Abstract
This study was carried out to investigate the effects of dietary lipid sources and meal frequency on growing performance and lipid metabolism in Sprague-Dawley strain male rats. The experiment was conducted in 4$\times$2 factorial arrangement with 4 sources of dietary lipid(palm oil, beef tallow, soybean oil and hydrogenated soyben oil) and 2 meal frequencies(ad-libitum or meal feeding). During the 4-week feeding period the rats were fed either ad-libitum (AL) or a single daily 3-hour meal (09 : 02-12 : 00) during the dark period. In vitro cultures were carried out to study the cholesterol synthetic activity in hte liver prepared from rats used in feeding trials. And in vitro cultures were also carried out to study the lipogenic and lipolytic activity in the liver and adipose tissues prepared from rats used in feeding trials. Present data indicated that body weight gain, feed intake and FER of AS(ad-libitum+soybean oil)and AHS(ad-libitum+hydrogenated soybean oil) group were significantly(p<0.05) higher than those of the other groups. It was found that the feed intake of MF group was much less than that of AL group. Total body weight gained by MF group was only 60% of AL group. Growing performance was not affected by dietary lipid sources. The cholesterol synthetic activity in liver tissues culture was markedly(p<0.05) increased in MF diets, especially in soybean oil group. The lipogenic activity in liver tissues culture of MP(meal feeding+palm oil) and MHS(meal feeding+hydrogenated soybean oil)group was significantly (p<0.05) higher than that of AP(ad-libitum+palm oil) group and AHS(ad-libitum+hydrogenated soybean oil) group(p<0.05). Rats fed ad-libitum+beef tallow and fed meal feeding+beef tallow showed significantly(p<0.05) higher lipogenesis than the other groups. It was apparent that the lipogenic activity in liver tissues culture was not affected by dietary lipid sources and meal frequency. Lipolytic activity in liver tissue culture was significantly(p<0.001)different with meal frequency; MF group was higher than AL group, but was not greatly affected by dietary lipid sources. In the in vitro studies with adipose tissue, MF diets increased the lipogenic activity and inhibited the lipolytic activity in adipocytes. The lipogenic activity in adipocytes was significantly (p<0.001) different with dietary lipid sources and found to be beef tallow group was the higherst, but the sources of lipid in the diet did not exert any effect on the lipolytic acitivity.
본 시험은 Sprague-Dawley 계통 흰쥐 수컷에게 지방의 종류와 식이급여 횟수를 달리하면서 급여하였을 때 성장 및 지방대사에 미치는 영향을 알아보고자 4종류의 지방(팜유, 우지, 대두유 및 경화대두유) 및 2종류의 식이급여형태(ad-libitum, 4$\times$meal feeding)를 달리하여 4$\times$2 요인시험으로 실시하였다. 4주간 시험식이를 ad-libitum(AL)군은 식이를 제한없이 자유롭게 섭취하도록 하였으며, meal feeding(MF)군은 1일 1회 즉, 09:00~12:00까지만 식이를 제한없이 급여하였다. 사양시험 종료후 간조직에서의 콜레스테롤합성 능력을 알아보기 위해 흰쥐의 간조직을 채취하여 in vitro 배양 시험을 실시하였다. 또한 간과 지방조직에서의 지방합성 및 분해 능력을 알아보기 위해 사양시험이 끝난 흰쥐의 간과 지방조직을 채위하여 in vitro 세포배양에서의 지방합성 능력과 지방분해 능력을 측정하였다. 본 시험에서 얻어진 결과를 요약하면 다음과 같다. 1) 성장하는 흰쥐의 증체량, 식이섭취량 및 식이효율은 AS(ad-libitum+hydrogenated soybean oil)군이 다른군에 비해 유의하게(p<0.05) 증가하였다. 식이지방의 종류에 의한 영향은 받지 않고, 식이급여형태에 의한 차이를 보여 MF군이 AL군에 비해 식이섭취량이 감소하였고, 중체량도 60%정도로 유의성있게(p<0.05)감소했다. 2) 간조직의 콜레스테롤합성 능력은 식이급여형태에 의한 차이를 보여 MF군이 AL군에 비해 간조직의 콜레스테롤합성 능력이 증가되는 경향을 (p<0.001) 보였는데 특히 불포화도가 높은 대두유군에서 유의성있게(p<0.05) 증가되었다. 3) 간조직의 in vitro 지방합성 능력은 MP(meal feeding+palm oil)군이 AP(ad-libitum+palm oil)군보다, MHS(meal feeding+hydrogenated soybean oil)군이 AHS(ad-libitum+hydrogenated soybean oil)군보다 유의하게(p<0.05) 증가했고, AB(ad-libium+beef tallow)군과 MB(meal feeding+beef tallow)군에서 지방합성 능력이 현저하게 증가되는 경향을(p<0.05)보였다. 식이급여형태나 식이지방의 종류에 대한 차이는 보이지 않았다. 간조직에서의 in virto 지방분해 능력은 MF군이 AL군에 비해 유의하게(P<0.001) 증가했고, 식이지방의 종류에 의한 차이는 나타나지 않았다. 4) 지방조의 in vitro 시험에 의하면 MF식이가 AL식이에 비해 지방합성 능력이 유의성있게(p<0.05) 증가하였으나, 지방분해 능력은 저하되었다(p<0.001). 식이지방의 종류에 의한 영향을 받아 우지군이 다른 지방군에 비해 지방합성 능력이 유의성있게(p<0.001) 증가되는 경향을 보였으나, 지방분해 능력은 식이지방의 종류에 의한 영향을 받지 않았다.