Location: Children's Nutrition Research CenterTitle: Nursing frequency alters circadian patterns of mammary gene expression in lactating mice) Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/19/2012
Publication Date: 7/15/2012
Citation: Hadsell, D.L., Olea, W., Rottman, L.W. 2012. Nursing frequency alters circadian patterns of mammary gene expression in lactating mice [abstract]. Proceedings of the ADSA-AMPA-ASAS-CSAS-WSASAS Joint Annual Conference, July 15-19, 2012, Phoenix, Arizona. 90(Suppl. 3):53. CDROM. Interpretive Summary:
Technical Abstract: Milking frequency impacts lactation in dairy cattle and in rodent models of lactation. The role of circadian gene expression in this process is unknown. The hypothesis tested was that changing nursing frequency alters the circadian patterns of mammary gene expression. Mid-lactation CD1 mice were studied in 2 groups, for up to 54 h. Ad-libitum (AL) nursed dams were allowed AL access to their litters for the entire study. Variably nursed (VN) dams were placed on a 4-time (4X) per day (d) schedule on d1, and an AL nursing schedule on d 2 of the study. Samples were collected at 6-h intervals (n = 3 dams/ treatment-time combination). Mammary gland (MG) weight was used to indicate the combined effects of secretory activity and suckling-dependent milk removal. Total MG RNA was analyzed by real-time qRT-PCR for the expression of Bmal, Per1, Per2, Lalba, and B4galt1. On d 1, MG weight in the AL dams exhibited circadian oscillations, with a peak at Zeitgeber time (ZT) 12 and a trough at ZT0. MG weight was higher (P < 0.01) in VN dams for the first 18 h on 4X, but then decreased. Placement of VN dams back onto AL nursing during d 2 of the study decreased (P < 0.01) MG weight during the subsequent 18 h. On d 1, both Bmal and Per2 mRNA levels exhibited circadian oscillations with peaks at ZT0 and 18, respectively, and troughs at ZT12 and 6, respectively. In AL dams, both Lalba and B4galt1 mRNAs also oscillated, with troughs at ZT12 and peaks at ZT18. Both Per2 and B4galt1 were affected (P < 0.05) by decreased nursing frequency in the VN dams on d 1. For Per2, the response was an increase in amplitude at ZT18 (P < 0.02), while B4galt1's expression pattern was decreased (P < 0.0001). These differences resolved during d 2 when VN dams were placed on AL nursing. These results support the conclusion that decreased nursing frequency alters circadian gene expression and could influence lactose synthesis through dampening the expression of B4galt1.