Department of Medicine, Christchurch School of Medicine and Health Sciences, University of Otago, Christchurch, PO Box 4345, 8140 Christchurch, New Zealand.
Metabolism. 2010 Jun;59(6):796-801. doi: 10.1016/j.metabol.2009.09.026. Epub 2009 Dec 16.
Previous studies in lambs and children show that the plasma concentration of amino terminal pro-C-type natriuretic peptide (NTproCNP), a stable product of proCNP, is strongly correlated with skeletal growth and markers of bone formation. Consistent with these findings, CNP expression is sensitive to nutritional status and is reduced by caloric restriction (CR) in both the fetus and the postnatal lamb. However, the effect of nutritional status on CNP in the adult, once linear growth is complete, is unknown. Hypothesizing that reduced CNP synthesis during CR is contingent on the presence of active growth plates, we studied the effect of CR ( 25% of maintenance) or loading (CL, 200% of maintenance) on CNP forms and alkaline phosphatase (ALP) in adult ewes and compared the findings to responses in a control group (C) fed a maintenance diet of 10.6 MJ of metabolizable energy. Live body weight was reduced (17%) in the CR group and increased (10%) in the CL group after 16 days of intervention. Plasma CNP concentration and ALP both fell in CR sheep and were significantly lower than C (P < .05 for both), returning toward basal levels 1 week after refeeding. In contrast, plasma NTproCNP did not differ (CR vs C). There were no significant changes in CNP forms and ALP in CL sheep compared with C. Fall in plasma CNP but not in NTproCNP in CR adult sheep suggests that CNP degradation (not synthesis) is altered, and contrasts with previous findings in growing lambs where CR reduces both CNP forms.
先前在羔羊和儿童身上的研究表明，氨基末端 pro-C 型利钠肽（proCNP 的稳定产物）的血浆浓度与骨骼生长和骨形成标志物密切相关。与这些发现一致，CNP 表达对营养状况敏感，在胎儿和产后羔羊中，热量限制（CR）会降低其表达。然而，营养状况对成年后 CNP 的影响（线性生长完成后）尚不清楚。我们假设 CR 期间 CNP 合成减少取决于生长板的活性，因此研究了 CR（维持量的 25%）或加载（CL，维持量的 200%）对成年母羊 CNP 形式和碱性磷酸酶（ALP）的影响，并将这些发现与对照组（C）的反应进行了比较，对照组喂食维持能量 10.6MJ 的日粮。在 16 天的干预后，CR 组的活体体重减轻（17%），CL 组的体重增加（10%）。CR 组的血浆 CNP 浓度和 ALP 均下降，且显著低于 C（两者均 P<0.05），重新喂食 1 周后恢复到基础水平。相比之下，血浆 NTproCNP 没有差异（CR 与 C 相比）。CL 组与 C 相比，CNP 形式和 ALP 均无明显变化。CR 成年绵羊血浆 CNP 下降但 NTproCNP 未下降表明 CNP 降解（而非合成）发生改变，与之前在生长羔羊中的发现相反，CR 降低了两种 CNP 形式。
