Identification and characterization of microvesicles secreted by 3T3-L1 adipocytes: redox- and hormone-dependent induction of milk fat globule-epidermal growth factor 8-associated microvesicles

The association between the size of adipocyte-derived extracellular vesicles and fasting serum triglyceride-glucose index as proxy measures of adipose tissue insulin resistance in a rat model of early-stage obesity

Introduction

Obesity is a complex disease that predisposes individuals to cardiometabolic alterations. It leads to adipose tissue (AT) dysfunction, which triggers insulin resistance (IR). This suggests that people with obesity develop local IR first and systemic IR later. AT secretes extracellular vesicles, which may be physiopathologically associated with the development of IR. Our aim was to evaluate the effect of a high-fat diet on different parameters of adiposity in a rat model of early-stage obesity and to determine if these parameters are associated with markers of systemic IR. In addition, we sought to explore the relationship between fasting blood measures of IR (Triglycerides/High Density Lipoprotein-cholesterol [TAG/HDL-c] and Triglycerides-Glucose Index [TyG Index]) with the size of adipocyte-derived extracellular vesicles (adEV).

Methods

We used a model of diet-induced obesity for ten weeks in Wistar rats exposed to a high-fat diet. Final weight gain was analyzed by Dual X-ray absorptiometry. Visceral obesity was measured as epididymal AT weight. IR was evaluated with fasting TyG Index & TAG/HDL-c, and adEV were isolated from mature adipocytes on ceiling culture.

Results

In the high-fat diet group, glucose and triglyceride blood concentrations were higher in comparison to the control group (Log2FC, 0.5 and 1.5 times higher, respectively). The values for TyG Index and adEV size were different between the control animals and the high-fat diet group. Multiple linear regression analyses showed that adEV size can be significantly associated with the TyG Index value, when controlling for epididymal AT weight.

Conclusion

Our results show that lipid and glucose metabolism, as well as the size and zeta potential of adEV are already altered in early-stage obesity and that adEV size can be significantly associated with liver and systemic IR, estimated by TyG Index.

The Role of Adipose Tissue-derived Exosomes in Chronic Metabolic Disorders

Excessive fat deposition in obese subjects promotes the occurrence of metabolic diseases, such as type 2 diabetes mellitus (T2DM), cardiovascular diseases, and non-alcoholic fatty liver disease (NAFLD). Adipose tissue is not only the main form of energy storage but also an endocrine organ that not only secretes adipocytokines but also releases many extracellular vesicles (EVs) that play a role in the regulation of whole-body metabolism. Exosomes are a subtype of EVs, and accumulating evidence indicates that adipose tissue exosomes (AT Exos) mediate crosstalk between adipose tissue and multiple organs by being transferred to targeted cells or tissues through paracrine or endocrine mechanisms. However, the roles of AT Exos in crosstalk with metabolic organs remain to be fully elucidated. In this review, we summarize the latest research progress on the role of AT Exos in the regulation of metabolic disorders. Moreover, we discuss the potential role of AT Exos as biomarkers in metabolic diseases and their clinical application.

An omics-based machine learning approach to predict diabetes progression: a RHAPSODY study

AIMS/HYPOTHESIS

People with type 2 diabetes are heterogeneous in their disease trajectory, with some progressing more quickly to insulin initiation than others. Although classical biomarkers such as age, HbA1c and diabetes duration are associated with glycaemic progression, it is unclear how well such variables predict insulin initiation or requirement and whether newly identified markers have added predictive value.

METHODS

In two prospective cohort studies as part of IMI-RHAPSODY, we investigated whether clinical variables and three types of molecular markers (metabolites, lipids, proteins) can predict time to insulin requirement using different machine learning approaches (lasso, ridge, GRridge, random forest). Clinical variables included age, sex, HbA1c, HDL-cholesterol and C-peptide. Models were run with unpenalised clinical variables (i.e. always included in the model without weights) or penalised clinical variables, or without clinical variables. Model development was performed in one cohort and the model was applied in a second cohort. Model performance was evaluated using Harrel's C statistic.

RESULTS

Of the 585 individuals from the Hoorn Diabetes Care System (DCS) cohort, 69 required insulin during follow-up (1.0-11.4 years); of the 571 individuals in the Genetics of Diabetes Audit and Research in Tayside Scotland (GoDARTS) cohort, 175 required insulin during follow-up (0.3-11.8 years). Overall, the clinical variables and proteins were selected in the different models most often, followed by the metabolites. The most frequently selected clinical variables were HbA1c (18 of the 36 models, 50%), age (15 models, 41.2%) and C-peptide (15 models, 41.2%). Base models (age, sex, BMI, HbA1c) including only clinical variables performed moderately in both the DCS discovery cohort (C statistic 0.71 [95% CI 0.64, 0.79]) and the GoDARTS replication cohort (C 0.71 [95% CI 0.69, 0.75]). A more extensive model including HDL-cholesterol and C-peptide performed better in both cohorts (DCS, C 0.74 [95% CI 0.67, 0.81]; GoDARTS, C 0.73 [95% CI 0.69, 0.77]). Two proteins, lactadherin and proto-oncogene tyrosine-protein kinase receptor, were most consistently selected and slightly improved model performance.

CONCLUSIONS/INTERPRETATION

Using machine learning approaches, we show that insulin requirement risk can be modestly well predicted by predominantly clinical variables. Inclusion of molecular markers improves the prognostic performance beyond that of clinical variables by up to 5%. Such prognostic models could be useful for identifying people with diabetes at high risk of progressing quickly to treatment intensification.

DATA AVAILABILITY

Summary statistics of lipidomic, proteomic and metabolomic data are available from a Shiny dashboard at https://rhapdata-app.vital-it.ch .

Lactadherin immunoblockade in small extracellular vesicles inhibits sEV-mediated increase of pro-metastatic capacities

BACKGROUND

Tumor-derived small extracellular vesicles (sEVs) can promote tumorigenic and metastatic capacities in less aggressive recipient cells mainly through the biomolecules in their cargo. However, despite recent advances, the specific molecules orchestrating these changes are not completely defined. Lactadherin is a secreted glycoprotein typically found in the milk fat globule membrane. Its overexpression has been associated with increased tumorigenesis and metastasis in breast cancer (BC) and other tumors. However, neither its presence in sEVs secreted by BC cells, nor its role in sEV-mediated intercellular communication have been described. The present study focused on the role of lactadherin-containing sEVs from metastatic MDA-MB-231 triple-negative BC (TNBC) cells (sEV-MDA231) in the promotion of pro-metastatic capacities in non-tumorigenic and non-metastatic recipient cells in vitro, as well as their pro-metastatic role in a murine model of peritoneal carcinomatosis.

RESULTS

We show that lactadherin is present in sEVs secreted by BC cells and it is higher in sEV-MDA231 compared with the other BC cell-secreted sEVs measured through ELISA. Incubation of non-metastatic recipient cells with sEV-MDA231 increases their migration and, to some extent, their tumoroid formation capacity but not their anchorage-independent growth. Remarkably, lactadherin blockade in sEV-MDA231 results in a significant decrease of those sEV-mediated changes in vitro. Similarly, intraperitoneally treatment of mice with MDA-MB-231 BC cells and sEV-MDA231 greatly increase the formation of malignant ascites and tumor micronodules, effects that were significantly inhibited when lactadherin was previously blocked in those sEV-MDA231.

CONCLUSIONS

As to our knowledge, our study provides the first evidence on the role of lactadherin in metastatic BC cell-secreted sEVs as promoter of: (i) metastatic capacities in less aggressive recipient cells, and ii) the formation of malignant ascites and metastatic tumor nodules. These results increase our understanding on the role of lactadherin in sEVs as promoter of metastatic capacities which can be used as a therapeutic option for BC and other malignancies.

A nanoemulsion targeting adipose hypertrophy and hyperplasia shows anti-obesity efficiency in female mice

Obesity often leads to severe medical complications. However, existing FDA-approved medications to combat obesity have limited effectiveness in reducing adiposity and often cause side effects. These medications primarily act on the central nervous system or disrupt fat absorption through the gastrointestinal tract. Adipose tissue enlargement involves adipose hyperplasia and hypertrophy, both of which correlate with increased reactive oxygen species (ROS) and hyperactivated X-box binding protein 1 (XBP1) in (pre)adipocytes. In this study, we demonstrate that KT-NE, a nanoemulsion loaded with the XBP1 inhibitor KIRA6 and α-Tocopherol, simultaneously alleviates aberrant endoplasmic reticulum stress and oxidative stress in (pre)adipocytes. As a result, KT-NE significantly inhibits abnormal adipogenic differentiation, reduces lipid droplet accumulation, restricts lipid droplet transfer, impedes obesity progression, and lowers the risk of obesity-associated non-alcoholic fatty liver disease in female mice with obesity. Furthermore, diverse administration routes of KT-NE impact its in vivo biodistribution and contribute to localized and/or systemic anti-obesity effectiveness.

(Patho)Physiology of Glycosylphosphatidylinositol-Anchored Proteins I: Localization at Plasma Membranes and Extracellular Compartments

Glycosylphosphatidylinositol (GPI)-anchored proteins (APs) are anchored at the outer leaflet of plasma membranes (PMs) of all eukaryotic organisms studied so far by covalent linkage to a highly conserved glycolipid rather than a transmembrane domain. Since their first description, experimental data have been accumulating for the capability of GPI-APs to be released from PMs into the surrounding milieu. It became evident that this release results in distinct arrangements of GPI-APs which are compatible with the aqueous milieu upon loss of their GPI anchor by (proteolytic or lipolytic) cleavage or in the course of shielding of the full-length GPI anchor by incorporation into extracellular vesicles, lipoprotein-like particles and (lyso)phospholipid- and cholesterol-harboring micelle-like complexes or by association with GPI-binding proteins or/and other full-length GPI-APs. In mammalian organisms, the (patho)physiological roles of the released GPI-APs in the extracellular environment, such as blood and tissue cells, depend on the molecular mechanisms of their release as well as the cell types and tissues involved, and are controlled by their removal from circulation. This is accomplished by endocytic uptake by liver cells and/or degradation by GPI-specific phospholipase D in order to bypass potential unwanted effects of the released GPI-APs or their transfer from the releasing donor to acceptor cells (which will be reviewed in a forthcoming manuscript).

Status quo of Extracellular Vesicle isolation and detection methods for clinical utility

Extracellular vesicles (EVs) are nano-sized particles that hold tremendous potential in the clinical space, as their biomolecular profiles hold a key to non-invasive liquid biopsy for cancer diagnosis and prognosis. EVs are present in most bodily fluids, hence are easily obtainable from patients, advantageous to that of traditional, invasive tissue biopsies and imaging techniques. However, there are certain constraints that hinder clinical use of EVs. The translation of EV biomarkers from "bench-to-bedside" is encumbered by the methods of EV isolation and subsequent biomarker detection currently implemented in laboratories. Although current isolation and detection methods are effective, they lack practicality, with their requirement for high bodily fluid volumes, low equipment availability, slow turnaround times and high costs. The high demand for techniques that overcome these limitations has resulted in significant advancements in nanotechnological devices. These devices are designed to integrate EV isolation and biomarker detection into a one-step method of direct EV detection from bodily fluids. This provides promise for the acceleration of EVs into current clinical standards. This review highlights the importance of EVs as cancer biomarkers, the methodological obstacles currently faced in clinical studies and how novel nanodevices could advance clinical translation.

Extracellular Vesicles from Adipose Tissue Could Promote Metabolic Adaptation through PI3K/Akt/mTOR

Extracellular vesicles (EVs) are nanoparticles secreted by cells under physiological and pathological conditions, such as metabolic diseases. In this context, EVs are considered potential key mediators in the physiopathology of obesity. It has been reported that EVs derived from adipose tissue (ADEVs) contribute to the development of a local inflammatory response that leads to adipose tissue dysfunction. In addition, it has been proposed that EVs are associated with the onset and progression of several obesity-related metabolic diseases such as insulin resistance. In particular, characterizing the molecular fingerprint of obesity-related ADEVs can provide a bigger picture that better reflects metabolic adaptation though PI3K/Akt/mTOR. Hence, in this review we describe the possible crosstalk communication of ADEVs with metabolically active organs and the intracellular response in the insulin signaling pathway.

Mesenchymal Stem Cell-Derived Exosomes: Applications in Regenerative Medicine

Exosomes are a type of extracellular vesicles, produced within multivesicular bodies, that are then released into the extracellular space through a merging of the multivesicular body with the plasma membrane. These vesicles are secreted by almost all cell types to aid in a vast array of cellular functions, including intercellular communication, cell differentiation and proliferation, angiogenesis, stress response, and immune signaling. This ability to contribute to several distinct processes is due to the complexity of exosomes, as they carry a multitude of signaling moieties, including proteins, lipids, cell surface receptors, enzymes, cytokines, transcription factors, and nucleic acids. The favorable biological properties of exosomes including biocompatibility, stability, low toxicity, and proficient exchange of molecular cargos make exosomes prime candidates for tissue engineering and regenerative medicine. Exploring the functions and molecular payloads of exosomes can facilitate tissue regeneration therapies and provide mechanistic insight into paracrine modulation of cellular activities. In this review, we summarize the current knowledge of exosome biogenesis, composition, and isolation methods. We also discuss emerging healing properties of exosomes and exosomal cargos, such as microRNAs, in brain injuries, cardiovascular disease, and COVID-19 amongst others. Overall, this review highlights the burgeoning roles and potential applications of exosomes in regenerative medicine.

Adipose Extracellular Vesicles in Intercellular and Inter-Organ Crosstalk in Metabolic Health and Diseases

Adipose tissue (AT) is a highly heterogeneous and dynamic organ that plays important roles in regulating energy metabolism and insulin sensitivity. In addition to its classical roles in nutrient sensing and energy storage/dissipation, AT secretes a large number of bioactive molecules (termed adipokines) participating in immune responses and metabolic regulation through their paracrine and/or endocrine actions. Adipose-derived extracellular vesicles (ADEVs), including exosomes, microvesicles (MVs), and apoptotic bodies, have recently emerged as a novel class of signal messengers, mediating intercellular communications and inter-organ crosstalk. In AT, ADEVs derived from adipocytes, immune cells, mesenchymal stem cells, endothelial cells are actively involved in modulation of immune microenvironment, adipogenesis, browing of white adipose tissue, adipokine release and tissue remodeling. Furthermore, ADEVs exert their metabolic actions in distal organs (such as liver, skeletal muscle, pancreas and brain) by sending genetic information (mainly in the form of microRNAs) to their target cells for regulation of gene expression. Here, we provide an updated summary on the nature and composition of ADEVs, and their pathophysiological functions in regulating immune responses, whole-body insulin sensitivity and metabolism. Furthermore, we highlight the latest clinical evidence supporting aberrant production and/or function of ADEVs as a contributor to obesity-related chronic inflammation and metabolic complications and discuss the opportunities and challenges in developing novel therapies by targeting ADEVs.

Adipocyte-derived extracellular vesicles modulate appetite and weight through mTOR signalling in the hypothalamus

AIM

Type 2 diabetes and obesity are diseases related to surplus energy in the body. Abnormal interaction between the hypothalamus and adipose tissues is a key trigger of energy metabolism dysfunction. Extracellular vesicles (EVs) regulate intercellular communication by transporting intracellular cargo to recipient cells thereby altering the function of recipient cells. This study aimed to evaluate whether adipocyte-derived EVs can act on hypothalamic neurons to modulate energy intake and to identify the EV-associated non-coding RNAs.

METHODS

Confocal imaging was used to trace the uptake of labelled adipocyte-derived exosomes by hypothalamic anorexigenic POMC neurons. The effects of adipocyte-derived EVs on the mammalian target of rapamycin (mTOR) signalling pathway in POMC neurons were evaluated based on mRNA and protein expression in vitro using quantitative real-time PCR and western blotting. In addition, adipocyte-derived EVs were injected into recipient mice, and changes in mice body weight and daily food intake were monitored. The biological effects of the EV-associated MALAT1 on POMC neurons were explored.

RESULTS

Adipocyte-derived EVs were successfully transferred into POMC neurons in vitro. Results showed that adipocytes of obese mice secreted MALAT1-containing EVs, which increased appetite and weight when administered to lean mice. Conversely, adipocyte-derived EVs from lean mice decreased food intake and weight when administered to obese mice.

CONCLUSION

Adipocyte-derived EVs play important roles in mediating the interaction between adipocytes and hypothalamic neurons. Adipocyte-derived EVs can regulate POMC expression through the hypothalamic mTOR signalling in vivo and in vitro, thereby affecting body energy intake.

[Research progress in adipose tissue promoted wound healing]

OBJECTIVE

To summarize recent progress in adipose tissue acting as a more efficient and ideal therapy to facilitate wound repair and evaluate the therapeutic values of adipose tissue.

METHODS

The related literature about adipose tissue for wound healing in recent years was reviewed and analyzed.

RESULTS

Enormous studies focus on the capacity of adipose tissue to accelerate wound healing including cellular components, extracellular matrix, and paracrine signaling have been investigated.

CONCLUSION

Adipose tissue has generated great interest in recent years because of unique advantages such as abundant and accessible source, thriven potential to enhance the regeneration and repair of damaged tissue. However, there is still a need to explore the mechanism that adipose tissue regulates cellular function and tissue regeneration in order to facilitate clinical application of adipose tissue in wound healing.

Inflammatory adipocyte-derived extracellular vesicles promote leukocyte attachment to vascular endothelial cells

BACKGROUND AND AIMS

Obesity is associated with an increased risk of cardiovascular disease, but the mechanisms involved are not completely understood. In obesity, the adipocyte microenvironment is characterised by both hypoxia and inflammation. Therefore, we sought to determine whether extracellular vesicles (EVs) derived from adipocytes in this setting might be involved in mediating cardiovascular disease, specifically by promoting leukocyte attachment to vascular endothelial cells.

METHODS

Mature 3T3-L1 adipocytes were incubated for 24 h under control, TNF-α (30 ng/mL), hypoxia (1% O₂), or TNF-α+hypoxia (30 ng/mL, 1% O₂) conditions. EVs were isolated by differential ultracentrifugation and analysed by nanoparticle tracking analysis. Primary human umbilical vein endothelial cells (HUVECs) were treated with EVs for 6 h before being lysed for Western blotting to investigate changes in adhesion molecule production, or for use in leukocyte attachment assays.

RESULTS

EVs from adipocytes treated with TNF-α and TNF-α+hypoxia increased vascular cell adhesion molecule (VCAM-1) production in HUVECs compared to basal level (4.2 ± 0.6 and 3.8 ± 0.3-fold increase, respectively (p < 0.05)), an effect that was inhibited by an anti-TNF-α neutralising antibody. Production of other adhesion molecules (E-selectin, P-selectin, platelet endothelial cell adhesion molecule and VE-Cadherin) was unchanged. Pre-incubating HUVECs with TNF-α+hypoxia EVs significantly increased leukocyte attachment compared to basal level (3.0 ± 0.4-fold increase (p < 0.05)).

CONCLUSIONS

Inflammatory adipocyte EVs induce VCAM-1 production in vascular endothelial cells, accompanied by enhanced leukocyte attachment. Preventing adipocyte derived EV-induced VCAM-1 upregulation may offer a novel therapeutic target in the prevention of obesity-driven cardiovascular disease.

Adipocytes suppress differentiation of muscle cells in a co-culture system

The development of adipose tissue in skeletal muscle is important for improving meat quality. However, it is still unclear how adipocytes grow in the proximity of muscle fibers. We hypothesized that adipocytes would suppress muscle cell growth so as to grow dominantly within muscle. In this study, we investigated the effect of adipocytes on the differentiation of muscle cells in a co-culture system. The fusion index of C2C12 myoblasts co-cultured with 3T3-L1 adipocytes was significantly lower than that of the control. The expression of myogenin and myosin heavy chain in C2C12 muscle cells co-cultured with 3T3-L1 adipocytes was significantly lower than in the control. Furthermore, the expression of Atrogin-1 and MuRF-1 was higher in C2C12 muscle cells co-cultured with 3T3-L1 adipocytes than the control. These results suggest that 3T3-L1 adipocytes suppress the differentiation of C2C12 myoblasts. In addition, 3T3-L1 adipocytes induced the expression and secretion of IL-6 in C2C12 muscle cells. The fusion index and myotube diameter were higher in C2C12 muscle cells co-cultured with 3T3-L1 cells in medium containing IL-6-neutralizing antibody than the control. Taken together, there is a possibility that adipocyte-induced IL-6 expression in muscle cells could be involved in the inhibition of muscle cell differentiation via autocrine.

Exosome and Macrophage Crosstalk in Sleep-Disordered Breathing-Induced Metabolic Dysfunction

Obstructive sleep apnea (OSA) is a highly prevalent worldwide public health problem that is characterized by repetitive upper airway collapse leading to intermittent hypoxia, pronounced negative intrathoracic pressures, and recurrent arousals resulting in sleep fragmentation. Obesity is a major risk factor of OSA and both of these two closely intertwined conditions result in increased sympathetic activity, oxidative stress, and chronic low-grade inflammation, which ultimately contribute, among other morbidities, to metabolic dysfunction, as reflected by visceral white adipose tissue (VWAT) insulin resistance (IR). Circulating extracellular vesicles (EVs), including exosomes, are released by most cell types and their cargos vary greatly and reflect underlying changes in cellular homeostasis. Thus, exosomes can provide insights into how cells and systems cope with physiological perturbations by virtue of the identity and abundance of miRNAs, mRNAs, proteins, and lipids that are packaged in the EVs cargo, and are secreted from the cells into bodily fluids under normal as well as diseased states. Accordingly, exosomes represent a novel pathway via which a cohort of biomolecules can travel long distances and result in the modulation of gene expression in selected and targeted recipient cells. For example, exosomes secreted from macrophages play a critical role in innate immunity and also initiate the adaptive immune response within specific metabolic tissues such as VWAT. Under normal conditions, phagocyte-derived exosomes represent a large portion of circulating EVs in blood, and carry a protective signature against IR that is altered when secreting cells are exposed to altered physiological conditions such as those elicited by OSA, leading to emergence of IR within VWAT compartment. Consequently, increased understanding of exosome biogenesis and biology should lead to development of new diagnostic biomarker assays and personalized therapeutic approaches. Here, the evidence on the major biological functions of macrophages and exosomes as pathophysiological effectors of OSA-induced metabolic dysfunction is discussed.

Applications of stem cell-derived exosomes in tissue engineering and neurological diseases

Exosomes are extracellular vesicles with diameters of 30-100 nm that are key for intercellular communication. Almost all types of cell, including dendritic cells, T cells, mast cells, epithelial cells, neuronal cells, adipocytes, mesenchymal stem cells, and platelets, can release exosomes. Exosomes are present in human body fluids, such as urine, amniotic fluid, malignant ascites, synovial fluid, breast milk, cerebrospinal fluid, semen, saliva, and blood. Exosomes have biological functions in immune response, antigen presentation, intercellular communication, and RNA and protein transfer. This review provides a brief overview of the origin, morphological characteristics, enrichment and identification methods, biological functions, and applications in tissue engineering and neurological diseases of exosomes.

Extracellular Vesicles from Hypoxic Adipocytes and Obese Subjects Reduce Insulin-Stimulated Glucose Uptake

SCOPE

We investigate the effects of extracellular vesicles (EVs) obtained from in vitro adipocyte cell models and from obese subjects on glucose transport and insulin responsiveness.

METHODS AND RESULTS

EVs are isolated from the culture supernatant of adipocytes cultured under normoxia, hypoxia (1% oxygen), or exposed to macrophage conditioned media (15% v/v). EVs are isolated from the plasma of lean individuals and subjects with obesity. Cultured adipocytes are incubated with EVs and activation of insulin signalling cascades and insulin-stimulated glucose transport are measured. EVs released from hypoxic adipocytes impair insulin-stimulated 2-deoxyglucose uptake and reduce insulin mediated phosphorylation of AKT. Insulin-mediated phosphorylation of extracellular regulated kinases (ERK1/2) is not affected. EVs from individuals with obesity decrease insulin stimulated 2-deoxyglucose uptake in adipocytes (p = 0.0159).

CONCLUSION

EVs released by stressed adipocytes impair insulin action in neighboring adipocytes.

Physiologic Impact of Circulating RBC Microparticles upon Blood-Vascular Interactions

Here, we review current data elucidating the role of red blood cell derived microparticles (RMPs) in normal vascular physiology and disease progression. Microparticles (MPs) are submicron-size, membrane-encapsulated vesicles derived from various parent cell types. MPs are produced in response to numerous stimuli that promote a sequence of cytoskeletal and membrane phospholipid changes and resulting MP genesis. MPs were originally considered as potential biomarkers for multiple disease processes and more recently are recognized to have pleiotropic biological effects, most notably in: promotion of coagulation, production and handling of reactive oxygen species, immune modulation, angiogenesis, and in initiating apoptosis. RMPs, specifically, form normally during RBC maturation in response to injury during circulation, and are copiously produced during processing and storage for transfusion. Notably, several factors during RBC storage are known to trigger RMP production, including: increased intracellular calcium, increased potassium leakage, and energy failure with ATP depletion. Of note, RMP composition differs markedly from that of intact RBCs and the nature/composition of RMP components are affected by the specific circumstances of RMP genesis. Described RMP bioactivities include: promotion of coagulation, immune modulation, and promotion of endothelial adhesion as well as influence upon vasoregulation via influence upon nitric oxide (NO) bioavailability. Of particular relevance, RMPs scavenge NO more avidly than do intact RBCs; this physiology has been proposed to contribute to the impaired oxygen delivery homeostasis that may be observed following transfusion. In summary, RMPs are submicron particles released from RBCs, with demonstrated vasoactive properties that appear to disturb oxygen delivery homeostasis. The clinical impact of RMPs in normal and patho-physiology and in transfusion recipients is an area of continued investigation.

Neuroprotective astrocyte-derived insulin/insulin-like growth factor 1 stimulates endocytic processing and extracellular release of neuron-bound Aβ oligomers

Synaptopathy underlying memory deficits in Alzheimer's disease (AD) is increasingly thought to be instigated by toxic oligomers of the amyloid beta peptide (AβOs). Given the long latency and incomplete penetrance of AD dementia with respect to Aβ pathology, we hypothesized that factors present in the CNS may physiologically protect neurons from the deleterious impact of AβOs. Here we employed physically separated neuron-astrocyte cocultures to investigate potential non-cell autonomous neuroprotective factors influencing AβO toxicity. Neurons cultivated in the absence of an astrocyte feeder layer showed abundant AβO binding to dendritic processes and associated synapse deterioration. In contrast, neurons in the presence of astrocytes showed markedly reduced AβO binding and synaptopathy. Results identified the protective factors released by astrocytes as insulin and insulin-like growth factor-1 (IGF1). The protective mechanism involved release of newly bound AβOs into the extracellular medium dependent upon trafficking that was sensitive to exosome pathway inhibitors. Delaying insulin treatment led to AβO binding that was no longer releasable. The neuroprotective potential of astrocytes was itself sensitive to chronic AβO exposure, which reduced insulin/IGF1 expression. Our findings support the idea that physiological protection against synaptotoxic AβOs can be mediated by astrocyte-derived insulin/IGF1, but that this protection itself is vulnerable to AβO buildup.

Influence of red blood cell-derived microparticles upon vasoregulation

Here we review recent data and the evolving understanding of the role of red blood cell-derived microparticles (RMPs) in normal physiology and in disease progression. Microparticles (MPs) are small membrane vesicles derived from various parent cell types. MPs are produced in response to a variety of stimuli through several cytoskeletal and membrane phospholipid changes. MPs have been investigated as potential biomarkers for multiple disease processes and are thought to have biological effects, most notably in: promotion of coagulation, production and handling of reactive oxygen species, immune modulation, angiogenesis, and in apoptosis. Specifically, RMPs are produced normally during RBC maturation and their production is accelerated during processing and storage for transfusion. Several factors during RBC storage are known to trigger RMP production, including: increased intracellular calcium, increased potassium leakage, and energy failure with ATP depletion. Of note, RMP composition differs from that of intact RBCs, and the nature and composition of RMP components are affected by both storage duration and the character of storage solutions. Recognised RMP bioactivities include: promotion of coagulation, immune modulation, and promotion of endothelial adhesion, as well as influence upon vasoregulation via nitric oxide (NO) scavenging. Of particular relevance, RMPs are more avid NO scavengers than intact RBCs and this feature has been proposed as a mechanism for the impaired oxygen delivery homeostasis that has been observed following transfusion. Preliminary human studies demonstrate that circulating RMP abundance increases with RBC transfusion and is associated with altered plasma vasoactivity and abnormal vasoregulation. In summary, RMPs are submicron particles released from stored RBCs, with demonstrated vasoactive properties that appear to disturb oxygen delivery homeostasis. The clinical impact of RMPs in transfusion recipients is an area of continued investigation.

miR-450a-5p within rat adipose tissue exosome-like vesicles promotes adipogenic differentiation by targeting WISP2

Adipose tissue is an active endocrine organ that can secrete a wide number of factors to regulate adipogenesis via paracrine signals. In addition to soluble proteins in adipose tissue, microRNAs (miRNAs) enriched in extracellular vesicles (EVs), such as exosomes or microvesicles, could modulate intercellular communications. In this study, we demonstrated that exosome-like vesicles derived from adipose tissue (Exo-AT) were internalized by adipose tissue-derived stem cells (ADSCs), and that these, in turn, induced adipogenesis. High-throughput sequencing showed that 45 miRNAs were enriched in Exo-AT, and 31.11% of them were associated with adipogenesis, compared with ADSC-derived exosome-like vesicles (Exo-ADSC). miR-450a-5p, one of the most abundant miRNAs in Exo-AT, was a proadipogenic miRNA. Further study demonstrated that miR-450a-5p promoted adipogenesis through repressing expression of WISP2 by targeting its 3' untranslated region. Additionally, Exo-AT could also downregulate the expression of WISP2, while miR-450a-5p inhibitor reversed this effect. Moreover, inhibition of miR-450a-5p impaired adipogenesis mediated by exosome-like vesicles. In conclusion, Exo-AT mediates adipogenic differentiation through a mechanism involving transfer of miR-450a-5p.

Extracellular Vesicles: Novel Mediators of Cell Communication In Metabolic Disease

Metabolic homeostasis emerges from the complex, multidirectional crosstalk between key metabolic tissues including adipose tissue, liver, and skeletal muscle. This crosstalk, traditionally mediated by hormones and metabolites, becomes dysregulated in human diseases such as obesity and diabetes. Extracellular vesicles (EVs; including exosomes) are circulating, cell-derived nanoparticles containing proteins and nucleic acids that interact with and modify local and distant cellular targets. Accumulating evidence, reviewed herein, supports a role for extracellular vesicles in obesity-associated metabolic disturbance, particularly the local and systemic inflammation characteristic of adipose and hepatic stress. As the practical and conceptual challenges facing the field are tackled, this emerging and versatile mode of intercellular communication may afford valuable insights and therapeutic opportunities in combatting these major threats to modern human health.

Exosomes as the source of biomarkers of metabolic diseases

Exosomes are extracellular vesicles that contain molecules that regulate the metabolic functions of adjacent or remote cells. Recent in vitro, in vivo and clinical studies support the hypothesis that exosomes released from various cell types play roles in the progression of metabolic disorders including type 2 diabetes. Based on this concept and advances in other diseases, the proteins, mRNA, microRNA and lipids in exosomes isolated from biological fluids have been proposed as biomarkers in metabolic disorders. However, several problems with the development of clinically applicable biomarkers have not been resolved. In this review, the biologic functions of exosomes are briefly introduced, and we discuss the technical and practical pros and cons of different methods of exosome isolation for the identification of exosomal biomarkers of metabolic disorders. Standardization of preanalytical variables and isolation of high-purity exosomes from fully characterized biological fluids will be necessary for the identification of useful exosomal biomarkers that can provide insights into the pathogenic mechanisms of complications of metabolic syndrome and of whole-body metabolism.

Clinical significance of elevated serum A-FABP and free fatty acid in neonates with hypoxic ischemic brain damage

The main function of adipocyte fatty acid-binding protein (A-FABP) is to regulate fatty acid metabolism as its molecular chaperone. The clinical significance of A-FABP in hypoxic-ischemic brain damage (HIBD) neonates is not yet clear. Free fatty acid (FFA) in cerebral cortex increases along with hypoxia ischemia degree. Thus, we aimed to investigate whether FFA can induce A-FABP expression and elevate the serum A-FABP level in HIBD neonates. In the present study, 42 HIBD neonates were selected including 11 cases as mild, 16 cases as moderate and 15 cases as severe. The serum was collected from peripheral vein at 72 h after the first visit (acute stage) and 7 days after birth (recovery stage), and the serum from 10 normal neonates was used as the control. The serum level of A-FABP and FFA in 42 neonates with acute phase and recovery phase HIBD were detected using ELISA and copper colorimetric method. The overall serum A-FABP content in HIBD neonates at the acute stage was significantly higher compared to the normal neonates (P<0.05). The serum A-FABP level in severe HIBD neonates was significantly higher than that in mild HIBD, moderate HIBD and normal neonates (P<0.05). The serum FFA level in HIBD neonates at the acute stage was 1,521.57±605.63 µmol/l, which was significantly higher than that in the normal neonates 838.24±294.22 µmol/l. The serum FFA levels in mild, moderate and severe HIBD neonates were significantly higher than those in the normal neonates. The overall A-FABP level in HIBD neonates at the recovery stage was significantly lower compared to the acute stage, which was significant in severe HIBD neonates. A-FABP levels in mild and moderate HIBD neonates at recovery stage were decreased compared with the acute stage, although there was no statistical difference. There was a positive correlation between serum A-FABP and FFA in HIBD neonates at acute stage (r=0.369, P<0.05). In conclusion, serum A-FABP and FFA levels were signifcantly increased in HIBD neonates at acute stage, and were positively correlated. The serum A-FABP level in HIBD neonates at recovery stage was significantly lower than that in the acute stage. The results suggested that serum A-FABP and FFA levels at acute stage can reflect the severity of HIBD. The detection of serum A-FABP and FFA can be applied as indicators for the early diagnosis of HIBD, but also provides a basis for the clinical evaluation of HIBD treatment.

Functional Role of Milk Fat Globule-Epidermal Growth Factor VIII in Macrophage-Mediated Inflammatory Responses and Inflammatory/Autoimmune Diseases

Inflammation involves a series of complex biological processes mediated by innate immunity for host defense against pathogen infection. Chronic inflammation is considered to be one of the major causes of serious diseases, including a number of autoimmune/inflammatory diseases, cancers, cardiovascular diseases, and neurological diseases. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a secreted protein found in vertebrates and was initially discovered as a critical component of the milk fat globule. Previously, a number of studies have reported that MFG-E8 contributes to various biological functions including the phagocytic removal of damaged and apoptotic cells from tissues, the induction of VEGF-mediated neovascularization, the maintenance of intestinal epithelial homeostasis, and the promotion of mucosal healing. Recently, emerging studies have reported that MFG-E8 plays a role in inflammatory responses and inflammatory/autoimmune diseases. This review describes the characteristics of MFG-E8-mediated signaling pathways, summarizes recent findings supporting the roles of MFG-E8 in inflammatory responses and inflammatory/autoimmune diseases, and discusses MFG-E8 targeting as a potential therapeutic strategy for the development of anti-inflammatory/autoimmune disease drugs.

Dynamics of protein secretion during adipocyte differentiation

The major functions of adipocytes include both lipid storage and the production of secretory factors. However, the type of proteins released from mouse 3T3-L1 cells during adipocyte differentiation remains poorly understood. We examined the dynamics of secreted proteins during adipocyte differentiation using mass spectrometry (MS) combined with an iTRAQ (®) labeling method that enables the simultaneous analysis of relative protein expression levels. A total of 215 proteins were identified and quantified from approximately 10 000 MS/MS spectra. Of these, approximately 38% were categorized as secreted proteins based on gene ontology classification. Adipokine secretion levels were increased with the progression of differentiation. By contrast, levels of fibril collagen components, such as subunits of type I and III collagens, were decreased during differentiation. Basement membrane components attained their peak levels at day 4 when small lipid droplets accumulated in differentiated 3T3-L1 cells. Simultaneously, peak levels of collagen microfibril components that comprise type V and VI collagen subunits were also observed. Our data demonstrated that extracellular matrix components were predominantly released during the early and middle stages of adipocyte differentiation, with a subsequent increase in the secretion of adipokines. This suggests that 3T3-L1 cells secrete adipokines after their ECM is constructed during adipocyte differentiation.

Possible roles of platelet-derived microparticles in atherosclerosis

Platelets and platelet-derived microparticles (PMPs) play important roles in cardiovascular diseases, especially atherosclerosis. Continued research has revealed that PMPs have numerous functions in atherosclerosis, not only in thrombosis formation, but also by induction of inflammation. PMPs also induce formation of foam cells. Recent evidence strongly indicates a significant role of PMPs in atherosclerosis. Here, current research on the function of PMPs in atherosclerosis is reviewed.

Mononuclear Phagocyte-Derived Microparticulate Caspase-1 Induces Pulmonary Vascular Endothelial Cell Injury

Lung endothelial cell apoptosis and injury occurs throughout all stages of acute lung injury (ALI/ARDS) and impacts disease progression. Lung endothelial injury has traditionally been focused on the role of neutrophil trafficking to lung vascular integrin receptors induced by proinflammatory cytokine expression. Although much is known about the pathogenesis of cell injury and death in ALI/ARDS, gaps remain in our knowledge; as a result of which there is currently no effective pharmacologic therapy. Enzymes known as caspases are essential for completion of the apoptotic program and secretion of pro-inflammatory cytokines. We hypothesized that caspase-1 may serve as a key regulator of human pulmonary microvascular endothelial cell (HPMVEC) apoptosis in ALI/ARDS. Our recent experiments confirm that microparticles released from stimulated monocytic cells (THP1) induce lung endothelial cell apoptosis. Microparticles pretreated with the caspase-1 inhibitor, YVAD, or pan-caspase inhibitor, ZVAD, were unable to induce cell death of HPMVEC, suggesting the role of caspase-1 or its substrate in the induction of HPMVEC cell death. Neither un-induced microparticles (control) nor direct treatment with LPS induced apoptosis of HPMVEC. Further experiments showed that caspase-1 uptake into HPMVEC and the induction of HPMVEC apoptosis was facilitated by caspase-1 interactions with microparticulate vesicles. Altering vesicle integrity completely abrogated apoptosis of HPMVEC suggesting an encapsulation requirement for target cell uptake of active caspase-1. Taken together, we confirm that microparticle centered caspase-1 can play a regulator role in endothelial cell injury.

Characterisation of adipocyte-derived extracellular vesicles released pre- and post-adipogenesis

Extracellular vesicles (EVs) are submicron vesicles released from many cell types, including adipocytes. EVs are implicated in the pathogenesis of obesity-driven cardiovascular disease, although the characteristics of adipocyte-derived EVs are not well described. We sought to define the characteristics of adipocyte-derived EVs before and after adipogenesis, hypothesising that adipogenesis would affect EV structure, molecular composition and function. Using 3T3-L1 cells, EVs were harvested at day 0 and day 15 of differentiation. EV and cell preparations were visualised by electron microscopy and EVs quantified by nanoparticle tracking analysis (NTA). EVs were then assessed for annexin V positivity using flow cytometry; lipid and phospholipid composition using 2D thin layer chromatography and gas chromatography; and vesicular protein content by an immuno-phenotyping assay. Pre-adipogenic cells are connected via a network of protrusions and EVs at both time points display classic EV morphology. EV concentration is elevated prior to adipogenesis, particularly in exosomes and small microvesicles. Parent cells contain higher proportions of phosphatidylserine (PS) and show higher annexin V binding. Both cells and EVs contain an increased proportion of arachidonic acid at day 0. PREF-1 was increased at day 0 whilst adiponectin was higher at day 15 indicating EV protein content reflects the stage of adipogenesis of the cell. Our data suggest that EV production is higher in cells before adipogenesis, particularly in vesicles <300 nm. Cells at this time point possess a greater proportion of PS (required for EV generation) whilst corresponding EVs are enriched in signalling fatty acids, such as arachidonic acid, and markers of adipogenesis, such as PREF-1 and PPARγ.

Microvesicles in the brain: Biomarker, messenger or mediator?

Microvesicles (MVs) are cell-derived vesicles produced after membrane remodeling of eukaryotic cells during activation or apoptosis. MVs are considered a novel biomarker/messenger for many diseases. Neurons, astrocytes, microglia, as well as neural stem cells, have been described to release MVs, many studies have demonstrated the involvement of platelets and endothelial MVs in some central nervous diseases. This review is focused on understanding the role of MVs in the brain; new findings demonstrated that MVs can contribute to the onset and progression of some neurodegenerative and neuroinflammatory diseases, as well as to the development and regeneration of the nervous system.

Lipid droplets in activated mast cells - a significant source of triglyceride-derived arachidonic acid for eicosanoid production

Mast cells are potent effectors of immune reactions and key players in various inflammatory diseases such as atherosclerosis, asthma, and rheumatoid arthritis. The cellular defense response of mast cells represents a unique and powerful system, where external signals can trigger cell activation resulting in a stimulus-specific and highly coordinated release of a plethora of bioactive mediators. The arsenal of mediators encompasses preformed molecules stored in cytoplasmic secretory granules, as well as newly synthesized proteinaceous and lipid mediators. The release of mediators occurs in strict chronological order and requires proper coordination between the endomembrane system and various enzymatic machineries. For the generation of lipid mediators, cytoplasmic lipid droplets have been shown to function as a major intracellular pool of arachidonic acid, the precursor for eicosanoid biosynthesis. Recent studies have revealed that not only phospholipids in mast cell membranes, but also triglycerides in mast cell lipid droplets are a substrate source for eicosanoid formation. The present review summarizes current knowledge about mast cell lipid droplet biology, and discusses expansions and challenges of traditional mechanistic models for eicosanoid production.

Adipokines influence the inflammatory balance in autoimmunity

Over the past few decades, our understanding of the role of adipose tissue has changed dramatically. Far from simply being a site of energy storage or a modulator of the endocrine system, adipose tissue has emerged as an important regulator of multiple important processes including inflammation. Adipokines are a diverse family of soluble mediators with a range of specific actions on the immune response. Autoimmune diseases are perpetuated by chronic inflammatory responses but the exact etiology of these diseases remains elusive. While researchers continue to investigate these causes, millions of people continue to suffer from chronic diseases. To this end, an increased interest has developed in the connection between adipose tissue-secreted proteins that influence inflammation and the onset and perpetuation of autoimmunity. This review will focus on recent advances in adipokine research with specific attention on a subset of adipokines that have been associated with autoimmune diseases.

Inflammation and the depot-specific secretome of human preadipocytes

OBJECTIVE

Visceral white adipose tissue (WAT) expansion and macrophage accumulation are associated with metabolic dysfunction. Visceral WAT typically shows greater macrophage infiltration. Preadipocytes show varying proinflammatory expression profiles among WAT depots. The objective was to examine the secretomes and chemoattractive properties of preadipocytes from visceral and subcutaneous WAT.

METHODS

A label-free quantitative proteomics approach was applied to study secretomes of subcutaneous and omental preadipocytes from obese subjects. Enzyme-linked immunosorbent assays and chemotaxis assays were used to confirm proinflammatory chemokine secretion between depots.

RESULTS

Preadipocyte secretomes showed greater variation between depots than did intracellular protein expression. Chemokines were the most differentially secreted proteins. Omental preadipocytes induced chemoattraction of macrophages and monocytes. Neutralizing antibodies to the identified chemokines reduced macrophage/monocyte chemoattraction. Subcutaneous preadipocytes treated with interleukin-6 (IL-6) resembled omental preadipocytes in terms of chemokine secretion and macrophage/monocyte chemoattraction. Janus-activated kinase (JAK1/2) protein expression, which transduces IL-6 signaling, was higher in omental than subcutaneous preadipocytes and WAT. Inhibiting JAK in omental preadipocytes decreased chemokine secretion and macrophage/monocyte chemoattraction to levels closer to that observed in subcutaneous preadipocytes.

CONCLUSIONS

Secretomes of omental and subcutaneous preadipocytes are distinct, with the former inducing more macrophage/monocyte chemoattraction, in part through IL-6/JAK-mediated signaling.

Adipogenic RNAs are transferred in osteoblasts via bone marrow adipocytes-derived extracellular vesicles (EVs)

Background

In osteoporosis, bone loss is accompanied by increased marrow adiposity. Given their proximity in the bone marrow and their shared origin, a dialogue between adipocytes and osteoblasts could be a factor in the competition between human Mesenchymal Stem Cells (hMSC) differentiation routes, leading to adipocyte differentiation at the expense of osteoblast differentiation. The adipocyte/osteoblast balance is highly regulated at the level of gene transcription. In our work, we focused on PPARgamma, CEBPalpha and CEBPdelta, as these transcription factors are seen as master regulators of adipogenesis and expressed precociously, and on leptin and adiponectin, considered as adipocyte marker genes. In 2010, our group has demonstrated, thanks to a coculture model, that in the presence of hMSC-derived adipocytes (hMSC-Adi), hMSC-derived osteoblasts (hMSC-Ost) express lesser amounts of osteogenic markers but exhibit the expression of typical adipogenic genes. Nevertheless, the mechanisms underlying this modulation of gene expression are not clarified. Recently, adipocytes were described as releasing extracellular vesicles (EVs), containing and transferring adipocyte specific transcripts, like PPARgamma, leptin and adiponectin. Here, we investigated whether EVs could be the way in which adipocytes transfer adipogenic RNAs in our coculture model.

Results

We observed in hMSC-Ost incubated in hAdi-CM an increase in the adipogenic PPARγ, leptin, CEBPα and CEBPδ transcripts as well as the anti-osteoblastic miR-138, miR30c, miR125a, miR-125b, miR-31 miRNAs, probably implicated in the observed osteocalcin (OC) and osteopontin (OP) expression decrease. Moreover, EVs were isolated from conditioned media collected from cultures of hMSC at different stages of adipocyte differentiation and these specific adipogenic transcripts were detected inside. Finally, thanks to interspecies conditioned media exposition, we could highlight for the first time a horizontal transfer of adipogenic transcripts from medullary adipocytes to osteoblasts.

Conclusions

Here, we have shown, for the first time, RNA transfer between hMSC-derived adipocytes and osteoblasts through EVs. Additional studies are needed to clarify if this mechanism has a role in the adipocytic switch driven on osteoblasts by adipocytes inside bone marrow and if EVs could be a target component to regulate the competition between osteoblasts and adipocytes in the prevention or in the therapy of osteoporosis and other osteopenia.

Exosomes participate in the alteration of muscle homeostasis during lipid-induced insulin resistance in mice

AIMS/HYPOTHESIS

Exosomes released from cells can transfer both functional proteins and RNAs between cells. In this study we tested the hypothesis that muscle cells might transmit specific signals during lipid-induced insulin resistance through the exosomal route.

METHODS

Exosomes were collected from quadriceps muscles of C57Bl/6 mice fed for 16 weeks with either a standard chow diet (SD) or an SD enriched with 20% palm oil (HP) and from C2C12 cells exposed to 0.5 mmol/l palmitate (EXO-Post Palm), oleate (EXO-Post Oleate) or BSA (EXO-Post BSA).

RESULTS

HP-fed mice were obese and insulin resistant and had altered insulin-induced Akt phosphorylation in skeletal muscle (SkM). They also had reduced expression of Myod1 and Myog and increased levels of Ccnd1 mRNA, indicating that palm oil had a deep impact on SkM homeostasis in addition to insulin resistance. HP-fed mouse SkM secreted more exosomes than SD-fed mouse SkM. This was reproduced in-vitro using C2C12 cells pre-treated with palmitate, the most abundant saturated fatty acid of palm oil. Exosomes from HP-fed mice, EXO-Post Palm and EXO-Post Oleate induced myoblast proliferation and modified the expressions of genes involved in the cell cycle and muscle differentiation but did not alter insulin-induced Akt phosphorylation. Lipidomic analyses showed that exosomes from palmitate-treated cells were enriched in palmitate, indicating that exosomes likely transfer the deleterious effect of palm oil between muscle cells by transferring lipids. Muscle exosomes were incorporated into various tissues in vivo, including the pancreas and liver, suggesting that SkM could transfer specific signals through the exosomal route to key metabolic tissues.

CONCLUSIONS/INTERPRETATION

Exosomes act as 'paracrine-like' signals and modify muscle homeostasis during high-fat diets.

Extracellular membrane vesicles secreted by mycoplasma Acholeplasma laidlawii PG8 are enriched in virulence proteins

Mycoplasmas (class Mollicutes), the smallest prokaryotes capable of self-replication, as well as Archaea, Gram-positive and Gram-negative bacteria constitutively produce extracellular vesicles (EVs). However, little is known regarding the content and functions of mycoplasma vesicles. Here, we present for the first time a proteomics-based characterisation of extracellular membrane vesicles from Acholeplasma laidlawii PG8. The ubiquitous mycoplasma is widespread in nature, found in humans, animals and plants, and is the causative agent of phytomycoplasmoses and the predominant contaminant of cell cultures. Taking a proteomics approach using LC-ESI-MS/MS, we identified 97 proteins. Analysis of the identified proteins indicated that A. laidlawii-derived EVs are enriched in virulence proteins that may play critical roles in mycoplasma-induced pathogenesis. Our data will help to elucidate the functions of mycoplasma-derived EVs and to develop effective methods to control infections and contaminations of cell cultures by mycoplasmas. In the present study, we have documented for the first time the proteins in EVs secreted by mycoplasma vesicular proteins identified in this study are likely involved in the adaptation of bacteria to stressors, survival in microbial communities and pathogen-host interactions. These findings suggest that the secretion of EVs is an evolutionally conserved and universal process that occurs in organisms from the simplest wall-less bacteria to complex organisms and indicate the necessity of developing new approaches to control infects.

Milk fat globule epidermal growth factor VIII signaling in arterial wall remodeling

Arterial inflammation and remodeling, important sequellae of advancing age, are linked to the pathogenesis of age-associated arterial diseases e.g. hypertension, atherosclerosis, and metabolic disorders. Recently, high-throughput proteomic screening has identified milk fat globule epidermal growth factor VIII (MFG-E8) as a novel local biomarker for aging arterial walls. Additional studies have shown that MFG-E8 is also an element of the arterial inflammatory signaling network. The transcription, translation, and signaling levels of MFG-E8 are increased in aged, atherosclerotic, hypertensive, and diabetic arterial walls in vivo as well as activated vascular smooth muscle cells (VSMC) and a subset of macrophages in vitro. In VSMC, MFG-E8 increases proliferation and invasion as well as the secretion of inflammatory molecules. In endothelial cells (EC), MFG-E8 facilitates apoptosis. In addition, MFG-E8 has been found to be an essential component of the endothelial-derived microparticles that relay biosignals and modulate arterial wall phenotypes. This review mainly focuses upon the landscape of MFG-E8 expression and signaling in adverse arterial remodeling. Recent discoveries have suggested that MFG-E8 associated interventions are novel approaches for the retardation of the enhanced rates of VSMC proliferation and EC apoptosis that accompany arterial wall inflammation and remodeling during aging and age-associated arterial disease.

Microparticles: a new perspective in central nervous system disorders

Microparticles (MPs) are a heterogeneous population of small cell-derived vesicles, ranging in size from 0.1 to 1 μm. They contain a variety of bioactive molecules, including proteins, biolipids, and nucleic acids, which can be transferred between cells without direct cell-to-cell contact. Consequently, MPs represent a novel form of intercellular communication, which could play a role in both physiological and pathological processes. Growing evidence indicates that circulating MPs contribute to the development of cancer, inflammation, and autoimmune and cardiovascular diseases. Most cell types of the central nervous system (CNS) have also been shown to release MPs, which could be important for neurodevelopment, CNS maintenance, and pathologies. In disease, levels of certain MPs appear elevated; therefore, they may serve as biomarkers allowing for the development of new diagnostic tools for detecting the early stages of CNS pathologies. Quantification and characterization of MPs could also provide useful information for making decisions on treatment options and for monitoring success of therapies, particularly for such difficult-to-treat diseases as cerebral malaria, multiple sclerosis, and Alzheimer's disease. Overall, studies on MPs in the CNS represent a novel area of research, which promises to expand the knowledge on the mechanisms governing some of the physiological and pathophysiological processes of the CNS.

Redox regulation of protein damage in plasma

The presence and concentrations of modified proteins circulating in plasma depend on rates of protein synthesis, modification and clearance. In early studies, the proteins most frequently analysed for damage were those which were more abundant in plasma (e.g. albumin and immunoglobulins) which exist at up to 10 orders of magnitude higher concentrations than other plasma proteins e.g. cytokines. However, advances in analytical techniques using mass spectrometry and immuno-affinity purification methods, have facilitated analysis of less abundant, modified proteins and the nature of modifications at specific sites is now being characterised. The damaging reactive species that cause protein modifications in plasma principally arise from reactive oxygen species (ROS) produced by NADPH oxidases (NOX), nitric oxide synthases (NOS) and oxygenase activities; reactive nitrogen species (RNS) from myeloperoxidase (MPO) and NOS activities; and hypochlorous acid from MPO. Secondary damage to proteins may be caused by oxidized lipids and glucose autooxidation.

In this review, we focus on redox regulatory control of those enzymes and processes which control protein maturation during synthesis, produce reactive species, repair and remove damaged plasma proteins. We have highlighted the potential for alterations in the extracellular redox compartment to regulate intracellular redox state and, conversely, for intracellular oxidative stress to alter the cellular secretome and composition of extracellular vesicles. Through secreted, redox-active regulatory molecules, changes in redox state may be transmitted to distant sites.

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Loss of redox homeostasis may affect the secretome content and protein concentration, transmitting redox signals to distant cells through extracellular vesicles.

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Damaged glycoforms may arise from oxidants or aberrant biosynthetic regulation.

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Reactive species generation by NOX and NOS is controlled through redox regulation.

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Cell surface and plasma thiol-oxidised proteins can be reduced and their activity modulated by thioredoxin, protein disulphide isomerase and reductases.

Mfge8 promotes obesity by mediating the uptake of dietary fats and serum fatty acids

Fatty acids are integral mediators of energy storage, membrane formation and cell signaling. The pathways that orchestrate uptake of fatty acids remain incompletely understood. Expression of the integrin ligand Mfge8 is increased in human obesity and in mice on a high-fat diet, but its role in obesity is unknown. We show here that Mfge8 promotes the absorption of dietary triglycerides and the cellular uptake of fatty acid and that Mfge8-deficient (Mfge8(-/-)) mice are protected from diet-induced obesity, steatohepatitis and insulin resistance. Mechanistically, we found that Mfge8 coordinates fatty acid uptake through αvβ3 integrin- and αvβ5 integrin-dependent phosphorylation of Akt by phosphatidylinositide-3 kinase and mTOR complex 2, leading to translocation of Cd36 and Fatp1 from cytoplasmic vesicles to the cell surface. Collectively, our results imply a role for Mfge8 in regulating the absorption and storage of dietary fats, as well as in the development of obesity and its complications.

Sorcin links calcium signaling to vesicle trafficking, regulates Polo-like kinase 1 and is necessary for mitosis

Sorcin, a protein overexpressed in many multi-drug resistant cancers, dynamically localizes to distinct subcellular sites in 3T3-L1 fibroblasts during cell-cycle progression. During interphase sorcin is in the nucleus, in the plasma membrane, in endoplasmic reticulum (ER) cisternae, and in ER-derived vesicles localized along the microtubules. These vesicles are positive to RyR, SERCA, calreticulin and Rab10. At the beginning of mitosis, sorcin-containing vesicles associate with the mitotic spindle, and during telophase are concentrated in the cleavage furrow and, subsequently, in the midbody. Sorcin regulates dimensions and calcium load of the ER vesicles by inhibiting RYR and activating SERCA. Analysis of sorcin interactome reveals calcium-dependent interactions with many proteins, including Polo-like kinase 1 (PLK1), Aurora A and Aurora B kinases. Sorcin interacts physically with PLK1, is phosphorylated by PLK1 and induces PLK1 autophosphorylation, thereby regulating kinase activity. Knockdown of sorcin results in major defects in mitosis and cytokinesis, increase in the number of rounded polynucleated cells, blockage of cell progression in G2/M, apoptosis and cell death. Sorcin regulates calcium homeostasis and is necessary for the activation of mitosis and cytokinesis.

Adipocyte fatty acid-binding protein is released from adipocytes by a non-conventional mechanism

Adipocyte fatty acid-binding protein (AFABP) is an adipokine, which induces insulin resistance. However, AFABP does not possess any secretion-directed signals and the mechanisms for AFABP release have not been thoroughly assessed so far. In the current study, mechanisms for AFABP secretion were elucidated in 3T3-L1 adipocytes in vitro in the presence or absence of hormonal stimulation, calcium ionophore and secretion inhibitors by cell fractionation experiments, immunoblotting and ELISAs. We demonstrate that AFABP secretion is upregulated during adipocyte differentiation. AFABP secretion is not influenced by treatment with protein secretion inhibitors that block vesicular traffic at the endoplasmic reticulum and the Golgi apparatus. AFABP is secreted partially by adipocyte-derived microvesicles (ADMs), an established mechanism for unconventional secretion from adipocytes. Both total and ADM-secreted AFABP are downregulated by insulin and upregulated by the calcium ionophore ionomycin. Furthermore, murine RAW 264.7 macrophages secrete AFABP and AFABP release from these cells is upregulated by lipopolysaccharide treatment. Taken together, these results suggest that AFABP is actively released by unconventional mechanisms and by ADMs from 3T3-L1 adipocytes. Furthermore, AFABP secretion from fat cells is regulated by insulin and intracellular calcium.

Amphipath-induced plasma membrane curvature controls microparticle formation from adipocytes: novel therapeutic implications for metabolic disorders

Microparticles produced from the membrane surface of adipocytes promote lipid biosynthesis and angiogenesis in adipose tissues. Thus, they are deeply associated with the onset of metabolic disorders. Despite our understanding of their roles in physiological or pathological responses, we know little about the mechanism by which microparticles are produced from adipocytes. Based on our previous studies using rat megakaryocytes or mast cells during exocytosis, we proposed that membrane curvature induced by amphiphilic reagents, such as chlorpromazine or salicylate, facilitate or inhibit the formation of microparticles. Since the plasma membranes in adipocytes share many common biophysiological features with those in megakaryocytes or mast cells during exocytosis, the same stimulatory or inhibitory mechanism of microparticle formation would exist in adipocytes. Therefore, we hypothesize here that amphiphilic reagents would also change the membrane curvature in adipocytes, and that such changes would facilitate or inhibit the microparticle formation from adipocytes. Our hypothesis is unique because it sheds light for the first time on the physiological mechanism by which microparticles are produced in adipocytes. It is also important because the idea could have novel therapeutic implications for metabolic disorders that are triggered by increases in the microparticle formation.

Serum circulating microRNA profiling for identification of potential type 2 diabetes and obesity biomarkers

Background and Aim

MicroRNAs are small non-coding RNAs that play important regulatory roles in a variety of biological processes, including complex metabolic processes, such as energy and lipid metabolism, which have been studied in the context of diabetes and obesity. Some particular microRNAs have recently been demonstrated to abundantly and stably exist in serum and to be potentially disease-specific. The aim of this profiling study was to characterize the expression of miRNA in serum samples of obese, nonobese diabetic and obese diabetic individuals to determine whether miRNA expression was deregulated in these serum samples and to identify whether any observed deregulation was specific to either obesity or diabetes or obesity with diabetes.

Patients and Methods

Thirteen patients with type 2 diabetes, 20 obese patients, 16 obese patients with type 2 diabetes and 20 healthy controls were selected for this study. MiRNA PCR panels were employed to screen serum levels of 739 miRNAs in pooled samples from these four groups. We compared the levels of circulating miRNAs between serum pools of each group. Individual validation of the twelve microRNAs selected as promising biomarkers was carried out using RT-qPCR.

Results

Three serum microRNAs, miR-138, miR-15b and miR-376a, were found to have potential as predictive biomarkers in obesity. Use of miR-138 or miR-376a provides a powerful predictive tool for distinguishing obese patients from normal healthy controls, diabetic patients, and obese diabetic patients. In addition, the combination of miR-503 and miR-138 can distinguish diabetic from obese diabetic patients.

Conclusion

This study is the first to show a panel of serum miRNAs for obesity, and compare them with miRNAs identified in serum for diabetes and obesity with diabetes. Our results support the use of some miRNAs extracted from serum samples as potential predictive tools for obesity and type 2 diabetes.