The Study On The Effects Of Angiotensin Ⅱ Receptor Blockers On The Proinflammatory Factors' Secretion And Metabolisms Of Glucose And Lipid Of The Adipose Tissue And The Adipocytes

The cluster of hypertension, diabetes mellitus, dyslipidemia and body obesity, collectively referred to as the metabolic syndrome, is a common cause of atherosclerotic cardiovascular diseases and one of the most serious threats to public health. Adipose tissue produces and secretes some proinflammatory factors. Dysregulated production of proinflammatory factors, such as tumor necrosis factor-α(TNFα), interleukin-1β(IL-1β) and iterleukin-6 (IL-6), is associated with the pathophysiology of obesity-related disorders.Patients with essential hypertension and obesity are at the increased risk of type 2 diabetes. Several recent clinical trials have suggested that blockade of the rennin-angiotensin system (RAS) may protect against the development of de-novo diabetes in 'at risk' patients. Evidences show that the RAS may have a direct role in the pathogenesis of diabetes. RAS components exist in the adipocyte, which makes the adipose tissue is the potential target of angiotensinâ…¡receptor blockers.In this context, the present study was designed to elucidate the effect of angiotensinâ…¡receptor blockers on the adipocytes in vivo and in vitro.Objective: To investigate the effect of angiotensinâ…¡type 1 receptor blockers on the proinflammatory factors' secretion and metabolisms of glucose and lipid of the the adipose tissue and adipocytes, and possible molecular mechanisms.Method: 1. in vivo study: 45 male Wistar rats were randomly divided into 3 groups: normal chow group (NC, n=15) fed with normal diet, high fat diet group (HF, n=15) fed with high fat diet, and high-fat diet with daily candesartan treatment group (HF+C, n=15) fed with high fat diet and given orally with candesartan 8 mg/kg per day. Body weight was measured weekly. Four weeks later, euglycemic-hyperinsulinemic clamp technique was performed to estimate the insulin sensitivity. After 12h fasting blood samples were collected from the abdominal aorta for measurement of the contents of blood glucose, and serum triglyceride (TG), total cholesterol (TC), LDL, HDL, and free fatty acid (FFA). Radioimmunoassay was used to detect the serum insulin. ELISA was used to mesure the level of the serum IL-1β, IL-6 and TNFα.2. in vitro study : 1) MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) was processed to determine the effects of various concentrations of Telmisartan (0.01ug/ml, 0.1ug/ml and 1ug/ml) on the proliferation of 3T3-L1 preadipocytes. 2) Various concentrations of Telmisartan and GW9662 (PPARγantagonist) were applied to interfere the early phase (12h and 24h) in the process of the induction of 3T3-L1 preadipocytes and oil red O staining were processed to determine the effect of telmisartan on the differentiation of 3T3-L1 preadipocytes. The expression of PPARγmRNA were obtained with quantitative real-time PCR (Q-PCR). 3) Various concentrations (0.01, 0.1, 1 and 10 ug/ml) of telmisartan were applied to interfere with the mature 3T3-L1 adipocytes. Free fatty acids,IL-6 and TNFαof cultured medium were evaluated. Oil red O staining was processed to determine the effects of telmisartan on the adipogenesis of 3T3-L1 adipocytes. ¹⁸F-FDG uptake levels were determined by cellular radioactivity measured after 25-min incubation. 4) The total RNA was isolated from the control group and the telmisartan group (0.1ug/mL) for hybridization experiment of the microarray. And the part of results was verified by Q-PCR.Results: 1. in vivo study: HF group was significantly higher than that of the HF+C goup (P<0.01). The epididymal and perirenal fat weights of the HF group were all significantly higher than those of the HF+C group and NC group (both P<0.01). The difference of the fasting blood glucose among the 3 groups was no significance (P>0.05). Serum levels of IL-6 and TNFαwere significantly decreased in the HF+C treated group, compared with the HF group [IL-6 54.03±13.32 pg/ml vs 85.35±16.93pg/ml (P <0.05); TNFα33.18±5.51 pg/ml vs 48.20±7.87 pg/ml (P<0.05)]. IL-1βlevel was no significantely different between the HF and HFD+C [41.04±10.12 pg/ml vs 29.72±7.66 pg/ml (P>0.05)]. The glucose infusion rate (GIR) of HF+C group was significantly higher than that of the HF group [22±5 mmol/L vs 14±4 mmol/L, (P＜0.01)].2. in vitro study: 1) MMT showed that Telmisartan (0.01-1.0ug/ml) had no effect on the proliferations of 3T3-L1 preadipocytes; 2) In the process of induction of 3T3-L1 preadipocytes, Telmisartan (0.1ug/ml) promoted the differention of the cells, and increased adiposity during the process of differentiation. At the same time, the expression of PPARγdetected by Q-PCR was increased by telmisartan. 3) Various concentrations of telmisartan were applied to interfere with the mature 3T3-L1 adipocytes. Telmisartan reduced the lipid storage and increased the ¹⁸F-FDG uptake of mature 3T3-L1 adipocytes in a dose-dependent manner. At the same time, Telmisartan reduced the levels of IL-6 and TNFαand increased that of FFAs in the cultural medium. One hundred and fifty seven genes differentially expressed between the groups were found by microarray. These were involved in lipid synthesis, eatabolism and transport in the adipocyte. Preliminary analyses of these gene functions and their relationship were performed. MAP kinas signaling pathway involving the secretion of proinflammatory factor and lipid metabolisms were affected by telmisartan. Up-regulation of Nos3 and CPT1A expression by telmisartan may also underlied the improvement in the lipid metabolisms.Conclusions: Candesartan might reduce the proinflammmatory factors, improve the lipid metabolisms and insulin resistance .And Telmisartan has important direct effects on the lipid metabolisms and the proinflammatory factors secretion of the adipocyte.These showed that some of the ARBs affected lipometabolisms and the proinflammatory factors secreted from adipocytes, and improve the insulin resistance.