| Objective:The incidence of diabetes and atherosclerosis increase in alarming and significantly affects the quality and life expectancy in current society. The cause (s) and mechanism remain largely unknown, and are thought to be polygenic in combination with a large spectrum of obesogenic environment. Food and beverages rich in energy, fat, sugar and lack of physical activity are now commonly found in modern societies. Such diets have long been recognized as major causes to the obesogenic environment in humans. The interactions of these diets with the physiological systems are thus an area of interest. The overall viewpoint of high-fat is that the more the caloric content derives from dietary fat, the heavier the body weight and less glucose-tolerant the animals become. It is also noted recently that part of insulin-resistant subjects are not obese. Ruderman introduced a new term "metabolically obese, normal-weight" (MONW) in 1981. He suggested that individuals exist who are not obese on the basis of height and weight, but metabolically abnormal similar to obese subjects. In our study, we aimed to study the inflammatory and oxidative stress state in a MONW model Sprague-Dawley rat made through high-fat and high-sucrose diet.Methods:1. Animal experiment:A total of 60 male SD rats,4 weeks old, weighing 60g-70g upon their arrival, were kept at appropriate temperature and humidity under a 12h ligh lark cycle and had ad libitum access to standard food and tap water for 4 weeks. And then, rats were randomly divided into two groups:(1)Standard Diet Group:20 control rats were fed a standard pelleted diet, (2)High-fat and High-sucrose Diet Group:40 rats received a pelleted high-fat and high-sucrose diet. Body weights were measured every week from the 8th week. In the morning of the 29th week, blood samples were collected from angular veins and centrifuged, and sera were kept in-80℃until analyzed. There were 6 rats dead during the experiment, so only 54 rats entered the final statistics,18 rats in the standard diet group,36 rats in the high-fat and high-sucrose diet group.2. To study inflammatory condition, we analyzed plasma high sensitive-C reactive protein (hs-CRP), monocyte chemoattractant protein-1 (MCP-1) and plasminogen activator inhibitor-1(PAI-1) in rats with commercially available ELISA kits for rats.3. In order to observe the influences of high-fat and high-sucrose diet on the state of oxidative stress in rats, serum malondialdehyde (MDA) levels and superoxide dismutase (SOD) activities were detected commercial methods.Results:1. High-fat and high-sucrose diet group did not have a significantly modified gain in body mass over the experiment compared with control group (189.19±59.38g vs 174.94±80.20g, t=-0.738, P=0.464). The final weights were similar between groups of the standard diet and high-fat and high-sucrose diet (447.89±22.77g vs 469.83±13.62g,t=-0.875, P=0.386).2. The level of plasma hs-CRP (1503.63±895.63ng/ml vs 896.99±506.72ng/ml, t=-3.173, P=0.003), MCP-1 (212.86±60.31pg/ml vs 162.00±38.63pg/ml, t=-3.252, P=0.002) and PAI-1 (10.31±2.33ng/ml vs 7.64±1.71ng/ml,t=-4.312, P=0.000) was higher in the high-fat and high-sucrose diet group and had significant statistical difference with the control group.3. The level of serum MDA (6.37±1.08nmol/L vs 5.68±0.75nmol/L, t=-2.425, P=0.019) increased and the level of SOD (334.40±61.35U/ml vs 383.98±52.74U/ml, t=2.927, P=0.005) was noted to decreased in the high-fat and high-sucrose diet group.Conclusion:The present study confirmed the usefulness of diet enriched in fat and sucrose to produce metabolic abnormalities mimicking the metabolically obese normal-weight state. This metabolically obese normal-weight rat model exhibited a chronic low level inflammatory state and oxidative stress.
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