Frataxin deficiency induces lipid accumulation and affects thermogenesis in brown adipose tissue

Riccardo Turchi, Flavia Tortolici, Giulio Guidobaldi, Federico Iacovelli, Mattia Falconi, Stefano Rufini, Raffaella Faraonio, Viviana Casagrande, Lorenzo De Angelis, Massimo Federici, Simone Carotti, Maria Francesconi, Maria Zingariello, Sergio Morini, Roberta Bernardini, Maurizio Mattei, Daniele Lettieri-Barbato, Katia Aquilano; bioRxiv 664649; doi:10.1101/664649

Decreased expression of the mitochondrial protein frataxin (FXN) causes Friedreich's ataxia (FRDA). FRDA is a neurodegenerative disease also characterized by systemic metabolic alterations that increase the risk of developing type 2 diabetes thus aggravating FRDA prognosis. Brown adipose tissue (BAT) is a mitochondria-enriched and anti-diabetic tissue that, in addition to its thermoregulatory role, turns excess energy into heat to maintain energy balance. Here we report that the FXN knock-in/knock-out (KIKO) mouse shows reduced energy expenditure and VO2, hyperlipidemia, decreased insulin sensitivity and enhanced circulating levels of leptin, recapitulating diabetes-like signatures. FXN deficiency leads to alteration of mitochondrial structure and oxygen consumption, decreased lipolysis and lipid accumulation in BAT. Transcriptomic data highlighted a blunted thermogenesis response, as several biological processes related to thermogenesis (e.g. response to temperature stimuli, mitochondrial gene transcription, triglyceride metabolism, adipogenesis) resulted affected in BAT of KIKO mice upon cold exposure. Decreased adaptation to cool temperature in association with limited PKA-mediated lipolysis and downregulation of the expression of the genes controlling mitochondrial metabolism and lipid catabolism were observed in KIKO mice. T37i brown adipocytes and primary adipocytes with FXN deficiency showed reduced thermogenesis and adipogenesis markers respectively recapitulating the molecular signatures detected in KIKO mice. Collectively our data point to BAT dysfunction in FRDA and suggest BAT as a promising target to overcome metabolic complications in FRDA.