α-Klotho expression determines nitric oxide synthesis in response to FGF-23 in human aortic endothelial cells

Fibroblast growth factor 23 inhibition attenuates steroid-induced osteonecrosis of the femoral head through pyroptosis

Steroid-induced osteonecrosis of the femoral head (SONFH) is the predominant cause of non-traumatic osteonecrosis of the femoral head (ONFH). Impaired blood supply and reduced osteogenic activity of the femoral head are the key pathogenic mechanisms of SONFH. Fibroblast growth factor 23 (FGF23) levels are not only a biomarker for early vascular lesions caused by abnormal mineral metabolism, but can also act directly on the peripheral vascular system, leading to vascular pathology. The aim of this study was to observe the role of FGF23 on bone microarchitecture and vascular endothelium, and to investigate activation of pyroptosis in SONFH. Lipopolysaccharide (LPS) combined with methylprednisolone (MPS) was applied for SONFH mouse models, and adenovirus was used to increase or decrease the level of FGF23. Micro-CT and histopathological staining were used to observe the structure of the femoral head, and immunohistochemical staining was used to observe the vascular density. The cells were further cultured in vitro and placed in a hypoxic environment for 12 h to simulate the microenvironment of vascular injury during SONFH. The effect of FGF23 on osteogenic differentiation was evaluated using alkaline phosphatase staining, alizarin red S staining and expression of bone formation-related proteins. Matrigel tube formation assay in vitro and immunofluorescence were used to detect the ability of FGF23 to affect endothelial cell angiogenesis. Steroids activated the pyroptosis signaling pathway, promoted the secretion of inflammatory factors in SONFH models, led to vascular endothelial dysfunction and damaged the femoral head structure. In addition, FGF23 inhibited the HUVECs angiogenesis and BMSCs osteogenic differentiation. FGF23 silencing attenuated steroid-induced osteonecrosis of the femoral head by inhibiting the pyroptosis signaling pathway, and promoting osteogenic differentiation of BMSCs and angiogenesis of HUVECs in vitro.

Local vascular Klotho mediates diabetes-induced atherosclerosis via ERK1/2 and PI3-kinase-dependent signaling pathways

BACKGROUND AND AIMS

Diabetes is one of the major causes of cardiovascular disease (CVD). As high as 29 % of patients with diabetes develop atherosclerosis. Vascular Smooth Muscle Cells (VSMCs) are a key mediator in the pathogenesis of atherosclerosis, generating pro-inflammatory and proliferative characteristics in atherosclerotic lesions.

METHODS

We used human atherosclerotic samples, developed diabetes-induced atherosclerotic mice, and generated loss of function and gain of function in Klotho human aortic smooth muscle cells to investigate the function of Klotho in atherosclerosis.

RESULTS

We found that Klotho expression is decreased in smooth muscle actin-positive cells in patients with diabetes and atherosclerosis. Consistent with human data, we found that Apoe knockout mice with streptozotocin-induced diabetes fed on a high-fat diet showed decreased expression of Klotho in SMCs. Additionally, these mice showed increased expression of TGF-β, MMP9, phosphorylation of ERK and Akt. Further, we utilized primary Human Aortic Smooth Muscle Cells (HASMCs) with d-glucose under dose-response and in time-dependent conditions to study the role of Klotho in these cells. Klotho gain of function and loss of function studies showed that Klotho inversely regulated the expression of atherosclerotic markers TGF-β, MMP2, MMP9, and Fractalkine. Further, High Glucose (HG) induced Akt, and ERK1/2 phosphorylation were enhanced or mitigated by endogenous Klotho deficiency or its overexpression respectively. PI3K/Akt and MAPK/ERK inhibition partially abolished the HG-induced upregulation of TGF-β, MMP2, MMP9, and Fractalkine. Additionally, Klotho knockdown increased the proliferation of HASMCs and enhanced α-SMA and TGF-β expression.

CONCLUSIONS

Taken together, these results indicate that local vascular Klotho is involved in diabetes-induced atherosclerosis, which is via PI3K/Akt and ERK1/2-dependent signaling pathways.

FGF23 and klotho at the intersection of kidney and cardiovascular disease

Cardiovascular disease is the leading cause of death in patients with chronic kidney disease (CKD). As CKD progresses, CKD-specific risk factors, such as disordered mineral homeostasis, amplify traditional cardiovascular risk factors. Fibroblast growth factor 23 (FGF23) regulates mineral homeostasis by activating complexes of FGF receptors and transmembrane klotho co-receptors. A soluble form of klotho also acts as a 'portable' FGF23 co-receptor in tissues that do not express klotho. In progressive CKD, rising circulating FGF23 levels in combination with decreasing kidney expression of klotho results in klotho-independent effects of FGF23 on the heart that promote left ventricular hypertrophy, heart failure, atrial fibrillation and death. Emerging data suggest that soluble klotho might mitigate some of these effects via several candidate mechanisms. More research is needed to investigate FGF23 excess and klotho deficiency in specific cardiovascular complications of CKD, but the pathophysiological primacy of FGF23 excess versus klotho deficiency might never be precisely resolved, given the entangled feedback loops that they share. Therefore, randomized trials should prioritize clinical practicality over scientific certainty by targeting disordered mineral homeostasis holistically in an effort to improve cardiovascular outcomes in patients with CKD.

The dysregulation of plasma miR-497/FGF23 axis, and its association with clinical characteristics and major adverse cardiovascular event in female premature acute coronary syndrome patients

AIM

MicroRNA-497 (miR-497) directly targets fibroblast growth factor 23 (FGF23) to participate in the pathology of acute coronary syndrome (ACS) by regulating atherosclerosis, inflammatory response, lipid metabolism, etc. This study intended to investigate the dysregulation of the miR-497/FGF23 axis, and its association with the major adverse cardiovascular event (MACE) in female premature ACS.

METHODS

MiR-497 and FGF23 from plasma samples were detected by RT-qPCR and ELISA in 979 newly diagnosed female premature ACS patients and 100 healthy controls (HCs). MACE was recorded during follow-up (median: 27.0, range: 1.0-54.0 months) in female premature ACS patients.

RESULTS

MiR-497/FGF23 axis was reduced in female premature ACS patients versus HCs [median (interquartile range): 0.7 (0.1-1.2) versus 1.9 (1.1-3.4)] (P < 0.001). Meanwhile, miR-497 negatively correlated with FGF23 in femal e premature ACS patients (P < 0.001), but not in HCs (P = 0.157). In female premature ACS patients, the miR-497/FGF23 axis was negatively associated with serum creatinine (P < 0.001), serum uric acid (P = 0.003), high-sensitivity C-reactive protein (P < 0.001), total cholesterol (P = 0.031), and low-density lipoprotein cholesterol (P = 0.003). The 1-year, 2-year, 3-year, and 4-year accumulating MACE rate was 2.9%, 8.6%, 16.7%, and 26.0%, respectively. Interestingly, a high level of miR-497/FGF23 axis predicted decreased accumulating MACE risk (P < 0.001). After adjustment by multivariate Cox's regression analysis, the high miR-497/FGF23 axis (hazard ratio (HR) = 0.005, P = 0.001) independently correlated with reduced accumulating MACE risk.

CONCLUSION

The plasma miR-497/FGF23 axis represents favorable kidney function, decreased inflammation, and reduced lipid level; meanwhile, this axis possesses prognostic value in predicting decreased accumulating MACE risk in female premature ACS patients.

Emerging role of α-Klotho in energy metabolism and cardiometabolic diseases

BACKGROUND AND AIM

Klotho was first identified as a gene associated with aging and longevity in 1997. α-Klotho is an anti-aging protein and its role in energy metabolism, various cardiovascular diseases (CVDs), and metabolic disorders is increasingly being recognized. In this review, we aimed to outline the potential protective role and therapeutic prospects of α-Klotho in energy metabolism and cardiometabolic diseases (CMDs).

METHODS

We comprehensively reviewed the relevant literature in PubMed using the keywords 'Klotho', 'metabolism', 'cardiovascular', 'diabetes', 'obesity', 'metabolic syndrome', and 'nonalcoholic fatty liver disease'.

RESULTS

α-Klotho can be divided into membrane-bound Klotho, secreted Klotho, and the most studied circulating soluble Klotho that can act as a hormone. Klotho gene polymorphisms have been implicated in energy metabolism and CMDs. α-Klotho can inhibit insulin/insulin growth factor-1 signaling and its overexpression can lead to a 'healthy insulin resistance' and may exert beneficial effects on the regulation of glycolipid metabolism and central energy homeostasis. α-Klotho, mainly serum Klotho, has been revealed to be protective against CVDs, diabetes and its complications, obesity, and nonalcoholic fatty liver disease. Human recombinant Klotho protein/Klotho gene delivery, multiple drugs, or natural products, and exercise can increase α-Klotho expression.

CONCLUSION

Overall, α-Klotho has demonstrated its potential as a promising target for modulating energy metabolism and CMDs, and further research is needed to explore its utilization in clinical practice in the future.

ADAM10 and ADAM17, Major Regulators of Chronic Kidney Disease Induced Atherosclerosis?

Chronic kidney disease (CKD) is a major health problem, affecting millions of people worldwide, in particular hypertensive and diabetic patients. CKD patients suffer from significantly increased cardiovascular disease (CVD) morbidity and mortality, mainly due to accelerated atherosclerosis development. Indeed, CKD not only affects the kidneys, in which injury and maladaptive repair processes lead to local inflammation and fibrosis, but also causes systemic inflammation and altered mineral bone metabolism leading to vascular dysfunction, calcification, and thus, accelerated atherosclerosis. Although CKD and CVD individually have been extensively studied, relatively little research has studied the link between both diseases. This narrative review focuses on the role of a disintegrin and metalloproteases (ADAM) 10 and ADAM17 in CKD and CVD and will for the first time shed light on their role in CKD-induced CVD. By cleaving cell surface molecules, these enzymes regulate not only cellular sensitivity to their micro-environment (in case of receptor cleavage), but also release soluble ectodomains that can exert agonistic or antagonistic functions, both locally and systemically. Although the cell-specific roles of ADAM10 and ADAM17 in CVD, and to a lesser extent in CKD, have been explored, their impact on CKD-induced CVD is likely, yet remains to be elucidated.

The role of Klotho and FGF23 in cardiovascular outcomes of diabetic patients with chronic limb threatening ischemia: a prospective study

Cardiovascular complications after lower extremity revascularization (LER) are common in diabetic patients with peripheral arterial disease (PAD) and chronic limb threatening ischemia (CLTI). The Klotho-fibroblast growth factor 23 (FGF23) axis is associated with endothelial injury and cardiovascular risk. We aimed to analyze the relationship between Klotho and FGF23 serum levels and the incidence of major adverse cardiovascular events (MACE) and major adverse limb events (MALE) after LER in diabetic patients with PAD and CLTI. Baseline levels of Klotho and FGF23, and their association with subsequent incidence of MACE and MALE were analyzed in a prospective, non-randomized study in a population of diabetic patients with PAD and CLTI requiring LER. A total of 220 patients were followed for 12 months after LER. Sixty-three MACE and 122 MALE were recorded during follow-up period. Baseline lower Klotho serum levels (295.3 ± 151.3 pg/mL vs. 446.4 ± 171.7 pg/mL, p < 0.01), whereas increased serum levels FGF23 (75.0 ± 11.8 pg/mL vs. 53.2 ± 15.4 pg/mL, p < 0.01) were significantly associated with the development of MACE. Receiver operating characteristic (ROC) analysis confirmed the predictive power of Klotho and FGF23 baseline levels. Furthermore, decreased Klotho levels were associated with the occurrence of MALE after LER (329.1 ± 136.8 pg/mL vs 495.4 ± 183.9 pg/mL, p < 0.01). We found that Klotho and FGF23 baseline levels are a potential biomarker for increased cardiovascular risk after LER in diabetic patients with PAD and CLTI.

A protective erythropoietin evolutionary landscape, NLRP3 inflammasome regulation, and multisystem inflammatory syndrome in children

The low incidence of pediatric severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and the associated multisystem inflammatory syndrome (MIS-C) lack a unifying pathophysiological explanation, impeding effective prevention and therapy. Activation of the NACHT, LRR, and PYD domains-containing protein (NLRP) 3 inflammasome in SARS-CoV-2 with perturbed regulation in MIS-C, has been reported. We posit that, early age physiological states and genetic determinants, such as certain polymorphisms of renin-angiotensin aldosterone system (RAAS) molecules, promote a controlled RAAS hyperactive state, and form an evolutionary landscape involving an age-dependent erythropoietin (EPO) elevation, mediating ancestral innate immune defenses that, through appropriate NLRP3 regulation, mitigate tissue injury and pathogen invasion. SARS-CoV-2-induced downregulation of angiotensin-converting enzyme (ACE)2 expression in endothelial cells (EC), impairment of endothelial nitric oxide (NO) synthase (eNOS) activity and downstream NO bioavailability, may promote a hyperactive RAAS with elevated angiotensin II and aldosterone that, can trigger, and accelerate NLRP3 inflammasome activation, while EPO-eNOS/NO abrogate it. Young age and a protective EPO evolutionary landscape may successfully inhibit SARS-CoV-2 and contain NLRP3 inflammasome activation. By contrast, increasing age and falling EPO levels, in genetically susceptible children with adverse genetic variants and co-morbidities, may lead to unopposed RAAS hyperactivity, NLRP3 inflammasome dysregulation, severe endotheliitis with pyroptotic cytokine storm, and development of autoantibodies, as already described in MIS-C. Our haplotype estimates, predicted from allele frequencies in population databases, are in concordance with MIS-C incidence reports in Europeans but indicate lower risks for Asians and African Americans. Targeted Mendelian approaches dissecting the influence of relevant genetic variants are needed.

Perioperative variation in serum FGF-23 level and its correlation with MACCE risk in unprotected left main coronary artery disease patients receiving coronary artery bypassing grafting

Objective

Fibroblast growth factor-23 (FGF-23) mediates vascular endothelial injury, inflammatory infiltration, and atherosclerosis, which could reflect major adverse cardiac and cerebrovascular event (MACCE) risk in several cardiovascular diseases. This study aims to further investigate the perioperative change of FGF-23, as well as its association with clinical characteristics and MACCE risk in unprotected left main coronary artery disease (ULMCAD) patients receiving coronary artery bypass grafting (CABG).

Methods

A total of 226 ULMCAD patients who underwent CABG were enrolled. Serum samples of the patients were collected on the day before CABG, the third day (D3) after CABG, and at discharge; then, the FGF-23 level was determined by enzyme-linked immunosorbent assay. The MACCE rate was recorded during a median follow-up of 25.5 (range: 2.0–46.0) months.

Results

The median, interquartile range (IQR), and range of FGF-23 level in ULMCAD patients receiving CABG were 717.0, 582.5–869.8, and 407.0–1765.0 pg/ml, respectively. FGF-23 level was increased in patients with both previous heart failure (P = 0.046) and chronic renal failure (P = 0.009) compared to those without. FGF-23 level increased from before surgery [median (IQR): 712.5 (574.5–879.8) pg/ml] to D3 [median (IQR): 844.0 (666.0–1072.5) pg/ml], then declined at discharge [median (IQR): 764.5 (569.3–986.8) pg/ml] (P < 0.001). Meanwhile, the preoperative FGF-23 level (P = 0.028), but not the FGF-23 level at discharge (P = 0.067) was positively correlated with the cumulative MACCE rate. Multivariable Cox's analyses found that preoperative FGF-23 level could independently predict cumulative MACCE rate [P = 0.015, hazards ratio (HR) = 2.940].

Conclusion

Preoperative FGF-23 level predicts higher MACCE risk in ULMCAD patients undergoing CABG surgery.

α-Klotho, Plasma Asymmetric Dimethylarginine, and Kidney Disease Progression

Rationale & Objective

We aimed to explore the associated factors of endothelial injury in chronic kidney disease (CKD) and the relationship between endothelial dysfunction and CKD prognosis.

Study Design

A prospective observational cohort study.

Setting & Participants

77 adults with CKD stages 1-5 were enrolled January 2010 to December 2010 and followed up until December 2015.

Exposure

Serum asymmetric dimethylarginine (ADMA) level at baseline, α-klotho, sodium-phosphorus synergistic transporter, and dimethylarginine-dimethylamine hydrolase expression in kidney biopsy samples.

Outcome

Initiation of kidney replacement therapy (KRT).

Analytical Approach

Kaplan-Meier analysis was used for evaluation of the incidence rate of KRT. All tests were 2 tailed, and statistical significance was defined as P < 0.05.

Results

Mean serum ADMA level of 77 patients was 64.3 ± 34.6 ng/mL. ADMA level increased with CKD stages (P = 0.06) and declining kidney function (r = −0.267; P = 0.02). The expression of α-klotho in kidney biopsy specimens also decreased. Median follow-up time was 56 (interquartile range, 50.5-62) months. Kaplan-Meier analyses showed that during a total follow-up of 6 years, the incidence of KRT initiation in the high-ADMA group was significantly higher than that in the low group (35.9% vs 13.2%; P = 0.03). ADMA level was negatively correlated with α-klotho (r = −0.233; P = 0.04) and positively correlated with phosphorus level (r = 0.243; P = 0.04). The expression of sodium-phosphorus synergistic transporter in kidney tubules, which promoted phosphorus reabsorption, and the expression of dimethylarginine-dimethylamine hydrolase isoform 1, which regulated ADMA, were decreased. Correlation analysis also showed that ADMA level decreased while age increased at baseline (r = −0.292; P = 0.01).

Limitations

Small sample size with limited longer-term follow-up.

Conclusions

Serum ADMA levels increased as kidney function declined, and high serum ADMA level was associated with incident kidney failure. Low tissue α-klotho and high levels of plasma phosphorus or tissue expression of type II sodium/phosphate cotransporter in the kidney are associated with higher circulating ADMA levels, suggesting that they may be involved in the pathogenesis of endothelial dysfunction in patients with CKD.

Patients with Earlobe Crease May Associate with Lower Concentration of the Age-Suppressing Hormone Klotho

Objective

Earlobe crease (ELC) has been considered as a skin sign of atherosclerosis, and its pathophysiological mechanism is still unclear. Our study aims to test the hypothesis that ELC patients with lower serum levels of the age-suppressing hormone Klotho, which is not only associated with premature aging but also with endothelial dysfunction, may be associated with atherosclerosis.

Methods

A total of 135 patients aged 40–68 years underwent coronary angiography. According to the presence or absence of coronary heart disease (CAD) and ELC, they were divided into three groups: CAD group and ELC group (ELC group, n = 45); no ELC group (non-ELC group, n = 45). There was no ELC or CAD in the control group (control group, n = 45). Serum Klotho concentration was obtained by enzyme-linked immunosorbent assay (ELISA).

Results

The Klotho level in the ELC group was 365.6 ± 38.1 pg/mL, while the Klotho level in the non-ELC group was 568.8 ± 44.9 pg/mL. It is worth noting that the Klotho level of the ELC group was significantly lower than that of the non-ELC group (P < 0.001). The serum Klotho level of the control group was higher than that of the non-ELC group (593.3±45.3 vs 568.8±44.9 pg/mL, P = 0.702), but the difference was not statistically significant. Multiple logistic regression analysis showed that the Klotho level is a parameter that affects the appearance of ELC.

Conclusion

Serum Klotho levels were considerably lower in patients with ELC. We concluded that the perturbations of Klotho in patients might be associated with ELC and with CAD.

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.

Association of KLOTHO polymorphisms with clinical complications of sickle cell anemia

The clinical and phenotypic heterogeneity of patients with sickle cell anemia (SCA) is influenced by environmental and genetic factors. Several genetic modifiers, such as the KLOTHO (KL) gene, have been associated with SCA clinical outcomes. The KL gene and its encoded proteins are implicated in important biological pathways, which affect the disease's pathophysiology, such as expression of adhesion molecules VCAM-1 and ICAM-1, oxidative stress, and nitric oxide biology. Here, we evaluated the clinical relevance of two polymorphisms found on the KL gene (rs685417 and rs211239) in 588 unrelated patients with SCA. Genotyping analyses were performed using the TaqMan system. The KL rs211239 was associated with increased number of vaso-occlusive crisis (VOCs) per year (P = 0.001), while KL rs685417 was associated with increased frequency of stroke (P = 0.034), priapism (P = 0.011), number of complications (P = 0.019), and with a lower incidence of priapism (P = 0.036). Additionally, the associations with VOCs, stroke, and priapism remained consistent in multivariate analyses (P < 0.05). Our data highlight the clinical importance of KL in SCA.

Exploiting the neuroprotective effects of α-klotho to tackle ageing- and neurodegeneration-related cognitive dysfunction

Cognitive dysfunction is a key symptom of ageing and neurodegenerative disorders, such as Alzheimer's disease (AD). Strategies to enhance cognition would impact the quality of life for a significant proportion of the ageing population. The α-klotho protein may protect against cognitive decline through multiple mechanisms: such as promoting optimal synaptic function via activation of N-methyl-d-aspartate (NMDA) receptor signalling; stimulating the antioxidant defence system; reducing inflammation; promoting autophagy and enhancing clearance of amyloid-β. However, the molecular and cellular pathways by which α-klotho mediates these neuroprotective functions have yet to be fully elucidated. Key questions remain unanswered: which form of α-klotho (transmembrane, soluble or secreted) mediates its cognitive enhancing properties; what is the neuronal receptor for α-klotho and which signalling pathways are activated by α-klotho in the brain to enhance cognition; how does peripherally administered α-klotho mediate neuroprotection; and what is the molecular basis for the beneficial effect of the VS variant of α-klotho? In this review, we summarise the recent research on neuronal α-klotho and discuss how the neuroprotective properties of α-klotho could be exploited to tackle age- and neurodegeneration-associated cognitive dysfunction.

Roles for fibroblast growth factor-23 and α-Klotho in acute kidney injury

Acute kidney injury is a global disease with high morbidity and mortality. Recent studies have revealed that the fibroblast growth factor-23-α-Klotho axis is closely related to chronic kidney disease, and has multiple biological functions beyond bone-mineral metabolism. However, although dysregulation of fibroblast growth factor-23-α-Klotho has been observed in acute kidney injury, the role of fibroblast growth factor-23-α-Klotho in the pathophysiology of acute kidney injury remains largely unknown. In this review, we describe recent findings regarding fibroblast growth factor-23-α-Klotho, which is mainly involved in inflammation, oxidative stress, and hemodynamic disorders. Further, based on these recent results, we put forth novel insights regarding the relationship between the fibroblast growth factor-23-α-Klotho axis and acute kidney injury, which may provide new therapeutic targets for treating acute kidney injury.

No significant association of serum klotho concentration with blood pressure and pulse wave velocity in a Chinese population

Klotho, an important anti-aging protein, may be related to elevated blood pressure (BP) and arterial stiffness. We aimed to investigate associations between the serum klotho concentration and peripheral/central BP and arterial stiffness based on the carotid–femoral pulse wave velocity (cfPWV) in a Chinese population. We invited all inhabitants aged ≥ 18 years in two Dali communities for participation. The SphygmoCor system was used to record radial arterial waveforms. Aortic waveforms were derived using a generalized transfer function. The central BP was assessed by calibrating the brachial BP, which was measured using an oscillometric device. The serum klotho concentration was measured using an enzyme-linked immunosorbent assay and logarithmically transformed. Of the 716 participants (mean age: 51.9 ± 12.6 years), 467 (65.2%) were women. The median serum klotho concentration was 381.8 pg/mL. The serum klotho concentration did not significantly differ between patients with and without hypertension (P > 0.05) and between those with and without arterial stiffness (cfPWV ≥ 10 m/s) (P > 0.05). After adjusting for confounders, the serum klotho concentration was not significantly associated with the peripheral or central BP (P > 0.05) and cfPWV (P > 0.05). Our data indicated that the serum klotho concentration was not associated with BP or cfPWV in the general Chinese population.

Why Should Growth Hormone (GH) Be Considered a Promising Therapeutic Agent for Arteriogenesis? Insights from the GHAS Trial

Despite the important role that the growth hormone (GH)/IGF-I axis plays in vascular homeostasis, these kind of growth factors barely appear in articles addressing the neovascularization process. Currently, the vascular endothelium is considered as an authentic gland of internal secretion due to the wide variety of released factors and functions with local effects, including the paracrine/autocrine production of GH or IGF-I, for which the endothelium has specific receptors. In this comprehensive review, the evidence involving these proangiogenic hormones in arteriogenesis dealing with the arterial occlusion and making of them a potential therapy is described. All the elements that trigger the local and systemic production of GH/IGF-I, as well as their possible roles both in physiological and pathological conditions are analyzed. All of the evidence is combined with important data from the GHAS trial, in which GH or a placebo were administrated to patients suffering from critical limb ischemia with no option for revascularization. We postulate that GH, alone or in combination, should be considered as a promising therapeutic agent for helping in the approach of ischemic disease.

Osteokines and the vasculature: a review of the in vitro effects of osteocalcin, fibroblast growth factor-23 and lipocalin-2

Bone-derived factors that demonstrate extra-skeletal functions, also termed osteokines, are fast becoming a highly interesting and focused area of cross-disciplinary endocrine research. Osteocalcin (OCN), fibroblast growth factor-23 (FGF23) and lipocalin-2 (LCN-2), produced in bone, comprise an important endocrine system that is finely tuned with other organs to ensure homeostatic balance and health. This review aims to evaluate in vitro evidence of the direct involvement of these proteins in vascular cells and whether any causal roles in cardiovascular disease or inflammation can be supported. PubMed, Medline, Embase and Google Scholar were searched for relevant research articles investigating the exogenous addition of OCN, FGF23 or LCN-2 to vascular smooth muscle or endothelial cells. Overall, these osteokines are directly vasoactive across a range of human and animal vascular cells. Both OCN and FGF23 have anti-apoptotic properties and increase eNOS phosphorylation and nitric oxide production through Akt signalling in human endothelial cells. OCN improves intracellular insulin signalling and demonstrates protective effects against endoplasmic reticulum stress in murine and human endothelial cells. OCN may be involved in calcification but further research is warranted, while there is no evidence for a pro-calcific effect of FGF23 in vitro. FGF23 and LCN-2 increase proliferation in some cell types and increase and decrease reactive oxygen species generation, respectively. LCN-2 also has anti-apoptotic effects but may increase endoplasmic reticulum stress as well as have pro-inflammatory and pro-angiogenic properties in human vascular endothelial and smooth muscle cells. There is no strong evidence to support a pathological role of OCN or FGF23 in the vasculature based on these findings. In contrast, they may in fact support normal endothelial functioning, vascular homeostasis and vasodilation. No studies examined whether OCN or FGF23 may have a role in vascular inflammation. Limited studies with LCN-2 indicate a pro-inflammatory and possible pathological role in the vasculature but further mechanistic data is required. Overall, these osteokines pose intriguing functions which should be investigated comprehensively to assess their relevance to cardiovascular disease and health in humans.

Reduced Levels of Anti-Ageing Hormone Klotho Predict Renal Function Decline in Type 2 Diabetes

CONTEXT AND OBJECTIVE

Soluble Klotho (sKlotho) is a circulating hormone with cardiovascular-renal protective effects. Whether sKlotho predicts estimated glomerular filtration rate (eGFR) decline in patients with type 2 diabetes mellitus (T2DM) with relatively preserved renal function is unknown.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

Single-center observational follow-up study of 101 patients with T2DM and eGFR >45 mL/min [91% on renin angiotensin system (RAS) blockade] followed for a median of 9 years (range, 2 to 13 years).

MAIN OUTCOME

Primary outcome was a >50% decline in eGFR. sKlotho, serum phosphorus, serum calcium, and fibroblast growth factor-23 levels were measured from stored samples collected at baseline. Patients were followed up with standardized clinical and biochemical measurements.

RESULTS

Patients with residual microalbuminuria (MA) despite RAS blockade (n = 53) had significantly lower levels of sKlotho [median, 184.7 pg/mL; interquartile range (IQR), 130.5 to 271.8 pg/mL) compared with patients without MA (n = 39; median, 235.2 pg/mL; IQR, 172.0 to 289.4 pg/mL; P = 0.03). Of the cohort, 21% reached the primary outcome. In a competing risk analysis, a 10% higher sKlotho level reduced the incidence of the primary outcome by 12% (hazard ratio, 0.27; 95% confidence interval, 0.15 to 0.52; P < 0.001] independent of traditional risk factors. Patients with sKlotho below the median of 204.4 pg/mL had nearly a fourfold higher cumulative incidence of the primary outcome compared with those above the median (24% vs 6.2%; P = 0.01).

CONCLUSIONS

In patients with T2DM with relatively preserved eGFR, reduced levels of sKlotho predict renal function decline independent of traditional risk markers. sKlotho is a biomarker of renal dysfunction and a potential treatment target for renoprotection in T2DM.

Upregulation of Klotho potentially inhibits pulmonary vascular remodeling by blocking the activation of the Wnt signaling pathway in rats with PM2.5-induced pulmonary arterial hypertension

We evaluated the effects of Klotho on pulmonary vascular remodeling and cell proliferation and apoptosis in rat models with PM2.5-induced pulmonary arterial hypertension (PAH) via the Wnt signaling pathway. After establishing rat models of PM2.5-induced PAH, these Sprague-Dawley male rats were randomized into control and model groups. Cells extracted from the model rats were sub-categorized into different groups. Activation of Wnt/β-catenin signaling transcription factor was detected by a TOPFlash/FOPFlash assay. A serial of experiment was conducted to identify the mechanism of Klotho on PHA via the Wnt signaling pathway. VEGF levels and PaCO₂ content were higher in the model group, while PaO_2, NO₂^- /NO₃^- content and Klotho level was lower compared to the control group. In comparison to the control group, the model group had decreased Klotho and Bax levels, and elevated Wnt-1, β-catenin, bcl-2, survivin, and PCNA expression, VEGF, IL-6, TNF-α, TNF-β1, and bFGF levels, as well as the percentage of pulmonary artery ring contraction. The Klotho vector, DKK-1 and DKK-1 + Klotho vector groups exhibited reduced cell proliferation, luciferase activity, and the expression of Wnt-1, β-catenin, bcl-2, survivin, and PCNA, as well as shortened S phase compared with the blank and NC groups. Compared with the Klotho vector and DKK-1 groups, the DKK-1 + Klotho vector groups had reduced cell proliferation, luciferase activity, and the expression of Wnt-1, β-catenin, bcl-2, survivin, and PCNA, as well as a shortened S phase. Conclusively, Klotho inhibits pulmonary vascular remodeling by inactivation of Wnt signaling pathway.

Growth Hormone (GH) and Cardiovascular System

This review describes the positive effects of growth hormone (GH) on the cardiovascular system. We analyze why the vascular endothelium is a real internal secretion gland, whose inflammation is the first step for developing atherosclerosis, as well as the mechanisms by which GH acts on vessels improving oxidative stress imbalance and endothelial dysfunction. We also report how GH acts on coronary arterial disease and heart failure, and on peripheral arterial disease, inducing a neovascularization process that finally increases flow in ischemic tissues. We include some preliminary data from a trial in which GH or placebo is given to elderly people suffering from critical limb ischemia, showing some of the benefits of the hormone on plasma markers of inflammation, and the safety of GH administration during short periods of time, even in diabetic patients. We also analyze how Klotho is strongly related to GH, inducing, after being released from the damaged vascular endothelium, the pituitary secretion of GH, most likely to repair the injury in the ischemic tissues. We also show how GH can help during wound healing by increasing the blood flow and some neurotrophic and growth factors. In summary, we postulate that short-term GH administration could be useful to treat cardiovascular diseases.