Peripheral artery calcifications evaluated by histology correlate to those detected by CT: relationships with fetuin-A and FGF-23.

BACKGROUND: Calcification of arteries is a frequent occurrence in hemodialysis (HD) patients and is linked to mortality. This study was conducted to evaluate the correspondence between coronary calcification scores and calcifications observed histologically in peripheral arteries in HD patients. In addition the association of humoral parameters including fetuin-A and fibroblast growth factor 23 (FGF-23) with arterial calcifications was studied. PATIENTS AND METHODS: HD patients (n=44) were studied with multislice computed tomography (CT) and histological quantification of arterial calcifications in the lower epigastric artery sampled at the time of renal transplant. In addition, humoral assays were performed including fetuin-A and FGF-23. RESULTS: There was a significant correlation between medial calcification of the artery and Agatston scores. Natural logarithm (Ln) FGF-23 significantly correlated to Ln Agatston score but not to Ln medial calcification. A significant negative correlation between fetuin-A and Ln FGF-23 was observed, changing to borderline significance after correction for age and Ln HD age. Ln Agatston score in a multiregression analysis was predicted by Ln FGF-23 and age. CONCLUSIONS: The association found between histologically evaluated calcification of the media of a peripheral artery in HD and the multislice CT Agatston scores is in favor of a generalized arterial calcification, either intimal or of tunica media, when calcium deposits are found in the coronary arteries. The association of FGF-23 with coronary calcification score, already reported, and less so with histological medial calcification is in favor of a link between the protein and intimal more than the medial calcification. FGF-23 may be considered a potential biomarker of arterial calcification in HD patients. The negative association between fetuin-A and FGF-23 may suggest a linkage between these humoral substances, vascular calcifications and mortality. The nature of this linkage requires further studies.

Risk factors of one year increment of coronary calcifications and survival in hemodialysis patients.

BACKGROUND: Heart and coronary calcifications in hemodialysis patients are of very common occurrence and linked to cardiovascular events and mortality. Several studies have been published with similar results. Most of them were mainly cross-sectional and some of the prospective protocols were aimed to evaluate the results of the control of altered biochemical parameters of mineral disturbances with special regard to serum calcium, phosphate and CaxP with the use of calcium containing and calcium free phosphate chelating agents. The aim of the present study was to evaluate in hemodialysis patients classic and some non classic risk factors as predictors of calcification changes after one year and to evaluate the impact of progression on survival. METHODS: 81 patients on hemodialysis were studied, with a wide age range and HD vintage. Several classic parameters and some less classic risk factors were studied like fetuin-A, CRP, 25-OHD and leptin. Calcifications, as Agatston scores, were evaluated with Multislice CT basally and after 12-18 months. RESULTS: Coronary artery calcifications were observed in 71 of 81 patients. Non parametric correlations between Agatston scores and Age, HD Age, PTH and CRP were significant. Delta increments of Agatston scores correlated also with serum calcium, CaxP, Fetuin-A, triglycerides and serum albumin. Logistic regression analysis showed Age, PTH and serum calcium as important predictors of Delta Agatston scores. LN transformation of the not normally distributed variables restricted the significant correlations to Age, BMI and CRP. Considering the Delta Agatston scores as dependent, significant predictors were Age, PTH and HDL. A strong association was found between basal calcification scores and Delta increment at one year. By logistic analysis, the one year increments in Agatston scores were found to be predictors of mortality. Diabetic and hypertensive patients have significantly higher Delta scores. CONCLUSIONS: Progression of calcification is of common occurrence, with special regard to elevated basal scores, and is predictive of survival. Higher predictive value of survival is linked to the one year increment of calcification scores. Some classic and non classic risk factors play an important role in progression. Some of them could be controlled with appropriate management with possible improvement of mortality.

"De medicina et morbis" from De rerum naturis by Rabano Mauro.

De rerum naturis from the Monastery of Montecassino (MS codex 132) by Rabano Mauro, is a medieval encyclopedia issued around the year 1025, in the Abbey of Montecassino, during the period of Abbot Teobaldo. It is a copy of a more ancient text, written almost certainly in the Abbey of Fulda 2 centuries before, when Rabano Mauro was the abbot - that is, in the Carolingian age. In the Book 18 there is a chapter entitled "De medicina et morbis," in which we find related the fundamental principles on which studies of the human body, illness and the principal medicinal herbs were based. The text is not intended for teaching the medical art, but has the precise objective of helping to form the cultured Christian, trying to combine the old Greek-Roman tradition with a mystical vision, giving a moral application according to the dictates of Jewish-Christian religion. This text is indicative of the fusion of the scientific and religious worlds in the West during the Middle Ages. This interpretation of the universe will last for about a millennium, and only the Renaissance will be able to separate the 2 worlds again.

Asymmetric dimethylarginine, vascular calcifications and parathyroid hormone serum levels in hemodialysis patients.

BACKGROUND: Asymmetric dimethylarginine (ADMA)is an endogenous amino acid similar to l-arginine and able to inhibit the enzyme endothelial nitric oxide synthase (eNOS). It is a factor of impaired nitric oxide (NO) synthesis. Serum levels of ADMA in chronic kidney disease (CKD) increase due to defective inactivation and excretion. High ADMA levels are associated with endothelial dysfunction and cardiovascular damage. A linkage between ADMA levels and vascular calcifications of CKD can therefore be hypothesized. This study explores also a possible relation between ADMA and parathyroid hormone (PTH) serum levels, which are known to be linked to increased rates of cardiovascular death. METHODS: The study was carried out in 79 patients on hemodialysis (HD), mean age 59.25 +/- 12 years. In all patients, serum ADMA, PTH, Ca, P, bone alkaline phosphatase (BALP), cholesterol and albumin were measured. In addition, the patients were subjected to multislice computed tomography for heart calcification evaluation. RESULTS: Correlation analysis of ADMA showed a significant relation with total and coronary calcium volumes, HD vintage, body mass index (BMI), cholesterol, serum albumin, PTH, natural logarithm of PTH (LnPTH) and BALP. Multiple regression analysis selected HD vintage, albumin and PTH as predictive variables for coronary calcium volume, while ADMA was excluded. With LnPTH as dependent variable, ADMA, serum calcium and BMI were predictive variables with R2 of 0.37. ADMA as dependent variable was also predicted by PTH, HD vintage, albumin and BMI. CONCLUSIONS: Despite the results of bivariate analysis showing a linkage between ADMA and cardiac and coronary calcifications, regression analysis showed only a spurious association. The strong positive correlation between ADMA and LnPTH, validated by the regression analysis, may suggesta link between ADMA and PTH-derived vascular damage. ADMA levels could be influenced by the severity of hyperparathyroidism and contribute to cardiovascular death linked to PTH of hemodialysis patients.

Immunohistochemical localization and mRNA expression of matrix Gla protein and fetuin-A in bone biopsies of hemodialysis patients.

Matrix Gla protein (MGP) and fetuin-A are inhibitors of arterial calcifications. In blood of rats, calcium-phosphate-fetuin-MGP complexes, produced in bone, have been identified. Indeed, an association between bone resorption, release of such complexes, and arterial calcifications has been reported. We have investigated the synthesis and localization of fetuin-A and MGP in bone of hemodialysis patients and the possible contribution of bone cells in arterial calcifications. Bone biopsies from 11 hemodialysis patients were used for histology, in situ hybridization of fetuin-A and MGP messenger RNA (mRNA), immunohistochemistry of fetuin-A, and total, carboxylated, and non-carboxylated MGP proteins. Patients showed various types of renal osteodystrophy, or normal bone. MGP was synthesized and expressed (total and carboxylated) by osteoblasts, osteocytes, and most osteoclasts, while fetuin-A by osteoblasts and osteocytes. Fetuin-A and carboxylated MGP proteins were positive in the calcified matrix, while total MGP was negative. Osteoid seams were negative to fetuin-A, lightly positive to carboxylated MGP, and occasionally positive to total MGP. Undercarboxylated MGP was mostly undetectable. In adult humans, fetuin-A is produced also by osteoblasts, and not only by hepatocytes, as previously believed. MGP, essentially carboxylated, is synthesized by osteoblasts and most osteoclasts. Increased bone turnover can be an important contributor to arterial calcifications.

Are PTH serum levels predictive of coronary calcifications in haemodialysis patients?

BACKGROUND: Cardiac calcifications are a frequent occurrence in uraemic subjects and are probably connected to the increased cardiovascular mortality of haemodialysis patients. There is substantial support to the hypothesis that low levels of serum PTH in haemodialysis patients are associated with increased vascular and cardiac calcium deposits, due to decreased buffering capacity of bone in low turnover osteodystrophy. The present study has been carried out on a cohort of patients on haemodialysis, with exclusion of previously parathyroidectomized patients, with the aim to evaluate the association between PTH serum levels and coronary calcifications. METHODS: The study has been carried out in a cohort of 197 haemodialysis patients. There were 133 males and 64 females. Twenty-two patients had diabetes mellitus. Average age was 58.6 +/- 12.9 years. Patients were divided into groups of intact PTH levels, 0-150 (A), 150-300 (B), 300-600 (C) and >600 (D) pg/ml. RESULTS: The values of coronary scores in the PTH groups were as follows: (A) 624.7 +/- 939, (B) 866.4 +/- 1080, (C) 1202.8 +/- 1742.3 and (D) 1872.7 +/- 2961.9. The difference between coronary calcium scores was significant (P < 0.01). A general linear model identified serum calcium and dialysis age as independent factors of calcium deposits in the high PTH group. CONCLUSIONS: No prominent association between low PTH serum levels and the severity of coronary calcium deposits in haemodialysis patients was found while increased levels of PTH, with special regard to very elevated levels, associated with more frequent hypercalcaemia and hyperphosphataemia, should be considered a major risk factor of coronary calcifications and cardiac events.

Renal osteodystrophy: alpha-Heremans Schmid glycoprotein/fetuin-A, matrix GLA protein serum levels, and bone histomorphometry.

BACKGROUND: Fetuin-A of hepatic origin circulates in large amounts in serum, but also is expressed in bone, where it is an inhibitor of transforming growth factor beta (TGF-beta)/bone morphogenetic protein (BMP) proteins. Together with matrix GLA protein (MGP), fetuin-A is able to make up a complex with calcium and phosphate that is more soluble than calcium and phosphate alone, preventing its deposition in extraskeletal tissues. Experimental results suggested that this complex is made at bone tissue level. The aim of this study is to evaluate whether serum fetuin-A and MGP are influenced by type of renal osteodystrophy, they correlate with bone histomorphometric and histodynamic parameters, and/or serum levels may influence bone turnover. METHODS: Thirty-eight hemodialysis patients who volunteered to undergo a bone biopsy were studied. Patients (27 men, 11 women) had a mean age of 55.2 +/- 11.8 years and dialysis vintage of 75.7 +/- 57.4 months. They were not administered vitamin D or drugs connected with mineral metabolism. They underwent transiliac bone biopsy after tetracycline labeling. Biopsies were performed for histological, histomorphometric, and histodynamic evaluation and aluminum histochemistry. Serum fetuin-A and MGP were measured by using enzyme-linked immunosorbent assay kits. RESULTS: Serum fetuin-A levels were significantly less than normal, whereas MGP levels were less than the normal average. Fetuin-A levels in patients with hyperparathyroidism, mixed osteodystrophy, and low-turnover osteodystrophy were 0.219 +/- 0.1, 0.27 +/- 0.1, and 0.197 +/- 0.1 ng/mL, respectively (P = not significant). Fetuin-A level significantly correlated inversely with values for several histomorphometric parameters, such as osteoid volume (OV/BV), osteoblastic surface (Ob.S/BS), osteoid surface (OS/BS), and osteoclastic surface (Oc.S/BS). Logistic regression showed odds ratios of 5.3 and 4.9 for the association of high fetuin-A levels with low values for OS/BS and Ob.S/BS, respectively. Results of multiple regression analysis with intact parathyroid hormone and fetuin-A levels as independent variables and OV/BV and Ob.S/BS as dependent variables showed that independent variables correlated significantly with dependent variables, positively for intact parathyroid hormone levels and inversely for fetuin-A levels. MGP levels in patients with hyperparathyroidism, mixed osteodystrophy, and low-turnover osteodystrophy were not significantly different (3.94 +/- 0.86, 3.40 +/- 0.99, and 5.64 +/- 2.4 nmol/L, respectively). By dividing MGP serum values into tertiles, mean values for OV/BV were different (analysis of variance, P < 0.04), with a greater value in the higher MGP tertile. By exclusion of 3 extravariant cases (>3 SDs greater than the mean), 1 case for each type of osteodystrophy, a significant correlation between bone formation rate and MGP serum level was found (P < 0.05). In addition, a significant correlation was found between MGP level and trabecular thickness. CONCLUSION: Fetuin-A and MGP levels correlated with bone formation parameters. This association could be caused by an effect of these proteins on bone formation, presumably mediated by the TGF-beta/BMP system. Fetuin-A, as opposed to MGP, is known to inhibit the TGF-beta/BMP complex, a protein-cytokine system that appears to be an important regulator of bone formation and probably a factor with an important role in renal osteodystrophy.

Cardiac calcifications: Fetuin-A and other risk factors in hemodialysis patients.

Cardiac calcifications are a frequent finding in hemodialysis for chronic renal failure. Several factors may play a role in the intimal and medial calcification of coronary arteries such as age and some known atherogenetic factors. In addition, Fetuin-A has been proposed as a protective agent through solubilization of calcium phosphate salt. Fetuin-A is also a marker of inflammatory-nutritional state, and its changes could be an expression of this condition. The aim of this cross-sectional study is to evaluate the relative importance of risk factors of calcifications with special regard to Fetuin-A. The study was conducted with 132 hemodialysis patients. They were subjected to multislice computed tomography for evaluation of calcium deposits in the heart. In addition, the patients were sampled for evaluation of calcium-phosphate parameters, lipid profile, nutritional and inflammatory markers, and also Fetuin-A. There was a wide variability of the extent of calcium deposits expressed as Agatston score, with only 9.3% of patients without calcifications. Age, hemodialysis age, sex, calcium-phosphate parameters, and lipid profile were important risk factors, together with nutritional and inflammatory status of the patients. An inverse correlation between coronary calcium score and Fetuin-A emerged from a multiple regression analysis. However, there was no significant difference in serum Fetuin-A among different grades of calcium score. By dividing the patients in tertiles of serum Fetuin-A, an association between low levels of Fetuin-A and high calcification score was found. Fetuin-A as dependent variable was strictly linked to prealbumin serum levels. In addition, there was a clear link between cardiac calcification scores and inflammatory-nutritional markers. Serum calcium and treatment with calcitriol emerged as predictive variables of coronary score.Fetuin-A could be involved in the process of calcification both in the case of markedly low serum levels, due to decreased prevention of calcium phosphate precipitation, and also as a marker of inflammation, a well-known risk factor of atherogenesis. Treatment with intravenous calcitriol could marginally enhance cardiac calcifications, probably through its hypercalcemic effect.

25-hydroxyvitamin D levels and bone histomorphometry in hemodialysis renal osteodystrophy.

BACKGROUND: The importance of 25-hydroxyvitamin D (25-OHD) serum levels in hemodialysis chronic renal failure has not been so far histologically evaluated. Information still lacking relate to the effect of 25-OHD deficiency on serum parathyroid hormone (PTH) levels and on bone and its relationship with calcitriol levels. METHODS: This retrospective study has been performed on a cohort of 104 patients on hemodialysis from more than 12 months, subjected to transiliac bone biopsy for histologic, histomorphometric, and histodynamic evaluation. The patients, 61 males and 43 females, mean age 52.9 +/- 11.7 years, hemodialysis length 97.4 +/- 61.4 months, were treated with standard hemodialysis and did not receive any vitamin D supplementation. Treatment with calcitriol was not underway at the time of the biopsy. Transiliac bone biopsies were performed after double tetracycline labels. In addition, serum intact PTH (iPTH), alkaline phosphatase, and 25-OHD were measured. Calcitriol serum levels was also measured in a subset of patients (N= 53). The patients were divided according to serum 25-OHD levels in three groups: (1) 0 to 15 (15 patients), (2) 15 to 30 (38 patients), and (3) >30 ng/mL (51 patients). RESULTS: There was no significant difference in average age, hemodialysis age, serum PTH [490 +/- 494, 670 +/- 627, and 489 +/- 436 pg/mL, respectively (mean +/- SD)], alkaline phosphatase, and calcitriol between the three groups. The parameters double-labeled surface, trabecular mineralizing surface, and bone formation rate were significantly lower in group 1 than in the other groups (P < 0.03, < 0.03, and < 0.02, respectively). Osteoblast surface and adjusted apposition rate were borderline significantly lower in group 1 (P < 0.06 and < 0.10). There was no statistical difference in the biochemical and bone parameters between groups 2 and 3. A positive significant correlation was found between several bone static and dynamic parameters and 25-OHD levels in the range 0 to 30 ng/mL, showing a vitamin D dependence of bone turnover at these serum levels. However, actual evidence of an effect on bone of 25-OHD deficiency was found at serum levels below 20 ng/mL. With increasing 25-OHD levels beyond 40 ng/mL, a downslope of parameters of bone turnover was also observed. CONCLUSION: Since PTH serum levels are equally elevated in low and high 25-OHD patients, while calcitriol levels are constantly low, an effect of 25-OHD deficiency (group 1) on bone, consisting of a mineralization and bone formation defect, can be hypothesized. The effect of vitamin D deficiency or bone turnover is found below 20 ng/mL. The optimal level of 25-OHD appears to be in the order of 20 to 40 ng/mL. Levels of the D metabolite higher than 40 ng/mL are accompanied by a reduction of bone turnover.