Lipasin, thermoregulated in brown fat, is a novel but atypical member of the angiopoietin-like protein family.

Overview

Hyperlipidemia is a major contributor to cardiovascular diseases. Members of the angiopoietin-like protein family (ANGPTLs) are important determinants of blood lipid levels. Lipasin, a newly identified gene that regulates serum triglycerides, is homologous to ANGPTL3's N-terminal domain, which is sufficient and necessary for blood lipid regulation. Brown fat is critical in mediating energy homeostasis. Thermogenesis is the primary function of brown fat, in which Lipasin and some ANGPTLs are abundant; it is unknown, however, whether these genes are thermoregulated. We therefore comprehensively examined the thermoregulation of Lipasin and ANGPTLs in brown fat. Here we show that Lipasin is a novel but atypical member of the ANGPTL family because it is within the same branch as ANGPTL3 and 4 by phylogenetic analysis. The mRNA levels of Lipasin are dramatically increased in the cold environment (4 °C for 4 h) whereas those of ANGPTL4 and ANGPTL2 are suppressed. Fasting dramatically suppresses Lipasin but increases ANGPTL4. High-fat diet treatment increases Lipasin, but reduces ANGPTL2. The distinct transcriptional regulations of Lipasin, ANGPTL2 and ANGPTL4 in brown fat in response to cold exposure and nutritional stimulation suggest distinct physiological roles for ANGPTL family members in mediating thermogenesis and energy homeostasis.