2026 ECNP Congress

PS02-2074

Restoring balance: how the ketogenic diet mitigates the long-lasting effects of prenatal stress

Floriana De Cillis — M. Marizzoni, S. Saleri, V. Begni, M.A. Riva, A. Cattaneo · University of Milan, Department of Pharmacological and Biomolecular Sciences, Milan, Italy

2026 ECNP Congress

Background

Early-life stress drives enduring alterations in HPA axis reactivity, immune function, and neurodevelopmental trajectories, increasing vulnerability to anxiety, cognitive impairment, and psychiatric disorders [1,2]. Among the biological systems implicated in these stress-related outcomes, the gut microbiota has emerged as a key mediator, modulating immune activation, intestinal barrier integrity, and brain function through the gut-brain axis [3]. Its disruption may represent a critical biological pathway linking environmental stress to long-term behavioural and neurobiological sequelae. The ketogenic diet (KD), characterised by high-fat and low-carbohydrate intake, has shown promising efficacy in reducing symptoms across several psychiatric conditions, including depression and anxiety disorders [4]. However, the biological mechanisms underlying its beneficial effects remain largely unknown, and its impact on gut microbiota composition, particularly in the context of early-life adversity, has not been systematically investigated. Here, using a well-established preclinical model of early-life stress, we examined whether KD exerts its effects by modulating cecal microbiota composition in male and female offspring exposed to prenatal stress.

Methods

Pregnant Sprague-Dawley rats were exposed to a well-established prenatal stress paradigm (PNS) from gestational day 14 to 21, consisting of restraint stress three times daily under bright light. After weaning (PND 21), control (CTRL) and PNS-exposed male and female offspring were randomly assigned to receive either a KD or a standard control diet. Animals were sacrificed at PND 48, at which point cecal content was collected. DNA was extracted from cecal content and amplified using primers targeting the V3–V4 hypervariable region of the bacterial 16S rRNA gene, followed by paired-end sequencing on the Illumina MiSeq platform. Raw sequencing data were processed in QIIME2, including denoising and chimera removal via the DADA2 plugin. Alpha and beta diversity were assessed using multiple metrics, and compositional differences at the genus level were identified using MaAsLin2.

Results

Cecal microbiota composition was significantly altered by KD in both sexes. KD reduced alpha diversity in both control and PNS animals (p ≤ 0.05). Beta diversity differed significantly between the KD and CTRLs, regardless of sex (p ≤ 0.05). At the genus level, KD significantly increased the relative abundance of Parabacteroides, Alistipes, and Alloprevotella, while markedly reducing Roseburia, Lachnospiraceae NK4A136 group, Muribaculaceae, and Incertae Sedis in male offspring (q < 0.10), compared to CTRLs. Similar compositional shifts were observed in females, where KD increased Parabacteroides, Alloprevotella, and Escherichia-Shigella, and decreased Roseburia, Lachnospiraceae NK4A136 group, Incertae Sedis, Oscillibacter, and Colidextribacter (q < 0.10), compared to CTRLs. Notably, Lactobacillus showed opposite KD-induced changes between sexes, increasing in females while decreasing in males, highlighting sex-specific microbiota responses to the KD.

Conclusions

These results demonstrate that KD significantly modulates cecal microbiota composition in both male and female offspring, inducing sex-specific taxonomic shifts at multiple phylogenetic levels. While some of these changes may influence gut-brain communication and metabolic homeostasis, the overall impact of KD on microbial communities appears complex. Future studies integrating functional microbiome analyses and behavioural outcomes will be needed to elucidate the mechanisms underlying KD-microbiota interactions in the context of early-life stress.

References

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  2. Fogelman N, Canli T. Early Life Stress, Physiology, and Genetics: A Review. Front Psychol. 2019 Aug 2;10:1668. doi: 10.3389/fpsyg.2019.01668. PMID: 31428006; PMCID: PMC6688564.
  3. Foster JA, Rinaman L, Cryan JF. Stress & the gut-brain axis: Regulation by the microbiome. Neurobiol Stress. 2017 Mar 19;7:124-136. doi: 10.1016/j.ynstr.2017.03.001. PMID: 29276734; PMCID: PMC5736941.
  4. Tillery EE, Ellis KD, Threatt TB, Reyes HA, Plummer CS, Barney LR. The use of the ketogenic diet in the treatment of psychiatric disorders. Ment Health Clin. 2021 May 12;11(3):211-219. doi: 10.9740/mhc.2021.05.211. PMID: 34026397; PMCID: PMC8120987.