PPARγ and the global map of adipogenesis and beyond

Di-(2-ethylhexyl) phthalate substitutes accelerate human adipogenesis through PPARγ activation and cause oxidative stress and impaired metabolic homeostasis in mature adipocytes

The obesity pandemic is presumed to be accelerated by endocrine disruptors such as phthalate-plasticizers, which interfere with adipose tissue function. With the restriction of the plasticizer di-(2-ethylhexyl)-phthalate (DEHP), the search for safe substitutes gained importance. Focusing on the master regulator of adipogenesis and adipose tissue functionality, the peroxisome proliferator-activated receptor gamma (PPARγ), we evaluated 20 alternative plasticizers as well as their metabolites for binding to and activation of PPARγ and assessed effects on adipocyte lipid accumulation. Among several compounds that showed interaction with PPARγ, the metabolites MINCH, MHINP, and OH-MPHP of the plasticizers DINCH, DINP, and DPHP exerted the highest adipogenic potential in human adipocytes. These metabolites and their parent plasticizers were further analyzed in human preadipocytes and mature adipocytes using cellular assays and global proteomics. In preadipocytes, the plasticizer metabolites significantly increased lipid accumulation, enhanced leptin and adipsin secretion, and upregulated adipogenesis-associated markers and pathways, in a similar pattern to the PPARγ agonist rosiglitazone. Proteomics of mature adipocytes revealed that both, the plasticizers and their metabolites, induced oxidative stress, disturbed lipid storage, impaired metabolic homeostasis, and led to proinflammatory and insulin resistance promoting adipokine secretion. In conclusion, the plasticizer metabolites enhanced preadipocyte differentiation, at least partly mediated by PPARγ activation and, together with their parent plasticizers, affected the functionality of mature adipocytes similar to reported effects of a high-fat diet. This highlights the need to further investigate the currently used plasticizer alternatives for potential associations with obesity and the metabolic syndrome.

Adipocyte CD1d Gene Transfer Induces T Cell Expansion and Adipocyte Inflammation in CD1d Knockout Mice

CD1d, a lipid Ag-presenting molecule for invariant NKT (iNKT) cells, is abundantly expressed on adipocytes and regulates adipose homeostasis through iNKT cells. CD1d gene expression was restored in visceral adipose tissue adipocytes of CD1d knockout (KO) mice to investigate the interactions between adipocytes and immune cells within adipose tissue. We developed an adipocyte-specific targeting recombinant adeno-associated viral vector, with minimal off-target transgene expression in the liver, to rescue CD1d gene expression in visceral adipose tissue adipocytes of CD1d KO mice, followed by assessment of immune cell alternations in adipose tissue and elucidation of the underlying mechanisms of alteration. We report that adeno-associated virus-mediated gene transfer of CD1d to adipocytes in CD1d KO mice fails to rescue iNKT cells but leads to massive and selective expansion of T cells within adipose tissue, particularly CD8⁺ T effector cells, that is associated with adipocyte NLRP3 inflammasome activation, dysregulation of adipocyte functional genes, and upregulation of apoptotic pathway proteins. An NLRP3 inhibitor has no effect on T cell phenotypes whereas depletion of CD8⁺ T cells significantly attenuates inflammasome activation and abolishes the dysregulation of adipocyte functional genes induced by adipocyte CD1d. In contrast, adipocyte overexpression of CD1d fails to induce T cell activation in wild-type mice or in invariant TCR α-chain Jα18 KO mice that have a normal lymphocyte repertoire except for iNKT cells. Our studies uncover an adipocyte CD1d → CD8⁺ T cell → adipocyte inflammasome cascade, in which CD8⁺ T cells function as a key mediator of adipocyte inflammation likely induced by an allogeneic response against the CD1d molecule.

P2X7 Activation Enhances Lipid Accumulation During Adipocytes Differentiation Through Suppressing the Expression of Sirtuin-3, Sirtuin-5, and Browning Genes

P2X7 signaling has been explored in adipose tissue because of its potential to promote ATP-activated inflammatory cascades during obesogenic environments. However, limited literature has investigated the role of the P2X7 receptor in lipid metabolism during adipocyte differentiation. This study sought to explore the regulatory roles of P2X7 in adipocytes. This study utilized the in vitro 3T3-L1 differentiation model. Lipid accumulation, intracellular triglyceride, and extracellular glycerol were determined. The selective P2X7 agonist BzATP and antagonist A438079 were administered to investigate the functions of P2X7. We found that the expression of P2X7 and the lipid accumulation increased during adipocyte differentiation from D0 to D4. When administered at D0/D2, A438079 attenuated, while BzATP enhanced the degree of lipid accumulation during adipocyte differentiation. Neither did BzATP and A438079 administration affect the expression of PPARγ and C/EBPα genes that increased at D4. In addition, both intracellular triglyceride and extracellular glycerol levels at D4 were reduced by A438079 treatment and enhanced by BzATP administration. When administered at stage 2 of adipocyte differentiation, BzATP consistently enhanced lipid accumulation and intracellular triglyceride and extracellular glycerol levels without affecting mRNA and protein levels of PPARγ and C/EBPα that increased at D4. However, treating A438079 or BzATP at D4 did not affect intracellular triglyceride formation and extracellular glycerol release in differentiated adipocytes at D7. Notably, BzATP administration at stage 2 exerted a concentration-dependent inhibition on the enhanced expression of PRDM16, PGC-1α, and UCP-1 at D4. Furthermore, BzATP administration at D0/D2 inhibited the protein and mRNA levels of sirtuin-3/5 at D4. BzATP treatment at stage 2 also suppressed the mRNA levels of sirtuin-3/5 genes upregulated by insulin. In conclusion, this study demonstrated P2X7 enhances lipid accumulation during adipogenesis by suppressing the expression of sirtuin-3/5 and the browning genes.

Novel Bacillus ginsengihumi CMRO6 Inhibits Adipogenesis via p38MAPK/Erk44/42 and Stimulates Glucose Uptake in 3T3-L1 Pre-Adipocytes through Akt/AS160 Signaling

The health benefits of probiotics have been known for decades, but there has only been limited use of probiotics in the treatment of obesity. In this study, we describe, for the first time, the role of cell-free metabolites (CM) from Bacillus ginsengihumi-RO6 (CMRO6) in adipogenesis and lipogenesis in 3T3-L1 pre-adipocytes. The experimental results show that CMRO6 treatment effectively reduced lipid droplet accumulation and the expression of CCAAT/enhancer-binding protein α and β (C/EBPα and C/EBPβ), peroxisome proliferator-activated receptor γ (PPAR-γ), serum regulatory binding protein 1c (SREBP-1c), fatty acid-binding protein 4 (FABP4), fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), phosphorylated p38MAPK, and Erk44/42. Additionally, CMRO6 treatment significantly increased glucose uptake and phosphorylated Akt (S473), AS160, and TBC1D1 protein expressions. Considering the results of this study, B. ginsengihumi may be a novel probiotic used for the treatment of obesity and its associated metabolic disorders.

USP22 regulates lipidome accumulation by stabilizing PPARγ in hepatocellular carcinoma

Elevated de novo lipogenesis is considered to be a crucial factor in hepatocellular carcinoma (HCC) development. Herein, we identify ubiquitin-specific protease 22 (USP22) as a key regulator for de novo fatty acid synthesis, which directly interacts with deubiquitinates and stabilizes peroxisome proliferator-activated receptor gamma (PPARγ) through K48-linked deubiquitination, and in turn, this stabilization increases acetyl-CoA carboxylase (ACC) and ATP citrate lyase (ACLY) expressions. In addition, we find that USP22 promotes de novo fatty acid synthesis and contributes to HCC tumorigenesis, however, this tumorigenicity is suppressed by inhibiting the expression of PPARγ, ACLY, or ACC in in vivo tumorigenesis experiments. In HCC, high expression of USP22 positively correlates with PPARγ, ACLY or ACC expression, and associates with a poor prognosis. Taken together, we identify a USP22-regulated lipogenesis mechanism that involves the PPARγ-ACLY/ACC axis in HCC tumorigenesis and provide a rationale for therapeutic targeting of lipogenesis via USP22 inhibition.

Different deubiquitinases are associated to cancer development. Here, the authors show that PPARgamma is stabilized by USP22-mediated deubiquitination leading to lipid accumulation and promoting hepatocellular carcinoma.

Molecular mechanisms of aberrant neutrophil differentiation in glycogen storage disease type Ib

Glycogen storage disease type Ib (GSD-Ib), characterized by impaired glucose homeostasis, neutropenia, and neutrophil dysfunction, is caused by a deficiency in glucose-6-phosphate transporter (G6PT). Neutropenia in GSD-Ib has been known to result from enhanced apoptosis of neutrophils. However, it has also been raised that neutrophil maturation arrest in the bone marrow would contribute to neutropenia. We now show that G6pt-/- mice exhibit severe neutropenia and impaired neutrophil differentiation in the bone marrow. To investigate the role of G6PT in myeloid progenitor cells, the G6PT gene was mutated using CRISPR/Cas9 system, and single cell-derived G6PT-/- human promyelocyte HL-60 cell lines were established. The G6PT-/- HL-60s exhibited impaired neutrophil differentiation, which is associated with two mechanisms: (i) abnormal lipid metabolism causing a delayed metabolic reprogramming and (ii) reduced nuclear transcriptional activity of peroxisome proliferator-activated receptor-γ (PPARγ) in G6PT-/- HL-60s. In this study, we demonstrated that G6PT is essential for neutrophil differentiation of myeloid progenitor cells and regulates PPARγ activity.

Heme oxygenase-1 induction by gallic acid-g-chitosan is an important event in modulating adipocyte differentiation

Obesity, one of the common worldwide chronic health diseases co-relates with adipogenesis. Adipogenesis is a complex biological action of the emergence of mature adipocytes from the differentiation of pre-adipocytes and the disfunction of this process leads to the development of metabolic issues in obesity. Recently, much attention has been paid to utilizing natural compounds to discover their biological activities. This study focused on investigating the probable anti-adipogenic effects of gallic acid-g-chitosan (GAC) and plain chitosan (PC) through regulating the heme oxygenase-1 (HO-1)/Nrf2 pathway on mesenchymal stem cells. Gallic acid is grafted onto the PC backbone to improve its specific physical and biological properties. GAC showed promising anti-adipogenic effects by enhancing HO-1 expression and lipolysis and as well as suppressing lipid accumulation, reactive oxygen species, and pro-inflammatory cytokines production, transcription factor expression compared to the PC treatment. On the contrary, zinc protoporphyrin ІX (ZnPP), a HO-1 inhibitor reversed these effects of GAC on adipogenesis. Taken all together, this study revealed that grafting GA onto the chitosan improved potential anti-adipogenic activity by induction of the HO-1/Nrf2 pathway on mesenchymal stem cells (MSCs). PRACTICAL APPLICATIONS: GAC is a well-known copolymer with versatile bioactivities such as antimicrobial, antioxidant, and anti-diabetic activity. However, the anti-adipogenic effect of GAC has not been explored in MSCs. This study demonstrated that GAC inhibited adipocyte differentiation in MSCs through HO-1 activation. These findings suggest that GAC can be applied practically from different perspectives. GAC can be applied in the pharmacological industry to the development of anti-obesity drugs, medicinal perspectives for the treatment of obesity and obesity-related diseases, and in the food industry as a functional food to promote health and decrease the risk of diseases.

Lipid Metabolism: Immune Regulation and Therapeutic Prospectives in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous disease characterized by the production of abnormal autoantibodies and immune complexes that can affect the organ and organ systems, particularly the kidneys and the cardiovascular system. Emerging evidence suggests that dysregulated lipid metabolism, especially in key effector cells, such as T cells, B cells, and innate immune cells, exerts complex effects on the pathogenesis and progression of SLE. Beyond their important roles as membrane components and energy storage, different lipids can also modulate different cellular processes, such as proliferation, differentiation, and survival. In this review, we summarize altered lipid metabolism and the associated mechanisms involved in the pathogenesis and progression of SLE. Furthermore, we discuss the recent progress in the role of lipid metabolism as a potential therapeutic target in SLE.

Isoform-specific functions of PPARγ in gene regulation and metabolism

In this study, Hu et al. investigated the specific functions of the two main PPARγ isoforms by generating mouse lines in which endogenous PPARγ1 and PPARγ2 were epitope-tagged to interrogate isoform-specific genomic binding, and mice deficient in either PPARγ1 or PPARγ2 to assess isoform-specific gene regulation. They show that PPARγ isoforms have specific and separable metabolic functions that may be targeted to improve therapy for insulin resistance and diabetes.

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor that is a vital regulator of adipogenesis, insulin sensitivity, and lipid metabolism. Activation of PPARγ by antidiabetic thiazolidinediones (TZD) reverses insulin resistance but also leads to weight gain that limits the use of these drugs. There are two main PPARγ isoforms, but the specific functions of each are not established. Here we generated mouse lines in which endogenous PPARγ1 and PPARγ2 were epitope-tagged to interrogate isoform-specific genomic binding, and mice deficient in either PPARγ1 or PPARγ2 to assess isoform-specific gene regulation. Strikingly, although PPARγ1 and PPARγ2 contain identical DNA binding domains, we uncovered isoform-specific genomic binding sites in addition to shared sites. Moreover, PPARγ1 and PPARγ2 regulated a different set of genes in adipose tissue depots, suggesting distinct roles in adipocyte biology. Indeed, mice with selective deficiency of PPARγ1 maintained body temperature better than wild-type or PPARγ2-deficient mice. Most remarkably, although TZD treatment improved glucose tolerance in mice lacking either PPARγ1 or PPARγ2, the PPARγ1-deficient mice were protected from TZD-induced body weight gain compared with PPARγ2-deficient mice. Thus, PPARγ isoforms have specific and separable metabolic functions that may be targeted to improve therapy for insulin resistance and diabetes.

Characterization of a Read-through Fusion Transcript, BCL2L2-PABPN1, Involved in Porcine Adipogenesis

cis-Splicing of adjacent genes (cis-SAGe) has been involved in multiple physiological and pathological processes in humans. However, to the best of our knowledge, there is no report of cis-SAGe in adipogenic regulation. In this study, a cis-SAGe product, BCL2L2–PABPN1 (BP), was characterized in fat tissue of pigs with RT-PCR and RACE method. BP is an in-frame fusion product composed of 333 aa and all the functional domains of both parents. BP is highly conserved among species and rich in splicing variants. BP was found to promote proliferation and inhibit differentiation of primary porcine preadipocytes. A total of 3074/44 differentially expressed mRNAs (DEmRs)/known miRNAs (DEmiRs) were identified in porcine preadipocytes overexpressing BP through RNA-Seq analysis. Both DEmRs and target genes of DEmiRs were involved in various fat-related pathways with MAPK and PI3K-Akt being the top enriched. PPP2CB, EGFR, Wnt5A and EHHADH were hub genes among the fat-related pathways identified. Moreover, ssc-miR-339-3p was found to be critical for BP regulating adipogenesis through integrated analysis of mRNA and miRNA data. The results highlight the role of cis-SAGe in adipogenesis and contribute to further revealing the mechanisms underlying fat deposition, which will be conductive to human obesity control.

Higher Expression of DNA (de)methylation-Related Genes Reduces Adipogenicity in Dental Pulp Stem Cells

Obesity is a significant health concern that has reached alarming proportions worldwide. The overconsumption of high-energy foods may cause metabolic dysfunction and promote the generation of new adipocytes by contributing to several obesity-related diseases. Such concerns demand a deeper understanding of the origin of adipocytes if we want to develop new therapeutic approaches. Recent findings indicate that adipocyte development is facilitated by tight epigenetic reprogramming, which is required to activate the gene program to change the fate of mesenchymal stem cells (MSCs) into mature adipocytes. Like adipose tissue, different tissues are also potential sources of adipocyte-generating MSCs, so it is interesting to explore whether the epigenetic mechanisms of adipogenic differentiation vary from one depot to another. To investigate how DNA methylation (an epigenetic mark that plays an essential role in controlling transcription and cellular differentiation) contributes to adipogenic potential, dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PLSCs) were analyzed during adipogenic differentiation in vitro. Here, we show that the capacity to differentiate from DPSCs or PLSCs to adipocytes may be associated with the expression pattern of DNA methylation-related genes acquired during the induction of the adipogenic program. Our study provides insights into the details of DNA methylation during the adipogenic determination of dental stem cells, which can be a starting point to identify the factors that affect the differentiation of these cells and provide new strategies to regulate differentiation and adipocyte expansion.

Regulatory mechanisms of the early phase of white adipocyte differentiation: an overview

The adipose organ comprises two main fat depots termed white and brown adipose tissues. Adipogenesis is a process leading to newly differentiated adipocytes starting from precursor cells, which requires the contribution of many cellular activities at the genome, transcriptome, proteome, and metabolome levels. The adipogenic program is accomplished through two sequential phases; the first includes events favoring the commitment of adipose tissue stem cells/precursors to preadipocytes, while the second involves mechanisms that allow the achievement of full adipocyte differentiation. While there is a very large literature about the mechanisms involved in terminal adipogenesis, little is known about the first stage of this process. Growing interest in this field is due to the recent identification of adipose tissue precursors, which include a heterogenous cell population within different types of adipose tissue as well as within the same fat depot. In addition, the alteration of the heterogeneity of adipose tissue stem cells and of the mechanisms involved in their commitment have been linked to adipose tissue development defects and hence to the onset/progression of metabolic diseases, such as obesity. For this reason, the characterization of early adipogenic events is crucial to understand the etiology and the evolution of adipogenesis-related pathologies, and to explore the adipose tissue precursors’ potential as future tools for precision medicine.

Antimicrobial production by perifollicular dermal preadipocytes is essential to the pathophysiology of acne

Innate immune defense against deep tissue infection by Staphylococcus aureus is orchestrated by fibroblasts that become antimicrobial when triggered to differentiate into adipocytes. However, the role of this process in noninfectious human diseases is unknown. To investigate the potential role of adipogenesis by dermal fibroblasts in acne, a disorder triggered by Cutibacterium acnes, single-cell RNA sequencing was performed on human acne lesions and mouse skin challenged by C. acnes. A transcriptome consistent with adipogenesis was observed within specific fibroblast subsets from human acne and mouse skin lesions infected with C. acnes. Perifollicular dermal preadipocytes in human acne and mouse skin lesions showed colocalization of PREF1, an early marker of adipogenesis, and cathelicidin (Camp), an antimicrobial peptide. This capacity of C. acnes to specifically trigger production of cathelicidin in preadipocytes was dependent on TLR2. Treatment of wild-type mice with retinoic acid (RA) suppressed the capacity of C. acnes to form acne-like lesions, inhibited adipogenesis, and enhanced cathelicidin expression in preadipocytes, but lesions were unresponsive in Camp^-/- mice, despite the anti-adipogenic action of RA. Analysis of inflamed skin of acne patients after retinoid treatment also showed enhanced induction of cathelicidin, a previously unknown beneficial effect of retinoids in difficult-to-treat acne. Overall, these data provide evidence that adipogenic fibroblasts are a critical component of the pathogenesis of acne and represent a potential target for therapy.

Adipose-tissue plasticity in health and disease

Adipose tissue, colloquially known as "fat," is an extraordinarily flexible and heterogeneous organ. While historically viewed as a passive site for energy storage, we now appreciate that adipose tissue regulates many aspects of whole-body physiology, including food intake, maintenance of energy levels, insulin sensitivity, body temperature, and immune responses. A crucial property of adipose tissue is its high degree of plasticity. Physiologic stimuli induce dramatic alterations in adipose-tissue metabolism, structure, and phenotype to meet the needs of the organism. Limitations to this plasticity cause diminished or aberrant responses to physiologic cues and drive the progression of cardiometabolic disease along with other pathological consequences of obesity.

The Role of Persistent Organic Pollutants in Obesity: A Review of Laboratory and Epidemiological Studies

Persistent organic pollutants (POPs) are considered as potential obesogens that may affect adipose tissue development and functioning, thus promoting obesity. However, various POPs may have different mechanisms of action. The objective of the present review is to discuss the key mechanisms linking exposure to POPs to adipose tissue dysfunction and obesity. Laboratory data clearly demonstrate that the mechanisms associated with the interference of exposure to POPs with obesity include: (a) dysregulation of adipogenesis regulators (PPARγ and C/EBPα); (b) affinity and binding to nuclear receptors; (c) epigenetic effects; and/or (d) proinflammatory activity. Although in vivo data are generally corroborative of the in vitro results, studies in living organisms have shown that the impact of POPs on adipogenesis is affected by biological factors such as sex, age, and period of exposure. Epidemiological data demonstrate a significant association between exposure to POPs and obesity and obesity-associated metabolic disturbances (e.g., type 2 diabetes mellitus and metabolic syndrome), although the existing data are considered insufficient. In conclusion, both laboratory and epidemiological data underline the significant role of POPs as environmental obesogens. However, further studies are required to better characterize both the mechanisms and the dose/concentration-response effects of exposure to POPs in the development of obesity and other metabolic diseases.

Latexin deficiency attenuates adipocyte differentiation and protects mice against obesity and metabolic disorders induced by high-fat diet

Obesity is a risk factor for many chronic diseases, and is associated with increased incidence rate of type 2 diabetes, hypertension, dyslipidemia and cardiovascular diseases. Adipocyte differentiation play critical role during development of obesity. Latexin (LXN), a mammalian carboxypeptidase inhibitor, plays important role in the proliferation and differentiation of stem cells, and highlights as a differentiation-associated gene that was significantly downregulated in prostate stem cells and whose expression increases through differentiation. However, it is unclear whether LXN is involved in adipocyte differentiation. The aim of this study was to evaluate the role of LXN on adipocyte differentiation, as well as its effects on high fat-induced obesity and metabolic disorders. In this study, we determine the expression of LXN in adipose tissue of lean and fat mice by Western blot, qPCR and immunohistochemistry. We found that LXN in fat tissues was continuous increased during the development of diet-induced obesity. We fed wild-type (WT) and LXN−/−mice with high-fat diet (HFD) to study the effects of LXN on obesity and related metabolic functions. We found that mice deficient in LXN showed resistance against high-fat diet (HFD)-induced obesity, glucose tolerance, insulin tolerance and hepatic steatosis. In vitro studies indicated that LXN was highly induced during adipocyte differentiation, and positively regulated adipocyte differentiation and adipogenesis in 3T3-L1 cells and primary preadipocytes. Functional analysis revealed that the expression of LXN was positively regulated by mTOR/RXR/PPARɤ signaling pathway during the differentiation of adipocytes, while LXN deletion decreased the protein level of PPARɤ in adipocyte through enhancing FABP4 mediated ubiquitination, which led to impaired adipocyte differentiation and lipogenesis. Collectively, our data provide evidence that LXN is a key positive regulator of adipocyte differentiation, and therapeutics targeting LXN could be effective in preventing obesity and its associated disorders in clinical settings.

Silk ProteinsEnriched Nanocomposite Hydrogels Based on Modified MMT Clay and Poly(2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropane Sulfonic Acid) Display Favorable Properties for Soft Tissue Engineering

Due to their remarkable structures and properties, three-dimensional hydrogels and nanostructured clay particles have been extensively studied and have shown a high potential for tissue engineering as solutions for tissue defects. In this study, four types of 2-hydroxyethyl methacrylate/2-acrylamido-2-methylpropane sulfonic acid/montmorillonite (HEMA/AMPSA/MMT) hydrogels enriched with sericin, and fibroin were prepared and studied in the context of regenerative medicine for soft tissue regenerative medicine. Our aim was to obtain crosslinked hydrogel structures using modified montmorillonite clay as a crosslinking agent. In order to improve the in vitro and in vivo biocompatibility, silk proteins were further incorporated within the hydrogel matrix. Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) were performed to prove the chemical structures of the modified MMT and nanocomposite hydrogels. Swelling and rheological measurements showed the good elastic behavior of the hydrogels due to this unique network structure in which modified MMT acts as a crosslinking agent. Hydrogel biocompatibility was assessed by MTT, LDH and LIVE/DEAD assays. The hydrogels were evaluated for their potential to support adipogenesis in vitro and human stem cells isolated from adipose tissue were seeded in them and induced to differentiate. The progress was assessed by evaluation of expression of adipogenic markers (ppar-γ2, perilipin) evaluated by qPCR. The potential of the materials to support tissue regeneration was further evaluated on animal models in vivo. All materials proved to be biocompatible, with better results on the 95% HEMA 5% AMPSA enriched with sericin and fibroin material. This composition promoted a better development of adipogenesis compared to the other compositions studied, due the addition of sericin and fibroin. The results were confirmed in vivo as well, with a better progress of soft tissue regeneration after implantation in mice. Therefore, hydrogel 95% HEMA 5% AMPSA enriched with sericin as well as fibroin showed the best results that recommend it for future soft tissue engineering application.

Molecular mechanism of benzo [a] pyrene regulating lipid metabolism via aryl hydrocarbon receptor

Background

Benzo [a] pyrene (BaP), a potent carcinogen, has been proved that it has toxicological effects via activation the aryl hydrocarbon receptor (AhR) pathway. AhR can participate in regulating lipogenesis and lipolysis. This topic will verify whether BaP regulates lipid metabolism via AhR.

Methods

(1) C57BL/6 mice were gavaged with BaP for 12 weeks to detect serum lipids, glucose tolerance, and insulin resistance. Morphological changes in white adipose tissue (WAT) were detected by Hematoxylin and Eosin staining. The mRNA expression levels of adipogenesis-related factors included recombinant human CCAAT/enhancer binding protein alpha (C/EBPα), peroxisome proliferator-activated receptor gamma (PPARγ), and fatty acid binding protein 4 (FABP₄) and inflammatory factors included nuclear factor kappa-B (NF-κB), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor alpha (TNF-α) were detected using PCR. (2) Neutral lipid content changes in differentiated 3 T3-L1 adipocytes treated with BaP with and w/o AhR inhibitor were detected by Oil red staining. The protein expression levels of adipogenesis- and decomposition-related factors included PPARγ coactivator-1 alpha (PGC-1α), and peroxisome proliferation-activated receptor alpha (PPARα) were detected using western blotting. The mRNA expression levels of inflammatory factors were detected using PCR.

Results

(1) BaP inhibited body weight gain, decreased lipid content, increased lipid levels, and decreased glucose tolerance and insulin tolerance in mice; (2) BaP reduced the expressions of C/EBPα, PPARγ, FABP₄, PGC-1α, and PPARα and increased the expressions of NF-κB, MCP-1, and TNF-α by activating AhR.

Conclusion

BaP inhibit fat synthesis and oxidation while inducing inflammation by activating AhR, leading to WAT dysfunction and causing metabolic complications.

A Multitarget Approach to Evaluate the Efficacy of Aquilaria sinensis Flower Extract against Metabolic Syndrome

Aquilaria sinensis (Lour.) Spreng is known for its resinous secretion (agarwood), often secreted in defense against injuries. We investigated the effects of A. sinensis flower extract (AF) on peroxisome proliferator-activated receptors alpha and gamma (PPARα and PPARγ), liver X receptor (LXR), glucose uptake, and lipid accumulation (adipogenesis). Activation of PPARα, PPARγ and LXR was determined in hepatic (HepG2) cells by reporter gene assays. Glucose uptake was determined in differentiated muscle (C2C12) cells using 2-NBDG (2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-D-glucose). Adipogenesis was determined in adipocytes (3T3-L1 cells) by Oil red O staining. At a concentration of 50 µg/mL, AF caused 12.2-fold activation of PPARα and 5.7-fold activation of PPARγ, while the activation of LXR was only 1.7-fold. AF inhibited (28%) the adipogenic effect induced by rosiglitazone in adipocytes and increased glucose uptake (32.8%) in muscle cells at 50 μg/mL. It was concluded that AF acted as a PPARα/γ dual agonist without the undesired effect of adipogenesis and exhibited the property of enhancing glucose uptake. This is the first report to reveal the PPARα/γ dual agonistic action and glucose uptake enhancing property of AF along with its antiadipogenic effect, indicating its potential in ameliorating the symptoms of metabolic syndrome.

Bi-directional gene activation and repression promote ASC differentiation and enhance bone healing in osteoporotic rats

Calvarial bone healing is challenging, especially for individuals with osteoporosis because stem cells from osteoporotic patients are highly prone to adipogenic differentiation. Based on previous findings that chondrogenic induction of adipose-derived stem cells (ASCs) can augment calvarial bone healing, we hypothesized that activating chondroinductive Sox Trio genes (Sox5, Sox6, Sox9) and repressing adipoinductive genes (C/ebp-α, Ppar-γ) in osteoporotic ASCs can reprogram cell differentiation and improve calvarial bone healing after implantation. However, simultaneous gene activation and repression in ASCs is difficult. To tackle this problem, we built a CRISPR-BiD system for bi-directional gene regulation. Specifically, we built a CRISPR-AceTran system that exploited both histone acetylation and transcription activation for synergistic Sox Trio activation. We also developed a CRISPR interference (CRISPRi) system that exploited DNA methylation for repression of adipoinductive genes. We combined CRISPR-AceTran and CRISPRi to form the CRISPR-BiD system, which harnessed three mechanisms (transcription activation, histone acetylation, and DNA methylation). After delivery into osteoporotic rat ASCs, CRISPR-BiD significantly enhanced chondrogenesis and in vitro cartilage formation. Implantation of the engineered osteoporotic ASCs into critical-sized calvarial bone defects significantly improved bone healing in osteoporotic rats. These results implicated the potential of the CRISPR-BiD system for bi-directional regulation of cell fate and regenerative medicine.

Case Report: A New Peroxisome Proliferator-Activated Receptor Gamma Mutation Causes Familial Partial Lipodystrophy Type 3 in a Chinese Patient

PURPOSE

Familial partial lipodystrophy type 3 (FPLD3) is an autosomal dominant disease. Patients typically present with loss of adipose tissue and metabolic complications. Here, we reported a Chinese FPLD3 patient with a novel PPARG gene mutation.

METHODS

A 16-year-old female patient and her relatives were assessed by detailed clinical and biochemical examinations. Sequencing was performed by using the extracted DNA. Moreover, we identified FPLD3 patients from previous studies, and according to the protein region affected by the gene mutation. We divided the patients into the DNA-binding domain (DBD) group or the ligand-binding domain (LBD) group, and compared the clinical features between the two groups.

RESULTS

We identified a novel gene mutation affecting the LBD of PPARγ c.929T > C (p.F310S). This mutation leads to the substitution of a phenylalanine by a serine. In our case, subcutaneous fat was significantly diminished in her face, hips and limbs. The patient was also presented with insulin resistance, diabetes mellitus, hypertriglyceridemia, fatty liver, liver dysfunction, albuminuria and diabetic peripheral neuropathy. After literature review, a total of 58 FPLD3 patients were identified and we found no difference in clinical features between the DBD group and LBD group (all P > 0.05).

CONCLUSIONS

A Chinese FPLD3 patient with a novel PPARG gene mutation is described. Our case emphasized the importance of physical examination and genetic testing in young patients with severe metabolic syndromes.

Physiological Convergence and Antagonism Between GR and PPARγ in Inflammation and Metabolism

Nuclear receptors (NRs) are transcription factors that modulate gene expression in a ligand-dependent manner. The ubiquitously expressed glucocorticoid receptor (GR) and peroxisome proliferator-activated receptor gamma (PPARγ) represent steroid (type I) and non-steroid (type II) classes of NRs, respectively. The diverse transcriptional and physiological outcomes of their activation are highly tissue-specific. For example, in subsets of immune cells, such as macrophages, the signaling of GR and PPARγ converges to elicit an anti-inflammatory phenotype; in contrast, in the adipose tissue, their signaling can lead to reciprocal metabolic outcomes. This review explores the cooperative and divergent outcomes of GR and PPARγ functions in different cell types and tissues, including immune cells, adipose tissue and the liver. Understanding the coordinated control of these NR pathways should advance studies in the field and potentially pave the way for developing new therapeutic approaches to exploit the GR:PPARγ crosstalk.

OUP accepted manuscript

Tight control of gene expression networks required for adipose tissue formation and plasticity is essential for adaptation to energy needs and environmental cues. However, the mechanisms that orchestrate the global and dramatic transcriptional changes leading to adipocyte differentiation remain to be fully unraveled. We investigated the regulation of nascent transcription by the sumoylation pathway during adipocyte differentiation using SLAMseq and ChIPseq. We discovered that the sumoylation pathway has a dual function in differentiation; it supports the initial downregulation of pre-adipocyte-specific genes, while it promotes the establishment of the mature adipocyte transcriptional program. By characterizing endogenous sumoylome dynamics in differentiating adipocytes by mass spectrometry, we found that sumoylation of specific transcription factors like PPARγ/RXR and their co-factors are associated with the transcription of adipogenic genes. Finally, using RXR as a model, we found that sumoylation may regulate adipogenic transcription by supporting the chromatin occurrence of transcription factors. Our data demonstrate that the sumoylation pathway supports the rewiring of transcriptional networks required for formation of functional adipocytes. This study also provides the scientists in the field of cellular differentiation and development with an in-depth resource of the dynamics of the SUMO-chromatin landscape, SUMO-regulated transcription and endogenous sumoylation sites during adipocyte differentiation.

The Anti-Obesity Potential of Cyperus rotundus Extract Containing Piceatannol, Scirpusin A and Scirpusin B from Rhizomes: Preclinical and Clinical Evaluations

PURPOSE

Obesity is a complex medical problem that increases the risk of other diseases like diabetes, cardiovascular diseases, and fatty liver disease. The present study evaluated the efficacy and safety of Cyperus rotundus rhizome extract (CRE), standardized to contain Piceatannol, Scirpusin A, and Scirpusin B (5% total Stilbenoids) in overweight individuals. The mechanism of activity was evaluated in a diet-induced mice model of obesity and adipocytes in vitro.

MATERIALS AND METHODS

The efficacy, safety, and tolerability of CRE were evaluated in 30 obese individuals with a BMI of 30 to 40 kg/m² for 90 days in a randomized, double-blind, parallel-group, placebo-controlled study. In vitro studies were carried out in differentiated 3T3 L1 adipocytes, and the therapeutic efficacy was evaluated in high-fat diet-induced obese mice.

RESULTS

The pilot clinical study showed a reduction in body weight with a significant decrease in waist circumference and BMI. The serum lipid profile showed a significant improvement in CRE-treated individuals. The extract was well tolerated, and no adverse effects were reported at the end of the study. CRE showed a dose-dependent adipogenesis reduction in vitro with an IC₅₀ value of 9.39 μg/mL, while oral administration of CRE reduced weight gain in diet-induced obese mice. The efficacy in mice was associated with reduced levels of leptin, corticosteroids, and serum lipid levels, with no adverse effects.

CONCLUSION

CRE has anti-adipogenic properties, is safe for human consumption, and effectively manages weight and hypercholesterolemia in overweight individuals.

TNFα Mediates Inflammation-Induced Effects on PPARG Splicing in Adipose Tissue and Mesenchymal Precursor Cells

Low-grade chronic inflammation and reduced differentiation capacity are hallmarks of hypertrophic adipose tissue (AT) and key contributors of insulin resistance. We identified PPARGΔ5 as a dominant-negative splicing isoform overexpressed in the AT of obese/diabetic patients able to impair adipocyte differentiation and PPARγ activity in hypertrophic adipocytes. Herein, we investigate the impact of macrophage-secreted pro-inflammatory factors on PPARG splicing, focusing on PPARGΔ5. We report that the epididymal AT of LPS-treated mice displays increased PpargΔ5/cPparg ratio and reduced expression of Pparg-regulated genes. Interestingly, pro-inflammatory factors secreted from murine and human pro-inflammatory macrophages enhance the PPARGΔ5/cPPARG ratio in exposed adipogenic precursors. TNFα is identified herein as factor able to alter PPARG splicing—increasing PPARGΔ5/cPPARG ratio—through PI3K/Akt signaling and SRp40 splicing factor. In line with in vitro data, TNFA expression is higher in the SAT of obese (vs. lean) patients and positively correlates with PPARGΔ5 levels. In conclusion, our results indicate that inflammatory factors secreted by metabolically-activated macrophages are potent stimuli that modulate the expression and splicing of PPARG. The resulting imbalance between canonical and dominant negative isoforms may crucially contribute to impair PPARγ activity in hypertrophic AT, exacerbating the defective adipogenic capacity of precursor cells.

Cross-Tissue Characterization of Heterogeneities of Mesenchymal Stem Cells and Their Differentiation Potentials

Mesenchymal stem/stromal cells (MSCs) are promising cell sources for regenerative medicine and the treatment of autoimmune disorders. Comparing MSCs from different tissues at the single-cell level is fundamental for optimizing clinical applications. Here we analyzed single-cell RNA-seq data of MSCs from four tissues, namely umbilical cord, bone marrow, synovial tissue, and adipose tissue. We identified three major cell subpopulations, namely osteo-MSCs, chondro-MSCs, and adipo/myo-MSCs, across all MSC samples. MSCs from the umbilical cord exhibited the highest immunosuppression, potentially indicating it is the best immune modulator for autoimmune diseases. MSC subpopulations, with different subtypes and tissue sources, showed pronounced differences in differentiation potentials. After we compared the cell subpopulations and cell status pre-and-post chondrogenesis induction, osteogenesis induction, and adipogenesis induction, respectively, we found MSC subpopulations expanded and differentiated when their subtypes consist with induction directions, while the other subpopulations shrank. We identified the genes and transcription factors underlying each induction at the single-cell level and subpopulation level, providing better targets for improving induction efficiency.

Comprehensive Analysis of the Transcriptome-Wide m6A Methylation Modification Difference in Liver Fibrosis Mice by High-Throughput m6A Sequencing

N6-Methyladenosine (m6A), a unique and common mRNA modification method in eukaryotes, is involved in the occurrence and development of many diseases. Liver fibrosis (LF) is a common response to chronic liver injury and may lead to cirrhosis and even liver cancer. However, the involvement of m6A methylation in the development of LF is still unknown. In this study, we performed a systematic evaluation of hepatic genome-wide m6A modification and mRNA expression by m6A-seq and RNA-seq using LF mice. There were 3,315 genes with significant differential m6A levels, of which 2,498 were hypermethylated and 817 hypomethylated. GO and KEGG analyses illustrated that differentially expressed m6A genes were closely correlated with processes such as the endoplasmic reticulum stress response, PPAR signaling pathway and TGF-β signaling pathway. Moreover, a total of 90 genes had both a significant change in the m6A level and mRNA expression shown by joint analysis of m6A-seq and RNA-seq. Hence, the critical elements of m6A modification, including methyltransferase WTAP, demethylases ALKBH5 and binding proteins YTHDF1 were confirmed by RT-qPCR and Western blot. In an additional cell experiment, we also observed that the decreased expression of WTAP induced the development of LF as a result of promoting hepatic stellate cell (HSC) activation. Therefore, this study revealed unique differential m6A methylation patterns in LF mice and suggested that m6A methylation was associated with the occurrence and course of LF to some extent.

Effect of Actin Alpha Cardiac Muscle 1 on the Proliferation and Differentiation of Bovine Myoblasts and Preadipocytes

Simple Summary

Marbling is an important factor affecting the quality of beef. The co-culture (myoblast-preadipocytes) system was successfully established in our lab in the early stage to simulate the internal environment of marbling. Within this environment, ACTC1 gene was a differentially expressed gene screened from the co-culture system. The gene was not expressed in monocultured adipocytes but was expressed in co-cultured adipocytes. Therefore, we hypothesize that the ACTC1 gene plays a role in the development of bovine myoblasts and preadipocytes. In this study, we explored the effect of ACTC1 gene on the proliferation and differentiation of bovine myoblasts and preadipocytes, aiming to discover the potential biological function of ACTC1 gene in muscle development and fat deposition. The results showed that ACTC1 could regulate the development of bovine myoblasts and preadipocytes, and ACTC1 could be used as an important target for improving beef quality in the future.

Abstract

Actin Alpha Cardiac Muscle 1 (ACTC1) gene is a differentially expressed gene screened through the co-culture system of myoblasts-preadipocytes. In order to study the role of this gene in the process of proliferation and differentiation of bovine myoblasts and preadipocytes, the methods of the knockdown, overexpression, and ectopic expression of ACTC1 were used in this study. After ACTC1 knockdown in bovine myoblasts and inducing differentiation, the sizes and numbers of myotube formation were significantly reduced compared to the control group, and myogenic marker genes—MYOD1, MYOG, MYH3, MRF4, MYF5, CKM and MEF2A—were significantly decreased (p < 0.05, p < 0.01) at both the mRNA and protein levels of myoblasts at different differentiation stages (D0, D2, D4, D6 and D8). Conversely, ACTC1 overexpression induced the inverse result. After ectopic expression of ACTC1 in bovine preadipocytes and induced differentiation, the number and size of lipid droplets were significantly higher than those of the control group, and the expression of adipogenic marker genes—FABP4, SCD1, PPARγ and FASN—were significantly increased (p < 0.05, p < 0.01) at the mRNA and protein levels of preadipocytes at different differentiation stages. Flow cytometry results showed that both the knockdown and overexpression of ACTC1 inhibited the normal cell cycle of myoblasts; however, ectopic expression of ACTC1 in adipocytes induced no significant cell cycle changes. This study is the first to explore the role of ACTC1 in bovine myogenesis and lipogenesis and demonstrates that ACTC1 promotes the differentiation of bovine myoblasts and preadipocytes, affecting the proliferation of myoblasts.

PPAR-gamma agonists: Potential modulators of autophagy in obesity

Autophagy pathways are involved in the pathogenesis of some obesity related health problems. As obesity is a nutrient sufficiency condition, autophagy process can be altered in obesity through AMP activated protein kinase (AMPK) inhibition. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) as the main modulator of adipogenesis process can be effective in the regulation of obesity related phenotypes. As well, it has been revealed that PPAR-gamma and its agonists can regulate autophagy in different normal or cancer cells. However, their effects on autophagy modulation in obesity have been investigated in the limited number of studies. In the current comprehensive mechanistic review, we aimed to investigate the possible mechanisms of action of PPAR-gamma on the process of autophagy in obesity through narrating the effects of PPAR-gamma on autophagy in the non-obesity conditions. Moreover, mode of action of PPAR-gamma agonists on autophagy related implications comprehensively reviewed in the various studies. Understanding the different effects of PPAR-gamma agonists on autophagy in obesity can help to develop a new approach to management of obesity.

Bisphenol S promotes fat storage in multiple generations of Caenorhabditis elegans in a daf-16/nhr-49 dependent manner

Bisphenol S (BPS) has been gradually used in all kinds of productions. Our previous study has demonstrated that BPS increases the obesogenic effects of a high-glucose diet through regulating lipid metabolism in Caenorhabditis elegans (C. elegans). Whether the effects pass on to the next generations remains uncovered. In the present study, C. elegans was selected as the model organism to investigate the effects of BPS on lipid metabolism in multiple generations. Oil Red O staining and triglyceride assays showed that multi-generational exposure to BPS in C. elegans significantly increased the fat accumulation in wild type worms, while not in the daf-16 gene-deficient worms. In addition, BPS affected the expressions of fat-7 and acs-2 in four generations of C. elegans. Furthermore, BPS promotes fat storage in C. elegans of multiple generations by the daf-16/nhr-49-mediated signaling pathway.

Dietary copper supplementation enhances lipolysis in Rex rabbits

BACKGROUND

Copper is an important regulator of lipid metabolism in mammals, as a cofactor of many enzymes and is involved in the lipolysis. Copper deficiency has been considered as a significant factor in human diseases related to abnormal lipid metabolism, while adding copper to the diet seems to be the simplest and most effective way to prevent copper deficiency.

AIMS

The aim of this study was to investigate the effects of dietary copper level on lipid metabolism in Rex Rabbits.

METHODS

A total of 120 90-d-old Rex Rabbits were randomly allotted into three treatments, with 40 replicates (20 males, 20 females) in each treatment (1 rabbit per replicate). The diets included 1) control (8.4 mg/kg), normal-copper diet (39.1 mg/kg), 3) high-copper diet (67.5 mg/kg). The trial including a one-week adaptation period and a five-week experimental period.

RESULT

The results showed that copper (39.1 mg/kg) diet increased average daily feed intake (ADFI) (P＜0.05, N = 34), and tended to increase the final body weight (FBW) (P = 0.0556, N = 34). Moreover, dietary copper addition (39.1 and 67.5 mg/kg) significantly increased the foreleg and hindleg weight (P＜0.05, N = 8), and decreased the weight of Perirenal fat and the concentration of triglycerides (TG) in the liver (P＜0.05, N = 8). The concentration of triglycerides (TG), epinephrine (EPI), and glucagon (GC) in serum were obviously higher than that in control group (P＜0.05, N = 8), and the concentration of insulin (INS), and very low-density lipoprotein (VLDL) in serum were significantly decreased (P＜0.05, N = 8). The copper group (39.1 mg/kg) showed up-regulated gene expression levels of carnitine palmitoyl transferases (CPT-1 and CPT-2) and peroxisome proliferator-activated receptor (PPAR-α) in liver (P < 0.05, N = 8) and down-regulated gene expression levels of fatty acid synthase (FAS) and Acetyl-CoA carboxylase (ACC) (P < 0.05, N = 8). In skeletal muscle, CPT-1, CPT-2, PPAR-α, fatty acid transport protein (FATP), fatty acid-binding protein (FABP) and lipoprotein lipase (LPL) levels were significantly up-regulated by copper treatment (P < 0.05, N = 8). Rex Rabbits receiving copper addition had higher CPT-1, CPT-2, PPAR-a and hormone-sensitive lipase (HSL) mRNA levels in adipose tissue (P < 0.05, N = 8).

CONCLUSION

Copper diets promoted skeletal muscle growth and reduced fat accumulation by enhancing fatty acid oxidation, at the same time, dietary copper inhibited De novo lipogenesis in the liver. PPAR-α signaling in liver, skeletal muscle and adipose tissues were involved in the regulation of lipid metabolism by copper.

Single-cell RNA Sequencing Reveals Heterogeneity of Cultured Bovine Satellite Cells

Skeletal muscle from meat-producing livestock such as cattle is a major source of food for humans. To improve skeletal muscle growth efficiency or quality in cattle, it is necessary to understand the genetic and physiological mechanisms that govern skeletal muscle composition, development, and growth. Satellite cells are the myogenic progenitor cells in postnatal skeletal muscle. In this study we analyzed the composition of bovine satellite cells with single-cell RNA sequencing (scRNA-seq). We isolated satellite cells from a 2-week-old male calf, cultured them in growth medium for a week, and performed scRNA-seq using the 10x Genomics platform. Deep sequencing of two scRNA-seq libraries constructed from cultured bovine satellite cells yielded 860 million reads. Cell calling analyses revealed that these reads were sequenced from 19,096 individual cells. Clustering analyses indicated that these reads represented 15 cell clusters that differed in gene expression profile. Based on the enriched expression of markers of satellite cells (PAX7 and PAX3), markers of myoblasts (MYOD1, MYF5), and markers of differentiated myoblasts or myocytes (MYOG), three clusters were determined to be satellite cells, two clusters myoblasts, and two clusters myocytes. Gene ontology and trajectory inference analyses indicated that cells in these myogenic clusters differed in proliferation rate and differentiation stage. Two of the remaining clusters were enriched with PDGFRA, a marker of fibro-adipogenic (FAP) cells, the progenitor cells for intramuscular fat, and are therefore considered to be FAP cells. Gene ontology analyses indicated active lipogenesis in one of these two clusters. The identity of the remaining six clusters could not be defined. Overall, the results of this study support the hypothesis that bovine satellite cells are composed of subpopulations that differ in transcriptional and myogenic state. The results of this study also support the hypothesis that intramuscular fat in cattle originates from fibro-adipogenic cells.

Alternatives for the worse: Molecular insights into adverse effects of bisphenol a and substitutes during human adipocyte differentiation

Bisphenol A (BPA), which is used in a variety of consumer-related plastic products, was reported to cause adverse effects, including disruption of adipocyte differentiation, interference with obesity mechanisms, and impairment of insulin- and glucose homeostasis. Substitute compounds are increasingly emerging but are not sufficiently investigated.We aimed to investigate the mode of action of BPA and four of its substitutes during the differentiation of human preadipocytes to adipocytes and their molecular interaction with peroxisome proliferator-activated receptor γ (PPARγ), a pivotal regulator of adipogenesis.Binding and effective biological activation of PPARγ were investigated by surface plasmon resonance and reporter gene assay, respectively. Human preadipocytes were continuously exposed to BPA, BPS, BPB, BPF, BPAF, and the PPARγ-antagonist GW9662. After 12 days of differentiation, lipid production was quantified via Oil Red O staining, and global protein profiles were assessed using LC-MS/MS-based proteomics. All tested bisphenols bound to human PPARγ with similar efficacy as the natural ligand 15d-PGJ2in vitroand provoked an antagonistic effect on PPARγ in the reporter gene assay at non-cytotoxic concentrations. During the differentiation of human preadipocytes, all bisphenols decreased lipid production. Global proteomics displayed a down-regulation of adipogenesis and metabolic pathways, similar to GW9662. Interestingly, pro-inflammatory pathways were up-regulated, MCP1 release was increased, and adiponectin decreased. pAKT/AKT ratios revealed significantly reduced insulin sensitivity by BPA, BPB, and BPS upon insulin stimulation.Thus, our results show that not only BPA but also its substitutes disrupt crucial metabolic functions and insulin signaling in adipocytes under low, environmentally relevant concentrations. This effect, mediated through inhibition of PPARγ, may promote hypertrophy of adipose tissue and increase the risk of developing metabolic syndrome, including insulin resistance.

Caudatin suppresses adipogenesis in 3T3-L1 adipocytes and reduces body weight gain in high-fat diet-fed mice through activation of hedgehog signaling

BACKGROUND

The regulative effects of caudatin, a C-21 steroid that is identified from Cynanchum bungee roots, on adipogenesis and obesity have not been studied. Many studies have demonstrated that the activation of hedgehog (Hh) signaling can help prevent obesity. Therefore, we hypothesized that caudatin can inhibit adipogenesis and obesity via activating the Hh signaling pathway.

METHODS

To investigate the effects of caudatin on adipogenesis in 3T3-L1 preadipocytes and high-fat diet induced obesity in C57BL/6 mice, in vitro and in vivo experiments were performed. For in vitro evaluation, Oil red O staining were used to represent lipid accumulation in differentiated 3T3-L1 adipocytes. For in vivo assessment, male 5 week-old C57BL/6 mice were fed with standard chow diet, high-fat diet (HFD), HFD with 25 mg/kg caudatin, HFD with 1mg/kg purmorpharmine for 10 weeks, respectively. Hh signaling and key adipogenic marker involved in adipogenesis were evaluated by real-time PCR and western blot. The adipocyte size of white adopose tissue and lipid storage of liver were visualized by hematoxylin and eosin staining. In addition, the expression of Gli1 and peroxisome proliferator-activated receptor γ (PPARγ) in white adipose tissue were investigated by immunohistochemistry staining.

RESULTS

Caudatin suppressed the accumulation of lipid droplets and downregulated the expression of key adipogenic factors, i.e., peroxisome proliferator-activated receptor γ PPARγ and CCAAT-enhancer binding protein α (C/EBPα), through activating Hh signaling in differentiated 3T3-L1 cells. Furthermore, caudatin and the Hh activator purmorpharmine significantly decreased body weight gain and white adipose tissue (WAT) weight in HFD-induced mice and affected adipogenic markers and Hh signaling mediators in WAT, which were in line with the in vitro experimental results.

CONCLUSION

To our best knowledge, it is the first report to demonstrate that caudatin downregulated adipocyte differentiation and suppressed HFD-induced body weight gain through activating the Hh signaling pathway, suggesting that caudatin can potentially counteract obesity.

Synthetic Triterpenoid RTA-408: Limits Radiation Damage to Normal Tissue

OBJECTIVES/HYPOTHESIS

To assess the efficacy and mechanism of action of a novel approach to mitigate acute and chronic radiation toxicity in a validated animal model.

STUDY DESIGN

Randomized, prospective study using an in vivo rat model.

METHODS

Experimental animal study utilizing Sprague-Dawley rats divided into three cohorts: 1) radiation + dimethyl sulfoxide (DMSO) (inert vehicle); 2) radiation + RTA-408 (therapeutic drug); and 3) no radiation + DMSO. All animals in the radiation cohorts underwent 40 Gy of radiation with subsequent inferior epigastric axial rotational flap 30 days later in all cohorts with percentage of flap necrosis and vascular density calculated by blinded observers. In a second experiment, an additional three cohorts, underwent serial punch biopsies of the abdominal skin before, during, and after radiation and drug/vehicle control treatment. Transcriptome analysis utilizing gene set enrichment analysis and digital polymerase chain reaction were performed at various time points.

RESULTS

The first experiment revealed average flap necrosis of 20% (95% confidence interval [CI] 16-45) in the radiation control group, 3% (95% CI 0-11) in the nonirradiated control, and 3% (95% CI 0.2-10) in the radiation group treated with RTA-408. Vascular density was preserved in the treatment group as compared to the radiated control. Nine rats were included in the second experiment, and transcriptome analyses in the treatment group revealed robust activation of antioxidant pathways with induced expression of genes associated with hypoxia and adipogenesis/angiogenesis.

CONCLUSIONS

Administration of RTA-408 during radiation treatment in a rat model resulted in transcriptome changes which appear to mitigate the toxic effects of radiation, preserving capillary networks and improving flap survival and tissue healing after subsequent surgery.

LEVEL OF EVIDENCE

Foundational Evidence, Animal Research Laryngoscope, 2021.

Disruption of Tumor Suppressors HNF4α/HNF1α Causes Tumorigenesis in Liver

The hepatocyte nuclear factor-4α (HNF4α) and hepatocyte nuclear factor-1α (HNF1α) are transcription factors that influence the development and maintenance of homeostasis in a variety of tissues, including the liver. As such, disruptions in their transcriptional networks can herald a number of pathologies, such as tumorigenesis. Largely considered tumor suppressants in liver cancer, these transcription factors regulate key events of inflammation, epithelial-mesenchymal transition, metabolic reprogramming, and the differentiation status of the cell. High-throughput analysis of cancer cell genomes has identified a number of hotspot mutations in HNF1α and HNF4α in liver cancer. Such results also showcase HNF1α and HNF4α as important therapeutic targets helping us step into the era of personalized medicine. In this review, we update current findings on the roles of HNF1α and HNF4α in liver cancer development and progression. It covers the molecular mechanisms of HNF1α and HNF4α dysregulation and also highlights the potential of HNF4α as a therapeutic target in liver cancer.

Multimodal Label-Free Monitoring of Adipogenic Stem Cell Differentiation Using Endogenous Optical Biomarkers

Stem cell-based therapies carry significant promise for treating human diseases. However, clinical translation of stem cell transplants for effective treatment requires precise non-destructive evaluation of the purity of stem cells with high sensitivity (<0.001% of the number of cells). Here, a novel methodology using hyperspectral imaging (HSI) combined with spectral angle mapping-based machine learning analysis is reported to distinguish differentiating human adipose-derived stem cells (hASCs) from control stem cells. The spectral signature of adipogenesis generated by the HSI method enables identifying differentiated cells at single-cell resolution. The label-free HSI method is compared with the standard techniques such as Oil Red O staining, fluorescence microscopy, and qPCR that are routinely used to evaluate adipogenic differentiation of hASCs. HSI is successfully used to assess the abundance of adipocytes derived from transplanted cells in a transgenic mice model. Further, Raman microscopy and multiphoton-based metabolic imaging is performed to provide complementary information for the functional imaging of the hASCs. Finally, the HSI method is validated using matrix-assisted laser desorption/ionization-mass spectrometry imaging of the stem cells. The study presented here demonstrates that multimodal imaging methods enable label-free identification of stem cell differentiation with high spatial and chemical resolution.

PPARγ Targets-Derived Diagnostic and Prognostic Index for Papillary Thyroid Cancer

Simple Summary

Through targeted next-generation sequencing of thyroid cancer-related genes in monozygotic twins with papillary thyroid cancer (PTC), we identified common variants of the gene encoding peroxisome proliferator activated receptor gamma (PPARG). Notably, the expression levels of PPARγ target genes were frequently deregulated in PTC compared to benign tissues and were closely associated with disease-specific survival (DSS) outcomes in a TCGA-PTC cohort. Machine learning-powered personalized scoring index comprising 10 PPARγ targets, termed as PPARGi, achieved a near-perfect accuracy in distinguishing cancers from benign tissues, and further identified a small subpopulation of patients at high-risk across different profiling platforms.

Abstract

In most cases, papillary thyroid cancer (PTC) is highly curable and associated with an excellent prognosis. Yet, there are several clinicopathological features that lead to a poor prognosis, underscoring the need for a better genomic strategy to refine prognostication and patient management. We hypothesized that PPARγ targets could be potential markers for better diagnosis and prognosis due to the variants found in PPARG in three pairs of monozygotic twins with PTC. Here, we developed a 10-gene personalized prognostic index, designated PPARGi, based on gene expression of 10 PPARγ targets. Through scRNA-seq data analysis of PTC tissues derived from patients, we found that PPARGi genes were predominantly expressed in macrophages and epithelial cells. Machine learning algorithms showed a near-perfect performance of PPARGi in deciding the presence of the disease and in selecting a small subset of patients with poor disease-specific survival in TCGA-THCA and newly developed merged microarray data (MMD) consisting exclusively of thyroid cancers and normal tissues.

Genome Profiling of H3k4me3 Histone Modification in Human Adipose Tissue during Obesity and Insulin Resistance

Background: Adipose tissue (AT) dysfunction is involved in obesity-related comorbidities. Epigenetic alterations have been recently associated with AT deterioration in obesity conditions. In this work, we profiled the H3K4me3 histone mark in human AT, with special emphasis on the changes in the pattern of histone modification in obesity and insulin resistance (IR). Visceral AT (VAT) was collected and subjected to chromatin immunoprecipitation (ChIP) using anti-H3K4me3 antibody and then sequenced to obtain the H3K4me3 genome profile. Results: We found that most of the H3K4me3 enriched regions were located in gene promoters of pathways related to AT biology and function. H3K4me3 enrichment at gene promoters was strongly related to higher mRNA levels. Differentially expressed genes in AT of patients classified as non-obese, obese with low IR, and obese with high IR could be regulated by differentially enriched H3K4me3; these genes encoded for pathways that could in part explain AT functioning during obesity and insulin resistance (e.g., extracellular matrix organization, PPARG signaling or inflammation). Conclusions: In conclusion, we emphasize the importance of the epigenetic mark H3K4me3 in VAT dysfunction in obesity and IR. The understanding of such mechanisms could give rise to the development of new epigenetic-based pharmacological strategies to ameliorate obesity-related comorbidities.

Pyruvate dehydrogenase kinase 1 and 2 deficiency reduces high-fat diet-induced hypertrophic obesity and inhibits the differentiation of preadipocytes into mature adipocytes

Obesity is now recognized as a disease. This study revealed a novel role for pyruvate dehydrogenase kinase (PDK) in diet-induced hypertrophic obesity. Mice with global or adipose tissue-specific PDK2 deficiency were protected against diet-induced obesity. The weight of adipose tissues and the size of adipocytes were reduced. Adipocyte-specific PDK2 deficiency slightly increased insulin sensitivity in HFD-fed mice. In studies with 3T3-L1 preadipocytes, PDK2 and PDK1 expression was strongly increased during adipogenesis. Evidence was found for epigenetic induction of both PDK1 and PDK2. Gain- and loss-of-function studies with 3T3-L1 cells revealed a critical role for PDK1/2 in adipocyte differentiation and lipid accumulation. PDK1/2 induction during differentiation was also accompanied by increased expression of hypoxia-inducible factor-1α (HIF1α) and enhanced lactate production, both of which were absent in the context of PDK1/2 deficiency. Exogenous lactate supplementation increased the stability of HIF1α and promoted adipogenesis. PDK1/2 overexpression-mediated adipogenesis was abolished by HIF1α inhibition, suggesting a role for the PDK-lactate-HIF1α axis during adipogenesis. In human adipose tissue, the expression of PDK1/2 was positively correlated with that of the adipogenic marker PPARγ and inversely correlated with obesity. Similarly, PDK1/2 expression in mouse adipose tissue was decreased by chronic high-fat diet feeding. We conclude that PDK1 and 2 are novel regulators of adipogenesis that play critical roles in obesity.

The discovery that two forms of a key enzyme appear to play a critical role in fat production triggered by overeating might lead to new approaches to prevent and treat obesity. Hyeon-Ji Kang at Kyungpook National University, Daegu, South Korea, and colleagues in South Korea and the USA examined the role of the enzymes pyruvate dehydrogenase kinase types 1 and 2 (PDK1/2). PDK enzymes regulate the activity of a multi-enzyme complex that catalyzes a key step in the use of glucose to provide energy stores for cells. Mice deficient in PDK2 were protected from diet-induced obesity, and PDK 1 and 2 activity was increased during the generation of fat cells. Studies using mice and human fat tissue confirmed that the enzymes regulate the development and growth of fat cells. Drugs inhibiting PDK enzymes might combat obesity.

Transcriptional characterization of subcutaneous adipose tissue in obesity affected women highlights metabolic dysfunction and implications for lncRNAs

Obesity is a complex disease with multifactorial causes, and its prevalence is becoming a serious health crisis. For this reason, there is a crucial need to identify novel targets and players. With this aim in mind, we analyzed via RNA-sequencing the subcutaneous adipose tissue of normal weight and obesity-affected women, highlighting the differential expression in the two tissues. We specifically focused on long non-coding RNAs, as 6 of these emerged as dysregulated in the diseased-tissue (COL4A2-AS2, RPS21-AS, PELATON, ITGB2-AS1, ACER2-AS and CTEPHA1). For each of them, we performed both a thorough in silico dissection and in vitro validation, to predict their function during adipogenesis. We report the lncRNAs expression during adipose derived stem cells differentiation to adipocytes as model of adipogenesis and their potential modulation by adipogenesis-related transcription factors (C/EBPs and PPARγ). Moreover, inhibiting CTEPHA1 expression we investigated its impact on adipogenesis-related transcription factors, showing its significative dysregulation of C/EBPα expression. Lastly, we dissected the subcellular localization, pathway involvement and disease-correlation for coding differentially expressed genes. Together, these findings highlight a transcriptional deregulation at the basis of obesity, impacted by both coding and long non-coding RNAs.

MiR-100 overexpression attenuates high fat diet induced weight gain, liver steatosis, hypertriglyceridemia and development of metabolic syndrome in mice

BACKGROUND

Diet-induced obesity can result in the development of a diverse spectrum of cardiovascular and metabolic diseases, including type 2 diabetes, dyslipidemia, non-alcoholic liver steatosis and atherosclerotic disease. MicroRNAs have been described to be important regulators of metabolism and disease development.

METHODS

In the current study, we investigated the effects of ubiquitous miR-100 overexpression on weight gain and the metabolic phenotype in a newly generated transgenic mouse strain under normal chow and high fat diet and used microarray expression analysis to identify new potential target genes of miR-100.

RESULTS

While transgenic overexpression of miR-100 did not significantly affect weight and metabolism under a normal diet, miR-100 overexpressing mice showed a reduced weight gain under a high fat diet compared to wildtype mice, despite an equal calorie intake. This was accompanied by less visceral and subcutaneous fat development and lover serum LDL cholesterol. In addition, transgenic miR-100 mice were more glucose tolerant and insulin sensitive and demonstrated increased energy expenditure under high fat diet feeding. A comprehensive gene expression profiling revealed the differential expression of several genes involved in lipid storage- and metabolism, among them CD36 and Cyp4A14. Our data showed a direct regulation of CD36 by miR-100, leading to a reduced fatty acid uptake in primary hepatocytes overexpressing miR-100 and the downregulation of several downstream mediators of lipid metabolism such as ACC1, FABP4, FAS and PPARγ in the liver.

CONCLUSIONS

Our findings demonstrate a protective role of miR-100 in high fat diet induced metabolic syndrome and liver steatosis, partially mediated by the direct repression of CD36 and attenuation of hepatic lipid storage, implicating miR-100 as a possible therapeutic target in liver steatosis.

Temporal correlation of morphological and biochemical changes with the recruitment of different mechanisms of reactive oxygen species formation during human SW872 cell adipogenic differentiation

Human SW872 preadipocyte conversion to mature adipocytes is associated with time-dependent changes in differentiation markers' expression and with morphological changes accompanied by the accumulation of lipid droplets (LDs) as well as by increased mitochondriogenesis and mitochondrial membrane potential. Under identical conditions, the formation of reactive oxygen species (ROS) revealed with a general probe was significant at days 3 and 10 of differentiation and bearly detectable at day 6. NADPH oxidase (NOX)-2 activity determined with an immunocytochemical approach followed a very similar pattern. There was no evidence of mitochondrial ROS (mROS), as detected with a selective fluorescence probe, at days 3 and 6, possibly due to the triggering of the Nrf-2 antioxidant response. mROS were instead clearly detected at day 10, concomitantly with the accumulation of very large LDs, oxidation of both cardiolipin and thioredoxin 2, and decreased mitochondrial glutathione. In conclusion, the morphological and biochemical changes of differentiating SW872 cells are accompanied by the discontinuous formation of ROS derived from NOX-2, increasingly implicated in adipogenesis and adipose tissue dysfunction. In addition, mROS formation was significant only in the late phase of differentiation and was associated with mitochondrial dysfunction.

PARPs in lipid metabolism and related diseases

PARPs and tankyrases (TNKS) represent a family of 17 proteins. PARPs and tankyrases were originally identified as DNA repair factors, nevertheless, recent advances have shed light on their role in lipid metabolism. To date, PARP1, PARP2, PARP3, tankyrases, PARP9, PARP10, PARP14 were reported to have multi-pronged connections to lipid metabolism. The activity of PARP enzymes is fine-tuned by a set of cholesterol-based compounds as oxidized cholesterol derivatives, steroid hormones or bile acids. In turn, PARPs modulate several key processes of lipid homeostasis (lipotoxicity, fatty acid and steroid biosynthesis, lipoprotein homeostasis, fatty acid oxidation, etc.). PARPs are also cofactors of lipid-responsive nuclear receptors and transcription factors through which PARPs regulate lipid metabolism and lipid homeostasis. PARP activation often represents a disruptive signal to (lipid) metabolism, and PARP-dependent changes to lipid metabolism have pathophysiological role in the development of hyperlipidemia, obesity, alcoholic and non-alcoholic fatty liver disease, type II diabetes and its complications, atherosclerosis, cardiovascular aging and skin pathologies, just to name a few. In this synopsis we will review the evidence supporting the beneficial effects of pharmacological PARP inhibitors in these diseases/pathologies and propose repurposing PARP inhibitors already available for the treatment of various malignancies.

Histone Deacetylase 3 Regulates Adipocyte Phenotype at Early Stages of Differentiation

Obesity is a condition characterized by uncontrolled expansion of adipose tissue mass resulting in pathological weight gain. Histone deacetylases (HDACs) have emerged as crucial players in epigenetic regulation of adipocyte metabolism. Previously, we demonstrated that selective inhibition of class I HDACs improves white adipocyte functionality and promotes the browning phenotype of murine mesenchymal stem cells (MSCs) C3H/10T1/2 differentiated to adipocytes. These effects were also observed in db/db and diet induced obesity mouse models and in mice with adipose-selective inactivation of HDAC3, a member of class I HDACs. The molecular basis of class I HDACs action in adipose tissue is not deeply characterized and it is not known whether the effects of their inhibition are exerted on adipocyte precursors or mature adipocytes. Therefore, the aim of the present work was to explore the molecular mechanism of class I HDAC action in adipocytes by evaluating the effects of HDAC3-specific silencing at different stages of differentiation. HDAC3 was silenced in C3H/10T1/2 MSCs at different stages of differentiation to adipocytes. shRNA targeting HDAC3 was used to generate the knock-down model. Proper HDAC3 silencing was assessed by measuring both mRNA and protein levels of mouse HDAC3 via qPCR and western blot, respectively. Mitochondrial DNA content and gene expression were quantified via qPCR. HDAC3 silencing at the beginning of differentiation enhanced adipocyte functionality by amplifying the expression of genes regulating differentiation, oxidative metabolism, browning and mitochondrial activity, starting from 72 h after induction of differentiation and silencing. Insulin signaling was enhanced as demonstrated by increased AKT phosphorylation following HDAC3 silencing. Mitochondrial content/density did not change, while the increased expression of the transcriptional co-activator Ppargc1b suggests the observed phenotype was related to enhanced mitochondrial activity, which was confirmed by increased maximal respiration and proton leak linked to reduced coupling efficiency. Moreover, the expression of pro-inflammatory markers increased with HDAC3 early silencing. To the contrary, no differences in terms of gene expression were found when HDAC3 silencing occurred in terminally differentiated adipocyte. Our data demonstrated that early epigenetic events mediated by class I HDAC inhibition/silencing are crucial to commit adipocyte precursors towards the above-mentioned metabolic phenotype. Moreover, our data suggest that these effects are exerted on adipocyte precursors.

microRNA-199a downregulation alleviates hyperuricemic nephropathy via the PPARγ/β-catenin axis

Hyperuricemia always develops into hyperuricemic nephropathy (HN). The role of microRNA (miR) in HN is less studied. We aimed to discuss the role of miR-199a in HN. The expression of miR-199a and PPARγ in renal tissues of HN rats was detected. The targeting relation between miR-199a and PPARγ was verified. The contents of SCr, UA, BUN, and mALB, renal injury-relevant biomarkers were detected, and the pathological changes of renal tissue and renal interstitial fibrosis were observed by histological staining. After miR-199a and PPARγ knockdown, the contents of SCr, BUN, and mALB and renal interstitial fibrosis were estimated. Collectively, overexpression of miR-199a aggravated the renal injury in HN rats. By contrast, inhibition of miR-199a weakened renal injury, as evidenced by decreased contents of SCr, UA, BUN, and mALB, and mitigated renal interstitial fibrosis. miR-199a targeted PPARγ. Silencing of PPARγ upregulated the levels of downstream genes of β-catenin and the contents of SCr, UA, BUN, and mALB and deteriorated renal interstitial fibrosis. Moreover, the silencing of PPARγ blocked the alleviative effects of miR-199a inhibitor on the renal injury. Overall, miR-199a targets PPARγ and activates the β-catenin pathway, thus aggravating HN, which might provide a future target for the treatment of HN.

Nobiletin Attenuates Pathological Cardiac Remodeling after Myocardial Infarction via Activating PPARγ and PGC1α

Materials and Methods

C57BL/6 mice were treated with coronary artery ligation to generate an MI model, followed by treatment for 3 weeks with NOB (50 mg/kg/d) or vehicle (50 mg/kg/d), with or without the peroxisome proliferator-activated receptor gamma (PPARγ) inhibitor T0070907 (1 mg/kg/d). Cardiac function (echocardiography, survival rate, Evans blue, and triphenyl tetrazolium chloride staining), fibrosis (Masson's trichrome staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot (WB)), hypertrophy (haematoxylin-eosin staining, wheat germ agglutinin staining, and qRT-PCR), and apoptosis (WB and terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining) were evaluated. Hypoxia-induced apoptosis (TUNEL, WB) and phenylephrine- (PE-) induced pathological hypertrophy (immunofluorescence staining, qRT-PCR) models were established in primary neonatal rat ventricular myocytes (NRVMs). The effects of NOB with or without T0070907 were examined for the expression of PPARγ and PPARγ coactivator 1α (PGC1α) by WB in mice and NRVMs. The potential downstream effectors of PPARγ were further analyzed by WB in mice.

Results

Following MI in mice, NOB intervention enhanced cardiac function across three predominant dimensions of pathological cardiac remodeling, which reflected in decreasing cardiac fibrosis, apoptosis, and hypertrophy decompensation. NOB intervention also alleviated apoptosis and hypertrophy in NRVMs. NOB intervention upregulated PPARγ and PGC1α in vivo and in vitro. Furthermore, the PPARγ inhibitor abolished the protective effects of NOB against pathological cardiac remodeling during the progression from MI to CHF. The potential downstream effectors of PPARγ were nuclear factor erythroid 2-related factor 2 (Nrf-2) and heme oxygenase 1 (HO-1).

Conclusions

Our findings suggested that NOB alleviates pathological cardiac remodeling after MI via PPARγ and PGC1α upregulation.

Arrhythmogenic cardiomyopathy: pathogenesis, pro-arrhythmic remodelling, and novel approaches for risk stratification and therapy

Arrhythmogenic cardiomyopathy (ACM) is a life-threatening cardiac disease caused by mutations in genes predominantly encoding for desmosomal proteins that lead to alterations in the molecular composition of the intercalated disc. ACM is characterized by progressive replacement of cardiomyocytes by fibrofatty tissue, ventricular dilatation, cardiac dysfunction, and heart failure but mostly dominated by the occurrence of life-threatening arrhythmias and sudden cardiac death (SCD). As SCD appears mostly in apparently healthy young individuals, there is a demand for better risk stratification of suspected ACM mutation carriers. Moreover, disease severity, progression, and outcome are highly variable in patients with ACM. In this review, we discuss the aetiology of ACM with a focus on pro-arrhythmic disease mechanisms in the early concealed phase of the disease. We summarize potential new biomarkers which might be useful for risk stratification and prediction of disease course. Finally, we explore novel therapeutic strategies to prevent arrhythmias and SCD in the early stages of ACM.