Proteomic analysis for inhibitory effect of chitosan oligosaccharides on 3T3-L1 adipocyte differentiation

Impacts of chitosan and its nanoformulations on the metabolic syndromes: a review

A significant public health issue worldwide is metabolic syndrome, a cluster of metabolic illnesses that comprises insulin resistance, obesity, dyslipidemia, hyperglycemia, and hypertension. The creation of natural treatments and preventions for metabolic syndrome is crucial. Chitosan, along with its nanoformulations, is an oligomer of chitin, the second-most prevalent polymer in nature, which is created via deacetylation. Due to its plentiful biological actions in recent years, chitosan and its nanoformulations have drawn much interest. Recently, the chitosan nanoparticle-based delivery of CRISPR-Cas9 has been applied in treating metabolic syndromes. The benefits of chitosan and its nanoformulations on insulin resistance, obesity, diabetes mellitus, dyslipidemia, hyperglycemia, and hypertension will be outlined in the present review, highlighting potential mechanisms for the avoidance and medication of the metabolic syndromes by chitosan and its nanoformulations.

Studies on the partial characterization of extracted glycosaminoglycans from fish waste and its potentiality in modulating obesity through in-vitro and in-vivo

Glycosaminoglycans (GAGs) are bioactive polysaccharides or glycoconjugates found in the fish waste having significant health impacts. In the present study it has been attempted to extract GAGs from mackerel fish waste through chemical and enzymatic methods. Further, the extracted GAGs (e-GAGs) were analyzed for their composition (uronic acid, total sugar & sulfate), chemical characterization was carried out through techniques of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) & Proton NMR. Further, probable major GAGs present was identified by enzymatic digestion. The biological potential of the extracted glycoconjugate was assessed further through in-vitro and in-vivo studies. In-vitro biological activity showed good lipase inhibition (IC₅₀, 2.6 mg/mL) and bile acid binding properties (dose-dependent). Lipid accumulation lowered in the e-GAGs differentiated 3T3L1 preadipocyte cells have also been observed. The high fat fed animal (in-vivo) study showed ameliorative effect via reducing blood sugar∼1.28↓, lipid profile↓, plasma insulin∼3.5↓, improved glucose tolerance, and homeostatic model assessment for insulin resistance (HOMA-IR, ∼3.0↓). Furthermore, elimination of bile acid (BA) due to GAG-BA binding properties resultant in removal of elevated fecal triglyceride and cholesterol suggesting its lipid lowering activity. Regulation of various proteins linked to carbohydrate and lipid metabolism including fatty acid synthase (FAS), low density lipoproteins receptor (LDL-R), 7α-hydroxylase, glucose transporter-4 (GLUT4) and Peroxisome proliferator- activated receptor gamma (PPAR-γ) were significant (p < 0.05) with e-GAGs treatment when compared to HFD group. Thus, the e-GAGs showed potential hypolipidemic activity through elimination of bile acid binding property together with regulating the specific protein related to obesity and its associated complications.

Heme oxygenase-1 induction by gallic acid-g-chitosan is an important event in modulating adipocyte differentiation

Obesity, one of the common worldwide chronic health diseases co-relates with adipogenesis. Adipogenesis is a complex biological action of the emergence of mature adipocytes from the differentiation of pre-adipocytes and the disfunction of this process leads to the development of metabolic issues in obesity. Recently, much attention has been paid to utilizing natural compounds to discover their biological activities. This study focused on investigating the probable anti-adipogenic effects of gallic acid-g-chitosan (GAC) and plain chitosan (PC) through regulating the heme oxygenase-1 (HO-1)/Nrf2 pathway on mesenchymal stem cells. Gallic acid is grafted onto the PC backbone to improve its specific physical and biological properties. GAC showed promising anti-adipogenic effects by enhancing HO-1 expression and lipolysis and as well as suppressing lipid accumulation, reactive oxygen species, and pro-inflammatory cytokines production, transcription factor expression compared to the PC treatment. On the contrary, zinc protoporphyrin ІX (ZnPP), a HO-1 inhibitor reversed these effects of GAC on adipogenesis. Taken all together, this study revealed that grafting GA onto the chitosan improved potential anti-adipogenic activity by induction of the HO-1/Nrf2 pathway on mesenchymal stem cells (MSCs). PRACTICAL APPLICATIONS: GAC is a well-known copolymer with versatile bioactivities such as antimicrobial, antioxidant, and anti-diabetic activity. However, the anti-adipogenic effect of GAC has not been explored in MSCs. This study demonstrated that GAC inhibited adipocyte differentiation in MSCs through HO-1 activation. These findings suggest that GAC can be applied practically from different perspectives. GAC can be applied in the pharmacological industry to the development of anti-obesity drugs, medicinal perspectives for the treatment of obesity and obesity-related diseases, and in the food industry as a functional food to promote health and decrease the risk of diseases.

Deciphering Molecular Determinants Underlying Penicillium digitatum's Response to Biological and Chemical Antifungal Agents by Tandem Mass Tag (TMT)-Based High-Resolution LC-MS/MS

Penicillium digitatum is a widespread pathogen responsible for the postharvest decay of citrus, one of the most economically important crops worldwide. Currently, chemical fungicides are still the main strategy to control the green mould disease caused by the fungus. However, the increasing selection and proliferation of fungicide-resistant strains require more efforts to explore new alternatives acting via new or unexplored mechanisms for postharvest disease management. To date, several non-chemical compounds have been investigated for the control of fungal pathogens. In this scenario, understanding the molecular determinants underlying P. digitatum's response to biological and chemical antifungals may help in the development of safer and more effective non-chemical control methods. In this work, a proteomic approach based on isobaric labelling and a nanoLC tandem mass spectrometry approach was used to investigate molecular changes associated with P. digitatum's response to treatments with α-sarcin and beetin 27 (BE27), two proteins endowed with antifungal activity. The outcomes of treatments with these biological agents were then compared with those triggered by the commonly used chemical fungicide thiabendazole (TBZ). Our results showed that differentially expressed proteins mainly include cell wall-degrading enzymes, proteins involved in stress response, antioxidant and detoxification mechanisms and metabolic processes such as thiamine biosynthesis. Interestingly, specific modulations in response to protein toxins treatments were observed for a subset of proteins. Deciphering the inhibitory mechanisms of biofungicides and chemical compounds, together with understanding their effects on the fungal physiology, will provide a new direction for improving the efficacy of novel antifungal formulations and developing new control strategies.

The Role of Chitosan Oligosaccharide in Metabolic Syndrome: A Review of Possible Mechanisms

Metabolic syndrome, a cluster of metabolic disorders including central obesity, insulin resistance, hyperglycemia, dyslipidemia, and hypertension, has become a major public health problem worldwide. It is of great significance to develop natural products to prevent and treat metabolic syndrome. Chitosan oligosaccharide (COS) is an oligomer of chitosan prepared by the deacetylation of chitin, which is the second most abundant polymer in nature. In recent years, COS has received widespread attention due to its various biological activities. The present review will summarize the evidence from both in vitro and in vivo studies of the beneficial effects of COS on obesity, dyslipidemia, diabetes mellitus, hyperglycemia, and hypertension, and focus attention on possible mechanisms of the prevention and treatment of metabolic syndrome by COS.

Recent Updates in Pharmacological Properties of Chitooligosaccharides

Chemical structures derived from marine foods are highly diverse and pharmacologically promising. In particular, chitooligosaccharides (COS) present a safe pharmacokinetic profile and a great source of new bioactive polymers. This review describes the antioxidant, anti-inflammatory, and antidiabetic properties of COS from recent publications. Thus, COS constitute an effective agent against oxidative stress, cellular damage, and inflammatory pathogenesis. The mechanisms of action and targeted therapeutic pathways of COS are summarized and discussed. COS may act as antioxidants via their radical scavenging activity and by decreasing oxidative stress markers. The mechanism of COS antidiabetic effect is characterized by an acceleration of pancreatic islets proliferation, an increase in insulin secretion and sensitivity, a reduction of postprandial glucose, and an improvement of glucose uptake. COS upregulate the GLUT2 and inhibit digestive enzyme and glucose transporters. Furthermore, they resulted in reduction of gluconeogenesis and promotion of glucose conversion. On the other hand, the COS decrease inflammatory mediators, suppress the activation of NF-κB, increase the phosphorylation of kinase, and stimulate the proliferation of lymphocytes. Overall, this review brings evidence from experimental data about protective effect of COS.

Effect of the molecular weight of water-soluble chitosan on its fat-/cholesterol-binding capacities and inhibitory activities to pancreatic lipase

BACKGROUND

Obesity has become a worldwide burden to public health in recent decades. Given that obesity is caused by an imbalance between caloric intake and expenditure, and that dietary fat is the most important energy source of all macronutrients (by providing the most calories), a valuable strategy for obesity treatment and prevention is to block fat absorption via the gastrointestinal pathway. In this study, the fat- and cholesterol-binding capacities and the inhibition of pancreatic lipase by water-soluble chitosan (WSC) with different weight-average molecular weight (Mw) were tested and compared in vitro, in order to determine the anti-obesity effects of WSC and the influence of its Mw.

METHODS

In this study, WSC with different Mw (∼1,000, ∼3,000, ∼5,000, ∼7,000 and ∼9,000 Da) were prepared by oxidative degradation assisted with microwave irradiation. A biopharmaceutical model of the digestive tract was used to determine the fat- and cholesterol-binding capacity of WSC samples. The pancreatic lipase assays were based on p-nitrophenyl derivatives.

RESULTS

The results showed that all of the WSC samples exhibit great fat- and cholesterol-binding capacities. Within the testing range, 1 g of WSC sample could absorb 2-8 g of peanut oil or 50-65 mg of cholesterol, which are both significantly higher than the ability of cellulose to do the same. Meanwhile, all the WSC samples were proven to be able to inhibit pancreatic lipase activity to some extent.

DISCUSSION

Based on the results, we suggest that there is a significant correlation between the binding capacity of WSC and its Mw, as WSC2 (∼3,000 Da) shows the highest fat- and cholesterol-binding capacities (7.08 g g-1 and 63.48 mg g-1, respectively), and the binding ability of WSC declines as its Mw increases or decreases from 3,000 Da. We also suggest WSC as an excellent resource in the development of functional foods against obesity for its adsorption, electrostatic binding and entrapment of cholesterol, fat, sterols and triglycerides in the diet.

Antidiabetic effect of chitosan oligosaccharide (GO2KA1) is mediated via inhibition of intestinal alpha-glucosidase and glucose transporters and PPARγ expression

We have previously reported that administration of low molecular weight chitosan oligosaccharide (GO2KA1) significantly suppressed postprandial blood glucose rise with increased plasma adiponectin and HbA1c levels in animals and humans. However, the cellular mechanisms whereby GO2KA1 exerts antihyperglycemic effects still remain to be determined. Using intestinal Caco-2 cells and 3T3-L1 cells, here we show that GO2KA1 has dual modes of antidiabetic action by (1) inhibiting intestinal α-glucosidase as well as glucose transporters SGLT1 and GLUT2 that were distinct from the acarbose effect; (2) enhancing adipocyte differentiation, PPARγ expression and its target genes, such as FABP4, adiponectin, and GLUT4, whereas the effects were abolished by co-treatment with BADGE, a PPARγ antagonist. Moreover, GO2KA1 significantly increased glucose uptake, which was reduced in the presence of BADGE. Our data show that GO2KA1 may prevent hyperglycemia by inhibiting intestinal glucose digestion and transport and also enhance glucose uptake, at least in part, by upregulating adiponectin expression through PPARγ in adipocytes. These findings may provide potential molecular modes of action for the antidiabetic effects of chitosan oligosaccharide observed in clinical and animal studies. © 2016 BioFactors, 43(1):90-99, 2017.

Biologically active peptides: Processes for their generation, purification and identification and applications as natural additives in the food and pharmaceutical industries

Recent technological advances have created great interest in the use of biologically active peptides. Bioactive peptides can be defined as specific portions of proteins with 2 to 20 amino acids that have desirable biological activities, including antioxidant, anti-hypertensive, antithrombotic, anti-adipogenic, antimicrobial and anti-inflammatory effects. Specific characteristics, including low toxicity and high specificity, make these molecules of particular interest to the food and pharmaceutical industries. This review focuses on the production of bioactive peptides, with special emphasis on fermentation and enzymatic hydrolysis. The combination of different technologies and the use of auxiliary processes are also addressed. A survey of isolation, purification and peptide characterization methods was conducted to identify the major techniques used to determine the structures of bioactive peptides. Finally, the antioxidant, antimicrobial, anti-hypertensive, anti-adipogenic activities and probiotic-bacterial growth-promoting aspects of various peptides are discussed.

Anti-obese effect of glucosamine and chitosan oligosaccharide in high-fat diet-induced obese rats

Objective: This study is to evaluate the anti-obese effects of glucosamine (GLC) and chitosan oligosaccharide (COS) on high-fat diet-induced obese rats. Methods: The rats were randomly divided into twelve groups: a normal diet group (NF), a high-fat diet group (HF), Orlistat group, GLC high-, middle-, and low-dose groups (GLC-H, GLC-M, GLC-L), COS1 (COS, number-average molecular weight ≤1000) high-, middle-, and low-dose groups (COS1-H, COS1-M, COS1-L), and COS2 (COS, number-average molecular weight ≤3000) high-, middle-, and low-dose groups (COS2-H, COS2-M, COS2-L). All groups received oral treatment by gavage once daily for a period of six weeks. Results: Rats fed with COS1 gained the least weight among all the groups (P < 0.01), and these rats lost more weight than those treated with Orlistat. In addition to the COS2-H and Orlistat groups, the serum total cholesterol (CHO) and low-density lipoprotein cholesterol (LDL-C) levels were significantly reduced in all treatment groups compared to the HF group (P < 0.01). The various doses of GLC, COS1 and COS2 reduced the expression levels of PPARγ and LXRα mRNA in the white adipose tissue. Conclusions: The results above demonstrated that GLC, COS1, and COS2 improved dyslipidemia and prevented body weight gains by inhibiting the adipocyte differentiation in obese rats induced by a high-fat diet. Thus, these agents may potentially be used to treat obesity.

Supplementation of chitosan alleviates high-fat diet-enhanced lipogenesis in rats via adenosine monophosphate (AMP)-activated protein kinase activation and inhibition of lipogenesis-associated genes

This study investigated the role of chitosan in lipogenesis in high-fat diet-induced obese rats. The lipogenesis-associated genes and their upstream regulatory proteins were explored. Diet supplementation of chitosan efficiently decreased the increased weights in body, livers, and adipose tissues in high-fat diet-fed rats. Chitosan supplementation significantly raised the lipolysis rate; attenuated the adipocyte hypertrophy, triglyceride accumulation, and lipoprotein lipase activity in epididymal adipose tissues; and decreased hepatic enzyme activities of lipid biosynthesis. Chitosan supplementation significantly activated adenosine monophosphate (AMP)-activated protein kinase (AMPK) phosphorylation and attenuated high-fat diet-induced protein expressions of lipogenic transcription factors (PPAR-γ and SREBP1c) in livers and adipose tissues. Moreover, chitosan supplementation significantly inhibited the expressions of downstream lipogenic genes (FAS, HMGCR, FATP1, and FABP4) in livers and adipose tissues of high-fat diet-fed rats. These results demonstrate for the first time that chitosan supplementation alleviates high-fat diet-enhanced lipogenesis in rats via AMPK activation and lipogenesis-associated gene inhibition.

Recent advances in proteomic studies of adipose tissues and adipocytes

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

CLIC1 overexpression is associated with poor prognosis in gallbladder cancer

The chloride intracellular channel 1 (CLIC1) gene family is a recently identified class of Cl channel proteins. Although CLIC1 involvement is well established in some cancers such as gastric cancer and colon cancer, its expression pattern in gallbladder cancer (GBC) remains unknown. The aim of our study was to investigate the expression of CLIC1 in relation to progression and prognosis of GBC. Eight fresh gallbladder cancers paired with adjacent non-tumour tissues were quantified using real-time PCR and Western blot. Tissue samples from resected gallbladder cancer (n = 75) and cholelithiasis (n = 75) were evaluated for CLIC1 expression by immunohistochemical staining. Their expression was correlated with different clinicopathological parameters. CLIC1 expression was significantly higher (62.7 %) in gallbladder cancer than in cholelithiasis (21.3 %, p < 0.001). CLIC1 levels were associated with the histological grade, TNM stage and perineural invasion (p < 0.05), but not with patient age, sex, lymph node metastasis or gallbladder stones (p > 0.05). Univariate Kaplan-Meier analysis showed that a positive CLIC1 expression was associated with a decreased overall survival (p < 0.001). Multivariate Cox regression analysis showed that CLIC1 expression and histological grade were independent risk factors for overall survival. Therefore, the expression of CLIC1 is closely related to the progression of GBC and may be used as an effective marker for predicting the prognosis of this disease.

RNA-seq identified a super-long intergenic transcript functioning in adipogenesis

RNA transcripts are generally classified into polyA-plus and polyA-minus subgroups due to the presence or absence of a polyA tail at the 3′ end. Even though a number of physiologically and pathologically important polyA-minus RNAs have been recently identified, a systematic analysis of the expression and function of these transcripts in adipogenesis is still elusive. To study the potential function of the polyA-minus RNAs in adipogenesis, a dynamic expressional profiling was performed in the induced differentiation of 3T3-L1 cells. In addition to identifying thousands of novel intergenic transcripts, differentiation-synchronized expression was characterized for many of them. Among these, several large intergenic transcripts were found to be upregulated by more than 19-fold during differentiation. Further study demonstrated a fat tissue-specific expression pattern for these regions and identified an adipogenesis-associated long non-coding RNA. Collectively, these lines of evidence contribute to the characterization of a super-long intergenic transcript functioning in adipogenesis.

Assessment of chitosan-affected metabolic response by peroxisome proliferator-activated receptor bioluminescent imaging-guided transcriptomic analysis

Chitosan has been widely used in food industry as a weight-loss aid and a cholesterol-lowering agent. Previous studies have shown that chitosan affects metabolic responses and contributes to anti-diabetic, hypocholesteremic, and blood glucose-lowering effects; however, the in vivo targeting sites and mechanisms of chitosan remain to be clarified. In this study, we constructed transgenic mice, which carried the luciferase genes driven by peroxisome proliferator-activated receptor (PPAR), a key regulator of fatty acid and glucose metabolism. Bioluminescent imaging of PPAR transgenic mice was applied to report the organs that chitosan acted on, and gene expression profiles of chitosan-targeted organs were further analyzed to elucidate the mechanisms of chitosan. Bioluminescent imaging showed that constitutive PPAR activities were detected in brain and gastrointestinal tract. Administration of chitosan significantly activated the PPAR activities in brain and stomach. Microarray analysis of brain and stomach showed that several pathways involved in lipid and glucose metabolism were regulated by chitosan. Moreover, the expression levels of metabolism-associated genes like apolipoprotein B (apoB) and ghrelin genes were down-regulated by chitosan. In conclusion, these findings suggested the feasibility of PPAR bioluminescent imaging-guided transcriptomic analysis on the evaluation of chitosan-affected metabolic responses in vivo. Moreover, we newly identified that downregulated expression of apoB and ghrelin genes were novel mechanisms for chitosan-affected metabolic responses in vivo.

The expression and clinical significance of CLIC1 and HSP27 in lung adenocarcinoma

The purpose of this research was to study the roles of chloride intracellular channel protein 1 (CLIC1) and heat shock protein 27 (HSP27) in the clinical pathology of lung adenocarcinoma and to explore whether the expression of CLIC1 and HSP27 can be used as independent factors for the prediction of recurrence and prognosis after radical resection of lung adenocarcinoma. One hundred and three paraffin sections of lung adenocarcinoma tissues were collected, and the expression of CLIC1 and HSP27 was detected in these tumors using immunohistochemistry. The correlation of the expression of these two proteins with clinicopathological parameters and prognosis was statistically analyzed. In the 103 samples, the expression of HSP27 and CLIC1 was strongly positive in 61 (59.2%) and 49 cases (47.6%), respectively. Statistical analysis showed that the expression level of HSP27 did not significantly correlate with the patient's age, sex, degree of tumor differentiation, T staging of tumors, and TNM staging of tumors (p > 0.05), whereas the expression of CLIC1 did significantly correlate with T staging of tumors (p = 0.029). Univariate analysis indicated that the patient's ECOG score, T staging, N staging, TNM staging, and CLIC1 expression correlated with prognosis (p = 0.031, 0.001, 0.011, 0.013, and <0.001, respectively). Multivariate statistical analysis showed that age, T staging, and CLIC1 expression were independent associated factors for predicting the 5-year survival rate of patients (p = 0.026, 0.004, and <0.001, respectively). Age, T staging, and CLIC1 expression significantly correlated with the overall survival of post-operative lung adenocarcinoma patients. CLIC1 may be closely associated with the occurrence and development of lung adenocarcinoma and may be used as an effective marker for predicting the prognosis of this disease.

A potential role of IL-6 in the chito-oligosaccharide-mediated inhibition of adipogenesis

Recent studies have suggested that chito-oligosaccharides can have anti-adipogenic properties. The objectives of the present study were to evaluate the anti-adipogenic potential of four different chito-oligosaccharides (molecular weight (MW) < 1000, 1000-3000, 3000-5000 and 5000-10,000 Da) and to identify molecular mechanisms underlying the chito-oligosaccharide-mediated inhibition of adipogenesis. Mouse 3T3-L1 cells were allowed to differentiate in the presence of chito-oligosaccharide. At day 8 post-induction of differentiation, lipid accumulation, free glycerol release and the quantitative expression of adipogenic marker genes were evaluated. Chito-oligosaccharides had concentration- and MW-dependent inhibitory effects on lipid accumulation (P < 0·001 and < 0·05, respectively), as well as a concentration-dependent effect (P < 0·001) on free glycerol release and the expression of adipogenic marker genes. The 5000-10,000 Da chito-oligosaccharide was selected for subsequent molecular studies. A panel of forty-four lipid metabolic pathway-specific genes was analysed by quantitative real-time PCR. Chito-oligosaccharide-mediated inhibition of adipogenesis was associated with the up-regulation of the IL-6 gene at all concentrations of chito-oligosaccharide examined and the PG-endoperoxide synthase 2 (PTGS2) gene at higher concentrations of chito-oligosaccharide. The effect of chito-oligosaccharide on gene expression was validated by measuring IL-6 protein concentrations in the media. Finally, an IL-6 promoter assay was developed to characterise the effect of chito-oligosaccharide on the transcriptional activity of the IL-6 promoter, which was increased in a concentration-dependent manner (P < 0·001). We conclude that IL-6 is a candidate signalling molecule in the chito-oligosaccharide-mediated inhibition of adipogenesis in 3T3-L1 cells.

Attenuating effect of casein glycomacropeptide on proliferation, differentiation, and lipid accumulation of in vitro Sprague-Dawley rat preadipocytes

Food components with the ability to suppress preadipocyte proliferation and intracellular lipid accumulation may be helpful in the prevention of obesity, which is a worldwide health concern. Casein glycomacropeptide (GMP), which has pronounced gastric inhibitory activity, could potentially possess fat synthesis inhibition properties and an obesity-alleviating capacity. The objective of the present study was to investigate the effect of GMP on the proliferation and differentiation of preadipocytes as well as triglyceride accumulation and glycerol-3-phosphate dehydrogenase activity in preadipocytes isolated from Sprague-Dawley rats. Different dosages (0, 0.31, 0.625, 1.25, 2.5, and 5.0 mg/mL) of GMP were co-incubated with preadipocytes. The proliferation activity of preadipocytes significantly decreased in the GMP-treated group compared with that of the control group without GMP supplementation. The GMP exhibited an inhibitory effect against preadipocyte proliferation in a dose-dependent manner; the maximal antiproliferative effect was obtained with 2.5 mg/mL. The GMP also attenuated differentiation, as revealed by decreased lipid content, and the effect was more pronounced when cells were treated with GMP before or at the beginning of differentiation induction than at later stages of cell differentiation. Cultured preadipocytes treated with GMP accumulated fewer triglycerides and had lower glycerol-3-phosphate dehydrogenase activity than did the control cells without GMP supplementation. In conclusion, GMP can inhibit the proliferation, differentiation, and lipid accumulation of preadipocytes in vitro.

Temporal profiling of the secretome during adipogenesis in humans

Adipose tissue plays a key role as a fat-storage depot and as an endocrine organ. Although mouse adipogenesis has been studied extensively, limited studies have been conducted to characterize this process in humans. We carried out a temporal proteomic analysis to interrogate the dynamic changes in the secretome of primary human preadipocytes as they differentiate into mature adipocytes. Using iTRAQ-based quantitative proteomics, we identified and quantified 420 proteins from the secretome of differentiated human adipocytes. Our results revealed that the majority of proteins showed differential expression during the course of differentiation. In addition to adipokines known to be differentially secreted in the course of adipocyte differentiation, we identified a number of proteins whose dynamic expression in this process has not been previously documented. They include collagen triple helix repeat containing 1, cytokine receptor-like factor 1, glypican-1, hepatoma-derived growth factor, SPARC related modular calcium binding protein 1, SPOCK 1, and sushi repeat-containing protein. A bioinformatics analysis using Human Protein Reference Database and Human Proteinpedia revealed that of the 420 proteins identified, 164 proteins possess signal peptides and 148 proteins are localized to the extracellular compartment. Additionally, we employed antibody arrays to quantify changes in the levels of 182 adipokines during human adipogenesis. This is the first large-scale quantitative proteomic study that combines two platforms, mass spectrometry and antibody arrays, to analyze the changes in the secretome during the course of adipogenesis in humans.

The secretome of adipocytes is regulated during the differentiation of preadipocytes into adipocytes. Using iTRAQ-based quantitative proteomics, we identified and quantified 420 proteins. Additionally, we employed antibody arrays to quantify changes in the levels of 182 adipokines. This is the first large-scale quantitative proteomic study that combines two platforms, mass spectrometry and antibody arrays, to analyze the changes in the secretome during the course of adipogenesis in humans.

Determination of substrate binding energies in individual subsites of a family 18 chitinase

Thermodynamic parameters for binding of N-acetylglucosamine (GlcNAc) oligomers to a family 18 chitinase, ChiB of Serratia marcescens, have been determined using isothermal titration calorimetry. Binding studies with oligomers of different lengths showed that binding to subsites -2 and +1 is driven by a favorable enthalpy change, while binding to the two other most important subsites, +2 and +3, is driven by entropy with unfavorable enthalpy. These remarkable unfavorable enthalpy changes are most likely due to favorable enzyme-substrate interactions being offset by unfavorable enthalpic effects of the conformational changes that accompany substrate-binding.

Platycodin D inhibits adipogenesis of 3T3-L1 cells by modulating Kruppel-like factor 2 and peroxisome proliferator-activated receptor gamma

In this study, platycodin D was found to inhibit intracellular triglyceride accumulation in 3T3-L1 cells with an IC(50) of 7.1 microM. The expression levels of genes involved in lipid metabolism such as fatty-acid-binding protein 4 and lipoprotein lipase were significantly downregulated following treatment with platycodin D. Treatment with platycodin D also resulted in a reduction of Peroxisome proliferator-activated receptor(PPAR)gamma expression and its binding to target DNA sequence. Among the various upstream regulators of PPARgamma, the expression of Kruppel-like factor(KLF)2, an anti-adipogenic factor, was significantly upregulated following platycodin D treatment. When the upregulation of KLF2 was inhibited by KLF2 siRNA, the expression and binding of PPARgamma to its target sequence were significantly recovered under these conditions. The results of this study suggested that anti-adipogenic effect of platycodin D involves the upregulation of KLF2 and subsequent downregulation of PPARgamma.

Shikonin inhibits fat accumulation in 3T3-L1 adipocytes

Shikonin, 5,6-dihydroxyflavone-7-glucuronic acid, is the main ingredient of Lithospermum erythrorhizon Sieb. et Zucc, and was reported to have various biological activities including antiinflammatory, anticancer, antimicrobial and others. This study aimed to elucidate, for the first time, the antiobesity activity of shikonin and its mechanism of action. Shikonin was found to inhibit fat droplet formation and triglyceride accumulation in 3T3-L1 adipocytes. The half inhibitory concentration, IC(50), for the inhibition of triglyceride accumulation was found to be 1.1 microM. The expression of genes involved in lipid metabolism, such as FABP4 and LPL, were significantly inhibited following shikonin treatment. Shikonin also inhibited the ability of PPAR gamma and C/EBP alpha, the major transcription factors of adipogenesis, to bind to their target DNA sequences. The expressions of mRNA and protein of PPAR gamma and C/EBPa were significantly down-regulated following shikonin treatment. Among the upstream regulators of adipogenesis, only SREBP1C was found to be down-regulated by shikonin. The results of this study suggest that shikonin down-regulates the expression of SREBP1C and subsequently the expression of PPAR gamma and C/EBP alpha. Together, these changes result in the down-regulation of lipid metabolizing enzymes and reduced fat accumulation.

Degradation of chitosans with chitinase G from Streptomyces coelicolor A3(2): production of chito-oligosaccharides and insight into subsite specificities

We have studied the degradation of soluble heteropolymeric chitosans with a bacterial family 19 chitinase, ChiG from Streptomyces coelicolor A3(2), to obtain insight into the mode of action of ChiG, to determine subsite preferences for acetylated and deacetylated sugar units, and to evaluate the potential of ChiG for production of chito-oligosaccharides. Degradation of chitosans with varying degrees of acetylation was followed using NMR for the identity (acetylated/deacetylated) of new reducing and nonreducing ends as well as their nearest neighbors and using gel filtration to analyze the size distribution of the oligomeric products. Degradation of a 64% acetylated chitosan yielded a continuum of oligomers, showing that ChiG operates according to a nonprocessive, endo mode of action. The kinetics of the degradation showed an initial rapid phase dominated by cleavage of three consecutive acetylated units (A; occupying subsites -2, -1, and +1), and a slower kinetic phase reflecting the cleavage of the glycosidic linkage between a deacetylated unit (D, occupying subsite -1) and an A (occupying subsite +1). Characterization of isolated oligomer fractions obtained at the end of the initial rapid phase and at the end of the slower kinetic phase confirmed the preference for A binding in subsites -2, -1, and +1 and showed that oligomers with a deacetylated reducing end appeared only during the second kinetic phase. After maximum conversion of the chitosan, the dimers AD/AA and the trimer AAD were the dominating products. Degradation of chitosans with varying degrees of acetylation to maximum degree of scission produced a wide variety of oligomer mixtures, differing in chain length and composition of acetylated/deacetylated units. These results provide insight into the properties of bacterial family 19 chitinases and show how these enzymes may be used to convert chitosans to several types of chito-oligosaccharide mixtures.

Identification and characterization of molecular targets of natural products by mass spectrometry

Natural products, and their derivatives and mimics, have contributed to the development of important therapeutics to combat diseases such as infections and cancers over the past decades. The value of natural products to modern drug discovery is still considerable. However, its development is hampered by a lack of a mechanistic understanding of their molecular action, as opposed to the emerging molecule-targeted therapeutics that are tailored to a specific protein target(s). Recent advances in the mass spectrometry-based proteomic approaches have the potential to offer unprecedented insights into the molecular action of natural products. Chemical proteomics is established as an invaluable tool for the identification of protein targets of natural products. Small-molecule affinity selection combined with mass spectrometry is a successful strategy to "fish" cellular targets from the entire proteome. Mass spectrometry-based profiling of protein expression is also routinely employed to elucidate molecular pathways involved in the therapeutic and possible toxicological responses upon treatment with natural products. In addition, mass spectrometry is increasingly utilized to probe structural aspects of natural products-protein interactions. Limited proteolysis, photoaffinity labeling, and hydrogen/deuterium exchange in conjunction with mass spectrometry are sensitive and high-throughput strategies that provide low-resolution structural information of non-covalent natural product-protein complexes. In this review, we provide an overview on the applications of mass spectrometry-based techniques in the identification and characterization of natural product-protein interactions, and we describe how these applications might revolutionize natural product-based drug discovery.

Protein hydrolysates from beta-conglycinin enriched soybean genotypes inhibit lipid accumulation and inflammation in vitro

Obesity is a worldwide health concern and a well recognized predictor of premature mortality associated with a state of chronic inflammation. The objective was to evaluate the effect of soy protein hydrolysates (SPH) produced from different soybean genotypes by alcalase (SAH) or simulated gastrointestinal digestion (SGIH) on lipid accumulation in 3T3-L1 adipocytes. The anti-inflammatory effect of SPH produced by alcalase on LPS-induced macrophage RAW 264.7 cell line was also investigated. SAH (100 microM) derived from soybean enriched in beta-conglycinin (BC) (up to 47% total protein) decreased lipid accumulation (33-37% inhibition) through downregulation of gene expression of lipoprotein lipase (LPL) and fatty acid synthase (FAS). SGIH (100 microM) inhibited lipid accumulation to a lesser extent (8-14% inhibition) through inhibition of LPL gene expression. SAH (5 microM) decreased the production of nitric oxide (NO) (18-35%) and prostaglandin E(2) (PGE(2)) (47-71%) and the expression of inducible nitric oxide synthase (iNOS) (31-53%) and cycloxygenase-2 (COX-2) (30-52%). This is the first investigation showing that soy hydrolysates inhibit LPS-induced iNOS/NO and COX-2/PGE(2 )pathways in macrophages. Soybeans enriched in BCs can provide hydrolysates that limit fat accumulation in fat cells and inflammatory pathways in vitro and therefore warrant further studies as a healthful food.

Plasma proteome analysis for anti-obesity and anti-diabetic potentials of chitosan oligosaccharides in ob/ob mice

Altered levels of adipokines, derived as a result of distorted adipocytes, are the major factors responsible for changing biochemical parameters in obesity that leads to the development of metabolic disorders such as insulin resistance and atherosclerosis. In our previous reports, chitosan oligosaccharides (CO) were proved to inhibit the differentiation of 3T3-L1 adipocytes. In the present study, an attempt was made to investigate the anti-obesity and anti-diabetic effect of CO on ob/ob mice, by means of differential proteomic analysis of plasma. This was followed by immunoblotting, and gene expression in adipose tissue to clarify the molecular mechanism. CO treatment showed reduced diet intake (13%), body weight gain (12%), lipid (29%) and glucose levels (35%). 2-DE results showed differential levels of five proteins namely RBP4, apoE, and apoA-IV by >2-fold down-regulation and by >2-fold of apoA-I and glutathione peroxidase (GPx) up-regulation after CO treatment. Immunoblotting studies of adiponectin and resistin showed amelioration in their levels in plasma. Furthermore, the results of gene expressions for adipose tissue specific TNF-alpha, and IL-6 secretary molecules were also down-regulated by CO treatment. Gene expressions of PPAR gamma in adipose tissue were in good agreement with the ameliorated levels of adipokines, thereby improving the pathological state. Taken together, CO might act as a potent down-regulator of obesity-related gene expression in ob/ob mice that may normalize altered plasma proteins to overcome metabolic disorders of obesity.

Inhibitory effect of deep-sea water on differentiation of 3T3-L1 adipocytes

Currently, the utilization of deep-sea water (DSW) is receiving much attention due to its high productivity, large quantity, and potential for biological application. The 3T3-L1 cell line is a well-established and commonly used in vitro model to assess adipocyte differentiation. Over the course of several days, confluent 3T3-L1 cells can be converted to adipocytes in the presence of an adipogenic cocktail. In this study, the effects of DSW on differentiation adipocyte 3T3-L1 cells were studied. DSW significantly decreased lipid accumulation, a marker of adipogenesis, in a dose-dependent manner. DSW of hardness 1,000 was the most effective for inhibiting adipocyte differentiation without any cytotoxicity. DSW significantly reduced expression mRNA levels of PPARgamma and C/EBPalpha and protein levels of fatty-acid-binding protein and adiponectin. Our results suggest a potential role for DSW as anti-obesity agents by inhibiting adipocyte differentiation mediated through the down-regulated expression of adipogenic transcription factors and adipocyte-specific proteins.

Novel insights into adipogenesis from omics data

Obesity, the excess accumulation of adipose tissue, is one of the most pressing health problems in both the Western world and in developing countries. Adipose tissue growth results from two processes: the increase in number of adipocytes (hyperplasia) that develop from precursor cells, and the growth of individual fat cells (hypertrophy) due to incorporation of triglycerides. Adipogenesis, the process of fat cell development, has been extensively studied using various cell and animal models. While these studies pointed out a number of key factors involved in adipogenesis, the list of molecular components is far from complete. The advance of high-throughput technologies has sparked many experimental studies aimed at the identification of novel molecular components regulating adipogenesis. This paper examines the results of recent studies on adipogenesis using high-throughput technologies. Specifically, it provides an overview of studies employing microarrays for gene expression profiling and studies using gel based and non-gel based proteomics as well as a chromatin immunoprecipitation followed by microarray analysis (ChIP-chip) or sequencing (ChIP-seq). Due to the maturity of the technology, the bulk of the available data was generated using microarrays. Therefore these data sets were not only reviewed but also underwent meta analysis. The review also shows that large-scale omics technologies in conjunction with sophisticated bioinformatics analyses can provide not only a list of novel players, but also a global view on biological processes and molecular networks. Finally, developing technologies and computational challenges associated with the data analyses are highlighted, and an outlook on the questions not previously addressed is provided.

Proteomic and transcriptomic study on the action of a cytotoxic saponin (Polyphyllin D): induction of endoplasmic reticulum stress and mitochondria-mediated apoptotic pathways

Polyphyllin D (PD) is a potent cytotoxic saponin found in Paris polyphylla. In the present study, bioinformatic, proteomic and transcriptomic analyses were performed to study the mechanisms of action of PD on human nonsmall cell lung cancer (NSCLC) cell line (NCI-H460). Using a gene expression-based bioinformatic tool (connectivity map), PD was identified as a potential ER stress inducer. Our proteomic and transcriptomic analyses revealed that PD treatment led to upregulation of typical ER stress-related proteins/genes including glucose-regulated protein 78 (BiP/GRP78) and protein disulfide isomerase (PDI). In particular, elevated expression of C/EBP homologous transcription factor (chop) and activation of caspase-4 occurred at early time point (8 h) of PD treatment, signifying an initial ER stress-mediated apoptosis. Induction of tumor suppressor p53, disruption of mitochondrial membrane, activation of caspase-9 and caspase-3 were detected upon prolonged PD treatment. Collectively, these data revealed that PD induced the cytotoxic effect through a mechanism initiated by ER stress followed by mitochondrial apoptotic pathway. The ability of activating two major pathways of apoptosis makes PD an attractive drug lead for anticancer therapeutics.

Board-invited review: the biology and regulation of preadipocytes and adipocytes in meat animals

The quality and value of the carcass in domestic meat animals are reflected in its protein and fat content. Preadipocytes and adipocytes are important in establishing the overall fatness of a carcass, as well as being the main contributors to the marbling component needed for consumer preference of meat products. Although some fat accumulation is essential, any excess fat that is deposited into adipose depots other than the marbling fraction is energetically unfavorable and reduces efficiency of production. Hence, this review is focused on current knowledge about the biology and regulation of the important cells of adipose tissue: preadipocytes and adipocytes.