The present study was designed to determine whether Fructus Ligustri Lucidi (FLL) ethanol extract can directly regulate vitamin D metabolism both in vivo and in vitro.
Eleven-month-old, aged Sprague-Dawley sham-operated and ovariectomized (OVX) female rats were fed a normal-calcium (Ca) diet (0.6% Ca, 0.65% phosphorus) and received either FLL (700 mg/kg) or vehicle daily for 12 weeks. The in vitro effects of FLL on vitamin D metabolism were studied using primary cultures of the rat renal proximal tubules. mRNA and protein expressions of 25-hydroxyvitamin D-1α hydroxylase (1-OHase) and vitamin D receptor (VDR) in the kidney and proximal tubule were measured using real-time polymerase chain reaction and Western blotting, respectively. The concentrations of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) synthesized by renal 1-OHase were measured by a competitive enzyme immunoassay.
FLL treatment significantly increased serum 1,25(OH)2D3 levels in both sham (P < 0.01) and OVX (P < 0.05) rats. FLL increased renal 1-OHase and VDR protein and mRNA expressions in sham rats. Protein expression of renal 1-OHase, but not VDR, was also up-regulated in OVX rats during FLL treatment. 1-OHase mRNA and 1-OHase activity were increased by FLL treatment in primary cultures of renal proximal tubule cells.
FLL could increase the circulating levels of 1,25(OH)2D3 in vivo in aged female rats by directly stimulating 1-OHase activity. Thus, it might be an ideal oral agent that can help to improve the ability to induce 1,25(OH)2D3 synthesis and Ca balance in postmenopausal women who are of high risk of developing osteoporosis.
The present study demonstrates that Fructus Ligustri Lucidi ethanol extract can directly regulate vitamin D metabolism both in vivo and in vitro. Fructus Ligustri Lucidi might be an ideal oral agent for postmenopausal women to improve 1, 25(OH)2D3 biosynthesis and calcium balance.
From the 1Central Laboratory of the Institute of Molecular Technology for Drug Discovery and Synthesis, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, People's Republic of China; 2Department of Medical Psychology and Psychiatry, Medical College of Qingdao University, Qingdao, People's Republic of China; 3Shenzhen Research Institute of The Hong Kong Polytechnic University, State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Shenzhen, People's Republic of China; 4Center of System Biomedical Sciences, University of Shanghai for Science and Technology, Shanghai, People's Republic of China; and 5School of Chinese Medicine, The Chinese University of Hong Kong, Hong Kong SAR, People's Republic of China.
Received February 3, 2010; revised and accepted March 16, 2010.
Funding/support: This work was supported by the Niche Area Research Scheme (1-BB8N) and Research Studentship from the Research Committee of The Hong Kong Polytechnic University.
Financial disclosure/conflicts of interest: None reported.
Address correspondence to: Man-Sau Wong, PhD, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, People's Republic of China. E-mail: bcmswong@polyu.edu.hk
