Research Paper
ZHANG Yuan-Yuan, ZHANG Meng, ZHU Yue, QIAN Shuai-Wei, KOU Xian-Juan
Type 2 diabetes mellitus(T2DM) is a metabolic disease that causes cognitive dysfunction. The level of autophagy in the brain is associated with decreased cognitive function in T2DM. Exercise can improve T2DM cognition, but the exact mechanism remains unclear. The purpose of this study was to investigate the role of autophagy in improving cognitive dysfunction in T2DM mice with different forms of exercise intervention and its molecular mechanism. C57BL/6 male 4-week-old mice were randomly divided into control group (C), T2DM model group (DM), T2DM exercise group and T2DM autophagy inhibitor group. T2DM mice were fed with high fat diet combined with intraperitoneal injection of STZ. In the exercise group, treadmill exercise (T), climbing ladder (R) and treadmill exercise combined climbing ladder (M) were used for intervention. Chloroquine (CQ) (10mg/kg) was injected into the inhibitor group, which was divided into T2DM plus inhibitor group (DM+CQ) and DM+CQ+ treadmill intervention group (DM+T+CQ). Immunofluorescence staining showed that the three exercise interventions could decrease the number of Iba-1 positive cells and fluorescence intensity in hippocampal tissue of T2DM mice (P<0.05), and decrease NLRP3 fluorescence intensity in microglia cells (P<0.05). Western blot showed that the three exercise interventions could decrease the expression of iNOS, GFAP and Iba-1 proteins and increase the expression of Arg-1 protein in hippocampus of T2DM mice, and all the proteins show significant differences in M group (P<0.05). The three exercise interventions could reduce the expression of NLRP3 complex protein in the hippocampus of T2DM mice, and there were significant differences in M group (P<0.05) and in T group (P<0.05) except for NLRP3 protein. The three exercise interventions could decrease the protein levels of Bax and p62, and increase the protein levels of Bcl-2 and LC3 in hippocampus of T2DM mice, and there were significant differences in M group and T group (P<0.05). After addition of CQ, water maze results showed that inhibition of autophagy aggravated cognitive impairment in T2DM mice (P<0.05), and reduced the protective effect of exercise on cognition in T2DM mice. Immunofluorescence staining and Western blot showed that DM+T+CQ group had autophagy dysfunction compared with T group. Western blot results showed that compared with DM group, the expression levels of iNOS, GFAP, NLRP3, Cleaved caspase-1, Iba-1, Caspase-1 and Bax were significantly increased in DM+CQ group (P<0.05). Compared with T group, NLRP3, Cleaved caspase-1 and Bax proteins in DM+T+CQ group were significantly increased (P<0.05), and Bcl-2 protein was significantly decreased (P<0.05). In conclusion, different forms of exercise intervention can improve neuroinflammation and neuronal apoptosis in T2DM mice. Comprehensive comparison shows that treadmill exercise and treadmill combined with climbing ladder have better effects.The mechanism may be that exercise activates neuronal autophagy, reduces neuroinflammation and glial cell activation, and inhibits neuronal apoptosis.