Smoking has been associated with low bone density, fractures and poor intestinal calcium absorption. Calcium absorption is a critical factor in calcium balance in postmenopausal women but the mechanisms causing decreased absorption efficiency in postmenopausal smokers are controversial and poorly defined. We performed a cross-sectional study of 405 postmenopausal women attending a clinic for the management of osteoporosis to compare intestinal calcium absorption efficiency, serum vitamin D metabolites and parathyroid hormone levels in postmenopausal women who had never smoked, who were smokers previously or who were current smokers, to examine the relationships between these variables in smokers. Two hundred and fifty-two of the women had never smoked, 79 had smoked previously and 74 were current smokers. The hourly fractional rate of calcium absorption was similar in non-smokers and those who had previously smoked. Radiocalcium absorption was less in the 74 smokers compared with the 331 non-smokers [0.60 (0.29 SD) vs 0.71 (0.27); p = 0.004], as were serum calcitriol (p<0.001) and parathyroid hormone (PTH) (p<0.01). There was no difference in the relationship between calcium absorption and serum calcitriol between smokers (r = 0.38) and non-smokers (r = 0.28); hence the impaired calcium absorption in the smokers was almost entirely attributable to suppression of the PTH-calcitriol endocrine axis. In postmenopausal women smoking is associated with a reduction in calcium absorption efficiency due to suppression of the PTH-calcitriol axis. This impairment of calcium absorption could lead to accelerated bone loss and limit the usefulness of dietary calcium supplementation.

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Cells respond to changes in the environment by altering their phenotype. The ability to influence cell behavior by modifying their environment provides an opportunity for therapeutic application, for example, to promote faster wound healing in response to skin injury. Here, we have modified the preparation of an aluminium oxide template to generate large uniform membranes with differing nano-pore sizes. Epidermal cells (keratinocytes) and dermal cells (fibroblasts) readily adhere to these nanoporous membranes. The pore size appears to influence the rate of cell proliferation and migration, important aspects of cell behavior during wound healing. The suitability of the membrane to act as a dressing after a burn injury was assessed in vivo; application of the membrane demonstrated adherence and conformability to the skin surface of a pig, with no observed degradation or detrimental effect on the repair. Our results suggest that keratinocytes are sensitive to changes in topography at the nanoscale level and that this property may be exploited to improve wound repair after tissue injury.