LDH Lactate Dehydrogenase and Follicle Stem Cell Metaboli…

Metabolism Meets Hair Biology: Why Energy Production Matters

Hair follicle stem cells face a fundamental metabolic choice: whether to remain quiescent (resting) or to activate and proliferate. This choice is not just about receiving the right growth signals — it also requires a metabolic switch that provides the energy and building blocks needed for rapid cell division. At the center of this metabolic switch lies lactate dehydrogenase (LDH), an enzyme that may be far more important for hair growth than its humble reputation suggests.

LDH Lactate Dehydrogenase and Follicle Stem Cell Metabolism Switch

The connection between LDH, stem cell metabolism, and hair growth was highlighted by a 2020 study from the Cotsarelis laboratory at the University of Pennsylvania. They demonstrated that hair follicle stem cells in telogen rely primarily on oxidative phosphorylation (OXPHOS) — the efficient, mitochondria-based energy production pathway. But when stem cells activate at the start of anagen, they switch to aerobic glycolysis (the Warburg effect), producing lactate as a byproduct even in the presence of oxygen. LDH is the enzyme that catalyzes this lactate production.

The Two Faces of Lactate Dehydrogenase

LDH exists as two main subunits that combine to form five tetrameric isoforms:

LDHA (LDH5, M4): Preferentially converts pyruvate to lactate. Favors glycolysis. This is the isoform that increases when stem cells activate.
LDHB (LDH1, H4): Preferentially converts lactate back to pyruvate. Favors oxidative metabolism. This is the dominant isoform in quiescent stem cells.

The LDHA/LDHB ratio determines the metabolic direction of the cell:

High LDHA/LDHB: Glycolytic metabolism, lactate production, rapid ATP generation — the activated stem cell state
Low LDHA/LDHB: Oxidative metabolism, efficient but slower ATP production — the quiescent stem cell state

Why Hair Follicle Stem Cells Need the Glycolytic Switch

When a stem cell transitions from quiescence to proliferation, its energy demands change dramatically:

Speed of ATP Production

Glycolysis produces ATP approximately 100 times faster than oxidative phosphorylation. While it yields less ATP per glucose molecule (2 vs. 36), the speed advantage is critical for rapidly dividing cells that need immediate energy for DNA replication, protein synthesis, and cell division.

Biosynthetic Precursors

Glycolytic intermediates feed into multiple biosynthetic pathways:

Ribose-5-phosphate: Needed for nucleotide synthesis (DNA/RNA production)
Serine and glycine: Needed for protein synthesis and one-carbon metabolism
Acetyl-CoA: Needed for lipid synthesis (new cell membranes)

These precursors are essential for making the macromolecules needed to double the cell’s contents before division.

Lactate as a Signaling Molecule

The lactate produced by LDHA is not just waste — it functions as a signaling molecule:

HIF-1α stabilization: Lactate inhibits prolyl hydroxylase, stabilizing HIF-1α even under normoxic conditions. This creates a pseudo-hypoxic state that promotes glycolytic gene expression and angiogenesis.
Receptor-mediated signaling: Lactate activates GPR81 (HCAR1), a lactate receptor on nearby cells, modulating their behavior.
Epigenetic effects: Lactate can be converted to lactyl-CoA and used for histone lactylation, a post-translational modification that regulates gene expression.

LDH and Hair Follicle Cycling

The metabolic state of follicle stem cells changes through the hair cycle:

Telogen (Resting Phase)

Bulge stem cells are quiescent with low LDHA expression. They rely on OXPHOS for their modest energy needs. Their mitochondria are functional but not highly active. This metabolic state is maintained by BMP signaling from the niche, which suppresses glycolytic gene expression.

Early Anagen (Activation)

When Wnt signaling and other activation signals reach the bulge stem cells, they upregulate LDHA and switch to glycolysis. This metabolic switch is essential — experiments show that blocking LDHA prevents stem cell activation and anagen initiation. The lactate produced by activated stem cells also signals to surrounding cells, promoting the angiogenesis needed to support the growing follicle.

Mid-Anagen (Growth Phase)

The hair matrix keratinocytes — the rapidly dividing cells that produce the hair shaft — are among the most glycolytically active cells in the body. They express high levels of LDHA and produce large amounts of lactate. This lactate creates a microenvironment that supports the high metabolic demand of the growing follicle.

Catagen (Regression)

As catagen begins, LDHA expression decreases and the metabolic state shifts back toward OXPHOS. The reduced glycolytic capacity may be one factor that limits the ability of follicle cells to sustain proliferation.

Implications for Hair Loss

Metabolic Insufficiency in Miniaturized Follicles

Miniaturized follicles in androgenetic alopecia may have impaired metabolic switching. If stem cells cannot efficiently upregulate LDHA and switch to glycolysis, they cannot generate the energy needed for robust anagen. This creates a scenario where the stem cells receive activation signals but cannot execute the metabolic program needed to respond.

Age-Related Metabolic Decline

Mitochondrial function declines with age, reducing the OXPHOS capacity of quiescent stem cells. This may impair their ability to maintain quiescence properly and to switch efficiently to glycolysis when activated. Age-related LDH expression changes may also contribute.

The LDH-Minoxidil Connection

Minoxidil’s potassium channel opening effect increases cellular membrane potential and ATP consumption, which indirectly stimulates glycolytic metabolism. This may be one reason why minoxidil promotes anagen — it creates a metabolic demand that favors the glycolytic switch.

Therapeutic Approaches Targeting Follicle Metabolism

Glycolytic Promoters

Compounds that promote the glycolytic switch could help activate dormant stem cells:

AICAR (AMPK activator): Promotes metabolic reprogramming toward glycolysis
DCA (dichloroacetate): Actually inhibits glycolysis (by activating pyruvate dehydrogenase), which would be counterproductive — this illustrates the need for careful pathway understanding

Mitochondrial Support

Supporting mitochondrial function in quiescent stem cells could improve their readiness for activation:

Coenzyme Q10: Supports electron transport chain function
PQQ (pyrroloquinoline quinone): Promotes mitochondrial biogenesis
NAD+ precursors (NMN, NR): Support mitochondrial function and sirtuin activity

HIF-1α Modulation

Since HIF-1α drives glycolytic gene expression including LDHA, modulating HIF-1α could influence the metabolic switch:

DMOG (dimethyloxalylglycine): A prolyl hydroxylase inhibitor that stabilizes HIF-1α. Topical application could promote glycolytic switching in follicle stem cells.
DMOOG: A more selective HIF-1α stabilizer with potential for topical use

Key Takeaways

Hair follicle stem cells must switch metabolisms to activate — the transition from OXPHOS to glycolysis, driven by LDHA, is essential for anagen initiation.
LDHA upregulation is not optional — blocking LDH prevents stem cell activation in experimental models.
Lactate is a signaling molecule, not just waste — it promotes angiogenesis, HIF-1α signaling, and epigenetic changes that support hair growth.
Metabolic insufficiency may contribute to miniaturization — if stem cells cannot execute the glycolytic switch, they cannot sustain robust anagen.
Minoxidil may work partly through metabolic effects — its ATP-consuming mechanism may favor the glycolytic switch.
Mitochondrial support and HIF-1α modulation are emerging strategies — these approaches target the metabolic foundation of hair growth.

NAD+ and the Metabolic-Regenerative Axis in Hair Follicles

The connection between NAD+ (nicotinamide adenine dinucleotide) and hair follicle metabolism is increasingly recognized as central to the follicle’s regenerative capacity. NAD+ is a critical cofactor for multiple enzymes involved in energy metabolism, DNA repair, and epigenetic regulation, including the sirtuins (SIRT1-7) and PARPs.

In hair follicle stem cells, NAD+ levels decline with age, paralleling the decline in regenerative capacity. SIRT1, which depends on NAD+ for its deacetylase activity, plays several roles relevant to hair follicle biology:

Deacetylation of β-catenin: Promotes its nuclear translocation and Wnt target gene activation
Deacetylation of p53: Reduces p53-mediated apoptosis in follicle cells
Regulation of PGC-1α: Promotes mitochondrial biogenesis, supporting the oxidative metabolism of quiescent stem cells
Anti-senescence activity: SIRT1 activation delays stem cell senescence through multiple mechanisms

Supplementation with NAD+ precursors (NMN or NR) has shown promising results in rejuvenating aged stem cells in animal models. A 2022 study demonstrated that NR supplementation improved hair follicle cycling in aged mice, with treated animals showing more robust anagen re-entry compared to untreated controls.

This NAD+-sirtuin-metabolism axis connects to LDH through the glycolytic pathway: the glycolytic switch that activates stem cells requires NAD+ as a cofactor for glyceraldehyde-3-phosphate dehydrogenase (GAPDH). If NAD+ levels are insufficient, even the LDHA-driven glycolytic switch cannot be executed properly, leaving stem cells metabolically stranded.

microRNA-Based Diagnostics for Hair Loss Subtyping

The miRNA expression profile of hair follicles could potentially be used to subtype different forms of hair loss, enabling more targeted treatment selection. A 2023 study used small RNA sequencing of plucked hair follicles to identify miRNA signatures that distinguished androgenetic alopecia from telogen effluvium with 89% accuracy. This non-invasive diagnostic approach could help clinicians choose the most appropriate treatment, avoiding the trial-and-error approach that characterizes much of current hair loss management.

LDH Lactate Dehydrogenase and Follicle Stem Cell Metabolism Switch