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Aging Promotes Metabolic Dysfunction-associated Steatotic Liver Disease and Multi-Organ Dysfunction by Inducing Ferroptotic Stress

ABSTRACT: Aging is an inevitable consequence of living that undermines cellular resiliency to cause tissue degeneration and eventual multi-organ dysfunction. Susceptibility to biological consequences of aging varies among organs and individuals. Stressors that challenge resiliency unmask these differences. Hence, aging increases the risk for failure of many metabolically-stressed organs and exacerbates liver degeneration related to obesity and diabetes. We discovered that aging promotes ferroptosis, a type of metabolism-regulated cell death, in hepatocytes. Hepatocytes that have launched the ferroptotic death program adapt their metabolism to survive but become damaged and dysfunctional. Metabolic stressors amplify this, increasing the burden of ferroptosis-adapted cells and liver damage. Blocking ferroptotic signaling in old livers reduces accumulation of adapted hepatocytes and reverts livers to a more youthful resilient state despite exogenous stressors. Ferroptosis is also induced in other organs that are damaged by chronic metabolic stress, identifying ferroptosis as a tractable conserved mechanism for aging-related multi-organ dysfunction.

ORGANISM(S): Mus musculus

PROVIDER: GSE262457 | GEO | 2024/07/01

REPOSITORIES: GEO

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Project description:Ferroptosis is a form of regulated cell death characterized by iron-dependent lipid peroxidation. While ferroptosis has been identified as a mechanism for suppressing cancer, its overall physiological significance remains poorly understood. Recent studies have revealed that labile iron and lipid peroxides are released from ferroptotic cells, leading to the propagation of ferroptosis through lipid peroxidation. However, other specific effects of secreted factors derived from ferroptotic cells remain unclear. We constructed a model cell system capable of inducing ferroptosis by re-expressing the transcription factor BACH1, a potent inducer of ferroptosis, in immortalized mouse embryonic fibroblasts (iMEFs). We investigated the impact of the secreted factors from ferroptotic cells with the iMEFs. As a result, we observed that the administration of supernatant media from ferroptotic iMEFs activated proliferation of hepatoma cells and suppressed cellular senescence-like features. This suggested that ferroptotic MEFs secrete anti-senescent substances. Transcriptome analysis of ferroptotic MEFs revealed an increase in the secretion of longevity factor FGF21 in a BACH1-dependent manner. Furthermore, the anti-senescent effects of the supernatant media from these ferroptotic cells were canceled by the knockout of Fgf21. Totally, it is suggested that BACH1 promotes ferroptosis in fibroblasts and contributes to the suppression of cellular senescence in neighboring cells by inducing FGF21 secretion from fibroblasts. It was also discovered that BACH1 not only activates indirectly the transcription of FGF21 by enhancing ferroptotic stress but also increases FGF21 protein level by suppressing the selective autophagic degradation of FGF21 through the transcriptional repression for Sqstm1 and Lamp2a. This represents a dual mechanism of FGF21 upregulation mediated by BACH1, suggesting that BACH1 is a potent inducer of FGF21 expression. It was also found that the BACH1-ferroptosis-FGF21 axis can suppress obesity of mice under high fat diet or short lifespan of progeria mice, closely associated phenotypes with aging. The inhibition of these aging-related phenotypes is considered to be a novel physiological significance of ferroptosis, and BACH1 is considered to function as a longevity gene by promoting ferroptotsis and subsequent FGF21 expression.

Project description:Older age is a major risk factor for damage to many tissues, including liver. Aging undermines resiliency (i.e., the ability to recover from injury) and impairs liver regeneration. The mechanisms whereby aging reduces resiliency are poorly understood. Hedgehog is a signaling pathway with critical mitogenic and morphogenic functions during development. Recent studies indicate that Hedgehog regulates metabolic homeostasis in adult liver. The present study evaluates the hypothesis that Hedgehog signaling becomes dysregulated in hepatocytes during aging, resulting in decreased resiliency and therefore, impaired regeneration and enhanced vulnerability to damage. Methods: Partial hepatectomy (PH) was performed on young and old wild type mice and Smoothened (Smo)-floxed mice treated with AAV8-TBG luciferase (control) or AAV8-TBG-Cre vectors to conditionally delete Smo and disrupt Hedgehog signaling specifically in hepatocytes. Changes in signaling were correlated with changes in regenerative responses and compared among groups. Results: Old livers had fewer hepatocytes proliferating after PH. RNA sequencing identified Hedgehog as a top down-regulated pathway in old hepatocytes before and after the regenerative challenge. Deleting Smo in healthy young hepatocytes before PH prevented Hedgehog pathway activation after PH and inhibited regeneration. GO analysis demonstrated that both old and Smo-deleted young hepatocytes had activation of pathways involved in innate immune responses and suppression of several signaling pathways that control liver growth and metabolism including insulin-like growth factor, Wnt and NOTCH. Hedgehog inhibition promoted telomere shortening and mitochondrial dysfunction in hepatocytes, consequences of aging that promote inflammation and impair tissue growth and metabolic homeostasis. Conclusion: Hedgehog signaling is dysregulated in old hepatocytes. This accelerates aging, resulting in decreased resiliency and therefore, impaired liver regeneration and enhanced vulnerability to damage.

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Aging Promotes Metabolic Dysfunction-associated Steatotic Liver Disease and Multi-Organ Dysfunction by Inducing Ferroptotic Stress

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