Endothelial dysfunction aggravates arterial media calcification in warfarin administered rats.

Arterial media calcification is an active cell process. This encompasses osteochondrogenic transdifferentiation of vascular smooth muscle cells followed by the deposition of calcium-phosphate crystals. Increasing evidence suggests a significant role for endothelial cells (ECs) in the development of arterial media calcification. This manuscript explores a role for endothelial dysfunction in the disease progression of arterial media calcification. Male rats were randomly assigned to four different groups. The first group received standard chow. The second group was given L-NAME (≈50 mg kg-1 · d-1 ), to induce endothelial dysfunction, in addition to standard chow. The third group and fourth group received a warfarin-supplemented diet to induce mild calcification and the latter group was co-administered L-NAME. Prior to sacrifice, non-invasive measurement of aortic distensibility was performed. Animals were sacrificed after 6 weeks. Arterial media calcification was quantified by measuring aortic calcium and visualized on paraffin-embedded slices by the Von Kossa method. Arterial stiffness and aortic reactivity was assessed on isolated carotid segments using specialized organ chamber setups. Warfarin administration induced mineralization. Simultaneous administration of warfarin and L-NAME aggravated the arterial media calcification process. Through organ chamber experiments an increased vessel tonus was found, which could be linked to reduced basal NO availability, in arteries of warfarin-treated animals. Furthermore, increased calcification because of L-NAME administration was related to a further compromised endothelial function (next to deteriorated basal NO release also deteriorated stimulated NO release). Our findings suggest early EC changes to impact the disease progression of arterial media calcification.

Effects of medicagenic acid metabolites, originating from biotransformation of an Herniaria hirsuta extract, on calcium oxalate crystallization in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Herniaria hirsuta is traditionally used in Moroccan folk medicine for treatment of urinary stones and as a diuretic. It is rich in saponins, which are known to be deglycosylated in the colon, whereafter aglycones such as medicagenic acid are absorbed and further metabolized in the liver. AIM OF THE STUDY: A sample of hepatic metabolites of medicagenic acid, with medicagenic acid glucuronide as the most abundant one, was evaluated for in vitro activity against urinary stones. A crystallization assay and a crystal-cell interaction assay were used to evaluate in vitro activity of hepatic metabolites of medicagenic acid on CaC2O4 (calciumoxalate) crystals, present in the majority of urinary stones. MATERIALS AND METHODS: In the crystallization assay the effects on nucleation of Ca2+ and C2O42- and aggregation of the CaC2O4 crystals are studied. In the crystal-cell interaction assay crystal retention is investigated by determining the amount of Ca2+ bound to injured monolayers of MDCK I cells. RESULTS: Results of the crystallization assay showed a tentative effect on crystal aggregation. The crystal-cell interaction assay showed a significant inhibition of crystal binding, which may reduce crystal retention in the urinary tract. CONCLUSIONS: As both formation of crystals by inhibiting aggregation and retention of crystals is affected, the beneficial effect of H. hirsuta against urinary stones may at least in part be attributed to medicagenic acid metabolites, indicating that saponins containing medicagenic acid may act as prodrugs.

Chronic Kidney Disease-Induced Arterial Media Calcification in Rats Prevented by Tissue Non-Specific Alkaline Phosphatase Substrate Supplementation Rather Than Inhibition of the Enzyme.

Patients with chronic kidney disease (CKD) suffer from arterial media calcification and a disturbed bone metabolism. Tissue-nonspecific alkaline phosphatase (TNAP) hydrolyzes the calcification inhibitor pyrophosphate (PPi) into inorganic phosphate (Pi) and thereby stimulates arterial media calcification as well as physiological bone mineralization. This study investigates whether the TNAP inhibitor SBI-425, PPi or the combination of both inhibit arterial media calcification in an 0.75% adenine rat model of CKD. Treatments started with the induction of CKD, including (i) rats with normal renal function (control diet) treated with vehicle and CKD rats treated with either (ii) vehicle, (iii) 10 mg/kg/day SBI-425, (iv) 120 µmol/kg/day PPi and (v) 120 µmol/kg/day PPi and 10 mg/kg/day SBI-425. All CKD groups developed a stable chronic renal failure reflected by hyperphosphatemia, hypocalcemia and high serum creatinine levels. CKD induced arterial media calcification and bone metabolic defects. All treatments, except for SBI-425 alone, blocked CKD-related arterial media calcification. More important, SBI-425 alone and in combination with PPi increased osteoid area pointing to a less efficient bone mineralization. Clearly, potential side effects on bone mineralization will need to be assessed in any clinical trial aimed at modifying the Pi/PPi ratio in CKD patients who already suffer from a compromised bone status.

Renoprotective effects of sucroferric oxyhydroxide in a rat model of chronic renal failure.

INTRODUCTION: Sucroferric oxyhydroxide (PA21) is an efficacious, well-tolerated iron-based phosphate binder and a promising alternative to existing compounds. We compared the effects of PA21 with those of a conventional phosphate binder on renal function, mineral homeostasis and vascular calcification in a chronic kidney disease-mineral and bone disorder (CKD-MBD) rat model. METHODS: To induce stable renal failure, rats were administered a 0.25% adenine diet for 8 weeks. Concomitantly, rats were treated with vehicle, 2.5 g/kg/day PA21, 5.0 g/kg/day PA21 or 3.0 g/kg/day calcium carbonate (CaCO3). Renal function and calcium/phosphorus/iron metabolism were evaluated during the study course. Renal fibrosis, inflammation, vascular calcifications and bone histomorphometry were quantified. RESULTS: Rats treated with 2.5 or 5.0 g/kg/day PA21 showed significantly lower serum creatinine and phosphorus and higher ionized calcium levels after 8 weeks of treatment compared with vehicle-treated rats. The better preserved renal function with PA21 went along with less severe anaemia, which was not observed with CaCO3. Both PA21 doses, in contrast to CaCO3, prevented a dramatic increase in fibroblast growth factor (FGF)-23 and significantly reduced the vascular calcium content while both compounds ameliorated CKD-related hyperparathyroid bone. CONCLUSIONS: PA21 treatment prevented an increase in serum FGF-23 and had, aside from its phosphate-lowering capacity, a beneficial impact on renal function decline (as assessed by the renal creatinine clearance) and related disorders. The protective effect of this iron-based phosphate binder on the kidney in rats, together with its low pill burden in humans, led us to investigate its use in patients with impaired renal function not yet on dialysis.

Inhibition of vascular calcification by inositol phosphates derivatized with ethylene glycol oligomers.

Myo-inositol hexakisphosphate (IP6) is a natural product known to inhibit vascular calcification (VC), but with limited potency and low plasma exposure following bolus administration. Here we report the design of a series of inositol phosphate analogs as crystallization inhibitors, among which 4,6-di-O-(methoxy-diethyleneglycol)-myo-inositol-1,2,3,5-tetrakis(phosphate), (OEG2)2-IP4, displays increased in vitro activity, as well as more favorable pharmacokinetic and safety profiles than IP6 after subcutaneous injection. (OEG2)2-IP4 potently stabilizes calciprotein particle (CPP) growth, consistently demonstrates low micromolar activity in different in vitro models of VC (i.e., human serum, primary cell cultures, and tissue explants), and largely abolishes the development of VC in rodent models, while not causing toxicity related to serum calcium chelation. The data suggest a mechanism of action independent of the etiology of VC, whereby (OEG2)2-IP4 disrupts the nucleation and growth of pathological calcification.

Human health risk associated with the management of phosphorus in freshwaters using lanthanum and aluminium.

The use of geo-engineering materials to manage phosphorus in lakes has increased in recent years with aluminium and lanthanum based materials being most commonly applied. Hence the potential impact of the use of these compounds on human health is receiving growing interest. This review seeks to understand, evaluate and compare potential unintended consequences on human health and ecotoxicological risks associated with the use of lanthanum- and aluminium-based materials to modify chemical and ecological conditions in water bodies. In addition to their therapeutic use for the reduction of intestinal phosphate absorption in patients with impaired renal function, the phosphate binding capacity of aluminium and lanthanum also led to the development of materials used for water treatment. Although lanthanum and aluminium share physicochemical similarities and have many common applications, their uptake and kinetics within the human body and living organisms importantly differ from each other which is reflected in a different toxicity profile. Whilst a causal role in the development of neurological pathologies, skeletal lesions, hematopoietic disorders and respiratory effects has unequivocally been demonstrated with increased exposure to aluminium, studies until now have failed to find such a clear association after exposure to lanthanum although caution is warranted. Our review indicates that lanthanum and aluminium have a distinctly different profile with respect to their potential effects on human health. Regular monitoring of both aluminium and lanthanum concentrations in lanthanum-/aluminium-treated water by the responsible authorities is recommended to avoid acute accidental or chronic low level accumulation.

Characterization of an Animal Model to Study Risk Factors and New Therapies for the Cardiorenal Syndrome, a Major Health Issue in Our Aging Population.

BACKGROUND: The cardiorenal syndrome (CRS) is a major health problem in our aging population. The term was introduced to cover disorders of the kidneys and heart, whereby dysfunction of one organ may induce dysfunction of the other. As the natural history of the CRS is mostly slow, hence difficult to explore in clinical trials, adequate animal models combining cardiovascular and renal disease are required. Therefore, we developed and characterized a usable model for CRS type 4, i.e. chronic kidney disease (CKD) causing cardiac dysfunction. METHODS: CKD was induced in rats by supplementing the diet with adenine. During 8 weeks, several aspects of CRS were studied: CKD, mineral-bone disorder (MBD), cardiovascular disease, and (iron-deficiency) anemia. Hereto, the following parameters were monitored: serum creatinine, calcium, phosphate, FGF23, dynamic bone parameters, aortic Ca deposits, heart weight, serum NT-proANP, Hct, Hb, reticulocytes, spleen iron, and serum hepcidin. RESULTS: Animals developed a severe CKD together with a disturbed mineral balance as reflected by the increased serum creatinine and phosphorus levels and decreased serum calcium levels; and in association herewith aberrations in hormonal levels of FGF-23. In turn, the well-known and highly undesirable complications of CKD, i.e. high turnover bone disease and pathological vessel calcification were induced. Furthermore (iron-deficiency) anemia developed quickly. CONCLUSION: The animal model described in this article in many aspects mimics the human situation of the CRS type 4 and will be useful to concomitantly evaluate the effects of new treatment strategies on the various aspects of CRS.

DPP IV inhibitor treatment attenuates bone loss and improves mechanical bone strength in male diabetic rats.

Dipeptidyl peptidase IV (DPP IV) modulates protein activity by removing dipeptides. DPP IV inhibitors are currently used to improve glucose tolerance in type 2 diabetes patients. DPP IV substrates not only increase insulin secretion but also affect bone metabolism. In this study, the effect of DPP IV inhibitor sitagliptin on bone was evaluated in normal and streptozotocin-induced diabetic rats. This study included 64 male Wistar rats divided into four groups (n = 16): two diabetic and two control groups. One diabetic and one control group received sitagliptin through drinking water. Tibiae were scanned every 3 wk using an in vivo µCT scanner. After 6 and 12 wk, rats were euthanized for histomorphometric analysis of bone parameters. The mechanical resistance of femora to fracture was assessed using a three-point bending test, and serum levels of bone metabolic markers were measured. Efficient DPP IV inhibition was achieved in sitagliptin-treated groups. Trabecular bone loss, the decrease in trabecular number, and the increase in trabecular spacing was attenuated through sitagliptin treatment in diabetic rats, as shown by in vivo µCT. Bone histomorphometry was in line with these results. µCT analysis furthermore showed that sitagliptin prevented cortical bone growth stagnation in diabetic rats, resulting in stronger femora during three-point bending. Finally, the serum levels of the resorption marker CTX-I were significantly lower in sitagliptin-treated diabetic animals compared with untreated diabetic animals. In conclusion, sitagliptin treatment attenuates bone loss and increases bone strength in diabetic rats probably through the reduction of bone resorption and independent of glycemic management.