塑化劑是一個廣泛應用於塑膠製品的人工合成物質，適當的塑化劑可以改變塑膠物質的質 地，有便於業者對產品包裝的選擇以利消費者使用，常見的添加物為 di(2-ethylhexyl) phthalate (DEHP)，塑化劑不但是一種化學物質還是一個環境荷爾蒙，進入人體後會轉變 為 mono-(2-ethylhexyl) phthalate (MEHP) 進行代謝，過量的塑化劑進入人體內會造成肝、 腎、前列腺等等的癌症生成，以及海綿體的異常。過去發現 DEHP 會去影響 PPAR 的路 徑，DEHP / MEHP 可以透過活化 PPARs 的細胞核受體來促進過氧化氫體的增生，促使許 多代謝途徑像是脂肪酸代謝、過氧化氫分解及膽固醇生合成等也因此被促進。此外 DEHP 還會與 TRPV1 這個受體鈣離子通道做結合，目前的研究主要在探討 100 μM MEHP 對於 C2C12 肌肉細胞的分化後其代謝基因的影響，以及粒線體 fission and fusion 和過氧化氫體 數量的影響，並透過管餵 DEHP (200 mg/kg/14 days) 於 TRPV1-/-並檢測對 gastrocnemius 代 謝基因的影響。我們發現肌細胞分化後處於 MEHP （100 μM）的環境下肌管變細長之外， 且 PDK4 基因表現量上升了，則表示細胞減少了對於葡萄糖的使用率，而過氧化氫體的數 量沒有明顯變化，但粒線體 fission 比例上升了，然而 fission 的比例增加表明為了維持原有 的 ATP 的量並使細胞避免走向凋亡或者是避免突變的發生所形成的一個保護機制，而在管 餵 DEHP 後的 TRPV1-/-其 gastrocnemius 在 mtDNA/ncDNA level 的量則是下降的。而 RNA level 的結果可以看到 TRPV1-/-的 PDK4 下降了，表明塑化劑確實有透過 TRPV1 channel 來 影響身體代謝的方式，並對於肌肉有明顯的改變養分選擇的偏好，另外在心臟採血後血清 測量中的血糖、三酸甘油酯、膽固醇皆沒有明顯差異，然而詳細的機制還未釐清，透過了 解塑化劑對於肌細胞的粒線體以及過氧化氫體的影響，並檢測 TRPV1-/-肌細胞的代謝基因 的影響有助於對代謝症候群患者的預防與治療。;Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer for most PVC based medical devices and the addition of DEHP can increase the flexibility of plastic products. Many of these plasticizers act as endocrine disrupters and have been linked to the rise of metabolic disorders. Phthalates have been demonstrated to bind to peroxisome proliferator-activated receptors (PPARs); however, recent evidences also suggest the involvement of multiple non-PPARα pathways in DEHP-induced carcinogenesis. Transient receptor potential channel-vanilloid subfamily member 1 (TRPV1) in skeletal muscle (SKM) is mainly located in the sarcoplasmic reticulum (SR) responding for load signal induced Ca+2 release and contraction, and it is of interest to test whether DEHP can regulate its channel activity and result in metabolic changes in SKM. In the present study, C2C12 myotubes was treated with MEHP (100 μM) for 4 days in vitro and mice were treated with DEHP (200 mg/kg) for 14 days in vivo to observe the effects of DEHP/MEHP on SKM metabolism. We found that DEHP/MEHP could change SKM metabolism and the expression of some metabolic genes, such as PDK4, was markedly up-regulated after treatment with DEHP/MEHP. But the same phenomenon was not observed in TRPV1-/- mice, in which PDK4 gene is down-regulated, suggesting that a switch of nutrient utilization has occurred. Furthermore, the mitochondrial content in cells was examined and a down regulation by DEHP was discovered in TRPV-/- but not in wildtype mice. In addition, treatment of C2C12 myoblasts with MEHP (100μM) changed mitochondrial morphology implying functional alteration. Our results support the notion that DEHP/MEHP is a strong modulator of metabolism in SKM.
