Lower risk for cardiovascular mortality in oral 1alpha-hydroxy vitamin D3 users in a haemodialysis population

Epidemiology of vitamin D in health and disease

Results from ecological, case-control and cohort studies have shown that vitamin D reduces the risk of bone fracture, falls, autoimmune diseases, type 2 diabetes, CVD and cancer. However, there is still epidemic vitamin D insufficiency especially among individuals living at high latitudes or with dark skin. Serum levels of 25-hydroxyvitamin D (25(OH)D) are considered the best biomarker of vitamin D nutritional status. Appropriate sunshine exposure or oral supplementation is necessary to maintain sufficient vitamin D status, which is generally accepted as serum 25(OH)D>75 nmol/l. Immunoassays, especially RIA, have been primarily used to measure serum 25(OH)D while liquid chromatography-MS (LC-MS) is considered the 'gold standard'. There is significant disparity among the immunoassays, and all immunoassays have considerable bias compared with LC-MS methods. Because of the variations among the results from these different assays, it is necessary that assay-specific reference ranges be established or standardisation of the assays take place. The present review focuses on ecological, case-control, and cohort studies that investigated the role of vitamin D in health and disease. In addition, analytical techniques used in laboratory evaluation of vitamin D nutritional status are also critically reviewed. The majority of the literature included in the present review is selected from that searchable in PubMed up to the end of September 2008.

Does vitamin D modulate asymmetric dimethylarginine and C-reactive protein concentrations?

BACKGROUND

Vitamin D deficiency is associated with significant increases in the incidence of cardiovascular risk factors and mortality. However, the mechanisms underlying this association remain unclear. The current study evaluated the possible relationships among vitamin D status, endothelial dysfunction, and inflammation.

METHODS

Plasma concentrations of 25-hydroxyvitamin D(3) were determined by radioimmunoassay in a normal population cohort (n=253) aged 51 to 77 years (mean 63.4+/-6 years). Asymmetric dimethylarginine, a marker/mediator of endothelial dysfunction, was assayed by high-performance liquid chromatography. High-sensitivity C-reactive protein levels were used as a marker of inflammatory activation.

RESULTS

On univariate analyses, low 25-hydroxyvitamin D(3) levels were inversely correlated with asymmetric dimethylarginine concentrations, high-sensitivity C-reactive protein levels, and body mass index. Seasonal fluctuations in 25-hydroxyvitamin D(3) levels were associated with reciprocal asymmetric dimethylarginine concentration fluctuations. Hypertension and treatment with an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker also were associated with low 25-hydroxyvitamin D(3) levels. On multiple linear analysis, both asymmetric dimethylarginine (beta=-0.19, P=.003) and high-sensitivity C-reactive protein (beta=-0.14, P=.03) concentrations were inversely correlated with plasma 25-hydroxyvitamin D(3) concentrations; other significant correlates were male gender (beta=0.19, P=.003), calcium levels (beta=0.14, P=.03), and use of angiotensin-converting enzyme inhibitor (beta=-0.17, P=.007).

CONCLUSION

Low 25-hydroxyvitamin D(3) levels are associated with markers of endothelial dysfunction and inflammatory activation, representing potential mechanisms for incremental coronary risk.

New therapies: calcimimetics, phosphate binders and vitamin D receptor activators

At present, new compounds are available to treat secondary hyperparathyroidism, namely calcimimetics, novel phosphorus binders and also novel vitamin D receptor activators. Calcimimetics increase the sensitivity of the parathyroid gland to calcium through spatial configurational changes of the calcium-sensing receptor. In addition, experimental studies have demonstrated that calcimimetics also upregulate both the calcium-sensing receptor and the vitamin D receptor. They are efficacious in children, though the experience in paediatric chronic kidney disease is still limited. Sevelamer, lanthanum carbonate and magnesium iron hydroxycarbonate are novel phosphorus binders available on the market. Several studies have demonstrated their efficacy and safety up to 6 years, though costs are the main limitation for a wider use. Since almost all the experience available on the new phosphorus binders comes from its use in adults, studies on children are needed in order to confirm the efficacy and safety of these products. Other new salts and polymers are also being developed. New vitamin D receptor activators, such as paricalcitol, are as effective at suppressing parathyroid hormone (PTH) as the traditional vitamin D receptor activators used for the past two decades, but they have a better and safer profile, showing fewer calcaemic and phosphoraemic effects while preserving the desirable effects of the vitamin D receptor activators on the cardiovascular system, hypertension, inflammation and fibrosis. Their use in children with chronic kidney disease has revealed similar responses to those of adults. The novel compounds discussed in this review should facilitate and improve the management of mineral and bone disorders in children with chronic kidney disease.

Relation of oral 1alpha-hydroxy vitamin D3 to the progression of aortic arch calcification in hemodialysis patients

The role of decreased active vitamin D levels on vascular calcification has not been elucidated in hemodialysis (HD) patients. The aim of the present study was to evaluate the relationship between progression of aortic arch calcification (AoAC) and prescribed dose of 1alpha-hydroxy vitamin D. The enrolled study subjects were 65 (40 men and 25 women) HD patients. Calcification of the aortic arch was semiquantitatively estimated with a score (AoACS) on plain chest radiology. Change in AoACS (DeltaAoACS) was obtained by subtracting the baseline AoACS value from the follow-up AoACS value. The second assessment was performed from 2 years after the first determination. The nonprogressors (63.2 +/- 14.5 years) were significantly younger than the progressors (68.2 +/- 10.8 years) (P = 0.0419). In addition, prescribed dose of 1alpha-hydroxy vitamin D3 was significantly higher in the nonprogressors (125.5 +/- 109.1 microg) than progressors (84.8 +/- 81.1 microg) (P = 0.0371). Multiple regression analysis revealed prescribed dose of 1alpha-hydroxy vitamin D(3) (beta value = -0.324, P = 0.0051) as well as DBP (beta value = -0.418, P = 0.007), serum levels of P (beta value = 0.333, P = 0.006) and C-reactive protein (beta value = 0.237, P = 0.0048) to be significant independent determinants of DeltaAoACS. In conclusion, the evaluation of AoACS on chest radiography is a very simple tool in HD patients. Active vitamin D therapy seems to protect patients from developing vascular calcification.

Vitamin D receptor activators induce an anticalcific paracrine program in macrophages: requirement of osteopontin

OBJECTIVE

Vascular calcification is highly correlated with morbidity and mortality, and it is often associated with inflammation. Vitamin D may regulate vascular calcification and has been associated with cardiovascular survival benefits.

METHODS AND RESULTS

We developed a macrophage/smooth muscle cell (SMC) coculture system and examined the effects of vitamin D receptor activators (VDRA), calcitriol and paricalcitol, on SMC matrix calcification. We found that treatment of SMC alone with VDRA had little effect on phosphate-induced SMC calcification in vitro. However, coculture with macrophages promoted SMC calcification, and this was strikingly inhibited by VDRA treatment. Several VDRA-induced genes, including bone morphogenetic protein-2 (BMP2), tumor necrosis factor-alpha, and osteopontin, were identified as candidate paracrine factors for the protective effect of VDRA. Of these, osteopontin was further investigated and found to contribute significantly to the inhibitory actions of VDRA on calcification in macrophage/SMC cocultures.

CONCLUSIONS

The ability of VDRA to direct a switch in the paracrine phenotype of macrophages from procalcific to anticalcific may contribute to their observed cardiovascular survival benefits.

Administration of alfacalcidol for patients with predialysis chronic kidney disease may reduce cardiovascular disease events

BACKGROUND

Besides its effect on calcium metabolism, vitamin D may play a part in preventing the onset and progression of cardiovascular disease (CVD) events. Only a few reports on the studies relating to whether vitamin D may reduce CVD events in patients with predialysis chronic kidney disease (CKD) are available, and many ambiguities remain.

METHODS

We conducted a retrospective cohort study of 665 patients with predialysis CKD. With log-rank test using the Kaplan-Meyer survival curve, comparison of incidences of CVD events, CVD-related mortality, and all-cause mortality were made between patients in the alfacalcidol treatment group (107 patients) in the predialysis stage to whom alfacalcidol 0.25-0.5 microg/day was orally administered for at least 24 weeks, and patients in the nontreatment group (558 patients) who received no administration of alfacalcidol or other type of activated vitamin D and its analogues. Patients to whom alfacalcidol administration was discontinued within 24 weeks as well as initiation of dialysis of <24 weeks were excluded for this study. Factors relating to CVD events were examined using Cox's proportional hazards analysis.

RESULTS

The mean follow-up period was 55.1 +/- 38.9 months in the alfacalcidol treatment group and 41.9 +/- 38.4 months in the nontreatment group. CVD events occurred in 172 patients during the follow-up period, and 74 of those occurred during the predialysis period. In the alfacalcidol treatment group, the incidence of cumulative CVD events was significantly lower. In relation to all-cause deaths and CVD-related deaths, the cumulative mortality rate was significantly lower in the alfacalcidol treatment group during the follow-up period. Throughout the follow-up period, the association between CVD events and alfacalcidol use was detected when adjusted for age, sex, diabetes, hypertension, use of renin-angiotensin system inhibitors, estimated glomerular filtration rate, and albumin and parathyroid hormone.

CONCLUSION

These data showed that oral administration of alfacalcidol for predialysis CKD patients was associated with reduced risk for CVD.

Vitamin D compounds for people with chronic kidney disease not requiring dialysis

BACKGROUND

Vitamin D compounds are used to suppress elevated serum parathyroid hormone (PTH) in people with chronic kidney disease (CKD).

OBJECTIVES

To assess the efficacy of vitamin D therapy on biochemical, bone, cardiovascular, and mortality outcomes in people with CKD and not requiring dialysis.

SEARCH STRATEGY

We searched The Cochrane Renal Group's specialised register, Cochrane's Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and reference lists of retrieved articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing different forms, schedules, or routes of administration of vitamin D compounds for people with CKD not requiring dialysis were included. Vitamin D compounds were defined as established (calcitriol, alfacalcidol, 24,25(OH)(2)vitamin D(3)) or newer (doxercalciferol, maxacalcitol, paricalcitol, falecalcitriol) vitamin D compounds.

DATA COLLECTION AND ANALYSIS

Data were extracted by two authors. Statistical analyses were performed using the random effects model. Results were summarized as risk ratio (RR) for dichotomous outcomes or mean differences (MD) for continuous outcomes with 95% confidence intervals (CI).

MAIN RESULTS

Sixteen studies (894 patients) were included. No formulation, route, or schedule of vitamin D compound was found to alter the mortality risk or need for dialysis. Vitamin D compounds significantly lowered serum PTH (4 studies, 153 patients: MD -49.34 pg/mL, 95% CI -85.70 to -12.97 (-5.6 pmol/L, 95% CI -9.77 to -1.48)) and were more likely to reduce serum PTH > 30% from baseline value (264 patients: RR 7.87, 95% CI 4.87 to 12.73). Vitamin D treatment was associated with increased end of treatment serum phosphorus (3 studies, 140 patients: MD 0.37 mg/dL, 95% CI 0.09, 0.66 (0.12 mmol/L, 95% CI 0.03, 0.21)) and serum calcium (5 studies, 184 patients: MD 0.20 mg/dL, 95% CI 0.17 to 0.23 (0.05 mmol/L, 95% CI 0.04 to 0.06)). Few data were available comparing intermittent with daily vitamin D administration, or other schedules of dosing.

AUTHORS' CONCLUSIONS

There are not sufficient data to determine the effect of vitamin D compounds on mortality and cardiovascular outcomes in people with CKD not requiring dialysis. While vitamin D compounds reduce serum PTH (49.3 pg/mL (5.6 pmol/L)) compared with placebo, the relative clinical benefits of PTH lowering versus treatment-related increases in serum phosphorus and calcium remain to be understood.

Vitamin D compounds for people with chronic kidney disease requiring dialysis

BACKGROUND

Clinical guidelines recommend vitamin D compounds to suppress serum parathyroid hormone (PTH) in chronic kidney disease (CKD), however treatment may be associated with increased serum phosphorus and calcium, which are associated with increased mortality in observational studies. Observational data also indicate vitamin D therapy may be independently associated with reduced mortality in CKD.

OBJECTIVES

We assessed the effects of vitamin D compounds on clinical, biochemical, and bone outcomes in people with CKD and receiving dialysis.

SEARCH STRATEGY

We searched The Cochrane Renal Group's specialised register, Cochrane's Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and reference lists of retrieved articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) in subjects with CKD and requiring dialysis that assessed treatment with vitamin D compounds.

DATA COLLECTION AND ANALYSIS

Data was extracted by two authors. Results are summarised as risk ratios (RR) for dichotomous outcomes or mean differences (MD) for continuous outcomes, with 95% confidence intervals (CI).

MAIN RESULTS

Sixty studies (2773 patients) were included. No formulation, route, or schedule of administration was associated with altered risks of death, bone pain, or parathyroidectomy. Marked heterogeneity in reporting of outcomes resulted in few data available for formal meta-analysis. Compared with placebo, vitamin D compounds lowered serum PTH at the expense of increasing serum phosphorus. Trends toward increased hypercalcaemia and serum calcium did not reach statistical significance but may be clinically relevant. Newer vitamin D compounds (paricalcitol, maxacalcitol, doxercalciferol) lowered PTH compared with placebo, with increased risks of hypercalcaemia, although inadequate data were available for serum phosphorus. Intravenous vitamin D may lower PTH compared with oral treatment, and be associated with lower serum phosphorus and calcium levels, although limitations in the available studies precludes a conclusive statement of treatment efficacy. Few studies were available for intermittent versus daily and intraperitoneal versus oral administration or directly comparative studies of newer versus established vitamin D compounds.

AUTHORS' CONCLUSIONS

We confirm that vitamin D compounds suppress PTH in people with CKD and requiring dialysis although treatment is associated with clinical elevations in serum phosphorus and calcium. All studies were inadequately powered to assess the effect of vitamin D on clinical outcomes and until such studies are conducted the relative importance of changes in serum PTH, phosphorus and calcium resulting from vitamin D therapy remain unknown. Observational data showing vitamin D compounds may be associated with improved survival in CKD need to be confirmed or refuted in specifically designed RCTs.

Significant association of fracture of the lumbar spine with mortality in female hemodialysis patients: a prospective observational study

Prevalent fracture of the lumbar spine is established as a predictor of increased mortality in the general population. To examine whether this association is retained in hemodialysis patients, we conducted a single-center prospective observational study in 635 hemodialysis patients (60.3 + or - 12.0 years old, male/female 369/266). Patients were divided into two groups (with and without lumbar fracture, assessed by simple lateral radiograph), and survival was followed for an average of 53.8 months. Lumbar fracture was present in 62 patients (9.76%; male 9.76%, female 9.77%). During the follow-up period, there were 176 all-cause deaths (27.7%; male 27.6%, female 27.8%), of which 72 were from cardiovascular diseases. In Kaplan-Meier analysis, all-cause and noncardiovascular mortality rates, but not cardiovascular mortality, were significantly higher in patients with fracture than in those without (P < 0.0001). In multivariate Cox proportional hazard analysis, the presence of lumbar fracture was significantly associated with increased noncardiovascular mortality (HR = 2.035, 95% CI 1.135-3.652, P < 0.05) after adjustment for age, duration of hemodialysis, presence of diabetes, body mass index, and serum calcium, phosphate, and albumin. Significantly higher all-cause and noncardiovascular mortality rates were also evident for patients with fracture in separate analyses in males and females, but multivariate analysis showed a significant association of lumbar fracture with increased all-cause (HR = 2.151, 95% CI 1.033-4.478, P < 0.05) and noncardiovascular (HR = 2.637, 95% CI 1.014-6.858, P < 0.05) mortality rates only in females. In conclusion, lumbar fracture is significantly associated with all-cause mortality in female patients.

Seasonality of mortality: the September phenomenon in Mediterranean countries

BACKGROUND

Seasonal increases in the mortality rate have been associated with excessively cold or hot weather. We evaluated monthly patterns of mortality in selected countries.

METHODS

We analyzed all-cause mortality statistics from 5 European Mediterranean countries (Cyprus, France, Greece, Italy, Spain), Sweden, North America (United States and Canada), Australia, New Zealand and Japan. We extracted and tabulated data on monthly all-cause mortality in the general population from the earliest to the latest year that records were available.

RESULTS

We identified relevant data for a period of 2-57 years in each country. In the Mediterranean countries, the lowest average daily mortality was observed in September (all countries, 125/168 [74%] years). The fewest deaths were in August in Sweden (14/20 [70%] years) and North America (32/50 [64%] years). The fewest deaths in Japan occurred in July (2/2 [100%] years). In the southern hemisphere, the lowest mortality in Australia occurred in March (7/10 [70%] years) and in February for New Zealand (cumulative over 24 years).

INTERPRETATION

Mortality in the general population declines in the late summer to early fall months in the countries evaluated. Environmental parameters may partly account for these associations, and further research is needed on the contribution of additional factors such as summer vacations.

Statins and vitamin D: a friendly association in pre-dialysis patients

The increased mortality rate observed in patients with chronic kidney disease is related to the high prevalence of cardiovascular disease in this population. Recently, it has been shown that interventional therapy with statins and/or vitamin D could improve the outcomes of these patients. The aim of this study was to identify the risk factors for mortality in a group of patients with chronic kidney disease (stages 4 and 5--pre-dialysis) and verify whether vitamin D and statins could change the outcome. We included 95 patients (mean age--69.4) with stages 4 and 5 (pre-dialysis) of our "low-clearance" outpatient clinic, with an average eGFR of 16.9 ml/min and a mean follow-up of 24.1 months. Several biological, nutritional, laboratory and inflammatory parameters were analysed at baseline. Our population was divided into three groups: G-I, patients not medicated with either vitamin D or statins; G-II, patients medicated with either vitamin D or statins; and G-III, patients medicated with vitamin D and statins. We found (ANOVA) that the serum levels of pre-albumin (P = 0.018) and PTH (P = 0.03) were lower in G-I. Concerning the inflammatory parameters, G-I showed higher levels of hsCRP (P = 0.014) and a trend to higher IL-6 levels (P = 0.077). We found the actuarial survival at 30 months (Kaplan-Meier), to be 56.4% in G-I, 82.3% in G-II and 100% in G-III (log rank = 13.08 P = 0.0014). Using the Cox proportional hazards model, we found that the existence of coronary artery disease (P = 0.0001) and the absence of medication with vitamin D and/or statins (P = 0.005) independently influenced the mortality of our patients. In conclusion, we found, in our study, that patients under vitamin D and statins (with a synergistic effect) were less inflamed and showed a lower mortality rate.

Low plasma level of cathelicidin antimicrobial peptide (hCAP18) predicts increased infectious disease mortality in patients undergoing hemodialysis

BACKGROUND

Human cathelicidin antimicrobial protein (hCAP18) is an antimicrobial and immunomodulatory peptide that has pleiotropic effects and is transcriptionally regulated by vitamin D. Because the administration of vitamin D analogues has been linked to decreased mortality among patients with end-stage renal disease, we hypothesized that low hCAP18 levels would identify those who are at increased risk of death attributable to infection while undergoing hemodialysis.

METHODS

We performed a case-control study nested in a prospective cohort of patients (n = 10,044) initiating incident hemodialysis. Case patients (n = 81) were those who died of an infectious disease within 1 year; control patients (n = 198) were those who survived at least 1 year while undergoing dialysis.

RESULTS

Mean (+/-SD) baseline levels of hCAP18 in case patients and control patients were 539 +/- 278 ng/mL and 650 +/- 343 ng/mL, respectively (P = .006). hCAP18 levels had a modest correlation with 1,25-dihydroxyvitamin D levels r = 0.23; P = .053) but not with 25-hydroxyvitamin D levels r = -0.06; P = .44). Patients with hCAP18 levels in the lowest tertile had a 2-fold increased risk (odds ratio, 2.1; 95% confidence interval, 1.2-3.5) of death attributable to infection; after multivariable adjustment, this relationship remained statistically significant (odds ratio, 3.7; 95% confidence interval, 1.2-11.2).

CONCLUSIONS

In individuals initiating chronic hemodialysis, low baseline levels of hCAP18, a vitamin D-regulated antimicrobial protein, are independently associated with an increased risk of death attributable to infection.

A new role for vitamin D receptor activation in chronic kidney disease

Vitamin D has proven to be much more than a simple "calcium hormone." The fact that the vitamin D receptor has been found in cells not related to mineral metabolism supports that statement. The interest of nephrologists in vitamin D and its effects beyond mineral metabolism has increased over the last few years, evidencing the importance of this so-called "sunshine hormone." In the present review, we highlight the most recent developments in the traditional use of vitamin D in chronic kidney disease (CKD) patients, namely, the control of secondary hyperparathyroidism (sHPT). Furthermore, we also explore the data available regarding the new possible therapeutic uses of vitamin D for the treatment of other complications present in CKD patients, such as vascular calcification, left ventricular hypertrophy, or proteinuria. Finally, some still scarce but very promising data regarding a possible role of vitamin D in kidney transplant patients also are reviewed. The available data point to a potential beneficial effect of vitamin D in CKD patients beyond the control of mineral metabolism.

Does vitamin D protect against cardiovascular disease?

Because of its role in maintaining bone density, vitamin D has long been recognized as critical to the health of women, a group at disproportionate risk of osteoporosis. Recent data from epidemiologic and laboratory studies suggest that vitamin D may also protect against the development of cardiovascular and other chronic diseases. Because three quarters of US women (and men) have suboptimal vitamin D status, many experts advocate increasing daily recommended intakes from 200-600 IU to at least 1,000 IU, which may indeed be a prudent strategy. However, data from large randomized clinical trials testing sufficiently high doses of this vitamin for cardiovascular disease prevention--as well as to assess the overall balance of benefits and risks of such supplementation--are needed.

Update on the treatment of chronic kidney disease-mineral and bone disorder

Chronic kidney disease (CKD) is associated with increased morbidity and mortality. Mineral metabolism disturbances appear to contribute to the high mortality rate. A CKD-mineral bone disorder (CKD-MBD) has recently been defined as a systemic disorder manifested by one or a combination of abnormalities in bone biopsy, laboratory parameters and/or vascular or other soft-tissue calcifications. New available treatments have contributed to move from the former treatment paradigm of renal osteodystrophy to CKD-MBD management, beyond mere control of parathyroid hormone (PTH) and trying to improve cardiovascular or survival outcomes. Thus, the recommended multidisciplinary approach among nurses, dieticians and clinicians, helping not only through dietary assessment but also through education, behaviour control and by increasing the patient's personal motivation, may have additional important benefits. This article will review the current therapeutic approach with phosphate binders including the latest developments, vitamin D derivatives and selective vitamin D receptor activators as well as the new calcimimetics, all used in the treatment of this systemic disease.

Vitamin D and vascular calcification in chronic kidney disease

Vascular calcification is frequently observed and is closely associated with cardiovascular mortality in patients with chronic kidney disease (CKD). Vascular calcification is largely divided into two types. One is atherosclerotic intimal layer calcification and the other is medial layer calcification (Monckeberg's calcification). The latter is more common in patients with CKD than in general population. Evidence is growing that vascular calcification is a regulated active process as well as a passive process resulting from elevated serum phosphate (P) and an increase in the calcium phosphate (Ca x P) product leading to oversaturated plasma. Proving the active process, in vitro studies have demonstrated that the transformation of vascular smooth muscle cells (VSMCs) into osteoblast-like cells is a crucial mechanism in the progression of vascular calcification. Reduction of the activity of systemic and local inhibitors has also been recognized to be important. The link between vitamin D and vascular calcification is complex. Experimental and clinical researches have revealed that both vitamin D excess and vitamin D deficiency have been shown to be associated with vascular calcification in uremic milieu. On the other hand, although there are some biases, recent large observational studies have demonstrated that vitamin D has beneficial effects on the mortality of patients with CKD independent of serum Ca, P, and parathyroid hormone levels, likely due to its activation of the vitamin D receptor in vasculature and cardiac myocytes. Further prospective studies are necessary to evaluate the direct effect of vitamin D on vascular calcification in order to improve the cardiovascular health of patients with CKD.

Vascular calcification: the killer of patients with chronic kidney disease

Cardiovascular complications are the leading cause of death in patients with chronic kidney disease (CKD). Vascular calcification is a common complication in CKD, and investigators have demonstrated that the extent and histoanatomic type of vascular calcification are predictors of subsequent vascular mortality. Although research efforts in the past decade have greatly improved our knowledge of the multiple factors and mechanisms involved in vascular calcification in patients with kidney disease, many questions remain unanswered. No longer can we accept the concept that vascular calcification in CKD is a passive process resulting from an elevated calcium-phosphate product. Rather, as a result of the metabolic insults of diabetes, dyslipidemia, oxidative stress, uremia, and hyperphosphatemia, "osteoblast-like" cells form in the vessel wall. These mineralizing cells as well as the recruitment of undifferentiated progenitors to the osteochondrocyte lineage play a critical role in the calcification process. Important transcription factors such as Msx 2, osterix, and RUNX2 are crucial in the programming of osteogenesis. Thus, the simultaneous increase in arterial osteochondrocytic programs and reduction in active cellular defense mechanisms creates the "perfect storm" of vascular calcification seen in ESRD. Innovative clinical studies addressing the combined use of inhibitors that work on vascular calcification through distinct molecular mechanisms, such as fetuin-A, osteopontin, and bone morphogenic protein 7, among others, will be necessary to reduce significantly the accrual of vascular calcifications and cardiovascular mortality in kidney disease. In addition, the roles of oxidative stress and inflammation on the fate of smooth muscle vascular cells and their function deserve further translational investigation.

Potential for vitamin D receptor agonists in the treatment of cardiovascular disease

Vitamin D(3) is made in the skin and modified in the liver and kidney to form the active metabolite, 1,25-dihydroxyvitamin D(3) (calcitriol). Calcitriol binds to a nuclear receptor, the vitamin D receptor (VDR), and activates VDR to recruit cofactors to form a transcriptional complex that binds to vitamin D response elements in the promoter region of target genes. During the past three decades the field has focused mainly on the role of VDR in the regulation of parathyroid hormone, intestinal calcium/phosphate absorption and bone metabolism; several VDR agonists (VDRAs) have been developed for the treatment of osteoporosis, psoriasis and hyperparathyroidism secondary to chronic kidney disease (CKD). Emerging evidence suggests that VDR plays important roles in modulating cardiovascular, immunological, metabolic and other functions. For example, data from epidemiological, preclinical and clinical studies have shown that vitamin D and/or 25(OH)D deficiency is associated with increased risk for cardiovascular disease (CVD). However, VDRA therapy seems more effective than native vitamin D supplementation in modulating CVD risk factors. In CKD, where decreasing VDR activation persists over the course of the disease and a majority of the patients die of CVD, VDRA therapy was found to provide a survival benefit in both pre-dialysis and dialysis CKD patients. Although VDR plays an important role in regulating cardiovascular function and VDRAs may be potentially useful for treating CVD, at present no VDRA is approved for CVD, and also no serum markers, beside parathyroid hormone in CKD, exist to indicate the efficacy of VDRA in CVD.

The use of vitamin D analogues in chronic kidney diseases: possible mechanisms beyond bone and mineral metabolism

Chronic kidney disease (CKD) is a common and costly medical condition, and currently available therapeutic options remain unsatisfactory. Vitamin D analogues are widely used for the bone and mineral disorder associated with CKD. However, accumulating evidence suggests that vitamin D analogues may have actions other than their effects on bone and mineral metabolism. In this article, we review the following aspects on the use of vitamin D analogues for the treatment of CKD: (1) epidemiological studies showing that patients with late-stage CKD have better survival than untreated patients; (2) animal studies showing that vitamin D analogues may retard the progression of CKD; (3) human studies on the anti-proteinuric and possibly renal protecting effects of vitamin D analogues in CKD and (4) the potential mechanisms of its therapeutic benefit. Nonetheless, definitive proof of the clinical benefits by randomized control trial would be necessary before one could advocate the routine use of vitamin D analogues for the treatment of CKD patients.

Progression of coronary calcification in pediatric chronic kidney disease stage 5

Coronary artery calcification (CAC) is common in adults with chronic kidney disease (CKD) and progresses with time. However, data are limited for younger patients. We have previously reported CAC in eight of 53 children with CKD. After 2 years, CAC evaluation was repeated in 48 patients. The median CAC score (CACS) increased from 101.3 (1473.6 +/- 1978.6, range 8.5-4332) to 1759.2 (2236.4 +/- 2463.3, range 0-5858) Agatston units (AU). When the individual changes in CACS were evaluated one by one, we showed a mild decrease in two patients on hemodialysis (HD) and in one transplant (Tx) recipient, a moderate increase in one patient on HD, one on peritoneal dialysis (PD) and one Tx recipient, and a large increase in one HD patient. Also, CAC disappeared in one HD patient. All patients with no calcification at baseline remained calcification-free at follow-up. To obtain the individual cumulative exposure, we calculated time-averaged mean values, using the laboratory values from the beginning of dialysis to the first and second multidetector spiral computed tomography (MDCT) scans (baseline and final values, respectively). Final CACS was positively related to final calcium-phosphorus (CaxP) product, while CAC progression was inversely associated with final serum albumin level. This report is the first study with the largest number and the youngest cohort to document the natural history of coronary calcification.

Role of vitamin D in chronic kidney disease

Decline in renal function is related directly to cardiovascular mortality. However, traditional risk factors do not fully account for the high mortality in these patients. Activated vitamin D, a hormone produced by the proximal convoluted tubule of the kidney, appears to have beneficial effects beyond suppressing parathyroid hormone (PTH). However, activated vitamin D also can cause hypercalcemia and hyperphosphatemia in chronic kidney disease. Newer agents such as vitamin D receptor activators (eg, paricalcitol) suppress PTH with reduced risk of hypercalcemia and hyperphosphatemia. Recent evidence from animal and preliminary human studies supports an association between vitamin D receptor activators and reduced risk of cardiovascular disease deaths, irrespective of PTH levels. New pathways of vitamin D regulation also have been discovered, involving fibroblast growth factor-23 and klotho. Although considerable work has been performed to advance our understanding of the effects of vitamin D in health and chronic kidney disease, more investigations and randomized trials need to be performed to elucidate the mechanistic underpinnings of these effects.

Vitamin D levels and their relationship with cardiac biomarkers in chronic hemodialysis patients

Vitamin D insufficiency may be associated with cardiovascular (CV) mortality in HD patients. To test this hypothesis, we cross-sectionally measured 25-hydroxyvitamin D (25D), 1,25-dihydroxyvitamin D (1,25D), cardiac troponin T (cTnT), and N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) in chronic HD patients. Sixty-five patients (M:F=31:34, age 52.2+/-13.2 yr, DM 41.5%) were selected. Along with the expected low levels of 1,25D, 59 (90.8%) patients had 25D insufficiency (<30 ng/mL) among whom 15 (23.1%) were 25D deficient (<10 ng/mL). The 25D levels showed a negative correlation with cTnT levels (Spearman's rho=-0.44, p<0.01) but not with NT-pro-BNP levels (Spearman's rho=-0.17, p=0.17). The 1,25D levels, however, did not show any relationship with either cTnT or NT-pro-BNP. In multivariate analysis, being male and having low levels of 25D were independent risk factors associated with cTnT elevation (beta=0.44, p<0.01 and beta=-0.48, p<0.01, respectively). In conclusion, not only 1,25D but also 25D are commonly decreased in HD patients. Lower 25D levels appear to be associated with cTnT elevation, predicting worse CV outcome, and are possible to involve cardiac hypertrophy or coronary artery disease.

Treatment of secondary hyperparathyroidism in CKD patients with cinacalcet and/or vitamin D derivatives

The discovery of the calcium-sensing receptor (CaR) 15 yr ago was rapidly followed by the development of drugs modulating its activity, the so-called calcimimetics (increasing the CaR signal) and calcilytics (decreasing the CaR signal). The indication for calcimimetics is treatment of primary and secondary hyperparathyroidism, whereas calcilytics have potential for treatment of osteoporosis. A large number of clinical studies has shown that cinacalcet, the only presently available calcimimetic, effectively reduces serum parathyroid hormone in dialysis patients with secondary hyperparathyroidism. In contrast to the effect of active vitamin D derivatives, it simultaneously decreases serum calcium and phosphorus. Experimental studies showed a concomitant decrease in parathyroid hyperplasia. In the treatment of secondary hyperparathyroidism of dialysis patients, important questions remain unresolved, for example, whether there are reasons to prefer calcimimetics to active vitamin D derivatives and whether combined administration offers advantages compared with calcimimetics or active vitamin D given in isolation. For lowering parathyroid hormone, available evidence from recent studies suggests that combination therapy should be preferred to single drug treatment because of less side-effects and greater efficacy in controlling parathyroid overfunction. Future randomized controlled trial must answer whether calcimimetics impact on cardiovascular events or survival and whether in this respect there are differences between vitamin D sterols and calcimimetics.

Vitamin D and diabetic nephropathy

Diabetic nephropathy (DN) is the most common renal complication of diabetes mellitus and a leading cause of end-stage renal disease. The renin-angiotensin system (RAS) is a major mediator of progressive renal injury in DN, and RAS inhibitors have been used as the mainstay treatment for DN. One major problem limiting the efficacy of the RAS inhibitors is the compensatory renin increase caused by disruption of renin feedback inhibition. Vitamin D negatively regulates the RAS by suppressing renin expression and thus plays a renoprotective role in DN. Diabetic vitamin D receptor-null mutant mice develop more severe renal injuries because of more robust RAS activation. Combination therapy with an RAS inhibitor and a vitamin D analogue markedly ameliorates renal injuries due to blockade of the compensatory renin increase by the analogue. These most recent data demonstrate that vitamin D and its analogues have renoprotective and therapeutic potentials in DN through targeting the RAS.

Role of cinacalcet in management of mineral bone disorder in chronic kidney disease (control of calcium, phosphorus and parathyroid hormone)

The management of hemodialysis patients with chronic kidney disease-mineral bone disorder includes treatment to control levels of calcium, phosphorus and parathyroid hormone, so as to prevent bone and soft-tissue complications. Recently, pleiotropic effects of active vitamin D have attracted much attention, and its effect on outcome has also gained recognition. However, administration of active vitamin D may cause hypercalcemia and hyperphosphatemia. Now, the use of a novel class of drugs, cinacalcet hydrochloride, has been proposed as a strategy to reduce parathyroid hormone secretion, while decreasing levels of serum calcium, phosphorus, and calcium x phosphorus products. Among subjects with secondary hyperparathyroidism undergoing hemodialysis, combined therapy with cinacalcet and vitamin D sterols improved achievement of the biochemical targets for chronic kidney disease-mineral bone disorder recommended by the guidelines.

The survival advantage for haemodialysis patients taking vitamin D is questioned: findings from the Dialysis Outcomes and Practice Patterns Study

BACKGROUND

Retrospective studies of haemodialysis patients from large dialysis organizations in the United States have indicated that intravenous vitamin D may be associated with a survival benefit. However, patients prescribed vitamin D are generally healthier than those who are not, suggesting that treatment by indication may have biased previous findings. Additionally, no survival benefit associated with vitamin D has been shown in a recent meta-analysis in CKD patients. Because treatment-by-indication bias due to both measured and unmeasured confounders cannot be completely accounted for in standard regression or marginal structural models (MSMs), this study evaluates the association between vitamin D and mortality among participants in the Dialysis Outcomes and Practice Patterns Study (DOPPS) using standard regression and MSMs with an expanded set of covariates, as well as by instrumental variable models to minimize potential bias due to unmeasured confounders.

METHODS

Data from 38 066 DOPPS participants from 12 countries between 1996 and 2007 were analysed. Mortality risk was assessed using standard baseline and time-varying Cox regression models, adjusted for demographics and detailed comorbidities, and MSMs. In models similar to instrumental variable analysis, the facility percentage of patients prescribed vitamin D, adjusted for the patient case mix, was used to predict patient-level mortality.

RESULTS

Vitamin D prescription was significantly higher in the USA compared to other countries. On average, patients prescribed vitamin D had fewer comorbidities compared to those who were not. Vitamin D therapy was associated with lower mortality in adjusted time-varying standard regression models [relative ratio (RR) = 0.92 (95% confidence interval: 0.87-0.96)] and baseline MSMs [RR = 0.84 (0.78-0.98)] and time-varying MSMs [RR = 0.78 (0.73-0.84)]. No significant differences in mortality were observed in adjusted baseline standard regression models for patients with or without vitamin D prescription [RR = 0.98 (0.93-1.02)] or for patients in facility practices where vitamin D prescription was more frequent [RR for facilities in 75th versus 25th percentile of vitamin D prescription = 0.99 (0.94-1.04)].

CONCLUSIONS

Vitamin D was associated with a survival benefit in models prone to bias due to unmeasured confounding. In agreement with a meta-analysis of randomized controlled studies, no difference in mortality was observed in instrumental variable models that tend to be more independent of unmeasured confounding. These findings indicate that a randomized controlled trial of vitamin D and clinical outcomes in haemodialysis patients are needed and can be ethically conducted.

Systematic review of the evidence underlying the association between mineral metabolism disturbances and risk of all-cause mortality, cardiovascular mortality and cardiovascular events in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a powerful risk factor for all-cause mortality and its most common aetiology, cardiovascular (CV) mortality. Mineral metabolism disturbances occur very early during the course of CKD but their control has been poor. A number of studies have assessed the relationship between all-cause mortality, CV mortality and events with mineral disturbances in CKD patients, but with considerable discrepancy and heterogeneity in results. Thus, a systematic review was conducted to assess methodological and clinical heterogeneity by comparing designs, analytical approaches and results of studies.

METHODS

Medline, EMBASE and Cochrane databases were systematically searched for articles published between January 1980 and December 2007.

RESULTS

Thirty-five studies were included in the review. All-cause mortality was the most commonly assessed outcome (n = 29). Data on CV mortality risk (n = 11) and CV events (congestive heart failure, stroke, myocardial infarction) (n = 4) are limited. The studies varied in populations scrutinized, exposure assessments, covariates adjusted and reference mineral levels used in risk estimation. A significant risk of mortality (all-cause, CV) and of CV events was observed with mineral disturbances. The data supported a greater mortality risk with phosphorus, followed by calcium and parathyroid hormone (PTH). The threshold associated with a significant all-cause mortality risk varied from 3.5-3.9 mg/dL (reference: 2.5-2.9) to 6.6-7.8 mg/dL (reference: 4.4-5.5) for high phosphorus, <3 mg/dL (reference: 5-7) to <5 mg/dL (reference: 5-6) for low phosphorus, 9.7-10.2 mg/dL (reference: < or =8.7) to >10.5 mg/dL (reference: 9-9.5) for high calcium, < or =8.8 mg/dL (reference: >8.8) to <9 mg/dL (reference: 9-9.5) for low calcium and >300 pg/mL (reference: 200-300) to >480 pg/mL (reference: < or =37) for PTH. Thresholds at which the CV mortality risk significantly increased were >5.5 (reference: 3.5-5.5) and >6.5 mg/dL (reference: <6.5) for phosphorus and >476.1 pg/mL (reference: <476.1) for PTH.

CONCLUSIONS

Serious limitations were observed in the quality and methodology across studies. In spite of enormous heterogeneity across studies, a significant mortality risk was observed with mineral disturbances in dialysis patients. Data on risk in pre-dialysis patients were less conclusive due to even more limited (numerically) evidence.

Vitamin D levels and patient outcome in chronic kidney disease

Vitamin D deficiency has been linked to cardiovascular disease and early mortality in patients on hemodialysis; however, it is not known if the same association exists at earlier stages of chronic kidney disease. To determine this we enrolled 168 consecutive new referrals to a chronic kidney disease clinic over a 2 year period and followed them for up to 6 years. All patients were clinically stable and had an estimated glomerular filtration rate (eGFR) at stage 2 or less and were without an imminent need for dialysis. Baseline 25-hydroxyvitamin D levels directly and significantly correlated with eGFR. After an average follow-up of 48 months, 48 patients started dialysis and 78 had died. In crude analyses, 25-hydroxyvitamin D predicted both time to death and end-stage renal disease. A dual-event Cox's model confirmed 25-hydroxyvitamin D as an independent predictor of study outcomes when adjusted for age, heart failure, smoking, C-reactive protein, albumin, phosphate, use of converting enzyme inhibitors or angiotensin receptor blockers, and eGFR. Our study shows that plasma 25-hydroxyvitamin D is an independent inverse predictor of disease progression and death in patients with stage 2-5 chronic kidney disease.

Vitamin D and human health: lessons from vitamin D receptor null mice

The vitamin D endocrine system is essential for calcium and bone homeostasis. The precise mode of action and the full spectrum of activities of the vitamin D hormone, 1,25-dihydroxyvitamin D [1,25-(OH)(2)D], can now be better evaluated by critical analysis of mice with engineered deletion of the vitamin D receptor (VDR). Absence of a functional VDR or the key activating enzyme, 25-OHD-1alpha-hydroxylase (CYP27B1), in mice creates a bone and growth plate phenotype that mimics humans with the same congenital disease or severe vitamin D deficiency. The intestine is the key target for the VDR because high calcium intake, or selective VDR rescue in the intestine, restores a normal bone and growth plate phenotype. The VDR is nearly ubiquitously expressed, and almost all cells respond to 1,25-(OH)(2)D exposure; about 3% of the mouse or human genome is regulated, directly and/or indirectly, by the vitamin D endocrine system, suggesting a more widespread function. VDR-deficient mice, but not vitamin D- or 1alpha-hydroxylase-deficient mice, and man develop total alopecia, indicating that the function of the VDR and its ligand is not fully overlapping. The immune system of VDR- or vitamin D-deficient mice is grossly normal but shows increased sensitivity to autoimmune diseases such as inflammatory bowel disease or type 1 diabetes after exposure to predisposing factors. VDR-deficient mice do not have a spontaneous increase in cancer but are more prone to oncogene- or chemocarcinogen-induced tumors. They also develop high renin hypertension, cardiac hypertrophy, and increased thrombogenicity. Vitamin D deficiency in humans is associated with increased prevalence of diseases, as predicted by the VDR null phenotype. Prospective vitamin D supplementation studies with multiple noncalcemic endpoints are needed to define the benefits of an optimal vitamin D status.

Serum beta2-microglobulin level is a significant predictor of mortality in maintenance haemodialysis patients

BACKGROUND

Beta(2)-microglobulin (beta(2)-M) is recognized as a surrogate marker of middle-molecule uraemic toxins and is a key component in the genesis of dialysis-associated amyloidosis. Few studies have evaluated the association of beta(2)-M levels with clinical outcome in dialyzed patients.

METHODS

The prognostic implication of serum beta(2)-M levels for the survival of haemodialysis patients was examined in 490 prevalent haemodialysis patients (60.1 +/- 11.8 years, haemodialysis duration of 87.4 +/- 75.7 months, 288 males and 202 females; 24% diabetics). The patients were divided into two groups according to their serum beta(2)-M levels: lower beta(2)-M group (n = 245) with serum beta(2)-M <32.2 mg/L (the median serum beta(2)-M) and higher beta(2)-M group (n = 245) with that >or=32.2 mg/L.

RESULTS

During the follow-up period of 40 +/- 15 months, there were 91 all-cause deaths, and out of them, 36 were from cardiovascular diseases. Kaplan-Meier analysis revealed that all-cause mortality in the higher beta(2)-M group was significantly higher compared to that in the lower beta(2)-M group (P < 0.001). Multivariate Cox proportional hazards analyses showed that serum beta(2)-M level was a significant predictor for all-cause mortality (hazard ratio, 1.05; 95% CI, 1.01-1.08; P = 0.005), and for non-cardiovascular mortality (hazard ratio, 1.06; 95% CI, 1.02-1.10; P = 0.006), after adjustment for age, gender, haemodialysis duration, the presence of diabetes, serum albumin and serum C-reactive protein.

CONCLUSION

These results demonstrate that the serum beta(2)-M level is a significant predictor of mortality in haemodialysis patients, independent of haemodialysis duration, diabetes, malnutrition and chronic inflammation, suggesting the clinical importance of lowering serum beta(2)-M in these patients.

25-hydroxyvitamin D levels and the risk of mortality in the general population

BACKGROUND

In patients undergoing dialysis, therapy with calcitriol or paricalcitol or other vitamin D agents is associated with reduced mortality. Observational data suggests that low 25-hydroxyvitamin D levels (25[OH]D) are associated with diabetes mellitus, hypertension, and cancers. However, whether low serum 25(OH)D levels are associated with mortality in the general population is unknown.

METHODS

We tested the association of low 25(OH)D levels with all-cause, cancer, and cardiovascular disease (CVD) mortality in 13 331 nationally representative adults 20 years or older from the Third National Health and Nutrition Examination Survey (NHANES III) linked mortality files. Participant vitamin D levels were collected from 1988 through 1994, and individuals were passively followed for mortality through 2000.

RESULTS

In cross-sectional multivariate analyses, increasing age, female sex, nonwhite race/ethnicity, diabetes, current smoking, and higher body mass index were all independently associated with higher odds of 25(OH)D deficiency (lowest quartile of 25(OH)D level, <17.8 ng/mL [to convert to nanomoles per liter, multiply by 2.496]), while greater physical activity, vitamin D supplementation, and nonwinter season were inversely associated. During a median 8.7 years of follow-up, there were 1806 deaths, including 777 from CVD. In multivariate models (adjusted for baseline demographics, season, and traditional and novel CVD risk factors), compared with the highest quartile, being in the lowest quartile (25[OH]D levels <17.8 ng/mL) was associated with a 26% increased rate of all-cause mortality (mortality rate ratio, 1.26; 95% CI, 1.08-1.46) and a population attributable risk of 3.1%. The adjusted models of CVD and cancer mortality revealed a higher risk, which was not statistically significant.

CONCLUSION

The lowest quartile of 25(OH)D level (<17.8 ng/mL) is independently associated with all-cause mortality in the general population.

Mortality reduction by vitamin D receptor activation in end-stage renal disease: a commentary on the robustness of current data

BACKGROUND

Debate exists about assumed mortality effects of the use of vitamin D receptor activators (VDRA) in haemodialysis patients.

METHODS

In the absence of randomized controlled trials (RCTs), current knowledge comes from several large observational studies that examined the association between the use of VDRA and mortality. In these trials, modern but complicated statistical analysis has been performed, attempting to minimize potential bias of suboptimal study design. This complexity may lead to suspicion about study results, and for this reason these results may be discarded for everyday clinical practice.

RESULTS

In the current commentary, several crucial aspects of applied statistics are highlighted, attempting to aid practicing clinicians to properly weigh these study results in a balanced way. The difference between historical and retrospective cohort analysis is addressed, as well as the use of sensitivity analysis and propensity scores. The impact of confounding, mediation and effect modification for these studies on VDRA use is discussed.

CONCLUSIONS

It is concluded that the results from these studies appear quite robust and consistent. Furthermore, there is an increasing amount of data from experimental data suggesting mechanisms for observed beneficial effects. However, it must be kept in mind that VDRA can have adverse effects and that observational data can never replace RCTs.

1,25-dihydroxyvitamin D3 regulates VEGF production through a vitamin D response element in the VEGF promoter

In previous studies we have demonstrated that the active form of vitamin D (1,25(OH)(2)D(3)) increases vascular endothelial growth factor (VEGF) expression and release in vascular smooth muscle cells (VSMC) in vitro. However, the mechanism by which 1,25(OH)(2)D(3) increases VEGF production is currently unknown. In this work, we demonstrated binding of vitamin D receptor to two response elements in the VEGF promoter. We performed promoter transactivation analysis and we observed that, in 293T cells, VEGF promoter was activated after vitamin D treatment. Using site-directed mutagenesis we have shown that both response elements are important for VEGF promoter activity. Therefore, the increase in VEGF expression and secretion induced by 1,25(OH)(2)D(3) in VSMC in vitro could be explained by direct binding of the vitamin D receptor, as a transcription factor, to VEGF promoter. These results could explain part of the beneficial effects of vitamin D treatment in renal patients by a possible VEGF-mediated improvement of the endothelial dysfunction.

Calcitriol blunts pro-atherosclerotic parameters through NFkappaB and p38 in vitro

BACKGROUND

Disturbances in vitamin D(3) metabolism are associated with an increased cardiovascular morbidity and mortality. The aim of this study was to assess the effects of calcitriol, the active metabolite of vitamin D3, on pro-atherosclerotic parameters in human umbilical vein cord endothelial cells (HUVEC).

MATERIALS AND METHODS

Calcitriol at 10(-10) and/or 10(-9) mol L(-1) was given to cultured HUVEC which were either non-stimulated or lipopolysaccharide (LPS) stimulated. Inter cellular adhesion molecule-1 and platelet-endothelial cell adhesion molecule-1, were determined by flow cytometry analysis. The receptor of advanced glycation end product (RAGE) and interleukin-6 (IL-6) mRNA expressions by RT-PCR and IL-6 secretion by enzyme-linked immunosorbent assay (ELISA). Nuclear p65 DNA-binding activity was measured by transcription factor assay kit and the inhibitor-kappaBalpha (IkappaBalpha), phosphorylated-IkappaBalpha (P-IkappaBalpha) and phosphorylated-p38 mitogen-activated protein kinase (MAPK) protein levels were determined by Western blot. Results Calcitriol decreased the adhesion molecules expression, as well as the LPS-induced mRNA expressions of RAGE and IL-6 and LPS induced IL-6 secretion. Furthermore, the LPS induced nuclear factor kappaB (NFkappaB)-p65 DNA-binding activity was also decreased by calcitriol. IkappaBalpha levels were increased and p-IkappaBalpha levels decreased after calcitriol treatment. The increased levels of activated p38 MAPK after LPS treatment were also decreased due to pre-incubation with calcitriol.

CONCLUSIONS

The decreased NFkappaB and p38 activities followed by calcitriol treatment may explain the anti-inflammatory/atherosclerotic properties of calcitriol that were observed previously and were emphasized in this study, demonstrating the inhibitory effect of calcitriol on the pro-inflammatory parameters: adhesion molecules, RAGE and IL-6.

Oral active vitamin D is associated with improved survival in hemodialysis patients

Injection of active vitamin D is associated with better survival of patients receiving chronic hemodialysis. Since in many countries oral active vitamin D administration is the most common form of treatment for secondary hyperparathyroidism we determined the survival benefit of oral active vitamin D in hemodialysis patients from six Latin America countries (FME Register as part of the CORES study) followed for a median of 16 months. Time-dependent Cox regression models, after adjustment for potential confounders, showed that the 7,203 patients who received oral active vitamin D had significant reductions in overall, cardiovascular, infectious and neoplastic mortality compared to the 8,801 patients that had not received vitamin D. Stratified analyses found a survival advantage in the group that had received oral active vitamin D in 36 of the 37 strata studied including that with the highest levels of serum calcium, phosphorus and parathyroid hormone. The survival benefit of oral active vitamin D was seen in those patients receiving mean daily doses of less than 1 microg with the highest reduction associated with the lowest dose. Our study shows that hemodialysis patients receiving oral active vitamin D had a survival advantage inversely related to the vitamin dose.

Paricalcitol reduces albuminuria and inflammation in chronic kidney disease: a randomized double-blind pilot trial

Vitamin D receptor activation is associated with improved survival in patients with chronic kidney disease, but the mechanism of this benefit is unclear. To better understand the effects of vitamin D on endothelial function, blood pressure, albuminuria, and inflammation in patients with chronic kidney disease (2 patients stage 2, remaining stage 3), we conducted a pilot trial in 24 patients who were randomly allocated equally to 3 groups to receive 0, 1, or 2 microg of paricalcitol, a vitamin D analog, orally for 1 month. Placebo-corrected change in flow mediated dilatation with a 1-microg dose was 0.5% and 0.4% with a 2-microg dose (P>0.2). At 1 month, the treatment:baseline ratio of high sensitivity C-reactive protein was 1.5 (95% CI: 1.1 to 2.1; P=0.02) with placebo, 0.8 (95% CI: 0.3 to 1.9; P=0.62) with a 1-microg dose, and 0.5 (95% CI: 0.3 to 0.9; P=0. 03) with a 2-microg dose of paricalcitol. At 1 month, the treatment:baseline ratio of 24-hour albumin excretion rate was 1.35 (95% CI: 1.08 to 1.69; P=0.01) with placebo, 0.52 (95% CI: 0.40 to 0.69; P<0.001) with a 1-microg dose, and 0.54 (95% CI: 0.35 to 0.83; P=0. 01) with a 2-microg dose (P<0.001 for between group changes). No differences were observed in iothalamate clearance, 24-hour ambulatory blood pressure, or parathyroid hormone with treatment or on washout. Thus, paricalcitol-induced reduction in albuminuria and inflammation may be mediated independent of its effects on hemodynamics or parathyroid hormone suppression. Long-term randomized, controlled trials are required to confirm these benefits of vitamin D analogs.