摘要:流行病學與基礎研究皆指出慢性發炎與現代疾病的密切關係,包括肥胖、風濕性關節炎、心血管疾病、第二型糖尿病、潰瘍性腸炎與各式癌症等。在病理機制上,慢性發炎參與疾病的形成是一漫長且複雜的過程,最重要的特徵即發炎或免疫細胞的浸潤與發炎分子過度表現,引起細胞與組織的生理功能受損。已知環境因素會導致基因改變(genetic change)而起始疾病或癌症的形成,然而近十幾年的研究指出異常(aberrant)epigenetics作用或許才足以解釋現代疾病的多樣性與複雜性,例如人類遺傳性疾病。Epigenetics是指在不影響DNA序列的情況下調控基因表現的作用,常見的方式如DNA methylation與histone acetylation,且在生物體的發育生長過程中相當重要。近期研究顯示,epigenetics作用失常會直接影響發炎分子的表現或藉由活化轉錄因子促使基因表現,皆為影響慢性發炎與現代疾病發展的重要機制。就疾病化學預防的思維觀之,由於epigenetics作用是可逆的,相較於改變基因序列或抑制突變基因表現,藉由調節epigenetics控制基因表現而抑制慢性發炎與疾病形成或許為更適切的化學預防策略。柑橘為台灣最具農產價值的作物,然而相較於果肉的利用性,果皮因附加價值不高而大多用於製作肥料或被視為廢棄物。我們先前研究發現,柑橘果皮中富含polymethoxyflavone(PMFs)與hydroxyl PMFs(OH-PMFs),且具有抗癌、抗發炎、抑制腫瘤生長與腸癌形成的活性。在儲藏期間,果皮中的PMFs會轉變成hydroxyl PMFs,並顯現出較佳的生理活性,包括抑制腸癌細胞生長、抑制發炎分子表現與皮膚腫瘤形成,以及抑制3T3-L1細胞脂肪形成等,此外我們也發現OH-PMFs具有調控epigenetics作用的特性;這些研究數據顯示OH-PMFs在抗發炎與疾病化學預防上的研究潛力。鑒於疾病化學預防的立場,與慢性發炎衍生疾病中epigenetics作用的可逆性,此四年期計畫將延續我們先前的研究,探討OH-PMFs藉由調節epigenetics作用而抑制慢性發炎相關疾病產生的功效與分子機制,計畫時程與目標包括:【第一年】以小鼠皮膚模式探討OH-PMFs抑制發炎、腫瘤形成的功效以及調控epigenetic作用之活性與機制;【第二年】餵食OH-PMFs抑制潰瘍性腸炎衍生結腸直腸癌的活性與分子機制;【第三年】探討餵食OH-PMFs抑制高脂飼料(HFD)誘導肥胖之功效,與其抗發炎之活性與機制與【第四年】乳化型(emulsion)與官能基修飾acetylation-PMFs之抗發炎活性探討。我們期望藉由此計畫闡述飲食攝取OH-PMFs之疾病化學預防功效,並說明調節慢性發炎對於預防現代疾病觀念的重要性,與鑑定OH-PMFs調節epigenetics作用的標的分子;且希望藉由探討OH-PMFs的劑型(emulsion)與官能基差異對其生物利用性與生理活性的影響,應用至未來保健食品開發的可行性,進一步改善國人健康並提升柑橘果皮廢棄物附加價值與產業發展前景。
Abstract: Numerous epidemiological and experimental data has demonstrated a direct link between chronic inflammation and complex diseases such as obesity, rheumatoid arthritis, cardiovascular disease, type 2 diabetes, inflammatory bowel disease and several types of cancer. The major mechanisms by which inflammation is contribute to chronic diseases are infiltration of inflammatory/immune cells and over-production of inflammatory mediators that result in damage of cellular and tissue function. A growing body of literature addressing environmental factors such as infection or diet is known to cause diseases and cancer development through genetic change. However, genetics per se cannot explain the vast diversity of phenotypes such as heritable disease but aberrant epigenetics. Epigenetics is defined as the study of mitotically and meiotically heritable changes in gene function that are not dependent on DNA sequence, such as DNA methylation and histone acetylation that are important for organism development. Recently, studies have shown that aberrant epigenetics are involved in chronic inflammation and diverse diseases through directly regulation of inflammatory genes expression and acts on transcription factors along with epigenetic phenomena. Thus, based on the principles of chemoprevention, targeting on modulation of epigenetics-mediated chronic inflammation and diseases will be more beneficial for preventive strategy. Citrus is one of the most important agriculture in Taiwan. However, compare to the economic value, peels are less utilization and as by-products. It has been found polymethoxyflavone (PMFs) and hydroxyl PMFs (OH-PMFs) are a unique class of flavonoids that almost exclusively exists in citrus genus, especially in the peel. In our pervious studies, we found OH-PMFs exhibit a broad spectrum of biological activity, including anti-inflammation, anti-skin carcinogenesis, and anti-colonic tumorigenesis. OH-PMFs can be formed from their corresponding PMFs counterparts by hydrolysis during storage. In recent studies, we found OH-PMFs showed much stronger activity on inhibition of colon caner cells growth, suppression of inflammatory mediators and skin carcinogenesis as well as colonic tumorigenesis, and inhibits adipogenesis in 3T3-L1 adipocytes. In addition, we also found OH-PMFs exhibit epigenetics regulation properties. Because the epigenetics are reversible, these results indicated the strongly potential of OH-PMFs on chronic inflammation and chemoprevention through targeting on epigenetic regulation. With this proposed four-year study, we will extend the preliminary study to investigate the efficacy of OH-PMFs on inhibition of chronic inflammation-associated disease through regulating epigenetics. The individual goal and study design are listed below: 1st year, we will investigate the anti-infalmmatory and anti-skin carcinogeneic effect of OH-PMFs and their epigenetic regulation mechanism by using skin-two stage carcinogenesis model. 2nd year: inhibitory effects of dietary OH-PMFs on AOM/DSS-induced colonic tumorigenesis. 3rd year: anti-inflammatory efficacy of dietary OH-PMFs on inhibition of HFD-induced obesity. 4th year: anti-inflammation and chemopreventive efficacy of emulsion OH-PMFs and acetyl PMFs (Ac-PMFs). The present project will provide scientific evidence of dietary OH-PMFs for prevention of inflammation-associated chronic diseases. We expect to clarify the promising molecular targets of OH-PMFs on regulation of epigenetics. Moreover, investigation of chemopreventive property on emulsion OH-PMFs and elucidate the structural feature on the type of functional group of PMFs will be useful for further application of functional food. Finally, we also expect to promote the people’s health and the utilization of citrus peel.