🧬 BDNF Extraction Viewer

High-fat diet (HFD)-induced obesity impairs cognition and hippocampal neurogenesis, linked to reduced metabolic flexibility between mitochondrial fatty acid β-oxidation (FAO) and cytosolic de novo lipogenesis (DNL). It is not fully understood if switching to a high-carbohydrate diet (HCD) or a ketogenic diet (KD) could reverse these HFD-induced deficits, or if they do so through different mechanisms. Male C57BL/6J mice received HFD for 8 weeks to induce obesity. Mice were then either maintained on the HFD or switched to an HCD or KD for an additional 8 weeks. We evaluated systemic metabolism (body weight, serum biochemistry), tissue-specific metabolic remodeling (RNA-seq, histology, RT-qPCR, Western blot) and cognitive function (Y-maze test, novel object recognition test). Both HCD and KD interventions reversed HFD‑induced systemic abnormalities, including reducing ALT/AST, cholesterol, and LDL, and attenuating hepatic steatosis and adipocyte hypertrophy. Metabolically, KD markedly increased β‑hydroxybutyrate, whereas HCD showed a distinct triglyceride profile. Both diets improved hippocampus-dependent working and recognition memory. Hippocampal RNA‑seq revealed diet-specific mechanisms. HCD enriched anabolic processes, including upregulation of glucose transporters (Glut 1, 2, 3, 4) and DNL pathway (ACLY-ACC-FASN-SCD1). Conversely, KD enriched AMPK signaling, increasing monocarboxylate transporters (Mct 1, 2, 4) for ketone uptake and activating the neurotrophic AMPK-ERK-CREB-BDNF pathway. In conclusion, post-HFD switching to HCD or KD restores hippocampal structure and cognition via complementary mechanisms. HCD drives a substrate-centric, lipogenic program supporting proliferation, whereas KD engages a signaling-centric, neurotrophic program enhancing plasticity. Metabolic flexibility is a promising target for obesity-associated cognitive decline.