Impact and related mechanisms of glucose fluctuations on aortic fibrosis in type 1 diabetic rats / 中华心血管病杂志

ABSTRACT

Objective: To investigate the impact and related mechanisms of glucose fluctuations on aortic fibrosis in rats with type 1 diabetes mellitus. Methods: After injection of streptozotocin (STZ), male Sprague Dawley (SD) (8-12 weeks) rats (n=24) were randomly divided into three groups in accordance with the random number table controlled STZ-induced diabetes (C-STZ) group (n=8); uncontrolled STZ-induced diabetes (U-STZ) group (n=8); STZ-induced diabetes with glucose fluctuations (STZ-GF) group (n=8). After three weeks, rats were sacrificed and aorta was obtained, aortic fibrosis was detected by Masson trichrome staining. The expression of collagen type 1 (collagen Ⅰ) was tested by immunofluorescence. The expression of runt-related transcription factor 2 (Runx2) was tested by immunohistochemistry. The mRNA levels of collagen Ⅰ and Runx2 were detected by quantitative real-time PCR (qRT-PCR). The protein expressions of collagen Ⅰ, Runx2 and nuclear factor (NF)-κB were determined by Western blot. Primary rat aortic smooth muscle cells (VSMCs) were cultured in three conditions normal glucose (NG), high glucose (HG) and glucose fluctuations (GF). Cells in GF group were incubated for 72 hours with glucose alternating between 5.5 and 25 mmol/L every 12 hours. TPCA-1, the inhibitor of NF-κB, the expression of collagenⅠin different groups of cells was tested by immunofluorescence. The protein expressions of collagen Ⅰ, Runx2 and NF-κB were also determined by Western blot. Results: (1) The quantitative ratios of the area of fibrosis in the C-STZ group, U-STZ group, STZ-GF group were (8.42±0.10)%, (21.30±0.74)% and (44.39±1.09)% (P<0.05), respectively. The means of integral optical density (IOD) of collagenⅠ in the three groups were 11.92±0.88, 50.04±3.56 and 77.52±2.69, respectively (P<0.05). The mRNA levels of collagenⅠ in the three groups were 1.00±0.10, 2.02±0.28 and 2.83±0.33, respectively (P<0.05). The protein expressions of collagenⅠ in the three groups were 1.05±0.03, 2.06±0.32 and 4.93±0.25, respectively (P<0.05). (2) The average IOD of Runx2 in the three groups were 150.00±7.35, 204.84±2.32 and 391.48±7.13, respectively (P<0.05). The mRNA levels of Runx2 in the three groups were 1.02±0.02, 1.27±0.04 and 2.18±0.12, respectively (P<0.05). The protein expressions of Runx2 in the three groups were 1.03±0.01, 2.34±0.36 and 4.52±0.75, respectively (P<0.05). (3) The protein expressions of NF-κB in the three groups were 1.02±0.01, 1.96±0.13 and 2.64±0.21, respectively (P<0.05). (4) In vitro, application of inhibitor of NF-κB reversed glucose fluctuations-induced upregulation of protein levels of Col Ⅰ and Runx2 (P<0.05). Conclusion: Glucose fluctuations could aggravate aortic fibrosis through activating Runx2 via NF-κB signaling pathways.