Sevelamer attenuates the progression of coronary and aortic calcification in hemodialysis patients

Cardiovascular risk in stage 4 and 5 nephropathy

Severity of heart disease of almost all types, as well as mortality risk associated with heart disease, increases in step with severity of kidney disease, although not necessarily in a linear fashion. Heart failure is more common and just as lethal as ischemic heart disease in patients with severe chronic kidney disease (CKD). The incidence of nonfatal heart disease in dialysis and transplant populations has now been described in detail. Although standard risk factors for heart disease that are more common among patients with CKD than in the general population do not adequately explain the greatly increased risk of heart disease in patients with severe CKD, neither do as yet identified "nontraditional" risk factors. However, in addition to the factors not common in the general population, such as anemia, hyperphosphatemia, and markers of systemic inflammation, patients with CKD in the modern era may also exhibit excessive thrombotic tendencies. Screening for heart disease in this population relies mainly on dobutamine stress echocardiography or nuclear scintigraphy. The role of electron beam CT (EBCT) scanning is currently controversial. The indications for coronary angiography are the same for patients with CKD as for the general population, but patients with CKD are at greatly increased risk for contrast-associated nephropathy, the least controversial preventive therapy, which consists of isotonic saline and N-acetylcysteine. Finally, patients with CKD do not currently receive adequate medical therapy for prevention and treatment of heart disease.

A simple vascular calcification score predicts cardiovascular risk in haemodialysis patients

BACKGROUND

Cardiovascular morbidity and mortality are highly prevalent in haemodialysis (HD) patients and have been recently associated with vascular calcifications. The objective of our study was to assess the value of a simple vascular calcification score for the prediction of cardiovascular death, cardiovascular hospitalizations and fatal and non-fatal cardiovascular events in HD patients, and to correlate this score with cardiovascular disease and with other known predictors of vascular disease.

METHODS

In this observational, prospective study 123 chronic HD patients (75 males and 48 females; 20% diabetic) were included, who were on low-flux HD treatment for 46.6+/-52 months (mean+/-SD). We set up a simple vascular calcification score based on plain radiographic films of pelvis and hands. Brachial pulse pressure and mean arterial pressure (MAP) were measured and cardiovascular events and hospitalization episodes were assessed.

RESULTS

During an observational period of 37 months there were 17 cardiovascular deaths; 28 patients needed cardiovascular hospitalizations and 32 patients suffered fatal and non-fatal cardiovascular events. Coronary artery disease was diagnosed in 43 patients (35%), peripheral arterial disease in 33 patients (26.8%), cerebrovascular disease in 16 patients (13%) and vascular disease (coronary artery disease or peripheral arterial disease or cerebral vascular disease) in 61 patients (49.6%). By binary logistic regression, diabetes (P = 0.01), male sex (P<0.001), age (P = 0.02), HD duration (P = 0.02) and MAP (P = 0.03) were independently associated with a vascular score > or =3. This score > or =3 was independently associated with coronary artery disease (P = 0.008), peripheral arterial disease (P<0.001) and vascular disease (P = 0.001). Patients with a vascular calcification score > or =3 had a 3.9-fold higher risk of cardiovascular mortality (P = 0.03), a 2.8-fold higher risk of cardiovascular hospitalizations (P = 0.02) and a 2.3-fold higher risk of fatal or non-fatal cardiovascular events (P = 0.04).

CONCLUSIONS

The present vascular calcification scoring represents a simple tool for the assessment of cardiovascular risk related with vascular calcifications in chronic HD patients.

Arterial stiffness in predialysis patients with uremia

BACKGROUND

Hemodialysis patients have advanced arterial wall stiffening as shown by increased aortic pulse wave velocity (PWV), an independent predictor of cardiovascular mortality. We compared aortic PWV of uremic patients before starting hemodialysis treatment with that of patients on maintenance hemodialysis.

METHODS

The subjects were 71 patients with end-stage renal disease (ESRD) before starting hemodialysis (predialysis group), 144 patients on maintenance hemodialysis, and 140 healthy control subjects. These three groups were all nondiabetic and comparable in age and gender.

RESULTS

The hemodialysis group had greater aortic PWV than the healthy subjects, and the predialysis patients showed a still higher value than the hemodialysis group. Multiple regression analysis in the total subjects revealed that the presence of renal failure was significantly associated with increased aortic PWV independent of age, gender, blood pressure, body mass index, smoking, high-density lipoprotein (HDL) and nonhigh-density lipoprotein (non-HDL) cholesterol levels. In contrast, hemodialysis was associated with decreased aortic PWV independent of renal failure and the other factors. Further analyses in the combined uremic patients again indicated the favorable impact of hemodialysis on aortic PWV independent of the classical risk factors, use of antihypertensive medications, including angiotensin-converting enzyme inhibitors and calcium channel blockers, hematocrit, serum calcium, phosphorus, parathyroid hormone levels, and the use of calcium carbonate. Insulin resistance using homeostasis model assessment (HOMA-IR) was associated with increased aortic PWV.

CONCLUSION

Aortic stiffening was present in uremic patients before starting hemodialysis treatment and no adverse effect of hemodialysis was observed, suggesting the important roles of renal failure and/or metabolic alterations secondary to renal failure in arterial stiffness in patients with uremia.

Atherosclerosis in Dialyzed Patients

In the recent HEMO study, the most common cause of death in dialyzed patients was ischemic heart disease. In Europe there are regional differences, but the mortality due to cardiovascular disease is also very high. The long-lasting controversy whether the high incidence and prevalence of atherosclerotic manifestations (particularly ischemic heart disease) may be explained by known risk factors, or non-traditional risk factors are also involved seems to be partially solved with the increasing evidence that the latter hypothesis is true. Thus, together with classic risk factors such as hypertension, dyslipidemia and diabetes, other situations such as microinflammation, increased concentration of asymmetrical dimethyl-L-arginine, disturbed phosphate metabolism and anemia may represent important risk factors for accelerated atherosclerosis in dialyzed patients.

Clinical practice guidelines for managing dyslipidemias in kidney transplant patients: a report from the Managing Dyslipidemias in Chronic Kidney Disease Work Group of the National Kidney Foundation Kidney Disease Outcomes Quality Initiative

The incidence of cardiovascular disease (CVD) is very high in patients with chronic kidney (CKD) disease and in kidney transplant recipients. Indeed, available evidence for these patients suggests that the 10-year cumulative risk of coronary heart disease is at least 20%, or roughly equivalent to the risk seen in patients with previous CVD. Recently, the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (K/DOQI) published guidelines for the diagnosis and treatment of dyslipidemias in patients with CKD, including transplant patients. It was the conclusion of this Work Group that the National Cholesterol Education Program Guidelines are generally applicable to patients with CKD, but that there are significant differences in the approach and treatment of dyslipidemias in patients with CKD compared with the general population. In the present document we present the guidelines generated by this workgroup as they apply to kidney transplant recipients. Evidence from the general population indicates that treatment of dyslipidemias reduces CVD, and evidence in kidney transplant patients suggests that judicious treatment can be safe and effective in improving dyslipidemias. Dyslipidemias are very common in CKD and in transplant patients. However, until recently there have been no adequately powered, randomized, controlled trials examining the effects of dyslipidemia treatment on CVD in patients with CKD. Since completion of the K/DOQI guidelines on dyslipidemia in CKD, the results of the Assessment of Lescol in Renal Transplantation (ALERT) Study have been presented and published. Based on information from randomized trials conducted in the general population and the single study conducted in kidney transplant patients, these guidelines, which are a modified version of the K/DOQI dyslipidemia guidelines, were developed to aid clinicians in the management of dyslipidemias in kidney transplant patients. These guidelines are divided into four sections. The first section (Introduction) provides the rationale for the guidelines, and describes the target population, scope, intended users, and methods. The second section presents guidelines on the assessment of dyslipidemias (guidelines 1-3), while the third section offers guidelines for the treatment of dyslipidemias (guidelines 4-5). The key guideline statements are supported mainly by data from studies in the general population, but there is an urgent need for additional studies in CKD and in transplant patients. Therefore, the last section outlines recommendations for research.

Management of Hyperphosphataemia in Dialysis Patients

Phosphorus control remains a relevant clinical problem in dialysis patients. With age, however, serum phosphorus level decreases significantly because of a spontaneous decrease in protein intake. Older patients usually need lower doses of phosphorus binders. Nevertheless, hyperphosphataemia is observed in a quarter of patients aged >65 years. Phosphorus retention is related to an imbalance between phosphorus intake and removal by dialysis, and is usually aggravated when vitamin D analogues are employed. Hyperphosphataemia induces secondary hyperparathyroidism and the development of osteitis fibrosa. Recent publications describe an association between phosphorus retention and increased calcium and phosphorus product (Ca2+ x P), with significant progression of tissue calcification and higher mortality risk. Dietary intervention, phosphorus removal during dialysis and phosphorus binders are current methods for the management of hyperphosphataemia. However, the phosphorus removed by standard haemodialysis is insufficient to achieve a neutral phosphorus balance when protein intake is >50 g/day. Additional protein restriction may impose the risk of a negative protein balance. More frequent dialysis may help to control resistant hyperphosphataemia. Phosphorus binders constitute the mainstay of serum phosphorus level control in end-stage renal disease patients. Aluminium-based phosphorus binders, associated with toxic effects, have largely been substituted by calcium-based phosphorus binders. However, widespread use of calcium-based phosphorus binders has evidenced the frequent appearance of hypercalcaemia and long-term progressive cardiovascular calcification. Sevelamer, a relatively new phosphorus binder, has proved efficacious in lowering serum phosphorus and parathyroid hormone (PTH) levels without inducing hypercalcaemia. Furthermore, several investigators have reported that sevelamer may prevent progression of coronary calcification. However, its efficacy in severe cases of hyperphosphataemia remains to be confirmed in large series. There are no specific guidelines for phosphorus control in the elderly. Until more information is available, levels of mineral metabolites should be targeted in the same range as those recommended for the general population on dialysis (calcium 8.7-10.2 mg/dL, phosphorus 3.5-5.5 mg/dL and Ca2+ x P 50-55 mg2/dL2). PTH values over 120 ng/L help to avoid adynamic bone disease. Since elderly patients have a higher incidence of adynamic bone (which buffers less calcium) and vascular calcification, sevelamer should be the phosphorus binder of choice in this population; but sevelamer is costly and its long-term efficacy has not been definitively validated. Patients with low normal levels of calcium may receive calcium-based phosphorus binders with little risk. Patients with low values of PTH and high normal calcium should receive sevelamer. Tailored combinations of calcium-based phosphorus binders and sevelamer should be considered, and calcium dialysate concentration adjusted accordingly.

Inflammation and atherosclerosis in end-stage renal disease

Atherosclerosis is a multifaceted process which may be initiated by various insults to vascular endothelium. Independently of the nature of the offending factor, the endothelial dysfunction that results from the initial insult is characterized by increased adhesiveness of the endothelium to leukocytes and platelets and by the synthesis of vasoactive molecules, cytokines and procoagulant factors. This defensive response is characterized by classical inflammatory changes and may lead to plaque formation, luminal obstruction and plaque rupture. Factors involved in arterial damage in end-stage renal disease (ESRD) span from classical risk factors to disease-peculiar factors (anemia, secondary hyperparathyroidism and exposure to bioincompatible dialysis membranes and/or contaminated dialysis fluid) and to emerging and novel risk factors such as hyperhomocysteinemia, infections and accumulation of the endogenous inhibitor of NO synthase, asymmetric dimethylarginine (ADMA). There is strong and consistent evidence that acute phase reactants like C-reactive protein and cytokines like IL-beta, TNF-alpha and IL-6 are independently associated with death and atherosclerosis in ESRD patients. The experimental and epidemiological data collected thus far coherently show that endothelial dysfunction resulting from inflammation may promote abnormal vascular behavior and thrombosis in ESRD. There are several possible therapeutic approaches for reducing the risk excess associated with inflammation in ESRD. These possibilities range from drugs interfering with the angiotensin system or with adrenergic activity to anti-inflammatory and antilipid agents to vitamins, antioxidants, to the amino acid precursor of nitric oxide, L-arginine, and perhaps to antibiotics. The intellectual framework is well delineated but very few controlled trials have been performed or are underway in patients with ESRD.

Management of secondary hyperparathyroidism: the importance and the challenge of controlling parathyroid hormone levels without elevating calcium, phosphorus, and calcium-phosphorus product

Secondary hyperparathyroidism (HPT) is a common complication of chronic kidney disease (CKD) that can lead to clinically significant bone disease. Additional consequences of secondary HPT, such as soft-tissue and vascular calcification, cardiovascular disease, and calcific uremic arteriolopathy, may contribute to the increased risk of cardiovascular morbidity and mortality among CKD patients. Secondary HPT arises from disturbances in calcium, phosphorus, vitamin D and parathyroid hormone metabolism, which develop early in the course of CKD and become more prominent as kidney function declines. The standard therapies currently recommended to correct mineral metabolism and bone disease in these patients include calcium supplementation, dietary phosphorus restriction, phosphate-binding agents, and treatment with vitamin D sterols. However, such medications often have significant effects on the serum levels of calcium and phosphorus, which result in exacerbation of the disease and significant extraskeletal morbidity and mortality. Thus, there is a need to identify more effective treatment approaches. This review discusses the pathophysiology of secondary HPT, the challenges faced in the management of this disorder, and the impact of current treatment options on patients' risks of morbidity and mortality. In addition, the development of new, more physiologically relevant therapies, which may lead to successful management of secondary HPT, is reviewed.

The impact of calcimimetics on mineral metabolism and secondary hyperparathyroidism in end-stage renal disease

The impact of calcimimetics on mineral metabolism and secondary hyperparathyroidism in end-stage renal disease. Secondary hyperparathyroidism is often complicated by elevations in calcium and phosphorus either as a result of the disease per se or due to toxicity from current therapeutic options. These disturbances in mineral metabolism limit the successfulness of therapy and have been implicated as contributing to the development and progression of vascular calcification, an important and often overlooked component of cardiovascular disease in patients on dialysis. Phosphorus, active vitamin D, and calcium all play important roles in the pathogenesis of secondary hyperparathyroidism; however, serum calcium is the primary regulator of minute-to-minute parathyroid hormone secretion. Small changes in serum calcium are detected by a cell surface calcium sensing receptor that has recently been cloned. Calcimimetic agents modulate the activity of the calcium-sensing receptor and result in profound reductions in levels of circulating parathyroid hormone. Additionally, these agents result in decreases in serum calcium, phosphorus, and calcium-phosphorus product. Recently completed phase 2 clinical trials with the second-generation calcimimetic agent cinacalcet HCl confirm that this agent represents a safe and effective novel therapeutic agent which has the potential to dramatically alter the treatment and complications associated with secondary hyperparathyroidism in patients on dialysis.

Management of secondary hyperparathyroidism of dialysis patients

Hyperphosphatemia, vitamin D deficiency, and resulted hypocalcemia have been regarded as classical pathogeneses of secondary hyperparathyroidism. These factors have been treated by the administration of phosphorus binder and vitamin D derivatives. However, these therapies have not brought about a successful result for the prevention and treatment of secondary hyperparathyroidism. The reason could be mainly attributed to the hypercalcemia that results from the administration of calcium salts as a phosphorus binder and the calcemic action of vitamin D. To prevent hypercalcemia, non-calcium containing phosphorus binder (sevelamer hydrochloride) and vitamin D analogues, which suppress PTH secretion with minimum calcemic action, have been developed. These new vitamin D analogues include 19-nor-1-alpha, 25-dihydroxyvitamin D2 (paricalcitol), 1-alpha-hydroxyvitamin D2 (doxercalciferol), 22oxa-calcitriol (maxacalcitol) and F6-calcitriol (falecalcitriol). Furthermore, calcimimetics that stimulate calcium-sensing receptor of parathyroid cells as calcium and suppress PTH secretion are now under clinical trial. Percutaneous direct injection therapy of vitamin D, vitamin D analogue or calcimimetics into parathyroid gland has also been reported. The combination of these new strategies is expected to effectively and safely suppresses secondary hyperparathyroidism that has been resistant to conventional medical treatments.

Calcium-containing phosphate binder use associated with accelerated atherosclerotic coronary calcification

OBJECTIVE

To report parameters and outcomes of phosphorus management in a maintenance hemodialysis patient who experienced atherosclerotic coronary calcification leading to myocardial infarction; to evaluate the role that high calcium intake over 6 years may have played in his coronary artery disease before the dangers of excess calcium intake in phosphorus management were recognized; and to describe an optimized therapeutic approach that provided improved mineral control.

DESIGN

Case study.

SETTING

A large outpatient in-center hemodialysis treatment unit.

MAIN OUTCOME MEASURES

Serum calcium, serum phosphorus, Ca x P product.

RESULTS

The year before his cardiac event, the patient's mean serum calcium was 9.6 mg/dL, mean serum phosphorus was 5.9 mg/dL, and mean Ca x P product was 57 mg2/dL2. Serum calcium peaked at 10.8 mg/dL shortly before his cardiac event. Treatment phases included high-dose calcium acetate (10 g Ca/day), low-dose calcium acetate (4 g Ca/day), low-dose calcium acetate plus low-dose sevelamer hydrochloride (4 g Ca/day plus 2.4 to 4.8 g sevelamer/day), and low-dose calcium acetate plus higher-dose sevelamer hydrochloride (4 g Ca/day plus 4.0 to 12.0 g sevelamer/day). With calcium acetate and sevelamer doses optimized, serum phosphorus levels and Ca x P products continued decreasing, with mean values of 5.99 mg/dL and 50.7 mg2/dL2, respectively, and serum calcium remained stable at a mean of 8.5 mg/dL. The patient has had no further myocardial infarctions.

CONCLUSIONS

This case illustrates how our growing understanding of phosphorus management and the addition of a calcium-free binder to our therapeutic armamentarium have improved phosphorus and calcium balance, reducing the risk of cardiovascular calcification.

Impact of dyslipidemia in end-stage renal disease

Heart disease is a major cause of morbidity and mortality among patients with renal failure. Premature atherosclerotic coronary heart disease is driven by multiple risk factors, including dyslipidemia and oxidative stress. In the nondialysis population, there is overwhelming evidence that treatment of dyslipidemia can significantly improve cardiovascular outcomes. Accumulating data indicate that dialysis patients have atherogenic lipid abnormalities. Although LDL cholesterol (LDL-C) levels in patients who undergo hemodialysis are normal or near normal, increased oxidized LDL-C, triglycerides, and lipoprotein (a) [Lp(a)]; decreased HDL cholesterol (HDL-C); and triglyceride-rich VLDL have been noted. Patients who receive peritoneal dialysis have a more atherogenic lipid profile with increased LDL-C, apolipoprotein B, oxidized LDL-C, triglycerides, and Lp(a) and decreased HDL-C. Furthermore, the LDL particles of peritoneal dialysis patients are small and dense. However, there is a dearth of information regarding the goals, efficacy, and safety of dyslipidemia treatment among dialysis patients. Given the strong evidence of risk reduction and the benefits of lipid-lowering treatment in the nondialysis population, the emerging consensus is that dialysis patients should be treated aggressively for dyslipidemia to an LDL-C goal below 100 mg/dl. Although physicians and patients may be reluctant to add medications because of concerns about polypharmacy, potential decreased compliance, and increased cost, the use of agents such as sevelamer that can serve multiple functions, including phosphate control, lipid lowering (decreased LDL-C and total cholesterol), and anti-inflammatory effects (decreased high-sensitivity C-reactive protein), should be explored and considered for patients who would benefit from such treatment.

The effects of sevelamer and calcium acetate on proxies of atherosclerotic and arteriosclerotic vascular disease in hemodialysis patients

BACKGROUND

We recently determined that in hemodialysis patients, the use of calcium salts to correct hyperphosphatemia led to progressive coronary artery and aortic calcification as determined by sequential electron beam tomography (EBT) while the use of the non-calcium-containing binder sevelamer did not. Whether the specific calcium preparation (acetate vs. carbonate) might influence the likelihood of progressive calcification was debated.

METHODS

To determine whether treatment with calcium acetate was specifically associated with hypercalcemia and progressive vascular calcification, we conducted an analysis restricted to 108 hemodialysis patients randomized to calcium acetate or sevelamer and followed for one year.

RESULTS

The reduction in serum phosphorus was roughly equivalent with both agents (calcium acetate -2.5 +/- 1.8 mg/dl vs. sevelamer -2.8 +/- 2.0 mg/dl, p = 0.53). Subjects given calcium acetate were more likely to develop hypercalcemia (defined as an albumin-corrected serum calcium > or =10.5 mg/dl) (36 vs. 13%, p = 0.015). Treatment with calcium acetate (mean 4.6 +/- 2.1 g/day - equivalent to 1.2 +/- 0.5 g of elemental calcium) led to a significant increase in EBT-determined calcification of the coronary arteries (mean change 182 +/- 350, median change +20, p = 0.002) and aorta (mean change 181 +/- 855, median change +73, p < 0.0001). These changes were similar in magnitude to those seen with calcium carbonate. There were no significant changes in calcification among sevelamer-treated subjects.

CONCLUSION

Despite purported differences in safety and efficacy relative to calcium carbonate, calcium acetate led to hypercalcemia and progressive vascular calcification in hemodialysis patients.

Slowing the progression of vascular calcification in hemodialysis

Hyperphosphatemia and secondary hyperparathyroidism are common complications of ESRD (chronic kidney disease stage 5) that, when untreated, may result in increased morbidity and mortality. Hyperphosphatemia and hypercalcemia have been associated with increased coronary artery calcification. Achieving control of serum phosphorus without increasing serum calcium is an important goal for patients with ESRD. Although calcium-based phosphate binders effectively reduce serum phosphorus and parathyroid hormone concentrations, these agents can lead to hypercalcemia and have been associated with increased vascular calcification. The phosphorus binder sevelamer was developed to overcome the limitations associated with the usual management of hyperphosphatemia and secondary hyperparathyroidism (i.e., mineral salts). Sevelamer, a nonabsorbable hydrogel, is as efficacious as calcium-based phosphate binders for reducing serum phosphorus but does not cause hypercalcemia or other adverse metabolic effects. Sevelamer also exhibits beneficial effects on lipids, consistently and significantly decreasing LDL cholesterol and increasing HDL cholesterol in most studies. In a head-to-head randomized clinical trial, sevelamer and calcium-based binders achieved similarly excellent phosphorus control, but the use of calcium-based binders led to significantly higher serum calcium concentrations and an increased incidence of hypercalcemia and unintended suppression of parathyroid hormone. Treatment with calcium-based binders also led to the progression of coronary artery and aortic calcification, whereas sevelamer attenuated or arrested progression. Strategies that use oral calcium and vitamin D in patients with ESRD should be reexamined, and the potential advantages of sevelamer should be considered when selecting a primary agent to reduce serum phosphorus in hemodialysis patients.

Cardiovascular calcifications in uremic patients: clinical impact on cardiovascular function

Cardiovascular disease is the leading cause of mortality among patients with ESRD (chronic kidney disease stage 5). Left ventricular hypertrophy and arterial diseases are the two principal risk factors for cardiovascular mortality in hemodialysis patients. Epidemiologic studies show that damage to large conduit arteries contributes to morbidity and mortality in patients with chronic kidney disease. Atherosclerosis is primarily an intimal disease characterized by the presence of plaques and occlusive lesions. Although atherosclerosis is the most frequent underlying cause of cardiovascular disease in patients with ESRD, it represents only one form of structural response to metabolic and hemodynamic alterations that interfere with the process of aging. Arterial alterations in ESRD include nonocclusive arterial remodeling accompanying the growing hemodynamic burden and humoral abnormalities that are associated with chronic uremia. The consequences of these alterations are different from those attributed to atherosclerotic plaques and are characterized principally by hardening (stiffening) of arteries. Arteriosclerosis, characterized by stiffening of the aorta and large capacitative arteries, is a major determinant of left ventricular pressure overload and of abnormal coronary perfusion. Atherosclerosis and arteriosclerosis are frequently comorbid and characterized by a high degree of both intimal and medial calcifications in patients with ESRD. The extent of calcifications and the degree of arterial stiffening are independent predictors of mortality. Studies in patients with ESRD have shown that attenuation of arterial stiffness can have a favorable effect, associated with regression of left ventricular hypertrophy, on survival. Calcium-free, metal-free phosphate binders such as sevelamer can reduce calcification scores.

Sevelamer

Hyperphosphataemia in patients with chronic renal failure has traditionally been treated with calcium- and aluminium-containing phosphate binders. This article briefly discusses the rationale and complications of these treatments and reviews sevelamer that is a novel non-calcium-, non-aluminium-containing phosphate binder and the evidence to support its use in clinical practice.

Sevelamer hydrochloride prevents ectopic calcification and renal osteodystrophy in chronic renal failure rats

BACKGROUND

Hyperphosphatemia is associated with severe complications, including ectopic calcification of soft tissues, secondary hyperparathyroidism, and renal osteodystrophy (ROD). Sevelamer hydrochloride is a nonabsorbed calcium- and metal-free phosphate binder that lowers serum phosphorus levels in hemodialysis patients. This study examined the efficacy of sevelamer in preventing ectopic calcification of soft tissues and ROD in adenine-induced renal failure rats.

METHODS

Male, 12-week-old Wistar-Jcl rats were freely fed an adenine diet (0.75 g adenine in 100 g normal diet) for four weeks. After three weeks of the adenine diet, when serum phosphorus levels had significantly increased, the rats were freely fed a normal diet that contained 1% or 2% of sevelamer for another five weeks. Time course changes of serum levels of phosphorus, calcium, and parathyroid hormone (PTH) were measured. At the end of the study, calcium and phosphorus levels in the heart and aorta were measured, and the calcification of kidney, heart, aorta, and stomach were histopathologically examined. The severity of ROD was evaluated by a histopathologic and morphometric analysis of the femurs.

RESULTS

Compared with the adenine controls (N = 10), the sevelamer-treated (1%, N = 6; and 2%, N = 10) groups of adenine-induced renal failure rats had reduced serum phosphorus, serum calcium x phosphorus product, and serum PTH levels. Moreover, in the treatment groups, sevelamer suppressed calcification of the aorta media, and also the osteoid volume, fibrosis volume, and porosity ratio of femurs.

CONCLUSION

These results suggest that sevelamer treatment might contribute to the suppression of ectopic calcification and ROD.

Survival of patients undergoing hemodialysis with paricalcitol or calcitriol therapy

BACKGROUND

Elevated calcium and phosphorus levels after therapy with injectable vitamin D for secondary hyperparathyroidism may accelerate vascular disease and hasten death in patients undergoing long-term hemodialysis. Paricalcitol, a new vitamin D analogue, appears to lessen the elevations in serum calcium and phosphorus levels, as compared with calcitriol, the standard form of injectable vitamin D.

METHODS

We conducted a historical cohort study to compare the 36-month survival rate among patients undergoing long-term hemodialysis who started to receive treatment with paricalcitol (29,021 patients) or calcitriol (38,378 patients) between 1999 and 2001. Crude and adjusted survival rates were calculated and stratified analyses were performed. A subgroup of 16,483 patients who switched regimens was also evaluated.

RESULTS

The mortality rate among patients receiving paricalcitol was 3417 per 19,031 person-years (0.180 per person-year), as compared with 6805 per 30,471 person-years (0.223 per person-year) among those receiving calcitriol (P<0.001). The difference in survival was significant at 12 months and increased with time (P<0.001). In the adjusted analysis, the mortality rate was 16 percent lower (95 percent confidence interval, 10 to 21 percent) among paricalcitol-treated patients than among calcitriol-treated patients. A significant survival benefit was evident in 28 of 42 strata examined, and in no stratum was calcitriol favored. At 12 months, calcium and phosphorus levels had increased by 6.7 and 11.9 percent, respectively, in the paricalcitol group, as compared with 8.2 and 13.9 percent, respectively, in the calcitriol group (P<0.001). The two-year survival rate among patients who switched from calcitriol to paricalcitol was 73 percent, as compared with 64 percent among those who switched from paricalcitol to calcitriol (P=0.04).

CONCLUSIONS

Patients who receive paricalcitol while undergoing long-term hemodialysis appear to have a significant survival advantage over those who receive calcitriol. A prospective, randomized study is critical to confirm these findings.

Coronary artery, aortic wall, and valvular calcification in nondialyzed individuals with type 2 diabetes and renal disease

BACKGROUND

Individuals with end-stage renal disease (ESRD) have highly prevalent and severe vascular and valvular calcification. We undertook this study to test the hypothesis that vascular and valvular calcification begins and is often severe long before diabetic renal disease progresses to ESRD.

METHODS

A total of 32 nondialyzed individuals with type 2 diabetes mellitus and diabetic renal disease (albumin excretion rate>30 microg/min) [mean glomerular filtration rate (GFR), 49.8 +/- 6.1 mL/min/1.73 m2] were identified and compared with a group of 18 normoalbuminuric diabetics. We used 3:1 matching to identify 95 nondiabetic controls without renal disease, matched for age, gender, ethnicity, and the presence/absence of dyslipidemia, hypertension, and known coronary artery disease (CAD).

RESULTS

Using electron beam computed tomography (CT), the prevalence of coronary artery calcification was significantly greater among diabetic renal disease individuals (prevalence, 94% vs. 59%, P < 0.001; median score, 238 vs. 10, P < 0.001) than the nondiabetic controls. The coronary artery calcification scores were significantly more severe among diabetic renal disease individuals than either the diabetic or nondiabetic controls. Among individuals with diabetic renal disease, the coronary artery calcification and aortic wall calcification scores were several-fold greater among those with known CAD than among those without. There was also a significantly greater prevalence of aortic and mitral valve calcification among diabetic renal disease individuals than nondiabetic controls (aortic, 23% vs. 6%, P = 0.03; mitral, 25% vs. 2%, P < 0.001). Multivariate analysis using all three groups reproduced these findings and also consistently identified age and diabetic renal disease as additional predictors for the presence or severity of coronary artery and aortic wall calcification.

CONCLUSION

In this first, systematic analysis among nondialyzed individuals with diabetic renal disease, these data demonstrate that vascular and valvular calcification is present and often severe long before the disease progresses to ESRD. The data also suggest that the coronary artery and aortic wall calcification may represent atherosclerosis.

Calcium salts in the treatment of hyperphosphatemia in hemodialysis patients

PURPOSE OF REVIEW

Hyperphosphatemia in patients with end-stage renal disease leads to secondary hyperparathyroidism and renal osteodystrophy, and is independently associated with mortality risk. How hyperphosphatemia increases mortality risk is unknown but it may promote cardiovascular calcification. It is recommended that dialysis patients be treated to maintain normal serum phosphorus. Although calcium-based phosphate binders are cost-effective, their long-term safety has been questioned because of their postulated role in progression of cardiovascular calcification. In this regard, sevelamer hydrochloride has been recommended as an alternative phosphate binder. In this review, we will examine these issues and provide rational guidelines for the use of calcium-based phosphate binders.

RECENT FINDINGS

Results from the calcium acetate Renagel evaluation study indicate that calcium acetate is more effective than sevelamer in controlling serum phosphorus and calcium x phosphorus product in hemodialysis patients. However, in the Treat-to-Goal study dialysis patients treated with sevelamer had less progression of coronary and aortic calcification than patients treated with calcium-containing binders. The mechanism underlying the slower rate of progression of cardiovascular calcification in sevelamer-treated patients remains uncertain but may relate to decreased calcium loading or to dramatic reductions in LDL cholesterol.

SUMMARY

At present, evidence incriminating calcium-containing phosphate binders in the progression of cardiovascular calcification in end-stage renal disease remains largely circumstantial. As calcium acetate is more efficacious and cost-effective than sevelamer, it remains an accepted first-line drug. Treatment with sevelamer hydrochloride should be considered for patients with persistent hypercalcemia during calcium-based binder therapy despite appropriate adjustment of vitamin D therapy.

Randomized, double-blind, placebo-controlled, dose-titration, phase III study assessing the efficacy and tolerability of lanthanum carbonate: a new phosphate binder for the treatment of hyperphosphatemia

BACKGROUND

Lanthanum carbonate is a novel, non-calcium, non-aluminum phosphate binder under evaluation for the treatment of hyperphosphatemia in end-stage renal disease (ESRD) patients receiving either hemodialysis or continuous ambulatory peritoneal dialysis.

METHODS

This 16-week study assessed the control of serum phosphorus with lanthanum carbonate, and its effects on serum calcium, calcium x phosphorus product, and parathyroid hormone (PTH). Hemodialysis patients > or =18 years old entered into a 1- to 3-week washout period during which serum phosphorus levels rose to >5.9 mg/dL (1.90 mmol/L). In total, 126 patients were titrated with lanthanum carbonate at doses containing 375, 750, 1,500, 2,250, or 3,000 mg/d elemental lanthanum, given in divided doses with meals over a 6-week period, to achieve serum levels < or =5.9 mg/dL. By the end of dose titration, 11/126 (9%) patients received < or =750 mg/d of lanthanum, 25 (20%) received 1,500 mg/d, 37 (29%) received 2,250 mg/d, and 53 (42%) received 3,000 mg/d. Following titration, patients were randomized to receive either lanthanum carbonate or placebo during a 4-week, double-blind maintenance phase.

RESULTS

At the study endpoint, the mean difference in serum phosphorus between the lanthanum carbonate and placebo treatment arms was 1.91 mg/dL (0.62 mmol/L) (P < 0.0001). Calcium x phosphorus product (P < 0.0001) and serum PTH levels (P < 0.01) were also significantly lower with lanthanum carbonate versus placebo. The incidence of drug-related adverse events was similar between placebo- and lanthanum carbonate-treated patients.

CONCLUSION

Lanthanum carbonate is an effective and well-tolerated agent for the treatment of hyperphosphatemia in patients with ESRD.

Vascular calcification in chronic renal failure

The prevalence and extent of vascular calcification (VC) increases rapidly with time on dialysis. There is increasing evidence that medial calcification of conduit arteries, without intimal disease, is associated with important abnormalities of vascular compliance and increased risk of cardiovascular death. Coronary artery calcification is also common in end-stage renal disease, but further research is required to determine how much of this calcification is in the form of calcified intimal atherosclerotic plaque and how much in the tunica media. Calcific uraemic arteriolopathy causes a syndrome of ischaemic necrosis of the skin and subcutaneous tissue and appears to be increasing in incidence. At all sites, arterial calcification is a biologically controlled process, with expression in vascular smooth muscle cells of genes usually expressed in osteoblasts and the formation of hydroxyapatite. High extracellular phosphate concentration induces these phenotypic changes in vitro, and much of the clinical evidence supports hyperphosphataemia as the major driver of VC. Whether warfarin treatment plays a role, by inhibiting production of vitamin-K-dependent inhibitors of calcification in humans, remains uncertain but possible. High doses of prescribed calcium-based phosphate binders are associated with VC, whereas use of sevelamer to achieve the same serum phosphate level greatly retards progression of coronary and aortic calcification. The biological mechanism by which positive calcium balance and/or episodes of hypercalcaemia promotes VC remains unclear. Treatment of established calcific uraemic arteriolopathy consists of aggressive reduction of serum calcium x phosphate product; the roles of hyperbaric oxygen, steroid therapy, and non-warfarin anticoagulation remain uncertain.

A multicenter study on the effects of lanthanum carbonate (Fosrenol) and calcium carbonate on renal bone disease in dialysis patients

BACKGROUND

Lanthanum carbonate (LC) (Fosrenol) is a novel new treatment for hyperphosphatemia. In this phase III, open-label study, we compared the effects of LC and calcium carbonate (CC) on the evolution of renal osteodystrophy (ROD) in dialysis patients.

METHODS

Ninety-eight patients were randomized to LC (N = 49) or CC (N = 49). Bone biopsies were taken at baseline and after one year of treatment. Acceptable paired biopsies were available for static and dynamic histomorphometry studies in 33 LC and 30 CC patients. Blood samples were taken at regular intervals for biochemical analysis and adverse events were monitored.

RESULTS

LC was well tolerated and serum phosphate levels were well controlled in both treatment groups. The incidence of hypercalcemia was lower in the LC group (6% vs. 49% for CC). At baseline, subtypes of ROD were similarly distributed in both groups, with mixed ROD being most common. At one-year follow-up in the LC group, 5 of 7 patients with baseline low bone turnover (either adynamic bone or osteomalacia), and 4 of 5 patients with baseline hyperparathyroidism, had evolved toward a normalization of their bone turnover. Only one lanthanum-treated patient evolved toward adynamic bone compared with 6 patients in the CC group. In the LC group, the number of patients having either adynamic bone, osteomalacia, or hyperpara decreased overall from 12 (36%) at baseline to 6 (18%), while in the calcium group, the number of patients with these types of ROD increased from 13 (43%) to 16 (53%).

CONCLUSION

LC is a poorly absorbed, well-tolerated, and efficient phosphate binder. LC-treated dialysis patients show almost no evolution toward low bone turnover over one year (unlike CC-treated patients), nor do they experience any aluminum-like effects on bone.

Assessment of vascular calcification in ESRD patients using spiral CT

BACKGROUND

Dialysis patients have increased vascular calcification of the coronary arteries and aorta by electron beam CT scan. The purpose of the present study was to utilize an alternative machine, spiral CT, to assess calcification in end-stage renal disease (ESRD) patients.

METHODS

Two groups of patients with ESRD were evaluated: group 1, those receiving a renal transplant (n=38); and group 2, those remaining on dialysis (n=33). All patients underwent quad-slice spiral CT with retrospective gating to evaluate coronary artery and aorta calcification scores. Both area (Agatston method) and volume calculations were utilized, with retrospective gating in all but 16 subjects. Laboratory tests, medications and clinical characteristics were analysed.

RESULTS

Using spiral CT, the intra-reader variability for coronary artery calcification (after correction for very low scores) was 0.9% mean / 0% median using the area (Agatston method) and 2.9% mean / 0% median using volume calculations. Group 1 patients were younger, more likely to be Caucasian and on peritoneal dialysis, had lower serum calcium and higher C-reactive protein levels than group 2. In patients without vs those with coronary artery calcification, only longer duration of dialysis (34+/-64 vs 55+/-50 months, P=0.004; r=0.39, P=0.005) and increasing age (39+/-13 vs 54+/-10 years, P<0.001; r=0.29, P=0.039) were associated, whereas only increasing age was associated with aorta calcification.

CONCLUSION

In ESRD patients, the factors correlating with coronary calcification were duration of dialysis and advancing age, whereas only age correlated with aorta calcification. Spiral CT offers an alternative technique for the assessment of these changes.

Cardiovascular complications in chronic kidney disease

The risk for cardiovascular disease (CVD) morbidity and mortality remains alarmingly high in all stages of chronic kidney disease (CKD). CVD often begins before end-stage renal disease (ESRD), and patients with reduced kidney function are more likely to die of CVD than to develop ESRD. Three pathological forms of CVD should be considered in patients with CKD: alterations in cardiac geometry, including left ventricular hypertrophy, atherosclerosis, and arteriosclerosis. All are highly prevalent in patients with CKD. Although patients with CKD share many of the same risk factors for CVD as the general population, there are a number of uremia-related risk factors, such as anemia and alterations in calcium/phosphorus metabolism, that also play a role in promoting CVD. Treatment of both traditional and uremia-related risk factors should be initiated in the earlier stages of CKD. Additional clinical trials with a goal to reduce CVD are urgently needed in CKD.

Use of active vitamin D sterols in patients with chronic kidney disease, stages 3 and 4

This paper reviews randomized controlled trials and other reported data on the use of the active vitamin D sterols, such as calcitriol, alfacalcidol, and doxercalciferol, in the management of secondary hyperparathyroidism in patients with mild-to-moderate renal insufficiency (stage 3 or 4 chronic kidney disease). Data on potential benefits, including improved histologic abnormalities of bone from secondary hyperparathyroidism, increased bone mineral density, and a reduction of elevated parathyroid hormone levels, are documented. Consideration is given to the risks of such therapy, which include the production of hypercalcemia, more rapid progression of renal insufficiency, the induction of adynamic bone "disease," and accelerated vascular and soft tissue calcification. The low therapeutic index, or "benefit/risk ratio" of calcitriol and alfacalcidol, the sterols currently licensed for such treatment, is recognized. It is recommended that phosphate-restricted diets, phosphate-binding agents, and oral calcium supplements be given adequate trials before starting calcitriol or alfacalcidol. If PTH levels cannot be controlled by these measures, initial doses of these sterols and the proper surveillance during treatment are given. It is emphasized that the risks of hypercalcemia are likely to increase as the degree of kidney failure worsens. Further research using the "less calcemic" vitamin D sterols is clearly needed.

Traditional and emerging cardiovascular risk factors in end-stage renal disease

Patients with end-stage renal disease face a particularly high risk of cardiovascular disease and total mortality. Part of their increased risk is due to a higher prevalence of established risk factors, such as arterial hypertension, diabetes, smoking, and anemia. Hypertension and diabetes have a very high prevalence in dialysis patients and play a major role in their high mortality and morbidity. Hyperparathyroidism, hyperhomocysteinemia and disordered lipid metabolism represent factors that are peculiarly altered by the uremic state. Inflammatory processes, high sympathetic activity, and the accumulation of an endogenous inhibitor of NO synthase (ADMA), have recently emerged as cardiovascular risk factors of paramount importance. Sleep apnea has been linked with nocturnal hypertension and could be implicated in the high prevalence of concentric hypertrophy of the left ventricle in these patients. Hypertension control, as well as appropriate treatment of anemia and cessation of smoking, constitutes a fundamental area of intervention in dialysis patients. It appears possible that, in the near future, control of chronic inflammatory processes of high sympathetic activity and endothelial dysfunction will further help to curb the exceedingly high cardiovascular mortality of patients on chronic dialysis treatment.

Dialysis modalities and dyslipidemia

Progressive renal failure is accompanied by dyslipidemia, which is reflected in an abnormal apolipoprotein profile. It is characterized by increased concentrations of intact and partially metabolized triglyceride-rich apoB-containing lipoproteins. They occur preferentially in very-low density lipoprotein (VLDL) and low-density lipoprotein (LDL) as a result of impaired metabolism and clearance. Hemodialysis can moderately attenuate the renal dyslipidemia. In contrast, peritoneal dialysis is associated with further aggravation, including an increase of cholesterol-rich apoB-containing lipoproteins.

Thrombosis in end-stage renal disease

Although renal failure has classically been associated with a bleeding tendency, thrombotic events are common among patients with end-stage renal disease (ESRD). A variety of thrombosis-favoring hematologic alterations have been demonstrated in these patients. In addition, "nontraditional" risk factors for thrombosis, such as hyperhomocysteinemia, endothelial dysfunction, inflammation, and malnutrition, are present in a significant proportion of chronic dialysis patients. Hemodialysis (HD) vascular access thrombosis, ischemic heart disease, and renal allograft thrombosis are well-recognized complications in these patients. Deep venous thrombosis and pulmonary embolism are viewed as rare in chronic dialysis patients, but recent studies suggest that this perception should be reconsidered. Several ESRD treatment factors such as recombinant erythropoietin (EPO) administration, dialyzer bioincompatibility, and calcineurin inhibitor administration may have prothrombotic effects. In this article we review the pathogenesis and clinical manifestations of thrombosis in ESRD and evaluate the evidence that chronic renal failure or its management predisposes to thrombotic events.

[Atherosclerosis and uremia: signifance of non-traditional risk factors]

Arteriosclerosis, atherosclerosis and vascular calcification are causally related to the high morbidity and mortality of patients with chronic renal failure. Oxidative stress and carbonyl stress of uremia, dialysis procedure and/or intravenous iron therapy result in AGE (advanced glycation end-product), ALE (advanced lipoxidation end-product) and AOPP (advanced oxidation protein product) formation, favouring together with elevated CRP (C-reactive protein) levels the development of cardiovascular and cerebrovascular complications. Enhanced plasma levels of homocysteine and ADMA (asymmetric dimethylarginine) contribute to this process. In addition, in chronic renal insufficiency hyperphosphatemia and an enhanced calcium x phosphorus ion product are associated with the morbidity and mortality of the patients, particularly in the presence of fetuin deficiency. Phosphorus, AGEs and AOPPs, beside other factors, catalyze the conversion of vascular smooth muscle cells to osteoblast--like cells (particularly in the presence of monocytes/macrophages), resulting in bone matrix protein formation. Other risk factors, such as age, male sex, smoking, hypertension, diabetes, chronic inflammation, insulin resistance or dyslipidemia (enhanced non-HDL-cholesterol) also contribute to the atherosclerotic risk profile of the patient with chronic renal insufficiency. While there is growing understanding of the mechanisms involved in arteriosclerosis, atherosclerosis and vascular calcification in uremia, we are still missing effective therapeutic maneuvers for reduction of excess mortality in uremic patients.

Diagnosis and therapy of coronary artery disease in renal failure, end-stage renal disease, and renal transplant populations

Even though cardiovascular disease is the leading cause of death in patients with CRF and end-stage renal disease (ESRD), ill-conceived notions have led to therapeutic nihilism as the predominant strategy in the management of cardiovascular disease in these populations. The recent data clearly support the application of proven interventions in the general population, such as angiotensin-converting enzyme inhibitors and statins to patients with CRF and ESRD. The advances in coronary stents and intracoronary irradiation have decreased the restenosis rates in renal failure patients. Coronary artery bypass with internal mammary graft might be the procedure of choice for coronary revascularization in these patients. The role of screening for asymptomatic coronary disease is established as a pretransplant procedure, but it is unclear whether this will be applicable to all patients with ESRD. Future studies need to focus on unraveling the mechanisms by which uremia leads to increased cardiovascular events to design optimal therapies targeted toward these mechanisms and improve cardiovascular outcomes.

Risk factors for coronary artery disease in patients with renal failure

Cardiovascular mortality is markedly increased in patients with end-stage renal disease (ESRD), particularly those receiving dialysis. Coronary artery disease is the most important cause of death in these patients. As in the general population, older age, male gender, and the postmenopausal state in women are cardiovascular risk factors in patients with ESRD. However, hypertension, diabetes mellitus, and dyslipidemia, known to promote cardiovascular disease in the general population, are particularly likely to do so in patients with ESRD because of their high prevalence in this population. In addition, nontraditional cardiovascular risk factors, such as hyperhomocystinemia, inflammation, elevated calcium x phosphate product, endothelial dysfunction, and oxidant stress, occur frequently in patients with ESRD. Vigorous treatment of modifiable cardiovascular risk factors has reduced cardiovascular risk in patients without ESRD. The extent to which such risk factor modification would alter cardiovascular risk in ESRD remains uncertain.

The renal dietitian's role in managing hyperphosphatemia and secondary hyperparathyroidism in dialysis patients: a national survey

PURPOSE

To survey the medical nutrition therapy practices of renal dietitians for the treatment of bone mineral metabolism.

OBJECTIVES

To obtain data on phosphorus diet prescription levels. To determine allied team involvement for phosphate binder and Vitamin D therapies. To assess the frequency and target levels for monitoring serum calcium, phosphorus, -phosphorus product, intact PTH and alkaline phosphatase.

METHODS

Two renal dietitians from the National Kidney Foundation-Council on Renal Nutrition developed a 5-question survey. This was posted on both the RenalRD Listserv and the NKF-CRN website from January 1 through February 15, 2001. Dietitians were asked to respond using facsimile, e-mail or reply by mail.

RESULTS

One hundred and thirty-one surveys were received representing all major dialysis providers in the United States, the British Virgin Islands, and Japan. Results included information for peritoneal and hemodialysis patients. Five different methods for dosing phosphate binders were determined. Prescribed phosphate binders included calcium acetate, sevelamer hydrochloride, and calcium carbonate. 108 out of 131 dietitian respondents (82.5%) have a medical protocol in place for vitamin D therapy. Of the respondents, 47% were directly responsible for implementing the vitamin D protocol. Paricalcitol was the most widely used form of IV Vitamin D. Biochemistry results were as follows: calcium, 16 different ranges from 8.0 mg/dL to 11.5 mg/dL; phosphorus, 13 different ranges from 2.5 mg/dL to 6.5 mg/dL; calcium-phosphorus product, 13 different ranges from 55-75; iPTH, 20 different ranges from 50-300 pg/mL; alkaline phosphatase, 18 different ranges from no records being monitored to a level of 500 mg/dL.

CONCLUSION

The survey revealed a large variability in the treatment of bone mineral metabolism. Improved clinical practice guidelines for the health care team are being developed with the National Kidney Foundation (NKF)-Kidney Disease Outcomes and Quality Initiative (KDOQI) bone disease management workgroup.

Meta-analysis of the effect of sevelamer on phosphorus, calcium, PTH, and serum lipids in dialysis patients

Hyperphosphatemia and dyslipidemia are common clinically significant conditions in end-stage renal disease (ESRD). Hyperphosphatemia management is essential; however, use of calcium-based phosphate binder has been associated with elevated risk of cardiac calcification in ESRD, increasing risks for cardiovascular disease and death. An alternative to calcium-based phosphate binders is sevelamer hydrochloride, a calcium-free, metal-free, nonabsorbed polymer that binds phosphate effectively. We conducted a meta-analysis on the effects of sevelamer hydrochloride on parameters of mineral metabolism (serum phosphorous, calcium, Ca x P, and iPTH) and the lipid profile (total, LDL, HDL, and non-HDL cholesterol, and triglycerides) in dialysis patients. After application of inclusion/exclusion criteria, 17 core studies were statistically analyzed to determine the sevelamer treatment effect on the study parameters as demonstrated by simple, n-weighted, and inverse variance-weighted mean changes. Analysis of inverse variance-weighted mean changes indicated that sevelamer treatment was associated with a 2.14 mg/dL drop in serum phosphorus (P <.001), no significant overall effect on calcium (0.09 mg/dL, P =.364), significant decline in Ca x P product (15.91 mg(2)/dL(2), P <.001), 35.99 pg/mL reduction in iPTH (P =.026), significant reduction in total cholesterol (30.58 mg/dL, P <.001), 31.38 mg/dL drop in LDL cholesterol (P <.001), significant increase in HDL cholesterol (4.09 mg/dL, P =.008), and a significant reduction in triglycerides (22.04 mg/dL, P x.001). This meta-analysis suggests that sevelamer offers a dual therapeutic benefit in dialysis patients-a population at high risk for cardiovascular disease-by improving phosphorus control and the lipid profile, without altering serum calcium.

Uremia induces the osteoblast differentiation factor Cbfa1 in human blood vessels

BACKGROUND

Bone matrix proteins are expressed in calcified arteries from dialysis patients, suggesting that vascular smooth muscle cells (VSMCs) may transform to osteoblast-like cells. One of the key transcriptional regulators of osteoblast differentiation is Cbfa1. Thus, we hypothesized that this may be a key factor in arterial calcification.

METHODS

To test this hypothesis, we examined sections of the inferior epigastric artery from uremic patients for the presence of Cbfa1 and type I collagen and osteopontin by in situ hybridization and immunostaining. We also examined the effect of pooled uremic sera from dialysis patients on the expression of Cbfa1 by reverse transcription-polymerase chain reaction (RT-PCR) in bovine VSMCs in vitro.

RESULTS

Cbfa1 and osteopontin were expressed in both the media and the intima in vessels that were calcified, but there was only minimal staining in non-calcified vessels. In vitro studies demonstrated that pooled uremic serum, compared to pooled control human serum induced the expression of Cbfa1 by RT-PCR in bovine VSMCs in a time-dependent, nonphosphorus-mediated mechanism.

CONCLUSION

These results support that Cbfa1 is a key regulatory factor in the vascular calcification observed in dialysis patients and is up-regulated in response to many uremic toxins.