Long-term alcohol consumption in the rat affects femur cross-sectional geometry and bone tissue material properties

Background: Alcohol consumption previously has been demonstrated to reduce the density and strength of cortical bone of young, actively growing rats. Osteoblast activity and trabecular bone volume were also significantly lowe r. A germane question arising from these studies is whether the detrimental effects would persist into adulthood. To address this issue, a long-term s tudy was undertaken with animals that consumed alcohol throughout their lif e and into old age. Methods: One-month-old female Sprague-Dawley rats were divided into three d iet groups: alcohol-fed, pair-fed, and chow-fed. The alcohol-fed animals re ceived a modified Lieber-DeCarli diet that contained 35% ethanol-derived ca lories. The pair-fed group served as a caloric-equivalent control, and the chow-fed animals served as a completely untreated control. Animals were eut hanized after five time periods on the diets that represented three stages of the life span: young (3 months), adult (6, 9, 12 months), and aged (18 m onths). The left femur was isolated and mechanically tested in 3-point bend ing for mechanical properties. Results: In the young animals, alcohol consumption produced dramatic reduct ions in both extrinsic (whole bone) and intrinsic (tissue material) propert ies, which is consistent with results from previous studies on growing rats . For the adult animals, however, the alcohol groups were only slightly low er and the differences were not statistically significant. The aged animals showed diminished properties due to alcohol, but only for the intrinsic ma terial properties. The extrinsic properties remained similar to controls as a result of greater radial expansion in the femur diaphysis. Despite the c ross-sectional areas being the same, this expansion gave rise to higher cro ss-sectional moment of inertia values in the alcohol animals. The thickness of the cortical wall was lowest in the alcohol group at all time points. Conclusions: Long-term alcohol consumption produced two major effects in th e oldest animals studied: the quality of the cortical bone tissue was dimin ished, as evidenced by reduced elastic modulus and ultimate strength values , and the bone seemed to compensate for this by expanding the cross-section to produce larger cross-sectional moment of inertia values. The reduced bo ne tissue quality is consistent with the lower ash percent values in the al cohol animals, but other factors such as the quality of the collagen and mi neral crystal may also be important contributors.