Metformine as a Protective Factor of Mortality in Type 2 Diabetic Patients Admitted to the ICU for Septic Shock: a Multicentre Retrospective Cohort Study.

Septic shock is one of the leading causes of admission to intensive care units (ICU), with an incidence of approximately 19 million patients per year worldwide. Despite progress made in the management of patients suffering from this condition, mortality and morbidity remain high and show little improvement. Indeed, according to studies, the mortality rate of septic shock ranges from 25 to 30%. Diabetic patients, due to their susceptibility to infections and greater vulnerability, represent a significant proportion of patient cohorts in septic shock. Moreover, diabetes is a factor of poor prognosis during septic shock.

Metformin, an oral anti-diabetic treatment, is currently considered the first-line therapy for type 2 diabetes. It modifies glucose metabolism by inhibiting, notably at the mitochondrial level, the electron transport chain through the inhibition of complex I. This inhibition of complex I decreases mitochondrial production of Adenosine Triphosphate (ATP) and induces activation of AMPK, a key enzyme in energy metabolism. Thus, metformin is responsible for an increase in glycolysis and an inhibition of gluconeogenesis in the liver.

During septic shock, mitochondrial ATP production is limited due to decreased arterial oxygen transport, leading to tissue hypoxia and mitochondrial dysfunction. This results in increased anaerobic energy production through activation of glycolysis, and consequently, increased lactate production responsible for metabolic acidosis. Several studies focusing on septic shock have observed that hyperlactatemia during the initial hours of management is a factor of poor prognosis.

Given the alterations in mitochondrial metabolism caused by metformin, which may exacerbate hyperlactatemia, its potential accumulation in cases of acute renal failure, the hepatic metabolism of lactate, and the deleterious consequences of lactic metabolic acidosis, it is recommended to discontinue metformin during septic shock. However, despite these recommendations, some studies suggest a lower mortality rate in septic shock patients treated with metformin, despite older age, higher rates of cardiovascular disease, and renal failure.

The first hypothesis is that patients on metformin may have better adaptation of their energy metabolism during a significant drop in oxygen supply (a mitochondrial adaptive mechanism reducing energy needs), which limits oxidative stress and its harmful effects. The second hypothesis is that metformin has an immunomodulatory role, resulting in a more moderate inflammatory response in case of infection, and thus less endothelial and visceral dysfunction. Thus, metformin, through modification of mitochondrial metabolism, appears to have pleiotropic, anti-inflammatory, antithrombotic, and vasoactive effects that could be beneficial in septic shock. The benefit of metformin in patients with septic shock therefore needs to be clarified through well-conducted large cohort studies.