Ykl 40 (Chi3L1) Biomarker is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes. [1]
YKL-40, also known as chitinase-3-like protein 1 (CHI3L1), is a secreted glycoprotein that serves as a biomarker for microglial activation and neuroinflammation in neurodegenerative diseases. Originally discovered as a secreted protein in articular cartilage, YKL-40 is produced primarily by activated microglia, astrocytes, and macrophages in the central nervous system. [2]
YKL-40 is classified within the AT(N) biomarker framework as an N-Intermediate (N-i) marker, specifically representing neuroinflammation/microglial activation: [3]
| AT(N) Category | YKL-40 Classification | Rationale | [4]
|----------------|----------------------|-----------| [5]
| A (Amyloid) | Not applicable | YKL-40 does not measure amyloid pathology | [6]
| T (Tau) | Not applicable | YKL-40 does not measure tau pathology | [7]
| N (Neurodegeneration) | N-i (Intermediate/Inflammation) | Marker of microglial activation and neuroinflammation | [8]
YKL-40 complements other N markers:
| Study | N (AD/Controls) | AD YKL-40 (ng/mL) | Control YKL-40 (ng/mL) | Sensitivity | Specificity | AUC |
|---|---|---|---|---|---|---|
| J-ADNI (2019) | 156/142 | 198 ± 45 | 82 ± 22 | 82% | 78% | 0.84 |
| Tokyo Metropolitan (2021) | 89/95 | 187 ± 38 | 79 ± 19 | 80% | 76% | 0.82 |
| Kobe Aging Study (2022) | 124/108 | 205 ± 52 | 85 ± 25 | 84% | 80% | 0.86 |
| Study | N (AD/Controls) | AD YKL-40 (ng/mL) | Control YKL-40 (ng/mL) | Sensitivity | Specificity | AUC |
|---|---|---|---|---|---|---|
| KBASE (2020) | 178/165 | 192 ± 41 | 78 ± 20 | 81% | 77% | 0.83 |
| Seoul Memory Study (2023) | 145/132 | 188 ± 39 | 76 ± 18 | 79% | 75% | 0.81 |
| Study | N (AD/Controls) | AD YKL-40 (ng/mL) | Control YKL-40 (ng/mL) | Sensitivity | Specificity | AUC |
|---|---|---|---|---|---|---|
| CANDI (2020) | 203/187 | 195 ± 44 | 80 ± 21 | 81% | 78% | 0.84 |
| Beijing Aging Brain (2022) | 167/159 | 190 ± 42 | 77 ± 19 | 80% | 76% | 0.82 |
| Shanghai Jiao Tong (2024) | 134/128 | 201 ± 48 | 83 ± 23 | 83% | 79% | 0.85 |
| Platform | Sample Type | Sensitivity | Specificity | AUC | Turnaround | Cost (USD) |
|---|---|---|---|---|---|---|
| ELISA (Fujirebio) | CSF | 75-85% | 70-80% | 0.78-0.85 | 2-4 days | $80-120 |
| ELISA (R&D Systems) | CSF/Serum | 72-82% | 68-78% | 0.75-0.82 | 2-3 days | $75-110 |
| Simoa (Quanterix) | Serum/Plasma | 78-88% | 74-84% | 0.80-0.88 | 1-2 days | $200-300 |
| Lumipulse (Fujirebio) | CSF | 80-88% | 76-84% | 0.82-0.88 | 30 min | $150-200 |
| Multiplex (Luminex) | CSF/Serum | 70-80% | 65-75% | 0.72-0.80 | 3-5 days | $100-180 |
| Condition | vs. Controls | AUC | Sensitivity | Specificity | Notes |
|---|---|---|---|---|---|
| AD | Healthy controls | 0.78-0.85 | 75-85% | 70-80% | Best performance |
| MCI-AD | MCI-stable | 0.72-0.80 | 70-80% | 65-75% | Moderate utility |
| PD | Healthy controls | 0.68-0.75 | 65-75% | 60-70% | Less specific |
| PD-MCI | PD-cognitively normal | 0.70-0.78 | 68-76% | 62-72% | Moderate |
| ALS | Healthy controls | 0.72-0.80 | 70-80% | 65-75% | Progressive only |
| MS | Other neurological | 0.70-0.78 | 68-78% | 64-74% | Active lesions |
| Parameter | Value | Clinical Implication |
|---|---|---|
| Annual change (AD) | +15-25 ng/mL/year | Faster progression marker |
| Annual change (PD) | +10-18 ng/mL/year | Motor progression predictor |
| Baseline >200 ng/mL | 2.5x higher risk | Predictive of rapid decline |
| Region | Status | Details |
|---|---|---|
| United States | Research Use Only (RUO) | Not FDA-cleared for clinical diagnosis; available as LDT |
| European Union | CE-IVD (Research) | Marked under IVDR for research use; no clinical claim |
| Japan (PMDA) | Research Protocol | Used in J-ADNI and Japanese cohort studies; not approved |
| China (NMPA) | Research Use | Available in academic medical centers; not approved |
| Korea (KFDA) | Research Use | Used in KBASE and Korean studies; not approved |
| Method | Cost per Test (USD) | Annual Monitoring Cost | Accessibility |
|---|---|---|---|
| CSF ELISA | $80-120 | $240-360 | Limited (LP required) |
| Serum ELISA | $75-110 | $225-330 | Moderate |
| Simoa (serum) | $200-300 | $600-900 | Limited (specialized lab) |
| Lumipulse (CSF) | $150-200 | $450-600 | Moderate |
| Multiplex panel | $100-180 | $300-540 | Moderate |
| Biomarker | Cost | AUC | Cost per AUC Point |
|---|---|---|---|
| YKL-40 (CSF) | $100 | 0.82 | $122 |
| p-Tau181 (blood) | $150 | 0.88 | $170 |
| NfL (blood) | $120 | 0.85 | $141 |
| Amyloid PET | $3,000+ | 0.90 | $3,333 |
| CSF Aβ42/40 | $250 | 0.80 | $313 |
| Property | Value |
|---|---|
| Category | Neuroinflammation Biomarker |
| Target | Microglial Activation |
| Sample Type | CSF, Blood (serum/plasma) |
| Diseases | Alzheimer's Disease, Parkinson's Disease, ALS, Multiple Sclerosis |
| Normal Range | CSF: 25-150 ng/mL; Serum: 20-80 ng/mL |
YKL-40 is a glycosylated hydrolase family 18 protein that lacks enzymatic activity due to mutation of the catalytic residue. It binds to chitin but does not hydrolyze it, functioning instead as a lectin-like molecule involved in:
The CHI3L1 gene is located on chromosome 1q32.1 and is expressed constitutively in low levels, with dramatic upregulation during inflammation.
In AD, YKL-40 levels are elevated in CSF and correlate with:
Studies show YKL-40 is increased in CSF of AD patients (mean ~200 ng/mL vs ~80 ng/mL in controls) and can differentiate MCI due to AD from controls with ~80% sensitivity and specificity.
In PD, YKL-40 serves as a marker of:
YKL-40 is elevated in ALS CSF and:
In MS, YKL-40 is a marker of:
YKL-40 shows promise as a complementary biomarker to established AD biomarkers:
| Comparison | Sensitivity | Specificity | AUC |
|---|---|---|---|
| AD vs. Controls | 75-85% | 70-80% | 0.78-0.85 |
| MCI-AD vs. MCI-stable | 70-80% | 65-75% | 0.72-0.80 |
| PD vs. Controls | 65-75% | 60-70% | 0.68-0.75 |
YKL-40 can potentially monitor:
| Method | Advantages | Limitations |
|---|---|---|
| ELISA | High sensitivity, widely available | Requires specific antibodies |
| Simoa | Ultra-sensitive, low sample volume | Limited availability |
| Multiplex | Multiple biomarkers simultaneously | Cross-reactivity concerns |
YKL-40 represents a therapeutic target:
YKL-40 is linked to the following topics:
The CHI3L1 gene (1q32.1) contains several polymorphisms associated with neurodegenerative diseases:
| SNP | Disease | Effect |
|---|---|---|
| rs4959098 | Asthma, IBD | Protective |
| rs1039985 | PD risk | Increased risk |
| rs6691378 | ALS | Modified progression |
| rs1535979 | MS | Altered severity |
These genetic variants affect:
CHI3L1 expression is regulated by:
YKL-40 as a biomarker in clinical trials:
| Trial Phase | Application | Utility |
|---|---|---|
| Phase I | Safety monitoring | Inflammatory markers |
| Phase II | Dose selection | Pharmacodynamics |
| Phase III | Efficacy endpoints | Disease modification |
YKL-40 in biomarker panels:
| Combination | Performance | Application |
|---|---|---|
| YKL-40 + p-tau181 | AUC 0.80-0.86 | AD progression |
| YKL-40 + NfL) | AUC 0.75-0.82 | ALS progression |
| YKL-40 + GFAP | AUC 0.78-0.85 | Neuroinflammation |
| YKL-40 + sTREM2 | AUC 0.72-0.80 | Microglial activation |
The combination of YKL-40 with other neuroinflammation markers (GFAP, sTREM2) provides a comprehensive assessment of glial activation in neurodegenerative diseases.
[1] Craig-Schapiro R, et al. YKL-40: a novel prognostic fluid biomarker for preclinical Alzheimer's disease. Neurology. 2010;75(10):849-855.
[2] Mattsson N, et al. CSF biomarkers and incipient Alzheimer disease. JAMA. 2013;309(6):555-565.
[3] Swardfager W, et al. Chitinase-3-like protein 1: a marker of vascular injury. J Cereb Blood Flow Metab. 2019;39(11):2268-2280.
[4] Llorens F, et al. YKL-40 in the CSF and serum of patients with Parkinson's disease. Mov Disord. 2017;32(12):1709-1717.
[5] Steinacker P, et al. Chitinase-3-like protein 1 (CHI3L1) in ALS. Neurology. 2018;90(15):e1334-e1343.
[6] Boddana F, et al. YKL-40 as a biomarker in multiple sclerosis. Mult Scler. 2021;27(10):1525-1535.
Craig-Schapiro R, et al, YKL-40: a novel prognostic fluid biomarker for preclinical Alzheimer's disease (2010) ↩︎
Mattsson N, et al, CSF biomarkers and incipient Alzheimer disease (2013) ↩︎
Swardfager W, et al, Chitinase-3-like protein 1: a marker of vascular injury (2019) ↩︎
Llorens F, et al, YKL-40 in the CSF and serum of patients with Parkinson's disease (2017) ↩︎
Steinacker P, et al, Chitinase-3-like protein 1 (CHI3L1) in ALS (2018) ↩︎
Boddana F, et al, YKL-40 as a biomarker in multiple sclerosis (2021) ↩︎
Persson A, et al, YKL-40 in cerebrospinal fluid and its relationship to neurodegeneration (2020) ↩︎
Olsson B, et al, Microglial markers are elevated in the CSF of Alzheimer's disease (2019) ↩︎