The Good Neighbor: Coping With Insulin Resistance by Modulating Adipose Tissue Endothelial Cell Function

Adipose endothelial cells mastering adipose tissues metabolic fate

Dynamic communication within adipose tissue depends on highly vascularized structural characteristics to maintain systemic metabolic homoeostasis. Recently, it has been noted that adipose endothelial cells (AdECs) act as essential bridges for biological information transmission between adipose-resident cells. Hence, paracrine regulators that mediate crosstalk between AdECs and adipose stromal cells were summarized. We also highlight the importance of AdECs to maintain adipocytes metabolic homoeostasis by regulating insulin sensitivity, lipid turnover and plasticity. The differential regulation of AdECs in adipose plasticity often depends on vascular density and metabolic states. Although choosing pro-angiogenic or anti-angiogenic therapies for obesity is still a matter of debate in clinical settings, the growing numbers of drugs have been confirmed to play an anti-obesity effect by affecting vascularization. Pharmacologic angiogenesis intervention has great potential as therapeutic strategies for obesity.

Vascular Endothelial Regulation of Obesity-Associated Insulin Resistance

Obesity is a worldwide epidemic that predisposes individuals to metabolic complications, such as type 2 diabetes mellitus and non-alcoholic fatty liver disease, all of which are related to an imbalance between food intake and energy expenditure. Identification of the pathogenic molecular mechanisms and effective therapeutic approaches are urgently needed. A well-accepted paradigm is that crosstalk between organs/tissues contributes to diseases. Endothelial dysfunction characterizes metabolic disorders and the related vascular complications. Over the past two decades, overwhelming studies have focused on mechanisms that lead to endothelial dysfunction. New investigations, however, have begun to appreciate the opposite direction of the crosstalk: endothelial regulation of metabolism, although the underlying mechanisms remain to be elucidated. This review summarizes the evidence that supports the concept of endothelial regulation of obesity and the associated insulin resistance in fat, liver, and skeletal muscles, the classic targets of insulin. Outstanding questions and future research directions are highlighted. Identification of the mechanisms of vascular endothelial regulation of metabolism may offer strategies for prevention and treatment of obesity and the related metabolic complications.

Thirty Years of Saying NO: Sources, Fate, Actions, and Misfortunes of the Endothelium-Derived Vasodilator Mediator

Endothelial cells control vascular tone by releasing nitric oxide (NO) produced by endothelial NO synthase. The activity of endothelial NO synthase is modulated by the calcium concentration and by post-translational modifications (eg, phosphorylation). When NO reaches vascular smooth muscle, soluble guanylyl cyclase is its primary target producing cGMP. NO production is stimulated by circulating substances (eg, catecholamines), platelet products (eg, serotonin), autacoids formed in (eg, bradykinin) or near (eg, adiponectin) the vascular wall and physical factors (eg, shear stress). NO dysfunction can be caused, alone or in combination, by abnormal coupling of endothelial cell membrane receptors, insufficient supply of substrate (l-arginine) or cofactors (tetrahydrobiopterin), endogenous inhibitors (asymmetrical dimethyl arginine), reduced expression/presence/dimerization of endothelial NO synthase, inhibition of its enzymatic activity, accelerated disposition of NO by reactive oxygen species and abnormal responses (eg, biased soluble guanylyl cyclase activity producing cyclic inosine monophosphate) of the vascular smooth muscle. Major culprits causing endothelial dysfunction, irrespective of the underlying pathological process (aging, obesity, diabetes mellitus, and hypertension), include stimulation of mineralocorticoid receptors, activation of endothelial Rho-kinase, augmented presence of asymmetrical dimethyl arginine, and exaggerated oxidative stress. Genetic and pharmacological interventions improve dysfunctional NO-mediated vasodilatations if protecting the supply of substrate and cofactors for endothelial NO synthase, preserving the presence and activity of the enzyme and reducing reactive oxygen species generation. Common achievers of such improvement include maintained levels of estrogens and increased production of adiponectin and induction of silent mating-type information regulation 2 homologue 1. Obviously, endothelium-dependent relaxations are not the only beneficial action of NO in the vascular wall. Thus, reduced NO-mediated responses precede and initiate the atherosclerotic process.

The future of pleiotropic therapy in heart failure. Lessons from the benefits of exercise training on endothelial function

A novel generation of drugs is introduced in the treatment of heart failure (HF). These drugs, including phosphodiesterase-5 inhibitors, guanylate cyclase stimulators and activators, share the feature that their action is either endothelial-mediated or substitutes for endothelial pathways, in particular the nitric oxide-cyclic guanosine monophosphate pathway, thereby influencing homeostatic balances in virtually each organ system in a pleiotropic fashion. Unfortunately, recent clinical trials with some of these drugs have shown disappointing results, at least in the setting of HF with a preserved ejection fraction. This suggests that their clinical use may require approaches that diverge from traditional pharmacological approaches, the latter often titrated on the effects of drugs on haemodynamic parameters or single biomarkers. In this paper we preconize that HF drugs with an endothelial profile should be applied conform to principles of endothelial physiology and systems pharmacology. This type of drug therapy should be viewed as a systems physio-pharmacological intervention and its clinical use accustomed to systems pharmacological principles, comparable to the systemic endothelial-mediated benefits induced by exercise training in HF. We will review the actions of these drugs and define criteria to which trials with these drugs should comply in order to increase chances of success.