A polysaccharide from Grifola frondosa relieves insulin resistance of HepG2 cell by Akt-GSK-3 pathway
Authors: Xiaohong Cao
Yuanyuan Zhang
Chunling Wang
Xiaolei Ma
Yuanyuan Chen
Lihua Hou
Fuchuan Zhou
Journal: Glycoconjugate journal (2014)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: Grifola frondosa; polysaccharide; hyperglycemic activity; insulin resistance; HepG2 cell
Affiliations: Key Laboratory of Food Nutrition and Safety, Ministry of Education, College of Food Engineering and Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, People's Republic of China.

Abstract:  Grifola frondosa is an important fungal research resource. However, there was little report about hyperglycemic activity of Grifola frondosa polysaccharide on insulin resistance in vitro. In this study, the hypoglycemic activity of a polysaccharide obtained from Grifola frondosa (GFP) on HepG2 cell and hpyerglycemic mechanism were investigated. The purity of the isolated polysaccharides was examined by HPLC. In this research, it was found that GFP enhanced the absorption of glucose of HepG2 cells in a dose dependent manner at 24 h of 30 ugmL⁻¹. GC-MS and FT-IR spectroscopy analysis results showed that glucose and galactose were the dominant monosaccharides in GFP and the major component of GFP was β-pyranoside. Western-blotting results showed that the HepG2 cell model treated with GFP activated the insulin receptor protein (IRS) in the cell membrane and increased phosphorylated-AktSer473 expression, which had an inhibition of glycogen synthase kinase (GSK-3). The down-regulation of GSK-3 stimulated synthesis of intracellular glycogen. The results above suggested that the GFP increased the metabolism of glucose and stimulated synthesis of intracellular glycogen through the Akt/GSK-3 pathway. 

Retracted: No

PubPeer comments:
 Figure 1. * Red boxes: An area in panel b (aligned electrospun PVDF) appears to also be visible - not once but twice - in panel c (aligned electrospun PVDF CNT). * Blue boxes: Another area in panel b is visible - just once - in panel c. * Yellow boxes (updated after being notified by a Twitter user): Another area from panel b appears to be visible in panel c. ![file] , 
 1. It was a mistake and unintentionally taken by accident. It is an image generated when [X] learn and practice image processing software (phtotshop) between 3rd u2013 30th May 2017. She saved the image as PVDF-CNT which she thought that the image for PVDF-CNT shall look like that. Unfortunately, she saved this practice image free-minded in the same folder which all real PVDF-CNT images (taken on 30th May 2017) also there. It was unintentionally taken by accident. As the meeting file and email I provided to the journal editor on 5th Dec., there is no reason for us to fake photos because we do have SEM images. 2. The use of high-speed rolls to produce highly aligned fiber membranes is well known and widely used in opening literatures. An aligned fiber image should be obtained as expected. Therefore, I did not pay too much attention to check the detail of the SEM images in Fig.1. All three SEM images (Figure 1(a)(b)(c)) are only used to show the appearance of the fiber membrane in this study. Please also note that these images will not affect the significances of this article (piezo performance output). That is, this SEM image is not the focus of this article. 3. As shown in the attached file to the Journal editor: colleen20170503Meeting.pptx, the image of fig.1 (b) was first reported in our lab meeting on 3rd May 2017. Follow by an E-mail sent on 30th May 2017, SEM images took on PVDF CNT fiber membranes were obtained. Due to the regulation of the SEM Lab, all SEM images shall be sent out for saving via email (To avoid computer virus infection). Thus, [X] sent the images to [Y] (This email will be forwarded to the editor also). All those information are trying to support that we do have the SEM images one year before the paper submitted date (28 May 2018). Thus, there is no reason for us to fake photos. However, I donu2019t know and understand why Colleen made and provided the wrong image (Fig.1 (C) in original paper). As I know, it is an image generated by practice image processing software (phtotshop) and stored by mistake. 4. A corrected Figure 1 for substituting as shown below which we have changed a new image (Fig 1(C)). 5. All detail information already provided to the journal editor. I apology for all the problems caused and hope you can accept my correction. , 
 Dear Dr. Wu, Thank you for your explanation. I am not the editor, but if I was, I would not accept a new figure for a correction. Your reply contains several arguments that authors frequently use here on PubPeer but do not hold a lot of ground. * You blame one of the junior scientists, even give us her name. It sounds like you might be throwing someone under the bus. All authors are responsible for checking the contents of the paper. In particular, the senior corresponding author is responsible for teaching proper housekeeping , that is, to make sure that images and other data are named and stored properly. * Your group published a photoshopped image, and that is just not ok. The story about practicing photoshopping sounds strange; image processing in scientific figures is best be done in Adobe Illustrator (vector based), not Photoshop (pixel based), as to preserve the integrity of the whole image. I find it very concerning that PIs teach their staff how to use Photoshop. And if the story is indeed true, that means that one of the authors has been extremely sloppy about careful data storage, which casts serious doubt about the rest of the experiments reported in this paper as well. * You also use the argument that other people have produced the same fiber, but that does not diminish my concerns about this paper. Your paper and the image of concern is supposed to tell the reader that *your* lab produced this fiber. * You claim the SEM image is not the focus of the paper; yet it was featured in the graphical abstract. See image below. * I do not understand the argument that there is no reason for you to fake photos. Maybe you can explain? ![file] , 
 There is actually more (except from the low quality of science and discussion) The FTIR data for the PVDF CNT looks like a smooth version of the PVDF data - I don t think that CNTs have such a smoothing effect FTIR. ![file] The electromechnical measurment data of figure 4b,c which is again PVDF and PVDF CNT seems very similar all the way to the peak patterns. I attach the figures and some extracts from (b) and (c) shown below - no stretching or anything just copy-paste ![file] ,