Klotho depletion contributes to increased inflammation in kidney of the db/db mouse model of diabetes via RelA (serine)536 phosphorylation

Inflammation-Induced Klotho Deficiency: A Possible Key Driver of Chronic Kidney Disease Progression

Chronic kidney disease (CKD) is influenced by inflammation, a critical factor in its progression. However, the underlying mechanism through which inflammation contributes to CKD is still obscure. The Klotho protein, which is predominantly found in the kidneys, is known for its protective functions, including anti-inflammatory, anti-aging, antioxidant, and anti-fibrotic effects. A myriad of studies have suggested that inflammation in CKD leads to a decrease in Klotho expression, diminishing Klotho protection capabilities and exacerbating kidney damage, thereby promoting CKD progression. These findings suggest that Klotho deficiency could be a crucial link between inflammation and CKD progression. However, the mechanism regarding their relationship is still unclear. The reduction in Klotho due to inflammation may be attributed to epigenetic mechanisms, such as DNA methylation, histone deacetylation, transcription factor, microRNA (miRNA) regulation and long non-coding RNA (lncRNA) regulation or non-epigenetic factors, such as endoplasmic reticulum (ER) stress and ER-associated degradation (ERAD), which affect Klotho protein metabolism. Through these pathways, inflammation triggers a decrease in Klotho expression, further driving CKD progression. Notably, Klotho also exerts a strong anti-inflammatory effect by inhibiting key inflammatory factors and pathways, suggesting that there is intricate crosstalk between inflammatory factors and Klotho in CKD. This review highlights how inflammation suppresses the expression of Klotho and further contributes to the development and exacerbation of CKD. By focusing on the interplay between inflammation and Klotho, the present review provides novel potential therapeutic strategies such as correcting epigenetic and non-epigenetic abnormalities for treating CKD by targeting this specific axis.

Combining Network Pharmacological Analysis and Animal Experiments to Explore the Pharmacological Mechanism of Zhangyanming Tablets in Diabetic Retinopathy

Background

Zhangyanming Tablets (ZYMT) is a proprietary Chinese medicine containing a variety of traditional Chinese medicines, which can be used to treat a wide range of eye diseases, but its exact effect on diabetic retinopathy (DR) and the specific mechanism are still unclear. This study aims to investigate the ameliorative effects and specific mechanisms of ZYMT on DR.

Methods

Key regulatory genes and potential therapeutic targets of ZYMT for DR were evaluated using network pharmacological analysis. Diabetic db/db mice were given low-dose ZYMT (330 mg/kg) and high-dose ZYMT (660 mg/kg), and relevant metabolic indices were tested. Histochemical staining and optical coherence tomography angiography (OCTA) were used to evaluate the histopathological structure of mice retina, RT-qPCR, TUNEL staining and immunofluorescence staining were used to evaluate the anti-apoptosis and anti-angiogenesis effect of ZYMT on DR.

Results

The results of network topology analysis showed that the top 10 Traditional Chinese Medicine (TCM) ingredients of ZYMT were quercetin, luteolin, kaempferol, wogonin, naringenin, β-sitosterol, baicalein, isorhamnetin, acacetin, and stigmasterol. ZYMT treats DR through key nodes such as AKT1, TNF, MAPK8, RELA, VEGFA, HIF1A, IL6, CASP3, BCL2, STAT3, and ICAM1. ZYMT has a direct effect on DR rather than secondary improvement of metabolic indices. Tissue staining demonstrated that ZYMT improved retinal vascular morphology and delayed retinal thinning in db/db mice. The OCTA imaging also showed that ZYMT increased blood flow density in db/db mice. TUNEL staining and RT-qPCR results showed that ZYMT could reduce the apoptosis of retinal cells in db/db mice, and RT-qPCR and immunofluorescence staining showed that ZYMT could inhibit retinal neovascularization.

Conclusion

This study found the potential target of ZYMT to ameliorate DR through network pharmacological analysis, and verified that ZYMT can improve DR by exerting anti-apoptosis and anti-neovascularization.

Long-term effects of s-KL treatment in wild-type mice: Enhancing longevity, physical well-being, and neurological resilience

Aging is a major risk factor for pathologies including sarcopenia, osteoporosis, and cognitive decline, which bring suffering, disability, and elevated economic and social costs. Therefore, new therapies are needed to achieve healthy aging. The protein Klotho (KL) has emerged as a promising anti-aging molecule due to its pleiotropic actions modulating insulin, insulin-like growth factor-1, and Wnt signaling pathways and reducing inflammatory and oxidative stress. Here, we explored the anti-aging potential of the secreted isoform of this protein on the non-pathological aging progression of wild-type mice. The delivery of an adeno-associated virus serotype 9 (AAV9) coding for secreted KL (s-KL) efficiently increased the concentration of s-KL in serum, resulting in a 20% increase in lifespan. Notably, KL treatment improved physical fitness, related to a reduction in muscle fibrosis and an increase in muscular regenerative capacity. KL treatment also improved bone microstructural parameters associated with osteoporosis. Finally, s-KL-treated mice exhibited increased cellular markers of adult neurogenesis and immune response, with transcriptomic analysis revealing induced phagocytosis and immune cell activity in the aged hippocampus. These results show the potential of elevating s-KL expression to simultaneously reduce the age-associated degeneration in multiple organs, increasing both life and health span.

Aging Impairs the Capacity of Cardiac Functional Recovery Following Endotoxemia: Modulation of Myocardial Klotho Level for Remedy

INTRODUCTION

Endotoxemic/septic cardiac dysfunction occurs frequently in elderly patients undergoing major surgery and contributes to postsurgery morbidity and mortality. This study evaluated the effect of aging on cardiac functional recovery following endotoxemia and explored therapeutic approaches for promotion of the recovery.

METHODS

A small dose of endotoxin (0.5 mg/kg, iv) was administered to young adult (3-4 mo) and old (18-22 mo) mice with or without subsequent treatment with recombinant interleukin-37 (IL-37, 50 μg/kg, iv) or recombinant Klotho (10 μg/kg, iv). Cardiac function was analyzed using a microcatheter at 24, 48, and 96 h following administration of endotoxin. Myocardial levels of Klotho, intercellular adhesion molecule-1, and IL-6 were determined by immunoblotting and Enzyme-linked immunosorbent assay.

RESULTS

Compared to young adult endotoxemic mice, old endotoxemic mice had worse cardiac dysfunction accompanied by greater myocardial levels of intercellular adhesion molecule-1 and IL-6 at each time point and failed to fully recover cardiac function by 96 h. The exacerbated and prolonged myocardial inflammation and cardiac dysfunction in old endotoxemic mice were associated with lower myocardial Klotho level and its further reduction by endotoxemia. Interestingly, recombinant IL-37 up-regulated myocardial Klotho level in old mice with or without endotoxemia and treatment of old endotoxemic mice with IL-37 improved myocardial inflammation resolution and cardiac functional recovery. Similarly, recombinant Klotho suppressed myocardial inflammatory response and promoted inflammation resolution in old endotoxemic mice, leading to complete recovery of cardiac function by 96 h.

CONCLUSIONS

Myocardial Klotho insufficiency in old mice exacerbates myocardial inflammatory response, impairs inflammation resolution and hinders cardiac functional recovery. IL-37 is capable of up-regulating myocardial Klotho level to promote myocardial inflammation resolution and cardiac functional recovery in old endotoxemic mice.

Klotho antiaging protein: molecular mechanisms and therapeutic potential in diseases

Klotho, initially introduced as an anti-aging protein, is expressed in the brain, pancreas, and most prominently in the kidney. The two forms of Klotho (membrane-bound and soluble form) have diverse pharmacological functions such as anti-inflammatory, anti-oxidative, anti-fibrotic, tumour-suppressive etc. The membrane-bound form plays a pivotal role in maintaining kidney homeostasis by regulating fibroblast growth factor 23 (FGF 23) signalling, vitamin D metabolism and phosphate balance. Klotho deficiency has been linked with significantly reduced protection against various kidney pathological phenotypes, including diabetic kidney disease (DKD), which is a major cause of chronic kidney disease leading to end-stage kidney disease. Owing to the pleiotropic actions of klotho, it has shown beneficial effects in DKD by tackling the complex pathophysiology and reducing kidney inflammation, oxidative stress, as well as fibrosis. Moreover, the protective effect of klotho extends beyond DKD in other pathological conditions, including cardiovascular diseases, alzheimer's disease, cancer, inflammatory bowel disease, and liver disease. Therefore, this review summarizes the relationship between Klotho expression and various diseases with a special emphasis on DKD, the distinct mechanisms and the potential of exogenous Klotho supplementation as a therapeutic strategy. Future research into exogenous Klotho could unravel novel treatment avenues for DKD and other diseases.

Klotho protein: A key modulator of aging and COVID-19 severity

The COVID-19 pandemic has drawn significant attention to factors affecting disease severity, especially in older adults. This study explores the relationship between Klotho, an anti-aging protein, and COVID-19 severity. Conducted at Tehran's Firouzgar Hospital, this case-control study involved 279 participants, assessing serum levels of Klotho, inflammatory markers (C-reactive protein (CRP), Interleukin 6 (IL-6)), and Vitamin D. The findings indicate significantly lower Klotho levels in COVID-19 patients, especially those in the ICU, which correlate with elevated inflammatory markers and reduced Vitamin D levels. This inverse relationship between Klotho levels and disease severity underscores the protein's potential modulatory role in the inflammatory response to COVID-19. The study not only highlights the importance of Klotho as a biomarker for aging and disease severity but also suggests its potential therapeutic value in managing COVID-19, offering a novel perspective on targeting aging-related pathways to mitigate the impact of the disease. These insights open new avenues for research and intervention strategies to leverage anti-aging mechanisms to combat COVID-19 and potentially other age-related diseases.

Potential of Klotho as a Biomarker for Overwork: A Study of Frontline Medical Workers

OBJECTIVE

This study evaluates the utility of serum s-αKlotho levels as a quantifiable biomarker for overwork.

METHODS

Frontline medical workers aged 20-55 years from Yiling People's Hospital of Yichang were recruited. Criteria included nonsmokers, non-heavy drinkers, no chronic medication use, and no acute illnesses recently. Participants worked over 10 hours per day, 60 hours weekly, and had at least 3 years of experience. A control group was matched except for work conditions. Data were collected through surveys, and serum levels were measured.

RESULTS

Significant differences in serum Klotho were found between overwork and control groups. The overwork group had higher median s-αKlotho levels (49.99 pg/mL) compared to controls (27.88 pg/mL).

CONCLUSION

Overworked medical workers exhibited elevated serum s-αKlotho, suggesting s-αKlotho as a potential biomarker for overwork. Future research should use multicenter designs with larger samples to validate findings.

Predictive value of bone metabolism markers in the progression of diabetic kidney disease: a cross-sectional study

Objective

This study aimed to investigate the relationship between bone metabolism markers, including serum klotho, fibroblast growth factor 23 (FGF23), 25(OH)D3, iPTH, calcium (Ca), and PHOS and the progression of diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM). Additionally, the predictive value of these markers for DKD progression was evaluated.

Methods

This study involved 126 patients with T2DM between May 2021 and March 2023. DKD staging was assessed based on urinary protein excretion rates and estimated glomerular filtration rate (eGFR). The study evaluated serum concentrations of klotho, FGF23, 25(OH)D3, iPTH, Ca and PHOS across various stages and examined their relationships with clinical parameters. Receiver operating characteristic (ROC) curve analysis was utilized to determine the predictive accuracy of these bone metabolism markers for DKD. Multivariate linear and logistic regression analyses identified risk factors linked to DKD severity.

Results

Among the 126 participants, 30 had non-DKD with normal proteinuria, while 96 had DKD, categorized as 31 with stage III DKD (microproteinuria), 34 with stage IV DKD, and 31 with stage V DKD (massive proteinuria). With advancing DKD from stage III to V, levels of klotho, 25(OH)D3, and Ca decreased significantly, whereas FGF23, iPTH and PHOS levels increased markedly. Klotho is significantly positively correlated with eGFR (r = 0.285, P = 0.001.) and negative correlations with serum creatinine (Scr) and UACR (r = -0.255, P = 0.004; r = -0.260, P = 0.011). FGF23 was positively related to systolic blood pressure (SBP) (r = 0.224, P = 0.012), but negatively with eGFR (r = -0.294, P = 0.001). Additionally, 25(OH)D3 exhibited significant negative correlations with several adverse clinical biomarkers, and both iPTH, Ca and PHOS were strongly associated with DKD progression (P<0.05). ROC analysis showed high predictive accuracy for DKD using these bone metabolism markers, with a combined area under the curve (AUC) of 0.846. Multivariate logistic regression analysis reinforced the significance of these markers in DKD progression.

Conclusion

Bone metabolism markers, such as klotho, FGF23, 25(OH)D3, iPTH, Ca and PHOS are intricately linked to DKD progression and may function as valuable predictive biomarkers.

Association between renal α-klotho and renal pathology among patients with chronic kidney disease

INTRODUCTION

This study was designed to investigate whether renal α-klotho levels are associated with renal pathology. This is the first report on patients with chronic kidney disease (CKD).

METHODS

We conducted a retrospective observational study. A total of 65 CKD patients were enrolled. Serum and renal biopsy samples were collected. Estimated glomerular filtration rate (eGFR) was examined by biochemical test. And α-klotho expressions were assessed by RT-PCR and immunohistochemistry. In addition, detailed microscopic findings were reviewed.

RESULTS

Renal α-klotho levels are associated positively with eGFR, and negatively with renal pathology, including interstitial fibrosis, inflammatory cell infiltration, and tubular atrophy.

CONCLUSIONS

The renal α-klotho is related to renal pathology.

Klotho accelerates the progression of polycystic ovary syndrome through promoting granulosa cell apoptosis and inflammation†

The morbidity of polycystic ovary syndrome (PCOS) is in highly increasing rate nowadays. PCOS not only affects the fertility in women, but also threatens the health of whole life. Hence, to find the prognostic risk factors is of great value. However, the effective predictors in clinical practice of PCOS are still in blackness. In this study, we found Klotho (KL) was increased in follicular fluid (FF) and primary luteinized granulosa cells (GCs) from PCOS patients with hyperandrogenism. Furthermore, we found follicular KL was negatively correlated with numbers of mature oocytes, and positively correlated with serum testosterone, LH, and LH/FSH levels menstrual cycle and number of total antral follicles in PCOS patients. In primary luteinized GCs, the increased KL was accompanied with upregulation of cell apoptosis and inflammation-related genes. In ovaries of PCOS mice and cultured human KGN cell line, KL was up-regulated and accompanied by apoptosis, inflammation, and mitochondrial dysfunction. Therefore, our findings suggest new mechanisms for granulosa cell injury and revealed to target inhibit KL maybe a new therapeutic strategy for treatment of PCOS.

Fibroblast growth-factor 23-Klotho axis is associated with systemic inflammation and myokine profile in children with chronic kidney disease

BACKGROUND

Chronic kidney disease is linked to a disturbed fibroblast growth factor-23 (FGF23)-Klotho axis and an imbalance between myostatin and insulin-like growth factor-1 (IGF-1) expression. This cross-sectional study investigates the association of the FGF23-Klotho axis and myokine profile with serum interleukin-6 (IL-6) and their interactions in pediatric patients.

METHODS

Serum calcium, phosphorus, 25-hydroxyvitamin D, parathormone, c-terminal FGF23, a-Klotho, myostatin, follistatin, IGF-1, and IL-6 were measured in 53 patients with GFR < 60 ml/min/1,73m2. Myostatin to lean mass (LM) and to IGF-1 ratios were calculated. IL-6 level > 3rd quartile was considered as high.

RESULTS

Myostatin, IGF-1, and follistatin were correlated to LM (rs = 0.513, p < 0.001, rs = 0.652, p < 0.001, rs=-0.483, p < 0.001). Myostatin and follistatin were correlated to IGF-1 (rs = 0.340, p = 0.014, rs=-0.385, p = 0.005). Myostatin/LM but not myostatin or myostatin/IGF-1 ratio was significantly higher in CKD 5D patients (p = 0.001,p = 0.844, p = 0.111). Among mineral bone parameters, lnFGF23 was correlated to lnIL-6 (rs = 0.397, p = 0.004) and associated with high IL-6 (OR 1.905, 95% CI 1.023-3.548). Among myokines, myostatin/IGF-1 ratio was correlated to lnIL-6 (rs = 0.395, p = 0.004) and associated with high IL-6 (OR 1.113, 95% CI 1.028-1.205). All associations were adjusted to CKD stage. Myostatin was correlated to lnFGF23 (rs = 0.331, p = 0.025) and myostatin/IGF-1 ratio to lnKlotho (rs=-0.363, p = 0.013), after adjustment for CKD stage, lnIL-6 and other mineral bone parameters.

CONCLUSIONS

In pediatric CKD, FGF23 and myostatin/IGF-1 ratio are associated with IL-6, indicating a link between systemic inflammation, mineral bone, and myokine disorders. The correlations between myostatin and FGF23 and between myostatin/IGF-1 and Klotho suggest an interaction between mineral bone and muscle metabolism.

Sex-specific modulation of renal epigenetic and injury markers in aging kidney

Sex differences in renal physiology and pathophysiology are now well established in rodent models and in humans. Epigenetic programming is known to be a critical component of renal injury, as studied mainly in male rodent models; however, not much is known about the impact of biological sex and age on the kidney epigenome. We sought to determine the influence of biological sex and age on renal epigenetic and injury markers, using male and female mice at 4 mo (4M; young), 12 mo (12M), and 24 mo (24M; aged) of age. Females had a significant increase in kidney and body weights and serum creatinine levels and a decrease in serum albumin levels from 4M to 24M of age, whereas minor changes were observed in male mice. Kidney injury molecule-1 levels in serum and renal tissue greatly enhanced from 12M to 24M in both males and females. Circulating histone 3 (H3; damage-associated molecular pattern molecules) levels extensively increased with age; however, males had higher levels than females. Overall, females had markedly high histone acetyltransferase (HAT) activity than age-matched males. Aged mice had decreased HAT activity and increased histone deacetylase activity than sex-matched 12M mice. Aged females had substantially decreased renal H3 methylation at lysine 9 and 27 and histone methyltransferase (HMT) activity than aged male mice. Antiaging protein Klotho levels were significantly higher in young males than age-matched females and decreased substantially with age in males, whereas epigenetic repressor of Klotho, trimethylated H3K27, and its HMT enzyme, enhancer of zeste homolog 2, increased consistently with age in both sexes. Moreover, nuclear translocation and activity of proinflammatory transcription factor nuclear factor-κB (p65) were significantly higher in aged mice. Taken together, our data suggest that renal aging lies in a range between normal and diseased kidneys but may differ between female and male mice, highlighting sex-related differences in the aging process.NEW & NOTEWORTHY Although there is evidence of sex-specific differences in kidney diseases, most preclinical studies have used male rodent models. The clinical data on renal injury have typically not been stratified by sex. Our findings provide convincing evidence of sex-specific differences in age-regulated epigenetic alterations and renal injury markers. This study highlights the importance of including both sexes for better realization of underlying sex differences in signaling mechanisms of aging-related renal pathophysiology.

Anti-Inflammatory Role of the Klotho Protein and Relevance to Aging

The α-Klotho protein (hereafter Klotho) is an obligate coreceptor for fibroblast growth factor 23 (FGF23). It is produced in the kidneys, brain and other sites. Klotho insufficiency causes hyperphosphatemia and other anomalies. Importantly, it is associated with chronic pathologies (often age-related) that have an inflammatory component. This includes atherosclerosis, diabetes and Alzheimer's disease. Its mode of action in these diseases is not well understood, but it inhibits or regulates multiple major pathways. Klotho has a membrane form and a soluble form (s-Klotho). Cytosolic Klotho is postulated but not well characterized. s-Klotho has endocrine properties that are incompletely elucidated. It binds to the FGF receptor 1c (FGFR1c) that is widely expressed (including endothelial cells). It also attaches to soluble FGF23, and FGF23/Klotho binds to FGFRs. Thus, s-Klotho might be a roaming FGF23 coreceptor, but it has other functions. Notably, Klotho (cell-bound or soluble) counteracts inflammation and appears to mitigate related aging (inflammaging). It inhibits NF-κB and the NLRP3 inflammasome. This inflammasome requires priming by NF-κB and produces active IL-1β, membrane pores and cell death (pyroptosis). In accord, Klotho countered inflammation and cell injury induced by toxins, damage-associated molecular patterns (DAMPs), cytokines, and reactive oxygen species (ROS). s-Klotho also blocks the TGF-β receptor and Wnt ligands, which lessens fibrotic disease. Low Klotho is associated with loss of muscle mass (sarcopenia), as occurs in aging and chronic diseases. s-Klotho counters the inhibitory effects of myostatin and TGF-β on muscle, reduces inflammation, and improves muscle repair following injury. The inhibition of TGF-β and other factors may also be protective in diabetic retinopathy and age-related macular degeneration (AMD). This review examines Klotho functions especially as related to inflammation and potential applications.

Correlation of serum Klotho, fetuin-A, and MGP levels with coronary artery calcification in maintenance hemodialysis patients

OBJECTIVE

This study was to investigate the role of serum Klotho, fetuin-A, and Matrix Gla Protein (MGP) in Coronary Artery Calcification (CAC) in patients with Maintenance Hemodialysis (MHD) and their predictive value for CAC.

METHODS

100 patients receiving MHD were selected. Serum Klotho, fetuin-A, and MGP levels were detected by ELISA. CAC scores were assessed by coronary CT scan. Multifactor analysis was used to evaluate the risk factors affecting CAC. The ability of serum Klotho, fetuin-A, and MGP levels to diagnose CAC was evaluated by receiver operating characteristic curves.

RESULTS

Serum Klotho, fetuin-A, and MGP were independent risk factors for CAC. Serum Klotho, fetuin-A, and MGP were valuable in the diagnosis of CAC in MHD patients.

CONCLUSION

There is a close relationship between Klotho, fetuin-A, and MGP levels in MHD patients and CAC.

Delaying Renal Aging: Metformin Holds Promise as a Potential Treatment

Given the rapid aging of the population, age-related diseases have become an excessive burden on global health care. The kidney, a crucial metabolic organ, ages relatively quickly. While the aging process itself does not directly cause kidney damage, the physiological changes that accompany it can impair the kidney's capacity for self-repair. This makes aging kidneys more susceptible to diseases, including increased risks of chronic kidney disease and end-stage renal disease. Therefore, delaying the progression of renal aging and preserving the youthful vitality of the kidney are crucial for preventing kidney diseases. However, effective strategies against renal aging are still lacking due to the underlying mechanisms of renal aging, which have not been fully elucidated. Accumulating evidence suggests that metformin has beneficial effects in mitigating renal aging. Metformin has shown promising anti-aging results in animal models but has not been tested for this purpose yet in clinical trials. These findings indicate the potential of metformin as an anti-renal aging drug. In this review, we primarily discuss the characteristics and mechanisms of kidney aging and the potential effects of metformin against renal aging.

The interaction between klotho protein and epigenetic alteration in diabetes and treatment options

Introduction

Klotho is a membrane protein predominantly expressed in the kidneys, and its discovery was serendipitously made through gene-targeting experiments conducted on mice. Klotho has a favorable role in the regulation of multiple cellular processes, such as aging, oxidative stress, inflammation, and apoptosis. This regulation occurs through the targeting of diverse signaling molecules, cell membrane receptors, and ion channels, achieved by physical contacts or enzymatic activities of Klotho. This review examines the role of Klotho in the epigenetic regulation of molecules associated with diabetes.

Methods

Authors conducted a thorough literature search using the PubMed®, Web of Science™, and Scopus®. Relevant articles up to September 2023, published in the English language were considered. We reviewed research databases searching for studies that included keywords klotho, epigenetic, and diabetes.

Results

14 related papers about epigenetic modification of proteins involved in diabetes pathogenesis were selected to be included in this narrative review. In the studies, the kidney was the most investigated organ regarding this correlation. Also, phosphorylation and methylation were the common epigenetic modifications of proteins by Klotho.

Conclusion

Klotho has a significant role in the maturation of adipocytes and the regulation of systemic glucose metabolism, exhibiting a strong association with the pathogenesis of diabetes. Both epigenetic alterations and the modulation of protein phosphorylation by Klotho play significant roles in the regulation of Klotho expression and the modulation of other molecules implicated in the etiology of diabetes.

Bioactive fiber-reinforced hydrogel to tailor cell microenvironment for structural and functional regeneration of myotendinous junction

Myotendinous junction (MTJ) injuries are prevalent in clinical practice, yet the treatment approaches are limited to surgical suturing and conservative therapy, exhibiting a high recurrence rate. Current research on MTJ tissue engineering is scarce and lacks in vivo evaluation of repair efficacy. Here, we developed a three-dimensional-printed bioactive fiber-reinforced hydrogel containing mesenchymal stem cells (MSCs) and Klotho for structural and functional MTJ regeneration. In a rat MTJ defect model, the bioactive fiber-reinforced hydrogel promoted the structural restoration of muscle, tendon, and muscle-tendon interface and enhanced the functional recovery of injured MTJ. In vivo proteomics and in vitro cell cultures elucidated the regenerative mechanisms of the bioactive fiber-reinforced hydrogel by modulating oxidative stress and inflammation, thus engineering an optimized microenvironment to support the survival and differentiation of transplanted MSCs and maintain the functional phenotype of resident cells within MTJ tissues, including tendon/muscle cells and macrophages. This strategy provides a promising treatment for MTJ injuries.

Urinary Excretion of Biomolecules Related to Cell Cycle, Proliferation, and Autophagy in Subjects with Type 2 Diabetes and Chronic Kidney Disease

Dysregulation of cell cycle, proliferation, and autophagy plays a pivotal role in diabetic kidney disease. In this study, we assessed urinary excretion of molecular regulators of these processes that mediate their effects via the PI3K/AKT/mTOR pathway in subjects with long-term type 2 diabetes (T2D) and different patterns of chronic kidney disease (CKD). We included 140 patients with T2D and 20 non-diabetic individuals in a cross-sectional study. Urinary PTEN, Beclin-1, sirtuin 1 (SIRT1), Klotho, fibroblast growth factor 21 (FGF21), and connective tissue growth factor (CTGF) were assessed using ELISA. Patients with T2D, when compared to control, demonstrated increased excretion of PTEN, Beclin-1, SIRT1, FGF21, CTGF, and decreased urinary Klotho (all p < 0.05). In the diabetic group, PTEN, FGF21, and CTGF were significantly higher in patients with declined renal function, while Klotho was lower in those with elevated albuminuria. FGF21 and PTEN correlated inversely with the estimated glomerular filtration rate. There was a negative correlation between Klotho and urinary albumin-to-creatinine ratio. In multivariate models, Klotho and PTEN were associated with albuminuric CKD independently. The results provide further support for the role of PTEN, BECN1, FGF21, Klotho, and CTGF in development albuminuric and non-albuminuric CKD in diabetes.

Lower serum Klotho level and higher systemic immune-inflammation index: an inverse correlation

OBJECTIVES

Klotho, an anti-aging protein, has been identified to control tissue inflammatory responses. The objective of this research is to determine the linkage between soluble Klotho (S-Klotho) level and systemic immune-inflammation index (SII).

METHODS

Eligible participants with complete information of S-Klotho level and SII were selected from the National Health and Nutrition Examination Surveys (NHANES). Subsequently, weighted multivariate linear regression and subgroup analysis were carried out to evaluate the association.

RESULTS

Totally, 11,108 adults with complete data on S-Klotho level, SII and other important covariates were included in final analysis. Multivariate liner regression revealed that high level of S-Klotho was associated with low level of SII after multivariate adjustments (β=-0.08, 95%CI:-0.10- -0.05, P < 0.01). When classifying S-Klotho into tertiles, participants in S-Klotho tertile 3 (Q3) showed a decrease in SII level compared with those in the lowest tertile (Q1) (β=-45.44, 95%CI:-64.41- -26.47, P < 0.01 ). The negative associations remained significant regardless of age and gender, and varied depending on smoking status and BMI subgroups.

CONCLUSION

S-Klotho level was negatively related to SII after controlling for covariates. Further studies need to validate current findings and explore the fundamental mechanisms.

Advances in understanding and treating diabetic kidney disease: focus on tubulointerstitial inflammation mechanisms

Diabetic kidney disease (DKD) is a serious complication of diabetes that can lead to end-stage kidney disease. Despite its significant impact, most research has concentrated on the glomerulus, with little attention paid to the tubulointerstitial region, which accounts for the majority of the kidney volume. DKD's tubulointerstitial lesions are characterized by inflammation, fibrosis, and loss of kidney function, and recent studies indicate that these lesions may occur earlier than glomerular lesions. Evidence has shown that inflammatory mechanisms in the tubulointerstitium play a critical role in the development and progression of these lesions. Apart from the renin-angiotensin-aldosterone blockade, Sodium-Glucose Linked Transporter-2(SGLT-2) inhibitors and new types of mineralocorticoid receptor antagonists have emerged as effective ways to treat DKD. Moreover, researchers have proposed potential targeted therapies, such as inhibiting pro-inflammatory cytokines and modulating T cells and macrophages, among others. These therapies have demonstrated promising results in preclinical studies and clinical trials, suggesting their potential to treat DKD-induced tubulointerstitial lesions effectively. Understanding the immune-inflammatory mechanisms underlying DKD-induced tubulointerstitial lesions and developing targeted therapies could significantly improve the treatment and management of DKD. This review summarizes the latest advances in this field, highlighting the importance of focusing on tubulointerstitial inflammation mechanisms to improve DKD outcomes.

Association between Serum α-Klotho Levels and Behçet Disease

BACKGROUND

Endothelial dysfunction (ED) has a well-known role in promoting vascular inflammation in Behçet disease (BD). α-klotho is involved in regulation of endothelial function, and its reduction has been reported to be associated with ED.

OBJECTIVE

To assess serum α-klotho in patients with BD, compared with healthy control individuals.

METHODS

In a cross-sectional study, 55 patients with BD and 30 age- and sex-matched healthy controls were enrolled, and their serum levels of α-klotho were measured.

RESULTS

Common clinical symptoms in patients with BD were oral aphthous ulcers, uveitis, and genital ulcers. Median (IQR) serum α-klotho levels in the BD and control groups were 0.30 (0.20-0.70) and 1.00 (0.70-2.52) ng/mL, respectively. The difference was statistically significant (P = .005). No significant correlation was observed between serum α-klotho and age (r = 0.194; P = .14). Serum α-klotho levels in patients with uveitis were significantly lower.

CONCLUSION

α-klotho may have a role in the pathogenesis of ED and is a potential biomarker for uveitis in BD.

Klotho inhibits the activation of NLRP3 inflammasome to alleviate lipopolysaccharide-induced inflammatory injury in A549 cells and restore mitochondrial function through SIRT1/Nrf2 signaling pathway

Acute lung injury is a severe clinical condition constituting a major cause of mortality in intensive care units. This study aimed to investigate the role of klotho in alleviating lipopolysaccharide (LPS)-induced acute lung injury. LPS-induced acute lung injury was used to simulate the acute lung injury caused by severe pneumonia in vitro. The viability and apoptosis of A549 cells were detected by cell counting kit-8 assay and flow cytometry. The inflammatory response, oxidative stress, and mitochondrial function in A549 cells were analyzed by commercial assay kits and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolyl carbocyanine iodide (JC-1) staining. The expression of apoptosis-related proteins, Sirtuin 1 (SIRT1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway-related proteins, and NOD-like receptor family pyrin domain containing 3 (NLRP3) expression in A549 cells was detected by western blot. The mtDNA synthase level in A549 cells was analyzed by reverse transcription-quantitative polymerase chain reaction. The results showed that, klotho had no cytotoxic effect on A549 cells. The viability and mitochondrial function were inhibited and apoptosis, inflammatory response, and oxidative stress were aggravated in LPS-induced A549 cells, which were all reversed by klotho. Klotho activated the SIRT1/Nrf2 signaling pathway to inhibit the LPS-induced NLRP3 inflammasome activation in A549 cells. However, EX527, a SIRT1 inhibitor, attenuated the klotho effect to suppress viability and mitochondrial function and promoted apoptosis, inflammatory response, and oxidative stress of A549 cells. In conclusion, klotho inhibited the activation of NLRP3 inflammasome to alleviate LPS-induced inflammatory injury of A549 cells and restore mitochondrial function through activating the SIRT1/Nrf2 signaling pathway.

Association of Klotho with Coronary Artery Disease in Subjects with Type 2 Diabetes Mellitus and Preserved Kidney Function: A Case-Control Study

Circulating Klotho levels are significantly reduced in subjects with type 2 diabetes mellitus (T2DM) and in kidney disease patients. In this work, the relationship between Klotho levels and the coronary artery disease (CAD) burden in subjects with T2DM and preserved kidney function was analyzed. For this, we performed a cross-sectional case-control study involving 133 subjects with T2DM and 200 age-, sex- and CAD-incidence-matched, non-diabetic patients undergoing non-emergency diagnostic coronary angiography. All of them were non-albuminuric and with normal glomerular filtration rates. The concentrations of serum Klotho, fibroblast growth factor 23, and inflammatory markers were also measured. As expected, the serum Klotho concentration was lower in the T2DM group (12.3% lower, p = 0.04). However, within the group of patients with T2DM, those subjects with CAD presented significantly higher Klotho levels than those without significant coronary stenosis (314.5 (6.15-562.81) vs. 458.97 (275.2-667.2) pg/mL; p = 0.02). Multiple regression analysis revealed that serum Klotho was positively related with stenosis values exclusively in subjects with T2DM (adjusted R2 = 0.153, p < 0.01). Moreover, logistic regression analysis showed that Klotho was positively associated with the presence of significant CAD in the group of T2DM patients (OR: 1.001; p = 0.041). Our data suggest that higher levels of circulating Klotho in subjects with T2DM and preserved kidney function are associated with the presence of significant CAD.

Associations between klotho and telomere biology in high stress caregivers

Aging biomarkers may be related to each other through direct co-regulation and/or through being regulated by common processes associated with chronological aging or stress. Klotho is an aging regulator that acts as a circulating hormone with critical involvement in regulating insulin signaling, phosphate homeostasis, oxidative stress, and age-related inflammatory functioning. Both klotho and telomere length are biomarkers of biological aging and decrease with age; however, the relationship between them is not well understood. Here we test the association between klotho levels and the telomere length of specific sorted immune cells among a healthy sample of mothers caregiving for a child with autism spectrum disorder (ASD; i.e., experiencing higher caregiving stress) or a child without ASD, covarying age and body mass index, in order to understand if high stress associated with caregiving for a child with an ASD may be involved in any association between these aging biomarkers. In 178 caregiving women (n = 90 high-stress mothers of children with ASD, n = 88 low-stress mothers of neurotypical children), we found that klotho levels were positively associated with telomere length in PBMCs (an effect driven by CD4+ and CD8+CD28- T cells) among high-stress mothers of children with an ASD but not among low-stress mothers of neurotypical children. There were no significant associations between klotho and telomerase activity in either group, across cell types assessed here. Our results suggest that klotho levels and telomere length may be associated through a coordinated downregulation of longevity factors occurring under higher stress caregiving conditions.

Diabetic complications and prospective immunotherapy

The incidence of Diabetes Mellitus is increasing globally. Individuals who have been burdened with diabetes for many years often develop complications as a result of hyperglycemia. More and more research is being conducted highlighting inflammation as an important factor in disease progression. In all kinds of diabetes, hyperglycemia leads to activation of alternative glucose metabolic pathways, resulting in problematic by-products including reactive oxygen species and advanced glycation end products. This review takes a look into the pathogenesis of three specific diabetic complications; retinopathy, nephropathy and neuropathy as well as their current treatment options. By considering recent research papers investigating the effects of immunotherapy on relevant conditions in animal models, multiple strategies are suggested for future treatment and prevention of diabetic complications with an emphasis on molecular targets associated with the inflammation.

Up-regulation of Myocardial Klotho Expression to Promote Cardiac Functional Recovery in Old Mice following Endotoxemia

Objective

Endotoxemic cardiac dysfunction contributes to greater morbidity and mortality in elderly patients with sepsis. This study tested the hypothesis that Klotho insufficiency in aging heart exaggerates and prolongs myocardial inflammation to hinder cardiac function recovery following endotoxemia.

Methods

Endotoxin (0.5 mg/kg, iv) was administered to young adult (3-4 months) and old (18-22 months) mice with or without subsequent treatment with recombinant interleukin-37 (IL-37, 50 μg/kg, iv) or recombinant Klotho (10 μg/kg, iv). Cardiac function was analyzed using a microcatheter 24, 48 and 96 h later. Myocardial levels of Klotho, ICAM-1, VCAM-1 and IL-6 were determined by immunoblotting and ELISA.

Results

In comparison to young adult mice, old mice had worse cardiac dysfunction accompanied by greater myocardial levels of ICAM-1, VCAM-1 and IL-6 at each time point following endotoxemia and failed to fully recover cardiac function by 96 h. The exacerbated myocardial inflammation and cardiac dysfunction were associated with endotoxemia-caused further reduction of lower myocardial Klotho level in old mice. Recombinant IL-37 promoted inflammation resolution and cardiac functional recovery in old mice. Interestingly, recombinant IL-37 markedly up-regulated myocardial Klotho levels in old mice with or without endotoxemia. Similarly, recombinant Klotho suppressed myocardial inflammatory response and promoted inflammation resolution in old endotoxemic mice, leading to complete recovery of cardiac function by 96 h.

Conclusion

Myocardial Klotho insufficiency in old endotoxemic mice exacerbates myocardial inflammatory response, impairs inflammation resolution and thereby hinders cardiac functional recovery. IL-37 is capable of up-regulating myocardial Klotho expression to improve cardiac functional recovery in old endotoxemic mice.

Early diabetic kidney disease: Focus on the glycocalyx

The incidence of diabetic kidney disease (DKD) is sharply increasing worldwide. Microalbuminuria is the primary clinical marker used to identify DKD, and its initiating step in diabetes is glomerular endothelial cell dysfunction, particularly glycocalyx impairment. The glycocalyx found on the surface of glomerular endothelial cells, is a dynamic hydrated layer structure composed of pro-teoglycans, glycoproteins, and some adsorbed soluble components. It reinforces the negative charge barrier, transduces the shear stress, and mediates the interaction of blood corpuscles and podocytes with endothelial cells. In the high-glucose environment of diabetes, excessive reactive oxygen species and proinflammatory cytokines can damage the endothelial glycocalyx (EG) both directly and indirectly, which induces the production of microalbuminuria. Further research is required to elucidate the role of the podocyte glycocalyx, which may, together with endothelial cells, form a line of defense against albumin filtration. Interestingly, recent research has confirmed that the negative charge barrier function of the glycocalyx found in the glomerular basement membrane and its repulsion effect on albumin is limited. Therefore, to improve the early diagnosis and treatment of DKD, the potential mechanisms of EG degradation must be analyzed and more responsive and controllable targets must be explored. The content of this review will provide insights for future research.

Nephroprotective and nephrotoxic effects of Rhubarb and their molecular mechanisms

Rhubarb, in the form of a traditional Chinese medicine, is used in the treatment of chronic kidney disease (CKD). Previous studies have demonstrated that Rhubarb possesses a good nephroprotective effect, which primarily protects the kidneys from fibrosis, oxidation, inflammation, autophagy, and apoptosis. However, studies have shown that the long-term inappropriate use of Rhubarb may cause damage to renal function. Therefore, how to correctly understand and scientifically evaluate the pharmacodynamics and toxicity of Rhubarb with regard to CKD is a scientific question that urgently needs to be answered. In this review, we explain and illustrate how Rhubarb exerts its nephroprotective effect against CKD. We also describe the mechanisms of action that may cause its nephrotoxicity. Valuable and practical clinical guidance is proposed with regard to methods for mitigating the nephrotoxicity of Rhubarb.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

Repurposing drugs for highly prevalent diseases: pentoxifylline, an old drug and a new opportunity for diabetic kidney disease

Diabetic kidney disease is one of the most frequent complications in patients with diabetes and constitutes a major cause of end-stage kidney disease. The prevalence of diabetic kidney disease continues to increase as a result of the growing epidemic of diabetes and obesity. Therefore, there is mounting urgency to design and optimize novel strategies and drugs that delay the progression of this pathology and contain this trend. The new approaches should go beyond the current therapy focussed on the control of traditional risk factors such as hyperglycaemia and hypertension. In this scenario, drug repurposing constitutes an economic and feasible approach based on the discovery of useful activities for old drugs. Pentoxifylline is a nonselective phosphodiesterase inhibitor currently indicated for peripheral artery disease. Clinical trials and meta-analyses have shown renoprotection secondary to anti-inflammatory and antifibrotic effects in diabetic patients treated with this old known drug, which makes pentoxifylline a candidate for repurposing in diabetic kidney disease.

Neuroprotective action of α-Klotho against LPS-activated glia conditioned medium in primary neuronal culture

The α-Klotho is an anti-aging protein that, when overexpressed, extends the life span in humans and mice. It has an anti-inflammatory and protective action on renal cells by inhibiting NF-κB activation and production of inflammatory cytokines in response to TNF-α. Furthermore, studies have shown the neuroprotective effect of α-Klotho against neuroinflammation on different conditions, such as aging, animal models of neurodegenerative diseases, and ischemic brain injury. This work aimed to evaluate the effects of α-Klotho protein on primary glial cell culture against the proinflammatory challenge with LPS and how this could interfere with neuronal health. Cortical mixed glial cells and purified astrocytes were pretreated with α- α-Klotho and stimulated with LPS followed by TNFα, IL-1β, IL-6, IFN-γ levels, and NF-κB activity analysis. Conditioned medium from cortical mixed glia culture treated with LPS (glia conditioned medium (GCM) was used to induce neuronal death of primary cortical neuronal culture and evaluate if GCM-KL (medium from glia culture pretreated α-Klotho followed by LPS stimulation) or GCM + LPS in the presence of KL can reverse the effect. LPS treatment in glial cells induced an increase in proinflammatory mediators such as TNF-α, IL-1β, IL-6, and IFN-γ, and activation of astrocyte NF-κB. GCM treated-cortical neuronal culture induced a concentration-dependent neuronal death. Pretreatment with α-Klotho decreased TNF-α and IL-6 production, reverted NF-κB activation, and decreased neuronal death induced by GCM. In addition, KL incubation together with GCM + LPS completely reverts the neuronal toxicity induced by low concentration of GCM-LPS. These data suggest an anti-inflammatory and neuroprotective effect of α-Klotho protein in the CNS. This work demonstrated the therapeutic potential of α-Klotho in pathological processes which involves a neuroinflammatory component.

Serum Levels of α-Klotho, Inflammation-Related Cytokines, and Mortality in Hemodialysis Patients

It has been hypothesized that α-Klotho deficiency might contribute to chronic inflammation in patients with end-stage renal disease (ESRD), especially those on hemodialysis (HD). Serum Klotho levels by some authors are considered a potential predictor of cerebrovascular events. Therefore, we analyzed serum levels of α-Klotho with ELISA and inflammation-related cytokines in HD patients. Sixty-seven HD patients and 19 healthy people were recruited between November 2017 and June 2021. A Cytometric Bead Array (CBA) was used to determine the level of different cytokines: IL-12p70, TNF, IL-10, IL-6, IL-1β, and IL-8. A human Klotho ELISA kit was used to determine the level of α-Klotho in the plasma samples of HD patients. There was no difference in serum levels of α-Klotho between HD patients and healthy people. Patients had increased serum IL-6 and IL-8. Significant positive correlations existed between the concentration of α-Klotho and the serum concentrations of IL-12p70, IL-10, and IL-1β. However, in a multivariable linear regression analysis, only patients' age was associated independently with α-Klotho level. Serum α-Klotho was not associated with higher mortality risk in HD patients. While these results draw attention to potential relationships between α-Klotho proteins and inflammatory markers in HD patients, our cross-sectional study could not confirm the pathogenic link between α-Klotho, inflammation, and cardiovascular mortality.

Targeting Immune Senescence in Atherosclerosis

Atherosclerosis is one of the main underlying causes of cardiovascular diseases (CVD). It is associated with chronic inflammation and intimal thickening as well as the involvement of multiple cell types including immune cells. The engagement of innate or adaptive immune response has either athero-protective or atherogenic properties in exacerbating or alleviating atherosclerosis. In atherosclerosis, the mechanism of action of immune cells, particularly monocytes, macrophages, dendritic cells, and B- and T-lymphocytes have been discussed. Immuno-senescence is associated with aging, viral infections, genetic predispositions, and hyperlipidemia, which contribute to atherosclerosis. Immune senescent cells secrete SASP that delays or accelerates atherosclerosis plaque growth and associated pathologies such as aneurysms and coronary artery disease. Senescent cells undergo cell cycle arrest, morphological changes, and phenotypic changes in terms of their abundances and secretome profile including cytokines, chemokines, matrix metalloproteases (MMPs) and Toll-like receptors (TLRs) expressions. The senescence markers are used in therapeutics and currently, senolytics represent one of the emerging treatments where specific targets and clearance of senescent cells are being considered as therapy targets for the prevention or treatment of atherosclerosis.

The association between serum soluble Klotho and chronic kidney disease among us adults ages 40 to 79 years: Cross-sectional study

Background

Chronic kidney disease (CKD) is diagnosed in more than 26 million U.S. people, which increases the risk of many adverse events. α-Klotho was reported to have potential effects on kidney function. The purpose of this study was to investigated whether CKD prevalence is associated with α-Klotho levels in the U.S. people aged 40-79 years.

Methods

Thirteen thousand five hundred eighty-nine participates in the National Health and Nutrition Examination Survey 2007-2016 aged 40-79 with information of Klotho and kidney function were included. The association between CKD and Klotho was calculated using multivariate linear or logistic regression models with adjustment of several possibly confounding variables. Subgroup analyses stratified by age, BMI, and diabetes mellitus were conducted. The non-linear relationship between Klotho and dependent variables with a non-normality of residues was assessed using smooth curve fitting and the segmented regression (also known as piece-wise regression) models.

Results

Among 13,589 participants, the median of Klotho levels was 803.10 pg/mL, mean eGFR of all participants was 86.96 (SD = 19.88) mL/min/1.73 m2, and CKD was diagnosed in 20.11% of them (N = 2733). In the fully adjusted model, eGFR was positively associated with Klotho (β = 5.14, 95%CI 4.13-6.15, p < 0.001), while CKD was negatively associated with Klotho (stage ≧ 1, OR = 0.62, 95% CI 0.50-0.76, p < 0.001; stage ≧ 3, OR = 0.31, 95% CI 0.24-0.41, p < 0.001). The non-linear relationship showed that occurrence of CKD stage> 1 and albuminuria were negatively associated with Klotho when Klotho smaller than turning point (for whether CKD stage> 1, turning point K = 6.85, Klotho < K, OR = 0.44, p < 0.001; for albuminuria, turning point K = 6.84, Klotho < K, OR = 0.59, p < 0.001).

Conclusion

Serum soluble Klotho levels were positively associated with eGFR and negatively associated with the prevalence of CKD, especially in elderly, obese, and diabetic patients.

Research Progress on the Positive and Negative Regulatory Effects of Rhein on the Kidney: A Review of Its Molecular Targets

Currently, both acute kidney injury (AKI) and chronic kidney disease (CKD) are considered to be the leading public health problems with gradually increasing incidence rates around the world. Rhein is a monomeric component of anthraquinone isolated from rhubarb, a traditional Chinese medicine. It has anti-inflammation, anti-oxidation, anti-apoptosis, anti-bacterial and other pharmacological activities, as well as a renal protective effects. Rhein exerts its nephroprotective effects mainly through decreasing hypoglycemic and hypolipidemic, playing anti-inflammatory, antioxidant and anti-fibrotic effects and regulating drug-transporters. However, the latest studies show that rhein also has potential kidney toxicity in case of large dosages and long use times. The present review highlights rhein's molecular targets and its different effects on the kidney based on the available literature and clarifies that rhein regulates the function of the kidney in a positive and negative way. It will be helpful to conduct further studies on how to make full use of rhein in the kidney and to avoid kidney damage so as to make it an effective kidney protection drug.

KL-FGF23-VD Axis in Improving Late-Onset Alzheimer's Disease by Modulating IKK/NF-κB Signal Pathway

Materials and Methods

LOAD rats and Aβ microglia were constructed by using Aβ 1-40 and IBO mixture. The effect of KL-FGF23-VD axis on LOAD was investigated by transfecting overexpressing and interfering with KL gene adenovirus, and IKK-16 was added to Aβ microglia to explore the effect of KL-FGF23-VD axis on regulation of IKK/NF-κB signaling pathway.

Results

The results showed that, in KL-OE group, FGF23 was decreased in the hippocampus of LOAD rats compared with control and KL-si, and the trend was opposite in the KL-si group. The KL-FGF23-VD axis can alleviate inflammatory response, reduce the deposition of Aβ, and inhibit activation of the NF-κB pathway and neuron apoptosis in brain tissue of LOAD rats. In Aβ microglia, the expression of KL-FGF23-VD axis was consistent with animal experiments. The KL-FGF23-VD axis can inhibit the expression of Aβ microglia inflammatory factors and the activation of microglia and NF-κB pathway. Meanwhile, IKK expression was decreased in KL-OE group compared with KL-si and Control. In the IKK-16 addition group, the ability of KL-FGF23-VD axis to inhibit the activation of microglia and NF-κB pathway was enhanced.

Conclusions

These findings suggest a potential role of the KL-FGF23-VD axis in AD treatment by regulating the IKK/NF-κB pathway.

Klotho-derived peptide 6 ameliorates diabetic kidney disease by targeting Wnt/β-catenin signaling

Diabetic kidney disease (DKD) is one of the most common and devastating complications of diabetic mellitus, and its prevalence is rising worldwide. Klotho, an anti-aging protein, is kidney protective in DKD. However, its large size, prohibitive cost and structural complexity hamper its potential utility in clinics. Here we report that Klotho-derived peptide 6 (KP6) mimics Klotho function and ameliorates DKD. In either an accelerated model of DKD induced by streptozotocin and advanced oxidation protein products in unilateral nephrectomized mice or db/db mice genetically prone to diabetes, chronic infusion of KP6 reversed established proteinuria, attenuated glomerular hypertrophy, mitigated podocyte damage, and ameliorated glomerulosclerosis and interstitial fibrotic lesions, but did not affect serum phosphorus and calcium levels. KP6 inhibited β-catenin activation in vivo and blocked the expression of its downstream target genes in glomerular podocytes and tubular epithelial cells. In vitro, KP6 prevented podocyte injury and inhibited β-catenin activation induced by high glucose without affecting Wnt expression. Co-immunoprecipitation revealed that KP6 bound to Wnt ligands and disrupted the engagement of Wnts with low density lipoprotein receptor-related protein 6, thereby interrupting Wnt/β-catenin signaling. Mutated KP6 with a scrambled amino acid sequence failed to bind Wnts and did not alleviate DKD in db/db mice. Thus, our studies identified KP6 as a novel Klotho-derived peptide that ameliorated DKD by blocking Wnt/β-catenin. Hence, our findings also suggest a new therapeutic strategy for the treatment of patients with DKD.

Pathobiology of the Klotho Antiaging Protein and Therapeutic Considerations

The α-Klotho protein (henceforth denoted Klotho) has antiaging properties, as first observed in mice homozygous for a hypomorphic Klotho gene (kl/kl). These mice have a shortened lifespan, stunted growth, renal disease, hyperphosphatemia, hypercalcemia, vascular calcification, cardiac hypertrophy, hypertension, pulmonary disease, cognitive impairment, multi-organ atrophy and fibrosis. Overexpression of Klotho has opposite effects, extending lifespan. In humans, Klotho levels decline with age, chronic kidney disease, diabetes, Alzheimer’s disease and other conditions. Low Klotho levels correlate with an increase in the death rate from all causes. Klotho acts either as an obligate coreceptor for fibroblast growth factor 23 (FGF23), or as a soluble pleiotropic endocrine hormone (s-Klotho). It is mainly produced in the kidneys, but also in the brain, pancreas and other tissues. On renal tubular-cell membranes, it associates with FGF receptors to bind FGF23. Produced in bones, FGF23 regulates renal excretion of phosphate (phosphaturic effect) and vitamin D metabolism. Lack of Klotho or FGF23 results in hyperphosphatemia and hypervitaminosis D. With age, human renal function often deteriorates, lowering Klotho levels. This appears to promote age-related pathology. Remarkably, Klotho inhibits four pathways that have been linked to aging in various ways: Transforming growth factor β (TGF-β), insulin-like growth factor 1 (IGF-1), Wnt and NF-κB. These can induce cellular senescence, apoptosis, inflammation, immune dysfunction, fibrosis and neoplasia. Furthermore, Klotho increases cell-protective antioxidant enzymes through Nrf2 and FoxO. In accord, preclinical Klotho therapy ameliorated renal, cardiovascular, diabetes-related and neurodegenerative diseases, as well as cancer. s-Klotho protein injection was effective, but requires further investigation. Several drugs enhance circulating Klotho levels, and some cross the blood-brain barrier to potentially act in the brain. In clinical trials, increased Klotho was noted with renin-angiotensin system inhibitors (losartan, valsartan), a statin (fluvastatin), mTOR inhibitors (rapamycin, everolimus), vitamin D and pentoxifylline. In preclinical work, antidiabetic drugs (metformin, GLP-1-based, GABA, PPAR-γ agonists) also enhanced Klotho. Several traditional medicines and/or nutraceuticals increased Klotho in rodents, including astaxanthin, curcumin, ginseng, ligustilide and resveratrol. Notably, exercise and sport activity increased Klotho. This review addresses molecular, physiological and therapeutic aspects of Klotho.

Low Klotho/Fibroblast Growth Factor 23 Ratio Is an Independent Risk Factor for Renal Progression in Chronic Kidney Disease: Finding From KNOW-CKD

Background

We aimed to evaluate soluble Klotho and circulating fibroblast growth factor 23 (FGF23) ratio as a risk factor for renal progression, cardiovascular (CV) events, and mortality in chronic kidney disease (CKD).

Methods

We analyzed 2,099 subjects from a CKD cohort whose soluble Klotho and C-terminal FGF23 levels were measured at enrollment. The Klotho to FGF23 ratio was calculated as Klotho values divided by FGF23 values + 1 (hereinafter called the Klotho/FGF23 ratio). Participants were categorized into quartiles according to Klotho/FGF23 ratio. The primary outcome was renal events, defined as the doubling of serum creatinine, 50% reduction of estimated glomerular filtration rate from the baseline values, or development of end-stage kidney disease. The secondary outcomes consisted of CV events and death. Changes in CV parameters at the time of enrollment and during follow-up according to the Klotho/FGF23 ratio were also examined.

Results

During the follow-up period of 64.0 ± 28.2 months, 735 (35.1%) and 273 (13.0%) subjects developed renal events and composite outcomes of CV events and death, respectively. After adjustment, the first (HR: 1.36; 95% CI: 1.08–1.72, P = 0.010) and second (HR: 1.45; 95% CI: 1.15–1.83, P = 0.002) quartiles with regard to the Klotho/FGF23 ratio showed elevated risk of renal events as compared to the fourth quartile group. There was no significant association between Klotho/FGF23 ratio and the composite outcome of CV events and death. The prevalence of left ventricular hypertrophy and vascular calcification was higher in the low Klotho/FGF23 ratio quartiles at baseline and at the fourth-year follow-up.

Conclusions

Low Klotho/FGF23 ratio was significantly associated with increased renal events in the cohort of Korean predialysis CKD patients.

Sex-specific effects of daily tadalafil on diabetic heart kinetics in RECOGITO, a randomized, double-blind, placebo-controlled trial

Cyclic GMP-phosphodiesterase type 5 (PDE5) inhibition has been shown to counteract maladaptive cardiac changes triggered by diabetes in some but not all studies. We performed a single-center, 20-week, double-blind, randomized, placebo-controlled trial (NCT01803828) to assess sex differences in cardiac remodeling after PDE5 inhibition in patients with diabetic cardiomyopathy. A total of 122 men and women (45 to 80 years) with long-duration (>3 years) and well-controlled type 2 diabetes mellitus (T2DM; HbA1c < 86 mmol/mol) were selected according to echocardiographic signs of cardiac remodeling. Patients were randomly assigned (1:1) to placebo or oral tadalafil (20 mg, once daily). The primary outcome was to evaluate sex differences in cardiac torsion change. Secondary outcomes were changes in cardiovascular, metabolic, immune, and renal function. At 20 weeks, the treatment-by-sex interaction documented an improvement in cardiac torsion (-3.40°, -5.96; -0.84, P = 0.011) and fiber shortening (-1.19%, -2.24; -0.14, P = 0.027) in men but not women. The primary outcome could not be explained by differences in cGMP concentrations or tadalafil pharmacodynamics. In both sexes, tadalafil improved hsa-miR-199-5p expression, biomarkers of cardiovascular remodeling, albuminuria, renal artery resistive index, and circulating Klotho concentrations. Immune cell profiling revealed an improvement in low-grade chronic inflammation: Classic CD14⁺⁺CD16^- monocytes reduced, and Tie2⁺ monocytes increased. Nine patients (14.5%) had minor adverse reactions after tadalafil administration. Continuous PDE5 inhibition could offer a strategy to target cardiorenal complications of T2DM, with sex- and tissue-specific responses. Further studies are needed to confirm Klotho and hsa-miR-199-5p as markers for T2DM complications.

Serum α- Klotho Protein Can Be an Independent Predictive Marker of Oxidative Stress (OS) and Declining Glomerular Function Rate in Chronic Kidney Disease (CKD) Patients

Introduction

Chronic kidney disease (CKD) has been recognized as a global health problem. Progression of CKD to advanced stages is associated with a significant increase in the generation of reactive oxygen species (ROS). An antiaging protein, α-Klotho, is found expressed in the distal convoluted tubules of the kidney where, predominantly, it works to increase calcium absorption and potassium excretion in distal tubule via N-linked glycans. The association of serum α-Klotho with oxidative stress, inflammation, and fibrosis, as seen in CKD, highlights its importance for studying disease prognosis with declining glomerular function rate (GFR).

Material and methods

This was a case-control study consisting of 90 subjects. Fifty diagnosed cases of CKD attending the department of nephrology, SCB Medical College, Cuttack, Odisha, were included, and 40 age and sex-matched healthy volunteers were taken as control. Serum α-Klotho levels were measured using enzyme-linked immunosorbent assay kits. Oxidative stress by estimating the total oxidant load by ferrous oxidation-xylenol orange version 2 (FOX2) method and the total antioxidant capacity of serum by the ferric reducing ability of plasma (FRAP) method. Estimation of the estimated glomerular filtration rate (eGFR) was done using the Cockcroft and Gault equation.

Results

Serum α-Klotho (ng/ml) was found to be 2.59±0.98 in cases as compared to 0.24±0.09 in controls (p< 0.01). The serum total oxidant load (ng/ml) was 1.96±1.01 and 0.05±0.02 in cases and controls, respectively. Serum total antioxidant capacity (µM) was measured as 281.80±78.0 in cases and 862.82±51.86 in controls. (p< 0.01). Serum Klotho has a negative correlation with eGFR in CKD patients (r = -0.065; p = 0.648).

Conclusion

The serum α-Klotho level was significantly higher in CKD patients than in healthy volunteers. Both serum α-Klotho and oxidative stress were negatively correlated with eGFR in CKD patients. Serum α-Klotho can be a suitable biomarker in CKD patients with declining GFR.

AAV-mediated expression of secreted and transmembrane αKlotho isoforms rescues relevant aging hallmarks in senescent SAMP8 mice

Senescence represents a stage in life associated with elevated incidence of morbidity and increased risk of mortality due to the accumulation of molecular alterations and tissue dysfunction, promoting a decrease in the organism's protective systems. Thus, aging presents molecular and biological hallmarks, which include chronic inflammation, epigenetic alterations, neuronal dysfunction, and worsening of physical status. In this context, we explored the AAV9-mediated expression of the two main isoforms of the aging-protective factor Klotho (KL) as a strategy to prevent these general age-related features using the senescence-accelerated mouse prone 8 (SAMP8) model. Both secreted and transmembrane KL isoforms improved cognitive performance, physical state parameters, and different molecular variables associated with aging. Epigenetic landscape was recovered for the analyzed global markers DNA methylation (5-mC), hydroxymethylation (5-hmC), and restoration occurred in the acetylation levels of H3 and H4. Gene expression of pro- and anti-inflammatory mediators in central nervous system such as TNF-α and IL-10, respectively, had improved levels, which were comparable to the senescence-accelerated-mouse resistant 1 (SAMR1) healthy control. Additionally, this improvement in neuroinflammation was supported by changes in the histological markers Iba1, GFAP, and SA β-gal. Furthermore, bone tissue structural variables, especially altered during senescence, recovered in SAMP8 mice to SAMR1 control values after treatment with both KL isoforms. This work presents evidence of the beneficial pleiotropic role of Klotho as an anti-aging therapy as well as new specific functions of the KL isoforms for the epigenetic regulation and aged bone structure alteration in an aging mouse model.

Advances in the Progression and Prognosis Biomarkers of Chronic Kidney Disease

Chronic kidney disease (CKD) is one of the increasingly serious public health concerns worldwide; the global burden of CKD is increasingly due to high morbidity and mortality. At present, there are three key problems in the clinical treatment and management of CKD. First, the current diagnostic indicators, such as proteinuria and serum creatinine, are greatly interfered by the physiological conditions of patients, and the changes in the indicator level are not synchronized with renal damage. Second, the established diagnosis of suspected CKD still depends on biopsy, which is not suitable for contraindication patients, is also traumatic, and is not sensitive to early progression. Finally, the prognosis of CKD is affected by many factors; hence, it is ineviatble to develop effective biomarkers to predict CKD prognosis and improve the prognosis through early intervention. Accurate progression monitoring and prognosis improvement of CKD are extremely significant for improving the clinical treatment and management of CKD and reducing the social burden. Therefore, biomarkers reported in recent years, which could play important roles in accurate progression monitoring and prognosis improvement of CKD, were concluded and highlighted in this review article that aims to provide a reference for both the construction of CKD precision therapy system and the pharmaceutical research and development.

Relationship of Soluble Klotho and Early Stage of Diabetic Nephropathy: A Systematic Review and Meta-Analysis

BACKGROUND

Diabetic nephropathy (DN) is a chronic microvascular complication caused by long-term hyperglycemia in patients with diabetes and an important cause of end-stage renal disease. Although some studies have shown that soluble Klotho(sKlotho) levels of patients with DN are lower than those without DN, in the early stage of patients with DN with normal renal function and albuminuria, the change in sKlotho is still controversial.

AIM

This meta-analysis was conducted to statistically evaluate sKlotho levels in patients with DN.

METHODS

We searched the following electronic databases: Web of Science, Embase, PubMed, Google Scholar, and China National Knowledge Infrastructure (CNKI). The following search terms were used for the title or abstract: "diabetic kidney disease", "diabetic nephropathy", OR "DN" in combination with "Klotho". The meta-analysis results were presented as standardized mean differences (SMDs) with corresponding 95% confidence intervals (CIs).

RESULTS

Fourteen articles were included in the meta-analysis. In our meta-analysis, we found that the sKlotho level in patients with DN was significantly lower than that in patients without DN (SMD: -1.52, 95% CI [-2.24, -0.80]), and it was also significantly lower in the early stage of DN (SMD: -1.65, 95% CI [-2.60, -0.70]).

CONCLUSIONS

This systematic review was the first to evaluate the relationship between sKlotho levels and DN. The sKlotho level was significantly lower in the early stages of DN, indicating that sKlotho might be a new biomarker of DN in the future.

Serum α-KL, a potential early marker of diabetes complications in youth with T1D, is regulated by miRNA 192

Despite the wealth of information on biomarkers of diabetes complications in adults with type 1 diabetes, data in the pediatric population is limited. Diabetic nephropathy (DN), the leading cause of mortality in type 1 diabetes T1D), could be potentially missed in youth, as albuminuria, the current "gold" standard, may be transient and may not reflect permanent renal impairment. Soluble alpha KL has emerged as a potential marker of early diabetic nephropathy. Seventy-nine pediatric patients with type 1 diabetes meeting ISPAD criteria for nephropathy screening were consecutively recruited (90% Caucasian, 51% male, mean age 16.1 ± 3.1 years, duration of T1D 7.2 ± 3.9 years, 2-year average HbA1c 8.0 ± 1.3%, and serum and urine samples were collected for analysis. Serum Klotho (KL) and circulating miRNA levels of select miRNA involved in the pathogenesis of DN were estimated. KL had a strong inverse correlation with diabetes duration and HbA1c, two important risk factors in the development of diabetes complications. Serum miR-192 were negatively associated with KL among children with prolonged duration of diabetes (≥12 years) after adjustment for age and sex. In cell culture, overexpression of miR-192 significantly downregulated KL mRNA and protein levels, and reduced KL levels in the media. miR-192 mimic reduced luciferase activity in a reporter containing the KL 3' UTR (60% compared to controls, p<0.01), and the inhibitor rescued it. Deletion of a potential binding site for miR-192 in the KL 3'UTR completely abolished the effect of miR-192 in the reporter assay, suggesting that KL is a direct target gene of miR-192. Overexpression of miR-192 significantly increased oxidative stress (MDA) and expression of inflammatory and senescence markers IL-6 and p16. Inhibition of miR-192 significantly reduced levels of MDA, IL-6 and p16. In summary, we demonstrate an increase in miR-192 and a decrease in KL levels in children with prolonged duration of T1D. We demonstrate a novel role for miR-192 in directly regulating KL levels, and through that, senescence and oxidative stress, key pathological processes in the development of DN. miR-192 and/or KL levels are altered with severity and duration of diabetes and could serve as early biomarkers for DN.

Inflammation and Oxidative Stress in Chronic Kidney Disease and Dialysis Patients

Significance: Chronic kidney disease (CKD) can be regarded as a burden of lifestyle disease that shares common underpinning features and risk factors with the aging process; it is a complex constituted by several adverse components, including chronic inflammation, oxidative stress, early vascular aging, and cellular senescence. Recent Advances: A systemic approach to tackle CKD, based on mitigating the associated inflammatory, cell stress, and damage processes, has the potential to attenuate the effects of CKD, but it also preempts the development and progression of associated morbidities. In effect, this will enhance health span and compress the period of morbidity. Pharmacological, nutritional, and potentially lifestyle-based interventions are promising therapeutic avenues to achieve such a goal. Critical Issues: In the present review, currents concepts of inflammation and oxidative damage as key patho-mechanisms in CKD are addressed. In particular, potential beneficial but also adverse effects of different systemic interventions in patients with CKD are discussed. Future Directions: Senotherapeutics, the nuclear factor erythroid 2-related factor 2-kelch-like ECH-associated protein 1 (NRF2-KEAP1) signaling pathway, the endocrine klotho axis, inhibitors of the sodium-glucose cotransporter 2 (SGLT2), and live bio-therapeutics have the potential to reduce the burden of CKD and improve quality of life, as well as morbidity and mortality, in this fragile high-risk patient group. Antioxid. Redox Signal. 35, 1426-1448.

The role of FoxO1 and its modulation with small molecules in the development of diabetes mellitus: A review

Diabetes mellitus type 2 (T2D) is one of the metabolic disorders suffered by a global human being. Certain factors, such as lifestyle and heredity, can increase a person's tendency for T2D. Various genes and proteins play a role in the development of insulin resistance and ultimately diabetes in which one central protein that is discussed in this review is FoxO1. In this review, we regard FoxO1 activation as detrimental, promote high plasma glucose level, and induce insulin resistance. Indeed, many contrasting studies arise since FoxO1 is an important protein to alleviate oxidative stress and promote cell survival, for example, also by preventing hyperglycemic-induced cell death. Inter-relation to PPARG, another important protein in metabolism, is also discussed. Ultimately, we discussed contrasting approaches of targeting FoxO1 to combat diabetes mellitus by small molecules.

The correlation between fibroblast growth factor-23 and ESRD patients with hearing impairment

Background

End-stage renal disease (ESRD) patients often experience hearing impairment, resulting in a high rate of disability and a decline in their quality of life. Fibroblast growth factor-23 (FGF23) is a diagnostic biomarker for chronic kidney disease (CKD) and a pathogenic contributor to CKD progression. However, the correlation between FGF23 level and CKD patients with hearing impairment remains elusive. This study aimed to investigate the relationship between the FGF23 and ESRD accompanied with hearing impairment.

Methods

A total of 144 ESRD patients, who were admitted to the First Affiliated Hospital of Kunming Medical University from November to December 2020, were enrolled in this study. Firstly, 144 ESRD patients underwent pure-tone audiometry (PTA). Secondly, it was attempted to randomly select 20 ESRD patients with normal hearing, and 20 ESRD patients with hearing impairment (match ratio, 1:1). Age- and gender-matched healthy people (n = 20) were also recruited as controls group. The expression levels of FGF23 was detected by enzyme-linked immunosorbent assay (ELISA).

Results

The results of pure-tone audiometry showed that the prevalence of hearing impairment in ESRD patients was 80.5%. Male ESRD patients were more likely to develop hearing impairment compared to female patients. The incidence rate of hearing impairment at a high frequency was significantly higher than that at a low frequency (P < 0.01). The serum levels of FGF23, phosphorus, and parathyroid hormone (PTH) in ESRD patients with hearing impairment significantly increased compared with those with normal hearing and healthy controls.

Conclusion

ESRD patients had a higher risk of hearing loss, especially high-frequency hearing impairment. As FGF23 level increased, the risk of hearing loss was also elevated. The hearing impairment in ESRD patients was associated with the degree of kidney injury, and serum FGF23 level.