Semester

Summer

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Kimberly M. Barnes.

Abstract

Dietary conjugated linoleic acid (CLA) causes a body fat loss that is enhanced when mice are fed coconut oil (CO) compared to soy oil (SO). The objectives were to determine if CLA feeding altered proteins involved in lipolysis. Male mice (n = 80; 3 wk old) were fed 7% SO or CO diets for 6 wk then 0 or 0.5% CLA for 12d. A body fat index was calculated: (retroperitoneal (RP) + epididymal (EPI) fat pads)*100/body weight. Lipolysis was determined by non-esterified fatty acid (NEFA) and glycerol release from EPI & RP explants. The relative expression of perilipin, phosphorylated perilipin (P-perilipin), hormone sensitive lipase (HSL), phosphorylated HSL (P-HSL), adipocyte triglyceride lipase (ATGL), and adipocyte differentiation related protein (ADRP) were determined by western blotting. The body fat index was reduced by both CLA (P < 0.05) and CO (P < 0.001) but there was no interaction. NEFA release was increased by CLA in CO-fed mice (2.94 and 8.63 mumol/g; P < 0.05) but not in SO-fed mice (1.76 vs 2.26 mumol/g tissue). Glycerol release was not affected by CO or CLA. Total perilipin had a main effect of oil source, where it was decreased by CO feeding (P < 0.05) but P-perilipin tended to be increased by CLA in SO-fed mice and decreased by CLA in CO-fed mice (P = 0.08). HSL expression had a main effect of oil source where CO feeding decreased the expression (P < 0.05), but P-HSL expression wasn't affected by diet. ATGL expression had a main effect of oil source, it was decreased by CO feeding (P < 0.01) but wasn't altered by CLA. This may indicate that the CLA-stimulated lipolysis in CO-fed mice is on the decline since P-perilipin, and P-HSL are associated with increased lipase activity. ADRP expression wasn't affected by any diet, suggesting that there is no significant de-differentiation of adipocytes in vivo. In conclusion coconut oil enhances the anti-obesity effect of CLA and this effect is, at least in part, due to enhanced lipolysis.

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