A Genetic Polymorphism (rs17251221) in the Calcium-Sensing Receptor Gene (CASR) Is Associated with Stone Multiplicity in Calcium Nephrolithiasis

Calcium nephrolithiasis is one of the most common causes of renal stones. While the prevalence of this disease has increased steadily over the last 3 decades, its pathogenesis is still unclear. Previous studies have indicated that a genetic polymorphism (rs17251221) in the calcium-sensing receptor gene (CASR) is associated with the total serum calcium levels. In this study, we collected DNA samples from 480 Taiwanese subjects (189 calcium nephrolithiasis patients and 291 controls) for genotyping the CASR gene. Our results indicated no significant association between the CASR polymorphism (rs17251221) and the susceptibility of calcium nephrolithiasis. However, we found a significant association between rs17251221 and stone multiplicity. The risk of stone multiplicity was higher in patients with the GG+GA genotype than in those with the AA genotype (chi-square test:P = 0.008;odds ratio  =  4.79;95% confidence interval, 1.44–15.92;Yates' correction for chi-square test:P = 0.013). In conclusion, our results provide evidence supporting the genetic effects of CASR on the pathogenesis of calcium nephrolithiasis

Deletion of PTH Rescues Skeletal Abnormalities and High Osteopontin Levels in Klotho−/− Mice

Maintenance of normal mineral ion homeostasis is crucial for many biological activities, including proper mineralization of the skeleton. Parathyroid hormone (PTH), Klotho, and FGF23 have been shown to act as key regulators of serum calcium and phosphate homeostasis through a complex feedback mechanism. The phenotypes of Fgf23−/− and Klotho−/− (Kl−/−) mice are very similar and include hypercalcemia, hyperphosphatemia, hypervitaminosis D, suppressed PTH levels, and severe osteomalacia/osteoidosis. We recently reported that complete ablation of PTH from Fgf23−/− mice ameliorated the phenotype in Fgf23−/−/PTH−/− mice by suppressing serum vitamin D and calcium levels. The severe osteomalacia in Fgf23−/− mice, however, persisted, suggesting that a different mechanism is responsible for this mineralization defect. In the current study, we demonstrate that deletion of PTH from Kl−/− (Kl−/−/PTH−/− or DKO) mice corrects the abnormal skeletal phenotype. Bone turnover markers are restored to wild-type levels; and, more importantly, the skeletal mineralization defect is completely rescued in Kl−/−/PTH−/− mice. Interestingly, the correction of the osteomalacia is accompanied by a reduction in the high levels of osteopontin (Opn) in bone and serum. Such a reduction in Opn levels could not be observed in Fgf23−/−/PTH−/− mice, and these mice showed sustained osteomalacia. This significant in vivo finding is corroborated by in vitro studies using calvarial osteoblast cultures that show normalized Opn expression and rescued mineralization in Kl−/−/PTH−/− mice. Moreover, continuous PTH infusion of Kl−/− mice significantly increased Opn levels and osteoid volume, and decreased trabecular bone volume. In summary, our results demonstrate for the first time that PTH directly impacts the mineralization disorders and skeletal deformities of Kl−/−, but not of Fgf23−/− mice, possibly by regulating Opn expression. These are significant new perceptions into the role of PTH in skeletal and disease processes and suggest FGF23-independent interactions of PTH with Klotho

Localization and function of the renal calcium-sensing receptor

The ability to monitor changes in the ionic composition of the extracellular environment is a crucial feature that has evolved in all living organisms. The cloning and characterization of the extracellular calcium-sensing receptor (CaSR) from the mammalian parathyroid gland in the early 1990s provided the first description of a cellular, ion-sensing mechanism. This finding demonstrated how cells can detect small, physiological variations in free ionized calcium (Ca 2+) in the extracellular fluid and subsequently evoke an appropriate biological response by altering the secretion of parathyroid hormone (PTH) that acts on PTH receptors expressed in target tissues, including the kidney, intestine, and bone. Aberrant Ca 2+ sensing by the parathyroid glands, as a result of altered CaSR expression or function, is associated with impaired divalent cation homeostasis. CaSR activators that mimic the effects of Ca 2+ (calcimimetics) have been designed to treat hyperparathyroidism, and CaSR antagonists (calcilytics) are in development for the treatment of hypercalciuric disorders. The kidney expresses a CaSR that might directly contribute to the regulation of many aspects of renal function in a PTH-independent manner. This Review discusses the roles of the renal CaSR and the potential impact of pharmacological modulation of the CaSR on renal function

Lactobacillus fermentum ME-3 – an antimicrobial and antioxidative probiotic

The paper lays out the short scientific history and characteristics of the new probiotic Lactobacillus fermentum strain ME-3 DSM-14241, elaborated according to the regulations of WHO/FAO (2002). L. fermentum ME-3 is a unique strain of Lactobacillus species, having at the same time the antimicrobial and physiologically effective antioxidative properties and expressing health-promoting characteristics if consumed. Tartu University has patented this strain in Estonia (priority June 2001, patent in 2006), Russia (patent in 2006) and the USA (patent in 2007). The paper describes the process of the identification and molecular typing of this probiotic strain of human origin, its deposition in an international culture collection, and its safety assessment by laboratory tests and testing on experimental animals and volunteers. It has been established that L. fermentum strain ME-3 has double functional properties: antimicrobial activity against intestinal pathogens and high total antioxidative activity (TAA) and total antioxidative status (TAS) of intact cells and lysates, and it is characterized by a complete glutathione system: synthesis, uptake and redox turnover. The functional efficacy of the antimicrobial and antioxidative probiotic has been proven by the eradication of salmonellas and the reduction of liver and spleen granulomas in Salmonella Typhimurium-infected mice treated with the combination of ofloxacin and L. fermentum strain ME-3. Using capsules or foodstuffs enriched with L. fermentum ME-3, different clinical study designs (including double-blind, placebo-controlled, crossover studies) and different subjects (healthy volunteers, allergic patients and those recovering from a stroke), it has been shown that this probiotic increased the antioxidative activity of sera and improved the composition of the low-density lipid particles (LDL) and post-prandial lipids as well as oxidative stress status, thus demonstrating a remarkable anti-atherogenic effect. The elaboration of the probiotic L. fermentum strain ME-3 has drawn on wide international cooperative research and has taken more than 12 years altogether. The new ME-3 probiotic-containing products have been successfully marketed and sold in Baltic countries and Finland

Autosomal dominant hypercalciuria in a mouse model due to a mutation of the epithelial calcium channel, TRPV5

Contains fulltext : 118040.pdf (publisher's version ) (Open Access)Hypercalciuria is a major cause of nephrolithiasis, and is a common and complex disorder involving genetic and environmental factors. Identification of genetic factors for monogenic forms of hypercalciuria is hampered by the limited availability of large families, and to facilitate such studies, we screened for hypercalciuria in mice from an N-ethyl-N-nitrosourea mutagenesis programme. We identified a mouse with autosomal dominant hypercalciuria (HCALC1). Linkage studies mapped the Hcalc1 locus to a 11.94 Mb region on chromosome 6 containing the transient receptor potential cation channel, subfamily V, members 5 (Trpv5) and 6 (Trpv6) genes. DNA sequence analysis of coding regions, intron-exon boundaries and promoters of Trpv5 and Trpv6 identified a novel T to C transition in codon 682 of TRPV5, mutating a conserved serine to a proline (S682P). Compared to wild-type littermates, heterozygous (Trpv5(682P/+)) and homozygous (Trpv5(682P/682P)) mutant mice had hypercalciuria, polyuria, hyperphosphaturia and a more acidic urine, and approximately 10% of males developed tubulointerstitial nephritis. Trpv5(682P/682P) mice also had normal plasma parathyroid hormone but increased 1,25-dihydroxyvitamin D(3) concentrations without increased bone resorption, consistent with a renal defect for the hypercalciuria. Expression of the S682P mutation in human embryonic kidney cells revealed that TRPV5-S682P-expressing cells had a lower baseline intracellular calcium concentration than wild-type TRPV5-expressing cells, suggesting an altered calcium permeability. Immunohistological studies revealed a selective decrease in TRPV5-expression from the renal distal convoluted tubules of Trpv5(682P/+) and Trpv5(682P/682P) mice consistent with a trafficking defect. In addition, Trpv5(682P/682P) mice had a reduction in renal expression of the intracellular calcium-binding protein, calbindin-D(28K), consistent with a specific defect in TRPV5-mediated renal calcium reabsorption. Thus, our findings indicate that the TRPV5 S682P mutant is functionally significant and study of HCALC1, a novel model for autosomal dominant hypercalciuria, may help further our understanding of renal calcium reabsorption and hypercalciuria