Microglial metabolic reprogramming refers to the dynamic shifts in cellular energy metabolism that microglia undergo in response to pathological stimuli in neurodegenerative diseases. This process involves a fundamental shift from oxidative phosphorylation (OXPHOS) in surveilling microglia to aerobic glycolysis in activated microglia, with profound implications for neuroinflammatory responses and disease progression [@yang2017].
Recent comprehensive reviews have synthesized the growing understanding of this phenomenon. A 2025 review in Molecular Neurobiology provides an updated synthesis of metabolic transitions from homeostasis to responsive states in microglia, highlighting metabolism-based targeted therapy approaches for neurodegeneration [@molneurobiol2025].
Metabolic States of Microglia
Homeostatic Microglia (OXPHOS-Dominant)
In the healthy brain, surveilling microglia rely primarily on oxidative phosphorylation for energy production. This metabolic state supports the sustained patrol and immune surveillance functions of homeostatic microglia. The mitochondria-dense cytoplasm enables efficient ATP production through the electron transport chain, with minimal glycolytic flux [Huang Y, et al. Metabolic reprogramming in microglia from Alzheimer's Disease brain. J Neuroinflammation. 2022;19(1):89](https://doi.org/10.1186/s12974-022-02456-2).
Activated Microglia (Glycolysis-Dominant)
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Microglial Metabolic Reprogramming
Introduction
Microglial metabolic reprogramming refers to the dynamic shifts in cellular energy metabolism that microglia undergo in response to pathological stimuli in neurodegenerative diseases. This process involves a fundamental shift from oxidative phosphorylation (OXPHOS) in surveilling microglia to aerobic glycolysis in activated microglia, with profound implications for neuroinflammatory responses and disease progression [@yang2017].
Recent comprehensive reviews have synthesized the growing understanding of this phenomenon. A 2025 review in Molecular Neurobiology provides an updated synthesis of metabolic transitions from homeostasis to responsive states in microglia, highlighting metabolism-based targeted therapy approaches for neurodegeneration [@molneurobiol2025].
Metabolic States of Microglia
Homeostatic Microglia (OXPHOS-Dominant)
In the healthy brain, surveilling microglia rely primarily on oxidative phosphorylation for energy production. This metabolic state supports the sustained patrol and immune surveillance functions of homeostatic microglia. The mitochondria-dense cytoplasm enables efficient ATP production through the electron transport chain, with minimal glycolytic flux [Huang Y, et al. Metabolic reprogramming in microglia from Alzheimer's Disease brain. J Neuroinflammation. 2022;19(1):89](https://doi.org/10.1186/s12974-022-02456-2).
Activated Microglia (Glycolysis-Dominant)
Upon disease-related activation, microglia shift toward aerobic glycolysis [@huang2018]:
Elevated glycolytic enzymes: Hexokinase 2 (HK2), phosphofructokinase (PFK), and pyruvate kinase M2 (PKM2) are strongly upregulated
Lactate production: Pyruvate is converted to lactate by LDH-A rather than entering the TCA cycle
Pentose phosphate pathway: Increased flux through PPP generates NADPH for [oxidative-stress](/mechanisms/oxidative-stress) production and nucleotide biosynthesis
Mitochondrial dysfunction: Progressive loss of mitochondrial membrane potential, reduced OXPHOS complex activity
Pro-inflammatory phenotype: Glycolytic metabolism sustains [NLRP3 inflammasome](/mechanisms/nlrp3-inflammasome) activation and cytokine production
Metabolically Exhausted Microglia
In chronic neurodegeneration, sustained glycolytic activation leads to metabolic exhaustion: [@bernier2020]
Energy crisis: Both OXPHOS and glycolysis become impaired, leading to ATP depletion
Impaired phagocytosis: Loss of energy supply prevents effective clearance of amyloid plaques and debris
Senescent phenotype: Metabolically exhausted [microglia](/cell-types/microglia) resemble senescent cells, with irreversible pro-inflammatory features
Lipid accumulation: Failure of fatty acid oxidation drives lipid droplet accumulation, producing the LDAM phenotype
Molecular Regulators
mTOR-HIF-1α Axis
The mechanistic target of rapamycin ([mTOR](/mechanisms/mtor-neurodegeneration)) is a central metabolic sensor that drives the glycolytic switch in microglia [@masuch2016]:
[TREM2](/proteins/trem2-protein)-[mTOR](/mechanisms/mtor-neurodegeneration) coupling: [TREM2](/proteins/trem2-protein) ligation by lipoproteins and [amyloid-beta](/proteins/amyloid-beta) activates PI3K-AKT-[mTOR](/mechanisms/mtor-neurodegeneration) signaling, increasing microglial metabolic capacity. [TREM2](/proteins/trem2-protein) loss-of-function variants (R47H, R62H) — which are Alzheimer's Disease risk factors — impair [mTOR](/mechanisms/mtor-neurodegeneration) activation, reducing both glycolytic and OXPHOS capacity and trapping microglia in a metabolically dysfunctional state [Ulland et al., 2017](https://doi.org/10.1016/j.cell.2017.07.023)
HIF-1α stabilization: [mTOR](/mechanisms/mtor-neurodegeneration) activates hypoxia-inducible factor 1-alpha (HIF-1α), the master transcriptional regulator of glycolytic gene expression. HIF-1α upregulates GLUT1, HK2, LDHA, and PDK1 (which blocks pyruvate entry into mitochondria)
Rapamycin effects: [mTOR](/mechanisms/mtor-neurodegeneration) inhibition by rapamycin reduces microglial glycolysis and inflammatory cytokine production, but also impairs beneficial [TREM2](/proteins/trem2-protein)-dependent responses, highlighting the dual nature of [mTOR](/entities/mtor) in neurodegeneration
AMPK Pathway
AMP-activated protein kinase (AMPK) is the counterregulator of [mTOR](/mechanisms/mtor-signaling-pathway) and promotes OXPHOS: [@zhang2019]
Energy sensing: AMPK is activated by high AMP/ATP ratio, sensing energy depletion
Therapeutic potential: AMPK activators (metformin, AICAR) can restore microglial OXPHOS and reduce neuroinflammation in preclinical models
Glycolytic Enzymes as Regulators
Several glycolytic enzymes have moonlighting functions that directly regulate microglial inflammatory responses: [@latta2015]
PKM2 (pyruvate kinase M2): In its dimeric form, PKM2 translocates to the nucleus and acts as a transcriptional coactivator for HIF-1α and STAT3, amplifying inflammatory gene expression. Pharmacological stabilization of PKM2 tetramers (using TEPP-46 or DASA-58) traps PKM2 in its enzymatic form, preventing nuclear translocation and reducing inflammation [Palsson-McDermott et al., 2015](https://doi.org/10.1016/j.cmet.2015.06.004)
HK2 (hexokinase 2): Beyond its glycolytic role, HK2 interacts with VDAC on the mitochondrial outer membrane, regulating [NLRP3 inflammasome](/mechanisms/nlrp3-inflammasome) activation
GAPDH: Undergoes post-translational modifications (succination, oxidation) in inflammatory microglia, affecting both glycolytic flux and gene regulation
Itaconate and the TCA Cycle
The TCA cycle intermediate itaconate has emerged as a key immunometabolite in microglia: [^9]
Immune-responsive gene 1 (IRG1/ACOD1): Produces itaconate from cis-aconitate in the TCA cycle
Therapeutic potential: Itaconate derivatives are being explored as anti-inflammatory therapeutics for neurodegeneration
Disease-Specific Metabolic Alterations
Alzheimer's Disease
In [Alzheimer's Disease](/diseases/alzheimers-disease), microglial metabolic reprogramming occurs in stages:
Early activation: [amyloid-beta](/proteins/amyloid-beta) oligomers trigger [TREM2](/proteins/trem2-protein)-mTOR-dependent glycolytic switch, initially enhancing microglial motility and phagocytosis — this may represent a protective response
Chronic glycolysis: Sustained [amyloid-beta](/proteins/amyloid-beta) exposure locks microglia in a glycolytic state with impaired OXPHOS. [Disease-associated microglia (DAM) show elevated HK2, PKM2, and LDHA expression
Metabolic exhaustion: In advanced disease, microglia surrounding dense-core plaques show both impaired glycolysis and OXPHOS, becoming metabolically inert and unable to restrict plaque growth
Spatial metabolic heterogeneity: Recent spatial transcriptomics studies reveal that microglial metabolic state varies with distance from amyloid plaques — plaque-proximal microglia are most glycolytic, while those further away maintain more homeostatic metabolism [Xu et al., 2025](https://doi.org/10.1186/s12974-025-03289-4)
Parkinson's Disease
In [Parkinson's disease](/diseases/parkinsons-disease):
[Dopamine](/entities/dopamine) depletion in the [substantia-nigra](/brain-regions/substantia-nigra) removes tonic inhibition of microglial activation, permitting metabolic reprogramming
ALS
In [ALS](/diseases/amyotrophic-lateral-sclerosis):
[SOD1](/proteins/sod1) mutant protein in microglia induces [mitochondrial dysfunction](/mechanisms/mitochondrial-dysfunction) and oxidative damage, forcing glycolytic dependence
[TDP-43](/proteins/tdp-43) pathology disrupts RNA processing of metabolic enzyme transcripts, altering the metabolic transcriptome
Several therapeutic approaches target microglial metabolism:
mTOR modulators: Rapamycin and its analogs reduce glycolytic inflammation but must be carefully dosed to preserve beneficial [TREM2](/proteins/trem2-protein)-mTOR signaling
AMPK activators: Metformin, AICAR, and the natural compound berberine promote OXPHOS and reduce neuroinflammation
HIF-1α inhibitors: Pharmacological inhibition of HIF-1α (using echinomycin, acriflavine) reduces glycolytic gene expression in activated microglia
Itaconate derivatives: 4-octyl itaconate and dimethyl itaconate activate anti-inflammatory pathways
NAD+ precursors: Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) restore mitochondrial function by replenishing NAD+ pools
Mitochondrial-Targeted Approaches
MitoQ and MitoTEMPO: Mitochondria-targeted antioxidants that reduce mitochondrial [oxidative-stress](/mechanisms/oxidative-stress) and preserve OXPHOS capacity
Urolithin A: Activates [mitophagy](/mechanisms/mitophagy), clearing damaged mitochondria and promoting biogenesis of healthy organelles
SS-31 (elamipretide): Stabilizes cardiolipin in the inner mitochondrial membrane, supporting electron transport chain function
Ketogenic and Dietary Approaches
Ketone bodies: β-hydroxybutyrate (BHB) can serve as alternative fuel for microglial OXPHOS, bypassing glycolytic impairment. BHB also inhibits [NLRP3 Inflammasome](/mechanisms/nlrp3-inflammasome) activation
Ketogenic diet: Preclinical studies show reduced neuroinflammation and improved microglial function in AD models fed ketogenic diets
Intermittent fasting: Enhances AMPK activation and mitophagy, potentially restoring microglial metabolic health