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1.
JBMR Plus ; 8(8): ziae075, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39238566

RESUMO

Diets containing inorganic phosphate additives are unbalanced with respect to calcium and these diets have been linked to the development of altered bone metabolism. Using 2 randomized cross-over studies in healthy humans, we (1) characterized the hormonal and urinary response to 2 meals with the same reported phosphorus amount (562-572 mg), where one was manufactured with inorganic phosphate additives and a comparatively lower Ca:P molar ratio (0.26 vs 0.48), and (2) assessed how acute homeostatic mechanisms adapt following 5-d exposure to recommended dietary phosphorus amount (~700 mg P/d) compared to a diet enriched with inorganic phosphate additives (~1100 mg P/d). Participants were then challenged with 500 mg of oral phosphorus in the form of inorganic phosphate after an overnight fast following each diet condition. Measurements included serum calcium, phosphate, PTH, and fibroblast growth factor 23 , vitamin D metabolites, and urine calcium and phosphate excretion. Following the meal containing inorganic phosphate additives with a low Ca:P ratio, serum phosphate was higher and more phosphate was excreted in the urine compared to the low additive meal. Although the Ca:P and calcium content was lower in the high additive meal, the same amount of calcium was excreted into the urine. Subsequently, increasing only dietary phosphate through additives resulted in lower 24-h excretion of calcium. The oral phosphate challenge promoted urinary calcium excretion, despite no consumption of calcium, which was attenuated when pre-acclimated to a high phosphate diet. These data suggest that ingestion of inorganic phosphate promotes calcium excretion, but homeostatic mechanisms may exist to reduce calcium excretion that are responsive to dietary intake of phosphate. Future studies are required to evaluate potential implication of diets enriched with inorganic phosphate additives on bone health.

2.
J Clin Endocrinol Metab ; 108(4): 909-919, 2023 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-36268820

RESUMO

CONTEXT: Dietary consumption of phosphate is increasing, and elevated serum phosphate is associated with increased cardiovascular disease (CVD) risk. Sex differences in phosphate homeostasis and response to changes in dietary phosphate intake, which are not captured by clinically measured analytes, may contribute to differences in CVD presentation and bone disease. OBJECTIVE: To assess sex differences in acute phosphate homeostasis in response to a single oral phosphate challenge. DESIGN: Cross-sectional. SETTING: General community. PARTICIPANTS: 78 participants (40-76 years) with measured glomerular filtration rate >60 mL/min/1.73 m2 and no clinically diagnosed CVD and 14 young healthy adults. MAIN OUTCOME MEASURES: To elucidate subtle alterations in phosphate homeostasis, we employ an acute challenge whereby the hormonal response, circulating mineral levels, and urinary excretion are assessed following an oral challenge of phosphate. RESULTS: Although both males and females had similar changes in circulating phosphate, calcium, and parathyroid hormone in response to the challenge, females excreted ∼1.9x more phosphate and ∼2.7x more calcium than males, despite not consuming calcium. These sex differences were recapitulated in healthy young adults. This excretion response did not correlate to age, serum phosphate, or estradiol levels. The females with greater excretion of phosphate had higher levels of bone resorption markers compared to formation markers. CONCLUSIONS: Taken together, these data identify sex differences in acute phosphate homeostasis, specifically that females may mobilize and excrete endogenous sources of calcium and phosphate in response to oral phosphate compared to males. While high levels of dietary phosphate negatively impact bone, our results suggest that females may incur more risk from these diets.


Assuntos
Cálcio , Doenças Cardiovasculares , Adulto Jovem , Feminino , Humanos , Masculino , Fosfatos , Estudos Transversais , Caracteres Sexuais , Cálcio da Dieta , Hormônio Paratireóideo , Homeostase
3.
Can J Kidney Health Dis ; 6: 2054358119856891, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31285829

RESUMO

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.

4.
J Exp Biol ; 219(Pt 5): 626-30, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26747905

RESUMO

Spreading depression (SD) is associated with large changes in extracellular ion concentrations and can be induced by impairing mechanisms of K(+) ion homeostasis. We tested activity dependence of SD in the locust model of ouabain-induced SD in the metathoracic ganglion. Wind activation of thoracic circuitry resulted in small increases of K(+) concentration that took 5-10 s to be cleared from the extracellular space. In the presence of the Na(+)/K(+)-ATPase inhibitor ouabain, wind stimulation every 30 s halved the latency to the first SD event and increased its duration. Wind stimulation was able to trigger the first event, suggesting that local activity could determine the origin of successive SD events. Perfusion with calcium-free saline blocked neural activity in the ganglion and prevented the occurrence of ouabain-induced SD. We conclude that ouabain-induced SD in the locust CNS is strongly dependent on the existing level of neural activity.


Assuntos
Locusta migratoria/fisiologia , Animais , Sistema Nervoso Central/efeitos dos fármacos , Sistema Nervoso Central/fisiologia , Espaço Extracelular/metabolismo , Homeostase , Masculino , Ouabaína/farmacologia , Potássio/metabolismo , Vento
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