RESUMO
Osteoporosis (OP) is a systemic skeletal disease that primarily affects the elderly population, which greatly increases the risk of fractures. Here we report that Kindlin-2 expression in adipose tissue increases during aging and high-fat diet fed and is accompanied by decreased bone mass. Kindlin-2 specific deletion (K2KO) controlled by Adipoq-Cre mice or adipose tissue-targeting AAV (AAV-Rec2-CasRx-sgK2) significantly increases bone mass. Mechanistically, Kindlin-2 promotes peroxisome proliferator-activated receptor gamma (PPARγ) activation and downstream fatty acid binding protein 4 (FABP4) expression through stabilizing fatty acid synthase (FAS), and increased FABP4 inhibits insulin expression and decreases bone mass. Kindlin-2 inhibition results in accelerated FAS degradation, decreased PPARγ activation and FABP4 expression, and therefore increased insulin expression and bone mass. Interestingly, we find that FABP4 is increased while insulin is decreased in serum of OP patients. Increased FABP4 expression through PPARγ activation by rosiglitazone reverses the high bone mass phenotype of K2KO mice. Inhibition of FAS by C75 phenocopies the high bone mass phenotype of K2KO mice. Collectively, our study establishes a novel Kindlin-2/FAS/PPARγ/FABP4/insulin axis in adipose tissue modulating bone mass and strongly indicates that FAS and Kindlin-2 are new potential targets and C75 or AAV-Rec2-CasRx-sgK2 treatment are potential strategies for OP treatment.
RESUMO
Objective@#To investigate the effects of Kindlin-2 on malignant phenotypes of human gallbladder cancer cells and discuss the mechanisms.@*Methods@#The expression level of Kindlin-2 in 30 cases of gallbladder cancer tissues and adjacent non-tumoral tissues collected from the First Affiliated Hospital of Zhengzhou University between September 2012 and May 2013 was assessed by real-time PCR and immunohistochemistry.Lentivirus-mediated Kindlin-2 overexpression was used in gallbladder cancer cell lines GBC-SD and SGC-996.Transwell assay and adhesion assay were investigated to explore the functional role of Kindlin-2 on gallbladder cancer cells.Western Blot was used to test the protein change of epithelial-mesenchymal transition(EMT) characteristics. The t-test was used to analyzed results.@*Results@#The RNA and protein levels of Kindlin-2 in gallbladder cancer tissues were higher than in the non-tumoral tissues (t=4.372, P=0.001; t=7.477, P=0.000). The expression level of Kindlin-2 in gallbladder cancer tissues was correlated with Nevin stage(χ2=5.932, P=0.035). Compared with control groups, the cell-matrix adhesion ability of GBC-SD and SGC-996 with Kindlin-2 overexpression was obviously promoted(1.66±0.03 vs. 1.07±0.22, t=2.710, P=0.041; 2.66±0.24 vs. 1.03±0.02, t=6.610, P=0.020). The number of GBC-SD and SGC-996 cells with Kindlin-2 overexpression passing through the Transwell chamber matrix increased significantly compared with the control groups(116.1±13.9 vs. 54.7±8.4, t=3.781, P=0.019; 136.3±7.5 vs. 64.3±6.4, t=7.302, P=0.002). The wound healing rate of GBC-SD with Kindlin-2 overexpression at 12-hour and 24-hour was higher than that of the group ((42.9±2.2)% vs. (29.7±1.7)%, t=4.690, P=0.009; (65.0±2.4)% vs.(40.4±2.0)%, t=7.945, P=0.001). The wound healing rate of SGC-996 with Kindlin-2 overexpression at 12-hour and 24-hour was also higher than that of the group ((32.9±1.3)% vs. (24.1±1.5)%, t=4.518, P=0.011; (51.3±1.1)% vs. (39.2±1.1)%, t=8.001, P=0.001). The characteristics of EMT were induced in gallbladder cancer cells with Kindlin-2 overexpression, including the up-regulation of N-cadherin, Vemintin and the down-regulation of E-cadherin.@*Conclusion@#The expression of Kindlin-2 is up-regulated in gallbladder cancer tissues and Kindlin-2 promoted the malignant phenotypes of gallbladder cancer cells partially by epithelial-mesenchymal transition.