Consumption of different sources of omega-3 polyunsaturated fatty acids by growing female rats affects long bone mass and microarchitecture

January 1, 2011 Human Health and Nutrition Data 0 Comments

Consumption of different sources of omega-3 polyunsaturated fatty acids by growing female rats affects long bone mass and microarchitecture

Year: 2011
Authors: Lukas, R. Gigliotti, J.C. Smith, B.J. Altman, S. Tou, J.C.
Publication Name: Bone
Publication Details: doi:10.1016/j.bone.2011.05.029


Omega 3 polyunsaturated fatty acids (n3 PUFAs) consumption has been reported to improve bone health. However, sources of n3 PUFAs differ in the type of fatty acids and structural form. The study objective was to determine the effect of various n3 PUFAs sources on bone during growth. Young (age 28 d) female Sprague Dawley rats were randomly assigned (n of 10/group) to a high fat 12% (wt) diet consisting of either corn oil (CO) or n3 PUFA rich, flaxseed (FO), krill (KO), menhaden (MO), salmon (SO) or tuna (TO) for 8 weeks. Bone mass was assessed by dual-energy X-ray absorptiometry (DXA) and bone microarchitecture by microcomputed tomography (μCT). Bone turnover markers were measured by enzyme immunoassay. Lipid peroxidation was measured by calorimetric assays. Results showed that rats fed TO, rich in docosahexaenoic acid (DHA, 22:6n3) had higher (P < 0.009) tibial bone mineral density (BMD) and bone mineral content (BMC) and lower (P = 0.05) lipid peroxidation compared to the CO fed rats. Reduced lipid peroxidation was associated with increased tibial BMD (r2 = 0.08, P  = 0.02) and BMC (r2 = 0.71, P = 0.01). On the other hand, rats fed FO or MO, rich in alpha-linolenic acid (ALA, 18:3n3), improved bone microarchitecture compared to rats fed CO or SO. Serum osteocalcin was higher (P = 0.03) in rats fed FO compared to rats fed SO. Serum osteocalcin was associated with improved trabecular bone micoarchitecture. The animal study results suggest consuming a variety of n3 PUFA sources to promote bone health during the growth stage. (Authors abstract)
After adolescence, bone formation begins to decline relative to the rate of bone resorption which eventually leads to bone loss. Loss of bone mineral and protein matrix leads to decreased bone strength and increased risk of osteoporosis. The omega-3 polyunsaturated fatty acids (n3 PUFAs) and lipid mediators derived from n3 PUFAs have been reported to have important roles in the regulation of bone metabolism. It has been reported that female rats fed flaxseed oil, rich in ALA, during the perinatal period improved bone mineral content (BMC) and bone mineral density (BMD) upon reaching adulthood (age 30 weeks). N3 PUFAs have been proposed to affect bone include altering calcium (Ca) balance, bone turnover, and inflammation. The n3 PUFAs also influence bone turnover by altering osteoclastic and osteoblastic differentiation and activity. The objective of this study was to determine the effects of feeding intact growing female rats different n3 PUFAs sources on bone mass, trabecular and cortical bone microarchitecture, and bone strength. This study demonstrated that growing female rats fed a high (12% by weight) fat diet as n3 PUFAs have a positive effect on the long bones. Rats fed FO had increased tibial trabecular bone microarchitecture indicated by significantly higher BV/TV compared to rats fed CO or SO. Rats fed FO or MO experienced significantly increased tibia trabecular number and connectivity compared to rats fed CO. Similarly, in the femur, rats fed FO or MO had higher BV/TV that was associated with a greater trabecular number and reduced trabecular separation compared to rats fed CO. The sources of ω-3 PUFA that improved bone microarchitecture quality were MO and particularly, FO. Thus ALA improved long bone microarchitecture in growing female rats. In our study, feeding sources of ω-3 PUFAs as FO or MO resulted in improved trabecular, but not cortical bone microarchitecture. This may be due to trabecular bone being more metabolically active and undergoing more rapid remodeling than cortical bone. KO-fed rats had lowerCa apparent absorption than FO-fed rats due to higher fecal Ca excretion. In the present study, rats fed FO showed improved trabecular bone microarchitecture compared to rats fed CO. In our study there was an association of increased serum osteocalcin concentration and improved trabecular bone microarchitecture parameters. Rats fed FO, rich in ALA, promoted bone formation indicated by higher serum osteocalcin and no differences in serum PYD compared to rats fed SO and TO. Rats fed FO or MO with the highest ALA content of the oil sources, resulted in improved bone microarchitecture associated with increased bone formation. None of the dietary sources of n3 PUFAs used in the study improved both bone mass and microarchitecture. Therefore, the study results suggest that rather than focusing on one source of n3 PUFAs, perhaps a variety of n3 PUFA sources including ALA, should be consumed in order to improve bone health during the growth stage. (Editors Comments)

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