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

Metformin inhibits subretinal fibrosis by activating Klotho by miR-126-5p

Subretinal fibrosis is a main cause of visual loss in patients with neovascular age-related macular degeneration (nAMD), for whom there has been a lack of effective medication. Metformin can improve inflammation and angiogenesis in eye diseases. This study aimed to investigate the mechanism by which metformin inhibits subretinal fibrosis. A subretinal fibrosis cell model was induced by treating human retinal pigment epithelial cells (ARPE-19) with TGF-β1, a subretinal fibrosis mouse model was induced by a laser, and both cells and mice were treated with metformin. Cell proliferation, migration, and invasion were detected by CCK-8, scratch, and Transwell assays. Western blotting and immunofluorescence were used to evaluate protein expression levels, and RT‒qPCR was used to detect gene expression levels. HE and Masson staining were used to observe the morphological changes in retinal and choroidal tissues. Metformin treatment inhibited the TGF-β1-induced proliferation, migration, invasion and epithelial‒mesenchymal transition (EMT) of ARPE-19 cells and effectively ameliorated laser-induced subretinal fibrosis in mice. Mechanistically, metformin inhibits the expression of miR-126-5p, promotes Klotho synthesis, slows the progression of subretinal fibrosis, and miR-126-5p targets and negatively regulates Klotho. Metformin activates Klotho by inhibiting miR-126-5p, thereby reversing TGF-β1-induced ARPE-19 cell EMT and improving laser-induced subretinal fibrosis in mice.

MiR-556-3p mediated repression of klotho under oxidative stress promotes fibrosis of renal tubular epithelial cells

Chronic kidney disease (CKD) is a global health issue characterized by renal fibrosis, which leads to irreversible tissue damage. Oxidative stress plays a key role in driving the fibrotic processes associated with CKD. This study investigates the roles of oxidative stress, miR-556-3p, and klotho in renal tubular epithelial cells, focusing on their influence on fibrotic pathways. Using human renal tubular epithelial cells HK-2, we conducted various in vitro assays to measure reactive oxygen species (ROS) levels, cell death, viability, and proliferation. Oxidative stress, induced by H2O2 treatment, was found to suppress klotho expression while increasing the expression of fibrotic markers. Overexpression of klotho mitigated these effects, highlighting its protective role against oxidative stress-induced fibrosis. Moreover, miR-556-3p was upregulated in response to oxidative stress activated transcription factor Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2), contributing to the suppression of klotho. Inhibition of Nrf2, a key regulator of oxidative stress responses, attenuated the expression of miR-556-3p and fibrotic markers. Targeting the Nrf2-miR-556-3p-klotho axis may offer novel therapeutic avenues to restore klotho levels and attenuate renal fibrosis. Our study contributes significantly to the understanding of the molecular mechanisms driving CKD progression and highlights potential targets for future pharmacological intervention.

Association of serum Klotho and fibroblast growth factor-23 levels with vascular calcification severity in patients with chronic kidney disease: an observational cohort study

PURPOSE

In patients with chronic kidney disease (CKD), vascular calcification (VC) is common and influences patient's outcome and prognosis. However, evaluation methods for VC severity are limited. Klotho and fibroblast growth factor-23 (FGF-23) are biomarkers associating with VC development. This study aimed to explore the association of serum Klotho and FGF-23 levels with VC severity in patients with non-dialysis CKD.

METHODS

Patients with non-dialysis CKD were enrolled during hospitalization and were divided into the following four groups on the basis of their coronary artery calcification (CAC) scores: non-VC (CAC scores = 0), mild VC (0 < CAC scores ≤ 100), moderate VC (100 < CAC scores ≤ 400), and severe VC groups (CAC scores > 400). Serum Klotho and FGF-23 levels among the different groups were compared.

RESULTS

A total of 154 non-dialysis CKD patients were enrolled. Correlation analysis showed that serum FGF-23 level (rho = 0.185, p = 0.022) was positively correlated with VC severity, whereas serum Klotho level (rho =  -  0.196, p = 0.015) was negatively correlated with VC severity in patients with CKD. Multivariable regression analysis showed that Klotho level [odd ratio (OR) = 0.998, 95% confidence interval (CI) 0.996-0.999, p = 0.001] served as a protective factor for VC severity in patients with CKD, whereas FGF-23 level (OR = 1.005, 95% CI 1.001-1.009, p = 0.020) was identified as risk factor for VC severity.

CONCLUSION

Serum Klotho and FGF-23 levels are potential predictors of VC severity in patients with non-dialysis CKD.

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.

A PDE1 inhibitor, vinpocetine, ameliorates epithelial-mesenchymal transition and renal fibrosis in adenine-induced chronic kidney injury in rats by targeting the DNMT1/Klotho/β-catenin/Snail 1 and MMP-7 pathways

Tubulointerstitial fibrosis (TIF) is present with chronic kidney disease (CKD). Vinpocetine (Vinpo) is used for treating cerebrovascular deficits, exhibiting some kidney-beneficial effects; however, its role in TIF is uncertain. So, the aim of this study was to investigate its potential impact on adenine-induced fibrotic CKD and explore the underlying mechanistic aspects. Eighteen male Wistar rats were categorized into three groups (n = 6 each). Group I was kept as controls and given saline; group II received adenine (300 mg/kg, twice weekly, i.p.) for induction of the CKD model; and group III was administered Vinpo (20 mg/kg/d, orally) concurrently with adenine. All treatments were administered for 4 weeks. Vinpo revealed an improvement in renal function and an alleviation of inflammation triggered by adenine via diminishing serum tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) levels. Further, Vinpo repressed the epithelial-mesenchymal transition (EMT) with preserved E-cadherin mRNA expression and lowered gene and immune expression of fibronectin and vimentin, respectively, besides attenuating the elevated G2/M arrest-related molecules (renal Ki67 protein contents and p21 gene expression). Renal pathological alterations caused by adenine were attenuated upon Vinpo administration. Interestingly, Vinpo suppressed abnormal renal β-catenin immunoreactivity, Snail 1, and MMP-7 gene expression while simultaneously restored Klotho protein expression by downregulating DNA methyltransferase 1 enzyme (DNMT1) protein expression in the kidney. These data indicated that Vinpo effectively mitigated EMT and G2/M arrest-induced renal fibrosis in adenine-induced CKD rats by targeting DNMT1-associated Klotho suppression, subsequently inhibiting β-catenin and its fibrotic downstream genes.

Mechanisms, Biomarkers, and Treatment Approaches for Diabetic Kidney Disease: Current Insights and Future Perspectives

Diabetic Kidney Disease (DKD) is the leading cause of end-stage renal disease (ESRD) worldwide. Among individuals with type 1 diabetes mellitus (T1DM), 30-40% are at risk of developing DKD. This review focuses on the mechanistic processes, available and emerging biomarkers for diagnosing, monitoring, and preventing DKD, as well as treatment options targeted at DKD patients. A literature search was conducted on PubMed and Scopus using specific keywords. Inclusion and exclusion criteria were applied to select the articles used for this review. The literature highlights various mechanisms involved in the progression of DKD to more severe stages. Additionally, several biomarkers have been identified, which aid in diagnosing and monitoring the disease. Furthermore, numerous treatment approaches are being explored to address the underlying causes of DKD. Advanced research is exploring new medications to aid in DKD remission; sodium-glucose cotransport (SGLT2) inhibitors and finerenone, in particular, are gaining attention for their novel renoprotective effects. DKD is a major complication of diabetes, marked by complex and multifactorial mechanisms. Thus, understanding these processes is essential for developing targeted therapies to potentially reverse DKD progression. Biomarkers show promise for early diagnosis and monitoring of disease progression, while current treatment strategies underscore the importance of a multifaceted approach.

Global research hotspots and trends in oxidative stress-related diabetic nephropathy: a bibliometric study

Background

Oxidative stress is widely acknowledged as a key pathogenic mechanism in diabetic nephropathy (DN). In recent years, the role of oxidative stress in DN has garnered increasing attention. However, no bibliometric analysis has yet been conducted on the relationship between oxidative stress and DN. This study aims to systematically analyze the relevant literature, identify trends in research, assess current hotspots, and predict future directions.

Methods

We retrieved literature related to oxidative stress and DN from the Web of Science Core Collection database. We analyzed data on publication volume, countries/regions, institutions, journals, keywords, and other relevant metrics using VOSviewer, the Bibliometrix R package, and CiteSpace.

Results

From 2014 to 2024, a total of 4076 publications related to oxidative stress and DN were published across 755 journals, showing a consistent upward trend each year. China and the United States are the leading contributors in this field and demonstrate close collaborative efforts. The top contributors by country, institution, journal, and author include: China (1919 publications), Jilin University and Central South University (69 publications each), BIOMEDICINE & PHARMACOTHERAPY (117 publications), and Prof. Sun Lin (33 publications). The most frequent keyword is "oxidative stress" (3683 occurrences). In the co-citation analysis, Alicic RZ's 2017 study was the most cited (144 citations). These findings highlight the critical importance of investigating the pathogenesis of DN from the oxidative stress perspective.

Conclusion

This study demonstrates a steady increase in research on oxidative stress in DN since 2014, highlighting its central role in the pathogenesis of DN. Future research should focus on the molecular mechanisms of oxidative stress in DN and explore its therapeutic potential, to provide new strategies for the prevention and treatment of DN.

Unveiling the Emerging Role of Klotho: A Comprehensive Narrative Review of an Anti-aging Factor in Human Fertility

Klotho, an anti-aging protein, plays a vital role in diverse biological functions, such as regulating calcium and vitamin D levels, preventing chronic fibrosis, acting as an antioxidant and anti-inflammatory agent, safeguarding against cardiovascular and neurodegenerative conditions, as well as exerting anti-apoptotic, anti-senescence effects. Additionally, it contributes to metabolic processes associated with diabetes and exhibits anti-cancer properties. This protein is commonly expressed in organs, such as kidneys, brain, pancreas, parathyroid glands, ovaries, and testes. Recent research has highlighted its significance in human fertility. This narrative review provides insight into the involvement of Klotho protein in male and female fertility, as well as its potential role in managing human infertility in the future. In this study, a search was conducted on literature spanning from November 1997 to June 2024 across multiple databases, including PUBMED, SCOPUS, and Google Scholar, focusing on Klotho proteins. The search utilized keywords, such as "discovery of Klotho proteins," "Biological functions of Klotho," "Klotho in female fertility," "Klotho and PCOS," "Klotho and cryopreservation," and "Klotho in male infertility." Inclusion criteria comprised full-length original or review articles, as well as abstracts, discussing the role of Klotho protein in human fertility, published in English in various peer-reviewed journals. Exclusion criteria involved articles published in languages other than English. Hence, due to its anti-aging characteristics, Klotho protein presents potential roles in male and female fertility and holds promising prospects for reproductive medicine. Further, it holds the potential to become a valuable asset in addressing infertility concerns for both males and females.

Inverse association between serum klotho levels and C-reactive protein levels in the US population: a cross-sectional study

BACKGROUND

The inverse relationship between serum Klotho levels and systemic inflammation, particularly C-reactive protein (CRP), has been suggested in limited studies. However, the association within a large and diverse population remains underexplored.

METHODS

We conducted a cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES) to investigate the association between serum Klotho levels and CRP among a nationally representative sample of the US population. Multiple linear regression analyses were performed to assess this relationship while adjusting for relevant covariates. Stratified analysis with interaction, restricted cubic splines (RCS) were employed to support the research objectives.

RESULTS

A total of 5901 participants had a mean age of 57.9 ± 11.0 years, with 49.4% of them being male and 50.6% of them being female. A negative association between serum Klotho and CRP was revealed in the fully adjusted model (β -0.26; 95% CI -0.41∼-0.11). When serum Klotho was taken as quartiles with Q1 as reference, the adjusted β that were lowest in Q4 were - 0.1 (95% CI -0.16∼-0.04, p-value = 0.002) in model 4, respectively. These statistics were robust in stratified analyses.

CONCLUSION

While our study demonstrates an inverse association between serum Klotho levels and CRP, suggesting a potential cardioprotective role of Klotho, it is important to note that our cross-sectional design does not permit the establishment of causality. Therefore, we cannot definitively conclude that increasing Klotho levels will directly reduce cardiovascular risk. Our findings do, however, highlight the need for further research to explore the potential of Klotho as a therapeutic target for cardiovascular health.

Vitamin D inhibits ferroptosis and mitigates the kidney injury of prediabetic mice by activating the Klotho/p53 signaling pathway

Diabetic nephropathy (DN) is a serious public health problem worldwide, and ferroptosis is deeply involved in the pathogenesis of DN. Prediabetes is a critical period in the prevention and control of diabetes and its complications, in which kidney injury occurs. This study aimed to explore whether ferroptosis would induce kidney injury in prediabetic mice, and whether vitamin D (VD) supplementation is capable of preventing kidney injury by inhibiting ferroptosis, while discussing the potential mechanisms. High-fat diet (HFD) fed KKAy mice and high glucose (HG) treated HK-2 cells were used as experimental subjects in the current study. Our results revealed that serious injury and ferroptosis take place in the kidney tissue of prediabetic mice; furthermore, VD intervention significantly improved the kidney structure and function in prediabetic mice and inhibited ferroptosis, showing ameliorated iron deposition, enhanced antioxidant capability, reduced reactive oxygen species (ROS) and lipid peroxidation accumulation. Meanwhile, VD up-regulated Klotho, solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) expression, and down-regulated p53, transferrin receptor 1 (TFR1) and Acyl-Coenzyme A synthetase long-chain family member 4 (ACSL4) expression. Moreover, we demonstrated that HG-induced ferroptosis is antagonized by treatment of VD and knockdown of Klotho attenuates the protective effect of VD on ferroptosis in vitro. In conclusion, ferroptosis occurs in the kidney of prediabetic mice and VD owns a protective effect on prediabetic kidney injury, possibly by via the Klotho/p53 pathway, thus inhibiting hyperglycemia-induced ferroptosis.

The mechanism and promising therapeutic strategy of diabetic cardiomyopathy dysfunctions: Focus on pyroptosis

Diabetes is a major risk factor for cardiovascular diseases, and myocardial damage caused by hyperglycemia is the main cause of heart failure. However, there is still a lack of systematic understanding of myocardial damage caused by diabetes. At present, we believe that the cellular inflammatory damage caused by hyperglycemia is one of the causes of diabetic cardiomyopathy. Pyroptosis, as a proinflammatory form of cell death, is closely related to the occurrence and development of diabetic cardiomyopathy. Therefore, this paper focuses on the important role of inflammation in the occurrence and development of diabetic cardiomyopathy. From the perspective of pyroptosis, we summarize the pyroptosis of different types of cells in diabetic cardiomyopathy and its related signaling pathways. It also summarizes the treatment of diabetic cardiomyopathy, hoping to provide methods for the prevention and treatment of diabetic cardiomyopathy by inhibiting pyroptosis.

α-Klotho prevents diabetic retinopathy by reversing the senescence of macrophages

BACKGROUND

Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus (DM) and a significant cause of acquired blindness in the working-age population worldwide. Aging is considered as an important risk factor for DR development. Macrophages in aged mice bear typical M2 marker proteins but simultaneously express a pro-inflammatory factor profile. This may explain why the level of intraocular inflammation does not decrease during proliferative diabetic retinopathy (PDR) despite the occurrence of neovascularization and fibrosis (M2 activation). α-Klotho (KL) was originally discovered as a soluble anti-aging factor, which is mainly expressed in kidney tubular epithelium, choroid plexus in the brain and secreted in the blood. However, the role of KL in DR pathophysiology has not been previously reported.

METHODS

Type 1 (streptozotocin [STZ]-induced) and type 2 (a high-fat diet along with a low dose of STZ) diabetic mouse models were established and injected with or without KL adenovirus via the tail vein for 12 weeks. Vldlr-/- mice were injected intravitreally with or without soluble KL protein from P8 to P15. The retinal structure and function were analyzed by electroretinogram and optical coherence tomography. The neovascular lesions were analyzed by retinal flat mount and RPE flat mount. The senescence markers, macrophage morphology, and KL expression levels were detected by immunofluorescence staining. A cell model was constructed using RAW264.7 cells stimulated by 4-hydroxynonenal (4HNE) and transfected with or without KL adenovirus. The senescence-associated secretory phenotypes were detected by qRT-PCR. Senescence was detected by SA-β-Gal staining. Serum, aqueous humor, and vitreous humor KL levels of proliferative diabetic retinopathy (PDR) patients were measured by enzyme-linked immunosorbent assay. Quantitative proteomics and bioinformatics were applied to predict the change of proteins and biological function after overexpression of KL in macrophages. The effects of KL on the HECTD1 binding to IRS1 were analyzed by bioinformatics, molecular docking, and Western Blot.

RESULTS

Serum, aqueous humor, and vitreous humor KL levels were lower in patients with PDR than in those with cataracts. KL relieved the retinal structure damage, improved retina function, and inhibited retinal senescence in diabetic mice. KL administration attenuated the neovascular lesions in VLDLR-/- mice by decreasing the secretion of VEGFA and FGF2 from macrophages. KL also protected RAW264.7 cells from 4HNE-induced senescence. Additionally, it inhibited E3 ubiquitin ligase HECTD1 expression in both diabetic mouse peripheral blood mononuclear cells and 4HNE-treated RAW264.7 cells. KL inhibited HECTD1 binding to IRS1 and reduced the ubiquitination of IRS1.

CONCLUSIONS

Macrophage aging is involved in DM-induced retinopathy. KL alleviates DM-induced retinal macrophage senescence by downregulating HECTD1 and decreasing IRS1 ubiquitination and degradation. Meanwhile, KL administration attenuated the neovascular lesions by altering the activation state of macrophages and decreasing the expression of VEGFA and FGF2.

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.

Relationship between uric acid to high-density cholesterol ratio (UHR) and circulating α-klotho: evidence from NHANES 2007-2016

OBJECTIVE

To investigate the relationship between uric acid to high-density lipoprotein cholesterol ratio (UHR) and circulating α-klotho levels in U.S. adults.

METHODS

A cross-sectional study used data from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. Circulating α-klotho was defined as the dependent variable and UHR was defined as the independent variable. Multivariable linear regression was performed to assess the relationship between the independent and dependent variables. The nonlinear relationship and effect size between UHR and α-klotho were evaluated using smooth curve fitting and threshold effect analysis. Subgroup analysis and sensitivity analysis were conducted to determine the stability of the results. The diagnostic performance of UHR and α-klotho in common elderly diseases was compared using ROC (Receiver Operating Characteristic) analysis.

RESULTS

Among 12,849 participants, there was a negative relationship between the UHR and circulating α-klotho. In the fully adjusted overall model, each unit increase in UHR was associated with a decrease of 4.1 pg/mL in α-klotho. The threshold effect analysis showed that before the inflection point of 8.2, each unit increase in UHR was associated with a decrease of 15.0 pg/mL in α-klotho; beyond the inflection point of 8.2, each unit increase in UHR was associated with a decrease of 2.8 pg/mL in α-klotho. Subgroup analyses and sensitivity analysis indicated that the relationship between UHR and α-klotho remained stable across most populations. The ROC diagnostic test indicated that the evaluative efficacy of UHR in diagnosing age-related diseases was comparable to that of α-klotho.

CONCLUSION

This study revealed that the UHR was associated with the circulating α-klotho concentration, with a negative association observed in most cases. This finding suggested that the UHR might be a promising indicator for evaluating circulating α-klotho levels.

Serum α-Klotho and fibroblast growth factor 23 levels are not associated with non-proliferative diabetic retinopathy in type 1 diabetes mellitus

Diabetic retinopathy is a commonly observed cause of blindness and is a common problem in individuals with diabetes. Recent investigations have showed the capability of serum α-Klotho and FGF 23 in mitigating the effects of diabetic retinopathy. This study aimed to discover the correlation between FGF 23, α-Klotho, and diabetic retinopathy in type 1 diabetics. This case-control study included 63 diabetic patients and 66 healthy controls. Following an overnight duration of fasting, morning blood samples were taken from both the patient and the control groups. The serum concentrations of α-Klotho and FGF 23 were quantified. An experienced ophthalmologist inspected the retinopathy. All participants in this study have moderate non-proliferative retinopathy. A p value under 0.05 was considered statistically significant. The mean α-Klotho level for retinopathic diabetic patients was 501.7 ± 172.2 pg/mL and 579.6 ± 312.1 pg/mL for non-retinopathic diabetic patients. In comparison, α-Klotho level of the control group was 523.2 ± 265.4 pg/mL (p = 0.531). The mean of FGF 23 level did not demonstrate a significant difference (p = 0.259). The mean FGF 23 level were 75.7 ± 14.0 pg/mL, 74.0 ± 14.8 pg/mL and 79.3 ± 14.4 pg/mL in groups, respectively. In conclusion, there was no significant difference in FGF 23 and α-Klotho levels between type 1 diabetics with and without retinopathy when compared to the control group.

Potential application of Klotho as a prognostic biomarker for patients with diabetic kidney disease: a meta-analysis of clinical studies

Background

Diabetic kidney disease (DKD) is a serious diabetic complication and the performance of serum Klotho in DKD's prognostic evaluation is controversial.

Objective

To assess the association of serum Klotho with adverse kidney and non-kidney clinical outcomes in patients with DKD.

Design

Clinical studies regarding the relationship of serum Klotho with DKD were included. Study quality was assessed using the Newcastle-Ottawa scale. Subgroup and sensitive analyses were performed to search for the source of heterogeneity.

Data sources and methods

We comprehensively searched PubMed, Embase, Web of Science, and Cochrane library databases up to 27 September 2022. The associations of Klotho with albuminuria, such as the urinary albumin creatinine ratio (UACR), kidney outcomes such as persistent albuminuria, estimated glomerular filtration rate decline, and non-kidney outcomes such as diabetic retinopathy, cardiovascular morbidity, and mortality, were evaluated. The indicators, such as the correlation coefficient (r), odds ratio (OR), relative risk, and hazard ratio, were retrieved or calculated from the eligible studies.

Results

In all, 17 studies involving 5682 participants fulfilled the inclusion criteria and were included in this meta-analysis. There was no significant association of serum Klotho with UACR in DKD patients [summary r, -0.28 (-0.55, 0.04)] with high heterogeneity. By contrast, a strong association was observed regarding serum Klotho with kidney outcomes [pooled OR, 1.60 (1.15, 2.23)], non-kidney outcomes [pooled OR, 2.78 (2.11, 3.66)], or combined kidney and non-kidney outcomes [pooled OR, 1.96 (1.45, 2.65)] with moderate heterogeneity. Subgroup analysis indicated that age, study design, and the estimated glomerular filtration rate may be the sources of heterogeneity.

Conclusion

A decreased serum Klotho level is possibly associated with an increased risk of developing kidney and non-kidney clinical outcomes in DKD patients; thus, Klotho may be a possible biomarker to predict DKD clinical outcomes. Additional studies are needed to clarify and validate Klotho's prognostic value.