Catherine Calzada

Extracellular vesicles (EVs) represent a cytokine‐independent pathway though which skeletal muscle (SkM) cells influence the fate of neighbouring cells, thereby regulating SkM metabolic homeostasis and regeneration. Although SkM‐EVs are increasingly being explored as a therapeutic strategy to enhance muscle regeneration or to induce the myogenic differentiation of induced pluripotent stem cells (iPSCs), the mechanisms governing their release from muscle cells remain poorly described. Moreover, because muscle regeneration involves a tightly regulated inflammatory response it also important to determine how inflammation alters SkM‐EV cargo and function in order to design more effective EV‐based therapies. To address this knowledge gap, we isolated and characterized the large and small EVs (lEVs, sEVs) released from SkM cells under basal conditions and in response to TNF‐α, a well‐established inflammatory mediator elevated in both acute muscle injury and chronic inflammatory conditions such as type 2 diabetes. We then evaluated the regenerative roles of these EV subtypes in vivo using a mouse model of cardiotoxin‐induced muscle injury, with a specific focus on their bioactive sphingolipid content. Using transmission, scanning or cryo‐electron microscopy, lipidomic profiling and an adenoviral construct to express labelled CD63 in myotubes, we demonstrated that SkM cells release both sEVs and lEVs primarily from the plasma membrane. Notably, sEVs were generated from specialized membrane folds enriched in the EV markers ALIX (ALG‐2 interacting protein X) and TSG101, as well as lipid raft‐associated lipids. During regeneration, sEVs promoted M1 macrophage polarization and migration and muscle stem cell (MuSC) differentiation, thereby accelerating muscle repair. In contrast, lEVs inhibited and promoted MuSC proliferation and impaired the transition from the pro‐inflammatory to the anti‐inflammatory response, an essential step for promoting MuSC differentiation. Treatment of isolated muscle fibres with SkM‐EVs revealed that the distinct effects of sEVs and lEVs on MuSC behaviour and macrophage phenotype could be largely explained by differences in their lipid composition, particularly the ratio of sphingosine‐1‐phosphate (S1P) subspecies. However, TNF‐α exposure altered these ratios in sEVs and impaired their regenerative functions on MuSC and their effect on macrophage migration and polarization. These results demonstrate for the first time the importance of the sphingolipid content of EVs released by skeletal muscle in their regenerative function within muscle tissue, largely explained by their role as carriers of different subspecies of sphingosine‐1‐phosphate. This suggests that modulating the sphingolipid composition of EVs could be a viable strategy to enhance the regenerative potential of muscle tissue in addition to therapeutic interventions.

Scope: The aim of this study is to examine whether postprandial (PP) triglyceride‐rich lipoproteins (TGRL) secreted after a moderate fat intake would activate platelets differently according to their fatty acid (FA) composition.Methods and results: In a parallel single‐blind randomized trial, 30 women with type 2 diabetes are assigned a breakfast containing 20 g lipids from butter versus hazelnut‐cocoa spread (HCS) rich in palm oil. Blood samples are collected at fasting and 4 h PP. FA composition of fasting and PP TGRL and their effects on the activation of platelets from healthy blood donors are assessed. Both breakfasts similarly increase plasma ApoB‐48, plasma, and TGRL triglycerides (p < 0.05). TGRL mean diameter increases after both breakfasts and is greater after the butter breakfast. Both breakfasts are rich in palmitic acid, and the HCS breakfast contains 45% oleic acid. TGRL FA composition reflects the dietary FA composition. Pre‐incubation of platelets with fasting and PP TGRL increases collagen‐stimulated aggregation (p < 0.01 vs control). Fasting and PP TGRL similarly increase agonist‐induced thromboxane B₂ concentrations, and this effect is concentration‐dependent for PP TGRL.Conclusion: PP TGRL from type 2 diabetic women after a palm‐oil spread versus butter‐based mixed meal induce similar acute in vitro platelet activation.

Chronic kidney disease is associated with an increased cardiovascular risk, and altered biological properties of high-density lipoproteins (HDL) may play a role in these events. This study aimed to describe the HDL proteome from non-diabetic hemodialysis patients and identify potential pathways affected by the dysregulated expression of HDL proteins. HDL were sampled from nine non-diabetic hemodialysis (HD) and eight control patients. Samples were analyzed using a nano-RSLC coupled with a Q-Orbitrap. Data were processed by database searching using SequestHT against a human Swissprot database and quantified with a label-free quantification approach. Proteins that were in at least five of the eight control and six of the nine HD patients were analyzed. Analysis was based on pairwise ratios and the ANOVA hypothesis test. Among 522 potential proteins, 326 proteins were identified to be in the HDL proteome from HD and control patients, among which 10 were significantly upregulated and nine downregulated in HD patients compared to the control patients (p < 0.05). Up and downregulated proteins were involved in lipid metabolism, hemostasis, wound healing, oxidative stress, and apoptosis pathways. This difference in composition could partly explain HDL dysfunction in the chronic kidney disease (CKD) population and participate in the higher cardiovascular risk observed in this population.

Chronic kidney disease (CKD) is associated with an enhanced oxidative stress and deep modifications in lipid and lipoprotein metabolism. First, many oxidized lipids accumulate in CKD and were shown to exert toxic effects on cells and tissues. These lipids are known to interfere with many cell functions and to be pro-apoptotic and pro-inflammatory, especially in the cardiovascular system. Some, like F2-isoprostanes, are directly correlated with CKD progression. Their accumulation, added to their noxious effects, rendered their nomination as uremic toxins credible. Similarly, lipoproteins are deeply altered by CKD modifications, either in their metabolism or composition. These impairments lead to impaired effects of HDL on their normal effectors and may strongly participate in accelerated atherosclerosis and failure of statins in end-stage renal disease patients. This review describes the impact of oxidized lipids and other modifications in the natural history of CKD and its complications. Moreover, this review focuses on the modifications of lipoproteins and their impact on the emergence of cardiovascular diseases in CKD as well as the appropriateness of considering them as actual mediators of uremic toxicity.