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.

Mesenchymal stem cells (MSCs) are adult multipotent stem cells that are able to differentiate into multiple specialized cell types including osteocytes, adipocytes, and chondrocytes. MSCs exert different functions in the body and have recently been predicted to have a major clinical/therapeutic potential. However, the mechanisms of self-renewal and tissue regeneration are not completely understood. It has been shown that the biological effect depends mainly on its paracrine action. Furthermore, it has been reported that the secretion of soluble factors and the release of extracellular vesicles, such as exosomes, could mediate the cellular communication to induce cell-differentiation/self-renewal. This review provides an overview of MSC-derived exosomes in promoting angiogenicity and of the clinical relevance in a therapeutic approach.

Abstract-D-Glucose infusion and gestational diabetes induce vasodilatation in humans and increase L-arginine Key Words: humans Ⅲ endothelium Ⅲ glucose Ⅲ arginine Ⅲ nitric oxide T he cationic amino acid L-arginine is the substrate for nitric oxide (NO) synthesis via endothelial NO synthase (eNOS) 1 and is taken up primarily by the Na ϩ -independent high-affinity (K m Ϸ100 to 400 mol/L) systems y ϩ /CAT-1 and y ϩ /CAT-2B (where CAT indicates cationic amino acid transporter) in human umbilical vein endothelial cells (HUVECs). 2,3 L-Arginine transport and NO synthesis (Larginine/NO pathway) are increased in HUVECs from patients with gestational diabetes. 2 Interestingly, long-term incubation (24 hours) of HUVECs from normal pregnancies with elevated D-glucose mimics the effect of gestational diabetes on the L-arginine/NO pathway. 4 In addition, elevated D-glucose for 24 hours 4,5 or 5 days 6 increases eNOS gene expression. A recent report shows that D-glucose infusion induces vasodilatation in humans, 7 and in animal models, an elevation of plasma D-glucose results in rapid (seconds to minutes) vasodilatation. 8 -10 Therefore, rapid fluctuations in the D-glucose level are crucial in maintaining human fetal endothelial function. [2][3][4][5]11 D-Glucose activates protein kinase C (PKC), an enzyme involved with long-term stimulation of the L-arginine/NO pathway, 5,12-14 and (within 1 hour) p42 and p44 mitogen-activated protein (MAP) kinases (p42/44 mapk ). 5,14,15 p42/44 mapk activation may itself be dependent on PKC activation and NO synthesis. 5,14 However, the effect of short-term incubation with elevated D-glucose on the endothelial L-arginine/NO pathway has not been investigated. 4,11,16,17 The present study shows that a 2-minute incubation with 25 mmol/L D-glucose increases L-arginine transport and NO synthesis in HUVECs. The underlying cellular mechanisms involve phosphorylation of eNOS at Ser 1177 via phosphatidylinositol 3-kinase (PI3-k) and activation of eNOS and p42/ p44 mapk by D-glucose. 18 Materials and Methods Cell CultureHuman umbilical vein endothelium was isolated (collagenase digestion 0.25 mg/mL) and cultured (37°C, 5% CO 2 , confluent passage 2) in medium 199 containing 5 mmol/L D-glucose, 10% newborn calf serum, 10% fetal calf serum, 3.2 mmol/L L-glutamine, 100 mol/L L-arginine, and 100 U/mL penicillin-streptomycin (primary culture medium). [2][3][4] Before an experiment (24 hours), the incubation medium was changed to serum-free medium 199.

The effects of elevated D‐glucose on adenosine transport were investigated in human cultured umbilical vein endothelial cells isolated from normal pregnancies. Elevated D‐glucose resulted in a time‐ (8‐12 h) and concentration‐dependent (half‐maximal at 10 ± 2 mM) inhibition of adenosine transport, which was associated with a reduction in the Vmax for nitrobenzylthioinosine (NBMPR)‐sensitive (es) saturable nucleoside with no significant change in Km. D‐Fructose (25 mM), 2‐deoxy‐D‐glucose (25 mM) or D‐mannitol (20 mM) had no effect on adenosine transport. Adenosine transport was inhibited following incubation of cells with the protein kinase C (PKC) activator phorbol 12‐myristate 13‐acetate (PMA; 100 nM, 30 min to 24 h). D‐Glucose‐induced inhibition of transport was abolished by calphostin C (100 nM, an inhibitor of PKC), and was not further reduced by PMA. Increased PKC activity in the membrane (particulate) fraction of endothelial cells exposed to D‐glucose or PMA was blocked by calphostin C but was unaffected by NG‐nitro‐L‐arginine methyl ester (L‐NAME; 100 μM, an inhibitor of nitric oxide synthase (NOS)) or PD‐98059 (10 μM, an inhibitor of mitogen‐activated protein kinase kinase 1). D‐Glucose and PMA increased endothelial NOS (eNOS) activity, which was prevented by calphostin C or omission of extracellular Ca2+ and unaffected by PD‐98059. Adenosine transport was inhibited by S‐nitroso‐N‐acetyl‐l,D‐penicillamine (SNAP; 100 μM, an NO donor) but was increased in cells incubated with L‐NAME. The effect of SNAP on adenosine transport was abolished by PD‐98059. Phosphorylation of mitogen‐activated protein kinases p44mapk (ERK1) and p42mapk (ERK2) was increased in endothelial cells exposed to elevated D‐glucose (25 mM for 30 min to 24 h) and the NO donor SNAP (100 μM, 30 min). The effect of D‐glucose was blocked by PD‐98059 or L‐NAME, which also prevented the inhibition of adenosine transport mediated by elevated D‐glucose. Our findings provide evidence that D‐glucose inhibits adenosine transport in human fetal endothelial cells by a mechanism that involves activation of PKC, leading to increased NO levels and p42‐p44mapk phosphorylation. Thus, the biological actions of adenosine appear to be altered under conditions of sustained hyperglycaemia.