Hyperinsulinemia-induced KLF5 mediates endothelial angiogenic dysfunction in diabetic endothelial cells

Krüpple-like factors in cardiomyopathy: emerging player and therapeutic opportunities

Cardiomyopathy, a heterogeneous pathological condition characterized by changes in cardiac structure or function, represents a significant risk factor for the prevalence and mortality of cardiovascular disease (CVD). Research conducted over the years has led to the modification of definition and classification of cardiomyopathy. Herein, we reviewed seven of the most common types of cardiomyopathies, including Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), diabetic cardiomyopathy, Dilated Cardiomyopathy (DCM), desmin-associated cardiomyopathy, Hypertrophic Cardiomyopathy (HCM), Ischemic Cardiomyopathy (ICM), and obesity cardiomyopathy, focusing on their definitions, epidemiology, and influencing factors. Cardiomyopathies manifest in various ways ranging from microscopic alterations in cardiomyocytes, to tissue hypoperfusion, cardiac failure, and arrhythmias caused by electrical conduction abnormalities. As pleiotropic Transcription Factors (TFs), the Krüppel-Like Factors (KLFs), a family of zinc finger proteins, are involved in regulating the setting and development of cardiomyopathies, and play critical roles in associated biological processes, including Oxidative Stress (OS), inflammatory reactions, myocardial hypertrophy and fibrosis, and cellular autophagy and apoptosis, particularly in diabetic cardiomyopathy. However, research into KLFs in cardiomyopathy is still in its early stages, and the pathophysiologic mechanisms of some KLF members in various types of cardiomyopathies remain unclear. This article reviews the roles and recent research advances in KLFs, specifically those targeting and regulating several cardiomyopathy-associated processes.

Predictors of subclinical atherosclerosis and microalbuminuria in middle-aged women: a cross-sectional study

BACKGROUND

Cardiovascular disease is of increasing concern in women. The aim was to assess the role of clinical and anthropometric measures in the development of subclinical atherosclerosis.

METHODS

A cross-sectional study in 203 Europid females to determine the prevalence of abnormal carotid intima-media thickness (CIMT) and associated clinical parameters.

RESULTS

The study population had a mean age of the 38.3±5.4 years, a median Body Mass Index of 29.25 (IQR 25.06-36.11) kg/m2 and median waist index (WI) of 1.15 (IQR 1.06-1.34). Increased CIMT was present in 169 (83.25%) participants. Linear regression analysis revealed WI to be the sole predictor of increased CIMT (β=24.387, P<0.001). Post-hoc ROC analysis revealed a WI of 1.12 has 62% sensitivity and 53% specificity for predicting increased CIMT (AUC 0.63, 95% CI 0.55-0.72, P=0.016). The median urinary albumin-creatinine ratio (ACR) was 4.4 mg/g, and the prevalence of microalbuminuria was 8.9%; serum triglycerides were the only independent predictor of ACR.

CONCLUSIONS

Atherosclerosis, as detected by abnormal CIMT, is very prevalent in middle-aged women. Waist index is the major predictor of subclinical atherosclerosis in a contemporary premenopausal female population. A WI of 1.12 exhibits relatively good sensitivity and specificity in predicting the presence of atherosclerosis in this patient population.

Participation of Krüppel-like Factors in Atherogenesis

Atherosclerosis is an important problem in modern medicine, the keys to understanding many aspects of which are still not available to clinicians. Atherosclerosis develops as a result of a complex chain of events in which many cells of the vascular wall and peripheral blood flow are involved. Endothelial cells, which line the vascular wall in a monolayer, play an important role in vascular biology. A growing body of evidence strengthens the understanding of the multifaceted functions of endothelial cells, which not only organize the barrier between blood flow and tissues but also act as regulators of hemodynamics and play an important role in regulating the function of other cells in the vascular wall. Krüppel-like factors (KLFs) perform several biological functions in various cells of the vascular wall. The large family of KLFs in humans includes 18 members, among which KLF2 and KLF4 are at the crossroads between endothelial cell mechanobiology and immunometabolism, which play important roles in both the normal vascular wall and atherosclerosis.

MicroRNA-375 repression of Kruppel-like factor 5 improves angiogenesis in diabetic critical limb ischemia

Peripheral artery disease (PAD) is an occlusive disease of limb arteries. Critical limb ischemia (CLI) is an advanced form of PAD that is prognostically worse in subjects with diabetes and can result in limb loss, gangrene, and death, although the underlying signaling mechanisms that contribute to its development remain poorly understood. By comparing plasma samples from diabetic humans with PAD and mouse models of PAD, we identified miR-375 to be significantly downregulated in humans and mice during progression to CLI. Overexpression of miR-375 was pro-angiogenic in endothelial cells in vitro and induced endothelial migration, proliferation, sprouting, and vascular network formation, whereas miR-375 inhibition conferred anti-angiogenic effects. Intramuscular delivery of miR-375 improved blood flow recovery to diabetic mouse hindlimbs following femoral artery ligation (FAL) and improved neovessel growth and arteriogenesis in muscle tissues. Using RNA-sequencing and prediction algorithms, Kruppel-like factor 5 (KLF5) was identified as a direct target of miR-375 and siRNA knockdown of KLF5 phenocopied the effects of miR-375 overexpression in vitro and in vivo through regulatory changes in NF-kB signaling. Together, a miR-375-KLF5-NF-kB signaling axis figures prominently as a potential therapeutic pathway in the development CLI in diabetes.

Mapping the cardiac vascular niche in heart failure

The cardiac vascular and perivascular niche are of major importance in homeostasis and during disease, but we lack a complete understanding of its cellular heterogeneity and alteration in response to injury as a major driver of heart failure. Using combined genetic fate tracing with confocal imaging and single-cell RNA sequencing of this niche in homeostasis and during heart failure, we unravel cell type specific transcriptomic changes in fibroblast, endothelial, pericyte and vascular smooth muscle cell subtypes. We characterize a specific fibroblast subpopulation that exists during homeostasis, acquires Thbs4 expression and expands after injury driving cardiac fibrosis, and identify the transcription factor TEAD1 as a regulator of fibroblast activation. Endothelial cells display a proliferative response after injury, which is not sustained in later remodeling, together with transcriptional changes related to hypoxia, angiogenesis, and migration. Collectively, our data provides an extensive resource of transcriptomic changes in the vascular niche in hypertrophic cardiac remodeling.

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.

Krüppel-like factor (KLF)5: An emerging foe of cardiovascular health

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors, which regulate various pathways that pertain to development, metabolism and other cellular mechanisms. KLF5 was first cloned in 1993 and by 1999, it was reported as the intestinal-enriched KLF. Beyond findings that have associated KLF5 with normal development and cancer, it has been associated with various types of cardiovascular (CV) complications and regulation of metabolic pathways in the liver, heart, adipose tissue and skeletal muscle. Specifically, increased KLF5 expression has been linked with cardiomyopathy in diabetes, end-stage heart failure, and as well as in vascular atherosclerotic lesions. In this review article, we summarize research findings about transcriptional, post-transcriptional and post-translational regulation of KLF5, as well as the role of KLF5 in the biology of cells and organs that affect cardiovascular health either directly or indirectly. Finally, we propose KLF5 inhibition as an emerging approach for cardiovascular therapeutics.

Oxidative Stress-Induced Hypermethylation of KLF5 Promoter Mediated by DNMT3B Impairs Osteogenesis by Diminishing the Interaction with β-Catenin

Aims: Emerging evidence suggests that the pathogenesis of osteoporosis, characterized by impaired osteogenesis, is shifting from estrogen centric to oxidative stress. Our previous studies have shown that the zinc-finger transcription factor krüppel-like factor 5 (KLF5) plays a key role in the degeneration of nucleus pulposus and cartilage. However, its role in osteoporosis remains unknown. We aimed to investigate the effect and mechanism of KLF5 on osteogenesis under oxidative stress. Results: First, KLF5 was required for osteogenesis and stimulated osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). KLF5 was hypermethylated and downregulated in ovariectomy-induced osteoporosis mice and in BMSCs treated with H2O2. Interestingly, DNA methyltransferases 3B (DNMT3B) upregulation mediated the hypermethylation of KLF5 induced by oxidative stress, thereby impairing osteogenic differentiation. The inhibition of KLF5 hypermethylation using DNMT3B siRNA or 5-AZA-2-deoxycytidine (5-AZA) protected osteogenic differentiation of BMSCs from oxidative stress. Regarding the downstream mechanism, KLF5 induced β-catenin expression. More importantly, KLF5 promoted the nuclear translocation of β-catenin, which was mediated by the armadillo repeat region of β-catenin. Consistently, oxidative stress-induced KLF5 hypermethylation inhibited osteogenic differentiation by reducing the expression and nuclear translocation of β-catenin. Innovation: We describe the novel effect and mechanism of KLF5 on osteogenesis under oxidative stress, which is linked to osteoporosis for the first time. Conclusion: Our results suggested that oxidative stress-induced hypermethylation of KLF5 mediated by DNMT3B impairs osteogenesis by diminishing the interaction with β-catenin, which is likely to contribute to osteoporosis. Targeting the hypermethylation of KLF5 might be a new strategy for the treatment of osteoporosis. Antioxid. Redox Signal. 35, 1-20.

Silencing of OIP5-AS1 Protects Endothelial Cells From ox-LDL-Triggered Injury by Regulating KLF5 Expression via Sponging miR-135a-5p

Background: Long non-coding RNAs (lncRNAs) have been implicated in the pathogenesis of atherosclerosis. LncRNA OIP5 antisense RNA 1 (OIP5-AS1) has been found to be associated with the development of atherosclerosis. In this study, we further investigated the molecular basis of OIP5-AS1 in atherosclerosis pathogenesis.

Methods: Oxidative low-density lipoprotein (ox-LDL) was used to treat human umbilical vein endothelial cells (HUVECs). The levels of OIP5-AS1, miR-135a-5p, and Krüppel-like factor 5 (KLF5) were detected by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. Cell viability, migration, and apoptosis were evaluated using the Cell Counting Kit-8 (CCK-8), Transwell, and flow cytometry, respectively. The levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and malondialdehyde (MDA) were determined with enzyme-linked immunosorbent assay (ELISA). Targeted interactions among OIP5-AS1, miR-135a-5p, and KLF5 were confirmed by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Animal studies were performed to assess the role of OIP5-AS1 in atherosclerosis progression in vivo.

Results: Our data showed the significant upregulation of OIP5-AS1 in atherosclerosis serum and ox-LDL-stimulated HUVECs. The silencing of OIP5-AS1 protected against ox-LDL-triggered cytotoxicity in HUVECs and diminished lipids secretion in ApoE^−/− mice. Moreover, OIP5-AS1 functioned as a molecular sponge of miR-135a-5p, and miR-135a-5p was a functional mediator of OIP5-AS1 in regulating ox-LDL-induced HUVEC injury. KLF5 was a direct target of miR-135a-5p, and the increased expression of miR-135a-5p alleviated ox-LDL-induced cytotoxicity by downregulating KLF5. Furthermore, OIP5-AS1 influenced KLF5 expression through sponging miR-135a-5p.

Conclusion: The current work identified that the silencing of OIP5-AS1 protected against ox-LDL-triggered cytotoxicity in HUVECs at least in part by influencing KLF5 expression via acting as a miR-135a-5p sponge.

Roles of Krüppel-like factor 5 in kidney disease

Transcription factor Krüppel-like factor 5 (KLF5) is a member of the Krüppel-like factors' (KLFs) family. KLF5 regulates a number of cellular functions, such as apoptosis, proliferation and differentiation. Therefore, KLF5 can play a role in many diseases, including, cancer, cardiovascular disease and gastrointestinal disorders. An important role for KLF5 in the kidney was recently reported, such that KLF5 regulated podocyte apoptosis, renal cell proliferation, tubulointerstitial inflammation and renal fibrosis. In this review, we have summarized the available information in the literature with a brief description on how transcriptional, post-transcriptional and post-translational modifications of KLF5 modulate its function in a variety of organs including the kidney with a focus of its importance on the pathogenesis of various kidney diseases. Furthermore, we also have outlined the current and possible mechanisms of KLF5 activation in kidney diseases. These studies suggest a need for more systemic investigations, particularly for generation of animal models with renal cell-specific deletion or overexpression of KLF5 gene to examine direct contributions of KLF5 to various kidney diseases. This will promote further experimentation in the development of therapies to prevent or treat various kidney diseases.

Current knowledge of Krüppel-like factor 5 and vascular remodeling: providing insights for therapeutic strategies

Vascular remodeling is a pathological basis of various disorders. Therefore, it is necessary to understand the occurrence, prevention, and treatment of vascular remodeling. Krüppel-like factor 5 (KLF5) has been identified as a significant factor in cardiovascular diseases during the last two decades. This review provides a mechanism network of function and regulation of KLF5 in vascular remodeling based on newly published data and gives a summary of its potential therapeutic applications. KLF5 modulates numerous biological processes, which play essential parts in the development of vascular remodeling, such as cell proliferation, phenotype switch, extracellular matrix deposition, inflammation, and angiogenesis by altering downstream genes and signaling pathways. Considering its essential functions, KLF5 could be developed as a potent therapeutic target in vascular disorders.