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BackgroundVascular calcification and increased mortality is now well linked in hemodialysis (HD) patients. Among the inhibitors and promoters of calcium-phosphate and bone metabolism, we studied Sclerostin, a glycoprotein mainly expressed by osteocytes, involved in regulating bone formation by inhibiting Wnt–β-catenin signaling. Studies demonstrated, in experimental CDK animal model, a positive association between Sclerostin production and dietary phosphate intake.Materials and MethodsWe investigated the relation between Sclerostin levels (SL) and dietary habits in 49 Caucasian HD patients (age 36–90, M/F 31/18, dialysis vintage 1–144 months). Nutrient intake was analyzed with 24 h-recall method. Serum Sclerostin was measured by ELISA method. Statistically analysis was performed by SPSS software.ResultsMean calcium and phosphate intake were 705 ± 584 and 1196 ± 498 mg/day, respectively. Serum SL (3356 ± 2118 pg/ml) were increased in HD patients. Positive correlation was found between serum SL and calcium (r = 0.33, p = 0.025) and phosphate intake (r = 0.34, p = 0.021). Patients with SL higher were older (p = 0.003), showed higher protein (p = 0.012), calcium (p = 0.017) and phosphate (p = 0.004) intake. Multiple linear regression testing Sclerostin as dependent variable (dialysis vintage, age, body-weight, serum calcium and phosphate, serum PTH, calcium and phosphate intake as independent variables) found that dietary phosphate intake was the only significant determinant of SL (r = 0.356, B = 1.5, p = 0.004). In Patients with calcium carbonate or acetate therapy (n = 31), serum SL was positively correlated with dietary calcium (r = 0.433, p = 0.017) and phosphate intake (r = 0.377, p = 0.04).ConclusionsThe dietary phosphate and calcium intake may influence serum Sclerostin levels and potentially affect bone remodeling or soft tissue calcification in HD patients.

A population of 503 adult Caucasians was recruited to evaluate the effect of diet on cardiovascular risk factors and its interaction with the genetic background. Nutritional data were collected by 24h recalls and Mediterranean diet adherence was investigated by QuADM-15 questionnaire. Anthropometric measurements (weight, height, and waist circumference), lipid profile, serum glucose, electrolytes, homocysteine and hpCRP were measured. The genome-wide tag-SNPs analysis was performed by Illumina 200K SNPs array, enriched by the imputation analysis. The Gene*Environment (G*E) analysis evaluated candidate genes and SNPs for the phenotypes HDL and LDL, and the interaction with diet (omnivores vs. vegetarians) and anthocyanins intake.The dietary habit analysis identified 120 vegetarians and 374 omnivores. The distribution of macronutrients showed, as expected, a higher intake of animal proteins, saturated fatty acids and lower fiber intake in the omnivores. The consumption of anthocyanins and polyphenols was low in the entire population. Correlations were found between diet habits (omnivores vs vegetarians) and BMI (p

BackgroundParathyroid tumors display reduced sensitivity to extracellular calcium ([Ca2+]o). The parathyroid cell sensitivity to [Ca2+]o is mediated by the calcium-sensing receptor (CASR), a G-protein-coupled receptor interacting with the scaffold protein filamin A (FLNA). We investigated: the FLNA expression in human parathyroid tumors, its effect on the CASR membrane stabilization, and on ERK signaling activation in HEK293 cells, the effect of the C-terminal CASR variants (R990G) on the interaction with FLNA.MethodsFLNA expression was analyzed by immunohistochemistry and immunofluorescence in parathyroid tumors and in cells from parathyroid adenomas (PAds). Endogenous FLNA in HEK293 cells transfected with the CASR variants was silenced by siRNA technique. Results FLNA expression was down-regulated in human parathyroid tumors; In 74 PAds, FLNA mRNA levels positively correlated with CASR levels. In HEK293 cells transfected with 990R-CASR or 990G-CASR, FLNA silencing reduced both the total and membrane protein expression levels. However, in presence of endogenous FLNA, 990G-CASR expression in cell membrane was higher than that of the 990R-CASR. FLNA loss reduced significantly p-ERK levels induced both 990R-CaSR and 990G-CaSR. Treatment with the CASR agonist R568 delete the effect of FLNA loss and restoring 990G-CASR sensitivity to [Ca2+]o in absence of FLNA.ConclusionsFLNA is down-regulated in parathyroid tumors and paralleled the CASR expression levels. Loss of FLNA reduced the CASR expression levels and the CASR-induced ERK phosphorylation. The CASR 990G allele was associated with increased sensitivity to [Ca2+]o, though FLNA was required to determine the 990G-CASR higher expression and activity than that of 990R-CASR protein.

BackgroundAutosomal Dominant Hypocalcemia (ADH) is an endocrine disorder due to activating mutations of the calcium-sensing receptor (CASR) gene that encodes for a plasma membrane G protein-coupled receptor. This protein plays a central role in maintaining calcium homeostasis. ADH is characterized by hypocalcemia and hypercalciuria with inappropriately low serum concentration of parathyroid hormone (PTH). We report on a young boy who presented hypocalcemia with hypercalciuria, hyperphosphatemia and low serum concentration of PTH.Materials and MethodsGenomic DNA was extracted from peripheral venous blood of a pediatric patient with ADH. Molecular screening of the CASR coding sequence was performed by sequence analysis with an ABI PRISM® 3100 Avant Genetic Analyzer. Site-directed mutagenesis was performed directly on CASR wild type cDNA, cloned in pCR3.1 plasmid to obtain CASR mutant plasmid. Functional properties of mutant receptor were studied in transiently transfected HEK-293 cells with the wild-type or mutated CASR. The ERK phosphorylation levels were measured by western blot analysis.ResultsWe detected a novel heterozygous deletion of a cytosine (c.2682delC) causing a frameshift and a premature stop codon resulting in a truncation of the CaSR's C-tail. HEK-293 cells transfection with CASR Mutant increased significantly (P = 0.02) p-ERK levels by 3.8 fold versus CASR wild type.ConclusionWe identified a novel CASR gene mutation in a young boy with ADH. Although the mutation leads to a truncation of the protein, it leads to a constitutive gain-of-function of the receptor. This finding is in line with the clinical phenotype observed in our patient.