The Krüppel-Like Factors and Control of Energy Homeostasis

White adipocytes in subcutaneous fat depots require KLF15 for maintenance in preclinical models

Healthy adipose tissue is essential for normal physiology. There are 2 broad types of adipose tissue depots: brown adipose tissue (BAT), which contains adipocytes poised to burn energy through thermogenesis, and white adipose tissue (WAT), which contains adipocytes that store lipids. However, within those types of adipose, adipocytes possess depot and cell-specific properties that have important implications. For example, the subcutaneous and visceral WAT confers divergent risk for metabolic disease. Further, within a depot, different adipocytes can have distinct properties; subcutaneous WAT can contain adipocytes with either white or brown-like (beige) adipocyte properties. However, the pathways that regulate and maintain this cell and depot-specificity are incompletely understood. Here, we found that the transcription factor KLF15 is required for maintaining white adipocyte properties selectively within the subcutaneous WAT. We revealed that deletion of Klf15 is sufficient to induce beige adipocyte properties and that KLF15's direct regulation of Adrb1 is a critical molecular mechanism for this process. We uncovered that this activity is cell autonomous but has systemic implications in mouse models and is conserved in primary human adipose cells. Our results elucidate a pathway for depot-specific maintenance of white adipocyte properties that could enable the development of therapies for obesity and associated diseases.

Npy transcription is regulated by noncanonical STAT3 signaling in hypothalamic neurons: Implication with lipotoxicity and obesity

Neuropeptide Y (Npy) is an abundant neuropeptide expressed in the central and peripheral nervous systems. NPY-secreting neurons in the hypothalamic arcuate nucleus regulate energy homeostasis, and Npy mRNA expression is regulated by peripheral nutrient and hormonal signals like leptin, interleukin-6 (IL-6), and fatty acids. This study demonstrates that IL-6, which phosphorylates tyrosine 705 (Y705) of STAT3, decreased Npy mRNA in arcuate immortalized hypothalamic neurons. In parallel, inhibitors of STAT3-Y705 phosphorylation, stattic and cucurbitacin I, robustly upregulated Npy mRNA. Chromatin-immunoprecipitation showed high baseline total STAT3 binding to multiple regulatory regions of the Npy gene, which are decreased by IL-6 exposure. The STAT3-Npy interaction was further examined in obesity-related pathologies. Notably, in four different hypothalamic neuronal models where palmitate potently stimulated Npy mRNA, Socs3, a specific STAT3 activity marker, was downregulated and was negatively correlated with Npy mRNA levels (R2 = 0.40, p < 0.001), suggesting that disrupted STAT3 signaling is involved in lipotoxicity-mediated dysregulation of Npy. Finally, human NPY SNPs that map to human obesity or body mass index were investigated for potential STAT3 binding sites. Although none of the SNPs were linked to direct STAT3 binding, analysis show that rs17149106 (-602 G > T) is located on an upstream enhancer element of NPY, where the variant is predicted to disrupt validated binding of KLF4, a known inhibitory cofactor of STAT3 and downstream effector of leptin signaling. Collectively, this study demonstrates that STAT3 signaling negatively regulates Npy transcription, and that disruption of this interaction may contribute to metabolic disorders.

A transcription factor (TF) inference method that broadly measures TF activity and identifies mechanistically distinct TF networks

TF profiler is a method of inferring transcription factor regulatory activity, i.e. when a TF is present and actively regulating transcription, directly directly from nascent sequencing assays such as PRO-seq and GRO-seq. Transcription factors orchestrate transcription and play a critical role in cellular maintenance, identity and response to external stimuli. While ChIP assays have measured DNA localization, they fall short of identifying when and where transcription factors are actively regulating transcription. Our method, on the other hand, uses RNA polymerase activity to infer TF activity across hundreds of data sets and transcription factors. Based on these classifications we identify three distinct classes of transcription factors: ubiquitous factors that play roles in cellular homeostasis, driving basal gene programs across tissues and cell types, tissue specific factors that act almost exclusively at enhancers and are themselves regulated at transcription, and stimulus responsive TFs which are regulated post-transcriptionally but act predominantly at enhancers. TF profiler is broadly applicable, providing regulatory insights on any PRO-seq sample for any transcription factor with a known binding motif.

Bovine enhancer-regulated circSGCB acts as a ceRNA to regulate skeletal muscle development via enhancing KLF3 expression

Skeletal muscle growth and development in livestock and poultry play a pivotal role in determining the quality and yield of meat production. However, the mechanisms of myogenesis are remained unclear due to it finely regulated by a complex network of biological macromolecules. In this study, leveraging previous sequencing data, we investigated a differentially expressed circular RNA (circSGCB) present in fetal and adult muscle tissues among various ruminant species, including cattle, goat, and sheep. Our analysis revealed that circSGCB is a single exon circRNA, potentially regulated by an adjacent bovine enhancer. Functional analysis through loss-of-function tests demonstrated that circSGCB exerts inhibitory effects on bovine myoblast proliferation while promoting myocytes generation. Furthermore, we discovered that circSGCB primarily localizes to the cytoplasm, where it functions as a molecular sponge by binding to bta-miR-27a-3p. This interaction releases the mRNAs of KLF3 gene and further activates downstream functional pathways. In vivo, studies provided evidence that up-regulation of KLF3 contributes to muscle regeneration. These findings collectively suggest that circSGCB operates via a competing endogenous RNA (ceRNA) mechanism to regulate KLF3, thereby influencing myogenesis in ruminants and highlights it may as potential molecular targets for enhancing meat production in livestock and poultry industries.

Malat1 regulates PMN-MDSC expansion and immunosuppression through p-STAT3 ubiquitination in sepsis

Myeloid-derived suppressor cells (MDSCs) expand during sepsis and contribute to the development of persistent inflammation-immunosuppression-catabolism syndrome. However, the underlying mechanism remains unclear. Exploring the mechanisms of MDSCs generation may provide therapeutic targets for improving immune status in sepsis. Here, a sepsis mouse model is established by cecal ligation and perforation. Bone marrow cells at different sepsis time points are harvested to detect the proportion of MDSCs and search for differentially expressed genes by RNA-sequence. In lethal models of sepsis, polymorphonuclear-MDSCs (PMN-MDSCs) decrease in early but increase and become activated in late sepsis, which is contrary to the expression of metastasis-associated lung adenocarcinoma transcript 1 (Malat1). In vivo, Malat1 inhibitor significantly increases the mortality in mice with late sepsis. And in vitro, Malat1 down-regulation increases the proportion of PMN-MDSCs and enhanced its immunosuppressive ability. Mechanistically, Malat1 limits the differentiation of PMN-MDSCs by accelerating the degradation of phosphorylated STAT3. Furthermore, Stattic, an inhibitor of STAT3 phosphorylation, improves the survival of septic mice by inhibiting PMN-MDSCs. Overall, the study identifies a novel insight into the mechanism of sepsis-induced MDSCs and provides more evidence for targeting MDSCs in the treatment of sepsis.

KLF3 promotes colorectal cancer growth by activating WNT1

OBJECTIVE

The function of Kruppel-like factor 3 (KLF3) remains largely unexplored in colorectal cancer (CRC).

METHODS

KLF3 expression in CRC was assessed through qPCR, western blotting, immunohistochemical assays, and The Cancer Genome Atlas (TCGA) database. The tumor-promoting capacity of KLF3 was explored by performing in vitro functional experiments using CRC cells. A subcutaneous nude mouse tumor assay was employed to evaluate tumor growth. To further elucidate the interaction between KLF3 and other factors, luciferase reporter assay, agarose gel electrophoresis, and ChIP analysis were performed.

RESULTS

KLF3 was downregulated in CRC tissue and cells. Silencing of KLF3 increased the potential of CRC cells for proliferation, migration, and invasion, while its activation decreased these processes. Downregulated KLF3 was associated with accelerated tumor growth in vivo. Mechanistically, KLF3 was discovered to target the promoter sequence of WNT1. Consequently, the diminished expression of KLF3 led to the buildup of WNT1 and the WNT/β-catenin pathway activation, consequently stimulating the progression of CRC.

CONCLUSIONS

This investigation suggests that the involvement of KLF3/WNT1 regulatory pathway contributes to the progression of CRC, thereby emphasizing its promise as an important focus for future therapies aimed at treating CRC.

Hypertrophic cardiomyopathy in MYBPC3 carriers in aging

Hypertrophic cardiomyopathy (HCM) is characterized by abnormal thickening of the myocardium, leading to arrhythmias, heart failure, and elevated risk of sudden cardiac death, particularly among the young. This inherited disease is predominantly caused by mutations in sarcomeric genes, among which those in the cardiac myosin binding protein-C3 (MYBPC3) gene are major contributors. HCM associated with MYBPC3 mutations usually presents in the elderly and ranges from asymptomatic to symptomatic forms, affecting numerous cardiac functions and presenting significant health risks with a spectrum of clinical manifestations. Regulation of MYBPC3 expression involves various transcriptional and translational mechanisms, yet the destiny of mutant MYBPC3 mRNA and protein in late-onset HCM remains unclear. Pathogenesis related to MYBPC3 mutations includes nonsense-mediated decay, alternative splicing, and ubiquitin-proteasome system events, leading to allelic imbalance and haploinsufficiency. Aging further exacerbates the severity of HCM in carriers of MYBPC3 mutations. Advancements in high-throughput omics techniques have identified crucial molecular events and regulatory disruptions in cardiomyocytes expressing MYBPC3 variants. This review assesses the pathogenic mechanisms that promote late-onset HCM through the lens of transcriptional, post-transcriptional, and post-translational modulation of MYBPC3, underscoring its significance in HCM across carriers. The review also evaluates the influence of aging on these processes and MYBPC3 levels during HCM pathogenesis in the elderly. While pinpointing targets for novel medical interventions to conserve cardiac function remains challenging, the emergence of personalized omics offers promising avenues for future HCM treatments, particularly for late-onset cases.

Zinc finger protein 189 promotes the differentiation of lamina propria T helper 17.1 cells in dextran sulfate sodium-induced colitis

The factors regulating the heterogeneity of interleukin-17A (IL-17A)-expressing CD4⁺ T cells in inflammatory bowel diseases remain unclear. In the current study, we characterised the expression and function of zinc finger protein 189 (ZFP189) in a murine colitis model. Mice were given dextran sulphate sodium to induce acute colitis. Flow cytometry was applied to recognise and enrich Th17 and Th17.1 cells based on the expression of IL-17A, interferon-γ (IFN-γ), C-X-C motif chemokine receptor 3 (CXCR3), and C-C motif chemokine receptor 4 (CCR4). The expression of ZFP189 in Th17 and Th17.1 cells was determined by Immunoblotting. Lentivirus-mediated ZFP189 knockdown was conducted to evaluate the effect of ZFP189 on the differentiation of Th17 and Th17.1 cells. The adoptive transfer was performed to analyse the pathogenicity of Th17.1 cells in vivo. We found that ZFP189 was mildly up-regulated in IL-17A-expressing CD4⁺ T cells in colonic lamina propria. Lamina propria Th17.1 cells expressed higher ZFP189 than Th17 cells. In vitro ZFP189 knockdown in CD4⁺ T cells did not impact Th17 cell differentiation but suppressed Th17.1 cell differentiation, as evidenced by lower T-box expressed in T cells (T-bet) and IFN-γ. When adoptively transferred into mice, ZFP189-deficient Th17.1 cells produced fewer IFN-γ, tumour necrosis factor-alpha (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) than ZFP189-expressing Th17.1 cells. Moreover, ZFP189-deficient Th17.1 cells induced less severe colitis than ZFP189-expressing Th17.1 cells, as evidenced by less body weight loss, a lower disease activity index, and a lower colon histological score. In summary, ZFP189 acts as a positive regulator of the differentiation and pathogenicity of lamina propria Th17.1 cells in colitis.

Krüppel-like Factor-9 and Krüppel-like Factor-13: Highly Related, Multi-Functional, Transcriptional Repressors and Activators of Oncogenesis

Specificity Proteins/Krüppel-like Factors (SP/KLF family) are a conserved family of transcriptional regulators. These proteins share three highly conserved, contiguous zinc fingers in their carboxy-terminus, requisite for binding to cis elements in DNA. Each SP/KLF protein has unique primary sequence within its amino-terminal and carboxy-terminal regions, and it is these regions which interact with co-activators, co-repressors, and chromatin-modifying proteins to support the transcriptional activation and repression of target genes. Krüppel-like Factor 9 (KLF9) and Krüppel-like Factor 13 (KLF13) are two of the smallest members of the SP/KLF family, are paralogous, emerged early in metazoan evolution, and are highly conserved. Paradoxically, while most similar in primary sequence, KLF9 and KLF13 display many distinct roles in target cells. In this article, we summarize the work that has identified the roles of KLF9 (and to a lesser degree KLF13) in tumor suppression or promotion via unique effects on differentiation, pro- and anti-inflammatory pathways, oxidative stress, and tumor immune cell infiltration. We also highlight the great diversity of miRNAs, lncRNAs, and circular RNAs which provide mechanisms for the ubiquitous tumor-specific suppression of KLF9 mRNA and protein. Elucidation of KLF9 and KLF13 in cancer biology is likely to provide new inroads to the understanding of oncogenesis and its prevention and treatments.

Fatty acid metabolism disorders and potential therapeutic traditional Chinese medicines in cardiovascular diseases

Cardiovascular diseases are currently the primary cause of mortality in the whole world. Growing evidence indicated that the disturbances in cardiac fatty acid metabolism are crucial contributors in the development of cardiovascular diseases. The abnormal cardiac fatty acid metabolism usually leads to energy deficit, oxidative stress, excessive apoptosis, and inflammation. Targeting fatty acid metabolism has been regarded as a novel approach to the treatment of cardiovascular diseases. However, there are currently no specific drugs that regulate fatty acid metabolism to treat cardiovascular diseases. Many traditional Chinese medicines have been widely used to treat cardiovascular diseases in clinics. And modern studies have shown that they exert a cardioprotective effect by regulating the expression of key proteins involved in fatty acid metabolism, such as peroxisome proliferator-activated receptor α and carnitine palmitoyl transferase 1. Hence, we systematically reviewed the relationship between fatty acid metabolism disorders and four types of cardiovascular diseases including heart failure, coronary artery disease, cardiac hypertrophy, and diabetic cardiomyopathy. In addition, 18 extracts and eight monomer components from traditional Chinese medicines showed cardioprotective effects by restoring cardiac fatty acid metabolism. This work aims to provide a reference for the finding of novel cardioprotective agents targeting fatty acid metabolism.

Nicotine induces macrophage pyroptosis via LINC01272/miR-515/KLF6 axis

Nicotine contributes to the causation of atherosclerosis, which the prominent cellular components are macrophages. Long non-coding RNAs (lncRNAs) play an important role in regulating cell functions such as cell proliferation, differentiation and programmed death. However, the function and mechanism of lncRNAs in nicotine-induced macrophage pyroptosis has not been reported. We screened the deferentially expressed lncRNAs of human carotid artery plaque (GSE97210) and verified them in nicotine-induced pyroptosis of macrophages. Results showed only LINC01272 was up-regulated in a dose-dependent manner in macrophages. The immunofluorescence staining result confirmed that interfering LINC01272 inhibited nicotine-induced macrophage pyroptosis. Through bioinformatics analysis, dual luciferase reporter gene assay and qPCR, we identified miR-515 was significantly negatively correlated with the expression of LINC01272, and KLF6 is the target gene of miR-515. Furthermore, our results demonstrated that LINC01272/miR-515/KLF6 axis meditated nicotine-induced macrophage pyroptosis. In addition, in human peripheral blood mononuclear cells of smoking populations, the expression of GSDMD-N, NLRP3, LINC01272 and KLF6 was significantly increased, while the level of miR-515 was reduced. This study confirmed that nicotine increases the expression of LINC01272 to competitively bind with miR-515 in macrophages, reducing the inhibitory effect of miR-515 on its target gene KLF6, which ultimately induces macrophage pyroptosis.

Decreased Expression of KLF4 Leading to Functional Deficit in Pediatric Patients with Intestinal Failure and Potential Therapeutic Strategy Using Decanoic Acid

Pediatric intestinal failure (IF) is the reduction in gut function to below the minimum necessary for the absorption of macronutrients and/or water and electrolytes, such that intravenous supplementation is required to maintain health and/or growth. The overall goal in treating IF is to achieve intestinal adaptation; however, the underlying mechanisms have not been fully understood. In this study, by performing single-cell RNA sequencing in pediatric IF patients, we found that decreased Kruppel-Like Factor 4 (KLF4) may serve as the hub gene responsible for the functional deficit in mature enterocytes in IF patients, leading to the downregulation of solute carrier (SLC) family transporters (e.g., SLC7A9) and, consequently, nutrient malabsorption. We also found that inducible KLF4 was highly sensitive to the loss of certain enteral nutrients: in a rodent model of total parenteral nutrition mimicking the deprivation of enteral nutrition, the expression of KLF4 dramatically decreased only at the tip of the villus and not at the bottom of crypts. By using IF patient-derived intestinal organoids and Caco-2 cells as in vitro models, we demonstrated that the supplementation of decanoic acid (DA) could significantly induce the expression of KLF4 along with SLC6A4 and SLC7A9, suggesting that DA may function as a potential therapeutic strategy to promote cell maturation and functional improvement. In summary, this study provides new insights into the mechanism of intestinal adaptation depending on KLF4, and proposed potential strategies for nutritional management using DA.

The Role of Krüppel-like Factors in Pancreatic Physiology and Pathophysiology

Krüppel-like factors (KLFs) belong to the family of transcription factors with three highly conserved zinc finger domains in the C-terminus. They regulate homeostasis, development, and disease progression in many tissues. It has been shown that KLFs play an essential role in the endocrine and exocrine compartments of the pancreas. They are necessary to maintain glucose homeostasis and have been implicated in the development of diabetes. Furthermore, they can be a vital tool in enabling pancreas regeneration and disease modeling. Finally, the KLF family contains proteins that act as tumor suppressors and oncogenes. A subset of members has a biphasic function, being upregulated in the early stages of oncogenesis and stimulating its progression and downregulated in the late stages to allow for tumor dissemination. Here, we describe KLFs' function in pancreatic physiology and pathophysiology.

The KLF7/PFKL/ACADL axis modulates cardiac metabolic remodelling during cardiac hypertrophy in male mice

The main hallmark of myocardial substrate metabolism in cardiac hypertrophy or heart failure is a shift from fatty acid oxidation to greater reliance on glycolysis. However, the close correlation between glycolysis and fatty acid oxidation and underlying mechanism by which causes cardiac pathological remodelling remain unclear. We confirm that KLF7 simultaneously targets the rate-limiting enzyme of glycolysis, phosphofructokinase-1, liver, and long-chain acyl-CoA dehydrogenase, a key enzyme for fatty acid oxidation. Cardiac-specific knockout and overexpression KLF7 induce adult concentric hypertrophy and infant eccentric hypertrophy by regulating glycolysis and fatty acid oxidation fluxes in male mice, respectively. Furthermore, cardiac-specific knockdown phosphofructokinase-1, liver or overexpression long-chain acyl-CoA dehydrogenase partially rescues the cardiac hypertrophy in adult male KLF7 deficient mice. Here we show that the KLF7/PFKL/ACADL axis is a critical regulatory mechanism and may provide insight into viable therapeutic concepts aimed at the modulation of cardiac metabolic balance in hypertrophied and failing heart.

Biochemical Activation and Regulatory Functions of Trans-Regulatory KLF14 and Its Association with Genetic Polymorphisms

Krüpple-Like family of transcription factor-14 (KLF14) is a master trans-regulatory gene that has multiple biological regulatory functions and is involved in many pathological mechanisms. It controls the expressions of several other genes which are involved in multiple regulatory functions. KLF14 plays a significant role in lipid metabolism, glucose regulation and insulin sensitivity. Cell apoptosis, proliferation, and differentiation are regulated by the KLF14 gene, and up-regulation of KLF14 prevents cancer progression. KLF14 has been used as an epigenetic biomarker for the estimation of chronological age due to the presence of different age-related CpG sites on genes that become methylated with age. Different genome-wide association studies have identified several KLF14 variants in adipose tissues. These single nucleotide polymorphisms in KLF14 have been associated with dyslipidemia, insulin resistance, and glucose intolerance. Moreover, the prevalence of genetic polymorphism is different in different populations due to ethnic differences and epigenetic modifications. In addition, environmental and physiological factors such as diet, age, gender, and obesity are also responsible for genetic mutations in KLF14.

Krüppel-like Factor 13 Promotes HCC Progression by Transcriptional Regulation of HMGCS1-mediated Cholesterol Synthesis

BACKGROUND AND AIMS

Krüppel-like factor (KLF) has a role in the occurrence, development and metabolism of cancer. We aimed to explore the role and potential molecular mechanism of KLF13 in the growth and migration of liver cancer cells.

METHODS

The expression of KLF13 in hepatocellular carcinoma (HCC) tissues was higher than that in normal tissues according to analysis of The Cancer Genome Atlas (TCGA) database. Lentiviral plasmids were used for overexpression and plasmid knockdown of KLF13. Real-time quantitative polymerase chain reaction (qPCR) and western blotting were used to detect mRNA and protein expression in HCC tissues and cells. Cell counting kit-8 (CCK-8), colony formation, cell migration and invasion, and flow cytometry assays were used to assess the in vitro function of KLF13 in HCC cells. The effect of KLF13 on xenograft tumor growth in vivo was evaluated. The cholesterol content of HCC cells was determined by an indicator kit. A dual-luciferase reporter assay and chromatin immunoprecipitation sequencing (ChIP-seq) revealed the binding relationship between KLF13 and HMGCS1.

RESULTS

The expression of KLF13 was upregulated in HCC tissues and TCGA database. KLF13 knockdown inhibited the proliferation, migration and invasion of HepG2 and Huh7 cells and increased the apoptosis of Huh7 cells. The opposite effects were observed with the overexpression of KLF13 in SK-Hep1 and MHCC-97H cells. The overexpression of KLF13 promoted the growth of HCC in nude mice and KLF13 transcription promoted the expression of HMGCS1 and the biosynthesis of cholesterol. KLF13 knockdown inhibited cholesterol biosynthesis mediated by HMGCS1 and inhibited the growth and metastasis of HCC cells.

CONCLUSIONS

KLF13 acted as a tumor promoter in HCC by positively regulating HMGCS1-mediated cholesterol biosynthesis.

Krüppel-like factor 2a (KLF2A) suppresses GCRV replication by upregulating serpinc1 expression in Ctenopharyngodon idellus kidney (CIK) cells

Krüppel-like factor 2a (KLF2A), a transcription factor of the krüppel-like family, is involved in regulating the immune molecules and is associated with viral infection. However, the function of KLF2A during viral infections in fish remains unclear. In this study, grass carp (Ctenopharyngodon idellus) was used to predict the target genes regulated by KLF2A. The results showed that the candidate target genes included four members of the serpin gene family (serpinb1l2, serpinc1, serpinh1a, and serpinh1b). Dual-luciferase experiments showed that klf2a positively regulates serpinc1 expression. Dose-dependent klf2a overexpression in C. idellus kidney (CIK) cells significantly upregulated the expression of serpinc1. Overexpressing klf2a or serpinc1 in CIK cells activated interferon responses and suppressed grass carp reovirus (GCRV) replication. Klf2a and serpinc1 co-expression inhibited GCRV replication. These results show that klf2a upregulates serpinc1 mRNA expression, promotes type 1 interferon responses, and suppresses GCRV infection. This study provides insights into the regulatory role and biological functions of KLF2A in host-virus interactions in fish.

KLF15 controls brown adipose tissue transcriptional flexibility and metabolism in response to various energetic demands

Brown adipose tissue (BAT) is a specialized metabolic organ responsible for non-shivering thermogenesis. Recently, its activity has been shown to be critical in systemic metabolic health through its utilization and consumption of macronutrients. In the face of energetically demanding states, metabolic flexibility and systemic coordination of nutrient partitioning is requisite for health and survival. In this study, we elucidate BAT's differential transcriptional adaptations in response to multiple nutrient challenges and demonstrate its context-dependent prioritization of lipid, glucose, and amino acid metabolism. We show that the transcription factor Krüppel-like factor 15 (KLF15) plays a critical role in BAT metabolic flexibility. BAT-specific loss of KLF15 results in widespread changes in circulating metabolites and severely compromised thermogenesis in response to high energy demands, indicative of impaired nutrient utilization and metabolic flexibility. Together, our data demonstrate KLF15 in BAT plays an indispensable role in partitioning resources to maintain homeostasis and ensure survival.

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.

Diallyl Trisulfide Prevents Adipogenesis and Lipogenesis by Regulating the Transcriptional Activation Function of KLF15 on PPARγ to Ameliorate Obesity

SCOPE

Diallyl trisulfide (DATS) is a bioactive compound in garlic. The anti-obesity effect of garlic oil has been reported, but the role and mechanism of DATS in preventing obesity remain to be explored.

METHODS AND RESULTS

We performed studies with high-fat-diet-induced obese mice and 3T3-L1 adipocytes. The results showed that DATS significantly reduced lipid accumulation and repaired disordered metabolism in vivo by restraining adipogenesis and lipogenesis, and promoting lipolysis and fatty acid oxidation in white adipose tissue. In cells, DATS played different roles at different stages of adipocyte differentiation. Notably, DATS reduced lipid accumulation mainly by inhibiting adipogenesis and lipogenesis at the late stage. KLF15 was knocked down in 3T3-L1 cells, which eliminated the inhibitory effect of DATS on adipogenesis and lipogenesis. The dual-luciferase reporter and ChIP assays indicated that DATS could inhibit the transcriptional activation function of KLF15 on PPARγ by inhibiting the binding of KLF15 to PPARγ promoter. The function comparison of structural analogs and the intervention of dithiothreitol showed that disulfide bond was crucial for DATS to work.

CONCLUSION

DATS prevents obesity by regulating the transcriptional activation function of KLF15 on PPARγ. This article is protected by copyright. All rights reserved.

Subversive molecular role of Krüppel-like factor 5 in extracellular matrix degradation and chondrocyte dedifferentiation

Osteoarthritis (OA) is the most common joint disorder worldwide and a leading cause of pain and disability. However, the pathogenesis of osteoarthritis has not been elucidated. Krüppel-like factor (KLF)-5 is involved in several biological processes, including inflammation and cell differentiation, but its role in OA has not been evaluated. In this study, we investigated the role of KLF-5 in chondrocyte differentiation. KLF-5 overexpression in chondrocytes induced a loss of type II collagen expression and sulfated proteoglycan synthesis at the transcriptional and translational levels. Based on immunofluorescence staining, the ectopic expression of KLF-5 reduced type II collagen expression. In contrast, with KLF-5-transfected cells, KLF-5 siRNA transfection-induced type II expression also blocked dedifferentiation caused by the overexpression of KLF-5. In zebra fish, KLF-5 reduced the sulfated proteoglycan synthesis of ceratobranchial cartilage. Our results suggest that KLF-5 plays a pivotal role in the dedifferentiation of rabbit articular cartilage and zebra fish, providing a basis for therapeutic strategy for osteoarthritis aimed at controlling cartilage destruction.

Glucose uptake by GLUT1 in photoreceptors is essential for outer segment renewal and rod photoreceptor survival

Photoreceptors consume glucose supplied by the choriocapillaris to support phototransduction and outer segment (OS) renewal. Reduced glucose supply underlies photoreceptor cell death in inherited retinal degeneration and age-related retinal disease. We have previously shown that restricting glucose transport into the outer retina by conditional deletion of Slc2a1 encoding GLUT1 resulted in photoreceptor loss and impaired OS renewal. However, retinal neurons, glia, and the retinal pigment epithelium play specialized, synergistic roles in metabolite supply and exchange, and the cell-specific map of glucose uptake and utilization in the retina is incomplete. In these studies, we conditionally deleted Slc2a1 in a pan-retinal or rod-specific manner to better understand how glucose is utilized in the retina. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic deletion of Slc2a1 from retinal neurons and Müller glia results in reduced OS growth and progressive rod but not cone photoreceptor cell death. Rhodopsin levels were severely decreased even at postnatal day 20 when OS length was relatively normal. Arrestin levels were not changed suggesting that glucose uptake is required to synthesize membrane glycoproteins. Rod-specific deletion of Slc2a1 resulted in similar changes in OS length and rod photoreceptor cell death. These studies demonstrate that glucose is an essential carbon source for rod photoreceptor cell OS maintenance and viability.

Serum and Soleus Metabolomics Signature of Klf10 Knockout Mice to Identify Potential Biomarkers

The transcription factor Krüppel-like factor 10 (Klf10), also known as Tieg1 for TGFβ (Inducible Early Gene-1) is known to control numerous genes in many cell types that are involved in various key biological processes (differentiation, proliferation, apoptosis, inflammation), including cell metabolism and human disease. In skeletal muscle, particularly in the soleus, deletion of the Klf10 gene (Klf10 KO) resulted in ultrastructure fiber disorganization and mitochondrial metabolism deficiencies, characterized by muscular hypertrophy. To determine the metabolic profile related to loss of Klf10 expression, we analyzed blood and soleus tissue using UHPLC-Mass Spectrometry. Metabolomics analyses on both serum and soleus revealed profound differences between wild-type (WT) and KO animals. Klf10 deficient mice exhibited alterations in metabolites associated with energetic metabolism. Additionally, chemical classes of aromatic and amino-acid compounds were disrupted, together with Krebs cycle intermediates, lipids and phospholipids. From variable importance in projection (VIP) analyses, the Warburg effect, citric acid cycle, gluconeogenesis and transfer of acetyl groups into mitochondria appeared to be possible pathways involved in the metabolic alterations observed in Klf10 KO mice. These studies have revealed essential roles for Klf10 in regulating multiple metabolic pathways whose alterations may underlie the observed skeletal muscle defects as well as other diseases.

KLF10 promotes nonalcoholic steatohepatitis progression through transcriptional activation of zDHHC7

Nonalcoholic steatohepatitis (NASH), characterized by hepatic steatosis, inflammation, and liver injury, has become a leading cause of end-stage liver diseases and liver transplantation. Krüppel-like factors 10 (KLF10) is a Cys2/His2 zinc finger transcription factor that regulates cell growth, apoptosis, and differentiation. However, whether it plays a role in the development and progression of NASH remains poorly understood. In the present study, we found that KLF10 expression was selectively upregulated in the mouse models and human patients with NASH, compared with simple steatosis (NAFL). Gain- and loss-of function studies demonstrated that hepatocyte-specific overexpression of KLF10 aggravated, whereas its depletion alleviated diet-induced NASH pathogenesis in mice. Mechanistically, transcriptomic analysis and subsequent functional experiments showed that KLF10 promotes hepatic lipid accumulation and inflammation through the palmitoylation and plasma membrane localization of fatty acid translocase CD36 via transcriptionally activation of zDHHC7. Indeed, both expression of zDHHC7 and palmitoylation of CD36 are required for the pathogenic roles of KLF10 in NASH development. Thus, our results identify an important role for KLF10 in NAFL-to-NASH progression through zDHHC7-mediated CD36 palmitoylation.

Transcription factors KLF15 and PPARδ cooperatively orchestrate genome-wide regulation of lipid metabolism in skeletal muscle

Skeletal muscle dynamically regulates systemic nutrient homeostasis through transcriptional adaptations to physiological cues. In response to changes in the metabolic environment (e.g., alterations in circulating glucose or lipid levels), networks of transcription factors and coregulators are recruited to specific genomic loci to fine-tune homeostatic gene regulation. Elucidating these mechanisms is of particular interest as these gene regulatory pathways can serve as potential targets to treat metabolic disease. The zinc-finger transcription factor Krüppel-like factor 15 (KLF15) is a critical regulator of metabolic homeostasis; however, its genome-wide distribution in skeletal muscle has not been previously identified. Here, we characterize the KLF15 cistrome in vivo in skeletal muscle and find that the majority of KLF15 binding is localized to distal intergenic regions and associated with genes related to circadian rhythmicity and lipid metabolism. We also identify critical interdependence between KLF15 and the nuclear receptor PPARδ in the regulation of lipid metabolic gene programs. We further demonstrate that KLF15 and PPARδ colocalize genome-wide, physically interact, and are dependent on one another to exert their transcriptional effects on target genes. These findings reveal that skeletal muscle KLF15 plays a critical role in metabolic adaptation through its direct actions on target genes and interactions with other nodal transcription factors such as PPARδ.

Chromatin accessibility landscape of stromal subpopulations reveals distinct metabolic and inflammatory features of porcine subcutaneous and visceral adipose tissue

Background

Fat accumulation in visceral adipose tissue (VAT) confers increased risk for metabolic disorders of obesity, whereas accumulation of subcutaneous adipose tissue (SAT) is associated with lower risk and may be protective. Previous studies have shed light on the gene expression profile differences between SAT and VAT; however, the chromatin accessibility landscape differences and how the cis-regulatory elements govern gene expression changes between SAT and VAT are unknown.

Methods

Pig were used to characterize the differences in chromatin accessibility between the two adipose depots-derived stromal vascular fractions (SVFs) using DNase-sequencing (DNase-seq). Using integrated data from DNase-seq, H3K27ac ChIP-sequencing (ChIP-seq), and RNA-sequencing (RNA-seq), we investigated how the regulatory locus complexity regulated gene expression changes between SAT and VAT and the possible impact that these changes may have on the different biological functions of these two adipose depots.

Results

SVFs form SAT and VAT (S-SVF and V-SVF) have differential chromatin accessibility landscapes. The differential DNase I hypersensitive site (DHS)-associated genes, which indicate dynamic chromatin accessibility, were mainly involved in metabolic processes and inflammatory responses. Additionally, the Krüppel-like factor family of transcription factors were enriched in the differential DHSs. Furthermore, the chromatin accessibility data were highly associated with differential gene expression as indicated using H3K27ac ChIP-seq and RNA-seq data, supporting the validity of the differential gene expression determined using DNase-seq. Moreover, by combining epigenetic and transcriptomic data, we identified two candidate genes, NR1D1 and CRYM, could be crucial to regulate distinct metabolic and inflammatory characteristics between SAT and VAT. Together, these results uncovered differences in the transcription regulatory network and enriched the mechanistic understanding of the different biological functions between SAT and VAT.

Krüppel-like factors in glycolipid metabolic diseases

Krüppel-like factors (KLFs) are a family of transcription factors characterised by zinc-finger structures at the C-terminal. They play the key roles in cell proliferation, differentiation, and migration, as well as in embryonic development. They have been widely expressed in multiple systems in vivo, and their dysregulation is closely associated with a variety of human diseases. Glycolipid metabolism is a complex physiological process which can be regulated at the transcriptional level. Glycolipid metabolic diseases, such as obesity, non-alcoholic fatty liver disease, diabetes, and their complications, are a serious threat to human health. Recently, increasing studies have shown that KLFs are closely related to glycolipid metabolism and energy balance of the liver, adipose tissue, heart, skeletal muscle, lung, pancreas, and nervous system. In this review, we focused on the correlation between the subtypes of the KLF family and glycolipid metabolic diseases to describe new directions and trends in endocrine and glycolipid metabolic disease treatments.

Insulin-like Growth Factor I Couples Metabolism with Circadian Activity through Hypo-Thalamic Orexin Neurons

Uncoupling of metabolism and circadian activity is associated with an increased risk of a wide spectrum of pathologies. Recently, insulin and the closely related insulin-like growth factor I (IGF-I) were shown to entrain feeding patterns with circadian rhythms. Both hormones act centrally to modulate peripheral glucose metabolism; however, whereas central targets of insulin actions are intensely scrutinized, those mediating the actions of IGF-I remain less defined. We recently showed that IGF-I targets orexin neurons in the lateral hypothalamus, and now we evaluated whether IGF-I modulates orexin neurons to align circadian rhythms with metabolism. Mice with disrupted IGF-IR activity in orexin neurons (Firoc mice) showed sexually dimorphic alterations in daily glucose rhythms and feeding activity patterns which preceded the appearance of metabolic disturbances. Thus, Firoc males developed hyperglycemia and glucose intolerance, while females developed obesity. Since IGF-I directly modulates orexin levels and hepatic expression of KLF genes involved in circadian and metabolic entrainment in an orexin-dependent manner, it seems that IGF-I entrains metabolism and circadian rhythms by modulating the activity of orexin neurons.

Aryl hydrocarbon receptor and Krüppel like factor 10 mediate a transcriptional axis modulating immune homeostasis in mosquitoes

Immune responses require delicate controls to maintain homeostasis while executing effective defense. Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor. The Krüppel-like factor 10 (KLF10) is a C2H2 zinc-finger containing transcription factor. The functions of mosquito AhR and KLF10 have not been characterized. Here we show that AhR and KLF10 constitute a transcriptional axis to modulate immune responses in mosquito Anopheles gambiae. The manipulation of AhR activities via agonists or antagonists repressed or enhanced the mosquito antibacterial immunity, respectively. KLF10 was recognized as one of the AhR target genes in the context. Phenotypically, silencing KLF10 reversed the immune suppression caused by the AhR agonist. The transcriptome comparison revealed that silencing AhR and KLF10 plus challenge altered the expression of 2245 genes in the same way. The results suggest that KLF10 is downstream of AhR in a transcriptional network responsible for immunomodulation. This AhR–KLF10 axis regulates a set of genes involved in metabolism and circadian rhythms in the context. The axis was required to suppress the adverse effect caused by the overactivation of the immune pathway IMD via the inhibitor gene Caspar silencing without a bacterial challenge. These results demonstrate that the AhR–KLF10 axis mediates an immunoregulatory transcriptional network as a negative loop to maintain immune homeostasis.

The transcription factor KLF14 regulates macrophage glycolysis and immune function by inhibiting HK2 in sepsis

Sepsis is a heterogeneous syndrome induced by a dysregulated host response to infection. Glycolysis plays a role in maintaining the immune function of macrophages, which is crucial for severely septic patients. However, how the pathways that link glycolysis and macrophages are regulated is still largely unknown. Here, we provide evidence to support the function of KLF14, a novel Krüppel-like transcription factor, in the regulation of glycolysis and the immune function of macrophages during sepsis. KLF14 deletion led to significantly increased mortality in lethal models of murine endotoxemia and sepsis. Mechanistically, KLF14 decreased glycolysis and the secretion of inflammatory cytokines by macrophages by inhibiting the transcription of HK2. In addition, we confirmed that the expression of KLF14 was upregulated in septic patients. Furthermore, pharmacological activation of KLF14 conferred protection against sepsis in mice. These findings uncover a key role of KLF14 in modulating the inflammatory signaling pathway and shed light on the development of KLF14-targeted therapeutics for sepsis.

KLF15 cistromes reveal a hepatocyte pathway governing plasma corticosteroid transport and systemic inflammation

Circulating corticosteroids orchestrate stress adaptation, including inhibition of inflammation. While pathways governing corticosteroid biosynthesis and intracellular signaling are well understood, less is known about mechanisms controlling plasma corticosteroid transport. Here, we show that hepatocyte KLF15 (Kruppel-like factor 15) controls plasma corticosteroid transport and inflammatory responses through direct transcriptional activation of Serpina6, which encodes corticosteroid-binding globulin (CBG). Klf15-deficient mice have profoundly low CBG, reduced plasma corticosteroid binding capacity, and heightened mortality during inflammatory stress. These defects are completely rescued by reconstituting CBG, supporting that KLF15 works primarily through CBG to control plasma corticosterone homeostasis. To understand transcriptional mechanisms, we generated the first KLF15 cistromes using newly engineered Klf153xFLAG mice. Unexpectedly, liver KLF15 is predominantly promoter enriched, including Serpina6, where it binds a palindromic GC-rich motif, opens chromatin, and transactivates genes with minimal associated direct gene repression. Overall, we provide critical mechanistic insight into KLF15 function and identify a hepatocyte-intrinsic transcriptional module that potently regulates systemic corticosteroid transport and inflammation.

The Role of KLF2 in the Regulation of Atherosclerosis Development and Potential Use of KLF2-Targeted Therapy

Kruppel like factor 2 (KLF2) is a mechanosensitive transcription factor participating in the regulation of vascular endothelial cells metabolism. Activating KLF2 in endothelial cells induces eNOS (endothelial nitric oxide synthase) expression, subsequent NO (nitric oxide) release, and vasodilatory effect. In addition, many KLF2-regulated genes participate in the anti-thrombotic, antioxidant, and anti-inflammatory activities, thereby preventing atherosclerosis development and progression. In this review, we summarise recent evidence suggesting that KLF2 plays a major role in regulating atheroprotective effects in endothelial cells. We also discuss several recently identified repurposed drugs and natural plant-based bioactive compounds with KLF2-mediated atheroprotective activities. Herein, we present a comprehensive overview of the role of KLF2 in atherosclerosis and as a pharmacological target for different drugs and natural compounds and highlight the potential application of these phytochemicals for the treatment of atherosclerosis.

Glucocorticoid-Mediated Developmental Programming of Vertebrate Stress Responsivity

Glucocorticoids, vertebrate steroid hormones produced by cells of the adrenal cortex or interrenal tissue, function dynamically to maintain homeostasis under constantly changing and occasionally stressful environmental conditions. They do so by binding and thereby activating nuclear receptor transcription factors, the Glucocorticoid and Mineralocorticoid Receptors (MR and GR, respectively). The GR, by virtue of its lower affinity for endogenous glucocorticoids (cortisol or corticosterone), is primarily responsible for transducing the dynamic signals conveyed by circadian and ultradian glucocorticoid oscillations as well as transient pulses produced in response to acute stress. These dynamics are important determinants of stress responsivity, and at the systemic level are produced by feedforward and feedback signaling along the hypothalamus-pituitary-adrenal/interrenal axis. Within receiving cells, GR signaling dynamics are controlled by the GR target gene and negative feedback regulator fkpb5. Chronic stress can alter signaling dynamics via imperfect physiological adaptation that changes systemic and/or cellular set points, resulting in chronically elevated cortisol levels and increased allostatic load, which undermines health and promotes development of disease. When this occurs during early development it can "program" the responsivity of the stress system, with persistent effects on allostatic load and disease susceptibility. An important question concerns the glucocorticoid-responsive gene regulatory network that contributes to such programming. Recent studies show that klf9, a ubiquitously expressed GR target gene that encodes a Krüppel-like transcription factor important for metabolic plasticity and neuronal differentiation, is a feedforward regulator of GR signaling impacting cellular glucocorticoid responsivity, suggesting that it may be a critical node in that regulatory network.

KLF10 integrates circadian timing and sugar signaling to coordinate hepatic metabolism

The mammalian circadian timing system and metabolism are highly interconnected, and disruption of this coupling is associated with negative health outcomes. Krüppel-like factors (KLFs) are transcription factors that govern metabolic homeostasis in various organs. Many KLFs show a circadian expression in the liver. Here, we show that the loss of the clock-controlled KLF10 in hepatocytes results in extensive reprogramming of the mouse liver circadian transcriptome, which in turn alters the temporal coordination of pathways associated with energy metabolism. We also show that glucose and fructose induce Klf10, which helps mitigate glucose intolerance and hepatic steatosis in mice challenged with a sugar beverage. Functional genomics further reveal that KLF10 target genes are primarily involved in central carbon metabolism. Together, these findings show that in the liver KLF10 integrates circadian timing and sugar metabolism-related signaling, and serves as a transcriptional brake that protects against the deleterious effects of increased sugar consumption.

Genome-wide identification, evolution of Krüppel-like factors (klfs) and their expressions during GCRV challenge in grass carp (Ctenopharyngodonidella)

The Krüppel-like factors (KLFs) are a family of transcription factors containing three highly conserved tandem zinc finger structures, and each member participates in multiple physiological and pathological processes. The publication of genome sequences and the application of bioinformatics tools have led to the discovery of numerous gene families in fishes. Here, 24 klf genes were re-annotated in grass carp. Subsequently, the number of klf family members were investigated in some representative vertebrate species. Then, a series of bioinformatics analysis showed that grass carp klfs in the same subfamily had similar genome structure patterns and conserved distribution patterns of motifs, which supported their molecular evolutionary relationships. Furthermore, the mRNA expression profiles showed that 24 grass carp klfs were ubiquitously expressed in 11 different tissues, and some of them displayed tissue-enriched expression patterns. Finally, the expressions of the evolutionarily expanded klf members (klf2a, 2b, 2l, 5a, 5b, 5l, 6a, 6b, 7a, 7b, 11a, 11b, 12a, 12b, 15 and 15l) during GCRV infection were also analyzed. The results suggested that grass carp klf genes with common evolutionary sources may share functional diversity and conservation. In conclusion, this study provides preliminary clues for further researches on grass carp klf members and their underlying transcriptional regulatory mechanisms during GCRV infection.

Glucocorticoid signaling and lipid metabolism disturbances in the liver of rats treated with 5α-dihydrotestosterone in an animal model of polycystic ovary syndrome

PURPOSE

Polycystic ovary syndrome (PCOS) is a complex reproductive disorder often associated with obesity, insulin resistance, and dyslipidemia. Hormonal changes in PCOS may also include altered glucocorticoid signaling. Our aim was to examine whether alterations in hepatic glucocorticoid signaling are associated with disturbances of glucose and lipid metabolism in animal model of PCOS.

METHODS

Female rats, 3 weeks old, were subcutaneously implanted with 5α-dihydrotestosterone (DHT) or placebo pellets for 90 days to induce PCOS. Expression of 11β-hydroxysteroid dehydrogenase 1 (11βHSD1) and A-ring reductases (5α and 5β), as well as intracellular distribution of glucocorticoid receptor (GR) and expression of its regulated genes were examined in the liver. Proteins of hepatic lipid and carbohydrate metabolism and markers of inflammation were also assessed.

RESULTS

DHT treatment induced increase in body and liver mass, as well as in triglycerides and free fatty acids levels in plasma. Elevation of 11βHSD1 and reduction of 5α-reductase expression was observed together with increased hepatic corticosterone concentration and nuclear GR activation. Induced expression of Krüppel-like factor 15 and decreased expression of genes for proinflammatory cytokines and de novo lipogenesis (DNL) were detected in the liver of DHT-treated rats, while DNL regulators and proinflammatory markers were not changed. However, increased mRNA levels of stearoyl-CoA desaturase and apolipoprotein B were observed in DHT animals.

CONCLUSIONS

DHT treatment stimulated hepatic glucocorticoid prereceptor metabolism through increased corticosterone availability which is associated with enhanced GR activation. This does not affect gluconeogenesis and DNL, but could be linked to stimulated triglyceride synthesis and hypertriglyceridemia.

Lymphedema alters lipolytic, lipogenic, immune and angiogenic properties of adipose tissue: a hypothesis-generating study in breast cancer survivors

Later stages of secondary lymphedema are associated with the massive deposition of adipose tissue (AT). The factors driving lymphedema-associated AT (LAT) expansion in humans remain rather elusive. We hypothesized that LAT expansion could be based on alterations of metabolic, adipogenic, immune and/or angiogenic qualities of AT. AT samples were acquired from upper limbs of 11 women with unilateral breast cancer-related lymphedema and 11 healthy women without lymphedema. Additional control group of 11 female breast cancer survivors without lymphedema was used to assess systemic effects of lymphedema. AT was analysed for adipocyte size, lipolysis, angiogenesis, secretion of cytokines, immune and stem cell content and mRNA gene expression. Further, adipose precursors were isolated and tested for their proliferative and adipogenic capacity. The effect of undrained LAT- derived fluid on adipogenesis was also examined. Lymphedema did not have apparent systemic effect on metabolism and cytokine levels, but it was linked with higher lymphocyte numbers and altered levels of several miRNAs in blood. LAT showed higher basal lipolysis, (lymph)angiogenic capacity and secretion of inflammatory cytokines when compared to healthy AT. LAT contained more activated CD4+ T lymphocytes than healthy AT. mRNA levels of (lymph)angiogenic markers were deregulated in LAT and correlated with markers of lipolysis. In vitro, adipose cells derived from LAT did not differ in their proliferative, adipogenic, lipogenic and lipolytic potential from cells derived from healthy AT. Nevertheless, exposition of preadipocytes to LAT-derived fluid improved their adipogenic conversion when compared with the effect of serum. This study presents results of first complex analysis of LAT from upper limb of breast cancer survivors. Identified LAT alterations indicate a possible link between (lymph)angiogenesis and lipolysis. In addition, our in vitro results imply that AT expansion in lymphedema could be driven partially by exposition of adipose precursors to undrained LAT-derived fluid.

Muscle Krüppel-like factor 15 regulates lipid flux and systemic metabolic homeostasis

Skeletal muscle is a major determinant of systemic metabolic homeostasis that plays a critical role in glucose metabolism and insulin sensitivity. By contrast, despite being a major user of fatty acids, and evidence that muscular disorders can lead to abnormal lipid deposition (e.g., nonalcoholic fatty liver disease in myopathies), our understanding of skeletal muscle regulation of systemic lipid homeostasis is not well understood. Here we show that skeletal muscle Krüppel-like factor 15 (KLF15) coordinates pathways central to systemic lipid homeostasis under basal conditions and in response to nutrient overload. Mice with skeletal muscle-specific KLF15 deletion demonstrated (a) reduced expression of key targets involved in lipid uptake, mitochondrial transport, and utilization, (b) elevated circulating lipids, (c) insulin resistance/glucose intolerance, and (d) increased lipid deposition in white adipose tissue and liver. Strikingly, a diet rich in short-chain fatty acids bypassed these defects in lipid flux and ameliorated aspects of metabolic dysregulation. Together, these findings establish skeletal muscle control of lipid flux as critical to systemic lipid homeostasis and metabolic health.

Cardiomyocyte Krüppel-Like Factor 5 Promotes De Novo Ceramide Biosynthesis and Contributes to Eccentric Remodeling in Ischemic Cardiomyopathy

BACKGROUND

We previously showed that cardiomyocyte Krϋppel-like factor (KLF) 5 regulates cardiac fatty acid oxidation. As heart failure has been associated with altered fatty acid oxidation, we investigated the role of cardiomyocyte KLF5 in lipid metabolism and pathophysiology of ischemic heart failure.

METHODS

Using real-time polymerase chain reaction and Western blot, we investigated the KLF5 expression changes in a myocardial infarction (MI) mouse model and heart tissue from patients with ischemic heart failure. Using 2D echocardiography, we evaluated the effect of KLF5 inhibition after MI using pharmacological KLF5 inhibitor ML264 and mice with cardiomyocyte-specific KLF5 deletion (αMHC [α-myosin heavy chain]-KLF5^-/-). We identified the involvement of KLF5 in regulating lipid metabolism and ceramide accumulation after MI using liquid chromatography-tandem mass spectrometry, and Western blot and real-time polymerase chain reaction analysis of ceramide metabolism-related genes. We lastly evaluated the effect of cardiomyocyte-specific KLF5 overexpression (αMHC-rtTA [reverse tetracycline-controlled transactivator]-KLF5) on cardiac function and ceramide metabolism, and rescued the phenotype using myriocin to inhibit ceramide biosynthesis.

RESULTS

KLF5 mRNA and protein levels were higher in human ischemic heart failure samples and in rodent models at 24 hours, 2 weeks, and 4 weeks post-permanent left coronary artery ligation. αMHC-KLF5^-/- mice and mice treated with ML264 had higher ejection fraction and lower ventricular volume and heart weight after MI. Lipidomic analysis showed that αMHC-KLF5^-/- mice with MI had lower myocardial ceramide levels compared with littermate control mice with MI, although basal ceramide content of αMHC-KLF5^-/- mice was not different in control mice. KLF5 ablation suppressed the expression of SPTLC1 and SPTLC2 (serine palmitoyltransferase [SPT] long-chain base subunit ()1 2, respectively), which regulate de novo ceramide biosynthesis. We confirmed our previous findings that myocardial SPTLC1 and SPTLC2 levels are increased in heart failure patients. Consistently, αMHC-rtTA-KLF5 mice showed increased SPTLC1 and SPTLC2 expression, higher myocardial ceramide levels, and systolic dysfunction beginning 2 weeks after KLF5 induction. Treatment of αMHC-rtTA-KLF5 mice with myriocin that inhibits SPT, suppressed myocardial ceramide levels and alleviated systolic dysfunction.

CONCLUSIONS

KLF5 is induced during the development of ischemic heart failure in humans and mice and stimulates ceramide biosynthesis. Genetic or pharmacological inhibition of KLF5 in mice with MI prevents ceramide accumulation, alleviates eccentric remodeling, and increases ejection fraction. Thus, KLF5 emerges as a novel therapeutic target for the treatment of ischemic heart failure.

Potential roles of mediator Complex Subunit 13 in Cardiac Diseases

Mediator complex subunit 13 (MED13, previously known as THRAP1 and TRAP240) is a subunit of the cyclin-dependent kinase 8 (CDK8) kinase module in the eukaryotic mediator complex. MED13 has been known to play critical roles in cell cycle, development, and growth. The purpose of this review is to comprehensively discuss its newly identified potential roles in myocardial energy metabolism and non-metabolic cardiovascular diseases. Evidence indicates that cardiac MED13 mainly participates in the regulation of nuclear receptor signaling, which drives the transcription of genes involved in modulating cardiac and systemic energy homeostasis. MED13 is also associated with several pathological conditions, such as metabolic syndrome and thyroid disease-associated heart failure. Therefore, MED13 constitutes a potential therapeutic target for the regulation of metabolic disorders and other cardiovascular diseases.

Inhibition of Embryonic HSP 90 Function Promotes Variation of Cold Tolerance in Zebrafish

Accumulating evidence indicates that heat shock protein 90 (HSP90) plays essential roles in modulation of phenotypic plasticity in vertebrate development, however, the roles of HSP90 in modulation of cold tolerance capacity in fish are still unclear. In the present study, we showed that transient inhibition of embryonic HSP90 function by a chemical inhibitor or low conductivity stress promoted variation of cold tolerance capacity in adult zebrafish. Further work showed that embryonic HSP90 inhibition enhanced cold tolerance in adult zebrafish could be transmitted to their offspring. RNA-seq data showed that embryonic HSP90 inhibition enhanced cold tolerance involves variation of gene expression related to proteasome, lysosome, autophagy, and ribosome. Experiments with zebrafish ZF4 cells showed that two differentially expressed genes atg9b and psmd12 were up-regulated by radicicol treatment and provided protective roles for cells under cold stress, indicating that up-regulation of autophagy and proteasome function contributes to enhanced cold tolerance. The present work sheds a light on the roles of HSP90 in regulation of phenotypic plasticity associated with thermal adaptation in fish.

Myeloid Krüppel-like factor 2 is a critical regulator of metabolic inflammation

Substantial evidence implicates crosstalk between metabolic tissues and the immune system in the inception and progression of obesity. However, molecular regulators that orchestrate metaflammation both centrally and peripherally remains incompletely understood. Here, we identify myeloid Krüppel-like factor 2 (KLF2) as an essential regulator of obesity and its sequelae. In mice and humans, consumption of a fatty diet downregulates myeloid KLF2 levels. Under basal conditions, myeloid-specific KLF2 knockout mice (K2KO) exhibit increased feeding and weight gain. High-fat diet (HFD) feeding further exacerbates the K2KO metabolic disease phenotype. Mechanistically, loss of myeloid KLF2 increases metaflammation in peripheral and central tissues. A combination of pair-feeding, bone marrow-transplant, and microglial ablation implicate central and peripheral contributions to K2KO-induced metabolic dysfunction observed. Finally, overexpression of myeloid KLF2 protects mice from HFD-induced obesity and insulin resistance. Together, these data establish myeloid KLF2 as a nodal regulator of central and peripheral metabolic inflammation in homeostasis and disease.

Inflammation contributes to the development of metabolic disease through incompletely understood mechanisms. Here the authors report that deletion of the transcription factor KLF2 in myeloid cells leads to increased feeding and weight gain in mice with concomitant peripheral and central tissue inflammation, while overexpression protects against diet-induced metabolic disease.

Exploring adipogenic and myogenic circulatory biomarkers of recurrent pressure injury risk for persons with spinal cord injury

Purpose:

To investigate linkages between circulatory adipogenic and myogenic biomarkers, gluteal intramuscular adipose tissue (IMAT), and pressure injury (PrI) history following spinal cord injury (SCI).

Methods:

This is an observational repeated-measures study of 30 individuals with SCI. Whole blood was collected regularly over 2-3 years. Circulatory adipogenic and myogenic gene expression was determined. IMAT was defined as above/below 15% (IMATd) or percentage (IMAT%). PrI history was defined as recurrent PrI (RPrI) or PrI number (n PrI). Model development used R packages (version 3.5.1). Univariate analysis screened for discriminating genes for downstream multivariate and combined models of averaged and longitudinal data for binary (RPrI/IMATd) and finer scales (n PrI/IMAT%).

Results:

For adipogenesis, Krüppel-like factor 4 was the top RPrI predictor together with resistin and cyclin D1, and sirtuin 2 was the top IMAT predictor. For myogenesis, the top RPrI predictor was dysferlin 2B, and pyruvate dehydrogenase kinase-4 was the top IMAT predictor together with dystrophin.

Conclusion:

Circulatory adipogenic and myogenic biomarkers have statistically significant relationships with PrI history and IMAT for persons with SCI. Biomarkers of interest may act synergistically or additively. Variable importance rankings can reveal nonlinear correlations among the predictors. Biomarkers of interest may act synergistically or additively, thus multiple genes may need to be included for prediction with finer distinction.

Krüppel-like factor 17 upregulates uterine corin expression and promotes spiral artery remodeling in pregnancy

Spiral artery remodeling is an important physiological process in the pregnant uterus which increases blood flow to the fetus. Impaired spiral artery remodeling contributes to preeclampsia, a major disease in pregnancy. Corin, a transmembrane serine protease, is up-regulated in the pregnant uterus to promote spiral artery remodeling. To date, the mechanism underlying uterine corin up-regulation remains unknown. Here we show that Krüppel-like factor (KLF) 17 is a key transcription factor for uterine corin expression in pregnancy. In cultured human uterine endometrial cells, KLF17 binds to the CORIN promoter and enhances the promoter activity. Disruption of the KLF17 gene in the endometrial cells abolishes CORIN expression. In mice, Klf17 is up-regulated in the pregnant uterus. Klf17 deficiency prevents uterine Corin expression in pregnancy. Moreover, Klf17-deficient mice have poorly remodeled uterine spiral arteries and develop gestational hypertension and proteinuria. Together, our results reveal an important function of KLF17 in regulating Corin expression and uterine physiology in pregnancy.

KLF15-activating Twist2 ameliorated hepatic steatosis by inhibiting inflammation and improving mitochondrial dysfunction via NF-κB-FGF21 or SREBP1c-FGF21 pathway

Twist-related protein 2 (TWIST2) is identified as a basic helix-loop-helix (b-HLH) transcription repressor by dimerizing with other b-HLH proteins. The significance of TWIST2 has been emphasized in various tumors; however, few studies report its functions in metabolism and metabolic diseases. Here we aimed to explore the novel role and regulation mechanism of TWIST2 in hepatic steatosis. Our results showed that Twist2 knockdown caused mice obesity, insulin resistance, and hepatic steatosis, which were accompanied with inflammation, endoplasmic reticulum stress, and mitochondrial dysfunction. In vitro, TWIST2 overexpression ameliorated hepatocellular steatosis, inhibited inflammation, and improved mitochondrial content and function with a fibroblast growth factor 21 (FGF21)-dependent pattern. NF-κB negatively regulated FGF21 transcription by directly binding to FGF21 promoter DNA, which was eliminated by TWIST2 overexpression by inhibiting NF-κB expression and translocation to nucleus. TWIST2 overexpression decreased intracellular reactive oxygen species level, increased mitochondrial DNA and biogenesis, and enhanced ATP production and antioxidation ability. Additionally, TWIST2 expression was repressed by insulin-targeting sterol regulatory element-binding protein 1c (SREBP1c) and forkhead box protein O1 and was enhanced by dexamethasone targeting Krüppel-like factor 15, which directly interacted with Twist2 promoter DNA. Together, our studies identify an important role and regulation mechanism of TWIST2 in maintaining hepatic homeostasis by ameliorating steatosis, inflammation, and oxidative stress via the NF-κB-FGF21 or SREBP1c-FGF21 pathway, which may provide a new therapeutic scheme for nonalcoholic fatty liver disease.-Zhou, L., Li, Q., Chen, A., Liu, N., Chen, N., Chen, X., Zhu, L., Xia, B., Gong, Y., Chen, X. KLF15-activating Twist2 ameliorated hepatic steatosis by inhibiting inflammation and improving mitochondrial dysfunction via NF-κB-FGF21 or SREBP1c-FGF21 pathway.

Taking KLF9 to "Cort" for crimes against metabolism

Glucocorticoids (GCs) are essential for proper glycemic control, but in excess, can lead to hyperglycemia and diabetes. In this issue of the JCI, Cui et al. elucidate a mechanism by which GCs regulate gluconeogenesis utilizing the transcription factor Krüppel-like factor 9 (KLF9) in physiology and disease settings. They report that KLF9 is a GC-inducible factor that ultimately increases the transcription of proliferator-activated receptor γ coactivator 1 α (PGC1α), resulting in gluconeogenesis. Given the high incidence of GC-induced diabetes, identification of this signaling axis provides, not only critical scientific insight, but also a foundation for preventative therapies for patients receiving chronic GC treatment.