维生素A缺乏与免疫功能障碍

本文综述了维生素Ａ缺乏在器官、细胞、分子、基因水平上对免疫功能的影响，并讨论了其引起免疫功能障碍的可能机制。     

维生素A缺乏对儿童免疫功能的影响

本实验以2～7岁幼儿园儿童为研究对象进行膳食调查、体格检查及血液学分析。排除营养不良、近期感染等因素的影响。由于未发现维生素A(VA)缺乏体征,根据血清VA水平筛选出VA缺乏或不足(VA<0.0070mmol/L为缺乏,<0.011mmol/L为不足)和正常对照儿童(VA>0.011mmol/L)。于补充VA前后,检测免疫学指标。结果表明:VA缺乏对儿童IgG、IgA、IgM及PHA皮试等无明显影响;而对S-IgA、C_3,溶菌酶及PHA淋巴细胞转化,缺乏组和对照组相比,差异有显著性;经过补充VA三个月后,上述免疫指标均能恢复。由此表明:即便是VA亚临床缺乏,对免疫功能的影响亦是多方面的,经过短期改善VA摄入。低下的免疫功能是可逆转的。     

维生素A对免疫功能的影响

维生素A(VitA)对维持人体的许多正常生理功能及生物化学反应均有作用。它与视觉的关系以及在维持正常上皮细胞生长、分化等方面的作用人们已有较多的认识。近年来发现VitA与机体免疫功能有关,它能抑制肿瘤的发生,提高机体的抗感染能力。本文拟对VitA与免疫功能的关系作一综述。     

维生素A营养状况对青年免疫功能的影响及补充效果观察

本文筛选血红蛋白、血清白蛋白及维生素Ｅ在正常范围的健康青年７１名，测定血清维生素Ａ含量及６项免疫学指标。结果显示，血清维生素Ａ平均含量为１．３６±０．４３μｍｏｌ／Ｌ。与各项免疫指标的相关分析，维生素Ａ与外周血Ｔ淋巴细胞百分数和淋巴细胞转化率间呈显著正相关（ｒ＝０．２３６６，Ｐ＜０．０５，ｒ＝０．３０８６，Ｐ＜０．０１），与其它免疫指标未见显著相关性。维生素Ａ含量较低人群的外周血Ｔ淋巴细胞百分数及淋巴细胞转化率明显低于维生素Ａ含量正常人群（Ｐ＜０．０５），于补充维生素Ａ后显著升高（Ｐ＜０．０１）。血清ＩｇＧ、ＩｇＡ、ＩｇＭ含量在两组人群间及补充前后无显著性差别。研究结果表明，维生素Ａ对维持和增强人体细胞免疫功能具有一定作用，对体液免疫功能未见显著影响。     

补充维生素A和维生素C对营养缺乏所致免疫功能低下的影响

为观察补充维生素Ａ和维生素Ｃ对营养缺乏所致免疫功能低下的影响，以大鼠为动物模型，从孕１６天至生后第４５天进行限食喂养，第３６至第４５天时补充ＶＡ或ＶＣ。结果表明：营养缺乏的大鼠胸腺萎缩，脾淋巴细胞ＩｇＭ－抗体形成细胞的数目减少，对ＣｏｎＡ及ＬＰＳ刺激后的增殖反应降低；补充ＶＡ可明显增加胸腺的重量，脾淋巴细胞的增殖反应及抗体生成，而补充ＶＣ效果不明显。提示补充ＶＡ可增强机体的免疫功能，对防治感染具有重要意义     

维生素A对脐血淋巴细胞免疫功能的作用

【目的】　观察孕后期补充维生素A对脐血淋巴细胞免疫功能的作用。　【方法】　采用社区干预实验 ,选择 71例孕后期健康孕妇 ,分为两组。一组为干预组 (3 3例 ) ,孕妇于孕第 7、8个月分别口服 10万单位维生素A胶囊 ;一组为对照组 (3 8例 )。收集所有孕妇分娩时的脐血 ,立即分离脐血淋巴细胞 ,分两组进行培养 ,对照组加上刺激物SAC ,干预组加SAC与RA共同刺激 ,培养满 7天收集细胞上清液 ,并分析上清中IgM水平。　【结果】　本地区孕妇维生素A膳食摄入低于 80 %RDA。两组血清维生素A水平一致。经干预后 ,两组脐血维生素A水平差异无显著性 ;脐血与母血清维生素A比较显示脐血维生素A水平明显低于母血 ,两者有显著相关性。体外试验结果显示 ,生理浓度 (1x10 6M )的视黄酸 (RA)可以提高脐血淋巴细胞产生抗体IgM的能力 ,平均提高 0 .8倍 ,但是干预组与对照组比较 ,此上升幅度差异无显著性。　【结论】　体外试验证实RA(1x10 6M )可以提高脐血淋巴细胞IgM的生成水平。但孕后期补充维生素A对提高脐血维生素A水平及脐血淋巴细胞IgM的生成能力无明显作用。因此 ,维生素A在胎盘的转运机制及孕妇维生素A干预的方法还有待进一步研究。     

维生素A对大鼠免疫功能的影响

本实验在喂大鼠以维生素A缺乏的基本饲料的基础上,通过补充两倍于大鼠正常生理需要量的维生素A(400IU/100g基本饲料),研究了维生素A对机体免疫功能的影响,同时观察在这两种不同的维生素A营养状况下农药西维因的毒性作用。结果表明,补充维生素A可以提高血清总补体活性,降低血清溶菌酶含量,促进机体产生特异性的溶血素抗体;在维生素A营养缺乏的状态下,农药西维因可抑制特异性溶血素抗体的产生,而在维生素A营养充裕时,这种作用则消失。     

维生素A对免疫功能的影响

通过动物实验和临床观察表明，维生素Ａ对免疫功能起着非常重要的作用，如对免疫器官胸腺及淋巴脾脏的影响，对细胞免疫、血液免疫的影响等，并指出了有关维生素Ａ的研究方向和临床意义。     

维生素A对铁代谢和免疫功能的影响

维生素Ａ (ＶｉｔＡ)是较早被认识的维生素 ,对其维持视觉、控制细胞分化、维持上皮完整性、促进生长发育等功能已有所阐述。由于近年对它在调节机体铁营养状况、改善贫血、促进免疫功能、增强抗感染力方面的新发现 ,再一次提出对ＶｉｔＡ重新认识的新探索。现就ＶｉｔＡ对铁代谢、促进免疫的调节作用综述如下。维生素Ａ与贫血及铁代谢的关系1　动物实验　Ｆｉｎｄｌａｙ曾报告ＶｉｔＡ缺乏的大鼠骨髓出现胶质变性的斑点 ,如动物能长期存活 ,造血组织最后几乎全部被纤维基质代替。进一步的动物实验未能证实上述的骨髓改变 ,仅观察到骨髓的红…     

维生素A对免疫功能的影响

通过动物实验和临床观察表明,维生素A对免疫功能起着非常重要的作用．如对免疫器官胸腺及淋巴脾脏的影响,对细胞免疫、血液免疫的影响等,并指出了有关维生素A的研究方向和临床意义。     

三种维生素A干预方法对小儿抗感染免疫的作用

目的通过3种形式维生素A干预试验,观察小儿血清维生素A水平的变化及感染性疾病发生的情况。方法149名观察对象被随机分为4组:孕后期干预组:孕7、8个月分别给予孕母10万IU的维生素A;哺乳期干预组:产后1周内给予母亲20万IU的维生素A;小儿干预组:出生后4、5个月分别给予小儿10万IU的维生素A;对照组:未给予母亲或小儿任何干预。所有对象均随访至出生后1年,观察呼吸道与消化道感染性疾病发病情况。结果孕妇膳食维生素A摄入不足(总平均<80%RDA),所生小儿中有46%3个月时血清维生素A浓度低于正常范围(<1.05μmol/L)。小儿干预组小儿血清维生素A水平明显增高,生后3个月～1岁增长1.0倍;孕后期干预组与哺乳期干预组小儿血清维生素A无显著变化。尽管维生素A干预对腹泻、总呼吸道感染无明显保护作用,但小儿干预组小儿出生后1年内下呼吸道感染的年人均发病率(2%)明显低于对照组。结论维生素A干预,尤其是对小儿直接干预的方法可以直接改善小儿血清维生素A水平,并能降低其下呼吸道感染的发病率。     

学龄前儿童维生素A营养状况与干预效果观察

目的通过调查北京近郊农村学龄前儿童维生素A摄入与血清维生素A水平,为评价和改善我国学龄前儿童维生素A营养状况提供依据.方法对北京近郊农村272名3～7岁儿童采用膳食记录法进行膳食调查,采用高效液相色谱法检测血清维生素A含量,对其中血清维生素A＜0.73μmol·L-1的30名儿童给予口服维生素A胶丸(每丸1.25万IU)每周2次,每次1丸,连续6周,同时对家长进行营养知识教育,干预结束后重复测定血清维生素A含量.结果受检儿童每日维生素A平均摄入量为384.3±227.0μgRE,仅占RNA的58.2%.血清VA含量平均为1.12±0.06μmol·L-1,其中血清维生素A＜1.05μmol·L-1占受检儿童的44.08%,并有6.12%受检儿童血清维生素A＜0.70μmol·L-1,血清维生素A正常者仅占55.92%.对血清维生素A＜0.73μmol·L-1的30名儿童给予VA干预后,血清VA提高至1.47μmol·L-1.结论在经济状况有了一定改善之后,学龄前儿童仍然存在着维生素A摄入不足,部分儿童血清维生素A水平较低,应予以重视和改善.     

营养缺乏及补充维生素A对大鼠胸腺凋亡的影响

以大鼠为动物模型观察限食及补充维生素Ａ（ ＶＡ） 对大鼠胸腺细胞凋亡的影响。结果：限食５０ ％ 的大鼠胸腺的重量明显降低,并出现胸腺的囊性变等病理改变,补充维生素Ａ 后有明显好转。应用原位末端标记技术（ＴＵＮＥＬ） 研究表明,限食组大鼠胸腺凋亡的细胞数为２７ ％ ,补充ＶＡ 后降低为１５－３ ％ ,但仍较正常对照组高（Ｐ＜ ０－０１） 。结果表明ＶＡ 可能是通过促进胸腺细胞ｂｃｌ２ｍ ＲＮＡ 的表达而抑制凋亡。     

维生素D和钙对2型糖尿病的预防作用

越来越多的证据表明维生素D和钙在2型糖尿病的发病过程中发挥重要作用；联合补充维生素D和钙可预防2型糖尿病的发生，且对2型糖尿病高危人群如糖耐量异常者的作用尤为明显。本文综述了维生素D和钙的营养状况与2型糖尿病之间的关系、补充维生素D和钙对糖代谢的影响以及预防作用的可能机制。     

微量元素和人体免疫功能

微量元素对正常免疫功能的维持具有重要作用。反复感染时不仅有免疫功能受损，而且伴有多种微量元素缺乏或失衡，临床上及时补充多种维生素、微量元素制剂，能改善免疫功能，防治反复感染。     

Complex Effects of Vitamin E and Vitamin C Supplementation on in Vitro Neonatal Mononuclear Cell Responses to Allergens

Low maternal dietary vitamin E (but not vitamin C) intake during pregnancy has been associated with increased in vitro cord blood mononuclear cell (CBMC) proliferative responses, childhood wheezing and asthma. We investigated whether these associations reflect direct effects of vitamin E by investigating the effects of supplementing CBMC cultures with physiological concentrations of vitamin E. CBMC from seventy neonates were cultured supplemented with either nothing, α-tocopherol or ascorbic acid. Proliferative, IFN-γ, IL-4, IL-10 and TGF-β responses were measured. In general, vitamin E supplementation was associated with a trend for reduced proliferative responses after stimulation with antigens and house dust mite, and with increased proliferation after stimulation with timothy grass allergen. There was a trend for CBMC cultures to exhibit decreased secretion of IFN-γ, IL-10 and IL-4. Supplementation with vitamin C had no effect on CBMC proliferation, but increased IFN-γ and IL-4 production, and decreased IL-10 production. In conclusion, in vitro vitamin E and C supplementation of CBMC modifies neonatal immune function, but not in a manner predicted by observational epidemiological studies. The observed associations between vitamin E and childhood respiratory disease are complex, and the nature and form of nutritional intervention need to be carefully considered before inclusion in trials.     

维生素A及维生素C对肺巨噬细胞产生活性氧及细胞因子的影响

目的 为观察维生素 A(VA)及维生素 C(VC)对肺巨噬细胞(肺 Mφ)功能的影响.方法 以大鼠为动物模型观察VA及VC对大鼠肺Mφ产生自由基(Q_2~-,H_2O_2)及细胞因子(IL-1,TNF-α)的影响.结果 补充 VA及 VC均明显增加肺Mφ的吞噬功能及O_2~-、H_2O_2 产生(P<0.01);补充 VA可明显增加细胞因子(IL-1,TNF-α)的产生(P<0.05),而补充VC效果不明显.结论 适当补充VA可活化肺Mφ,对防治呼吸道感染有重要意义.     

The Influence of Vitamin A Supplementation on Iron Status

Vitamin A (VA) and iron deficiencies are important nutritional problems, affecting particularly preschool children, as well as pregnant and lactating women. A PubMed (National Library of Medicine, National Institutes of Health, Bethesda, MD, USA) literature review was carried out to search for clinical trials published from 1992 to 2013 that assessed the influence of vitamin A supplementation on iron status. Simultaneous use of iron and vitamin A supplements seemed to be more effective to prevent iron deficiency anemia than the use of these micronutrients alone. Some studies did not include a placebo group and only a few of them assessed vitamin A status of the individuals at baseline. Moreover, the studies did not consider any inflammatory marker and a reasonable number of iron parameters. Another important limitation was the lack of assessment of hemoglobin variants, especially in regions with a high prevalence of anemia. Assessment of hemoglobin variants, inflammatory markers and anemia of chronic inflammation would be important to the studies investigated. Studies involving different populations are necessary to elucidate the interaction between the two micronutrients, especially regarding iron absorption and modulation of erythropoiesis.     

Effects on Serum Inflammatory Cytokines of Cholecalciferol Supplementation in Healthy Subjects with Vitamin D Deficiency

The effects of different cholecalciferol supplementation regimens on serum inflammatory cytokines in healthy subjects with vitamin D deficiency are still lacking. This is a single-center, open-label, randomized, parallel group study involving healthy subjects deficient in vitamin D (baseline 25OHD < 20 ng/mL) receiving oral cholecalciferol with three different dosing regimens: Group A: 10,000 IU/day for 8 weeks followed by 1000 IU/day for 4 weeks; Group B: 50,000 IU/week for 12 weeks and Group C: 100,000 IU every other week for 12 weeks. IL-17A, IL-6, IL-8, IL-10, IL-23 and TNFα were measured at baseline and at week 4, 8, 12, and 16. 75 healthy subjects were enrolled (58.7% female), with an average age of 34.1 ± 10.2 years. No statistical differences were observed among groups at baseline for either IL-6, IL-17A, IL-23, IL-8 or IL-10 at any time point; TNFα was indetectable. Concerning the whole sample, the time trend analysis showed a statistically significant linear trend for decreasing values over the treatment period for IL-6 (p = 0.016) and IL-17A (p = 0.006), while no significant time trends were observed for the other teste cytokines. No significant differences were found in the serum concentrations of the tested cytokines between week 12 and week 16. In young healthy individuals deficient in vitamin D, cholecalciferol administration showed a decrease in the serum IL-6 and IL-17A concentrations, without marked differences using the three regimens.     

Effects of Vitamin D3 and Calcium Supplementation on Serum Levels of Tocopherols,Retinol, and Specific Vitamin D Metabolites

γ-Tocopherol (γT) protects against DNA-damaging effects of nitrogen oxides, yet its physiologic regulation in vivo is unknown. Observational studies indicate inverse associations of 25[OH]-vitamin D with γT and leptin. To determine whether vitamin D₃ supplementation alters levels of lipid-soluble micronutrients, serum samples (N = 85 subjects) from a randomized, double-blind, placebo-controlled clinical trial of vitamin D₃ (800 IU) and calcium (2 g), alone and in combination, were analyzed for lipid micronutrients and specific vitamin D metabolites at baseline and after 6 mo of supplementation. Serum 25[OH]-vitaminD₃ levels increased 55% (P < 0.0001) and 48% (P = 0.0005), whereas 25[OH]-vitaminD₂ levels were lower by 48% (P = 0.26) and 21% (P = 0.36) in the vitamin D₃ and vitamin D₃ plus calcium groups, respectively. At baseline, γT levels were inversely associated with 25[OH]D (r = ?0.31, P = 0.004). With vitamin D₃ plus calcium treatment, serum α-tocopherol decreased 14% (P = 0.04), whereas similar changes in γT (19% lower, P = 0.14) were observed. No significant effects were observed for D₃ supplementation on leptin or retinol levels. These results are consistent with the hypothesis that vitamin D₃ ± calcium affects serum tocopherol and 25[OH]D₂ levels; however, studies using larger, more homogeneous populations are warranted.