Sleep-disordered breathing, circulating exosomes, and insulin sensitivity in adipocytes

Abstract

BackgroundSleep-disordered-breathing (SDB), which is characterized by chronic intermittent hypoxia (IH) and sleep fragmentation (SF), is a prevalent condition that promotes metabolic dysfunction, particularly among patients suffering from obstructive hypoventilation syndrome (OHS). Exosomes are generated ubiquitously, are readily present in the circulation, and their cargo may exert substantial functional cellular alterations in both physiological and pathological conditions. However, the effects of plasma exosomes on adipocyte metabolism in patients with OHS or in mice subjected to IH or SF mimicking SDB are unclear.MethodsExosomes from fasting morning plasma samples from obese adults with polysomnographically-confirmed OSA before and after 3 months of adherent CPAP therapy were assayed. In addition, C57BL/6 mice were randomly assigned to (1) sleep control (SC), (2) sleep fragmentation (SF), and (3) intermittent hypoxia (HI) for 6 weeks, and plasma exosomes were isolated. Equivalent exosome amounts were added to differentiated adipocytes in culture, after which insulin sensitivity was assessed using 0 nM and 5nM insulin-induced pAKT/AKT expression changes by western blotting.ResultsWhen plasma exosomes were co-cultured and internalized by human naïve adipocytes, significant reductions emerged in Akt phosphorylation responses to insulin when compared to exosomes obtained after 24 months of adherent CPAP treatment (n=24; p<0.001), while no such changes occur in untreated patients (n=8). In addition, OHS exosomes induced significant increases in adipocyte lipolysis that were attenuated after CPAP, but did not alter pre-adipocyte differentiation. Similarly, exosomes from SF- and IH-exposed mice induced attenuated p-AKT/total AKT responses to exogenous insulin and increased glycerol content in naïve murine adipocytes, without altering pre-adipocyte differentiation.ConclusionsUsing in vitro adipocyte-based functional reporter assays, alterations in plasma exosomal cargo occur in SDB, and appear to contribute to adipocyte metabolic dysfunction. Further exploration of exosomal miRNA signatures in either human subjects or animal models and their putative organ and cell targets appears warranted.

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

“…OSA is particularly present among obese individuals and can affect at least 4–10% of all adults, with recent epidemiological studies reporting much higher prevalence [ 6 , 7 , 8 ]. Patients with OSA are at greater risk for metabolic dysfunction including insulin resistance, type 2 diabetes mellitus, dyslipidemia, and display evidence of adipose tissue inflammation and dysfunction [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Of note, both IH and SF have been independently associated with metabolic dysfunction, and acute exposures to IH were shown to decrease insulin sensitivity in healthy human volunteers [ 16 , 17 ].…”

Epigenetics dysfunction in morbid obesity with or without obstructive sleep apnoea: the EPIMOOSA study

“…A sub-analysis of the HIPARCO clinical trial [37] revealed that a panel of miRNAs could be used to reliably predict which patients with refractory hypertension and OSA would respond better to CPAP therapy in terms of reducing their blood pressure. An experiment conducted by Khalyfa et al [45] found a possible pathophysiological relationship among the circulating miR-NAs of obese patients with OSA, adipocyte alterations, and the mechanisms of insulin resistance [45].…”

Plasma Extracellular Vesicles in Children with OSA Disrupt Blood–Brain Barrier Integrity and Endothelial Cell Wound Healing In Vitro

“…Plasma EVs isolation and characterization from blood samples were performed using a previously described protocol that enriches for exosomes [6,42]. Indeed, negative stain electron microscopy showed vesicles in typical shaped morphology ( Figure 2A) [32,38,43], and as shown in Figure 2B, unique exosome markers were used to conclusively identify EVs using flow cytometry of isolated EVs derived from CO, OSA-NC(−), or OSA-NC(+). As shown in Figure 2B, each image was stained separately with a different antibody using two different negative controls (all reagents without antibody and no EVs (negative #1), all reagents without EVs (negative #2)).…”

“…EVs were quantified using enzymatic fluorescent assay (FluoroCet #FCET96A quantitation kit; System Biosciences, Mountain View, CA, USA) according to the manufacturer's protocols [32]. The assay was used to measure the esterase activity of cholesteryl ester transfer protein (CETP) activity, and the standard curve was calibrated to known EVs counts.…”

“…Exosomes, a class of extracellular vesicles, are very small vesicles ranging in size from 30 to 120 nm. These vesicles are generated by many, if not all, cells in the body, and can perhaps be detected in all biological fluids [27,[31][32][33][34][35], where they participate in a vast array of physiological processes, and more specifically, mediate critical aspects of intercellular communication [36] through delivery of their functional cargo [31,34,[37][38][39][40].…”