Mistlberger R E, Houpt T A, Moore-Ede M C
Department of Physiology and Biophysics, Harvard Medical School, Boston, Massachusetts.
J Biol Rhythms. 1990 Spring;5(1):35-46. doi: 10.1177/074873049000500104.
Food-restricted rats anticipate a fixed daily mealtime by entrainment of a circadian timekeeping mechanism separate from that which generates daily light-entrainable activity rhythms. The entrainment pathways and rhythm-generating substrates for food-anticipatory rhythms are unknown. In this study, we attempted to define minimal food-related stimuli necessary or sufficient for food anticipation by employing schedules of restricted macronutrient availability, with or without free access to a complementary diet. Rats did not anticipate a daily meal of protein, carbohydrate, or fat, as measured by tilt-cage, running-wheel, or food-bin activity, when they had free access to other nutrients. However, rats did anticipate single-macronutrient meals when they were limited to only two, larger, complementary meals each day (protein-fat, protein-carbohydrate) providing a reduced total number of calories. Previous work has shown that caloric restriction per se is not a prerequisite for food anticipation. In combination with that study, the present results indicate that the size of a nutrient meal, in absolute terms or relative to total daily nutrient intake, is of pre-eminent importance in determining its value as a synchronizer of anticipatory rhythms. The results further suggest that physiological responses unique to the ingestion and absorption of any particular macronutrient are not necessary components of the entrainment pathway.
食物受限的大鼠通过一种与产生每日光可调节活动节律的生物钟计时机制不同的机制来预测固定的每日进餐时间。食物预期节律的调节途径和节律产生基质尚不清楚。在本研究中，我们试图通过采用限制常量营养素供应的方案（无论是否可自由获取补充饮食）来确定食物预期所必需或足够的最小食物相关刺激。当大鼠可自由获取其他营养素时，通过倾斜笼、转轮或食物箱活动测量发现，它们不会预测每日的蛋白质、碳水化合物或脂肪餐。然而，当大鼠每天仅被限制为两顿较大的补充餐（蛋白质 - 脂肪、蛋白质 - 碳水化合物），从而减少总热量摄入时，它们确实会预测单一常量营养素餐。先前的研究表明，热量限制本身并非食物预期的先决条件。结合该研究，目前的结果表明，从绝对或相对于每日总营养素摄入量来看，营养素餐的大小在确定其作为预期节律同步器的价值方面具有至关重要的意义。结果还进一步表明，任何特定常量营养素摄入和吸收所特有的生理反应并非调节途径的必要组成部分。
