EFFECTS OF INHALED FLUTICASONE PROPIONATE ON EXTRINSIC TONGUE MUSCLES IN RATS.J Appl Physiol (1985) 2020JA
Obstructive Sleep Apnea (OSA) is more common in patients with asthma and inhaled corticosteroids may contribute to OSA pathogenesis in these patients. This study tested effects of orally inhaled fluticasone propionate (FP) on extrinsic tongue muscles.
Unanesthetized rats were treated with FP or Placebo for 28 days. On day 29, tongue retrusive and protrusive functions were tested via hypoglossal nerve stimulation under a state of anesthesia, followed by genioglossus (GG), styloglossus (SG) and hyoglossus (HG) muscle extraction, after euthanasia, for histology (myosin heavy chain [MHC] fibers and laminin content reflecting extracellular matrix [ECM]).
On protrusive testing, FP increased %maximum tetanic force at 40 Hz (p=0.03 vs. P) and endurance index (p=0.029 vs. placebo). On retrusive testing, FP increased maximum twitch (p=0.026 vs. placebo) and tetanic forces (p=0.02 vs. placebo) with no effect on endurance index. On histology, FP increased GG cross-sectional area of MHC Type IIa (p =0.036 vs. placebo) and IIb (p=0.057 vs. placebo) fibers and HG MHC IIx fibers (p=0.065). The FP group had significantly increased laminin-stained areas, of greatest magnitude in the HG muscle.
FP affects tongue protrusive and retrusive functions differently, concurrent with a shift in MHC fibers and increased ECM accumulation. These differential alterations may destabilize the tongue's "muscle hydrostat" during sleep and promote collapse.