Role of kruppel-like transcription factors in adipogenesis

A review of the role of transcription factors in regulating adipogenesis and lipogenesis in beef cattle

In the past few decades, genomic selection and other refined strategies have been used to increase the growth rate and lean meat production of beef cattle. Nevertheless, the fast growth rates of cattle breeds are often accompanied by a reduction in intramuscular fat (IMF) deposition, impairing meat quality. Transcription factors play vital roles in regulating adipogenesis and lipogenesis in beef cattle. Meanwhile, understanding the role of transcription factors in regulating adipogenesis and lipogenesis in beef cattle has gained significant attention to increase IMF deposition and meat quality. Therefore, the aim of this paper was to provide a comprehensive summary and valuable insight into the complex role of transcription factors in adipogenesis and lipogenesis in beef cattle. This review summarizes the contemporary studies in transcription factors in adipogenesis and lipogenesis, genome-wide analysis of transcription factors, epigenetic regulation of transcription factors, nutritional regulation of transcription factors, metabolic signalling pathways, functional genomics methods, transcriptomic profiling of adipose tissues, transcription factors and meat quality and comparative genomics with other livestock species. In conclusion, transcription factors play a crucial role in promoting adipocyte development and fatty acid biosynthesis in beef cattle. They control adipose tissue formation and metabolism, thereby improving meat quality and maintaining metabolic balance. Understanding the processes by which these transcription factors regulate adipose tissue deposition and lipid metabolism will simplify the development of marbling or IMF composition in beef cattle.

Reconstructed Human Skin with Hypodermis Shows Essential Role of Adipose Tissue in Skin Metabolism

BACKGROUND

Dysregulation of skin metabolism is associated with a plethora of diseases such as psoriasis and dermatitis. Until now, reconstructed human skin (RhS) models lack the metabolic potential of native human skin, thereby limiting their relevance to study human healthy and diseased skin. We aimed to determine whether incorporation of an adipocyte-containing hypodermis into RhS improves its metabolic potential and to identify major metabolic pathways up-regulated in adipose-RhS.

METHODS

Primary human keratinocytes, fibroblasts and differentiated adipose-derived stromal cells were co-cultured in a collagen/fibrin scaffold to create an adipose-RhS. The model was extensively characterized structurally in two- and three-dimensions, by cytokine secretion and RNA-sequencing for metabolic enzyme expression.

RESULTS

Adipose-RhS showed increased secretion of adipokines. Both RhS and adipose-RhS expressed 29 of 35 metabolic genes expressed in ex vivo native human skin. Addition of the adipose layer resulted in up-regulation of 286 genes in the dermal-adipose fraction of which 7 were involved in phase I (CYP19A1, CYP4F22, CYP3A5, ALDH3B2, EPHX3) and phase II (SULT2B1, GPX3) metabolism. Vitamin A, D and carotenoid metabolic pathways were enriched. Additionally, pro-inflammatory (IL-1β, IL-18, IL-23, IL-33, IFN-α2, TNF-α) and anti-inflammatory cytokine (IL-10, IL-12p70) secretion was reduced in adipose-RhS.

CONCLUSIONS

Adipose-RhS mimics healthy native human skin more closely than traditional RhS since it has a less inflamed phenotype and a higher metabolic activity, indicating the contribution of adipocytes to tissue homeostasis. Therefore it is better suited to study onset of skin diseases and the effect of xenobiotics.

The kruppel-like factor (KLF) family, diseases, and physiological events

The Kruppel-Like Factor family of regulatory proteins, which has 18 members, is transcription factors. This family contains zinc finger proteins, regulates the activation and suppression of transcription, and binds to DNA, RNA, and proteins. Klfs related to the immune system are Klf1, Klf2, Klf3, Klf4, Klf6, and Klf14. Klfs related to adipose tissue development and/or glucose metabolism are Klf3, Klf7, Klf9, Klf10, Klf11, Klf14, Klf15, and Klf16. Klfs related to cancer are Klf3, Klf4, Klf5, Klf6, Klf7, Klf8, Klf9, Klf10, Klf11, Klf12, Klf13, Klf14, Klf16, and Klf17. Klfs related to the cardiovascular system are Klf4, Klf5, Klf10, Klf13, Klf14, and Klf15. Klfs related to the nervous system are Klf4, Klf7, Klf8, and Klf9. Klfs are associated with diseases such as carcinogenesis, oxidative stress, diabetes, liver fibrosis, thalassemia, and the metabolic syndrome. The aim of this review is to provide information about the relationship of Klfs with some diseases and physiological events and to guide future studies.

Identification of genetic associations and functional SNPs of bovine KLF6 gene on milk production traits in Chinese holstein

BACKGROUND

Our previous research identified the Kruppel like factor 6 (KLF6) gene as a prospective candidate for milk production traits in dairy cattle. The expression of KLF6 in the livers of Holstein cows during the peak of lactation was significantly higher than that during the dry and early lactation periods. Notably, it plays an essential role in activating peroxisome proliferator-activated receptor α (PPARα) signaling pathways. The primary aim of this study was to further substantiate whether the KLF6 gene has significant genetic effects on milk traits in dairy cattle.

RESULTS

Through direct sequencing of PCR products with pooled DNA, we totally identified 12 single nucleotide polymorphisms (SNPs) within the KLF6 gene. The set of SNPs encompasses 7 located in 5' flanking region, 2 located in exon 2 and 3 located in 3' untranslated region (UTR). Of these, the g.44601035G > A is a missense mutation that resulting in the replacement of arginine (CGG) with glutamine (CAG), consequently leading to alterations in the secondary structure of the KLF6 protein, as predicted by SOPMA. The remaining 7 regulatory SNPs significantly impacted the transcriptional activity of KLF6 following mutation (P < 0.005), manifesting as changes in transcription factor binding sites. Additionally, 4 SNPs located in both the UTR and exons were predicted to influence the secondary structure of KLF6 mRNA using the RNAfold web server. Furthermore, we performed the genotype-phenotype association analysis using SAS 9.2 which found all the 12 SNPs were significantly correlated to milk yield, fat yield, fat percentage, protein yield and protein percentage within both the first and second lactations (P < 0.0001 ~ 0.0441). Also, with Haploview 4.2 software, we found the 12 SNPs linked closely and formed a haplotype block, which was strongly associated with five milk traits (P < 0.0001 ~ 0.0203).

CONCLUSIONS

In summary, our study represented the KLF6 gene has significant impacts on milk yield and composition traits in dairy cattle. Among the identified SNPs, 7 were implicated in modulating milk traits by impacting transcriptional activity, 4 by altering mRNA secondary structure, and 1 by affecting the protein secondary structure of KLF6. These findings provided valuable molecular insights for genomic selection program of dairy cattle.

Integrated LC/MS-based lipidomics and transcriptomics analyses revealed lipid composition heterogeneity between pectoralis intramuscular fat and abdominal fat and its regulatory mechanism in chicken

Intramuscular fat (IMF) content is conducive to multiple meat quality properties, while abdominal fat (AF) is treated as waste product in chicken industry. However, the heterogeneity and distinct regulatory mechanisms of lipid composition between the IMF and AF are still unclear. In this study, we carried out non-targeted lipidomics analyses of pectoralis IMF and AF, and detected a total of 423 differential lipid molecules (DLMs) between chicken IMF and AF, including 307 up-regulated and 116 down-regulated DLMs in pectoral IMF. These DLMs exhibited the definite alteration of lipid composition. The up-reglated DLMs in IMF were mainly glycerophospholipids (GPs), including the bulk of phosphatidylcholines (PC, PC (P) and PC (O)), phosphatidylethanolamines (PE, PE (P) and PE (O)), phosphatidylglycerols (PG) and phosphatidylinositol (PI), while the up-reglated DLMs in AF were mainly glycerolipids (GLs), including most of triacylglycerols (TG) and diacylglycerols (DG). We further identified 28 main DLMs contributing to the heterogeneous deposition of IMF and AF, including 11 TGs common to IMF and AF, 12 PCs/PC (P)s specific to IMF and 5 DGs specific to AF. Further integration of transcriptome with the main DLMs by weighted gene co-expression network analysis (WGCNA), we found five key gene sets that included 386 unique genes promoting IMF deposition in pectoralis, 213 unique genes promoting AF deposition, 6 unique genes detrimental to AF deposition, 7 common genes that promote IMF deposition in pectoralis while adversely affect AF deposition, and 28 genes that only promoted IMF deposition in pectoralis but had no effect on AF deposition. In addition, we also observed the expression characteristics of key genes in vivo and in vitro, and found that transmembrane protein family gene TMEM164 might be mainly involved in the positive regulation of intramuscular fat deposition in pectoralis and zinc finger protein family gene ZNF488 had a potential unique positive regulatory function on abdominal fat deposition. These findings provide new perspectives for understanding IMF and AF heterodeposition and will serve as a valuable information resource for improving meat quality via breeding selection in chicken.

Increased body mass index is linked to systemic inflammation through altered chromatin co-accessibility in human preadipocytes

Obesity-induced adipose tissue dysfunction can cause low-grade inflammation and downstream obesity comorbidities. Although preadipocytes may contribute to this pro-inflammatory environment, the underlying mechanisms are unclear. We used human primary preadipocytes from body mass index (BMI) -discordant monozygotic (MZ) twin pairs to generate epigenetic (ATAC-sequence) and transcriptomic (RNA-sequence) data for testing whether increased BMI alters the subnuclear compartmentalization of open chromatin in the twins' preadipocytes, causing downstream inflammation. Here we show that the co-accessibility of open chromatin, i.e. compartmentalization of chromatin activity, is altered in the higher vs lower BMI MZ siblings for a large subset ( ~ 88.5 Mb) of the active subnuclear compartments. Using the UK Biobank we show that variants within these regions contribute to systemic inflammation through interactions with BMI on C-reactive protein. In summary, open chromatin co-accessibility in human preadipocytes is disrupted among the higher BMI siblings, suggesting a mechanism how obesity may lead to inflammation via gene-environment interactions.

Neglected PTM in Animal Adipogenesis: E3-mediated Ubiquitination

Ubiquitination is a widespread post-transcriptional modification (PTM) that occurs during protein degradation in eukaryotes and participates in almost all physiological and pathological processes, including animal adipogenesis. Ubiquitination is a cascade reaction regulated by the activating enzyme E1, conjugating enzyme E2, and ligase E3. Several recent studies have reported that E3 ligases play important regulatory roles in adipogenesis. However, as a key influencing factor for the recognition and connection between the substrate and ubiquitin during ubiquitination, its regulatory role in adipogenesis has not received adequate attention. In this review, we summarize the E3s' regulation and modification targets in animal adipogenesis, explain the regulatory mechanisms in lipogenic-related pathways, and further analyze the existing positive results to provide research directions of guiding significance for further studies on the regulatory mechanisms of E3s in animal adipogenesis.

Comparative three-dimensional genome architectures of adipose tissues provide insight into human-specific regulation of metabolic homeostasis

Elucidating the regulatory mechanisms of human adipose tissues (ATs) evolution is essential for understanding human-specific metabolic regulation, but the functional importance and evolutionary dynamics of three-dimensional (3D) genome organizations of ATs are not well defined. Here, we compared the 3D genome architectures of anatomically distinct ATs from humans and six representative mammalian models. We recognized evolutionarily conserved and human-specific chromatin conformation in ATs at multiple scales, including compartmentalization, topologically associating domain (TAD), and promoter-enhancer interactions (PEI), which have not been described previously. We found PEI are much more evolutionarily dynamic with respect to compartmentalization and topologically associating domain. Compared to conserved PEIs, human-specific PEIs are enriched for human-specific sequence, and the binding motifs of their potential mediators (transcription factors) are less conserved. Our data also demonstrated that genes involved in the evolutionary dynamics of chromatin organization have weaker transcriptional conservation than those associated with conserved chromatin organization. Furthermore, the genes involved in energy metabolism and the maintenance of metabolic homeostasis are enriched in human-specific chromatin organization, while housekeeping genes, health-related genes, and genetic variations are enriched in evolutionarily conserved compared to human-specific chromatin organization. Finally, we showed extensively divergent human-specific 3D genome organizations among one subcutaneous and three visceral ATs. Together, these findings provide a global overview of 3D genome architecture dynamics between ATs from human and mammalian models and new insights into understanding the regulatory evolution of human ATs.

Integrative genomic analyses in adipocytes implicate DNA methylation in human obesity and diabetes

DNA methylation variations are prevalent in human obesity but evidence of a causative role in disease pathogenesis is limited. Here, we combine epigenome-wide association and integrative genomics to investigate the impact of adipocyte DNA methylation variations in human obesity. We discover extensive DNA methylation changes that are robustly associated with obesity (N = 190 samples, 691 loci in subcutaneous and 173 loci in visceral adipocytes, P < 1 × 10-7). We connect obesity-associated methylation variations to transcriptomic changes at >500 target genes, and identify putative methylation-transcription factor interactions. Through Mendelian Randomisation, we infer causal effects of methylation on obesity and obesity-induced metabolic disturbances at 59 independent loci. Targeted methylation sequencing, CRISPR-activation and gene silencing in adipocytes, further identifies regional methylation variations, underlying regulatory elements and novel cellular metabolic effects. Our results indicate DNA methylation is an important determinant of human obesity and its metabolic complications, and reveal mechanisms through which altered methylation may impact adipocyte functions.

Krüppel-like factor 2: a central regulator of B cell differentiation and plasma cell homing

The development of B cells, their activation and terminal differentiation into antibody-producing plasma cells are characterized by alternating phases of proliferation and quiescence that are controlled by complex transcriptional networks. The spatial and anatomical organization of B cells and plasma cells inside lymphoid organs as well as their migration within lymphoid structures and between organs are prerequisites for the generation and the maintenance of humoral immune responses. Transcription factors of the Krüppel-like family are critical regulators of immune cell differentiation, activation, and migration. Here, we discuss the functional relevance of Krüppel-like factor 2 (KLF2) for B cell development, B cell activation, plasma cell formation and maintenance. We elaborate on KLF2-mediated regulation of B cell and plasmablast migration in the context of immune responses. Moreover, we describe the importance of KLF2 for the onset and the progression of B cell-related diseases and malignancies.

Krüppel-like Factors 4 and 5 in Colorectal Tumorigenesis

Krüppel-like factors (KLFs) are transcription factors regulating various biological processes such as proliferation, differentiation, migration, invasion, and homeostasis. Importantly, they participate in disease development and progression. KLFs are expressed in multiple tissues, and their role is tissue- and context-dependent. KLF4 and KLF5 are two fascinating members of this family that regulate crucial stages of cellular identity from embryogenesis through differentiation and, finally, during tumorigenesis. They maintain homeostasis of various tissues and regulate inflammation, response to injury, regeneration, and development and progression of multiple cancers such as colorectal, breast, ovarian, pancreatic, lung, and prostate, to name a few. Recent studies broaden our understanding of their function and demonstrate their opposing roles in regulating gene expression, cellular function, and tumorigenesis. This review will focus on the roles KLF4 and KLF5 play in colorectal cancer. Understanding the context-dependent functions of KLF4 and KLF5 and the mechanisms through which they exert their effects will be extremely helpful in developing targeted cancer therapy.

Genome-wide survey identifies TNNI2 as a target of KLF7 that inhibits chicken adipogenesis via downregulating FABP4

Krüppel-like factor 7 (KLF7) negatively regulates adipocyte differentiation; however, the mechanism underlying its activity in mammals and birds remains poorly understood. To identify genome-wide KLF7-binding motifs in preadipocytes, we conducted a chromatin immunoprecipitation-sequencing analysis of immortalized chicken preadipocytes (ICP2), which revealed 11,063 specific binding sites. Intergenic binding site analysis showed that KLF7 regulates several novel factors whose functions in chicken and mammal adipogenesis are underexplored. We identified a novel regulator, troponin I2 (TNNI2), which is positively regulated by KLF7. TNNI2 is downregulated during preadipocyte differentiation and acts as an adipogenic repressor at least in part by repressing FABP4 promoter activity. In conclusion, we demonstrated that KLF7 functions through cis-regulation of TNNI2, which inhibits adipogenesis. Our findings not only provide the first genome-wide picture of KLF7 associations in preadipocytes but also identify a novel function of TNNI2.

Neonatal intake of Omega-3 fatty acids enhances lipid oxidation in adipocyte precursors

Establishing metabolic programming begins during fetal and postnatal development, and early-life lipid exposures play a critical role during neonatal adipogenesis. We define how neonatal consumption of a low omega-6 to -3 fatty acid ratio (n6/n3 FA ratio) establishes FA oxidation in adipocyte precursor cells (APCs) before they become adipocytes. In vivo, APCs isolated from mouse pups exposed to the low n6/n3 FA ratio had superior FA oxidation capacity, elevated beige adipocyte mRNAs Ppargc1α, Ucp2, and Runx1, and increased nuclear receptor NR2F2 protein. In vitro, APC treatment with NR2F2 ligand-induced beige adipocyte mRNAs and increased mitochondrial potential but not mass. Single-cell RNA-sequencing analysis revealed low n6/n3 FA ratio yielded more mitochondrial-high APCs and linked APC NR2F2 levels with beige adipocyte signatures and FA oxidation. Establishing beige adipogenesis is of clinical relevance, because fat depots with energetically active, smaller, and more numerous adipocytes improve metabolism and delay metabolic dysfunction.

SP and KLF Transcription Factors in Cancer Metabolism

Tumor development and progression depend on reprogramming of signaling pathways that regulate cell metabolism. Alterations to various metabolic pathways such as glycolysis, oxidative phosphorylation, lipid metabolism, and hexosamine biosynthesis pathway are crucial to sustain increased redox, bioenergetic, and biosynthesis demands of a tumor cell. Transcription factors (oncogenes and tumor suppressors) play crucial roles in modulating these alterations, and their functions are tethered to major metabolic pathways under homeostatic conditions and disease initiation and advancement. Specificity proteins (SPs) and Krüppel-like factors (KLFs) are closely related transcription factors characterized by three highly conserved zinc fingers domains that interact with DNA. Studies have demonstrated that SP and KLF transcription factors are expressed in various tissues and regulate diverse processes such as proliferation, differentiation, apoptosis, inflammation, and tumorigenesis. This review highlights the role of SP and KLF transcription factors in the metabolism of various cancers and their impact on tumorigenesis. A better understanding of the role and underlying mechanisms governing the metabolic changes during tumorigenesis could provide new therapeutic opportunities for cancer treatment.

KLF6 facilitates differentiation of odontoblasts through modulating the expression of P21 in vitro

Multiple signaling pathways are involved in the regulation of cell proliferation and differentiation in odontogenesis and dental tissue renewal, but the details of these mechanisms remain unknown. Here, we investigated the expression patterns of a transcription factor, Krüppel-like factor 6 (KLF6), during the development of murine tooth germ and its function in odontoblastic differentiation. KLF6 was almost ubiquitously expressed in odontoblasts at various stages, and it was co-expressed with P21 (to varying degrees) in mouse dental germ. To determine the function of Klf6, overexpression and knockdown experiments were performed in a mouse dental papilla cell line (iMDP-3). Klf6 functioned as a promoter of odontoblastic differentiation and inhibited the proliferation and cell cycle progression of iMDP-3 through p21 upregulation. Dual-luciferase reporter assay and chromatin immunoprecipitation showed that Klf6 directly activates p21 transcription. Additionally, the in vivo study showed that KLF6 and P21 were also co-expressed in odontoblasts around the reparative dentin. In conclusion, Klf6 regulates the transcriptional activity of p21, thus promoting the cell proliferation to odontoblastic differentiation transition in vitro. This study provides a theoretical basis for odontoblast differentiation and the formation of reparative dentine regeneration.

A microRNA Cluster Controls Fat Cell Differentiation and Adipose Tissue Expansion By Regulating SNCG

The H19X-encoded miR-424(322)/503 cluster regulates multiple cellular functions. Here, it is reported for the first time that it is also a critical linchpin of fat mass expansion. Deletion of this miRNA cluster in mice results in obesity, while increasing the pool of early adipocyte progenitors and hypertrophied adipocytes. Complementary loss and gain of function experiments and RNA sequencing demonstrate that miR-424(322)/503 regulates a conserved genetic program involved in the differentiation and commitment of white adipocytes. Mechanistically, it is demonstrated that miR-424(322)/503 targets γ-Synuclein (SNCG), a factor that mediates this program rearrangement by controlling metabolic functions in fat cells, allowing adipocyte differentiation and adipose tissue enlargement. Accordingly, diminished miR-424(322) in mice and obese humans co-segregate with increased SNCG in fat and peripheral blood as mutually exclusive features of obesity, being normalized upon weight loss. The data unveil a previously unknown regulatory mechanism of fat mass expansion tightly controlled by the miR-424(322)/503 through SNCG.

The Crowded Uterine Horn Mouse Model for Examining Postnatal Metabolic Consequences of Intrauterine Growth Restriction vs. Macrosomia in Siblings

Differential placental blood flow and nutrient transport can lead to both intrauterine growth restriction (IUGR) and macrosomia. Both conditions can lead to adult obesity and other conditions clustered as metabolic syndrome. We previously showed that pregnant hemi-ovariectomized mice have a crowded uterine horn, resulting in siblings whose birth weights differ by over 100% due to differential blood flow based on uterine position. We used this crowded uterus model to compare IUGR and macrosomic male mice and also identified IUGR males with rapid (IUGR-R) and low (IUGR-L) postweaning weight gain. At week 12 IUGR-R males were heavier than IUGR-L males and did not differ from macrosomic males. Rapid growth in IUGR-R males led to glucose intolerance compared to IUGR-L males and down-regulation of adipocyte signaling pathways for fat digestion and absorption and type II diabetes. Macrosomia led to increased fat mass and altered adipocyte size distribution compared to IUGR males, and down-regulation of signaling pathways for carbohydrate and fat digestion and absorption relative to IUGR-R. Clustering analysis of gonadal fat transcriptomes indicated more similarities than differences between IUGR-R and macrosomic males compared to IUGR-L males. Our findings suggest two pathways to adult metabolic disease: macrosomia and IUGR with rapid postweaning growth rate.

Adipose and non-adipose perspectives of plant derived natural compounds for mitigation of obesity

ETHNOPHARMACOLOGICAL RELEVANCE

Phyto-preparations and phyto-compounds, by their natural origin, easy availability, cost-effectiveness, and fruitful traditional uses based on accumulated experiences, have been extensively explored to mitigate the global burden of obesity.

AIM OF THIS REVIEW

The review aimed to analyse and critically summarize the prospect of future anti-obesity drug leads from the extant array of phytochemicals for mitigation of obesity, using adipose related targets (adipocyte formation, lipid metabolism, and thermogenesis) and non-adipose targets (hepatic lipid metabolism, appetite, satiety, and pancreatic lipase activity). Phytochemicals as inhibitors of adipocyte differentiation, modulators of lipid metabolism, and thermogenic activators of adipocytes are specifically discussed with their non-adipose anti-obesogenic targets.

MATERIALS AND METHODS

PubMed, Google Scholar, Scopus, and SciFinder were accessed to collect data on traditional medicinal plants, compounds derived from plants, their reported anti-obesity mechanisms, and therapeutic targets. The taxonomically accepted name of each plant in this review has been vetted from "The Plant List" (www.theplantlist.org) or MPNS (http://mpns.kew.org).

RESULTS

Available knowledge of a large number of phytochemicals, across a range of adipose and non-adipose targets, has been critically analysed and delineated by graphical and tabular depictions, towards mitigation of obesity. Neuro-endocrinal modulation in non-adipose targets brought into sharp dual focus, both non-adipose and adipose targets as the future of anti-obesity research. Numerous phytochemicals (Berberine, Xanthohumol, Ursolic acid, Guggulsterone, Tannic acid, etc.) have been found to be effectively reducing weight through lowered adipocyte formation, increased lipolysis, decreased lipogenesis, and enhanced thermogenesis. They have been affirmed as potential anti-obesity drugs of future because of their effectiveness yet having no threat to adipose or systemic insulin sensitivity.

CONCLUSION

Due to high molecular diversity and a greater ratio of benefit to risk, plant derived compounds hold high therapeutic potential to tackle obesity and associated risks. This review has been able to generate fresh perspectives on the anti-diabetic/anti-hyperglycemic/anti-obesity effect of phytochemicals. It has also brought into the focus that many phytochemicals demonstrating in vitro anti-obesogenic effects are yet to undergo in vivo investigation which could lead to potential phyto-molecules for dedicated anti-obesity action.

Krüppel-like Factor 2 (KLF2) in Immune Cell Migration

Krüppel-like factor 2 (KLF2), a transcription factor of the krüppel-like family, is a key regulator of activation, differentiation, and migration processes in various cell types. In this review, we focus on the functional relevance of KLF2 in immune cell migration and homing. We summarize the key functions of KLF2 in the regulation of chemokine receptors and adhesion molecules and discuss the relevance of the KLF2-mediated control of immune cell migration in the context of immune responses, infections, and diseases.

Molecular mechanism of anti-adipogenic effect of vitexin in differentiating hMSCs

In this study, we evaluated a detailed molecular mechanism of anti-adipogenic activity of vitexin, apigenin flavone glucoside, present in germinated fenugreek seeds, in differentiating human mesenchymal stem cells (hMSCs). The lipid content of differentiated adipocytes was estimated by ORO staining. Effect on mitotic clonal expansion was checked by cell cycle analysis. Expression of early and terminal adipocyte differentiation markers, anti- and pro-adipogenic transcription factors and signalling intermediates regulating them was evaluated at RNA and protein level. We found vitexin to be non-cytotoxic up to 20 μM at which intracellular lipid accumulation was significantly decreased. Cell cycle analysis suggested that vitexin does not affect mitotic clonal expansion. Expression of early and late differentiation markers, such as CEBPα, CEBPβ, PPARγ, FABP4, perilipin, adiponectin and Glut4 was significantly reduced in the presence of vitexin. Expression of KLF4 and KLF15, positive regulators of PPARγ, was decreased, whereas that of negative regulators, namely KLF2, GATA2, miR20a, miR27a, miR27b, miR128, miR130a, miR130b, miR182 and miR548 increased with vitexin treatment. This effect was mediated by the activation of the AMP-activated protein kinase (AMPK) pathway via the activation of LepR and additionally by inhibiting ROS. Thus, our results showed that vitexin regulates the expression of PPARγ and inhibits adipogenesis of hMSCs at an early stage of differentiation.

KLF4 Inhibits the Differentiation of Goat Intramuscular Preadipocytes Through Targeting C/EBPβ Directly

Intramuscular fat (IMF) deposition is a complicated process, and most of the underlying regulators of this biological process are unknown. Here, we cloned the intact CDS of KLF4 gene, investigated the role of KLF4 by gaining or losing function in vitro and further explored the pathways of KLF4 regulating differentiation of intramuscular preadipocytes in goat. Our results show that goat KLF4 gene consists of 1,536 bp encoding a protein of 486 amino acids. The expression of KLF4 is higher in the lung while lower in the heart and muscle in goat. Knockdown of KLF4 mediated by siRNA technique significantly promotes intramuscular preadipocyte lipid accumulation and upregulates mRNA expression of adipogenic related genes including C/EBPα, C/EBPβ, and PPARγ in vivo cultured cells. Consistently, overexpression of KLF4 inhibits intramuscular adipocyte lipid accumulation and significantly downregulation gene expression of C/EBPβ, PPARγ, aP2, and Pref-1. Further, we found that other members of KLFs were upregulated or downregulated after interference or overexpression of KLF4, including KLF2 and KLF5-7. We also found that C/EBPβ was a potential target of KLF4, because it had an opposite expression pattern with KLF4 during the differentiation of intramuscular preadipocytes and had putative binding sites of KLF4. The dual-luciferase reporter assay indicated that overexpression of KLF4 inhibited the transcriptional activity of C/EBPβ. These results demonstrate that KLF4 inhibits the differentiation of intramuscular preadipocytes in goat by targeting C/EBPβ.

3D Adipose Tissue Culture Links the Organotypic Microenvironment to Improved Adipogenesis

Obesity and type 2 diabetes are strongly associated with adipose tissue dysfunction and impaired adipogenesis. Understanding the molecular underpinnings that control adipogenesis is thus of fundamental importance for the development of novel therapeutics against metabolic disorders. However, translational approaches are hampered as current models do not accurately recapitulate adipogenesis. Here, a scaffold-free versatile 3D adipocyte culture platform with chemically defined conditions is presented in which primary human preadipocytes accurately recapitulate adipogenesis. Following differentiation, multi-omics profiling and functional tests demonstrate that 3D adipocyte cultures feature mature molecular and cellular phenotypes similar to freshly isolated mature adipocytes. Spheroids exhibit physiologically relevant gene expression signatures with 4704 differentially expressed genes compared to conventional 2D cultures (false discovery rate < 0.05), including the concerted expression of factors shaping the adipogenic niche. Furthermore, lipid profiles of >1000 lipid species closely resemble patterns of the corresponding isogenic mature adipocytes in vivo (R2 = 0.97). Integration of multi-omics signatures with analyses of the activity profiles of 503 transcription factors using global promoter motif inference reveals a complex signaling network, involving YAP, Hedgehog, and TGFβ signaling, that links the organotypic microenvironment in 3D culture to the activation and reinforcement of PPARγ and CEBP activity resulting in improved adipogenesis.

Adipogenesis and therapeutic potentials of antiobesogenic phytochemicals: Insights from preclinical studies

Obesity is one of the most serious public health problems in both developed and developing countries in recent years. While lifestyle and diet modifications are the most important management strategies of obesity, these may be insufficient to ensure long-term weight reduction in certain individuals and alternative strategies including pharmacotherapy need to be considered. However, drugs option remains limited due to low efficacy and adverse effects associated with their use. Hence, identification of safe and effective alternative therapeutic agents remains warranted to combat obesity. In recent years, bioactive phytochemicals are considered as valuable sources for the discovery of new pharmacological agents for the treatment of obesity. Adipocyte hypertrophy and hyperplasia increases with obesity and undergo molecular and cellular alterations that can affect systemic metabolism giving rise to metabolic syndrome and comorbidities such as type 2 diabetes and cardiovascular diseases. Many phytochemicals have been reported to target adipocytes by inhibiting adipogenesis, inducing lipolysis, suppressing the differentiation of preadipocytes to mature adipocytes, reducing energy intake, and boosting energy expenditure mainly in vitro and in animal studies. Nevertheless, further high-quality studies are needed to firmly establish the clinical efficacy of these phytochemicals. This review outlines common pathways involved in adipogenesis and phytochemicals targeting effector molecules of these pathways, the challenges faced and the way forward for the development of phytochemicals as antiobesity agents.

Garcinia cambogia attenuates adipogenesis by affecting CEBPB and SQSTM1/p62-mediated selective autophagic degradation of KLF3 through RPS6KA1 and STAT3 suppression

The overexpansion of adipose tissues leads to obesity and eventually results in metabolic disorders. Garcinia cambogia (G. cambogia) has been used as an antiobesity supplement. However, the molecular mechanisms underlying the effects of G. cambogia on cellular processes have yet to be fully understood. Here, we discovered that G. cambogia attenuated the expression of CEBPB (CCAAT/enhancer binding protein (C/EBP), beta), an important adipogenic factor, suppressing its transcription in differentiated cells. In addition, G. cambogia inhibited macroautophagic/autophagic flux by decreasing autophagy-related gene expression and autophagosome formation. Notably, G. cambogia markedly elevated the expression of KLF3 (Kruppel-like factor 3 (basic)), a negative regulator of adipogenesis, by reducing SQSTM1/p62-mediated selective autophagic degradation. Furthermore, increased KLF3 induced by G. cambogia interacted with CTBP2 (C-terminal binding protein 2) to form a transcriptional repressor complex and inhibited Cebpa and Pparg transcription. Importantly, we found that RPS6KA1 and STAT3 were involved in the G. cambogia-mediated regulation of CEBPB and autophagic flux. In an obese animal model, G. cambogia reduced high-fat diet (HFD)-induced obesity by suppressing epididymal and inguinal subcutaneous white adipose tissue mass and adipocyte size, which were attributed to the regulation of targets that had been consistently identified in vitro. These findings provide new insight into the mechanism of G. cambogia-mediated regulation of adipogenesis and suggest molecular links to therapeutic targets for the treatment of obesity.

Effect of Temperature and Selection for Growth on Intracellular Lipid Accumulation and Adipogenic Gene Expression in Turkey Pectoralis Major Muscle Satellite Cells

As multipotential stem cells, satellite cells (SCs) have the potential to express adipogenic genes resulting in lipid synthesis with thermal stress. The present study determined the effect of temperature on intracellular lipid synthesis and adipogenic gene expression in SCs isolated from the pectoralis major (p. major) muscle of 7-day-old fast-growing modern commercial (NC) turkeys compared to SCs from unselected slower-growing turkeys [Randombred Control Line 2 (RBC2)]. Since proliferating and differentiating SCs have different responses to thermal stress, three incubation strategies were used: (1) SCs proliferated at the control temperature of 38°C and differentiated at 43° or 33°C; (2) SCs proliferated at 43° or 33°C and differentiated at 38°C; or (3) SCs both proliferated and differentiated at 43°, 38°, or 33°C. During proliferation, lipid accumulation increased at 43°C and decreased at 33°C with the NC line showing greater variation than the RBC2 line. During proliferation at 43°C, peroxisome proliferator-activated receptor-γ (PPARγ) and neuropeptide-Y (NPY) expression was reduced to a greater extent in the NC line than the RBC2 line. At 33°C, expression of PPARγ, NPY, and CCAAT/enhancer-binding protein-β (C/EBPβ) was upregulated, but only in the RBC2 line. During differentiation, both lines showed greater changes in lipid accumulation and in C/EBPβ and NPY expression if the thermal challenge was initiated during proliferation. These data suggest that adipogenic gene expression is more responsive to thermal challenge in proliferating SCs than in differentiating SCs, and that growth-selection has increased temperature sensitivity of SCs, which may significantly affect breast muscle structure and composition.

FGF10 and Lipofibroblasts in Lung Homeostasis and Disease: Insights Gained From the Adipocytes

Adipocytes not only function as energy depots but also secrete numerous adipokines that regulate multiple metabolic processes, including lipid homeostasis. Dysregulation of lipid homeostasis, which often leads to adipocyte hypertrophy and/or ectopic lipid deposition in non-adipocyte cells such as muscle and liver, is linked to the development of insulin resistance. Similarly, an altered secretion profile of adipokines or imbalance between calorie intake and energy expenditure is associated with obesity, among other related metabolic disorders. In lungs, lipid-laden adipocyte-like cells known as lipofibroblasts share numerous developmental and functional similarities with adipocytes, and similarly influence alveolar lipid homeostasis by facilitating pulmonary surfactant production. Unsurprisingly, disruption in alveolar lipid homeostasis may propagate several chronic inflammatory disorders of the lung. Given the numerous similarities between the two cell types, dissecting the molecular mechanisms underlying adipocyte development and function will offer valuable insights that may be applied to, at least, some aspects of lipofibroblast biology in normal and diseased lungs. FGF10, a major ligand for FGFR2b, is a multifunctional growth factor that is indispensable for several biological processes, including development of various organs and tissues such as the lung and WAT. Moreover, accumulating evidence strongly implicates FGF10 in several key aspects of adipogenesis as well as lipofibroblast formation and maintenance, and as a potential player in adipocyte metabolism. This review summarizes our current understanding of the role of FGF10 in adipocytes, while attempting to derive insights on the existing literature and extrapolate the knowledge to pulmonary lipofibroblasts.

Cooperation of ATF4 and CTCF promotes adipogenesis through transcriptional regulation

Adipogenesis is a multi-step process orchestrated by activation of numerous TFs, whose cooperation and regulatory network remain elusive. Activating transcription factor 4 (ATF4) is critical for adipogenesis, yet its regulatory network is unclarified. Here, we mapped genome-wide ATF4 binding landscape and its regulatory network by Chip-seq and RNA-seq and found ATF4 directly modulated transcription of genes enriching in fat cell differentiation. Motifs of TFs especially CTCF were found from ATF4 binding sites, suggesting a direct role of ATF4 in regulating adipogenesis associated with CTCF and other TFs. Deletion of CTCF attenuated adipogenesis while overexpression enhanced adipocyte differentiation, indicating CTCF is indispensable for adipogenesis. Intriguingly, combined analysis of Chip-seq data of these two TFs showed that ATF4 co-localized with CTCF in the promoters of key adipogenic genes including Cebpd and PPARg and co-regulated their transactivation. Moreover, ATF4 directly regulated CTCF expression and interacted with CTCF in differentiated 3T3-L1 cells. In vivo, downregulation of ATF4 suppressed the expression of CTCF, Cebpd, and PPARg, leading to reduced adipose tissue expansion in refeeding mice. Consistently, mRNA expression of ATF4 and CTCF was positively correlated with each other in human subcutaneous adipose tissue and inversely associated with BMI, indicating a possible involvement of these two TFs in adipose development. Taken together, our data propose for the first time that ATF4 and CTCF work cooperatively to control adipogenesis and adipose development via orchestrating transcription of adipogenic genes. Our findings reveal novel therapeutic targets in obesity treatment.

Analysis of long non-coding RNAs in skeletal muscle of Bama Xiang pigs in response to heat stress

The aim of this study was to identify differentially expressed long non-coding RNAs (lncRNAs) molecules and predict their target genes related to muscle development and lipid metabolism in longissimus dorsi (LD) muscles of Bama Xiang pigs under constant heat stress. Ten male Bama Xiang pigs with an average initial body weight of 14 kg were randomly divided into control group (22°C) and heat stress (35 °C) group. The experiment lasted for 28 days. All the pigs were slaughtered at the end of the experiment, and LD muscles were collected for muscle quality analysis and transcriptome sequencing. Heat stress reduced meat quality of Bama Xiang pigs. lncRNAs in LD were identified systematically by deep RNA sequencing between the two groups. The results showed that 365 lncRNAs from the LD were identified, including 128 intergenic lncRNAs, 82 intronic lncRNAs, and 155 anti-sense lncRNAs. The differences lie in transcript of length, number of exons and wider size distribution, and expression level per KB fragment in three subtypes of lncRNAs. The three types of transposable elements coverage, including Line/L1, SINE/tRNA, and LTR/ERVL-MaLR, are the highest in mRNA and the three subtypes of lncRNAs in pigs. lncRNAs and mRNAs were different in comparison of features. The results predicted the target genes of the significant differentially expressed lncRNAs related to muscle development and lipid metabolism. This is the first study to expand the knowledge about muscle-related lncRNAs biology in Bama Xiang pigs under heat stress and will contribute to the development of alleviating the adverse effects of heat stress on pork quality targeting lncRNAs.

Single-cell RNA sequencing of preadipocytes reveals the cell fate heterogeneity induced by melatonin

Obesity is a global epidemic health disorder and associated with several diseases. Body weight-reducing effects of melatonin have been reported; however, no investigation toward examining whether the beneficial effects of melatonin are associated with preadipocyte heterogeneity has been reported. In this study, we profiled 25 071 transcriptomes of normal and melatonin-treated preadipocytes using scRNA-seq. By tSNE analysis, we present a cellular-state landscape for melatonin-treated preadipocytes that covers multiple-cell subpopulations, defined as cluster 0 to cluster 13. Cluster 0 and cluster 1 were the largest components of normal and melatonin-treated preadipocytes, respectively. G0S2, an inhibitor of adipose triglyceride lipase (ATGL), was significantly upregulated in cluster 0 and downregulated in cluster 1. We redefined cluster 0 as the G0S2-positive cluster (G0S2⁺ ) and cluster 1 as the G0S2-negative cluster (G0S2^- ). Through pseudotime analysis, the G0S2^- cluster cell differentiation trajectory was divided into three major structures, that is, the prebranch, the lipid catabolism branch, and the cell fate 2 branch. In vitro, G0S2 knockdown enhanced the expression levels of ATGL, BAT markers and fatty acid oxidation-related genes, but inhibited C/EBPα and PPARγ expression. In vivo, knockdown of G0S2 reduced the body weight gain in high-fat-fed mice. The beneficial effects of the G0S2^- cell cluster in promoting lipolysis and inhibiting adipogenesis are dependent on two major aspects: first, downregulation of the G0S2 gene in the G0S2^- cluster, resulting in activation of ATGL, which is responsible for the bulk of triacylglycerol hydrolase activity; and second, upregulation of FABP4 in the G0S2^- cluster, resulting in inhibition of PPARγ and further reducing adipogenesis.

Effects of Ginsenoside Rg3 on Inhibiting Differentiation, Adipogenesis, and ER Stress-Mediated Cell Death in Brown Adipocytes

Objectives

Ginsenoside Rg3 (Rg3), a main active component of Panax ginseng, has various therapeutic properties in literatures, and it has been studied for its potential use in obesity control due to its antiadipogenic effects in white adipocytes. However, little is known about its effects on brown adipocytes.

Methods

The mechanisms through which Rg3 inhibits differentiation, adipogenesis, and ER stress-mediated cell death in mouse primary brown adipocytes (MPBAs) are explored.

Results

Rg3 significantly induced cytotoxicity in differentiated MPBAs but not in undifferentiated MPBAs. Rg3 treatment downregulated the expression of differentiation and adipogenesis markers and the level of perilipin in MPBAs while upregulating the expression of lipolytic Kruppel-like factor genes. Rg3 also induced lipolysis and efflux of triglycerides from MPBAs and subsequently increased proinflammatory cytokine levels. Notably, Rg3 treatment resulted in elevation of ER stress and proapoptotic markers in MPBAs.

Conclusions

Our results demonstrate that Rg3 is able to selectively exert cytotoxicity in differentiated MPBAs while leaving undifferentiated MPBAs intact, resulting in the induction of ER stress and subsequent cell death in MPBAs via regulation of various genes related to adipocyte differentiation, adipogenesis, lipolysis, and inflammation. These results indicate that further studies on the potential therapeutic applications of Rg3 are warranted.

KLF2 Inhibits Chicken Preadipocyte Differentiation at Least in Part via Directly Repressing PPARγ Transcript Variant 1 Expression

Peroxisome proliferator-activated receptor gamma (PPARγ) is the master regulatory factor of preadipocyte differentiation. As a result of alternative splicing and alternative promoter usage, PPARγ gene generates multiple transcript variants encoding two protein isoforms. Krüppel-like factor 2 (KLF2) plays a negative role in preadipocyte differentiation. However, its underlying mechanism remains incompletely understood. Here, we demonstrated that KLF2 inhibited the P1 promoter activity of the chicken PPARγ gene. Bioinformatics analysis showed that the P1 promoter harbored a conserved putative KLF2 binding site, and mutation analysis showed that the KLF2 binding site was required for the KLF2-mediated transcription inhibition of the P1 promoter. ChIP, EMSA, and reporter gene assays showed that KLF2 could directly bind to the P1 promoter regardless of methylation status and reduced the P1 promoter activity. Consistently, histone modification analysis showed that H3K9me2 was enriched and H3K27ac was depleted in the P1 promoter upon KLF2 overexpression in ICP1 cells. Furthermore, gene expression analysis showed that KLF2 overexpression reduced the endogenous expression of PPARγ transcript variant 1 (PPARγ1), which is driven by the P1 promoter, in DF1 and ICP1 cells, and that the inhibition of ICP1 cell differentiation by KLF2 overexpression was accompanied by the downregulation of PPARγ1 expression. Taken together, our results demonstrated that KLF2 inhibits chicken preadipocyte differentiation at least inpart via direct downregulation of PPARγ1 expression.

miR-32-5p Regulates Lipid Accumulation in Intramuscular Fat of Erhualian Pigs by Suppressing KLF3

Intramuscular fat (IMF) and subcutaneous fat (SCF) are important traits affecting the economics of the pork industry, in which less SCF and more IMF content is desirable. However, the mechanisms that regulate IMF and SCF content are not clear yet. In this study, we demonstrate that KLF3 (Krüppel-like factor 3) was negatively correlated with IMF content in the longissimus dorsi muscle of Erhualian pigs. In addition, the expression level of KLF3 was significantly higher in IMF than SCF. Overexpression and knockdown experiments revealed that KLF3 could suppress adipocyte differentiation in vitro by downregulating adipogenic markers, including PPARG, C/EBPA, and FABP4. Luciferase activity analysis proved that miR-32-5p was able to suppress KLF3. Notably, miR-32-5p level was negatively correlated to KLF3 mRNA level in both IMF and SCF tissues. The same relationship was proved in samples with different IMF content. Further studies showed that miR-32-5p could promote adipocyte differentiation via inhibiting KLF3. Our results suggest that the miR-32-5p-KLF3 pathway is involved in the regulation of differential fat deposition of IMF and SCF tissues.

New insights of Krüppel-like transcription factors in adipogenesis and the role of their regulatory neighbors

Obesity is a serious public health problem associated with predisposition to develop metabolic diseases. Over the past decade, several studies in vitro and in vivo have shown that the activity of Krüppel-like factors (KLFs) regulates adipogenesis, adipose tissue function and metabolism. Comprehension of both the origin and development of adipocytes and of adipose tissue could provide new insights into therapeutic strategies to contend against obesity and related metabolic diseases. This review focus on the transcriptional role that KLF family members play during adipocyte differentiation, describes their main interactions and the mechanisms involved in this fine-tuned developmental process. We also summarize new findings of the involvement of several effectors that modulate KLFs expression during adipogenesis, including growth factors, circadian clock proteins, interleukins, nuclear receptors, protein kinases and importantly, microRNAs. Thus, KLFs regulation by these factors and emerging molecules might constitute a potential therapeutic target for anti-obesity intervention.

X chromosome dosage of histone demethylase KDM5C determines sex differences in adiposity

Males and females differ in body composition and fat distribution. Using a mouse model that segregates gonadal sex (ovaries and testes) from chromosomal sex (XX and XY), we showed that XX chromosome complement in combination with a high-fat diet led to enhanced weight gain in the presence of male or female gonads. We identified the genomic dosage of Kdm5c, an X chromosome gene that escapes X chromosome inactivation, as a determinant of the X chromosome effect on adiposity. Modulating Kdm5c gene dosage in XX female mice to levels that are normally present in males resulted in reduced body weight, fat content, and food intake to a degree similar to that seen with altering the entire X chromosome dosage. In cultured preadipocytes, the levels of KDM5C histone demethylase influenced chromatin accessibility (ATAC-Seq), gene expression (RNA-Seq), and adipocyte differentiation. Both in vitro and in vivo, Kdm5c dosage influenced gene expression involved in extracellular matrix remodeling, which is critical for adipocyte differentiation and adipose tissue expansion. In humans, adipose tissue KDM5C mRNA levels and KDM5C genetic variants were associated with body mass. These studies demonstrate that the sex-dependent dosage of Kdm5c contributes to male/female differences in adipocyte biology and highlight X-escape genes as a critical component of female physiology.

Novel Insights into Adipogenesis from the Perspective of Transcriptional and RNA N6-Methyladenosine-Mediated Post-Transcriptional Regulation

Obesity is a critical risk factor causing the development of metabolic diseases and cancers. Its increasing prevalence worldwide has aroused great concerns of the researchers on adipose development and metabolic function. During adipose expansion, adipogenesis is a way to store lipids as well as to avoid lipotoxicity in other tissues, and may be an approach to offset the negative metabolic effects of obesity. In this Review, the transcriptional regulation of adipogenesis is outlined to characterize numerous biological processes in research on the determination of adipocyte fate and regulation of adipogenic differentiation. Notably, one of the post-transcriptional modifications of mRNA, namely, N6-methyladenosine (m6A), has been recently found to play a role in adipogenesis. Here, the roles of m6A-related enzymes and proteins in adipogenesis, with a particular focus on how these m6A-related proteins function at different stages of adipogenesis, are mainly discussed. The Review also highlights the coordination role of the transcriptional and post-transcriptional (RNA m6A methylation) regulation in adipogenesis and related biological processes. In this context, a better understanding of adipogenesis at both the transcriptional and post-transcriptional levels may facilitate the development of novel strategies to improve metabolic health in obesity.

Regulation of adipocyte differentiation by clusterin-mediated Krüppel-like factor 5 stabilization

Clusterin (CLU) is a heterodimeric glycoprotein involved in a range of biological processes. We investigated the function of CLU as a novel regulator of adipogenesis. CLU expression increased during 3T3-L1 preadipocyte differentiation. CLU overexpression promoted adipogenic differentiation of preadipocytes and increased the mRNA levels of adipogenic markers including peroxisome proliferator-activated receptor γ (Pparg) and CCAAT enhancer-binding protein α (Cebpa). Conversely, knockdown of CLU attenuated adipogenesis and reduced transcript levels of Pparg and Cebpa. However, the promoter activities of both the Pparg and the Cebpa gene were not affected by alteration of CLU expression on its own. Additionally, the protein level of Krüppel-like factor 5 (KLF5), an upstream transcription factor of Pparg and Cebpa involved in adipogenic differentiation, was upregulated by CLU overexpression, although the mRNA level of Klf5 was not altered by changes in the expression level of CLU. Cycloheximide chase assay showed that the increased level of KLF5 by CLU overexpression was due to decreased degradation of KLF5 protein. Interestingly, CLU increased the stability of KLF5 by decreasing KLF5 ubiquitination. CLU inhibited the interaction between KLF5 and F-box/WD repeat-containing protein 7, which is an E3 ubiquitin ligase that targets KLF5. The adipogenic role of CLU was also addressed in mesenchymal stem cells (MSCs) and Clu^-/- mouse embryonic fibroblasts (MEFs). Furthermore, CLU enhanced KLF5-mediated transcriptional activation of both the Cebpa and the Pparg promoter. Taken together, these results suggest that CLU is a novel regulator of adipocyte differentiation by modulating the protein stability of the adipogenic transcription factor KLF5.

Role of KLF2: New insight in inflammatory acne pathogenesis

BACKGROUND

Acne is an inflammatory skin condition of pilosebaceous unit. Its pathogenesis is multifactorial with a central role of inflammatory and pro-inflammatory cytokines mediators. Downregulated Kruppel-like factor 2 (KLF2) leads to rapid secretion of many cytokines that are involved in acne pathogenesis.

AIMS

This study aimed at evaluating the level of KLF2 mRNA, clarifying its role in acne pathogenesis and its relation to acne lesion type, degree of severity, and outcome.

PATIENTS AND METHODS

The level of KLF2 mRNA was measured in 100 patients with acne and 50 age- and sex-matched healthy controls by using quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

The value of KLF2 mRNA was lower in acne patients than control group (P < .001), being lowest in inflammatory acne group (grades III, IV, and V) than noninflammatory acne group (grades I and II) and highest in the control group (P < .001). KLF2 mRNA was decreased significantly with increased acne severity grade (P < .001). KLF2 mRNA was lower in cases healed by scars than those healed by postinflammatory hyperpigmentation.

CONCLUSIONS

Decreased serum level of KLF2 is not only a claimed for AV pathogenesis but also a predictor for degree of acne severity and outcome.

Transcription Factor KLF14 and Metabolic Syndrome

Metabolic syndrome (MetSyn) is a combination of metabolic abnormalities that lead to the development of cardiovascular disease (CVD) and Type 2 Diabetes (T2D). Although various criteria for defining MetSyn exist, common abnormalities include abdominal obesity, elevated serum triglyceride, insulin resistance, and blood glucose, decreased high-density lipoprotein cholesterol (HDL-C), and hypertension. MetSyn prevalence has been increasing with the rise of obesity worldwide, with significantly higher prevalence in women compared with men and in Hispanics compared with Whites. Affected individuals are at a higher risk of developing T2D (5-fold) and CVD (2-fold). Heritability estimates for individual components of MetSyn vary between 40 and 70%, suggesting a strong contribution of an individual's genetic makeup to disease pathology. The advent of next-generation sequencing technologies has enabled large-scale genome-wide association studies (GWAS) into the genetics underlying MetSyn pathogenesis. Several such studies have implicated the transcription factor KLF14, a member of the Krüpple-like factor family (KLF), in the development of metabolic diseases, including obesity, insulin resistance, and T2D. How KLF14 regulates these metabolic traits and increases the risk of developing T2D, atherosclerosis, and liver dysfunction is still unknown. There have been some debate and controversial results with regards to its expression profile and functionality in various tissues, and a systematic review of current knowledge on KLF14 is lacking. Here, we summarize the research progress made in understanding the function of KLF14 and describe common attributes of its biochemical, physiological, and pathophysiological roles. We also discuss the current challenges in understanding the role of KLF14 in metabolism and provide suggestions for future directions.

Knockdown of KLF9 promotes the differentiation of both intramuscular and subcutaneous preadipocytes in goat

KLF9 is reported to promote adipocyte differentiation in 3T3-L1 cells and pigs. However, the roles of KLF9 in adipocytes differentiation of goat remain unknown. In this study, the expression profiles of KLF9 were different between subcutaneous and intramuscular preadipocytes of goat during differentiation process. After silencing KLF9 gene, the lipid droplets were increased in both two types of adipocytes. In subcutaneous preadipocyte with silencing KLF9, the expressions of C/EBPβ, PPARγ, LPL, KLF1-2, KLF5, and KLF17 genes were up-regulated, while KLF12, KLF4, and KLF13 genes were down-regulated in expression level. In intramuscular preadipocyte, aP2, C/EBPα, KLF2-3, KLF5, and KLF7 gene were up-regulated, and Pref-1 gene was down-regulated. In addition, the binding sites of KLF9 existed in the promoters of aP2, C/EBPα, C/EBPβ, LPL and Pref-1. Taken together, KLF9 play a negative role in the differentiation of both intramuscular and subcutaneous preadipocytes in goats, but the functional mechanism may be different.

Adipocyte dedifferentiation in health and diseases

Adipose tissues collectively as an endocrine organ and energy storage are crucial for systemic metabolic homeostasis. The major cell type in the adipose tissue, the adipocytes or fat cells, are remarkably plastic and can increase or decrease their size and number to adapt to changes in systemic or local metabolism. Changes in adipocyte size occur through hypertrophy or atrophy, and changes in cell numbers mainly involve de novo generation of new cells or death of existing cells. Recently, dedifferentiation, whereby a mature adipocyte is reverted to an undifferentiated progenitor-like status, has been reported as a mechanism underlying adipocyte plasticity. Dedifferentiation of mature adipocytes has been observed under both physiological and pathological conditions. This review covers several aspects of adipocyte dedifferentiation, its relevance to adipose tissue function, molecular pathways that drive dedifferentiation, and the potential of therapeutic targeting adipocyte dedifferentiation in human health and metabolic diseases.

Transcription Factor KLF2 and Its Role in the Regulation of Inflammatory Processes

KLF2 is a member of the Krüppel-like transcription factor family of proteins containing highly conserved DNA-binding zinc finger domains. KLF2 participates in the differentiation and regulation of the functional activity of monocytes, T lymphocytes, adipocytes, and vascular endothelial cells. The activity of KLF2 is controlled by several regulatory systems, including the MEKK2,3/MEK5/ERK5/MEF2 MAP kinase cascade, Rho family G-proteins, histone acetyltransferases CBP and p300, and histone deacetylases HDAC4 and HDAC5. Activation of KLF2 in endothelial cells induces eNOS expression and provides vasodilatory effect. Many KLF2-dependent genes participate in the suppression of blood coagulation and aggregation of T cells and macrophages with the vascular endothelium, thereby preventing atherosclerosis progression. KLF2 can have a dual effect on the gene transcription. Thus, it induces expression of multiple genes, but suppresses transcription of NF-κB-dependent genes. Transcription factors KLF2 and NF-κB are reciprocal antagonists. KLF2 inhibits induction of NF-κB-dependent genes, whereas NF-κB downregulates KLF2 expression. KLF2-mediated inhibition of NF-κB signaling leads to the suppression of cell response to the pro-inflammatory cytokines IL-1β and TNFα and results in the attenuation of inflammatory processes.

Systematic Transcriptome and Regulatory Network Analyses Reveal the Hypoglycemic Mechanism of Dendrobium fimbriatum

Type 2 diabetes (T2D) is a long-term metabolic disorder disease characterized by high blood sugar and relative lack of insulin. Previous studies have demonstrated that Dendrobium has potent glucose-lowing effects and may serve as add-ons or alternatives to classic medications for T2D prevention and treatment, but the underlying molecular mechanisms were still unclear. We performed biochemical and transcriptional profiling (RNA sequencing [RNA-seq] and microRNA sequencing [miRNA-seq]) analyses on the pancreas and liver of Dendrobium fimbriatum extract (DFE)-fed diabetic rats and control animals. Our sequencing and experimental data indicated that DFE significantly alleviated diabetes symptoms through inhibiting inflammation and preventing islet cell apoptosis in diabetic pancreas. Transcription factors in Stat/nuclear factor κB (NF-κB)/Irf families combined with miR-148a/375/9a served as key regulators in the inflammation and apoptosis pathways under DFE administration. Meanwhile, DFE improved the energy metabolism, lipid transport, and oxidoreductase activity in the liver, and thus decreased lipid accumulation and lipotoxicity-induced hepatocyte apoptosis. Our findings revealed that DFE may serve as a potential therapeutic agent to prevent T2D, and also showed the combination of transcriptome profiling and regulatory network analysis could act as an effective approach for investigating potential molecular mechanisms of traditional Chinese medicine on diseases.

Genetic variants in the TORC2 gene promoter and their association with body measurement and carcass quality traits in Qinchuan cattle

The TORC2 gene is responsible for nutrient metabolism, gluconeogenesis, myogenesis and adipogenesis through the PI3K-Akt, AMPK, glucagon and insulin resistance signaling pathways. Sequencing of PCR amplicons explored three novel SNPs at loci g.16534694G>A, g.16535011C>T, and g.16535044A>T in the promoter region of the TORC2 gene in the Qinchuan breed of cattle. Allelic and genotypic frequencies of these SNPs deviated from Hardy-Weinberg equilibrium (HWE) (P < 0.05). SNP1 genotype GG, SNP2 genotype CT and SNP3 genotype AT showed significantly (P <0.05) larger body measurement and improved carcass quality traits. Haplotype H1 (GCA) showed significantly (p<0.01) higher transcriptional activity (51.44%) followed by H4 (ATT) (34.13%) in bovine preadipocytes. The diplotypes HI-H3 (GG-CC-AT), H1-H2 (GG-CT-AT) and H3-H4 (GA-CT-TT) showed significant (P<0.01) associations with body measurement and improved carcass quality traits. Analysis of the relative mRNA expression level of the TORC2 gene in different tissues within two different age groups revealed a significant increase (P<0.01) in liver, small intestine, muscle and fat tissues with growth from calf stage to adult stage. We can conclude that variants mapped within TORC2 can be used in marker-assisted selection for carcass quality and body measurement traits in breed improvement programs of Qinchuan cattle.

Fibroblast growth factor 21 regulates lipid accumulation and adipogenesis in goat intramuscular adipocyte

Fibroblast growth factor 21 (FGF21) plays a critical role in the regulation of lipid metabolism; however, its function in goat intramuscular fat (IMF) deposition remains unknown. To explore the role of FGF21 for goat IMF deposition, we performed gain and loss function of FGF21 in intramuscular adipocyte. Our results showed that overexpression of FGF21 mediated by adenovirus inhibits lipid accumulation of goat intramuscular adipocyte, accompanied by down-regulating the mRNA levels of peroxisome proliferator activated receptor γ (PPARγ), adipocyte fatty acid-binding protein 2 (aP2) and sterol regulatory element-binding protein 1 (SREBP1), but up-regulating counterpart of preadipocyte factor1 (Pref1). Conversely, siRNAs knocking down FGF21 promotes the expression of PPARγ and CCAAT/enhancer binding protein-α (C/EBPα) but suppressed that of lipoprotein lipase (LPL) and Pref1. Meanwhile, we found that FGF21 regulates the expression of many KLFs transcription factors, such as KLF3, 7, 9, 11, 14, and 16. These findings demonstrate a key role of FGF21 as a negative factor in the regulation of adipogenic differentiation in goat intramuscular preadipocyte.

The effects of vitamin A supplementation during late-stage pregnancy on longissimus dorsi muscle tissue development, birth traits, and growth performance in postnatal Korean native calves

OBJECTIVE

This study investigated the effects of vitamin A (VA) supplementation during late-stage pregnancy on longissimus dorsi muscle tissue development, birth traits, and growth performance of postnatal Korean native calves.

METHODS

In the preliminary experiment, twenty-six pregnant cattle (initial body weight [BW] = 319 kg (standard deviation [SD] = 30.1; 1st parity) were randomly assigned to the control and treatment groups. The treatment group received VA supplementation at 24,000 IU/d from gestational day 225 until delivery. In the main experiment, twelve pregnant cattle (initial BW = 317 kg [SD = 31.3]; 1st parity) were treated with VA supplementation at 24,000 IU/d (gestational days 150 to 225) and at 78,000 IU/d (gestational day 225 until delivery). Serum VA levels were analyzed in pregnant cattle, and the growth performance, gene expression, and serum VA levels were analyzed in the offspring.

RESULTS

Serum VA levels in pregnant cattle decreased the late gestation in both experiments (p<0.001). In the main experiment, pregnant cattle at parturition and offspring at birth in the treatment group had higher serum VA levels than those in the control group (p<0.05). In the treatment groups, an increased birth weight was observed in the main experimental group (p = 0.022), and a tendency (p = 0.088) toward an increased birth weight was observed in the preliminary experimental group. However, no differences were observed in the feed intake, average daily gain, gain-to-feed ratio, or BW of 31-day-old calves. Gene expression was analyzed in longissimus dorsi muscles of 31-day-old calves. VA supplementation in pregnant cattle stimulated postnatal muscle development in offspring by elevating myogenic factor 5 (MYF5), MYF6, and myoblast determination levels (p<0.05). Moreover, preadipocyte-related marker genes such as extracellular signal-regulated kinase 2 and krüppel-like factor 2 were higher in the treatment group than in the control group (p<0.05).

CONCLUSION

VA supplementation (78,000 IU/d) in late-stage pregnant cattle maintained serum VA levels. In addition, 78,000 IU/d VA supplementation increased the birth weight and expression of genes related to muscle and preadipocyte development in offspring. Overall, 78,000 IU/d VA supplementation in pregnant cattle is beneficial to newborn calves.

1α, 25-dihydroxy Vitamin D3 containing fractions of Catharanthus roseus leaf aqueous extract inhibit preadipocyte differentiation and induce lipolysis in 3T3-L1 cells

BACKGROUND

To investigate the potential of Catharanthus roseus leaf aqueous crude extract (CRACE) as a regulator of adipocyte development and function.

METHODS

3T3-L1 adipogenesis model was used to investigate the effect of CRACE on adipogenesis. 3T3-L1 preadipocytes (for adipogenic differentiation) and mature 3T3-L1 adipocytes (for adipocyte function) were treated with non-toxic doses of CRACE. The outcomes were corroborated by intracellular lipid accumulation, expression of pro-and anti-adipogenic effector molecules. To investigate CRACE mediated lipolysis, cAMP accumulation, glycerol release and phosphorylation of key effector molecules were tested in treated mature adipocytes. Finally, the extract was fractionated to identify the active molecule/s in the extract.

RESULTS

CRACE significantly reduced adipocyte differentiation by modulating PPARγ expression. At early stage CRACE directly targeted Lipin1 expression and consequently impacted KLF7, subsequently expression of GATA2, CEBPα, SREBP1c were targeted, with PPARγ expression, particularly curtailed. While CRACE significantly reduced several lipogenic genes like FAS and GPD1 in mature adipocytes, concomitantly, it greatly increased lipolysis resulting in decreased lipid accumulation in mature adipocytes. The increase in lipolysis was due to decreased Akt activation, increased cAMP level, and PKA activity. The fractionation of CRACE allowed identification of two fractions with potent anti-adipogenic activity. Both the fractions contained 1α, 25-dihydroxy Vitamin D3 as major component.

CONCLUSIONS

1α, 25-dihydroxy Vitamin D3 containing CRACE can be developed into an effective anti-obesity formulation that decreases adipogenesis and increases lipid catabolism.

Krüppel-like factor KLF9 inhibits chicken intramuscular preadipocyte differentiation

1. Poultry meat quality is affected by many factors, among which intramuscular fat (IMF) is predominant. IMF content affects tenderness, juiciness and flavour of meat. Krüppel-like transcriptional factors (KLFs) are important regulators of adipocyte differentiation. However, little is known about the KLF9 gene associated with poultry IMF deposition, especially intramuscular adipocyte differentiation.2. Previous work has shown that chicken KLF9 was differentially expressed during adipogenesis of intramuscular preadipocytes differentiation. In this study, the function of KLF9 in chicken intramuscular preadipocytes differentiation was investigated.3. In the chicken preadipocyte differentiation model, KLF9 expression showed a major increase with adipogenic induction. Overexpression of KLF9 down-regulated the expression of the adipogenic marker gene AP2, and impaired triglyceride accumulation. Knockdown of KLF9 in chicken intramuscular preadipocytes increased the expression of PPARG, CEBPA and AP2. In addition, it was proposed that KLF9 may regulate adipogenesis via lncRNAs NONGGAT002209.2, NONGGAT003346.2, NONGGAT000436.2 and NONGGAT006302.2 in chicken.4. The data supported a novel role of KLF9 in regulating chicken intramuscular preadipocyte differentiation. Such findings may contribute to a more thorough understanding of chicken IMF deposition and the improvement of poultry meat quality.