Sphingosine kinase 1 participates in insulin signalling and regulates glucose metabolism and homeostasis in KK/Ay diabetic mice.
OBJECTIVE
The aim of this study was to determine the potential role of sphingosine kinase 1 (SPHK1), a key sphingolipid metabolic enzyme, in glucose metabolism and homeostasis.


METHODS
SMMC-7721 hepatoma cells and C2C12 myotube cells were used to explore the role of SPHK1 in glucose uptake in vitro. KK/Ay type 2 diabetic mice, which were transfected with adenovirus harbouring the human SPHK1 gene by i.v. injection, were used to investigate the glucose-lowering effects of SPHK1 in vivo.


RESULTS
The basal glucose uptake and the insulin-stimulated glucose uptake in both 7721 cells and C2C12 cells were markedly enhanced when SPHK1 was overexpressed by adenovirus-mediated gene transfer, whereas they were substantially reduced when the expression of SPHK1 was inhibited or the activity of SPHK1 was blocked. Insulin could activate SPHK1 of both cell lines in a dose-dependent manner. SPHK1 gene delivery significantly reduced the blood glucose level of KK/Ay diabetic mice, but had no effect on that of normal animals. It also attenuated elevated levels of plasma insulin, NEFA, triacylglycerol, cholesterol and LDL, significantly ameliorated hyperglycaemia-induced injury of liver, heart and kidney, and enhanced phosphorylation of insulin-signalling kinases such as Akt and glycogen synthase kinase 3beta in livers of the diabetic animals.


CONCLUSIONS
SPHK1 is involved in insulin signalling and plays an important role in the regulation of glucose and fat metabolism; adenovirus-mediated SPHK1 gene transfer might provide a novel strategy in the treatment of type 2 diabetes mellitus.
Ma
M M
MM
School of Chemical Engineering and Technology, Tianjin University, Tianjin, People's Republic of China.
Chen
J L
JL
Wang
G G
GG
Wang
H
H
Lu
Y
Y
Li
J F
JF
Yi
J
J
Yuan
Y J
YJ
Zhang
Q W
QW
Mi
J
J
Wang
L Sh
LSh
Duan
H F
HF
Wu
C T
CT
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D045744:Cell Line, Tumor; D003921:Diabetes Mellitus, Experimental; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D018014:Gene Transfer Techniques; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D000099157:Sphingosine Kinase
D005947:Glucose; D007328:Insulin; D017853:Phosphotransferases (Alcohol Group Acceptor); D034741:RNA, Small Interfering; D000099157:Sphingosine Kinase