D-ꞵ-hydroxybutyrate stabilizes hippocampal CA3-CA1 circuit during acute insulin resistance

1. The brain primarily relies on glycolysis for mitochondrial respiration but switches to alternative fuels such as ketone bodies (KBs) when less glucose is available. Neuronal KB uptake, which does not rely on glucose transporter 4 (GLUT4) or insulin, has shown promising clinical applicability in alleviating the neurological and cognitive effects of disorders with hypometabolic components. However, the specific mechanisms by which such interventions affect neuronal functions are poorly understood. In this study, we pharmacologically blocked GLUT4 to investigate the effects of exogenous KB D-ꞵ-hydroxybutyrate (D-ꞵHb) on mouse brain metabolism during acute insulin resistance (AIR). We found that both AIR and D-ꞵHb had distinct impacts across neuronal compartments: AIR decreased synaptic activity and long-term potentiation (LTP) and impaired axonal conduction, synchronization, and action potential (AP) properties, while D-ꞵHb rescued neuronal functions associated with axonal conduction, synchronization, and LTP. 2. Significance statement This study investigates the impact of acute insulin resistance on the functionality of the hippocampal circuit and the potential protective effects of ketone body supplementation. By inhibiting GLUT4 receptors to induce acute insulin resistance, we reveal several detrimental changes caused by impaired neuronal glucose uptake. These changes include impairments in synaptic activity, axonal conduction, and neuronal firing properties. The study further examines the distinctive effects of acute insulin resistance and the rescue agent D-βHb on synaptic activity, long-term potentiation, axonal conduction, synchronization, and neuronal firing. By shedding light on neuronal responses during insulin resistance, this investigation advances our understanding of neurological disorders associated with hypometabolism and highlights the potential therapeutic value of D-βHb.