White Adipose Tissue Of Mice Research Articles

116-OR: Lipocalin-Type Prostaglandin D2 Synthase Depletion Induces Adipose Tissue Dysfunction in Response to High-Fat Diet

Adipose tissue dysfunction is the primary defect in obesity which contributes to the development of dyslipidemia, insulin resistance, cardiovascular diseases, type 2 diabetes, nonalcoholic fatty liver disease and some cancers. Previous study from our lab implicated the role of lipocalin-type prostaglandin D2 synthase (L-PGDS) in glucose intolerance and atherosclerosis. Our lab also showed the development of NAFLD in L-PGDS knockout mice on both low fat and high fat diet. In the present study, we examined the role of L-PGDS in adipose tissue in response to high fat diet. We found decreased expression of L-PGDS in visceral and subcutaneous white adipose tissue (WAT) of C57BL/6 mice after 12 weeks on high fat diet (HFD). Our study showed increased fat content in L-PGDS KO mice as compared to control C57BL/6 mice after 14 weeks on HFD. Histological analysis showed hypertrophied adipocytes in visceral WAT of L-PGDS KO mice as compared to control mice. Furthermore, we found increased expression of the lipogenesis genes LXRα, SREBP-1c and FAS in visceral WAT of L-PGDS KO mice after 14 weeks on HFD. L-PGDS KO mice showed reduced gene expression of adiponectin and PPARγ in visceral WAT on HFD. The plasma adiponectin level was also decreased in L-PGDS KO mice. We conclude that absence of L-PGDS has a deleterious effect on adipose tissue functioning which further reduces insulin sensitivity in adipose tissue. Thus, our study suggests L-PGDS as a novel therapeutic target for the treatment of obesity-associated metabolic syndrome. Disclosure A. Srivastava: None. T. Palaia: None. C. Hall: None. J. Lee: None. M. Stevenson: None. L. Ragolia: None. Funding American Heart Association (15GRNT22420001); George Link, Jr. Foundation Inc. (3500-7294)

Sexual Dimorphic Effects of Exercise Training on Subcutaneous White Adipose Tissue of Mice.

Obesity is estimated to affect more than 600 million people worldwide (1). The strong relationship between obesity and multiple diseases, including type 2 diabetes, has motivated ongoing research aimed at understanding the fundamental biology of adipose tissue. Adipocytes can be characterized as white, brown, or beige. White adipocytes are crucial for energy (triglyceride) storage (2). White adipocytes also release numerous signaling molecules (adipokines) that have endocrine, paracrine, and/or autocrine functions. Distinctive physiological purposes and metabolic features have been documented for visceral versus subcutaneous white adipose tissue (WAT) depots (3). The primary feature of brown adipocytes is their exceptional capacity for heat generation. Beige adipocytes, which are interspersed in WAT depots, also have substantial thermogenic capacity. However, brown and beige adipocytes arise from distinct lineages (4). A variety of interventions, including exposure to cold ambient temperature, β-adrenergic activation, and physical exercise, can stimulate the induction and activation of beige adipocytes. Unraveling the remarkable complexity and adaptive potential of adipose tissue continues to be a crucial, but challenging, task. Research performed 30–40 years ago revealed that in rats, chronically performed exercise can modify metabolic properties of WAT, including insulin-stimulated glucose uptake and the activity of mitochondrial enzymes (5,6). Nonetheless, it was remarkable when recent research …

332-OR: Pharmacological Inhibition of CREBZF Improves Insulin Resistance by Altering Activation of Macrophage in Adipose Tissue of Diet-Induced Obese Mice

Obesity and type 2 diabetes are associated with chronic inflammation response in adipose tissue, in which macrophage activation and infiltration are hallmark characteristics. However, the molecular mechanism of this association remains largely unknown. Here, we report that CREBZF, a newly characterized transcription factor for insulin-induced lipogenesis, functions as a key regulator in adipose tissue macrophage and couples inflammatory signals to systemic insulin resistance in obesity. Myeloid cell-specific CREBZF knockout (CREBZF MKO) mice were generated by crossing floxed CREBZF mice with LysM-Cre transgenic mice. A small molecule (LIC902) was identified as a CREBZF inhibitor using a luciferase reporter-based high-throughput screening, which is shown to repress expression levels of CREBZF in the macrophage, such as J774. We found that ablation of CREBZF in myeloid cells or administration of LIC902 attenuates insulin resistance and hyperglycemia in mice fed with high-fat high-sucrose (HFHS) diet. Intriguingly, myeloid CREBZF deficiency or LIC902 treatment causes a profound reduction of infiltrated macrophages and reverses M1/M2 imbalance in white adipose tissue of mice fed with HFHS diet, suggesting important roles of CREBZF in regulating macrophage polarization in adipose tissue. CREBZF is capable of potentiating NF-κB signaling in the macrophage as evidenced by increased phosphorylation of p65, whereas CREBZF deficiency or inhibition of CREBZF activity results in the opposite effect. These data indicate that CREBZF plays a critical role in the regulation of innate immune response in the macrophage and maintains whole-body glucose homeostasis. Pharmacological manipulation of CREBZF may provide novel opportunities for treating metabolic diseases such as insulin resistance and type 2 diabetes. Disclosure Y. Liu: None. S. Wei: None. Z. Wang: None. X. Sun: None. Y. Jiang: None. X. Dai: None. Y. Li: None. A. Cui: None. Z. Hu: None. Z. Liu: None. W. Su: None. Z. Zheng: None. D. Ding: None. F. Ma: None. Y. Xue: None. G. Cai: None. Funding National Key Research and Development Program of China (2019YFA0802502); National Natural Science Foundation of China (81925008); Shanghai Science and Technology Commission (19140903300)

Curcumin Reduces Hepatic and White Adipose Tissue Inflammation and Expression of Specific Zinc Transporters in Diet-Induced Obese Mice

Abstract Objectives Obesity is a complex metabolic disease, that is often associated with non-alcoholic fatty liver disease (NAFLD). Inflammation is a common feature of both diseases. Curcumin, a traditionally used spice in Asia, exerts anti-inflammatory effects in liver and white adipose tissue (WAT) of diet-induced obese (DIO) mice. However, mechanisms involved in these beneficial effects remain obscure. Zinc is an important micronutrient involved in inflammatory responses. Whole-body zinc homeostasis plays a critical role in decreasing tissue specific inflammation. Zinc homeostasis is maintained mainly by zinc transporters known as ZnT (zinc transporters) and Zip (Zrt and Irt-like proteins) family. We propose that zinc transporters may contribute to curcumin's protective metabolic effects. Thus, the objective of this research was to determine curcumin's effects on inflammatory markers and zinc transporters in liver and WAT from DIO mice. Methods Male B6 mice were fed a HFD (45% kcal fat) or HFD supplemented with 0.4% (w/w) curcumin (HFC) for fourteen weeks. Serum triglycerides (TG) and free fatty acid (FFA) levels were measured. mRNA levels for inflammatory markers and zinc transporters were determined in WAT and liver by qRT-PCR. Results No significant changes were observed in body weight, serum TG and FFA levels with curcumin supplementation. However, gene expression of inflammatory markers, including Stat1, and Nf-KB subunit p65 were significantly reduced in liver and WAT from HFC group compared to HF (P < 0.05). Furthermore, curcumin reduced hepatic zinc transporters Zip10, Zip14, ZnT10 but increased ZnT9 expression. In WAT, curcumin significantly reduced mRNA levels for Zip1, Zip14, ZnT1, and ZnT7 (P < 0.05). Conclusions Our results indicate that zinc transporters may in part mediate the anti-inflammatory properties of curcumin, particularly Zip14, in WAT and liver of DIO mice. Future mechanistic studies are necessary to establish whether zinc transporters are required for curcumin's anti-inflammatory effects in obesity and associated NAFLD. Funding Sources AHA grant# 19AIREA34450279.

202-OR: Cell-Autonomous Impairment of BCAA Catabolism in White Adipocytes Leads to Systemic Metabolic Dysregulation

Increased levels of serum branched-chain amino acids (BCAA) is associated with obesity, insulin resistance (IR), and type 2 diabetes (T2D). However, the mechanisms that trigger perturbations in BCAA homeostasis, and whether elevated BCAA causes obesity and other metabolic impairments or is a consequence of them is not clear. Young knock-in mice bearing the human T2D-linked R1788W variant in the cytoskeletal protein ankyrin-B (AnkB) show normal body weight and composition. These mice display increased glucose uptake by white adipose tissue (WAT) due to deficient internalization of the glucose transporter GLUT4. We reported that sustained elevation in glucose disposal in WAT leads to the onset of increased adiposity, lipotoxicity, systemic inflammation, and IR in AnkB mutant mice with age or in young animals fed Western diets. Non-obese R1788W AnkB mice also exhibit transcriptional changes consistent with lower BCAA catabolism in WAT. Here, we show that AnkB deficits impair BCAA catabolism in WAT prior to the onset of obesity. Lean R1788W AnkB mice show reduction in surface levels of the BCAA transporter Asct2 and BCAA uptake together with downregulation of BCAA catabolic enzymes in WAT. These deficits are concomitant with elevations in serum levels of BCAA and related acylcarnitines. Reduced expression of BCAA catabolic enzymes was also observed in WAT of lean WAT-specific AnkB KO mice. In contrast, AnkB deficiency did not alter BCAA oxidation in skeletal muscle (SKM), brown adipose tissue, or liver. Studies in control and R1788W AnkB mice fed isocaloric low and high fat (HFD) diets enriched in BCAA suggest that BCAA elevation triggers mitochondrial dysfunction, impairments in insulin secretion by the pancreas and in insulin signaling in SKM. Our data indicates that elevated circulating BCAA impair glucose tolerance and insulin sensitivity independently of obesity, and that these deleterious effects are potentiated by HFD. Disclosure J. Tzeng: None. A. Aguillard: None. D. Lorenzo: None. Funding American Diabetes Association (1-19-JDF-081 to D.L.)

Honokiol Alleviates High-Fat Diet-Induced Obesity of Mice by Inhibiting Adipogenesis and Promoting White Adipose Tissue Browning.

Simple SummaryThe browning of white adipose tissue can change the body’s energy distribution and improve the disorder of energy metabolism through the expression of the iconic protein UCP1 to achieve beneficial effects on the body. As a natural plant functional component, polyphenols have been found to induce the browning of white adipose tissue, such as resveratrol and catechin. Honokiol is one of the main components in Magnolia officinalis, a traditional Chinese medicine in China. Modern pharmacological tests have proven that, like many plant functional components, honokiol has broad-spectrum antibacterial, anti-tumor, anti-inflammatory, and anti-oxidation effects. However, the effect of honokiol on inducing the browning of white adipose tissue and improving energy metabolism disorder has not been reported. In this study, a high-fat diet-induced obese model was established, and proteomic analysis was performed. It was found that honokiol could promote the browning of white adipose tissue in high-fat fed mice. The AMPK-ACC-CPT1A and C/EBPα-SOAT1 pathways may be the important molecular mechanisms of the browning induced by honokiol.Honokiol (HON) is one of the main biological active components of the traditional Chinese medicine Magnolia officinalis and has many health benefits. The aim of this study was to investigate whether HON could alleviate obesity in mice by inhibiting adipogenesis and promoting the browning of white adipose tissue (WAT). C57BL/6 mice were divided into five groups and fed with a normal diet (ND), high-fat diet (HFD), or HFD supplemented with 200 (H200), 400 (H400), or 800 (H800) mg/kg BW HON for 8 weeks. The results showed that the mice fed HFD plus HON had lower body fat ratios (BFRs) and smaller adipocyte diameters in the epididymal WAT compared with those of the HFD group. With a proteomics analysis, the HON group upregulated 30 proteins and downregulated 98 proteins in the epididymal WAT of mice, and the steroid O-acyltransferase 1 (SOAT1) was screened as a key protein. The HON supplement prevented HFD-induced adipogenesis by reduced the mRNA and protein expression of SOAT1 and CCAAT/enhancer-binding protein-α (C/EBPα), suggesting that SOAT1 might play an important role in regulating adipogenesis. Moreover, HON treatment increased the expression of proteins related to the classical pathways of energy and lipid metabolism, such as AMP-activated kinase (AMPK) and acetyl-CoA carboxylase (ACC), and promoted the browning of epididymal WAT by upregulation of the protein expression of uncoupling protein 1 (UCP1) in the HFD mice. In conclusion, these results suggest that HON supplements could prevent increases in body fat for HFD mice by suppressing adipogenesis and promoting WAT browning.

Activation of GCN2 in macrophages promotes white adipose tissue browning and lipolysis under leucine deprivation.

We have previously shown that leucine deprivation stimulates browning and lipolysis in white adipose tissue (WAT), which helps to treat obesity. Adipose tissue macrophages (ATMs) significantly influence WAT browning and lipolysis. However, it is unclear whether ATMs are involved in leucine deprivation-induced browning and lipolysis in WAT; the associated signals remain to be elucidated. Here, we investigated the role of ATMs and the possible mechanisms involved in WAT browning and lipolysis under leucine-deprivation conditions. In this study, macrophages were depleted in mice by injecting clodronate-liposomes (CLOD) into subcutaneous white adipose tissues. Then, mice lacking general control nonderepressible 2 kinase (GCN2), which is a sensor of amino acid starvation, specifically in Lyz2-expressing cells, were generated to investigate the changes in leucine deprivation-induced WAT browning and lipolysis. We found leucine deprivation decreased the accumulation and changed the polarization of ATMs. Ablation of macrophages by CLOD impaired WAT browning and lipolysis under leucine-deprivation conditions. Mechanistically, leucine deprivation activated GCN2 signals in macrophages. Myeloid-specific abrogation of GCN2 in mice blocked leucine deprivation-induced browning and lipolysis in WAT. Further analyses revealed that GCN2 activation in macrophages reduced the expression of monoamine oxidase A (MAOA), resulting in increased norepinephrine (NE) secretion from macrophages to adipocytes, and this resulted in enhanced WAT browning and lipolysis. Moreover, the injection of CL316,243, a β3-adrenergic receptor agonist, and inhibition of MAOA effectively increased the level of NE, leading to the enhancement of browning and lipolysis of WAT in myeloid GCN2 knockout mice under leucine deprivation. Collectively, our results demonstrate a novel function of GCN2 signals in macrophages, that is, regulating WAT browning and lipolysis under leucine deprivation. Our study provides important hints for possible treatment for obesity.

Deregulation of Ca2+-Signaling Systems in White Adipocytes, Manifested as the Loss of Rhythmic Activity, Underlies the Development of Multiple Hormonal Resistance at Obesity and Type 2 Diabetes.

Various types of cells demonstrate ubiquitous rhythmicity registered as simple and complex Ca2+-oscillations, spikes, waves, and triggering phenomena mediated by G-protein and tyrosine kinase coupled receptors. Phospholipase C/IP3-receptors (PLC/IP3R) and endothelial NO-synthase/Ryanodine receptors (NOS/RyR)–dependent Ca2+ signaling systems, organized as multivariate positive feedback generators (PLC-G and NOS-G), underlie this rhythmicity. Loss of rhythmicity at obesity may indicate deregulation of these signaling systems. To issue the impact of cell size, receptors’ interplay, and obesity on the regulation of PLC-G and NOS-G, we applied fluorescent microscopy, immunochemical staining, and inhibitory analysis using cultured adipocytes of epididumal white adipose tissue of mice. Acetylcholine, norepinephrine, atrial natriuretic peptide, bradykinin, cholecystokinin, angiotensin II, and insulin evoked complex [Ca2+]i responses in adipocytes, implicating NOS-G or PLC-G. At low sub-threshold concentrations, acetylcholine and norepinephrine or acetylcholine and peptide hormones (in paired combinations) recruited NOS-G, based on G proteins subunits interplay and signaling amplification. Rhythmicity was cell size- dependent and disappeared in hypertrophied cells filled with lipids. Contrary to control cells, adipocytes of obese hyperglycemic and hypertensive mice, growing on glucose, did not accumulate lipids and demonstrated hormonal resistance being non responsive to any hormone applied. Preincubation of preadipocytes with palmitoyl-L-carnitine (100 nM) provided accumulation of lipids, increased expression and clustering of IP3R and RyR proteins, and partially restored hormonal sensitivity and rhythmicity (5–15% vs. 30–80% in control cells), while adipocytes of diabetic mice were not responsive at all. Here, we presented a detailed kinetic model of NOS-G and discussed its control. Collectively, we may suggest that universal mechanisms underlie loss of rhythmicity, Ca2+-signaling systems deregulation, and development of general hormonal resistance to obesity.

Environmental activation of a hypothalamic BDNF-adipocyte IL-15 axis regulates adipose-natural killer cells

Physical and social environments influence immune homeostasis within adipose tissue, yet the mechanisms remain poorly defined. We report that an enriched environment (EE) housing modulates the immune cell population in white adipose tissue of mice including an increase in the abundance of natural killer (NK) cells. EE upregulates the expression of IL-15 and its receptor IL-15Rα specifically within mature adipocytes. Mechanistically, we show that hypothalamic brain-derived neurotrophic factor (BDNF) upregulates IL-15 production in adipocytes via sympathetic β-adrenergic signaling. Overexpressing BDNF mediated by recombinant adeno-associated virus (rAAV) vector in the hypothalamus expands adipose NK cells. Conversely, inhibition of hypothalamic BDNF signaling via gene transfer of a dominant negative TrkB receptor suppresses adipose NK cells. In white adipose tissue, overexpression of IL-15 using an adipocyte-specific rAAV vector stimulates adipose NK cells and inhibits the progression of subcutaneous melanoma, whereas local IL-15 knockdown blocks the EE effect. These results suggest that bio-behavioral factors regulate adipose NK cells via a hypothalamic BDNF-sympathoneural-adipocyte IL-15 axis. Targeting this pathway may have therapeutic significance for cancer.

Distinct roles of adipose triglyceride lipase and hormone‐sensitive lipase in the catabolism of triacylglycerol estolides

Branched esters of fatty acids and hydroxy fatty acids (FAHFAs) belong to a wide range group of lipids, some of which have anti-inflammatory and anti-diabetic properties. FAHFAs themselves belong to oligomeric FA esters, known as estolides. Depending on structure, they are divided in subfamilies (e.g. palmitic acid esters of hydroxy stearic acid, PAHSAs) including several regioisomers with different position of the branching position (e.g. 9-PAHSA). In human and mice tissue, glycerol-bound FAHFAs in triacylglycerols (TAGs), named TAG estolides, serve as metabolite reservoir of FAHFAs mobilized by lipases upon demand. Here, we studied the role of two major metabolic lipases, adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), in TAG estolide and FAHFA degradation. We synthesized a panel of twenty TAG estolide isomers with different FAHFAs groups varying in branching position, chain length, saturation grade, and position on the glycerol backbone. An in silico mass spectra library was developed of all predicted catabolic intermediates. Homogenates of HEK293T cells overexpressing ATGL, or HSL were used for the determination of TAG estolide hydrolase activity of HSL and ATGL in the presence or absence of comparative gene identification-58 (CGI-58). White adipose tissue from ad libitum fed and fasted wild-type and global HSL knock-out mice was collected and TAG estolides were quantified. We found that ATGL alone or coactivated by CGI-58 efficiently liberated FAHFAs from TAG estolides with a preference for more compact substrates where the estolide branching point is located near the glycerol ester bond. ATGL also participated in transesterification and remodeling reactions leading to the formation of TAG estolides with alternative acyl compositions. HSL represented a much more potent estolide bond hydrolase for both TAG estolides and free FAHFAs. FAHFA and TAG estolide accumulation in white adipose tissue of mice lacking HSL argued for a functional role of HSL in estolide catabolism in vivo. Our data show that ATGL and HSL participate in the metabolism of estolides and TAG estolides in distinct manners and are likely to affect the lipokine function of FAHFAs.

An immune‐neuron axis guides adipose tissue loss in cancer‐associated cachexia

Cancer-associated cachexia (CAC) is a hypermetabolic syndrome characterized by weight loss due to the atrophy of adipose tissue and skeletal muscle. CAC occurs in almost 80% of neoplastic diseases and causes death in more than 20% of cancer patients. The underlying mechanisms of the disease are poorly understood and no effective treatment for CAC is currently available. Recently, we and others demonstrated that a phenotypic switch from white- to beige adipocytes, a phenomenon called browning, accompanies CAC and contributes to increased energy dissipation. However, detailed mechanisms underlying this white to beige transition in CAC remained elusive. Here we show that cachexigenic tumors cause the activation of a type 2 immune response in white adipose tissue (WAT), which is functionally intertwined with neuron outgrowth, beta-adrenergic activation, and subsequent WAT browning. Immunohistochemical- and whole-mount immunofluorescence analyses revealed enhanced peripheral sympathetic neuron projections in cachectic WAT of mice and human patients. Using peripheral dopamine beta-hydroxylase (DBH) deficient mice, we demonstrate that local production of catecholamines by intra-adipose tissue neurons is responsible for increased lipolysis and initiation of the browning process. In vitro studies revealed that the increase in neuron arborization is promoted by alternatively activated macrophages which generate a neuroprotective environment covering the neurotoxic proinflammatory signals produced by cachexigenic tumors. In accordance with this concept, tumor-bearing mice that lack the interleukin-4 receptor exhibited a diminished type-2 immune response, attenuated neuronal outgrowth, and reduced browning of WAT compared to tumor-bearing wild type mice. Overall, our findings indicate that an immune–sympathetic neuron crosstalk increases local catecholamine production, lipolysis, and UCP-1 expression in WAT, thereby contributing to energy dissipation, and adipose tissue loss in CAC.

Irisin induces white adipose tissue browning in mice as assessed by magnetic resonance imaging.

This study aimed to track and evaluate the effect of low-dose irisin on the browning of white adipose tissue (WAT) in mice using magnetic resonance imaging (MRI) noninvasively in vivo. Mature white adipocytes extracted from mice were cultured, induced and characterized before being treated by irisin. The volume and fat fraction of WAT were quantified using MRI in normal chow diet and high fat mice after injection of irisin. The browning of cultured white adipocytes and WAT in mice were validated by immunohistochemistry and western blotting for uncoupling protein 1 (UCP1) and deiodinase type II (DIO2). The serum indexes were examined with high fat diet after irisin intervention. UCP1 and DIO2 in adipocytes showed increases responding to the irisin treatment. The size of white adipocytes in mice receiving irisin intervention was reduced. MRI measured volumes and fat fraction of WAT were significantly lower after Irisin treatment. Blood glucose and cholesterol levels were reduced in high fat diet mice after irisin treatment. Irisin intervention exerted browning of WAT, resulting reduction of volume and fat fraction of WAT as measured by MRI. Furthermore, it improved the condition of mice with diet-induced obesity and related metabolic disorders.

Calorie Restriction and SIRT1 Overexpression Induce Different Gene Expression Profiles in White Adipose Tissue in Association with Metabolic Improvement.

Calorie restriction (CR) exerts multiple effects on health, including the amelioration of systemic insulin resistance. Although the precise mechanisms by which CR improves glucose homeostasis remain poorly defined, SIRT1 has been suggested to act as a central mediator of the cellular responses to CR. Here, we aim at identifying the mechanisms by which CR and SIRT1 modulate white adipose tissue (WAT) function, a key tissue in the control of glucose homeostasis. A gene expression profiling study using DNA microarrays is conducted in WAT of control and SIRT1 transgenic mice fed ad libitum (AL) and mice subjected to 40% CR. Gene expression profiling reveals a relatively low degree of overlap between the transcriptional programs regulated by SIRT1 and CR. Gene networks related to extracellular matrix appear commonly downregulated by SIRT1/CR, whereas mitochondrial biogenesis is enhanced exclusively by CR. Moreover, WAT inflammation is reduced by CR and SIRT1, although their anti-inflammatory effects appeared to be achieved by regulating different gene networks related to the immune system. In WAT, SIRT1 does not mediate most of the effects of CR on gene expression. Still, gene networks differentially regulated by SIRT1 and CR converge to reduce WAT inflammation.

Integrins and extracellular matrix proteins modulate adipocyte thermogenic capacity

Obesity and the metabolic disease epidemic has led to an increase in morbidity and mortality. A rise in adipose thermogenic capacity via activation of brown or beige fat is a potential treatment for metabolic diseases. However, an understanding of how local factors control adipocyte fate is limited. Mice with a null mutation in the laminin α4 (LAMA4) gene (KO) exhibit resistance to obesity and enhanced expression of thermogenic fat markers in white adipose tissue (WAT). In this study, changes in WAT extracellular matrix composition in the absence of LAMA4 were evaluated using liquid chromatography/tandem mass spectrometry. KO-mice showed lower levels of collagen 1A1 and 3A1, and integrins α7 (ITA7) and β1 (ITB1). ITA7-ITB1 and collagen 1A1-3A1 protein levels were lower in brown adipose tissue compared to WAT in wild-type mice. Immunohistochemical staining confirmed lower levels and different spatial distribution of ITA7 in KO-WAT. In culture studies, ITA7 and LAMA4 levels decreased following a 12-day differentiation of adipose-derived stem cells into beige fat, and knock-down of ITA7 during differentiation increased beiging. These results demonstrate that extracellular matrix interactions regulate adipocyte thermogenic capacity and that ITA7 plays a role in beige adipose formation. A better understanding of the mechanisms underlying these interactions can be used to improve systemic energy metabolism and glucose homeostasis.

Signal Transducer and Activator of Transcription 3 (STAT3) Suppresses STAT1/Interferon Signaling Pathway and Inflammation in Senescent Preadipocytes.

Obesity promotes premature aging and dysfunction of white adipose tissue (WAT) through the accumulation of cellular senescence. The senescent cells burden in WAT has been linked to inflammation, insulin-resistance (IR), and type 2 diabetes (T2D). There is limited knowledge about molecular mechanisms that sustain inflammation in obese states. Here, we describe a robust and physiologically relevant in vitro system to trigger senescence in mouse 3T3-L1 preadipocytes. By employing transcriptomics analyses, we discovered up-regulation of key pro-inflammatory molecules and activation of interferon/signal transducer and activator of transcription (STAT)1/3 signaling in senescent preadipocytes, and expression of downstream targets was induced in epididymal WAT of obese mice, and obese human adipose tissue. To test the relevance of STAT1/3 signaling to preadipocyte senescence, we used Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR associated protein 9 (CRISPR/Cas9) technology to delete STAT1/3 and discovered that STAT1 promoted growth arrest and cooperated with cyclic Guanosine Monophosphate-Adenosine Monophosphate (GMP-AMP) synthase-stimulator of interferon genes (cGAS-STING) to drive the expression of interferon β (IFNβ), C-X-C motif chemokine ligand 10 (CXCL10), and interferon signaling-related genes. In contrast, we discovered that STAT3 was a negative regulator of STAT1/cGAS-STING signaling—it suppressed senescence and inflammation. These data provide insights into how STAT1/STAT3 signaling coordinates senescence and inflammation through functional interactions with the cGAS/STING pathway.

Exercise Training Promotes Sex-Specific Adaptations in Mouse Inguinal White Adipose Tissue.

Recent studies demonstrate that adaptations to white adipose tissue (WAT) are important components of the beneficial effects of exercise training on metabolic health. Exercise training favorably alters the phenotype of subcutaneous inguinal WAT (iWAT) in male mice, including decreasing fat mass, improving mitochondrial function, inducing beiging, and stimulating the secretion of adipokines. In this study, we find that despite performing more voluntary wheel running compared with males, these adaptations do not occur in the iWAT of female mice. Consistent with sex-specific adaptations, we report that mRNA expression of androgen receptor coactivators is upregulated in iWAT from trained male mice and that testosterone treatment of primary adipocytes derived from the iWAT of male, but not female mice, phenocopies exercise-induced metabolic adaptations. Sex specificity also occurs in the secretome profile, as we identify cysteine-rich secretory protein 1 (Crisp1) as a novel adipokine that is only secreted from male iWAT in response to exercise. Crisp1 expression is upregulated by testosterone and functions to increase glucose and fatty acid uptake. Our finding that adaptations to iWAT with exercise training are dramatically greater in male mice has potential clinical implications for understanding the different metabolic response to exercise training in males and females and demonstrates the importance of investigating both sexes in studies of adipose tissue biology.

Nobiletin activates thermogenesis of brown and white adipose tissue in high-fat diet-fed C57BL/6 mice by shaping the gut microbiota.

Increasing energy expenditure by activating thermogenesis in brown and beige adipocytes is a critical approach to protect against obesity. Here, we investigated the action and mechanism of a natural polymethoxyflavone on adaptive thermogenesis in high-fat diet-induced obesity mouse model. Nobiletin treatment significantly ameliorated obesity, alleviated the whitening of brown adipose tissue, and promoted browning of white adipose tissue in mice fed a high-fat diet. Gut microbiota analysis and metabolomic profiling revealed that nobiletin treatment resulted in a composition shift in the gut microbiota thereby altering fermentation products acetate levels in the host feces and serum. Further, transplantation of the microbiota from nobiletin-treated mice to microbiota-depleted mice activated brown adipose tissue activity, promoted beige adipocytes formation, and improved high-fat diet-induced obesity. Our results indicate that nobiletin could be used as a dietary therapy to prevent HFD-induced obesity, and provide a potential target-specific gut microbial species-driven mechanism for activating thermogenesis in brown and beige adipocytes.

Overexpression of Adiponectin Receptor 1 Inhibits Brown and Beige Adipose Tissue Activity in Mice.

Adult humans and mice possess significant classical brown adipose tissues (BAT) and, upon cold-induction, acquire brown-like adipocytes in certain depots of white adipose tissues (WAT), known as beige adipose tissues or WAT browning/beiging. Activating thermogenic classical BAT or WAT beiging to generate heat limits diet-induced obesity or type-2 diabetes in mice. Adiponectin is a beneficial adipokine resisting diabetes, and causing “healthy obese” by increasing WAT expansion to limit lipotoxicity in other metabolic tissues during high-fat feeding. However, the role of its receptors, especially adiponectin receptor 1 (AdipoR1), on cold-induced thermogenesis in vivo in BAT and in WAT beiging is still elusive. Here, we established a cold-induction procedure in transgenic mice over-expressing AdipoR1 and applied a live 3-D [18F] fluorodeoxyglucose-PET/CT (18F-FDG PET/CT) scanning to measure BAT activity by determining glucose uptake in cold-acclimated transgenic mice. Results showed that cold-acclimated mice over-expressing AdipoR1 had diminished cold-induced glucose uptake, enlarged adipocyte size in BAT and in browned WAT, and reduced surface BAT/body temperature in vivo. Furthermore, decreased gene expression, related to thermogenic Ucp1, BAT-specific markers, BAT-enriched mitochondrial markers, lipolysis and fatty acid oxidation, and increased expression of whitening genes in BAT or in browned subcutaneous inguinal WAT of AdipoR1 mice are congruent with results of PET/CT scanning and surface body temperature in vivo. Moreover, differentiated brown-like beige adipocytes isolated from pre-adipocytes in subcutaneous WAT of transgenic AdipoR1 mice also had similar effects of lowered expression of thermogenic Ucp1, BAT selective markers, and BAT mitochondrial markers. Therefore, this study combines in vitro and in vivo results with live 3-D scanning and reveals one of the many facets of the adiponectin receptors in regulating energy homeostasis, especially in the involvement of cold-induced thermogenesis.

Exercise reduces metabolic burden while altering the immune system in aged mice.

Although several evidence has suggested the impact of exercise on the prevention of aging phenotypes, few studies have been conducted on the mechanism by which exercise alters the immune-cell profile, thereby improving metabolism in senile obesity. In this study, we confirmed that 4-week treadmill exercise sufficiently improved metabolic function, including increased lean mass and decreased fat mass, in 88-week-old mice. The expression level of the senescence marker p16 in the white adipose tissue (WAT) was decreased after 4-weeks of exercise. Exercise induced changes in the profiles of immune-cell subsets, including natural killer (NK) cells, central memory CD8+ T cells, eosinophils, and neutrophils, in the stromal vascular fraction of WAT. In addition, it has been shown through transcriptome analysis of WAT that exercise can activate pathways involved in the interaction between WAT and immune cells, in particular NK cells, in aged mice. These results suggest that exercise has a profound effect on changes in immune-cell distribution and senescent-cell scavenging in WAT of aged mice, eventually affecting overall energy metabolism toward a more youthful state.

White Adipose Tissue Autophagy and Adipose-Liver Crosstalk Exacerbate Nonalcoholic Fatty Liver Disease in Mice

Background & AimsAlthough nonalcoholic fatty liver disease (NAFLD) is closely associated with obesity, the role of adipose tissue in NAFLD is not well-understood. Because autophagy has been reported to be involved in the degradation of lipid droplets, we investigated the role of adipose tissue autophagy in the liver pathogenesis of NAFLD.MethodsC57BL/6J mice and adipocyte-specific Atg7-knockout mice (Adipoq-Atg7 KO mice) were fed a high-fat diet (HFD).ResultsHFD feeding for up to 4 months increased both inguinal and epididymal white adipose tissue (iWAT and eWAT, respectively; the former represents subcutaneous fat, and the latter represents visceral fat) in mice. After HFD feeding, autophagy flux in both types of white adipose tissue was increased, and the levels of Rubicon, a negative autophagy regulator, were decreased, suggesting autophagy promotion. Adipoq-Atg7 KO mice exhibited suppressed autophagy in both iWAT and eWAT. Adipocyte-specific Atg7 KO enhanced HFD-induced iWAT hypertrophy. On the other hand, eWAT levels in Adipoq-Atg7 KO mice were increased after 1 month of HFD feeding but decreased after 4 months of HFD feeding compared with those in wild-type controls. Cleaved caspase 3 and JNK pathway protein expression in eWAT was increased without cytokine elevation in Adipoq-Atg7 KO mice fed an HFD compared with wild-type mice fed an HFD. Adipocyte-specific Atg7 KO decreased serum free fatty acid levels and ameliorated HFD-induced steatosis, liver inflammation, and fibrosis.ConclusionsAutophagy was enhanced in the white adipose tissues of mice fed an HFD. Autophagy inhibition in white adipose tissues ameliorated the liver pathology of NAFLD via adipose-liver crosstalk.