Abstract
This study was carried out to investigate the effects of different sources and level of dietary lipid on lecithin : cholesterol acyltrasferase activity and cholesterol metabolism in male rats of Sprague-Dawley strain. The effects of different lipid sources was compared with sardine oil($\omega$3 EPA and DHA), beef tallow(SFA), perilla oil($\omega$3 linolenic acid) and corn oil($\omega$6 linoleic acid). Diets were formulated in such a way that 10%, 20% and 40% dietary energy were supplied with each of four experimental lipid sources. Control diet contained only non-lipid energy. A total number of 78 rats, equally divided into 13 groups, were fed the experimental diets for a period of 6 weeks. In vitro cultures were also carried out to study the cholesterol synthetic activity in the liver prepared from rats used in feeding trials. The concentration of plasma total cholesterol, HDL-cholesterol, LDL-cholesterol and HDL-C/T/C(total cholesterol) ratio were significantly (p<0.001) influenced by dietary lipid sources. Higher HDL-cholesterol and lower LDL-cholesterol concentration in plasma were obtained in rats fed $\omega$3 fatty acid supplemented diets(sardine oil and perilla oil group) compared to diets containing $\omega$6 and saturated fatty acid(corn oil and beef tallow group). In total cholesterol concentration of plasma, beef tallow group was significantly (p<0.001) higher than other lipid groups, and non-lipid group was significantly(p<0.05) higher than the lipid supplemented groups. The activity of lecithin : cholesterol acyltransferase(LCAT) in plasma was greatly(p<0.001) affected by dietary lipid sources and levels. In LCAT acivity of plasma, lipid supplemented groups were significantly(p<0.05) higher than non-lipid group, vegetable oil groups were significantly (p<0.001) higher than animal fat groups, and sardine oil group were significalylty (p<0.001) higher than beef tallow group. Also perilla oil group was significanlty (p<0.05) higher than corn oil group, and sardine oil group was significantly (p<0.05) higher than perilla oil group. Low lipid group, compared with medium or high lipid group, showed higher activity of LCAT in plasma. In cholesterol synthetic activity of liver tissues culture, sardine oil group($\omega$3 EPA and DHA) was significantly(p<0.001) higher than other lipid groups, non-lipid group was significantly(p<0.001) higher than the lipid supplemented groups, and amimal fat group were significantly(p<0.001) higher than vegetable oil groups, but the synthetic activity was not affected by dietary lipid levels.
본 실험은 식이내 지방의 종류와 수준이 흰쥐의 LCAT활성 및 콜레스테롤 대사에 어떻게 영향을 미치는가를 알아보기 위하여 실시되었다. 식이지바의 종류는 정어리유($\omega$3 linolenic acid) 및 옥수수기름 ($\omega$6 linolic acid)의 네 처리로 나누고 각 처리마다 지방의 수준을 총 에너지의 10%, 20%, 40%등 세수준으로 모두 12군을 두었으며, 식이지바의 무첨가군을 대조구로 두었다. 총 78마리의 Sprague-Dawley 계통 흰쥐 수컷에게 시험식이를 6주간 자유급여하였다. 사양시험 종료 후 간조직에서의 콜레스테롤 합성능력을 알아보기 위해 흰쥐의 간조직을 채취하여 in vitro 배양시험을 실시하였다. 본 시험에서 얻어진 결과를 요약하면 다음과 같다. 1) 혈장 총 콜레스테롤, HDL-콜레스테롤. LDL-콜레스테롤농도 및 HDL-C/T-C비율은 식이지방의 종류에 의해 유의하게(p<0.001) 영향을 받았다. ($\omega$3지방산을 많이 함유한 군(정어리유와 들기름)이 ($\omega$6지방산과 포화지방산을 많이 함유한 군(옥수수기름과 우지)에 비해 혈장내 HDL-콜레스테롤농도가 유의성있게(p<0.001)증가하였고, LDL-콜레스테롤농도는 유의성있게(p<0.05) 감소하였다. 혈장내 콜레스테롤농도는 우지군이 다른지방군에 비해(p<0.001),무지방식이군이 식이지방첨가군에 비해 유의하게(p<0.05)영향을 받았다. 2) 혈장 lecithiin : cholesterol acyltransferase(LCAT) 활성은 식이지방첨가군이 무지방식이군보다(p<0.001), 식물성유지군이 동물성지방군보다(p<0.001), 정어리유군이 우지군보다(p<0.001), 들기름군이 옥수수기름군보다(p<0.05), 정어리유군이 들기름군보다 유의성있게(p<0.05) 증가하였다. 저지방식이군이 중지방식이군과 고지방식이군에 비해 혈장내 LCAT 활성이 유의하게9p<0.001) 증가하였다. 3) 간의 콜레스테롤합성 능력은 정어리유군이 다른지방군보다(p<0.001), 무지방식이군이 식이지방첨가군보다(p<0.001), 동물성지방군의 식물성유지군보다 유의하게(p<0.001) 증가하였으나, 식이 지방의 수준에 의한 차이는 나타나지 않았다.