White Adipose Tissue Morphology Research Articles

Adipose Tissue Analysis Toolkit (ATAT) for automated analysis of adipocyte size and extracellular matrix in white adipose tissue.

The pathological expansion of white adipose tissue (WAT) in obesity involves adipocyte hypertrophy accompanied by expansion of the collagen-rich pericellular extracellular matrix (ECM) and development of crown-like structures (CLS). Traditionally, WAT morphology is assessed through immunohistochemical analysis of WAT sections. However, manual analysis of large histological sections is time-consuming, and the available digital tools for analyzing adipocyte size and pericellular ECM are limited. To address this gap, the authors developed the Adipose Tissue Analysis Toolkit (ATAT), an ImageJ plugin facilitating analysis of adipocyte size, WAT ECM, and CLS. ATAT utilizes local and image-level differentials in pixel intensity to independently threshold image background, distinguishing adipocyte-free tissue without user input. It accurately captures adipocytes in histological sections stained with common dyes and automates the analysis of adipocyte cross-sectional area, total-field, and localized region-of-interest ECM. ATAT allows fully automated batch analysis of histological images using default or user-defined adipocyte detection parameters. ATAT provides several advantages over existing WAT image analysis tools, enabling high-throughput analyses of adipocyte-specific parameters and facilitating the assessment of ECM changes associated with WAT remodeling due to weight changes and other pathophysiological alterations that affect WAT function.

LncRNA U90926 is dispensable for the development of obesity-associated phenotypes invivo.

Obesity is a global health problem characterized by excessive fat accumulation, driven by adipogenesis and lipid accumulation. Long non-coding RNAs (lncRNAs) have recently been implicated in regulating adipogenesis and adipose tissue function. Mouse lncRNA U90926 was previously identified as a repressor of invitro adipogenesis in 3T3-L1 preadipocytes. Consequently, we hypothesized that, invivo, U90926 may repress adipogenesis, and hence its deletion would increase weight gain and adiposity. We tested the hypothesis by applying U90926-deficient (U9-KO) mice to a high-throughput phenotyping pipeline. Compared with WT, U9-KO mice showed no major differences across a wide range of behavioral, neurological, and other physiological parameters. In mice fed a standard diet, we have found no differences in obesity-related phenotypes, including weight gain, fat mass, and plasma concentrations of glucose, insulin, triglycerides, and free fatty acids, in U9-KO mice compared to WT. U90926 deficiency lacked a major effect on white adipose tissue morphology and gene expression profile. Furthermore, in mice fed a high-fat diet, we found increased expression of U90926 in adipose tissue stromal vascular cell fraction, yet observed no effect of U90926 deficiency on weight gain, fat mass, adipogenesis marker expression, and immune cell infiltration into the adipose tissue. These data suggest that the U90926 lacks an essential role in obesity-related phenotypes and adipose tissue biology invivo.

Combined effects of intermittent fasting with swimming-based high intensity intermittent exercise training in Wistar rats

High caloric intake and physical inactivity are known precursors to the development of several chronic metabolic diseases. For obesity and sedentarism, High Intensity Intermittent Exercise (HIIE) and Intermittent Fasting (IF) have emerged as individual strategies to attenuate their negative effects by improving metabolism. To study their combined effects, Wistar male rats (n = 74, 60 days old) were divided into four groups: Sedentary Control (C), swimming-based HIIE only (HIIE), Intermittent Fasting only (IF), and swimming-based HIIE associated with Intermittent Fasting (HIIE/IF). Over an eight-week period swimming performance, body composition, weight and feeding behavior were analyzed. The final morphology of white adipose tissue showed a significant reduction in adipocyte size consistent with a higher number of cells per area in exercised animals (vs C and IF, p < 0.05), which also displayed characteristics of browning through UCP-1 levels and CD31 staining. These results suggest that the increased performance in the HIIE/IF group is, in part, by modifications of WAT metabolism through the browning process.

SEX-DEPENDENT EFFECTS OF ADIPOCYTE STAT3 INHIBITION ON THE INFLAMMATORY RESPONSE DURING SEVERE SEPSIS.

Introduction: Sepsis is a dysregulated host response to infection that can lead to life-threatening organ dysfunction. Clinical and animal studies consistently demonstrate that female subjects are less susceptible to the adverse effects of sepsis, demonstrating the importance of understanding how sex influences sepsis outcomes. The signal transducer and activator of transcription 3 (STAT3) pathway are a major signaling pathway that facilitates inflammation during sepsis. STAT3 is abundantly expressed in white adipose tissue; however, little is known about the contribution of white adipose tissue STAT3 activation during sepsis. We hypothesize that adipocyte STAT3 inhibition during severe sepsis will exaggerate the inflammatory response and impact organ injury, in a sex-dependent manner. Methods: We generated STAT3 flox/flox (wild-type [WT]) and adipocyte STAT3 knock out (A-STAT3 KO) mice using Cre-lox technology. Studies were done in 12- to 16-week-old male and female mice. Polymicrobial sepsis was induced by cecal ligation and puncture (CLP). Control nonseptic mice did not undergo CLP (0 h CLP). Tissues were harvested 18 h after CLP. Body composition was determined by echo magnetic resonance imaging. Energy metabolism was determined by indirect calorimetry. White adipose tissue morphology was determined by hematoxylin and eosin staining, while STAT3 activation in the white adipose tissue was determined by western blot analysis and immunohistochemistry staining of STAT3 activation/phosphorylation at tyrosine 705. Plasma cytokines (TNF-α, IL-6, and leptin) were determined by luminex assay. Neutrophil infiltration of the lung and liver was assessed by myeloperoxidase activity assay. Histological signs of organ injury on lung and liver tissue were assessed by hematoxylin and eosin staining. Liver injury was further assessed by measuring plasma alanine and aspartate aminotransferase. In a separate cohort of mice, sepsis was induced by CLP and mice were monitored every 6-12 h over a 7-day period to assess survival rate. Results: We demonstrate that neither body composition nor energy metabolism is altered with adipocyte STAT3 inhibition in male or female mice, under nonseptic conditions. Sepsis was associated with reduced adipocyte size in female WT and A-STAT3 KO mice, suggesting that this event is STAT3 independent. Sepsis did not alter adipocyte size in male WT and A-STAT3 KO mice, suggesting that this event is also sex dependent. Although STAT3 phosphorylation at tyrosine 705 expression is negligible in male and female A-STAT3 KO mice, septic female WT and A-STAT3 KO mice have higher white adipose tissue STAT3 activation than male WT and A-STAT3 KO mice. Adipocyte STAT3 inhibition did not alter the proinflammatory cytokine response during sepsis in male or female mice, as measured by plasma TNF-α, IL-6, and leptin levels. Adipocyte STAT3 inhibition reduced lung neutrophil infiltration and histological signs of lung injury during sepsis in male mice. On the contrary, adipocyte STAT3 inhibition had no effect on lung neutrophil infiltration or lung injury in female mice. We further demonstrate that neither liver neutrophil infiltration nor histological signs of liver injury are altered by adipocyte STAT3 inhibition during sepsis, in male or female mice. Lastly, adipocyte STAT3 inhibition did not affect survival rate of male or female mice during sepsis. Conclusions: Our study demonstrates that sex influences white adipose tissue STAT3 activation and morphology during sepsis, which is not dependent on the presence of functional STAT3 in mature adipocytes. Furthermore, genetic inhibition of adipocyte STAT3 activation in male, but not female mice, results in reduced lung neutrophil infiltration and lung injury during sepsis. The results from our study demonstrate the importance of considering biological sex and the white adipose tissue as potential sources and targets of inflammation during sepsis.

Yerba mate consumption by ovariectomized rats alters white adipose tissue

IntroductionMenopause and post-menopause are characterized by low levels of estrogen that can be associated with the emergence of metabolic diseases. While hormone replacement therapy can alleviate many symptoms, it can also exacerbate other diseases such as breast cancer. In the search for natural alternatives, Ilex paraguariensis (Yerba Mate) has been identified as a potential therapy for the onset of obesity. Here, the effect of MATE consumption on white adipose tissue (WAT) was studied in ovariectomized rats, an animal model for post-menopause hormone loss. MethodsFour groups of animals were used: ovariectomy with MATE (OVX MATE) and without MATE (OVX), as well as sham surgery with MATE (Sham MATE) and without MATE (Sham). MATE was provided by gavage at 1 g/kg of body weight for eight weeks before measuring biochemical parameters in plasma and characterizing WAT morphology. ResultsThe consumption of Yerba MATE significantly decreased weight gain in ovariectomized rats and presented near control levels of triglycerides, total cholesterol, and LDL. A morphometric analysis of WAT showed a significant decrease in the area occupied by adipocytes in the group that consumed MATE. Finally, MATE consumption increased the UCP1 content in the WAT of the ovariectomized group. Yerba MATE treatment was also associated with higher levels of SIRT1 protein. ConclusionMATE consumption has a preventive effect on the weight gain observed in ovariectomized rats and potential benefits in naturally avoiding the onset of obesity post menopause.

LBSUN129 Adipose Tissue Analysis Toolkit (at-at): An Imagej Plugin For Automated Analysis Of Adipocyte Number, Size, And Pericellular Fibrosis In Histological Sections

Abstract Obesity-induced pathological expansion of white adipose tissue (WAT) involves adipocyte hypertrophy that occurs in tandem with the development of pericellular fibrosis. Other pathophysiological states, such as cancer and HIV, are also associated with fibrotic transformation of WAT depots. Aging, obesity, inactivity, and estrogen deficiency are also associated with an increase in bone marrow adiposity. Disease-associated changes in WAT morphology are typically assessed using histochemical analysis of WAT sections. However, manual analysis of large histological sections of WAT or bone marrow adipose tissue can be very time-consuming, while digital tools for the analysis of adipocyte size and pericellular fibrosis are limited. In response to this need, we have developed the Adipose Tissue Analysis Toolkit (AT-AT), a plugin for the open-source image analysis software ImageJ. AT-AT employs both local and global differentials in pixel intensity to threshold background apart from adipocyte-free tissue without user input. The AT-AT accurately captures adipocyte perimeter, maximum diameter, minimum diameter, and density per square millimeter of tissue in histological sections stained with common histological dyes, and performs automatic analysis of adipocyte cross-sectional area as well as pericellular fibrosis. AT-AT enables fully-automated analysis of batches of histological images using either default or user-defined adipocyte detection parameters including minimum circularity as well as minimum and maximum cross-sectional area. Likewise, users may set parameters for the thresholding algorithms, including the number of localized thresholds to be calculated in each image. AT-AT's thresholding techniques confer uniquely high resistances to both false-negative and false-positive detection events by comparison to other open-source adipocyte analysis software. They also enable superior measurement of adipocyte morphology, especially in the case of low-magnification images. AT-AT features several quality-of-life features, including automatic summarization of batch-collected data, the implementation of its thresholding algorithms as independent ImageJ commands, and an optional histogram builder. AT-AT can enhance the rigor and reproducibility of adipose tissue research. AT-AT will become available as a plugin for ImageJ in the fall of 2022. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Maternal Vitamin D Deficiency in Mice Increases White Adipose Tissue Inflammation in Offspring.

Vitamin D is acknowledged to play an important biological and metabolic role in adipose tissue, which is also the main storage site for this vitamin. Its anti-inflammatory effect in adipocytes and adipose tissue has notably been highlighted in adult mice. This vitamin is also crucial during fetal development since maternal vitamin D deficiency is suspected to program future metabolic disorders. Based on these observations, the aim of this study was to evaluate the consequences of maternal vitamin D deficiency (VDD) on white adipose tissue inflammation in adult offspring fed with normal or obesogenic diet (high-fat diet). White adipose tissue morphology, RNA and miRNA expression profiles, and signaling pathways were studied in adult males and females. In males, a HF diet coupled with maternal VDD increased expression of RNA and miRNA linked to inflammation leading to over-representation of inflammatory pathways. Interestingly, genomic and epigenetic profiles were associated with activation of the NF-kB signaling pathway and adiposity index. In females, no major modulation of inflammatory pathways was observed under VDD, contrarily to males. We concluded that maternal VDD coupled with HF diet activated inflammatory pathway in adipose tissue of the offspring, in a sex-dependent manner. Such activation is strongly related to activation of NF-kB signaling and increased adiposity only in males.

Subcutaneous adipose tissue expansion mechanisms are similar in early and late onset overweight/obesity

Background/objectiveThe development of overweight/obesity associates with alterations in white adipose tissue (WAT) cellularity (fat cell size/number) and lipid metabolism, in particular lipolysis. If these changes differ between early/juvenile (EOO < 18 years of age) or late onset overweight/obesity (LOO) is unknown and was presently examined.Subjects/methodsWe included 439 subjects with validated information on body mass index (BMI) at 18 years of age. Using this information and current BMI, subjects were divided into never overweight/obese (BMI < 25 kg/m2), EOO and LOO. Adipocyte size, number, morphology (size in relation to body fat) and lipolysis were determined in subcutaneous abdominal WAT. Body composition and WAT distribution was assessed by dual-X-ray absorptiometry.ResultsCompared with never overweight/obese, EOO and LOO displayed larger WAT amounts in all examined depots, which in subcutaneous WAT was explained by a combination of increased size and number of fat cells in EOO and LOO. EOO had 40% larger subcutaneous fat mass than LOO (p < 0.0001). Visceral WAT mass, WAT morphology and lipolysis did not differ between EOO and LOO except for minor differences in men between the two obesity groups. On average, the increase in BMI per year was 57% higher in subjects with EOO compared to LOO (p < 0.0001).ConclusionEarly onset overweight/obesity causes a more rapid and pronounced accumulation of subcutaneous WAT than adult onset. However, fat mass expansion measures including WAT cellularity, morphology and fat cell lipolysis do not differ in an important way suggesting that similar mechanisms of WAT growth operate in EOO and LOO.

Renin-angiotensin system modulation through enalapril and/or exercise training improves visceral adiposity in obese mice

IntroductionObesity-related metabolic diseases occur as a result of disruptions in white adipose tissue (WAT) plasticity, especially through visceral fat accumulation and adipocyte hypertrophy. This study aimed to evaluate the impact of renin–angiotensin system (RAS) and bradykinin receptors modulation by enalapril treatment and/or exercise training on WAT morphology and related deleterious outcomes. MethodsMale C57BL/6 mice were fed either a standard chow or a high-fat (HF) diet for 16 weeks. At the 8th week, HF-fed animals were divided into sedentary (HF), enalapril treatment (HF-E), exercise training (HF-T), and enalapril treatment plus exercise training (HF-ET) groups. Following the experimental protocol, body mass gain, adiposity index, insulin resistance, visceral WAT morphometry, renin-angiotensin system, and bradykinin receptors were evaluated. ResultsThe HF group displayed increased adiposity, larger visceral fat mass, and adipocyte hypertrophy, which was accompanied by insulin resistance, overactivation of Ang II/AT1R arm, and favoring of B1R in bradykinin receptors profile. All interventions ameliorated visceral adiposity and related outcomes by favoring the Ang 1–7/MasR arm and the B2R expression in B1R/B2R ratio. However, combined therapy additively reduced Ang II/Ang 1–7 ratio. ConclusionOur results suggest that Ang 1–7/MasR arm and B2R activation might be relevant targets in the treatment of visceral obesity.

Sclerostin Influences Exercise-Induced Adaptations in Body Composition and White Adipose Tissue Morphology in Male Mice.

Sclerostin is an inhibitor of the osteogenic Wnt/β-catenin signaling pathway that also has an endocrine role in regulating adipocyte differentiation and metabolism. Additionally, subcutaneous white adipose tissue (scWAT) sclerostin content decreases following exercise training (EXT). Therefore, we hypothesized that EXT-induced reductions in adipose tissue sclerostin may play a role in regulating adaptations in body composition and whole-body metabolism. To test this hypothesis, 10-week-old male C57BL/6J mice were either sedentary (SED) or performing 1 hour of treadmill running at ~65% to 70% maximum oxygen consumption (VO2max ) 5 day/week (EXT) for 4 weeks and had subcutaneous injections of either saline (C) or recombinant sclerostin (S) (0.1 mg/kg body mass) 5 day/week; thus, making four groups (SED-C, EXT-C, SED-S, and EXT-S; n= 12/group). No differences in body mass were observed between experimental groups, whereas food intake was higher in EXT (p= 0.03) and S (p= 0.08) groups. There was a higher resting energy expenditure in all groups compared to SED-C. EXT-C had increased lean mass and decreased fat mass percentage compared to SED-C and SED-S. No differences in body composition were observed in either the SED-S or EXT-S groups. Lower scWAT (inguinal), epididymal white adipose tissue (eWAT) (visceral epididymal) mass, and scWAT adipocyte cell size and increased percentage of multilocular cells in scWAT were observed in the EXT-C group compared to SED-C, whereas lower eWAT was only observed in the EXT-S group. EXT mice had increased scWAT low-density lipoprotein receptor-related protein 4 (Lrp4) and mitochondrial content and sclerostin treatment only inhibited increased Lrp4 content with EXT. Together, these results provide evidence that reductions in resting sclerostin with exercise training may influence associated alterations in energy metabolism and body composition, particularly in scWAT. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Systemic Nanoparticle-Mediated Delivery of Pantetheinase Vanin-1 Regulates Lipolysis and Adiposity in Abdominal White Adipose Tissue.

Lipolysis in white adipose tissue (WAT) occurs in response to nutritional signals and helps to regulate lipid turnover/adiposity in animals. However, the causal relationships and the mechanisms controlling WAT morphology are not clear. In this report, Vanin‐1, a pantetheinase, is shown to be a novel determinant for lipolysis and adiposity. The expression of Vanin‐1 in the abdominal WAT is positively correlated with lipolysis both in mice and in humans. Mice with global Vanin‐1 deficiency exhibit adipocyte hypertrophy and impaired lipolysis. Use of a nanosystem comprising P3‐peptide, chitosan oligosaccharide lactate, and polyethylene glycol that controls Vanin‐1 expression in the abdominal WAT shows that WAT‐specific Vanin‐1 knockdown blocks fasting‐induced lipolysis and prevents WAT loss. However, WAT‐specific Vanin‐1 mRNA restoration rescues impaired lipolysis and improves glucose/insulin intolerance in diabetic db/db mice. Mechanistically, Vanin‐1 induces PPARγ activity and subsequently facilitates its activation on the proximal promoters of lipolytic genes. Thus, an essential role of Vanin‐1 in the regulation of lipolysis and adiposity is revealed, and a functional RNA delivering strategy for specific intervention of Vanin‐1 expression in WAT is shown. These findings provide a promising approach to treat metabolic diseases caused by dysregulation of Vanin‐1 and lipolysis.

287-OR: Acute Exercise Enhances the Differentiation Rate of Human Adipocyte Precursor Cells

The direct effects of exercise on white adipose tissue morphology and metabolic function remain unclear, due in large part to confounding effects of the reduction in fat mass that often accompanies exercise training. The purpose of this study was to determine if a session of endurance exercise could impact the rate of adipogenesis. Eight lean, healthy human subjects performed a single session of exercise (1 hour of endurance exercise at 65% of their maximal aerobic capacity; VO2max). Blood samples were collected without prior exercise (No-EX) and immediately after exercise (EX). Serum was extracted, and human adipocyte precursor cells were incubated for 72 hours in vitro in either the No-EX or EX serum. This serum preincubation was immediately followed by a standard 14-day differentiation protocol. On both days 3 and 9 of differentiation, mRNA expression levels of differentiation markers, PPARG and FABP4, were significantly greater (P&amp;lt;0.01) in cells preincubated in the EX vs. No-EX serum (e.g., Day 3 PPARG expression: 11.4±0.6 vs. 8.3±0.4 2-∆Ct; P=0.005, and Day 9 FABP4 expression: 2185±82 vs. 1619±98 2-∆Ct; P&amp;lt;0.0001). In addition, after 14 days of differentiation, we also found significantly greater protein abundance of important lipolytic and esterification regulators, G0S2, ATGL, HSL and GPAT1 (all P&amp;lt;0.05). As expected, compared with No-EX, the EX sera had greater concentrations of IL-6, lactate, fatty acids, epinephrine, and growth hormone, some of which may contribute to the enhanced adipogenic signaling after exercise. In summary, factors released into the circulation during and/or immediately after a session of endurance exercise can accelerate the rate of differentiation in human adipocyte precursor cells. Enhanced adipogenic signaling in response to exercise may have metabolic health benefits by priming adipose tissue for a more effective energy storage during periods of weight gain. Disclosure P. Varshney: None. L.M. Guth: None. C.M. Anderson: None. A. Raajendiran: None. M.J. Watt: None. J.F. Horowitz: Research Support; Self; American Diabetes Association. Funding National Institutes of Health (R01DK077966, T32DK101357)

Inhibition of PRMT3 activity reduces hepatic steatosis without altering atherosclerosis susceptibility in apoE knockout mice

The nuclear receptor liver X receptor (LXR) impacts on cholesterol metabolism as well as hepatic lipogenesis via transcriptional regulation. It is proposed that inhibition of the protein arginine methyltransferase 3 (PRMT3) uncouples these two transcriptional pathways in vivo by acting as a specific lipogenic coactivator of LXR. Here we validated the hypothesis that treatment with the allosteric PRMT3 inhibitor SGC707 will diminish the hepatic steatosis extent, while leaving global cholesterol metabolism, important in cholesterol-driven pathologies like atherosclerosis, untouched. For this purpose, 12-week old hyperlipidemic apolipoprotein E knockout mice were fed a Western-type diet for six weeks to induce both hepatic steatosis and atherosclerosis. The mice received 3 intraperitoneal injections with SGC707 or solvent control per week. Mice chronically treated with SGC707 developed less severe hepatic steatosis as exemplified by the 51% reduced (P < 0.05) liver triglyceride levels. In contrast, the extent of in vivo macrophage foam cell formation and aortic root atherosclerosis was not affected by SGC707 treatment. Interestingly, SGC707-treated mice gained 94% less body weight (P < 0.05), which was paralleled by changes in white adipose tissue morphology, i.e. reduction in adipocyte size and browning.In conclusion, we have shown that through PRMT3 inhibitor treatment specific functions of LXR involved in respectively the development of fatty liver disease and atherosclerosis can be uncoupled, resulting in an overall diminished hepatic steatosis extent without a negative impact on atherosclerosis susceptibility. As such, our studies highlight that PRMT3 inhibition may constitute a novel therapeutic approach to limit the development of fatty liver disease in humans.

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.

The nuclear retinoid-related orphan receptor RORα controls circadian thermogenic programming in white fat depots.

The ROR α‐deficient staggerer (sg/sg) mouse is lean and resistant to diet‐induced obesity. Its thermogenic activity was shown to be increased not only in brown adipose tissue (BAT), but also in subcutaneous white adipose tissue (WAT) where UCP1 content was enhanced, however, without Prdm16 coexpression. Our observation of partial multilocular lipid morphology of WAT in sg/sg mice both in the inguinal and perigonadal sites led us to focus on the phenotype of both fat depots. Because ROR α is a nuclear factor acting in the clock machinery, we looked at the circadian expression profile of genes involved in thermogenesis and browning in WAT and BAT depots of sg/sg and WT mice, through real‐time quantitative PCR and western blotting. This 24‐h period approach revealed both a rhythmic expression of thermogenic genes in WAT and an increased browning of all the WAT depots tested in sg/sg mice that indeed involved the canonical browning process (through induction of Pgc‐1α and Prdm16). This was associated with an enhanced isoproterenol‐induced oxygen consumption rate of WAT explants from sg/sg mice, which was reproducible in WT explants by treatment with a ROR α inverse agonist SR 3335, that induced a parallel increase in the UCP1 protein. Inhibitors of browning differentiation, such as TLE3 and RIP140, could be new targets of ROR α that would be rather implicated in the whitening of adipocytes. Our study showed the pivotal role of ROR α as an inhibitor of the thermogenic program in WAT, the role that could be counteracted in vivo with the ROR α antagonists currently in development.

Dietary Quercetin Attenuates Adipose Tissue Expansion and Inflammation and Alters Adipocyte Morphology in a Tissue-Specific Manner

Chronic inflammation in adipose tissue may contribute to depot-specific adipose tissue expansion, leading to obesity and insulin resistance. Dietary supplementation with quercetin or botanical extracts containing quercetin attenuates high fat diet (HFD)-induced obesity and insulin resistance and decreases inflammation. Here, we determined the effects of quercetin and red onion extract (ROE) containing quercetin on subcutaneous (inguinal, IWAT) vs. visceral (epididymal, EWAT) white adipose tissue morphology and inflammation in mice fed low fat, high fat, high fat plus 50 μg/day quercetin or high fat plus ROE containing 50 μg/day quercetin equivalents for 9 weeks. Quercetin and ROE similarly ameliorated HFD-induced increases in adipocyte size and decreases in adipocyte number in IWAT and EWAT. Furthermore, quercetin and ROE induced alterations in adipocyte morphology in IWAT. Quercetin and ROE similarly decreased HFD-induced IWAT inflammation. However, quercetin and red onion differentially affected HFD-induced EWAT inflammation, with quercetin decreasing and REO increasing inflammatory marker gene expression. Quercetin and REO also differentially regulated circulating adipokine levels. These results show that quercetin or botanical extracts containing quercetin induce white adipose tissue remodeling which may occur through inflammatory-related mechanisms.

FAM13A and POM121C are candidate genes for fasting insulin: functional follow-up analysis of a genome-wide association study

Aims/hypothesisBy genome-wide association meta-analysis, 17 genetic loci associated with fasting serum insulin (FSI), a marker of systemic insulin resistance, have been identified. To define potential culprit genes in these loci, in a cross-sectional study we analysed white adipose tissue (WAT) expression of 120 genes in these loci in relation to systemic and adipose tissue variables, and functionally evaluated genes demonstrating genotype-specific expression in WAT (eQTLs).MethodsAbdominal subcutaneous adipose tissue biopsies were obtained from 114 women. Basal lipolytic activity was measured as glycerol release from adipose tissue explants. Adipocytes were isolated and insulin-stimulated incorporation of radiolabelled glucose into lipids was used to quantify adipocyte insulin sensitivity. Small interfering RNA-mediated knockout in human mesenchymal stem cells was used for functional evaluation of genes.ResultsAdipose expression of 48 of the studied candidate genes associated significantly with FSI, whereas expression of 24, 17 and 2 genes, respectively, associated with adipocyte insulin sensitivity, lipolysis and/or WAT morphology (i.e. fat cell size relative to total body fat mass). Four genetic loci contained eQTLs. In one chromosome 4 locus (rs3822072), the FSI-increasing allele associated with lower FAM13A expression and FAM13A expression associated with a beneficial metabolic profile including decreased WAT lipolysis (regression coefficient, R = −0.50, p = 5.6 × 10−7). Knockdown of FAM13A increased lipolysis by ~1.5-fold and the expression of LIPE (encoding hormone-sensitive lipase, a rate-limiting enzyme in lipolysis). At the chromosome 7 locus (rs1167800), the FSI-increasing allele associated with lower POM121C expression. Consistent with an insulin-sensitising function, POM121C expression associated with systemic insulin sensitivity (R = −0.22, p = 2.0 × 10−2), adipocyte insulin sensitivity (R = 0.28, p = 3.4 × 10−3) and adipose hyperplasia (R = −0.29, p = 2.6 × 10−2). POM121C knockdown decreased expression of all adipocyte-specific markers by 25–50%, suggesting that POM121C is necessary for adipogenesis.Conclusions/interpretationGene expression and adipocyte functional studies support the notion that FAM13A and POM121C control adipocyte lipolysis and adipogenesis, respectively, and might thereby be involved in genetic control of systemic insulin sensitivity.

Raspberry Supplementation Improves Insulin Signaling and Promotes Brown-Like Adipocyte Development in White Adipose Tissue of Obese Mice.

Excessive lipid accumulation in white adipose tissue (WAT) leads to chronic inflammation and metabolic dysfunction. Raspberry (RB) contains high amount of polyphenols and dietary fibers. The objective of the study is to evaluate the effects of RB supplementation on WAT morphology, inflammation, and insulin signaling in high fat diet (HFD)-induced obese mice, and further explore the underlying mechanisms. C57BL/6J mice are fed with a control diet or a HFD supplemented with 0 or 5% freeze dried RB for 12 weeks. RB supplementation decreases WAT hypertrophy induced by HFD and suppresses pro-inflammatory cytokines expression and macrophage infiltration in WAT. Meanwhile, RB addition improves insulin sensitivity of HFD-mice. Additionally, RB supplementation drives the browning of WAT (beige adipogenesis), which is associated with elevated PGC-1α and FNDC5/irisin contents. Consistently, the content of beige adipocyte markers including UCP1, PRDM16, Cytochrome C, Cidea, and Elvol3 is enhanced in HFD-mice, which are correlated with increased AMPK phosphorylation and Sirt1 protein contents. Dietary RB attenuated adipocyte hypertrophy and inflammation of WAT in HFD-mice and improves insulin sensitivity and beige adipogenesis, which is associated with increased FNDC5/irisin content and activation of AMPK/Sirt1 pathway. RB supplementation provides a promising strategy to prevent diet-induced obesity.

MicroRNAs-361-5p and miR-574-5p associate with human adipose morphology and regulate EBF1 expression in white adipose tissue.

Reduced adipose expression of the transcription factor Early B cell factor 1 (EBF1) is linked to white adipose tissue (WAT) hypertrophy. We aimed to identify microRNAs (miRNAs) associated with WAT hypertrophy and EBF1 regulation. We mapped WAT miRNA expression from 26 non-obese women discordant in WAT morphology and determined EBF1 activity in the non-obese and 30 obese women. Expression of 15 miRNAs was higher in hypertrophy and 10 were predicted to target EBF1. Binding of miR-365-5p/miR-574-5p were validated with 3'-UTR assay. Overexpression of miR-365-5p or miR-574-5p reduced EBF1 while inhibition of miR-574 increased EBF1 expression in human adipocytes invitro. Additive effects on EBF1 were observed when concomitantly overexpressing both miRNAs. EBF1 targets were affected by over expression/inhibition of either miRNAs. Finally, miR-365-5p/miR-574-5p expression in 56 individuals correlated significantly with EBF1 activity. Our results suggest that miR-365-5p and miR-574-5p may be linked to WAT hypertrophy via effects on EBF1 expression.

Genetic disruption of uncoupling protein 1 in mice renders brown adipose tissue a significant source of FGF21 secretion.

ObjectiveCirculating fibroblast growth factor 21 (FGF21) is an important auto- and endocrine player with beneficial metabolic effects on obesity and diabetes. In humans, thermogenic brown adipose tissue (BAT) was recently suggested as a source of FGF21 secretion during cold exposure. Here, we aim to clarify the role of UCP1 and ambient temperature in the regulation of FGF21 in mice.MethodsWildtype (WT) and UCP1-knockout (UCP1 KO) mice, the latter being devoid of BAT-derived non-shivering thermogenesis, were exposed to different housing temperatures. Plasma metabolites and FGF21 levels were determined, gene expression was analyzed by qPCR, and tissue histology was performed with adipose tissue.ResultsAt thermoneutrality, FGF21 gene expression and serum levels were not different between WT and UCP1 KO mice. Cold exposure led to highly increased FGF21 serum levels in UCP1 KO mice, which were reflected in increased FGF21 gene expression in adipose tissues but not in liver and skeletal muscle. Ex vivo secretion assays revealed FGF21 release only from BAT, progressively increasing with decreasing ambient temperatures. In association with increased FGF21 serum levels in the UCP1 KO mouse, typical FGF21-related serum metabolites and inguinal white adipose tissue morphology and thermogenic gene expression were altered.ConclusionsHere we show that the genetic ablation of UCP1 increases FGF21 gene expression in adipose tissue. The removal of adaptive nonshivering thermogenesis renders BAT a significant source of endogenous FGF21 under thermal stress. Thus, the thermogenic competence of BAT is not a requirement for FGF21 secretion. Notably, high endogenous FGF21 levels in UCP1-deficient models and subjects may confound pharmacological FGF21 treatments.