The Impact of Vitamin D3 Supplementation on Mechanisms of Cell Calcium Signaling in Chronic Kidney Disease

Modulation of cardiometabolic risk and CardioRenal syndrome by oral vitamin D3 supplementation in Black and White Southern Sahara residents with chronic kidney disease Stage 3: focus on racial and ethnic disparities

OBJECTIVES

Several studies have shown that cholecalciferol supplementation (25OHD-S) in chronic kidney disease (CKD) improves kidney injury by reducing fibrosis-related vascular calcification and declining apoptosis-linked nephron damage.

METHODS

The oral 25OHD-S was evaluated in 60,000 IU/month/36 weeks versus in 2000 IU/d/24 weeks in CKD Stage 3 with serum 25OHD level < 20 ng/mL. The study was undertaken on 156 black subjects and 150 white subjects Southern Sahara (SS). All biomarkers of cardiometabolic (CMet) and cardiorenal (CRenal) syndrome, Renin-angiotensin-aldosterone system (RAAS) profile, secondary hyperparathyroidism (SHPT), N-terminal pro B-type natriuretic peptide (NT-proBNP), Troponin T (cTnT) and atherogenicity risk were assessed by biochemical methods. Estimate glomerular filtration rate (eGFR) by chronic CKD-EPI equation formula. Total serum vitamin D by liquid chromatography-tandem mass spectrometry (MS).

RESULTS

Vitamin D deficiency alters in the same manner CMet, CRenal, and others biomarkers in both groups SS; however, these disorders are more acute in blacks compared to whites SS. Oral 25OHD-S a highlighted improvement of eGFR drop, SHPT decrease, decline proteinuria, and cardiac failure risk (NT-proBNP and cTnT) attenuation. Concomitantly, 25OHD-S normalizes Renin, Aldosterone, and Angiotensin System (RAAS) activity. Nevertheless, homocysteine and Lp (a) do not modulate by 25OHD-S.

CONCLUSIONS

The oral vitamin D3 supplementation, according the dose, and the treatment duration does not like in black-skinned people versus to white-skinned inhabitants, while the 02 groups are native to the same Saharan environment. It emerge that a high intermittent dose through an extensive supplementation (60,000 IU/36 weeks) was more effective in black subjects. At opposite, a lower dose during a short period supplementation is sufficient (2000 IU/24 weeks) in white subjects.

Intracellular calcium increases in vascular smooth muscle cells with progression of chronic kidney disease in a rat model

Background

Vascular smooth muscle cells (VSMCs) exhibit phenotypic plasticity, promoting vascular calcification and increasing cardiovascular risk. Changes in VSMC intracellular calcium ([Ca 2+ ] i ) are a major determinant of plasticity, but little is known about changes in [Ca 2+ ] i in chronic kidney disease (CKD). We have previously demonstrated such plasticity in aortas from our rat model of CKD and therefore sought to examine changes in [Ca 2+ ] i during CKD progression.

Materials and Methods

We examined freshly isolated VSMCs from aortas of normal rats, Cy/+ rats (CKD) with early and advanced CKD, and advanced CKD rats treated without and with 3% calcium gluconate (CKD + Ca 2+ ) to lower parathyroid hormone (PTH) levels. [Ca 2+ ] i was measured with fura-2.

Results

Cy/+ rats developed progressive CKD, as assessed by plasma levels of blood urea nitrogen, calcium, phosphorus, parathyroid hormone and fibroblast growth factor 23. VSMCs isolated from rats with CKD demonstrated biphasic alterations in resting [Ca 2+ ] i : VSMCs from rats with early CKD exhibited reduced resting [Ca 2+ ] i , while VSMCs from rats with advanced CKD exhibited elevated resting [Ca 2+ ] i . Caffeine-induced sarcoplasmic reticulum (SR) Ca 2+ store release was modestly increased in early CKD and was more drastically increased in advanced CKD. The advanced CKD elevation in SR Ca 2+ store release was associated with a significant increase in the activity of the sarco-endoplasmic reticulum Ca 2+ ATPase (SERCA); however, SERCA2a protein expression was decreased in advanced CKD. Following SR Ca 2+ store release, recovery of [Ca 2+ ] i in the presence of caffeine and extracellular Ca 2+ was attenuated in VSMCs from rats with advanced CKD. This impairment, together with reductions in expression of the Na + /Ca 2+ exchanger, suggest a reduction in Ca 2+ extrusion capability. Finally, store-operated Ca 2+ entry (SOCE) was assessed following SR Ca 2+ store depletion. Ca 2+ entry during recovery from caffeine-induced SR Ca 2+ store release was elevated in advanced CKD, suggesting a role for exacerbated SOCE with progressing CKD.

Conclusions

With progressive CKD in the Cy/+ rat there is increased resting [Ca 2+ ] i in VSMCs due, in part, to increased SOCE and impaired calcium extrusion from the cell. Such changes may predispose VSMCs to phenotypic changes that are a prerequisite to calcification.