Department of Animal Science, Purdue University , West Lafayette, IN 47907 , USA.
Biol Open. 2012 Jun 15;1(6):570-81. doi: 10.1242/bio.2012687. Epub 2012 Apr 30.
Altered gravity load induced by spaceflight (microgravity) and centrifugation (hypergravity) is associated with changes in circadian, metabolic, and reproductive systems. Exposure to 2-g hypergravity (HG) during pregnancy and lactation decreased rate of mammary metabolic activity and increased pup mortality. We hypothesize HG disrupted maternal homeorhetic responses to pregnancy and lactation are due to changes in maternal metabolism, hormone concentrations, and maternal behavior related to gravity induced alterations in circadian clocks. Effect of HG exposure on mammary, liver and adipose tissue metabolism, plasma hormones and maternal behavior were analyzed in rat dams from mid-pregnancy (Gestational day [G]11) through early lactation (Postnatal day [P]3); comparisons were made across five time-points: G20, G21, P0 (labor and delivery), P1 and P3. Blood, mammary, liver, and adipose tissue were collected for analyzing plasma hormones, glucose oxidation to CO(2) and incorporation into lipids, or gene expression. Maternal behavioral phenotyping was conducted using time-lapse videographic analyses. Dam and fetal-pup body mass were significantly reduced in HG in all age groups. HG did not affect labor and delivery; however, HG pups experienced a greater rate of mortality. PRL, corticosterone, and insulin levels and receptor genes were altered by HG. Mammary, liver and adipose tissue metabolism and expression of genes that regulate lipid metabolism were altered by HG exposure. Exposure to HG significantly changed expression of core clock genes in mammary and liver and circadian rhythms of maternal behavior. Gravity load alterations in dam's circadian system may have impacted homeorhetic adaptations needed for a successful lactation.
航天飞行（微重力）和离心力（超重力）引起的重力负荷变化与昼夜节律、代谢和生殖系统的变化有关。在妊娠和哺乳期暴露于 2-g 超重力（HG）会降低乳腺代谢活性并增加幼仔死亡率。我们假设 HG 破坏了母体对妊娠和哺乳的同源适应反应，这是由于与重力引起的昼夜节律变化相关的母体代谢、激素浓度和母体行为的变化。分析了妊娠中期（妊娠第 11 天[G11]）至早期哺乳期（产后第 3 天[P3]）的母体大鼠暴露于 HG 对乳腺、肝脏和脂肪组织代谢、血浆激素和母体行为的影响；在五个时间点进行了比较：G20、G21、P0（分娩）、P1 和 P3。收集血液、乳腺、肝脏和脂肪组织，用于分析血浆激素、葡萄糖氧化为 CO2 和掺入脂质，或基因表达。使用延时视频分析进行母体行为表型分析。在所有年龄组中，HG 均显著降低了母鼠和胎儿-幼仔的体重。HG 不影响分娩；然而，HG 幼仔的死亡率更高。PRL、皮质酮和胰岛素水平及其受体基因受 HG 影响。HG 暴露还改变了乳腺、肝脏和脂肪组织代谢以及调节脂质代谢的基因的表达。HG 暴露显著改变了乳腺和肝脏中核心时钟基因的表达以及母体行为的昼夜节律。母体昼夜节律系统中重力负荷的改变可能会影响成功哺乳所需的同源适应。
