Ageing and human bone collagen synthesis

A loss of bone mineral density and collagen concentration occurs with ageing, but possible deficits in human bone collagen synthesis have not previously been examined. We studied 4 healthy elderly men (age 62 ± 7 y) and 2 healthy postmenopausal elderly women (55,62y) in the post absorptive state and compared the results with those from our previously published data for young healthy men. Subjects fasted overnight, were given a flooding dose of 1‐ 13 C proline over 3 min with an iliac crest biopsy being taken under local anesthesia and mild sedation 120 min later. There were no differences in the rate of immature bone collagen synthesis between the elderly and young men (NaCl fraction: 0.57±0.18 v 0.57±0.10 %.h −1 ; HOAc fraction: 0.23±0.10 v 0.24±0.05 %.h −1 respectively), but the rate of mature bone collagen synthesis was less in the elderly than the young men (pepsin fraction: 0.04±0.01 v 0.07±0.01 %.h −1 , P< 0.002; hot water fraction: 0.04±0.01 v 0.06±0.01 %.h −1 , P<0.002, respectively). In elderly women the pattern of rates of collagen synthesis was different to that in men with lower rates of immature collagen synthesis than in the young men (NaCl: 0.36 %.h −1 ; HOAc: 0.17 %.h −1 ) and higher rates of mature collagen synthesis (pepsin: 0.08 %.h −1 ; hot water: 0.08 %.h −1 ). Ageing in men does not appear to effect osteoblasts ability to synthesis collagen but extracellular processing into fibrillar collagen appears to be defective, whereas in women procollagen synthesis may be decreased. Supported by The Wellcome Trust, Diabetes UK, UK MRC, BBSRC.