Cannabinoid receptor expression in femora and tibiae of C57/blk6 mice fed DHA and relationship to bone ash and BMC (1032.2)

Abstract

Although the endocannabinoid system (ECS) acts in most peripheral tissues its biology remains largely unexplored in organs besides the brain. The ECS utilizes cannabinoid receptors, CB1 and CB2, and lipid ligands derived from polyunsaturated fatty acids (PUFA) including the n‐3 PUFA. Given the current epidemic of osteoporosis we sought to examine the role of the ECS in bone. Male C57/blk6 mice were fed a semi‐purified diet (AIN 93M) with either DHA (n‐3 PUFA) containing lipid or control lipid for 118 d to assess changes in growth and skeletal metabolism. No difference was observed in body weight during the study. Mice femora and tibiae were collected at 62 and 118 d of the feeding study. DXA analysis showed a higher BMC per body weight in mice after 62 d of DHA feeding compared to the controls. Femora and tibiae ash weight was higher in the DHA fed mice at 118 d. At day 118, mice on both diets were found to have higher expression of CB1 than CB2 in subarticular chondrocytes in the femur and to a lesser extent in tibiae. In trabecular bone, DHA fed mice had a higher level of CB2 expression compared to controls. It is noteworthy that CB2 has been previously shown to promote osteoblast bone remodeling. Taken together, these findings demonstrate that DHA diet fed mice have a higher BMC per body weight and femora/tibiae ash that may be associated to a change in the skeletal topography of the ECS receptors.