Adiponectin, adiponectin receptors, and epigenetic regulation of adipogenesis

Adiponectin rescues synaptic plasticity in the dentate gyrus of a mouse model of Fragile X Syndrome

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and is the leading known single-gene cause of autism spectrum disorder. Patients with FXS display varied behavioural deficits that include mild to severe cognitive impairments in addition to mood disorders. Currently, there is no cure for this condition; however, there is an emerging focus on therapies that inhibit mechanistic target of rapamycin (mTOR)-dependent protein synthesis owing to the clinical effectiveness of metformin for alleviating some behavioural symptoms in FXS. Adiponectin (APN) is a neurohormone that is released by adipocytes and provides an alternative means to inhibit mTOR activation in the brain. In these studies, we show that Fmr1 knockout mice, like patients with FXS, show reduced levels of circulating APN and that both long-term potentiation (LTP) and long-term depression (LTD) in the dentate gyrus (DG) are impaired. Brief (20 min) incubation of hippocampal slices in APN (50 nM) was able to rescue both LTP and LTD in the DG and increased both the surface expression and phosphorylation of GluA1 receptors. These results provide evidence for reduced APN levels in FXS playing a role in decreasing bidirectional synaptic plasticity and show that therapies which enhance APN levels may have therapeutic potential for this and related conditions.This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

Bacoside-A repressed the differentiation and lipid accumulation of 3T3-L1 preadipocytes by modulating the expression of adipogenic genes

Obesity is one of the more complicated diseases, it can induce numerous life-threatening diseases mainly diabetes mellitus, cardiovascular disease, hypertension, and certain cancers. In this study, we assessed the efficacy of bacoside-A (a dammarane-type triterpenoid saponin derived from the plant Bacopa monniera Linn.) on the adipogenesis of 3T3-L1 preadipocytes. Results of this study illustrated that bacoside-A decreased the differentiation of 3T3-L1 cell, as evidenced by diminution of lipid droplets, which contains triglycerides and other lipids. During the differentiation process, transcription factors, which are mainly participating in adipogenesis such us CCAAT/enhancer-binding protein α (C/EBPα) and C/EBPβ, peroxisome proliferator-activated receptor-γ (PPARγ), and sterol regulatory element-binding protein-1c (SREBP-1c), expressions were significantly suppressed by bacoside-A. In addition, bacoside-A showed a potent reduction in genes precise to adipocytes such as lipoprotein lipase (LPL), fatty acid synthase (FAS), adipocyte fatty acid-binding protein (FABP4), and leptin expressions. Further, bacoside-A stimulated the phosphorylation of acetyl CoA carboxylase (ACC) and AMP-activated protein kinase (AMPK). These results demonstrated that bacoside-A has anti-adipogenic effects by regulating the transcription factors involved in adipocyte differentiation. Therefore, bacoside-A might be considered as a potent therapeutic agent for alleviating obesity and hyperlipidemia.

Major Depressive Disorder and Gut Microbiota: Role of Physical Exercise

Major depressive disorder (MDD) has a high prevalence and is a major contributor to the global burden of disease. This psychiatric disorder results from a complex interaction between environmental and genetic factors. In recent years, the role of the gut microbiota in brain health has received particular attention, and compelling evidence has shown that patients suffering from depression have gut dysbiosis. Several studies have reported that gut dysbiosis-induced inflammation may cause and/or contribute to the development of depression through dysregulation of the gut-brain axis. Indeed, as a consequence of gut dysbiosis, neuroinflammatory alterations caused by microglial activation together with impairments in neuroplasticity may contribute to the development of depressive symptoms. The modulation of the gut microbiota has been recognized as a potential therapeutic strategy for the management of MMD. In this regard, physical exercise has been shown to positively change microbiota composition and diversity, and this can underlie, at least in part, its antidepressant effects. Given this, the present review will explore the relationship between physical exercise, gut microbiota and depression, with an emphasis on the potential of physical exercise as a non-invasive strategy for modulating the gut microbiota and, through this, regulating the gut-brain axis and alleviating MDD-related symptoms.

Adiponectin Modulates Smooth Muscle Cell Morpho-Functional Properties in Murine Gastric Fundus via Sphingosine Kinase 2 Activation

Adipokines are peptide hormones produced by the adipose tissue involved in several biological functions. Among adipokines, adiponectin (ADPN) has antidiabetic and anti-inflammatory properties. It can also modulate food intake at central and peripheral levels, acting on hypothalamus and facilitating gastric relaxation. ADPN exerts its action interacting with two distinct membrane receptors and triggering some well-defined signaling cascades. The ceramidase activity of ADPN receptor has been reported in many tissues: it converts ceramide into sphingosine. In turn, sphingosine kinase (SK) phosphorylates it into sphingosine-1 phosphate (S1P), a crucial mediator of many cellular processes including contractility. Using a multidisciplinary approach that combined biochemical, electrophysiological and morphological investigations, we explored for the first time the possible role of S1P metabolism in mediating ADPN effects on the murine gastric fundus muscle layer. By using a specific pharmacological inhibitor of SK2, we showed that ADPN affects smooth muscle cell membrane properties and contractile machinery via SK2 activation in gastric fundus, adding a piece of knowledge to the action mechanisms of this hormone. These findings help to identify ADPN and its receptors as new therapeutic targets or as possible prognostic markers for diseases with altered energy balance and for pathologies with fat mass content alterations.

Weizmannia coagulans BC2000 Plus Ellagic Acid Inhibits High-Fat-Induced Insulin Resistance by Remodeling the Gut Microbiota and Activating the Hepatic Autophagy Pathway in Mice

(1) Background: Ellagic acid (EA) acts as a product of gut microbiota transformation to prevent insulin resistance, which is limited by high-fat diet (HFD)-induced dysbiosis. The aim of this study was to investigate the synergistic effects and mechanisms of supplementation with the probiotic Weizmannia coagulans (W. coagulans) on the prevention of insulin resistance by EA; (2) Methods: C57BL/6J mice were divided into five groups (n = 10/group): low-fat-diet group, high-fat-diet group, EA intervention group, EA + W. coagulans BC77 group, and EA + W. coagulans BC2000 group; (3) Result: W. coagulans BC2000 showed a synergistic effect on EA's lowering insulin resistance index and inhibiting high-fat diet-induced endotoxemia. The combined effect of BC2000 and EA activated the autophagy pathway in the mouse liver, a urolithin-like effect. This was associated with altered β-diversity of gut microbiota and increased Eggerthellaceae, a potential EA-converting family. Ellagic acid treatment alone and the combined use of ellagic acid and W. coagulans BC77 failed to activate the hepatic autophagy pathway; (4) Conclusions: W. coagulans BC2000 can assist EA in its role of preventing insulin resistance. This study provides a basis for the development of EA-rich functional food supplemented with W. coagulans BC2000.

Role of Adiponectin Peptide I (APNp1) in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disease that can cause central vision loss, particularly in the elderly population. There are 2 classes of AMD, wet-type and dry-type. Wet-type involves excess angiogenesis around the macula, referred to as choroidal neovascularization (CNV). This can result in leaky vessels, often causing more severe vision loss than dry-type AMD. Adiponectin peptide 1 (APNp1) has been shown to slow the progression of CNV. Here, we used a mouse model and FITC-labeled APNp1 to determine if APNp1 could be delivered effectively as an eye drop. Our experiment revealed that topically applied FITC-APNp1 could reach the macula of the eye, which is crucial for treating wet-type AMD. We also tested delivery of APNp1 via injection of an adeno-associated virus (AAV) vector in a mouse model of CNV. AAV is a harmless virus easy to manipulate and is very often used for protein or peptide deliveries. Results revealed an increase in the expression of APNp1 in the retina and choroid over a 28-day period. Finally, we investigated the mechanism by which APNp1 affects CNV by examining the expression of adiponectin receptor 1 (AdipoR1) and proliferating cell nuclear antigen (PCNA) in the retinal and choroidal tissue of the mouse eyes. AdipoR1 and PCNA were overexpressed in these tissues in mice with laser-induced CNV compared to naïve mice. Based on our data shown here, we think it will enhance our understanding of APNp1 as a therapeutic agent for wet-type AMD and possible treatment alternatives that could be more beneficial for patients.

Cornus mas L. Increases Glucose Uptake and the Expression of PPARG in Insulin-Resistant Adipocytes

Cornus mas L., also known as cornelian cherry (CM), is a species that has long been cultivated in many different countries. In numerous scientific reports, cornelian cherry is used to treat numerous diseases and conditions. The presented study evaluated the effect of red and yellow Cornus mas L. extract on insulin sensitivity in adipocytes. 3T3-L1 fibroblasts as well as human SAT-derived and VAT-derived adipocytes were differentiated in vitro, and insulin resistance was induced using palmitic acid (16:0). The effect of CM fruit extract was analyzed in terms of glucose uptake and insulin signaling gene expression. In the glucose uptake test after insulin stimulation, a significant increase in glucose uptake was demonstrated in cells treated with CM fruit extracts. Furthermore, CM fruit extracts increased the expression of insulin signaling genes in adipocytes stimulated with insulin in control cells and adipocytes treated with CM extract. Additionally, a significant increase in peroxisome proliferator activated receptor gamma (PPARG) expression was observed in cells supplemented with CM extract. In conclusion, studies have shown that CM fruits can overcome insulin resistance and thus they have a positive effect on cell metabolism.

Effects of Nigella sativa supplementation on blood concentration and mRNA expression of TNF-α, PPAR-γ and adiponectin, as major adipogenesis-related markers, in obese and overweight women: a crossover, randomised-controlled trial

Adipocyte expansion through adipogenesis can offset the adverse metabolic effects of obesity. Nigella sativa (NS) (black seed) oil is shown to have therapeutic features in the management of obesity. NS oil might have beneficial changes in obese populations through mediating serum levels of adipogenesis-related parameters and relative transcriptional gene-diet interactions (nutrigenomics), though no previous studies assessed this mechanism in overweight/obese participants. This study assessed the effects of NS oil supplements on blood concentration and mRNA expression levels of TNF-α, PPAR-γ and serum adiponectin and expression of AdipoR1, as major adipogenesis and obesity-related parameters, in overweight/obese women using a cross-over design. Eligible women were randomised to receive either NS oil supplements (2000 mg/d) or placebo. Two periods of interventions (8 weeks in each) were cross-changed by a 4-week washout period. An individualised diet plan without calorie deficits was given to participants to match their energy/macronutrient intakes. The Pkcross procedure and intention-to-treat analysis were performed using Stata. Cohen's d(d) was estimated to measure the magnitude of the effects. Forty-six participants were included. NS oil capsules reduced transcription levels ((d = -2·31), P < 0·001) and blood concentrations of TNF-α ((d = -0·29), P < 0·001). AdipoR1 expression (d = 2·24, P < 0·001) and serum adiponectin (d = 0·88, P < 0·001) showed a significant augmentation with a medium-high effect size, as did gene expression (d = 0·69, P < 0·001) and serum levels of PPAR-γ (d = 0·97, P < 0·001). There was a moderate but significant decrease in body weight (d = 0·6, P < 0·001). The present beneficial findings would provide strong information for future nutrigenomics/clinical trial studies assessing the role of NS in the management of obesity and other comorbidities.

An adiponectin receptor agonist promote osteogenesis via regulating bone-fat balance

OBJECTIVES

Adiponectin signalling has been considered to be a promising target to treat diabetes-related osteoporosis. However, contradictory results regarding bone formation were observed due to the various isoforms of adiponectin. Therefore, it would be necessary to investigate the effect of adiponectin receptor signals in regulating bone-fat balance.

MATERIALS AND METHODS

We primarily applied a newly found specific activator for adiponectin receptor, AdipoRon, to treat bone metabolism-related cells to investigate the role of Adiponectin receptor signals on bone-fat balance. We then established femur defect mouse model and treated them with AdipoRon to see whether adiponectin receptor activation could promote bone regeneration.

RESULTS

We found that AdipoRon could slightly inhibit the proliferation of pre-osteoblast and pre-osteoclast, but AdipoRon showed no effect on the viability of mesenchymal stromal cells. AdipoRon could remarkably promote cell migration of mesenchymal stromal cells. Additionally, AdipoRon promoted osteogenesis in both pre-osteoblasts and mesenchymal cells. Besides, AdipoRon significantly inhibited osteoclastogenesis via its direct impact on pre-osteoclast and its indirect inhibition of RANKL in osteoblast. Moreover, mesenchymal stromal stems cells showed obviously decreased adipogenesis when treated with AdipoRon. Consistently, AdipoRon-treated mice showed faster bone regeneration and repressed adipogenesis.

CONCLUSIONS

Our study demonstrated a pro-osteogenic, anti-adipogenic and anti-osteoclastogenic effect of adiponectin receptor activation in young mice, which suggested adiponectin receptor signalling was involved in bone regeneration and bone-fat balance regulation.

Adiponectin enhances the bioenergetics of cardiac myocytes via an AMPK- and succinate dehydrogenase-dependent mechanism

Adiponectin is one of the most abundant circulating hormones, which through adenosine monophosphate-activated protein kinase (AMPK), enhances fatty acid and glucose oxidation, and exerts a cardioprotective effect. However, its effects on cellular bioenergetics have not been explored. We have previously reported that 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR, an AMPK activator) enhances mitochondrial respiration through a succinate dehydrogenase (SDH or complex II)-dependent mechanism in cardiac myocytes, leading us to predict that Adiponectin would exert a similar effect via activating AMPK. Our results show that Adiponectin enhances basal mitochondrial oxygen consumption rate (OCR), ATP production, and spare respiratory capacity (SRC), which were all abolished by the knockdown of AMPKγ1, inhibition of SDH complex assembly, via the knockdown of the SDH assembly factor 1 (Sdhaf1), or inhibition of SDH activity. Additionally, Adiponectin alleviated hypoxia-induced reductions in OCR and ATP production, in a Sdhaf1-dependent manner, whereas overexpression of Sdhaf1 confirmed its sufficiency for mediating these effects. Importantly, the levels of holoenzyme SDH under the various conditions correlated with OCR. We also show that the effects of Adiponectin, AMPK, Sdhaf1, as well as, SDH complex assembly all required sirtuin 3 (Sirt3). In conclusion, Adiponectin potentiates mitochondrial bioenergetics via promoting SDH complex assembly in an AMPK-, Sdhaf1-, and Sirt3-dependent fashion in cardiac myocytes.

Enhancement of Hippocampal Plasticity by Physical Exercise as a Polypill for Stress and Depression: A Review

Generation of newborn neurons that form functional synaptic connections in the dentate gyrus of adult mammals, known as adult hippocampal neurogenesis, has been suggested to play critical roles in regulating mood, as well as certain forms of hippocampus-dependent learning and memory. Environmental stress suppresses structural plasticity including adult neurogenesis and dendritic remodeling in the hippocampus, whereas physical exercise exerts opposite effects. Here, we review recent discoveries on the potential mechanisms concerning how physical exercise mitigates the stressrelated depressive disorders, with a focus on the perspective of modulation on hippocampal neurogenesis, dendritic remodeling and synaptic plasticity. Unmasking such mechanisms may help devise new drugs in the future for treating neuropsychiatric disorders involving impaired neural plasticity.

Modulation of adiponectin receptors AdipoR1 and AdipoR2 by phage display-derived peptides in in vitro and in vivo models

Type 2 diabetes (T2D) is often linked to metabolic syndrome, which assembles various risk factors related to obesity. Plasma levels of adiponectin are decreased in T2D and obese subjects. Aiming to develop a peptide able to bind adiponectin receptors and modulate their signalling pathways, a 12-amino acid sequence homologous in AdipoR1/R2 has been targeted by phage display with a linear 12-mer peptide library. The selected peptide P17 recognises AdipoR1/R2 expressed by skeletal muscle, liver and pancreatic islets. In HepaRG and C2C12 cells, P17 induced the activation of AMPK (AMPKα-pT172) and the expression of succinate dehydrogenase and glucokinase; no cytotoxic effects were observed on HepaRG cells. In db/db mice, P17 promoted body weight and glycaemia stabilisation, decreased plasma triglycerides to the range of healthy mice and increased adiponectin (in high fat-fed mice) and insulin (in chow-fed mice) levels. It restored to the range of healthy mice the tissue levels and subcellular distribution of AdipoR1/R2, AMPKα-pT172 and PPARα-pS12. In liver, P17 reduced steatosis and apoptosis. The docking of P17 to AdipoR is reminiscent of the binding mechanism of adiponectin. To conclude, we have developed an AdipoR1/AdipoR2-targeted peptide that modulates adiponectin signalling pathways and has therapeutic relevance for T2D and obesity associated pathologies.

Kojyl Cinnamate Ester Derivatives Increase Adiponectin Expression and Stimulate Adiponectin-Induced Hair Growth Factors in Human Dermal Papilla Cells

Adiponectin (APN), released mainly from adipose tissue, is a well-known homeostatic factor for regulating glucose levels, lipid metabolism, and insulin sensitivity. A recent study showed that human hair follicles express APN receptors and the presence of APN-mediated hair growth signaling, thereby suggesting that APN is a potent hair growth-promoting adipokine. Previously, kojyl cinnamate ester derivatives (KCEDs) were synthesized in our institute as new anti-aging or adiponectin-/adipogenesis-inducing compounds. Here, we tested the activity of these derivatives to induce endogenous APN secretion. Among the derivatives, KCED-1 and KCED-2 showed improved activity in inducing APN mRNA expression, secretion of APN protein, and adipogenesis in human subcutaneous fat cells (hSCFs) when compared with the effects of Seletinoid G, a verified APN inducer. When human follicular dermal papilla cells were treated with the culture supernatant of KCED-1- or KCED-2-treated hSCFs, the mRNA expression of APN-induced hair growth factors such as insulin-like growth factor, hepatocyte growth factor, and vascular endothelial growth factor was upregulated compared with that in the control. Taken together, our study shows that among kojyl cinnamate ester derivatives, KCED-1, KCED-2, as well as Seletinoid G are effective inducers of endogenous APN production in subcutaneous fat tissues, which may in turn contribute to the promotion of hair growth in the human scalp.

Dissecting features of epigenetic variants underlying cardiometabolic risk using full-resolution epigenome profiling in regulatory elements

Sparse profiling of CpG methylation in blood by microarrays has identified epigenetic links to common diseases. Here we apply methylC-capture sequencing (MCC-Seq) in a clinical population of ~200 adipose tissue and matched blood samples (N_total~400), providing high-resolution methylation profiling (>1.3 M CpGs) at regulatory elements. We link methylation to cardiometabolic risk through associations to circulating plasma lipid levels and identify lipid-associated CpGs with unique localization patterns in regulatory elements. We show distinct features of tissue-specific versus tissue-independent lipid-linked regulatory regions by contrasting with parallel assessments in ~800 independent adipose tissue and blood samples from the general population. We follow-up on adipose-specific regulatory regions under (1) genetic and (2) epigenetic (environmental) regulation via integrational studies. Overall, the comprehensive sequencing of regulatory element methylomes reveals a rich landscape of functional variants linked genetically as well as epigenetically to plasma lipid traits.

Obesity and related metabolic complications represent an important health burden. Here the authors carry out a methylC-capture sequencing-based epigenome-wide association study to link circulating plasma lipid levels, CpG methylation and cardiometabolic risk across adipose and blood tissues.

Paradoxical effects of the epigenetic modifiers 5-aza-deoxycytidine and suberoylanilide hydroxamic acid on adipogenesis

Adipogenesis is an important biological process that is linked to obesity and metabolic disorders. On the other hand, fat regeneration is crucial as a restorative approach following mastectomy or severe burn injury. Furthermore, optimizing an in-vitro model of adipogenesis, which would help in understanding the possible effects and/or side effects of fat-soluble drugs and anti-obesity remedies, in addition to the developmental studies. Epigenetic is an important factor that is involved in cellular differentiation and commitment. This study aimed at investigating the effect of DNA methylation and histone deactylases inhibitors, 5-Aza-deoxycytidine (5-Aza-dC) and Suberoylanilide hydroxamic acid (SAHA), on the adipogenic differentiation process. The two modifiers were applied according to our previously published protocol, followed by three cycles of a classical, two-step adipogenesis protocol. The cells pretreated with SAHA showed enhanced expression of the many adipogenic genes, including peroxisome proliferator-activated receptor-γ as well as the accumulation of intracytoplasmic fat as shown by oil red and Nile red staining and the secretion of adipokines, such as MCP-1 and IP-10. On contrary, 5-Aza-dC inhibited all these markers. In conclusion, adding the reported step with SAHA to the differentiation protocols could have an impact on the progress of the in-vitro fat regenerative approach. The possible role of 5-Aza-dC in the inhibition of adipogenesis can be of clinical interest and will need further characterization in the future.

The Action of Polyphenols in Diabetes Mellitus and Alzheimer's Disease: A Common Agent for Overlapping Pathologies

Diabetes Mellitus (DM) and Alzheimer's disease (AD) are two prevalent diseases in modern societies, which are caused mainly by current lifestyle, aging and genetic alterations. It has already been demonstrated that these two diseases are associated, since individuals suffering from DM are prone to develop AD. Conversely, it is also known that individuals with AD are more susceptible to DM, namely type 2 diabetes (T2DM). Therefore, these two pathologies, although completely different in terms of symptomatology, end up sharing several mechanisms at the molecular level, with the most obvious being the increase of oxidative stress and inflammation. Polyphenols are natural compounds widely spread in fruits and vegetables whose dietary intake has been considered inversely proportional to the incidence of DM and AD. So, it is believed that this group of phytochemicals may have preventive and therapeutic potential, not only by reducing the risk and delaying the development of these pathologies, but also by improving brain's metabolic profile and cognitive function. The aim of this review is to understand the extent to which DM and AD are related pathologies, the degree of similarity and the relationship between them, to detail the molecular mechanisms by which polyphenols may exert a protective effect, such as antioxidant and anti-inflammatory effects, and highlight possible advantages of their use as common preventive and therapeutic alternatives.

Adipocytokines in Rheumatoid Arthritis: The Hidden Link between Inflammation and Cardiometabolic Comorbidities

Rheumatoid arthritis is a chronic autoimmune disease affecting typically synovial joints and leading to progressive articular damage, disability, and reduced quality of life. Despite better recent therapeutic strategies improving long-term outcomes, RA is associated with a high rate of comorbidities, infections, malignancies, and cardiovascular disease (CVD). Remarkably, some well-known pathogenic proinflammatory mediators in RA, such as interleukin-1β (IL-1β) and tumor necrosis factor (TNF), may play a pivotal role in the development of CVD. Interestingly, different preclinical and clinical studies have suggested that biologic agents commonly used to treat RA patients may be effective in improving CVD. In this context, the contribution of adipocytokines has been suggested. Adipocytokines are pleiotropic molecules, mainly released by white adipose tissue and immune cells. Adipocytokines modulate the function of different tissues and cells, and in addition to energy homeostasis and metabolism, amplify inflammation, immune response, and tissue damage. Adipocytokines may contribute to the proinflammatory state in RA patients and development of bone damage. Furthermore, they could be associated with the occurrence of CVD. In this study, we reviewed available evidence about adipocytokines in RA, because of their involvement in disease activity, associated CVD, and possible biomarkers of prognosis and treatment outcome and because of their potential as a possible new therapeutic target.

Inhibition of Adipocyte Differentiation by Anthocyanins Isolated from the Fruit of Vitis coignetiae Pulliat is Associated with the Activation of AMPK Signaling Pathway

Anthocyanins are naturally occurring water-soluble polyphenolic pigments in plants that have been shown to protect against cardiovascular diseases, and certain cancers, as well as other chronic human disorders. However, the anti-obesity effects of anthocyanins are not fully understood. In this study, we investigated the effects of anthocyanins isolated from the fruit of Vitis coignetiae Pulliat on the adipogenesis of 3T3-L1 preadipocytes. Our data indicated that anthocyanins attenuated the terminal differentiation of 3T3-L1 preadipocytes, as confirmed by a decrease in the number of lipid droplets, lipid content, and triglyceride production. During this process, anthocyanins effectively enhanced the activation of the AMP-activated protein kinase (AMPK); however, this phenomenon was inhibited by the co-treatment of compound C, an inhibitor of AMPK. Anthocyanins also inhibited the expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein a and b, and sterol regulatory element-binding protein-1c. In addition, anthocyanins were found to potently inhibit the expression of adipocyte-specific genes, including adipocyte fatty acid-binding protein, leptin, and fatty acid synthase. These results indicate that anthocyanins have potent anti-obesity effects due to the inhibition of adipocyte differentiation and adipogenesis, and thus may have applications as a potential source for an anti-obesity functional food agent.

Ethanol extracts of Aster yomena (Kitam.) Honda inhibit adipogenesis through the activation of the AMPK signaling pathway in 3T3-L1 preadipocytes

The leaves of Aster yomena (Kitam.) Honda have long been used as a traditional herb for treating disorders including coughs, asthma, and insect bites. According to recent studies, A. yomena leaf extracts have several pharmacological properties, including anti-inflammatory, antioxidant, and anti-asthmatic activities. However, little information is available regarding their anti-obesity effect. In this study, we investigated the inhibitory effect of the ethanol extracts of A. yomena leaves (EEAY) on adipocyte differentiation and adipogenesis using 3T3-L1 preadipocytes. When 3T3-L1 preadipocytes were treated with various concentrations of EEAY (ranging from non-toxic), the number of lipid droplets, lipid content, and triglyceride production, the typical characteristics of adipocytes, were suppressed in a concentration-dependent manner. During this process, EEAY significantly reduced the expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein α and β, and sterol regulatory element-binding protein-1c. In addition, EEAY was also found to potently inhibit the expression of adipocyte-specific genes, including adipocyte fatty acid-binding protein and leptin. In particular, EEAY treatment effectively enhanced the activation of the AMP-activated protein kinase (AMPK) signaling pathway; however, the co-treatment with compound C, an inhibitor of AMPK, significantly restored the EEAY-induced inhibition of pro-adipogenic transcription factors and adipocyte-specific genes. These results indicate that EEAY may exert an anti-obesity effect by controlling the AMPK signaling pathway, suggesting that the leaf extract of A. yomena may be a potential anti-obesity agent.

The Role of Tissue Macrophage-Mediated Inflammation on NAFLD Pathogenesis and Its Clinical Implications

The obese phenotype is characterized by a state of chronic low-grade systemic inflammation that contributes to the development of comorbidities, including nonalcoholic fatty liver disease (NAFLD). In fact, NAFLD is often associated with adipocyte enlargement and consequent macrophage recruitment and inflammation. Macrophage polarization is often associated with the proinflammatory state in adipose tissue. In particular, an increase of M1 macrophages number or of M1/M2 ratio triggers the production and secretion of various proinflammatory signals (i.e., adipocytokines). Next, these inflammatory factors may reach the liver leading to local M1/M2 macrophage polarization and consequent onset of the histological damage characteristic of NAFLD. Thus, the role of macrophage polarization and inflammatory signals appears to be central for pathogenesis and progression of NAFLD, even if the heterogeneity of macrophages and molecular mechanisms that govern their phenotype switch remain incompletely understood. In this review, we discuss the role of adipose and liver tissue macrophage-mediated inflammation in experimental and human NAFLD. This focus is relevant because it may help researchers that approach clinical and experimental studies on this disease advancing the knowledge of mechanisms that could be targeted in order to revert NAFLD-related fibrosis.

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.

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.

Adipose tissue immune response: novel triggers and consequences for chronic inflammatory conditions

Adipose tissue inflammation mediates the association between excessive body fat accumulation and several chronic inflammatory diseases. A high prevalence of obesity-associated adipose tissue inflammation was observed not only in patients with cardiovascular conditions but also in patients with inflammatory bowel diseases, abdominal aortic aneurysm, or cardiorenal syndrome. In addition to excessive caloric intake, other triggers promote visceral adipose tissue inflammation followed by chronic, low-grade systemic inflammation. The infiltration and accumulation of immune cells in the inflamed and hypertrophied adipose tissue promote the production of inflammatory cytokines, contributing to target organ damages. This comorbidity seems to delimit subgroups of individuals with systemic adipose tissue inflammation and more severe chronic inflammatory diseases that are refractory to conventional treatment. This review highlights the association between adipose tissue immune response and the pathophysiology of visceral adiposity-related chronic inflammatory diseases, while suggesting several new therapeutic strategies.

Biochemical alterations during the obese-aging process in female and male monosodium glutamate (MSG)-treated mice

Obesity, from children to the elderly, has increased in the world at an alarming rate over the past three decades, implying long-term detrimental consequences for individual’s health. Obesity and aging are known to be risk factors for metabolic disorder development, insulin resistance and inflammation, but their relationship is not fully understood. Prevention and appropriate therapies for metabolic disorders and physical disabilities in older adults have become a major public health challenge. Hence, the aim of this study was to evaluate inflammation markers, biochemical parameters and glucose homeostasis during the obese-aging process, to understand the relationship between obesity and health span during the lifetime. In order to do this, the monosodium glutamate (MSG) obesity mice model was used, and data were evaluated at 4, 8, 12, 16 and 20 months in both female and male mice. Our results showed that obesity was a major factor contributing to premature alterations in MSG-treated mice metabolism; however, at older ages, obesity effects were attenuated and MSG-mice became more similar to normal mice. At a younger age (four months old), the Lee index, triglycerides, total cholesterol, TNF-α and transaminases levels increased; while adiponectin decreased and glucose tolerance and insulin sensitivity levels were remarkably altered. However, from 16 months old-on, the Lee index and TNF-α levels diminished significantly, while adiponectin increased, and glucose and insulin homeostasis was recovered. In summary, MSG-treated obese mice showed metabolic changes and differential susceptibility by gender throughout life and during the aging process. Understanding metabolic differences between genders during the lifespan will allow the discovery of specific preventive treatment strategies for chronic diseases and functional decline.

Metabolic effects of the HIV protease inhibitor--saquinavir in differentiating human preadipocytes

BACKGROUND

The iatrogenic, HIV-related lipodystrophy is associated with development of the significant metabolic and cardiovascular complications. The underlying mechanisms of antiretroviral (ARV) drugs are not completely explored.

METHODS

The aim of the study was to characterize effects of the protease inhibitor (PI)--saquinavir (SQV) on metabolic functions, and gene expression during differentiation in cells (Chub-S7) culture.

RESULTS

SQV in concentrations observed during antiretroviral therapy (ART) significantly decreased mitochondrial membrane potential (MMP), oxygen consumption and ATP generation. The effects were greater in already differentiated cells. This was accompanied by characteristic changes in the expression of the genes involved in endoplasmic reticulum (ER) stress, and differentiation (lipid droplet formation) process such as: WNT10a, C/EBPa, AFT4, CIDEC, ADIPOQ, LPIN1.

CONCLUSIONS

The results indicate that SQV affects not only metabolic (mitochondrial) activity of adipocytes, but affects the expression of genes related to differentiation and to a lesser extent to cell apoptosis.

Epigenetic effects of natural polyphenols: a focus on SIRT1-mediated mechanisms

Polyphenols are a class of natural compounds widely distributed in fruits, vegetables, and plants. They have been reported to possess a wide range of activities in prevention and alleviation of various diseases like cancer, neuroinflammation, diabetes, and aging. Polyphenols are effective against chronic diseases and recent reports indicated strong epigenetic effects of polyphenols. Most of the studies investigating epigenetic effects of natural polyphenols have focused on their beneficial effects in cancer treatment. However, epigenetic defects have been demonstrated in many other diseases as well, and application of polyphenols to modulate the epigenome is becoming an interesting field of research. This review summarizes the effects of natural polyphenols in modulating epigenetic-related enzymes as well as their effect in prevention and treatment of chronic diseases with a focus on SIRT1 modulation. We have also discussed the relation between the structure and function of epigenetic-modifying polyphenols.

Lower ratio of high-molecular-weight adiponectin level to total may be associated with coronary high-risk plaque

Background

Although high-molecular-weight (HMW) adiponectin is believed to protect against atherosclerosis, the association between HMW adiponectin and the composition of coronary plaques is unknown. We evaluated whether the HMW to total adiponectin ratio was associated with the presence of coronary plaque and its composition using multi-slice computed tomography coronary angiography (MSCTCA).

Methods

Serum total and HMW adiponectin levels were measured in 53 consecutive patients (age, 71) with >50% coronary artery stenosis detected by MSCTCA. A low-attenuation coronary plaque was defined as a plaque with a mean CT density <50 Hounsfield units. Multivariate logistic regression analyses were performed to evaluate the predictors of the presence of low-attenuation coronary plaques, which is thought to be high risk, on CT.

Results

Decreased serum levels of total as well as HMW adiponectin were significantly associated with the presence of at least one calcified or non-calcified coronary artery plaque (total adiponectin level: odds ratio 0.76, 95% CI 0.58–0.99, P = 0.048; HMW adiponectin level: odds ratio 0.65, 95% CI 0.42–0.99, P = 0.047). A low ratio of HMW to total adiponectin was significantly associated with the presence of low-attenuation coronary plaques (4.55, 1.94–21.90, P = 0.049). However, neither the total adiponectin nor the HMW adiponectin level was associated with the presence of low-attenuation coronary plaques.

Conclusion

Lower total or HMW adiponectin levels are associated with the presence of calcified and non-calcified coronary plaques, whereas a lower ratio of HMW to total adiponectin associated with the presence of low-attenuation coronary plaques (thought to be high risk). Measurement of total and HMW adiponectin levels and the HMW to total adiponectin ratio may be useful for risk stratification of coronary artery plaques.

Insulin resistance: metabolic mechanisms and consequences in the heart

Insulin resistance is a characteristic feature of obesity and type 2 diabetes mellitus and impacts the heart in various ways. Impaired insulin-mediated glucose uptake is a uniformly observed characteristic of the heart in these states, although changes in upstream kinase signaling are variable and dependent on the severity and duration of the associated obesity or diabetes mellitus. The understanding of the physiological and pathophysiological role of insulin resistance in the heart is evolving. To maintain its high energy demands, the heart is capable of using many metabolic substrates. Although insulin signaling may directly regulate cardiac metabolism, its main role is likely the regulation of substrate delivery from the periphery to the heart. In addition to promoting glucose uptake, insulin regulates long-chain fatty acid uptake, protein synthesis, and vascular function in the normal cardiovascular system. Recent advances in understanding the role of metabolic, signaling, and inflammatory pathways in obesity have provided opportunities to better understand the pathophysiology of insulin resistance in the heart. This review will summarize our current understanding of metabolic mechanisms for and consequences of insulin resistance in the heart and will discuss potential new areas for investigating novel mechanisms that contribute to insulin resistance in the heart.

Adiponectin: a biomarker for rheumatoid arthritis?

Recent achievements in the biology and the function of adipose tissue have regarded white adipose tissue (WAT) as an important endocrine and secretory organ. Releasing a series of multiple-function mediators, WAT is involved in a wide spectrum of diseases, including not only cardiovascular and metabolic complications, such as atherosclerosis and type 2 diabetes, but also inflammatory- and immune-related disorders, such as rheumatoid arthritis (RA) and osteoarthritis (OA). A large number of these mediators, called adipokines, such as tumor necrosis factor alpha (TNF-α), leptin, adiponectin, resistin, chemerin, interleukin-6 (IL-6), visfatin, and so on have been identified and studied widely. Important advances related to these proteins shed new insights into the pathophysiological mechanisms of many complicated diseases, although details of which remain unclear. Adiponectin, one of the most widely investigated adipokine, has been shown to possess both anti- and pro-inflammatory effects. RA is a chronic systemic inflammatory-related autoimmune disease. Accumulated evidence has demonstrated that cytokines and adipokines play an important role in the pathogenesis of RA. In this review, we have summarized the most recent advances in adiponectin research in the context of RA, focusing primarily on its effect on RA-related cells, its regulation on pro-inflammatory cytokines, as well as its validation as a biomarker for RA.