Effects of alpha-Lipoic Acid on Bone Metabolism in Rats with Low Bone Mass

Abstract

Background: Growing evidence has shown a biochemical link between increased oxidative stress and reduced bone density. In our previous study, α-lipoic acid (α-LA), a thiol antioxidant, suppressed both osteoclastogenesis and bone resorption, and also prevented TNF-α-induced apoptosis of osteoblast lineages. The effects of α-LA were investigated on bone metabolism in rats with a low bone mass. Methods: An ovariectomy (OVX) or Talc injection (inflammation-mediated osteopenia, IMO) was performed in 12 week old female Sprague-Dawley rats. Diets cont aining either 0.3%, 0.5% or 1.0% α-LA were administered to the OVX rats for 16 weeks, and to the IMO rats for 21 days. The bone mineral densities (BMD) of the anterior-posterior lumbar spine and total femur were measured using dual-energy X-ray absorptiometry (Hologic QDR 4500-A), with small animal software. The plasma bone specific alkaline phosphatase activity (BSAP) and urinary free deoxypyridinoline concentration (DPD) were determined using enzyme immunoassay methods. Results: The body weights were significantly decreased in the OVX rats on the diets containing 0.3 and 0.5% α-LA than in the OVX control. No significant differences in the BMD at either site were noted between rats administered the diets with or without α-LA. However, the administration of various doses of α-LA noticeably decreased the level of urinary DPD in both the OVX a nd IMO rats. High doses of α-LA (0.5% and/or 1.0%) also decreased the levels of plasma BSAP in both models. Conclusion: Although no increase in BMD was demonstrated by the administration of α-LA, these results suggest that α-LA suppresses the rates of bone turnover in rats with a low bone mass (J Kor Soc Endocrinol 20:476～487, 2005).