Abstract
Abnormality of skin collagen metabolism is one of main causes for ultraviolet (UV) induced skin ageing. It has been shown that single UV irradiation decreases procollagen mRNA expression and increases matrix metalloproteinases mRNA expression in dermis, and that chronic UV irradiation decreases collagen amount and induces wrinkle formation. Amino acid is known to regulate protein metabolism, in general. Therefore, we investigated effects of UV irradiation and orally administrated various amino acids on skin collagen synthesis rate. Hr-1 hairless mice (male, 8weeks old) were irradiated with UVB (66 J/cm2) twice at one day interval, and then fasted for 16hr. Fractional synthesis rate (FSR) of skin tropocollagen was measured by flooding dose method using stable isotope L-[ring-2H5]Phenylalanine. We confirmed that dermal tropocollagen FSR was decreased by UVB irradiation. Subsequently, FSR of dermal tropocollagen was measured at 30 min after oral administration of amino acid (1g/kg) in UVB irradiated mice. Neither branched-chain amino acids (BCAA), Arginine (Arg), Glutamine (Gln), nor Glutamate, but amino acids mixtures, BCAA+Arg+Gln and BCAA+Gln increased dermal tropocollagen synthesis. It is suggested that the combination of BCAA and glutamine is key for recovery of dermal collagen synthesis impaired by UV irradiation.
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