Autophagy, FGF21 and glucagon during critical illness: interactions and therapeutic perspectives
Multiple organ failure is a leading cause of morbidity and mortality among critically ill patients, of which the underlying mechanisms are incompletely understood. In this project, we investigated the underlying metabolic mechanisms of critical illness induced organ failure. We identified a crucial role of autophagy in the pathogenesis of organ failure and discovered Fibroblast Growth Factor 21 as new adaptive cellular stress-induced hormone, which opens new therapeutic perspectives for the treatment of multiple organ failure. Finally, we showed that glucagon is a key mediator of the deranged amino acid metabolism during critical illness by promoting hepatic amino acid catabolism, without affecting muscle wasting.
Energy expenditure and nutritional therapy in critically ill patients
In critically ill patients, a multitude of factors are responsible for the metabolic state and energy expenditure (EE). In daily clinical practice, patients are frequently left without adequate prescription of calories and proteins. This clinical research enlarged the knowledge in this field. Physicians in charge of nutritional therapy use total energy expenditure to guide their nutritional prescription. Indirect calorimetry (IC) is increasingly advocated to determine basal metabolic rate. We evaluated the indications, feasibility and the use of IC. We assessed whether measurements obtained by IC reached agreement with the results of mathematical equations used to calculate EE. We developed the technical possibility and a theoretical model to perform IC in an ECMO-setting. After evaluation of available research data, we suggest recommendations for nutritional therapy in patients undergoing continuous renal replacement therapy.
Brain and sepsis: from macro to microcirculation
Brain dysfunction is a frequent complication of sepsis and is usually defined as "sepsis-associated encephalopathy" (SAE). Its pathophysiology is complex and related to a number of processes and pathways, while the exact mechanisms producing neurological impairment in septic patients have not been completely elucidated. Alterations in cerebral blood flow (CBF) have been suggested as a key component for the development of SAE. More importantly, the natural mechanisms that protect the brain from reduced/inadequate CBF can be impaired in septic patients, especially in those with shock, and this further contributes to cerebral ischemia if blood pressure drops below a critical threshold. Hypercapnia is associated with a narrower autoregulatory plateau, which may potentially results in large CBF variations when mean arterial pressure (MAP) varies within usual targets. Finally, as SAE occurs also in patients without hemodynamic instability, alterations in brain tissue perfusion could occur independently from hypotension; thus, alterations in cerebral microcirculation, which largely regulates regional flow and blood-cellular nutrients exchanges, could contribute to SAE.
Pathophysiology of cholestatic liver dysfunction during critical illness
ICU patients commonly develop cholestatic liver dysfunction, which has been associated with adverse outcome. Cholestasis or decreased bile flow can lead to an accumulation of bilirubin/bile acids and is presumed to induce cell damage. This research focused on unravelling the hepatobiliary changes at biochemical/molecular level during critical illness and the possibility that mild hyperbilirubinemia may be adaptive and beneficial.
Metabolic stress, mitochondria and organ failure during critical illness: Underlying mechanisms revealing therapeutic potential”
In this project, we studied mechanisms how prevention of hyperglycemia and relative starvation may protect against critical illness-induced multiple organ failure. A crucial role for mitochondrial damage was found. Moreover, activation of autophagy - an essential cellular repair process that is potently suppressed by nutrients and by anabolic hormones - was identified as potential therapeutic strategy for this condition.
Nutrients, insulin and muscle wasting during critical illness
We gained more insight in the impact of the combination of intravenous nutrition with the infusion of insulin to maintain normoglycemia, on severe muscle wasting during prolonged critical illness. We concluded that parenteral feeding during critical illness may reduce muscle catabolism at the expense of a threat to vital organs by impairing autophagy, the physiological systems to clear cellular damage.
Computerized data management in the Intensive Care Unit : Predictive modeling, time series analysis and opportunities for support of care
The amount of patient related data generated in the ICU exceeds human cognitive capacity by far. Computerized data analysis, using automatically learning methods, allows to develop applications such as clinical decision support tools and predictive models, adapted to a specific clinical context. This doctoral project is a first step in this exciting and novel research domain.
Peripheral and Respiratory Muscle Weakness in ICU : Causes and Consequences
We showed that normalising glycaemia reduced the incidence of CIP/CIM and the need for prolonged mechanical ventilation in a medical ICU. This benefit was confirmed in a meta-analysis and in daily care. Diaphragmatic force measured with bilateral anterior magnetic phrenic nerve stimulation showed a logarhitmtic decline with increasing duration of mechanical ventilation, fitting the concept of ventilator induced diaphragmatic function.