Resting energy expenditure in patients with thermal injuries

Effects of a caspase and a calpain inhibitor on resting energy expenditures in normal and hypermetabolic rats: a pilot study

Several diseases induce hypermetabolism, which is characterized by increases in resting energy expenditures (REE) and whole body protein loss. Exaggerated protein degradation is thought to be the driving force underlying this response. The effects of caspase and calpain inhibitors on REE in physiological and hypermetabolic conditions, however, are unknown. Thus, we studied whether MDL28170 (calpain inhibitor) or z-VAD-fmk (caspase inhibitor) affect REE under physiological conditions and during hypermetabolism post-burn. Rats were treated five times weekly and observed for 6 weeks. Treatment was started 2 h (early) or 48 h (late) after burn. In normal rats, MDL28170 transiently increased REE to 130 % of normal during week 2-4. z-VAD-fmk reduced REE by 20-25 % throughout the observation period. Within 14 days after burns, REE increased to 130+/-5 %. Whereas MDL28170/early treatment did not affect REE, MDL28170/late transiently increased REE to 180+/-10 % of normal by week 4 post-burn. In contrast, with z-VAD-fmk/early REE remained between 90-110 % of normal post-burn. z-VAD-fmk/late did not affect burn-induced increases in REE. These data suggest that caspase cascades contribute to the development of hypermetabolism and that burn-induced hypermetabolism can be pharmacologically modulated. Our data point towards caspase cascades as possible therapeutic targets to attenuate hypermetabolism after burns, and possibly in other catabolic disease processes.

Activities of nonlysosomal proteolytic systems in skeletal and cardiac muscle during burn-induced hypermetabolism

The aim of this study was to assess the activity of nonlysosomal proteolytic systems in skeletal and cardiac muscle during burn-induced hypermetabolism (BHM) in rats. Rats underwent 30% TBSA scald burn or sham injury and were observed for up to 42 days. Body weights and resting energy expenditures were determined weekly. Skeletal (soleus/pectoral) muscle and hearts were harvested on days 0 (=control), 7, 14, 21, and 42 after burn. Calpain, caspase-1, caspase-3/7, caspase-6, caspase-8, caspase-9, and proteasome peptidase activities were measured in tissue extracts. Hypermetabolism developed within 3 weeks after burns, as documented by increased resting energy expenditures and decreased body weights on postburn days 21 to 42 (P < 0.05 vs control). Calpain activities did not show significant alterations. Pan caspase activities increased by time and were significantly increased in skeletal and cardiac muscle extracts during hypermetabolism. Although increases in caspase-1, caspase-8, and caspase-9 activities were predominantly responsible for elevated pan caspase activities in skeletal muscle, increases in caspase-6 activities dominated in the heart. Proteasome peptidase activities in skeletal muscle extracts were not significantly altered. Proteasome peptidase activities in heart extracts increased time dependently and were significantly increased during BHM. Activation of caspase cascades during BHM constitutes a uniform response in skeletal and cardiac muscle and may contribute to enhanced metabolic protein turnover. Activation of myocardial proteasome activities may reflect persistent cardiac stress. Further exploration of caspase cascades and the proteasome as therapeutic targets to influence long-term consequences of BHM appears justified.