Adipocyte Differentiation Of Cells Research Articles

Capsaicin Modulates Adipocyte Cell Differentiation and Inflammatory Gene Expression

Capsaicin Modulates Adipocyte Cell Differentiation and Inflammatory Gene Expression

Characterizing 3T3-L1 MBX Adipocyte Cell Differentiation Maintained with Fatty Acids as an In Vitro Model to Study the Effects of Obesity.

The increasing prevalence of obesity has prompted intensive research into understanding its role in pathogenesis and designing appropriate treatments. To determine the signals generated from the interaction of fat cells with a target organ, a reliable white adipocyte model in vitro is needed. Differentiated fibroblasts are the most extensively studied using in vitro cell models of white adipocytes. However, it can be argued that differentiated fibroblasts minimally recapitulate the consequences of obesity. Here, we describe 3T3-L1 MBX cells as a culture model for studying obese adipocytes and their effects. Differentiation of 3T3-L1 MBX cells was at first optimized and then maintained in the presence of fatty acids cocktail combination to induce the obese condition. Lipid accumulation and adipokine secretion profiles were analyzed. Results showed that fatty acid-maintained, differentiated 3T3-L1 MBX cells had significantly greater accumulation of lipids and significant changes in the adipokine secretions in comparison to differentiated 3T3-L1 MBX cells maintained in medium without fatty acids. To elucidate the molecular changes associated with adipogenesis and lipid accumulation profile of 3T3-L1 MBX cells, we have also explored the expression of some of the regulatory proteins related to the development and maintenance of adipocytes from the preadipocyte lineage.

Discovery of the First Raptor (Regulatory-Associated Protein of mTOR) Inhibitor as a New Type of Antiadipogenic Agent.

Raptor, a regulatory-associated protein of mTOR, has been genetically proved to be an important regulator in lipogenesis. However, its druggable potential is rarely investigated, largely due to the lack of an inhibitor. In this study, the antiadipogenic screening of a daphnane diterpenoid library followed by target fishing led to the identification of a Raptor inhibitor, 1c (5/7/6 carbon ring with orthoester and chlorine functionalities). Pharmacodynamic studies verified that 1c is a potent and tolerable antiadipogenic agent in vitro and in vivo. Mechanistic studies revealed that the targeting of Raptor by 1c could block the formation of mTORC1 and then downregulate the downstream S6K1- and 4E-BP1-mediated C/EBPs/PPARγ signaling, eventually retarding adipocyte cell differentiation at the early stage. These findings suggest that Raptor can be explored as a novel therapeutic target for obesity and its related complications, and 1c as the first Raptor inhibitor may provide a new therapeutic option for these conditions.

Obeticholic acid ameliorates obesity and hepatic steatosis by activating brown fat.

Obeticholic acid (OCA) is exemplified as a potent drug for treating primary biliary cirrhosis and nonalcoholic fatty liver disease by inhibiting bile acid synthesis. However, it remains unclear whether the effect of OCA is mediated by the function of brown adipose tissue (BAT). In the present study, brown adipogenesis differentiation in vitro and db/db mouse model treated with OCA were used to assess the anti-obesity function by body weight tracking, O2 consumption, food intake, physical activity, glucose tolerance tests. In addition, uncoupling protein 1 (Ucp1) protein expression in brown adipose tissue was measured by western blotting, morphometry of brown adipose tissue was analyzed by hematoxylin and eosin staining. Hepatic steatosis was detected by Oil-Red O staining and serological analysis was performed to assess the effect of OCA on hyperlipidemia. OCA treatment enhanced brown adipocyte cell differentiation and upregulated the expression of the BAT-specific gene Ucp1) in C3H10T1/2 cells in vitro. Consistent with these findings, OCA increased whole-body energy metabolism and glucose homeostasis by enhancing BAT activity in vivo, and ultimately decreased body weight gain in db/db mice. In addition, the results demonstrated that spontaneous hepatic steatosis in db/db mice was ameliorated following OCA treatment. In summary, OCA functioned as a BAT activator to help ameliorate obesity and maintain glucose homeostasis in db/db mice. The present results may provide a novel potential therapeutic approach to activate brown fat in patients with obesity and other metabolic disorders.

Akt Is S-Palmitoylated: A New Layer of Regulation for Akt.

The protein kinase Akt/PKB participates in a great variety of processes, including translation, cell proliferation and survival, as well as malignant transformation and viral infection. In the last few years, novel Akt posttranslational modifications have been found. However, how these modification patterns affect Akt subcellular localization, target specificity and, in general, function is not thoroughly understood. Here, we postulate and experimentally demonstrate by acyl-biotin exchange (ABE) assay and 3H-palmitate metabolic labeling that Akt is S-palmitoylated, a modification related to protein sorting throughout subcellular membranes. Mutating cysteine 344 into serine blocked Akt S-palmitoylation and diminished its phosphorylation at two key sites, T308 and T450. Particularly, we show that palmitoylation-deficient Akt increases its recruitment to cytoplasmic structures that colocalize with lysosomes, a process stimulated during autophagy. Finally, we found that cysteine 344 in Akt1 is important for proper its function, since Akt1-C344S was unable to support adipocyte cell differentiation in vitro. These results add an unexpected new layer to the already complex Akt molecular code, improving our understanding of cell decision-making mechanisms such as cell survival, differentiation and death.

Multiexponential T2 relaxometry of benign and malignant adipocytic tumours

BackgroundWe investigated a recently proposed multiexponential (Mexp) fitting method applied to T2 relaxometry magnetic resonance imaging (MRI) data of benign and malignant adipocytic tumours and healthy subcutaneous fat. We studied the T2 distributions of the different tissue types and calculated statistical metrics to differentiate benign and malignant tumours.MethodsTwenty-four patients with primary benign and malignant adipocytic tumours prospectively underwent 1.5-T MRI with a single-slice T2 relaxometry (Carr-Purcell-Meiboom-Gill sequence, 25 echoes) prior to surgical excision and histopathological assessment. The proposed method adaptively chooses a monoexponential or biexponential model on a voxel basis based on the adjusted R2 goodness of fit criterion. Linear regression was applied on the statistical metrics derived from the T2 distributions for the classification.ResultsHealthy subcutaneous fat and benign lipoma were better described by biexponential fitting with a monoexponential and biexponential prevalence of 0.0/100% and 0.2/99.8% respectively. Well-differentiated liposarcomas exhibit 17.6% monoexponential and 82.4% biexponential behaviour, while more aggressive liposarcomas show larger degree of monoexponential behaviour. The monoexponential/biexponential prevalence was 47.6/52.4% for myxoid tumours, 52.8/47.2% for poorly differentiated parts of dedifferentiated liposarcomas, and 24.9/75.1% pleomorphic liposarcomas. The percentage monoexponential or biexponential model prevalence per patient was the best classifier distinguishing between malignant and benign adipocytic tumours with a 0.81 sensitivity and a 1.00 specificity.ConclusionsHealthy adipose tissue and benign lipomas showed a pure biexponential behaviour with similar T2 distributions, while decreased adipocytic cell differentiation characterising aggressive neoplasms was associated with an increased rate of monoexponential decay curves, opening a perspective adipocytic tumour classification.

Citrus aurantium L. Dry Extracts Ameliorate Adipocyte Differentiation of 3T3-L1 Cells Exposed to TNFα by Down-Regulating miR-155 Expression

Citrus aurantium L. dry extracts (CAde) improve adipogenesis in vitro. These effects are dependent from an early modulation of CCAAT/enhancer-binding protein beta (C/Ebpβ) expression and cyclic Adenosine Monophosphate (cAMP) response element-binding protein (CREB) activation. C/Ebpβ and Creb are also targets of miR-155. This study investigated whether CAde regulates miR-155 expression in the early stages of adipogenesis and whether it ameliorates adipocyte differentiation of cells exposed to tumor necrosis factor-alpha (TNFα). Adipogenic stimuli (AS) were performed in 3T3-L1 pre-adipocytes treated with CAde, TNFα, or both. Gene and miRNA expression were determined by quantitative real-time PCR. Adipogenesis was evaluated by Oil-Red O staining. CAde treatment enhanced AS effects during the early adipogenesis phases by further down-regulating miR-155 expression and increasing both C/Ebpβ and Creb mRNA and protein levels. At variance, TNFα inhibited 3T3-L1 adipogenesis and abolished AS effects on miR-155, C/Ebpβ, and Creb expression. However, in cells exposed to TNFα, CAde improved adipocyte differentiation and restored the AS effects on miRNA and gene expression at early time points. In conclusion, this study identified miR-155 down-regulation as part of the mechanism through which CAde enhances adipogenesis of pre-adipocytes in vitro. Furthermore, it provides evidence of CAde efficacy against TNFα negative effects on adipogenesis.

OR20-03 Transcriptional Changes in Lipid Metabolism of Adipocytes Derived from Subcutaneous Abdominal Adipose Stem Cells of Normal-Weight Polycystic Ovary Syndrome Women

Normal-weight polycystic ovary syndrome (PCOS) women exhibit increased adipose insulin resistance in vivo (1) accompanying enhanced subcutaneous (SC) abdominal adipose stem cell (ASC) development to adipocytes with greater lipid accumulation per cell in vitro (2). To determine whether this phenomenon is associated with abnormal adipogenic gene transcription during ASC differentiation into adipocytes, SC abdominal ASCs isolated from three non-Hispanic Caucasian normal-weight PCOS women and three age- and BMI-matched controls were cultured in adipogenic differentiation medium for 3–12 days. After RNA isolation, gene expression levels were determined by RNA sequencing at days 3, 7, and 12. Differentially expressed genes were filtered for significance (padj<0.05) and fold change (>2-fold); upstream regulator genes and gene ontology (GO) functions were determined using Ingenuity Pathway Analysis. Gene set enrichment analysis (GSEA) also was used to identify enriched cellular processes (3). Differentially expressed genes in PCOS vs. control cells were either upregulated (466, 768 and 441 genes on days 3, 7 and 12, respectively) or downregulated (742, 974 and 605 genes on days 3, 7 and 12, respectively) over time, with critical genes governing adipocyte cell differentiation in PCOS cells increased 2–6 fold at days 3, 7 and 12 (PPARγ, CEBPα, ADIPOQ, AGPAT2, FABP4, LPL, PLIN1). The predicted upstream regulator genes TGFβ1 (an adipogenic inhibitor) and TNF (a pro-inflammatory adipokine) were significantly reduced in PCOS relative to control cells at all time points. The GO functions lipid oxidation and free fatty acid (FFA) beta-oxidation were enriched amongst upregulated genes in PCOS cells across all time points, while acylglycerol synthesis was increased at days 7 and 12 alone (z>2, p<0.05, all GO functions). In parallel, GSEA showed in PCOS cells significantly increased transcripts related to oxidative phosphorylation, peroxisome activity and adipogenesis at all time points (p<0.05). Thus, adipocytes derived from SC abdominal ASCs of normal-weight PCOS women exhibit early activation of adipogenic genes, potentially underlying their exaggerated lipid accumulation in vitro, as previously described (2). These PCOS-related changes in gene expression involve an increase in both oxidative phosphorylation and FFA beta oxidation, which could disrupt the balance between energy production and lipid storage, particularly when caloric intake exceeds energy utilization.

Changes in the Main Bone Marrow Cell Subpopulations May Potentially Contribute to the Initiation of Acute Myeloid Leukemia

Introduction: In acute myeloid leukemia (AML), differentiation and proliferation of early progenitors is inhibited, leading to blast accumulation in the bone marrow (BM) and in the peripheral blood (PB). Hematopoietic stem cells (HSCs) reside in specialized BM microenvironment (ME), mainly containing osteocytes and adipocytes, derived from BM mesenchymal stem cells (MSCs). Recent studies suggest a possible role of the ME in various hematological malignancies, that either serves as a potential source of an altered milieu or mediates abnormal interaction with HSCs. BM ME contributes to disease pathogenesis, chemotherapy resistance and recurrence in certain types of hematological cancers, but there is limited evidence that BM cells themselves may initiate AML. BM derived MSCs are characterized by a potential to mainly differentiate to adipocytes, osteocytes or chondrocytes. Our experiments have revealed an imbalance between osteocytes and adipocytes in the BM of AML patients that is not observed in the BM of healthy donors. We hypothesize that this imbalance could result in the development of leukemic stem cells/pre-leukemic cells, leading to leukemia initiation. The current study aimed to characterize the composition of AML BM derived adipocytes and osteocytes and evaluate the ability of these subpopulations to support AML cell viability. Methods: Secreted levels of adipogenic and osteogenic biomarkers in the BM plasma were measured using ELISA. The potential of AML MSCs to differentiate to adipocytes and osteocytes was assessed using FACS analysis. Exome sequencing was applied for genetic alteration screening in AML MSCs. Obtained adipocytes and osteocytes were separately co-cultured with AML cells and colony forming unit (CFU) assays were used to evaluate AML cell viability. ProcartaPlex immunoassay was used to evaluate levels of cytokines and other potential mediators secreted to the conditioned media. Results: The study included BM samples of 10 AML patients and 13 healthy donors. Levels of secreted FABP4 and osteocalcin biomarkers were reduced in AML plasma (279.7±164 pg/ml and 0.00057±0.017 pg/ml, respectively) compared to that of healthy controls (1230±1502 pg/ml and 0.0016±0.00052 pg/ml, respectively), with P=0.02 for FABP4 and P=0.017 for osteocalcin. According to adipocyte cell differentiation, patients were divided into two clusters. Cluster-1 demonstrated a higher expression level of FABP4 (mean 65.2±11.4%) compared to healthy controls (mean: 47.5±19.2 %; P=0.05), while cluster-2 exhibited a lower level of FABP4 expression (mean 30.78±6.1%) than healthy controls (mean 47.6±19.2%; P=0.01). A nonsynonymous somatic mutation in the AHNAK2 gene (V3209L) was found in patients' mesenchymal stromal cells. A statistically significant reduction in AML cell proliferation (P&lt;0.01) was revealed following co-culture with adipocyte cells of cluster-1 patients. Of the 10 cytokines tested, only ANG1 levels were significantly elevated in the co-culture of adipocytes from cluster-1 (189.5±17.3pg/ml), cluster-2 (258.08±34.33pg/ml) or osteocytes (392.04±58.3pg/ml) with AML cells of the same patients compared to the levels observed in controls (0.002±0.052pg/ml for adipocytes and 168.663pg/ml for osteocytes; P&lt;0.01). Conclusions: The current study has demonstrated that changes in the secretion of stromal specific biomarkers and in the MSC ability to differentiate to adipocytes and osteocytes indicate impaired functional properties of BM MSCs in AML. Within the adipocyte subpopulation in the AML BM, clusters with either increased or inhibited adipogenesis have been revealed. These variations in adipocyte and osteocyte cells reflect interpatient heterogeneity in AML BM subpopulations. The AHNAK2 gene mutation found in AML MSCs in our study and the previously suggested role of this gene in adipocyte differentiation regulation, may explain in part the phenotype diversity observed in AML patients. Adipocyte cells, derived from an AML patient, were found to inhibit normal hematopoiesis in HSCs of the same patient. This specific crosstalk may be related to the elevated levels of ANG1 mediating abnormal signals from adipocytes to HSCs. Overall, the findings of this study may support the contribution of abnormal composition of the main BM subpopulations to leukemogenesis and could ultimately pave the way to novel therapeutic strategies targeting the BM niche. Disclosures No relevant conflicts of interest to declare.

Effect of ACSL3 Expression Levels on Preadipocyte Differentiation in Chinese Red Steppe Cattle

Domestic cattle are an important type of livestock, with beef production playing a major role in the agricultural economy. Adipocyte levels and fat content are interrelated, with meat quality being highly dependent on its fat content and distribution. Acyl-CoA synthetases of long-chain (ACSL) fatty acids (FAs) play an integral role in virtually every metabolic pathway in mammalian biochemistry, including complex lipid biosynthesis, protein modification, and β-oxidation processes. ACSL3 activity is also known to be associated with adipocyte differentiation; however, its biological mechanism of action is currently unclear. Gene expression in subcutaneous preadipocytes isolated from subcutaneous deposits of Chinese Red Steppe cattle has been studied using in vitro cell transfection, real-time polymerase chain reaction and western blot analysis. The lipid and triglyceride contents of lipid droplets have also been measured to verify the levels of gene expression. These combined studies show that ACSL3 is induced during adipocyte differentiation, with its overexpression promoting an increase in the triglyceride content of lipid droplets. Furthermore, mRNA and protein expression levels for adipocyte differentiation marker genes, such as peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα), were markedly increased during mature adipocyte cell differentiation. Knockdown of ACSL3 expression using ACSL3 small interfering RNAs (siRNAs) resulted in a decrease in lipid content of cattle adipocytes, providing further evidence that ACSL3 plays a key role in the differentiation process.

ANTIHYPERGLYCEMIC ACTIVITY OF TINOCRISPOSIDE BY STIMULATING 3T3-L1 ADIPOCYTE CELL DIFFERENTIATION

Objective: The aim of this study is to investigate the antihyperglycemic activity of tinocrisposide by stimulating 3T3-L1 adipocyte cell differentiation. Tinocrisposide is a furanoditerpene glycoside that was isolated from Tinospora crispa (Menispermaceae).Methods: Adipocyte cell differentiation activity of tinocrisposide in interval concentrations of 50, 25, 12.5, and 6.25 μg/ml has been investigated on 3T3-L1 cell line using insulin of 1 μg/ml as a positive and Dulbecco’s modified Eagle media (DMEM) as a negative control group. The effect of tinocrisposide was quantified with oil red O staining method by measuring an absorbance of lipid solution in isopropanol at a wavelength (λ) of 520 nm.Results: Tinocrisposide in the concentrations of 50, 25, 12.5, and 6.25 μg/ml insulin of 1 μg/ml and DMEM groups showed absorbance value of 0.7669, 0.7253, 0.6563, 0.6481, 0.954, and 0.2653, respectively. It was found that there was a significant difference statistically in lipid droplets accumulation among all groups (p&lt;0.05) and tinocrisposide at a concentration of 50 μg/ml showed the highest lipid droplets accumulation in 3T3-L1 adipocyte cells.Conclusion: From the study, it could be concluded that tinocrisposide was able to stimulate the differentiation of adipocyte cell and had antihyperglycemic activity.

Retraction for Melillo et al., "Critical Role of the HMGI(Y) Proteins in Adipocytic Cell Growth and Differentiation".

Retraction for Melillo et al., "Critical Role of the HMGI(Y) Proteins in Adipocytic Cell Growth and Differentiation".

Integrated Analysis of MiRNA and Genes Associated with Meat Quality Reveals that Gga-MiR-140-5p Affects Intramuscular Fat Deposition in Chickens

Background/Aims: Poultry meat quality is affected by many factors, among which intramuscular fat (IMF) is predominant. IMF content affects the tenderness, juiciness, and favor of chicken. An increasing number of studies are focusing on the functions of microRNAs (miRNAs) during the adipogenic process. However, little is known about miRNAs associated with poultry IMF deposition, especially intramuscular adipocyte differentiation. Methods: The IMF content of two physiological stages was measured, and miRNA-Seq and RNA-Seq data were integrated and analyzed. A chicken intramuscular adipocyte cell differentiation model was constructed. A luciferase reporter assay, miRNA overexpression, and Oil Red O staining were used to confirm the targets of gga-miR-140-5p. Results: Our results showed that late-laying-period hens, which had a higher IMF content, exhibited lower global expression levels of miRNAs than juvenile hens. A total of 104 differentially expressed (DE) miRNAs were identified between the two groups. Integrated analysis of differentially expressed genes and DE miRNAs identified a total of 378 miRNA-mRNA pairs. Functional enrichment analysis revealed that these intersecting genes are involved in ubiquitin-mediated proteolysis, the peroxisome proliferator-activated receptor signaling pathway, glycerophospholipid metabolism, and fatty acid elongation and degradation pathways. Furthermore, we demonstrated that gga-miR-140-5p promoted intramuscular adipocyte differentiation via targeting retinoid X receptor gamma. Conclusion: Our findings may contribute to a more thorough understanding of chicken IMF deposition and the improvement of poultry meat quality.

Integrated stress response activation by sleep fragmentation during late gestation in mice leads to emergence of adverse metabolic phenotype in offspring

BackgroundLate gestational sleep fragmentation (SF) is highly prevalent particularly in obese women, and induces metabolic dysfunction in adult offspring mice. SF induces activation of the integrated stress response (ISR), which might be involved in metabolic disorders. We hypothesized that adult offspring of double mutant mice (DM) involving the critical ISR genes CHOP and GADD34 would be protected from developing obesity and insulin resistance following SF. MethodsTime-pregnant CHOP/GADD34 DM and wild type (WT) mice were randomly assigned to sleep control (SC) or SF conditions during the last 5days of gestation. At 24-weeks of age, body weight, fat mass, and HOMA-IR were assessed in the offspring. Tregs lymphocytes, Lyc6chigh, M1 and M2 macrophages were examined in visceral white adipose tissues (vWAT) using flow cytometry. The effects of plasma exosomes on adipocyte cell line proliferation, differentiation and insulin sensitivity were also evaluated. ResultsSF-WT male showed significant increases in body weight, vWAT mass and HOMA-IR compared to SC-WT mice, while SF had no effect in SF-DM mice. Inflammatory macrophages (Ly-6chigh) and the ratio of M1/M2 macrophages were increased while FoxP3+ Tregs counts were decreased in SF-WT but not in SF-DM mice. Exosomes from SF-WT, but not from the SF-DM offspring increased pre-adipocyte proliferation and differentiation, and decreased in vitro adipocyte insulin sensitivity. ConclusionActivation of the ISR during late gestation, as induced by late gestational SF, appears to underlie some of the transgenerational modifications in metabolic genes ultimately contributing to a metabolic syndrome phenotype in adult offspring.

Identification of a Chemical Probe for Family VIII Bromodomains through Optimization of a Fragment Hit.

The acetyl post-translational modification of chromatin at selected histone lysine residues is interpreted by an acetyl-lysine specific interaction with bromodomain reader modules. Here we report the discovery of the potent, acetyl-lysine-competitive, and cell active inhibitor PFI-3 that binds to certain family VIII bromodomains while displaying significant, broader bromodomain family selectivity. The high specificity of PFI-3 for family VIII was achieved through a novel bromodomain binding mode of a phenolic headgroup that led to the unusual displacement of water molecules that are generally retained by most other bromodomain inhibitors reported to date. The medicinal chemistry program that led to PFI-3 from an initial fragment screening hit is described in detail, and additional analogues with differing family VIII bromodomain selectivity profiles are also reported. We also describe the full pharmacological characterization of PFI-3 as a chemical probe, along with phenotypic data on adipocyte and myoblast cell differentiation assays.

The biological effects of hsa-miR-1908 in human adipocytes

MicroRNAs (miRNAs) are small non-coding RNAs involved in the regulation of gene expression. MiR-1908 is a recently identified miRNA that is highly expressed in human adipocytes. However, it is not known what role of miR-1908 is involved in the regulation of human adipocytes. In this study, we demonstrate that the level of miR-1908 increases during the adipogenesis of human multipotent adipose-derived stem (hMADS) cells and human preadipocytes-visceral. Overexpression of miR-1908 in hMADS cells inhibited adipogenic differentiation and increased cell proliferation, suggesting that miR-1908 is involved in the regulation of adipocyte cell differentiation and metabolism, and, thus, may have an effect on human obesity.

CBX7 gene expression plays a negative role in adipocyte cell growth and differentiation.

ABSTRACTWe have recently generated knockout mice for the Cbx7 gene, coding for a polycomb group protein that is downregulated in human malignant neoplasias. These mice develop liver and lung adenomas and carcinomas, which confirms a tumour suppressor role for CBX7. The CBX7 ability to downregulate CCNE1 expression likely accounts for the phenotype of the Cbx7-null mice.Unexpectedly, Cbx7-knockout mice had a higher fat tissue mass than wild-type, suggesting a role of CBX7 in adipogenesis. Consistently, we demonstrate that Cbx7-null mouse embryonic fibroblasts go towards adipocyte differentiation more efficiently than their wild-type counterparts, and this effect is Cbx7 dose-dependent. Similar results were obtained when Cbx7-null embryonic stem cells were induced to differentiate into adipocytes. Conversely, mouse embryonic fibroblasts and human adipose-derived stem cells overexpressing CBX7 show an opposite behaviour.These findings support a negative role of CBX7 in the control of adipocyte cell growth and differentiation.

The good, the bad and the ugly? The role of exercise on obesity‐induced chemerin expression

Exercise has been shown to alleviate insulin resistance in obesity‐induced diabetes. Although chemerin, a recently discovered adipokine, has been involved in chemotaxis and adipocyte cell‐differentiation in vitro, its role in vivo is still unclear.PurposeTo determine the effect of exercise on obesity‐induced chemerin expression.MethodsForty‐four mice (DIO C57Bl/6J) were separated into 2 cohorts: high fat diet (HFD) n=22 and normal diet (ND) n=22. Following a 12 week‐feeding period, glucose tolerance test was performed with blood samples taken at 0, 30, 60, 90, and 120 min. Chemerin plasma concentration and protein expression were assessed using ELISA and western blot respectively.ResultsHFD induced diabetes. Diabetes resulted in enhanced circulating chemerin levels (ND: 134.63ng/ml vs. HFD: 193.38ng/ml p=0.0009). At 30 min following glucose gavage, circulating chemerin level was significantly higher in HFD compared to ND group (179.6 vs. 112.8 ng/ml respectively P=0.0036). Our preliminary data suggested that exercise upregulated chemerin expression in adipose tissue.ConclusionOur data suggest that exercise regulates diabetes‐increased chemerin expression. A better understanding of chemerin regulation by exercise need to be further studied as it may represent a novel therapeutic target.Study supported by Syracuse University and the School of Education creative writing grant.

Effect of insulin analogues on 3t3-l1 adipogenesis and lipolysis

Insulin has several biological functions besides glycaemic control. We investigated and compared the effects of six different commercial insulins on adipocyte cell differentiation, the lipolytic activity of differentiated cells, and the expression levels of genes involved in adipogenesis and associated with insulin activity. 3T3-L1 cells were induced to differentiate with six commercial insulins: glargine, lispro, aspart, detemir, NPH and regular recombinant human insulin (used as control). Cell differentiation, lipolysis and gene expression were measured at day 7 (D7) and day 10 (D10) after induction of differentiation in these cells. The highest values of cell differentiation and lipolysis were found at D10 for all the insulins used. Preadipocyte differentiation differed at both times depending on the insulin used, with detemir insulin being the least adipogenic. The PPARγ mRNA level varied according to the insulin and was a good genetic marker of adipogenesis at D7. Cells treated with glargine insulin showed the highest lipolysis and HSL expression on both days. Gene expression levels of InsR, SREBP-1c and SCD-1 differed depending on the insulin studied. Detemir insulin was the least adipogenic of the insulins tested, whereas treatment with glargine insulin tended to produce the highest lipolysis levels. Under these experimental conditions, the modifications made in commercial insulins to improve glycaemic control also affect adipocyte differentiation, the lipolysis level of differentiated cells, and the expression of different genes that can modify metabolic pathways independently of glucose metabolism.

Genotype and Tissue-Specific Effects on Alternative Splicing of the Transcription Factor 7-Like 2 Gene in Humans

Context: Noncoding single-nucleotide polymorphisms (SNPs) within the TCF7L2 gene are confirmed risk factors for type 2 diabetes, but the mechanism by which they increase risk is unknown. Objective: We hypothesized that associated SNPs alter TCF7L2 splicing and that splice forms have altered biological roles. Design: Splice forms and 5′ and 3′ untranslated regions were characterized in sc adipose, muscle, liver, HepG2 cells, pancreas, and islet. Isoform-specific transcript levels were quantified in sc adipose. Alternative splice forms were characterized in HepG2 liver cells under glucose and insulin conditions and in SGBS cells with differentiation. Major isoforms were characterized by transfection. Setting: The study was conducted at an ambulatory general clinical research center. Patients: Patients included 78 healthy, nondiabetic study subjects characterized for insulin sensitivity and secretion. Results: We identified 32 alternatively spliced transcripts and multiple-length 3′ untranslated region transcripts in adipose, muscle, islet, and pancreas. Alternative exons 3a, 12, 13, and 13a were observed in all tissues, whereas exon 13b was islet specific. Transcripts retaining exons 13 and 13a but not total TCF7L2 transcripts were significantly correlated with both obesity measures (P < 0.01) and rs7903146 genotype (P < 0.026) in sc adipose. Insulin (5–10 nM) suppressed all TCF7L2 isoforms in SGBS cells but suppressed exon 13a-containing isoforms most significantly (P < 0.001). The isoform distribution differed throughout SGBS cell differentiation. Isoforms with predicted early stop codons yielded stable proteins of the predicted size, bound β-catenin, and targeted correctly to the nucleus. Conclusions: Intronic TCF7L2 variants may regulate alternative transcript isoforms, which in turn may have distinct physiologic roles. a a a Page 1 of 16 Genotype and Tissue-Specific Effects on Alternative Splicing of the Transcription Factor ... 6/19/2014 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2841530/?report=printable Type 2 diabetes (T2D) is among the common, complex diseases for which genetic predisposition is well accepted (1). Grant et al. (2) reported the association of single-nucleotide polymorphisms (SNPs) in the transcription factor 7-like 2 gene (TCF7L2), and this association has been convincingly replicated as the strongest genetic risk factor for T2D (3). Nonetheless, the SNPs implicated are intronic (4) and are not associated with total TCF7L2 transcripts in adipose and muscle (5). Physiological studies of TCF7L2 risk variants have most consistently demonstrated reduced insulin secretion in large epidemiology studies (6,7,8), but other findings suggest a broader role consistent with widespread gene expression (5,9,10,11). TCF7L2 plays a key role in the Wnt signaling pathway (12) and may be important in the expansion and maintenance of β-cell mass (9). However, both increased and decreased TCF7L2 expression in β-cells has been associated with altered insulin secretion and apoptosis in human islets (11,13). Other studies suggested reduced glucagon-like peptide (GLP)-1 induced insulin secretion among carriers (14) or altered proinsulin processing (15). GLP-1 and GLP-1 agonists may act through TCF7L2 and the Wnt pathway to expand and maintain β-cell mass (12). Whereas recent data strongly support a role for TCF7L2 in the β-cell, the means by which intronic variants alter β-cell function or mass remain unclear. Wnt signaling is known to be important in other tissues, including adipose (16), and the proinflammatory cytokine TNFα may inhibit adipogenesis by way of β-catenin/TCF7L2 signaling (17). Studies from our laboratory and others supported a role for TCF7L2 SNPs in altered insulin sensitivity (10), but we and others (5) failed to find a genotype effect on total adipose TCF7L2 transcript levels (5,18,19). Reports of differences in TCF7L2 expression between visceral and sc adipose are inconsistent (18,20,21). The T2D-associated TCF7L2 variants are located in a linkage disequilibrium block that encompasses introns 3 and 4. The T allele of SNP rs7903146 showed reduced binding to protein factors in several cell lines (22), but the relevance of this finding to T2D risk is uncertain. Previous studies suggested multiple TCF7L2 splice forms in tumor tissue (23) and while this work was in preparation, tissue-specific splicing was confirmed in pancreatic islets, lymphocytes, skeletal muscle, and adipose tissue in nondiabetic human subjects (24,25). We hypothesized that TCF7L2 susceptibility variants act by altering the levels of specific transcript isoforms and that splice forms differ in biological function. We characterized the transcript isoforms and untranslated regions in human tissues relevant to diabetes and quantified isoform-specific transcript levels by genotype in nondiabetic subjects. To examine the physiological role of transcript isoforms, we examined the isoform distribution in response to glucose and insulin and during adipocyte cell differentiation. Finally, we determined whether transcript isoforms yielded stable, nuclear targeted proteins that properly bound β-catenin. Materials and Methods