Phosphate toxicity: a stealth biochemical stress factor?

Phosphate toxicity and SERCA2a dysfunction in sudden cardiac arrest

Almost half of the people who die from sudden cardiac arrest have no detectable heart disease. Among children and young adults, the cause of approximately one-third of deaths from sudden cardiac arrest remains unexplained after thorough examination. Sudden cardiac arrest and related sudden cardiac death are attributed to dysfunctional cardiac ion-channels. The present perspective paper proposes a pathophysiological mechanism by which phosphate toxicity from cellular accumulation of dysregulated inorganic phosphate interferes with normal calcium handling in the heart, leading to sudden cardiac arrest. During cardiac muscle relaxation following contraction, SERCA2a pumps actively transport calcium ions into the sarcoplasmic reticulum, powered by ATP hydrolysis that produces ADP and inorganic phosphate end products. Reviewed evidence supports the proposal that end-product inhibition of SERCA2a occurs as increasing levels of inorganic phosphate drive up phosphate toxicity and bring cardiac function to a sudden and unexpected halt. The paper concludes that end-product inhibition from ATP hydrolysis is the mediating factor in the association of sudden cardiac arrest with phosphate toxicity. However, current technology lacks the ability to directly measure this pathophysiological mechanism in active myocardium, and further research is needed to confirm phosphate toxicity as a risk factor in individuals with sudden cardiac arrest. Moreover, phosphate toxicity may be reduced through modification of dietary phosphate intake, with potential for employing low-phosphate dietary interventions to reduce the risk of sudden cardiac arrest.

Intratumoral Pi deprivation benefits chemoembolization therapy via increased accumulation of intracellular doxorubicin

It is a decade-long controversy that transarterial chemoembolization (TACE) has definite priority over transarterial embolization (TAE) in treating patients with hepatocellular carcinoma (HCC), since HCC cells are regularly resistant to chemotherapy by enhanced expression of proteins that confer drug resistance, and ABC transporters pump the intracellular drug out of the cell. We addressed this issue by modulating the chemo-environment. In an animal model, sevelamer, a polymeric phosphate binder, was introduced as an embolic agent to induce intratumoral inorganic phosphate (Pi) starvation, and trans-arterially co-delivered with doxorubicin (DOX). The new type of TACE was named as DOX-TASE. This Pi-starved environment enhanced DOX tumoral accumulation and retention, and DOX-TASE thereby induced more severe tumor necrosis than that induced by conventional TACE (C-TACE) and drug-eluting bead TACE (D-TACE) at the same dose. In vitro tests showed that Pi starvation increased the cellular accumulation of DOX in an irreversible manner and enhanced cytotoxicity and cell apoptosis by suppressing the expression of ABC transporters (P-glycoprotein (P-gp), BCRP, and MRP1) and the production of intracellular ATP. Our results are indicative of an alternative interventional therapy combining chemotherapy with embolization more effectively.

The emerging role of phosphorus in human health

Phosphorus, an essential nutrient, performs vital functions in skeletal and non-skeletal tissues and is pivotal for energy production. The last two decades of research on the physiological importance of phosphorus have provided several novel insights about its dynamic nature as a nutrient performing functions as a phosphate ion. Phosphorous also acts as a signaling molecule and induces complex physiological responses. It is recognized that phosphorus homeostasis is critical for health. The intake of phosphorus by the general population world-wide is almost double the amount required to maintain health. This increase is attributed to the incorporation of phosphate containing food additives in processed foods purchased by consumers. Research findings assessed the impact of excessive phosphorus intake on cells' and organs' responses, and highlighted the potential pathogenic consequences. Research also identified a new class of bioactive phosphates composed of polymers of phosphate molecules varying in chain length. These polymers are involved in metabolic responses including hemostasis, brain and bone health, via complex mechanism(s) with positive or negative health effects, depending on their chain length. It is amazing, that phosphorus, a simple element, is capable of exerting multiple and powerful effects. The role of phosphorus and its polymers in the renal and cardiovascular system as well as on brain health appear to be important and promising future research directions.

Stress, inflammation, depression, and dementia associated with phosphate toxicity

Depression and dementia are predicted to increase within aging global populations. Pathophysiological effects of phosphate toxicity, dysregulated amounts of accumulated phosphorus in body tissue, are under-investigated in association with stress, inflammation, depression, and dementia. A comparative analysis of concepts in cited sources from the research literature was used to synthesize novel themes exploring the disease-oriented neuroscience effects of phosphate toxicity. Phosphate toxicity is associated with activation of cellular stress response systems and inflammation. Cortisol released by the hypothalamic-pituitary-adrenal axis responds to stress and inflammation associated with phosphate toxicity and depression. In a reciprocal interaction, phosphate toxicity is capable of harming adrenal gland function, possibly leading to adrenal insufficiency and depression. Furthermore, Alzheimer's disease is associated with hyperphosphorylated tau which self-assembles into neurofibrillary tangles from excessive amounts of phosphate in the brain and central nervous system. Future research should investigate dietary phosphate modification to reduce potential pathophysiological effects of phosphate toxicity in stress, inflammation, depression, and cognitive decline which affects global populations.

Overconsumption of sugar-sweetened beverages: Why is it difficult to control?

The consumption of sugar-sweetened beverages is a known contributory factor of childhood obesity that is documented around the globe. More importantly, reducing the consumption of sugar-sweetened beverages could reduce weight gain among overweight or obese children. Although sugar is present in many natural foods, artificial sugar is added into sugar-sweetened beverages, which has little or no nutritional value. However, the calories obtained from the sugar-sweetened beverages are linked to overweight and obesity, and an increase serving sizes of sugar-sweetened beverages over the years partly contributed to the alarming rise of childhood obesity around the globe. The sugar-sweetened beverages not only contain a high amount of sugar, but also contain a high amount of phosphate, and the possibility exists for an enhancing dual adverse health effects of sugar and phosphate. Increasing health awareness and limiting marketing approaches targeted towards the younger population are essential to reduce long-term health burdens that are linked to the overconsumption of sugar-sweetened beverages.

Potential interaction of inflammatory hyperemia and hyperphosphatemia in tumorigenesis

The present article proposes that the association of inflammation with cancer is potentially mediated by the interaction of inflammatory hyperemia and hyperphosphatemia. Hyperemia increases blood flow rate and blood volume, and hyperphosphatemia is caused by elevated serum levels of dysregulated inorganic phosphate. It is hypothesized that the interaction of inflammatory hyperemia and hyperphosphatemia circulates increased amounts of inorganic phosphate to the tumor microenvironment, where increased uptake of inorganic phosphate through sodium-phosphate cotransporters is sequestered in cells. Elevated levels of intracellular phosphorus increase biosynthesis of ribosomal RNA, leading to increased protein synthesis that supports tumor growth. The present article also proposes that the interaction of inflammatory hyperemia and hyperphosphatemia may help explain a chemopreventive mechanism associated with NSAIDs.

Dysregulated Phosphate Metabolism, Periodontal Disease, and Cancer: Possible Global Health Implications

An association between periodontal disease and cancer has been established in recent studies, but no common etiology has been identified in the hopes of reducing the global burden of these non-communicable diseases. This perspective article hypothesizes that the determinant mediating the association of periodontal disease with cancer is dysregulated phosphate metabolism. Phosphate, an essential dietary micronutrient, is dysregulated in chronic kidney disease, and both cancer and periodontal disease are associated with chronic kidney disease. Reviewed evidence includes the association between phosphate toxicity and cancer development, and the association between periodontal disease and chronic kidney disease-mineral and bone disorder includes conditions such as ectopic calcification and bone resorption, which may be indirectly related to periodontal disease. Dental calculus in periodontal disease contains calcium phosphate crystals that are deposited from excess calcium and phosphate in saliva. Alveolar bone resorption may be linked systemically to release of parathyroid hormone in response to hypocalcemia induced by hyperphosphatemia. More research is needed to examine the role of dysregulated phosphate metabolism in periodontal disease.

Dietary phosphate toxicity: an emerging global health concern

Phosphate is a common ingredient in many healthy foods but, it is also present in foods containing additives and preservatives. When found in foods, phosphate is absorbed in the intestines and filtered from the blood by the kidneys. Generally, any excess is excreted in the urine. In renal pathologies, however, such as chronic kidney disease, a reduced renal ability to excrete phosphate can result in excess accumulation in the body. This accumulation can be a catalyst for widespread damage to the cellular components, bones, and cardiovascular structures. This in turn can reduce mortality. Because of an incomplete understanding of the mechanism for phosphate homeostasis, and the multiple organ systems that can modulate it, treatment strategies designed to minimize phosphate burden are limited. The Recommended Dietary Allowance (RDA) for phosphorous is around 700 mg/day for adults, but the majority of healthy adult individuals consume far more phosphate (almost double) than the RDA. Studies suggest that low-income populations are particularly at risk for dietary phosphate overload because of the higher amounts of phosphate found in inexpensive, processed foods. Education in nutrition, as well as access to inexpensive healthy food options may reduce risks for excess consumption as well as a wide-range of disorders, ranging from cardiovascular diseases to kidney diseases to tumor formation. Pre-clinical and clinical studies suggest that dietary phosphate overload has toxic and prolonged adverse health effects. Improved regulations for reporting of phosphate concentrations on food labels are necessary so that people can make more informed choices about their diets and phosphate consumption. This is especially the case given the lack of treatments available to mitigate the short and long-term effects of dietary phosphate overload-related toxicity. Phosphate toxicity is quickly becoming a global health concern. Without measures in place to reduce dietary phosphate intake, the conditions associated with phosphate toxicity will likely to cause untold damage to the wellbeing of individuals around the world.

Can adverse effects of excessive vitamin D supplementation occur without developing hypervitaminosis D?

Vitamin D is a fat-soluble hormone that has endocrine, paracrine and autocrine functions. Consumption of vitamin D-supplemented food & drugs have increased significantly in the last couple of decades due to campaign and awareness programs. Despite such wide use of artificial vitamin D supplements, serum level of 25 hydroxyvitamin D does not always reflect the amount of uptake. In contrast to the safe sunlight exposure, prolonged and disproportionate consumption of vitamin D supplements may lead to vitamin D intoxication, even without developing hypervitaminosis D. One of the reasons why vitamin D supplementation is believed to be safe is, it rarely raises serum vitamin D levels to the toxic range even after repeated intravenous ingestion of extremely high doses of synthetic vitamin D analogs. However, prolonged consumption of vitamin D supplementation may induce hypercalcemia, hypercalciuria and hyperphosphatemia, which are considered to be the initial signs of vitamin D intoxication. It is likely that calcium and phosphorus dysregulation, induced by exogenous vitamin D supplementation, may lead to tissue and organ damages, even without developing hypervitaminosis D. It is needed to be emphasized that, because of tight homeostatic control of calcium and phosphorus, when hypercalcemia and/or hyperphosphatemia is apparent following vitamin D supplementation, the process of tissue and/or organ damage might already have been started.

Phosphate toxicity and tumorigenesis

In this article, we briefly summarized evidence that cellular phosphate burden from phosphate toxicity is a pathophysiological determinant of cancer cell growth. Tumor cells express more phosphate cotransporters and store more inorganic phosphate than normal cells, and dysregulated phosphate homeostasis is associated with the genesis of various human tumors. High dietary phosphate consumption causes the growth of lung and skin tumors in experimental animal models. Additional studies show that excessive phosphate burden induces growth-promoting cell signaling, stimulates neovascularization, and is associated with chromosome instability and metastasis. Studies have also shown phosphate is a mitogenic factor that affects various tumor cell growth. Among epidemiological evidence linking phosphate and tumor formation, the Health Professionals Follow-Up Study found that high dietary phosphate levels were independently associated with lethal and high-grade prostate cancer. Further research is needed to determine how excessive dietary phosphate consumption influences initiation and promotion of tumorigenesis, and to elucidate prognostic benefits of reducing phosphate burden to decrease tumor cell growth and delay metastatic progression. The results of such studies could provide the basis for therapeutic modulation of phosphate metabolism for improved patient outcome.

Effects of vitamin D status on oral health

Normal humans of all ages have the innate ability to produce vitamin D following sunlight exposure. Inadequate vitamin D status has shown to be associated with a wide variety of diseases, including oral health disorders. Insufficient sunlight exposure may accelerate some of these diseases, possibly due to impaired vitamin D synthesis. The beneficial effects of vitamin D on oral health are not only limited to the direct effects on the tooth mineralization, but are also exerted through the anti-inflammatory functions and the ability to stimulate the production of anti-microbial peptides. In this article, we will briefly discuss the genesis of various oral diseases due to inadequate vitamin D level in the body and elucidate the potential benefits of safe sunlight exposure for the maintenance of oral and general health.

Sunlight exposure: Do health benefits outweigh harm?

Vitamin D is a fat-soluble vitamin whose levels within the body are elevated following sunlight exposure. Numerous studies have shown that sunlight exposure can provide protection to a wide variety of diseases, ranging from different types of tumors to hypertension to type 1 diabetes to multiple sclerosis. Moreover, studies have shown that avoiding sunlight may influence the initiation and progression of some of these diseases. Avoidance of sunlight, coupled with the inclination towards consuming supplements, is becoming the primary choice to obtain vitamin D. The purpose of this article is to present evidences from published literature, to show that the expected benefits of vitamin D supplements are minimized by the potential risk of cardiovascular events and beyond. Since hypovitaminosis D status usually reflects reduced sunlight exposure, the obvious primary replacement should be safe sunlight exposure, and not exogenous supplements.

Vitamin D status among the juvenile population: A retrospective study

Vitamin D deficiency is a clinical problem and recently we have shown that 82.5% of our entire study cohort had inadequate serum 25(OH)D levels. In this study, we analysed serum 25(OH)D levels of juvenile patients admitted to the Burjeel Hospital of VPS Health care in Abu Dhabi, United Arab Emirates (UAE) from October 2012 to September 2014. Out of a total of 7883 juvenile patients considered in this study, almost 58.1% of females and 43.3% of males in the age group of 1-18 years were found to have low serum 25(OH)D levels (<50nmol/L). According to the coefficient of variation, females had significantly higher variability among juveniles (63.8%) than males (49.9%). Among the juveniles group of patients, age appears to be an important determining factor for defining vitamin D deficiency.The risk of deficiency (<30nmol/L) was found to be present in 31.4% of patients in the age group of 10-12 years, followed by 50.4% of patients in the age group of 13-15 years and 52.9% of patients in the age group of 16-18 years. The analysed age groups of females were found to have lower levels of 25(OH)D than males. It is important and perhaps alarming to note that such high rate of vitamin D deficiency is present in the juvenile age.

Dietary phosphorus burden increases cariogenesis independent of vitamin D uptake

An association between excessive sugar consumption and dental decay, particularly in children, has been well-established. In this study we have analyzed whether consumption of phosphorus, an important ingredient of sugary drinks, has any association with the evolvement of dental decay. Food consumption, gingival redness and dental decay were evaluated in a total of 8,317 children with the mean age of 9.99+0.68 years with a strong gender bias (p<0.0005); boys being more affected than girls. Our results showed a significant association (p=0.044) between dental decay and calorie-adjusted sugar intake. Presence of gingival inflammation also correlated (p=0.008) with the formation of dental decay. In addition, decayed teeth were positively associated with increased salivary levels of adiponectin (p=0.0002) and matrix degrading MMP-9 (p=0.015), while negatively associated with salivary levels of the vascular endothelial growth factor (VEGF; p=0.008). More importantly, we found a statistically significant correlation (p=0.0008) between calorie-adjusted dietary phosphorus intake and occurrence of dental decay. Our analyzed results also showed a significantly high percentage of dental decay in children who consumed a diet, low in sugar but high in phosphorus (6.58%, n=661), compared to those who consumed a low sugar and low phosphorus containing diet (5.02%, n=413). Finally, we did not find any significant association between vitamin D uptake and the genesis of dental decay. From these results, we concluded that both high sugar and high phosphate consumption can influence evolvement of dental decay, and that, a healthier diet could be achieved by reducing consumption of dental cariogenic dietary factors, sugar and phosphate.