Training effects on skeletal muscle calcium handling in human chronic heart failure.

PURPOSE: Patients with chronic heart failure (CHF) typically complain about skeletal muscle fatigue. In rat experiments, reduced intracellular calcium release seems to be related to fatigue development in normal skeletal muscle but not in muscle from rats with CHF. We therefore hypothesize that training may not improve intracellular calcium cycling to the same extent in muscles from patients with CHF compared with healthy controls (HC). METHODS: Thirteen HC and 11 CHF patients performed 6 wk of unilateral knee extensor endurance training. Computed tomographic examinations of the thigh and biopsies of vastus lateralis were obtained bilaterally before and after the training period. RESULTS: Peak power of the trained leg was 10% and 14% greater than that in the untrained leg in HC and CHF, respectively. For the HC, training resulted in a higher Ca2+ release rate and a lower leak in the trained leg associated with a tendency of increased ryanodine receptor (RyR) content with reduced phosphorylation level. In the trained leg of CHF patients, RyR content was reduced without associated changes of either Ca2+ leak or release rate. CONCLUSIONS: Training in HC has an effect on Ca2+ leak and release of the sarcoplasmic reticulum, but in CHF patients, training is achieved without such changes. Thus, calcium handling seems not to be the site of decreased exercise tolerance in CHF.

Temporary fatigue and altered extracellular matrix in skeletal muscle during progression of heart failure in rats.

Patients with congestive heart failure (CHF) experience increased skeletal muscle fatigue. The mechanism underlying this phenomenon is unknown, but a deranged extracellular matrix (ECM) might be a contributing factor. Hence, we examined ECM components and regulators in a rat postinfarction model of CHF. At various time points during a 3.5 mo-period after induction of CHF in rats by left coronary artery ligation, blood, interstitial fluid (IF), and muscles were sampled. Isoflurane anesthesia was employed during all surgical procedures. IF was extracted by wicks inserted intermuscularly in a hind limb. We measured cytokines in plasma and IF, whereas matrix metalloproteinase (MMP) activity and collagen content, as well as the level of glycosaminoglycans and hyaluronan were determined in hind limb muscle. In vivo fatigue protocols of the soleus muscle were performed at 42 and 112 days after induction of heart failure. We found that the MMP activity and collagen content in the skeletal muscles increased significantly at 42 days after induction of CHF, and these changes were time related to increased skeletal muscle fatigability. These parameters returned to sham levels at 112 days. VEGF in IF was significantly lower in CHF compared with sham-operated rats at 3 and 10 days, but no difference was observed at 112 days. We conclude that temporary alterations in the ECM, possibly triggered by VEGF, are related to a transient development of skeletal muscle fatigue in CHF.