Overexpression of kinase-negative protein kinase Cdelta in pancreatic beta-cells protects mice from diet-induced glucose intolerance and beta-cell dysfunction.
OBJECTIVE
In vitro models suggest that free fatty acid-induced apoptotic beta-cell death is mediated through protein kinase C (PKC)delta. To examine the role of PKCdelta signaling in vivo, transgenic mice overexpressing a kinase-negative PKCdelta (PKCdeltaKN) selectively in beta-cells were generated and analyzed for glucose homeostasis and beta-cell survival.


METHODS
Mice were fed a standard or high-fat diet (HFD). Blood glucose and insulin levels were determined after glucose loads. Islet size, cleaved caspase-3, and PKCdelta expression were estimated by immunohistochemistry. In isolated islet cells apoptosis was assessed with TUNEL/TO-PRO3 DNA staining and the mitochondrial potential by rhodamine-123 staining. Changes in phosphorylation and subcellular distribution of forkhead box class O1 (FOXO1) were analyzed by Western blotting and immunohistochemistry.


RESULTS
PKCdeltaKN mice were protected from HFD-induced glucose intolerance. This was accompanied by increased insulin levels in vivo, by an increased islet size, and by a reduced staining of beta-cells for cleaved caspase-3 compared with wild-type littermates. In accordance, long-term treatment with palmitate increased apoptotic cell death of isolated islet cells from wild-type but not from PKCdeltaKN mice. PKCdeltaKN overexpression protected islet cells from palmitate-induced mitochondrial dysfunction and inhibited nuclear accumulation of FOXO1 in mouse islet and INS-1E cells. The inhibition of nuclear accumulation of FOXO1 by PKCdeltaKN was accompanied by an increased phosphorylation of FOXO1 at Ser256 and a significant reduction of FOXO1 protein.


CONCLUSIONS
Overexpression of PKCdeltaKN in beta-cells protects from HFD-induced beta-cell failure in vivo by a mechanism that involves inhibition of fatty acid-mediated apoptosis, inhibition of mitochondrial dysfunction, and inhibition of FOXO1 activation.
Hennige
Anita M
AM
Department of Internal Medicine, Division of Endocrinology, Diabetology, Vascular Medicine, Nephrology, and Clinical Chemistry, University of Tũbingen, Tũbingen, Germany.
Ranta
Felicia
F
Heinzelmann
Isabel
I
Düfer
Martina
M
Michael
Diana
D
Braumüller
Heidi
H
Lutz
Stefan Z
SZ
Lammers
Reiner
R
Drews
Gisela
G
Bosch
Fatima
F
Häring
Hans-Ulrich
HU
Ullrich
Susanne
S
D000818:Animals; D017209:Apoptosis; D001786:Blood Glucose / Q000378:metabolism; D018929:Cell Culture Techniques; D016923:Cell Death; D004032:Diet; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000235:genetics; D005786:Gene Expression Regulation; D018149:Glucose Intolerance / Q000517:prevention & control*; D007328:Insulin / Q000032:analysis / Q000097:blood / Q000235:genetics / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D051745:Protein Kinase C-delta / Q000172:deficiency / Q000235:genetics*; D020112:Rhodamine 123 / Q000494:pharmacology
D001786:Blood Glucose; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D007328:Insulin; D020112:Rhodamine 123; D051745:Protein Kinase C-delta