Genes In 3T3-L1 Adipocytes Research Articles

Dapagliflozin promotes white adipose tissue browning though regulating angiogenesis in high fat induced obese mice

Browning of white adipose tissue (WAT) is become an appealing target for therapeutics in the treatment of obesity and related metabolic diseases. Dapagliflozin is widely used in the treatment of type 2 diabetes, and it is also found that the drug exhibits regulate systemic metabolism such as obesity, insulin resistance and hepatic steatosis. However, the precise role of dapagliflozin on WAT remodeling remains to be elucidated. The current study aimed to explore the role of dapagliflozin on WAT browning in high-fat diet (HFD)-induced obese mice. Male C57BL/6J mice (n = 6 per group) were used to establish obesity model by following feeding with HFD for 6 weeks. The mice were randomly treated with or without dapagliflozin for the experimental observation. The volume and fat fraction of WAT were quantified, H&E, UCP-1 staining and immunohistochemistry were conducted to investigate the white-to-brown fat conversion and angiogenesis in WAT respectively. Quantitative real-time polymerase chain reaction (qPCR) was employed to explore the mRNA expression levels of genes related to fat browning and angiogenesis in WAT. Subsequently, 3T3-L1 cells were used to explore the effect of dapagliflozin on preadipocytes differentiation in vitro. Our results demonstrated that dapagliflozin could reduce body weight gain and promote WAT browning in HFD induced obese mice via regulating lipogenesis and angiogenesis in WAT. Furthermore, dapagliflozin reduce cells differentiation, up-regulate the expression of WAT browning and angiogenesis genes in 3T3-L1 adipocytes in vitro. In conclusion, dapagliflozin can potentially promote WAT browning in HFD induced obese mice via improving lipogenesis and angiogenesis in WAT.

P31-055-23 Immature Ginger Reduces Lipogenesis by Down Regulating Acyl CoA Carboxylase and Phosphoenolpyruvatecarboxykinase-1 Genes in 3T3-L1 Adipocytes

P31-055-23 Immature Ginger Reduces Lipogenesis by Down Regulating Acyl CoA Carboxylase and Phosphoenolpyruvatecarboxykinase-1 Genes in 3T3-L1 Adipocytes

Immature ginger reduces triglyceride accumulation by downregulating Acyl CoA carboxylase and phosphoenolpyruvate carboxykinase-1 genes in 3T3-L1 adipocytes.

Obesity is the underlying risk factor for major metabolism complications, including non-alcoholic-fatty liver disease, atherosclerosis, and cardiovascular disease. The adipose tissue is a vital endocrine organ that plays a role in the synthesis and storage of lipid and, therefore, is a contributory factor to the development and progression of obesity. A growing interest in nutraceuticals suggests that natural products can alleviate the risk factors and may be effective in mitigating obesity. The objective of this study was to examine the underlying mechanisms of immature ginger on adipocyte differentiation and lipogenesis in a 3T3-L1 cellular model. Ginger samples, extracted in 80% methanol, were dried and resuspended in DMSO at 50 μg/mL as stock solution. For analysis, the extracted samples were further diluted in media. Effects on adipogenesis were evaluated by determining lipid droplet and triglyceride accumulation, whereas effects on lipogenesis were determined by measuring triglyceride contents and fatty acid profile. The expression of key regulatory genes involved in adipogenesis and lipogenesis was also determined. Our data indicate that the intracellular lipid accumulation decreased significantly by 15 or 25% on treatment with 25 or 50 μg/mL of ginger extract. Consistent with these data, significantly reduced triglyceride levels by 30 or 50% were observed on 25 or 50 μg/mL treatment with ginger extracts, respectively. In addition, ginger treatment significantly inhibited the differentiation-induced de novo lipogenesis and Δ9 desaturase activity. Furthermore, ginger treatment reduced adipogenesis genes, C/ebpβ and C/ebpδ, expression by 47 or 64%, respectively, but significantly increased Pparγ expression by 60% and adiponectin by 75%. Ginger extracts had no effect on Fas genes but reduced lipogenesis genes, acyl CoA carboxylase (Acc) expression by two-fold, and phosphoenolpyruvate carboxy kinase 1 (Pepck1) expression by 50%. Our findings suggest immature ginger can potentially inhibit lipogenesis pathways by limiting the channeling of glucose carbon in fatty acid synthesis by inhibiting the expression of ACC and glycerol production via inhibiting the expression of PEPCK, which consequently inhibits triglyceride formation.

Taste 2 Receptor Is Involved in Differentiation of 3T3-L1 Preadipocytes

Expression of taste 2 receptor (T2R) genes, also known as bitter taste receptor genes, has been reported in a variety of tissues. The white adipose tissue of mice has been shown to express Tas2r108, Tas2r126, Tas2r135, Tas2r137, and Tas2r143, but the function of T2Rs in adipocytes remains unclear. Here, we show that fasting and stimulation by bitter compounds both increased Tas2r expression in mouse white adipose tissue, and serum starvation and stimulation by bitter compounds both increased the expression of Tas2r genes in 3T3-L1 adipocytes, suggesting that T2Rs have functional roles in adipocytes. RNA sequencing analysis of 3T3-L1 adipocytes stimulated by epicatechin, the ligand of Tas2r126, suggested that this receptor may play a role in the differentiation of adipocytes. Overexpression of Tas2r126 in 3T3-L1 preadipocytes decreases fat accumulation after induction of differentiation and reduces the expression of adipogenic genes. Together, these results indicate that Tas2r126 may be involved in adipocyte differentiation.

Tanshinone 1 prevents high fat diet-induced obesity through activation of brown adipocytes and induction of browning in white adipocytes

AimIncreasing brown adipocytes activity and inducting browning of white adipocytes are potential therapeutic targets for the treatment of obesity. In the present study, we investigated the effects of Tanshinone 1 (Tan 1), a major compound from Salvia miltiorrhiza Bunge, on the activation of brown adipocytes and browning of white adipocytes in vivo and in vitro. Materials and methodsExpression of genes associated with brown adipocyte function including thermogenesis, mitochondria biogenesis and fatty acid oxidation was examined in brown adipose tissue (BAT) and white adipose tissue (WAT) of high fat diet (HFD)-fed obese mice administrated with Tan 1 or in immortalized brown adipocytes (iBAs) and 3T3-L1 adipocytes treated with Tan 1. Mitochondria DNA (mtDNA) content, lipolysis and phosphorylated AMP-activated protein kinase (AMPK) were further assessed in Tan 1 treated-iBAs and 3T3-L1 adipocytes. Key findingsThe administration of Tan 1 protected against HFD-induced obesity in mice, which was associated with enhanced expression of brown adipocyte function-related genes in BAT and WAT. Tan 1 treatment also upregulated brown adipocyte function-related genes in iBA and induced beige adipocytes genes in 3T3-L1 adipocytes, resulting in increased mtDNA content and lipolysis. Tan 1 activated AMPK in BAT and WAT of HFD-fed obese mice as well as in iBAs and 3T3-L1 adipocytes. Inhibition of AMPK by compound C prevented Tan 1-induced expression of beige adipocytes genes. SignificanceThese results indicate that Tan 1 activates brown adipocytes and induces browning of white adipocytes, which may contribute to anti-obesity activity of Tan 1.

Medium-chain fatty acids enhance expression and histone acetylation of genes related to lipid metabolism in insulin-resistant adipocytes

BackgroundThe expressions of genes related to lipid metabolism are decreased in adipocytes with insulin resistance. In this study, we examined the effects of fatty acids on the reduced expressions and histone acetylation of lipid metabolism-related genes in 3T3-L1 adipocytes treated with insulin resistance induced by tumor necrosis factor (TNF)-α. MethodsShort-, medium-, and long-chain fatty acid were co-administered with TNF-α in 3T3-L1 adipocytes. Then, mRNA expressions and histone acetylation of genes involved in lipid metabolism were determined using mRNA microarrays, qRT-PCR, and chromatin immunoprecipitation assays. ResultsWe found in microarray and subsequent qRT-PCR analyses that the expression levels of several lipid metabolism-related genes, including Gpd1, Cidec, and Cyp4b1, were reduced by TNF-α treatment and restored by co-treatment with a short-chain fatty acid (C4: butyric acid) and medium-chain fatty acids (C8: caprylic acid and C10: capric acid). The pathway analysis of the microarray showed that capric acid enhanced mRNA levels of genes in the PPAR signaling pathway and adipogenesis genes in the TNF-α-treated adipocytes. Histone acetylation around Cidec and Gpd1 genes were also reduced by TNF-α treatment and recovered by co-administration with short- and medium-chain fatty acids. General significanceMedium- and short-chain fatty acids induce the expressions of Cidec and Gpd1, which are lipid metabolism-related genes in insulin-resistant adipocytes, by promoting histone acetylation around these genes.

Positive metabolic effects of selected probiotic bacteria on diet-induced obesity in mice are associated with improvement of dysbiotic gut microbiota.

Given the rising evidence that gut malfunction including changes in the gut microbiota composition, plays a major role in the development of obesity and associated metabolic diseases, the exploring of novel probiotic bacteria with potential health benefits has attracted great attention. Recently Lactobacillus spp., exert potent anti-obesity effects by regulating key transcriptional and translational factors in adipose tissues. However, the molecular mechanism behind the anti-obesity effect of probiotics is not yet fully understood. Therefore, we investigated the effect of Lactobacillus plantarum A29 on the expression of adipogenic and lipogenic genes in 3T3-L1 adipocytes and high-fat diet (HFD)-fed mice. We observed that the treatment of 3T3-L1 adipocytes with the cell-free metabolites of L plantarum inhibited their differentiation and fat depositions via downregulating the key adipogenic transcriptional factors (PPAR-γ, C/EBP-α, and C/EBP-β) and their downstream targets (FAS, aP2, ACC, and SREBP-1). Interestingly, supplementation with L plantarum reduced the fat mass and serum lipid profile concurrently with downregulation of lipogenic gene expression in the adipocytes, resulting in reductions in the bodyweight of HFD-fed obese mice. L plantarum treatment attenuated the development of obesity in HFD-fed mice via the activation of p38MAPK, p44/42, and AMPK-α by increasing their phosphorylation. Further analysis revealed that A29 modulated gut-associated microbiota composition. Thus, A 29 potential probiotic strain may alleviate the obesity development and its associated metabolic disorders via inhibiting PPARγ through activating the p38MAPK and p44/42 signaling pathways.

Sinapic Acid Promotes Browning of 3T3-L1 Adipocytes via p38 MAPK/CREB Pathway.

Sinapic acid is a plant-derived phenolic compound, which acts as an antioxidant, anticancer, and anti-inflammatory agent. Although sinapic acid is valuable in a variety of therapeutic applications, its role in the improvement of obesity-related metabolic disease is relatively unexplored. Brown-like adipocytes (beige adipocytes) are characterized by a high concentration of mitochondria and high expression of uncoupling protein 1 (UCP1), which has specific functions in energy expenditure and thermogenesis. This study assessed the browning effects of sinapic acid in 3T3-L1 adipocytes. We investigated the expression of beige marker genes in 3T3-L1 adipocytes treated with sinapic acid. Sinapic acid increased the expression of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and UCP1. Sinapic acid also promoted mitochondrial biogenesis by dose-dependently upregulating the oxygen consumption rate and enhancing the expression of representative subunits of oxidative phosphorylation complexes. In addition, treatment with p38 mitogen-activated protein kinase (MAPK) inhibitor and cAMP response element binding (CREB) inhibitor decreased the expressions of genes associated with thermogenesis, mitochondrial biogenesis, and oxidative phosphorylation. In summary, sinapic acid initiates browning 3T3-L1 adipocytes via the p38 MAPK/CREB signaling pathway. Thus, sinapic acid may have potential therapeutic implication in obesity.

Effects of Brown Rice and Germinated Brown Rice Extracts from Thai Rice Cultivars (PL2 and KDML105) on Adipogenic, Adipocytokine, and Antioxidant Genes in 3T3-L1 Adipocytes

Effects of Brown Rice and Germinated Brown Rice Extracts from Thai Rice Cultivars (PL2 and KDML105) on Adipogenic, Adipocytokine, and Antioxidant Genes in 3T3-L1 Adipocytes

High phosphate diet suppresses lipogenesis in white adipose tissue.

Excessive phosphate intake has been positively associated with renal and vascular dysfunction, conversely negatively associated with body fat accumulation. We investigated the effect of a high-phosphate diet on the expression of lipid metabolic genes in white adipose tissue and liver. Male 8-week-old Sprague–Dawley rats were fed a control diet containing 0.6% phosphate or a high-phosphate diet containing 1.5% phosphate for 4 weeks. In comparison to the control group, the HP group showed a significantly lower body fat mass and fasting plasma insulin level alongside decreased lipogenic and increased lipolytic gene expression in visceral fat. Additionally, the expression of genes involved in hepatic lipogenesis, hepatic glycogenesis, and triglyceride accumulation decreased in the high-phosphate group. Exogenous phosphate, parathyroid hormone, and fibroblast growth factor 23 did not directly affect the expression of lipolytic or lipogenic genes in 3T3-L1 adipocytes and HepG2 hepatocytes. Thus, the high-phosphate diet suppressed the activity of white adipose tissue by increasing lipolytic gene expression and decreasing lipogenic gene expression. These effects could have been caused by the lowered fasting plasma insulin level that occurred in response to the high-phosphate diet, but were not directly caused by the increases in plasma phosphate or phosphaturic hormones.

Korean Red Ginseng (Panax ginseng) Potentiates the Inhibitory Actions of Testosterone on Obesity and Adipogenesis in High Fat Diet-Fed Castrated Mice

It has been suggested that ginseng is beneficial for ameliorating the aging males symptoms, such as weight gain, fatigue, erectile dysfunction, and depression, in elderly men with testosterone deficiency. We thus investigated the effects of Korean red ginseng (Panax ginseng C.A. Meyer; Araliaceae) on obesity in a mouse model of testosterone deficiency (castrated C57BL/6J mice). The effects of ginseng extract (GE) and/or testosterone on obesity and adipogenesis in high-fat diet (HFD)-fed castrated C57BL/6J mice and 3T3-L1 adipocytes were examined using in vivo and in vitro approaches. After feeding mice a HFD for 8 weeks, we found that mice also receiving GE and/or testosterone showed decreased body weight, adipose tissue mass, adipocyte size, and hepatic lipid accumulation compared with untreated HFD-fed mice. Expression of adipogenic genes (PPARγ, C/EBPα, and aP2) was decreased by GE and/or testosterone in adipose tissues. Consistent with the in vivo data, lipid accumulation and the mRNA expression of adipogenesis genes in 3T3-L1 adipocytes were decreased by GE, ginsenosides, and testosterone. The inhibitory effects of GE (or ginsenosides) were comparable to those of testosterone, and the effects of co-treatment with GE (or ginsenosides) and testosterone were greater than those of testosterone alone in vivo and in vitro. Our results indicate that ginseng may be able to potentiate the inhibitory effects of testosterone on obesity and adipogenesis in HFD-fed castrated mice, providing possible therapeutic implications in men with testosterone deficiency.

Impaired histone deacetylases 5 and 6 expression mimics the effects of obesity and hypoxia on adipocyte function

ObjectiveThe goal of the study was to investigate the role of histone deacetylases (HDACs) in adipocyte function associated with obesity and hypoxia. MethodsTotal proteins and RNA were prepared from human visceral adipose tissues (VAT) of human obese and normal weight subjects and from white adipose tissue (WAT) of C57Bl6-Rj mice fed a normal or high fat diet (HFD) for 16 weeks. HDAC activity was measured by colorimetric assay whereas the gene and protein expression were monitored by real-time PCR and by western blotting, respectively. RNA interference (RNAi) was used to silence the expression of genes in 3T3-L1 adipocytes. ResultsTotal HDAC activity was decreased in VAT and WAT from obese individuals and from mice fed a HFD, respectively. The HDAC activity reduction was associated with decreased HDAC5/Hdac5 and HDAC6/Hdac6 expression in human and mice adipocyte fraction. Similarly, hypoxia hampered total Hdac activity and reduced the expression of Hdac5 and Hdac6 in 3T3-L1 adipocytes. The decrease of both Hdac5 and Hdac6 by hypoxia was associated with altered expression of adipokines and of the inducible cAMP early repressor (Icer), a key repressor that is defective in human and mice obesity. Silencing of Icer in adipocytes reproduced the changes in adipokine levels under hypoxia and obesity, suggesting a causative effect. Finally, modeling the defect of the two Hdacs in adipocytes by RNAi or selective inhibitors mimicked the effects of hypoxia on the expression of Icer, leading to impairment of insulin-induced glucose uptake. ConclusionHdac5 and Hdac6 expression are required for the adequate expression of Icer and adipocyte function. Altered adipose expression of the two Hdacs in obesity by hypoxia may contribute to the development of metabolic abnormalities.

Leukemia Cells Resident in Adipose Tissue Display a Pro-Inflammatory Phenotype and Induce Lipolysis and Atrophy of Adipose Tissue

Aberrant function of adipose tissue (AT) is seen in several diseases including cancer. Studies show that AT facilitates the progression of tumors through paracrine signaling of adipokines as well as regulation of cancer cell metabolism. However, the mechanism by which cancer cells corrupt the normal function of AT to gain proliferative and survival advantages is unknown. Using a murine model of blast crisis CML, we have shown enrichment of phenotypically primitive leukemia cells (Sca+/lin- leukemia cells, termed "PLCs") in the gonadal AT (GAT) as well as a fatty acid oxidation (FAO) regulatory role of AT. In this study, we evaluated the functional alteration of GAT in leukemic mice. We hypothesized that resident leukemia cells change the characteristics of GAT to obtain metabolic benefits.To test this hypothesis, we first examined whether PLCs in GAT differed from PLCs in other tissues including bone marrow, spleen and peripheral blood. To this end, we utilized RNA-seq to obtain a genome-wide transcriptional profile of PLCs in different tissues. We found PLCs in GAT had a distinct gene expression pattern with enrichment of inflammatory response genes. Specifically, pro-inflammatory cytokines and chemokines were highly expressed by PLCs in GAT (Figure 1). Furthermore, the expression of those genes was also increased in the stromal vascular fraction (SVF) of GAT, indicating resident leukemia cells induced inflammation in GAT. Collectively, these results suggest that leukemia cells found in GAT are distinct from leukemia cells in other tissues and may alter the function of GAT.Another characteristic observed in our model was atrophy of GAT (Figure 2) as well as loss of body weight during leukemia progression, indicating the presence of cancer cachexia. Loss of GAT was also found prior to loss of body weight, suggesting the presence of a pre-cachexia stage. We speculated that atrophy of GAT was due to lipolysis induced by inflammation. Indeed, leukemic GAT released more free fatty acid (FFA) and had a lipolytic pattern of adipokines compared to normal GAT. Elevated FFA and lipolytic adipokines were also detected in leukemic serum. Together, these observations demonstrate that GAT in leukemic mice is lipolytic.To gain insights into mechanisms involved in lipolysis of leukemic GAT, we examined expression of lipolysis-related genes (Figure 3). We found that leukemic GAT had increased expression of the adipose triglyceride lipase (Atgl), which is a rate-limiting lipase controlling lipolysis, and reduced expression of lipoprotein lipase (Lpl), whose expression correlates with the influx of fatty acids into adipocytes. Additionally, decreased expression of the cell death activator CIDE-A (Cidea), which is a lipid droplet (LD) associated protein that shields LDs from lipases and inhibits lipolysis, was found in leukemic GAT. Together, these findings suggest that regulation of lipid metabolism is disrupted in leukemic GAT, leading to lipolysis.To test whether resident leukemia cells contribute to the atrophy of GAT, we examined the lipolytic effect of the pro-inflammatory cytokines and chemokines that were highly expressed by PLCs in GAT. We found that IL-1β and CSF2 induced lipolysis and engendered similar gene expression patterns of lipolysis-related genes in 3T3-L1 adipocytes. Notably, palmitate induced the expression of IL-1β in leukemia cells while it had an opposite effect in naive hematopoietic cells, implying a positive feedback loop where inflammation induces lipolysis which induces IL-1β which in turn augments inflammation. Additionally, an increased amount of IL-1β was observed in leukemic serum. Taken together, these data suggest that resident leukemia cells contribute to the atrophy of GAT through paracrine signaling of pro-inflammatory agents. This phenomenon appears to benefit leukemia cells by fostering FAO and metabolic properties that enhance leukemia cell survival.Thus, targeting pathways that mediate inflammation and/or lipolysis may create a microenvironment that is less favorable to leukemia cells. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

PPARγ partial agonist GQ-16 strongly represses a subset of genes in 3T3-L1 adipocytes

Thiazolidinediones (TZDs) are peroxisome proliferator-activated receptor gamma (PPARγ) agonists that improve insulin resistance but trigger side effects such as weight gain, edema, congestive heart failure and bone loss. GQ-16 is a PPARγ partial agonist that improves glucose tolerance and insulin sensitivity in mouse models of obesity and diabetes without inducing weight gain or edema. It is not clear whether GQ-16 acts as a partial agonist at all PPARγ target genes, or whether it displays gene-selective actions. To determine how GQ-16 influences PPARγ activity on a gene by gene basis, we compared effects of rosiglitazone (Rosi) and GQ-16 in mature 3T3-L1 adipocytes using microarray and qRT-PCR. Rosi changed expression of 1156 genes in 3T3-L1, but GQ-16 only changed 89 genes. GQ-16 generally showed weak effects upon Rosi induced genes, consistent with partial agonist actions, but a subset of modestly Rosi induced and strongly repressed genes displayed disproportionately strong GQ-16 responses. PPARγ partial agonists MLR24 and SR1664 also exhibit disproportionately strong effects on transcriptional repression. We conclude that GQ-16 displays a continuum of weak partial agonist effects but efficiently represses some negatively regulated PPARγ responsive genes. Strong repressive effects could contribute to physiologic actions of GQ-16.

Arachidonic acid has a dominant effect to regulate lipogenic genes in 3T3-L1 adipocytes compared to omega-3 fatty acids

BackgroundThe effects of long-chain n-3 and n-6 polyunsaturated fatty acids (PUFA) on the regulation of adipocytes metabolism are well known. These fatty acids are generally consumed together in our diets; however, the metabolic regulation of adipocytes in the presence of these fatty acids when given together is not known.ObjectiveTo investigate the effects of n-3 PUFA and arachidonic acid (AA), an n-6 PUFA, on the regulation of adipogenic and lipogenic genes in mature 3T3-L1 adipocytes.Methods3T3-L1 adipocytes were incubated in the presence or absence of 100 µM of eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA; docosapentaenoic acid, DPA and AA, either alone or AA+n-3 PUFA; control cells received bovine serum albumin alone. The mRNA expression of adipogenic and lipogenic genes was measured. The fatty acid composition of adipocytes was analyzed using gas chromatography.ResultsIndividual n-3 PUFA or AA had no effect on the mRNA expression of peroxisome-proliferator-activated receptor-γ; however, AA+EPA and AA+DPA significantly increased (P<0.05) the expression compared to control cells (38 and 42%, respectively). AA and AA+EPA increased the mRNA expression of acetyl-CoA carboxylase 1 (P<0.05). AA treatment decreased the mRNA expression of stearoyl-CoA desaturase (SCD1) (P<0.01), while n-3 PUFA, except EPA, had no effect compared to control cells. AA+DHA and AA+DPA inhibited SCD1 gene expression (P<0.05) suggesting a dominant effect of AA. Fatty acids analysis of adipocytes revealed a higher accretion of AA compared to n-3 PUFA.ConclusionsOur findings reveal that AA has a dominant effect on the regulation of lipogenic genes in adipocytes.

Cinnamaldehyde Contributes to Insulin Sensitivity by Activating PPARδ, PPARγ, and RXR.

Cinnamon is a traditional folk herb used in Asia and has been reported to have antidiabetic effects. Our previous study showed that cinnamaldehyde (CA), a major effective compound in cinnamon, exhibited hypoglycemic and hypolipidemic effects together in db/db mice. The aim of the present study was to elucidate the molecular mechanisms of the effects of CA on the transcriptional activities of three peroxisome proliferator-activated receptors, (PPAR) α, δ, and γ. We studied the effects of CA through a transient expression assay with TSA201 cells, derivatives of human embryonic kidney cell line (HEK293). Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis was also performed to evaluate mRNA expression levels. We show here that CA induced PPARδ, PPARγ and retinoid X receptor (RXR) activation. CA may activate PPARγ in a different manner than pioglitazone, as CA selectively stimulated PPARγ S342A mutant while pioglitazone did not. In addition, CA and L-165041 had a synergistic effect on PPARδ activation. To gather the biological evidence that CA increases PPARs transcription, we further measured the expressions of PPARδ and PPARγ target genes in 3T3-L1 adipocytes. The data showed CA induced the expression of PPARδ and PPARγ target genes, namely aP2 and CD36, in differentiated adipocytes. As a result, PPARδ, PPARγ and their heterodimeric partner RXR appear to play a part in the CA action in the target tissues, thereby enhancing insulin sensitivity and fatty acid β-oxidation and energy uncoupling in skeletal muscle and adipose tissue.

Increased GIP signaling induces adipose inflammation via a HIF-1α-dependent pathway and impairs insulin sensitivity in mice.

Glucose-dependent insulinotropic polypeptide (GIP) is a gut hormone secreted in response to dietary fat and glucose. The blood GIP level is elevated in obesity and diabetes. GIP stimulates proinflammatory gene expression and impairs insulin sensitivity in cultured adipocytes. In obesity, hypoxia within adipose tissue can induce inflammation. The aims of this study were 1) to examine the proinflammatory effect of increased GIP signaling in adipose tissues in vivo and 2) to clarify the association between GIP and hypoxic signaling in adipose tissue inflammation. We administered GIP intraperitoneally to misty (lean) and db/db (obese) mice and examined adipose tissue inflammation and insulin sensitivity. We also examined the effects of GIP and hypoxia on expression of the GIP receptor (GIPR) gene and proinflammatory genes in 3T3-L1 adipocytes. GIP administration increased monocyte chemoattractant protein-1 (MCP-1) expression and macrophage infiltration into adipose tissue and increased blood glucose in db/db mice. GIPR and hypoxia-inducible factor-1α (HIF-1α) expressions were positively correlated in the adipose tissue in mice. GIPR expression increased dramatically in differentiated adipocytes. GIP treatment of adipocytes increased MCP-1 and interleukin-6 (IL-6) production. Adipocytes cultured either with RAW 264 macrophages or under hypoxia expressed more GIPR and HIF-1α, and GIP treatment increased gene expression of plasminogen activator inhibitor 1 and IL-6. HIF-1α gene silencing diminished both macrophage- and hypoxia-induced GIPR expression and GIP-induced IL-6 expression in adipocytes. Thus, increased GIP signaling plays a significant role in adipose tissue inflammation and thereby insulin resistance in obese mice, and HIF-1α may contribute to this process.

Soyasaponins Aa and Ab exert an anti-obesity effect in 3T3-L1 adipocytes through downregulation of PPARγ.

Saponins are a diverse group of biologically functional products in plants. Soyasaponins are usually glycosylated, which give rise to a wide diversity of structures and functions. In this study, we investigated the effects and molecular mechanism of soyasaponins Aa and Ab in regulating adipocyte differentiation and expression of adipogenic marker genes in 3T3-L1 adipocytes. Soyasaponins Aa and Ab dose-dependently inhibited the accumulation of lipids and the expression of adiponectin, adipocyte determination and differentiation factor 1/sterol regulatory element binding protein 1c, adipocyte fatty acid-binding protein 2, fatty acid synthase, and resistin in 3T3-L1 adipocytes. In addition, soyasaponins Aa and Ab suppressed the transcriptional activity of peroxisome proliferator-activated receptor γ (PPARγ) in HEK 293T cells. Furthermore, we confirmed that the expression of PPARγ and of CCAAT-enhancer-binding protein α (C/EBPα) was suppressed at both the mRNA and protein levels in 3T3-L1 adipocytes by treatment with soyasaponins Aa and Ab. Taken together, these findings indicate that soyasaponin Aa and Ab markedly inhibit adipocyte differentiation and expression of various adipogenic marker genes through the downregulation of the adipogenesis-related transcription factors PPARγ and C/EBPα in 3T3-L1 adipocytes.

Effect of diacylglycerol acyltransferase 2 overexpression in 3T3-L1 is associated to an increase in mono-unsaturated fatty acid accumulation.

BackgroundFatty acid (FA) composition is the most important parameter affecting the flavor and nutritional value of the meat. The final and the only committed step in the biosynthesis of triglycerides is catalyzed by diacylglycerol acyltransferase 2 (DGAT2). The role of DGAT2 in lipid accumulation has been demonstrated in adipocytes, However, little is known about the effect of DGAT2 on the FA composition of these cells.MethodsTo investigate the role of DGAT2 in regulating lipid accumulation, FA composition and the expression of adipogenic genes, we cloned the open reading frame of the porcine DGAT2 gene and established 3T3-L1 cells that overexpressed DGAT2. Cells were then cultured in differentiation medium (DM) without FA, with a mixture of FAs (FA-DM), or containing a 13C stable isotope-labeled FA mixture (IFA-DM). The FA composition of adipocytes was analyzed by gas chromatography–mass spectrometry and gas chromatography-isotope ratio mass spectrometry. Quantitative PCR and western blotting were employed to detect expression of adipogenic genes in 3T3-L1 adipocytes cultured with FA-DM for 12 d.ResultsThe triacylglyceride (TAG) content was significantly higher in 3T3-L1 adipocytes overexpressing DGAT2 than in control cells. When cultured in DM or FA-DM for 12 d, cells overexpressing DGAT2 showed a higher proportion of unsaturated FAs (C16:1 and C18:1). However, when cells overexpressing DGAT2 were cultured with FA-DM for 30 min, the FA composition was almost identical to that of controls. Further, the proportion of stable isotope-labeled FAs were similar in 3T3-L1 adipocytes overexpressing DGAT2 and control cells cultured in IFA-DM for 12 d. These results collectively indicate that the higher proportion of mono-unsaturated FAs, C16:1 and C18:1, may originate from de novo FA synthesis but not from the uptake of specific FAs from the medium. This hypothesis is further supported by evidence that both mRNA and protein expression of genes involved in FA synthesis (ACACA, FASN, SCD1, and A-FABP) were significantly higher in cells overexpressing DGAT2 than in control cells.ConclusionsIn conclusion, our study revealed that TAG accumulation, the proportion of MUFAs, and the expression of adipogenic genes were higher in 3T3-L1 cells overexpressing DGAT2 than in control cells.

Aging differentially alters the expression of angiogenic genes in a tissue-dependent manner

Organ functions are altered and impaired during aging, thereby resulting in increased morbidity of age-related diseases such as Alzheimer’s disease, diabetes, and heart failure in the elderly. Angiogenesis plays a crucial role in the maintenance of tissue homeostasis, and aging is known to reduce the angiogenic capacity in many tissues. Here, we report the differential effects of aging on the expression of angiogenic factors in different tissues, representing a potentially causes for age-related metabolic disorders. PCR-array analysis revealed that many of angiogenic genes were down-regulated in the white adipose tissue (WAT) of aged mice, whereas they were largely up-regulated in the skeletal muscle (SM) of aged mice compared to that in young mice. Consistently, blood vessel density was substantially reduced and hypoxia was exacerbated in WAT of aged mice compared to that in young mice. In contrast, blood vessel density in SM of aged mice was well preserved and was not different from that in young mice. Moreover, we identified that endoplasmic reticulum (ER) stress was strongly induced in both WAT and SM during aging in vivo. We also found that ER stress significantly reduced the expression of angiogenic genes in 3T3-L1 adipocytes, whereas it increased their expression in C2C12 myotubes in vitro. These results collectively indicate that aging differentially affects the expression of angiogenic genes in different tissues, and that aging-associated down-regulation of angiogenic genes in WAT, at least in part through ER stress, is potentially involved in the age-related adipose tissue dysfunction.