Eckardt K, Sell H, Taube A, Koenen M, Platzbecker B, Cramer A, Horrighs A, Lehtonen M, Tennagels N, Eckel J
Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Auf'm Hennekamp 65, 40225, Duesseldorf, Germany.
Diabetologia. 2009 Apr;52(4):664-74. doi: 10.1007/s00125-008-1240-4. Epub 2008 Dec 17.
AIMS/HYPOTHESIS: Cannabinoid type 1 receptor (CB1R) antagonists such as rimonabant (Rim) represent a novel approach to treat obesity and related metabolic disorders. Recent data suggest that endocannabinoids are also produced by human adipocytes. Here we studied the potential involvement of endocannabinoids in the negative crosstalk between fat and muscle.
The protein level of CB1R in human skeletal muscle cells (SkM) during differentiation was analysed using western blotting. SkM were treated with adipocyte-conditioned medium (CM) or anandamide (AEA) in combination with the CB1R antagonists Rim or AM251, and insulin-stimulated Akt phosphorylation and glucose uptake were determined. Furthermore, signalling pathways of CB1R were investigated.
We revealed an increase of CB1R protein in SkM during differentiation. Twenty-four hour incubation of SkM with CM or AEA impaired insulin-stimulated Akt(Ser473) phosphorylation by 60% and up to 40%, respectively. Pretreatment of cells with Rim or AM251 reduced the effect of CM by about one-half, while the effect of AEA could be prevented completely. The reduction of insulin-stimulated glucose uptake by CM was completely prevented by Rim. Short-time incubation with AEA activated extracellular regulated kinase 1/2 and p38 mitogen-activated protein kinase, and impaired insulin-stimulated Akt(Ser473) phosphorylation, but had no effect on Akt(Thr308) and glycogen synthase kinase 3alpha/beta phosphorylation. In addition, enhanced IRS-1 (Ser307) phosphorylation was observed.
CONCLUSIONS/INTERPRETATION: Our results show that the CB1R system may play a role in the development of insulin resistance in human SkM. The results obtained with CM support the notion that adipocytes may secrete factors which are able to activate the CB1R. Furthermore, we identified two stress kinases in the signalling pathway of AEA and enhanced IRS-1(Ser307) phosphorylation, potentially underlying the development of insulin resistance.
目的/假设：大麻素1型受体（CB1R）拮抗剂，如利莫那班（Rim），是治疗肥胖及相关代谢紊乱的一种新方法。近期数据表明，内源性大麻素也由人类脂肪细胞产生。在此，我们研究了内源性大麻素在脂肪与肌肉之间负性相互作用中的潜在作用。
采用蛋白质印迹法分析人骨骼肌细胞（SkM）分化过程中CB1R的蛋白水平。用脂肪细胞条件培养基（CM）或花生四烯乙醇胺（AEA）联合CB1R拮抗剂Rim或AM251处理SkM，测定胰岛素刺激的Akt磷酸化和葡萄糖摄取。此外，研究了CB1R的信号通路。
我们发现SkM在分化过程中CB1R蛋白增加。SkM与CM或AEA孵育24小时，分别使胰岛素刺激的Akt（Ser473）磷酸化受损60%和高达40%。用Rim或AM251预处理细胞可使CM的作用降低约一半，而AEA的作用可被完全阻断。Rim可完全阻断CM对胰岛素刺激的葡萄糖摄取的降低作用。与AEA短期孵育可激活细胞外调节激酶1/2和p38丝裂原活化蛋白激酶，并损害胰岛素刺激的Akt（Ser473）磷酸化，但对Akt（Thr308）和糖原合酶激酶3α/β磷酸化无影响。此外，还观察到胰岛素受体底物-1（Ser307）磷酸化增强。
结论/解读：我们的结果表明，CB1R系统可能在人类SkM胰岛素抵抗的发生中起作用。CM实验结果支持脂肪细胞可能分泌能够激活CB1R的因子这一观点。此外，我们在AEA信号通路中鉴定出两种应激激酶，并发现胰岛素受体底物-1（Ser307）磷酸化增强，这可能是胰岛素抵抗发生的潜在原因。
