Insulin exocytosis in Goto-Kakizaki rat beta-cells subjected to long-term glinide or sulfonylurea treatment.
Sulfonylurea and glinide drugs display different effects on insulin granule motion in single beta-cells in vitro. We therefore investigated the different effects that these drugs manifest towards insulin release in an in vivo long-term treatment model. Diabetic GK (Goto-Kakizaki) rats were treated with nateglinide, glibenclamide or insulin for 6 weeks. Insulin granule motion in single beta-cells and the expression of SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins were then analysed. Perifusion studies showed that decreased first-phase insulin release was partially recovered when GK rats were treated with nateglinide or insulin for 6 weeks, whereas no first-phase release occurred with glibenclamide treatment. In accord with the perifusion results, TIRF (total internal reflection fluorescence) imaging of insulin exocytosis showed restoration of the decreased number of docked insulin granules and the fusion events from them during first-phase release for nateglinide or insulin, but not glibenclamide, treatment; electron microscopy results confirmed the TIRF microscopy data. Relative to vehicle-treated GK beta-cells, an increased number of SNARE clusters were evident in nateglinide- or insulin-treated cells; a lesser increase was observed in glibenclamide-treated cells. Immunostaining for insulin showed that nateglinide treatment better preserved pancreatic islet morphology than did glibenclamide treatment. However, direct exposure of GK beta-cells to these drugs could not restore the decreased first-phase insulin release nor the reduced numbers of docked insulin granules. We conclude that treatment of GK rats with nateglinide and glibenclamide varies in long-term effects on beta-cell functions; nateglinide treatment appears overall to be more beneficial.
Kawai
Junko
J
Department of Biochemistry, Kyorin University School of Medicine, Mitaka, Tokyo 181-8611, Japan.
Ohara-Imaizumi
Mica
M
Nakamichi
Yoko
Y
Okamura
Tadashi
T
Akimoto
Yoshihiro
Y
Matsushima
Satsuki
S
Aoyagi
Kyota
K
Kawakami
Hayato
H
Watanabe
Takashi
T
Watada
Hirotaka
H
Kawamori
Ryuzo
R
Nagamatsu
Shinya
S
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D003510:Cyclohexanes / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology; D005089:Exocytosis / Q000187:drug effects* / Q000502:physiology; D005905:Glyburide / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects / Q000473:pathology; D008297:Male; D000077715:Nateglinide; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D050600:SNARE Proteins / Q000378:metabolism; D013453:Sulfonylurea Compounds / Q000494:pharmacology*; D013997:Time Factors
D001786:Blood Glucose; D003510:Cyclohexanes; D007004:Hypoglycemic Agents; D007328:Insulin; D050600:SNARE Proteins; D013453:Sulfonylurea Compounds; D000077715:Nateglinide; D010649:Phenylalanine; D005905:Glyburide