Calcium-phosphate metabolism parameters and erythrocyte Ca 2+ concentration in autosomal dominant polycystic kidney disease patients with normal renal function

Abstract

IntroductionThe aim of this study was to assess calcium-phosphate metabolism of autosomal dominant polycystic kidney disease (ADPKD) patients with a special consideration to the following serum parameters: calcium (Ca2+), inorganic phosphate (Pi), parathyroid hormone (PTH) and intracellular erythrocyte calcium ([Ca2+]i) concentrations.Material and methodsThe study included 49 adult ADPKD patients (19 males, 30 females) aged 36 ±11 years with normal renal function and no diagnosis of diabetes as well as 50 healthy controls (22 males, 28 females) matched for age and gender. Serum concentrations of sodium (Na+), potassium (K+) and magnesium (Mg2+) ions and Pi were determined with an indirect ion-selective method, while Ca2+ concentration was measured with a direct ion-selective method. The PTH was detected using a radioimmunometric method. [Ca2+]i concentration was determined with the Ca2+ sensitive fluorescent dye Fura-2 method.ResultsIn the ADPKD group, when compared to controls, the following concentrations were significantly higher: serum Ca2+ (1.18 ±0.06 mmol/l vs. 1.15 ±0.06 mmol/l, p = 0.0085), [Ca2+]i (146.9 ±110.0 nmol/l vs. 96.5 ±52.7 nmol/l, p = 0.0075), serum Na+ (139.4 ±2.7 mmol/l vs. 138.5 ±2.1 mmol/l, p = 0.060, borderline significance), and PTH (15.5 ±6.8 pg/ml vs. 13.6 ±5.3 pg/ml, p = 0.066, borderline significance), while serum Mg2+ was significantly lower (0.81 ±0.09 mmol/l vs. 0.85 ±0.05 mmol/l, p = 0.021). In the ADPKD group we observed significant negative correlations of PTH with Ca2+ serum concentrations (Rs = –0.32, p = 0.025) and with estimated glomerular filtration rate (Rs = –0.31, p = 0.033).ConclusionsThe erythrocyte Ca2+ concentration is elevated in ADPKD patients with normal renal function. It may result from a dysfunction of mutated polycystins which can affect various aspects of electrolyte metabolism.

Autosomal Dominant Polycystic Kidney Disease and Hypertension are Associated with Left Ventricular Mass in a Gender-Dependent Manner

“…Impairment of intracellular Ca 2+ homeostasis and mitochondrial function has been implicated in the development of LVH [28,29]. In our recent study [30] we have found that ADPKD patients with normal renal function had higher Ca 2+ concentrations in serum and erythrocytes and higher serum PTH levels (borderline significance) compared with non-ADPKD controls. This may indicate that the natural course of ADPKD leads to disorders of calcium metabolism preceding the onset of renal failure.…”

Markers of increased cardiovascular risk in patients with chronic kidney disease

“…Our study also revealed a correlation between osteocalcin level and inorganic P and between osteoprotegerin and inorganic P and CRP. In patients with CKD, it is well established that hyperphosphataemia is associated with the development of vascular calcification [ 38 , 44 , 77 – 82 ]. Recent studies have demonstrated that high extracellular phosphate levels induce the transformation of VSMCs into osteoblast-like cells, which suggests that vascular calcification is an active process.…”

ADPKD protects against diabetogenic effects associated with genetically-predicted lactase persistence.

“…Pathogenic PKD1 or PKD2 mutations that abrogate complex formation, compromise cell surface expression of PKD1, or reduce TRPP2 channel activity suppress activation by WNTs [32]. It is worth noting that we have previously reported an increase in Ca 2+ concentration in the erythrocytes of our ADPKD patients with normal renal function [33].…”