Tetrahydrobiopterin improves diastolic dysfunction by reversing changes in myofilament properties

► Diastolic dysfunction is associated with reduced cross-bridge kinetics. ► The reduced cross-bridge kinetics is associated with S-glutathionylation of MyBP-C. ► BH4 treatment reversed reduced cross-bridge kinetics and diastolic dysfunction. ► The effect of BH4 correlated with a reduction in S-glutathionylation of MyBP-C. ► BH4 treatment may work by preventing this oxidative modification.