ABC | Volume 110, Nº6, June 2018

Original Article Oishi et al Endothelial dysfunction and blood pressure in rats Arq Bras Cardiol. 2018; 110(6):558-567 Table 2 – Quantitative values obtained from morphometrical analysis of thoracic aorta thickness from control group (CT, n = 7) and high-fat group (HFD, n = 7) rats. Results are expressed as means ± SD. * P < 0.05, compared with CT group; + p < 0.05, within-group comparison (0 vs . 6, 6 vs . 12, 12 vs . 18, 18 vs . 24 weeks) Weeks Media Thickness (µm) Internal diameter (ID) (µm) Media:lumen ratio CT HFD CT HFD CT HFD 0 157.99 ± 7.18 157.88 ± 4.75 2830.64 ± 75.20 2832.64 ± 75.98 0.056 ± 0.00 0.056 ± 0.01 6 163.51 ± 7.51 163.64 ± 11.98 2967.21 ± 177.85+ 2919.31 ± 145.46 0.054 ± 0.00 0.056 ± 0.00 12 162.82 ± 6.67 164.64 ± 9.64 2976.80 ± 167.73 2876.36 ± 99.89+ 0.055 ± 0.01 0.057 ± 0.00 18 161.65 ± 9.95 178.20 ± 5.26 *+ 2987.53 ± 156.18 2854.40 ± 133.40 0.054 ± 0.00 0.062 ± 0.00*+ 24 164.21 ± 9.51 181.96 ± 9.73 * 3045.25 ± 168.01 2835.53 ± 167.74* 0.054 ± 0.00 0.064 ± 0.01* significant. Chen et al. 36 found that the high‑fat diet induced the increase in media thickness after 9 weeks. Our findings are in good agreement with these reports. High-fat diet can also induce vascular pathogenesis, including effects on the aorta, leading to changes in vascular structure. Clinical and experimental studies have shown that increased body mass index is often associated with stiffening and increased arterial wall thickness. 37 These alterations found in this study are important predictors of increased cardiovascular mortality. Previous studies in animals suggested that hypertension is associated with an increased formation of reactive oxygen species (ROS) from all layers of the vascular wall. 38 In agreement with these results, our findings showed an increase in lipid peroxidation (used as a marker of oxidative stress) in aortic rings at the same time that SBP increased, starting at 12 weeks. Moreover, Kobayasi et al. 30 found a reduced antioxidant activity, increased local vascular inflammation and impaired endothelium-dependent relaxation in mice fed on a high fat diet at 16 weeks. The release of IL-6, mainly from abdominal adipocyte sources might have a pivotal role in the relationship between oxidative stress and endothelial dysfunction. IL-6 and TNF- α contribute to CRP elevation, a marker of low-grade inflammatory state, and also have a close relationship with endothelial dysfunction. 23 As mentioned earlier, obesity is commonly associated with oxidative stress, 39 which is able to modify vascular tonus by impeding NO bioavailability and/or signaling. 38 We have observed that 6 weeks of high-fat diet decreased NO circulating levels without significant effects on aortic lipid peroxidation at this point of obesity progression. Thus, these results suggest that the decrease in circulating NO levels precedes the increase in oxidative stress. During the oxidative stress state, excessive production of ROS reduces the bioactivity of NO due to its rapid oxidative inactivation by the ROS superoxide (O 2 − ). 38 According to Victor et al., 40 while visceral fat stores expand, adipocytes generate increasing levels of ROS. In the present study, the high-fat diet induced the accumulation of abdominal fat that could trigger lipid peroxidation in the aorta at 12 weeks, which persists up to 24 weeks. One limitation of this study was the fact that visceral fat mass was evaluated by dissection of adipose tissue. Dual-energy X-ray absorptiometry (DXA), the gold standard method for assessment of body fat mass, would provide more comprehensive data of body composition; but, unfortunately, the method could not be performed in this study. Our data suggest that even at early stages of development, obesity (6 weeks) can trigger chronic inflammation and impairment of endothelial function. This impairment appears most closely related to inflammatory cytokines and expansion of VAT. Conclusion In conclusion, development of obesity first led to a reduction of endothelial function, which continued to decline over the weeks, and to systemic inflammation, followed by an increase in blood pressure, lipid peroxidation and changes in aortic structure. Our work is relevant in showing the relationship of obesity with chronic inflammation, endothelial dysfunction and hypertension. Despite many studies in this area, the results we found are a further step towards to the development of therapeutic strategies to prevent these abnormalities. Author contributions Conception and design of the research and Obtaining financing: Oishi JC, Duarte ACGO, Rodrigues GJ; Acquisition of data: Oishi JC, Castro CA, Silva KA, Fabricio V, Cárnio EC, Duarte ACGO, Rodrigues GJ; Analysis and interpretation of the data: Oishi JC, Castro CA, Silva KA, Fabricio V, Cárnio EC, Phillips SA, Duarte ACGO, Rodrigues GJ; Statistical analysis: Oishi JC; Writing of the manuscript: Oishi JC, Castro CA, Silva KA, Fabricio V, Duarte ACGO, Rodrigues GJ; Critical revision of the manuscript for intellectual content: Oishi JC, Castro CA, Silva KA, Cárnio EC, Phillips SA, Duarte ACGO, Rodrigues GJ. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding This study was funded by CNPq and partially funded by FAPESP. 565