The Effect Of SRAGE Gene Expression On Metabolic Disturbance, Inflammation Status And Organ Injury In High-fat Diet Rats

Background & objectivesHigh fat diet is the characteristic of current food intake style, and it accelerates the invasion of arthrosclerosis, dyslipideamia and insulin resistance. Recent studies showed that chronic inflammation is related to insulin resistance closely. Modern food-style is characterized by high fat and high calorie. High fat food cooked in high temperature contains high level of advanced glycation end products(AGE) or glycotoxin. Interaction of AGE with their receptor RAGE can induce oxidative stress (through NADPH and NF-κB pathway and activation of macrophages) and cause proinflammatory cytokine production. Once taken high fat diet can increase AGE in circulation, induce oxidative stress in body.We aimed to observe the influence of ectopic expression of sRAGE on oxidative stress, lipid metabolism, insulin actin, liver, kidney and aortic intima of rats that fed with high-fat diet.Methods1. Animal experiment: 20 SD Rats (6 weeks old, 150-160g weight), were fed with high fat diet for 8 weeks and randomly divided into two groups: High fat sRAGE group, high fat control group. In high-fat sRAGE group rats were given plasmid pLNCX₂-sRAGE intramuscularly. In high fat control group rats were given with plasmid pLNCX₂ intramuscularly. Plasmid was injected in the 9st, 12rd, 15th week and executed in the 17th week. 8 rats were simultaneously raised with normal chew for 16 weeks and killed at the same time (designed as normal diet control group). For the method of plasmid injection, plasmids were injected into quadriceps muscle of thigh bilaterally (300μg each) after surgical exposure. In five minutesafter injection electric pulses (voltage 200V/cm,pulse 9 and frequency 1Hz) were applied by two stainless steel needle electrodes placed about 20 mm apart in parallel of the injection area.2. 500-1000μl of blood sample was collected from tail bleeding before and every week after injection, serum malondialdehyde (MDA) levels and superoxide dismutatse (SOD) activities were detected with commercial kits. Before executed, fasting plasma glucose and body weight were measured. After executed, liver, kidneys and aorta were incised, serum was collected for measurement of insulin, triglyceride, total cholesterol, TNF-α, high sensitive CRP, SOD, MDA. Liver, kidney and thoracic aortic were stained with HE. Kidney TGF-1 and liver NF-B expression were detected immunohistochemically.Results1. High-fat diet increased weight, serum insulin, triglyceride, total cholesterol, high sensitive CRP and TNF-αcompared with normal chew rats. There was no difference in fasting glycemia. sRAGE gene injection decreased TNF-α, insulin significantly and had no effects on body weight and high sensitive CRP, increased triglyceride significantly compared with high fat control rats. Interestingly sRAGE injection increased triglycerides level significantly compared to high fat control and normal chew rats.2. High fat diet increased MDA level and decreased SOD activity compare to normal chew rats. One week after injection with sRAGE gene with high fat diet, MDA level began to decrease, and lasted for 3 weeks, increased on the third week, repeated injections had the same effect. SOD activity began increase after injection of sRAGE gene, but only became significant on the third week. Repeated injection resulted in continued increase in SOD activity until the level of normal chew rat was reached. No such effects were observed in high fat control rats.3. On HE slide no apparent atherosclerosis was observed in any of the different group of rats. However, the completeness of aortic wall in high fat sRAGE rat was more contact than high fat control rats. Glomerular mesangium and extracellular matrix volume increased, the TGF-β1 expression was high in high-fat control group compared to high fat sRAGE rats, but those of high fat sRAGE rats still increased compared to normalchew rats. It was found the liver NF-κB expression in both rats of high-fat diet increased, but sRAGE injection ameliorated significantly the liver NF-κB expression compared to high fat controls.ConclusionsHigh-fat diet increases oxidative stress level in rat, decreases antioxidant capacity. sRAGE gene injection could reduce the level of oxidative stress, enhance the antioxidant capacity.High-fat meal causes insulin resistance and cholesterol levels, and induces early abnormalities in aortic wall, liver and kidney. sRAGE gene injection can ameliorate all those changes to some extent.In conclusion, sRAGE gene injection might be used in prevention of high fat diet induced metabolic abnormality and organic injuries.