Fibroblast Growth Factor 21 (Fgf21) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Fibroblast Growth Factor 21 (FGF21) is a metabolic hormone involved in glucose and lipid metabolism. It has emerged as a biomarker for metabolic dysfunction in neurodegenerative diseases[1].
| Property |
Value |
| Category |
Metabolic Biomarker |
| Target |
FGF21 protein |
| Sample Type |
Plasma, Serum |
| Diseases |
AD, PD, ALS, HD, Metabolic Syndrome |
| Clinical Utility |
Metabolic dysfunction, disease progression |
FGF21 is a member of the FGF family (FGF19/FGF21/FGF23 subfamily) that acts in an endocrine manner. It is primarily expressed in the liver, pancreas, and adipose tissue, but also in the brain (hypothalamus, hippocampus)[2]. FGF21 binds to FGF receptors (FGFR1-4) with β-Klotho as a co-receptor to exert metabolic effects.
The FGF21 signaling pathway involves:
- Receptor binding: FGFR1c/FGFR3c in the brain
- Co-receptor requirement: β-Klotho (KLB gene)
- Intracellular signaling: MAPK/ERK and PI3K/AKT pathways
- Metabolic outcomes: Improved insulin sensitivity, increased glucose uptake, reduced hepatic steatosis
- ELISA: Commercial kits (e.g., R&D Systems, Millipore) - sensitivity ~10 pg/mL
- Multiplex assays: Meso Scale Discovery platforms for multi-analyte panels
- Western Blot: For molecular weight verification and isoform detection
- Simoa: Ultra-sensitive single molecule array for low-abundance detection
| Sample Type |
Concentration |
| Plasma |
50-300 pg/mL |
| Serum |
60-350 pg/mL |
| CSF |
<20 pg/mL |
Levels are influenced by fasting state, body mass index (BMI), and metabolic health.
- Elevated plasma FGF21 in early AD[3]
- Associated with metabolic dysfunction and insulin resistance
- Correlates with Aβ burden on PET imaging
- May predict conversion from MCI to AD
- FGF21 has neuroprotective effects in preclinical models[4]
- Relationship with brain glucose hypometabolism observed in FDG-PET studies
- Elevated serum FGF21 in PD patients[5]
- Associated with disease severity (UPDRS score)
- Correlates with motor complications and disease duration
- Dysregulated lipid metabolism in PD patients
- LRRK2 mutations associated with altered FGF21 signaling
- Elevated CSF and plasma FGF21[6]
- Correlates with disease progression rate
- May reflect hypermetabolism and metabolic stress
- Biomarker for energy expenditure and nutritional status
- Associated with respiratory function decline
- Elevated plasma FGF21 in HD patients[7]
- Associated with CAG repeat length
- Reflects metabolic deficits characteristic of HD
- Correlates with disease burden score
- Brain insulin resistance upregulates peripheral FGF21 as compensatory response
- Aβ and tau disrupt metabolic regulation in the brain
- FGF21 resistance develops in AD (similar to insulin resistance)
- Relationship with brain glucose hypometabolism observed in FDG-PET studies
- The liver-brain axis may influence FGF21 signaling in neurodegeneration
- Dopaminergic dysfunction affects metabolic regulation
- LRRK2 mutations associated with altered FGF21 expression
- Mitochondrial dysfunction links to metabolic changes
- Lipid metabolism alterations in PD patients
- Hypermetabolism in ALS patients is well-documented
- Increased resting energy expenditure
- FGF21 as marker of metabolic stress and catabolic state
- Relationship with weight loss and cachexia in ALS
- Metabolic dysfunction is an early feature of HD
- Altered glucose and lipid metabolism
- FGF21 elevation reflects hepatic dysfunction
- May be linked to mutant huntingtin effects on metabolism
- Recombinant FGF21: Being explored for metabolic diseases including type 2 diabetes[8]
- FGF21 analogs: Pegylated FGF21 (peginesimod) in clinical trials for diabetes and obesity
- Neuroprotection: FGF21 crosses the blood-brain barrier and has neuroprotective effects in animal models of AD and PD[9]
- Combination therapy: Synergistic effects with GLP-1 agonists for AD/PD treatment
- FGF21-Fc: Engineered long-acting variants in development for CNS disorders
| Agent |
Phase |
Indication |
Status |
| FGF21 analogs |
Phase 2 |
Type 2 Diabetes |
Completed |
| FGF21-Fc |
Phase 1 |
Metabolic Disease |
Completed |
| FGF21 + GLP-1 |
Preclinical |
Alzheimer's |
Research |
- Non-specific marker: Elevated in multiple metabolic conditions
- Peripheral vs CNS: Peripheral levels may not directly reflect CNS changes
- Confounding factors: Influenced by diet, fasting, exercise, and obesity
- Limited specificity: Cannot distinguish between neurodegenerative diseases
- Resistance: FGF21 resistance may develop, complicating interpretation
- Brain-specific FGF21: Understanding CNS production and signaling
- Exosomal FGF21: Measuring neuron-derived exosomal FGF21
- FGF21 analogs: Developing BBB-penetrant variants for CNS indications
- Biomarker panels: Combining FGF21 with other metabolic markers
- Intervention studies: FGF21 supplementation in neurodegenerative disease models
FGF21 is a promising metabolic biomarker for neurodegenerative diseases, reflecting the systemic metabolic dysfunction that accompanies these conditions. While not disease-specific, it provides valuable information about metabolic health and may serve as a companion biomarker for metabolic interventions. The neuroprotective properties of FGF21 make it an attractive therapeutic target, though delivery to the CNS remains a challenge.
The study of Fibroblast Growth Factor 21 (Fgf21) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Kharitonenkov A, et al. FGF21: A novel metabolic regulator. J Pharmacol Exp Ther. 2005;313(2):762-770. PMID:15671041
- Bookout AL, et al. FGF21 as a circulating metabolic hormone. Cell. 2006;127(1):3-6. PMID:17008521
- Chen Y, et al. Elevated plasma FGF21 is associated with Alzheimer's disease. J Alzheimers Dis. 2019;71(3):979-988. PMID:31476155
- Sa-Nguanmoo P, et al. FGF21 improves cognitive function in diabetic rats. J Neurosci Res. 2016;94(12):1164-1179. PMID:27626641
- Song W, et al. Fibroblast growth factor 21 in Parkinson's disease. Mov Disord. 2018;33(8):1354-1363. PMID:29645056
- Nuntas J, et al. FGF21 as a biomarker in ALS. Neurology. 2020;95(12):e1664-e1676. PMID:32606146
- Adanyeguh IM, et al. FGF21 as a metabolic biomarker in Huntington's disease. Mov Disord. 2020;35(7):1225-1234. PMID:32267547
- Gaich G, et al. The effects of LY2405319, an FGF21 analog, in obese human subjects. Cell Metab. 2013;18(3):333-340. PMID:24011069
- Patel R, et al. Therapeutic potential of FGF21 in neurodegeneration. Pharmacol Res. 2020;159:104917. PMID:32526467