High-Fat Diet-Induced Obesity Model Does Not Promote Endothelial Dysfunction via Increasing Leptin/Akt/eNOS Signaling

Experimental studies show that the unsaturated high-fat diet-induced obesity promotes vascular alterations characterized by improving the endothelial L-arginine/Nitric Oxide (NO) pathway. Leptin seems to be involved in this process, promoting vasodilation via increasing NO bioavailability. The aim of this study was to test the hypothesis that unsaturated high-fat diet-induced obesity does not generate endothelial dysfunction via increasing the vascular leptin/Akt/eNOS signaling. Thirty-day-old male Wistar rats were randomized into two groups: control (C) and obese (Ob). Group C was fed a standard diet, while group Ob was fed an unsaturated high-fat diet for 27 weeks. Adiposity, hormonal and biochemical parameters, and systolic blood pressure were observed. Concentration response curves were performed for leptin or acetylcholine in the presence or absence of Akt and NOS inhibitor. Our results showed that an unsaturated high-fat diet promoted a greater feed efficiency (FE), elevation of body weight and body fat (BF), and an adiposity index, characterizing a model of obesity. However, comorbidities frequently associated with experimental obesity were not visualized, such as glucose intolerance, dyslipidemia and hypertension. The evaluation of the endothelium-dependent relaxation with acetylcholine showed no differences between the C and Ob rats. After NOS inhibition, the response was completely abolished in the Ob group, but not in the C group. Furthermore, Akt inhibition completely blunted vascular relaxation in the C group, but not in the Ob group, which was more sensitive to leptin-induced vascular relaxation. L-NAME incubation abolished the relaxation in both groups at the same level. Although Akt inhibitor pre-incubation reduced the leptin response, group C was more sensitive to its effect. In conclusion, the high-unsaturated fat diet-induced obesity improved the vascular reactivity to leptin and does not generate endothelial dysfunction, possibly by the increase in the vascular sensitivity to leptin and increasing NO bioavailability. Moreover, our results suggest that the increase in NO production occurs through the increase in NOS activation by leptin and is partially mediated by the Akt pathway

Alterações cardiovasculares e desenvolvimento de obesidade em animais submetidos à dieta hipercalórica e estresse crônico

O estresse é entendido como um processo complexo e multidimensional, cuja resposta adaptativa é vista como um processo dinâmico no qual mecanismos fisiológicos do indivíduo mudam continuamente para ajustarem-se ao ambiente. Esse fator pode contribuir para alterações na função cardíaca, associada, ou não, ao trânsito de Ca2+ e a alteração vascular devido ao aumento da atividade da via l-arginina/óxido nítrico. A obesidade é uma doença complexa, caracterizada pelo acúmulo excessivo de tecido adiposo, levando a disfunções cardíacas e vasculares, que podem estar envolvidas com alteração no fluxo de Ca2+ e comprometimento da resposta vasodilatadora. O estresse é considerado um fator ambiental, portanto, responsável por alterações no balanço energético e peso corpóreo, uma vez que o peso corpóreo é a interação entre fatores genéticos e ambientais. Devido à escassez de estudos que avaliam o estresse crônico e dieta hipercalórica nas alterações cardiovasculares, e considerando a hipótese de que esta associação é capaz de atenuar o desenvolvimento da obesidade e intensificar as alterações cardiovasculares, o objetivo do presente trabalho foi confirmar essa hipótese em animais submetidos à dieta hipercalórica e ao estresse crônico. Ratos machos Wistar, divididos em quatro grupos: DN: dieta normocalórica; DN/Es: dieta normocalórica e submetidos ao estresse crônico; DH: dieta hipercalórica; DH/Es: dieta hipercalórica e submetidos ao estresse crônico, foram avaliados quanto aos perfis nutricionais, metabólicos e a remodelação cardiovascular. Os dados demonstraram que o estresse crônico impediu o desenvolvimento da obesidade, e em oposição à hipótese, o estresse crônico melhorou a função cardíaca e vascular, independente do tipo de dieta utilizadaThe stress is a complex and multidimensional process, the adaptive response is a dynamic process, in which individual physiologic mechanisms change to adjust to the environment, that causes alteration in the cardiac function, involved, or not, with Ca2+ flux and vascular alterations due to the increase of the l-arginine/nitric oxide pathway activity. The obesity is a complex disease, characterized by the excess of adipose tissue that causes cardiac and vascular dysfunction, involved with Ca2+ flux alterations and injury the vasodilating response. The stress is considered an environmental factor, therefore, it is responsible for the energetic balance alterations and weight gain, once the body weight is an interaction between genetic and environmental factors. There are few studies about chronic stress associated with the hypercaloric diet that evaluate the cardiovascular alterations, and considering the idea that this association can decrease the obesity development and increase the cardiovascular alterations, the aim of this research was evaluate the cardiovascular alterations and the obesity development in animals submitted to the hypercaloric diet and chronic stress. Male Wistar rats were separated into four groups: DN: standard diet; DN/Es: standard diet and chronic stress; DH: hypercaloric diet; DH/Es: hypercaloric diet and chronic stress were evaluated in relation to the nutritional and metabolic profile and cardiovascular remodellating. The data show that the chronic stress inhibited the obesity development, and different of the initial idea, the chronic stress improved the cardiac and vascular function, in both dietsConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

A possible increase of activity of endothelial l-arginine/nitric oxide pathway in aortas of diet-induced obesity rats

The obesity is associated with cardiovascular disorders. The aim of present purpose was test the hypothesis that the diet-induced obesity is able to generate a vascular adaptive response in aortic rings; this response could be mediated by NO pathway. The present work used Thirty-day-old male Wistar rats (70-100 g) were distributed into two groups: control (C) and obese (Ob). The obesity was induced through of hypercaloric diet during 15 weeks, the vascular response was assessed through different protocols of vascular reactivity studies and characterization of obesity was also evaluated. The obesity was characterized for decreased of glucose tolerance, hyperinsulinemia, hyperleptinemia and rise of adiposity index. In relation to vascular alterations, the diet-induced obesity generated decreased maximal response to noradrenaline, response which was abolished with presence of L-NAME, and increased relaxing to acetylcholine. There was no difference between groups in the blood pressure. The vascular responses observed in present work might have occurred with the aim of decrease of cardiovascular risk linked with obesity pathology; these findings suggest that obesity can be considered a paradoxical disorder.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Vitamin D Induces Increased Systolic Arterial Pressure via Vascular Reactivity and Mechanical Properties

Background/Aims: The aim of this study was to evaluate whether supplementation of high doses of cholecalciferol for two months in normotensive rats results in increased systolic arterial pressure and which are the mechanisms involved. Specifically, this study assesses the potential effect on cardiac output as well as the changes in aortic structure and functional properties.Methods: Male Wistar rats were divided into three groups: 1) Control group (C, n = 20), with no supplementation of vitamin D, 2) VD3 (n = 19), supplemented with 3,000 IU vitamin D/kg of chow; 3) VD10 (n = 21), supplemented with 10,000 IU vitamin D/kg of chow. After two months, echocardiographic analyses, measurements of systolic arterial pressure (SAP), vascular reactivity, reactive oxygen species (ROS) generation, mechanical properties, histological analysis and metalloproteinase-2 and -9 activity were performed.Results: SAP was higher in VD3 and VD10 than in C rats (p = 0.001). Echocardiographic variables were not different among groups. Responses to phenylephrine in endothelium-denuded aortas was higher in VD3 compared to the C group (p = 0.041). Vascular relaxation induced by acetylcholine (p = 0.023) and sodium nitroprusside (p = 0.005) was impaired in both supplemented groups compared to the C group and apocynin treatment reversed impaired vasodilation. Collagen volume fraction (<0.001) and MMP-2 activity (p = 0.025) was higher in VD10 group compared to the VD3 group. Elastin volume fraction was lower in VD10 than in C and yield point was lower in VD3 than in C.Conclusion: Our findings support the view that vitamin D supplementation increases arterial pressure in normotensive rats and this is associated with structural and functional vascular changes, modulated by NADPH oxidase, nitric oxide, and extracellular matrix components.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Data on the vascular mechanical properties and Metalloproteinase-2 and -9 activities by gelatin zimography.

<p>Data are expressed as mean ± standard deviation of mean or median with 25 and 75 percentiles, numbers in parentheses indicate the numbers of animals included in each experimental group. C: control group (no supplementation with vitamin D); VD3: supplemented with 3,000 IU VD/kg of chow; VD10: supplemented with 10,000 IU VD/kg of chow. * p<0.05 versus control group; # p<0.05 versus VD3 group.</p

Summary of pD₂ and Maximal Response values.

<p>Data are expressed as mean ± standard deviation of mean or median with 25 and 75 percentiles; numbers in parentheses indicate the numbers of animals included in each experimental group. C: control group (no supplementation with vitamin D); VD3: supplemented with 3,000 IU VD/kg of chow; VD10: supplemented with 10,000 IU VD/kg of chow. pD₂: indicates -log EC₅₀ (the concentration of agonist producing half-maximal response); Phe: phenylephrine; E⁺: endothelium-intact vessels; E⁻: endothelium-denuded vessels; Ach: acetylcholine; SNP: sodium nitroprusside. * p<0.05 versus control group.</p

Systolic arterial pressure, body weight and echocardiographic data.

<p>Data are expressed as mean ± standard deviation of mean or median with 25 and 75 percentiles. n: number of rats. C: control group (no supplementation with vitamin D); VD3: supplemented with 3,000 IU VD/kg of chow; VD10: supplemented with 10,000 IU VD/kg of chow. BW: body weight; SAP: Systolic arterial pressure; HR: heart rate; CO: cardiac output; EF: ejection fraction; E: E wave; A: A wave; LA: left atrium; LVEDD: left ventricular (LV) end-diastolic diameter; LVM: left ventricular mass. * p<0.05 versus control group.</p

Elastin content in the aortic sections and fragmentation of elastic fibers in the VD10 group.

<p>Photographs of aortic samples (400×) stained by Calleja. C: control group (no supplementation with vitamin D); VD3: supplemented with 3,000 IU VD/kg of chow; VD10: supplemented with 10,000 IU VD/kg of chow.</p

Vitamin D and food ingestion, serum calcium and phosphorus and plasma 25 (OH) D₃.

<p>Data are expressed as mean ± standard deviation of mean or median with 25 and 75 percentiles, numbers in parentheses indicate the numbers of animals included in each experimental group. C: control group (no supplementation with vitamin D); VD3: supplemented with 3,000 IU VD/kg of chow; VD10: supplemented with 10,000 IU VD/kg of chow; 25 (OH) D₃: plasma 25-hydroxycholecalciferol; Ca: serum calcium; P: serum phosphorus. * p<0.05 versus control group; # p<0.05 versus VD3 group.</p