title: Lipid esterification and synthesis by the IEC-6 intestinal epithelial crypt cell line: effect of transforming growth factor beta.
abstract: The capacity of immature intestinal epithelial crypt cells to synthesize lipids and the factors that promote their differentiation remain largely unknown. We examined the profile of lipids synthesized by a normal rat intestinal epithelial crypt cell line (IEC-6) and determined the effects of transforming growth factor beta (TGF beta), a putative crypt cell differentiating factor, on their lipid handling. Incubation of IEC-6 cells with [14C]oleic acid (20 h) resulted in lipid esterification and synthesis, mainly as triglycerides (TGs, 57 +/- 0.6%) and phospholipids (PLs, 30 +/- 0.6%), with a PL/TG ratio of 0.53. When cells were pulsed (2.5 h) with [14C]oleic acid and then maintained 20 h in medium alone, a significant elevation of the PL/TG ratio (10.2 +/- 1.3, p < 0.01) was observed, primarily accounted for by a significant decrease of the TG fraction (p < 0.01). IEC-6 cells secreted only trace amounts of lipids under the latter experimental condition. Incubation with TGF beta (20 h) significantly inhibited IEC-6 cell proliferation but did not promote the expression of cell sucrase activity. TGF beta induced a significant increase in the cellular composition of PL (p < 0.05) and a decrease in the TG fraction (p < 0.02), after a 2.5-h pulse of [14C]oleic acid. Lipid production was unaffected by TGF beta during the 20-h incubation with [14C]oleic acid. Lipid secretion into the medium remained negligible in the presence of TGF beta, after 2.5 h of incubation with substrate as above. Our findings suggest that immature crypt IEC-6 cells are capable of lipid esterification and synthesis but secrete minute amounts of lipoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Gastroenterology-Nutrition Unit, Hôpital Ste-Justine, Montréal, QC, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Mehran
authors.forename: E
authors.initials: E
authors.lastname: Seidman
authors.forename: C
authors.initials: C
authors.lastname: Gurbindo
authors.forename: E
authors.initials: E
authors.lastname: Levy
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004952:Esters / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D050356:Lipid Metabolism; D008055:Lipids / Q000096:biosynthesis; D009829:Oleic Acids / Q000378:metabolism; D051381:Rats; D013393:Sucrase / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D004952:Esters; D008055:Lipids; D009829:Oleic Acids; D016212:Transforming Growth Factor beta; D013393:Sucrase