식이성지방 n-6/n-3비(1 : 2) 및 포화지방산:단순불포화지방산:다가불포화지방산비(1:1:1)를 일정하게 조정한 조건하에서 n-3계 지방산, ${alpha}-LA(C_{18:3}),;EPA(C_{20:5}),;DHA(C_{22:6})$를 함유시킨 식이를 조제하여 성장기 SD-계 흰쥐 수컷에 2주간 급여하여 간장, 혈청의 Triacylglycerol(TG)농도 및 간장 TG 합성에 관여하는 효소 활성에 대하여 검토하였다. 본 실험에 사용한 EPA 및 DHA 는 순도 98%로서 고도로 정제한 ethyl ester 형태로 식이에 첨가하였다. 그 결과, ${alpha}-LA$군에 비하여 EPA군 및 DHA군에서 간장 및 혈청 TG 농도는 유의적으로 감소하였으나, 총콜레스테롤 농도는 유의차가 인정되지 않았다. 간장의 인지질 농도는 DHA군에서만 유의적으로 증가하였다. 간장 막 결합성 phosphatidate phosphohydrolas(PAP)성은 간장TG 농도와 같은 경향으로서 EPA와 DHA군에서 유의하게 감소하였으며 Diacylglycerol acyltransferase(DGAT) 활성은 각 군간에는 변화가 없었다. 따라서, 간장TG 농도와 간장 막결합성 PAP활성과의 사이에 높은 상관관계(r=0.84)를 나타내어 간장TG 합성억제가 인정되었다. 지방산 합성계 효소의 활성도는 EPA및 DHA군에서 감소하였다. 이상의 결과로부터 n-3계 지방산, EPA 및 DHA에 의한 간장 및 혈청 TG 농도의 감소는 막 결합형 PAE 활성과 저해에 의한 간장TG 합성 및 지방산 합성 저해가 관여하는 것이 시사되었다.
We studied the difference effects of dietary ${alpha}-linolenic;acid;({alpha}-LA,;18:3;n-3)$, eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) on the lowering of triacylglycerol in the liver and serum on lipid metabolism in rats. Rats were fed semipurified diets containing 10% fat with constant polyunsaturated/monounsaturated/saturated fatty acids (1:1:1) and n-6/n-3 ratio (1:2). EPA (98%) and DHA (98%) were added in diets as the ethyl esters. The concentration of liver triacylglycerol was significantly lower in rats fed both EPA and DHA than in those fed ${alpha}-LA$. The concentration of liver phospholipid was significantly higher in rats fed DHA than in those fed ${alpha}-LA$ and EPA. Both EPA and DHA reduced serum triacylglycerol concentration compared with ${alpha}-LA$, but this effect was more pronounced in the EPA diet. The activity of phophatidate phosphohydrolase in the liver microsome was significantly lower in rats fed both EPA and DHA than in those fed ${alpha}-LA$. but, there was no significant difference on the activities of diacylglycerol acyltransferase among the three groups. The concentration of liver triacylglycerol were correlated with changes in the microsomal phosphatidate phosphohydrolase activity (r=0.84). Hepatic NADPH generating enzyme, glucose-6-phosphate dehydrogenase was more effective to reduce the activity in rats fed both EPA and DHA than in those fed ${alpha}-LA$. In conclusion, EPA or DHA reduced the hepatic triacylglycerol concentration by inhibiting microsomal phosphatidate phosphohydrolase, thereby inhibiting synthesis of triacylglycerol in the liver.
