Enhanced lumbar spine bone mineral content in piglets fed arachidonic acid and docosahexaenoic acid is modulated by severity of growth restriction

The small size for gestational age (SGA) neonate has reduced bone mass, even after adjustment for body size, compared with those born appropriate size for gestational age (AGA). The SGA neonate also has low arachidonic acid (AA) and DHA status at birth. Data from a variety of animal models clearly indicate that dietary n-3 and n-6 long-chain PUFA positively influence bone mass and metabolism. However, such intervention has never been applied to the SGA neonate and since they are born with lower long-chain PUFA status it is possible that a higher amount of supplementation is required. The objective of the present study was to test for such benefits of long-chain PUFA in the SGA piglet that is known to have low bone mass at birth and to establish if a dose–response relationship exists based on severity of growth restriction.
Therefore in the present 15 d study, two levels of dietary AA and DHA (6:1 ratio of AA:DHA diets, 0.6:0.1 or 1.2:0.2 g/100 g dietary fat) vs. a control diet were tested for effects on growth, fatty acid status, whole-body and regional bone mineral content (BMC) and metabolism in SGA piglets categorised as either very low birth weight (VLBW; <1,0 kg; n 12) or low birth weight (LBW; 1.1 to 1.2 kg; n 18).

Growth was not influenced by diet, yet the LBW piglets fed 0.6:0.1 AA and DHA as g/100 g fat had elevated BMC in the spine, whereas the VLBW piglets had higher BMC of the spine if fed the higher intake of AA and DHA. In both weight categories, the higher intake of AA and DHA lowered bone resorption relative to controls, whereas bone formation was unchanged. Tissue fatty acid concentrations reflected dietary AA and DHA, especially trabecular bone of VLBW piglets. Whether the enhanced lumbar spine BMC is due to enhanced Ca absorption and thus suppression of bone resorption remains to be established.