Objective To explore the effects and related mechanism of Exendin-4 on secretion of extracellular matrix in high glucose-induced glomerular mesangial cells(GMCs). Methods GMCs were incubated in medium with glucose or Exendin-4 for the four groups: normal glucose group(NG group): cells were treated in medium with 5.6 mmol/L glucose; NG with Exendin-4 treatment group(NGE group): cells were treated with 5.6 mmol/L glucose and Exendin-4; high glucose group(HG group): cells were cultured with 30 mmol/L glucose; HG with Exendin-4 treatment group(HGE group): cells were treated with 30 mmol/L glucose and Exendin-4 at concentration of 3, 5, 10, 15, 30 nmol/L separately, which were cultured for 12, 24, 48 hours. GMCs treated with Exendin-4 were determined by assessing proliferation using a CCK8 method. The levels of fibronectin(FN), collagen type Ⅳ(Col-Ⅳ)in the cell supernatant were measured using enzyme-linked immunosorbent assay(ELISA). The gene levels of Col-Ⅳ, FN, and expression of inflammatory mediators including monocyte chemotactic protein 1(MCP-1), tumor necrosis factor-α(TNF-α), intercellular cell adhesion molecule-1(ICAM-1), transforming growth factor-β1(TGF-β1)were evaluated using reverse transcription PCR(RT-PCR); The expression of nuclear transcription factor-κB(NF-κB), glucagon-like peptide-l receptor(GLP-1R), and phosphorylation levels of mitogen-activated protein kinases(MAPKs)were evaluated by Western blot. Results(1)After treatment with 10 nmol/L Exendin-4 for 24 hour, the proliferation rate of GMCs was significantly decreased compared with 3 nmol/L, 5 nmol/L Exendin-4 treatment(P<0.05), while there was no difference compared with 15 nmol/L, 30 nmol/L Exendin-4 treatment(both P>0.05). (2)The gene expression of FN, Col-Ⅳ and the inflammatory mediators, MCP-1, TNF-α, ICAM-1, TGF-β1 in HG group were significantly increased compared with the NG group,(all P<0.05). After treatment with Exendin-4, the levels of FN, Col-Ⅳ and the gene expression of TNF-α, MCP-1, ICAM-1, TGF-β1 were decreased(all P<0.05). (3)Compared with NG group, the expression of NF-κB and the phosphorylation of extracellular regulated protein kinases(p-Erk1/2), Jun N-terminal kinase(p-JNK)and, p38MAPK(p-p38MAPK)in the group of HG group were increased significantly, accompanied by the decrease of GLP-1R protein level(all P<0.05). Importantly, Exendin-4 treatment significantly reduced protein expression of p-Erk1/2, p-JNK, and NF-κB(all P<0.05), and the level of GLP-1R protein increased(P<0.05). Furthermore, specific Erk1/2, JNK or NF-κB inhibitors markedly blocked Exendin-4-mediated decrease in the levels of FN, Col-Ⅳ. Conclusion Exendin-4 treatment inhibits the secretion of extracellular matrix potentially through Erk1/2, JNK/NF-κB signaling in higher glucose induced GMCs.

Objective To explore the effects of glucagon-like peptide-1 (GLP-1) analogues liraglutide on renal tissues of diabetic rats and its mechanism.Methods Forty male SD rats were randomly divided into four groups:normal control rats (NC group),normal control rats with liraglutide treatment (NCL group),diabetic rats (DM group) and diabetic rats with liraglutide treatment.The body weight,glycosylated hemoglobin (HbA1c),albuminuria/creatinine (A/C),kidney index (KI,kidney mass/body mass) were detected after 8 weeks treatment.The gene expression of tumor necrosis factor-or (TNF-α),and interleukin-6 (IL-6),interleukin-1β (IL-1β),monocyte chemotactic protein-1 (MCP-1),type Ⅳ collagen,and transforming growth factor-β1 (TGF-β1) were measured by real time PCR.The protein expression of COL-Ⅳ,NF-κB,GLP-1R and phosphorylation levels of ERK,JNK and p38MAPK were evaluated by Western blotting.Results Compared to NC group,the body weight in DM group was reduced,and HbAlc,KI,A/C levels were significantly increased (P ＜ 0.05).The gene expression of TNF-α,IL-6,IL-1β,MCP-1,TGF-β1 and COL-Ⅳ was increased (P ＜ 0.05).Moreover,the protein expression of NF-κB in the nucleus of the kidney tissues and the phosphorylation levels of ERK,JNK and p38MAPK were significantly increased in DM group,accompanied by the decline of GLP-1R protein level (P ＜ 0.05).After 8 weeks of liraglutide treatment,the urinary protein excretion was reduced,and the gene expressions of TNF-α,IL-6,IL-1β,MCP-1,TGF-β1,COL-Ⅳ were inhibited.Importantly,the phosphorylation levels of ERK and JNK were significantly inhibited and the expression of NF-κB protein in the nucleus of the kidney tissue was reduced (P ＜ 0.05).These changes may be associated with the increased expression of GLP-1R after liraglutide treatment.However,blood glucose and the body weight in DML group rats had no significant changes after liraglutide treatment.Conclusion Liraglutide has a protective effect on renal tissues through inhibiting ERK and JNK phosphorylation and related inflammation in diabetic rats.

Objective To explore the effects and mechanism of exendin-4 on the secretion of extracellular matrix in high glucose-cultured glomerular mesangial cells (GMCs).Methods GMCs were cultured in vitro and divided into 4 groups:normal control (NC) group,normal control with exendin-4 (NCE)group,high glucose (HG) group,high glucose with exendin-4 (HGE) group.Cells in HGE group were treated with 3,5,10,15 or 30 nmol/L exendin-4 for about 12,24 or 48 hours,respectively.The proliferation and cell activity of GMCs were used to assess the most suitable culture time and concentration using Cell Counting Kit-8.The levels of fibronectin (FN) and collagen type Ⅳ in the cell supernatant were measured by ELISA.The levels of collagen type Ⅳ,FN,monocyte chemotactic protein-1 (MCP-1),tumor necrosis factor (TNF)-or,intercellular cell adhesion molecule-1 (ICAM-1),transforming growth factor-β1 (TGF-β1)were evaluated by RT-PCR.The expression of nuclear factor-κB (NF-κB) in each group was analyzed by Western blotting.Results (1) After treated by 10 nmol/L exendin-4 for 24 hours,the growth rate of GMCs cultured in high glucose was significantly decreased compared with 3 nmol/L or 5 nmol/L(F =120.808,P ＜ 0.05),but not different from 15 nmol/L or 20 nmol/L (all P ＞ 0.05).(2) Compared with NC group and NCE group,the expression of FN,collagen type Ⅳ,as well as their mRNA level and the inflammatory mediators such as MCP-1,TNF-α,ICAM-1 and TGF-β1 were significantly increased in HG group(F =6.894-166.914,all P ＜ 0.05).Compared with HG group,the protein and mRNA level of FN and collagen type Ⅳ,and the expression of TNF-α,MCP-1,ICAM-1 and TGF-β1 were inhibited greatly in HGE group (F =6.894-166.914,all P ＜ 0.05).(3) Compared with NC group and NCE group,the expression of NF-κB increased significantly in HG group (F =133.1,P ＜ 0.05).Compared with HG group,the expression of NF-κB was suppressed significantly in HGE group (F =133.1,P ＜ 0.05).Conclusion Exendin-4 inhibits the secretion of extracellular matrix of GMCs cultured in high glucose,and the mechanism is associated with the inhibition of inflammation induced by NF-κB.