The mechanisms by which both heterozygous peroxisome proliferator-activated receptor gamma (PPARgamma) deficiency and PPARgamma agonist improve insulin resistance

Toona sinensis leaf extract inhibits lipid accumulation through up-regulation of genes involved in lipolysis and fatty acid oxidation in adipocytes

Toona sinensis leaf (TSL) has been shown to lower plasma triacylglycerol levels and diminish the size of visceral fat cells in vivo. The molecular mechanism of TSL ethanol extract (TSL-E) on lipid metabolism in 3T3-L1 adipocytes was investigated in this study. Oil Red O staining as well as immunoblotting, real-time PCR, and dual-Luciferase reporter system were performed to investigate the effect of TSL-E on lipid accumulation and the regulation of lipid metabolism, respectively. In addition, active compounds in the TSL-E were analyzed by HPLC. TSL-E significantly decreased lipid accumulation, stimulated free fatty acid (FFA) release, and up-regulated peroxisome proliferator-activated receptor-α (PPARα) and genes involved in peroxisomal (acyl-CoA oxidase) and mitochondrial (uncouple protein 3) fatty acid oxidation. TSL-E also up-regulated cytoplasmic triacylglycerol hydrolysis gene (adipose triglyceride lipase) and genes related to fatty acid oxidation (AMP-activated protein kinase, acetyl-CoA carboxylase, carnitine palmitoyltransferase I, PPARγ, and adiponectin). The major constituents directly inducing PPARα transactivity in TSL-E are gallic acid, rutin, palmitic acid, linoleic acid, and α-linolenic acid. These results indicate that the inhibitory effect of TSL-E on lipid accumulation was through PPARα activation and further up-regulation of PPARα-mediated genes plus up-regulation of cytoplasmic genes involved in lipid catabolism.

What we talk about when we talk about fat

There has been an upsurge of interest in the adipocyte coincident with the onset of the obesity epidemic and the realization that adipose tissue plays a major role in the regulation of metabolic function. The past few years, in particular, have seen significant changes in the way that we classify adipocytes and how we view adipose development and differentiation. We have new perspective on the roles played by adipocytes in a variety of homeostatic processes and on the mechanisms used by adipocytes to communicate with other tissues. Finally, there has been significant progress in understanding how these relationships are altered during metabolic disease and how they might be manipulated to restore metabolic health.

An in vitro study reveals nutraceutical properties of Ananas comosus (L.) Merr. var. Mauritius fruit residue beneficial to diabetes

BACKGROUND

Rapid urbanisation and nutritional transition is fuelling the increased global incidence of type 2 diabetes. Pineapple fruit residue was explored for its nutraceutical properties as an alternative or adjunct to currently available treatment regime. Ethyl acetate and methanolic extracts of pineapple fruit residue were evaluated for anti-diabetic activity in cell free and cell based systems. Specifically, we assessed: (1) antioxidant potential, (2) anti-glycation potential, (3) carbohydrate digestive enzyme inhibition, and (4) lipid accumulation and glycerol-3-phosphate dehydrogenase activity in differentiating 3T3-L1 cells.

RESULTS

The active components in the ethyl acetate and methanolic extracts were identified as sinapic acid, daucosterol, 2-methylpropanoate, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, methyl 2-methylbutanoate and triterpenoid ergosterol using DART/HRMS and ESI/HRMS. Micronutrient analysis revealed the presence of magnesium, potassium and calcium. Adipogenic potential, anti-glycation property of the ethyl acetate extract, and DNA damage protection capacity of the methanolic extract are promising.

CONCLUSION

Results from this study clearly indicate that pineapple fruit residue could be utilised as a nutraceutical against diabetes and related complications.

Back to the heart: the protective role of adiponectin

Cardiovascular disease (CVD) is the leading cause of death worldwide and the prevalence of obesity and diabetes are increasing. In obesity, adipose tissue increases the secretion of bioactive mediators (adipokines) that may represent a key mechanism linking obesity to CVD. Adiponectin, extensively studied in metabolic diseases, exerts anti-diabetic, anti-atherogenic and anti-inflammatory activities. Due to these positive actions, the role of adiponectin in cardiovascular protection has been evaluated in recent years. In particular, for its potential therapeutic benefits in humans, adiponectin has become the subject of intense preclinical research. In the cardiovascular context, understanding of the cellular and molecular mechanisms underlying the adiponectin system, throughout its secretion, regulation and signaling, is critical for designing new drugs that target adiponectin system molecules. This review focused on recent advances regarding molecular mechanisms related to protective effects of the adiponectin system on both cardiac and vascular compartments and its potential use as a target for therapeutic intervention of CVD.

The therapeutic potential of nuclear receptor modulators for treatment of metabolic disorders: PPARγ, RORs, and Rev-erbs

Nuclear receptors (NRs) play central roles in metabolic syndrome, making them attractive drug targets despite the challenge of achieving functional selectivity. For instance, members of the thiazolidinedione class of insulin sensitizers offer robust efficacy but have been limited due to adverse effects linked to activation of genes not involved in insulin sensitization. Studies reviewed here provide strategies for targeting subsets of PPARγ target genes, enabling development of next-generation modulators with improved therapeutic index. Additionally, emerging evidence suggests that targeting the NRs ROR and Rev-erb holds promise for treating metabolic syndrome based on their involvement in circadian rhythm and metabolism.

Antidiabetic Effects of Carassius auratus Complex Formula in High Fat Diet Combined Streptozotocin-Induced Diabetic Mice

Carassius auratus complex formula, including Carassius auratus, Rhizoma dioscoreae, Lycium chinense, and Rehmannia glutinosa Libosch, is a combination prescription of traditional Chinese medicine, which has always been used to treat diabetes mellitus in ancient China. In this study, we provided experimental evidence for the use of Carassius auratus complex formula in the treatment of high fat diet combined streptozotocin- (STZ-) induced type 2 diabetes. Carassius auratus complex formula aqueous extract was prepared and the effects of it on blood glucose, serum insulin, adipose tissue weight, oral glucose tolerance test (OGTT), total cholesterol, and triglyceride (TG) levels in mice were measured. Moreover, adiponectin, TG synthesis related gene expressions, and the inhibitory effect of aldose reductase (AR) were performed to evaluate its antidiabetic effects. After the 8-week treatment, blood glucose, insulin levels, and adipose tissue weight were significantly decreased. OGTT and HOMA-IR index showed improved glucose tolerance. It could also lower plasma TG, TC, and liver TG levels. Furthermore, Carassius auratus complex formula could inhibit the activity of AR and restore adiponectin expression in serum. Based on these findings, it is suggested that Carassius auratus complex formula possesses potent anti-diabetic effects on high fat diet combined STZ-induced diabetic mice.

Resistance to diet-induced obesity and associated metabolic perturbations in haploinsufficient monocarboxylate transporter 1 mice

The monocarboxylate transporter 1 (MCT1 or SLC16A1) is a carrier of short-chain fatty acids, ketone bodies, and lactate in several tissues. Genetically modified C57BL/6J mice were produced by targeted disruption of the mct1 gene in order to understand the role of this transporter in energy homeostasis. Null mutation was embryonically lethal, but MCT1 (+/-) mice developed normally. However, when fed high fat diet (HFD), MCT1 (+/-) mice displayed resistance to development of diet-induced obesity (24.8% lower body weight after 16 weeks of HFD), as well as less insulin resistance and no hepatic steatosis as compared to littermate MCT1 (+/+) mice used as controls. Body composition analysis revealed that reduced weight gain in MCT1 (+/-) mice was due to decreased fat accumulation (50.0% less after 9 months of HFD) notably in liver and white adipose tissue. This phenotype was associated with reduced food intake under HFD (12.3% less over 10 weeks) and decreased intestinal energy absorption (9.6% higher stool energy content). Indirect calorimetry measurements showed ∼ 15% increase in O₂ consumption and CO₂ production during the resting phase, without any changes in physical activity. Determination of plasma concentrations for various metabolites and hormones did not reveal significant changes in lactate and ketone bodies levels between the two genotypes, but both insulin and leptin levels, which were elevated in MCT1 (+/+) mice when fed HFD, were reduced in MCT1 (+/-) mice under HFD. Interestingly, the enhancement in expression of several genes involved in lipid metabolism in the liver of MCT1 (+/+) mice under high fat diet was prevented in the liver of MCT1 (+/-) mice under the same diet, thus likely contributing to the observed phenotype. These findings uncover the critical role of MCT1 in the regulation of energy balance when animals are exposed to an obesogenic diet.

Daidzein regulates proinflammatory adipokines thereby improving obesity-related inflammation through PPARγ

SCOPE

Daidzein was recently reported to act like an activator of peroxisome proliferator-activated receptor γ (PPARγ) thereby enhancing differentiation of adipocytes. Although PPARγ plays a role in adipokine expression, it has not been well researched whether daidzein affects expression of adipokines. This study aimed to clarify the effects of daidzein on proinflammatory adipokines and adipose inflammation causing insulin resistance in obesity.

METHODS AND RESULTS

3T3-L1 adipocytes were treated with daidzein or genistein. Diet-induced obese C57BL/6J mice were fed high-fat high-sucrose diets with daidzein (1.0 g/kg chow) for 12 wk. The results showed that both isoflavones, especially daidzein, stimulated adipogenic differentiation in 3T3-L1 adipocytes with the activation of PPARγ. Daidzein also increased adiponectin expression and decreased MCP-1 expression with the consistent regulation of their secretion. In obese mice, daidzein inhibited hypertrophy in fat cell size and improved insulin sensitivity, concomitant with upregulation of PPARγ in fat tissue. Decreased expression of MCP-1 and TNF-α, and increased expression of adiponectin were also observed in adipose tissue of daidzein-fed mice. Additionally, daidzein administration significantly inhibited macrophage accumulation in adipose tissue.

CONCLUSION

Daidzein regulates adipokine expression through the PPARγ, thereby improving the adverse effects of adipose inflammation, such as insulin resistance, in obesity.

Up-regulation of adiponectin expression in antigravitational soleus muscle in response to unloading followed by reloading, and functional overloading in mice

The purpose of this study was to investigate the expression level of adiponectin and its related molecules in hypertrophied and atrophied skeletal muscle in mice. The expression was also evaluated in C2C12 myoblasts and myotubes. Both mRNA and protein expression of adiponectin, mRNA expression of adiponectin receptor (AdipoR) 1 and AdipoR2, and protein expression of adaptor protein containing pleckstrin homology domain, phosphotyrosine binding domain, and leucine zipper motif 1 (APPL1) were observed in C2C12 myoblasts. The expression levels of these molecules in myotubes were higher than those in myoblasts. The expression of adiponectin-related molecules in soleus muscle was observed at mRNA (adiponectin, AdipoR1, AdipoR2) and protein (adiponectin, APPL1) levels. The protein expression levels of adiponectin and APPL1 were up-regulated by 3 weeks of functional overloading. Down-regulation of AdipoR1 mRNA, but not AdipoR2 mRNA, was observed in atrophied soleus muscle. The expression of adiponectin protein, AdipoR1 mRNA, and APPL1 protein was up-regulated during regrowth of unloading-associated atrophied soleus muscle. Mechanical loading, which could increase skeletal muscle mass, might be a useful stimulus for the up-regulations of adiponectin and its related molecules in skeletal muscle.

D-psicose increases energy expenditure and decreases body fat accumulation in rats fed a high-sucrose diet

We investigated the anti-obesity effects of D-psicose by increasing energy expenditure in rats pair-fed the high-sucrose diet (HSD). Wistar rats were divided into two dietary groups: HSD containing 5% cellulose (C) and 5% d-psicose (P). The C dietary group was further subdivided into two groups: rats fed the C diet ad libitum (C-AD) and pair-fed the C diet along with those in the P group (C-PF). Resting energy expenditure during darkness and lipoprotein lipase activity in the soleus muscle were significantly higher in the P group than in the C-PF group. Serum levels of glucose, leptin and adiponectin; glucose-6-phosphate dehydrogenase activities in the liver and perirenal adipose tissue; and body fat accumulation were all significantly lower in the P group than in the C-PF group. The anti-obesity effects of D-psicose could be induced not only by suppressing lipogenic enzyme activity but also by increasing EE in rats.

Intrahepatic lipid, not visceral or muscle fat, is correlated with insulin resistance in older, female rhesus macaques

OBJECTIVE

Little is known of the effect of body composition on glucose metabolism in the aging female non-human primate. These variables in older female Rhesus macaques were studied.

DESIGN AND METHODS

Female Rhesus macaques (Macaca mulatta, n = 19, age range 23-30 years) underwent magnetic resonance imaging and (1) H spectroscopy to quantify total abdominal fat, visceral fat (VF), subcutaneous fat (SF) area, extramyocellular lipid (EMCL), intramyocellular lipid (IMCL) and intrahepatic lipid (IHL) content, and DEXA scan for whole body composition. A subgroup (n = 12) underwent a fasting blood draw and intravenous glucose tolerance test.

RESULTS

SF correlated with homeostatic model assessment of insulin resistance (HOMAIR ) and quantitative insulin sensitivity check index (QUICKI), but not after adjustment for fat mass. IHL demonstrated the strongest correlation with HOMAIR , QUICKI and calculated insulin sensitivity index (CSI ), and remained significant after adjustment for fat mass. VF, IMCL, and EMCL did not correlate with any of our measures of insulin sensitivity.

CONCLUSIONS

Despite a greater amount of VF compared to SF, VF was not associated with markers of insulin resistance (IR) in the older female monkey. Instead, IHL is a marker for IR in the fasting and post-prandial state in these animals.

Gene expression profiling of SIRT1, FoxO1, and PPARγ in backfat tissues and subcutaneous adipocytes of Lilu bulls

The temporal pattern of gene expression of sirtuin 1 (SIRT1), forkhead box O1 (FoxO1), and peroxisome proliferator-activated receptor-γ (PPARγ) in differentiating bovine preadipocytes and in backfat tissue from Lilu bulls 12, 18, 24, and 30 months old was investigated using real-time quantitative PCR; Carcass characteristics and adipocyte diameters were also measured. The upregulation of PPARγ and the downregulation of SIRT1 and FoxO1 were observed in the backfat tissue of Lilu cattle with increasing age. Moreover, the results showed that fat accumulation in Lilu cattle may primarily be related to an increase in mature fat cell numbers after 18 months of age. The present study indicates SIRT1 may play an important role in the development of bovine adipose tissue in vivo. Although SIRT1, FoxO1, and PPARγ expression appeared to be nonlinear during the stages of preadipocyte differentiation, these genes play an important role during bovine adipocyte development in Lilu cattle.

Exercise- and resveratrol-mediated alterations in adipose tissue metabolism

Owing to its obligatory role in locomotion and the fact that it accounts for the vast majority of whole-body glucose and lipid oxidation, much work has focused on studying the biochemical adaptations that occur in skeletal muscle in response to exercise. However, over the past several years there has been a growing appreciation that adipose tissue is an important player in regulating systemic carbohydrate and lipid homeostasis. Despite this, the examination of how exercise alters adipose tissue function and metabolism is, when compared with skeletal muscle, in its infancy. The purpose of the current review is to highlight some of the recent findings from our laboratory and others that focus on the emerging area of adipose tissue exercise biochemistry. Specifically, the role of exercise on the induction of mitochondrial and glyceroneogenic enzymes will be examined and will be compared with the well-characterized effects of thiazolidinediones, which are insulin-sensitizing drugs. A particular emphasis will be placed on the role of interleukin-6 in mediating the effects of exercise. Finally, we will discuss recent data from our laboratory demonstrating beneficial effects of resveratrol supplementation on adipose tissue metabolism.

Pioglitazone leads to an inactivation and disassembly of complex I of the mitochondrial respiratory chain

BACKGROUND

Thiazolidinediones are antidiabetic agents that increase insulin sensitivity but reduce glucose oxidation, state 3 respiration, and activity of complex I of the mitochondrial respiratory chain (MRC). The mechanisms of the latter effects are unclear. The aim of this study was to determine the mechanisms by which pioglitazone (PGZ), a member of the thiazolidinedione class of antidiabetic agents, decreases the activity of the MRC. In isolated mitochondria from mouse liver, we measured the effects of PGZ treatment on MRC complex activities, fully-assembled complex I and its subunits, gene expression of complex I and III subunits, and [3H]PGZ binding to mitochondrial complexes.

RESULTS

In vitro, PGZ decreased activity of complexes I and III of the MRC, but in vivo only complex I activity was decreased in mice treated for 12 weeks with 10 mg/kg/day of PGZ. In vitro treatment of isolated liver mitochondria with PGZ disassembled complex I, resulting in the formation of several subcomplexes. In mice treated with PGZ, fully assembled complex I was increased and two additional subcomplexes were found. Formation of supercomplexes CI+CIII2+CIVn and CI+CIII2 decreased in mouse liver mitochondria exposed to PGZ, while formation of these supercomplexes was increased in mice treated with PGZ. Two-dimensional analysis of complex I using blue native/sodium dodecyl sulfate polyacrylamide gel electrophoresis (BN/SDS-PAGE) showed that in vitro PGZ induced the formation of four subcomplexes of 600 (B), 400 (C), 350 (D), and 250 (E) kDa, respectively. Subcomplexes B and C had NADH:dehydrogenase activity, while subcomplexes C and D contained subunits of complex I membrane arm. Autoradiography and coimmunoprecipitation assays showed [3H]PGZ binding to subunits NDUFA9, NDUFB6, and NDUFA6. Treatment with PGZ increased mitochondrial gene transcription in mice liver and HepG2 cells. In these cells, PGZ decreased intracellular ATP content and enhanced gene expression of specific protein 1 and peroxisome-proliferator activated receptor (PPAR)γ coactivator 1α (PGC-1α).

CONCLUSIONS

PGZ binds complex I subunits, which induces disassembly of this complex, reduces its activity, depletes cellular ATP, and, in mice and HepG2 cells, upregulates nuclear DNA-encoded gene expression of complex I and III subunits.

Role of insulin resistance in the pathogenesis and development of type 2 diabetes in WBN/Kob-Lepr(fa) rats

WBN/Kob-Lepr^fa (fa/fa) rats have been identified as a new animal model of type 2 diabetes (T2DM), as they are characterized by impaired pancreatic insulin secretion and severe insulin resistance. Our previous study demonstrated impaired insulin secretion and its involvement in hyperglycemia in fa/fa rats. The present study was aimed at elucidating the role of insulin resistance in the development and progression of diabetes in these animals. Troglitazone (TGZ) was used as an insulin sensitizer. Insulin resistance and insulin secretory capacity were measured by a homeostasis model assessment of insulin resistance and the area under the blood concentration–time curve for plasma insulin levels after intravenous glucose tolerance testing, respectively. The fa/fa rats exhibited marked insulin resistance between 5 and 11 weeks of age, compared with age-matched Wistar rats. The insulin secretory capacity of fa/fa rats was higher than that of Wistar rats at 5 weeks of age, but decreased by 50% between 9 and 11 weeks of age. The fa/fa rats were fed a standard diet, with or without 0.2% w/w TGZ, for 4 weeks. Treatment with TGZ significantly improved insulin resistance, hyperglycemia and hypertriglyceridemia in both prophylactic and therapeutic study groups. These results suggest that insulin resistance is markedly involved in the development and progression of T2DM in fa/fa rats.

Metabolic and other effects of pioglitazone as an add-on therapy to metformin in the treatment of polycystic ovary syndrome (PCOS)

Insulin resistance is a key pathogenic defect of the clustered metabolic disturbances seen in polycystic ovary syndrome (PCOS). Metformin is an insulin sensitizer acting in the liver and the peripheral tissues that ameliorates the metabolic and reproductive defects in PCOS. In addition, pioglitazone is an insulin sensitizer used in diabetes mellitus type 2 (T2DM), improving insulin resistance (IR) in adipose tissue and muscles. In T2DM, these drugs are also used as a combined treatment due to their "add-on effect" on insulin resistance. Although the beneficial role of troglitazone (a member of the thiazolidinediones (TZDs) family) in PCOS has been shown in the past, currently only pioglitazone is available in the market. A few small randomized controlled trials have directly compared the effectiveness of pioglitazone in women with PCOS, while there are a limited number of small studies that support the beneficial metabolic add-on effect of pioglitazone on metformin-treated PCOS women as compared to metformin or pioglitazone monotherapy. These findings suggest a potentially promising role for combined pioglitazone/metformin treatment in the management of PCOS in metformin-resistant patients. In view of recent concerns regarding pioglitazone usage and its associated health risk, we aim to compare the pros and cons of each drug regarding their metabolic and other hormonal effects in women with PCOS and to explore the possible beneficial effect of combined therapy in certain cases, taking into consideration the teratogenic effect of pioglitazone. Finally, we discuss the need for a randomized controlled trial that will evaluate the metabolic and other hormonal effects of combined metformin/pioglitazone treatment in PCOS with selective treatment targets.

Association between the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma gene and strength athlete status

Background

The 12Ala allele of the Peroxisome Proliferator-Activated Receptor gamma gene (PPARG) Pro12Ala polymorphism produces a decreased binding affinity of the PPARγ2 protein, resulting in low activation of the target genes. The 12Ala allele carriers display a significantly improved insulin sensitivity that may result in better glucose utilisation in working skeletal muscles. We hypothesise that the PPARG 12Ala allele could be associated with strength athlete status in Polish athletes.

Methodology

The genotype distribution of PPARG Pro12Ala was examined in 660 Polish athletes. The athletes were stratified into four subgroups: endurance, strength-endurance, sprint-strength and strength. Control samples were prepared from 684 unrelated sedentary volunteers. A χ² test was used to compare the PPARG Pro12Ala allele and genotype frequencies between the different groups of athletes and control subjects. Bonferroni’s correction for multiple testing was applied.

Results

A statistically significant higher frequency of PPARG 12Ala alleles was observed in the subgroup of strength athletes performing short-term and very intense exertion characterised by predominant anaerobic energy production (13.2% vs. 7.5% in controls; P = 0.0007).

Conclusion

The PPARG 12Ala allele may be a relevant genetic factor favouring strength abilities in professional athletes, especially in terms of insulin-dependent metabolism, a shift of the energy balance towards glucose utilisation and the development of a favourable weight-to-strength ratio.

Black soybean seed coat extract ameliorates hyperglycemia and insulin sensitivity via the activation of AMP-activated protein kinase in diabetic mice

Black soybean seed coat has abundant levels of polyphenols such as anthocyanins (cyanidin 3-glucoside; C3G) and procyanidins (PCs). This study found that dietary black soybean seed coat extract (BE) ameliorates hyperglycemia and insulin sensitivity via the activation of AMP-activated protein kinase (AMPK) in type 2 diabetic mice. Dietary BE significantly reduced blood glucose levels and enhanced insulin sensitivity. AMPK was activated in the skeletal muscle and liver of diabetic mice fed BE. This activation was accompanied by the up-regulation of glucose transporter 4 in skeletal muscle and the down-regulation of gluconeogenesis in the liver. These changes resulted in improved hyperglycemia and insulin sensitivity in type 2 diabetic mice. In vitro studies using L6 myotubes showed that C3G and PCs significantly induced AMPK activation and enhanced glucose uptake into the cells.

Association of Pro12Ala (rs1801282) variant of PPAR gamma with rheumatoid arthritis in a Pakistani population

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) belongs to a receptor superfamily of ligand-activated transcription factors, encoded by PPARG gene. Role of PPARγ has been well established in variety of metabolic disorders and in regulation of inflammation. In the present study, we aimed to investigate the association of PPARG (Pro12Ala; rs1801282) in clinically definite Pakistani Rheumatoid Arthritis (RA) patients and matching controls. The genotypes of the Pro12Ala variant in the PPARG were determined in a sample of 300 Pakistanis, including 150 RA cases and 150 controls. The genotyping was performed using Amplification Refractory Mutation System-Polymerase Chain Reaction (ARMS-PCR) method, and the data was analyzed through Graphpad Prism 5 V software. Allele-specific primer set (two forward: PPARG-F1, PPARG-F2 and a common reverse primer: PPARG-R) was used for amplification, and the product was resolved on 2 % agarose gel. The CC (ProPro) genotype has higher frequency in controls than RA cases [75 (50.0 %) vs. 51 (34.0 %)], whereas the CG (ProAla) genotype has relatively same frequencies in both cases and controls [72 (48.0 %) vs. 70 (46.6 %)]. However, significantly higher frequency of GG (AlaAla) genotype was observed in cases [27 (18.0 %) vs. 5 (3.3 %); χ2 18.54; p < 0.0001]. Furthermore, the minor allele G has significantly higher allele frequency in cases having same trend and direction of association (OR 1.991(1.412-2.808); p < 0.0001). These observations suggest that Pro12Ala (rs1801282), a coding variant in the PPARG gene, is associated with Rheumatoid Arthritis in Pakistanis.

Peroxisome proliferator activated receptor (PPAR)-gamma concentrations in childhood obesity

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) are nuclear proteins that regulate transcriptional responses to peroxisome proliferators. There has been limited research concerned with the childhood expression of these receptors. In this study, we aimed to evaluate PPAR-gamma (PPAR-γ) concentrations and their relationship to body mass index (BMI), ratio of waist and hip, blood pressure levels, insulin resistance and lipid profile in obese children and adolescents.

SUBJECTS AND METHODS

Children aged 8-16 years old were included in the study; 44 obese children and 25 healthy children were taken into the study. Blood pressure and waist-hip circumference of obese patients were measured. Following a 12-hour nighttime fasting, venous blood samples were taken, including blood glucose, insulin, lipid profile, liver function tests and PPAR-γ concentrations, and all samples were analyzed at the same time.

FINDINGS

PPAR-γ concentrations were 0.226 + 0.128 in obese children and 0.547 + 0.546 in the control group. PPAR-γ concentrations were lower in obese children and this difference was statistically significant (p = 0.008). PPAR-γ concentrations of control children were 2.42-fold higher than obese children. There was a negative correlation between PPAR-γ concentrations and waist circumference, and a positive correlation between birth weight and PPAR-γ concentrations in obese children.

CONCLUSION

In our study we found that PPAR-γ concentrations were low in obese children. In adults, treatment modalities aimed at enhancing the activation of PPAR in obesity lead to a decrease in obesity, insulin resistance, dyslipidemia and cardiovascular disease and this gives hope that similar treatment modalities can be used for children.

Validation of the Antidiabetic and Hypolipidemic Effects of Hawthorn by Assessment of Gluconeogenesis and Lipogenesis Related Genes and AMP-Activated Protein Kinase Phosphorylation

Since with the increased use of antidiabetic and antihyperlipidemic effect of phytonutrients for daily supplement has gained considerable attention worldwide, we examine the effect and molecular mechanism of Crataegus pinnatifida Bge. var. major N.E. Br. (hawthorn) by quantifying the expression of hepatic gluconeogenesis and lipogenesis on diabetes and dyslipidemia in high-fat (HF)-fed C57BL/6J mice. Firstly, mice were divided randomly into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed a 45% HF diet for 8 weeks. Afterwards, the CON group was treated with vehicle, whereas the HF group was subdivided into five groups and was given orally hawthorn extract (including 0.2, 0.5, 1.0 g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks afterward. Diabetic mice showed an increase in plasma glucose and insulin. Glucose lowering was comparable with Rosi-treated mice. This study demonstrated that hawthorn was effective in ameliorating the HF diet-induced hyperglycemia, hypertriglyceridemia and hypercholesterolaemia. Hawthorn extract significantly increases the hepatic protein contents of AMP-activated protein kinase (AMPK) phosphorylation and reduces expression of phosphenol pyruvate carboxykinase (PEPCK) and glucose production. Furthermore, hawthorn decreased in hepatic triacylglycerol and cholesterol synthesis (including sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), SREBP2). An increase in expressions of apoA-I gene and high-density lipoprotein cholesterol (HDL-C) was detected in HF-fed mice treated with high dose hawthorn. Our data suggest that hawthorn extract are capable of decreasing glucose production and triacylglycerol synthesis by inducing AMPK-phosphorylation and hawthorn is a candidate source of antidiabetic and antihyperlipidemic phytonutrients factors.

Induction of peroxisome proliferator-activated receptor γ (PPARγ)-mediated gene expression by tomato (Solanum lycopersicum L.) extracts

Since beneficial effects related to tomato consumption partially overlap with those related to peroxisome proliferator-activated receptor γ (PPARγ) activation, our aim was to test extracts of tomato fruits and tomato components, including polyphenols and isoprenoids, for their capacity to activate PPARγ using the PPARγ2 CALUX reporter cell line. Thirty tomato compounds were tested; seven carotenoids and three polyphenols induced PPARγ2-mediated luciferase expression. Two extracts of tomato, one containing deglycosylated phenolic compounds and one containing isoprenoids, also induced PPARγ2-mediated expression at physiologically relevant concentrations. Furthermore, enzymatically hydrolyzed extracts of seven tomato varieties all induced PPARγ-mediated expression, with a 1.6-fold difference between the least potent and the most potent variety. The two most potent varieties had high flavonoid content, while the two least potent varieties had low flavonoid content. These data indicate that extracts of tomato are able to induce PPARγ-mediated gene expression in vitro and that some tomato varieties are more potent than others.

Peroxisome proliferator-activated receptor δ: a multifaceted metabolic player

PURPOSE OF REVIEW

Therapeutic strategies to alleviate the growing epidemic of insulin-resistant syndromes (obesity and type 2 diabetes) as well as the conferred cardiovascular disease risk remain sparse. The peroxisome proliferator-activated receptor δ (PPARδ) has emerged as a versatile regulator of lipid homeostasis and inflammatory signaling, making it an attractive therapeutic target for the treatment and prevention of type 2 diabetes and atherosclerosis.

RECENT FINDINGS

PPARδ activation regulates lipid homeostasis and inflammatory signaling in a variety of cell types, conferring protection from metabolic disease and atherosclerosis. Specifically, PPARδ activation in the liver stimulates glucose utilization and inhibits gluconeogenesis, which improves insulin resistance and hyperglycemia. In macrophages, PPARδ-specific activation with synthetic agonists inhibits VLDL-induced triglyceride accumulation and inflammation. In mice, PPARδ agonists halt the progression of atherosclerosis and stabilize existing lesions by promoting an anti-inflammatory milieu within the diseased macrovasculature. In humans, PPARδ activation improves insulin sensitivity and reduces atherogenic dyslipidemia via a mechanism complementary to statin monotherapy.

SUMMARY

Recent advances in the understanding of PPARδ reveal that activation of this receptor represents a multifaceted therapeutic strategy for the prevention and treatment of insulin-resistant syndromes and atherosclerosis.

Lucidone from Lindera erythrocarpa Makino fruits suppresses adipogenesis in 3T3-L1 cells and attenuates obesity and consequent metabolic disorders in high-fat diet C57BL/6 mice

Obesity is associated with an increased risk of development of numerous diseases including type 2 diabetes, hypertension, hyperlipidemia, and cardiovascular disease. In this study, we investigated the effects of lucidone in vitro on gene expression during adipogenesis in 3T3-L1 cells and in vivo on high-fat diet induced obesity in C57BL/6 mice. Lucidone at 40 μmol/L suppressed adipogenesis in 3T3-L1 cells by reducing transcription levels of adipogenic genes, including PPARγ, C/EBPα, LXR-α, LPL, aP2, GLUT4 and adiponectin. Five-week-old male C57BL/6 mice fed a high fat diet (60% energy from fat) supplemented with lucidone at a dosage of 1250 mg/kg of diet for 12 weeks had reduced body and liver weight, reduced epididymal and perirenal adipose tissue, decreased food efficiency (percentage of weight gain divided by food intake), and lowered plasma cholesterol, triglyceride, glucose, and insulin levels. Dissection of adipose tissue from lucidone-treated mice showed a reduction in the average fat-cell size and percentage of large adipocytes. These results provide evidence that dietary intake of lucidone alleviates high fat diet-induced obesity in C57BL/6 mice and reveals the potential of lucidone as a nutraceutical to prevent obesity and consequent metabolic disorders.

Diverse coactivator recruitment through differential PPARγ nuclear receptor agonism

The PPARγ nuclear receptor regulates the expression of genes involved in lipid and carbohydrate metabolism, and it has protective effects in some patients with type 2 diabetes. Nevertheless, the therapeutic value of the PPARγ nuclear receptor protein is limited due to the secondary effects of some PPARγ ligands. Because the downstream effects of PPARγ are determined by the binding of specific cofactors that are mediated by ligand-induced conformational changes, we evaluated the differential effects of various ligands on the binding of certain cofactors associated with PPARγ. The ligands used were rosiglitazone for treating type 2 diabetes and telmisartan for treating arterial hypertension. Functional, phenotypic, and molecular studies were conducted on pre-adipocyte 3T3-L1 and functional studies in U2OS cells. The moderating influence of various cofactor families was evaluated using transient transfection assays. Our findings confirm that telmisartan has a partial modulating effect on PPARγ activity compared to rosiglitazone. The cofactors SRC1 and GRIP1 mediate the activity of telmisartan and rosiglitazone and partially determine the difference in their effects. Studying the modulating activity of these cofactors can provide interesting insights for developing new therapeutic approaches for certain metabolic diseases.

Doxorubicin treatment inhibits PPARγ and may induce lipotoxicity by mimicking a type 2 diabetes-like condition in rodent models

Doxorubicin-treated animals show elevated serum triglyceride and blood glucose levels. Adipocytes play an important role in buffering blood glucose and lipids. A raise in serum lipid level triggers adipogenesis in order to increase the lipid absorption capacity of adipose tissue. Doxorubicin inhibits adipogenesis through the down-regulation of PPARγ, a crucial component of the lipid metabolic pathway which controls the expression of glucose and fatty acid transporters. Doxorubicin-mediated down-regulation of PPARγ inhibits blood glucose and lipid clearance thereby causing hyperglycemia and hyperlipidemia resulting in lipotoxicity, glucotoxicity, inflammation and insulin resistance. Therefore we hypothesize that doxorubicin treatment could mimic a type 2 diabetic condition.

Plant extracts of winter savory, purple coneflower, buckwheat and black elder activate PPAR-γ in COS-1 cells but do not lower blood glucose in Db/db mice in vivo

The aim of this study was to investigate possible blood glucose-lowering effects of plant extracts in vivo for which prior to this a peroxisome proliferator-activated receptor-γ activity in vitro was observed. The ability of extracts of winter savory, purple coneflower, buckwheat and black elder to dose-dependently activate peroxisome proliferator-activated receptor-γ was determined in a reporter gene assay in COS-1 cells. For evaluation of glucose-lowering effects in vivo, db/db mice were fed a diet containing either rosiglitazone (0.02 g/kg diet, positive control) or one of the plant extracts (0.1 and 1 g/kg diet) for four weeks. Apart from glucose, insulin, triacylglycerols, non-esterified fatty acids, cholesterol and adiponectin were determined in plasma. All plant extracts showed a dose-dependent peroxisome proliferator-activated receptor-γ-activating effect in vitro. In db/db mice none of the plant extracts exerted glucose-lowering effects at the used dosages compared to rosiglitazone. Non-esterified fatty acids, triacylglycerols, cholesterol, insulin and adiponectin in plasma were not altered by the plant extracts as well. Although dose-dependent peroxisome proliferator-activated receptor-γ activity could be shown in COS-1 cells, the experiments in db/db mice lacked to confirm any anti-diabetic effect of the plant extracts in vivo and emphasizes the importance of verifying cell culture data using an appropriate in vivo model.

Loss of toll-like receptor 3 function improves glucose tolerance and reduces liver steatosis in obese mice

OBJECTIVE

Emerging evidence suggests a link between innate immunity and development of type 2 diabetes mellitus (T2D); however, the molecular mechanisms linking them are not fully understood. Toll-like Receptor 3 (TLR3) is a pathogen pattern recognition receptor that recognizes the double-stranded RNA of microbial or mammalian origin and contributes to immune responses in the context of infections and chronic inflammation. The objective of this study was to determine whether TLR3 activity impacts insulin sensitivity and lipid metabolism.

MATERIALS AND METHODS

Wild type (WT) and TLR3 knock-out (TLR3(-/-)) mice were fed a high fat diet (HFD) and submitted to glucose tolerance tests (GTTs) over a period of 33 weeks. In another study, the same group of mice was treated with a neutralizing monoclonal antibody (mAb) against mouse TLR3.

RESULTS

TLR3(-/-) mice fed an HFD developed obesity, although they exhibited improved glucose tolerance and lipid profiles compared with WT obese mice. In addition, the increase in liver weight and lipid content normally observed in WT mice on an HFD was significantly ameliorated in TLR3(-/-) mice. These changes were accompanied by up-regulation of genes involved in cholesterol efflux such as PPARδ, LXRα, and LXRα-targeting genes and down-regulation of pro-inflammatory cytokine and chemokine genes in obese TLR3(-/-) mice. Furthermore, global gene expression profiling in liver demonstrated TLR3-specific changes in both lipid biosynthesis and innate immune response pathways.

CONCLUSIONS

TLR3 affects glucose and lipid metabolism as well as inflammatory mediators, and findings in this study reveal a new role for TLR3 in metabolic homeostasis. This suggests antagonizing TLR3 may be a beneficial therapeutic approach for the treatment of metabolic diseases.

Cirsium japonicum flavones enhance adipocyte differentiation and glucose uptake in 3T3-L1 cells

Cirsium japonicum flavones have been demonstrated to possess anti-diabetic effects in diabetic rats, but the functional mechanism remains unknown. The nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) plays an important role in glucose and lipid homeostasis. In this study, we report the effects of Cirsium japonicum flavones (pectolinarin and 5,7-dihydroxy-6,4-dimethoxy flavone) on PPARγ activation, adipocyte differentiation, and glucose uptake in 3T3-L1 cells. Reporter gene assays and Oil Red O staining showed that Cirsium japonicum flavones induced PPARγ activation and enhanced adipocyte differentiation of 3T3-L1 cells in a dose-dependent manner. In addition, Cirsium japonicum flavones increased the expression of PPARγ target genes, such as adiponectin and glucose transporter 4 (GLUT4), and enhanced the translocation of intracellular GLUT4 to the plasma membrane. In mature 3T3-L1 adipocytes, Cirsium japonicum flavones significantly enhanced the basal and insulin-stimulated glucose uptake. The flavones-induced effects in 3T3-L1 cells were abolished by the PPARγ antagonist, GW9662, and by the phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin. This study suggests that Cirsium japonicum flavones promote adipocyte differentiation and glucose uptake by inducing PPARγ activation and then modulating the insulin signaling pathway in some way, which could benefit diabetes patients.

Novel therapeutics and targets for the treatment of diabetes

The microvascular complications of insufficiently controlled diabetes (neuropathy, retinopathy and nephropathy) and the marked increased risk of macrovascular events (e.g., stroke and myocardial infarction) have a dire impact on society in both human and economic terms. In Type 1 diabetes total β-cell loss occurs. In Type 2 diabetes, partial β-cell loss occurs before diagnosis, and the progressive β-cell loss during the life of the patient increases the severity of the disease. In patients with diabetes, increased insulin resistance in the muscle and liver are key pathophysiologic defects. In addition, defects in metabolic processes in the fat, GI tract, brain, pancreatic α-cells and kidney are detrimental to the overall health of the patient. This review addresses novel therapies for these deficiencies in clinical and preclinical evaluation, emphasizing their potential to address glucose homeostasis, β-cell mass and function, and the comorbidities of cardiovascular disease and obesity.

Regulation of lipid accumulation in 3T3-L1 cells: insulin-independent and combined effects of fatty acids and insulin

The insulin-independent and combined effects of fatty acids (FA; linoleic and oleic acids) and insulin in modulating lipid accumulation and adipogenesis in 3T3-L1 cells was investigated using a novel protocol avoiding the effects of a complex hormone 'induction' mixture. 3T3-L1 cells were cultured in Dulbecco's modified Eagle's medium (DMEM) plus serum (control) or in DMEM plus either 0.3 mmol/l linoleic or oleic acids with 0.3 mmol/l FA-free bovine serum albumin in the presence or absence of insulin. Cells were cultured for 4 to 8 days and cell number, lipid accumulation, peroxisome proliferator-activated receptor-gamma (PPAR-γ) and glucose transporter 4 (GLUT-4) protein expression were determined. Cell number appeared to be decreased in comparison with control cultures. In both oleic acid and linoleic acid-treated cells, notably in the absence (and presence) of insulin, oil-red O stain-positive cells showed abundant lipid. The percentage of cells showing lipid accumulation was greater in FA-treated cultures compared with control cells grown in DMEM plus serum (P < 0.001). Treatment with both linoleic and oleic acid-containing media evoked higher levels of PPAR-γ than observed in control cultures (P < 0.05). GLUT-4 protein also increased in response to treatment with both linoleic and oleic acid-containing media (P < 0.001). Lipid accumulation in 3T3-L1 cells occurs in response to either oleic or linoleic acids independently of the presence of insulin. Both PPAR-γ and GLUT-4 protein expression were stimulated. Both proteins are considered markers of adipogenesis, and these observations suggest that these cells had entered the physiological state broadly accepted as differentiated. Furthermore, 3T3-L1 cells can be induced to accumulate lipid in a serum-free medium supplemented with FA, without the use of induction protocols using complex hormone mixtures. We have demonstrated a novel model for the study of lipid accumulation that will improve the understanding of adipogenesis in adipocyte lineage cells.

Preventive effects of branched-chain amino acid supplementation on the spontaneous development of hepatic preneoplastic lesions in C57BL/KsJ-db/db obese mice

Obesity and its associated disorders, such as non-alcoholic steatohepatitis, increase the risk of hepatocellular carcinoma. Branched-chain amino acids (BCAA), which improve protein malnutrition in patients with liver cirrhosis, reduce the risk of hepatocellular carcinoma in these patients with obesity. In the present study, the effects of BCAA supplementation on the spontaneous development of hepatic premalignant lesions, foci of cellular alteration, in db/db obese mice were examined. Male db/db mice were given a basal diet containing 3.0% of either BCAA or casein, a nitrogen-content-matched control of BCAA, for 36 weeks. On killing the mice, supplementation with BCAA significantly inhibited the development of foci of cellular alteration when compared with casein supplementation by inhibiting cell proliferation, but inducing apoptosis. BCAA supplementation increased the expression levels of peroxisome proliferator-activated receptor-γ, p21(CIP1) and p27(KIP1) messenger RNA and decreased the levels of c-fos and cyclin D1 mRNA in the liver. BCAA supplementation also reduced both the amount of hepatic triglyceride accumulation and the expression of interleukin (IL)-6, IL-1β, IL-18 and tumor necrosis factor-α mRNA in the liver. Increased macrophage infiltration was inhibited and the expression of IL-6, TNF-α, and monocyte chemoattractant protein-1 mRNA in the white adipose tissue were each decreased by BCAA supplementation. BCAA supplementation also reduced adipocyte size while increasing the expression of peroxisome proliferator-activated receptor-α, peroxisome proliferator-activated receptor-γ and adiponectin mRNA in the white adipose tissue compared with casein supplementation. These findings indicate that BCAA supplementation inhibits the early phase of obesity-related liver tumorigenesis by attenuating chronic inflammation in both the liver and white adipose tissue. BCAA supplementation may be useful in the chemoprevention of liver tumorigenesis in obese individuals.

Effect of the PPARG2 Pro12Ala polymorphism and clinical risk factors for diabetes mellitus on HbA1c in the Japanese general population

Background

Although the peroxisome proliferator-activated receptor-γ2 (PPARG2) Pro12Ala gene variant is associated with diabetes mellitus, the associations and interactions of this polymorphism and known clinical risk factors with glycated hemoglobin (HbA1c) remain poorly understood. We investigated if carrying the Ala allele was inversely associated with HbA1c level and examined possible interactions.

Methods

This cross-sectional analysis used data collected from 1281 men and 1356 women aged 40 to 69 years who completed the baseline survey of the Japan Multi-Institutional Collaborative Cohort Study. PPARG2 polymorphism was determined by multiplex polymerase chain reaction (PCR)-based Invader assay. Multiple linear regression and ANCOVA were used to control for confounding variables (age, body mass index [BMI], energy intake, alcohol, smoking, physical activity, and family history of diabetes) and examine possible interactions.

Results

After adjustment, the Ala allele was significantly inversely associated with HbA1c in women but not in men. Older age, BMI, and family history of diabetes were associated with higher HbA1c in both sexes. When stratified by PPARG2 genotype, these associations were observed in subjects with the Pro12Pro genotype but not in Ala allele carriers. A significant interaction of genotype and BMI on HbA1c was observed in women. Older age, BMI, and family history of diabetes were significantly associated with high-normal HbA1c (≥5.7% NGSP), whereas PPARG2 polymorphism was not.

Conclusions

Although PPARG2 Pro12Ala polymorphism might attenuate associations between known risk factors and HbA1c level, it had a small effect on high-normal HbA1c, as compared with clinical risk factors, in the general population.

Update on pparγ and nonalcoholic Fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common initial presentation of obesity and insulin resistance. Uninterrupted progression of hepatic lipid accumulation often leads to fatty liver disease and eventually cirrhosis. Insulin resistance is one of the characteristics of type 2 diabetes. Several types of treatment have been employed against type 2 diabetes some of which ameliorate NAFLD. The frequent line of treatment to improve insulin sensitivity is the use of thiazolidinediones (TZD) which activate the nuclear receptor, peroxisome proliferator activated receptor gamma (Pparγ). Although TZDs are proven to be very effective in promoting insulin sensitivity, its actions on Pparγ have been complicated, specifically on NAFLD. According to studies in different models, Pparγ manifests both beneficial and undesirable effects on NAFLD. This paper will focus on the current knowledge of Pparγ and its effect on NAFLD.

Feasibility of structural modification of retinoid X receptor agonists to separate blood glucose-lowering action from adverse effects: studies in KKA(y) type 2 diabetes model mice

Retinoid X receptor (RXR) agonists are reported to exhibit blood glucose-lowering action owing to peroxisome proliferator-activated receptor (PPAR)/RXR or liver X receptor (LXR)/RXR activation, but may also cause adverse effects such as blood triglyceride elevation. In order to examine the feasibility of separating the glucose-lowering action from the adverse effects, we examined the effects of RXR agonists (NEt-TMN), NEt-3IB, and NEt-3IP, which have different heterodimer-activating patterns, in KKA(y) type 2 diabetes model mice. We found that NEt-3IB induced lower degrees of hepatomegaly and blood triglyceride (TG) elevation than the other RXR agonists, even though all of them showed similar blood glucose-lowering action on repeated administration. These findings indicate that structural modification of RXR agonists is a potentially effective strategy to reduce adverse effects while retaining desired activities.

Fargesin improves lipid and glucose metabolism in 3T3-L1 adipocytes and high-fat diet-induced obese mice

This study examined the effects of fargesin, a neolignan isolated from Magnolia plants, on obesity and insulin resistance and the possible mechanisms involved in these effects in 3T3-L1 adipocytes and high-fat diet (HFD)-induced obese mice. Fargesin promoted the glucose uptake in 3T3-L1 adipocytes. In HFD-induced obese mice, fargesin decreased the body weight gain, white adipose tissue (WAT), and plasma triglyceride, non-esterified fatty acid and glucose levels, and improved the glucose tolerance. Fargesin increased glucose transporter 4 (GLUT4) protein expression and phosphorylation of Akt, AMP-activated protein kinase (AMPK), and acetyl-CoA carboxylase (ACC) in both 3T3-L1 adipocytes and WAT of HFD-induced obese mice. Fargesin also decreased the mRNA expression levels of fatty acid oxidation-related genes, such as peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyltransferase-1 (CPT-1), uncoupling protein-2 (UCP-2) and leptin in WAT. Taken together, the present findings suggest that fargesin improves dyslipidemia and hyperglycemia by activating Akt and AMPK in WAT.

Suppression of PDGF-induced PI3 kinase activity by imatinib promotes adipogenesis and adiponectin secretion

Improved glucose and lipid metabolism is a unique side effect of imatinib therapy in some chronic myeloid leukaemia (CML) patients. We recently reported that plasma levels of adiponectin, an important regulator of insulin sensitivity, are elevated following imatinib therapy in CML patients, which could account for these improved metabolic outcomes. Adiponectin is secreted exclusively from adipocytes, suggesting that imatinib modulates adiponectin levels directly, by transcriptional upregulation of adiponectin in pre-existing adipocytes, and/or indirectly, by stimulating adipogenesis. In this report, we have demonstrated that imatinib promotes adipogenic differentiation of human mesenchymal stromal cells (MSCs), which in turn secrete high-molecular-weight adiponectin. Conversely, imatinib does not stimulate adiponectin secretion from mature adipocytes. We hypothesise that inhibition of PDGFRα (PDGFRA) and PDGFRβ (PDGFRB) is the mechanism by which imatinib promotes adipogenesis. Supporting this, functional blocking antibodies to PDGFR promote adipogenesis and adiponectin secretion in MSC cultures. We have shown that imatinib is a potent inhibitor of PDGF-induced PI3 kinase activation and, using a PI3 kinase p110α-specific inhibitor (PIK-75), we have demonstrated that suppression of this pathway recapitulates the effects of imatinib on MSC differentiation. Furthermore, using mitogens that activate the PI3 kinase pathway, or MSCs expressing constitutively activated Akt, we have shown that activation of the PI3 kinase pathway negates the pro-adipogenic effects of imatinib. Taken together, our results suggest that imatinib increases plasma adiponectin levels by promoting adipogenesis through the suppression of PI3 kinase signalling downstream of PDGFR.

The estrogenic endocrine disrupting chemical bisphenol A (BPA) and obesity

There is increasing experimental and epidemiological evidence that fetal programming of genetic systems is a contributing factor in the recent increase in adult obesity and other components of metabolic syndrome. In particular, there is evidence that epigenetic changes associated with the use of manmade chemicals may interact with other factors that influence fetal and postnatal growth in contributing to the current obesity epidemic. The focus of this review is on the developmental effects of estrogenic endocrine disrupting chemicals (EDCs), and more specifically on effects of exposure to the estrogenic EDC bisphenol A (BPA), on adipocytes and their function, and the ultimate impact on adult obesity; BPA exposure also results in impaired reproductive capacity. We discuss the interaction of EDCs with other factors that impact growth during fetal and neonatal life, such as placental blood flow and nutrient transport to fetuses, and how these influence fetal growth and abnormalities in homeostatic control systems required to maintain normal body weight throughout life.

Determinants of evolving metabolic and cardiovascular benefit/risk profiles of rosiglitazone therapy during the natural history of diabetes: molecular mechanisms in the context of integrated pathophysiology

Rosiglitazone is a thiazolidinedione, a synthetic PPARγ receptor agonist with insulin-sensitizing properties that is used as an antidiabetic drug. In addition to improving glycemic control through actions in metabolic target tissues, rosiglitazone has numerous biological actions that impact on cardiovascular homeostasis. Some of these actions are helpful (e.g., improving endothelial function), whereas others are potentially harmful (e.g., promoting fluid retention). Since cardiovascular morbidity and mortality are major endpoints for diabetes, it is essential to understand how the natural history of diabetes alters the net benefits and risks of rosiglitazone therapy. This complex issue is an important determinant of optimal use of rosiglitazone and is critical for understanding cardiovascular safety issues. We give special attention to the effects of rosiglitazone in diabetic patients with stable coronary artery disease and the impact of rosiglitazone actions on atherosclerosis and plaque instability. This provides a rational conceptual framework for predicting evolving benefit/risk profiles that inform optimal use of rosiglitazone in the clinical setting and help explain the results of recent large clinical intervention trials where rosiglitazone had disappointing cardiovascular outcomes. Thus, in this perspective, we describe what is known about the molecular mechanisms of action of rosiglitazone on cardiovascular targets in the context of the evolving pathophysiology of diabetes over its natural history.

Tumor cell-educated periprostatic adipose tissue acquires an aggressive cancer-promoting secretory profile

BACKGROUND/AIMS

The microenvironment produces important factors that are crucial to prostate cancer (PCa) progression. However, the extent to which the cancer cells stimulate periprostatic adipose tissue (PPAT) to produce these proteins is largely unknown. Our purpose was to determine whether PCa cell-derived factors influence PPAT metabolic activity.

METHODS

Primary cultures of human PPAT samples from PCa patients (adipose tissue organotypic explants and primary stromal vascular fraction, SVF) were stimulated with conditioned medium (CM) collected from prostate carcinoma (PC3) cells. Cultures without CM were used as control. We used multiplex analysis and ELISA for protein quantification, qPCR to determine mitochondrial DNA (mtDNA) copy number and zymography for matrix metalloproteinase activity, in order to evaluate the response of adipose tissue explants and SVFs to PC3 CM.

RESULTS

Stimulation of PPAT explants with PCa PC3 CM induced adipokines associated with cancer progression (osteopontin, tumoral necrosis factor alpha and interleukin-6) and reduced the expression of the protective adipokine adiponectin. Notably, osteopontin protein expression was 13-fold upregulated. Matrix metalloproteinase 9 activity and mitochondrial DNA copy number were higher after stimulation with cancer CM. Stromovascular cells from PPAT in culture were not influenced by tumor-derived factors.

CONCLUSION

The modulation of adipokine expression by tumor CM indicates the pervasive extent to which tumor cells command PPAT to produce factors favorable to their aggressiveness.