Early macrophage response to obesity encompasses Interferon Regulatory Factor 5 regulated mitochondrial architecture remodelling.

Adipose tissue macrophages (ATM) adapt to changes in their energetic microenvironment. Caloric excess, in a range from transient to diet-induced obesity, could result in the transition of ATMs from highly oxidative and protective to highly inflammatory and metabolically deleterious. Here, we demonstrate that Interferon Regulatory Factor 5 (IRF5) is a key regulator of macrophage oxidative capacity in response to caloric excess. ATMs from mice with genetic-deficiency of Irf5 are characterised by increased oxidative respiration and mitochondrial membrane potential. Transient inhibition of IRF5 activity leads to a similar respiratory phenotype as genomic deletion, and is reversible by reconstitution of IRF5 expression. We find that the highly oxidative nature of Irf5-deficient macrophages results from transcriptional de-repression of the mitochondrial matrix component Growth Hormone Inducible Transmembrane Protein (GHITM) gene. The Irf5-deficiency-associated high oxygen consumption could be alleviated by experimental suppression of Ghitm expression. ATMs and monocytes from patients with obesity or with type-2 diabetes retain the reciprocal regulatory relationship between Irf5 and Ghitm. Thus, our study provides insights into the mechanism of how the inflammatory transcription factor IRF5 controls physiological adaptation to diet-induced obesity via regulating mitochondrial architecture in macrophages.

Towards individualised and optimalised positioning of non-ventilated COVID-19 patients: Putting the affected parts of the lung(s) on top?

The outbreak of COVID-19 led to an unprecedented inflow of hospitalised patients with severe acute respiratory syndrome (SARS), requiring high-flow non-invasive oxygenation, if not invasive mechanical ventilation. While the best option in terms of non-invasive systems of oxygen delivery is still a matter of debate, it also remains unclear as to whether or not the optimal in-bed positioning of patients might also help to improve their oxygen saturation levels. On the basis of three representative cases, it is possible to propose the following hypotheses: (i) how patients are positioned has a strong influence on their oxygen saturation levels; (ii) saturation-optimalised positions are patient-specific; (iii) prone positions require ergonomic devices; and (iv) saturation-optimalised positions should aim to place the most affected part(s) of the lung(s) on top. Considered together, these hypotheses have led us to recommend that COVID-19 patients should undergo a specific assessment at admission to determine their saturation-optimalised in-bed position. However, further studies are still needed to assess the benefits of such a strategy on clinical outcomes.