Circulating Exosome-like Vesicles From Humans With Simple Obesity Inhibit Islet Β-cell Proliferation And Carry Altered Protein Cargos

Backgroud: As a worldwide epidemic,obesity increases the risk of some chronic diseases,such as atherosclerosis,cardiovascular problems,non-alcoholic fatty liver,and Type 2 diabetes mellitus(T2DM).The progressive decline of the β-cell mass is one primary pathogenesis of T2 DM.Thus,preserving β-cell mass and its insulin secretory function is fundamental in the prevention and therapeutic management of T2 DM.Despite β-cell mass expands adaptively to obesity,a majority of obese people develop eventually into T2 DM.This indicates that there might be potential negative regulatory mechanisms that limit the adaptive expansion of β-cell mass in response to obesity.Exosome-like vesicles(ELVs)are the smallest class of extracellular vesicles,and they range in diameter from 30 to 100 nm.ELVs contain bioactive proteins,lipids,and a broad range of nucleic acids,which can be uptake by the recipient cells and delivery the cargos into the recipient cells.Upon internalization,the recipient cells respond to the transferred ELVs contents by modulating its gene expression.Thus,ELVs can function as essential messengers of biological signal transmission between cells.Pathological conditions associated with T2DM(such as high blood glucose,inflammation,hypoxia,and fatty acids)can alter the quantity and components of ELVs.The modified cargos of ELVs can be either enter the blood circulation or be taken up by neighboring cells or macrophages,which can lead to impaired β-cell mass and function and insulin signaling.Yet,the involvement of circulating ELVs in β-cell function has been scarcely reported.Objective:To investigate whether the circulating ELVs from humans with simple obesity could be a mediator for adaptive β-cell mass expansion.Methods: Between June 2017 and July 2019,102 healthy volunteers with normal weight and 81 subjects with simple obesity were recruited.ELVs were isolated by ultra-centrifugation.The proliferation of β-cells were measured by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)and 5-ethynl-2’-deoxyuridine(Ed U)in Min6 cell line or primary islets.The apoptosis of β-cells were measured by Flow Cytometer.Insulin secretion was measured by glucose-stimulated insulin secretion.m RNA expression of genes was quantified by RNA-sequencing or RT-q PCR.Protein components in ELVs were identified and quantified by Quantitative Proteomic Analysis and further verified by western blot and ELISA.Results: Circulating ELVs from subjects with simple obesity inhibitedβ-cell proliferation without affecting its apoptosis,inflammation,and secretion.The protein levels of Rictor and Omentin-1 were decreased in circulating ELVs from subjects with simple obesity and associated with the enlarged visceral fat mass,hypertriglyceridemia,and insulin resistance.Adipocytes were a source for the secretion of exosomal Omentin-1.Conclusions: The pathologic condition in obesity could modify the circulating ELVs protein cargo,and these altered ELVs of obese people can participate in regulating the proliferation of β-cells,which is actually a potential mechanism that restricts the compensatory proliferation of β-cells when obese.