Agriophyllum Oligosaccharides Ameliorate Diabetic Insulin Resistance Through INS-R/IRS/Glut4-Mediated Insulin Pathway in db/db Mice and MIN6 Cells

Shuyin Bao; Xiuzhi Wang; Sung Bo Cho; Yan-Ling Wu; Chengxi Wei; Shuying Han; Liming Bao; Qiong Wu; Wuliji Ao; Ji-Xing Nan

doi:10.3389/fphar.2021.656220

Agriophyllum Oligosaccharides Ameliorate Diabetic Insulin Resistance Through INS-R/IRS/Glut4-Mediated Insulin Pathway in db/db Mice and MIN6 Cells

Front Pharmacol. 2021 Aug 23:12:656220. doi: 10.3389/fphar.2021.656220. eCollection 2021.

Authors

Shuyin Bao^{1

2}, Xiuzhi Wang^{3

4}, Sung Bo Cho⁵, Yan-Ling Wu¹, Chengxi Wei², Shuying Han⁶, Liming Bao⁵, Qiong Wu⁷, Wuliji Ao^{4

5}, Ji-Xing Nan^{1

8}

Affiliations

¹ Key Laboratory for Traditional Chinese Korean Medicine of Jilin Province, College of Pharmacy, Yanbian University, Yanji, China.
² Medical College, Inner Mongolia University for Nationalities, Tongliao, China.
³ Department of Medicines and Foods, Tongliao Vocational College, Tongliao, China.
⁴ The Research Institute of Traditional Mongolian Medicine Engineering Technology, Tongliao, China.
⁵ College of Traditional Mongolian Medicine, Inner Mongolia University for Nationalities, Tongliao, China.
⁶ Basic Medical College, North China University of Science and Technology, Tangshan, China.
⁷ Department of Cardiology, Tongliao Second People's Hospital, Tongliao, China.
⁸ Clinical Research Center, Yanbian University Hospital, Yanji, China.

Abstract

We have previously reported that Agriophyllum oligosaccharides (AOS) significantly enhance glycemic control by increasing the activation of insulin receptor (INS-R), insulin receptor substrate-2 (IRS-2), phosphatidylinositol 3 kinase (PI3K), protein kinase B (AKT), peroxisome proliferator-activated receptor (PPAR)-γ, and glucose transporter 4 (Glut4) proteins in hepatic tissues. However, the effect of glucose control by AOS on the regulation of pancreatic tissues in db/db mice and MIN6 cells remains to be determined. An oral dose of AOS (380 or 750 mg/kg) was administered to type-2 diabetic db/db mice for 8 weeks to determine whether AOS regulates glucose by the INS-R/IRS/Glut4-mediated insulin pathway. Meanwhile, the effects of AOS on glucose uptake and its related signaling pathway in MIN6 cells were also investigated. The results showed that the random blood glucose (RBG) level in the AOS-treated group was lower than that in the control group. AOS reduced the levels of glycated hemoglobin (HbA1c) and free fatty acid (FFA) and significantly improved the pathological changes in the pancreatic tissues in db/db mice. Moreover, immunohistochemical analysis revealed that the expression of INS-R, IRS-1, IRS-2, and Glut4 was increased in the AOS-treated group than in the model group. Further, in vitro experiments using MIN6 cells showed that AOS regulated INS-R, IRS-1, IRS-2, and Glut4 protein and mRNA levels and attenuated insulin resistance and cell apoptosis. The results of both in vitro and in vivo experiments were comparable. Ultra-performance liquid chromatography coupled with time-of-flight mass spectrometric analysis of AOS with precolumn derivatization with 3-amino-9-ethylcarbazole (AEC) tentatively identified five types of sugars: glucose, lactose, rutinose, glucuronic acid, and maltotriose. Our present study clearly showed that AOS is efficacious in preventing hyperglycemia, possibly by increasing insulin sensitivity and improving IR by regulating the INS-R/IRS/Glut4 insulin signal pathway. Therefore, AOS may be considered as a potential drug for diabetes treatment.

Keywords: Agriophyllum oligosaccharides (AOS); INS-R/IRS/Glut4 insulin pathway; T2DM; db/db mice; insulin resistance.