EFFECT OF DIETARY DOCOSAHEXAENOIC ACID ON IN-VITRO THERMOGENESIS AND FATTY-ACID COMPOSITIONS OF BROWN ADIPOSE-TISSUE

Brown adipose tissue (BAT) is a major organ of nonshivering thermogene sis during cold acclimation, overfeeding, and nonthermal restraint str ess. An increased unsaturation of fatty acids of membrane phospholipid in BAT has been shown to be closely associated with an enhanced funct ion of this tissue as reported in other tissues. In the previous study , we found that among fatty acids detected, the n-3 polyunsaturated fa tty acid docosahexaenoic acid (DHA) in BAT phospholipid is the only fa tty acid that altered concomitantly with a change in the in vitro ther mogenic capacity for nonshivering thermogenesis of BAT from cold accli mated and restrained rats. To examine the effect of dietary DHA on fat ty acid composition of phospholipid and in vitro BAT thermogenic activ ity, rats were fed a standard diet supplemented with purified DHA for 4 or 16 weeks. Dietary DHA for 4 or 16 weeks increased DHA level in BA T phospholipid, and it also decreased arachidonic acid. The unsaturati on index increased and remained unchanged under DHA feeding for 4 and 16 weeks, respectively. In vitro thermogenic activity of BAT remained unchanged and decreased under dietary DHA for 4 and 16 weeks, respecti vely. These findings indicate that dietary DHA could increase DHA leve l in phospholipid of BAT, but it could not improve in vitro BAT thermo genic response.