Signal transducer and activator of transcription 3 (STAT3) regulates adipocyte differentiation via peroxisome-proliferator-activated receptor gamma (PPARgamma)

Non-Coding RNAs in Regulating Fat Deposition in Farm Animals

Fat deposition represents a crucial feature in the expenditure of physical energy and affects the meat quality of farm animals. It is regulated by multiple genes and regulators. Of them, non-coding RNAs (ncRNAs) play a critical role in modulating the fat deposition process. As well as being an important protein source, farm animals can be used as medical models, so many researchers worldwide have explored their mechanism of fat deposition. This article summarizes the transcription factors, regulatory genes, and signaling pathways involved in the molecular regulation process of fat deposition; outlines the progress of researching the roles of microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs) in fat deposition in common farm animals including pigs, cattle, sheep, ducks, and chickens; and identifies scientific problems in the field that must be further investigated. It has been demonstrated that ncRNAs play a critical role in regulating the fat deposition process and have great potential in improving meat quality traits.

Deciphering adipose development: Function, differentiation and regulation

The overdevelopment of adipose tissues, accompanied by excess lipid accumulation and energy storage, leads to adipose deposition and obesity. With the increasing incidence of obesity in recent years, obesity is becoming a major risk factor for human health, causing various relevant diseases (including hypertension, diabetes, osteoarthritis and cancers). Therefore, it is of significance to antagonize obesity to reduce the risk of obesity-related diseases. Excess lipid accumulation in adipose tissues is mediated by adipocyte hypertrophy (expansion of pre-existing adipocytes) or hyperplasia (increase of newly-formed adipocytes). It is necessary to prevent excessive accumulation of adipose tissues by controlling adipose development. Adipogenesis is exquisitely regulated by many factors in vivo and in vitro, including hormones, cytokines, gender and dietary components. The present review has concluded a comprehensive understanding of adipose development including its origin, classification, distribution, function, differentiation and molecular mechanisms underlying adipogenesis, which may provide potential therapeutic strategies for harnessing obesity without impairing adipose tissue function.

Differential chromatin accessibility and Gene Expression Associated with Backfat Deposition in pigs

BACKGROUND

Backfat serves as a vital fat reservoir in pigs, and its excessive accumulation will adversely impact pig growth performance, farming efficiency, and pork quality. The aim of this research is to integrate assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and RNA sequencing (RNA-seq) to explore the molecular mechanisms underlying porcine backfat deposition.

RESULTS

ATAC-seq analysis identified 568 genes originating from 698 regions exhibiting differential accessibility, which were significantly enriched in pathways pertinent to adipocyte differentiation and lipid metabolism. Besides, a total of 283 transcription factors (TFs) were identified by motif analysis. RNA-seq analysis revealed 978 differentially expressed genes (DEGs), which were enriched in pathways related to energy metabolism, cell cycle and signal transduction. The integration of ATAC-seq and RNA-seq data indicates that DEG expression levels are associated with chromatin accessibility. This comprehensive study highlights the involvement of critical pathways, including the Wnt signaling pathway, Jak-STAT signaling pathway, and fatty acid degradation, in the regulation of backfat deposition. Through rigorous analysis, we identified several candidate genes (LEP, CTBP2, EHHADH, OSMR, TCF7L2, BCL2, FGF1, UCP2, CCND1, TIMP1, and VDR) as potentially significant contributors to backfat deposition. Additionally, we constructed TF-TF and TF-target gene regulatory networks and identified a series of potential TFs related to backfat deposition (FOS, STAT3, SMAD3, and ESR1).

CONCLUSIONS

This study represents the first application of ATAC-seq and RNA-seq, affording a novel perspective into the mechanisms underlying backfat deposition and providing invaluable resources for the enhancement of pig breeding programs.

Threonine Deficiency Increases Triglyceride Deposition in Primary Duck Hepatocytes by Reducing STAT3 Phosphorylation

Liver lipid metabolism disruption significantly contributes to excessive fat buildup in waterfowl. Research suggests that the supplementation of Threonine (Thr) in the diet can improve liver lipid metabolism disorder, while Thr deficiency can lead to such metabolic disorders in the liver. The mechanisms through which Thr regulates lipid metabolism remain unclear. STAT3 (signal transducer and activator of transcription 3), a crucial transcription factor in the JAK-STAT (Janus kinase-signal transducer and activator of transcription) pathway, participates in various biological processes, including lipid and energy metabolism. This research investigates the potential involvement of STAT3 in the increased lipid storage seen in primary duck hepatocytes as a result of a lack of Thr. Using small interfering RNA and Stattic, a specific STAT3 phosphorylation inhibitor, we explored the impact of STAT3 expression patterns on Thr-regulated lipid synthesis metabolism in hepatocytes. Through transcriptome sequencing, we uncovered pathways related to lipid synthesis and metabolism jointly regulated by Thr and STAT3. The results showed that Thr deficiency increases lipid deposition in primary duck hepatocytes (p < 0.01). The decrease in protein and phosphorylation levels of STAT3 directly caused this deposition (p < 0.01). Transcriptomic analysis revealed that Thr deficiency and STAT3 knockdown jointly altered the mRNA expression levels of pathways related to long-chain fatty acid synthesis and energy metabolism (p < 0.05). Thr deficiency, through mediating STAT3 inactivation, upregulated ELOVL7, PPARG, MMP1, MMP13, and TIMP4 mRNA levels, and downregulated PTGS2 mRNA levels (p < 0.01). In summary, these results suggest that Thr deficiency promotes lipid synthesis, reduces lipid breakdown, and leads to lipid metabolism disorders and triglyceride deposition by downregulating STAT3 activity in primary duck hepatocytes.

Epigallocatechin gallate suppresses mitotic clonal expansion and adipogenic differentiation of preadipocytes through impeding JAK2/STAT3-mediated transcriptional cascades

BACKGROUND

Mitotic clonal expansion (MCE) is a prerequisite for preadipocyte differentiation and adipogenesis. Epigallocatechin gallate (EGCG) has been shown to inhibit preadipocyte differentiation. However, the exact molecular mechanisms are still elusive.

PURPOSE

This study investigated whether EGCG could inhibit adipogenesis and lipid accumulation by regulating the cell cycle in the MCE phase of adipogenesis and its underlying molecular mechanisms.

METHOD

3T3-L1 preadipocytes were induced to differentiate by a differentiation cocktail (DMI) and were treated with EGCG (25-100 μM) for 9, 18, and 24 h to examine the effect on MCE, or eight days to examine the effect on terminal differentiation. C57BL/6 mice were fed a high-fat diet (HFD) for three months to induce obesity and were given EGCG (50 or 100 mg/kg) daily by gavage.

RESULTS

We showed that EGCG significantly inhibited terminal adipogenesis and lipid accumulation in 3T3-L1 cells and decreased expressions of PPARγ, C/EBPα, and FASN. Notably, at the MCE phase, EGCG regulated the cell cycle in sequential order, induced G0/G1 arrest at 18 h, and inhibited the G2/M phase at 24 h upon DMI treatment. Meanwhile, EGCG regulated the expressions of cell cycle regulators (cyclin D1, cyclin E1, CDK4, CDK6, cyclin B1, cyclin B2, p16, and p27), and decreased C/EBPβ, PPARγ, and C/EBPα expressions at MCE. Mechanistic studies using STAT3 agonist Colivelin and antagonist C188-9 revealed that EGCG-induced cell cycle arrest in the MCE phase and terminal adipocyte differentiation was mediated by the inhibition of JAK2/STAT3 signaling cascades and STAT3 (Tyr705) nuclear translocation. Furthermore, EGCG significantly protected mice from HFD-induced obesity, reduced body weight and lipid accumulations in adipose tissues, reduced hyperlipidemia and leptin levels, and improved glucose intolerance and insulin sensitivity. Moreover, RNA sequencing (RNA-seq) analysis showed that the cell cycle changes in epididymal white adipose tissue (eWAT) were significantly enriched upon EGCG treatment. We further verified that EGCG treatment significantly reduced expressions of adipogenic factors, cell cycle regulators, and p-STAT3 in eWAT.

CONCLUSION

EGCG inhibits MCE, resulting in the inhibition of early and terminal adipocyte differentiation and lipid accumulation, which were mediated by inhibiting p-STAT3 nucleus translocation and activation.

Unraveling the intricate relationship between lipid metabolism and oncogenic signaling pathways

Lipids, the primary constituents of the cell membrane, play essential roles in nearly all cellular functions, such as cell-cell recognition, signaling transduction, and energy provision. Lipid metabolism is necessary for the maintenance of life since it regulates the balance between the processes of synthesis and breakdown. Increasing evidence suggests that cancer cells exhibit abnormal lipid metabolism, significantly affecting their malignant characteristics, including self-renewal, differentiation, invasion, metastasis, and drug sensitivity and resistance. Prominent oncogenic signaling pathways that modulate metabolic gene expression and elevate metabolic enzyme activity include phosphoinositide 3-kinase (PI3K)/AKT, MAPK, NF-kB, Wnt, Notch, and Hippo pathway. Conversely, when metabolic processes are not regulated, they can lead to malfunctions in cellular signal transduction pathways. This, in turn, enables uncontrolled cancer cell growth by providing the necessary energy, building blocks, and redox potentials. Therefore, targeting lipid metabolism-associated oncogenic signaling pathways could be an effective therapeutic approach to decrease cancer incidence and promote survival. This review sheds light on the interactions between lipid reprogramming and signaling pathways in cancer. Exploring lipid metabolism as a target could provide a promising approach for creating anticancer treatments by identifying metabolic inhibitors. Additionally, we have also provided an overview of the drugs targeting lipid metabolism in cancer in this review.

Knockdown of LAP2α inhibits adipogenesis of human adipose-derived stem cells and ameliorates high-fat diet-induced obesity

Adipogenesis, a pivotal cellular process involving the differentiation of mesenchymal stem cells (MSCs) to mature adipocytes, plays a significant role in various physiological functions. Dysregulation of adipogenesis is implicated in conditions such as obesity. However, the complete molecular understanding of adipogenesis remains elusive. This study aimed to uncover the novel role of lamina-associated polypeptide 2 alpha (LAP2α) in human adipose-derived stem cells (hASCs) adipogenesis and its impact on high-fat diet (HFD)-induced obesity and associated metabolic disturbances. LAP2α expression was assessed during the adipogenic differentiation of hASCs using RT-qPCR and western blotting. The functional role of LAP2α in adipogenesis was explored both in vitro and in vivo through loss- and gain-of-function studies. Moreover, mice with HFD-induced obesity received lentivirus injection to assess the effect of LAP2α knockdown on fat accumulation. Molecular mechanisms underlying LAP2α in adipogenic differentiation were investigated using RT-qPCR, Western blotting, immunofluorescence staining, and Oil Red O staining. LAP2α expression was upregulated during hASCs adipogenic differentiation. LAP2α knockdown hindered adipogenesis, while LAP2α overexpression promoted adipogenic differentiation. Notably, LAP2α deficiency resisted HFD-induced obesity, improved glucose intolerance, mitigated insulin resistance, and prevented fatty liver development. Mechanistically, LAP2α knockdown attenuated signal transducer and activator of transcription 3 (STAT3) activation by reducing the protein level of phosphorylated STAT3. A STAT3 activator (Colivelin) counteracted the negative impact of LAP2α deficiency on hASCs adipogenic differentiation. Taken together, our current study established LAP2α as a crucial regulator of hASCs adipogenic differentiation, unveiling a new therapeutic target for obesity prevention.

Equisetin inhibits adiposity through AMPK-dependent regulation of brown adipocyte differentiation

Obesity has a significant impact on endocrine function, which leads to metabolic diseases including diabetes, insulin resistance, and other complications associated with obesity. Development of effective and safe anti-obesity drugs is imperative and necessary. Equisetin (EQST), a tetramate-containing marine fungal product, was reported to inhibit bacterial fatty acid synthesis and affect mitochondrial metabolism. It is tempting to speculate that EQST might have anti-obesity effects. This study was designed to explore anti-obesity effects and underlying mechanism of EQST on 3T3-L1 adipocytes differentiated from 3T3-L1 cells. Oil Red O staining showed that EQST reduced lipid accumulation in 3T3-L1 adipocytes. Quantitative real-time polymerase chain reaction and Western blot analysis revealed that EQST significantly inhibited expression of adipogenesis/lipogenesis-related genes C/ebp-α, Ppar-γ, Srebp1c, Fas, and reduced protein levels. There was also increased expression of key genes and protein levels involved in lipolysis (Perilipin, Atgl, Hsl), brown adipocyte differentiation (Prdm16, Ucp1), mitochondrial biogenesis (Pgc1α, Tfam) and β-oxidation Acsl1, Cpt1. Moreover, mitochondrial content, their membrane potential ΔΨM, and respiratory chain genes Mt-Co1, Cox7a1, Cox8b, and Cox4 (and protein) exhibited marked increase in expression upon EQST treatment, along with increased protein levels. Importantly, EQST induced expression and activation of AMPK, which was compromised by the AMPK inhibitor dorsomorphin, leading to rescue of EQST-downregulated Fas expression and a reduction of the EQST-increased expression of Pgc1α, Ucp1, and Cox4. Together, EQST robustly promotes fat clearance through the AMPK pathway, these results supporting EQST as a strong candidate for the development into an anti-obesity therapeutic agent.

CircRNA-5335 Regulates the Differentiation and Proliferation of Sheep Preadipocyte via the miR-125a-3p/STAT3 Pathway

The content of intramuscular fat (IMF) from preadipocytes is proportional to meat quality in livestock. However, the roles of circRNAs in IMF deposition in sheep are not well known. In this study, we show that circRNA-5335/miR-125a-3p/STAT3 play a crucial adjective role in the proliferation and differentiation of sheep preadipocytes. In this study, we characterized the roles of differentially expressed circRNA-5335/miR-125a-3p/STAT3, which were screened from sheep of different months of age and based on sequencing data. Firstly, the expression profiles of circRNA-5335/miR-125a-3p/STAT3 were identified during the differentiation of preadipocytes in vitro by RT-qPCR and WB. Then, the targeting relationship of the circRNA-5335/miR-125a-3p/STAT3 was verified by dual-luciferase reporter assays. The results of RT-qPCR, CCK8, EdU and Oil Red O staining assay showed that miR-125a-3p suppressed the differentiation and raised the proliferation of preadipocytes by targeting STAT3. As a competing endogenous RNA, the downregulation of circRNA-5335 decreased the expression of STAT3 by increasing miR-125a-3p, which inhibited the differentiation of preadipocytes and promoted proliferation. Our present study demonstrates the functional significance of circRNA-5335/miR-125a-3p/STAT3 in the differentiation of sheep preadipocytes, and provides novel insights into exploring the mechanism of IMF.

The oncogenic mechanisms of the Janus kinase-signal transducer and activator of transcription pathway in digestive tract tumors

Digestive tract tumors are heterogeneous and involve the dysregulation of multiple signaling pathways. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway plays a notable role in the oncogenesis of digestive tract tumors. Typically activated by pro-inflammatory cytokines, it regulates important biological processes, such as cell growth, differentiation, apoptosis, immune responses, and inflammation. The aberrant activation of this pathway manifests in different forms, including mutations in JAKs, overexpression of cytokine receptors, and sustained STAT activation, and contributes to promoting the malignant characteristics of cancer cells, including uncontrolled proliferation, resistance to apoptosis, enhanced invasion and metastasis, angiogenesis, acquisition of stem-like properties, and drug resistance. Numerous studies have shown that aberrant activation of the JAK-STAT pathway is closely related to the development and progression of digestive tract tumors, contributing to tumor survival, angiogenesis, changes in the tumor microenvironment, and even immune escape processes. In addition, this signaling pathway also affects the sensitivity of digestive tract tumors to chemotherapy and targeted therapy. Therefore, it is crucial to comprehensively understand the oncogenic mechanisms underlying the JAK-STAT pathway in order to develop effective therapeutic strategies against digestive tract tumors. Currently, several JAK-STAT inhibitors are undergoing clinical and preclinical trials as potential treatments for various human diseases. However, further investigation is required to determine the role of this pathway, as well as the effectiveness and safety of its inhibitors, especially in the context of digestive tract tumors. In this review, we provide an overview of the structure, classic activation, and negative regulation of the JAK-STAT pathway. Furthermore, we discuss the pathogenic mechanisms of JAK-STAT signaling in different digestive tract tumors, with the aim of identifying potential novel therapeutic targets. Video Abstract.

Anti‑adipogenic effect and underlying mechanism of lignan‑enriched nutmeg extract on 3T3‑L1 preadipocytes

Nutmeg is the seed derived from Myristica fragrans. Nutmeg seeds contain alkylbenzene derivatives such as myristicin, which are toxic to the human organism, and lignan compounds such as nectandrin B, which possess anti-aging and anti-diabetic properties. However, the anti-adipogenic, prolipolytic and anti-inflammatory effects of lignan-enriched nutmeg extract (LNX) on preadipocytes remain unclear. In the present study, the effects of LNX on lipid accumulation, glycerol release and inflammatory cyclooxygenase-2 (COX-2) expression in differentiated 3T3-L1 preadipocytes were investigated. Oil red O staining demonstrated that treatment with LNX resulted in a concentration-dependent reduction in lipid accumulation in differentiating 3T3-L1 preadipocytes without affecting cell growth. Mechanistically, LNX treatment at 6 µg/ml led to a reduction in phosphorylation levels of signal transducer and activator of transcription 3 (STAT3), whereas it did not influence the peroxisome proliferator-activated receptor gamma (PPAR-γ) and CCAAT enhancer binding protein alpha (C/EBP-α) expression levels during 3T3-L1 preadipocyte differentiation. In addition, LNX treatment at 6 µg/ml led to a decrease in fatty acid synthase (FAS) expression levels on day (D) 2, but not D5 and D8, during preadipocyte differentiation. Treatment with LNX at 6 µg/ml did not affect the expression levels of perilipin A during preadipocyte differentiation. In differentiated 3T3-L1 adipocytes, LNX treatment at 6 µg/ml did not stimulate glycerol release and hormone-sensitive lipase phosphorylation, which are known lipolysis hallmarks. Furthermore, LNX treatment at the doses tested had no effect on tumor necrosis factor alpha-induced COX-2 expression in 3T3-L1 preadipocytes. Collectively, these results demonstrated that LNX has an anti-adipogenic effect on differentiating 3T3-L1 preadipocytes, which is mediated by the downregulation of STAT3 phosphorylation and FAS expression.

STAT3 as a therapeutic target in the metformin-related treatment

Signal transducers and activators of transcription 3 (STAT3) signaling plays an important role in mediating tumor progression, inflammation, cardiovascular disease, and other pathological processes.In recent years, STAT3 as a therapeutic target has received extensive attention. It is well known that metformin can play the role of hypoglycemia by activating AMP-activated protein kinase (AMPK) through inhibition of mitochondrial ATP production.However, AMPK is not required for metformin activity.Although the application of STAT3 as a therapeutic target of metformin is still in the initial research stage, the importance of STAT3 in the mechanism of metformin is gradually being recognizedand further studies are needed to demonstrate the important role of the STAT3 regulatory network in the regulation of diseases by metformin. Here, we reviewed in detail that metformin inhibits the progression of various diseases like tumors, autoimmune diseases and hormone-related diseases by regulating multiple signaling pathways such as JAK/STAT3 and mTOR/STAT3 signaling centered on STAT3. We also summarized recent advances of STAT3 inhibitors combined with metformin in the treatment of diseases.We emphasized that STAT3 signaling, as an AMPK-independent signaling pathway, may be an important target for metformin in clinical therapy.

Dietary n-3 and n-6 polyunsaturated fatty acids differentially modulate the adiponectin and leptinmediated major signaling pathways in visceral and subcutaneous white adipose tissue in high fat diet induced obesity in Wistar rats

Obesity is a chronic metabolic disease that involves excessive accumulation of fat in white adipose tissue (WAT). Apart from storing excess fats, WAT also serves as an important endocrine organ secreting adipocytokines such as adiponectin and leptin. Adiponectin and leptin bind to their transmembrane receptors adiponectin receptor 1 (AdipoR1)/adiponectin receptor 2 (AdipoR2) and Ob-R, respectively, and mediate their effect on metabolism by regulating multiple downstream targets. Dietary fat is considered the main culprit behind obesity development. Numerous preclinical studies have highlighted role of essential polyunsaturated fatty acids (PUFAs), particularly n-3 PUFAs, in prevention of obesity. Despite emerging data, there still is no clear understanding of the mechanism of action of n-3 PUFAs and n-6 PUFAs on adipose tissue function in two functionally and anatomically different depots of WAT: visceral and subcutaneous. We designed this study using a high fat diet (HFD) fed rodent model of obesity to test our hypothesis that n-3 and n-6 PUFAs possibly differentially modulate adipokine secretion and downstream metabolic pathways such as peroxisome proliferator-activated receptor-γ (PPAR-γ), protein kinase B (AKT)-forkhead box O1 (FOXO1), and Janus kinase-signal transducer and activator of transcription in obesity. The results of the current study showed that n-3 PUFAs upregulate the expression of AdipoR1/R2 and ameliorate the effects of HFD by modulating adipogenesis via PPAR-γ and by improving glucose tolerance and lipid metabolism via AKT-FOXO1 axis in fish oil fed rats. However, n-6 PUFAs did not show any remarkable change compared with HFD fed animals. Our study highlights that n-3 PUFAs modulate expression of various targets in adiponectin and leptin signaling cascade, bringing about an overall reduction in obesity and improvement in adipose tissue function in HFD induced obesity.

p52 signaling promotes cellular senescence

Background

Nuclear factor-κB is a multi-subunit transcription factor that plays a central role in cellular senescence. We previously reported that an increase in the p52 subunit is seen in senescent cells and aged tissue. In the current work, we examined the mechanism by which p52 is activated and whether the increase in p52 promotes senescence.

Results

Using both primary mouse embryonic fibroblasts (MEFs) and WI-38 human lung fibroblasts, we examined cells after serial passage and following prolonged culture. An increase in p52 was found in the nucleus relative to pre-senescent cells. The increase in p52 protein was not reflected by an increase in NFKB2 mRNA or by an increase in the abundance of upstream activating kinases, IKKα and NIK. To examine whether p52 promotes senescence, we over-expressed mature p52 in primary MEFs. Significantly more senescence was seen compared to control, a finding not seen with p52 mutated at critical DNA binding residues. In addition, blocking p52 nuclear translocation with the peptide inhibitor, SN52, decreased β-galactosidase (β-gal) formation. Subsequent filtration studies demonstrated that proteins in conditioned media (CM) were necessary for the increase in p52 and mass spectrometry identified S100A4 and cyclophilin A (CYPA) as potential factors in CM necessary for induction of p52. The requirement of these proteins in CM for induction of p52 was confirmed using depletion and supplementation studies. In addition, we found that activation of STAT3 signaling was required for the increase in p52. Finally, genome wide ChIP-sequencing analysis confirmed that there is an increase in p52 chromatin enrichment with senescence and identified several downstream factors whose expression is regulated by increased p52 binding.

Conclusions

These results demonstrate that p52 nuclear translocation is increased in senescent cells by factors in conditioned media and that mature p52 induces cellular senescence. The data are consistent with the prior observation that p52 is elevated in aged tissue and support the hypothesis that p52 contributes to organismal aging.

Supplementary information

The online version contains supplementary material available at 10.1186/s13578-022-00779-6.

Histone methyltransferase Smyd2 drives adipogenesis via regulating STAT3 phosphorylation

Adipogenesis is a complex cascade involved with the preadipocytes differentiation towards mature adipocytes, accelerating the onset of obesity. Histone methyltransferase SET and MYND domain-containing protein 2 (Smyd2), is involved in a variety of cellular biological functions but the epigenetic regulation of Smyd2 in adipogenesis and adipocyte differentiation remains unclear. Both Smyd2 siRNA and LLY-507, an inhibitor of Smyd2, were used to examine the effect of Smyd2 on adipogenesis and adipocyte differentiation in vitro. Smyd2 heterozygous knockout (Smyd2^+/-) mice were also constructed to validate the relationship between Smyd2 and adipogenesis in vivo. We found that Smyd2 is abundant in white adipose tissue and closely correlated with adipocyte differentiation. Knockdown or inhibition of Smyd2 restrained adipocyte differentiation in vitro, which requires the phosphorylation of STAT3. In vivo functional validation, Smyd2^+/- mice exert significant fat loss but not susceptible to HFD-induced obesity. Taken together, our findings revealed that Smyd2 is a novel regulator of adipocyte differentiation by regulating the phosphorylation of STAT3, which provides insights into the effects of epigenetic regulation in adipogenesis. Inhibition of Smyd2 might represent a viable strategy for anti-adipogenesis and maybe further alleviate obesity-related diseases in humans.

N6-Methyladenosine Methylome Profiling of Muscle and Adipose Tissues Reveals Methylase-mRNA Metabolic Regulatory Networks in Fat Deposition of Rex Rabbits

N6-methyladenosine (m6A) is the most prevalent internal form of modification in messenger RNA in higher eukaryotes and plays an important role in cancer, immunity, reproduction, development, and fat deposition. Intramuscular fat is the main factor used to measure the meat quality of an animal. The deposition of intramuscular fat and perirenal fat increases with age. However, there is no data on m6A modification of Rex rabbits and its potential biological roles in adipose deposition and muscle growth. Here, we performed two high-throughput sequencing methods, m6A-modified RNA immunoprecipitation sequence (MeRIP-seq) and RNA sequence (RNA-seq), to identify key genes with m6A modification on fat deposition in the muscle and adipose tissues of Rex rabbits. Then, qRT-PCR was used to identify the differently methylated genes related to fat deposition. Our findings showed that there were 12,876 and 10,973 m6A peaks in the rabbit muscle and adipose tissue transcriptomes, respectively. Stop codons, 3′-untranslated regions, and coding regions were found to be mainly enriched for m6A peaks. In addition, we found 5 differential methylases and 12 key genes of methylation modification related to fat deposition between muscle and adipose tissues samples. The expression levels of six random key genes were significantly higher in the fat than that in the muscle of Rex rabbits at different stages (p < 0.01). Finally, five differential methylases were found to regulate adipogenesis by affecting the expression of screened genes in different ways. These findings provided a theoretical basis for our future research on the function of m6A modification during the growth of fat deposits.

Topical VX-509 attenuates psoriatic inflammation through the STAT3/FABP5 pathway in keratinocytes

BACKGROUND

Psoriasis is a chronic inflammatory disease, with lesions mainly manifesting as scaly erythematous plaques. The mild or moderate of psoriasis is the main type of patients in hospital, and topical application remains the preferred treatment option for psoriasis therapy, therefore, the development of novel topical agents has an essential role in psoriasis therapy.

OBJECTIVE

To identify potential drugs for psoriasis topical treatment.

METHODS

We performed drug screening by Imiquimod (IMQ)-induced psoriatic like inflammation in mouse model, followed mouse epidermis by RNA-seq to find the key molecules affecting the drug. The qRT-PCR, WB were performed to test mRNA and protein expression, and Chip assay had been conducted to examine Stat3 bound to promoter of FABP5.

RESULTS

In this study, we identified VX-509, which topical application significantly attenuated IMQ-induced psoriatic like inflammation in mouse model. And then, we verified Epidermal Fatty acid binding protein (E-FABP/FABP5) was significantly decreased in VX-509 treated mouse epidermis by RNA-seq. FABP5 is a key molecule in lipid metabolism, administration of FABP5 inhibitor or knock down of FABP5 expression remarkably abrogated psoriatic inflammation as well as lipid metabolism. Mechanistically, our finding showed that VX-509 blocked IL-22 induced signaling pathway, particular in activation of Stat3. Furthermore, we identified Stat3 is a transcriptional factor associated with FABP5 promoters and VX-509 treatment remarkably attenuated IL-22-induced FABP5 expression through Stat3 in KCs.

CONCLUSIONS

This study demonstrated administration of VX-509 is a potential promising topical drug for treatment of psoriasis, FABP5 is a critical targeted molecule in psoriasis therapy.

STAT3 Is the Master Regulator for the Forming of 3D Spheroids of 3T3-L1 Preadipocytes

To elucidate the currently unknown mechanisms responsible for the diverse biological aspects between two-dimensional (2D) and three-dimensional (3D) cultured 3T3-L1 preadipocytes, RNA-sequencing analyses were performed. During a 7-day culture period, 2D- and 3D-cultured 3T3-L1 cells were subjected to lipid staining by BODIPY, qPCR for adipogenesis related genes, including peroxisome proliferator-activated receptor γ (Pparγ), CCAAT/enhancer-binding protein alpha (Cebpa), Ap2 (fatty acid-binding protein 4; Fabp4), leptin, and AdipoQ (adiponectin), and RNA-sequencing analysis. Differentially expressed genes (DEGs) were detected by next-generation RNA sequencing (RNA-seq) and validated by a quantitative reverse transcription–polymerase chain reaction (qRT–PCR). Bioinformatic analyses were performed on DEGs using a Gene Ontology (GO) enrichment analysis and an Ingenuity Pathway Analysis (IPA). Significant spontaneous adipogenesis was observed in 3D 3T3-L1 spheroids, but not in 2D-cultured cells. The mRNA expression of Pparγ, Cebpa, and Ap2 among the five genes tested were significantly higher in 3D spheroids than in 2D-cultured cells, thus providing support for this conclusion. RNA analysis demonstrated that a total of 826 upregulated and 725 downregulated genes were identified as DEGs. GO enrichment analysis and IPA found 50 possible upstream regulators, and among these, 6 regulators—transforming growth factor β1 (TGFβ1), signal transducer and activator of transcription 3 (STAT3), interleukin 6 (IL6), angiotensinogen (AGT), FOS, and MYC—were, in fact, significantly upregulated. Further analyses of these regulators by causal networks of the top 14 predicted diseases and functions networks (IPA network score indicated more than 30), suggesting that STAT3 was the most critical upstream regulator. The findings presented herein suggest that STAT3 has a critical role in regulating the unique biological properties of 3D spheroids that are produced from 3T3-L1 preadipocytes.

Regulation of Methylase METTL3 on Fat Deposition

N6-methyladenosine (m6A) is the most prevalent and abundant type of internal post-transcriptional RNA modification in eukaryotic cells. METTL3 is a methylation modifying enzyme, which can directly or indirectly affect biological processes, such as RNA degradation, translation and splicing. In addition, it was found that 67% of 3'-UTR regions containing m6A sites had at least one miRNA binding site, and the number of m6A at 3'-UTR sites was closely related to the binding sites of miRNA. With the improvement of human living standards, obesity has become a very serious and urgent problem. The essence of obesity is the accumulation of excess fat. Exploring the origin and development mechanisms of adipocyte from the perspective of fat deposition has always been a hotspot in the field of adipocyte research. The aim of the present review is to focus on METTL3 regulating fat deposition through mRNA/adipocyte differentiation axis and pri-miRNA/pre-miRNA/target genes/adipocyte differentiation and to provide a theoretical basis according to the currently available literature for further exploring this association. This review may provide new insights for obesity, fat deposition disease and molecular breeding.

STAT3 as a mediator of oncogenic cellular metabolism: Pathogenic and therapeutic implications

The oncogenic transcription factor signal transducer and activator of transcription 3 (STAT3) is activated constitutively in a wide array of human cancers. It is an appealing molecular target for novel therapy as it directly regulates expression of genes involved in cell proliferation, survival, angiogenesis, chemoresistance and immune responsiveness. In addition to these well-established oncogenic roles, STAT3 has also been found to mediate a wide array of functions in modulating cellular behavior. The transcriptional function of STAT3 is canonically regulated through tyrosine phosphorylation. However, STAT3 phosphorylated at a single serine residue can allow incorporation of this protein into the inner mitochondrial membrane to support oxidative phosphorylation (OXPHOS) and maximize the utility of glucose sources. Conflictingly, its canonical transcriptional activity suppresses OXPHOS and favors aerobic glycolysis to promote oncogenic behavior. Apart from mediating the energy metabolism and controversial effects on ATP production, STAT3 signaling modulates lipid metabolism of cancer cells. By mediating fatty acid synthesis and beta oxidation, STAT3 promotes employment of available resources and supports survival in the conditions of metabolic stress. Thus, the functions of STAT3 extend beyond regulation of oncogenic genes expression to pleiotropic effects on a spectrum of essential cellular processes. In this review, we dissect the current knowledge on activity and mechanisms of STAT3 involvement in transcriptional regulation, mitochondrial function, energy production and lipid metabolism of malignant cells, and its implications to cancer pathogenesis and therapy.

Torreya nucifera seed oil improves 3T3-L1 adipocyte differentiation

BACKGROUND

Adipose tissue is a critical regulator of lipid storage and endocrine function. Impairment of the recruitment of new adipocytes in the adipose tissue is associated with ectopic fat accumulation, diabetes and insulin resistance. Torreya nucifera, an evergreen conifer that grows in warm temperate climates, has been found to exert beneficial effects against inflammation, infection and diabetes. However, the molecular mechanisms responsible for these effects at the cellular level remain unknown. This study aimed to investigate effects of Torreya nucifera seed oil (TNSO) on 3T3-L1 adipocyte differentiation and its underlying regulatory mechanism.

METHODS

To investigate the effects of TNSO on adipocyte differentiation, 3T3-L1 cells were induced to differentiate for 5 days in the presence of 0.75 μL/mL TNSO. Oil Red O staining and an assay for intracellular triglyceride were performed to determine the extent of lipid accumulation in 3T3-L1 cells. To elucidate the underlying mechanism of TNSO, adipogenic gene expression was analyzed using quantitative real-time PCR. Moreover, we monitored TNSO-derived activation of PPARγ and STAT3 with 3T3-L1 reporter cell lines engineered to secrete Gaussia luciferase upon the interaction of a transcription factor to its DNA binding element.

RESULTS

Oil Red O staining revealed that TNSO improved the differentiation of 3T3-L1 preadipocytes into mature adipocytes. The mRNA levels of adipogenic genes, including adiponectin, fatty acid synthase (FAS) and adipocyte fatty acid-binding protein (FABP4), were upregulated and intracellular triglyceride levels increased upon TNSO treatment. We also established that adipocyte differentiation was improved by TNSO-derived activation of PPARγ and STAT3.

CONCLUSIONS

Our results suggest that TNSO improves adipocyte differentiation by regulating the activation of adipogenic transcription factors, indicating that it may serve as a potential treatment strategy for adipocyte dysfunction.

Sex-specific remodeling of T-cell compartment with aging: Implications for rat susceptibility to central nervous system autoimmune diseases

The incidence of multiple sclerosis (MS) and susceptibility of animals to experimental autoimmune encephalomyelitis (EAE), the most commonly used experimental model of MS, decrease with aging. Generally, autoimmune diseases develop as the ultimate outcome of an imbalance between damaging immune responses against self and regulatory immune responses (keeping the former under control). Thus, in this review the age-related changes possibly underlying this balance were discussed. Specifically, considering the central role of T cells in MS/EAE, the impact of aging on overall functional capacity (reflecting both overall count and individual functional cell properties) of self-reactive conventional T cells (Tcons) and FoxP3+ regulatory T cells (Tregs), as the most potent immunoregulatory/suppressive cells, was analyzed, as well. The analysis encompasses three distinct compartments: thymus (the primary lymphoid organ responsible for the elimination of self-reactive T cells - negative selection and the generation of Tregs, compensating for imperfections of the negative selection), peripheral blood/lymphoid tissues ("afferent" compartment), and brain/spinal cord tissues ("target" compartment). Given that the incidence of MS and susceptibility of animals to EAE are greater in women/females than in age-matched men/males, sex as independent variable was also considered. In conclusion, with aging, sex-specific alterations in the balance of self-reactive Tcons/Tregs are likely to occur not only in the thymus/"afferent" compartment, but also in the "target" compartment, reflecting multifaceted changes in both T-cell types. Their in depth understanding is important not only for envisaging effects of aging, but also for designing interventions to slow-down aging without any adverse effect on incidence of autoimmune diseases.

Chrysanthemum indicum suppresses adipogenesis by inhibiting mitotic clonal expansion in 3T3-L1 preadipocytes

Herbs have been of interest to treat diseases, including obesity, owing to their various bioactive constituents that exhibit therapeutic and prophylactic properties. The present study examined the anti-adipogenic effects and mechanisms of Chrysanthemum indicum aqueous extract (CAE) in 3T3-L1 preadipocytes. CAE comprises 1,3-dicaffeoylquinic acid, chlorogenic acid, kaempferol-3-O-glucoside, caffeic acid, and apigenin, which were corresponded with previous reports. CAE inhibited the accumulation of lipid droplets and significantly alleviated the expression of lipogenesis- and adipogenesis-associated biomarkers. Treatment with CAE inhibited the mitotic clonal expansion (MCE), corroborated by cell cycle arrest at the G₀ /G₁ phase, and mitigated the expression of cell cycle progression-associated proteins and in addition to phosphorylation of MCE-promoting transcription factors. Moreover, CAE downregulated the activation of Akt and extracellular signal-regulated kinase 1/2 signaling pathways. In summary, CAE facilitates adipogenic inhibition during the early phase of differentiation, especially MCE, and its phenolic compounds can contribute to its anti-obesogenic properties. PRACTICAL APPLICATIONS: Chrysanthemum indicum has been mainly used as traditional herbal tea and drinks. Chrysanthemum indicum aqueous extract (CAE) inhibits adipogenesis by suppressing mitotic clonal expansion during the early phase of differentiation in 3T3-L1 preadipocytes. 1,3-Dicaffeoylquinic acid, chlorogenic acid, kaempferol-3-O-glucoside, caffeic acid, and apigenin were detected in CAE. Based on these findings, CAE can be used as nutraceutical agents for prevention and treatment of obesity.

Role of long non-coding RNAs in adipogenesis: State of the art and implications in obesity and obesity-associated diseases

Obesity is an evolutionary, chronic, and relapsing disease that consists of a pathological accumulation of adipose tissue able to increase morbidity for high blood pressure, type 2 diabetes, metabolic syndrome, and obstructive sleep apnea in adults, children, and adolescents. Despite intense research over the last 20 years, obesity remains today a disease with a complex and multifactorial etiology. Recently, long non-coding RNAs (lncRNAs) are emerging as interesting new regulators as different lncRNAs have been found to play a role in early and late phases of adipogenesis and to be implicated in obesity-associated complications onset. In this review, we discuss the most recent advances on the role of lncRNAs in adipocyte biology and in obesity-associated complications. Indeed, more and more researchers are focusing on investigating the underlying roles that these molecular modulators could play. Even if a significant number of evidence is correlation-based, with lncRNAs being differentially expressed in a specific disease, recent works are now focused on deeply analyzing how lncRNAs can effectively modulate the disease pathogenesis onset and progression. LncRNAs possibly represent new molecular markers useful in the future for both the early diagnosis and a prompt clinical management of patients with obesity.

Investigation of the Molecular Mechanisms by Which Endothelin-3 Stimulates Preadipocyte Growth

Endothelins induce many biological responses, and they are composed of three peptides: ET-1, ET-2, and ET-3. Reports have indicated that ET-1 regulates cell proliferation, adipogenesis, and other cell responses and that ET-3 stimulates the growth of gastrointestinal epithelial cells and melanocytes. However, the signalling pathways of ET3 that mediate the growth of fat cells are still unclear. Using 3T3-L1 white preadipocytes, we found that ET-3 induced increases in both cell number and BrdU incorporation. Pretreatment with an ETAR antagonist (but not an ETBR antagonist) blocked the ET-3-induced increases in both cell number and BrdU incorporation. Additionally, BQ610 suppressed the ET-3-induced increases in phosphorylation of AMPK, c-JUN, and STAT3 proteins, and pretreatment with specific inhibitors of AMPK, JNK/c-JUN, or JAK/STAT3 prevented the ET-3-induced increases in phosphorylation of AMPK, c-JUN, and STAT3, respectively. Neither p38 MAPK inhibitor nor PKC inhibitor altered the effects of ET-3 on cell growth. These data suggest that ET-3 stimulates preadipocyte growth through the ETAR, AMPK, JNK/c-JUN, and STAT3 pathways. Moreover, ET-3 did not alter HIB1B brown preadipocyte and D12 beige preadipocyte growth, suggesting a preadipocyte type-dependent effect. The results of this study may help explain how endothelin mediates fat cell activity and fat cell-associated diseases.

Inhibition of Lipid Accumulation and Cyclooxygenase-2 Expression in Differentiating 3T3-L1 Preadipocytes by Pazopanib, a Multikinase Inhibitor

Pazopanib is a multikinase inhibitor with anti-tumor activity. As of now, the anti-obesity effect and mode of action of pazopanib are unknown. In this study, we investigated the effects of pazopanib on lipid accumulation, lipolysis, and expression of inflammatory cyclooxygenase (COX)-2 in differentiating and differentiated 3T3-L1 cells, a murine preadipocyte. Of note, pazopanib at 10 µM markedly decreased lipid accumulation and triglyceride (TG) content during 3T3-L1 preadipocyte differentiation with no cytotoxicity. Furthermore, pazopanib inhibited not only expression of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), and perilipin A but also phosphorylation of signal transducer and activator of transcription (STAT)-3 during 3T3-L1 preadipocyte differentiation. In addition, pazopanib treatment increased phosphorylation of cAMP-activated protein kinase (AMPK) and its downstream effector ACC during 3T3-L1 preadipocyte differentiation. However, in differentiated 3T3-L1 adipocytes, pazopanib treatment did not stimulate glycerol release and hormone-sensitive lipase (HSL) phosphorylation, hallmarks of lipolysis. Moreover, pazopanib could inhibit tumor necrosis factor (TNF)-α-induced expression of COX-2 in both 3T3-L1 preadipocytes and differentiated cells. In summary, this is the first report that pazopanib has strong anti-adipogenic and anti-inflammatory effects in 3T3-L1 cells, which are mediated through regulation of the expression and phosphorylation of C/EBP-α, PPAR-γ, STAT-3, ACC, perilipin A, AMPK, and COX-2.

Control of adipogenic commitment by a STAT3-VSTM2A axis

White adipose tissue (WAT) is a dynamic organ that plays crucial roles in controlling metabolic homeostasis. During development and periods of energy excess, adipose progenitors are recruited and differentiate into adipocytes to promote lipid storage capability. The identity of adipose progenitors and the signals that promote their recruitment are still incompletely characterized. We have recently identified V-set and transmembrane domain-containing protein 2A (VSTM2A) as a novel protein enriched in preadipocytes that amplifies adipogenic commitment. Despite the emerging role of VSTM2A in promoting adipogenesis, the molecular mechanisms regulating Vstm2a expression in preadipocytes are still unknown. To define the molecular mechanisms controlling Vstm2a expression, we have treated preadipocytes with an array of compounds capable of modulating established regulators of adipogenesis. Here, we report that Vstm2a expression is positively regulated by PI3K/mTOR and cAMP-dependent signaling pathways and repressed by the MAPK pathway and the glucocorticoid receptor. By integrating the impact of all the molecules tested, we identified signal transducer and activator of transcription 3 (STAT3) as a novel downstream transcription factor affecting Vstm2a expression. We show that activation of STAT3 increased Vstm2a expression, whereas its inhibition repressed this process. In mice, we found that STAT3 phosphorylation is elevated in the early phases of WAT development, an effect that strongly associates with Vstm2a expression. Our findings identify STAT3 as a key transcription factor regulating Vstm2a expression in preadipocytes.NEW & NOTEWORTHY cAMP-dependent and PI3K-mTOR signaling pathways promote the expression of Vstm2a. STAT3 is a key transcription factor that controls Vstm2a expression in preadipocytes. STAT3 is activated in the early phases of WAT development, an effect that strongly associates with Vstm2a expression.

GRIM19 Impedes Obesity by Regulating Inflammatory White Fat Browning and Promoting Th17/Treg Balance

Obesity, a condition characterized by excessive accumulation of body fat, is a metabolic disorder related to an increased risk of chronic inflammation. Obesity is mediated by signal transducer and activator of transcription (STAT) 3, which is regulated by genes associated with retinoid-interferon-induced mortality (GRIM) 19, a protein ubiquitously expressed in various human tissues. In this study, we investigated the role of GRIM19 in diet-induced obese C57BL/6 mice via intravenous or intramuscular administration of a plasmid encoding GRIM19. Splenocytes from wild-type and GRIM19-overexpressing mice were compared using enzyme-linked immunoassay, real-time polymerase chain reaction, Western blotting, flow cytometry, and histological analyses. GRIM19 attenuated the progression of obesity by regulating STAT3 activity and enhancing brown adipose tissue (BAT) differentiation. GRIM19 regulated the differentiation of mouse-derived 3T3-L1 preadipocytes into adipocytes, while modulating gene expression in white adipose tissue (WAT) and BAT. GRIM19 overexpression reduced diet-induced obesity and enhanced glucose and lipid metabolism in the liver. Moreover, GRIM19 overexpression reduced WAT differentiation and induced BAT differentiation in obese mice. GRIM19-transgenic mice exhibited reduced mitochondrial superoxide levels and a reciprocal balance between Th17 and Treg cells. These results suggest that GRIM19 attenuates the progression of obesity by controlling adipocyte differentiation.

Garcinia cambogia suppresses adipogenesis in 3T3-L1 cells by inhibiting p90RSK and Stat3 activation during mitotic clonal expansion

Obesity is associated with an increase in adipose tissue, which is mediated by hyperplasia and hypertrophy. Therefore, inhibiting cell proliferation during mitotic clonal expansion (MCE) is one of the major strategies for preventing obesity. The antagonistic effects of Garcinia cambogia (G. cambogia) on obesity have been studied in animal experimental models. However, the effects of G. cambogia extract on MCE, and the underlying molecular mechanisms, are poorly understood. In this study, 3T3-L1 cells were used to investigate whether G. cambogia extract affected cell proliferation during MCE and to identify target molecules for any anti-adipogenic activity. G. cambogia extract suppressed isobutylmethylxanthine and dexamethasone-and-insulin (MDI)-induced adipogenesis at an early stage by attenuating MCE. In G. cambogia extract-treated preadipocytes, MDI-induced cell proliferation and cell cycle progression were inhibited by G₀ /G₁ arrest due to an increase in p21 and p27 expression, and inhibition of cyclin-dependent kinase 2, cyclin E1 expression, and retinoblastoma (Rb) phosphorylation. In addition, the MDI-induced phosphorylation and subsequent translocation into the nucleus of p90 ribosomal S6 kinase (p90RSK) and signal transducer and activator of transcription (Stat) 3 were suppressed. Specific inhibitors of p90RSK (FMK) and Stat3 (stattic) regulated cell proliferation and adipogenesis. In conclusion, this study demonstrated that G. cambogia extract inhibited MCE by regulating p90RSK, Stat3, and cell cycle proteins, leading to G₀ /G₁ arrest. These findings provide new insight into the mechanism by which G. cambogia suppresses adipocyte differentiation and show that p90RSK is critical for adipogenesis as a new molecular target.

Catecholamines suppress fatty acid re-esterification and increase oxidation in white adipocytes via STAT3

Catecholamines stimulate the mobilization of stored triglycerides in adipocytes to provide fatty acids (FAs) for other tissues. However, a large proportion is taken back up and either oxidized or re-esterified. What controls the disposition of these FAs in adipocytes remains unknown. Here, we report that catecholamines redirect FAs for oxidation through the phosphorylation of signal transducer and activator of transcription 3 (STAT3). Adipocyte STAT3 is phosphorylated upon activation of β-adrenergic receptors, and in turn suppresses FA re-esterification to promote FA oxidation. Adipocyte-specific Stat3 KO mice exhibit normal rates of lipolysis, but exhibit defective lipolysis-driven oxidative metabolism, resulting in reduced energy expenditure and increased adiposity when they are on a high-fat diet. This previously unappreciated, non-genomic role of STAT3 explains how sympathetic activation can increase both lipolysis and FA oxidation in adipocytes, revealing a new regulatory axis in metabolism.

The resistant starch from sorghum regulates lipid metabolism in menopausal rats via equol

Equol is a metabolite of daidzein and has a higher biological activity than daidzein. High levels of non-starch polysaccharides can stimulate fermentation in the intestine leading to rapid conversion of daidzein into equol that has great potential to reduce obesity in postmenopausal women. In the present study, female Sprague-Dawley rats were used to establish a menopausal model by oral administration of formestane and to compare the protective effect of resistant starch on lipid metabolism, with or without soybean feed. The resistant starch was found to effectively control body weight and adipose tissue quality, while increasing the high-density lipoprotein cholesterol (HDL-C) concentration and lowering the glycerol, triacylglycerols (TG), total cholesterol (TC), and low density lipoprotein cholesterol (LDL-C) concentrations with soybean feed. Equol inhibited the expression of SREBPC1 gene by inhibiting SHP in the liver via transcription factor FXR, thereby inhibiting the synthesis of triglyceride and fatty acid in the liver. PRACTICAL APPLICATIONS: Intake of a certain amount of resistant starch while eating the soy product can better regulate lipid metabolism in menopausal obese rats compared to consumption of resistant starch alone. Studies have shown that resistant starch converts daidzein to Equol by regulating the structure of the intestinal flora and acts as an estrogen in menopausal rats. This research will further expand the health applications of resistant starch and provide useful information for the food industry.

Wu-Mei-Wan prevents high-fat diet-induced obesity by reducing white adipose tissue and enhancing brown adipose tissue function

BACKGROUND

Wu-Mei-Wan, a classic traditional Chinese herb medicine, is one of the most important formulations to treat digestive diseases from ancient times to the present. Our previous study showed that WMW treatment can prevent T2DM in db/db mice, which motivating the application of WMW on metabolic disorders.

PURPOSE

Obesity and its comorbid diseases have increased dramatically and are now a worldwide health problem. There is still a lack of satisfactory treatment strategies for obesity. This work was designed to assess the effect and related mechanism of WMW on high fat diet (HFD)-induced obese mice model.

METHODS

Obese mice were induced by HFD. Thetherapeutic effect of WMW were analyzed by examining body and adipose tissue weight, metabolic profile and energy expenditure. Adipose tissue phenotype was determined by histological staining and the mitochondrial content was examined by transmission electron microscopy (TEM). Immunohistochemical and immunofluorescence staining, RT-qPCR and Western blot analysis were used to evaluate expression of key molecules in adipose tissue.

RESULTS

WMW treatment significantly protects HFD-induced obesity. Here we showed that WMW limits weight gain, improves metabolic profile and increases energy expenditure. WMW inhibits the hypertrophy and hyperplasia of white adipocytes, the mechanism involving the inhibition of TLR3/IL-6/JAK1/STAT3 pathway. In brown adipose tissue (BAT), WMW promotes thermogenicprogramme without affecting cell proliferation. The activated BMP7/ Smad1/5/9 pathway is considered to be one of the explanations for the effect of WMW on BAT.

CONCLUSION

Our results suggested that WMW can prevent obesity and its underlying mechanisms are associated with reducing white adipose tissue and enhancing brown adipose tissue function.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

HMGA Genes and Proteins in Development and Evolution

HMGA (high mobility group A) (HMGA1 and HMGA2) are small non-histone proteins that can bind DNA and modify chromatin state, thus modulating the accessibility of regulatory factors to the DNA and contributing to the overall panorama of gene expression tuning. In general, they are abundantly expressed during embryogenesis, but are downregulated in the adult differentiated tissues. In the present review, we summarize some aspects of their role during development, also dealing with relevant studies that have shed light on their functioning in cell biology and with emerging possible involvement of HMGA1 and HMGA2 in evolutionary biology.

Apigenin inhibits STAT3/CD36 signaling axis and reduces visceral obesity

Visceral obesity is the excess deposition of visceral fat within the abdominal cavity that surrounds vital organs. Visceral obesity is directly associated with metabolic syndrome, breast cancer and endometrial cancer. In visceral obese subjects, signal transducer and activator of the transcription 3 (STAT3) in adipocytes is constitutively active. In this study, we aimed to screen for dietary herbal compounds that possess anti-visceral obesity effect. Apigenin is abundant in fruits and vegetables. Our data show that apigenin significantly reduces body weight and visceral adipose tissue (VAT), but not subcutaneous (SAT) and epididymal adipose tissues (EAT), of the high fat diet (HFD)-induced obese mice. Mechanistic studies show that HFD increases STAT3 phosphorylation in VAT, but not in SAT and EAT. Further studies suggest that apigenin binds to non-phosphorylated STAT3, reduces STAT3 phosphorylation and transcriptional activity in VAT, and consequently reduces the expression of STAT3 target gene cluster of differentiation 36 (CD36). The reduced CD36 expression in adipocytes reduces the expression of peroxisome proliferator-activated receptor gamma (PPAR-γ) which is the critical nuclear factor in adipogenesis. Our data show that apigenin reduces CD36 and PPAR-γ expressions and inhibits adipocyte differentiation; overexpression of constitutive active STAT3 reverses the apigenin-inhibited adipogenesis. Taken together, our data suggest that apigenin inhibits adipogenesis via the STAT3/CD36 axis. Our study has delineated the mechanism of action underlying the anti-visceral obesity effect of apigenin, and provide scientific evidence to support the development of apigenin as anti-visceral obesity therapeutic agent.

m6A methylation modulates adipogenesis through JAK2-STAT3-C/EBPβ signaling

N⁶-methyladenosine (m⁶A), the most abundant internal mRNA modification in eukaryotes, plays a vital role in regulating adipogenesis. However, its underlying mechanism remains largely unknown. Here, we reveal that deletion of m⁶A demethylase FTO in porcine and mouse preadipocytes inhibits adipogenesis through JAK2-STAT3-C/EBPβ signaling. Mechanistically, FTO deficiency suppresses JAK2 expression and STAT3 phosphorylation, leading to attenuated transcription of C/EBPβ, which is essential for the early stage of adipocyte differentiation. Using dual-luciferase assay, we validate that knockdown of FTO reduces expression of JAK2 in an m⁶A-dependent manner. Furthermore, we find that m⁶A "reader" protein YTHDF2 directly targets m⁶A-modified transcripts of JAK2 and accelerates mRNA decay, which results in decreased JAK2 expression and inactivated JAK2-STAT3-C/EBPβ signaling, thereby inhibiting adipogenesis. Collectively, our results provide a novel insight into the molecular mechanism of m⁶A methylation in post-transcriptional regulation of JAK2-STAT3-C/EBPβ signaling axis and highlight the crucial role of m⁶A modification and its modulators in adipogenesis.

Expression of GHR and Downstream Signaling Genes in Human Adipose Tissue-Relation to Obesity and Weight Change

CONTEXT

GH is a strong regulator of metabolism. In obesity, both GH secretion and adipose tissue GHR gene expression are decreased. More detailed information on the regulation of GHR, STAT3/5, and downstream-regulated genes in human adipose tissue during diet-induced weight loss and weight gain is lacking.

OBJECTIVE

The aim of the present study was to investigate the gene expression patterns of GHR and the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway (JAK2, STAT3, STAT5A, and STAT5B) in human subcutaneous adipose tissue in relation to energy restriction and overfeeding.

DESIGN, PATIENTS, AND INTERVENTIONS

Tissue distribution was analyzed in a data set generated by RNA sequencing containing information on global expression in human tissues. Subcutaneous adipose tissue or adipocyte gene expression (measured by DNA microarrays) was investigated in the following settings: (i) individuals with obesity vs individuals with normal weight; (ii) energy restriction; and (iii) overfeeding.

RESULTS

GHR expression was decreased in subjects with obesity compared with subjects with normal weight (P < 0.001). It was increased in response to energy restriction and decreased in response to overfeeding (P = 0.015 and P = 0.030, respectively). STAT3 expression was increased in subjects with obesity (P < 0.001). It was decreased during energy restriction and increased during overfeeding (P = 0.004 and P = 0.006, respectively). STAT3-regulated genes showed an overall view of overexpression in obesity.

CONCLUSIONS

The results of the present study have shown that GHR, STAT3, and STAT3-regulated genes are dynamically, and reciprocally, regulated at the tissue level in response to energy restriction and overfeeding, suggesting that GH signaling is perturbed in obesity.

Effect of the TYK-2/STAT-3 pathway on lipid accumulation induced by mono-2-ethylhexyl phthalate

BACKGROUND

Mono-2-ethylhexyl phthalate (MEHP), an important metabolite of di (2-ethylhexyl) phthalate (DEHP), can induce lipid metabolic disorder. Previous studies have shown that MEHP promotes 3T3-L1 cell differentiation; however, the underlying mechanism is unclear. The present study was performed to investigate the effect of the TYK-2/STAT-3 pathway on lipid accumulation induced by MEHP.

METHODS

A 3T3-L1 precursor adipocyte differentiation model was exposed to MEHP. 3-Isobutyl-1-methylxanthine (IBMX), dexamethasone (DEX), and insulin were used to establish the 3T3-L1 precursor adipocyte differentiation model. Then the model cells were exposed to MEHP for 8 d. The lipid droplet formation in 3T3-L1 cells was determined with Oil-Red-O staining, and isopropyl alcohol was used to extract the lipid droplets for quantification. Flow cytometry was used to detect the intracellular reactive oxygen species (ROS) and mitochondrial membrane potential. Quantitative real-time polymerase chain reaction (qPCR) was used to detect mRNA expression, and western blotting was used to detect the expression of proteins encoded by TYK-2/STAT-3 pathway genes and adipogenesis-related genes.

RESULTS

MEHP treatment, compared with the control treatment, significantly promoted the differentiation of 3T3-L1 cells and increased the expression of STAT-3 mRNA and protein and P-STAT3 protein in the cells. In addition, MEHP down-regulated the phosphorylation of STAT-3 in mitochondria. MEHP was found to influence the mitochondrial membrane potential and intracellular ROS levels.

CONCLUSION

MEHP may affect adipocyte differentiation and lead to lipid accumulation through the TYK-2/STAT-3 pathway.

STAT3 suppresses Wnt/β-catenin signaling during the induction phase of primary Myf5+ brown adipogenesis

Thermogenic fat is a promising target for new therapies in diabetes and obesity. Understanding how thermogenic fat develops is important to develop rational strategies to treat obesity. Previously, we have shown that Tyk2 and STAT3, part of the JAK-STAT pathway, are necessary for proper development of classical brown fat. Using primary preadipocytes isolated from newborn mice we demonstrate that STAT3 is required for differentiation and robust expression of Uncoupling Protein 1 (UCP1). We also confirm that STAT3 is necessary during the early induction stage of differentiation and is dispensable during the later terminal differentiation stage. The inability of STAT3-/- preadipocytes to differentiate can be rescued using Wnt ligand secretion inhibitors when applied during the induction stage. Through chemical inhibition and RNAi, we show that it is the canonical β-catenin pathway that is responsible for the block in differentiation; inhibition or knockdown of β-catenin can fully rescue adipogenesis and UCP1 expression in the STAT3-/- adipocytes. During the induction stage, Wnts 1, 3a, and 10b have increased expression in the STAT3-/- adipocytes, potentially explaining the increased levels and activity of β-catenin. Our results for the first time point towards an interaction between the JAK/STAT pathway and the Wnt/β-catenin pathway during the early stages of in-vitro adipogenesis.

LY3009120, a pan-Raf kinase inhibitor, inhibits adipogenesis of 3T3-L1 cells by controlling the expression and phosphorylation of C/EBP-α, PPAR-γ, STAT‑3, FAS, ACC, perilipin A, and AMPK

Excessive preadipocyte differentiation/adipogenesis is closely linked to the development of obesity. LY3009120 is a pan‑Raf kinase inhibitor and is known for its anticancer activities. In the present study, the effect of LY3009120 on 3T3‑L1 cell adipogenesis was investigated. The differentiation of 3T3‑L1 preadipocytes into adipocytes was measured by Oil Red O staining and AdipoRed assay. Changes of cellular protein expression and phosphorylation levels in differentiating 3T3‑L1 preadipocytes in the absence or presence of LY3009120 were determined by western blotting analysis. Cell count assay was used to assess the cytotoxicity of LY3009120 on 3T3‑L1 cells. At 0.3 µM, LY3009120 markedly inhibited lipid accumulation and decreased triglyceride content in differentiating 3T3‑L1 cells. However, it had minimal effect on the elevated expression and phosphorylation of three Raf kinase isoforms (C‑Raf, A‑Raf, and B‑Raf) observed in the cells. LY3009120 reduced not only the expression of CCAAT/enhancer‑binding protein‑α (C/EBP‑α), peroxisome proliferator‑activated receptor‑γ (PPAR‑γ), fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), and perilipin A, but also reduced the phosphorylation of signal transducer and activator of transcription‑3 (STAT‑3) in differentiating 3T3‑L1 cells. LY3009120 also increased the phosphorylation of adenosine 3',5'‑cyclic monophosphate (cAMP)‑activated protein kinase (AMPK), but did not affect the phosphorylation or expression of liver kinase B1 in these cells. In summary, this is the first report, to the best of our knowledge, demonstrating that LY3009120 has an anti‑adipogenic effect on 3T3‑L1 cells, which may be mediated through control of the expression and phosphorylation of C/EBP‑α, PPAR‑γ, STAT‑3, FAS, ACC, perilipin A, and AMPK.

The fruits of Gleditsia sinensis Lam. inhibits adipogenesis through modulation of mitotic clonal expansion and STAT3 activation in 3T3-L1 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Gleditsia sinensis Lam. (G. sinensis) has been used in Oriental medicine for tumor, thrombosis, inflammation-related disease, and obesity.

AIM OF THE STUDY

The pharmacological inhibitory effects of fruits of G. sinensis (GFE) on hyperlipidemia have been reported, but its inhibitory effects on adipogenesis and underlying mechanisms have not been elucidated. Herein we evaluated the anti-adipogenic effects of GFE and described the underlying mechanisms.

MATERIALS AND METHODS

The effects of ethanol extracts of GFE on adipocyte differentiation were examined in 3T3-L1 cells using biochemical and molecular analyses.

RESULTS

During the differentiation of 3T3-L1 cells, GFE significantly reduced lipid accumulation and downregulated master adipogenic transcription factors, including CCAAT/enhancer-binding protein-α and peroxisome proliferator-activated receptor-γ, at mRNA and protein levels. These changes led to the suppression of several adipogenic-specific genes and proteins, including fatty acid synthase, sterol regulatory element-binding protein 1, stearoyl-CoA desaturase-1, and acetyl CoA carboxylase. However, the inhibitory effects of GFE on lipogenesis were only shown when GFE is treated in the early stage of adipogenesis within the first two days of differentiation. As a potential mechanism, during the early stages of differentiation, GFE inhibited cell proliferation by a decrease in the expression of DNA synthesis-related proteins and increased p27 expression and suppressed signal transducer and activator of transcription 3 (STAT3) activation induced in a differentiation medium.

CONCLUSIONS

GFE inhibits lipogenesis by negative regulation of adipogenic transcription factors, which is associated with GFE-mediated cell cycle arrest and STAT3 inhibition.

Jak-TGFβ cross-talk links transient adipose tissue inflammation to beige adipogenesis

The transient activation of inflammatory networks is required for adipose tissue remodeling including the "browning" of white fat in response to stimuli such as β3-adrenergic receptor activation. In this process, white adipose tissue acquires thermogenic characteristics through the recruitment of so-called beige adipocytes. We investigated the downstream signaling pathways impinging on adipocyte progenitors that promote de novo formation of adipocytes. We showed that the Jak family of kinases controlled TGFβ signaling in the adipose tissue microenvironment through Stat3 and thereby adipogenic commitment, a function that was required for beige adipocyte differentiation of murine and human progenitors. Jak/Stat3 inhibited TGFβ signaling to the transcription factors Srf and Smad3 by repressing local Tgfb3 and Tgfb1 expression before the core transcriptional adipogenic cascade was activated. This pathway cross-talk was triggered in stromal cells by ATGL-dependent adipocyte lipolysis and a transient wave of IL-6 family cytokines at the onset of adipose tissue remodeling induced by β3-adrenergic receptor stimulation. Our results provide insight into the activation of adipocyte progenitors and are relevant for the therapeutic targeting of adipose tissue inflammatory pathways.

STAT3: The art of multi-tasking of metabolic and immune functions in obesity

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that has recently attracted increased attention. Accumulating studies have demonstrated that STAT3 plays an important role in various diseases, such as cancer and ischemic injury. In light of the distinctive effects of STAT3 on the regulation of metabolism and immune responses, we present the elaborate network of STAT3 in obesity. In this review, we first introduce the general background of STAT3, including a discussion regarding the STAT family and the characterization and regulation of STAT3. Then, we describe the STAT3 signaling network and its pathophysiological roles in lipid and glucose metabolism and immune function. Finally, we highlight the research progress regarding STAT3 in obesity. The information presented here may be useful for the design of future studies and may highlight the potential of STAT3 as a future therapeutic target for obesity.

AZD1208, a pan-Pim kinase inhibitor, inhibits adipogenesis and induces lipolysis in 3T3-L1 adipocytes

The proviral integration moloney murine leukaemia virus (Pim) kinases, consisting of Pim-1, Pim-2 and Pim-3, are involved in the control of cell growth, metabolism and differentiation. Pim kinases are emerging as important mediators of adipocyte differentiation. AZD1208 is a pan-Pim kinase inhibitor and is known for its anti-cancer activity. In this study, we investigated the effect of AZD1208 on adipogenesis and lipolysis in 3T3-L1 cells, a murine preadipocyte cell line. AZD1208 markedly suppressed lipid accumulation and reduced triglyceride contents in differentiating 3T3-L1 cells, suggesting the drug's anti-adipogenic effect. On mechanistic levels, AZD1208 reduced not only the expressions of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC) and perilipin A but also the phosphorylation of signal transducer and activator of transcription-3 (STAT-3) in differentiating 3T3-L1 cells. Remarkably, AZD1208 increased cAMP-activated protein kinase (AMPK) and LKB-1 phosphorylation while decreased intracellular ATP contents in differentiating 3T3-L1 cells. Furthermore, in differentiated 3T3-L1 adipocytes, AZD1208 also partially promoted lipolysis and enhanced the phosphorylation of hormone-sensitive lipase (HSL), a key lipolytic enzyme, indicating the drug's HSL-dependent lipolysis. In summary, the findings show that AZD1208 has anti-adipogenic and lipolytic effects on 3T3-L1 adipocytes. These effects are mediated by the expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, ACC, perilipin A, STAT-3, AMPK and HSL.

Ginsenoside Rg5: Rk1 Exerts an Anti-obesity Effect on 3T3-L1 Cell Line by the Downregulation of PPARγ and CEBPα

Background: Obesity, a global health problem and a chronic disease, is associated with increased risk of developing type 2 diabetes and coronary heart diseases. A wide variety of natural remedies have been explored for their obesity treatment potential. Objective: The anti-adipogenic effect of ginsenoside Rg5:Rk1 (Rg5:Rk1) on 3T3-L1 mature adipocytes was investigated. Materials and Methods: To elucidate the anti-obesity effect of Rg5:Rk1, a mixture of protopanaxadiol type ginsenosides isolated from Panax ginseng Meyer in a 3T3-L1 adipocytes. In order to determine the anti-obesity effect of Rg5:Rk1, based on oil Red O Staining, triglyceride (TG) content in adipose cells was assessed. Furthermore, to elucidate the possible mechanism of Rg5:RK1 effect on lipid accumulation, mRNA and protein expression analyses of adipocyte markers such as STAT3, PPARγ, CBEPα and ap2 were carried out. Results: Rg5:Rk1 treatment showed an inhibition of lipid droplet accumulation and decrease of TG content. In addition, expression of STAT3, PPARγ, CEBPα and ap2 were decreased in a dose dependent manner. Similarly, the Rg5:Rk1 treatment reduced PPARγ and CEBPα protein expression. Conclusion: Rg5:Rk1 treatment exhibits anti-adipogenic activity by down-regulation of the STAT3/ PPARg/CEBPa signaling pathway in 3T3-L1 adipocyte cell line.

Identification of zinc finger protein Bcl6 as a novel regulator of early adipose commitment

Adipose tissue is a key determinant of whole-body metabolism and energy homeostasis. Unravelling the transcriptional regulatory process during adipogenesis is therefore highly relevant from a biomedical perspective. In these studies, zinc finger protein B-cell lymphoma 6 (Bcl6) was demonstrated to have a role in early adipogenesis of mesenchymal stem cells. Bcl6 is enriched in preadipose versus non-preadipose fibroblasts and shows upregulated expression in the early stage of adipogenesis. Gain- and loss-of-function studies revealed that Bcl6 acts as a key regulator of adipose commitment and differentiation both in vitro and ex vivo. RNAi-mediated knockdown of Bcl6 in C3H10T1/2 cells greatly inhibited adipogenic potential, whereas Bcl6 overexpression enhanced adipogenic differentiation. This transcription factor also directly or indirectly targets and controls the expression of some early and late adipogenic regulators (i.e. Zfp423, Zfp467, KLF15, C/EBPδ, C/EBPα and PPARγ). We further identified that Bcl6 transactivated the signal transducers and activators of transcription 1 (STAT1), which was determined as a required factor for adipogenesis. Moreover, overexpression of STAT1 rescued the impairment of adipogenic commitment and differentiation induced by Bcl6 knockdown in C3H10T1/2 cells, thereby confirming that STAT1 is a downstream direct target of Bcl6. This study identifies Bcl6 as a positive transcriptional regulator of early adipose commitment.