Clonogenicity gives important information about the cellular reproductive potential following ionizing irradiation, but an abortive colony that fails to continue to grow remains poorly characterized. It was recently reported that the fraction of abortive colonies increases with increasing dose. Thus, we set out to investigate the production kinetics of abortive colonies using a model of branching processes.
We firstly plotted the experimentally determined colony size distribution of abortive colonies in irradiated normal human fibroblasts, and found the linear relationship on the log-linear or log-log plot. By applying the simple model of branching processes to the linear relationship, we found the persistent reproductive cell death (RCD) over several generations following irradiation. To verify the estimated probability of RCD, abortive colony size distribution (≤15 cells) and the surviving fraction were simulated by the Monte Carlo computational approach for colony expansion. Parameters estimated from the log-log fit demonstrated the good performance in both simulations than those from the log-linear fit. Radiation-induced RCD, i.e. excess probability, lasted over 16 generations and mainly consisted of two components in the early (<3 generations) and late phases. Intriguingly, the survival curve was sensitive to the excess probability over 5 generations, whereas abortive colony size distribution was robust against it. These results suggest that, whereas short-term RCD is critical to the abortive colony size distribution, long-lasting RCD is important for the dose response of the surviving fraction.
Our present model provides a single framework for understanding the behavior of primary cell colonies in culture following irradiation.
Diastolic heart failure (HF) i.e., “HF with preserved ejection fraction” (HF-preserved EF) accounts for up to 50% of all HF presentations; however there have been no therapeutic advances. This stems in part from an incomplete understanding about HF-preserved EF. Hypertension is the major cause of HF-preserved EF whilst HF-preserved EF is also highly associated with obesity. Similarly, excessive reactive oxygen species (ROS), i.e., oxidative stress occurs in hypertension and obesity, sensitizing the heart to the renin-angiotensin-aldosterone system, inducing autophagic type-II programmed cell death and accelerating the propensity to adverse cardiac remodeling, diastolic dysfunction and HF. Adiponectin (APN), an adipokine, mediates cardioprotective actions but it is unknown if APN modulates cardiomyocyte autophagy. We tested the hypothesis that APN ameliorates oxidative stress-induced autophagy in cardiomyocytes. Isolated adult rat ventricular myocytes were pretreated with recombinant APN (30µg/mL) followed by 1mM hydrogen peroxide (H2O2) exposure. Wild type (WT) and APN-deficient (APN-KO) mice were infused with angiotensin (Ang)-II (3.2mg/kg/d) for 14 days to induced oxidative stress. Autophagy-related proteins, mTOR, AMPK and ERK expression were measured. H2O2 induced LC3I to LC3II conversion by a factor of 3.4±1.0 which was abrogated by pre-treatment with APN by 44.5±10%. However, neither H2O2 nor APN affected ATG5, ATG7, or Beclin-1 expression. H2O2 increased phospho-AMPK by 49±6.0%, whilst pretreatment with APN decreased phospho-AMPK by 26±4%. H2O2 decreased phospho-mTOR by 36±13%, which was restored by APN. ERK inhibition demonstrated that the ERK-mTOR pathway is involved in H2O2-induced autophagy. Chronic Ang-II infusion significantly increased myocardial LC3II/I protein expression ratio in APN-KO vs. WT mice. These data suggest that excessive ROS caused cardiomyocyte autophagy which was ameliorated by APN by inhibiting an H2O2-induced AMPK/mTOR/ERK-dependent mechanism. These findings demonstrate the anti-oxidant potential of APN in oxidative stress-associated cardiovascular diseases, such as hypertension-induced HF-preserved EF.
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
Diet-induced obesity is associated with metabolic heart disease characterized by left ventricular (LV) hypertrophy and diastolic dysfunction. Polyphenols such as resveratrol (RSV) and the synthetic flavonoid derivative S17834 exert beneficial systemic and cardiovascular effects in a variety of settings including diabetes and chronic hemodynamic overload.
Methods and Results
We characterized the structural and functional features of a mouse model of diet-induced metabolic syndrome, and used the model to test the hypothesis that the polyphenols prevent myocardial hypertrophy and diastolic dysfunction. Male C57BL/6J mice were fed a normal diet or a diet high in fat and sugar (HFHS) with or without concomitant treatment with S17834 or RSV for up to 8 months. HFHS diet-fed mice developed progressive LV hypertrophy and diastolic dysfunction with preservation of systolic function in association with myocyte hypertrophy and interstitial fibrosis. In HFHS-fed mice there was increased myocardial oxidative stress with evidence of oxidant-mediated protein modification via tyrosine nitration and 4-OH-2-nonenol (HNE) adduction. HFHS-fed mice also exhibited increases in plasma fasting glucose, insulin and HOMA-IR indicative of insulin resistance. Treatment with S17834 or RSV prevented LV hypertrophy and diastolic dysfunction. For S17834, these beneficial effects were associated with decreases in oxidant-mediated protein modifications and hyper-insulinemia, and increased plasma adiponectin.
RSV and S17834 administered concurrently with a HFHS diet prevent the development of LV hypertrophy, interstitial fibrosis and diastolic dysfunction. Multiple mechanisms may contribute to the beneficial effects of the polyphenols including a reduction in myocardial oxidative stress and related protein modifications, amelioration of insulin resistance and increased plasma adiponectin. The polyphenols RSV and S17834 may be of value in the prevention of diet-induced metabolic heart disease.
left ventricular hypertrophy; diastolic dysfunction; 4-OH-2-nonenol; metabolic syndrome; oxidative stress
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.
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
Adiponectin (APN) is an adipose tissue-derived factor with anti-inflammatory and vascular protective properties whose levels paradoxically decrease with increasing body fat. In this study, APN’s role in the early development of ALI to lipopolysaccharide (LPS) was investigated. Intra-tracheal (i.t.) LPS elicited an exaggerated systemic inflammatory response in APN-deficient (APN−/−) mice compared to wild-type (wt) littermates. Increased lung injury and inflammation were observed in APN−/− mice as early as 4 hours after delivery of LPS. Targeted gene expression profiling performed on immune and endothelial cells isolated from lung digests 4 hours after LPS administration showed increased pro-inflammatory gene expression (e.g. IL-6) only in endothelial cells of APN−/− mice when compared to wt mice. Direct effects on lung endothelium were demonstrated by APN’s ability to inhibit LPS-induced IL-6 production in primary human endothelial cells in culture. Furthermore, T-cadherin-deficient (T-cad−/−) mice that have significantly reduced lung airspace APN but high serum APN levels had pulmonary inflammatory responses after i.t. LPS that were similar to those of wt mice. These findings indicate the importance of serum APN in modulating LPS-induced ALI and suggest that conditions leading to hypoadiponectinemia (e.g. obesity) predispose to development of ALI through exaggerated inflammatory response in pulmonary vascular endothelium.
Adiponectin; acute lung injury; endothelium; T-cadherin
The worldwide epidemic of obesity has brought cons iderable attention to research aimed at understanding the biology of adipocytes (fat cells) and the events occurring in adipose tissue (fat) and in the bodies of obese individuals. Accumulating evidence indicates that obesity causes chronic low-grade inflammation and that this contributes to systemic metabolic dysfunction that is associated with obesity-linked disorders. Adipose tissue functions as a key endocrine organ by releasing multiple bioactive substances, known as adipose-derived secreted factors or adipokines, that have pro-inflammatory or anti-inflammatory activities. Dysregulated production or secretion of these adipokines owing to adipose tissue dysfunction can contribute to the pathogenesis of obesity-linked complications. In this Review, we focus on the role of adipokines in inflammatory responses and discuss their potential as regulators of metabolic function.
Follistatin-like 1 (FSTL1) is an extracellular glycoprotein that is found in human serum. Recent work suggests that FSTL1 is secreted in response to ischemic injuries and that its overexpression is protective in the heart and vasculature.
Methods and Results
Here, we examined serum FSTL1 levels in patients with chronic heart failure with left ventricular (LV) ejection fraction <40% (n=86). The distribution of the sample, from these chronic heart failure patients, was separated into three tertiles of low, medium and high FSTL1 levels. Serum FSTL1 levels were increased 56% above age- and gender-matched, healthy controls. Diabetes mellitus, brain natriuretic peptide level, left atrial size, LV posterior wall thickness, LV end-diastolic diameter and LV mass were significant determinants of FSTL1 serum levels by bivariate analysis. After controlling for significant covariates, FSTL1 levels predicted LV hypertrophy (as measured by LV mass index) by multivariate linear regression analysis (P<0.001). Unadjusted survival analysis demonstrated increased mortality in patients with increasing FSTL1 levels (P=0.09). After adjusting for significant parameters, patients with increased FSTL1 remained at the highest risk of death [hazard ratio (95% confidence limits) 1.028, (0.98 and 1.78)]; (P=0.26). To determine whether elevated FSTL1 may be derived from the myocardium, FSTL1 protein expression was measured in samples from explanted, failing (n=18) and non-failing human hearts (n=7). LV failing hearts showed 2.5-fold higher FSTL1 protein levels than non-failing control hearts (P<0.05).
Elevated serum FSTL1 in human heart failure patients was associated with LV hypertrophy. Further studies on the role of FSTL1 as a biomarker in chronic systolic heart failure are warranted.
follistatin-like 1; systolic heart failure; left ventricular hypertrophy
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
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.
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
TGF-β family cytokines have diverse actions in the maintenance of cardiac homeostasis. Activin A is a member of this family whose regulation and function in heart is not well understood at a molecular level. Follistatin-like 3 (Fstl3) is an extracellular regulator of Activin A protein, and its function in the heart is also unknown.
Methods and Results
We analyzed the expression of various TGF-β superfamily cytokines and their binding partners in mouse heart. Activin βA and Follistatin-like 3 (Fstl3) were upregulated in models of myocardial injury. Overexpression of Activin A with an adenoviral vector (Ad-actβA) or treatment with recombinant Activin A protein protected cultured myocytes from hypoxia/reoxygenation- induced apoptosis. Systemic overexpression of Activin A in mice, by intravenous injection of Ad-actβA, protected hearts from ischemia/reperfusion injury. Activin A induced the expression of Bcl-2, and ablation of Bcl-2 by siRNA abrogated its protective action in myocytes. The protective effect of Activin A on cultured myocytes was abolished by treatment with Fstl3 or by a pharmacological Activin receptor-Like Kinase (ALK) inhibitor. Cardiac specific Fstl3 knock-out mice showed significantly smaller infarcts after ischemia/reperfusion injury that was accompanied by reduced apoptosis.
Activin A and Fstl3 are induced in heart by myocardial stress. Activin A protects myocytes from death and this activity is antagonized by Fstl3. Thus, the relative expression levels of these factors following injury is a determinant of cell survival in the heart.
myocytes; apoptosis; reperfusion; Activin A; Follistatin-like 3
In contrast to the well-established role of oxidative muscle fibers in regulating whole-body metabolism, little is known about the function of fast/glycolytic muscle fibers in these processes. Here, we generated a skeletal muscle-specific, conditional transgenic mouse expressing a constitutively active form of Akt1. Transgene activation led to muscle hypertrophy due to the growth of type IIb muscle fibers, which was accompanied by an increase in strength. Akt1 transgene induction in diet-induced obese mice led to reductions in body weight and fat mass, resolution of hepatic steatosis, and improved metabolic parameters. Akt1-mediated skeletal muscle growth opposed the effects of a high-fat/high-sucrose diet on transcript expression patterns in the liver and increased hepatic fatty acid oxidation and ketone body production. Our findings indicate that an increase in fast/glycolytic muscle mass can result in the regression of obesity and metabolic improvement through its ability to alter fatty acid oxidation in remote tissues.
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.
Adiponectin is a fat-derived plasma protein that has cardioprotective roles in obesity-linked diseases. Because cyclooxygenase 2 (COX-2) is an important modulator of endothelial function, we investigated the possible contribution of COX-2 to adiponectin-mediated vascular responses in a mouse hind limb model of vascular insufficiency. Ischemic insult increased COX-2 expression in endothelial cells of wild-type mice, but this induction was attenuated in adiponectin knockout mice. Ischemia-induced revascularization was impaired in mice in which the Cox-2 gene is deleted in Tie2-Cre-expressing cells. Adenovirus-mediated overexpression of adiponectin enhanced COX-2 expression and revascularization of ischemic limbs in control mice, but not in targeted Cox-2-deficient mice. In cultured endothelial cells, adiponectin protein increased COX-2 expression, and ablation of COX-2 abrogated the adiponectin-stimulated increases in endothelial cell migration, differentiation, and survival. Ablation of calreticulin (CRT) or its adaptor protein CD91 diminished adiponectin-stimulated COX-2 expression and endothelial cell responses. These observations provide evidence that adiponectin promotes endothelial cell function through CRT/CD91-mediated increases in COX-2 signaling. Thus, disruption of the adiponectin-COX-2 regulatory axis in endothelial cells could participate in the pathogenesis of obesity-related vascular diseases.
FGF21 functions as a metabolic regulator. The FGF21 transcript is reported to be abundantly expressed in liver, but little is known about the regulation of FGF21 expression in other tissues. In this study, we show that levels of FGF21 protein expression were similar in skeletal muscle and liver from fasted mice. FGF21 transcript and protein expression were upregulated in gastrocnemius muscle of skeletal muscle-specific Akt1 transgenic mice. Serum concentration of FGF21 was also increased by Akt1 transgene activation. In cultured skeletal muscle cells, FGF21 expression and secretion was regulated by insulin, Akt transduction and LY294002. These data indicate that skeletal muscle is a source of FGF21 and that its expression is regulated by a PI3-kinase/Akt1 signaling pathway-dependent mechanism.
FGF21; Akt; metabolism; transcript; transgenic mice
Obesity is characterized by low-grade systemic inflammation. Adiponectin is an adipose tissue-derived hormone, which is downregulated in obesity. Adiponectin displays protective actions on the development of various obesity-linked diseases. Several clinical studies demonstrate the inverse relationship between plasma adiponectin levels and several inflammatory markers including C-reactive protein. Adiponectin attenuates inflammatory responses to multiple stimuli by modulating signaling pathways in a variety of cell types. The anti-inflammatory properties of adiponectin may be a major component of its beneficial effects on cardiovascular and metabolic disorders including atherosclerosis and insulin resistance. In this reviews, we focus on the role of adiponectin in regulation of inflammatory response and discuss its potential as an antiinflammatory marker.
adiponectin; anti-inflammatory; cardioprotection; biomarker
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.
The fat-derived hormone adiponectin has been shown to have a protective role in macrovascular disorders. However, nothing is known about the function of adiponectin in retinal microvessel disease. Here, we investigated the causal role of adiponectin in retinal vessel formation and inflammation under conditions of hypoxia. When neonatal mice were subjected to ischemia-induced retinopathy, pathological retinal neovascularization during ischemia was exacerbated in adiponectin-knockout (APN-KO) mice compared with wild-type mice (neovascular area: 17.0±1.0% versus 11.7±0.6%, respectively). APN-KO mice also exhibited increased leukocyte adhesion (2.3±0.4-fold) and tumor necrosis factor (TNF)-α expression (2.6±0.2-fold) in hypoxic retina. Adenovirus-mediated overexpression of adiponectin in wild-type and APN-KO mice attenuated hypoxia-induced pathological retinal neovascularization by 35% in wild-type mice and by 40% in APN-KO mice and leukostasis by 64% in wild-type mice and by 75% in APN-KO mice, which were associated with reduced TNF-α production. TNF-α blockade diminished the enhanced pathological neovascularization in APN-KO mice by 34%, and the inhibitory effects of adiponectin overexpression on retinal neovascularization and leukocyte adhesion were abolished in mice lacking TNF-α. These data provide evidence that adiponectin protects against retinal vessel injury following pathological stimuli through modulation of TNF-α inflammatory responses.
adiponectin; neovascularization; ischemia; inflammation; angiogenesis