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BACKGROUND – Sepsis is characterized by an overwhelming systemic inflammatory response to infection that may lead to multiple organ failure and death in over 20% of the estimated 49 million annual cases worldwide. Because sepsis-related inflammatory processes disturbing cardiac and endothelial cells homeostasis are still poorly understood, only few therapeutic strategies reached added-value efficacy in terms of mortality reduction in the critical care units. Using an innovative transgenic mouse line to detect the acute changes of newly synthetized proteins, we propose to assess the protein expression profile of cardiomyocytes and endothelial cells in a murine model of polymicrobial sepsis. METHODS – The Cre-recombinase mediated expression of mutant L274G-methionyl-tRNA synthetase (MetRS*) in transgenic mouse crosses enables the selective in vivo incorporation of azidonorleucine (ANL), a non-canonical methionine analog, in newly synthetized proteins. MetRS* mice expressing CDH5-creERT2 (CDH5, endothelial cells) or αMHC-MerCreMer (MCM, cardiomyocytes) underwent CLP (cecal ligation and puncture). The sepsis model was validated by echocardiography, inflammatory cytokine profiling and histology. Labeling efficiency of nascent proteins from MCM and CDH5 cells (heart and lung) were visualized by FUNCAT (Fluorescence non-canonical amino acid tagging) or purified by BONCAT (bioorthogonal non-canonical amino acid tagging) for mass spectrometry analysis. RESULTS – Significant elevation of circulating inflammatory cytokines proves the systemic inflammatory state of mice submitted to CLP compared to SHAM mice. Our experimental model also displays a significant impairment of the LV function at both systolic (reduced cardiac index) and diastolic levels (increased E/A and isovolumic relaxation time) confirming hemodynamics alteration related to sepsis. Metascape analysis showed expression changes for several proteins involved in the acute response to stress in both MCM and CDH5 samples. Overall, nascent protein synthesis is mainly reduced in MCM samples in sepsis (14 up/98 down), something not observed in CDH5 samples both in the heart (69 up/97 down) and in the lungs (137 up/43 down). Alterations in metabolic pathways such as pyruvate metabolism and glycolysis/gluconeogenesis were only observed in MCM samples while protein associated with focal adhesion, for example, was observed in heart and lungs CDH5 samples. CONCLUSIONS – The results of this study provide a better understanding of which proteins are altered in specific cell types in a sepsis model. We confirmed previously identified markers of inflammatory response in tissues, while identifying new protein candidates and signaling pathways that may contribute to key steps of sepsis detrimental effects and thus, offering potential new therapeutic avenues to curb the fatal outcomes of this disease. Supported by Canadian Institute of Health Research (CIHR) - Project Grants (399567) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Background: We previously revealed that oral administration of the β3-adrenergic receptor (AR) agonist mirabegron only elicited small increases in brown adipose tissue (BAT) thermogenesis when ingested at the maximal allowable dose (200 mg). This led to off-target binding of the β1- and β2-AR, thereby increasing cardiovascular responses and white adipose tissue lipolysis, respectively. We hypothesize that a balanced activation between β1- and β3-AR is key to stimulating metabolic benefits without cardiovascular side effects. Method: We performed a randomized crossover trial in 8 lean men over two study days. The intervention consisted of oral administration of mirabegron (200 mg) with or without the cardio selective β1-AR antagonist bisoprolol (10 mg). Dynamic [11C]-acetate and 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET/CT scans were performed sequentially starting at 210 min after oral administration of mirabegron ± bisoprolol. Results: Compared to baselines measures, mirabegron alone or with bisoprolol increased energy expenditure (EE) by 27% (+18.2±6.7 kcal/h) and 11% (7.4±8.1 kcal/h), respectively. However, EE was significantly lower when mirabegron was co-ingested with bisoprolol (P=0.0402) Compared to room temperature, mirabegron alone increased BAT oxidative metabolism (0.631±0.267 vs 1.695±1.097 min-1 from the [11C]-acetate, P=0.0421), but was not different from mirabegron with bisoprolol (1.273±0.651 min-1). Metabolic rate of glucose in BAT, measured using [18F]FDG PET, was significantly higher with mirabegron than mirabegron combined with bisoprolol (24±10 vs 16±8 nmol/g/min, P=0.0284). Mirabegron also increased systolic blood pressure (+5±5 vs -6±10 mmHg, P=0.0252) and heart rate (6±7 vs -5±6 beats·min-1, P=0.0081) relative to baseline levels, which was prevented with bisoprolol. The glycerolipid-fatty acid cycling was not different between mirabegron without or with bisoprolol treatment (total cycling: 118.1±346.9 vs 168.5±439.5 μmol·min-1, P=0.8023). Conclusion: The administration of a β1-AR antagonist decreases the adverse cardiovascular effects of mirabegron. However, at the provided dose, it also restricts the stimulating effects of mirabegron on the thermogenesis. Public foundation grants This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.