The risk of nephrolithiasis is causally related to inactive matrix Gla protein, a marker of vitamin K status: a Mendelian randomization study in a Flemish population

Associations of Indoxyl Sulfate and p-cresyl Sulfate with Serum Uncarboxylated Matrix γ-carboxyglutamate Protein in Chronic Kidney Disease Patients

BACKGROUND

Indoxyl sulfate (IS) and p-cresyl sulfate (PCS) are two important protein-bound uremic retention solutes. Increased serum levels of IS and PCS are associated with cardiovascular calcification. Matrix γ-carboxyglutamate protein (MGP) is a potent inhibitor of vascular calcification and inactivated uncarboxylated MGP (ucMGP) is related to vascular calcification. Nevertheless, whether serum levels of IS and PCS are associated with the serum ucMGP level in chronic kidney disease (CKD) patients with different stages is unknown.

METHODS

This cross-sectional study enrolled 90 patients in different stages of chronic kidney disease. Serum levels of IS and PCS were determined. The serum concentration of ucMGP was measured with an enzyme-linked immunosorbent assay. Independent associations between serum total IS and PCS with ucMGP were evaluated.

RESULTS

The mean serum level of ucMGP in participants of this study is 10.78 ±5.22 μg/mL. Serum levels of the two above-mentioned uremic toxins and ucMGP were elevated commensurately with deteriorating renal function. The serum level of ucMPG was associated with total IS (r = 0.456, p < 0.001) and total PCS (r =0.413, p < 0.001) levels. Multiple linear regression analysis showed that ucMGP was significantly related to levels of IS (β = 0.442, p <0.001), but not the level of PCS concentrations after adjusting for other confounding variables.

CONCLUSION

Our study showed that a higher serum IS level was independently associated with ucMGP in deteriorating CKD. Therefore, it would be worthwhile to investigate the effect of IS on ucMGP in the pathogenesis of vascular calcification in future studies.

Is a Vitamin K Epoxide Reductase Complex Subunit 1 (VKORC1) Polymorphism a Risk Factor for Nephrolithiasis in Sarcoidosis?

Sarcoidosis is a systemic inflammatory disorder characterized by granuloma formation in various organs. It has been associated with nephrolithiasis. The vitamin K epoxide reductase complex subunit 1 (VKORC1) gene, which plays a crucial role in vitamin K metabolism, has been implicated in the activation of proteins associated with calcification, including in the forming of nephrolithiasis. This study aimed to investigate the VKORC1 C1173T polymorphism (rs9934438) in a Dutch sarcoidosis cohort, comparing individuals with and without a history of nephrolithiasis. Retrospectively, 424 patients with sarcoidosis were divided into three groups: those with a history of nephrolithiasis (Group I: n = 23), those with hypercalcemia without nephrolithiasis (Group II: n = 38), and those without nephrolithiasis or hypercalcemia (Group III: n = 363). Of the 424 sarcoidosis patients studied, 5.4% had a history of nephrolithiasis (Group I), only two of whom possessed no VKORC1 polymorphisms (OR = 7.73; 95% CI 1.79-33.4; p = 0.001). The presence of a VKORC1 C1173T variant allele was found to be a substantial risk factor for the development of nephrolithiasis in sarcoidosis patients. This study provides novel insights into the genetic basis of nephrolithiasis in sarcoidosis patients, identifying VKORC1 C1173T as a potential contributor. Further research is warranted to elucidate the precise mechanisms and explore potential therapeutic interventions based on these genetic findings.

Matrix gla protein, a potential marker of tissue remodelling and physiological ageing of the gut in crohn's disease

BACKGROUND

The inactive dephosphorylated and uncarboxylated form of the matrix Gla protein (dp-ucMGP) has been shown to be increased in plasma of inflammatory bowel disease (IBD) patients. Our aim was to assess if the plasmatic level of dp-ucMGP could reflect disease endoscopic activity, presence of strictures and cumulative structural bowel damage in Crohn's disease (CD) patients.

METHODS

The plasmatic level of dp-ucMGP was measured in a monocentric cohort of prospectively recruited patients. The analysis was done by chemiluminescent immunoassay on blood samples collected the day of a planned ileocolonoscopy. In addition to classical clinical data (gender, age, body mass index (BMI), disease duration, current treatment), endoscopic data (disease location, Crohn's Disease Endoscopic Index of Severity (CDEIS), mucosal healing (MH), presence of 9 CD lesion types) and biological markers (faecal calprotectin and C-reactive protein (CRP)) were collected. The association between dp-ucMGP level and Lémann index was also investigated. Univariate linear regression was used to investigate the relationship between dp-ucMGP level and different parameters collected.

RESULTS

A total of 82 ileocolonoscopies and dp-ucMGP assays were performed in 75 CD patients (45 females; 37 ileocolonic, 19 ileal and 19 colonic diseases) between October 2012 and November 2019. A total of 24 patients (29.3%) showed MH. The dp-ucMGP levels were not associated with MH, CDEIS, faecal calprotectin or CRP levels. Plasmatic dp-ucMGP levels increased significantly with age (p = 0.0032), disease duration (p = 0.0033), corticosteroids use (p = 0.019) and tended to increase in patients with intestinal strictures (p = 0.086) but not with the Lémann index.

CONCLUSION

The significant increase of plasmatic dp-ucMGP levels with age, disease duration and the trend observed in patients with non-ulcerated strictures may suggest that this extracellular matrix protein could be a marker of tissue remodelling and physiological ageing of the gut.

Vitamins as regulators of calcium-containing kidney stones - new perspectives on the role of the gut microbiome

Calcium-based kidney stone disease is a highly prevalent and morbid condition, with an often complicated and multifactorial aetiology. An abundance of research on the role of specific vitamins (B6, C and D) in stone formation exists, but no consensus has been reached on how these vitamins influence stone disease. As a consequence of emerging research on the role of the gut microbiota in urolithiasis, previous notions on the contribution of these vitamins to urolithiasis are being reconsidered in the field, and investigation into previously overlooked vitamins (A, E and K) was expanded. Understanding how the microbiota influences host vitamin regulation could help to determine the role of vitamins in stone disease.

The biological responses of vitamin K2: A comprehensive review

Vitamin K1 (VitK1) and Vitamin K2 (VitK2), two important naturally occurring micronutrients in the VitK family, found, respectively, in green leafy plants and algae (VitK1) and animal and fermented foods (VitK2). The present review explores the multiple biological functions of VitK2 from recently published in vitro and in vivo studies, including promotion of osteogenesis, prevention of calcification, relief of menopausal symptoms, enhancement of mitochondrial energy release, hepato- and neuro-protective effects, and possible use in treatment of coronavirus disease. The mechanisms of action associated with these biological effects are also explored. Overall, the findings presented here suggest that VitK, especially VitK2, is an important nutrient family for the normal functioning of human health. It acts on almost all major body systems and directly or indirectly participates in and regulates hundreds of physiological or pathological processes. However, as biological and clinical data are still inconsistent and conflicting, more in-depth investigations are warranted to elucidate its potential as a therapeutic strategy to prevent and treat a range of disease conditions.

Evaluation of inactive Matrix-Gla-Protein (MGP) as a biomarker for incident and recurrent kidney stones

BACKGROUND

Matrix-Gla-protein (MGP) is an inhibitor of vascular calcification. Its dephosphorylated and uncarboxylated inactive form, dpucMGP, is a marker of vitamin K status and of cardio-vascular outcomes in chronic kidney disease. We hypothesized that higher serum dpucMGP would be a biomarker of kidney stone disease.

METHODS

We measured serum dpucMGP in incident symptomatic kidney stone-formers and non-stone formers at a baseline visit. Symptomatic stone recurrence was assessed in the stones formers over a 5-year period. The association of dpucMGP with incident or recurrent kidney stones was assessed with and without adjustment for clinical, blood, and urine characteristics.

RESULTS

There was no significant difference in serum dpucMGP level between 498 stone formers and 395 non-stone former (510 vs 501 pmol/L; p = 0.66). In a multivariable model adjusting for clinical, blood and urine chemistries, higher MGP was associated with lower risk of stone formation (OR = 0.674, 95% CI 0.522-0.870), contrary to previous reports. Among 375 stone formers with 5 years of follow-up, 79 (21%) had symptomatic recurrence. No difference in serum dpucMGP was evident in recurrent versus non-recurrent stone-formers (482 vs 502 pmol/L; p = 0.26). Serum dpucMGP was correlated with cystatin C levels in non stone-formers, incident stone-formers and recurrent stone-formers (r > 0.3, p < 0.0001).

CONCLUSION

Elevated serum dpucMGP was not associated with incident or recurrent symptomatic kidney stone events. However, higher level of dpucMGP was associated with lower risk of kidney stone in a multivariable logistic regression model.

Vitamin K-Dependent Matrix Gla Protein as Multifaceted Protector of Vascular and Tissue Integrity

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Association of the Inactive Circulating Matrix Gla Protein with Vitamin K Intake, Calcification, Mortality, and Cardiovascular Disease: A Review

Matrix Gla Protein (MGP), a small Gla vitamin K-dependent protein, is the most powerful natural occurring inhibitor of calcification in the human body. To become biologically active, MGP must undergo vitamin K-dependent carboxylation and phosphorylation. Vitamin K deficiency leads to the inactive uncarboxylated, dephosphorylated form of MGP (dpucMGP). We aimed to review the existing data on the association between circulating dpucMGP and vascular calcification, renal function, mortality, and cardiovascular disease in distinct populations. Moreover, the association between vitamin K supplementation and serum levels of dpucMGP was also reviewed.

High Concentration of Calcium Promotes Mineralization in NRK-52E Cells Via Inhibiting the Expression of Matrix Gla Protein

OBJECTIVE

To address whether matrix Gla protein (MGP) can inhibit mineralization in normal rat kidney tubular cells (NRK-52E) under high concentration of calcium.

MATERIALS AND METHODS

NRK-52E cells were treated with high concentration of calcium. The viability and apoptosis of cells were detected by cell counting kit-8 and flow cytology, respectively. Real-time-polymerase chain, Western blotting, and immunofluorescence analysis were conducted to detect the expression of MGP. Cells were transfected with plasmid-MGP or siRNA-MGP for up- or down-regulation of the expression of MGP, respectively. Rat recombinant MGP was also used as supplementation of exogenous MGP. Alizarin red staining was conducted to detect the adherent and deposition of calcium salt.

RESULTS

High concentration of calcium suppressed MGP expression in NRK-52E cells. There was significant mineralization when NRK-52E cells were treated with high concentration of calcium. Supplementation with exogenous rat recombinant MGP and overexpression of endogenous MGP both decreased the adherent and deposition of calcium salt to NRK-52E cells, while silence of MGP showed reverse results.

CONCLUSION

MGP plays an inhibitory role in the stone formation. However, high concentration of calcium significantly inhibits the expression of MGP and then promotes mineralization in NRK-52E cells.

Desphospho-uncarboxylated matrix Gla protein is a novel circulating biomarker predicting deterioration of renal function in the general population

BACKGROUND

Recent studies showing an inverse association between estimated glomerular filtration rate (eGFR), a microvascular trait, and inactive desphospho-uncarboxylated matrix Gla protein (dp-ucMGP) support the hypothesis that after vitamin K-dependent activation, matrix Gla protein (MGP) is renoprotective, but these were limited by their cross-sectional design.

METHODS

In 1009 randomly recruited Flemish (50.6% women), we assessed the association between eGFR and plasma dp-ucMGP, using multivariable-adjusted analyses.

RESULTS

From baseline to follow-up 8.9 years later (median), dp-ucMGP increased by 23.0% whereas eGFR decreased by 4.05 mL/min/1.73 m2 (P < 0.001). In 938 participants with baseline eGFR ≥60 mL/min/1.73 m2, the incidence of eGFR <60 mL/min/1.73 m2 at follow-up was 8.0% versus 4.1% in the top versus the bottom halve of baseline dp-ucMGP. For a 5-fold higher plasma dp-ucMGP at baseline, eGFR at follow-up decreased by 3.15 mL/min/1.73 m2 [95% confidence interval (CI) 1.26-5.05; P = 0.001]. The hazard ratio expressing the risk of progression to eGFR <60 mL/min/1.73 m2 was 3.49 (95% CI 1.45-8.40; P = 0.005). The hazard ratio relating the presence of microalbuminuria at follow-up to baseline dp-ucMGP was 4.70 (95% CI 1.57-14.1; P = 0.006).

CONCLUSIONS

In conclusion, circulating inactive dp-ucMGP, a biomarker of poor vitamin K status, predicts renal dysfunction. Possible underlying mechanisms include protection by activated MGP against calcification and inhibition of the bone morphogenetic protein-signalling pathway.

Epidemiological and histological findings implicate matrix Gla protein in diastolic left ventricular dysfunction

OBJECTIVES

A novel paradigm of diastolic left ventricular (LV) dysfunction proposes involvement of the cardiac microvasculature. Vitamin K dependent matrix Gla protein (MGP) plays a role in preserving microcirculatory integrity. We hypothesized that LV filling pressure-a measure of diastolic LV dysfunction-increases with higher plasma level of inactive desphospho-uncarboxylated MGP (dp-ucMGP). We also studied the distribution of active and inactive MGP in human myocardium.

METHODS

We measured echocardiographic diastolic LV function and plasma dp-ucMGP (ELISA) in 668 Flemish and for replication in 386 Swiss.

RESULTS

Among Flemish and Swiss, E/e' (6.78 vs. 6.73) and dp-ucMGP (3.94 μg/L vs. 4.20 μg/L) were similarly distributed. In multivariable-adjusted models, for each doubling of dp-ucMGP, E/e' increased by 0.26, 0.33 and 0.31 in Flemish, Swiss and both cohorts combined (P≤0.026); the odds ratios for having E/e' ≥ 8.5 were 1.99, 3.29 and 2.36, respectively (P≤0.017). Cardiac biopsies from patients with ischemic or dilated cardiomyopathy and healthy hearts (n = 4 for each) were stained with conformation-specific MGP antibodies. In diseased compared with normal hearts, uncarboxylated inactive MGP was more prevalent (P≤0.004) in the perivascular matrix and interstitium (204.4 vs. 8.6 μm2 per field) and phosphorylated active MGP in and around capillaries and interstitial cells (31.3 vs. 6.6 number of positive capillaries and cells per field).

CONCLUSIONS

Our study supports a role of activated MGP in maintaining myocardial integrity and diastolic LV performance and can potentially be translated into new strategies for managing diastolic LV dysfunction and preventing its progression to heart failure.