Thesis
Adrenergic regulation of adipose tissue lipolysis in transition dairy cattle based on genetic merit and energy intake
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/103330
Abstract
In lactating dairy cattle the adipose tissue stores energy as triacylglycerol (TAG) that can be used during early lactation. Breakdown of TAG (lipolysis) is regulated by stimulation of the beta-2 adrenergic receptors ([Beta]2AR) leading to activation of hormone-sensitive lipase (HSL). It is not known whether control of lipolysis is also a function of increased expression of mRNA for the ß2-adrenergic receptor, HSL, and perilipin (PLIN). A decrease in rates of lipogenesis (fatty acid synthesis) also occurs in early lactation. Therefore, objectives of this project were to help define adipocyte responses to lactation and energy deficit, including changes in expression of proteins known to control lipid metabolism. Cows were selected for genetic merit (high merit, HM; low merit, LM) based on sire predicted transmitting ability of milk (PTAM) and fed to requirements (NE) or to 90% of energy requirements (LE). We took adipose tissue biopsies at 21 and 7 days prepartum; and 7, 28, and 56 DIM to determine rates of lipogenesis and lipolysis; and to measure gene expression of key lipolytic genes ([Beta]2, HSL, and PLIN). The cows on the LE diet consumed 12% less feed prepartum and 16% less feed postpartum. Dietary energy restriction decreased milk production overall but HM, LE fed animals produced more milk (P < 0.03). Serum glucose was relatively unchanged and serum NEFA were highest at 7 DIM (P < 0.02). The slowest rates of lipogenesis occurred at 7 and 28 DIM (P < 0.001). HM cows had faster rates than LM cows (P < 0.04) and dietary restriction further decreased (P < 0.05) lipogenesis in early lactation. Lipolysis increased (P < 0.03) in early lactation in a pattern consistent with differences in milk production. The expression of [Beta]2AR, HSL, and PLIN did not change expression in NE cows due to lactation, but expression was decreased in early lactation by dietary restriction (P < 0.05). Data from this experiment support the hypothesis that regulation of adipose tissue metabolism in lactation is a function of diet and genetic merit and is controlled by multiple mechanisms including gene transcription and post-translational protein modifications.
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Details
- Title
- Adrenergic regulation of adipose tissue lipolysis in transition dairy cattle based on genetic merit and energy intake
- Creators
- Shawnese Marie Rocco
- Contributors
- J. P. McNamara (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Animal Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525078401842
- Language
- English
- Resource Type
- Thesis