For many years, cardiovascular disease (CVD) has been the leading cause of death around the world. Often associated with CVD are comorbidities such as obesity, abnormal lipid profiles and insulin resistance. Insulin is a key hormone that functions as a regulator of cellular metabolism in many tissues in the human body. Insulin resistance is defined as a decrease in tissue response to insulin stimulation thus insulin resistance is characterized by defects in uptake and oxidation of glucose, a decrease in glycogen synthesis, and, to a lesser extent, the ability to suppress lipid oxidation. Literature widely suggests that free fatty acids are the predominant substrate used in the adult myocardium for ATP production, however, the cardiac metabolic network is highly flexible and can use other substrates, such as glucose, lactate or amino acids. During insulin resistance, several metabolic alterations induce the development of cardiovascular disease. For instance, insulin resistance can induce an imbalance in glucose metabolism that generates chronic hyperglycemia, which in turn triggers oxidative stress and causes an inflammatory response that leads to cell damage. Insulin resistance can also alter systemic lipid metabolism which then leads to the development of dyslipidemia and the well-known lipid triad: (1) high levels of plasma triglycerides, (2) low levels of high-density lipoprotein, and (3) the appearance of small dense low-density lipoproteins. This triad, along with endothelial dysfunction, which can also be induced by aberrant insulin signaling, contribute to atherosclerotic plaque formation. Regarding the systemic consequences associated with insulin resistance and the metabolic cardiac alterations, it can be concluded that insulin resistance in the myocardium generates damage by at least three different mechanisms: (1) signal transduction alteration, (2) impaired regulation of substrate metabolism, and (3) altered delivery of substrates to the myocardium. The aim of this review is to discuss the mechanisms associated with insulin resistance and the development of CVD. New therapies focused on decreasing insulin resistance may contribute to a decrease in both CVD and atherosclerotic plaque generation.

There is increasing evidence that miRNAs, which are enriched in nanovesicles called exosomes, are important regulators of gene expression. When compared with normal pregnancies, pregnancies with gestational diabetes mellitus (GDM) are associated with skeletal muscle insulin resistance as well as increased levels of circulating placental exosomes. Here we investigated whether placental exosomes in GDM carry a specific set of miRNAs associated with skeletal muscle insulin sensitivity. Exosomes were isolated from chorionic villous (CV) explants from both women with Normal Glucose Tolerant (NGT) and GDM pregnancies. Using miRNA sequencing, we identified a specific set of miRNAs selectively enriched with exosomes and compared with their cells of origin indicating a specific packaging of miRNAs into exosomes. Gene target and ontology analysis of miRNA differentially expressed in exosomes secreted in GDM compared with NGT are associated with pathways regulating cell migration and carbohydrate metabolism. We determined the expression of a selected set of miRNAs in placenta, plasma, and skeletal muscle biopsies from NGT and GDM. Interestingly, the expression of these miRNAs varied in a consistent pattern in the placenta, in circulating exosomes, and in skeletal muscle in GDM. Placental exosomes from GDM pregnancies decreased insulin-stimulated migration and glucose uptake in primary skeletal muscle cells obtained from patients with normal insulin sensitivity. Interestingly, placental exosomes from NGT increase migration and glucose uptake in response to insulin in skeletal muscle from diabetic subjects. These findings suggest that placental exosomes might have a role in the changes on insulin sensitivity in normal and GDM pregnancies.

Extracellular vesicles (EVs) are membrane-bound vesicles released into the extracellular space by almost all types of cells. EVs can cross the physiological barriers, and a variety of biological fluids are enriched in them. EVs are a heterogeneous population of vesicles, including exosomes, microvesicles, and apoptotic bodies. The different subpopulations of vesicles can be differentiated by size and origin, in which exosomes (~100 nm and from endocytic origin) are the most studied so far. EVs have essential roles in cell-to-cell communication and are critical modulators of immune response under normal and pathological conditions. Pregnancy is a unique situation of immune-modulation in which the maternal immune system protects the fetus from allogenic rejection and maintains the immunosurveillance. The placenta is a vital organ that performs a multitude of functions to support the pregnancy. The EVs derived from the human placenta have crucial roles in regulating the maternal immune response for successful pregnancy outcome. Placenta-derived vesicles perform a myriad of functions like suppression of immune reaction to the developing fetus and establishment and maintenance of a systemic inflammatory response to combat infectious intruders. A fine-tuning of these mechanisms is quintessential for successful completion of pregnancy and healthy outcome for mother and fetus. Dysregulation in the mechanisms mentioned above can lead to several pregnancy disorders. In this review, we summarize the current literature regarding the critical roles played by the EVs in immunomodulation during pregnancy with particular attention to the placenta-derived exosomes.