Duane W C, Ginsberg R L, Bennion L J
J Lipid Res. 1976 May;17(3):211-9.
The effects of a four to six day fast on gallbladder bile lipid composition, bile acid pool size, bile acid composition, and cholic acid metabolism have been determined in normal human subjects. Total bile acid pool size and cholic acid pool size were measured before and after fasting by a one-sample technique previously validated in our laboratory. The rate of synthesis of cholic acid and its fractional turnover rate before fasting were measured using standard techniques. Estimates of fasting cholic acid synthesis rate and fractional turnover rate were calculated as daily averages from the change in cholic acid pool size, in combination with the change in cholic acid specific activity, during the fasting period. Since these estimates are approximate, a maximum value for cholic acid synthesis rate during fasting was also determined by assuming that the entire change in cholic acid specific activity during the fasting period occurred instantaneously. The molar percent of cholesterol in gallbladder bile was reduced in eight of nine subjects after a four to six day fast (p less than .01; mean reduction 30.5%). The molar percents of bile acid and phospholipid were not significantly altered by fasting. The cholesterol saturation index, calculated on the basis of these data, was reduced by an average of 31.0% after a four to six day fast (p less than .02). The average daily cholic acid synthesis rate and the fractional turnover rate were reduced in all six subjects on whom isotope kinetic studies were carried out. The mean decrease in synthesis rate was 68.5% (p less than .05; range 55.2-79.8%) while the mean decrease in fractional turnover rate was 64.4% (p less than .05; range 30.2-100%). Reduction in synthesis rate was confirmed by the determination of maximum fasting synthesis of cholic acid, which averaged 61.1% lower than synthesis in the fed period. Fasting had no consistent effect on total bile acid pool size, cholic acid pool size, or bile acid species composition.
在正常人类受试者中，已确定了四至六天禁食对胆囊胆汁脂质成分、胆汁酸池大小、胆汁酸成分及胆酸代谢的影响。禁食前后，通过我们实验室先前验证过的单样本技术测量了总胆汁酸池大小和胆酸池大小。使用标准技术测量了禁食前胆酸的合成速率及其分数周转率。禁食期间胆酸合成速率和分数周转率的估计值是根据胆酸池大小的变化以及胆酸比活性的变化，计算为每日平均值。由于这些估计值是近似值，还通过假设禁食期间胆酸比活性的整个变化瞬间发生，确定了禁食期间胆酸合成速率的最大值。九名受试者中有八名在四至六天禁食后，胆囊胆汁中胆固醇的摩尔百分比降低（p小于0.01；平均降低30.5%）。禁食对胆汁酸和磷脂的摩尔百分比没有显著影响。根据这些数据计算的胆固醇饱和指数在四至六天禁食后平均降低了31.0%（p小于0.02）。在进行同位素动力学研究的所有六名受试者中，胆酸的平均每日合成速率和分数周转率均降低。合成速率的平均降低为68.5%（p小于0.05；范围为55.2 - 79.8%），而分数周转率的平均降低为64.4%（p小于0.05；范围为30.2 - 100%）。通过测定禁食期间胆酸的最大合成量，证实了合成速率的降低，其平均值比进食期的合成量低61.1%。禁食对总胆汁酸池大小、胆酸池大小或胆汁酸种类组成没有一致的影响。
