New possibilities for slowing or even reversing the ageing process have been raised by a study, published in the journal Cell this week, which seems to show that genetics rather than tissue damage is the reason animals grow old.

    Conventionally, scientists have argued that ageing is the inevitable consequence of wear and tear on cells and tissues over time: toxins, ionising radiation, disease and stress all play a part in contributing to decline and death. 

    Now a team under Stuart Kim at Stanford University, working on minute nematode worms, has found that hundreds of genes implicated in the ageing process are turned on by a biological switch called elt-3, which becomes more abundant as the animal grows older.

    The scientists tried to age the worms artificially by subjecting them to stresses such as heat and radiation but none of these had any effect on the ageing genes. Prof Kim concluded that the higher level of elt-3 in older animals is the result of control mechanisms gone wrong, something he calls “developmental drift”. 

    If ageing is not the result of chemical catastrophe but driven by changes in regulatory genes, it could, in theory at any rate, be slowed down or stopped. Prof Kim cannot yet say whether developmental drift occurs in humans. 

    《細(xì)胞》雜志(Cell)上周刊登的一項(xiàng)研究提出了減緩甚至扭轉(zhuǎn)衰老過(guò)程的新可能性。該研究顯示，動(dòng)物變老是由遺傳學(xué)原因而非組織受損造成的。

    科學(xué)家們傳統(tǒng)上認(rèn)為，老化是細(xì)胞和組織長(zhǎng)期磨損和破裂的必然結(jié)果：毒素、電離輻射、疾病和壓力都會(huì)促使動(dòng)物衰老和死亡。

    現(xiàn)在，由斯坦福大學(xué)(Stanford University)的斯圖爾特•金(Stuart Kim)帶領(lǐng)的一個(gè)小組，正在對(duì)微小的線蟲(chóng)展開(kāi)研究。他們發(fā)現(xiàn)，一種被稱為ELT-3的生物學(xué)開(kāi)關(guān)能夠啟動(dòng)數(shù)百個(gè)涉及老化過(guò)程的基因，而當(dāng)線蟲(chóng)變老時(shí)，ELT-3變得更加豐富。

    科學(xué)家們嘗試人為使這些線蟲(chóng)變老。他們讓線蟲(chóng)受到熱和輻射等壓力，但是這些都不能對(duì)涉及老化過(guò)程的基因產(chǎn)生影響。金因此得出結(jié)論：越老的動(dòng)物，其ELT-3的豐富度越高，而這是控制機(jī)制出錯(cuò)的結(jié)果。他稱這種現(xiàn)象為 “發(fā)育漂變”(Developmental Drift)。

    如果老化不是化學(xué)過(guò)程造成的災(zāi)難結(jié)果，而是由于控制它的基因發(fā)生了改變，那么從理論上說(shuō)，在任何水平上，老化速度都可以被減緩甚至停止。但是金還不能確定，發(fā)育漂變是否也出現(xiàn)在人類身上。