Hormone that acts as a blood lipid regulator by regulating serum triglyceride levels (PubMed:22569073, PubMed:22809513, PubMed:23150577, PubMed:24043787). May be involved in the metabolic transition between fasting and refeeding: required to direct fatty acids to adipose tissue for storage in the fed state (PubMed:24043787). According to a report, may act by promoting ANGPTL3 cleavage (PubMed:23150577). According to another study, not required for cleavage of ANGPTL3 (PubMed:24043787). Interacts with ANGPTL3. Expressed in liver and fat. Enriched in white and brown adipose tissues. Expressed during adipogenesis. Highly up-regulated following high-fat diet treatment. Down-regulated upon fasting. Strongly induced in the cold environment (4 Degrees Celsius for 4 hours). Proteolytically cleaved at the N-terminus. Reduced levels of serum triglyceride (PubMed:20562862, PubMed:24043787). Mice gain weight more slowly than wild-type littermates due to a reduction in adipose tissue accretion. Plasma levels of triglycerides are similar to wild-type animals in the fasted state but decreased after refeeding. The lower triglyceride levels are associated with a reduction in very low density lipoprotein secretion and an increase in lipoprotein lipase (LPL) activity (PubMed:24043787). Glucose and insulin tolerance are not affected and no alterations in glucose homeostasis are observed in mice fed either a chow or high fat diet (PubMed:24043787). Moreover, deletion does not affect the compensatory proliferation of pancreatic beta cells in response to insulin resistance induced by a high-fat diet or treatment with the insulin antagonist S961 (PubMed:25417115). Belongs to the ANGPTL8 family. Initially reported to specifically promote pancreatic beta cell proliferation without insulin resistance and to promote beta cell mass expansion, thereby improving glucose tolerance (PubMed:23623304). However, this result could not be confirmed by further studies and the original paper was later retracted (PubMed:28038792). The lack of a role in beta cell proliferation was also confirmed in another study (PubMed:25417115).