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Title: ETHANOL-INDUCED INHIBITION OF ANABOLIC BONE REBUILDING IN POST-WEANING RATS INVOLVES INCREASED OXIDATIVE STRESS AND TNF-ALPHA IN RATS FED VIA TOTAL ENTERAL NUTRITION

Author
item SHANKAR, KARTIK - ACNC/UAMS
item HIDESTRAND, MATS - ACNC/UAMS
item LIU, XIAOLI - ACNC/UAMS
item CHEN, JINRAN - ACNC/UAMS
item PERRIEN, DANIEL - UAMS
item SKINNER, ROBERT - UAMS
item LUMPKIN, CHARLES - ACHRI/UAMS
item BADGER, THOMAS - ACNC/UAMS
item RONIS, MARTIN - ACNC/UAMS

Submitted to: Endocrine Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2006
Publication Date: 6/23/2006
Citation: Shankar, K., Hidestrand, M., Liu, X., Chen, J., Perrien, D., Skinner, R.A., Lumpkin, C.K., Badger, T.M., Ronis, M.J. 2006. Ethanol-induced inhibition of anabolic bone rebuilding in post-weaning rats involves increased oxidative stress and tnf-alpha in rats fed via total enteral nutrition [abstract]. The Endocrine Society, 88th Annual Meeting, June 23-27, 2006, Boston, Massachusetts. 2006 CDROM. Program No. P3-70.

Interpretive Summary: Consumption of alcohol (ethanol) during pregnancy remains to be an important public health issue, primarily due the effects on the growing baby. However, the harmful effects of alcohol on the mother, especially on the maternal skeleton remain unclear. Specifically, the post-lactation period when active rebuilding of the skeleton in the mother is occurring is a period susceptible to the detrimental effects of alcohol. To examine this issue we have undertaken studies using post-weaning rats and fed them nutritionally sufficient diets either with or without alcohol. The studies show that consumption of alcohol is harmful to the bones, as both the density and mineral content of the bones (and hence strength) were decreased in rats consuming alcohol. Further, the way alcohol causes this decrease in bone health appears to be related to the ability of alcohol to produce harmful reactive intermediates in the bone called reactive oxygen species. These appear to activate chemical signals called cytokines (like TNF-Alpha) and halt the formation/maturation of new bone forming cells (osteoblasts). These effects of alcohol can be reversed by antioxidants like N-acetyl cysteine. Further, our studies also indicate that consumption of alcohol diverts the new bone forming oteoblasts to become fat-laden adipocytes, hence decreasing the strength and density of the bone. These findings may have important implications for the long-term health consequences of post-weaning mothers consuming alcohol.

Technical Abstract: Lactation-induced bone loss is promptly restored in the post-weaning period by a process of anabolic rebuilding, the endocrine and molecular basis of which still remains enigmatic. Ethanol (EtOH) consumption during this post-weaning period prevents the recovery of bone density and may be a significant risk factor in predisposing to later-life osteoporosis. To investigate the molecular mechanisms underlying EtOH-induced inhibition of anabolic rebuilding, time impregnated Sprague Dawley rats (n = 10/group) were intragastrically cannulated. Litters were culled to 5 female and 5 male pups/dam and total litter weights/per dam equalized. All dams were chow-fed ad libitum throughout gestation and lactation until weaning (PND17). Following weaning, dams were fed either isocaloric control or EtOH (13 g/kg/d) containing liquid diets at 220 Kcal/kg/d, via total enteral nutrition. In separate experiments, control and EtOH-fed groups were given either recombinant sTNF-R1 (2 mg/kg, sc, in PBS every other day, Amgen, Thousand Oaks, CA) or dietary N-acetyl cysteine (NAC, 1.2 g/kg/d). After two weeks of infusion, all rats were sacrificed and serum, left and right tibia were collected. pQCT analyses showed that trabecular BMD was 21% lower in the EtOH-fed group compared to control rats at 2 weeks post-weaning. 'Ct analyses showed increased trabecular spacing (~200%) and decreased BV/TV (to ~ 45% of control) and connective density (to ~ 33% of control) by EtOH (p<0.05). Dietary NAC consumption reversed both the loss in trabecular BMD and changes observed by 'CT. Histomorphometric analyses of H&E stained tibia from EtOH-fed rats revealed marked (~ 300%) increase in fat volume (fatV/TV) and profound reduction (to ~ 40% of control) in BV/TV, suggesting a shift in commitment and/or differentiation of osteoblast progenitor cells towards adipocyte lineage. Consistent with these data, mRNA expression of adipocyte specific PPAR-' and aP2 was increased (p<0.05) in bone-marrow of EtOH-fed rats. NAC consumption remarkably reversed the adipogenic changes induced by EtOH, suggesting a role for oxidative stress in this process. In addition, immunostaining of TNF-' was ~ 500% greater in EtOH-fed rats, an effect abolished by NAC treatment. Further, treatment of rats with sTNF-R1 also rescued rats from EtOH-induced bone loss, mechanistically linking increased oxidative stress and TNF-' in mediating EtOH-bone loss and altered differentiation of osteoblast precursors into adipocytes.