Perinatal Calorie Restriction with IUGR Perturbs Hepatic Circadian Cycling in Rat Male Offspring

Aside from the perinatal complications associated with low birth weight, individuals born with intra-uterine growth restriction suffer from chronic diseases late in life that ultimately lead to a shortened lifespan. These late life metabolic sequelae of low birth weight include obesity and metabolic syndrome, diabetes mellitus, cardiovascular disease, hypertension, stroke, dyslipidemia, and non-alcoholic fatty liver disease/steatohepatitis. Animal models employing perinatal calorie restriction recapitulate the observations made in humans. Interestingly, if continued calorie restriction is employed post-natally the late life sequelae of intra-uterine growth restriction are ameliorated. These observations linking both fetal and early post natal growth to later health is now termed the developmental origins of health and disease. To further our understanding of the mechanism of how early growth affects late life health we have employed Affymetrix microarray-based expression profiling to characterize hepatic gene expression in a rat model of maternal semi-nutrient restriction. In these experiments we have limited maternal calorie intake to 50% of normal so as to create 3 groups of animals: Control (Con) male offspring born to mothers who were fed normally throughout gestation and lactation; intra-uterine calorie restricted male offspring (IUCR) born to mothers who had 50% restriction of calories from e11 to e21; and combined intra-uterine and post-natal calorie restriction (IPCR) male offspring who were born to mothers who received calorie restriction during both fetal growth (e11 to e21) and post-natally (p1-p21). Livers were collected at p21(day 21 of life) for Con and IPCR groups (IUCR withheld owing to ‘catch up” growth), and at p450 (day 450 of life) for Con, IUCR, and IPCR. The profiling data reveals clear alteration of circadian cycling at P21, and subtle changes for circadian gene expression at p450. In addition, a clear transcriptional response is found during active calorie restriction at p21 but an absence of a transcriptional response late in life at p450.除了与低出生体重相关的围产期并发症外，宫内生长受限（intra-uterine growth restriction）个体在晚年还会罹患多种慢性疾病，最终导致寿命缩短。低出生体重带来的晚年代谢后遗症包括肥胖、代谢综合征、糖尿病（diabetes mellitus）、心血管疾病、高血压、脑卒中、血脂异常，以及非酒精性脂肪性肝病/脂肪性肝炎。采用围产期热量限制的动物模型可重现人类中的上述观察结果。有趣的是，若在产后持续实施热量限制，宫内生长受限所致的晚年代谢后遗症可得到改善。这些将胎儿期与早期产后生长和晚年健康状况相关联的研究发现，如今被称为健康与疾病的发育起源（developmental origins of health and disease）理论。为进一步阐明早期生长如何影响晚年健康的具体机制，本研究采用基于Affymetrix微阵列的表达谱分析技术，对母体半营养限制大鼠模型的肝脏基因表达特征进行了系统表征。本实验中将母体的热量摄入限制为正常水平的50%，以此构建三组雄性大鼠实验分组：对照组（Con）：子代雄性大鼠的母亲在整个妊娠和哺乳期间均正常进食；宫内热量限制组（IUCR）：子代雄性大鼠的母亲在胚胎第11天至第21天期间接受50%的热量限制；宫内联合产后热量限制组（IPCR）：子代雄性大鼠的母亲在胎儿生长阶段（胚胎第11天至第21天）以及产后阶段（产后第1天至第21天）均接受了热量限制。研究分别在产后第21天采集对照组与联合限制组的肝脏样本（宫内限制组因存在追赶生长未采集该时间点样本），并在产后第450天采集对照组、宫内限制组以及联合限制组的肝脏样本。表达谱数据分析结果显示，在产后第21天，肝脏的昼夜节律循环发生了显著改变；而在产后第450天，节律基因的表达仅出现轻微变化。此外，在热量限制干预活跃期的产后第21天，可观察到明确的转录应答，但在晚年阶段的产后第450天则未检测到显著的转录应答。