Guoxian Ding

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.

BVT.2733, a selective 11β-hydroxysteroid dehydrogenase type 1 inhibitor, attenuates obesity and inflammation in diet-induced obese mice.

Background Inhibition of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is being pursued as a new therapeutic approach for the treatment of obesity and metabolic syndrome. Therefore, there is an urgent need to determine the effect of 11β-HSD1 inhibitor, which suppresses glucocorticoid action, on adipose tissue inflammation. The purpose of the present study was to examine the effect of BVT.2733, a selective 11β-HSD1 inhibitor, on expression of pro-inflammatory mediators and macrophage infiltration in adipose tissue in C57BL/6J mice. Methodology/Principal Findings C57BL/6J mice were fed with a normal chow diet (NC) or high fat diet (HFD). HFD treated mice were then administrated with BVT.2733 (HFD+BVT) or vehicle (HFD) for four weeks. Mice receiving BVT.2733 treatment exhibited decreased body weight and enhanced glucose tolerance and insulin sensitivity compared to control mice. BVT.2733 also down-regulated the expression of inflammation-related genes including monocyte chemoattractant protein 1 (MCP-1), tumor necrosis factor alpha (TNF-α) and the number of infiltrated macrophages within the adipose tissue in vivo. Pharmacological inhibition of 11β-HSD1 and RNA interference against 11β-HSD1 reduced the mRNA levels of MCP-1 and interleukin-6 (IL-6) in cultured J774A.1 macrophages and 3T3-L1 preadipocyte in vitro. Conclusions/Significance These results suggest that BVT.2733 treatment could not only decrease body weight and improve metabolic homeostasis, but also suppress the inflammation of adipose tissue in diet-induced obese mice. 11β-HSD1 may be a very promising therapeutic target for obesity and associated disease.

Expression Profiling of PPARγ-Regulated MicroRNAs in Human Subcutaneous and Visceral Adipogenesis in both Genders

Clinical evidence shows that visceral fat accumulation decreases whereas sc fat increases in patients treated with thiazolidinediones (TZDs), a type of peroxisome proliferator-activated receptor (PPAR)γ agonist. To clarify the molecular mechanism of the differential effects of PPARγ agonists on sc and visceral adipose, we investigated expression profiling of PPARγ-regulated micro-RNAs (miRNAs) using miRNA microarray. The level of 182 miRNAs changed in human sc adipose treated with pioglitazone, whereas only 46 miRNAs changed in visceral adipose. Among these miRNAs, 27 miRNAs changed in both human sc and visceral adipocytes. Specifically, 7 miRNAs changed at the same direction in sc and visceral adipocytes, whereas 20 miRNAs changed at opposite directions in these two fat depots. Bioinformatics analysis showed that these miRNAs and the predicted target genes were involved in TGF-β-, Wnt/β-catenin-, and insulin-signaling pathways and related to metabolic regulation or cell cycle. Among the miRNAs changed at the same direction in sc and visceral adipocytes, miR-378, located in the first intron of PPARγ coactivator 1β (PGC1β), was coordinately expressed with PGC1β during adipogenesis. Moreover, miR-378 and PGC1β were both up-regulated by PPARγ agonist. We also provided evidence that miR-378 promoted adipogenesis in sc fat, but not in visceral fat. These results display miRNAs expression profiling altered in sc and visceral adipogenesis regulated by PPARγ and suggest a potential mechanism underlying the differential effects of TZDs on the 2 fat depot accumulations.

Identification of sucrose non-fermenting related kinase (SNRK) as a suppressor of adipocyte inflammation

In this study, the role of sucrose non-fermenting–related kinase (SNRK) in white adipocyte biology was investigated. SNRK is abundantly expressed in adipose tissue, and the expression level is decreased in obese mice. SNRK expression is repressed by inflammatory signals but increased by insulin sensitizer in cultured adipocytes. In vivo, adipose tissue SNRK expression can be decreased by lipid injection but enhanced by macrophage ablation. Knocking down SNRK in cultured adipocytes activates both JNK and IKKβ pathways as well as promotes lipolysis. Insulin-stimulated Akt phosphorylation and glucose uptake are impaired in SNRK knockdown adipocytes. Phosphoproteomic analysis with SNRK knockdown adipocytes revealed significantly decreased phosphorylation of 49 proteins by 25% or more, which are involved in various aspects of adipocyte function with a clear indication of attenuated mTORC1 signaling. Phosphorylation of 43 proteins is significantly increased by onefold or higher, among which several proteins are known to be involved in inflammatory pathways. The inflammatory responses in SNRK knockdown adipocytes can be partially attributable to defective mTORC1 signaling, since rapamycin treatment activates IKKβ and induces lipolysis in adipocytes. In summary, SNRK may act as a suppressor of adipocyte inflammation and its presence is necessary for maintaining normal adipocyte function.

Assessment of Fat distribution and Bone quality with Trabecular Bone Score (TBS) in Healthy Chinese Men.

Whether fat is beneficial or detrimental to bones is still controversial, which may be due to inequivalence of the fat mass. Our objective is to define the effect of body fat and its distribution on bone quality in healthy Chinese men. A total of 228 men, aged from 38 to 89 years, were recruited. BMD, trabecular bone score (TBS), and body fat distribution were measured by dual-energy X-ray absorptiometry. Subcutaneous and visceral fat were assessed by MRI. In the Pearson correlation analysis, lumbar spine BMD exhibited positive associations with total and all regional fat depots, regardless of the fat distribution. However, the correlation disappeared with adjusted covariables of age, BMI, HDL-C, and HbA1c%. TBS was negatively correlated with fat mass. In multiple linear regression models, android fat (and not gynoid, trunk, or limbs fat) showed significant inverse association with TBS (β = −0.611, P < 0.001). Furthermore, visceral fat was described as a pathogenic fat harmful to TBS, even after adjusting for age and BMI (β = −0.280, P = 0.017). Our findings suggested that body fat mass, especially android fat and visceral fat, may have negative effects on bone microstructure; whereas body fat mass contributes to BMD through mechanical loading.

Determination of UCP1 expression in subcutaneous and perirenal adipose tissues of patients with hypertension

The objective of this study is to determine the property of human perirenal adipose tissue (PAT) and assess the adipose property of PAT in hypertension. Ninety-four patients, including 64 normotensive patients (T-NP) and 30 hypertensive patients (HP), who underwent renal surgery were included. Expression analysis was performed using quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry in PAT and back subcutaneous adipose tissue (bSAT) depots. Compared with bSAT, PAT adipocytes were smaller, and the expressions of uncoupling protein-1 (UCP1) mRNA and protein were markedly higher, while the mRNA expressions of markers for classic beige and white adipocytes were lower in PAT. Immunohistochemistry analysis showed more multilocular UCP1-positive adipocytes in PAT than in bSAT. UCP1 expressions were lower in PAT in HP than in the T-NP or age- and body mass index-matched NP groups. Bigger unilocular adipocytes with less UCP1 staining in PAT were detected in HP than in NP group, although no such difference was observed in bSAT. PAT acts as a brown-like fat. UCP1 expression of PAT was lower in HP than in normotensive patients. UCP1 expression of PAT may serve as a protective indicator for hypertension.

Opposing effects on cardiac function by calorie restriction in different-aged mice

Calorie restriction (CR) increases average and maximum lifespan and exhibits an apparent beneficial impact on age‐related diseases. Several studies have shown that CR initiated either in middle or old age could improve ischemic tolerance and rejuvenate the aging heart; however, the data are not uniform when initiated in young. The accurate time to initiate CR providing maximum benefits for cardiac remodeling and function during aging remains unclear. Thus, whether a similar degree of CR initiated in mice of different ages could exert a similar effect on myocardial protection was investigated in this study. C57BL/6 mice were subjected to a calorically restricted diet (40% less than the ad libitum diet) for 3 months initiated in 3, 12, and 19 months. It was found that CR significantly reversed the aging phenotypes of middle‐aged and old mice including cardiac remodeling (cardiomyocyte hypertrophy and cardiac fibrosis), inflammation, mitochondrial damage, telomere shortening, as well as senescence‐associated markers but accelerated in young mice. Furthermore, whole‐genome microarray demonstrated that the AMP‐activated protein kinase (AMPK)–Forkhead box subgroup ‘O’ (FOXO) pathway might be a major contributor to contrasting regulation by CR initiated in different ages; thus, increased autophagy was seen in middle‐aged and old mice but decreased in young mice. Together, the findings demonstrated promising myocardial protection by 40% CR should be initiated in middle or old age that may have vital implications for the practical nutritional regimen.

Molecular Mechanisms of 2, 3′, 4, 4′, 5-Pentachlorobiphenyl-Induced Thyroid Dysfunction in FRTL-5 Cells

Polychlorinated biphenyls (PCBs) can severely interfere with multiple animals and human systems. To explore the molecular mechanisms underlying 2, 3′, 4, 4′, 5- pentachlorobiphenyl (PCB118)-induced thyroid dysfunction, Fischer rat thyroid cell line-5(FRTL-5) cells were treated with either different concentrations of PCB118 or dimethyl sulfoxide (DMSO). The effects of PCB118 on FRTL-5 cells viability and apoptosis were assessed by using a Cell Counting Kit-8 assay and apoptosis assays, respectively. Quantitative real-time polymerase chain reaction was used to quantify protein kinase B (Akt), Forkhead box protein O3a (FoxO3a), and sodium/iodide symporter (NIS) mRNA expression levels. Western blotting was used to detect Akt, phospho-Akt (p-Akt), FoxO3a, phospho-FoxO3a (p-FoxO3a), and NIS protein levels. Luciferase reporter gene technology was used to detect the transcriptional activities of FoxO3a and NIS promoters. The effects of the constitutively active Akt (CA-Akt) and dominant-negative Akt (DN-Akt) plasmids on p-Akt, p-FoxO3a, and NIS levels were examined in PCB118-treated FRTL-5 cells. The effects of FoxO3a siRNA on FoxO3a, p-FoxO3a, and NIS protein levels were examined in the PCB118-treated FRTL-5 cells. The effects of pcDNA3 (plsmid vectors designed for high-level stable and transient expression in mammalian host)-FoxO3a on NIS promoter activity were examined in the PCB118-treated FRTL-5 cells. Our results indicated that relatively higher PCB118 concentrations can inhibit cell viability in a concentration- and time-dependent manner. Akt, p-Akt, and p-FoxO3a protein or mRNA levels increased significantly in PCB118-treated groups and NIS protein and mRNA levels decreased considerably compared with the control groups. FoxO3a promoter activity increased significantly, whereas NIS promoter activity decreased. These effects on p-FoxO3a and NIS could be decreased by the DN-Akt plasmid, enhanced by the CA-Akt plasmid, and blocked by FoxO3a siRNA. The overexpressed FoxO3a could reduce NIS promoter activity. Our results suggested that PCB118 induces thyroid cell dysfunction through the Akt/FoxO3a/NIS signaling pathway.

Glucocorticoids Suppress the Browning of Adipose Tissue via miR-19b in Male Mice

Physiological levels of glucocorticoids (GCs) are required for proper metabolic control, and excessive GC action has been linked to a variety of pandemic metabolic diseases. MicroRNA (miRNA)-19b plays a critical role in the pathogenesis of GC-induced metabolic diseases. This study explored the potential of miRNA-based therapeutics targeting adipose tissue. Our results showed that overexpressed miR-19b in stromal vascular fraction (SVF) cells derived from subcutaneous adipose tissue had the same effects as dexamethasone (DEX) treatment on the inhibition of adipose browning and oxygen consumption rate. The inhibition of miR-19b blocked DEX-mediated suppression of the expression of browning marker genes as well as the oxygen consumption rate in differentiated SVF cells derived from subcutaneous and brown adipose tissue. Overexpressed miR-19b in SVF cells derived from brown adipose tissue had the same effects as DEX treatment on the inhibition of brown adipose differentiation and energy expenditure. Glucocorticoids transcriptionally regulate the expression of miR-19b via a GC receptor-mediated direct DNA binding mechanism. This study confirmed that miR-19b is an essential target for GC-mediated control of adipose tissue browning. It is hoped that the plasticity of the adipose organ can be exploited in the next generation of therapeutic strategies to combat the increasing incidence of metabolic diseases, including obesity and diabetes.

MiR-27b-3p Regulation in Browning of Human Visceral Adipose Related to Central Obesity: MiR-27b-3p in Browning of Human VAT

Given the rising prevalence of central obesity and the discovery that beige cells appear within white adipose tissue, strategies to enhance these energy‐expending adipocytes or “browning” within white adipose depots have become of therapeutic interest to combat obesity and its associated disorders. This study focused on, the role of microRNA (miRNA)‐27b‐3p in human visceral adipose tissue (VAT) browning.