魚油對於小鼠脂肪組織巨噬細胞堆積及發炎反應之影響研究

The Effect of Fish Oil Diet on Adipose Tissue Macrophage Accumulation and Inflammation in ob/ob Mice

賴雅芬(Ya-Fen Lai)

指導教授 ： 呂紹俊

國立臺灣大學/醫學院/生物化學暨分子生物學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01285

摘要

肥胖是導致胰島素抗拒及第二型糖尿病的危險因子。近年來研究顯示在遺傳或高脂飲食導致的肥胖鼠中，其脂肪組織會分泌細胞激素吸引巨噬細胞滲入至脂肪組織，導致脂肪組織中巨噬細胞(adipose tissue macrophage, ATM)的堆積，這些ATM大多會聚集在壞死的脂肪細胞周圍以清除其殘骸，並釋放前發炎性物質使脂肪組織產生慢性發炎反應，而進一步導致胰島素抗拒。
在動物實驗中已知魚油具有抗發炎的效果，並能減緩大鼠或小鼠中胰島素抗拒的現象，因此我們推測魚油可能會藉由降低ATM的含量來改善胰島素抗拒。第一次實驗係以9週齡ob/ob鼠為動物模式，將之分為三組，分別餵與低脂飼料(4%大豆油；LF組)、高豬油飼料(4%大豆油+20%豬油；Lard組)或高魚油飼料(4%大豆油+20%魚油；FO組)，飼養10.5週後FO組的體重、脂肪組織重量及血液中葡萄糖和膽固醇的濃度皆顯著低於Lard組，然而FO組ATM表面抗原的表現量卻和Lard組沒有差異，顯示魚油並不會降低ATM的含量，但魚油卻能減緩ob/ob鼠胰島素抗拒的現象，因此我們推測FO組中所含的ATM其特性和生理意義可能和Lard組中具發炎性的ATM有所不同。
為了進一步探討FO組中所含的ATM之生理意義，於是我們以7週齡的ob/ob鼠進行第二次實驗，將之分為四組，除了LF組、Lard組及FO組外，另新增一組添加Thiazolidinedione (TZD)藥物的高豬油飲食組(4%大豆油+20%豬油+0.0012% Rosiglitazone；Rosi組)作為參考。四組於飼養7週後，FO組的體重、脂肪組織重量及血液中葡萄糖和膽固醇的濃度皆顯著低於Lard組，而脂肪組織免疫組織染色及定量聚合

關鍵字

肥胖 ； 脂肪組織 ； 魚油 ； 發炎反應 ； 巨噬細胞 ； 胰島素抗拒

並列摘要

Obesity is a risk factor for the development of insulin resistance and type II diabetes. Recent studies suggest that the adipose tissues of genetic or high-fat diet induced obese mice secrete cytokines to recruit macrophage infiltration, which leads to adipose tissue macrophage (ATM) accumulation. The ATM will localize with necrotic adipocytes to phagocyte the debris, and release proinflammmatory cytokines to invoke inflammatory response in adipose tissue leading to insulin resistance.
Fish oil is known to ameliorate insulin resistance and inflammation in rodents, so we speculated that fish oil diet might decrease ATM content to ameliorate insulin resistance. Based on the hypothesis, we studied the effect of high fat diet rich in lard or fish oil on macrophage accumulation in ob/ob mice. In the first experiment, 9-week old ob/ob mice were divided into three groups and were fed with low fat (LF, 4% soybean oil), high fat-lard (Lard, 4% soybean oil + 20% lard) or high fat-fish oil diet ( FO, 4% soybean oil + 20% fish oil) for 10.5 weeks. Final body weights, adipose weights, plasma glucose and cholesterol of FO group were significantly lower than that of Lard group. However, the expression level of ATM surface marker was not different between the FO and Lard groups, which indicated that fish oil did not decrease ATM content, although fish oil can ameliorate insulin resistance in ob/ob mice. We speculated that the characters and physiological significance of ATM in FO group might be different from that of Lard group.
To further investigate the physiological significance of ATM accumulation in FO group, 7-week old ob/ob mice were divided into four groups and were fed with low fat, high fat-lard, high fat-fish oil or rosiglitazone (Rosi) supplemented high fat lard diet (4% soybean oil + 20% lard + 0.0012% rosiglitazone) in the second experiment. After 7 weeks of feeding, final body weights, adipose weights, plasma glucose and cholesterol of FO group were significantly lower than that of Lard group. From the result of immunochemistry and quantitative PCR, we confirmed that the ATM content in FO group was not different from that of Lard group, whereas rosiglitazone decreased the ATM content. Furthermore, TUNEL assay suggested that the content of apoptotic cells in adipose tissues of FO group was higher than that in adipose tissues of Lard group. Analysis of adipose tissue morphology revealed that the average size of adipocytes in FO group was smaller than that of Lard group. From above, we speculate that fish oil will promote apoptosis of large adipocytes thus recruit macrophage infiltration to phagocyte apoptotic cells. Unlike necrotic cells, apoptotic cells may not invoke inflammatory response. The expression level of inflammatory gene such as iNOS was significantly lower in FO group than that of Lard group, and the expression level of anti-inflammatory gene such as IL-10 was higher in FO group than that of Lard group. Taken together, the physiological significance of ATM in FO group is tending to phagocyte apoptotic cells, and the majority of ATM in FO group may have anti-inflammatory or less inflammatory character. In contrast, rosiglitazone decreases inflammatory ATM to ameliorate insulin resistance. The mechanism of insulin sensitivity improvement by rosiglitazone and fish oil is not the same.

並列關鍵字

Obesity ； Adipose tissue ； Fish oil ； Inflammation ； Macrophage ； Insulin resistance.

參考文獻

黃莉婷 (2005) 魚油對小鼠脂肪組織基因表現之影響研究。國立台灣大學生化學暨分子生物學研究所碩士論文。

Abbott, W.G., and Foley, J.E. (1987). Comparison of body composition, adipocyte size, and glucose and insulin concentrations in Pima Indian and Caucasian children. Metab. Clin. Exp. 36, 576-579.

Abel, E.D., Peroni, O., Kim, J.K., Kim, Y.B., Boss, O., Hadro, E., Minnemann, T., Shulman, G.I., and Kahn, B.B. (2001). Adipose-selective targeting of the GLUT4 gene impairs insulin action in muscle and liver. Nature 409, 729-733.

al-Shurbaji, A., Larsson-Backstrom, C., Berglund, L., Eggertsen, G., and Bjorkhem, I. (1991). Effect of n-3 fatty acids on the key enzymes involved in cholesterol and triglyceride turnover in rat liver. Lipids 26, 385-389.

Albu, J.B., Murphy, L., Frager, D.H., Johnson, J.A., and Pi-Sunyer, F.X. (1997). Visceral fat and race-dependent health risks in obese nondiabetic premenopausal women. Diabetes 46, 456-462.