Obese states characterized by chronic inflammation are closely linked to the development of metabolic dysfunction. We identified adipolin/CTRP12 as an insulin-sensitizing and anti-inflammatory adipokine. Although obese conditions down-regulate adipolin expression, its molecular mechanism is largely unknown. Here we show that the transcriptional regulator Krüppel-like factor (KLF) 15 is involved in the regulation of adipolin expression in adipocytes. White adipose tissue from diet-induced obese (DIO) mice showed decreased expression of KLF9 and KLF15 among several KLFs, which was accompanied by reduced expression of adipolin. In cultured 3T3L1 adipocytes, treatment with TNFα significantly reduced the mRNA levels of KLF9, KLF15 and adipolin. Adenovirus-mediated overexpression of KLF15 but not KLF9 reversed TNFα-induced reduction of adipolin expression in adipocytes. Conversely, gene targeting ablation of KLF15 attenuated adipolin expression in adipocytes. Expression of KLF15 but not KLF9 enhanced the promoter activity of adipolin in HEK293 cells. Pretreatment of 3T3L1 adipocytes with the JNK inhibitor SP600125, but not p38 MAPK inhibitor SB203580 blocked the inhibitory effects of TNFα on adipolin and KLF15 expression. These data suggest that adipose inflammation under conditions of obesity suppresses adipolin expression via JNK-dependent down-regulation of KLF15 in adipocytes.
Obesity is linked with an increased risk of lymphedema, which is a serious clinical problem. Adiponectin is a circulating adipokine that is down‐regulated in obese states. We investigated the effects of adiponectin on lymphatic vessel formation in a model of lymphedema and dissected its mechanisms.
Methods and Results
A mouse model of lymphedema was created via ablation of tail surface lymphatic network. Adiponectin‐knockout mice showed the greater diameter of the injured tail compared with wild‐type mice, which was associated with lower numbers of lymphatic endothelial cells (LECs). Systemic delivery of adiponectin reduced the thickness of the injured tail and enhanced LEC formation in wild‐type and adiponectin‐knockout mice. Adiponectin administration also improved the edema of injured tails in obese KKAy mice. Treatment with adiponectin protein stimulated the differentiation of human LECs into tubelike structures and increased LEC viability. Adiponectin treatment promoted the phosphorylation of AMP‐activated protein kinase (AMPK), Akt, and endothelial nitric oxide synthase n LECs. Blockade of AMPK or Akt activity abolished adiponectin‐stimulated increase in LEC differentiation and viability and endothelial nitric oxide synthase phosphorylation. Inhibition of AMPK activation also suppressed adiponectin‐induced Akt phosphorylation in LECs. In contrast, inactivation of Akt signaling had no effects on adiponectin‐mediated AMPK phosphorylation in LECs. Furthermore, adiponectin administration did not affect the thickening of the damaged tail in endothelial nitric oxide synthase–knockout mice.
Adiponectin can promote lymphatic vessel formation via activation of AMPK/Akt/endothelial nitric oxide synthase signaling within LECs, thereby leading to amelioration of lymphedema.
adiponectin; Akt; AMPK; eNOS; lymphangiogenesis
Adiponectin, an anti-inflammatory cytokine produced by adipose tissue, has been shown to modulate survival in animal models of critical illness. We examined the association between plasma adiponectin and clinical outcomes in critically ill patients with acute respiratory failure.
Secondary analysis of a single-center, randomized controlled trial.
Medical intensive care unit of a university-based, tertiary medical center.
One hundred seventy-five subjects with acute respiratory failure enrolled in randomized, controlled pilot trial of trophic vs. full-caloric enteral feeding (EDEN pilot study).
Measurements and Main Results
Adiponectin measured within 48 hrs of respiratory failure (Apn1) was inversely correlated with body mass index (r = −0.25, p = .007) and was higher in females (median, 12.6 µg/mL; interquartile range, 7.6–17.1) than males (9.45 µg/mL; 6.2–14.2; p = .02). Adiponectin increased at day 6 (Apn1: 11.4 µg/mL [6.6 –15.3] vs. Apn6: 14.1 µg/mL [10.3–18.6], p < .001). This increase was significant only in survivors (Δ adiponectin in survivors: 3.9 ± 6 µg/mL, n = 80, p < .001 vs. Δ in nonsurvivors: 1.69 ± 4.6 µg/mL, n = 14, p =.19). Higher Apn1 was significantly associated with 28-day mortality (odds ratio 1.59 per 5-µg/mL increase; 95% confidence interval 1.15–2.21; p = .006). No measured demographic, clinical, or cytokine covariates, including interleukin-6, interleukin-8, interleukin-10, interleukin-1β, interleukin-12, tumor necrosis factor-α, and interferon-γ, were confounders or effect modifiers of this association between adiponectin and mortality.
Independent of measured covariates, increased plasma adiponectin levels measured within 48 hrs of respiratory failure are associated with mortality. This finding suggests that factors derived from adipose tissue play a role in modulating the response to critical illness.
adiponectin; respiratory insufficiency; critical illness; biologic markers; epidemiology; translational research
Adiponectin plays a protective role in the development of obesity-linked disorders. We demonstrated that adiponectin exerts beneficial actions on acute ischemic injury in mice hearts. However, the effects of adiponectin treatment in large animals and its feasibility in clinical practice have not been investigated. This study investigated the effects of intracoronary administration of adiponectin on myocardial ischemia-reperfusion (I/R) injury in pigs.
Methods and Results
The left anterior descending coronary artery was occluded in pigs for 45 minutes and then reperfused for 24 hours. Recombinant adiponectin protein was given as a bolus intracoronary injection during ischemia. Cardiac functional parameters were measured by a manometer-tipped catheter. Apoptosis was evaluated by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling staining. Tumor necrosis factor-α and interleukin-10 transcripts were analyzed by real-time polymerase chain reaction. Serum levels of derivatives of reactive oxygen metabolites and biological antioxidant potential were measured. Adiponectin protein was determined by immunohistochemical and Western blot analyses. Intracoronary administration of adiponectin protein led to a reduction in myocardial infarct size and improvement of left ventricular function in pigs after I/R. Injected adiponectin protein accumulated in the I/R-injured heart. Adiponectin treatment resulted in decreased tumor necrosis factor-α and increased interleukin-10 mRNA levels in the myocardium after I/R. Adiponectin-treated pigs had reduced apoptotic activity in the I/R-injured heart and showed increased biological antioxidant potential levels and decreased derivatives of reactive oxygen metabolite levels in the blood stream after I/R.
These data suggest that adiponectin protects against I/R injury in a preclinical pig model through its ability to suppress inflammation, apoptosis, and oxidative stress. Administration of intracoronary adiponectin could be a useful adjunctive therapy for acute myocardial infarction.
adiponectin; myocardial infarction; reperfusion
Angiogenic cell therapy represents a novel strategy for ischemic diseases, but some patients show poor responses. We investigated the therapeutic potential of an induced pluripotent stem (iPS) cell sheet created by a novel magnetite tissue engineering technology (Mag-TE) for reparative angiogenesis. Mouse iPS cell-derived Flk-1+ cells were incubated with magnetic nanoparticle-containing liposomes (MCLs). MCL-labeled Flk-1+ cells were mixed with diluted extracellular matrix (ECM) precursor and a magnet was placed on the reverse side. Magnetized Flk-1+ cells formed multi-layered cell sheets according to magnetic force. Implantation of the Flk-1+ cell sheet accelerated revascularization of ischemic hindlimbs relative to the contralateral limbs in nude mice as measured by laser Doppler blood flow and capillary density analyses. The Flk-1+ cell sheet also increased the expressions of VEGF and bFGF in ischemic tissue. iPS cell-derived Flk-1+ cell sheets created by this novel Mag-TE method represent a promising new modality for therapeutic angiogenesis.
Reactive Oxygen Species (ROS) serve signaling functions in the vasculature, and hypoxia has been associated with increased ROS production. NADPH oxidase 4 (Nox4) is an ROS-producing enzyme that is highly expressed in the endothelium, yet its specific role is unknown. We sought to determine the role of Nox4 in the endothelial response to hypoxia.
Methods and Results
Hypoxia induced Nox4 expression both in vitro and in vivo and overexpression of Nox4 was sufficient to promote endothelial proliferation, migration, and tube formation. To determine the in vivo relevance of our observations, we generated transgenic mice with endothelial-specific Nox4 overexpression using the VE-cadherin promoter (VECad-Nox4 mice). In vivo, the VECad-Nox4 mice had accelerated recovery from hind limb ischemia and enhanced aortic capillary sprouting. Because endothelial nitric oxide synthase (eNOS) is involved in endothelial angiogenic responses and eNOS is activated by ROS, we probed the effect of Nox4 on eNOS. In cultured ECs overexpressing Nox4 we observed a significant increase in eNOS protein expression and activity. To causally address the link between eNOS and Nox4 we crossed our transgenic Nox4 mice with eNOS-/- mice. Aorta from these mice did not demonstrate enhanced aortic sprouting and VECad-Nox4 mice on the eNOS-/- background did not demonstrate enhanced recovery from hind limb ischemia.
Collectively, we demonstrate that augmented endothelial Nox4 expression promotes angiogenesis and recovery from hypoxia in an eNOS-dependent manner.
NADPH oxidase 4; Reactive Oxygen Species; Endothelium; Angiogenesis; Endothelial Nitric Oxide Synthase
The insulin-sensitizing agents referred to as thiazolidinediones (TZDs) possess anti-atherogenic and anti-inflammatory actions that contribute to protection against diabetic macrovascular complications. However, little is known about the effects of TZDs on retinal microvessel disorders. Here, we investigated whether TZDs modulate retinal vessel formation in a mouse model of oxygen- retinopathy.
Methods and Results
Neonatal mice were subjected to ischemia-induced retinopathy to produce pathological neovascular tuft formation. Pioglitazone (10 mg/kg/day), rosiglitazone (10 mg/kg/day) or vehicle was given by gavage once a day from postnatal day 7 (P7) to P17. Systemic treatment of wild-type (WT) mice with TZDs led to a significant decrease in pathological retinal neovascularization during ischemia compared with vehicle treatment, which was accompanied by increased plasma levels of the fat-derived hormone adiponectin. In contrast to WT mice, TZDs had no effects on ischemia-induced pathological retinal vessel formation in adiponectin-knockout (APN-KO) mice. Pioglitazone reduced tumor necrosis factor (TNF)-α expression in ischemic retina in WT mice but not in APN-KO mice. Furthermore, pioglitazone increased plasma adiponectin levels in TNF-α-KO mice but did not affect ischemia-induced pathological retinal neovascularization in this strain.
These data show that TZDs attenuate pathological retinal microvessel formation through adiponectin-mediated modulation of TNF-α production.
pioglitazone; adiponectin; neovascularization; ischemia; angiogenesis
Acute coronary syndrome is a leading cause of death in developed countries. Follistatin-like 1 (FSTL1) is a myocyte-derived secreted protein that is upregulated in the heart in response to ischemic insult. Here, we investigated the therapeutic impact of FSTL1 on acute cardiac injury in small and large preclinical animal models of ischemia/reperfusion and dissected its molecular mechanism.
Methods and Results
Administration of human FSTL1 protein significantly attenuated myocardial infarct size in a mouse or pig model of ischemia/reperfusion, which was associated with a reduction of apoptosis and inflammatory responses in the ischemic heart. Administration of FSTL1 enhanced the phosphorylation of AMP-activated protein kinase in the ischemia/reperfusion–injured heart. In cultured cardiac myocytes, FSTL1 suppressed apoptosis in response to hypoxia/reoxygenation and lipopolysaccharide-stimulated expression of proinflammatory genes through its ability to activate AMP-activated protein kinase. Ischemia/reperfusion led to enhancement of bone morphogenetic protein-4 expression and Smad1/5/8 phosphorylation in the heart, and FSTL1 suppressed the increased phosphorylation of Smad1/5/8 in ischemic myocardium. Treating cardiac myocytes with FSTL1 abolished the bone morphogenetic protein-4 –stimulated increase in apoptosis, Smad1/5/8 phosphorylation, and proinflammatory gene expression. In cultured macrophages, FSTL1 diminished lipopolysaccharide-stimulated expression of proinflammatory genes via activation of AMP-activated protein kinase and abolished bone morphogenetic protein-4 – dependent induction of proinflammatory mediators.
Our data indicate that FSTL1 can prevent myocardial ischemia/reperfusion injury by inhibiting apoptosis and inflammatory response through modulation of AMP-activated protein kinase– and bone morphogenetic protein-4 – dependent mechanisms, suggesting that FSTL1 could represent a novel therapeutic target for post-myocardial infarction, acute coronary syndrome.
apoptosis; inflammation; ischemia; myocytes; cardiac; reperfusion
Lymphedema is one of the serious clinical problems that can occur after surgical resection of malignant tumors such as breast cancer or intra‐pelvic cancers. However, no effective treatment options exist at present. Here, we report that implantation of adipose‐derived regenerative cells (ADRCs) can induce lymphangiogenesis in a mouse model of reparative lymphedema.
Methods and Results
ADRCs were isolated from C57BL/6J mice. To examine the therapeutic efficacy of ADRC implantation in vivo, we established a new mouse model of tail lymphedema. Lymphedema was improved significantly by local injection of ADRCs (P<0.05). Histological analysis revealed that lymphatic capillary density was greater in the ADRC group than in the phosphate‐buffered saline control group (P<0.01). Tissue expression of vascular endothelial growth factor C mRNA and plasma levels of vascular endothelial growth factor C were greater in the ADRC group than in the control group (P<0.01 and P<0.05, respectively). ADRCs released vascular endothelial growth factor C, which directly stimulated lymphangiogenesis. Implantation of ADRCs also enhanced recruitment of bone marrow–derived M2 macrophages, which served as lymphatic endothelial progenitor cells.
Implantation of autologous ADRCs could be a useful treatment option for patients with severe lymphedema via mediation of lymphangiogenesis. (J Am Heart Assoc. 2012;1:e000877 doi: 10.1161/JAHA.112.000877.)
adipose tissue; adipose‐derived regenerative cells; lymphedema; lymphangiogenesis; vascular endothelial growth factor C; macrophages
Omentin is an adipocytokine that is abundantly expressed in visceral fat tissue. We investigated the association of omentin with the number of metabolic risk factors.
The study population comprised 201 Japanese men who underwent annual health checkups. Plasma omentin levels were determined by enzyme-linked immunosorbent assay. We divided the subjects into 4 groups according to omentin levels. A reduction of plasma omentin levels significantly correlated with an increase in the mean number of metabolic risk factors such as increased waist circumference, dyslipidemia, high blood pressure and glucose intolerance.
Circulating omentin levels negatively correlated with the multiplicity of metabolic risk factors, suggesting that omentin acts as a biomarker of metabolic disorders.
Omentin; Adipocytokine; Metabolic disorders; Risk factors; Biomarkers
Advanced age is associated with decreased stem cell activity. However, the effect of aging on the differentiation capacity of induced pluripotent stem (iPS) cells into cardiovascular cells has not been fully clarified. We investigated whether iPS cells derived from young and old mice are equally capable of differentiating into vascular progenitor cells, and whether these cells regulate vascular responses in vivo. iPS cells from mouse embryonic fibroblasts (young) or 21 month-old mouse bone marrow (old) were used. Fetal liver kinase-1 positive (Flk-1+) cells, as a vascular progenitor marker, were induced after 3 to 4 days of culture from iPS cells derived from young and old mice. These Flk-1+ cells were sorted and shown to differentiate into VE-cadherin+ endothelial cells and α-SMA+ smooth muscle cells. Tube-like formation was also successfully induced in both young and old murine Flk-1+ cells. Next, hindlimb ischemia was surgically induced, and purified Flk-1+ cells were directly injected into ischemic hindlimbs of nude mice. Revascularization of the ischemic hindlimb was significantly accelerated in mice transplanted with Flk-1+ cells derived from iPS cells from either young or old mice, as compared to control mice as evaluated by laser Doppler blood flowmetry. The degree of revascularization was similar in the two groups of ischemic mice injected with iPS cell-derived Flk-1+ cells from young or old mice. Transplantation of Flk-1+ cells from both young and old murine iPS cells also increased the expression of VEGF, HGF and IGF mRNA in ischemic tissue as compared to controls. iPS cell-derived Flk-1+ cells differentiated into vascular progenitor cells, and regulated angiogenic vascular responses both in vitro and in vivo. These properties of iPS cells derived from old mice are essentially the same as those of iPS cells from young mice, suggesting the functionality of generated iPS cells themselves to be unaffected by aging.
Adiponectin is an adipocyte-derived protein that is down-regulated in obesity-linked disorders. Variants of the adiponectin gene (ADIPOQ) have been shown to affect adiponectin level. We have now examined the relation of polymorphisms of ADIPOQ to adiponectin concentration and to metabolic disorders in the Kita-Nagoya Genomic Epidemiology study, a population-based study of elderly Japanese. The genomic region including ADIPOQ was genotyped for 30 single nucleotide polymorphisms in 500 subjects of a screening population with the use of a fluorescence- or colorimetry-based allele-specific DNA primer–probe assay system. Four polymorphisms were then selected for genotyping in an additional 2797 subjects. Serum adiponectin level was negatively associated with metabolic abnormalities after adjustment for age and sex. The minor alleles of the rs1656930, Ile164Thr, and rs9882205 polymorphisms were associated with a low serum adiponectin level. Whereas the minor alleles of rs1656930 and rs9882205 were common (minor allele frequency of 6.2 and 38.5%, respectively), that of Ile164Thr was rare (0.9%). The minor allele of rs1656930 was positively associated with systolic blood pressure and the prevalence of hypertension. The association of rs1656930 with adiponectin level was replicated in an independent population. A subject with the 164Thr/Thr genotype had an extremely low serum adiponectin level (0.6 μg/ml) and the phenotype of metabolic syndrome. Our results suggest that a common variant of ADIPOQ, the minor allele of rs1656930, is associated with hypoadiponectinemia and hypertension. Screening for a common genetic background underlying low adiponectin levels might provide important information for assessment and management of metabolic disorders.
adiponectin; polymorphism; metabolic disorder; hypertension; epidemiology
Although increasing evidence indicates that an adipokine adiponectin exerts protective actions on heart, its effects on coronary angiogenesis following pressure overload have not been examined previously. Because disruption of angiogenesis during heart growth leads to contractile dysfunction and heart failure, we hypothesized that adiponectin modulates cardiac remodeling in response to pressure overload through its ability to regulate adaptive angiogenesis.
Methods and Results
Adiponectin-knockout (APN-KO) and wild-type (WT) mice were subjected to pressure overload caused by transverse aortic constriction (TAC). APN-KO mice exhibited greater cardiac hypertrophy, pulmonary congestion, left ventricular (LV) interstitial fibrosis and LV systolic dysfunction after TAC surgery compared with WT mice. APN-KO mice also displayed reduced capillary density in the myocardium after TAC, which was accompanied by a significant decrease in expression of vascular endothelial growth factor (VEGF) and phosphorylation of AMP-activated protein kinase (AMPK). Inhibition of AMPK in WT mice resulted in aggravated LV systolic function, attenuated myocardial capillary density and decreased VEGF expression in response to TAC. The adverse effects of AMPK inhibition on cardiac function and angiogenic response following TAC were diminished in APN-KO mice relative to WT mice. Moreover, adenovirus-mediated VEGF delivery reversed the TAC-induced deficiencies in cardiac microvessel formation and ventricular function observed in the APN-KO mice. In cultured cardiac myocytes, adiponectin treatment stimulated VEGF production, which was inhibited by inactivation of AMPK signaling pathway.
Adiponectin deficiency can accelerate the transition from cardiac hypertrophy to heart failure during pressure overload through disruption of AMPK-dependent angiogenic regulatory axis.
adiponectin; AMPK; cardiac angiogenesis; pressure overload; heart failure
Adipose tissue secretes proteins referred to as adipokines, many of which promote inflammation and disrupt glucose homeostasis. Here we show that secreted frizzled-related protein 5 (Sfrp5), a protein previously linked to the Wnt signaling pathway, is an anti-inflammatory adipokine whose expression is perturbed in models of obesity and type 2 diabetes. Sfrp5-deficient mice fed a high-calorie diet developed severe glucose intolerance and hepatic steatosis, and their adipose tissue showed an accumulation of activated macrophages that was associated with activation of the c-Jun N-terminal kinase signaling pathway. Adenovirus-mediated delivery of Sfrp5 to mouse models of obesity ameliorated glucose intolerance and hepatic steatosis. Thus, in the setting of obesity, Sfrp5 secretion by adipocytes exerts salutary effects on metabolic dysfunction by controlling inflammatory cells within adipose tissue.
The Gipie/GRP78 interaction serves as a molecular switch for the regulation of the apoptotic signaling pathway, which appears to contribute to the protection of endothelial cells from endoplasmic reticulum stress-induced apoptosis.
Continued exposure of endothelial cells to mechanical/shear stress elicits the unfolded protein response (UPR), which enhances intracellular homeostasis and protect cells against the accumulation of improperly folded proteins. Cells commit to apoptosis when subjected to continuous and high endoplasmic reticulum (ER) stress unless homeostasis is maintained. It is unknown how endothelial cells differentially regulate the UPR. Here we show that a novel Girdin family protein, Gipie (78 kDa glucose-regulated protein [GRP78]-interacting protein induced by ER stress), is expressed in endothelial cells, where it interacts with GRP78, a master regulator of the UPR. Gipie stabilizes the interaction between GRP78 and the ER stress sensor inositol-requiring protein 1 (IRE1) at the ER, leading to the attenuation of IRE1-induced c-Jun N-terminal kinase (JNK) activation. Gipie expression is induced upon ER stress and suppresses the IRE1-JNK pathway and ER stress-induced apoptosis. Furthermore we found that Gipie expression is up-regulated in the neointima of carotid arteries after balloon injury in a rat model that is known to result in the induction of the UPR. Thus our data indicate that Gipie/GRP78 interaction controls the IRE1-JNK signaling pathway. That interaction appears to protect endothelial cells against ER stress-induced apoptosis in pathological contexts such as atherosclerosis and vascular endothelial dysfunction.
Adiponectin, an adipocytokine, is secreted by adipocytes and mediates anti-hypertrophic and anti-inflammatory effects in the heart. Plasma concentrations of adiponectin are decreased in obesity, insulin resistance and obesity-associated conditions such as hypertension and coronary heart disease. However, a paradoxical increase in adiponectin levels is observed in human systolic heart failure (HF). We sought to investigate the determinants of adiponectin levels in patients with chronic systolic HF. Total adiponectin levels were measured in 99 patients with stable HF and left ventricular (LV) ejection fraction (EF) <40%. Determinants of adiponectin levels by univariate analysis were included in a multivariate linear regression model. At baseline patients were 62% black, 63% male, mean age of 60±13 years, LVEF of 21±9% and a body mass index (BMI) of 30.6±6.7kg/m2. Mean adiponectin levels were 15.8±15µg/ml. Beta-blocker use, BMI, and blood urea nitrogen (BUN) were significant determinants of adiponectin levels by multivariate analysis. LV mass, structure, and LVEF were not related to adiponectin levels by multivariate analysis. Interestingly, the effect of beta-blocker therapy was most marked in non-obese patients with BMI < 30kg/m2. In conclusion, in chronic systolic HF patients, beta-blocker therapy is correlated with lower adiponectin levels, especially in non-obese patients. This relation should be taken into account when studying the complex role of adiponectin in chronic systolic HF.
Adiponectin; chronic systolic heart failure; beta-blockers
Induced pluripotent stem (iPS) cells are the novel stem cell population induced from somatic cells. It is anticipated that iPS will be used in the expanding field of regenerative medicine. Here, we investigated whether implantation of fetal liver kinase-1 positive (Flk-1+) cells derived from iPS cells could improve angiogenesis in a mouse hind limb model of ischemia.
Flk-1+ cells were induced from iPS cells after four to five days of culture. Hind limb ischemia was surgically induced and sorted Flk-1+ cells were directly injected into ischemic hind limbs of athymic nude mice. Revascularization of the ischemic hind limb was accelerated in mice that were transplanted with Flk-1+ cells compared with control mice, which were transplanted with vehicle, as evaluated by laser Doppler blood flowmetry. Transplantation of Flk-1+ cells also increased expression of VEGF mRNA in ischemic tissue compared to controls.
Direct local implantation of iPS cell-derived Flk-1+ cells would salvage tissues from ischemia. These data indicate that iPS cells could be valuable in the therapeutic induction of angiogenesis.
Obesity-related disorders are associated with the development of ischemic heart disease. Adiponectin is a circulating adipose-derived cytokine that is downregulated in obese individuals and after myocardial infarction. Here, we examine the role of adiponectin in myocardial remodeling in response to acute injury. Ischemia-reperfusion in adiponectin-deficient (APN-KO) mice resulted in increased myocardial infarct size, myocardial apoptosis and tumor necrosis factor (TNF)-α expression compared with wild-type mice. Administration of adiponectin diminished infarct size, apoptosis and TNF-α production in both APN-KO and wild-type mice. In cultured cardiac cells, adiponectin inhibited apoptosis and TNF-α production. Dominant negative AMP-activated protein kinase (AMPK) reversed the inhibitory effects of adiponectin on apoptosis but had no effect on the suppressive effect of adiponectin on TNF-α production. Adiponectin induced cyclooxygenase (COX)-2–dependent synthesis of prostaglandin E2 in cardiac cells, and COX-2 inhibition reversed the inhibitory effects of adiponectin on TNF-α production and infarct size. These data suggest that adiponectin protects the heart from ischemia-reperfusion injury through both AMPK- and COX-2–dependent mechanisms.
Patients with diabetes and other obesity-linked conditions have increased susceptibility to cardiovascular disorders1. The adipocytokine adiponectin is decreased in patients with obesity-linked diseases2. Here, we found that pressure overload in adiponectin-deficient mice resulted in enhanced concentric cardiac hypertrophy and increased mortality that was associated with increased extracellular signal-regulated kinase (ERK) and diminished AMP-activated protein kinase (AMPK) signaling in the myocardium. Adenovirus-mediated supplemention of adiponectin attenuated cardiac hypertrophy in response to pressure overload in adiponectin-deficient, wild-type and diabetic db/db mice. In cultures of cardiac myocytes, adiponectin activated AMPK and inhibited agonist-stimulated hypertrophy and ERK activation. Transduction with a dominant-negative form of AMPK reversed these effects, suggesting that adiponectin inhibits hypertrophic signaling in the myocardium through activation of AMPK signaling. Adiponectin may have utility for the treatment of hypertrophic cardiomyopathy associated with diabetes and other obesity-related diseases.
Obesity-related disorders are closely associated with the pathogenesis of cardiovascular disease. Adiponectin is a circulating adipose tissue-derived hormone that is down-regulated in obese individuals. Hypoadiponectinemia has been identified as an independent risk factor for type 2 diabetes, coronary artery disease, and hypertension, and experimental studies show that adiponectin plays a protective role in the development of insulin resistance, atherosclerosis, and inflammation. More recent findings have shown that adiponectin directly affects signaling in myocardial cells and exerts beneficial actions on the heart after pressure overload and ischemia–reperfusion injury. This review focuses on the role of adiponectin in the regulation of myocardial remodeling and acute cardiac injury.
Obesity-linked diseases are associated with suppressed endothelial progenitor cell (EPC) function. Adiponectin is an adipose-derived protein that is downregulated in obese and diabetic subjects. Here, we investigated the effects of adiponectin on EPCs. EPC levels did not increase in adiponectin deficient (APN-KO) in response to hindlimb ischemia. Adenovirus-mediated delivery of adiponectin increased EPC levels in both WT and APN-KO mice. Incubation of human peripheral blood mononuclear cells with adiponectin led to an increase of the number of EPCs. Adiponectin induced EPC differentiation into network structures and served as a chemoattractant in EPC migration assays. These data suggest that hypoadiponectinemia may contribute to the depression of EPC levels that are observed in patients with obesity-related cardiovascular disorders.
adiponectin; angiogenesis; endothelial progenitor cells
The adipose-derived plasma protein, adiponectin (APN), has various protective effects on cardiovascular diseases. In this study, we show that endogenous APN is required for full cyclooxygenase-2 (COX-2) induction by ischemia-reperfusion injury in the heart in vivo. In rat neonatal cardiac myocytes, APN-induced COX-2 expression was reduced by treatment with a sphingosine kinase-1 (SphK-1) inhibitor or siRNA targeting SphK-1. Treatment with a sphingosine-1-phosphate (S1P) receptor antagonist also diminished COX-2 expression in response to APN stimulation. These findings suggest that APN is a physiological regulator of COX-2 signaling in the heart and that this regulation occurs in part via a SphK-1–S1P receptor dependent mechanism in cardiac myocytes.
adiponectin; cyclooxygenase-2; sphingosine kinase-1; cardiac myocytes
There is an association between obesity and heart failure associated with LV dysfunction. Adiponectin is an adipocyte-derived hormone that is downregulated in obesity. Here, we examined the role of adiponectin in cardiac remodeling after myocardial infarction with loss- and gain-of-function genetic manipulations in an experimental model.
Myocardial infarction was created in adiponectin-deficient (APN-KO) and wild-type (WT) mice by the permanent ligation of the left anterior descending (LAD) artery. For some experiments, adenoviral vectors expressing adiponectin or β-galactosidase were delivered systemically. Cardiac structure and function were assessed by echocardiographic and Millar catheter measurements. Myocardial capillary density was assessed by staining with anti-CD31 antibody. Myocyte apoptotic activity was determined by TUNEL-staining. Myocardial interstitial fibrosis was evaluated by Masson’s trichrome staining.
APN-KO mice showed exacerbated left ventricular (LV) dilation, myocyte hypertrophy and contractile dysfunction compared with WT mice at 4 weeks after LAD ligation. Impaired LV function in APN-KO mice was coupled to myocyte hypertrophy, increased apoptotic activity and interstitial fibrosis in the remote zone, and reduced capillary density in the infarct border zone. No difference in infarct size was observed between WT and APN-KO mice. Administration of adenovirus-mediated adiponectin in WT mice resulted in decreased LV dilatation and improved LV function that was associated with increased capillary density in the infarct border zone and decreased myocyte hypertrophy, diminished myocardial apoptosis and decreased interstitial fibrosis in the remote zone.
These data suggest that adiponectin protects against the development of systolic dysfunction after myocardial infarction through its abilities to suppress cardiac hypertrophy and interstitial fibrosis, and protect against myocyte and capillary loss.
heart failure; ischemia; myocytes; ventricular function