CYP24A1 and KL polymorphisms are associated with the extent of vascular calcification but do not improve prediction of cardiovascular events

Matrix Gla protein polymorphism rs1800802 is associated with atheroma plaque progression and with cardiovascular events in a chronic kidney disease cohort

Background

Chronic kidney disease (CKD) is associated with increased atherosclerotic burden and higher risk for cardiovascular events (CVE). Atherosclerosis has a significant genetic component and, in CKD, it is influenced by mineral metabolism alterations. Therefore, genetic modifications of mineral metabolism-related proteins could affect atherosclerosis in CKD patients. In the present study we investigated the role of single nucleotide polymorphisms (SNPs) of the matrix gamma-carboxy glutamic acid protein (MGP) on atherosclerosis progression and CVE in a CKD cohort.

Methods

A total of 2187 CKD patients from the Observatorio Nacional de Aterosclerosis en Nefrologia (NEFRONA) study were genotyped for SNPs present in the matrix gamma-carboxy glutamic acid (Gla) protein (MGP) gene. Atheromatosis was detected by vascular ultrasound. Progression of atheromatosis, defined as an increase in territories with plaque, was assessed after 24 months. Patients were followed for 48 months for CVE. Association of SNPs with plaque progression was assessed by logistic regression and their capacity to predict CVE by Cox regression.

Results

Three SNPs of the MGP gene were analyzed. No association of the rs4236 or the rs1800801 SNPs was detected with any of the outcomes. However, patients homozygotes for the minor allele of the rs1800802 SNP showed higher adjusted risk for plaque progression [odds ratio 2.3 (95% confidence interval 1.06-4.9)] and higher risk of suffering a CVE [hazard ratio 2.16 (95% confidence interval 1.13-4.12)] compared with the rest of genotypes. No association of the SNP with total or dp-ucMGP levels was found in a subsample.

Conclusions

The rs1800802 polymorphism of MGP is associated with plaque progression and CVE in CKD patients.

FGF23 and klotho at the intersection of kidney and cardiovascular disease

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

Protective association of Klotho rs495392 gene polymorphism against hepatic steatosis in non-alcoholic fatty liver disease patients

Background/Aims

Non-alcoholic fatty liver disease (NAFLD) is closely associated with metabolic dysfunction. Among the multiple factors, genetic variation acts as important modifiers. Klotho, an enzyme encoded by the klotho (KL) gene in human, has been implicated in the pathogenesis of metabolic dysfunctions. However, the impact of variants in KL on NAFLD risk remains poorly understood. The aim of this study was to investigate the impact of KL rs495392 C>A polymorphism on the histological severity of NAFLD.

Methods

We evaluated the impact of the KL rs495392 polymorphism on liver histology in 531 Chinese with NAFLD and replicated that in the population-based Rotterdam Study cohort. The interactions between the rs495392, vitamin D, and patatin-like phospholipase domain containing 3 (PNPLA3) rs738409 polymorphism were also analyzed.

Results

Carriage of the rs495392 A allele had a protective effect on steatosis severity (odds ratio [OR], 0.61; 95% confidence interval [CI], 0.42–0.89; P=0.010) in Chinese patients. After adjustment for potential confounders, the A allele remained significant with a protective effect (OR, 0.66; 95% CI, 0.45–0.98; P=0.040). The effect on hepatic steatosis was confirmed in the Rotterdam Study cohort. Additional analysis showed the association between serum vitamin D levels and NAFLD specifically in rs495392 A allele carriers, but not in non-carriers. Moreover, we found that the rs495392 A allele attenuated the detrimental impact of PNPLA3 rs738409 G allele on the risk of severe hepatic steatosis.

Conclusions

The KL rs495392 polymorphism has a protective effect against hepatic steatosis in patients with NAFLD.