影響3T3-L1細胞株分泌細胞激素之食材對高油飲食小鼠的免疫調節作用

Abstract

肥胖者體內處於低程度發炎現象而導致了胰島素抗性，脂肪組織內的巨噬細胞型態也影響著胰島素敏感性，有研究指出脂肪細胞所分泌的IL-4會促進M2巨噬細胞生成而具有抗發炎增加胰島素敏感性的功效。本研究首先以3T3-L1脂肪細胞株，篩選具促進IL-4分泌量及降低lipopolysaccharide (LPS) 刺激下 IL-6與MCP-1促發炎細胞激素分泌量之抗胰島素抗性潛力食材樣品。篩選結果顯示，苦瓜(bitter gourd powder, BGP)、靈芝免疫調節蛋白(Ganoderma microsporum immunomodulatory protein, GMI)及食品級靈芝免疫調節蛋白 (f-GMI)均可顯著促進IL-4分泌且抑制成熟脂肪細胞IL-6與MCP-1。 正常飲食 (AIN-76) 情況下，給予C57BL/6J小鼠餵食GMI後具有降低血糖的效果。但在高油飲食誘發肥胖的動物模式下，餵食BGP、GMI與f-GMI，5週後發現f-GMI與BGP都具有降低空腹血糖的功效，而BGP更具有降低HOMA-IR index的能力。 In vivo，體重與脂肪組織IL-4基因表現量達顯著負相關 (r = -0.46, p＝0.0001) ，血糖與脂肪組織IL-4基因表現量兩項指標也有顯著負相關 (r = -0.31, p＝0.01)，顯示體重及血糖增加會降低脂肪組織IL-4的表現量；體重與脾臟分泌IL-4含量也呈顯著負相關 (r = -0.28, p ＝0.01)，顯示肥胖者體內較傾向Th1免疫反應。在脂肪組織，BGP與f-GMI均可顯著促進IL-4表現及M2 巨噬細胞生成，肝臟中M2 巨噬細胞生成的現象也顯著較HF組高。在高油飲食誘發胖小鼠肥胖模式下，餵食BGP與f-GMI的小鼠脾臟細胞在Con A刺激下，IFN-gamma 及IL-2分泌量顯著下降，顯示此兩食材樣品均有助於改善肥胖小鼠體內傾向Th1免疫反應的情形。綜合以上實驗結果得知，BGP及f-GMI可能藉由提高IL-4表現量，促進脂肪組織及肝臟M2 巨噬細胞生成；以及降低Th1細胞激素IFN-gamma及IL-2而具有改善肥胖發炎及胰島素抗性的現象。

Obesity is associated with low-grade system inflammation that results in insulin resistance. Adipose tissue macrophage (ATM) phenotype switch could affect insulin sensitivity. Adipocyte-derived IL-4 could promote M2 macrophage phenotype switch as well as ameliorate insulin resistance. First, using 3T3-L1 cell culture, potential dietary components which could increase IL-4 secretion as well as inhibit LPS-stimulated pro-inflammatory cytokines, IL-6 and MCP-1, were identified. The results showed BGP (Bitter gourd poeder, BGP), GMI(Ganoderma Modulatory Immunoglobulin, GMI) and f-GMI (Food Ganoderma Modulatory Immunoglobulin, f-GMI) could inhibit pro-inflammation cytokines secretion and increase IL-4 secretion. These dietary components were subsequently tested to verify their ability to ameliorate insulin resistance. In vivo, GMI improved blood sugar of C57BL/6J mice that were fed the AIN-76 diet with 50% sucrose. Improvement of fasting blood sugar could be observed in C57BL/6J mice that were fed a 30% fat diet supplemented with BGP or f-GMI for 5 weeks. BGP also decreased HOMA-IR index. BGP increased IL-4 mRNA expression in adipose tissue as well as M2 phenotype switch in adipose tissue and liver. f-GMI increased M2 phenotype switch in adipose tissue. In liver, f-GMI increased M2 phenotype switch and IL-4 mRNA expression. BGP and f-GMI significantly lowered IFN-gamma and IL-2 secretion from Con A-stimulated splenocytes. Furthermore, negative correlations were observed between body weight and IL-4 mRNA expression in adipose tissue (r = －0.46, p ＝＜0.0001), and between blood sugar and IL-4 mRNA expression in adipose tissue (r = －0.31, p ＝0.01). The results show high body weight and blood sugar could inhibit IL-4 mRNA expression in adipose tissue. There was also a negative correlation between body weight and IL-4 secretion from splenocyte (r = －0.28, p ＝0.01), which suggests that obesity is prone to Th1 immune response. In conclusion, BGP and f-GMI increase M2 phenotype switch in adipose tissue and liver through IL-4 secretion. BGP and f-GMI could reduce IFN-gamma and IL-2 secretion from Con A-stimulated splenocytes. The aforementioned dietary components ameliorate insulin resistance through their inhibition of Th1 immune response abilities.