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Digestion of ceramide by human milk bile salt-stimulated lipase

Nyberg, L; Farooqi, Aijaz; Bläckberg, Lars; Nilsson, Åke LU ; Duan, Rui-Dong LU and Hernell, Olle (1998) In Journal of Pediatric Gastroenterology and Nutrition - Jpgn 27(5). p.560-567
Abstract
BACKGROUND
There is a renewed interest in metabolism of sphingolipids because of their role in signal transduction. Sphingomyelin is the dominating phospholipid in human milk but its metabolism and possible function in the gastrointestinal tract of breast fed infants is unknown. We explored whether bile salt-stimulated milk lipase has a role in sphingolipid metabolism.
METHODS
In vitro assays of sphingomyelinase and ceramidase activities, using radiolabeled substrates, human milk samples and purified native and recombinant variants of bile salt-stimulated milk lipase with or without known activators or inhibitors.
RESULTS
Human whey and purified lipase catalysed hydrolysis of palmitoyl-labeled ceramide with the highest... (More)
BACKGROUND
There is a renewed interest in metabolism of sphingolipids because of their role in signal transduction. Sphingomyelin is the dominating phospholipid in human milk but its metabolism and possible function in the gastrointestinal tract of breast fed infants is unknown. We explored whether bile salt-stimulated milk lipase has a role in sphingolipid metabolism.
METHODS
In vitro assays of sphingomyelinase and ceramidase activities, using radiolabeled substrates, human milk samples and purified native and recombinant variants of bile salt-stimulated milk lipase with or without known activators or inhibitors.
RESULTS
Human whey and purified lipase catalysed hydrolysis of palmitoyl-labeled ceramide with the highest rate around pH 8.5-9.0. 1 mg of lipase hydrolysed 0.7 micromol ceramide in one hour at pH 8.5 in presence of 4 mM bile salt. The activity of whey was inhibited by antibodies towards human bile salt-stimulated milk lipase, indicating that this lipase accounted for virtually all ceramidase activity in the milk. In contrast, bile salt-stimulated milk lipase showed no activity against sphingomyelin. However we give evidence of a separate, hitherto unknown, acid sphingomyelinase in human milk. Under the used in vitro conditions this sphingomyelinase could account for hydrolysis of half of milk sphingomyelin in one hour.
CONCLUSIONS
Human milk bile salt-stimulated milk lipase hydrolyses ceramide and may thus have a role in sphingomyelin digestion, but only after initial hydrolysis to ceramide and phosphorylcholine. Part of the latter could be carried out in the stomach by the acid milk sphingomyelinase now described. We speculate that these two milk enzymes may be of importance for optimal use of human milk sphingolipids. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Pediatric Gastroenterology and Nutrition - Jpgn
volume
27
issue
5
pages
8 pages
publisher
Lippincott Williams & Wilkins
ISSN
1536-4801
DOI
10.1097/00005176-199811000-00013
language
English
LU publication?
no
id
ff36b496-7556-42b9-827f-15c50efa2eed
date added to LUP
2019-02-03 16:08:00
date last changed
2019-05-06 04:00:38
@article{ff36b496-7556-42b9-827f-15c50efa2eed,
  abstract     = {BACKGROUND<br/>There is a renewed interest in metabolism of sphingolipids because of their role in signal transduction. Sphingomyelin is the dominating phospholipid in human milk but its metabolism and possible function in the gastrointestinal tract of breast fed infants is unknown. We explored whether bile salt-stimulated milk lipase has a role in sphingolipid metabolism.<br/>METHODS<br/>In vitro assays of sphingomyelinase and ceramidase activities, using radiolabeled substrates, human milk samples and purified native and recombinant variants of bile salt-stimulated milk lipase with or without known activators or inhibitors.<br/>RESULTS<br/>Human whey and purified lipase catalysed hydrolysis of palmitoyl-labeled ceramide with the highest rate around pH 8.5-9.0. 1 mg of lipase hydrolysed 0.7 micromol ceramide in one hour at pH 8.5 in presence of 4 mM bile salt. The activity of whey was inhibited by antibodies towards human bile salt-stimulated milk lipase, indicating that this lipase accounted for virtually all ceramidase activity in the milk. In contrast, bile salt-stimulated milk lipase showed no activity against sphingomyelin. However we give evidence of a separate, hitherto unknown, acid sphingomyelinase in human milk. Under the used in vitro conditions this sphingomyelinase could account for hydrolysis of half of milk sphingomyelin in one hour.<br/>CONCLUSIONS<br/>Human milk bile salt-stimulated milk lipase hydrolyses ceramide and may thus have a role in sphingomyelin digestion, but only after initial hydrolysis to ceramide and phosphorylcholine. Part of the latter could be carried out in the stomach by the acid milk sphingomyelinase now described. We speculate that these two milk enzymes may be of importance for optimal use of human milk sphingolipids.},
  author       = {Nyberg, L and Farooqi, Aijaz and Bläckberg, Lars and Nilsson, Åke and Duan, Rui-Dong and Hernell, Olle},
  issn         = {1536-4801},
  language     = {eng},
  number       = {5},
  pages        = {560--567},
  publisher    = {Lippincott Williams & Wilkins},
  series       = {Journal of Pediatric Gastroenterology and Nutrition - Jpgn},
  title        = {Digestion of ceramide by human milk bile salt-stimulated lipase},
  url          = {http://dx.doi.org/10.1097/00005176-199811000-00013},
  volume       = {27},
  year         = {1998},
}