FGF6 and FGF9 regulate UCP1 expression independent of brown adipogenesis

Identification of key genes regulating brown adipose tissue thermogenesis in goat kids (Capra hircus) by using weighted gene co-expression network analysis

Brown adipose tissue (BAT) is crucial for the maintenance of body temperature in newborn animals through non-shivering thermogenesis (NST). However, which kind key genes involved in the regulation of BAT thermogenesis and the internal regulation mechanism of heat production in goat BAT were still unclear. In this study, we analyzed the perirenal adipose tissue transcriptome of Dazu black goats from 0, 7, 14, 21 and 28 days after birth using weighted gene co-expression network analysis (WGCNA) to identify key genes involved in the thermogenesis of BAT. Genes were classified into 22 co-expression modules by WGCNA. The turquoise module exhibited high gene expression in D0, with generally lower expression in the later dates. This pattern is consistent with the rapid color, morphological, and thermogenic changes observed in perirenal adipose tissue shortly after birth. GO functional annotation revealed that the genes in the turquoise module were significantly enriched in the mitochondrion, mitochondrial protein-containing complex, cytoplasm, and mitochondrial inner membrane. KEGG pathway enrichment analysis indicated that these genes were predominantly enriched in the signaling pathways of oxidative phosphorylation, thermogenesis, and TCA cycle. By combining the gene co-expression network analysis of the turquoise module genes and the differentially expression genes (DEG) analysis, we identified 5 candidate key genes (ACO2, MRPS27, IMMT, MRPL12, and TUFM) involved in regulation of perirenal adipose tissue thermogenesis. This finding offer candidate genes that in the regulation of BAT thermogenesis and body temperature maintenance in goat kids.

FGF-based drug discovery: advances and challenges

The fibroblast growth factor (FGF) family comprises 15 paracrine-acting and 3 endocrine-acting polypeptides, which govern a multitude of processes in human development, metabolism and tissue homeostasis. Therapeutic endocrine FGFs have recently advanced in clinical trials, with FGF19 and FGF21-based therapies on the cusp of approval for the treatment of primary sclerosing cholangitis and metabolic syndrome-associated steatohepatitis, respectively. By contrast, while paracrine FGFs were once thought to be promising drug candidates for wound healing, burns, tissue repair and ischaemic ailments based on their potent mitogenic and angiogenic properties, repeated failures in clinical trials have led to the widespread perception that the development of paracrine FGF-based drugs is not feasible. However, the observation that paracrine FGFs can exert FGF hormone-like metabolic activities has restored interest in these FGFs. The recent structural elucidation of the FGF cell surface signalling machinery and the formulation of a new threshold model for FGF signalling specificity have paved the way for therapeutically harnessing paracrine FGFs for the treatment of a range of metabolic diseases.

The GIP receptor activates futile calcium cycling in white adipose tissue to increase energy expenditure and drive weight loss in mice

Obesity is a chronic disease that contributes to the development of insulin resistance, type 2 diabetes (T2D), and cardiovascular risk. Glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) and glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) co-agonism provide an improved therapeutic profile in individuals with T2D and obesity when compared with selective GLP-1R agonism. Although the metabolic benefits of GLP-1R agonism are established, whether GIPR activation impacts weight loss through peripheral mechanisms is yet to be fully defined. Here, we generated a mouse model of GIPR induction exclusively in the adipocyte. We show that GIPR induction in the fat cell protects mice from diet-induced obesity and triggers profound weight loss (∼35%) in an obese setting. Adipose GIPR further increases lipid oxidation, thermogenesis, and energy expenditure. Mechanistically, we demonstrate that GIPR induction activates SERCA-mediated futile calcium cycling in the adipocyte. GIPR activation further triggers a metabolic memory effect, which maintains weight loss after the transgene has been switched off, highlighting a unique aspect in adipocyte biology. Collectively, we present a mechanism of peripheral GIPR action in adipose tissue, which exerts beneficial metabolic effects on body weight and energy balance.

Crosstalk between fat tissue and muscle, brain, liver, and heart in obesity: cellular and molecular perspectives

A high-fat diet and physical inactivity are key contributors to obesity, predisposing individuals to various chronic diseases, such as cardiovascular disease and diabetes, which involve multiple organs and tissues. To better understand the role of multi-organ interaction mechanisms in the rising incidence of obesity and its associated chronic conditions, treatment and prevention strategies are being extensively investigated. This review examines the signaling mechanisms between different tissues and organs, with a particular focus on the crosstalk between adipose tissue and the muscle, brain, liver, and heart, and potentially offers new strategies for the treatment and management of obesity and its complications.

Spop deficiency impairs adipogenesis and promotes thermogenic capacity in mice

As the adaptor protein that determines substrate specificity of the Cul3-SPOP-Rbx1 E3 ligase complex, SPOP is involved in numerous biological processes. However, its physiological connections with adipogenesis and thermogenesis remain poorly understood. In the current study, we report that the conditional knockout of Spop in mice results in substantial changes in protein expression, including the upregulation of a critical factor associated with thermogenesis, UCP1. Loss of SPOP also led to defects in body weight gain. In addition, conditional knockout mice exhibited resistance to high-fat-diet-induced obesity. Proteomics analysis found that proteins upregulated in the knockout mice are primarily enriched for functions in glycolysis/gluconeogenesis, oxidative phosphorylation, and thermogenesis. Furthermore, Spop knockout mice were more resilient during cold tolerance assay compared with the wild-type controls. Finally, the knockout of SPOP efficiently impaired adipogenesis in primary preadipocytes and the expression of associated genes. Collectively, these findings demonstrate the critical roles of SPOP in regulating adipogenesis and thermogenic capacity in mice.

Population structure and selective signature analysis of local sheep breeds in Xinjiang, China based on high-density SNP chip

The frigid and droughty climate of Xinjiang in China has given rise to unique indigenous sheep breeds with robust adaptability and resistance. To investigate the genetic mechanism of adaptability of Xinjiang sheep to the local extreme environment, we conducted population genetic structure analyses for three native Xinjiang sheep breeds: Altay sheep (ALT), Bashbay Sheep (BSBC), and Duolang sheep (DLC), as well as two foreign sheep breeds: Suffolk and Dorset, using the Ovine Infinium HD SNP BeadChip(680 K). Our findings revealed distinct genetic and evolutionary histories between Xinjiang and foreign sheep breeds. Principal Component Analysis (PCA) and phylogenetic tree effectively differentiate these five sheep breeds based on their geographical origins, and the domestication level of Xinjiang sheep is comparatively lower than that of foreign sheep breeds. Furthermore, by utilizing three selective signature methods, namely Fixation Index (Fst), Cross Population Extended Haplotype Homozygosity Test (XP-EHH), and Nucleotide Diversity (π), we have successfully identified 22 potential candidate genes. Among these genes, there are TBXT, PDGFD, and VEGFA, which are closely related to tail type and lipid metabolism; VIL1, SLC11A1, and ZBTB46, which are associated with immune function; and candidate genes such as BNC1, HDAC1, and BMP5, which impact sheep reproductive traits. This study establishes a foundation for conserving and utilizing local sheep germplasm resources in Xinjiang and provides molecular insights into the genetic mechanisms governing sheep adaptation to extreme cold and arid environments.

m6A mRNA methylation in brown fat regulates systemic insulin sensitivity via an inter-organ prostaglandin signaling axis independent of UCP1

Brown adipose tissue (BAT) regulates systemic metabolism by releasing signaling lipids. N6-methyladenosine (m6A) is the most prevalent and abundant post-transcriptional mRNA modification and has been reported to regulate BAT adipogenesis and energy expenditure. Here, we demonstrate that the absence of m6A methyltransferase-like 14 (METTL14) modifies the BAT secretome to improve systemic insulin sensitivity independent of UCP1. Using lipidomics, we identify prostaglandin E2 (PGE2) and prostaglandin F2a (PGF2a) as BAT-secreted insulin sensitizers. PGE2 and PGF2a inversely correlate with insulin sensitivity in humans and protect mice from high-fat-diet-induced insulin resistance by suppressing specific AKT phosphatases. Mechanistically, METTL14-mediated m6A promotes the decay of PTGES2 and CBR1, the genes encoding PGE2 and PGF2a biosynthesis enzymes, in brown adipocytes via YTHDF2/3. Consistently, BAT-specific knockdown of Ptges2 or Cbr1 reverses the insulin-sensitizing effects in M14KO mice. Overall, these findings reveal a novel biological mechanism through which m6A-dependent regulation of the BAT secretome regulates systemic insulin sensitivity.

Slit3 Fragments Orchestrate Neurovascular Expansion and Thermogenesis in Brown Adipose Tissue

Brown adipose tissue (BAT) represents an evolutionary innovation enabling placental mammals to regulate body temperature through adaptive thermogenesis. Brown adipocytes are surrounded by a dense network of blood vessels and sympathetic nerves that support their development and thermogenic function. Cold exposure stimulates BAT thermogenesis through the coordinated induction of brown adipogenesis, angiogenesis, and sympathetic innervation. However, how these distinct processes are coordinated remains unclear. Here, we identify Slit guidance ligand 3 (Slit3) as a new niche factor that mediates the crosstalk among adipocyte progenitors, endothelial cells, and sympathetic nerves. We show that adipocyte progenitors secrete Slit3 which regulates both angiogenesis and sympathetic innervation in BAT and is essential for BAT thermogenesis in vivo. Proteolytic cleavage of Slit3 generates secreted Slit3-N and Slit3-C fragments, which activate distinct receptors to stimulate angiogenesis and sympathetic innervation, respectively. Moreover, we introduce bone morphogenetic protein-1 (Bmp1) as the first Slit protease identified in vertebrates. In summary, this study underscores the essential role of Slit3-mediated neurovascular network expansion in enabling cold-induced BAT adaptation. The co-regulation of neurovascular expansion by Slit3 fragments provides a bifurcated yet harmonized approach to ensure a synchronized response of BAT to environmental challenges. This study presents the first evidence that adipocyte progenitors regulate tissue innervation, revealing a previously unrecognized dimension of cellular interaction within adipose tissue.

Exerkines: Benign adaptation for exercise and benefits for non-alcoholic fatty liver disease

Exercise has multiple beneficial effects on human metabolic health and is regarded as a "polypill" for various diseases. At present, the lack of physical activity usually causes an epidemic of chronic metabolic syndromes, including obesity, cardiovascular diseases, and non-alcoholic fatty liver disease (NAFLD). Remarkably, NAFLD is emerging as a serious public health issue and is associated with the development of cirrhosis and hepatocellular carcinoma. Unfortunately, specific drug therapies for NAFLD and its more severe form, non-alcoholic steatohepatitis (NASH), are currently unavailable. Lifestyle modification is the foundation of treatment recommendations for NAFLD and NASH, especially for exercise. There are under-appreciated organs that crosstalk to the liver during exercise such as muscle-liver crosstalk. Previous studies have reported that certain exerkines, such as FGF21, GDF15, irisin, and adiponectin, are beneficial for liver metabolism and have the potential to be targeted for NAFLD treatment. In addition, some of exerkines can be modified for the new proteins and get enhanced functions, like IL-6/IC7Fc. Another importance of exercise is the physiological adaptation that combats metabolic diseases. Thus, this review aims to summarize the known exerkines and utilize a multi-omics mining tool to identify more exerkines for the future research. Overall, understanding the mechanisms by which exercise-induced exerkines exert their beneficial effects on metabolic health holds promise for the development of novel therapeutic strategies for NAFLD and related diseases.

The fundamentals of fibroblast growth factor 9

Fibroblast growth factor 9 (FGF9) was first identified during a screen for factors acting on cells of the central nervous system (CNS). Research over the subsequent two decades has revealed this protein to be a critically important and elegantly regulated growth factor. A hallmark control feature is reciprocal compartmentalization, particularly during development, with epithelium as a dominant source and mesenchyme a prime target. This mesenchyme selectivity is accomplished by the high affinity of FGF9 to the IIIc isoforms of FGFR1, 2, and 3. FGF9 is expressed widely in the embryo, including the developing heart and lungs, and more selectively in the adult, including the CNS and kidneys. Global Fgf9-null mice die shortly after birth due to respiratory failure from hypoplastic lungs. As well, their hearts are dilated and poorly vascularized, the skeleton is small, the intestine is shortened, and male-to-female sex reversal can be found. Conditional Fgf9-null mice have revealed CNS phenotypes, including ataxia and epilepsy. In humans, FGF9 variants have been found to underlie multiple synostoses syndrome 3, a syndrome characterized by multiple joint fusions. Aberrant FGF9 signaling has also been implicated in differences of sex development and cancer, whereas vascular stabilizing effects of FGF9 could benefit chronic diseases. This primer reviews the attributes of this vital growth factor.

Genome-Wide Association Study of Conformation Traits in Brazilian Holstein Cattle

The linear conformation of animals exerts an influence on health, reproduction, production, and welfare, in addition to longevity, which directly affects the profitability of milk-producing farms. The objectives of this study were (1) to perform genome-wide association studies (GWASs) of conformation traits, namely the Rump, Feet and Legs, Mammary System, Dairy Strength, and Final Classification traits, and (2) to identify genes and related pathways involved in physiological processes associated with conformation traits in Brazilian Holstein cattle. Phenotypic and genotypic data from 2339 Holstein animals distributed across the states of Rio Grande do Sul, Paraná, São Paulo, and Minas Gerais were used. The genotypic data were obtained with a 100 K SNP marker panel. The single-step genome-wide association study (ssGWAS) method was employed in the analyses. Genes close to a significant SNP were identified in an interval of 100 kb up- and downstream using the Ensembl database available in the BioMart tool. The DAVID database was used to identify the main metabolic pathways and the STRING program was employed to create the gene regulatory network. In total, 36 significant SNPs were found on 15 chromosomes; 27 of these SNPs were linked to genes that may influence the traits studied. Fourteen genes most closely related to the studied traits were identified, as well as four genes that showed interactions in important metabolic pathways such as myogenesis, adipogenesis, and angiogenesis. Among the total genes, four were associated with myogenesis (TMOD2, TMOD3, CCND2, and CTBP2), three with angiogenesis (FGF23, FGF1, and SCG3), and four with adipogenesis and body size and development (C5H12orf4, CCND2, EMILIN1, and FGF6). These results contribute to a better understanding of the biological mechanisms underlying phenotypic variability in conformation traits in Brazilian Holstein cattle.

Fgf9 regulates bone marrow mesenchymal stem cell fate and bone-fat balance in osteoporosis by PI3K/AKT/Hippo and MEK/ERK signaling

Bone-fat balance is crucial to maintain bone homeostasis. As common progenitor cells of osteoblasts and adipocytes, bone marrow mesenchymal stem cells (BMSCs) are delicately balanced for their differentiation commitment. However, the exact mechanisms governing BMSC cell fate are unclear. In this study, we discovered that fibroblast growth factor 9 (Fgf9), a cytokine expressed in the bone marrow niche, controlled bone-fat balance by influencing the cell fate of BMSCs. Histomorphology and cytodifferentiation analysis showed that Fgf9 loss-of-function mutation (S99N) notably inhibited bone marrow adipose tissue (BMAT) formation and alleviated ovariectomy-induced bone loss and BMAT accumulation in adult mice. Furthermore, in vitro and in vivo investigations demonstrated that Fgf9 altered the differentiation potential of BMSCs, shifting from osteogenesis to adipogenesis at the early stages of cell commitment. Transcriptomic and gene expression analyses demonstrated that FGF9 upregulated the expression of adipogenic genes while downregulating osteogenic gene expression at both mRNA and protein levels. Mechanistic studies revealed that FGF9, through FGFR1, promoted adipogenic gene expression via PI3K/AKT/Hippo pathways and inhibited osteogenic gene expression via MAPK/ERK pathway. This study underscores the crucial role of Fgf9 as a cytokine regulating the bone-fat balance in adult bone, suggesting that FGF9 is a potentially therapeutic target in the treatment of osteoporosis.

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.

Roles of fibroblast growth factors in the treatment of diabetes

Diabetes affects about 422 million people worldwide, causing 1.5 million deaths each year. However, the incidence of diabetes is increasing, including several types of diabetes. Type 1 diabetes (5%-10% of diabetic cases) and type 2 diabetes (90%-95% of diabetic cases) are the main types of diabetes in the clinic. Accumulating evidence shows that the fibroblast growth factor (FGF) family plays important roles in many metabolic disorders, including type 1 and type 2 diabetes. FGF consists of 23 family members (FGF-1-23) in humans. Here, we review current findings of FGFs in the treatment of diabetes and management of diabetic complications. Some FGFs (e.g., FGF-15, FGF-19, and FGF-21) have been broadly investigated in preclinical studies for the diagnosis and treatment of diabetes, and their therapeutic roles in diabetes are currently under investigation in clinical trials. Overall, the roles of FGFs in diabetes and diabetic complications are involved in numerous processes. First, FGF intervention can prevent high-fat diet-induced obesity and insulin resistance and reduce the levels of fasting blood glucose and triglycerides by regulating lipolysis in adipose tissues and hepatic glucose production. Second, modulation of FGF expression can inhibit renal and cardiac fibrosis by regulating the expression of extracellular matrix components, promote diabetic wound healing process and bone repair, and inhibit cancer cell proliferation and migration. Finally, FGFs can regulate the activation of glucose-excited neurons and the expression of thermogenic genes.

Transplantation of committed pre-adipocytes from brown adipose tissue improves whole-body glucose homeostasis

Obesity and its co-morbidities including type 2 diabetes are increasing at epidemic rates in the U.S. and worldwide. Brown adipose tissue (BAT) is a potential therapeutic to combat obesity and type 2 diabetes. Increasing BAT mass by transplantation improves metabolic health in rodents, but its clinical translation remains a challenge. Here, we investigated if transplantation of 2-4 million differentiated brown pre-adipocytes from mouse BAT stromal fraction (SVF) or human pluripotent stem cells (hPSCs) could improve metabolic health. Transplantation of differentiated brown pre-adipocytes, termed "committed pre-adipocytes" from BAT SVF from mice or derived from hPSCs improves glucose homeostasis and insulin sensitivity in recipient mice under conditions of diet-induced obesity, and this improvement is mediated through the collaborative actions of the liver transcriptome, tissue AKT signaling, and FGF21. These data demonstrate that transplantation of a small number of brown adipocytes has significant long-term translational and therapeutic potential to improve glucose metabolism.

Hydroxy-α-sanshool from the fruits of Zanthoxylum bungeanum Maxim. promotes browning of white fat by activating TRPV1 to induce PPAR-γ deacetylation

BACKGROUND

Accumulating evidence suggested increasing energy expenditure is a feasible strategy for combating obesity, and browning of white adipose tissue (WAT) to promote thermogenesis might be one of the attractive ways. Hydroxy-α-sanshool (HAS), a natural amide alkaloid extracted from the fruits of Zanthoxylum bungeanum Maxim, possesses lots of benefits in lipid metabolism regulation.

METHODS

The anti-obesity effect of HAS was investigated by establishing an animal model of obesity and a 3T3-L1 differentiation cell model. Effects of HAS on the whole-body fat and liver of obese mice, and the role of HAS in inducing browning of white fat were studied by Micro CT, Metabolic cage detection, Cell mitochondrial pressure detection, transmission electron microscopy and cold exposure assays. Furthermore, the Real-time PCR (qPCR), digital PCR (dPCR), western blot, Co-immunoprecipitation (Co-IP), molecular docking, drug affinity responsive target stability (DARTS), Cellular thermal shift assay (CETSA) and other methods were used to investigate the target and mechanisms of HAS.

RESULTS

We found that treatment with HAS helped mice combat obesity caused by a high fat diet (HFD) and improve metabolic characteristics. In addition, our results suggested that the anti-obesity effect of HAS is related to increase energy consumption and thermogenesis via induction of browning of WAT. The further investigations uncovered that HAS can up-regulate UCP-1 expression, increase mitochondria number, and elevate the cellular oxygen consumption rates (OCRs) of white adipocytes. Importantly, the results indicated that browning effects of HAS is closely associated with SIRT1-dependent PPAR-γ deacetylation through activating the TRPV1/AMPK pathway, and TRPV1 is the potential drug target of HAS for the browning effects of WAT.

CONCLUSIONS

Our results suggested the HAS can promote browning of WAT via regulating AMPK/SIRT-1/PPARγ signaling, and the potential drug target of HAS is the membrane receptor of TRPV1.

Loss of Uncoupling Protein 1 Expression in the Subcutaneous Adipose Tissue Predicts Childhood Obesity

Stimulation of thermogenesis by inducing uncoupling protein 1 (UCP1) expression in adipocytes is thought to promote weight loss by increasing energy expenditure, and it is postulated that the human newborn has thermogenic subcutaneous fat depots. However, it remains unclear whether a relevant number of UCP1-expressing (UCP1+) adipocytes exist in the early postnatal life. Here we studied the distribution of UCP1 and the expression of thermogenic genes in the subcutaneous adipose tissues of the human fetus, infant and child. We show that the deep layer of human fetal and neonatal subcutaneous fat, particularly the abdominal wall, is rich in UCP1+ adipocytes. These adipocytes develop in the late third trimester and persist throughout childhood, expressing a panel of genes linked to mitochondrial biogenesis and thermogenesis. During the early childhood adiposity rebound-a critical phase that determines obesity risk later in life-the absence of adipose tissue UCP1 expression in children with normal body mass index (BMI) correlates with an obesity-associated gene expression signature. Finally, UCP1 expression is negatively correlated with BMI z-score and adipocyte size in infants and children. Overall, our results show that the absence of UCP1 expression in adipose tissue is an early indicator of adipose tissue expansion in children.

HDAC11 inhibition triggers bimodal thermogenic pathways to circumvent adipocyte catecholamine resistance

Stimulation of adipocyte β-adrenergic receptors (β-ARs) induces expression of uncoupling protein 1 (UCP1), promoting nonshivering thermogenesis. Association of β-ARs with a lysine-myristoylated form of A kinase-anchoring protein 12 (AKAP12, also known as gravin-α) is required for downstream signaling that culminates in UCP1 induction. Conversely, demyristoylation of gravin-α by histone deacetylase 11 (HDAC11) suppresses this pathway. Whether inhibition of HDAC11 in adipocytes is sufficient to drive UCP1 expression independently of β-ARs is not known. Here, we demonstrate that adipocyte-specific deletion of HDAC11 in mice leads to robust induction of UCP1 in adipose tissue (AT), resulting in increased body temperature. These effects are mimicked by treating mice in vivo or human AT ex vivo with an HDAC11-selective inhibitor, FT895. FT895 triggers biphasic, gravin-α myristoylation-dependent induction of UCP1 protein expression, with a noncanonical acute response that is posttranscriptional and independent of protein kinase A (PKA), and a delayed response requiring PKA activity and new Ucp1 mRNA synthesis. Remarkably, HDAC11 inhibition promotes UCP1 expression even in models of adipocyte catecholamine resistance where β-AR signaling is blocked. These findings define cell-autonomous, multimodal roles for HDAC11 as a suppressor of thermogenesis, and highlight the potential of inhibiting HDAC11 to therapeutically alter AT phenotype independently of β-AR stimulation.

Adipose tissue-derived lipokines in metabolism

Adipose tissue is a crucial regulator of metabolism with functions that include energy storage and dissipation as well as the secretion of bioactive molecules. As the largest endocrine organ in the body, the adipose tissue produces diverse bioactive molecules, including peptides, metabolites, and extracellular vesicles, which communicate with and modulate the function of other organs. In recent years, lipid metabolites, also known as lipokines, have emerged as key signaling molecules that actively participate in multiple metabolic processes. This review highlights the latest advances in adipose tissue-derived lipokines and their underlying cellular and molecular functions. Furthermore, we offer our perspective on the future directions for adipose-derived bioactive lipids and potential therapeutic implications for obesity and its associated complications.

Reverse-ChIP Techniques for Identifying Locus-Specific Proteomes: A Key Tool in Unlocking the Cancer Regulome

A phenotypic hallmark of cancer is aberrant transcriptional regulation. Transcriptional regulation is controlled by a complicated array of molecular factors, including the presence of transcription factors, the deposition of histone post-translational modifications, and long-range DNA interactions. Determining the molecular identity and function of these various factors is necessary to understand specific aspects of cancer biology and reveal potential therapeutic targets. Regulation of the genome by specific factors is typically studied using chromatin immunoprecipitation followed by sequencing (ChIP-Seq) that identifies genome-wide binding interactions through the use of factor-specific antibodies. A long-standing goal in many laboratories has been the development of a 'reverse-ChIP' approach to identify unknown binding partners at loci of interest. A variety of strategies have been employed to enable the selective biochemical purification of sequence-defined chromatin regions, including single-copy loci, and the subsequent analytical detection of associated proteins. This review covers mass spectrometry techniques that enable quantitative proteomics before providing a survey of approaches toward the development of strategies for the purification of sequence-specific chromatin as a 'reverse-ChIP' technique. A fully realized reverse-ChIP technique holds great potential for identifying cancer-specific targets and the development of personalized therapeutic regimens.

Transcriptomic Analysis Reveals Fibroblast Growth Factor 11 (FGF11) Role in Brown Adipocytes in Thermogenic Regulation of Goats

Brown adipose tissue (BAT) is the main site of adaptive thermogenesis, generates heat to maintain body temperature upon cold exposure, and protects against obesity by promoting energy expenditure. RNA-seq analysis revealed that FGF11 is enriched in BAT. However, the functions and regulatory mechanisms of FGF11 in BAT thermogenesis are still limited. In this study, we found that FGF11 was significantly enriched in goat BAT compared with white adipose tissue (WAT). Gain- and loss-of-function experiments revealed that FGF11 promoted differentiation and thermogenesis in brown adipocytes. However, FGF11 had no effect on white adipocyte differentiation. Furthermore, FGF11 promoted the expression of the UCP1 protein and an EBF2 element was responsible for UCP1 promoter activity. Additionally, FGF11 induced UCP1 gene expression through promoting EBF2 binding to the UCP1 promoter. These results revealed that FGF11 promotes differentiation and thermogenesis in brown adipocytes but not in white adipocytes of goats. These findings provide evidence for FGF11 and transcription factor regulatory functions in controlling brown adipose thermogenesis of goats.

m 6 A mRNA Methylation in Brown Adipose Tissue Regulates Systemic Insulin Sensitivity via an Inter-Organ Prostaglandin Signaling Axis

Brown adipose tissue (BAT) has the capacity to regulate systemic metabolism through the secretion of signaling lipids. N6-methyladenosine (m 6 A) is the most prevalent and abundant post-transcriptional mRNA modification and has been reported to regulate BAT adipogenesis and energy expenditure. In this study, we demonstrate that the absence of m 6 A methyltransferase-like 14 (METTL14), modifies the BAT secretome to initiate inter-organ communication to improve systemic insulin sensitivity. Importantly, these phenotypes are independent of UCP1-mediated energy expenditure and thermogenesis. Using lipidomics, we identified prostaglandin E2 (PGE2) and prostaglandin F2a (PGF2a) as M14 KO -BAT-secreted insulin sensitizers. Notably, circulatory PGE2 and PGF2a levels are inversely correlated with insulin sensitivity in humans. Furthermore, in vivo administration of PGE2 and PGF2a in high-fat diet-induced insulin-resistant obese mice recapitulates the phenotypes of METTL14 deficient animals. PGE2 or PGF2a improves insulin signaling by suppressing the expression of specific AKT phosphatases. Mechanistically, METTL14-mediated m 6 A installation promotes decay of transcripts encoding prostaglandin synthases and their regulators in human and mouse brown adipocytes in a YTHDF2/3-dependent manner. Taken together, these findings reveal a novel biological mechanism through which m 6 A-dependent regulation of BAT secretome regulates systemic insulin sensitivity in mice and humans.

Highlights

Mettl14 KO -BAT improves systemic insulin sensitivity via inter-organ communication; PGE2 and PGF2a are BAT-secreted insulin sensitizers and browning inducers;PGE2 and PGF2a sensitize insulin responses through PGE2-EP-pAKT and PGF2a-FP-AKT axis; METTL14-mediated m 6 A installation selectively destabilizes prostaglandin synthases and their regulator transcripts; Targeting METTL14 in BAT has therapeutic potential to enhance systemic insulin sensitivity.

Abstract Figure

Exercise training remodels inguinal white adipose tissue through adaptations in innervation, vascularization, and the extracellular matrix

Inguinal white adipose tissue (iWAT) is essential for the beneficial effects of exercise training on metabolic health. The underlying mechanisms for these effects are not fully understood, and here, we test the hypothesis that exercise training results in a more favorable iWAT structural phenotype. Using biochemical, imaging, and multi-omics analyses, we find that 11 days of wheel running in male mice causes profound iWAT remodeling including decreased extracellular matrix (ECM) deposition and increased vascularization and innervation. We identify adipose stem cells as one of the main contributors to training-induced ECM remodeling, show that the PRDM16 transcriptional complex is necessary for iWAT remodeling and beiging, and discover neuronal growth regulator 1 (NEGR1) as a link between PRDM16 and neuritogenesis. Moreover, we find that training causes a shift from hypertrophic to insulin-sensitive adipocyte subpopulations. Exercise training leads to remarkable adaptations to iWAT structure and cell-type composition that can confer beneficial changes in tissue metabolism.

HDAC11 inhibition triggers bimodal thermogenic pathways to circumvent adipocyte catecholamine resistance

Stimulation of adipocyte β-adrenergic receptors (β-ARs) induces expression of uncoupling protein 1 (UCP1), promoting non-shivering thermogenesis. Association of β-ARs with a lysine myristoylated form of A-kinase anchoring protein 12 (AKAP12)/gravin-α is required for downstream signaling that culminates in UCP1 induction. Conversely, demyristoylation of gravin-α by histone deacetylase 11 (HDAC11) suppresses this pathway. Whether inhibition of HDAC11 in adipocytes is sufficient to drive UCP1 expression independently of β-ARs is not known. Here, we demonstrate that adipocyte-specific deletion of HDAC11 in mice leads to robust induction of UCP1 in adipose tissue (AT), resulting in increased body temperature. These effects are mimicked by treating mice in vivo or human AT ex vivo with an HDAC11-selective inhibitor, FT895. FT895 triggers biphasic, gravin-α myristoylation-dependent induction of UCP1 protein expression, with a non-canonical acute response that is post-transcriptional and independent of protein kinase A (PKA), and a delayed response requiring PKA activity and new Ucp1 mRNA synthesis. Remarkably, HDAC11 inhibition promotes UCP1 expression even in models of adipocyte catecholamine resistance where β-AR signaling is blocked. These findings define cell autonomous, multi-modal roles for HDAC11 as a suppressor of thermogenesis, and highlight the potential of inhibiting HDAC11 to therapeutically alter AT phenotype independently of β-AR stimulation.

Generation of Brown Fat-Specific Knockout Mice Using a Combined Cre-LoxP, CRISPR-Cas9, and Adeno-Associated Virus Single-Guide RNA System

Brown adipose tissue (BAT) is an adipose depot specialized in energy dissipation that can also serve as an endocrine organ via the secretion of bioactive molecules. The creation of BAT-specific knockout mice is one of the most popular approaches for understanding the contribution of a gene of interest to BAT-mediated energy regulation. The conventional gene targeting strategy utilizing the Cre-LoxP system has been the principal approach to generate tissue-specific knockout mice. However, this approach is time-consuming and tedious. Here, we describe a protocol for the rapid and efficient knockout of a gene of interest in BAT using a combined Cre-LoxP, CRISPR-Cas9, and adeno-associated virus (AAV) single-guide RNA (sgRNA) system. The interscapular BAT is located in the deep layer between the muscles. Thus, the BAT must be exposed in order to inject the AAV precisely and directly into the BAT within the visual field. Appropriate surgical handling is crucial to prevent damage to the sympathetic nerves and vessels, such as the Sultzer's vein that connects to the BAT. To minimize tissue damage, there is a critical need to understand the three-dimensional anatomical location of the BAT and the surgical skills required in the technical steps. This protocol highlights the key technical procedures, including the design of sgRNAs targeting the gene of interest, the preparation of AAV-sgRNA particles, and the surgery for the direct microinjection of AAV into both BAT lobes for generating BAT-specific knockout mice, which can be broadly applied to study the biological functions of genes in BAT.

Genome-Wide Identification and Characterization of Bovine Fibroblast Growth Factor (FGF) Gene and Its Expression during Adipocyte Differentiation

Fibroblast growth factor (FGF) family genes are a class of polypeptide factors with similar structures that play an important role in regulating cell proliferation and differentiation, nutritional metabolism, and neural activity. In previous studies, the FGF gene has been widely studied and analyzed in many species. However, the systematic study of the FGF gene in cattle has not been reported. In this study, 22 FGF genes distributed on 15 chromosomes were identified in the Bos taurus genome and clustered into seven subfamilies according to phylogenetic analysis and conservative domains. Collinear analysis showed that the bovine FGF gene family was homologous to Bos grunniens, Bos indicus, Hybrid-Bos taurus, Bubalus bubalis, and Hybrid-Bos indicus, and tandem replication and fragment replication were the key driving forces for the expansion of the gene family. Tissue expression profiling showed that bovine FGF genes were commonly expressed in different tissues, with FGF1, FGF5, FGF10, FGF12, FGF16, FGF17, and FGF20 being highly expressed in adipose tissue. In addition, real-time fluorescence quantitative PCR (qRT-PCR) detection showed that some FGF genes were differentially expressed before and after adipocyte differentiation, indicating their diverse role in the formation of lipid droplets. This study made a comprehensive exploration of the bovine FGF family and laid a foundation for further study on the potential function in the regulation of bovine adipogenic differentiation.

SIRT7 suppresses energy expenditure and thermogenesis by regulating brown adipose tissue functions in mice

Brown adipose tissue plays a central role in the regulation of the energy balance by expending energy to produce heat. NAD⁺-dependent deacylase sirtuins have widely been recognized as positive regulators of brown adipose tissue thermogenesis. However, here we reveal that SIRT7, one of seven mammalian sirtuins, suppresses energy expenditure and thermogenesis by regulating brown adipose tissue functions. Whole-body and brown adipose tissue-specific Sirt7 knockout mice have higher body temperature and energy expenditure. SIRT7 deficiency increases the protein level of UCP1, a key regulator of brown adipose tissue thermogenesis. Mechanistically, we found that SIRT7 deacetylates insulin-like growth factor 2 mRNA-binding protein 2, an RNA-binding protein that inhibits the translation of Ucp1 mRNA, thereby enhancing its inhibitory action on Ucp1. Furthermore, SIRT7 attenuates the expression of batokine genes, such as fibroblast growth factor 21. In conclusion, we propose that SIRT7 serves as an energy-saving factor by suppressing brown adipose tissue functions.

Cooling down with Entresto. Can sacubitril/valsartan combination enhance browning more than coldness?

BACKGROUND

It is a growing importance to induce a new treatment approach to encourage weight loss but also to improve maintenance of lost weight. It has been shown that promotion of brown adipose tissue (BAT) function or acquisition of BAT characteristics in white adipose tissue (terms referred as "browning") can be protective against obesity.

MAIN TEXT

Amongst numerous established environmental influences on BAT activity, cold exposure is the best interested technique due to its not only effects on of BAT depots in proliferation process but also de novo differentiation of precursor cells via β-adrenergic receptor activation. A novel combination drug, sacubitril/valsartan, has been shown to be more efficient in reducing cardiovascular events and heart failure readmission compared to conventional therapy. Also, this combination of drugs increases the postprandial lipid oxidation contributing to energy expenditure, promotes lipolysis in adipocytes and reduces body weight. To date, there is no research examining potential of combined sacubitril/valsartan use to promote browning or mechanisms in the basis of this thermogenic process.

CONCLUSION

Due to the pronounced effects of cold and sacubitril/valsartan treatment on function and metabolism of BAT, the primary goal of further research should focused on investigation of the synergistic effects of the sacubitril/valsartan treatment at low temperature environmental conditions.

The biological actions of prostanoids in adipose tissue in physiological and pathophysiological conditions

Adipose tissue has been established as an endocrine organ that plays an important role in maintaining metabolic homeostasis. Adipose tissue releases several bioactive molecules called adipokines. Inflammation, dysregulation of adipokine synthesis, and secretion are observed in obesity and related diseases and cause adipose tissue dysfunction. Prostanoids, belonging to the eicosanoid family of lipid mediators, can be synthesized in adipose tissue and play a critical role in adipose tissue biology. In this review, we summarized the current knowledge regarding the interaction of prostanoids with adipokines, the expression of prostanoid receptors, and prostanoid synthase enzymes in adipose tissues in health and disease. Furthermore, the involvement of prostanoids in the physiological function or dysfunction of adipose tissue including inflammation, lipolysis, adipogenesis, thermogenesis, browning of adipocytes, and vascular tone regulation was also discussed by examining studies using pharmacological approaches or genetically modified animals for prostanoid receptors/synthase enzymes. Overall, the present review provides a perspective on the evidence from literature regarding the biological effects of prostanoids in adipose tissue. Among prostanoids, prostaglandin E2 (PGE₂) is prominent in regards to its substantial role in both adipose tissue physiology and pathophysiology. Targeting prostanoids may serve as a potential therapeutic strategy for preventing or treating obesity and related diseases.

Combined analysis of differentially expressed lncRNAs and miRNAs in liver tissues of high-fat fed rabbits by transcriptome sequencing

High-fat diet could lead to a series of metabolic diseases, including obesity, and its mechanism is not clear. In this study, the rabbit individuals were fed with high-fat diet, the liver tissues were collected, high-throughput sequencing technology was used to reveal the expression of lncRNA and miRNA difference, and the molecular regulation mechanism of lncRNA-miRNA. A total of 24,615 DE lncRNAs and 52 DE miRNAs were identified, including 15 novel discovered DE miRNAs (5 upregulated and 10 downregulated). Furthermore, five miRNAs and three mRNAs were verified by qRT-PCR, and the results showed that the expression of the DE miRNAs and DE lncRNAs in the two groups was consistent with our sequencing results. GO and KEGG analyzed 7,57,139 target genes respectively, enriching the pathways related to lipid metabolism, including mucin O-glycan biosynthesis pathway, insulin resistance and glucagon signaling pathway. Moreover, 65 targeting relationships were obtained. Among them, LOC103348122/miR-450a-5p, LOC103350359/miR-450a-3p and LOC103350429/miR-148a-5p were proposed the first time. Significantly, LOC103348122/miR-450a-5p and LOC103350429/miR-148a-5p were related to lipid metabolism in the liver. This study is of great significance to the CeRNA regulatory network related to lipid metabolism in the liver of rabbits, and provides a basis for understanding hepatic steatosis in rabbits.

Sodium butyrate attenuated diet-induced obesity, insulin resistance and inflammation partly by promoting fat thermogenesis via intro-adipose sympathetic innervation

Emerging evidence suggests that butyrate, a short-chain fatty acid, may have beneficial effects on obesity and its associated metabolic comorbidities, but the related molecular mechanism is largely unknown. This study aims to investigate the role of butyrate in diet-induced obesity and metabolic disorders and the relevant regulatory mechanisms. Here, dietary supplementation with Sodium butyrate (NaB) was carried out in mice fed with a high-fat diet (HFD) or chow diet. At week 14, mice on HFD displayed an obese phenotype and down-regulated expression of thermogenic regulators including Ucp-1 and Pgc-1α in adipose tissue. Excitingly, NaB add-on treatment abolished these detrimental effects. Moreover, the obesity-induced insulin resistance, inflammation, fatty liver, and intestinal dysfunction were also attenuated by NaB administration. Mechanistically, NaB can promote fat thermogenesis via the increased local sympathetic innervation of adipose tissue, and blocking the β3-adrenergic signaling pathway by 6-hydroxydopamine abolished NaB-induced thermogenesis. Our study reveals a potential pharmacological target for NaB to combat obesity and metabolic disorders.

Adipocyte-based high throughput screening for anti-obesity drug discovery: Current status and future perspectives

Drug discovery for obesity treatment, particularly bodily slimming, is a topic of timely importance that requires continued investigation, as the current therapies have limited efficacy with many adverse effects. Obesity is associated with adipose tissue expansion, where the size and number of adipocytes increase. Over the past few decades, high-throughput/content screening (HTS/HCS) has been carried out on morphological changes in adipose tissues and adipocytes for the development of anti-obesity therapies. Increased understating of current adipocyte-based HTS/HCS technology will facilitate drug screening for obesity and weight control.

Severe iatrogenic hypoglycaemia modulates the fibroblast growth factor protein response

INTRODUCTION

There is evidence that fibroblast growth factor (FGF) levels may be implicated in hypoglycaemia, with FGF19 being a potential contributor to insulin-independent pathways driving postprandial hypoglycaemia following bariatric surgery and basic FGF (FGF2) being elevated following mild hypoglycaemia occurring after the glucose tolerance test. However, their response following severe iatrogenic hypoglycaemia is unknown and therefore this pilot exploratory study was undertaken.

METHODS

A case-control study of aged-matched type 2 diabetes (T2D; n = 23) and control (n = 23) subjects who underwent a hyperinsulinaemic clamp, initially to euglycaemia in T2D (5 mmol/L; 90 mg/dl), and then to hypoglycaemia (<2 mmol/L; <36 mg/dl) with subsequent follow-up time course to 24 h. FGF and FGF receptor proteins were determined by Slow Off-rate Modified Aptamer (SOMA)-scan plasma protein measurement.

RESULTS

At baseline, FGF12 (p = .006) was higher and FGF20 (p = .004) was lower in T2D versus controls. At hypoglycaemia, FGF7 was lower in T2D. Post-hypoglycaemic levels of FGF18, FGF19, FGF20 and FGF23 were lower while FGF12 and FGF16 were higher in T2D versus control at different time points. No differences between T2D and controls were seen for FGF1, FGF2, FGF4, FGF6, FGF8, FGF9, FGF10, FGF21 or any of the FGF receptors. At 24 h post-hypoglycaemia, FGF20 (p = .01) differed between controls and T2D, while the levels for the other proteins measured returned to baseline. None of the FGF proteins altered from baseline to euglycaemia when clamped in T2D subjects. FGF23 negatively correlated with fasting blood glucose, but no FGFs correlated with body mass index in T2D.

CONCLUSION

Severe transient hypoglycaemia modulated FGF7, 16, 19, 20 and 23 (known to be associated with diabetes), together with FGF18 and 12, not previously reported to be associated with diabetes but that may be important in the pathophysiology of hypoglycaemia; FGF20 remained low at 24 h. Taken together, these data suggest that recurrent hypoglycaemia may contribute to the development of complications through changes in FGF proteins.

Age-dependent changes of hindgut microbiota succession and metabolic function of Mongolian cattle in the semi-arid rangelands

Dietary changes have significant effects on gut microbiota and host health. Weaning is an important stage of dietary change in ruminants. The gastrointestinal tract (GIT) microbiota of calf in the early life undergo some changes, and the plasticity of the calf is beneficial to cope with these changes and challenges. However, the complex development of hindgut microorganisms in post-weaning ruminants is not fully understood. In this study, we used 16S rRNA sequencing and untargeted metabolomic analysis to determine the cecal and colonic bacterial community and associated metabolome of Mongolian cattle at age of the 5th (at weaning), 18th, and 36th months. Moreover, the maturation patterns of the hindgut bacterial community and the dynamic changes of metabolites were also explored. Sequencing results showed that Firmicutes and Bacteroidetes were the dominant phyla in the cecum and colon. The linear discriminant analysis (LDA) effect size (LEfSe) analysis revealed bacterial features that were stage-specific in the cecum and colon. The relative abundance of Ruminococcaceae, a microbial family related to fiber degradation, gradually increased with age in the cecum, while the relative abundance of Bacteroides and Alistipes, which are related to immunity, gradually increased in the colon. The differential metabolites in the cecum and colon were mainly enriched in steroid hormone biosynthesis, primary bile acid biosynthesis, and arachidonic acid metabolism between different ages of Mongolian cattle after weaning. Consequently, this dual omics analysis provided important information on the changes in microbial and metabolite interactions in Mongolian cattle after weaning. The microorganisms and metabolites in the cecum and colon further enhanced the abiotic stress resistance of Mongolian cattle to the harsh environment. The information obtained in this study is of great significance for future strategies of cecum and colon microbiota regulation of post-weaning Mongolian cattle in the harsh Mongolian Plateau ecosystem.

PGE2 -EP3 axis promotes brown adipose tissue formation through stabilization of WTAP RNA methyltransferase

Brown adipose tissue (BAT) functions as a thermogenic organ and is negatively associated with cardiometabolic diseases. N⁶ -methyladenosine (m⁶ A) modulation regulates the fate of stem cells. Here, we show that the prostaglandin E₂ (PGE₂ )-E-prostanoid receptor 3 (EP3) axis was activated during mouse interscapular BAT development. Disruption of EP3 impaired the browning process during adipocyte differentiation from pre-adipocytes. Brown adipocyte-specific depletion of EP3 compromised interscapular BAT formation and aggravated high-fat diet-induced obesity and insulin resistance in vivo. Mechanistically, activation of EP3 stabilized the Zfp410 mRNA via WTAP-mediated m⁶ A modification, while knockdown of Zfp410 abolished the EP3-induced enhancement of brown adipogenesis. EP3 prevented ubiquitin-mediated degradation of WTAP by eliminating PKA-mediated ERK1/2 inhibition during brown adipocyte differentiation. Ablation of WTAP in brown adipocytes abrogated the protective effect of EP3 overexpression in high-fat diet-fed mice. Inhibition of EP3 also retarded human embryonic stem cell differentiation into mature brown adipocytes by reducing the WTAP levels. Thus, a conserved PGE₂ -EP3 axis promotes BAT development by stabilizing WTAP/Zfp410 signaling in a PKA/ERK1/2-dependent manner.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

The fibroblast growth factor receptor antagonist SSR128129E inhibits fat accumulation via suppressing adipogenesis in mice

BACKGROUND

AS an allosteric inhibitor of fibroblast growth factor receptors (FGFRs), SSR128129E (SSR) extensively inhibits the fibroblast growth factor (FGF) signaling. Given the metabolic importance of FGFs and the global epidemic of obesity, we explored the effect of SSR on fat metabolism.

METHODS AND RESULTS

Three-week-old male mice were administered intragastrically with SSR (30 mg/kg/day) or PBS for 5 weeks. The effects of SSR on white and brown fat metabolism were investigated by respiratory metabolic monitoring, histological assessment and molecular analysis. Results indicated that SSR administration significantly reduced the body weight gain and the fat content of mice. SSR did not increase, but decreased the thermogenic capability of both brown and white fat. However, SSR markedly suppressed adipogenesis of adipose tissues. Further study demonstrated the involvement of ERK signaling in the action of SSR.

CONCLUSIONS

SSR may be a promising drug candidate for the prevention of obesity via suppressing adipogenesis. However, the influence of SSR on thermogenesis in humans should be further investigated before its clinical application.

Factors affecting the induction of uncoupling protein 1 in C2C12 myogenic cells

Brown/beige adipocytes, which are derived from skeletal muscle/smooth muscle-lineage cells, consume excess energy as heat through the expression of mitochondrial uncoupling protein 1 (UCP1). Previous studies have shown that forced expression of PR/SET domain (PRDM)-16 or early B-cell factor (EBF)-2 induced UCP1-positive adipocytes in C2C12 myogenic cells. Here, we explored the culture conditions to induce Ucp1 expression in C2C12 cells without introducing exogenous genes. Treatment with rosiglitazone (a peroxisome proliferator-activated receptor (PPAR)-γ agonist), GW501516 (a PPARδ agonist), and bone morphogenetic protein (BMP)-7 for 8 days efficiently increased Ucp1 expression in response to treatment with forskolin, an activator of the protein kinase A pathway. BMP7 dose-dependently increased forskolin-induced Ucp1 expression in the presence of rosiglitazone and GW501516; however, GW501516 was not required for Ucp1 induction. Additionally, the structurally related proteins, BMP6 and BMP9, efficiently increased forskolin-induced Ucp1 expression in rosiglitazone-treated cells. UCP1 protein was localized in cells with lipid droplets, but adipocytes were not always positive for UCP1. Continuous treatment with BMP7 was needed for the efficient induction of Ucp1 by forskolin treatment. Significant expression of Prdm16 was not detected, irrespective of the treatment, and treatment with rosiglitazone, GW501516, and BMP7 did not affect the expression levels of Ebf2. Fibroblast growth factor receptor (Fgfr)-3 expression levels were increased by BMP9 in rosiglitazone-treated cells, and molecules that upregulate Fgfr3 transcription partly overlapped with those that stimulate Ucp1 transcription. The present results provide basic information on the practical differentiation of myogenic cells to brown adipocytes.

FGF9 Alleviates the Fatty Liver Phenotype by Regulating Hepatic Lipid Metabolism

Although the fatty liver has been linked to numerous impairments of energy homeostasis, the molecular mechanism responsible for fatty liver development remains largely unknown. In the present study, we show that fibroblast growth factors 9 (FGF9) expression is increased in the liver of diet-induced obese (DIO), db/db, and ob/ob mice relative to their respective controls. The long-term knockdown of hepatic FGF9 expression mediated by adeno-associated virus expressing FGF9-specific short hairpin RNA (AAV-shFGF9) aggravated the fatty liver phenotype of DIO mice. Consistently, downregulation of FGF9 expression mediated by adenovirus expressing FGF9-specific shRNA (Ad-shFGF9) in the primary hepatocyte promoted the cellular lipid accumulation, suggesting that FGF9 exerts its effects in an autocrine manner. In contrast, adenoviruses expressing FGF9 (Ad-FGF9) mediated FGF9 overexpression in the liver of DIO mice alleviated hepatic steatosis and improved the insulin sensitivity and glucose intolerance. Moreover, the liver-specific FGF9 transgenic mice phenocopied the Ad-FGF9-infected mice. Mechanistically, FGF9 inhibited the expression of genes involved in lipogenesis and increased the expression of genes involved in fatty acid oxidation, thereby reducing cellular lipid accumulation. Thus, targeting FGF9 might be exploited to treat nonalcoholic fatty liver disease (NAFLD) and metabolic syndrome.

Sestrin2 ablation attenuates the exercise-induced browning of white adipose tissue in C57BL/6J mice

AIM

With exercise, white adipose tissues (WAT) are readily convertible to a "brown-like" state, altering from lipid-storing to energy-catabolizing function, which counteracts obesity and increases insulin sensitivity. Sestrin2 (SESN2) is a stress-inducible protein that can regulate the cold-induced increase of uncoupling protein 1 (UCP1), which is paramount for the thermogenic capacity of brown-like WAT. This study aimed to elucidate the necessity of SESN2 in mediating exercise-induced browning of WAT.

METHODS

We used 8-week, male wild-type and SESN2 knockout C57BL/6J mice to explore the potential role of SESN2 in the exercise-induced WAT browning process. Over a 3-week intervention (sedentary versus treadmill exercise, normal chow versus 60% high-fat diet), we examined the exercise-induced alterations of the browning phenotype in different depots of white fat. In vitro, 3T3-L1 pre-adipocytes and primary adipocytes were used to determine the potential mechanism.

RESULTS

Our data revealed that SESN2 was required for the exercise-induced subcutaneous WAT (scWAT) browning. This may be mediated by higher fibronectin type III domain containing 5 (FNDC5) contents in scWAT locally, rather than skeletal muscle FNDC5 expression and circulating serum irisin levels. SESN2 ablation significantly impaired the exercise-improved glucose metabolism, where browning of scWAT may serve as an essential pathway. Moreover, SESN2 ablation significantly attenuated the exercise-promoted respiratory exchange ratio and indexes of energy metabolism (oxygen uptake and energy expenditure).

CONCLUSION

Taken together, our results provided evidence that SESN2 is a key integrating factor in driving the diverse metabolic benefits conferred by aerobic exercise.

A Mixture of Endocrine Disrupting Chemicals Associated with Lower Birth Weight in Children Induces Adipogenesis and DNA Methylation Changes in Human Mesenchymal Stem Cells

Endocrine Disrupting Chemicals (EDCs) are man-made compounds that alter functions of the endocrine system. Environmental mixtures of EDCs might have adverse effects on human health, even though their individual concentrations are below regulatory levels of concerns. However, studies identifying and experimentally testing adverse effects of real-life mixtures are scarce. In this study, we aimed at evaluating an epidemiologically identified EDC mixture in an experimental setting to delineate its cellular and epigenetic effects. The mixture was established using data from the Swedish Environmental Longitudinal Mother and child Asthma and allergy (SELMA) study where it was associated with lower birth weight, an early marker for prenatal metabolic programming. This mixture was then tested for its ability to change metabolic programming of human mesenchymal stem cells. In these cells, we assessed if the mixture induced adipogenesis and genome-wide DNA methylation changes. The mixture increased lipid droplet accumulation already at concentrations corresponding to levels measured in the pregnant women of the SELMA study. Furthermore, we identified differentially methylated regions in genes important for adipogenesis and thermogenesis. This study shows that a mixture reflecting human real-life exposure can induce molecular and cellular changes during development that could underlie adverse outcomes.

Role of Distinct Fat Depots in Metabolic Regulation and Pathological Implications

People suffering from obesity and associated metabolic disorders including diabetes are increasing exponentially around the world. Adipose tissue (AT) distribution and alteration in their biochemical properties play a major role in the pathogenesis of these diseases. Emerging evidence suggests that AT heterogeneity and depot-specific physiological changes are vital in the development of insulin resistance in peripheral tissues like muscle and liver. Classically, AT depots are classified into white adipose tissue (WAT) and brown adipose tissue (BAT); WAT is the site of fatty acid storage, while BAT is a dedicated organ of metabolic heat production. The discovery of beige adipocyte clusters in WAT depots indicates AT heterogeneity has a more central role than hither to ascribed. Therefore, we have discussed in detail the current state of understanding on cellular and molecular origin of different AT depots and their relevance toward physiological metabolic homeostasis. A major focus is to highlight the correlation between altered WAT distribution in the body and metabolic pathogenesis in animal models and humans. We have also underscored the disparity in the molecular (including signaling) changes in various WAT tissues during diabetic pathogenesis. Exercise-mediated beneficial alteration in WAT physiology/distribution that protects against metabolic disorders is evolving. Here we have discussed the depot-specific biochemical adjustments induced by different forms of exercise. A detailed understanding of the molecular details of inter-organ crosstalk via substrate utilization/storage and signaling through chemokines provide strategies to target selected WAT depots to pharmacologically mimic the benefits of exercise countering metabolic diseases including diabetes.

Sirtuin function and metabolism: Role in pancreas, liver, and adipose tissue and their crosstalk impacting bone homeostasis

Mammalian sirtuins (SIRT1-7) are members of the nicotine adenine dinucleotide (NAD+)-dependent family of enzymes critical for histone deacetylation and posttranslational modification of proteins. Sirtuin family members regulate a wide spectrum of biological processes and are best known for maintaining longevity. Sirtuins are well characterized in metabolic tissues such as the pancreas, liver and adipose tissue (AT). They are regulated by a diverse range of stimuli, including nutrients and metabolic changes within the organism. Indeed, nutrient-associated conditions, such as obesity and anorexia nervosa (AN), were found to be associated with bone fragility development in osteoporosis. Interestingly, it has also been demonstrated that sirtuins, more specifically SIRT1, can regulate bone activity. Various studies have demonstrated the importance of sirtuins in bone in the regulation of bone homeostasis and maintenance of the balance between bone resorption and bone formation. However, to understand the molecular mechanisms involved in the negative regulation of bone homeostasis during overnutrition (obesity) or undernutrition, it is crucial to examine a wider picture and to determine the pancreatic, liver and adipose tissue pathway crosstalk responsible for bone loss. Particularly, under AN conditions, sirtuin family members are highly expressed in metabolic tissue, but this phenomenon is reversed in bone, and severe bone loss has been observed in human subjects. AN-associated bone loss may be connected to SIRT1 deficiency; however, additional factors may interfere with bone homeostasis. Thus, in this review, we focus on sirtuin activity in the pancreas, liver and AT in cases of over- and undernutrition, especially the regulation of their secretome by sirtuins. Furthermore, we examine how the secretome of the pancreas, liver and AT affects bone homeostasis, focusing on undernutrition. This review aims to lead to a better understanding of the crosstalk between sirtuins, metabolic organs and bone. In long term prospective it should contribute to promote improvement of therapeutic strategies for the prevention of metabolic diseases and the development of osteoporosis.

Latest Advancements on Combating Obesity by Targeting Human Brown/Beige Adipose Tissues

Obesity is defined as overaccumulation of white adipose tissue in the body, mainly under the skin (subcutaneous adiposity) or in the abdominal cavity (visceral adiposity). It could be the origin of various metabolic disorders including hypertension, hyperlipidemia, type 2 diabetes, cardiovascular diseases etc. Active adipose tissue was discovered in humans through ¹⁸F-fluorodeoxyglucose Positron Emission Tomography coupled with Computer Tomography (¹⁸F FDG-PET/CT), which was initially performed for tumor scanning. Since human active adipose tissue is probably composed of brown and beige adipose tissues and they burn white adipose tissue to generate heat, targeting human brown/beige adipose tissue to induce their thermogenic function is considered significant to combat obesity. In this review, we describe the latest advancements on promising therapeutic strategies to combat obesity by targeting human thermogenic adipose tissues to achieve further metabolic balance in humans.

Knockdown of long non-coding RNA NEAT1 relieves inflammation of ulcerative colitis by regulating the miR-603/FGF9 pathway

Ulcerative colitis (UC) is a significant threat to human life. Hence, there is an urgent requirement to understand the mechanism of UC progression and to develop novel therapeutic interventions for the treatment of UC. The present study aimed to evaluate the potential significance of long non-coding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1) in the progression of UC. NEAT1 expression was detected in colonic mucosa samples from patients with UC and healthy individuals. Fetal human cells (FHCs) were treated with different concentrations of lipopolysaccharides (LPS) to induce UC-caused inflammatory injury, and the effects of NEAT1 knockdown were investigated on cytokines production, cell apoptosis and viability. Furthermore, the correlation and regulation between NEAT1 and microRNA (miRNA/miR)-603 and the fibroblast growth factor 9 (FGF9) pathway were investigated. The results demonstrated that NEAT1 expression was upregulated in the colonic mucosa tissues of patients with UC. In addition, significant cell injury was observed in FHCs treated with different concentrations of LPS, with decreased cell viability, and increased apoptosis and inflammatory cytokines production. Conversely, NEAT1 knockdown significantly reduced LPS-induced cell injury in FHCs, which was achieved through negative regulation of miR-603 expression. Furthermore, FGF9 was negatively regulated by miR-603, and thus, FGF9 was identified as a potential target of miR-603. Notably, FGF9 knockdown reversed the suppressing effects of miR-603 on LPS-induced injury in FHCs. Taken together, the results of the present study suggest that NEAT1 contributes to the development of UC by regulating the miR-603/FGF9 pathway.

Signaling Lipidomic Analysis of Thermogenic Adipocytes

Brown adipose tissue is a thermogenic organ that possesses anti-diabetic and anti-obesogenic potential. There has recently been growing interest on the secretory role of brown adipose tissue in regulating whole-body metabolism. Several signaling lipids, including 12-HEPE and 12,13-diHOME, have been shown to be secreted by brown adipose tissue and have demonstrated roles in regulating whole-body energy metabolism. Lipidomics platforms that broadly characterize the signaling lipidome can deconvolute the underlying biology of the lipid metabolites having a broad systemic impact on physiology. Herein, we describe how to perform and analyze LC-MS/MS signaling lipidomics on mature brown adipocytes.

Regulatory modules of human thermogenic adipocytes: functional genomics of large cohort and Meta-analysis derived marker-genes

Background

Recently, ProFAT and BATLAS studies identified brown and white adipocytes marker genes based on analysis of large databases. They offered scores to determine the thermogenic status of adipocytes using the gene-expression data of these markers. In this work, we investigated the functional context of these genes.

Results

Gene Set Enrichment Analyses (KEGG, Reactome) of the BATLAS and ProFAT marker-genes identified pathways deterministic in the formation of brown and white adipocytes. The collection of the annotated proteins of the defined pathways resulted in expanded white and brown characteristic protein-sets, which theoretically contain all functional proteins that could be involved in the formation of adipocytes. Based on our previously obtained RNA-seq data, we visualized the expression profile of these proteins coding genes and found patterns consistent with the two adipocyte phenotypes. The trajectory of the regulatory processes could be outlined by the transcriptional profile of progenitor and differentiated adipocytes, highlighting the importance of suppression processes in browning. Protein interaction network-based functional genomics by STRING, Cytoscape and R-Igraph platforms revealed that different biological processes shape the brown and white adipocytes and highlighted key regulatory elements and modules including GAPDH-CS, DECR1, SOD2, IL6, HRAS, MTOR, INS-AKT, ERBB2 and 4-NFKB, and SLIT-ROBO-MAPK. To assess the potential role of a particular protein in shaping adipocytes, we assigned interaction network location-based scores (betweenness centrality, number of bridges) to them and created a freely accessible platform, the AdipoNET (https//adiponet.com), to conveniently use these data. The Eukaryote Promoter Database predicted the response elements in the UCP1 promoter for the identified, potentially important transcription factors (HIF1A, MYC, REL, PPARG, TP53, AR, RUNX, and FoxO1).

Conclusion

Our integrative approach-based results allowed us to investigate potential regulatory elements of thermogenesis in adipose tissue. The analyses revealed that some unique biological processes form the brown and white adipocyte phenotypes, which presumes the existence of the transitional states. The data also suggests that the two phenotypes are not mutually exclusive, and differentiation of thermogenic adipocyte requires induction of browning as well as repressions of whitening. The recognition of these simultaneous actions and the identified regulatory modules can open new direction in obesity research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08126-8.