Loop diuretics affect skeletal myoblast differentiation and exercise-induced muscle hypertrophy

Area of Science:

• Physiology
• Molecular Biology
• Biochemistry

Background:

• Muscle wasting (sarcopenia) increases morbidity and mortality in various conditions.
• Na+-K+-2Cl- cotransporter 1 (NKCC1) is present in skeletal muscle but its role in myogenesis is unknown.
• NKCC1 influences membrane potential and ion currents in muscle cells.

Purpose of the Study:

• To investigate the physiological role of NKCC1 in myogenesis and skeletal muscle hypertrophy.
• To determine the effect of NKCC1 inhibition on muscle cell differentiation and growth.
• To explore the involvement of NKCC1 in exercise-induced muscle adaptations.

Main Methods:

• Utilized C2C12 murine skeletal myoblasts for in vitro studies.
• Employed NKCC1 inhibitors (bumetanide and furosemide) to block transporter activity.
• Analyzed protein levels of NKCC1, myogenin, and myosin heavy chain (MHC) during differentiation.
• Investigated NKCC1 phosphorylation and levels in mouse skeletal muscle after exercise.
• Assessed myofiber size and exercise-induced hypertrophy with and without bumetanide treatment.

Main Results:

• NKCC1 protein levels increased during myoblast differentiation, correlating with myogenic markers.
• NKCC1 inhibition significantly suppressed myoblast fusion and expression of myogenin and MHC.
• Exercise increased NKCC1 phosphorylation and total levels in skeletal muscle.
• Exercise-induced myofiber hypertrophy was impaired by bumetanide administration.
• Sarcopenia in patients on loop diuretics may be linked to NKCC1 inhibition.

Conclusions:

• NKCC1 plays a vital role in skeletal muscle development (myogenesis).
• NKCC1 is essential for exercise-induced skeletal muscle hypertrophy.
• Loop diuretic treatment, by inhibiting NKCC1, may contribute to sarcopenia in certain patient populations.