黄秋葵多糖调节PEPCK和AMPK表达抑制高脂饮食小鼠肝糖异生

Okra polysaccharide inhibiting hepatic gluconeogenesis by regulating PEPCK and AMPK in high fat diet mice

目的观察黄秋葵多糖对持续高脂饮食小鼠葡萄糖代谢、胰岛素敏感性及糖异生的影响及其机制。方法 2015年4—9月于上海中医药大学附属普陀医院中心实验室进行实验。CD47/BL雄性小鼠40只,随机分为高脂饮食组(H组)、西格列汀组(S组)、黄秋葵多糖低剂量组(OPL组)、黄秋葵多糖高剂量组(OPH组)。小鼠高脂饮食喂养8周后,S组予西格列汀10 mg·kg^(-1)·d^(-1),OPL组予黄秋葵多糖150 mg·kg^(-1)·d^(-1),OPH组予黄秋葵多糖300 mg·kg^(-1)·d^(-1)。干预10周后行葡萄糖耐量、胰岛素耐量、丙酮酸耐量实验,检测肝脏糖异生关键酶PEPCK、转录因子PGC-1α、KLF15等mRNA水平,以及肝脏AMPK表达。PAS染色观察肝糖原沉积。结果葡萄糖耐量实验:OPL组60 min血糖显著低于H组[(17.71±4.05)mmol/L vs.(21.79±2.59)mmol/L,q=3.561,P=0.029];OPH组30min、60 min血糖低于H组[(23.90±5.43)mmol/L vs.(29.07±3.38)mmol/L,(16.43±4.42)mmol/L vs.(21.79±2.59)mmol/L,q=3.204、3.792,P=0.036、0.015]。丙酮酸耐量实验:OPL组15 min、30 min血糖明显低于H组[(12.01±1.14)mmol/L vs.(14.69±1.68)mmol/L,(14.18±1.46)mmol/L vs.(16.82±2.74)mmol/L,q=5.668、3.623,P=0.002、0.02];OPH组15 min、30 min、60 min血糖均显著低于H组[(11.62±1.98)mmol/L vs.(14.69±1.68)mmol/L、(12.63±1.51)mmol/L vs.(16.82±2.74)mmol/L,(11.59±1.97)mmol/L vs.(15.42±2.01)mmol/L,q=5.281、5.978、5.930,P=0.002、0.001、0.004]。胰岛素耐量实验:OPH组90 min、120 min血糖显著低于H组[(4.35±1.28)mmol/L vs.(6.29±2.52)mmol/L,(5.83±1.03)mmol/L vs.(8.48±1.92)mmol/L,q=3.065、5.387,P=0.044、0.001]。肝糖异生相关因子及AMPK检测结果:OPH组肝脏PEPCK、PGC-1α、KLF15mRNA表达较H组明显下调[(0.705±0.172)vs.(1.013±0.249),(0.785±0.123)vs.(0.968毒0.280),(0.676±0.080)vs.(0.904±0.192),q=4.304、3.295、4.617,P=0.008、0.033、0.013];OPH组肝脏AMPK mRNA表达较H组显著增加[(1.078±0.185)vs.(0.535±0.155),q=3.175,P=0.039]。Western blot显示OPH组、OPL组肝脏PGC-1α、KLF15蛋白水平显著低于H组。肝脏糖原染色:OPH组肝糖原沉积明显高于H组[(14.06±2.98)%vs.(10.20±4.79)%,q=3.070、P=0.044]。结论黄秋葵多糖能改善高脂诱导的胰岛素抵抗小鼠葡萄糖代谢和外周胰岛素敏感性、抑制丙酮酸糖异生。黄秋葵多糖可能通过下调肝脏PGC-1α和KLF15表达,促进AMPK转录,抑制PEPCK基因转录。

Objective To observe the influence of okra polysaccharide（OP） on glucose levels,insulin resistance,and gluconeogenesis in high fat diet mice and to explore the possible mechanisms.Methods Forty CD47/BL male mice were divided into 4 groups（the OPL,OPH,S,and H groups）.After 8 week high fat diet（HFD）,the OPL,OPH,and S groups received low dose OP（150 mg·kg^-1· d^-1）,high dose OP（300 mg·kg^-1·d^-1）,and sitagliptin（10 mg·kg^-1·d^-1）by daily gavage respectively.And the H group was simultaneously perfused with the same volume of saline.Glucose tolerance test（OGTT）,pyruvic acid tolerance test（PTT）,and insulin tolerance test（ITT） were undertaken after 10 weeks and the levels of PEPCK,G6 Pase,PGC 1α,KLF15 in liver were detected.Hepatic glycogen deposition was observed using periodic acid SchifF（PAS） staining.Results OGTT showed that OPL group had lower glucose levels at 60 minutes than H group[（17.71 ±4.05） mmol/L,（21.79 ±2.59） mmol/L,q =3.561,P =0.029）],and OPH group had decreased glucose levels at 30 and 60 minutes[（23.90 ±5.43） mmol/L,（16.43 ±4.42） mmol/L）]than H group[（29.07 ±3.38） mmol/L,（21.79 ±2.59） mmol/L,（q =3.204,P =0.036;q =3.792,P =0.015）].During PTT,OPL group had lower glucose levels at 15 and 30 minutes[（12.01 ±1.14） mmol/L,（14.18 ±1.46） mmol/L]than H group[（14.69 ± 1.68）mmol/L,16.82 ±2.74） mmol/L,（q = 5.668,P = 0.002;q = 3.623,P = 0.02）].And the glucose levels of OPH group went down at 15,30,and 60 minutes[（11.62 ± 1.98） mmol/L,（12.63 ±1.51） mmol/L,（11.59 ±1.97） mmol/L]compared with H group[（14.69±1.68） mmol/L,（16.82 ±2.74） mmol/L,（15.42 ±2.01）mmol/L,（q =5.281,P =0.002;q =5.978,P =0.001;g =5.930,P =0.004）].ITT expressed that OPH group had declined glucose levels at 60 and 90 minutest（4.35 ± 1.28） mmol/L,（5.83 ±1.03） mmol/L]than H group[（6.29 ±2.52） mmol/L,（8.48 ±1.92） mmol/L（q = 3.065,P =0.044;q =5.387,P =0.001）].Less expression of PEPCK,PGC lot,and KLF15 mRNA and unregulated level of AMPK mRNA in liver were found in OPH group（0.705 ± 0.172）,（0.785 ± 0..123）,（0.676 ± 0.080）,（1.078 ±0.185） compared with those in H group[（1.013±0.249）,（0.968 ±0.280）,（0.904 ±0.192）,（0.535±0.155）（q =4.304,P =0.008;q =3.295,P =0.033;q =4.617,P =0.013;q =3.175,P =0.039）].The protein levels of PGC 1α and KLF15 were significantly reduced in OPH and OPL groups than in H mice.OPH group had elevated hepatic glycogen deposition compared with Hgroup[（14.06 ±2.98,10.20±4.79）%（q =3.070,P =0.044）].Conclusion Our study suggests that okra polysaccharide ameliorates glucose metabolism and inhibits gluconeogenesis in insulin resistant mice.Downregulated PEPCK,PGC la,and KLF15 levels and increased AMPK expression were probably involved.