title: Oxidized but not acetylated low-density lipoprotein reduces preproinsulin mRNA expression and secretion of insulin from HIT-T15 cells.
abstract: We examined the effect of oxidized low-density lipoprotein (oxLDL) on the insulin secretion in the culture of HIT-T15 cell line, an islet beta-cell line derived from a hamster pancreatic tumor. In order to check the uptake of modified LDL by HIT-T15 cells, we prepared DiI-labeled native LDL (nLDL), acetylated LDL (AcLDL), and oxLDL. After the addition of each LDL into the cultures of HIT-T15 cells, fluorescence microscopic study was done. It was suggested that AcLDL and oxLDL were taken up by HIT-T15 cells, as well as nLDL. mRNA expression of the LDL receptor, CD36, and SR-B1 was detected in HIT-T15 by RT-PCR. The medium insulin level was measured in the culture of HIT-T15 cells with each LDL. oxLDL significantly reduced the insulin secretion stimulated by various concentrations of glucose, the intracellular content of insulin, and the expression of preproinsulin mRNA compared to the control cultures without LDL addition. In contrast, nLDL and AcLDL had no effect on the insulin secretion, the intracellular insulin level, or the expression of preproinsulin mRNA. MTT assay findings (reflecting cell numbers) were not different between cultures with and without LDLs. These results indicated that oxLDL disturbed the insulin metabolism of HIT-T15 cells.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, Nippon Medical School, 1-1-5 Sendagi, Tokyo 113-8603, Japan.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Okajima
authors.forename: Mikiko
authors.initials: M
authors.lastname: Kurihara
authors.forename: Chihaya
authors.initials: C
authors.lastname: Ono
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tanimura
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sugihara
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tatsuguchi
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Teruo
authors.initials: T
authors.lastname: Miyazawa
authors.forename: Shinichi
authors.initials: S
authors.lastname: Oikawa
mesh_terms: D000107:Acetylation; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D011384:Proinsulin / Q000235:genetics* / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism
chemical_list: D007328:Insulin; D008077:Lipoproteins, LDL; D011498:Protein Precursors; D012333:RNA, Messenger; D011973:Receptors, LDL; C013737:preproinsulin; D011384:Proinsulin