Actions
of Conjugated Linoleic Acid on Bone Metabolism
Bruce Watkins(1,2), Yong Li(1),
Hugh Lippman(1), Shulin Feng(1),
Mark Seifert(2)
(1)Department of Food Science, Center for Enhancing Foods
to Protect Health, Purdue University
(2)Department of Anatomy and Cell Biology, IU School of Medicine
Investigations on conjugated linoleic acid (CLA) in growing male rats, estrogen-deficient OVX rats, and osteoblast cell cultures indicate that the amount and type of CLA isomers influence bone metabolism. The actions of CLA isomers include their effects on moderating bone modeling, serum biomarkers of bone formation, transcription factors associated with osteoblast differentiation, and nodule formation in calvarial cell cultures. Supplementing diets with CLA isomers resulted in their enrichment in all bone tissue compartments of rats. When supplied at 1% of the diet to male rats CLA isomers depressed ex vivo PGE2 production in bone organ culture, serum IGF-I, and bone formation rate. In a subsequent study, a lower dietary level (0.5%) of CLA rescued bone formation rate in male growing rats that were given a diet containing a high level of n-6 fatty acids. Decreases in serum osteocalcin level and bone specific alkaline phosphatase activity were observed in rats fed CLA. Studies also demonstrated that CLA reduced transcription factor proteins involved in osteoblast differentiation. DEXA analysis of bone mineral content in OVX rats did not improve with CLA supplementation. Research on CLA revealed that the actions of these isomers in rat bone are dependent on the type of CLA isomer and the dietary ratio of n-6/n-3 fatty acids.
