Another consequence of smoking is that it upsets the process the body uses to restore skin by reducing the amount of the protein collagen present in the skin. Collagen produces new, healthy skin and is the connective tissue that constitutes about 80% of normal skin. When someone smokes, they effectively diminish the amount of nutrients stored in the skin, meaning that less collagen is available to repair damage. The key to the renewal process is the enzyme Matrix Metalloproteinase-1 (MMP-1), which breaks down fibrous collagen, old skin and elastic tissue. Before the body can make new skin, it needs to break down the old and this is achieved by MMP-1 destroying the fibres that form collagen. The problem for smokers is that smoking activates more of this enzyme than is normally present in non-smokers, creating a shortage of collagen. (3.) Without sufficient collagen for renewal, the skin gradually loses its elasticity, becoming dry and wrinkly. The concentration of MMP-1 in smoker's skin was the subject of a study headed by Professor Antony Young and his colleagues at Guy's, Kings and St Thomas' School of Medicine in London. Their tests found that considerably more MMP-1 genetic material was present in the buttock skin of smokers when compared to that of non-smokers.In another study, Akimichi Morita and researchers at Nagoya City University Medical School added drops of smoke solution to dishes of human fibroblasts, the skin cells that produce collagen. The smoke was sucked from cigarettes and pumped through saline solution. After only one day, those cells exposed to cigarette smoke produced considerably more MMP, and up to 40% less collagen, than normal skin cells would. The more concentrated smoke was introduced to the skin cells in this way, the more the production of collagen was affected. With less collagen available, the result was an increase in those symptoms associated with the aging of the skin.(3.) Lahmann, C., J. Bergemann et al., 'Matrix Metalloproteinase-1 and Skin Aging in Smokers', The Lancet, 2001. 24:935-936.