CREG1 promotes uncoupling protein 1 expression and brown adipogenesis in vitro

A comparative assessment of reference genes in mouse brown adipocyte differentiation and thermogenesis in vitro

Adipogenic differentiation and thermogenesis in brown adipose tissue (BAT) undergo dynamic processes, altering phenotypes and gene expressions. Proper reference genes in gene expression analysis are crucial to mitigate experimental variances and ensure PCR efficacy. Unreliable reference genes can lead to erroneous gene expression quantification, resulting in data misinterpretation. This study focused on identifying suitable reference genes for mouse brown adipocyte research, utilizing brown adipocytes from the Ucp1-luciferase ThermoMouse model. Comparative analysis of gene expression data under adipogenesis and thermogenesis conditions was conducted, validating 13 housekeeping genes through various algorithms, including DeltaCq, BestKeeper, geNorm, Normfinder, and RefFinder. Tbp and Rer1 emerged as optimal references for Ucp1 and Pparg expression in brown adipogenesis, while Tbp and Ubc were ideal for the expression analysis of these target genes in thermogenesis. Conversely, certain conventional references, including Actb, Tubb5, and Gapdh, proved unstable as reference genes under both conditions. These findings stress the critical consideration of reference gene selection in gene expression analysis within specific biological systems to ensure accurate conclusions.

Creg1 Regulates Erythroid Development via TGF-β/Smad2-Klf1 Axis in Zebrafish

Understanding the regulation of normal erythroid development will help to develop new potential therapeutic strategies for disorders of the erythroid lineage. Cellular repressor of E1A-stimulated genes 1 (CREG1) is a glycoprotein that has been implicated in the regulation of tissue homeostasis. However, its role in erythropoiesis remains largely undefined. In this study, it is found that CREG1 expression increases progressively during erythroid differentiation. In zebrafish, creg1 mRNA is preferentially expressed within the intermediate cell mass (ICM)/peripheral blood island (PBI) region where primitive erythropoiesis occurs. Loss of creg1 leads to anemia caused by defective erythroid differentiation and excessive apoptosis of erythroid progenitors. Mechanistically, creg1 deficiency results in reduced activation of TGF-β/Smad2 signaling pathway. Treatment with an agonist of the Smad2 pathway (IDE2) could significantly restore the defective erythroid development in creg1-/- mutants. Further, Klf1, identified as a key target gene downstream of the TGF-β/Smad2 signaling pathway, is involved in creg1 deficiency-induced aberrant erythropoiesis. Thus, this study reveals a previously unrecognized role for Creg1 as a critical regulator of erythropoiesis, mediated at least in part by the TGF-β/Smad2-Klf1 axis. This finding may contribute to the understanding of normal erythropoiesis and the pathogenesis of erythroid disorders.

Molecular targets for management of diabetes: Remodelling of white adipose to brown adipose tissue

Diabetes mellitus is a disorder characterised metabolic dysfunction that results in elevated glucose level in the bloodstream. Diabetes is of two types, type1 and type 2 diabetes. Obesity is considered as one of the major reasons intended for incidence of diabetes hence it turns out to be essential to study about the adipose tissue which is responsible for fat storage in body. Adipose tissues play significant role in maintaining the balance between energy stabilization and homeostasis. The three forms of adipose tissue are - White adipose tissue (WAT), Brown adipose tissue (BAT) and Beige adipose tissue (intermediate form). The amount of BAT gets reduced, and WAT starts to increase with the age. WAT when exposed to certain stimuli gets converted to BAT by the help of certain transcriptional regulators. The browning of WAT has been a matter of study to treat the metabolic disorders and to initiate the expenditure of energy. The three main regulators responsible for the browning of WAT are PRDM16, PPARγ and PGC-1α via various cellular and molecular mechanism. Presented review article includes the detailed elaborative aspect of genes and proteins involved in conversion of WAT to BAT.

Pleurotus abieticola Polysaccharide Alleviates Hyperlipidemia Symptoms via Inhibition of Nuclear Factor-κB/Signal Transducer and Activator of Transcription 3-Mediated Inflammatory Responses

Hyperlipidemia (HLP) is a metabolic syndrome induced by obesity, which has been widely recognized as a significant threat to human health. Pleurotus abieticola, an edible lignin-degrading fungus, remains relatively understudied in terms of its bioactivity and medicinal properties. In this study, the lipid-lowering effect of Pleurotus abieticola polysaccharide (PAPS1) was systematically explored in high-fat diet (HFD)-induced HLP mice. The findings demonstrated that the administration of PAPS1 significantly inhibited bodyweight gain, ameliorated blood glucose and lipid levels, reduced fat accumulation, and mitigated hepatic injury in HLP mice. In addition, PAPS1 demonstrated the capability to increase the levels of three distinct fecal metabolites while simultaneously reducing the levels of eight other fecal metabolites in HLP mice. According to biological detection, PAPS1 reduced the hepatic level of reactive oxygen species (ROS) and pro-inflammatory factors, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, -6, -17A, -22, and -23, and increased the expression of anti-inflammatory factor IL-10. Combined with proteomics, Western blot and immunohistochemistry analysis showed that PAPS1 exerted suppressive effects on inflammation and oxidative damage by inhibiting the nuclear factor-κB (NF-κB)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in HLP mice. These findings offer evidence supporting the effectiveness of PAPS1 as a therapeutic agent in reducing lipid levels through its targeting of chronic inflammation.

Bidirectional effect of vitamin D on brown adipogenesis of C3H10T1/2 fibroblast-like cells

Background

Brown adipose tissue (BAT) dissipates caloric energy as heat and plays a role in glucose and lipid metabolism. Therefore, augmentation and activation of BAT are the focus of new treatment strategies against obesity, a primary risk factor of metabolic syndrome. The vitamin D system plays a crucial role in mineral homeostasis, bone metabolism, and cell proliferation and differentiation. In this study, we investigated the effects of vitamin D₃ [1,25(OH)₂D₃] on brown adipocyte differentiation.

Methods

The mouse fibroblast-like cell line C3H10T1/2 was differentiated into brown adipocytes in the presence of 1,25(OH)₂D₃. The effect of 1,25(OH)₂D₃ on brown adipocyte differentiation was assessed by measuring lipid accumulation, the expression of related genes, and cytotoxicity. The viability of C3H10T1/2 cells was measured using the Cell Counting Kit-8 assay. Gene expression was investigated using quantitative reverse transcription-polymerase chain reaction. Protein expression was estimated using western blotting.

Results

1,25(OH)₂D₃ inhibited adipocyte differentiation and exerted a cytotoxic effect at 1 nM. However, in the physiological concentration range (50-250 pM), 1,25(OH)₂D₃ promoted uncoupling protein 1 (UCP1) expression in C3H10T1/2 cells. This effect was not observed when 1,25(OH)₂D₃ was added 48 h after the initiation of differentiation, suggesting that the vitamin D system acts in the early phase of the differentiation program. We showed that 1,25(OH)₂D₃ increased the expression of two key regulators of brown adipogenesis, PR domain containing 16 (Prdm16) and peroxisome proliferator-activated receptor γ coactivator-1α (Pgc1α ). Furthermore, 1,25(OH)₂D₃ increased Ucp1 expression in 3T3-L1 beige adipogenesis in a dose-dependent manner.

Conclusion

These data indicate the potential of vitamin D and its analogs as therapeutics for the treatment of obesity and related metabolic diseases.

CREG1 stimulates AMPK phosphorylation and glucose uptake in skeletal muscle cells

The cellular repressor of adenovirus early region 1A-stimulated gene 1 (CREG1) is a secreted glycoprotein involved in cell differentiation and energy metabolism. It also binds to insulin-like growth factor 2 receptor (IGF2R), a protein implicated in muscle regeneration. However, whether CREG1 regulates the regeneration and metabolism of skeletal muscles via IGF2R remains unclear. This study investigates the role of CREG1 in skeletal muscle regeneration and glucose uptake in C2C12 myotubes and a cardiotoxin (CTX)-induced mouse skeletal muscle regeneration model. CTX-treated skeletal muscle showed significantly higher levels of IGF2R, CREG1, phospho-AMPKα Thr¹⁷², and GLUT4 proteins. Similarly, treatment of myotubes with CREG1 also stimulated AMPKα phosphorylation and GLUT4 expression. CREG1-induced AMPKα phosphorylation and 2DG uptake in myotubes were suppressed by IGF2R knockdown and Compound C, an AMPK inhibitor. These results suggest that CREG1 stimulates glucose uptake in skeletal muscles partially through AMPK activation. Hence, CREG1 plays an essential role in muscle regeneration by affecting glucose metabolism in skeletal muscles.

CREG1 improves diet-induced obesity via uncoupling protein 1-dependent manner in mice

Thermogenic brown and beige adipocytes express uncoupling protein 1 (UCP1) and stimulate energy metabolism, protecting against obesity and metabolic diseases such as type 2 diabetes and hyperlipidemia. Cellular repressor of E1A-stimulated genes 1 (CREG1) can stimulate thermogenic fat formation, induce UCP1, and reduce diet-induced obesity (DIO) in mice at normal room temperature. In this study, we investigated the effect of CREG1 administration and the importance of UCP1 in DIO inhibition under thermoneutral conditions at 30°C, which attenuate thermogenic fat formation. Interestingly, subcutaneous administration of recombinant CREG1 protein via an osmotic pump in C57BL/6J mice for four weeks increased UCP1 expression in interscapular brown adipose tissue (IBAT), inhibited visceral white fat hypertrophy with partial browning, and reduced DIO compared with that in PBS-treated mice. The mRNA expression of energy metabolism-related genes was significantly increased in the IBAT of CREG1-treated mice compared to that in PBS-treated mice. In contrast, adipocyte-specific overexpression of CREG1 failed to improve DIO in UCP1-knockout mice at thermoneutrality. Our results indicate the therapeutic potential of CREG1 administration for obesity under thermogenic fat-attenuating conditions and highlight the indispensable role of UCP1 in the DIO-inhibitory effect of CREG1.

CREG1 administration stimulates BAT thermogenesis and improves diet-induced obesity in mice

Brown and beige adipocytes, which express thermogenic uncoupling protein-1 (UCP1), stimulate glucose and lipid metabolism, improving obesity and metabolic diseases such as type 2 diabetes and hyperlipidemia. Overexpression of cellular repressor of E1A-stimulated genes 1 (CREG1) promotes adipose tissue browning and inhibits diet-induced obesity (DIO) in mice. In this study, we investigated the effects of CREG1 administration on DIO inhibition and adipose browning. Subcutaneous administration of recombinant CREG1 protein to C57BL/6 mice stimulated UCP1 expression in interscapular brown adipose tissue (IBAT) and improved DIO, glucose tolerance, and fatty liver compared with those in PBS-treated mice. Injection of Creg1-expressing adenovirus into inguinal white adipose tissue (IWAT) significantly increased browning and mRNA expression of beige adipocyte marker genes compared with that in mice injected with control virus. The effect of Creg1 induction on beige adipocyte differentiation was supported in primary culture using preadipocytes isolated from IWAT of Creg1-transgenic mice compared with that of wild-type mice. Our results indicate a therapeutic effect of CREG1 on obesity and its associated pathology and a potential of CREG1 to stimulate brown/beige adipocyte formation.

A novel function of CREG in metabolic disorders

Metabolic disorders are public health problems that require prevention and new efficient drugs for treatment. Cellular repressor of E1A-stimulated genes (CREG) is ubiquitously expressed in mature tissues and cells in mammals and plays a critical role in keeping cells or tissues in a mature, homeostatic state. Recently, CREG turns to be an important mediator in the development of metabolic disorders. Here in this review, we briefly discuss the structure and molecular regulation of CREG along with the therapeutic strategy to combat the metabolic disorders.

CREG1 promotes lysosomal biogenesis and function

CREG1 is a small glycoprotein which has been proposed as a transcription repressor, a secretory ligand, a lysosomal, or a mitochondrial protein. This is largely because of lack of antibodies for immunolocalization validated through gain- and loss-of-function studies. In the present study, we demonstrate, using antibodies validated for immunofluorescence microscopy, that CREG1 is mainly localized to the endosomal-lysosomal compartment. Gain- and loss-of-function analyses reveal an important role for CREG1 in both macropinocytosis and clathrin-dependent endocytosis. CREG1 also promotes acidification of the endosomal-lysosomal compartment and increases lysosomal biogenesis. Functionally, overexpression of CREG1 enhances macroautophagy/autophagy and lysosome-mediated degradation, whereas knockdown or knockout of CREG1 has opposite effects. The function of CREG1 in lysosomal biogenesis is likely attributable to enhanced endocytic trafficking. Our results demonstrate that CREG1 is an endosomal-lysosomal protein implicated in endocytic trafficking and lysosomal biogenesis.Abbreviations: AIFM1/AIF: apoptosis inducing factor mitochondria associated 1; AO: acridine orange; ATP6V1H: ATPase H+ transporting V1 subunit H; CALR: calreticulin; CREG: cellular repressor of E1A stimulated genes; CTSC: cathepsin C; CTSD: cathepsin D; EBAG9/RCAS1: estrogen receptor binding site associated antigen 9; EIPA: 5-(N-ethyl-N-isopropyl)amiloride; ER: endoplasmic reticulum; GFP: green fluorescent protein; HEXA: hexosaminidase subunit alpha; IGF2R: insulin like growth factor 2 receptor; LAMP1: lysosomal associated membrane protein 1; M6PR: mannose-6-phosphate receptor, cation dependent; MAPK1/ERK2: mitogen-activated protein kinase 1; MTORC1: mechanistic target of rapamycin kinase complex 1; PDIA2: protein disulfide isomerase family A member 2; SQSTM1/p62: sequestosome 1; TF: transferrin; TFEB: transcription factor EB.

Effects of CREG1 on Age-Associated Metabolic Phenotypes and Renal Senescence in Mice

Cellular repressor of E1A-stimulated genes 1 (CREG1) is a secreted glycoprotein that accelerates p16-dependent cellular senescence in vitro. We recently reported the ability of CREG1 to stimulate brown adipogenesis using adipocyte P2-CREG1-transgenic (Tg) mice; however, little is known about the effect of CREG1 on aging-associated phenotypes. In this study, we investigated the effects of CREG1 on age-related obesity and renal dysfunction in Tg mice. Increased brown fat formation was detected in aged Tg mice, in which age-associated metabolic phenotypes such as body weight gain and increases in blood glucose were improved compared with those in wild-type (WT) mice. Blood CREG1 levels increased significantly in WT mice with age, whereas the age-related increase was suppressed, and its levels were reduced, in the livers and kidneys of Tg mice relative to those in WT mice at 25 months. Intriguingly, the mRNA levels of Ink4a, Arf, and senescence-associated secretory phenotype (SASP)-related genes and p38MAPK activity were significantly lowered in the aged kidneys of Tg mice, in which the morphological abnormalities of glomeruli as well as filtering function seen in WT kidneys were alleviated. These results suggest the involvement of CREG1 in kidney aging and its potential as a target for improving age-related renal dysfunction.

Strawberry (Fragaria × ananassa cv. Romina) methanolic extract promotes browning in 3T3-L1 cells

In recent years, the conversion of white adipocytes to brown-like adipocytes by pharmacological and dietary compounds has gained attention as an effective strategy to fight obesity. Strawberry bioactive compounds present several biological activities including antioxidant, anti-inflammatory, anti-cancer, anti-atherosclerotic and antiadipogenic properties. However, to the best of our knowledge, the possible role of strawberry bioactive compounds in white adipose tissue (WAT) browning has never been explored. Our results demonstrated that a strawberry methanolic extract (SE) significantly reduced 3T3-L1 pre-adipocytes differentiation, and down-regulated the mRNA expression of the adipogenic transcription factors CCAAT/enhancer-binding protein (C/REB- α) and peroxisome proliferation-activated receptor (PPAR-γ). It also down-regulated the mRNA expression of resistin and angiotensinogen, two genes considered as markers of white adipocytes, while increased the mRNA expression of pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4) and uncoupling protein 1 (UCP1) which, conversely, are brown adipocyte-specific markers. Likewise, SE stimulated AMP-activated protein kinase (AMPKα), sirtuin 1 (Sirt1) and the peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC-1α), suggesting a possible increase in mitochondrial biogenesis. It also stimulated oxygen consumption rate and uncoupled respiration. Taken together, all these results suggest that SE induces brown fat-like phenotype in 3T3-L1 cells and may have potential therapeutic implications for treatment and/or prevention of obesity.

Murine in vitro cellular models to better understand adipogenesis and its potential applications

Adipogenesis has been extensively studied using in vitro models of cellular differentiation, enabling long-term regulation of fat cell metabolism in human adipose tissue (AT) material. Many studies promote the idea that manipulation of this process could potentially reduce the prevalence of obesity and its related diseases. It has now become essential to understand the molecular basis of fat cell development to tackle this pandemic disease, by identifying therapeutic targets and new biomarkers. This review explores murine cell models and their applications for study of the adipogenic differentiation process in vitro. We focus on the benefits and limitations of different cell line models to aid in interpreting data and selecting a good cell line model for successful understanding of adipose biology.

The secreted inhibitor of invasive cell growth CREG1 is negatively regulated by cathepsin proteases

Previous clinical and experimental evidence strongly supports a breast cancer-promoting function of the lysosomal protease cathepsin B. However, the cathepsin B-dependent molecular pathways are not completely understood. Here, we studied the cathepsin-mediated secretome changes in the context of the MMTV-PyMT breast cancer mouse model. Employing the cell-conditioned media from tumor-macrophage co-cultures, as well as tumor interstitial fluid obtained by a novel strategy from PyMT mice with differential cathepsin B expression, we identified an important proteolytic and lysosomal signature, highlighting the importance of this organelle and these enzymes in the tumor micro-environment. The Cellular Repressor of E1A Stimulated Genes 1 (CREG1), a secreted endolysosomal glycoprotein, displayed reduced abundance upon over-expression of cathepsin B as well as increased abundance upon cathepsin B deletion or inhibition. Moreover, it was cleaved by cathepsin B in vitro. CREG1 reportedly could act as tumor suppressor. We show that treatment of PyMT tumor cells with recombinant CREG1 reduced proliferation, migration, and invasion; whereas, the opposite was observed with reduced CREG1 expression. This was further validated in vivo by orthotopic transplantation. Our study highlights CREG1 as a key player in tumor–stroma interaction and suggests that cathepsin B sustains malignant cell behavior by reducing the levels of the growth suppressor CREG1 in the tumor microenvironment.

Lack of UCP1 stimulates fatty liver but mediates UCP1-independent action of beige fat to improve hyperlipidemia in Apoe knockout mice

Brown adipose tissue (BAT) plays a critical role in lipid metabolism and may protect from hyperlipidemia; however, its beneficial effect appears to depend on the ambient temperature of the environment. In this study, we investigated the effects of uncoupling protein 1 (UCP1) deficiency on lipid metabolism, including the pathophysiology of hyperlipidemia, in apolipoprotein E knockout (APOE-KO) mice at a normal (23 °C) and thermoneutral (30 °C) temperature. Unexpectedly, UCP1 deficiency caused improvements in hyperlipidemia, atherosclerosis, and glucose metabolism, regardless of an increase in hepatic lipid deposition, in Ucp1/Apoe double-knockout (DKO) mice fed a high-fat diet at 23 °C, with BAT hyperplasia and robust browning of inguinal white adipose tissue (IWAT) observed. Proteomics and gene expression analyses revealed significant increases in many proteins involved in energy metabolism and strong upregulation of brown/beige adipocyte-related genes and fatty acid metabolism-related genes in browned IWAT, suggesting an induction of beige fat formation and stimulation of lipid metabolism in DKO mice at 23 °C. Conversely, mRNA levels of fatty acid oxidation-related genes decreased in the liver of DKO mice. The favorable phenotypic changes were lost at 30 °C, with BAT whitening and disappearance of IWAT browning, while fatty liver further deteriorated in DKO mice compared with that in APOE-KO mice. Finally, longevity analysis revealed a significant lifespan extension of DKO mice compared with that of APOE-KO mice at 23 °C. Irrespective of the fundamental role of UCP1 thermogenesis, our results highlight the importance of beige fat for the improvement of hyperlipidemia and longevity under the atherogenic status at normal room temperature.

Lyophilized Maqui (Aristotelia chilensis) Berry Induces Browning in the Subcutaneous White Adipose Tissue and Ameliorates the Insulin Resistance in High Fat Diet-Induced Obese Mice

Maqui (Aristotelia Chilensis) berry features a unique profile of anthocyanidins that includes high amounts of delphinidin-3-O-sambubioside-5-O-glucoside and delphinidin-3-O-sambubioside and has shown positive effects on fasting glucose and insulin levels in humans and murine models of type 2 diabetes and obesity. The molecular mechanisms underlying the impact of maqui on the onset and development of the obese phenotype and insulin resistance was investigated in high fat diet-induced obese mice supplemented with a lyophilized maqui berry. Maqui-dietary supplemented animals showed better insulin response and decreased weight gain but also a differential expression of genes involved in de novo lipogenesis, fatty acid oxidation, multilocular lipid droplet formation and thermogenesis in subcutaneous white adipose tissue (scWAT). These changes correlated with an increased expression of the carbohydrate response element binding protein b (Chrebpb), the sterol regulatory binding protein 1c (Srebp1c) and Cellular repressor of adenovirus early region 1A-stimulated genes 1 (Creg1) and an improvement in the fibroblast growth factor 21 (FGF21) signaling. Our evidence suggests that maqui dietary supplementation activates the induction of fuel storage and thermogenesis characteristic of a brown-like phenotype in scWAT and counteracts the unhealthy metabolic impact of an HFD. This induction constitutes a putative strategy to prevent/treat diet-induced obesity and its associated comorbidities.

CREG1 stimulates brown adipocyte formation and ameliorates diet-induced obesity in mice

Increased formation of brown and beige adipocytes is critical for adaptive thermogenesis to maintain homeothermy in cold or to circumvent diet-induced obesity (DIO). Cellular repressor of adenovirus early region 1A-stimulated genes 1 (CREG1) exhibits the ability to stimulate brown adipogenesis, including the induction of uncoupling protein 1 (UCP1), in vitro. Thus, we aimed to clarify whether CREG1 promotes brown adipocyte formation and inhibits DIO at the whole-animal level. In mouse brown adipose tissue (BAT), CREG1 expression was markedly increased in cold but was decreased under thermoneutrality, suggesting CREG1 involvement in BAT thermogenesis. Moreover, in BAT and white adipose tissue, expression of UCP1 and fibroblast growth factor-21 and browning were both significantly higher in adipocyte P2-Creg1-transgenic (Tg) mice than in wild-type (WT) littermates. Following stimulation with a β3-adrenergic agonist, energy consumption was elevated in the Tg mice, which showed increased resistance to DIO and improvement of obesity-associated complications including fatty liver relative to WT mice. The CREG1 stimulatory effect on brown adipogenesis was confirmed in Tg-BAT primary cultures. It was also found that CREG1 binds to retinoid X receptor α, which interacts with thyroid hormone receptor for brown adipogenesis. Our findings demonstrate that CREG1 stimulates brown adipocyte formation and browning, ameliorating obesity and its related pathology in vivo.-Hashimoto, M., Kusudo, T., Takeuchi, T., Kataoka, N., Mukai, T., Yamashita, H. CREG1 stimulates brown adipocyte formation and ameliorates diet-induced obesity in mice.