【摘要】：1.研究背景 世界衛(wèi)生組織(wHO)認(rèn)為,在發(fā)展中國(guó)家,超過(guò)2億人存在鐵缺乏。而2002年中國(guó)居民營(yíng)養(yǎng)與健康狀況調(diào)查顯示,全國(guó)平均貧血率為20.1%。由此可見(jiàn),鐵缺乏及其所導(dǎo)致的貧血,是世界范圍內(nèi)普遍存在的公共衛(wèi)生問(wèn)題。 生物利用率是正常身體功能所利用的礦物質(zhì)在食品總礦物質(zhì)中所占的比例,所以說(shuō),生物利用率是研究礦物質(zhì)吸收的關(guān)鍵。影響鐵生物利用率的因素包括鐵的化學(xué)形態(tài)、人體的生理因素、鐵轉(zhuǎn)運(yùn)吸收機(jī)制以及膳食因子。食物環(huán)境對(duì)鐵生物利用率的影響主要是由于不同的食物環(huán)境和人體環(huán)境中鐵的化學(xué)形態(tài)不同,諸如離子化程度、化合價(jià)以及與食物中其它成分是否能形成絡(luò)合物及絡(luò)合物的溶解性與穩(wěn)定性。食物中存在的膳食因素有的明顯具有還原性和絡(luò)合性,會(huì)影響鐵的存在形式,進(jìn)而可能會(huì)影響影響鐵的吸收率 本部分研究首先探討維生素C、半胱氨酸等具有還原性的膳食因素對(duì)鐵價(jià)念的影響以及相應(yīng)條件下Caco-2細(xì)胞的鐵吸收情況,同時(shí)研究賴氨酸、組氨酸、半胱氨酸、植酸鹽、酒石酸等具有絡(luò)合性的膳食因素對(duì)鐵的絡(luò)合狀態(tài)的影響。 2.研究方法 首先,本研究將改良并確立一種可行的鐵價(jià)態(tài)分析方法。其次,在模擬生理?xiàng)l件下,利用之前確立的方法和參考方法,分析食物組分對(duì)鐵的價(jià)態(tài)和絡(luò)合狀態(tài)的影響情況。最后,利用Caco-2細(xì)胞模型分析不同膳食因素對(duì)Fe(Ⅱ)或Fe(Ⅲ)吸收率的影響,并且通過(guò)劑量反應(yīng)關(guān)系和聯(lián)系膳食因素的化學(xué)結(jié)構(gòu),探討膳食因素影響鐵吸收的原因和機(jī)制。 2.1基于鄰二氮菲的鐵價(jià)態(tài)分析方法的改良 (1)吸收波長(zhǎng)的確定。 (2)設(shè)立避光對(duì)照組,分別顯色測(cè)定吸光度。 (3)比較氯化銨、EDTA、NTA三種金屬掩蔽劑是否對(duì)Fe(Ⅱ)的測(cè)定有干擾。 (4)比較NTA掩蔽劑和顯色劑直接分光光度法測(cè)量Fe(Ⅱ)的準(zhǔn)確度。 (5)比較還原法和雙波長(zhǎng)分光光度法測(cè)定總鐵的準(zhǔn)確度。 2.2體外模擬生理?xiàng)l件下探討膳食因子對(duì)鐵存在形態(tài)的影響 (1)體外模擬人體生理?xiàng)l件。 (2)測(cè)定膳食因子對(duì)鐵的螯合能力。 (3)測(cè)定膳食因子對(duì)鐵的還原能力。 2.3食品組分對(duì)鐵的生物利用率的影響及作用機(jī)制的研究 (1)建立Caco-2細(xì)胞模型并進(jìn)行吸收實(shí)驗(yàn)。 (2)采用酸法消化結(jié)合ICP-AES測(cè)定鐵含量。 3.研究結(jié)果 3.1基于鄰二氮菲的鐵價(jià)態(tài)分析方法的改良 采用掩蔽劑可以很好的解決光化學(xué)反應(yīng)問(wèn)題,比較適合的Fe(Ⅲ)掩蔽劑為NTA。顯色劑直接分光法適用范圍較窄,當(dāng)總鐵中的Fe(Ⅲ)含量≥52%時(shí),方法相對(duì)誤差較大,變得不穩(wěn)定,而總鐵中的Fe(Ⅲ)含量≤90%時(shí),NTA掩蔽法即可使用。應(yīng)用兩種控制圖及95%置信區(qū)間圖證明,還原法更準(zhǔn)確可靠。 3.2體外模擬生理?xiàng)l件下探討膳食因子對(duì)鐵存在形態(tài)的影響 (1)在體外模擬生理?xiàng)l件下,隨著抗壞血酸／半胱氨酸與Fe(Ⅲ)的摩爾比增加,其還原率不斷增加。 (2)在相同摩爾比下,不同有機(jī)酸對(duì)Fe(Ⅱ)的絡(luò)合能力不同；在同一種有機(jī)酸不同摩爾比下,隨著草酸/植酸與Fe(Ⅱ)摩爾比的增加,其對(duì)Fe(Ⅱ)的絡(luò)合率升高。 (3)在相同摩爾比下,不同氨基酸對(duì)Fe(Ⅱ)的絡(luò)合能力不同；在同一種氨基酸不同摩爾比下,隨著半胱氨酸/甲硫氨酸/賴氨酸/亮氨酸/色氨酸/纈氨酸/異亮氨酸/組氨酸與Fe(Ⅱ)摩爾比的增加,其對(duì)Fe(Ⅱ)的絡(luò)合率升高。 3.3食品組分對(duì)鐵的生物利用率的影響及作用機(jī)制的研究 (1)Fe(Ⅱ)對(duì)照組吸收率明顯高于Fe(Ⅲ)對(duì)照組吸收率,這證明了Fe(Ⅱ)通過(guò)DMT1及NRAMP2進(jìn)入腸上皮細(xì)胞機(jī)制的存在。同時(shí),除1：1摩爾比組外,還原率和吸收率高度正相關(guān),這說(shuō)明抗壞血酸的還原性在促進(jìn)鐵吸收過(guò)程中作用很大。 (2)酒石酸對(duì)Fe(Ⅱ)的吸收存在促進(jìn)作用。酒石酸對(duì)Fe(Ⅱ)吸收的影響明顯和絡(luò)合率呈正相關(guān)。植酸對(duì)鐵吸收的最大抑制作用發(fā)生在兩者摩爾濃度比為10：1,超過(guò)該值后其抑制作用無(wú)顯著增加。草酸對(duì)Fe(Ⅱ)吸收的影響復(fù)雜：(1)在Fe(Ⅱ)/草酸的摩爾比≥1：5時(shí),草酸表現(xiàn)為抑制作用；(2)在Fe(Ⅱ)/草酸的摩爾比等于1：10時(shí),表現(xiàn)為促進(jìn)作用；(3)在Fe(Ⅱ)／草酸的摩爾比≤1：50時(shí),草酸作用不明顯。 (3)半胱氨酸對(duì)Fe(Ⅲ)和Fe(Ⅱ)的吸收具有明顯的促進(jìn)作用,Fe(Ⅲ)的還原率和吸收率存在很強(qiáng)的正相關(guān),其對(duì)Fe(Ⅲ)還原作用是影響其吸收的關(guān)鍵因素。 (4)本次研究將氨基酸分為三組,并且結(jié)合這些種類氨基酸供／吸電子效應(yīng)及相應(yīng)化學(xué)結(jié)構(gòu)分析了其影響機(jī)制。
[Abstract]:1. research background
The World Health Organization (WHO) believes that iron deficiency exists in more than 200 million people in developing countries. The 2002 National Survey on Nutrition and Health Status of Chinese Residents shows that the national average anemia rate is 20.1%. Thus, iron deficiency and anemia caused by iron deficiency are widespread public health problems worldwide.
Bioavailability is the proportion of minerals used by normal body function in total minerals of food, so bioavailability is the key to the study of mineral absorption. Factors affecting iron bioavailability include chemical forms of iron, physiological factors of the human body, iron transport and absorption mechanisms, and dietary factors. The effects of food and human environments on the availability of iron are mainly due to the different chemical forms of iron, such as ionization degree, valence, solubility and stability of complexes and complexes with other components in food. The existing form of ring iron may affect the absorption rate of iron.
In this part, the effects of reducing dietary factors such as vitamin C and cysteine on iron valence and iron uptake by Caco-2 cells under the corresponding conditions were investigated. The effects of complex dietary factors such as lysine, histidine, cysteine, phytate and tartaric acid on iron complexation were also studied.
2. research methods
Firstly, this study will improve and establish a feasible method of iron valence analysis. Secondly, under simulated physiological conditions, the effects of food components on the valence and complexation of iron are analyzed by using the previously established methods and reference methods. Finally, Caco-2 cell model is used to analyze the absorption of Fe (II) or Fe (III) by different dietary factors. The effect of dietary factors on iron absorption was investigated by dose-response relationship and chemical structure of dietary factors.
2.1 an improved method for analyzing iron valence state based on adjacent two phenanthrene
(1) determination of absorption wavelength.
(2) set up a light avoiding control group, and measure the absorbance separately.
(3) compare whether the three metal masking agents of ammonium chloride, EDTA and NTA interfere with the determination of Fe (II).
(4) to compare the accuracy of Fe (II) measurement with NTA masking agent and chromogenic reagent directly spectrophotometric method.
(5) to compare the accuracy of the reduction method and the dual wavelength spectrophotometry for the determination of total iron.
2.2. Effects of dietary factors on iron speciation in vitro under simulated physiological conditions
(1) simulate human physiological conditions in vitro.
(2) determine the chelating ability of dietary factors to iron.
(3) to determine the reduction ability of dietary factors to iron.
2.3 effect of food components on iron bioavailability and its mechanism
(1) establish Caco-2 cell model and conduct absorption experiments.
(2) determination of iron content by acid digestion combined with ICP-AES.
3. research findings
3.1 an improved method for analyzing iron valence state based on adjacent two phenanthrene
Using masking agent can solve the problem of photochemical reaction very well. The suitable Fe(III) masking agent is NTA. The application range of direct Spectrophotometry with color reagent is narrow. When the content of Fe(III) in total iron is more than 52%, the relative error of the method is large and becomes unstable. When the content of Fe(III) in total iron is less than 90%, NTA masking method can be used. The graph and the 95% confidence interval diagram show that the reduction method is more accurate and reliable.
3.2. Effects of dietary factors on iron speciation in vitro under simulated physiological conditions
(1) Under simulated physiological conditions in vitro, the reduction rate of ascorbic acid/cysteine increased with the increase of molar ratio of ascorbic acid/cysteine to Fe(III).
(2) At the same molar ratio, the complexing ability of different organic acids to Fe(II) is different, and the complexing rate of oxalic acid/phytic acid to Fe(II) increases with the increase of the molar ratio of oxalic acid/phytic acid to Fe(II).
(3) At the same molar ratio, the complexation ability of different amino acids to Fe(II) is different; at the same molar ratio of amino acids, the complexation rate of Fe(II) increases with the increase of the molar ratio of cysteine/methionine/lysine/leucine/tryptophan/valine/isoleucine/histidine to Fe(II).
3.3 effect of food components on iron bioavailability and its mechanism
(1) The absorption rate of Fe (II) in the control group was significantly higher than that in the Fe (III) control group, which proved the existence of the mechanism of Fe (II) entering intestinal epithelial cells through DMT1 and NRAMP2. In addition, there was a highly positive correlation between the reduction rate and the absorption rate except for the 1:1 molar ratio group, indicating that the reducibility of ascorbic acid played an important role in promoting iron absorption.
(2) Tartaric acid can promote the absorption of Fe (II). The effect of tartaric acid on the absorption of Fe (II) is obviously positively correlated with the complexation rate. The maximum inhibitory effect of phytic acid on the absorption of Fe (II) occurs at the molar concentration ratio of 10:1. The inhibitory effect of phytic acid on the absorption of Fe (II) does not increase significantly when the molar concentration ratio exceeds this value. When the molar ratio of acid is more than 1:5, oxalic acid shows inhibition; (2) when the molar ratio of Fe (II) / oxalic acid is equal to 1:10, oxalic acid shows promotion; (3) when the molar ratio of Fe (II) / oxalic acid is less than 1:50, oxalic acid has no obvious effect.
(3) Cysteine can obviously promote the absorption of Fe (III) and Fe (II). There is a strong positive correlation between the reduction rate and the absorption rate of Fe (III). The reduction effect of cysteine on Fe (III) is the key factor affecting its absorption.
(4) In this study, amino acids were divided into three groups, and the mechanism was analyzed by combining the electron-donating and electron-absorbing effects of these amino acids and their corresponding chemical structures.
【學(xué)位授予單位】：中國(guó)疾病預(yù)防控制中心
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：R151.2

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