Effect of endogenous insulin-like growth factor and stem cell factor on diabetic colonic dysmotility.

AIM: To investigate whether the reduction of stem cell factor (SCF) is mediated by decreased endogenous insulin-like growth factor (IGF)-1 in diabetic rat colon smooth muscle. METHODS: Sixteen Sprague-Dawley rats were randomly divided into two groups: control group and streptozotocin-induced diabetic group. After 8 wk of streptozotocin administration, colonic motility function and contractility of circular muscle strips were measured. The expression of endogenous IGF-1 and SCF was tested in colonic tissues. Colonic smooth muscle cells were cultured from normal adult rats. IGF-1 siRNA transfection was used to investigate whether SCF expression was affected by endogenous IGF-1 expression in smooth muscle cells, and IGF-1 induced SCF expression effects were studied. The effect of high glucose on the expression of endogenous IGF-1 and SCF was also investigated. RESULTS: Diabetic rats showed prolonged colonic transit time (252 ± 16 min vs 168 ± 9 min, P < 0.01) and weakness of circular muscle contraction (0.81 ± 0.09 g vs 2.48 ± 0.23 g, P < 0.01) compared with the control group. Endogenous IGF-1 and SCF protein expression was significantly reduced in the diabetic colonic muscle tissues. IGF-1 and SCF mRNA expression also showed a paralleled reduction in diabetic rats. In the IGF-1 siRNA transfected smooth muscle cells, SCF mRNA and protein expression was significantly decreased. IGF-1 could induce SCF expression in a concentration and time-dependent manner, mainly through the extracellular-signal-regulated kinase 1/2 signal pathway. High glucose inhibited endogenous IGF-1 and SCF expression and the addition of IGF-1 to the medium reversed the SCF expression. CONCLUSION: Myopathy may resolve in colonic motility dysfunction in diabetic rats. Deficiency of endogenous IGF-1 in colonic smooth muscle cells leads to reduction of SCF expression.

[Insulin-like growth factor 1 regulates expression of stem cell factor through ERKMAPK signaling pathway in gastric smooth muscle cell].

OBJECTIVE: To explore the effect and the intracellular signal transduction pathway of insulin-like growth factor 1 (IGF-1) on the expression of stem cell factor (SCF) in gastric smooth muscle cells (SMC). METHODS: Gastric SMC from SD rats were cultured by enzymolysis and identified by α-actin immunofluorescence methods. Western blot and quantitative reverse transcription-polymerase chain reaction were used to examine the expression of SCF in gastric SMC:(1) The level of SCF after gastric SMC were cultured with IGF-1. (2) The level of SCF after IGF-1 receptor (IGF-1Rα) monoclonal antibody were added. (3) Another SMC were pretreated with specific mitogen-activated protein kinase (MEK) inhibitor PD-98059 and phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor LY-294002, and investigate expression of SCF in gastric SMC. RESULTS: A very low level of SCF was expressed in gastric SMC cultured in bovine serum free medium. A low concentration of IGF-1 (5 and 10 µg/L) had no effect on the expression of SCF (both P>0.05), but the expressions of SCF mRNA and protein increased in IGF-1 at a higher concentration (50, 100 and 150 µg/L) (2.79, 5.51 and 5.35-fold in protein respectively, 1.81, 2.54 and 2.38-fold in mRNA respectively, all P<0.05), and IGF-1 in 100 µg/L may be the effective final concentration (all P<0.05). The peak of SCF increment was at the 16th hour with IGF-1 (2.36-fold in protein, 5.51-fold in mRNA, all P<0.05). The expression of SCF could be inhibited by IGF-1 receptor monoclonal antibody in a dose-dependent manner (all P<0.05). The IGF-1-induced SCF expression was reduced significantly by a pretreatment of PD-98059 (23% in protein and 48% in mRNA, P<0.05). And LY-294002 had no effect on the expression of SCF (P>0.05). CONCLUSION: The SCF expression in gastric SMC is stimulated by IGF-1 in both dose- and time-dependent manners through IGF-1R in which ERKMAPK signal transduction may play an important role.

T300A polymorphism of ATG16L1 and susceptibility to inflammatory bowel diseases: a meta-analysis.

AIM: To evaluate the association of the autophagy-related 16-like 1 (ATG16L1) T300A polymorphism (rs2241880) with predisposition to inflammatory bowel diseases (IBD) by means of meta-analysis. METHODS: Publications addressing the relationship between rs2241880/T300A polymorphism of ATG16L1 and Crohn's disease (CD) and ulcerative colitis (UC) were selected from the MEDLINE and EMBASE databases. To make direct comparisons between the data collected in these studies, the individual authors were contacted when necessary to generate a standardized set of data from these studies. From these data, odds ratio (OR) with 95% confidence interval (CI) were calculated. RESULTS: Twenty-five studies of CD were analyzed, 14 of which involved cases of UC. The variant G allele of ATG16L1 was positively associated with CD (OR = 1.32, 95% CI: 1.26-1.39, P < 0.00001) and UC (OR = 1.06, 95% CI: 1.01-1.10, P = 0.02). For child-onset IBD, a higher G allele frequency was found for cases of CD (OR = 1.35, 95% CI: 1.16-1.57, P = 0.0001) than for cases of UC (OR = 0.98, 95% CI: 0.81-1.19, P = 0.84) relative to controls. CONCLUSION: The ATG16L1 T300A polymorphism contributes to susceptibility to CD and UC in adults, but different in children, which implicates a role for autophagy in the pathogenesis of IBD.