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The Slc25a47 locus is a novel determinant of hepatic mitochondrial function implicated in liver fibrosis

ABSTRACT: Background & Aims: Transporters of the SLC25 mitochondrial carrier superfamily bridge cytoplasmic and mitochondrial metabolism by channeling metabolites across mitochondrial membranes and are pivotal for metabolic homeostasis. Despite their physiological relevance as gatekeepers of cellular metabolism, most of the SLC25 family members remain uncharacterized. We undertook a comprehensive tissue distribution analysis of all Slc25 family members across metabolic organs and identified SLC25A47 as a liver-specific mitochondrial carrier. Method: We used a murine loss-of-function (LOF) model to unravel the role of this transporter in mitochondrial and hepatic homeostasis. We performed extensive metabolic phenotyping and molecular characterization of Slc25a47hep-/- mice. Results: Slc25a47hep-/- mice displayed a wide variety of metabolic abnormalities, as a result of sustained energy deficiency in the liver originating from impaired mitochondrial respiration in this organ. This mitochondrial phenotype was associated with a robust activation of the mitochondrial stress response in the liver, which in turn, induced the secretion of several mitokines, amongst which FGF21 played a preponderant role in the translation of the effects of the MSR on systemic physiology. To dissect the FGF21-dependent and -independent physiological changes induced by the loss of Slc25a47, we generated a double Slc25a47-Fgf21 LOF mouse model, and demonstrated that several aspects of the hypermetabolic state was entirely driven by hepatic secretion of FGF21. On the other hand, the metabolic fuel inflexibility induced by loss of Slc25a47 could not be rescued by genetical removal of Fgf21. Conclusion: Collectively, our data place SLC25A47 at the center of mitochondrial homeostasis, which upon dysfunction triggers robust liver-specific and systemic adaptive stress responses.

ORGANISM(S): Mus musculus

PROVIDER: GSE195479 | GEO | 2022/06/21

REPOSITORIES: GEO

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Project description:Chronic stress leads post-traumatic stress disorder (PTSD) and to metabolic complications, including fatty liver. It is feasible, that stress immediately initiates molecular mechanisms to alter energy metabolism and glucose homeostasis which interfere with hepatic lipid accumulation after stress recovery. We aim to elucidate these molecular mechanisms of long term stress effects on metabolism and focus on physiological adaptation and the role of FGF21, which is protective in hepatic lipid accumulation. Methods FGF21 knockout and control mice were exposed to chronic variable stress (Cvs) and recovered for 3 months to simulate PTSD. We determined in vivo and ex vivo energy metabolism, mitochondrial function by extracellular flux analysis, alterations in DNA modifying enzymes and gene regulation immediately after stress and after the recovery period to determine long term alterations. Results Chronic stress leads to reduced insulin sensitivity and hepatic lipid accumulation with increased fatty acid uptake (FAU), stress-induced lipolysis, and reduction in NAD+/NAD ratio and Sirt activity. Immediately after stress, PPARa and SREBP-1 target genes are differentially regulated and are involved in the development of stress-induced fatty liver. After recovery, insulin sensitivity increases but insulin-induced de novo lipogenesis (DNL) is reduced and FAU is increased. HDAC and MT activity are suppressed, whereas HAT activity increases, linking metabolic adjustments to transcriptional regulators. Thus, key metabolic genes are differentially regulated and secreted proteins indicate the activation of liver disease by Cvs only in FGF21WT. GR binding to the Cd36 promoter is altered. After stress recovery, serum FGF21 is increased and protects against lipid accumulation. FGF21 interacts by attenuating DNL, increasing FAU and HAT activity, and balancing mitochondrial activity. Higher long-term stress-induced activation and binding of GR to the FGF21 promoter may contribute to the prolonged FGF21 release. Conclusions We show that previous stress exposure determines predisposition to fatty liver disease is regulated by FGF21. Immediately after Cvs, altered gene regulation and activity of DNA-modifying enzymes determine the metabolic late effects seen in PTSD. FGF21 functions after chronic stress exposure i) to protect against hepatic lipid accumulation, ii) to maintain mitochondrial capacity, and iii) to mediate in the modulation of DNA-modifying enzymes. These findings highlight the protective role of FGF21 even in stress-induced hepatic lipid accumulation.

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The Slc25a47 locus is a novel determinant of hepatic mitochondrial function implicated in liver fibrosis

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