Klotho inhibits angiotensin II-induced cardiac hypertrophy, fibrosis, and dysfunction in mice through suppression of transforming growth factor-β1 signaling pathway

The Aging Heart in Focus: The Advanced Understanding of Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) accounts for 50% of heart failure (HF) cases, making it the most common type of HF, and its prevalence continues to increase in the aging society. HFpEF is a systemic syndrome resulting from many risk factors, such as aging, metabolic syndrome, and hypertension, and its clinical features are highly heterogeneous in different populations. HFpEF syndrome involves the dysfunction of multiple organs, including the heart, lung, muscle, and vascular system. The heart shows dysfunction of various cells, including cardiomyocytes, endothelial cells, fibroblasts, adipocytes, and immune cells. The complex etiology and pathobiology limit experimental research on HFpEF in animal models, delaying a comprehensive understanding of the mechanisms and making treatment difficult. Recently, many scientists and cardiologists have attempted to improve the clinical outcomes of HFpEF. Recent advances in clinically related animal models and systemic pathology studies have improved our understanding of HFpEF, and clinical trials involving sodium-glucose cotransporter 2 inhibitors have significantly enhanced our confidence in treating HFpEF. This review provides an updated comprehensive discussion of the etiology and pathobiology, molecular and cellular mechanisms, preclinical animal models, and therapeutic trials in animals and patients to enhance our understanding of HFpEF and improve clinical outcomes.

The role of Klotho and sirtuins in sleep-related cardiovascular diseases: a review study

The prevalence of sleep disorders has been reported from 1.6% to 56.0%, worldwide. Sleep deprivation causes cardiovascular diseases (CVDs) including atherosclerosis, vascular aging, hypertension, heart dysfunction, reduced heart rate variability, and cardiac arrhythmia. Reduced tissue oxygen causes various CVDs by activating pro-inflammatory factors and increasing oxidative stress. Sleep disorders are more important and prevalent in older people and cause more severe cardiovascular complications. On the other hand, the reduction of Klotho level, an age-dependent protein whose expression decreases with age, is associated with age-related diseases. Sirtuins, class III histone deacetylases, also are among the essential factors in postponing cellular aging and increasing the lifespan of organisms, and they do this by regulating different pathways in the cell. Sirtuins and Klotho play an important role in the pathophysiology of CVDS and both have anti-oxidative stress and anti-inflammatory activity. Studies have shown that the levels of Klotho and sirtuins are altered in sleep disorders. In this article, alterations of Klotho and sirtuins in sleep disorders and in the development of sleep-related CVDs were reviewed and the possible signaling pathways were discussed. The inclusion criteria were studies with keywords of different types of sleep disorders and CVDs, klotho, SIRT1-7, and sirtuins in PubMed, Scopus, Embase، Science Direct، Web of Sciences and Google Scholar by the end of 2023. The studies revealed there is a bidirectional relationship between sleep disorders and the serum and tissue levels of Klotho and sirtuins and sleep related-CVDs.

The Pathophysiological Associations Between Obesity, NAFLD, and Atherosclerotic Cardiovascular Diseases

Obesity, non-alcoholic fatty liver disease (NAFLD), and atherosclerotic cardiovascular diseases are common and growing public health concerns. Previous epidemiological studies unfolded the robust correlation between obesity, NAFLD, and atherosclerotic cardiovascular diseases. Obesity is a well-known risk factor for NAFLD, and both of them can markedly increase the odds of atherosclerotic cardiovascular diseases. On the other hand, significant weight loss achieved by lifestyle modification, bariatric surgery, or medications, such as semaglutide, can concomitantly improve NAFLD and atherosclerotic cardiovascular diseases. Therefore, certain pathophysiological links are involved in the development of NAFLD in obesity, and atherosclerotic cardiovascular diseases in obesity and NAFLD. Moreover, recent studies indicated that simultaneously targeting several mechanisms by tirzepatide and retatrutide leads to greater weight loss and markedly improves the complications of metabolic syndrome. These findings remind the importance of a mechanistic viewpoint for breaking the association between obesity, NAFLD, and atherosclerotic cardiovascular diseases. In this review article, we mainly focus on shared pathophysiological mechanisms, including insulin resistance, dyslipidemia, GLP1 signaling, inflammation, oxidative stress, mitochondrial dysfunction, gut dysbiosis, renin-angiotensin-aldosterone system (RAAS) overactivity, and endothelial dysfunction. Most of these pathophysiological alterations are primarily initiated by obesity. The development of NAFLD further exacerbates these molecular and cellular alterations, leading to atherosclerotic cardiovascular disease development or progression as the final manifestation of molecular perturbation. A better insight into these mechanisms makes it feasible to develop new multi-target approaches to simultaneously unhinge the deleterious chain of events linking obesity and NAFLD to atherosclerotic cardiovascular diseases.

New insights into the role of Klotho in inflammation and fibrosis: molecular and cellular mechanisms

As the body's defense mechanism against damage and infection, the inflammatory response is a pathological process that involves a range of inflammatory cells and cytokines. A healthy inflammatory response helps the body repair by eliminating dangerous irritants. However, tissue fibrosis can result from an overly intense or protracted inflammatory response. The anti-aging gene Klotho suppresses oxidation, delays aging, and fosters development of various organs. Numerous investigations conducted in the last few years have discovered that Klotho expression is changed in a variety of clinical diseases and is strongly linked to the course and outcome of a disease. Klotho functions as a co-receptor for FGF and as a humoral factor that mediates intracellular signaling pathways such as transforming growth factor β (TGF-β), toll-like receptors (TLRs), nuclear factor-kappaB (NF-κB), renin -angiotensin system (RAS), and mitogen-activated protein kinase (MAPK). It also interferes with the phenotype and function of inflammatory cells, such as monocytes, macrophages, T cells, and B cells. Additionally, it regulates the production of inflammatory factors. This article aims to examine Klotho's scientific advances in terms of tissue fibrosis and the inflammatory response in order to provide novel therapy concepts for fibrotic and inflammatory disorders.

U-shaped association between serum Klotho and all-cause mortality in US cardiovascular patients: a prospective cohort study

Background

Increased levels of serum Klotho have been associated with a reduced risk of several cardiovascular diseases (CVD). However, limited studies exist on the association between serum Klotho and mortality in patients with CVD.

Methods

We collected data from CVD patients in the National Health and Nutrition Examination Survey (NHANES) spanning 2007 to 2016. We linked NHANES data with the National Death Index to determine the survival status of participants. Univariate and multivariable Cox regression models were used to investigate the relationship between serum Klotho levels and mortality in CVD patients. The relationship between serum Klotho quartiles and mortality in CVD patients was visualized using Kaplan-Meier (KM) curves and restricted cubic spine. Finally, subgroup analyses were used to examine the association between serum Klotho and all-cause mortality in different populations.

Results

1905 patients with CVD were finally enrolled in our study with a mean follow-up of 7.1 years. The average age of the participants was 63.4 years, with 58.40% being male. KM showed that lower Klotho levels were associated with lower survival rates. After adjusting for potential confounders, patients with higher serum Klotho levels had lower all-cause mortality (Q1: 1.00, Q2: 0.58 (0.42-0.80), Q3: 0.69 (0.47-1.01), and Q4:0.64 (0.45-0.92). However, the relationship between serum Klotho levels and cardiovascular mortality was not statistically significant. Dose-response analysis shows a U-shaped relationship between serum Klotho levels and all-cause mortality in patients with CVD (P nonlinear=0.002). Subgroup analysis indicated that participants with a history of hypertension had a higher risk of all-cause mortality in serum Klotho Q4 compared to Q1 (P trend <0.05).

Conclusion

The relationship between serum Klotho levels and all-cause mortality in CVD patients exhibits a U-shaped association. The underlying mechanisms of this association need further investigation.

Development and Evaluation of a Water-Free In Situ Depot Gel Formulation for Long-Acting and Stable Delivery of Peptide Drug ACTY116

In situ depot gel is a type of polymeric long-acting injectable (pLAI) drug delivery system; compared to microsphere technology, its preparation process is simpler and more conducive to industrialization. To ensure the chemical stability of peptide ACTY116, we avoided the use of harsh conditions such as high temperatures, high shear mixing, or homogenization; maintaining a water-free and oxygen-free environment was also critical to prevent hydrolysis and oxidation. Molecular dynamics (MDs) simulations were employed to assess the stability mechanism between ACTY116 and the pLAI system. The initial structure of ACTY116 with an alpha helix conformation was constructed using SYBYL-X, and the copolymer PLGA was generated by AMBER 16; results showed that PLGA-based in situ depot gel improved conformational stability of ACTY116 through hydrogen bonds formed between peptide ACTY116 and the components of the pLAI formulation, while PLGA (Poly(DL-lactide-co-glycolide)) also created steric hindrance and shielding effects to prevent conformational changes. As a result, the chemical and conformational stability and in vivo long-acting characteristics of ACTY116 ensure its enhanced efficacy. In summary, we successfully achieved our objective of developing a highly stable peptide-loaded long-acting injectable (LAI) in situ depot gel formulation that is stable for at least 3 months under harsh conditions (40 °C, above body temperature), elucidating the underlying stabilisation mechanism, and the high stability of the ACTY116 pLAI formulation creates favourable conditions for its in vivo pharmacological activity lasting for weeks or even months.

Fibroblast growth factor 23 during septic shock and myocardial injury in ICU patients

Objective

Fibroblast growth factor 23 (FGF23) has been recognized as an important biomarker of cardiovascular disease and is closely related to inflammation over the past decade. This study aimed to assess the relationship between FGF23 and myocardial injury in patients with sepsis.

Methods

We sequentially measured serum FGF23, Klotho, biomarkers of inflammation (CRP, IL-6 and WBC), myocardial injury (cTnI and N-terminal B-type natriuretic peptide) and sepsis (procalcitonin) at peak of intercurrent septic shock and after complete resolution or before death in a series of 29 patients with septic shock. 29 healthy adults without infections were used as controls.

Results

There was a difference in serum FGF23 level between patients with septic shock and healthy adults (p < 0.0001), and the peak level of FGF23 in septic shock in the survivor group was higher than that after complete remission (p < 0.0001). No statistical difference was found in the level of FGF23 before and after treatment in the death group (p = 0.0947). At the peak of septic shock, FGF23 was significantly correlated with inflammatory markers, CRP (r = 0.8063, p < 0.0001), PCT (r = 0.6091, p = 0.0005) and WBC (r = 0.8312, p < 0.0001), while the correlation with IL-6 was not statistically significant (r = 0.0098, p = 0.9598). At the same time, it was found that FGF23 was significantly correlated with myocardial injury markers, cTNI (r = 0.8475, p < 0.0001) and NTproBNP (r = 0.8505, p < 0.0001). Nevertheless, FGF23 and klotho are not correlated (r = 0.2609, p = 0.1717).

Conclusion

In conclusion, in patients with septic shock and myocardial injury, the exacerbation of inflammation in the septic process was accompanied by a abnormal increase of circulating FGF23 level. FGF23 also subsided after the improvement of inflammation, and the opposite was true for patients who did not survive. The up-regulation of FGF23 may be involved in the response of patients to septic shocks, and it is also speculated that FGF23 is involved in the myocardial injury of septic shock.

AMPK signaling inhibits the differentiation of myofibroblasts: impact on age-related tissue fibrosis and degeneration

Disruption of the extracellular matrix (ECM) and an accumulation of fibrotic lesions within tissues are two of the distinctive hallmarks of the aging process. Tissue fibroblasts are mesenchymal cells which display an impressive plasticity in the regulation of ECM integrity and thus on tissue homeostasis. Single-cell transcriptome studies have revealed that tissue fibroblasts exhibit a remarkable heterogeneity with aging and in age-related diseases. Excessive stress and inflammatory insults induce the differentiation of fibroblasts into myofibroblasts which are fusiform contractile cells and abundantly secrete the components of the ECM and proteolytic enzymes as well as many inflammatory mediators. Detrimental stresses can also induce the transdifferentiation of certain mesenchymal and myeloid cells into myofibroblasts. Interestingly, many age-related stresses, such as oxidative and endoplasmic reticulum stresses, ECM stiffness, inflammatory mediators, telomere shortening, and several alarmins from damaged cells are potent inducers of myofibroblast differentiation. Intriguingly, there is convincing evidence that the signaling pathways stimulated by the AMP-activated protein kinase (AMPK) are potent inhibitors of myofibroblast differentiation and accordingly AMPK signaling reduces fibrotic lesions within tissues, e.g., in age-related cardiac and pulmonary fibrosis. AMPK signaling is not only an important regulator of energy metabolism but it is also able to control cell fate determination and many functions of the immune system. It is known that AMPK signaling can delay the aging process via an integrated signaling network. AMPK signaling inhibits myofibroblast differentiation, e.g., by suppressing signaling through the TGF-β, NF-κB, STAT3, and YAP/TAZ pathways. It seems that AMPK signaling can alleviate age-related tissue fibrosis and degeneration by inhibiting the differentiation of myofibroblasts.

Inhibition of EZH2 mitigates peritoneal fibrosis and lipid precipitation in peritoneal mesothelial cells mediated by klotho

BACKGROUND

Peritoneal fibrosis caused by long-term peritoneal dialysis (PD) is the main reason why patients withdraw from PD treatment. Lipid accumulation in the peritoneum was shown to participate in fibrosis, and klotho is a molecule involved in lipid metabolism. GSK343 (enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) inhibitor) has been verified to inhibit epithelial mesenchymal transdifferentiation (EMT) and peritoneal fibrosis, but its related mechanism remains unclear. This study aimed to investigate whether lipid accumulation was involved in the effect of GSK343 and its related mechanism.

MATERIALS AND METHODS

First, the expression of EZH2, klotho and EMT indices in human peritoneal mesothelial cells (HMrSV5) incubated with high glucose (HG) levels was detected. After EZH2 was inhibited by GSK343, Western blot (WB), wound healing and Transwell assays were used to explore the effect of GSK343. EZH2 and klotho expression was also detected. Oil red O and Nile red staining and triglyceride (TG) detection kits were used to detect lipid accumulation. A rescue experiment with small interfering RNA specific for klotho (si-klotho) on the basis of GSK343 was also conducted to verify that GSK343 exerted its effect via klotho. In in vivo experiments, rats were administered GSK343, and the related index was assessed.

RESULTS

In our study, we revealed that the expression of EZH2 was significantly upregulated and klotho was significantly downregulated in HMrSV5 cells induced by high glucose. With the aid of GSK343, we found that lipid deposition caused by HG was significantly decreased. In addition, EMT and fibrosis were also significantly alleviated. Moreover, GSK343 could also restore the downregulation of klotho. To further verify whether klotho mediated the effect of EZH2, a rescue experiment with si-klotho was also conducted. The results showed that si-klotho could counteract the protective effect of GSK343 on high glucose-induced lipid accumulation and fibrosis. In vivo experiments also revealed that GSK343 could relieve peritoneal fibrosis, lipid deposition and EMT by mitigating EZH2 and restoring klotho expression.

CONCLUSIONS

Combining these findings, we found that EZH2 regulated lipid deposition, peritoneal fibrosis, and EMT mediated by klotho. To our knowledge, this is the first study to demonstrate the effect of the EZH2-klotho interaction on peritoneal fibrosis. Hence, EZH2 and klotho could act as potential targets for the treatment of peritoneal fibrosis.

Klotho inhibits IGF1R/PI3K/AKT signalling pathway and protects the heart from oxidative stress during ischemia/reperfusion injury

Ischemia/reperfusion injury (IRI) of the heart involves the activation of oxidative and proapoptotic pathways. Simultaneously Klotho protein presents anti-aging, antiapoptotic and antioxidative properties. Therefore, this study aimed to evaluate the effect of Klotho protein on oxidative stress in hearts subjected to IRI. Isolated rat hearts perfused with the Langendorff method were subjected to ischemia, followed by reperfusion, in the presence or absence of recombinant rat Klotho protein. The factors involved in the activation of insulin-like growth factor receptor (IGF1R)/phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) signalling pathway were evaluated. IRI caused activation of the IGF1R (p = 0.0122)/PI3K (p = 0.0022) signalling, as compared to the aerobic control group. Infusion supply of Klotho protein during IRI significantly reduced the level of phospho-IGF1R (p = 0.0436), PI3K (p = 0.0218) and phospho-AKT (p = 0.0020). Transcriptional activity of forkhead box protein O3 (FOXO3) was reduced (p = 0.0207) in hearts subjected to IRI, compared to aerobic control. Administration of Klotho decreased phosphorylation of FOXO3 (p = 0.0355), and enhanced activity of glutathione peroxidase (p = 0.0452) and superoxide dismutase (p = 0.0060) in IRI + Klotho group. The levels of reactive oxygen/nitrogen species (ROS/RNS) (p = 0.0480) and hydrogen peroxide (H2O2) (p = 0.0460), and heart injury (p = 0.0005) were significantly increased in hearts from the IRI group in comparison to the aerobic group. Klotho reduced NADPH oxidase 2 (NOX2) (p = 0.0390), ROS/RNS (p = 0.0435) and H2O2 (p = 0.0392) levels, and heart damage (p = 0.0286) in the hearts subjected to IRI. In conclusion, Klotho contributed to the protection of the heart against IRI and oxidative stress via inhibition of the IGF1R/PI3K/AKT pathway, thus can be recognized as a novel cardiopreventive/cardioprotective agent.

High glucose dialysate-induced peritoneal fibrosis: Pathophysiology, underlying mechanisms and potential therapeutic strategies

Peritoneal dialysis is an efficient renal replacement therapy for patients with end-stage kidney disease. However, continuous exposure of the peritoneal membrane to dialysate frequently leads to peritoneal fibrosis, which alters the function of the peritoneal membrane and results in withdrawal from peritoneal dialysis in patients. Among others, high glucose dialysate is considered as a predisposing factor for peritoneal fibrosis in patients on peritoneal dialysis. Glucose-induced inflammation, metabolism disturbance, activation of the renin-angiotensin-aldosterone system, angiogenesis and noninflammation-induced reactive oxygen species are implicated in the pathogenesis of high glucose dialysate-induced peritoneal fibrosis. Specifically, high glucose causes chronic inflammation and recurrent peritonitis, which could cause migration and polarization of inflammatory cells, as well as release of cytokines and fibrosis. High glucose also interferes with lipid metabolism and glycolysis by activating the sterol-regulatory element-binding protein-2/cleavage-activating protein pathway and increasing hypoxia inducible factor-1α expression, leading to angiogenesis and peritoneal fibrosis. Activation of the renin-angiotensin-aldosterone system and Ras-mitogen activated protein kinase signaling pathway is another contributing factor in high glucose dialysate-induced fibrosis. Ultimately, activation of the transforming growth factor-β1/Smad pathway is involved in mesothelial-mesenchymal transition or epithelial-mesenchymal transition, which leads to the development of fibrosis. Although possible intervention strategies for peritoneal dialysate-induced fibrosis by targeting the transforming growth factor-β1/Smad pathway have occasionally been proposed, lack of laboratory evidence renders clinical decision-making difficult. We therefore aim to revisit the upstream pathways of transforming growth factor-beta1/Smad and propose potential therapeutic targets for high glucose-induced peritoneal fibrosis.

Lung cancer-derived exosomal miR-132-3p contributed to interstitial lung disease development

PURPOSE

Interstitial lung diseases (ILDs) have high morbidity and mortality and poor prognosis. The significance of microRNAs (miRNAs) was highlighted in ILDs development. Currently, we attempted to confirm the functions of lung cancer-derived exosomal miR-132-3p and reveal the underlying mechanism.

METHOD

Characteristics of exosomes were verified by transmission electron microscope (TEM), nanoparticle tracking analysis, and Western blot assay. Exosome uptake for the normal human lung fibroblasts (NHLF) was assessed using a PKH67 staining assay. MTT and colony formation assays were applied to examine the proliferation abilities of NHLF. The interaction between miR-132-3p and sprouty1 (SPRY1) was confirmed by a luciferase reporter assay.

RESULTS

Lung cancer-derived exosomes promoted normal human lung fibroblast activation. Exosome inhibitor GW4869 reversed the effects of Exo on NHLF. Subsequently, miR-132-3p in lung cancer-derived exosomes activated the normal human lung fibroblast and promoted interstitial lung disease development ex vivo. Next, SPRY1 was verified to be the binding protein of miR-132-3p, and sh-SPRY1 abrogated the effects of the miR-132-3p inhibitor on NHLF.

CONCLUSION

Exosomal miR-132-3p from A549 cells accelerated the development of interstitial lung disease through binding to SPRY1, which might serve as an important target for ILDs.

Gentisic acid protects against diabetic nephropathy in Nicotinamide-Streptozotocin administered male mice by attenuating oxidative stress and inflammation: The role of miR-200a/Keap1/Nrf2 pathway, renin-angiotensin system (RAS) and NF-кB

Oxidative stress and inflammation play a pivotal role in the pathogenesis of diabetic nephropathy (DN). Local renin-angiotensin systems (RAS) contribute to the pathogenesis and progression of DN by exacerbating oxidative stress and inflammation.Gentisic acid (GA), a phenolic compound and also a metabolite of aspirin, is reported to possess antioxidant and anti-inflammatory properties. However, the protective effects of GA against DN remain to be elucidated. Nicotinamide (110 mg/kg) and streptozotocin (65 mg/kg) were used to induce diabetes in male mice. Oral administration of GA once daily for 2 weeks (100 mg/kg) ameliorated diabetes-induced renal injury by reducing plasma creatinine, urea, blood urea nitrogen, and urinary albuminuria levels. Diabetic mice showed a significant increase in total oxidant status and malondialdehyde, along with decreased catalase, superoxide dismutase, and glutathione peroxidase in the kidney tissue, which was ameliorated in the GA-treated mice. Histopathological analysis showed that GA treatment reduced diabetes-induced renal injury. Furthermore, GA treatment was associated with the downregulation of miR-125b, nuclear factor kappa beta (NF-кB), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and upregulation of interleukin-10 (IL-10), miR-200a, and nuclear factor erythroid 2-related factor 2 (Nrf2) in the renal tissue. GA treatment also downregulated angiotensin-converting enzyme 1 (ACE1), angiotensin II receptor 1 (AT1R), and NADPH oxidase 2 (NOX 2) and upregulated angiotensin-converting enzyme 2 (ACE2). In conclusion, the ameliorative effects of GA against DN may be attributed to its powerful antioxidant and anti-inflammatory properties through the downregulation of NF-кB, upregulation of Nrf2, and modulation of RAS in renal tissue.

Klotho improves cardiac fibrosis, inflammatory cytokines, ferroptosis, and oxidative stress in mice with myocardial infarction

The anti-aging protein Klotho has been associated with cardiovascular health protection. Nevertheless, the protective mechanism remains unknown. The present study is aimed at exploring the effect of Klotho on cardiac remodeling and its potential mechanism in mice with myocardial infarction (MI). We used left anterior coronary artery descending ligation to develop an MI model for in vivo analyses. In contrast, H9C2 cells and cardiac fibroblasts were used to establish the oxygen-glucose deprivation (OGD) model in in vitro analyses. In vivo and in vitro models were treated with Klotho. Compound C, an AMPK signaling inhibitor, was used to determine whether Klotho's effects are mediated through the AMPK/mTOR signaling pathway. Echocardiography, Masson trichrome staining, immunofluorescence, immunohistochemistry, real-time polymerase chain reaction (RT-PCR), and western blot were used to detect the related indicators. The findings of the in vivo model indicate that Klotho treatment improved the mice's cardiac function, reduced cardiac fibrosis, and attenuated myocardial inflammatory factors, ferroptosis, and oxidative stress. The results of the in vitro model were in line with the findings of in vivo modeling. An AMPK inhibitor, Compound C, reversed all these effects. In conclusion, Klotho potentially improves cardiac remodeling in MI mice by regulating AMPK/mTOR signaling, demonstrating Klotho as an effective MI therapeutic agent.

Hypertension and cardiomyopathy associated with chronic kidney disease: epidemiology, pathogenesis and treatment considerations

Chronic kidney disease (CKD) is a complex condition with a prevalence of 10-15% worldwide. An inverse-graded relationship exists between cardiovascular events and mortality with kidney function which is independent of age, sex, and other risk factors. The proportion of deaths due to heart failure and sudden cardiac death increase with progression of chronic kidney disease with relatively fewer deaths from atheromatous, vasculo-occlusive processes. This phenomenon can largely be explained by the increased prevalence of CKD-associated cardiomyopathy with worsening kidney function. The key features of CKD-associated cardiomyopathy are increased left ventricular mass and left ventricular hypertrophy, diastolic and systolic left ventricular dysfunction, and profound cardiac fibrosis on histology. While these features have predominantly been described in patients with advanced kidney disease on dialysis treatment, patients with only mild to moderate renal impairment already exhibit structural and functional changes consistent with CKD-associated cardiomyopathy. In this review we discuss the key drivers of CKD-associated cardiomyopathy and the key role of hypertension in its pathogenesis. We also evaluate existing, as well as developing therapies in the treatment of CKD-associated cardiomyopathy.

Association between serum Klotho concentration and heart failure in adults, a cross-sectional study from NHANES 2007-2016

BACKGROUND

Limited data exist on the association between serum Klotho concentration and heart failure (HF).

METHODS AND RESULTS

We conducted a cross-sectional study of 13,625 participants aged 40-79 years in the National Health and Nutrition Examination Survey (NHANES) 2007-2016. Multivariable logistic regression models were used to examine the association between serum Klotho concentration (ln transformation) and HF. A total of 533 (2.9%) participants were identified to have HF, and participants with the lowest tertiles of serum Klotho concentration had the highest percentage of HF (T1: 3.8% vs. T2: 2.8% and T3: 2.1%, P < 0.001). After adjusting for potential confounders, ln (Klotho) was negatively and independently associated with the risk of HF (OR= 0.55, 95% CI 0.36-0.84). Meanwhile, compared with the T1 group, a higher serum Klotho concentration was associated with a lower risk of HF (tertile 2: OR = 0.93, 95% CI: 0.69-1.29, tertile 3: OR = 0.75, 95% CI: 0.52-1.09, P for trend 0.022). Finally, subgroup analyses indicated that lower Klotho concentrations significantly correlated with an increased risk of HF in half of the subgroups.

CONCLUSION

Serum Klotho concentration was consistently and negatively associated with the presence of HF among US middle-aged and older adults.

Interleukin-6 blockade reduces salt-induced cardiac inflammation and fibrosis in subtotal nephrectomized mice

Cardiovascular disease is the most common comorbidity in patients with chronic kidney disease (CKD), affecting both their prognosis and quality of life. Cardiac fibrosis is common in patients with CKD with left ventricular diastolic dysfunction, and it is associated with increased risk of heart failure and mortality. Recent evidence suggests that high salt intake activates immune responses associated with local accumulation of sodium. We reported that high salt intake promotes cardiac inflammation in subtotal nephrectomized (Nx) mice. We investigated the effects of administration of MR16-1, a rat anti-mouse monoclonal interleukin (IL)-6 receptor antibody, in Nx mice with salt loading (Nx-salt). Expression of monocyte chemoattractant protein-1, tumor necrosis factor-α, IL-1β, and IL-6 mRNAs and macrophage infiltration was significantly reduced in the heart of Nx-salt mice treated with MR16-1 (Nx-salt-MR16-1) compared with Nx-salt mice treated with control rat rat IgG1 (Nx-salt-rat IgG1). Correspondingly, cardiac fibrosis was significantly attenuated in Nx-salt-MR16-1 mice compared with Nx-salt-rat IgG1 mice. Furthermore, in the heart of Nx-salt-MR16-1 mice, expression of mRNA for nicotinamide adenine dinucleotide phosphate oxidase-2, an oxidative stress marker, was significantly downregulated compared with Nx-salt-rat IgG1 mice. Increases in cardiac metabolites, including histidine and γ-butyrobetaine, were also reversed by IL-6 blockade treatment. In conclusion, IL-6 blockade exerts anti-inflammatory, antifibrotic, and partial antioxidative effects in the heart of Nx-salt mice.NEW & NOTEWORTHY In the present study, IL-6 blockade exerted anti-inflammatory, antifibrotic, and partial antioxidative effects on the hearts of mice with CKD on a high-salt diet. Therefore, IL-6 potentially mediates cardiac fibrosis induced by high salt intake in patients with CKD, a finding with therapeutic implications. Of note, the next therapeutic implication may simply be the reinforcement of low-salt diets or diuretics and further research on the anti-inflammatory effects of these measures rather than IL-6 blockade with high-salt diet.

Synthesis and Characterization of Fucoidan-Chitosan Nanoparticles Targeting P-Selectin for Effective Atherosclerosis Therapy

Atherosclerosis is the key pathogenesis of cardiovascular diseases; oxidative stress, which is induced by the generated excess reactive oxygen species (ROS), has been a crucial mechanism underlying this pathology. Nanoparticles (NPs) represent a novel strategy for the development of potential therapies against atherosclerosis, and multifunctional NPs possessing antioxidative capacities hold promise for amelioration of vascular injury caused by ROS and for evading off-target effects; materials that are currently used for NP synthesis often serve as vehicles that do not possess intrinsic biological activities; however, they may affect the surrounding healthy environment due to decomposition of products. Herein, we used nontoxic fucoidan, a sulfated polysaccharide derived from a marine organism, to develop chitosan–fucoidan nanoparticles (CFNs). Then, by binding to P-selectin, an inflammatory adhesion exhibited molecule expression on the endothelial cells and activated platelets, blocking leukocyte recruitment and rolling on platelets and endothelium. CFNs exhibit antioxidant and anti-inflammatory properties. Nevertheless, by now, the application of CFNs for the target delivery regarding therapeutics specific to atherosclerotic plaques is not well investigated. The produced CFNs were physicochemically characterized using transmission electron microscopy (TEM), together with Fourier transform infrared spectroscopy (FTIR). Evaluations of the in vitro antioxidant as well as anti-inflammatory activities exhibited by CFNs were based on the measurement of their ROS scavenging abilities and investigating inflammatory mediator levels. The in vivo pharmacokinetics and binding efficiency of the CFNs to atherosclerotic plaques were also evaluated. The therapeutic effects indicated that CFNs effectively suppressed local oxidative stress and inflammation by targeting P-selectin in atheromatous plaques and thereby preventing the progression of atherosclerosis.

Dopamine receptor 3: A mystery at the heart of cardiac fibrosis

Dopamine receptors have been extensively studied in the mammalian brain and spinal cord, as dopamine is a vital determinant of bodily movement, cognition, and overall behavior. Thus, dopamine receptor antagonist antipsychotic drugs are commonly used to treat multiple psychiatric disorders. Although less discussed, these receptors are also expressed in other peripheral organ systems, such as the kidneys, eyes, gastrointestinal tract, and cardiac tissue. Consequently, therapies for certain psychiatric disorders which target dopamine receptors could have unidentified consequences on certain functions of these peripheral tissues. The existence of an intrinsic dopaminergic system in the human heart remains controversial and debated within the literature. Therefore, this review focuses on literature related to dopamine receptors within cardiac tissue, specifically dopamine receptor 3 (D3R), and summarizes the current state of knowledge while highlighting areas of research which may be lacking. Additionally, recent findings regarding crosstalk between D3R and dopamine receptor 1 (D1R) are examined. This review discusses the novel concept of understanding the role of the loss of function of D3R may play in collagen accumulation and cardiac fibrosis, eventually leading to heart failure.

Cardioprotection of Klotho against myocardial infarction-induced heart failure through inducing autophagy

Myocardial infarction (MI) is the most common cause of heart failure (HF) worldwide. The aim of this study was to investigate the role of Klotho in cardiac function and remodeling as well as its underlying mechanism in mice with MI-induced HF. For in vivo analyses, MI or sham MI were established in C57BL/6 mice. For in vitro analyses, the H9C2 cells were used to establish a model of oxygen glucose deprivation (OGD). The In vivo and in vitro models were treated with or without Klotho. 3-methyladenine (3-MA) was used to inhibit autophagy in MI mice and H9C2 cells. Cardiac function, cardiac fibrosis, cardiomyocyte autophagy, inflammatory cytokines and myocardial apoptosis were measured. Our results revealed that Klotho significantly improved cardiac function and remodeling, reduced cardiac fibrosis, and suppressed the levels of myocardial inflammatory factors and apoptosis in MI-induced HF model. Klotho enhanced autophagy in cardiomyocytes and inhibited PI3K/AKT/mTOR signaling pathway in the mouse model of MI. Similar observations were made in the OGD model after treatment with Klotho. However, the cardioprotective effects of Klotho was significantly suppressed by 3-MA. Our data indicate that Klotho exerts its cardioprotective effects against MI-induced HF by inducing autophagy through the inhibition of PI3k/AKT/mTOR signaling pathway.

MicroRNA-34a: A Novel Therapeutic Target in Fibrosis

Fibrosis can occur in many organs, and severe cases leading to organ failure and death. No specific treatment for fibrosis so far. In recent years, microRNA-34a (miR-34a) has been found to play a role in fibrotic diseases. MiR-34a is involved in the apoptosis, autophagy and cellular senescence, also regulates TGF-β1/Smad signal pathway, and negatively regulates the expression of multiple target genes to affect the deposition of extracellular matrix and regulate the process of fibrosis. Some studies have explored the efficacy of miR-34a-targeted therapies for fibrotic diseases. Therefore, miR-34a has specific potential for the treatment of fibrosis. This article reviews the important roles of miR-34a in fibrosis and provides the possibility for miR-34a as a novel therapeutic target in fibrosis.

RNA sequencing reveals novel LncRNA/mRNAs co-expression network associated with puerarin-mediated inhibition of cardiac hypertrophy in mice

Background

Evidence has demonstrated that puerarin is a potential medicine for the treatment of cardiac hypertrophy. However, the precise underlying molecular mechanisms of the protective effect of puerarin are still unclear. Here, we aimed to explore the regulatory mechanisms of lncRNAs/mRNAs co-expression network in a cardiac hypertrophy mouse model after puerarin treatment.

Methods

A mouse model of cardiac hypertrophy was established by transverse aortic constriction (TAC). The echocardiography, tissue staining and western blot were used to examine the protective effect of puerarin. Then RNA sequencing (RNA-seq) was carried out to analyze systematically mRNAs and lncRNAs expression. The target lncRNA were confirmed using qRT-PCR. Moreover, a coding/non-coding gene co-expression network were established to find the interaction of lncRNA and mRNAs. The biological process, cellular component, molecular function and pathways of different expression mRNAs targeted by lncRNA were explored using Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis.

Results

Puerarin exhibited an obvious inhibitory effect in cardiac hypertrophy in TAC model. RNA-seq analysis was performed to investigate the lncRNAs and mRNAs expression patterns of cardiomyocytes in sham and TAC groups treated with or without puerarin. RNA-seq identified that TAC downregulated four lncRNAs, which could be revised by puerarin treatment (|log2 Fold change| > 2 and FDR < 0.05). Among them, expression alterations of lncRNA Airn (antisense of Igf2r non-protein coding RNA) was confirmed by qRT-PCR. Pearson's correlation coefficients of co-expression levels suggested that there was an interactive relationship between Airn and 2,387 mRNAs (r > 0.95 or r < -0.95). Those co-expressed mRNAs were enriched in some important biological processes such as translational initiation, cell proliferation, insulin-like growth factor binding and poly(A) RNA binding. KEGG analyses suggested that those Airn-interacted mRNAs were enriched in endocytosis, signaling pathways regulating pluripotency of stem cells and the Jak-STAT pathway.

Conclusion

Puerarin may exert beneficial effects on cardiac hypertrophy through regulating the lncRNAs/mRNAs co-expression network.

Research progress on drugs targeting the TGF-β signaling pathway in fibrotic diseases

Tissue fibrosis is a key factor leading to disability and death worldwide; however, thus far, there are no approved treatments for fibrosis. Transforming growth factor (TGF)-β is a major pro-fibrotic cytokine, which is expected to become a target in the treatment of fibrosis; however, since TGF-β has a wide range of biological functions involving a variety of biological processes in the body, a slight change in TGF-β may have a systematic effect. Indiscriminate inhibition of TGF-β can lead to adverse reactions, which can affect the efficacy of treatment. Therefore, it has become very important to explore how both the TGF-β signaling pathway is inhibited and the safe and efficient TGF-β small molecule inhibitors or neutralizing antibodies are designed in the treatment of fibrotic diseases. In this review, we mainly discuss the key role of the TGF-β signaling pathway in fibrotic diseases, as well as the development of fibrotic drugs in recent years, and explore potential targets in the treatment of fibrotic diseases in order to guide subsequent drug development.

Prokaryotic expression, purification and evaluation of anti-cardiac fibrosis activity of recombinant TGF-β latency associated peptide

BACKGROUND

Cardiac fibrosis refers to the abnormal accumulation of extracellular matrix in the heart, which leads to the formation of cardiac scars. It causes systolic and diastolic dysfunction, and ultimately leads to cardiac dysfunction and arrhythmia. TGF-β1 is an important regulatory factor involved in cardiac fibrosis. Studies have shown that the N-terminal latency associated peptide (LAP) must be removed before TGF-β1 is activated. We hypothesize that recombinant LAP may inhibit cardiac fibrosis induced by TGF-β1. To evaluate anti-cardiac fibrosis activity of recombinant LAP, an experimental study was carried out and is reported here.

METHODS

The pET28a-LAP plasmid was constructed and transformed into E. coli C43 (DE3) competent cells. The recombinant LAP protein was purified by Ni affinity chromatography. The cells were treated with TGF-β1 at different concentrations for 24 h. The expression of α-SMA was detected by Western blot. RTCA was used to detect the effect of recombinant LAP on the proliferation of H9C2 cells induced by 10 ng/mL TGF-β1. To detect the effect of LAP on the expression of fibrosis-related proteins, H9C2 cells were treated with 10 ng/mL TGF-β1 for 24 h, then added 60 μg/mL recombinant LAP for 48 h. The LAP group was treated with 60 μg/mL recombinant LAP alone. The LAP pre-protection group was treated with 10 ng/mL TGF-β1 and 60 μg/mL recombinant LAP at the same time. Western blot and immunofluorescence were used to detect the expression of α-SMA, collagen I and fibronectin and p-Smad2.

RESULTS

The recombinant LAP was prokaryotic expressed and purified. 10 ng/mL was determined as the optimal working concentration of TGF-β1 to induce H9C2 cells fibrosis. RTCA results showed that 60 μg/mL LAP could effectively inhibit the proliferation of H9C2 cells induced by TGF-β1. Immunofluorescence results showed that compared with the control group, the fluorescence intensities of α-SMA, collagen I and FN increased significantly after TGF-β1 treatment. The fluorescence intensities in the TGF-β1+LAP group decreased significantly. Western blot results showed that 60 μg/mL LAP could inhibit the increase of α-SMA, collagen I and FN expression in H9C2 cells induced by TGF-β1. Compared with the control, the LAP alone group has no significant difference in α-SMA and p-Smad2 expression level. The expression of α-SMA and p-Smad2 in the TGF-β1 model group was significantly increased compared with the control group. Compared with the TGF-β1 group, both TGF-β1+LAP group and LAP pre-protection group significantly reduced the increase in α-SMA and p-Smad2 levels.

CONCLUSIONS

Recombinant LAP was prokaryotic expressed and purified. The results showed that recombinant LAP can inhibit the cell proliferation and expression increase of α-SMA, collagen I, fibronectin and p-Smad2 in H9C2 cells induced by TGF-β1. These results suggested that recombinant LAP might inhibit TGF-β1-induced fibrosis of H9C2 cells through the TGF-β/Smad pathway.

Guanxin V protects against ventricular remodeling after acute myocardial infarction through the interaction of TGF-β1 and Vimentin

BACKGROUND

Our previous study demonstrated that Guanxin V (GXV), a traditional Chinese herbal medicine, has a significant therapeutic effect on ventricular remodeling. However, the mechanistic action of GXV in ventricular remodeling warrants clarification.

PURPOSE

Here, we aimed to explore the anti-ventricular remodeling contribution of GXV and to provide an experimental basis for clinical generalization.

METHODS

A ventricular remodeling model after acute myocardial infarction was constructed in Syrian hamsters. The echocardiography and biochemical indices of cardiac function and remodeling were evaluated in different groups. Moreover, we built a remodeling model in cardiomyocytes and further explored the mechanism. Transmission electron microscopy was used to observe the ultrastructure of cardiomyocytes. The vital markers involved in the signaling pathway were detected by RT-qPCR and immunoblotting. Transforming growth factor beta 1 (TGF-β1) was overexpressed with lentivirus to verify the necessity of TGF-β1 in GXV's anti-ventricular remodeling effect. Finally, co-immunoprecipitation was conducted to test the interaction of TGF-β1 and Vimentin.

RESULTS

In hamster cardiac remodeling induced by acute myocardial infarction, GXV alleviated apoptosis, cardiac hypertrophy, and cardiac remodeling, and even improved cardiac function. Mechanistically, GXV inhibited the remodeling process by directly targeting TGF-β1. Overexpression of TGF-β1 exacerbated the ventricular remodeling, whereas GXV reversed this dysregulation. GXV also decreased the up-regulated Vimentin level in pathological ventricular remodeling. Moreover, the interaction of Vimentin and TGF-β1 was confirmed by co-immunoprecipitation, and GXV impeded this interaction.

CONCLUSION

We showed that the interaction of Vimentin and TGF-β1 may be a novel target for ventricular remodeling and that GXV might be a new agent to fight against ventricular remodeling by targeting TGF-β1 and impeding its interaction with Vimentin.

Klotho and Mesenchymal Stem Cells: A Review on Cell and Gene Therapy for Chronic Kidney Disease and Acute Kidney Disease

Chronic kidney disease (CKD) and acute kidney injury (AKI) are public health problems, and their prevalence rates have increased with the aging of the population. They are associated with the presence of comorbidities, in particular diabetes mellitus and hypertension, resulting in a high financial burden for the health system. Studies have indicated Klotho as a promising therapeutic approach for these conditions. Klotho reduces inflammation, oxidative stress and fibrosis and counter-regulates the renin-angiotensin-aldosterone system. In CKD and AKI, Klotho expression is downregulated from early stages and correlates with disease progression. Therefore, the restoration of its levels, through exogenous or endogenous pathways, has renoprotective effects. An important strategy for administering Klotho is through mesenchymal stem cells (MSCs). In summary, this review comprises in vitro and in vivo studies on the therapeutic potential of Klotho for the treatment of CKD and AKI through the administration of MSCs.

The Potential of Gamma Secretase as a Therapeutic Target for Cardiac Diseases

Heart diseases are some of the most common and pressing threats to human health worldwide. The American Heart Association and the National Institute of Health jointly work to annually update data on cardiac diseases. In 2018, 126.9 million Americans were reported as having some form of cardiac disorder, with an estimated direct and indirect total cost of USD 363.4 billion. This necessitates developing therapeutic interventions for heart diseases to improve human life expectancy and economic relief. In this review, we look into gamma-secretase as a potential therapeutic target for cardiac diseases. Gamma-secretase, an aspartyl protease enzyme, is responsible for the cleavage and activation of a number of substrates that are relevant to normal cardiac development and function as found in mutation studies. Some of these substrates are involved in downstream signaling processes and crosstalk with pathways relevant to heart diseases. Most of the substrates and signaling events we explored were found to be potentially beneficial to maintain cardiac function in diseased conditions. This review presents an updated overview of the current knowledge on gamma-secretase processing of cardiac-relevant substrates and seeks to understand if the modulation of gamma-secretase activity would be beneficial to combat cardiac diseases.

Macrophage depletion protects against endothelial dysfunction and cardiac remodeling in angiotensin II hypertensive mice

Objective: Hypertension is associated with a low-grade systemic inflammation in cardiovascular system. Macrophage infiltration may initiate an inflammatory process that contributes to vascular and ventricular remodeling in hypertensive human and mice. The present study investigated the effect of chemical depletion of macrophage using liposome encapsulated clodronate (LEC) on cardiac hypertrophy and remodeling in angiotensin (Ang) II hypertensive mice.Methods: C57BL/6 mice received an Ang II (1.1 mg/kg/day with a minipump) infusion for 2 weeks to induce hypertension. Endothelium-dependent relaxation (ED) was examined by organ bath, hematoxylin and staining and Masson-Trichrome staining were used to evaluate aorta and cardiac hypertrophy and fibrosis.Results: Ang II infusion significantly increased systolic blood pressure (SBP), cardiac hypertrophy and fibrosis, and impaired EDR accompanied by increased macrophage infiltration in the heart. Treatment with LEC significantly lowered Ang II-induced cardiac hypertrophy and fibrosis and cardiac macrophage infiltration, and improved EDR with a mild reduction in SBP. Ang II increased the expression of inflammatory cytokines tumor necross factor alpha and interleukin 1 beta and profibrotic factors transforming growth factor beta 1 and fibronectin in the heart, with was reduced by LEC treatment. Treatment with LEC prevented Ang II-induced the phosphorphorylation of ERK1/2 and c-Jun-N-terminal kinase.Conclusions: Our study suggests that cardiac macrophage may be critical for hypertensive cardiac hypertrophy and remodeling, the underlying mechanisms may involve initial heart inflammation and the activation of hypertrophic MAPKs pathway.

Parkia speciosa Hassk. Empty Pod Extract Alleviates Angiotensin II-Induced Cardiomyocyte Hypertrophy in H9c2 Cells by Modulating the Ang II/ROS/NO Axis and MAPK Pathway

Cardiac hypertrophy is characteristic of heart failure in patients who have experienced cardiac remodeling. Many medicinal plants, including Parkia speciosa Hassk., have documented cardioprotective effects against such pathologies. This study investigated the activity of P. speciosa empty pod extract against cardiomyocyte hypertrophy in H9c2 cardiomyocytes exposed to angiotensin II (Ang II). In particular, its role in modulating the Ang II/reactive oxygen species/nitric oxide (Ang II/ROS/NO) axis and mitogen-activated protein kinase (MAPK) pathway was examined. Treatment with the extract (12.5, 25, and 50 μg/ml) prevented Ang II-induced increases in cell size, NADPH oxidase activity, B-type natriuretic peptide levels, and reactive oxygen species and reductions in superoxide dismutase activity. These were comparable to the effects of the valsartan positive control. However, the extract did not significantly ameliorate the effects of Ang II on inducible nitric oxide synthase activity and nitric oxide levels, while valsartan did confer such protection. Although the extract decreased the levels of phosphorylated extracellular signal-related kinase, p38, and c-Jun N-terminal kinase, valsartan only decreased phosphorylated c-Jun N-terminal kinase expression. Phytochemical screening identified the flavonoids rutin (1) and quercetin (2) in the extract. These findings suggest that P. speciosa empty pod extract protects against Ang II-induced cardiomyocyte hypertrophy, possibly by modulating the Ang II/ROS/NO axis and MAPK signaling pathway via a mechanism distinct from valsartan.

CircHIPK3 Plays Vital Roles in Cardiovascular Disease

Circular RNAs (circRNAs) are covalently closed RNAs that function in various physiological and pathological processes. CircRNAs are widely involved in the development of cardiovascular disease (CVD), one of the leading causes of morbidity and mortality worldwide. CircHIPK3 is generated from the second exon of the HIPK3 gene, a corepressor of homeodomain transcription factors. As an exonic circRNA (ecRNA), circHIPK3 is produced through intron-pairing driven circularization facilitated by Alu elements. In the past 5 years, a growing number of studies have revealed the multifunctional roles of circHIPK3 in different diseases, such as cancer and CVD. CircHIPK3 mainly participates in CVD pathogenesis through interacting with miRNAs. This paper summarizes the current literature on the biogenesis and functions of circHIPK3, elucidates the role of circHIPK3 in different CVD patterns, and explores future perspectives.

An Insight on Multicentric Signaling of Angiotensin II in Cardiovascular system: A Recent Update

The multifaceted nature of the renin-angiotensin system (RAS) makes it versatile due to its involvement in pathogenesis of the cardiovascular disease. Angiotensin II (Ang II), a multifaceted member of RAS family is known to have various potential effects. The knowledge of this peptide has immensely ameliorated after meticulous research for decades. Several studies have evidenced angiotensin I receptor (AT1 R) to mediate the majority Ang II-regulated functions in the system. Functional crosstalk between AT1 R mediated signal transduction cascades and other signaling pathways has been recognized. The review will provide an up-to-date information and recent discoveries involved in Ang II receptor signal transduction and their functional significance in the cardiovascular system for potential translation in therapeutics. Moreover, the review also focuses on the role of stem cell-based therapies in the cardiovascular system.

Klotho Protein and Cardio-Vascular System

Klotho protein affects a number of metabolic pathways essential for pathogenesis of cardio-vascular diseases and their prevention. It inhibits lipid peroxidation and inflammation, as well as prevents endothelial injury and calcification of blood vessels. Klotho decreases rigidity of blood vessels and suppresses development of the heart fibrosis. Low level of its expression is associated with a number of diseases. Cardioprotective effect of klotho is based on its ability to interact with multiple receptors and ion channels. Being a pleiotropic protein, klotho could be a useful target for therapeutic intervention in the treatment of cardio-vascular diseases. In this review we present data on pharmaceuticals that stimulate klotho expression and suggest some promising research directions.

Implication of RAS in Postnatal Cardiac Remodeling, Fibrosis and Dysfunction Induced by Fetal Undernutrition

Fetal undernutrition is a risk factor for cardiovascular diseases. Male offspring from rats exposed to undernutrition during gestation (MUN) exhibit oxidative stress during perinatal life and develop cardiac dysfunction in ageing. Angiotensin-II is implicated in oxidative stress-mediated cardiovascular fibrosis and remodeling, and lactation is a key developmental window. We aimed to assess if alterations in RAS during lactation participate in cardiac dysfunction associated with fetal undernutrition. Control dams received food ad libitum, and MUN had 50% nutrient restriction during the second half of gestation. Both dams were fed ad libitum during lactation, and male offspring were studied at weaning. We assessed: ventricular structure and function (echocardiography); blood pressure (intra-arterially, anesthetized rats); collagen content and intramyocardial artery structure (Sirius red, Masson Trichromic); myocardial and intramyocardial artery RAS receptors (immunohistochemistry); plasma angiotensin-II (ELISA) and TGF-β1 protein expression (Western Blot). Compared to Control, MUN offspring exhibited significantly higher plasma Angiotensin-II and a larger left ventricular mass, as well as larger intramyocardial artery media/lumen, interstitial collagen and perivascular collagen. In MUN hearts, TGF-β1 tended to be higher, and the end-diastolic diameter and E/A ratio were significantly lower with no differences in ejection fraction or blood pressure. In the myocardium, no differences between groups were detected in AT1, AT2 or Mas receptors, with MrgD being significantly lower in the MUN group. In intramyocardial arteries from MUN rats, AT1 and Mas receptors were significantly elevated, while AT2 and MrgD were lower compared to Control. Conclusions. In rats exposed to fetal undernutrition, RAS disbalance and associated cardiac remodeling during lactation may set the basis for later heart dysfunction.

Renin-angiotensin system and inflammation update

The most classical view of the renin-angiotensin system (RAS) emphasizes its role as an endocrine regulator of sodium balance and blood pressure. However, it has long become clear that the RAS has pleiotropic actions that contribute to organ damage, including modulation of inflammation. Angiotensin II (Ang II) activates angiotensin type 1 receptors (AT1R) to promote an inflammatory response and organ damage. This represents the pathophysiological basis for the successful use of RAS blockers to prevent and treat kidney and heart disease. However, other RAS components could have a built-in capacity to brake proinflammatory responses. Angiotensin type 2 receptor (AT2R) activation can oppose AT1R actions, such as vasodilatation, but its involvement in modulation of inflammation has not been conclusively proven. Angiotensin-converting enzyme 2 (ACE2) can process Ang II to generate angiotensin-(1-7) (Ang-(1-7)), that activates the Mas receptor to exert predominantly anti-inflammatory responses depending on the context. We now review recent advances in the understanding of the interaction of the RAS with inflammation. Specific topics in which novel information became available recently include intracellular angiotensin receptors; AT1R posttranslational modifications by tissue transglutaminase (TG2) and anti-AT1R autoimmunity; RAS modulation of lymphoid vessels and T lymphocyte responses, especially of Th17 and Treg responses; interactions with toll-like receptors (TLRs), programmed necrosis, and regulation of epigenetic modulators (e.g. microRNAs and bromodomain and extraterminal domain (BET) proteins). We additionally discuss an often overlooked effect of the RAS on inflammation which is the downregulation of anti-inflammatory factors such as klotho, peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), transient receptor potential ankyrin 1 (TRPA1), SNF-related serine/threonine-protein kinase (SNRK), serine/threonine-protein phosphatase 6 catalytic subunit (Ppp6C) and n-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP). Both transcription factors, such as nuclear factor κB (NF-κB), and epigenetic regulators, such as miRNAs are involved in downmodulation of anti-inflammatory responses. A detailed analysis of pathways and targets for downmodulation of anti-inflammatory responses constitutes a novel frontier in RAS research.

The Multifunctional Contribution of FGF Signaling to Cardiac Development, Homeostasis, Disease and Repair

The current focus on cardiovascular research reflects society’s concerns regarding the alarming incidence of cardiac-related diseases and mortality in the industrialized world and, notably, an urgent need to combat them by more efficient therapies. To pursue these therapeutic approaches, a comprehensive understanding of the mechanism of action for multifunctional fibroblast growth factor (FGF) signaling in the biology of the heart is a matter of high importance. The roles of FGFs in heart development range from outflow tract formation to the proliferation of cardiomyocytes and the formation of heart chambers. In the context of cardiac regeneration, FGFs 1, 2, 9, 16, 19, and 21 mediate adaptive responses including restoration of cardiac contracting rate after myocardial infarction and reduction of myocardial infarct size. However, cardiac complications in human diseases are correlated with pathogenic effects of FGF ligands and/or FGF signaling impairment. FGFs 2 and 23 are involved in maladaptive responses such as cardiac hypertrophic, fibrotic responses and heart failure. Among FGFs with known causative (FGFs 2, 21, and 23) or protective (FGFs 2, 15/19, 16, and 21) roles in cardiac diseases, FGFs 15/19, 21, and 23 display diagnostic potential. The effective role of FGFs on the induction of progenitor stem cells to cardiac cells during development has been employed to boost the limited capacity of postnatal cardiac repair. To renew or replenish damaged cardiomyocytes, FGFs 1, 2, 10, and 16 were tested in (induced-) pluripotent stem cell-based approaches and for stimulation of cell cycle re-entry in adult cardiomyocytes. This review will shed light on the wide range of beneficiary and detrimental actions mediated by FGF ligands and their receptors in the heart, which may open new therapeutic avenues for ameliorating cardiac complications.

MicroRNA-132 attenuated cardiac fibrosis in myocardial infarction-induced heart failure rats

The aim of the present study was to determine the effect of microRNA (miR)-132 on cardiac fibrosis in myocardial infarction (MI)-induced heart failure and angiotensin (Ang) II-treated cardiac fibroblasts (CFs). Experiments were carried out in Sprague-Dawley rat treatment with ligation of left coronary artery to induce heart failure, and in CFs administration of Ang II to induce fibrosis. The level of miR-132 was increased in the heart of rats with MI-induced heart failure and the Ang II-treated CFs. In MI rats, left ventricle (LV) ejection fraction, fractional shortening, the maximum of the first differentiation of LV pressure (LV +dp/dtmax) and decline (LV -dp/dtmax) and LV systolic pressure (LVSP) were reduced, and LV end-systolic diameter (LVESD), LV end-diastolic diameter (LVEDD), LV volumes in systole (LVVS) and LV volumes in diastole (LVVD) were increased, which were reversed by miR-132 agomiR but deteriorated by miR-132 antagomiR. The expression levels of collagen I, collagen III, transforming growth factor-β (TGF-β), and α-smooth muscle actin (α-SMA) were increased in the heart of rat with MI-induced heart failure and CFs administration of Ang II. These increases were inhibited by miR-132 agomiR but enhanced by miR-132 antagomiR treatment. MiR-132 inhibited PTEN expression, and attenuated PI3K/Akt signal pathway in CFs. These results indicated that the up-regulation of miR-132 improved the cardiac dysfunction, attenuated cardiac fibrosis in heart failure via inhibiting PTEN expression, and attenuating PI3K/Akt signal pathway. Up-regulation of miR-132 may be a strategy for the treatment of heart failure and cardiac fibrosis.

Klotho supplementation attenuates blood pressure and albuminuria in murine model of IgA nephropathy

BACKGROUND

Klotho interacts with various membrane proteins, such as transforming growth factor-β (TGFβ) and insulin-like growth factor (IGF) receptors. The renal expression of klotho is diminished in chronic kidney disease.

METHOD

In this study, we assessed the effects of klotho supplementation on a murine model of IgA nephropathy. Twenty-four-week-old hyper serum IgA (HIGA) mice were subcutaneously injected daily with recombinant human klotho protein (20 μg/kg per day) or the vehicle. After 2 months, the mice were killed using an anesthesia overdose and their kidneys were harvested for analysis.

RESULTS

Supplementation of exogenous klotho protein reduced SBP, albuminuria, 8-epi-prostaglandin F2α excretion, glomerular filtration rate, renal angiotensin II concentration, and angiotensinogen expression in HIGA mice. Additionally, it enhanced renal expression of superoxide dismutase (SOD) and renal klotho itself. The findings using laser-manipulated microdissection demonstrated that klotho supplementation reduced the glomerular expression of TGFβ, fibronectin, and IGF, and increased the glomerular expression of connexin (Cx) 40.

CONCLUSION

These results indicate that klotho supplementation reduces blood pressure by suppressing the renin--angiotensin system in HIGA mice. Klotho inhibits IGF signaling to preserve glomerular Cx40 levels, ameliorating albuminuria in HIGA mice. Klotho protein supplementation attenuates mesangial expansion by inhibiting TGFβ signaling in HIGA mice.

The HIF-1α/p53/miRNA-34a/Klotho axis in retinal pigment epithelial cells promotes subretinal fibrosis and exacerbates choroidal neovascularization

Wet age‐related macular degeneration (wAMD), characterized by choroidal neovascularization (CNV), is a leading cause of irreversible vision loss among elderly people in developed nations. Subretinal fibrosis, mediated by epithelial‐mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells, leads to unsuccessful anti‐vascular endothelial growth factor (VEGF) agent treatments in CNV patients. Under hypoxic conditions, hypoxia‐inducible factor‐1α (HIF‐1α) increases the stability and activation of p53, which activates microRNA‐34a (miRNA‐34a) transcription to promote fibrosis. Additionally, Klotho is a target gene of miRNA‐34a that inhibits fibrosis. This study aimed to explore the role of the HIF‐1α/p53/miRNA‐34a/Klotho axis in subretinal fibrosis and CNV. Hypoxia‐induced HIF‐1α promoted p53 stability, phosphorylation and nuclear translocation in ARPE‐19 cells (a human RPE cell line). HIF‐1α‐dependent p53 activation up‐regulated miRNA‐34a expression in ARPE‐19 cells following hypoxia. Moreover, hypoxia‐induced p53‐dependent miRNA‐34a inhibited the expression of Klotho in ARPE‐19 cells. Additionally, the HIF‐1α/p53/miRNA‐34a/Klotho axis facilitated hypoxia‐induced EMT in ARPE‐19 cells. In vivo, blockade of the HIF‐1α/p53/miRNA‐34a/Klotho axis alleviated the formation of mouse laser‐induced CNV and subretinal fibrosis. In short, the HIF‐1α/p53/miRNA‐34a/Klotho axis in RPE cells promoted subretinal fibrosis, thus aggravating the formation of CNV.

RAS inhibition in resident fibroblast biology

Angiotensin II (Ang II) is a primary mediator of profibrotic signaling in the heart and more specifically, the cardiac fibroblast. Ang II-mediated cardiomyocyte hypertrophy in combination with cardiac fibroblast proliferation, activation, and extracellular matrix production compromise cardiac function and increase mortality in humans. Profibrotic actions of Ang II are mediated by increasing production of fibrogenic mediators (e.g. transforming growth factor beta, scleraxis, osteopontin, and periostin), recruitment of immune cells, and via increased reactive oxygen species generation. Drugs that inhibit Ang II production or action, collectively referred to as renin angiotensin system (RAS) inhibitors, are first line therapeutics for heart failure. Moreover, transient RAS inhibition has been found to persistently alter hypertensive cardiac fibroblast responses to injury providing a useful tool to identify novel therapeutic targets. This review summarizes the profibrotic actions of Ang II and the known impact of RAS inhibition on cardiac fibroblast phenotype and cardiac remodeling.

Klotho: a link between cardiovascular and non-cardiovascular mortality

Klotho is a membrane-bound protein acting as an obligatory coreceptor for fibroblast growth factor 23 (FGF23) in the kidney and parathyroid glands. The extracellular portion of its molecule may be cleaved and released into the blood and produces multiple endocrine effects. Klotho exerts anti-inflammatory and antioxidative activities that may explain its ageing suppression effects evidenced in mice; it also modulates mineral metabolism and FGF23 activities and limits their negative impact on cardiovascular system. Clinical studies have found that circulating Klotho is associated with myocardial hypertrophy, coronary artery disease and stroke and may also be involved in the pathogenesis of salt-sensitive hypertension with a mechanism sustained by inflammatory cytokines. As a consequence, patients maintaining high serum levels of Klotho not only show decreased cardiovascular mortality but also non-cardiovascular mortality. Klotho genetic polymorphisms may influence these clinical relationships and predict cardiovascular risk; rs9536314 was the polymorphism most frequently involved in these associations. These findings suggest that Klotho and its genetic polymorphisms may represent a bridge between inflammation, salt sensitivity, hypertension and mortality. This may be particularly relevant in patients with chronic kidney disease who have decreased Klotho levels in tissues and blood.

MicroRNA-21 Mediates a Positive Feedback on Angiotensin II-Induced Myofibroblast Transformation

Objective

Post myocardial infarction (MI) fibrosis has been identified as an important factor in the progression of heart failure. Previous studies have revealed that microRNA-21 (miR-21) plays an important role in the pathogenesis of fibrosis. The purpose of this study was to explore the role of miR-21 in post-MI cardiac fibrosis.

Material and Methods

MI was established in wild-type (WT) and miR-21 knockout (KO) mice. Primary mice cardiac fibroblasts (CFs) were isolated from WT and miR-21 KO mice and were treated with angiotensin II (Ang II) or Sprouty1 (Spry1) siRNA. Histological analysis and echocardiography were used to determine the extent of fibrosis and cardiac function.

Results

Compared with WT mice, miR-21 KO mice displayed smaller fibrotic areas and decreased expression of fibrotic markers and inflammatory cytokines. In parallel, Ang II-induced myofibroblasts transformation was partially inhibited upon miR-21 KO in primary CFs. Mechanistically, we found that the expression of Spry1, a previously reported target of miR-21, was markedly increased in miR-21 KO mice post MI, further inhibiting ERK1/2 activation. In vitro studies showed that Ang II activated ERK1/2/TGF-β/Smad2/3 pathway. Phosphorylated Smad2/3 further enhanced the expression of α-SMA and FAP and may promote the maturation of miR-21, thereby downregulating Spry1. Additionally, these effects of miR-21 KO on fibrosis were reversed by siRNA-mediated knockdown of Spry1.

Conclusion

Our findings suggest that miR-21 promotes post-MI fibrosis by targeting Spry1. Furthermore, it mediates a positive feedback on Ang II, thereby inducing the ERK/TGF-β/Smad pathway. Therefore, targeting the miR-21–Spry1 axis may be a promising therapeutic option for ameliorating post-MI cardiac fibrosis.

Melatonin alleviates angiotensin-II-induced cardiac hypertrophy via activating MICU1 pathway

Mitochondrial calcium uptake 1 (MICU1) is a pivotal molecule in maintaining mitochondrial homeostasis under stress conditions. However, it is unclear whether MICU1 attenuates mitochondrial stress in angiotensin II (Ang-II)-induced cardiac hypertrophy or if it has a role in the function of melatonin. Here, small-interfering RNAs against MICU1 or adenovirus-based plasmids encoding MICU1 were delivered into left ventricles of mice or incubated with neonatal murine ventricular myocytes (NMVMs) for 48 h. MICU1 expression was depressed in hypertrophic myocardia and MICU1 knockdown aggravated Ang-II-induced cardiac hypertrophy in vivo and in vitro. In contrast, MICU1 upregulation decreased cardiomyocyte susceptibility to hypertrophic stress. Ang-II administration, particularly in NMVMs with MICU1 knockdown, led to significantly increased reactive oxygen species (ROS) overload, altered mitochondrial morphology, and suppressed mitochondrial function, all of which were reversed by MICU1 supplementation. Moreover, peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α)/MICU1 expression in hypertrophic myocardia increased with melatonin. Melatonin ameliorated excessive ROS generation, promoted mitochondrial function, and attenuated cardiac hypertrophy in control but not MICU1 knockdown NMVMs or mice. Collectively, our results demonstrate that MICU1 attenuates Ang-II-induced cardiac hypertrophy by inhibiting mitochondria-derived oxidative stress. MICU1 activation may be the mechanism underlying melatonin-induced protection against myocardial hypertrophy.

The Protective Role of Klotho in CKD-Associated Cardiovascular Disease

Background

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality in advanced CKD. The major pathological changes of CKD-associated CVD are severe vascular media calcification, aberrant cardiac remodeling such as hypertrophy and fibrosis, as well as accelerated atherosclerosis. α-Klotho is proposed as an anti-aging gene, which is primarily expressed in the kidney. Recent studies reveal that α-Klotho deficiency is associated with profound cardiovascular dysfunction. Of note, CKD represents extremely declined α-Klotho levels, hinting that α-Klotho deficiency may be implicated in the pathogenesis of CKD-associated CVD.

Summary

Based on the pathogenic mechanism of α-Klotho deficiency and decreased Klotho levels in the circulation even early in stage 1 of CKD, α-Klotho serves as a sensitive biomarker for renal insufficiency and also a novel predictor of risk of overall mortality of CVD events in CKD. Meanwhile, loss of Klotho resulted from kidney dysfunction markedly contributes to the progressive development of CKD and CVD. By contrast, prevention of Klotho decline using exogenous supplementation or genetically activated ways by several mechanisms can dramatically mitigate cardiac dysfunction, prevent vascular calcification, and retard the progression of CKD-accelerated atherosclerosis.

Key Messages

Klotho deficiency is proposed as a novel predictive biomarker as well as a pathogenic contributor to CVD events in CKD. In the future, Klotho may be a crucial potential therapeutic strategy to decrease the burden of CVD comorbidity with CKD in clinics.

The prognostic value of soluble Klotho in patients with haemodialysis: a systematic review and meta-analysis

Aim:

The correlation between soluble Klotho (sKlotho) levels and clinical outcomes remains inconclusive for patients undergoing maintenance haemodialysis (MHD). We aimed to evaluate the potential predictive significance of sKlotho in this population by conducting a meta-analysis.

Methods:

PubMed, Embase, Web of Science and Cochrane Library were comprehensively searched for studies concerning the association between sKlotho level and clinical outcomes including cardiovascular (CV) events and all-cause mortality. The pooled hazard ratios (HR) and 95% confidence intervals (CI) were generated using either random or fixed effects models. Sensitivity and subgroup analyses were used to explore heterogeneity sources.

Results:

Eight prospective studies with 992 MHD participants were included and reduced sKlotho levels predicted more adverse outcomes in this meta-analysis. The pooled HRs and 95% CIs related to CV events, mortality, or composite outcomes were 1.73 (95% CI 1.08–2.76, p = 0.02), 2.34 (95% CI 1.34–2.07, p = 0.003) or 1.75 (95% CI 1.19–2.57, p = 0.005). Moderate heterogeneity was observed in the composite adverse outcomes (I² = 57%, p = 0.05). Age and sKlotho level were the main sources of heterogeneities in the subgroup analysis.

Conclusion:

Lower sKlotho levels were associated with more CV events and all-cause mortality, suggesting that sKlotho may have predictive value in CKD patients receiving haemodialysis.

Increased Plasma Level of Longevity Protein Klotho as a Potential Indicator of Cognitive Function Preservation in Patients With Schizophrenia

Cognitive impairments are a core feature of schizophrenia. Klotho is an anti-aging protein with demonstrated cognitive-enhancing effects on the brain. The purpose of this study was to investigate the differences in levels of plasma klotho between patients with schizophrenia and healthy controls, as well as the relationship between klotho level and cognitive function in patients. Forty patients with schizophrenia and 40 gender- and age-matched healthy individuals were recruited. Positive and Negative Syndrome Scale (PANSS) was used to assess the psychopathology of patients. A neuropsychological battery was performed to evaluate the cognitive function of participants. Plasma klotho was measured using enzyme-linked immunosorbent assay. We show that patients with schizophrenia performed worse in the neurocognitive tests than the healthy controls. The levels of plasma klotho were significantly higher in schizophrenia patients than in healthy controls (p < 0.001). In patients, plasma klotho levels were positively correlated with cognitive function with regard to attention (p = 0.010), working memory (p < 0.001), verbal memory (p = 0.044), executive function (p < 0.001), and composite cognitive score (p < 0.001). Stepwise linear regression analysis shows that executive function had the highest correlation with plasma klotho levels (β = 0.896, t = 8.290, p < 0.001). Collectively, these results indicate that anti-aging protein klotho may be implicated in the pathogenesis of schizophrenia, and increased klotho may act as a compensatory factor for the preservation of cognitive function in schizophrenia. Further studies are needed to investigate the dynamic changes of klotho and the mechanisms by which klotho modulates cognition in schizophrenia.

Clinical Potential of Targeting Fibroblast Growth Factor-23 and αKlotho in the Treatment of Uremic Cardiomyopathy

Chronic kidney disease is highly prevalent, affecting 10% to 15% of the adult population worldwide and is associated with increased cardiovascular morbidity and mortality. As chronic kidney disease worsens, a unique cardiovascular phenotype develops characterized by heart muscle disease, increased arterial stiffness, atherosclerosis, and hypertension. Cardiovascular risk is multifaceted, but most cardiovascular deaths in patients with advanced chronic kidney disease are caused by heart failure and sudden cardiac death. While the exact drivers of these deaths are unknown, they are believed to be caused by uremic cardiomyopathy: a specific pattern of myocardial hypertrophy, fibrosis, with both diastolic and systolic dysfunction. Although the pathogenesis of uremic cardiomyopathy is likely to be multifactorial, accumulating evidence suggests increased production of fibroblast growth factor-23 and αKlotho deficiency as potential major drivers of cardiac remodeling in patients with uremic cardiomyopathy. In this article we review the increasing understanding of the physiology and clinical aspects of uremic cardiomyopathy and the rapidly increasing knowledge of the biology of both fibroblast growth factor-23 and αKlotho. Finally, we discuss how dissection of these pathological processes is aiding the development of therapeutic options, including small molecules and antibodies, directly aimed at improving the cardiovascular outcomes of patients with chronic kidney disease and end-stage renal disease.

Contribution of TGF-Beta-Mediated NLRP3-HMGB1 Activation to Tubulointerstitial Fibrosis in Rat With Angiotensin II-Induced Chronic Kidney Disease

Fibrosis is a common phenotype that often leads to the progression of blood pressure-induced chronic kidney disease (CKD). TGF-beta plays an important role in promoting pathogenesis, and NLRP3 is a critical mediator in the progression of blood pressure-induced CKD. However, the pathophysiological roles of the TGF-beta-mediated NLRP3 pathway in modulating fibrosis in blood pressure-induced CKD have not been elucidated. The present study aims to investigate the contribution of TGF-beta-mediated NLRP3 inflammasome to renal fibrosis in rats with high blood pressure. By treating rats with angiotensin II (Ang II) for 14 days, we observed the development of fibrosis, characterized by epithelial-mesenchymal transition (EMT) markers [alpha-smooth muscle actin (alpha-SMA), MMP-2, and MMP-9]. Immunohistochemical analysis further revealed that TGF-beta and NLRP3 inflammasome activation [high-mobility group box 1 (HMGB1), IL-1beta, and NLRP3] were significantly upregulated in the kidney of rats with Ang II-induced hypertension. Interestingly, we observed that Ang II could not increase the production of NLRP3 proteins, but TGF-beta could induce NLRP3 protein expression in cultured NRK-52E cells. Furthermore, we speculated that TGF-beta played a pathogenic role in Ang II-induced CKD because TGF-beta induced the activation of NLRP3 inflammasomes and Gasdermin D cleavage expression. We also proved that the pharmacological inhibition of NLRP3 by ISO caused a decrease in TGF-beta-induced NLRP3 inflammasome activation and the expression of EMT markers (alpha-SMA and CollagenI) and Gasdermin D cleavage. Collectively, these results suggest that TGF-beta-mediated NLRP3 inflammasome activation may cause the release of HMGB1 and an increase in Gasdermin D cleavage in NRK-52E, thereby contributing to renal fibrosis in Ang II-induced CKD. These findings provide novel insights into the pathogenic role of NLRP3 in CKD associated with high blood pressure.

FGF23 expression is stimulated in transgenic α-Klotho longevity mouse model

Observations in transgenic α-Klotho (Kl) mice (KlTg) defined the antiaging role of soluble Klotho (sKL130). A genetic translocation that elevates sKL levels in humans is paradoxically associated with increased circulating fibroblast growth factor 23 (FGF23) levels and the potential of both membrane KL (mKL135) and sKL130 to act as coreceptors for FGF23 activation of fibroblast growth factor receptors (FGFRs). Neither FGF23 expression nor the contributions of FGF23, mKL135, and sKL130 codependent and independent functions have been investigated in KlTg mice. In the current study, we examined the effects of Kl overexpression on FGF23 levels and functions in KlTg mice. We found that mKL135 but not sKL130 stimulated FGF23 expression in osteoblasts, leading to elevated Fgf23 bone expression and circulating levels in KlTg mice. Elevated FGF23 suppressed 1,25(OH)2D and parathyroid hormone levels but did not cause hypophosphatemic rickets in KlTg mice. KlTg mice developed low aldosterone-associated hypertension but not left ventricular hypertrophy. Mechanistically, we found that mKL135 and sKL130 are essential cofactors for FGF23-mediated ERK activation but that they inhibited FGF23 stimulation of PLC-γ and PI3K/AKT signaling. Thus, increased longevity in KlTg mice occurs in the presence of excess FGF23 that interacts with mKL and sKL to bias FGFR pathways.