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

Hypertension modifies the association between serum Klotho and chronic kidney disease in US adults with diabetes: a cross-sectional study of the NHANES 2007-2016

CONTEXT

The association between serum soluble Klotho (sKlotho) and chronic kidney disease (CKD) in individuals with diabetes mellitus (DM) remains controversial, and the influence of hypertension on this association is inconclusive.

OBJECTIVE

This study aims to investigate the joint association of sKlotho and hypertension with CKD prevalence in adults with DM.

METHODS

This cross-sectional study included 3,302 adults with DM from the National Health and Nutrition Examination Survey (2007-2016). Multivariate logistic regression analysis stratified by hypertension was used to assess the association between sKlotho and CKD prevalence. Moreover, the interaction between hypertension and sKlotho on CKD was evaluated.

RESULTS

Among individuals with DM, a significant association between sKlotho levels and CKD prevalence was observed only in those with hypertension. CKD prevalence was significantly lower in individuals with high sKlotho (≥ 806 pg/mL) than in those with low sKlotho (< 806 pg/mL) [adjusted OR = 0.54 (95% CI: 0.41-0.72); p < 0.001]. Moreover, a significant interaction between hypertension and sKlotho on CKD prevalence was observed among adults with DM [Multiplicative scale: OR = 0.65 (95% CI: 0.42-0.99); RERI = -0.80 (95% CI: -1.49 to -0.10); AP = -0.51 (95% CI: -0.90 to -0.12); SI = 0.44 (95% CI: 0.30-0.66)].

CONCLUSIONS

Among DM adults, hypertension modified the association between sKlotho levels and CKD prevalence. Both additive and multiplicative interactions were observed between hypertension and sKlotho levels on CKD. The causalities between hypertension, Klotho, and CKD in diabetic patients need further exploration, and underlying mechanisms warrants elucidation.

Association between serum α-klotho levels and the incidence of diabetic kidney disease and mortality in type 2 diabetes: evidence from a Chinese cohort and the NHANES database

BACKGROUND

The α-klotho is crucial in diabetes and its related complications. This study seeks to explore the link between α-klotho levels and the risk of diabetic kidney disease (DKD) as well as all-cause and cardiovascular mortality among individuals with type 2 diabetes mellitus (T2DM).

METHODS

The investigation involved 126 Chinese T2DM patients and 4,451 individuals from the National Health and Nutrition Examination Survey (NHANES) database. To evaluate the relationship between α-klotho levels and DKD risk, multivariate logistic regression was utilized. Additionally, restricted cubic spline (RCS) regression analysis was conducted to examine the nonlinear relationship between α-klotho levels and DKD incidence. RCS analysis was employed to explore the correlation between α-klotho and both all-cause and cardiovascular mortality.

RESULTS

In the Chinese cohort, α-klotho levels were notably elevated in T2DM group compared to DKD group. The NHANES data revealed a significant inverse relationship between α-klotho levels and DKD risk. Nonlinear analysis further illustrated a substantial nonlinear connection between α-klotho levels and DKD risk. Serum α-klotho levels below 880.78 pg/mL were linked to increased DKD risk in T2DM patients. When compared to the T2DM group, the DKD group had markedly higher all-cause and cardiovascular mortality rates, with the α-klotho low group (e.g., Q1) exhibiting lower survival compared to other groups. Cox regression findings indicated that elevated α-klotho levels could mitigate all-cause mortality in T2DM patients. The relationship between α-klotho levels and all-cause mortality was also nonlinear, with the minimal risk found at α-klotho levels between 776.95 pg/mL and 812.69 pg/mL, varying by gender.

CONCLUSION

There exists a notable association between α-klotho levels and DKD risk, along with mortality in T2DM patients, with varying effects based on gender. These results highlight the potential importance of α-klotho as both a biomarker and a therapeutic target.

Association between composite dietary antioxidant index and increased urinary albumin excretion: a population-based study

Introduction

The Albumin-Creatinine Ratio (ACR) is a key biomarker for early kidney disease detection and is predictive of chronic kidney disease (CKD) progression and associated cardiovascular risks. Antioxidant diets, indicated by the Composite Dietary Antioxidant Index (CDAI), may reduce oxidative stress and alter albumin urinary excretion rates. This study explores the relationship between CDAI and albuminuria.

Materials and methods

Data on intake of vitamins A, C, E, zinc, selenium, and beta-carotene from the NHANES database (2007-2018) were used to compute CDAI scores. To measure urinary albumin, the ACR levels were assessed. The association between CDAI and ACR was analyzed through multivariate logistic regression, subgroup analysis, and interaction tests, incorporating a generalized additive model (GAM) to evaluate potential non-linear relationships.

Results

A total of 28,601 participants were included with an average CDAI of 0.302 ± 3.895. Those in higher CDAI quartiles showed a reduced likelihood of elevated ACR. The prevalence of increased ACR decreased across the CDAI quartiles from 13.89% in Q1 to 10.11% in Q4. Higher CDAI scores were inversely related to ACR (OR: 0.99, 95% CI: 0.97-1.00), with a significant interaction effect by BMI (p = 0.0048). In males, a distinct L-shaped relationship was noted, with a negative correlation between CDAI and ACR to the left of the inflection point at 0.53 (OR: 0.95, 95% CI: 0.91-0.98).

Conclusion

Increasing CDAI is associated with lower ACR and reduced risk of albuminuria, suggesting that dietary antioxidants may benefit renal and cardiovascular health.

Association Between Serum α-Klotho Levels and Diabetic Kidney Disease Prevalence in Middle-Aged and Elderly US Patients with Diabetes: A Cross-Sectional Study Using NHANES 2007-2016 Data

INTRODUCTION

Diabetic kidney disease (DKD) represents a significant microvascular complication associated with diabetes and serves as a major contributor to end-stage renal disease. While many studies have highlighted the renal protective effects of the anti-aging protein Klotho, the potential link between Klotho and DKD within individuals with diabetes remains a subject of debate, and comprehensive studies utilizing large population-based databases are still needed.

METHODS

This cross-sectional study, which is representative of the national population, examined data from US patients with diabetes aged 40-79 years, collected during the 2007-2016 cycles of the National Health and Nutrition Examination Survey (NHANES). Serum α-Klotho levels were determined using enzyme-linked immunosorbent assay (ELISA) techniques. Given that serum Klorho levels are not normally distributed, our analysis is based on values converted from the natural logarithm of Klotho. To assess the association between Klotho levels and the prevalence of DKD, multivariate regression models were utilized, taking into account potential confounding factors. Furthermore, we applied smooth curve fitting and segmented regression analyses to investigate possible threshold effects and identify inflection points. Subgroup analyses and cross-tests were performed to assess the consistency of associations in the general population.

RESULTS

The investigation included 4490 individuals with diabetes, with an median age of 60.0 years and 48.2% of them being male. Among these participants, 1352 (30.1%) were diagnosed with DKD. The fully adjusted model (model 3) indicated a significant inverse relationship between Klotho levels and DKD prevalence. Statistical analysis showed that in fully adjusted model 3, each 1-unit increase in log-transformed Klotho was associated with a 42% reduction in DKD prevalence [OR 0.58, 95% CI (0.42, 0.80), p = 0.002]. Further analysis using smooth curve fitting revealed a U-shaped relationship between Klotho levels and DKD prevalence, with an inflection point at 6.82 (after natural logarithm conversion).

CONCLUSIONS

This study identified a U-shaped relationship between Klotho levels and the prevalence of DKD in middle-aged and older adults with diabetes in the USA, with an inflection point of 6.82 (after natural logarithm conversion). Prior to this threshold, the relationship between Klotho and DKD prevalence was negatively correlated, while after the inflection point, the relationship became positive. Future studies are recommended to investigate the causal relationship behind this relationship.

The relationship of serum klotho levels and triglyceride glucose index-related indicators

BACKGROUND

Klotho, an anti-aging protein, is linked to energy metabolism. There is limited research on the association of serum klotho and triglyceride glucose (TyG) index-related indicators. Our research aims to investigate the relationship of serum klotho with TyG-BMI (body mass index), TyG-WC (waist circumference), and TyG-WHtR (waist-to-height ratio).

METHODS

From 2007 to 2016, we examined 6,370 participants in the National Health and Nutrition Examination Survey (NHANES). The enzyme-linked immunosorbent assay (ELISA) was utilized to measure serum klotho. We calculated the TyG-BMI, TyG-WC, and TyG-WHtR based on fasting triglycerides, fasting glucose, BMI, WC, and WHtR. Multiple linear regression analysis was used to evaluate the association of serum klotho with TyG-BMI, TyG-WC, and TyG-WHtR. Additionally, generalized additive model (GAM) and smoothing curves were used to evaluate the linear and nonlinear relationships. A piecewise regression model was also utilized to test for threshold effects and determine the breakpoints. Finally, the potential independent associations of serum klotho with TyG-BMI, TyG-WC, and TyG-WHtR were further explored using subgroup analysis.

RESULTS

We observed a statistically significant difference in serum klotho levels across different quartiles of the population. Based on the multiple linear regression analysis, serum klotho levels were negatively associated with TyG-related indicators. There was a nonlinear relationship between the serum klotho and TyG-BMI, TyG-WC, and TyG-WHtR. The segmented regression analysis revealed that the breakpoints of TyG-BMI, TyG-WC, and TyG-WHtR were 5.42, 6.67, and 1.89, respectively. Subgroup analysis showed that TyG-related indicators interacted with gender and diabetes.

CONCLUSIONS

In this study, a negative and nonlinear relationship was identified between serum klotho and TyG-related indicators. Further research is needed to clarify the potential mechanisms that may link serum klotho to TyG-BMI, TyG-WC, and TyG-WHtR.

Lamivudine protects mice from gastric ulcer by activating PGK1 to suppress ferroptosis

Gastric ulcer is a highly prevalent digestive tract disease across the world, which is recurrent and hard to cure, sometimes transforming into gastric cancer if left untreated, posing great threat to human health. To develop new medicines for gastric ulcer, we ran a series of screens with ethanol stress model in GES-1 cells, and we uncovered that lamivudine rescued cells from ethanol toxicity. Then, we confirmed this discovery using the well-established ethanol-induced gastric ulcer model in mice and our findings suggest that lamivudine can directly activate phosphoglycerate kinase 1 (PGK1, EC 2.7.2.3), which binds and stimulates superoxide dismutase 1 (SOD1, EC 1.15.1.1) to inhibit ferroptosis and ultimately improve gastric ulcer. Moreover, AAV-PGK1 exhibited comparable gastroprotective effects to lamivudine. The findings are expected to offer novel therapeutic strategies for gastric ulcer, encompassing both lamivudine and AAV-PGK1.

Klotho exerts protection in chronic kidney disease associated with regulating inflammatory response and lipid metabolism

BACKGROUND

The anti-aging protein Klotho plays a protective role in kidney disease, but its potential as a biomarker for chronic kidney disease (CKD) is controversial. Additionally, the main pathways through which Klotho exerts its effects on CKD remain unclear. Therefore, we used bioinformatics and clinical data analysis to determine its role in CKD.

RESULTS

We analyzed the transcriptomic and clinical data from the Nephroseq v5 database and found that the Klotho gene was mainly expressed in the tubulointerstitium, and its expression was significantly positively correlated with estimated glomerular filtration rate (eGFR) and negatively correlated with blood urea nitrogen (BUN) in CKD. We further found that Klotho gene expression was mainly negatively associated with inflammatory response and positively associated with lipid metabolism in CKD tubulointerstitium by analyzing two large sample-size CKD tubulointerstitial transcriptome datasets. By analyzing 10-year clinical data from the National Health and Nutrition Examination Survey (NHANES) 2007-2016, we also found that Klotho negatively correlated with inflammatory biomarkers and triglyceride and positively correlated with eGFR in the CKD population. Mediation analysis showed that Klotho could improve renal function in the general population by modulating the inflammatory response and lipid metabolism, while in the CKD population, it primarily manifested by mediating the inflammatory response. Restricted cubic spline (RCS) analysis showed that the optimal concentration range for Klotho to exert its biological function was around 1000 pg/ml. Kaplan-Meier curves showed that lower cumulative hazards of all-cause mortality in participants with higher levels of Klotho. We also demonstrated that Klotho could reduce cellular inflammatory response and improve cellular lipid metabolism by establishing an in vitro model similar to CKD.

CONCLUSIONS

Our results suggest that Klotho exerts protection in CKD, which may be mainly related to the regulation of inflammatory response and lipid metabolism, and it can serve as a potential biomarker for CKD.

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.

The Role of Autophagy in Type 2 Diabetic Kidney Disease Management

Diabetic kidney disease (DKD), or diabetic nephropathy (DN), is one of the most prevalent complications of type 2 diabetes mellitus (T2DM) and causes severe burden on the general welfare of T2DM patients around the world. While several new agents have shown promise in treating this condition and potentially halting the progression of the disease, more work is needed to understand the complex regulatory network involved in the disorder. Recent studies have provided new insights into the connection between autophagy, a physiological metabolic process known to maintain cellular homeostasis, and the pathophysiological pathways of DKD. Typically, autophagic activity plays a role in DKD progression mainly by promoting an inflammatory response to tissue damage, while both overactivated and downregulated autophagy worsen disease outcomes in different stages of DKD. This correlation demonstrates the potential of autophagy as a novel therapeutic target for the disease, and also highlights new possibilities for utilizing already available DN-related medications. In this review, we summarize findings on the relationship between autophagy and DKD, and the impact of these results on clinical management strategies.

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

BACKGROUND AND AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Klotho: A new therapeutic target in diabetic retinopathy?

Klotho (Kl) is considered an antiaging gene, mainly for the inhibition of the insulin-like growth factor-1 signaling. Kl exists as full-length transmembrane, which acts as co-receptor for fibroblast growth factor receptor, and in soluble forms (sKl). The sKl may exert pleiotropic effects on organs and tissues by regulating several pathways involved in the pathogenesis of diseases associated with oxidative and inflammatory state. In diabetic Patients, serum levels of Kl are significantly decreased compared to healthy subjects, and are related to duration of diabetes. In diabetic retinopathy (DR), one of the most common microvascular complications of type 2 diabetes, serum Kl levels are negatively correlated with progression of the disease. A lot of evidences showed that Kl regulates several mechanisms involved in maintaining homeostasis and functions of retinal cells, including phagocytosis, calcium signaling, secretion of vascular endothelial growth factor A (VEGF-A), maintenance of redox status, and melanin biosynthesis. Experimental data have been shown that Kl exerts positive effects on several mechanisms involved in onset and progression of DR. In particular, treatment with Kl: (1) Prevents apoptosis induced by oxidative stress in human retinal endothelial cells and in retinal pigment epithelium (RPE) cells; (2) reduces secretion of VEGF-A by RPE cells; and (3) decreases subretinal fibrosis and preserves autophagic activity. Therefore, Kl may become a novel biomarker and a good candidate for the treatment of DR.

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.

Association between serum Klotho levels and the prevalence of diabetes among adults in the United States

BACKGROUND

Diabetes is a critical contributor to the pathogenesis of cardiovascular diseases. Klotho is an anti-aging protein with cardiovascular-renal protective effects. However, the relationship between serum Klotho levels and diabetes remains poorly understood.

OBJECTIVES

This study aimed to investigate the relationship between serum Klotho levels and diabetes in US adults.

METHODS

We analyzed the cross-sectional data obtained from 13751 subjects aged 40-79 years in the National Health and Nutrition Examination Survey (NHANES) (2007-2016). Serum Klotho concentration was measured using an enzyme-linked immunosorbent assay (ELISA) and categorized into four quartiles (Q1-Q4). Multivariate logistic regression and restricted cubic spline (RCS) regression were conducted to explore the association between serum Klotho levels and the prevalence of diabetes.

RESULTS

As compared with quartile 1, serum Klotho levels in quartiles 2-4 yielded odds ratios (OR) (95% CI) of diabetes of 0.96 (0.80-1.15), 0.98 (0.82-1.18), and 1.25 (1.04-1.50), respectively, after covariate adjustment (P for trend = 0.018). The results implied an increased risk of diabetes. The RCS plot showed a U-shaped relationship linking serum Klotho levels with diabetes (P for nonlinearity = 0.003).

CONCLUSIONS

In summary, a nonlinear and positive association was found between serum Klotho levels and the prevalence of diabetes. Further study is needed to verify the causality of this association and elucidate the underlying mechanisms.

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.

Novel biomarkers and therapeutic approaches for diabetic retinopathy and nephropathy: Recent progress and future perspectives

The global burden due to microvascular complications in patients with diabetes mellitus persists and even increases alarmingly, the intervention and management are now encountering many difficulties and challenges. This paper reviews the recent advancement and progress in novel biomarkers, artificial intelligence technology, therapeutic agents and approaches of diabetic retinopathy and nephropathy, providing more insights into the management of microvascular complications.