leptin and Friedreich-Ataxia

In Friedreich's ataxia (FRDA), the most affected tissues are not accessible to sampling and available transcriptomic findings originate from blood-derived cells and animal models. Herein, we aimed at dissecting for the first time the pathophysiology of FRDA by means of RNA-sequencing in an affected tissue sampled in vivo.. Skeletal muscle biopsies were collected from seven FRDA patients before and after treatment with recombinant human Erythropoietin (rhuEPO) within a clinical trial. Total RNA extraction, 3'-mRNA library preparation and sequencing were performed according to standard procedures. We tested for differential gene expression with DESeq2 and performed gene set enrichment analysis with respect to control subjects.. FRDA transcriptomes showed 1873 genes differentially expressed from controls. Two main signatures emerged: (1) a global downregulation of the mitochondrial transcriptome as well as of ribosome/translational machinery and (2) an upregulation of genes related to transcription and chromatin regulation, especially of repressor terms. Downregulation of the mitochondrial transcriptome was more profound than previously shown in other cellular systems. Furthermore, we observed in FRDA patients a marked upregulation of leptin, the master regulator of energy homeostasis. RhuEPO treatment further enhanced leptin expression.. Our findings reflect a double hit in the pathophysiology of FRDA: a transcriptional/translational issue and a profound mitochondrial failure downstream. Leptin upregulation in the skeletal muscle in FRDA may represent a compensatory mechanism of mitochondrial dysfunction, which is amenable to pharmacological boosting. Skeletal muscle transcriptomics is a valuable biomarker to monitor therapeutic interventions in FRDA.

Topics: Animals; Erythropoietin; Friedreich Ataxia; Humans; Iron-Binding Proteins; Leptin; Muscle, Skeletal; RNA; Transcriptome

Decreased expression of mitochondrial frataxin (FXN) causes Friedreich's ataxia (FRDA), a neurodegenerative disease with type 2 diabetes (T2D) as severe comorbidity. Brown adipose tissue (BAT) is a mitochondria-enriched and anti-diabetic tissue that turns excess energy into heat to maintain metabolic homeostasis. Here we report that the FXN knock-in/knock-out (KIKO) mouse shows hyperlipidemia, reduced energy expenditure and insulin sensitivity, and elevated plasma leptin, recapitulating T2D-like signatures. FXN deficiency leads to disrupted mitochondrial ultrastructure and oxygen consumption as well as lipid accumulation in BAT. Transcriptomic data highlights cold intolerance in association with iron-mediated cell death (ferroptosis). Impaired PKA-mediated lipolysis and expression of genes controlling mitochondrial metabolism, lipid catabolism and adipogenesis were observed in BAT of KIKO mice as well as in FXN-deficient T37i brown and primary adipocytes. Significant susceptibility to ferroptosis was observed in adipocyte precursors that showed increased lipid peroxidation and decreased glutathione peroxidase 4. Collectively our data point to BAT dysfunction in FRDA and suggest BAT as promising therapeutic target to overcome T2D in FRDA.

Topics: Adipocytes; Adipose Tissue, Brown; Animals; Cold Temperature; Cyclic AMP-Dependent Protein Kinases; Diabetes Mellitus, Type 2; Ferroptosis; Frataxin; Friedreich Ataxia; Hyperlipidemias; Insulin Resistance; Iron-Binding Proteins; Leptin; Lipid Metabolism; Lipolysis; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Electron, Transmission; Mitochondria; Oxidative Stress; Phospholipid Hydroperoxide Glutathione Peroxidase; RNA-Seq; Thermogenesis