Adiponectin Knockout Mice Research Articles

Myocardial mitochondrial and contractile function are preserved in mice lacking adiponectin.

Adiponectin deficiency leads to increased myocardial infarct size following ischemia reperfusion and to exaggerated cardiac hypertrophy following pressure overload, entities that are causally linked to mitochondrial dysfunction. In skeletal muscle, lack of adiponectin results in impaired mitochondrial function. Thus, it was our objective to investigate whether adiponectin deficiency impairs mitochondrial energetics in the heart. At 8 weeks of age, heart weight-to-body weight ratios were not different between adiponectin knockout (ADQ-/-) mice and wildtypes (WT). In isolated working hearts, cardiac output, aortic developed pressure and cardiac power were preserved in ADQ-/- mice. Rates of fatty acid oxidation, glucose oxidation and glycolysis were unchanged between groups. While myocardial oxygen consumption was slightly reduced (-24%) in ADQ-/- mice in isolated working hearts, rates of maximal ADP-stimulated mitochondrial oxygen consumption and ATP synthesis in saponin-permeabilized cardiac fibers were preserved in ADQ-/- mice with glutamate, pyruvate or palmitoyl-carnitine as a substrate. In addition, enzymatic activity of respiratory complexes I and II was unchanged between groups. Phosphorylation of AMP-activated protein kinase and SIRT1 activity were not decreased, expression and acetylation of PGC-1α were unchanged, and mitochondrial content of OXPHOS subunits was not decreased in ADQ-/- mice. Finally, increasing energy demands due to prolonged subcutaneous infusion of isoproterenol did not differentially affect cardiac contractility or mitochondrial function in ADQ-/- mice compared to WT. Thus, mitochondrial and contractile function are preserved in hearts of mice lacking adiponectin, suggesting that adiponectin may be expendable in the regulation of mitochondrial energetics and contractile function in the heart under non-pathological conditions.

FGF21 attenuates pathological myocardial remodeling following myocardial infarction through the adiponectin-dependent mechanism

Ischemic heart disease is one of the leading causes of death. Fibroblast growth factor 21 (FGF21) is a circulating factor with an anti-diabetic property. Skeletal muscle is an important source of FGF21 production. Here, we investigated whether skeletal muscle-derived FGF21 modulates cardiac remodeling in a murine model of myocardial infarction. Myocardial infarction was produced in C57BL/6J wild-type (WT) mice by the permanent ligation of the left anterior descending coronary artery (LAD). Adenoviral vectors expressing FGF21 (Ad-FGF21) or control β-galactosidase were intramuscularly injected into mice at 3 days before permanent LAD ligation. Intramuscular injection of Ad-FGF21 increased plasma FGF21 levels in WT mice compared with control. Treatment of WT mice with Ad-FGF21 led to improvement of left ventricular systolic dysfunction and dilatation at 2 weeks after LAD ligation. Ad-FGF21 administration to WT mice also led to enhancement of capillary density in the infarct border zone, and reduction of myocyte apoptosis in the remote zone, which were accompanied by decreased expression of pro-inflammatory cytokines. Furthermore, treatment of WT mice with Ad-FGF21 increased plasma levels of adiponectin, which is a cardioprotective adipokine. The beneficial effects of Ad-FGF21 on cardiac dysfunction and inflammatory response after myocardial infarction were diminished in adiponectin-knockout mice. These data suggest that muscle-derived FGF21 ameliorates adverse cardiac remodeling after myocardial infarction, at least in part, through an adiponectin-dependent mechanism.

ADIPONECTIN LIMITS MONOCYTIC MICROPARTICLE-INDUCED INFLAMMASOME ACTIVATION AND ENDOTHELIAL DYSFUNCTION

Monocytic microparticles (mono-MPs) are small vesicles (100-1000 nm) that are shed from monocytes following cellular activation or apoptosis. Levels of mono-MPs are heightened in the inflammatory state and mono-MPs have been reported to play a fundamental role at all stages of the atherothrombotic process. Alterations in monocyte-endothelial cell (EC) interaction mediate immune activation and propagate inflammation within the developing atheroma. Adiponectin is an anti-inflammatory adipokine that primes monocyte differentiation into anti-inflammatory M2 macrophages vs. pro-inflammatory M1 macrophages and inhibits EC activation thereby retarding plaque development. The goal of this work was to uncover the mechanistic root underlying the pathophysiological and clinical benefits of adiponectin. Specifically, we hypothesized that mono-MPs trigger NLRP3 inflammasome-dependent EC activation and adiponectin inhibits this phenomenon, in part, through limiting mono-MP production and activation. Mono-MPs were characterized using electron microscopy, flow cytometry and NanoSight microscopy. Exosomes were excluded based on size and absence of the MP-specific marker phosphatidylyserine. Studies were conducted with THP-1 monocytes and peritoneal monocytes isolated from adiponectin knockout (Adipoq-/-) mice. We evaluated the effects of lipopolysaccharide (LPS; 5 μg/ml, 24 h) and recombinant adiponectin (10 μg/ml) on mono-MP production, expression of the NLRP3 inflammasome and its components, and key downstream inflammatory factors. We also studied how MPs alter the expression of critical adhesion molecules and inflammatory transcription factors in human umbilical vein endothelial cell (HUVEC) cultures. Inflammasome activation was examined in mono-MPs derived from THP-1 cells. Imaging analysis confirmed that the mono-MPs isolated were sized 100-1000 nm and expressed phosphatidylyserine. Absence of exosomes in the final mono-MP samples was further confirmed by a lack of CD63 expression. LPS concentration-dependently increased MP generation by THP-1 monocytes. Adiponectin suppressed MP release in untreated and LPS-stimulated monocytes. LPS-treated mono-MPs exhibited a marked upregulation in the NLRP3 inflammasome and its components - ASC, caspase-1, pro-IL1β and IL1β. Adiponectin attenuated these changes. Mono-MP-HUVEC co-cultures revealed significant increases in markers of endothelial activation (ICAM-1, VCAM-1) and inflammatory transcription factors (p-IkB, p-NFkB and p-ERK-1). Adiponectin inhibited these outcomes. Compared to monocytes from Adipoq+/+ mice, those from Adipoq-/- littermates showed a ∼6-fold greater production of MPs (Cd11b+/Ly6Chi/AnnexinV+) following LPS stimulation. We report a novel mechanism through which mono-MPs sustain NLRP3 inflammasome activation and endothelial dysfunction. These data reveal a previously unknown atheroprotective mechanism for adiponectin that may account for the inverse association observed between circulating adiponectin levels and the risk of diabetes and obesity.

UNDERSTANDING THE ROLE OF ADIPONECTIN PROCESSING IN AMELIORATING INSULIN RESISTANCE AND RELATED COMPLICATIONS

BACKGROUND: The rising prevalence of obesity is recognized as one of the most important risk factors for the development of diabetes and associated cardiovascular complications. The precise mechanisms that link obesity to diabetes and increased atherosclerotic vascular diseases are not yet fully understood. Insulin resistance, a decreased sensitivity to the actions of insulin, results in impaired glucose metabolism and contributes to the cardiovascular complications associated with diabetes. Secretion of adiponectin, an antiatherogenic and anti-diabetic adipokine is decreased in obesity, as fat accumulates and adipocytes enlarge. Even though a link between adipose dysfunction, insulin resistance and diabetes has been identified, the direct physiological effects of adiponectin processing on obesity induced diabetes have yet to be investigated. Recently, it was hypothesized that full-length adiponectin (fAcrp) is inactive and that globular adiponectin (gAcrp) is the functional adipokine. Our group has identified thrombin and not trypsin or leukocyte elastase as generally believed, as the protease responsible for generating gAcrp. Preliminary studies showed that the gAcrp and not fAcrp inhibited the proliferation of primary smooth muscle cells in vitro in response to PDGF. Hence we hypothesize that the generation of gAcrp from fAcrp is essential for eliciting the beneficial actions of adiponectin in reversing insulin resistance. Our aim is to compare the effects of different forms of adiponectin namely fAcrp, gAcrp and prAcrp (protease resistant mutant of fAcrp that cannot be cleaved into gAcrp) on insulin resistance. METHODS AND RESULTS: In in vivo studies, we will use a dietinduced obese adiponectin knockout mouse model and compare the ability of different adiponectin forms to rescue the metabolic phenotype of these mice. In in vitro studies, human umbilical vein endothelial cells (HUVEC) and hepatoma cells (HepG2) will be serum starved prior to treatment with different forms of adiponectin and activation of downstream molecular signatories such as AMPKa, MAPK p44/42, p38 MAPK, ACC and Akt will be measured by Western blotting. The purified recombinant fAcrp and prAcrp proteins were tested for sensitivity to thrombin in an in vitro cleavage assay. Recombinant fAcrp was digested in a dose dependent manner. CONCLUSION: Treatment of fAcrp but not prAcrp with thrombin resulted in the formation of gAcrp. The expression level of adiponectin receptor1, receptor2 and T-cadherin was similar in different primary human endothelial cells and hepatoma cells. Serum starvation of HUVECs for 6hours in 0% FBS and 16hours in 0.5% FBS was optimum for MAPK p44/42 and AMPK regulation by adiponectin. 428 MAXIMAL CCA IMT AND CARDIOVASCULAR OUTCOMES

Adiponectin Stimulates Autophagy and Reduces Oxidative Stress to Enhance Insulin Sensitivity During High-Fat Diet Feeding in Mice

Numerous studies have characterized the antidiabetic effects of adiponectin, yet the precise cellular mechanisms in skeletal muscle, in particular, changes in autophagy, require further clarification. In the current study, we used a high-fat diet (HFD) to induce obesity and insulin resistance in wild-type (WT) or adiponectin knockout (Ad-KO) mice with and without adiponectin replenishment. Temporal analysis of glucose tolerance and insulin sensitivity using hyperinsulinemic-euglycemic clamp and muscle insulin receptor substrate and Akt phosphorylation demonstrated exaggerated and more rapid HFD-induced insulin resistance in skeletal muscle of Ad-KO mice. Superoxide dismutase activity, the reduced glutathione-to-glutathione disulfide ratio, and lipid peroxidation indicated that HFD-induced oxidative stress was corrected by adiponectin. Gene array analysis implicated several antioxidant enzymes, including Gpxs, Prdx, Sod, and Nox4, in mediating this effect. Adiponectin also attenuated palmitate-induced reactive oxygen species production in cultured myotubes and improved insulin-stimulated glucose uptake in primary muscle cells. Increased LC3-II and decreased p62 expression suggested that HFD induced autophagy in muscle of WT mice; however, these changes were not observed in Ad-KO mice. Replenishing adiponectin in Ad-KO mice increased LC3-II and Beclin1 and decreased p62 protein levels, induced fibroblast growth factor-21 expression, and corrected HFD-induced decreases in LC3, Beclin1, and ULK1 gene expression. In vitro studies examining changes in phospho-ULK1 (Ser555), LC3-II, and lysosomal enzyme activity confirmed that adiponectin directly induced autophagic flux in cultured muscle cells in an AMPK-dependent manner. We overexpressed an inactive mutant of Atg5 to create an autophagy-deficient cell model, and together with pharmacological inhibition of autophagy, demonstrated reduced insulin sensitivity under these conditions. In summary, adiponectin stimulated skeletal muscle autophagy and antioxidant potential to reduce insulin resistance caused by HFD.

Impaired adiponectin signaling contributes to disturbed catabolism of branched-chain amino acids in diabetic mice.

The branched-chain amino acids (BCAA) accumulated in type 2 diabetes are independent contributors to insulin resistance. The activity of branched-chain α-keto acid dehydrogenase (BCKD) complex, rate-limiting enzyme in BCAA catabolism, is reduced in diabetic states, which contributes to elevated BCAA concentrations. However, the mechanisms underlying decreased BCKD activity remain poorly understood. Here, we demonstrate that mitochondrial phosphatase 2C (PP2Cm), a newly identified BCKD phosphatase that increases BCKD activity, was significantly downregulated in ob/ob and type 2 diabetic mice. Interestingly, in adiponectin (APN) knockout (APN(-/-)) mice fed with a high-fat diet (HD), PP2Cm expression and BCKD activity were significantly decreased, whereas BCKD kinase (BDK), which inhibits BCKD activity, was markedly increased. Concurrently, plasma BCAA and branched-chain α-keto acids (BCKA) were significantly elevated. APN treatment markedly reverted PP2Cm, BDK, BCKD activity, and BCAA and BCKA levels in HD-fed APN(-/-) and diabetic animals. Additionally, increased BCKD activity caused by APN administration was partially but significantly inhibited in PP2Cm knockout mice. Finally, APN-mediated upregulation of PP2Cm expression and BCKD activity were abolished when AMPK was inhibited. Collectively, we have provided the first direct evidence that APN is a novel regulator of PP2Cm and systematic BCAA levels, suggesting that targeting APN may be a pharmacological approach to ameliorating BCAA catabolism in the diabetic state.

Adiponectin protects against acetaminophen-induced mitochondrial dysfunction and acute liver injury by promoting autophagy in mice

Acetaminophen (APAP) overdose causes hepatic necrosis and acute liver injury by inducing mitochondrial dysfunction and damage. Although the biochemical pathways that mediate APAP-induced hepatotoxicity have been well studied, the body's defense mechanism to attenuate this disease remains elusive. This study investigated the roles of adiponectin, an adipocyte-secreted adipokine with pleiotropic protective effects against obesity-related metabolic dysfunction, in the pathogenesis of APAP-induced liver injury in mice. Adiponectin knockout (ADN KO) and C57 wild type mice were treated with an overdose of APAP, followed by histological and biochemical evaluation of liver injury and activation of autophagy. The mechanism of adiponectin in APAP-induced hepatocytic toxicity was also explored in primary cultured hepatocytes. APAP overdose triggers a marked accumulation of adiponectin in injured liver tissues. ADN KO mice exhibit severely exacerbated mitochondrial dysfunction and damage, oxidative stress and necrosis and much higher mortality in response to APAP overdose, whereas these changes are reversed by a single injection of adiponectin. Mechanistically, adiponectin induces autophagosome formation by AMP-activated protein kinase (AMPK)-dependent activation of the Unc-51-like kinase 1, consequently leading to the removal of damaged mitochondria from hepatocytes. The protective effects of adiponectin against APAP-induced mitochondrial damage, oxidative stress and necrosis are abrogated by blockage of AMPK or pharmacological inhibition of autophagy. Our findings suggest that the APAP-induced accumulation of adiponectin in liver tissues serves as an adaptive mechanism to ameliorate hepatotoxicity by promoting autophagy-mediated clearance of damaged mitochondria. Adiponectin agonists may represent a promising therapy for the drug-induced acute liver failure.

Adiponectin Ameliorates Experimental Periodontitis in Diet-Induced Obesity Mice

Adiponectin is an adipokine that sensitizes the body to insulin. Low levels of adiponectin have been reported in obesity, diabetes and periodontitis. In this study we established experimental periodontitis in male adiponectin knockout and diet-induced obesity mice, a model of obesity and type 2 diabetes, and aimed at evaluating the therapeutic potential of adiponectin. We found that systemic adiponectin infusion reduced alveolar bone loss, osteoclast activity and infiltration of inflammatory cells in both periodontitis mouse models. Furthermore, adiponectin treatment decreased the levels of pro-inflammatory cytokines in white adipose tissue of diet-induced obesity mice with experimental periodontitis. Our in vitro studies also revealed that forkhead box O1, a key transcriptional regulator of energy metabolism, played an important role in the direct signaling of adiponectin in osteoclasts. Thus, adiponectin increased forkhead box O1 mRNA expression and its nuclear protein level in osteoclast-precursor cells undergoing differentiation. Inhibition of c-Jun N-terminal kinase signaling decreased nuclear protein levels of forkhead box O1. Furthermore, over-expression of forkhead box O1 inhibited osteoclastogenesis and led to decreased nuclear levels of nuclear factor of activated T cells c1. Taken together, this study suggests that systemic adiponectin application may constitute a potential intervention therapy to ameliorate type 2 diabetes-associated periodontitis. It also proposes that adiponectin inhibition of osteoclastogenesis involves forkhead box O1.

Adiponectin inhibits murine pancreatic cancer growth.

Adiponectin is an adipose tissue-derived secretory hormone whose plasma concentrations are lower in obese individuals. Obesity is a risk factor for the development and growth of pancreatic cancer, and hypoadiponectinemia was suggested to be involved in the growth of Pan02 murine pancreatic cancer cells that were inoculated into the flanks of congenitally obese mice. The aim of this study was to clarify the role of adiponectin in the growth of pancreatic cancer cells. We examined the effect of adiponectin on the growth of Pan02 cells using recombinant adiponectin and adiponectin knockout mice. The in vitro treatment of Pan02 cells with adiponectin inhibited cellular proliferation that was accompanied by increased apoptosis and caspase-3 and caspase-7 activities. Transplantation of Pan02 cells into the pancreas of knockout mice resulted in a larger tumor volume with fewer terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells compared with wild-type mice. The results indicate that adiponectin directly suppresses the proliferation of Pan02 cells.

Pharmacological ceramide reduction alleviates alcohol-induced steatosis and hepatomegaly in adiponectin knockout mice.

Hepatosteatosis, the ectopic accumulation of lipid in the liver, is one of the earliest clinical signs of alcoholic liver disease (ALD). Alcohol-dependent deregulation of liver ceramide levels as well as inhibition of AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor α (PPAR-α) activity are thought to contribute to hepatosteatosis development. Adiponectin can regulate lipid handling in the liver and has been shown to reduce ceramide levels and activate AMPK and PPAR-α. However, the mechanisms by which adiponectin prevents alcoholic hepatosteatosis remain incompletely characterized. To address this question, we assessed ALD progression in wild-type (WT) and adiponectin knockout (KO) mice fed an ethanol-containing liquid diet or isocaloric control diet. Adiponectin KO mice relative to WT had increased alcohol-induced hepatosteatosis and hepatomegaly, similar modest increases in serum alanine aminotransferase, and reduced liver TNF. Restoring circulating adiponectin levels using recombinant adiponectin ameliorated alcohol-induced hepatosteatosis and hepatomegaly in adiponectin KO mice. Alcohol-fed WT and adiponectin KO animals had equivalent reductions in AMPK protein and PPAR-α DNA binding activity compared with control-fed animals. No difference in P-AMPK/AMPK ratio was detected, suggesting that alcohol-dependent deregulation of AMPK and PPAR-α in the absence of adiponectin are not primary causes of the observed increase in hepatosteatosis in these animals. By contrast, alcohol treatment increased liver ceramide levels in adiponectin KO but not WT mice. Importantly, pharmacological inhibition of de novo ceramide synthesis in adiponectin KO mice abrogated alcohol-mediated increases in liver ceramides, steatosis, and hepatomegaly. These data suggest that adiponectin reduces alcohol-induced steatosis and hepatomegaly through regulation of liver ceramides, but its absence does not exacerbate alcohol-induced liver damage.

Adiponectin reduces thermogenesis by inhibiting brown adipose tissue activation in mice.

Adiponectin is an adipocyte-derived hormone that plays an important role in energy homeostasis. The main objective of this study was to investigate whether or not adiponectin regulates brown adipose tissue (BAT) activation and thermogenesis. Core body temperatures (CBTs) of genetic mouse models were monitored at room temperature and during cold exposure. Cultured brown adipocytes and viral vector-mediated gene transduction were used to study the regulatory effects of adiponectin on Ucp1 gene expression and the underlying mechanisms. The CBTs of adiponectin knockout mice (Adipoq(-/-)) were significantly higher than those of wild type (WT) mice both at room temperature and during the cold (4°C) challenge. Conversely, reconstitution of adiponectin in Adipoq(-/-) mice significantly blunted β adrenergic receptor agonist-induced thermogenesis of interscapular BAT. After 10 days of intermittent cold exposure, Adipoq(-/-) mice exhibited higher UCP1 expression and more brown-like structure in inguinal fat than WT mice. Paradoxically, we found that the anti-thermogenic effect of adiponectin requires neither AdipoR1 nor AdipoR2, two well-known adiponectin receptors. In sharp contrast to the anti-thermogenic effects of adiponectin, AdipoR1 and especially AdipoR2 promote BAT activation. Mechanistically, adiponectin was found to inhibit Ucp1 gene expression by suppressing β3-adrenergic receptor expression in brown adipocytes. This study demonstrates that adiponectin suppresses thermogenesis, which is likely to be a mechanism whereby adiponectin reduces energy expenditure.

Effect of adiponectin on cardiac β-catenin signaling pathway under angiotensin II infusion

Obesity is associated with heart failure and cardiac hypertrophy. Adiponectin has been shown to play a protective role for cardiovascular diseases. The β-catenin signaling pathway is deeply involved in cardiac hypertrophy. However, the effect of adiponectin on β-catenin signaling has not been investigated in cardiac hypertrophy. Present study aimed to clarify the involvement of adiponectin and β-catenin signaling pathway in the mouse model of angiotensin II (AngII)-induced cardiac hypertrophy. In hearts of Wild type (WT) mice, AngII dose-dependently augmented cytosolic β-catenin protein level. WT and adiponectin knockout (Adipo-KO) mice were administered with AngII at 2.4mg/kg/day for 14days and were also injected with adenovirus expressing the adiponectin (Ad-Adipo) or the β-galactosidase (Ad-βgal). Cardiac mRNA levels relating to hypertrophy and β-catenin signaling were increased in Adipo-KO mice and these changes were reversed by Ad-Adipo. Phosphorylation of Akt was increased in Adipo-KO mice and such increases were reversed by Ad-Adipo. Furthermore, the phosphorylation of glycogen synthase kinase 3β (GSK3β) at Ser9 and cytosolic β-catenin level were increased in Adipo-KO mice and they were significantly reduced by Ad-Adipo treatment. Phosphorylation of mammalian target of rapamycin (mTOR) was reduced by Ad-Adipo-mediated adiponectin supplementation in WT and Adipo-KO mice. The current study suggests that adiponectin attenuates AngII-induced cardiac hypertrophic signals partly through Akt/GSK3β/β-catenin and Akt/mTOR pathways.

Adiponectin ameliorates endotoxin-induced acute cardiac injury.

Background. Obesity is a risk factor for cardiovascular disease. Increasing evidence suggests that reduced levels of the adipocyte-derived plasma protein adiponectin are associated with an increased cardiovascular risk. Here, we examined the effects of adiponectin on lipopolysaccharide- (LPS-) induced acute cardiac injury in vivo. Methods and Results. A single dose of LPS (10 mg/kg) was intraperitoneally injected into wild-type (WT) and adiponectin-knockout (APN-KO) mice. Following LPS administration, APN-KO mice had exacerbation of left ventricular (LV) systolic dysfunction compared with WT mice. Administration of LPS to WT and APN-KO mice led to an increased expression of inflammatory cytokines including TNF-α and IL-6 in the heart, but the magnitude of this induction was greater in APN-KO mice compared to WT mice. Systemic delivery of an adenoviral vector expressing adiponectin (Ad-APN) improved LPS-induced LV dysfunction in APN-KO mice, and this effect was accompanied by the reduced expression of TNF-α and IL-6 in the heart. Administration of etanercept, a soluble TNF receptor abolished the reduced LV contractile function in response to LPS in APN-KO mice. Conclusion. These results suggest that adiponectin protects against LPS-induced acute cardiac injury by suppressing cardiac inflammatory responses, and could represent a potential therapeutic target in sepsis-associated myocardial dysfunction.

Tracing the movement of adiponectin in a parabiosis model of wild-type and adiponectin-knockout mice

Adiponectin is exclusively synthesized by adipocytes and exhibits anti-diabetic, anti-atherosclerotic and anti-inflammatory properties. Hypoadiponectinemia is associated in obese individuals with insulin resistance and atherosclerosis. However, the mechanisms responsible for hypoadiponectinemia remain unclear. Here, we investigated adiponectin movement using hetero parabiosis model of wild type (WT) and adiponectin-deficient (KO) mice. WT mice were parabiosed with WT mice (WT–WT) or KO mice (WT–KO) and adiponectin levels were measured serially up to 63days after surgery. In the WT–KO parabiosis model, circulating adiponectin levels of the WT partners decreased rapidly, on the other hand, those of KO partners increased, and then these reached comparable levels each other at day 7. Circulating adiponectin levels decreased further to the detection limit of assay, and remained low up to day 63. However, adiponectin protein was detected in the adipose tissues of not only the WT partner but also WT–KO mice. In the diet-induced obesity model, high adiponectin protein levels were detected in adipose stromal vascular fraction of diet-induced obese KO partner, without changes in its binding proteins. The use of parabiosis experiments shed light on movement of native adiponectin among different tissues such as the state of hypoadiponectinemia in obesity.

Role of adiponectin in the metabolic effects of cannabinoid type 1 receptor blockade in mice with diet-induced obesity

The adipocyte-derived hormone adiponectin promotes fatty acid oxidation and improves insulin sensitivity and thus plays a key role in the regulation of lipid and glucose metabolism and energy homeostasis. Chronic cannabinoid type 1 (CB1) receptor blockade also increases lipid oxidation and improves insulin sensitivity in obese individuals or animals, resulting in reduced cardiometabolic risk. Chronic CB1 blockade reverses the obesity-related decline in serum adiponectin levels, which has been proposed to account for the metabolic effects of CB1 antagonists. Here, we investigated the metabolic actions of the CB1 inverse agonist rimonabant in high-fat diet (HFD)-induced obese adiponectin knockout (Adipo(-/-)) mice and their wild-type littermate controls (Adipo(+/+)). HFD-induced obesity and its hormonal/metabolic consequences were indistinguishable in the two strains. Daily treatment of obese mice with rimonabant for 7 days resulted in significant and comparable reductions in body weight, serum leptin, free fatty acid, cholesterol, and triglyceride levels in the two strains. Rimonabant treatment improved glucose homeostasis and insulin sensitivity to the same extent in Adipo(+/+) and Adipo(-/-) mice, whereas it reversed the HFD-induced hepatic steatosis, fibrosis, and hepatocellular damage only in the former. The adiponectin-dependent, antisteatotic effect of rimonabant was mediated by reduced uptake and increased β-oxidation of fatty acids in the liver. We conclude that reversal of the HFD-induced hepatic steatosis and fibrosis by chronic CB1 blockade, but not the parallel reduction in adiposity and improved glycemic control, is mediated by adiponectin.

Is the lack of adiponectin associated with increased ER/SR stress and inflammation in the heart?

Objective To study whether there is an association between adiponectin and endoplasmic reticulum/sarcoplasmic reticulum (ERSR) stress. Research design Eleven-month-old male wild-type (WT) and adiponectin knockout (ADKO) mice were placed on chow or high fat diet for 12 weeks. The changes in ER stress and inflammatory genes were determined in the epididymal adipose, as well as heart tissue of adult WT and ADKO mice. To understand the role of ER/SR stress in the regulation of adiponectin, we studied the effect of tunicamycin or palmitate on H9C2 cardiomyoblasts in culture. To demonstrate the protective role of adiponectin, we studied the effect of purified adiponectin on the regulation of ERSR stress genes and inflammation in H9C2 cardiomyoblasts. Results (1) High fat diet increased TNFα in adipose tissue of ADKO mice. (2) ERSR stress genes, HSPa5, ERN1, and GADD34, and inflammation response genes, TNFα and CD68, were increased in heart of ADKO mice. High fat diet did not further increase the effect. (3) Induction of ERSR stress by tunicamycin in H9C2 resulted in the upregulation of ERSR stress response genes along with downregulation of adiponectin, adiponectin receptors 1 and 2, and Serca2A. ER stress was accompanied by down regulation of Iкβα and an increase in HSPa5 proteins. (4) Adiponectin decreased ERSR stress and inflammation response genes and increased Serca2A in to H9C2 cardiomyoblasts. Conclusion The lack of adiponectin is associated with increased ER/SR stress and inflammation in the heart. Adiponectin provides a protective effect by lowering inflammation and ER/SR stress along with increasing Serca2A in H9C2 cells.

Validation of Noninvasive Morphological and Diffusion Imaging in Mouse Emphysema by Micro–Computed Tomography and Hyperpolarized 129Xe Magnetic Resonance Imaging

Animal disease models are pivotal in investigating the pathogenesis of emphysema and developing novel drugs, but the modalities to evaluate murine emphysema models have been of limited validity and sensitivity. In this study, we evaluated hyperpolarized (129)Xe magnetic resonance imaging (MRI) and micro-computed tomography (micro-CT) compared with traditional methods, such as plethysmography and histology. Elastase-treated mice and adiponectin knockout mice were used as murine emphysema models to evaluate these modalities. Three weeks after elastase administration, significant and heterogeneous emphysema was evaluated according to the mean linear intercept and plethysmography parameters. Notably, the distribution of low-density areas, as examined by micro-CT, correlated with the mean linear intercept and plethysmography parameters in whole lungs. These correlations were also observed in regional areas. Furthermore, we introduced hyperpolarized (129)Xe MRI, which can evaluate gas exchange between the alveoli and blood during spontaneous breathing. Parameters of gas exchange (fD) and alveolar size (Vs/Va) were significantly decreased in elastase-treated mice, and moderately correlated with the plethysmography parameters. Of importance, we could detect a decrease of the fD value in low-density areas with micro-CT, suggesting that gas exchange decreased in emphysematous lesions. Likewise, these parameters (fD and Vs/Va) were also decreased in adiponectin knockout mice, which exhibit emphysema with a homogeneous distribution. We demonstrated the feasibility of (129)Xe MRI and micro-CT in combination with traditional modalities. These noninvasive modalities provide complementary data that can be used for repeated estimations of regional gas exchange and lung morphology.

Adiponectin attenuates osteolysis in aseptic loosening of total hip replacements

Joint replacements have a longer durability in patients with high serum levels of adiponectin (APN) than in patients with low levels. We aimed to characterize the unknown pathophysiological effects of APN on wear particle-induced inflammation, apoptosis and osteolysis. Immunohistochemistry was performed to detect APN, its receptors and apoptosis in patients with and without aseptic loosening. Additionally, APN knockout mouse studies and pharmacological intervention of APN were performed in an established calvarial mouse model. Osteolysis and inflammation were quantified by histomorphometry and microcomputed tomography, apoptosis by immunohistochemistry and TUNEL assay. In a cell culture model, human monocyte-derived macrophages were incubated with or without metal wear debris particles and partially treated with APN. Expression of APN, AdipoR1 and calreticulin in specimens from patients with aseptic loosening were significantly higher than in patients without aseptic loosening. Administration of APN in mice significantly reduced wear particle-induced inflammation, osteolysis and the number of caspase-3-positive macrophages. The cell culture model showed that APN leads to significantly lower values of TNF-α. These findings support a prominent role of APN in the development of particle-induced osteolysis and APN may be therapeutically useful in patients with aseptic loosening.

Adiponectin Protein Exists in Aortic Endothelial Cells

AimsInflammation is closely associated with the development of atherosclerosis and metabolic syndrome. Adiponectin, an adipose-derived secretory protein, possesses an anti-atherosclerotic property. The present study was undertaken to elucidate the presence and significance of adiponectin in vasculature.Methods and ResultsImmunofluorescence staining was performed in aorta of wild-type (WT) mice and demonstrated that adiponectin was co-stained with CD31. Thoracic aorta was cut through and then aortic intima was carefully shaved from aorta. Western blotting showed the existence of adiponectin protein in aortic intima, while there was no adiponectin mRNA expression. Adiponectin knockout (Adipo-KO) and WT mice were administered with a low-dose and short-term lipopolysaccharide (LPS) (1 mg/kg of LPS for 4 hours). The endothelium vascular adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) were highly increased in Adipo-KO mice compared to WT mice after LPS administration.ConclusionsAdiponectin protein exists in aortic endothelium under steady state and may protect vasculature from the initiation of atherosclerosis.

GW24-e1276 Hypoadiponectinemia induces vascular insulin resistance in normotensive young spontaneously hypertensive rats and the underlying mechanisms

ObjectivesVascular insulin resistance contributes to elevated peripheral vascular resistance and subsequent hypertension. However, the mechanism responsible for inducing vascular insulin resistance in prehypertension remains elusive. The present study aimed to...