Involvement of protein tyrosine phosphatases in adipogenesis: new anti-obesity targets?

SHP2 regulates adipose maintenance and adipocyte-pancreatic cancer cell crosstalk via PDHA1

Adipocytes are the most abundant cell type in the adipose tissue, and their dysfunction is a significant driver of obesity-related pathologies, such as cancer. The mechanisms that (1) drive the maintenance and secretory activity of adipocytes and (2) mediate the cancer cellular response to the adipocyte-derived factors are not fully understood. To address that gap of knowledge, we investigated how alterations in Src homology region 2-containing protein (SHP2) activity affect adipocyte function and tumor crosstalk. We found that phospho-SHP2 levels are elevated in adipose tissue of obese mice, obese patients, and differentiating adipocytes. Immunofluorescence and immunoprecipitation analyses as well as in-silico protein-protein interaction modeling demonstrated that SHP2 associates with PDHA1, and that a positive association promotes a reactive oxygen species (ROS)-driven adipogenic program. Accordingly, this SHP2-PDHA1-ROS regulatory axis was crucial for adipocyte maintenance and secretion of interleukin-6 (IL-6), a key cancer-promoting cytokine. Mature adipocytes treated with an inhibitor for SHP2, PDHA1, or ROS exhibited an increased level of pro-lipolytic and thermogenic proteins, corresponding to an increased glycerol release, but a suppression of secreted IL-6. A functional analysis of adipocyte-cancer cell crosstalk demonstrated a decreased migration, invasion, and a slight suppression of cell cycling, corresponding to a reduced growth of pancreatic cancer cells exposed to conditioned media (CM) from mature adipocytes previously treated with inhibitors for SHP2/PDHA1/ROS. Importantly, PDAC cell growth stimulation in response to adipocyte CM correlated with PDHA1 induction but was suppressed by a PDHA1 inhibitor. The data point to a novel role for (1) SHP2-PDHA1-ROS in adipocyte maintenance and secretory activity and (2) PDHA1 as a regulator of the pancreatic cancer cells response to adipocyte-derived factors.

Effect of Abutilon indicum (L) Extract on Adipogenesis, Lipolysis and Cholesterol Esterase in 3T3-L1 Adipocyte Cell Lines

Abutilon indicum (L) is an Indian traditional plant used for the treatment of diabetes and heart diseases. The present study is to evaluate the functional of A. indicum leaf extract as insulin like character to inhibit lipolysis and stimulates Adipogenesis activity. The ability of the A. indicum leaf extract in anti-obesity effect of Adipogenesis, lipolysis and cholesterol esterase functions can be predicted by using 3T3-L1 adipocyte cell lines. Substances were isolated from A. indicum leaves and the double filtered crude sample were used for Adipogenesis, lipolysis and cholesterol esterase activity using 3T3-L1 adipocytes at different concentrations. We used differential media-I, differential media-II and maintenance media (MM1) at concentrations of 20, 40, 60, 80, 100, 200 and 400 µg/mL respectively. In addition to the extract, there is a significance increase in glycerol release (p < 0.001) compared with crude and reference compounds. Cholesterol esterase activity predicts the IC50 = 27.11 µg/mL of orlistat positive control compare with IC50 = 8.158 µg/mL of crude extract. Based on the observation, A. indicum leaf extract can promotes lipolysis and differentiated adipocytes. It is potentially used as adjuvant in the treatment of Type 2 diabetes.

Advances in multi-omics study of biomarkers of glycolipid metabolism disorder

Glycolipid metabolism disorder are major threats to human health and life. Genetic, environmental, psychological, cellular, and molecular factors contribute to their pathogenesis. Several studies demonstrated that neuroendocrine axis dysfunction, insulin resistance, oxidative stress, chronic inflammatory response, and gut microbiota dysbiosis are core pathological links associated with it. However, the underlying molecular mechanisms and therapeutic targets of glycolipid metabolism disorder remain to be elucidated. Progress in high-throughput technologies has helped clarify the pathophysiology of glycolipid metabolism disorder. In the present review, we explored the ways and means by which genomics, transcriptomics, proteomics, metabolomics, and gut microbiomics could help identify novel candidate biomarkers for the clinical management of glycolipid metabolism disorder. We also discuss the limitations and recommended future research directions of multi-omics studies on these diseases.

Chebulinic Acid Suppresses Adipogenesis in 3T3-L1 Preadipocytes by Inhibiting PPP1CB Activity

Depletion of protein phosphatase-1 catalytic subunit beta (PPP1CB), a serine/threonine protein phosphatase and potent adipogenic activator, suppresses the differentiation of 3T3-L1 preadipocytes into mature adipocytes. Therefore, PPP1CB is considered as a potential therapeutic target for obesity. We screened 1033 natural products for PPP1CB inhibitors and identified chebulinic acid, which is abundantly present in the seeds of Euphoria longana and fruits of Terminalia chebula. Chebulinic acid strongly inhibited the hydrolysis of 6,8-difluoro-4-methylumbelliferyl phosphate by PPP1CB (IC₅₀ = 300 nM) and demonstrated potent antiadipogenic effects in 3T3-L1 preadipocytes in a concentration-dependent manner. Additional studies have demonstrated that chebulinic acid suppresses early differentiation by downregulating key transcription factors that control adipogenesis in 3T3-L1 cells. These results suggested that chebulinic acid may be a potential therapeutic agent for treating obesity by inhibiting PPP1CB activity.

Evaluation of Anti-Obesity Activity of an Herbal Formulation (F2) in DIO Mice Model and Validation of UPLC-DAD Method for Quality Control

Obesity is considered a chronic metabolic disorder that can be associated with multiple medical complications. Currently, there is no or limited curative therapy for obesity. This study focused on the assessment of anti-obesity activity and UPLC standardization of a polyherbal formulation (F2). An anti-obesity activity was investigated using the diet-induced obese (DIO) mice model, where obesity was developed in C57BL/6J mice by providing a high-fat diet (HFD) for five weeks without treating drugs. After the successful development of obesity, the obese mice were treated with F2 for seven weeks with continuing HFD feeding. The major obesity-related parameters such as body weight gain, food efficiency ratio, serum lipid profile, and white adipose tissue (WAT) mass were found to be significantly reduced in F2 treated obese mice. These results were supported by the down-regulation of specific adipogenic transcription factors (PPARγ, SREBP-1c, and ap2) in epididymal WAT. Histological evaluation of liver and WAT also revealed reduced fat deposition in the tissues by F2 compared to the HFD control group. The overall observations indicated that the F2 exhibited pronounced obesity-controlling activity through the inhibition of adipocyte differentiation and triglyceride accumulation in the tissues, and serum lipid depletion. In addition, F2 ameliorated obesity-induced insulin resistance. Furthermore, the UPLC-DAD method for quality control of F2 was validated and standardized using five reference compounds: astragalin, ellagic acid, fisetin, fustin, and sulfuretin.

Anti-obesity effects of Celastrus orbiculatus extract containing celastrol on canine adipocytes

From 50 to 60% of companion animals in the United States are overweight or obese and this obesity rate is rising. As obesity is associated with a number of health problems, an agent that can help weight loss in pets and assist in clinically managing obesity through veterinary prescription foods and medication would be beneficial. Many studies have shown that celastrol, a phytochemical compound found in Celastrus orbiculatus extract (COE), has anti-obesity and anti-inflammatory effects, although these effects have not yet been determined in canine or canine-derived cells. The objective of this study was to investigate the effects of celastrol on the adipogenic differentiation and lipolysis of canine adipocytes. Primary preadipocytes were isolated from the gluteal region of a beagle dog and the primary adipocytes were differentiated into mature adipocytes by adipocyte differentiation media containing isobutylmethylxanthine, dexamethasone, and insulin. In a water-soluble tetrazolium (WST) assay, the cell viability of mature adipocytes was decreased after treatment with COE (0, 0.93, 2.32, and 4.64 nM celastrol) in a concentration-dependent manner, although preadipocytes were not affected. Oil Red O (ORO) staining revealed that COE inhibited the differentiation into mature adipocytes and lipid accumulation in adipocytes. In addition, treatment with COE significantly reduced triglyceride content and increased lipolytic activities by 1.5-fold in canine adipocytes. Overall, it was concluded that COE may enhance anti-obesity activity in canine adipocytes by inhibiting lipid accumulation and increasing lipolytic activity.

Hypolipidemic effects of herbal extracts by reduction of adipocyte differentiation, intracellular neutral lipid content, lipolysis, fatty acid exchange and lipid droplet motility

An increase in adipose tissue is caused by the increased size and number of adipocytes. Lipids accumulate in intracellular stores, known as lipid droplets (LDs). Recent studies suggest that parameters such as LD size, shape and dynamics are closely related to the development of obesity. Berberine (BBR), a natural plant alkaloid, has been demonstrated to possess anti-obesity effects. However, it remains unknown which cellular processes are affected by this compound or how effective herbal extracts containing BBR and other alkaloids actually are. For this study, we used extracts of Coptis chinensis, Mahonia aquifolium, Berberis vulgaris and Chelidonium majus containing BBR and other alkaloids and studied various processes related to adipocyte functionality. The presence of extracts resulted in reduced adipocyte differentiation, as well as neutral lipid content and rate of lipolysis. We observed that the intracellular fatty acid exchange was reduced in different LD size fractions upon treatment with BBR and Coptis chinensis. In addition, LD motility was decreased upon incubation with BBR, Coptis chinensis and Chelidonium majus extracts. Furthermore, Chelidonium majus was identified as a potent fatty acid uptake inhibitor. This is the first study that demonstrates the selected regulatory effects of herbal extracts on adipocyte function.

Inhibitory Effects of Vanadium-Binding Proteins Purified from the Sea Squirt Halocynthia roretzi on Adipogenesis in 3T3-L1 Adipocytes

The inhibitory effects of vanadium-binding proteins (VBPs) from the blood plasma and the intestine of sea squirt on adipogenesis in 3T3-L1 adipocytes were examined. 3T3L-1 cells treated with VBP _{blood plasma} decreased markedly the lipid content in maturing pre-adipocytes in a dose-dependent manner, whereas VBP _intestine did not show significant effects on lipid accumulation. Both VBPs did not have significant effect on cell viability. In order to demonstrate the anti-adipogenic effects of VBP _{blood plasma}, the expressions of several adipogenic transcription factors and enzymes were investigated by Reverse Transcriptase-Polymerase Chain Reaction. VBP _{blood plasma} down-regulated the expressions of transcription factors; PPAR-γ, C/EBP-α, SREBP1, and FAS, but did not have significant effects on the expressions of lipolytic enzymes; HSL and LPL. Both the crude and purified VBPs significantly increased the mRNA levels of Wnt10b, FZ1, LRP6, and β-catenin, while decreased the expression of GSK-3β. Hence, VBP _{blood plasma} inhibited adipogenesis by activating WNT/β-catenin pathway via the activation of Wnt10b. Based on the findings, VBP _{blood plasma} decreased lipid accumulation which was mediated by decreasing adipogenesis, not by lipolysis. Therefore, VBP _{blood plasma} could be used to treat obesity.

Penta-O-galloyl-β-d-glucose, a hydrolysable tannin from Radix Paeoniae Alba, inhibits adipogenesis and TNF-α-mediated inflammation in 3T3-L1 cells

Penta-O-galloyl-β-d-glucose (PGG) was purified and identified from Radix Paeoniae Alba by HSCCC and HPLC/ESI-MS, and its inhibitory effects on adipogenesis and TNF-α-induced inflammation were assessed in 3T3-L1 cell line. The results showed that PGG dose-dependently reduced intracellular lipids accumulation, and this involved decrease the expression levels of major adipogenic markers, PPARγ, C/EBP α, through MAPKs inhibition. This was accompanied by a reduction of lipogenic genes, ACC, FAS, and SCD-1, involved in fatty acid synthesis. Furthermore, PGG also inhibited TNF-α-induced expression of inflammatory cytokines including IL-6 and MCP-1 in the matured 3T3-L1 adipocytes. The inhibitions were likely mediated by blocking the MAPKs and NF-κB activation. These findings highlighted that PGG could serve as a potent therapeutic agent for controlling obesity and obesity-related chronic inflammation.

Raspberry Ketone Reduced Lipid Accumulation in 3T3-L1 Cells and Ovariectomy-Induced Obesity in Wistar Rats by Regulating Autophagy Mechanisms

This study aimed to determine the antiobesity effects of raspberry ketone (RK), one of the major aromatic compounds contained in raspberry, and its underlying mechanisms. During adipogenesis of 3T3-L1 cells, RK (300 μM) significantly reduced lipid accumulation and downregulated the expression of CCAAT/enhancer-binding protein α (C/EBPα), peroxisome proliferation-activated receptor γ (PPARγ), fatty acid-binding protein 4 (FABP4), and fatty acid synthase (FAS). RK also reduced the expression of light chain 3B (LC3B), autophagy-related protein 12 (Atg12), sirtuin 1 (SIRT1), and phosphorylated-tuberous sclerosis complex 2 (TSC2), whereas it increased the level of p62 and phosphorylated-mammalian target of rapamycin (mTOR). Daily administration of RK decreased the body weight (ovariectomy [Ovx] + RK, 352.6 ± 5 vs Ovx, 386 ± 5.8 g; P < 0.05), fat mass (Ovx + RK, 3.2 ± 0.05 vs Ovx, 5.0 ± 0.4 g; P < 0.05), and fat cell size (Ovx + RK, 6.4 ± 0.6 vs Ovx, 11.1 ± 0.7 × 10³ μm²; P < 0.05) in Ovx-induced obesity in rats. The expression of PPARγ, C/EBPα, FAS, and FABP4 was significantly reduced in the Ovx + RK group compared with that in the Ovx group. Similar patterns were observed in autophagy-related proteins and endoplasmic reticulum stress proteins. These results suggest that RK inhibited lipid accumulation by regulating autophagy in 3T3-L1 cells and Ovx-induced obese rats.

Methyltransferase and demethylase profiling studies during brown adipocyte differentiation

Although brown adipose tissue is important with regard to energy balance, the molecular mechanism of brown adipocyte differentiation has not been extensively studied. Specifically, regulation factors at the level of protein modification are largely unknown. In this study, we examine the changes in the expression level of enzymes which are involved in protein lysine methylation during brown adipocyte differentiation. Several enzymes, in this case SUV420H2, PRDM9, MLL3 and JHDM1D, were found to be up-regulated. On the other hand, Set7/9 was significantly down-regulated. In the case of SUV420H2, the expression level increased sharply during brown adipocyte differentiation, whereas the expression of SUV420H2 was marginally enhanced during the white adipocyte differentiation. The knock-down of SUV420H2 caused the suppression of brown adipocyte differentiation, as compared to a scrambled control. These results suggest that SUV420H2, a methyltransferase, is involved in brown adipocyte differentiation, and that the methylation of protein lysine is important in brown adipocyte differentiation. [BMB Reports 2016; 49(7): 388-393]

Set7/9, a methyltransferase, regulates the thermogenic program during brown adipocyte differentiation through the modulation of p53 acetylation

Brown adipose tissue, which is mainly composed of brown adipocytes, plays a key role in the regulation of energy balance via dissipation of extra energy as heat, and consequently counteracts obesity and its associated-disorders. Therefore, brown adipocyte differentiation should be tightly controlled at the multiple regulation steps. Among these, the regulation at the level of post-translational modifications (PTMs) is largely unknown. Here, we investigated the changes in the expression level of the enzymes involved in protein lysine methylation during brown adipocyte differentiation by using quantitative real-time PCR (qPCR) array analysis. Several enzymes showing differential expression patterns were identified. In particular, the expression level of methyltransferase Set7/9 was dramatically repressed during brown adipocyte differentiation. Although there was no significant change in lipid accumulation, ectopic expression of Set7/9 led to enhanced expression of several key thermogenic genes, such as uncoupling protein-1 (UCP-1), Cidea, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and PR domain containing 16 (PRDM16). In contrast, knockdown of endogenous Set7/9 led to significantly reduced expression of these thermogenic genes. Furthermore, suppressed mitochondrial DNA content and decreased oxygen consumption rate were also detected upon Set7/9 knockdown. We found that p53 acetylation was regulated by Set7/9-dependent interaction with Sirt1. Based on these results, we suggest that Set7/9 acts as a fine regulator of the thermogenic program during brown adipocyte differentiation by regulation of p53 acetylation. Thus, Set7/9 could be used as a valuable target for regulating thermogenic capacity and consequently to overcome obesity and its related metabolic diseases.

Silica nanoparticles inhibit brown adipocyte differentiation via regulation of p38 phosphorylation

Nanoparticles are of great interest due to their wide variety of biomedical and bioengineering applications. However, they affect cellular differentiation and/or intracellular signaling when applied and exposed to target organisms or cells. The brown adipocyte is a cell type important in energy homeostasis and thus closely related to obesity. In this study, we assessed the effects of silica nanoparticles (SNPs) on brown adipocyte differentiation. The results clearly showed that brown adipocyte differentiation was significantly repressed by exposure to SNPs. The brown adipocyte-specific genes as well as mitochondrial content were also markedly reduced. Additionally, SNPs led to suppressed p38 phosphorylation during brown adipocyte differentiation. These effects depend on the size of SNPs. Taken together, these results lead us to suggest that SNP has anti-brown adipogenic effect in a size-dependent manner via regulation of p38 phosphorylation.

Platycodon grandiflorum A. De Candolle Ethanolic Extract Inhibits Adipogenic Regulators in 3T3-L1 Cells and Induces Mitochondrial Biogenesis in Primary Brown Preadipocytes

This study was designed to evaluate the effects of Platycodon grandiflorum A. DC. ethanolic extract (PG) on obesity in brown/white preadipocytes. The effect of PG on the differentiation and mitochondrial biogenesis of brown adipocytes is still not examined. An in vivo study showed that PG induced weight loss in mice with high-fat-diet-induced obesity. PG successfully suppressed the differentiation of 3T3-L1 cells by down-regulating cellular induction of the peroxisome proliferators activated receptor γ (PPARγ), CCAAT enhancer binding protein α (C/EBPα), lipin-1, and adiponectin but increasing expression of silent mating type information regulation 2 homologue 1 (SIRT1) and the phosphorylation of AMP-activated protein kinase α (AMPKα). The effect of PG on the adipogenic factors was compared with that of its bioactive compound platycodin D. In addition, PG increased expressions of mitochondria-related genes, including uncoupling protein 1 (UCP1), peroxisome proliferator activated receptor-coactivator 1 α (PGC1α), PR domain containing 16 (PRDM16), SIRT3, nuclear respiratory factor (NRF), and cytochrome C (CytC) in primary brown adipocytes. These results indicate that PG stimulates the differentiation of brown adipocytes through modulation of mitochondria-related genes and could offer clinical benefits as a supplement to treat obesity.

Berberine Suppresses Adipocyte Differentiation via Decreasing CREB Transcriptional Activity

Berberine, one of the major constituents of Chinese herb Rhizoma coptidis, has been demonstrated to lower blood glucose, blood lipid, and body weight in patients with type 2 diabetes mellitus. The anti-obesity effect of berberine has been attributed to its anti-adipogenic activity. However, the underlying molecular mechanism remains largely unknown. In the present study, we found that berberine significantly suppressed the expressions of CCAAT/enhancer-binding protein (C/EBP)α, peroxisome proliferators-activated receptor γ2 (PPARγ2), and other adipogenic genes in the process of adipogenesis. Berberine decreased cAMP-response element-binding protein (CREB) phosphorylation and C/EBPβ expression at the early stage of 3T3-L1 preadipocyte differentiation. In addition, CREB phosphorylation and C/EBPβ expression induced by 3-isobutyl-1-methylxanthine (IBMX) and forskolin were also attenuated by berberine. The binding activities of cAMP responsive element (CRE) stimulated by IBMX and forskolin were inhibited by berberine. The binding of phosphorylated CREB to the promoter of C/EBPβ was abrogated by berberine after the induction of preadipocyte differentiation. These results suggest that berberine blocks adipogenesis mainly via suppressing CREB activity, which leads to a decrease in C/EBPβ-triggered transcriptional cascades.

Recent advances in proteomic studies of adipose tissues and adipocytes

Obesity is a chronic disease that is associated with significantly increased levels of risk of a number of metabolic disorders. Despite these enhanced health risks, the worldwide prevalence of obesity has increased dramatically over the past few decades. Obesity is caused by the accumulation of an abnormal amount of body fat in adipose tissue, which is composed mostly of adipocytes. Thus, a deeper understanding of the regulation mechanism of adipose tissue and/or adipocytes can provide a clue for overcoming obesity-related metabolic diseases. In this review, we describe recent advances in the study of adipose tissue and/or adipocytes, focusing on proteomic approaches. In addition, we suggest future research directions for proteomic studies which may lead to novel treatments of obesity and obesity-related diseases.

MAP kinase phosphatase DUSP1 is overexpressed in obese humans and modulated by physical exercise

Chronic low-grade inflammation and dysregulation of the stress defense system are cardinal features of obesity, a major risk factor for the development of insulin resistance and diabetes. Dual-specificity protein phosphatase 1 (DUSP1), known also as MAP kinase phosphatase 1 (MKP1), is implicated in metabolism and energy expenditure. Mice lacking DUSP1 are resistant to high-fat diet-induced obesity. However, the expression of DUSP1 has not been investigated in human obesity. In the current study, we compared the expression pattern of DUSP1 between lean and obese nondiabetic human subjects using subcutaneous adipose tissue (SAT) and peripheral blood mononuclear cells (PBMCs). The levels of DUSP1 mRNA and protein were significantly increased in obese subjects with concomitant decrease in the phosphorylation of p38 MAPK (p-p38 MAPK) and PGC-1α and an increase in the levels of phospho-JNK (p-JNK) and phospho-ERK (p-ERK). Moreover, obese subjects had higher levels of circulating DUSP1 protein that correlated positively with various obesity indicators, triglycerides, glucagon, insulin, leptin, and PAI-1 (P < 0.05) but negatively with V̇O(2max) and high-density lipoprotein (P < 0.05). The observation that DUSP1 was overexpressed in obese subjects prompted us to investigate whether physical exercise could reduce its expression. In this study, we report for the first time that physical exercise significantly attenuated the expression of DUSP1 in both the SAT and PBMCs, with a parallel increase in the expression of PGC-1α and a reduction in the levels of p-JNK and p-ERK along with attenuated inflammatory response. Collectively, our data suggest that DUSP1 upregulation is strongly linked to adiposity and that physical exercise modulates its expression. This gives further evidence that exercise might be useful as a strategy for managing obesity and preventing its associated complications.

Protein tyrosine phosphatase profiling studies during brown adipogenic differentiation of mouse primary brown preadipocytes

There is a correlation between obesity and the amount of brown adipose tissue; however, the molecular mechanism of brown adipogenic differentiation has not been as extensively studied. In this study, we performed a protein tyrosine phosphatase (PTP) profiling analysis during the brown adipogenic differentiation of mouse primary brown preadipocytes. Several PTPs, including PTPRF, PTPRZ, and DUSP12 showing differential expression patterns were identified. In the case of DUSP12, the expression level is dramatically downregulated during brown adipogenesis. The ectopic expression of DUSP12 using a retroviral expression system induces the suppression of adipogenic differentiation, whereas a catalytic inactive DUSP12 mutant showed no effect on differentiation. These results suggest that DUSP12 is involved in brown adipogenic differentiation and may be used as a target protein for the treatment or prevention of obesity by the regulation of brown adipogenic differentiation.

Acceleration of adipogenic differentiation via acetylation of malate dehydrogenase 2

Previously, we identified proteins showing a differential acetylation pattern during adipogenic differentiation. Here, we examined the role of malate dehydrogenase 2 (MDH2) acetylation in the adipogenesis of 3T3-L1 preadipocytes. The acetylation level of MDH2 showed a dramatic increase during adipogenesis. The overexpression of wild-type MDH2 induced the significant acceleration of adipogenic differentiation. On the other hand, the acetylation-block mutant MDH2 showed significantly reduced adipogenic differentiation compared to the wild type. MDH2 acetylation enhances its enzymatic activity and consequently intracellular NADPH level. These results suggest that the acetylation of MDH2 was affected by the cellular energy state and subsequently regulated adipogenic differentiation.

Investigation of adipocyte proteome during the differentiation of brown preadipocytes

Brown adipocytes oxidize fatty acids to produce heat in response to cold or caloric overfeeding. The motivation and function of the development of brown fat may thus counteract obesity, though this remains uncertain. We investigated the brown adipocyte proteome by two-dimensional gel electrophoresis followed by mass spectrometry. Comparative analyses of proteins focused on total protein spots to filter differentially expressed proteins during the differentiation of mouse primary brown preadipocytes. A Western blot analysis was performed to verify the target proteins. The results indicated that 10 protein spots were differentially expressed with significant changes, including the three up-regulated proteins of prohibitin, hypoxanthine-guanine phosphoribosyltransferase, and enoyl-CoA hydratase protein; the 5 down-regulated proteins of triosephosphate isomerase, elongation factor 2, α-tropomyosin slow, endophilin-B1, and cofilin-1 (CFL1); and the two unequivocally expressed proteins of peroxiredoxin-1 and collagen α-1(i) chain precursor. We found that during brown adipogenesis, CFL1 has an inhibitory effect on brown adipocyte differentiation. The overexpression of CFL1 inhibited the brown fat deposition and repressed the brown marker genes UCP1, PRDM16, PGC-1α and PPARγ via actin dynamics and polymerization. These observations may be novel findings that bring new insight into the detailed mechanisms of brown adipogenesis and identify possible therapeutic targets for anti-obesity.

BIOLOGICAL SIGNIFICANCE

We use 2-DE to compare the proteomes of adipocytes during the brown adipogenesis of primary mouse preadipocytes. We identified 10 proteins that are differentially expressed. Among these, we found that the actin binding protein CFL1 inhibits the differentiation of brown preadipocytes. CFL1 overexpressing cells showed lower deposition of brown fat droplets, and the brown marker genes of UCP1, PRDM16, PGC-1α and PPARγ were decreased through actin dynamics and polymerization.

Gender-specific metabolomic profiling of obesity in leptin-deficient ob/ob mice by 1H NMR spectroscopy

Despite the numerous metabolic studies on obesity, gender bias in obesity has rarely been investigated. Here, we report the metabolomic analysis of obesity by using leptin-deficient ob/ob mice based on the gender. Metabolomic analyses of urine and serum from ob/ob mice compared with those from C57BL/6J lean mice, based on the (1)H NMR spectroscopy in combination with multivariate statistical analysis, revealed clear metabolic differences between obese and lean mice. We also identified 48 urine and 22 serum metabolites that were statistically significantly altered in obese mice compared to lean controls. These metabolites are involved in amino acid metabolism (leucine, alanine, ariginine, lysine, and methionine), tricarbocylic acid cycle and glucose metabolism (pyruvate, citrate, glycolate, acetoacetate, and acetone), lipid metabolism (cholesterol and carnitine), creatine metabolism (creatine and creatinine), and gut-microbiome-derived metabolism (choline, TMAO, hippurate, p-cresol, isobutyrate, 2-hydroxyisobutyrate, methylamine, and trigonelline). Notably, our metabolomic studies showed distinct gender variations. The obese male mice metabolism was specifically associated with insulin signaling, whereas the obese female mice metabolism was associated with lipid metabolism. Taken together, our study identifies the biomarker signature for obesity in ob/ob mice and provides biochemical insights into the metabolic alteration in obesity based on gender.

Dual-specificity phosphatase 10 controls brown adipocyte differentiation by modulating the phosphorylation of p38 mitogen-activated protein kinase

Background

Brown adipocytes play an important role in regulating the balance of energy, and as such, there is a strong correlation between obesity and the amount of brown adipose tissue. Although the molecular mechanism underlying white adipocyte differentiation has been well characterized, brown adipocyte differentiation has not been studied extensively. Here, we investigate the potential role of dual-specificity phosphatase 10 (DUSP10) in brown adipocyte differentiation using primary brown preadipocytes.

Methods and Results

The expression of DUSP10 increased continuously after the brown adipocyte differentiation of mouse primary brown preadipocytes, whereas the phosphorylation of p38 was significantly upregulated at an early stage of differentiation followed by steep downregulation. The overexpression of DUSP10 induced a decrease in the level of p38 phosphorylation, resulting in lower lipid accumulation than that in cells overexpressing the inactive mutant DUSP10. The expression levels of several brown adipocyte markers such as PGC-1α, UCP1, and PRDM16 were also significantly reduced upon the ectopic expression of DUSP10. Furthermore, decreased mitochondrial DNA content was detected in cells expressing DUSP10. The results obtained upon treatment with the p38 inhibitor, SB203580, clearly indicated that the phosphorylation of p38 at an early stage is important in brown adipocyte differentiation. The effect of the p38 inhibitor was partially recovered by DUSP10 knockdown using RNAi.

Conclusions

These results suggest that p38 phosphorylation is controlled by DUSP10 expression. Furthermore, p38 phosphorylation at an early stage is critical in brown adipocyte differentiation. Thus, the regulation of DUSP10 activity affects the efficiency of brown adipogenesis. Consequently, DUSP10 can be used as a novel target protein for the regulation of obesity.

Retinoic acid inhibits adipogenesis via activation of Wnt signaling pathway in 3T3-L1 preadipocytes

Although retinoic acid (RA) is well known to inhibit the differentiation of 3T3-L1 cells into adipocytes both in vivo and in vitro, its molecular mechanism is not fully understood. In this report, we investigate the inhibitory mechanism of adipocyte differentiation by RA in 3T3-L1 cells. Because both RA and Wnt are known to inhibit adipogenesis at a common step involving the inhibition of PPAR-γ expression, we focused on the crosstalk between these two signaling pathways. We found that RA treatment resulted in a dramatic inhibition of adipogenesis, especially at an early phase of differentiation, and led to increased β-catenin protein expression. Moreover, RA enhances the transcriptional activity of β-catenin as well as Wnt gene expression during adipogenesis. Taken together, the present study demonstrated that Wnt/β-catenin signaling may be associated with the RA-induced suppression of adipogenesis and may cooperatively inhibit adipocyte differentiation.