White Adipose Tissue Expansion Research Articles

Deletion of Impdh2 in adipocyte precursors limits the expansion of white adipose tissue and enhances metabolic health with overnutrition

The equilibrium between the hypertrophic growth of existing adipocytes and adipogenesis is vital in managing metabolic stability in white adipocytes when faced with overnutrition. Adipogenesis has been established as a key player in combating metabolic irregularities caused by various factors. However, the benefits of increasing adipogenesis-mediated white adipose tissue (WAT) expansion for metabolic health regulation remain uncertain. Our findings reveal an increase in Impdh2 expression during the adipogenesis phase, both in vivo and in vitro. Xmp enhances adipogenic potential by fostering mitotic clonal expansion (MCE). The conditional knockout of Impdh2 in adipocyte progenitor cells(APCs) in adult and aged mice effectively curbs white adipose tissue expansion, ameliorates glucose tolerance, and augments energy expenditure under high-fat diet (HFD). However, no significant difference is observed under normal chow diet (NCD). Concurrently, the knockout of Impdh2 in APCs significantly reduces the count of new adipocytes induced by HFD, without affecting adipocyte size. Mechanistically, Impdh2 regulates the proliferation of APCs during the MCE phase via Xmp. Exogenous Xmp can significantly offset the reduction in adipogenic abilities of APCs due to Impdh2 deficiency. In summary, we discovered that adipogenesis-mediated WAT expansion, induced by overnutrition, also contributes to metabolic abnormalities. Moreover, the pivotal role of Impdh2 in regulating adipogenesis in APCs offers a novel therapeutic approach to combat obesity.

PDGFRβ + cell HIF2α is dispensable for white adipose tissue metabolic remodeling and hepatic lipid accumulation in obese mice

BackgroundObesity is associated with extensive white adipose tissue (WAT) expansion and remodeling. Healthy WAT expansion contributes to the maintenance of energy balance in the liver, thereby ameliorating obesity-related hepatic steatosis. Tissue-resident mesenchymal stromal cell populations, including PDGFRβ + perivascular cells, are increasingly recognized pivotal as determinants of the manner in which WAT expands. However, the full array of regulatory factors controlling WAT stromal cell functions remains to be fully elucidated. Hypoxia-inducible factors (HIFs) are critical regulators in WAT stromal cell populations such as adipocyte precursor cells (APCs). It is revealed that HIF1α activation within PDGFRβ + stromal cells results in the suppression of de novo adipogenesis and the promotion of a pro-fibrogenic cellular program in obese animals. However, the role of HIF2α in PDGFRβ + cells remains undetermined in vivo.MethodsNew genetic models were employed in which HIF1α (encoded by the Hif1a gene) and HIF2α (encoded by the Epas1 gene) are selectively inactivated in PDGFRβ + cells in an inducible manner using tamoxifen (TAM). With these models, both in vitro and in vivo functional analysis of PDGFRβ + cells lacking HIF proteins were performed. Additionally, comprehensive metabolic phenotyping in diet-induced mouse models were performed to investigate the roles of PDGFRβ + cell HIF proteins in WAT remodeling, liver energy balance and systemic metabolism.ResultsUnlike HIF1α inactivation, the new findings in this study suggest that inducible ablation of HIF2α in PDGFRβ + cells does not cause apparent effects on WAT expansion induced by obesogenic diet. The adipogenic ability of PDGFRβ + APCs is not significantly altered by genetic HIF2α ablation. Moreover, no difference of key parameters associated with healthy WAT remodeling such as improvements of WAT insulin sensitivity, reduction in metabolic inflammation, as well as changes in liver fat accumulation or systemic glucose metabolism, is detected in PDGFRβ + cell Epas1-deficient mice.ConclusionThe new findings in this study support that, in contrast to HIF1α, PDGFRβ + cell HIF2α appears dispensable for WAT metabolic remodeling and the resulting effects on liver metabolic homeostasis in diet-induced obesity, underscoring the isoform-specific roles of HIFα proteins in the regulation of adipose tissue biology.

Design, synthesis, 2D-QSAR, molecular dynamic simulation, and biological evaluation of topiramate–phenolic acid conjugates as PPARγ inhibitors

Abstract Background Obesity is a precursor for many co-morbid diseases. One of the main triggering factors for obesity is the abnormal expansion of white adipose tissue characterized by high rates of genesis and differentiation of precursor cells into mature adipocytes. As a result, targeting adipogenesis and adipogenic transcription factors opens new roadmaps for developing novel antiobesity pharmacotherapies. The present study was intended to rationally develop topiramate–phenolic acid conjugate for targeting obesity via inhibition of PPARγ which is often considered as the master regulator of adipogenesis. Results 2D QSAR models were built to foretell PPARγ inhibitory activity of designed conjugates. The models presented excellent robustness, goodness of fit, and predictive capability compounds. The highest PPARγ inhibitory activity was predicted for T3 (topiramate–caffeic acid conjugate) with a pIC50 value of 7.08 µM. Molecular docking was performed for all the designed conjugates against PPARγ (PDB ID: 3VSO). The highest binding affinity was exhibited by T3 (− 11.27 kcal/mol) and displayed strong and stable interactions with the receptor within the allosteric pocket in comparison to the irreversible PPARγ antagonist, GW9662 (binding affinity, − 9.0 kcal/mol). These results were confirmed by subjecting the best-docked molecules to molecular dynamic simulations. The PPARγ–T3 complex was observed to be most stable with maximum number of hydrogen bonds (maximum observed RMSD = 0.57 Å at 100 ns) in comparison to PPARγ–topiramate and PPARγ–caffeic acid complexes. Consequently, T3 was synthesized and further subjected to in vitro screening. The TR-FRET assay established T3 as a PPARγ antagonist (IC50 = 6.78 µM). T3 also significantly reduced the lipid buildup in the 3T3-L1 adipocytes in a dose-dependent manner. In addition, T3 also reduced the protein expression levels of PPARγ as evidenced from western blot results. Conclusions Studies clearly indicated that T3 reduces adipose tissue cell differentiation by downstreaming PPARγ expression at protein levels, thereby emerging as a novel scaffold for antiobesity pharmacotherapy. Graphical abstract

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.

Effects of Citrus depressa Hayata juice on high-fat diet-induced obesity in HBV transgenic mice

The present study investigated the potential anti-obesity properties of Citrus depressa Hayata (CDH) juice in HBV transgenic mice, as well as the impact of fermentation on the effectiveness of the juice. The results revealed that fermentation increased the levels of polyphenols and hesperidin in CDH juice. The animal study demonstrated that both juices were effective in mitigating the weight gain induced by a high-fat diet by correcting metabolic parameter imbalances, reducing hepatic lipid accumulation, and reversing hepatic immune suppression. Furthermore, fermented juice exhibited superior efficacy in managing body weight and inhibiting the expansion of white adipose tissue (WAT). Fermented juice significantly enhanced adiponectin production and PPARγ expression in WAT, while also reducing hypertrophy. This study offers valuable insights into the potential role of CDH juices in combating obesity associated with high fat consumption and underscores the promise of CDH juice as a functional beverage.

Kuanoniamine C Suppresses Adipogenesis and White Adipose Tissue Expansion by Modulating Mitochondrial Function.

Obesity is characterized by the excessive accumulation of fat to adipose tissue, which is related to abnormal increasing white adipose tissue (WAT) in the body, and it upregulates the risk of multiple diseases. Here, kuanoniamine C, which is a pyridoacridine alkaloid, suppressed the differentiation of pre-adipose cells into white adipocytes via the modulation of mitochondrial function, and inhibited WAT expansion in the early phase of high-fat-diet-induced obesity model. Pharmacological analysis revealed that inhibition of mitochondrial respiratory complex II, which new target of kuanoniamine C, activated reactive oxygen species (ROS)-extracellular signal-regulated kinase (ERK)-β-catenin signaling, and this signaling was antagonized by insulin-, IBMX-, and dexamethasone-induced adipogenesis. Therefore, the kuanoniamine C might prevent abnormal WAT expansion even when eating a diet that is not calorie restricted.

The Optimal Dose of the Green Tea and Coffee Extracts to Suppress the Expression of PPAR-γ and C/EBP-α on Differentiated 3T3-L1 Adipocytes

Obesity is the excess fat content in the body caused by the expansion of white adipose tissue. This condition begins with the differentiation of adipose tissue that is known to be controlled by 2 main transcription factors, such as Peroxisome Proliferator-Activated Receptor-γ (PPAR-γ) and CCAAT Enhancer-Binding Protein-α (C/EBP-α). Their activation and collaboration are critical for developing functioning adipocytes and preserving metabolic balance in adipose tissue. Research on the benefits of natural bioactive components that regulate adipogenesis has recently become an exciting focus. Foodstuffs reported to affect this condition positively include green coffee and green tea. The primary substance in green coffee is chlorogenic acid (CGA), meanwhile in green tea is epigallocatechin gallate (EGCG). Based on medical benefit potential, the present study evaluated the dose that produced the best effect on PPAR-γ and C/EBP-α expression between single and combined doses compared to undifferentiated adipocytes (3T3-L1). 3T3-L1 were cultured and divided into negative (NEG) and positive (DIF) groups. The DIF group is obtained by induction of differentiation, then divided into seventeen therapeutic doses. At the end of therapy, cells were fixed to measure the expression of PPAR-γ and C/EBP-α using the immunocytochemistry method. The DIF group produced the highest expression of PPAR-γ and C/EBP-α. Among the single-dose group, the lowest PPAR-γ was found in C320 and C/EBP-α in the T320 group. Meanwhile, the dose with the lowest PPAR-γ and C/EBP-α expression was found in the combination of green tea and coffee (TC) 160/80 (p-value = 0.00). The findings of this study showed that a combination of green tea and coffee extracts at doses of 160/80 has the potential for anti-obesity by suppressing the differentiation of 3T3-L1 into adipocytes by reducing the expression of PPAR-γ and C/EBP-α. HIGHLIGHTS Obesity is the excess fat content in the body caused by the expansion of white adipose tissue. This condition begins with the differentiation of adipose tissue that is known to be controlled by Peroxisome Proliferator-Activated Receptor-γ (PPAR-γ) and CCAAT Enhancer-Binding Protein-α (C/EBP-α) Natural bioactive components that regulate adipogenesis in green coffee are chlorogenic acid (CGA) and epigallocatechin gallate found in green tea (EGCG). Based on this potential, the present study evaluated the dose that produced the best effect on PPARɣ and C/EBP-α protein expression between single and combined doses compared to undifferentiated adipocytes (3T3-L1) Based on this study, the differentiated group of adipocytes (DIF) produced the highest expression of PPAR-γ and C/EBP-α. Among the single dose group, which showed the lowest average value of PPARɣ was C320, and for C/EBP-α was the T320 group. Meanwhile, the dose with the lowest PPAR-γ and C/EBP-α expression came from the combination of green tea and coffee (TC) 160/80 (p-value = 0.00) So, this research shows that green tea and green coffee extract significantly affected the expression of PPAR-γ and C/EBP-α. Green tea and coffee extracts at doses of TC 160/80 have the potential for anti-obesity by suppressing the differentiation of 3T3-L1 into adipocytes by reducing the expression of PPAR-γ and C/EBP-α GRAPHICAL ABSTRACT

GADD45A regulates subcutaneous fat deposition and lipid metabolism by interacting with Stat1

BackgroundObesity, characterized by excessive white adipose tissue expansion, is associated with several metabolic complications. Identifying new adipogenesis regulators may lead to effective therapies for obesity-induced metabolic disorders.ResultsHere, we identified the growth arrest and DNA damage-inducible A (GADD45A), a stress-inducible histone-folding protein, as a novel regulator of subcutaneous adipose metabolism. We found that GADD45A expression was positively correlated with subcutaneous fat deposition and obesity in humans and fatty animals. In vitro, the gain or loss function of GADD45A promoted or inhibited subcutaneous adipogenic differentiation and lipid accumulation, respectively. Using a Gadd45a-/- mouse model, we showed that compared to wild-type (WT) mice, knockout (KO) mice exhibited subcutaneous fat browning and resistance to high-fat diet (HFD)-induced obesity. GADD45A deletion also upregulated the expression of mitochondria-related genes. Importantly, we further revealed that the interaction of GADD45A with Stat1 prevented phosphorylation of Stat1, resulting in the impaired expression of Lkb1, thereby regulating subcutaneous adipogenesis and lipid metabolism.ConclusionsOverall, our results reveal the critical regulatory roles of GADD45A in subcutaneous fat deposition and lipid metabolism. We demonstrate that GADD45A deficiency induces the inguinal white adipose tissue (iWAT) browning and protects mice against HFD-induced obesity. Our findings provide new potential targets for combating obesity-related metabolic diseases and improving human health.

Adipose METTL14-Elicited N6 -Methyladenosine Promotes Obesity, Insulin Resistance, and NAFLD Through Suppressing β Adrenergic Signaling and Lipolysis.

White adipose tissue (WAT) lipolysis releases free fatty acids as a key energy substance to support metabolism in fasting, cold exposure, and exercise. Atgl, in concert with Cgi-58, catalyzes the first lipolytic reaction. The sympathetic nervous system (SNS) stimulates lipolysis via neurotransmitter norepinephrine that activates adipocyte β adrenergic receptors (Adrb1-3). In obesity, adipose Adrb signaling and lipolysis are impaired, contributing to pathogenic WAT expansion; however, the underling mechanism remains poorly understood. Recent studies highlight importance of N6 -methyladenosine (m6A)-based RNA modification in health and disease. METTL14 heterodimerizes with METTL3 to form an RNA methyltransferase complex that installs m6A in transcripts. Here, this work shows that adipose Mettl3 and Mettl14 are influenced by fasting, refeeding, and insulin, and are upregulated in high fat diet (HFD) induced obesity. Adipose Adrb2, Adrb3, Atgl, and Cgi-58 transcript m6A contents are elevated in obesity. Mettl14 ablation decreases these transcripts' m6A contents and increases their translations and protein levels in adipocytes, thereby increasing Adrb signaling and lipolysis. Mice with adipocyte-specific deletion of Mettl14 are resistant to HFD-induced obesity, insulin resistance, glucose intolerance, and nonalcoholic fatty liver disease (NAFLD). These results unravel a METTL14/m6A/translation pathway governing Adrb signaling and lipolysis. METTL14/m6A-based epitranscriptomic reprogramming impairs adipose Adrb signaling and lipolysis, promoting obesity, NAFLD, and metabolic disease.

Leptin: A Heavyweight Player in Obesity-Related Cancers.

Obesity, defined as the abnormal or excessive expansion of white adipose tissue, has reached pandemic proportions and is recognized as an important health concern since it is a common root for several comorbidities, including malignancies. Indeed, the current knowledge of the white adipose tissue, which shifts its role from an energy storage tissue to an important endocrine and metabolic organ, has opened up new avenues for the discovery of obesity's effects on tumor biology. In this review, we will report the epidemiological studies concerning the strong impact of obesity in several types of cancer and describe the mechanisms underlying the heterotypic signals between cancer cell lines and adipocytes, with particular emphasis on inflammation, the insulin/IGF-1 axis, and adipokines. Among the adipokines, we will further describe the in vitro, in vivo, and clinical data concerning the role of leptin, recognized as one of the most important mediators of obesity-associated cancers. In fact, leptin physiologically regulates energy metabolism, appetite, and reproduction, and several studies have also described the role of leptin in affecting cancer development and progression. Finally, we will summarize the newest pharmacological strategies aimed at mitigating the protumorigenic effects of leptin, underlining their mechanisms of action.

309-OR: Adipose RNA N6-Methyladenosine (m6A) Modification Promotes Obesity and Insulin Resistance through Suppressing Lipolysis

Excessive white adipose tissue (WAT) promotes insulin resistance and nonalcoholic fatty liver disease (NAFLD) in obesity; however, the WAT expansion mechanism remains poorly understood. We reported that WAT lipolysis is suppressed in obesity, likely contributing to WAT growth. Adipose triglyceride lipase (Atgl) catalyzes the lipolysis reaction, and its lipolytic activity is increased by phosphorylation and binding to cofactor Cgi58. The sympathetic nervous system activates adipocyte β adrenergic receptor (Adrb)/cAMP/PKA pathway to stimulate lipolysis via Atgl and Cgi58. In this study, we have identified a novel m6A modification of Adrb, Atgl, and Cgi58 transcripts that promotes obesity and metabolic disorders. We found that obesity was associated with increased expression of adipose Mettl3 and Mettl14 and elevated m6A levels in WAT. Mettl14 directly binds to Mettl3 to form a methyltransferase complex that catalyzes m6A on RNA. Insulin also increased Mettl14 expression and m6A levels in adipocytes. We generated adipocyte-specific Mettl14 knockout mice (Mettl14 Δfat) and placed mice on a high fat diet (HFD). Remarkably, Mettl14 Δfat mice, both males and females, were resistant to HFD-induced obesity, insulin resistance, and NAFLD. Adipose Adrb2/3, Atgl, and Cgi58 protein levels were significantly upregulated in Mettl14 Δfat mice and consequently, adipose β adrenergic signaling and lipolysis were significantly higher in Mettl14 Δfat than in Mettl14f/f mice. Mettl14 deficiency dramatically decreased the m6A content of Adrb2/3, Atgl, and Cgi58 transcripts in WAT; strikingly, m6A inhibition markedly increased translational rates of these transcripts in adipocytes. Collectively, these results unravel a previously unrecognized adipose Mettl14/m6A/translation axis that promotes obesity, insulin resistance, and NAFLD by suppressing adipose β adrenergic signaling, lipolysis, and fatty acid oxidation. Disclosure Q.Kang: None. L.Rui: None. D.Ren: None. Funding National Institutes of Health (R01DK130111)

Fat and the brain: its connection and implication in AD pathogenesis

AbstractBackgroundAlzheimer’s disease (AD) is a complex disorder and multiple cellular and molecular mechanisms are involved in AD onset and progression. Recent evidences has suggested that metabolic alterations are an important pathological feature in disease progression in AD. Likewise, diabetes and obesity, two mayor metabolic illnesses, are risk factors for AD. These two overwhelming diseases are associated with a significant expansion of white adipose tissue. Here, we hypothesize that the white adipose tissue may serve as a key communicator organ between the brain and peripheral metabolic illnesses and affecting both types of disorders.MethodWe used histological stains, immunohistochemistry and biochemical means to determine changes in the white adipose tissue from WT and db/db mice. Moreover, similar techniques were used in the brain of 3xTg‐AD mice that received white fat pads from WT and db/db donors to determine any changes in amyloid and tau pathology.ResultOur study shows that recipient 3xTg‐AD mice from db/db fat pads mice develop profound changes in tau pathology due to increased CDK5 expression compared to 3xTg‐AD mice that received fad pads from WT mice. This increment in tau level was associated with elevated levels in IL‐1β and profound microglia activation. Moreover, we found the opposite effect on amyloid pathology, in which insoluble Aβ levels and Thioflavin positive plaques were reduced in recipient 3xTg‐AD mice from db/db fat pads compared to 3xTg‐AD mice that received fad pads from WT mice. These reduction in Aβ levels were correlated with an increment in microglia phagocytic capacity.ConclusionOverall, our study demonstrate a novel important crosstalk between Alzheimer´s disease and diabetes type II through white adipose cells and a differential effect on tau and Aβ pathology mediated by an activated immune response.

Obesity and prostate cancer - microenvironmental roles of adipose tissue.

Obesity is known to have important roles in driving prostate cancer aggressiveness and increased mortality. Multiple mechanisms have been postulated for these clinical observations, including effects of diet and lifestyle, systemic changes in energy balance and hormonal regulation and activation of signalling by growth factors and cytokines and other components of the immune system. Over the past decade, research on obesity has shifted towards investigating the role of peri-prostatic white adipose tissue as an important source of locally produced factors that stimulate prostate cancer progression. Cells that comprise white adipose tissue, the adipocytes and their progenitor adipose stromal cells (ASCs), which proliferate to accommodate white adipose tissue expansion in obesity, have been identified as important drivers of obesity-associated cancer progression. Accumulating evidence suggests that adipocytes are a source of lipids that are used by adjacent prostate cancer cells. However, results of preclinical studies indicate that ASCs promote tumour growth by remodelling extracellular matrix and supporting neovascularization, contributing to the recruitment of immunosuppressive cells, and inducing epithelial-mesenchymal transition through paracrine signalling. Because epithelial-mesenchymal transition is associated with cancer chemotherapy resistance and metastasis, ASCs are considered to be potential targets of therapies that could be developed to suppress cancer aggressiveness in patients with obesity.

Adipose tissue expansion in obesity, health, and disease.

White adipose tissue (WAT) expands under physiological conditions via an increase in adipocyte size (hypertrophy) and/or number (hyperplasia; adipogenesis), and the ability of WAT to expand to accommodate energy demands is a significant determinant of metabolic health status. Obesity is associated with impaired WAT expansion and remodeling, which results in the deposition of lipids to other non-adipose organs, leading to metabolic derangements. Although increased hyperplasia has been implicated as a cornerstone in promoting healthy WAT expansion, recent developments suggest that the role of adipogenesis as a contributing factor in the transition from impaired subcutaneous WAT expansion to impaired metabolic health remains up for debate. This mini-review will summarize recent developments and highlight emerging concepts on the features of WAT expansion and turnover, and the significance in obesity, health, and disease.

SENP2 knockdown in human adipocytes reduces glucose metabolism and lipid accumulation, while increases lipid oxidation

Adipose tissue is one of the main regulative sites for energy metabolism. Excess lipid storage and expansion of white adipose tissue (WAT) is the primary contributor to obesity, a strong predisposing factor for development of insulin resistance. Sentrin-specific protease (SENP) 2 has been shown to play a role in metabolism in murine fat and skeletal muscle cells, and we have previously demonstrated its role in energy metabolism of human skeletal muscle cells. In the present work, we have investigated the impact of SENP2 on fatty acid and glucose metabolism in primary human fat cells by using cultured primary human adipocytes to knock down the SENP2 gene. Glucose uptake and oxidation, as well as accumulation and distribution of oleic acid into complex lipids were decreased, while oleic acid oxidation was increased in SENP2-knockdown cells compared to control adipocytes. Furthermore, lipogenesis was reduced by SENP2-knockdown in adipocytes. Although TAG accumulation relative to total uptake was unchanged, there was increased mRNA expression of metabolically relevant genes such as UCP1 and PPARGC1A and mRNA and proteomic data revealed increased levels of mRNA and proteins related to mitochondrial function by SENP2-knockdown. In conclusion, SENP2 is an important regulator of energy metabolism in primary human adipocytes and its knockdown reduce glucose metabolism and lipid accumulation, while increasing lipid oxidation in human adipocytes.

GPS2-mediated regulation of the adipocyte secretome modulates adipose tissue remodeling at the onset of diet-induced obesity

ObjectiveDysfunctional, unhealthy expansion of white adipose tissue due to excess dietary intake is a process at the root of obesity and Type 2 Diabetes development. The objective of this study is to contribute to a better understanding of the underlying mechanism(s) regulating the early stages of adipose tissue expansion and adaptation to dietary stress due to an acute, high-fat diet (HFD) challenge, with a focus on the communication between adipocytes and other stromal cells. MethodsWe profiled the early response to high-fat diet exposure in wildtype and adipocyte-specific GPS2-KO (GPS2-AKO) mice at the cellular, tissue and organismal level. A multi-pronged approach was employed to disentangle the complex cellular interactions dictating tissue remodeling, via single-cell RNA sequencing and FACS profiling of the stromal fraction, and semi-quantitative proteomics of the adipocyte-derived exosomal cargo after 5 weeks of HFD feeding. ResultsOur results indicate that loss of GPS2 in mature adipocytes leads to impaired adaptation to the metabolic stress imposed by HFD feeding. GPS2-AKO mice are significantly more inflamed, insulin resistant, and obese, compared to the WT counterparts. At the cellular level, lack of GPS2 in adipocytes impacts upon other stromal populations, with both the eWAT and scWAT depots exhibiting changes in the immune and non-immune compartments that contribute to an increase in inflammatory and anti-adipogenic cell types. Our studies also revealed that adipocyte to stromal cell communication is facilitated by exosomes, and that transcriptional rewiring of the exosomal cargo is crucial for tissue remodeling. Loss of GPS2 results in increased expression of secreted factors promoting a TGFβ-driven fibrotic microenvironment favoring unhealthy tissue remodeling and expansion. ConclusionsAdipocytes serve as an intercellular signaling hub, communicating with the stromal compartment via paracrine signaling. Our study highlights the importance of proper regulation of the ‘secretome’ released by energetically stressed adipocytes at the onset of obesity. Altered transcriptional regulation of factors secreted via adipocyte-derived exosomes (AdExos), in the absence of GPS2, contributes to the establishment of an anti-adipogenic, pro-fibrotic adipose tissue environment, and to hastened progression towards a metabolically dysfunctional phenotype.

Infection-elicited microbiota promotes host adaptation to nutrient restriction

The microbiota performs multiple functions vital to host fitness, including defense against pathogens and adaptation to dietary changes. Yet, how environmental challenges shape microbiota resilience to nutrient fluctuation remains largely unexplored. Here, we show that transient gut infection can optimize host metabolism toward the usage of carbohydrates. Following acute infection and clearance of the pathogen, mice gained more weight as a result of white adipose tissue expansion. Concomitantly, previously infected mice exhibited enhanced carbohydrate (glucose) disposal and insulin sensitivity. This metabolic remodeling depended on alterations to the gut microbiota, with infection-elicited Betaproteobacteria being sufficient to enhance host carbohydrate metabolism. Further, infection-induced metabolic alteration protected mice against stunting in the context of limited nutrient availability. Together, these results propose that alterations to the microbiota imposed by acute infection may enhance host fitness and survival in the face of nutrient restriction, a phenomenon that may be adaptive in settings where both infection burden and food precarity are prevalent.

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.

OPA1 Regulates Lipid Metabolism and Cold-Induced Browning of White Adipose Tissue in Mice.

Mitochondria play a vital role in white adipose tissue (WAT) homeostasis including adipogenesis, fatty acid synthesis, and lipolysis. We recently reported that the mitochondrial fusion protein optic atrophy 1 (OPA1) is required for induction of fatty acid oxidation and thermogenic activation in brown adipocytes. In the current study we investigated the role of OPA1 in WAT function in vivo. We generated mice with constitutive or inducible knockout of OPA1 selectively in adipocytes. Studies were conducted under baseline conditions, at thermoneutrality, following high-fat feeding or during cold exposure. OPA1 deficiency reduced mitochondrial respiratory capacity in white adipocytes, impaired lipolytic signaling, repressed expression of de novo lipogenesis and triglyceride synthesis pathways, and promoted adipose tissue senescence and inflammation. Reduced WAT mass was associated with hepatic triglycerides accumulation and glucose intolerance. Moreover, mice deficient for OPA1 in adipocytes had impaired adaptive thermogenesis and reduced cold-induced browning of subcutaneous WAT and were completely resistant to diet-induced obesity. In conclusion, OPA1 expression and function in adipocytes are essential for adipose tissue expansion, lipid biosynthesis, and fatty acid mobilization of WAT and brown adipocytes and for thermogenic activation of brown and beige adipocytes.

Brown to White Fat Transition Overlap With Skeletal Muscle During Development of Larger Mammals: Is it a Coincidence?

In mammals, adipose tissues and skeletal muscles (SkMs) play a major role in the regulation of energy homeostasis. Recent studies point to a possibility of dynamic interplay between these 2 sites during development that has pathophysiological implications. Among adipose depots, brown adipose tissue (BAT) is the major energy-utilizing organ with several metabolic features that resemble SkM. Both organs are highly vascularized, innervated, and rich in mitochondria and participate in defining the whole-body metabolic rate. Interestingly, in large mammals BAT depots undergo a striking reduction and concomitant expansion of white adipose tissue (WAT) during postnatal development that shares temporal and molecular overlap with SkM maturation. The correlation between BAT to WAT transition and muscle development is not quite apparent in rodents, the predominantly used animal model. Therefore, the major aim of this article is to highlight this process in mammals with larger body size. The developmental interplay between muscle and BAT is closely intertwined with sexual dimorphism that is greatly influenced by hormones. Recent studies have pointed out that sympathetic inputs also determine the relative recruitment of either of the sites; however, the role of gender in this process has not been studied. Intriguingly, higher BAT content during early postnatal and pubertal periods positively correlates with attainment of better musculature, a key determinant of good health. Further insight into this topic will help in detailing the developmental overlap between the 2 seemingly unrelated tissues (BAT and SkM) and design strategies to target these sites to counter metabolic syndromes.