The brain is a big energy consumer, and efficiently outcompetes other organs for glucose to meet its energy needs. This ‘selfish’ behaviour is understandable — the brain has crucial roles in controlling essential physiological functions, such as breathing and heartbeat, and in other actions vital for survival. Similarly, the immune system fiercely protects us from pathogens, which requires energy for immune cell proliferation and to combat infections. When activated, immune cells alter their metabolism and demand glucose from other organs, which parallels the ‘selfish’ behaviour of the brain. But what happens when the energy demands of these two systems clash?

A study by Kealy et al. shed light on the consequences of competition between the brain and immune system for glucose during acute inflammation. In this study, the authors aimed to uncover mechanisms that underlie delirium, a state of severe cognitive dysfunction — particularly in older individuals (in whom acute inflammation is a common trigger).