The differential effects of age on the association of KLOTHO gene polymorphisms with coronary artery disease

Association of KLOTHO gene variants with metabolic and renal function parameters in Mexican patients living with type 2 diabetes

Objective

Type 2 diabetes (T2D) and high blood pressure are the main causes of chronic kidney disease (CKD) in adulthood. Both metabolic and oxidative stresses driven by hyperglycemia as well as genetic factors have been suggested as pathogenic causes of renal failure. Some single nucleotide variants (SNVs) on gene coding KLOTHO (KL) have been implicated in several clinical scenarios including hypertension, diabetes, and cardiovascular disease. The aim of this study was to analyze the association of rs1207568 (-395G > A), rs953614 (+ 1062T > G) and rs564481 (+ 1818 C > T) SNVs with metabolic and renal function parameters in Mexican patients living with type 2 diabetes.

Methods

A cross-sectional study was conducted in 637 Mexican patients with T2D, and/or hypertension without previous diagnosis of CKD. Anthropometric, metabolic, and renal function parameters were determined. Patients were genotyped for rs1207568, rs953614 and rs564481 SNVs and associations under a dominant genetic model were analyzed by logistic regression.

Results

For rs9536314, G-allele showed to be protective for hypo-HDL-C, albuminuria, and CKD. Carriers of minor allele of rs564481 had low odds for high glucose levels. No differences in genotype nor allele frequencies between the patients and the reference population were observed.

Conclusion

In Mexican patients living with type 2 diabetes, KL variant rs9536314 was found associated with low odds of hypo-HDL cholesterol, albuminuria and presence of CKD. Meanwhile the consensus of soluble KLOTHO measurement is reached, genetic variants in the KL gene could be considered as genetic markers for CKD susceptibility in patients at high-risk of vascular complications.

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.

Association between Serum Soluble α-Klotho and Urinary Albumin Excretion in Middle-Aged and Older US Adults: NHANES 2007-2016

(1) Background: Preclinical and clinical studies on the anti-aging effect of α-Klotho are emerging. Urinary albumin excretion (UAE) is a well-known biomarker of kidney injury and generalized damage in the cardiovascular system. However, the potential relationship between α-Klotho and UAE is limited and controversial. This study aimed to quantify this relationship in the general middle-aged and elderly population from the National Health and Nutrition Survey (NHANES) 2007-2016. (2) Methods: Serum α-Klotho was measured by enzyme-linked immunosorbent assay. UAE was assessed by the albumin-to-creatinine ratio (ACR). After adjusting for several confounding variables, the relationship between α-Klotho and ACR was analyzed by weighted multivariable logistic regression, subgroup analysis, and interaction tests. A generalized additive model (GAM) with smooth functions using the two-piecewise linear regression model was used to examine the potential nonlinear relationship between α-Klotho and ACR. (3) Results: Among 13,584 participants aged 40-79 years, we observed an independent and significant negative correlation between α-Klotho and ACR (β = -12.22; 95% CI, -23.91, -0.53, p = 0.0448) by multivariable logistic regression analysis, especially in those with age ≥ 60 years, pulse pressure (PP) ≥ 60 mmHg, hypertension or diabetes. We further discovered the nonlinear relationship between α-Klotho and ACR by GAM, revealing the first negative and then positive correlations with an inflection point of 9.91 pg/mL between α-Klotho and ACR. (4) Conclusions: A dose-response relationship between α-Klotho and ACR was demonstrated, and the negative correlation therein indicated that α-Klotho has potential as a serum marker and prophylactic or therapeutic agent despite its metabolic and effective mechanisms needing to be further explored.

A study of the molecular mechanism of quercetin and dasatinib combination as senolytic in alleviating age-related and kidney diseases

Aging is a significant risk factor for the majority of prevalent human illnesses. The chance of having severe chronic conditions grows dramatically with advancing age. Indeed, more than 90% of people over 65 get at least one chronic disease, including diabetes, heart disease, malignancy, memory loss, and kidney disease, whereas more than 70% have two or more of these ailments. Mouse and human aging lead to increased senescent cells and decreased klotho concentrations. Mice lacking the protein α-klotho show faster aging, similar to human aging. α-Klotho upregulation extends life and slows or suppresses the onset of many age-related illnesses and kidney diseases. Like the consequences of α-klotho deficiency, senescent cell accumulation is linked to tissue dysfunction in various organs and multiple age-related kidney diseases. In addition, α-klotho and cell senescence are negatively and presumably mechanistically linked. Earlier research has demonstrated that klotho exerts its protective effects in age-related and kidney disease by interacting with Wnt ligands, serving as an endogenous antagonist of Wnt/β-catenin signaling. In addition, decreasing senescent cell burden with senolytics, a class of drugs that remove senescent cells selectively and extend the life span of mice. In this work, we are studying the molecular mechanism of the combination of quercetin and dasatinib as senolytic in easing age-related chronic renal illness by altering the level of klotho/Wnt/β-catenin. PRACTICAL APPLICATIONS: There is an inverse relationship between the onset and the development of age-related disorders and cellular senescence and Klotho. Earlier attempts to suppress transforming growth factor-beta 1 (TGF-β1) in kidney disease with anti-TGF-β1 antibodies were ineffective, and this should be kept in mind. Senolytic medications may benefit from targeting senescent cells, which enhances the protective factor α-klotho. In addition, our study provides a unique, translationally feasible route for creating orally active small compounds to enhance α-klotho, which may also be a valuable biomarker for age-related kidney disease. Additionally, other aspects of aging can be affected by senolytics, such as limiting age-related mitochondrial dysfunction, lowering inflammation and fibrosis, blunting reactive oxygen species (ROS) generation, decreasing deoxyribonucleic acid (DNA) damage, and reinforcing insulin sensitivity. Senolytic agents have been shown to increase adipose progenitor and cardiac progenitor cell activity in aging animals and animals with cellular senescence-related diseases, such as heart, brain, and kidney disease.

Investigation of Klotho G395A and C1818T Polymorphisms and Their Association with Serum Glucose Level and Risk of Type 2 Diabetes Mellitus

Objective: The objective was to study the association of Klotho gene G395A and C1818T single nucleotide polymorphisms with glycemia, serum, glycosylated hemoglobin (HbA1c) level and the risk of type 2 diabetes mellitus (T2DM) in the Pashtun population of Pakistan. Methods: In this study, 195 normal individuals and 217 T2DM patients were enrolled. All subjects were divided into three groups, namely overall subjects (control + T2DM patients), control individuals and T2DM patients, and their fasting glucose, HbA1c level, lipid profile and C1818T and G395A polymorphisms were determined. Results: The allele frequencies of G395A in overall subjects were 0.568 for A and 0.432 for G. Similarly, allele frequencies for G395A in overall subjects were 0.597 and 0.403 for C and T alleles, respectively. The AA genotype of G395A was observed to be a risk factor for T2DM. In normal individuals, no significant (p > 0.05) association was observed between klotho C1818T and G395A polymorphisms and hyperglycemia. In overall subjects, the C1818T polymorphism was associated (p < 0.05) with high fasting glucose and HbA1c levels in female subjects only. In T2DM patients, both C1818T and G395A polymorphisms were found to be significantly (p < 0.05) associated with high fasting glucose and HbA1c levels both in males and females. Conclusion: The G395A polymorphism was observed to increase the risk of T2DM. Both C1818T and G395 were associated with high fasting glucose and HbA1c levels in T2DM patients.

S-Klotho level and physiological markers of cardiometabolic risk in healthy adult men

S-Klotho is perceived as a biomarker of healthy aging that has been shown to be inversely associated with cardiometabolic risk in elderly individuals. The aim of this study was to test if s-Klotho level is associated with cardiometabolic risk markers in younger healthy men in order to verify the possible role of s-Klotho level as an early marker of cardiometabolic risk. A cross-sectional study was conducted among 186 healthy men (M_age=35.33, SD_age=3.47) from a Western urban population. Serum basal levels of s-Klotho, lipid profile, homocysteine, glycemia markers, C-reactive protein, liver transaminases and creatinine were evaluated. Also, blood pressure was measured and cardiometabolic risk score and homeostatic model assessment for insulin resistance (HOMA-IR) were calculated. Testosterone and cortisol levels, self-reported psychological stress, physical activity, smoking in the past, alcohol use and body adiposity were controlled for. We found no relationship between levels of s-Klotho and physiological markers of cardiometabolic risk in the studied population. The results were similar when controlled for adiposity, testosterone level, physical activity, alcohol use and smoking in the past. We suggest that s-Klotho level is not an early marker of cardiometabolic risk in younger middle-aged healthy men.

Circulating α-klotho regulates metabolism via distinct central and peripheral mechanisms

Emerging evidence implicates the circulating α-klotho protein as a prominent regulator of energy balance and substrate metabolism, with diverse, tissue-specific functions. Despite its well-documented ubiquitous role inhibiting insulin signaling, α-klotho elicits potent antidiabetic and anti-obesogenic effects. α-Klotho facilitates insulin release and promotes β cell health in the pancreas, stimulates lipid oxidation in liver and adipose tissue, attenuates hepatic gluconeogenesis, and increases whole-body energy expenditure. The mechanisms underlying α-klotho's peripheral functions are multifaceted, including hydrolyzing transient receptor potential channels, stimulating integrin β1➔focal adhesion kinase signaling, and activating PPARα via inhibition of insulin-like growth factor receptor 1. Moreover, until recently, potential metabolic roles of α-klotho in the central nervous system remained unexplored; however, a novel α-klotho➔fibroblast growth factor receptor➔PI3kinase signaling axis in the arcuate nucleus of the hypothalamus has been identified as a critical regulator of energy balance and glucose metabolism. Overall, the role of circulating α-klotho in the regulation of metabolism is a new focus of research, but accumulating evidence identifies this protein as an encouraging therapeutic target for Type 1 and 2 Diabetes and obesity. This review analyzes the new literature investigating α-klotho-mediated regulation of metabolism and proposes impactful future directions to progress our understanding of this complex metabolic protein.

The association between Single Nucleotide Polymorphisms of Klotho Gene and Mortality in Elderly Men: The MrOS Sweden Study

The Klotho (KL) gene is involved in phosphate homeostasis. Polymorphisms in this gene have been reported to be associated with the risk of cardiovascular disease. Here we used computational tools to predict the damage-associated single nucleotide polymorphisms (SNPs) in the human KL gene. We further investigated the association of SNPs in the KL gene and mortality in the Swedish multicenter prospective Osteoporotic Fractures in Men (MrOS) cohort. This study included 2921 men (aged 69-81 years) with mean 4.49 ± 1.03 years follow-up. 18 SNPs in the KL gene were genotyped using Sequenom. These SNPs were identified by in silico tools for the coding and noncoding genome to predict the damaging SNPs. After quality analyses, SNPs were analyzed for mortality risk using two steps approach on logistic regression model screening and then Cox regression model confirmation. Two non-synonymous SNPs rs9536314 and rs9527025 were found to be potentially damaging SNPs that affect KL protein stability and expression. However, these two SNPs were not statistically significantly associated with all-cause mortality (crude Hazard ratio [HR] 1.72, 95% confidence interval [CI] 0.96-3.07 in rs9536314; crude HR 1.82, 95% CI 0.998-3.33 in rs9527025) or cardiovascular mortality (crude HR 1.52, 95% CI 0.56-4.14 in rs9536314; crude HR 1.54, 95% CI 0.55-4.33 in rs9527025) in additive model using Cox regression analysis. In conclusion, these two potentially damaging SNPs (rs9536314 and rs9527025) in the KL gene were not associated with all-cause mortality or cardiovascular mortality in MrOs cohort. Larger scales studies and meta-analysis are needed to confirm the correlation between polymorphisms of the KL gene and mortality.

KLOTHO polymorphisms and age-related outcomes in community-dwelling older subjects: The São Paulo Ageing & Health (SPAH) Study

Defective KLOTHO gene expression in mice led to a syndrome resembling human ageing. This study evaluated three KLOTHO polymorphisms, namely G395A, C1818T, and C370S, in an elderly population (mean age of 73 years) and their associations with ageing-related outcomes (cardiovascular events, kidney function, osteoporosis, sarcopenia) and mortality. Estimated glomerular filtration rates (eGFR) was lower in subjects with 1818TT (P = 0.047) and 370SS (P = 0.046) genotypes. The 1818TT genotype (P = 0.006) and 1818T allele were associated with higher frequency of myocardial infarction (MI) (CC:1.7% vs. CT + TT:7.0%; P = 0.002). The 370SS genotype was associated with lower stroke frequency (P = 0.001). MI (OR 3.35 [95% CI: 1.29–8.74]) and stroke (OR 3.64 [95% CI: 1.48–8.97]) were associated with mortality. Regarding MI, logistic regression showed 1818T allele was a risk factor for death-related MI (OR 4.29 [95% CI: 1.60–11.52]; P = 0.003), while 370C was protective (OR 0.03 [95% CI: 0.01–0.08]; P < 0.001). Regarding stroke, the 395A and 370C alleles were protective factors (respectively: OR 0.28 [95% CI: 0.20–0.80]; P = 0.018; OR 0.10 [95% CI: 0.05–0.18]; P < 0.001). This is the first study to determine potential associations between common ageing-related outcomes/mortality and KLOTHO polymorphisms. The 1818T allele was a risk factor for MI-related death. The 395A and 370C alleles were protective factors for stroke-related death in elderly from community.

Klotho: An Elephant in Aging Research

The year 2017 marked the 20th anniversary of the first publication describing Klotho. This single protein was and is remarkable in that its absence in mice conferred an accelerated aging, or progeroid, phenotype with a dramatically shortened life span. On the other hand, genetic overexpression extended both health span and life span by an impressive 30%. Not only has Klotho deficiency been linked to a number of debilitating age-related illnesses but many subsequent reports have lent credence to the idea that Klotho can compress the period of morbidity and extend the life span of both model organisms and humans. This suggests that Klotho functions as an integrator of organ systems, making it both a promising tool for advancing our understanding of the biology of aging and an intriguing target for interventional studies. In this review, we highlight advances in our understanding of Klotho as well as key challenges that have somewhat limited our view, and thus translational potential, of this potent protein.

Klotho and vitamin D in multiple sclerosis: an Italian study

INTRODUCTION

Low vitamin D levels have been recognised as an important risk factor for autoimmune diseases, including multiple sclerosis (MS). MS is a multifactorial disease, the pathogenesis of which contributes both to genetic and environmental factors. Polymorphisms in genes codifying molecules involved in vitamin D homeostasis have been associated with hypovitaminosis D. However, the influence of polymorphisms of Klotho, which codify a protein with a pivotal role in vitamin D metabolism, have never been investigated. The aim of this study was to evaluate the association among genetic variants of Klotho, namely rs1207568 and rs9536314, serum 25(OH)D₃ levels, and multiple sclerosis (both risk and disease progression).

MATERIAL AND METHODS

107 patients with MS and 133 healthy controls were enrolled in this study. Serum 25(OH)D₃ levels and genotyping of Klotho SNPs were evaluated in all participants by high-performance liquid chromatography and real-time polymerase chain reaction, respectively.

RESULTS

Allelic and genotypic frequencies did not differ between patients and controls. Concerning rs1207568, we found a trend toward lower serum 25(OH)D₃ levels in MS patients with A allele (mutant), both in heterozygosis (AG) and in homozygosis (AA), in comparison to MS patients with G allele in homozygosis (GG) (AG + AA 20.5 ±6.3 µg/l; GG 22.5 ±7.5 µg/l, p = 0.07).

CONCLUSIONS

Our findings did not identify a role of Klotho in the genetic susceptibility to MS.

Klotho Protein Reduced the Expression of Matrix Metalloproteinase-1 (MMP-1) and Matrix Metalloproteinase-3 (MMP-3) in Fibroblasts from Patients with Pelvic Organ Prolapse (POP) by Down-Regulating the Phosphorylation of ERK1/2

Background

Pelvic organ prolapse (POP) is due to age-related atrophy and the weakening of the tissues of the pelvic floor, with degradation of collagen and extracellular matrix (ECM) by metalloproteinases (MMPs). This study aimed to investigates the role of the age-related enzyme klotho, encoded by the KL gene, in cultured fibroblasts obtained from patients with POP and the levels of reactive oxygen species (ROS), interleukin-6 (IL-6), and MMPs.

Material/Methods

Pelvic floor fibroblasts were obtained from connective tissue from three patients with POP and three normal subjects. Cell proliferation and ROS production were measured using a cell counting kit-8 (CCK-8) assay and flow cytometry. Levels of interleukin-6 (IL-6), klotho, metalloproteinase-1 (MMP-1), MMP-3, extracellular signal-regulated kinases 1/2 (ERK1/2), and p-ERK1/2 were measured by enzyme-linked immunoassay (ELISA), quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot.

Results

In cultured pelvic floor fibroblasts from patients with POP, the expression of klotho protein and klotho mRNA were significantly down-regulated in fibroblasts from patients with POP compared with normal fibroblasts. Klotho supplementation in cultured fibroblasts for patients with POP included increased cell growth, reduced expression of ROS reduction, and reduced the secretion of IL-6. Using qRT-PCR and Western blot, klotho supplementation of fibroblasts from patients with POP increased cell growth and reduced the levels of IL-6 and ROS in a dose-dependent way.

Conclusions

Klotho protein reduced the expression of MMP-1 and MMP-3 in fibroblasts from patients with POP by down-regulating the phosphorylation of ERK1/2.

Association of klotho gene polymorphism and the regulation of calcium-phosphate metabolism disorders in patients with end-stage renal disease

BACKGROUND

Klotho G-395-A gene polymorphism is associated with several diseases; however, its association with calcium-phosphate metabolism disorders in end-stage renal disease (ESRD) is unknown.

METHODS

A total of 137 patients with ESRD and 80 healthy adults (control) were enrolled in the study. Patients with ESRD were divided into three subgroups: haemodialysis (A1, n = 52), peritoneal dialysis (A2, n = 30), and non-dialysis (A3, n = 55). The klotho G-395-A genotype was detected by TaqMan PCR assay, and ELISA was used to detect the soluble klotho protein (sKL) and fibroblast growth factor (FGF23). Intact parathyroid hormone (iPTH) and other related clinical biochemical parameters were also analyzed for all subjects.

RESULTS

(i) Three genotypes (GG, GA and AA) of KL G-395A were detected, and a significant difference between the ESRD and control groups was observed, (ii) sKL was inversely associated with FGF23 in each subgroup and phosphate and positively associated with calcium in A1 and A3. FGF23 was positively associated with phosphate and inversely associated with calcium in each subgroup, (iii) a statistical difference in levels of sKL and FGF23 was observed between GG and AA, as well as between GA and AA. The expression of sKL was lowest and the level of FGF23 was highest in AA and (iv). GA + AA genotypes and FGF23 were risk factors and sKL might be protective factor of calcium-phosphate metabolism disorders.

CONCLUSION

Soluble klotho protein and FGF23 were associated with the regulation of calcium and phosphate metabolism, and the A allele of the G-395A klotho gene polymorphism could be a risk factor on calcium-phosphate metabolism disorders in patients with ESRD.

Klotho gene polymorphisms are associated with healthy aging and longevity: Evidence from a meta-analysis

Klotho gene polymorphisms have been implicated in healthy aging, but inconsistences in findings from previous case-control studies have raised concerns regarding the associations between KLOTHO gene polymorphisms and susceptibility to aging-related diseases and longevity. Hence, this meta-analysis was performed. We assessed the associations between two polymorphisms (G-395 A/rs1207568 and F352 V/rs9536314) and five parameters (urolithiasis, cognitive impairment, cardiovascular disease, cancer, and longevity) by calculating pooled odds ratios with 95% confidence intervals. According to the pooled results, the G allele of the G-395 A polymorphism conferred a significantly higher risk of urolithiasis; G-395 A was related to the susceptibility to cardiovascular disease under allele, dominant, and recessive models. There was no significant association between the G-395 A polymorphism and cognitive impairment among the elderly. The F allele of the F352 V polymorphism protected against breast and ovarian cancer susceptibility. Interestingly, based on the results of the subgroup analysis, the F352 V polymorphism was associated with the overall risk of neoplasms in BRCA1 mutation carriers but not in BRCA2 mutation carriers. Moreover, the F allele played a protective role in determining human longevity. In conclusion, Klotho G-395 A polymorphisms were associated with urolithiasis and cardiovascular disease but not with cognitive impairment. Additionally, Klotho F352 V polymorphisms were associated with cancers and longevity.

Association of Klotho gene polymorphism with hypertension and coronary artery disease in an Iranian population

Background

Klotho, possibly an age-regulating protein, is considered an important factor contributing to the lifespan and pathophysiology of hypertension and coronary artery disease (CAD). The present study was carried out aiming to investigate the association of Klotho-rs564481 (C1818T) gene polymorphism with hypertension and CAD.

Methods

A total of 286 CAD-suspicious subjects were entered into this case-control study. The polymorphism was investigated in hypertensive patients with no CAD (H-Tens, n = 60); hypertensive patients with CAD (CAD + H-Tens, n = 95); CAD patients with no hypertension (CAD, n = 61); and non-hypertensive non-CAD subjects, which were regarded as the control group (Ctrl, n = 70). Genotype and allele frequencies were assessed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

Results

A significant difference was found in allele frequency of Klotho C1818T among the four research groups (P = 0.03). It was also found that wild-type homozygote subjects were negatively associated with hypertension as compared to heterozygote ones (OR = 0.07 [95% CI: 0.008–0.69] P = 0.02). Moreover, in the subgroups older than 57 years old, dominant genetic model demonstrated a negative association with CAD combined with hypertension (OR = 0.31 [95% CI: 0.10–0.95] P = 0.04).

Conclusions

In conclusion, Klotho C1818T variant may be associated with a decreased risk of hypertension. Moreover, aging enhanced positive effects of the Klotho polymorphism on CAD combined with hypertension, indicating the possibility that the KLOTHO gene might play a part in the age-related occurrence of CAD combined with hypertension.

Growth Hormone (GH) and Cardiovascular System

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

FGF23-αKlotho as a paradigm for a kidney-bone network

The vertebrate endoskeleton is not a mere frame for muscle attachment to facilitate locomotion, but is a massive organ integrated with many physiologic functions including mineral and energy metabolism. Mineral balance is maintained by tightly controlled ion fluxes that are external (intestine and kidney) and internal (between bone and other organs), and are regulated and coordinated by many endocrine signals between these organs. The endocrine fibroblast growth factors (FGFs) and Klotho gene families are complex systems that co-evolved with the endoskeleton. In particular, FGF23 and αKlotho which are primarily derived from bone and kidney respectively, are critical in maintaining mineral metabolism where each of these proteins serving highly diverse roles; abound with many unanswered questions regarding their upstream regulation and downstream functions. Genetic lesions of components of this network produce discreet disturbances in many facets of mineral metabolism. One acquired condition with colossal elevations of FGF23 and suppression of αKlotho is chronic kidney disease where multiple organ dysfunction contributes to the morbidity and mortality. However, the single most important group of derangements that encompasses the largest breadth of complications is mineral metabolism disorders. Mineral metabolic disorders in CKD impact negatively and significantly on the progression of renal disease as well as extra-renal complications. Knowledge of the origin, nature, and impact of phosphate, FGF23, and αKlotho derangements is pivotal to understanding the pathophysiology and treatment of CKD.

Serum Klotho (but not haplotypes) associate with the post-myocardial infarction status of older adults

OBJECTIVES:

The number of deaths from vascular diseases is incredibly high worldwide, and reliable markers for major events are still needed. The current cross-sectional study investigated the association of Klotho haplotypes and Klotho serum levels with classic risk factors and a clinical history of vascular events.

METHODS:

Clinical, anthropometric, biochemical and nutritional assessments were conducted with 168 older adults, complemented by genotyping (rs9536314 and rs9527025) and the detection of serum Klotho (ELISA).

RESULTS:

Klotho levels and haplotypes did not associate with most classic risk factors for vascular events, including markers such as C-reactive protein and homocysteine. A positive association was only found between Klotho levels and the previous occurrence of a myocardial infarction by both correlational (p=0.006) and variance analyses (p<0.001), and these associations were independent of the context.

CONCLUSION:

Our results suggest that serum Klotho is higher in individuals with a clinical history of myocardial infarction but not with a history of coronary artery disease or stroke. None of the Klotho haplotypes were associated with the variables investigated herein.

Relationship between atherosclerosis and knee osteoarthritis as graded by radiography and ultrasonography in females

[Purpose] The aim of this study was to assess the relationship between atherosclerosis and knee osteoarthritis grade in women as assessed by both ultrasonography and radiography. [Subjects and Methods] Seventy women diagnosed with knee osteoarthritis were classified into two groups according to cartilage grading/radiographic grading. Patients with Kellgren-Lawrence grades 1 and 2 were included in group 1, while those with Kellgren-Lawrence grades 3 and 4 were included in group 2. Patients with cartilage grades 1-3 were included in group 1, while those with cartilage grades 4-6 were included in group 2. Patients were clinically assessed using a visual analog scale and the Western Ontario and McMaster Universities Arthritis Index. Radiographic osteoarthritis grade was scored using the Kellgren and Lawrence grading system. Using ultrasonography, symptomatic knees were graded and evaluated for distal femoral cartilage thickness. Carotid intima-media thickness and serum lipid levels were measured to assess atherosclerosis. [Results] Carotid intima-media thickness measurements were higher in group 2 than in group 1 as determined by the Kellgren-Lawrence and cartilage grading systems. Carotid intima-media thickness measurements were positively correlated with both the ultrasonographic cartilage grade and Kellgren-Lawrence. [Conclusion] The results of this study suggest that osteoarthritis as assessed by ultrasonography was successful and comparable to assessment with radiography. We showed a correlation between atherosclerosis and ultrasonographic knee osteoarthritis grade.

Interleukin-18 gene polymorphism and risk of CVD in older patients with type 2 diabetes mellitus

OBJECTIVE

Interleukin-18 (IL-18), a proinflammatory cytokine, plays a key role in the acute and chronic inflammatory processes. It is associated with risk of developing cardiovascular disease (CVD). The aim of this study was to evaluate association between G(-137)C polymorphism (rs187238) in the IL-18 gene and risk of diabetes and CVD in type 2 diabetes patients.

METHODS

We examined 1548 T2DM patients and 590 controls. All subjects were genotyped for the G(-137)C promoter region polymorphism by polymerase chain reaction (PCR-SSP).

RESULTS

Genotype distribution of the G(-137)C polymorphism showed no significant difference between T2DM patients and controls (p=0.115). An association with CVD was analyzed in two age groups: ⩾65 and <65years. In patients younger than 65years there was a tendency to association of CC genotype with CAD (OR 1.87, 95% CI 1.0-3, p=0.051). In contrast, in subjects aged 65 or older, the C allele and CC genotype showed the significant association with the presence of CVD, with the OR 1.99, p=0.001 and OR 5.31, p=0.006, respectively. The C allele carriers showed the higher prevalence of CVD compared to non-carriers (61% vs. 39%, p<0.0001).

CONCLUSION

Older T2DM patients carrying the C allele of IL-18 G(-137)C polymorphism have a significantly increased risk of CVD.

Klotho, the Holy Grail of the kidney: from salt sensitivity to chronic kidney disease

The Klotho gene displays an extremely shortened life span with loss of function missense mutations leading to premature multiple organ failure, thus resembling human premature aging syndromes. The transmembrane form of Klotho protein functions as an obligatory co-receptor for FGF23. Klotho and FGF23 are crucial components for the regulation of vitamin D metabolism and subsequently blood phosphate levels. The secreted Klotho protein has multiple regulatory functions, including effects on electrolyte homeostasis, on growth factor pathways as well as on oxidative stress, which are currently the object of extensive research. Klotho protein deficiency is observed in many experimental and clinical disease models. Genetic polymorphisms such as the G-395A polymorphism in the promoter region of the Klotho gene have been associated with the development of essential hypertension. The kidneys are the primary site of Klotho production, and renal Klotho is decreased in CKD, followed by a reduction in plasma Klotho. Klotho deficiency has been both associated with progression of CKD as well as with its cardinal systemic manifestations, including cardiovascular disease. Thus, Klotho has been suggested both as a risk biomarker for early detection of CKD and additionally as a potential therapeutic tool in the future.

G-395A polymorphism in the promoter region of the KLOTHO gene associates with reduced cognitive impairment among the oldest old

This study aimed to examine the possible association between G-395A polymorphism in the promoter region of the KLOTHO gene and cognitive impairment among Chinese nonagenarians and centenarians. This study is a secondary analysis of the Project of Longevity and Aging in Dujiangyan (PLAD) study. Community-dwelling Chinese people aged 90 years or older were included. G-395A (rs1207568) genotyping in the promoter region of the KLOTHO gene was performed using the TaqMan allelic discrimination assay. Cognitive function was assessed with the mini-mental status examination (MMSE). A total of 706 participants (68.0 % female; mean age 93.5 ± 3.6 years) were included. The KLOTHO G-395A polymorphism genotype frequencies for the whole sample were 2.0 % AA, 30.3 % GA, and 67.7 % GG. The GG genotype frequencies for the cognitive impairment and control groups were 70.2 and 62.7 %, respectively. Cognitive impairment prevalence was significantly lower in the GA+AA group than in the GG genotype group (61.4 vs. 69.0 %, p = 0.044). GA+AA genotype subjects had a significantly lower risk of cognitive impairment (odds ratio 0.66; 95 % confidence interval 0.44 to 0.98) than GG genotype individuals after adjusting for age, gender, and other relevant risk factors. KLOTHO G-395A polymorphism associates with reduced cognitive impairment in a sample of Chinese nonagenarians and centenarians.

Klotho in cardiovascular disease: Current and future perspectives

Protein Klotho, beyond its role as a regulator of the phosphatemia, is also involved in the maintaining of the cardiovascular health, being associated its alterations with the development of cardiovascular damage and increased morbi-mortality. For all this, nowadays Klotho is the subject of a thorough research which is focused on uncover its intimate mechanisms of action, and in analyzing the utility of its modulation as a potential strategy with clinical applicability. Molecular mechanisms of Klotho are not well understood but an emerging research area links Klotho deficiency with vascular pathology. Changes in this protein have been associated with cardiovascular-related complications like inflammation, vascular calcification, and endothelial dysfunction. All this is particularly relevant if considering the recent discovery of Klotho expression in vascular tissue.

Implications of Klotho in vascular health and disease

Cardiovascular disease (CVD) is a prevalent condition in general population and the first cause of death overall. Klotho, a pleiotropic protein related to longevity that acts as a co-receptor of the fibroblast growth factor 23, has been proposed as a key regulator of the development of CVD. In the few clinical studies made, it has been observed a relationship between low levels of soluble Klotho and the occurrence and severity of CVD, as well as a reduction of cardiovascular risk when they are high. Also, different polymorphisms of human Klotho gene have been related to the incidence of cardiovascular events. Moreover, several experimental studies indicate that this protein acts in the maintenance of vascular homeostasis. Klotho improves endothelial dysfunction through promotion of NO production and mediates anti-inflammatory and anti-aging effects such as suppression of adhesion molecules expression, attenuation of nuclear factor-kappa B or inhibition of Wnt signaling. Furthermore, this protein is related to the attenuation of vascular calcification as well as prevention of cardiac hypertrophy. The expression of this protein in the vascular wall implies a new scenario for the treatment of vascular disorders. The purpose of this review is to provide an overview of the relationship between the Klotho protein and CVD, in addition to its role in the maintenance of functional vascular integrity.

The effect of osteoarthritis on 1-year risk of ischemic heart disease following total knee arthroplasty

To evaluate the long-term risk of ischemic heart disease (IHD) following total knee arthroplasty (TKA), we conducted a retrospective cohort study using data from the National Health Insurance Research Database of Taiwan. We evaluated 3599 primary TKA patients and 14,396 matched control patients. We further classified all patients into those with and without osteoarthritis (OA). The incidence rate of IHD was significantly higher among the TKA patients than among the matched control patients (1.13 vs 0.69 per 1000 person-months, P<.05). However, after controlling for OA, this difference was non-significant (HR=1.18, 95% confidence interval (CI): 0.63-2.20, P>.05). Our study results indicate that underlying OA conditions are predominantly responsible for increased long-term risk of IHD in TKA patients.

Association of Klotho and interleukin 6 gene polymorphisms with aging in Han Chinese population

Certain gene polymorphisms are associated with human aging. This study investigated polymorphisms of a metabolism-related gene, Klotho, and an inflammatory gene, IL6, for association with the aging process in a healthy Han Chinese population. A total of 482 healthy subjects were recruited and divided into aging and young groups according to chronological age and biological age. Snapshots were used to detect a Klotho gene tag SNP (rs571118) and the F-SNPs rs9536314 (F352V) and rs9527025 (C370S), and an interleukin 6 (IL-6) gene tag SNP (rs1524107) and the F-SNPs rs1800795 (-174G/C) and rs1800796 (-572G/C). Klotho F352V and IL-6-174G/C was G homozygous, C370S was T homozygous while IL-6-572G/C MAF less than 5%. There was a statistically significant difference in the Klotho rs571118 SNP between chronological age groups, but not biological age groups. However, other SNPs, including IL-6 gene SNPs, didn't correlate with age in the Han Chinese population. Human aging is a complex process that includes chronological and biological aging. Our current data showed that Klotho gene rs571118 SNP was associated with chronological aging, but not biological aging, in a Han Chinese population. Further study will investigate genetic build up for the difference between chronological and biological aging.

Biochemical and functional characterization of the klotho-VS polymorphism implicated in aging and disease risk

Klotho (KL) is an age-regulating protein named after the Greek goddess who spins the thread of life. Mice deficient in KL are normal throughout development, but rapidly degenerate and display a variety of aging-associated abnormalities that eventually lead to decreased life expectancy. While multiple genetic association studies have identified KL polymorphisms linked with changes in disease risk, there is a paucity of concrete mechanistic data to explain how these amino acid substitutions alter KL protein function. The KLVS polymorphism is suggested to lead to changes in protein trafficking although the mechanism is unclear. Our studies have sought to further investigate the functional differences in the KLVS variant that result in increased risk of many age-related diseases. Our findings suggest that the F352V and C370S substitutions lead to alterations in processing as seen by differences in shedding and half-life. Their co-expression in KLVS results in a phenotype resembling wild-type, but despite this intragenic complementation there are still changes in homodimerization and interactions with FGFR1c. Taken together, these studies suggest that KLVS leads to altered homodimerization that indirectly leads to changes in processing and FGFR1c interactions. These findings help elucidate the functional differences that result from the VS polymorphism, which will help clarify how alterations in KL function can lead to human disease and affect cognition and lifespan.

The association of Klotho polymorphism with disease progression and mortality in IgA nephropathy

BACKGROUNDS

IgA nephropathy (IgAN) is the most common primary glomerulonephritis causing end stage renal disease (ESRD), and vasculopathy is known to involve disease progression. Klotho, a gene related to aging, has been reported to play a role in atherosclerosis and endothelial dysfunction. We investigated whether klotho gene polymorphism affect clinical course of IgAN.

METHODS

The data registered for PREMIER study which enrolled the patients with biopsy proven IgAN were analyzed. Two single nucleotide polymorphisms for klotho gene, G395A of promoter region and C1818T of exon 4, were examined, and investigated the association klotho genotypes with the progression of IgAN and patient survival.

RESULTS

Clinical data from 973 patients confirmed about survival were analyzed. The allele frequency was 0.830 and 0.170 for allele G and A, and 0.816 and 0.184 for allele C and T, which were complied with Hardy-Weinberg equilibrium (p=0.996 and 0.531 respectively). Death was observed more frequently in A-allele carriers of G395A polymorphism (0.7 vs. 2.6 %, GG vs. GA+AA, p=0.022). Renal survival in Kaplan-Meier survival curve was also worse in same group (p=0.04).

CONCLUSION

Klotho gene polymorphism was associated with patient survival and disease progression of IgAN.

The role of Klotho in energy metabolism

A disproportionate expansion of white adipose tissue and abnormal recruitment of adipogenic precursor cells can not only lead to obesity but also impair glucose metabolism, which are both common causes of insulin resistance and diabetes mellitus. The development of novel and effective therapeutic strategies to slow the progression of obesity, diabetes mellitus and their associated complications will require improved understanding of adipogenesis and glucose metabolism. Klotho might have a role in adipocyte maturation and systemic glucose metabolism. Klotho increases adipocyte differentiation in vitro, and mice that lack Klotho activity are lean owing to reduced white adipose tissue accumulation; moreover, mice that lack the Kl gene (which encodes Klotho) are resistant to obesity induced by a high-fat diet. Knockout of Kl in leptin-deficient Lep(ob/ob) mice reduces obesity and increases insulin sensitivity, which lowers blood glucose levels. Energy metabolism might also be influenced by Klotho. However, further studies are needed to explore the possibility that Klotho could be a novel therapeutic target to reduce obesity and related complications, and to determine whether and how Klotho might influence the regulation and function of a related protein, β-Klotho, which is also involved in energy metabolism.

Klotho locus, metabolic traits, and serum hemoglobin in hospitalized older patients: a genetic association analysis

Klotho (KL) gene has been involved in severe alterations of physiological biochemical parameters leading to premature aging-like phenotypes and strikingly shortening lifespan. KL participates to the regulation of a number of intracellular biochemical pathways, including lipid profile and glucose metabolism. Aim of this study was to investigate the possible association between KL locus and biological parameters commonly accepted as indicators of the clinical status in hospitalized older patients. We genotyped the single-nucleotide polymorphisms (SNPs) rs9536314, rs1207568, and rs564481 at the KL locus in 594 hospitalized older patients (65-99 years), consecutively attending a geriatric ward, and tested the association of these KL variants with biological quantitative traits using analyses of covariance and genetic risk score models. Significant associations of rs9536314 with serum levels of hemoglobin, albumin, and high-density lipoprotein cholesterol (HDL-C) as well as significant associations of rs564481 with serum levels of hemoglobin, fasting insulin, and fasting glucose were observed. Gender-segregated analyses confirmed these associations, and suggested that the associations of KL genotypes with HDL-C, fasting glucose and fasting insulin levels may be driven by the female gender, while the association with serum levels of hemoglobin may be driven by the male gender. The association of KL genotypes with creatinine levels was found only in females, while the association with insulin-like growth factor-1 (IGF-1) and lymphocytes count (LC) was found only in males. The genetic risk score (GRS) models further confirmed significant associations among KL SNPs and hemoglobin, total cholesterol, and HDL-C. Gender-segregated analyses with the GRS-tagged approach confirmed the associations with HDL-C, fasting glucose, and fasting insulin levels in females, and with hemoglobin and LC in males. Our findings suggested that KL locus may influence quantitative traits such as serum levels of lipid, fasting glucose, albumin and hemoglobin in hospitalized older patients, with some gender differences suggested for creatinine, IGF-1 levels, and LC, thus being one of the genetic factors possibly contributing to age-related diseases and longevity.

VEGF gene mRNA expression in patients with coronary artery disease

To assess the expression of vascular endothelium growth factor (VEGF) mRNA in unstimulated peripheral blood mononuclear cells of patients with and without coronary artery disease (CAD). We also studied whether the functional VEGF -2,578C/A polymorphism may influence the level of VEGF mRNA expression in individuals undergoing coronary angiography because chest pain. We assessed 50 consecutive patients with angiographically confirmed CAD (CAD+). Also, 50 consecutive individuals with normal coronary studies were included in the study for comparison. VEGF mRNA expression was examined using quantitative real-time PCR and genotyping for VEGF -2,578C/A was performed using ARMS-PCR technique. VEGF mRNA expression was significantly decreased in CAD+ patients when compared to CAD- individuals (p = 0.01). The frequency of VEGF -2578 allele C and genotype CC was increased in CAD+ patients. In this regard, homozygosity for the CC genotype was more commonly observed in CAD+ (30 %) than in those without CAD disease (18 %). However, the difference was slightly out of the range of significance (p = 0.1). In addition, a trend for reduction in the expression of VEGF mRNA was observed when patients carrying the VEGF -2,578AA genotype were compared with those VEGF -2,578AC heterozygous or those homozygous for the VEGF -2,578CC genotype. VEGF gene expression is decreased in individuals with CAD+ disease. The VEGF -2,578C/A polymorphism may influences the expression of VEGF.

Secreted klotho and chronic kidney disease

Soluble Klotho (sKl) in the circulation can be generated directly by alterative splicing of the Klotho transcript or the extracellular domain of membrane Klotho can be released from membrane-anchored Klotho on the cell surface. Unlike membrane Klotho which functions as a coreceptor for fibroblast growth factor-23 (FGF23), sKl, acts as hormonal factor and plays important roles in anti-aging, anti-oxidation, modulation of ion transport, and Wnt signaling. Emerging evidence reveals that Klotho deficiency is an early biomarker for chronic kidney diseases as well as a pathogenic factor. Klotho deficiency is associated with progression and chronic complications in chronic kidney disease including vascular calcification, cardiac hypertrophy, and secondary hyperparathyroidism. In multiple experimental models, replacement of sKl, or manipulated up-regulation of endogenous Klotho protect the kidney from renal insults, preserve kidney function, and suppress renal fibrosis, in chronic kidney disease. Klotho is a highly promising candidate on the horizon as an early biomarker, and as a novel therapeutic agent for chronic kidney disease.

Plasma klotho and cardiovascular disease in adults

OBJECTIVES

To determine whether plasma klotho, a recently discovered hormone that has been implicated in atherosclerosis, is related to prevalent cardiovascular disease (CVD) in adults.

DESIGN

Cross-sectional.

SETTING

Population-based sample of adults residing in Tuscany, Italy.

PARTICIPANTS

One thousand twenty-three men and women aged 24 to 102 participating in the Invecchiare in Chianti (InCHIANTI) study.

MEASUREMENTS

Anthropometric measures, plasma klotho, fasting plasma total, high-density lipoprotein cholesterol (HDL-C), triglycerides, glucose, creatinine, C-reactive protein (CRP). Clinical measures: medical assessment, diabetes mellitus, hypertension, coronary heart disease, heart failure, stroke, peripheral artery disease, cancer, chronic kidney disease. Logistic regression models were used to examine the relationship between plasma klotho and prevalent CVD.

RESULTS

Of 1,023 participants, 259 (25.3%) had CVD. Median (25th, 75th percentile) plasma klotho concentrations were 676 pg/mL (530, 819 pg/mL). Plasma klotho was correlated with age (correlation coefficient (r) = -0.14, P < .001), HDL-C (r = 0.11, P<.001), and CRP (r = -0.10, P < .001) but not systolic blood pressure, fasting plasma glucose, or renal function. Plasma klotho age-adjusted geometric means were 626 pg/mL (95% confidence interval (CI) = 601-658 pg/mL) in participants with CVD and 671 pg/mL (95% CI = 652-692 pg/mL) in those without CVD (P = .001). Adjusting for traditional cardiovascular risk factors (age, sex, smoking, total cholesterol, HDL-C, systolic blood pressure, and diabetes mellitus), log plasma klotho was associated with prevalent CVD (odds ratio per 1 standard deviation increase = 0.85, 95% CI = 0.72-0.99).

CONCLUSION

In community-dwelling adults, higher plasma klotho concentrations are independently associated with a lower likelihood of having CVD.

Plasma klotho and cardiovascular disease in adults

OBJECTIVES

To determine whether plasma klotho, a recently discovered hormone that has been implicated in atherosclerosis, is related to prevalent cardiovascular disease (CVD) in adults.

DESIGN

Cross-sectional.

SETTING

Population-based sample of adults residing in Tuscany, Italy.

PARTICIPANTS

One thousand twenty-three men and women aged 24 to 102 participating in the Invecchiare in Chianti (InCHIANTI) study.

MEASUREMENTS

Anthropometric measures, plasma klotho, fasting plasma total, high-density lipoprotein cholesterol (HDL-C), triglycerides, glucose, creatinine, C-reactive protein (CRP). Clinical measures: medical assessment, diabetes mellitus, hypertension, coronary heart disease, heart failure, stroke, peripheral artery disease, cancer, chronic kidney disease. Logistic regression models were used to examine the relationship between plasma klotho and prevalent CVD.

RESULTS

Of 1,023 participants, 259 (25.3%) had CVD. Median (25th, 75th percentile) plasma klotho concentrations were 676 pg/mL (530, 819 pg/mL). Plasma klotho was correlated with age (correlation coefficient (r) = -0.14, P < .001), HDL-C (r = 0.11, P<.001), and CRP (r = -0.10, P < .001) but not systolic blood pressure, fasting plasma glucose, or renal function. Plasma klotho age-adjusted geometric means were 626 pg/mL (95% confidence interval (CI) = 601-658 pg/mL) in participants with CVD and 671 pg/mL (95% CI = 652-692 pg/mL) in those without CVD (P = .001). Adjusting for traditional cardiovascular risk factors (age, sex, smoking, total cholesterol, HDL-C, systolic blood pressure, and diabetes mellitus), log plasma klotho was associated with prevalent CVD (odds ratio per 1 standard deviation increase = 0.85, 95% CI = 0.72-0.99).

CONCLUSION

In community-dwelling adults, higher plasma klotho concentrations are independently associated with a lower likelihood of having CVD.

Plasma klotho and mortality risk in older community-dwelling adults

BACKGROUND

The aging-suppressor gene klotho encodes a single-pass transmembrane protein that in mice is known to extend life span when overexpressed and resemble accelerated aging when expression is disrupted. It is not known whether there is a relationship between plasma levels of secreted klotho protein and longevity in humans.

METHODS

We measured plasma klotho in 804 adults, greater than or equal to 65 years, in the InCHIANTI study, a longitudinal population-based study of aging in Tuscany, Italy.

RESULTS

During 6 years of follow-up, 194 (24.1%) of the participants died. In a multivariate Cox proportional hazards model, adjusting for age, sex, education, body mass index, physical activity, total cholesterol, high-density lipoprotein cholesterol, cognition, 25-hydroxyvitamin D, parathyroid hormone, serum calcium, mean arterial pressure, and chronic diseases, participants in the lowest tertile of plasma klotho (<575 pg/mL) had an increased risk of death compared with participants in the highest tertile of plasma klotho (>763 pg/mL; hazards ratio 1.78, 95% confidence interval 1.20-2.63).

CONCLUSIONS

In older community-dwelling adults, plasma klotho is an independent predictor of all-cause mortality. Further studies are needed to elucidate the potential biological mechanisms by which circulating klotho could affect longevity in humans.

The presence of total knee or hip replacements due to osteoarthritis enhances the positive association between hand osteoarthritis and atherosclerosis in women: the AGES-Reykjavik study

OBJECTIVE

This study examines the relationship between total knee replacements (TKR), total hip replacements (THR) or replacements of either joint (total joint replacement; TJR) due to osteoarthritis and atherosclerosis in a large population-based study.

METHODS

The participants were 2195 men and 2975 women, mean age 76 ± 6 years. The osteoarthritis data were analysed in relation to measures of atherosclerosis, including carotid artery intima media thickness and plaque severity (ultrasound), coronary and aortic calcifications (CT), cerebral white matter lesions (MRI) and a history of previous cardiac and cerebral events.

RESULTS

The prevalence of TKR was 223 (4.3%) and THR 316 (6.1%). The presence of TJR in women was associated with a non-significant trend towards increased carotid plaque severity, coronary calcifications and periventricular white matter hyperintensities (PVH) but not with a history of cardiac or cerebral events. No associations were seen in men. When TJR were grouped according to the presence or absence of hand osteoarthritis (HOA) there was a highly significant association in the order -TJR/-HOA < +TJR/-HOA < -TJR/+HOA < +TJR/+HOA, for carotid plaque severity, coronary calcifications and PVH.

CONCLUSION

The presence of TJR did not show a significant independent association with atherosclerosis but enhanced the strength of the positive association between HOA and subclinical atherosclerosis in women.

Lack of association of Klotho gene variants with valvular and vascular calcification in Caucasians: a candidate gene study of the Framingham Offspring Cohort

BACKGROUND

Valvular and vascular calcification are important early aging phenotypes and represent risk factors for cardiovascular morbidity and mortality. Klotho is a gene primarily expressed in the kidney that has an important role in calcium-phosphate homeostasis. The functional KL-VS variant of Klotho has been associated with aging and cardiovascular disease in human studies, but its role in valvular and vascular calcification remains unknown. We performed a candidate gene study in the Framingham Offspring Cohort to evaluate the effect of KL-VS variant of the Klotho gene on valvular calcification.

METHODS

We analyzed the Klotho KL-VS genotype (rs9536314) from the Affymetrix 550K genome-wide dataset, distributed by dbGAP, on 1389 cases and 2139 controls from the Framingham Heart Study Offspring Cohort. Allele and genotype frequencies were compared between cases and controls. Valvular calcification was defined as presence of calcification on the mitral annulus or the aortic valve as determined by echocardiography. A sensitivity analysis of coronary artery calcification by electron beam computed tomography was performed on 1363 patients.

RESULTS

The frequency of the TT versus the TG allele was not different between the cases and the controls (39 versus 41%). The KL-VS variant of Klotho was not associated with valvular or vascular calcification, despite adequate power to detect association (86% for odds ratios ≥1.2). In sensitivity analyses, no association (P > 0.001) between other common variants of Klotho, β-Klotho or fibroblast growth factor-23 and the end points of valvular or vascular calcification was observed.

CONCLUSIONS

In our adequately powered candidate gene study, we did not observe an association with the functional KL-VS variant of Klotho and presence of valvular or vascular calcification. Future studies aimed at combining cohorts with echocardiographic phenotypes need to be conducted to identify genetic variants associated with valvular calcification.

Influence of Klotho genotypes on plasma NO(x) levels in South Indian population

INTRODUCTION

Despite experimental evidences of the influence of the aging suppressor gene Klotho, on the modulation of endothelial nitric oxide synthase (eNOS) activity and nitric oxide (NO) production, the contribution of its variants to the phenotypic variance of plasma nitrite and nitrate (NO(x)) has not been addressed to date. In the present study, we aimed to determine the influence of two exonic variants, KL-VS and C1818T of Klotho, on circulating NO(x) levels in South Indian population.

MATERIALS AND METHODS

We genotyped the two Klotho KL-VS and C1818T variants in 429 healthy South Indians and measured their plasma NO(x) concentrations by the Griess method.

RESULTS

Genotype frequencies were compared in subjects with low and high NO(x) levels. An age-specific association of the Klotho C1818T variant was found with plasma NO(x) levels in subjects aged >40 years (p=0.027); the CC homozygotes were more prevalent in the low compared to the high plasma NO(x) group. However, the variant was not associated with plasma NO(x) levels in subjects aged≤40 years (p=0.799). The KL-VS variant did not have any influence on plasma NO(x) status (p=0.260).

CONCLUSIONS

Our results suggest that the effect of Klotho C1818T variant on levels of plasma NO(x) becomes pronounced with age probably implying the adaptive capability of Klotho alleles to meet the age-related increasing physiological load.

Association of exonic variants of Klotho with metabolic syndrome in Asian Indians

BACKGROUND

Klotho, an anti-aging gene, is a functional candidate for metabolic syndrome. We conducted a cross-sectional study to evaluate the association of the genetic variants of Klotho with metabolic syndrome and surrogates of insulin resistance in Asian Indians.

METHODS

We recruited 428 clinically normal subjects for the study. Genotyping was done by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

Significant and borderline associations of the KL-VS (OR=15.88 [95%CI, 2.56-98.70], p=0.003) and C1818T (OR=0.28 [95%CI, 0.07-1.07], p=0.063) variants of the Klotho gene, respectively, were observed with metabolic syndrome. The association of the KL-VS variant with metabolic syndrome could be linked to its observed influence on high blood glucose (OR=6.92 [95% CI=1.75-27.44], p=0.006), high blood pressure (OR=5.21 [95%CI=1.00-38.43], p=0.046), insulin resistance (OR=3.59, [95%CI=1.01-12.79], p=0.048) and trend towards its association with hypertriglyceridemia (OR=3.69 [95%CI=0.92-14.77], p=0.065).

CONCLUSIONS

The genetic variants of Klotho might predict risk for metabolic syndrome and insulin resistance in Asian Indians. However, larger studies in other ethnic populations are warranted to determine the role of these gene variants in the etiology of metabolic syndrome.

Genetic polymorphisms and the cardiovascular risk of non-steroidal anti-inflammatory drugs

The cardiovascular safety of cyclooxygenase-2-selective (coxibs) and nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) is of concern, although most users remain free of adverse outcomes. A gene-drug interaction could modulate this cardiovascular risk through prostaglandin synthesis or inflammatory pathways. From an existing acute coronary syndrome cohort (Recurrence and Inflammation in the Acute Coronary Syndromes Study) (n = 1,210), a case-only study was performed by identifying 115 patients exposed to NSAIDs (rofecoxib [n = 43], celecoxib [n = 49], or nonselective NSAIDs [n = 23]) and 345 unexposed patients matched for age, gender, and hospital center. These patients were genotyped for 115 candidate single-nucleotide polymorphisms (SNPs). Statistically significant associations between NSAID exposure and 9 SNPs in 6 genes were observed. Analyzing patients exposed only to coxibs and their matched unexposed cases, significant associations remained for 5 SNPs at 4 loci (prostaglandin-endoperoxide synthase-1 [PTGS1], chromosome 9p21.3, C-reactive protein [CRP], and klotho [KL]). Two independent SNPs from the PTGS1 gene gave similar results under a recessive model, with odds ratios for the association with NSAID exposure of 6.94 (95% confidence interval 1.35 to 35.65, p = 0.016) and 7.11 (95% confidence interval 1.38 to 36.74, p = 0.033). A significant association was also observed for a SNP in the CRP gene (rs1205) (additive odds ratio 1.64, 95% confidence interval 1.18 to 2.27, p = 0.003). In conclusion, these findings suggest that genetic variability may contribute to the susceptibility for acute coronary syndromes observed in some NSAID users. In particular, genetic polymorphisms in the PTGS1 and CRP genes appear to be candidates for a possible gene-drug interaction influencing the acute coronary risk associated with NSAID use, but these findings will require confirmation in larger cohorts.

The relationship between Receptor Activator of Nuclear Factor-kappaB Ligand (RANKL) gene polymorphism and aortic calcification in Korean women

The aim of this study was to investigate the relationship between RANKL gene polymorphisms and aortic calcification in Korean women. In 237 healthy Korean women, aortic calcification in thoracic and abdominal aorta was examined in simple radiologic method and lumbar spine and femoral neck BMD were examined by dual energy X-ray absorptiometry. Serum OPG levels, bone turnover markers, such as ALP levels and urine deoxypyridinoline levels, and urine calcium excretion were measured. Genotyping of two RANKL gene polymorphisms, rs2277438 and rs9594782, was performed by allelic discrimination using the 5' nuclease polymerase chain reaction assay. The subjects with CT/CC genotypes of the rs9594782 polymorphism had a 3.9 times higher risk of aortic calcification compared with TT genotype. This significance was significant even after adjustment for age, BMI, blood pressure, fasting plasma glucose, serum high and low-density lipoprotein cholesterol levels. Mean levels of urine deoxypyridinoline were significantly higher in the subjects with AG/GG genotypes of the rs2277438 polymorphism compared with AA genotype, and this significance was persistent even after adjustment for age and BMI. There were no associations of mean values for age, BMI, serum OPG and ALP levels, urine calcium excretion, and BMD with RANKL gene polymorphisms. The RANKL gene rs9594782 polymorphism was associated with aortic calcification in Korean women. Rs2277438 polymorphism showed significant association with urine deoxypyridinoline levels, a bone resorption marker. These results suggest its role on vascular calcification and bone metabolism in humans.

Inhibition of osteoclast formation and function by bicarbonate: role of soluble adenylyl cyclase

High [HCO(3)(-)] inhibits and low [HCO(3)(-)] stimulates bone resorption, which mediates part of the effect of chronic acidosis or acid feeding on bone. Soluble adenylyl cyclase (sAC) is a bicarbonate sensor that can potentially mediate the effect of bicarbonate on osteoclasts. Osteoclasts were incubated in 0, 12, and 24 mM HCO(3)(-) at pH 7.4 for 7-8 days and assayed for tartrate-resistant acid phosphatase (TRAP) and vacuolar-ATPase expression, and H+ accumulation. Total number and area of TRAP (+) multinucleated osteoclasts was decreased by HCO(3)(-) in a dose-dependent manner. V-ATPase expression and H+ accumulation normalized to cell cross-sectional area or protein were not significantly changed. The HCO(3)(-) -induced inhibition of osteoclast growth and differentiation was blocked by either 2-hydroxyestradiol, an inhibitor of sAC or sAC knockdown by sAC specific siRNA. The model of HCO(3)(-) inhibiting osteoclast via sAC was further supported by the fact that the HCO(3)(-) dose-response on osteoclasts is flat when cells were saturated with 8-bromo-cAMP, a permeant cAMP analog downstream from sAC thus simulating sAC activation. To confirm our in vitro findings in intact bone, we developed a 1-week mouse calvaria culture system where osteoclasts were shown to be viable. Bone volume density (BV/TV) determined by micro-computed tomography (microCT), was higher in 24 mM HCO(3)(-) compared to 12 mM HCO(3)(-) treated calvaria. This HCO(3)(-) effect on BV/TV was blocked by 2-hydroxyestradiol. In summary, sAC mediates the inhibition of osteoclast function by HCO(3)(-), by acting as a HCO(3)(-) sensor.