[Effects of early insulin therapy on nuclear factor kappaB pathway in skeletal muscle of diabetes: experiment with rats].
OBJECTIVE
To investigate the effect of early insulin therapy on the nuclear factor kappaB (NF-kappaB) pathway and inflammatory cytokine responses in skeletal muscle in type 2 diabetes mellitus (DM).


METHODS
SD rats underwent intraperitoneal injection of streptozotocin to establish DM models and then divided into 5 groups: early un-treated group, early gliclazide treated group (receiving gliclazide since the third day after blood glucose increase for 3 weeks for 3 weeks), early insulin treated group (receiving insulin since the third day after blood glucose increase for 3 weeks for 3 weeks), late un-treated group, and late insulin treated group (receiving insulin since the fourth week after blood glucose increase for 3 weeks). By the end of treatment the rats were killed. Homogenate of skeletal muscle was made. The NF-kappaB P65 DNA binding was assayed by ELISA-based assay kit. Real time PCR was used to detect the mRNA expression levels of the gene of the cytokines: glucose transporter 4 (Glut4), inhibitor kappaB (IkappaBalpha), IL-1beta, IL-6, and tumor necrosis factor (TNF)-alpha. And Glut4 and IkappaBalpha protein expression levels were assayed by Western blotting.


RESULTS
The Glut4 mRNA level in the skeletal muscle of the untreated DM rats decreased by 59% and the Glut4 protein level in the muscle cell membrane decreased by 69%. Insulin treatment and gliclazide treatment increased the Glut4 mRNA expression by 17% and 13% respectively, increased the Glut4 protein expression in cell membrane by 23% and 10% respectively, and decreased the Glut4 protein expression in the cytoplasm. In the DM rats the IkappaBalpha protein expression in the skeletal muscle was significantly lower (P < 0.05) and the NF-kappaB P65 DNA binding activity increased, and TNF-alpha, IL-1B, and IL-6 expression levels were up-regulated in comparison with the normal control group. Early treatment of insulin and gliclazide increased the IkappaBalpha protein expression, decreased the NF-kappaB P65 DNA binding activity and the TNF-alpha expression in the skeletal muscle.


CONCLUSIONS
Early insulin treatment inhibits the NFkappaB activity and inflammatory cytokine responses in skeletal muscle that are involved in the amelioration of insulin resistance in type 2 DM. Such results may be due to indirect antiinflammatory effects of insulin relieving glucotoxicity and lipotoxicity in peripheral tissues.
Bi
Yan
Y
Department of Endocrinology, the Third Affiliated Hospital, Sun Yat-sen University, Guangzhou 510630, China.
Sun
Wei-ping
WP
Chen
Xiang
X
Cai
Meng-yin
MY
Liang
Hua
H
Zhu
Yan-hua
YH
He
Xiao-ying
XY
Yu
Qiu-qiong
QQ
Li
Ming
M
Weng
Jian-ping
JP
D000818:Animals; D016207:Cytokines / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism*; D004195:Disease Models, Animal; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000627:therapeutic use*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
D016207:Cytokines; D051275:Glucose Transporter Type 4; D007328:Insulin; D016328:NF-kappa B; C495694:Slc2a4 protein, rat