Effect And Mechanism Of Urolithin A On Chronic Alcohol-induced Senescence Of Pancreatic β-cells In Mice

Chronic alcohol consumption is the third largest health risk factor in the world,increasing the risk of rat isletβ-cells senescence,which is closely related to the occurrence and development of the diabetes mellitus.Foodborne polyphenols have antioxidant activity,so that play a significant role in anti-aging and improving insulin resistance with few side effects.Therefore,it is of great significance to explore the role of foodborne polyphenols in improving alcohol-induced isletβ-cells senescence.Urolithin A（UA）is a major Urolithin substance that is metabolized by intestinal microorganisms after ingestion of ellagitannins and ellagic acid by mammals.UA prolonging life-span by activating mitochondrial autophagy has been demonstrated by animal experiments and clinical trials.Meanwhile,UA has potential protective effects on pancreatic injuries.However,whether UA can improve alcohol-induced pancreaticβ-cells senescence and its mechanism have not been reported.In this study,whether UA could improve alcohol-induced senescence of MIN6 cells（mice isletβ-cells）had been investigated.Then,alcoholic liquid feed was used to simulate the drinking in normal population and obese population,respectively.So,the ameliorative effects of UA on the aging ofβ-cells in mice induced by chronic alcohol consumption or chronic alcohol consumption combined with high fat diet was determined in vivo.Finally,the key targets and mechanisms of UA were studied.The positive and negative confirmatory experiments were conducted using gene overexpression and gene silencing techniques.The main results were as follows.（1）UA delays alcohol-induced MIN6 cells senescence:UA delays alcohol-induced MIN6cell senescence in a dose-dependent manner.Compared with the alcohol-induced group,after the intervention with 10μM UA,the number of senescent MIN6 cell is reduced by 53%and the number of S-phase MIN6 cell is increased by 45%.Both Ki-67 protein expression and glucose-stimulated insulin secretion（GSIS）are increased by about twice.Additionally,UA significantly restores the alcohol-induced Ca²⁺disorder in aging MIN6 cells,which is associated with cellular ATP/ADP ratio recovery and mediates GSIS.Furthermore,the alcohol-induced oxidative stress damage of MIN6 cells can be antagonized by UA.（2）UA delays chronic alcohol-induced isletβ-cells senescence in mice:UA can enter the blood circulation through the wall of the digestive tract and reach the pancreas.The UA concentration in pancreas reaches a peak of 371.14 ng/g at about 3 h.The body weight and fasting blood glucose in mice are not affected by UA and chronic alcohol consumption.The dysfunction of glucose and lipid metabolism and the impairment of liver and kidney function in chronic alcohol consumption mice are significantly restored by UA.Additionally,the number of aging pancreaticβ-cells in mice is nearly tripled by chronic alcohol consumption compared with control group.After the UA intervention,the chronic alcohol-induced decline in the total number of miceβ-cells is reversed,the aging ofβ-cells is delayed and the proliferation ability ofβ-cells is improved.Furthermore,the pancreatic inflammation and systemic inflammation are alleviated by UA through the NLRP3/IL-1βpathway.The inflammatory microenvironment of islet cells is also improved by UA.Moreover,the chronic alcohol-induced pancreatic oxidative stress damage in mice is restored by UA.Chronic alcohol consumption combined with high fat diet induces energy imbalance in mice and has more significant effects on the aging of pancreaticβ-cells.The apoptosis of pancreaticβ-cells is also induced by it.The apoptosis of mice islet cells induced by chronic alcohol consumption combined with high fat diet can be antagonized by UA.（3）UA delays alcohol-induced isletβ-cells senescence by improving endoplasmic reticulum stress:The chronic alcohol-induced isletβ-cells aging in mice can be improved by UA through regulating endoplasmic reticulum stress.Chronic alcohol consumption mainly activates ATF6 and IRE1-XBP1 pathways in agingβ-cells,while the chronic alcohol consumption combined with high fat diet also activates PERK pathway to increase the CHOP expression and induce apoptosis.Grp94 gene is significantly up-regulated in MIN6 cells exposed to alcohol,and UA antagonizes this change.The arrest of G0/G1 phase,decrease of GSIS and increase of senile cells in MIN6 cells can be directly induced by Grp94overexpression.In Grp94⁺MIN6 cells,the effects of UA on improving cell senescence decrease,while in Grp94^-MIN6 cells,alcohol has no effect on inducing cell senescence.In conclusion,this study found that the Grp94 gene expression in MIN6 cells was significantly up-regulated by alcohol.The endoplasmic reticulum stress was improved by UA targeting Grp94,thus delaying alcohol-induced aging of pancreaticβ-cells.This research intended to provide a new nutritional strategy for preventing the aging of pancreaticβ-cells and even the occurrence and development of diabetes mellitus in people who drink alcohol for a long time.We also aim at providing a theoretical basis for the development and utilization of UA and UA-rich foods.