Pavlovic 2019 MiP2019

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Barbara Cannon
Effects of therapeutic metformin concentration on mitochondria in muscle cells.

Link: MiP2019

Pavlovic K, Krako Jakovljevic N, Isakovic AM, Markovic I, Lalic NM (2019)

Event: MiP2019

COST Action MitoEAGLE

Metformin is an antidiabetic drug that exerts its effects by inhibition of hepatic gluconeogenesis and upregulation of glucose uptake in peripheral tissues, such as skeletal muscle. Despite being used in clinical practice for over 60 years, its cellular mechanisms of action and molecular targets have not been elucidated yet. Proposed mechanisms of action are activation of AMPK and inhibition of complex I of the respiratory chain. Many in vitro studies claim that metformin inhibits complex I, but the concentrations used in these studies are usually a lot higher than the plasma concentrations in patients taking the drug orally. [1] The aim of our research was to explore the effects of therapeutic metformin concentration on cell viability and mitochondrial respiration of C2C12 cells.

C2C12 mouse myoblast cell line was treated with a wide range of metformin concentrations (3-12800 µM) for cell viability assays, and with two different metformin concentrations (50 µM and 5 mM) for measuring mitochondrial respiration. Cell viability was measured by crystal violet and acid phospatase assays, and mitochondrial respiration by high resolution respirometry, with Oroboros O2k.

Metformin treatment did not cause a decrease in cell viability in the micromolar range (3-800 µM), but milimolar concentrations (3 and 13 mM) caused a significant decrease in cell viability. Respirometric analysis showed that 5 mM metformin caused a decrease in ROUTINE and OXPHOSCI, while OXPHOSCII was unaltered, both with long (24 h) and short (metformin titration directly in the chamber) treatment. On the contratry, 50 µM treatment caused a slight increase in ROUTINE, OXPHOSCI and OXPHOSCII when cells are treated with metformin for 24 h, but there is no change in any of the respiratory states when using the short treatment.

According to these results metformin concentration that has been found to cause complex I inhibition (5 mM) is cytotoxic to muscle cells. The concentration that is comparable to that found in vivo (50 µM) is not cytotoxic to C2C12 cells and does not cause inhibition of complex I activity. Thus, this raises the question if the therapeutic effects of metformin can be ascribed to complex I inhibition in vivo.


Bioblast editor: Plangger M, Tindle-Solomon L O2k-Network Lab: RS Belgrade Lalic NM


Labels: MiParea: Respiration, Pharmacology;toxicology 


Organism: Mouse  Tissue;cell: Skeletal muscle  Preparation: Intact cells 


Coupling state: ROUTINE, OXPHOS  Pathway: N, S  HRR: Oxygraph-2k 


Affiliations

Pavlovic K(1), Krako Jakovljevic N(1), Isakovic AM(2), Marković I(2), Lalic NM(1)
  1. Clinic Endocrinology, Diabetes Metabolic Diseases, CCS
  2. Inst Medical Clinical Biochemistry, Fac Medicine, Univ Belgrade. – kasja.pavlovic@med.bg.ac.rs

References

  1. Fontaine E (2018) Metformin-induced mitochondrial complex I inhibition: facts, uncertainties, and consequences. Front Endocrinol (Lausanne) 9:753.