The Mechanism And Relationship Of Retinol Binding Protein 4 And Metabolism Syndrome

Objective:To study the relationship of retinol binding protein 4 and metabolism syndrome, this study illuminated the relationships of serum RBP4, body fat, glucose and lipid metabolism,and liver function,and the influence of serum RBP4 in coronary artery disease and type 2 diabetes. To discover new treatment of metabolism syndrome, we hypothesized statins could regulation the level of RBP4.Methods:Serum RBP4 in coronary artery disease and type 2 diabetes were measured by ELISA.We assayed relationships of serum RBP4, body fat, glucose and lipid metabolism,and liver function The rat models with metabolism syndrome induced by high fat and high salt diets were successfully founded. We employed the method of RT-PCR to relatively quantify RBP4 and adiponectin mRNA levels in the epididymal adipose, liver and heart.and we also employed the method of Western-blot to quantify RBP4 level in the epididymal adipose, liver and heart. Serum RBP4,IL-6and MDAwere measured by ELISA. After the treatment of 3T3-L1 adipocytes with Simvastatin by different concentration and action time,we employed the method of RT-PCR to relatively quantify RBP4and adiponectin mRNA levels,and employed the method of Western-blot to quantify RBP4 level. IL-6and MDAwere measured by ELISA.Results:Serum RBP4 was elevated in coronary artery disease and type 2 diabetes, and it was positively correlated with WHR, TG and age. RBP4 level of rats with metabolism syndrome was obviously elevated in the epididymal adipose, liver and heart,and Serum RBP4,IL-6and MDAwere also elevated.e We employed the method of Western-blot and RT-PCR to quantify RBP4 level after the treatment of Simvastatin.Conclusion:RBP4 was related with the parameters about insulin resistance, not closely related with coronary artery disease.RBP4 was expressed elevatly in the rat models with metabolism syndrome,and implied that RBP4 could be a serum marker for identifying metabolic syndrome. Simvastatin was found sufficiently to suppress RBP4 expression.in 3T3-L1 adipocytes. More and more study supports the insulin resistance may be the core of the metabolism syndrome. Retinol-binding protein-4 (RBP4) is an hepatic protein functioning as the principal transporter for retinol (vitamin A) in circulation.Recently, Yang et al.identified RBP4 as an adipokine whose elevation contributes to the pathogenesis of insulin resistance in mice. Serum RBP4 levels have been found to be positively associated with triglyceride accumulation in erum, visceral adipose tissue, the liver, and even skeletal muscle. Human studies suggest that RBP4 maybe involved in the development of dyslipidemia and cardiovascular. However, how RPB4 expression is regulated remains largely unknown. In the present study, we investigated the relationship of RPB4 and metabolism syndrome.Part 1 The clinical study on patients without coronary artery disease,patients only with with coronary artery disease, patients with coronary artery disease and type 2 diabetes, and their serum retinol bindingprotein 4Objective:Yang et al identified a new protein associated with insulin resistance-retinol binding protein(RBP4). serum RBP4 was confirmted elevated in obesity and type 2 diabetes. RBP4 was mainly expressed and secreted by liver, adipose, muscle, kidney and myocardial tissues, and therelationship of serum RBP4 and heart was still controversial. In short, the human study on RBP4 was limited and its pathophysiological roles in human should be further explored. By the clinical research, this study illuminated that:1. The change of serum RBP4 in patients without coronary artery disease, patients only with coronary artery disease, patients with both coronary artery disease and type 2 diabetes2. The relationships of serum RBP4, body fat, glucose and lipid metabolism, and liver function.Subjects and methods:120 enrolled subjects, aged from40 to80, after PCI,were divided into 3 groups:normal control(NC) (n=30), coronary artery disease(CHD) (n=45), both coronary artery disease and type 2 diabetes mellitus (CHD+T2DM) (n=45), We measured body mass index (BMI), waist-to-hip ratio (WHR). We assayed plasma glucose (FPG), Glycated Hemoglobin Alc (HbAlc), alanine aminotransferase(ALT), total cholesterol (TC), triglycerides (TG), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C),RBP4 in fasting state.Results:1. After adjustment of age, men had higher serum RBP4 level than women [(7.19±0.48 vs.6.56±0.50) ug/L, P<0.05]。After age and sex adjusted, serum RBP4 levels inCHD+T2DM were significantly elevated compared to the NC group and CHD group [(9.39±0.92) ug/L vs. (7.493±0.61,6.67±0.93) ug/L,均P <0.05].2. There is no significant difference between NC and CHD [(7.493±0.62 vs 6.7±0.93) ug/L, P>0.05]3. Simple correlation analyses showed that serum RBP4 was correlated with BMI, WHR and TG,it had no significant correlation with ALT and AST. Multiple linear regression analyses reveal that WHR, TG and age.Part 1 conclusion:1. Serum RBP4 was elevated in patients with coronary artery disease and type 2 diabetes, not patients with only coronary artery disease.2. Serum RBP4 was positively correlated with WHR, TG and age.3. It demonstrated that RBP4 was related with the parameters about insulin resistance,and implied that RBP4 could be a serum marker for identifying metabolic syndrome.4. The coronary artery disease and T2DM patients in our study had higher ALT and AST which inferred that there would be lipid accumulating in their livers to some extent,whereas we did not find the facts that RBP4 was associated with ALT and AST inthese groups.Part 2 The expression levels of retinol binding protein 4 in serum, liver, myocardial tissues and adipose on rats with metabolism syndromeObjective:RBP4 was produced in many tissues.This study explored the RBP4 levels in various tissues on rats with metabolism syndrome fed on high fat and high salt diets.Materials and methods:25 SD male rats were randomed at 2 months of age into 2 groups:one group received normal chow(NC), the others high-fat feeding(HF) group respectively, the high fat diet supplied 49% of the calories as fat for establishing metabolic syndrome model. Body weight, blood pressure, heart rate, FBG, and FINS were detected every month, plasma lipid, free fatty acid(FFA) were examined every two months, euglycemic hyperinsulinemic clamp and glucose tolerance test were performed at 32 week. Heart, liver and epididymal adipose was isolated for histopathologic, morphometric examination and the ratio of heart weight to body weight. We employed the method of RT-PCR to relatively quantify RBP4and AdiponectinmRNA levels in the liver.,epididymal adipose and myocardial tissues. And we employed the method of western-blot to relatively quantify RBP4 in theliver.,epididymal adipose and myocardial tissue. Serum RBP4,IL-6and MDAwere measured by ELISA.Results:1. MS groups had impaired glucose and insulin tolerance, and lipid disorders. They also had higher fasting glucose and insulin levels, larger fat to body weight ratio, and more fat accumulation in liver than those in NC group Serum RBP4 of rats with metabolism syndrome was elevated in NC group. [(1.74±0.13 vs 0.96±0.38)ug/L, P<0.05]2. RBP4 mRNA levels of liver and epididymal adipose in MS group was higher than those in NC group, RBP4 mRNA levels of heart was almost the same of those in NC group.3.IL-6 and MDA levels in MS group was higher than those in NC group. IL-6[(0.71±0.07vs 0.48±0.03)ng/L, P< 0.05],MDA[(5.37±2.95vs 0.77±0.30)nmol/mgprot, P<0.01],Part 2 conclusion:1. The rat models with metabolism syndrome induced by high fat and high salt diets were successfully founded.2. RBP4 was closely related with glucose and lipid metabolism,and insulin resistance, which indicated that RBP4 might be a biological marker for metabolic syndrome.3. Metabolism syndrome coule stimulate the expression of immunity cytokines and the production of oxidative stress.Part 3 The influence of Simvastatin on the expression of RBP4 in 3T3-L1 adipocytes.Objective:The discovery of the function of RBP4 provided the treatment target on insulin resistance and diabetes. Simvastatin had effects of losing weight and increasing insulin sensitivity. We hypothesized Simvastatin coule affect the expression levels of RPB4 in 3T3-L1 adipocytes.Materials and methods:After 90% of the 3T3-Llcells had acquired the adipose phenotype, Simvastatin was dissolved in DMSO and added into fresh medium on day 7, with the doses of 0.1,1 uM。We employed the method of RT-PCR to assay adipocyte RBP4mRNA,AdiponectinmRNA and PPARγmRNA level at 24 h and 48h after addition of Simvastatin.We also employed the method of western-blot to relatively quantify RBP4 in different time after the addition of Simvastatin. IL-6and MDAwere measured by ELISA.Results:1 Simvastatin downregulated RBP4 mRNA expression in 3T3-L1 adipocytes, and upregulated adiponectin mRNA and PPARyexpression.2. Simvastatin downregulated IL-6 expression IL-6 (35.08±2.30,30.85±2.82, 25.72±5.64,21.59±4.71,21.37±3.89) ng/L, also downregulated MDA expression (0.39±0.01,0.29±0.01,0.26±0.02,0.24±0.02,0.21±0.01) nmol/mgprot.Part 3 conclusion:1. Simvastatin downregulated RBP4 mRNA expression in 3T3-L1 adipocytes, which may contribute to insulin sensitization.2. Simvastatin repressed immunity cytokines and oxidative stress.