Quantifying Plasma Lipoprotein Lipase Activity

This assay was performed following established methods as described previously [18 (link)]. Briefly, a blood sample was collected from the patient following an overnight fast and 10 min after the intravenous administration of heparin (60 IU/kg of body weight). Blood plasma was prepared by centrifugation at 400 g for 30 min. To assess LPL activity, we initially quantified plasma total lipase activity and hepatic lipase activity through an LPL-mediated lipolysis reaction. This was carried out using a free fatty acid (FFA) release assay kit [Wako kit# NEFA-HR(2), Japan], with TG-rich plasma obtained from Gpihbp11-deficient (Gpihbp11^–/–) mice as the substrate for lipolysis. In the case of the plasma hepatic lipase activity assay, the sample was pretreated with 1 M NaCl and incubated for 60 min at 4 °C to inactivate the LPL. Subtracting hepatic lipase activity from total lipase activity provided a measure of plasma LPL activity. Both assays were conducted with three technical replicates. The reference value for normal LPL activity was derived from data obtained from 10 healthy volunteers at our center, consisting of 5 males and 5 females with an average age of 28.8 years.