title: Diurnal variation in lipoprotein lipase activity.
abstract: BACKGROUND
  We investigated whether variations in lipoprotein lipase activity, a key post-prandial enzyme involved in the removal of circulating dietary triglycerides, could contribute to the previously described nocturnal lipid intolerance.
  
  
  METHODS
  We studied lipoprotein lipase activity in 12 healthy volunteers (five women, seven men) at 11:30 h and 23:30 h on two separate occasions. Subjects consumed a high-fat mixed meal at 07:30 h for the morning study or 19:30 h for the evening study. Then, after a 4-h fast, subjects were given an intravenous bolus of 7,500 U heparin. Blood samples were collected before and 15 min after heparin administration for measurement of lipoprotein lipase, hepatic lipase, triglycerides and non-esterified fatty acids concentrations.
  
  
  RESULTS
  Post-prandial post-heparin lipoprotein lipase activity was greater in the morning than in the evening (16.5 +/- 1.4 versus 14.4 +/- 1.0 micromol oleate/mL/h; P< 0.05). Post-prandial post-heparin hepatic lipase activity was also greater in the morning than in the evening (8.7 +/- 1.5 versus 81 +/- 1.6 micromol oleate/mL/h; P= 0.002). There were no other significant diurnal differences.
  
  
  CONCLUSIONS
  We report a diurnal variation in post-prandial lipoprotein lipase activity. This is consistent with the notion that decreased nocturnal insulin sensitivity extends to insulin's actions on lipoprotein lipase and provides a possible explanation for nocturnal lipid intolerance.
authors.affiliation: School of Biological Sciences, University of Surrey, Guildford, UK.
authors.forename: M P
authors.initials: MP
authors.lastname: Arasaradnam
authors.forename: L
authors.initials: L
authors.lastname: Morgan
authors.forename: J
authors.initials: J
authors.lastname: Wright
authors.forename: R
authors.initials: R
authors.lastname: Gama
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D008049:Lipase / Q000032:analysis* / Q000187:drug effects / Q000378:metabolism; D008071:Lipoprotein Lipase / Q000097:blood* / Q000187:drug effects; D008099:Liver / Q000201:enzymology; D008297:Male; D019518:Postprandial Period / Q000502:physiology*
chemical_list: D006493:Heparin; D008049:Lipase; D008071:Lipoprotein Lipase