ObjectiveTo observe the effects of TR3 receptor agonist 6-mercaptopurine(6-MP) on the glucose and lipid metabolism and NF-κB p65/CylinD1 pathway in streptozotocin (STZ)-induced diabetic apolipoprotein E knockout(ApoE^-/-) mice, and explore the possible mechanism of TR3 receptors in improving diabetic atherosclerosis.

MethodsForty ApoE^-/- mice were randomly divided into the ApoE^-/- group, STZ-ApoE^-/- group, STZ-ApoE^-/- +6-MP5(5 mg·kg^-1·d^-1) and STZ-ApoE^-/- +6-MP10(10 mg·kg^-1·d^-1) group(10 rats each group).The 6-MP intraperitoneal injection was implemented, once a day, for 8 weeks.The diabetic animal model was established using intraperitoneal injection of STZ.The levels of blood glucose and blood lipid were determined using the blood glucose test strip and the enzymic method or selective homogeneous method, respectively.The Western-blotting was used to detect the protein levels of NF-κB p65/CylinD1 in thoracic aorta tissue, the lipid deposition in the thoracic aortic intima was observed by oil red O staining, and the patch area in the thoracic aorta was measured using HE staining.

ResultsCompared with the ApoE^-/- mice group, the levels of blood glucose, triglyceride(TG), total cholesterol(TCHO) and low-density lipoprotein-cholesterol(LDL-C) significantly increased in STZ-ApoE^-/- group(P < 0.05), and the level of TR3 receptor agonist 6-MP decreased the levels of plasma glucose and lipid with dose-dependently.Comapred the STZ-ApoE^-/- group, the levels of the blood glucose and TG, LDL-A and TC significantly decreased in the STZ-ApoE^-/- +6-MP5 group(P < 0.05).Compared with the ApoE^-/- group, the levels of NF-κB p65 and CylinD1 remarkably increased in the STZ-ApoE^-/- group(P < 0.05).The 6-MP reduced the expression level of NF-κB p65/CylinD1 protein in thoracic aorta of diabetic ApoE^-/- mice in a dose-dependent manner, and the protein level of NF-κB p65/CylinD1 in STZ-ApoE^-/- +6-MP5 group were significantly lower than that in STZ-ApoE^-/- group(P < 0.05).The differences of the levels of NF-κB p65/CylinD1 in thoracic aorta between STZ-ApoE^-/- +6-MP10 group and STZ-ApoE^-/- +6-MP5 group were statistically significnat(P < 0.05).The results of oil red O staining showed that 6-MP inhibited the intima lipid deposition in the thoracic aorta of STZ-ApoE^-/- mice in a dose-dependent manner.The results of HE staining showed that 6-MP reduced the area of intima plaque and formation of vacuoles(lipids) inside plaque, and inhibited the proliferation of smooth muscle layer around plaque and plaque base in the thoracic aorta of STZ-ApoE^-/- mice in a dose-dependent manner.Compared with the STZ-ApoE^-/- group, the plaque area in the STZ-ApoE^-/- +6-MP5 group significantly reduced(P < 0.05), and further reduced in the STZ-ApoE^-/- 6-MP10 group(P < 0.01).

ConclusionsThe TR3 receptor agonist 6-MP can significantly decrease the formation of atherosclerosis in diabetic ApoE^-/- mice, which may be related to the improvement of glycolipid metabolism and inhibition of NF-κB p65/CylinD1 signaling pathway.