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ORIGINAL RESEARCH ARTICLE

Isomer-Specific Effects of Conjugated Linoleic Acid on Mineralized Bone Nodule Formation from Human Osteoblast-LikeCells

Ilana Platt^*, Leticia G. Rao and Ahmed El-Sohemy^*,1

^* Department of Nutritional Sciences, University of Toronto, Toronto, Ontario M5S 3E2, Canada; Calcium Research Laboratory, Division of Endocrinology and Metabolism, St. Michael’s Hospital and Department of Medicine, University of Toronto, Toronto, Ontario M5B 1A6, Canada

To whom requests for reprints should be addressed at ¹ Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Fitzgerald Building, 150 College Street, Toronto, Ontario, Canada, M5S 3E2. E-mail: a.el.sohemy{at}utoronto.ca

Mixed isomers of conjugated linoleic acid (CLA) have been shown to have variable effects on bone formation and resorption in animals. The variable effects of CLA on bone physiology may be due to the different isomers present in common commercial preparations of CLA, and the effects of the predominant individual isomers (9cis,11trans and 10trans,12cis CLA) are not clear. The objective of this study was to determine the effects of individual and mixed isomers of CLA on mineralized bone nodule formation and alkaline phosphatase (ALP) activity in vitro using long-term cultures of SaOS-2 cells. Mineralized bone nodules were stained using the von Kossa method, and ALP activity in cell lysates was measured as a marker of early osteoblast differentiation. The 9cis,11trans isomer increased the number (~4- to 11-fold) and size (~2- to 5-fold) of mineralized bone nodules from 25 to 100 µM, but the 10trans,12cis isomer did not. The increase in mineralized bone nodule formation by 9cis,11trans CLA was accompanied by a variable increase in ALP activity. These results show that the 9cis,11trans isomer of CLA increases the formation of mineralized bone nodules using bone cells of human origin, and provide evidence for isomer-specific effects of CLA on bone health.

Key Words: conjugated linoleic acid • osteoporosis • SaOS-2 cells • bone • alkaline phosphatase