Jiedu Tongluo Tiaogan Prescription Protects Pancreatic β Cell by Targeting NLRP3 Inflammasome via TGR5/cAMP Signaling Pathway / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo investigate the intervention effect of Jiedu Tongluo Tiaogan prescription （JTTP） in protecting pancreatic β cells by targeting the bile acid Takeda G protein-coupled receptor 5 （TGR5）/cyclic adenosine monophosphate （cAMP） signaling pathway against NOD-like receptor protein 3 （NLRP3） inflammasome. MethodThirty-two male SPF-grade db/db mice were randomly divided into the model group， low-dose JTTP group （3.6 g·kg-1）， high-dose JTTP group （7.2 g·kg-1）， and metformin group （0.2 g·kg-1）. Eight db/m mice were assigned to the blank control group. The mice were treated with drugs for 8 weeks， and fasting blood glucose （FBG） was measured every 2 weeks. Oral glucose tolerance tests （OGTT） were conducted after the last administration. Enzyme-linked immunosorbent assay （ELISA） was performed to detect fasting insulin （FINS）， and the homeostasis model assessment of β-cell function （HOMA-β）， interleukin-6 （IL-6）， tumor necrosis factor-α （TNF-α）， and IL-1β levels were calculated. Hematoxylin-eosin （HE） staining was used to observe pathological changes in mouse pancreatic tissue. Immunofluorescence was performed to detect insulin expression in mouse pancreatic tissue. Western blot and real-time quantitative polymerase chain reaction （Real-time PCR） were used to detect the expression of proteins and mRNAs of key targets in the TGR5/cAMP signaling pathway and NLRP3 inflammasome. ResultCompared with blank group， FBG， OGTT， FINS， IL-6， TNF-α and IL-1β in model group were significantly increased （P<0.01）. Compared with model group， after 6 weeks of drug treatment， FBG level in JTTP group and metformin group decreased significantly （P<0.01）. The results of OGTT experiment showed that compared with model group， the blood glucose levels of mice in each administration group were decreased at all time points （P<0.05， P<0.01）， and the levels of FINS， TNF-α and IL-6 in JTTP dose groups and metformin group were significantly decreased. The level of IL-1β in JTTP high-dose group and metformin group was significantly decreased （P<0.01）. Pancreatic pathology showed that the islets in the model group were irregular in shape， uneven in distribution， and showed signs of atrophy. The prognosis of JTTP was that the cell count increased and the boundary was clearer. Immunofluorescence results showed that the islet cells in the blank group were arranged in an orderly and full shape with appropriate insulin secretion， while the islet cells in model group were distorted in shape， atrophy in structure and less insulin secretion. The insulin content of mice in JTTP and metformin group was significantly increased. Compared with blank group， mRNA expressions of NLRP3， apoptosis-related spot-like protein （ASC） and Caspase-1 in pancreatic tissues of model group were significantly increased （P<0.01）. Compared with model group， JTTP high-dose group and metformin group promoted the up-regulation of TGR5 and cAMP mRNA， and down-regulated the mRNA expressions of NLRP3， ASC and Caspase-1 （P<0.05， P<0.01）. Compared with blank group， the expression of TGR5 protein in model group was significantly decreased （P<0.01）. Compared with model group， TGR5 protein in JTTP high-dose group and metformin group was significantly increased （P<0.01）.