title: Two cases with transient lipoprotein lipase (LPL) activity impairment: evidence for the possible involvement of an LPL inhibitor.
abstract: Two independent severe hypertriglyceridemic infants with transiently impaired lipoprotein lipase (LPL) activity were observed and the causes were explored. Both infants were female, born prematurely with low birth weight and developed hypertriglyceridemia (Fredrickson type V hyperlipidemia: high VLDL and low LDL/HDL) a few months after birth. While mass levels of their post-heparin plasma LPL and apoprotein C-II (apo C-II), a physiological activator of LPL, were normal, their post-heparin plasma LPL activities were remarkably impaired. Both of their mothers' post-heparin plasma LPL activities were slightly or moderately impaired as well, without a decrease in the LPL mass level. No mutations in the genes for LPL and apo C-II were detected in either patient. In an in vitro study with their serum at onset, we could not detect any distinct circulating inhibitors for LPL. There was no data supporting infection or autoimmune diseases, which might have an impact on LPL activity, during the follow-up period. Levels of their plasma triglyceride (TG) and total cholesterol (TC) were decreased quickly by a dietary intervention with medium-chain triglyceride (MCT) milk and kept normal even after stopping the intervention at around age 1 year. However, their low post-heparin LPL activity persisted and returned to normal at around age 2 years. Their low HDL cholesterol levels persisted even after recovery of the TG and TC levels, although lecithin:cholesterol acyltransferase (LCAT) and cholesterol-ester-transfer protein (CETP), two key enzymes of HDL metabolism, were normal throughout the course. The exact reasons why their post-heparin LPL activities were impaired for a certain period and why their HDL cholesterol levels have remained low are still unclear.
  
  
  CONCLUSIONS
  Transiently impaired LPL activity with no defect in LPL enzyme induced severe hypertriglyceridemia in infants. The transient occurrence of inhibitor(s) for LPL was proposed.
authors.affiliation: Department of Pediatrics, Hokkaido University School of Medicine, Kita-ku N. 15 W.7, 060-8638, Sapporo, Japan. nagasa-hirono@k2.dion.ne.jp.|Department of Pediatrics, Saitama Medical College, Moroyama-cho, 350-0495, Saitama, Japan. nagasa-hirono@k2.dion.ne.jp.
authors.forename: H
authors.initials: H
authors.lastname: Nagasaka
authors.affiliation: Department of Pediatrics, Hokkaido University School of Medicine, Kita-ku N. 15 W.7, 060-8638, Sapporo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kikuta
authors.affiliation: Department of Clinical Laboratory, Hokkaido University Hospital, 060-8648, Sapporo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Chiba
authors.affiliation: Department of Laboratory Medicine, Toho University Sakura Hospital, Sakura, Sakura City, 285-0841, Chiba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Murano
authors.affiliation: Department of Pediatrics, Saitama Medical College, Moroyama-cho, 350-0495, Saitama, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Harashima
authors.affiliation: Department of Pediatrics, Saitama Medical College, Moroyama-cho, 350-0495, Saitama, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ohtake
authors.affiliation: Department of Pediatrics, Saitama Medical College, Moroyama-cho, 350-0495, Saitama, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Senzaki
authors.affiliation: Department of Pediatrics, Saitama Medical College, Moroyama-cho, 350-0495, Saitama, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Sasaki
authors.affiliation: Fourth Department of Internal Medicine, Saitama Medical College, Moroyama-cho, 350-0495, Saitama, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Inoue
authors.affiliation: Fourth Department of Internal Medicine, Saitama Medical College, Moroyama-cho, 350-0495, Saitama, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Katayama
authors.affiliation: Department of Laboratory Medicine, Toho University Sakura Hospital, Sakura, Sakura City, 285-0841, Chiba, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shirai
authors.affiliation: Department of Pediatrics, Hokkaido University School of Medicine, Kita-ku N. 15 W.7, 060-8638, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D002648:Child; D002675:Child, Preschool; D008076:Cholesterol, HDL / Q000097:blood; D005260:Female; D006801:Humans; D006954:Hyperlipoproteinemia Type V / Q000097:blood / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D008076:Cholesterol, HDL; D008071:Lipoprotein Lipase