Degree Type

Dissertation

Date of Award

2013

Degree Name

Doctor of Philosophy

Department

Animal Science

First Advisor

Diane M. Spurlock

Abstract

Proper lipid metabolism is essential to the maintenance of milk production and fitness in the modern dairy cow. Little is known about the regulation of lipid metabolism in adipose tissue in dairy cattle, including the roles of adipokines and lipid droplet associated proteins. Therefore, the objectives of this study were to characterized changes in transcript abundances of adipokines during three different energy altering models, and lipid droplet associated proteins throughout the transition period and with leptin induced lipolysis. Transcript abundances of leptin decreased during feed restriction, while angiopoietin like protein 4 (ANGPTL4) increased during early lactation, feed restriction, and following growth hormone administration. Therefore, reduced lipid uptake by adipose tissue during declining energy balance may be due to ANGPTL4 inhibiting lipoprotein lipase. Phosphorylation of hormone sensitive lipase (HSL) and perilipin increased during early lactation, but protein abundance of adipose triglyceride lipase (ATGL), the rate limiting step in lipolysis, decreased. Unlike lipid catabolism during early lactation, leptin induced lipolysis was mild, and protein abundance of ATGL and phosphorylation of STAT3 increased. These responses were attenuated with the addition of a STAT3 inhibitor. Therefore, leptin increased ATGL protein abundance through STAT3. This novel regulation of ATGL by STAT3 demonstrates a potential mechanism that allows for the differential regulation of HSL and ATGL. In conclusion, this research identified two novel mechanisms of lipid metabolism in dairy cattle which may allow for the development of strategies to optimize lipid metabolism.

Copyright Owner

Dawn Koltes

Language

en

File Format

application/pdf

File Size

200 pages

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