Human Subcutaneous White Adipose Tissue Research Articles

Role of human Kallistatin in glucose and energy homeostasis in mice

ObjectiveKallistatin (KST), also known as SERPIN A4, is a circulating, broadly acting human plasma protein with pleiotropic properties. Clinical studies in humans revealed reduced KST levels in obesity. The exact role of KST in glucose and energy homeostasis in the setting of insulin resistance and type 2 diabetes is currently unknown. MethodsKallistatin mRNA expression in human subcutaneous white adipose tissue (sWAT) of 47 people with overweight to obesity of the clinical trial “Comparison of Low Fat and Low Carbohydrate Diets With Respect to Weight Loss and Metabolic Effects (B-SMART)” was measured. Moreover, we studied transgenic mice systemically overexpressing human KST (hKST-TG) and wild type littermate control mice (WT) under normal chow (NCD) and high-fat diet (HFD) conditions. ResultsIn sWAT of people with overweight to obesity, KST mRNA increased after diet-induced weight loss. On NCD, we did not observe differences between hKST-TG and WT mice. Under HFD conditions, body weight, body fat and liver fat content did not differ between genotypes. Yet, during intraperitoneal glucose tolerance tests (ipGTT) insulin excursions and HOMA-IR were lower in hKST-TG (4.42 ± 0.87 AU, WT vs. 2.20 ± 0.27 AU, hKST-TG, p < 0.05). Hyperinsulinemic euglycemic clamp studies with tracer-labeled glucose infusion confirmed improved insulin sensitivity by higher glucose infusion rates in hKST-TG mice (31.5 ± 1.78 mg/kg/min, hKST-TG vs. 18.1 ± 1.67 mg/kg/min, WT, p < 0.05). Improved insulin sensitivity was driven by reduced hepatic insulin resistance (clamp hepatic glucose output: 7.7 ± 1.9 mg/kg/min, hKST-TG vs 12.2 ± 0.8 mg/kg/min, WT, p < 0.05), providing evidence for direct insulin sensitizing effects of KST for the first time. Insulin sensitivity was differentially affected in skeletal muscle and adipose tissue. Mechanistically, we observed reduced Wnt signaling in the liver but not in skeletal muscle, which may explain the effect. ConclusionsKST expression increases after weight loss in sWAT from people with obesity. Furthermore, human KST ameliorates diet-induced hepatic insulin resistance in mice, while differentially affecting skeletal muscle and adipose tissue insulin sensitivity. Thus, KST may be an interesting, yet challenging, therapeutic target for patients with obesity and insulin resistance.

Abstract 101: Similar Cd28 + Delta T Effector Memory Cell Subpopulations Are Present In Murine Perivascular Tissues Of Angiotensin II-infused Male Mice And Subcutaneous White Adipose Tissue Of Obese Women

Introduction: The innate-like γδ T cells play a role in angiotensin II (AngII)-induced hypertension, mesenteric artery injury and T cell activation in mesenteric vessels/perivascular adipose tissue (MV/PVAT) in mice. Blood γδ T cells frequency is associated with systolic blood pressure in humans. Obesity was associated with small artery injury in subcutaneous white adipose tissue (WAT) and is a risk factor for hypertension in humans. We hypothesized that single cell RNA sequencing (scRNA-seq) in MV/PVAT of AngII-infused vs control mice and in subcutaneous WAT of obese vs lean humans will reveal γδ T cell subpopulations involved in hypertension, vascular injury and T cell activation. Methods: Male C57BL/6J mice were infused SC or not with 490 ng/kg/min AngII for 14 days (n=3). Hypertension was confirmed by tail cuff blood pressure measurement. MV/PVAT were collected, and T cells were isolated and used for scRNA-seq. γδ T cell subpopulations were studied by subclustering T cells expressing the T cell receptor δ constant chain. Cell subpopulations were validated by flow cytometry. Subcutaneous WAT CD45 + cell ScRNA-seq data of 3 lean and 3 obese women were obtained from GEO NCBI database (GSE155960) and γδ T cell subpopulations analyzed as above. Results: ScRNA-seq identified 6 murine and 9 human δ T cell subclusters. AngII increased Cd28 high (% of T cells: 3.6±0.9 vs 1.4±0.2) and Trdv4 + δ T effector memory (EM) cells (7.3±1.3 vs 3.4±1.7) and lowered resting δ T cells (1.0±0.2 vs 4.2±1.5) in mice. Cd28 high δ T EM and resting δ T cell study by flow cytometry using unique marker pairs, CD28 + SELL - and CD28 - SELL + , showed that AngII increased CD28 + SELL - (cell number: 376±48 vs 220±40) and decreased CD28 - SELL + δ T cells (23±4 vs 45±4) in MV/PVAT. Cd28 / CD28 subclustering of δ T cells identified 4 human and murine cell populations and showed that AngII increased Cd28 + γδ natural killer T EM (% of T cells: 1.9±0.3 vs 0.5±0.2) and Cd28 high δ T EM cell subpopulations (1.6±0.5 vs 0.2±0.1) in mice, and that CD28 + δ T EM-1 cell subpopulation tended to be increased in obese vs lean women. Conclusion: ScRNA-seq revealed similar δ T EM cell subpopulations expressing CD28 in murine MV/PVAT and human subcutaneous WAT that could play a role in hypertension, vascular injury and T cell activation.

Effect of Simvastatin Treatment on Mitochondrial Function and Inflammatory Status of Human White Adipose Tissue.

Statin therapy has shown pleiotropic effects affecting both mitochondrial function and inflammatory status. However, few studies have investigated the concurrent effects of statin exposure on mitochondrial function and inflammatory status in human subcutaneous white adipose tissue. In a cross-sectional study, we investigated the effects of simvastatin on mitochondrial function and inflammatory status in subcutaneous white adipose tissue of 55 human participants: 38 patients (19 females/19 males) in primary prevention with simvastatin (> 40 mg/d, > 3 mo) and 17 controls (9 females/8 males) with elevated plasma cholesterol. The 2 groups were matched on age, body mass index, and maximal oxygen consumption. Anthropometrics and fasting biochemical characteristics were measured. Mitochondrial respiratory capacity was assessed in white adipose tissue by high-resolution respirometry. Subcutaneous white adipose tissue expression of the inflammatory markers IL-6, chemokine (C-C motif) ligand 2 (CCL2), CCL-5, tumor necrosis factor-α, IL-10, and IL-4 was analyzed by quantitative PCR. Simvastatin-treated patients showed lower plasma cholesterol (P < .0001), low-density lipoprotein (P < .0001), and triglyceride levels (P = .0116) than controls. Simvastatin-treated patients had a lower oxidative phosphorylation capacity of mitochondrial complex II (P = .0001 when normalized to wet weight, P < .0001 when normalized to citrate synthase activity [intrinsic]), and a lower intrinsic mitochondrial electron transport system capacity (P = .0004). Simvastatin-treated patients showed higher IL-6 expression than controls (P = .0202). Simvastatin treatment was linked to mitochondrial respiratory capacity in human subcutaneous white adipose tissue, but no clear link was found between statin exposure, respiratory changes, and inflammatory status of adipose tissue.

Comprehensive Analysis of circRNA Expression Profiles in Human Brown Adipose Tissue.

Brown adipose tissue (BAT) can rapidly generate heat and improve energy metabolism. Circular RNAs (circRNAs) are cellular endogenous non-coding RNAs, which can regulate the development and progress of different diseases. However, the role of circRNAs in human BAT is not fully understood. Here, we analyzed the differentially expressed circRNAs (DECs) in human BAT, as well as in white adipose tissue (WAT), and identified new biomarkers of BAT. Three human BAT and three human subcutaneous WAT samples were selected, and circRNA microarray was performed. Additionally, quantitative real-time polymerase chain reaction (qRT-PCR) was applied to determine the expression of six circRNAs. Finally, the functional analysis was performed by bioinformatics. Compared to WAT, 152 upregulated circRNAs and 201 downregulated circRNAs were identified in BAT. The DECs were further subjected to GO and KEGG enrichment analysis. Several circRNAs, for example, hsa_circ_0006168, hsa_circ_26337 and hsa_circ_0007507 were found upregulated and hsa_circ_0030162 was found downregulated in human BAT compared to WAT. This study profiles the circRNA expression in human BAT and WAT, and suggests hsa_circ_0006168, hsa_circ_26337, hsa_circ_0007507, and hsa_circ_0030162 as novel biomarkers for human BAT.

PMON280 Effect of Gender Affirming Hormone Therapy (GAHT) on Adipose Tissue Morphology and Metabolism in Transgender Individuals

Abstract Background Circulating sex hormones exert unique effects on metabolism, leading to sexual dimorphism in white adipose tissue distribution and function. The gender affirming hormone therapy (GAHT) or cross-sex hormone therapy (CSHT) for transgender patients lower the endogenous sex hormones while raising the opposite sex hormones. Sex hormones are known to have a significant impact on white adipose tissue and metabolism. However, long-term metabolic changes with GAHT in transgender individuals have not been studied, nor are the underlying mechanisms properly elucidated. Hypothesis We test the hypothesis that GAHT will result in sexual dimorphic changes in morphology and function of white adipose tissue according to the type of sex hormones used and the native sex of the patients. Aim 1 To study the effect of cross-sex hormones on clinical parameters such as blood pressure, weight, waist-hip circumference ratio, serum lipids, insulin sensitivity Aim 2 To study the changes in human subcutaneous white adipose tissue (SWAT) distribution and expansion with GAHT Aim 3 To study changes in circulating metabolites and adipokines, and pro-inflammatory and pro-fibrotic gene expression in SWAT with GAHT. Methodology 31 hormone-naive patients (19 Male-to-Female; MtF and 12 Female-to-Male; FtM) were enrolled in the longitudinal study and followed up for 3 years. Clinical parameters and blood samples were gathered at baseline and at 6 month intervals. DXA scans and fat biopsies (peri-umbilical SWAT) were performed at baseline and at 1 year intervals. Results The results presented here compare baseline and at 1 year of GAHT. There was an increase in total cholesterol in the MtF group. HOMA-IR, total fat mass and visceral fat mass increased in MtF group, while they decreased in the FtM group. In MtF group, lean mass and bone mineral content (BMC) decreased at 1 year, but no change was observed in the FtM group. On histological assessment, fat cell size increased in MtF group, while it decreased in the FtM group. Conclusion In MtF transgender patients, androgen deprivation and estrogen treatment resulted in reduced insulin sensitivity together with a rise in total cholesterol possibly via a decrease in lean mass and adipose tissue expansion through significant adipocyte hypertrophy. In FtM transgender patients, testosterone treatment caused improved insulin sensitivity possibly via a decrease in total and visceral fat mass. The greatest strengths of our project include its longitudinal nature over 3 years to capture long-term effects in the same patients as well as deeper mechanistic insights into the underlying metabolite, adipokine and gene expression changes. The limitations of our study include the small sample size with heterogeneity of study population in terms of demographics and lifestyles. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Dysregulation of Subcutaneous White Adipose Tissue Inflammatory Environment Modelling in Non-Insulin Resistant Obesity and Responses to Omega-3 Fatty Acids - A Double Blind, Randomised Clinical Trial.

BackgroundObesity is associated with enhanced lipid accumulation and the expansion of adipose tissue accompanied by hypoxia and inflammatory signalling. Investigation in human subcutaneous white adipose tissue (scWAT) in people living with obesity in which metabolic complications such as insulin resistance are yet to manifest is limited, and the mechanisms by which these processes are dysregulated are not well elucidated. Long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFAs) have been shown to modulate the expression of genes associated with lipid accumulation and collagen deposition and reduce the number of inflammatory macrophages in adipose tissue from individuals with insulin resistance. Therefore, these lipids may have positive actions on obesity associated scWAT hypertrophy and inflammation.MethodsTo evaluate obesity-associated tissue remodelling and responses to LC n-3 PUFAs, abdominal scWAT biopsies were collected from normal weight individuals and those living with obesity prior to and following 12-week intervention with marine LC n-3 PUFAs (1.1 g EPA + 0.8 g DHA daily). RNA sequencing, qRT-PCR, and histochemical staining were used to assess remodelling- and inflammatory-associated gene expression, tissue morphology and macrophage infiltration.ResultsObesity was associated with scWAT hypertrophy (P < 0.001), hypoxia, remodelling, and inflammatory macrophage infiltration (P = 0.023). Furthermore, we highlight the novel dysregulation of Wnt signalling in scWAT in non-insulin resistant obesity. LC n-3 PUFAs beneficially modulated the scWAT environment through downregulating the expression of genes associated with inflammatory and remodelling pathways (P <0.001), but there were altered outcomes in individuals living with obesity in comparison to normal weight individuals.ConclusionOur data identify dysregulation of Wnt signalling, hypoxia, and hypertrophy, and enhanced macrophage infiltration in scWAT in non-insulin resistant obesity. LC n-3 PUFAs modulate some of these processes, especially in normal weight individuals which may be preventative and limit the development of restrictive and inflammatory scWAT in the development of obesity. We conclude that a higher dose or longer duration of LC n-3 PUFA intervention may be needed to reduce obesity-associated scWAT inflammation and promote tissue homeostasis.Clinical Trial Registration www.isrctn.com, identifier ISRCTN96712688.

Visualization of sympathetic neural innervation in human white adipose tissue.

Obesity, defined as an excess of adipose tissue that adversely affects health, is a major cause of morbidity and mortality. However, to date, understanding the structure and function of human adipose tissue has been limited by the inability to visualize cellular components due to the innate structure of adipocytes, which are characterized by large lipid droplets. Combining the iDISCO and the CUBIC protocols for whole tissue staining and optical clearing, we developed a protocol to enable immunostaining and clearing of human subcutaneous white adipose tissue (WAT) obtained from individuals with severe obesity. We were able to perform immunolabelling of sympathetic nerve terminals in whole WAT and subsequent optical clearing by eliminating lipids to render the opaque tissue completely transparent. We then used light sheet confocal microscopy to visualize sympathetic innervation of human WAT from obese individuals in a three-dimensional manner. We demonstrate the visualization of sympathetic nerve terminals in human WAT. This protocol can be modified to visualize other structures such as blood vessels involved in the development, maintenance and function of human adipose tissue in health and disease.

Modification of subcutaneous white adipose tissue inflammation by omega-3 fatty acids is limited in human obesity-a double blind, randomised clinical trial.

SummaryBackgroundObesity is associated with enhanced inflammation. However, investigation in human subcutaneous white adipose tissue (scWAT) is limited and the mechanisms by which inflammation occurs have not been well elucidated. Marine long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFAs) have anti-inflammatory actions and may reduce scWAT inflammation.MethodsSubcutaneous white adipose tissue (scWAT) biopsies were collected from individuals living with obesity (n=45) and normal weight individuals (n=39) prior to and following a 12-week intervention with either 3 g/day of a fish oil concentrate (providing 1.1 g eicosapentaenoic acid (EPA) + 0.8 g docosahexaenoic acid (DHA)) or 3 g/day of corn oil. ScWAT fatty acid, oxylipin, and transcriptome profiles were assessed by gas chromatography, ultra-pure liquid chromatography tandem mass spectrometry, RNA sequencing and qRT-PCR, respectively.FindingsObesity was associated with greater scWAT inflammation demonstrated by lower concentrations of specialised pro-resolving mediators (SPMs) and hydroxy-DHA metabolites and an altered transcriptome with differential expression of genes involved in LC n-3 PUFA activation, oxylipin synthesis, inflammation, and immune response. Intervention with LC n-3 PUFAs increased their respective metabolites including the SPM precursor 14-hydroxy-DHA in normal weight individuals and decreased arachidonic acid derived metabolites and expression of genes involved in immune and inflammatory response with a greater effect in normal weight individuals.InterpretationDownregulated expression of genes responsible for fatty acid activation and metabolism may contribute to an inflammatory oxylipin profile and limit the effects of LC n-3 PUFAs in obesity. There may be a need for personalised LC n-3 PUFA supplementation based on obesity status.FundingEuropean Commission Seventh Framework Programme (Grant Number 244995) and Czech Academy of Sciences (Lumina quaeruntur LQ200111901).

Macrophages expressing uncoupling protein 1 increase in adipose tissue in response to cold in humans

Acute cold induces beige adipocyte protein marker expression in human subcutaneous white adipose tissue (SC WAT) from both the cold treated and contralateral leg, and the immune system regulates SC WAT beiging in mice. Cold treatment significantly increased the gene expression of the macrophage markers CD68 and 86 in SC WAT. Therefore, we comprehensively investigated the involvement of macrophages in SC WAT beiging in lean and obese humans by immunohistochemistry. Cold treatment significantly increased CD163/CD68 macrophages in SC WAT from the cold treated and contralateral legs of lean and obese subjects, and had similar effects on CD206/CD68 macrophages, whereas the effects on CD86/CD68 macrophages were inconsistent between lean and obese. However, linear regression analysis did not find significant relationships between the change in macrophage numbers and the change in UCP1 protein abundance. A high percentage of CD163 macrophages in SC WAT expressed UCP1, and these UCP1 expressing CD163 macrophages were significantly increased by cold treatment in SC WAT of lean subjects. In conclusion, our results suggest that CD163 macrophages are involved in some aspect of the tissue remodeling that occurs during SC WAT beiging in humans after cold treatment, but they are likely not direct mediators of the beiging process.

Quiescence, Stemness and Adipogenic Differentiation Capacity in Human DLK1-/CD34+/CD24+ Adipose Stem/Progenitor Cells.

We explore the status of quiescence, stemness and adipogenic differentiation capacity in adipose stem/progenitor cells (ASCs) ex vivo, immediately after isolation from human subcutaneous white adipose tissue, by sorting the stromal vascular fraction into cell-surface DLK1+/CD34−, DLK1+/CD34dim and DLK1−/CD34+ cells. We demonstrate that DLK1−/CD34+ cells, the only population exhibiting proliferative and adipogenic capacity, express ex vivo the bonafide quiescence markers p21Cip1, p27Kip1 and p57Kip2 but neither proliferation markers nor the senescence marker p16Ink4a. The pluripotency markers NANOG, SOX2 and OCT4 are barely detectable in ex vivo ASCs while the somatic stemness factors, c-MYC and KLF4 and the early adipogenic factor C/EBPβ are highly expressed. Further sorting of ASCs into DLK1−/CD34+/CD24− and DLK1−/CD34+/CD24+ fractions shows that KLF4 and c-MYC are higher expressed in DLK1−/CD34+/CD24+ cells correlating with higher colony formation capacity and considerably lower adipogenic activity. Proliferation capacity is similar in both populations. Next, we show that ASCs routinely isolated by plastic-adherence are DLK1−/CD34+/CD24+. Intriguingly, CD24 knock-down in these cells reduces proliferation and adipogenesis. In conclusion, DLK1−/CD34+ ASCs in human sWAT exist in a quiescent state, express high levels of somatic stemness factors and the early adipogenic transcription factor C/EBPβ but senescence and pluripotency markers are barely detectable. Moreover, our data indicate that CD24 is necessary for adequate ASC proliferation and adipogenesis and that stemness is higher and adipogenic capacity lower in DLK1−/CD34+/CD24+ relative to DLK1−/CD34+/CD24− subpopulations.

Subcutaneous white adipose tissue: The deepest layer of the cutaneous immune barrier.

Mammalian skin, the outer covering of the body, is composed of three layers, i.e. the epidermis, the dermis and the subcutaneous white adipose tissue (SWAT). While the contribution of epidermis and dermis to the skin's immune function is well established, the role, if any, of SWAT in this regard has yet to be determined. Human SWAT is made up of lobules which consist mainly of adipocytes and are subdivided and separated from each other by vascularized septae of connective tissue. An immunophenotypic analysis of liposuction-derived SWAT demonstrated that healthy subcutaneous fat tissue, although showing no overt signs of inflammation, harbors an indigenous system of immunocytes. As opposed to epidermis and dermis, they belong mainly to the mononuclear phagocyte lineage and, to a lesser extent, represent T-lymphocytes. Their phenotype indicates that these two major subsets of SWAT leukocytes are primarily concerned with ant-inflammatory and/or regulatory functions. It thus appears that SWAT is more than a cushion protecting against mechanical trauma, and may subserve immunomodulatory functions aimed at preventing or, at least, mitigating exaggerated immune and/or inflammatory reactions..

269-OR: miR-409-3p Regulates Angiogenesis Brown Fat Adiposity and Insulin Resistance

White and brown adipose tissues are highly vascularized organs, capable of plasticity based on metabolic demands and energy expenditure, which if maladaptive can lead to insulin resistance. Critical gaps remain in our understanding of how angiogenesis impacts adipose tissue dysfunction and overall metabolism. MicroRNAs (miRs) are implicated in the regulation of the angiogenic response to pathophysiological stimuli. Function of miRNAs regulating the angiogenic response in diet-induced insulin resistance remains poorly understood. Using a miRNA-Seq approach, we identified that miR-409-3p expression was significantly increased in endothelial cells (ECs) of brown adipose tissue (BAT) of diet-induced obese (DIO) mice and in human diabetic plasma samples compared to nondiabetic patients. Overexpression of miR-409-3p markedly inhibited EC growth and migration, whereas miR-409-3p inhibition had the opposite effects. miR-409-3p targets the 3’UTR of Zinc Finger E-box binding Homeobox 1 (ZEB1). Overexpression of miR-409-3p decreased ZEB1 expression in ECs and in human subcutaneous white adipose tissue (sWAT). SiRNA knock down of ZEB1 expression in ECs phenocopied the effects of miR-409-3p overexpression and significantly decreased cell proliferation and migration. In addition, 3T3-L1 cells co-cultured with supe harvested from ECs deficient in miR-409-3p had increased expression of brown fat markers (UCP1, Cidea, PGC1-α) by RT-qPCR and Western blot analyses. Systemic intravenous delivery of LNA-anti-miR-409-3p inhibitor to DIO mice significantly increased angiogenesis by CD31 staining, accompanied by higher UCP-1 in BAT and sWAT by RT-qPCR, Western blot and immunohistochemistry analyses, while improving glucose tolerance and overall metabolism. miR-409-3p plays a key regulatory role between impaired angiogenesis in diet-induced obesity and adipose tissue dysfunction, an effect that could be exploited for therapeutic intervention in obesity-induced insulin resistance. Disclosure D.R. Becker-Greene: None. H. Li: None. W. Wu: None. D. Ozdemir: None. I. Hollan: None. M.W. Feinberg: None. B. Icli: None. Funding American Diabetes Association (1-16-JDF-046 to B.I.)

Human adipose stromal-vascular fraction self-organizes to form vascularized adipose tissue in 3D cultures

Native human subcutaneous adipose tissue (AT) is well organized into unilocular adipocytes interspersed within dense vascularization. This structure is completely lost under standard culture conditions and may impair the comparison with native tissue. Here, we developed a 3-D model of human white AT reminiscent of the cellular architecture found in vivo. Starting with adipose progenitors derived from the stromal-vascular fraction of human subcutaneous white AT, we generated spheroids in which endogenous endothelial cells self-assembled to form highly organized endothelial networks among stromal cells. Using an optimized adipogenic differentiation medium to preserve endothelial cells, we obtained densely vascularized spheroids containing mature adipocytes with unilocular lipid vacuoles. In vivo study showed that when differentiated spheroids were transplanted in immune-deficient mice, endothelial cells within the spheroids connected to the recipient circulatory system, forming chimeric vessels. In addition, adipocytes of human origin were still observed in transplanted mice. We therefore have developed an in vitro model of vascularized human AT-like organoids that constitute an excellent tool and model for any study of human AT.

Transforming Growth Factor-β3 Regulates Adipocyte Number in Subcutaneous White Adipose Tissue

White adipose tissue (WAT) mass is determined by adipocyte size and number. While adipocytes are continuously turned over, the mechanisms controlling fat cell number in WAT upon weight changes are unclear. Herein, prospective studies of human subcutaneous WAT demonstrate that weight gain increases both adipocyte size and number, but the latter remains unaltered after weight loss. Transcriptome analyses associate changes in adipocyte number with the expression of 79 genes. This gene set is enriched for growth factors, out of which one, transforming growth factor-β3 (TGFβ3), stimulates adipocyte progenitor proliferation, resulting in a higher number of cells undergoing differentiation invitro. The relevance of these observations was corroborated invivo where Tgfb3+/- mice, in comparison with wild-type littermates, display lower subcutaneous adipocyte progenitor proliferation, WAT hypertrophy, and glucose intolerance. TGFβ3 is therefore a regulator of subcutaneous adipocyte number and may link WAT morphology to glucose metabolism.

Long Non-Coding RNAs Associated with Metabolic Traits in Human White Adipose Tissue

Long non-coding RNAs (lncRNAs) belong to a recently discovered class of molecules proposed to regulate various cellular processes. Here, we systematically analyzed their expression in human subcutaneous white adipose tissue (WAT) and found that a limited set was differentially expressed in obesity and/or the insulin resistant state. Two lncRNAs herein termed adipocyte-specific metabolic related lncRNAs, ASMER-1 and ASMER-2 were enriched in adipocytes and regulated by both obesity and insulin resistance. Knockdown of either ASMER-1 or ASMER-2 by antisense oligonucleotides in in vitro differentiated human adipocytes revealed that both genes regulated adipogenesis, lipid mobilization and adiponectin secretion. The observed effects could be attributed to crosstalk between ASMERs and genes within the master regulatory pathways for adipocyte function including PPARG and INSR. Altogether, our data demonstrate that lncRNAs are modulators of the metabolic and secretory functions in human fat cells and provide an emerging link between WAT and common metabolic conditions.

Caloric Restriction and Diet-Induced Weight Loss Do Not Induce Browning of Human Subcutaneous White Adipose Tissue in Women and Men with Obesity

Caloric restriction (CR) is standard lifestyle therapy inobesity management. CR-induced weight loss improves the metabolic profile of individuals with obesity. In mice, occurrence of beige fat cells in white fat depots favors a metabolically healthy phenotype, and CR promotes browning of white adipose tissue (WAT). Here, human subcutaneous abdominal WAT samples were analyzed in 289 individuals with obesity following a two-phase dietary intervention consisting of an 8week very low calorie diet and a 6-month weight-maintenance phase. Before the intervention, we show sex differences and seasonal variation, with higher expression of brown and beige markers in women with obesity and during winter, respectively. The very low calorie diet resulted in decreased browning of subcutaneous abdominal WAT. During the whole dietary intervention, evolution of body fat and insulin resistance was independent of changes in brown and beige fat markers. These data suggest that diet-induced effects on body fat and insulin resistance are independent of subcutaneous abdominal WAT browning in people with obesity.

Single cell transcriptomics suggest that human adipocyte progenitor cells constitute a homogeneous cell population

Regulation of adipose tissue stem cells (ASCs) and adipogenesis impact the development of excess body fat-related metabolic complications. Animal studies have suggested the presence of distinct subtypes of ASCs with different differentiation properties. In addition, ASCs are becoming the biggest source of mesenchymal stem cells used in therapies, which requires deep characterization. Using unbiased single cell transcriptomics we aimed to characterize ASC populations in human subcutaneous white adipose tissue (scWAT). The transcriptomes of 574 single cells from the WAT total stroma vascular fraction (SVF) of four healthy women were analyzed by clustering and t-distributed stochastic neighbor embedding visualization. The identified cell populations were then mapped to cell types present in WAT using data from gene expression microarray profiling of flow cytometry-sorted SVF. Cells clustered into four distinct populations: three adipose tissue-resident macrophage subtypes and one large, homogeneous population of ASCs. While pseudotemporal ordering analysis indicated that the ASCs were in slightly different differentiation stages, the differences in gene expression were small and could not distinguish distinct ASC subtypes. Altogether, in healthy individuals, ASCs seem to constitute a single homogeneous cell population that cannot be subdivided by single cell transcriptomics, suggesting a common origin for human adipocytes in scWAT.

Silencing of the small GTPase DIRAS3 induces cellular senescence in human white adipose stromal/progenitor cells.

Inhibition of Akt-mTOR signaling protects from obesity and extends life span in animals. In the present study, we analyse the impact of the small GTPase, GTP-binding RAS-like 3 (DIRAS3), a recently identified weight-loss target gene, on cellular senescence in adipose stromal/progenitor cells (ASCs) derived from human subcutaneous white adipose tissue (sWAT). We demonstrate that DIRAS3 knock-down (KD) in ASCs induces activation of Akt-mTOR signaling and proliferation arrest. DIRAS3 KD ASCs lose the potential to form colonies and are negative for Ki-67. Moreover, silencing of DIRAS3 results in a premature senescence phenotype. This is characterized by senescence-associated β-galactosidase positive enlarged ASCs containing increased p16INK4A level and activated retinoblastoma protein. DIRAS3 KD ASCs form senescence-associated heterochromatic foci as shown by increased level of γ-H2A.X positive foci. Furthermore, these cells express a senescence-associated secretory phenotype characterized by increased interleukin-8 secretion. Human DIRAS3 KD ASCs develop also a senescence phenotype in sWAT of SCID mice. Finally, we show that DIRAS3 KD in ASCs stimulates both adipogenic differentiation and premature senescence. In conclusion, our data suggest that silencing of DIRAS3 in ASCs and subsequently hyper-activation of Akt-mTOR drives adipogenesis and premature senescence. Moreover, differentiating ASCs and/or mature adipocytes may acquire features of cellular senescence.

Erythropoietin does not activate erythropoietin receptor signaling or lipolytic pathways in human subcutaneous white adipose tissue in vivo.

BackgroundErythropoietin (Epo) exerts direct effects on white adipose tissue (WAT) in mice in addition to its erythropoietic effects, and in humans Epo increases resting energy expenditure and affect serum lipid levels, but direct effects of Epo in human WAT have not been documented. We therefore investigated the effects of acute and prolonged Epo exposure on human WAT in vivo.MethodData were obtained from two clinical trials: 1) acute Epo exposure (rHuEpo, 400 IU/kg) followed by WAT biopsies after 1 h and 2) 10 weeks treatment with the erythropoiesis-stimulating agent (ESA) Darbepoietin-alpha. Biopsies were analyzed by PCR for Epo receptor (Epo-R) mRNA. A new and highly specific antibody (A82, Amgen) was used to evaluate the presence of Epo-R by western blot analysis in addition to Epo-R signaling proteins (Akt, STAT5, p70s6k, LYN, and p38MAPK), activation of lipolytic pathways (ATGL, HSL, CGI-58, G0S2, Perilipin, Cidea, Cidec, AMPK, and ACC), and mitochondrial biogenesis (VDAC, HSP90, PDH, and SDHA).ResultsNo evidence of in vivo activation of the Epo-R in WAT could be documented despite detectable levels of Epo-R mRNA.ConclusionThus, in contradiction to animal studies, Epo treatment within a physiological relevant range in humans does not exert direct effects in a subcutaneous WAT.

Biomarkers of browning of white adipose tissue and their regulation during exercise- and diet-induced weight loss ,

Background: A hypothesis exists whereby an exercise- or dietary-induced negative energy balance reduces human subcutaneous white adipose tissue (scWAT) mass through the formation of brown-like adipocyte (brite) cells. However, the validity of biomarkers of brite formation has not been robustly evaluated in humans, and clinical data that link brite formation and weight loss are sparse.Objectives: We used rosiglitazone and primary adipocytes to stringently evaluate a set of biomarkers for brite formation and determined whether the expression of biomarker genes in scWAT could explain the change in body composition in response to exercise training combined with calorie restriction in obese and overweight women (n = 79).Design: Gene expression was derived from exon DNA microarrays and preadipocytes from obesity-resistant and -sensitive mice treated with rosiglitazone to generate candidate brite biomarkers from a microarray. These biomarkers were evaluated against data derived from scWAT RNA from obese and overweight women before and after supervised exercise 5 d/wk for 16 wk combined with modest calorie restriction (∼0.84 MJ/d).Results: Forty percent of commonly used brite gene biomarkers exhibited an exon or strain-specific regulation. No biomarkers were positively related to weight loss in human scWAT. Greater weight loss was significantly associated with less uncoupling protein 1 expression (P = 0.006, R2 = 0.09). In a follow-up global analysis, there were 161 genes that covaried with weight loss that were linked to greater CCAAT/enhancer binding protein α activity (z = 2.0, P = 6.6 × 10−7), liver X receptor α/β agonism (z = 2.1, P = 2.8 × 10−7), and inhibition of leptin-like signaling (z = −2.6, P = 3.9 × 10−5).Conclusion: We identify a subset of robust RNA biomarkers for brite formation and show that calorie-restriction–mediated weight loss in women dynamically remodels scWAT to take on a more-white rather than a more-brown adipocyte phenotype.