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ieckol, a phlorotannin isolated from a browneaweed, Ecklonia cava, inhibits adipogenesishrough AMP-activated protein kinase (AMPK)ctivation in 3T3-L1 preadipocytes

eok-Chun Koa, Myoungsook Leeb, Ji-Hyeok Leea, Seung-Hong Leec,unsook Limd, You-Jin Jeona,e,∗

Department of Marine Life Sciences, Jeju National University, Jeju 690-756, Republic of KoreaDepartment of Food and Nutrition, Sungshin Women’s University, Seoul 136-742, Republic of KoreaDivision of Food Bioscience, Konkuk University, Chungju, Chungbuk 380-701, Republic of KoreaDepartment of Food and Nutrition, Kyung Hee University, Seoul 130-701, Republic of KoreaAqua Green Technology Co. Ltd., Jeju Bio-industry Center, Jeju 690-121, Republic of Korea

r t i c l e i n f o

rticle history:

eceived 13 May 2013

eceived in revised form

October 2013

ccepted 13 October 2013

vailable online 23 October 2013

eywords:

iekol

cklonia cava

a b s t r a c t

In this study, we assessed the potential inhibitory effect of 5 species of brown seaweeds

on adipogenesis the differentiation of 3T3-L1 preadipocytes into mature adipocytes by

measuring Oil-Red O staining. The Ecklonia cava extract tested herein evidenced profound

adipogenesis inhibitory effect, compared to that exhibited by the other four brown sea-

weed extracts. Thus, E. cava was selected for isolation of active compounds and finally

the three polyphenol compounds of phlorotannins were obtained and their inhibitory

effect on adipogenesis was observed. Among the phlorotannins, dieckol exhibited great-

est potential adipogenesis inhibition and down-regulated the expression of peroxisome

proliferator-activated receptor-� (PPAR�), CCAAT/enhancer-binding proteins (C/EBP�), sterol

regulatory element-binding protein 1 (SREBP1) and fatty acid binding protein 4 (FABP4) in

dipogenesis

T3-L1 preadipocytes

MPK

a dose-dependent manner. The specific mechanism mediating the effects of dieckol was

confirmed by AMP-activated protein kinase (AMPK) activation. These results demonstrate

inhibitory effect of dieckol compound on adipogenesis through the activation of the AMPK

signal pathway.

increases in the number and size of mature adipocytes

. Introduction

urrently, obesity has become one of the most commonetabolic syndromes, and has come to pose a major

orldwide threat to human health (Kim et al., 2011).besity is a serious chronic health problem, because it

s a high risk factor for type 2 diabetes, hypertension

∗ Corresponding author at: Department of Marine Life Sciences, Jeju Nael.: +82 64 754 3475; fax: +82 64 756 3493.

E-mail address: youjinj@jejunu.ac.kr (Y.-J. Jeon).382-6689/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.etap.2013.10.011

© 2013 Elsevier B.V. All rights reserved.

and cardiovascular disease, including atherosclerosis, hyper-lipidemia and myocardial infarction (Giri et al., 2006;Kim and Kong, 2010). Cellular and molecular studiesshow that the development of obesity is characterized by

tional University, Jeju 690-756, Republic of Korea.

in the body produced by differentiation and mitogenesis(Herberg et al., 1974; Kim and Kong, 2010; Kim et al.,2010).

p h a

1254 e n v i r o n m e n t a l t o x i c o l o g y a n d

The 3T3-L1 preadipocyte cell line is model for investigat-ing the differentiation of adipocytes and several stages relatedto obesity (Guo and Liao, 2000; Kim and Kong, 2010). Thedifferentiation of preadipocytes into adipocytes is accompa-nied by sequential expression and activation of transcriptionfactors governing expression of adipocyte-specific markers,such as CCAAT/enhancer binding proteins � (C/EBP�), per-oxisome proliferator-activated receptor-� (PPAR�) and basichelix–loop–helix family (ADD1/SREBP-1) (Ha et al., 2010; Kimet al., 2010). These factors play an important role in the regu-lation of adipogenesis by modulating the expression of theirtarget genes in a coordinated fashion (Kang et al., 2011). More-over, AMP-activated protein kinase (AMPK) is one of the wellcharacterized and an important target for the prevention andtreatment of obesity (Kim and Kong, 2010; Lee et al., 2009).AMPK complex is a heterorimer, which functions as a cellu-lar energy sensor and has been shown to positively correlatedwith glucose and lipid homeostasis in adipocytes (Unger, 2004;Winder and Thomson, 2007).

Seaweeds are known to provide an abundance of bioac-tive compounds with valuable biomedical and pharmaceuticalpotential (Lee et al., 2010). Among the seaweeds, brownseaweeds possess a variety of biological compounds, includ-ing fucoxanthin, fucoidan, phycocolloids and polyphenol-containing phlorotannins (Halliwell and Gutteridge, 1999).Many reports on phlorotannins of brown seaweeds havepointed out a variety of biological effects, including anti-diabetes (Lee et al., 2010), anti-oxidant (Ahn et al., 2007),anti-hypertensive (Wijesinghe et al., 2011), anti-plasmininhibitor (Nakayama et al., 1989), anti-allergic (Sugiura et al.,2006) and hepatoprotective (Kang et al., 2012) effects. How-ever, there currently is insufficient evidence for the effects ofphlorotannins from brown seaweeds on adipogenesis relatedto obesity. Also, marine natural products provide a rich sourceof chemical diversity that can be used to design and developnew, potentially useful therapeutic agents.

The objectives of the current study were to isolatephlorotannins from Ecklonia cava based on the results of ana-lytical data, and to evaluate its inhibitory effects of adiogenesisand the expression levels of adipocyte marker proteins andgenes in 3T3-L1 preadipocytes. In order to screen a propersample having higher effect, we measured the differenti-ation inhibitory effect of extracts from the five species ofbrown seaweeds; E. cava was selected for further experiments,owing to its higher differentiation inhibitory effect in 3T3-L1preadipocytes.

2. Materials and methods

2.1. Materials

The brown seaweeds include Sargassum thunbergii, Ishige oka-murae, E. cava, Padina arborescens and Undaria wrightii werecollected from the coast of Jeju Island, South Korea. Salt, sand

and epiphytes were using tap water. Then the samples wererinsed carefully with fresh water and freeze-dried. Dried sea-weeds were ground and sifted through a 50-mesh standardtesting sieve.

r m a c o l o g y 3 6 ( 2 0 1 3 ) 1253–1260

Dulbecco’s modified Eagle’s medium (DMEM), fetal bovineserum (FBS), bovine serum (BS), Phosphate-buffered saline(pH 7.4; PBS) and penicillin–streptomycin (PS) were pur-chased from Gibco BRL (Grand Island, NY, USA). Antibodies toPPAR�, C/EBP�, FABP4, phospho-AMPK (Thr172) and phospho-ACC were purchased were from Cell Signaling Technology(Bedford, MA, USA). Antibody to SREBP-1 and GAPDH wereobtained from Santa Cruz Biotechnology (Santa Cruz, CA,USA). 3-Isobutyl-1-methylxanthine (IBMX), dexamethasone,insulin, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetra-zolium bromide (MTT) were obtained from Sigma ChemicalCo. (St. Louis, MO, USA). All other reagents were of the highestgrade available commercially.

2.2. Extraction procedure of extracts from brownseaweeds

The brown seaweeds powder (2 g) was extracted three timeswith 80% methanol (100 ml) and filtered. After filtration,methanolic extracts were evaporated to dryness under vac-uum and dissolved in DMSO, and then used for experiments,adjusting the final concentration of DMSO in the culturemedium to <0.1%.

2.3. Isolation and structural identification ofphlorotannins

The brown seaweed powder (500 g) was extracted three timeswith 80% methanol and filtered. The filtrate was then evap-orated at 40 ◦C to obtain the methanol extract, which wasdissolved in water, then partitioned with ethyl acetate. Theethyl acetate fraction was mixed with Celite. The mixedCelite was dried and packed into a glass column, and elutedin the order of hexane, methylene chloride, diethyl ether,and methanol. The diethyl ether fraction was subjected toSephadex LH-20 column chromatography using stepwise gra-dient chloroform/methanol (2/1–0/1) solvents system, andthen finally purified by reverse-phase high performance liquidchromatography (HPLC) using a Waters HPLC system equippedwith a Waters 2998 photodiode array detector to give threekinds of phlorotannins including dieckol, 6,6′-bieckol andphlorofucofuroeckol A. The structures of the phlorotanninswere identified by comparing the NMR spectral data withthose in existing literature. The chemical structures of thephlorotannins are indicated in Fig. 2A.

2.4. Cell culture and differentiation

3T3-L1 preadipocytes were obtained from American Type Cul-ture Collection (Rockville, MD, USA) were cultured in DMEMcontaining 1% PS and 10% bovine calf serum (Gibco BRL) at37 ◦C under a 5% CO2 atmosphere. To induce differentiation,2-day post confluent preadipocytes (designated day 0) werecultured in MDI differentiation medium (DMEM containing1% PS, 10% FBS, 0.5 mM IBMX, 0.25 �M dexamethasone and5 �g/ml insulin) for 2 days. The cells were then cultured for

another 2 days in DMEM containing 1% PS, 10% FBS and 5 �g/mlinsulin. Thereafter, the cells were maintained in post differ-entiation medium (DMEM containing 1% PS and 10% FBS),with replacement of the medium every 2 days. To examine the

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ffects of test samples on the differentiation of preadipocyteso adipocytes, the cells were cultured with MDI in the pres-nce of test samples. Differentiation, as measured by thexpression of adipogenic markers and the appearance of lipidroplets, was complete on day 8.

.5. Cytotoxic assessment using MTT assay

T3-L1 preadipocytes seeded in a 24-well plate. After seeding,he cells were treated with test samples. The cells were thenncubated for an additional 48 h at 37 ◦C. MTT stock solution50 �l; 2 mg/ml in PBS) was then added to each well to a totaleaction volume of 250 �l. After 4 h of incubation, the platesere centrifuged (800 × g, 5 min), and the supernatants werespirated. The formazan crystals in each well were dissolvedn 150 �l of dimethylsulfoxide (DMSO), and the absorbance was

easured with an ELISA plate reader at 540 nm.

.6. Determination of lipid accumulation by Oil Red Otaining

fter adipocyte differentiation, the cells were stained with Oiled O, an indicator of cell lipid content with slight modifi-ations. Briefly, cells were washed with phosphate-bufferedaline, fixed with 10% buffered formalin and stained with Oiled O solution (0.5 g in 100 ml isopropanol) for 60 min. Afteremoving the staining solution, the dye retained in the cellsas eluted into isopropanol and optical density was measured

t 520 nm.

.7. Quantitative real-time polymerase chain reactionPCR) analysis

NA was extracted from frozen cells using the RNeasy miniit (Qiagen). For real-time PCR, first-strand complementaryNA (cDNA) was synthesized from 1 �g total RNA using

he Advantage RT-for-PCR Kit (Clontech). Relative messen-er RNA levels were determined by real-time PCR usingightCycler 480 SYBR Green I Mater mix (Roche; Germany)nd aLightCycler 480 (Roche; Germany). All cDNA levelshere normalized to the level of ubiquitin cDNA. Sam-les were amplified using the following sense primer andntisense primer: forward 5′-AGC-TCA-TCC-CAG-AGC-TGA-CG-3′ and reverse 5′-CAT-ACT-TGG-CAG-GTT-TCT-CCA-3′

or GAPDH; forward 5′-TTT-TCA-AGG-GTG-CCA-GTT-TC-3′

nd reverse 5′-AAT-CCT-TGC-CCC-TCT-GAG-AT-3′ for PPAR�;orward 5′-TGT-TGG-CAT-CCT-GCT-ATG-TG-3′ and reverse′-AGG-GAA-AGC-TTT-GGG-GTC-TA-3′ for SREBP-1; forward′-TTA-CAA-CAG-GCC-AGG-TTT-CC-3′ and reverse 5′-GGC-GG-CGA-CAT-ACA-GTA-CA-3′ for C/EBP�; forward 5′-TCA-CT-GGA-AGA-CAG-CTC-CT-3′ and reverse 5′-AAT-CCC-CAT-TA-CGC-TGA-TG-3′ for FABP4.

.8. Western blot analysis

ells were lysed in lysis buffer (20 mM Tris, 5 mM EDTA, 10 mM

a4P2O7, 100 mM NaF, 2 mM Na3VO4, 1% NP-40, 10 mg/mlprotinin, 10 mg/ml leupeptin and 1 mM PMSF) for 60 minnd then centrifuged at 12,000 rpm for 15 min at 0 ◦C. Therotein concentrations were determined by using the BCATM

a c o l o g y 3 6 ( 2 0 1 3 ) 1253–1260 1255

protein assay kit. The lysate containing 40 �g of protein wassubjected to electrophoresis on a sodium dodecyl sulfate(SDS)-polyacrylamide gel, and the gel was transferred ontoa nitrocellulose membrane. The membrane was blocked in5% non fat dry milk in TBST (25 mM Tris–HCl, 137 mM NaCl,2.65 mM KCl, 0.05% Tween 20, pH 7.4) for 2 h. The primary anti-bodies were used at a 1:1000 dilution. Membranes incubatedwith the primary antibodies at 4 ◦C overnight. Thereafter, themembranes were washed with TBST and then incubated withthe secondary antibodies used at 1:3000 dilutions. Signalswere developed using an ECL Western blotting detection kitand exposed to X-ray films.

2.9. Statistical analysis

All measurements were repeated three times. The results wereanalyzed using the student t-test. Statistical significance wasaccepted at a level of p < 0.05.

3. Results

3.1. Cytotoxicity and inhibitory effect of adipogenesis

The effects of the brown seaweed extracts on cell viabilityin 3T3-L1 preadipocytes were measured via the MTT assay.According to the results, all the extract from the brownseaweeds did not show any cytotoxicity up to a 48 h incu-bation period in 3T3-L1 preadipocytes at the highest dosetested, a concentration of 100 �g/ml (Fig. 1A). To examine theanti-adipogenic potential of the extracts on differentiationof preadipocytes into adipocytes, 3T3-L1 preadipocytes weredifferentiated with all the extracts for 8 days (from days 0to 8). Lipid accumulation as a major marker of adipogene-sis was quantified at the end of differentiation period (day 8)by Oil-Red O staining (Fig. 1B). Among the tested brown sea-weed extracts, the highest adipogenesis inhibition effect wasobserved for the E. cava extract, thus, E. cava was selected forthe further isolation of active compounds. The three polyphe-nols of phlorotannins were successfully isolated and thenemployed in the additional experiments.

In this study, 3T3-L1 cells were treated with thephlorotannins to determine the cytotoxic effects for fur-ther experiments. The cell viability data confirmed that thephlorotannins were non-cytotoxic in 3T3-L1 cells (Fig. 2B).Therefore, it was determined that the phlorotannins couldbe used in the further experiments. Microscopic inspectionof the phlorotannins-treated cells cultured under optimal dif-ferentiation conditions revealed a significant reduction in theaccumulation of intracellular lipids. The inhibitory effects ofthe phlorotannins on adipogenesis in 3T3-L1 adipocytes weremeasured via Oil-Red O staining (Fig. 2C). The absorbance val-ues of eluted Oil-Red O solution in adipocytes represent lipiddroplet accumulation in the cytoplasm as well as a quantita-tive analysis of neutral lipid content. Therefore, lipid contentfrom fully differentiated adipocytes was stained with Oil-Red

O staining solution and the absorbance was compared. Whenthe phlorotannins were applied to cultures, lipid accumula-tion decreased during adipocyte differentiation. Of the threephlorotannins, dieckol possessed the greatest anti-adipogenic

1256 e n v i r o n m e n t a l t o x i c o l o g y a n d p h a r m a c o l o g y 3 6 ( 2 0 1 3 ) 1253–1260

Fig. 1 – Inhibitory effect of extracts from brown seaweeds on lipid accumulation in 3T3-L1 cells. (A) Effects of extracts frombrown seaweeds on the cell viability of 3T3-L1 preadipocytes treated for 48 h; (B) Lipid accumulation was determined bymeasuring Oil-Red O staining. Each value is expressed as the mean ± standard error of triplicate experiments. *p < 0.05indicates significantly different to untreated group. (A) Sargassum thunbergii; (B) Ishige okamurae; (C) Ecklonia cava; (D) Padina

arborescens; (E) Undaria wrightii.

potential. These results indicate that dieckol may effectivelyblock preadipocytes differentiation.

3.2. Effect of dieckol on the expression ofadipogenic-specific genes

We tested the inhibitory effects of dieckol on the differentia-tion of 3T3-L1 preadipocytes. The inhibitory effect of dieckolon the expression of transcription factors such as SREBP-1,C/EBP�, FABP4 and PPAR� was investigated using quantitativereal-time PCR (qPCR) (Fig. 3). Compared to the other differenti-ated adipocytes, the presence of dieckol significantly reducedthe expression of SREBP-1, C/EBP�, FABP4 and PPAR� andinduced down-regulation of them.

3.3. Effect of dieckol on the expression ofadipogenic-specific protein and AMPK activity

Through Western blotting, we confirmed whether dieckolaffects the protein expression of the key adipocytes tran-

scription factors, SREBP-1, C/EBP�, FABP4 and PPAR�. Dieckolmarkedly suppressed the protein expression of SREBP-1,C/EBP�, FABP4 and PPAR� in a dose-dependent man-ner (Fig. 4A). Also, to determine whether inhibition of

adipogenesis by dieckol is mediated by AMPK activation,the protein level of phosphorylated AMPK and acetyl-CoAcarboxylase (p-ACC) was compared. Dieckol enhanced phos-phorylation of AMPK and ACC in a dose-dependent manner(Fig. 4B). These results suggest that dieckol inhibits adipogen-esis by AMPK activation.

4. Discussion

Possible mechanisms for the reduction of obesity involveeither decreasing energy/food intake and increasing energyexpenditure, inhibiting preadipocyte differentiation, lipogen-esis and proliferation as well as promoting of the oxidationof glucose and/or fatty acids and the lipolysis of matureadipocytes (Evans et al., 2002; Wang and Jones, 2004). It isknown that the differentiation of preadipocytes into matureadipocytes and fat accumulation plays a key role in the devel-opment of obesity (Jeon et al., 2004). Many natural productshave been evaluated for their ability to inhibit the differentia-

tion of preadipocytes (An et al., 2012; Ahn et al., 2008; Ghoshet al., 2012; Ha et al., 2010; Sakurai et al., 2009), and interest inexploring the applications of medicinally beneficial productshas increased (Kessler et al., 2001).

e n v i r o n m e n t a l t o x i c o l o g y a n d p h a r m a c o l o g y 3 6 ( 2 0 1 3 ) 1253–1260 1257

Fig. 2 – (A) Chemical structures of phlorotannins isolated from Ecklonia cava. (B) Effects of phlorotannins on the cell viabilityof 3T3-L1 preadipocytes treated for 48 h. (C) Oil-Red O staining at day 8 with phlorotannins 100 �M. Lipid accumulationdetermined by absorbance at 520 nm. Each value is expressed as the mean ± standard error of triplicate experiments.* (A) D

siwbownOTiAi

p < 0.05 indicates significantly different to untreated group.

In the present study, we selected E. cava among the 5pecies of brown seaweeds due to its higher differentiationnhibitory effect in 3T3-L1 cells. Thereafter, phlorotanninsere isolated from E. cava and its anti-adipogenic effect

y measuring lipid accumulation as well as the expressionf several genes and proteins associated with adipogenesisas investigated in differentiated 3T3-L1 cells. Phlorotan-ins isolated from E. cava reduced absorbance values of theil-Red O solution eluted in the cytoplasm of treated cells.his suggests that phlorotannins inhibit adipogenesis dur-

ng adipocyte differentiation by reducing lipid accumulation.mong the tested phlorotannins, dieckol showed the highest

nhibitory effect of adipogenesis. The biological polyphenolic

ieckol; (B) 6,6′-bieckol; (C) phlorofucoeckol A.

compounds referred to as phlorotannins is rich in many brownseaweeds like E. cava (Heo et al., 2005). Previously, it has beenreported that phlorotannins components of E. cava such aseckol, dieckol, 6,6′-bieckol and phlorofucofuroeckol A, whichare mainly oligomeric polyphenols composed of phlorogluci-nol unit, exercise influence on biological effects (Kang et al.,2005). Among the phlorotannins, dieckol has become one ofthe major and most active compounds (Lee et al., 2010).

Adipogenesis is a physiological process resulting in the dif-ferentiation of undifferentiated preadipocytes (Otto and Lane,

2005). During differentiation of preadipocyte into adipocytes,adipogenesis is stimulated through the action of transcrip-tion factors such as PPAR�, C/EBP�, FABP4 and SREBP-1 (White

1258 e n v i r o n m e n t a l t o x i c o l o g y a n d p h a r m a c o l o g y 3 6 ( 2 0 1 3 ) 1253–1260

Fig. 3 – Dieckol suppress the expression of PPAR�, C/EBP�, SREBP-1 and FABP4 in 3T3-L1 adipocytes as examined byquantitative real-time PCR analysis. Confluent 3T3-L1 preadipocytes in medium with or without different concentrations ofdieckol for 8 days (from days 0 to 8) were differentiated into adipocytes. Each value is expressed as the mean ± standard

ly di

error of triplicate experiments. *p < 0.05 indicates significant

and Stephens, 2010). The activation of C/EBP� promote dif-ferentiation of preadipocytes through cooperation with PPAR�

resulting in transactivation of adipocyte-specific genes suchas FABP and fatty acid synthase (FAS) (Farmer, 2005; Haet al., 2010). SREBP-1 is the earliest transcription factor, whichalso appears to be involved in adipocyte differentiation, andincreases the expression of several lipogenic genes, includ-ing lipoprotein lipase (LPL), ACC and FAS (Ha et al., 2010;Kang et al., 2011). Therefore, over expression of these tran-scription factors can accelerate adipogenesis. To evaluatewhether dieckol possesses the ability to inhibit adipocytedifferentiation through PPAR�, C/EBP�, FABP4 and SREBP-1,the expression of genes and proteins was measured usingquantitative real-time PCR and Western blotting analysis.The results presented here indicate that dieckol significantlydown-regulated PPAR�, C/EBP�, FABP4 and SREBP-1 at the geneand protein levels, compared to control adipocytes. In ourprevious study, we isolated dieckol from E. cava and demon-strated the effect of its weight loss in db/db mouse model (Kanget al., 2013). Obesity is characterized by the generation of newadipocytes and the hypertrophy in the body as produced byadipocytes differentiation (Ahn et al., 2008). Therefore, adi-pogenesis inhibition could be important tool for prevention

against obesity. As a result with previous study, anti-obesityeffect of the dieckol may act through inhibiting the fat sizeand number increment by adipogenesis inhibition.

fferent to untreated group.

AMPK activation is associated with the activation and reg-ulation of downstream target genes that belong to diversesignaling pathways in various tissues (Kim and Kong, 2010).AMPK is emerging as a potentially interesting target for thetreatment of obesity, especially because it could play a princi-pal role for inhibition of adipogenesis in 3T3-L1 cells by naturalcompounds (Ahn et al., 2008; Ha et al., 2010; Kim and Kong,2010; Moon et al., 2007). Therefore, controlling obesity throughAMPK modulation is recognized as a major field of scientificresearch. In an attempt to elucidate the molecular mechanismby which dieckol inhibits adipogenesis, the protein level ofphosphorylated AMPK and its substrate, ACC was measured.Treatment with dieckol induced the phosphorylation of AMPKand ACC. Therefore, the results of this study suggest thatdieckol attenuates adipogenesis through the up-regulation ofAMPK activity. Obesity is one of the most important risk fac-tor for type 2 diabetes (Lieberman, 2003). Dieckol, a kind ofphlorotannin, is a polyphenolic compound that has been iso-lated from E. cava, and was show in previous study to havepotent blood glucose lowering effect by the AMPK activation(Kang et al., 2013). Along with the previous study, dieckol canpossess the anti-adipogenic and anti-diabetic effect throughAMPK activation.

In conclusion, dieckol, a marine seaweed polyphenolexhibited prominent anti-adipogenic effect and inhibits adi-pogenesis through down-regulation of PPAR�, C/EBP�, FABP4

e n v i r o n m e n t a l t o x i c o l o g y a n d p h a r m a c o l o g y 3 6 ( 2 0 1 3 ) 1253–1260 1259

Fig. 4 – Dieckol suppress the expression of PPAR�, C/EBP�, SREBP-1 and FABP4 in 3T3-L1 adipocytes as examined byWestern blot analysis. (A) Confluent 3T3-L1 preadipocytes in medium with or without different concentrations of dieckol for8 days (from days 0 to 8) were differentiated into adipocytes. (B) The effects of dieckol on phosphorylation of AMPK (Thr172)a

aoTt

C

T

A

Tta

r

A

nd ACC.

nd SREBP-1 in 3T3-L1 cells. Moreover, the inhibitory effectf dieckol on adipogenesis was associated AMPK activation.herefore, dieckol may be an effective candidate for preven-

ing obesity or obesity-related diseases.

onflict of interest

he authors declare no conflict of interest.

cknowledgment

his research was supported by Technology Commercializa-ion Support Program, Ministry for Food, Agriculture, Forestrynd Fisheries, Republic of Korea.

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