CTNNB1/β-catenin dysfunction contributes to adiposity by regulating the cross-talk of mature adipocytes and preadipocytes

Recent insights on the impact of SWELL1 on metabolic syndromes

SWELL1 is a key component of the volume-regulated anion channel (VRAC) and participates in cell volume regulation as an ion channel plasma membrane protein. While early studies focused on its role in immune cell development and tumor progression, recent studies have revealed that SWELL1 plays an important role in metabolic diseases. Studies have shown that SWELL1 is extensively involved in physiological processes in peripheral metabolic tissues, including adipocyte hypertrophy, skeletal muscle volume regulation, insulin secretion, and hepatic lipid metabolism through interactions with the insulin signaling pathway. These functions play key roles in the pathogenesis of obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic fatty liver disease (NAFLD), suggesting that SWELL1 may be a new target for the treatment of metabolic diseases. In this review, we focus on the structural and functional characteristics of SWELL1 to provide an in-depth explanation of its role in the development of metabolic syndrome, especially the regulation of the insulin signaling pathway, and provide a basis for the development of therapeutic strategies for metabolic diseases targeting SWELL1.

LGR4 is a key regulator of hepatic gluconeogenesis

AIMS/HYPOTHESIS

Emerging evidence underscored the significance of leucine-rich repeat-containing G protein-coupled receptor (LGR) 4 in endocrine and metabolic disorders. Despite this, its role in LGR4 in hepatic glucose metabolism remains poorly understood. In this study we set out to test whether LGR4 regulates glucose production in liver through a specific signaling pathway.

METHODS

Hepatic glucose production and gluconeogenic gene expressions were detected after silence of LGR4 in three obese mice models. Then, whole-body LGR4-deficient (LGR4 KO) mice, liver-specific LGR4 knockout (LGR4LKO) mice, and liver-specific LGR4 overexpression (LGR4LOV) mice were generated, in which we analyzed the effects of LGR4 on hepatic glucose metabolism upon HFD feeding, among which live imaging and quantitative analysis of hepatic phosphoenolpyruvate carboxykinase (PEPCK)-luciferase activity were conducted.

RESULTS

LGR4 expression was significantly upregulated in the liver of three obese mouse models, and presented dynamic expression patterns in response to nutritional fluxes. We utilized global and liver-specific LGR4 knockouts (LGR4LKO), along with adenoviral-mediated LGR4 knockdown in mice, to show improved glucose tolerance and decreased hepatic gluconeogenesis. Specifically, the expression of rate-limiting gluconeogenic enzymes, PEPCK was significantly downregulated. Conversely, mouse model with adenovirus-mediated LGR4 overexpression (LGR4LOV) exhibited elevated gluconeogenesis and PEPCK expression and reversed the suppression observed in LGR4 knockout models. Notably, neither RANKL nor PKA signaling pathways, which were reported to take part in LGR4's function, were involved in the process of LGR4 regulating PEPCK. Instead, TopFlash reporter system and inhibitors application suggested that LGR4's influence on hepatic gluconeogenesis operates through the canonical Wnt/β-catenin/TCF7L2 signaling pathway.

CONCLUSIONS/INTERPRETATION

Overall, these findings underscore a novel mechanism by which LGR4 regulates hepatic gluconeogenesis, presenting a potential therapeutic target for diabetes management.

Corporate genome screening India (CoGsI) identified genetic variants association with T2D in young Indian professionals

Rising cases of type 2 diabetes (T2D) in India, especially in metropolitan cities is an increasing concern. The individuals that were most affected are young professionals working in the corporate sector. However, the corporate sector has remained the least explored for T2D risk predisposition. Considering corporate employees' lifestyles and the role of gene-environment interaction in T2D susceptibility, the study aims to find genetic variants associated with T2D predisposition. In this first kind of study, 680 young professionals (284 T2D cases, and 396 controls) were diagnosed and screened for 2658 variants on an array designed explicitly for the CoGsI study. The variant filtering was done at Bonferroni p-value of 0.000028. The genetic data was analysed using PLINK v1.09, SPSS, R programming, VEP tool, and FUMA GWAS tool. Interestingly, 42 variants were associated with the T2D risk. Out of 42, three missense variants (rs1402467, rs6050, and rs713598) in Sulfotransferase family 1 C member 4 (SULT1C4), Fibrinogen Alpha Chain (FGA), and Taste 2 Receptor Member 38 (TAS2R38) and two untranslated region (UTR) variants (rs1063320 and rs6296) in Major Histocompatibility Complex, Class I, G (HLA-G) and 5-Hydroxytryptamine Receptor 1B (HTR1B) were associated with the T2D risk. CoGsI identified potential genomic markers increasing susceptibility to the early onset of T2D. Present findings provide insights into mechanisms underlying T2D manifestation in corporate professionals due to genetics interacting with occupational stress and urban lifestyles.

Key questions and gaps in understanding adipose tissue macrophages and early-life metabolic programming

The global obesity epidemic, with its associated comorbidities and increased risk of early mortality, underscores the urgent need for enhancing our understanding of the origins of this complex disease. It is increasingly clear that metabolism is programmed early in life and that metabolic programming can have life-long health consequences. As a critical metabolic organ sensitive to early-life stimuli, proper development of adipose tissue (AT) is crucial for life-long energy homeostasis. Early-life nutrients, especially fatty acids (FAs), significantly influence the programming of AT and shape its function and metabolism. Of growing interest are the dynamic responses during pre- and postnatal development to proinflammatory omega-6 (n6) and anti-inflammatory omega-3 (n3) FA exposures in AT. In the US maternal diet, the ratio of "pro-inflammatory" n6- to "anti-inflammatory" n3-FAs has grown dramatically due to the greater prevalence of n6-FAs. Notably, AT macrophages (ATMs) form a significant population within adipose stromal cells, playing not only an instrumental role in AT formation and maintenance but also acting as key mediators of cell-to-cell lipid and cytokine signaling. Despite rapid advances in ATM and immunometabolism fields, research has focused on responses to obesogenic diets and during adulthood. Consequently, there is a significant gap in identifying the mechanisms contributing metabolic health, especially regarding lipid exposures during the establishment of ATM physiology. Our review highlights the current understanding of ATM diversity, their critical role in AT, their potential role in early-life metabolic programming, and the broader implications for metabolism and health.

NR2F2 Reactivation in Early-life Adipocyte Stem-like Cells Rescues Adipocyte Mitochondrial Oxidation

In humans, perinatal exposure to an elevated omega-6 (n6) relative to omega-3 (n3) Fatty Acid (FA) ratio is associated with the likelihood of childhood obesity. In mice, we show perinatal exposure to excessive n6-FA programs neonatal Adipocyte Stem-like cells (ASCs) to differentiate into adipocytes with lower mitochondrial nutrient oxidation and a propensity for nutrient storage. Omega-6 FA exposure reduced fatty acid oxidation (FAO) capacity, coinciding with impaired induction of beige adipocyte regulatory factors PPARγ, PGC1α, PRDM16, and UCP1. ASCs from n6-FA exposed pups formed adipocytes with increased lipogenic genes in vitro, consistent with an in vivo accelerated adipocyte hypertrophy, greater triacylglyceride accumulation, and increased % body fat. Conversely, n6-FA exposed pups had impaired whole animal 13C-palmitate oxidation. The metabolic nuclear receptor, NR2F2, was suppressed in ASCs by excess n6-FA intake preceding adipogenesis. ASC deletion of NR2F2, prior to adipogenesis, mimicked the reduced FAO capacity observed in ASCs from n6-FA exposed pups, suggesting that NR2F2 is required in ASCs for robust beige regulator expression and downstream nutrient oxidation in adipocytes. Transiently re-activating NR2F2 with ligand prior to differentiation in ASCs from n6-FA exposed pups, restored their FAO capacity as adipocytes by increasing the PPARγ-PGC1α axis, mitochondrial FA transporter CPT1A, ATP5 family synthases, and NDUF family Complex I proteins. Our findings suggest that excessive n6-FA exposure early in life dampens an NR2F2-mediated induction of beige adipocyte regulators, resulting in metabolic programming that is shifted towards nutrient storage.

Bioactive Peptides from Meretrix lusoria Enzymatic Hydrolysate as a Potential Treatment for Obesity in db/db Mice

Obesity is acknowledged as a significant risk factor for cardiovascular disease, often accompanied by increased inflammation and diabetes. Bioactive peptides derived from marine animal proteins show promise as safe and effective anti-obesity agents by regulating adipocyte differentiation through the AMPK signaling pathway. Therefore, this study aims to investigate the anti-obesity and anti-diabetic effects of bioactive compounds derived from a Meretrix lusoria Protamex enzymatic hydrolysate (MLP) fraction (≤1 kDa) through a 6-week treatment (150 mg/kg or 300 mg/kg, administered once daily) in leptin receptor-deficient db/db mice. The MLP treatment significantly decreased the body weight, serum total cholesterol, triglycerides, and LDL-cholesterol levels while also exhibiting a beneficial effect on hepatic and serum marker parameters in db/db mice. A histological analysis revealed a reduction in hepatic steatosis and epididymal fat following MLP treatment. Furthermore, poor glucose tolerance was improved, and hepatic antioxidant enzyme activities were elevated in MLP-treated mice compared to db/db control mice. Western blot analysis showed an increased expression of the AMPK protein after MLP treatment. In addition, the expression of lipogenic genes decreased in db/db mice. These findings indicate that bioactive peptides, which are known to regulate blood glucose levels, lipid metabolism, and adipogenesis, could be beneficial functional food additives and pharmaceuticals.

Impaired Remodeling of White Adipose Tissue in Obesity and Aging: From Defective Adipogenesis to Adipose Organ Dysfunction

The adipose organ adapts and responds to internal and environmental stimuli by remodeling both its cellular and extracellular components. Under conditions of energy surplus, the subcutaneous white adipose tissue (WAT) is capable of expanding through the enlargement of existing adipocytes (hypertrophy), followed by de novo adipogenesis (hyperplasia), which is impaired in hypertrophic obesity. However, an impaired hyperplastic response may result from various defects in adipogenesis, leading to different WAT features and metabolic consequences, as discussed here by reviewing the results of the studies in animal models with either overexpression or knockdown of the main molecular regulators of the two steps of the adipogenesis process. Moreover, impaired WAT remodeling with aging has been associated with various age-related conditions and reduced lifespan expectancy. Here, we delve into the latest advancements in comprehending the molecular and cellular processes underlying age-related changes in WAT function, their involvement in common aging pathologies, and their potential as therapeutic targets to influence both the health of elderly people and longevity. Overall, this review aims to encourage research on the mechanisms of WAT maladaptation common to conditions of both excessive and insufficient fat tissue. The goal is to devise adipocyte-targeted therapies that are effective against both obesity- and age-related disorders.

A macrophage-collagen fragment axis mediates subcutaneous adipose tissue remodeling in mice

Efficient removal of fibrillar collagen is essential for adaptive subcutaneous adipose tissue (SAT) expansion that protects against ectopic lipid deposition during weight gain. Here, we used mice to further define the mechanism for this collagenolytic process. We show that loss of collagen type-1 (CT1) and increased CT1-fragment levels in expanding SAT are associated with proliferation of resident M2-like macrophages that display increased CD206-mediated engagement in collagen endocytosis compared to chow-fed controls. Blockage of CD206 during acute high-fat diet-induced weight gain leads to SAT CT1-fragment accumulation associated with elevated inflammation and fibrosis markers. Moreover, these SAT macrophages' engagement in collagen endocytosis is diminished in obesity associated with elevated levels collagen fragments that are too short to assemble into triple helices. We show that such short fragments provoke M2-macrophage proliferation and fibroinflammatory changes in fibroblasts. In conclusion, our data delineate the importance of a macrophage-collagen fragment axis in physiological SAT expansion. Therapeutic targeting of this process may be a means to prevent pathological adipose tissue remodeling, which in turn may reduce the risk for obesity-related metabolic disorders.

Disruption of CerS6-mediated sphingolipid metabolism by FTO deficiency aggravates ulcerative colitis

BACKGROUND AND AIMS

Deregulation of RNA N6-methyladenosine (m6A) modification in intestinal epithelial cells (IECs) influences intestinal immune cells and leads to intestinal inflammation. We studied the function of fat mass-and obesity-associated protein (FTO), one of the m6A demethylases, in patients with ulcerative colitis (UC).

METHODS

We analysed colon tissues of Ftoflox/flox; Villin-cre mice and their Ftoflox/flox littermates with dextran sulfate sodium (DSS) using real-time PCR and 16s rRNA sequencing. RNA and methylated RNA immunoprecipitation sequencing were used to analyse immunocytes and IECs. Macrophages were treated with conditioned medium of FTO-knockdown MODE-K cells or sphingosine-1-phosphate (S1P) and analysed for gene expression. Liquid chromatograph mass spectrometry identified C16-ceramide.

RESULTS

FTO downregulation was identified in our in-house cohort and external cohorts of UC patients. Dysbiosis of gut microbiota, increased infiltration of proinflammatory macrophages, and enhanced differentiation of Th17 cells were observed in Ftoflox/flox;Villin-cre mice under DSS treatment. FTO deficiency resulted in an increase in m6A modification and a decrease in mRNA stability of CerS6, the gene encoding ceramide synthetase, leading to the downregulation of CerS6 and the accumulation of S1P in IECs. Subsequentially, the secretion of S1P by IECs triggered proinflammatory macrophages to secrete serum amyloid A protein 1/3, ultimately inducing Th17 cell differentiation. In addition, through bioinformatic analysis and experimental validation, we identified UC patients with lower FTO expression might respond better to vedolizumab treatment.

CONCLUSIONS

FTO downregulation promoted UC by decreasing CerS6 expression, leading to increased S1P accumulation in IECs and aggravating colitis via m6A-dependent mechanisms. Lower FTO expression in UC patients may enhance their response to vedolizumab treatment.

Transferrin receptor levels and its rare variant are associated with human obesity

AIM

Iron homeostasis is critical for functional respiratory chain complex of mitochondrial, thus potentially contributing to fat biology and energy homeostasis. Transferrin receptor (Tfrc) binds to transferrin for extracellular iron uptake and is recently reported to be involved in brown fat development and functionality. However, whether TFRC levels and variants are associated with human obesity is unknown.

METHODS

To investigate the association of TFRC levels and variants with human obesity, fat biopsies were obtained from surgery. Exon-sequencing and genetic assessments were conducted of a case-control study. For TFRC levels assessment in fat biopsy, 9 overweight and 12 lean subjects were involved. For genetic study, obese (n = 1271) and lean subjects (n = 1455) were involved. TFRC levels were compared in abdominal mesenteric fat of pheochromocytoma patients versus control subjects, and overweight versus lean subjects. For genetic study, whole-exome sequencing of obese and matched control subjects were conducted and analyzed. In addition, the possible disruption in protein stability of TFRC variant was assessed by structural and molecular analysis.

RESULTS

TFRC levels are increased in human browning adipose tissue and decreased in fat of overweight patients. Besides, TFRC levels are negatively correlated with body mass index and positively correlated with uncoupling protein 1 levels. Furthermore, a rare heterozygous missense variant p.I337V in TFRC shows a tendency to enrich in obese subjects. Structural and functional study reveals impaired protein stability of the TFRC variant compared to wild-type.

CONCLUSIONS

Reduced TFRC levels and its rare variant p.I337V with protein instability are associated with human obesity.

Hypertonicity induces mitochondrial extracellular vesicles (MEVs) that activate TNF-α and β-catenin signaling to promote adipocyte dedifferentiation

BACKGROUND

Recent studies demonstrated that elevated osmolarity could induce adipocyte dedifferentiation, representing an appealing procedure to generate multipotent stem cells. Here we aim to elucidate the molecular mechanisms that underlie osmotic induction of adipocyte reprogramming.

METHODS

To induce dedifferentiation, the 3T3-L1 or SVF adipocytes were cultured under the hypertonic pressure in 2% PEG 300 medium. Adipocyte dedifferentiation was monitored by aspect ratio measurement, Oil Red staining and qPCR to examine the morphology, lipid droplets, and specific genes of adipocytes, respectively. The osteogenic and chondrogenic re-differentiation capacities of dedifferentiated adipocytes were also examined. To investigate the mechanisms of the osmotic stress-induced dedifferentiation, extracellular vesicles (EVs) were collected from the reprograming cells, followed by proteomic and functional analyses. In addition, qPCR, ELISA, and TNF-α neutralizing antibody (20 ng/ml) was applied to examine the activation and effects of the TNF-α signaling. Furthermore, we also analyzed the Wnt signaling by assessing the activation of β-catenin and applying BML-284, an agonist of β-catenin.

RESULTS

Hypertonic treatment induced dedifferentiation of both 3T3-L1 and the primary stromal vascular fraction (SVF) adipocytes, characterized by morphological and functional changes. Proteomic profiling revealed that hypertonicity induced extracellular vesicles (EVs) containing mitochondrial molecules including NDUFA9 and VDAC. Functionally, the mitochondrial EVs (MEVs) stimulated TNF-α signaling that activates Wnt-β-catenin signaling and adipocyte dedifferentiation. Neutralizing TNF-α inhibited hypertonic dedifferentiation of adipocytes. In addition, direct activation of Wnt-β-catenin signaling using BML-284 could efficiently induce adipocyte dedifferentiation while circumventing the apoptotic effect of the hypertonic treatment.

CONCLUSIONS

Hypertonicity prompts the adipocytes to release MEVs, which in turn enhances the secretion of TNF-α as a pro-inflammatory cytokine during the stress response. Importantly, TNF-α is essential for the activation of the Wnt/β-catenin signaling that drives adipocyte dedifferentiation. A caveat of the hypertonic treatment is apoptosis, which could be circumvented by direct activation of the Wnt/β-catenin signaling using BML-284.

Wnt/β-catenin signaling activation promotes lipogenesis in the steatotic liver via physical mTOR interaction

Background and aims

Wnt/β-catenin signaling plays an important role in regulating hepatic metabolism. This study is to explore the molecular mechanisms underlying the potential crosstalk between Wnt/β-catenin and mTOR signaling in hepatic steatosis.

Methods

Transgenic mice (overexpress Wnt1 in hepatocytes, Wnt+) mice and wild-type littermates were given high fat diet (HFD) for 12 weeks to induce hepatic steatosis. Mouse hepatocytes cells (AML12) and those transfected to cause constitutive β-catenin stabilization (S33Y) were treated with oleic acid for lipid accumulation.

Results

Wnt+ mice developed more hepatic steatosis in response to HFD. Immunoblot shows a significant increase in the expression of fatty acid synthesis-related genes (SREBP-1 and its downstream targets ACC, AceCS1, and FASN) and a decrease in fatty acid oxidation gene (MCAD) in Wnt+ mice livers under HFD. Wnt+ mice also revealed increased Akt signaling and its downstream target gene mTOR in response to HFD. In vitro, increased lipid accumulation was detected in S33Y cells in response to oleic acid compared to AML12 cells reinforcing the in vivo findings. mTOR inhibition by rapamycin led to a down-regulation of fatty acid synthesis in S33Y cells. In addition, β-catenin has a physical interaction with mTOR as verified by co-immunoprecipitation in hepatocytes.

Conclusions

Taken together, our results demonstrate that β-catenin stabilization through Wnt signaling serves a central role in lipid metabolism in the steatotic liver through up-regulation of fatty acid synthesis via Akt/mTOR signaling. These findings suggest hepatic Wnt signaling may represent a therapeutic strategy in hepatic steatosis.

Sex hormone-binding globulin improves lipid metabolism and reduces inflammation in subcutaneous adipose tissue of metabolic syndrome-affected horses

Equine metabolic syndrome (EMS) is a steadily growing endocrine disorder representing a real challenge in veterinary practice. As a multifactorial condition, EMS is characterized by three main metabolic abnormalities including insulin resistance, increased adiposity or obesity and hoof laminitis. Adipose tissue dysfunction is recognized as a core pathophysiological determinant of EMS, as it strongly participates to lipotoxicity and systemic metaflammation, both of which have been closely linked to the development of generalized insulin resistance. Besides, sex hormone binding globulin (SHBG) is an important sex steroids transporters that has been recently proposed as an important metabolic mediator. Therefore, the aim of this study was to verify whether SHBG treatment may ameliorate subcutaneous adipose tissue metabolic failure under EMS condition in terms of lipidome homeostasis, lipid metabolism programs, insulin signalling and local inflammation. Subcutaneous adipose tissue (SAT) biopsies were collected post-mortem from healthy (n = 3) and EMS (n = 3) slaughtered horses. SHBG protein has been applied to SAT samples from EMS horses for 24 h at a final concentration of 50 nM, while control groups (healthy and untreated EMS) were cultured in the presence of SHBG-vehicle only. Tissues from all groups were afterwards secured for downstream analysis of gene expression using RT-qPCR, protein levels by Western blot and ELISA assay and lipidomics through GC-MS technique. Obtained results showcased that SHBG intervention efficiently normalized the altered fatty acids (FAs) profiles by lowering the accumulation of saturated and trans FAs, as well as the pro-inflammatory arachidonic and linoleic acids. Moreover, SHBG showed promising value for the regulation of adipocyte lipolysis and engorgement by lowering the levels of perilipin-1. SHBG exerted moderated effect toward SCD1 and FASN enzymes expression, but increased the LPL abundance. Interestingly, SHBG exhibited a negative regulatory effect on pro-adipogenic stimulators and induced higher expression of KLF3, IRF3 and β-catenin, known as strong adipogenesis repressors. Finally, SHBG protein showed remarkable ability in restoring the insulin signal transduction, IR/IRS/Pi3K/AKT phosphorylation events and GLUT4 transporter abundance, and further attenuate pro-inflammatory response by lowering IL-6 tissue levels and targeting the PDIA3/ERK axis. Overall, the obtained data clearly demonstrate the benefice of SHBG treatment in the regulation of adipose tissue metabolism in the course of EMS and provide new insights for the development of molecular therapies with potential translational application to human metabolic disorders.

The cerebellum plays more than one role in the dysregulation of appetite: Review of structural evidence from typical and eating disorder populations

OBJECTIVE

Dysregulated appetite control is characteristic of anorexia nervosa (AN), bulimia nervosa (BN), and obesity (OB). Studies using a broad range of methods suggest the cerebellum plays an important role in aspects of weight and appetite control, and is implicated in both AN and OB by reports of aberrant gray matter volume (GMV) compared to nonclinical populations. As functions of the cerebellum are anatomically segregated, specific localization of aberrant anatomy may indicate the mechanisms of its relationship with weight and appetite in different states. We sought to determine if there were consistencies in regions of cerebellar GMV changes in AN/BN and OB, as well as across normative (NOR) variation.

METHOD

Systematic review and meta-analysis using GingerALE.

RESULTS

Twenty-six publications were identified as either case-control studies (nOB  = 277; nAN/BN  = 510) or regressed weight from NOR data against brain volume (total n = 3830). AN/BN and OB analyses both showed consistently decreased GMV within Crus I and Lobule VI, but volume reduction was bilateral for AN/BN and unilateral for OB. Analysis of the NOR data set identified a cluster in right posterior lobe that overlapped with AN/BN cerebellar reduction. Sensitivity analyses indicated robust repeatability for NOR and AN/BN cohorts, but found OB-specific heterogeneity.

DISCUSSION

Findings suggest that more than one area of the cerebellum is involved in control of eating behavior and may be differentially affected in normal variation and pathological conditions. Specifically, we hypothesize an association with sensorimotor and emotional learning via Lobule VI in AN/BN, and executive function via Crus I in OB.

Multi-tissue epigenetic analysis identifies distinct associations underlying insulin resistance and Alzheimer's disease at CPT1A locus

BACKGROUND

Insulin resistance (IR) is a major risk factor for Alzheimer's disease (AD) dementia. The mechanisms by which IR predisposes to AD are not well-understood. Epigenetic studies may help identify molecular signatures of IR associated with AD, thus improving our understanding of the biological and regulatory mechanisms linking IR and AD.

METHODS

We conducted an epigenome-wide association study of IR, quantified using the homeostatic model assessment of IR (HOMA-IR) and adjusted for body mass index, in 3,167 participants from the Framingham Heart Study (FHS) without type 2 diabetes at the time of blood draw used for methylation measurement. We identified DNA methylation markers associated with IR at the genome-wide level accounting for multiple testing (P < 1.1 × 10-7) and evaluated their association with neurological traits in participants from the FHS (N = 3040) and the Religious Orders Study/Memory and Aging Project (ROSMAP, N = 707). DNA methylation profiles were measured in blood (FHS) or dorsolateral prefrontal cortex (ROSMAP) using the Illumina HumanMethylation450 BeadChip. Linear regressions (ROSMAP) or mixed-effects models accounting for familial relatedness (FHS) adjusted for age, sex, cohort, self-reported race, batch, and cell type proportions were used to assess associations between DNA methylation and neurological traits accounting for multiple testing.

RESULTS

We confirmed the strong association of blood DNA methylation with IR at three loci (cg17901584-DHCR24, cg17058475-CPT1A, cg00574958-CPT1A, and cg06500161-ABCG1). In FHS, higher levels of blood DNA methylation at cg00574958 and cg17058475 were both associated with lower IR (P = 2.4 × 10-11 and P = 9.0 × 10-8), larger total brain volumes (P = 0.03 and P = 9.7 × 10-4), and smaller log lateral ventricular volumes (P = 0.07 and P = 0.03). In ROSMAP, higher levels of brain DNA methylation at the same two CPT1A markers were associated with greater risk of cognitive impairment (P = 0.005 and P = 0.02) and higher AD-related indices (CERAD score: P = 5 × 10-4 and 0.001; Braak stage: P = 0.004 and P = 0.01).

CONCLUSIONS

Our results suggest potentially distinct epigenetic regulatory mechanisms between peripheral blood and dorsolateral prefrontal cortex tissues underlying IR and AD at CPT1A locus.

Oxymatrine relieves high-fructose/fat-induced obesity via reprogramming the activity of lipid metabolism-related enhancer

Introduction

Emerging evidence demonstrates that the high-fructose and high-fat diet (HFHF) induced obesity and fatty liver disease has become one of the most common metabolic disorders worldwide. Therefore, innovative investigations on compounds targeting obesity and fatty liver diseases are urgently needed.

Methods

The high-throughput natural compounds screen was performed to screen the important compounds. A rat HFHF model was constructed, the regulatory function of Oxymatrine in HFHF-induced obesity was further explored.

Results

We identified Oxymatrine, a natural compound extracted from Sophora flavescens, showed a potential compacity in high-fat diet-induced fatty liver disease. We found that oxymatrine significantly inhibited HFHF-induced obesity using a rat HFHF model. Additionally, we found that oxymatrine altered the enhancer landscape of subcutaneous adipose tissues by ChIP-seq analysis using antibodies against the H3K27ac histone modification. Motif enrichment analysis showed the Smad motif was significantly enriched in enhancers altered post-oxymatrine treatment. Further chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) analysis and luciferase reporter assays showed oxymatrine alters the binding of Smad3 on the enhancer regions of B-cell lymphoma 2 (Bcl2) and the enhancer activity of Bcl2.

Discussion

Together, our study highlighted oxymatrine could suppress high-fructose and high-fat diet-induced obesity by inhibiting the suppressor of mothers against decapentaplegic 3 (Smad3) binding on obesity-related enhancers.

The rs1421085 variant within FTO promotes brown fat thermogenesis

One lead genetic risk signal of obesity-the rs1421085 T>C variant within the FTO gene-is reported to be functional in vitro but lacks evidence at an organism level. Here we recapitulate the homologous human variant in mice with global and brown adipocyte-specific variant knock-in and reveal that mice carrying the C-allele show increased brown fat thermogenic capacity and resistance to high-fat diet-induced adiposity, whereas the obesity-related phenotypic changes are blunted at thermoneutrality. Both in vivo and in vitro data reveal that the C-allele in brown adipocytes enhances the transcription of the Fto gene, which is associated with stronger chromatin looping linking the enhancer region and Fto promoter. Moreover, FTO knockdown or inhibition effectively eliminates the increased thermogenic ability of brown adipocytes carrying the C-allele. Taken together, these findings identify rs1421085 T>C as a functional variant promoting brown fat thermogenesis.

Network-medicine approach for the identification of genetic association of parathyroid adenoma with cardiovascular disease and type-2 diabetes

Primary hyperparathyroidism is caused by solitary parathyroid adenomas (PTAs) in most cases (⁓85%), and it has been previously reported that PTAs are associated with cardiovascular disease (CVD) and type-2 diabetes (T2D). To understand the molecular basis of PTAs, we have investigated the genetic association amongst PTAs, CVD and T2D through an integrative network-based approach and observed a remarkable resemblance. The current study proposed to compare the PTAs-associated proteins with the overlapping proteins of CVD and T2D to determine the disease relationship. We constructed the protein-protein interaction network by integrating curated and experimentally validated interactions in humans. We found the $11$ highly clustered modules in the network, which contain a total of $13$ hub proteins (TP53, ESR1, EGFR, POTEF, MEN1, FLNA, CDKN2B, ACTB, CTNNB1, CAV1, MAPK1, G6PD and CCND1) that commonly co-exist in PTAs, CDV and T2D and reached to network's hierarchically modular organization. Additionally, we implemented a gene-set over-representation analysis over biological processes and pathways that helped to identify disease-associated pathways and prioritize target disease proteins. Moreover, we identified the respective drugs of these hub proteins. We built a bipartite network that helps decipher the drug-target interaction, highlighting the influential roles of these drugs on apparently unrelated targets and pathways. Targeting these hub proteins by using drug combinations or drug-repurposing approaches will improve the clinical conditions in comorbidity, enhance the potency of a few drugs and give a synergistic effect with better outcomes. This network-based analysis opens a new horizon for more personalized treatment and drug-repurposing opportunities to investigate new targets and multi-drug treatment and may be helpful in further analysis of the mechanisms underlying PTA and associated diseases.

Characteristic and fate determination of adipose precursors during adipose tissue remodeling

Adipose tissues are essential for actively regulating systemic energy balance, glucose homeostasis, immune responses, reproduction, and longevity. Adipocytes maintain dynamic metabolic needs and possess heterogeneity in energy storage and supply. Overexpansion of adipose tissue, especially the visceral type, is a high risk for diabetes and other metabolic diseases. Changes in adipocytes, hypertrophy or hyperplasia, contribute to the remodeling of obese adipose tissues, accompanied by abundant immune cell accumulation, decreased angiogenesis, and aberrant extracellular matrix deposition. The process and mechanism of adipogenesis are well known, however, adipose precursors and their fate decision are only being defined with recent information available to decipher how adipose tissues generate, maintain, and remodel. Here, we discuss the key findings that identify adipose precursors phenotypically, with special emphasis on the intrinsic and extrinsic signals in instructing and regulating the fate of adipose precursors under pathophysiological conditions. We hope that the information in this review lead to novel therapeutic strategies to combat obesity and related metabolic diseases.

Human RSPO1 Mutation Represses Beige Adipocyte Thermogenesis and Contributes to Diet-Induced Adiposity

Recent genetic evidence has linked WNT downstream mutations to fat distribution. However, the roles of WNTs in human obesity remain unclear. Here, the authors screen all Wnt-related paracrine factors in 1994 obese cases and 2161 controls using whole-exome sequencing (WES) and identify that 12 obese patients harbor the same mutations in RSPO1 (p.R219W/Q) predisposing to human obesity. RSPO1 is predominantly expressed in visceral fat, primarily in the fibroblast cluster, and is increased with adiposity. Mice overexpressing human RSPO1 in adipose tissues develop obesity under a high-fat diet (HFD) due to reduced brown/beige fat thermogenesis. In contrast, Rspo1 ablation resists HFD-induced adiposity by increasing thermogenesis. Mechanistically, RSPO1 overexpression or administration significantly inhibits adipocyte mitochondrial respiration and thermogenesis via LGR4-Wnt/β-catenin signaling pathway. Importantly, humanized knockin mice carrying the hotspot mutation (p.R219W) display suppressed thermogenesis and recapitulate the adiposity feature of obese carriers. The mutation disrupts RSPO1's electrostatic interaction with the extracellular matrix, leading to excessive RSPO1 release that activates LGR4-Wnt/β-catenin signaling and attenuates thermogenic capacity in differentiated beige adipocytes. Therefore, these findings identify that gain-of-function mutations and excessive expression of RSPO1, acting as a paracrine Wnt activator, suppress fat thermogenesis and contribute to obesity in humans.

HnRNPA2B1 Aggravates Inflammation by Promoting M1 Macrophage Polarization

Macrophages have critical contributions to both acute and chronic inflammatory diseases, for example, bowel disease and obesity, respectively. However, little is known about the post-transcriptional regulatory mechanisms in macrophage-mediated inflammatory diseases. hnRNPA2B1 (A2B1) is an RNA binding protein for mRNA fate determination. We showed that hnRNPA2B1 mRNA levels were increased in colon in dextran sodium sulfate (DSS)-induced colitis mice and in epididymal white adipose tissue (eWAT) and spleen of high-fat-diet (HFD)-induced obese mice. Consistently, mice with haploinsufficiency of A2B1 (A2B1 HET) are protected against DSS-induced acute colitis and HFD-induced obesity, with decreased M1 macrophages polarization in colon, eWAT and spleen. Mechanistically, A2B1 mRNA and protein levels were increased in LPS-stimulated RAW 264.7 macrophages, and A2B1 enhanced RNA stability of pro-inflammatory genes Tnfα, Il-6 and Il-1β for the regulation of macrophages polarization. Interestingly, A2B1 HET mice exhibited reduced white fat expansion, which was influenced by macrophages, since conditioned medium from macrophages with A2B1 manipulation significantly changed preadipocyte proliferation. Our data demonstrate that A2B1 plays a vital role in macrophage-mediated inflammation via regulating mRNA stability, suggesting that A2B1 may be served as a promising target for the intervention of acute and chronic inflammatory diseases.

Expression and Function of BMP and Activin Membrane-Bound Inhibitor (BAMBI) in Chronic Liver Diseases and Hepatocellular Carcinoma

BAMBI (bone morphogenetic protein and activin membrane-bound inhibitor) is a transmembrane pseudoreceptor structurally related to transforming growth factor (TGF)-β type 1 receptors (TGF-β1Rs). BAMBI lacks a kinase domain and functions as a TGF-β1R antagonist. Essential processes such as cell differentiation and proliferation are regulated by TGF-β1R signaling. TGF-β is the best-studied ligand of TGF-βRs and has an eminent role in inflammation and fibrogenesis. Liver fibrosis is the end stage of almost all chronic liver diseases, such as non-alcoholic fatty liver disease, and at the moment, there is no effective anti-fibrotic therapy available. Hepatic BAMBI is downregulated in rodent models of liver injury and in the fibrotic liver of patients, suggesting that low BAMBI has a role in liver fibrosis. Experimental evidence convincingly demonstrated that BAMBI overexpression is able to protect against liver fibrosis. Chronic liver diseases have a high risk of hepatocellular carcinoma (HCC), and BAMBI was shown to exert tumor-promoting as well as tumor-protective functions. This review article aims to summarize relevant studies on hepatic BAMBI expression and its role in chronic liver diseases and HCC.

A role for β-catenin in diet-induced skeletal muscle insulin resistance

A central characteristic of insulin resistance is the impaired ability for insulin to stimulate glucose uptake into skeletal muscle. While insulin resistance can occur distal to the canonical insulin receptor-PI3k-Akt signaling pathway, the signaling intermediates involved in the dysfunction are yet to be fully elucidated. β-catenin is an emerging distal regulator of skeletal muscle and adipocyte insulin-stimulated GLUT4 trafficking. Here, we investigate its role in skeletal muscle insulin resistance. Short-term (5-week) high-fat diet (HFD) decreased skeletal muscle β-catenin protein expression 27% (p = 0.03), and perturbed insulin-stimulated β-cateninS552 phosphorylation 21% (p = 0.009) without affecting insulin-stimulated Akt phosphorylation relative to chow-fed controls. Under chow conditions, mice with muscle-specific β-catenin deletion had impaired insulin responsiveness, whereas under HFD, both mice exhibited similar levels of insulin resistance (interaction effect of genotype × diet p < 0.05). Treatment of L6-GLUT4-myc myocytes with palmitate lower β-catenin protein expression by 75% (p = 0.02), and attenuated insulin-stimulated β-catenin phosphorylationS552 and actin remodeling (interaction effect of insulin × palmitate p < 0.05). Finally, β-cateninS552 phosphorylation was 45% lower in muscle biopsies from men with type 2 diabetes while total β-catenin expression was unchanged. These findings suggest that β-catenin dysfunction is associated with the development of insulin resistance.

A single cell-based computational platform to identify chemical compounds targeting desired sets of transcription factors for cellular conversion

Cellular conversion can be induced by perturbing a handful of key transcription factors (TFs). Replacement of direct manipulation of key TFs with chemical compounds offers a less laborious and safer strategy to drive cellular conversion for regenerative medicine. Nevertheless, identifying optimal chemical compounds currently requires large-scale screening of chemical libraries, which is resource intensive. Existing computational methods aim at predicting cell conversion TFs, but there are no methods for identifying chemical compounds targeting these TFs. Here, we develop a single cell-based platform (SiPer) to systematically prioritize chemical compounds targeting desired TFs to guide cellular conversions. SiPer integrates a large compendium of chemical perturbations on non-cancer cells with a network model and predicted known and novel chemical compounds in diverse cell conversion examples. Importantly, we applied SiPer to develop a highly efficient protocol for human hepatic maturation. Overall, SiPer provides a valuable resource to efficiently identify chemical compounds for cell conversion.

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 (VO_2max ) 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).

MicroRNAs: a crossroad that connects obesity to immunity and aging

Obesity is characterized by an elevated amount of fat and energy storage in the adipose tissue (AT) and is believed to be the root cause of many metabolic diseases (MDs). Obesity is associated with low-grade chronic inflammation in AT. Like obesity, chronic inflammation and MDs are prevalent in the elderly. The resident immune microenvironment is not only responsible for maintaining AT homeostasis but also plays a crucial role in stemming obesity and related MDs. Mounting evidence suggests that obesity promotes activation in resident T cells and macrophages. Additionally, inflammatory subsets of T cells and macrophages accumulated into the AT in combination with other immune cells maintain low-grade chronic inflammation. microRNAs (miRs) are small non-coding RNAs and a crucial contributing factor in maintaining immune response and obesity in AT. AT resident T cells, macrophages and adipocytes secrete various miRs and communicate with other cells to create a potential effect in metabolic organ crosstalk. AT resident macrophages and T cells-associated miRs have a prominent role in regulating obesity by targeting several signaling pathways. Further, miRs also emerged as important regulators of cellular senescence and aging. To this end, a clear link between miRs and longevity has been demonstrated that implicates their role in regulating lifespan and the aging process. Hence, AT and circulating miRs can be used as diagnostic and therapeutic tools for obesity and related disorders. In this review, we discuss how miRs function as biomarkers and impact obesity, chronic inflammation, and aging.

m6A demethylase FTO regulate CTNNB1 to promote adipogenesis of chicken preadipocyte

BACKGROUND

N6-methyladenosine (m⁶A) is an abundant post-transcriptional RNA modification that affects various biological processes. The fat mass and obesity-associated (FTO) protein, a demethylase encoded by the FTO gene, has been found to regulate adipocyte development in an m⁶A-dependent manner in multiple species. However, the effects of the m⁶A methylation and FTO demethylation functions on chicken adipogenesis remain unclear. This study aims to explore the association between m⁶A modification and chicken adipogenesis and the underlying mechanism by which FTO affects chicken preadipocyte development.

RESULTS

The association between m⁶A modification and chicken lipogenesis was assessed by treating chicken preadipocytes with different doses of methyl donor betaine and methylation inhibitor cycloleucine. The results showed that betaine significantly increased methylation levels and inhibited lipogenesis, and the inverse effect was found in preadipocytes after cycloleucine treatment. Overexpression of FTO significantly inhibited m⁶A levels and promoted proliferation and differentiation of chicken preadipocytes. Silencing FTO showed opposite results. Mechanistically, FTO overexpression increased the expression of catenin beta 1 (CTNNB1) by improving RNA stability in an m⁶A-dependent manner, and we proved that FTO could directly target CTNNB1. Furthermore, CTNNB1 may be a positive regulator of adipogenesis in chicken preadipocytes.

CONCLUSIONS

m⁶A methylation of RNA was negatively associated with adipogenesis of chicken preadipocytes. FTO could regulate CTNNB1 expression in a demethylation manner to promote lipogenesis.

Signaling pathways in obesity: mechanisms and therapeutic interventions

Obesity is a complex, chronic disease and global public health challenge. Characterized by excessive fat accumulation in the body, obesity sharply increases the risk of several diseases, such as type 2 diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, and is linked to lower life expectancy. Although lifestyle intervention (diet and exercise) has remarkable effects on weight management, achieving long-term success at weight loss is extremely challenging, and the prevalence of obesity continues to rise worldwide. Over the past decades, the pathophysiology of obesity has been extensively investigated, and an increasing number of signal transduction pathways have been implicated in obesity, making it possible to fight obesity in a more effective and precise way. In this review, we summarize recent advances in the pathogenesis of obesity from both experimental and clinical studies, focusing on signaling pathways and their roles in the regulation of food intake, glucose homeostasis, adipogenesis, thermogenesis, and chronic inflammation. We also discuss the current anti-obesity drugs, as well as weight loss compounds in clinical trials, that target these signals. The evolving knowledge of signaling transduction may shed light on the future direction of obesity research, as we move into a new era of precision medicine.

Discovery and functional assessment of a novel adipocyte population driven by intracellular Wnt/β-catenin signaling in mammals

Wnt/β-catenin signaling has been well established as a potent inhibitor of adipogenesis. Here, we identified a population of adipocytes that exhibit persistent activity of Wnt/β-catenin signaling, as revealed by the Tcf/Lef-GFP reporter allele, in embryonic and adult mouse fat depots, named as Wnt⁺ adipocytes. We showed that this β-catenin-mediated signaling activation in these cells is Wnt ligand- and receptor-independent but relies on AKT/mTOR pathway and is essential for cell survival. Such adipocytes are distinct from classical ones in transcriptomic and genomic signatures and can be induced from various sources of mesenchymal stromal cells including human cells. Genetic lineage-tracing and targeted cell ablation studies revealed that these adipocytes convert into beige adipocytes directly and are also required for beige fat recruitment under thermal challenge, demonstrating both cell autonomous and non-cell autonomous roles in adaptive thermogenesis. Furthermore, mice bearing targeted ablation of these adipocytes exhibited glucose intolerance, while mice receiving exogenously supplied such cells manifested enhanced glucose utilization. Our studies uncover a unique adipocyte population in regulating beiging in adipose tissues and systemic glucose homeostasis.

GREM2 is associated with human central obesity and inhibits visceral preadipocyte browning

Background

Methods

Findings

Interpretation

Funding

LncRNA THUMPD3-AS1 enhances the proliferation and inflammatory response of chondrocytes in osteoarthritis

OBJECTIVE

Long noncoding RNAs (lncRNAs) regulate the occurrence and development of osteoarthritis (OA), whereas the biological roles and mechanisms of the lncRNA THUMPD3-AS1 (THUMPD3 antisense RNA 1) in OA remain still unclear. This study described the role and molecular mechanism of lncRNA THUMPD3-AS1 in regulating OA biology.

METHOD

The knee normal and OA cartilage tissues from ten participants were sequenced to reveal the differentially expressed lncRNAs. The interleukin (IL)-1β-stimulated C28/I2 cell served as OA cells. Flow cytometry assays, Western blot, enzyme-linked immunosorbent assays were used for our experiments.

RESULTS

The results revealed that lncRNA THUMPD3-AS1 was downregulated in OA cartilage tissues and IL-1β-stimulated chondrocyte cell line. Overexpression of lncRNA THUMPD3-AS1 alleviated cell apoptosis and facilitated inflammatory responses, whereas knockdown had opposite effects. LncRNA THUMPD3-AS1 markedly increased the cyclin E2, cyclin-dependent kinase 4, B-cell lymphoma 2, tumor necrosis factor-α, nitric oxide, and IL-6 levels, and decreased the caspase-3 level. Furthermore, the target proteins of phosphorylation were identified as nuclear factor-κB p65 and mitogen-activated protein kinase p38, which could be indirectly suppressed by lncRNA THUMPD3-AS1 knockdown.

CONCLUSION

Our findings highlight the different effects of lncRNA THUMPD3-AS1 on cell apoptosis and inflammatory response, which extend the multiple functions of lncRNA epigenetics in OA biology.

Metabolic Contributions of Wnt Signaling: More Than Controlling Flight

The canonical Wnt signaling pathway is ubiquitous throughout the body and influences a diverse array of physiological processes. Following the initial discovery of the Wnt signaling pathway during wing development in Drosophila melanogaster, it is now widely appreciated that active Wnt signaling in mammals is necessary for the development and growth of various tissues involved in whole-body metabolism, such as brain, liver, pancreas, muscle, and adipose. Moreover, elegant gain- and loss-of-function studies have dissected the tissue-specific roles of various downstream effector molecules in the regulation of energy homeostasis. This review attempts to highlight and summarize the contributions of the Wnt signaling pathway and its downstream effectors on whole-body metabolism and their influence on the development of metabolic diseases, such as diabetes and obesity. A better understanding of the Wnt signaling pathway in these tissues may aid in guiding the development of future therapeutics to treat metabolic diseases.

Wnt Signaling: From Mesenchymal Cell Fate to Lipogenesis and Other Mature Adipocyte Functions

Wnt signaling is an ancient and evolutionarily conserved pathway with fundamental roles in the development of adipose tissues. Roles of this pathway in mesenchymal stem cell fate determination and differentiation have been extensively studied. Indeed, canonical Wnt signaling is a significant endogenous inhibitor of adipogenesis and promoter of other cell fates, including osteogenesis, chondrogenesis, and myogenesis. However, emerging genetic evidence in both humans and mice suggests central roles for Wnt signaling in body fat distribution, obesity, and metabolic dysfunction. Herein, we highlight recent studies that have begun to unravel the contributions of various Wnt pathway members to critical adipocyte functions, including carbohydrate and lipid metabolism. We further explore compelling evidence of complex and coordinated interactions between adipocytes and other cell types within adipose tissues, including stromal, immune, and endothelial cells. Given the evolutionary conservation and ubiquitous cellular distribution of this pathway, uncovering the contributions of Wnt signaling to cell metabolism has exciting implications for therapeutic intervention in widespread pathologic states, including obesity, diabetes, and cancers.

Integrative proteomic network analyses support depot-specific roles for leucine rich repeat LGI family member 3 in adipose tissues

LGI family member 3 (LGI3) is a member of the LGI protein family. In our previous studies, LGI3 was determined to be expressed in adipose tissues, skin and the brain, where it served as a pleiotropic cytokine. The results indicated that LGI3 levels are increased in adipose tissues of obese individuals in comparison with control individuals and that LGI3 suppressed adipogenesis via its receptor, disintegrin and metalloproteinase domain-containing protein 23. Additionally, it was reported that LGI3 upregulates tumor necrosis factor-α and downregulated adiponectin and hypothesized that LGI3 may act as a proinflammatory adipokine involved in adipose tissue inflammation. In the present study, cytokine arrays were used to analyze cytokine levels in adipose tissues and plasma of LGI3-knockout mice and signaling protein arrays used to analyze the expression and phosphorylation of these proteins in LGI3-treated preadipocytes. The results suggested that expression levels of 129 gene products (24 cytokines and 105 signaling proteins) were altered in response to LGI3 deficiency or LGI3 treatment, respectively. Protein-protein interaction network analysis of LGI3-regulated gene products revealed that 94% of the gene products (21 cytokines and 100 signaling proteins) formed an interaction network cluster. Functional enrichment analysis for the LGI3-regulated gene products, including those from our previous studies, revealed an association with numerous biological processes, including inflammatory responses, cellular differentiation and development and metabolic regulation. Gene co-expression network analysis revealed that these LGI3-regulated gene products were involved in various biological processes in an overlapping and differential manner between subcutaneous and visceral adipose tissues. Notably, inflammatory responses were more strongly associated with the LGI3-regulated gene co-expression network in visceral adipose tissues than in subcutaneous adipose tissues. Analysis of expression quantitative trait loci identified four single nucleotide variants that affect expression of LGI3 in an adipose depot-specific manner. Taken together, the results suggested that LGI3 may serve depot-specific roles as an adipokine in adipose tissues.

Effect of left or right gastric artery interventional embolization on obesity and ghrelin/leptin expression in pigs

OBJECTIVE

To investigate the effect of left or right gastric artery interventional embolization on obesity and ghrelin/leptin expression in pigs.

METHODS

Thirty-two female Wuzhishan pigs aged 3-4 months were randomly divided into four groups, with eight pigs in each group: obesity + left gastric artery embolization group, obesity + right gastric artery embolization group, obesity + sham surgery group and healthy control group. The body weight and serum levels of ghrelin, leptin, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) before the operation, one month and three months after the operation, and the gastric pathology three months after the operation were compared.

RESULTS

The preoperative body weight, ghrelin level, leptin level, IL-6 level and TNF-α level of the obesity + sham surgery group, obesity + left gastric artery embolization group and obesity + right gastric artery embolization group were higher than those of the healthy control group (all P<0.05). One month after the operation, the body weight, ghrelin level, leptin level, IL-6 level and TNF-α level of the obesity + sham surgery group, obesity + left gastric artery embolization group and obesity + right gastric artery embolization group were higher than those of the healthy control group. The body weight, ghrelin level, IL-6 level and TNF-α level of the obesity + sham surgery group were higher than those of the obesity + left artery embolization group and obesity + right gastric artery embolization group (all P<0.05). Three months after the operation, the body weight, ghrelin level, leptin level, IL-6 level and TNF-α level of the obesity + sham surgery group were higher than those of the obesity + left artery embolization group, obesity + right artery embolization group and the healthy control group (all P<0.05).

CONCLUSION

Left or right gastric artery interventional embolization in pigs can effectively reduce body weight, which may be related to the reduced secretion of ghrelin, leptin and inflammatory factors. However, the clinical application and safety of left or right gastric artery embolization still need further study.

Effects of normobaric cyclic hypoxia exposure on mesenchymal stem-cell differentiation-pilot study on bone parameters in elderly

BACKGROUND

Mesenchymal stem cells (MSC) of bone marrow are the progenitor of osteoblasts and adipocytes. MSC tend to differentiate into adipocytes, instead of osteoblasts, with aging. This favors the loss of bone mass and development of osteoporosis. Hypoxia induces hypoxia inducible factor 1α gene encoding transcription factor, which regulates the expression of genes related to energy metabolism and angiogenesis. That allows a better adaptation to low O2 conditions. Sustained hypoxia has negative effects on bone metabolism, favoring bone resorption. Yet, surprisingly, cyclic hypoxia (CH), short times of hypoxia followed by long times in normoxia, can modulate MSC differentiation and improve bone health in aging.

AIM

To evaluate the CH effect on MSC differentiation, and whether it improves bone mineral density in elderly.

METHODS

MSC cultures were induced to differentiate into osteoblasts or adipocytes, in CH (3% O2 for 1, 2 or 4 h, 4 d a week). Extracellular-matrix mineralization and lipid-droplet formation were studied in MSC induced to differentiate into osteoblast or adipocytes, respectively. In addition, gene expression of marker genes, for osteogenesis or adipogenesis, have been quantified by quantitative real time polymerase chain reaction. The in vivo studies with elderly (> 75 years old; n = 10) were carried out in a hypoxia chamber, simulating an altitude of 2500 m above sea level, or in normoxia, for 18 wk (36 CH sessions of 16 min each). Percentages of fat mass and bone mineral density from whole body, trunk and right proximal femur (femoral, femoral neck and trochanter) were assessed, using dual-energy X-ray absorptiometry.

RESULTS

CH (4 h of hypoxic exposure) inhibited extracellular matrix mineralization and lipid-droplet formation in MSC induced to differentiate into osteoblasts or adipocytes, respectively. However, both parameters were not significantly affected by the other shorter hypoxia times assessed. The longest periods of hypoxia downregulated the expression of genes related to extracellular matrix formation, in MSC induced to differentiate into osteoblasts. Interestingly, osteocalcin (associated to energy metabolism) was upregulated. Vascular endothelial growth factor an expression and low-density lipoprotein receptor related protein 5/6/dickkopf Wnt signaling pathway inhibitor 1 (associated to Wnt/β-catenin pathway activation) increased in osteoblasts. Yet, they decreased in adipocytes after CH treatments, mainly with the longest hypoxia times. However, the same CH treatments increased the osteoprotegerin/receptor activator for nuclear factor kappa B ligand ratio in both cell types. An increase in total bone mineral density was observed in elderly people exposed to CH, but not in specific regions. The percentage of fat did not vary between groups.

CONCLUSION

CH may have positive effects on bone health in the elderly, due to its possible inhibitory effect on bone resorption, by increasing the osteoprotegerin / receptor activator for nuclear factor kappa B ligand ratio.

JUP/plakoglobin is regulated by salt-inducible kinase 2, and is required for insulin-induced signalling and glucose uptake in adipocytes

BACKGROUND

Salt-inducible kinase 2 (SIK2) is abundant in adipocytes, but downregulated in adipose tissue from individuals with obesity and insulin resistance. Moreover, SIK isoforms are required for normal insulin signalling and glucose uptake in adipocytes, but the underlying molecular mechanisms are currently not known. The adherens junction protein JUP, also termed plakoglobin or γ-catenin, has recently been reported to promote insulin signalling in muscle cells.

OBJECTIVE

The objective of this study was to analyse if JUP is required for insulin signalling in adipocytes and the underlying molecular mechanisms of this regulation.

METHODS

Co-expression of SIK2 and JUP mRNA levels in adipose tissue from a human cohort was analysed. siRNA silencing and/or pharmacological inhibition of SIK2, JUP, class IIa HDACs and CRTC2 was employed in 3T3-L1- and primary rat adipocytes. JUP protein expression was analysed by western blot and mRNA levels by qPCR. Insulin signalling was evaluated by western blot as levels of phosphorylated PKB/Akt and AS160, and by monitoring the uptake of ³H-2-deoxyglucose.

RESULTS

mRNA expression of SIK2 correlated with that of JUP in human adipose tissue. SIK2 inhibition or silencing resulted in downregulation of JUP mRNA and protein expression in 3T3-L1- and in primary rat adipocytes. Moreover, JUP silencing reduced the expression of PKB and the downstream substrate AS160, and consequently attenuated activity in the insulin signalling pathway, including insulin-induced glucose uptake. The known SIK2 substrates CRTC2 and class IIa HDACs were found to play a role in the SIK-mediated regulation of JUP expression.

CONCLUSIONS

These findings identify JUP as a novel player in the regulation of insulin sensitivity in adipocytes, and suggest that changes in JUP expression could contribute to the effect of SIK2 on insulin signalling in these cells.

Wnt/β-catenin signaling regulates adipose tissue lipogenesis and adipocyte-specific loss is rigorously defended by neighboring stromal-vascular cells

OBJECTIVE

Canonical Wnt/β-catenin signaling is a well-studied endogenous regulator of mesenchymal cell fate determination, promoting osteoblastogenesis and inhibiting adipogenesis. However, emerging genetic evidence in humans links a number of Wnt pathway members to body fat distribution, obesity, and metabolic dysfunction, suggesting that this pathway also functions in adipocytes. Recent studies in mice have uncovered compelling evidence that the Wnt signaling pathway plays important roles in adipocyte metabolism, particularly under obesogenic conditions. However, complexities in Wnt signaling and differences in experimental models and approaches have thus far limited our understanding of its specific roles in this context.

METHODS

To investigate roles of the canonical Wnt pathway in the regulation of adipocyte metabolism, we generated adipocyte-specific β-catenin (β-cat) knockout mouse and cultured cell models. We used RNA sequencing, ChIP sequencing, and molecular approaches to assess expression of Wnt targets and lipogenic genes. We then used functional assays to evaluate effects of β-catenin deficiency on adipocyte metabolism, including lipid and carbohydrate handling. In mice maintained on normal chow and high-fat diets, we assessed the cellular and functional consequences of adipocyte-specific β-catenin deletion on adipose tissues and systemic metabolism.

RESULTS

We report that in adipocytes, the canonical Wnt/β-catenin pathway regulates de novo lipogenesis (DNL) and fatty acid monounsaturation. Further, β-catenin mediates effects of Wnt signaling on lipid metabolism in part by transcriptional regulation of Mlxipl and Srebf1. Intriguingly, adipocyte-specific loss of β-catenin is sensed and defended by CD45^-/CD31^- stromal cells to maintain tissue-wide Wnt signaling homeostasis in chow-fed mice. With long-term high-fat diet, this compensatory mechanism is overridden, revealing that β-catenin deletion promotes resistance to diet-induced obesity and adipocyte hypertrophy and subsequent protection from metabolic dysfunction.

CONCLUSIONS

Taken together, our studies demonstrate that Wnt signaling in adipocytes is required for lipogenic gene expression, de novo lipogenesis, and lipid desaturation. In addition, adipose tissues rigorously defend Wnt signaling homeostasis under standard nutritional conditions, such that stromal-vascular cells sense and compensate for adipocyte-specific loss. These findings underscore the critical importance of this pathway in adipocyte lipid metabolism and adipose tissue function.

Wntless regulates lipogenic gene expression in adipocytes and protects against diet-induced metabolic dysfunction

OBJECTIVE

Obesity is a key risk factor for many secondary chronic illnesses, including type 2 diabetes and cardiovascular disease. Canonical Wnt/β-catenin signaling is established as an important endogenous inhibitor of adipogenesis. This pathway is operative in mature adipocytes; however, its roles in this context remain unclear due to complexities of Wnt signaling and differences in experimental models. In this study, we used novel cultured cell and mouse models to investigate functional roles of Wnts secreted from adipocytes.

METHODS

We generated adipocyte-specific Wntless (Wls) knockout mice and cultured cell models to investigate molecular and metabolic consequences of disrupting Wnt secretion from mature adipocytes. To characterize Wls-deficient cultured adipocytes, we evaluated the expression of Wnt target and lipogenic genes and the downstream functional effects on carbohydrate and lipid metabolism. We also investigated the impact of adipocyte-specific Wls deletion on adipose tissues and global glucose metabolism in mice fed normal chow or high-fat diets.

RESULTS

Many aspects of the Wnt signaling apparatus are expressed and operative in mature adipocytes, including the Wnt chaperone Wntless. Deletion of Wntless in cultured adipocytes results in the inhibition of de novo lipogenesis and lipid monounsaturation, likely through repression of Srebf1 (SREBP1c) and Mlxipl (ChREBP) and impaired cleavage of immature SREBP1c into its active form. Adipocyte-specific Wls knockout mice (Wls-/-) have lipogenic gene expression in adipose tissues and isolated adipocytes similar to that of controls when fed a normal chow diet. However, closer investigation reveals that a subset of Wnts and downstream signaling targets are upregulated within stromal-vascular cells of Wls-/- mice, suggesting that adipose tissues defend loss of Wnt secretion from adipocytes. Interestingly, this compensation is lost with long-term high-fat diet challenges. Thus, after six months of a high-fat diet, Wls-/- mice are characterized by decreased adipocyte lipogenic gene expression, reduced visceral adiposity, and improved glucose homeostasis.

CONCLUSIONS

Taken together, these studies demonstrate that adipocyte-derived Wnts regulate de novo lipogenesis and lipid desaturation and coordinate the expression of lipogenic genes in adipose tissues. In addition, we report that Wnt signaling within adipose tissues is defended, such that a loss of Wnt secretion from adipocytes is sensed and compensated for by neighboring stromal-vascular cells. With chronic overnutrition, this compensatory mechanism is lost, revealing that Wls-/- mice are resistant to diet-induced obesity, adipocyte hypertrophy, and metabolic dysfunction.

Analysis of β-catenin association with obesity in African Americans with premalignant and malignant colorectal lesions

BACKGROUND

African Americans (AA) are at high risk for Colorectal Cancer (CRC). Studies report a 30-60% increase in CRC risk with physical inactivity, obesity and metabolic syndrome. Activation of the WNT/β-catenin (CTNNB1) signaling pathway plays a critical role in colorectal carcinogenesis. Accumulating evidence also indicates a role of WNT-CTNNB1 signaling in obesity and metabolic diseases.

AIM

To examine the association between obesity, β-Catenin expression and colonic lesions in African Americans.

METHODS

We reviewed the pathology records of 152 colorectal specimens from 2010 to 2012 (46 CRCs, 74 advanced adenomas and 32 normal colon tissues). Tissue Microarrays (TMA) were constructed from these samples. Immunohistochemistry (IHC) for CTNNB1 (β-Catenin; clone β-Catenin-1) was performed on the constructed TMAs. The IHC results were evaluated by 2 pathologists and the nuclear intensity staining was scored from 0 to 4. BMI, sex, age, location of the lesion and other demographic data were obtained.

RESULTS

Positive nuclear staining in normal, advanced adenoma and CRC was 0, 24 and 41%, respectively (P < 0.001). CRC was asso ciated with positive status for nuclear CTNNB1 intensity (adjusted OR: 3.40, 95%CI = 1.42-8.15, P = 0.006 for positive nuclear staining) compared to non-CRC samples (Normal or advanced adenoma). Nuclear staining percentage has a fair diagnostic ability for CRC with an AUC of 0.63 (95%CI = 0.55-0.71). Overweight/obese patients (BMI > 25) did not show a significant difference in (p = 0.3) nuclear CTNNB1 staining (17% positive in normal weight vs. 27% positive in overweight/obese). The association between nuclear intensity and CRC was not different between normal and overweight patients (P for interaction = 0.6). The positive nuclear CTNNB1status in CRC stage III and IV (35% of all CRC) was not different from stage I and II (50% vs. 36%, respectively, P = 0.4).

CONCLUSION

In our study, advanced adenoma and CRC were associated with activation of β-catenin in physically fit, overweight and obese patients. Thus, obesity and WNT/β-Catenin pathway seem to be independent in African American patients. WNT/β-Catenin signaling pathway has a potential to be used as an effector in colon carcinogenic transformation. Whether or not BMI is a modifier of this pathway needs to be investigated further.

Analysis of β-catenin association with obesity in African Americans with premalignant and malignant colorectal lesions

BACKGROUND

African Americans (AA) are at high risk for Colorectal Cancer (CRC). Studies report a 30-60% increase in CRC risk with physical inactivity, obesity and metabolic syndrome. Activation of the WNT/β-catenin (CTNNB1) signaling pathway plays a critical role in colorectal carcinogenesis. Accumulating evidence also indicates a role of WNT-CTNNB1 signaling in obesity and metabolic diseases.

AIM

To examine the association between obesity, β-Catenin expression and colonic lesions in African Americans.

METHODS

We reviewed the pathology records of 152 colorectal specimens from 2010 to 2012 (46 CRCs, 74 advanced adenomas and 32 normal colon tissues). Tissue Microarrays (TMA) were constructed from these samples. Immunohistochemistry (IHC) for CTNNB1 (β-Catenin; clone β-Catenin-1) was performed on the constructed TMAs. The IHC results were evaluated by 2 pathologists and the nuclear intensity staining was scored from 0 to 4. BMI, sex, age, location of the lesion and other demographic data were obtained.

RESULTS

Positive nuclear staining in normal, advanced adenoma and CRC was 0, 24 and 41%, respectively (P < 0.001). CRC was asso ciated with positive status for nuclear CTNNB1 intensity (adjusted OR: 3.40, 95%CI = 1.42-8.15, P = 0.006 for positive nuclear staining) compared to non-CRC samples (Normal or advanced adenoma). Nuclear staining percentage has a fair diagnostic ability for CRC with an AUC of 0.63 (95%CI = 0.55-0.71). Overweight/obese patients (BMI > 25) did not show a significant difference in (p = 0.3) nuclear CTNNB1 staining (17% positive in normal weight vs. 27% positive in overweight/obese). The association between nuclear intensity and CRC was not different between normal and overweight patients (P for interaction = 0.6). The positive nuclear CTNNB1status in CRC stage III and IV (35% of all CRC) was not different from stage I and II (50% vs. 36%, respectively, P = 0.4).

CONCLUSION

In our study, advanced adenoma and CRC were associated with activation of β-catenin in physically fit, overweight and obese patients. Thus, obesity and WNT/β-Catenin pathway seem to be independent in African American patients. WNT/β-Catenin signaling pathway has a potential to be used as an effector in colon carcinogenic transformation. Whether or not BMI is a modifier of this pathway needs to be investigated further.

Functions of Circular RNAs in Regulating Adipogenesis of Mesenchymal Stem Cells

The mesenchymal stem cells (MSCs) are known as highly plastic stem cells and can differentiate into specialized tissues such as adipose tissue, osseous tissue, muscle tissue, and nervous tissue. The differentiation of mesenchymal stem cells is very important in regenerative medicine. Their differentiation process is regulated by signaling pathways of epigenetic, transcriptional, and posttranscriptional levels. Circular RNA (circRNA), a class of noncoding RNAs generated from protein-coding genes, plays a pivotal regulatory role in many biological processes. Accumulated studies have demonstrated that several circRNAs participate in the cell differentiation process of mesenchymal stem cells in vitro and in vivo. In the current review, characteristics and functions of circRNAs in stem cell differentiation will be discussed. The mechanism and key role of circRNAs in regulating mesenchymal stem cell differentiation, especially adipogenesis, will be reviewed and discussed. Understanding the roles of these circRNAs will present us with a more comprehensive signal path network of modulating stem cell differentiation and help us discover potential biomarkers and therapeutic targets in clinic.

Revealing the Interactions Between Diabetes, Diabetes-Related Diseases, and Cancers Based on the Network Connectivity of Their Related Genes

Diabetes-related diseases (DRDs), especially cancers pose a big threat to public health. Although people have explored pathological pathways of a few common DRDs, there is a lack of systematic studies on important biological processes (BPs) connecting diabetes and its related diseases/cancers. We have proposed and compared 10 protein-protein interaction (PPI)-based computational methods to study the connections between diabetes and 254 diseases, among which a method called DIconnectivity_eDMN performs the best in the sense that it infers a disease rank (according to its relation with diabetes) most consistent with that by literature mining. DIconnectivity_eDMN takes diabetes-related genes, other disease-related genes, a PPI network, and genes in BPs as input. It first maps genes in a BP into the PPI network to construct a BP-related subnetwork, which is expanded (in the whole PPI network) by a random walk with restart (RWR) process to generate a so-called expanded modularized network (eMN). Since the numbers of known disease genes are not high, an RWR process is also performed to generate an expanded disease-related gene list. For each eMN and disease, the expanded diabetes-related genes and disease-related genes are mapped onto the eMN. The association between diabetes and the disease is measured by the reachability of their genes on all eMNs, in which the reachability is estimated by a method similar to the Kolmogorov-Smirnov (KS) test. DIconnectivity_eDMN achieves an area under receiver operating characteristic curve (AUC) of 0.71 for predicting both Type 1 DRDs and Type 2 DRDs. In addition, DIconnectivity_eDMN reveals important BPs connecting diabetes and DRDs. For example, "respiratory system development" and "regulation of mRNA metabolic process" are critical in associating Type 1 diabetes (T1D) and many Type 1 DRDs. It is also found that the average proportion of diabetes-related genes interacting with DRDs is higher than that of non-DRDs.