Smokers look older than non-smokers of the same age, probably because they have higher levels of MMP-1 (matrix metalloproteinase 1) in their skin, according to a study in 24 March Lancet. MMP-1 is a zinc-dependent metalloproteinase that degrades collagen, which is important in maintaining the mechanical/elastic properties of connective tissue in the skin.

Lahmann et al from Guy's, King's and St Thomas' School of Medicine, London, used PCR to measure mRNA in the buttock skin of 14 smokers and 19 non-smokers. They found significantly more MMP-1 mRNA in the skin of smokers than in non-smokers. But the quantity of mRNA for the tissue inhibitor of metalloproteinases 1 (TIMP-1) did not differ between non-smokers and smokers (Lancet 2001, 357:935-936).

These findings confirm similar in vitro results in dermal fibroblasts and the authors suggest that MMP-1 might be important in the face-ageing effects of tobacco smoking, perhaps in combination...