Investigation On The Change Of HMGA1 Expression In Diabetic Rat Aorta

Objective To establish a rat model of type 2 diabetes induced by high-sucrose-high-fat diets combined with single low-dose STZ intraperitoneal injection and to observe the change of the expression of HMGA1 m RNA and protein in the aorta and to investigate the possible pathological factors influencing the expression of HMGA1, making an attempt to provide a new insight to the pathogenesis of diabetic vascular complications and prevention strategies.Methods Thirty male Sprague-Dawley rats,4-weeks of age, were randomly divided into 3 groups: nomal control group(NC group), high-sucrose-high-fat diets group(HSFDs group) and diabetic group(DM group). Control group was fed with regular chow diet, and other two groups were high-sucrose-high-fat diets. Before and after 4-week feeding, the body weight and the serum level of blood glucose(BG), fasting insulin(FINS) and lipids(TG, TC, LDL and HDL) were determined. At the 4th week, diabetic group were injected intraperitoneally(IP) with a low dose of streptozotocin(30mg/kg). Three days later, the nonfasting blood glucose(NFBG)was measured to observe the change of blood glucose every week. Finally, rats were sacrificed at the eighth week and blood samples were collected for FINS, lipid(TG, TC, LDL and HDL) and Glycosylated haemoglobin(Hb A1c) assay. Abdominal aorta tissues were collected for determing the m RNA and protein expression levels of HMGA1 by q RT-PCR, Western-blotting and Immunohistochemistry(IHC), respectively. The correlation of HMGA1 m RNA and protein expression with FPG, NFBG, TC, TG, LDL, HDL and FINS was analyzed by Spearman rank correlation analysis.Results At the beginning and the 4th week, the levels of BW, FBG, NFBG, FINS and insulin sensitivity index( ISI) were not statisticantly different among three groups(P>0.05). At the beginning, the levels of TC, TG, LDL and HDL also were not statisticantly different among three groups(P>0.05). The level of NFBG was elevated(>11.1mmol/l) on the 3rd, 10 th and 21 st day after streptozotocin injection. At the 8th week, the levels of FBG,NFBG, Hb A1 c, TG, TC, LDL and HDL were significantly increased in DM group compared to NC and HSFDs group(P<0.05), but BW, FINS, ISI were significantly lower(P<0.05). The levels of BW, FINS, TC and LDL in HSFDs group were significantly higher compared to NC group(P<0.05), but ISI were significantly lower(P<0.05).(2) According to q RT-PCR analysis of HMGA1 m RNA expression in rat abdominal aorta, the HMGA1 m RNA levels in aorta from DM group was significantly higher than that of NC and HSFDs group(P<0.05). Meanwhile, the expression of HMGA1 m RNA in HSFDs group was slightly increased compared to NC group, but there was no statistical difference(P>0.05).(3) With Western-blot and immunohistochemical analysis, the same trend was found regarding HMGA1 protein expression in rat abdominal aorta.In addition, It was found that HMGA1 protein was mainly expressed in the nucler of vascular smooth muscle cells( VSMCs).(4) Hematoxylin-eosin staining(HE staining) of rat abdominal aorta showed the structure of endotheliocyte in rat,s aorta of NC group was clearly, intima was smooth, vascular smooth cells and outer loose connective tissue were dense and arranged in an orderly manner. But the endotheliocytes in rat′ s aorta of DM group were nonsequence, vascular media was thickening and cytoplasmic matrix of vascular smooth cells were loose. The aortic morphology of HSFDs group fell in between above groups. In addition, the vascular intima-media thickness(IMT) of DM group was significantly increased compared to NC and HSFDs group(P<0.05), and the vascular IMT of HSFDs group was also significantly higher than that of NC group(P<0.05).(5) Spearman rank correlation analysis demonstrated HMGA1 m RNA and protein expression in rat aorta had a positive correlation with levels of FBG(HMGA1 m RNA: r=0.424, P=0.039, HMGA1 protein(IOD): r=0.549, P=0.005), NFBG(HMGA1 m RNA: r=0.522, P=0.016, HMGA1 protein(IOD):r=0.616, P=0.025), TC(HMGA1 m RNA: r=0.544, P=0.006, HMGA1 protein(IOD): r=0.726, P=0.000) and LDL(HMGA1 m RNA: r=0.564, P=0.015, HMGA1 protein(IOD): r=0.659, P=0.014), but not with TG, HDL and FINS.Conclusion(1) The rat model of type 2 diabetes could be induced successfully by high-sucrose-high-fat diets combined with single low-dose STZ intraperitoneal injection.(2) The morphological change that vascular media was thickening and cytoplasmic matrix of vascular smooth cells were loose occured in aorta of diabetic rats; The expression of HMGA1 m RNA and protein was increased in diabetic rat′ s aorta.(3) HMGA1 expression had a positive correlation with levels of FBG, NFBG, TC and LDL, and which were possible pathological factors influencing the expression of HMGA1.