Increased muscle mass and mitochondrial content in chronically ischemic skeletal muscle

Abstract

Studies in patients with peripheral arterial disease (PAD) have demonstrated alterations in leg skeletal muscle and its mitochondria. In patients with unilateral PAD, some of these changes are not limited to the ischemic limb (IL), but also affect the contra-lateral nonischemic one (NIL). We developed an animal model of unilateral hindlimb ischemia to further examine these alterations. Six month old, C57BL/6 mice (N = 12) underwent unilateral common femoral artery ligation/division (12 IL) and sham contra-lateral operation (12 NIL). An additional 6 mice (12 limbs) had no operation and served as controls (CON). At 12 weeks after initial operation the deep red gastrocnemius was harvested with wet weight and total protein measured. Mitochondrial content was evaluated by measuring the activity of citrate synthase (enzyme specific for mitochondrial content). The protein content per unit of wet weight and mitochondrial content per unit of protein were also calculated as indices of the relative protein and mitochondrial density in the muscle. IL had significantly higher wet weight, protein content and citrate synthase activity compared to both NIL and CON hindlimbs. There was no difference between NIL and CON limbs. Protein and mitochondrial density were no different in IL, NIL and CON limbs. In our model chronic ischemia is associated with a significant increase of muscle mass and total mitochondrial content. Ischemic muscle appears to hypertrophy while maintaining its overall protein and mitochondrial density. Unilateral hindlimb ischemia resulted in no significant changes in the contra-lateral nonischemic limb. TABLE—ABSTRACT P83Wet weight (mg)Protein content (mg)Citrate synthase (umol/min)Protein/ weight %Citrate synthase/ proteinIL11.7 ± .4§€1.2 ± .1§€1.7 ± .5§€12.7 ± .61.5 ± .8NIL9.9 ± .31.0 ± .11.4 ± .814.4 ± 1.21.4 ± .9CON9.3 ± .5.8 ± .11.3 ± .113.2 ± 1.01.5 ± .1§= significant when compared to NIL,€= significant compared to CON.