Phosphorus Consumption Within 1 Hour Prior to Blood Work and Associated Serum Levels of Phosphate, Calcium, and PTH in Adult Patients Receiving Hemodialysis Treatment.

BACKGROUND: While dietary intake is known to influence serum markers of chronic kidney disease-mineral and bone disorder (CKD-MBD), the effects of recent food and beverage intake, particularly phosphorus consumption on these serum markers (phosphate, calcium, and parathyroid hormone [PTH]), are unknown in hemodialysis patients. An understanding of these effects could have direct and important implications on the management of CKD-MBD. OBJECTIVE: To determine whether serum phosphate, calcium, and PTH levels were higher in hemodialysis patients who had consumed dietary phosphorus within 1 hour prior to their routine dialysis-related blood work (non-phosphorus-fasted) compared with patients who did not (phosphorus-fasted). DESIGN: Observational, cross-sectional study. SETTING: Kingston Health Sciences Center-Kingston General Hospital Site and its affiliated satellite hemodialysis units. PATIENTS: Two hundred fifty-four adult patients receiving outpatient hemodialysis treatment for end-stage kidney disease were recruited. MEASUREMENTS: The main measurements for this study included an assessment of dietary phosphorus intake as well as serum phosphate, calcium, PTH, albumin, Kt/V, and urea reduction ratio. METHODS: A direct patient interview was performed to assess dietary phosphorus intake within 1 hour prior to routine dialysis-related blood work. The Canadian Nutrient File was then used to estimate dietary phosphorus based on the specific foods and beverages (including portion sizes and brands where applicable) identified in the interview. Serum measures of phosphate, PTH, calcium, albumin, and dialysis adequacy (Kt/V and urea reduction ratio) were obtained from participants' routine dialysis-related blood work. RESULTS: Non-phosphorus-fasted participants had nonsignificantly higher serum PTH levels compared to phosphorus-fasted participants (61.2 ± 64.7 vs 47.9 ± 39.7, P = .05). Non-phosphorus-fasted participants with PTH levels at the Kidney Disease Improving Global Outcomes (KDIGO) "target" (between 15 and 60 pmol/L) had significantly higher serum phosphate levels relative to phosphorus-fasted participants (1.6 ± 0.3 vs 1.4 ± 0.4, P = .006). In non-phosphorus-fasted participants, there was a nonsignificant association between the number of items containing inorganic phosphate additives and higher levels of serum phosphate and lower levels of serum calcium. LIMITATIONS: Some limitations include the cross-sectional nature of this study, self-reporting biases and estimates (as opposed to direct measurements) related to the dietary assessment, and the use of single (and not serial) assessments of serum measures. CONCLUSIONS: Dietary phosphorus intake in close proximity to blood work may contribute to subtle alterations in some key serum CKD-MBD parameters in adult outpatient hemodialysis patients but may not meaningfully alter CKD-MBD management.

CONTEXTE: Alors que l'alimentation est connue pour influencer les marqueurs sériques des troubles minéraux et osseux associés à l'insuffisance rénale chronique (TMO-IRC), les effets d'une consommation récente de nourriture et de boisson, particulièrement de phosphore, sur ces mêmes marqueurs sériques (phosphate, calcium et hormone parathyroïde [PTH]), demeurent inconnus chez les patients hémodialysés. Une meilleure connaissance de ces effets pourrait avoir une influence majeure et directe sur la prise en charge des TMO-IRC. OBJECTIF: Déterminer si les taux sériques de phosphate, de calcium et de PTH sont plus élevés chez les patients hémodialysés ayant consommé des aliments contenant du phosphore dans l'heure précédant les analyses sanguines de routine liées à la dialyse (analyse sanguine de routine), lorsque comparés aux taux des patients n'en ayant pas consommé (patients à jeun). TYPE D'ÉTUDE: Une étude transversale observationnelle. CADRE: Le Kingston Health Sciences Centre, sur le site de l'hôpital général de Kingston, et ses unités satellites d'hémodialyse. SUJETS: L'étude porte sur 244 patients adultes atteints d'insuffisance rénale terminale et recevant des traitements ambulatoires d'hémodialyse. MESURES: Les principales mesures incluaient l'évaluation de l'apport en phosphore alimentaire, la mesure des taux sériques de phosphate, de calcium, de PTH et d'albumine, de même que le Kt/V et le taux de réduction de l'urée. MÉTHODOLOGIE: Les patients ont été questionnés sur leur consommation de phosphore dans les heures précédant l'analyse sanguine de routine liée à la dialyse. Le Fichier canadien des éléments nutritifs a par la suite été employé pour estimer la quantité de phosphore alimentaire selon les aliments et les boissons consommés (portions et marque du produit, lorsque disponibles). Les mesures sériques de phosphate, de PTH, de calcium et d'albumine, de même que l'efficacité de la dialyse (Kt/V et taux de réduction de l'urée) ont été obtenues par les analyses sanguines de routine. RÉSULTATS: Les participants qui avaient consommé du phosphore n'ont pas présenté un taux de PTH sérique plus élevé que les patients à jeun (61,2 ± 64,7 contre 47,9 ± 39,7; P = 0,05). Les sujets ayant consommé du phosphore et dont les taux de PTH sériques se situaient dans la « cible ¼ du KDIGO (Kidney Disease Improving Global Outcomes), soit entre 15 et 60 pmol/L, présentaient des taux de phosphate sérique significativement plus élevés que les sujets à jeun (1,6 ± 0,3 contre 1,4 ± 0,4; P = .006). En outre, chez les patients ayant consommé du phosphore, une association non significative a été observée entre le nombre d'aliments contenant des additifs phosphatés inorganiques qui avaient été consommés et des taux sériques plus élevés en phosphate et plus faibles en calcium. LIMITES: La nature transversale de l'étude, de possibles biais et estimations dus à l'auto-évaluation des apports alimentaires (par rapport à une mesure directe) et le recours à des mesures uniques (et non en série) pour les analyses sanguines constituent les limites. CONCLUSION: La consommation de phosphore alimentaire dans les heures précédant l'analyse sanguine est susceptible d'introduire de légères altérations pour certains paramètres sériques clés du TMO-IRC chez les adultes recevant des traitements ambulatoires d'hémodialyse, sans toutefois altérer la gestion du TMO-IRC de façon significative.

The Heart and Kidney: Abnormal Phosphate Homeostasis Is Associated With Atherosclerosis.

CONTEXT: Phosphate has gained recognition as a risk factor for adverse cardiovascular outcomes, potentially due to accelerated vascular calcification. Fibroblast growth factor-23 (FGF-23) is a counter-regulatory hormone that increases renal phosphate excretion to maintain normal levels. OBJECTIVE: The purpose of the study was to determine the association of phosphate and FGF-23 to atherosclerosis. DESIGN AND SETTING: A prospective cohort study (n = 204) of outpatients referred for coronary angiography over of a 1-year recruitment period at the Kingston General Hospital. INTERVENTION: Blood was collected, and a focused carotid ultrasound was performed. MAIN OUTCOME MEASURE: Degree of angiographic coronary artery disease was scored. Carotid maximum plaque height, total area, grayscale median, and tissue pixel distribution were measured. Plasma phosphate was assessed by mineral assay and FGF-23 by ELISA. RESULTS: Carotid plaque burden [total plaque area (TPA)] was associated with higher levels of phosphate (TPA, r = 0.20, P < 0.01) and FGF-23 (r = 0.19, P < 0.01). FGF-23 was associated with increased plaque % calcium-like tissue. Participants with no coronary artery disease had significantly lower phosphate levels. Phosphate was associated with higher grayscale median (GSM) in male subjects but with lower GSM in female subjects. FGF-23 was associated with increased plaque % fat in male subjects but increased plaque % calcium in female subjects. CONCLUSIONS: Phosphate was independently associated with the severity of atherosclerosis in terms of plaque burden and composition. FGF-23 was associated with plaque calcification. These findings suggest that abnormal phosphate homeostasis may play an under-recognized but potentially modifiable role in cardiovascular disease.

Circulating Gas6 is associated with reduced human carotid atherosclerotic plaque burden in high risk cardiac patients.

OBJECTIVE: Pre-clinical studies suggest that growth arrest-specific protein 6 (Gas6), a member of the vitamin K dependent family of proteins, is implicated in atherosclerosis. A role for Gas6 in stabilizing atherosclerotic plaque has been suggested. Our aim was to determine the association between Gas6 and measures of carotid artery atherosclerosis in humans undergoing elective coronary angiography. Secondary aims were to determine the association between Gas6 and sex, diabetes, and obesity. METHODS: In 204 outpatients referred for coronary angiography, EDTA plasma was collected and a focused carotid ultrasound performed. Degree of angiographic coronary artery disease was scored. Carotid intima media thickness as well as maximum plaque height, plaque area, and grayscale median were measured by vascular sonography. Gas6 was assessed by enzyme-linked immunosorbent assay. RESULTS: We found that Gas6 concentrations were lower in males and were associated with diabetes, obesity, and lower kidney function. After adjustment for age, sex, kidney function, BMI and traditional cardiac risk factors; diabetes was associated with higher levels of Gas6, whilst there was a significant inverse relationship between Gas6 and total plaque area. Gas6 was inversely associated with maximum plaque height and total plaque area in adjusted multi-variable models. CONCLUSIONS: We observed higher levels of Gas6 in participantswith adverse cardiovascular risk profiles (e.g. diabetes, obesity) yet Gas6 was independently associated with reduced plaque height and total plaque area. These findings suggest that Gas6 may play a role in human atherosclerotic plaque remodeling.