(-)-Epigallocatechin 3-gallate protects pancreatic ß-cell against excessive autophagy-induced injury through promoting FTO degradation.

Excessive macroautophagy/autophagy leads to pancreatic ß-cell failure that contributes to the development of diabetes. Our previous study proved that the occurrence of deleterious hyperactive autophagy attributes to glucolipotoxicity-induced NR3C1 activation. Here, we explored the potential protective effects of (-)-epigallocatechin 3-gallate (EGCG) on ß-cell-specific NR3C1 overexpression mice in vivo and NR3C1-enhanced ß cells in vitro. We showed that EGCG protects pancreatic ß cells against NR3C1 enhancement-induced failure through inhibiting excessive autophagy. RNA demethylase FTO (FTO alpha-ketoglutarate dependent dioxygenase) caused diminished m6A modifications on mRNAs of three pro-oxidant genes (Tlr4, Rela, Src) and, hence, oxidative stress occurs; by contrast, EGCG promotes FTO degradation by the ubiquitin-proteasome system in NR3C1-enhanced ß cells, which alleviates oxidative stress, and thereby prevents excessive autophagy. Moreover, FTO overexpression abolishes the beneficial effects of EGCG on ß cells against NR3C1 enhancement-induced damage. Collectively, our results demonstrate that EGCG protects pancreatic ß cells against NR3C1 enhancement-induced excessive autophagy through suppressing FTO-stimulated oxidative stress, which provides novel insights into the mechanisms for the anti-diabetic effect of EGCG.Abbreviation 3-MA: 3-methyladenine; AAV: adeno-associated virus; Ad: adenovirus; ALD: aldosterone; AUC: area under curve; ßNR3C1 mice: pancreatic ß-cell-specific NR3C1 overexpression mice; Ctrl: control; CHX: cycloheximide; DEX: dexamethasone; DHE: dihydroethidium; EGCG: (-)-epigallocatechin 3-gallate; FTO: FTO alpha-ketoglutarate dependent dioxygenase; GSIS: glucose-stimulated insulin secretion; HFD: high-fat diet; HG: high glucose; i.p.: intraperitoneal; IOD: immunofluorescence optical density; KSIS: potassium-stimulated insulin secretion; m6A: N6-methyladenosine; MeRIP-seq: methylated RNA immunoprecipitation sequencing; NO: nitric oxide; NR3C1/GR: nuclear receptor subfamily 3, group C, member 1; NR3C1-Enhc.: NR3C1-enhancement; NAC: N-acetylcysteine; NC: negative control; PBS: phosphate-buffered saline; PI: propidium iodide; OCR: oxygen consumption rate; Palm.: palmitate; RELA: v-rel reticuloendotheliosis viral oncogene homolog A (avian); RNA-seq: RNA sequencing; O2.-: superoxide anion; SRC: Rous sarcoma oncogene; ROS: reactive oxygen species; T2D: type 2 diabetes; TEM: transmission electron microscopy; TLR4: toll-like receptor 4; TUNEL: terminal dUTP nick-end labeling; UTR: untranslated region; WT: wild-type.

A comparative study of the ameliorative effects of hyaluronic acid oligosaccharides and hyaluronic acid on DSS-induced colitis in mice and research on relevant mechanisms.

As a dietary supplement, hyaluronic acid (HA) has exhibited appreciable immunomodulatory activity and an ameliorative effect on rodent colitis. However, its high viscosity is not only refractory to absorb through the gut, but also causes flatulence. In contrast to HA, hyaluronic acid oligosaccharides (o-HAs) can overcome the above-mentioned constraints, but their treatment effect still remains ill-defined contemporarily. Herein, the current study intends to compare the modulatory effects of HA and o-HA on colitis and assess the underlying molecular mechanism. We first showed that o-HA had a better preventive effect than HA in alleviating colitis symptoms, as evidenced by lower body weight loss, lower disease activity index scores, a lower inflammatory response (TNF-α, IL-6, IL-1ß, p-NF-κB), and more intact colon epithelial integrity in vivo. The best efficiency was observed in the o-HA treated group with a dosage of 30 mg kg-1. In an in vitro barrier function assay, o-HA exerted a better protective effect on the transepithelial electrical resistance (TEER), FITC permeability, and wound healing and modulated the expression of tight junction (TJ) proteins (ZO-1, occludin) in lipopolysaccharide (LPS)-stimulated Caco-2 cells. In summary, both HA and o-HA showed the potential to reduce inflammation and ameliorate intestinal damage in DSS-induced colitis and LPS-induced inflammation, but o-HA had improved outcomes. The results also provided a glimpse of the latent mechanism by which HA and o-HA enhanced intestinal barrier function via MLCK/p-MLC signaling pathway suppression.