Inhibition of adipocyte differentiation by phytoestrogen genistein through a potential downregulation of extracellular signal-regulated kinases 1/2 activity

Autophagy characteristics of phytoestrogens in management and prevention of diseases: A narrative review of in-vivo and in-vitro studies

Phytoestrogens are non-steroid polyphenolic materials present in 300 plants. Regarding their structural similarities to estradiol, phytoestrogens attach to estrogen receptors and display anti- or pro-estrogenic activities. This review explored phytoestrogens' potential advantages and autophagy properties in light of their future application for disease management, highlighting how phytoestrogens could modulate autophagy. Research has examined the prospective benefits of phytoestrogens for the anticipation and management of various conditions, including signs of menopause, tumors, skin deterioration, osteoporosis, heart disease, neurodegenerative conditions, disorders of the immune system, and metabolic syndrome, owing to their therapeutic effects. As phytoestrogens can activate or inhibit autophagy, which has antioxidant, apoptotic, anti-mutagenic, anticancer, transcriptional, and genomic impacts on cancer and aging illnesses, phytoestrogens could influence diseases through the modulation of autophagy. The collaborative research on animal models, utilization of genetic techniques, and administration of pharmacologically active substances has indicated the possible therapeutic benefits of autophagy modulation in various illnesses. Further research is required to illustrate the pathways by which phytoestrogens modulate autophagy and the possible therapeutic effects on these diseases.

FNDC5 Promotes Adipogenic Differentiation of Primary Preadipocytes in Mashen Pigs

Fibronectin type III domain-containing protein 5 (FNDC5) plays an important role in fat deposition, which can be cut to form Irisin to promote fat thermogenesis, resulting in a decrease in fat content. However, the mechanism of FNDC5 related to fat deposition in pigs is still unclear. In this research, we studied the expression of FNDC5 on different adiposes and its function in the adipogenic differentiation of primary preadipocytes in Mashen pigs. The expression pattern of FNDC5 was detected by qRT-PCR and Western blotting in Mashen pigs. FNDC5 overexpression and interference vectors were constructed and transfected into porcine primary preadipocytes by lentivirus. Then, the expression of key adipogenic genes was detected by qRT-PCR and the content of lipid droplets was detected by Oil Red O staining. The results showed that the expression of FNDC5 in abdominal fat was higher than that in back subcutaneous fat in Mashen pigs, whereas the expression in back subcutaneous fat of Mashen pigs was significantly higher than that of Large White pigs. In vitro, FNDC5 promoted the adipogenic differentiation of primary preadipocytes of Mashen pigs and upregulated the expression of genes related to adipogenesis, but did not activate the extracellular signal-regulated kinase (ERK) signaling pathway. This study can provide a theoretical basis for FNDC5 in adipogenic differentiation in pigs.

G protein-coupled estrogen receptor 1 mediates proliferation and adipogenic differentiation of goat adipose-derived stem cells through ERK1/2-NF-κB signaling pathway

Adipose tissue formation and moderate fat deposition are important for the production performance and eating quality of livestock meats. The self-renewal and adipogenic differentiation of adipose-derived stem cells are responsible for the formation and development of adipose tissue. In addition, estrogen targeting G protein-coupled estrogen receptor 1 (GPER1) has been reported to modulate cell proliferation and differentiation during tissue and organ development. However, the potential correlation among estrogen, GPER1, proliferation, and adipogenic differentiation in goat adipose-derived stem cells (gADSCs) is still unclear. Herein, we demonstrated that 17β-estradiol enhances the proliferative ability of gADSCs, indicated by the increased cell number and cell viability, accompanied by up-regulated expressions of cyclin D1 and PCNA. Meanwhile, the adipogenic differentiation is promoted by 17β-estradiol, supported by higher ccumulation of intracellular lipids and increased expressions of PPARγ, ACC, and FABP4. Notably, these activities are all obviously reduced by administration with GPER1 antagonist G15, but GPER1 agonist G1 enhances cell proliferation and adipogenic differentiation. Moreover, GPER1 silencing diminishes cell proliferation and adipogenic differentiation. In parallel, 17β-estradiol elevates the protein level of nuclear p-p65. Furthermore, the phosphorylation of p65 is enhanced by G1 but inhibited by G15 and GPER1 silencing. In addition, the phosphorylation of p65 is mediated by ERK1/2, suggesting that estrogen targeting GPER1 regulates cell proliferation and adipogenic differentiation of gADSCs through the ERK1/2-NF-κB signaling pathway. This study may provide a strong theoretical basis for improving meat quality, flavor, and cold resistance of livestock.

Sex Differences in Glomerular Protein Expression and Effects of Soy-Based Diet on Podocyte Signaling

Background:

Kidney disease is a major public health issue arising from loss of glomerular podocyte function, and there are considerable sex differences in its prognosis. Evidence suggests a renoprotective effect of estrogen and soy diet-derived phytoestrogens, although the molecular basis for this is poorly understood.

Objective:

Here, we aim to assess sex differences in expression of key proteins associated with podocyte survival and determine the effects of dietary soy on glomerular and podocyte signaling.

Methods:

Male and female FVB mice were fed control, low (1%), and high (20%) doses of isolated soy protein (ISP) in utero and until 100 days of age. Spot urine was collected to measure proteinuria and isolated glomeruli were used to quantify activated and total levels of nephrin, Akt, and ERK1/2. To investigate protective effects of specific soy phytoestrogens, cultured podocytes were treated with or without daidzein and subject to control or high glucose as a model of podocyte injury.

Results:

Nephrin and Akt were elevated at baseline in glomeruli from females compared to males. Both sexes that were fed 1% and 20% ISP displayed robust increases in total glomerular Akt compared to controls, and these effects were more prominent in females. A similar trend at both doses in both sexes was observed with activated Akt and total nephrin. Notably, males exclusively showed increased phosphorylation of nephrin and extracellular signal-regulated kinase (ERK) at the 1% ISP dose; however, no overt changes in urinary albumin excretion or podocin levels were observed, suggesting that the soy diets did not impair podocyte function. Finally, in cultured male and female podocytes, daidzein treatment suppressed high glucose-induced ERK activation.

Conclusions:

Together, our findings reveal a putative mechanism to explain the protective influence of sex on kidney disease progression, and they provide further evidence to support a beneficial role for dietary soy in preserving glomerular function.

Myostatin suppresses adipogenic differentiation and lipid accumulation by activating crosstalk between ERK1/2 and PKA signaling pathways in porcine subcutaneous preadipocytes

The current study was undertaken to determine the effect of myostatin (MSTN) on lipid accumulation in porcine subcutaneous preadipocytes (PSPAs) and to further explore the potential molecular mechanisms. PSPAs isolated from Meishan weaned piglets were added with various concentrations of MSTN recombinant protein during the entire period of adipogenic differentiation process. Results showed that MSTN treatment significantly reduced the lipid accumulation, intracellular triglyceride (TG) content, glucose consumption and glycerol phosphate dehydrogenase activity, while increased glycerol and free fatty acid release. Consistent with above results, the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway was obviously activated and thus key adipogenic transcription factors peroxisome proliferator-activated receptor-gamma (PPAR-γ), CCAAT/enhancer-binding protein-alpha (C/EBP-α) and their downstream engymes fatty acid synthase and acetyl-CoA carboxylase were all inhibited. However, chemical inhibition of ERK1/2 signaling pathway by PD98059 markedly reversed the decreased TG content by increasing PPAR-γ expression. In addition, MSTN activated the cyclic AMP/protein kinase A (cAMP/PKA) pathway and stimulated lipolysis by reducing the expression of antilipolytic gene perilipin, thus elevated key lipolytic enzymes adipose triglyceride lipase and hormone-sensitive lipase expression and enzyme activity. On the contrary, pretreatment with PKA inhibitor H89 significantly reversed TG accumulation by increasing PPAR-γ expression and thus inhibiting ERK1/2, perilipin and HSL phosphorylation, supporting the crosstalk between PKA and ERK1/2 pathways in both the anti-adipogenic and pro-lipolytic effects. In summary, our results suggested that MSTN suppressed adipogenesis and stimulated lipolysis, which was mainly mediated by activating crosstalk of ERK1/2 and PKA signaling pathways, and consequently decreased lipid accumulation in PSPAs, our findings may provide novel insights for further exploring MSTN as a potent inhibitor of porcine subcutaneous lipid accumulation.

Glycyrrhizic acid suppresses early stage of adipogenesis through repression of MEK/ERK-mediated C/EBPβ and C/EBPδ expression in 3T3-L1 cells

Glycyrrhizic acid (GA), a major constituent of the root of licorice (Glycyrrhiza glabra), and has various biological activities, including anti-obesity property. However, the molecular mechanism of anti-adipogenic effect of GA is still unclear. In this study, we investigated the anti-adipogenic effects of GA in mouse adipocytic 3T3-L1 cells and elucidated its underlying molecular mechanism. GA decreased the intracellular triglyceride level. The expression levels of the adipogenic and lipogenic genes were lowered by treatment with GA in a concertation-dependent manner. In contrast, GA did not affect the lipolytic gene expression and the released glycerol level. GA suppressed the early stage of adipogenesis when it was added for 0-3 h after initiation of adipogenesis. Moreover, GA reduced the mRNA levels of CCAAT/enhancer binding protein (C/EBP) β and C/EBPδ, both of which activate the early stage of adipogenesis. Furthermore, GA decreased phosphorylation of extracellular signal-regulated kinase [ERK: p44/42 mitogen-activated protein kinase (MAPK)] in the early stage of adipogenesis. In addition, a MAPK kinase (MEK) inhibitor, PD98059 reduced the C/EBPβ and C/EBPδ gene expression. These results indicate that GA suppressed the early stage of adipogenesis through repressing the MEK/ERK-mediated C/EBPβ and C/EBPδ expression in 3T3-L1 cells. Thus, GA has an anti-adipogenic ability and a possible agent for treatment of obesity.

The Role of Isoflavones in Type 2 Diabetes Prevention and Treatment-A Narrative Review

Given the growing number of type 2 diabetic individuals and the substantial social and financial costs associated with diabetes management, every effort should be made to improve its prevention and treatment methods. There is an ongoing search for natural dietary compounds that could be used for this purpose. This narrative review focuses on the therapeutic potential of isoflavones in diabetes prevention and treatment. This review summarizes (i) the molecular mechanisms of isoflavones action that are critical to their anti-diabetic properties; (ii) preclinical (in vitro and in vivo) studies evaluating the influence of isoflavones on the function of key organs involved in the pathogenesis of diabetes; and (iii) epidemiological studies and clinical trials that assessed the effectiveness of isoflavones in the prevention and treatment of type 2 diabetes in humans. Apart from discussing the effects of isoflavones on the function of organs “classically” associated with the pathogenesis of diabetes (pancreas, liver, muscles, and adipose tissue), the impact of these compounds on other organs that contribute to the glucose homeostasis (gastrointestinal tract, kidneys, and brain) is also reviewed.

Targeting Abdominal Obesity and Its Complications with Dietary Phytoestrogens

In the assessment of the health risk of an obese individual, both the amount of adipose tissue and its distribution and metabolic activity are essential. In adults, the distribution of adipose tissue differs in a gender-dependent manner and is regulated by sex steroids, especially estrogens. Estrogens affect adipocyte differentiation but are also involved in the regulation of the lipid metabolism, insulin resistance, and inflammatory activity of the adipose tissue. Their deficiency results in unfavorable changes in body composition and increases the risk of metabolic complications, which can be partially reversed by hormone replacement therapy. Therefore, the idea of the supplementation of estrogen-like compounds to counteract obesity and related complications is compelling. Phytoestrogens are natural plant-derived dietary compounds that resemble human estrogens in their chemical structure and biological activity. Supplementation with phytoestrogens may confer a range of beneficial effects. However, results of studies on the influence of phytoestrogens on body composition and prevalence of obesity are inconsistent. In this review, we present data from in vitro, animal, and human studies regarding the role of phytoestrogens in adipose tissue development and function in the context of their potential application in the prevention of visceral obesity and related complications.

SIRT5 inhibits bovine preadipocyte differentiation and lipid deposition by activating AMPK and repressing MAPK signal pathways

SIRT5 (sirtuin 5) is located in the mitochondria and plays an important role in biological processes such as maintaining the balance of lipid metabolism and promoting fatty acid oxidation mobilization. In this study, the bovine preadipocyte differentiation and obese mouse models were constructed; combined with transcriptome sequencing (RNA-seq) and morphological identification, the regulatory and molecular mechanisms underlying the effects of SIRT5 on bovine preadipocyte differentiation and lipid metabolism were studied. The results reveal that during the differentiation of preadipocytes, SIRT5 inhibited the expression of key genes that promote lipid formation and differentiation in fatty acid biosynthesis and PPAR pathways. SIRT5 significantly activated the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway and repressed the mitogen-activated protein kinase (MAPK) pathway. Eventually, SIRT5 significantly inhibited the differentiation of bovine preadipocytes and simultaneously inhibited lipid synthesis and lipid deposition in adipocytes. The verification experiments performed using obese mice also yielded consistent results in vivo.

Potential Non-neoplastic Applications for Polyphenols in Stem Cell Utilization

While polyphenols may have important effects on pluripotential stem cells that make them noteworthy as potential antineoplastic agents, their action on stem cells may portend other health benefits, such as treatments for cardiovascular and neurocognitive disorders. Resveratrol, the beststudied polyphenol, has been found to enable stem cells to differentiate into cardiomyocytes, neurons, osteocytes, and pancreatic beta cells, as well as facilitating augmentation of stem cell populations and protecting them from toxic injury. Curcumin protects mesenchymal stem cells from toxicity, and prevents them from facilitating chondrocytic hypertrophy. Quercetin enabled osteocytic and pancreatic beta cell differentiation, and protected neuronal stem cells from injury. Epigallocatechin gallate prevented damage to osteocyte precursors and averted differentiation into undesirable adipocytes. Genistein facilitated osteogenesis while preventing adipogenesis. Several other polyphenols, daidzein, caffeic and chlorogenic acid, kaempferol, and piceatannol, protect stems cells from reactive oxygen species and foster stem cells differentiation away from adipocytic and toward osteocytic lineages. Further research should better elucidate the pharmacokinetic profiles of each polyphenol, explore novel delivery systems, and expand investigation beyond rodent models to additional species.

Effects of Genistein on Differentiation and Viability of Human Visceral Adipocytes

Obesity can lead to pathological growth of adipocytes by inducing inflammation and oxidative stress. Genistein could be a potential candidate for the treatment of obesity due to its antioxidant properties. Specific kits were used to examine the effects of genistein vs adiponectin on human visceral pre-adipocytes differentiation, cell viability, mitochondrial membrane potential, and oxidative stress in pre-adipocytes and in white/brown adipocytes. Western Blot was performed to examine changes in protein activation/expression. Genistein increased human visceral pre-adipocytes differentiation and browning, and caused a dose-related improvement of cell viability and mitochondrial membrane potential. Similar effects were observed in brown adipocytes and in white adipocytes, although in white cells the increase of cell viability was inversely related to the dose. Moreover, genistein potentiated AMP-activated protein kinase (AMPK)/mitofusin2 activation/expression in pre-adipocytes and white/brown adipocytes and protected them from the effects of hydrogen peroxide. The effects caused by genistein were similar to those of adiponectin. The results obtained showed that genistein increases human visceral pre-adipocytes differentiation and browning, protected against oxidative stress in pre-adipocytes and white/brown adipocytes through mechanisms related to AMPK-signalling and the keeping of mitochondrial function.

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

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

Effects of Low-Protein Diets Supplemented with Branched-Chain Amino Acid on Lipid Metabolism in White Adipose Tissue of Piglets

This study evaluated the effect of branched-chain amino acid (BCAA) supplementation in low-protein diets on lipid metabolism in dorsal subcutaneous adipose (DSA), abdominal subcutaneous adipose (ASA), and perirenal adipose (PRA) tissues. A total of 24 piglets were allotted to four treatments, and each group was fed the adequate protein (AP) diet, low-protein (LP) diet, LP diet supplemented with BCAA (LP + B), or LP diet supplemented with twice BCAA (LP + 2B). Serum concentrations of leptin in the BCAA-supplemented treatments were higher (P < 0.01) than in the AP treatment, but lower (P < 0.01) than in the LP treatment. In DSA, the mRNA and protein levels for lipogenic-related genes were highest in the LP treatment and lowest in the LP + 2B treatment. However, in ASA and PRA, the expression levels for those genes were significantly elevated in the LP + 2B treatment. In conclusion, BCAA supplementation could alter the body fat condition, and this effect was likely modulated by the expression of lipid metabolic regulators in DSA, ASA, and PRA in a depot-specific manner.

Soy and the soy isoflavone genistein promote adipose tissue development in male mice on a low-fat diet

PURPOSE

Several nutrients act as phytoestrogens, being anti-adipogenic when consumed with a fat-rich diet. Their effect on a low-fat diet (LFD) background is unknown. We tested soy and genistein effects on adipose tissue in LFD-fed mice and genistein activity in the 3T3-L1 adipogenesis model.

METHODS

C57BL/6 J male mice were fed an 8.5% soy-supplemented LFD (SS-LFD) or a soy-free LFD (SF-LFD) for 147 days. Groups of 3-week-old (pubertal) and 6-week-old (adult) mice on the SF-LFD were also treated with 17ß-estradiol (E2, 5 µg/kg/day) ip or pure genistein (5 mg/kg/day) by gavage for 15 days. Body fat deposition and gene expression profiles were evaluated. E2 and genistein effects on ERα, ERβ and PPARγ transcriptional activities were characterized in ERα- or ERβ-transfected 3T3L1 cells during differentiation, by the use of reporter plasmids.

RESULTS

The SS-LFD group increased fat mass compared with the SF-LFD group. Genistein alone increased while E2 decreased fat pads in the 15-day-treated mice. In visceral fat, genistein differentially regulated 13 metabolic pathways compared to E2. PPARγ-controlled genes were downregulated by E2, while they were upregulated by genistein. In 3T3-L1 cells, genistein activated ERβ-driven transcription, differentiation and lipid accumulation, while inhibited ERα-driven transcription, without effects on lipid accumulation. E2 activated both ERs only in preadipocytes. In differentiated untransfected cells, genistein inhibited PPARγ, while activated PPARγ in the presence of ERβ.

CONCLUSIONS

Soy and genistein at nutritional doses induce fat development in LFD-fed mice and adipogenesis in 3T3-L1 cells, with a mechanism that involves, at least in vitro, ERβ and is dependent on cell differentiation stage.

Systemic injection of CK2.3, a novel peptide acting downstream of bone morphogenetic protein receptor BMPRIa, leads to increased trabecular bone mass

Bone Morphogenetic Protein 2 (BMP2) regulates bone integrity by driving both osteogenesis and osteoclastogenesis. However, BMP2 as a therapeutic has significant drawbacks. We have designed a novel peptide CK2.3 that blocks the interaction of Casein Kinase 2 (CK2) with Bone Morphogenetic Protein Receptor type Ia (BMPRIa), thereby activating BMP signaling pathways in the absence of ligand. Here, we show that CK2.3 induced mineralization in primary osteoblast cultures isolated from calvaria and bone marrow stromal cells (BMSCs) of 8 week old mice. Further, systemic tail vein injections of CK2.3 in 8 week old mice resulted in increased bone mineral density (BMD) and mineral apposition rate (MAR). In situ immunohistochemistry of the femur found that CK2.3 injection induced phosphorylation of extracellular signal-related kinase (ERK), but not Smad in osteocytes and osteoblasts, suggesting that CK2.3 signaling occurred through Smad independent pathway. Finally mice injected with CK2.3 exhibited decreased osteoclast differentiation and osteoclast activity. These data indicate that the novel mimetic peptide CK2.3 activated BMPRIa downstream signaling to enhance bone formation without the increase in osteoclast activity that accompanies BMP 2 stimulation.

Extracellular regulated protein kinases 1/2 phosphorylation is required for hepatic differentiation of human umbilical cord-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) have the capacity to restore liver function by differentiating into hepatocyte like cells. However, the underlying mechanisms are not well understood. Here, we have investigated the signals involved in the hepatic differentiation of human umbilical cord-derived mesenchymal stem cells (hUCMSCs). hUCMSCs were treated with mouse fetal liver-conditioned medium (FLCM) to induce hepatic differentiation. Flow cytometry, reverse transcription PCR, real-time PCR, immunocytochemistry, and polymerase chain reaction (PCR) array were used to detect the expression of MSC- and hepotocyte-specific markers in FLCM-treated hUCMSCs. Urea production and cytochrome P450 3A4 (CYP3A4) activity were used as indicators to evaluate liver cell characteristics. Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) was analyzed in hUCMSCs by Western blotting. Following FLCM treatment, expression of MSC-specific markers decreased, while hepatocyte-specific gene expression was increased. Urea production, albumin secretion, glycogen storage, and CYP3A4 activity were significantly enhanced in FLCM-treated cells. In addition, ERK1/2 phosphorylation was increased in a time-dependent manner through Raf/MEK/ERK pathway, and phosphorylation was sustained at a high level during hepatic induction. Inhibition of ERK1/2 activation by U0126 (an ERK1/2 inhibitor) and pFLAG-CMV-ERK1(K71R) (negative mutant of ERK1) reversed the expression of liver-specific genes in hUCMSCs and affected hepatic function significantly. In summary, this work shows that ERK1/2 phosphorylation plays an important role in inducing hepatic differentiation of hUCMSCs in FLCM.

miR-21 modulates the ERK-MAPK signaling pathway by regulating SPRY2 expression during human mesenchymal stem cell differentiation

The ERK-MAPK signaling pathway plays a pivotal role during mesenchymal stem cell (MSC) differentiation. Studies have demonstrated that ERK-MAPK promotes adipogenesis and osteogenesis through the phosphorylation of differentiation-associated transcription factors and that it is the only active signaling in all three lineages (adipogenic, chondrogenic, and osteogenic) during MSC differentiation. Recent studies pointed to the significant roles of microRNA-21 (miR-21) during several physiological and pathological processes, especially stem cell fate determination. The miR-21 expression pattern is also correlated with ERK-MAPK activity. Here, we found that miR-21 expression is elevated and associated with an increased differentiation potential in MSCs during adipogenesis and osteogenesis. The overexpression of miR-21 elevated the expression level of the differentiation-associated genes PPARγ and Cbfa-1 during MSC differentiation, whereas miR-21 knockdown reduced the expression level of both genes. The ERK-MAPK signaling pathway activity had an increasing tendency to respond to miR-21 upregulation and a decreasing tendency to respond to miR-21 down-regulation during the first 4 days of adipogenesis and osteogenesis. Our data indicate that miR-21 modulated ERK-MAPK signaling activity by repressing SPRY2 expression, a known regulator of the receptor tyrosine kinase (RTK) signaling pathway, to affect the duration and magnitude of ERK-MAPK activity. The ERK-MAPK signaling pathway was regulated by Sprouty2 (SPRY2) expression via a miR-21-mediated mechanism during MSC differentiation.

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

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

Feeding soy protein isolate and treatment with estradiol have different effects on mammary gland morphology and gene expression in weanling male and female rats

Isoflavones are phytochemical components of soy diets that bind weakly to estrogen receptors (ERs). To study potential estrogen-like actions of soy in the mammary gland during early development, we fed weanling male and female Sprague-Dawley rats a semipurified diet with casein as the sole protein source from postnatal day 21 to 33, the same diet substituting soy protein isolate (SPI) for casein, or the casein diet supplemented with estradiol (E2) at 10 μg/kg/day. In contrast to E2, the SPI diet induced no significant change in mammary morphology. In males, there were 34 genes for which expression was changed ≥2-fold in the SPI group vs. 509 changed significantly by E2, and 8 vs. 174 genes in females. Nearly half of SPI-responsive genes in males were also E2 responsive, including adipogenic genes. Serum insulin was found to be decreased by the SPI diet in males. SPI and E2 both downregulated the expression of ERα ( Esr1) in males and females, and ERβ ( Esr2) only in males. Chromatin immunoprecipitation revealed an increased binding of ERα to the promoter of the progesterone receptor ( Pgr) and Esr1 in both SPI- and E2-treated males compared with the casein group but differential recruitment of ERβ. ER promoter binding did not correlate with differences in Pgr mRNA expression. This suggests that SPI fails to recruit appropriate co-activators at E2-inducible genes. Our results indicate that SPI behaves like a selective estrogen receptor modulator rather than a weak estrogen in the developing mammary gland.

Shikonin suppresses ERK 1/2 phosphorylation during the early stages of adipocyte differentiation in 3T3-L1 cells

Background

The naphthoquinone pigment, shikonin, is a major component of Lithospermum erythrorhizon and has been shown to have various biological functions, including antimicrobial, anti-inflammatory, and antitumor effects. In this study, we investigated the effect of shikonin on adipocyte differentiation and its mechanism of action in 3T3-L1 cells.

Methods

To investigate the effects of shikonin on adipocyte differentiation, 3T3-L1 cells were induced to differentiate using 3-isobutyl-1-methylzanthine, dexamethasone, and insulin (MDI) for 8 days in the presence of 0–2 μM shikonin. Oil Red O staining was performed to determine the lipid accumulation in 3T3-L1 cells. To elucidate the anti-adipogenic mechanism of shikonin, adipogenic transcription factors, the phosphorylation levels of ERK, and adipogenic gene expression were analyzed by Western blotting and quantitative real-time PCR. To further confirm that shikonin inhibits adipogenic differentiation through downregulation of ERK 1/2 activity, 3T3-L1 cells were treated with shikonin in the presence of FGF-2, an activator, or PD98059, an inhibitor, of the ERK1/2 signaling pathway.

Results

Shikonin effectively suppressed adipogenesis and downregulated the protein levels of 2 major transcription factors, PPARγ and C/EBPα, as well as the adipocyte specific gene aP2 in a dose-dependent manner. qRT-PCR analysis revealed that shikonin inhibited mRNA expression of adipogenesis-related genes, such as PPARγ, C/EBPα, and aP2. Adipocyte differentiation was mediated by ERK 1/2 phosphorylation, which was confirmed by pretreatment with PD98059 (an ERK 1/2 inhibitor) or FGF-2 (an ERK 1/2 activator). The phosphorylation of ERK1/2 during the early stages of adipogenesis in 3T3-L1 cells was inhibited by shikonin. We also confirmed that FGF-2-stimulated ERK 1/2 activity was attenuated by shikonin.

Conclusions

These results demonstrate that shikonin inhibits adipogenic differentiation via suppression of the ERK signaling pathway during the early stages of adipogenesis.

Inhibition of CK2 binding to BMPRIa induces C2C12 differentiation into osteoblasts and adipocytes

BMP2 is a growth factor that regulates the cell fate of mesenchymal stem cells into osteoblast and adipocytes. However, the detailed signaling pathways and mechanism are unknown. We previously reported a new interaction of Casein kinase II (CK2) with the BMP receptor type-Ia (BMPRIa) and demonstrated using mimetic peptides CK2.1, CK2.2 and CK2.3 that the release of CK2 from BMPRIa activates Smad signaling and osteogenesis. Previously, we showed that mutation of these CK2 sites on BMPRIa (MCK2.1 (476S-A), MCK2.2 (324S-A) and MCK2.3 (214S-A)) induced osteogenesis. However, one mutant MCK2.1 induced osteogenesis similar to overexpression of wild type BMPRIa, suggesting that the effect of this mutant on mineralization was due to overexpression. In this paper we investigated the signaling pathways involved in the CK2-BMPRIa mediated osteogenesis and identified a new signaling pathway activating adipogenesis dependent on the BMPRIa and CK2 association. Further the mechanism for adipogenesis and osteogenesis is specific to the CK2 interaction site on BMPRIa. In detail our data show that overexpression of MCK2.2 induced osteogenesis was dependent on Caveolin-1 (Cav1) and the activation of the Smad and mTor pathways, while overexpression of MCK2.3 induced osteogenesis was independent of Caveolin-1 without activation of Smad pathway. However, MCK2.3 induced osteogenesis via the MEK pathway. The adipogenesis induced by the overexpression of MCK2.2 in C2C12 cells was dependent on the p38 and ERK pathways as well as Caveolin-1. These data suggest that signaling through BMPRIa used two different signaling pathways to induce osteogenesis dependent on CK2. Additionally the data supports a signaling pathway initiated in caveolae and one outside of caveolae to induce mineralization. Moreover, they reveal the signaling pathway of BMPRIa mediated adipogenesis.

Transcriptional regulation of adipocyte formation by the liver receptor homologue 1 (Lrh1)-Small hetero-dimerization partner (Shp) network

Altered adipose tissue formation is a well-known effectors of obesity and T2D. Here, we describe the role of Lrh1 and its co-repressor Shp in the control of adipocyte formation. Expression of Lrh1 in the pre-adipocyte containing SVF is induced in obese mice models and humans while Shp expression is reduced. We demonstrate, that Lrh1 is an inhibitor of adipogenesis while Shp acts functions as an activator through repression of Lrh1 activity. This regulation is at least in part modulated by estradiol conversion through the regulation of Cyp19a1 gene expression. In vivo, loss of Lrh1 leads to induced adipogenesis, while loss of Shp causes uncontrolled activation of Lrh1 and reduced adipogenesis. As Shp expression has been linked to the development of obesity and metabolic disorders, it is possible that alterations of the Shp/Lrh1 network lead to changes in adipocyte formation, which might contribute to the development of obesity associated T2D.

Aristolochia manshuriensis Kom inhibits adipocyte differentiation by regulation of ERK1/2 and Akt pathway

Aristolochia manshuriensis Kom (AMK) is a traditional medicinal herb used for the treatment of arthritis, rheumatism, hepatitis, and anti-obesity. Because of nephrotoxicity and carcinogenicity of AMK, there are no pharmacological reports on anti-obesity potential of AMK. Here, we showed AMK has an inhibitory effect on adipocyte differentiation of 3T3-L1 cells along with significantly decrease in the lipid accumulation by downregulating several adipocyte-specific transcription factors including peroxisome proliferation-activity receptor γ (PPAR-γ), CCAAT/enhancer binding protein α (C/EBP-α) and C/EBP-β, which are critical for adipogenesis in vitro. AMK also markedly activated the extracellular signal-regulated protein kinase 1/2 (ERK1/2) pathway including Ras, Raf1, and mitogen-activated protein kinase kinase 1 (MEK1), and significantly suppressed Akt pathway by inhibition of phosphoinositide-dependent kinase 1 (PDK1). Aristolochic acid (AA) and ethyl acetate (EtOAc) fraction of AMK with AA were significantly inhibited TG accumulation, and regulated two pathway (ERK1/2 and Akt) during adipocyte differentiation, and was not due to its cytotoxicity. These two pathways were upstream of PPAR-γ and C/EBPα in the adipogenesis. In addition, gene expressions of secreting factors such as fatty acid synthase (FAS), adiponectin, lipopreotein lipase (LPL), and aP2 were significantly inhibited by treatment of AMK during adipogenesis. We used the high-fat diet (HFD)-induced obesity mouse model to determine the inhibitory effects of AMK on obesity. Oral administration of AMK (62.5 mg/kg/day) significantly decreased the fat tissue weight, total cholesterol (TC), and low density lipoprotein-cholesterol (LDL-C) concentration in the blood. The results of this study suggested that AMK inhibited lipid accumulation by the down-regulation of the major transcription factors of the adipogensis pathway including PPAR-γ and C/EBP-α through regulation of Akt pathway and ERK 1/2 pathway in 3T3-L1 adipocytes and HFD-induced obesity mice, and AA may be main act in inhibitory effects of AMK during adipocyte differentiation.

Genistein promotes insulin action through adenosine monophosphate-activated protein kinase activation and p70 ribosomal protein S6 kinase 1 inhibition in the skeletal muscle of mice fed a high energy diet

Genistein (GEN), a soy isoflavone, exerts insulin-sensitizing actions in animals; however, the underlying mechanisms have not been determined. Because GEN is a known activator of adenosine monophosphate-activated protein kinase (AMPK), we hypothesize that GEN activates insulin signaling through AMPK activation. To test this hypothesis, a high fat-high fructose diet (HFFD)-fed mice model of insulin resistance was administered GEN, and the insulin signaling pathway proteins in the skeletal muscle were examined. Hyperglycemia and hyperinsulinemia observed in HFFD-fed mice were significantly lowered by GEN. GEN increased insulin-stimulated tyrosine phosphorylation of insulin receptor-β and insulin receptor substrate (IRS) 1 but down-regulated IRS-1 serine phosphorylation in the skeletal muscle of HFFD-fed mice. Furthermore, GEN treatment improved muscle IRS-1-associated phospatidylinositol-3 kinase expression, phosphorylation of Akt at Ser(473), and translocation of glucose transporter subtype 4. Phosphorylation of AMPK at Thr(172) and acetyl coenzyme A carboxylase (ACC) at Ser(79) was augmented, whereas phosphorylation of p70 ribosomal protein S6 kinase 1 at Thr(389) was significantly decreased after GEN treatment in the skeletal muscle of HFFD-fed mice. These results suggest that GEN might improve insulin action in the skeletal muscle by targeting AMPK.

Phytoestrogen calycosin-7-O-β-D-glucopyranoside ameliorates advanced glycation end products-induced HUVEC damage

Vasculopathy including endothelial cell (EC) apoptosis and inflammation contributes to the high incidence of stroke and myocardial infarction in diabetic patients. The aim of the present study was to investigate the effect of calycosin-7-O-β-D-glucopyranoside (CG), a phytoestrogen, on advanced glycation end products (AGEs)-induced HUVEC damage. We observed that CG can significantly ameliorate AGEs-induced HUVEC oxidative stress and apoptosis. The ratio of SOD/MDA was significantly increased to the normal level by CG pretreatment. CG preincubation dramatically increased anti-apoptotic Bcl-2 while decreased pro-apoptotic Bax and Bad expressions as detected by immunocytochemistry. Moreover, CG ameliorated macrophage migration and adhesion to HUVEC; the monocyte chemotactic protein-1 and interleukin-6 levels in the culture supernatant were dramatically reduced by CG as determined by ELISA; the expressions of inflammatory proteins including ICAM-1, TGF-β1, and RAGE in both protein and mRNA levels were significantly reduced to the normal level by CG pretreatment as determined by immunocytochemistry and real-time RT-PCR. The intracellular investigation suggests that CG can reverse AGEs-activated ERK1/2 and NF-κB phosphorylation, in which estrogen receptors were involved in. Our results strongly indicate that CG can modulate EC dysfunction by ameliorating AGEs-induced cell apoptosis and inflammation.

Determination of osteogenic or adipogenic lineages in muscle-derived stem cells (MDSCs) by a collagen-binding peptide (CBP) derived from bone sialoprotein (BSP)

Bone sialoprotein (BSP) is a mineralized, tissue-specific, non-collagenous protein that is normally expressed only in mineralized tissues such as bone, dentin, cementum, and calcified cartilage, and at sites of new mineral formation. The binding of BSP to collagen is thought to be important for initiating bone mineralization and bone cell adhesion to the mineralized matrix. Several recent studies have isolated stem cells from muscle tissue, but their functional properties are still unclear. In this study, we examined the effects of a synthetic collagen-binding peptide (CBP) on the differentiation efficiency of muscle-derived stem cells (MDSCs). The CBP sequence (NGVFKYRPRYYLYKHAYFYPHLKRFPVQ) corresponds to residues 35-62 of bone sialoprotein (BSP), which are located within the collagen-binding domain in BSP. Interestingly, this synthetic CBP inhibited adipogenic differentiation but increased osteogenic differentiation in MDSCs. The CBP also induced expression of osteoblastic marker proteins, including alkaline phosphatase (ALP), type I collagen, Runt-related transcription factor 2 (Runx2), and osteocalcin; prevented adipogenic differentiation in MDSCs; and down-regulated adipose-specific mRNAs, such as adipocyte protein 2 (aP2) and peroxisome proliferator-activated receptor γ. The CBP increased Extracellular signal-regulated kinases (ERK) 1/2 protein phosphorylation, which is important in lineage determination. These observations suggest that this CBP determines the osteogenic or adipogenic lineage in MDSCs by activating ERK1/2. Taken together, a novel CBP could be a useful candidate for regenerating bone and treating osteoporosis, which result from an imbalance in osteogenesis and adipogenesis differentiation.

Calycosin protects HUVECs from advanced glycation end products-induced macrophage infiltration

ETHNOPHARMACOLOGICAL RELEVANCE

Astragali radix is a traditional Chinese medicine that has long been used for treatment of diabetes and diabetes-associated disease, but its active component and mechanism on the disease is not well defined.

AIM OF THE STUDY

Infiltration of leukocytes within the glomeruli and vasculature is one of the early and characteristic features of diabetic nephropathy. Advanced glycation end products (AGEs) play pivotal role in the progression of diabetic-associated diseases. The present study was designed to explore the therapeutic effect of calycosin, an active component from A. radix, on AGEs-induced macrophages infiltration in HUVECs.

MATERIALS AND METHODS

Transwell HUVEC-macrophage co-culture system was established to evaluate macrophage migration and adhesion. Immunocytochemistry was applied to examine TGF-beta1, ICAM-1 and RAGE protein expressions; real-time PCR was carried out to determine mRNA expression of TGF-beta1, ICAM-1 and RAGE. Immunofluorescence was carried out to observe estrogen receptor-alpha, ICAM-1, RAGE expression and the phosphorylation status of ERK1/2 and NF-κB.

RESULTS

Calycosin significantly reduced AGEs-induced macrophage migration and adhesion to HUVEC. Pre-treatment with calycosin strikingly down-regulated HUVEC TGF-beta1, ICAM-1 and RAGE expressions in both protein and mRNA levels. Furthermore, calycosin incubation significantly increased estrogen receptor expression and reversed AGEs-induced ERK1/2 and NF-κB phosphorylation and nuclear translocation in HUVEC, and this effect of calycosin could be inhibited by estrogen receptor inhibitor, ICI182780.

CONCLUSIONS

These findings suggest that calycosin can reduce AGEs-induced macrophage migration and adhesion to endothelial cells and relieve the local inflammation; furthermore, this effect was via estrogen receptor-ERK1/2-NF-κB pathway.

Nanoscale surfaces for the long-term maintenance of mesenchymal stem cell phenotype and multipotency

There is currently an unmet need for the supply of autologous, patient-specific stem cells for regenerative therapies in the clinic. Mesenchymal stem cell differentiation can be driven by the material/cell interface suggesting a unique strategy to manipulate stem cells in the absence of complex soluble chemistries or cellular reprogramming. However, so far the derivation and identification of surfaces that allow retention of multipotency of this key regenerative cell type have remained elusive. Adult stem cells spontaneously differentiate in culture, resulting in a rapid diminution of the multipotent cell population and their regenerative capacity. Here we identify a nanostructured surface that retains stem-cell phenotype and maintains stem-cell growth over eight weeks. Furthermore, the study implicates a role for small RNAs in repressing key cell signalling and metabolomic pathways, demonstrating the potential of surfaces as non-invasive tools with which to address the stem cell niche.

Isoflavones and PPAR Signaling: A Critical Target in Cardiovascular, Metastatic, and Metabolic Disease

Isoflavone intake through foods and dietary supplements has both health advocates and critics. The latter come from a concern about the estrogenic effects of isoflavones in certain species. However, careful removal of isoflavones and other estrogens from the diet of rodents leads to the metabolic syndrome. These results suggest that isoflavones have other mechanisms of action, potentially those involving regulation of fatty acid metabolism via the nuclear receptors PPARα and PPARγ. The goal of this paper was to examine the evidence for isoflavone/PPAR signaling and to identify diseases in which such signaling would have an important impact. It is therefore of note that investigators using a chemical structure approach to discover PPAR ligands identified isoflavones as the best structures in the library of compounds that they tested. Future studies will involve careful identification of the underlying mechanisms whereby isoflavones have their action via PPAR signaling.

17β-Estradiol inhibition of PPARγ-induced adipogenesis and adipocyte-specific gene expression

AIM

To investigate the molecular interaction of peroxisome proliferator-activated receptor γ (PPARγ) with 17β-estradiol (E) in the regulation of adipogenesis.

METHODS

Female ovariectomized (OVX) mice and differentiated 3T3-L1 adipocytes were treated with combinations of the PPARγ agonist troglitazone or E, and the variables and determinants of adipogenesis were measured using in vivo and in vitro approaches.

RESULTS

Troglitazone (250 mg·kg(-1)·d(-1) for 13 weeks) decreased the size of adipocytes without the change in white adipose tissue (WAT) mass and increased the expression of adipocyte-specific genes, such as PPARγ, adipocyte fatty acid binding protein, and lipoprotein lipase, compared with OVX control mice. E (0.05 mg/pellet, sc implanted) significantly reduced WAT mass, adipocyte size, and adipose marker gene expression. When mice were concomitantly treated with troglitazone and E, E blunted the effects of troglitazone on WAT mass, adipocyte size, and adipose PPARγ target gene expression. Consistent with the in vivo data, E (10 μmol/L) treatment inhibited lipid accumulation and the expression of adipocyte-specific genes caused by troglitazone (10 μmol/L) in 3T3-L1 cells. E (10 μmol/L) also decreased troglitazone-induced PPARγ reporter activity through both estrogen receptor (ER) α and ERβ. Mechanistic studies indicated that E (0.1 μmol/L) decreased the DNA binding of PPARγ induced by troglitazone (1 μmol/L) and inhibited the recruitment of the PPARγ coactivator CREB-binding protein.

CONCLUSION

These results suggest that in vivo and in vitro treatment of E interferes with the actions of PPARγ on adipogenesis by down-regulating adipogenesis-related genes, which are mediated through the inhibition of PPARγ coactivator recruitment. In addition, it is likely that the activities of PPARγ activators may be enhanced in estrogen-deficient states.

Effects of genistein on beta-catenin signaling and subcellular distribution of actin-binding proteins in human umbilical CD105-positive stromal cells

This study was performed to define the roles of actin-binding proteins in the regulation of actin filament assembly associated with cellular signal transduction pathways in stromal cell proliferation. Genistein, a tyrosine protein kinase inhibitor, decreased the intracellular Ca(2+) and attenuated cell proliferation and DNA synthesis through the beta-catenin and cyclin D1 pathway in human umbilical CD105-positive cells. Immunoprecipitation studies using anti-beta-actin antibody revealed that several actin-binding proteins implicated in cells include formin-2 (FMN-2), caldesmon (CaD), tropomyosin (Tm), and profilin. Protein levels of these proteins in whole cell lysates were not significantly changed by genistein. Three Tm isoforms, Tm-1, Tm-2, and Tm-4, were found to be present in cells. Genistein caused a reduction in levels of mRNAs coding for Tm-1 and Tm-4, but had no significant effect on Tm-2 mRNA levels. Immunofluorescence confocal scanning microscopy indicated that changes in the subcellular distribution of Tm and CaD, in which the diffuse cytosolic staining was shifted to show colocalization with actin stress fibers. In contrast, genistein-induced accumulation of FMN-2 and profilin in the peri-nuclear area. Silencing of FMN-2 by small interfering RNA resulted in increases of intracellular Ca(2+) and rendered genistein resistance in decreasing intracellular Ca(2+) in cells. These results provide the novel findings that genistein acts by modulating the cellular distribution of actin-binding proteins in association with alterations of cellular signal transduction pathways in human stromal cell proliferation.

Estrogen receptor mediates the effects of pseudoprotodiocsin on adipogenesis in 3T3-L1 cells

Estrogen receptors (ERs) play a pivotal role in adipogenesis; therefore, compounds targeting ERs may also affect fat formation. Recent studies have shown that the Dioscorea plant (commonly called yam) exhibits an antiobesity effect on rodents. However, the active compounds and underlying mechanisms responsible for this effect are not yet fully understood. We evaluated the effects of pseudoprotodiocsin (PPD), a steroid saponin from Dioscorea nipponica Makino (a type of Dioscorea), on adipogenesis and the mechanisms underlying this effect. Treatment with PPD at the onset of adipogenic differentiation resulted in significantly decreased adipogenesis in both in vitro and in vivo experimental systems. An increased amount of ERalpha mRNA, protein, and the accumulation of ERalpha in the nucleus were also observed. However, the expression pattern of ERbeta was not altered. Furthermore, the antiadipogenic effect of PPD was found to be ER dependent. It was also accompanied by the decreased expression of several genes involved in adipogenesis, including lipoprotein lipase (LPL), leptin, CCAAT/enhancer-binding-protein-alpha (C/EBPalpha), and peroxisome proliferator-activated receptor-gamma (PPARgamma), as well as the increased expression of some negative factors of adipogenesis, including preadipocyte factor 1 (Pre-1), GATA-binding protein 2 (GATA-2), GC-induced leucine-zipper protein (GILZ), and C/EBP homologous protein (CHOP-10). In addition to its estrogenic action, PPD also abolished the p38 mitogen-activated protein kinase (p38 MAPK) activation. Our results suggest that PPD inhibits adipogenesis in an ER-dependent manner and induces the expression of ERalpha. These findings may provide a lead toward a novel agent that can be used to treat obesity.

Potential health-modulating effects of isoflavones and metabolites via activation of PPAR and AhR

Isoflavones have multiple actions on cell functions. The most prominent one is the activation of estrogen receptors. Other functions are often overlooked, but are equally important and explain the beneficial health effects of isoflavones. Isoflavones are potent dual PPARα/γ agonists and exert anti-inflammatory activity, which may contribute to the prevention of metabolic syndrome, atherosclerosis and various other inflammatory diseases. Some isoflavones are potent aryl hydrocarbon receptor (AhR) agonists and induce cell cycle arrest, chemoprevention and modulate xenobiotic metabolism. This review discusses effects mediated by the activation of AhR and PPARs and casts a light on the concerted action of isoflavones.

Mesenchymal stem cells cultured under hypoxia escape from senescence via down-regulation of p16 and extracellular signal regulated kinase

Hypoxia has been considered to affect the properties of tissue stem cells including mesenchymal stem cells (MSCs). Effects of long periods of exposure to hypoxia on human MSCs, however, have not been clearly demonstrated. MSCs cultured under normoxic conditions (20% pO(2)) ceased to proliferate after 15-25 population doublings, while MSCs cultured under hypoxic conditions (1% pO(2)) retained the ability to proliferate with an additional 8-20 population doublings. Most of the MSCs cultured under normoxic conditions were in a senescent state after 100days, while few senescent cells were found in the hypoxic culture, which was associated with a down-regulation of p16 gene expression. MSCs cultured for 100days under hypoxic conditions were superior to those cultured under normoxic conditions in the ability to differentiate into the chondro- and adipogenic, but not osteogenic, lineage. Among the molecules related to mitogen-activated protein kinase (MAPK) signaling pathways, extracellular signal regulated kinase (ERK) was significantly down-regulated by hypoxia, which helped to inhibit the up-regulation of p16 gene expression. Therefore, the hypoxic culture retained MSCs in an undifferentiated and senescence-free state through the down-regulation of p16 and ERK.

Dose-dependent effects of soy phyto-oestrogen genistein on adipocytes: mechanisms of action

The potential role of genistein in the prevention and treatment of obesity has attracted much attention among public and medical communities. Conversely, increasing evidence indicates that genistein as an endocrine-disrupting substance is likely to play a role in the aetiology of obesity. This review focuses on the role of soy phyto-oestrogen genistein in adipocytes and the underlying mechanisms of action. Genistein dose-dependently inhibits and stimulates adipogenesis in vitro. Increasing evidence shows that genistein dose-dependently influences obesity in both male and female animals. Dose-dependent effects of genistein on adipocytes vary with factors such as age and gender of animals. In addition, the role of developmental exposure of genistein in adult obesity has been discussed. Genistein, different from oestrogen, concurrently activates nuclear receptors, oestrogen receptors and peroxisome proliferator-activated receptors, and it inhibits various enzyme activities. The balance among these pleiotrophic effects of genistein determines its dose-dependent effects on adipocyte differentiation and function. Current data suggest that genistein could regulate adiposity. However, it remains uncertain whether genistein plays a beneficial role in the prevention and treatment of obesity. Additional evidence is required before firm conclusions showing that genistein decreases adiposity.

Inhibition of ERK promotes collagen gel compaction and fibrillogenesis to amplify the osteogenesis of human mesenchymal stem cells in three-dimensional collagen I culture

Tissue morphogenesis remains one of the least understood problems in cell and developmental biology. There is a disconnect between the mechanisms that apply to two-dimensional (2D) cultures and those seen in vivo. Three-dimensional (3D) culture presents a complex stimulus triggering cellular responses that are only partially understood. We compared 2D and 3D cultures of human mesenchymal stem cells in the presence of mitogen-activated protein kinase kinase (MEK) inhibitor, PD98059, to determine the role of extracellular signal-related kinase (ERK) in collagen-induced differentiation. 3D collagen I culture enhanced and accelerated the osteogenic differentiation of human mesenchymal stem cells (hMSC). Contrary to 2D results, the addition of PD98059 induced a significant amplification of osteogenic gene expression and matrix mineralization in 3D cultures. The inhibition of ERK altered cell-mediated compaction, proliferation, and resulted in the development of distinct tissue microstructure. Therefore, we suggest that the ability to reorganize collagen in 3D is an important step in ERK-mediated osteogenic differentiation. This work aims to propose a correlation between osteogenic differentiation and hMSC-directed collagen I remodeling. We present a potential mechanistic link (ERK) through which the three dimensionality of an engineered tissue acts to differentially induce and maintain cellular phenotype during tissue development.

Naringenin and hesperetin induce growth arrest, apoptosis, and cytoplasmic fat deposit in human preadipocytes

Citrus flavonoids are reported to be promising bioactive compounds against hyperlipidemia and lipid biosynthesis. However, the mechanism of the lipid lowering effect by flavonoids remains unknown. The present study examines the effect of some flavanones on the adipocytic conversion of the human preadipocyte cell line, AML-I. Among four structure-related flavanones including naringenin, naringenin-7-rhamnoglucoside (naringin), hesperetin, and hesperetin-7-rhamnoglucoside (hesperidin), the aglycones such as naringenin and hesperetin exhibited the growth arrest of AML-I cells. When the cells were examined by Annexin V-FITC staining method, it was noticed that growth arrest was induced by apoptotic cell death. In the study of apoptosis-related protein in the naringenin-treated cells, anti-apoptotic proteins such as p-Akt, NF-kappaB, and Bcl-2 were decreased, and pro-apoptotic protein Bad was accumulated by Western blot analysis. Interestingly, exposure of AML-I cells to naringenin or hesperetin during short-term cultures increased cytoplasmic lipid droplets by Sudan Black B staining. Furthermore, expression of fatty acid synthase (FAS) and peroxisome proliferator activated receptor (PPAR)-gamma was enhanced in naringenin-treated cells. These data suggest that apoptosis by flavanones does not inhibit the adipocytic conversion of AML-I preadipocytes. The result also indicates that adipocyte may not be a direct target for the lipid-lowering activity of the flavanones.