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The effect of dietary n-3 fatty acids on prostaglandin E2 (PGE2) and leukotriene C4 (LTC4) levels in rat salivary glands and gingiva was examined in two separate nutritional studies. In the first set of experiments, two groups of male weanling Sprague-Dawley rats were fed semipurified diets containing 10% corn oil (control group) or 10% menhaden oil (experimental group). Rats were killed after 8 wk on the diets; the fatty acid composition of total phospholipids and the concentrations of PGE2 and its precursor, arachidonic acid, were measured in gingiva and submandibular salivary glands (SMSG). Dietary n-3 fatty acids were incorporated into the tissue phospholipids. Arachidonic acid levels were reduced by 56% in gingiva and SMSG of rats fed menhaden oil compared with the control rats fed the diet containing corn oil. The concentrations of PGE2 in SMSG and gingiva of rats fed the diet containing menhaden oil were reduced by 74% and 83%, respectively. In a subsequent nutritional study, we tested whether the diet-induced reduction in tissue arachidonic acid levels would also result in a corresponding decrease in LTC4 production. Three groups of rats were fed diets containing 5% corn oil (group 1), 4% ethyl ester concentrate of n-3 fatty acids plus 1% corn oil (group 2), or 5% ethyl ester concentrate of n-3 fatty acids (group 3). After 6 wk of feeding, gingiva and SMSG were analyzed for arachidonic acid content and in vitro production of LTC4.(ABSTRACT TRUNCATED AT 250 WORDS)

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A previous study showed that certain dietary lipids can alter arachidonic acid concentrations in alveolar bone. Because arachidonic acid is a precursor of prostaglandin (PG) E2, which is known to play an important role in orthodontic tooth movement, the purpose of the present study was to determine the effect of dietary lipids on PGE2 levels and tooth movement. Two groups of male Sprague-Dawley rats (20/group) were fed nutritionally adequate purified diets containing 10% corn oil (group I, rich in n-6 fatty acids) or 9% ethyl ester concentrate of n-3 fatty acids + 1% corn oil (group II rich in n-3 fatty acids). After 5 weeks of feeding the diets, orthodontic force of 56 g was applied to the maxillary incisors to tip them distally. Prior to killing the rats at day 4 and 8 of orthodontic force application, tooth movement was measured by computerized image analysis. Premaxillae were dissected out free of soft tissue and incisors. The alveolar bone was frozen in liquid nitrogen, pulverized, and lipids were extracted. The concentrations of arachidonic acid and fatty acid composition of total phospholipids were measured by gas chromatography. PGE2 levels were measured by enzyme immunoassay. Arachidonic acid and PGE2 concentration were significantly lower (P < 0.001) in alveolar bone of rats in group II than in group I. The tooth movement was also significantly lower (P < 0.02) in group II than in group I at both 4 and 8 days. The results suggest that PGE2 levels in alveolar bone and orthodontic tooth movement can be affected by the type of dietary fat.

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