PD599 - LOSS OF MITOCHONDRIAL FITNESS IS AN EARLY EVENT IN THE DEVELOPMENT OF FATTY ACID-INDUCED INSULIN RESISTANCE IN SKELETAL MUSCLE CELLS

PD599

LOSS OF MITOCHONDRIAL FITNESS IS AN EARLY EVENT IN THE DEVELOPMENT OF FATTY ACID-INDUCED INSULIN RESISTANCE IN SKELETAL MUSCLE CELLS

S. Orlando^1,*, L. Ortega², A. Creus², K. Kurek², Y. Zhang², S. Li², S. Mohapatra², A. Corral², I. Palacios-Marin², C. Vales-Villamarin², S. Redondo², M. del Mar Romero², F. Tambaro¹, M. Todorcevic², L. Herrero², D. Sebastian², M. Muscaritoli¹

¹Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy, ²Department of Biochemistry and Physiology, Institute of Biomedicine of the University of Barcelona (IBUB), Barcelona, Spain

Rationale: Rationale: Patients with sarcopenic obesity (SO) often exhibit insulin resistance (IR), which impairs glucose uptake in skeletal muscle (SM). Obesity is associated with mitochondrial alterations in SM, which contribute to the development of IR. However, the origin of mitochondrial dysfunction in obesity, and whether it is a cause or a consequence of IR, remains debated. This study aims to investigate the origin and the temporal dynamics of mitochondrial dysfunction in SM in an in vitro model of obesity.

Methods: Methods: C2C12 myoblasts were treated with palmitate (PA, 0.15 mM) or BSA (control, C) for 16h or at 1h, 3h, and 6h. Insulin signalling was assessed by the p-AKT/AKT ratio using Western Blot. Cells were incubated with MitoTracker Deep Red ± Bafilomycin A1 to evaluate mitophagy flux. Mitochondrial function was evaluated by the extracellular flux analyzer (Seahorse Biosciences). MitoQC-expressing myoblasts were fixed and stained to evaluate mitophagy and mitochondrial morphology.

Results: Results: After 16h of PA treatment, we observed in C2C12 myoblasts a decrease in mitophagy flux, a lower mitochondrial respiratory capacity, and a decrease in AKT-mediated insulin signalling. To establish the temporal sequence of these events, we performed a time-course analysis at 1, 3, and 6h of PA treatment. We observed that after a transient increase in mitolysosome number, PA treatment first induced mitochondrial fragmentation and inhibited mitophagy, followed by mitochondrial dysfunction, ultimately leading to insulin resistance.  

Conclusion: Conclusion: Based on these results in vitro, we postulate that loss of mitochondrial fitness is an early event in the development of obesity-induced IR in SM. Further investigations are ongoing to better understand mitophagy impairment and to assess lysosomal mass and degradative activity under PA conditions.

Disclosure of Interest: None declared