Effect of zinc supplementation on ethanol-mediated bone alterations

Ethanol consumption leads to bone alterations, mainly osteoporosis. Ethanol itself may directly alter bone synthesis, but other factors, such as accompanying protein malnutrition--frequently observed in alcoholics, chronic alcoholic myopathy with muscle atrophy, alcohol induced hypogonadism or hypercortisolism, or liver damage, may all contribute to altered bone metabolism. Some data suggest that zinc may exert beneficial effects on bone growth. Based on these facts, we analyzed the relative and combined effects of ethanol, protein malnutrition and treatment with zinc, 227 mg/l in the form of zinc sulphate, on bone histology, biochemical markers of bone formation (osteocalcin) and resorption (urinary hydroxyproline excretion), and hormones involved in bone homeostasis (insulin growth factor 1 (IGF-1), vitamin D, parathormone (PTH), free testosterone and corticosterone), as well as the association between these parameters and muscle fiber area and liver fibrosis, in eight groups of adult Sprague Dawley rats fed following the Lieber de Carli model during 5 weeks. Ethanol showed an independent effect on TBV (F=14.5, p<0.001), causing it to decrease, whereas a low protein diet caused a reduction in osteoid area (F=8.9, p<0.001). Treatment with zinc increased osteoid area (F=11.2, p<0.001) and serum vitamin D levels (F=3.74, p=0.057). Both ethanol (F=45, p<0.001) and low protein diet (F=46.8, p<0.01) decreased serum osteocalcin levels. Ethanol was the only factor independently related with serum IGF-1 (F=130.24, p<0.001), and also showed a synergistic interaction with protein deficiency (p=0.027). In contrast, no change was observed in hydroxyproline excretion and serum PTH levels. No correlation was found between TBM and muscle atrophy, liver fibrosis, corticosterone, or free testosterone levels, but a significant relationship was observed between type II-b muscle fiber area and osteoid area (rho=0.34, p<0.01). Osteoporosis is, therefore, present in alcohol treated rats. Both alcohol and protein deficiency lead to reduced bone formation. Muscle atrophy is related to osteoid area, suggesting a role for chronic alcoholic myopathy in decreased bone mass. Treatment with zinc increases osteoid area, but has no effect on TBV.