共軛亞麻油酸 (Conjugated Linoleic Acid, CLA) 是一群含 18 個碳、具共軛雙鍵的脂肪酸，為 ω-6 必需脂肪酸亞麻油酸的立體異構物。 CLA可透過抑制脂肪細胞中過氧化酶體增生活化受體 (Peroxisome Proliferators Activated Receptor gamma, PPARγ) 的表現，進而降低脂肪組織。近年來研究指出 PPARγ 具有促進抗氧化能力之作用。本實驗室亦於先前研究發現，餵食CLA四週後除了會降低小鼠脂肪組織外，亦提升維生素 E 的營養狀況。本研究目的在於探討 CLA 對維生素 E 的營養狀況或抗氧化能力的影響是否與 PPAR 之調節有關。方法：將40隻6週大C57BL/6J male mice 經適應兩週後，依飼料組成不同分成下列五組： C 組 (控制組)、CLA 組 (1 % CLA)、R 組 (0.0625% rosiglitazone, ROSI, PPARγ誘導劑)、CR 組(1% CLA + 0.0625% ROSI)、VE 組(3750 ppm -tocopherol, 相當於AIN-93G飼料維生素 E 含量的 50 倍)。飼養期間收集尿液，四週後取得血液、肝臟、脂肪及其他組織。分析項目包含 PPAR 相關指標 (脂聯素) 與抗氧化指標如 -生育醇濃度、還原態 Glutathione (GSH)、Total antioxidant、8-Isoprostane、抗氧化酵素活性以及脂質過氧化物 (TBARS) 等。結果: 以血漿脂聯素濃度作為 PPAR 之表現指標，結果以 CLA 組顯著最低而 R 組與 CR 組則顯著最高， C 組居中，此趨勢與本試驗模式符合。血漿、肝臟與 EP 之 -生育醇濃度，顯著以 CLA 組和 VE 組最高， CR 組次之， R 組與 C 組顯著最低。腎臟、睪丸、脾臟、心臟的 -生育醇濃度則以VE 組顯著最高 (p<0.05)。尿液 8-isoprostane 濃度以 CLA 和 CR 兩組顯著高於 C 組 (p<0.05)，但 R 組則無影響。肝臟抗氧化酵素方面， CAT (catalase) 活性以 CLA 與 CR 組顯著降低(p<0.05)，但是 R 組則無影響； GPx (glutathione peroxidase) 活性以 R 組顯著高於 CLA 組 (p<0.05)。 SOD (superoxide dismutase) 活性、血漿總抗氧化能力及組織 TBARS、GSH 濃度於五組皆無顯著差異。結論：本實驗結果指出 CLA 會提升肝臟維生素 E 及尿液 8-isoprostane 濃度並降低肝臟 CAT 活性，在 CR 組 (CLA＋R) 亦出現相似情況，但CR 組在肝臟、EP、α-生育醇濃度仍顯著低於CLA組，而CAT活性仍顯著高於CLA組。因此推測 CLA 可透過抑制 PPARγ 來影響脂肪組織生成並降低血漿脂聯素濃度，且對於體內氧化壓力、肝臟 CAT 活性與維生素 E 營養之影響可能與 PPARγ之表現或脂聯素之生成量有直接影響關係。 Conjugated linoleic acid (CLA) is a collective term for the positional and geometric isomers of a conjugated diene of linoleic acid (C18:2, n-6). CLA increases vitamin E status in mice in our previous study. CLA was found to be an inhibitor of Peroxisome Proliferators Activator Receptor gamma (PPARγ) and caused reduction of adipose tissue. Recently, PPARγ was reported to be involved in antioxidant ability. The aim of this study is to investigate whether the PPARregulation is involved in vitamin E status and antioxidant system in mice fed with CLA. Methods: Forty C57BL/6J mice were divided into five groups and fed 5% lipid as soybean oil alone (C), 4% soybean oil supplemented with 1% CLA (CLA group), 5% soybean oil with rosiglitazone 0.0625% (R group), 1% CLA and rosiglitazone (CR group) or 5% lipid with a vitamin E supplement (VE group) for four weeks. Results: The levels of plasma adiponectin (as the biomarker of PPARr expression) significantly decreased in CLA group but increased in R and CR groups. Both the CLA and VE diets resulted in a significant increase in the -tocopherol concentration in liver and epididymal adipose tissues (p<0.05). In CR group, the α-tocopherol levels in liver and adipose tissue showed significantly higher then that in R group; but showed significantly lower then that in CLA group. The reduced catalase activity and increased levels of urine 8-isoprstane was found in CLA and CR groups, however, there were no significant changes in the R groups (PPAR inducer) or VE group compared to C group. Levels of reduced glutathione, total antioxidant and thiobarbituric acid-reactive substances in the tissues examined showed no significant difference among the five groups. Conclusion: The increase in liver vitamin E status and reduced liver catalase activity in CLA-fed mice somehow due to the effect of PPARγ inhibition.
