Transcriptional and post-translational regulation of adiponectin

ZFP36L1 and AUF1 Induction Contribute to the Suppression of Inflammatory Mediators Expression by Globular Adiponectin via Autophagy Induction in Macrophages

Adiponectin, a hormone predominantly originated from adipose tissue, has exhibited potent anti-inflammatory properties. Accumulating evidence suggests that autophagy induction plays a crucial role in anti-inflammatory responses by adiponectin. However, underlying molecular mechanisms are still largely unknown. Association of Bcl-2 with Beclin-1, an autophagy activating protein, prevents autophagy induction. We have previously shown that adiponectin-induced autophagy activation is mediated through inhibition of interaction between Bcl-2 and Beclin-1. In the present study, we examined the molecular mechanisms by which adiponectin modulates association of Bcl-2 and Beclin-1 in macrophages. Herein, we demonstrated that globular adiponectin (gAcrp) induced increase in the expression of AUF1 and ZFP36L1, which act as mRNA destabilizing proteins, both in RAW 264.7 macrophages and primary peritoneal macrophages. In addition, gene silencing of AUF1 and ZFP36L1 caused restoration of decrease in Bcl-2 expression and Bcl-2 mRNA half-life by gAcrp, indicating crucial roles of AUF1 and ZFP36L1 induction in Bcl-2 mRNA destabilization by gAcrp. Moreover, knock-down of AUF1 and ZFP36L1 enhanced interaction of Bcl-2 with Beclin-1, and subsequently prevented gAcrp-induced autophagy activation, suggesting that AUF1 and ZFP36L1 induction mediates gAcrp-induced autophagy activation via Bcl-2 mRNA destabilization. Furthermore, suppressive effects of gAcrp on LPS-stimulated inflammatory mediators expression were prevented by gene silencing of AUF1 and ZFP36L1 in macrophages. Taken together, these results suggest that AUF1 and ZFP36L1 induction critically contributes to autophagy induction by gAcrp and are promising targets for anti-inflammatory responses by gAcrp.

Role of Adiponectin in Central Nervous System Disorders

Adiponectin, the most abundant plasma adipokine, plays an important role in the regulation of glucose and lipid metabolism. Adiponectin also possesses insulin-sensitizing, anti-inflammatory, angiogenic, and vasodilatory properties which may influence central nervous system (CNS) disorders. Although initially not thought to cross the blood-brain barrier, adiponectin enters the brain through peripheral circulation. In the brain, adiponectin signaling through its receptors, AdipoR1 and AdipoR2, directly influences important brain functions such as energy homeostasis, hippocampal neurogenesis, and synaptic plasticity. Overall, based on its central and peripheral actions, recent evidence indicates that adiponectin has neuroprotective, antiatherogenic, and antidepressant effects. However, these findings are not without controversy as human observational studies report differing correlations between plasma adiponectin levels and incidence of CNS disorders. Despite these controversies, adiponectin is gaining attention as a potential therapeutic target for diverse CNS disorders, such as stroke, Alzheimer's disease, anxiety, and depression. Evidence regarding the emerging role for adiponectin in these disorders is discussed in the current review.

Serum adiponectin/Ferritin ratio in relation to the risk of type 2 diabetes and insulin sensitivity

AIMS

Body iron inhibits the metabolism of adiponectin, an insulin sensitizing adipokine. We investigated the relationships of baseline and average of 4-year change in values of serum adiponectin (sA), serum ferritin (sF) and sA/sF ratio on type 2 diabetes (T2D) risk and insulin sensitivity (Matsuda ISI) and secretion (disposition index; DI₃₀).

METHODS

Prospective analyses were conducted in participants with impaired glucose tolerance of the Finnish Diabetes Prevention Study (n = 516) recruited in 1993-1998. Cox and linear regression analyses were used to investigate the associations of sA, sF and sA/sF ratio, as continuous variables, with incident T2D, Matsuda ISI, and DI₃₀.

RESULTS

During the mean follow-up of 8.2 years, 157 incident T2D cases occurred (intervention group, n = 65 and control group, n = 92). In adjusted models, baseline sA and sA/sF ratio were inversely associated with T2D risk (HR = 0.49, 95% CI 0.31-0.76, P = 0.002 and HR = 0.83, 95% CI 0.70-0.99, P = 0.044, respectively). Furthermore, a direct association was observed with Matsuda ISI (β=0.13, 95% CI 0.03-0.22, P = 0.009, for sA and β=0.04, 95% CI 0.01-0.07, P = 0.035, for sA/sF ratio) during the average 4-year follow-up. The changes in sA and sA/sF ratio were also inversely associated with T2D risk (HR = 0.36, 95% CI 0.20-0.63, P < 0.001 and HR = 0.76, 95% CI 0.62-0.92, P = 0.006, respectively), and directly with Matsuda ISI (β=0.27, 95% CI 0.17-0.38, P < 0.001, for sA and β=0.07, 95% CI 0.03-0.11, P < 0.001, for sA/sF ratio). No consistent associations were found with DI_30. CONCLUSIONS: Baseline levels and changes during the follow-up in sA and sA/sF ratio are related to T2D risk and insulin sensitivity.

Adiponectin as a potential therapeutic target for the treatment of restenosis

Restenosis is a pathologic re-narrowing of a coronary artery lesion after mechanical injury. Its pathophysiological mechanisms have not been fully elucidated at present, but are thought to include inflammation, vascular smooth muscle cell (VSMC) proliferation, and matrix remodeling, beginning with insufficient endothelium healing. Restenosis presents with angina symptoms or acute coronary syndromes and lead to a revascularization, either with coronary artery bypass or repeat percutaneous coronary intervention. Some studies have reported that hypoadiponectinemia has been an independent risk factor for the onset of acute coronary syndromes and restenosis. Accumulating evidence shows that low concentrations of adiponectin may be involved in impairing endothelium functions, inflammation, and VSMC proliferation that lead to restenosis. Preclinical studies have proven that adiponectin promotes endothelium healing, effectively inhibits inflammation, and maintains contractile phenotypes of VSMCs, indicating that it may be developed as a new therapeutic target for the treatment of restenosis.

Variation in x-box binding protein 1 (XBP1) expression and its dependent endoplasmic reticulum chaperones does not regulate adiponectin secretion in dairy cows

Adiponectin is an insulin-sensitizing hormone produced predominantly by adipose tissue; it circulates as oligomers of 3, 6, 18, or more units. Plasma adiponectin might be involved in the development of insulin resistance in transition dairy cows because it falls to a nadir around parturition. The possibility that this regulation occurs through a post-transcriptional mechanism was suggested in a previous study that showed unchanged adiponectin mRNA abundance combined with reduced expression of endoplasmic reticulum (ER) chaperones implicated in assembly of adiponectin oligomers. Expression of ER chaperones is controlled by x-box binding protein 1 (XBP1) and activating transcription factor 6 (ATF6), suggesting a model whereby transcriptional regulation of ER chaperones during the transition period contributes to the regulation of adiponectin production. In support of this model, XBP1 expression in adipose tissue, measured either as the active spliced XBP1 mRNA or as the total of all XBP1 mRNA isoforms, was 45% lower on d 8 of lactation than 4 wk before parturition; ATF6 mRNA abundance remained unchanged over the same period. To assess the functional importance of XBP1, preadipocytes isolated from pregnant cows were differentiated into adipocytes that secrete adiponectin. Infection of differentiating cells with an adenovirus expressing the active spliced version of bovine XBP1 did not alter adiponectin mRNA but increased the expression of ER chaperones 1.5- to 5-fold. Despite the latter, XBP1 overexpression did not affect the total amount of adiponectin secreted in medium. In additional experiments, adiponectin production was dependent on exogenous lipid in the medium and was reduced during incubation with tumor necrosis factor-α (TNFα). Accordingly, we asked whether the repressive effects of these factors on adiponectin production were related to a reduction in the expression of adiponectin or determinants of ER function (XBP1, ATF6, and ER chaperones). Exogenous lipid had no effect on the expression of any of these genes, whereas TNFα repressed adiponectin mRNA abundance by 61% but had little effect on determinants of ER function. Overall, this work shows that XBP1 is a positive regulator of ER chaperone expression in adipose tissue but provides no support for XBP1 and its dependent ER chaperones in the regulation of adiponectin production in bovine adipocytes. Mechanisms accounting for reduced plasma adiponectin in transition cows remain poorly understood.

Does the Additional Component of Calf Circumference Refine Metabolic Syndrome in Correlating With Cardiovascular Risk?

CONTEXT

Calf circumference (CC) was a useful anthropometric tool, but there was limited study on the effect of CC on metabolic syndrome (MetS) for cardiovascular risk.

OBJECTIVE

The objective of our study was to determine whether adding CC as a component of MetS refined correlating MetS with cardiovascular, all-cause, and cancer mortality risks.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

From the National Health and Nutrition Examination Survey data set for 1999 through 2002, we analyzed four types of MetS: (1) increased waist circumference and two or more of four MetS components (WaistMetS); (2) decreased CC and two or more of four MetS components (CalfMetS); (3) increased waist-to-calf ratio and two or more of four MetS components (WCRMetS); and (4) decreased CC and three or more of five MetS components (CC+MetS).

PRIMARY OUTCOME MEASURE

The cause-specific hazard ratios were measured as categorized by the four types of MetS.

RESULTS

For cardiovascular mortality, the adjusted hazard ratios for WaistMetS, CalfMetS, WCRMetS, and CC+MetS were 1.867, 1.871, 1.949, and 2.306, respectively (all P < 0.001). Notably, CalfMetS showed the strongest positive correlation with serum C-reactive protein levels, and WCRMetS had the strongest positive relationship with homeostasis model assessment of insulin resistance.

CONCLUSIONS

Adding CC to the components of MetS correlated with higher cardiovascular and all-cause mortality risk than the traditional definition of MetS.

Ameliorative effect of panaxynol on the reduction in high-molecular-weight adiponectin secretion from 3T3-L1 adipocytes treated with palmitic acids

Reduced plasma levels of the high-molecular weight (HMW) form of adiponectin, rather than total adiponectin levels, have been shown to be closely associated with various metabolic diseases including insulin resistance, type 2 diabetes, and cardiovascular disease. Therefore, we sought to explore active, naturally occurring compounds that promote the recovery of HMW adiponectin secretion suppressed by palmitic acid in our model. A total of 90 crude drug extracts were screened for the ability to augment HMW adiponectin secretion from 3T3-L1 adipocytes treated with palmitic acid. Panaxynol was isolated from Saposhnikovia divaricata as an active compound with HMW adiponectin promoting properties. Peroxisome proliferator-activated receptor-γ (PPARγ) agonists are reported to increase the secretion of HMW adiponectin, although the effects of panaxynol were found to be independent of PPARγ activation. When the underlying mechanisms were further examined, panaxynol was found to inhibit the palmitic-acid-induced downregulation of forkhead box O1 (FoxO1) protein, and the anti-lipotoxic effects were abolished by a FoxO1 inhibitor. Furthermore, CCAAT/enhancer-binding protein-α (C/EBPα) mRNA levels were also increased by panaxynol. Reactive oxygen species have critical roles in the reduction in HMW adiponection secretion by palmitic acid; however, panaxynol reduced this increase in reactive oxygen species generation, followed by reductions in markers of endoplasmic reticulum stress and inflammation. Taken together, these findings suggest that panaxynol ameliorates the impaired HMW adiponection secretion in adipocytes treated with palmitic acid by restoring FoxO1 expression, owing to inhibition of reactive oxygen species generation, in a PPARγ-independent manner.

Salivary adiponectin concentration in healthy adult males in relation to anthropometric measures and fat distribution

Objectives. Body fat content, fat distribution, and adiponectin level are important variables in the development of obesity related complications. Anthropometric indices may provide an economic and faster method in measuring the risk for complications through their predictive effect of fat distribution and adiponectin concentration. We aimed to determine, which of the waist circumference (WC), waist-to-hip ratio (WHR), and body mass index (BMI) may be the best predictor for the total fat percentage (WF), visceral fat level (VF), and subcutaneous whole-body fat (SCWBF). We aimed also to investigate the potential use of the anthropometric measures and fat distribution as predictors for the salivary adiponectin level in the healthy adult males. Subjects. A total of 88 adult males aged between 18−25 years with a wide range of BMI were studied. Anthropometric indices were measured using standardized methods and salivary adiponectin level was assessed using an enzyme-linked immunosorbent assay. Results. In path analysis of the Structural Equation Model (SEM) using IBM@SPSS AMOS, version22, BMI and WC, but not WHR, were strong predictors for WF and SCWBF (p<0.05). BMI but not WC was a strong predictor for VF (p<0.001). WF was strong predictor for SCWBF (p<0.001), but not for VF. BMI, WC, WHR, WF, VF, and SCWBF were poor predictors of the salivary adiponectin level. Conclusion. BMI is the best predictor for the total body fat and fat distribution. However, WHR seems to be of a little value and the salivary adiponectin level independent of BMI and body fat in healthy adult Malay males.

Resveratrol Cardioprotection Against Myocardial Ischemia/Reperfusion Injury Involves Upregulation of Adiponectin Levels and Multimerization in Type 2 Diabetic Mice

Downregulation of adiponectin (APN) multimerization is significantly correlated with the aggravation of myocardial ischemia/reperfusion (MI/R) injury in type 2 diabetes mellitus (T2DM). Resveratrol (RSV) upregulates APN multimerization in adipocytes, but whether RSV improves endogenous APN multimerization and thus attenuates MI/R injury in T2DM mice has never been investigated. T2DM mice were treated with 10 mg/kg RSV daily for 3 weeks, followed by 30 minutes of myocardial ischemia and 3 hours or 24 hours of reperfusion. RSV administration alleviated MI/R injury in diabetic mice, as evidenced by reduced infarct size, cardiomyocyte apoptosis, and caspase-3 activity, and improved cardiac function. Moreover, RSV reversed the downregulated APN levels and multimerization both in plasma and adipose tissue, accompanied by increased disulfide bond A oxidoreductase-like protein (DsbA-L) expression in T2DM mice. Conversely, serving as a key downstream molecule of APN in ameliorating MI/R injury, inhibition of AMP-activated protein kinase (AMPK) significantly attenuated the cardioprotective effects of RSV. In conclusion, long-term administration of RSV upregulates adiponectin levels and multimerization in T2DM mice, consequently attenuating MI/R injury partially through APN-AMPK signaling.

Synthetic peptides designed to modulate adiponectin assembly improve obesity-related metabolic disorders

BACKGROUND AND PURPOSE

Adiponectin, an adipokine possessing profound insulin-sensitizing and anti-inflammatory properties, is a potent biotherapeutic agent . The trimeric adiponectin subunit assembles into hexameric and functionally important higher molecular weight (HMW) forms, controlled by the endoplasmic reticulum protein 44 (ERp44). Obesity-induced ER stress decreases the HMW form in serum, contributing to the development of insulin resistance and Type 2 diabetes. In this study, a panel of synthetic peptides, designed to target ERp44-adiponectin interactions, were tested for their effects on circulating levels of HMW adiponectin.

EXPERIMENTAL APPROACH

Peptides derived from the ERp44 binding region of adiponectin and immunoglobulin IgM were synthesized with or without a cell-penetrating sequence. Cultures of 3T3-L1 adipocytes were incubated with the peptides for assessing the assembly and secretion of HMW adiponectin. Mice given standard chow or a high-fat diet were treated acutely or chronically, with the peptides to investigate the therapeutic effects on insulin sensitivity and energy metabolism.

RESULTS

The designed peptides interfered with ERp44-adiponectin interactions and modulated adiponectin assembly and release from adipocytes. In particular, IgM-derived peptides facilitated the release of endogenous adiponectin (especially the HMW form) from adipose tissue, enhanced its circulating level and the ratio of HMW-to-total-adiponectin in obese mice. Long-term treatment of mice fed with high-fat diet by IgM-derived peptides reduced the circulating lipid levels and improved insulin sensitivity.

CONCLUSIONS AND IMPLICATIONS

Targeting ERp44-adiponectin interactions with short peptides represents an effective strategy to treat of obesity-related metabolic disorders, such as insulin resistance and Type 2 diabetes.

Adiponectin Mediates Dietary Omega-3 Long-Chain Polyunsaturated Fatty Acid Protection Against Choroidal Neovascularization in Mice

Purpose

Neovascular age-related macular degeneration (AMD) is a major cause of legal blindness in the elderly. Diets with omega3-long-chain-polyunsaturated-fatty-acid (ω3-LCPUFA) correlate with a decreased risk of AMD. Dietary ω3-LCPUFA versus ω6-LCPUFA inhibits mouse ocular neovascularization, but the underlying mechanism needs further exploration. The aim of this study was to investigate if adiponectin (APN) mediated ω3-LCPUFA suppression of neovessels in AMD.

Methods

The mouse laser-induced choroidal neovascularization (CNV) model was used to mimic some of the inflammatory aspect of AMD. CNV was compared between wild-type (WT) and Apn^−/− mice fed either otherwise matched diets with 2% ω3 or 2% ω6-LCPUFAs. Vldlr^−/− mice were used to mimic some of the metabolic aspects of AMD. Choroid assay ex vivo and human retinal microvascular endothelial cell (HRMEC) proliferation assay in vitro was used to investigate the APN pathway in angiogenesis. Western blot for p-AMPKα/AMPKα and qPCR for Apn, Mmps, and IL-10 were used to define mechanism.

Results

ω3-LCPUFA intake suppressed laser-induced CNV in WT mice; suppression was abolished with APN deficiency. ω3-LCPUFA, mediated by APN, decreased mouse Mmps expression. APN deficiency decreased AMPKα phosphorylation in vivo and exacerbated choroid-sprouting ex vivo. APN pathway activation inhibited HRMEC proliferation and decreased Mmps. In Vldlr^−/− mice, ω3-LCPUFA increased retinal AdipoR1 and inhibited NV. ω3-LCPUFA decreased IL-10 but did not affect Mmps in Vldlr^−/− retinas.

Conclusions

APN in part mediated ω3-LCPUFA inhibition of neovascularization in two mouse models of AMD. Modulating the APN pathway in conjunction with a ω3-LCPUFA-enriched-diet may augment the beneficial effects of ω3-LCPUFA in AMD patients.

WSF-P-1, a novel AMPK activator, promotes adiponectin multimerization in 3T3-L1 adipocytes

Adiponectin, an adipokine with insulin-sensitizing effect, is secreted from adipocytes into circulation as high, medium, and low molecular weight forms (HMW, MMW, and LMW). The HMW adiponectin oligomers possess the most potent insulin-sensitizing activity. WSF-P-1(N-methyl-1,2,3,4,5,6-hexahydro-1,1,5,5-tetramethyl-7H-2,4α-methanonaphthalen-7-amine) is derived from natural sesquiterpene longifolene by chemical modifications. We found that WSF-P-1 activates AMPK in both 3T3-L1 adipocytes and 293T cells in this study. Activation of AMPK by WSF-P-1 promotes the assembly of HMW adiponectin and increases the HMW/total ratio of adiponectin in 3T3-L1 adipocytes. We demonstrated that the Ca²⁺-dependent CaMKK signaling pathway is involved in WSF-P-1-induced AMPK activation and adiponectin multimerization. WSF-P-1 also activates GLUT1-mediated glucose uptake in 3T3-L1 adipocytes, making it a potential drug candidate for the treatment of type 2 diabetes, obesity, and other obesity-related metabolic diseases.

Protein Kinase C β: a New Target Therapy to Prevent the Long-Term Atypical Antipsychotic-Induced Weight Gain

Antipsychotic drugs are currently used in clinical practice for a variety of mental disorders. Among them, clozapine is the most effective medication for treatment-resistant schizophrenia and is most helpful in controlling aggression and the suicidal behavior in schizophrenia and schizoaffective disorder. Although clozapine is associated with a low likelihood of extrapyramidal symptoms and other neurological side effects, it is well known for the weight gain and metabolic side effects, which expose the patient to a greater risk of cardiovascular disorders and premature death, as well as psychosocial issues, leading to non-adherence to therapy. The mechanisms underlying these iatrogenic metabolic disorders are still controversial. We have therefore investigated the in vivo effects of the selective PKCβ inhibitor, ruboxistaurin (LY-333531), in a preclinical model of long-term clozapine-induced weight gain. Cell biology, biochemistry, and behavioral tests have been performed in wild-type and PKCβ knockout mice to investigate the contribution of endogenous PKCβ and its pharmacological inhibition to the psychomotor effects of clozapine. Finally, we also shed light on a novel aspect of the mechanism underlying the clozapine-induced weight gain, demonstrating that the clozapine-dependent PKCβ activation promotes the inhibition of the lipid droplet-selective autophagy process. This paves the way to new therapeutic approaches to this serious complication of clozapine therapy.

Targeting P-selectin glycoprotein ligand-1/P-selectin interactions as a novel therapy for metabolic syndrome

Obesity-induced insulin resistance and metabolic syndrome continue to pose an important public health challenge worldwide as they significantly increase the risk of type 2 diabetes and atherosclerotic cardiovascular disease. Advances in the pathophysiologic understanding of this process has identified that chronic inflammation plays a pivotal role. In this regard, given that both animal models and human studies have demonstrated that the interaction of P-selectin glycoprotein ligand-1 (PSGL-1) with P-selectin is not only critical for normal immune response but also is upregulated in the setting of metabolic syndrome, PSGL-1/P-selectin interactions provide a novel target for preventing and treating resultant disease. Current approaches of interfering with PSGL-1/P-selectin interactions include targeted antibodies, recombinant immunoglobulins that competitively bind P-selectin, and synthetic molecular therapies. Experimental models as well as clinical trials assessing the role of these modalities in a variety of diseases have continued to contribute to the understanding of PSGL-1/P-selectin interactions and have demonstrated the difficulty in creating clinically relevant therapeutics. Most recently, however, computational simulations have further enhanced our understanding of the structural features of PSGL-1 and related glycomimetics, which are responsible for high-affinity selectin interactions. Leveraging these insights for the design of next generation agents has thus led to development of a promising synthetic method for generating PSGL-1 glycosulfopeptide mimetics for the treatment of metabolic syndrome.

Adiponectin/resistin interplay in serum and in adipose tissue of obese and normal-weight individuals

BACKGROUND

The interplay between adiponectin and resistin, the two adipokines of opposite effects, may determine the metabolic profile of obese individuals and development of obesity-related complications. The current study was conducted to assess how adiponectin/resistin interplay in sera and adipose tissues may influence the metabolic profile of obese and normal-weight subjects.

METHODS

Concentrations of adiponectin and resistin were measured on protein level by immunoassay in visceral and subcutaneous adipose tissues from 50 obese (body mass index > 40 kg/m²) and 28 normal-weight (body mass index 20-24.9 kg/m²) individuals. Simultaneously expression of ADIPOQ and RETN (encoding adiponectin and resistin, respectively) was assessed on mRNA level by real-time PCR.

RESULTS

ADIPOQ mRNA (P = 0.0001) and adiponectin protein (P = 0.0013) levels were lower, while RETN mRNA (P = 0.0338) and resistin (P < 0.0001)-higher in subcutaneous adipose tissues of obese subjects. ADIPOQ and RETN mRNA levels did not correlate with protein concentrations in the investigated adipose tissues. In obesity adiponectin serum concentrations correlated positively with ADIPOQ mRNA in subcutaneous adipose tissue (P = 0.005) and negatively with protein levels in visceral adipose tissue (P = 0.001). Obesity was associated with higher adiponectin-resistin index value in sera (P < 0.0001) and decreased in subcutaneous adipose tissue (P < 0.001), but only adiponectin-resistin index measured in sera was significantly higher in obese with the metabolic syndrome (P = 0.04).

CONCLUSIONS

Obesity affects synthesis of adiponectin and resistin mainly in subcutaneous adipose tissue. The adiponectin-resistin index assessed in the adipose tissues has a different prognostic value compared to the adiponectin-resistin index in serum and does not reflect a metabolic risk in obese individuals.

Pleiotropic effects of niacin: Current possibilities for its clinical use

Niacin was the first hypolipidemic drug to significantly reduce both major cardiovascular events and mortality in patients with cardiovascular disease. Niacin favorably influences all lipoprotein classes, including lipoprotein[a],and belongs to the most potent hypolipidemic drugs for increasing HDL-C. Moreover, niacin causes favorable changes to the qualitative composition of lipoprotein HDL. In addition to its pronounced hypolipidemic action, niacin exerts many other, non-hypolipidemic effects (e.g., antioxidative, anti-inflammatory, antithrombotic), which favorably influence the development and progression of atherosclerosis. These effects are dependent on activation of the specific receptor HCA2. Recent results published by the two large clinical studies, AIM-HIGH and HPS2-THRIVE, have led to the impugnation of niacin's role in future clinical practice. However, due to several methodological flaws in the AIM-HIGH and HPS2-THRIVE studies, the pleiotropic effects of niacin now deserve thorough evaluation. This review summarizes the present and possible future use of niacin in clinical practice in light of its newly recognized pleiotropic effects.

Fibroblast growth factor 21 reverses suppression of adiponectin expression via inhibiting endoplasmic reticulum stress in adipose tissue of obese mice

Fibroblast growth factor 21 (FGF21) has recently emerged as a novel endocrine hormone involved in the regulation of glucose and lipid metabolism. However, the exact mechanisms whereby FGF21 mediates insulin sensitivity remain not fully understood. In the present study, FGF21was administrated in high-fat diet-induced obese mice and tunicamycin-induced 3T3-L1 adipocytes, and metabolic parameters, endoplasmic reticulum (ER) stress indicators, and insulin signaling molecular were assessed by Western blotting. The administration of FGF21 in obese mice reduced body weight, blood glucose and serum insulin, and increased insulin sensitivity, resulting in alleviation of insulin resistance. Meanwhile, FGF21 treatment reversed suppression of adiponectin expression and restored insulin signaling via inhibiting ER stress in adipose tissue of obese mice. Additionally, suppression of ER stress via the ER stress inhibitor tauroursodeoxycholic acid increased adiponectin expression and improved insulin resistance in obese mice and in tunicamycin-induced adipocytes. In conclusion, our results showed that the administration of FGF21 reversed suppression of adiponectin expression and restored insulin signaling via inhibiting ER stress under the condition of insulin resistance, demonstrating the causative role of ER stress in downregulating adiponectin levels.

Effect of High-Fat Diet on the Formation of Pulmonary Neutrophil Extracellular Traps during Influenza Pneumonia in BALB/c Mice

Obesity is an independent risk factor for severe outcome of influenza infection. Higher dietary fat consumption has been linked to greater morbidity and severe influenza in mouse models. However, the extent of generation of neutrophil extracellular traps (NETs or NETosis) in obese individuals during influenza pneumonia is hitherto unknown. This study investigated pulmonary NETs generation in BALB/c mice fed with high-fat diet (HFD) and low-fat diet (LFD), during the course of influenza pneumonia. Clinical disease progression, histopathology, lung reactive oxygen species, and myeloperoxidase activity were also compared. Consumption of HFD over 18 weeks led to significantly higher body weight, body mass index, and adiposity in BALB/c mice compared with LFD. Lethal challenge of mice (on HFD and LFD) with influenza A/PR/8/34 (H1N1) virus led to similar body weight loss and histopathologic severity. However, NETs were formed at relatively higher levels in mice fed with HFD, despite the absence of significant difference in disease progression between HFD- and LFD-fed mice.

Review: adiponectin in retinopathy

Neovascular eye diseases are a major cause of blindness including retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration in which new vessel formation is driven by hypoxia or metabolic abnormalities affecting the fuel supply. White-adipose-tissue derived adipokines such as adiponectin modulate metabolic responses. Increasing evidence shows that lack of adiponectin may result in retinal neovascularization. Activation of the adiponectin pathway may in turn restore energy metabolism, to suppress the drive for compensatory but ultimately pathological neovessels of retinopathy. In this review, we will summarize our current knowledge of the role of adiponectin in eye diseases of premature infants, diabetic patients as well as the elderly. Further investigations in this field are likely to lead to new preventative approaches for these diseases.

Reduced circulating oxytocin and High-Molecular-Weight adiponectin are risk factors for metabolic syndrome

The neurohypophysial hormone, oxytocin, is involved in the regulation of energy metabolism. Adiponectin (APN) is an adipose tissue-specific serum protein that inversely associates with metabolic syndrome (MetS). High-molecular-weight adiponectin (HMW APN) is considered the active form. In the present study, we aimed to determine the relationships of oxytocin and HMW APN to MetS and investigate whether or not the combination of oxytocin and HMW APN is associated with further metabolic abnormalities compared to each of them alone. A total of 170 subjects (75 with MetS and 95 non-MetS) were enrolled. Anthropometric parameters, oral glucose tolerance test (OGTT), blood lipids, hs-CRP, oxytocin and HMW APN levels were measured. Compared with non-MetS subjects, serum oxytocin and HMW APN levels were significantly lower in subjects with MetS (P<0.01). We then classified the subjects into three groups: high oxytocin and high HMW APN levels (high score group), low oxytocin and low HMW APN levels (low score group) and others. Participants in low score group showed the worst metabolic profiles and were more likely to have MetS compared to the other two group. In Spearman rank correlation coefficient, the classification by the combination of oxytocin and HMW APN was significantly correlated with a larger number of metabolic risk factors compared with classification by each of them alone. Individuals with low circulating oxytocin levels coupled with low HMW APN levels were at significantly increased risk of MetS. The combination of both markers would be useful for identifying MetS high risk patients.

A possible connection between tumor necrosis factor alpha and adropin levels in polycystic ovary syndrome

CONTEXT

Adropin is a peptide hormone implicated in the regulation of insulin sensitivity and energy homeostasis. Polycystic ovary syndrome (PCOS) is a metabolic and reproductive disease associated with insulin resistance. It has been demonstrated that various inflammatory markers increased in PCOS including TNF-α. TNF-α regulates the secretion of certain peptides which play a crucial role in glucose and lipid homeostasis. There is also some evidence of a link between TNF-α and adropin.

OBJECTIVE

To ascertain whether there is an association between circulating adropin levels and TNF-α in PCOS.

PATIENTS AND DESIGN

152 women with PCOS and 152 age- and body mass index-matched controls without PCOS were recruited for this cross-sectional study.

MAIN OUTCOME MEASURES

Adropin and TNF-α levels were measured using ELISA.

RESULTS

Adropin levels were lower in the PCOS group compared with the control group (7.43 ± 0.79 vs. 9.42 ± 0.76 ng/ml, P < 0.001), whereas TNF-α levels were higher (49.93 ± 3.39 vs. 35.83 ± 2.47 pg/ml, P < 0.001). A strongly negative correlation was found between circulating adropin levels and TNF-α levels in women with PCOS (r = -0.407, P < 0.001). Binary logistic regression analysis revealed that decreased adropin levels were significantly associated with high odds of having PCOS, although, after adjustment for TNF-α, this link vanished. Additionally, multiple linear regression analysis showed that HOMA-IR and TFN-α independently predicted adropin levels.

CONCLUSIONS

Serum adropin levels are significantly decreased in PCOS and are inversely associated with TNF-α. Further dissection of the nature of this association can open new therapeutic options for metabolic diseases.

Depot-specific effects of treadmill running and rutin on white adipose tissue function in diet-induced obese mice

White adipose tissue (WAT) is a critical organ involved in regulating metabolic homeostasis under obese condition. Strategies that could positively affect WAT function would hold promise for fighting against obesity and its complications. The aim of the present study is to explore the effects of treadmill exercise training and rutin intervention on adipose tissue function from diet-induced obese (DIO) mice and whether fat depot-specific effects existed. In epididymal adipose tissue, high-fat diet (HFD) resulted in reduction in adiponectin mRNA expression, peroxisome proliferator-activated receptors (PPAR)-γ and DsbA-L protein expression, elevation in endoplasmic reticulum (ER) stress markers including 78 kDa glucose-regulated protein (GRP-78), C/EBP homologous protein (CHOP) and p-c-Jun N-terminal kinase (JNK). Isoproterenol-stimulated lipolysis and insulin stimulated Akt phosphorylation ex vivo were blunted from HFD group. The combination of rutin with exercise (HRE) completely restored GRP78 and p-JNK protein expression to normal levels, as well as blunted signaling ex vivo. In inguinal adipose tissue, HFD led to increased adiponectin mRNA expression, PPAR-γ, GRP78, and p-JNK protein expression, and reduction in DsbA-L. HRE is effective for restoring p-JNK, PPAR-γ, and DsbA-L. In conclusion, depot-specific effects may exist in regard to the effects of rutin and exercise on key molecules involved in regulating adipose tissue function (i.e., ER stress markers, PPAR-γ and DsbA-L, adiponectin expression, and secretion, ex vivo catecholamine stimulated lipolysis and insulin stimulated Akt phosphorylation) from DIO mice.

The FGF21-adiponectin axis in controlling energy and vascular homeostasis

Whole-body energy metabolism and cardiovascular homeostasis are tightly controlled processes that involve highly coordinated crosstalk among distal organs. This is mainly achieved by a large number of hormones released from each organ. Among them, fibroblast growth factor 21 (FGF21) and adiponectin have recently gained considerable attention, since both of them possess multiple profound protective effects against a myriad of cardio-metabolic disorders. Despite their distinct structures and production sites, these two hormones share striking functional similarity. This dichotomy is recently reconciled by the demonstration of the FGF21-adiponectin axis. In adipocytes, both transcription and secretion of adiponectin are strongly induced by FGF21, which is partially dependent on PPARγ activity. Furthermore, the glucose-lowering, lipid-clearing, and anti-atherosclerotic functions of FGF21 are diminished in adiponectin-null mice, suggesting that adiponectin serves as an obligatory mediator of FGF21-elicited metabolic and vascular benefits. However, in both animals and human subjects with obesity, circulating FGF21 levels are increased whereas plasma adiponectin concentrations are reduced, perhaps due to FGF21 resistance, suggesting that dysfunctional FGF21-adiponectin axis is an important contributor to the pathogenesis of obesity-related cardio-metabolic syndrome. The FGF21-adiponectin axis protects against a cluster of cardio-metabolic disorders via mediating multi-organ communications, and is a promising target for therapeutic interventions of these chronic diseases.

Proteomic study of periovarian adipose tissue in 17β-estradiol-treated and untreated ovariectomized rats

Taking into account the sexual dimorphism previously found in white adipose tissue (WAT) regarding mitochondrial function and biogenesis, as well as insulin sensitivity, the aim of this study was to go further into the role of sex hormones in this dimorphism. To achieve this objective, we used ovariectomized rats and performed a screening by means of proteomic analyses of the periovarian WAT, combined with a study of the protein levels of specific factors involved in mitochondrial function. Rats were ovariectomized at 5 weeks of age and subcutaneously injected every 48 h with corn-oil (OVX group) or with 17β-estradiol (E2, 10 μg/kg body mass; OVX + E2 group) for 4 weeks prior to sacrifice. Beside proteomic analysis, protein levels of Transcription Factor A, Mitochondrial (TFAM), cytochrome oxidase (COX)II, and COXIV were determined by Western blot, and mRNA levels of peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, ERα, ERβ, lipoprotein lipase (LPL), peroxisome proliferator-activated receptor-γ (PPARγ), and adiponectin were quantified by real-time PCR. Our results show that ovariectomy leads to an increase in anabolic processes and inflammatory protein levels as well as to a decrease in some of the markers of mitochondrial function, which are restored, at least in part, by E2 supplementation. Indeed, this E2 supplementation seems to be counteracted by a decline in ERα and in the ERα to ERβ ratio values that could be directed to avoid an over-stimulation of the E2 signaling pathway, given the possibility of an activation of extra-gonadal steroid biosynthetic pathways.

AMPK/Mitochondria in Metabolic Diseases

The obtaining of nutrients is the most important task in our lives. Energy is central to life's evolutions; this was one of the aspect that induced the selection of the more adaptable and more energetically profitable species. Nowadays things have changed in our modern society. A high proportion of people has access to plenty amount of food and the obesity appear as one of the pathological characteristics of our society. Energy is obtained essentially in the mitochondria with the transfer of protons across the inner membrane that produce ATP. The exactly regulation of the synthesis and degradation of ATP (ATP ↔ ADP + phosphate) is essential to all form of life. This task is performed by the 5' adenosine monophosphate-activated protein kinase (AMPK). mtDNA is highly exposed to oxidative damage and could play a central role in human health and disease. This high potential rate of abnormalities is controlled by one of the most complex mechanism: the autophagy. AMPK appears to be the key cellular energy sensor involved in multiple cellular mechanisms and is essential to have a good metabolic homeostasis to face all the aggression and start the inflammatory reaction. Therefore its disturbances have been related with multiple diseases. Recent findings support the role of AMPK in inflammation and immunity such as Metabolic Syndrome, Obesity and Diabetes. All these Metabolic Disorders are considered pandemics and they need an adequate control and prevention. One important way to achieve it is deepen in the pathogenic mechanisms. Mitochondria and AMPK are the key elements through which it happen, their knowledge and research allow us to a better management. The discovery and use of drugs that can modulate them is imperative to improve our way of manage the metabolic disorders.

Serum Adiponectin Level as a Predictor of Subclinical Cushing's Syndrome in Patients with Adrenal Incidentaloma

Subclinical Cushing's syndrome (SCS) is a condition of slight but chronic cortisol excess in patients with adrenal incidentaloma (AI) without typical signs and symptoms of Cushing's syndrome. Adiponectin has potent roles in modulating energy balance and metabolic homeostasis and acts in opposition to glucocorticoids. This study aimed to evaluate adiponectin level in SCS and nonfunctional AI (NAI) patients and its relation with metabolic parameters. Patients with AI (n = 40) and metabolically healthy controls (n = 30) were included. In AI patients and controls, detailed medical history assessment, physical examinations, anthropometric measurements, and laboratory measurements were performed. Age, body mass index, waist circumference, and lipid profiles were significantly higher and waist-to-hip ratio and adiponectin level were significantly lower in the AI patients than in the controls. The midnight cortisol and urinary free cortisol levels were significantly higher in the SCS patients (n = 8) than in the NAI patients (n = 32). Adiponectin level of the SCS group was significantly lower than those of the NAI and control groups. The sensitivity and specificity for an adiponectin level of ≤13.00 ng/mL in predicting the presence of SCS were 87.5% and 77.4%, respectively. In conclusion, adiponectin is valuable in predicting the presence of SCS in AI patients.

Dietary regulation of adiponectin by direct and indirect lipid activators of nuclear hormone receptors

Adiponectin is an adipokine mainly secreted by adipocytes that presents antidiabetic, anti-inflammatory, and antiatherogenic functions. Therefore, modulation of adiponectin expression represents a promising target for prevention or treatment of several diseases including insulin resistance and type II diabetes. Pharmacological agents such as the nuclear hormone receptor synthetic agonists like peroxisome proliferator activated receptor γ agonists are of particular interest in therapeutic strategies due to their ability to increase the plasma adiponectin concentration. Nutritional approaches are also of particular interest, especially in primary prevention, since some active compounds of our diet (notably vitamins, carotenoids, or other essential nutrients) are direct or indirect lipid-activators of nuclear hormone receptors and are modifiers of adiponectin expression and secretion. The aim of the present review is to summarize current knowledge about the nutritional regulation of adiponectin by derivatives of active compounds naturally present in the diet acting as indirect or direct activators of nuclear hormone receptors.

N-Acetylneuraminic acid attenuates hypercoagulation on high fat diet-induced hyperlipidemic rats

Background and objective

N-Acetylneuraminic acid (Neu5Ac), a type of sialic acid, has close links with cholesterol metabolism and is often used as a biomarker in evaluating the risk of cardiovascular diseases. However, most studies on the health implications of Neu5Ac have focused on its effects on the nervous system, while its effects on cardiovascular risk factors have largely been unreported. Thus, the effects of Neu5Ac on coagulation status in high fat diet (HFD)-induced hyperlipidemic rats were evaluated in this study.

Methods

Sprague Dawley male rats were divided into five different groups and fed with HFD alone, HFD low-dose Neu5Ac, HFD high-dose Neu5Ac, HFD simvastatin (10 mg/kg day), and normal pellet alone. Food was given ad libitum while body weight of rats was measured weekly. After 12 weeks of intervention, rats were sacrificed and serum and tissue samples were collected for biochemistry and gene expression analysis, respectively.

Results

The results showed that Neu5Ac could improve lipid metabolism and hyperlipidemia-associated coagulation. Neu5Ac exerted comparable or sometimes better physiological effects than simvastatin, at biochemical and gene expression levels.

Conclusions

The data indicated that Neu5Ac prevented HFD-induced hyperlipidemia and associated hypercoagulation in rats through regulation of lipid-related and coagulation-related genes and, by extension, induced metabolite and protein changes. The implications of the present findings are that Neu5Ac may be used to prevent coagulation-related cardiovascular events in hyperlipidemic conditions. These findings are worth studying further.

Immunoproteasome subunit LMP7 Deficiency Improves Obesity and Metabolic Disorders

Inflammation plays an important role in the development of obesity and metabolic disorders; however, it has not been fully understood how inflammation occurs and is regulated in their pathogenesis. Low-molecular mass protein-7 (LMP7) is a proteolytic subunit of the immunoproteasome that shapes the repertoire of antigenic peptides on major histocompatibility complex class I molecule. In this study, we investigated the role of LMP7 in the development of obesity and metabolic disorders using LMP7-deficient mice. LMP7 deficiency conveyed resistant to obesity, and improved glucose intolerance and insulin sensitivity in mice fed with high-fat diet (HFD). LMP7 deficiency decreased pancreatic lipase expression, increased fecal lipid contents, and inhibited the increase of plasma triglyceride levels upon oral oil administration or HFD feeding. Using bone marrow-transferred chimeric mice, we found that LMP7 in both bone marrow- and non-bone marrow-derived cells contributes to the development of HFD-induced obesity. LMP7 deficiency decreased inflammatory responses such as macrophage infiltration and chemokine expression while it increased serum adiponection levels. These findings demonstrate a novel role for LMP7 and provide new insights into the mechanisms underlying inflammation in the pathophysiology of obesity and metabolic disorders.

Adiporedoxin, an upstream regulator of ER oxidative folding and protein secretion in adipocytes

Objective

Adipocytes are robust protein secretors, most notably of adipokines, hormone-like polypeptides, which act in an endocrine and paracrine fashion to affect numerous physiological processes such as energy balance and insulin sensitivity. To understand how such proteins are assembled for secretion we describe the function of a novel endoplasmic reticulum oxidoreductase, adiporedoxin (Adrx).

Methods

Adrx knockdown and overexpressing 3T3-L1 murine adipocyte cell lines and a knockout mouse model were used to assess the influence of Adrx on secreted proteins as well as the redox state of ER resident chaperones. The metabolic phenotypes of Adrx null mice were characterized and compared to WT mice. The correlation of Adrx levels BMI, adiponectin levels, and other inflammatory markers from adipose tissue of human subjects was also studied.

Results

Adiporedoxin functions via a CXXC active site, and is upstream of protein disulfide isomerase whose direct function is disulfide bond formation, and ultimately protein secretion. Over and under expression of Adrx in vitro enhances and reduces, respectively, the secretion of the disulfide-bonded proteins including adiponectin and collagen isoforms. On a chow diet, Adrx null mice have normal body weights, and glucose tolerance, are moderately hyperinsulinemic, have reduced levels of circulating adiponectin and are virtually free of adipocyte fibrosis resulting in a complex phenotype tending towards insulin resistance. Adrx protein levels in human adipose tissue correlate positively with adiponectin levels and negatively with the inflammatory marker phospho-Jun kinase.

Conclusion

These data support the notion that Adrx plays a critical role in adipocyte biology and in the regulation of mouse and human metabolism via its modulation of adipocyte protein secretion.

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Adrx is an adipocyte specific, endoplasmic reticulum oxidoreductase upstream of disulfide bond formation.

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Adrx over and under expression in vitro results enhanced and decreased protein secretion, respectively.

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Mice lacking Adrx have lower levels of circulating adiponectin and decreased fibrosis.

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Adrx is expressed in human adipocytes and down regulated in proportion to the level of inflammation.

Differential effects of leptin on adiponectin expression with weight gain versus obesity

Background/Objective

Adiponectin exerts beneficial effects by reducing inflammation, and improving lipid metabolism and insulin-sensitivity. Although adiponectin is lower in obese individuals, whether weight gain reduces adiponectin expression in humans is controversial. We sought to investigate the role of weight gain, and consequent changes in leptin, on altering adiponectin expression in humans.

Methods/Results

Forty four normal-weight healthy subjects were recruited (mean age 29 years; 14 women) and randomized to either gain 5% of body weight by 8-weeks of overfeeding (n=34) or maintain weight (n=10). Modest weight gain of 3.8 ± 1.2 kg resulted in increased adiponectin (p=0.03) while weight maintenance resulted in no changes in adiponectin. Further, changes in adiponectin correlated positively with changes in leptin (p=0.0085). In-vitro experiments using differentiated human white preadipocytes showed that leptin increased adiponectin mRNA and protein expression, while a leptin-antagonist had opposite effects. To understand the role of leptin in established obesity, we compared adipose tissue samples obtained from normal weight versus obese subjects. We noted, first, that leptin activated cellular signaling pathways and increased adiponectin mRNA in adipose tissue from normal-weight participants, but did not do so in adipose tissue from obese participants; and second, that obese subjects had increased caveolin-1 expression, which attenuates leptin-dependent increases in adiponectin.

Conclusions

Modest weight gain in healthy individuals is associated with increases in adiponectin, which correlate positively with changes in leptin. In-vitro, leptin induces adiponectin expression which is attenuated by increased caveolin-1 expression. Additionally, adipose tissue from obese subjects shows increased caveolin-1 expression, and impaired leptin signaling. This leptin signal impairment may prevent concordant increases in adiponectin in obese subjects despite their high levels of leptin. Therefore, impaired leptin signaling may contribute to low adiponectin expression in obesity and may provide a target for increasing adiponectin expression, hence improving insulin sensitivity and cardio-metabolic profile in obesity.

Delivery of Adipose-Derived Stem Cells Attenuates Adipose Tissue Inflammation and Insulin Resistance in Obese Mice Through Remodeling Macrophage Phenotypes

Adipose-derived stem cells (ADSCs) have been used to control several autoimmune or inflammatory diseases due to immunosuppressive properties, but their role in obesity-associated inflammation remains unestablished. This study aims to evaluate the effects of ADSCs on obesity-induced white adipose tissue (WAT) inflammation and insulin resistance. We found that diet-induced obesity caused a remarkable reduction of ADSC fraction in mouse WAT. Delivery of lean mouse-derived ADSCs, which could successfully locate into WAT of obese mice, substantially improved insulin action and metabolic homeostasis of obese mice. ADSC treatment not only reduced adipocyte hypertrophy but also attenuated WAT inflammation by reducing crown-like structures of macrophages and tumor necrosis factor (TNF)-α secretion. Importantly, ADSC treatment remodeled the phenotypes of adipose-resident macrophages from proinflammatory M1 toward anti-inflammatory M2-like subtypes, as characterized by decreased MHC class II-expressing but increased interleukin (IL)-10-producing macrophages together with low expression of TNF-α and IL-12. Coculture of ADSCs through the transwell or conditional medium with induced M1 macrophages also reproduced the phenotypic switch toward M2-like macrophages, which was substantiated by elevated arginase 1, declined inducible nitric oxide synthase, inhibition of NF-κB activity, and activation of STAT3/STAT6. Taken together, our data support that ADSC supplement in obese mice could sustain IL-10-producing M2-like macrophages in WAT through paracrine action, thereby suggesting the crucial role of ADSCs in resolving WAT inflammation, maintaining adipose homeostasis, and proposing a potential ADSC-based approach for the treatment of obesity-related diseases.

Gene expression levels of Casein kinase 1 (CK1) isoforms are correlated to adiponectin levels in adipose tissue of morbid obese patients and site-specific phosphorylation mediated by CK1 influences multimerization of adiponectin

White adipose tissue has now been recognized as an important endocrine organ secreting bioactive molecules termed adipocytokines. In obesity, anti-inflammatory adipocytokines like adiponectin are decreased while pro-inflammatory factors are over-produced. These changes contribute to the development of insulin resistance and obesity-associated diseases. Since members of the casein kinase 1 (CK1) family are involved in the regulation of various signaling pathways we ask here whether they are able to modulate the functions of adiponectin. We show that CK1δ and ε are expressed in adipose tissue and that the expression of CK1 isoforms correlates with that of adiponectin. Furthermore, adiponectin co-immunoprecipitates with CK1δ and CK1ε and is phosphorylated by CK1δ at serine 174 and threonine 235, thereby influencing the formation of adiponectin oligomeric complexes. Furthermore, inhibition of CK1δ in human adipocytes by IC261 leads to an increase in basal and insulin-stimulated glucose uptake. In summary, our data indicate that site-specific phosphorylation of adiponectin, especially at sites targeted by CK1δ in vitro, provides an additional regulatory mechanism for modulating adiponectin complex formation and function.

Dietary ω-3 polyunsaturated fatty acids decrease retinal neovascularization by adipose-endoplasmic reticulum stress reduction to increase adiponectin

BACKGROUND

Retinopathy of prematurity (ROP) is a vision-threatening disease in premature infants. Serum adiponectin (APN) concentrations positively correlate with postnatal growth and gestational age, important risk factors for ROP development. Dietary ω-3 (n-3) long-chain polyunsaturated fatty acids (ω-3 LCPUFAs) suppress ROP and oxygen-induced retinopathy (OIR) in a mouse model of human ROP, but the mechanism is not fully understood.

OBJECTIVE

We examined the role of APN in ROP development and whether circulating APN concentrations are increased by dietary ω-3 LCPUFAs to mediate the protective effect in ROP.

DESIGN

Serum APN concentrations were correlated with ROP development and serum ω-3 LCPUFA concentrations in preterm infants. Mouse OIR was then used to determine whether ω-3 LCPUFA supplementation increases serum APN concentrations, which then suppress retinopathy.

RESULTS

We found that in preterm infants, low serum APN concentrations positively correlate with ROP, and serum APN concentrations positively correlate with serum ω-3 LCPUFA concentrations. In mouse OIR, serum total APN and bioactive high-molecular-weight APN concentrations are increased by ω-3 LCPUFA feed. White adipose tissue, where APN is produced and assembled in the endoplasmic reticulum, is the major source of serum APN. In mouse OIR, adipose endoplasmic reticulum stress is increased, and APN production is suppressed. ω-3 LCPUFA feed in mice increases APN production by reducing adipose endoplasmic reticulum stress markers. Dietary ω-3 LCPUFA suppression of neovascularization is reduced from 70% to 10% with APN deficiency. APN receptors localize in the retina, particularly to pathologic neovessels.

CONCLUSION

Our findings suggest that increasing APN by ω-3 LCPUFA supplementation in total parental nutrition for preterm infants may suppress ROP.

A comprehensive review of metabolic syndrome affecting erectile dysfunction

INTRODUCTION

Metabolic syndrome (MetS) is the most important public health issue threatening the health of men and women all over the world. Its current prevalence (i.e., approximately 30%) is continuously increasing. MetS by itself is considered a risk factor for erectile dysfunction (ED).

AIM

To focus on the definition epidemiology, pathogenesis, and possible mechanistic links between MetS and ED in order to provide guidelines for treating such individuals.

METHODS

The search strategies yielded total records screened from PubMed.

MAIN OUTCOME MEASURES

Regardless of the definition, MetS consists of insulin resistance, hypertension, dyslipidemia, and obesity. MetS is not an end disease but is a disorder of energy utilization and storage.

RESULTS

The prevalence of ED in patients with MetS is almost twice than in those without MetS, and about 40% of patients with ED have MetS. An important mechanism linking MetS and ED is hypogonadism.

CONCLUSIONS

Recognizing through ED, underlying conditions such as hypogonadism, diabetes and MetS might be a useful motivation for men to improve their health-related choices. The clinical management of MetS can be done by therapeutic interventions that include lifestyle modifications, hormone replacement alone or in combination with phosphodiesterase 5 inhibitors, and other pharmacological treatments.

Lycopene-rich tomato oleoresin modulates plasma adiponectin concentration and mRNA levels of adiponectin, SIRT1, and FoxO1 in adipose tissue of obese rats

Aim:

To investigate whether lycopene can modulate adiponectin levels and SIRT1 and FoxO1 gene expression in the adipose tissue of diet-induced obese rats.

Methods:

Male Wistar rats were first fed with hypercaloric diet (HD, n = 12) for 6 weeks, and afterward, these rats were randomly assigned to receive HD ( n = 6) or HD with lycopene-rich tomato oleoresin (equivalent to lycopene 10 mg/kg body weight (BW)/day, HD + L, n = 6) by gavage for additional 6 weeks. Plasma lycopene and adiponectin levels were analyzed by high-performance liquid chromatography and immunoassay, respectively. The messenger RNA (mRNA) expressions of adiponectin, Sirtuin 1 (SIRT1), Forkhead box O 1 (FoxO1), fatty acid translocase/cluster of differentiation 36 (FAT/CD36), and PPARγ in adipose tissues were determined by quantitative polymerase chain reaction.

Results:

Lycopene was detected in the plasma of rats in HD + L group but not in the HD group. Although both BW and adiposity were not different between the two groups, there was a significant increase in both plasma concentration and mRNA expression of adiponectin in the adipose tissue of the HD + L group. In addition, the lycopene supplementation upregulated mRNA expressions of SIRT1, FoxO1, and FAT/CD36 but downregulated PPARγ in adipose tissue of obese rats.

Conclusion:

These data suggest that lycopene, in the concentration used, is not toxic and also its health benefits in adipose tissue may play a role against obesity-related complications.

Obesity and coronary microvascular disease - implications for adipose tissue-mediated remote inflammatory response

It is believed that obesity has detrimental effects on the coronary circulation. These include immediate changes in coronary arterial vasomotor responsiveness and the development of occlusive large coronary artery disease. Despite its critical role in regulating myocardial perfusion, the altered behavior of coronary resistance arteries, which gives rise to coronary microvascular disease (CMD) is poorly understood in obesity. A chronic, low-grade vascular inflammation has been long considered as one of the main underlying pathology behind CMD. The expanded adipose tissue and the infiltrating macrophages are the major sources of pro-inflammatory mediators that have been implicated in causing inadequate myocardial perfusion and, in a long term, development of heart failure in obese patients. Much less is known the mechanisms regulating the release of these cytokines into the circulation that enable them to exert their remote effects in the coronary microcirculation. This mini review aims to examine recent studies describing alterations in the vasomotor function of coronary resistance arteries and the role of adipose tissue-derived pro-inflammatory cytokines and adipokines in contributing to CMD in obesity. We provide examples of regulatory mechanisms by which adipokines are released from adipose tissue to exert their remote inflammatory effects on coronary microvessels. We identify some of the important challenges and opportunities going forward.

Essential roles of insulin, AMPK signaling and lysyl and prolyl hydroxylases in the biosynthesis and multimerization of adiponectin

Post-translational modifications (PTMs) of the adiponectin molecule are essential for its full bioactivity, and defects in PTMs leading to its defective production and multimerization have been linked to the mechanisms of insulin resistance, obesity, and type-2 diabetes. Here we observed that, in differentiated 3T3-L1 adipocytes, decreased insulin signaling caused by blocking of insulin receptors (InsR) with an anti-InsR blocking antibody, increased rates of adiponectin secretion, whereas concomitant elevations in insulin levels counteracted this effect. Adenosine monophosphate-activated protein kinase (AMPK) signaling regulated adiponectin production by modulating the expression of adiponectin receptors, the secretion of adiponectin, and eventually the expression of adiponectin itself. We found that lysyl hydroxylases (LHs) and prolyl hydroxylases (PHs) were expressed in white-adipose tissue of ob/ob mice, wherein LH3 levels were increased compared with controls. In differentiated 3T3-L1 adipocytes, both non-specific inhibition of LHs and PHs by dipyridyl, and specific inhibition of LHs by minoxidil and of P4H with ethyl-3,4-dihydroxybenzoate, caused significant suppression of adiponectin production, more particularly of the higher-order isoforms. Transient gene knock-down of LH3 (Plod3) caused a suppressive effect, especially on the high molecular-weight (HMW) isoforms. These data indicate that PHs and LHs are both required for physiological adiponectin production and in particular are essential for the formation/secretion of the HMW isoforms.

Obesity, inflammation, and insulin resistance

White adipose tissue (WAT) is considered an endocrine organ. When present in excess, WAT can influence metabolism via biologically active molecules. Following unregulated production of such molecules, adipose tissue dysfunction results, contributing to complications associated with obesity. Previous studies have implicated pro- and anti-inflammatory substances in the regulation of inflammatory response and in the development of insulin resistance. In obese individuals, pro-inflammatory molecules produced by adipose tissue contribute to the development of insulin resistance and increased risk of cardiovascular disease. On the other hand, the molecules with anti-inflammatory action, that have been associated with the improvement of insulin sensitivity, have your decreased production. Imbalance of these substances contributes significantly to metabolic disorders found in obese individuals. The current review aims to provide updated information regarding the activity of biomolecules produced by WAT.

MicroRNA-378 regulates adiponectin expression in adipose tissue: a new plausible mechanism

Aims

Mechanisms regulating adiponectin expression have not been fully clarified. MicroRNAs (miRNAs), small non-coding RNAs that regulate gene expression, are involved in biological processes, including obesity and insulin resistance. We evaluated whether the miRNA-378 pathway is involved in regulating adiponectin expression.

Methods and Results

First, we determined a putative target site for miRNA-378 in the 3 prime untranslated region (3'UTR) of the adiponectin gene by in silico analysis. The levels of adiponectin mRNA and protein were decreased in 3T3-L1 cells overexpressing the mimic of miRNA-378. Luminescence activity in HEK293T cells expressing a renilla-luciferase-adiponectin-3'UTR sequence was inhibited by overexpressing the mimic of miRNA-378, and the decrease was reversed by adding the inhibitor of miRNA-378. Moreover, we confirmed the inhibitory effects of the mimic were cancelled in a deleted mutant of the miR-378 3′-UTR binding site. Addition of tumor necrosis factor-α (TNFα) led a upregulation of miR-378 and downregulation of adiponectin at mRNA and protein levels in 3T3-L1 cells. Level of miR-378 was higher and mRNA level of adiponectin was lower in diabetic ob/ob mice than those of normal C57BL/6 mice and levels of miR378 and adiponectin were negatively well correlated (r = −0.624, p = 0.004).

Conclusions

We found that levels of miRNA-378 could modulate adiponectin expression via the 3'UTR sequence-binding site. Our findings warrant further investigations into the role of miRNAs in regulating the adiponectin expression.

Role of adiponectin system in insulin resistance

The knowledge of the pathogenesis of obesity and its metabolic sequelae has significantly advanced over the last few decades and adipose tissue is now considered a link between obesity and insulin resistance. Adiponectin, one of the major adipocyte-secreted proteins, has attracted scientific interest in recent years and has been extensively studied both in human and animal models. Adiponectin exerts insulin-sensitizing effects through binding to its receptors, leading to activation of AMPK, PPAR-α, and potentially other unknown molecular pathways. In obesity-linked insulin resistance, both adiponectin and adiponectin receptors are downregulated, leading to activation of signaling pathways involved in metabolism regulation. Up-regulation of adiponectin/adiponectin receptors or enhancing adiponectin receptor function may be an interesting therapeutic strategy for obesity-linked insulin resistance. In this review we will focus on the recent research related to the relationship between the adiponectin system and insulin resistance. The potential use of adiponectin or its receptor for therapeutic intervention will be also discussed.