Lower concentrations of serum phosphorus within the normal range could be associated with less calcification of the coronary artery in Koreans with normal renal function

Urinary Phosphorus Excretion and Cardiovascular Outcomes in Patients with Pre-Dialysis Chronic Kidney Disease: The KNOW-CKD Study

The relationship between 24-h urinary phosphorus excretion (24 h UPE) and cardiovascular disease in patients with pre-dialysis chronic kidney disease (CKD) has rarely been studied, despite the fact that the relationship between serum phosphorus level and the risk of a cardiovascular event is well established. A total of 1701 patients with pre-dialysis CKD were finally included for the analyses and were divided into tertiles by 24 h UPE (first tertile (T1, 349.557 (mean) ± 88.413 (standard deviation)), second tertile (T2, 557.530 ± 50.738), and third tertile (T3, 851.695 ± 171.593). The study outcome was a six-point major adverse cardiac event (MACE). The median follow-up duration was 7.992 years. Kaplan-Meier curve analysis visualized that the cumulative incidences of a six-point MACE (p = 0.029) significantly differed from 24 h UPE levels, as the incidence rate of the study outcomes was highest in T1 and lowest in T3. Cox proportional hazard models unveiled that, compared to T1, the risk of a six-point MACE was significantly decreased in T3 (adjusted hazard ratio (HR) 0.376, 95% confidence interval (CI) 0.207 to 0.683). The restricted cubic spline curve analysis visualized an inverted S-shaped association between 24 h UPE level and the risk of a six-point MACE, indicating a significantly increased risk of a six-point MACE in patients with a low 24 h UPE level. In conclusion, low 24 h UPE is associated with adverse cardiovascular outcomes in patients with CKD. Our finding emphasizes that low 24 h UPE should not be a reliable marker for dietary restriction of phosphorus that essentially leads to better outcomes in patients with CKD.

Pathophysiology and Clinical Impacts of Chronic Kidney Disease on Coronary Artery Calcification

The global prevalence of chronic kidney disease (CKD) has increased in recent years. Adverse cardiovascular events have become the main cause of life-threatening events in patients with CKD, and vascular calcification is a risk factor for cardiovascular disease. Vascular calcification, especially coronary artery calcification, is more prevalent, severe, rapidly progressive, and harmful in patients with CKD. Some features and risk factors are unique to vascular calcification in patients with CKD; the formation of vascular calcification is not only influenced by the phenotypic transformation of vascular smooth muscle cells, but also by electrolyte and endocrine dysfunction, uremic toxin accumulation, and other novel factors. The study on the mechanism of vascular calcification in patients with renal insufficiency can provide a basis and new target for the prevention and treatment of this disease. This review aims to illustrate the impact of CKD on vascular calcification and to discuss the recent research data on the pathogenesis and factors involved in vascular calcification, mainly focusing on coronary artery calcification, in patients with CKD.

Kidney function, bone-mineral metabolism markers, and calcification of coronary arteries, aorta, and cardiac valves in older adults

BACKGROUND AND AIMS

The contribution of kidney dysfunction, especially at mild-to-moderate stages, and bone-mineral metabolism (BMM) markers to vascular calcification remains controversial or unclear. We comprehensively evaluated the association of kidney and BMM markers with coronary artery calcification (CAC) and extra-coronary calcification (ECC).

METHODS

In 1931 ARIC participants (age 73-95 years) without coronary heart disease at visit 7 (2018-19), we investigated the associations of estimated glomerular filtration rate (eGFR) (with creatinine, cystatin C, and both) and five serum BMM markers (calcium, fibroblast growth factor 23, magnesium, parathyroid hormone, and phosphorus) with high CAC and ECC (sex-race specific ≥75th vs. <75th percentile Agatston score) or any vs. zero CAC and ECC using multivariable logistic regression. For eGFR and BMM markers, we took their weighted cumulative averages from visit 1 (1987-89) to visit 5 (2011-13).

RESULTS

Lower eGFR, regardless of equations used, was not robustly associated with high CAC or ECC. Among BMM markers, only higher phosphorus levels, even within the normal range, showed robust associations with high CAC (only when modeled continuously) and ECC, independently of kidney function (e.g., odds ratio 1.94 [95%CI 1.38-2.73] for high aortic valve calcification, in the highest vs. lowest quartile). Results were generally consistent when analyzing any CAC or ECC, although cystatin C-based eGFR <60 mL/min/1.73 m2 became significantly associated with mitral valve calcification (odds ratio 1.69 [1.10-2.60]).

CONCLUSIONS

Among kidney and BMM measures tested, only serum phosphorus demonstrated robust associations with both CAC and ECC, supporting a key role of phosphorus in the pathophysiology of vascular calcification.

Serum biomarkers for arterial calcification in humans: A systematic review

Aim

To clarify the role of mediators of ectopic mineralization as biomarkers for arterial calcifications.

Methods

MEDLINE and Embase were searched for relevant literature, until January 4th 2022. The investigated biomarkers were: calcium, phosphate, parathyroid hormone, vitamin D, pyrophosphate, osteoprotegerin, receptor activator of nuclear factor-kappa B ligand (RANKL), fibroblast growth factor-23 (FGF-23), Klotho, osteopontin, osteocalcin, Matrix Gla protein (MGP) and its inactive forms and vitamin K. Studies solely performed in patients with kidney insufficiency or diabetes mellitus were excluded.

Results

After screening of 8985 articles, a total of 129 articles were included in this systematic review. For all biomarkers included in this review, the results were variable and more than half of the studies for each specific biomarker had a non-significant result. Also, the overall quality of the included studies was low, partly as a result of the mostly cross-sectional study designs. The largest body of evidence is available for phosphate, osteopontin and FGF-23, as a little over half of the studies showed a significant, positive association. Firm statements for these biomarkers cannot be drawn, as the number of studies was limited and hampered by residual confounding or had non-significant results. The associations of the other mediators of ectopic mineralization with arterial calcifications were not clear.

Conclusion

Associations between biomarkers of ectopic mineralization and arterial calcification are variable in the published literature. Future longitudinal studies differentiating medial and intimal calcification could add to the knowledge of biomarkers and mechanisms of arterial calcifications.

•

We researched the association between biomarkers and arterial calcifications.

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This review focused on biomarkers of bone metabolism and Matrix Gla protein.

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Associations between biomarkers and arterial calcification are variable.

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Future studies should differentiate between medial and intimal calcifications.

Effects of Normal Reference Range of Phosphorus and Corresponding PTH on Endothelial Function in CKD Patients

Introduction

Endothelial dysfunction commonly occurs in chronic kidney disease (CKD) patients and increases the risk for cardiovascular disease. Among CKD patients, biomarkers involved in the pathogenesis of CKD-mineral bone disorder (CKD-MBD), such as phosphorus, parathyroid hormone, and fibroblast growth factor 23, are associated with endothelial dysfunction. We investigated whether these biomarkers induce endothelial dysfunction in CKD patients with normal phosphorus levels.

Methods

This cross-sectional study examined CKD patients with normal phosphorus levels; patients with an estimated glomerular filtration rate (eGFR) &lt;15 or who were under dialysis were excluded. Iontophoresis with laser doppler flowmetry (ILDF) and peripheral arterial tonometry were performed to assess endothelial function in 85 patients. Pearson's correlation coefficient, multiple regression, and mediation analyses were performed to examine the association between CKD-MBD biomarkers and endothelial dysfunction.

Results

Endothelial dysfunction was observed in all subjects with a low response to ILDF and 27% of subjects according to peripheral arterial tonometry. Acetylcholine (Ach)-induced ILDF was significantly associated with eGFR (r = 0.22, P = 0.04), intact parathyroid hormone (iPTH; r = −0.46, P &lt; 0.01), and VCAM-1 (r = −0.36, P &lt; 0.01). The reactive hyperemia index (RHI) was significantly related to phosphorus levels (r = 0.32, P &lt; 0.01) and iPTH (r = −0.39, P = 0.02). After adjusting for eGFR, iPTH and VCAM-1 remained independent factors for predicting endothelial dysfunction measured using Ach-induced ILDF. In addition, iPTH and phosphorus levels were independent predictors for endothelial dysfunction measured using RHI in the eGFR-adjusted model. Mediation analyses showed that the individual indirect effects of iPTH were significantly affected ILDF and RHI.

Conclusion

Serum levels of phosphorus and iPTH are associated with endothelial dysfunction, even in CKD patients with normal phosphorus levels.

Association between serum phosphorus and subclinical coronary atherosclerosis in asymptomatic Korean individuals without kidney dysfunction

BACKGROUND

There are limited data regarding the relation between serum phosphorus concentration (SPC) and subclinical coronary atherosclerosis in the asymptomatic healthy population without kidney dysfunction.

OBJECTIVES

We aimed to investigate the relation between SPC and characteristics of atherosclerotic plaques and cardiac events according to SPCs using a large cohort of asymptomatic Korean individuals.

METHODS

We evaluated 6329 asymptomatic Korean individuals [mean age: 53.6 ± 7.6 y, 4611 men (72.9%)] without kidney dysfunction and coronary artery disease who voluntarily underwent coronary computed tomography angiography (CCTA) as part of a general health examination. Study participants were stratified into quartiles according to their SPCs (≤3.0, 3.1-3.3, 3.4-3.7, ≥3.8 mg/dL). The degree and extent of subclinical coronary atherosclerosis were evaluated with CCTA. Stenosis of diameter ≥50% was defined as significant. A cardiac event was defined as a composite of all-cause death, myocardial infarction, unstable angina, and coronary revascularization.

RESULTS

After adjustment for cardiovascular disease risk factors, the risk of any atherosclerotic plaque was significantly higher with increasing SPC quartiles (P = 0.001). In particular, the risk of calcified plaque increased in the second (OR: 1.27; 95% CI: 1.07, 1.51; P = 0.006), third (OR: 1.39; 95% CI: 1.17, 1.64; P < 0.001), and fourth SPC quartiles (OR: 1.50; 95% CI: 1.24, 1.82; P < 0.001) compared with that in the first quartile. However, there were no significant differences in the adjusted ORs for noncalcified plaque, mixed plaque, or significant stenosis. During a follow-up of median 5.4 y, there was no significant difference in cardiac events between the SPC quartiles.

CONCLUSIONS

In asymptomatic Korean individuals without kidney dysfunction, a high SPC was an independent predictor of calcified plaques without any difference in cardiac events. Further long-term prospective studies are required to validate these results.

Effects of serum phosphorus on vascular calcification in a healthy, adult population: A systematic review

Cardiovascular disease has been associated with elevated serum phosphorus levels, which have been associated with cardiovascular mortality. This is commonly seen in the chronic kidney disease (CKD) population where studies have shown that high phosphorus levels cause coronary artery calcification. Although studies have independently associated vascular stiffness and serum phosphorus in those with and without CKD, there are fewer data in individuals without CKD. Therefore, the aim of this systematic review was to analyze whether serum phosphorus levels are associated with cardiovascular calcification in healthy individuals. A systematic review of the literature that was conducted revealed 10 articles, all cross-sectional studies, that met eligibility criteria. These criteria were peer-reviewed studies on a healthy, adult population written in the English language. Studies lacking data on serum phosphorus and measured to assess its association with vascular calcification were excluded. Studies on subjects with CKD, other chronic diseases, or on children were also excluded. Of the 10 studies located, 8 indicated an association between serum phosphorus and vascular calcification. One study did not indicate an association. One study indicated a statistically significant association between serum phosphorus and vascular calcification prevalence, but not incidence. Studies were limited since no randomized controlled trials were available. This systematic review generates gaps in research. Due to considerable amounts of phosphorus additives in the food supply, there may be a connection to dietary phosphorus and vascular calcification. Additionally, phosphorus binders may assist in the prevention of vascular calcification but have not been studied in a healthy population. Further study on both dietary phosphorus restriction and phosphorus binders is needed. While 8 out of 10 cross-sectional studies found an association in this systematic review, the topic of vascular calcification and serum phosphorus needs further study if a cause and effect relationship is to be detected.

Reduced Serum Phosphorus Levels Were Associated with Metabolic Syndrome in Men But Not in Women: A Cross-Sectional Study among the Japanese Population

BACKGROUND

Reduced serum phosphorus (SP) levels are reported to be associated with insulin resistance and metabolic syndrome (MetS). However, there have been a few gender-specific studies although SP levels are substantially different between men and women.

METHODS

This is a cross-sectional study. A total of 16,041 subjects (9,076 men and 6,965 women) were analyzed. The subjects were divided into 3 groups of gender-specific tertiles based on phosphorus levels: the lowest (T1), middle (T2), and the highest (T3).

RESULTS

SP levels were significantly lower in subjects with MetS than in those without MetS in men but not in women. Waist circumference and fasting plasma glucose were negatively and high-density lipoprotein cholesterol was positively correlated with SP levels both in men and women. Blood pressure (BP) and triglycerides (TG) were negatively correlated with SP levels in men, while they were positively correlated with SP levels in women. Lower SP levels were associated with the prevalence of MetS in men (T1; 19.9%, T2; 16.9%, and T3; 14.3%; p < 0.001) but not in women (T1; 14.1%, T2; 16.6%, and T3; 15.3%; p = 0.282).

CONCLUSION

BP and TG were unexpectedly positively correlated with SP levels in women. Reduced SP levels were associated with MetS in men but not in women.

Interaction of Serum Phosphate with Age as Predictors of Cardiovascular Risk Scores in Stable Renal Transplant Recipients

We calculated rate of changes in the cardiovascular risk calculator for renal transplant recipients (CRCRTR) major adverse cardiac events (MACE) in clinically stable renal transplant recipients (RTRs) to identify covariables that associate with fast cardiovascular (CV) risk progression. CRCRTR-MACE scores were calculated on 139 patients in 2011 and 2014. Score changes above and below median changes in scores were labeled fast or slow CV risk progression. Multivariate analysis (MVA) was performed to identify variables significant to percentage changes in scores. Receiver-operating characteristic (ROC) analysis was performed to define sensitivity and specificity of factors significant to fast score progression. Follow-up was 2.61 (2.02-4.47) years. Slow and fast progressions were present in 50.4 and 49.6% of patients, with a median change of 25.8% (- 92.1 to 1,444.7%). MVA showed percentage changes in age and serum phosphate were the only significant variables impacting fast progression in scores. ROC showed 2011 serum phosphate of 1.15 mmol/L to predict fast progression (area under the curve [AUC] of 0.628, p > 0.0126). Age older than 45 years combined with 2011 serum phosphate above 1.15 mmol/L had a significant AUC of 0.781, p < 0.0010 interleukin (IL)-1A and IL-28A were significant associates with serum phosphate above 1.1 mmol/L in the MVA. Changes in CV risk in RTR over time are highly variable. Serum phosphate, even within upper normal levels, predicts worsening of CV risk scores in stable RTR.

Serum Phosphorus Concentration and Coronary Artery Calcification in Subjects without Renal Dysfunction

Serum phosphorus (P) concentration is associated with coronary artery calcification (CAC) as well as cardiovascular events in patients with chronic kidney disease. It has been suggested that this relationship is extended to subjects without renal dysfunction, but further explorations in diverse races and regions are still needed. We performed a cross-sectional study of 2,509 Korean subjects (Far Eastern Asian) with an estimated glomerular filtration rate of ≥60 ml/min/1.73m² and who underwent coronary computerized tomography. Serum P concentration was divided into pre-determined 4 categories: ≤3.2, 3.2< to ≤3.6, 3.6< to ≤4.0 and >4.0 mg/dL. Agatston score (AS), an index of CAC, was divided into 3 categories: 0, 0< to ≤100, and >100. A multinomial logit model (baseline outcome: AS = 0) was applied to estimate the odds ratio (OR) for each serum P category (reference: ≤3.2mg/dL). Mean age of subjects was 53.5±9.1 years and 36.9% were female. In the adjusted model, serum P concentration of 3.6< to ≤4.0 mg/dL and >4.0 mg/dL showed high ORs for AS of >100 [OR: 1.58, 95% confidence interval (CI): 1.04–2.40 and OR: 2.11, 95% CI: 1.34–3.32, respectively]. A unit (mg/dL) increase in serum P concentration was associated with 50% increase in risk of AS >100 (OR: 1.50, 95% CI: 1.16–1.94). A higher serum P concentration, even within a normal range, may be associated with a higher CAC in subjects with normal renal function.

Composition of dietary macronutrient intake is not associated with prevalence of coronary artery calcification in healthy Korean adults

BACKGROUND AND AIMS

There is little information supporting the relationships between macronutrients and pre-clinical atherosclerosis. The aim of this study was to identify whether dietary macronutrient content is related with CAC.

METHODS

10,793 healthy Korean adults in a cohort were enrolled. Subjects were divided into CAC (CAC score >0) or non-CAC group (CAC score = 0). Intake of energy, carbohydrate (CHO), protein and fat were obtained using food frequency questionnaire (FFQ). Macronutrient composition was expressed as the ratio of energy from each macronutrient to total energy. Subjects were classified into three groups according to tertiles of intake for each macronutrient. To investigate the association between macronutrient intake and CAC, multiple regression analysis was conducted according to tertile groups of each macronutrient.

RESULTS

The prevalence of CAC significantly differed among tertile groups of CHO and fat intake in men (p < 0.001, p < 0.01) and women (p < 0.05, p < 0.01). However, multiple logistic regression analysis revealed that the odds ratios (ORs) for CAC were not significantly different among tertile groups of each macronutrient intake after adjustment in men (CHO: OR = 0.965 [95% CI = 0.826-1.129]; protein: OR = 1.029 [95% CI = 0.881-1.201]; fat: OR = 1.015 [95% CI = 0.868-1.188]) and women (CHO: OR = 1.158 [95% CI = 0.550-2.438]; protein: OR = 1.261 [95% CI = 0.629-2.528]; fat: OR = 0.625 [95% CI = 0.286-1.365]).

CONCLUSIONS

The prevalence of CAC may not be associated with composition of dietary macronutrient intake in in healthy Korean adults.

Abnormalities in renal tubular phosphate handling in children with sickle cell disease

BACKGROUND

The mechanisms responsible for the hyperphosphatemia in patients with sickle cell disease (SCD) and preserved glomerular filtration rate (GFR) are not fully understood. The role of fibroblast growth factor 23 (FGF23), a phosphaturic hormone has not been investigated in SCD. Hence, we evaluated parameters of renal tubular phosphorus handling and their relation to prevailing FGF23 levels in a cohort of young SCD patients.

METHODS

Renal tubular phosphate handling and circulating levels of various analytes including FGF23 and parathyroid hormone (PTH) were measured in 24 children with SCD and normal estimated GFR in a cross sectional study. Correlation and regression analysis were employed to derive relationships between serum phosphorus and several variables.

RESULTS

Most children showed elevated age- adjusted serum phosphorus (5.1 ± 0.7 mg/dl) levels. Tubular re-absorption of phosphorus(TRP) (96.3 ± 2.1%) and tubular maximum re-absorption of phosphorus per unit volume of GFR (TMP/GFR) (4.9 ± 0.6 mg/dl) were both elevated. Plasma intact FGF23 concentrations were elevated (81 ± 38 pg/ml) while the average PTH values were normal in most patients (50 ± 27 pg/ml). Univariate analysis showed significant correlations of serum phosphorus with TMP/GFR, alkaline phosphatase, age, lactate dehydrogenase (LDH), and log intact FGF23. TMP/GFR correlated with log intact FGF23 (r = 0.5, P< or = 0.01) but not with PTH. Multiple regression analysis yielded an independent relationship of serum phosphorus with TMP/GFR.

CONCLUSION

The elevated serum phosphorus concentrations with simultaneously increased TMP/GFR and elevated FGF23 levels collectively suggest that patients with SCD display proximal tubular resistance to the action of FGF23 before any decline in GFR.

Phosphorus supplement alters postprandial lipemia of healthy male subjects: a pilot cross-over trial

BACKGROUND

Epidemiological studies have found a U-shaped relationship between serum phosphorus and cardiovascular disease (CVD). The mechanism(s) behind such a relationship are poorly understood. Phosphorus (P) is reported to improve insulin sensitivity, which is involved in lipid metabolism, and thus we were interested in determining the impact of phosphorus ingestion on postprandial lipemia, a recognized CVD risk factor.

FINDINGS

A within-subject study design was conducted, whereby 8 healthy male subjects received a high fat meal (330 Kcal; 69% energy from fat; 35 mg of phosphorus) with placebo or phosphorus (500 mg) in a random order. Postprandial blood samples (~10 ml) were collected every hour for 6 hours after meal ingestion. Changes in different parameters were analyzed using a 2-factor repeated-measure ANOVA. In the phosphorus (P) supplemented group, postprandial serum P increased (p=0.00), while changes in insulin, non-esterified fatty acids (NEFA) and triglyceride (TG) were not significantly different than that of placebo. Concurrently, phosphorus supplementation increased postprandial concentrations of apolipoprotein B48 (ApoB48) (p<0.05) and decreased that of apolipoprotein B100 (ApoB100) (p<0.05).

CONCLUSIONS

Phosphorus supplementation (500 mg) of the meal seems to alter the different components of postprandial lipemia. These findings highlight the potential role of phosphorus in CVD.

Dietary intake of calcium and phosphorus and serum concentration in relation to the risk of coronary artery calcification in asymptomatic adults

OBJECTIVE

The current data regarding the association between calcium and phosphorus and cardiovascular disease are lacking. The aim of this study was to explore whether dietary calcium and phosphorus intake and their serum levels are associated with the prevalence of coronary artery calcification (CAC) using cardiac computed tomography in asymptomatic participants without a history of chronic kidney disease or cardiovascular disease.

APPROACH AND RESULTS

A cross-sectional study was performed in 23 652 Korean participants (40.8±7.3 years, male 83.5%) without chronic kidney disease (estimated glomerular filtration rate≥60 mL/min per 1.73 m(2)) or clinically overt cardiovascular disease, who underwent cardiac computed tomographic estimation of CAC scores as part of a general health checkup in addition to completing a self-administered food frequency questionnaire. We assessed the relationship of dietary calcium and phosphorus intake and serum levels with CAC scores using both multivariate-adjusted Tobit models and multinomial logistic regression models. Neither dietary calcium nor phosphorus intake was consistently associated with CAC scores. However, the serum calcium, phosphorus, and calcium-phosphorus product levels were significantly associated with the CAC score ratios. In multivariable-adjusted models, the CAC score ratios (95% confidence intervals) comparing the highest quartiles of serum calcium, phosphorus, and calcium-phosphorus product levels to the lowest quartiles were 1.89 (1.36-2.64), 3.33 (2.55-4.35), and 3.98 (3.00-5.28), respectively (P for trend <0.001).

CONCLUSIONS

Elevated serum levels of calcium, phosphorus, and calcium-phosphorus product, but not dietary consumption, are associated with increased CAC scores. Our findings should be explored in further research.

Coronary artery calcification in chronic kidney disease: An update

Arterial calcification is a well-recognized complication of advanced atherosclerosis. Chronic kidney disease (CKD) is characterized by significantly more pronounced, disseminated and fast-progressing calcification of the vascular system, including the coronary arteries. New computed tomography-based imaging techniques allow for the noninvasive assessment and monitoring of calcification in different vascular sites. Coronary artery calcification (CAC) develops early in the course of CKD and is tightly associated with mineral and bone disorders, which include but are not limited to secondary hyperparathyroidism. In this review, recent data on the pathogenesis of CAC development and progression are discussed, with a special emphasis on fibroblast growth factor 23 and its co-receptor, klotho. The prevalence, progression and prognostic significance of CAC are reviewed separately for patients with end-stage renal disease treated with dialysis, kidney transplant recipients and patients with earlier stages of CKD. In the last section, therapeutic considerations are discussed, with special attention paid to the importance of treatment that addresses mineral and bone disorders of CKD.

Associations among total and food additive phosphorus intake and carotid intima-media thickness--a cross-sectional study in a middle-aged population in Southern Finland

Background

Dietary phosphorus (P) intake in Western countries is 2- to 3-fold higher than recommended, and phosphate is widely used as a food additive in eg. cola beverages and processed meat products. Elevated serum phosphate concentrations have been associated with cardiovascular disease (CVD) risk factors and CVD itself in several studies in patients with renal dysfunction and in a few studies in the general population. Carotid intima-media thickness (IMT) is a CVD risk factor, thus the aim of the study was to determine if an association between dietary P, especially food additive phosphate (FAP), intake, and IMT exists.

Methods

Associations among total phosphorus (TP) and FAP intake and carotid IMT were investigated in a cross-sectional study of 37- to 47-year-old females (n = 370) and males (n = 176) in Finland. Associations among TP intake, FAP intake, and IMT were tested by analysis of covariance (ANCOVA) in quintiles (TP) and sextiles (FAP) using sex, age, low-density/high-density lipoprotein cholesterol ratio, smoking status, and IMT sonographer as covariates.

Results

No significant associations were present between TP or FAP intake and IMT (p > 0.05, ANCOVA), but in between-group comparisons some differences were found indicating higher IMT among subjects with higher P intake. When testing for a significant linear trend with contrast analysis, a positive trend was observed between energy-adjusted TP intake and IMT among all subjects (p = 0.039), and among females a tendency for a trend existed (p = 0.067). Among all subjects, a significant positive linear trend was also present between FAP intake and IMT (p = 0.022); this trend was also seen in females (p = 0.045). In males, no significant associations or trends were noted between TP or FAP intake and IMT (p > 0.05).

Conclusions

Our results indicate that a significant linear trend exists between energy-adjusted TP intake and FAP intake, and IMT among all subjects. Based on these results, high dietary P intake should be further investigated due to its potential association with adverse cardiovascular health effects in the general population.

Public health impact of dietary phosphorus excess on bone and cardiovascular health in the general population

This review explores the potential adverse impact of the increasing phosphorus content in the American diet on renal, cardiovascular, and bone health of the general population. Increasingly, studies show that phosphorus intakes in excess of the nutrient needs of a healthy population may significantly disrupt the hormonal regulation of phosphate, calcium, and vitamin D, which contributes to disordered mineral metabolism, vascular calcification, impaired kidney function, and bone loss. Moreover, large epidemiologic studies suggest that mild elevations of serum phosphate within the normal range are associated with cardiovascular disease (CVD) risk in healthy populations without evidence of kidney disease. However, few studies linked high dietary phosphorus intake to mild changes in serum phosphate because of the nature of the study design and inaccuracies in the nutrient composition databases. Although phosphorus is an essential nutrient, in excess it could be linked to tissue damage by a variety of mechanisms involved in the endocrine regulation of extracellular phosphate, specifically the secretion and action of fibroblast growth factor 23 and parathyroid hormone. Disordered regulation of these hormones by high dietary phosphorus may be key factors contributing to renal failure, CVD, and osteoporosis. Although systematically underestimated in national surveys, phosphorus intake seemingly continues to increase as a result of the growing consumption of highly processed foods, especially restaurant meals, fast foods, and convenience foods. The increased cumulative use of ingredients containing phosphorus in food processing merits further study given what is now being shown about the potential toxicity of phosphorus intake when it exceeds nutrient needs.

Candidate gene association study of coronary artery calcification in chronic kidney disease: findings from the CRIC study (Chronic Renal Insufficiency Cohort)

OBJECTIVES

This study sought to identify loci for coronary artery calcification (CAC) in patients with chronic kidney disease (CKD).

BACKGROUND

CKD is associated with increased CAC and subsequent coronary heart disease (CHD), but the mechanisms remain poorly defined. Genetic studies of CAC in CKD may provide a useful strategy for identifying novel pathways in CHD.

METHODS

We performed a candidate gene study (∼2,100 genes; ∼50,000 single nucleotide polymorphisms [SNPs]) of CAC within the CRIC (Chronic Renal Insufficiency Cohort) study (N = 1,509; 57% European, 43% African ancestry). SNPs with preliminary evidence of association with CAC in CRIC were examined for association with CAC in the PennCAC (Penn Coronary Artery Calcification) (N = 2,560) and AFCS (Amish Family Calcification Study) (N = 784) samples. SNPs with suggestive replication were further analyzed for association with myocardial infarction (MI) in the PROMIS (Pakistan Risk of Myocardial Infarction Study) (N = 14,885).

RESULTS

Of 268 SNPs reaching p < 5 × 10(-4) for CAC in CRIC, 28 SNPs in 23 loci had nominal support (p < 0.05 and in same direction) for CAC in PennCAC or AFCS. Besides chr9p21 and COL4A1, known loci for CHD, these included SNPs having reported genome-wide association study association with hypertension (e.g., ATP2B1). In PROMIS, 4 of the 23 suggestive CAC loci (chr9p21, COL4A1, ATP2B1, and ABCA4) had significant associations with MI, consistent with their direction of effect on CAC.

CONCLUSIONS

We identified several loci associated with CAC in CKD that also relate to MI in a general population sample. CKD imparts a high risk of CHD and may provide a useful setting for discovery of novel CHD genes and pathways.