Mediates inactivation of the lipoprotein lipase LPL, and thereby plays a role in the regulation of triglyceride clearance from the blood serum and in lipid metabolism (PubMed:15837923, PubMed:17609370, PubMed:29899519). May also play a role in regulating glucose homeostasis and insulin sensitivity (PubMed:15837923, PubMed:29899519). Inhibits proliferation, migration, and tubule formation of endothelial cells and reduces vascular leakage (PubMed:14583458, PubMed:17130448, PubMed:21832056). Upon heterologous expression, inhibits the adhesion of endothelial cell to the extracellular matrix (ECM), and inhibits the reorganization of the actin cytoskeleton, formation of actin stress fibers and focal adhesions in endothelial cells that have adhered to ANGPTL4-containing ECM (in vitro) (By similarity). Depending on context, may modulate tumor-related angiogenesis (Probable). Mediates inactivation of the lipoprotein lipase LPL, and thereby plays an important role in the regulation of triglyceride clearance from the blood serum and in lipid metabolism. Has higher activity in LPL inactivation than the uncleaved protein. Homooligomer; disulfide-linked via Cys residues in the N-terminal part of the protein (PubMed:14583458). The homooligomer undergoes proteolytic processing to release the ANGPTL4 C-terminal chain, which circulates as a monomer. The homooligomer unprocessed form is able to interact with the extracellular matrix (By similarity). The unprocessed form interacts with the extracellular matrix. This may constitute a dynamic reservoir, a regulatory mechanism of the bioavailability of ANGPTL4. Detected in liver and kidney (PubMed:10698685, PubMed:17609370). Predominantly expressed in adipose tissue and is strongly up-regulated by fasting in white adipose tissue and liver. Detected in endothelial cells in the capillary plexus, veins and arteries in the retina at 2, 12 and 17 days after birth (PubMed:21832056). Expressed at low levels in most organs and connective tissue at 13.5 dpc. Between 15.5 dpc and 18.5 dpc, strongest expression in brown fat. Induced in interstitial capillaries in response to hind leg ischemia (PubMed:17068295). Alterations in nutrition and leptin administration are found to modulate the expression in vivo. N-glycosylated. Forms disulfide-linked dimers and tetramers. Cleaved into a smaller N-terminal chain and a larger chain that contains the fibrinogen C-terminal domain; both cleaved and uncleaved forms are detected in the extracellular space. The cleaved form is not present within the cell. Pups are born at less than the expected Mendelian rate, indicative of significant embryonic lethality. No obvious phenotype after birth; mice are viable and fertile (PubMed:21832056). Mutant mice have reduced circulating triglyceride and cholesterol levels when fed a high-fat diet (PubMed:17609370, PubMed:29899519). Besides, they display 30% lower non-fasted blood glucose levels and improved glucose tolerance when fed a high-fat diet. In contrast, glucose levels and glucose tolerance are not different from wild-type when mice are kept on a normal diet (PubMed:29899519). The retinal vascular network displays subtle alterations, including a somewhat larger diameter of veins and capillaries. Pups display a delay in pericyte spreading on newly formed capillaries in the retina, and defects in the organization of endothelial cell tight junctions. In retinas from 17 day old animals, hypoxia-induced pathological neovascularization is strongly reduced (PubMed:21832056). Some studies observed decreased survival of suckling pups and of adults kept on a high-fat diet due to intestinal pathologies, with lipogranulomatous lesions of the intestines and their draining lymphatics and mesenteric lymph nodes (PubMed:17609370). Other studies observed no such effects (PubMed:29899519). Upon heterologous expression under the control of the keratinocyte promoter in the skin, inhibits tumor-associated angiogenesis and tumor growth (PubMed:14583458). In xenograft models, it inhibits both intra- and extravasation of tumor cells as well as vascular permeability leading to inhibition of metastases. Expression by tumor cells induces reorganization of the actin cytoskeleton through inhibition of actin stress fiber formation and vinculin localization at focal contacts. It might prevent the metastatic process by inhibiting vascular activity as well as tumor cell motility and invasiveness (PubMed:17130448).