The fasting-induced adipose factor (FIAF, ANGPTL4, PGAR, HFARP) was identified as an adipocytokine up-regulated by fasting, by peroxisome proliferator-activated receptor agonists, and by hypoxia. At the protein level, in human and mouse blood plasma, FIAF was found to be present both as a native protein and in a truncated form. Differentiation of mouse 3T3-L1 adipocytes was associated with the production of truncated FIAF, whereas in human white adipose tissue and SGBS adipocytes, only the native FIAF could be detected. Interestingly, the truncated FIAF was produced by human liver.
Experimental data suggest that FIAF is mainly presented in human blood plasma in a truncated form (FIAF-S2), whose level is increased by fenofibrate treatment. Levels of both truncated and native FIAF showed marked inter individual variation but were not associated with body mass index and were not influenced by prolonged semistarvation.
The lyophilized protein should be stored desiccated at -20°C. The reconstituted protein can be stored for at least one week at 4°C. For long-term storage of the reconstituted protein, aliquot into working volumes and store at -20°C in a manual defrost freezer. Avoid Repeated Freeze Thaw Cycles.
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Recombinant Human Angiopoietin-Like Protein-4 (rhANGPTL4) is widely used in research due to its multifaceted roles in regulating vascular biology, metabolism, inflammation, and tissue repair. Its application enables precise investigation of these processes in both physiological and pathological contexts.
Key scientific reasons to use rhANGPTL4 in research include:
Vascular Permeability and Angiogenesis: ANGPTL4 modulates endothelial cell function, vascular permeability, and promotes angiogenesis, making it valuable for studies on wound healing, tumor biology, and vascular disorders.
Metabolic Regulation: ANGPTL4 is a central regulator of lipid metabolism by inhibiting lipoprotein lipase (LPL), affecting triglyceride levels and fatty acid delivery to tissues. This is crucial for research on metabolic diseases, obesity, and cardiovascular risk.
Inflammation and Barrier Protection: ANGPTL4 protects against acute colonic inflammation and maintains the integrity of epithelial and endothelial barriers, relevant for studies on inflammatory bowel disease, sepsis, and tissue injury.
Disease Biomarker and Therapeutic Target: ANGPTL4 is emerging as a diagnostic and prognostic biomarker in kidney diseases (e.g., diabetic kidney disease, lupus nephritis), and its dysregulation is implicated in various pathologies, supporting its use in translational and clinical research.
Cell Signaling and Immune Modulation: ANGPTL4 influences chemokine signaling, immune cell infiltration, and oxidative stress responses, providing a tool to dissect immune regulation and cell signaling pathways.
Typical research applications of recombinant ANGPTL4 include:
In vitro assays to study endothelial cell function, angiogenesis, and wound healing.
In vivo models to investigate inflammation, tissue repair, and metabolic regulation.
ELISA standards for quantifying ANGPTL4 in biological samples.
Mechanistic studies on lipid metabolism and vascular biology.
Best practices: Use recombinant ANGPTL4 in controlled experimental systems to dissect its domain-specific effects (N-terminal vs. C-terminal), dose-response relationships, and context-dependent functions. Select carrier-free or BSA-containing preparations based on your assay requirements.
In summary, rhANGPTL4 is a versatile tool for research in vascular biology, metabolism, inflammation, and disease biomarker discovery, enabling mechanistic and translational studies across multiple biomedical fields.
Recombinant Human Angiopoietin-Like Protein-4 (ANGPTL4) can be used as a standard for quantification or calibration in ELISA assays, provided it is compatible with the antibodies and assay format of your specific ELISA. This is a common practice in quantitative ELISA development and is supported by both commercial kit protocols and published literature.
Key considerations and supporting details:
Standard Curve Construction: Quantitative ELISAs for ANGPTL4 typically use recombinant human ANGPTL4 to generate the standard curve, with concentrations spanning the assay’s validated range (e.g., 0.19–25 ng/mL or similar). This allows for accurate quantification of ANGPTL4 in biological samples by comparing sample absorbance to the standard curve.
Assay Compatibility: The recombinant standard must be recognized by the capture and detection antibodies used in your ELISA. Most commercial kits and custom assays are designed to detect both natural and recombinant forms of ANGPTL4, but you should confirm that your recombinant protein matches the epitope(s) targeted by the antibodies in your assay.
Protein Form and Purity: Ensure the recombinant ANGPTL4 is of high purity and in the correct form (full-length or relevant fragment) as required by your assay. Some kits specify which domain or isoform their antibodies recognize. Using a mismatched form could affect quantification accuracy.
Validation: If you are developing your own ELISA or substituting the standard in a commercial kit, validate the recombinant standard by running a standard curve and confirming parallelism with endogenous ANGPTL4 in your sample matrix. This ensures that the recombinant protein behaves similarly to the native protein in your assay conditions.
Kit-Specific Recommendations: Some commercial ELISA kits advise against mixing standards or components from different sources or manufacturers, as this can affect assay performance and quantification accuracy. Always follow the kit’s instructions regarding standards.
Summary Table: Use of Recombinant ANGPTL4 as ELISA Standard
Requirement
Details/Best Practice
Protein identity
Must match the epitope(s) recognized by assay antibodies
Purity and form
Use high-purity, correctly folded, and relevant isoform/domain
Standard curve range
Prepare serial dilutions within the validated range of your assay
Validation
Confirm parallelism and recovery in your sample matrix
Kit compatibility
Do not mix standards/components from different kits unless validated
In conclusion: You can use recombinant human ANGPTL4 as a standard for ELISA quantification if it is compatible with your assay’s antibodies and format, and you validate its performance in your specific application. Always consult your assay protocol and, if using a commercial kit, adhere to the manufacturer’s recommendations regarding standards.
Recombinant Human Angiopoietin-Like Protein-4 (ANGPTL4) has been validated in published research for applications in metabolic regulation, angiogenesis, vascular permeability, inflammation, cancer biology, kidney disease biomarkers, wound healing, and cardiovascular disease models.
Key validated applications include:
Metabolic Regulation and Diabetes Research: ANGPTL4 has been used to study its effects on glucose homeostasis, lipid metabolism, and insulin sensitivity. Recombinant ANGPTL4 was shown to decrease blood glucose, improve glucose tolerance, and modulate lipid profiles in mouse models and human studies, supporting its use in metabolic disease research.
Angiogenesis and Vascular Biology: Recombinant ANGPTL4 has been validated in assays for promoting or inhibiting angiogenesis, including in vitro tube formation assays with human endothelial cells and in vivo neovascularization models. It is also used to study vascular permeability and endothelial cell function.
Inflammation and Wound Healing: Topical and systemic administration of recombinant ANGPTL4 has been shown to accelerate wound reepithelialization and modulate inflammatory responses, particularly in diabetic wound models.
Cancer Research: ANGPTL4 is used to investigate mechanisms of tumorigenesis, metastasis, and cancer cell stemness, as well as its role in regulating tumor angiogenesis and vascular permeability.
Kidney Disease Biomarker and Pathophysiology: ANGPTL4 is validated as a biomarker for diabetic kidney disease (DKD), lupus nephritis, and other renal pathologies. Recombinant ANGPTL4 is used in in vitro and in vivo models to study podocyte dysfunction, glomerular permeability, and renal inflammation.
Cardiovascular Disease Models: ANGPTL4 is used to study atherosclerosis, plaque stability, and vascular inflammation. It has been shown to decrease atherosclerotic plaque formation and modulate vascular smooth muscle cell phenotype.
Immunoassays and Antibody Validation: Recombinant ANGPTL4 is used as a standard or antigen in ELISA, immunoprecipitation, and antibody validation protocols, supporting its use in quantitative and qualitative protein detection assays.
Cellular and Molecular Mechanism Studies: Recombinant ANGPTL4 is applied in studies of fatty acid uptake, endothelial cell metabolism, and signaling pathway modulation, including effects on CD36, FATP4, and CPT1A expression.
Summary Table: Validated Applications of Recombinant Human ANGPTL4
These applications are supported by a broad range of in vitro and in vivo studies, as well as clinical biomarker research, demonstrating the versatility of recombinant ANGPTL4 in biomedical research.
To reconstitute and prepare Recombinant Human Angiopoietin-Like Protein-4 (ANGPTL4) for cell culture experiments, follow these steps:
Reconstitution: Dissolve the lyophilized ANGPTL4 protein in sterile phosphate-buffered saline (PBS) to a concentration of 250 μg/mL. Some sources recommend a broader range (e.g., 0.1–1.0 mg/mL in sterile deionized water), but PBS is generally preferred for cell culture compatibility.
Mixing: Gently pipette up and down or swirl the vial to ensure complete dissolution. Avoid vigorous vortexing to prevent protein denaturation.
Aliquoting: After reconstitution, aliquot the solution to avoid repeated freeze-thaw cycles, which can degrade the protein.
Storage:
Short-term: Store aliquots at 4°C for up to 1 week.
Long-term: Store at –20°C or lower for several months. Avoid repeated freeze-thaw cycles.
Carrier Protein (Optional): If using the carrier-free version, consider adding 0.1% BSA or 5–50% glycerol to enhance stability, especially for long-term storage or if the protein will be used at low concentrations. However, avoid carrier proteins if they may interfere with your assay.
Preparation for Cell Culture:
Before adding to cells, dilute the reconstituted ANGPTL4 to the desired working concentration using cell culture medium.
Filter-sterilize the final solution if sterility is a concern and the protein is not already sterile-filtered.
Summary Table: ANGPTL4 Reconstitution and Handling
Step
Recommendation
Reconstitution
250 μg/mL in sterile PBS (or 0.1–1.0 mg/mL in water)
Mixing
Gentle pipetting/swirl, avoid vigorous vortexing
Aliquoting
Yes, to avoid freeze-thaw cycles
Storage
4°C (1 week), –20°C (months)
Carrier protein
Optional: 0.1% BSA or 5–50% glycerol
Cell culture prep
Dilute in medium, filter-sterilize if needed
Additional Notes:
Always consult the specific product datasheet for your ANGPTL4 preparation, as formulation and recommended reconstitution buffer may vary by manufacturer and protein fragment.
For functional assays, confirm that the buffer and additives are compatible with your cell type and experimental design.
If you need protocol details for a specific ANGPTL4 fragment (e.g., N-terminal vs. C-terminal), or have unique assay requirements, please specify for tailored guidance.
Products are for research use only. Not for use in diagnostic or therapeutic procedures.
