Phosphoproteome reveals molecular mechanisms of aberrant rhythm in neurotransmitter-mediated islet hormone secretion in diabetic mice

Berberine enhances the function of db/db mice islet β cell through GLP-1/GLP-1R/PKA signaling pathway in intestinal L cell and islet α cell

Background: The evidence on berberine stimulating the secretion of GLP-1 in intestinal L cell has been studied. However, few research has explored its role on generating GLP-1 of islet α cell. Our experiment aims to clarify the mechanism of berberine promoting the secretion of GLP-1 in intestinal L cell and islet α cell, activating GLP-1R and its downstream molecules through endocrine and paracrine ways, thus improving the function of islet β cell and treating T2DM. Methods: After confirming that berberine can lower blood glucose and improve insulin resistance in db/db mice, the identity maintenance, proliferation and apoptosis of islet cells were detected by immunohistochemistry and immunofluorescence. Then, the activation of berberine on GLP-1/GLP-1R/PKA signaling pathway was evaluated by Elisa, Western blot and PCR. Finally, this mechanism was verified by in vitro experiments on Min6 cells, STC-1 cells and aTC1/6 cells. Results: Berberine ameliorates glucose metabolism in db/db mice. Additionally, it also increases the number and enhances the function of islet β cell. This process is closely related to improve the secretion of intestinal L cell and islet α cell, activate GLP-1R/PKA signaling pathway through autocrine and paracrine, and increase the expression of its related molecule such as GLP-1, GLP-1R, PC1/3, PC2, PKA, Pdx1. In vitro, the phenomenon that berberine enhanced the GLP-1/GLP-1R/PKA signal pathway had also been observed, which confirmed the results of animal experiments. Conclusion: Berberine can maintain the identity and normal function of islet β cell, and its mechanism is related to the activation of GLP-1/GLP-1R/PKA signal pathway in intestinal L cell and islet α cell.

Acetylcholine promotes chronic stress-induced lung adenocarcinoma progression via α5-nAChR/FHIT pathway

Chronic stress significantly elevates the expression levels of various neurotransmitters in the tumour microenvironment, thereby promoting the cell growth and metastasis of lung adenocarcinoma (LUAD). However, the role of chronic stress in the progression of LUAD remains unclear. In this study, we found that chronic restraint stress increases the levels of the neurotransmitter acetylcholine (ACh), and the α5-nicotinic acetylcholine receptor (α5-nAChR) and decreased fragile histidine triad (FHIT) expression in vivo. Crucially, the increased ACh levels promoted LUAD cell migration and invasion via modulation of the α5-nAChR/DNA methyltransferase 1 (DNMT1)/FHIT axis. In a chronic unpredictable stress (CUMS) mouse model, chronic stress promotes tumour development, accompanied by changes in α5-nAChR, DNMT1, FHIT, and vimentin. Together, these findings reveal a novel chronic stress-mediated LUAD signalling pathway: chronic stress enforces lung adenocarcinoma cell invasion and migration via the ACh/α5-nAChR/FHIT axis, which could be a potential therapeutic target for chronic stress-related LUAD.

Imaging changes in the polarity of lipid droplets during NAFLD-Induced ferroptosis via a red-emitting fluorescent probe with a large Stokes shift

Cell death resulting from ferroptosis is a consequence of the accumulation of lipid peroxides that are produced when lipids and reactive oxygen species (ROS) interact. This process is dependent on iron and alters the structure and polarity of lipid droplets (LDs). Unlike reactive fluorescent probes, environment-sensitive fluorescent probes can accurately monitor metabolic activities by sensing the intracellular environment of living organisms. To this end, we developed a polarity-sensitive fluorescent probe LIP-Ser that anchors to LDs and can be used to monitor changes in the polarity of LDs during ferroptosis by in situ imaging. LIP-Ser has a red-emitting (λ_em = 634 nm) and a large Stokes shift (Δλ = 161 nm in 1,4-dioxane), which avoids it from autofluorescence interference and crosstalk between excitation and emission spectra, thereby preventing low signal-to-noise ratio and severe fluorescence self-quenching during imaging. Additionally, LIP-Ser is used in this study to demonstrate that non-alcoholic fatty liver disease (NAFLD) promotes ferroptosis at the cellular and in vivo levels, and that inhibition of cellular ferroptosis effectively reduces the damage caused by NAFLD to cells and mouse liver tissue.

Therapeutic potential of vasoactive intestinal peptide and its receptor VPAC2 in type 2 diabetes

Owing to the increasing prevalence of type 2 diabetes, the development of novel hypoglycemic drugs has become a research hotspot, with the ultimate goal of developing therapeutic drugs that stimulate glucose-induced insulin secretion without inducing hypoglycemia. Vasoactive intestinal peptide (VIP), a 28-amino-acid peptide, can stimulate glucose-dependent insulin secretion, particularly by binding to VPAC2 receptors. VIP also promotes islet β-cell proliferation through the forkhead box M1 pathway, but the specific molecular mechanism remains to be studied. The clinical application of VIP is limited because of its short half-life and wide distribution in the human body. Based on the binding properties of VIP and VPAC2 receptors, VPAC2-selective agonists have been developed to serve as novel hypoglycemic drugs. This review summarizes the physiological significance of VIP in glucose homeostasis and the potential therapeutic value of VPAC2-selective agonists in type 2 diabetes.