Intensive Statin Therapy Compromises the Adiponectin-AdipoR Pathway in the Human Monocyte-Macrophage Lineage.

Background and Purpose- Statins are widely used for cardiovascular disease prevention through cholesterol-lowering and anti-inflammatory effects. Adiponectin, an anti-inflammatory adipokine, acts via two receptors, AdipoR1 and AdipoR2, to exert atheroprotective effects on the vasculature. We investigated whether statins can modulate the adiponectin-AdipoR pathway in the human monocyte-macrophage lineage. Methods- Monocytes were isolated from the whole blood of patients with severe carotid atherosclerosis (cross-sectional study) or from patients with cardiovascular risk factors (longitudinal study) and assessed for AdipoR1 and AdipoR2 gene expression using quantitative real-time polymerase chain reaction. In vitro, THP-1 (Tamm-Horsfall protein 1) macrophages were treated with increasing atorvastatin or rosuvastatin doses for 24- or 72-hours to determine the effect of statins on AdipoR expression and activity. Macrophage cytokine secretion (IL [interleukin]-1ß, IL-10, IL-6, and TNF [tumor necrosis factor]-α) was assessed by electrochemiluminescence. Results- AdipoR1 and AdipoR2 mRNA expression on circulating monocytes from patients with carotid atherosclerosis, was significantly lower by 1.36- and 1.17-fold, respectively, in statin users versus statin-naïve patients. Specifically, patients on high doses of atorvastatin (40-80 mg) or rosuvastatin (20-40 mg) had significantly lower AdipoR gene expression versus statin-naïve patients. Similarly, in the longitudinal in vivo study, longer atorvastatin/rosuvastatin treatment (≥5 months) in patients with cardiovascular risk factors resulted in lower AdipoR gene expression on circulating monocytes versus prestatin levels. In vitro, higher statin doses and longer exposure resulted in a greater decrease in AdipoR mRNA expression and greater macrophage secretion of pro-inflammatory cytokines, IL-1ß, IL-6, and TNF-α. High statin doses also reduced adiponectin's capacity to suppress intracellular cholesteryl ester levels in oxLDL (oxidized LDL)-loaded macrophages, with rosuvastatin exhibiting higher potency than atorvastatin. Conclusions- Our in vivo and in vitro studies identified a novel pleiotropic property of statins in modulating the adiponectin-AdipoR pathway in the human monocyte-macrophage lineage, where intensive statin therapy compromised the expression and function of adiponectin and its receptors.

Wolfberry-Derived Zeaxanthin Dipalmitate Attenuates Ethanol-Induced Hepatic Damage.

SCOPE: Besides abstinence and nutritional support, there is no proven clinical treatment for patients with alcoholic fatty liver disease (AFLD). Here, the therapeutic effects and mechanisms of action of wolfberry-derived zeaxanthin dipalmitate (ZD) on AFLD models are demonstrated. METHODS AND RESULTS: The hepatoprotective effects of ZD are evaluated in vitro and in vivo. Direct interacting receptors of ZD on cell membranes are identified by liver-specific knockdown and biophysical measurements. Downstream signaling pathways are delineated using molecular and cellular biological methods. It is demonstrated that ZD attenuates hepatocyte and whole-liver injury in ethanol-treated cells (dose: 1 µm) and a chronic binge AFLD rat model (dose: 10 mg kg-1 ), respectively. The direct targets of ZD on the cell membrane include receptor P2X7 and adiponectin receptor 1 (adipoR1). Signals from P2X7 and adipoR1 modulate the phosphatidylinositide 3-kinase-Akt and/or AMP-activated protein kinase-FoxO3a pathways, to restore mitochondrial autophagy (mitophagy) functions suppressed by ethanol intoxication. In addition, ZD alleviates hepatic inflammation partially via the inhibition of Nod-like receptor 3 inflammasome, whose activation is a direct consequence of suppressed mitophagy. Liver-specific inhibition of receptors or mitophagy significantly impairs the beneficial effects of ZD. CONCLUSIONS: ZD is an effective and promising agent for the potential treatment of AFLD.

Telmisartan attenuates diabetic nephropathy progression by inhibiting the dimerization of angiotensin type-1 receptor and adiponectin receptor-1.

AIMS: The heterodimerization of angiotensin II receptors (AT1R and AT2R) with adiponectin receptor AdipoR1 and AdipoR2 may instigate high glucose (HG)-induced renal tubulointerstitial injury. This study examined the effect of telmisartan on diabetic nephropathy (DN) and its underlying mechanism. MAIN METHODS: Diabetes was induced in rats through a single intraperitoneal injection of streptozotocin. Diabetic rats treated with or without the intravenous injection of AdipoR1 siRNA were intragastrically administered with 5 mg/kg/d telmisartan or a vehicle for 12 weeks. The rat proximal tubular epithelial cell line NRK-52E was treated with HG (30 mmol/L) with or without telmisartan (10 µM) for 48 h. KEY FINDINGS: In streptozotocin-induced diabetic rats, telmisartan treatment could decrease the inulin clearance rate, restore the glomerular surface area and mesangial area, alleviate renal fibrosis, and decrease urinary albumin excretion. Furthermore, diabetic rats exhibited increased AT1R-AdipoR1 heterodimers in the renal tubular compartment, which could be attenuated by telmisartan treatment, accompanied by a decrease in the expression level of cytokines MIP-1α, ICAM-1 and MCP-1. In vitro, HG promoted the dimerization formation of AT1R-AdipoR1 in cultured NRK-52E cells, but this effect was not found in NRK-52E cells transfected with the AdipoR1-G269E,G273E mutant. Telmisartan could inhibit HG-induced AT1R-AdipoR1 dimerization, downregulate the expression levels of inflammatory cytokines, and alleviate cell apoptosis in NRK-52E cells. Furthermore, AdipoR1 knockdown could abate the renoprotective benefits of telmisartan. SIGNIFICANCE: The heterodimerization of AT1R-AdipoR1 probably contributes to the renal injury of DN, and provides an additional mechanistic insight into how telmisartan prevents the development and progression of DN.

Gamma Oryzanol Treats Obesity-Induced Kidney Injuries by Modulating the Adiponectin Receptor 2/PPAR-α Axis.

The kidney is an important organ in the maintenance of body homeostasis. Dietary compounds, reactive metabolites, obesity, and metabolic syndrome (MetS) can affect renal filtration and whole body homeostasis, increasing the risk of chronic kidney disease (CKD) development. Gamma oryzanol (γOz) is a compound with antioxidant and anti-inflammatory activity that has shown a positive action in the treatment of obesity and metabolic diseases. Aim. To evaluate the effect of γOz to recover renal function in obese animals by high sugar-fat diet by modulation of adiponectin receptor 2/PPAR-α axis Methods. Male Wistar rats were initially randomly divided into 2 experimental groups: control and high sugar-fat diet (HSF) for 20 weeks. When proteinuria was detected, HSF animals were allocated to receive γOz or maintain HSF for more than 10 weeks. The following were analyzed: nutritional and biochemical parameters, systolic blood pressure, and renal function. In the kidney, the following were evaluated: inflammation, oxidative stress, and protein expression by Western blot. Results. After 10 weeks of γOz treatment, γOz was effective to improve inflammation, increase antioxidant enzyme activities, increase the protein expression of adiponectin receptor 2 and PPAR-α, and recover renal function. Conclusion. These results permit us to confirm that γOz is able to modulate PPAR-α expression, inflammation, and oxidative stress pathways improving obesity-induced renal disease.

Impact of 1,25(OH) 2 D 3 on TG content in liver of rats with type 2 diabetes.

PURPOSE: To evaluate the effects of 1,25 dihydroxy vitamin D3 (1,25(OH)2D3) on the content of triglyceride (TG), as well as on the gene and protein expressions of adiponectin receptor 2 (AdipoR2), p38 mitogen-activated protein kinase (P38MAPK), and lipoprotein lipase (LPL) in the liver of rats with type 2 diabetes mellitus (T2DM) so as to provide theoretical basis for exploring the mechanism by which 1,25(OH)2D3 regulates TG. METHODS: Wistar rats were divided into four groups (n=25), with different treatments and detected the gene and protein expressions of AdipoR2, p38MAPK, and LPL in the liver tissue by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. Meanwhile, the content of TG in the liver tissue was detected by the Enzyme-linked immunosorbent assay. RESULTS: The expression of AdipoR2, p38MAPK, LPL gene and protein in the liver of VitD intervention group was significantly higher than that in T2DM group (P <0.05), while the TG content was significantly lower than that in T2DM group (P <0.05). CONCLUSION: 1,25(OH)2D3 can decrease the content of TG in the liver, and its mechanism may be achieved by upregulating the expressions of AdipoR2, p38MAPK, and LPL in the liver.

Impact of 1 25(OH) 2 D 3 on TG content in liver of rats with type 2 diabetes

Abstract Purpose: To evaluate the effects of 1,25 dihydroxy vitamin D3 (1,25(OH)2D3) on the content of triglyceride (TG), as well as on the gene and protein expressions of adiponectin receptor 2 (AdipoR2), p38 mitogen-activated protein kinase (P38MAPK), and lipoprotein lipase (LPL) in the liver of rats with type 2 diabetes mellitus (T2DM) so as to provide theoretical basis for exploring the mechanism by which 1,25(OH)2D3 regulates TG. Methods: Wistar rats were divided into four groups (n=25), with different treatments and detected the gene and protein expressions of AdipoR2, p38MAPK, and LPL in the liver tissue by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. Meanwhile, the content of TG in the liver tissue was detected by the Enzyme-linked immunosorbent assay. Results: The expression of AdipoR2, p38MAPK, LPL gene and protein in the liver of VitD intervention group was significantly higher than that in T2DM group (P <0.05), while the TG content was significantly lower than that in T2DM group (P <0.05). Conclusion: 1,25(OH)2D3 can decrease the content of TG in the liver, and its mechanism may be achieved by upregulating the expressions of AdipoR2, p38MAPK, and LPL in the liver.

Adiponectin inhibits oxidization-induced differentiation of T helper cells through inhibiting costimulatory CD40 and CD80.

Adiponectin is a multifunctional adipokine that has several oligomeric forms in the blood stream, which broadly regulates innate and acquired immunity. Therefore, in this study, we aimed to observe the differentiation of T helper (Th) cells and expression of costimulatory signaling molecules affected by adiponectin. The mRNA and protein expression levels of adiponectin and its receptors in oxidized low density lipoprotein cholesterol-treated endothelial cells were assayed by real time PCR and immunofluorescence. The endothelial cells were then treated with adiponectin with or without adipoR1 or adipoR2 siRNA and co-cultured with T lymphocytes. The distribution of Th1, Th2 and Th17 subsets were assayed by flow cytometry. The effects of adiponectin on costimulatory signaling molecules HLA-DR, CD80, CD86 and CD 40 was also assayed by flow cytometry. The results showed that endothelial cells expressed adiponectin and its receptor adipoR1 and adipoR2, but not T-cadherin. Adiponectin suppressed Th1 and Th17 differentiation through adipoR1 receptor, contributed to the inhibition of CD80 and CD40, and inhibited differentiation of Th1 and Th17 by inhibiting antigen presenting action.

Novel osmotin inhibits SREBP2 via the AdipoR1/AMPK/SIRT1 pathway to improve Alzheimer's disease neuropathological deficits.

Extensive evidence has indicated that a high rate of cholesterol biogenesis and abnormal neuronal energy metabolism play key roles in Alzheimer's disease (AD) pathogenesis. Here, for we believe the first time, we used osmotin, a plant protein homolog of mammalian adiponectin, to determine its therapeutic efficacy in different AD models. Our results reveal that osmotin treatment modulated adiponectin receptor 1 (AdipoR1), significantly induced AMP-activated protein kinase (AMPK)/Sirtuin 1 (SIRT1) activation and reduced SREBP2 (sterol regulatory element-binding protein 2) expression in both in vitro and in vivo AD models and in Adipo-/- mice. Via the AdipoR1/AMPK/SIRT1/SREBP2 signaling pathway, osmotin significantly diminished amyloidogenic Aß production, abundance and aggregation, accompanied by improved pre- and post-synaptic dysfunction, cognitive impairment, memory deficits and, most importantly, reversed the suppression of long-term potentiation in AD mice. Interestingly, AdipoR1, AMPK and SIRT1 silencing not only abolished osmotin capability but also further enhanced AD pathology by increasing SREBP2, amyloid precursor protein (APP) and ß-secretase (BACE1) expression and the levels of toxic Aß production. However, the opposite was true for SREBP2 when silenced using small interfering RNA in APPswe/ind-transfected SH-SY5Y cells. Similarly, osmotin treatment also enhanced the non-amyloidogenic pathway by activating the α-secretase gene that is, ADAM10, in an AMPK/SIRT1-dependent manner. These results suggest that osmotin or osmotin-based therapeutic agents might be potential candidates for AD treatment.

Adiponectin inhibits oxidization-induced differentiation of T helper cells through inhibiting costimulatory CD40 and CD80

Adiponectin is a multifunctional adipokine that has several oligomeric forms in the blood stream, which broadly regulates innate and acquired immunity. Therefore, in this study, we aimed to observe the differentiation of T helper (Th) cells and expression of costimulatory signaling molecules affected by adiponectin. The mRNA and protein expression levels of adiponectin and its receptors in oxidized low density lipoprotein cholesterol-treated endothelial cells were assayed by real time PCR and immunofluorescence. The endothelial cells were then treated with adiponectin with or without adipoR1 or adipoR2 siRNA and co-cultured with T lymphocytes. The distribution of Th1, Th2 and Th17 subsets were assayed by flow cytometry. The effects of adiponectin on costimulatory signaling molecules HLA-DR, CD80, CD86 and CD 40 was also assayed by flow cytometry. The results showed that endothelial cells expressed adiponectin and its receptor adipoR1 and adipoR2, but not T-cadherin. Adiponectin suppressed Th1 and Th17 differentiation through adipoR1 receptor, contributed to the inhibition of CD80 and CD40, and inhibited differentiation of Th1 and Th17 by inhibiting antigen presenting action.

[Effect of Dangua Recipe on Hepatic Adiponectin Receptor 2 Expression in Diabetic Apolipoprotein E Knockout Mice].

Objective To observe the effect of Dangua Recipe (DR) on adiponectin receptor 2 (AdipoR2) expression in liver of apolipoprotein E knockout (ApoE⁻¹â») diabetic mice. Methods Eight- week-old ApoE⁻¹â» mice were randomly divided into the model control group, the DR group, the pioglitazone group, and the combined treatment group. Besides, a C57 group was set up consisting of same age C57BL/ 6J mice. Streptozotocin (STZ) was injected to ApoE⁻¹â» mice in the four groups to induce diabetic model, and they were intervened by corresponding drugs. After 12 weeks the effect of DF on glucose-lipid metabolism was observed. mRNA and protein expressions of AdipoR2 in liver were detected. Histomorphological changes of the liver were observed by hematoxylineosin ( HE) staining, red Ο fat dyeing, and Masson staining, respectively. Results Contents of fasting blood glucose (FBG) , total cholesterol (TC) , and low-density lipoprotein cholesterol (LDL-C) were reduced more significantly in the DR group than in the model group. DR could promote liver expression of AdipoR2 mRNA and protein expressions in ApoE⁻¹â» mice, which was significantly higher than that of the model group (P <0. 01) , and better than that of pioglitazone (P <0. 05, P <0. 01). DR could improve ectopic fat deposition and fibrosis of liver cells in diabet- ic ApoE⁻¹â» mice significantly, which was better than that of the pioglitazone group and the combined treatment group. Conclusion DR could significantly improve liver lipid metabolism , and reduce liver fat deposition and fibrosis, which might possibly be associated with promoting AdipoR2 expression in liver.

CB1R antagonist increases hepatic insulin clearance in fat-fed dogs likely via upregulation of liver adiponectin receptors.

The improvement of hepatic insulin sensitivity by the cannabinoid receptor 1 (CB1R) antagonist rimonabant (RIM) has been recently been reported to be due to upregulation of adiponectin. Several studies demonstrated that improvement in insulin clearance accompanies the enhancement of hepatic insulin sensitivity. However, the effects of RIM on hepatic insulin clearance (HIC) have not been fully explored. The aim of this study was to explore the molecular mechanism(s) by which RIM affects HIC, specifically to determine whether upregulation of liver adiponectin receptors (ADRs) and other key genes regulated by adiponectin mediate the effects. To induce insulin resistance in skeletal muscle and liver, dogs were fed a hypercaloric high-fat diet (HFD) for 6 wk. Thereafter, while still maintained on a HFD, animals received RIM (HFD+RIM; n = 11) or placebo (HFD+PL; n = 9) for an additional 16 wk. HIC, calculated as the metabolic clearance rate (MCR), was estimated from the euglycemic-hyperinsulinemic clamp. The HFD+PL group showed a decrease in MCR; in contrast, the HFD+RIM group increased MCR. Consistently, the expression of genes involved in HIC, CEACAM-1 and IDE, as well as gene expression of liver ADRs, were increased in the HFD+RIM group, but not in the HFD+PL group. We also found a positive correlation between CEACAM-1 and the insulin-degrading enzyme IDE with ADRs. Interestingly, expression of liver genes regulated by adiponectin and involved in lipid oxidation were increased in the HFD+RIM group. We conclude that in fat-fed dogs RIM enhances HIC, which appears to be linked to an upregulation of the adiponectin pathway.

Effects of fenofibrate on adiponectin expression in retinas of streptozotocin-induced diabetic rats.

Adiponectin has been associated with increased risks of microvascular complications in diabetes; however, its role in the development of diabetic retinopathy (DR) is unknown. Fenofibrate is a lipid-lowering agent that has been shown to be capable of preventing DR progression. We investigated the expression of adiponectin and its receptors in DR and evaluated the effects of fenofibrate on their expression. The mRNA and protein levels of adiponectin and its receptors were elevated in retinas of streptozotocin-induced diabetic rats and were suppressed following fenofibrate treatment. Immunofluorescence staining demonstrated that adiponectin and adipoR1 were expressed in cells located within blood vessels, the retinal ganglion, and the inner nuclear layer. AdipoR1 was strongly expressed whereas adipoR2 was only weekly expressed in vascular endothelial cells. The in vitro experiments showed that adiponectin expression was induced by high glucose concentrations in RGC-5 and RAW264.7 cells and was suppressed following fenofibrate treatment. AdipoR1 and adipoR2 levels in RGC-5 cells were elevated in high glucose concentrations and suppressed by fenofibrate. Our results demonstrated that adiponectin may be a proinflammatory mediator in diabetic retinas and fenofibrate appears to modulate the expression of adiponectin and its receptors in diabetic retinas, effectively reducing DR progression.

GW4064, a farnesoid X receptor agonist, upregulates adipokine expression in preadipocytes and HepG2 cells.

AIM: To investigate the effect of GW4064 on the expression of adipokines and their receptors during differentiation of 3T3-L1 preadipocytes and in HepG2 cells. METHODS: The mRNA expression of farnesoid X receptor (FXR), peroxisome proliferator-activated receptor-gamma 2 (PPAR-γ2), adiponectin, leptin, resistin, adiponectin receptor 1 (AdipoR1), adiponectin receptor 2 (AdipoR2), and the long isoform of leptin receptor (OB-Rb) and protein levels of adiponectin, leptin, and resistin were determined using fluorescent real-time PCR and enzyme linked immunosorbent assay, respectively, on days 0, 2, 4, 6, and 8 during the differentiation of 3T3-L1 preadipocytes exposed to GW4064. Moreover, mRNA expression of AdipoR2 and OB-Rb was also examined using fluorescent real-time PCR at 0, 12, 24, and 48 h in HepG2 cells treated with GW4064. RESULTS: The mRNA expression of FXR, PPAR-γ2, adiponectin, leptin, resistin, AdipoR1, AdipoR2, and OB-Rb and protein levels of adiponectin, leptin, and resistin increased along with differentiation of 3T3-L1 preadipocytes (P < 0.05 for all). The mRNA expression of FXR, PPAR-γ2, adiponectin, leptin, and AdipoR2 in 3T3-L1 preadipocytes, and AdipoR2 and OB-Rb in HepG2 cells was significantly increased after treatment with GW4064, when compared with the control group (P < 0.05 for all). A similar trend was observed for protein levels of adipokines (including adiponectin, leptin and resistin). However, the expression of resistin, AdipoR1, and OB-Rb in 3T3-L1 cells did not change after treatment with GW4064. CONCLUSION: The FXR agonist through regulating, at least partially, the expression of adipokines and their receptors could offer an innovative way for counteracting the progress of metabolic diseases such as nonalcoholic fatty liver disease.

Effect of monomeric adiponectin on cardiac function and perfusion in anesthetized pig.

Adiponectin, the most abundant adipokine released by adipose tissue, appears to play an important role in the regulation of vascular endothelial and cardiac function. To date, however, the physiological effects of human monomeric adiponectin on the coronary vasculature and myocardial systo-diastolic function, as well as on parasympathetic/sympathetic involvement and nitric oxide (NO) release, have not yet been investigated. Thus, we planned to determine the primary in vivo effects of human monomeric adiponectin on coronary blood flow and cardiac contractility/relaxation and the related role of autonomic nervous system, adiponectin receptors, and NO. In 30 anesthetized pigs, human monomeric adiponectin was infused into the left anterior descending coronary artery at constant heart rate and arterial blood pressure, and the effects on coronary blood flow, left ventricular systo-diastolic function, myocardial oxygen metabolism, and NO release were examined. The mechanisms of the observed hemodynamic responses were also analyzed by repeating the highest dose of human monomeric adiponectin infusion after autonomic nervous system and NO blockade, and after specific adiponectin 1 receptor antagonist administration. Intracoronary human monomeric adiponectin caused dose-related increases of coronary blood flow and cardiac function. Those effects were accompanied by increased coronary NO release and coronary adiponectin levels. Moreover, the vascular effects of the peptide were prevented by blockade of ß2-adrenoceptors and NO synthase, whereas all effects of human monomeric adiponectin were prevented by adiponectin 1 receptor inhibitor. In conclusion, human monomeric adiponectin primarily increased coronary blood flow and cardiac systo-diastolic function through the involvement of specific receptors, ß2-adrenoceptors, and NO release.

Modulation of adiponectin as a potential therapeutic strategy.

Adiponectin is produced predominantly by adipocytes and plays an important role in metabolic and cardiovascular homeostasis through its insulin-sensitizing actions and anti-inflammatory and anti-atherogenic properties. Recently, it has been observed that lower levels of adiponectin can substantially increase the risk of developing type 2 diabetes, metabolic syndrome, atherosclerosis, and cardiovascular disease in patients who are obese. Circulating adiponectin levels are inversely related to the inflammatory process, oxidative stress, and metabolic dysregulation. Intensive lifestyle modifications and pharmacologic agents, including peroxisome proliferator-activated receptor-γ or α agonists, some statins, renin-angiotensin-aldosterone system blockers, some calcium channel blockers, mineralocorticoid receptor blockers, new ß-blockers, and several natural compounds can increase adiponectin levels and suppress or prevent disease initiation or progression, respectively, in cardiovascular and metabolic disorders. Therefore, it is important for investigators to have a thorough understanding of the interventions that can modulate adiponectin. Such knowledge may lead to new therapeutic approaches for diseases such as type 2 diabetes, metabolic syndrome, cardiovascular disease, and obesity. This review focuses on recent updates regarding therapeutic interventions that might modulate adiponectin.

MicroRNA-150 inhibits expression of adiponectin receptor 2 and is a potential therapeutic target in patients with chronic heart failure.

BACKGROUND: Adiponectin is an anti-inflammatory adipocytokine believed to be involved in the pathogenesis of chronic heart failure (CHF). We aimed to characterize the expression of adiponectin and its receptors in CHF and to assess the impact of microRNAs on the cardiac adiponectin system. METHODS: Expression of adiponectin and adiponectin receptors (ADIPOR1 and ADIPOR2) was studied by qPCR and immunohistochemistry in myocardial tissues of patients with end-stage CHF and control subjects. MicroRNA binding was evaluated by cloning of an ADIPOR2 3´-untranslated-region reporter construct and subsequent transfection experiments. Effects of miRNA transfection were analyzed in cardiomyocyte cell cultures by qPCR and Western blotting. Gene silencing of ADIPOR2 was performed by siRNA transfection, and the effects of hypoxia/serum starvation were analyzed by flow cytometry. RESULTS: Although CHF patients displayed elevated plasma adiponectin levels, myocardial adiponectin expression generally was very low. In CHF, cardiac ADIPOR1 expression increased by >4-fold, whereas the increase in ADIPOR2 was less than 2-fold. Reporter gene assays on constructs containing the ADIPOR2-3'-untranslated region suggest that microRNA-150 specifically repressed ADIPOR2 expression. Transfection of cardiomyocytes with premiR-150 precursor molecules resulted in 60% down-regulation of ADIPOR2 mRNA and a significant reduction of ADIPOR2 protein expression. MicroRNA-150 was substantially expressed in both normal and CHF myocardium, with a 1.7-fold higher expression in CHF. Finally, knock-down experiments elucidated a stress-protective role of ADIPOR2 in cardiomyocytes. CONCLUSIONS: MicroRNA-150 counteracts ADIPOR2 up-regulation in CHF and thus may contribute to adiponectin resistance. Targeting microRNA-150 may be a future strategy to restore cardioprotective adiponectin effects.

Phycocyanin prevents hypertension and low serum adiponectin level in a rat model of metabolic syndrome.

Endothelial dysfunction is associated with hypertension, atherosclerosis, and metabolic syndrome. Phycocyanin is a pigment found in the blue-green algae, Spirulina, which possesses antihypertensive effect. In this study, we hypothesized that phycocyanin derived from Spirulina exerts antihypertensive actions by improving endothelial dysfunction in metabolic syndrome. Spontaneously hypertensive/NIH-corpulent (SHR/NDmcr-cp) rats were divided into 4 groups then fed a normal diet with or without phycocyanin (2500-, 5000-, or 10,000-mg/kg diet) for 25 weeks. At 34 weeks of age, although systolic blood pressure was not significantly different among groups, phycocyanin-fed groups exhibited a dose-dependent decrease in blood pressure. Serum levels of adiponectin and messenger RNA levels of adiponectin and CCAAT/enhancer-binding protein α in the adipose tissue of rats fed diets containing phycocyanin tended to be higher than those of rats fed a normal diet, but the differences were not statistically significant. Immunohistochemistry analysis showed a significant and positive correlation between aortic endothelial nitric oxide synthase (eNOS) expression levels, a downstream target of the adiponectin receptor, and serum adiponectin levels, although there were no significant differences in eNOS expression among groups. There was also no significant correlation between eNOS expression levels and systolic blood pressure. These results suggest that long-term administration of phycocyanin may ameliorate systemic blood pressure by enhancing eNOS expression in aorta that is stimulated by adiponectin. Phycocyanin may be beneficial for preventing endothelial dysfunction-related diseases in metabolic syndrome.

Effect of telmisartan on the expression of adiponectin receptors and nicotinamide adenine dinucleotide phosphate oxidase in the heart and aorta in type 2 diabetic rats.

BACKGROUND: Diabetic cardiovascular disease is associated with decreased adiponectin and increased oxidative stress. This study investigated the effect of telmisartan on the expression of adiponectin receptor 2 (adipoR2) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits in the heart and the expression of adiponectin receptor 1 (adipoR1) in aorta in type 2 diabetic rats. METHODS: Type 2 diabetes was induced by high-fat and high-sugar diet and intraperitoneal injection of a low dose of streptozotocin (STZ). Heart function, adipoR2, p22phox, NOX4, glucose transporter 4(GLUT4), monocyte chemoattractant protein-1(MCP-1) and connective tissue growth factor (CTGF)in the heart, and adipoR1, MCP-1 and nuclear factor kappa B (NF-κB) in aorta were analyzed in controls and diabetic rats treated with or without telmisartan (5mg/kg/d) by gavage for 12 weeks. RESULTS: Heart function, plasma and myocardial adiponectin levels, the expression of myocardial adipoR2 and GLUT4 were significantly decreased in diabetic rats (P <0.05). The expression of myocardial p22phox, NOX4, MCP-1, and CTGF was significantly increased in diabetic rats (P <0.05). The expression of adipoR1 was decreased and the expression of MCP-1 and NF-κB was increased in the abdominal aorta in diabetic rats (P <0.05). Telmisartan treatment significantly attenuated these changes in diabetic rats (P <0.05). CONCLUSIONS: Our results suggest that telmisartan upregulates the expression of myocardial adiponectin, its receptor 2 and GLUT4. Simultaneously, it downregulates the expression of myocardial p22phox, NOX4, MCP-1, and CTGF, contributing so to the improvement of heart function in diabetic rats. Telmisartan also induces a protective role on the vascular system by upregulating the expression of adipoR1 and downregulating the expression of MCP-1 and NF-κB in the abdominal aorta in diabetic rats.

C1q/TNF-related proteins, a family of novel adipokines, induce vascular relaxation through the adiponectin receptor-1/AMPK/eNOS/nitric oxide signaling pathway.

OBJECTIVE: Reduced plasma adiponectin (APN) in diabetic patients is associated with endothelial dysfunction. However, APN knockout animals manifest modest systemic dysfunction unless metabolically challenged. The protein family CTRPs (C1q/TNF-related proteins) has recently been identified as APN paralogs and some CTRP members share APN's metabolic regulatory function. However, the vasoactive properties of CTRPs remain completely unknown. METHODS AND RESULTS: The vasoactivity of currently identified murine CTRP members was assessed in aortic vascular rings and underlying molecular mechanisms was elucidated in human umbilical vein endothelial cells. Of 8 CTRPs, CTRPs 3, 5, and 9 caused significant vasorelaxation. The vasoactive potency of CTRP9 exceeded that of APN (3-fold) and is endothelium-dependent and nitric oxide (NO)-mediated. Mechanistically, CTRP9 increased AMPK/Akt/eNOS phosphorylation and increased NO production. AMPK knockdown completely blocked CTRP9-induced Akt/eNOS phosphorylation and NO production. Akt knockdown had no significant effect on CTRP9-induced AMPK phosphorylation, but blocked eNOS phosphorylation and NO production. Adiponectin receptor 1, but not receptor 2, knockdown blocked CTRP9-induced AMPK/Akt/eNOS phosphorylation and NO production. Finally, preincubating vascular rings with an AMPK-inhibitor abolished CTRP9-induced vasorelaxative effects. CONCLUSION: We have provided the first evidence that CTRP9 is a novel vasorelaxative adipocytokine that may exert vasculoprotective effects via the adiponectin receptor 1/AMPK/eNOS dependent/NO mediated signaling pathway.

Pioglitazone upregulates adiponectin receptor 2 in 3T3-L1 adipocytes.

AIMS: Pioglitazone, a full peroxisome proliferator-activated receptor (PPAR)-γ agonist, improves insulin sensitivity by increasing circulating adiponectin levels. However, the molecular mechanisms by which pioglitazone induces insulin sensitization are not fully understood. In this study, we investigated whether pioglitazone improves insulin resistance via upregulation of either 2 distinct receptors for adiponectin (AdipoR1 or AdipoR2) expression in 3T3-L1 adipocytes. MAIN METHODS: Glucose uptake was evaluated by 2-[(3)H] deoxy-glucose uptake assay in 3T3-L1 adipocytes with pioglitazone treatment. AdipoR1 and AdipoR2 mRNA expressions were analyzed by qRT-PCR. KEY FINDINGS: We first confirmed that pioglitazone significantly increased insulin-induced 2-deoxyglucose (2-DOG) uptake in 3T3-L1 adipocytes. Next, we investigated the mRNA expression and regulation of AdipoR1 and AdipoR2 after treatment with pioglitazone. Interestingly, pioglitazone significantly induced AdipoR2 expression but it did not affect AdipoR1 expression. In addition, adenovirus-mediated PPARγ expression significantly enhanced the effects of pioglitazone on insulin-stimulated 2-DOG uptake and AdipoR2 expression in 3T3-L1 adipocytes. These data suggest that pioglitazone enhances adiponectin's autocrine and paracrine actions in 3T3-L1 adipocytes via upregulation of PPARγ-mediated AdipoR2 expression. Furthermore, we found that pioglitazone significantly increased AMP-activated protein kinase (AMPK) phosphorylation in insulin-stimulated 3T3-L1 adipocytes, but it did not lead to the phosphorylation of IRS-1, Akt, or protein kinase Cλ/ζ. SIGNIFICANCE: Our results suggest that pioglitazone increases insulin sensitivity, at least partly, by PPARγ-AdipoR2-mediated AMPK phosphorylation in 3T3-L1 adipocytes. In conclusion, the upregulation of AdipoR2 expression may be one of the mechanisms by which pioglitazone improves insulin resistance in 3T3-L1 adipocytes.