Dose response of bone mass to dietary arachidonic acid in piglets fed cow milk-based formula

Abstract

The addition of arachidonic acid (AA) and docosahexaenoic acid (DHA) to infant formula was recently approved in North America. In piglets, dietary AA is linked to elevations in bone mass. The objective was to investigate the effects of varied amounts of dietary AA on bone modeling and bone mass with the use of the piglet model for infant nutrition. Male piglets (n = 32) were randomly assigned to receive 1 of 4 formulas supplemented with AA (0.30%, 0.45%, 0.60%, or 0.75% of fat) plus DHA (0.1% of fat) from days 5 to 20 of life. Measurements included biomarkers of bone modeling, fatty acid status, and whole-body and femur bone mineral content; bone area was measured by dual-energy X-ray absorptiometry. Differences among groups were detected with two-factor analysis of variance. Regression analyses were used to determine factors responsible for bone mineral content after dietary AA was accounted for. Proportions of AA in plasma, liver, and adipose were modified by the dietary treatments, but bone modeling was not affected. Liver AA was positively related to plasma insulin-like growth factor 1 and calcitriol and urinary N-telopeptide. Whole-body bone mineral content was elevated in the piglets fed 0.60% and 0.75% AA and was best predicted by dietary AA and bone resorption. This study confirms that dietary AA alters bone mass and clarifies the best amount of AA to add to the diet of pigs born at term. Because the amount of dietary DHA was held constant, whether other amounts of DHA are related to bone mass requires investigation.