Ketone bodies as modulators of neuronal function: from cellular mechanisms in human hippocampal neurons in vitro to cognitive outcomes in vivo

This work investigates the impact of ketone metabolism on neuronal development, mitochondrial function and cognitive performance by integrating mechanistic analyses in a human stem cell derived neuronal model with a dietary intervention study in healthy adults. First, we established a simplified, scalable and cost-effective protocol for generating hippocampal neurons from human induced pluripotent stem cells (hiPSCs), preserving an active neurogenic niche composed of both immature and mature neuronal populations. Using this platform, we examined the effects of β-hydroxybutyrate (BOHB) on neuronal differentiation, dendritic maturation and bioenergetics. BOHB treatment did not modify neuronal yield or lineage specification, but significantly increased MAP2 expression, indicating enhanced dendritic arborization. Real-time PCR analyses showed upregulation of mitochondrial biogenesis regulators (PGC-1α, TFAM) and mitochondrial markers (MT-ND1, CS), while respirometric profiling revealed elevated basal respiration, increased maximal OCR and higher spare respiratory capacity. These findings demonstrate that BOHB promotes coordinated structural and metabolic maturation of hippocampal neurons by stimulating mitochondrial biogenesis and expanding mitochondrial capacity to support dendritic development. In parallel, we conducted an exploratory isocaloric ketogenic diet intervention in healthy young students to evaluate whether systemic ketosis modulates cognitive performance. After three weeks of dietary ketosis, participants exhibited faster completion times in visuomotor and processing-speed tasks (DST, TMT, Stroop) but showed decreased accuracy on a high-load working memory test (Aospan). These results suggest that ketosis may differentially influence cognitive domains, enhancing speeded processing while impairing complex working memory performance, potentially through stress-related mechanisms. Collectively, this work provides mechanistic evidence that ketone bodies enhance neuronal plasticity by boosting mitochondrial biogenesis and dendritic maturation and offers preliminary in vivo data indicating that ketogenic diet may exert specific effects on cognition. The combination of hiPSC-derived hippocampal modelling and controlled nutritional interventions highlights a translational framework for understanding how metabolism shapes neuronal function and cognitive outcomes and sets the stage for future investigations into metabolic modulation of brain plasticity, learning and neuronal resilience.