Dietary Ratio of PUFAs and DHA

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J Nutr Biochem. 2005 Aug 12; [Epub ahead of print]

Dietary ratio of n-6/n-3 PUFAs and docosahexaenoic

acid: actions on bone mineral and serum biomarkers in

ovariectomized rats.

Watkins BA, Li Y, Seifert MF.

Center for Enhancing Foods to Protect Health, Lipid

Chemistry and Molecular Biology Laboratory, Purdue

University, West Lafayette, IN 47907-2009, USA;

Department of Anatomy and Cell Biology, Indiana

University School of Medicine, Indianapolis, IN 46202,

USA.

Hypoestrogenic states escalate bone loss in animals

and humans. This study evaluated the effects of the

amount and ratio of dietary n-6 and n-3

polyunsaturated fatty acids (PUFAs) on bone mineral in

3-month-old sexually mature ovariectomized (OVX)

Sprague-Dawley rats. For 12 weeks, the rats were fed

either a high-PUFA (HP) or a low-PUFA (LP) diet with a

ratio of n-6/n-3 PUFAs of 5:1 (HP5 and LP5) or 10:1

(HP10 and LP10). All diets (modified AIN-93G) provided

110.4 g/kg of fat from safflower oil and/or

high-oleate safflower oil blended with n-3 PUFAs

(DHASCO oil) as a source of docosahexaenoic acid

(DHA). Fatty acid analyses confirmed that the dietary

ratio of 5:1 significantly elevated the amount of DHA

in the periosteum, marrow and cortical and trabecular

bones of the femur. Dual-energy X-ray absorptiometry

measurements for femur and tibia bone mineral content

(BMC) and bone mineral density showed that the

DHA-rich diets (HP5 and LP5) resulted in a

significantly lower bone loss among the OVX rats at 12

weeks. Rats fed the LP diets displayed the lowest

overall serum concentrations of the bone resorption

biomarkers pyridinoline (Pyd) and deoxypyridinoline,

whereas the bone formation marker osteocalcin was

lowest in the HP groups. Regardless of the dietary

PUFA content, DHA in the 5:1 diets (HP5 and LP5)

preserved rat femur BMC in the absence of estrogen.

This study indicates that the dietary ratio of n-6/n-3

PUFAs (LP5 and HP5) and bone tissue concentration of

total long-chain n-3 PUFAs (DHA) minimize femur bone

loss as evidenced by a higher BMC in OVX rats. These

findings show that dietary DHA lowers the ratio of

18:2n-6 (linoleic acid)/n-3 in bone compartments and

that this ratio in tissue correlates with reduced Pyd

but higher bone alkaline phosphatase activity and BMC

values that favor bone conservation in OVX rats.

PMID: 16102959 [PubMed - as supplied by publisher]

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