共軛脂肪酸對 C57BL/6J 雌鼠脂質代謝之影響

Effects of conjugated fatty acid on lipid metabolism in C57BL/6J female mice

王麗卉(Li-Hui Wang)

指導教授 ： 黃青真

國立臺灣大學/生命科學院/生化科技學系/碩士(2013年)

https://doi.org/10.6342/NTU.2013.00833

摘要

共軛脂肪酸為一群特殊脂肪酸。共軛亞麻油酸 (conjugated linoleic acid，CLA) 混合物 (9c,11t-CLA與10t,12c-CLA ) 或10t,12c-CLA可活化PPARα、降低體脂肪，但造成脂肪肝及胰島素抗性。本實驗室曾發現自山苦瓜分離之共軛次亞麻油酸9c,11t,13t-conjugated linolenic acid (CLN) 可活化PPAR α及PPAR γ。 本研究目的為探討CLA及CLN對小鼠脂質代謝之影響 (in vivo)。
C57BL/6J 雌鼠以實驗飼料分成四組並飼養五週: 基礎飼料 (B組，控制組)、1 % CLA 混合物 (9c,11t-CLA: 10t,12c-CLA = 1:1) (A組)、 1% crude 9c,11t,13t-CLN (純度76 %) (N組) 或1% pure 9c,11t,13t-CLN (純度99 %) (H組)。 與B組小鼠相比，A組肝臟重量增加、肝臟TG及CHOL含量較高 (p < 0.05)，但腎周圍脂肪組織(RWAT) TG含量顯著較低。N組與H組RWAT重量較大，但只有N組RWAT之TG含量較高 (p < 0.05)。 H組肝臟TG濃度及含量皆顯著低於B組 (p < 0.05)。新陳代謝儀分析顯示H組具較高呼吸商 (RQ)。N組禁食血清之葡萄糖、TG濃度顯著較高 (p < 0.05)。 A組非禁食血清胰島素濃度及禁食血清CHOL濃度顯著較高，但禁食血清TG濃度顯著較低 (p < 0.05)。
肝臟、RWAT、血清、肌肉以GC-FID分析脂肪酸組成。於四種組織中N、H組皆測得9c,11t,13t-CLN及 9c,11t-CLA，A組皆測得9c,11t-CLA 及10t,12c-CLA。與B組相較，A組肝臟MUFA含量較高、n-6 PUFA含量較低。A組肝臟delta-5-desaturase (D5D)、delta-6-desaturase (D6D) mRNA表現量與D5D index (C20:4 n-6/C20:3n-6)、D6D index (C18:3n-6/C18:2n-6)皆顯著低於B組 (p < 0.05)。 N組肝臟SCD1 (delta-9-desaturase, D9D) mRNA表現量顯著較低 (p < 0.05)，但D9D index (C16:1n-7/C16:0)則否。四組小鼠肝臟組織中，與脂質代謝相關基因之表現量皆無顯著差異。 肝、血清、RWAT、尿液經LC-MS分析並預測代謝物。經標準品確認A、H組Phe於肝臟含量降低、於血清含量較高 (p < 0.05)。
本實驗結果顯示，CLA混合物對脂肪組織重量無顯著差異，但造成脂肪肝；CLN增加脂肪組織重量，但無肝臟脂質堆積。CLA混合物降低肝臟D5D及D6D酵素活性，但CLN則否。高純度CLN能降低肝脂並提高RQ，低純度則否。兩組CLN餵食結果之差異，究與劑量或低純度CLN樣品含有其他活性成分有關，尚待進一步研究。

關鍵字

共軛亞麻油酸(CLA) ； 共軛次亞麻油酸(CLN) ； 脂肪酸組成 ； 脂質代謝

並列摘要

Conjugated linoleic acid (CLA) (a mixture of 9c,11t-CLA and 10t,12c-CLA or 10t,12c-CLA) were shown to activate peroxisome proliferator activated receptor (PPAR) alpha decrease body fat mass (BFM), but lead to fatty liver and insulin resistance. Previous study of our Lab demonstrated that 9c,11t,13t-conjugated linolenic acid (CLN) isolated from bitter gourd activated both PPAR alpha and gamma. This study aimed to examine effects of CLA and CLN on the lipid metabolism (in vivo).
Four groups of C57BL/6J female mice were respectively fed: a basal diet (control group, B group), basal diet supplemented with 1% CLA mixture (9c,11t-CLA: 10t,12c-CLA = 1:1) (A group), 1% crude CLN (76 % pure) (N group) or 1% pure CLN (99 % purity) (H group) for 5 weeks. Compared to the B group, the A group of mice had significantly higher liver weight and its TG and cholesterol content, but lower triglyceride (TG) concentration in the perirenal white adipose tissue (RWAT) (p < 0.05). The N and H groups had higher adipose weight but only the N group had higher RWAT TG content (p < 0.05). The H group showed significantly lower TG concentration and content in the liver (p < 0.05). Indirect calorimetry analysis showed that the H group had significantly higher Respiratory quotient (p < 0.05). The N group had higher fasting serum glucose and TG, while the A group had higher non-fasting serum insulin and fasting serum cholesterol, but lower fasting serum TG (p < 0.05).
Fatty acid compositions in liver, RWAT, serum and muscle were analyzed by GC-FID. Both 9c,11t,13t-CLN and 9c,11t-CLA were detected in serum and all 3 tissues of the H and N groups, while both 9c,11t-CLA and 10t,12c-CLA were detected in the A group. Compared to the B group, the A group had higher MUFA and lower n-6 PUFA in the liver, while the N group had lower n-6 PUFA in the liver.
The hepatic mRNA expressions of delta-5-desaturase (D5D), delta-6-desaturase (D6D), fatty acids D5D index (C20:4 n-6/C20:3n-6) and D6D index (C18:3n-6/C18:2n-6) were significantly lower in the A group (p < 0.05). The N group had lower SCD1 (delta-9-desaturase, D9D) hepatic mRNA (p < 0.05) but not lower D9D index (C16:1n-7/C16:0). No significant differences were observed in the mRNA of remaining lipid metabolism related genes in the liver among the 4 groups. Metabolites in liver, serum, RWAT, and urine of the 4 groups of mice were analyzed by using LC-MS and the metabolomics approach. Confirmed by standard compounds, phenylalanine was lower in the liver, but higher in the serum in both of A and H groups (p < 0.05).
In this study, the CLA mixture led to fatty liver without a reduction in the adipose mass. CLN increased adipose mass but not liver lipids. The CLA mixture also decreased liver D5D and D6D desaturation of fatty acids, but not CLN. Reduced liver lipids and elevated respiration quotient were only observed in mice fed pure CLN. Further study is needed to elucidate whether the dose or other constituents in the crude CLN sample might contribute to the differences between the crude and pure CLN fed mice.

並列關鍵字

conjugated linoleic acid (CLA) ； conjugated linolenic acid (CLN) ； fatty acid composition ； lipid metabolism

參考文獻

Adams, M., M. J. Reginato, D. Shao, M. A. Lazar & V. K. Chatterjee (1997) Transcriptional activation by peroxisome proliferator-activated receptor gamma is inhibited by phosphorylation at a consensus mitogen-activated protein kinase site. J Biol Chem, 272, 5128-32.

Azain, M. J., D. B. Hausman, M. B. Sisk, W. P. Flatt & D. E. Jewell (2000) Dietary conjugated linoleic acid reduces rat adipose tissue cell size rather than cell number. The Journal of nutrition, 130, 1548-1554.

Bajare, S., J. Anthony, A. Nair, R. Marita, A. Damre, D. Patel, C. Rao, H. Sivaramakrishnan & N. Deka (2012) Synthesis of N-(5-chloro-6-(quinolin-3-yloxy) pyridin-3-yl) benzenesulfonamide derivatives as non-TZD peroxisome proliferator-activated receptor γ (PPARγ) agonist. European journal of medicinal chemistry.

Balkan, J., O. Kanbagli, G. Mehmetcik, U. Mutlu-Turkoglu, G. Aykac-Toker & M. Uysal (2002) Increased lipid peroxidation in serum and low-density lipoproteins associated with aging in humans. Int J Vitam Nutr Res, 72, 315-20.

Banni, S., E. Angioni, V. Casu, M. P. Melis, G. Carta, F. P. Corongiu, H. Thompson & C. Ip (1999) Decrease in linoleic acid metabolites as a potential mechanism in cancer risk reduction by conjugated linoleic acid. Carcinogenesis, 20, 1019-1024.