Regulation of adipocyte gene expression in differentiation and syndromes of obesity/diabetes

The regulation of PKA signaling in obesity and in the maintenance of metabolic health

The cAMP-dependent protein kinase (PKA) system represents a primary cell-signaling pathway throughout systems and across species. PKA facilitates the actions of hormones, neurotransmitters and other signaling molecules that bind G-protein coupled receptors (GPCR) to modulate cAMP levels. Through its control of synaptic events, exocytosis, transcriptional regulation, and more, PKA signaling regulates cellular metabolism and emotional and stress responses making it integral in the maintenance and dysregulation of energy homeostasis. Neural PKA signaling is regulated by afferent and peripheral efferent signals that link specific neural cell populations to the regulation of metabolic processes in adipose tissue, liver, pancreas, adrenal, skeletal muscle, and gut. Mouse models have provided invaluable information on the roles for PKA subunits in brain and key metabolic organs. While limited, human studies infer differential regulation of the PKA system in obese compared to lean individuals. Variants identified in PKA subunit genes cause Cushing syndrome that is characterized by metabolic dysregulation associated with endogenous glucocorticoid excess. Under healthy physiologic conditions, the PKA system is exquisitely regulated by stimuli that activate GPCRs to alter intracellular cAMP concentrations, and by PKA cellular localization and holoenzyme stability. Adenylate cyclase activity generates cAMP while phosphodiesterase-mediated cAMP degradation to AMP decreases cAMP levels downstream of GPCRs. Chronic perturbations in PKA signaling appear to be capable of resetting PKA regulation at several levels; in addition, sex differences in PKA signaling regulation, while not well understood, impact the physiologic consequences of metabolic dysregulation and obesity. This review explores the roles for PKA signaling in the pathogenesis of metabolic diseases including obesity, type 2 diabetes mellitus and associated co-morbidities through neural-peripheral crosstalk and cAMP/PKA signaling pathway targets that hold therapeutic potential.

FPR2-based anti-inflammatory and anti-lipogenesis activities of novel meroterpenoid dimers from Ganoderma

Four pairs of novel meroterpenoid dimers, (±)-applandimeric acids A-D (1-4) with an unprecedented spiro[furo[3,2-b]benzofuran-3,2'-indene] core were isolated from the fruiting bodies of Ganoderma applanatum. Their planar structures were unambiguously determined via extensive spectroscopic analysis. Their relative and absolute configurations were confirmed through calculated internuclear distance, coupling constant, ¹³C NMR with DP4 + analysis and electronic circular dichroism (ECD). Furthermore, the molecular docking-based method was used to evaluate their interaction with formyl peptide receptor 2 (FPR2) associated with inflammation. Interestingly, (±)-applandimeric acid D (4) can bond with FPR2 by some key hydrogen bonds. Furthermore, an in vitro bioassay verified that 4 can inhibit the expression of FPR2 with IC₅₀ value of 7.93 μM. In addition, compared to the positive control LiCl (20 mM), 4 showed comparable anti-lipogenesis activity at the concentration of 20 μM. Meanwhile, 4 can suppress the protein levels of peroxisome proliferators-activated receptor-γ (PPAR-γ), CCAAT/enhancer-binding protein-β (C/EBP-β), adipocyte fatty acid-binding protein 4 (FABP4), and fatty acid synthase (FAS) through activating AMP-activated protein kinase (AMPK) signaling pathway. Thus, our findings indicate that compound 4 could be a lead compound to treat obesity and obesity-related diseases by inhibiting lipid accumulation in adipocyte and alleviating inflammation.

Effects of Bacillus Subtilis-Fermented White Sword Bean Extract on Adipogenesis and Lipolysis of 3T3-L1 Adipocytes

To investigate the adipogenesis and lipolysis effects of the Bacillus subtilis-fermented white sword bean extract (FWSBE) on 3T3-L1 adipocytes, we treated 3T3-L1 preadipocytes before and after differentiation with FWSBE and measured triglyceride, free glycerol, mRNA, and protein levels. First, FWSBE reduced the cell viability of 3T3-L1 pre-adipocytes under 1000 µg/mL conditions. Triglyceride accumulation in 3T3-L1 pre-adipocytes was suppressed, and free glycerol content in mature 3T3-L1 adipocytes was increased in the FWSBE treatment groups, indicating that FWSBE has anti-obesity effects. Further, FWSBE suppressed adipogenesis in 3T3-L1 pre-adipocytes by lowering the protein levels of C/EBPα, PPARγ, and FAS and increasing the level of pACC and pAMPK. Additionally, FWSBE promoted lipolysis in mature 3T3-L1 adipocytes by increasing the transcription levels of Ppara, Acox, and Lcad and the protein levels of pHSL and ATGL. Thus, we suggest that FWSBE can be a potential dietary supplement because of its anti-obesity properties.

TET1 promotes RXRα expression and adipogenesis through DNA demethylation

Adipose tissue is important for systemic metabolic homeostasis in response to environmental changes, and adipogenesis involves dynamic transcriptional regulation. Ten-eleven translocation (TET) enzymes (TET1, 2 and 3) oxidize the 5-methylcytosine (5mC) in DNA to 5-hydroxylmethylcytosine (5hmC), which associates with transcriptional activation. Step by step, 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) are further generated by TETs and the cytosine can be restored through base-excision repair. It is still unclear how DNA demethylation is involved in adipogenesis. Through a phenotypic screen, we found TET inhibition decreased adipocyte differentiation from mesenchymal stem cells (MSCs). Comparing with the undifferentiated MSCs, the differentiated adipocytes exhibited much higher levels of 5hmC and slightly increased 5fC and 5caC. Higher 5hmC was associated with better differentiation at single-cell level by image analysis. TET1 is upregulated in differentiation and depletion of it significantly impaired the gain of 5hmC. Furthermore, Tet1 depletion significantly hampered the adipocyte differentiation. Using RNA-seq, 5mC and 5hmC-DNA immunoprecipitation, we found that Tet1 knockout led to lower expression of genes associated with lipid metabolism and fat cell differentiation. Genes with loss of 5mC or gain of 5hmC in adipocytes include Lipe, Bmp4 and Rxra, etc. RXRα agonist partially rescued the inhibitory effect of Tet1 knockout for adipogenesis. So, Rxra is one of the critical TET1 modulated genes. Together, TET1-mediated active DNA demethylation plays an important role in adipogenesis.

Design, synthesis, and biological evaluation of novel sulindac derivatives as partial agonists of PPARγ with potential anti-diabetic efficacy

Peroxisome proliferator-activated receptor gamma (PPARγ) is a valuable drug target for diabetic treatment and ligands of PPARγ have shown potent anti-diabetic efficacy. However, to overcome the severe side effects of current PPARγ-targeted drugs, novel PPARγ ligands need to be developed. Sulindac, an identified ligand of PPARγ, is widely used in clinic as a non-steroidal anti-inflammatory drug. To explore its potential application for diabetes, we designed and synthesized a series of sulindac derivatives to investigate their structure-activity relationship as PPARγ ligand and potential anti-diabetic effect. We found that meta-substitution in sulindac's benzylidene moiety was beneficial to PPARγ binding and transactivation. Z rather than E configuration of the benzylidene double bond endowed derivatives with the selectivity of PPARγ activation. The indene fluorine is essential for binding and regulating PPARγ. Compared with rosiglitazone, compound 6b with benzyloxyl meta-substitution and Z benzylidene double bond weakly induced adipogenesis and PPARγ-targeted gene expression. However, 6b potently improved glucose tolerance in a diabetic mice model. Unlike rosiglitazone, 6b was devoid of apparent toxicity to osteoblastic formation. Thus, we provided some useful guidelines for PPARγ-based optimization of sulindac and an anti-diabetic lead compound with less side effects.

Farnesoid X receptor (FXR) agonist ameliorates systemic insulin resistance, dysregulation of lipid metabolism, and alterations of various organs in a type 2 diabetic kidney animal model

BACKGROUND

Farnesoid X receptor (FXR) plays a role in homeostasis of bile acid, lipid, and carbohydrate metabolism. However, the systemic effects of FXR in diabetic nephropathy are controversial. We aimed to clarify the systemic effects of FXR on various organs in a type 2 diabetic animal model.

METHODS

We treated db/db mice with the FXR agonist GW4064 for 3 months and evaluated insulin resistance, lipid metabolism, renal functional changes, and structural changes in organs including those of the kidney, liver, pancreas, adipose tissue, aorta, and heart.

RESULTS

The FXR agonist significantly improved plasma lipid profiles and insulin resistance and showed beneficial systemic effects on several organs. In the kidney, the FXR agonist ameliorated albuminuria, pro-fibrotic and pro-inflammatory changes and improved renal lipid metabolism. These changes were also associated with a decrease in lipid hydroperoxide in the kidney. Similar beneficial effects were shown in other organs, including restoration of pancreatic beta cell hypertrophy, hepatic steatosis and aortic medial hypertrophy, more differentiated phenotypic changes in adipose tissue, and improvement of cardiomyocyte disarray and left ventricular mass index.

CONCLUSIONS

The FXR agonist improves insulin resistance, renal lipid metabolism, and functional and structural changes in the kidney and other organs.

Chrysanthemum morifolium Flower Extract Inhibits Adipogenesis of 3T3-L1 Cells via AMPK/SIRT1 Pathway Activation

Chrysanthemum (Chrysanthemum morifolium Ramat) flowers (CF) are widely consumed as herbal tea in many countries, including China. The aim of the present study was to examine the anti-adipogenic effect of hot water extraction of CF (HCF) on 3T3-L1 cells and their underlying cellular mechanisms. HCF treatment inhibited lipid accumulation under conditions that did not show the toxicity of 3T3-L1 adipocytes. The activity of glycerol-3-phosphate dehydrogenase (GPDH), which plays an important role in glycerol lipid metabolism, was also reduced by HCF. Adipogenesis/lipogenesis-related mRNA expression levels of peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAAT/enhancer-binding protein-α (CEBP-α), sterol regulatory element-binding protein-1c (SREBP-1c), fatty acid-binding protein 4 (FABP4), acetyl-CoA carboxylase 1 (ACC1), and fatty acid synthase (FAS) were suppressed by HCF in a dose-dependent manner. Moreover, HCF increased activities of AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1), involved in lipid metabolism. These findings suggest that HCF inhibits adipocyte lipid accumulation through suppression of adipogenesis/lipogenesis-related gene expression and activation of the AMPK/SIRT1 pathway. Therefore, it suggests that HCF may be used as a potentially beneficial plant material for preventing obesity.

Biochanin A prevents 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced adipocyte dysfunction in cultured 3T3-L1 cells

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental pollutant. TCDD accumulates in the food chain, mainly in the fatty tissues of the human body where it causes various toxic effects. Biochanin A is a natural organic compound in the class of phytochemicals known as flavonoids. We investigated whether biochanin A suppresses TCDD-induced loss of adipogenic action using 3T3-L1 adipocytes as a cell culture model of wasting syndrome. In the present study, biochanin A suppressed TCDD-induced loss of lipid accumulation. Pretreating the cells with biochanin A increased the levels of the adipogenesis-associated factors peroxisome proliferator-activated receptor γ and adiponectin, which were inhibited by TCDD. TCDD decreased insulin-stimulated glucose uptake, which was effectively restored by pretreatment with biochanin A. Biochanin A also inhibited the TCDD-driven decrease in production of insulin receptor substrate-1 and glucose transporter 4. These results suggest a preventive effect of biochanin A against TCDD in the development of insulin resistance and diabetes. TCDD increased production of intracellular calcium ([Ca²⁺]_i), prostaglandin E₂, cytosolic phospholipase A2, and cyclooxygenase-1, while reducing the level of peroxisome proliferator-activated receptor gamma coactivator 1-alpha. However, biochanin A inhibited these TCDD-induced effects. We conclude that biochanin A is an attractive compound for preventing TCDD-induced wasting syndrome.

Supplementation of All-Trans-Retinoic Acid Below Cytotoxic Levels Promotes Adipogenesis in 3T3-L1 Cells

Vitamin A, referred to as retinol, is an essential nutrient that affects the cell growth and differentiation including adipogenesis. Although previous studies using supraphysiological doses (over 1 μM) of all-trans-retinoic acid (atRA) demonstrated antiadipogenic activity, effects of atRA at various levels on differentiation of 3T3-L1 preadipocytes have not been extensively investigated. Our study showed that the amount of cellular triacylglycerol (TAG) and intensities of Oil-Red-O staining were decreased by supplementing atRA (1 and 10 μM) but increased by low concentrations of atRA (0.01 to 100 nM) compared with the control. Also PPARγ and FABP4 were gradually overexpressed by atRA up to 1 nM but decreased at over 1 nM concentrations. Moreover, mitotic clonal expansion (MCE) and consequential growth-arrest were analyzed as important steps in adipogenesis of 3T3-L1 cells. The 1 nM group showed more cell proliferation and thereafter a higher ratio of the G0/G1 phase on Day 2. Protein levels of S/G2-phase factors were dose dependently increased by atRA up to 1 nM on Day 1, but the factors were highly expressed in higher doses on Day 2. G0/G1 markers were higher at the higher doses of atRA on Day 1; whereas, they were highly expressed in mild or medium doses on Day 2. These data indicate that atRA controls adipogenesis with accompanied changes in cell proliferation and follow-up growth-arrest. These results indicate that atRA can function both as a negative and positive regulator of adipogenesis depending on dosages, providing a strategy for achieving proper nutritional balance for treatment of obesity.

Anti-Obesity Activities of Chikusetsusaponin IVa and Dolichos lablab L. Seeds

Obesity, a condition where excess body fat accumulates to the extent, causes a negative effect on health. Previously, we reported the extract of Dolichos lablab L. (DLL-Ex) inhibited high-fat diet (HFD)-induced increases in body weight and body fat mass and ameliorated increases in body weight. In the present work, we studyed the molecular mechanism for the inhibitory effect of DLL-Ex or Chikusetsusaponin IVa (CS-IVa), as isolated from Dolichos lablab L. (DLL) seeds extract, on adipocyte differentiation. We evaluated the effect of DLL-Ex, an anti-obesity agent, and CS-IVa, an active component of DLL-Ex, on 3T3-L1 cell differentiation via Oil red O assay and Q-PCR, along with their effects on CCAAT element binding protein alpha (C/EBPα), peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FAS), and fatty acid-binding protein 4 (FABP4) mRNA transcriptions. FAS and FABP4 protein expression levels after exposure to CS-IVa were also tested. The results showed that DLL-Ex and CS-IVa have potent inhibitory activity on adipocyte differentiation. Therefore, DLL and CS-IVa may be developed as a functional food material to treat obesity.

Pathological Implication of Adipocytes in AAA Development and the Rupture

Abdominal aortic aneurysm (AAA) is a vascular disease that involves the gradual dilation of the abdominal aorta followed by its rupture. AAA is closely associated with weakening of the vascular wall due to oxidative stress, chronic inflammation, and degradation of the extracellular matrix. No effective drug therapy is currently available for preventing aneurysm progression or rupture. Adipocytes in the vascular wall are reportedly closely associated with AAA development and rupture. Fiber degradation in the aneurysm wall is enhanced by increased numbers of adipocytes, and rupture risk may increase as well. Recent studies suggested that appropriate control of adipocytes in the vascular wall may be an important strategy to prevent AAA rupture, and further studies may aid in the establishment of a method for preventing AAA rupture by therapeutic drugs or functional foods. In this review, we summarize adipocyte function and the correlation between AAA and adipocytes.

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

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

Anti-obesity molecular mechanism of soy isoflavones: weaving the way to new therapeutic routes

Obesity is ringing alarm bells globally. Advances in food science and nutrition research have been devoted to identifying food components that exert anti-obesity effects, as well as investigating the molecular mechanisms by which they modulate the progression of obesity. Soy foods have attracted much interest as high-protein components of the human diet and as unique sources of isoflavones. As they have similar chemical structures to endogenous estrogens, isoflavones are believed to interact with intracellular estrogen receptors, which results in reductions in the accumulation of lipids and the distribution of adipose tissue. Both in vitro and in vivo studies have revealed other signaling pathways in which isoflavones are involved in the inhibition of adipogenesis and lipogenesis by interacting with various transcription factors and upstream signaling molecules. Although the biological mechanisms that cause the biphasic effects of isoflavones and various controversial results remain unknown, it is noteworthy that isoflavones exhibit pleiotropic effects in the human body to regulate metabolism and balance, which may potentially prevent and treat obesity.

Palmitic Acid: Physiological Role, Metabolism and Nutritional Implications

Palmitic acid (PA) has been for long time negatively depicted for its putative detrimental health effects, shadowing its multiple crucial physiological activities. PA is the most common saturated fatty acid accounting for 20–30% of total fatty acids in the human body and can be provided in the diet or synthesized endogenously via de novo lipogenesis (DNL). PA tissue content seems to be controlled around a well-defined concentration, and changes in its intake do not influence significantly its tissue concentration because the exogenous source is counterbalanced by PA endogenous biosynthesis. Particular physiopathological conditions and nutritional factors may strongly induce DNL, resulting in increased tissue content of PA and disrupted homeostatic control of its tissue concentration. The tight homeostatic control of PA tissue concentration is likely related to its fundamental physiological role to guarantee membrane physical properties but also to consent protein palmitoylation, palmitoylethanolamide (PEA) biosynthesis, and in the lung an efficient surfactant activity. In order to maintain membrane phospholipids (PL) balance may be crucial an optimal intake of PA in a certain ratio with unsaturated fatty acids, especially PUFAs of both n-6 and n-3 families. However, in presence of other factors such as positive energy balance, excessive intake of carbohydrates (in particular mono and disaccharides), and a sedentary lifestyle, the mechanisms to maintain a steady state of PA concentration may be disrupted leading to an over accumulation of tissue PA resulting in dyslipidemia, hyperglycemia, increased ectopic fat accumulation and increased inflammatory tone via toll-like receptor 4. It is therefore likely that the controversial data on the association of dietary PA with detrimental health effects, may be related to an excessive imbalance of dietary PA/PUFA ratio which, in certain physiopathological conditions, and in presence of an enhanced DNL, may further accelerate these deleterious effects.

SCARA5 plays a critical role in the commitment of mesenchymal stem cells to adipogenesis

Mesenchymal stem cells have the capacity to give rise to multiple cell types, such as adipocytes, osteoblasts, chondrocytes, and myocytes. However, the molecular events responsible for the lineage specification and differentiation of mesenchymal stem cells remain unclear. Using gene expression profile studies, we determined that Scavenger receptor class A, member 5 (SCARA5) is a novel mediator of adipocyte commitment. SCARA5 was expressed at a higher level in committed A33 preadipocyte cells compared to C3H10T1/2 pluripotent stem cells. Gain- and loss-of-function studies likewise revealed that SCARA5 acts as a mediator of adipocyte commitment and differentiation in both A33 and C3H10T1/2 cells. RNAi-mediated knockdown of SCARA5 in A33 cells markedly inhibited the adipogenic potential, whereas overexpression of SCARA5 enhanced adipocyte differentiation in C3H10T1/2 cells. We also demonstrated that the focal adhesion kinase (FAK) and ERK signaling pathways is associated with the SCARA5-mediated response, thereby modulating adipocyte lineage commitment and adipocyte differentiation. Additionally, glucocorticoids induced the expression of SCARA5 in differentiating adipocytes through glucocorticoids response elements (GRE) in the SCARA5 promoter. Taken together, our study demonstrates that SCARA5 is a positive regulator in adipocyte lineage commitment and early adipogenesis in mesenchymal stem cells.

Fish collagen peptide inhibits the adipogenic differentiation of preadipocytes and ameliorates obesity in high fat diet-fed mice

Bioactivities of fish collagen peptide are now being elucidated in diverse biological systems. Here, we investigated the effect of fish collagen peptide on the adipogenic differentiation of 3T3-L1 preadipocytes and in obese mice fed a high fat diet (HFD). Subcritical water-hydrolyzed fish collagen peptide (SWFCP) significantly inhibited lipid accumulation during the differentiation of 3T3-L1 preadipocytes, which was accompanied by decreased expression of CCAAT-enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), and adipocyte protein 2 (aP2) genes, key regulators of differentiation and maintenance of adipocytes. SWFCP was also found to suppress the palmitate-induced accumulation of lipid vacuoles in hepatocytes. Oral administration of SWFCP significantly reduced HFD-induced body weight gain without a significant difference in food intake. Consistent with its effects in 3T3-L1 preadipocytes, SWFCP inhibited the expression of C/EBP-α, PPAR-γ, and aP2 in epididymal adipose tissue of mice fed a HFD, leading to a significant reduction in adipocyte size. Furthermore, SWFCP significantly reduced serum levels of total cholesterol, triglyceride, and low-density lipoprotein, and increased serum high-density lipoprotein. These observations suggest that SWFCP inhibits adipocyte differentiation through a mechanism involving transcriptional repression of the major adipogenic regulators C/EBP-α and PPAR-γ, thereby reducing body weight gain and adipogenesis in an animal model of obesity.

Cytoglobin: a potential marker for adipogenic differentiation in preadipocytes in vitro

Obesity, mainly characterized by the excess fat storage, is a global health problem resulting in serious morbidity and mortality. Identification of molecular mechanisms in adipogenic differentiation pathway might lead to development of new strategies for diagnosis, prevention and therapy of obesity and associated diseases. Discovery of new genes and proteins in the differentiation pathway could help to understand the key specific regulators of the adipogenesis. Cytoglobin (Cygb), identified as a new globin family member protein, is expressed in various tissues. Although its interaction with oxygen and nitric oxide indicates the potential role in antioxidant pathways, the exact role remains unclear. In the current study, expression level of Cygb was determined in proliferating and differentiating 3T3-F442A cells by gene expression and protein expression analysis. Results revealed that Cygb expression up-regulated in differentiated cells in parallel with adipogenic differentiation markers; PPARγ, CEBPα and FABP4 expressions. Besides, Cygb overexpression in preadipocytes contributed to the adipogenic differentiation as verified by detection of higher lipid droplets and increased PPARγ, CEBPα and FABP4 expressions with respect to control cells. These findings will shed light on the unknown roles of Cygb in adipogenesis and obesity.

Sigumjang (fermented barley bran) water-soluble extracts inhibit the expression of adipogenic and lipogenic regulators in 3T3-L1 adipocytes

Sigumjang prepared from fermented barley bran is a traditional fermented food found only in the Gyeongsang-do area of South Korea. There have been no studies reported to date despite the potential bioactivities of sigumjang. In this study, the anti-obesity activities of sigumjang extracts (SEs) during 3T3-L1 differentiation into adipocytes were investigated. SEs inhibited adipocyte differentiation by suppressing the CCAAT/enhancer binding protein-β and sterol regulatory element binding protein-1c expression in the early stage of differentiation, followed by the suppression of the peroxisome proliferator-activated receptor-γ, CCAAT/enhancer binding protein-α, and adiponectin. These changes in adipogenic markers induced inhibition of lipogenesis via down-regulation of mainly fatty acid synthase, acetyl-CoA carboxylase, fatty acid binding protein 4, and perilipin. These results were more significant in the extract of sigumjang fermented with isolated Bacillus amyloliquefaciens MFST compared to naturally fermented sigumjang group. SEs can be considered as a useful material for developing food with health benefits and anti-obesity properties.

Liver-specific ATP-citrate lyase inhibition by bempedoic acid decreases LDL-C and attenuates atherosclerosis

Despite widespread use of statins to reduce low-density lipoprotein cholesterol (LDL-C) and associated atherosclerotic cardiovascular risk, many patients do not achieve sufficient LDL-C lowering due to muscle-related side effects, indicating novel treatment strategies are required. Bempedoic acid (ETC-1002) is a small molecule intended to lower LDL-C in hypercholesterolemic patients, and has been previously shown to modulate both ATP-citrate lyase (ACL) and AMP-activated protein kinase (AMPK) activity in rodents. However, its mechanism for LDL-C lowering, efficacy in models of atherosclerosis and relevance in humans are unknown. Here we show that ETC-1002 is a prodrug that requires activation by very long-chain acyl-CoA synthetase-1 (ACSVL1) to modulate both targets, and that inhibition of ACL leads to LDL receptor upregulation, decreased LDL-C and attenuation of atherosclerosis, independently of AMPK. Furthermore, we demonstrate that the absence of ACSVL1 in skeletal muscle provides a mechanistic basis for ETC-1002 to potentially avoid the myotoxicity associated with statin therapy.

The Role of Adiponectin in Atherosclerosis and Thrombosis

Obesity is a major risk factor for morbidity and mortality from cardiovascular causes. Adiponectin has been identified recently as one of the adipocytokines with important metabolic effects. It can suppress atherogenesis by inhibiting the adherence of monocytes, reducing their phagocytic activity, and suppressing the accumulation of modified lipoproteins in the vascular wall. In addition, as adiponectin decrease endothelial damage and stimulates production of NO from vascular endothelial cells, hypoadiponectinemia may be partially contribute to thrombus formation.

Lipin1-Mediated Repression of Adipogenesis by Rutin

Rutin, also called rutoside or quercetin-3-O-rutinoside and sophorin, is a glycoside between the flavonol quercetin and the disaccharide rutinose. Although many effects of rutin have been reported in vitro and in vivo, the anti-adipogenic effects of rutin have not been fully reported. The aim of this study was to confirm how rutin regulates adipocyte related factors. In this study, rutin decreased the expressions of adipogenesis-related genes, including peroxisome proliferators, activated receptor [Formula: see text] (PPAR[Formula: see text], CCAAT/enhancer-binding protein [Formula: see text] (C/EBP[Formula: see text], fatty acid synthase, adipocyte fatty acid-binding protein, and lipoprotein lipase in 3T3-L1 cells. Rutin also repressed the expression of lipin1, which is an upstream regulator that controls PPAR[Formula: see text] and C/EBP[Formula: see text]. In addition, when 3T3-L1 was transfected with lipin1 siRNA to block lipin1 function, rutin did not affect the expressions of PPAR[Formula: see text] and C/EBP[Formula: see text]. These results suggest that rutin has an anti-adipogenic effect that acts through the suppression of lipin1, as well as PPAR[Formula: see text] and C/EBP[Formula: see text].

Design, synthesis and biological evaluation of a hybrid compound of berberine and magnolol for improvement of glucose and lipid metabolism

The discovery and structural optimization of lead compounds is the main task in the research and development of new drugs.

Cholecalciferol inhibits lipid accumulation by regulating early adipogenesis in cultured adipocytes and zebrafish

Cholecalciferol (CCF) is a common dietary supplement as a precursor of active vitamin D. In the present study, the effect of CCF on lipid accumulation was investigated in adipocyte cells and zebrafish models. CCF effectively inhibited lipid accumulation in both experimental models; this effect was attributed to the CCF-mediated regulation of early adipogenic factors. CCF down-regulated the expressions of CCAAT-enhancer-binding protein-β (C/EBPβ), C/EBPδ, Krueppel-like factor (KLF) 4, and KLF5, while KLF2, a negative adipogenic regulator, was increased by CCF treatment. CCF inhibited cell cycle progression of adipocytes through down-regulation of cyclin A and cyclinD; p-Rb was suppressed by CCF, but p27 was up-regulated with CCF treatment. This CCF-mediated inhibition of cell cycle progression is highly correlated to the inhibitions of extracellular signal-regulated kinase (ERK), serine threonine-specific kinase (AKT), and mammalian target of rapamycin (mTOR). Furthermore, CCF-induced inactivation of acetyl-CoA carboxylase (ACC), a fatty acid synthetic enzyme, with the activation of AMP-activated protein kinase α (AMPKα) was also observed. Consistent with the observations in adipocytes, CCF effectively inhibited lipid accumulation with the down-regulation of adipogenic factors in zebrafish. The present study indicates that CCF showed anti-adipogenic effect in adipocytes and zebrafish, and its inhibitory effect was involved in the regulation of early adipogenic events including cell cycle arrest and activation of AMPKα signaling.

Roots extracts of Adenophora triphylla var. japonica improve obesity in 3T3-L1 adipocytes and high-fat diet-induced obese mice

OBJECTIVE

To investigate the anti-obesity activity and the action mechanism of the roots of Adenophora triphylla var. japonica extract (ATE) in high-fat diet (HFD)-induced obese mice and 3T3-L1 adipocytes.

METHODS

The roots of Adenophora triphylla were extracted with 70% ethanol. To demonstrate the compounds, linoleic acid was analyzed by using gas chromatography; and the anti-obesity effects and possible mechanisms of ATE were examined in 3T3-L1 adipocytes and HFD-induced obese mice.

RESULTS

Treatment with ATE inhibited the lipid accumulation without cytotoxicity in 3T3-L1 adipocytes. Furthermore, 200 and 400 mg/kg ATE treatment significantly decreased the body weight gain, white adipose tissues (WATs) weight and plasma triglyceride level, while 100 and 200 mg/kg ATE treatment increased the plasma high-density lipoprotein cholesterol level in the HFD-induced obese mice, as compared with the HFD group. Treatment with 200 and 400 mg/kg ATE also lowered the size of adipocytes in adipose tissue and reduced the lipid accumulation in liver. ATE treatment showed significantly lower expression level of adipogenesis-related proteins, such as peroxisome proliferator-activated receptor γ, fatty acid binding protein (aP2), fatty acid synthase in 3T3-L1 adipocytes; and furthermore, decreased peroxisome proliferator-activated receptor γ, aP2, fatty acid synthase, sterol regulatory element binding protein-1c, and lipoprotein lipase mRNA expression levels in WAT of the HFD-induced obese mice.

CONCLUSIONS

These results suggested that the ATE has an anti-obesity effect, which may be elicited by regulating the expression of adipogenesis and lipogenesis-related genes and proteins in adipocytes and WAT of the HFD-induced obese mice.

Dieckol, a major phlorotannin in Ecklonia cava, suppresses lipid accumulation in the adipocytes of high-fat diet-fed zebrafish and mice: Inhibition of early adipogenesis via cell-cycle arrest and AMPKα activation

SCOPE

Dieckol is a major polyphenol of Ecklonia cava. This study demonstrates a mechanistic role for dieckol in the suppression of lipid accumulation using three models.

METHODS AND RESULTS

Mice were split into four experimental groups (n = 10 per group): normal diet, high-fat diet (HFD), and dieckol-supplemented diets. Dieckol-supplemented mice groups showed a significant decrease of body weight gain (38%) as well as fats of organs including epididymal (45%) compared with a HFD-fed group. LDL cholesterol level was reduced by 55% in dieckol-supplemented group. Adipogenic factors and lipid synthetic enzymes were analyzed via real-time PCR or immunoblotting. Dieckol regulated mRNA expressions of early adipogenic genes in 3T3-L1 cells. These results were reflected in downregulation of late adipogenic factors, resulting in a decrease in triacylglycerol content. These data were also verified in zebrafish and mouse models. Dieckol activated AMP-activated protein kinase α (AMPKα) signaling to inhibit lipid synthesis in 3T3-L1 and mouse model. Dieckol was also shown to inhibit mitotic clonal expansion via cell-cycle arrest.

CONCLUSION

Our data demonstrate that dieckol inhibits lipid accumulation via activation of AMPKα signaling and cell-cycle arrest.

The inhibitory effects of quercetin on obesity and obesity-induced inflammation by regulation of MAPK signaling

Quercetin is a flavonoid found in fruits, vegetables, leaves and grains. It has inhibitory, antiviral, antiasthma, anticancer and antiinflammatory effects. Research has suggested that obesity is linked to metabolic disorders. In this study, we examined the inhibitory effect of quercetin on lipid accumulation and obesity-induced inflammation using 3T3-L1, RAW264.7, zebrafish and mouse models. Quercetin suppressed protein levels of the key adipogenic factors C/EBPβ, C/EBPα, PPARγ and FABP4 and the TG-synthesis enzymes lipin1, DGAT1 and LPAATθ. Activation of m-TOR and p70S6K, which are related to insulin and adipogenesis, was down-regulated during adipogenesis in 3T3-L1 cells. Recent research suggested that MAPK signaling factors were involved in adipogenesis and inflammation and that the adipokines MCP-1 and TNF-α attracted macrophages into adipose tissue. Our data showed that quercetin inhibited the MAPK signaling factors ERK1/2, JNK and p38MAPK and MCP-1 and TNF-α in adipocytes and macrophages. Quercetin also inhibited secretion of the inflammatory cytokines IL-1β and IL-6 and stimulated that of IL-10, an antiinflammatory cytokine. In this study, we confirmed the inhibitory effects of quercetin in adipogenesis and inflammation using a mouse model. In mice, quercetin reduced body weight (almost 40%) and suppressed expression of adipogenic, lipogenic and inflammation-related cytokines. Our data demonstrated that quercetin inhibits lipid accumulation and obesity-induced inflammation in the cell and animal models. Our study suggested that quercetin may represent a potential therapeutic agent for other metabolic disorders by regulating obesity and obesity-induced inflammation.

The AMPK pathway mediates an anti-adipogenic effect of fruits of Hovenia dulcis Thunb

Hovenia dulcis Thunb. is well known as a treatment for liver disease. Several studies have demonstrated that extracts of Hovenia dulcis Thunb. or its purified compounds can serve as detoxifying agents for alcohol poisoning. However, its anti-obesity effect has not been reported thus far. In this study, the anti-obesity effect of water extracts from the fruits or stems of Hovenia dulcis Thunb. was examined in 3T3-L1 preadipocytes. The cellular lipid contents in 3T3-L1 adipocytes were assessed by Oil Red O staining. Fruits of Hovenia dulcis Thunb. (FHD) significantly inhibit lipid accumulation during adipogenesis in a dose-dependent manner, but not stems of Hovenia dulcis Thunb. FHD (100 μg ml(-1)) significantly down-regulates the expression of the peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein-α, adipocyte fatty acid-binding protein 2, adiponectin, and resistin, and the inhibition rates were 29.33%, 54.36%, 34.5%, 55.69%, and 60.39%, respectively. In addition, FHD (100 μg ml(-1)) also up-regulates the phosphorylation of AMP-activated protein kinase (AMPK)-α, liver kinase B1 as a major AMPK kinase, and the downstream substrate acetyl-CoA carboxylase, and the inhibition rates were 43.52%, 38.25%, and 20.39%, respectively. These results indicate that FHD has a significant anti-obesity effect through the modulation of the AMPK pathway, suggesting that FHD has a potential benefit in preventing obesity.

Small heterodimer partner-interacting leucine zipper protein inhibits adipogenesis by regulating peroxisome proliferator-activated receptor γ activity

AIMS

Adipocytes play a critical role in energy balance. Growth of fat tissue is achieved via an increase in adipocyte mass and the formation of newly differentiated adipocytes from precursor cells. Understanding the cellular and molecular mechanisms of adipocyte differentiation is crucial for the study of obesity- and fat-related diseases. The present study was designed to study whether small heterodimer partner-interacting leucine zipper protein (SMILE), a novel co-repressor, could regulate differentiation of adipocyte in 3T3-L1 cells.

MATERIALS AND METHODS

Treatment of endoplasmic stress inducers, thapsigargin and tunicamycin, inhibited adipocyte differentiation, stimulated Smile mRNA expression, and repressed the expression of adiponectin (Adipoq) in 3T3-L1 pre-adipocyte. Overexpression of SMILE in 3T3-L1 cells decreased the expression of the mRNA encoding Adipoq, a major marker of adipocytes, significantly. Furthermore, knockdown of SMILE recovered the thapsigargin-mediated repression of Adipoq transcription. Co-immunoprecipitation experiments revealed that SMILE interacted physically with PPARγ in 3T3-L1 cells. In addition, chromatin immunoprecipitation experiments revealed that SMILE suppressed the binding affinity of PPARγ for the Adipoq promoter.

KEY FINDINGS

We demonstrate that SMILE controls adipocyte differentiation by regulating the transactivity of peroxisome proliferator-activated receptor γ (PPARγ).

SIGNIFICANCE

These findings demonstrate that SMILE represses adipocyte differentiation by regulating PPARγ transactivity; hence, SMILE is a potential regulator of PPARγ-related diseases.

Effects of Polygonatum sibiricum rhizome ethanol extract in high-fat diet-fed mice

CONTEXT

The rhizome of Polygonatum sibiricum Redoute (Liliaceae) has long been used to treat diabetes-associated complications. However, the pharmacological mechanism of P. sibiricum on metabolic disorders is not clear.

OBJECTIVE

This study investigates the effect of an ethanol extract of P. sibiricum rhizomes (designated ID1216) on obesity conditions including weight loss in high-fat (HF) diet-fed mice and explores the potential underlying mechanisms.

METHODS

To identify the metabolic impact of the P. sibiricum rhizome extract, HF diet-fed mice were administered ID1216 orally at doses of 250 and 1000 mg/kg/d for 10 weeks, and various factors related to metabolic syndrome were analyzed. We also examined the effects of ID1216 on the expression of genes involved in adipogenesis and lipolysis in 3T3-L1 cells, as well as genes associated with energy homeostasis in C2C12 myocytes.

RESULTS

ID1216 administration led to significant decreases in body weight gain (37.5%), lipid accumulation in adipose tissues (52.8%), and the levels of plasma triglycerides (26.4%) and free fatty acids (28.1%) at a dose of 250 mg/kg/d, compared with the vehicle-treated group, as well as improved insulin resistance. In addition, ID1216 was found to regulate the expression of genes related to adipogenesis and fatty acid oxidation in 3T3-L1 cells and enhance the expression of genes that modulate energy homeostasis in C2C12 myocytes.

CONCLUSIONS

ID1216 may be a promising therapeutic agent for improving obesity conditions through the sirtuin-1 and peroxisome proliferator-activated receptor γ coactivator-1α pathway.

Ontogeny and polarization of macrophages in inflammation: blood monocytes versus tissue macrophages

The explosion of new information in recent years on the origin of macrophages in the steady-state and in the context of inflammation has opened up numerous new avenues of investigation and possibilities for therapeutic intervention. In contrast to the classical model of macrophage development, it is clear that tissue-resident macrophages can develop from yolk sac-derived erythro-myeloid progenitors, fetal liver progenitors, and bone marrow-derived monocytes. Under both homeostatic conditions and in response to pathophysiological insult, the contribution of these distinct sources of macrophages varies significantly between tissues. Furthermore, while all of these populations of macrophages appear to be capable of adopting the polarized M1/M2 phenotypes, their respective contribution to inflammation, resolution of inflammation, and tissue repair remains poorly understood and is likely to be tissue- and disease-dependent. A better understanding of the ontology and polarization capacity of macrophages in homeostasis and disease will be essential for the development of novel therapies that target the inherent plasticity of macrophages in the treatment of acute and chronic inflammatory disease.

Blockade of lipid accumulation by silibinin in adipocytes and zebrafish

Silibinin is a compound present mainly in milk thistle. In this study, we investigated the mechanism by which silibinin suppresses adipogenesis of 3T3-L1 cells, and evaluated the anti-adipogenic effect of silibinin in zebrafish. Silibinin reduced lipid accumulation by downregulating adipogenic factors, such as, peroxisome proliferator-activated receptor γ (PPARγ), CCAAT-enhancer binding protein α (C/EBPα), and fatty acid-binding protein 4 (FABP4). The reduction of these adipogenic protein levels was associated with the regulation of early adipogenic factors, such as, C/EBPβ and Krüppel-like factor 2 (KLF2), and was reflected in downregulation of lipid synthetic enzymes. Silibinin arrested cells in the G0/G1 phase of the cell cycle, accompanied by downregulation of cyclins and upregulation of p27, a cell cycle inhibitor. These results correlated with the finding of deactivation of extracellular signal-regulated kinase (ERK) and AKT, a serine/threonine-specific kinase. In addition, silibinin activated AMP-activated protein kinase α (AMPKα) to inhibit fatty acid synthesis. As observed in 3T3-L1 cells, silibinin inhibited lipid accumulation in zebrafish with the reduction of adipogenic factors and triglyceride levels. Our data revealed that silibinin inhibited lipid accumulation in 3T3-L1 cells and zebrafish, and this inhibitory effect was associated with abrogation of early adipogenesis via regulation of cell cycle and AMPKα signaling.

Kaempferol suppresses lipid accumulation by inhibiting early adipogenesis in 3T3-L1 cells and zebrafish

Kaempferol is a flavonoid present in Kaempferia galanga and Opuntia ficus indica var. saboten.

Coprinus comatus cap inhibits adipocyte differentiation via regulation of PPARγ and Akt signaling pathway

This study assessed the effects of Coprinus comatus cap (CCC) on adipogenesis in 3T3-L1 adipocytes and the effects of CCC on the development of diet-induced obesity in rats. Here, we showed that the CCC has an inhibitory effect on the adipocyte differentiation of 3T3-L1 cells, resulting in a significant decrease in lipid accumulation through the downregulation of several adipocyte specific-transcription factors, including CCAAT/enhancer binding protein β, C/EBPδ, and peroxisome proliferator-activated receptor gamma (PPARγ). Moreover, treatment with CCC during adipocyte differentiation induced a significant down-regulation of PPARγ and adipogenic target genes, including adipocyte protein 2, lipoprotein lipase, and adiponectin. Interestingly, the CCC treatment of the 3T3-L1 adipocytes suppressed the insulin-stimulated Akt and GSK3β phosphorylation, and these effects were stronger in the presence of an inhibitor of Akt phosphorylation, LY294002, suggesting that CCC inhibited adipocyte differentiation through the down-regulation of Akt signaling. In the animal study, CCC administration significantly reduced the body weight and adipose tissue weight of rats fed a high fat diet (HFD) and attenuated lipid accumulation in the adipose tissues of the HFD-induced obese rats. The size of the adipocyte in the epididymal fat of the CCC fed rats was significantly smaller than in the HFD rats. CCC treatment significantly reduced the total cholesterol and triglyceride levels in the serum of HFD rats. These results strongly indicated that the CCC-mediated decrease in body weight was due to a reduction in adipose tissue mass. The expression level of PPARγ and phospho-Akt was significantly lower in the CCC-treated HFD rats than that in the HFD obesity rats. These results suggested that CCC inhibited adipocyte differentiation by the down-regulation of major transcription factor involved in the adipogenesis pathway including PPARγ through the regulation of the Akt pathway in 3T3-L1 cells and HFD adipose tissue.

Discovery of a novel class of diacylglycerol acyltransferase 2 inhibitors with a 1H-pyrrolo[2,3-b]pyridine core

Diacylglycerol acyltransferase 2 (DGAT2), which catalyzes the final step in triacylglycerol (TG) synthesis, is a key enzyme associated with hepatic steatosis and insulin resistance. Here, using an in vitro screen of 20000 molecules, we identified a class of compounds with a substituted 1H-pyrrolo[2,3-b]pyridine core which proved to be potent and selective inhibitors of human DGAT2. Of these compounds, H2-003 and -005 exhibited a considerable reduction in TG biosynthesis in HepG2 hepatic cells and 3T3-L1 preadipose cells. These compounds exert DGAT2-specific-inhibitory activity, which was further confirmed in DGAT2- or DGAT1-overexpressing HEK293 cells. In addition, these compounds almost completely abolished lipid droplet formation in 3T3-L1 cells when co-treated with a DGAT1 inhibitor, which was not attained using either a DGAT2 or DGAT1 inhibitor alone. Collectively, we identified two DGAT2 inhibitors, H2-003 and -005. These compounds will aid in DGAT2-related lipid metabolism research as well as in therapeutic development for the treatment of metabolic diseases associated with excessive TG.

Ultraviolet B irradiation reduces the expression of adiponectin in ovarial adipose tissues through endocrine actions of calcitonin gene-related peptide-induced serum amyloid A

Ultraviolet (UV) B irradiation decreases blood adiponectin levels, but the mechanism is not well understood. This study investigated how UVB irradiation reduces adiponectin expression in ovarial adipose tissues. Female Hos:HR-1 hairless mice were exposed to UVB (1.6 J/cm²) irradiation and were killed 24 h later. UVB irradiation decreased the adiponectin protein level in the serum and the adiponectin mRNA level in ovarial adipose tissues. UVB irradiation also decreased the mRNA levels of peroxisome proliferator-activated receptor (PPAR) γ, CCAAT/enhancer binding protein (C/EBP) α, C/EBPβ, and fatty acid binding protein 4 (aP2) in ovarial adipose tissues. In contrast, UVB irradiation increased the mRNA levels of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 in ovarial adipose tissues. In the serum and liver, the levels of serum amyloid A (SAA), involved in PPARγ, C/EBPα, C/EBPβ, aP2, IL-6, and MCP-1 regulation, increased after UVB irradiation. The SAA gene is regulated by IL-1β, IL-6, and tumor necrosis factor-α, but only IL-6 expression increased in the liver after UVB irradiation. Additionally, in the liver, hypothalamus, and epidermis, UVB irradiation increased the expression of calcitonin gene-related peptide (CGRP), which upregulates SAA in the liver. Collectively, our results suggest that the CGRP signal induced by skin exposure to UVB transfers to the liver, possibly through the brain, and increases SAA production via IL-6 in the liver. In turn, serum SAA acts in an endocrine manner to decreases the serum adiponectin level by downregulating factors that regulate adiponectin expression in adipose tissues.

Opposite effects of 17-β estradiol and testosterone on mitochondrial biogenesis and adiponectin synthesis in white adipocytes

Sexual dimorphism has been found in both mitochondrial functionality and adiponectin expression in white adipose tissue, with female rats presenting more functional mitochondria than males and greater adiponectin expression. However, little is known about the role of sex hormones in this dimorphism. The aim was to elucidate the role of sex hormones in mitochondrial biogenesis and dynamics and in adiponectin synthesis in white adipocytes, and also to provide new evidence of the link between these processes. 3T3-L1 preadipocytes were differentiated and treated either with 17-β estradiol (E₂; 10  nM), progesterone (Pg), testosterone (1  μM both), or a combination of Pg or testosterone with flutamide (FLT; 10  μM) or E₂ (1  μM). The markers of mitochondrial biogenesis and dynamics and adiponectin expression were analyzed. E₂ induced mitochondrial proliferation and differentiation in 3T3-L1, although testosterone showed opposite effects. Pg treatment stimulated proliferation but impaired differentiation. In concerns mitochondrial dynamics, these hormones promoted fusion over fission. FLT treatment indicated that Pg elicits its effects on mitochondrial dynamics through the androgen receptor. E₂ coadministration with testosterone or Pg reversed its effects. In conclusion, our results show that E₂ induces stimulation of mitochondrial biogenesis in white adipocytes in vitro, especially in situations that imply an impairment of mitochondrial function, whereas testosterone would have opposite effects. Moreover, testosterone and Pg alter mitochondrial dynamics by promoting fusion over fission, while E₂ stimulates both processes. All these alterations run in parallel with changes in adiponectin expression, thus suggesting the existence of a link between mitochondrial biogenesis and dynamics and adiponectin synthesis in white adipocytes.

G protein-coupled receptors and adipogenesis: a focus on adenosine receptors

G-protein coupled receptors (GPCRs) are a large family of proteins that coordinate extracellular signals to produce physiologic outcomes. Adenosine receptors (AR) are one class of GPCRs that have been shown to regulate functions as diverse as inflammation, blood flow, and cellular differentiation. Adenosine signals through four GPCRs that either inhibit (A1AR and A3AR) or activate (A2aAR and A2bAR) adenylyl cyclase. This review will focus on the role of GPCRs, and in particular, adenosine receptors, in adipogenesis. Preadipocytes differentiate to mature adipocytes as the adipose tissue expands to compensate for the consumption of excess nutrients. These newly generated adipocytes contribute to maintaining metabolic homeostasis. Understanding the key drivers of this differentiation process can aid the development of therapeutics to combat the growing obesity epidemic and associated metabolic consequences. Although much literature has covered the transcriptional events that culminate in the formation of an adipocyte, less focus has been on receptor-mediated extracellular signals that direct this process. This review will highlight GPCRs and their downstream messengers as significant players controlling adipocyte differentiation.

Baicalein inhibits lipid accumulation by regulating early adipogenesis and m-TOR signaling

Baicalein is a type of flavonoid that originates from Scutellaria baicalensis. In this study, we examined how baicalein inhibits lipid accumulation during adipogenesis in 3T3-L1 cells. Our data show that baicalein inhibited lipid accumulation during adipogenesis in a dose-dependent manner. Baicalein inhibition was limited to the early adipogenic stage. Cell cycle analysis showed that baicalein induced cell cycle arrest in the G0/G1 phase through cyclin downregulation. In addition, baicalein suppressed the mRNA expression of early adipogenic factors leading to downregulation of late adipogenic factors at mRNA and protein levels. Inhibition of adipogenic factors by baicalein was correlated with downregulation of lipid synthetic enzymes. Additionally, baicalein negatively regulated the m-TOR signaling pathway involved in lipid accumulation during adipogenesis, thus inhibiting phosphorylation of m-TOR and p70S6K. In a zebrafish study, baicalein significantly reduced lipid accumulation in Nile Red staining. Consistent with a report using cell lines, mRNA expression of adipogenic factors was decreased in a dose-dependent manner by baicalein. This result reflects a reduction in total triglyceride levels based on a triglyceride assay. Our data suggest that baicalein inhibits lipid accumulation by controlling the cell cycle and m-TOR signaling in 3T3-L1 cells, and its anti-adipogenic effect was found in a zebrafish model.

Effects of phytoestrogens and other plant-derived compounds on mesenchymal stem cells, bone maintenance and regeneration

Phytoestrogens and other plant-derived compounds and extracts have been developed for the treatment of menopause-related complaints and disorders, e.g. hot flushes and osteoporosis. Since estrogens have been discussed to enhance the risk for hormone-sensitive cancers, research activities try to find alternatives. Phytoestrogens like genistein and resveratrol as well as other plant-derived compounds are capable of substituting for estrogens to some extent. Their effects on mesenchymal stem cells and the tissues derived therefrom have been investigated in vitro and in preclinical settings. Besides their well-known estrogenic, i.e. mainly antiresorptive effects on bone via estrogen receptor (ER) signalling, they also directly or indirectly affect osteogenic and adipogenic pathways. As a novel mechanism, phytoestrogens and plant-derived saponins and flavonoids like kaempferol and xanthohumol have been described to reciprocally affect the osteogenic versus the adipogenic differentiation pathway. Both, ER-mediated and other pathways mediate a shift towards osteogenesis by inhibiting PPARγ and C/EBPα, the key adipogenic transcription factors (TFs), while stimulating the key osteogenic TFs Runx2 and Sp7. Besides ER signalling, the broad spectrum of molecular mechanisms supporting osteogenesis comprises the modulation of PPARγ, Wnt/β-catenin, and Sirt1 signalling, which inversely influence the transcription or transactivation of osteogenic versus adipogenic TFs. Preventing the age- and hormone deficiency-related shift towards adipogenesis without provoking adverse estrogenic effects represents a very promising strategy for treating bone loss and other metabolic diseases beyond bone. Research on plant-derived compounds will have to be pursued in vitro as well as in preclinical studies and controlled clinical trials in humans are urgently needed. This article is part of a Special Issue entitled 'Phytoestrogens'.

Relationship of plasma adiponectin levels with acute coronary syndromes and coronary lesion severity in north Indian population

Adiponectin is an adipocyte specific cytokine which, in contrast to other adipokines, has been described to have antiinflammatory, antithrombotic, and anti-atherogenic properties. This study evaluates the association between plasma adiponectin levels with acute coronary syndrome (ACS) and angiographic coronary lesion severity in Indian population. Ninety patients included in the study were divided in two groups in 1 : 1 ratio—patients admitted with a diagnosis of ACS and those without ACS. Adiponectin and other risk markers are measured in forty-five consecutive patients in each group undergoing coronary angiography. Patients without ACS were found to have higher adiponectin (16.47 ± 7.88 μg/mL) levels than patients with ACS (9.03 ± 3.13 μg/mL) (P < 0.001). In multiple regression analysis adjusted for all other risk markers, higher adiponectin levels remain positively associated with a lower risk of ACS (P value > 0.002). The greatest increase in risk for ACS was seen at adiponectin levels ≤12.20 μg/mL in study subjects. The adiponectin levels were inversely related to the angiographic severity of coronary artery stenosis increases (P value > 0.02). The study concluded that higher adiponectin levels are independently associated with lower risk of ACS, and patients with severe angiographic coronary artery disease have lower levels of adiponectin.