| Objective: Macroangiopathy is the most serious chronic complication of type 2 diabetes mellitus (T2DM), which could results in coronary artery disease, cerebrovascular disease, gangrene of limbs. Therefore, its mutilation and fatality rate is high. The major pathological procedure of macroangiopathy is atherosclerosis (AS), which is a type of non-special inflammation and caused by multitude of cytokines and inflammatory factors. The small G protein Rho is a significant mesomerism molecule of cellular signal pathway, and has a role of tydrolization of omithine. Actived RhoA enables target molecule in downstream-ROCK, to regulate lots of behavior and function, including packing of cystoskeleton, activation of transcription factors, regulation of cell cycle, contraction and migration of SMC, and seretion of cytokines. Prenylation of protein Rho's C terminal shifts active GTP banding Rho to cell membrane, and then makes downstream reaction with effective protein. This prenylation can be inhibited by statins. The effect on adjustment of blood lipids of statins has been studied a lot . However, its another effect on the prohibition of AS has just been realised. The protein RhoA expression in aorta tissue were detected in order to discuss the association beween RhoA and macroangiopathy in T2DM. Furthermore, simvastatin was given to experimental rats to explain its mechanism of protective effects on aortopathy.Methods: Ten of fifty SD rats were taken out randomly to be normal control rats (group A) and the rest were taken for test rats. The control rats were fed with general diet while the test rats were fed with high-sugar-fat diet. Four weeks later, insulin resistance was induced in test group, then STZ 30 mg/kg was injected into abdominal cavity. At the end of 6 weeks, the rats whose fasting blood glucose (FBG) was greater than 7.8 mmol/L and insulin sensitivity decreased, were considered as T2DM rats. Them were divided randomly into 2 groups: T2DM model rats (group B), T2DM model rats treated with simvastatin (group C). The experiment lasted 14 weeks. At the end of 6 weeks, FBG, fasting insulin (FINS), insulin sensitivity index (ISI) in different group rats were measured. At the end of this experiment, FBG and serum lipids were detected. Aorta microstructure and ultrastructure were observed with light microscopes ( HE straining and Masson staining )and electron microscopes, and the area ratio of focus to vascular wall were measured. Elasticity of aorta were measured by isometric tension (isolated blood vessel ring assay). The protein expression level of RhoA in aorta wall were detected by immunohistochemical staining. These graphic results were analyzed with computer image-analysis system and the integral optical density (IOD) counts of RhoA were calculated. All the experimental data were dealt with SPSS11.0.Results1 Various indexes after 6 weeks: 2 weeks after STZ injection, FBG(12.99±1.16)mmol/L of test rats was higher compared to FBG(5.03±0.69)mmol/L of control rats (P<0.01) ; FINS 18.79(18.23, 19.29)mIU/L of test rats had unstatistics distinction compared to FINS 18.35(17.95, 18.98)mIU/L of control rats (P>0.05) ; ISI 0.0048(0.0045, 0.0053) was lower than ISI 0.0106(0.0103, 0.0112) of control rats (P<0.01). Thus far, the T2DM rat model was accomplished.2 Various biochemical indexes after 14 weeks: There was FBG (4.96±0.92)mmol/L in group A. FBG(13.15±1.18)mmol/L, TG, TC, LDL-C and VLDL-C of group B rats were all higher than those of group A rats, and HDL-C of group B rats was lower than that of group A rats (all P<0.05) . TG, TC, LDL-C and VLDL-C of group C rats were lower than those of group B rats, and HDL-C of group C rats was higher than that of group B rats (all P<0.05). FBG(12.70±3.54)mmol/L of group C rats had unstatistics distinction compared to control rats (P>0.05).3 Morphology: HE staining appeared that vessel wall of aorta in group A rats were in order, with clear demarcation of endomembrane, tunica media and adventitia, thin and flat endothelium cell, straight internal elastic membrane, which parallels with smooth muscle cell (SMC) regularly. Aorta wall in group B showed thickened endomembrane, which is partly composed of indiscriminate SMCs, swelling endothelial cells on the surface of focus, some of which overshoot, some ablate, even necrosis, and interior elasticity board has local aniso-thickness. It showed that SMCs proliferated in the tunica media and the arrangement of the middle elasticity board and SMCs fouled-up. Atherosclerotic plaque could be observed, whose surface is fibrous tissue, deeper is broken SMC, macrophage, foam cell, ectolipid, extracellular matrix. Aorta wall in group C ( treating with simvastatin ) , closed to normal, apeared flat thickening endomembrane, applan endothelial cell, proliferation of SMC more or less, without obvious plaque. The area ratio of focus to vascular wall in every group were as follows: group A 0.49±0.10%;group B 0.91±0.06%;group C 0.81±0.13%. The ratio in group B is larger than that in group A, and the ratio of group C is smaller than that in group B(all p<0.01). The ratio had positive correlation with the level of RhoA(r=0.837, p<0.01).TEM show endothelial cells of group B ablated , cytoplasm hydroped, mitochondrion mixed together, even had vacuole, RER broadened and degranulated, free ribosome decreased. Swelling endothelial cells, obvious thicken subendothelial layer, deleted or damaged cell membrane, etc had been observed in group C.4 Tension test shown that, the contraction of diabetic rats aorta was significantly increased compared with that in control group when stimulated by KCl and PE, and the relaxation of the diabetic rats aorta was reduced compared with that in control group when stimulated by acetylcholin.5 The level of RhoA in aorta: The IOD (788.21±13.29) of RhoA in group B was 2.89 times that (272.95±18.44) in group A. And the IOD(592.72±7.84) in group C was 25% less than that in group B (P<0.05). The analysis shown that the expression level of RhoA has a positive correlation with FBG, LDL-C, VLDL-C, the ratio of focus to vascular wall,and maximal tension 60 mmol/L KCl (r=0.837, 0.648, 0.568, 0.837 and 0.913 P<0.01), a negative correlation with HDL-C (r=-0.781, P<0.01) in experiment group.Conclusions1 Artherosclerosis was principal pathologic procedure of aorta lesion in T2DM.2 The enhanced contractile function and degraded diastolic function of aorta were found in T2DM rats.3 The increased level of RhoA in aorta of T2DM rats indicated that RhoA was a risk factor of the occurrence and development of artery lesion.4 The analysis shown that the aorta lesion was associated with the high level of RhoA. The study of RhoA and Rho inhibitor might provide a new method to prevent the aortopathy of T2DM.5 Simvastatin could protect aorta by adjustment of lipids and the inhibition of RhoA/ROCK pathway in T2DM.
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