Iron Deficiency Causes a Shift in AMP-Activated Protein Kinase (AMPK) Catalytic Subunit Composition in Rat Skeletal Muscle

• Main Author: Merrill, John
• Format: Others
• Published: BYU ScholarsArchive 2012
• Subjects: AMPK; AMPK alpha; iron deficiency; anemia; energy metabolism; skeletal muscle; Cell and Developmental Biology; Physiology
• Online Access: https://scholarsarchive.byu.edu/etd/3483; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4482&context=etd

To determine effects of iron deficiency on AMPK activation and signaling, as well as the AMPKα subunit composition in skeletal muscle, rats were fed a control (C=50-58 mg/kg Fe) or iron deficient (ID=2-6 mg/kg Fe) diet for 6-8 wks. Their respective hematocrits were 47.5% ± 1.0 and 16.5% ± 0.6. Iron deficiency resulted in 28.3% greater muscle fatigue (p<0.01) in response to 10 min of stimulation (1 twitch/sec) and was associated with a greater reduction in phosphocreatine (C: Resting 24.1 ± 0.9 micromol/g, Stim 13.1 ± 1.5 micromol/g; ID: Resting 22.7 ± 1.0 micromol/g, Stim 3.2 ± 0.7 micromol/g; p<0.01) and ATP levels (C: Resting 5.89 ± 0.48 micromol/g, Stim 6.03 ± 0.35 micromol/g; ID: Resting 5.51 ± 0.20 micromol/g, Stim 4.19 ± 0.47 micromol/g; p<0.05). AMPK activation increased with stimulation in muscles of C and ID animals. A reduction in Cytochrome c and other iron-dependent mitochondrial proteins was observed in ID animals (p<0.01). The AMPK catalytic subunit (alpha) was also examined because both isoforms are known to play different roles in responding to energy challenges. In ID animals, AMPK alpha2 subunit protein content was reduced to 71.6% of C (p<0.05), however this did not result in a significant difference in resting AMPK alpha2 activity. AMPK alpha1 protein was unchanged, however an overall increase in AMPK alpha1 activity was observed (C: 0.91 pmol/mg/min; ID: 1.63 pmol/mg/min; p<0.05). Resting phospho Acetyl CoA Carboxylase (pACC) was unchanged. This study indicates that chronic iron deficiency causes a shift in the expression of AMPK alpha subunit composition and potentially altered sensitivity to cellular energy challenges.