The most common cause of death in the intensive care unit (ICU) is the development of multiorgan dysfunction syndrome (MODS). Besides life-supporting treatments, no cure exists, and its mechanisms ...are still poorly understood. Catalytic iron is associated with ICU mortality and is known to cause free radical-mediated cellular toxicity. It is thought to induce excessive lipid peroxidation, the main characteristic of an iron-dependent type of cell death conceptualized as ferroptosis. Here we show that the severity of multiorgan dysfunction and the probability of death are indeed associated with plasma catalytic iron and lipid peroxidation. Transgenic approaches underscore the role of ferroptosis in iron-induced multiorgan dysfunction. Blocking lipid peroxidation with our highly soluble ferrostatin-analogue protects mice from injury and death in experimental non-septic multiorgan dysfunction, but not in sepsis-induced multiorgan dysfunction. The limitations of the experimental mice models to mimic the complexity of clinical MODS warrant further preclinical testing. In conclusion, our data suggest ferroptosis targeting as possible treatment option for a stratifiable subset of MODS patients.
Diabetic Kidney Disease (DKD) is a major microvascular complication for diabetic patients and is the most common cause of chronic kidney disease (CKD) and end-stage renal disease. Antidiabetic drugs, ...such as metformin and canagliflozin, have been shown to exert renoprotective effects. Additionally, quercetin recently showed promising results for the treatment of DKD. However, the molecular pathways through which these drugs exert their renoprotective effects remain partly unknown. The current study compares the renoprotective potential of metformin, canagliflozin, metformin + canagliflozin, and quercetin in a preclinical rat model of DKD. By combining streptozotocin (STZ) and nicotinamide (NAD) with daily oral N(ω)-Nitro-L-Arginine Methyl Ester (L-NAME) administration, DKD was induced in male Wistar Rats. After two weeks, rats were assigned to five treatment groups, receiving vehicle, metformin, canagliflozin, metformin + canagliflozin, or quercetin for a period of 12 weeks by daily oral gavage. Non-diabetic vehicle-treated control rats were also included in this study. All rats in which diabetes was induced developed hyperglycemia, hyperfiltration, proteinuria, hypertension, renal tubular injury and interstitial fibrosis, confirming DKD. Metformin and canagliflozin, alone or together, exerted similar renoprotective actions and similar reductions in tubular injury and collagen accumulation. Renoprotective actions of canagliflozin correlated with reduced hyperglycemia, while metformin was able to exert these effects even in the absence of proper glycemic control. Gene expression revealed that the renoprotective pathways may be traced back to the NF-κB pathway. No protective effect was seen with quercetin. In this experimental model of DKD, metformin and canagliflozin were able to protect the kidney against DKD progression, albeit in a non-synergistic way. These renoprotective effects may be attributable to the inhibition of the NF-κB pathway.
The alternative phosphate binder calcium acetate/magnesium carbonate (CaMg) effectively reduces hyperphosphatemia, the most important inducer of vascular calcification, in chronic renal failure ...(CRF). In this study, the effect of low dose CaMg on vascular calcification and possible effects of CaMg on bone turnover, a persistent clinical controversy, were evaluated in chronic renal failure rats. Adenine-induced CRF rats were treated daily with 185 mg/kg CaMg or vehicle for 5 weeks. The aortic calcium content and area% calcification were measured to evaluate the effect of CaMg. To study the effect of CaMg on bone remodeling, rats underwent 5/6th nephrectomy combined with either a normal phosphorus diet or a high phosphorus diet to differentiate between possible bone effects resulting from either CaMg-induced phosphate deficiency or a direct effect of Mg. Vehicle or CaMg was administered at doses of 185 and 375 mg/kg/day for 8 weeks. Bone histomorphometry was performed. Aortic calcium content was significantly reduced by 185 mg/kg/day CaMg. CaMg ameliorated features of hyperparathyroid bone disease. In CRF rats on a normal phosphorus diet, the highest CaMg dose caused an increase in osteoid area due to phosphate depletion. The high phosphorus diet combined with the highest CaMg dose prevented the phosphate depletion and thus the rise in osteoid area. CaMg had no effect on osteoblast/osteoclast or dynamic bone parameters, and did not alter bone Mg levels. CaMg at doses that reduce vascular calcification did not show any harmful effect on bone turnover.
Renal osteodystrophy (ROD) is a complex and serious complication of chronic kidney disease (CKD), a major global health problem caused by loss of renal function. Currently, the gold standard to ...accurately diagnose ROD is based on quantitative histomorphometric analysis of trabecular bone. Although this analysis encompasses the evaluation of osteoblast and osteoclast number/activity, tfigurehe interest in osteocytes remains almost nihil. Nevertheless, this cell type is evidenced to perform a key role in bone turnover, particularly through its production of various bone proteins, such as sclerostin. In this study, we aim to investigate, in the context of ROD, to which extent an association exists between bone turnover and the abundance of osteocytes and osteocytic sclerostin expression in both the trabecular and cortical bone compartments. Additionally, the effect of parathyroid hormone (PTH) on bone sclerostin expression was examined in parathyroidectomized rats. Our results indicate that PTH exerts a direct inhibitory function on sclerostin, which in turn negatively affects bone turnover and mineralization. Moreover, this study emphasizes the functional differences between cortical and trabecular bone, as the number of (sclerostin-positive) osteocytes is dependent on the respective bone compartment. Finally, we evaluated the potential of sclerostin as a marker for CKD and found that the diagnostic performance of circulating sclerostin is limited and that changes in skeletal sclerostin expression occur more rapidly and more pronounced. The inclusion of osteocytic sclerostin expression and cortical bone analysis could be relevant when performing bone histomorphometric analysis for diagnostic purposes and to unravel pathological mechanisms of bone disease.
Both calcium-containing and noncalcium-containing phosphate binders can increase gastrointestinal calcium absorption. Previously, we observed that lanthanum carbonate administration to rats with ...renal failure is not associated with increased calciuria. Additionally, lanthanum carbonate treatment in dialysis patients has been associated with a less pronounced initial decrease in serum parathyroid hormone compared with other phosphate binders. For 8 days, male Wistar rats received a diet supplemented with 2% lanthanum carbonate, 2% sevelamer, 2% calcium carbonate, or 2% cellulose. Calciuria was found to be increased in animals with normal renal function treated with sevelamer or calcium carbonate but not with lanthanum carbonate. In animals with renal failure, cumulative calcium excretion showed similar results. In rats with normal renal function, serum ionized calcium levels were increased after 2 days of treatment with sevelamer, while calcium carbonate showed a smaller increase. Lanthanum carbonate did not induce differences. In animals with renal failure, no differences were found between sevelamer-treated, calcium carbonate-treated, and control groups. Lanthanum carbonate, however, induced lower ionized calcium levels within 2 days of treatment. These results were confirmed in normal human volunteers, who showed lower net calcium absorption after a single dose of lanthanum carbonate compared with sevelamer carbonate. In conclusion, these two noncalcium-containing phosphate-binding agents showed a differential effect on gastrointestinal calcium absorption. These findings may help to improve the management of calcium balance in patients with renal failure, including concomitant use of vitamin D.
Various biochemical markers have been evaluated in dialysis patients for the diagnosis of renal osteodystrophy (ROD). However, their value in predialysis patients with end-stage renal failure (ESRF) ...is not yet clear.
Bone histomorphometric evaluation was performed and biochemical markers of bone turnover were determined in serum of an unselected predialysis ESRF population (N = 84).
Significant (P < 0.005) differences between the five groups with ROD (ie, normal bone N = 32, adynamic bone ABD; N = 19, hyperparathyroidism N = 8, osteomalacia OM; N = 10, and mixed lesion N = 15) were noted for intact parathyroid hormone, total (TAP) and bone alkaline phosphatase (BAP), osteocalcin (OC), and serum calcium levels. Serum creatinine and (deoxy)pyridinoline levels did not differ between groups. For the diagnosis of ABD, an OC level of 41 μg/L or less (≤7.0 nmol/L) had a sensitivity of 83% and specificity of 67%. The positive predictive value (PPV) for the population under study was 47%. The combination of an OC level of 41 ng/L or less (≤7.0 nmol/L) with a BAP level of 23 U/L or less increased the sensitivity, specificity, and PPV to 72%, 89%, and 77%, respectively. ABD and normal bone taken as one group could be detected best by a BAP level of 25 U/L or less and TAP level of 84 U/L or less, showing sensitivities of 72% and 88% and specificities of 76% and 60%, corresponding with PPVs of 89% and 85%, respectively. In the absence of aluminum or strontium exposure, serum calcium level was found to be a useful index for the diagnosis of OM.
OC, TAP, BAP, and serum calcium levels are useful in the diagnosis of ABD, normal bone, and OM in predialysis patients with ESRF.
The remnant kidney rat model has been extensively used for the evaluation of bone changes due to uremia. The present study aimed to assess the effect of the dietary phosphorus availability and of the ...severity of renal failure on bone histomorphometric changes and various biochemical markers over time in this model. Chronic renal failure (CRF) was induced in male Wistar rats by 5 6th nephrectomy. Half of the number of animals received a standard rat diet (STD) (0.67% P, containing low bioavailable phosphorus of plant origin); the other animals were fed a high phosphorus diet (HPD) (0.93% P, containing inorganic phosphorus with high bioavailability). Every two weeks, blood and urine samples were collected. At sacrifice after 6 or 12 weeks, bone samples were taken for the measurement of histological and histodynamic parameters. Serum creatinine measurements indicated the development of mild to moderate renal failure in both diet groups. Phosphaturia was unexpectedly low in all animals that received the STD, indicating relative phosphorus depletion despite the normal dietary phosphorus content. In the HPD CRF group, a decrease in calcemia and a rise in phosphatemia were seen after 12 weeks of CRF, which were more pronounced in animals with higher serum creatinine. Serum iPTH levels were distinctly increased in CRF rats fed a HPD, especially those with more pronounced renal failure. Serum osteocalcin and to a lesser extend tartrate-resistant acid phosphatase and urinary pyridinoline and deoxypyridinoline crosslinks were higher in the CRF animals compared to the shams, particularly in the animals of the HPD group with more pronounced CRF. In both diet groups, the CRF animals had significantly higher amounts of osteoid compared to shams. Only the animals that received a HPD developed distinct histological signs of secondary hyperparathyroidism (sHPTH), that is, an increased bone formation rate, mineral apposition rate, osteoblast perimeter, and eroded perimeter. Again, this effect was most prominent in rats with more severe CRF. In conclusion, data of the present study indicate that in experimental studies using the remnant kidney rat model, both the dietary phosphorus bioavailability and the degree of renal failure in the development of hyperparathyroidism should be considered.
Vascular calcification significantly contributes to mortality in chronic kidney disease (CKD) patients. Sevelamer and pyrophosphate (PPi) have proven to be effective in preventing vascular ...calcification, the former by controlling intestinal phosphate absorption, the latter by directly interfering with the hydroxyapatite crystal formation. Since most patients present with established vascular calcification, it is important to evaluate whether these compounds may also halt or reverse the progression of preexisting vascular calcification. CKD and vascular calcification were induced in male Wistar rats by a 0.75 % adenine low protein diet for 4 weeks. Treatment with PPi (30 or 120 µmol/kg/day), sevelamer carbonate (1500 mg/kg/day) or vehicle was started at the time point at which vascular calcification was present and continued for 3 weeks. Hyperphosphatemia and vascular calcification developed prior to treatment. A significant progression of aortic calcification in vehicle-treated rats with CKD was observed over the final 3-week period. Sevelamer treatment significantly reduced further progression of aortic calcification as compared to the vehicle control. No such an effect was seen for either PPi dose. Sevelamer but not PPi treatment resulted in an increase in both osteoblast and osteoid perimeter. Our study shows that sevelamer was able to reduce the progression of moderate to severe preexisting aortic calcification in a CKD rat model. Higher doses of PPi may be required to induce a similar reduction of severe established arterial calcification in this CKD model.
Background. During the last few years the spectrum of renal osteodystrophy (ROD) in dialysis patients has been studied thoroughly and the prevalence of the various types of ROD has changed ...considerably. Whereas until a decade ago most patients presented with secondary hyperparathyroidism (HPTH), adynamic bone (ABD) has become the most common lesion within the dialysis population over the last few years. Much less is known about the spectrum of ROD in end‐stage renal failure (ESRF) patients not yet on dialysis. Methods. Transiliac bone biopsies were taken in an unselected group of 84 ESRF patients (44 male, age 54±12 years) before enrolment in a dialysis programme. All patients were recruited within a time period of 10 months from various centres (n=18) in Macedonia. Calcium carbonate was the only prescribed medication in patients followed up by the outpatient clinic. Results. HPTH was found in only 9% of the patients, whilst ABD appeared to be the most frequent renal bone disease as it was observed in 23% of the cases next to normal bone (38%). A relatively high number of patients (n=10; 12%) fulfilled the criteria of osteomalacia (OM). Mixed osteodystrophy (MX) was diagnosed in 18% of the subjects. There was no significant difference between groups in age, creatinine, or serum and bone strontium and aluminium levels. Patient characteristics associated with ABD included male gender and diabetes, whilst OM was associated with older age (>58 years). Conclusions. In an unselected population of ESRF patients already, 62% of them have an abnormal bone histology. ABD is the most prevalent type of ROD in this population. In the absence of aluminium or strontium accumulation the relatively high prevalence of a low bone turnover as expressed by either normal bone or ABD and OM is striking.
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