FAOBlue (Fatty Acid Oxidation Detection Reagent)
FAOBlue™ (Fatty Acid Oxidation Detection Reagent)
Directly detects fatty acid β-oxidation (FAO) activity in live cells; FAO releases a coumarin dye that fluoresces blue (Ex 405 nm / Em 460 nm).
For Research Use Only.
Tip — The Best Match Bundle Products for Lipid Metabolism Research: LipiDye II (lipid droplet staining) with FAOBlue (Fatty Acid Oxidation Detection Reagent). View the bundle
Shipping: Room temperature. The reagent ships as a stable powder.
Overview
FAOBlue is a fluorescent detection system for studying the catabolic pathway of energy production. It visualizes fatty acid β-oxidation (FAO), the common pathway of fatty acid degradation, as blue fluorescence. FAO activity, which was previously difficult to measure, can be measured by fluorescence imaging simply by adding the dye to cells.
Background: Fatty Acid β-Oxidation
Fatty acids (FAs) are the basic building blocks of a wide variety of lipids, are essential components of cells, and are one of the primary sources of energy. The major pathway for FA degradation is mitochondrial FA β-oxidation (FAO), a key metabolic pathway for energy homeostasis in organs such as the liver, heart and skeletal muscle.
FAO is a complex biochemical process involving many enzymes. First, FAs are converted to acyl-CoA by the acyl-CoA synthetase family. Second, acyl-CoA enters mitochondria via the carnitine shuttle. In the mitochondrial matrix, acyl-CoA (Cn) is converted to acyl-CoA (Cn-2) and acetyl-CoA by four stepwise reactions:
Acetyl-CoA is further converted to ATP. The resulting acyl-CoA (Cn-2) enters another FAO cycle to produce acyl-CoA (Cn-4).
Abnormal FAO is involved in diseases such as obesity and fatty liver disease (MASLD). Although measuring FAO activity in diseased cells is important, available methods are limited because of the complexity of the pathway. Only a few indirect methods, such as radioisotope-labeled fatty acids or oxygen-consumption measurement, are commonly used.
Detection Principle
FAOBlue is the world-first reagent for directly measuring FAO activity in living cells. Before FAO metabolism it is non-fluorescent under 405 nm excitation; the coumarin released by FAO cycles fluoresces strongly blue under 405 nm excitation.
FAOBlue is a coumarin dye carrying a nonanoic acid (C9) protected by an acetoxymethyl ester.
The FAOBlue-based FAO assay measures FAO activity with an easy procedure. Inhibition of the carnitine shuttle by etomoxir greatly diminishes the fluorescence enhancement in living cells, which indicates that FAOBlue mainly detects mitochondrial FAO activity.
Key Features & Applications
Measures FAO activity directly in living cells, not through radioisotopes or oxygen consumption.
Add the dye to cells, incubate, wash and image with 405 nm excitation.
Relative quantification of FAO activity.
Evaluation of drug effect on FAO activity.
Components & Specifications
The following components are included with this product.
| Size | 0.2 mg (0.2 mg ≈ 21–84 mL working solution (5–20 µM) ≈ 200–800 wells at 100 µL) |
|---|---|
| Molecular formula | C24H31NO9 |
| Molecular weight | 477.51 g/mol |
| Solubility | Soluble in DMSO |
| Storage | -20°C (long-term storage) |
| Size | 500 mL |
|---|---|
| Sterile | Filtered 0.1-micron membrane TWICE, 0.04-micron membrane ONCE |
| Storage | 2-8°C, away from bright light |
| Component | HEPES (at pH 7.4): 20 mM (4766.024 mg/L) Sodium chloride (NaCl): 107 mM (6253.08 mg/L) Potassium chloride (KCl): 6 mM (447.309 mg/L) Magnesium sulfate (MgSO4): 1.2 mM (144.439 mg/L) Calcium chloride (CaCl2): 2 mM (221.960 mg/L) |
Optical Properties
Reconstitution & Storage
Experimental Guide
Absorbance and Fluorescence Spectra of FAOBlue and the Coumarin Derivative
Absorbance (left) and fluorescence (right) spectra of FAOBlue (blue line) and the coumarin-derivative dye released after FAO metabolism (red line) in PBS buffer (pH 7.4).
- Absorbance spectra: The absorption peak of the coumarin-derivative dye is clearly shifted by FAO from the peak of FAOBlue.
- Fluorescence spectra: When both compounds are excited at 405 nm, the coumarin-derivative dye shows strong blue fluorescence while FAOBlue emits little fluorescence.
Imaging Guide
Confocal laser microscopy: Use the 405 nm laser of the microscope. A 405 nm laser detects only the fluorescent signal from the coumarin-derivative dye.
Epifluorescence microscopy — the excitation filter is critical. Commercial DAPI filters are not compatible with this reagent, because DAPI filters excite both FAOBlue and the coumarin-derivative dye. Excitation filters that pass 390-450 nm light are recommended.
Protocol: General Procedure
Application Data
Visualization of FAO Activity in Four Cancer Cell Lines
Four cancer cell lines (HepG2, LNCaP, HeLa and A549) were treated with FAOBlue in HBS buffer with or without pre-treatment with etomoxir (40 µM, 3 hours), a potent FAO inhibitor. After FAOBlue incubation, blue fluorescence (Ex 405 nm / Em 430-480 nm) was observed. All cell lines showed blue fluorescence in the cytosol, and etomoxir pre-treatment clearly decreased the fluorescence intensity, indicating that the blue fluorescence derived from FAO activity in the cells.
| Cell line | FAOBlue | Incubation |
|---|---|---|
| HepG2 | 5 µM | 30 min |
| LNCaP | 20 µM | 120 min |
| HeLa | 20 µM | 120 min |
| A549 | 5 µM | 30 min |
Perturbation of FAO Activity by Drugs
HepG2 cells were pre-incubated with 200 µM AICAR, an FAO activator via AMPK activation, for 3 hours, or with 200 µM ranolazine, a partial FAO inhibitor, for 12 hours. The cells were then incubated with 5 µM FAOBlue for 30 min. Compared with control cells, AICAR pre-treatment significantly increased blue fluorescence intensity, while ranolazine pre-treatment clearly decreased it. Ex 405 nm / Em 430-480 nm.
Quantitative Analysis of Drug Effects on FAO Activity
ND630, an inhibitor of acetyl-CoA carboxylase, is considered a potential drug for MASLD. HepG2 cells were pre-incubated with various concentrations of ND630 for 4 hours, then treated with 5 µM FAOBlue for 30 min. Blue fluorescence intensity was quantified at each ND630 concentration. Ex 405 nm / Em 430-480 nm.
Analysis of FAO Activity in a MASH Model Mouse
MASH (formerly NASH) shows low FA metabolic activity. Control healthy mice and MASH model mice were orally administered 400 mg/kg bezafibrate, a therapeutic agent for MASH. After 4 weeks of administration, primary hepatocytes were isolated from control and MASH model mice and cultured in culture dishes, then treated with 5 µM FAOBlue for 30 min and imaged. Compared with control cells, hepatocytes from MASH model mice showed low FAO activity, and bezafibrate dramatically recovered their FAO activity. FAOBlue is a powerful tool for estimating drug effects and efficiency on FAO activity.
The detailed procedure of the mouse experiment is described in Ref. 1. Ex 405 nm / Em 430-480 nm.
Webinar: FAOBlue (Fatty Acid Oxidation Detection Reagent)
Lipid Metabolism Research Tools
Featured in BioTechniques. An international life-science journal.
Research Applications
FAOBlue directly measures fatty acid oxidation (FAO) activity across diverse biological systems. Unlike indirect methods such as oxygen consumption or radioisotopes, it allows real-time, fluorescence-based visualization of mitochondrial β-oxidation.
Studies of metabolic dysfunction, particularly in the liver and heart.
- MASLD/NAFLD: Yu et al. (2025) and Chen et al. (2023) used FAOBlue to show how protein interactions (Asprosin-FABP5) or exercise-induced pathways (Cdo1-AMPK) modulate fatty acid breakdown in liver steatosis.
- Cardiac health: Tian et al. (2023) showed that VDAC1 overexpression alleviates cardiac fibrosis by regulating fatty acid metabolism.
- Kidney injury: Yuan et al. (2025) found that inhibiting FAO via PRMT1-mediated methylation exacerbates crystal-induced kidney injury.
Assessment of the metabolic state of immune cells, which often shift their energy source during activation.
- T-cell function: Enhancing FAO alleviates autoimmunity in T cells (Masuyama et al., 2024).
- Antitumor immunity: Madhu Malinee et al. (2022) showed that mitochondrial biogenesis enhances antitumor immunity in a mouse model.
Cancer cells often rewire their metabolism to survive harsh conditions.
- Survival mechanisms: Xiong et al. (2024) used FAOBlue in breast cancer cells under glucose starvation.
- Therapeutic response: Nandi et al. (2024) showed that targeting FAO enhances response to HER2-targeted therapy.
Applications in biological timing and stress.
- Embryonic dormancy: Lipid metabolism maintains mammalian embryos in diapause (Weijden et al., 2024).
- Cellular senescence: Yamauchi et al. (2024) found that mitochondrial fatty acid oxidation drives senescence.
- Neurogenesis: Jia et al. (2026) showed that sevoflurane impairs neurogenesis and cognitive function by inhibiting FAO in neural stem/progenitor cells.
Featured Publication
Ordering Information
| Product | Cat No. | Size | Order |
|---|---|---|---|
| FAOBlue (Fatty Acid Oxidation Detection Reagent) | FNK-FDV-0033 | 0.2 mg + 500 mL HBS | Current page |
References
This product was commercialized and is sold by Funakoshi Co., Ltd. based on the research of Professor Akio Ojida (chemical biology), Graduate School of Pharmaceutical Sciences, Kyushu University. Research use only; not for diagnostic or therapeutic use.
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