Deletion of the androgen receptor in adipose tissue in male mice elevates retinol binding protein 4 and reveals independent effects on visceral fat mass and on glucose homeostasis

Testosterone deficiency is epidemic in obese ageing males with type 2 diabetes, but the direction of causality remains unclear. Testosterone-deficient males and global androgen receptor (AR) knockout mice are insulin resistant with increased fat, but it is unclear whether AR signaling in adipose tissue mediates body fat redistribution and alters glucose homoeostasis. To investigate this, mice with selective knockdown of AR in adipocytes (fARKO) were generated. Male fARKO mice on normal diet had reduced perigonadal fat but were hyperinsulinemic and by age 12 months, were insulin deficient in the absence of obesity. On high-fat diet, fARKO mice had impaired compensatory insulin secretion and hyperglycemia, with increased susceptibility to visceral obesity. Adipokine screening in fARKO mice revealed a selective increase in plasma and intra-adipose retinol binding protein 4 (RBP4) that preceded obesity. AR activation in murine 3T3 adipocytes downregulated RBP4 mRNA. We conclude that AR signaling in adipocytes not only protects against high-fat diet-induced visceral obesity but also regulates insulin action and glucose homeostasis, independently of adiposity. Androgen deficiency in adipocytes in mice resembles human type 2 diabetes, with early insulin resistance and evolving insulin deficiency.

Involvement of the MAPK and PI3K pathways in chitinase 3-like 1-regulated hyperoxia-induced airway epithelial cell death

BACKGROUND

Exposure to 100% oxygen causes hyperoxic acute lung injury characterized by cell death and injury of alveolar epithelial cells. Recently, the role of chitinase 3-like 1 (CHI3L1), a member of the glycosyl hydrolase 18 family that lacks chitinase activity, in oxidative stress was demonstrated in murine models. High levels of serum CHI3L1 have been associated with various diseases of the lung, such as asthma, chronic obstructive pulmonary disease, and cancer. However, the role of CHI3L1 in human airway epithelial cells undergoing oxidative stress remains unknown. In addition, the signaling pathways associated with CHI3L1 in this process are poorly understood.

PURPOSE

In this study, we demonstrate the role of CHI3L1, along with the MAPK and PI3K signaling pathways, in hyperoxia-exposed airway epithelial cells.

METHOD

The human airway epithelial cell line, BEAS-2B, was exposed to >95% oxygen (hyperoxia) for up to 72h. Hyperoxia-induced cell death was determined by assessing cell viability, Annexin-V FITC staining, caspase-3 and -7 expression, and electron microscopy. CHI3L1 knockdown and overexpression studies were conducted in BEAS-2B cells to examine the role of CHI3L1 in hyperoxia-induced apoptosis. Activation of the MAPK and PI3K pathways was also investigated to determine the role of these signaling cascades in this process.

RESULTS

Hyperoxia exposure increased CHI3L1 expression and apoptosis in a time-dependent manner. CHI3L1 knockdown protected cells from hyperoxia-induced apoptosis. In contrast, CHI3L1 overexpression promoted cell death after hyperoxia exposure. Finally, phosphorylation of ERK1/2, p38, and Akt were affected by CHI3L1 knockdown.

CONCLUSION

This study indicates that CHI3L1 is involved in hyperoxia-induced cell death, suggesting that CHI3L1 may be one of several cell death regulators influencing the MAPK and PI3K pathways during oxidative stress in human airway epithelial cells.

Genetic polymorphisms in adipokine genes and the risk of obesity: a systematic review and meta-analysis

Polymorphisms in adipokine genes, such as leptin (LEP), leptin receptor (LEPR), resistin (RETN), adiponectin (ADIPOQ), interleukin-1β (IL-1β), IL-6 (IL-6), and tumor necrosis factor-α (TNF-α) may be involved in the development of obesity. We conducted a systematic review of published evidence on the association between different adipokine genes and the risk of obesity. Librarian-designed searches of PubMed and HuGeNet, review of reference lists from published reviews and content expert advice identified potentially eligible studies. The genotyping information and polymorphisms of different adipokine genes, numbers of genotyped cases and controls and frequencies of genotypes were extracted from 48 eligible studies included in this review. Twenty-one polymorphisms each associated with obesity in at least one study were identified. Polymorphisms in the adipokine genes, LEP, LEPR, and RETN were not associated with obesity susceptibility, whereas ADIPOQ G276T (T vs. G: odds ratio (OR), 1.59; 95% confidence interval (CI), 1.39-1.81), IL-1β C3953T (CC vs. CT+TT: OR, 1.61; 95% CI, 1.18-2.20), and TNF-α G308A (GG vs. GA+AA: OR, 1.19; 95% CI, 1.02-1.39) polymorphisms were associated with an increased risk of obesity. The IL-6 G174C polymorphism was also associated obesity when using allelic comparisons, the recessive genetic model and the dominant genetic model with OR (95% CI) of 1.95 (1.37-2.77), 1.44 (1.15-1.80), and 1.36 (1.16-1.59), respectively. No significant evidence of publication bias was present. However, these "null" results were underpowered due to a small pooled sample size, and analysis of additional case-control studies with larger sample sizes should provide further clarifications.

[The role of feeding behaviour hormones in the development of cholelithiasis]

THE PURPOSE. To analyze the possible association between gallstone disease (GSD), and some adipokine: leptin, adiponectin, ghrelin, resistin, kaheksin (TNFalpha), visfatin. RECENT EVIDENCE IN THE LITERATURE. The prevalence of GSD increases by a factor not so much with age (in women - 6.0%, 7.9%, 8.5% and 18.6%, respectively, four age decade from 25 to 64 years - according to the epidemiological study in the frame of the WHO "Monica" in Novosibirsk in 1994-1995 years), but with metabolic disorders: GSD diagnosed in 17.6% in diabetes mellitus, in obesity III-IV degree - up to 100%. Leptin regulates the expression of genes responsible for the pathogenesis of cholesterol GSD -cholecystokinin receptor gene A, acetylcholine receptor beta2, Ca-calmodulin-dependent protein kinase, mucin3, carboxylesterazy, HMG-CoA reductase. Was found negative correlation of GSD with adiponectin levels and positive - with visfatin levels. Elevated ghrelin levels performs protective role to GSD (OR = 0,27, p = 0,02). In the analysis of GSD-associated regions on chromosome 1 p, genes TNFR2 receptor and TNFRSF1B included in a number of positional candidate genes.

Identification of BMP and activin membrane-bound inhibitor (BAMBI) as a potent negative regulator of adipogenesis and modulator of autocrine/paracrine adipogenic factors

Adipose tissue dysfunction underpins the association of obesity with type 2 diabetes. Adipogenesis is required for the maintenance of adipose tissue function. It involves the commitment and subsequent differentiation of preadipocytes and is coordinated by autocrine, paracrine, and endocrine factors. We previously reported that fibroblast growth factor-1 (FGF-1) primes primary human preadipocytes and Simpson Golabi Behmel syndrome (SGBS) preadipocytes and increases adipogenesis through a cascade involving extracellular signal-related kinase 1/2 (ERK1/2). Here, we aimed to use the FGF-1 system to identify novel adipogenic regulators. Expression profiling revealed bone morphogenetic protein (BMP) and activin membrane-bound inhibitor (BAMBI) as a putative FGF-1 effector. BAMBI is a transmembrane protein and modulator of paracrine factors that regulate adipogenesis, including transforming growth factor (TGF) superfamily members (TGF-β and BMP) and Wnt. Functional investigations established BAMBI as a negative regulator of adipogenesis and modulator of the anti- and proadipogenic effects of Wnt3a, TGF-β1, and BMP-4. Further studies showed that BAMBI expression levels are decreased in a mouse model of diet-induced obesity. Collectively, these findings establish BAMBI as a novel, negative regulator of adipogenesis that can act as a nexus to integrate multiple paracrine signals to coordinate adipogenesis. Alterations in BAMBI may play a role in the (patho)physiology of obesity, and manipulation of BAMBI may present a novel therapeutic approach to improve adipose tissue function.

The chitinase-like protein YKL-40 modulates cystic fibrosis lung disease

The chitinase-like protein YKL-40 was found to be increased in patients with severe asthma and chronic obstructive pulmonary disease (COPD), two disease conditions featuring neutrophilic infiltrates. Based on these studies and a previous report indicating that neutrophils secrete YKL-40, we hypothesized that YKL-40 plays a key role in cystic fibrosis (CF) lung disease, a prototypic neutrophilic disease. The aim of this study was (i) to analyze YKL-40 levels in human and murine CF lung disease and (ii) to investigate whether YKL-40 single-nucleotide polymorphisms (SNPs) modulate CF lung disease severity. YKL-40 protein levels were quantified in serum and sputum supernatants from CF patients and control individuals. Levels of the murine homologue BRP-39 were analyzed in airway fluids from CF-like βENaC-Tg mice. YKL-40SNPs were analyzed in CF patients. YKL-40 levels were increased in sputum supernatants and in serum from CF patients compared to healthy control individuals. Within CF patients, YKL-40 levels were higher in sputum than in serum. BRP-39 levels were increased in airways fluids from βENaC-Tg mice compared to wild-type littermates. In both CF patients and βENaC-Tg mice, YKL-40/BRP-39 airway levels correlated with the severity of pulmonary obstruction. Two YKL-40 SNPs (rs871799 and rs880633) were found to modulate age-adjusted lung function in CF patients. YKL-40/BRP-39 levelsare increased in human and murine CF airway fluids, correlate with pulmonary function and modulate CF lung disease severity genetically. These findings suggest YKL-40 as a potential biomarker in CF lung disease.

Overexpression of chitinase 3-like 1/YKL-40 in lung-specific IL-18-transgenic mice, smokers and COPD

We analyzed the lung mRNA expression profiles of a murine model of COPD developed using a lung-specific IL-18-transgenic mouse. In this transgenic mouse, the expression of 608 genes was found to vary more than 2-fold in comparison with control WT mice, and was clustered into 4 groups. The expression of 140 genes was constitutively increased at all ages, 215 genes increased gradually with aging, 171 genes decreased gradually with aging, and 82 genes decreased temporarily at 9 weeks of age. Interestingly, the levels of mRNA for the chitinase-related genes chitinase 3-like 1 (Chi3l1), Chi3l3, and acidic mammalian chitinase (AMCase) were significantly higher in the lungs of transgenic mice than in control mice. The level of Chi3l1 protein increased significantly with aging in the lungs and sera of IL-18 transgenic, but not WT mice. Previous studies have suggested Chi3l3 and AMCase are IL-13-driven chitinase-like proteins. However, IL-13 gene deletion did not reduce the level of Chi3l1 protein in the lungs of IL-18 transgenic mice. Based on our murine model gene expression data, we analyzed the protein level of YKL-40, the human homolog of Chi3l1, in sera of smokers and COPD patients. Sixteen COPD patients had undergone high resolution computed tomography (HRCT) examination. Emphysema was assessed by using a density mask with a cutoff of -950 Hounsfield units to calculate the low-attenuation area percentage (LAA%). We observed significantly higher serum levels in samples from 28 smokers and 45 COPD patients compared to 30 non-smokers. In COPD patients, there was a significant negative correlation between serum level of YKL-40 and %FEV(1). Moreover, there was a significant positive correlation between the serum levels of YKL-40 and LAA% in COPD patients. Thus our results suggest that chitinase-related genes may play an important role in establishing pulmonary inflammation and emphysematous changes in smokers and COPD patients.

Hormonal mechanisms underlying the relationship between obesity and breast cancer

Given the worldwide epidemic of obesity, it is inevitably an increasingly common comorbidity for women who develop breast cancer; therefore, it is critical to understand its impact on this disease. This review focuses on the influence of obesity on breast cancer development and progression and describes the hormonal factors that may underlie the observations, with particular emphasis on the roles of estrogen, insulin/insulin-like growth factor axis, and adipokines.

Molecular cloning, tissue distribution and ontogenetic expression of Xiang pig chemerin and its involvement in regulating energy metabolism through Akt and ERK1/2 signaling pathways

Chemerin, as a new member of adipokines family, is highly expressed in adipose tissue in rodent and its expression increases with obesity. Moreover, chemerin has been reported to have significant relationship with metabolic syndrome and insulin sensitivity. Here, the gene encoding chemerin from Xiang pig was cloned. The open reading frame of this cDNA encodes 163 deduced amino acid residues. The putative protein has a N-terminal signaling peptide and a nuclear localization signal profile which are highly conserved among the vertebrate orthologs. Both chemerin and chemerinR are highly expressed in lung, kidney and small intestine in adult Xiang pig. Besides these tissues, chemerin is abundant in liver and backfat, and chemerinR is abundant in spleen and skeletal muscle. We also investigated the age-dependent expression of chemerin in suckling Xiang piglets in various tissues, which showed an interaction between age and segments in abundance of chemerin and chemerinR from day 1 to day 21. For chemerinR, it was abundant in skeletal muscle of both adult and fetal Xiang pig. Further, we treated differentiated C2C12 cells with chemerin. The result showed that chemerin regulated energy metabolism partly through Akt and ERK1/2 signaling pathway. Taken together, our findings provide basic molecular information for the deeper investigation on the function of chemerin.

The adipokine zinc-α2-glycoprotein activates AMP kinase in human primary skeletal muscle cells

CONTEXT

Zinc-α2-glycoprotein (ZAG) induces lipid mobilization in adipose tissue (AT) and stimulates energy utilization in AT and skeletal muscle by up-regulation of UCP isoforms and GLUT4.

OBJECTIVE

Our study aimed to investigate whether ZAG activates AMPKα, an important regulator of energy metabolism, in human skeletal muscle cells (SkMc).

MATERIALS AND METHODS

SkMc were treated with recombinant ZAG, and activation of AMPKα and ACC, protein abundance of GLUT4, and UCP2 and UCP3 gene expression were analysed.

RESULTS

Treatment of SkMc with ZAG induced short-time phosphorylation of AMPKα and ACC. Furthermore, AMPKα phosphorylation was elevated after 24 h, while for ACC no activation was observed. GLUT4 level was increased by 1.3-fold. However, UCP2 and UCP3 expression remained unaltered.

DISCUSSION AND CONCLUSION

These results show that ZAG leads to phosphorylation of AMPKα and ACC, thereby activating a pathway central to the regulation of energy metabolism. This mechanism may be involved in mediating the effects of ZAG in relation to increased energy utilization.

The effect of very-low-calorie diet on mRNA expression of inflammation-related genes in subcutaneous adipose tissue and peripheral monocytes of obese patients with type 2 diabetes mellitus

CONTEXT

Low-grade inflammation links obesity, type 2 diabetes mellitus (T2DM), and cardiovascular diseases.

OBJECTIVE

To explore the expression profile of genes involved in inflammatory pathways in adipose tissue and peripheral monocytes (PM) of obese patients with and without T2DM at baseline and after dietary intervention.

DESIGN

Two-week intervention study with very-low-calorie diet (VLCD).

SETTING

University hospital.

PATIENTS

Twelve obese females with T2DM, 8 obese nondiabetic females (OB) and 15 healthy age-matched females.

INTERVENTION

Two weeks of VLCD (2500 kJ/d).

MAIN OUTCOME MEASURES

Metabolic parameters, circulating cytokines, hormones, and mRNA expression of 39 genes in sc adipose tissue (SCAT) and PM.

RESULTS

Both T2DM and OB group had significantly increased serum concentrations of circulating proinflammatory factors (C-reactive protein, TNFα, IL-6, IL-8), mRNA expression of macrophage antigen CD68 and proinflammatory chemokines (CCL-2, -3, -7, -8, -17, -22) in SCAT and complementary chemokine receptors (CCR-1, -2, -3, -5) and other proinflammatory receptors (toll-like receptor 2 and 4, TNF receptor superfamily 1A and 1B, IL-6R) in PM, with OB group showing less pronounced chemoattracting and proinflammatory profile compared to T2DM group. In T2DM patients VLCD decreased body weight, improved metabolic profile, and decreased mRNA expression of up-regulated CCRs in PM and chemokines [CCL 8, chemokine (C-X-C motif) ligand 10] in SCAT. VLCD markedly increased mRNA expression of T-lymphocyte attracting chemokine CCL-17 in SCAT.

CONCLUSION

Obese patients with and without T2DM have increased mRNA expression of chemotactic and proinflammatory factors in SCAT and expression of corresponding receptors in PM. Two weeks of VLCD significantly improved this profile in T2DM patients.

Exposure to an organometal compound stimulates adipokine and cytokine expression in white adipose tissue

OBJECTIVE

White adipose tissue (WAT) is now considered a defined tissue capable of interactions with other organ systems. WAT role in elevating the level of systemic chronic inflammation suggests that alterations in this tissue as the result of disease or environmental factors may influence the development and progression of various obesity-related pathologies. This study investigated WAT cell-specific responses to an organometal compound, trimethyltin (TMT), to determine possible contribution to induced inflammation.

METHODS

Human primary mature adipocytes and macrophage differentiated THP-1 cells were cultured in TMT presence and relative toxicities and different adipokine levels were determined. The inflammatory response was examined in TMT presence for primary cells from obese ob/ob mice WAT, and after TMT injection in ob/ob mice.

RESULTS

Both adipocytes and macrophages were resistant to cell death induced by TMT. However, adipocytes cultured in TMT presence showed increased expression of TNFα and IL-6, and modified leptin levels. In macrophage cultures, TMT also increased TNFα and IL-6, while MCP-1 and MIP-1α were decreased. In vivo, a single injection of TMT in ob/ob mice, elevated TNFα, MIP-1α and adiponectin in WAT.

CONCLUSIONS

Elevation of the inflammatory related products can be induced by chemical exposure in adipocytes and macrophages, as well as murine WAT. These data suggest that numerous factors, including a systemic chemical exposure, can induce an inflammatory response from the WAT. Furthermore, when characterizing both chemical-induced toxicity and the progression of the chronic inflammation associated with elevated WAT content, such responses in this target tissue should be taken into consideration.

Obesity related kidney disease

Obesity is a risk factor for both de novo disease and as a complication of existing chronic kidney disease. Obesity related disease is characterized by albuminuria, glomerulomegaly and secondary focal glomerulosclerosis. Traditionally altered renal hemodynamics causing hyperfiltration and upregulated renin angiotensin system have been associated with these changes. Recently identified circulating factors produced by fat stores such as adiponectin, leptin and inflammatory markers have shown to directly affect the cells in the renal glomeruli and cause pathological changes. Weight loss, blockade of the renin angiotensin system and restoration of adipokine levels may be beneficial to ameliorate the progression of obesity related disease.

Epicardial fat gene expression after aerobic exercise training in pigs with coronary atherosclerosis: relationship to visceral and subcutaneous fat

Epicardial adipose tissue (EAT) is contiguous with coronary arteries and myocardium and potentially may play a role in coronary atherosclerosis (CAD). Exercise is known to improve cardiovascular disease risk factors. The purpose of this study was to investigate the effect of aerobic exercise training on the expression of 18 genes, measured by RT-PCR and selected for their role in chronic inflammation, oxidative stress, and adipocyte metabolism, in peri-coronary epicardial (cEAT), peri-myocardial epicardial (mEAT), visceral abdominal (VAT), and subcutaneous (SAT) adipose tissues from a castrate male pig model of familial hypercholesterolemia with CAD. We tested the hypothesis that aerobic exercise training for 16 wk would reduce the inflammatory profile of mRNAs in both components of EAT and VAT but would have little effect on SAT. Exercise increased mEAT and total heart weights. EAT and heart weights were directly correlated. Compared with sedentary pigs matched for body weight to exercised animals, aerobic exercise training reduced the inflammatory response in mEAT but not cEAT, had no effect on inflammatory genes but preferentially decreased expression of adiponectin and other adipocyte-specific genes in VAT, and had no effect in SAT except that IL-6 mRNA went down and VEGFa mRNA went up. We conclude that 1) EAT is not homogeneous in its inflammatory response to aerobic exercise training, 2) cEAT around CAD remains proinflammatory after chronic exercise, 3) cEAT and VAT share similar inflammatory expression profiles but different metabolic mRNA responses to exercise, and 4) gene expression in SAT cannot be extrapolated to VAT and heart adipose tissues in exercise intervention studies.

Cinnamon extract regulates glucose transporter and insulin-signaling gene expression in mouse adipocytes

Cinnamon extracts (CE) are reported to have beneficial effects on people with normal and impaired glucose tolerance, the metabolic syndrome, type 2 diabetes, and insulin resistance. However, clinical results are controversial. Molecular characterization of CE effects is limited. This study investigated the effects of CE on gene expression in cultured mouse adipocytes. Water-soluble CE was prepared from ground cinnamon (Cinnamomum burmannii). Quantitative real-time PCR was used to investigate CE effects on the expression of genes coding for adipokines, glucose transporter (GLUT) family, and insulin-signaling components in mouse 3T3-L1 adipocytes. CE (100 μg/ml) increased GLUT1 mRNA levels 1.91±0.15, 4.39±0.78, and 6.98±2.18-fold of the control after 2-, 4-, and 16-h treatments, respectively. CE decreased the expression of further genes encoding insulin-signaling pathway proteins including GSK3B, IGF1R, IGF2R, and PIK3R1. This study indicates that CE regulates the expression of multiple genes in adipocytes and this regulation could contribute to the potential health benefits of CE.

Human epicardial adipokine messenger RNAs: comparisons of their expression in substernal, subcutaneous, and omental fat

We compared the gene expression of inflammatory and other proteins by real-time quantitative polymerase chain reaction in epicardial, substernal (mediastinal) and subcutaneous sternal, upper abdominal, and leg fat from coronary bypass patients and omental (visceral) fat from extremely obese women undergoing bariatric surgery. We hypothesized that (1) epicardial fat would exhibit higher expression of inflammatory messenger RNAs (mRNAs) than substernal and subcutaneous fat and (2) epicardial mRNAs would be similar to those in omental fat. Epicardial fat was clearly different from substernal fat because there was a far higher expression of haptoglobin, prostaglandin D(2) synthase, nerve growth factor beta, the soluble vascular endothelial growth factor receptor (FLT1), and alpha1 glycoprotein but not of inflammatory adipokines such as monocyte chemoattractant protein-1, interleukin (IL)-8, IL-1beta, tumor necrosis factor alpha, serum amyloid A, plasminogen activator inhibitor-1, or adiponectin despite underlying coronary atherosclerosis. However, the latter inflammatory adipokines as well as most other mRNAs were overexpressed in epicardial fat as compared with the subcutaneous depots except for IL-8, fatty acid binding protein 4, the angiotensin II receptor 1, IL-6, and superoxide dismutase-2. Relative to omental fat, about one third of the genes were expressed at the same levels, whereas monocyte chemoattractant protein-1, cyclooxygenase-2, plasminogen activator inhibitor-1, IL-1beta, and IL-6 were expressed at far lower levels in epicardial fat. In conclusion, epicardial fat does not appear to be a potentially more important source of inflammatory adipokines than substernal mediastinal fat. Furthermore, the expression of inflammatory cytokines such as IL-6 and IL-1beta is actually higher in omental fat from obese women without coronary atherosclerosis. The data do not support the hypothesis that most of the inflammatory adipokines are expressed at high levels in epicardial fat of humans.

Insulin-sensitive obesity

The association between obesity and impaired insulin sensitivity has long been recognized, although a subgroup of obese individuals seems to be protected from insulin resistance. In this study, we systematically studied differences in adipose tissue biology between insulin-sensitive (IS) and insulin-resistant (IR) individuals with morbid obesity. On the basis of glucose infusion rate during euglycemic hyperinsulinemic clamps, 60 individuals with a BMI of 45 +/- 1.3 kg/m(2) were divided into an IS and IR group matched for age, sex, and body fat prior to elective surgery. We measured fat distribution, circulating adipokines, and parameters of inflammation, glucose, and lipid metabolism and characterized adipose tissue morphology, function, and mRNA expression in abdominal subcutaneous (sc) and omental fat. IS compared with IR obese individuals have significantly lower visceral fat area (138 +/- 27 vs. 316 +/- 91 cm(2)), number of macrophages in omental adipose tissue (4.9 +/- 0.8 vs. 13.2 +/- 1.4%), mean omental adipocyte size (528 +/- 76 vs. 715 +/- 81 pl), circulating C-reactive protein, progranulin, chemerin, and retinol-binding protein-4 (all P values <0.05), and higher serum adiponectin (6.9 +/- 3.4 vs. 3.4 +/- 1.7 ng/ml) and omental adipocyte insulin sensitivity (all P values <0.01). The strongest predictors of insulin sensitivity by far were macrophage infiltration together with circulating adiponectin (r(2) = 0.98, P < 0.0001). In conclusion, independently of total body fat mass, increased visceral fat accumulation and adipose tissue dysfunction are associated with IR obesity. This suggests that mechanisms beyond a positive caloric balance such as inflammation and adipokine release determine the pathological metabolic consequences in patients with obesity.

Cloning, expression analysis, and regulatory mechanisms of bovine chemerin and chemerin receptor

Recently, we reported that chemerin, a new adipokine, is highly expressed in the adipose tissue, up-regulated during adipocyte differentiation, and regulates adipogenesis via its own receptor in mice. The objectives of this study were to clone chemerin and its receptor from the adipose tissues of Japanese Black cattle and to investigate the expression of these genes in 16 different tissues. We compared the gene expression of chemerin and its receptor between adipocytes and stromal-vascular (S-V) cells (non-adipocytes) prepared from subcutaneous adipose tissue. In addition, we investigated the mRNA expression levels of chemerin and its receptor in bovine differentiated adipocytes. The DNA sequences of bovine chemerin and its receptor were determined, and they were found to be highly homologous to those of humans, mice, and pigs. The amino acid sequences predicted for the full-length cDNA of bovine chemerin and its receptor were also similar to those of humans, mice, and pigs, suggesting that these genes have similar functions. Bovine chemerin mRNA was highly expressed in the adipose and liver tissues, and the transcripts of chemerin receptor were widely expressed in several tissues including adipose, muscle, liver, and brain tissues. The expression of bovine chemerin mRNA was higher in adipocytes than in S-V cells prepared from adipose tissue. The transcripts of chemerin and its receptor were up-regulated during adipocyte differentiation. Treatment with tumor necrosis factor (TNF)-alpha (10 ng/mL) in bovine differentiated adipocytes increased the mRNA expression of chemerin and its receptor. These results indicate that chemerin, a new adipokine highly expressed in the adipocytes of bovine adipose tissue, is the TNF-alpha-up-regulated gene with a role in adipogenesis.

Vitamin C inhibits leptin secretion and some glucose/lipid metabolic pathways in primary rat adipocytes

Antioxidant-based treatments are emerging as an interesting approach to possibly counteract obesity fat accumulation complications, since this is accompanied by an increased systemic oxidative stress. The aim of this study was to analyze specific metabolic effects of vitamin C (VC) on epididymal primary rat adipocytes. Cells were isolated and incubated for 72 h in culture medium, in the absence or presence of 1.6 nM insulin, within a range of VC concentrations (5-1000 microM). Glucose- and lipid-related variables as well as the secretion/expression patterns of several obesity-related genes were assessed. It was observed that VC dose dependently inhibited glucose uptake and lactate production, and also reduced glycerol release in both control and insulin-treated cells. Also, VC caused a dramatic concentration-dependent fall in leptin secretion especially in insulin-stimulated cells. In addition, VC (200 microM) induced Cdkn1a and Casp8, partially inhibited Irs3, and together with insulin drastically reduced Gpdh (listed as Gpd1 in the MGI database) gene expressions. Finally, VC and insulin down-regulatory effects were observed on extracellular and intracellular reactive oxygen species production respectively. In summary, this experimental assay describes a specific effect of VC in isolated rat adipocytes on glucose and fat metabolism, and on the secretion/expression of important obesity-related proteins.

Weight loss after gastric bypass surgery in women is followed by a metabolically favorable decrease in 11beta-hydroxysteroid dehydrogenase 1 expression in subcutaneous adipose tissue

BACKGROUND AND AIMS

The role of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) in the pathogenesis of obesity has been elucidated in humans and in various rodent models. Obesity is accompanied by disturbances in glucocorticoid metabolism, circulating adipokine levels, and fatty acid (FA) reesterification. This study was undertaken to evaluate glucocorticoid metabolism in sc fat before and after weight loss and to explore putative associations between 11beta-HSD1 and leptin, adiponectin, and FA recycling.

SUBJECTS AND METHODS

Twenty-seven obese (mean body mass index 44.4 + or - 4.4 kg/m(2)) women underwent gastric bypass surgery. Subcutaneous fat biopsies were collected before and 2 yr after surgery. The expression of 11beta-HSD1, leptin, adiponectin, and phosphoenolpyruvate carboxykinase (PEPCK) mRNA was evaluated with real-time PCR. Serum leptin and adiponectin protein levels were estimated by ELISA.

RESULTS

Two years after gastric bypass surgery, significant reductions were observed in the mean body mass index (from 44.4 to 30.8 kg/m(2)) and mean waist circumference (from 121.9 to 90.6 cm). After weight loss, 11beta-HSD1 mRNA expression decreased 4-fold (P < 0.001). Both leptin and adiponectin mRNA expression decreased, with concomitantly decreased circulating leptin and increased circulating adiponectin levels. PEPCK mRNA expression did not change.

CONCLUSION

Weight loss after gastric bypass surgery was followed by metabolically favorable changes in insulin sensitivity, circulating leptin and adiponectin, and peripheral glucocorticoid metabolism. A significant reduction in 11beta-HSD1 expression was observed in sc adipose tissue after weight loss. This suggests that up-regulation of 11beta-HSD1 is a consequence, rather than a cause, of obesity.

Identification of nesfatin-1 in human and murine adipose tissue: a novel depot-specific adipokine with increased levels in obesity

Nesfatin-1 is a recently identified anorexigenic peptide derived from its precursor protein, nonesterified fatty acid/nucleobindin 2 (NUCB2). Although the hypothalamus is pivotal for the maintenance of energy homeostasis, adipose tissue plays an important role in the integration of metabolic activity and energy balance by communicating with peripheral organs and the brain via adipokines. Currently no data exist on nesfatin-1 expression, regulation, and secretion in adipose tissue. We therefore investigated NUCB2/nesfatin-1 gene and protein expression in human and murine adipose tissue depots. Additionally, the effects of insulin, dexamethasone, and inflammatory cytokines and the impact of food deprivation and obesity on nesfatin-1 expression were studied by quantitative RT-PCR and Western blotting. We present data showing NUCB2 mRNA (P < 0.001), nesfatin-1 intracellular protein (P < 0.001), and secretion (P < 0.01) were significantly higher in sc adipose tissue compared with other depots. Also, nesfatin-1 protein expression was significantly increased in high-fat-fed mice (P < 0.01) and reduced under food deprivation (P < 0.01) compared with controls. Stimulation of sc adipose tissue explants with inflammatory cytokines (TNFalpha and IL-6), insulin, and dexamethasone resulted in a marked increase in intracellular nesfatin-1 levels. Furthermore, we present evidence that the secretion of nesfatin-1 into the culture media was dramatically increased during the differentiation of 3T3-L1 preadipocytes into adipocytes (P < 0.001) and after treatments with TNF-alpha, IL-6, insulin, and dexamethasone (P < 0.01). In addition, circulating nesfatin-1 levels were higher in high-fat-fed mice (P < 0.05) and showed positive correlation with body mass index in human. We report that nesfatin-1 is a novel depot specific adipokine preferentially produced by sc tissue, with obesity- and food deprivation-regulated expression.

Coffee and caffeine ameliorate hyperglycemia, fatty liver, and inflammatory adipocytokine expression in spontaneously diabetic KK-Ay mice

Epidemiological surveys have demonstrated that habitual coffee consumption reduces the risk of type 2 diabetes. The aim of this work was to study the antidiabetic effect of coffee and caffeine in spontaneously diabetic KK-A(y) mice. KK-A(y) mice were given regular drinking water (controls) or 2-fold diluted coffee for 5 weeks. Coffee ingestion ameliorated the development of hyperglycemia and improved insulin sensitivity. White adipose tissue mRNA levels of inflammatory cytokines (MCP-1, IL-6, and TNFalpha), adipose tissue MCP-1 concentration, and serum IL-6 concentration in the coffee group were lower than the control group. Moreover, coffee ingestion improved the fatty liver. Caffeine ingestion as drinking water also caused an amelioration of hyperglycemia and an improvement of fatty liver. These results suggest that coffee exerts a suppressive effect on hyperglycemia by improving insulin sensitivity, partly due to reducing inflammatory cytokine expression and improving fatty liver. Moreover, caffeine may be one of the effective antidiabetic compounds in coffee.

Plasma adipokines, bone mass, and hip geometry in rural Chinese adolescents

CONTEXT

Adipokines have been linked to bone phenotypes recently, but with conflicting results. Few such studies have been conducted in adolescents.

OBJECTIVE

The aim of the study was to examine the associations of adiponectin and leptin with multiple bone phenotypes in Chinese adolescents and estimate the genetic contribution to these associations.

DESIGN AND SETTING

This was a cross-sectional study conducted in rural China.

PARTICIPANTS

A total of 675 males and 575 females aged 13-21 yr were included.

OUTCOME MEASURES

Fat mass (FM), lean mass (LM), bone area (BA), bone mineral content (BMC), cross-sectional area (CSA), and section modulus (SM) were measured by dual-energy x-ray absorptiometry. Plasma adipokine concentration was determined using sandwich immunoassays.

RESULTS

Adiponectin was inversely associated with all BMCs in males (P < 0.01), but not in females, after adjusting for LM, body weight, or BMI singly, or for LM and FM simultaneously. No such relationships were observed for CSA or SM in both genders. Leptin was inversely associated with all BAs, total-hip BMC, CSA, and SM in both genders, when adjusting for body weight or BMI. These associations, except for whole-body BA and lumbar spine BA in females, disappeared when simultaneously adjusting for LM and FM. By Cholesky decomposition models using twin design, significant genetic correlations were detected between adiponectin and total-hip BMC in males and between leptin and total-hip BMC in both genders.

CONCLUSIONS

We demonstrated that adiponectin and leptin were inversely associated with adolescent bone phenotypes but showed differential associations by gender, type of bone phenotypes, and adjustment of FM. This study also suggested that adipokines and bone phenotypes may share a common set of genes.

Cinnamon extract regulates plasma levels of adipose-derived factors and expression of multiple genes related to carbohydrate metabolism and lipogenesis in adipose tissue of fructose-fed rats

We reported earlier that dietary cinnamon extract (CE) improves systemic insulin sensitivity and dyslipidemia by enhancing insulin signaling. In the present study, we have examined the effects of CE on several biomarkers including plasma levels of adipose-derived adipokines, and the potential molecular mechanisms of CE in epididymal adipose tissue (EAT). In Wistar rats fed a high-fructose diet (HFD) to induce insulin resistance, supplementation with a CE (Cinnulin PF, 50 mg/kg daily) for 8 weeks reduced blood glucose, plasma insulin, triglycerides, total cholesterol, chylomicron-apoB48, VLDL-apoB100, and soluble CD36. CE also inhibited plasma retinol binding protein 4 (RBP4) and fatty acid binding protein 4 (FABP4) levels. CE-induced increases in plasma adiponectin were not significant. CE did not affect food intake, bodyweight, and EAT weight. In EAT, there were increases in the insulin receptor ( IR) and IR substrate 2 ( IRS2) mRNA, but CE-induced increases in mRNA expression of IRS1, phosphoinositide-3-kinase, AKT1, glucose transporters 1 and 4 , and glycogen synthase 1 expression and decreased trends in mRNA expression of glycogen synthase kinase 3beta were not statistically significant. CE also enhanced the mRNA levels of ADIPOQ, and inhibited sterol regulatory element binding protein-1c mRNA levels. mRNA and protein levels of fatty acid synthase and FABP4 were inhibited by CE and RBP4, and CD36 protein levels were also decreased by CE. These results suggest that CE effectively ameliorates circulating levels of adipokines partially mediated via regulation of the expression of multiple genes involved in insulin sensitivity and lipogenesis in the EAT.

Maternal parity and its effect on adipose tissue deposition and endocrine sensitivity in the postnatal sheep

Maternal parity influences size at birth, postnatal growth and body composition with firstborn infants being more likely to be smaller with increased fat mass, suggesting that adiposity is set in early life. The precise effect of parity on fat mass and its endocrine sensitivity remains unclear and was, therefore, investigated in the present study. We utilised an established sheep model in which perirenal-abdominal fat mass (the major fat depot in the neonatal sheep) increases approximately 10-fold over the first month of life and focussed on the impact of parity on glucocorticoid sensitivity and adipokine expression in the adipocyte. Twin-bearing sheep of similar body weight and adiposity that consumed identical diets were utilised, and maternal blood samples were taken at 130 days of gestation. One offspring from each twin pair was sampled at 1 day of age, coincident with the time of maximal recruitment of uncoupling protein 1 (UCP1), whilst its sibling was sampled at 1 month, when UCP1 had disappeared. Plasma leptin was lower in nulliparous mothers than in multiparous mothers, and offspring of nulliparous mothers possessed more adipose tissue with increased mRNA abundance of leptin, glucocorticoid receptor and UCP2, adaptations that persisted up to 1 month of age when gene expression for interleukin-6 and adiponectin was also raised. The increase in fat mass associated with firstborn status is therefore accompanied by a resetting of the leptin and glucocorticoid axis within the adipocyte. Our findings emphasise the importance of parity in determining adipose tissue development and that firstborn offspring have an increased capacity for adipogenesis which may be critical in determining later adiposity.

Expression of adipokines and estrogen receptors in adipose tissue and placenta of patients with gestational diabetes mellitus

The purpose of this study was to assess the expression profile of genes with potential role in the development of insulin resistance (adipokines, cytokines/chemokines, estrogen receptors) in subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT) and placenta of pregnant women with gestational diabetes mellitus (GDM) and age-matched women with physiological pregnancy at the time of Caesarean section. qRT-PCR was used for expression analysis of the studied genes. Leptin gene expression in VAT of GDM group was significantly higher relative to control group. Gene expressions of interleukin-6 and interleukin-8 were significantly increased, whereas the expressions of genes for estrogen receptors alpha and beta were significantly reduced in SAT of GDM group relative to controls, respectively. We found no significant differences in the expression of any genes of interest (LEP, RETN, ADIPOR1, ADIPOR2, TNF-alpha, CD68, IL-6, IL-8, ER alpha, ER beta) in placentas of women with GDM relative to controls. We conclude that increased expression of leptin in visceral adipose depot together with increased expressions of proinflammatory cytokines and reduced expressions of estrogen receptors in subcutaneous fat may play a role in the etiopathogenesis of GDM.

G1359A polymorphism of the cannabinoid receptor gene (CNR1) and insulin resistance in patients with diabetes mellitus type 2

BACKGROUND

A silent intragenic biallelic polymorphism (1359 G/A) (rs1049353) of the CB1 gene resulting in the substitution of the G to A at nucleotide position 1359 in codon 435 (Thr), was reported as a common polymorphism in Caucasian populations.

OBJECTIVE

The aim of our study was to investigate the influence of the missense polymorphism (G1359A) of CB1 receptor gene on obesity anthropometric parameters, cardiovascular risk factors and adipocytokines in patients with obesity and diabetes mellitus type 2.

DESIGN

A population of 60 naïve diabetic patients was analyzed. An indirect calorimetry, tetrapolar electrical bioimpedance, blood pressure, a serial assessment of nutritional intake with 3 days written food records and biochemical analysis (lipid profile, adipocytokines, insulin, CRP and lipoprotein-a) were performed. The statistical analysis was performed for the combined G1359A and A1359A as a group and wild type G1359G as second group, with a dominant model.

RESULTS

The mean age was 57.44 +/- 11.7 years and the mean BMI 37.84 +/- 6.4, with 14 males and 46 females. Thirty-five patients (58.3%) had genotype G1359G (wild type group) and 25 (42.7%) patients G1359A (mutant type group). Age was similar in both groups (wild type: 56.3 +/- 11.8 years vs mutant group: 58.7 +/- 10 years:ns). Sex distribution was similar in both groups (wild vs mutant type groups), males (22.9% vs 24%) and females (77.1% vs 76%). No differences were detected between groups in anthropometric parameters, cardiovascular risk factors, dietary intake and adipocytokines levels.

CONCLUSION

The finding of this study is the lack of association of G1359A polymorphism of CB receptor 1 gene with obesity, cardiovascular risk factors and adipocytokines.

Circulating and adipose tissue gene expression of zinc-alpha2-glycoprotein in obesity: its relationship with adipokine and lipolytic gene markers in subcutaneous and visceral fat

CONTEXT

Zinc-alpha2-glycoprotein (ZAG) is a soluble protein similar to the class I major histocompatibility complex heavy chain, which has been implicated in lipid catabolism. We hypothesized that ZAG mRNA expression in adipose tissue may be linked with lipolytic and adipokine gene expression and have a close relationship with clinical phenotype.

OBJECTIVES

The objective of the study was to analyze ZAG gene expression in human adipose tissue from lean and obese subjects. ZAG circulating plasma levels and its relationship with cardiometabolic risk factors were also studied.

DESIGN

Seventy-three Caucasian (43 male and 30 female) subjects were included. Plasma and adipose tissue [sc (SAT) and visceral (VAT)] from the same patient were studied. mRNA of PPARgamma, hormone-sensitive lipase (HSL), adipose triglyceride lipase, adiponectin, omentin, visfatin, and ZAG were quantified. Plasma concentrations of ZAG were determined with ELISA.

RESULTS

ZAG plasma levels showed a negative correlation with insulin (r = -0.39; P = 0.008) and the homeostasis model assessment for insulin resistance index (r = -0.36; P = 0.016). No differences in ZAG circulating levels according to body mass index classification were observed. ZAG expression in SAT was significantly reduced in overweight and obese individuals compared with lean subjects (P < 0.001 and P = 0.007, respectively). ZAG mRNA expression in both SAT and VAT depots were negatively correlated with many clinical and metabolic cardiovascular risk factors. After multiple linear regression analysis, SAT ZAG was mainly predicted by adiponectin mRNA expression (B = 0.993; P < 0.0001) and plasma triglyceride levels (B = -0.565; P = 0.006). VAT ZAG expression was predicted by adiponectin expression (B = 0.449; P < 0.0001), and HSL VAT expression (B = 0.180; P = 0.023).

CONCLUSIONS

The present study provides evidence of a role of ZAG gene in adipose tissue metabolism, with a close association with adiponectin gene expression in sc and visceral fat.

Antiobesity effects of yerba maté extract (Ilex paraguariensis) in high-fat diet-induced obese mice

Because the potential of yerba maté (Ilex paraguariensis) has been suggested in the management of obesity, the aim of the present study was to evaluate the effects of yerba maté extract on weight loss, obesity-related biochemical parameters, and the regulation of adipose tissue gene expression in high-fat diet-induced obesity in mice. Thirty animals were randomly assigned to three groups. The mice were introduced to standard or high-fat diets. After 12 weeks on a high-fat diet, mice were randomly assigned according to the treatment (water or yerba maté extract 1.0 g/kg). After treatment intervention, plasma concentrations of total cholesterol, high-density lipoprotein cholesterol, triglyceride, low-density lipoprotein (LDL) cholesterol, and glucose were evaluated. Adipose tissue was examined to determine the mRNA levels of several genes such as tumor necrosis factor-alpha (TNF-alpha), leptin, interleukin-6 (IL-6), C-C motif chemokine ligand-2 (CCL2), CCL receptor-2 (CCR2), angiotensinogen, plasminogen activator inhibitor-1 (PAI-1), adiponectin, resistin, peroxisome proliferator-activated receptor-gamma(2) (PPAR-gamma(2)), uncoupling protein-1 (UCP1), and PPAR-gamma coactivator-1 alpha (PGC-1 alpha). The F4/80 levels were determined by immunoblotting. We found that obese mice treated with yerba maté exhibited marked attenuation of weight gain, adiposity, a decrease in epididymal fat-pad weight, and restoration of the serum levels of cholesterol, triglycerides, LDL cholesterol, and glucose. The gene and protein expression levels were directly regulated by the high-fat diet. After treatment with yerba maté extract, we observed a recovery of the expression levels. In conclusion, our data show that yerba maté extract has potent antiobesity activity in vivo. Additionally, we observed that the treatment had a modulatory effect on the expression of several genes related to obesity.

Influence of Ala54Thr polymorphism of fatty acid-binding protein 2 on histological alterations and insulin resistance of non alcoholic fatty liver disease

A transition G to A at codon 54 of fatty acid binding protein type 2 (FABP2) produces an amino acid substitution (Ala 54 to Thr 54). This amino acid substitution was associated with modifications of insulin resistance, adipokines and insulin concentrations. The aim of this study was to evaluate the influence of Ala54Thr polymorphism in the FABP2 gene on the histological alterations of non-alcoholic fatty liver disease (NAFLD) and insulin resistance. Thirty subjects with the presence of biopsy-proven NAFLD were enrolled for this study. Glucose, Insulin, Insulin resistance (HOMA), total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, resistin, leptin, adiponectin, interleukin-6 and TNF-alfa serum levels were measured at basal time. A tetrapolar bioimpedance, BMI, waist circumference, waist to hip ratio, blood pressure and a prospective serial assessment of nutritional intake with 3 days written food records were examined. Genotype of Ala54Thr FABP2 gene polymorphism was studied. The mean age was 41.6 +/- 11 years and the mean BMI 29.2 +/- 6.6 with 24 males (80%) and 6 females (20%). Fifteen patients (50%) had the genotype Ala54/Ala54 (wild type group) and 15 (50%) patients Ala54/Thr54 (13 patients) or Thr54/Thr54 (2 patients) (mutant type group). Both genotype groups have the similar anthropometric parameters. Serum aspartate aminotransferase and alcaline phosfatase were higher in wild type group than mutant type group, with an unclear explanation. Dietary intake was similar in both groups. A non-statistical significant low levels of adiponectin in mutant group was observed. No differences were detected among other adipokines. There were no differences between genotypes in histological results of inflammation (portal or lobular inflammation) or grade of steatosis or fibrosis. In conclusion, the present study demonstrates that the polymorphism Ala54Thr of FABP in patients with NAFLD doesn't predict liver histological changes, nor both insulin resistance and serum adipokines variations.

Expression changes of angiotensin II pathways and bioactive mediators during human preadipocytes-visceral differentiation

Obesity is a worldwide serious health problem; and it may result in a wide range of complications, such as hypertension and diabetes mellitus. As a consequence, molecular identification on the differentiation of preadipocytes and the generation of bioactive mediators is crucial in understanding the formation and development of obesity and obesity-associated health problems. In addition, exhaustive exhibition and purposeful control of adipocytes formation also play critical roles in the plastic and reconstructive surgical procedures. The primary purpose of this study was to exhibit the expression changes of angiotensin II (Ang II) pathways and 2 vital adipokines, leptin and resistin, during human preadipocytes-visceral differentiation by real-time quantitative reverse transcription-polymerase chain reaction. The present result indicated that the generation of Ang II during preadipocytes differentiation was achieved through both renin-angiotensin system pathway and non-renin-angiotensin system pathways, and the latter may be more important in this process. Gene expression of Ang II receptor type 1 and 2 increased in the initial phase of differentiation and then quickly decreased after 9 days. Moreover, the expression of both leptin and resistin increased significantly during preadipocyte-adipocyte conversion. The present work provided a fundamental understanding of human visceral preadipocytes differentiation molecularly. It may promote the understanding of obesity and obesity-associated diseases to some extent. However, there is still a long way to go to treat obesity and its complications effectively; and more efforts should be devoted urgently.

Effects of pyridoxamine (K-163) on glucose intolerance and obesity in high-fat diet C57BL/6J mice

Advanced glycation end products (AGEs) contribute to the pathogenesis of diabetes-associated complications. Previously, we reported the possible effect of pyridoxamine (K-163), an AGE inhibitor, on improvement of glucose intolerance in type 2 diabetes mellitus KK-A(y)/Ta mice. Recently, AGEs and oxidative stress have been shown to induce insulin resistance. The objective of the present study is to examine the effect of pyridoxamine on glucose intolerance and oxidative stress. C57BL/6J mice were divided into 3 groups as follows: low-fat diet, high-fat diet, and high-fat diet with pyridoxamine treatment. Body and adipose tissue weight, serum insulin, hydrogen peroxide, malondialdehyde and AGE, and urinary 8-hydroxy-2'-deoxyguanosine levels were measured. Nicotinamide adenine dinucleotide phosphate subunits, antioxidant enzymes, and adipocytokine messenger RNA expressions in the adipose tissues were evaluated. Akt/protein kinase B activity and glucose transporter 4 translocation in skeletal muscle were also evaluated. Body and adipose tissue weights of the pyridoxamine treatment group were significantly decreased compared with those of the high-fat diet group. Pyridoxamine attenuated serum hydrogen peroxide, malondialdehyde and AGE, and urinary 8-hydroxy-2'-deoxyguanosine and nicotinamide adenine dinucleotide phosphate oxidase expression; increased antioxidant enzyme expression; and improved dysregulation of adipocytokines in adipose tissues. Pyridoxamine improved blood glucose levels after glucose injection and fasting hyperinsulinemia. Suppressed Akt/protein kinase B activity and glucose transporter 4 translocation in skeletal muscle in high-fat diet mice were improved by pyridoxamine treatment. It appears that the antioxidative effect of pyridoxamine is associated with improvement of glucose intolerance and obesity in C57BL/6J mice fed a high-fat diet. We assume that pyridoxamine may be useful in the treatment of the obesity-associated metabolic syndrome.

Genetic variation in adipokine genes and risk of colorectal cancer

OBJECTIVE

Obesity has been related to an increased risk of colorectal cancer (CRC). Adipokines produced by the adipose tissue are directly linked to obesity and may thus contribute to the pathogenesis of CRC. We hypothesized that potentially functional polymorphisms in the adipokine genes leptin (LEP), leptin receptor (LEPR), resistin (RETN), and adiponectin (ADIPOQ) may be associated with CRC.

DESIGN AND METHODS

We studied the association of four putatively functional single nucleotide polymorphisms (SNPs) with CRC risk using a hospital-based study design with 702 cases and 752 controls from the Czech Republic. We used likelihood ratio tests to select the best model to represent the relationship between genotypes and risk of CRC. Age-adjusted odds ratios (ORs) under the best model were calculated for each SNP. Previous genotyping data on insulin (INS)-related genes were used to explore interactions between genes in obesity- and diabetes-related pathways by using two independent methods, logistic regression, and multifactor-dimensionality reduction.

RESULTS

A trend to associate between the RETN SNP rs1862513 (C-420G) and CRC risk was observed (per allele OR 1.18, 95% confidence interval (0.99-1.40). Statistically, significant interactions were observed between the INS SNP rs3842754 (+1127INSPstI) genotypes and both the LEPR SNP rs1137101 (Q223R) and the ADIPOQ SNP rs266729 (C-11374G) genotypes.

CONCLUSIONS

Our results suggest that variants in the adipokine genes may affect CRC risk in combination with variants in diabetes-related genes.

Pioglitazone reduces inflammatory responses of human adipocytes to factors secreted by monocytes/macrophages

Infiltration of monocyte-derived macrophages into adipose tissue may contribute to tissue and systemic inflammation and insulin resistance. We hypothesized that pioglitazone (Pio) could specifically reduce the inflammatory response of adipocytes to factors released by monocytes/macrophages. We show that macrophage factors (Mphi-factors) greatly increase expression levels of proinflammatory adipokines, chemokines, and adhesion molecules in human subcutaneous and visceral adipose tissue (SAT and VAT) as well as in adipocytes (up to several hundredfold of control). Compared with SAT, VAT showed enhanced basal and Mphi-factor-induced inflammatory responses. Mphi-factors also induced greater lipolysis in adipocytes, as assessed by concentrations of glycerol released from the cells (196 +/- 13 vs. 56 +/- 7 microM in control, P < 0.05). Pretreatment of adipose tissue or adipocytes with Pio reduced these responses to Mphi-factors (by 13-86%, P < 0.05) and prevented Mphi-factor suppression of adiponectin expression. Furthermore, Pio pretreatment of adipocytes and macrophages tended to further reduce inflammatory responses of adipocytes to Mphi-factors and monocyte adhesion to Mphi-factor-activated adipocytes. In support of these in vitro data, media conditioned by monocytes isolated from impaired glucose-tolerant subjects treated with Pio (compared with placebo) induced release of lower concentrations of proinflammatory adipokines and glycerol (100 +/- 7 vs. 150 +/- 15 microM, P < 0.05) from adipocytes. In summary, Pio decreases inflammatory responses in adipose tissue/cells induced by monocytes/macrophages by acting on either or both cell types. These beneficial effects of Pio may attenuate proinflammatory responses resulting from monocyte/macrophage infiltration into adipose tissue and suppress tissue inflammation resulting from the interaction between both cell types.

Effects of exercise and low-fat diet on adipose tissue inflammation and metabolic complications in obese mice

Adipose tissue inflammation causes metabolic disturbances, including insulin resistance and hepatic steatosis. Exercise training (EX) may decrease adipose tissue inflammation, thereby ameliorating such disturbances, even in the absence of fat loss. The purpose of this study was to 1) compare the effects of low-fat diet (LFD), EX, and their combination on inflammation, insulin resistance, and hepatic steatosis in high-fat diet-induced obese mice and 2) determine the effect of intervention duration (i.e., 6 vs. 12 wk). C57BL/6 mice (n = 109) fed a 45% fat diet (HFD) for 6 wk were randomly assigned to an EX (treadmill: 5 days/wk, 6 or 12 wk, 40 min/day, 65-70% Vo(2max)) or sedentary (SED) group. Mice remained on HFD or were placed on a 10% fat diet (LFD) for 6 or 12 wk. Following interventions, fat pads were weighed and expressed relative to body weight; hepatic steatosis was assessed by total liver triglyceride and insulin resistance by HOMA-IR and glucose AUC. RT-PCR was used to determine adipose gene expression of MCP-1, F4/80, TNF-alpha, and leptin. By 12 wk, MCP-1, F4/80, and TNF-alpha mRNA were reduced by EX and LFD. Exercise (P = 0.02), adiposity (P = 0.03), and adipose F4/80 (P = 0.02) predicted reductions in HOMA-IR (r(2) = 0.75, P < 0.001); only adiposity (P = 0.04) predicted improvements in hepatic steatosis (r(2) = 0.51, P < 0.001). Compared with LFD, EX attenuated increases in adiposity, hepatic steatosis, and adipose MCP-1 expression from 6 to 12 wk. There are unique metabolic consequences of a sedentary lifestyle and HFD that are most evident long term, highlighting the importance of both EX and LFD in preventing obesity-related metabolic disturbances.

[Human genetic mutations and polymorphisms of adipocytokines relating to obesity]

Human gene mutations and polymorphisms of adipocytokines, adipocyte-derived bioactive molecules, have been reported to be implicated in the pathogenesis of obesity. Leptin and its receptor gene mutations are well-established in the development of severe obesity. Among early onset severe obese patients, the prevalence of various leptin-receptor gene mutations was about 3%. The polymorphisms of adiponectin, another important adipocytokine with anti-atherogenic and anti-diabetic properties, are reported to associate with the pathophysiology but not with the severity of obesity. Adipocytokine dysregulation due to lifestyle-mediated obesity would be common at this stage, although further study of adipocytokine mutation should be necessary.

Changes in adipose tissue gene expression and plasma levels of adipokines and acute-phase proteins in patients with critical illness

Insulin resistance develops rapidly during critical illness. The release of adipokines from adipose tissue is thought to play a key role in the development of insulin resistance, as are elevated levels of acute-phase proteins. The aim of this study was to identify changes in adipose tissue gene expression and plasma levels of adipokines and acute-phase proteins during critical illness. From 8 patients with subarachnoidal hemorrhage, consecutive blood samples and adipose tissue biopsies were obtained at 3 time points, twice during intensive care (1-2 days [IC1] and 7-9 days after subarachnoidal hemorrhage) and once after 8 months (recovery). The patients received a continuous insulin infusion to maintain normal glucose levels reflecting insulin resistance. The DNA microarray analysis showed increased zink-alpha2 glycoprotein (ZAG) and phospholipase A2, group IIA messenger RNA levels during intensive care compared with recovery (P < .05). Real-time polymerase chain reaction confirmed the increased expression of ZAG and phospholipase A2, group IIA. Plasma levels of ZAG, serum amyloid A, and C-reactive protein were higher at 7 to 9 days after subarachnoidal hemorrhage compared with either IC1 or recovery (P = .0001); and plasma levels of retinol-binding protein 4 and adiponectin were lower at IC1 compared with recovery (P = .05). The described changes in adipose tissue gene expression and plasma levels of adipokines and acute-phase proteins may influence the development of insulin resistance during critical illness.

Acylation stimulating protein but not complement C3 associates with metabolic syndrome components in Chinese children and adolescents

OBJECTIVE

Childhood obesity is increasing worldwide and is increasingly associated with metabolic syndrome (MetS). Our aim was to examine acylation stimulating protein (ASP) and its precursor complement C3, in normal, overweight, and obese Chinese children and adolescents, and the relationships with body size, blood parameters, pubertal development, family environment, and MetS.

METHODS

Children and adolescents (n=1603) from 6 to 18 years, boys (n=873) and girls (n=730), including normal weight (n=603), overweight (n=291) and obese (n=709) were assessed for body size parameters, pubertal development, blood lipids, glucose, insulin, ASP, and C3.

RESULTS

ASP levels were increased in overweight and obese versus normal weight (P<0.001), while C3 showed little variation. This effect of overweight/obesity remained throughout early stages when boys and girls were separated by pubertal development or age, although age and pubertal status itself had no effect. Separation based on ASP quintiles demonstrated significant associations with blood cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL-Chol), glucose, insulin, and homeostatic model assessment of insulin resistance in boys, and LDL-Chol, high-density lipoprotein cholesterol, and glucose in girls. A positive correlation with mother's body mass index in boys and girls (P=0.002 and P=0.014 respectively) as well as birth weight (P<0.001) was noted. MetS was strongly associated with increased ASP, the presence of a single MetS factor (especially hypertension, central obesity, or hyperglycemia) was associated with increased ASP.

CONCLUSION

Changes in the plasma adipokine ASP in early obesity are associated with blood lipid and glucose modifications, family environment, and distinct MetS risk factors.

[Adipokine genetics: unbalanced protein secretion by human adipose tissue as a cause of the metabolic syndrome]

Subcutaneous and visceral adipose compartments act, not only as fatty acid depots, but also as active endocrine organs that undergo hyperplastic changes and significantly enhance their function in obesity. Akipokines and other proteins secreted by both adipocytes and stromal cells play a central role in peripheral insulin resistance and the metabolic syndrome (MS). Minor alleles of the adipokine genes substantially contribute to MS. The most important consequence of MS is low-level systemic inflammation supported by adipose-specific synthesis of proinflammatory soluble molecules. Proinflammatory signals are secreted into the bloodstream and spread to peripheral tissues that contain their receptors. The signals provided by adipose tissue stimulate the development of secondary complications of MS, including cardiovascular disorders (CVDs) and nonalcoholic fatty liver disease. The review describes the physiological effects of adiponectin, leptin, resistin, visfatin, and apelin and the influence of the minor alleles of the adipokine genes on the development of the secondary complications of MS.

Prolactin release by adipose explants, primary adipocytes, and LS14 adipocytes

BACKGROUND

Prolactin (PRL) is a multifunctional hormone produced in humans by both pituitary and extrapituitary sites, including adipose tissue.

OBJECTIVES

Our objectives were to: 1) compare PRL secretion by sc and visceral adipose explants and mature adipocytes from obese and nonobese patients; and 2) examine the effects of insulin and selected cytokines on PRL gene expression and release from primary adipocytes and LS14 adipocytes.

DESIGN AND SUBJECTS

Adipose tissue was obtained from morbidly obese [body mass index (BMI) > 40 kg/m(2)] and nonobese (BMI <30 kg/m(2)) patients. Explants and isolated mature adipocytes were incubated for 10 d. Primary adipocytes or LS14 cells were used before or after differentiation and incubated with the test compounds for 24 h. PRL release was analyzed by a bioassay, and PRL expression was determined by real-time PCR.

RESULTS

PRL release from explants and mature adipocytes increased in a time-dependent manner indicating removal from inhibition. Visceral explants from obese patients showed higher PRL release than that from sc explants; both types of explants from nonobese patients released similar amounts of PRL. Analysis of data from 50 patients revealed an inverse relationship between PRL release from sc depots and BMI. Insulin suppressed PRL expression and release from differentiated adipocytes but moderately stimulated PRL release from nondifferentiated cells. The cAMP elevating compound forskolin increased PRL release in both cell types.

CONCLUSIONS

PRL should be recognized as an important adipokine whose release is regulated by insulin and is affected by obesity in a depot-specific manner.

A new organotypic culture of adipose tissue fragments maintains viable mature adipocytes for a long term, together with development of immature adipocytes and mesenchymal stem cell-like cells

Adipose tissue that consists of mature and immature adipocytes is suggested to contain mesenchymal stem cells (MSCs), but a culture system for analyzing their cell types within the tissue has not been established. Here we show that three-dimensional collagen gel culture of rat sc adipose tissue fragments maintained viable mature adipocytes for a long term, producing immature adipocytes and MSC-like cells from the fragments, using immunohistochemistry, ELISA, and real time RT-PCR. Bromodeoxyuridine uptake of mature adipocytes was detected. Adiponectin and leptin, and adipocyte-specific genes of adiponectin, leptin, and PPAR-gamma were detected in culture assembly, whereas the lipogenesis factor insulin (20 mU/ml) and inflammation-related agent TNF-alpha (2 nm) increased and decreased, respectively, all of their displays. Both spindle-shaped cell types with oil red O-positive lipid droplets and those with expression of MSC markers (CD105 and CD44) developed around the fragments. The data indicate that adipose tissue-organotypic culture retains unilocular structure, proliferative ability, and some functions of mature adipocytes, generating both immature adipocytes and CD105+/CD44+ MSC-like cells. This suggests that our method will open up a new way for studying both multiple cell types within adipose tissue and the cell-based mechanisms of obesity and metabolic syndrome.

Birth weight and gender determine expression of adipogenic, lipogenic and adipokine genes in perirenal adipose tissue in the young adult sheep

Epidemiological studies have demonstrated that low birth weight is associated with an increased incidence of visceral obesity and metabolic disorders in later life. In the present study, we have determined the impact of birth weight and gender on gene expression in visceral adipose tissue (VAT) in the young adult sheep. Lambs (n=19, birth weight range 2.6-7.55 kg) were born at term and growth monitored for 22.4+/-0.2 weeks, when body composition was determined by Dual X-ray Absorptiometry (DXA) and samples of VAT and subcutaneous (SCAT) adipose tissue collected. Plasma samples were collected at post-mortem for the determination of free fatty acids (FFA), glucose and insulin concentrations. Peroxisome-Proliferator Activated Receptor-gamma (PPARgamma), glycerol-3-phosphate dehydrogenase (G3PDH), lipoprotein lipase (LPL), adiponectin and leptin mRNA expression was determined by qRT-PCR. Fractional growth rate in postnatal weeks 1-3 was inversely related to birth weight in both males and females (R2=0.22, P<0.05, n=19). PPARgamma mRNA expression in VAT, but not SCAT, was inversely related to birth weight (R2=0.60, P<0.01, n=18). In males, but not females, PPARgamma mRNA in VAT was directly related to G3PDH mRNA expression (R2=0.69, P<0.01, n=9). Plasma FFA concentrations were inversely related to birth weight in both males and females (R2=0.22, P<0.05, n=19). These findings demonstrate that low birth weight is associated with an increased expression of a key adipogenic factor in visceral adipose tissue in young adulthood. In males, this is associated with an increased expression of lipogenic genes, and this may contribute to the increased propensity for visceral obesity in low birth weight males compared to females.

Effects of the new C1q/TNF-related protein (CTRP-3) "cartonectin" on the adipocytic secretion of adipokines

BACKGROUND

Cartonectin (collagenous repeat-containing sequence of 26-kDa protein; CORS-26) was described as a new adipokine of the C1q/TNF molecular superfamily C1q/TNF-related protein-3 (CTRP-3), secreted by the adipocytes of mice and humans. The receptor and function of cartonectin are unknown and the recombinant protein is not commercially available.

OBJECTIVE

To investigate the effects of recombinant cartonectin on the secretion of adipokines such as adiponectin, leptin, and resistin from adipocytes of human and murine origin. The effect of the BMI of the adipocyte donor was also investigated.

METHODS AND PROCEDURES

Human adipocytes from pooled lean and preobese healthy individuals and murine 3T3-L1 adipocytes were used for stimulation experiments. Recombinant cartonectin was expressed in insect H5 cells. Adipokine secretion was measured using enzyme-linked immunosorbent assay. In addition, western blot analysis and luciferase reporter gene assays were employed.

RESULTS

Cartonectin (1, 10, 50, and 250 ng/ml) in higher doses stimulates the secretion of adiponectin and resistin from murine adipocytes. This effect is not caused by an induction of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) protein expression, as confirmed by western blot analysis. Also, luciferase reporter gene assay revealed that cartonectin failed to induce luciferase activity at the peroxisome proliferator-activated receptor responsive element site containing the adiponectin/luciferase promoter fragment. Human adipocytes from lean individuals secrete higher amounts of adiponectin and leptin when compared with adipocytes of individuals with a preobesity BMI (25-30 kg/m(2)). Cartonectin failed to stimulate adiponectin or leptin secretion from human adipocytes, irrespective of the BMI value.

DISCUSSION

Cartonectin is a new adipokine that differentially regulates the secretion of classical adipokines, with marked differences between the human and the murine systems. These effects are species-dependent, while basal adipokine secretion is influenced by the BMI.

Wdnm1-like, a new adipokine with a role in MMP-2 activation

White adipose tissue functions in energy storage and as an endocrine organ. DNA microarray analysis led us to identify Wdnm1-like, a distant member of the whey acidic protein/four-disulfide core (WAP/4-DSC) family, as a differentiation-dependent gene in white and brown adipogenesis. Wdnm1-like is a novel 6.8-kDa protein, and Western blot analysis reveals secretion into culture media. Wdnm1-like transcript is selectively expressed in adipose tissue and liver and is enriched approximately 500-fold in white adipose depots vs. brown. Cellular fractionation of WAT demonstrates Wdnm1-like transcript expression is restricted to the adipocyte population. Studies in 3T3-L1 preadipocytes, an in vitro model of white adipogenesis, indicate Wdnm1-like transcript increases within 6 h of adipogenic induction with an approximately 17,000-fold increase by day 7. Dramatic upregulation of Wdnm1-like also accompanies white adipogenesis of ScAP-23 preadipocytes and primary preadipocytes. TNF-alpha treatment of 3T3-L1 adipocytes increased Wdnm1-like transcript level 2.4-fold and was attenuated by pretreatment with the p38 MAP kinase inhibitor SB203580. A number of WAP/4-DSC family proteins function as protease inhibitors. This, taken with the role of extracellular remodeling in adipogenesis, led us to address effects of Wdnm1-like on matrix metalloproteinase (MMP) activity. Gelatin zymography of HT1080 fibrosarcoma cells transfected with a Wdnm1-like expression construct revealed markedly increased levels of active MMP-2. Our findings identify a new member of the adipocyte "secretome" that functions to enhance MMP-2 activity. We postulate that Wdnm1-like may play roles in remodeling of the extracellular milieu in adipogenesis, as well as in tumor microenvironments where adipocytes are key stromal components.

Comparison of messenger RNA distribution for 60 proteins in fat cells vs the nonfat cells of human omental adipose tissue

The messenger RNA (mRNA) distribution of 60 proteins was examined in the 3 fractions obtained by collagenase digestion (fat cells and the nonfat cells comprising the tissue remaining after collagenase digestion [matrix] and the stromovascular cells) of omental adipose tissue obtained from morbidly obese women undergoing bariatric surgery. Fat cells were enriched by at least 3-fold as compared with nonfat cells in the mRNAs for retinol binding protein 4, angiotensinogen, adipsin, glutathione peroxidase 3, uncoupling protein 2, peroxisome proliferator-activated receptor gamma, cell death-inducing DFFA-like effector A, fat-specific protein 27, 11beta-hydroxysteroid dehydrogenase 1, glycerol channel aquaporin 7, NADPH:quinone oxidoreductase 1, cyclic adenosine monophosphate phosphodiesterase 3B, glyceraldehyde-3-phosphate dehydrogenase, insulin receptor, and amyloid A1. Fat cells were also enriched by at least 26-fold in the mRNAs for proteins involved in lipolysis such as hormone-sensitive lipase, lipoprotein lipase, adipose tissue triglyceride lipase, and FAT/CD36. The relative distribution of mRNAs in cultured preadipocytes was also compared with that of in vitro differentiated adipocytes derived from human omental adipose tissue. Cultured preadipocytes had far lower levels of the mRNAs for inflammatory proteins than the nonfat cells of omental adipose tissue. The nonfat cells were enriched by at least 5-fold in the mRNAs for proteins involved in the inflammatory response such as tumor necrosis factor alpha, interleukin lbeta, cyclooxygenase 2, interleukin 24, interleukin 6, and monocyte chemoattractant protein 1 plus the mRNAs for osteopontin, vaspin, endothelin, angiotensin II receptor 1, butyrylcholinesterase, lipocalin 2, and plasminogen activator inhibitor 1. The cells in the adipose tissue matrix were enriched at least 3-fold as compared with the isolated stromovascular cells in the mRNAs for proteins related to the inflammatory response, as well as osteopontin and endothelial nitric oxide synthase. We conclude that the mRNAs for inflammatory proteins are primarily present in the nonfat cells of human omental adipose tissue.

Insulin increases tristetraprolin and decreases VEGF gene expression in mouse 3T3-L1 adipocytes

OBJECTIVES

Tristetraprolin (TTP) family proteins (TTP/ZFP36; ZFP36L1, ZFP36L2, ZFP36L3) destabilize adenylate uridylate-rich element-containing mRNAs encoding cytokines, such as tumor necrosis factor (TNF) and vascular endothelial growth factor (VEGF). Little is known about the expression and insulin regulation of TTP and related genes in adipocytes. We analyzed the relative abundance of TTP family mRNAs in 3T3-L1 adipocytes compared to RAW264.7 macrophages and investigated insulin effects on the expression of 43 genes in 3T3-L1 adipocytes.

METHODS AND PROCEDURES

Insulin was added to mouse 3T3-L1 adipocytes. Relative abundance of mRNA levels was determined by quantitative real-time PCR. TTP and ZFP36L1 proteins were detected by immunoblotting.

RESULTS

Zfp36l1 and Zfp36l2 genes were expressed at eight- to tenfold higher than Ttp in adipocytes. Zfp36l3 mRNA was detected at approximately 1% of Ttp mRNA levels in adipocytes and its low level expression was confirmed in RAW cells. Insulin at 10 and 100 nmol/l increased Ttp mRNA levels by five- to sevenfold, but decreased those of Zfp36l3 by 40% in adipocytes after a 30-min treatment. Immunoblotting showed that insulin induced TTP but did not affect ZFP36L1 protein levels in adipocytes. Insulin decreased mRNA levels of Vegf and a number of other genes in adipocytes.

DISCUSSION

Insulin induced Ttp mRNA and protein expression and decreased Vegf mRNA levels in adipocytes. Zfp36l3 mRNA was detected, for the first time, in cells other than mouse placenta and extraembryonic tissues. This study established a basis for the investigation of TTP and VEGF genes in the regulation of obesity and suggested that Vegf mRNA may be a target of TTP in fat cells.

Mineralocorticoid receptor blockade reverses obesity-related changes in expression of adiponectin, peroxisome proliferator-activated receptor-gamma, and proinflammatory adipokines

BACKGROUND

In obesity, decreases in adiponectin and increases in proinflammatory adipokines are associated with heart disease. Because adipocytes express mineralocorticoid receptor (MR) and MR blockade reduces cardiovascular inflammation and injury, we tested the hypothesis that MR blockade reduces inflammation and expression of proinflammatory cytokines in adipose tissue and increases adiponectin expression in adipose tissue and hearts of obese mice.

METHODS AND RESULTS

We determined the effect of MR blockade (eplerenone, 100 mg/kg per day for 16 weeks) on gene expression in retroperitoneal adipose and heart tissue from obese, diabetic db/db mice (n=8) compared with untreated obese, diabetic db/db mice (n=10) and lean, nondiabetic db/+ littermates (n=11). Expression of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, plasminogen activator inhibitor type 1, and macrophage protein CD68 increased, and expression of adiponectin and peroxisome proliferator-activated receptor-gamma decreased in retroperitoneal adipose tissue from obese versus lean mice. In addition, adiponectin expression in heart was reduced in obese versus lean mice. MR blockade prevented these obesity-related changes in gene expression. Furthermore, treatment of undifferentiated preadipocytes with aldosterone (10(-8) mol/L for 24 hours) increased mRNA levels of tumor necrosis factor-alpha and monocyte chemoattractant protein-1 and reduced mRNA and protein levels of peroxisome proliferator-activated receptor-gamma and adiponectin, supporting a direct aldosterone effect on gene expression.

CONCLUSIONS

MR blockade reduced expression of proinflammatory and prothrombotic factors in adipose tissue and increased expression of adiponectin in heart and adipose tissue of obese, diabetic mice. These effects on adiponectin and adipokine gene expression may represent a novel mechanism for the cardioprotective effects of MR blockade.