Pre beta 1-HDL, a putative discoid-shaped high-density lipoprotein (HDL) is known to participate in the retrieval of cholesterol from peripheral tissues. In this Study, to clarify potential sources of this lipoprotein, we conducted heparin injection oil four Japanese Volunteer men and found that serum triglyceride (TG) level decreased in parallel with the increase in serum nonesterified fatty acids and plasma lipoprotein lipase (LPL) protein mass after heparin injection. Plasma pre beta 1-HDL showed considerable increases at 15 min after the helparin injection in all of the subjects. In contrast, serum HDL-C levels did not change. Gel filtration with fast protein liquid chromatography system (FPLC) study on lipoprotein profile revealed that in post-heparin plasma, low-density lipoprotein and alpha HDL fractions did not change, whereas there was a considerable decrease in very low-density lipoprotein (VLDL,) fraction and all increase ill pre beta 1-HDL fraction when compared with those in pre-heparin plasma. We also conducted in vitro analysis on whether pre beta 1-HDL was produced during VLDL lipolysis by LPL. One hundred microliters of VLDL extracted from pooled serum by Ultracentrifugation was incubated with purified bovine milk LPL at 37 degrees C for 0-120 min. Pre beta 1-HDL concentration increased in a dose dependent manner with increased concentration of added LPL, in the reaction mixture and with increased incubation time, indicating that pre beta 1-HDL. was produced during lipolysis of VLDL, by LPL. Taken these in vivo and in vitro analysis together, we suggest that lipolysis of VLDL, particle by LPL is an important source for formation of pre beta 1-HDL. (C) 2008 Elsevier Inc. All rights reserved.