This study evaluated the effect of a fat blend containing long-chain (LC) n-3 PUFA on bone mineral density (BMD) and bone metabolism in gonad-intact middle-aged male rats (12 months old, n 28). Seven rats were killed on day 0 of dietary intervention to determine the baseline BMD. The remaining rats (seven per group) were fed a diet with one of the following dietary lipid treatments (g/kg diet): 167 g safflower oil þ 33 g menhaden oil (N6 þ N3 diet, control), 200 g safflower oil (N6 diet, almost devoid of LC n-3 PUFA), or 190 g menhaden oil þ 10 g corn oil (N3 diet, rich in LC n-3 PUFA) for 20 weeks. After 20 weeks, all dietary treatment groups had a lower BMD compared with the baseline reference. However, rats fed the N3 diet had the highest bone mineral content and cortical þ subcortical BMD compared with those fed the N6 and control N6 þ N3 diet. Compared with the control (N6 þ N3) group, rats fed the N3 diet had higher values for serum insulin-like growth factor-I, parathyroid hormone, 1,25-(OH) 2 vitamin D 3 and bone-specific alkaline phosphatase activity, but lower bone NO production and urinary Ca, whereas rats fed the N6 diet had higher bone prostaglandin E 2 production and serum pyridinoline. These findings indicate a protective action of LC n-3 PUFA on ageing-induced bone loss in gonad-intact middle-aged male rats through a modulation of local factors and systemic calcitrophic hormones.
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.
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