Improvement of bone quality in gonad-intact middle-aged male rats by long-chain n-3 polyunsaturated fatty acid

The effect of long-chain n-3 polyunsaturated fatty acid (PUFA) on bone measurements was evaluated in gonad-intact middle-aged male rats. Seven rats were killed on day 0 of dietary intervention to determine bone parameters at baseline. Experimental rats (7/group) were fed one of the following lipid treatments (g/kg diet): 167 g safflower oil + 33 g menhaden oil (N6+N3 diet, control), 200 g safflower oil (N6 diet), or 190 menhaden oil + 10 g corn oil (N3 diet). After 20 weeks of dietary treatment, all groups had lower values for peak load and ultimate stiffness in femurs compared to baseline values. Rats fed the N3 diet had the highest values for peak load, ultimate stiffness, and Young's modulus compared with those fed the N6 and control diets. Compared to baseline, all dietary treatment groups had significantly lower values for trabecular thickness and number in proximal tibia but higher values for trabecular separation and formation rate in proximal tibia and endocortical bone formation rate in tibial shaft. Compared with the control group, rats fed the N3 diet had lower values for formation rate, osteoclast number, and eroded surface in proximal tibia but higher values for periosteal mineral apposition and formation rates in tibia shaft. These findings indicate that a diet rich in long-chain n-3 PUFA mitigate aging-induced loss of bone integrity in intact middle-aged male rats through reducing bone turnover rate by suppressing both bone formation and resorption as a result of a larger net bone volume and modulating endocortical and cancellous bone compartments.