| Summary: | 碩士 === 國立屏東科技大學 === 生物科技系所 === 104 === High-fat and imbalanced diets have led to a significant increase in obesity in modern populations. Statistics compiled by the Noncommunicable Diseases Risk Factor Collaboration (NCD-RisC) indicate that the proportion of obese individuals in the global population has increased from 9.6% in 1975 to 25.7% in 2014, among which 14.9% are female. Due to inherent differences in fat storage and metabolism, the issue of obesity is much more severe in women than in men. Obesity is a risk factor of a number of diseases and leads to vascular diseases. A previous study in our laboratory linked obesity to differences in oxidative stress in different vascular beds. The growing obese population is also increasing the burden on society and medical care systems. Thus, preventing obesity and reducing the risks that obesity incurs are crucial issues, the solutions to which include exercise and changing one’s lifestyle, particularly one’s dietary habits. Many studies have proven that moderately reducing calorie intake facilitates weight management and reduces free radicals as well as oxidative stress, which in turn slow down aging and even extends life spans. In view of the above, this study investigated whether differences in sensitivity exist in the functional disorders of different aortic vascular beds
caused by high-fat diets and whether calorie restriction (CR) can improve the functions of damaged blood vessels via oxidative stress reduction.
In this study, we used 6-week-old female Wistar rats and randomly divided them into three groups: normal diet group (ND group), high-fat diet group (HFD group), and high-fat diet with calorie restriction group (HFD+CR group). High-fat diet induced body weight percentage in HFD related groups. When high-fat diet rat body weight higher 30% than ND group defined obese rat models. Maintain 10 weeks. Obese rats were randomly divided into HFD group and HFD+CR group. HFD group remain treated with high-fat diet. HFD+CR group was treated with normal diet and 40% calorie restriction. Until reduced the weight. And close ND group. Maintain 10 weeks. We also collect blood to further diagnose the level of triglyceride (TG) and total cholesterol (TC). At the end of study, we sacrificed the rats to isolate the thoracic aorta and abdominal aorta for vascular function assay. Potassium chloride (KCl; L-type voltage-gated calcium channel agonist) and phenylephrine (PE; α1-adrenergic receptor agonist) are used to evaluate the vascular smooth muscle contractile response whereas acetylcholine (ACh; NO-cyclic GMP pass way stimulator) and sodium nitroprusside (SNP; NO donor) are used to evaluate vasorelaxation reaction. Nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor is used to evaluate the endothelium-dependent basal NO release. At the same time, we used lucigenin-based chemiluminescence assay to determine various tissues basal reactive oxygen species (bROS) and the NADPH-related oxidase activity.
Experimental results show that：(1)HFD group have an average body weight of 537.7±20.4g, which was significantly higher than ND group 356.9±5.2g. The body weight of HFD+CR group reduced to 316.8±2g, which was significantly lower than HFD group.(2) The BMI of HFD group was 0.97±0.02 g/cm2, significantly higher than ND group 0.73±0.02 g/cm2, and the BMI of HFD+CR group is 0.59±0.01 g/cm2 , which was significantly lower than HFD group. (3)The TG level of HFD group (165.4±41.7 mg/dL) was significantly higher than ND group (51.2±6.2 mg/dL), and HFD group (51.7±7.7 mg/dL) was significantly reduce than HFD group. (4) But, the concentration of TC was similar between HFD (67.4±3.5 mg/dL) and ND (69.3±4.4 mg/dL) groups, and also similar with HFD+CR (68.2±3.3 mg/dL). (5)The KCl-mediated vasocontraction of thoracic aorta in HFD group and HFD+CR group was similar to ND group, and HFD+CR group was also similar with HFD group; The vasocontraction of abdominal aorta in HFD group was similar to ND group whereas HFD+CR group was significantly higher than HFD group in 30mM~90Mm. (6) The PE-mediated vasocontraction of thoracic aorta in HFD group was significantly lower than ND group in concentration of 3×10-8M~10-5M, whereas HFD+CR group was significantly higher than HFD group in concentration of 3×10-8M~10-5M; The vasocontraction of abdominal aorta in HFD group is similar to ND group, but HFD+CR group was significantly higher than HFD group in 3×10-8M~10-5M.
(7) The ACh-mediated endothelium-dependent vasorelaxation of thoracic aorta in HFD group was significantly lower than ND group in concentration of 3×10-8M~10-5M, whereas HFD+CR group was similar to HFD group; abdominal aorta vasodilation of HFD group was significantly lower than ND group in 10-7M~10-5M, HFD+CR group was similar with HFD group. (8) The SNP-mediated endothelium-independent vasorelaxation of thoracic aorta in HFD group was similar to ND group, whereas HFD+CR group was similar to HFD group; this phenomenon was also observed in abdominal aorta between HFD group and ND group, HFD+CR group and HFD group. (9) The bNO released by thoracic aorta in HFD group was similar to ND group, but HFD+CR group was significantly lower with compared to HFD group; bNO released by abdominal aorta in HFD group was similar to ND group, but HFD+CR group was significantly lower than HFD group. (10) The smooth muscle of thoracic aorta vascular in HFD group was 231.30±7.29μm, which was significantly higher than ND group 204.00±8.06μm, whereas HFD+CR group 200.0±7.07μm was significantly lower than HFD group. Abdominal aorta vascular wall of HFD group was 175.00±3.99μm, which was significantly higher than ND group 156.30±7.30μm. However, HFD+CR group 170.00±9.05μm was similar to HFD group. (11) The bROS of thoracic aorta, abdominal aorta, adipose tissue and small intestine released in HFD group were similar with ND group. However, in HFD+CR group, the bROS released by thoracic aorta and abdominal aorta were significantly higher than HFD group. (12) The NADPH-related oxidase activity in thoracic aorta and abdominal aorta was similar in both HFD group and ND group. The activity of adipose tissue and small intestine in HFD group was significantly higher than ND group; HFD+CR group thoracic aorta, adipose and small intestine were significantly lower than HFD group, but abdominal aorta was higher than HFD group. The aforementioned results revealed that a high-fat diet caused vascular dysfunctions in the thoracic aorta (e.g., dysfunction of the α1-adrenergic receptor in the vascular smooth muscle, dysfunction of endothelium-dependent relaxation, and vascular smooth muscle proliferation) and in the abdominal aorta (e.g., dysfunction of endothelium-dependent relaxation and vascular smooth muscle proliferation). However, a caloric restriction approach was administer to successfully inverse the phenomena regarding the dysfunction of the α1-adrenergic receptor in the vascular smooth muscle as well as vascular smooth muscle proliferation, both of which were caused by a high-fat diet; nevertheless, damages in the abdominal aorta were not reversed. The caloric restriction also altered the increased NADPH oxidase activity in fat and intestinal tissues. Therefore, we recommend that obese patients in the high-risk group for cardiovascular disease receive regular follow-up examinations of the vascular function in their thoracic aorta.
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