Published online before print December 24, 2007, doi: 10.1161/CIRCULATIONAHA.107.725044
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(Circulation. 2008;117:216-223.)
© 2008 American Heart Association, Inc.
Stroke |
Adiponectin Prevents Cerebral Ischemic Injury Through Endothelial Nitric Oxide Synthase–Dependent Mechanisms
From the Stroke and Neurovascular Regulation Laboratory (M.N., J.Q., C.K., H.K.S., M.A.M.), Department of Neurology and Radiology, Massachusetts General Hospital & Harvard Medical School, Charlestown, Mass, and Molecular Cardiology/Whitaker Cardiovascular Institute (Y.I., A.H., R.S., N.O.), Boston University School of Medicine, Boston, Mass.
Correspondence to Noriyuki Ouchi, MD, PhD, Molecular Cardiology/Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany St, W611, Boston, MA 02118. E-mail nouchi{at}bu.edu
Received July 6, 2007; accepted November 8, 2007.
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Abstract |
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Background— Adiponectin is a fat-derived plasma protein that has beneficial actions on cardiovascular disorders. A low level of plasma adiponectin is associated with increased mortality after ischemic stroke; however, the causal role of adiponectin in ischemic stroke is unknown.
Methods and Results— To explore the role of adiponectin in the development of acute cerebral injury, we subjected adiponectin-deficient (APN-KO) and wild-type (WT) mice to 1 hour of middle cerebral artery occlusion followed by 23 hours of reperfusion. APN-KO mice exhibited enlarged brain infarction and increased neurological deficits after ischemia-reperfusion compared with WT mice. Conversely, adenovirus-mediated supplementation of adiponectin significantly reduced cerebral infarct size in WT and APN-KO mice. APN-KO mice showed decreased cerebral blood flow during ischemia by laser speckle flowmetry methods. Adiponectin colocalized within the cerebral vascular endothelium under transient ischemic conditions by immunohistochemical analysis. Phosphorylation of endothelial nitric oxide synthase in ischemic brain tissues and the production of nitric oxide metabolites in plasma were attenuated in APN-KO mice compared with WT mice. Adenovirus-mediated administration of adiponectin stimulated endothelial nitric oxide synthase phosphorylation and nitric oxide metabolites during cerebral ischemia in both WT and APN-KO mice. Neuronal nitric oxide synthase expression during ischemia did not differ between WT and APN-KO mice. Adenovirus-mediated delivery of adiponectin did not affect brain infarction in mice deficient in endothelial nitric oxide synthase.
Conclusions— These data provide causal evidence that adiponectin exerts a cerebroprotective action through an endothelial nitric oxide synthase–dependent mechanism. Adiponectin could represent a molecular target for the prevention of ischemic stroke.
Key Words: adiponectin • stroke • cerebral ischemia • reperfusion • nitric oxide synthase
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Introduction |
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Ischemic stroke is a major cause of death and disability in Western countries.1 Obesity and obesity-linked diseases including hypertension and type 2 diabetes mellitus are well-documented risk factors for stroke2; however, the molecular link between obesity and the development of ischemic stroke has not been fully clarified. Adiponectin, also referred to as ACRP30, AdipoQ, and gelatin-binding protein-28, is a fat-derived secreted protein that is expressed specifically in adipose tissue.3–6 Importantly, an inverse association is observed between plasma adiponectin levels and fat accumulation.7 Clinically, plasma adiponectin levels negatively correlate with risk factors for ischemic heart disease, including dyslipidemia, high blood pressure, and high C-reactive protein levels.7,8 Furthermore, hypoadiponectinemia, defined as a low plasma adiponectin level (<4 µg/mL), is closely associated with increased risk of type 2 diabetes mellitus, hypertension, and coronary heart disease.7–9 These findings suggested that hypoadiponectinemia could contribute to the development of various obesity-linked complications.
Clinical Perspective p 223
Several experimental studies show that adiponectin-deficient (APN-KO) mice exhibit diet-induced insulin resistance,10,11 exacerbated myocardial remodeling in response to pressure overload,12 and severe cardiac injury after ischemia-reperfusion.13,14 Conversely, adiponectin replenishment stimulates insulin sensitivity15 and inhibits pathological cardiac hypertrophy12 and ischemia-induced myocardial damage.14 These protective actions of adiponectin are due at least in part to its ability to stimulate AMP-activated protein kinase (AMPK) signaling in the target organs. These data indicate that adiponectin plays protective roles in the development of obesity-linked heart and metabolic diseases. Adiponectin also exerts beneficial actions on vascular diseases. APN-KO mice develop impaired ischemia-induced angiogenesis in a mouse model of vascular insufficiency16 and an excessive vascular remodeling response to injury.17 Adiponectin overexpression reduces atherosclerotic lesion formation in a mouse model of atherosclerosis.18 However, the molecular mechanisms of vascular protection by adiponectin remain unclear.
Recently, a clinical study has suggested an association between hypoadiponectinemia and increased mortality after ischemic stroke and a negative correlation between adiponectin levels and initial infarct volume.19 Furthermore, a cross-sectional study showed that plasma adiponectin levels are decreased in patients with ischemic cerebrovascular disease.20 However, the involvement of adiponectin in cerebrovascular disease has not been examined experimentally. Here, we investigate the causal role of adiponectin in the development of ischemic stroke. We examined the effects of adiponectin on cerebral infarct, blood flow, and endothelial nitric oxide synthase (eNOS) signaling in response to ischemia with loss-of-function and gain-of-function genetic manipulations. Our findings suggest that adiponectin confers resistance to acute cerebral ischemic damage through eNOS-dependent vascular protective actions.
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Methods |
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Phospho-eNOS (Ser1177) antibody was purchased from Cell Signaling Technology (Danvers, Mass). eNOS antibody was purchased from Santa Cruz Biotechnology (Santa Cruz, Calif). Neuronal nitric oxide synthase (nNOS) antibody was purchased from BD Transduction Laboratories (Lexington, Ky). Actin antibody was purchased from Sigma (St Louis, Mo). Adiponectin/Acrp30 antibody was purchased from R&D Systems (Minneapolis, Minn). CD31 antibody was purchased from BD Pharmingen (San Diego, Calif). Adenoviral vectors containing the gene for β-galactosidase (Ad-β-gal) and full-length mouse adiponectin (Ad-APN) have been described previously.12
Induction of Middle Cerebral Artery Occlusion
Studies using mice were approved by local committee review and were conducted according to the National Institute of Health’s "Guide for the Care and Use of Laboratory Animals." Male adiponectin-deficient (APN-KO) mice, eNOS-deficient (eNOS-KO) mice, and wild-type (WT) mice in a C57/BL6 background were used for the present study. Mice 10 to 12 weeks old were anesthetized with 2% isoflurane and maintained on 1% to 1.5% isoflurane in 70% nitrous oxide and 30% oxygen by face mask. Rectal temperature was maintained between 36.5°C and 37.5°C with a homeothermic blanket. Focal cerebral ischemia was induced by occluding the middle cerebral artery (MCA) by the intraluminal filament technique, as described previously.21,22 We introduced a silicon-coated 8-0 monofilament in the internal carotid artery and advanced it so as to occlude the MCA. The filament was withdrawn 1 hour after occlusion. In all animals, regional cerebral blood flow (CBF) was measured by laser Doppler (PF2B; Perimed, Stockholm, Sweden) with a flexible probe to confirm the achievement of consistent and similar levels of ischemic induction. In randomly selected animals, the left femoral artery was cannulated for mean arterial blood pressure and blood gas determination. Arterial blood gas (pH, PaO2, and PaCO2) was analyzed with a blood gas/pH analyzer (Corning 178, CIBA-Corning Diagnostics, Medfield, Mass). In some experiments, 2x108 plaque-forming units of Ad-APN or Ad-β-gal was delivered into the jugular vein of mice 5 days before the ischemic injury. Mouse adiponectin levels were determined by ELISA kit (Otsuka Pharmaceutical Co Ltd, Tokyo, Japan).12 In some experiments, nitrate/nitrite concentrations were measured with a nitrate/nitrite colorimetric assay kit (Cayman Chemical Co, Ann Arbor, Mich).
Neurological Score
Neurological deficit was scored according to the criteria of Hara et al,21 whereby a score of 0 indicates no deficits (normal), 1 indicates a failure to extend the forepaw (mild), 2 indicates contralateral circling (moderate), and 3 indicates loss of walking or righting reflex (severe). Assessments were made 24 hours after the ischemic insult in a blinded fashion.
Determination of Infarct Size
Brains were removed at 24 hours after MCA occlusion. Cerebral infarct size was determined on 2,3,5-triphenyltetrazolium chloride (TTC)–stained, 2-mm-thick brain sections. Infarction areas were quantified with MCID M4 image-analysis software (Imaging Research Inc, St Catherines, Ontario, Canada). To account for and eliminate the effects of swelling/edema, infarction volume was calculated by an indirect measurement by summing the volumes of each section with the following formula: contralateral hemisphere (mm3)–undamaged ipsilateral hemisphere (mm3).
Laser Speckle Flowmetry
Laser speckle flowmetry (LSF)was used to study the spatiotemporal characteristics of CBF changes during focal cerebral ischemia in mice as described previously.23 Briefly, a CCD camera (Cohu Inc, Poway, Calif) was positioned above the head, and a laser diode (780 nm) was used to illuminate the intact skull surface in a diffuse manner. The penetration depth of the laser was 
500 µm. Raw speckle images were used to compute speckle contrast, which is a measure of speckle visibility related to the velocity of the scattering particles and, therefore, CBF. The speckle contrast is defined as the ratio of the SD of pixel intensities to the mean pixel intensity in a small region of the image. Ten consecutive raw speckle images were acquired at 15 Hz (an image set), processed by computing the speckle contrast with a sliding grid of 7x7 pixels, and averaged to improve signal-to-noise ratio. Relative CBF images (percentage of baseline) were calculated by computing the ratio of a baseline image of correlation time values to subsequent images. Laser speckle perfusion images were started 1 minute before distal MCA occlusion and continued throughout the experiment. Ischemic CBF deficit was analyzed 2-dimensionally over time by quantifying the area of cortex (mm2) with either severe (0% to 20% residual CBF, representing core) or moderate (21% to 30% residual CBF, representing penumbra) CBF reduction by use of a thresholding paradigm.
Immunohistochemical Analysis
Mice were euthanized at 30 minutes or 24 hours after induction of ischemia. Mice were transcardially perfused with cold heparinized saline to eliminate the interference of circulating adiponectin for nonspecific staining, and brains were fixed with 4% phosphate-buffered paraformaldehyde. Forty-micrometer-thick coronal brain sections were prepared and incubated with anti-adiponectin antibody or control IgG antibody. In some experiments, double-fluorescence staining was performed on brain sections. Sections were stained with anti-CD31 antibody, followed by treatment with Cy2-conjugated secondary antibody to detect CD31, and subsequently with anti-adiponectin antibody, followed by treatment with rhodamine-conjugated secondary antibody to detect adiponectin. Fluorescent-stained sections were analyzed by confocal microscopy (Bio-Rad MRC 1024; Bio-Rad, Hercules, Calif).
Western Blot Analysis
Brain tissues were collected at 0, 30, and 60 minutes after induction of ischemia. Proteins were isolated according to standard techniques, separated by 10% SDS/PAGE gel, and transferred onto PVDF membrane. Immunoblot analysis was performed with the indicated antibodies followed by incubation with secondary antibody conjugated with horseradish peroxidase.
Absolute CBF Measurements
Animals were anesthetized with isoflurane as described above. The right femoral artery and jugular vein were cannulated with PE-10 polyethylene tubing. Arterial blood was withdrawn continuously from the femoral artery at a rate of 0.3 mL/min (Stoelting, Wood Dale, Ill). One microcurie of N-isopropyl-[methyl 1,3-14C]-p-iodoamphetamine (American Radiolabeled Chemicals Inc, St Louis, Mo) was injected into the jugular vein. Twenty seconds after injection, the animal was decapitated, and the blood withdrawal terminated simultaneously. The brain was removed and then dissected into right and left hemispheres and subdivided into cortex striatum and cerebellum regions. After the addition of ScintiGest tissue solubilizer (Fisher Scientific, Pittsburgh, Pa) and incubation (50°C for 6 hours), scintillation fluid and H2O2 were added. Twelve hours after shaking, radioactivity in brain and blood was measured by liquid scintillation spectrometry (RackBeta 1209, LKB, Bromma, Sweden). CBF was calculated according to the previously described method.24
Statistical Analysis
All data are expressed as mean±SD or SEM as indicated in the Figure legends. The mean value was compared between 2 groups with an unpaired t test. Comparison among >3 groups was performed by ANOVA with Fisher test. A value of P<0.05 was accepted as statistically significant.
The authors had full access to the data and take full responsibility for its integrity. All authors have read and agree to the manuscript as written.
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Adiponectin Deficiency Results in Increased Cerebral Injury After Ischemia-Reperfusion
To elucidate the impact of adiponectin on cerebral ischemic damage, we examined the response to ischemic injury in APN-KO mice. WT and APN-KO mice in a C57BL/6 background were subjected to 1 hour of MCA occlusion via intraluminal filament followed by 23 hours of reperfusion. Representative photographs of brain tissues stained with 2% TTC at 24 hours after ischemia to detect infarct area in WT and APN-KO mice are shown in Figure 1A. Quantitative analysis revealed that APN-KO mice developed significantly larger infarcts at 24 hours after transient ischemia than WT mice (75.1±20.9 versus 49.0±15.4 mm3, respectively; Figure 1B). Neurological deficits, determined by monitoring of ambulatory activity at 24 hours after ischemia, were significantly increased in APN-KO mice compared with WT mice (neurological score 1.9±0.3 versus 0.8±0.7, respectively; Figure 1C). Mean arterial blood pressure and arterial blood gas (pH, PaO2, and PaCO2) before and after ischemia did not differ between WT and APN-KO mice (Table). These data show that a deficiency of endogenous adiponectin promotes cerebral ischemic injury.
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To investigate whether adiponectin supplementation could modulate cerebral infarct size in response to ischemia, we systemically delivered adenoviral vectors that expressed either murine adiponectin (Ad-APN) or β-galactosidase (Ad-β-gal) as a control into APN-KO and WT mice through the jugular vein 5 days before transient ischemia. At the time of surgery, plasma adiponectin levels were <0.05 µg/mL in Ad-β-gal–treated APN-KO mice, 19.2±5.2 µg/mL in Ad-APN–treated APN-KO mice, 10.1±1.8 µg/mL in Ad-β-gal–treated WT mice, and 20.6±4.6 µg/mL in Ad-APN–treated WT mice. APN-KO mice receiving Ad-APN showed a significant decrease in infarct volumes at 24 hours after transient ischemia compared with mice treated with Ad-β-gal (22.7±9.9 versus 67.6±13.5 mm3, respectively; Figure 1D), which suggests that adiponectin overexpression reduced the increased infarct size observed in APN-KO mice. Ad-APN treatment significantly reduced infarct volumes in WT mice after transient ischemia compared with Ad-β-gal (26.3±11.8 versus 51.8±6.8 mm3, respectively; Figure 1D). These data show that a 2-fold overexpression of adiponectin protects the brain from damage after ischemia-reperfusion.
Reduced CBF During Ischemia in APN-KO Mice
Because an increase in collateral blood flow protects against stroke, the changes in CBF in APN-KO and WT mice during ischemia were assessed with an LSF technique. For these assays, distal MCA occlusion was used to cause ischemic injury, and CBF dynamics were measured transcranially during ischemia.23 Representative photographs of the changes in CBF below 30% (blue) at 1 hour after distal MCA occlusion in WT and APN-KO mice are shown in Figure 2A. APN-KO mice exhibited larger areas of reduced CBF (
30% of baseline) than WT mice (13.2±1.2 versus 8.5±1.6 mm2, respectively; Figure 2B). Similarly, the penumbra area showing moderate ischemia with 21% to 30% residual CBF was significantly larger in APN-KO mice than in WT mice (Figure 2B). The area of cortex with 20% residual CBF (core) did not differ between APN-KO and WT mice (Figure 2B), and the absolute blood flow under nonischemic conditions as measured by the [14C]-iodoamphetamine technique did not differ between WT and APN-KO mice (Figure 2C). These data show that adiponectin ablation leads to reduced collateral blood flow during ischemia.
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) and APN-KO (
) mice were determined by [14C] iodoamphetamine method. Data are presented as mean±SD.
Accumulation of Adiponectin Into Injured Vascular Endothelium
To investigate the localization of adiponectin in ischemic brain tissues, its presence was assessed by immunohistochemical analysis. Representative photographs of brain tissue stained with anti-adiponectin antibodies are shown in Figure 3A. Adiponectin was clearly visible in brain sections from WT mice at 30 minutes after brain ischemia, whereas little or no signal of adiponectin was seen in the homologous nonischemic contralateral cortex. Dual-immunofluorescence staining was performed on adiponectin (red) and CD31 (green), an endothelial cell marker. Merged images demonstrated that these proteins colocalized (yellow) in ischemic brain (Figure 3B). Adiponectin costaining with CD31 was still detected in ischemic brain in WT mice at 24 hours after cerebral ischemia-reperfusion (Figure 3B); however, adiponectin mRNA was not upregulated in brain tissue after ischemia (data not shown). Double-fluorescence staining also revealed adiponectin and CD31 colocalization at 30 minutes after induction of cerebral ischemia in ischemic brain of APN-KO mice 5 days after systemic administration of Ad-APN (Figure 3B). Collectively, these data suggest that adiponectin accumulates at the endothelium of the ischemic cortex in response to cerebral ischemia and that adiponectin originates from an extravascular source.
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Reduced eNOS Activation in Response to Ischemia in APN-KO Mice
eNOS and vascular nitric oxide (NO) play important roles in maintenance of CBF and contribute to protection against brain injury after ischemia.25,26 To analyze the potential role of eNOS in adiponectin-mediated regulation of ischemic injury, the phosphorylation of eNOS at Ser1177 in brain tissues was assessed by Western blotting. Basal levels of eNOS phosphorylation in brain tissues did not differ between WT and APN-KO mice (Figure 4A). An increase in eNOS phosphorylation was detected in brains of WT mice at 30 and 60 minutes after the induction of ischemia; however, eNOS phosphorylation after ischemia was markedly diminished in APN-KO mice. Total eNOS protein levels before and during ischemia did not differ between WT and APN-KO mice (Figure 4A), and no significant difference in eNOS mRNA level was found in ischemic brains between WT and APN-KO mice (data not shown). nNOS protein levels were increased in brains of WT and APN-KO mice at 60 minutes after induction of ischemia (Figure 4B); however, no significant differences in nNOS protein levels before and during ischemia were observed between WT and APN-KO mice. Consistent with the observations of eNOS phosphorylation, ischemic injury increased plasma concentrations of nitrate/nitrite (NO metabolites) in WT mice by a factor of 2.7, but this induction was significantly attenuated in APN-KO mice (Figure 4C). Basal plasma levels of NO metabolite did not differ between the 2 strains of mice (Figure 4C).
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To examine the impact of adiponectin overexpression on eNOS signaling during ischemia, Ad-APN and Ad-β-gal were systemically injected into WT and APN-KO mice 5 days before cerebral ischemia. Ad-APN treatment significantly promoted eNOS phosphorylation in ischemic brains in both WT and APN-KO mice compared with Ad-β-gal treatment (Figure 4D). Similarly, plasma NO metabolites were increased in WT and APN-KO mice after Ad-APN treatment (Figure 4E).
To further assess the contribution of eNOS signaling to the cerebroprotective action of adiponectin in vivo, we systemically injected Ad-APN or Ad-β-gal into eNOS-KO mice in a C57BL/6 background 5 days before induction of ischemia. At the time of surgery, circulating adiponectin levels increased to a level 2.3±0.2 times higher in Ad-APN–treated eNOS-KO mice than in Ad-β-gal–treated eNOS-KO mice (17.0±1.8 and 7.5±2.0 µg/mL, respectively; P<0.05). In contrast to WT mice (Figure 1D), treatment with Ad-APN did not affect infarct size after ischemia-reperfusion injury in eNOS-KO mice (Figure 4F). Collectively, these data suggest that the protective action of adiponectin on ischemic stroke is eNOS-dependent.
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Discussion |
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In the present study, we demonstrate for the first time that an adipose-derived hormone adiponectin protects the brain from acute ischemic injury in a mouse model of MCA occlusion. APN-KO mice exhibit increased cerebral infarct size after ischemia-reperfusion, whereas supplementation of exogenous adiponectin clearly suppressed infarct size in both APN-KO and WT mice. Ischemic stroke occurs with many obesity-related disorders that are associated with hypoadiponectinemia.2,7 Epidemiological studies have shown that hypoadiponectinemia could be a useful biomarker for the presence of ischemic stroke and increased mortality after ischemic stroke.19,20 The present observations indicate that adiponectin acts as an endogenous modulator of brain injury in response to acute ischemia and that hypoadiponectinemia participates in the exacerbated ischemic stroke. Thus, agents that increase circulating adiponectin levels could represent a potential therapeutic target for the prevention of ischemic stroke.
The beneficial effects of adiponectin on ischemic injury are due at least in part to its vascular protective actions, which involve eNOS-dependent mechanisms. It has been shown that adiponectin stimulates eNOS phosphorylation and NO production in cultured endothelial cells.27,28 Consistent with these findings, the injury-induced increase in eNOS phosphorylation was diminished in ischemic brains of APN-KO mice in the present study. In contrast, eNOS activation in nonischemic brains did not differ between WT and APN-KO mice, and nNOS expression level in brain during ischemia was the same in WT and APN-KO mice. Notably, the cerebroprotective actions of adiponectin were abolished in eNOS-KO mice. In addition, adiponectin accumulated to the vascular endothelium in brain after acute ischemia. Furthermore, studies have shown that eNOS contributes to vascular protection and plays an important protective role in the regulation of brain damage after ischemia.25,26 Collectively, these observations suggest that the adiponectin-eNOS regulatory signaling axis functions to modulate vascular function under ischemic conditions, protecting against cerebral injury after stoke.
In the present study, administration of adiponectin stimulated eNOS phosphorylation in ischemic brains of WT and APN-KO mice. Residue 1177 of eNOS (in humans) is a known substrate for AMPK.29 We have previously demonstrated that adiponectin stimulates eNOS phosphorylation in cultured endothelial cells by promoting AMPK signaling.27 Similarly, AMPK signaling is found to mediate adiponectin-stimulated NO production in endothelial cells through its ability to phosphorylate eNOS.28 These data suggest that adiponectin activates eNOS in cerebral vascular endothelium through AMPK signaling.
An increase in CBF contributes to protection against ischemic stroke. eNOS-KO mice show reduced blood flow in ischemic brain and enhanced brain infarcts after MCA occlusion.25 Administration of NO donors increases CBF in ischemic regions and attenuates brain infarction.30 We found that APN-KO mice show decreased collateral blood flow in brain during ischemia, which is accompanied by reduced eNOS activation in ischemic cerebral tissues. In contrast, CBF under nonischemic conditions was the same in WT and APN-KO mice. These data suggest that adiponectin confers resistance to brain injury through modulation of CBF during ischemia, which is dependent on eNOS signaling.
NO production during cerebral ischemia is derived from both eNOS and nNOS.31 The increase in plasma NO production in response to ischemia was diminished in APN-KO mice. In parallel, eNOS phosphorylation during ischemia was reduced in APN-KO mice compared with WT mice. In contrast, no significant differences in nNOS expression in ischemic brains were observed between WT and APN-KO mice. Therefore, adiponectin deficiency may mainly affect eNOS-derived NO production during cerebral ischemia. However, the enzymatic activity of nNOS after ischemia was not examined in the present study, and we cannot exclude the possibility that adiponectin deficiency suppresses ischemia-mediated nNOS activity, resulting in reduction of plasma NO metabolites.
It has been shown previously that adiponectin accumulates at sites of damaged endothelium. Adiponectin protein was detected in the catheter-injured vessel walls but not in the intact artery by immunohistochemistry.32 Adiponectin is also detected in endothelium of injured human aorta but not in intact vessel walls.33 Recently, we found that adiponectin protein was observed in vasculature of ischemic heart in a mouse model of ischemia-reperfusion.34 In agreement with these observations, endogenous adiponectin was detected in injured vascular endothelium in WT mice until 24 hours after cerebral ischemia-reperfusion. In addition, administration of adenovirus-mediated adiponectin in APN-KO mice results in the detection of adiponectin protein in damaged vascular endothelium during cerebral ischemia. The mechanism of adiponectin accumulation in injured endothelium remains unclear. Adiponectin exhibits adherent properties, binding to collagen I and III, which are predominantly extracellular matrices in the vasculature.32,35 Thus, adiponectin may accumulate into injured vessels through its binding to extracellular matrices such as collagen I and III.
A previous report showed that eNOS-KO mice in a mixed background of 129/SV and C57BL/6 exhibited larger infarct size (21%) after permanent cerebral ischemia than WT mice when both male and female mice were analyzed together.25 In the present study, infarct volumes in male eNOS-KO mice were smaller than in WT mice (15.8%), but this was not statistically significant. The discrepancy between the present data and the previous study may result from differences in background strains, gender, and the procedure of brain ischemia (transient versus permanent).
In summary, we demonstrate a molecular link of obesity to the development of ischemic stroke by providing in vivo evidence that the fat-derived cytokine adiponectin functions to protect against ischemic brain injury. The activity of adiponectin is mediated in part by its ability to activate eNOS. Because dysregulation of the eNOS signaling pathway could contribute to endothelial dysfunction, atherogenesis, and impaired angiogenesis, the present findings suggest a new mechanism by which hypoadiponectinemia causes the pathogenesis of obesity-linked vascular complications.
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Acknowledgments |
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We thank Dr Kenneth Walsh for careful reading of this manuscript and Shumei Qiu and Yumei Wang for technical assistance.
Sources of Funding
This work was supported by an American Heart Association Scientist Development Grant to Dr Ouchi and Northeast Affiliate National Institutes of Health grant (P50 NS10828) to Dr Moskowitz. Dr Nishimura was supported by grants from the Uehara Memorial Foundation.
Disclosures
None.
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Guest Editor for this article was Roberto Bolli, MD.
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Circulation 2008 117: 127.
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