Anti-adipogenesis by 6-thioinosine is mediated by downregulation of PPAR gamma through JNK-dependent upregulation of iNOS

Neuronostatin regulates proliferation and differentiation of rat brown primary preadipocytes

Neuronostatin suppresses the differentiation of white preadipocytes. However, the role of neuronostatin in brown adipose tissue remains elusive. Therefore, we investigated the impact of neuronostatin on the proliferation and differentiation of isolated rat brown preadipocytes. We report that neuronostatin and its receptor (GPR107) are synthesized in brown preadipocytes and brown adipose tissue. Furthermore, neuronostatin promotes the replication of brown preadipocytes via the AKT pathway. Notably, neuronostatin suppresses the expression of markers associated with brown adipogenesis (PGC-1α, PPARγ, PRDM16, and UCP1) and reduces cellular mitochondria content. Moreover, neuronostatin impedes the differentiation of preadipocytes by activating the JNK signaling pathway. These effects were not mimicked by somatostatin. Our results suggest that neuronostatin is involved in regulating brown adipogenesis.

The Past and Present Lives of the Intraocular Transmembrane Protein CD36

Cluster of differentiation 36 (CD36) belongs to the B2 receptors of the scavenger receptor class B family, which is comprised of single-chain secondary transmembrane glycoproteins. It is present in a variety of cell types, including monocytes, macrophages, microvascular endothelial cells, adipocytes, hepatocytes, platelets, skeletal muscle cells, kidney cells, cardiomyocytes, taste bud cells, and a variety of other cell types. CD36 can be localized on the cell surface, mitochondria, endoplasmic reticulum, and endosomes, playing a role in lipid accumulation, oxidative stress injury, apoptosis, and inflammatory signaling. Recent studies have found that CD36 is expressed in a variety of ocular cells, including retinal pigment epithelium (RPE), retinal microvascular endothelial cells, retinal ganglion cells (RGC), Müller cells, and photoreceptor cells, playing an important role in eye diseases, such as age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma. Therefore, a comprehensive understanding of CD36 function and downstream signaling pathways is of great significance for the prevention and treatment of eye diseases. This article reviews the molecular characteristics, distribution, and function of scavenger receptor CD36 and its role in ophthalmology in order to deepen the understanding of CD36 in eye diseases and provide new ideas for treatment strategies.

New understanding of Angelica sinensis polysaccharide improving fatty liver: The dual inhibition of lipid synthesis and CD36-mediated lipid uptake and the regulation of alcohol metabolism

Angelica sinensis polysaccharide (ASP) has presented increasingly recognized lipid regulation and antioxidant abilities. However, there is little direct evidence to explain why ASP possesses the observed lipid-lowering and anti-oxidation effects. In vivo and in vitro models of alcoholic fatty liver disease (AFLD) were established to examine the direct effect of ASP on hepatic fat accumulation. Our results showed that the lipid-lowering effect of ASP might result from the dual inhibition of lipid synthesis and CD36-mediated lipid uptake. The antioxidation of ASP might be attributed to the reversal of alcohol metabolic pathways from CYP2E1 catalysis to ADH catalysis. Taken together, the study demonstrated the direct role of ASP in lipid metabolism for the first time and revealed the underlying mechanism of reducing ROS, providing an available strategy for ASP as a potential agent to treat AFLD.

Transcription Factor 21 Promotes Chicken Adipocyte Differentiation at Least in Part via Activating MAPK/JNK Signaling

The molecular mechanisms of transcription factor 21 (TCF21) in regulating chicken adipogenesis remain unclear. Thus, the current study was designed to investigate the signaling pathway mediating the effect of TCF21 on chicken adipogenesis. Immortalized chicken preadipocytes cell line (ICP), a preadipocyte cell line stably overexpressing TCF21 (LV-TCF21) and a control preadipocyte cell line (LV-control) were used in the current study. We found that the phosphorylation of c-Jun N-terminal kinases (JNK) was significantly elevated in LV-TCF21 compared to LV-control. After treating ICP cells with a JNK inhibitor SP600125, the differentiation of ICP was inhibited, as evidenced by decreased accumulation of lipid droplets and reduced expression of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), adipocyte fatty acid binding protein (A-FABP), and lipoprotein lipase (LPL). Moreover, we found that the inhibition of JNK by SP600125 remarkably impaired the ability of TCF21 to drive adipogenesis. Taken together, our results suggest that TCF21 promotes the differentiation of adipocytes at least in part via activating MAPK/JNK pathway.

Combined Anti-Adipogenic Effects of Hispidulin and p-Synephrine on 3T3-L1 Adipocytes

Hispidulin is abundant in Arrabidaea chica, Crossostephium chinense, and Grindelia argentina, among others. p-Synephrine is the main phytochemical constituent of Citrus aurantium. It has been used in combination with various other phytochemicals to determine synergistic effects in studies involving human participants. However, there have been no reports comparing the anti-adipogenic effects of the combination of hispidulin and p-synephrine. The current study explores the anti-adipogenic effects of hispidulin alone and in combination with p-synephrine in a murine preadipocyte cell line, 3T3-L1. Co-treatment resulted in a greater inhibition of the formation of red-labeled lipid droplets than the hispidulin or p-synephrine-alone treatments. Co-treatment with hispidulin and p-synephrine also significantly inhibited adipogenic marker proteins, including Akt, mitogen-activated protein kinases, peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein alpha, glucocorticoid receptor, and CCAAT/enhancer-binding protein β. Although further studies are required to assess the effects of each drug on pharmacokinetic parameters, a combination treatment with hispidulin and p-synephrine may be a potential alternative strategy for developing novel anti-obesity drugs.

Combined Beneficial Effect of Genistein and Atorvastatin on Adipogenesis in 3T3-L1 Adipocytes

Genistein (4,5,7-trihydroxyisoflavone) is abundant in various dietary vegetables, especially soybeans, and is known to have not only an estrogenic effect but also an antiadipogenic effect. Atorvastatin (dihydroxy monocarboxylic acid) is a statin used to prevent heart disease. Although genistein and atorvastatin have been reported to possess antiadipogenic effects, their combined effects are still unclear. The aim of the current study was to explore whether the combination of genistein and atorvastatin at low concentrations significantly suppresses adipogenesis in a murine preadipocyte cell line (3T3-L1) compared to treatment with genistein or atorvastatin alone. Our results showed that cotreatment with 50 µM genistein and 50 nM atorvastatin significantly suppressed preadipocyte differentiation, whereas when each compound was used alone, there was no inhibitory effect. Additionally, cotreatment with genistein and atorvastatin significantly downregulated adipogenic marker proteins, including mitogen-activated protein kinases (MAPKs), peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein alpha (C/EBPα), glucocorticoid receptor (GR), and CCAAT/enhancer-binding protein β (C/EBPβ). This is the first evidence of the combined antiadipogenic effects of genistein and atorvastatin. Although additional experiments are required, combinational treatment with genistein and atorvastatin may be an alternative treatment for menopause-associated lipid metabolic disorders and obesity.

The Glitazars Paradox: Cardiotoxicity of the Metabolically Beneficial Dual PPARα and PPARγ Activation

The most common complications in patients with type-2 diabetes are hyperglycemia and hyperlipidemia that can lead to cardiovascular disease. Alleviation of these complications constitutes the major therapeutic approach for the treatment of diabetes mellitus. Agonists of peroxisome proliferator-activated receptor (PPAR) alpha and PPARγ are used for the treatment of hyperlipidemia and hyperglycemia, respectively. PPARs belong to the nuclear receptors superfamily and regulate fatty acid metabolism. PPARα ligands, such as fibrates, reduce circulating triglyceride levels, and PPARγ agonists, such as thiazolidinediones, improve insulin sensitivity. Dual-PPARα/γ agonists (glitazars) were developed to combine the beneficial effects of PPARα and PPARγ agonism. Although they improved metabolic parameters, they paradoxically aggravated congestive heart failure in patients with type-2 diabetes via mechanisms that remain elusive. Many of the glitazars, such as muraglitazar, tesaglitazar, and aleglitazar, were abandoned in phase-III clinical trials. The objective of this review article pertains to the understanding of how combined PPARα and PPARγ activation, which successfully targets the major complications of diabetes, causes cardiac dysfunction. Furthermore, it aims to suggest interventions that will maintain the beneficial effects of dual PPARα/γ agonism and alleviate adverse cardiac outcomes in diabetes.

Knockout of NOS2 Promotes Adipogenic Differentiation of Rat MSCs by Enhancing Activation of JAK/STAT3 Signaling

Mesenchymal stromal cells (MSCs) are a heterogeneous population of cells that possess multilineage differentiation potential and extensive immunomodulatory properties. In mice and rats, MSCs produce nitric oxide (NO), as immunomodulatory effector molecule that exerts an antiproliferative effect on T cells, while the role of NO in differentiation was less clear. Here, we investigated the role of NO synthase 2 (NOS2) on adipogenic and osteogenic differentiation of rat MSCs. MSCs isolated from NOS2-null (NOS2^–/–) and wild type (WT) Sprague–Dawley (SD) rats exhibited homogenous fibroblast-like morphology and characteristic phenotypes. However, after induction, adipogenic differentiation was found significantly promoted in NOS2^–/– MSCs compared to WT MSCs, but not in osteogenic differentiation. Accordingly, qRT-PCR revealed that the adipogenesis-related genes PPAR-γ, C/EBP-α, LPL and FABP4 were markedly upregulated in NOS2^–/– MSCs, but not for osteogenic transcription factors or marker genes. Further investigations revealed that the significant enhancement of adipogenic differentiation in NOS2^–/– MSCs was due to overactivation of the STAT3 signaling pathway. Both AG490 and S3I-201, small molecule inhibitors that selectively inhibit STAT3 activation, reversed this adipogenic effect. Furthermore, after high-fat diet (HFD) feeding, knockout of NOS2 in rat MSCs resulted in significant obesity. In summary, NOS2 is involved in the regulation of rat MSC adipogenic differentiation via the STAT3 signaling pathway.

Anti-obesity effect of Melandrium firmum Rohrbach extract in 3T3-L1 cells and high-fat diet-induced obese C57BL/6N mice

In this study, we first investigated the influence of Melandrium firmum Rohrbach (MF) on the accumulation of lipid content in 3T3-L1 cells and in vitro results showed that MF extraction suppressed the differentiation of 3T3-L1 pre-adipocytes in a concentration-dependent manner without showing cytotoxicity. Hence, we studied the effects of MF on preventing obesity in C57BL/6N mice. The results showed that MF decreased food efficiency ratio, body weight, epididymal adipose and hepatic tissue weight, hepatic lipid metabolites, and triacylglycerol and cholesterol serum levels, when compared with the high-fat diet group. Moreover, MF significantly inhibited the expression of genes related to adipogenesis, such as PPAR-γ, C/EBP-α, and aP2, and those related to lipogenesis, such as SREBP-1c, FAS, SCD-1, and CD36 in epididymal adipose and liver tissues. These anti-adipogenic and anti-lipogenic effects of MF suggest that it could be used as a food including potential functional ingredient to prevent high-fat diet-induced obesity.

Nitric oxide balances osteoblast and adipocyte lineage differentiation via the JNK/MAPK signaling pathway in periodontal ligament stem cells

Background

Critical tissues that undergo regeneration in periodontal tissue are of mesenchymal origin; thus, investigating the regulatory mechanisms underlying the fate of periodontal ligament stem cells could be beneficial for application in periodontal tissue regeneration. Nitric oxide (NO) regulates many biological processes in developing embryos and adult stem cells. The present study was designed to investigate the effects of NO on the function of human periodontal ligament stem cells (PDLSCs) as well as to elucidate the underlying molecular mechanisms.

Methods

Immunofluorescent staining and flow cytometry were used for stem cell identification. Western blot, reverse transcription polymerase chain reaction (RT-PCR), immunofluorescent staining, and flow cytometry were used to examine the expression of NO-synthesizing enzymes. The proliferative capacity of PDLSCs was determined by EdU assays. The osteogenic potential of PDLSCs was tested using alkaline phosphatase (ALP) staining, Alizarin Red staining, and calcium concentration detection. Oil Red O staining was used to analyze the adipogenic ability. Western blot, RT-PCR, and staining were used to examine the signaling pathway.

Results

Human PDLSCs expressed both inducible NO synthase (iNOS) and endothelial NO synthase (eNOS) and produced NO. Blocking the generation of NO with the NOS inhibitor l-N^G-monomethyl arginine (l-NMMA) had no influence on PDLSC proliferation and apoptosis but significantly attenuated the osteogenic differentiation capacity and stimulated the adipogenic differentiation capacity of PDLSCs. Increasing the physiological level of NO with NO donor sodium nitroprusside (SNP) significantly promoted the osteogenic differentiation capacity but reduced the adipogenic differentiation capacity of PDLSCs. NO balances the osteoblast and adipocyte lineage differentiation in periodontal ligament stem cells via the c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) signaling pathway.

Conclusions

NO is essential for maintaining the balance between osteoblasts and adipocytes in PDLSCs via the JNK/MAPK signaling pathway.

Graphical Abstract

NO balances osteoblast and adipocyte lineage differentiation via JNK/MAPK signaling pathway

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0869-2) contains supplementary material, which is available to authorized users.

IGFBP2 enhances adipogenic differentiation potentials of mesenchymal stem cells from Wharton's jelly of the umbilical cord via JNK and Akt signaling pathways

Mesenchymal stem cell (MSC)-mediated tissue engineering represents a promising strategy to address adipose tissue defects. MSCs derived from Wharton’s jelly of the umbilical cord (WJCMSCs) may serve as an ideal source for adipose tissue engineering due to their abundance, safety profile, and accessibility. How to activate the directed differentiation potentials of WJCMSCs is the core point for their clinical applications. A thorough investigation of mechanisms involved in WJCMSC adipogenic differentiation is necessary to support their application in adipose tissue engineering and address shortcomings. Previous study showed, compared with periodontal ligament stem cells (PDLSCs), WJCMSCs had a weakened adipogenic differentiation potentials and lower expression of insulin-like growth factor binding protein 2 (IGFBP2). IGFBP2 may be involved in the adipogenesis of MSCs. Generally, IGFBP2 is involved in regulating biological activity of insulin-like growth factors, however, its functions in human MSCs are unclear. Here, we found IGFBP2 expression was upregulated upon adipogenic induction, and that IGFBP2 enhanced adipogenic differentiation of WJCMSCs and BMSCs. Moreover, IGFBP2 increased phosphorylation of c-Jun N-terminal kinase (p-JNK) and p-Akt, and activated JNK or Akt signaling significantly promoted adipogenic differentiation of MSCs. Furthermore, inhibitor-mediated blockage of either JNK or Akt signaling dramatically reduced IGFBP2-mediated adipogenic differentiation. And the JNK inhibitor, SP600125 markedly blocked IGFBP2-mediated Akt activation. Moreover, IGFBP2 was negatively regulated by BCOR, which inhibited adipogenic differentiation of WJCMSCs. Overall, our results reveal a new function of IGFBP2, providing a novel insight into the mechanism of adipogenic differentiation and identifying a potential target mediator for improving adipose tissue engineering based on WJCMSCs.

PPARs: Protectors or Opponents of Myocardial Function?

Over 5 million people in the United States suffer from the complications of heart failure (HF), which is a rapidly expanding health complication. Disorders that contribute to HF include ischemic cardiac disease, cardiomyopathies, and hypertension. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor family. There are three PPAR isoforms: PPARα, PPARγ, and PPARδ. They can be activated by endogenous ligands, such as fatty acids, as well as by pharmacologic agents. Activators of PPARs are used for treating several metabolic complications, such as diabetes and hyperlipidemia that are directly or indirectly associated with HF. However, some of these drugs have adverse effects that compromise cardiac function. This review article aims to summarize the current basic and clinical research findings of the beneficial or detrimental effects of PPAR biology on myocardial function.

Role of c-Jun N-terminal kinase in the osteogenic and adipogenic differentiation of human adipose-derived mesenchymal stem cells

Although previous studies have characterized the osteogenic potential of adipose-derived mesenchymal stem cells (AMSCs) in vitro and in vivo, the molecular mechanism involved remains to be fully determined. Previously, we demonstrated that the ERK pathway plays an important role in osteogenesis and regulation of the balance between osteogenesis and adipogenesis. Here, we explored the possible role of JNKs in osteogenesis and adipogenesis of AMSCs. JNK activation in osteo-induced AMSCs was initiated at 15 min, peaked at 30 min, and declined from 45 min to basal levels. Inhibition of the JNK signaling pathway using SP600125 blocked osteogenic differentiation in a dose-dependent manner, which was revealed by an ALP activity assay, extracellular calcium deposition detection, and expression of osteogenesis-relative genes (Runx2, ALP, and OCN) via RT-PCR and real-time PCR. However, blockage of JNK did not induce a switch between osteogenesis and adipogenesis of AMSCs in the presence of dexamethasone, which is different from that of blockage of ERK. Significantly, the blockage of JNK activation in adipo-induced AMSCs by SP600125 stimulated adipogenic differentiation, which was confirmed by Oil Red O staining to detect intracellular lipid droplets, and RT-PCR and real-time PCR analysis for expression of adipogenesis-relative genes (PPARγ2 and aP2). This study suggested a potential function of the JNK pathway in committing osteogenic and adipogenic differentiation of AMSCs in vitro. However, blockage of the JNK pathway is not sufficient to induce a switch from osteogenesis to adipogenesis of AMSCs.