Targeting adiponectin for cardioprotection

Adiponectin is an adipose tissue-derived plasma protein which has a reduced concentration in subjects with obesity-related diseases. Adiponectin has antidiabetic and anti-inflammatory characteristics, which lead to beneficial actions on various obesity-linked complications. Recent experimental findings have shown that adiponectin contributes to protection against cardiac remodelling after pressure overload and cardiac injury following ischaemia–reperfusion. Thus, adiponectin could emerge as a potential cardioprotective agent for the treatment of several pathological heart conditions.     

The role of the adipocyte hormone adiponectin in cardiovascular disease

Adiponectin, a novel hormone made by fat tissue, regulates energy metabolism and endothelial activation. Serum levels of adiponectin are reduced in conditions that are associated with an increased risk of cardiovascular disease, such as diabetes and the metabolic syndrome. Adiponectin trimers assemble into higher-order oligomers, which have different signaling properties. Adiponectin trimers and a C-terminal globular domain activate AMP-activated protein kinase, whereas hexamer and high-molecular weight isoforms activate nuclear factor-kappa B signaling pathways. Exogenous adiponectin corrects metabolic defects that are associated with insulin resistance, and might protect the endothelium from the progression of cardiovascular disease. Receptors for adiponectin have been described and might provide future therapeutic targets for the treatment of cardiovascular disease.     

脂联素在心血管疾病中的研究进展

脂联素（Adiponectin,APN）是由脂肪细胞分泌的一种血浆蛋白,其血浆中含量丰富,大约为5—30mg／1。目前的研究证实,脂联素在2型糖尿病,冠心病,高血压病中降低,在心力衰竭中显著升高,脂联素水平能预示2型糖尿病和冠心病的发展,并在临床试验中表现出增强胰岛素敏感性、抗动脉粥样硬化、抗炎,预测死亡率等作用,本文就脂联素及其在心血管疾病中的研究进展做一综述。     

原发性高血压患者血清脂联素及其基因多态性与冠心病的相关性研究

【摘要】目的探讨原发性高血压患者血清脂联素水平及其基因单核苷酸多态性（SNP）rs266729、rs7649121、 rs1501299、rs3774262与冠心病及冠脉病变程度的关系。方法以高血压患者414例（其中单纯高血压患者180例,高血压合并冠心病患者234例）和正常对照组185例为研究对象,应用酶联免疫吸附法（ELISA）测定血清脂联素水平,聚合酶链反应-限制性片段长度多态性（PCR-RFLP）法检测脂联素rs266729、rs7649121、rs1501299、rs3774262位点多态性。结果高血压合并冠心病组脂联素水平较对照组和单纯高血压组显著降低。脂联素rs7649121位点杂合子AT基因型较AA基因型可降低冠心病风险（校正OR=0.566,95%CI0.346~0.925,P=0.023）。多元Logistic回归分析显示年龄、LDL-C为冠心病的危险因素,脂联素为冠心病的保护因素。随着病变支数增加,脂联素水平呈逐渐降低趋势。脂联素SNP位点基因型对血清脂联素水平无明显影响。结论脂联素水平降低是高血压患者发生冠心病的独立危险因素,且随着冠脉病变程度的加重,脂联素水平逐渐降低。脂联素rs7649121位点多态性可能与高血压患者并发冠心病有关。     

脂联素与代谢综合征

脂联素（APN）在＋276T/G、＋45T/G、164I/T、＋10211T/G、-11391G/A、-11377G/C等位点的基因多态性与代谢综合征（MS）及其相关性疾病有关。APN水平与三酰甘油（TG）、总胆固醇（TC）、低密度脂蛋白胆固醇（LDL-C）、高密度脂蛋白胆固醇（HDL-C）独立相关,血清APN水平降低是独立于体脂因素的胰岛素敏感性的因素之一,APN与2型糖尿病（T2DM）呈强负相关,APN水平与高血压发病呈独立负相关,低APN水平是MS的一个独立危险因素,血清APN水平降低是MS的特征性标志。APN水平与无粥样斑块的颈动脉内膜中层厚度呈负相关,是动脉粥样硬化早期的独立预测因子。APN与MS密切相关。     

Adiponectin: a key fat-derived molecule regulating inflammation

Adiponectin is the abundant adipocyte-derived protein with well-established anti-atherogenic and insulin-sensitising properties. Besides these well characterised biological functions, recent evidence supports a strong anti-inflammatory function. Whereas initial studies demonstrated that adiponectin suppresses the production of the potent pro-inflammatory cytokine TNF-alpha, current studies showed that this adipokine also induces various anti-inflammatory cytokines, such as IL-10 or -1 receptor antagonists. These effects are paralleled by various other immune-regulatory properties, such as specific effects on endothelial cell functions. These in vitro effects are directly translated into various animal models of inflammation, demonstrating a potent anti-inflammatory effect for adiponectin. Thiazolidinediones selectively upregulate peroxisome-proliferator-activated receptor-gamma, leading to increased tissue and serum concentrations of adiponectin. Adiponectin has emerged as a key mediator regulating and affecting the balance between fat and inflammation. Therefore, either adiponectin itself or its inducing agents, such as thiazolidinediones, might be of key therapeutic interest in the near future far beyond diseases being associated with insulin resistance.     

Adiponectin and cardiovascular health: an update

The global epidemic of obesity is accompanied by an increased prevalence of cardiovascular disease (CVD), in particular stroke and heart attack. Dysfunctional adipose tissue links obesity to CVD by secreting a multitude of bioactive lipids and pro-inflammatory factors (adipokines) with detrimental effects on the cardiovascular system. Adiponectin is one of the few adipokines that possesses multiple salutary effects on insulin sensitivity and cardiovascular health. Clinical investigations have identified adiponectin deficiency (hypoadiponectinaemia) as an independent risk factor for CVD. In animals, elevation of plasma adiponectin by either pharmacological or genetic approaches alleviates obesity-induced endothelial dysfunction and hypertension, and also prevents atherosclerosis, myocardial infarction and diabetic cardiomyopathy. Furthermore, many therapeutic benefits of the peroxisome-proliferator activated receptor gamma agonists, the thiazolidinediones, are mediated by induction of adiponectin. Adiponectin protects cardiovascular health through its vasodilator, anti-apoptotic, anti-inflammatory and anti-oxidative activities in both cardiac and vascular cells. This review summarizes recent findings in the understanding of the physiological role and clinical relevance of adiponectin in cardiovascular health, and in the identification of the receptor and postreceptor signalling events that mediate the cardiovascular actions of adiponectin. It also discusses adiponectin-targeted drug discovery strategies for treating obesity, diabetes and CVD. LINKED ARTICLES: This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.     

Serum adiponectin concentrations during treatment with olanzapine or risperidone: a pilot study

Adiponectin is a recently identified adipocyte-derived protein, which is associated with glucose metabolism, insulin sensitivity and adiposity. The aim of this study was to explore the alterations in serum adiponectin concentration during treatment with olanzapine or risperidone. Serum concentrations of adiponectin were investigated in body mass index (BMI, kg/m2)- and age-matched groups of non-diabetic, non-obese schizophrenic patients receiving a stable dose of olanzapine (n = 18) or risperidone (n = 15) for 4 weeks or more, and of mentally and physically healthy volunteers (n = 17). Patients undergoing treatment with olanzapine or risperidone had significantly higher adiponectin concentrations than the healthy volunteers, even after controlling for BMI. Adiponectin concentrations decreased with increasing BMI in patients taking olanzapine, while elevated levels were observed in patients taking risperidone, regardless of adiposity. This preliminary cross-sectional study indicates that adiponectin is involved in the regulation of glucose metabolism and weight in schizophrenic patients during treatment with olanzapine or risperidone, presumably showing a normalizing effect on metabolic abnormality.     

Cytokines in alcoholic liver disease

Alcoholic liver disease (ALD) is associated with a spectrum of liver injury ranging from steatosis and steatohepatitis to fibrosis and cirrhosis. While multifactorial pathogenesis plays a role in the disease progression, enhanced inflammation in the liver during ethanol exposure is a major feature of ALD. Dysregulated cytokine metabolism and activity are crucial to the initiation of alcohol-induced liver injury. The pro-inflammatory cytokine tumor necrosis factor (TNF-α) has been demonstrated to be one of the key factors in the various aspects of pathophysiology of ALD. The immunomodulatory cytokines such as interleukin 10 and interleukin 6 play roles in exerting hepatic protective effects. Adiponectin is an adipose tissue–derived hormone, which displays protective actions on ethanol-induced liver injury. Treatment for mice with adiponectin decreases TNF-α expression, steatosis and prevents alcohol-induced liver injury. Adiponectin exerts its anti-inflammatory effects via suppression of TNF-α expression and induction of anti-inflammatory cytokines such as IL-10. Adiponectin attenuates alcoholic liver injury by the complex network of multiple signaling pathways in the liver, leading to enhanced fatty acid oxidation and reduced steatosis. Interactions between pro- and anti-inflammatory cytokines such as TNFα and adiponectin and other cytokines are likely to play important roles in the development and progression of alcoholic liver disease.     

Adiponectin and its potential in the treatment of obesity, diabetes and insulin resistance

Adiponectin is a protein hormone produced exclusively by adipocytes. Its circulating levels are decreased in individuals with obesity, atherosclerosis and insulin resistance, suggesting that its deficiency may have a causal role in the etiopathogenesis of these diseases. Studies have shown that adiponectin administration in rodents has insulin-sensitizing, anti-atherogenic and anti-inflammatory effects and under certain settings also decreases body weight. Therefore, adiponectin replacement in humans may represent a promising approach to prevent and/or treat obesity, insulin resistance and type 2 diabetes; however, clinical studies with adiponectin administration need to be conducted to confirm this hypothesis. Current experimental and clinical data regarding adiponectin physiology and pathophysiology are detailed in this review.     

Adiponectin: a link between obesity and cancer

Adiponectin, an insulin-sensitising hormone produced by adipocytes, has direct antidiabetic, antiatherogenic, anti-inflammatory and antiangiogenic properties. Circulating adiponectin levels are lower in obesity, a disease state that is associated with certain malignancies. Recently, accumulating evidence suggests that adiponectin may have an important protective role in carcinogenesis. There is also evidence that at least some, if not most, cancer cell types express adiponectin receptors; thus adiponectin may act on tumour cells directly by binding and activating adiponectin receptors and downstream signalling pathways. Through its antiangiogenic properties, and also possibly through other mechanisms regulating cell proliferation discussed in this review, adiponectin may prove to be an effective novel anticancer agent. Large association and prospective studies to assess adiponectin levels in relation to risk from cancer, as well as mechanistic studies to prove adiponectin’s role in the development of malignancies, and interventional trials to address potential roles of adiponectin in cancer pathogenesis and therapeutics are needed.     

Adiponectin receptor signalling in the brain

Adiponectin is an important adipocyte-derived hormone that regulates metabolism of lipids and glucose, and its receptors (AdipoR1, AdipoR2, T-cadherin) appear to exert actions in peripheral tissues by activating the AMP-activated protein kinase, p38-MAPK, PPARα and NF-kappa B. Adiponectin has been shown to exert a wide range of biological functions that could elicit different effects, depending on the target organ and the biological milieu. There is substantial evidence to suggest that adiponectin receptors are expressed widely in the brain. Their expression has been detected in regions of the mouse hypothalamus, brainstem, cortical neurons and endothelial cells, as well as in whole brain and pituitary extracts. While there is now considerable evidence for the presence of adiponectin and its receptors in the brain, their precise roles in brain diseases still remain unclear. Only a few research studies have looked at this facet of adiponectins in brain disorders. This brief review will describe the evidence for important functions by adiponectin, its structure and known actions, evidence for expression of AdipoRs in the brain, their involvement in brain disorders and the therapeutic potential of agents that could modify AdipoR signalling.     

Increased levels of adiponectin and resistin in alcohol dependence--possible link to craving

Recent studies suggested a role of appetite regulating peptides like leptin and ghrelin in alcohol dependence and particularly in the neurobiology of alcohol craving. Aim of the present study was to investigate alterations of the adipocytokines adiponectin and resistin in alcohol-dependent patients. We analyzed a sample of 88 patients at admission for alcohol detoxification and after 1 week of withdrawal treatment in comparison to 89 healthy controls. Adiponectin and resistin serum levels were measured using commercial ELISA kits. The extent of alcohol craving was obtained using the Obsessive Compulsive Drinking Scale (OCDS). Adiponectin and resistin serum levels were significantly elevated in patients with alcohol dependence at both dates (admission and after 1 week of treatment) compared to healthy controls. Adiponectin decreased significantly during the course of withdrawal (T=3.44, p=0.001) while resistin serum levels showed a slight increase (T=-1.83, p=0.071). In a multivariate approach the extent of alcohol craving was significantly associated with adiponectin but not with resistin serum levels in male patients (Beta=-0.255, p=0.025). Results for female patients were not significant. Our findings provide first evidence for an alteration of the adipocytokines adiponectin and resistin during alcohol withdrawal. Furthermore, adiponectin may be involved in the neurobiology of alcohol craving, possibly via its effects on the hypothalamic circuits.     

Adiponectin and cardiovascular disease: mechanisms and new therapeutic approaches

Adiponectin is an abundant plasma protein secreted from adipocytes. Its role in energy homeostasis is well-known, including the regulation of hydrocarbons and lipids metabolism as well as the improvement of insulin resistance. It has been thought to be a key molecule in the development of type 2 diabetes mellitus and metabolic syndrome, which are epidemiological targets for preventing cardiovascular disease. In addition to beneficial metabolic effects, adiponectin seems to have anti-inflammatory, anti-atherosclerotic and vasoprotective actions. Furthermore, adiponectin affects signalling in myocardial cells and exerts beneficial actions on the heart after pressure overload and ischemia-reperfusion injury. The ability of adiponectin to reduce insulin resistance in conjunction with its antiinflammatory and cardioprotective properties makes this adipocytokine a promising therapeutic target. On clinical interest, agents that enhance endogenous adiponectin production or action have potential for the treatment of cardiovascular disease. Management strategies that increase adiponectin levels include weight reduction, Mediterranean diet, thiazolidinediones, antihypertensive and lipid lowering drugs. Current knowledge on the main actions of adiponectin and therapeutic approaches for cardiovascular disease is summarized in this review.     

持续性皮下胰岛素输注对初诊2型糖尿病患者脂联素水平的影响

目的探讨持续性皮下胰岛素输注（Continuous Subcutaneous Insulin Infusion,CSII）注射对初诊2型糖尿病患者脂联素水平的影响。方法将42例初诊2型糖尿病患者随机分为治疗组和对照组,治疗组采用CSII,对照组仅皮下胰岛素注射,2组治疗前及治疗后2周后,采用ELISA进行脂联素水平及HOMA指数、血脂水平评估。结果治疗组2周后,对照组及治疗组与治疗前对比脂联素均显著升高,治疗组比较对照组游离脂肪酸下降更明显,差异有统计学意义（P〈0．01）。脂联素水平与HOMA指数（P〈0．01）、游离脂肪酸（P〈0．05）、三酰甘油水平（P〈0．05）显著相关,与胆固醇、高密度脂蛋白、低密度脂蛋白无关（P〉0．05）。结论持续性皮下胰岛素输注均能快速有效的提高初诊2型糖尿病患者脂联素水平。     

Adiponectin: a link between obesity and cancer

Adiponectin, an insulin-sensitising hormone produced by adipocytes, has direct antidiabetic, antiatherogenic, anti-inflammatory and antiangiogenic properties. Circulating adiponectin levels are lower in obesity, a disease state that is associated with certain malignancies. Recently, accumulating evidence suggests that adiponectin may have an important protective role in carcinogenesis. There is also evidence that at least some, if not most, cancer cell types express adiponectin receptors; thus adiponectin may act on tumour cells directly by binding and activating adiponectin receptors and downstream signalling pathways. Through its antiangiogenic properties, and also possibly through other mechanisms regulating cell proliferation discussed in this review, adiponectin may prove to be an effective novel anticancer agent. Large association and prospective studies to assess adiponectin levels in relation to risk from cancer, as well as mechanistic studies to prove adiponectin's role in the development of malignancies, and interventional trials to address potential roles of adiponectin in cancer pathogenesis and therapeutics are needed.     

Adiponectin alleviates exacerbation of airway inflammation and oxidative stress in obesity-related asthma mice partly through AMPK signaling pathway

Adiponectin plays a role in asthma and obesity, but its effects and mechanism in obesity-related asthma remain elusive. This study aimed to evaluate the effects of adiponectin on airway inflammation and oxidative stress and to determine its mechanism in obesity-related asthma. Male C57BL6/J mice fed with a high-fat diet to induce obesity were sensitized and challenged with ovalbumin to induce asthma, and treated with adiponectin (1 mg/kg) and AMP-activated protein kinase (AMPK) inhibitor compound C (20 mg/kg) twice before the first ovalbumin challenge. We found exogenous adiponectin significantly reduced airway resistance, inflammatory infiltration in lung tissue, and cell counts in bronchoalveolar lavage fluid. Adiponectin inhibited great levels of eotaxin, myeloperoxidase, tumor necrosis factor-α, 8‑hydroxy‑2′‑deoxyguanosine, and nitric oxide in obesity-related asthma mice. Moreover, we found increased nuclear factor kappa B p65, inducible nitric oxide synthase and B-cell lymphoma 2 protein expression were down-regulated with adiponectin administration. Additionally, adiponectin elevated the lower levels of pAMPK and AMPK activity in lung tissue. These protective effects of adiponectin were reversed after treatment with the AMPK inhibitor compound C. Thus, we conclude that adiponectin alleviates exacerbation of airway inflammation and oxidative stress in a murine model of obesity-related asthma partly through AMPK signaling pathway.     

Adiponectin plasma levels are increased by atorvastatin treatment in subjects at high cardiovascular risk

Adiponectin can suppress atherogenesis by inhibiting the adherence of monocytes, reducing their phagocytic activity, and suppressing the accumulation of modified lipoproteins in the vascular wall. Contradictory data have been reported about the effect of statins on adiponectin plasma levels. In this work, adiponectin plasma levels were measured in 102 statin-free subjects from the Spanish population of the Achieve Cholesterol Targets Fast with Atorvastatin Stratified Titration (ACTFAST) study, a 12-week, prospective, multi-centre, open-label trial which enrolled subjects with coronary heart disease, coronary heart disease-equivalent or a 10-year coronary heart disease risk >20%. Subjects were assigned to atorvastatin (10-80 mg/day) based on low-density lipoprotein (LDL)-cholesterol concentration at screening. For comparison, age and gender-matched blood donors (N=40) were used as controls. Control subjects did not present hypertension, hypercholesterolemia, diabetes, metabolic syndrome and history of cardiovascular diseases. Adiponectin levels were diminished in patients at high cardiovascular risk compared with control subjects [4166 (3661-4740) vs 5806 (4764-7075) ng/ml respectively; geometric mean (95% CI); P<0.0001]. In the whole population, atorvastatin treatment increased adiponectin levels [9.7 (3.2-16.7);% Change (95% CI); P=0.003]. This increment was in a dose-dependent manner; maximal effect observed with atorvastatin 80 mg/d [24.7 (5.7-47.1); P=0.01]. Adiponectin concentrations were positively correlated with high-density lipoprotein-cholesterol both before and after atorvastatin treatment. No association was observed between adiponectin and LDL-cholesterol before and after atorvastatin treatment. In conclusion, atorvastatin increased adiponectin plasma levels in subjects at high cardiovascular risk, revealing a novel anti-inflammatory effect of this drug.     

Adiponectin protects human neuroblastoma SH-SY5Y cells against acetaldehyde-induced cytotoxicity

Acetaldehyde, an inhibitor of mitochondrial function, has been widely used as a neurotoxin because it elicits a severe Parkinson's disease-like syndrome with elevation of the intracellular reactive oxygen species (ROS) level and apoptosis. Adiponectin, secreted from adipose tissue, mediates systemic insulin sensitivity with liver and muscle as target organs. In this study, we investigated the protective effects of adiponectin on acetaldehyde-induced apoptosis in human neuroblastoma SH-SY5Y cells and attempted to examine its mechanism. Acetaldehyde-induced apoptosis was moderately reversed by adiponectin treatment. Our results suggest that the protective effects of adiponectin on acetaldehyde-induced apoptosis may be ascribed to ability to induce the expression of anti-oxidant enzymes and to regulate Bcl-2 and Bax expression. These data indicate that adiponectin may provide a useful therapeutic strategy for the prevention of progressive neurodegenerative disease such as Parkinson's disease.