Disuse exaggerates the detrimental effects of alcohol on cortical bone.
BACKGROUND
Alcohol abuse is associated with an increased risk for osteoporosis. However, comorbidity factors may play an important role in the pathogenesis of alcohol-related bone fractures. Suboptimal mechanical loading of the skeleton, an established risk factor for bone loss, may occur in some alcohol abusers due to reduced physical activity, muscle atrophy, or both. The effect of alcohol consumption and reduced physical activity on bone metabolism has not been well studied. The purpose of this study was to determine whether mechanical disuse alters bone metabolism in a rat model for chronic alcohol abuse.


METHODS
Alcohol was administered in the diet (35% caloric intake) of 6-month-old male rats for 4 weeks. Rats were hindlimb-unloaded the final 2 weeks of the experiment to prevent dynamic weight bearing. Afterward, cortical bone histomorphometry was evaluated at the tibia-fibula synostosis.


RESULTS
At the periosteal surface of the tibial diaphysis, alcohol and hindlimb unloading independently decreased the mineralizing perimeter, mineral apposition rate, and bone formation rate. In addition, alcohol, but not hindlimb unloading, increased endocortical bone resorption. The respective detrimental effects of alcohol and hindlimb unloading to inhibit bone formation were additive; there was no interaction between the two variables.


CONCLUSIONS
Reduced weight bearing accentuates the detrimental effects of alcohol on cortical bone in adult male rats by further inhibiting bone formation. This finding suggests that reduced physical activity may be a comorbidity factor for osteoporosis in alcohol abusers.
Hefferan
Theresa E
TE
Department of Orthopedics, Mayo Clinic, Rochester, Minnesota 55905, USA.
Kennedy
Angela M
AM
Evans
Glenda L
GL
Turner
Russell T
RT
D000818:Animals; D001862:Bone Resorption / Q000139:chemically induced / Q000473:pathology; D000431:Ethanol / Q000494:pharmacology*; D019417:Hindlimb Suspension / Q000009:adverse effects*; D008297:Male; D010012:Osteogenesis / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D011916:Rats, Inbred F344; D013977:Tibia / Q000187:drug effects* / Q000473:pathology / Q000502:physiology
D000431:Ethanol