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Melatonin ameliorates simulated-microgravity-induced mitochondrial dysfunction and lipid metabolism dysregulation in hepatocytes

ABSTRACT: The liver is an essential multifunctional organ, which constantly communicates with nearly all tissues. It has raised the concern that microgravity exposure can lead to liver dysfunction and metabolic syndromes. However, systematic studies, molecular mechanisms, and intervention measures of the adverse effects of microgravity on hepatocytes are limited. In this study, we utilized the Random Positioning Machine culture system to investigate the adverse effects on hepatocytes under simulated microgravity (SMG). Our results showed that SMG impaired hepatocyte viability, causing cell cycle arrest and apoptosis. Compared to normal gravity (NG), it also triggered lipid accumulation, elevated triglyceride (TG) and ROS levels, and impaired mitochondria function in hepatocytes. Furthermore, RNA-seq results showed that SMG upregulated genes implicated in lipid metabolisms, including PPARγ, PLIN2, CD36, FABPs, etc.. Importantly, all these defects can be suppressed by melatonin, a potent antioxidant secreted by the pineal gland, suggesting its potential use as a novel strategy of therapeutic intervention.

ORGANISM(S): Mus musculus

PROVIDER: GSE228604 | GEO | 2023/04/04

REPOSITORIES: GEO

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Project description:Aims/hypothesis: While lipid deposition in skeletal muscle is considered to be involved in obesity-associated insulin resistance, neutral intramyocellular lipid (IMCL) accumulation per se does not necessarily induce insulin resistance. We previously demonstrated that overexpression of the lipid droplet coat protein perilipin 2 augments intramyocellular lipid content while improving insulin sensitivity. Another member of the perilipin family, perilipin 5 (PLIN5), is predominantly expressed in oxidative tissues like skeletal muscle. Here we investigated the effects of PLIN5 overexpression M-bM-^@M-^S in comparison with effects of PLIN2 M-bM-^@M-^S on skeletal muscle lipid levels, gene expression profiles and insulin sensitivity. Methods: Gene electroporation was used to overexpress PLIN5 in tibialis anterior muscle of rats fed a high fat diet. Eight days after electroporation, insulin-mediated glucose uptake in skeletal muscle was measured by means of a hyperinsulinemic euglycemic clamp. Electron microscopy, fluorescence microscopy and lipid extractions were performed to investigate IMCL accumulation. Gene expression profiles were obtained using microarrays. Results: TAG storage and lipid droplet size increased upon PLIN5 overexpression. Despite the higher IMCL content, insulin sensitivity was not impaired and DAG and acylcarnitine levels were unaffected. In contrast to the effects of PLIN2 overexpression, microarray data analysis revealed a gene expression profile favoring FA oxidation and improved mitochondrial function. Conclusions/interpretation: Both PLIN2 and PLIN5 increase neutral IMCL content without impeding insulin-mediated glucose uptake. As opposed to the effects of PLIN2 overexpression, overexpression of PLIN5 in skeletal muscle promoted expression of a cluster of genes under control of PPARM-NM-1 and PGC1M-NM-1 involved in FA catabolism and mitochondrial oxidation. Rats received a high fat diet for 3 weeks; 2 weeks after start of the diet intervention Plin5 (OXPAT) or Plin2 (ADRP) were overexpressed in either the right or left tibialis anterior muscle. One week later pooled tibialis anterior muscle samples were analysed on microarrays.

Project description:Gravitational biology and its effects on cancer cells are of great interest, especially today that space is more accessible than ever. Despite advances in space research, little is known about the impact of microgravity on tumor and its biology and data from the literature are often contradictory due to different setup, experimental designs and analyzed time-points. Exploiting the Random Positioning machine we evaluated on pancreatic cancer cells the effects of long-term exposure to simulated microgravity (SMG) performing a large proteomic, lipidomic and transcriptional analysis at 1, 7 and 9 days. Results indicate that SMG affects cellular morphology through a time-dependent activation of “Regulation of actin-based motility by Rho”and “Cdc42” pathways that contribute to the dynamic actin rearrangement involved in the formation of 3D spheroidal structures and in the enhancement of epithelial-to mesenchymal transition. To support energy stress remediation and counteract massive apoptosis activation and cell proliferation inhibition, induced by SMG, tumor cells downregulate the protein translational machinery, and undergo a metabolic reprogramming orchestrated by the activation of HIF-1a and PI3K/Akt pathways. These two pathways pave the way for glucose metabolism encouraging upregulation of glycolysis, mitochondrial activity, Tri-carboxylic acid cycle and fatty acid synthesis (rather than B oxidation), suggesting a de novo synthesis of triglycerides involved in the formation of membrane lipid bilayer and signaling mediators. This metabolic plasticity, typical of cancer stem cells, is in accordance with the SMG-mediated activation of PI3K/Akt/NFkB/ERK5/IL-8 signaling axis that significantly upregulates the expression of stem-associated proteins and expansion of cancer stem cells with a more mesenchymal phenotype and improved migratory capability. Altogether, our findings clearly indicate that microgravity induces cancer cell transformation towards the acquisition of cancer stem cell-like features, with a more aggressive and metastatic potential and pave the base for future study of response to anti neoplastic drugs under simulated microgravity.

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Melatonin ameliorates simulated-microgravity-induced mitochondrial dysfunction and lipid metabolism dysregulation in hepatocytes

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