膳食脂肪酸对正常和携瘤小鼠血浆脂肪酸谱的影响

EFFECTS OF HIGH FAT DIETS ON PLASMA FATTY-ACID PROFILES IN TUMOR-FREE AND TUMOR-BEARING MICE

目的研究膳食中的脂肪酸对正常和携瘤小鼠血浆脂肪酸谱的影响并研究肿瘤代谢是否影响血浆脂肪酸谱。方法正常(无瘤)鼠和携瘤鼠在两个独立的实验中分别进行。每个实验均包含普通餐和4种高脂餐。这些高脂餐均含20%(质量比w/w)的脂肪,因脂肪来源的不同而分别富含饱和脂肪酸(SFA,月桂酸C12:0和肉豆蔻酸C14:0),单不饱和脂肪酸(MUFA,油酸C18:1),n-6多不饱和脂肪酸(n-6PUFA,亚油酸C18:2)和n-3多不饱和脂肪酸(n-3PUFA,亚麻酸C18:3)。在正常鼠实验中,20只雄性Balb/C小鼠被随机分成普通饲料对照(NC)组和4个高脂餐组(即SFA组、MUFA组、n-6PUFA组、n-3PUFA组),用相应的饲料喂养6w。在另一实验中,48只雄性Balb/C裸鼠被随机分成2个正常饲料组和4个高脂餐组。将Mia Pa Ca2人胰腺癌细胞移植到除一个普通饲料组外的5组裸鼠皮下。将6组动物用相应的饲料喂养7w。每一实验结束后,用气相色谱的方法分析血浆脂肪酸谱的变化。结果以普通餐组为对照组,血浆脂肪酸变化如下:(1)在无瘤和携瘤两种状态下,属于SFA的C12:0和C14:0含量在SFA组增高(P<0.01)而属于MUFA的C18:1在MUFA组增高(P<0.01)。(2)在无瘤状态下,属于n-6PUFA的C18:2在n-6PUFA组没有显著变化(P>0.05),且与n-3PUFA组相比还有降低。而在携瘤状态下,C18:2的含量在n-6PUFA组却有增高趋势。(3)在无瘤和携瘤两种状态下,属于n-3PUFA的C18:3的含量在n-3PUFA组增高(P<0.01)。结论 1.当无瘤鼠进食4种高脂餐时,餐中富含的SFA,MUFA和n-3PUFA可在血浆中增高,而餐中富含的n-6PUFA则不高。2.携瘤鼠对实验餐的反应与无瘤鼠大体相同,但n-6PUFA高脂餐也可增进携瘤鼠血浆中的n-6PUFA。3.癌细胞对n-6PUFA代谢的影响导致了血浆n-6PUFA在无瘤和携瘤鼠间的差异,该差异可能对癌症的诊断和治疗有所帮助。

Objective To investigate the impacts of different high fat diets（HFDs） on plasma fatty-acid profiles in normal（tumor-free） mice and in tumor-bearing athymic mice. Methods Two experiments using tumor-free mice and tumor-bearing athymic mice were carried out, respectively. Each experiment consisted of groups using normal diet and using four HFDs. The predominant fatty acids in these HFDs were the saturated fatty acids（SFAs） of lauric and myristic acids, the monounsaturated fatty acid（MUFA） of oleic acid, the n-6 polyunsaturated fatty acid（n-6 PUFA） of linoleic acid, and the n-3 polyunsaturated fatty acid（n-3 PUFA） of linolenic acid respectively. In one experiment, twenty male Balb/C mice were randomly divided into a normal-diet control（NC） group and four HFD groups（i.e. SFA group, MUFA group, n-6 PUFA group, and n-3 PUFA group） and fed the corresponding diets for six weeks. In another experiment, forty-eight male Balb/C athymic mice were randomly divided into two normal-diet groups and four HFD groups and fed the corresponding diets for 7 weeks. The Mia Pa Ca2 human pancreatic cancer cells were transplanted into five groups of athymic mice except the normal-diet group. Plasma fatty acid profiles were analyzed by gas chromatography. Results Compared to normal-diet group,plasma fatty acids were changed as follows：（1） In both tumor-free and tumor-carrying mice, the SFAs of lauric acid（C12：0） and myristic acid（C14：0） were increased in the SFA group（P〈0.01） and the MUFA of oleic acid（C18：1） was increased in the MUFA group（P〈0.01）.（2） In tumor-free mice, the n-6 PUFA of linoleic acid（C18：2） was not significantly changed in n-6 PUFA group（P〉0.05）. Rather, it was decreased, as compared the corresponding linoleic-acid level seen in the n-3 PUFA group. In tumor carriers, however, a moderate increase of linoleic acid（C18：2） was seen in the n-6 PUFA group.（3） In both tumor-free mice and tumor carriers, the n-3 PUFA of linolenic acid（C18：3） was increased in the n3 PUFA group（P〈0.01）. Conclusion（1）When tumor-free mice were fed HFDs, the fatty acids characterizing these diets increased in the plasma with the exception of the tumor-free mice fed the linoleic acid-enriched HFD.（2）When tumor-bearing mice were fed HFDs, the results were nearly similar to those as seen when tumor-free Balb/c mice were fed the same HFDs. When the tumor-bearing athymic mice were fed the linoleic acid（n-6 PUFA）-enriched HFD, a moderate increase of linoleic acid was seen in the plasma.（3）The effects of cancer cells on n-6 PUFA metabolism may be helpful in the diagnosis and treatment of the pancreatic cancer.