New insights into inhibitors of adipogenesis

Chrysanthemum morifolium Flower Extract Ameliorates Obesity-Induced Inflammation and Increases the Muscle Mitochondria Content and AMPK/SIRT1 Activities in Obese Rats

Decreased energy expenditure and chronically positive energy balance contribute to the prevalence of obesity and associated metabolic dysfunctions, such as dyslipidemia, hepatic fat accumulation, inflammation, and muscle mitochondrial defects. We investigated the effects of Chrysanthemum morifolium Ramat flower extract (CE) on obesity-induced inflammation and muscle mitochondria changes. Sprague-Dawley rats were randomly divided into four groups and fed either a normal diet, 45% high-fat diet (HF), HF containing 0.2% CE, or 0.4% CE for 13 weeks. CE alleviated HF-increased adipose tissue mass and size, dyslipidemia, hepatic fat deposition, and systematic inflammation, and increased energy expenditure. CE significantly decreased gene expression involved in adipogenesis, pro-inflammation, and the M1 macrophage phenotype, as well as glycerol-3-phosphate dehydrogenase (GPDH) and nuclear factor-kappa B (NF-kB) activities in epididymal adipose tissue. Moreover, CE supplementation improved hepatic fat accumulation and modulated gene expression related to fat synthesis and oxidation with an increase in adenosine monophosphate-activated protein kinase (AMPK) activity in the liver. Furthermore, CE increased muscle mitochondrial size, mitochondrial DNA (mtDNA) content, and gene expression related to mitochondrial biogenesis and function, including sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), and PGC-1α-target genes, along with AMPK-SIRT1 activities in the skeletal muscle. These results suggest that CE attenuates obesity-associated inflammation by modulating the muscle AMPK-SIRT1 pathway.

Alginate derived functional oligosaccharides: Recent developments, barriers, and future outlooks

Alginate is a biopolymer used extensively in the food, pharmaceutical, and chemical industries. Alginate oligosaccharides (AOS) derived from alginate exhibit superior biological activities and therapeutic potential. Alginate lyases with characteristic substrate specificity can facilitate the production of a broad array of AOS with precise structure and functionality. By adopting innovative analytical tools in conjunction with focused clinical studies, the structure-bioactivity relationship of a number of AOS has been brought to light. This review covers fundamental aspects and recent developments in AOS research. Enzymatic and microbial processes involved in AOS production from brown algae and sequential steps involved in AOS structure elucidation are outlined. Biological mechanisms underlying the health benefits of AOS and their potential industrial and therapeutic applications are elaborated. Withal, various challenges in AOS research are traced out, and future directions, specifically on recombinant systems for AOS preparation, are delineated to further widen the horizon of these exceptional oligosaccharides.

Macrotyloma uniflorum a plant food alleviates the metabolic syndrome through modulation of adipokines and PPARs

A sedentary lifestyle combined with the intake of high-calorie diet has been the paramount cause of metabolic syndrome (MS) which is now a serious concern of public health worldwide as it involves the coexistence of hypertension, hyperlipidemia, glucose intolerance, and obesity. Hence, identifying a suitable strategy to overcome the worldwide menace of MS is imperative. Macrotyloma uniflorum a lesser known legume is highly nutritious and notable for its ethano-medicinal potential. Herein, the influence of M. uniflorum in high-fat dietinduced metabolic changes in a rodent model of metabolic syndrome was evaluated. Serum levels of glucose, total cholesterol, triglycerides, VLDL-c, and bodyweight were decreased, whereas HDL-c was increased in M. uniflorum-treated MS rats. The protein expression (AMPK-α, PPAR-α, and PPAR-γ) and gene expression (leptin, adiponectin, resistin, UCP2, NF-κB, and IL-6) results are impressive to highlight that M. uniflorum modulates the pathological conditions of MS and proves to be cardioprotective. Furthermore, the histopathological analysis confirmed the pathological changes and substantiates the influence of M. uniflorum to overcome MS. The HPLC and GC (MS) profiling reveals the presence of an array of polyphenols such as rutin (694.61 μg/g), catechin (500.12 μg/g), epicatechin (158.10 μg/g), gallic acid (17.98 μg/g), ferulic acid (10.911 μg/g), daidzein (6.51 μg/g), and PUFA, respectively, which probably exhibits the therapeutic effect on MS and associated complications by modulating lipid metabolism and adipogenesis. PRACTICAL APPLICATIONS: Metabolic disorders like CVD and diabetes are leading cause of mortality and morbidity worldwide. With emerging issues on adverse effects of modern drugs, the emphasis on "Food is Medicine and Medicine as Food" has taken dramatic dimensions in the healthcare sector. Therefore, nutraceuticals are in great demand in the developed world off late. Legumes, are potent elements in a balanced diet next to cereals. Exploring the medicinal properties of legumes could bring a revolution in public health and nutraceutical industries. This study scientifically validated the phytochemicals in M. uniflorum for its functional potential in the management of Metabolic Syndrome (MS). This study would help the nutraceutical industries to develop functional foods using M. uniflorum seeds to make porridges and soups or nutraceutical supplements with the bioflavonoids isolated from M. uniflorum for the management of metabolic disorders by mitigating hyperlipidemia, oxidative stress, and inflammation.

Polyphenols and obesity prevention: critical insights on molecular regulation, bioavailability and dose in preclinical and clinical settings

Obesity represents one of the most important public health challenges of the 21st century and is characterized by a multifactorial etiology in which environmental, behavioral, metabolic, and genetic factors work together. Despite the rapid increase in prevalence of obesity in the last decades, especially in children, it remains a preventable disease. To battle obesity a multisector approach promoting healthier lifestyle in terms of physical activity and nutrition is needed. Specifically, biologically active dietary compounds, as polyphenols, are able to modulate the expression of genes involved in the development and progression of obesity and its comorbidities as demonstrated by multiple studies using different obesity models. However, human studies focusing on the transcriptomic modulation by polyphenols in obese patients are still limited and do not often recapitulate the results obtained in preclinical setting likely due to the underestimation of some variables such as bioavailability, dose and form (native vs. metabolized) of polyphenols used. The aim of this review is to summarize the state-of-art of nutrigenomic in vitro, in vivo and ex vivo studies as well as clinical trials based on dietary polyphenols to fight obesity. We also critical discuss the variables to be considered to fill the gap between preclinical and clinical settings.

Carnosic Acid Modulates Increased Hepatic Lipogenesis and Adipocytes Differentiation in Ovariectomized Mice Fed Normal or High-Fat Diets

As postmenopausal women experience a rapid increase in cardiovascular disease (CVD) risk with an increase in abdominal fat, dietary interventions to reduce CVD risk have been emphasized. This study was aimed at investigating the effect of a high-fat diet (HFD) in combination with an ovariectomy on liver and adipose tissue fat metabolism. The efficacy of carnosic acid (CA) supplementation in the suppression of HFD- and ovariectomy-induced obesity was also evaluated. Ovariectomized (OVX) or sham-operated mice at eight weeks of age were fed with a normal diet (ND), HFD, ND and 0.02% CA, or HFD and 0.02% CA for 12 weeks. All of the animals were sacrificed at the age of 20 weeks. The blood and tissue markers of the lipogenesis and adipocyte differentiation were measured. As expected, ovariectomy decreased the uterus weight and serum 17β-estradiol concentration. The HFD and ovariectomy significantly contributed to increases in the body weight and total fat mass, which were effectively inhibited by CA supplementation. The circulating concentrations of insulin, leptin, and TG (triglyceride) were significantly higher in the HFD group, and the concentrations were two to five times higher in the OVX and HFD group compared with those of the ND group. The CA supplementation significantly lowered the insulin, leptin, and TG concentrations in the OVX and HFD mice. The hepatic protein expressions of pAMPK and pACC were up-regulated by CA supplementation in OVX mice fed either ND or HFD. The expressions of hepatic SREBP1c and FAS mRNA were the highest in the OVX and HFD group, which were suppressed by CA supplementation. The adipose tissue PPARγ, aP2, and lipoprotein lipase (LPL) mRNA expressions were up-regulated by a HFD or ovariectomy, while they were significantly reduced in the mice fed a CA supplemented diet. The TNF-α and IL-6 mRNA levels in the adipose tissue were decreased by providing CA in the OVX groups. These results suggest that HFD and ovariectomy independently contribute to body fat accumulation, and CA effectively alleviated the ovariectomy-induced increases in lipogenesis and adipocyte differentiation. Further human trials are required in order to evaluate the efficacy of rosemary-derive CA as natural anti-adipogenic compounds, especially in postmenopausal women.

Effects of a medicinal plant Macrotyloma uniflorum (Lam.) Verdc.formulation (MUF) on obesity-associated oxidative stress-induced liver injury

Obesity is a global health burden due to lifestyle modifications that have a strong association with a high incidence of diseases, such as dyslipidemia, glucose intolerance, nonalcoholic fatty liver diseases, diabetes, hypertension, coronary heart disease and cancer. The aim of the present study is to investigate the protective effects of a Macrotyloma uniflurom formulation (MUF) against high-fat diet (HFD)-induced oxidative stress and inflammation in obese rats. Male albino Wistar rats were fed a high-fat diet for 6 weeks to facilitate fat-induced oxidative stress and were simultaneously treated with MUF (400 mg/kg b.w.) through oral gavage from the third week onwards during the treatment phase. At the end of the experimental period, hepatic and oxidative stress markers were examined. The mRNA expression levels of inflammatory marker genes [Tumor Necrosis Factor-α (TNF-α) and Interleukin-6 (IL-6)] were also determined by reverse transcriptase-polymerase chain reaction in liver tissue. Hepatic marker enzymes (aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and gamma glutamyl transferase) and lipid peroxidation markers (Thiobarbituric acid reactive substances and LOOH) were significantly increased in HFD-fed rats, and administration of MUF resulted in remarkable suppression of these markers. Administration of MUF to HFD rats enhanced the activity of enzymatic (superoxide dismutase, catalase and glutathione peroxidase and non-enzymatic (vitamin E, vitamin C and glutathione) antioxidants compared to HFD-fed rats. An anti-inflammatory effect of MUF was demonstrated by attenuating gene expression of TNF-α and IL-6. Therefore, the results of this study indicate that MUF could be a strong herbal therapeutic alternative for the protection of the liver as well as prevention and treatment of high-fat-induced oxidative stress and inflammation.

Anti-Adipogenic Effects of Ethanol Extracts Prepared from Selected Medicinal Herbs in 3T3-L1 Cells

Obesity is a major risk factor for various metabolic diseases such as cardiovascular disease, hypertension, and type 2 diabetes mellitus. In this study, we prepared ethanol extracts from Agastache rugosa (ARE), Chrysanthemum zawadskii (CZE), Mentha arvensis (MAE), Perilla frutescens (PFE), Leonurus sibiricus (LSE), Gardenia jasminoides (GJE), and Lycopus coreanus (LCE). The anti-oxidant and anti-adipogenic effects were evaluated. The IC₅₀ values for ascorbic acid and LCE against 2,2-diphenyl-1-picrylhydrazyl radicals were 246.2 μg/mL and 166.2 μg/mL, respectively, followed by ARE (186.6 μg/mL), CZE (198.6 μg/mL), MAE (337.1 μg/mL), PFE (415.3 μg/mL), LSE (548.2 μg/mL), and GJE (626.3 μg/mL). In non-toxic concentration ranges, CZE had a strong inhibitory effect against 3T3-L1 adipogenes (84.5%) than those of the other extracts. Furthermore, the anti-adipogenic effect of CZE is largely limited in the early stage of adipogenesis, and we revealed that the inhibitory role of CZE in adipogenesis is required for the activation of Wnt signaling. Our results provide scientific evidence that the anti-adipogenic effect of CZE can be applied as an ingredient for the development of functional foods and nutri-cosmetics for obesity prevention.

Antioxidant and anti-adipogenic activities of chestnut (Castanea crenata) byproducts

The antioxidant and anti-adipogenic activities of chestnut byproducts were evaluated. At 100 μg/mL, the methanol extract (ME) scavenged 34.2% of DPPH and 78.8% of ABTS radicals. The DPPH and ABTS radical scavenging activity of the water extract (WE) was found to be low (13.7 and 33.1%, respectively) compared with controls. WE and ME dose-dependently inhibited lipid accumulation of 3T3-L1 adipocytes. WE and ME at 100 μg/mL suppressed 3T3-L1 adipogenesis by 71.0 and 96.5%, respectively, when compared with mature adipocytes. The results indicated that WE and ME inhibited adipocyte differentiation by down-regulating the mRNA expression levels of CCAAT/enhancer binding protein (C/EBP)-β, C/EBPα, and peroxisome proliferator-activated receptor (PPAR)-γ in 3T3-L1 cells. Our study also revealed that WE and ME inhibited pre- and early stage adipogenesis in 3T3-L1 cells. The results suggest that chestnut byproducts are a promising source of antioxidant and antiobesity molecules.

Anti-oxidant and anti-adipogenic effects of acorn (Quercus acutissima CARR.) shell extracts via regulation of wnt signaling in 3T3-L1 cells

Acorn (Quercus acutissima CARR.) is a nut from the Fagaceae family that has been used in traditional medicine for many years. However, shells from acorns are regarded as a by-product and are mostly discarded. Anti-adipogenic activities of acorn shells were investigated using 3T3-L1 cells and methanol shell extracts (AE-M). AE-M demonstrated Cu²⁺-chelation activities and anti-oxidant activities via reduction of oxidative stress levels induced using AAPH. Six days after adipocyte differentiation, 50 and 100 μg/mL AE-M completely suppressed 3T3-L1 adipogenesis and the anti-adipogenic effect was stronger than for the positive control 50 μM quercetin. Treatment with AE-M in 3T3-L1 cells reduced mRNA expression levels of adipogenic genes. AE-M-inhibition was found in pre-adipogenic, early, and intermediate stages of adipogenesis in 3T3-L1 cells. The Wnt/β-catenin signaling pathway is required for AE-M-inhibition of 3T3-L1 adipogenesis.

Anti-adipocyte Differentiation Activity and Chemical Composition of Essential Oil from Artemisia annua

Artemisia annua L. essential oil (AAEO) has diverse properties including antibacterial, antioxidant, antinociceptive, and antimicrobial activities. However, the effect of AAEO on obesity remains to be investigated. In this study, we analyzed the compounds of AAEO and explored the effect of AAEO on the differentiation of preadipocyte into adipocyte using preadipocyte cell line 3T3-L1. Total yield of AAEO from 20 kg A. annua leaf and flower was 0.5%, v/w. Gas chromatography-mass spectrometry analysis showed that AAEO contained 34 compounds. 3T3-L1 cells incubated in 3-isobutyl-1-methylxanthine / dexamethasone / insulin (MDI)-containing medium showed increased accumulation of lipid droplets. This increased response was suppressed by treatment with AAEO. Expressions of obesity-related proteins (PPARγ, C/EBPα, SREBP-1c, FAS, and ACC) were increased in 3T3-L1 cells cultured in MDI medium and these responses were decreased by treatment with AAEO. These findings demonstrate that AAEO may suppress 3T3-L1 cell differentiation by inhibiting adipogenesis and activation of lipid metabolism-related proteins.

Evaluation of anti-obesity activities of ethanolic extract of Terminalia paniculata bark on high fat diet-induced obese rats

BACKGROUND

The prevalence and severity of obesity and associated co-morbidities are rapidly increasing across the world. Natural products-based drug intervention has been proposed as one of the crucial strategies for management of obesity ailments. This study was designed to investigate the anti-obesity activities of ethanolic extract of Terminalia paniculata bark (TPEE) on high fat diet-induced obese rats.

METHODS

LC-MS/MS analysis was done for ethanolic extract of T. paniculata bark. Male Sprague-Dawley (SD) rats were randomly divided into six groups of six each, normal diet fed (NC), high fat diet-fed (HFD), HFD+ orlistat (standard drug control) administered, and remaining three groups were fed with HFD + TPEE in different doses (100,150 and 200 mg/kg b. wt). For induction of obesity rats were initially fed with HFD for 9 weeks, then, (TPEE) was supplemented along with HFD for 42 days. Changes in body weight, body composition, blood glucose, insulin, tissue and serum lipid profiles, atherogenic index, liver markers, and expression of adipogenesis-related genes such as leptin, adiponectin, FAS, PPARgamma, AMPK-1alpha and SREBP-1c, were studied in experimental rats. Also, histopathological examination of adipose tissue was carried out.

RESULTS

Supplementation of TPEE reduced significantly (P < 0.05) body weight, total fat, fat percentage, atherogenic index, blood glucose, insulin, lipid profiles and liver markers in HFD-fed groups, in a dose-dependent manner. The expression of adipogenesis-related genes such as Leptin, FAS, PPARgamma, and SREBP-1c were down regulated while Adiponectin and AMPK-1alpha were up regulated in TPEE + HFD-fed rats. Furthermore, histopathological examination of adipose tissue revealed the alleviating effect of TPEE which is evident by reduced size of adipocytes.

CONCLUSIONS

Together, the biochemical, histological and molecular studies unambiguously demonstrate the potential anti adipogenic and anti obesity activities of TPEE promoting it as a formidable candidate to develop anti obesity drug.

Sinensetin enhances adipogenesis and lipolysis by increasing cyclic adenosine monophosphate levels in 3T3-L1 adipocytes

Sinensetin is a rare polymethoxylated flavone (PMF) found in certain citrus fruits. In this study, we investigated the effects of sinensetin on lipid metabolism in 3T3-L1 cells. Sinensetin promoted adipogenesis in 3T3-L1 preadipocytes growing in incomplete differentiation medium, which did not contain 3-isobutyl-1-methylxanthine. Sinensetin up-regulated expression of the adipogenic transcription factors peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein (C/EBP) α, and sterol regulatory element-binding protein 1c. It also potentiated expression of C/EBPβ and activation of cAMP-responsive element-binding protein. Sinensetin enhanced activation of protein kinase A and increased intracellular cAMP levels in 3T3-L1 preadipocytes. In mature 3T3-L1 adipocytes, sinensetin stimulated lipolysis via a cAMP pathway. Taken together, these results suggest that sinensetin enhances adipogenesis and lipolysis by increasing cAMP levels in adipocytes.

HIV/AIDS and lipodystrophy: implications for clinical management in resource-limited settings

Introduction

Lipodystrophy is a term used to describe a metabolic complication of fat loss, fat gain, or a combination of fat loss and gain, which is associated with some antiretroviral (ARV) therapies given to HIV-infected individuals. There is limited research on lipodystrophy in low- and middle-income countries, despite accounting for more than 95% of the burden of HIV/AIDS. The objective of this review was to evaluate the prevalence, pathogenesis and prognosis of HIV-related lipoatrophy, lipohypertrophy and mixed syndrome, to inform clinical management in resource-limited settings.

Methods

We conducted a structured literature search using MEDLINE electronic databases. Relevant MeSH terms were used to identify published human studies on HIV and lipoatrophy, lipohypertrophy, or mixed syndrome in low-, low-middle- and upper-middle-income countries through 31 March 2014. The search resulted in 5296 articles; after 1599 studies were excluded (958 reviews, 641 non-human), 3697 studies were extracted for further review. After excluding studies conducted in high-income settings (n=2808), and studies that did not meet inclusion criteria (n=799), 90 studies were included in this review.

Results and Discussion

Of the 90 studies included in this review, only six were from low-income countries and eight were from lower middle-income economies. These studies focused on lipodystrophy prevalence, risk factors and side effects of antiretroviral therapy (ART). In most studies, lipodystrophy developed after the first six months of therapy, particularly with the use of stavudine. Lipodystrophy is associated with increased risk of cardiometabolic complications. This is disconcerting and anticipated to increase, given the rapid scale-up of ART worldwide, the increasing number and lifespan of HIV-infected patients on long-term therapy, and the emergence of obesity and non-communicable diseases in settings with extensive HIV burden.

Conclusions

Lipodystrophy is common in resource-limited settings, and has considerable implications for risk of metabolic diseases, quality of life and adherence. Comprehensive evidence-based interventions are urgently needed to reduce the burden of HIV and lipodystrophy, and inform clinical management in resource-limited settings.

GATA binding protein 2 mediates leptin inhibition of PPARγ1 expression in hepatic stellate cells and contributes to hepatic stellate cell activation

Hepatic stellate cell (HSC) activation is a crucial step in the development of liver fibrosis. Peroxisome-proliferator activated receptor γ (PPARγ) exerts a key role in the inhibition of HSC activation. Leptin reduces PPARγ expression in HSCs and plays a unique role in promoting liver fibrosis. The present studies aimed to investigate the mechanisms underlying leptin regulation of PPARγ1 (a major subtype of PPARγ) in HSCs in vivo and in vitro. Results revealed a leptin response region in mouse PPARγ1 promoter and indicated that the region included a GATA binding protein binding site around position -2323. GATA binding protein-2 (GATA-2) could bind to the site and inhibit PPARγ1 promoter activity in HSCs. Leptin induced GATA-2 expression in HSCs in vitro and in vivo. GATA-2 mediated leptin inhibition of PPARγ1 expression by its binding site in PPARγ1 promoter in HSCs and GATA-2 promoted HSC activation. Leptin upregulated GATA-2 expression through β-catenin and sonic hedgehog pathways in HSCs. Leptin-induced increase in GATA-2 was accompanied by the decrease in PPARγ expression in HSCs and by the increase in the activated HSC number and liver fibrosis in vivo. Our data might suggest a possible new explanation for the promotion effect of leptin on liver fibrogenesis.

Dohaekseunggi-tang extract inhibits obesity, hyperlipidemia, and hypertension in high-fat diet-induced obese mice

Background

Dohaekseunggi-tang (DHSGT) is a traditional plant-based medicine prescribed to promote blood circulation and to treat obesity and hypertension. The present study aimed to identify potential anti-obesity activities of DHSGT extract.

Methods

Anti-obesity, anti-hyperlipidemic, and anti-hypertensive effects of orally-administered DHSGT extract were evaluated in high-fat diet- (HFD)-induced obese mice. Serum biochemistry profiles and expression of diverse metabolic regulatory gene mRNAs in mouse visceral fat were assessed by RT-PCR. The effects of DHSGT on angiotensin-1 converting enzyme (ACE) and pancreatic lipase activities were determined using in vitro inhibition assays.

Results

Oral DHSGT treatment reduced obese HFD C57BL/6 J mouse body weight, liver and adipose tissue mass, adipocyte size, and blood pressure versus untreated HFD mice. DHSGT also decreased serum total cholesterol, LDL-cholesterol, triglyceride, glucose, and leptin concentrations, and increased HDL-cholesterol and adiponectin levels in HFD mice. Furthermore, DHSGT markedly increased mRNA expression of peroxisome proliferator activated receptor-gamma, uncoupling protein-2, and adiponectin in visceral adipose tissue of HFD mice. In vitro tests revealed that DHSGT effectively inhibited porcine pancreatic lipase and ACE activities, with IC₅₀ values of 7.58 mg/ml and 0.56 mg/ml, respectively.

Conclusions

These results validate traditional knowledge and suggest that DHSGT may be potentially useful for managing hyperlipidemia, hyperglycemia, hypertension, and obesity.

Novel insights of dietary polyphenols and obesity

The prevalence of obesity has steadily increased over the past three decades both in the United States and worldwide. Recent studies have shown the role of dietary polyphenols in the prevention of obesity and obesity-related chronic diseases. Here, we evaluated the impact of commonly consumed polyphenols, including green tea catechins, especially epigallocatechin gallates, resveratrol and curcumin, on obesity and obesity-related inflammation. Cellular studies demonstrated that these dietary polyphenols reduce viability of adipocytes and proliferation of preadipocytes, suppress adipocyte differentiation and triglyceride accumulation, stimulate lipolysis and fatty acid β-oxidation, and reduce inflammation. Concomitantly, the polyphenols modulate signaling pathways including the adenosine-monophosphate-activated protein kinase, peroxisome proliferator activated receptor γ, CCAAT/enhancer binding protein α, peroxisome proliferator activator receptor gamma activator 1-alpha, sirtuin 1, sterol regulatory element binding protein-1c, uncoupling proteins 1 and 2, and nuclear factor-κB that regulate adipogenesis, antioxidant and anti-inflammatory responses. Animal studies strongly suggest that commonly consumed polyphenols described in this review have a pronounced effect on obesity as shown by lower body weight, fat mass and triglycerides through enhancing energy expenditure and fat utilization, and modulating glucose hemostasis. Limited human studies have been conducted in this area and are inconsistent about the antiobesity impact of dietary polyphenols probably due to the various study designs and lengths, variation among subjects (age, gender, ethnicity), chemical forms of the dietary polyphenols used and confounding factors such as other weight-reducing agents. Future randomized controlled trials are warranted to reconcile the discrepancies between preclinical efficacies and inconclusive clinic outcomes of these polyphenols.

Nutraceuticals and regulation of adipocyte life: premises or promises

Obesity is the actual worldwide health threat, that is associated with an increased number of metabolic disorders and diseases. Following the traditional hypothesis stating that in obesity hypertrophic adipocytes trigger the adipose tissue hyperplasia, strategies to treat obesity have increased fat researches of the molecular processes that achieve adipocyte enlargement and formation that finally increase body fat mass. Moreover, a new cell type was recently identified, the "brite" adipocyte that presents a unique gene expression profile of compared to both brown and white adipocytes. Therapies against obesity, targeting these cells and their pathways, would include the induction of lipolysis and apoptosis or the inhibition of differentiation and adipogenesis. However, it should be noted that both the increase of adipocyte size and number take place in association with positive energy balance. According to the adipose tissue expansion hypothesis, adipogenesis could be related with improved metabolic health of obese people, taking back the adipose mass to a traditionally site of lipid storage. Furthermore, new perspectives in fat biology suggest that the conversion of white-to-brown adipocytes and their metabolism could be exploited for the development of therapeutic approaches against obesity-associated diseases and for the regulation of energy balance. Drugs currently available to treat obesity generally have unpleasant side effects. A novel promising approach is the usage of dietary supplements and plant products that could interfere on the life cycle of adipocyte. Here, various dietary bioactive compounds that target different stages of adipocyte life cycle and molecular and metabolic pathways are reviewed.

6-gingerol prevents adipogenesis and the accumulation of cytoplasmic lipid droplets in 3T3-L1 cells

6-Gingerol ((S)-5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-3-decanone) is one of the pungent constituents of Zingiber zerumbet (L) Smith (Zingiberaceae family). In this study, we investigated the effects of 6-gingerol on the inhibition of adipogenesis in 3T3-L1 cells. After treatment with 6-gingerol in differentiation medium for 4 or 8 days, the 3T3-L1 cells were lysed for experimental analysis. Cells were stained with Oil-Red-O to detect oil droplets in adipocytes. The 3T3-L1 cells were lysed and measured for triglyceride contents. The protein expression of adipogenesis-related transcription factor was evaluated by Western blot analysis. 6-Gingerol suppressed oil droplet accumulation and reduced the droplet size in a concentration (5-15 μg/ml)- and time-dependent manner. Treatment of 3T3-L1 cells with 6-gingerol reduced the protein levels of peroxisome proliferator-activated receptor (PPAR)γ and CCAAT/enhancer-binding protein (C/EBP)α. Additionally, the protein levels of fatty acid synthase (FAS) and adipocyte-specific fatty acid binding protein (aP2) decreased upon treatment with 6-gingerol. Meanwhile, 6-gingerol diminished the insulin-stimulated serine phosphorylation of Akt (Ser473) and GSK3β (Ser9). These results suggest that 6-gingerol effectively suppresses adipogenesis and that it exerts its role mainly through the significant down-regulation of PPARγ and C/EBPα and subsequently inhibits FAS and aP2 expression. 6-Gingerol also inhibited differentiation in 3T3-L1 cells by attenuating the Akt/GSK3β pathway. Our findings provide important insights into the mechanisms underlying the anti-adipogenic activity of 6-gingerol.

The LIM-only protein FHL2 controls mesenchymal cell osteogenic differentiation and bone formation through Wnt5a and Wnt10b

Wnt signaling is an important pathway that controls the osteogenic differentiation of mesenchymal stromal cells (MSC). We previously showed that FHL2, a LIM-only protein with four and a half LIM domains, controls MSC osteogenic differentiation via the canonical Wnt/β-catenin signaling. In this study, we investigated the role of Wnt proteins in the regulation of MSC differentiation by FHL2. We found that Wnt3a increased FHL2 mRNA expression in murine C3H10T1/2 mesenchymal cells. Silencing FHL2 using short hairpin (sh) RNA attenuated β-catenin transcriptional activity and osteogenic differentiation induced by Wnt3a. In addition, FHL2 silencing reduced the expression of the key molecules Wnt5a and Wnt10b and osteoblast gene expression. Wnt10b overcomes the negative effect of FHL2 knockdown on osteoblast gene expression in vitro. To confirm this finding in vivo, we analyzed the expression of these Wnt molecules in FHL2 deficient mice. Histomorphometric analyses showed that FHL2 knockout decreased trabecular number and thickness and reduced bone mass in 15-month old mice. This phenotype was associated with decreased Wnt5a and Wnt10b and lower than normal c-myc, cyclin D1 and osteoblast gene expression in the bone marrow. Ex vivo analysis showed decreased basal and Wnt3a-induced Wnt5a and Wnt10b mRNA expression in FHL2-deficient bone marrow cells, further indicating that this defect may contribute to the reduced osteoblast function in FHL2 deficient mice. In contrast, the decreased adipogenesis induced by FHL2 deficiency in vitro and in vivo was linked to increased Foxo1 expression. Collectively, the results provide evidence for a previously unrecognized mechanism by which FHL2 controls the osteogenic differentiation of MSC, bone formation and bone mass through modulation of Wnt molecules.

Identification of RIFL, a novel adipocyte-enriched insulin target gene with a role in lipid metabolism

To identify new genes that are important in fat metabolism, we utilized the Lexicon-Genentech knockout database of genes encoding transmembrane and secreted factors and whole murine genome transcriptional profiling data that we generated for 3T3-L1 in vitro adipogenesis. Cross-referencing null models evidencing metabolic phenotypes with genes induced in adipogenesis led to identification of a new gene, which we named RIFL (refeeding induced fat and liver). RIFL-null mice have serum triglyceride levels approximately one-third of wild type. RIFL transcript is induced >100-fold during 3T3-L1 adipogenesis and is also increased markedly during adipogenesis of murine and human primary preadipocytes. siRNA-mediated knockdown of RIFL during 3T3-L1 adipogenesis results in an ~35% decrease in adipocyte triglyceride content. Murine RIFL transcript is highly enriched in white and brown adipose tissue and liver. Fractionation of WAT reveals that RIFL transcript is exclusive to adipocytes with a lack of expression in stromal-vascular cells. Nutritional and hormonal studies are consistent with a prolipogenic function for RIFL. There is evidence of an approximately eightfold increase in RIFL transcript level in WAT in ob/ob mice compared with wild-type mice. RIFL transcript level in WAT and liver is increased ~80- and 12-fold, respectively, following refeeding of fasted mice. Treatment of 3T3-L1 adipocytes with insulin increases RIFL transcript ≤35-fold, whereas agents that stimulate lipolysis downregulate RIFL. Interestingly, the 198-amino acid RIFL protein is predicted to be secreted and shows ~30% overall conservation with the NH(2)-terminal half of angiopoietin-like 3, a liver-secreted protein that impacts lipid metabolism. In summary, our data suggest that RIFL is an important new regulator of lipid metabolism.

Immature Citrus sunki peel extract exhibits antiobesity effects by β-oxidation and lipolysis in high-fat diet-induced obese mice

The peel of Citrus sunki HORT. ex TANAKA has been widely used in traditional Asian medicine for the treatment of many diseases, including indigestion and bronchial asthma. In this study, we investigated the antiobesity activity of immature C. sunki peel extract (designated CSE) using high-fat diet (HFD)-induced obese C57BL/6 mice and mature 3T3-L1 adipocytes. In the animal study, body weight gain, adipose tissue weight, serum total cholesterol, and triglyceride in the CSE-administered group decreased significantly compared to the HFD group. Also, CSE supplementation reduced serum levels of glutamic pyruvic transaminase, glutamic oxaloacetic transaminase, and lactate dehydrogenase. Moreover, it significantly decreased the accumulation of fatty droplets in liver tissue, suggesting a protective effect against HFD-induced hepatic steatosis. Dietary supplementation with CSE reversed the HFD-induced decrease in the phosphorylation levels of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), which are related to fatty acid β-oxidation, in the epididymal adipose tissue. Also, CSE increased AMPK and ACC phosphorylation in mature 3T3-L1 adipocytes. CSE also enhanced lipolysis by phosphorylation of cAMP-dependent protein kinase (PKA) and hormone-sensitive lipase (HSL) in mature 3T3-L1 adipocytes. These results suggest that CSE had an antiobesity effect via elevated β-oxidation and lipolysis in adipose tissue.

Reduction of body weight, liver steatosis and expression of stearoyl-CoA desaturase 1 by the isoflavone daidzein in diet-induced obesity

BACKGROUND AND PURPOSE

The lack of safe and effective treatments for obesity has increased interest in natural products that may serve as alternative therapies. From this perspective, we have analysed the effects of daidzein, one of the main soy isoflavones, on diet-induced obesity in rats.

EXPERIMENTAL APPROACH

Rats made obese after exposure to a very (60%) high fat-content diet were treated with daidzein (50 mg·kg(-1)) for 14 days. The dose was selected on the basis of the acute effects of this isoflavone on a feeding test. After 14 days, animals were killed and plasma, white and brown adipose tissue, muscle and liver studied for the levels and expression of metabolites, proteins and genes relevant to lipid metabolism.

KEY RESULTS

A single treatment (acute) with daidzein dose-dependently reduced food intake. Chronic treatment (daily for 14 days) reduced weight gain and fat content in liver, accompanied by high leptin and low adiponectin levels in plasma. While skeletal muscle was weakly affected by treatment, both adipose tissue and liver displayed marked changes after treatment with daidzein, affecting transcription factors and lipogenic enzymes, particularly stearoyl coenzyme A desaturase 1, a pivotal enzyme in obesity. Expression of uncoupling protein 1, an important enzyme for thermogenesis, was increased in brown adipose tissue after daidzein treatment.

CONCLUSIONS AND IMPLICATIONS

These results support the use of isoflavones in diet-induced obesity, especially when hepatic steatosis is present and open a new field of use for these natural products.

Dehydrodiconiferyl alcohol isolated from Cucurbita moschata shows anti-adipogenic and anti-lipogenic effects in 3T3-L1 cells and primary mouse embryonic fibroblasts

A water-soluble extract from the stems of Cucurbita moschata, code named PG105, was previously found to contain strong anti-obesity activities in a high fat diet-induced obesity mouse model. One of its biological characteristics is that it inhibits 3T3-L1 adipocyte differentiation. To isolate the biologically active compound(s), conventional solvent fractionation was performed, and the various fractions were tested for anti-adipogenic activity using Oil Red O staining method. A single spot on thin layer chromatography of the chloroform fraction showed a potent anti-adipogenic activity. When purified, the structure of its major component was resolved as dehydrodiconiferyl alcohol (DHCA), a lignan, by NMR and mass spectrometry analysis. In 3T3-L1 cells, synthesized DHCA significantly reduced the expression of several adipocyte marker genes, including peroxisome proliferator-activated receptor γ (Pparg), CCAAT/enhancer-binding protein α (Cebpa), fatty acid-binding protein 4 (Fabp4), sterol response element-binding protein-1c (Srebp1c), and stearoyl-coenzyme A desaturase-1 (Scd), and decreased lipid accumulation without affecting cell viability. DHCA also suppressed the mitotic clonal expansion of preadipocytes (an early event of adipogenesis), probably by suppressing the DNA binding activity of C/EBPβ, and lowered the production level of cyclinA and cyclin-dependent kinase 2 (Cdk2), coinciding with the decrease in DNA synthesis and cell division. In addition, DHCA directly inhibited the expression of SREBP-1c and SCD-1. Similar observations were made, using primary mouse embryonic fibroblasts. Taken together, our data indicate that DHCA may contain dual activities, affecting both adipogenesis and lipogenesis.

Obesity short-circuits stemness gene network in human adipose multipotent stem cells

The discovery of adipose multipotent stem cells has provided new insights to explore cellular mechanisms involved in adipose tissue function. In the present work, we aimed to evaluate how the adipogenic environment influences the stemness of the resident multipotent stem cells. To achieve this goal, human omental multipotent stem cells (hO-MSCs) were isolated, expanded, and characterized in both healthy lean and morbidly obese individuals. We observed decreased cell proliferation, premature senescence, and increased cytokine secretion associated with increasing body mass index of the patients. Consistent with the latter finding, the hO-MSCs derived from patients with morbid obesity lose their multilineage differentiation capacity associated with a dysregulation in the Wnt, Notch, and Sonic Hedgehog signaling pathways. Moreover, microRNAs involved in the regulation of stemness, cell differentiation, and senescence were also up-regulated in obese individuals. Altogether, our data show that obesity causes a general short circuit in the stemness gene network of hO-MSCs.

Cancer-associated adipocytes exhibit an activated phenotype and contribute to breast cancer invasion

Early local tumor invasion in breast cancer results in a likely encounter between cancer cells and mature adipocytes, but the role of these fat cells in tumor progression remains unclear. We show that murine and human tumor cells cocultivated with mature adipocytes exhibit increased invasive capacities in vitro and in vivo, using an original two-dimensional coculture system. Likewise, adipocytes cultivated with cancer cells also exhibit an altered phenotype in terms of delipidation and decreased adipocyte markers associated with the occurrence of an activated state characterized by overexpression of proteases, including matrix metalloproteinase-11, and proinflammatory cytokines [interleukin (IL)-6, IL-1β]. In the case of IL-6, we show that it plays a key role in the acquired proinvasive effect by tumor cells. Equally important, we confirm the presence of these modified adipocytes in human breast tumors by immunohistochemistry and quantitative PCR. Interestingly, the tumors of larger size and/or with lymph nodes involvement exhibit the higher levels of IL-6 in tumor surrounding adipocytes. Collectively, all our data provide in vitro and in vivo evidence that (i) invasive cancer cells dramatically impact surrounding adipocytes; (ii) peritumoral adipocytes exhibit a modified phenotype and specific biological features sufficient to be named cancer-associated adipocytes (CAA); and (iii) CAAs modify the cancer cell characteristics/phenotype leading to a more aggressive behavior. Our results strongly support the innovative concept that adipocytes participate in a highly complex vicious cycle orchestrated by cancer cells to promote tumor progression that might be amplified in obese patients.

Lentiviral-mediated interleukin-4 and interleukin-13 RNA interference decrease airway inflammation and hyperresponsiveness

Interleukin (IL)-4 and IL-13 are two key cytokines released from activated T helper type 2 (Th2) cells and strongly associated with asthma and allergic disease. We applied silencing of the IL-4 and IL-13 gene expression by RNA interference delivered by a lentiviral vector to evaluate the therapeutic role of IL-4 and IL13 short hairpin RNAs (shRNAs) in a murine model of asthma. Mice were sensitized with ovalbumin (OVA), and one treatment of IL-4 and IL-13 shRNA lentiviral vector (Lenti-si-IL-4 and Lenti-si-IL-13) was instilled intratracheally 48 hr before challenge. After three challenges of OVA antigen, mice were assessed for airway inflammation and hyperresponsiveness. With infection of Lenti-si-IL-4 and Lenti-si-IL-13 in EL-4 cells, both RNA and protein expressions of IL-4 and IL-13 were obviously abrogated. Furthermore, intratracheal instillation of Lenti-si-IL-4 and Lenti-si-IL-13 in OVA-immunized mice resulted in a strong inhibition of local IL-4 and IL-13 cytokine release. Treatment with Lenti-si-IL-4 and Lenti-si-IL-13 successfully alleviated OVA-induced airway eosinophilia and Th2 cell cytokine release. Finally, to determine airway hyperresponsiveness by enhanced pause and pulmonary resistance in noninvasive and invasive body plethysmography, we found that administration of Lenti-si-IL-4 and Lenti-si-IL-13 markedly decreased airway hyperresponsiveness in OVA-immunized mice. These results suggest that inhibition of IL-4 and IL-13 gene expression by shRNA lentiviral vector markedly inhibits antigen-induced airway inflammation and hyperresponsiveness in mice.

A water-soluble extract of Petalonia binghamiae inhibits the expression of adipogenic regulators in 3T3-L1 preadipocytes and reduces adiposity and weight gain in rats fed a high-fat diet

We previously showed that an ethanolic extract of the edible brown algae Petalonia binghamiae promotes the differentiation of 3T3-L1 preadipocytes and decreases hyperglycemia in streptozotocin-induced diabetic mice. Here, we report that a water-soluble extract of P. binghamiae thalli, prepared by enzymatic digestion, inhibits preadipocyte differentiation and adipogenesis in a dose-dependent manner. In differentiating 3T3-L1 preadipocytes, the extract (designated PBEE) decreased the expression of peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding proteins α and β, and fatty acid-binding protein aP2. It also inhibited the mitotic clonal expansion process of adipocyte differentiation, and it inhibited insulin-stimulated uptake of glucose into mature 3T3-L1 adipocytes by reducing phosphorylation of insulin receptor substrate-1. In rats with high-fat diet (HFD)-induced obesity, PBEE exhibited potent anti-obesity effects. In this animal model, increases in body weight and fat storage were suppressed by the addition of PBEE to the drinking water at 500 mg/L for 30 days. PBEE supplementation reduced serum levels of glutamic pyruvic and glutamic oxaloacetic transaminases and increased the serum level of high-density lipoprotein cholesterol. Moreover, it significantly decreased the accumulation of lipid droplets in liver tissue, suggesting a protective effect against HFD-induced hepatic steatosis. Taken together, these data demonstrate that PBEE inhibits preadipocyte differentiation and adipogenesis in cultured cells and in rodent models of obesity.

[Adipose tissue as a therapeutic target in obesity]

Obesity is characterized by an increase of adipose tissue as a result of a positive imbalance between food intake and energy expenditure. Recent studies have indicated that adipocyte function is more complex than expected, since these cells have multiple functions and are integrated in a homeostatic network to optimize energy resources. As metabolic sensors in the body, adipocytes and the surrounding stromal vascular cells produce and secrete autocrine, paracrine and endocrine factors, able to regulate aspects involved in the development of adipocytes, as well as effects in peripheral organs important for metabolism. Regulation of these endocrine factors could lead to new therapeutic approaches targeted at aspects related to adipogenesis, preadipocyte proliferation and differentiation, inflammatory cytokine release and secretion, adipose tissue vascularization, and regulation of lipid metabolism or, alternatively, regulation of energy dissipation in mitochondria. In the study of the mechanisms of adipogenesis and remodulation of adipose tissue with respect to adipocyte size and function, an alternative and unorthodox strategy to improve obesity-associated metabolic complications could consist of increasing the storage capacity of adipose tissue to prevent a toxic response known as lipotoxicity.

Perilla leaf extract ameliorates obesity and dyslipidemia induced by high-fat diet

The objective of this study was to evaluate the antiobesity effect of perilla leaf extract (PLE) in animal models of high fat diet-induced obesity. C57BL/6J mice were fed a standard diet (STD) or high fat diet (HFD) for 5 weeks to induce obesity. The experimental groups were four groups with 10 mice per group and fed for 4 weeks: a STD group, a HFD group, a HFD containing 1% PLE (HFD+PLE 1%) group and a HFD containing 3% PLE (HFD+PLE 3%) group. The PLE supplementation significantly decreased body weight gain, food efficiency ratio, and relative liver and epididymal fat mass compared with those of the HFD group. Also, triglyceride, total cholesterol and LDL levels in the plasma were significantly reduced by PLE supplementation compared with the HFD group. Histological changes in the liver of the PLE supplemented group showed an inhibition of steatosis induced by HFD. Furthermore, PLE reversed the HFD induced changes in the expression patterns of epididymal adipose tissue genes: acetyl CoA carboxylase (ACC), glycerol-3-phosphate dehydrogenase (GPDH) and peroxisome proliferator-activated receptor gamma (PPARgamma). These results suggest that the PLE supplement suppressed body weight gain and improved the blood lipid profiling, in part by down-regulating adipogenic transcription factor and other specific target genes.

Downregulated expression of the secreted glycoprotein follistatin-like 1 (Fstl1) is a robust hallmark of preadipocyte to adipocyte conversion

Obesity is a public health crisis in the United States. Targeting preadipocyte to adipocyte conversion may be an effective approach to regulate adipose mass. Using differential screening we identified Fstl1, a secreted glycoprotein with roles in immunomodulation, cell growth, cardioprotection, and vascularization, as a "preadipokine". Fstl1 is highly expressed in 3T3-L1 preadipocytes and dramatically downregulated early in their differentiation to adipocytes. Northern blot analysis of murine tissues reveals white adipose tissue (WAT), lung and heart as primary sites of Fstl1 transcript expression. In WAT, Fstl1 transcript is restricted to the preadipocyte-containing stromal-vascular cell population. Time course studies in multiple adipogenesis models reveal downregulation of Fstl1 is a hallmark of white and brown adipocyte conversion. By Western blot, we show culture media of 3T3-L1 preadipocytes contains high levels of Fstl1 protein that rapidly decline in adipocyte conversion. Moreover, we observe a correlation between preadipocyte phenotype and Fstl1 expression in that TNFalpha-mediated de-differentiation of 3T3-L1 adipocytes is accompanied by re-expression of Fstl1 transcript and protein. Treatment of 3T3-L1 preadipocytes with a panel of 18 hormones and other agents revealed the demethylating agent 5-aza-cytidine decreases Fstl1 transcript and protein levels by approximately 90%. Furthermore, of 10 additional preadipocyte-expressed genes analyzed we find Pref-1, Col1A1, Sca-1/Ly6a, Lox and Thbs2, are also downregulated by 5-aza-cytidine. Using luciferase reporter constructs containing 791 or 3922 bp of the Fstl1 5' flanking region, we determine negative transcriptional regulation by Kruppel-like factor 15. Together, our data suggest downregulation of Fstl1 expression may be an important feature of preadipocyte to adipocyte conversion.

Anti-obesity effects of Juniperus chinensis extract are associated with increased AMP-activated protein kinase expression and phosphorylation in the visceral adipose tissue of rats

This study evaluates the protective effect of Juniperus chinensis hot water extract (JCE) against high-fat-diet (HFD)-induced obesity and its molecular mechanisms in the visceral adipose tissue of rats. JCE supplementation significantly lowered body weight gain, visceral fat-pad weights, blood lipid levels, and blood insulin and leptin levels of rats rendered obese by an HFD. Feeding with JCE significantly reversed the HFD-induced down-regulation of the epididymal adipose tissue genes implicated in adipogenesis, such as the peroxisome proliferator-activated receptors gamma2 (PPARgamma2), adipocyte protein 2 (aP2), sterol regulatory element binding protein 1c (SREBP1c), fatty acid synthase (FAS), and HMG-CoA reductase (HMGR), as well as those involved in uncoupled respiration, such as the uncoupling protein 2 (UCP2) and uncoupling protein 3 (UCP3). Dietary supplementation with JCE also reversed the HFD-induced decreases in the AMP-activated protein kinase (AMPK) and the acetyl-CoA carboxylase 2 (ACC2) expressions at both the mRNA and protein levels and restored the HFD-induced inhibitions in the AMPK and ACC2 phosphorylation, which are related to fatty acid beta-oxidation, in the epididymal adipose tissue. This study reports, for the first time, that the JCE can have an anti-obesity effect in a rodent model with HFD-induced obesity through an enhanced gene transcription of the uncoupling protein as well as an elevated AMPK protein expression and phosphorylation in the visceral adipose tissue.

The effects of soy isoflavones on obesity

Over the last decades, the prevalence of obesity and related diseases has increased rapidly in the Western world. Obesity is a disorder of energy balance and is associated with hyper-insulinemia, insulin resistance, and abnormalities in lipid metabolism, and it is one of the most important risk factors in the development of Type II diabetes, cardiovascular disease, atherosclerosis, and certain cancers. Because of the lower frequency of these diseases in Asian countries, attention has been turned toward the Asian diet, which consists highly of soy and soy-based products. The health benefits associated with soy consumption have been linked to the content of isoflavones, the main class of the phytoestrogens. As a result of their structural similarities to endogenous estrogens, isoflavones elicit weak estrogenic effects by competing with 17beta-estradiol (E2) for binding to the intranuclear estrogen receptors (ERs) and exert estrogenic or antiestrogenic effects in various tissues. The estrogenic activities of soy isoflavones are thought to play an important role in their health-enhancing properties. Additionally, the isoflavones have been proved to exert non-ER-mediated effects through numerous other pathways. Genistein, daidzein, and glycitein are the principal isoflavones in soy. Genistein is the most thoroughly examined of these, because it is the most prevalent isoflavone in soy and the most active of these compounds, because of its higher binding affinity for the ER. Genistein and daidzein can be obtained in high levels in humans under certain nutritional conditions, and epidemiologic and laboratory data suggest that these compounds could have health benefits in human obesity. This review will focus on the latest results of research on isoflavones and their effect on obesity in cell cultures, rodents, and humans.

Role of adipocyte disdifferentiation in insulin resistance and nonalcoholic fatty liver disease

Adipocytes, major components of white adipose (WAT), are mainly involved in energy storage and considered an endocrine organ. The energy homeostasis is maintained by the normal differentiation of adipocytes. Abnormal adipocyte differentiation, caused by change of transcription regulation factors and adipokines, can interfere with insulin signaling transduction, thus causing insulin resistance (IR). IR is the key tache of nonalcoholic liver disease (NAFLD), while abnormal adipocyte differentiation is directly related to NAFLD. This article mainly discusses the relationship of abnormal adipocyte differentiation to IR as well as its effects on NAFLD.

Characterization of ScAP-23, a new cell line from murine subcutaneous adipose tissue, identifies genes for the molecular definition of preadipocytes

The 3T3-L1 model of in vitro adipogenesis has provided key insights into the molecular nature of this process. However, given that 3T3-L1 are of an embryonic origin, it is not clear to what extent they represent adipogenesis as it occurs in white adipose tissue (WAT). With the goal of better defining preadipocytes and adipogenesis in WAT, we have generated a new cell culture model from adipocyte precursors present in C57BL/6 mouse subcutaneous WAT. ScAP-23 preadipocytes show fibroblastic morphology, and on treatment with dexamethasone, 3-methylisobutylxanthine, insulin, and indomethacin, convert to nearly 100% adipocyte morphology. ScAP-23 adipocytes contain abundant lipid droplets and express transcripts for PPARγ, C/EBP family, and SREBP-1c transcription factors, SCD1, aFABP, ATGL, GLUT4, FAS, LDL, and GPDH, and are insulin responsive. Differential screening of 1,176 genes using nylon DNA arrays identified 10 transcripts enriched in ScAP-23 adipocytes vs. preadipocytes and 26 transcripts enriched in ScAP-23 preadipocytes vs. adipocytes. Semiquantitative or real-time PCR analyses identified a common cohort of 14 transcripts markedly downregulated in both ScAP-23 and 3T3-L1 adipogenesis. These included catenin-β1, chemokine ligand-2, serine or cysteine peptidase inhibitor f1, aurora kinase B, thrombospondin2, and solute carrier-7a5. Five of these transcripts (Ccl2, Serpinf1, Aurkb, Thbs2, and Slc7a5) demonstrated at least a twofold increase in WAT from obese ( ob/ob) mice compared with that of wild-type mice. This suggests that comparative gene expression studies of ScAP-23 and 3T3-L1 adipogenesis may be particularly fruitful in identifying preadipocyte-expressed genes that play a role in adipose tissue physiology and/or pathophysiology.

NRF2 modulates aryl hydrocarbon receptor signaling: influence on adipogenesis

The NF-E2 p45-related factor 2 (NRF2) and the aryl hydrocarbon receptor (AHR) are transcription factors controlling pathways modulating xenobiotic metabolism. AHR has recently been shown to affect Nrf2 expression. Conversely, this study demonstrates that NRF2 regulates expression of Ahr and subsequently modulates several downstream events of the AHR signaling cascade, including (i) transcriptional control of the xenobiotic metabolism genes Cyp1a1 and Cyp1b1 and (ii) inhibition of adipogenesis in mouse embryonic fibroblasts (MEFs). Constitutive expression of AHR was affected by Nrf2 genotype. Moreover, a pharmacological activator of NRF2 signaling, CDDO-IM {1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole}, induced Ahr, Cyp1a1, and Cyp1b1 transcription in Nrf2+/+ MEFs but not in Nrf2-/- MEFs. Reporter analysis and chromatin immunoprecipitation assay revealed that NRF2 directly binds to one antioxidant response element (ARE) found in the -230-bp region of the promoter of Ahr. Since AHR negatively controls adipocyte differentiation, we postulated that NRF2 would inhibit adipogenesis through the interaction with the AHR pathway. Nrf2-/- MEFs showed markedly accelerated adipogenesis upon stimulation, while Keap1-/- MEFs (which exhibit higher NRF2 signaling) differentiated slowly compared to their congenic wild-type MEFs. Ectopic expression of Ahr and dominant-positive Nrf2 in Nrf2-/- MEFs also substantially delayed differentiation. Thus, NRF2 directly modulates AHR signaling, highlighting bidirectional interactions of these pathways.

Medical sequencing at the extremes of human body mass

Body weight is a quantitative trait with significant heritability in humans. To identify potential genetic contributors to this phenotype, we resequenced the coding exons and splice junctions of 58 genes in 379 obese and 378 lean individuals. Our 96-Mb survey included 21 genes associated with monogenic forms of obesity in humans or mice, as well as 37 genes that function in body weight-related pathways. We found that the monogenic obesity-associated gene group was enriched for rare nonsynonymous variants unique to the obese population compared with the lean population. In addition, computational analysis predicted a greater fraction of deleterious variants within the obese cohort. Together, these data suggest that multiple rare alleles contribute to obesity in the population and provide a medical sequencing-based approach to detect them.

dlk1/FA1 Regulates the Function of Human Bone Marrow Mesenchymal Stem Cells by Modulating Gene Expression of Pro-inflammatory Cytokines and Immune Response-related Factors

dlk1/FA1 (delta-like 1/fetal antigen-1) is a member of the epidermal growth factor-like homeotic protein family whose expression is known to modulate the differentiation signals of mesenchymal and hematopoietic stem cells in bone marrow. We have demonstrated previously that Dlk1 can maintain the human bone marrow mesenchymal stem cells (hMSC) in an undifferentiated state. To identify the molecular mechanisms underlying these effects, we compared the basal gene expression pattern in Dlk1-overexpressing hMSC cells (hMSC-dlk1) versus control hMSC (negative for Dlk1 expression) by using Affymetrix HG-U133A microarrays. In response to Dlk1 expression, 128 genes were significantly up-regulated (with >2-fold; p < 0.001), and 24% of these genes were annotated as immune response-related factors, including pro-inflammatory cytokines, in addition to factors involved in the complement system, apoptosis, and cell adhesion. Also, addition of purified FA1 to hMSC up-regulated the same factors in a dose-dependent manner. As biological consequences of up-regulating these immune response-related factors, we showed that the inhibitory effects of dlk1 on osteoblast and adipocyte differentiation of hMSC are associated with Dlk1-induced cytokine expression. Furthermore, Dlk1 promoted B cell proliferation, synergized the immune response effects of the bacterial endotoxin lipopolysaccharide on hMSC, and led to marked transactivation of the NF-kappaB. Our data suggest a new role for Dlk1 in regulating the multiple biological functions of hMSC by influencing the composition of their microenvironment "niche." Our findings also demonstrate a role for Dlk1 in mediating the immune response.

Inhibition of the anti-adipogenic Hedgehog signaling pathway by cyclopamine does not trigger adipocyte differentiation

Dysregulation of Hedgehog signaling can lead to several pathologies such as congenital defects and cancer. Here, we show that Hedgehog signaling is active in undifferentiated 3T3-L1 cells and decreases during adipocyte differentiation. Interestingly, this is paralleled by a decrease in Indian Hedgehog expression. We then tested if this down-regulation was sufficient to induce adipocyte differentiation. To this end, we demonstrate that the well-characterized Hedgehog inhibitor cyclopamine induced a decrease in Hedgehog signaling, similar to the one observed during adipocyte differentiation. However, cyclopamine did not induce nor potentiate adipocyte differentiation, as monitored by triglyceride staining and by the expression of several adipocyte markers: aP2, adipsin, C/EBPalpha, and Pref-1. Moreover, cyclopamine cannot substitute for other components of the differentiation medium: insulin, dexamethasone or IBMX. These results indicate that although Hedgehog signaling decreases during adipocyte differentiation, this down-regulation is not sufficient to trigger adipocyte differentiation. This suggests that Hedgehog signaling is an inadequate pharmacological target for patient suffering from syndromes associated with a decrease in fat mass, such as the ones observed in lipodystrophies.

Role of adipose tissue as an inflammatory organ in human diseases

Reviews on the inflammatory role of adipose tissue outside the field of metabolism are rare. There is increasing evidence provided by numerous basic research studies from nearly all internal medicine subspecializations that adipocytes and adipocytokines are involved in primary inflammatory processes and diseases. Therefore, it is the aim of the present review to discuss and to summarize the current knowledge on the inflammatory role of adipocytokines and special types of regional adipocytes such as retroorbital, synovial, visceral, subdermal, peritoneal, and bone marrow adipocytes in internal medicine diseases. Future clinical and therapeutic implications are discussed.

Transcriptional regulation of metabolism

Our understanding of metabolism is undergoing a dramatic shift. Indeed, the efforts made towards elucidating the mechanisms controlling the major regulatory pathways are now being rewarded. At the molecular level, the crucial role of transcription factors is particularly well-illustrated by the link between alterations of their functions and the occurrence of major metabolic diseases. In addition, the possibility of manipulating the ligand-dependent activity of some of these transcription factors makes them attractive as therapeutic targets. The aim of this review is to summarize recent knowledge on the transcriptional control of metabolic homeostasis. We first review data on the transcriptional regulation of the intermediary metabolism, i.e., glucose, amino acid, lipid, and cholesterol metabolism. Then, we analyze how transcription factors integrate signals from various pathways to ensure homeostasis. One example of this coordination is the daily adaptation to the circadian fasting and feeding rhythm. This section also discusses the dysregulations causing the metabolic syndrome, which reveals the intricate nature of glucose and lipid metabolism and the role of the transcription factor PPARgamma in orchestrating this association. Finally, we discuss the molecular mechanisms underlying metabolic regulations, which provide new opportunities for treating complex metabolic disorders.

A PYY Q62P variant linked to human obesity

Peptide YY (PYY) has been implicated in the control of food intake through functional studies in rodents and humans. To investigate whether genetic alterations within this gene result in abnormal weight in humans, we sequenced its coding exons and splice sites in a large cohort of extremely obese [n = 379; average body mass index (BMI), 49.0 kg/m2] and lean (n = 378; average BMI, 19.5 kg/m2) individuals. In total, three rare non-synonymous variants were identified, only one of which, PYY Q62P, exhibited familial segregation with body mass. Through serendipity, previous studies based on cell culture revealed this precise variant to have altered receptor-binding selectivity in vitro. We further show, using mouse peptide injection experiments, that while the wild-type PYY peptide reduces food intake, the mutant PYY 62P had an insignificant effect in reducing food intake in vivo. Taken together, these results are the first to support that rare sequence variants within PYY can influence human susceptibility to obesity.

Keynote review: the adipocyte as a drug discovery target

The adipocyte has pleiotropic functions beyond the storage of energy in times of nutrient abundance. Considerable efforts in adipocyte biology within the past ten years have emphasized the important role of adipose tissue in processes as diverse as energy metabolism, inflammation and cancer. Adipocytes are able to communicate with the brain and peripheral tissues implementing metabolic signals such as satiety, food intake and energy expenditure. Despite its huge pharmacological potential, only a small number of clinical applications interfere directly with adipocyte physiology. Here, we want to highlight various areas of adipocyte physiology that have not yet been explored pharmacologically and emphasize some of the limitations associated with these pharmacotherapies.