What Is ANGPTL8? Definition and What Research Reports

Definition

ANGPTL8 (angiopoietin-like protein 8), also known in the literature as betatrophin, lipasin, RIFL and TD26, is a small secreted protein produced chiefly by the liver and by white and brown adipose tissue that circulates in blood and participates in the regulation of triglyceride-rich lipoprotein metabolism. A physiological review described ANGPTL8 as acting together with ANGPTL3 and ANGPTL4 to control lipoprotein lipase (LPL) activity and thereby the partitioning of circulating triglycerides between tissues (PMID 34338039). In glossary terms, ANGPTL8 is best understood as an endogenous regulatory protein and a measurable blood analyte, not as a compound that is administered.

What Class of Molecule It Is

ANGPTL8 belongs to the angiopoietin-like (ANGPTL) family. Unlike most family members, it is unusually short and lacks the C-terminal fibrinogen-like domain found in ANGPTL3 and ANGPTL4, which is why much of the published work treats it as a partner or cofactor rather than as an independently acting ligand. The same physiological review grouped ANGPTL3, ANGPTL4 and ANGPTL8 as the principal ANGPTL regulators of lipoprotein metabolism and described how they form complexes that modulate LPL (PMID 34338039). A 2025 biochemical paper reported that the ANGPTL3/8 complex behaves as an atypical unfoldase, regulating intravascular lipolysis by catalysing the unfolding of lipoprotein lipase (PMID 40112106).

Where It Comes From

ANGPTL8 is encoded by the ANGPTL8 gene in humans and is expressed in a nutritionally responsive manner, with liver and adipose tissue the dominant sources described in the lipoprotein-metabolism literature (PMID 34338039). Transcriptional control has also been studied: researchers reported that the zinc finger protein ZNF638 regulated triglyceride metabolism via ANGPTL8 in an estrogen-dependent manner (PMID 38211696).

How the Term Is Used in Research

The word "ANGPTL8" appears in the literature in three broad ways, and distinguishing them avoids most of the confusion around the term:

• As a gene or protein under genetic manipulation. Animal studies delete, silence or inhibit ANGPTL8 to observe metabolic consequences; for example, researchers reported that adipocyte-specific Angptl8 deletion improved glucose and energy metabolism and obesity-associated inflammation in mice (PMID 39640567).
• As part of a complex. Much of the mechanistic work concerns ANGPTL3/8 and ANGPTL4/8 rather than the monomer, and one study reported that ANGPTL3/8 regulated intravascular lipolysis by unfolding lipoprotein lipase (PMID 40112106).
• As a circulating biomarker. Clinical and observational papers measure serum ANGPTL8 (often reported under the older name betatrophin) and compare concentrations across groups, as in a study that evaluated serum ANGPTL8/betatrophin and cartonectin/CTRP3 levels in diabetic and non-diabetic retinopathy (PMID 36597238).

Importantly, ANGPTL8 is not used in the published literature the way short synthetic peptides are used — it is not described as an administered research peptide with a dosing schedule. The verified studies summarised here examined genetic deletion, pharmacological inhibition or antibody-based blockade in animals, biochemical behaviour in vitro, and blood concentrations in people.

What the Published Literature Reports

Lipoprotein and triglyceride metabolism

The central theme across the literature is lipid handling. A physiological review described ANGPTL3, ANGPTL4 and ANGPTL8 as regulators of lipoprotein lipase activity and triglyceride trafficking (PMID 34338039), and a 2025 biochemistry paper reported that ANGPTL3/8 acted as an atypical unfoldase that unfolded lipoprotein lipase to control intravascular lipolysis (PMID 40112106). Because ANGPTL8 is functionally linked to ANGPTL3, it also appears in discussions of ANGPTL3-directed lipid-lowering strategies, and a lipidology review examined ANGPTL3 as a therapeutic target (PMID 34581310). Upstream regulation has been mapped as well, with researchers reporting that ZNF638 influenced triglyceride metabolism through ANGPTL8 in an estrogen-dependent fashion (PMID 38211696).

Organ and tissue models

Beyond plasma lipids, ANGPTL8 has been examined in several organ systems. One study reported that ANGPTL8 accelerated liver fibrosis mediated by high-fat-diet-induced inflammatory activity via LILRB2/ERK signalling pathways (PMID 36031141). In the heart, researchers reported that ANGPTL8 acted as a negative regulator in pathological cardiac hypertrophy (PMID 35851270) — a direction of effect opposite to the liver finding, which is one reason the field describes ANGPTL8 as context-dependent. In the brain, a 2024 neuroinflammation study reported that inhibition of ANGPTL8 protected against diabetes-associated cognitive dysfunction by reducing synaptic loss via the PirB signalling pathway (PMID 39095838). In adipose tissue, the study of adipocyte-specific Angptl8 deletion reported improvements in glucose and energy metabolism and in obesity-associated inflammation in mice (PMID 39640567).

Human measurement and association studies

Circulating ANGPTL8 has been surveyed in cardio-metabolic contexts; a clinical chemistry review discussed ANGPTL8 in cardio-metabolic diseases (PMID 34023284). A 2025 cohort analysis examined associations of ANGPTL proteins and complexes with progression of coronary artery calcification and with coronary events (PMID 40819411). The protein has also been measured in non-cardiometabolic settings: an obstetric study assessed serum betatrophin/ANGPTL8 levels in pregnancies affected by hyperemesis gravidarum (PMID 29754072), and an ophthalmology paper compared serum ANGPTL8/betatrophin and CTRP3 in diabetic and non-diabetic retinopathy (PMID 36597238). These are association measurements, not demonstrations that changing ANGPTL8 changes outcomes in people.

Related Terms at a Glance

Safety and Adverse Events: What Studies Report

The verified literature covered here does not describe ANGPTL8 being administered to humans as a peptide product, so there is no human dosing or adverse-event dataset to summarise from these sources. What is reported instead is direction of effect in models: researchers reported that ANGPTL8 accelerated liver fibrosis under high-fat-diet conditions via LILRB2/ERK signalling (PMID 36031141), while a separate study reported that ANGPTL8 acted as a negative regulator of pathological cardiac hypertrophy (PMID 35851270). Those opposing findings illustrate why the review literature on ANGPTL8 in cardio-metabolic diseases treats its net role as unsettled (PMID 34023284). This page is for educational purposes only and is not medical advice; consult a licensed physician about any health question or laboratory result.

Summary

ANGPTL8 is an endogenous, liver- and adipose-derived secreted protein of the angiopoietin-like family that works largely through complexes with ANGPTL3 and ANGPTL4 to regulate lipoprotein lipase and triglyceride metabolism (PMID 34338039). Published work spans biochemistry (PMID 40112106), animal models of liver, heart, brain and adipose tissue (PMID 39640567), and human biomarker associations with coronary artery calcification and coronary events (PMID 40819411).

References

• Regulation of lipoprotein metabolism by ANGPTL3, ANGPTL4, and ANGPTL8 (American Journal of Physiology. Endocrinology and Metabolism, 2021)
• ANGPTL3/8 is an atypical unfoldase that regulates intravascular lipolysis by catalyzing unfolding of lipoprotein lipase (PNAS, 2025)
• Zinc finger protein ZNF638 regulates triglyceride metabolism via ANGPTL8 in an estrogen dependent manner (Metabolism, 2024)
• ANGPTL8 accelerates liver fibrosis mediated by HFD-induced inflammatory activity via LILRB2/ERK signaling pathways (Journal of Advanced Research, 2023)
• ANGPTL8 is a negative regulator in pathological cardiac hypertrophy (Cell Death & Disease, 2022)
• Adipocyte Angptl8 deletion improves glucose and energy metabolism and obesity associated inflammation in mice (iScience, 2024)
• Inhibition of ANGPTL8 protects against diabetes-associated cognitive dysfunction by reducing synaptic loss via the PirB signaling pathway (Journal of Neuroinflammation, 2024)
• Associations of ANGPTL proteins and complexes with progression of coronary artery calcification and coronary events (Atherosclerosis, 2025)
• ANGPTL8 in cardio-metabolic diseases (Clinica Chimica Acta, 2021)
• ANGPTL3 as therapeutic target (Current Opinion in Lipidology, 2021)
• Serum betatrophin/angiopoietin-like protein 8 (ANGPTL8) levels in pregnancies affected by hyperemesis gravidarum (European Journal of Obstetrics, Gynecology, and Reproductive Biology, 2018)
• Evaluation of Serum ANGPTL8/Betatrophin and Cartonectin/CTRP3 Levels in Diabetic and Non-Diabetic Retinopathy (JCPSP, 2023)