, recent insights into peroxisome organisation through super-resolution microscopy are discussed. Finally, we address new roles for peroxisomes in immune and defence mechanisms and in human disorders, and for peroxisomal functions in different cell/tissue types, in particular their contribution to organ-specific pathologies.

Maternal protein deficiency impairs peroxisome biogenesis and leads to oxidative stress and ferroptosis in liver of fetal growth restriction offspring

Maternal protein malnutrition leads to liver dysfunction and increases susceptibility to nonalcoholic fatty liver disease in adult fetal growth restriction (FGR) offspring, yet the underlying mechanism remains unknown. Peroxisomes play vital roles in fatty acid β-oxidation (FAO) and detoxification of reactive oxygen species (ROS). Using a well-defined rat model, the peroxins (PEXs), fatty acid metabolic enzymes, and oxidase stress regulators were investigated in the liver of FGR offspring. The results revealed that PEX3, 11b, 14, and 19 were obviously reduced in the fetal liver and lasted to adulthood, suggesting a decrease in the biogenesis and division of peroxisomes. FA metabolism enzymes and ferroptosis regulators were deregulated. To further investigate this association, small interfering RNA was employed to achieve knockdown (KD) of PEX14 in BRL cells (a rat hepatocyte line). PEX14 KD led to dysregulation of PEXs and long-chain FAs accumulation. PEX14 deficiency caused ROS accumulation and lipid peroxidation, finally induced regulated cell death (including apoptosis, autophagy, and ferroptosis). Double knock down (DKD) of PEX14 and fatty acyl-CoA reductase 1 (FAR1) revealed that PEX14 KD-induced ferroptosis was related with enhanced FAR1 level. DKD of PEX14 and Atg5 further confirmed that PEX14 KD-induced cell death was partly autophagy-dependent. Overall, these data demonstrate a vital role for PEX14 in maintaining peroxisome function and liver physiology, and suggest that hepatocyte peroxisome defects partly explain liver dysplasia and lipid metabolism disorders in fetal original liver disease.

Peroxins in Peroxisomal Receptor Export System Contribute to Development, Stress Response, and Virulence of Insect Pathogenic Fungus Beauveria bassiana

In filamentous fungi, recycling of receptors responsible for protein targeting to peroxisomes depends on the receptor export system (RES), which consists of peroxins Pex1, Pex6, and Pex26. This study seeks to functionally characterize these peroxins in the entomopathogenic fungus Beauveria bassiana. BbPex1, BbPex6, and BbPex26 are associated with peroxisomes and interact with each other. The loss of these peroxins did not completely abolish the peroxisome biogenesis. Three peroxins were all absolutely required for PTS1 pathway; however, only BbPex6 and BbPex26 were required for protein translocation via PTS2 pathway. Three gene disruption mutants displayed the similar phenotypic defects in assimilation of nutrients (e.g., fatty acid, protein, and chitin), stress response (e.g., oxidative and osmotic stress), and virulence. Notably, all disruptant displayed significantly enhanced sensitivity to linoleic acid, a polyunsaturated fatty acid. This study reinforces the essential roles of the peroxisome in the lifecycle of entomopathogenic fungi and highlights peroxisomal roles in combating the host defense system.

EPHX2 Inhibits Colon Cancer Progression by Promoting Fatty Acid Degradation

Tumor cells use metabolic reprogramming to keep up with the need for bioenergy, biosynthesis, and oxidation balance needed for rapid tumor division. This phenomenon is considered a marker of tumors, including colon cancer (CRC). As an important pathway of cellular energy metabolism, fatty acid metabolism plays an important role in cellular energy supply and oxidation balance, but presently, our understanding of the exact role of fatty acid metabolism in CRC is limited. Currently, no lipid metabolism therapy is available for the treatment of CRC. The establishment of a lipidmetabolism model regulated by oncogenes/tumor suppressor genes and associated with the clinical characteristics of CRC is necessary to further understand the mechanism of fatty acid metabolism in CRC. In this study, through multi-data combined with bioinformatic analysis and basic experiments, we introduced a tumor suppressor gene, EPHX2, which is rarely reported in CRC, and confirmed that its inhibitory effect on CRC is related to fatty acid degradation.