尼克酰胺降低妊娠期糖尿病大鼠的血糖水平以及调控线粒体超氧水平研究

目的：探讨尼克酰胺对妊娠期糖尿病的潜在治疗效果及其可能的抗氧化作用机制。方法：取妊娠第0天的9～11周龄雌性SD大鼠以链脲佐菌素35 mg/kg进行单次腹腔注射，构建妊娠期糖尿病大鼠模型；从妊娠第6天至第20天分别给予不同剂量（0、50、100、200 mg/kg）尼克酰胺灌胃。将大鼠分为无妊娠糖尿病的正常对照组、未给药的妊娠糖尿病对照组（0 mg/kg）和给尼克酰胺小（50 mg/kg）、中（100 mg/kg）、大（200 mg/kg）剂量各组，每组8只。在妊娠第21天检测各组大鼠空腹血糖。检测各组胎鼠脑组织和大鼠骨骼肌组织的线粒体超氧水平和抗氧化酶活性。分别应用实时荧光定量PCR和蛋白质印迹法检测各组骨骼肌组织超氧化物歧化酶（SOD1和SOD2）、过氧化氢酶（CAT）和线粒体去乙酰化酶（SIRT3）的表达量。结果：尼克酰胺各组血糖降低，其神经元线粒体超氧水平均低于糖尿病对照组（均P<0.05）。尼克酰胺各组骨骼肌组织中SOD2 mRNA/蛋白水平和活性均高于糖尿病对照组（均P<0.05），而组织中CAT的表达量和活性差异均无统计学意义（均P>0.05）。与糖尿病对照组比较，尼克酰胺各组SIRT3的表达均增加（均P<0.05），线粒体SOD2蛋白乙酰化水平均降低（均P<0.05）。结论：尼克酰胺降低妊娠糖尿病大鼠的空腹血糖水平，并可能通过促进SIRT3蛋白功能降低线粒体SOD2蛋白乙酰化水平、增强SOD2活性从而降低妊娠期糖尿病大鼠的线粒体超氧水平。
Abstract: Objective: To investigate the effects of nicotinamide (NAM) on blood glucose level and anti-oxidative enzyme activity in gestational diabetic (GDM) rats. Methods: GDM model was induced by injection of STZ (35 mg/kg) in pregnant female Sprague-Dawley rats. Nicotinamide was given to GDM rats by gavage at 50, 100 or 200 mg/kg q.d from gestational d 6 to d 20. The rats were divided into normal control group, GDM group (0 mg/kg), low-dose NAM group (50 mg/kg), middle-dose NAM group (100 mg/kg) and high-dose NAM group (200 mg/kg) with 8 animals in each group. When rats were sacrificed at d 21, the blood glucose level was measured; skeletal muscle and fetal brain samples were collected. The expression and activity of anti-oxidative enzymes, including superoxide dismutase (SOD1, SOD2), catalase (CAT) and sirtuin-3 (SIRT3) were measured by RT-PCR and Western blot. Results: Nicotinamide significantly lowered the blood glucose in GDM rats and decreased mitochondrial superoxide level in the fetal cortical neurons. SOD2 was induced in skeletal muscle by nicotinamide in GDM rats (P<0.05), while no significant change was observed in the expression of CAT (P>0.05). Nicotinamide increased SIRT3 expression (P<0.05) and decreased deacetylation of SOD2 in skeletal muscle of GDM rats (P<0.05). Conclusion: Nicotinamide can lower the blood glucose level in GDM rats, and decrease mitochondrial superoxide level, which is associated with promoting SIRT3 activity to deacetylate SOD2 and elevate SOD2 activity in GDM rats. Key words: Diabetes, gestational/drug therapy Niacinamide/padministration & dosage Niacinamide/therapeutic use Mitochondria Superoxide dismutase/blood Catalase/blood Disease models, animal