Adipose Tissue-specific Gene Research Articles

Abstract 4434: Cancer cell-derived adrenomedullin downregulates Zeb1 in adipocytes to induce adipolysis and promote breast cancer progression

Abstract Background: Once breast carcinoma in situ breaks through the basement membrane, it preferentially invades the lipid-rich microenvironment around the mammary gland, which indicates a poor prognosis. However, the detailed mechanisms of this interaction remain elusive. Here, we describe bidirectional communication between breast cancer cells and cancer-associated adipocytes (CAAs). Different from the common hormone-driven mechanism of lipolysis of adipocytes, we found that CAAs perform a unique lipolysis program, and Zeb1 plays an important role in this lipolysis process. Methods: Fabp4-cre;Zeb1-/- as adipose tissue-specific Zeb1 gene knockout homozygous mice and Fabp4-cre;Zeb1 tg as adipose tissue-specific Zeb1 gene overexpression mice were constructed to study mammary gland development and perform orthotopic tumor transplantation experiments. Tetracycline-induced Zeb1-overexpressing stable cells were constructed from mouse preadipocytes 3T3-L1 to study phenotypes of lipolysis. Single-cell sequencing, targeted lipidomics, and RNA sequencing analysis were used to investigate the interaction between cancer cells and adipocytes. Western blotting and immunohistochemical staining assays were used to detect the expression Zeb1 at the cellular level, in mouse models and in patient tissue samples. Results: Our results indicated that breast cancer cell-derived adrenomedullin (ADM) significantly down-regulates Zeb1 expression in adipocytes, which drives downstream gene expression of Pnpla2/HSL/SCD1 and induces adipocyte lipolysis into CAA, a process that results in the release of excess palmitoleic acid. Consequently, we proved that palmitoleic acid could replace arachidonic acid (ARA) in the phospholipid sn-2 position of breast cell membrane, which enhances the fluidity and invasiveness of cancer cells. In addition, overexpression of Zeb1 in adipocytes reduces the ability of cancer cells to induce adipolysis and inhibits the malignant progression of cancer cells. Conclusion: These results indicate that Zeb1 plays a pivotal role as core transcriptional factor in CAA lipolysis. The interaction between breast cancer cells and adipocytes leads to the reprogramming of metabolism within their tumor microenvironment, which may become a new target for breast cancer treatment. Citation Format: Lixia Cao, Xiao Chen, Yi Shi, Shuang Yang. Cancer cell-derived adrenomedullin downregulates Zeb1 in adipocytes to induce adipolysis and promote breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4434.

Construction of a molecular regulatory network related to fat deposition by multi-tissue transcriptome sequencing of Jiaxian red cattle

Intramuscular fat (IMF) refers to the fat that accumulates between muscle bundles or within muscle cells, whose content significantly impacts the taste, tenderness, and flavor of meat products, making it a crucial economic characteristic in livestock production. However, the intricate mechanisms governing IMF deposition, involving non-coding RNAs (ncRNAs), genes, and complex regulatory networks, remain largely enigmatic. Identifying adipose tissue-specific genes and ncRNAs is paramount to unravel these molecular mysteries. This study, conducted on Jiaxian red cattle, harnessed whole transcriptome sequencing to unearth the nuances of circRNAs and miRNAs across seven distinct tissues. The interplay of these ncRNAs was assessed through differential expression analysis and network analysis. These findings are not only pivotal in unveiling the intricacies of fat deposition mechanisms but also lay a robust foundation for future research, setting the stage for enhancing IMF content in Jiaxian red cattle breeding.

1655-P: GLP-1R Is Required for Resveratrol in Exerting Its Metabolic Beneficial Effect in HFD-Challenged Male Mice

The beneficial effects of dietary polyphenols including resveratrol have been elucidated during the past 2-3 decades, yet the mechanism underlying their metabolic functions remains elusive or even controversial. Recent investigations revealed that hepatic hormone FGF21 is the common target for both GLP-1RAs and dietary polyphenol intervention. Here we utilized wild type (WT) and GLP-1R-/- mice to access whether GLP-1R is required for resveratrol to exert its beneficial effects. In WT male mice with HFD challenge, concomitant resveratrol intervention (REV-I) for 12 weeks reduced body weight gain and improved glucose tolerance, while in male GLP-1R-/- mice, such metabolic effects were lost. In WT mouse liver and epididymal white adipose tissue (eWAT), REV-I ameliorated HFD-induced FGF21 resistant and stimulated a battery of genes that are involved in lipid homeostasis. In addition, HFD-induced alterations on expressions of a battery of adipose tissue specific genes including those encode for leptin and adiponectin were reversed by concomitant REV-I. REV-I was also shown to exert anti-inflammatory effects in the ileum of WT mice fed with HFD. Specifically, genes that encode for a battery of pro-inflammatory markers including IL-1β and IFN-γ were significantly elevated by HFD challenge, while REV-I attenuated their expression. HFD challenge also reduced IL-10 mRNA level in the WT mouse ileum, while REV-I restored the expression. Together, we bring a novel player GLP-1R to explore the mechanism underlying the metabolic functions of resveratrol. Collectively, we conclude that the metabolic beneficial effects of resveratrol on reducing body weight gain and improving glucose disposal require GLP-1R. Disclosure J.Feng: None. W.Shao: None. T.Jin: None. Funding Canadian Institutes of Health Research

Creatine ameliorates high-fat diet-induced obesity by regulation of lipolysis and lipophagy in brown adipose tissue and liver

Diet-induced obesity in mice and humans is commonly associated with an imbalance between energy intake and expenditure. Reportedly, creatine can enhance energy expenditure in brown adipose tissue and reduce hepatic triglycerides accumulation; however, the molecular mechanism underlying the role of exogenous creatine supplementation in regulating lipid droplet mobilization remains elusive. Herein, we employed a high-fat diet (HFD)- induced mouse model to investigate the role of creatine in regulating lipolysis and lipophagy in brown adipose tissue and the liver. Exogenous creatine supplementation ameliorated HFD-induced obesity, increased insulin sensitivity and improved glucose homeostasis. Creatine supplementation enhanced the expression of uncoupling protein 1 (UCP1), cell death-inducing DNA fragmentation factor alpha-like effector A (CIDEA), and other brown adipose tissue-specific thermogenic genes Cpt1a, Gyk, and Pgc1β in brown adipose tissue. Furthermore, creatine inhibited the expression of CIDEA, which promotes hepatic lipid accumulation. Creatine stimulated the expression of triglyceride lipase adipose triglyceride lipase, and phospho-hormone-sensitive lipase (HSL) induced increased lipolysis in brown adipose tissue and the liver. Meanwhile, reduced LC3B expression was accompanied by an increased level of p62 in HFD-fed mice, indicating diminished basal autophagy in brown adipose tissue and the liver; however, creatine enhanced P62/LC3B induced lipophagy in brown adipose tissue and the liver. Collectively, our results suggest that creatine may function as a brown adipose tissue activator to increase whole-body energy metabolism via coordinated lipolysis and lipophagy in brown adipose tissue and the liver.

Liraglutide stimulates the β-catenin signaling cascade in mouse epididymal fat tissue.

Although canonical Wnt signaling pathway activation was shown to negatively regulate adipogenesis, recent investigations suggest that Wnt pathway effectors TCF7L2 and β-catenin (β-cat) in adipose tissues are also involved in energy homeostasis during adulthood. In assessing the metabolic beneficial effect of GLP-1-based diabetes drugs in high-fat diet (HFD)-challenged mice, we observed that liraglutide treatment affected the expression of a battery of adipose tissue-specific genes, including those that encode adiponectin and leptin, mainly in epididymal white adipose tissue (eWAT). Fourteen-week HFD challenge repressed TCF7L2 and β-cat S675 phosphorylation in eWAT, while such repression was reversed by liraglutide treatment (150 µg/kg body weight daily) during weeks 10-14. In Glp1r-/-mice, liraglutide failed in stimulating TCF7L2 or β-cat in eWAT. We detected Glp1r expression in mouse eWAT and its level is enriched in its stromal vascular fraction (SVF). Mouse eWAT-SVF showed reduced expression of Tcf7l2 and its Tcf7l2 level could not be stimulated by liraglutide treatment; while following adipogenic differentiation, rat eWAT-SVF showed elevated Tcf7l2 expression. Direct in vitro liraglutide treatment in eWAT-SVF stimulated CREB S133, β-cat S675 phosphorylation, and cellular cAMP level. Thus, cAMP/β-cat signaling cascade can be stimulated by liraglutide in eWAT via GLP-1R expressed in eWAT-SVF.

Cloning and functional verification of a porcine adipose tissue-specific promoter

BackgroundFat deposition is an important economic trait in pigs. In the past decades, many genes regulating porcine fat deposition were identified by Omics technology and verified by cell biology studies. Using genetically modified pigs to investigate the function of these genes in vivo is necessary before applying in breeding. However, lack of tissue-specific promoters of pigs hinders the generation of adipose tissue-specific genetically modified pigs.ResultsIn order to identify a porcine adipose tissue-specific promoter, we used the software Digital Differential Display (DDD) to screen 99 genes highly expressed in porcine adipose tissue. GO and KEGG enrichment analysis indicated that the 99 genes were mainly related to lipid metabolism. Q-PCR proved that LGALS12 was an adipose tissue-specific gene. Five truncated fragments of the LGALS12 promoter were cloned and the 4 kb fragment (L-4 kb) exhibited a high level of promoter activity in adipocytes and no promoter activity in non-adipocytes. Following co-transfection with adipogenic transcription factors, the promoter activity of L-4 kb was enhanced by PPARγ, C/EBPβ, and KLF15, whereas it was suppressed by KLF4. Finally, we demonstrated that L-4 kb can drive APOR gene expression to exert its function in adipocytes.ConclusionsThis study demonstrates that porcine LGALS12 is an adipose tissue-specific gene, and identified the 4 kb fragment of LGALS12 promoter that exhibited adipocyte-specific promoter activity. These results provide new evidence for understanding porcine fat deposition and a promoter element for adipose tissue-specific genetic modification in pigs.HighlightsIdentified porcine LGALS12 as an adipose tissue-specific gene.Truncated LGALS12 promoter (L-4 kb) showed adipose tissue-specific promoter activity.Identified transcription factors involved in the regulation of L-4 kb promoter activity.

Screening of Bovine Tissue-Specific Expressed Genes and Identification of Genetic Variation Within an Adipose Tissue-Specific lncRNA Gene.

Global classification of bovine genes is important for studies of biology and tissue-specific gene editing. Herein, we classified the tissue-specific expressed genes and uncovered an important variation in the promoter region of an adipose tissue-specific lncRNA gene. Statistical analysis demonstrated that the number of genes specifically expressed in the brain was the highest, while it was lowest in the adipose tissues. A total of 1,575 genes were found to be significantly higher expressed in adipose tissues. Bioinformatic analysis and qRT-PCR were used to uncover the expression profiles of the 23 adipose tissue-specific and highly expressed genes in 8 tissues. The results showed that most of the 23 genes have higher expression level in adipose tissue. Besides, we detected a 12 bp insertion/deletion (indel) variation (rs720343880) in the promoter region of an adipose tissue-specific lncRNA gene (LOC100847835). The different genotypes of this variation were associated with carcass traits of cattle. Therefore, the outcomes of the present study can be used as a starting point to explore the development of cattle organs and tissues, as well as to improve the quality of cattle products.

DNA Microarray-Based Global Gene Expression Profiling in Human Amniotic Epithelial Cells Predicts the Potential of Microalgae-Derived Squalene for the Nervous System and Metabolic Health

In recent years, perinatal stem cells, such as human amniotic epithelial cells (hAECs), have attracted increasing interest as a novel tool of stem cell-based high-throughput drug screening. In the present study, we investigated the bioactivities of squalene (SQ) derived from ethanol extract (99.5%) of a microalgae Aurantiochytrium Sp. (EEA-SQ) in hAECs using whole-genome DNA microarray analysis. Tissue enrichment analysis showed that the brain was the most significantly enriched tissue by the differentially expressed genes (DEGs) between EEA-SQ-treated and control hAECs. Further gene set enrichment analysis and tissue-specific functional analysis revealed biological functions related to nervous system development, neurogenesis, and neurotransmitter modulation. Several adipose tissue-specific genes and functions were also enriched. Gene-disease association analysis showed nervous system-, metabolic-, and immune-related diseases were enriched. Altogether, our study suggests the potential health benefits of microalgae-derived SQ and we would further encourage investigation in EEA-SQ and its derivatives as potential therapeutics for nervous system- and metabolism-related diseases.

Association of PRDM16 rs12409277 and CtBP2 rs1561589 gene polymorphisms with lipid profile of adolescents.

Positive regulatory domain containing 16 (PRDM16) protein represents the key regulator of brown adipose tissue (BAT) development. It induces brown fat phenotype and represses white adipose tissue specific genes through the association with C-terminal binding co-repressor proteins (CtBP1 and CtBP2). In healthy adults presence of BAT has been associated with lower glucose, total cholesterol and low-density lipoprotein (LDL) cholesterol levels. Our aim was to analyze the association of PRDM16 gene (rs12409277) and CtBP2 gene (rs1561589) polymorphisms with body mass index (BMI), fasting glucose level and lipid profile of adolescents. Our study included 295 healthy school children, 145 boys (49.2%) and 150 girls (50.8%), 15 years of age. Genotypes for the selected polymorphisms were detected by the real-time PCR method. Age, gender, height, weight, lipid profile (total cholesterol, high-density lipoprotein (HDL) cholesterol, LDL cholesterol, triglycerides) and fasting glucose levels were recorded. We did not find a statistically significant association of rs12409277 and rs1561589 polymorphisms with BMI, fasting glucose and lipid profile of adolescents. We further analyzed the combined effect of the two SNPs and the statistical analysis showed that carriers of CT genotype of rs12409277 polymorphism and GG genotype of rs1561589 polymorphism had significantly lower total cholesterol (p = 0.001) and LDL cholesterol (p = 0.008) levels compared to all other groups of genotypes. Our study suggests that rs12409277 and rs1561589 polymorphism might have an influence on total and LDL cholesterol levels in adolescents. Larger studies should be performed in order to confirm our results.

Dietary Silk Peptide Prevents High-Fat Diet-Induced Obesity and Promotes Adipose Browning by Activating AMP-Activated Protein Kinase in Mice.

Obesity is associated with metabolic syndrome and other chronic diseases, and is caused when the energy intake is greater than the energy expenditure. We aimed to determine the mechanism whereby acid-hydrolyzed silk peptide (SP) prevents high-fat diet-induced obesity, and whether it induces browning and fatty acid oxidation (FAO) in white adipose tissue (WAT), using in vivo and ex vivo approaches. We determined the effects of dietary SP in high-fat diet-fed obese mice. The expression of adipose tissue-specific genes was quantified by western blotting, qRT-PCR, and immunofluorescence analysis. We also investigated whether SP directly induces browning in primarily subcutaneous WAT-derived adipocytes. Our findings demonstrate that SP has a browning effect in WAT by upregulating AMP-activated Protein Kinase (AMPK) phosphorylation and uncoupling protein 1 (UCP1) expression. SP also suppresses adipogenesis and promotes FAO, implying that it may have potential as an anti-obesity drug.

OR01-3 MicroRNA-34a-Mediated FGF21 Resistance in the Adipose Tissue Contributes to Insulin Resistance and Hypoadiponectinemia in Diet-Induced Obesity

Background and Objective: Fibroblast growth factor 21 (FGF21) is a metabolic hormone with multiple beneficial effects on glucose and lipid homeostasis, in part mediated through its stimulatory effect on adiponectin secretion. However, FGF21 circulating levels are paradoxically elevated in obesity, type 2 diabetes and other obesity-related disorders, suggesting the presence of FGF21 resistance in obesity. MicroRNA-34a (miR-34a) is the most highly elevated microRNA in white adipose tissues of obese mice and a conserved miR-34a seed sequence had been detected within the 3’UTR of FGFR1 and β-klotho. Here we sought to investigate the mediatory role of miR-34a in FGF21resistance. Methods: miR-34a expression and the corresponding changes in the expression of FGFR1 and β-klotho were assessed in visceral adipose tissue from mice with or without diet-induced obesity (DIO). Luciferase assay was used to examine the binding capacity of miR-34a to the FGF21 receptor complex. The ability to reverse FGF21 resistance via inhibiting adipose miR-34a in vivo was evaluated by both lentivirus-mediated miR-34a sponge and adipose tissue specific genetic depletion. Results: A consistent elevation of miR-34a expression in the adipose tissue was observed during the development of DIO, accompanied by a progressive increase in serum FGF21 levels. Following a transient increase at 4 weeks, mRNA levels of FGFR1 and β-klotho markedly decreased with DIO, accompanied by progressive resistance to the actions of exogenous FGF21, in terms of lowering of hyperglycemia and hyperinsulinemia, and adiponectin stimulation. Site-directed mutagenesis and luciferase activity studies showed that miR-34a suppressed the expression of FGFR1 and β-klotho and also adiponectin secretion. Blocking miR-34a actions by in vivo lentivirus-mediated miR-34a sponge or adipose tissue specific gene knock-out counteracted the reduction of FGFR1 and β-klotho expressions in mice with DIO and restored the ability of FGF21 to induce adiponectin secretion in their adipose tissue. Conclusion: During the development of obesity, a progressive increase of miR-34a in visceral adipose tissue is accompanied by a decline in FGF21 sensitivity, leading to hypoadiponectinemia and insulin resistance. The possibility of selective inhibition of miR-34a in the adipose tissue, as a therapeutic approach to obesity-related metabolic disorders, warrants further investigation. Acknowledgement: This work was supported by a grant from the Health & Medical Research Fund (02132836).

Vasodilator-Stimulated Phosphoprotein: Regulators of Adipokines Resistin and Phenotype Conversion of Epicardial Adipocytes.

BackgroundEndothelial dysfunction plays a central part in the pathogenesis of coronary atherosclerosis. The adipokine resistin is one of the key players in endothelial cell dysfunction. In addition, the role of epicardial fat in coronary artery endothelial dysfunction is also emphasized.We investigated whether vasodilator-stimulated phosphoprotein (VASP) is involved in resistin-related endothelial dysfunction and the phenotype conversion of epicardial adipocytes.Material/MethodsCell proliferation and migration were evaluated by MTT and Transwell chamber assay, respectively. Next, we took epicardial fat samples from patients with valvular heart disease and non-coronary artery disease. Gene expression was determined by reverse transcription-quantitative polymerase chain reaction and relative abundance of the protein by Western blotting.ResultsResistin induced endothelial proliferation and migration in a dose-dependent manner. Both resistin-induced cell proliferation and migration were effectively blocked by ablation of VASP. The brown adipose tissue-specific genes for uncoupling protein 1 (UCP-1) and PR-domain-missing16 (PRDM16) decreased, but the white adipose tissue-specific genes for resistin and RIP140 increased in VASP-deficient adipocytes compared with the LV-sicntr group. However, disruption of the Ras homolog gene family member A (RhoA) /Rho-associated kinase (ROCK) in VASP-deficient adipocytes with specific inhibitors inverted the adipocyte phenotype existing in VASP-deficient adipocytes. Furthermore, the expressions of proinflammatory cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemoattractantprotein-1 (MCP-1) in VASP-deficient adipocytes were markedly upregulated compared with the LV-sicntr group.ConclusionsThese results suggest a physiological role for VASP in coronary atherosclerosis through regulating adipokine resistin and phenotype conversion of epicardial adipose tissue.

Quercetin, a functional compound of onion peel, remodels white adipocytes to brown-like adipocytes

Adipocyte browning is a promising strategy for obesity prevention. Using onion-peel-derived extracts and their bioactive compounds, we demonstrate that onion peel, a by-product of onion, can change the characteristics of white adipocytes to those of brown-like adipocytes in the white adipose tissue of mice and 3T3-L1 cells. The expression of the following brown adipose tissue-specific genes was increased in the retroperitoneal and subcutaneous adipose tissues of 0.5% onion-peel-extract-fed mice: PR domain-containing 16, peroxisome proliferator-activated receptor gamma coactivator 1α, uncoupling protein 1, fibroblast growth factor 21 and cell death-inducing DFFA-like effector. In 3T3-L1 adipocytes, onion peel extract induced the expression of brown adipose tissue-specific genes and increased the expression of carnitine palmitoyltransferase 1α. This effect was supported by decreased lipid levels and multiple small-sized lipid droplets. The ethyl acetate fraction of the onion peel extract that contained the highest proportion of hydrophobic molecules showed the same browning effect in 3T3-L1 adipocytes. A high-performance liquid chromatography analysis further identified quercetin as a functional compound in the browning effect of onion peel. The quercetin-associated browning effect was mediated in part by the activation of AMP-activated protein kinase. In summary, our study provides the first demonstration of the browning effects of onion peel and quercetin using both animal and cell models. This result indicates that onion peel has the potential to remodel the characteristics of white adipocytes to those of brown-like adipocytes.

Polycaprolactone nanofibrous mesh reduces foreign body reaction and induces adipose flap expansion in tissue engineering chamber.

Tissue engineering chamber technique can be used to generate engineered adipose tissue, showing the potential for the reconstruction of soft tissue defects. However, the consequent foreign body reaction induced by the exogenous chamber implantation causes thick capsule formation on the surface of the adipose flap following capsule contracture, which may limit the internal tissue expansion. The nanotopographical property and architecture of nanofibrous scaffold may serve as a promising method for minimizing the foreign body reaction. Accordingly, electrospinning porous polycaprolactone (PCL) nanofibrous mesh, a biocompatible synthetic polymer, was attached to the internal surface of the chamber for the reducing local foreign body reaction. Adipose flap volume, level of inflammation, collagen quantification, capsule thickness, and adipose tissue-specific gene expression in chamber after implantation were evaluated at different time points. The in vivo study revealed that the engineered adipose flaps in the PCL group had a structure similar to that in the controls and normal adipose tissue structure but with a larger flap volume. Interleukin (IL)-1β, IL-6, and transforming growth factor-β expression decreased significantly in the PCL group compared with the control. Moreover, the control group had much more collagen deposition and thicker capsule than that observed in the PCL group. These results indicate that the unique nanotopographical effect of electrospinning PCL nanofiber can reduce foreign body reaction in a tissue engineering chamber, which maybe a promising new method for generating a larger volume of mature, vascularized, and stable adipose tissue.

17β-Estradiol suppresses visceral adipogenesis and activates brown adipose tissue-specific gene expression.

Both functional ovaries and estrogen replacement therapy (ERT) reduce the risk of type 2 diabetes (T2D). Understanding the mechanisms underlying the antidiabetic effects of 17β-estradiol (E2) may permit the development of a molecular targeting strategy for the treatment of metabolic disease. This study examines how the promotion of insulin sensitivity and weight loss by E2 treatment in high-fat-diet (HFD)-fed mice involve several anti-adipogenic processes in the visceral adipose tissue. Magnetic resonance imaging (MRI) revealed specific reductions in visceral adipose tissue volume in HFD+E2 mice, compared with HFD mice. This loss of adiposity was associated with diminished visceral adipocyte size and reductions in expression of lipogenic genes, adipokines and of the nuclear receptor nr2c2/tr4. Meanwhile, expression levels of adipose triglyceride lipase/pnpla2 and leptin receptor were increased. As mRNA levels of stat3, a transcription factor involved in brown adipose tissue differentiation, were also increased in visceral adipose, the expression of other brown adipose-specific markers was assessed. Both expression and immunohistochemical staining of ucp-1 were increased, and mRNA levels of dio-2, and of adrβ3, a regulator of ucp-1 expression during the thermogenic response, were increased. Furthermore, expression of cpt-1b, a brown adipose-specific gene involved in fatty acid utilization, was also increased. Methylation studies demonstrated that the methylation status of both dio-2 and adrβ3 was significantly reduced. These results show that improved glycemic control and weight loss due to E2 involve anti-adipogenic mechanisms which include suppressed lipogenesis and augmented fatty acid utilization, and in addition, the activation of brown adipose tissue-specific gene expression in association with E2-dependent epigenetic modifications in these genes.

Regulations of berberine on gene expression of BMP4 transcriptional pathways to improve visceral white adipose tissues insulin resistance in type 2 diabetic hamsters

To study the effects of berberine on the gene mRNA expressions of BMP4 transcriptional pathways and brown/white adipose tissue conversion transcriptional pathways in visceral white adipose tissues(VWAT) in type 2 diabetic hamsters and explore the relevant mechanisms. The obese insulin-resistant hamster model were induced by using high-fat diet, and then the type 2 diabetic hamster model was created through injection with low-dose streptozotocin in the obese insulin-resistant hamster model. After the modeling, the hamsters were randomly divided into normal control, obese insulin-resistant, type 2 diabetic and berberine-treated diabetic groups. After the nine-week treatment, real-time quantitative PCR was used to measure the changes in gene mRNA expressions of VWAT BMP4 transcriptional pathways, brown/white adipose tissue conversion transcriptional pathways and their target genes in different groups. The results showed that the gene mRNA expressions of BMP4, BMPRⅡ, BMPRlA, Smad1, Smad5, Smad8, p38/MAPK, ATF2, PRDM16, C/EBPβ, PGC1α, PPARγ and brown adipose tissue-specific genes was decreased and that of Smad6, Smurf1 and white adipose tissue-specific genes was increased in VWAT of model hamsters. Treatment with berberine regulated BMP4 transcriptional pathways and brown adipose tissue transcriptional pathways and induced the gene mRNA expression of brown adipose tissue-specific genes in VWAT to develop browning gene phenotype of white adipose tissues, and then improved fat-induced insulin resistance. These findings indicated that BMP4 transcriptional pathways involved in the formation of fat-induced visceral white adipose tissues insulin resistance (FIVWATIR) and the browning molecular mechanism of white adipose tissues induced by berberine.

Glucocorticoids Transcriptionally Regulate miR-27b Expression Promoting Body Fat Accumulation Via Suppressing the Browning of White Adipose Tissue

Long-term glucocorticoid (GC) treatment induces central fat accumulation and metabolic dysfunction. We demonstrate that microRNA-27b (miR-27b) plays a central role in the pathogenesis of GC-induced central fat accumulation. Overexpression of miR-27b had the same effects as dexamethasone (DEX) treatment on the inhibition of brown adipose differentiation and the energy expenditure of primary adipocytes. Conversely, antagonizing miR-27b function prevented DEX suppression of the expression of brown adipose tissue–specific genes. GCs transcriptionally regulate miR-27b expression through a GC receptor–mediated direct DNA-binding mechanism, and miR-27b suppresses browning of white adipose tissue (WAT) by targeting the three prime untranslated region of Prdm16. In vivo, antagonizing miR-27b function in DEX-treated mice resulted in the efficient induction of brown adipocytes within WAT and improved GC-induced central fat accumulation. Collectively, these results indicate that miR-27b functions as a central target of GC and as an upstream regulator of Prdm16 to control browning of WAT and, consequently, may represent a potential target in preventing obesity.

Chitooligosaccharide ameliorates diet-induced obesity in mice and affects adipose gene expression involved in adipogenesis and inflammation

Chitooligosaccharide (CO) has been reported to have potential antiobestic effects in a few studies, but the antiobesity properties of CO and its related mechanisms in models of dietary obesity remain unclear. We investigated the effect of CO on body weight gain, size of adipocytes, adipokines, and lipid profiles in high-fat (HF) diet-induced obese mice and on the gene expression in adipose tissue using a complementary DNA microarray approach to test the hypothesis that CO supplementation would alleviate HF diet-induced obesity by the alteration of adipose tissue-specific gene expression. Male C57BL/6N mice were fed a normal diet (control), HF diet, or CO-supplemented HF diet (1% or 3%) for 5 months. Compared with the HF diet mice, mice fed the 3% CO-supplemented diet gained 15% less weight but did not display any change in food and energy intake. Chitooligosaccharide supplementation markedly improved serum and hepatic lipid profiles. Histologic examination showed that epididymal adipocyte size was smaller in mice fed the HF + 3% CO. Microarray analysis showed that dietary CO supplementation modulated adipogenesis-related genes such as matrix metallopeptidases 3, 12, 13, and 14; tissue inhibitor of metalloproteinase 1; and cathepsin k in the adipose tissues. Twenty-five percent of the CO-responsive genes identified are involved in immune responses including the inflammatory response and cytokine production. These results suggest that CO supplementation may help ameliorate HF diet-induced weight gain and improve serum and liver lipid profile abnormalities, which are associated, at least in part, with altered adipose tissue gene expression involved in adipogenesis and inflammation.

Circadian rhythms in adipose tissue

Over the past decade, evidence has accumulated from basic science, clinical and epidemiological studies linking circadian mechanisms to adipose tissue biology and its related comorbidities, diabetes, metabolic syndrome and obesity. This review highlights recent in-vitro and in-vivo findings from murine, human and model organism studies. High-fat diets attenuate circadian mechanisms in murine adipose depots and these effects appear to be due to obesity rather than hyperglycemia. Deletion of circadian regulatory genes such as AMPK1 and nocturnin alter the circadian biology of adipose tissue. Unlike the mouse, circadian gene oscillation in human adipose tissue appears to be independent of BMI and diabetes status, suggesting that circadian mechanistic variation occurs across species. Clues for future directions in this emerging field come from studies of the hibernation and torpor state in mammals and infection models involving the Drosophila metabolic organ or 'fat body'. There is a growing consensus that circadian rhythms and metabolism are tightly regulated in adipose tissue and peripheral metabolic organs. Although central mechanisms are critical, autonomous clocks exist within the adipocytes themselves. Future circadian advances are likely to result from the studies of adipose tissue-specific gene deletions.

A Stratified Transcriptomics Analysis of Polygenic Fat and Lean Mouse Adipose Tissues Identifies Novel Candidate Obesity Genes

BackgroundObesity and metabolic syndrome results from a complex interaction between genetic and environmental factors. In addition to brain-regulated processes, recent genome wide association studies have indicated that genes highly expressed in adipose tissue affect the distribution and function of fat and thus contribute to obesity. Using a stratified transcriptome gene enrichment approach we attempted to identify adipose tissue-specific obesity genes in the unique polygenic Fat (F) mouse strain generated by selective breeding over 60 generations for divergent adiposity from a comparator Lean (L) strain.ResultsTo enrich for adipose tissue obesity genes a ‘snap-shot’ pooled-sample transcriptome comparison of key fat depots and non adipose tissues (muscle, liver, kidney) was performed. Known obesity quantitative trait loci (QTL) information for the model allowed us to further filter genes for increased likelihood of being causal or secondary for obesity. This successfully identified several genes previously linked to obesity (C1qr1, and Np3r) as positional QTL candidate genes elevated specifically in F line adipose tissue. A number of novel obesity candidate genes were also identified (Thbs1, Ppp1r3d, Tmepai, Trp53inp2, Ttc7b, Tuba1a, Fgf13, Fmr) that have inferred roles in fat cell function. Quantitative microarray analysis was then applied to the most phenotypically divergent adipose depot after exaggerating F and L strain differences with chronic high fat feeding which revealed a distinct gene expression profile of line, fat depot and diet-responsive inflammatory, angiogenic and metabolic pathways. Selected candidate genes Npr3 and Thbs1, as well as Gys2, a non-QTL gene that otherwise passed our enrichment criteria were characterised, revealing novel functional effects consistent with a contribution to obesity.ConclusionsA focussed candidate gene enrichment strategy in the unique F and L model has identified novel adipose tissue-enriched genes contributing to obesity.