Obesity, Inflammation, and Exercise Training: Relative Contribution of iNOS and eNOS in the Modulation of Vascular Function in the Mouse Aorta

Abstract

Background: The understanding of obsesity-related vascular dysfunction remains controversial mainly because of the diseases associated with vascular injury. Exercise training is known to prevent vascular dysfunction. Using an obesity model without comorbidities, we aimed at investigating the underlying mechanism of vascular dysfunction and how exercise interferes with this process.Methods: High-sugar diet was used to induce obesity in mice. Exercise training was performed 5 days/week. Body weight, energy intake, and adipose tissues were assessed; blood metabolic and hormonal parameters were determined; and serum TNFα was measured. Blood pressure and heart rate were assessed by plethysmography. Changes in aortic isometric tension were recorded on myograph. Western blot was used to analyze protein expression. Nitric oxide (NO) was evaluated using fluorescence microscopy. Antisense oligodeoxynucleotides were used for inducible nitric oxide synthase isoform (iNOS) knockdown.Results: Body weight, fat mass, total cholesterol, low-density lipoprotein cholesterol fraction, insulin, and leptin were higher in the sedentary obese group (SD) than in the sedentary control animals (SS). Exercise training prevented these changes. No difference in glucose tolerance, insulin sensitivity, blood pressure, and heart rate was found. Decreased vascular relaxation and reduced endothelial nitric oxide synthase (eNOS) functioning in the SD group were prevented by exercise. Contractile response to phenylephrine was decreased in the aortas of the wild SD mice, compared with that of the SS group; however, no alteration was noted in the SD iNOS−/− animals. The decreased contractility was endothelium-dependent, and was reverted by iNOS inhibition or iNOS silencing. The aortas from the SD group showed increased basal NO production, serum TNFα, TNF receptor-1, and phospho-IκB. Exercise training attenuated iNOS-dependent reduction in contractile response in high-sugar diet–fed animals, decreased iNOS expression, and increased eNOS expression.Conclusion: Obesity caused endothelium dysfunction, TNFα, and iNOS pathway up-regulation, decreasing vascular contractility in the obese animals. Exercise training was an effective therapy to control iNOS-dependent NO production and to preserve endothelial function in obese individuals.

Anti‐contractile effects of perivascular adipose tissue in thoracic aorta from rats fed a high‐fat diet: role of aerobic exercise training

“…Previous studies have shown the ability of exercise training in reducing circulatory TNF‐α, IL‐6 and IL‐1β levels, in both laboratory animals and humans . In addition, exercise training was effective in reducing inflammatory markers iNOS, TNFR, and phosphorylated IkB‐α in aorta of obese mice . Here, we demonstrated for the first time that the exercise training reduced the iNOS protein expression in PVAT, associated with normalization of anti‐contractile effect of PVAT in the TR‐HF group.…”

“…Differently from constitutive NOS (nNOS and eNOS), iNOS is able to produce a huge amount of NO . Interestingly, mice fed a high‐sugar diet for 8 weeks also exhibited elevated iNOS expression in aorta and reduced contractile response to PHE, which was associated with higher NO levels in the vascular tissue . The aortic vasoconstrictor response was normalized by knocking down iNOS, suggesting an important role for iNOS in the vascular changes in response to the early phase of obesity.…”

Obesity Induces Artery-Specific Alterations: Evaluation of Vascular Function and Inflammatory and Smooth Muscle Phenotypic Markers

“…L-NIL is considered to be a relative selective iNOS inhibitor, presenting IC50 values of 5.9, 138, and 35  μ M for inhibition of recombinant human iNOS, eNOS, and nNOS isoforms, respectively [39]. Our results suggest that, in thoracic aorta of C57BL/6, L-NIL may inhibit other NOS isoforms in a lower concentration, despite the fact that other studies have found an in situ selective iNOS inhibition in this artery [38, 40]. However, a role of iNOS could be excluded in the reduction of noradrenaline-contraction of thoracic aorta in obese mice because the gene expression of iNOS was similar in control and obese mice.…”

Physical activity protects NLRP3 inflammasome-associated coronary vascular dysfunction in obese mice

“…Silva et al. () reported that treadmill exercise training reversed downregulation of eNOS protein expression in the aorta of high‐sugary diet‐induced obese mice. Together these results suggest that voluntary running can restore NO signaling in the coronary microcirculation of diet‐induced obese mice.…”

“…For example, Ito et al (2015) found that running exercise improved a reduced formation of nitrate/nitrite metabolites in renal cortex and outer medullar of diabetic Zucker rats. Silva et al (2016) reported that treadmill exercise training reversed downregulation of eNOS protein expression in the aorta of high-sugary diet-induced obese mice. Together these results suggest that voluntary running can restore NO signaling in the coronary microcirculation of diet-induced obese mice.…”