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【medical-news】研究发现高摄入含有磷酸盐食品添
"Our results demonstrated that high phosphate intake strongly stimulates lung cancer development in lung cancer model mice," said lead author Myung-Haing Cho, DVM, PhD, from the College of Veterinary Medicine and Nano Systems Institute-National Core Research Center, at Seoul National University, in Korea. "These results suggest that careful regulation of dietary phosphate in lung cancer patients may be critical for lung cancer treatment as well as prevention."
"This is an experimental study and the implications for humans have to be in context," commented John Heffner, MD, past president of the American Thoracic Society. "But at the same time, this is a high-impact study. They are showing a biologic rationale as to the role of phosphate in fundamental cell changes. This is a valid laboratory model for cancer."
This is a high-impact study.
Inorganic phosphates play a critical role in diverse cellular functions and are essential to all living organisms. However, dietary intake of phosphates has greatly increased, as phosphate is now added to a large number of processed foods such as cheese, sausage, beverages, and bakery products. The study results suggest that a high intake of phosphates promotes tumorigenesis in lung cancer and that it may also contribute to the development of lung cancer in individuals who are predisposed to the disease.
Phosphate is added to a large variety of processed food products because of its ability to increase the quality of the food via improved water retention and texture. The authors note that surveys conducted in several countries indicate that phosphate intake has steadily risen, as the number of foods containing phosphate has increased by about 17% in the decade leading up to 1993. The data also suggest that the use of phosphate as a food additive may continue to increase.
There have been some concerns about the high phosphate content of processed food, but this study introduces new evidence, explained Dr. Heffner, who is also chair of medical education at the Providence Portland Medical Center, in Oregon. "I think we are going to see more studies and more case-control studies."
"The results do suggest that lung cancer patients undergoing therapy and those at a high risk for lung cancer might be cautious about maintaining a normal daily consumption of phosphate," said Dr. Heffner. "They might want to be more cautious about consuming processed foods."
He also pointed out that this model could possibly be extrapolated to other cancers. "They chose to study a model that addressed lung cancer, but it is conceivable that high phosphate intake could affect other types of tumors. This area of research does need to be explored."
Higher Intake Associated with Tumorigenesis
Research indicates that the Akt pathway plays an important role in lung tumorigenesis and that approximately 90% of non–small-cell lung cancers are associated with constitutive activation of the phosphatidylinositol 39-kinase (PI3K)/Akt pathway. Previous research by Dr. Cho and colleagues showed that a high dietary intake of phosphate might activate the Akt pathway in mouse lungs, and in vitro studies indicate that phosphate appears to be a stimulant that is capable of either increasing or decreasing the expression of a number of pivotal genes, such as those involved in the regulation of transcription, signal transduction, and cell cycle.
In the current study, the researchers sought to clarify the potential effects of high dietary intake of phosphate on lung cancer development, using K-rasLA1 lung cancer model mice and male urethane-induced lung cancer model mice. The mice were fed a diet containing 0.5% phosphate, which is considered a normal intake, and a diet containing 1.0% phosphate for 4 weeks. The development of lung cancer was evaluated by diverse methods.
"Although the 0.5% is defined as close to 'normal,' the average diet in most countries is closer to the 1.0% diet and may actually exceed it," Dr. Cho told Medscape Oncology. "Therefore, the 0.5% is actually a reduced phosphate diet by today's scale. Also, this diet is easily achievable in humans."
In this study, the high-phosphate diet contains 1% phosphorus, which is about 40 mg/day of daily intake, he added. "Such daily intake is about 1.4 to 1.6 times that of dietary reference intakes. Therefore, concentration of phosphate used in the current study is not a very high concentration but rather a concentration that seems to be over the normal intake level."
Their results showed that a higher dietary intake of phosphates strongly activated Akt signaling and increased lung tumorigenesis. High phosphate intake altered Akt signaling as well as cap-dependent protein translation and cell cycle, they note. In addition, it significantly stimulated cell proliferation in the lungs of K-rasLA1 mice.
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作者:admin@医学,生命科学 2011-08-05 17:13
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