Lactation Biology: Biology of Lactation

Mice raised on a coconut oil (CO)-containing diet for 6 wk prior to the addition of conjugated linoleic acid (CLA) are more sensitive to CLAinduced body fat loss than mice raised on a soy oil (SO)-containing diet. Coconut oil is deficient in essential fatty acids. However the addition of linoleic acid to a CO-containing diet did not alter the enhanced sensitivity to CLA. The objective of this study was to determine if CO enhances sensitivity of mice to CLA-induced body fat loss independent of an essential fatty acid deficiency. Eighty male mice (12 wk old) were fed a purified SO-containing diet for a 1 wk adaptation. Mice were then blocked by body weight and randomly allotted to a treatment diet. Diets were arraigned in a 2 x 2 factorial design with SO vs CO and 0 vs 0.5% CLA isomers. Mice were fed for 2 wk and body weight and feed intake were measured weekly. Mice were then killed and body fat and lean mass were determined by dual x-ray densitometry and fat pads and livers were weighed and collected. DNA fragmentation, indicative of apoptosis, was measured in one epididymal fat pad and is expressed as (fragmented DNA/total DNA)*100. CO-fed mice consumed more (P < 0.05) feed than SO-fed mice during both weeks of treatment but weighed less (P < 0.05) in the second wk. CO+CLA mice consumed less feed than CO mice but SO and SO+CLA mice did not differ in feed intake (CO x CLA interaction, P < 0.05). Both CO and CLA reduced (P < 0.001) body fat and fat pad weights. There was a trend for a CO x CLA interaction (P = 0.06) as CO+CLA mice were leaner than SO+CLA (11.94% vs 15.48% body fat, respectively). There were no differences in lean mass. CLA increased (P < 0.01) liver weight. There were no differences in DNA fragmentation but CLA did increase (P < 0.001) total DNA content of the fat pad. In summary both CO and CLA reduced body fat with a trend for an interaction. Therefore, feeding CO for a short time appears to increase the sensitivity of mice to CLA-induced body fat loss similar to a longer feeding period. This indicates that CO increases CLA-induced body fat loss in an essential fatty acid deficiency-independent manner.