scholarly journals Metformin Rapidly Increases Insulin Receptor Activation in Human Liver and Signals Preferentially through Insulin-Receptor Substrate-2

2003 ◽  
Vol 88 (3) ◽  
pp. 1323-1332 ◽  
Author(s):  
Jenny E. Gunton ◽  
Patric J. D. Delhanty ◽  
Shin-Ichiro Takahashi ◽  
Robert C. Baxter
Endocrinology ◽  
2001 ◽  
Vol 142 (5) ◽  
pp. 1835-1840 ◽  
Author(s):  
M. Karas ◽  
A. P. Koval ◽  
Y. Zick ◽  
D. LeRoith

Abstract Stimulation of the insulin or insulin-like growth factor (IGF)-I receptor results in activation of several signaling pathways. Proteins of the insulin receptor substrate (IRS) family play important roles in mediating these signaling cascades. To date, four members of the IRS family of docking proteins have been characterized. Recently, we have reported that stimulation of the IGF-I receptor in 293 HEK cells regulates interaction of the newly discovered IRS-4 molecule with the Crk family of proteins. In the present study, we characterize the molecular basis of these interactions. C- and N termini truncation analysis of IRS-4 demonstrated that the region between amino acids 678 and 800 of the IRS-4 molecule is involved in this interaction. This region contains a cluster of four tyrosines (Y700, Y717, Y743, and Y779). We hypothesize that one or more of these tyrosines are involved in the interaction between the SH2 domain of the Crk-II molecule when IRS-4 is phosphorylated upon IGF-I receptor activation. Additional mutational analyses confirmed this hypothesis. Interestingly, none of these four tyrosines was individually critical for the interaction between Crk-II and IRS-4, but when all four tyrosines were simultaneously mutated to phenylalanine, the IGF-I induced interaction between these molecules was abolished. Taken together, these results suggest a novel mechanism of Crk-II binding to tyrosine phosphorylated proteins.


2020 ◽  
Vol 19 (1) ◽  
pp. 106-114
Author(s):  
Guang Hao ◽  
Xiaoyu Ma ◽  
Mengru Jiang ◽  
Zhenzhen Gao ◽  
Ying Yang

This study examined the in vivo effects of Echinops spp. polysaccharide B on type 2 diabetes mellitus in Sprague-Dawley rats. We constructed a type 2 diabetes mellitus Sprague-Dawley rat models by feeding a high-fat and high-sugar diet plus intraperitoneal injection of a small dose of streptozotocin. Using this diabetic rat model, different doses of Echinops polysaccharide B were administered orally for seven weeks. Groups receiving Xiaoke pill and metformin served as positive controls. The results showed that Echinops polysaccharide B treatment normalized the weight and blood sugar levels in the type 2 diabetes mellitus rats, increased muscle and liver glycogen content, improved glucose tolerance, increased insulin secretion, and reduced glucagon and insulin resistance indices. More importantly, Echinops polysaccharide B treatment upregulated the expression of insulin receptor in the liver, skeletal muscles, and pancreas, and significantly improved the expression levels of insulin receptor substrate-2 protein in the liver and pancreas, as well as it increased insulin receptor substrate-1 expression in skeletal muscles. These two proteins play crucial roles in increasing insulin secretion and in controlling type 2 diabetes mellitus. The findings of the present study suggest that Echinops polysaccharide B could improve the status of diabetes in type 2 diabetes mellitus rats, which may be achieved by improving insulin resistance. Our study provides a new insight into the development of a natural drug for the control of type 2 diabetes mellitus.


Diabetologia ◽  
2002 ◽  
Vol 45 (12) ◽  
pp. 1697-1702 ◽  
Author(s):  
Björnholm M. ◽  
He A. ◽  
Attersand A. ◽  
Lake S. ◽  
Liu S. ◽  
...  

Author(s):  
Lingling Wu ◽  
Changping Fang ◽  
Jun Zhang ◽  
Yanchou Ye ◽  
Haiyan Zhao

<b><i>Objectives:</i></b> Insulin receptor substrate 1 (IRS1) is a crucial factor in the insulin signaling pathway. IRS1 gene polymorphism rs1801278 in mothers has been reported to be associated with gestational diabetes mellitus (GDM). However, it is not clear whether IRS1 gene polymorphism rs1801278 in fetuses is associated with their mothers’ GDM morbidity. The purpose of this study is to analyze the association between maternal, fetal, or maternal/fetal <i>IRS1</i> gene polymorphism rs1801278 and GDM risk. <b><i>Design:</i></b> The study was a single-center, prospective cohort study. In total, 213 pairs of GDM mothers/fetuses and 191 pairs of control mothers/fetuses were included in this study. They were recruited after they underwent oral glucose tolerance test during 24–28 weeks of gestation and followed up until delivery. All participants received the conventional interventions (diet and exercise), and no special therapy except routine treatment. <b><i>Methods:</i></b> A total of 213 pairs of GDM mothers/fetuses and 191 pairs of normal blood glucose pregnant mothers/fetuses were ge­notyped using PCR and DNA sequencing from January 2015 to September 2016. Maternal/fetal <i>IRS1</i> gene polymorphism rs1801278 was analyzed and compared between 2 groups. <b><i>Results:</i></b> There were no significant differences in the frequency of individual mothers’ or fetuses’ <i>IRS1</i> rs1801278 polymorphisms between 2 groups; if both the mothers and fetuses carried A allele, significantly lower GDM morbidity was observed in the mothers. <b><i>Limitations:</i></b> The sample size was relatively small as a single-center study. <b><i>Conclusions:</i></b> Our study suggested that maternal/fetal rs1801278 polymorphism of <i>IRS1</i> is a modulating factor in GDM; both mothers/fetuses carrying the A allele of rs1801278 may protect the mothers against the development of GDM.


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