Resistin With Inflammation And Atherosclerosis Atherosclerosis

Part onePlasma Resistin Is Increased in Patients with Unstable AngniaBackground: Resistin, a novel adipokine , was originally regarded to link insulin resistance and obesity in rodents. In rodents, resistin is derived almost exclusively from adipose tissue, however subsequent studies produced disparate findings regarding the role of resistin in obesity and insulin resistance in human. In contrast to rodents, resistin is expressed primarily in inflammatory cells in humans, especially macrophages. Studies have shown a potential role of resistin in atherosclerosis ,and resistin mRNA and protein have been reported to be present in atherosclerotic lesions in both huaman and mice. Resistin levels increased in patients with coronary artery disease (CAD), and it was an independent inflammatory marker of atherosclerosis in human.While data concerning resistin in different stages of CAD in Chinese people are lacking.Objective: The aim of this study was to assess whether plasma concentrations of resistin differed between patients with unstable and stable angina pectoris in China, and if any correlations existed among resistin levels, other inflammatory markers andmetabolic parameters.Methods : One hundred and forteen consecutive patients hospitalized for elective diagnostic coronary angiography were studied, including 46 patients with unstable angina (UAP), 37 with stable angina (SAP) and 31 control subjects. Clinical and biochemical characteristics were collected. The levels of high-sensitivity C-reactive protein (hs-CRP) were determined by immunoturbidometry. The endothelin-1 (ET-1) and insulin concentrations were determined by radioimmunoassay .Plasma resistin and Big endothelin concentrations were measured by ELISA.Results: Plasma concentrations of resistin were significantly increased in UAP group 12.09 (8.40,18.08)) in comparison with SAP (9.04 (7.09,11.44)) and control groups (8.71 (6.58 ,11.56)). No differences in resistin levels were found between patients with SAP and controls. We confirmed prior findings of positive correlations of resistin with age(R~2 =0.06, P =0.009), leukocyte counts(R~2 =0.05, P =0.013)and hs-CRP(R~2 =0.05, P =0.014). We also found that plasma resistin positively correlated with big-endothelin(R~2 =0.05, P=0.013) and ET-1 (R~2 =0.07, P=0.005). All of these associations remained significant after adjusting for age, sex and waist, excpt for big-endothelin.Conclusions: These findings suggested that resistin may be involved in the development of CAD through systemic inflammation and endothelial activation. Part two Effects of C-reactive on resistin expression in cultured human monocytesBackground : Atherosclerosis is an inflammatory disease. Resistin, a novel adipokine, was originally proposed as a link between obesity and insulin resistance/diabetes. Currently accumulating evidence indicates that resistin is involved in inflammatory response and atherosclerosis, and resistin is an inflammatory marker of atherosclerosis. C-reactive protein (CRP) is an important risk factor for coronary heart disease, and also modifies the expression of genes involved in atherogenesis. Consequently, CRP may not only be a nonspecific marker of inflammation, it is also possible that CRP plays a direct role in the pathogenesis of inflammation/ atherosclerosis. Clinical studies have shown a positive correlation between CRP and resistin. However whether low grade inflammation induces resistin expression or resistin is another inducer of CRP is not yet known. It is not clear about the effect of CRP on resistin expression in human monocytes.Objective: The aim of the present study was to assess the possible effects of CRP on the expression of resistin by cultured human monocytes.Methods : Human peripheral blood monocytes were isolated from the whole blood of healthy volunteers by density gradient centrifugation. For dose-dependent study, cells were incubated with varying concentrations of CRP (0, 5, 10, 25 and 50μg/ml, n=6 for each) for 24 h. To evaluate time-dependent effects of CRP, human monocytes were incubated with 25μg/ml of CRP for different time (0, 3, 6, 12, 24, n=6 for each point respectively). Quantitative real-time reverse transcription- polymerase chain reaction analyses were performed to analyze resistin mRNA gene expression.The resistin in supernatants of cultured medium was measured by ELISA. Results : After stimulation with CRP for 24 hours, resistin mRNA expression increased significantly in a concentration-dependent manner. At a concentration of 5μg/ml CRP, resistin mRNA expression increased 2.1 fold (p＜0.05) compared to unstimulated monocytes. This effect was maximal in the presence of 25μg/ml CRP (9.8 fold, p＜0.05). The effect of CRP on resistin protein was also concentration- dependent. Resistin level in supernatant of unstimulated monocytes was undetectable. But 24-hour incubation even with 5μg/ml CRP showed a significant induction of resistin protein(0.35±0.01ng/ml, p＜0.05). These changes were maximal with the concentration of 50μg/ml CRP(1.19±0.30ng/ml, p＜0.05). In a 24-hour time course study, CRP at a concentration of 25μg/mL induced resistin mRNA expression significantly within 3 hour(2.9 fold, P＜0.001), with a maximal effect at 24 hours (10 fold, P＜0.05). Resistin protein in medium was not detectable until incubation of monocytes with C RP for 6 hours (0.21±0.12ng/ml; p＜0.05). Then re sistin secretion increased with the time, reached the peak at 24 hours (0.89±0.16ng/ml; p＜0.05).Conclusions: CRP induced the expression of resistin in cultured human monocytes in a dose and time-dependent manner. Our findings strengthen the role of CRP in the pathogenesis of vascular inflammation and atherosclerosis, and may partly explain the increased levels of resistin in patients of acute coronary syndrome. Background: Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A(HMG-CoA) reductase (statins) have been widely used in medical routine practice, and they are reported to reduce greatly cardiovascular-related morbidity and mortality in patients with and without coronary disease. Recent studies have shown that statins possess anti-inflammatory properties that are independent of their lipid-lowering action. Atherosclerosis is an inflammatory disease. Resistin, a novel adipokine, was reported to be involved inflammatory response and atherosclerosis. CRP, an important risk factor for coronary heart disease, could also induce the expression of resistin in cultured human monocytes in a dose and time-dependent manner. However whether statins could modulate resistin expression induced by CRP in cultured human monocytes is not yet known.Objective: The aim of the present study was to assess the possible effects of statins on the expression of resistin induced by CRP in cultured human monocytes, as well as the possible signal pathway.Methods: Human peripheral blood monocytes were isolated from the whole blood of healthy volunteers by density gradient centrifugation. To evaluate the effects of statins on resistin production subjected to CRP, cells were pretreated with simvastain (0.1,1,10μM), or lovastain (0.1,1,10μM), or xuezhikang (25, 50,100μg/ml) respectively for 2 h, and then co-incubated with 25μg/ml CRP for 24 h. In additional experiments, isoprenoids were used to identify the mode of statins' action. Monocytes were incubated with different statins in the absence or presence of 100μM mevalonate or 10μM geranylgeranyl-pyrophosphate (GGPP) or 10μM farnesylpyrophosphate (FPP) for 2h, then co-incubated with CRP for 24 h. Quantitative real-time reverse transcription-polymerase chain reaction analyses were performed to analyze resistin mRNA gene expression. The resistin in supematants of cultured medium was measured using commercial assay kits by ELISAResults: Pre-incubation of monocytes with different concentrations of simvastatin and lovastatin suppressed the CRP-induced resistin expression in monocytes in a dose-dependent manner. 1μM statins significantly reduced the resistin mRNA levels (simvastain 55.4±4.2%, lovstatin 59.6±5.1% of CRP-treated cells, P＜0.05), and resistin protein in medium(simvastain 0.54±0.02ng/ml, lovstatin 0.58±0.08ng/ml, vs CRP-treated cells 0.89±0.16ng/ml, P＜0.05). Further co-treatment with 100μM mevalonate or 10μM GGPP, but not FPP almost reversed completely the inhibitory effects of statins on resistin expression. 50μg/ml xuezhikang also inhibited the resistin mRNA levels(34.9±5.4% of CRP-treated cells, P＜0.01) and protein(0.47±0.07ng/ml vs 0.89±0.16ng/ml, P＜0.01)markedly. While the inhibitory effect of xuezhikang on resistin expression only partly reversed by 100μM mevalonate and 10μM GGPP.Conclusions: Resistin expression induced by CRP were inhibited by different statins through interfering with cellular isoprenoid metabolism and GGPP-dependent processes. Our results contribute to the growing volume of evidence on the anti-inflammatory and anti-atherosclerotic effects of statins, and indicate that statins may control inflammatory responses partially by inhibiting expression of resistin.