Mark Wefers Bettink

Monitoring mitochondrial respiration 5 97 LPS - - T0 T1 0.0 0.5 1.0 1.5 2.0 ODR (normalized) LPS + - T0 T1 0.0 0.5 1.0 1.5 2.0 ODR (normalized) LPS + + T0 T1 0.0 0.5 1.0 1.5 2.0 ODR (normalized) T0 T1 -6 -4 -2 0 ODR (mmhg*s -1 ) * * LPS - - Time control Succinate LPS + - LPS ++ Oxygen disappearance rate * T0 T1 0.0 0.5 1.0 1.5 2.0 ODR (normalized) SC T0 T1 0.0 0.5 1.0 1.5 2.0 ODR (normalized) TC Normalized individual oxygen disappearance rate A B Figure 5. Panel A: ODR at T0 and T1 in the different experimental groups. Panel B: Percentage change in ODR . TC; time control, SC; methyl-succinate control, LPS --; endotoxemia, LPS +-; endotoxemia with fluid resuscitation, LPS ++; endotoxemia with fluid resuscitation and methyl- succinate administration, LPS; lipopolysaccharide, ODR; mitochondrial oxygen disappearance rate. T0 and T1 are the time points of ODR measurement. Data are presented as mean ± SD, * significant difference compared to baseline measurement, # significant difference compared to time control measurement (p<0.05); (8 rats/group).intergroup analysis T1: SC vs TC (p=0.034), LPS -- vs TC (p=0.0034) and LPS+- vs TC (p=0.0223) Discussion The major findings of this study are that in vivo respirometry and ex vivo respirometry provide different results in our endotoxemic rat model and that PpIX-TSLT provides a sensitive means to measure aspects of mitochondrial function in vivo . LPS decreased in vivo muscle ODR at the measured timepoints compared to a time control group, but no effect of LPS was found in ex vivo mitochondrial function tests. No change in mitochondrial function was found using the high-resolution respirometer nor using direct complex activity measurements. In an LPS-induced rat endotoxemia model we showed a decrease in in vivo mitochondrial function (ODR) using the PpIX-TSL technique, that could be prevented by pre-treatment with methyl-succinate. This result confirms the previously measured beneficial effects of methyl-succinate in ex vivo biopsies from