Mitotic clonal expansion: a synchronous process required for adipogenesis

PPA1 promotes adipogenesis by regulating the stability of C/EBPs

Adipogenesis significantly contributes to healthy adipose tissue expansion in obesity. Increasing adipocyte number or function to alleviate adipose tissue overload could serve as a therapeutic strategy for both lipodystrophy and obesity-related metabolic syndrome. Inorganic pyrophosphatase (PPA1) is an enzyme that catalyzes the hydrolysis of pyrophosphate (PPi) and is involved in many biochemical reactions, but its function in adipose tissue has not been studied previously. In this study, we demonstrated that adipose-specific PPA1 knockout (PPA1AKO) mice showed lipodystrophy and spontaneously developed hepatic steatosis and severe insulin resistance under normal chow diet feeding. PPA1 deficiency suppressed the differentiation of primary adipocyte precursors and 3T3-L1 cells. Notably, PPA1 overexpression can restore inhibited adipogenesis in preadipocytes isolated from db/db mice and type 2 diabetes patients. Mechanistic studies have revealed that PPA1 acts as a positive regulator of early adipocyte differentiation by promoting CCAAT/enhancer-binding proteinβ and δ (C/EBPβ and δ) protein stability. Moreover, the function of PPA1 in adipogenesis is independent of its PPi catalytic activity. Collectively, our in vivo and in vitro findings demonstrated that PPA1 is a novel critical upstream regulator of adipogenesis, controlling adipose tissue development and whole-body metabolic homeostasis.

Caveolin-2 controls preadipocyte survival in the mitotic clonal expansion for adipogenesis

Here, we report that Caveolin-2 (Cav-2) is a cell cycle regulator in the mitotic clonal expansion (MCE) for adipogenesis. For the G2/M phase transition and re-entry into the G1 phase, dephosphorylated Cav-2 by protein tyrosine phosphatase 1B (PTP1B) controlled epigenetic activation of Ccnb1, Cdk1, and p21 in a lamin A/C-dependent manner, thereby ensuring the survival of preadipocytes. Cav-2, associated with lamin A/C, recruited the repressed promoters of Ccnb1 and Cdk1 for activation, and disengaged the active promoter of p21 from lamin A/C for inactivation through histone H3 modifications at the nuclear periphery. Cav-2 deficiency abrogated the histone H3 modifications and impeded the transactivation of Ccnb1, Cdk1, and p21, leading to a delay in mitotic entry, retardation of re-entry into G1 phase, and the apoptotic cell death of preadipocytes. Re-expression of Cav-2 restored the G2/M phase transition and G1 phase re-entry, preadipocyte survival, and adipogenesis in Cav-2-deficient preadipocytes. Our study uncovers a novel mechanism by which cell cycle transition and apoptotic cell death are controlled for adipocyte hyperplasia.

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.

Anti-obesity effects of a standardized ethanol extract of Eisenia bicyclis by regulating the AMPK signaling pathway in 3T3-L1 cells and HFD-induced mice

Obesity requires treatment to mitigate the potential development of further metabolic disorders, including diabetes, hyperlipidemia, tumor growth, and non-alcoholic fatty liver disease. We investigated the anti-obesity effect of a 30% ethanol extract of Eisenia bicyclis (Kjellman) Setchell (EEB) on 3T3-L1 preadipocytes and high-fat diet (HFD)-induced obese C57BL/6 mice. Adipogenesis transcription factors including peroxisome proliferator-activated receptor (PPAR)γ, CCAAT/enhancer-binding protein-alpha (C/EBPα), and sterol regulatory element-binding protein-1 (SREBP-1) were ameliorated through the AMP-activated protein kinase (AMPK) pathway by EEB treatment in differentiated 3T3-L1 cells. EEB attenuated mitotic clonal expansion by upregulating cyclin-dependent kinase inhibitors (CDKIs) while downregulating cyclins and CDKs. In HFD-fed mice, EEB significantly decreased the total body weight, fat tissue weight, and fat in the tissue. The protein expression of PPARγ, C/EBPα, and SREBP-1 was increased in the subcutaneous fat and liver tissues, while EEB decreased the expression levels of these transcription factors. EEB also inhibited lipogenesis by downregulating acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) expression in the subcutaneous fat and liver tissues. Moreover, the phosphorylation of AMPK and ACC was downregulated in the HFD-induced mouse group, whereas the administration of EEB improved AMPK and ACC phosphorylation; thus, EEB treatment may be related to the AMPK pathway. Histological analysis showed that EEB reduced the adipocyte size and fat accumulation in subcutaneous fat and liver tissues, respectively. EEB promotes thermogenesis in brown adipose tissue and improves insulin and leptin levels and blood lipid profiles. Our results suggest that EEB could be used as a potential agent to prevent obesity.

Inhibition of the RPS6KA1/FoxO1 signaling axis by hydroxycitric acid attenuates HFD-induced obesity through MCE suppression

BACKGROUND

Because obesity is associated with a hyperplasia-mediated increase in adipose tissue, inhibiting cell proliferation during mitotic clonal expansion (MCE) is a leading strategy for preventing obesity. Although (-)-hydroxycitric acid (HCA) is used to control obesity, the molecular mechanisms underlying its effects on MCE are poorly understood.

PURPOSE

This study aimed to investigate the potential effects of HCA on MCE and underlying molecular mechanisms affecting adipogenesis and obesity improvements.

METHODS

Preadipocyte cell line, 3T3-L1, were treated with HCA; oil red O, cell proliferation, cell cycle, and related alterations in signaling pathways were examined. High-fat diet (HFD)-fed mice were administered HCA for 12 weeks; body and adipose tissues weights were evaluated, and the regulation of signaling pathways in epidydimal white adipose tissue were examined in vivo.

RESULTS

Here, we report that during MCE, HCA attenuates the proliferation of the preadipocyte cell line, 3T3-L1, by arresting the cell cycle at the G0/G1 phase. In addition, HCA markedly inhibits Forkhead Box O1 (FoxO1) phosphorylation, thereby inducing the expression of cyclin-dependent kinase inhibitor 1B and suppressing the levels of cyclin-dependent kinase 2, cyclin E1, proliferating cell nuclear antigen, and phosphorylated retinoblastoma. Importantly, we found that ribosomal protein S6 kinase A1 (RPS6KA1) influences HCA-mediated inactivation of FoxO1 and its nuclear exclusion. An animal model of obesity revealed that HCA reduced high-fat diet-induced obesity by suppressing adipocyte numbers as well as epididymal and mesenteric white adipose tissue mass, which is attributed to the regulation of RPS6KA1, FoxO1, CDKN1B and PCNA that had been consistently identified in vitro.

CONCLUSIONS

These findings provide novel insights into the mechanism by which HCA regulates adipogenesis and highlight the RPS6KA1/FoxO1 signaling axis as a therapeutic target for obesity.

CircMEF2C(2, 3) modulates proliferation and adipogenesis of porcine intramuscular preadipocytes by miR-383/671-3p/MEF2C axis

Circular RNA is a special category of non-coding RNA that has emerged as epigenetic regulator of adipose tissue development. However, the mechanism governing intramuscular adipogenesis of circRNA remains largely uncharted. In this study, circMEF2C(2, 3), looped by MEF2C exons 2 and 3, was identified from the pig MEF2C gene. Expression of circMEF2C(2, 3) is upregulated in early stage of intramuscular adipogenesis and muscular tissue of lean pigs (DLY pig). Subsequently, overexpression or knockdown of circMEF2C(2, 3) reflected that it participates in promoting proliferation and inhibiting adipogenic differentiation in porcine intramuscular preadipocytes and murine C3H10T1/2 cells. Mechanically, circMEF2C(2, 3) competitively combined with miR-383 and miR-671-3p to the 3'-UTR of MEF2C, which maintains MEF2C expression in regulating proliferation and adipogenesis. In summary, circMEF2C(2, 3) is a key regulator in the proliferation and adipogenic differentiation of intramuscular adipogenesis, suggesting its potential as a multi-target strategy for adipose development and associated diseases.

Impaired Remodeling of White Adipose Tissue in Obesity and Aging: From Defective Adipogenesis to Adipose Organ Dysfunction

The adipose organ adapts and responds to internal and environmental stimuli by remodeling both its cellular and extracellular components. Under conditions of energy surplus, the subcutaneous white adipose tissue (WAT) is capable of expanding through the enlargement of existing adipocytes (hypertrophy), followed by de novo adipogenesis (hyperplasia), which is impaired in hypertrophic obesity. However, an impaired hyperplastic response may result from various defects in adipogenesis, leading to different WAT features and metabolic consequences, as discussed here by reviewing the results of the studies in animal models with either overexpression or knockdown of the main molecular regulators of the two steps of the adipogenesis process. Moreover, impaired WAT remodeling with aging has been associated with various age-related conditions and reduced lifespan expectancy. Here, we delve into the latest advancements in comprehending the molecular and cellular processes underlying age-related changes in WAT function, their involvement in common aging pathologies, and their potential as therapeutic targets to influence both the health of elderly people and longevity. Overall, this review aims to encourage research on the mechanisms of WAT maladaptation common to conditions of both excessive and insufficient fat tissue. The goal is to devise adipocyte-targeted therapies that are effective against both obesity- and age-related disorders.

Isoeugenol Inhibits Adipogenesis in 3T3-L1 Preadipocytes with Impaired Mitotic Clonal Expansion

Isoeugenol (IEG), a natural component of clove oil, possesses antioxidant, anti-inflammatory, and antibacterial properties. However, the effects of IEG on adipogenesis have not yet been elucidated. Here, we showed that IEG blocks adipogenesis in 3T3-L1 cells at an early stage. IEG inhibits lipid accumulation in adipocytes in a concentration-dependent manner and reduces the expression of mature adipocyte-related factors including PPARγ, C/EBPα, and FABP4. IEG treatment at different stages of adipogenesis showed that IEG inhibited adipocyte differentiation by suppressing the early stage, as confirmed by lipid accumulation and adipocyte-related biomarkers. The early stage stimulates growth-arrested preadipocytes to enter mitotic clonal expansion (MCE) and initiates their differentiation into adipocytes by regulating cell cycle-related factors. IEG arrested 3T3-L1 preadipocytes in the G0/G1 phase of the cell cycle and attenuated cell cycle-related factors including cyclinD1, CDK6, CDK2, and cyclinB1 during the MCE stage. Furthermore, IEG suppresses reactive oxygen species (ROS) production during MCE and inhibits ROS-related antioxidant enzymes, including superoxide dismutase1 (SOD1) and catalase. The expression of cell proliferation-related biomarkers, including pAKT and pERK1/2, was attenuated by the IEG treatment of 3T3-L1 preadipocytes. These findings suggest that it is a potential therapeutic agent for the treatment of obesity.

Coffee, tea, and cocoa in obesity prevention: Mechanisms of action and future prospects

Obesity, a major public health problem, causes numerous complications that threaten human health and increase the socioeconomic burden. The pathophysiology of obesity is primarily attributed to lipid metabolism disorders. Conventional anti-obesity medications have a high abuse potential and frequently deliver insufficient efficacy and have negative side-effects. Hence, functional foods are regarded as effective alternatives to address obesity. Coffee, tea, and cocoa, three widely consumed beverages, have long been considered to have the potential to prevent obesity, and several studies have focused on their intrinsic molecular mechanisms in past few years. Therefore, in this review, we discuss the mechanisms by which the bioactive ingredients in these three beverages counteract obesity from the aspects of adipogenesis, lipolysis, and energy expenditure (thermogenesis). The future prospects and challenges for coffee, tea, and cocoa as functional products for the treatment of obesity are also discussed, which can be pursued for future drug development and prevention strategies against obesity.

Adipose tissue reconstruction facilitated with low immunogenicity decellularized adipose tissue scaffolds

There is currently an urgent need to develop engineered scaffolds to support new adipose tissue formation and facilitate long-term maintenance of function and defect repair to further generate prospective bioactive filler materials capable of fulfilling surgical needs. Herein, adipose regeneration methods were optimized and decellularized adipose tissue (DAT) scaffolds with good biocompatibility were fabricated. Adipose-like tissues were reconstructed using the DAT and 3T3-L1 preadipocytes, which have certain differentiation potential, and the regenerative effects of the engineered adipose tissuesin vitroandin vivowere explored. The method improved the efficiency of adipose removal from tissues, and significantly shortened the time for degreasing. Thus, the DAT not only provided a suitable space for cell growth but also promoted the proliferation, migration, and differentiation of preadipocytes within it. Following implantation of the constructed adipose tissuesin vivo, the DAT showed gradual degradation and integration with surrounding tissues, accompanied by the generation of new adipose tissue analogs. Overall, the combination of adipose-derived extracellular matrix and preadipocytes for adipose tissue reconstruction will be of benefit in the artificial construction of biomimetic implant structures for adipose tissue reconstruction, providing a practical guideline for the initial integration of adipose tissue engineering into clinical medicine.

Effects of maternal nutrient restriction during gestation on bovine serum microRNA abundance

The objective was to determine the effects of maternal nutrient restriction during gestation on serum microRNA (miRNA) abundance in cattle. Primiparous Angus-cross cows (n=22) were fed either control (CON; to gain 1 Kg/week) or nutrient restricted (NR; 0.55% NEm) diets based on National Research Council requirements. On day 30 of gestation, cows were blocked by body condition and randomly assigned to one of three diets: CON (n=8) days 30-190; NR (n=7) days 30-110 followed by CON days 110-190 (NR/C); or CON (n=7) days 30-110 followed by NR days 110-190 (C/NR). At 190 days of gestation, maternal serum was collected for RNA isolation and analyzed using a miRNA microarray of known Bos taurus sequences. Data were normalized using LOWESS and analyzed via ANOVA. At 190 days of gestation, 16 miRNAs exhibited differential abundance (P<0.05) between treatments. Cows that underwent NR, irrespective of when the insult occurred, had downregulated bta-miR-126-3p compared to CON cows. Bta-miR-16b was downregulated and three miRNAs upregulated in NR/C compared to C/NR and CON cows. Additionally, seven miRNAs were downregulated and four miRNAs upregulated in C/NR compared to NR/C and CON cows. Comparison of NR/C and C/NR cows revealed three differentially abundant (P<0.04) miRNAs (bta-miR-2487_L-2R-3_1ss15CT, bta-miR-215, and bta-miR-760-5p). Top KEGG pathway enrichment of target genes included: pathways in cancer, PI3K-Akt signaling, focal adhesion, Ras signaling, proteoglycans in cancer, and MAPK signaling. In summary, maternal nutrient restriction altered serum miRNA abundance profiles irrespective of the time at which the nutritional insult was induced.

SMYD3: a new regulator of adipocyte precursor proliferation at the early steps of differentiation

BACKGROUND

In obesity, adipose tissue undergoes a remodeling process characterized by increased adipocyte size (hypertrophia) and number (hyperplasia). The ability to tip the balance toward the hyperplastic growth, with recruitment of new fat cells through adipogenesis, seems to be critical for a healthy adipose tissue expansion, as opposed to a hypertrophic growth that is accompanied by the development of inflammation and metabolic dysfunction. However, the molecular mechanisms underlying the fine-tuned regulation of adipose tissue expansion are far from being understood.

METHODS

We analyzed by mass spectrometry-based proteomics visceral white adipose tissue (vWAT) samples collected from C57BL6 mice fed with a HFD for 8 weeks. A subset of these mice, called low inflammation (Low-INFL), showed reduced adipose tissue inflammation, as opposed to those developing the expected inflammatory response (Hi-INFL). We identified the discriminants between Low-INFL and Hi-INFL vWAT samples and explored their function in Adipose-Derived human Mesenchymal Stem Cells (AD-hMSCs) differentiated to adipocytes.

RESULTS

vWAT proteomics allowed us to quantify 6051 proteins. Among the candidates that most differentiate Low-INFL from Hi-INFL vWAT, we found proteins involved in adipocyte function, including adiponectin and hormone sensitive lipase, suggesting that adipocyte differentiation is enhanced in Low-INFL, as compared to Hi-INFL. The chromatin modifier SET and MYND Domain Containing 3 (SMYD3), whose function in adipose tissue was so far unknown, was another top-scored hit. SMYD3 expression was significantly higher in Low-INFL vWAT, as confirmed by western blot analysis. Using AD-hMSCs in culture, we found that SMYD3 mRNA and protein levels decrease rapidly during the adipocyte differentiation. Moreover, SMYD3 knock-down before adipocyte differentiation resulted in reduced H3K4me3 and decreased cell proliferation, thus limiting the number of cells available for adipogenesis.

CONCLUSIONS

Our study describes an important role of SMYD3 as a newly discovered regulator of adipocyte precursor proliferation during the early steps of adipogenesis.

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.

Stellera chamaejasme L. extract inhibits adipocyte differentiation through activation of the extracellular signal-regulated kinase pathway

Stellera chamaejasme L. (SCL) is a perennial herb with demonstrated bioactivities against inflammation and metabolic dysfunction. Adipocyte differentiation is a critical regulator of metabolic homeostasis and a promising target for the treatment of metabolic diseases, so we examined the effects of SCL on adipogenesis. A methanol extract of SCL dose-dependently suppressed intracellular lipid accumulation in adipocyte precursors cultured under differentiation induction conditions and reduced expression of the adipogenic transcription factors PPARγ and C/EBPα as well as the downstream lipogenic genes fatty acid binding protein 4, adiponectin, fatty acid synthase, and stearoyl-CoA desaturase. The extract also promoted precursor cell proliferation and altered expression of the cell cycle regulators cyclin-dependent kinase 4, cyclin E, and cyclin D1. In addition, SCL extract stimulated extracellular signal-regulated kinase (ERK) phosphorylation, while pharmacological inhibition of ERK effectively blocked the inhibitory effects of SCL extract on preadipocyte differentiation. These results suggest that SCL extract contains bioactive compounds that can suppress adipogenesis through modulation of the ERK pathway.

AP-1/C-FOS and AP-1/FRA2 differentially regulate early and late adipogenic differentiation of mesenchymal stem cells

Obesity is defined as an abnormal accumulation of adipose tissue in the body and is a major global health problem due to increased morbidity and mortality. Adipose tissue is made up of adipocytes, which are fat-storing cells, and the differentiation of these fat cells is known as adipogenesis. Several transcription factors (TFs) such as CEBPβ, CEBPα, PPARγ, GATA, and KLF have been reported to play a key role in adipogenesis. In this study, we report one more TF AP-1, which is found to be involved in adipogenesis. Human mesenchymal stem cells  were differentiated into adipocytes, and the expression pattern of different subunits of AP-1 was examined during adipogenesis. It was observed that C-FOS was predominantly expressed at an early stage (Day 2), whereas FRA2 expression peaked at later stages (Days 6 and 8) of adipogenesis. Chromatin immunoprecipitation-sequencing analysis revealed that C-FOS binds mainly to the promoters of WNT1, miR-30a, and ANAPC7 and regulates their expression during mitotic clonal expansion. In contrast, FRA2 binds to the promoters of CIDEA, NOTCH1, ARAF, and MYLK, regulating their expression and lipid metabolism. Data obtained clearly indicate that the differential expression of C-FOS and FRA2 is crucial for different stages of adipogenesis. This also raises the possibility of considering AP-1 as a therapeutic target for treating obesity and related disorders.

Gene Regulation and Mitochondrial Activity During White and Brown Adipogenesis Are Modulated by KDM5 Histone Demethylase

Body fat accumulation differs between males and females and is influenced by both gonadal sex (ovaries vs testes) and chromosomal sex (XX vs XY). We previously showed that an X chromosome gene, Kdm5c, is expressed at higher levels in females compared to males and correlates with adiposity in mice and humans. Kdm5c encodes a KDM5 histone demethylase that regulates gene expression by modulating histone methylation at gene promoters and enhancers. Here, we use chemical inhibition and genetic knockdown to identify a role for KDM5 activity during early stages of white and brown preadipocyte differentiation, with specific effects on white adipocyte clonal expansion, and white and brown adipocyte gene expression and mitochondrial activity. In white adipogenesis, KDM5 activity modulates H3K4 histone methylation at the Dlk1 gene promoter to repress gene expression and promote progression from preadipocytes to mature adipocytes. In brown adipogenesis, KDM5 activity modulates H3K4 methylation and gene expression of Ucp1, which is required for thermogenesis. Unbiased transcriptome analysis revealed that KDM5 activity regulates genes associated with cell cycle regulation and mitochondrial function, and this was confirmed by functional analyses of cell proliferation and cellular bioenergetics. Using genetic knockdown, we demonstrate that KDM5C is the likely KDM5 family member that is responsible for regulation of white and brown preadipocyte programming. Given that KDM5C levels are higher in females compared to males, our findings suggest that sex differences in white and brown preadipocyte gene regulation may contribute to sex differences in adipose tissue function.

Effect of YC-1102 on the Improvement of Obesity in High-Fat Diet-Induced Obese Mice

Obesity is one of the major risk factors for metabolic diseases worldwide. This study examined the effects of YC-1102, an extract derived from the roots of Rosa multiflora, on 3T3-L1 preadipocytes and high-fat diet (HFD)-induced obese mice. In vivo experiments involved the oral administration of YC-1102 (100, 150, and 200 mg/kg body weight) daily to mice for eight weeks. YC-1102 was found to downregulate the expressions of PPARγ and C/EBPα during adipogenesis, inhibiting adipocyte differentiation and upregulating the expression of PGC-1α for energy metabolism to enhance mitochondrial biogenesis and fatty acid oxidation. It has been shown that daily administration of YC-1102 to mice receiving a HFD prevented an increase in body weight and the accumulation of body fat. YC-1102 administration also reduced TG, TC, and LDL cholesterol levels, as well as glucose and leptin levels, and increased adiponectin levels, thus effectively inhibiting the metabolism of lipids. YC-1102-treated mice showed significant reductions in the mRNA expression of PPARγ and C/EBPα. The levels of PGC-1α involved in energy metabolism increased significantly in the YC-1102-treated mice when compared to the HFD-treated mice. According to the findings of this study, YC-1102 has a dual mechanism that reduces transcription factors that promote the differentiation of adipocytes and increases transcription factors that promote energy consumption.

GULP1 deficiency reduces adipogenesis and glucose uptake via downregulation of PPAR signaling and disturbing of insulin/ERK signaling in 3T3-L1 cells

Obesity and metabolic disorders caused by alterations in lipid metabolism are major health issues in developed, affluent societies. Adipose tissue is the only organ that stores lipids and prevents lipotoxicity in other organs. Mature adipocytes can affect themselves and distant metabolism-related tissues by producing various adipokines, including adiponectin and leptin. The engulfment adaptor phosphotyrosine-binding domain-containing 1 (GULP1) regulates intracellular trafficking of glycosphingolipids and cholesterol, suggesting its close association with lipid metabolism. However, the role of GULP1 in adipocytes remains unknown. Therefore, this study aimed to investigate the function of GULP1 in adipogenesis, glucose uptake, and the insulin signaling pathway in adipocytes. A 3T3-L1 cell line with Gulp1 knockdown (shGulp1) and a 3T3-L1 control group (U6) were established. Changes in shGulp1 cells due to GULP1 deficiency were examined and compared to those in U6 cells using microarray analysis. Glucose uptake was monitored via insulin stimulation in shGulp1 and U6 cells using a 2-NBDG glucose uptake assay, and the insulin signaling pathway was investigated by western blot analysis. Adipogenesis was significantly delayed, lipid metabolism was altered, and several adipogenesis-related genes were downregulated in shGulp1 cells compared to those in U6 cells. Microarray analysis revealed significant inhibition of peroxisome proliferator-activated receptor signaling in shGulp1 cells compared with U6 cells. The production and secretion of adiponectin as well as the expression of adiponectin receptor were decreased in shGulp1 cells. In particular, compared with U6 cells, glucose uptake via insulin stimulation was significantly decreased in shGulp1 cells through the disturbance of ERK1/2 phosphorylation. This is the first study to identify the role of GULP1 in adipogenesis and insulin-stimulated glucose uptake by adipocytes, thereby providing new insights into the differentiation and functions of adipocytes and the metabolism of lipids and glucose, which can help better understand metabolic diseases.

Cinnamyl Alcohol Attenuates Adipogenesis in 3T3-L1 Cells by Arresting the Cell Cycle

Cinnamyl alcohol (CA) is an aromatic compound found in several plant-based resources and has been shown to exert anti-inflammatory and anti-microbial activities. However, the anti-adipogenic mechanism of CA has not been sufficiently studied. The present study aimed to investigate the effect and mechanism of CA on the regulation of adipogenesis. As evidenced by Oil Red O staining, Western blotting, and real-time PCR (RT-PCR) analyses, CA treatment (6.25-25 μM) for 8 d significantly inhibited lipid accumulation in a concentration-dependent manner and downregulated adipogenesis-related markers (peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), fatty acid binding protein 4 (FABP4), adiponectin, fatty acid synthase (FAS)) in 3-isobutyl-1-methylxanthine, dexamethasone, and insulin(MDI)-treated 3T3-L1 adipocytes. In particular, among the various differentiation stages, the early stage of adipogenesis was critical for the inhibitory effect of CA. Cell cycle analysis using flow cytometry and Western blotting showed that CA effectively inhibited MDI-induced initiation of mitotic clonal expansion (MCE) by arresting the cell cycle in the G0/G1 phase and downregulating the expression of C/EBPβ, C/EBPδ, and cell cycle markers (cyclin D1, cyclin-dependent kinase 6 (CDK6), cyclin E1, CDK2, and cyclin B1). Moreover, AMP-activated protein kinase α (AMPKα), acetyl-CoA carboxylase (ACC), and extracellular signal-regulated kinase 1/2 (ERK1/2), markers of upstream signaling pathways, were phosphorylated during MCE by CA. In conclusion, CA can act as an anti-adipogenic agent by inhibiting the AMPKα and ERK1/2 signaling pathways and the cell cycle and may also act as a potential therapeutic agent for obesity.

Acetylation and deacetylation of histone in adipocyte differentiation and the potential significance in cancer

Adipocytes are derived from pluripotent mesenchymal stem cells and can develop into several cell types including adipocytes, myocytes, chondrocytes, and osteocytes. Adipocyte differentiation is regulated by a variety of transcription factors and signaling pathways. Various epigenetic factors, particularly histone modifications, play key roles in adipocyte differentiation and have indispensable functions in altering chromatin conformation. Histone acetylases and deacetylases participate in the regulation of protein acetylation, mediate transcriptional and post-translational modifications, and directly acetylate or deacetylate various transcription factors and regulatory proteins. The adipocyte differentiation of stem cells plays a key role in various metabolic diseases. Cancer stem cells(CSCs) play an important function in cancer metastasis, recurrence, and drug resistance, and have the characteristics of stem cells. They are expressed in various cell lineages, including adipocytes. Recent studies have shown that cancer stem cells that undergo epithelial-mesenchymal transformation can undergo adipocytic differentiation, thereby reducing the degree of malignancy. This opens up new possibilities for cancer treatment. This review summarizes the regulation of acetylation during adipocyte differentiation, involving the functions of histone acetylating and deacetylating enzymes as well as non-histone acetylation modifications. Mechanistic studies on adipogenesis and acetylation during the differentiation of cancer cells into a benign cell phenotype may help identify new targets for cancer treatment.

Branched-chain amino acids prevent obesity by inhibiting the cell cycle in an NADPH-FTO-m6A coordinated manner

Obesity has become a major health crisis in the past decades. Branched-chain amino acids (BCAA), a class of essential amino acids, exerted beneficial health effects with regard to obesity and its related metabolic dysfunction, although the underlying reason is unknown. Here, we show that BCAA supplementation alleviates high-fat diet (HFD)-induced obesity and insulin resistance in mice and inhibits adipogenesis in 3T3-L1 cells. Further, we find that BCAA prevent the mitotic clonal expansion (MCE) of preadipocytes by reducing cyclin A2 (CCNA2) and cyclin-dependent kinase 2 (CDK2) expression. Mechanistically, BCAA decrease the concentration of nicotinamide adenine dinucleotide phosphate (NADPH) in adipose tissue and 3T3-L1 cells by reducing glucose-6-phosphate dehydrogenase (G6PD) expression. The reduced NADPH attenuates the expression of fat mass and obesity-associated (FTO) protein, a well-known m6A demethylase, to increase the N6-methyladenosine (m6A) levels of Ccna2 and Cdk2 mRNA. Meanwhile, the high m6A levels of Ccna2 and Cdk2 mRNA are recognized by YTH N6-methyladenosine RNA binding protein 2 (YTHDF2), which results in mRNA decay and reduction of their protein expressions. Overall, our data demonstrate that BCAA inhibit obesity and adipogenesis by reducing CDK2 and CCNA2 expression via an NADPH-FTO-m6A coordinated manner in vivo and in vitro, which raises a new perspective on the role of m6A in the BCAA regulation of obesity and adipogenesis.

Deubiquitinase USP1 enhances CCAAT/enhancer-binding protein beta (C/EBPβ) stability and accelerates adipogenesis and lipid accumulation

Dysregulation of the ubiquitin-proteasome system has been implicated in the pathogenesis of several metabolic disorders, including obesity, diabetes, and non-alcoholic fatty liver disease; however, the mechanisms controlling pathogenic metabolic disorders remain unclear. Transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) regulates adipogenic genes. The study showed that the expression level of C/EBPβ is post-translationally regulated by the deubiquitinase ubiquitin-specific protease 1 (USP1) and that USP1 expression is remarkably upregulated during adipocyte differentiation and in the adipose tissue of mice fed a high-fat diet (HFD). We found that USP1 directly interacts with C/EBPβ. Knock-down of USP1 decreased C/EBPβ protein stability and increased its ubiquitination. Overexpression of USP1 regulates its protein stability and ubiquitination, whereas catalytic mutant of USP1 had no effect on them. It suggests that USP1 directly deubiquitinases C/EBPβ and increases the protein expression, leading to adipogenesis and lipid accumulation. Notably, the USP1-specific inhibitor ML323-originally developed to sensitize cancer cells to DNA-damaging agents-decreased adipocyte differentiation and lipid accumulation in 3T3-L1 cells without cytotoxicity. Oral gavage of ML323 was administered to HFD-fed mice, which showed weight loss and improvement in insulin and glucose sensitivity. Both fat mass and adipocyte size in white adipose tissues were significantly reduced by ML323 treatment, which also reduced the expression of genes involved in adipogenesis and inflammatory responses. ML323 also reduced lipid accumulation, hepatic triglycerides, free fatty acids, and macrophage infiltration in the livers of HFD-fed mice. Taken together, we suggest that USP1 plays an important role in adipogenesis by regulating C/EBPβ ubiquitination, and USP1-specific inhibitor ML323 is a potential treatment option and further study by ML323 is needed for clinical application for metabolic disorders.

Guanidinoacetic Acid Attenuates Adipogenesis through Regulation of miR-133a in Sheep

Guanidinoacetic acid (GAA) is an amino acid derivative, previously described in the skeletal muscle of vertebrates, that serves as an important regulator of cellular bioenergetics and has been widely used as a feed additive. Nevertheless, the effect of GAA on adipose tissue growth remains unclear. Here, we hypothesized that dietary GAA negatively affected adipose tissue development in lambs. Lambs were individually fed diets with (0.09%) or without GAA for 70 d ad libitum, and the subcutaneous adipose tissues were sampled for analysis. The results showed that dietary GAA supplementation decreased the girth rib (GR) value (p < 0.01) of lamb carcasses. Both real-time PCR and Western blot analysis suggested that dietary GAA inhibited the expression of adipogenic markers, including peroxisome proliferator-activated receptor γ (PPARγ, p < 0.05), CCAAT/enhancer-binding protein α (C/EBPα, p < 0.01) and sterol-regulatory-element-binding protein 1c (SREBP1C, p < 0.01) in subcutaneous adipose tissue. In vitro, GAA inhibited sheep stromal vascular fraction (SVF) cell proliferation, which was associated with downregulation of proliferating cell nuclear antigen (PCNA, p < 0.05), cyclin-dependent kinase 4 (CDK 4, p < 0.05) and cyclin D1 (p < 0.01). GAA suppressed adipogenesis of SVF cells. Furthermore, miRNA sequencing revealed that GAA affected the miRNA expression profile, and real-time PCR analysis confirmed that miR-133a expression in both subcutaneous adipose tissue and SVF cell was downregulated by GAA. Meanwhile, miR-133a promoted adipogenic differentiation of SVF cells by targeting Sirt1. miR-133a mimics alleviated the inhibitory effect of GAA on SVF cells' adipogenic differentiation. In summary, GAA attenuated adipogenesis of sheep SVF cells, which might occur through miR-133a-modulated Sirt1 expression.

Adrenergic Reprogramming of Preexisting Adipogenic Trajectories Steer Naïve Mural Cells Toward Beige Differentiation

In adult white adipose tissue, cold or β3-adrenoceptor activation promotes the appearance of thermogenic beige adipocytes. Our comprehensive single-cell analysis revealed that these cells arise through the reprogramming of existing adipogenic trajectories, rather than from a single precursor. These trajectories predominantly arise from SM22-expressing vascular mural progenitor cells. Central in this transition is the activation of Adrb3 in mature adipocytes, leading to subsequent upregulation of Adrb1 in primed progenitors. Under thermoneutral conditions, synergistic activation of both Adrb3 and Adrb1 recapitulates the pattern of cold-induced SM22+ cell recruitment. Lipolysis-derived eicosanoids, specifically docosahexaenoic acid (DHA) and arachidonic acid (AA) prime these processes and in vitro, were sufficient to recapitulate progenitor cells priming. Collectively, our findings provide a robust model for cold-induced beige adipogenesis, emphasizing a profound relationship between mature adipocytes and mural cells during cold acclimation, and revealing the metabolic potential of this unique cellular reservoir.

Protopanaxadiol-Enriched Rice Exerted Antiadipogenic Activity during 3T3-L1 Differentiation and Anti-Inflammatory Activity in 3T3-L1 Adipocytes

Ginseng is a traditional medicine with health benefits for humans. Protopanaxadiol (PPD) is an important bioactive compound found in ginseng. Transgenic rice containing PPD has been generated previously. In the present study, extracts of this transgenic rice were evaluated to assess their antiadipogenic and anti-inflammatory activities. During adipogenesis, cells were treated with transgenic rice seed extracts. The results revealed that the concentrations of the rice seed extracts tested in this study did not affect cell viability at 3 days post-treatment. However, the rice seed extracts significantly reduced the accumulation of lipids in cells and suppressed the activation of CCAAT/enhancer-binding protein α (C/EBPα) and peroxisome proliferator-activated receptor γ (PPARγ), which in turn inhibited the expression of adipogenesis-related mRNAs, such as adiponectin, PPARγ, C/EBPα, sterol regulatory element-binding protein 1, glucose transport member 4, and fatty acid synthase. In adipocytes, the extracts significantly reduced the mRNA expression of inflammation-related factors following LPS treatment. The activation of NF-κB p65 and ERK 1/2 was inhibited in extract-treated adipocytes. Moreover, treatment with extract #8 markedly reduced the cell population of the G2/M phase. Collectively, these results indicate that transgenic rice containing PPD may act as an obesity-reducing and/or -preventing agent.

Regulation of mitotic clonal expansion and thermogenic pathway are involved in the antiadipogenic effects of cyanidin-3-O-glucoside

Introduction: Obesity is a metabolic disease with an increase both in cell size (hypertrophy) and in cell number (hyperplasia) following differentiation of new adipocytes. Adipogenesis is a well-orchestrated program in which mitotic clonal expansion (MCE) occurs in the early step followed by the late terminal differentiation one. Methods: Aim of the study was to evaluate the in vitro effects of cyanidin-3-O-glucoside (C3G), an anthocyanin present in many fruits and vegetables, in the early or late phase of 3T3-L1 preadipocytes differentiation. Results: C3G exposure in the early phase of adipogenesis process induced a more marked reduction of CCAAT/enhancer-binding protein-β (C/EBPβ), peroxisome proliferator-activated receptor γ (PPAR-ɣ) and fatty acid synthase (Fasn) expression than late phase exposure and these effects were associated to a reduced MCE with cell cycle arrest at G0/G1 phase via p21 expression. Furthermore, C3G exposure during the early phase activated AMP-activated protein kinase (AMPK) pathway better than in the late phase promoting the enhancement of beige-like adipocytes. In fact, C3G induced thermogenic biomarkers uncoupling protein-1 (Ucp1) and peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (Pgc1) and these effects were more evident during early phase exposure. Conclusion: Our data demonstrate that C3G reduces the terminal adipogenic process affecting the early phase of differentiation and inducing a thermogenic program.

miR-486-5p Attenuates Steroid-Induced Adipogenesis and Osteonecrosis of the Femoral Head Via TBX2/P21 Axis

Enhanced adipogenic differentiation of mesenchymal stem cells (MSCs) is considered as a major risk factor for steroid-induced osteonecrosis of the femoral head (SOFNH). The role of microRNAs during this process has sparked interest. miR-486-5p expression was down-regulated significantly in femoral head bone tissues of both SONFH patients and rat models. The purpose of this study was to reveal the role of miR-486-5p on MSCs adipogenesis and SONFH progression. The present study showed that miR-486-5p could significantly inhibit adipogenesis of 3T3-L1 cells by suppressing mitotic clonal expansion (MCE). And upregulated expression of P21, which was caused by miR-486-5p mediated TBX2 decrease, was responsible for inhibited MCE. Further, miR-486-5p was demonstrated to effectively inhibit steroid-induced fat formation in the femoral head and prevented SONFH progression in a rat model. Considering the potent effects of miR-486-5p on attenuating adipogenesis, it seems to be a promising target for the treatment of SONFH.

Circadian mechanisms in adipose tissue bioenergetics and plasticity

The circadian clock plays an essential role in coordinating feeding and metabolic rhythms with the light/dark cycle. Disruption of clocks is associated with increased adiposity and metabolic disorders, whereas aligning feeding time with cell-autonomous rhythms in metabolism improves health. Here, we provide a comprehensive overview of recent literature in adipose tissue biology as well as our understanding of molecular mechanisms underlying the circadian regulation of transcription, metabolism, and inflammation in adipose tissue. We highlight recent efforts to uncover the mechanistic links between clocks and adipocyte metabolism, as well as its application to dietary and behavioral interventions to improve health and mitigate obesity.

Nicotinamide N-methyltransferase (NNMT) regulates the glucocorticoid signaling pathway during the early phase of adipogenesis

Obesity is associated with adipose tissue dysfunction through the differentiation and expansion of pre-adipocytes to adipocytes (hyperplasia) and/or increases in size of pre-existing adipocytes (hypertrophy). A cascade of transcriptional events coordinates the differentiation of pre-adipocytes into fully differentiated adipocytes; the process of adipogenesis. Although nicotinamide N-methyltransferase (NNMT) has been associated with obesity, how NNMT is regulated during adipogenesis, and the underlying regulatory mechanisms, remain undefined. In present study we used genetic and pharmacological approaches to elucidate the molecular signals driving NNMT activation and its role during adipogenesis. Firstly, we demonstrated that during the early phase of adipocyte differentiation NNMT is transactivated by CCAAT/Enhancer Binding Protein beta (CEBPB) in response to glucocorticoid (GC) induction. We found that Nnmt knockout, using CRISPR/Cas9 approach, impaired terminal adipogenesis by influencing the timing of cellular commitment and cell cycle exit during mitotic clonal expansion, as demonstrated by cell cycle analysis and RNA sequencing experiments. Biochemical and computational methods showed that a novel small molecule, called CC-410, stably binds to and highly specifically inhibits NNMT. CC-410 was, therefore, used to modulate protein activity during pre-adipocyte differentiation stages, demonstrating that, in line with the genetic approach, chemical inhibition of NNMT at the early stages of adipogenesis impairs terminal differentiation by deregulating the GC network. These congruent results conclusively demonstrate that NNMT is a key component of the GC-CEBP axis during the early stages of adipogenesis and could be a potential therapeutic target for both early-onset obesity and glucocorticoid-induced obesity.

Assessing Anti-Adipogenic Effects of Mango Leaf Tea and Mangiferin within Cultured Adipocytes

Obesity is a condition caused by surplus adipose tissue and is a risk factor for several diet-related diseases. Obesity is a global epidemic that has also been challenging to treat effectively. However, one promoted therapy to safely treat obesity is anti-adipogenic therapeutics. Therefore, identifying potent anti-adipogenic bioactive compounds that can safely be used clinically may effectively treat obesity in humans. Mango leaf has potential medicinal properties due to its many bioactive compounds that may enhance human health. Mangiferin (MGF) is a primary constituent in mango plants, with many health-promoting qualities. Therefore, this study investigated the effect of MGF, and tea brewed with mango leaves in cultured adipocytes. The anti-adipogenic efficacy of mango leaf tea (MLT) and MGF in 3T3-L1 cells were assessed, along with cell viability, triglyceride levels, adiponectin secretion, and glucose uptake analyzed. In addition, changes in the mRNA expression of genes involved in lipid metabolism within 3T3-L1 cells were determined using quantitative real-time PCR. Our results showed while both MLT and MGF increased glucose uptake in adipocytes, only MLT appeared to inhibit adipogenesis, as determined by decreased triglyceride accumulation. We also observed increased secretory adiponectin levels, reduced ACC mRNA expression, and increased FOXO1 and ATGL gene expression in 3T3-L1 cells treated with MLT but not MGF. Together, these results suggest that MLT may exhibit anti-adipogenic properties independent of MGF content.

Kctd17-mediated Chop degradation promotes adipogenic differentiation

Obesity is commonly associated with excessive adipogenesis, a process by which preadipocytes undergo differentiation into mature adipocytes; however, the mechanisms underlying adipogenesis are not completely understood. Potassium channel tetramerization domain-containing 17 (Kctd17) belongs to the Kctd superfamily and act as a substrate adaptor of the Cullin 3-RING E3 ubiquitin ligase, which is involved in a wide variety of cell functions. However, its function in the adipose tissue remains largely unknown. Here, we found that Kctd17 expression levels were increased in white adipose tissue, especially in adipocytes, in obese mice compared to lean control mice. Gain or loss of function of Kctd17 in preadipocytes inhibited or promoted adipogenesis, respectively. Furthermore, we found that Kctd17 bound to C/EBP homologous protein (Chop) to target it for ubiquitin-mediated degradation, and this process was likely associated with increased adipogenesis. In conclusion, these data suggest that Kctd17 plays an important role in adipogenesis and can be a novel therapeutic target for obesity.

Leuconostoc Citreum Inhibits Adipogenesis and Lipogenesis by Inhibiting p38 MAPK/Erk 44/42 and Stimulating AMPKα Signaling Pathways

Probiotics provide a range of health benefits. Several studies have shown that using probiotics in obesity treatment can reduce bodyweight. However, such treatments are still restricted. Leuconostoc citreum, an epiphytic bacterium, is widely used in a variety of biological applications. However, few studies have investigated the role of Leuconostoc spp. in adipocyte differentiation and its molecular mechanisms. Therefore, the objective of this study was to determine the effects of cell-free metabolites of L. citreum (LSC) on adipogenesis, lipogenesis, and lipolysis in 3T3-L1 adipocytes. The results showed that LSC treatment reduced the accumulation of lipid droplets and expression levels of CCAAT/ enhancer-binding protein-α & β (C/EBP-α & β), peroxisome proliferator-activated receptor-γ (PPAR-γ), serum regulatory binding protein-1c (SREBP-1c), adipocyte fatty acid binding protein (aP2), fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), resistin, pp38MAPK, and pErk 44/42. However, compared to control cells, adiponectin, an insulin sensitizer, was elevated in adipocytes treated with LSC. In addition, LSC treatment increased lipolysis by increasing pAMPK-α and suppressing FAS, ACC, and PPAR-γ expression, similarly to the effects of AICAR, an AMPK agonist. In conclusion, L. citreum is a novel probiotic strain that can be used to treat obesity and its associated metabolic disorders.

Mevalonate biosynthesis pathway regulates the development and survival of brown adipocytes

The high thermogenic activity of brown adipose tissue (BAT) has received considerable attention. Here, we demonstrated the role of the mevalonate (MVA) biosynthesis pathway in the regulation of brown adipocyte development and survival. The inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme in the MVA pathway and the molecular target of statins, suppressed brown adipocyte differentiation by suppressing protein geranylgeranylation-mediated mitotic clonal expansion. The development of BAT in neonatal mice exposed to statins during the fetal period was severely impaired. Moreover, statin-induced geranylgeranyl pyrophosphate (GGPP) deficiency led to the apoptosis of mature brown adipocytes. Brown adipocyte-specific Hmgcr knockout induced BAT atrophy and disrupted thermogenesis. Importantly, both genetic and pharmacological inhibition of HMGCR in adult mice induced morphological changes in BAT accompanied by an increase in apoptosis, and statin-treated diabetic mice showed worsened hyperglycemia. These findings revealed that MVA pathway-generated GGPP is indispensable for BAT development and survival.

Metallothionein 3 Inhibits 3T3-L1 Adipocyte Differentiation via Reduction of Reactive Oxygen Species

Metallothionein 3 (MT3), also known as a neuronal growth-inhibitory factor, is a member of the metallothionein family and is involved in a variety of biological functions, including protection against metal toxicity and reactive oxygen species (ROS). However, less is known about the role of MT3 in the differentiation of 3T3-L1 cells into adipocytes. In this study, we observed that MT3 levels were downregulated during 3T3-L1 adipocyte differentiation. Mt3 overexpression inhibited adipocyte differentiation and reduced the levels of the adipogenic transcription factors C/EBPα and PPARγ. Further analyses showed that MT3 also suppressed the transcriptional activity of PPARγ, and this effect was not mediated by a direct interaction between MT3 with PPARγ. In addition, Mt3 overexpression resulted in a decrease in ROS levels during early adipocyte differentiation, while treatment with antimycin A, which induces ROS generation, restored the ROS levels. Mt3 knockdown, on the other hand, elevated ROS levels, which were suppressed upon treatment with the antioxidant N-acetylcysteine. Our findings indicate a previously unknown role of MT3 in the differentiation of 3T3-L1 cells into adipocytes and provide a potential novel target that might facilitate obesity treatment.

Lanthanum nitrate inhibits adipogenesis in 3T3-L1 preadipocytes with a disorder of mitotic clonal expansion process

Lanthanum (La) as a rare earth element is widely used in agriculture, industry, and medicine. It has been suggested in several studies that La might influence glycolipid metabolism in vivo. In this study, we used 3T3-L1 preadipocytes as in vitro cell model to elucidate the effects of La(NO₃ )₃ on adipogenesis and the underlying mechanisms. The results showed that La(NO₃ )₃ could inhibit the adipogenic differentiation of 3T3-L1 preadipocytes, which showed a decrease in lipid accumulation and the downregulation of specific adipogenic transcription factors. La(NO₃ )₃ exerted its inhibitory effect mainly at the early differentiation stage. Furthermore, La(NO₃ )₃ influenced the S-phase entry and cell cycle process during the mitotic clonal expansion and regulated the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and expressions of the proteins in phosphatidylinositol 3-kinase (PI3K)/Akt pathway at the early stage of differentiation. Besides, La(NO₃ )₃ upregulated the expressions of wnt10b mRNA and β-catenin protein and promoted the nucleus translocation of β-catenin. Additionally, we found that La(NO₃ )₃ could promote the growth of 3T3-L1 preadipocytes both with and without MDI (3-isobutyl-1-methylxanthine [IBMX], dexamethasone [Dex], and insulin) stimulation. Collectively, these results indicated that La(NO₃ )₃ could inhibit adipogenesis in 3T3-L1 preadipocytes and influence cell proliferation.

Resveratrol butyrate esters inhibit lipid biosynthesis in 3T3-L1 cells by AMP-activated protein kinase phosphorylation

Resveratrol butyrate esters (RBEs), which are novel resveratrol-synthesized derivatives, exhibit increased biological activity. This study elucidated the effect of RBEs on fat metabolism and their anti-obesity characteristics. Their molecular mechanism was investigated in the 3T3-L1 murine preadipocyte cells and adipocytes. RBE doses of < 2 μM did not induce a significant change in the viability of 3T3-L1 adipocytes. After RBEs treatment, intracellular lipid droplet accumulation in 3T3-L1 adipocytes was stimulated by methylisobutylxanthine, dexamethasone, and insulin-containing medium. However, a significant dose-dependent reduction in intracellular lipid levels was observed. The mRNA levels of two adipogenic transcription factors (peroxisome proliferator-activated receptor [PPAR] and CCAAT/enhancer-binding proteins [C/EBP]) and lipogenic proteins (fatty acid-binding protein 4 [FABP4] and fatty acid synthase [FAS]) were significantly attenuated by RBE treatment in both MDI-stimulated and differentiated 3T3-L1 adipocytes. Moreover, the phosphorylation level of adenosine monophosphate-activated protein kinase (AMPK) also dramatically increased in the MDI + RBE-treated group compared to that in the MDI + vehicle-treated group. Collectively, our study provides strong evidence that RBEs inhibit adipogenesis by regulating adipogenic protein expression and increasing the p-AMPK/AMPK ratio. Future studies will be conducted on animal models to validate the application of RBEs as a functional food ingredient in improving human health.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05436-x.

Inhibitory Effect of Isopanduratin A on Adipogenesis: A Study of Possible Mechanisms

The root of Boesenbergia rotunda, a culinary plant commonly known as fingerroot, has previously been reported to possess anti-obesity activity, with four flavonoids identified as active principles, including pinostrobin, panduratin A, cardamonin, and isopanduratin A. However, the molecular mechanisms underlying the antiadipogenic potential of isopanduratin A remain unknown. In this study, isopanduratin A at non-cytotoxic concentrations (1-10 μM) significantly suppressed lipid accumulation in murine (3T3-L1) and human (PCS-210-010) adipocytes in a dose-dependent manner. Downregulation of adipogenic effectors (FAS, PLIN1, LPL, and adiponectin) and adipogenic transcription factors (SREBP-1c, PPARγ, and C/EBPα) occurred in differentiated 3T3-L1 cells treated with varying concentrations of isopanduratin A. The compound deactivated the upstream regulatory signals of AKT/GSK3β and MAPKs (ERK, JNK, and p38) but stimulated the AMPK-ACC pathway. The inhibitory trend of isopanduratin A was also observed with the proliferation of 3T3-L1 cells. The compound also paused the passage of 3T3-L1 cells by inducing cell cycle arrest at the G0/G1 phase, supported by altered levels of cyclins D1 and D3 and CDK2. Impaired p-ERK/ERK signaling might be responsible for the delay in mitotic clonal expansion. These findings revealed that isopanduratin A is a strong adipogenic suppressor with multi-target mechanisms and contributes significantly to anti-obesogenic activity. These results suggest the potential of fingerroot as a functional food for weight control and obesity prevention.

A Novel Mix of Polyphenols and Micronutrients Reduces Adipogenesis and Promotes White Adipose Tissue Browning via UCP1 Expression and AMPK Activation

Background: Obesity is a pandemic disease characterized by excessive severe body comorbidities. Reduction in fat accumulation represents a mechanism of prevention, and the replacement of white adipose tissue (WAT) with brown adipose tissue (BAT) has been proposed as one promising strategy against obesity. In the present study, we sought to investigate the ability of a natural mixture of polyphenols and micronutrients (A5⁺) to counteract white adipogenesis by promoting WAT browning. Methods: For this study, we employed a murine 3T3-L1 fibroblast cell line treated with A5⁺, or DMSO as control, during the differentiation in mature adipocytes for 10 days. Cell cycle analysis was performed using propidium iodide staining and cytofluorimetric analysis. Intracellular lipid contents were detected by Oil Red O staining. Inflammation Array, along with qRT-PCR and Western Blot analyses, served to measure the expression of the analyzed markers, such as pro-inflammatory cytokines. Results: A5⁺ administration significantly reduced lipids' accumulation in adipocytes when compared to control cells (p < 0.005). Similarly, A5⁺ inhibited cellular proliferation during the mitotic clonal expansion (MCE), the most relevant stage in adipocytes differentiation (p < 0.0001). We also found that A5⁺ significantly reduced the release of pro-inflammatory cytokines, such as IL-6 and Leptin (p < 0.005), and promoted fat browning and fatty acid oxidation through increasing expression levels of genes related to BAT, such as UCP1 (p < 0.05). This thermogenic process is mediated via AMPK-ATGL pathway activation. Conclusion: Overall, these results demonstrated that the synergistic effect of compounds contained in A5⁺ may be able to counteract adipogenesis and then obesity by inducing fat browning.

Chordin-like 1, a Novel Adipokine, Markedly Promotes Adipogenesis and Lipid Accumulation

White adipose tissue serves as a metabolically dynamic organ that can synthesize and secrete biologically active compounds such as adipokines as well as a caloric reservoir for maintaining energy homeostasis. Adipokines are involved in diverse biological and physiological processes and there have been extensive attempts to characterize the effects of over two dozen adipokines. However, many of these adipokines are produced by not only adipose tissue, but also other tissues. Therefore, investigations into the effects of adipokines on physiological functions have been challenged. In this regard, we aimed to identify a new secreted protein that is encoded by genes specifically expressed in white adipose tissue through analysis of multi-tissue transcriptome and protein expression. As a result, we report a novel adipokine that is encoded by the adipose-specific gene, chordin-like 1 (Chrdl1), which is specifically expressed in white adipose tissue in mice; this expression pattern was conserved in the human orthologous CHRDL1 gene. The expression of Chrdl1 was enriched in fat cells and developmentally regulated in vitro and in vivo, and moreover, its retrovirus-mediated overexpression and recombinant protein treatment led to markedly increased adipogenesis. Further pathway enrichment analysis revealed enriched pathways related to lipogenesis and adipogenic signaling. Our findings support a pro-adipogenic role of CHRDL1 as a new adipokine and pave the way toward animal studies and future research on its clinical implications and development of anti-obesity therapy.

Zinc finger protein 251 deficiency impairs glucose metabolism by inducing adipocyte hypertrophy

Zinc finger protein (ZFP) 251 is a member of the C2H2 ZFP family containing a Krüppel-associated box domain that might mainly act as a transcriptional repressor. However, its cellular function remains largely unknown. Here, we discovered that ZFP251 deficiency caused glucose intolerance in mice. This phenotype was associated with impaired insulin signaling due to hypertrophic changes in white adipose tissue (WAT). Gene ontology analysis revealed that ZFP251 deficiency affected the expression of genes associated with adipocyte differentiation and lipid and fatty acid metabolism. Consistent with in vivo results, hypertrophic changes were observed in Zfp251 knockdown (KD) 3T3-L1 adipocytes. In addition, Zfp251 KD 3T3-L1 preadipocytes exhibited cell cycle arrest in G0/G1 phase, leading to impaired differentiation into mature adipocytes, upon which abnormal mitotic clonal expansion and reduced expression of adipogenic markers were exhibited. These results suggest that ZFP251 deficiency causes impaired adipogenesis and adipocyte hypertrophy, leading to dysfunction of WAT.

Identification of DDX5 as an indispensable activator of the glucocorticoid receptor in adipocyte differentiation

The expression of CCAAT/enhancer-binding protein (C/EBP) family members and peroxisome proliferator-activated receptor γ (PPAR γ) is essential for the differentiation of pre-adipocyte 3T3-L1 cells into mature adipocytes induced by a combined stimulation with dexamethasone, 3-isobutyl-1-methylxanthine and insulin (DMI). We herein demonstrated that the RNA helicase DDX5, the expression of which was induced by DMI, played an important role in the adipocyte differentiation of 3T3-L1 cells. The DMI-induced accumulation of lipid droplets and expression of adipocyte markers in 3T3-L1 cells were significantly inhibited by the knockdown of DDX5. The knockdown of DDX5 interfered with the expressional induction of C/EBPδ, which was the first to be induced in the transcription factor cascade, and inhibited the subsequent expression of the other transcription factors, C/EBPβ, PPARγ and C/EBPα. DDX5 interacted with the glucocorticoid receptor (GR), which induced the expression of C/EBPδ. The knockdown of DDX5 failed to induce the nuclear translocation of GR, suggesting the essential role of DDX5 in the early stage of adipocyte differentiation. Furthermore, the reconstitution of DDX5, but not the DDX5 mutant (K144N) lacking RNA helicase activity, restored DMI-induced GR activation and adipocyte differentiation in 3T3-L1 cells in which DDX5 was knocked down, confirming that the RNA helicase activity of DDX5 is essential for adipogenesis. Collectively, these results revealed for the first time that DDX5 is necessary for GR activation and plays an essential role in early adipocyte differentiation.

Micro-Current Stimulation Can Modulate the Adipogenesis Process by Regulating the Insulin Signaling Pathway in 3T3-L1 Cells and ob/ob Mice

Obesity is a disease in which fat is abnormally or excessively accumulated in the body, and many studies have been conducted to overcome it with various techniques. In this study, we evaluated whether micro-current stimulation (MCS) can be applied to prevent obesity by regulating the adipogenesis through 3T3-L1 cells and ob/ob mice. To specify the intensity of MCS, Oil Red O staining was conducted with various intensities of MCS. Based on these, subsequent experiments used 200 and 400 μA for the intensity of MCS. The expressions of insulin signaling pathway-related proteins, including phosphorylation of IGF-1 and IR, were decreased in all MCS groups, and in turn, downstream signals such as Akt and ERK were decreased. In addition, MCS reduced the nucleus translocation of PPAR-γ and decreased the protein expression of C/EBP-α. In the ob/ob mouse model, MCS reduced body weight gain and abdominal adipose tissue volume. In particular, the concentration of triglycerides in serum was also decreased. Taken together, our findings showed that MCS inhibited lipid accumulation by regulating insulin signaling in 3T3-L1, and it was effective at reducing body weight and adipose tissue volume in ob/ob mice. These suggest that MCS may be a useful treatment approach for obesity.

Standardized Ethanol Extract of Cassia mimosoides var. nomame Makino Ameliorates Obesity via Regulation of Adipogenesis and Lipogenesis in 3T3-L1 Cells and High-Fat Diet-Induced Obese Mice

Obesity is a major cause of conditions such as type 2 diabetes and non-alcoholic fatty liver disease, posing a threat to public health worldwide. Here, we analyzed the anti-obesity effects of a standardized ethanol extract of Cassia mimosoides var. nomame Makino (EECM) in vitro and in vivo. Treatment of 3T3-L1 adipocytes with EECM suppressed adipogenesis and lipogenesis via the AMP-activated protein kinase pathway by downregulating the expression levels of CCAAT/enhancer-binding protein-alpha, peroxisome proliferator-activated receptor (PPAR)-γ, sterol regulatory element-binding protein-1, and fatty acid synthase and upregulating the acetyl-CoA carboxylase. EECM inhibited mitotic clonal expansion during early adipocyte differentiation. Oral administration of EECM for 10 weeks significantly alleviated body weight gain and body fat accumulation in high-fat diet (HFD)-fed mice. EECM mitigated adipogenesis and lipid accumulation in white adipose and liver tissues of HFD-induced obese mice. It regulated the levels of adipogenic hormones including insulin, leptin, and adipokine in the blood plasma. In brown adipose tissue, EECM induced the expression of thermogenic factors such as uncoupling protein-1, PPAR-α, PPARγ co-activator-1α, sirtuin 1, and cytochrome c oxidase IV. EECM restored the gut microbiome composition at the phylum level and alleviated dysbiosis. Therefore, EECM may be used as a promising therapeutic agent for the prevention of obesity.

Reorganization of the DNA replication landscape during adipogenesis is closely linked with adipogenic gene expression

The temporal order of DNA replication along the chromosomes is thought to reflect the transcriptional competence of the genome. During differentiation of mouse 3T3-L1 cells into adipocytes, cells undergo one or two rounds of cell division called mitotic clonal expansion (MCE). MCE is an essential step for adipogenesis; however, little is known about the regulation of DNA replication during this period. Here, we performed genome-wide mapping of replication timing (RT) in mouse 3T3-L1 cells before and during MCE, and identified a number of chromosomal regions shifting toward either earlier or later replication through two rounds of replication. These RT changes were confirmed in individual cells by single-cell DNA-replication sequencing. Coordinate changes between a shift toward earlier replication and transcriptional activation of adipogenesis-associated genes were observed. RT changes occurred before the full expression of these genes, indicating that RT reorganization might contribute to the mature adipocyte phenotype. To support this, cells undergoing two rounds of DNA replication during MCE had a higher potential to differentiate into lipid droplet-accumulating adipocytes, compared with cells undergoing a single round of DNA replication and non-replicating cells.

BAP31 depletion inhibited adipogenesis, repressed lipolysis and promoted lipid droplets abnormal growth via attenuating Perilipin1 proteasomal degradation

BAP31 expression was robustly decreased in obese white adipose tissue (WAT). To investigate the roles of BAP31 in lipid metabolism, adipocyte-specific conditional knockout mice (BAP31-ASKO) were generated. BAP31-ASKO mice grow normally as controls, but exhibited reduced lipid accumulation in WAT. Histomorphometric analysis reported increased adipocyte size in BAP31-ASKO mice. Mouse embryonic fibroblasts (MEFs) were induced to differentiation to adipocytes, showed reduced induction of adipogenic markers and attenuated adipogenesis in BAP31-deficient MEFs. BAP31-deficiency inhibited fasting-induced PKA signaling activation and the fasting response. β3-adrenergic receptor agonist-induced lipolysis also was reduced, accompanied by reduced free-fatty acids and glycerol release, and impaired agonist-induced lipolysis from primary adipocytes and adipose explants. BAP31 interacts with Perilipin1 via C-terminal cytoplasmic portion on lipid droplets (LDs) surface. Depletion of BAP31 repressed Perilipin1 proteasomal degradation, enhanced Perilipin1 expression and blocked LDs degradation, which promoted LDs abnormal growth and supersized LDs formation, resulted in adipocyte expansion, thus impaired insulin signaling and aggravated pro-inflammation in WAT. BAP31-deficiency increased phosphatidylcholine/phosphatidylethanolamine ratio, long chain triglycerides and most phospholipids contents. Overall, BAP31-deficiency inhibited adipogenesis and lipid accumulation in WAT, decreased LDs degradation and promoted LDs abnormal growth, pointing the critical roles in modulating LDs dynamics and homeostasis via proteasomal degradation system in adipocytes.

In-frame deletion of SMC5 related with the phenotype of primordial dwarfism, chromosomal instability and insulin resistance

BACKGROUND

SMC5/6 complex plays a vital role in maintaining genome stability, yet the relationship with human diseases has not been described.

METHODS

SMC5 variation was identified through whole-exome sequencing (WES) and verified by Sanger sequencing. Immunoprecipitation, cytogenetic analysis, fluorescence activated cell sorting (FACS) and electron microscopy were used to elucidate the cellular consequences of patient's cells. smc5 knockout (KO) zebrafish and Smc5K371del knock-in mouse models were generated by CRISPR-Cas9. RNA-seq, quantitative real-time PCR (qPCR), western blot, microquantitative computed tomography (microCT) and histology were used to explore phenotypic characteristics and potential mechanisms of the animal models. The effects of Smc5 knockdown on mitotic clonal expansion (MCE) during adipogenesis were investigated through Oil Red O staining, proliferation and apoptosis assays in vitro.

RESULTS

We identified a homozygous in-frame deletion of Arg372 in SMC5, one of the core subunits of the SMC5/6 complex, from an adult patient with microcephalic primordial dwarfism, chromosomal instability and insulin resistance. SMC5 mutation disrupted its interaction with its interacting protein NSMCE2, leading to defects in DNA repair and chromosomal instability in patient fibroblasts. Smc5 KO zebrafish showed microcephaly, short length and disturbed glucose metabolism. Smc5 depletion triggers a p53-related apoptosis, as concomitant deletion of the p53 rescued growth defects phenotype in zebrafish. An smc5K371del knock-in mouse model exhibited high mortality, severe growth restriction and fat loss. In 3T3-L1 cells, the knockdown of smc5 results in impaired MCE, a crucial step in adipogenesis. This finding implies that defective cell survival and differentiation is an important mechanism linking growth disorders and metabolic homeostasis imbalance.

UBE3D Regulates mRNA 3'-End Processing and Maintains Adipogenic Potential in 3T3-L1 Cells

We have previously described the role of an essential Saccharomyces cerevisiae gene, important for cleavage and polyadenylation 1 (IPA1), in the regulation of gene expression through its interaction with Ysh1, the endonuclease subunit of the mRNA 3'-end processing complex. Through a similar mechanism, the mammalian homolog ubiquitin protein ligase E3D (UBE3D) promotes the migratory and invasive potential of breast cancer cells, but its role in the regulation of gene expression during normal cellular differentiation has not previously been described. In this study, we show that CRISPR/Cas9-mediated knockout of Ube3d in 3T3-L1 cells blocks their ability to differentiate into mature adipocytes. Consistent with previous studies in other cell types, Ube3d knockout leads to decreased levels of CPSF73 and global changes in cellular mRNAs indicative of a loss of 3'-end processing capacity. Ube3d knockout cells also display decreased expression of known preadipogenic markers. Overexpression of either UBE3D or CPSF73 rescues the differentiation defect and partially restores protein levels of these markers. These results support a model in which UBE3D is necessary for the maintenance of the adipocyte-committed state via its regulation of the mRNA 3'-end processing machinery.

Epigenetic regulation of Cebpb activation by pY19-Caveolin-2 at the nuclear periphery in association with the nuclear lamina

Here, we show that Caveolin-2 (Cav-2) is an epigenetic regulator for adipogenesis. Upon adipogenic stimulation, inner nuclear membrane (INM)-targeted pY19-Cav-2 interacted with lamin A/C to disengage the repressed Cebpb promoter from lamin A/C, which facilitated the Cebpb promoter association with lamin B1. Consequently, pY19-Cav-2 recruited lysine demethylase 4b (KDM4b) for demethylation of histone H3 lysine 9 trimethylation (H3K9me3) and histone acetyltransferase GCN5 for acetylation of H3K27, and subsequently RNA polymerase II (Pol II) on Cebpb promoter for epigenetic activation of Cebpb, to initiate adipogenesis. Cav-2 knock-down abrogated the Cebpb activation and blocked the Pparg2 and Cebpa activation. Re-expression of Cav-2 restored Cebpb activation and adipogenesis in Cav-2-deficient preadipocytes. Our data identify a new mechanism by which the epigenetic activation of Cebpb is controlled at the nuclear periphery to promote adipogenesis.

Lipedema: Insights into Morphology, Pathophysiology, and Challenges

Lipedema is an adipofascial disorder that almost exclusively affects women. Lipedema leads to chronic pain, swelling, and other discomforts due to the bilateral and asymmetrical expansion of subcutaneous adipose tissue. Although various distinctive morphological characteristics, such as the hyperproliferation of fat cells, fibrosis, and inflammation, have been characterized in the progression of lipedema, the mechanisms underlying these changes have not yet been fully investigated. In addition, it is challenging to reduce the excessive fat in lipedema patients using conventional weight-loss techniques, such as lifestyle (diet and exercise) changes, bariatric surgery, and pharmacological interventions. Therefore, lipedema patients also go through additional psychosocial distress in the absence of permanent treatment. Research to understand the pathology of lipedema is still in its infancy, but promising markers derived from exosome, cytokine, lipidomic, and metabolomic profiling studies suggest a condition distinct from obesity and lymphedema. Although genetics seems to be a substantial cause of lipedema, due to the small number of patients involved in such studies, the extrapolation of data at a broader scale is challenging. With the current lack of etiology-guided treatments for lipedema, the discovery of new promising biomarkers could provide potential solutions to combat this complex disease. This review aims to address the morphological phenotype of lipedema fat, as well as its unclear pathophysiology, with a primary emphasis on excessive interstitial fluid, extracellular matrix remodeling, and lymphatic and vasculature dysfunction. The potential mechanisms, genetic implications, and proposed biomarkers for lipedema are further discussed in detail. Finally, we mention the challenges related to lipedema and emphasize the prospects of technological interventions to benefit the lipedema community in the future.

Chaperone-mediated autophagy regulates adipocyte differentiation

Adipogenesis is a tightly orchestrated multistep process wherein preadipocytes differentiate into adipocytes. The most studied aspect of adipogenesis is its transcriptional regulation through timely expression and silencing of a vast number of genes. However, whether turnover of key regulatory proteins per se controls adipogenesis remains largely understudied. Chaperone-mediated autophagy (CMA) is a selective form of lysosomal protein degradation that, in response to diverse cues, remodels the proteome for regulatory purposes. We report here the activation of CMA during adipocyte differentiation and show that CMA regulates adipogenesis at different steps through timely degradation of key regulatory signaling proteins and transcription factors that dictate proliferation, energetic adaptation, and signaling changes required for adipogenesis.